1 c e. cm . urgh,&c. T. BLIZARD CURLING, Esq. Lect. on Surg. and Assist. Surg. to the Lond. Hospital. G. P. DESHAYES, M.D. Paris. A. T. S. DODD, ESQ. H. DUTROCHET, M.D. W.F.EDWARDS, M.D. F.R.S. H. MILNE EDWARDS, M.D. Prof.ofNat. History to the College of Henry IV., and to the Central School of Arts and Manufactures, Paris. ARTHUR FARRE, M.D. F.R.S. Professor of Midwifery in King's College and Physician Accoucheur to King's College Hospital. R. D. GRAINGER, F.R.S. Lect. on Anat. and Phys. at St. Thomas's Hospital. R. E. GRANT, M.D. F.R.S. L. & E. Fell, of the Roy. Coll. of Physicians, Edinb. and Prof.of Comp. Anatomy and Zoology in Univ. College, &c. &.c. W. A. GUY, M.D. Prof. For. Med. King's College, London, and Physician to King's College Hospital. M. HALL, M.D. F.R.S. L. & E. London. HENRY HANCOCK, ESQ. Lect. on Anat. and Physiology at, and Surgeon to the Charing-Cross Hospital. ROBERT HARRISON, M.D. M.R.I.A. Prof, of Anat. and Surg. in the Univ. of Dublin JOHN HART, M.D. M.R.I.A. Prof, of Anat. in the Royal Coll. of Surf. Dublin. A. HIGGINSON, ESQ. Liverpool." ARTHUR JACOB, M.D. M.R.I.A. Professor of Anatomy and Physiology to the Royal College of Surgeons in Ireland. ' GEORGE JOHNSON, M.D. Assistant Physician to King's College Hospital, and resident Medical Tutor in King's College, London. T.RYMER JONES, F.R.S. Prof.of Comp. Anat., in King's College, London. T. WHARTON JONES, F.R.S. London. T. WILKINSON KING, ESQ. SAMUEL LANE, ESQ. Lecturer on Anatomy, St. George's Hospital, London. F. T. MACDOUGALL, ESQ. JOHN MALYN, Esq. C. MATTEUCCI. Professor of Physics in the University of Pisa. ROBERT MAYNE, M.D. Lect. on Anat. & Phys. Richmond Hospital, Dublin. W. A. MILLER, M.D. F.R.S. Professor of Chemistry in King's College, London. W. F. MONTGOMERY, M.D. M.R.I.A. Fellow of and Professor of Midwifery to the King and Queen's College of Physicians in Ireland. GEORGE NEWPORT, F.R.S. Vice-Pros, of the Entomological Society of London. R. OWEN, F.R.S. F.G.S. Hunterian Professor of Comparative Anatomy and Physiology to the Royal College of Surgeons in London. JAMES PAGET, ESQ. Lect. on Anat. & Phys. St. Bartholomew's Hospital. RICHARD PARTRIDGE, F.R.S. Prof.of Descrip. and Surg. Anat. in King's Coll. Lond. BENJAMIN PHILLIPS, F.R.S. London. Surgeon to the Westminster Hospital. SIMON ROOD PITTARD, ESQ. London. W. H. PORTER, ESQ. Prof, of Surgery to the Royal Poll, of Surg. in Ireland. J. C. PRICHARD, M.D. F.R.S. Corresponding Member of the Institute of France, Member of the Royal Academy of Medicine of Paris. G. O. REES, M.D. F.R.S. Assistant Physician to Guv's Hospital. J. REID, M.D. Prof, of Medicine in the University of St. Andrews. EDWARD RIGBY, M.D. F.L.S. Lect. on Midwifery at St. Bartholomew's Hospital. J. FORBES ROYLE, M.D. F.R.S. F.G.S. Professor of Materia Medicain King'sCollege, London. HENRY SEARLE, ESQ. London. W. SHARPEY, M.D. F.R.S. Prof, of Anat. and Physiol. in Univ. Coll. London. JOHN SIMON, F.R.S. Lecturer on Pathology, St. Thomas's Hospital. J. Y. SIMPSON, M.D. Fellow of the Royal College of Physicians, and Pro- fessor of Midwifery in the University of Edinburgh. SAMUEL SOLLY, F.R.S. Assistant Surgeon to St. Thomas's Hospital. GABRIEL STOKES, M.D. J. A. SYMONDS, M.D. Physician to the Bristol General Hospital, and Lectu- rer on the Theory and Practice of Medicine at the Bristol Medical School. ALLEN THOMSON, M.D. Fellow of the Royal College of Surgeons, and Professor of the Institutes of Medicine in the University of Edinburgh. JOHN TOMES, ESQ. Surgeon- Dentist to the Middlesex Hospital. WM. TREW, ESQ. W. VROLIK, Prof. Anat. and Phys. at the Athenaeum of Amsterdam. RUDOLPH WAGNER, M.D. Prof.of Med. & of Comp. Anat. in theRoy.Uni.Eilangen. W. H. WALSHE, M.D. Physician to University College Hospital. R. WILLIS, M.D. W. J. ERASMUS WILSON, F.R.S. Consulting Surgeon to the St. Pancnis Infirmary. CONTENTS OF THE THIRD VOLUME. nal ) Instinct Irritability Knee-Joint, Normal Anatomy Knee-Joint, Abnormal Anatomy of the Lacrymal Organs .... Larynx, Normal Ana- ) tomy ' Larynx, Abnormal ) Anatomy $ Leg, Regions of Leg, Muscles of .... Life Liver Luminousness, Animal Lymphatic & Lacteal ) System $ Lymphatic System, > Abnormal Anatomy ) Mammalia , Mammary Glands .... Marsupialia Membrane Meninges Microscope Milk Mollusca Monotremata Motion, Animal, in- } eluding Locomotion S Mucus Mucous Membrane . . Muscle Muscular Motion .... Page Dr. Alison 1 Dr. Marshall Hall 29 A. Higginson, Esq. 44 R. Adams, Esq. . . 48 T. W. Jones, Esq. 78 J. Bishop, Esq. .. 100 W.H. Porter, Esq. 114 A.T.S.Dodd.Esq. 126 A.T.S.Dodd, Esq. 137 Dr. Carpenter... . 141 E. Wilson, Esq... 160 Dr. Coldstream . . 197 S. Lane, Esq 205 Dr. Todd.. . 232 Professor Owen . . S. Solly, Esq. Professor Owen . , Dr. Todd Dr. Todd Dr. Carpenter. . . , Dr. G. O. Rees . . Professor Owen . . Professor Owen . , 234 245 331 331 331 358 363 366 J. Bishop, Esq. . . 407 Dr. G. O. Rees . . 481 W. Bowman, Esq. 484 W. Bowman, Esq. 506 W. Botcman, Esq. 519 Muscular System, Comp. Anatomy Myriapoda Neck, Muscles and Regions of the. . Nervous System . . Nerve Nervous System, Comp. Anatomy Nervous Centres, Normal Anatomy Nervous Centres, Abnormal Anat. Nervous System, } Physiology of the $ N inth Pair of N erves Nose Nutrition OZsophagus Optic Nerves Orbit Organic Analysis .. Osseous System, } Comp. Anatomy S Osseous Tissue .... Pachydermata . Pacinian Bodies . . Par Vagum. Parotid Region .... Parturition Penis Perineum Peritoneum Pharynx Pisces Professor R. Jones. Professor R. Jones. J. Simon, Esq. . . . Dr. Todd. Dr. Todd. J. Anderson, Esq. Dr. Todd.. Page 530 545 561 585 591 601 626 Dr. Todd 712 Dr. Todd.. 720c G. Stokes, Esq. . . , J. Paget, Esq. .. . Dr. Carpenter Dr. G. Johnson . . , Dr. Mayne , Dr. G. Johnson . . , Dr. Miller . 721 723 741 758 762 782 792 Professor R. Jones . . 820 J. Tomes, Esq 847 Professor R. Jonr s . . 858 W. Bowman, Esq... 876 Dr. J. Reid 881 Dr. G. Johnson .... 902 Dr. Rigby 904 E. Wilson, Esq 909 Dr. Mayne 919 S. R. Pittard, Esq. . . 935 W. Trew, Esq 945 Professor R. Jones.. 955 ERRATA IN VOLUME THE THIRD. Page 684, col. 2, line 44, after " medulla oblongata," insert " and the cerebrum."' 700, col. 2, line 1 9, for " testes," read " nates." line 20, for " nates," read " testes." line 36, for "thalami," read "thalamus." 708, col. 1, line 10, for "distend," read "exist." 711, col. 1, line 59,Jbr " optic thalami," read " hemispheres." 712, col. 2, line 40, for " Seinruch," read " Steinruch." line 41, Jor " Hermann, Nasse," read "Hermann Nasse." At page 902, see a list of Errata in the article PAR VAGUM. , THE ADDITIONAL ERRATA IN VOLUME THE THIRD. " six times," read " six lines.' 01- Page 71, col. 1, line 1 and 2,. /or 287, col. 1, line I, for " Peophagous," read " Poephagous. 351, col. 1, line 7, /or " made be made," read " may be made. ^ 361, col. 2, line 28 from bottom, for " analysis," read " analyses. 409, col. 1, fig. 207, Jraser* " B" at the angle which is not lettered. 41?' col' 2' Imes land's, for quadratus femoris," mid quadriceps extensor femoris 418* col l! line 26 from bottom, /or " separated," read " adapted." 433 col 1 line .5, /or" or d cd, in the second movement; the tail being, read u dcd ; in the second movement, the tail being." line 10, for " 6," read " ad." 441, col. 1, line 7, de/e " Sect. IV." 610, col. l.line 5, for " molar," read " motor. G67, col. 1, line 19, for " foramen," read " fore-arm. 715, col. 1, line 39, for " in membranous," read " in a membranous. 716' col. l! line 33 from bottom, /or " his," rend " this." 720x, col. 2, line 2 from bottom, > posterior and posterior," read " anterior and po terior." 722s col. 1, line 8 from bottom, for " cerebri," read " cerebelli." 751, col. 1, line 19, for " had," read " have." 83o' col. 1, line 10 from bottom, for " resemble,' read resembling. ' col. 2, line 6, /or " it," read " them." 849, col. 2, in description of cut, for " animal," read" earthy. may be inferred, with perfect confidence, to take place throughout the whole range of the animal kingdom, and even that some of them must be performed with greater energy and precision in some of the lower tribes than in man. The different external senses attain their highest perfection in different animals ; that of smell, for example, probably in the predaceous mammalia, that of touch in the antennae of insects, and that of sight in the predaceous birds ; it is not likely that any one is enjoyed in its highest perfection by man ; and what have been accurately distinguished from mere VOL. in. the emotions of fear, of joy, of affection, of anger, even of jealousy, are as distinctly indi- cated by their actions as by those of man ; that under the influence of these emotions their mental operations are excited or depressed, and their attention fixed or distracted, and their volition excited, as in our own case ; and that their actions are habitually guided by a clear perception, or rather, we should say, by conti- nual correct applications, of a first principle of belief, which is generally admitted to be an ultimate fact in the constitution of the human rnind, and on which much stress has been B THE C Y CLOP.EDI A OF ANATOMY AND PHYSIOLOGY. INSTINCT. This word is often applied to the mental acts of the lower animals, as if it were truly applicable to the whole of these acts ; but a little consideration will shew, jirst, that this word, in its more approved and correct acceptation, is applicable only to a part of the mental operations, which may be inferred from the observation of the actions and habits of animals ; and secondly, that in this restricted sense, the term is applicable to a part of the operations of the human mind itself; and that the subject of instinct cannot be tho- roughly understood, unless information regard- ing it is sought in the consciousness of our own minds, as well as in the observation of other living beings. The study of this subject is therefore equally important as a part of natural history, of mental philosophy, and of human physiology ; and is a good illustration of the necessity of this latter science being based on the observation and generalization of the laws and conditions of vital action through- out the whole extent of the animal creation. It is obvious, indeed, that various mental acts, of which we are conscious in ourselves, may be inferred, with perfect confidence, to take place throughout the whole range of the animal kingdom, and even that some of them must be performed with greater energy and precision in some of the lower tribes than in man. The different external senses attain their highest perfection in different animals ; that of smell, for example, probably in the predaceous mammalia, that of touch in the antennae of insects, and that of sight in the predaceous birds ; it is not likely that any one is enjoyed in its highest perfection by man ; and what have been accurately distinguished from mere VOL. III. sensations as the perceptions of external things, i. e. the notions as to the qualities of these, which naturally present themselves to our minds in consequence of sensations being felt, would seem in various instances to follow the sensa- tions more quickly and more surely in other animals than in us ; for it is generally allowed that what appear to be acquired perceptions of the eye to us, i. e. the notions of the distance, size, and form of visible objects, are instanta- neously made known to many of the lower animals the very first time that those objects make impressions on their retinae; the faculty of Intuition, which we must admit as part of the source of our own knowledge, appears to exist in greater perfection in other animals, and the notions of external things which they thus acquire are amply sufficient to regulate their muscular motions. It is equally plain that many of the strictly mental acts, of which our complex trains of thought are composed, are habitually performed by animals ; that they have a perfect recollec- tion of past sensations, implying the exercise of the powers of memory and of conception ; that the emotions of fear, of joy, of affection, of anger, even of jealousy, are as distinctly indi- cated by their actions as by those of man ; that under the influence of these emotions their mental operations are excited or depressed, and their attention fixed or distracted, and their volition excited, as in our own case ; and that their actions are habitually guided by a clear perception, or rather, we should say, by conti- nual correct applications, of a first principle of belief, which is generally admitted to be an ultimate fact in the constitution of the human mind, and on which much stress has been INSTINCT. tions, the sensations, the voluntary powers, the memory and instinct of the animals are all brought into play ; but we have no reason to believe that the animals performing them are capable of anticipating their ultimate result. In all cases, those actions which are en- titled to the appellation of Instinctive are ge- nerally xmderstood to be characterized by two marks, quite sufficient to distinguish them from the effects of voluntary power guided by rea- son : 1. That, although in many cases expe- rience is required to give the will command over the muscles concerned in them, yet the will, when under the influence of the instinc- tive determination, acts equally well the first time as the last ; no experience or education is required, in order that the different voluntary efforts requisite for these actions may follow one another with unerring precision; and 2. That they are always performed by the same species of animal nearly, if not exactly, in the same manner ; presenting no such variation of the means applied to the object in view, and admitting of no such improvements in the pro- gress of life or in the succession of ages, as we observe in the habits of individual men, or in the manners and customs of nations, adapted to the attainment of any particular ends by those voluntary efforts which are guided by Reason. " The manufactures of animals," says Dr. Reid, " differ from those of men in many striking particulars. No animal of the species can claim the invention. No animal ever in- troduced any new improvement, or variation from the former practice. Every one has equal skill from the beginning, without teaching, without experience or habits. Every one has its art by a kind of inspiration, i. e. the ability and inclination of working in it without any knowledge of its principles." A third distinc- tive mark, naturally resulting from the last, is at least equally characteristic, although much less generally observable, that these instinc- tive actions are seen to be performed in cir- cumstances which reason informs us to be such as to render them nugatory for the ends which are usually accomplished by them, and for which they are obviously designed. The efforts made by migratory birds, even when confined, at their usual period of migration, the mistake of the flesh-fly who deposits her eggs on the carrion-plant instead of a piece of meat,* or of the hen who sits on a pebble in- stead of an egg, or of the mule which remains immoveably fixed by terror instead of escaping from the flood which threatens to overwhelm it, (as exemplified in the inundation of the valley of Luisnes in Savoy in 1818,) or of the bee which gathers and stores up honey even in a climate where there is no winter, f are so many proofs, that an instinctive action is prompted by an impulse, which results merely from a particular sensation or emotion being felt, not by anticipation of the effect which the action will produce. * Kiiby. t See Kirby and Spcncr, Introduction to Ento- mology, vol. ii. p. 469. But, in order to have demonstrative proof of the essential difference between instinct and reason, and of the correctness of the view which we take of the nature of that mental impulse which prompts what we call the in- stinctive actions of animals, it is only neces- sary to reflect on what passes within ourselves on occasion of certain actions of the very same class being performed by us. It is dif- ficult, indeed, in adult age, to distinguish those actions which we perform instinctively from those which we have learnt by repeated efforts to perform habitually ; but in the case of infants we see complex actions, useful or necessary to the system, performed -with per- fect precision at a time when we are certain that the human intellect is quite incompetent to comprehend their importance or anticipate their effects ; yet we cannot doubt that it is by a mental impulse that they are excited, because we perform the same actions in the same cir- cumstances in adult age, and are then con- scious of the impulse which prompts them. " It is an instinct," says Bichat, " which I do not understand, and of which I cannot give the smallest account, which makes the infant, at the moment of birth, draw together its lips to commence the action of sucking," to be fol- lowed by the still more complex act of deglu- tition. " This cannot be ascribed to the mere novelty of the sensations which it experiences from external objects, for the general effect of such sensations is to determine various agita- tions or irregular movements indeed, but not an uniform movement, directed to a deter- minate end. If we examine different animals at the moment of birth, we shall see that the special instinct of each directs the execution of peculiar movements. Young quadrupeds seek the mammae of their mothers, birds of the order Gallinacese seize immediately the grain which is their appropriate nourishment, while the young of the Carnivorous birds merely open their mouths to receive the food which their parents bring to their nests. In general, it is very important to distinguish the irregular or varied movements which, at the moment of birth, are produced simply by the new sensations and excitements which the body receives, from those definite actions which are the effect of instinct, a cause of which we can give no further explanation." In fact, when we attend to the simple action of deglutition,* as performed in our mature years, we may be conscious that it results from the same instinctive impulse which guided it with unerring precision in the new-born infant, long before the voluntary power of simply raising the hand to the mouth had been ac- quired. If we were to consult only the grati- fication of our sensations, we should keep any grateful food in the mouth ; for when it is swal- lowed the gratification immediately resulting from it is at an end, and there is no peculiar pleasure attached, in other circumstances, to the mere act of deglutition; but all we can * [I. e. that part of the act which is dependent on the voluntary movement of the tongue to pass on the food to the isthmus faucium. ED.] INSTINCT. observe by attention to our own feelings on such occasions is, that while we feel the sen- sations of hunger and thirst, we feel also a pro- pensity, all but irresistible, to swallow what- ever grateful food or drink is in the mouth. This propensity is not only prior to reason, but stronger than reason, and prompts us to action more surely and more energetically than the mere recollection of the effects previously resulting from food or drink taken into the sto- mach could have done. If we reflect further, we shall find that there are various other sensations, with which we can feel, in our own persons, that an instinctive impulse is naturally linked. The term Appe- tite does not express the whole of these, although it is only by referring to the action which it uniformly prompts that an appetite can be distinguished from another sensation. Sympathetic movements, such as breathing, coughing, sneezing, vomiting, &c. are ascribed by VVhytt and others to sensations ; and laugh- ter, weeping, the expression of feeling in the countenance and features, &c. are strictly refer- able to emotions of mind, and in the perform- ance of all these actions, a propensity which may be called strictly instmotive, because prior to experience, and independent of reason- ing, may be frequently and distinctly felt, and is from the first equally effectual in exciting very complex muscular movements, as the impulse to swallow food in the mouth. We may specify several other kinds or modes of action, which we are all conscious of frequently per- forming, and which we perform on many oc- casions in obedience, not to any effort of reason, but to a truly instinctive impulse, natu- rally consequent on certain sensations or emotions, and felt even in adult age to be inde- pendent of, as they are in the infant prior to, any anticipation of remote consequences, viz. 1. those which are prompted by the instinct of self-preservation, (as the winking of the eye- lids when the eyes are threatened with injury, the shrinking of any limb or part of the body which is struck, the projection of the arms when we ate about to fall forwards on the face,* the act of crying from pain or from fear); 2. those which are prompted by the instinct of shame, as when the saliva escapes from the mouth, when the sphincters fail in their office, or the sense of modesty is out- raged ; 3. those which are prompted by the instinct of imitation, existing more or less in the early stage of all human existence, and whereby we are all led to fashion our language, manners, and habits, on the model of those around us, and particularly of those persons with whom we have either the most frequent inter- course, or the intercourse which is most fitted to make an impression on our minds ; 4. those which are prompted by the emotions of affec- * Let any one try the experiment of attempting to fall forward on his face, with his arms extended at his sides, and he will be immediately conscious of the instinctive impulse which urges him to throw forward his arms ; and which he feels dis- tinctly and resists with difficulty, even when he knows that he is about to fall only on soi't matter which cannot injure him. tion and pity, or still more decidedly by the impulse of maternal love, on witnessing the helpless condition of young infants.* We do not enter into details on these subjects at pre- sent, but merely mention them as examples, in which we may safely and legitimately avail ourselves of the evidence of consciousness to assure ourselves of the essential peculiarity, and of the paramount authority, of the in- stinctive impulse, as distinguished from the voluntary effort, which results from a train of reasoning. It has been often said that the nature of instinct is absolutely mysterious and inscru- table; but if what has now been stated be correct, this can be said of instinct only in the same sense in which it may be said of all mental acts without exception ; the essence of mind, like that of matter, being wholly in- scrutable. The characters of the instinctive impulse may be distinguished as clearly as those of any other mental act, in the only way in which any such act can be distin- guished, viz. by attention to our own conscious- ness ; although we never could have antici- pated a priori that this kind of mental impulse could have extended to so long continued and complex actions, and to the concerted ope- rations of so many individuals, as the operations of some animals indicate. Having satisfied ourselves of the existence of certain instinctive impulses, both in the lower animals and in ourselves, essentially dis- tinct from those voluntary efforts which are guided by reason, we need not be perplexed at finding that there is much difficulty in some individual instances, in determining to which class of mental acts particular actions ought to be referred. However difficult it may be in any in- dividual instance, to decide whether an action, of man or of animals, is the effect of a blind in- stinct, or of reason, anticipating and desiring its consequences, there can be no doubt or difficulty as to the fact, that these two distinct kinds of mental determination to the perform- ance of actions exist. Neither do we consider it of any import- ance to enter on the metaphysical speculations which ingenious men have hazarded at different times as to the nature of the agent, by which the instinctive actions may be supposed to be immediately excited. Some philosophers have been so strongly impressed with the admirable adaptation of means to ends which these phe- nomena present, in animals manifestly devoid of reason, that they have believed them to be in all cases the immediate offspring of the divine intelligence, and have expressed their theory in the form of an axiom, " Deus anima brutorum," which, it is humbly conceived, is admissible only in the same sense in which we assent to the more general assertion, " Deus anima mundi." Mr. Kirby, in his very learned and elaborate Bridgewater Treatise on the History, Habits, and Instincts of Animals, seems to favour the [* The greater number of the actions enumerated may, however, be accounted for on the principle of reflux nervous artion, now so generally admitted by physiologists, ED.] INSTINCT. idea which other philosophers have maintained, of intermediate agents between the Divine will and the living beings on earth, by which the actions of the latter are guided ;* but in pro- secuting this idea he is disposed to regard the proximate cause of instinct, as he expresses it, not as metaphysical, but merely as physical, and to suppose that "light, heat, and air, or any modification of them " may be the inter- mediate agents " employed by the Deity to excite and direct animals, when their intellect cannot, in their instinctive operations;" and that " the organization of the brain and nervous system may be so varied and formed by the Creator as to respond in the way that he wills, to pulses upon them from the physical powers of nature."f On this it may be observed that this last sentence expresses no more than the truth, whatever opinion we may form as to the mode, in which the response of the nervous system of an animal to the impressions made on it by physical agents takes place; but if it be meant by the expression, that the proximate cause of instinct is probably not metaphysical but physical, to exclude all mental operation, and all consciousness of effort, from the instinctive actions of animals, we can regard the theory only as a denial of all mental acts or affections in any of the lower animals, and as easily con- tradicted by the whole analogies of their struc- ture, by observation of their habits, and by the evidence of our own consciousness in the performance of those precisely similar instinc- tive actions which have been noticed above. It seems quite unreasonable to doubt that the immediate cause of all the actions that we call instinctive, is a strictly mtntnl effort, but the occurrence of that effort in every case when it is required must in all probability be always held as an ultimate Juft in the animal ceconomy ; and all speculations as to its inti- mate nature or proximate cause may be re- garded as mere conjectures, on a subject which is beyond the reach of the human faculties. Nor would any thing be gained, in the infer- ence as to final causes, from establishing any one of these conjectures ; for the mental constitution of man himself, and of the whole lower ani- mals, is equally a part of the contrivance of the Divine Artificer of the world, as the laws of motion or the properties of light. He who could make man after his own image could assuredly impart such mental propensities to other beings, as well as to man, as were ne- cessary for the ends for which the creation was designed. And when we attempt, in all hu- mility, but at the same time in confident re- liance on the mental powers which He has vouchsafed to us, to draw inferences as to His existence and attributes from the study of created things, we do so, not by vainly attempt- ing to comprehend the nature of the energy by which any of the changes (physical or mental) occurring around us are effected, but simply by observing the adaptation of means to ends in those regular and uniform laws which we are * Sec vol. ii. p. 243-4. t Vol. ii. p. 255-6. enabled to infer from the observation of such changes, which we ascribe to His authority, and beyond which we feel that it is not yet given us, by any exercise of our minds, to ascend. In enabling us to draw those in- ferences, the instincts of animals, as we shall afterwards state, are of peculiar importance ; but the inferences are the same, whatever opi- nion we may adopt as to the mode in which the Divine Intelligence so indicated rules the wills of the animal creation. Having said so much of the characteristics of this class of phenomena, and endeavoured to set them in the proper point of view, we shall next offer a very rapid sketch of the varied instincts exhibited in the different tribes of animals, arranging them simply according to the purposes which they seem destined to serve, and shall conclude with a few general reflections. It may be premised that it certainly seems reasonable a priori to suppose, that the struc- ture of the nervous system, and 1 especially of the brain, of different animals, will bear some relation to the kind of instinctive propensities which they exhibit. In the size of the sen- sitive and motor nerves, and portions of the cerebro-spinal axis whence these originate, par- ticularly the spinal tord, medulla oblongata, and optic lobes (or corpora quadrigemina), in the higher animals, this relation may be distinctly perceived; and it has been further confidently stated by some phrenologists, that strong evi- dence of certain of their peculiar doctrines may be deduced from observation of the size and form of the brains of animals, as compared with their instincts ; but this last speculation certainly cannot be carried further than the vertebrated animals, which form but a small part of the living beings that are continually guided and ruled by the laws of instinct; and even in them no such relation of the size and form of the brain, or of any part of the brain, to the general intelligence of an animal, or to any par- ticular instinct, has been fully ascertained. In- deed, until some such essential difference shall be observed between the habits and instincts of the dolphin, or other cetaceous animals, and the predaceous fishes, as may correspond to the extraordinary difference of the size and struc- ture of their brains, (that of the former being much larger in proportion to the spinal cord than the human brain, and of complex struc- ture, while that of the latter is not larger than the optic lobes or corpora quadrigemina of the same animal, and of very simple structure,) such speculations may be safely distrusted.* Mr. Kirby has stated that the principal in- stincts of animals may be referred to three heads; those relating to their food, those re- lating to their propagation and the care of their offspring, and those relating to their hybernation. But this enumeration is certainly defective, and indeed will hardly include several which * We cannot suppose this difference to be con- nected with the difference in the mode of respi- ration of these animals, because we know that the only part of the central masses of the nervous system of either, concerned in that function, is the medulla oblonguta. INSTINCT. he has himself accurately described. The fol- lowing appears a more comprehensive enume- ration. Three great classes of instinctive ac- tions may be distinguished ; the first designed for the preservation of individuals ; the second for the propagation and support of their off- spring; and the third for various purposes im- portant either to the race of animals exhibiting them, or to other animals, but not distinctly referable to either of the formei heads. Each of these classes admits of obvious sub- divisions. I. Of instincts designed for the preservation of the individuals exhibiting the>, we may enumerate the following : 1. All animals are endowed with instincts prompting them to some means of escaping or repelling injury or violence, but these are ex- ceedingly various, both as to the kind and as to the degree of complexity of the actions which they excite; from the simple retraction of the tentacula of the infusory Vorticella, or of the Medusa, Polype, or Actinia, up to the active and formidable resistance of the ele- phant or the tiger. The most common instinct of self-preservation excited by the emotion of fear, is that which prompts to flight, an in- stinct so obviously existing in the human species, that the effort by which it is resisted has in all ages been regarded with respect; and another very common propensity in animals is that which prompts to concealment. This is often combined with flight, as in most of the Carnivorous Mammalia, the Rodentia, the Ce- tacea, the diving birds, reptiles, insects, &c. ; but some of the higher animals, and many of the Mollusca and insects, and others of the lower tribes, remain quite motionless and counterfeit death when under the influence of fear ;* and it is remarkable that when the cir- cumstances of the animals render this mode of defence the most effectual, it is that adopted, in preference to flight, even by single species of families, the other members of which shew no such instinct, as in the case of the ptarmi- gan, which so frequently cowers among the grey lichen, or the snow on the mountain- tops, instead of taking wing like the moor fowl, or in that of the hedge-hog, which on occasion of any imminent danger makes no effort but that of coiling itself into a ball. In many instances the instinct either of flight or concealment is aided by very various special contrivances, equally instinctive, fitted either to deceive, or to alarm, or injure an assailant. Some even of the Mollusca, and some of the reptiles, as the toad, squirt water on him ; many reptiles and some lower animals, as the scorpion, bee, wasp, &c., even some of the gelatinous radiata,f have the power of emit- * " In this situation, spiders will suffer them- selves to be pierced with pins and torn to pieces, without discovering the smallest sign of pain. This simulation of death has been ascribed to a strong convulsion or stupor occasioned by terror ; but this solution of the phenomenon is erroneous. If the object of terror is removed, in a few se- conds the animal runs off with great rapidity." Duncan on Instinct. t Kirby, vol. i. p. 198. ting irritating matter of greater or less inten- sity ; the electrical animals, as the gymnotus and torpedo, use their appointed weapons ; the hedge-hog and porcupine oppose their sharp thorns to any one who attempts to molest them; many insects and some reptiles protect them- selves by emitting peculiarly fetid effluvia; the cuttle-fish tribe have the remarkable power of emitting an inky fluid which darkens the wa- ter and hides them ; and on the other hand there is reason to believe that the phosphores- cent light which so many marine animals ex- hibit, may be suddenly augmented on occa- sion of any threatening of injury, and serve as a means of defence.* (See LUMINOUSNESS.) The means of defence, and the instincts guid- ing them, in the case, not only of the higher Carnivorous animals, but many of the stronger of the Herbivorous classes, the elephant, the hog, the horse, the buffalo, the deer, &c. re- quire no illustration. The instinct which prompts many animals to utter cries when injured or threatened, (as well as on other occasions and for other purposes,) deserves notice as a means of protection, parti- cularly on this account, that as it is one of the instincts which most clearly extends to the human race, so we may perceive in man, as well as in some of the lower animals, that its use is not merely to frighten assailants, but especially to procure assistance and protection for the young animal from its parents. 2. The most conspicuous and most remark- ably varied of the instincts under this head are those by which the food of different ani- mals is procured. With the exception of the sponges, and some others of the lowest Zoo- phyta, in which the nourishment is supplied by currents, all animals have organs corresponding to a mouth and stomach, into which aliments are taken by a process of deglutition, imply- ing sensations and instinctive efforts conse- quent on these; and in the Articulata and Mollusca, the most important central organ of the nervous system seems to be the nervous collar surrounding the oesophagus, which in the vertebrated animals seems to be developed and subdivided into the first, fifth, and part of the eighth pairs of nerves, with the corres- ponding portions of the cerebro-spinal axis, by which the sensation of hunger is felt, the suitable nourishment discriminated, and the instinctive effort, whether of deglutition only, or of mastication more or less powerful ac- cording to the food, is excited. In some instances subsidiary instincts are also implanted in certain animals, which are essential to their digestion and nutrition. The art of cookery, as universally practised by the human race, may be said to be the result of experience; but this cannot be said of the pro- pensity of many animals to swallow salt, still less of the swallowing of gravel or pebbles by the graminivorous birds, or of the copious draughts of water, sufficient to store the nu- merous and peculiar cells of their first and second stomachs, which are taken by the camel * Ibid, vol. i. p. 178. INSTINCT. or llama before they enter on the deserts, and which enable them subsequently to subsist without water for many days. But the instincts by which animals are en- abled to search for and obtain food may be easily supposed to be much more numerous and varied than those by which they merely seize and swallow it, and in fact furnish the conditions by which the varieties of the whole structure of animals are chiefly determined. Probably the greatest number of animals are nourished by the vegetable world in the living or dead state, and are continually guided by sensations, to which instinctive efforts are at- tached, i. e. by appetites, in the selection of food, which may in general be found and seized without much difficulty. But through- out the whole animal kingdom, from the mi- croscopic animalcules up to the largest of the Mammalia, a very great number of carni- vorous animals are found, who subsist on, and continually repress the numbers of, the herbi- vorous tribes; and it may easily be supposed that the instincts implanted in these animals, which oppose and counteract the varying efforts at self-preservation already mentioned, will be more varied, and bear more marks of contri- vance and ingenuity. Accordingly, from the numerous Vorticellae, or other animalcules, of the order Rotatoria, which excite currents in the water around them, and so attract into their stomachs many of the smaller ani- malcules, up to the lion, the whale, or the eagle, we find an infinite number of con- trivances and instinctive propensities, served by organs, by which the predaceous animals, of all the orders, are enabled to prey on the others. The Polype, Echinus, and Actinia, for example, among the Zoophyta, seize their prey, as it is brought to them by the waves, with their numerous tentacula ; the Entozoa, and the leech and other of the Annelides, have the faculty and the necessary instinct of attach- ing themselves to the larger animals in the situations which suit them, as the Cirrhipedes or barnacles do to vegetable substances. The cuttle-fish and other predaceous Mollusca have legs furnished with admirably constructed suckers and powerful jaws, and most of the Crustacea have claws and mandibles, suf- ficient to enable them to seize and destroy ma- rine animals of very considerable size ; and it is unnecessary to enlarge on the powerful means of destruction, or on the instincts guid- ing their use, which are seen in many genera of each of the classes of vertebrated animals. There is often a peculiar instinct guiding each of the Carnivorous Mammalia to the part of the body of its victim where it can most easily inflict a mortal wound, to the throat in the case of a large animal, to the head in that of a small one, of which the cranium may be pierced. In the greater number of them, however, the instinctive actions by which their prey is obtained are distinguished only by power and violence ; and although much con- trivance is employed for adapting the different parts of the structure to the habits and des- tination of the animals, there is little apparent ingenuity in the modes in which the animals perform their office in creation. The attitude and gesture of the cat, the pointer, or the tiger, " slow stealing with crouched shoulders on his prey," is an example of instinctive con- trivance preliminary to the act of violence. The aspect and expression of many carnivo- rous animals, not only of the Mammalia and birds, but of the shark, the cuttle-fish, the scorpion, the tiger-beetle, &c., are so adapted to the feelings and instincts of the animals on which they feed, as often to deprive them of the power of flight or resistance; and it is maintained by many, that some of the predace- ous animals have the power of fascinating their prey by merely fixing their eyes on them. Many have ascribed this power to the serpent ; and Mr. Kirby asserts it with confidence of the fox.* A few only of the predaceous ani- mals, as the dog and wolf, have the instinct of associating together for procuring their prey. It has been stated that the pelican and the dog-fish have a similar instinct.f But the more striking indications of con- trivance in the actions prompted by this in- stinct are to be found in some of the less pow- erful of the carnivorous tribes. The Lophius Piscatorius or fishing-frog, although a large fish, having no strength or speed, obtains its prey by stratagem, plunging itself in mud, or covering itself with sea-weed: " it lets no part of it be perceived except the extremity of the filaments that fringe its body, which it agitates in different directions, so as to make them ap- pear like worms. The fishes, attracted by this apparent prey, approach and are seized by a single movement of the fishing-frog, and swal- lowed by his enormous throat, and retained by the innumerable teeth by which it is armed." J A still more singular art is practised by the Choetodon rostratus, which feeds on flies, and, as Sir Charles Bell states, actually takes aim at them, and shoots them with a drop of water. The instinct of the myrmecophaga or ant-eater, which protrudes the tongue to allure flies to settle on it, and then suddenly retracts it to devour them, also deserves notice. A more complex art is practised by the ant-lion, which digs a pitfall in the track usually followed by ants, and conceals itself in the bottom of it, waiting for its prey. But of all contrivances in the animal creation for procuring food, the most complex and artificial are those of the different genera of spiders, equally curious on account of the peculiar organs by which they spin their webs, as of the peculiar and varied instincts by which they are guided in using them. || For example, " any common black and white spider (Salticus Scenicus), which may always be seen in summer on sunny rails, &c., when it spies a fly at a distance, ap- proaches softly, step by step, and seems to measure his distance from it by the eye; then if he judges that he is within reach, first fixing * Vol. ii. p. 2fi9. t See Darwin's Zoon. vol. i. p. 229, 249. J See Kirby, vol. ii. p. 406, and pi. xiii. $ Bridirewater Treatise, p. 200. || See Kirby, vol. ii. p. 184 and 286. INSTINCT. a thread to the spot on which he is stationed, by means of his fore feet, which are much larger and longer than the others, he darts on his victim with such rapidity, and so true an aim, that he seldom misses it. He 13 pre- vented from falling by the thread just men- tioned, which acts as a kind of anchor, and enables him to recover his station.' 1 * Again, the kind of spider that has received the name of Geometric, " having laid the foundation of her net, and drawn the skeleton of it, by spinning a number of rays, converging to a centre, next proceeds, setting out from that point, to spin a spiral line of unadhesive web, like that of the rays, which it intersects, and after numerous circumvolutions finishes this at the circumference. This line, in conjunction with the rays, serves as a scaffolding for her to walk over, and also keeps the rays properly stretched. Her next labour is to spin a spiral or labyrinthiform line from the circumference towards the centre, but which stops somewhat short of it ; this line is the most important part of the snare. It consists of a fine thread, stud- ded with minute viscid globules, like dew,which by their viscid quality retain the insects which fly into the net. The snare being thus finished, the little geometrician selects a concealed spot in the vicinity, where she constructs a cell, in which she may hide herself and watch for game; of the capture of which she is informed by the vibrations of a line of communication, drawn between her cell and the centre of her snare."f 3. Many animals are guided by instinct to form habitations for themselves, of very various kinds, for protection against injury and against cold, from the simple contrivance of the earth- worm, which closes the orifice of its hole with leaves or straw, up to the elaborate structures of the bee, the ant, or the beaver. Here we observe a singular but easily understood diffe- rence between the inhabitants of water and air. The greater number of the more delicate animals that inhabit the sea, chiefly of the Mollusca and Crustacea, are provided by nature with shells, or very firm integuments, evidently for protec- tion against the violence of the waves, in the formation of which instinct has little or no share ; but there are some of the Annelides inhabiting water, as the Sabella and Terebella, and the larvae of some moths, which have a sin- gular instinct enabling them to form habitations sufficient for their own protection, " by collect- ing grains of sand and fragments ot decayed shells, &c. which they agglutinate together by means of a viscid exudation, so as to form a firm defensive covering, like a coat of mail." This may be stated as the intermediate link be- tween the habitations given to the Mollusca and Crustacea by nature, and those which many land animals have organs and instincts enabling them to form for themselves. " The manoeuvres of the terebella are best observed by taking it out of its tube and placing * Kirby. vol. ii. p . 298. t Ibid. p. 295. See also Darwin's Zoon. vol. i. p. 253. it under water upon sand. It is then seen to unfold all the coils of its body, to extend its tentacula in every direction, often to a length exceeding an inch and a half, and to catch, by their means, small fragments of shells and the larger particles of sand. These it drags to- wards its head, carrying them behind the scales which project from the anterior and lower part of the head, where they are immediately ce- mented by the glutinous matter which exudes from that part of the surface. Bending the head alternately from side to side, while it con- tinues to apply the materials of its tube, the terebella has very soon formed a complete collar, which it sedulously employs itself to lengthen at every part of the circumference with an activity and perseverance highly inte- resting. For the purpose of fixing the different fragments compactly, it presses them into their places with the erected scales, at the same time retracting the body. Hence the fragments, being raised by the scales, are generally fixed by their posterior edges, and thus, overlaying each other, often give the tube an imbricated appearance. " Having formed a tube of half an inch or an inch in length, the terebella proceeds to burrow ; for which purpose it directs its head against the sand, and contracting some of the posterior rings, effects a slight extension of the head, which thus slowly makes its way through the mass before it, availing itself of the materials which it meets with in its course, and so con- tinues to advance till the whole tube is com- pleted. After this has been accomplished, the animal turns itself within the tube, so that its head is next the surface, ready to receive the water which brings it food, and is instrumental in its respiration. In summer the whole task is completed in four or five hours ; but in cold weather, when the worm is more sluggish, and the gluten is secreted more scantily, its progress is considerably slower."* The habitation formed by the water-spider, which is not exposed to the violence of the sea, shews much greater delicacy of workmanship, as well as greater variety of instinct. " The insects that frequent the waters," says Kirby, " require, as well as those that inhabit the earth, predaceous animals to keep them within due limits, and the water-spider is one of the most remarkable on whom that office is imposed by the Creator. To this end her in- stinct instructs her to fabricate a kind of diving- bell, for which purpose she usually selects still waters. Her house is an oval cocoon filled with air, and lined with silk, from which threads issue in every direction, and are fast- ened to the surrounding plants ; >n this cocoon, which is open below, she watches for her prey, and even appears to pass the winter, when she closes the opening. It is most commonly en- tirely under water, but its inhabitant has filled it with air for respiration, by which she is ena- bled to live in it. She conveys the air in the following manner : she usually swims upon her back, when her abdomen is enveloped in a * Roget's Bridge-water Treatise, vol. i. p. 279. 10 INSTINCT. bubble of air, and appears like a globe of quick- silver; with this she enters her cocoon, and displacing an equal mass of water, again ascends for a second lading, till she has suffi- ciently filled her house with it, so as to expel all the water. The males construct similar habitations by the same manoeuvres. How these little animals can envelope their abdomen with an air-bubble, and retain it till they enter their cells, is still one of Nature's mysteries that have not been explained.'' We need say nothing of the habitations formed by solitary animals of the higher tribes, chiefly by burrowing under ground, for their own protection and comfort; but the most curi- ous of such solitary habitations on the earth's surface are also furnished by the tribe of spiders. " Some species of spiders, M. Audouin re- marks, are gifted with a particular talent for building : they hollow out dens ; they bore galleries ; they elevate vaults ; they build, as it were, subterranean bridges; they construct also entrances to their habitations, and adapt doors to them, which want nothing but bolts, for without any exaggeration, they work upon a hinge and are fitted to a frame. The interior of these habitations is not less remarkable lor the extreme neatness which reigns there; whatever be the humidity of the soil in which they are constructed, water never penetrates them ; the walls are nicely covered with a tapestry of silk, having usually the lustre of satin, and almost always of a dazzling white- ness. " The habitations of the species in question are found in an argillaceous kind of red earth, in which they bore tubes about three inches in depth and ten lines in width. The walls of these tubes are not left just as they are bored, but are covered with a kind of mortar, suffi- ciently solid to be easily separated from the mass that surrounds it." " The door that closes the apartment is still more remarkable in its structure. If the well were always open, the spider would sometimes be subject to the intru- sion of dangerous guests. Providence has there- fore instructed her to fabricate a very secure trap-door which closes the mouth of it. To judge of this door by its outward appearance, it appears to be formed of a mass of earth coarsely worked, and covered internally by a solid web, which would be sufficiently wonder- ful for an animal that seems to have no special organ for constructing it ; but when divided vertically, it is found to be a much more com- plicated fabric than its outward appearance in- dicates, it being formed of more than thirty alternate layers of earth and web emboxed, as it were, in each other, like a set of weights for small scales. "If these layers of web are examined, it will be seen that they all terminate in the hinge, so that the greater the volume of the door the more powerful is the hinge. The frame in which the tube terminates above, and to which the door is adapted, is thick, arising from the number of layers of which it consists, and which seem to correspond with those of the door; hence the formation of the door, the hinge, and the frame, seem to be a simultaneous operation ; except that in fabricating the first, the animal has to knead the earth as well as to spin the layers of web. By this admirable arrangement these parts always correspond with each other, and the strength of the hinge and the thickness of the frame will always be proportioned to the weight of the door. " The interior surface of the cover to the tube is not rough and uneven like its exterior, but perfectly smooth and even like the walls of the tube, being covered with a coating of white silk, but more firm, and resembling parchment, and remarkable for a series of minute orifioes placed in the side opposite the hinge, and ar- ranged in a semicircle ; there are about thirty of these orifices, the object of which, M. Au- douin conjectures, is to enable the animal to hold her door down in any case of emergency against external force, by the insertion of her claws into some of them."* But the most extraordinary habitations formed by the instincts of animals are those which are the joint result of the labours of communities; and here we observe the same difference as has been already noticed, between the inhabitants of the air and of the ocean. Many of the ani- mals that inhabit the latter are formed by na- ture, as Mr. Kirby expresses it, (and evidently with a view to the rude shocks to which they are exposed,) " into a body politic, consisting of many individuals, separate and distinct as inhabiting different cells, but still possessing a body in common, and many of them receiving benefit from the systole and diastole of a com- mon organ ; thus by a natural union is symbo- lized what in terrestrial animal communities re- sults from numerous wills uniting to effect a common object. The land, as far as I recol- lect, exhibits no instance of an aggregate animal, nor the ocean of one which, like the beaver, lemming, bee, wasp, &c. forms associations to build and inhabit a common house. "f And there is a curious family, named Salpa, in which the individuals are attached to each other almost like bees in their cells at birth, and are afterwards separated when they have acquired strength; thus forming the link be- tween the aggregated sea animals (such as Co- rals, Madrepores, Sertularia, Flustra, &c.) and the associated land animals. The habitations that are formed by animals of the latter description, although in very diffe- rent parts of the scale of beings, afford equally curious evidence of skill and contrivance, and of the wills of numerous individuals, bound together by a common instinct, as surely as the materials of which the aggregate animals are composed. Take, for example, the houses of beavers. " Beavers set about building some time in the month of August: those that erect their habitations in small rivers or creeks in which the water is liable to be drained off, with won- derful sagacity provide against that evil by * Kirby, vol. ii. p. 287, et scq. t Kubj, vol. i. p. 222. INSTINCT. 11 forming a dike across the stream, almost straight where the current is weak, but where it is more rapid, curving more or less, with the convex side opposed to the stream. They construct these dikes or dams of the same materials as they do their lodges, viz. of pieces of wood of any kind, of stones, mud, and sand. These causeways oppose a sufficient barrier to the force both of water and ice ; and as the willows, poplars, &c. &c. employed in constructing them often strike root in it, it becomes in time a green hedge in which the birds build their nests. " By means of these erections the water is kept at a sufficient height, for it is absolutely necessary that there should be at least three feet of water above the extremity of the entry into their lodges, without which, in the hard frosts, it would be entirely closed. This entry is not on the land side, because such an open- ing might let in wild animals, but towards the water. " They begin to excavate under water at the base of the bank, which they enlarge upwards gradually, and so as to form a declivity, till they reach the surface ; and of the earth which comes out of this cavity they form a hillock, with which they mix small pieces of wood and even stones ; they give this hillock the form of a dome from four to seven feet high, from ten to twelve long, and from eight to nine wide. As they proceed in heightening, they hollow it out below, so as to form the lodtre which is to receive the family. At the anterior part of this dwelling, they form a gentle declivity termina- ting at the water, so that they enter and go out under water. " The interior forms only a single chamber resembling an oven. At a little distance is the magazine for provisions. Here they keep in store the roots of the yellow water-lily, and the branches of the black spruce, the aspin, and the birch, which they are careful to plant in the mud. These form their subsistence. Their magazines sometimes contain a cart-load of these articles, and the beavers are so industrious that they are always adding to their store."' The nests so admirably constructed by what have been called the perfect societies of insects, the white ants or termites, the ants or formicae, the bees, wasps, and humble bees, are well known, and have been often described. The materials used by the two first genera are chiefly clay, with bits of straw or wood, cemented by animal secretions ; the bees manufacture wax for the purpose. " The wasps and hoi-nets are remarkable for the well-known curious papier-mache edifices, in the construction of which they employ fila- ments of wood, scraped from posts and rails witli their own jaws, mixed with saliva, of which the hexagonal cells in which they rear their young are formed, and often their combs are separated and supported by pillars of the same material ; and the external walls of their nests are formed by foliaceous layers of their ligneous paper." f * Kirby, vol. ii. p. 510. t Kirby, loc. cit. p. 335. " The tree-ants, again, are remarkable for forming their nests on the boughs of trees of different kinds; and their construction is sin- gular, both for the material and the architec- ture, and is indicative of admirable foresight and contrivance ; in shape they vary from glo- bular to oblong, the longest diameter being about ten inches, and the shortest eight. The nests consist of a multitude of thin leaves of cow-dung, imbricated like tiles upon a house, the upper leaf formed of one unbroken sheet covering the summit like a skull-cap. The leaves are placed one upon another in a wavy or scalloped manner, so that numerous little arched entrances are left, and yet the interior is perfectly secured from rain. They are usually attached near the extremity of a branch, and some of the twigs pass through the nest. A vertical section presents a number of irregular cells, formed by the same process as the exte- rior. Towards the interior the cells are more capacious than those removed from the centre, and an occasional dried leaf is taken advantage of to assist in their formation. The nurseries for the young broods in different stages of developement are in different parts of the nest."* What is most peculiar in the habitations of all these " perfect societies of insects," is the formation, by the same working members of these societies, of cells of different size and form, suited for the different classes or ranks of indi- viduals which, as we shall afterwards state, each of these associations comprises ; and the occasional alteration of the size and form of the cells, when circumstances occur, which will be afterwards mentioned, to make an alteration of their destination advisable. There are other examples among insects, of imperfect societies or associations, found tempo- rarily and during the larva state only, which unite in forming tents under which they feed, and which shelter them from sun and rain. This is done by the larvae of several species of butterfly and moth.-)~ 4. The next instincts which may be noticed under this head are those connected with the hi/ber-nation of animals ; for in almost every case in which this faculty (which is found so gene- rally in the lower tribes, particularly reptiles and insects, as well as in the order Cheiroptera and several others of the higher animals,) exists, there is attached to it some instinctive propensity, prompting the animal, even although it be not one of those which form houses for themselves, at least to search for some suitable residence in which it may be sheltered during the winter, whether under ground, under stones or timber, under the bark of trees, &c. ; and it is very re- markable that their hiding places are often found, or formed, long before the weather has become very cold. " I am led to believe from my own observation," says Mr. Spence, " that the days which the majority of coleopterous insects select for retiring to their hybernacula are some of the warmest days of autumn, when * Ibid. p. 340. t Spence and Kirby, vol. ii. p. 21. 12 INSTINCT. they may be seen in great numbers alighting on walls, rails, path-ways, &c."* Some insects, and many larvae (as the silk-worm) approaching to the 'state of pupse, form a covering for them- selves by exudations from their own bodies, likewise at some distance of time before the frosts set in. Many hybernating animals ex- hibit so little of any vital action as to require little or no nourishment during the winter, ex- cepting the product of absorption of their own fat; but it is also well known that many of different orders (as the beaver, the hedgehog, the squirrel, the dormouse, the bee, which are seldom or never quite torpid,) are guided by instinct to lay up stores of provisions, on which they subsist during the winter. Some of these, as the lemming, have been observed to spread out their stores to dry in fine weather. Some of the most curious of the provisions of this kind are the following : " There is an animal, the rat-hare, which is gifted by its Creator with a very singular in- stinct, on account of which it ought rather to be called the hay-maker, since man may or might have learned that part of the business of the agriculturist, which consists in providing a store of winter provender for his cattle, from this industrious animal. Professor Pallas was the first who described the quadruped exercising this remarkable function, and gave an account of it. The Tungusians, who inhabit the country beyond the lake of Baikal, call it Pika, which has been adopted as its trivial name. " About the middle of the month of August these little animals collect their winter's pro- vender, formed of select herbs, which they bring near their habitations and spread out to dry like hay. In September they form heaps or stacks of the fodder they have collected under places sheltered from rain or snow. Where many of them have laboured together, their stacks are sometimes as high as a man, and more than eight feet in diameter. A subterranean gallery leads from the burrow below the mass of hay, so that neither frost nor snow can intercept their communication with it. Pallas had the pa- tience to examine their provision of hay piece by piece, and found it to consist chiefly of the choicest grasses and the sweetest herbs, all cut when most vigorous, and dried so slowly as to form a green and succulent fodder; he found in it scarcely any ears or blossoms, or hard and woody stems, but some mixture of bitter herbs, probably useful to render the rest more whole- some."-t " Although," says Kirby, " ants during the cold winters in this country remain in a state of torpidity, and have no need of food, yet in warmer regions during the rainy seasons, when they are probably confined to their nests, a store of provisions may be necessary for them. Now although the rainy season, at least in America, is a season in which insects are full of life, yet the observation that ants may store up provi- sions in warm countries is confirmed by an account sent me by Colonel Sykes, with respect * Introduction to Entomology, vol. ii. p. 438. t Ib. p. 507. to another species which appears to belong to the same genus as the celebrated ants of visi- tation, by which the houses of the inhabitants of Surinam were said to be cleared periodically of their cock-roaches, mice, and even rats. The present species has been named by Mr. Hope the provident ant. These ants, after long-con- tinued rains during the monsoon, were found to bring up and lay upon the earth on a fine day, their stores of grass seeds and grains of Guinea corn, for the purpose of drying them. Many scores of these hoards were frequently observable on the extensive parade at Poona."* The great and important instinct of migration is another means by which the lives of many animals are preserved during winter. The number of species of birds, which pass the summer to bring forth their young in this country, but disappear from it in autumn, and are known to spend the winter in the south of Europe or Africa, has been stated at not less than five-sixths of the whole number resident here during the summer, and these are replaced by many other species, chiefly aquatic birds and waders, but likewise the fieldfares, redwings, starlings, &c. which have brought forth their young in the colder climates, and return here for the winter. There are others, as the crane and stork, which perform similar migrations, but are rarely seen in this country. The migra- tions of the larger birds from the northern regions are chiefly performed in large bodies, forming angular lines, very high in the air; those of the smaller birds of passage, swallows, singing birds, &c. that go southwards from hence, seem to take place less regularly, and have been less accurately observed. There are also many annual migrations from one part of this country to another, in spring and autumn, as of the plovers and lapwings, curlews, ring ouzels, &c. It is still doubtful with what sensations the propensity to perform these peri- odical migrations is chiefly connected, whether with changes of temperature, or deficiency of food, or with the changes of the sexual desire, (as maintained by Jenner.f) But it is certain that the migrations take place while the tem- perature is still such as is well borne by the animals ; indeed of most of the species of birds of passage some individuals are frequently observed not to migrate ; J and it is equally certain that most of the birds of passage do not gradually withdraw, as if following the gradual changes of the food on which they live, but go oft' suddenly, and perform their voyages, par- ticularly in autumn, so rapidly, as to be much exhausted and emaciated at the end of them ; so that it is certainly not under the influence of sensations gradually changing and tending to partial and successive changes of place, but under that of a strong determination, overcom- ing the motives to action which are usually predominant, and commanding strenuous and painful exertion at a time when no great incon- venience is felt, that these voyages are per- * Vol. ii. p. 344. i Phil. Trans. 1824. $ Sec Darwin, Zoouomia, sect. xvi. 12. INSTINCT. 13 formed. And if, with Darwin and some others, we doubt of the existence of a blind instinctive propensity as the cause of these movements, we have no resource but to ascribe them to a very high decree of intelligence, combined with much mental resolution, and extending to all or almost all the individuals of the species, enabling them to foresee evils that are still remote, and determining them to undergo labour, fatigue, and danger in order to avoid them. It has also been repeatedly ascertained that the same indi- viduals return after their six months of absence and long voyages, to the very spots where they had been brought forth, implying a power of discernment and recollection which appear to us quite inconceivable. Of such high qua- lities of mind we see no indications in the other actions of these birds, excepting only in their preparations for the nurture of their young ; and if they really possessed these qualities, we might expect with perfect confidence to see them devise many contrivances for their comfort and convenience, and to witness variations and im- provements in habits, which we know from the writings of the ancient naturalists to have been perfectly uniform and stationary at least since the time of Aristotle. There are some of the Mammalia, chiefly of the order Ruminantia, which likewise perform periodical migrations in the natural state, as has been particularly noticed in America, of the bison, the musk-ox, and rein-deer. A similar instinct has been observed in the quaggas in Africa ; and a singular observation, as shewing a variation of instinct according to varying cir- cumstances, was made by Dr. Richardson, that the American black bear, when lean, and from that cause unfitted for hybernation, migrates in severe winters from the northward into the United States. The periodical migrations of fishes appear to be designed for the benefit of their offspring, not for their own preservation; and there are other migrations, in immense numbers, of various kinds of animals which are not periodical, and of which the object is still obscure, but which do not fall under the present head. II. Of instincts Jo?'' the propagation and support of offspring. Of the very curiously varied instincts of animals connected with the propagation and support of their off- spring, we need not dwell on those which must necessarily attend the very various kinds of organs (so well arranged and de- scribed by Cuvier), by which the impreg- nation of the ova in the different tribes of animals is effected the instincts, e. g. which prompt most male fishes to impregnate eggs already laid, and many reptiles to impregnate them at the moment of their emission from the body of the female, or which guide the different warm-blooded animals in the different modes of their sexual intercourse. The in- stincts which enable animals to anticipate and provide for the wants of their young are still more varied, and imply mental processes of greater complexity. The most important of these may be referred to the following heads. 1. This is probably one object of the migra- tions of birds above-mentioned, and certainly the main object of the migrations of great swarms of fishes, both in the sea, and of those which ascend the rivers ; to which the same observations, as to the return to the same spot whence they had formerly departed, and as to the labours and hazard which the instinct im- pels them to incur, are in many instances appli- cable. " The cod-fah makes for the coast at spawn- ing time, going northward ; this takes place towards the end of winter, or the beginning of spring. " The mackarel hybernates in the Arctic, Antarctic, and Mediterranean Seas, where it is stated to select certain depths of the sea called by the natives Barachouas, which are so land- locked, that the water is as calm at all times as in the most sheltered pools. " It is in these that the mackarel, directed by instinct, pass the winter. In the spring they emerge in infinite shoals from their hiding places, and proceed southward for the purposes of depositing their eggs in more genial seas. " What the mackarel is' to the north of Europe, the thunny is to the south. It de- posits its esgs in May and June, when it enters the Mediterranean, seeking the shores in shoals arranged in the form of a parallelogram, or as some say, a triangle, and making a great noise and stir. " The herring may be said to inhabit the arctic seas of Europe, Asia, and America, from whence they annually migrate at different times in search of food, and to deposit their spawn. Their shoals consist of millions of myriads, and are many leagues in width, many fathoms in thickness, and so dense that the fishes touch each other." " The largest and strongest are said to lead the shoals, which seem to move in a certain order, and to divide into bands as they proceed, visiting the shores of various islands and countries, and enriching their in- habitants." " They seek places for spawning where stones and marine plants abound, against which they rub themselves alternately on each side, all the while moving their fins with great rapidity." " In temperate climates the salmon quits the sea early in the spring, when the waves are driven by a strong wind against the river currents." " They leave the sea in numerous bands formed with great regularity. The largest individual, which is usually a female, takes the lead, and is followed by others of the same sex, two and two, each pair being at the distance of from three to six feet from the preceding one ; next come the old, and after them the young males in the same order." " They employ only three months in ascending to the sources of the Maraguon, the current of which is remarkably rapid, which is at the rate of nearly forty miles a day ; in a smooth stream or lake their progress would increase in a four-fold ratio. Their tail is a very powerful organ, and its muscles have wonderful energy ; by placing it in their mouth, they make of it a very elastic spring, for, letting it go with violence, they raise themselves in the air to the 14 INSTINCT. height of from twelve to fifteen feet, and so clear the cataract that impedes their course ; if they fail in their first attempt, they continue their efforts till they have accomplished it. The female is stated to hollow out a long and deep excavation in the gravelly bed of the river to receive her spawn."* A similar periodical emigration has been ob- served in other animals, particularly in some of the Crustacea. " Several of the crabs forsake the waters for a time, and return to them to cast their spawn ; but the most celebrated of all is that known by the name of land-crab, and alluded to by Dr. Paley as the violet-crab, and which is called by the French the tourlounm. They are natives of the West Indies and South Ame- rica. In the rainy season, in May and June, their instinct impels them to seek the sea, that they may fulfil the great law of their Creator, and cast their spawn. They descend the moun- tains, which are their usual abode, in such numbers that the roads and woods are covered witli them." " They are said to halt twice every day, and to travel chiefly in the night. Arrived at the sea-shore, they are there reported to bathe three or four times, when retiring to the neighbouring plains or woods, they repose for some time, and then the females return to the water, and commit their eggs to the waves. This business dispatched, they endeavour to regain, in the same order, the country they had left, and by the same route, but only the most vigorous can reach the mountains. "f The object of all these migrations is, that the female animals may have an opportunity of de- positing their eggs where they will be in circum- stances suited to their development, particularly as to the essential requisites, exposure to heat and to air. 2. The same object, the choice of a suitable place for depositing their eggs, is accomplished in other instances by very different instincts im- planted in female animals. " Repiiles," says Kirby, " and Fishes do not feel the instinctive love for their young, after birth, which is ex- hibited by quadrupeds and birds, but are in- variably instructed by the Creator to select a place in which their eggs can be hatched either by artificial or solar heat." Many of them likewise, as the salmon, dig holes before depositing them, for their protection. Those of the serpents which are not ovo-viviparous, bury their eggs in sand, or in heaps of fer- menting matter. The Saurians also select a proper place for their eggs, the crocodile, e.g. the sands beside rivers ; " one species of sala- mander commits a single egg to a leaf of Persicaria, protects it by carefully doubling the leaf, and then proceeding to another, repeats the manoeuvre till her oviposition is finished. Toads and frogs lay their eggs in water, sur- rounded by a gelatinous envelope which forms the first nourishment of the embryo," corres- ponding to the albumen of the bird's egg. In like manner every insect is directed by nature to place its eggs in situations where its Kirby, vol. i. t Ibid. young, when disclosed, will find its appro- priate nourishment ; some burrowing in the earth for this purpose ; many flies in dead animal matter about to putrefy ; many in dif- ferent parts of living vegetables;* bees and ants in the cells where they are to be fed by the working members of their hives, &c. A spe- cies of the ichneumon fly and some of the wasps have been observed to bury caterpillars along with their eggs, on which their larvae are to feed, and another fly to deposit its eggs on the back of a caterpillar, when the larvae feed on the secretion by which the covering of the pupa is to be formed.f 3. The instincts called into action in the nidification, particularly of birds, are so nume- rous, varied, and admirably adapted to their purpose, as to have called forth admiration in all ages. The pairing of the parent birds at the beginning of spring, when the labour is to begin ; the choice of a place suited to the habits of the species, on the ground, under ground, in rocks, on the edge of lakes or of the sea, in marshes, in bushes, on trees, on buildings of all descriptions ; the choice of the materials, and the labour exerted for com- pleting the work ; some using clay, some sand, some moss, some leaves, some straw or twigs, some moss or lichen ; many forming a rough outside of materials hardly to be distinguished from the surrounding objects, while the inside is warm and smooth ; some building in very pe- culiar forms to impede the access to their young ; the tailor-bird sewing leaves together with distinct stitches, and the Java swallows forming their gelatinous nests, as the bees manufacture their waxen cells, from the contents and secre- tions of their own stomachs ; all furnish proofs of contrivance too obvious and too nearly ad- justed to varying circumstances, to have es- caped the attention even of careless observers. Many of the Mammalia make some kind of provision, although less artificial, for the re- ception of their progeny. " Cats search about inquisitively for a concealed situation ; bur- rowing animals retire to the bottom of their burrows, and several of the Rodentia make beds of their own hair to receive their young ; " all beasts of prey, whose progeny come into the world blind and helpless, have some kind of retreat in which they supply them at once with warmth and nourishment. Many insects, also, besides those which associate in hives, use various precautions for the covering and pro- tection of their eggs. 4. The instinct of incubation, which forms the next part of the provisions for the repro- duction of birds, the extraordinary change then effected in the habits of the female bird, par- ticularly when attended and cheered, as hap- pens in so many cases, by the equally temporary instinct of song of the male bird, is another natural phenomenon too striking and interesting to have escaped observation ; and the object of * In this choice insects seem to be guided by the sense of smell, at least in the case where the food of the larvae to be brought forth is different from that of the parent. t Darwin. INSTINCT. 15 this provision of nature has been fully elucidated by the observations of Reaumur and many others as to the efficacy of artificial heat in procuring the development of the chick. 5. The instincts of many parent animals are likewise the means adopted by nature for pro- curing nourishment for the young. This is observed as to those of the lower orders whose young are brought forth in circumstances ren- dering it impossible for them to procure their own food (as the bee and wasp), and also as to the carnivorous tribes, both of birds and quad- rupeds ; the exertion requisite for procuring their prey being beyond the power of the young- animal, the instinct of the parent supplies the defect. In most cases fresh supplies of food are daily or even hourly brought to the young animals, but in some instances stores of nou- rishment are provided for the young of the higher animals, equally as for those of the bee or ant; the pelican brings a large supply in his pouch from a single fishing; and according to the observations of an author in the Magazine of Natural History, some of the carnivorous animals have the curious instinct of storing up with this view animals not dead, but stupified by injury of the brain. " I dug out," says he, " five young pole-cats, comfortably imbedded in dry withered grass ; and in a side hole, of proper dimensions for such a larder, I poked out forty large frogs and two toads, all alive, but merely capable of sprawling a little. On examination 1 found that the whole number, toads and all, had been purposely and dex- trously bitten through the brain."* Lastly, the young of all warm-blooded animals being unable for some time after they come into the world to maintain their own temperature, would soon perish of cold, even if capable of procuring their own food, but for the protection they receive from their parents. This seems to be the most general final cause of the crrogyjj or maternal affection so strongly implanted in all these animals, and to which so much of the first period of the existence of their offspring is intrusted, but of which there is little trace in the lower tribes. As, however, the dangers to which these young animals are exposed are numerous and varied, so nature has provided against them, not by a propensity to the performance of one kind of action only, but by a vigilant and permanent feeling which controls all the habits of the parent animal, and prompts many actions, some of which are strictly instinctive, while others ought rather to be called voluntary, but are quite at variance with the ordinary habits of the animals. Every one must be aware of the increased ferocity given to the female carnivo- rous animals during the time that they are occupied with the care of their young, and of the resolution with which birds, at other seasons pacific and even timid, will resent any intrusion on their nests or young broods ; of the provi- dent care of the cat or the lioness, which carries her young in her mouth, and of almost all fe- male warm-blooded animals, which gather them * Magazine, &c. vol. vi. p. 206. close to their bodies for protection from cold ; of the anxiety of the hen which has sat on duck's eggs, when the ducklings take to the water; of the resolution and ingenuity with which the lapwing fixes on herself the attention of passengers who may come near her nest, See. But what most distinctly indicates that all this care and anxiety are unconnected with any such anticipation of the results as would be acquired by a process of reasoning, is the absolute indif- ference which succeeds, when the parent animal at length sees her offspring independent of her assistance " And once rejoicing, never knows them more." III. Various instinctive propensities may be observed in animals, the object of which is the advantage of the race or of the animal creation generally, rather than of the individual or his progeny, and some the object of which is still obscure. Some of these are, like the maternal affection last mentioned, obviously partaken by the human race, or even chiefly perceptible in those animals which have much con- nexion with man. The instinctive attachments not only of dogs but various domestic animals to their masters or attendants, of cats to houses, of sheep to particular hills or pastures, might be illustrated by many curious anecdotes, and seem to be very similar to the feelings which, after being fully developed in the human race, and strengthened and extended by the reflective powers of the human mind, obtain the names of family affection, of local attachment, of patriotism, &c. If the instinct of modesty exists in hardly any animals, the desire of clean- liness may be observed in many. The instinct of imitation, formerly noticed, and which is of so essential importance to all human enterprises in which the cooperation of numbers is re- quired, is perhaps more distinctly observable in individual monkeys than in any other ani- mals, although it is probable that a similar feeling may be part of the bond of association by which many animals are congregated toge- ther in the mode to be presently noticed. The intuitive perception of the signs of emotion or passion in the countenance and gestures which precedes and excites the tendency to imitation in man, is obviously common to us with many other animals. In fact, although we rigidly maintain the essential superiority of the intellect of man over that of all other animals, we have already stated that the greater number of the active powers of the human mind which furnish the chief motives to action are on the same footing with those which operate on the lower animals. Not only are our appetites similar to theirs, but the greater number of the desires of which we are conscious are either shared with us by them, or at least would seem to belong to the same class as their instincts. Thus the desire of approbation is quite obvious at least in some of the domestic animals, and the desire of society, as observed by Stewart, seems to act very generally, although variously, in the ani- mal creation. The desire of power may be thought to be more peculiar to man, and we 16 INSTINCT. have every reason to believe that no other ani- mal can reflect on the possession of power in the abstract, or indulge in the imagination of scenes in which it is to be exerted, or rejoice in the acquisition of wealth of any kind, as the means of exercising power and procuring pleasure, independently of the actual enjoy- ment of them ; but many of the practical exemplifications of this desire come into direct comparison with, and probably involve feelings very similar to, the instincts of animals. Thus the pleasure which men feel in exerting power over the elements around them may be seen, in the case of children, to be prior to the expe- rience of any practical advantage from the arts of architecture, of mechanics, or of navigation ; and it may be confidently asserted, that but for this pleasure attending the exercise of those arts (and which may be supposed to be very similar to that which animates the beaver, the bird, or the ant in their respective labours,) they could never have been prosecuted with success. So also the pleasure which man in all ages has felt both in hunting and destroying animals, and also in acquiring dominion over them and sub- jecting them to his power, is clearly quite different from the anticipation of the useful purposes to which, whether dead or living, they may be applied, and appears precisely similar, both in its nature and in its object or final cause, to some of the instincts of animals. Indeed, in conformity to what has been already said of the essential peculiarities of the human intellect, it is only those motives to action which imply the previous formation of general notions or abstract ideas, that we can regard as peculiar to man ; and we may accord- ingly state that the desire of knowledge (we may even say more specifically, of scientific knowledge, ' rerum cognoscere causas ) and the sense of obligation religious and moral, are the motives to action which we believe to be truly peculiar to the human race. The most important instinct of animals refer- able to this head, clearly and strongly felt like- wise by man, (although combined in his case with many other feelings,) is the instinct of congregation. More or less of the desire of society is seen in a greafl majority of animals; but we may refer to this head many actions of animals, wherein many individuals of the same species cooperate, of which the object is in many instances still obscure, but to which the animals are impelled with an energy, and fre quently a self-devotion, attesting the strength of the mental feeling, and completely super- seding their usual habits. Messrs. Spence and Kirby enumerate not less than five kinds of association of insects to form what they term imperfect societies. " The first of these associations (for the sake of company only) consists chiefly of insects in their perfect state. The little beetles called whirlwigs, which may be seen clustering in groups under warm banks in every river and every pool, wheeling round and round with great velocity, at your approach dispersing and diving under water, but as soon as you retire resuming their accustomed movements, seem to be under the influence of the social principle, and to form their assemblies for no other purpose than to enjoy together in the sun- beam the mazy dance. Impelled by the same feeling, in the very depth of winter, even when the earth is covered with snow, the tribes of Tipulidtf (usually but improperly called gnats) assemble in sheltered situations at mid-day where the sun shines, and form themselves into choirs that alternately rise and fall with rapid evolutions. " Another association is that of males during the season of pairing. Of this nature seems to be that of the cockchafer and fernchafer, which, at certain periods of the year and hours of the day, hover over the summits of the trees and hedges like swarms of bees. " The males of another root-devouring beetle (Hoplia argentea, F.) assemble by myriads before noon in the meadows, when in these infinite hosts you will not find a single female. " The next description of insect associations is of those that congregate for the purpose of travelling or emigrating together. De Geer has given an account of the larvae of certain gnats (Tipulte, L.) which assemble in considerable numbers for this purpose, so as to form a band of a finger's breadth, and of one or two yards in length. And what is remarkable, while upon their march, which is very slow, they adhere to each other by a kind of glutinous secretion. " Kuhn mentions another of the Tipulida, the larvas of which live in society and emigrate in files. " But of insect emigrants none are more celebrated than the locusts, which, when arrived at their perfect state, assemble in such numbers as in their flight to intercept the sun-beams and to darken whole countries, passing from one region to another, and laying waste kingdom after kingdom. " The same tendency to shift their quarters has been observed in our little indigenous devourers, the Aphides. " It is the general opinion in Norfolk, Mr. Marshall informs us, that the saw-fly ( Tenthredo) comes from over sea. A farmer declared he saw them arrive in clouds so as to darken the air; the fishermen asserted that they had repeatedly seen flights of them pass over their heads when they were at a distance from land, and on the beach and cliffs they were in such quantities that they might have been taken up by shovels full. Three miles in- land they were described as resembling swarms of bees. " It is remarkable that of the emigrating insects here enumerated, the majority, for in- stance the Libellulae, the Coccinellee, Carabi, Cicadoe, &c. are not usually social insects, but seem to congregate, like swallows, merely for the purpose of emigration. " The next order of imperfect associations is that of those insects which feed together. " Two populous tribes, the great devastators of the vegetable world, the one in warm and the other in cold climates, to which 1 have already alluded under the head of emigrations, INSTINCT. 17 I mean Aphides and Locusts, are the best examples of this order. " So much as the world has suffered from these animals, it is extraordinary that so few observations have been made upon their history, economy, and mode of proceeding. " The eggs of the locusts were no sooner hatched in June," says Dr. Shaw, " than each of the broods collected itself into a compact body, of a furlong or more in square, and then marching directly forwards towards the sea, they let nothing escape them ; they kept their ranks like men iifwar, climbing over as they advanced every tree or wall that was in their way ; nay, they entered into our very houses and bed- chambers like so many thieves. A day or two after one of these hordes was in motion, others were already hatched to march and glean after them. Having lived near a month in this manner they arrived at their full growth, and threw off their ni/mpha state by casting their outward skin." " The transformation was per- formed in seven or eight minutes, after which they lay for a short time in a torpid and seem- ingly languishing condition; but as soon as the sun and the air had hardened their wings by dry- ing up the moisture that remained on them after casting their sloughs, they re-assumed their former voracity with an addition of strength and agility." " According to Jackson they have a govern- ment amongst themselves similar to that of the bees and ants; and when the king of the locusts rises, the whole body follow him, not one soli- tary straggler being left behind. But that locusts have leaders like the bees or ants, dis- tinguished from the rest by the size and splen- dour of their wings, is a circumstance that has not yet been established by any satisfactory evidence; indeed, very strong reasons maybe urged against it." " The last order of imperfect associations approaches nearer to perfect societies, and is that of those insects which the social principle urges to unite in some common work for the benefit of the community. " Many larvae of Lepidoptera associate with this view, some of which are social only during part of their existence, and others during the whole of it. " A still more singular and pleasing spectacle when their regiments march out to forage, is exhibited by the Processionary Bombyx. This moth, which is a native of France and has not yet been found in this country, inhabits the oak. Each family consists of from 600 to 800 individuals. When young, they have no fixed habitation, but encamp sometimes in one place and sometimes in another under the shelter of their web ; but when they have attained two- thirds of their growth, they weave for themselves a common tent. About sun-set the regiment leaves its quarters; or, to make the metaphor harmonize with the trivial name of the animal, the monks their coenobium. At their head is a chief, by whose movements their procession is regulated. When he stops all stop, and pro- ceed when he proceeds ; three or four of his immediate followers succeed in the same line, VOL. III. the head of the second touching the tail of the first ; then comes an equal series of pairs, next of threes, and so on as far as fifteen or twenty. The whole procession moves regularly on with an even pace, each file treading on the steps of those that precede it. If the leader, arriving at a particular point, pursues a different direc- tion, all march to that point before they turn."* Examples of occasional associations, more or less resembling all these, and of which the object is in many instances still obscure, may be found in all the classes of the higher ani- mals, as is obvious, when we consider to how many tribes of animals the term gregarious is usually applied, e. g. to almost all the Rumi- nantia, some of the Pachydermata, and a few of the Rodentia. Some of the genus Muridse (rats and mice) have been long known to migrate, occasionally, in a manner resembling the locusts. " The general residence of the lem- ming," says Pallas, " is in the mountainous parts of Lapland and Norway, from which tracts at uncertain periods it descends in im- mense troops, and by its incredible numbers becomes a temporary scourge to the country, devouring the grain and herbage, and com- muting devastations equal to those of an army of locusts." " It is observable that their chief emigrations are made in the autumns of such years as are followed by severe winters." " The ground over which they have passed appears at a distance as if it had been ploughed, the grass being devoured to the roots in numerous stripes or parallel paths, of one or two spans broad, and at the distance of some yards from each other." " The army moves chiefly at night, or early in the morning. No obstacles that they meet in their way have any effect in altering their route, neither fires, nor deep ravines, nor torrents, nor marshes, nor lakes ; they proceed obstinately in a straight line, and hence many thousands perish in the waters." " If disturbed, in swimming over a lake, by oars or poles, they will not recede, but keep swim- ming directly on, and soon get into regular order again." " In their passage over land, if attacked by men, they will raise themselves up, uttering a kind of barking sound, and fly at the legs of their invaders, and will fasten so fiercely on the end of a stick, as to suffer them- selves to be swung about without quitting their hold, and are with great difficulty put to flight." " The major part of these hosts is destroyed by various enemies, as owls, hawks, weasels, ex- clusively of the number that perish in the waters, so that but a small part survive to return, as they are sometimes observed to do, to their native mountains." The campagnol, or short-tailed rat, has been known to com- mit similar ravages in France. It is obvious here, that under the influence of this instinct, and of the excitement of numbers (in which, as in our own race, the principle of imitation is probably much concerned) the usual motives to action of these animals are superseded, and their usual habits changed. We are still uncertain as to the use, or final * Introduction to Entomology, letter xvi. c 18 INSTINCT. cause, of the various congregations of birds that we daily witness, and of the varying" habits which they then exhibit crows, e. g. herons, and many water birds, roosting and bringing forth their young in large irregular societies ; the crows, besides, assembling at particular hours of the day, at all seasons ; some of the genus Parus, particularly the great and long-tailed titmouse, feeding in small flocks at all seasons ; plovers and lapwings keeping separate during the season of hatching and rearing their offspring, but assembling in flocks after their young have attained matu- rity; most of the birds of this country in the depth of winter associating in flocks much greater than can be necessary for the sake of warmth ; the hen chaffinches, and perhaps the females of other birds, congregating separately; many of these flocks consisting of multi- tudes moving quite irregularly, but all of them having apparently some means of intercom- munication or agreement ; some of them, as the starlings, performing very singular evo- lutions in concert; and many, as wild geese and other water-birds, always showing the dis- position to fly in regular lines. The greatest of all the congregations of birds are those of the migrating pigeons in America, described by Audubon, as forming clouds which pass over the whole extent of a town for several hours together, and as settling on ex- tensive districts of the woods in such multi- tudes as to cause much devastation among the branches. But the most extraordinary of all the asso- ciations of animals are those which have re- ceived the title of the perfect societies of in- sects, the bees, wasps, hornets and ants in the order of Hymenoptera, and the white ants or termites, in that of Neuroptera. The most important facts as to them seem to have been ascertained, partly by numerous former ob- servers, but chiefly by the Ilubers, Latreille, and others in the present age. The essential peculiarity of these associations of insects appears to be the complete sepa- ration of the males and females, on whom the propagation of the species depends, from the working members of the communities, by whom the habitations are constructed, and who pro- cure food both for the young and for the more perfect insects. In the case of the bees, the only prolific female is the queen-bee; the males are the drones; the working bees, constituting the mass of the community, are sterile females, and the larvae and pupae are confined to the cells and helpless ; the ants appear to differ from these only in the perfect females being much more numerous (only a few, however, being retained in each ant-hill); but the termites difier, in the larvae and even the pupae being working members, the males and females, when brought to perfection, always wandering abroad, and one of each sex in the perfect state only existing in each nest, being in fact forcibly detained there. Among these animals there is also a separate class, believed to be analogous to the working bees, i. e. to be sttrile females, larger than the labourers, and which are thought to act exclu- sively as the soldiers of the community, the smaller working ants (larvae) always disap- pearing, and these larger and fiercer animals shewing -themselves, when any of the works are attacked.* These associations differ from all others existing among animals, in the extraordinary instinct of respect and devotion shewn by the working members to the impregnated female, single in each swarm of bees, and in each nest of termites, and few in number in each nest of ants, and with this instinct most of their other peculiarities seem to be connected. But it is justly observed by Mr. Spence, that if we suppose all the labours of the bees and the ants to be guided by instincts, we must ne- cessarily attribute to these animals a much greater number and variety of instinctive pro- pensities, and more extraordinary modifications of them to suit varying circumstancts of their condition, than to any of what are usually called the higher animals. " In the common duck, one instinct leads it at its birth from the egg to rush to the water ; another to seek its proper food ; a third to pair witli its mate; a fourth to form a nest; a fifth to sit upon its eggs till hatched ; a sixth to assist the young ducklings in extricating them- selves from the shell ; and a seventh to defend them when in danger until able to provide for themselves : and it would not be easy as far as my knowledge extends, to add many more instinctive actions to the enumeration, or to adduce many specimens of the superior classes of animals endowed with a greater number. " But how vastly more manifold are the instincts of the majority of insects! " As the most striking example of the whole, I shall select the hive-bee, begging you to bear in mind that I do not mean to include those exhibited by the queen, the drones, or even those of the workers, termed by Huber cirieres (wax- makers) ; but only to enumerate those presented by that portion of the workers, termed by Huber nourrices or petites abeilles, upon whom, with the exception of making wax, laying the foundation of the cells, and col- lecting honey for being stored, the principal labours of the hive devolve. " By one instinct bees are directed to send out scouts previously to their swarming in search of a suitable abode ; and by another to rush out of the hive after the queen that leads forth the swarm, and follow wherever she bends her course. Having taken possession of their new abode, whether of their own selection or prepared for them by the hand of man, a third instinct teaches them to cleanse it from all im- purities ; a fourth to collect propolis, and with it to stop up every crevice except the entrance : a fifth to ventilate the hive for preserving the purity of the air ; and a sixth to keep a con- stant guard at the door. " In constructing the houses and streets of their new city, or the cells and combs, there are probably several distinct instincts exercised ; * See Spence and Kirby, vol. ii. p. 39. INSTINCT. 19 but not to leave room for objection, 1 shall regard them as the result of one only: yet the operations of polishing the interior of the cells, and soldering their angles and orifices with propolis, which are sometimes not under- taken for weeks after the cells are built; and the obscure but still more curious one of var- nishing them with the yellow tinge observable in old combs, seem clearly referable to at least two distinct instincts. " In their out-of-door operations several dis- tinct instincts are concerned. By one they are led to extract honey from the nectaries of flowers ; by another to collect pollen after a process involving very complicated manipu- lations, and requiring a singular apparatus of brushes and baskets ; and that must surely be considered a third which so remarkably and beneficially restricts each gathering to the same plant. It is clearly a distinct instinct which inspires bees with such dread of rain, that even if a cloud pass before the sun, they return to the hive in the greatest haste. " Several distinct instincts, again, are called into action in the important business of feeding the young brood. One teaches them to swal- low pollen, not to satisfy the calls of hunger, but that it may undergo in their stomach an elaboration fitting it for the food of the grubs ; and another to regurgitate it when duly con- cocted, and to administer it to their charge, proportioning the supply to the a?e and con- dition of the recipients. A third informs them when the young grubs have attained their full growth, and directs them to cover their cells with a waxen lid, convex in the male cells, but nearly flat in those of workers, and by a fourth, as soon as the young bees have burst into day, they are impelled to clean out the deserted tenements and make them ready for new oc- cupants. " Numerous as are the instincts already mentioned, the list must yet include those connected with that mysterious principle which binds the working bees of a hive to their queen : the singular imprisonment in which they retain the young queens that are to lead off a swarm, until their wings be sufficiently expanded to enable them to fly the moment they are at liberty, gradually paring away the waxen wall that confines them to an extreme thinness, and only suffering it to be broken down at the precise moment required ; the attention with which in these circumstances they feed the imprisoned queen by frequently putting honey on her proboscis, protruded from a small orifice in the lid of her cell ; the watchfulness with which, when at the period of swarming more queens than one are re- quired, they place a guard over the cells of those undisclosed, to preserve them from the jealous fury of their excluded rivals ; the exquisite calculation with which they inva- riably release the oldest queens the first from their confinement ; the singular love of mo- narchical dominion, by which, when two queens in other circumstances are produced, they are led to impel them to combat until one is de- stroyed ; the ardent devotion which binds them to the fate and fortune of the survivor; the distraction which they manifest at her loss, and their resolute determination not to accept of any stranger until an interval has elapsed sufficiently long to allow of no chance of the return of their rightful sovereign ; and (to omit a further enumeration) the obedience which in the utmost noise and confusion they shew to her well-known hum. " I have now instanced at least thirty dis- tinct instincts with which every individual of the nurses amongst the working-bees is en- dowed ; and if to the account be added their care to carry from the hive the dead bodies of any of the community ; their pertinacity in their battles, in directing their sting at those parts only of the bodies of their adversaries which are penetrable by it; their annual autum- nal murder of the drones, &c. Sec.- it is cer- tain that this number might be very consider- ably increased, perhaps doubled."* To these instincts, in the case of some species of ants we shall certainly have to add those by which they are guided in carrying on a regular system of warfare, either with other hives of the same species or with other species, in subjuga- ting and bringing up as workers or slaves those that they have subdued, and likewise in sub- jecting to their dominion tribes of Aphides.f But all this becomes still more surprising, because more at variance with the usual in- stincts of animals, when we consider the power of adapting their operations to changes in their circumstances, which such associations of in- sects possess. " It is," says Mr. Spence, " in the deviations of the instincts of insects and their accommoda- tion to circumstances, that the exquisiteness of these faculties is most decidedly manifested. The instincts of the larger animals seem capable of but slight modification. They are either ex- ercised in their full extent or not at all. A bird, when its nest is pulled out of a bush, though it should be laid uninjured close by, never attempts to replace it in its situation ; it contents itself with building another. But in- sects in similar contingencies often exhibit the most ingenious resources, their instincts surpri- singly accommodating themselves to the new circumstances in which they are placed, in a manner more wonderful and incomprehensible than the existence of the faculties themselves." This observation we support by various in- stances taken from the history of different in- sects ; but the most extraordinary are from the societies of insects of which we now speak ; and of these the following are only a specimen. " The combs of bees are always at an uniform distance from each other, namely, about one- third of an inch, which is just wide enough to allow them to pass easily, and have access to the young brood. On the approach of winter, when their honey-cells are not sufficient in number to contain all the stock, they elongate them considerably, and thus increase their capa- * Introduction to Entomology, vol. ii. p. 498 et seq. f Introd. to Entomology, letter xvii. c 2 20 INSTINCT. city. By this extension the intervals between the combs are unavoidably contracted ; but in winter well-stored magazines are essential, while from their state ot comparative inactivity spa- cious communications are less necessary. On the return of spring, however, when the cells are wanted for the reception of eggs, the bees contract the elongated cells to their former dimensions, and thus re-establish the just dis- tances between the combs which the care of their brood requires. But this is not all. Not only do they elongate the cells of the old combs when there is an extraordinary harvest of honey, but they actually give to the new cells which they construct on this emergency, a much greater diameter as well as a greater depth. " The queen-bee, in ordinary circumstances, places each egg in the centre of the pyramidal bottom of the cell, where it remains fixed by its natural gluten : but in an experiment of Huber, one whose fecundation had been re- tarded, had the first segments of her abdomen so swelled that she was unable to reach the bottom of the cells. She therefore attached her eggs (which were those of males) to their lower side, two lines from the mouth. As the larvae always pass that state in the place where they are deposited, those hatched from the eggs in question remained in the situation assigned them. But the working bees, as if aware that in these circumstances the cells would be too short to contain the larvae when fully grown, extended t/ieir length, even before the eggs were hatched. " The working bees, in closing up the cells containing larva?, invariably give a convex lid to the large cells of drones, and one nearly flat to the smaller cells of workers; but in an ex- periment instituted by Huber to ascertain the influence of the size of the cells on that of the included larva, he transferred the larvae of workers to the cells of drones. What was the result ? Did the bees still continue blindly to exercise their ordinary instinct ? On the con- trary, they now placed a nearly flat lid upon these large cells, as if well aware of their being occupied by a different race of inhabitants." But the most extraordinary of all these varia- tions of the operations of bees are seen in two cases which have been often produced for the sake of experiment, and of which the result appears to have been repeatedly and carefully observed. ' If a hive be in possession of a queen duly fertilized, and consequently sure, the next sea- son, of a succession of males, all the drones, towards the approach of winter, are massacred by the workers with the most unrelenting fero- city. This would seem to be an impulse as naturally connected with the organization and very existence of the workers, as that which leads them to build cells or store up honey. But however certain the doom of the drones if the hive be furnished with a duly fertilized queen, their undisturbed existence through the winter is equally certain if the hive has lost its sovereign, or if her impregnation has been so retarded as to make a succession of males in the spring doubtful ; in such a hive the workers do not destroy a single drone, though the hot- test persecution rages in all the hives around them." Again, " in a hive which no untoward event has deprived of its queen, the workers take no other active steps in the education of her suc- cessors, those of which one is to occupy her place when she has flown oft' at the head of a new swarm in spring, than to prepare a certain number of cells of extraordinary capacity for their reception while in the egg, and to feed them when become grubs with a peculiar food until they have attained maturity. This, there- fore, is their ordinary instinct ; and it may hap- pen that the workers of a hive may have no neces- sity, for a long series of successive generations, to exercise any other. But suppose them to lose their queen. Far from sinking into that inac- tive despair which was formerly attributed to them, after the commotion which the rapidly- circulated news of their calamity gave birth to has subsided, they betake themselves with an alacrity from which man, when under misfor- tune, might deign to take a lesson, to the repa- ration of their loss. Several ordinary cells are without delay pulled down and converted into a variable number of royal cells, capacious enough for the education of one or more queen- grubs selected out of the unhoused working grubs which in this pressing emergency are mercilessly sacrificed and fed with the appro- priate royal food to maturity. Thus sure of once more acquiring a head, the hive return to their ordinary labours, and in about sixteen days one or more queens are produced, one of which steps into day and assumes the reins of state." There can be no doubt that the perfect order and regularity seen in all the operations of these societies of insects could not be main- tained without some mode of communication among the different individuals concerned in these operations ; and it appears distinctly that such means of communication exist, and that it is in consequence of their being exercised, for example, that a swarm of bees, when it leaves a hive, takes the direction to a spot pre- viously fixed on, and carefully examined, by a small number of scouts, as observed by Mr. Knight.* When such facts are duly considered, we cannot be surprised to find so intelligent a na- turalist as Mr. Spence acknowledging that he had at one time arranged them as indications of reason in these animals. But on further consideration, we shall probably see cause to acquiesce in his later and more matured judg- ment, which ascribes them to strictly instinc- tive, although singularly varying propensities ; chiefly on two grounds, which exactly corre- spond to what was stated in the beginning of this paper as the most distinctive characters of instinct : 1 . that although various contrivances are fallen on by all bees to enable them to con- tinue their usual operations under varying ex- ternal circumstances, yet there is no such variety observed either in the conduct of individuals * Phil. Trans. 1807. INSTINCT. 21 of the species or in the conduct of different communities, as we cannot doubt must occur if the inhabitants of every hive were guided, on such unusual occasions, by processes of reason- ing, by observation of the laws of nature, by experience, and anticipation of the effects of their actions. If such mental processes were their guide, we should certainly observe a diffe- rence in the conduct of experienced workers, and of those just emerged from their pupae ; and we should observe some variety in the ex- pedients adopted in different hives for meeting such accidents or difficulties. 2. While the varying operations of these animals for one particular end, the preservation of their own lives and the perpetuation of their species, are planned and combined in such a manner as to indicate consummate intelligence as to what is essential for that purpose, all these indications of instinct are limited to that object, and we see no evidence of the exercise of their senses suggesting to them any other trains of thought, or exciting them to the prosecution of other objects, such as a number of human intellects capable of planning and executing such works would certainly, sooner or later, attempt to accomplish. The degree of uniformity seen in their operations, and the limitation of the ob- jects on which their faculties are exerted, are therefore our reason for thinking (although we do not wish to express ourselves with absolute confidence on the subject) that the mental pro- cesses concerned, even in those the most elabo- rate and artificial of the works of animals, be- long to the same class as those notions of man which are prompted by his instinctive propen- sities as distinguished from his reason. At the same time it ought to be stated, that there are many acts of individual animals, or of particular communities, in which we must admit that, although instinct is concerned, it must be guided by mental operations, in which short processes of reasoning, involving certain general ideas, must have been concerned. Several instances, quoted by Mr. Spence, seem hardly to admit of any other interpretation, e. g. the following from Huber. The bees of some of his neighbours protected themselves against the attacks of the death's-head moth, (Sphinx atropos,) by so closing the entrance of the hive with walls, arcades, &c. built of a mixture of wax and propolis, that these ma- rauders could no longer intrude themselves. Pure instinct would have taught " the bees to fortify themselves on the Jirst attack ; if the occupants of a hive had been taken unawares by these gigantic aggressors one night, on the second at least the entrance should have been barricadoed. But it appears clear, from the statement of Huber, that it was not until the hives had been repeatedly attacked, and robbed of nearly their whole slock of honey, that the bees betook themselves to the plan so success- fully adopted for the security of their remaining treasures ; so that reason, taught by experience, seems to have called into action their dormant instinct.'' Again, " a German artist, a man of strict vera- city, states that in his journey through Italy he was an eye-witness to the following occurrence. He observed a species of Scarabaeus busily en- gaged in making, for the reception of its egg, a pellet of dung, which when finished it rolled to the summit of a small hillock, and repeatedly suffered to tumble down its side, apparently for the sake of consolidating it by the earth which each time adhered to it. During this process the pellet unluckily fell into an adjoin- ing hole, out of which all the efforts of the beetle to extricate it were in vain. After several ineffectual trials, the insect repaired to an ad- joining heap of dung, and soon returned with three of his companions. All four now applied their united strength to the pellet, and at length succeeded in pushing it out ; which being done, the three assistant beetles left the spot and returned to their own quarters."* A number of other instances have been col- lected by Mr. Duncan. " Professor Fischer has published an account of a hen, which hen made use of the artificial heat of a hotbed to hatch her eggs." " A fact is stated by Reaumur of some ants, which, finding they could derive heat from a bee-hive, contrived to avail themselves of it by placing their larvae between the hive and an exterior covering." " Dr. Darwin observed a wasp with a large fly nearly as big as itself; finding it too heavy, it cut off the head and the abdomen, and then carried off the remainder, with the wings at- tached to it, into the air : but again finding the breeze act on the wings, and impede its pro- gress, it descended, and deliberately cut off the wings. Instinct might have taught it to cut off the wings of all insects previous to flying away with them ; but here it attempted to fly with the wings on, was impeded by a certain cause, discovered what that cause was, and alighted to remove it. Is not this a comparison of ideas, and deducing consequences from pre- mises ?" " M. de la Loubiere, in his relation of Siam, says, that in a part of that kingdom which lies open to great inundations, all the ants make their settlements on trees ; no ants' nests are to be seen any where else. Whereas in our country the ground is their only habitation." " We sometimes kill a cockroach," says Ligon in his history of Barbadoes, quoted by Spence, " and throw him on the ground, and mark what the ants will do with him ; his body is bigger than a hundred of them, and yet they will find the means to lay hold of him and lift him up; and having him above ground, away they carry him ; and some go by as ready assistants if any be weary, and some are officers that lead and shew the way ; and if the van-couriers perceive that the body of the cockroach lies across, and will not pass through the hole or arch through which they mean to carry him, order is given, and the body turned endways, and this is done a foot before they come to the hole, and without stop or stay/'f * Introd. to Entomology, vol. ii. j). 525. t History of Barbadoes, p. 63. 22 INSTINCT. Colonel Sykes communicated to Mr. Kirby a singular anecdote of some of the black ants in India, which had been prevented, for some time, from getting to some sweatmeats, by having the legs of the table on which they stood immersed in basins filled with water, and besides painted with turpentine. After a time, however, the ants again reached the sweatmeats ; and it was found that they did so by letting themselves drop from the wall, above the table, on the cloth which covered it* " In Senegal, where the heat is great, the ostrich neglects her eggs during the day, but sits on them at night. At the Cape of Good Hope, however, where the degree of heat is less, the ostrich, like other birds, sits upon her eggs both day and night." " Rabbits dig holes in the ground for warmth and protection ; but after continuing long in a domestic state, that resource being unnecessary, they seldom burrow." "A dog in a monastery, perceiving that the monks received their meals by rapping at a buttery-door, contrived to do so likewise, and when the allowance was pushed through, and the door shut, ran off with it. This was re- peated till the theft was detected." " A dog belonging to Mr. Taylor, a clergy- man, who lived at Colton, near Wolseley Bridge, was accused of killing many sheep. Complaints were made to his master, who as- serted that the thing was impossible, because he was muzzled every night. The neighbours persisting in the charge, the dog one night was watched, and he was seen to draw his neck out of the muzzle, then to go into a field, and eat as much of a sheep as satisfied his appetite. He next went into the river to wash his mouth, and returned afterwards to his kennel, put his head into the muzzle again, and lay very qui- etly down to sleep." " I observed," says the Rev. J. Hall in his Travels in Scotland, " two magpies hopping round a gooseberry bush, in a small garden near a poor-looking house, in a peculiar manner, and flying in and out of the bush. I stepped aside to see what they were doing, and found from the poor man and his wife, that as there are no trees all around, these magpies several succeeding years had built their nest, and brought up their young, in this bush ; and that foxes, cats, hawks, &c. might not interrupt them, they had barricadoed not only their nest, but had encircled the bush with briers and thorns in a formidable manner ; nay, so com- pletely, that it would have cost even a fox, cunning as he is, some days' labour to get into that nest. " The materials in the inside of the nest were soft, warm, and comfortable ; but all on the outside, so rough, so strong, and firmly en- twined with the bush, that without a hedge- knife, hatch-bill, or something of the kind, even a man could not, without much pain and trouble, get at their young; as from the outside to the inside of the nest extended as long as my arm. * Bridgewater Treatise, vol. ii. p. 342. " These magpies had been faithful to one another for several summers, and drove off their young, as well as every one else who at- tempted to take possession of their nest. This they carefully repaired and fortified in the spring with strong rough prickly sticks, that they sometimes brought to it by uniting their force, one at each end, pulling it along, when they were not able to lift it from the ground."* Such examples leave no reasonable ground for doubt, that on certain subjects at least some animals are capable of short and simple processes of reasoning or of imagination, which appear to imply the perception of general truths, and the formation of certain general ideas, and that the difference, formerly stated between the operations of their minds and ours, in that respect, is one of degree only, not absolutely of kind. But this admission, it must be remembered, does by no means di- minish the force of the considerations formerly adduced to establish the essential distinction between the instinctive determinations prompt- ing the usual actions of animals, and some of those of men, and those volitions, whether in animals or men, which are consequent on the exercise of reason, and on such anticipation of their consequences as a process of reasoning only can afford. It is worth while to mention that in some instances animals have been thought to be pos- sessed of a faculty resembling reason, on ac- count of actions, very wonderful indeed, but which the possession of reason would not have enabled them to perform. Thus there are many instances of animals finding their way to their usual place of residence, after being re- moved from it in such a way as to prevent the mere act of recollection guiding them back. Mr. Duncan^ mentions having seen a pigeon, which had been brought from London, let loose on Magdalen Bridge, in Oxford. " It flew first towards the north, but after several gyrations in the air, it flew directly east, and reached London within the appointed time, which was, I believe, three hours." And Mr. Spence gives an anecdote, well authenticated, of an ass from Gibraltar, thrown overboard from a vessel at a distance of 200 miles, which swam ashore, and in a few days afterwards pre- sented himself for admission when the gate of the fortress was opened in the morning. Two instances, equally extraordinary, have been stated on unexceptionable authority to the pre- sent writer ; one of a pointer which had been sent from Durham to the neighbourhood of Edinburgh by sea, and made his way back in a few days by land, to his master's house in the former county ; the other of a kitten, which had been brought in a carriage a distance of above forty miles, to Edinburgh, and made its way back in a few days to its place of nativity in Stirlingshire, in doing which it must have crossed several bridges. Similar facts have been ascertained in several instances as to sheep ; and the cases of the swallow and of the Duncan's Lectures on Instinct, Ibid. INSTINCT. 23 salmon, returning to the spots where they were bred after their long migrations, are clearly analogous. But in such cases it is obvious that the pos- session of reason could not have enabled these animals, alone and unassisted, to find their way ; neither was the result properly referable to instinct, this term being properly applicable only to the feeling of attachment which prompted the return home, not to the know- ledge which the animals somehow acquired where their home was to be found. The only term properly applicable to the acquisition of this knowledge is intuition, and they should be added to other facts, which shew that in va- rious instances animals acquire, by the exercise of their senses, information as to external things, more obviously distinct from the sensa- tions themselves, than those perceptions which Dr. Reid has so clearly shewn to be strictly intuitive inferences, drawn by the human in- tellect from the intimations of the senses. There is yet another fact well ascertained of late years regarding the instincts of animals, which we must not omit to state, because it is the only one which gives plausibility to the notion of Darwin, that sensations and experi- ence would explain the whole phenomena of instinct. This is the fact, which seems well ascertained as to certain animals at least, which is very probably true of man, and sus- ceptible of important practical application in his case, that the acquired habits of one gene- ration may become instinctive propensities in the next. Thus it has been often observed that the progeny of well-trained pointers learn to point with very little instruction. It is stated by Darwin that dogs in the wild state, both in Africa and America, have been observed not to bark, that they gradually acquire that note from European dogs ; and that the latter, when turned loose, retain it for three or four generations, and gradually lose it ; and it has been ascertained that in South America, when horses which had been taught to amble had been allowed to run wild, their progeny for two or three generations continued to practice that pace, and then lost it.* Of the existence of such acquired instincts, therefore, there can be no doubt; but it need hardly be said that it is quite incompetent to explain the perfect uni- formity and the skilful contrivance observed in the instincts of animals ; both because its ope- ration seems too limited, and because that sup- position would only remove the difficulty as to the continuance of the instinctive operations from the present to the early generations of animals. In reviewing the varied phenomena of which we have given this hasty sketch, it is impos- sible not to be struck with the very important share which they occupy in the provisions by which the earth's surface is made a scene of continual activity and change. It is interest- ing to reflect on the different powers, to the This principle has been lately investigated and illustrated by Mr. Knight, in a paper read before the Royal Society of London. operation of which we can trace the unceasing changes continually taking place around us, and particularly on the gradation, and very gradual transition that may be observed, from those by which inanimate matter is continually moved and changed, up to those which ema- nate from the intellect of man. By the ori- ginal impulse given to the world, and by the laws of gravitation and of motion impressed on all matter, the greater and more striking movements of the inanimate world around us are continually determined ; and by the laws of chemistry, these movements are made sub- servient to constant changes in the composition of the inanimate world. Again, by the laws which were impressed on the lower class of living beings at the time of their introduction into the world, and by the consequently in- cessant reproduction of vital affinities, which it is in vain to attempt to resolve into the che- mistry of dead matter, a constant succession of living vegetable structures is determined, merely by the agency of air and water, heat and light, on those already existing. By the peculiar chemical operation of these living structures, the air, the water, and all the ma- terials of the earth's surface are subjected to peculiar and continual changes, implying slow but incessant movements, which seem clearly to indicate attractions and repulsions, peculiar to the state of vitality. It is still perhaps doubtful whether in the case of vegetables a property of vital contraction is to be added to the active powers of nature. In immediate but still obscure connection with the lowest of the vegetable creation are the lowest of the animals, where we see the first and slightest indications of sersations, and the feeblest mo- tions consequent on sensations, which we judge to be similar to those that we ourselves ex- perience and excite ; and here also the vital power of contraction, on which the whole life and activity of animals essentially depends, first clearly manifests itself. Then tracing the animal creation upwards, we find that the world contains an infinite number and variety of sentient beings, the provisions for whose enjoyment we may well believe to have been the main object of Providence in all the ar- rangements on the surface of the earth ; and to which are granted, in a pretty uniform grada- tion, more and more of the sensations and mental faculties by which nature is made known, and of the powers by which she may be controlled, until we arrive at the intellect and the capacity of Man. It appears farther that the maintenance, and reproduction, and the very existence of these animal structures are entrusted in part to the sensations of which they are made susceptible, and to the voluntary powers with which they are invested ; but that the introduction of these spontaneous powers into the regulation of their ceconomy is so very gradual, that it is hardly possible to say where the movements which result only from physical (although vital) causes terminate, and those which are excited by mental acts begin; hardly possible, for example, to say, at least as to many animals, 24 INSTINCT. whether the reflex function of Dr. Mar- shall Hall, on which respiration, degluti- tion, the evacuation of the bowels and blad- der, &c. depend, is to be regarded as the re- sult of a merely physical impression on the nerves and spinal cord, like the impression of blood on the heart; or whether the sensations which naturally accompany these actions are, in the natural state, part of the cause which excites them. But that even when the volun- tary powers of animals are certainly the means employed for the ends of their creation, they are still very generally guided by the superior intelligence which has framed both their phy- sical and mental constitution, and which rules the mental but instinctive efforts consequent on the sensations that are felt, as surely as the laws of muscular contraction rule the move- ments of the heart ; and it is into the hands of man alone that the reins of voluntary power are absolutely resigned. And when we thus pass in review the sen- sorial and voluntary powers of animals, we are naturally led to the question, whether there is really in our own case so great an exception to those laws of nature which regulate all the other members of the animal creation; whe- ther, admitting the essential superiority of the intellect or reason of man, the different desires and motives to action, which are implanted in him, are not equally subject to the control of the power that gives them, and whether their consequences are not as exactly ruled by laws and as fully anticipated, as those of the in- stincts of animals. Without entering fully on this abstruse ques- tion, we would take the liberty of remarking, in the view of placing it in its simplest form before our readers, that as the intimations of our own consciousness are the ultimate foun- dation of all the knowledge that we have or can have of our own minds, and as certain of the intuitive principles of belief which our minds naturally suggest to us must be trusted, if we are to inquire into the subject at all ; so the only question that can " be reasonably proposed on this point is, whether there is any good reason for suspecting that the belief of our own free-will, which naturally attends cer- tain of the operations of our minds, is a de- ception; and that the analogy of other ani- mals is only applicable to the subject in so far as it can throw light on that question. Now, we find that the works of man, which we ascribe to his reason, and in the execution of which the consciousness of his free-will intervenes, are essentially different from those which we ascribe to the blind instincts of ani- mals, in the total absence (already noticed) of that uniformity which is so leading a charac- teristic of the effects of the latter; and we may reasonably assert that this is just the difference to be expected between the works of man and of other animals, on the supposition that the power concerned in the former is not subject to the direct influence and control of that higher intellect, by which the laws and limits of that concerned in the latter are irrevocably set ; and therefore, that there exists no such analogy between the works of man and of other animals as need induce us to suspect, that the evidence of his consciousness on the point in question is not to be trusted. At the same time it ought to be observed, and perhaps has not been duly remarked, not only that the desires which are the principal motives to human action, are analogous to, sometimes identical with, the instincts of ani- mals, (many of them having been evidently given him with the same intention, and with a clear perception of their general result on his condition,) but also that the constitution of the human mind appears from the intimations of our own consciousness to be such, as to allow of interposition of a superior power, controlling in a certain degree the will of man, without making itself obvious to his mind. For it is admitted by the soundest metaphy- sicians, that the only truly voluntary power which we are conscious of possessing over the train of thought in our minds, and therefore ultimately over many of our actions, operates only indirectly.* We have no power of de- termining the thoughts that succeed one ano- ther or regulating the order of their succes- sion ; and although various laws of association have been laid down, by which many of the component parts of the train appear to be con- nected, yet it will hardly appear to any one who reflects on the operations of his mind, that all the thoughts which succeed one ano- ther can be ascertained to have such bonds of connection with one another. At all events, the only strictly voluntary power which we are conscious that we possess, is that of singling out and detaining any particular portion of the train, whereby it may be made to predominate in the mind, and to produce practical results which might not otherwise have followed ; and even this kind of influence over the train of thought is not exercised exclusively by volition, but is produced in a great measure also by other causes, physical and moral. Now if this be so, how can we deny the possibility of a superior intelligence retaining a power of con- trolling the acts of any individual human mind, or of any number of minds, either by suggest- ing particular thoughts, or by causing the mind to dwell upon particular thoughts in preference to others, without its sense of its own volun- tary power being interrupted or withdrawn, nay, without the spontaneous voluntary power being really suspended, the only difference beins in the degree of influence which it exerts over the train of thought and consequent vo- litions? It has been said that the expression in Pope's Universal Prayer * " So completely is the current of thoughts in the mind," says Stewart, " subjected to physical laws, that it has been justly observed by Lord Kames that we cannot, by an effort of our will, call up any one thought, and that the train of our ideas depends on causes which operate in a man- ner inexplicable by us. This observation, although it has been censured as paradoxical, is almost self- evident ; for to call up any particular thought sup- poses it to be already in the mind." Elements, (clamo); Fr. Larynx ; Germ. KehlkopJ ; Ital. Laringe. The larynx is a complex piece of mechanism resembling a kind of box, (piris cava,) composed of an assemblage of carti- lages, the density and elasticity of which serve to protect its more delicate tissues, and to allow the free transmission of air for respira- tion. It is also exquisitely adapted for the production of voice. The larynx is situated in the mesial line, and opens superiorly into the pharynx, and inferiorly into the trachea. It occupies the anterior superior part of the neck, immediately below the os hyoides, and before the pharynx, which lies between it and the vertebral column. In front it is very superficial, being covered only by the sub-hyoidean muscles, and the common integuments. It admits of various kinds of motion : 1, those of elevation and depression parallel to the long axis of the body; 2, those complex movements within it which take place during respiration and the production of vocal sounds. The larynx considered with reference to the trachea, presents an enlargement denominated Fig. 18. the cnput asperse asteria, or the head of the trachea. The absolute volume of the larynx varies with the age and sex of the individual : its magnitude is much more considerable in men than in women ; in the former it acquires an extraordinary developement at the age of puberty. In eunuchs, however, this enlarge- ment does not take place. The larynx does not represent any regular geometrical figure; it may be denned as an irregular, inverted, truncated cone, whose sec- tions at the apex and base are elliptical, but approaching nearly to a circle at its junction with the trachea. This organ is perfectly symmetrical, which, however, applies to one of its sections only, viz. that of its mesial plane, or axis major ; consequently, all the others must be unsym- metrical : the section made at right angles to it, or in its axis minor, gives the relative situa- tion of its internal mechanism, as mjigs. 18 and 19, which should be carefully studied, with reference to the physiology of this organ. fi'g.19. The anterior transverse section of the larynx and trachea, a, the epiglottis ; b, b, the horns of the os hyoides ; c, c, the inferior thyro-arytenoid liga- ments (chorda: vocales) ; d, d, the thyro-arytenoid muscles ; e, e, section of the thyroid cartilage ; f, f, the superior boundaries of the ventricles ; g, g, 'section of the cricoid ; h, the trachea ; I, I, the ventricles. The posterior view. The letters c, d, e, g, h, re- present corresponding sections of the same parts ; b, b, the arytenoid cartilages invested by mucous membrane ; n, the pharynx laid open. The larynx is composed of several structures, which may be classed as follows : 1, the car- tilages ; 2, the ligaments ; 3, the muscles ; 4, the mucous membrane ; 5, the mucous glands ; 6, the arteries and veins ; and, lastly, the nerves. The cartilages of the larynx are nine in NORMAL ANATOMY OF THE LARYNX. 101 number,* of which three are single and un- symmetrical, the epiglottis, thyroid, and cri- coid ; two are placed laterally, and form a pair, called the arytenoids. Upon the summits of these are found two minute cartilaginous bodies, termed cornicula ; the remaining two (which, however, are not always present) are situated anterior to the arytenoids, and in- volved in the aryteno-epiglottic folds, named the cuneiform cartilages. The cricoid cartilage. Gr. x^ixo?, a ring, &>?; Lat. Cartilugo anmdiformis ; Fr. Cri- coide on unnulaire ; Germ. Ringknorpel ; Ital. Cricoide. This cartilage, situated at the base of the larynx, which it supports, is the thickest and strongest of the whole assemblage of car- tilages. It is connected to the first ring of the trachea by elastic ligaments and mucous mem- brane. Its form, that of a ring, is not quite circular, but approaching to an elliptical figure. It is shallow in front, at c, e, (fig.%0,) but it is thicker and deeper than the first ring of the trachea; and, posteriorly, it is considerably deeper than at its anterior part, in the propor- tion of eight to two and a-half. Fig. 20. A B A, an anterior, B, the side view of the cricoid cartilage ; a, the posterior superior margin -, b, b, the crico-arylenoid articulating surface; b,g,f,e, the superior descending margin ; d, e, the trachea! aperture of the cricoid ; a, d, the greatest, a, e, the least depth of surface ; a, e, the obliquity of the superior section to the axis ; h, the left surface articulating with the inferior cornua of the thyroid cartilage. The anterior external surface gives attach- ment to the crico-thyroid muscles (see Jig. 26); more posteriorly we find an apophysis for the articulation of the thyroid (h,Jig. 20, B). Its posterior surface is divided into two equal por- tions by a vertical ridge along its middle line, a, d, Jig. 20, B. This ridge, which was first noticed by Galen, gives attachment to some longitudinal fibres of the oesophagus. On each side of it a concave surface is observed, which gives origin to the crico-arytenoidei postici, e, e,fig. 27. The internal surface is smooth, and lined by the mucous membrane of the larynx. The inferior margin is horizontal, and nearly circu- * Galen describes only three, j^ovJpo? 6wsosi$>)?, lar; but the superior, which is bevelled obliquely inwards and upwards, about c, e, (fig- 20,) ascends backwards in the direction ofe,f,g, b, (Jig. 20,) being slightly curved downwards between Jf and g. The anterior superior outline of this cartilage presents that of the section of a cylinder, whose obliquity to its axis is in the direction , e, and therefore is elliptical. It recedes anteriorly from the lower margin of the thyroid cartilage in the direction of g,f, e, (fig. 20,) leaving an interval called the crico-thyroid space, a, (fg.W, B,) which is occupied by the crico-thyroid ligament ; on each side, in the lines e, f, g, by the lateral liga- ments, and more posteriorly by the crico- arytenoidei laterales, in the space,/", g, to the external side of b (fig. 20). The posterior superior margin is horizontal on each side of a, (fig. 20,) and parallel to the inferior at d, having at b and b an oblong, oblique, and slightly cylindrical surface, in- clined upwards and outwards for the articu- lation of the arytenoid cartilages. These sur- faces are considered by Willis as " portions of cylinders, whose axes are inclined both with respect to the horizontal and vertical sections." In the vertical section, the projection of this articulating axis is in the position G, C, (fig. 28,) and in the horizontal, in the line O, P, (fig. 30.) Between these surfaces is a slight depression for the insertion of the arytenoid muscles. The thyroid cartilage. Syn. Lat. Cartilago scutiformis ; Fr. Thyroids; Germ.Schildknor- pel. This cartilage derives its name from flt/gsof, a shield, and &;, form. It embraces the cricoid in a manner analogous to the carapax of the tortoise. It is formed to protect the internal mechanism of the larynx, both in front and at both sides, but is open behind. It serves Fig. 21. An angular view of the thyroid cartilage, a, the notch ; b, b, the superior cornua ; c,c, the inferior cornua ; g, g, the superior tubercles ; h, h, the in- ferior tubercles; e, e, the wings of the thyroid ; i, a, i, the superior margin ; h, d, h, the inferior margin ; a, d, the mesial line ; f t the pomum. as a fulcrum and lever for the action of several muscles. It is composed of two quadrilateral lamina; uniting in front at the mesial line (a, d, NORMAL ANATOMY OF THE LARYNX. 102 Jig. 21): the angle of union becomes more acute as it approaches towards d. The prominence of this angle on the mesial line constitutes what is called the pomum Adami, which is more developed in the male than in the female sex, and becomes more conspicuous after the age of puberty; it maybe readily felt in the living subject. On the four posterior angles of the thyroid are situated four cornua, or horns ; two superior, 6, b, and two inferior, c c, (fig- 21); they appear mere prolong- ations of the posterior margins ; the superior being longer than the inferior are called the great horns; they are articulated to the os hyoides by ligaments, which allow a motion for the approximation and recession of the la- rynx to and from the os hyoides. The inferior horns are shorter, curved forwards, and arti- culated at their extremities to the cricoid by oblique planes, directed forwards and inwards. On each wing of the thyroid there are two tubercles, one on the superior, and the other on the inferior margin (g, g, and h, h,fig- 21). The superior tubercles are the largest. A small ridge passes obliquely across the external sur- face of the wings from g to h, extending from the base of one tubercle to the other, dividing each wing into two unequal segments, of which three-fourths are anterior and superior, and one-fourth posterior and inferior to the ridge. The anterior margin of the ridge gives attach- ment to the hyo-thyroid, and lies under the sterno-hyoid muscles, and the posterior to the inferior constrictor of the pharynx and sterno- thyroid muscles. The posterior or hollow surface of the angle formed by the junction of the alse of the thy- roid gives attachment on each side of the me- sial line to the thyro-arytenoid ligaments (chordtz vocales) and muscles. The wings are concave internally for the lodgement of the thyro-arytenoidei and crico-arytenoidei laterales muscles, and give attachment at their poste- rior margins to the membrane of the pharynx. The superior margin of each wing is curved in the line i, a, i, (Jig- 21,) and gives at- tachment in its whole length to the thyro- hyoid membrane : it is deeply notched at a, immediately above the pomum Adami. It is less deep, and more broad and round in women than in men. Near the superior tubercles there is a notch, sometimes a foramen for the transmission of the superior laryngeal nerve. The inferior margin of the thyroid is nearly horizontal, and is shorter than the superior : there is a slight prominence at a, (Jig. 21,) to which is attached the crico-thyroid ligament. Between the in- ferior tubercles at h, h, (Jig- 21,) and the in- ferior cornua, the lower margin is arched rather deeply. The posterior surface and margin of the wings of the thyroid are ridged, and give attachment to several muscles ; it rests against the vertebral column, which forms a base to the arc of the thyroid, and protects the internal structure of the larynx. The an/tenaid cartilages. Syn. : Gr. at>vrc(.ti/rjti$n<;, Galen ; Lat. Cartilagines ary- tenoidees ; Fr. Cartilages aryteno'ides ; Germ. Giessbeckenknorpel. The arytenoid cartilages are two very irregularly formed bodies, situated on the articulating surface of the posterior, inner, and upper margin of the cricoid, (b, 6, Jig. 20,) in such a manner as to resemble the mouth of an ewer ; hence their name. They may be considered of a triangular or pyramidal figure, having their bases spread out, (a and a, Jig. 22,) and presenting surfaces for the attach- ment of ligaments and the action of muscles. We observe, 1, on their posterior aspect, triangular concave surfaces, between f and e, (fig. 22,) occupied by the oblique and trans- verse arytenoid muscles. 2. Anteriorly, con- vex, triangular surfaces, d, 6, (Jig- 22,) with Fig. 22. A fide view of the arytenoid cartilages, a, the base and position of the crico-arytenoid articulating grooves ; b, e, the posterior concave surface ; c, the lateral prominence ; /, the corniculum laryngis ; g, the vertical portion of the cuneiform cartilage. ridges, (b, fig. 27,) for the attachment of the superior thyro-arytenoid ligaments. 3. La- terally, cavities for the insertion of the thyro- arytenoid muscles, and lodgment of the cunei- form cartilages, (g,Jig- 22). 4. Internally, surfaces reciprocally parallel, lined with mu- cous membrane, which permit their close ap- proximation. 5. Bases, on which are oblique, curved, oval grooves, a and a, (Jig. 22,) cor- responding to the articulating surfaces of the cricoid ; there are also on each of these bases two prominences, one lateral, (c, Jig. 22,) which gives attachment (I, Jig. 27,) to the crico-arytenoideus lateralis and posticus mus- cles ; the other anterior, giving attachment (V, fig. 29) to the inferior thyro-arytenoid ligament. The latter prominence projects over the vocal tube one-fifth of an inch in the male, and one-seventh in the female. On the sum- mit of the vertical prominences (J\J\fig- 22) is situated a small appendage called corniculum laryngis. The arytenoid cartilages have ex- tensive freedom of motion, consisting of a rota- tory, round the articulating axis of the cricoid, O, P (fig. 30); and a sliding motion, trans- verse to their axis of articulation about the point B (fig. 30). The cornicula laryngis. Syn. Capitula San- torini ; tubercles of Santorini ; cartilagines comic ulis ; Santorinischer Knorpel, Germ. These are two very small cartilaginous bodies first described by Santorini, from whom they de- rive their name. Their figure is nearly triangular with a flat smooth surface at their bases, arti- culated with some freedom of motion to the apices of the arytenoid cartilages. They NORMAL ANATOMY OF THE LARYNX. 103 lengthen the arm of the vertical lever of the arytenoid, and yield to any oblique force directed upon them. The cuneiform cartilages, ('Syn. cartilagines cuneiformes, sen WrisbergiuiKEJ) are two small cylindrical cartilaginous bodies, situated im- mediately in front of the vertical prominence of the arytenoid cartilages in the fold of mu- cous membrane g, (jig. 22.) They present a vertical and horizontal prominence in the shape of the letter L, and partake of the form of the arytenoid cartilages. They are not always pre- sent, and their existence in man is denied by Cruveilhier :* this however is an error. Both Cuvierf and WolrTJ have confounded them with the cornicula or cartilages of Santorini. In the Quadrumana they are conspicuous, having the superior vocal ligaments attached to their bases, and they appear afterwards to con- nect them with the arytenoid cartilages. The cuneiform cartilages are sometimes described by Cruveilhier and other writers (though inac- curately) as the arytenoid glands. They serve as a link of connection between the arytenoid cartilages and superior ligaments. The epiglottis, from sort, upon, yXwrra, the tongue. Syn. KX^OV, Hipp. Liguln, Gal. Operculum, Cic. || Cartilago epiglottidis. Epiglotte, Fr. Ke/ildeckel, Germ. The epi- glottis is a cartilaginous valve, situated at the base of the tongue, and covering the opening of the larynx. The direction of the epiglottis is vertical, except during the act of deglutition, when it becomes horizontal. In form it has been compared to a cordate leaf, (Jig. 23,) or that of the artichoke. The di- mensions vary with the volume of the larynx. The anterior aspect of the epiglottis is convex, the posterior concave ; it is partly free and partly connected : the free portion projects above the level of the base of the tongue. It is lined by the mucous membrane : the centre of its superior margin is very slightly notched. Inferiorly it terminates by a kind of pedicle, very thin and delicate, which is attached to the angle of the thyroid immediately above the plane of the thyro-arytenoid ligaments. Nu- merous foramina are observed, perforating its substance (f f, Jig. 23), rendering the struc- ture of this cartilage less dense than that of the thyroid or cricoid cartilage. It is consi- dered to be more brittle, in consequence of the cohesion of its particles being affected by these perforations. Its elasticity, however, is augmented by each perforation admitting some fasciculi of the yellow elastic ligament which is expanded, and, as it were, rivetted on its an- terior aspect. In the larger Ruminantia, such as the ox, this structure is very conspicuous, the thickness of the elastic tissue being nearly equal to that of the epiglottis itself. This ligament is disposed so as to secure perma- nently the return of the epiglottis after its de- * Anat. Descript. t Le9ons Anat. Comp. % De organo vocis Majnnaalium. In Lib. Morh. 1. || De Nat. Deor. ii. p. 54. Fig. 23. A posterior angular view of the cartilages of the larynx, exposing the rugged and perforated structure of the epiglottis after the removal of the mucmis membrane and the yellow elastic ligamentous tissues, (Drawn from a preparation in the Museum of King's College, London.} a a, the arytenoid cartilages ; 6 b, the superior cornua ; c, the right inferior cornu ; d, the posterior surface of the cricoid catilage; e, the fora men for the transit of the superior laryngeal nerve ; f f, the perforation of the epiglottis ; i, the superior margin of the thyroid \ t, the trachea j h, the right inferior tubercle. pression in the act of deglutition, indepen- dently of any muscular fibres. Its perforations have been described as giving lodgement to " muciparous follicles," but their office seems not to have been hitherto thoroughly investi- gated. Articulations and ligaments of the larynx. The articulations are divided, first, into those connecting the larynx with surrounding struc- tures, called extrinsic articulations ; and, se- condly, those peculiar to the larynx itself, termed intrinsic articulations. Extrinsic articulations. The hyo-thyroid 104 NORMAL ANATOMY OF THE LARYNX. articulation. The thyroid cartilage is united to the os hyoides by three ligaments : the mid- dle and two lateral. 1st. The ligamentum thyro-hyoideum medium is a lax yellow tissue arising from the superior margin of the thyroid, and inserted into the inner margin of the os hyoides : it is thicker and denser at its middle part ; its lateral borders are involved with the surrounding cellular membrane. The anterior surface in its middle is situated immediately under the integuments, having its sides co- vered by the thyro-hyoidei muscles, (g, fig. 25) and its posterior surface corresponding with the form of the epiglottis. 2d. The ligamenta hyo-thyroidea lateralia are small round liga- ments on each side of the larynx, connecting the tubercles of the great horns of the os hy- oides with the extremities of the superior cor- nua of the thyroid cartilage (c c. Jig. 24). In the substance of these ligaments there are often found small osseous or cartilaginous bodies. The articulations of the thyroid cartilage Fig. 24. A mesial section of the larynx, from Lauth. The mucous membrane and muscles are removed to expose the elastic ligaments. a, the epiglottis; b, the hyo-epiglottic ligaments; c c, the lateral thyro-hyoid ligaments ; e, a portion of the glosso-epiglottic ligament ; f, the crico-thy- roid ligament ; g i, the junction of the crico-thy- roid, and lateral crico-thyroid ligament ; ri , the attachment of the lateral crico-thyroid ligaments to the base of the arytenoid cartilage ; n, the elas- tic ligament lining the bottom of the ventricles ; o, the superior inner margin of the cricoid cartilage ; the lateral ligamentous connection with the inferior vocal cord ; /, the superior vocal cord ; the right arytenoid cartilage. with the os hyoides are furnished with syno- vial membranes. The ligaments of the epiglottis. The epi- glottis gives attachment to three ligaments, which contribute to its elasticity and the stabi- lity of its position. 1. The ligamentum thyro-epiglottideum arises from the mesial line below the notch of the superior angle of the thyroid, and is inserted into the base of the epiglottis. It binds the epiglottis to the thyroid cartilage. 2d. The ligamentum hyo-epiglottideum arises from the inner surface of the base of the os hyoides; its fibres passing horizontally are inserted into the anterior surface of the epiglottis ; its action tends to keep the position of the epiglottis per- manently vertical. 3d. The ligamentum glosso- epigluttideum arises from the base of the tongue ; it lies in the median mucous folds be- tween the tongue and epiglottis, and is inserted into the anterior surface of the epiglottis im- mediately above the ligamentum hyo-epiglot- tideum. Its action is nearly the same as that of the last-named ligament, but it is also con- nected with the motions of the base of the tongue. The tracheo-cricoidean articulation. The lower margin of the cricoid cartilage is arti- culated with the first ring of the trachea by a series of the same ligamentous fibres which connect the rings of the trachea with each other. At the anterior mesial base of the cricoid there are found additional ligamentous fibres. The elastic tissue which connects the larynx with the trachea permits considerable freedom in the multiplied movements of the neck without im- peding the regular transmission of the atmos- phere. In these movements the first ring of the trachea passes within the inferior margin of the cricoid cartilage. The intrinsic articulations of the larynx are, 1st, the crico-thyroid ; 2d, the crico-arytenoid. Besides these may be included the articulation of the arytenoid with the cartilages of Santorini. The cuneiform cartilages are generally unarticu- lated in man. The crico-thyroid articulation. The inferior cornua of the thyroid are curved forwards and inwards. Their extremities present oblique planes directed inwards and downwards, which are firmly attached by a capsular ligament to the oblique discs on the sides of the cricoid, directed upwards and outwards. The ligament of this joint is of an orbicular form, radiating in oblique fasciculi, the pos- terior fibres of which extend nearly to the crico- arytenoid articulation. The crico-thyroid ligament. Syn. Pyrami- dal, or conoid ligament. Lat. Ligamentum crico-tliyroidenm. Fr. Membrane, ou liga- ment thijro-crico'idien moyen. The crico- thyroid ligament is a very thick, strong, yellow elastic ligament, arising from the mesial line of the inferior margin of the thyroid ; it then crosses the crico-thyroid space, and is inserted into the superior mar- gin of the cricoid. This ligament supports the anterior part of the cricoid cartilage, and NORMAL ANATOMY OF THE LARYNX. 105 trachea in conjunction with the crico- thyroid muscle. The nature and position of the arti- culation of the thyroid, with the cricoid, render the force of this ligament of great utility and importance. The lateral crico-thyroid ligament, lig. crico- thyroid lateralc, arises immediately at the side of the crico-arytenoid articulation. Some fas- ciculi, according to Cruveilhier and Lauth, are attached to the bases of the arytenoids, others are reflected horizontally forwards to the in- ferior margin of the cricoid. It is bounded externally by the thyro-arytenoideus and crico- arytenoideus lateralis, and lined internally by tlie mucous membrane of the larynx. T/ie crico-arytenoid articulation. The ob- lique articulating convex surface of the cricoid is received in a corresponding channel or groove at the base of the arytenoid cartilage. The ligament arises from the cricoid, and ra- diates both anteriorly and posteriorly round the base of the arytenoid cartilage; a fasciculus is reflected along the base of its anterior mem- brane behind the attachment of the thyro-ary- tenoid ligament. The crico-arytenoid liga- ment is thick and strong, yet sufficiently loose to permit a diversity of motion. Some anato- mists divide the ligament into anterior and posterior. The articulation is lined and lubri- cated by a synovial membrane. The tln/ro-arytenoid ligaments. Syn. Chor- da vacates, Ferrein. Slim inlander, Germ. These ligaments, as their name implies, con- nect the thyroid with the arytenoid cartilages, and are instrumental in the production of voice. There are on each side two vocal cords, a su- perior and an inferior; the cavities between these ligaments are termed the ventricles of the larynx. The inferior thyro-arytenoid ligaments, or, as they are often denominated, " the true ligaments of the glottis," are much thicker and stronger than the superior : they present the form of nearly rectangular parallelograms, and are stretched horizontally across the long axis of the larynx, from the anterior horizontal tubercle of the arytenoids, to the angle formed by the junction of the wings of the thyroid (c, jig. 27). On their outer side these ligaments are connected with the thyro-arytenoid mus- cles ; their anterior extremities are inserted into the thyroid, the posterior to the arytenoid car- tilages ; the internal margins are free to vibrate. On exposing them by the removal of the mu- cous membrane they are found less than their apparent volume. Immediately after death they are semi-transparent, very elastic, and composed of parallel fibres. They are con- nected with, and form a continuation of the ligamentum crico-thyroideum lateralis (k,jig. 24). The length of the vocal ligaments varies with the general dimensions of the larynx : in the adult male they are much longer than in the female. In infancy they are very short, and increase from that period to the age of puberty in an arithmetical ratio. Thus, if at one year old their length in parts of an inch is 0,2500, at five years they will be 0,3333, at nine 0,4166, and at fourteen 0,4999 : these are close approximations. The superior thyro-arytenoid ligaments or superior vocal cords are, in centra-distinction to the inferior, denominated (though incorrectly) the false ligaments : they are of less thickness and strength than the inferior ligaments, and are further removed from the axis of the larynx (/, fig. 24). They arise from the internal angle of the thyroid, and are inserted into the middle of the anterior superior prominence of the arytenoid cartilages (jig. 4); they are composed of a few slender fasciculi of elastic fibres, approaching less nearly the mesial plane than the inferior ligaments ; they appear more prominent, in consequence of their form- ing the roof of the ventricles. They are in the same plane as the aryteno-epiglottic muscle, and are connected with the fibres of the lateral crico-thyroid ligaments. According to M. Lauth there is a connexion between the crico-thyroid, the lateral crico- thyroid, and tliyro-arytenoid ligaments bv three fasciculi, one of which is vertical, one hori- zontal, and one ascending (g, h, n, fig. 24), the first of these being the crico-thyroid; the second the lateral ; the third connects the thyro- arytenoid with the superior thyro-aryterioid ligaments, and lines the bottom of the ventricles. M. Lauth considers also that the thyro-epi- glottic, the hyo-epiglottic, and glosso-epiglottic ligaments are composed of the same elastic tissue. Mu'ller and Cruveilhier concur in these views. They certainly appear of the same colour and texture under the microscope, and undergo the same change by exposure to the atmosphere : they also possess the same cohe- sive elastic properties. The strength of the inferior thyro-arytenoid ligaments is so great that they will tear away the cartilage to which they are attached without being injured, and will support the force of many pounds weight. Muscles. The motions of the larynx are exceedingly complex, and are performed by two sets of muscles, which are divided into two classes: 1, the extrinsic; and, 2, the intrin- sic muscles. The muscles which elevate the larynx are the digastrici, stylo-hyoidei, mylo- hyoidei, genio-hyoidei, and hyo-glossi, and those pharyngeal muscles which are inserted into the cricoid and thyroid cartilages. The muscles which antagonize these and lower the larynx are the sterno-hyoidei, the omo-hyoidti, the sterno-thyroidei, and the thyro-hyoidei. The os hyoides is the centre of motion for the action of these muscles. (See NECK, MUSCLES OF THE.) We shall here confine our description to the Intrinsic muscles of the larynx, Syn. ; mus- cles intrinsiques, Cruveilhier. The muscles of this division comprise those acting exclusively on the larynx itself. There are four pairs and one single: 1, the c rico-thyroidei ; 2, the crico-arytenoidei postici ; 3, crico-arytenoidei laterales ; 4, tliyro-arytenoidei ; and, 5, aryte- noideus, which, from a difference in the direc- tion of certain of its fibres, is divided into the oblique and transverse. Independently of these, there are some muscular fasciculi, named the thyro-epiglottidei and the aryteno-epiglottidei. The crico-t/iyruidei. These are very short, 106 NORMAL ANATOMY OF THE LARYNX. thick, almost quadrangular-shaped muscles, situated on each side of the anterior part of the larynx : they arise from the anterior and inferior surface of the cricoid cartilage, on each side of the median line. The fibres are fleshy : the most internal directed obliquely upwards and outwards (m, Jig. 25), the central very Fig. 25. Fig. 26. A side view of the larynx with the os hyoidei attached, a, the thyro-hyoideus muscle ; b, the middle thyro-hyoid ligament ; e, the pomum ; d, the crico- thyroid ligament; m, the crico-thyroid muscle; O N, the direction of the inferior fibres of the crico- thyroid lying nearly perpendicular to the axis of the crico-thyroid articulation ; f, the trachea ; n n, the insertion of the thyro-hyoid muscle and mem- brane to the inner margin of the os hyoides. obliquely, and the inferior almost horizontally to the inferior margin of the thyroid and to the inferior horn : others are inserted into the pos- terior surface of the thyroid. A portion of this muscle is prolonged to the inferior constrictor of the pharynx. Each crico-thyroid muscle is covered by the sterno-thyroideus, and lies external to the crico- arytenoid lateralis and the thyro-arytenoideus. The triangular space between the crico-thyroidei is occupied by the crico-thyroid membrane. The action of the crico-thyroidei is to rotate the cricoid on the thyroid. The superior and middle fibres are at the greatest distance from the axis of rotation (N, Jig. 26), and conse- quently acting as if at the arm of a long lever. In this action the anterior superior margin of the cricoid is elevated towards the inferior edge of the thyroid from /to/' (Jig. 26), by which the posterior upper margin of the cricoid is carried backwards from B to B' indicated by the dotted line 1, 2, 3, 4, 5, (fg. 26), and as the space is greater from A B'' than A B, it is manifest that the space in the mesial plane A view of the left side of the larynx to illustrate the functions of the thyro-arytenoid, the sterno-thyroid, and crico-thyroid muscles. The dotted line 1, 2, 3, 4, 5, shows the position of the cricoid cartilage when the crico-thyroid mus- cles have closed the crico-thyroid space ; m, the crico-thyroid muscle ; N, the crico-thyroid articu- lating axis ; A B and B A, the directions of the force of the thyro-arytenoideus muscle ; R S, the direction of the force of the sterno-thyroideus muscle meeting that of the thyro-arytenoideus in R ; R N, the resultant of the combined muscular forces R P and R S ; O N and P N are perpendi- cular lines drawn from the directions of the forces of the thyro-arytenoideus and sterno-thyroideus muscles to the common axis of rotation ; they are also the "cosines of the angles R N O, R N P, and B N P, and show the amount of force on the axis of the sterno-thyroideus and thyro-arytenoideus muscles respectively; R' and A' are the points which R and A must pass through when the thy- roid is rotated forwards on the cricoid ; A, the point opposite which the thyro-arytenoideus is in- serted into the posterior angle of the thyroid carti- lage ; B, the point on which the thyro-arytenoid acts in rotating B towards A ; ff, the crico-thy- roid space ; h, the trachea. must be enlarged to an amount equal to the difference of the distance A B and A B' (fig. 26). The action of this muscle, therefore, is to stretch the thyro-arytenoid ligaments. The direction of the force of the inferior horizontal fibres of the crico-thyroid which are lying parallel to the line O N (Jig. 25 and 26) being nearly perpendicular to the axis of rotation, can have, consequently, little or no effect, until the superior fibres have (by raising the cricoid) pro- duced an angle with the axis N (Jig. 25) ; they assist only when the crico-thyroid space is diminished. It has been commonly supposed that it is the thyroid which is drawn forwards on the cricoid, and Cruveilhier adopts this sup- position ; but it has been refuted by Magendie, and not only do we observe that the attach- ments of the crico-thyroidei are mechanically directed to produce a rotatory motion of the cricoid, but the latter has no fixed point of NORMAL ANATOMY OF THE LARYNX. 107 Fig. 27. Fig. 28. A side view of the larynx, the left wing of the thyroid and the mucous membrane removed, and the fibres of the arytenoid muscle depressed to expose the liga- ments and chink of the glottis. a, the internal surface of the right wing of the thyroid ; b b, the arytenoid cartilages ; c, the thyro- arytenoid ligament ; d, the thyro-arytenoideus muscle ; d', the thyro-arytenoideus superior vel minor; e e, the crico-arytenoidei postici ; f, the crico-arytenoideus lateralis ; n, the cricoid carti- lage ; h, the trachea ; I, the external prominence of the arytenoid cartilage. attachment or muscles appropriated to fix it as a fulcrum for motions in an opposite sense. The crico-arytenoideus lateralis is an irregu- lar quadrilateral muscle, arising from the supe- rior margin of the cricoid, from thence passing upwards and backwards, (f,fg. 28). It is in- serted into the posterior surface of the external prominence of the arytenoid cartilage by a tendon common to it and the thyro-ary tenoid muscle. It is deeply seated under cover of the thyroid car- tilage and crico-thyroid muscle. The action of this muscle has caused much diversity of opi- nion. Cowper, Ilaller, Magendie, and others consider that it opens the glottis ; but Bichat and Soemmering that it closes it. Its action has, however, been mechanically solved in the following manner by Willis. The arytenoid cartilage is loosely fixed to the cricoid by liga- ments already described at B (Jigs. 28 and 29). The direction of the force of this muscle is represented by the line N X (Jig. 30), having its point of insertion into the cricoid about X. The fibres in passing thence to the arytenoid (f, .fig. 28) lie nearly parallel to the projection of the axis of motion, G C ; the tension of this muscle in the direction N X (Jigs. 29 and 30) A section of the larynx similar to that of fig. 27, with the thyro-arytenoideus muscle removed to give a full view of the thyro-ary tenoid ligaments, and the rima glottidis lying in the direction of A and B. The line G C is the vertical projection of the crico- arytenoid articulating axis ; cc,f, g,h, represent the same parts as injig. 27. tends to bring N X B into the same straight line and approximate the point V to the mesial plane; and as N is above the line joining B X, it will depress N and still more V, because the cartilage turns on the articulating surface be- neath Q. The action, therefore, of this muscle is to approximate the anterior arytenoid promi- nences and depress them. The arytenoideus (obliquus and transversus). Modern anatomists consider this as one muscle, but owing to the obliquity of the fibres of one of its fasciculi with respect to the other, some have made a division of it into arytenoideus obliquus and a transversus. It is a very short thick muscle, occupying the concavities on the posterior surface of the arytenoid cartilages and the interval between them. It consists of two layers; the superficial layer, which is composed of the oblique fibres, which arise from the base of the right arytenoid, and crossing the fibres of the deep-seated layer, are inserted into the summit of the left arytenoid cartilage : this is the arytenoideus obliquus of Albinus. The deep-seated layer is thicker and stronger than the superficial ; its fibres, which are directed transversely from one arytenoid to the other, constitute the arytenoideus transversus of Albi- nus. The arytenoid muscle is covered pos- teriorly with mucous membrane, which is con- nected to it by loose cellular substance, in which some mucous follicles are found; anteriorly it 108 NORMAL ANATOMY OF THE LARYNX. corresponds with the posterior surfaces of the arytenoid cartilages, and is connected by some muscular fibres and membrane with the supe- rior margin of the cricoid cartilage and with the whole length of the internal margins of the arytenoid cartilages. The immediate effect of the contraction of the arytenoid muscles is to approximate the posterior internal surfaces of the arytenoid cartilages, but their action, at the same time, tends to separate the anterior pro- minences, and to open the chink of the glottis. To counteract this effect the action of the crico- arytenoideus lateralis is called simultaneously into play, and the joint effect of these two muscular forces, represented by the lines N X and NY (Jig. 30,) produce a resultant in the direction of W N ; hence the crico-arytenoideus lateralis and the arytenoideus muscle acting together tend to close the glottis posteriorly. The thyro-arytenoideus. This is one of the most important, most complicated, and perhaps least understood of any of the muscles of the larynx. It arises from the side of the angle of the thyroid cartilage, occupying about two-thirds of its height, and reaches within two or three lines of its superior margin. The central fibres are directed horizontally back- wards and outwards, slightly inclined upwards, and inserted into the prominence and concavity on the lateral surface of the arytenoidf/, Jig. 27). The superior fibres terminate in the external ridge of the arytenoid ; some of them pass round the arytenoid, and enclose the arytenoid muscle like a sphincter.* The inferior fibres which arise near the median plane (k, 29) are inserted, at a greater distance from it, into the arytenoid cartilages (f, fig. 30) ; some ex- ternal fibres are directed more eccentrically Fig. 29. Fig. 30. A view of the larynx from above. (From Mr. Willis.) The mucous membrane is removed to shew the ligaments and muscles of the glottis. "N F, N F, the arytenoid cartilages ; T V, the vocal ligaments ; N X, the right crico-arytenoideus lateralis, the left is removed ; Xt> L, the ring of the cricoid capable of rotating on the axis R S ; e e, the crico-aryte- noidei postici ; E, the junction of the wings of the thyroid. Lauth, Mem. de 1'Acad. deMed. 1835. A portion of Jig. 29 enlarged to demonstrate the di- rection and result of the forces of the muscles of the larynx. O P, the horizontal projection of the axis of articulation ; T V, the vocal ligament ; g h, the direction of the force of the thyro-arytenoideus ; N X, of the crico-arytenoideus lateralis; N W, of the crico-arytenoideus posticus ; N Y, of the arytenoideus transversus. upwards and backward, corresponding to the superior ligaments and ventricles, where, ac- cording to Lauth, they terminate without reaching the arytenoid. Some fibres of the thyro-arytenoid take an oblique direction back- wards and downwards, arising immediately below the superior internal margin of the angle of the thyroid, and are inserted into the ver- tical prominence of the arytenoid cartilage : they are sometimes detached from those passing horizontally, as in d, (fig 28,) constituting the thyro-arytenoidei superiores of Albinus, but they are sometimes described as one muscle. The thyro-arytenoideus corresponds to the internal surface of the thyroid cartilage, from which it is separated by some loose cellular and adipose tissue. Internally it is in contact with the inferior vocal ligament, which lies in contact with the thickest part of this muscle, the bulk of which causes the vocal ligaments on each side to project towards the mesial line and contracts the aperture of the larynx. Some anatomists consider that the thyro-arytenoid ligaments consist of nothing more than the tendons of these muscles; it is not difficult, however, to prove the contrary by dissection. The functions of the thyro-arytenoidei, con- cerning which there has been much diversity of opinion, produce several changes in the rela- tive position of the internal mechanism of the larynx, and therefore they require rigid inves- tigation. The effects of these muscles may be considered, first, with respect to the tension of the vocal ligaments; secondly, to the aper- ture of the glottis. We observe that the points of attachment (at dd' I, Jig. 27) of the thyro- arytenoid are situated within those at A B, (Jig.28); and, as the arytenoid cartilage is tied by ligamentous fibres to the point B, it follows that the contraction of this muscle will draw upon the point B, through the interposed arytenoid cartilage : if A be made the fixed point, the contraction of this muscle will draw the point B towards A by rotating the cricoid on the thy- roid. If, on the contrary, B be fixed, then A will approach B by the rotation of the thyroid on the cricoid. In both these cases the dis- tance from A to B is diminished, and as the vocal ligaments are situated in a direct line NORMAL ANATOMY OF THE LARYNX. 109 passing through A and B, this muscle must consequently relax them. The closing of the anterior and central por- tion of the glottis by these muscles, or that part lying between T and V (Jig- 29), is effected, according to Mr. Willis, partly by the approach of the point V of the arytenoids towards T arising from the obliquity of the axis of rota- tion, and partly by the swelling of the muscle whilst contracting to approximate the arytenoid cartilages tending to nil the space T N X V (Jig. 29), and to close tightly the sides of the passage below the vocal ligaments; thus clos- ing the anterior and central portions of the glottis. The question as to how A is made a fixed point, in the above demonstration, remains to be solved. Mr. Willis remarks that while all writers agree that the crico-thyroidei serve to approximate the cricoid cartilage to the thyroid, either by raising the cricoid or by depressing; the thyroid, none of them have shown how the cartilages are to be separated again. Let us investigate this proposition. In order that the motions necessary to dilate the crico-thyroid space be effected by mus- cular motion, it is obvious that A must be made a fixed point, so that B' may be drawn to B (fig. 26), by which _/' ascends to j\ the object in question (Jig. 26). It is clear that the crico-thyroid muscle cannot be employed in this instance, as it has been already shewn that its action is to force B to B' andy'toy"; whereas we have now to reverse the direction, and to bring back B' to B, so thaty'' may de- scend to _/. The sterno-thyroidei are the only muscles, which by their origin, insertion, and direction of force are calculated to effect this purpose ; the insertion of one of these muscles being about the point 11 at an angle with the axis It N (Jig. 26), its force in the line R O S (fig. 26) cutting the right line O N at O ; the effect of which will be to draw forwards and downwards the thyroid cartilage from A to A', and the point R R'; these muscles have the advantage of acting on the extremities of a lever equal to the line O N. When any force equal to that in R S is acting simultaneously with that of the thyro-arytenoideus, in the di- rection A R P B perpendicular to R S, the composition of these forces R S and A 11 P B will produce a resultant in the diagonal R N, which will cut the axis N ; and as by hypo- thesis the forces R O and R P are equals, R and consequently A will be fixed points ; but the attachment of the thyro-arytenoid at B makes an angle with the axis in the line B N, and the perpendicular cutting the direction of the force of this muscle produced to the axis is PN; thus whilst the sterno-thyroid has, by its action on the lever O N, fixed the points A and R, the thyro-arytenoid may act with an equal force at the point B on the lever P N ; but as the force P N is produced on the cricoid (which is free to move by the relaxing of the crico-thyroid), the result will be to rotate the point B towards A, and depress the point/' to f, and thus the question is solved. In the preceding demonstration it must be remem- bered that the point R is assumed to be that in which the whole of the sterno-thyroid is in- serted, whereas it is expanded upon the surface around the oblique Ttde,e, but any of its fibres below R will have the same effect as if at R, provided they are in the line O S. It must also be borne in mind that the thyro- hyoid prolongs the action of the stei no-thyroid to the os hyoides ; but in this instance the os hyoides itself descends simultaneously with the expansion of the crico-thyroid space, and we know that the sterno-thyroid is always in action during the descent of the larynx. There is, however, very little muscular force required for rotating the cricoid in the direction in ques- tion. It is therefore evident that the sterno- thyroid is the antagonist to the thyro-arytenoid, and that, in this instance, during the rotation of the cricoid on the thyroid in the direction B B P A must be the antagonist to the crico- thyroid. From the preceding demonstrations we con- clude that when the crico-thyroidei, the thyro- arytenoidei, the crico-arytenoidei laterales, and the arytenoid muscles are acting simultane- ously, the chink of the glottis is entirely closed. Another function of the thyro-arytenoidei re- lates to their effects during the production of vocal sounds, which will be considered in the article VOICE. In order that the glottis may be closed in the manner just described, it is necessary that the crico-thyroid assisted by the sterno-thyroid should have fixed the fulcrum for the play of these muscular motions. The crico-arytenoidei postici. The intrinsic muscles of the larynx already described tend, more or less, to affect the antero-posterior di- ameter of the laryx, the tension of the thyro- arytenoid ligaments, or the contraction of the chink of the glottis. The crico-arytenoidei postici have altogether a different tendency. They are a pair of muscles arising at the pos- terior surface of the cricoid (e e,fgs. 27&28); the superior and middle fibres ascend obliquely, the inferior nearly vertically to be inserted into the lateral prominences at the bases of the ary- tenoid cartilages, anterior to the crico-aryte- noidei laterales. These muscles lie under the mucous mem- brane of the pharynx, and upon the posterior surface of the cricoid. The contraction of these muscles is gene- rally said to draw the arytenoids backwards, outwards, and downwards, and to open the glottis posteriorly. This view is in a great degree, but not strictly, accurate. The crico- arytenoideus posticus being inserted into the arytenoid cartilage at N has the effect of acting as on the arm of a short lever at N, and of rotating it upon the axis O P, in the direction of N W, which is directly opposed to the direc- tion of the force of the crico-arytenoideus late- ralis, which is represented by W N, therefore the effect of this muscle is to separate the vocal ligaments, and consequently to open the chink of the glottis. Mr. Willis remarks that the thyro-arytenoidei postici do not draw the ary- tenoids backwards, as described by anatomists, which implies that the posterior fasciculi of the 110 NORMAL ANATOMY OF THE LARYNX. ligamentous fibres of the crico-arytenoid arti- culation at B (Jig. 30) are relaxed ; for, al- though some fibres lying nearest the mesial plane are directed to draw the arytenoids to- wards B, they are counteracted by the fibres lying furthest from it, and by assuming the whole to act together, the resultant will be as nearly as possible perpendicular to the axis of articulation O P, which would open the glottis ; and therefore he concludes that the force of the thyro-arytenoidei postici in a direction back- wards may be neglected. Bichat erroneously considered that they assist the thyro-aryte- noidei and crico-arytenoidei in drawing the thyro-arytenoid ligaments very tense.* The thyro-epiglottidei. These are a pair of small muscles situated between the anterior sur- face of the thyroid cartilage and epiglottis; they arise from the internal surface of the thyroid near its middle, and not far from the origin of the thyro-arytenoidei ; their fibres are directed upwards and forwards to the base of the epi- glottis, to which they are inserted behind the ligamenta thyro-epiglottidea. Their action is to depress the epiglottis. The aryteno-epiglottidei are two small mus- cles, arising from the superior pyramid of the arytenoid cartilages posterior to the arytenoid muscles, or from the fibrous raphe situated vertically behind them ; they pass upwards and forwards to the sides of the epiglottis, and upon the posterior border of the thyro-epiglottic membrane. Action. Owing to the direction of their fibres, the thyro- and aryteno-epiglottidei tend to depress the epiglottis, or rather to effect the tension of the aryteno-epiglottic mucous folds. The action of the intrinsic muscles of the larynx may be briefly recapitulated as follows : The crico-arytenoidei postici open the glottis; all the other muscles close it. The arytenoideus obliquus and arytenoideus transversus approximate the arytenoid cartilages posteriorly. The crico-arytenoidei laterales and the thyro-arytenoidei bring them in contact anteriorly. The thyro-arytenoidei close the centre of the glottis, and with the crico-thyroidei, assisted by the sterno-thyroidei, regulate the tension, position, and vibrating length of the chordae vocales. The crico-thyroidei and sterno-thyroidei an- tagonise the thyro-arytenoidei, and in stretch- ing the crico-thyroid ligament, the sterno-thy- roidei with the thyro-arytenoidei antagonise the crico-thyroidei. The crico-arytenoidei laterales, and thyro- arytenoidei, and the arytenoideus obliquus and transversus antagonise the crico-arytenoidei postici. These last-named muscles likewise may be said to antagonize all the muscles which close the glottis. The genio-glossi, the linguales, the stylo- pharyngei, and crico-pharyngei, and hyo-glossi, are muscles associated in common with the mo- * Quand les thyro-arytenoidiens ot criro-arytc- noidiens lateraux d'une part, et les crico-arytenoi- diens postcricurs d'une autrc part agisscnt simul- tancment. les ligamens thyro-arytenoidiens sont fortcincnt icndus. tions of the tongue, pharynx, and larynx, and belong rather to the structure and functions of the two former of these organs than to the larynx, and consequently are considered only as auxiliary. The motions of the internal mechanism of the larynx being effected by muscles, whose forces are directed, with respect to each other, in various degrees of obliquity, and in different planes, and producing by their combination results which can only be demonstrated on me- chanical principles, it has been deemed desira- ble to introduce them into the preceding inves- tigations to insure greater precision of detail and accuracy of result, and the more especially as we find in the works of our best anatomical writers the most discordant opinions, based ap- parently upon mere hypothesis or superfical observation, and without reference to any data or principle from whence their conclusions are drawn. The perusal of the works of Albinus,* IJal- ler,f Cowper,| Sb'emmerino, Meckel,|| Bi- chat,1T Magendie,** and Bell,ft confirm these remarks ; exceptions to these observations are found in the works of Borelli,}! Barthez, E. and W. Weber,|||| Bernouilli,UH Barclay,*** and Willis ;tff from the invaluable investiga- tions of the latter much assistance has been de- rived. Bloodvessels. The arteries of the larynx are derived from the superior thyroid, a branch of the external carotid and from the inferior thyroid, a branch of the subclavian. Small veins accom- pany the arteries and empty themselves into the neighbouring trunks. Structures called glands. The arytenoid gland. Syn. Glandulte. arytenoidece, Mor- gagni, Bichat, Cloquet ; cnrtilugo cunei- Jbrmis, Wrisberg, Bandt. The arytenoid gland is an inappropriate designation given to the cuneiform cartilage by Morgagni,|JJ; whose views of the structure of this body are adopted by Bichat, Cloquet,|||||| and Cru- * Historia Musculorum, lib. ii. chap. 2. t Elem. Pbys. torn. iii. j Anat. of the human body. De Corporis Hum. Struct. jj Traite Generate, torn. x. Tf Traite d'Anat. desc. torn. ii. ** Physiol. ft Anat. of the human body. $} De motu animalium. Lugd. Batav. 1685. Nouvelle mechanique des mouvemens de 1'Homme et des Animaux, 1798. (HI Mechanik der Menschlichen Gehwerkzeuge, mit xvii Taf Gbtt. 1836-8. 1111 De motu musculorum. *** The muscular motions of the human body. ttt Cambridge Phil. Trans. 1833. tJJ Constant glandulae arytaenoidzpae ex granosa substantial livido albescente, de qua utilem oblini- endo laryngi succum maxime inter edenduin, aut vociferandum, appressa epiglottis j vel conlracti vicini musculi exprimunt. II apparoit que les deux glandes arytenoides ne sont que des glandes muqueuses plus prononcees que celles qui entourent le reste de la membrane laryngee, mais qu'elles ont absolument le meme usage. Op. cit. p. 386. Ullll Les glandes sont formees de petits grains arrondis, assez consistans, d'une couleur grisatre. Op. cit. NORMAL ANATOMY OF THE LARYNX. Ill veilhier.* The description given of it by Morgagni is, that it consists of a granular sub- stance of a livid whitish colour, from which under the pressure of the epiglottic or neigh- bouring muscles a fluid is poured out. Wris- bergf described it as a cartilage under the name of cuneiform. Cuvier and Wolff, as before stated, have confounded it with the cartilage of Santorini. Morgagni appears to have mistaken for glandular the yellow elastic tissue pene- trating its body. Lauth describes some mucous follicles about its base and internal surface, but he opposes the views of Morgagni on the constitution of this body. This body is some- times absent in the human subject, but scarcely ever in the quadrumana. Its structure is de- cidedly cartilaginous. The epiglottic gland. Syn. glandula epi- glottidis, Fab. Cass. Morg. The epiglottic gland is a name given to a mass of yellow ligamentous adipose and cellular substance, situated in the triangular space between the anterior surface of the epiglottis and the angle of the thyroid cartilage ; it is bounded anteriorly by the thyro-hyoid membrane, above by the thyro-epiglottic mucous membrane and ligament; below, by the union of the epiglottis with the thyroid cartilage, and on each side by the mucous membrane passing from the thyroid to the epiglottis. Berengarius speaks of it as a fleshy gland : Steno and many others as com- posed of granules, whose ducts perforate the epiglottis and open on its posterior surface. Fabricius, Casserius, and Morgagni J have de- scribed and figured these supposed granules and ducts. Bichat, Cloquet,|| Quain,H and most modern anatomists adopt the same views. Morgagni, upon the same supposition as he had formed of the nature of the elastic tissue, considers the composition of the epiglottis to be chiefly glandular. Cloquet and Bichat admit the difficulty of detecting any follicular structure, nor could we discover any under the microscope ; and from what has been already stated on the structure of the epiglottis, we conclude, as of the arytenoid, that the structure which enjoys the name of epiglottic gland is not glandular. Mucous membrane. The mucous membrane of the larynx is continuous with that which covers the mouth and pharynx. The posterior surface of the larynx is bounded by the pharynx, and is lined by mucous membrane both on its * Traite d'Anat. t Primae lineae phys. anat. a de Haller, ed.Wris- berg. Getting. 1780-8. p. 157. $ Morg. advers. anat. om. tab. ii. p. 48. " Get espacc est occupe par un corps manifeste- ment celluleux, et graisseux, dans sa plus grande partie, mais qui est inferieurement recouvre de petits grains glandulenx, tantot agglommeres, tantot isoles, lesquels envoient sensiblement des prolonge- mens dans les trous dont est percee 1'epiglotte : les prolongemens paroissent s'ouvrir sur sa surface laryngee, aux orifices qu'on y distingue. Quelque- fois les petits corps glanduleux sont tellemcnt masques par cette graisse jaunatre, qu'on ne peut les distinguer." Traite d'Anat. dcscript. torn. ii. p. 385. Anat. descript. p. 245. Elem. of Anat. p. 858. \ anterior and posterior surfaces. If the state- ment of Cruveilhier be correct, this singular duplication is not to be found elsewhere in the animal economy ; afterwards it is reflected over the surface of the base of the tongue, and lines the interior surface of the epiglottis ; in this space it forms threefolds, called glosso-epiglottic, often described as the middle, and two lateral, which adhere closely to the surface of the epi- glottis. The mucous membrane being reflected over the free part of the epiglottis, to which it rather closely adheres, then lines its posterior surface and dips into the larynx. A duplication called the aryteno-epiglottic fold passes from each side of the lateral mar- gin of the epiglottis to the vertical apophysis of the arytenoid cartilage. This membrane is connected posteriorly with the mucous coat of the pharynx, and lines the posterior surface of the larynx ; it is reflected over the arytenoid cartilages, and with the aryteno-epiglottic fold forms the posterior and lateral superior margin of the larynx ; covers the superior thyro-aryte- noid ligaments, penetrates to the bottom of the ventricles; from thence, after lining the inferior thyro-arytenoid ligaments, it passes through the chink of the glottis, covers the thyro and crico- arytenoideus lateralis muscles, and the internal surface of the cricoid cartilages, and becomes the investing membrane of the trachea. The laryngeal membrane is perforated by numerous mucous orifices of a peculiar pale rose-colour, and is remarkable for its great sen- sibility, more especially in the region above the rima glottidis. 2V;e rima glottidis. Syn. cavum sen sinus la- ryngis The chink of the larynx is an aperture directed horizontally, connecting the supra and infra-Iaryngeal regions, and allowing the free transmission of air in respiration. It is bound- ed posteriorly by the arytenoid cartilages, ary- tenoid muscle and mucous membrane ; laterally by the arytenoid cartilages and the thyro-aryte- noid ligaments, which, with the mucous mem- brane reflected over them, present nearly rect- angular-shaped valves, attached on three sides, leaving one, bounding the glottis, free; ante- riorly by the angle of the thyroid. Immedi- ately above it are the ventricles, one on each side. The intrinsic muscles of the larynx not only contribute to its functions in the produc- tion of voice, but determine its form. The form of the chink of the glottis is variable; in the state of repose, or that of ordinary respiration, it is triangular, the aperture dilating during inspiration and contracting during expiration. When the arytenoids are separated to the great- est extent by the crico-arytenoidei postici, it assumes a lozenge form ; if the posterior bases of the arytenoids are closed by the arytenoid muscles it becomes an ellipse ; if the anterior apophyses of the arytenoids meet by the action of the crico-arytenoidei laterales, the chink may be divided into two parts. The length of the chink of the glottis is very variable, and bears a relation to that of the thyro-arytenoid ligaments ; like the latter, it increases with age in an arith- metical proportion until the period of puberty ; at that time its length in the. male sex under- 112 NORMAL ANATOMY OF THE LARYNX. goes a sudden development, whilst in the female it remains stationary. The comparative length of the chink in the male and female is proportional to the relative lengths of the vocal ligaments already detailed. The length of the rima glot- tidis bears no relation to the stature of the indi- vidual. In the adult male it is about eleven lines, of which the boundaries formed by the arytenoid cartilages are four, and the thyro-ary- tenoid ligaments seven lines. In the male and female it is on a mean average as three in the former to two in the latter. In a female, M. Lauth however found the rima glottidis to mea- sure from ten to eleven lines, whilst that of a tall male extended only from eight to nine lines; but this is a rare instance. The pomum Adami on the thyroid has a corresponding concavity within, which affords a greater length in the mesial section of the larynx, and which tends to increase the longi- tudinal dimensions of the glottis. In several of the ruminantia the concavity is very con- spicuous.* The breadth of the glottis is much less than its length. In a state of repose its transverse section is not more in the adult than about two or three lines, or with respect to its length as two to eleven, but the diameter varies with the intensity of the forces of the intrinsic muscles of the larynx. The ventricles. Ventricule ou sinus du larynx. Cruv. These are oval or elliptical cavities directed from before backwards, between the superior and inferior ligaments. The depths of the ventricles are effected by the distance from the free margin of the vocal ligaments to the internal surface of the thyroid, or rather to the thyro-arytenoid muscles, which constitute the bottom of the ventricles. The internal part of the posterior cavity of the ventricles is enlarged and deepened by a duplicature of the mucous membrane passing external to the arytenoid cartilage, which has been described by Mor- gagni, and recently more particularly by Mr. Hiltonf under the name sacculus laryngis. The ventricles are prolonged anteriorly, extend- ing along the vocal cords on each side of the epiglottis. In size the ventricles vary with the general dimensions of the larynx ; they are each divided into an interior and posterior cavity by a transverse ridge. The ventricles afford greater freedom of motion to the inferior thyro-arytenoid ligaments. Nerves. The larynx is exquisitely sensible, and, as we have seen, combines complex and delicate motions with secreting surfaces. These properties result from its nervous endowment, which is derived from two branches of the pneumo-gastric nerve, namely, the superior and the inferior laryngeal nerves. It will be unnecessary to enter into any de- tailed description of these nerves here. Their distribution will be found fully described in the article PAR VAGUM, to which we refer. Let it suffice to mention, that the superior la- ryngeal nerve by its external branch gives fila- ments, 1, to the inferior constrictor of the pha- * Vide Pallas Spicil. Zool. Trans, xii. t Guy's Hosp. Reports, No. v. Fifr. 31. A view, from Mr. Swan, of the superior and inferior laryngeal nerves. a, a portion of the tongue ; b, the epiglottis ; c, the thyroid cartilage"; d, the posterior arytenoid muscle divided for show- ing a branch of the recurrent nerve passing to the oblique and transverse muscles ; e, the lateral crico-arytenoid muscle ; f, the thyro-arytenoid muscle ; g, the arytenoideus obliquus ; h, the ary- tenoideus transversus ; i, the crico-thyroid ; ;', 1, the superior laryngeal nerve; 2, a branch of this nerve to the membrane connected with that covering the epiglottis ; 3, a branch of the superior laryngeal to the membrane placed between the superior extremities of the arytenoid cartilage ; 4, the recurrent nerve ; 5, a branch of the recur- rent given off to the membrane lying between the larynx and pharynx ; 6, a branch of the recurrent nerve to communicate with a branch of the supe- rior laryngeal nerve ; 7, a branch of the recurrent to the posterior crico-arytenoid muscle ; 8, a branch to the crico-thyroid and crico-arytenoid muscles ; 9, a branch giving filaments to the posterior crico- arytenoid, and passing between this muscle and the arytrnoid cartilage, to terminate in the oblique and transverse arytenoid muscles. rynx; 2, to the thyro-hyoid muscle and mem- brane ; 3, to the laryngeal plexus ; 4, to the crico-thyroid muscle; 5, to the thyroid gland. The internal branch of the superior laryngeal nerve supplies filaments, 1, to the epiglottis; 2, to the adipose and mucous membrane ; 3, to the arytenoid muscles ; 4, to the thyro- arytenoideus; .5, to the crico-arytenoideus late- ralis; 6, a descending anastomotic branch to the NORMAL ANATOMY OF THE LARYNX. 113 recurrent; and, 7, to the aryteno-epigloltic niucous folds and muscles. The inferior laryngeal or recurrent nerve gives filaments, 1, to the pneumo-gastric and cardiac plexus; 2, to the pharynx; 3, to the trachea ; 4, to the oesophagus ; 5, to the crico- arytenoideus posticus ; 6, to the arytenoideus obliquus and trans versu s ; 7, to the crico- arytenoideus lateralis and thyro-arytenoideus ; 8, an anastomosing branch to the superior laryngeal. Our knowledge of the anatomical distribu- tion of the laryngeal nerves, and of the func- tions of the intrinsic muscles of the larynx, are sufficient, independently of experiment, to demonstrate the inaccuracy of the well known assertion of M. Magendie, supported by Clo- quet, Pinel, Percy, and several others, that the recurrent nerve presides over those actions which open the glottis, whilst the superior la- ryngeal influences those muscles which close the glottis. The principal facts opposed to this theory of M. Magendie may be briefly stated as follows. 1 . It was well known long- before the promulgation of Magendie's views that the inferior laryngeal nerve gave to the arytenoid muscle a filament which had been described by Andersch,* Bichat,f and Mec- kel,|. and subsequently by Schlemm BischofF, Swan, Cruveilhier, Dr. Reid, and others, there- fore it has been sufficiently demonstrated that the recurrent nerve supplies the muscles that close, as well as those which open the glottis. 2. M. Magendie has stated that the crico- arytenoideus lateralis and thyro-arytenoideus opened the glottis, whereas in the preceding details it has been proved that these muscles close it. 3. The loss of voice which follows the section of the recurrent nerves results from the paralysis of all the muscles (except the crico-thyroid) which both open and close the glottis, a fact proved by the experiments of Le Gallois and Dr. Reid. The limned space allotted to this article will only permit us to notice the conclusions to which recent expe- rimenters have arrived respecting the functions of the laryngeal nerves. The external branch of the superior laryngeal is composed chiefly of motor fibres, and it controls the action of the crico-thyroid and the other muscles to which it gives filaments. The internal branch of the superior laryngeal is composed of sensi- tive fibres, which confer the most exquisite sensibility on the mucous membrane of the larynx, more especially in its supra-glottideal region. It is therefore the sensitive and the excitor nerve of the larynx. The inferior la- ryngeal supplies the muscles that both open and close the glottis, and is chiefly a nerve of motion when it reaches the larynx, but a few of its fibres go to the mucous membrane. The union of the superior with the inferior laryngeal branch by an anastomosing filament, preserves a reciprocal play in the functions of these * Fragmentum descr. nervor. t Traite d'Anat. torn. iii. p. 216. J Man. d'Anat. torn. iii. p. 66. VOL. III. nerves : whilst the branches anastomosing with the sympathetic, connect the larynx with the ganglionic system ; the pulmonary and cardiac branches connect it with the respiratory and circulating systems, and thus associate the larynx with those vital functions. The laryn- geal nerves also belonging to the reflex system, impressions made on the sensitive filaments of the larynx are reflected to the medulla ob- longata, and propagated by a circuitous route to the motor filaments of the recurrent, so that a long interval is traversed in circulating an impression from the sensitive to the motor nerves of the larynx; but according to the esti- mate made of the speed with which an impulse is propagated along a nerve, which is assumed to be equal to that of electricity, the time occu- pied to transmit an impression from the fila- ments of sensation to those of motion must be inappreciable to our senses. Other important physiological considerations result from recent experimental researches, those of Le Gallois and Dr. Reid in particular. 1. With respect to the motions of the glottis during respiration, the dilatation during inspiration, and contrac- tion during expiration, are the effects of the play of muscular force in opposition to the direction of the current of air in its passage to and from the lungs, the tendency of which is to produce the reverse action.* There is a constant periodical oscillatory motion of the arytenoid cartilages, revolving upon the axis of articulation, O P, (Jig. 30,) at every expiration and inspiration ; hence the necessity of a syno- vial membrane to lubricate the crico-arytenoid articulation. 2. When the recurrent nerves are diseased, compressed, or cut, so as to para- lyse the crico-arytenoideus posticus, the power of muscular action in opposition to the direction of the inspired air is lost. The valves of the glottis are drawn downwards with the air, the anterior apophysis of the arytenoid cartilages rotated inwards, the chink closes, symptoms of suffocation supervene, and asphyxia results. When spasmodic closure of the chink of the glottis occurs, the obstacle to the ingress of air is increased by convulsive attempts to draw in the breath, which causes a rarefaction of the air below the glottis, and augments the atmos- pheric pressure above it ; and the chest thus, says Dr. Ley, " becomes hermetically sealed." If the aperture of the glottis be partially open, the air rushing through it causes a stndulous sound ( ' laryngismus stridulus), whilst in ano- ther position of the glottis the crowing inspi- ration is produced ; this effect arises (accord- ing to Dr. Ley) from the chink of the glottis being partially open for the admission of air, and remaining so until an explosive expiration such as screaming, coughing, or belching, me chanically bursts open the floodgates, and terminates the paroxysm. * In the production of these periodical move- ments, the action of the muscles is involuntary, but in their action for the purposes of voice, they be- come subordinate to the will, and therefore belong also to the voluntary system. I 114 ABNORMAL ANATOMY OF THE LARYNX. Asphyxia is often delayed by the posterior chink of the glottis being retained partially open, in consequence of the coincident para- lysed force of the arytenoid muscles, and by the great inclination of the crico-arytenoid articu- lating axis, with respect to its vertical section, preventing the approximation of the arytenoid cartilages by which the posterior part only of the chink can be closed. When any irritation is produced on the exquisitely sensitive mucous membrane of the larynx, it transmits a reflex action to the motor filaments of the recurrent, and the glottis is spasmodically closed, without any such morbid condition of the recurrent nerve as Dr. Ley supposed necessary. The larynx, when dissected out, and cleared of its extrinsic structures, presents on its ante- rior aspect the free margin of the epiglottis, the notch of the thyroid, the pomum Adami, its mesial line, the crico-thyroid space, and liga- ment, and the anterior border of the cricoid cartilage. On each side of the larynx are observable a portion of the wings of the thyroid, the crico- thyroid muscle, the great and lesser cornu, the superior and inferior tubercles, the oblique ridge, the superior and inferior margins of the thyroid, the side of the cricoid, with a portion of the lateral crico-thyroid ligament, and the superior, inferior, and posterior margins of the cricoid. On the posterior aspect are observable, the posterior free surface of the epiglottis, the ary- tenoid cartilages and muscles, the aryteno- epiglottic mucous folds, the crico-arytenoidei postici muscles, the vertical ridge of the cricoid, the posterior margins of the thyroid, and the posterior surface of the cricoid cartilages. In the internal surface, from above, we ob- serve the superior margin of the thyroid carti- lage and great cornua, forming the superior boundary of the larynx, the superior margin and notch of the epiglottis, the cornicula la- ryngis, the arytenoid and cuneiform cartilages, the aryteno-epiglottic mucous folds, the supe- rior and inferior vocal ligaments, the ventricles, the rima glottidis, and the mucous membrane. Looking from below upwards, we perceive the inferior circular margin of the cricoid, the membrane lining its internal surface, the infe- rior aspect of the thyro-arytenoid ligaments, and the rima glottidis. The preceding outline of the general anatomy of the larynx will give the reader an idea of its manifold structures, its exquisite sensibility, its complex motions, its connection with the process of deglutition, and its admirable adapt- ation for the production of sound, and may serve to impress a conviction that it is one of the most elaborate and perfect specimens of mechanism in the human body.* BIBLIOGRAPHY. Galeni Opera, de locis affectis, lib. i. cap. 6, p. 6. Vesalius, De corp. humani fabrica, Basiliae, fol. 1555. J. Casserius, de org. vocis et auditu, Ferrara, 1600. Riolamts, Opera. Anat. Paris, fol. 1649. Bidloo, Anat. Humani Corp. * For the description of the vocal functions, see the Article VOICE. Amstel. fol. 1685. Malpighi, Opera omnia, Lond. fol. 1687. Cowper, Myotomia reformats, Lond. 8vo. 1694, p. 80. Dodart, Mem. de 1' Acad. Roy. des Sciences, 1700. Morgagni, Advers. Anat. omnia, Lugd. 1718. Santorini, Observations Anat. Venice, 4to. 1724. Albinus, Hist. Muscul. Hominis, Leidz Batavorum, 4to., 1734. Ferrein, Mem. de 1'Acad. Royale, 1741, p. 400. Pic- colomini, Anat. Int. Veronse, fol. 1754, p. 15, 45, 53. Duverney, Onvres Anat. Paris, 8vo. 1761, p. 91. Winslow, Anat. Edinb. 8vo. 1763. Vicq d'Azyr, Mem. de 1'Acad. Royale. 1779. Haller, El. Physiol. Soemmering, De corp. humani struct.. vol. vi. Tra- jecti ad Moenum, 8vo. 1801. Savart, Ann. de Chimie et de Physique, Paris, 8vo. 1825. Ben- nati, Recherches sur la Mechanisme de la Voix, 8vo. Pans, 1832. Willis, Camb. Phil. Trans, vol. iv. p. 323, Camb. 1832. Cloquet, Traite d'Anat. descrip. Paris, 8vo. 1834. Lauth, Mem. de 1'Acad. Royale de Med. 1835. P. Broc, Traite d'Anat. descrip. Paris, 1837, p. 527. The prin- cipal systems of anatomy. (J. Bishop.) LARYNX. (MORBID ANATOMY AND PATHO- LOGY.) The importance of this organ to life, and even when existence is not actually en- dangered, to the comfort and well-being of the individual, must render any deviation from its healthy and normal condition in the highest de- gree interesting to the pathologist : nor will that interest be diminished by reflecting on the paramount value of a knowledge of these de- viations to every practical physician. Small in size and composed of few and apparently sim- ple structures its functions so obvious that any imperfection in their performance could be quickly perceived and readily understood it would appear only reasonable to suppose that its various pathological conditions should have been observed, and the symptoms connected with them long since collected and arranged. Yet, such is not the history of the pathology of the larynx : on the contrary, it presents itself to us with all the interest of a new discovery, and whatever is known on the subject is the result of investigations made within the last few years. We have the opinion of the late Dr. Cheyne, (no mean authority on the subject,) that in the year 1800, " perhaps there was not in Britain more than one individual, namely Monro, who was acquainted with the true na- ture of the disease of which. General Wash- ington died acute laryngitis ; " and the same writer goes on to shew that in ten years subse- quent to that general's death, Dr. Baillie, then at the head of the medical profession in Eng- land, admitted that he was ignorant of the nature of the same malady. But without reverting so far back, I may be permitted 1o state, that within a comparatively recent period I can personally remember the lack of know- ledge that obtained amongst medical practi- tioners in this particular, and the deplorable results that too frequently ensued : and al- though it may be gratifying to reflect on the altered condition of things at present, yet it must be obvious that a subject so short a time under investigation cannot be expected to have been thoroughly worked out. Much as has been brought forward perhaps more remains behind, and any person now attempting to give ABNORMAL ANATOMY OF THE LARYNX. 115 a exact and adequate description of the pa- thology of this organ, may probably find it ne- cessary to bespeak a very considerable degree of indulgence. Accustomed to consider laryngeal disease practically, and more particularly with refe- rence to operation, I find it difficult to bind myself down to mere pathological arrangement, or to attempt a satisfactory classification. True, {ike other organs, the larynx is composed of different structures, in each of which disease will assume the character peculiar to itself, and exhibit the appropriate appearances in an exa- mination after death, but it rarely happens that morbid actions are so limited in extent, as to exist and produce their proper results in one tissue without the participation more or less of the others. This will produce confusion, and render it a matter of difficulty to connect symp- toms with the existing pathological conditions that occasion them, and may be adduced as an objection to any attempt at arrangement founded upon structure alone: yet there really can be no classification altogether exempt from the same or a similar observation, and there- fore I shall adopt this one as having the merit of the greatest simplicity. Following this view then, I find the larynx to be composed of the following structures, viz. : 1. Mucous membrane, exhibiting all the va- rieties of inflammation that are observed in that tissue when situated in other organs. Thus inflammation here may be acute or chronic, phlegmonous or erysipelatous, idiopathic or symptomatic, and attended by fever of a ty- phoid or an inflammatory type. And these varieties producing different effects or results. Thus we have examples of acute idiopathic in- flammation with fever of a sthenic kind in the croup of children, producing the adventitious membrane, and in the laryngitis of adults, that terminates so frequently in oedema ; and of the same local disease with asthenic fever in the diphtherite and in erysipelas: whilst accident furnishes numerous instances of the results of symptomatic inflammation in the consequences of burns, scalds, penetrating wounds, and the swallowing of caustic poisons. As happens so constantly in other structures, chronic in- flammation is here best known by the changes it induces, and furnishes us with abundant specimens of hypertrophy or thickening of the membrane, and of the different forms of ul- ceration. 2. Submucous tissue, which is the seat of cedematous effusions, and of the sloughy and pu- trid matter produced by diffuse inflammation. 3. Cartilage, in which we remark great and important varieties of disease, such as inflam- mation, ulceration, mortification, degeneration into an earthy unorganized material, atrophy, hypertrophy, and some alterations of shape and structure probably depending on scrofula or other constitutional taint. 4. Muscle, the seat of those spasmodic ac- tions so frequent and so perilous in laryngeal affections, and perhaps occasionally of gout and rheumatism also. 5. Ligaments. I know not whether disease ever originates in these structures, but there can be no doubt that they are sometimes removed by ulceration, and there is reason to believe that great inconvenience and even danger may be occasioned by a preternatural relaxation of some of them. 1. Acute inflammation of the mucous mem- brane is always in the first instance attended by a change of colour more or less intense ac- cording to its situation, being comparatively pale where it is closely attached to a subjacent cartilage, but of a deep and concentrated red tint, verging on purple, where it is more loosely connected by the intervention of cellular tissue or muscle. The membrane is also swollen, soft and pulpy, these characters being likewise influenced by the nature of its connection to subjacent parts, and I believe the usual symptom of inflammation, "pain," is not ab- sent, although the mental agony attendant on obstructed respiration renders this a secondary consideration to the patient : certainly in the laryngitis of the adult, pressure on the pomum Adami is very sensibly felt. In connexion with these changes the functions of the organ are interrupted and impaired. The usual secretion of the membrane is diminished in quantity, or perhaps ceases altogether, and hence the sen- sation of dryness or huskiness in the throat, and the peculiar solitary ringing cough that uniformly is present. The voice is also in- jured, being occasionally nearly if not altoge- ther lost, and there is difficulty of breathing accompanied by a harsh stridulous sound ; this latter being caused by the mechanical obstruc- tion to the passage of air produced either by tumefaction or by spasm. Having continued a given time, and the first stage of inflammation of the larynx if very acute is usually but short, certain results or effects are developed, which, differing in the child and the adult, require a brief separate notice for each. The acute laryngitis of the child, or croup, although generally commencing in the larynx alone, and sometimes altogether confined to it, is by no means uniformly so : on the contrary, it not only may commence in or extend to the trachea, but possibly have its origin in the bronchial cells, and pass thence upwards along the tubes. It may also perhaps not be strictly correct to arrange croup amongst the diseases that are preceded or accompanied by inflam- matory fever, for occasionally it makes its at- tack without any previous warning whatever, and a child that had retired in apparently per- fect health may arouse and alarm its attendants in the middle of the night with the sounds of that dry, harsh, and incessant cough, and that loud and stridulous respiration which afford to the practised ear the painful but unerring evi- dence of the nature of the mischief present. In either case, however, the disease hastens to its second pathological state, in which the evi- dences of increased vascularity begin to disap- pear, and are succeeded by the secretion or effusion of a viscid tenacious lymph, which, assuming the form of a membrane, has ob- i 2 116 ABNORMAL ANATOMY OF THE LARYNX. tained the name of the false or adventitious membrane of croup. This substance is of a pale yellow colour, viscid and tenacious ; more generally found in the larynx than the trachea ; seldom occupying the entire circumference of the tube ; unorganized ; incapable of becoming the medium of union between opposing sur- faces, and with a strong disposition to separate from the surface on which it was originally formed. It usually commences in the larynx, and travels downwards along the trachea; more rarely it seems to begin in the ramifications of the bronchial cells; and again, still more sel- dom is the entire of the mucous membrane attacked at once, and the adventitious mem- brane thrown out over its whole extent. Con- sidered as a pathological production, this false membrane of croup presents some curious and interesting subjects for observation, for although so generally met with that by some it has been regarded as the essential characteristic of the disease, yet perhaps it is not invariably or ne- cessarily so ; at least I have seen cases so far resembling croup in all their stages, that they could not be distinguished from it during life, in which dissection subsequently shewed the mucous membrane swollen, and soft, and pulpy, with copious submucous effusion, yet without the formation of a single flake of lymph. Possibly in the few cases of this de- scription that came under my observation, the disease had proceeded with a rapidity which proved fatal before the membrane had time to have been formed. Again, it is the only* instance of lymph being produced on a mucous surface as the result of active acute inflamma- tion. In chronic affections membranous layers of lymph are often formed, and in different situations, as in the bronchial cells and the mucous coat of the intestines, but the acute produces it alone in the structures that are the seat of croup. And lastly, it appears that this effect of inflammation is restricted to patients under twelve years of age. Mr. Ryland, in his excellent treatise on the larynx, has published a table from Bricheteau, by which it is shewn from the experience of fourteen distinguished authors, that croup " has never occurred at a later age than twelve years, and very rarely at that age." My friend, Dr. W. Stokes, con- siders the cases published as examples of croup occurring in the adult as not being inflamma- tory croup at all, but analogous to the diphthe- rite of Bretonneau, which will be shewn to be a very different disease indeed. Such is the pathological condition of the parts in the second stage of croup a condition indicated by the increased difficulty of breath- ing the pale and swollen countenance the straining eye the dilated nostril and the purple lip; by the occasional expectoration of some portions of the false membrane ; and (as hap- pens in every affection of the larynx) by severe and protracted spasms of the glottis. If the patient still continues unrelieved, the third and ' For an apparent exception to this rule, see a case published in the Dub. Journ. of Med. Science, September 1838, No. 40, vol. 14. last stage supervenes. The child still breathes with difficulty, but with increasing languor : its countenance is pale; its lip bloodless; there are generally convulsions, in one of which the fatal event may take place ; or else he sinks gradually, exhausted and worn out, and dies comatose. And we are to look for the actual and immediate cause of death not to the larynx but to the lungs and brain. No matter how much the membrane may be swollen, or how extensively the false mem- brane may have been formed, the rimais not completely closed, and the patient dies, not because there is an absolute insufficiency of air to provide for the arterial ization of the blood, but because some change has taken place in the organ by which this most important func- tion is performed. When the thorax is opened the lung does not collapse under the influence of atmospheric pressure : when the lung is cut into, it is found to be loaded with dark blood and with frothy serum, the effusion of which latter is often so abundant as nearly to fill the trachea. The brain, if examined, is found congested, and not unfrequently is there an effusion of serous fluid into its ventricles. The acute inflammation of the mucous mem- brane of the larynx bears no resemblance in the adult to that "in the child, excepting only in the agonizing difficulty of respiration and the fatality of the result, but the pathological con- ditions are different, and therefore is the disease in the adult far more manageable. I can scarcely conceive, much less describe the ex- istence of acute laryngitis to any dangerous extent in the membrane alone without the participation of the submucous tissue, in which the perilous tumefaction is generally, if not al- ways, seated ; I shall, therefore, as I have hi- therto done, consider this affection in connec- tion with its principal pathological result the formation of an oedematous effusion. Mucous membranes in every situation seem to be connected to the adjacent tissues by that species of cellular membrane termed reticular, as a provision that the courses of the canals of which they form so important a part should not be impeded by any accumulation of fat : and this reticular membrane is more or less lax according to the nature and consistence of the subjacent structure. Where mucous mem- brane is attached to bone, the nature of the connecting medium is so short and close, that in many instances it is scarcely observable, and the membrane, in addition to its own func- tions, appears to perform that of a periosteum, whilst in other situations, as in the intestine, it is so lax as to allow the organ to become dis- tended to an almost unlimited extent. The usual effect of inflammation on this reticular tissue is an effusion of a serous fluid within its cells, and the production of O3dema ; but this is of little consequence where the tissue is dense and close, and perhaps of still less where the organ is widely distensible. The larynx, however, presents an organ of a mixed character the mucous membrane is here at- tached to muscle and to ligament, and these ABNORMAL ANATOMY OF THE LARYNX. again are supported and restrained by resisting cartilages externally, so that if the submucous tissue which is here so loose as to allow the membrane to be thrown into natural folds, should become the seat of infiltration, the swelling so produced cannot take a direction outwards, but must tend to compress and close the aperture of the glottis. This is the oedema of the glottis, a formidable and too often a fatal affection, but nevertheless present- ing very considerable pathological varieties. Thus it is sometimes attended by fever, and forms only part of a more extended inflamma- tion, involving tonsils and fauces, pharynx and larynx : again, it is purely local, confined to the larynx alone, and so entirely free from any accompanying fever, that the patient only com- plains of the difficulty of breathing and the cough. It is often idiopathic, but may be produced by injury, and is a common result of swallowing caustic poisons and boding water ; nor is it in this latter respect confined to the adult, for I have thus seen the superior aper- ture of tiie glottis, in a very young child, pursed up and closed as if by the drawing of a running string. It may be situated only in a part of the larynx, the rest remaining free ; thus it is no uncommon occurrence to see only one side of the glottis puffed and swollen, and the slit-like aperture thus converted into a curve; but the most interesting because the most prac- tical illustrations of partial oedema will be found in cases published by Sir Henry Marsh, in which the disease appeared to be confined to the epiglottis alone.'* Lastly, I believe it is possible to have this oedema produced without any external evidence of inflammation. In the Museum of the School of Park-street there is a preparation shewing it as apparently occa- sioned by the vicinity of a large carcinomatous tumour. Considering the pathology of this affection, the degrees of inconvenience and of danger likely to result from it will be easily under- stood. The symptoms will be, a loss or imper- fection of voice, which is generally very well marked, the utmost effort at articulation amount- ing to no more than an indistinct whisper ; and difficulty of respiration, including cough and other signs of local irritation. The danger will probably be in proportion to the rapidity with which the effusion is formed, for life may be maintained with a wonderfully diminished supply of air to the lungs, provided the dimi- nution takes place gradually and slowly: but it may not arise solely from this cause, for here, as in every other form of laryngeal disease, spas- modic exacerbations are painfully frequent, and place the patient's life in momentary danger. Dissection, therefore, developes three different causes of death. One, the most infrequent where the patient has perished by spasm : the glottis, although swollen, is still pervious - perhaps apparently sufficiently so for the ordi- * See Dub. Journ. of Med. Science, March 1838, v. 13, no. 37. This excellent paper of Sir H. Marsh's contains many illustrations of the same tact. nary purposes of respiration ; but in order to observe the relaxation after spasm, several hours must be allowed to elapse between death and the post-mortem examination, for the bodies of those who die of laryngeal disease become ex- tremely rigid, and remain in this state a consi- derable time. A second, in which the effusion having been poured out with great rapidity, the rima is found mechanically blocked up, and immediate suffocation occasioned : in this case neither the lungs nor brain are engaged, at least not necessarily. The third is, where the dis- ease has lasted three or four days or more, the oedema has been developed but slowly, and the diminution of the supply of air been less sudden : in these cases, besides the symptoms of strangulation, others, indicative of a con- gested condition of the lung and brain, are observed during the latter periods of existence, and corresponding morbid appearances are dis- coverable after death. Very severe inflammatory affections of the mucous membrane of the larynx are unfortu- nately too frequent to admit of doubt or to create difficulty ; but a good deal of confusion has arisen from an attempt to identify them, or some of them, with croup, because an exuda- tion takes place from the surface in some re- spects resembling the adventitious membrane formed in the latter disease. One of these has been described with graphic accuracy by M. Bretonneau of Tours, by him supposed to be the same with croup, and named Diphlherite : but although the differences between these af- fections have been observed and pointed out, the name is still frequently applied (I fear) without very precise ideas attached to it. The exact disease described by Bretonneau I do not profess to have ever seen, neither have I heard of it, unless in one instance in a family in this country which lost four of its young and inte- resting members by a visitation at least bearing some resemblance to it. In hospital I have heard the name applied to some throats which I never should have thought of identifying with that described by the French writer, and I feel satisfied that the attempt to mix up different and it may be opposite diseases under one generic name has done anything but simplify the study of pathology. If, however, by asthenic croup or diphtherite is meant the peculiar local disease which accompanies the eruption of scarlatina anginosa, or which is frequently met with without any cutaneous eruption, especially in adults which is ac- companied throughout by low and typhoid fever, and is often propagable by contagion- then is the affection well known and its de- scription easy: but it bears no similitude what- ever to inflammatory croup. For besides that the constitutional affections are totally oppo- site, a circumstance of the greatest importance as influencing the progress of the respective cases, the local symptoms and appearances have marked and distinct characters. Thus the as- thenic angina is always ushered in by shivering and other precursors of fever ; the soreness of the throat is intense from the very commence- 118 ABNORMAL ANATOMY OF THE LARYNX. ment, and the part is even painful on pressure externally ; every attempt to swallow is so dreadfully distressing that patients will suffer to be half-famished rather than attempt to get down a spoonful of fluid. In attempting to examine the throat there is often great diffi- culty, because the patient either cannot, or from the pain it occasions, will not open his mouth; but if it can be seen, it is observed to be of a deep red colour, verging on purple, sometimes diffused over the surface, sometimes in patches, and even from an early period abundantly covered by a thick glairy tenacious mucus that it is difficult to wipe from it. If the disease is severe, the membrane soon be- comes sloughy : " the colour of the slough is grey or ashey : in some few instances it appears brown ; its edges are abrupt and well defined, and it is surrounded by inflammation of an intensely deep red colour. The slough is in general slow in separating, and when thrown oft' it appears to resemble a membrane of viscid lymph not unlike the adventitious substance formed in croup, and the surface underneath looks of a bright red colour, is nearly level with the adjoining parts of the membrane, and seems more like the blush of erythema than the relic of mortification. I believe that wher- ever croup has appeared to have been conta- gious it will be found that malignant scarla- tina has prevailed also; and that the occur- rence of the laryngeal or tracheal disease was occasioned by the spreading of the inflamma- tion from the fauces to the windpipe, or per- haps by the actual presence of one of these sloughing ulcers in the immediate neighbour- hood of the glottis."* Such is the description of the effects of an- gina maligna on the mucous membrane written in the year 1825, but without any suspicion on the part of the writer that it could ever be ranged by the side of the affection termed croup : for besides the essentially opposite characters of the fever in each, which by them- selves would be all-sufficient, there are the following differences. The angina maligna, diphtherite, or by what other appellation it is to be known, for with respect to it we enjoy a most happy abundance of nomenclature, com- mences always in the fauces, and when it at- tacks the windpipe, which is by no means very frequent, it does so secondarily by spreading to it; whereas croup seldom or never com- mences in the fauces unless when it appears as the sequela of some serious injury, such as the swallowing of boiling water. Cynanche ma- ligna even locally is not confined to the mucous membrane, as is evidenced by the intense pain in swallowing, the difficulty of opening the mouth, the enlargement, suppuration, and even gangrene of some of the adjacent glands; and it occasionally exhibits something like a me- tastatic transfer of disease to some important organ, such as the brain or liver. And even when recovery takes place, the difference is still remarkable: it is slow, often imperfect, Potter on the larynx and trachea, p. 17. and followed by anasarca or some similar Evi- dence of a broken and cachectic habit. This is not the place to enter more fully into the examination of these two diseases, which the reader will find admirably contrasted in -Dr. W. Stokes' work on diseases of the chest, where the angina is spoken of under the name of secondary croup. There remain two other affections of the larynx to be noticed accompanied by asthenic fever, in both of which the pathological con- dition of the submucous tissue is of great im- portance, viz. erysipelas and diffuse inflamma- tion. I believe the larynx is very seldom the primary or original seat of an erysipelatous attack, at least such has not come under my observation ; but I have not infrequently seen it seized either by the spreading of the disease from the head and face, or by some species of metastasis. The constitutional symptoms during life are of a low and typhoid character; the local, those of painful and difficult deglutition and respiration, and the termination (as far as I know) always fatal. Nor are the appear- ances after death always satisfactory, for, as in other cases of erysipelas, the tumefaction often subsides and the colour fades very soon after death. In most instances, however, we find the mucous membrane of a pale yellow colour and apparently greatly thickened : the sub- mucous tissue filled sometimes with serum, sometimes with a gelatinous lymph, and some- times with a sloughy and putrid matter ; the natural folds of the organ obliterated, and the rima more or less blocked up and closed by the thickening and tumefaction of the adjacent parts. But one of the most curious affections to which the larynx is liable is that of diffuse in- flammation. I say " curious," because it is not necessary that the mucous membrane should be inflamed or thickened or otherwise engaged, or that there should be any remarkable swel- ling of the parts, and yet the breathing is harsh, sibilous, or croupy, as if from the presence of some mechanical obstruction. In these cases, which are always fatal, the cellular tissue is the seat of the disease, and is found filled with offensive purulent matter and flakes of unor- ganized lymph, sometimes around the la-ynx, trachea, and oesophagus, sometimes at the front of the throat, and not infrequently extending to a considerable distance down into the ante- rior mediastinum. Chronic inflammation of the mucous mem- brane of the larynx resembles in its effects a similar form of disease in other structures, ex- cept that as the aperture of the glottis is small, and its functions essential to life, the same de- gree of alteration or of disorganization cannot have place here that may occur in other situa- tions without the patient generally experiencing a degree of distress that will at least direct his attention to the subject. Still is this affection sufficiently insidious, and its progress in many instances so slow, that often irremediable mis- chief is produced before assistance is sought for : and thus it happens that we are obliged to speak of chronic inflammation, not with re- ABNORMAL ANATOMY OF THE LARYNX. 119 ference to its commencement or the early pe- riods of its progress, but to its effects or pro- ducts, which, exhibiting various forms of de- rangement and disorganization, shew to the morbid anatomist the length of time the work of destruction must have been in operation, and the extraordinary changes of shape and form and structure that may occasionally be endured consistently with the maintenance of a miserable existence. The simplest form of altered structure in the mucous membrane that I am aware of is that effected by a slow but progressive deposit (pro- bably of lymph) within its substance, which renders it firmer, thicker, and more solid ; and although this must occasion inconvenience and difficulty of respiration to a certain extent, and is troublesome from the dry cough and occa- sional spasmodic exacerbations that accompany it, yet perhaps, whilst restricted to this stage, it is seldom perilous to life. But these altera- tions of structure, particularly if neglected, are seldom quiescent, and however slow in their progress have a tendency to move forward either to a morbid or perhaps malignant change of the tissues, or to the partial removal of these by the process of ulceration. Thus, ulcers of the larynx, however heretofore overlooked by pathologists, are now found to be extremely common, and I know of nothing more diffi- cult than to subject ths numerous varieties of them to any form of classification. They cannot be arranged according to structure, for they are very seldom so superficial or so insulated as to engage the mucous membrane alone ; neither can they be classed according to the symptoms they occasion, for the suffering of the patient or even his ultimate danger does not seem entirely to depend on their extent or character. The most practically useful division of these ulcers would be as to their exciting cause if it could always be discovered ; yet even here there is so much uncertainty of symptom during life and such diversity of appearance after death as to render the subject obscure and unsatisfactory. In some instances the larynx becomes the seat of idiopathic ulceration, that is, the dis- ease seems to have been occasioned by cold or other causes of local irritation at least such is the only explanation to be offered. " Thus the laryngeal surface of the epiglottis and the in- ternal parts of the organ itself may be studded over with numerous minute aphthous ulcera- tions ; sometimes the edges are marked by a yellow line of superficial excoriation, bordered by a deep blush of inflammation; and in these cases I have always observed, during life, that great pain and difficulty of deglutition accom- panied the symptoms of dyspnoea, and often formed the most prominent feature of the case. Occasionally the ulceration is deep and foul, and spreads with an almost phagedenic de- structiveness : these sporadic sores, usually commencing above, either in the soft palate or the back of the pharynx and spreading down- wards, too often involve the destruction of the patient. Occurring as they constantly do in bad and cachectic habits, they are little under the control of medicine, and operation, how- ever it may prolong existence, scarcely holds out a hope of ultimate recovery." In other cases the ulceration seems to be sympathetic, and either precedes or follows certain affections of the lung. Thus in cases of tubercular consumption, aphonia is often a very distressing symptom, sometimes accom- panied by difficult respiration, and occasionally by painful deglutition. In these instances not only is the larynx studded over with specks of ulceration, but the trachea and bronchial tubes leading to the cavity in the lung present a similar appearance, as if the matter possessed some corrosive quality and its passage over the mucous membrane became the cause of its ulceration. These appearances have been too frequently observed not to have attracted the notice of the morbid anatomist, but still it is extremely difficult to connect them with dis- ease of the lung in the relation of cause and effect, for sometimes the loss or imperfection of voice precedes or at least is amongst the earliest symptoms of consumption, and in other instances it only becomes manifest in the very latest stages. It is easy to conceive that the presence of an ulcer in the larynx, by pro- ducing difficult breathing and occasioning a diminution of the supply of air, may deter- mine the development of an abscess in a scro- fulous lung already well disposed to such dis- ease; but when the ulceration has occurred at a late period, and the difficulty of swallowing, the aphonia, and stridulous breathing appear among the closing symptoms of consumption, it will be difficult to account for the appear- ances observed, unless by supposing them to be sympathetically produced. But of all the causes from which ulcerations of the larynx are known to proceed, some specific or constitutional taint seems to be the most influential, such as syphilis, scrofula, mer- cury, or a combination of two or more of these. As far as my own observation extends, I cannot say I have ever seen the larynx engaged in a case of venereal where no mercury had been used, but on the other hand there is scarcely any organ more likely to be attacked where the me- dicine has been imperfectly or improperly used, or in which the attack is more perilous and unmanageable. Sometimes the larynx becomes ulcerated in consequence of phagedena or other destructive form of the disease spreading down- wards from the throat or fauces, but more fre- quently is it engaged alone. The ulcers here are seldom solitary, but present several spots of ulceration, and in some cases are so extensive that the whole configuration of the organ is spoiled and lost, the epiglottis being partially or entirely removed, and the chordae vocales and ventricles carried away. The surface of this extensive ulceration is irregular, warty, and gives the appearance of uneven granulation, and there are chaps and fissures that pass deeply into the substance of the subjacent car- tilage, portions of which are removed. When the ulcers are more superficial they very often exhibit the herpetic appearance and the ten- dency to spread observed in mercurial sores, 120 ABNORMAL ANATOMY OF THE LARYNX. healing in one situation whilst fresh ones break out in the neighbourhood, and cicatrizing with a depressed surface and evident loss of sub- stance. With respect to symptoms, the loss or imperfection of voice will very much depend on the situation of the ulcers; but the diffi- culty of breathing and general distress are by no means criteria by which the extent of de- struction of parts can be estimated, for some- times there is uncommon suffering where the ulceration is extremely limited. Very fre- quently these ulcers (particularly if the epi- glottis is engaged) produce symptoms of diffi- cult deglutition, exactly resembling those of stricture of the oesophagus : but this is only during the time the sores are actually open, for, when healed, swallowing is performed with astonishing facility, even although the greater part of the epiglottis may have been carried away. But the most interesting fact in connexion with these ulcers is, that by rest and proper treatment they are susceptible of cure, and for- tunate it is that by means of operation we are enabled to afford this important organ the requi- site degree of repose. Mr. Carmichael has published two most interesting cases illustrative of this fact ; in which the patients recovered, and in which we have consequently a right to infer that the ulcerations healed. In the summer of 1838 I operated on a woman in the Meath Hospital, who had symptoms of such extensive destruction of parts as must have proved fatal, but who nevertheless recovered with a complete capability of breathing through the rima, but with nearly a total loss of voice. The healing of this kind of ulceration may be inferred from that case also, but it is proved by the following observation : " In the Museum of the School of Park-street, Dublin, is a preparation taken from a poor woman who had been an inmate of the Meath Hospital ten or eleven different times for venereal ulceration of the larynx, and finally died there quite suddenly, as if from the effects of spasm. It shews where a large por- tion of the epiglottis had been removed, the ulcer having healed by a puckered cicatrix. From below the left ventricle a longitudinal scar extended a full inch and a half down into the trachea, the contraction of which had di- minished the calibre of that part of the tube very sensibly The right ventricle was totally obliterated, and on different spots about the superior part of the trachea there were several small pale depressed cicatrices, evidently the results of former sores that had been open at different periods at which she had been in the hospital. The only ulcer that existed at the time of her death was a very small one, with ragged irregular edges, situated midway be- tween the natural position of the right ventricle and the root of the epiglottis." The softer tissues of the larynx are also occa- sionally liable to gangrene, circumscribed' con- fined to the organ itself and not exhibiting any tendency to spread. Of this I have as yet seen but one example, and that one under circum- stances that rendered it doubtful whether the disease should not be considered as sympathetic with a similar affection of the lung. It was the case of a man who died in hospital of gan- grene of the lung supervening on acute pneu- monia. Seven days before his death he was attacked with symptoms of laryngeal disease, hoarseness, with difficult and laborious breath- ing, which gradually increased until the voice was nearly lost and respiration quite stridulous. After death, besides the gangrene of the lung, a gangrenous ulcer was found, involving the chordae vocales at the left side : its surface was about the size of a shilling, and of a dirty green colour ; its edges quite sloughy, and its centre excavated to a considerable depth : the mucous membrane around highly vascular and covered with a pellicle of lymph. 3. The cartilages of the larynx are subject to very important diseases, some of which seem to be peculiar to fibro-cartilage in this particular situation, and all of which are attended with in- convenience and danger by reason of their interfering with the function of the organ. I shall commence with that which I believe to be the most frequent, the most important, and the most fatal ; indeed, when allowed to run its own course it is always destructive, and when the patient's life is preserved by art, it is with the alternative of breathing for ever afterwards through an artificial aperture. In consequence of the similarity of symptoms between this and phthisis pulmonalis, it has obtained the name of phthisis laryngea. The exact manner in which this disease com- mences and the causes that lead to its produc- tion have not yet been so accurately ascertained as to admit of no farther doubt or question ; for instance, Mr. Ryland seems to think that " in most instances it is secondary to some inflam- matory affection of the laryngeal mucous mem- brane or its subjacent tisssue," whereas I have ventured to believe that the original morbid action was set up in the cartilage itself and was proper and peculiar to it ; at the same time it must be confessed that I have seen it apparently produced by the presence of an abscess in the immediate vicinity, and I believe there can be no doubt of its being an occasional sequela of typhus fever. Theessence ofthedisease seems to be a change of structure in some of the cartilages, followed by the death and disorganization of the newly formed material, and an attempt at its removal by abscess and ulceration. Thus on a post-mortem examination of one of these cases an abscess is always found in the situation of some of the cartilages very generally of the broad posterior part of the cricoid : and this abscess has burst by one or more openings, one of them being very frequently just behind and above the rima. On cutting into the cavity of the abscess, besides the matter, which is green- ish, putrid, and abominably fetid, particles of a grey or white earthy material are found, and there are always portions of bone, thin, ragged at the edges, white and perfectly dead. When the disease has so far progressed, there is always other and more extensive mischief; the exterior parts in the neighbourood are swelled and thick- ened, the mucous membrane ulcerated ; the arytenoid cartilages often detached ; and the ABNORMAL ANATOMY OF THE LARYNX. 121 epiglottis, in every case that I have seen, more or less removed by ulceration. The whole con- figuration of the organ is lost or spoiled, and scarcely bears a resemblance to the natural shape and appearance of a healthy larynx. We cannot even form a conjecture of the causes that occasion this formidable disease, or of the circumstances that dispose to its production. At some time beyond the middle period of life the cartilages of the larynx, except the epiglottis, and often of the trachea also, become converted into bone, and from the circumstance of carious bone being so constantly found in these ab- scesses, it would appear that it is either during the process of ossification or immediately after- wards that the disease commences. I have always imagined that it was at the former of these periods, and that the affection was pro- duced by some imperfection or irregularity in, or deviation from, the ordinary and natural pro- cess in a word, that this earthy unorganized material was formed instead of healthy bone. I had once an opportunity of seeing a case which I regarded as an example of the commencement of this disease, in the person of a man who, having suffered from laryngeal symptoms for some months, suddenly died in the M eath II ospital, ap- parently from the effects of spasm. " On slitting up the larynx, the cricoid cartilage appeared to be highly vascular and organised. Its substance was internally as red as blood, and in three or four places there were specks of an earthy white substance that crackled under the knife, and was evidently of the same nature with that usually found in caries of the laryngeal cartilages." I am aware that one case can prove but little, particularly in pathological science, but oppor- tunities of seeing the incipient stages of such an affection as this must be very rare, and every case ought to be recorded that will in any man- ner tend to throw light on a disease the etiology of which is so extremely obscure. However occasioned, this earthy degeneration of the laryngeal cartilages is an extremely in- sidious disease, its approach being so gradual as scarcely to alarm the patient, and its progress slow. There is usually sore throat and difficulty of swallowing, although this latter is not neces- sarily a constant symptom; hoarseness, and at first but trirlingly impeded respiration. These inconveniences in the commencement are not such as to produce much distress; for I have known one patient suffer for three months and another nearly nine, beforeeitherapplied for relief, and in both the disease had a fatal termination. Afterwards, however, the symptoms become much more aggravated, the difficulty of breath- ing is exceedingly distressing, and there are exa- cerbations that bring the patient to the point of death by suffocation. I have already noticed one case in which dissolution took place at a very early period, and when the occurrence could only be explained t)y the suddenness and severity of the spasm. At length, as the dys- pnoea becomes extreme, the patient suddenly experiences some partial relief; his cough, which was before teasingand troublpsome,now becomes softer, and the expectoration free and copious. This latter has all the characters of purulent matter, and there are, mixed with it, particles of that white, gritty, earthy substance already described. Occasionally, pieces of the size of a pea of this unorganised substance are coughed up, and when they appear they leave very little doubt of the nature of the complaint. Towards the latter end of the disease the breathing be- comes loud and sonorous, with a whistling noise, so as to be heard at a considerable dis- tance. The cough is incessant ; the expectora- tion copious, with a peculiarly fetid gangrenous smell ; the patient's breath has this odour also, which may also be regarded as an unfavourable symptom. There is at all times convulsive struggling for breath, with occasional exacerba- tions. In most cases, but not in all, the chest becomes affected ; there is pain in some one part of it or other, with a sensation of tightness round the thorax as if the patient could not draw a full inspiration. His strength seems to give way rapidly under these symptoms ; his body becomes emaciated ; he has night sweats accompanied with excessive restlessness ; and at last he sinks exhausted in the struggle and dies. Throughout the entire progress of the dis- ease there is seldom any well-marked paroxysm of fever, although the pulse is never much under JOO ; however, this may be attributed to the constant irritation under which the patient labours. The tongue is usually clean ; the ap- petite i.'Ood in some instances ravenous ; and the general functions of the body, with the exception of respiration, seem to suffer but little. The countenance is always pale, with that sickly dirty hue that characterises hectic fever. The expression evinces great anxiety ; and this is so remarkable that patients suffering under this species of cynanche often seem to bear a strong resemblance to each other. It is now familiarly known to surgeons that even this dreadful condition is not utterly di- vested of hope, and patients in whom this dis- ease had wrought such ravages as to render the larynx quite unfit for the performance of its functions, nevertheless survived for years after an artificial opening had been practised in the trachea. Some of these patients have since died, and thus in a limited degree afforded op- portunity for examining the extent of destruc- tion produced, as well as proving the all-im- portant practical fact, that ulcerations here, how- ever extensive, are capable of being cicatrized if the organ is only left in a state of repose. In the Museum of the Royal College of Surgeons in Ireland is the larynx of a patient who lived for more than two years after having been ope- rated on by Mr. Purdon of Belfast, and the following are the appearances exhibited by the preparation. About half the epiglottis had been carried away, and the edge of the remnant is cicatrized. The space between the root of the epiglottis and the rima, rough on its sur- face, irregular and warty. The ventricles altered in shape, diminished in size, but not ob- literated. The dimensions of the rima greatly diminished. The canal of the larynx is not more than one-third of its natural size, and is lined by a thick uneven membrane, evidently 122 ABNORMAL ANATOMY OF THE LARYNX. the product of cicatrization, and the place which should have been occupied by the broad por- tion of the cricoid cartilage exhibits an empty cavity, as if that structure had been removed by absorption or some other process, and nothing deposited in its room. One of the pa- tients on whom I operated in the year 1829 died about a year since in the Fever Hospital, and the larynx was examined by the surgeon of that institution, Mr. Trant ; it presented ap- pearances so nearly similar to the above as not to require particular detail, and quite sufficient to shew that the original destruction had been such as totally to preclude the possibility of the organ ever being capable subsequently of performing the ordinary function of respi- ration. The cartilages of the larynx are also liable to mortification following on inflammation, and apparently produced by the causes that induce gangrene in other structures. I suppose this affection to be extremely rare, as I have met with but two cases, and have not heard of its being observed by others. In one of these cases a large abscess existed in front of the larynx and upper part of the trachea, in which the thyroid cartilage lay like a foreign substance entirely denuded, mortified, and abominably offensive, its appearance resembling that of wetted rotten leather. The front of the cricoid cartilage and of the two upper rings of the trachea had been removed by mortification also. The lining membrane of the larynx was thickened, corru- gated, and had a granular appearance ; part of it was ulcerated, through which the abscess had communicated with the pharynx. The remnant of this larynx is preserved in the pathological collection of the School in Park-street, and shews that at least five-eighths of the organ had been totally and entirely destroyed. It proves that such a disease must be utterly hopeless and irremediable, and that, quite independent of the constitutional derangement that must lead to its formation and accompany its progress, no chance could exist of cicatrization and subse- quent recovery. Occasionally, although I should suppose very rarely, the cartilages of the larynx are the sub- jects of an alteration of structure strongly re- sembling the ordinary product of scrofula. Of this I have seen but one specimen, for which I am indebted to the kindness of my friend Dr. Benson. December, 1838. A man, set. 39, was received into the City of Dublin Hospital, under the care of Dr. B. for the treatment of what was considered to be chronic rheumatism. It was soon discovered that the pains were not rheumatic, but most probably depended on cerebral disease. The larynx presented a firm tumour externally, and there was an almost total loss of voice. He died, and after death scrofulous tubercles were discovered in the brain. The larynx was of a healthy structure in every part except in the thyroid cartilage, the alse of which were converted into a firm scrofu- lous mass, about the size of a large chesnut on each side. The scrofulous or tubercular matter appeared to have been deposited originally in the centre of each ala. The margins and cor- nua of the cartilage were unaltered, and lh cartilaginous structure seemed to lose itself in- sensibly on the surface of the tumour. This very interesting preparation is preserved in the Museum of the Royal College of Sur- geons in Ireland. Besides these deviations from the ordinary healthy conditions of the cartilages of the la- rynx, it is certain that one at least of them pre- sents appearances of abnormal changes both of size and shape. Morbid thickening or hyper- trophy of the epiglottis, as well as its opposite state of contraction or shrivelling, have been spoken of by authors, but I have never been fully satisfied that the former of these was not rather the result of a thickened condition of the mucous membrane than of the cartilage itself, and I believe the latter never is seen unless as the consequence of previous ulceration. A de- viation from its usual shape is by no means very uncommon in this cartilage, most instances of which are trivial and unimportant, and are probably congenital ; but in some few instances the change is more remarkable. One of these has been noticed by Dr. Stokes in the chapter of his work which treats of diseases of the la- rynx and trachea, and by him it is termed the leaf-like expansion of the epiglottis. He de- scribes it thus : " This has not been described by any author, but a most remarkable preparation of the disease exists in the Museum of the School of Anatomy and Medicine in Park- street. The epiglottis is thinned and singularly elongated, and its form so altered as to repre- sent the shape of a battledore, the narrow ex- tremity being next the glottis. In the prepara- tion alluded to it is fully two inches in length, and coincides with double perforating ulcers of the ventricles. Nothing is known as to the history of the case, but I have seen more or less of a similar alteration in other cases of la- ryngeal disease." In a paper professedly devoted to abnormal anatomy, I know not whether I am warranted in noticing derangements of function, unat- tended by any lesion of structure discoverable by dissection, yet there are some of these ex- hibited by the epiglottis which seem deserving of the attention of the physiologist. The use ascribed to this cartilage of protecting the la- rynx during the process of deglutition is well known, yet observation has furnished us with examples of exceptions to this use, both posi- tively and negatively ; for, as when this valvular structure is altogether removed (by experiment in animals and by disease in man), the larynx is nevertheless often found able to protect itself, and the subject to swallow both liquidsand solids without much, and occasionally without any in- convenience, so, on the other hand, it is a fact which cannot be controverted, that the epiglottis sometimes seems to be deprived of its protec- tive sensibility, and permits the free introduction into the windpipe of substances attempted to be swallowed. This latter fact I first noticed in the case of a Wapiti deer which was bronchoto- mized by Sir Philip Crampton : it frequently discharged portions of its food through the wound, and yet after death the larynx in all its ABNORMAL ANATOMY OF THE LARYNX. 123 parts was found apparently perfect in its orga- nization. But not to rely on observations made on the inferior animal, a case soon afterwards occurred in the Richmond Surgical Hospital, of a young female wounded in the trachea rather low down in the neck. From this wound por- tions of the ingesta frequently escaped, and yet after death the larynx was found healthy, its organization complete, and no unnatural communication whatever between the oesophagus and windpipe in any part or situation what- ever. I have since had a precisely similar case under my care in the Meath Hospital. These are instances in which the epiglottis seems inert, and the larynx is left patulous and unprotected ; there are other cases in which it appears to be morbidly active, although it is difficult to ex- plain the agency by which such activity is pro- duced. In prosecuting some experiments on the subject of asphyxia, a stout middle-sized dog was let down into a brewing vat that had been emptied of the fermenting liquor about ten minutes previously; he was to all appear- ance perfectly dead in two minutes. After al- lowing the "body to remain thus for twenty minutes, it was examined : the glottis was found to be of a very pale colour, and the rima completely shut up by the close approximation of the arytenoid cartilages. The epiglottis was shut down like a lid upon a box, so as perfectly to close the superior aperture of the larynx : this latter was a curious appearance, and I know not what muscles could produce the effect, but the fact was witnessed by Dr. Hart, now one of the professors of practical anatomy in the College of Surgeons, by Dr. Young, and others. I am also ignorant as to whether a similar condition of the epiglottis obtains in men who have been suffocated by carbonic acid ; human subjects are seldom examined so soon after falling into a state of asphyxia as to allow of the immediate appearances being ob- served, and yet information on this point would be of great value in determining the suitable means for attempting resuscitation. The most difficult part of the pathology of the larynx to contend with is that which has reference to muscular organization, and unfor- tunately it is that which has been least ex- amined, or on which examination has thrown the faintest and most unsatisfactory light. Furnished with an exquisitely delicate and beautiful arrangement of muscle, the normal actions of which are exemplified in the pro- duction of the different sounds of the voice, and in giving force to the exit of the air in coughing, sneezing, &c. it would appear only reasonable to suppose that the functional de- rangements of the larynx should be accom- panied by some appreciable corresponding le- sion of its muscular apparatus ; yet such does not seem to be the case, at least not invariably, and we sometimes find the voice impaired or perhaps lost, the muscles of the organ ex- hibiting their ordinary appearance, and again remarkable and seemingly important lesions without much injury to voice or respiration. Under these circumstances we must speak of the morbid appearances that have been ob- served in the first instance, and consider the irregularities of function afterwards. The muscles of the larynx are sometimes found in a state of extraordinary develope- ment amounting almost to hypertrophy. I know not how far this may be considered to be an abnormal condition, or whether it may not be the natural result of great and constant em- ployment of the organ : reasoning from ana- logy this latter seems more probable, but dis- section has hitherto thrown no light upon the subject. They are likewise subject to atrophy or wasting, the fibres appearing thin, pale, and attenuated. Andral mentions cases of loss of voice in which he sometimes found the fibres of the thyro-arytenoid muscle wonderfully atro- phied, and sometimes separated from each other by some morbid secretion, either of pus or tubercular matter. I have been informed by Sir P. Crampton that he has seen in the Mu- seum of the Veterinary College in London, several preparations illustrative of the disease termed " roaring" in the horse, which seems to be produced by an atrophy of the arytenoid muscles. A relaxation is thus effected which allows to the arytenoid cartilages an unnatural degree of mobility. Whilst the animal is at rest or moving slowly, the current of air passes gently, and there is no " roaring;" but when he is put to greater speed and respiration becomes more hurried or more forced, the little valves are acted on, the rima is proportionably closed, the breathing becomes stridulous, and that pe- culiar noise so well known to persons conver- sant with horses is produced. Lesion of function in the muscles of the la- rynx exhibits itself in the opposite conditions of atony and spasm. Examples of the former are to be found in some cases of partial pa- ralysis where the patients become totally in- capable of uttering any sound, however in- distinct and inarticulate ; in the hoarseness and sometimes loss of voice that suddenly attacks young persons, particularly females, from ex- posure to cold and damp ; and perhaps fre- quently in the sympathetic aphonia that precedes or attends on phthisis. On the pathology of these affections morbid anatomy has thrown but little light, nor is it surprising that the subject has attracted a minor degree of attention, when it is recollected that the more severe laryngeal symptom, that of difficult respiration, is seldom or never present. I have had two cases of aphonia attended with pain and soreness in the larynx, which, under an idea that the disease was either gout or rheumatism, I treated with colchicum with apparently favourable results. I know not whether the supposition that the la- rynx may be the seat of either of these painful affections is correct or not, but I see no reason why it should enjoy so fortunate an exemption. However, although atony of the muscles of the larynx may not be attended with much peril, a spasmodic action of them is always eminently perilous, sometimes destroying life with a ra- pidity that almost precludes the possibility of assistance. There can, therefore, be few sub- jects more interesting to the practitioner, and 124 ABNORMAL ANATOMY OF THE LARYNX. although, as might be expected, the causes that produce these terrific affections have not been explained, yet it may be desirable to examine inlo the symptoms and some of the circum- stances that occasionally precede or accompany them. Spasm of the glottis is either idiopathic or symptomatic. The idiopathic occurs, as far as I know, only in children, as in the " spasmodic croup," or laryngismus stridulus, unless we also choose to include within this class the hysteric dyspnoea that occurs in young females. The symptomatic occurs as indicative of, or in connexion with, 1. The application of some deleterious sub- stance to the larynx, as carbonic acid, boiling- water, or steam. 2. The application of some irritating mate- rial, as a paiticle of salt. 3. The presence of a foreign body within the trachea or bronchial tubes. 4. The presence of a foreign body in the oesophagus. 5. The existence (occasionally) of an aneur- ism of the aorta. 6. The existence of any other disease within the larynx or trachea. Any of these latter may be present in the adult or the child indif- ferently. Few diseases have attracted more attention than the spasmodic croup of children ; few have been more accurately described as to symptoms, and in none is our pathological in- formation more deficient; a fact that may al- most be proved by the number of different names by which it has been designated. It is the asthma of infants of Millar; the cerebral croup of Pretty ; the spasm of the glottis of Marsh ; the spasmodic croup of other writers ; and the laryngismus stridulus of Mason Good and Ley. It occurs in very young children, with a peculiar difficulty of breathing, attack- ing for the most part suddenly, accompanied by a crowing sound, and oftentimes with a sus- pension of respiration for several seconds. This difficulty of respiration varies in intensity from a single crow to a more prolonged paro- xysm threatening suffocation, and terminates when in recovery by a long deep-drawn respi- ration, with a peculiar sthdulous noise; when in death, by such convulsive struggles as misjht lead, and indeed have led, to a belief that the cerebrum was engaged. Pallid and exhausted, the child falls lifeless upon the nurse's arm, and is then generally said to have died in a fit. In these cases there is no cough ; no raucal sound of voice; no continued stridulous breathing, except an occasional mucous rattle heard only while the infant sleeps be con- sidered as such ; there is no fever ; and on ex- amination after death no trace of inflammation, nor indeed any deviation from the ordinary healthy appearance of the organ, can be disco- vered. Under these circumstances, patholo- gists had no method of explaining the pheno- mena but by spasm, an irregular and invo- luntary contraction of the muscles of the larynx closing up the rima glottidis to a LM eater or k'ss extent, and in proportion to such closure in- terfering with and obstructing respiration. But what is the cause of this spasm ? Some have supposed it to have an intimate con- nexion with an hydrocephalic tendency, be- cause it has been sometimes seen in children with large heads and sluggish dispositions, and because signs of cerebral congestion have been discovered after death ; but I have seen the di- sease prove fatal to the liveliest and apparently most healthy children, and the congestion may just as well be the consequence as the cause of the closure of the glottis. Others again have referred it to the general constitutional irri- tation that proceeds from painful dentition, and doubtless cases have occurred in which the crowing respiration was relieved by successive scar.fications of the gums, according as each tooth became prominent underneath ; but this, although teaching an important practical lesson, leaves the pathological connexion between the facts in as much obscurity as ever. Accord- ing to others there is a constitutional tendency to this disease in some children, a fact which it must be conceded has been painfully exempli- fied in more families than one ; but this here- ditary disposition to disease, although abun- dantly obvious, is too imperfectly understood to be discussed with any thing approaching to pathological accuracy. Lastly, improper or un- wholesome food, indifferent clothing, a close and tainted atmosphere, and exposure to vicis- situdes of climate, have been regarded as in- fluential exciting causes, and change of circum- stances in these respects has often produced an almost magical amendment in the condition of our little patients ; but still we are at a loss to discover the immediate modus operand! of these pernicious influences, or why they should be determined to the larynx in the form of an in- voluntary spastic contraction of its muscles. Other causes have been assigned for the pro- duction of this disease, some of which are eminently deserving of attention ; at the same time it may be observed that its being attri- buted to such a number of influences shews that its real exciting cause is probably still unknown. For instance, either this disease or an affection bearing a strong resemblance to it, has been described by Dr. Kopp, and after- wards by Dr. Hirsch of Kbnigsberg, under the name of thymic asthma, and by them attri- buted to an hypertrophied condition of the thymus gland, which by its weight and volume presses on the heart, the lungs, the large arte- rial and venous vessels, and prevents the free exercise of their functions. Dr. Montgomery has published an interesting paper on this sub- ject, in which he attributes the sudden death to an enlargement of this gland, whether that arises from hypertrophy of its substance or an alteration of its structure from scrofula or other disease ; and explains how agitation or excite- ment may suddenly distend and increase the size of the organ in such a manner as to affect materially the condition of the surrounding parts. Again, in the work by Dr. Ley already referred to, a different explanation has been offered. Apparently relying on the experi- ABNORMAL ANATOMY OF THE LARYNX. 125 mental researches of Magendie and Le Gallois, lie supposes that, if the recurrent nerves are compressed to such an extent as to have their functions impaired, the glottis, under the in- fluence of the superior laryngeal branches, would become and continue fast closed. The cause of the disease then, according to him, will be found in some tumour, scrofulous or otherwise, so situated as to create an injurious degree of compression on the recurrent nerves. That an enlargement of the thymus gland may, from its situation, produce great and serious in- convenience, it would be absurd to question, and perhaps there is sufficient evidence to shew that it may occasion the symptoms and results of this very disease : but it is far from being proved that spasm of the glottis may not occur, and even prove fatal in cases where no such enlargement existed. Alterations of size, shape, and structure, even if rapid, take place gradu- ally, and their results should be gradual also, whereas this disease has been known to destroy its victim in its first and only paroxysm ; and moreover, if structural change in the gland was its sole exciting cause, it would be difficult to account for its sudden disappearance on the removal of the child to the country and its diet being changed. Whilst therefore it may not be denied that hypertrophy of the thymus can occasion the phenomena by others attributed to spasm of the glottis, there is not sufficient proof of its being the general or even frequent cause of this peculiar disease. I shall have occasion to notice the supposed consequences of pressure on the recurrent nerves hereafter. It is questionable how far spasm occasioned by the contact of noxious or irritating sub- stances can justly be termed sympathetic, for they are the results of an application of a di- rect stimulus : it is immediate in its effects, and more or less complete according to the nature or quality of the exciting cause. Death from total submersion in carbonic acid gas occurs so quickly as almost to seem instan- taneous, and the spasm entirely occludes the glottis. The mildest form of spasm seems to be that occasioned by the accidental admission of some particle of food which is usually expelled again very quickly by a cough suf- ficiently distressing but seldom dangerous: yet instances have been known of the apparently trifling occurrence of the introduction of a par- ticle of salt being attended by a fatal result. However, when spasm is, or appears to be produced by the presence of a foreign body in the oesophagus or the trachea, or by the pres- sure of an aneurismal tumour, it is evidently sympathetic, and it may be interesting to in- quire into the evidence by which such relation of cause and effect is established. I had formerly entertained the opinion that spasm of the glottis should be the consequence of some irritation applied to the larynx itself, and not external to or at a distance from it, and therefore that the presence of a foreign body in the oesophagus ought not to hold a place amongst its exciting causes. I have since, however, altered my views on the subject, and indeed, when we consider the number of cir- cumstances under which this morbid action may occur, we cannot be justified in denying it in this case in opposition to most respectable testimony. Mr. Kirby has published a case in the Dublin Hospital Reports, in which death was apparently produced by spasm of the glot- tis in consequence of the lodgment of pieces of meat and bone in the oesophagus : and Dr. Stokes saw an instance in which a piece of money was lodged in the oesophagus and where croupy breathing and other laryngeal sym- ptoms were manifestly the result. In this lat- ter instance the foreign body was not lodged in the fauces or pharynx. I have myself seen cases to corroborate the above, but it is need- less to swell this article with proofs of a patho- logical fact that will probably not be called in question. It is probably a new observation at all events it is one of great pathological interest, that spasm of the glottis may be produced by the presence of a foreign body lodged within the bronchi. In the month of May, 1836, a child was brought from the country and placed under the care of my friend Mr. Cu- sack : his father's account of the case was that he had swallowed a small pebble, was instantly seized with a violent paroxysm of cough, had croupy or sonorous breathing ever since the accident with occasional remissions and exacer- bations, but was sometimes brought to the verge of suffocation. The stethoscopic indi- cations were that the foreign body was loose and mobile within the trachea. I assisted Mr. C. in performing the operation of tracheotomy on this child ; but, although the aperture in the windpipe was made very large, no stone was expelled, and the size of the organ did not admit of the employment of any forceps with which we were furnished. Immediately on the opening into the windpipe being perfected the croupy breathing disappeared, neither was there a severe paroxysm of cough experienced afterwards, and the father, either doubting that the foreign body had ever obtained admittance, or dissatisfied at its not being removed, car- ried him off to the country contrary to the wishes and advice of his medical attendants. We afterwards heard that the little pebble had been coughed up in about three weeks after he left town, but have not been informed as to the ultimate termination of the ca^e. On the 13th of September, 1839, a child, aged three years and a half, was brought to the Meath Hospital : he had, half an hour pre- viously, swallowed a small stone, and was in- stantly seized with a violent cough which con- tinued up to the period of admission. His breathing was quite stridulous countenance expressive of great distress face and lips lived efforts at respiration hurried and gasp- ing. The left side of the chest heaved vio- lently, the right was comparatively quiet : re- spiration very weak and interrupted in the right lung, in the left loud and puerile : no dulness over either lung on percussion. I per- formed the operation of tracheotomy, but no foreign body was expelled, and yet the little patient experienced the greatest relief. The 126 REGIONS OF THE LEG. trachea was too small to allow of the intro- duction of any instrument for the extraction of the offending substance if such was there, so J merely satisfied myself with keeping the wound open, in the hope of its being coughed up. Whenever from any accident the wound in the throat became obstructed, the breathing became dreadfully oppressed, but he obtained instant relief when it was opened again and cleaned. Such were the phenomena of the case generally up to the 6th of October, when it was found that the wound had gradually closed and healed so as to leave the artificial opening very small, and on that day, in con- sequence of the increased difficulty of breath- ing, I was obliged to open up the whole wound anew. This second operation afforded im- mediate relief. On the Gth of December the wound being again nearly healed, in a despe- rate fit of coughing he expelled a small stone about half an inch long by about two lines broad, through the rima glottidis. There were many other interesting facts con- nected with this case, which I omit here, my object being only to show that the difficult re- spiration which rendered the operation neces- sary was not caused by the mechanical occlu- sion of the bronchi by the presence of the stone, but had its seat in the larynx. The child had always repose when not called upon to employ the rima in respiration, although the stone was present in one or other of the bron- chi, and in this case it was remarkable that it shifted its position, as proved by stethoscopic evidence. It is sufficiently well known that the pres- sure of an aneurism, and of course of any other tumour, on the trachea or bronchi will produce difficult respiration to such an extent as to simulate laryngitis and to place the pa- tient's life in imminent peril. This has been supposed to proceed from the mechanical ob- struction given to the passage of the air by the compression of the tumour, and I shall not deny that this cause may occasion inconveni- ence, but still may be allowed to doubt that it produces the stridulous breathing and other laryngeal symptoms at least in the majority of cases. In the month of July, 1837, I was requested by another practitioner to see a case of acute laryngitis and to operate if I deemed it necessary. The case appeared to be seriously urgent : the man seemed to be on the point of suffocation ; and having made some inquiries as to the history, and particularly as to the con- dition of the chest as ascertained by auscul- tation, I operated immediately. The relief was as marked and as decided as I had ever seen in any laryngeal affection ; and, after allowing the patient two or three hours' repose, I had him removed to the Meath Hospital, in order to be under my own immediate care. He died on the fourth day afterwards from the bursting of an aneurism of the aorta within the chest, and on examination the larynx was found in a perfectly healthy and normal condition ; yet was it evident, from the relief experienced on the opening being made below it, that the ob- struction to respiration that existed during life had been caused within this organ. Those who, with Le Gallois and Magendie, explain spasm of the glottis by a compression exer- cised^ on the recurrent nerves, may possibly consider that the aneurism in this case pro- duced such pressure, and I am not in a con- dition to deny it, because the sac was collapsed and empty, and I could not say what pressure it might have created directly or indirectly when tense and full of blood. But the sac in no situation lay in contact with the nerve, or seemed to hold any relation to it that would lead to such a conclusion. I may add, inci- dentally, that I have seen aneurismal tumours which must have implicated this nerve, in which the spasmodic difficulty of breathing did not exist, and therefore whilst I believe that spasm of the glottis may be produced in consequence of, or in connexion with, the ex- istence of some tumour compressing the trachea or bronchi, I cannot (in the present state of our knowledge) yield to the opinion that refers it so entirely to a compression of the recurrent nerve. The ligaments of the larynx are, of course, liable to disease. Thus, during life, we argue on the possibility of an abnormal state of ten- sion or relaxation, from observing certain alte- rations of the tone of voice which are thus supposed to be capable of being explained : but the most frequent morbid appearance found after death is ulceration, although there is no evidence of its ever commencing in these struc- tures. In all cases of phthisis laryngea, the ligaments suffer severely and in some are actu- ally destroyed ; for the expulsion of the ary- tenoid cartilages by coughing is no infrequent symptom of that disease, and it could not other- wise occur. I have often imagined that this ulceration of the ligaments was one cause of the difficult respiration, particularly in cases where there is a marked difference between in- spiration and expiration, by allowing to the arytenoid cartilages too great a degree of mo- bility, and permitting them to be thrown down on the rima. When the connexions between the cricoid and arytenoid cartilages are cut across posteriorly, it is easy to lay the latter down in such a manner as nearly to obliterate the rima ; and if a similar division be effected by disease, why may not these little bodies, become loose, be acted on by the current of air and shut like a valve in every act of in- spiration ? ( W. H. Porter.) LEG (REGIONS OF THE). If the importance of a part, and the interest connected with the study of its structure and its diseases, be mea- sured by the general amount of suffering through it entailed upon mankind, by its ex- treme liability to accident and injury, and by its value in the general movements and well being of the body, certainly the leg would possess claims to our consideration greater than any other portion of the system of the same extent. From the integument to the bone, and from the knee to the ankle, every part of it is the frequent subject of disease, more or less REGIONS OF THE LEG. 127 interfering with the comfort, if not with the health, of the entire system. It is composed of two bones, the tibia and fibula, with accompanying masses of muscles both before and behind, which act upon the foot. If we divide the leg into anterior, external, and posterior regions, we find in the anterior the tibialis anticus muscle, the extensor com- munis digitorum, extensor proprius pollicis, and peroneus tertius ; in the external region, the peroneus longus and brevis ; and poste- riorly, the two gastrocnemii, popliteus, plantaris, tibialis posticus, flexor longus digitorum, and flexor longus pollicis. Among these are run- ning the anterior and posterior tibial and pero- neal arteries, with their accompanying veins, nerves, and absorbents ; all these bound toge- ther, and supported by strong fascial coverings, and enveloped in the general integument. Be- tween this and the fascia just mentioned, is an important layer of cellular tissue, (fascia super- ficialis,) enclosing the two saphenae veins, major and minor, and the superficial nerves and ab- sorbents. It may be well to make some few obser- vations upon the external form and characters of the leg, before describing the deeper seated parts. The leg, comprising all that part of the lower extremity between the knee above and the ankle below, is somewhat of a conoidal tapering figure, rather flattened on its anterior and outer aspect, full and round posteriorly. This shape renders permanent compression by means of a bandage very difficult. The con- traction of the gastrocnemii, especially during walking, rarely fails in a short time to separate the turns of the bandage below, causing the lower ones to overlap each other, and producing constriction, irritation, and excoriation of the skin, above the malleoli. If this difficulty were more considered, and the importance of the bandage in diseases of the leg duly appre- ciated, we should see more pains taken in ac- quiring the art of its application than is now common; though we are happy to find that the minor operations of surgery are now beginning to receive much more attention than formerly, and to form a part of the general system of demonstrative instruction. Assuredly the ag- gregate amount of suffering relieved would be far greater by attention to these minutiae of surgery, than by the more striking, though not more important details of operations, which to the mass of practitioners can occur but seldom, if at all. The projection of the muscles at the back part of the leg, produced by the two gastro- cnemii, and known under the name of the calf, forms a characteristic peculiar to man. No inferior animal possesses it, not even the ourang outang ; and the feeble and uncertain gait of these animals, when in the erect position, at once demonstrates the value of the muscles of the calf of the leg, and that this position is natural only to man himself. The form and expression of this part of the leg varies much according to age, sex, and general habit. In infancy the gastrocnemii, in common with the developement of the whole lower extremity, are small and feeble. The upper extremities are, in early infancy, even larger than the lower ; these latter do not acquire their full growth and proportions till adult age. In the female, the general form of the leg is less marked and prominent, and more rounded than in the male, while, in this last, the leg presents every pos- sible variety of proportion, according as habits of exercise on foot, robust health, or long conti- nued sickness, has invigorated or enfeebled the muscular system at large, or this portion of it in particular. The broad and rounded surface of the calf of the leg is contracting as it de- scends, and at the lower part projects like a kind of cord, representing the tendo Achillis. In contraction, the calf shows two portions, marked out by a double fissure, which indi- cates the situation where the gastrocnemius join the soleus, the lower elevation being formed by this last muscle, which extends lower down the leg than the gastrocnemius. This projection of the soleus is in some much more marked than in others, and is indicative of considerable power when it reaches lower down, much more so than when the whole prominence of the calf is high up. In persons celebrated for pedestrian powers we have observed this projection of the soleus in a marked degree. In the anterior region of the leg, the form is considerably flatter than in the posterior, and narrows as we proceed downwards, at the lower part becoming almost round. During extension of the foot, this region is marked by longitudinal elevations and depressions, indi- cative of the situations of the muscles, and of the connecting portions of aponeurosis. An examination of these points will assist us in cutting down upon the arteries here, as the depressions mark the exact boundaries of the muscles, being produced by the aponeurotic processes, which dip between them. The integument of the anterior region, gene- rally covered with hair in man, and of a some- what dense structure, enjoys sufficient mobility to admit of wounds being united by the first intention, provided the loss of substance be not great. Not being very extensible, abscesses, tumours, &c., have great difficulty in projecting externally in front of the limb, and consequently for the most part remain more or less flattened. The posterior part of the leg has an integument more soft and elastic, and possessing fewer hairs than the anterior, particularly on the inner side. The position of the skin, with relation to the parts which it covers, occasions a marked difference in the mode of repairing the ravages of extensive ulcerations or sloughings. On the front and outer part of the leg, where the skin is somewhat stretched over the tibia and fibula, the process of cicatrization can only draw together the sound parts to a small de- gree. In consequence the healing process is slower in completion, and the cicatrix less de- pressed in proportion than when it is situated posteriorly. On the contrary, in this latter situation, the skin being stretched only over soft parts, when a considerable portion of it has been destroyed, the contractile force of the new REGIONS OF THE LEG. skin has full opportunity to exert itself, and this it does sometimes to a degree that is re- markable, acting as a sort of ligature upon the back part of the leg. We have seen a case where, by the cicatrization of an old and very extensive ulcer, the lower part of the calf of the leg, viewed in profile, had an appearance as if more than half the entire leg had been cut away.* The most dense and strung part of the integument of the leg is over the inner side of the tibia where this forms the only covering of the bone, while at the upper and back part of the leg the skin is exceedingly thin and deli- cate, and devoid of hairs. We may here re- mark, in illustration of the properties of the integuments of the leg, important in relation to surgery, that the contractile property of the skin is usefully exemplified in amputation, when, should the flap of the integument be more extensive than we desire, even to a great de- gree, we always find that in the progress of the case it contracts so much as to exhibit no re- dundance in the end ; in fact that a large quantity of integument, however unsightly, is far less to be dreaded than the opposite defect. It is not our intention here to enter minutely upon the diseases of the parts we are now de- scribing, but we cannot refrain from alluding to a state of disease of the integuments which we have never seen but in the leg, and of which we have met with no account in books. It consists in a soft elastic swelling, generally occupying the entire circumference of the leg, for the lower third or fourth of its length, though often much less. The skin over it is considerably redder than natural, and of a somewhat dark colour. It is not at all tender to the touch, but is exceedingly painful when the foot is down and in exercise ; on pressing the finger firmly upon it no pit is left, but the skin is very white until the capillaries fill again, which they do slowly. Should the skin ulce- rate, the sore is very slow in healing, and gene- rally has a brownish unhealthy look, but the state in question often lasts for years without any ulceration occurring. The disease is very indolent, neither increasing nor diminishing in extent for many years. We have not been able to trace it satisfactorily to any cause more than too much standing. All the cases observed by us have occurred in females between the ages of twenty and forty, whose employment kept them very much on foot. It appears to us to consist in a varicose state of the capillaries of the cellular tissue and inner side of the cutis. No treatment that we have employed has had anything more than a temporary effect. Pres- sure, as long as it is continued, relieves it ; but all the morbid symptoms return upon the remedy being omitted. Immediately under the skin lies the cellular tissue, which is a part of the general cellular investment of the body, and is here known as the superficial fascia of the leg. It is gene- rally pretty thick, and is easily dissected back in amputations. Placed between two solid layers, the aponeurosis and skin, it easily in- * See article CICATRIX. flames and may become the seat of extensive inflammation and abscess. When the inflam- mation has terminated in gangrene, the slough- ing process in this cellular tissue is very rapid and often very uncontroulable ; and where this destruction has occurred to considerable ex- tent, in the after process of reparation the new cellular web is so short, close, and inelastic, as to materially impede the freedom of movement in the limb. When pus has been formed, the facility which the loose texture of the super- ficial fascia offers for its spreading in all direc- tions, points out the necessity for early and free incisions through the integuments ; and even before this stage of the inflammation, and while it is in its most active state, the same bold practice offers us the best means of arresting its progress. This cellular layer is the seat of the effusion in phlegmonous erysipelas, anasarca, phlegmasia dolens, and partially so in ele- phantiasis. The distension which this tissue and the integument over it undergo in the dis- eases just mentioned, is occasionally enormous, and affords a striking contrast between the elastic properties of the natural and adventitious structures. W'hen anasarca distends a leg upon which an old cicatrix exists, the newly formed cellular web of this part is so little elastic and so little admits the fluid into its cells, that a considerable depression is seen here in the midst of the general swelling. Imbedded in this superficial fascia we find a number of veins which are various in size, none very large in the natural state, numerous, and here possessed of more surgical interest and importance than in any other superficial region of the body. They are principally ar- ranged in two sets ; one commencing about the inner ankle, and running along the inner side of the calf, terminates just below the knee by one trunk called the internal or major saphena. The other set form the saphena minor, by coining from the outer ankle, along the outer and back part of the leg, and termi- nating in the popliteal vein in the middle of the ham. This vein is superficial only in the lower two-thirds of the leg ; after this, it passes through the layers of the aponeurosis, and runs under it till its termination. This is the more ordinary course of them, but no part of the circulating system is more various than these superficial veins in their divisions and arrange- ment. These veins, by becoming varicose, frequently occasion great suffering to the pa- tient, and annoyance to the surgeon, by the difficulty of their cure. The saphena major is more liable to this state of disease than the minor; indeed few persons whose habits are to be much in the erect posture appear to attain middle age without being more or less troubled by it. The deeper seated veins, which accompany the arteries, lie imbedded among the muscles, and from them receive considerable passive support, in sustaining the weight of the column of blood above them, and still more in an active sense, when, in contracting, the muscles swell and press against their sides, and thus assist in forcing onwards their contents. But these REGIONS OF THE LEG. superficial veins are without this important help. Their sides are supported, on one hand, by the yielding layer of the fascia and muscles, and, on the other, by the integument. When, therefore, any impediment presents itself to the free transmission of the blood through the femoral, popliteal, or iliac veins, or even by the mere weight of the ascending column of blood, in persons who stand much, it is the superficial veins that suffer most, and a perma- nently dilated state is the frequent result. The pathology of varicose veins has not re- ceived the attention which it deserves, and hence the conflicting opinions as to the precise nature of their origin ; we must even now con- fess with Delpech that the nature and causes of the disease are unknown. It is quite clear that that state of disease of the veins commonly termed varicose comprehends more than one pathological condition, and probably has more than one mode of origin. Every instance of an enlarged vein cannot be considered as a varix, unless we confound under the same denomination a condition of the vessel natural and healthy except in regard to its size, neither originating nor terminating in a morbid condi- tion, with every variety and degree of disease accompanied with enlarged capacity of the vein. \Ve have seen the veins of the abdomen en- larged so as to fulfil the office of the vena cava inferior, which was obliterated. But there was not the slightest mark of disease in these super- ficial vessels. The uterine veins, also, in preg- nancy become enlarged in a similar manner, thus answering to the call for the increased circulation of blood in the uterus. This state of the vessels has been aptly termed hyper- trophy, and the term varix has been restricted to permanently dilated states of the veins, at- tended with the accumulation of dark blood, which more or less generally becomes coagu- lated and adherent to the parietes of the vessels. Of this latter species Andral enumerates six varieties : 1st, simple dilatation without any other change, such dilatation affecting either their whole length, or occurring at intervals ; 2d, dilatation, either uniform or at intervals, with a thinned stale of the veins at the dilated points ; 3d, uniform dilatation with thickening of the venous coats ; 4th, dilatation at inter- vals with thickening of the dilated points ; 5th, dilatation, with the addition of septa within the vein, whereby the cavity is divided into little cells in which the blood lodges and coagulates ; O O 7 6th, a similar disposition combined with per- forations in the parietes of the veins, which communicate with the surrounding cellular tissue in a more or less diseased state by nume- rous small apertures. From repeated observa- tion of its practical importance we should be inclined to add to this list one other variety, viz. when the varicose state had extended into, or existed distinctly in, the capillaries of the skin. We believe that in those troublesome ulcers known as varicose we shall frequently, if not generally, find this state of the minuter veins and capillaries, and we are more inclined to attribute the pain and the obstinate character of these ulcers to the pathological condition now VOL. III. mentioned than to the mere vicinity of an en- larged vein as it passes through the superficial fascia. The causes of the diseased state in question have been variously stated, nor do opinions yet agree upon it, some attributing it to mechanical influence, and others supposing a morbid tendency. Both these causes pro- bably act in different instances, or even co- operate in the same case ; we shall now only mention in illustration of the effect produce- able by the mechanical influence of too much standing, that it is not necessary to suppose that the valves are either destroyed or even materially injured in structure to nullify their agency in supporting the column of blood above them, since ever so small a communi- cation between the two columns, the upper and the under, is sufficient to destroy all the beneficial agency of the valves as supporters of the gravitating fluid in the veins. Therefore a dilatation of the vein merely enough to draw the opposed edges of the valve ever so little apart, or even a thickening of the valves pre- venting the accurate coaptation of their edges, will be sufficient to prevent their power of support to the superincumbent column, and as far through the vein as this defective state of the valves may exist, so far will the gravi- tating column of blood be virtually unbroken and entire, and in the same proportion will the tendency to the varicose state be increased. This reasoning will explain many, probably the majority of cases where the morbid dila- tation having once begun goes on to increase rapidly by the continued operation of this ex- citing cause. That there are other causes capable of producing this state of the veins cannot be disputed ; indeed the occurrence of it in parts not likely to be affected by the up- right position, and even in several different parts of the body of the same subject, shews that there is occasionally a morbid tendency in the venous system to this particular state, which acts independently of any mechanical cause; but we believe that this predisposing cause is not necessary to the production of the disease, and that the morbid tendency, when it is met with, should be regarded rather as the exception than as the rule. In considering the causes of the disease in question, we should not lose sight of the rela- tive proportion of the deep and superficial venous circulations of the lower extremities, a proportion varying in almost every individual. In one, the superficial veins are large and nu- merous, and lie immediately under the skin ; in another, they are few and small. It is ob- vious, that in the first case the blood retained by this route bears a large proportion to that passing through the deep set, much larger than it would in the latter case. In the first in- stance, therefore, these vessels will have a greater proportional weight of blood to sustain and transmit, than in the second ; while, in those individuals who have the superficial cir- culation small, the blood is chiefly returned by the deep set, which, from circumstances before mentioned, are more equal to the task, and in such persons the diseased stnte in question K 130 REGIONS OF THE LEG. rarely occurs. This we conceive to be a ratio- nal and practical explanation of phenomena which are otherwise obscure. It seems probable that that most troublesome ulcer, the varicose, is kept up, and the difficulty of its healing produced not by the irritation occasioned by the mere vicinity of the enlarged veins, but from the actually varicose state of the capillaries of the skin at that part ; at least we have found such a state of the vessels fre- quently, if not generally, to co-exist with this species of ulcer. The depth of the cellular layer (superficial fascia) in which these veins lie should be accurately understood and borne in mind in performing the operation of passing a needle under the vein for the cure of varices, according to Velpeau's plan (a method which we have adopted with considerable success.) Should the needle be passed so deep as to reach the fascia, the inflammation would pro- bably be severe, at any rate sufficient to com- plicate needlessly the operation. The thickness of the cellular layer varies in different subjects, according as it is distended more or less with fat or with accidental effusion ; it is rarely, however, less than two lines in depth, thus affording abundance of room for the transmis- sion of the needle. The size of these veins of the leg in the healthy state is at the most not larger than a small goose-quill, but when varicose they sometimes swell to the size of the finger, and we lately saw a varicose enlargement of the saphena major a little below the knee, of the size of a large hen's egg ; the quantity of blood that may in a short time be lost from them may hence be conceived. On the anterior region the veins are few, and varices but rarely occur compara- tively. On the inner region the saphena major lies close upon the bone in part of its course, and even indents it deeply when distention has continued long. In cutting upon the vein in this situation, we must bear in mind the conti- guity of the internal saphenus nerve, whose situation, with relation to the vein, varies much, sometimes being before, sometimes behind it. We cannot, therefore, lay down any rule for its avoidance, unless it be to open the vein parallel to its length. The saphena minor has a nerve running with it, which in phlebotomy must be avoided with the same precaution as the nerve on the inner side. The two nerves found imbedded in this su- perficial layer of the leg are, 1st, the internal saphenus, which is the largest, and is passing from the inner side of the knee to the inner side of the foot, accompanying the saphena major vein; 2d, the external saphenus or com- inunicans tibialis from the tibial nerve, which runs near the saphena minor through the lower part of its course. Imbedded in the superficial fascia, we also find a set of lymphatics, principally on the inner side of the leg, receiving part of those from the sole and dorsum of the foot, while those absorbents which accompany the sa- phena minor are receiving their commence- ment entirely from the sole of the foot. All of these superficial lymphatics ascend to the inner side of the thigh, and terminate in the inguinal glands. Hence diseases of the sub- cutaneous cellular tissue of the leg exert their influence upon the superficial glands of the groin, and are not unfrequently the cause of disease in them, which, without due inquiry, might erroneously be attributed to disease of the genital organs. The aponeurosis. of the leg forms an important part of its economy. It is a dense tendinous structure, which immediately invests the mus- cles, and partly affords them origin. In conse- quence of its strength and want of elasticity, it prevents swelling in deep-seated inflamma- tions, and we are consequently obliged to divide it early and freely, particularly when suppuration already exists, and when the mat- ter would otherwise burrow among the muscles. On the anterior region it is strong, very dis- tinct, and tense. In its superior fifth, it gives attachment to the fibres of the tibialis anticus, extensor communis digitorum, and peroneus longus. Below, it is pierced by the anterior tibial and musculo-cutaneous nerves. It is attached above to the heads of the tibia and fibula, and along the crest of the tibia, stretching from this to the anterior edge of the fibula. At the upper third of the leg, it sends processes backwards between the muscles, to be attached to the bones, thus forming sheaths for the muscles, and affording to their fibres a greater extent of origin. At the lower two- thirds of the leg, the fascia is closely attached to the intermuscular tissue, but has here no septa from its own structure. At the lower third, it binds the tendons firmly down in their places, and by its transverse fibres opposite the ankle forms the anterior annular ligament of that part.* From the anterior edge of the fibula, this fascia passes over the two peronei muscles, and is again inserted on the posterior border of the bone, forming a sheath for these muscles, and dividing them from the soleus. The observations made above on the surgical treatment of purulent collections refer especi- ally to this anterior portion of the fascia of the leg, on account of its greater strength, density, and inelasticity. At the back part of the leg, the aponeurosis is a continuation of that of the ham. We may consider it as formed of two principal layers; one superficial, and the other deep. Attached to the posterior border of the fibula externally, and to the inner margin of the tibia internally, the first appears to arise from the expansion of the tendons of the sartorius, gracilis, and semi- tendinosus. Applied over the posterior surface of the calf, it is lost below in the fibre-cellular tissue surrounding the heel. This portion being thin and yielding, it allows deep-seated ab- scesses to become superficial with great facility. The second layer is a continuation of the apo- neurosis of the popliteal cavity, and descends between the two layers of muscles ; but split- ting into two, at the point where the soleus de- taches itself from the deep parts, one of its divisions follows the anterior surface of the * See ANKLE-JOINT, REGIONS OF. REGIONS OF THE LEG. 131 tendo Achillis, of which it completes the fibrous canal, formed posteriorly by the super- ficial layer; the other remains applied over the posterior surface of the deep muscles, and both arrive at the heel. In its inferior third, this aponeurosis thus circumscribes three spaces. One is filled by the tendon of the muscles of the calf. The se- cond incloses the flexor muscles of the toes, and the vessels. The third, which separates the two others, lies between the tendo Achillis and the posterior surface of the last-named muscles. The latter is remarkable, from being filled with fat and fibrous filaments, interlaced in various directions.* We have, for convenience of description, de- tailed the anatomy of the superficial parts of the leg, without particular reference to the re- gional divisions, which become more defined, distinct, and practical as we investigate the re- lations of the deeper seated parts, and to which we shall therefore now limit ourselves. In the anterior region, comprising all those muscles which rest upon the tibio-fibular fossa, we find, on dissecting the fascia from the upper part, only two muscles exposed, viz. the tibialis anticus and extensor communis digitorum. Lower down, we see in addition the extensor proprius pollicis coming out between the two last, and theperoneus tertius a slip of the outer side of the extensor communis. These four are, as it were, bound down in a canal, formed anteriorly by the aponeurosis, posteriorly by the tibia, fibula, and interosseous ligament. The direction of the tibialis anticus, its size, and boundaries should be borne in mind, as these form the surest guide for cutting down upon the anterior tibial artery. This muscle is of a prismatic form, tapering downwards, and its outer edge is indicated externally by a sulcus in the integuments made more apparent by extension of the foot. It is found more ac- curately by tracing a line from the middle of the space between the crest of the tibia and the fibula to the middle of the instep ; and here, between this muscle and the extensor communis, the artery runs. The external mus- cles are the peronei longus and brevis ; they are enveloped in a sheath of the aponeurosis, and are applied, for some extent, to the exter- nal surface of the fibula. They are completely separated from the extensors and from all the muscles of the posterior region by the two apo- neurotic septa attached to the anterior and posterior edges of the bone. The adherence of the muscular fibres continuing until just above the outer malleolus, a transverse section, in the two superior thirds, does not entirely destroy their action upon the foot, while, lower down, it would render abduction almost impossible. We have not heard of an instance of the entire rupture of any of these muscles, nor is it an accident likely to occur, as they are not, from their situation, likely to be called upon for any very great exertion of power; but these muscles are occasionally liable to the accidental rupture * See Velpeau's Anatomy of Regions, translated by Hancock. of some of their fibres, a circumstance attended with much more pain and distress in moving than the apparently slight nature of the accident might lead us to expect. We have had lately a case of this kind under our care, where the suffering and the injury to the movements of the foot were so great as at first to lead us to suspect a much more serious extent of injury than really existed. It was occasioned by at- tempting to push along a sack of corn with both knees, both feet being on the ground, and the heels raised, while the upper part of the sack was held in the arms. The only artery of importance in this region is the anterior tibial. It commences from the trunk of the popliteal nearly at right angles, traverses the opening in the upper part of the interosseous ligament, close to the neck of the fibula, and below the head of the tibia. The angular curve which the artery makes at this part of its course, according to M. Kibes, ac- counts for the great retraction of it after ampu- tation of the leg.* It descends upon the inter- osseous ligament, in the direction of a line drawn from the middle of the space between the head of the fibula and the crest of the tibia, to the middle of the instep. Through the upper part of its course it lies upon the in- teiosseous ligament; as it descends it gradually advances upon the tibia, and runs upon the anterior surface of this bone through its lower third. It is found at the upper third of the leg, between the tibialis anticus and extensor communis digitorum; in the middle third, its course is between the tibialis anticus and the extensor longus pollicis, and about four inches above the ankle-joint it passes obliquely under the tendon of this last muscle, and then is found between its tendon and that of the ex- tensor communis. It runs between two veins through its whole course. The nerve is on its outer side above ; in front in the middle; and internal below. An extensible but resistant cellular sheath unites the whole. It is evident, that in the upper part of its course the artery will be found much deeper than at the lower, when it is lying among the tendons, but in the living subject the natural state of tension of the muscles keeps these tendons more elevated than after death, and we shall consequently find the artery, even in this situation, deeper than from dissection we might have been led to an- ticipate. The surgeon will find little difficulty in discovering this artery when it is required to be tied. The marks for his guidance are clear, and the situation of the vessel on the whole pretty uniform ; but owing to the depth of its situation above, and to the immediate vicinity of the veins and nerve, some difficulty will be experienced in excluding these from the liga- ture. The only branch from it of any surgical importance is the recurrent tibial. This arises just after the trunk has passed through the in- terosseous ligament, and passes upwaids in nu- merous branches to the parts below and to the outer side of the knee-joint, anastomosing freely with the inferior external articular artery. These * See Velpeau's Anatomy of Regions, p. 473. K 2 132 REGIONS OF THE LEG. anastomoses form an important part of that system of collateral circulation by which the stream of blood is continued to the leg and foot, after the obliteration of the popliteal artery. The anterior tibial artery may require to be tied in case of wound or aneurism. In wounds of the dorsal artery of the foot, it may be advi- sable to put a ligature at the lower third of the leg, when the anterior tibial is running between the tendons. Its course may be here ascer- tained by feeling its pulsation, or by observing the line of the tendon of the extensor proprius pollicis, on the fibular side of which it here lies. When about to tie it higher up, the incision in the integuments and fascia must be the more free in proportion as it is nearer the knee ; and it may sometimes be advisable even to divide some of the fibres of the fascia transversely, to permit more freely the retraction of the muscu- lar sides of the cut. In dissection, we so easily separate the inuscles and expose the artery, that we may underrate the difficulty attending the operation of tying it. The depth at which it lies in this part, the constant contraction of the muscles, and the difficulty of retracting the sides of the incision, occasioned by the strong aponeuroses, all constitute considerable obsta- cles to the operation. This artery was subcu- taneous in a case related by Pelletan, and is occasionally very small indeed, or even abso- lutely wanting. The first anomaly we have se- veral times seen in dissection, and an instance of the latter is related by Huguier.* In these cases a large branch of the peroneal, which had passed through the interosseous ligament a little above the ankle-joint, supplied the place of the lower part of the artery. In a case which was met with by Velpeau, he found this artery not perforating the interosseous ligament at all, but winding round the fibula just below the head of this bone, and in company with the musculo-cutaneous nerve.f The artery is accompanied by two veins, one placed on each side, throughout its course. The anterior tibial nerve, which is a branch from the peroneal, runs on the fibular side of the artery first, and then obliquely crosses it, sometimes again passing outwards, towards the lower part of the leg. The deep-seated lym- phatics following the course of the vessels, deep-seated disease of the front of the leg may produce alteration of the glands of the ham. A lymphatic gland is found in front of the an- terior tibial vessels, a little below the opening of the interosseous ligament through which the vessels pass. In the posterior region of the leg the mus- cles are arranged in two distinct layers, the superficial, composed of the gastrocnemius, soleus, and plantaris ; the deep, of the popli- teus, the tibialis posticus, the flexor communis digitorum, and flexor longus pollicis. The gastrocnemius becomes tendinous, considerably higher in the calf than the soleus, sending off its broad thin tendon about the middle of the leg, to unite with that of the soleus, about the junction of its middle and lower thirds. The soleus, beginning its origin lower than the last muscle, from the bones of the leg, con- tinues its muscular fibres lower in proportion, in this respect varying considerably in different subjects. These two muscles, arising above by their distinct heads, and having but one insertion below, form in fact but one muscle, which Meckel has named the triceps surce. Their common tendon is of a strength proportioned to that of the muscles themselves, and is therefore exceedingly powerful. Notwithstand- ing; the combined action of the muscles is occa- sionally too much for the tendon, and in leap- ing, dancing, or other similar movements, it is sometimes ruptured. After this accident, the difficulty of cure results, not so much from the injury done to the tendon itself, as from the difficulty of bringing the two ends into apposi- tion. In fact, complete union never occurs, the utmost extension of the foot never bringing the lower portion so high as the upper is re- tracted by the muscles. The union, however, which is of a cellular structure, becomes suffi- ciently strong to be perfectly serviceable. Boyer speaks of a partial rupture of the tendo Achillis, and describes with precision the symp- toms, but we apprehend this form of the acci- dent is very rare.* The pathology of club- foot, which has only of late years been clearly understood, shows that permanent retraction of the muscles of the calf, either primary or se- condary, is its most frequent cause, and the division of the tendo Achillis and the other tendons of this part has in consequence been resorted to with great success.f The plan of operating which our experience leads us to prefer, is to insert a sharp-pointed bistoury through the skin, and pass it behind the tendon with its flat side towards it, till having reached its farther side, the edge is turned, and the tendon is divided in the withdrawal, without more division of the skin than the mere punc- ture. If the tendon is kept tense during the operation by the forcible flexion of the foot, and is not quite divided at one stroke, the undivided tendinous fibres are pulled and stretched, and partially torn from their lateral attachments, which occasions a sort of hissing noise, which is not heard when the force is not applied, till after the entire division of the tendon. The union here takes place in the same manner as in rupture of the tendon, but the treatment proceeds upon a somewhat diffe- rent principle, since it is in this latter case the intention to keep the divided ends apart, and the foot is therefore placed at right angles, while, in the ruptured tendon, the foot is ex- tended, in order to approximate the ends as much as possible. The extreme contraction of the muscle, in club-foot, leaves no possibility of further retraction of the upper part of the 137. : See Velpeau's Anatomy of Regions, p. 474. See Velpeau's Mcdecine Operatoire, torn. iii. * See Uoyt .95. t See Listen's Practical Surgery, p Maladies Chirurgicales, torn. ii. 154. REGIONS OF THE LEG. 133 tendon, therefore tlic whole separation, after the division, is performed by the moving of the lower part. The powerful muscles, now described, are never known to be ruptured themselves, the tendon, as we have seen, yielding first, but a partial rupture of their fibres is not very uncommon, and is indicated by the same pain- ful symptoms as were alluded to in speaking of the anterior muscles. It is worth remarking, on the great power of these muscles, that, great as is the force required, to elevate the whole body, by acting upon the heel, yet the muscles of the calf are not nearly so soon fatigued in walking as those on the front of the leg, whose labour is merely the elevation of the foot and toes, and of this every one must be sensible after unusually long exercise on foot. Between the gastrocnemius and the soleus is the plantaris tendon, a long slender slip, which, after crossing between the muscles, runs on the inner side of the tendo Achillis, to its insertion. The belly of this little muscle is under the outer head of the gastrocnemius, close to the origin of which it arises. Authors describe the symptoms attendant upon rupture of this tendon, but the diagnosis of injury to so small and deep-seated an organ must be so uncertain, that we should be much more in- clined to refer them to an injury of some of the fibres of the great muscles of the calf, es- pecially when we compare the power of the plantaris with that of its tendon, the passive strength of the latter appearing greatly superior to the active force of the former.* Between the lower part of the tendo Achillis and the tendons of the deep layer of muscles, there is a considerable layer of cellular tissue, con- taining fat, and this is often the seat of trouble- some chronic inflammation; and if suppuration follows, the abscess is often very difficult of healing, from the constant movement of the tendon, and the result is a troublesome sinuous ulcer, which can only be healed by keeping the foot entirely at rest. The deep muscles, bound down in the pos- terior interosseal space, by the inter-muscular layer of the aponeurosis, are found lying in this order; the flexor digitorum communis, placed innermost, upon the back of the tibia; the flexor longus pollicis, on the fibula, and the tibialis posticus between them, and partly con- cealed by them. Upon this last muscle are situated the posterior tibial vessels and nerves. As they all of them have to pass nearly behind the inner ankle, the two outermost are gradu- ally approaching to the flexor communis, as they descend, till they are nearly in contact one with the other. As all these tendons, either primarily or secondarily, act upon the ankle- joint, their action is retained after rupture or division of the tendo Achillis, so that the power of extension of the foot still remains, though in a feeble degree. The arteries of this region are the posterior tibia! and peroneal, and are given off from the termination of the popliteal. The anterior ti- Src Dictiounaire des Sciences Medicales, ar- ticle Jambc. bial also has here a course of a few lines, from its origin, till it perforates the interosseous liga- ment. The posterior tibial maybe considered as the continuation of the trunk of the popliteal. It commences about an inch below the origin of the anterior tibial, and where the popliteal divides into this artery and the peroneal. The course of the posterior tibial may be defined by a line drawn from the middle of the ham, to a spot half an inch behind the inner mal- leolus. In this course it is accompanied by two veins, one on either side, also by the poste- rior tibial nerve ; in the upper part of the leg, this nerve lies to the inner or tibial side of the artery ; it soon, however, passes over it, and inferiorly it lies to its outer or fibular side. The posterior tibial artery is covered, in the upper and middle thirds of the leg, by the gas- trocnemius and soleus muscles, but in the lower third only by the integuments, and by the su- perficial and deep fasciae of the leg. In the upper third of its course, this artery rests upon the tibialis posticus muscle, in the middle third upon the flexor digitorum communis, and in the inferior third some fat and cellular membrane separate it from the tibia, and from the internal lateral ligament of the ankle-joint. In the inferior third of the leg, the posterior tibial artery runs nearly parallel to the inner edge of the tendo Achillis ; between the os calcis and malleolus interims, it lies nearly in contact with the sheath of the flexor digitorum communis.* The only branch of surgical in- terest given off by this artery in the leg is the nutritious artery of the tibia, which comes off about its upper third, and in amputation at this part sometimes bleeds freely. In putting a ligature upon this artery, the difficulties attendant upon the operation vary according to the situation at which we seek for it. It is favourably circumstanced for opera- tion in the inferior third of its course, being covered in the two upper thirds by the muscles of the calf. It may require to be tied for a wound in the sole of the foot, or for one behind the inner ankle. In either of these cases the artery may be found and tied with facility be- hind the inner malleolus. (See ANKLE-JOINT, REGION or.) When, however, it is deemed de- sirable to tie it at the lower third of the leg, it will be readily found by an incision of from two to three inches in length, performed mid- way between the inner border of the tibia and the tendo Achillis. After the division of the integuments, the superficial fascia, and the deep fascia, the artery will be met with di- rectly under the incision. Its accompanying- veins sometimes completely conceal it ; the nerve is here on the fibular side of it. In case of secondary hemorrhage after this operation, or in case of aneurism of the pos- terior tibial artery, forming in consequence of a wound of the artery in this situation, it may be necessary either to tie this vessel higher up in the leg, or to tie the popliteal femoral artery itself; it has been deemed prudent to give the patient the chance of success from the former * See article ANKLE-JoiNT, REGION or. 134 REGIONS OF THE LEG. operation, before having recourse to so severe and hazardous a measure as that of tying the femoral or popliteal artery. The operation of tying the posterior tibial artery in the middle of the leg will be found much more difficult than either of the other situations mentioned, as this vessel here lies at such a depth from the surface, and is covered by the gastrocnemius and internal head of the solens, which in this situation is attached to the tibia. To expose the artery here, the leg should be bent, the foot extended, and both laid on the outer side. The incision must be of considerable length, not less than four inches, along the inner edge of the tibia. The integuments and fascia being divided, (care being at the same time taken to avoid the saphena vein,) the edge of the gastrocnemins muscle will be exposed ; this will be easily raised and drawn to one side. The soleus must next be divided from its attachment to the tibia, and at the bottom of this incision will be discovered some dense aponeurotic fibres, which are part of the deep fascia of the leg. The muscular fibres in the incision must now be held wide apart, and carefully sepa- rated from this deep fascia preparatory to its division, and immediately underneath this fascia lies the artery, with its accompanying veins, one on each side, with the nerve on its inner or tibial side, and here situated about an inch from the edge of the tibia. On the dead subject this operation is not attended with much difficulty ; in the living, however, the case is very different; the mus- cles are then rigid and unyielding, and when the fascia which covers them is divided, they leave their natural situation, and become much elevated, so as to make the situation of the artery appear as a deep cavity, at the bottom of which the vessel is placed. The contraction of the muscles has been found in some cases so great an impediment to the operation, as to require the transverse division of part of the muscle. The operation of cutting directly from behind, through the fibres of the gas- trocnemius, is obviously still more objection- able, from the cause just mentioned. The second terminating branch of the pop- liteal artery is the peroneal. This is situated deeply, along the posterior part of the leg, taking the direction of the fibula ; hence it is sometimes called fibular. It commences about an inch or two below the lower border of the poplitens muscle, after perforating the tibialis posticus at the commencement of its course, and descends, almost perpendicularly, towards the outer ankle. In this course, it lies close upon the fibula, between the flexor proprius pollicis and flexor digitorum communis. On reaching the lower extremity of the interos- seous ligament, it divides into two branches, the anterior and posterior peroneal, the first of which passes through the aperture at this part of the interosseous ligament, and both of these run to the outer side of the foot. This artery is so small and so deeply seated, that its wounds are rare and unimportant. Hence but little has been said of its ligature, which would be very difficult, and could only be per- formed at the middle of the external side of the leg. We should then divide the same parts as for the tibial, but on the opposite side, and as it is enveloped in the fibres of the flexor longus pollicis, we must also detach this muscle from the fibula. Each of these arteries of the posterior region is accompanied by two veins, which fre- quently overlap the artery so as to conceal it from view, in the operation of securing it; they are also so adherent to its coats as to occa- sion some difficulty in separating them, so as to avoid including them in the ligature, parti- cularly where the artery, as in the present in- stance, is deep-seated. The best mode of accomplishing this is to insinuate the aneu- rismal needle first on one side, and then upon the other, not attempting to bring it out on the opposite side of the artery, till, by this means, the lateral attachments are separated. The deep nerve which accompanies the posterior tibial artery is the tibial, and is of considerable size, being the continuation of the trunk of the popliteal. It is situated, at first, to the outer side of the artery, and lower down it runs nearly behind it, and so close to it, that without care it maybe injured, included in the same ligature, or even tied for that vessel. It may not be amiss here to observe on the distinctive marks by which the nerve may be recognized, when passing the ligature under the artery, that besides the most essential, the absence of pulsation, which may occur even to the artery itself from accidental causes, the inexperienced operator will find considerable assistance from the following, viz. the firm, round, cord-like feel of the nerve, while the artery has a flattened yielding feel when pressed between the finger and thumb, and the whitish, somewhat glistening, and promi- nent round appearance of the nerve, the artery having a somewhat reddish colour, and a flat- tened, thick, and riband-like appearance, as it is raised upon the aneurism needle. When the cut extremities of the two are seen toge- ther, after an amputation, of course the round open mouth of the one, and the prominent stump of the other, like a tight packet of thread cut across, are readily recognizable. The lymphatics of these deep parts accom- pany the bloodvessels, and pass to the glands of the ham ; hence diseases occurring in the parts beneath the aponeurosis of the leg exert their influence on the glands of the popliteal space. The two bones of the leg united by the interosseous ligament form an elongated fossa in front which is closed in by the aponeurosis, and is larger at the union of its two superior thirds than at its extremities. The muscles being imbedded here are difficult to cut in circular amputations, at the same time that its depth prevents the formation of a good flap. Posteriorly, they form a gutter, or fossa, larger than the preceding, but also much more shal- low, excepting at the lower part. Hence the deep muscles are easily comprehended in the REGIONS OF THE LEG. 135 flap in amputation. In the circular operation the section of the flesh, which can only be effected by passing the point of the knife transversely over the bottom of the interosseous fossae, is equally difficult in the flap method, in making the anterior flap, in consequence of the depth of the space in which the muscles are lodged. The difference of size of the two bones and the posterior relative situation of the fibula renders some precaution necessary in dividing them with the saw. The foot must be turned in, so as to bring the fibula a little forward, and care must be taken to commence the section upon the tibia as being the longest and strongest, but to finish the section of the fibula first, since it is too thin and mobile to support the movements of the saw without breaking at the termination. In amputation above the tubercle of the tibia, it has been held advisable to remove the head of the fibula from its joint, since this small portion of the bone is of no advantage to the stump and by its mobility may be some hindrance in the after treatment. (See KNEE-JOINT.) The small size and moveable nature of the fibula constitutes some difficulty in the treat- ment of fractures of the leg, since the appli- cation of the ordinary bandages, &c., would have a tendency to press the bone inwards against the tibia, and we not unfrequently see, in old united fractures of these bones, this deformity to have been produced, in all proba- bility, from want of due precaution in the ap- plication of bandages. The defect may be obviated by proper care, that neither the splints nor the cushions should take any bearing upon the fibula itself except at its two extremities, and great assistance may be derived from proper pressure, before and behind, upon the muscles, gently forcing them against the inter- osseous ligament and bearing outwards the bone attached to it. After amputation of the leg, the tibia pre- sents a triangular surface, having the apex for- wards. As the skin covering it is hereby in- vested with the subcutaneous layer, it may, by pressure against this projection, ulcerate, or slough, and thus expose the bone. The great means for obviating this accident is to have a good supply of integument in the flap, so that, in bringing the parts together afterwards, they may not be drawn too tight over the bone. While this rule is attended to all will go on well, whereas when the integument is left scanty, nothing can prevent unpleasant consequences. ]t may often, however, be advisable to remove with the saw the projecting angle of bone, and as a matter of precaution we generally do this, though not attaching much importance to it.* In amputating above the tuberosity of the tibia, we run the risk of opening into the knee- joint, as the synovial membrane is sometimes prolonged thus far. According to M. Lenoir the synovial cavity of the knee is continuous with that of the superior tibio-fibular articu- lation, once in four times. f There are always * See Bell's Operative Surgery, vol. ii. p. 2'2. t Sec Velpcau's Anatomy of Regions, p. 484. three principal vessels to be tied in this ope- ration : first, the anterior tibial, which is found, with its collateral nerve, close upon the inter- osseous ligament; secondly, the posterior ti- bial, in contact with the deep layer of the aponeurosis, and having its nerve to its outer side ; and, thirdly, the peroneal, which is found imbedded in the flexor longus pollicis muscle, and may be readily tied without fear of injuring any nerve. These three arteries sometimes retract so far into the flesh after amputation, that to secure the anterior tibial it is necessary to cut through the interosseous ligament to the extent of some lines. This probably arises principally from the attachment of the muscles to the whole parietes of the interosseous fossa, while the vessels, enveloped by elastic cellular tissue, retract considerably. It must be borne in mind, that in whatever situation the amputation may be performed, if it be the flap operation the arteries of the flap are much more difficult to be found and se- cured, owing to the oblique nature of the sec- tion, than where, as in the circular operation, the muscles and vessels are cut transversely through. When the amputation is just below the tu- berosity of the tibia, the nutritious artery has here sometimes a volume sufficient to require a ligature. With the exception of this last, the arteries to be tied will be nearly tiie same, in whatever part of the length of the leg the amputation is performed. The muscular branches seldom occasion much inconvenience from haemorrhage. It may not be out of place here to remark on the subject of amputations of the leg, that the division of the bones high up may often save the knee, and thus give a good bearing for a wooden leg, but that we are too often apt to act upon the principle that, in amputations below the knee, this joint must necessarily be the bearing point ; whereas we are convinced that a much more useful stump is gained by saving as much as possible of the leg, at least as far as half of its length, with the view of applying the wooden leg to the stump itself, and so preserving entirely the use of the knee- joint. We have now adopted this plan, with the most perfect success, in several instances, and always to the great comfort and satisfaction of the patient. Indeed, the loss of the limb, which is thus remedied, is really little felt, when compared with the great inconvenience of making the knee the bearing point, and thus taking away all the benefit of it as a joint. The reason why this mode of operating has not been more generally adopted, appears to us to consist in the fear that the cicatrix of the stump is ill able to bear the weight of the body in walking, when pressed between the ends of the two bones and the artificial leg. But be- sides that by the flap amputation in the middle of the leg, (the best possible situation for this operation; when practicable,) a soft cushion of muscle can be added to the integumental covering to obviate the effects of pressure, the fact is that in the application of the artificial leg to this stump, the bearing is not entirely 136 REGIONS OF THE LEG. upon the slump itself, but it is divided between this and some part of the anterior surface of the leg, generally falling most powerfully about the tubercle of the tibia. The bearing on the anterior part of the leg is so strong, that unless the precaution is taken of well padding that part of the wooden box, the pain occasioned by the pressure entirely pre- vents the use of the wooden leg ; but by the use of this precaution all inconvenience is ob- viated, and by this support to the weight of the body a valuable help is found for the pre- vention of injury to the cicatrix of the stump. The French surgeons used to recommend this mode of applying the artificial leg, but only in cases of conical stump, or at least where the integuments were from excess of inflammation after the amputation closely ad- herent to the bones.* But we have found it applicable to every case of amputation below the knee. The superiority which this wooden leg gives to amputations below the knee over all those at the ankle and through the joints of the foot is obvious. Besides saving the extra pain and risk of inflammation, it affords a much better point of support than the muti- lated foot can form. The anterior surface of the tibia being sub- cutaneous, and not covered by any artery of importance, indicates the region which should be chosen for exposing, when we would re- move a portion, trephine, extract sequestra, balls, &c. Superiorly, as its external region is only covered by the origin of thetibialis anticus muscle, it is favourable to the same operation. This consideration is the more important since the publication of the very valuable observa- tions of Sir B. Brodie on abscess in the can- cellated structure of the tibia, a disease which till then was little understood and scarcely at all described, and which, from our own expe- rience, we are inclined to think has not un fre- quently cost the patient a limb, which by a more correct knowledge of the disease might have been saved.-f The periosteum of this anterior surface is the subject of troublesome inflammation more fre- quently than that of the other parts of the bone, in consequence of its greater exposure. Com- mon inflammation of it is often productive of abscess, necrosis, &c., or in a scrofulous dia- thesis, of caries ; while syphilitic inflammation is here showing itself in the form of nodes, occasioning great trouble to the surgeon and suffering to the patient, and generally leaving some permanent thickening. These nodes, which, as we have said, generally occur on the anterior surface of the bone, are sometimes thrown out upon the external and posterior parts, and when they do thus occur are doubly embarrassing to the surgeon from their deep situation among the muscles, and from the general similarity of the symptoms to mus- cular rheumatism ; the extreme tenderness of * See Dictionnairc des Sciences Medicales, Art. Jambe. t See also some excellent practical observations on tbe subject in Liston's Elements of Practical Surgery, p. 95. the periosteal inflammation, much more acute than that of rheumatism, and the more circum- scribed nature of this tenderness, are signs which will facilitate the diagnosis, a subject, however, upon which it is not here the place to dilate. In the foetus, the tibia presents merely a slight curve anteriorly, which appears to be augmented in the adult by the weight of the body. The posterior muscles, stronger and more numerous, acting on the flexible bones, concur to the same end. Thus, in fractures, particularly from indirect causes, the angle formed by the fragments of the tibia is almost always in front, and the limb bends in the situation of the fracture. Experience proves that the two bones of the leg are more frequently broken together than singly, a fact ascribed by Boyer to the strength of the knee and ankle-joints. The direction of an oblique fracture of the tibia is generally from below upwards and from within out- wards, a circumstance due to the form of the bone. The end of the upper fragment then presents itself under the skin, at the front and main part of the leg. The most frequent situa- tion of fracture of either of the bones of the leg is at the lower third; this, in the tibia, is readily accounted for by its being here more exposed to injury and being smaller and weaker than elsewhere ; in the fibula, on the contrary, this part is not weaker, but is here placed more superficial, the upper part being completely covered and much defended by a cushion of muscle. Fractures of the tibia at its upper part are less liable to displacement than lower down on account of the greater thickness of the bone, but the vicinity to the knee-joint here increases the danger of a fracture consi- derably. In consequence of the thickness of the bone at this point, fractures here are ordi- narily transverse, while the abundance of spongy tissue causes them to unite quickly and easily. The tibia is more frequently ^broken by itself than the fibula because it alone sus- tains the whole weight of the body, while the fibula has nothing to support. In fact if the fibula is generally broken at the same time with the tibia, the injury to the fibula is but subsequent to the other, and takes place be- cause this slender bone is not capable of bear- ing the weight of the body, the impulse of ex- ternal violence, or even the action of the mus- cles, after the tibia has given way.* There is rarely much displacement, as re- gards the length of the bones, at whatever point their fractures may have occurred, unless the cause has continued to act after the solu- tion of continuity. This appears to result from the muscles being inserted over the whole of the bony surfaces. When the fibula alone has been broken, there is very little deformity resulting, as the principal support of the limb still remains, particularly if the injury has resulted from external violence. When however the cause * See Cooper's Surgical Dictionary, article Frac- ture. MUSCLES OF THE LEG. 137 of the fracture is found in a violent twist of the ankle with dislocation, the deformity occa- sioned by this state of the joint is more or less considerable, according to the degree of this displacement. (A. T. S. Dodd.) MUSCLES OF THE LEG. The muscles lying on the bones of the leg, both before and behind, are, with the exception of one, pro- perly muscles of the ankle-joint and foot, since their primary action is exclusively upon these parts. (See article FOOT, MUSCLES OF.) For the convenience, however, of description they will here be demonstrated according to their si- tuation. The muscles of the leg may be classed into anterior, external, and posterior. The anterior lying in the space between the tibia and fi- bula are four in number, consisting of tibialis anticus, extensor proprius pollicis, extensor longus digitorum, and peroneus tertius. The tibialis anticus and extensor longus alone are seen at the upper part of the leg on removing the deep fascia ; the extensor proprius pol- licis emerging from between these muscles about one-third down the leg, and the peroneus tertius shewing itself as a separate slip of the extensor longus, about the same height, and at its fibular side. 1. Tibialis (tnlicus lies upon the fibular and anterior surface of the tibia; arises, principally muscular, from the fibular side of the tibia, through its two upper thirds, from its tuber- osity and spine, and from a small portion of the interosseous ligament, from the fascia of the leg, and from an aponeurotic septum placed between it and the extensor digitorum longus. The muscle is larger above than below; its fleshy fibres converge to a strong tendon which crosses from the outside to the fore part of the tibia, passes through a distinct ring of the annular ligament near the ankle, runs over the astragalus and os naviculare, and is inserted into the upper part of the os cuneiforme in- ternum, and base of the metatarsal bone of the great toe. The insertion of the tendon is con- cealed in part by the adductor and flexor brevis of the great toe. Between the tendon of this muscle and the os cuneiforme we find a small bursa mucosa. This muscle is covered in front by the fascia of the leg, to which it adheres superiorly ; behind it is in contact with the tibia and interosseous ligament, on the fibular side with the extensor digitorum communis, and extensor proprius pollicis. Its action is to flex the foot upon the leg by elevating the an- terior part of the foot. 2. Extensor longns digitorum. This mus- cle occupies the fibular side of the tibio-fi- bular fossa, as the last filled the inner side. This is a tapering muscle also; it arises ten- dinous and muscular from the fibular or outer part of the head of the tibia, from the head of the fibula, and from the anterior angle of that bone almost its whole length, and from part of the tibial side of it also ; it also takes origin from the interosseous ligament, from the fascia of the leg, and from the aponeurotic septum situated between this muscle and the last. Below the middle of the leg it splits into four tendons. These pass under the ante- rior annular ligament in one common sheath with the peroneus tertius. They then run along the dorsum of the foot, spreading as they go, and are inserted into the root of the first pha- lanx of each of the four smaller toes. To- wards their termination each of ihe tendons ex- pands into an aponeurosis, covering the upper surface of the phalanges, and this is strengthened by the tendons of the extensor brevis and gives attachment to the lumbricales and interossei. This muscle is covered in front by the fascia of the leg, the annular ligament and the in- tegument; posteriorly it rests upon the fibula, the interosseous ligament, and the tibia; exter- nally it is in relation with the peronei muscles, internally with the tibialis anticus, and extensor proprius pollicis; along its lower and fibular border lies the peroneus tertius. On the dor- sum of the foot its four tendons cross obliquely over those of the flexor brevis digitorum. Action. To extend all the joints of the four smaller toes, and to bend the ankle-joint. 3. Extensor proprius pollicis lies between the two last muscles. Its origin is hidden by them. It commences about one-third down the leg, from the smooth surface of the fibula, between the anterior and tibial angles of that bone, of which surface it occupies part, through the middle third of its length, also from the lower two-thirds of the interosseous ligament. The fleshy fibres run obliquely forward into a tendon placed at the anterior border of the muscle, which after passing beneath the an- terior annular ligament, and along the dorsum of the foot, is inserted into the bases of the first and second phalanges of the great toe. Action. To extend the great toe, and to bend the ankle. By its fibular side this muscle is in relation with the extensor digitorum communis ; by its inner side with the tibialis anticus and anterior tibial vessels. The anterior border is covered by these two muscles, as low as about the middle of the leg, and inferiorly by the anterior annular ligament, under which it passes in a separate groove, and by the integuments. The posterior border rests upon the fibula and in- terosseous ligament, and it crosses in its course over the lower end of the tibia the ankle-joint, the anterior tibial vessels, and dorsum of the foot. 4. Peroneus tertius. This, which is in fact a mere slip of the extensor digitorum com- munis, and is situated on its fibular side, is so closely connected with it at its origin that it can with difficulty be separated. It arises from the lower third of the fibula, being at- tached to the anterior border and inner surface of the bone ; also from the interosseous liga- ment, and from an aponeurosis which connects it on the outer side with the peroneus brevis. It is inserted by a flat tendon into the fibular side of the base of the metatarsal bone of the little toe. Its action is to assist in flexing the foot upon the leg. It is in contact with the fascia of the leg 138 MUSCLES OF THE LEG. nteriorly, with the fibula and interosseous ligament posteriorly, with the peronens brevis on the fibular side, and with the extensor com- munis on the tibial side. Its tendon passes in the same sheath with that of the common ex- tensor, under the annular ligament. A very slight effort of the extensor com- nnmis and extensor proprius pollicis extends the digital phalanges, and, if their action be continued, they will be made to bend the foot upon the leg. This they are enabled to do by the manner in which their line of direction is altered by the annular ligament of the ankle- joint, as it gives them all the mechanical ad- vantage of a pulley. The tibialis anticus and the peroneus tertius are the direct flexors of the foot on the leg, and if either act separately, it will give a slight inclination towards the cor- responding side, and thus the last-named muscle forms one of that important set whose action is, by elevating the outer side of the foot, to throw the weight of the body on the inner side.* In the erect position these muscles take their fixed point below, and, by drawing on the bones of the leg, keep them perpen- dicular on the foot. The external muscles of the leg are two, the peroneus longus and brevis. They occupy the whole length of the outer side of the fibula, and are placed between the extensors and flexors. 1. Peroneus longus is a long powerful muscle, arising from a small portion of the fibular side of the head of the tibia, from the upper third of the outer side of the fibula, and from the fascia of the leg and its intermuscular pro- cesses. Proceeding obliquely downwards, the fibres are attached to a strong tendon, which passes, in contact with the peroneus brevis, along a groove at the back of the outer mal- leolus, enclosed in a synovial sheath. The tendon then passes through a deep sulcus in the cuboid bone, behind the base of the meta- tarsal bone of the little toe, winding obliquely across the sole of the foot, covered by the muscles of this part, till it is inserted into the internal cuneiform bone and base of the meta- tarsal bone of the great toe. In the tendon opposite the cuboid bone, is usually found a sesamoid bone. A bursal sheath encloses it in its passage across the foot. The action of this important muscle is to assist in extending the foot upon the leg, but principally to elevate the outer side of the foot, and thus regulate the bearing of the leg so as to throw the prin- cipal part of the weight upon the great toe.f This muscle is in contact on its outer side with the fascia of the leg. Indeed this apo- neurosis almost invests it, dipping between it and the flexor behind and extensors before. The peroneus is in contact with the fibula on its inner side above, lower down it rests upon the peroneus brevis. When passing across the foot it lies close to the bones, and conse- quently is covered by all the muscles of the sole. 2. Peroneus brevis is situated at the outer * For further observations upon the action of the peronei muscles, see article FOOT, MUSCLES OF. f See also Quain's Manual of Anatomy. side of the leg, but lower down as to its at- tachments than the preceding muscle. It arises fleshy from the lower half of the outer side of the fibula to near the outer malleolus. It sends off a roundish strong tendon, which passes in the same groove behind the outer malleo- lus, and in the same synovial sheath as the pre- ceding muscle, but after passing the malleolus it has a sheath proper to itself. It is inserted into the base of the metatarsal bone of the little toe. Connected on its outer side to the peroneus longus, on the inner side to the fibula, anteriorly to the common extensor and pero- neus tertius, and posteriorly to the flexor longus pollicis. The action of these two muscles is peculiar. By the change in their direction, after turning behind the outer ankle, they are enabled to draw the foot back, and so extend it on the leg ; The penoneus tertius is on the contrary a flexor ; it lies before the fibula, and combines in this action with the tibialis anticus to assist the flexor. When, however, the three peronei act together, and without the other flexors, their combined action is to evert the sole of the foot, and thus counterbalance the effect of the feeble- ness of the outer side of the foot by trans- ferring the superincumbent weight to the inner side. This action is particularly exemplified in skaiting, but it is essential to every move- ment of ordinary progression. (See article FOOT, MUSCLES OF.) "When the foot is the fixed point, the peronei act by keeping the fibula and the whole leg steady, and thus, as in the act of standing on one foot, counter- acting the tendency of the body to fall in- wards. The posterior region of the leg comprises seven muscles, six of which are acting on the foot and toes, and one is proper to the knee- joint. We shall examine them as they are met with in dissection, and shall therefore describe them as forming two layers, superficial and deep. The first contains three muscles: 1. gas- trocnemius; 2. soleus ; 3. plantaris. 1. Gastrocnemius. This is situated imme- diately under the aponeurosis, and is a power- ful muscle, broad and flat anteriorly, and con- vex posteriorly, and forming the greater part of what is called the calf. It arises by two distinct heads from the back and upper part of the two condyles of the femur, of which the inner is the longer, and somewhat larger. These heads have between them a broad sulcus, which forms the lower part of the pop- liteal space. They unite a little below the knee-joint, in a middle tendinous line, and below the middle of the tibia send off a flat tendon which unites with the tendon of the soleus, a little above the ankle. The posterior surface is covered by the fascia of the leg ; anteriorly it rests upon the popli- teus, soleus, and plantaris, and popliteal vessels. When its heads pass over the cun- dyles of the femur, they are guarded by synovial bursre. 2. Soleus. This is the second portion of that great muscle of the leg which has been MUSCLES OF THE LEG. 139 named by Meckel the triceps sura:. It is seen immediately on raising the last muscle. It arises from two distinct situations ; first, from the upper and back part of the head of the fibula, and from the posterior surface and outer edge of that bone for some way down. Se- cond, from the oblique ridge on the posterior surface of the tibia, just below the popliteus, and from the inner edge of that bone during the middle third of its length. From these two attachments the muscle almost imme- diately forms a thick fleshy belly, which de- scends lower than the gastrocnemius before it sends off its tendon. This, which is fiat and strong, soon unites to the tendon of the gastro- cnemius to form the tendo Achillis, and is then passing to be inserted into the upper and back part of the projecting portion of the os calcis. At its insertion there is a small bursa between the upper part of the bone and the tendon. The soleus is in contact with the gastro- cnemius posteriorly ; below its fleshy fibres ap- pear on each side of the tendon of that muscle. Between its two origins the posterior tibial vessels and nerve are passing, defended from pressure by the tendinous expansion which is on the under side of the muscle, and which spreads across from tibia to fibula. This muscle is also in contact with the plantaris, the tendon of which crosses it obliquely from without to within. In front it rests upon the deep layer of muscles and upon the posterior tibial vessels. The tendo Achillis is the thickest and strongest tendon in the body ; it tapers down- wards nearly to the heel, and before its attachment expands again a little. It lies immediately under the skin, and between it and the bones is a considerable layer of cel- lular tissue containing fat. The action of the two last described muscles is to elevate the os calcis, and thereby to lift up the whole body. When this is done on one foot in the act of progression, the other is capable of being carried forward unimpeded by the irregularities of the surface. When the foot is the fixed point, the soleus by acting on the tibia and fibula fixes the leg, while the gastrocnemius fixes the femur, or by acting further, draws it backward so as to bend the knee and lower the body. 3. Plantaris. This little muscle is entirely covered by the outer head of the gastro- cnemius. It arises from the upper part of the external condyle of the femur, and from the posterior ligament of the knee-joint. Its mus- cular structure is only about two inches in length, and it sends its long slender tendon downwards and inwards, between the two great muscles of the calf, emerging from between them just where their two tendons unite; it then passes down in contact with the edge of the tendo Achillis, to be inserted into the heel at the inner side of that tendon. The action of the plantaris is to assist the great extensors of the foot, and to draw upon the capsule of the knee-joint, so as to prevent any ill effects upon that ligament from the motions of the knee-joint. It is occasionally deficient. The deep layer of muscles consists of four : 1. popliteus; 2. flexor longus digitorum ; 3. flexor longus pollicis ; 4. tibialis posticus. They lie in close contact with the bones, and the last three of them are covered by the deep fascia of the leg. This membrane is a thin expansion, dense in structure, connected on each side with the borders of the bones, and towards the ankles with the sheaths of the tendons ; and if traced along the interval between the inner ankle and the heel, it will be found to cover the vessels and to terminate at the internal annular liga- ment. Immediately underneath it we find the deep layer of muscles now under consi- deration. 1. Popliteus is situated below and behind the knee-joint, is flat and somewhat triangular, being broader below than above. Arises within the capsular ligament of the knee-joint, by a round tendon, from the under and back part of the outer condyle of the femur; ad- heres to the posterior and outer surface of the external semilunar cartilage; perforates the back part of the capsular ligament, and forms a fleshy belly which runs obliquely downwards and inwards. It is covered by a thin tendi- nous fascia from the tendon of the semi-membra- nosus ; inserted broad, thin, and fleshy into an oblique ridge on the posterior surface of the tibia, a little below its head, and into the trian- gular space above that ridge. Action, to bend the knee-joint, and when bent, to roll it so as to turn the toes inwards. 2. Flexor longus digitorum is thin and pointed at its commencement, but gradually increases, and then diminishes again as its fibres end in a tendon. Arises fleshy from the posterior flattened surface of the tibia, be- tween its internal and external angles, be- low the attachment of the soleus, and con- tinues to arise from the bone to within two or three inches of the ankle. The fibres run obliquely into a tendon, which is situated on the posterior edge of the muscle. This tendon runs in a groove of the tibia, behind the inner ankle, and then passing obliquely forwards into the sole of the foot, receives in its passage a strong slip from the tendon of the flexor longus pollicis. It then divides into four tendons, which pass through the slits in the tendons of the flexor brevis digitorum, and as they run along the under surface of the toes they are bound down by strong fibrous sheaths, within which there are also little accessory ligaments assist- ing in fixing them. They are inserted into the bases of the extreme phalanges of the four lesser toes. The action of this muscle is to flex all the four smaller toes, and to assist in elevating the foot upon the toes. Previously to its division, the tendon of the flexor longus gives insertion to an accessory muscle of considerable power (flexor ucces- sorius), which connects it to the calcaneum, and materially modifies the direction of its action upon the toes. Close to the point of division, the tendons give origin to four small 140 MUSCLES OF THE LEG. muscles (lumbricales), which may also be con- sidered as accessories to the flexor longus. When passing behind the inner malleolus, this tendon is in contact with that of the tibialis posticus, which lies close to the bone. They are inclosed in separate sheaths of synovial mem- brane. In the leg this muscle is bound down by the deep fascia, and covered partly by the posterior tibial vessels which separate it from the soleus; its anterior surface rests against the tibia, and overlaps the tibialis posticus muscle ; in the foot, its tendon lies between those of the flexor longus polhcis which are above it, and the flexor brevis digitorum which lies beneath it. 3. Flexor longus pollicis is shorter but stronger than the former muscle. It is si- tuated the outermost of the three deep muscles of the leg, in contact with the fibula. It arises tendinous and fleshy from the lower half of the posterior surface and outer edge of the fibula, with the exception of the undermost portion. The fleshy fibres terminate in a tendon which passes behind the inner ankle, through a groove in the tibia ; next through a groove in the astragalus ; crosses in the sole of the foot the tendon of the flexor longus digi- torum, to which it gives a slip of tendon ; passes between the t%vo heads of the flexor brevis pollicis, and then runs in a sheath of tendinous structure which binds it to the under surface of the phalanx, and is inserted into the base of the last phalanx of the great toe. The relations of this muscle in the leg are, pos- teriorly it is covered by the deep fascia, which separates it from the soleus; anteriorly it is in contact with the fibula, and overlaps the tibialis posticus muscle and the peroneal ar- tery. Its connections in the foot have been explained above. The action of the flexor longus pollicis is not confined to the great toe ; by means of the slip of tendon, which it gives to the flexor longus digitorum, it acts also upon all the toes, and secondarily upon the foot itself, assisting powerfully in the elevation of the heel in progression. But the mode of action of this muscle, and its complicated rela- tions with the other muscles of the foot, are too curious to be passed over with a slight ex- amination ; in fact, we think it may clearly be shewn that there is here one of the most curious and beautiful arrangements and successions of muscular action to be met with in the whole system. ^\ e have elsewhere shewn that, from the peculiar form of the foot, the action of the peroneus longus is essential to transmit the burden of progression from the weaker to the stronger side of the foot. (See article FOOT, MUSCLES OF.) Let us now follow on the pro- gress of the foot in the act of walking, and we shall readily perceive the succession of action of its different parts, and the functions which each muscle performs. It is evident that the smaller toes being shorter than the large one, and nearer to the heel, they will, in the act of elevating the heel and propelling forward the body, come to their bearing on the ground somewhat before the great toe, their action being, in fact, by the breadth of base which they give to steady the onward progress of the body, and to deliver over accurately and se- curely the weight to the great toe, the main organ of propulsion of the body. In order to accomplish this to the best effect, it is neces- sary that the succession of actions should be accurate and complete, and that the muscles of the smaller toes should exert themselves be- fore that of the great toe. To this end the flexor longus pollicis gives a slip to the flexor of the toes, and by the commencement of its action, which merely firmly plants the great toe against the ground, rouses the muscles of the other toes, assisting them to complete their part of the process, while its own labour continues and is at its height when theirs is necessarily accomplished and at an end. Thus, by a beautiful combination and series of actions, the powerful effort of the great extensors of the foot is controlled and guided to its proper end, first by the peronei, next by the flexors of the smaller toes, assisted by the long flexor of the great toe ; and the body propelled onwards and balanced on this toe, the action is com- pleted by the further effort of this one power- ful muscle. The economy of muscular power is here not less striking than the combination of action, for the flexor longus pollicis being inserted into the last phalanx of the great toe, its own proper action is not called for till after the muscles of the other toes have performed their part; this muscle, therefore, considerably the most powerful of all this deep layer, were it not for the simple expedient of the slip of communication to the other flexors, would be comparatively useless until the last moment of the propulsion onwards of the body. But now it lends its powerful assistance to the weaker muscles previous to its own peculiar effort, and when all its power is called for, the collateral demand has ceased. 4. Tibialis posticus is situated on the back of the leg between the last-named muscles. It arises fleshy from the posterior surface both of the tibia and fibula, immediately below the upper articulations of these bones with each other. Between the two portions of this at- tachment is an angular opening through which the anterior tibial vessels are transmitted. The muscle also arises from the whole interosseous ligament ; from the angles of the bones to which that ligament is attached, and from two- thirds of the flat posterior surface of the fi- bula. The fibres run obliquely towards a round tendon, which passes behind the inner ankle, through a groove in the tibia. It is here situated close to the bone enclosed in a sepa- rate synovial sheath. It is inserted into the tubercle on the plantar surface of the os navi- culare, sending tendinous filaments to most of the other bones of the tarsus, and to the meta- tarsal bones of the second and middle toes. This muscle is covered at the lower part of its origin by the flexor longus digitorum and flexor longus pollicis, and cannot be seen till those muscles are separated. But superiorly it is covered by the soleus only, and here the poste- rior tibial vessels rest upon it. Its anterior surface is in contact with the interosseous ligu- LIKE. 141 ment, the tibia and fibula. Its tendon runs close to the inner ankle and tarsal bones, and where it slides under the astragalus, is thick- ened by a cartilaginous or bony deposit within its fibres, analogous in force and use to the sesamoid bones in other situations. Its action is to extend the foot upon the leg, and to turn the sole of the foot inwards. (A. T. S. Dodd.) LIFE. Few abstract terras have been em- ployed in a greater variety of significations, or more frequently without any definite meaning at all, than the one now to be considered. And there is none regarding which it is more essential to possess correct ideas, in order to attain the fundamental truths of physiological science. The prevalence of what we deem very erroneous notions on this subject, will oblige us to follow a different plan in its treat- ment, from that which we should have adopted if our duty had been merely to give an expo- sition of the present state of our knowledge respecting it. We shall commence by offering a short statement of our own views, in order that we may, in the brief historical summary which it vvill be proper to include in this ar- ticle, more concisely indicate what we regard as the errors and inconsistencies of the prin- cipal theories which have obtained credit at various times. We shall subsequently con- sider more in detail some of the questions which require fuller discussion. I. GENERAL VIEWS. We shall define LIFE to be the state of action peculiar to an or- ganised bod)/ or organism. This state com- mences with the first production of the germ; it is manifested in the phenomena of growth and reproduction ; and it terminates in the death of the organised structure, when its component parts are disintegrated, more or less completely, by the operation of the com- mon laws of matter. This definition differs but little from that given in many physiological works " Life is the sum of the actions of an organised being;" and we apprehend that we are more in accordance with the common usage of the term, in employing it to designate rather the state or condition of the being exhibiting those actions, than the actions themselves. In this sense alone it is properly contrary to Death, the condition of an organised body in which not only have its peculiar actions ceased, but its distinguishing properties been abolished (see DEATH); and it is then also contradistin- guished from dormant vitality, a state fre- quently observed, in which living actions are suspended, but the vital properties of the or- ganism retained, so as to be capable of again exhibiting them when the requisite conditions are supplied. Life or vital activity, then, manifests itself to us in a great variety of ways, in all those phe- nomena, in short, which it is the province of the physiologist to consider. The changes ex- hibited by any one living being, in its normal condition at least, have one manifest tendency, the preservation of its existence as a perfect structure ; by these it is enabled to counteract the ever-operating influence of chemical and physical laws, and to resist, to a greater or less extent, the injurious effects of external agen- cies. The first inquiiy, then, which we have to make, in the inductive study of physiology, is into the conditions of these phenomena; and as in this process we follow precisely the same track as that over which the physical philo- sopher has already passed, we may advantage- ously avail ourselves of his guidance in it. In seeking to establish the laws by which the universe is governed, or, in other words, to obtain general expressions of the conditions under which its changes take place, the en- quirer first collects, by observation or expe- riment,* a sufficient number of instances having an obvious relation to one another, with the view of determining the circumstances com- mon to all. The facility with which this pro- cess is performed will obviously depend upon the simplicity of the phenomena, and the rea- diness with which they admit of comparison. Where their antecedents are uniformly the same, they only need to be associated a suf- ficient number of times, for the mind to be satisfied of the constancy of the relation ; and the general law of the effects is easily deduced. Thus, the law of gravitation is ascertained by the comparison of a number of corresponding but not identical phenomena; and the nume- rical ratio is established which governs the attracting force. To extend the application of this law, however, to phenomena that seemed beyond its pale, required the almost super- human genius of a Newton; but the idea, once conceived, was easily carried out when the re- quisite data were attained. But what is the nature of the law of which we have just spo- ken as regulating the attractive force? It is simply an expression of the property with which the Creator has endowed all forms of matter, that its masses shall attract or tend to approach each other in a degree which varies in a certain ratio to their mass and distance. This property, it must be recollected, is only assumed to exist, as the common cause of the actions constantly occurring under our notice. If none of these actions were witnessed by man, -if, for example, but one mass of matter existed in the universe, it might be endowed with this and every other property which we are accustomed to regard as essential to matter; and yet, from gravitation never being called into action, the mind would remain ignorant of the attribute. Such a common cause, the conditions of whose action are so simple and uniform that we can account for, and even predict, by a process of deduction, all the phenomena which it can operate to produce, may be regarded for a time as an ultimate fact. It may still, how- ever, be capable of union with other facts of a * For the proper distinction between these modes of research, and their respective applications to physiology, see Brit, and For. Med. Review, April 1838, pp. 320 e t seq. 142 LIFE. similar order, under a still more comprehen- sive expression.* But it is not in every de- partment of science that the same facility in the attainment of general laws exists. Where the phenomena are of such a complex nature that the operation of the real cause is, as it were, masked by the influence of concurrent conditions, or where (as often happens in phy- siology) the effects of the same apparent cause are totally different according to the instru- ments through which it operates, it is obvious that there will be great difficulty in the first stage of the inductive process that of the clas- sification of phenomena, so great, indeed, that it may be regarded as one of the principal obstacles to the advancement of those branches of science in which it presents itself. Of all the branches of physical science, that of me- teorology is the most obscure and apparently uncertain, and bears most resemblance to phy- siology. The changes which it concerns are daily and hourly occurring under our observation ; and the general laws which govern them are tolerably well ascertained ; yet the mode in which their actions are com- bined is so peculiar, as hitherto to have baffled the most persevering and penetrating enquirers, in their attempts to explain or predict their operation. But no one thence feels justified in assuming the existence of any new or un- known cause, capable of controlling or sub- verting the influence of the rest ; and such a proceeding would not be justifiable, until all their possible modes of action have been ascer- tained and put aside, leaving certain residual phenomena not otherwise to be accounted for. The peculiar difficulties which beset the in- vestigation of the laws of vital action have greatly retarded our acquaintance with them, and have even led to the belief that the induc- tive process is not applicable to them. These difficulties have arisen, in the first place, from the obstacles in the way of the collection of phenomena ; secondly, from the peculiarly com- plex nature of these phenomena ; and, thirdly, from the vague hypotheses which have pre- vented them from being classed as simple facts on which generalisations are to be erected, or effects whose sources are to be ascertained, but which have clothed them in the delusive aspect of laws or causes. Until, therefore, the prin- ciples of philosophical induction are thoroughly understood, the peculiar combinations in which vital phenomena present themselves to our notice, their apparent dissimilarity from the changes which we witness in the world around, and their obvious adaptation to particular ends, might lead us astray into the labyrinth of un- profitable speculation with regard to the pre- siding agencies by which they are governed ; and the retrospective view which we shall pre- sently take will afford many examples of this error, even in recent times, and will in fact show that the legitimate objects of investiga- * Such would seem to be the tendency of certain recent speculations in regard to gravitation, mole- cular and electrical attraction, and chemical affinity. tion, and the true mode of pursuing them, are only now beginning to be understood. When we observe the circumstances under which vital actions occur, we perceive that at least two conditions are required for their pro- duction. The first is a structure in that pecu- liar state which is termed organised (see OR- GANISATION); the second is a stimulus of some kind fitted to act upon it. Now this is no more than what we observe in the world around, where every action involves two con- ditions of a corresponding character. When water is changed into steam, for example, it is by the stimulus of heat. When a stone falls to the ground, it is by the attraction which the mass of the earth exercises over its own. The difference consists in the peculiarity of the actions exhibited by living beings, which are not identical with those elsewhere presented to us, and which we cannot imitate by any phy- sical or chemical operations. Whilst the me- chanical philosopher, then, refers to the pro- perty of gravitation as the cause of the effect just mentioned, the physiologist refers to the capability of exhibiting vital actions, when excited by certain stimuli, as the property of the tissue which manifests them. Thus, when he witnesses the contraction of a muscle, under the stimulus of innervation or of galvanism, Sec. he regards the effect as due to a property of contractility inherent in the muscle, and standing in precisely the same relation to its organic structure, as gravity to matter in ge- neral. So far, however, the advance in our in- quiry is more apparent than real ; since it may fairly be said that, to speak of contractility as the character of a body exhibiting contractions, is merely a change in words without absolute gain. But, having done this, we are led to inquire the conditions under which this con- tractility operates ; and to analyse a number of phenomena apparently dissimilar, so as to at- tain the general law of its action. In this man- ner we proceed in regard to other classes of phenomena; and we shall thus acquire (when our data are sufficiently precise and extensive) a knowledge of the properties of all the tissues or organised structures which compose the living body, and of the phenomena which their single or combined operation will pro- duce, under the influence of their respective stimuli. But the physiologist will not stop here. He will seek to inquire to what these properties are due, which are so different from anything exhibited by the same matter before it had be- come a part of the organised system. And, if he consider the matter in all its bearings, with a total dismissal of prejudice, he will be unable, we think, to arrive at any other conclu- sion than that they are due to the act of organi- sation, which, in combining the inorganic ele- ments into new compounds, and giving them a peculiar structure, calls out or developes in them properties which had previously existed in a dormant state, but required these circum- stances for their manifestation. To this ques- tion, however, we shall presently return, when LIFE. 143 considering other views which have been en- tertained respecting it. We shall now take a retrospective glance at the II. HISTORY or OPINIONS. In the earlier ages of the world, before the true method of philosophising on any subject was under- stood, it was considered as a sufficient ex- planation of any phenomenon to apply to it some abstract term, expressing a vague idea of a property inherent in the body which ex- hibited it, without attempting to ascertain the conditions of its operation.* Thus, all the phenomena of the movements of the heavenly bodies were attributed to the agency of a " principle of motion," the laws of which were scarcely even sought for. In like manner, the simple optical fact that, when the sun's light passes through a hole, the bright image, if formed at a considerable distance from it, is always round, instead of imitating the figure of the aperture, was attributed by Aristotle to the " circular nature" of the sun's light; whilst the mere consideration that the rays of light travel in straight lines, would, if properly applied, have explained this pheno- menon, not only as regards the sun, but in the case of any other round luminous body placed at a sufficient distance. It is not wonderful, then, that the still more intricate nature of the phenomena exhibited by living beings, the obvious tendency of those presented by each individual towards the same end, and the se- ductive simplicity of the hypothesis, should have induced the philosophers of that age to regard all vital actions as the immediate results of one common cause; but that such a belief should have maintained its ground, with but little alteration, to the present day, can only be regarded as a proof of the lamentable de- ficiency in truly philosophical views among the cultivators of physiology. To the supposed cause of vital phenomena the term Life was applied by the older philo- * This mode of philosophising has been very happily ridiculed by Kontenelle. " Let us ima- gine," he says, " all the sages collected at an opera the Pythagorases, Platos, Aristotles, and all those great names which now-a-days make such a noise in our ears let us suppose that they see the flight of Phaeton as he is represented carried off by the Winds ; that they cannot perceive the cords to which he is attached, and that they are quite ignorant of everything behind the scenes. It is a secret virtue, says one of them, that curries off Phaeton. Phaeton, says another, is composed of certain numbers which cause him to ascend. A third says, Phaeton has a certain affection for the top of the stage ; he does not feel at his ease when he is not there. Phaeton, says a fourth, is not formed to fly ; but he likes better to fly than to leave the stage empty ; and a hundred other ab- surdities of this kind, that would have ruind the reputation of antiquity, if the reputation of anti- quity for wisdom could have been ruined. At last come Descartes and some other moderns, who say, Phaeton ascends because he is drawn by cords, and because a weight more heavy than he is descending as a counterpoise. Thus to see nature as it really is, is to see the back of the stage at the opera. "- Quoted in Brown's Lectures on Mental Philosophy, Lect. v. sophers, who regarded it as a distinct entity or substance, material or immaterial, residing in certain forms of matter ; and the cause, both of their organisation, and of the peculiar actions exhibited by them.* Every sect had its own notion of the origin and nature of this entity; some regarding it as a kind of fire ; others as a kind of air, ether, or spirit; and others, again, merely as a kind of water. The fable of Pro- metheus embodies this doctrine in a mytho- logical form, the artist being described as vivi- fying his clay statues by fire stolen from the chariot of the sun. Whatever was the idea entertained as to the character of this agent, all regarded it as universally pervading the world, and as actuating all its operations in the capacity of a life or soul; whilst a special division of it a divinte particulu aura regu- lated the concerns of each individual organism. The opinions of Aristotle on this subject are very interesting, as presenting evidence of the tendency of his powerful mind to elevate itself above the level of his age, and as showing how completely even he was bound down by the prevalent tendency to hypothetical specu- lation, which seemed to offer so easy a solu- tion to all the mysteries of Nature. " In con- sidering what holds the fabric of the universe together, and forms out of the discordant ele- ments a harmonious whole, he infers from analogy that it must be something similar in kind to that which forms and holds together an organised body, namely, a principle of life; and that this principle, from the appearance of order and design displayed in the universe, must also have intelligence." " Besides this supreme animating principle (u<7t;), the au- thor and preserver of all, there are many others which, by delegated powers, organise the bo- dies of animals and plants, so that all organised bodies whatever are to be considered as con- structed by and constructed for their animating principles, which, like the great animating principle, from being invisible to mortal eyes, indicate their existence, their energies, and their species, only through the medium of the structures which they form. Now, of these structures they are not only the efficient causes but, in his opinion, the formal and the final ; the causes of their motions, growth, and nu- trition ; the causes which give them a character and form ; the causes on whose account they exist ; and even the causes of their being after- wards liable to corruption, as nothing is cor- rupted but what has been nourished, and has some time or other partaken of life. But, besides being causes of organised structures in these different senses, they are subordinate to a higher power, which prescribes their operations, not merely with reference to their separate and individual plans, but with a reference at the same time to that general and comprehensive * The term "Vv)(* was applied by the Grecian philosophers to designate this animating prin- ciple, which included, with what is now known as the vital principle, the sensory and intellectual faculties. To the series of vital actions which, by many modern physiologists, is spoken of as Life, the term Zwi was given by the Greeks. 144 LIFE. plan on which the universe itself is constructed. It is under the influence of such a power that every particular species of soul regularly con- structs a system of organs adapted to its func- tions ; and every species of soul appears uni- formly to have its own species of body." * Now it is a little singular that, whilst the ten- dency of modern philosophy has been to ex- plode the idea of any secondary existence acting beneath the Creator on the constitution and actions of the universe, but to refer all its phenomena to the continued operation of the laws which He first impressed on matter, physiologists, neglecting the obvious analogy between the actions of the universe and those of any single organised being (the Macrocosm and Microcosm) pointed out by Aristotle, should have retained, with but little modifica- tion, his opinion regarding the second ; and should still attribute ihe phenomena of life to a secondary agency existing in each being and modifying the ordinary laws of matter to its purposes. This subject, however, we shall dismiss for the present, to return to it here- after. The mode of explaining vital phenomena which has been adduced as an example of early speculation on the subject, appears to have resulted from two tendencies that may be observed to characterise the unenlightened mind both in past ages, and at the present time. The first is that which may be considered as natural to man in the infancy of philosophy, to regard all matter, at least the grosser forms of it, as essentially inert, and therefore to attribute all spontaneous motion to a union of the thing moved with some substantial moving cause. Now, although modern science has given a more correct explanation of the causes of mo- tion in the inorganic world, and has shown that, so far from being inert, every particle of matter is capable of exhibiting actions of va- rious kinds when placed in certain relations to others, the superficial enquirer still regards matter as inert quoad vital actions, and is un- willing to attribute them to any possible ope- ration of its properties. And in this mode of reasoning he would seem borne out by the peculiar history of organised beings, the phe- nomena of their origin, growth, decline, dis- solution, and decay, the contemplation of which, with the desire of accounting for them, occasions the second tendency to which we have alluded ; that, namely, to infer from this history the existence of an unknown something, which during the living state preserves the in- tegrity of the body, and the loss of which occasions the disintegration of the fabric. Thus it has happened that the doctrine of the animating principle has retained its hold over the public mind from the earliest ages of the world to the present day ; and the vestiges of the opinions of the early Greek philosophers may be traced in the expressions, vital spark, vital spirit, breath of life, and others which are still prevalent. * Barclay on Life anil Organisation, pp. 429- 433. The chief modification which these doctrines have undergone, in their transit to modern physiologists, has been the separation of the vital principle the entity which is supposed to effect the organisation of the body, and to employ that organism as the instrument of its operations from the soul or mental principle, which is concerned in a series of actions en- tirely distinct. It is somewhat singular, how- ever, that even Aristotle regarded the vovi; or reasoning faculties as separable from the re- mainder of the Vv/jr), and as capable of ex- isting independently of the body ; and a sub- division of this kind was adopted by the Roman philosophers, who designated the vital and sensitive principles by the term Anima, whilst to the rational they applied the name of Animus. We shall not follow these doctrines through all the modifications which resulted from the unfathomable profundity of some systems of philosophy, and the pretending shallowness of others ; but shall proceed at once to the more modern opinions, which are either openly professed at the present time, or lurk in the unillumined corners in which the heterogeneous relics of former systems find a hiding place, whose darkness is congenial to their disunited formlessness. The ancient doctrine of the identity of the vital with the mental principle was revived by Stahl in a somewhat altered form. This philo- sopher maintained that the rational soul is the primum movens of organisation ; that it is the ultimate and sole cause of organic activity; and that by its operation, according to certain fixed laws, it preserves the body from decay and cures the effects of disease. Still, however, a distinction was drawn by him between the acts of the animus and the anima, which was not ob- served by his followers, who have regarded him as wishing to identify them. He looked upon them as the common effects of one principle ; and his great error was in supposing that any analogy or parallelism existed between them. Now it is necessary to bear this doctrine con- stantly in mind when reading the works of many of the physiologists of the last century, otherwise their meaning will be greatly mis- understood. In the writings of Whytt, for example, we constantly find actions referred to the soul as their cause, when it is perfectly evident that the author did not mean that the mind (as it is now termed) was at all concerned in them. This was the case with his whole class of vital and involuntary motions, to the production of which, he expressly states, con- sciousness is not always necessary. Although there are few if any philosophers who would avow such a doctrine as that of Stahl at the present time, we trace its effects very evidently exerted upon popular opinion. We have known it maintained by many well-informed persons, that the phenomena of life and mind are obviously so closely connected, that, to refer one class to the operation of the properties of matter without an independent controlling- entity, in other words, to set aside the doc- trine of a vital principle, necessarily implies the relinquishment of the idea of mind as a LIFE. 145 distinct existence. Nothing, however, can be more absurd than such a dogma. The two classes of phenomena are not connected other- wise than by a very remote analogy. All the phenomena of Life (putting aside, of course, those psychical changes with which we are contrasting them) concern matter only, and consist in its actions and reactions, and there is nothing in them related to feeling or con- sciousness ; it is but reasonable, then, to refer them to the laws of matter if we can do so. But the phenomena of mind are universally allowed to be of a very different character; there is nothing tangible or material about them ; and, whether we regard them as causes or results of material changes, our reasons must have a very different basis than the existence or non-ex, stence of a vital principle. On this point all the most intelligent of modern writers are fully agreed.* The doctrine of" the vital principle," which is at present very commonly received under some form or other, may be regarded as having been first put forth in a distinct form by Barthez, who invented this term to signify something distinct from either mind or body, but never- theless capable of existing by itself. The vis medicatrix nature, which figures so promi- nently in the theories of Hoffmann and Cullen, is nothing more than the same hypothetical agent under a different name ; for by this term was denoted a " sort of in-dwelling guardian of the body," which " presides over its func- tions in the state of health ; and, when any accidental cause of disturbance has given rise to a temporary disorder in the system, exerts itself to the best of its ability, with a sort of instinctive effort, often well directed, though sometimes liable to mistake, to restore the healthful and regular condition."! No one can have observed the phenomena of Life in morbid conditions of the body without witness- ing examples of the tendency to reparation in the various parts which have suffered from the ravages of disease or injury ; but this tendency results, like their ordinary operations, from their original constitution as parts of an or- ganised system, and not from any independent agent whose existence can be demonstrated ; so that if the common phrase, " the healing power of Nature," be employed at all, it should * Thus Mr. Abernethy, in his Exposition of Hunter's Theory of Life, contended against con- founding perception and intelligence with mere vitality. Dr. Prichard remaiks (Review of the Doctrine of a Vital Principle, p. 71,) that the con- scious principle or mind and the vital principle, " supposing for a moment that both really exist, are entirely distinct in their nature and attributes." And Dr. Alison's authority fully coincides with those already quoted. " Whatever notion we may entertain respecting the existence of a vital prin- ciple, it has no connexion with our notion respect- ing the existence of mind." (Outlines of Phvsio- logy, p. 3.) These three physiologists may be regarded as fairly representing three different classes of opinions regarding the vital principle ; the first being a zealous partizan of its claim to be considered a distinct entity, the second as zealous an opponent of the doctrine, and the third taking an intermediate position. f Prichard, op. cit. p. 17. VOL. III. only be used as a general term for the expres- sion of this tendency. Precisely the same may be said of the " Nisus Formativus," or Bil- dungstrieb of Blumenbach. If it be employed merely as a general expression of phenomena evidently directed by their unknown cause or causes towards the same end, it is unobjection- able ; but care must be taken lest it be sup- posed that something has been gained by such a generalisation, which, in fact, merely refers to the final cause and not to the efficient cause, and does not, therefore, carry us forward one step in the inquiry into the latter. If, on the other hand, it is intended thus to designate an agent whose operations produce these pheno- mena, it cannot be distinguished in any way from that commonly spoken of as the vital principle. Of a similar character would seem to be the "organic agent" of Dr. Prout, the "organic force" of Miiller and other German physiologists. If by them are intended any entities separate from matter, or any forces distinct from those which the action of its properties creates, they evidently come under the same category.* We arrive, then, at last at the doctrine of the vital principle, which, since the time of Hunter, has prevailed in Britain, especially amongst his disciples, until a comparatively recent period, when its unphilosophical charac- ter, its inability to explain the phenomena of Life, and the absence of any valid evidence for such an hypothesis, have been made appa- rent. It is not easy to discover, however, from his writings, what were the precise opinions of Hunter upon this topic ; for the inquirer is constantly perplexed by the peculiar vagueness of his expressions, which, if taken in a rigid sense, would indicate ideas quite opposed to one another. Thus, we find him at one time speaking of the brain as itself the maleria vita in a concentrated state, and speculating that " something similar to the materials of the brain is diffused through the body, and even contained in the blood." But he elsewhere intimates his opinion that the principle of life is independent of organisation, a something superadded to the organised structure, as mag- netism to iron, or electricity to various sub- stances with which it may be connected. This view was warmly espoused by Mr. Abernethy ; so warmly, indeed, that he almost transforms the analogy into identity, maintaining that " if the vital principle of Mr. Hunter be not * Such expressions, says Rudolph!, (Translation by How, p. 216,) may be approved of " when it is wished briefly to mention the unknown cause of life ; but it is extremely objectionable to presume that they have thereby explained anything. Au- thors generally commence at first with the modest declaration that they mean, by the void vital power, no more than the unknown origin of life ; but this mask of modesty is presently thrown aside, and they proceed as if the thing bad been quite clearly proved. It is now become a something which is imparted to the body in a certain quantum ; and they talk of increased and diminished, exalted and fallen vital power, &c., and thus they have a Dcus ex mtirhina which must hel|> them through all obstacles. In such a case was Brown with his Excitability." 140 LIFE. electricity, at least we have reason to believe it is of a similar nature, and has the power of regulating electrical operations." We shall now inquire into the precise import attached to the term by those who continue to employ it. It has been well remarked by Mr. Mayo that the word principle, " charac- teristic of a less advanced state of science, has been generally employed (as the final letters of the alphabet are used by algebraists) to denote an unknown element, which, when thus ex- pressed, is more conveniently analysed." Thus, it has been customary to speak of the principle of gravity, of electricity, or of magnetism, as the unknown causes of certain phenomena, whilst these are imperfectly comprehended. In so far, however, as the laws of these pheno- mena are understood; they terminate in referring all the results to simple properties of matter, from which they may be deduced by demon- strative reasoning, just as geometrical theorems from the postulates on which they are founded. But in the science of physiology the term has been employed in a less justifiable sense. It must be admitted on all hands, that the condi- tions of vital phenomena are not yet determined with sufficient precision to enable us to refer all observed facts, through the medium of general laws, to simple vital properties ; and there would be no objection, save the proba- bility of its abuse, to the employment of the term " Vital Principle," like " Nisus formati- vus" or " Organic Force," as a convenient ex- pression for the sum of the unknown powers which are developed by the action of these properties. But to this limit physiologists have unfortunately not restricted themselves. They have regarded it as a distinct entity en- dowed with properties of its own, in virtue of which it acts upon matter,- removing its par- ticles from the pale of physical and chemical laws, transforming them into organised tis- sues, endowing these tissues with new pro- perties, prompting their actions, preserving their composition in defiance of external in- fluences which would tend to disintegrate them, and finally quitting them, or being itself worn out with them, so as to leave the frame- work without its protecting influence, deprived of which it speedily falls to decay. Of the character of this principle, its expo- sitors leave us very much in the dark. Of all modern writers, Dr. Prout is probably the one who has most plainly expressed himself on it. In his Gulstonian Lectures* he informs us that, " In all cases it must be considered an ultimate principle, endowed by the Creator with a faculty little short of intelligence, by means of which it is enabled to construct such a mecha- nism, from natural elements, and by the aid of natural agencies, as to render it capable of taking further advantage of their properties, and of making them subservient to its use." The fallacies involved in this supposition have been elsewhere so ably exposedf that we shall not here stop to discuss it; but in our survey * Medical Gazette, vol. viii. p. 261. t Roberton on Lite and Mind, p. 36 et seq. of the nature and causes of vital actions, we shall take occasion to inquire whether any such hypothesis is called for, or whether it is not worse than useless by complicating what is otherwise readily explicable on simple and phi- losophical principles. III. NATURE AND CAUSES OF VITAL ACTION. It has been already pointed out that all the changes in the external world are the results of the properties of inorganic matter, called into exercise by the means appropriate to excite or stimulate each to activity; and we may further observe that these means are different for each property. Thus, to develope the dormant pro- perty of gravitation in any mass of matter, we should only have to bring it within the sphere of attraction of any other mass. But to develope the dormant electrical property of a loadstone, a mass of iron alone would serve. Every operation in chemistry is founded- upon the same principle, each substance acted upon being capable of responding, in a manner peculiar to itself, to the influence of agents brought to bear upon it. Now, however fami- liar this idea may seem, it has been too much neglected in the investigation of vital pheno- mena; and notwithstanding that we always find a similarity of action, when the organised structure, on the one hand, and the stimuli which call its properties into activity, on the other, are identical and a difference in either of these conditions always producing a diffe- rence in the result, physiologists have been in the habit of looking to some other agency for the cause of the variation. It is true that we occasionally meet with instances in which the result is different, without our being able to detect any change in either of the conditions ; but, knowing as we do how very slight an alteration in the structure of a tissue or organ will at once destroy or entirely change its vital properties, we cannot wonder that they should undergo important modifications without their sources being perceptible to our present means of research ; and, as will hereafter be more fully shown, every extension of our powers of observation renders this doctrine more probable. When we analyse the mass of phenomena which are presented to us by the vital actions of the organised world, we find that they are susceptible of reduction into distinct classes, by which the study of them is much facilitated. Thus, all living beings introduce into their own structure alimentary materials derived from external sources ; and all likewise submit their fluid ingredients to the influence of the element they inhabit, in such a manner that a reciprocal change occurs between them. In this mode we arrive at the notion of the distinct Junctions of living beings, each of which may be regarded (in its simplest form) as a group of phenomena of similar character and referable to the same causes. Thus, the function of respiration, when stripped of all the acts some- times associated with it, is essentially the same throughout the whole organized world ;* and the simplicity of the changes involved in it, * See Prin. of Gen. and Comp. Phys. ch. ix. LIFE. 147 together with the facility with which it may be made the subject of experiment, render our knowlege of its character and conditions nearly complete. When we have analysed these groups of vital phenomena and satisfied ourselves of the conditions under which they occur, we are brought to the conclusion that for each a parti- cular organ or species of structure is appro- priated in the organized system, and that its action is dependent upon the excitation of its properties by agents external to it, just as in the inorganic world. This dependence of life upon external stimuli has been completely overlooked by the advocates of the vital prin- ciple ; and it is probably to Brown, with all his faults and absurdities, that we owe the first prominent enunciation of the fact. When these stimuli are withdrawn, vital action ceases ; though, under favourable conditions, vitality or the vital properties of the organism may be retained. (Sect. VI.) Every class of organs in the living body may be said to require its particular stimulus for the display of its properties. Thus, regarding the whole structure as a series of assimilating organs capable of converting nutrient mate- rials into structures like their own, and of thus causing them to exhibit vital properties we may say that the supply of these nutrient ma- terials in a fluid state is the stimulus to their action. Again, to the excretory organs the required stimulus is the presence of certain superabundant and therefore injurious elements in the nutritious fluid . To the action of the muscular system the excitement of innervation, or the application of a physical stimulus, is necessary. In all classes of living beings we find these functional changes performed under conditions which are essentially the same ; and hence we are enabled to arrive at the laws which regulate each. These are not the only conditions required, however; for others of a still more general nature are constantly, and therefore impercepti- bly, operating. All vital actions, for example, require a certain amount of heat for their per- formance, and the amount varies in different cases. This is no more, however, than what we meet with in the inorganic world ; for many chemical and physical operations can only take place within certain limits of temperature, and these sometimes very circumscribed. The pre- sence of light, again, is essential to many others, especially in the vegetable kingdom ; but this, again, finds its parallel in the inorganic world, many chemical decompositions (which indeed bear a remarkable analogy with the changes which this agent produces in the green parts of plants when exposed to an atmosphere contain- ing carbonic acid) being due to its influence. And although, with regard to electricity as a vital stimulus, our absolute knowledge is still less, what we do know leads to the belief that it is an agent of at least as much importance in the vital economy as in the operations of in- organic nature. There is nothing, then, in the nature or con- ditions of vital actions considered individually, which need cause us to reason upon them in any other way than we do upon the phenomena of the inorganic world ; and it is obviously unphilosophical to assume an agency which is not required to account for them. It must be recollected, too, that the onus probandi rests with those who make the assumption, and not with those who maintain the analogy in the character of vital phenomena to those of the universe at large. The assumption may be easily shown to be not only useless, but insuffi- cient to explain phenomena without calling to its aid the very principles which have been shown to be themselves competent. Thus, the physiologist who traces the operation of the vital principle in the function of secretion, is compelled to allow that, as by one principle so great a variety of products are eliminated by the various glands from one material, the diffe- rence in the results must be due to some difference in the structure of the organs respec- tively concerned. And it may then be fairly inquired of him, " If the difference in the glandular structure and action is capable of giving rise to so great a variety in the products, with the cooperation of this one vital principle, how can it be proved that this difference in the glandular structure and action may not be capa- ble of giving rise to the same result by itself, and without the aid of any such adjunct at all?"* A similar question might be put with regard to any other class of actions, in which, under the same general conditions, the results are modified by the peculiar characters of the instruments or organs respectively employed ; and, as a nega- tive reply must be given equally to all, it may be safely affirmed that no reasoning can deduce the doctrine of a vital principle from the phe- nomena of life separately considered. But the advocates of the doctrine rely much upon the peculiar adaptation of the various changes taking place in each being to the pur- poses of its existence ; and assume that this adaptation can only result from the control of a subordinate presiding agent constantly exercised over each. Here, again, we find such a doctrine not only unsupported by, but manifestly inconsistent with, the analogies of nature. No reflecting mind has any doubt that this earth and its inhabitants form a system, of which every part is perfectly adapted to the rest, (so that we might almost call it an or- ganised one, if the idea of a particular struc- ture were not involved in the term,) and of which all the actions and changes, however in appearance contrary, have one common ten- dency the ultimate happiness of the creatures of Infinite Benevolence. The same may be said of it in regard to its relations with the system of which it forms a part ; and probably of that system with regard to the universe in which it is but a speck. So far as we can un- derstand the working of the laws by which that universe is governed, we see them all mutu- ally adapted to the same ends, whether we consider the welfare of the whole system, or of our own comparatively insignificant planet, with * Prichard on the Vital Principle, p. 100. L 2 148 LIFE. its countless living inhabitants. Have we, then, any more reason to assume that a vital prin- ciple or organic agent governs the concerns of each of these beings, than to suppose that the Creator has delegated to a subordinate the care of each individual globe ? Or is it not more consistent to suppose that upon the elements of all He impressed those simple properties, from whose mutual actions, foreseen and pro- vided for in the laws according to which they operate, all the varieties of change which it was His intention to produce, should necessa- rily result? By another illustration of a different cha- racter we hope to set this point in a still clearer light, and to be able to dismiss the subject without entering upon it as an abstract question. We shall suppose a young physio- logist, entirely ignorant of physical science, but educated in implicit faith in the vital principle, witnessing for the first time the action of a steam-engine. Here he would perceive a ma- chine composed of a number of dissimilar parts connected together, and moving by some secret agency which he desires to unveil. We may imagine him trying various experiments upon its functions, such as shutting off the communication between the boiler and the cy- linder, or between the cylinder and the con- denser, or applying cold where heat should be, and kindling a fire under the cold-water cistern. Hence he may arrive at the just con- clusion that the actions performed by each part, when the machine was in regular opera- tion, have all a tendency towards one common object the maintenance of its moving power. He will also perceive that these actions are as dissimilar as the structure of the parts exhi- biting them ; and he will not escape being sur- prised that the opposite influences of heat and cold should be essential to their production. Hence he may safely conclude that the whole series of phenomena is due to one presiding agency a "steam-engine principle," by the operation of which upon the material structure, its actions are produced, and made to har- monize with each other, and with their ultimate object. And this conviction would be very much strengthened if he saw the machine en- dowed (as we may, for illustration, imagine quite possible) with the means of supplying its own wants, regularly adding fuel to its fire, and cold water to its condensing cistern, and even repairing for itself the loss it sustains by wear of material. Would such a person, en- tirely unacquainted with the properties of steam, be acting more unphilosophically in en- tertaining this notion, than in attributing the actions exhibited by living beings to the opera- tion of a vital principle ? We think not. In each case the machine or organism is framed to take advantage of the properties with which the Creator first endowed matter; and the dif- ference is that, while the design of man con- structed the first to bring into operation those properties which alone he can control, the de- sign of Omnipotence constructed the second, and adapted it todevelope properties of matter, which can only be exercised under the condi- tions which a living being supplies, and of which man, therefore, cannot avail himself. We may conclude, then, that if we can refer vital actions to the properties of the organs which exhibit them, called into operation by their appropriate stimuli, we do not require any other explanation of their mutual adapta- tion and dependence than the original design of the Creator. " No agent," it has been well remarked, " can be required to adjust and re- gulate the actions which ensue from this mu- tual adaptation, since they are, like all other phenomena in the universe, under the control of laws inseparable from their very existence." But the question next arises, by what means haveorganised bodies become possessed of these peculiar properties ? It is, as we have before remarked, a mere verbal alteration to attribute the vital actions of an organ to its peculiar pro- perties ; since we understand by these proper- ties only the capability of giving rise to the changes which we witness, and we only know of their existence by the observation of these changes. The real causes of the phenomena must be sought for in the events which were concerned in the formation of the structure, and its first endowment with the properties which it exhibits ; and this leads us to consider, IV. THE CONNECTION BETWEEN VITA- LITY AND ORGANISATION. When our en- quiry into the laws of Physics terminates in referring any of its phenomena to the action of one of the universal properties of matter, we feel satisfied that we can trace the operation of second causes no higher; and that the existence of this property as inseparable from matter, and therefore as essential to our idea of it, is the immediate result of the will of the Creator. But in a great variety of instances we cannot do so ; and we observe properties restricted to and inseparable from certain forms of matter, the laws of whose action, however, are as de- finite as in the first case. Such properties, therefore, form a part of our notion of those particular forms of matter ; thus, the magnetic properties of iron, or the energetic attraction which potassium has for oxygen, are characte- ristics of these substances, which combine with others to distinguish them in our minds from other forms of matter possessing many properties in common with them. But these properties will not be manifested except under peculiar conditions ; and according to the ra- rity of the occurrence of those conditions will be the probability of our remaining ignorant of the property. \Ve are obliged to admit, therefore, that every form of matter with which we are acquainted may have properties of which we know nothing, simply because it has not been placed in the circumstances adapted to call them into activity ; since it is only by an fiction of some kind that the mind can become cognisant of their existence. W r e see, then, that it is very possible that all matter, or at least all those forms of it capable of becoming organised, may be possessed of properties which shall give rise to the actions termed vital, when they are placed in certain condi- tions; and that the mere absence of any mani- LIFE. 149 festation of these, while the substance remains in the condition of inorganic matter, is no proof that they do not appertain to it. We find nothing, then, in our fundamental ideas of matter, to oppose the doctrine that vital properties are developed in it by the very act of organisation. But we shall consider the question in another point of view. We are constantly witnessing examples of the total change effected upon the properties of certain forms of matter by their entrance into new combinations. Thus, how completely different are the properties of a salt from those of the acid and alkali which unite to form it. And we are not obliged to have recourse to chemical union for cases of such a change; since there are examples in which mere mechanical admixture of the particles of different bodies will produce the same. How different, for instance, are the properties of gunpowder from those of any of its ingredients. They are all combustible it is true ; but in a manner as unlike it as each other. Does any one think of assigning any other cause to these changes than the act of combination or admixture ? Does he seek for it in the operation of a saline property super- added to the compound of acid arid alkali; or of a combustible principle presiding over the combined actions of the nitre, sulphur, and charcoal, and directing them to one common object? If not, why should he adopt a different course in regard to vital properties ? In our investigation of natural phenomena, we never observe a substance endowed with new properties, without it has undergone some change in its own condition, of which altered state these properties are the necessary attend- ants. Unless, therefore, an instance could be produced in which the same form of matter shall at one time evince properties of which it is proved to be destitute at another, we have no right to speak of any property as distinct from the matter which exhibits it, or as capable of being supcradded to it or subtracted from it. It may be desirable for us to pause here, in order to examine a case in which it has been alleged that such an addition takes place, and which has been used as an analogical argument in support of the doctrine of a vital principle. It has been commonly said that a living body, in assimilating and organising the nutrient matter by which the changes essential to its ex- istence are maintained, superadds or communi- cates to it by a separate act, those vital proper- ties of which it was itself previously possessed ; and there is no more difficulty, it has been argued, in conceiving how vital properties may be communicated to organised matter, than in understanding how magnetic properties may be superinduced upon iron. But the analogy is based upon a false conception of the latter process, which is really conformable in cha- racter to those by which gravitation or any other properties of matter are brought into ac- tion. For the so-called communication of magnetic properties to iron is nothing more than the production of a change in the condi- tions of the metal, by which its electric proper- ties are manifested in a manner peculiar to itself, and caused to give rise to magnetic powers. If, then, an analogy exists between the two processes, (which can scarcely be de- nied,) it leads us to the belief that, just as mag- netic powers are developed in iron, when the metallic mass is placed in a condition to mani- fest them, so the very act of organization deve- lopes vital powers in the tissues which it constructs. For no one can assert that there does not exist in every uncombined particle of matter which is capable of being assimilated, the ability to exhibit vital actions when placed in the requisite conditions ; in other words, when made a part of a living system by the process of organisation. It is only the com- plexity of the conditions required to manifest it, which prevents our recognising this capabi- lity as a common property of matter, or at least of those forms of it which we know by expe- rience to enter into the composition of organised structures. Such are the conclusions to which we are led by the general comparison of vital phenomena with those of the external world ; and it would be difficult, we might say impossible, to prove that there is anything in the former which re- moves them from the pale of such reasoning. In fact, it appears to us that observation of them alone would lead to similar inferences. We perceive organisation and vital properties simultaneously communicated to the germ by the structures of its parent ; those vital proper- ties confer upon it the means of itself assimi- lating, and thereby endowing with vitality, the materials supplied by the inorganic world. It is very true that in this germ we cannot per- ceive a single trace of the future being, the various organs and structures of which are evolved during its development. But these are not evolved in any other way than by the progressive extension and complication of the parts of the original germ. If we witnessed the aggregation of inorganic matter to form a head in one place, a trunk in another, and limbs in a third, and the subsequent union of these, we might be disposed to suspect the existence of some invisible agent which di- rected and controlled the operation ; but we can trace nothing in the real process but the effect of the properties with which the struc- ture of the germ is endowed at the same time and by the same act that it is organised by the parent. Nor is there anything in the subsequent life of the being that op- poses such a view ; on the contrary, much that confirms it. As long as each tissue retains its normal constitution, renovated by the ac- tions of absorption and deposition by which that constitution is preserved, and surrounded by those concurrent conditions which a living system alone can afford, so long, we have reason to believe, it will retain its vital proper- ties, and no longer. And just as we have no evidence of the existence of vital properties in any other form of matter than that denomi- nated organised, so have we no reason to be- lieve that organised matter can retain its regular constitution, and be subjected to its appro- priate stimuli, without exhibiting vital actions. The advance of pathological science renders it every day more probable that derangement in 150 LIFE. function always results, either from some struc- tural alteration (although this may be of a kind imperceptible to our senses), or from some change in the character of the stimuli by which the properties of the organ are called into action. There is no difficulty, therefore, in accounting on this view for the death of the whole system on the cessation of any one function ; since any perturbation in the train of vital actions will not merely disturb the regularity of all, but, if sufficiently serious, will check those nutrient processes on the uninterrupted continuance of which the vital properties of the several parts depend ; the degree of that dependence being proportioned to their respective tendencies to spontaneous decomposition if not thus renewed. Still, the vital properties of in- dividual parts may be retained for a consi- derable period after general or somatic death (see DEATH) has taken place; and vital actions may continue, as already stated, so long as the conditions which they require in the living body are supplied. So far from a dead body having " all the organization it ever had whilst alive," as has been often maintained by the upholders of a separate vital principle, it will be found, on a more minute survey, that no single portion of it is existing under the same circumstances in these two states;* and there is good reason to believe that those agents which destroy life with the least apparent or- ganic change, produce structural alterations which are not the less important because more minute. Some instances of this kind will be presently noticed (Sect. V.). We must confess ourselves at a loss to understand how the gra- dual death of individual parts of the body can be explained upon the doctrine of the vital principle, without supposing that it may be split into as many individual existences as there are organs in the system ; such an idea would then coincide with that of the superadded pro- perties of which we have endeavoured to show the fallacy, and all the arguments derived from the unity of its operations would fall to the ground. One often repeated objection to the doctrine thot vitality results from organisation may, we think, be easily disposed of, as it is more spe- cious than real. It is considered by some to be a sufficient disproof of this doctrine, to refer to the universally-admitted fact, that the exist- ence of organisation implies a previous exist- ence of life ; and thence to infer that life cannot be at the same time the cause and the consequence. But this is a sort of paradox which reminds us of the question that puzzled the profound casuists of yore " Whether does the bird spring from the egg or the egg from the bird ?" It is evident that the life of any indi- vidual being may be the consequence of the action of stimuli upon its organism, just as the bird is produced by warmth from the egg ; and yet that the organisation of its structure may be the result of the previous existence of life in the parent, just as the egg is produced by a bird. We are only referred backwards, there- fore, in our enquiry into the efficient cause of the development of vital properties, to the first creation of each organism. Here some would maintain that the Creator formed a vital prin- ciple or organic agent, and then set it to or- ganise the body. But we apprehend that this is an assumption which we have no right to make; and that it is more philosophical, be- cause more consistent with what we elsewhere witness, to suppose that the Creator, in first forming matter, endowed it with properties in virtue of which it became capable of exhi- biting vital actions or life, when first combined by Him into an organised structure ; and that the Parent of all thus impressed upon the elements of which each created being was composed, the spirit* of the laws which should in future govern its growth and reproduction, just as Pie impressed upon the bodies com- posing the planetary system that mode of action whose subsequent continuance has given us the notion of the laws of gravitation and of motion. To account for the perpetuation of the race, we require nothing but the continued operation of those laws ; in other words, the continuance of the same mode of action, by which particles of inorganic matter are succes- sively organised, and, qua organised, become ca- pable of performing vital actions, a part of which consists in the production of correspond- ing changes on other materials. The actions performed by living beings are not all, however, immediately dependent upon the operation of the vital properties of their organs ; since many are evidently conformable to physical laws, and the properties of the or- gans by which they are performed are common to them with many kinds of inorganic matter, and are exhibited by dead as well as by living organised substances, as long as no obvious change takes place in their composition. Of this kind are the property of elasticity in va- rious tissues, especially certain of a ligamentous character ; and that by which endosmuse takes place through certain membranes. It may be observed, however, that the existence of such properties in the tissues of the living body obviously depends upon a certain arrangement of their ultimate molecules, which can only be maintained by the exercise of their nutrient functions ; and that any irregularity in the latter, still more their entire cessation, will speedily impair the properties, by giving free course to the constant tendency to decomposi- tion in the tissues which exhibit them. And further, it may be remarked that in most in- stances these properties are dependent for their excitement to action in the living body, upon those truly vital processes which no mecha- nical contrivances or chemical operations can produce or imitate. Between these two extreme classes of phe- nomena, the purely physical, and the purely vital there is a third, of a very peculiar and perplexing character. We allude to the ac- tions concerned in preparing the materials for organisation out of the aliment received into the system. Many are disposed to regard these as of a vital character, and to consider that, as See Prichard on the Vital Principle, p. 117. Herschel's Preliminary Discourse, p. 37. LIFE. 151 soon as the living body has begun to chancre the composition of the substances upon which it acts, it endows them with a new set of affinities, contrary to those which it before possessed when subject to the operations of chemistry. Others, again, are content to refer the opera- tions in question at once to the ever-ready vital principle, which, according to them, produces and directs these changes in the organism, and, so long as it resides there, keeps in check the natural tendency of its structure to decay. We are inclined to believe, on the other hand, that the operations in question are immediately due to the agency of the same laws as those which preside over inorganic matter, operating, how- ever, under conditions which the living or- ganism alone can supply. We shall now examine what evidence may be produced in favour of this opinion, and how far it is con- sistent with the general phenomena of life. V. CHANGES IN COMPOSITION. The ali- mentary materials which serve as the food of the living organism, cannot be appropriated by its several tissues, and rendered like themselves in structure and properties, until they have un- dergone certain changes in composition, by which the proximate principles are produced. It is by the organisation of these compounds, that the constant disintegration of the elemen- tary parts of the living system is compensated, and those vital properties maintained, the exer- cise of which forms an essential part of the circle of actions involved in life. Another class of changes in composition consists in the production, from the same materials, of the peculiar ingredients which characterise each se- creted product; some of these may be regarded as directly eliminated from the nutritious in- gredients of the blood, in the same manner as are the solid tissues themselves; whilst others would rather seem to result from the new com- bination of the disintegrated elements, which are taken up and removed by the current of the circulation, and carried to organs destined to separate them entirely from the living portions of the system. All these changes are frequently said to be effected by a vital chemistry ; or (to speak in more precise language) to result from the operation of vital affinities, of a different character from those ordinary chemical affinities which produce the well-known changes in the inorganic world. In conformity with the New- tonian direction to avoid unnecessarily multi- plying causes;, we shall briefly examine the grounds upon which this hypothesis is based, and enquire whether it is requisite for the ex- planation of phenomena, or even gives vis any assistance in our researches. The chief ground for the assumption of a distinct set of vital affinities appears to be, that the mode of union of the elements of the organic compounds is essentially different from that which prevails in the inorganic world ; and that the chemist, who has the power of effecting or controlling those changes which are produced by physical laws, and can therefore imitate to a great extent the immense variety of combinations which the mineral kingdom af- fords, is unable to effect or control the action of similar materials, so as to produce any of the class of organic compounds or proximate prin- ciples. It has, until very recently, been re- garded as a distinctive character of organic compounds, that their elements are combined in ternary or quaternary arrangements of com- plex nature, in which each ingredient is equally united with all the rest; whilst all inorganic substances admit of being ultimately resolved into simple binary combinations. Thus/zArira is regarded as composed of 6 parts of carbon, 2 of oxygen, 5 of hydrogen, and 1 of nitrogen ; and these elements are imagined to form a qua- ternary compound, all having a mutual attraction for each other ; whilst carbonate of ammonia, which consists of 1 carbon, 2 oxygen, 3 hy- drogen, and 1 nitrogen, is a binary combination of two other binary compounds, carbonic acid and ammonia. But on this it may be remarked, that there are undoubtedly some proximate principles, (that is to say, the simplest forms to which organic compounds can be reduced, without altogether disuniting them into their ultimate elements,) which consist of two ele- ments alone, and which exist in this simple form in living bodies. Such are some of the compounds of carbon and hydrogen. Further, the rapid progress of analytic research is leading to the belief that the complex arrangements just referred to may be resolved into those of a binary character; so that most organic com- pounds may be regarded as resulting from the union of others of simpler nature, just as a salt is formed by the union of an acid and an alkali. The discovery of cyanogen, and of its capabi- lity of acting as a. compound radical, uniting, like chlorine or iodine, with hydrogen to form an acid, and even occasionally serving, like oxygen or sulphur, in combination with some metals, as the base or alkali to such an acid, was the first step in a career of brilliant disco- veries, which, even at the present day, may be regarded as scarcely commenced. When cy- anogen combines with a metal, the combination is in reality a ternary one, although in all its properties it has a binary character. Thus, the cyanuret of silver (whose ultimate composition is 1 part of the metal, with 2 carbon, and 1 nitrogen,) will form a salt, in which it acts as the acid or negative ingredient, with the cya- nuret of potassium ; and the soluble cyanurets will form salts with the chlorides or iodides of the metals, thus establishing their claim to a binary character. But still further; cyanogen in combination with iron appears itself to act as a compound radical, combining as a simple body with other elementary substances.* From the analogy afforded by this and other in- stances, many chemists are now disposed to look upon the combination of the oxy-salts in a new light. It is suspected that, vhen sul- phuric acid and soda are brought together, the resulting compound is not formed by the union of an atom of the acid with an atom of the alkali, but by the generation of a new com- pound radical, sulphatoxygen, consisting of 1 part of sulphur with 4 of oxygen, which unites * Licbig, iii Turner's Chemistry, 6th cd. p. 776". 152 LIFE. as a simple body, like chlorine, iodine, or cya- nogen, with the metal sodium.* It will be seen, then, that the tendency of modern researches in inorganic chemistry is to prove, that the mode of combination which characterises the union of its elements, is not by any means so simple as it has been usually supposed; but that a binary, a ternary, and perhaps even a quaternary compound, may perform the part of an element, combining with other elements which are really simple, to form what are regarded as simple binary com- pounds. We shall now enquire what reason there is for believing that the compounds with which organic chemistry supplies us, have a similar constitution. VVe must be content, however, with selecting one or two examples from among the vast number which the in- dustry of analytic chemists is constantly bring- ing to light. The vegetable alkaloids have been generally regarded as proximate principles, not to be separated into simple compounds without an entire disunion of their elements. They all contain one equivalent of nitrogen ; and there is good reason to suspect that this element is not equally combined with all the rest, but exists in union with hydrogen in the form of ammonia, to which the alkaline power of these substances is due. Again, camphor was long considered a proximate principle of ternary composition ; but it is now found to be an oxide of camphene, a compound radical con- sisting of carbon and hydrogen, which will unite, like cyanogen, with simple bodies ; form- ing camphoric acid with another equivalent of oxygen, and entering with chlorine, &c. into other compounds. Lastly, urea may be men- tioned, in which the four elements that com- pose it may be regarded as existing in several forms of binary combination. It contains these elements in the following proportions : 2 oxy- gen, 4 hydrogen, 2 carbon, and 2 nitrogen. These may be considered as existing in the form of cyanic acid, ammonia, and water; one equivalent of each of these forming cyanate of ammonia; and, in fact, by the artificial union of these compounds, urea has actually been produced. It is by no means certain, however, that these compounds exist as such in urea ; and various ideas of its composition are enter- tained by chemists, on which this is not the place to comment. Our object is simply to show the analogy in the composition of the products of vital chemistry with that of the ar- tificial compounds whose formation is subject to none but physical laws. Why the chemist is not more successful in imitating in his labo- ratory the operations of the living economy, will presently become subject for consideration. An argument employed by many physiolo- gists for the existence of a distinct set of vital affinities, is founded upon the evident truth, that the tissues and fluids which maintain a certain composition when possessed of vitality, speedily resolve themselves into new combina- tions when this has become extinct. Hence it is inferred that the affinities which hold toge- " See Graham's Chemistry, p. 158 et scq. ther the elements during life, are of a different nature from those which operate in producing their subsequent separation. Now, it may be objected to this inference, that no solid or fluid compounds which have a disposition to spon- taneous decay after death, can continue to exist without change during life ; that the activity of the processes of interstitial absorption and re- position seems to bear a pretty constant ratio, in every case, with the natural tendency to de- composition ; and that the maintenance of the original combination is not so much owing to anything peculiar in the affinities which hold together its elements, as to the constant removal of particles in a state of incipient decay, and their replacement by others freshly united. Thus, we find that all the most permanent parts of the animal frame, such as the massive skele- tons of the polypifera, the calcareous tegument of the mollusca, or the bony scales of fishes, to the possible duration of which geologists scarcely dare to assign a limit, are extravascular in the living animal, undergoing scarcely any interstitial change when once formed. Next to these in order of durability are the osseous structures of animals, and the woody fibre of plants, whose connection with the circulating system appears rather adapted to meet the exi- gencies of growth, injury, or disease, than to maintain a constant change required by the ten- dency to decomposition. When we examine the softer tissues, on the other hand, we find that the rapidity of interstitial change fully compensates for the increased tendency to de- cay; and that the perfect exercise of their respective functions imperatively demands the constant maintenance of their normal constitu- tion. Moreover, there are many organic com- pounds which are as permanent as those formed in the laboratory of the chemist ; of this kind are gum, sugar, and many other proximate prin- ciples, which simply require for their preserva- tion such external conditions as are necessary to prevent the spontaneous decomposition of many inorganic bodies. The degree in which these are subject to ordinary chemical opera- tions will be presently mentioned. It appears, then, to be an inference better founded on fact than that first mentioned, that the preservation of the normal constitution of organic com- pounds in the living body, is dependent on the continuance of the vital actions of the eco- nomy, rather than due to its mere possession of the property of vitality. In fact, that may be reasonably maintained as an inference from these phenomena, which we have already at- tempted to prove on other grounds; that the vitality of each tissue, that is to say, its posses- sion of vital properties, is dependent on the perfect condition of its organisation, and that, so far from preserving the organism from decay, it merely remains until decay has commenced. These inferences are, we think, fully borne out by the two following facts. When life is being extinguished by starvation, the whole body ex- hales a putrid odour even before the occurrence of death, and rapidly passes into putrefaction afterwards : here it would seem that the process of spontaneous decomposition, which we have LIFE. 153 represented as constantly occurring in the tis- sues, lias been unbalanced by the reposition of nutrient materials ; and that it has therefore manifested itself in the body even during life. Again, when spontaneous gangrene occurs from obstruction to the circulation, decomposi- tion slowly supervenes in the part from which the supply of nutrient fluid is cut off; and coincident with its progress is the extinction of the vital properties, constituting molecular death. (See vol. i. p. 791.) Corresponding changes may result in the whole body when the nutritive functions are interrupted, not by obstruction to the motion of the circulating fluid, but by depravation of its character ; and we then perceive the vital properties of each tissue impaired in a degree correspondent to the dependence of the integrity of its structure upon the constant renewal of its elements. The presumed impossibility of forming, by the chemical combination of their elements, any of the class of organic compounds or prox- imate, principles, is regarded by many physiolo- gists as in itself a sufficient ground for the as- sumption that the affinities which act in the living body are different from those which we recognize in the inorganic world. The fact, however, which we have already noticed re- garding the artificial production of urea is one which powerfully opposes such an assump- tion.* This is slurred over by Muller, with the remark that it can scarcely be considered as organic matter, being rather an excretion than a component of the body a distinction which does not remove it from the pale of the operation of the supposed laws of vital affi- nity. Seeing the vast progress which organic chemistry has made during the last few years, and the rapid increase of our knowledge re- garding not merely the composition but the mutual relations of the class of bodies under consideration, we cannot but think it premature to assert that other compounds may not be pro- duced in a similar manner. Be it observed, however, that the doctrine for which we are now arguing only concerns the production of those compounds which are destined either to be thrown off from the system, or to undergo subsequent organisation ; and cannot apply to those in which the process of organisation, and the consequent development of vital properties have already commenced. This distinction is a very important one, and may, we think, by being kept steadily in view, save much un- successful because mis-directed labour. If, for example, our view be correct, it may be pos- sible for the chemist to produce the gum or sugar which he finds in the ascending sap of plants ; but he can never hope to imitate the latex or elaborated sap, which already shows traces of organisation and of the possession of vital properties. In like manner the formation of albumen may be a worthy object of his endeavours, whilst these would be totally fruit- less if directed to the production of fibrin, * We do not quote any others reported to possess the same character, such as the production of fatty matter by Borard and Hatchett, because they still require confirmation. which differs from it but littJe if at all in che- mical constitution, but which is endowed in its fluid state with properties that nothing but the influence of a living system can generate. But quitting these speculations, we shall in- quire what positive evidence niay be produced of the operation of chemical affinities in the changes of composition that form so important a part of vital action. Many facts might be collected which favour such a belief; but the following must here suffice. In the progress of vegetation we have frequent occasion to observe the conversion of gum and of fecula, which consists of gum enclosed in vesicles, into sugar. This takes place in germination, in the budding of the potato and other fleshy stems, in flowering, in the ripening of fruit, as well as in many other instances; in all these in which fecula is the subject of the change, it would seem that this product, having been stored away out of the current of the circu- lation against the time of need, is to be again brought into use, and to supply the pabulum of young or rapidly-growing parts by conver- sion into sugar. These changes are effected ir various modes. Where gum is the subject of the conversion, we commonly find an acid employed to produce it, as in the ripening of fruits, where lignin as well as gum seems to undergo this change. The chemist can pro- duce the same effect by digesting gum or lignin with an acid at a certain temperature. Again, where the conversion of fecula into sugar takes place as one of the ordinary processes of the vegetable economy, it is effected by the pro- duction of a secretion termed diastase, which occasions both the rupture of the starch-vesicles and the change of their contained gum into sugar. This diastase, which is abundantly stored up in the neighbourhood of the eyes or buds of the potato, may be separately obtained by the chemist; and it acts as effectually in his laboratory as in that of the vegetable organism. Further, he can imitate its effects by other che- mical agents; for, by the joint operation of heat and acid, he can produce the same trans- formation. These are among the remarkable instances of the catalytic action recently described by Berzelius,* which is common to organic and inorganic operations, and which is not yet found to be comprehensible within the known laws of chemical affinity. The peculiarity of the action consists in the production by one body, A, of a change in the composition of another, B C, without itself undergoing any alteration. Thus, the peroxide of hydrogen, which is readily decomposed by any substance having an affinity for oxygen, is also decom- posed by some which themselves undergo no change, such as the metals and the fibrin of the blood ; these produce in it a state analogous to fermentation, oxygen escaping and water being left. Again, not only decompositions but new combinations may be effected in this manner. Thus, most metals at high temperatures, and platinum in a state of minute division at low temperatures, as well as various porous sub- * Edinb. Phil. Journal., vol, xxi. 154 LIFE. stances slightly heated, produce the union of oxygen and hydrogen in an explosive mixture. The action of sulphuric acid on alcohol in pro- ducing ether, without itself undergoing change, appears referable to the same class along with those just described. We may consider it proved, then, that many substances possess the power of exercising upon compound bodies an influence essentially distinct from what is known as chemical affinity an influence which consists in the production of a displacement and new arrangement of their elements, without themselves directly participating in it. Assu- redly such a power, which is capable of effect- ing chemical reactions in inorganic substances as well as in organised bodies, though still too little known to be accurately explained, must play a far more important part throughout na- ture than we have hitherto been led to suppose. " In defining it a new power," says Berzelius with philosophic caution, " I am far from wishing to deny that some connexion exists between its influences and the electro-chemical ones with which we are familiar. On the con- trary, I am very much disposed to recognize it as a peculiar manifestation of these same influences."* Another interesting series of facts, which seem to confirm the theory of the operation of chemical affinity in the living body, is that which relates to the evolution of electricity during the ordinary processes of growth both in plants and animals. The late researches of Dr. Faraday have fully proved the identity of electrical attraction with chemical affinity, and have shown that all chemical changes are at- tended with a disturbance of electric equili- brium. If, therefore, the changes occasioned by the growth of organised systems are imme- diately governed by laws similar to those which preside over inorganic matter, we should ex- pect to find that electricity is constantly being developed by them in the same manner as we obtain it by chemical decomposition or recom- position. There is no deficiency of evidence that such is the case, as the results of late inquiries most abundantly testify .f That chemists have not been more successful in imitating the operations of vital chemistry, by the artificial production of organic com- pounds, is due not only to their ignorance of the composition of such bodies, but to their want of acquaintance with the form or con- dition in which they must be brought together, in order to enter into the desired union. F^very one conversant with chemical operations is well aware of the important influence thus exerted. A slight change of temperature, for example, often reverses the affinities of a body: and many elements are susceptible of particular actions when in a nascent state (i. e. when in the act * This eminent chemist has been quoted as an advocate of the doctrine of vital affinities. If such was formerly held by him, it is evident, from the tenor of the communication here referred to, that he has abandoned it. t See the Author's essay on the laws regulating vital and physical phenomena, in Edinb. PJiilos. Journal for Apiil 1838; and Principles of General and Comparative Physiology, p. 379 et seq. of being freed from some other combination) which in their ordinary condition could not be so affected. When it is considered, therefore, how little we know of the operation of such conditions in the laboratory of life, no surprise will be felt that its results should often appear contrary to what might have been anticipated. No reasonable ground has yet been adduced for supposing that, if we had the power of bringing together the elements of any organic compound in their requisite states and propor- tions, the result would be any other than that which it is found to be in the living body; for the agency of vitality, as Dr. Prout justly re- marks, " does not change the properties of the elements, but simply combines them in modes which we cannot imitate." It is hoped that the foregoing statements will have established the probability (which is all that the present state of our knowledge on these subjects will allow us to assert) that the affinities which hold together the elements of living bodies, and which govern the elaboration of organic products, are the same as those con- stantly operating in the world around. It would seem, at any rate, premature to assert that the operations of vital chemistry are di- rected by distinct laws and due to new forces. The designations organic and vital affinity seem to have been employed by some writers to express only the peculiarities of the circum- stances and conditions under which these laws usually operate, rather than any real difference in the nature of the powers thettiselves. And others appear to use them as provisional terms only, referring those effects to the operation of vitality which chemistry is not yet in a condi- tion to explain. In the former sense it is ma- nifest that such employment of the term is in- jurious as leading to misconception. In the latter it is harmless, if it do not check inquiry and create a prejudice against the reception of new facts. The period when all difficulty shall have vanished from the application of chemical laws to the phenomena of the vital economy may be very far distant ; and in the mean time " we must be content with gathering a few in- dications which occasionally break out from the clouds of mystery in which the subject is ob- scured." But it must not be left out of view that every fresh discovery adds to the number of these indications, and that they all point in the same direction ; so that the probability of the universal operation of chemical affinity in the living body becomes every day more strong, and the difficulty in proving the existence of a distinct set of vital affinities is constantly be- coming less easily surmounted. VI. VITALITY IN A DORMANT OR INACTIVE CONDITION. There are many organised beings at particular periods of whose existence all vital action seems to be suspended ; and this may result either from the absence of the sti- muli necessary to maintain it, or from some change in the organism itself, by which it be- comes for a time less capable of responding to these stimuli. When vital action is suspended from the deficiency of external stimuli, one of two things must happen ; either the vitality of the organism will be destroyed by the disin- LIFE. 155 tegration of its tissues; or it may be preserved in consequence of the absence of those agents which ordinarily excite decomposition. The occasional suspension of vital action from a change in the organism itself, appears usually to result from a general law of periodicity, whicli affects, more or less, all organised beings, producing the phenomena of sleep, hybernation, &c.; but it may also arise from particular causes operating within the system, as in syncope. Each of these cases will now be separately considered. Dormant vitality of seeds, eggs, 4'<"- The condition of organised beings of which we have first to treat that in which vital action is sus- pended from the absence of the stimuli ne- cessary to maintain it, and vitality never- theless preserved is manifested in the most remarkable manner by the reproductive germs which are periodically separated from plants and animals, and which are endowed with the power of developing themselves into new indi- viduals when the requisite conditions are sup- plied to them. In the lowest classes of each kingdom, it would appear that these germs are liberated from the parent unprovided with any means for the continuance of their development ; and that from the first, therefore, they rely upon the surrounding elements for all the conditions of their active existence. It is beautifully pro- vided that, in proportion to the probable defi- ciency of some of these, should be the tenacity with which the apparently lifeless germs re- tain their vitality. The sporules of the fungi, which can only subsist on decaying organised matter, seem universally diffused through the atmosphere, and ready to vegetate with the most extraordinary rapidity whenever a fitting- nidus is afforded for their development. This, at least, appears the only feasible mode of ex- plaining their appearance in the forms of mould, mildew, &c. on all decaying surfaces ; and that there is no improbability in the suppo- sition itself is shown by the estimate of Fries, who states that a single individual of reti- cularia maxima will emit above 10,000,000 of these germs, so minute as when collected to be scarcely visible to the naked eye, rather re- sembling thin smoke, and so light as to be wafted by every movement of the atmosphere, so that, he remarks, " it is difficult to conceive a place from which they can be excluded." It seems more than probable that in a similar manner is to be explained the appearance of infusorial animalcules in all situations adapted to their existence ; and that their germs are constantly and universally diffused through the air, ready to commence the active exercise of their dormant properties whenever they meet with the stimuli to their development afforded by warmth, moisture, and decomposing organic, matter.* We have no means of ascertaining the length of time during which this dormant vi- tality may be preserved. It would be difficult to assign a limit to it, since it is scarcely con- ceivable that any change can occur in the struc- * For an important experiment on this subject recently performed by Schultz, see Edinburgh Phi- losophical Journal, Oct. 1837. ture of these minute desiccated points which they do not undergo during the first few hours of their aerial residence ; and we have no reason to believe that vitality can be de- stroyed without change of structure. With re- gard to the seeds of phanerogamic plants, we have more certain evidence, and this of a very interesting character. It is to be remarked, however, that in them, as in the eggs of higher animals, there is, besides the germ it- self, a reservoir of nutriment supplied by the parent, which enables the germ to continue its development up to the point at which it be- comes fit to maintain its own existence, with- out any other than the ordinary assistance of vital stimuli. The germination of a seed, for example, requires only warmth, moisture, and the access of air, and is further accelerated by the absence of light ; and the hatching of an egg is dependent only on a temperature more or less elevated and the presence of air. Hence the necessity for so great a tenacity of vitality as that possessed by the germs of the simpler classes does not exist, and although under favourable circumstances the vitality of seeds may be prolonged for an almost indefinite period, they are more susceptible of the inju- rious influence of external agents, and their fertility is destroyed by changes of condition which would have no effect in the former case ; whilst the eggs of animals appear still less tena- cious of vitality, although in a few instances capable of retaining it for some time, even under considerable disadvantages, as will be presently noticed. The seeds of most plants which inhabit tem- perate climates are adapted to remain dormant during the winter, and may be preserved in dry air and moderate temperature for a consi- derable time. Some of those which had been kept in the Herbarium of Tournefort for up- wards of a century were found to have pre- served their fertility. But with regard to those which are brought from tropical climates there is greater uncertainty, and unless they have been carefully excluded from the contact of air and from variations of temperature, a large pro- portion are usually unproductive. Cases are of no unfrequent occurrence in which ground that has been turned up spontaneously produces plants dissimilar to any in their neighbourhood. There is no doubt that in some of these the seed is conveyed by the wind, and becomes developed in spots which afford congenial soil, in the same manner as the germs of fungi and infusoria. Thus it is commonly ob- served that clover is ready to spring up on soils which have been rendered alkaline by the strewing of wood-ashes, or the burning of weeds ; and it is stated by Professor Graham that after any hill-pasture in Scotland has been laid dry and limed and the surface broken, white clover always makes its appearance. But there are many authentic facts which can only be explained on the supposition that the seeds of the newly-appearing plants have lain for a long period imbedded in the soil, at such a distance from the surface as to prevent the access of air and moisture, and that, retaining their vitality under these circumstances, they 156 LIFE. have been excited to germination when at last exposed to the requisite conditions.* Most physiologists, at least, are content to adopt this explanation, seeing that it is con- formable to what is otherwise known of the persistence of vitality in seeds ; but it has been recently maintained that in such instances a spontaneous production takes places, similar to that which many philosophers have supposed to occur among the lower tribes of organised beings.f This is not the place to discuss such a theory, of which it would not perhaps be very difficult to show the absurdity; but the following case furnishes, we apprehend, a very satisfactory proof that seeds may preserve their vitality for an unlimited time, when the ex- ternal conditions are such as to prevent either the active exercise of their properties or the disorganisation of their structure. " 1 have now before me," says Professor Lindley,^ " three plants of raspberries whichhave been raised in the gardens of the Horticultural Society, from seeds taken from the stomach of a man, whose skele- ton was found thirty feet below the surface of the earth, at the bottom of a barrow which was opened near Dorchester. lie had been buried with some coins of the Emperor Hadrian, and it is probable, therefore, that the seeds were six- teen or seventeen hundred years old." In regard to eggs, no such examples are, we believe, on record ; nevertheless, there are some tribes of animals whose eggs are capable of being preserved for a considerable length of time, and of undergoing very severe treatment without loss of their vitality. Most insects de- posit their eggs sufficiently early in the summer for the larvae to be hatched and attain their full growth before the autumn deprives them of their supply of food, and these pass the winter in the pupa state. But there are some which do not begin to lay until the activity of vegetation has nearly ceased, and their eggs remain undeveloped until the ensuing spring arouses both the animal and vegetable creation into life. The curious instincts which lead these insects to choose secure places for the de- position of their eggs, and to use other means of protecting them against cold and moisture, are described by Mr. Kirby; and the same author points out the beautiful correspondence between the temperature required for the de- velopment of the buds of the plant and of the larvae that prey upon them. It has been men- tioned in a former article|| that the eggs of the slug are capable of enduring a temperature of 40, and of being completely desiccated, with- out losing their fertility ; and it can scarcely be doubted, therefore, that these might preserve their vitality like the seeds of plants for an un- * For several cases of this kind related on the authority of Professor Graham, see Dr. Pilchard's Physical History of Man, third edit. vol. i. p. 39, &c. ; and for a very curious instance communicated to the author of this article, see his Principles of General and Comparative Physiology, p. 141. t See Dr. Weissenborn's papers in the Philo- sophical Magazine for 1838. J Introduction to Uotany, p. 298. $ Kirhy and Spence's Entomology, vol. ii. p. 443. II Vol. ii. p. 402. limited period, if neither aroused into activity nor disorganised by decomposing agents. It will scarcely be denied that the agents which are known to destroy the vitality of seeds and eggs are such as are calculated to produce important changes in their structure and composition, even though these be of a kind inappreciable by our present means of re- search. Thus most seeds are killed by a tem- perature of 160, which is that at which rup- ture of the vesicles of fecula takes place, and the application of heat sufficient to destroy the vitality of an egg coagulates its albumen. An electric shock is well known to be a powerful means of instantaneously extinguishing the vital properties of eggs or seeds ; and although the precise alterations which it effects in the struc- ture or composition of their parts is not under- stood, it cannot be doubted that important or- ganic changes are produced by so powerful an agent. Cold, in like manner, probably acts injuriously on most eggs and seeds as upon plants, by causing the rupture of the cells of their tissues through the expansion of the con- tained fluids in the act of freezing. We do not mean to say that other changes are not also produced by such agents, but we mention these as evidences of the position with which we started that vitality is not destroyed by the influence of external agents without a structural change of some kind being induced by their operation. But it is not during their embryo state merely, that the vital actions of living beings may be suspended by the deficiency of external stimuli, and yet their vitality be preserved. Both the vegetable and animal kingdoms afford numerous examples of such an occurrence at all periods of existence, especially among their lower tribes. Mosses, for instance, often ap- pear completely desiccated in dry weather, and seem as if dead ; whilst, on the application of moisture, they revive in all their pristine beauty. The curious Lycopodium of Peru exhibits this torpor in a still more remarkable manner. When desiccated by drought, it folds in its leaves and contracts its roots so as to form a ball, which, apparently quite devoid of anima- tion, is driven hither and thither by the wind ; as soon, however, as it reaches a moist situa- tion, it sends down its roots into the soil, and unfolds to the atmosphere its leaves, which, from a dingy brown, speedily change to the bright green of active vegetation. The rose of Jericho is the subject of similar transforma- tions. Instances exactly parallel are furnished by the animal kingdom. The common wheel- animalcule is one of the most remarkable, being capable of desiccation so complete as to splinter if touched with the point of a needle, and still preserving its vitality so as to revive when moistened.* In animals reduced to a * This fact has been denied by some naturalists ; but the author can positively assert it from his own experience. See Principles of Gen. and Comp. Physiology, p. 90, note. From experiments subse- quent to the one there related, he is inclined to believe that of two species of Rotifer, so nearly allied as to be usually considered the same, one is thus revivinable, and the other not. LIFE. 157 state of torpidity by cold, some vital action usually continues ; and such cases cannot therefore be adduced under the present head. But instances are by no means rare in which the whole body has been frozen, and vital action has of course been completely suspended, yet without the destruction of the power of renew- ing them under more favourable circumstances. Lister first noticed that he had found caterpil- lars so frozen, lhat when dropped into a glass they chinked like stones, but nevertheless re- vived ; and this statement has been confirmed by Bonnet and others. The Papilla Brassicee lias been produced from a larva which had been exposed to a frost of Fahr., and which had become a lump of ice. Fishes are occasion- ally found imbedded in the ice of arctic seas; and some of these revive when thawed. This tenacity of life appears greater, however, in the species which are confined to shallow lakes or ponds, and which have not the power, there- fore, of escaping from the effects of cold. This is perhaps the proper place to mention those undoubted cases in which insects have been apparently killed by immersion in water or spirit, continued for a long period, and have yet revived on exposure to the air and sun. Without multiplying facts, then, it may be safely affirmed that many organised beings may retain their vital properties, in some in- stances to an unlimited duration, while all vital activity or life is completely suspended, through the absence of the stimuli necessary to main- tain it ; and that this preservation of vitality bears so close a relation to the resistance offered, by the structure and composition of the sub- stance possessing it, to the influence of disin- tegrating agents, that it may reasonably be considered as a result of the maintenance of its normal constitution. The physiologist is not yet in a condition to explain those diffe- rences in structure and composition which enable some organisms to offer a much greater re- sistance to such injurious influences than others ; but he considers himself entitled to assume that such exist in all, since there are many instances in which he is able to detect them. Suspension of vital action under other cir- cumstances. We have next to consider those cases in which vitality is rendered for a time dormant, by causes originating in the system itself, rather than by the %vithdrawal of external stimuli. Under this head we may place all those phenomena to which the name of hyber- nation is usually given ; but which, as will presently be seen, cannot be appropriately de- signated by that term. The greater number of plants indigenous to temperate climates un- dergo an annual series of phases, in which their vegetative processes exhibit every grada- tion from a torpor apparently complete to the most surprising activity. In many, indeed, this series of phases constitutes the whole of life ; the individual ceasing to exist as soon as it has been once performed, and a new genera- tion called into existence. In many more, a total suspension of activity appears to take place, as may be observed in plants whose stems die annually, whilst the roots retain their vitality. This condition exactly resembles that of certain animals which pass the winter in a state of profound torpor. In those, however, whose stems are woody and persistent, vital action does not seem to be completely checked even by a frosty atmosphere ; as late experi- ments show that a movement of sap takes place, though to a trifling degree, in the depth of winter. And, lastly, in evergreen plants, these changes of condition are less complete ; the activity of the vegetative processes being diminished by the partial withdrawal of their appropriate stimuli, but not being altogether suspended. Now although it is unquestion- able that this series of changes is greatly influ- enced by the successive alterations in the ex- ternal conditions of the beings, which the revolution of the seasons induces, it does not admit of doubt that it is originally dependent on the peculiar constitution of the organism, by which a periodical diminution of its activity is occasioned. For nothing will prevent a plant from shedding its leaves nearly at its usual time ; and although by artificial heat, or by removal to a warmer climate, a new crop may be brought out within a short interval, this can only be effected by keeping in a state of activity the processes which ought to be at rest, so that an injurious influence is exerted on the general system like that which results from artificially- prolonged watchfulness in animals. When a plant is reduced, by the periodical decay of its stem and leaves, to the state of a bulb or root, it seems almost to revert to that remarkable condition already described as peculiar to seeds ; the vitality of the structure being capable of remaining dormant for a considerable time, and of being then aroused into full activity by the appropriate stimuli. We are not aware of any authentic facts which fix the limit to the dura- tion of this condition. Instances have been related of the growth of bulbs unrolled from the envelopes of Egyptian mummies ; but there is reason to believe that deception has been practised on this point upon the too-ready credulity of travellers. However, there can be no doubt that, under favourable circumstances, bulbs and roots may be preserved for many years ; the conditions necessary for thisobject being such as neither excite the vitality of the structure to action, nor occasion the disintegration of the latter and the consequent loss of its properties. The animal kingdom presents us with condi- tions very analogous to those just alluded to. In a large proportion of those inhabiting tem- perate climates, there is a periodic diminution of vital activity during the colder part of the year; but this, in the higher tribes at least, scarcely amounts to an absolute suspension, since the circulation, and the functions of nu- trition and secretion which depend on it, are carried on, though feebly. (See HYBERNATION.) It is easy to understand why this must be the case. The softer portions of the animal frame, which are most concerned in the processes of organic life, are not periodically cast off and renewed like the corresponding parts of plants ; and, if their integrity were not maintained by the circulation of nutritious fluid during their 158 LIFE. inactive state, their normal constitution would be soon affected by their proneness to de- composition, and their peculiar properties be consequently lost. Amongst cold-blooded ani- mals, however, we find instances of more com- plete suspension of vital actions, which may even be prolonged for a considerable period. Thus, Spallanzani kept frogs, salamanders, and snakes, in a torpid state, in an ice-house, where they remained three years and a half, and rea- dily revived when again exposed to the influ- ence of a warm atmosphere. Insects, in their pupa state, may be regarded as analogous to plants reduced to bulbs. Although the dura- tion of this torpid condition is ordinarily deter- minate for each species, and although some changes occur during its continuance which scarcely warrant us in characterising the state as one of entire inactivity, there are some in- stances which prove that it may be prolonged for an almost indefinite period, under particular circumstances. The degree of temperature to which pupae are exposed seems to have the same kind of influence over them as on the eggs of insects. Thus Reaumur found that pupiE, which would not naturally have been disclosed until May, might be caused to un- dergo their metamorphosis in a fortnight during the depth of winter, by the influence of artifi- cial heat; and, on the other hand, that their change might be delayed a whole year beyond its usual time, by the prolonged influence of a cold atmosphere. We can scarcely imagine, however, that temperature is the sole agent in accelerating or retarding the final metamor- phosis. If the caterpillar of Pupilio Machu- on, one of those which has annually a double brood, becomes a pupa in July, the butterfly will appear in thirteen days ; if not until Sep- tember, it will not make its appearance until the June following, that is, not in less than nine or ten months. Here it is evident that the torpor has been prolonged from some cause in- herent in the system itself, for the purpose of preventing the disclosure of the butterfly at too early a period of the season. A still more cu- rious proof of this tendency to prolonged tor- pidity during the pupa state is the following. If a number of the pupae of the Eriogaster lanestris, a moth whose larvae are common on the blackthorn in June, be selected at the same time, and placed in the same circum- stances, the greater number of them will dis- close the perfect insect in the February follow- ing ; some not until the February of the year ensuing; and the remainder not before the same month in the third year. The same has been observed of the Arcica mcndica, of which thirty-six pupae, grown from eggs laid by the same parent, produced twelve perfect insects in each of the three following seasons.* The// cause of this curious tendency may be, as sur- mised by Mr. Kirby, to secure the race from being cut off by unfavourable seasons, or by some extraordinary increase of its natural ene- mies. But its efficient cause can only be looked for in some modification of the properties of * Kirby and Spence's Entomology, vol. iii.'p. 266. the organism analogous to that which produces the phenomena of hybernation in other animals. The same periodicity, manifesting itself, not in obedience to a diminished temperature, but at the season of greatest heat, is observed in tro- pical climates. Many tribes of insects in the torrid zone seem to retire to places of retreat during the parching droughts of summer, and make their appearance again during the rainy season, when vegetation is in the highest luxu- riance. We here trace the same beautiful adaptation of the phases of animal and vege- table life as in the former instances ; but the efficient cause which induces these changes must be different. Our limits do not allow us to dilate upon one very interesting department of this subject the prolongation of dormant vitality under particular circumstances in frogs and other reptiles. Many marvellous stories of this kind are on record ; such as the inclosure of these animals in solid blocks of granite or other igneous rocks, which no well-informed person can credit. There are, however, a sufficient number of authentic cases to prove, in the esti- mation of those who have fairly examined them, that toads and other reptiles may be en- closed in masses of rock apparently solid, or in the substance of the trunks of trees, and that they may preserve their vitality under such circumstances for a very long period. In the former instances, it would appear that the ani- mal has fallen into a chink or crevice, which has been gradually filled up by the washing-in of gravel or other materials disposed to soli- dify ; and that thus the appearance of a solid mass has been given, when in reality some com- munication has existed between the cavity and the external air. It is by no means impossible, moreover, that these animals might be found imbedded in the sandstones at present in course of formation in many localities ; these rocks possessing considerable hardness, but being at the same time sufficiently porous to allow of the slow passage of air through their substance. Where toads have become im- bedded in crevices of trees, and been sur- rounded by new layers of wood, it is evident that a direct communication with the atmos- phere will probably exist by means of the ori- ginal crevice, although it may be much nar- rowed ; but even if this be not the case, the porosity of the wood will furnish the required condition. Some amount of access of air would seem, from the experiments of M. Ed- wards and Dr. Buckland, to be essential to the prolonged vitality of toads enclosed in solid masses ; and this will probably maintain a very feeble respiratory action upon the blood through the general surface, just sufficient to prevent the decomposition of the body. Vital action cannot, therefore, be regarded as so completely extinct under these circumstances as in some of the cases formerly mentioned, where the ap- plication of cold lias not only completely checked it, but has also done away with the necessity for it, by completely subduing the tendency to decomposition. In the human economy, as in that of other LIFE. 159 non-hybernating animals, it is only occasion- ally that anything approaching to this suspen- sion of vital action can occur. That which takes place during sleep only relates to the sensorial functions ; the organic changes expe- riencing but little diminution in activity. The closeness of the connection between their vital operations, and the immediate dependence of these upon external stimuli, involve the de- struction of life when they are totally with- drawn ; and it is only under peculiar conditions of the organism itself, that we ever witness a suspension of vital action without the speedy supervention of death. Indeed it may be fairly questioned whether such suspension can ever completely take place ; and whether the changes which occur in the periphery of the circulation are not continuing, however feebly, even when no action can be detected at the centre. This condition is termed syncope ; and its phenomena will be more fully detailed here- after. (See SYNCOPE.) We are inclined to think that, where a state of apparent death has conti- nued for some days, vital action was never entirely suspended ; though perhaps its cessa- tion may be more complete where the syncope is but transient. Such would seem to be the case where individuals have recovered from a submersion under water, which has been pro- longed beyond the few minutes that suffice to produce asphyxia. It is generally supposed, and we think with reason, that the mental emo- tion experienced at the moment of submersion produces a state of syncope ; and that the or- ganism, being in that state less dependent on external stimuli than when in a more active condition, can bear privations which would be otherwise fatal, just as is known to be the case with hybernating animals, the pupa of insects, &c. The well-known case of Col. Townsend appears to us to prove that an apparent cessa- tion of vital action does not imply its entire extinction ; since when no changes could be detected by his medical attendants, he was vo- luntarily acting on his system both to retard and renew its usual functions. Dr. Cleghorn of Glasgow knew an individual who could control the action of his heait, so as to be able to feign death at pleasure. Although in these cases we may be disin- clined to admit the total suspension of vital action, there can be no doubt that it may occur in portions of the human body under the influ- ence of cold, and that, if carefully treated, it may be again renewed. Nay more; there is undoubted evidence that portions of the body, after being totally separated from it, may be reunited and made again to form integrant parts of the structure, if no disorganisation has taken place in the interval. That such an occurrence is perfectly consonant with the doctrines which we have maintained regarding the connection between vitality and organisation will be at once evident ; but we do not see how it can be satisfactorily explained by the advocates of the doctrine of a separate life or vital principle. Does the finger or nose which has been cut off carry with it a chip or off-shoot of the parent vital principle or organic agent ? If so, when does that quit its material tenement ? There is no evidence of its existence in the separated part, which is completely dead to the general structure, and which nothing prevents from speedy decay, if its vital actions be not soon renewed. And if it be supposed to remain, it must again become merged in its parent prin- ciple, when re-union of the divided parts has taken place, or must submit to it like a dutiful child. There is no end to the absurdities in which those may be involved, who adhere with pertinacity to a doctrine so useless and so un- philosophical as that of a single controlling agent or power, presiding over the affairs of each organism. It is with much satisfaction that the author of the foregoing article (which was written above a year ago) refers his readers to the re- cently published Supplement on the Atomic Theory, by Dr. Daubeny, for a full discussion of the question briefly considered in V. The conclusions at which the learned Professor has arrived are of precisely the same character as those for which the author has here argued, and are expressed in almost the same language. The following passages may be extracted from among many of great interest. " There is little doubt that it will eventually appear, that all the secretions or excretions of animals and vegetables are only so far de- pendent upon life, inasmuch as, in consequence of the favourable temperature which it sustains, the constant circulation of the fluids it occasions, and their exposure to external agents in vessels of different shapes and dimensions, a mechani- cal separation of the ingredients of the blood is effected in some instances, and a chemical change produced in its composition by catalytic action in others." "The putrefaction of vege- table and animal matters appears to be produced, not by any sudden cessation of those affinities which had previously bound their respective elements together, but by the predominance over them of the natural forces, which we may without much difficulty conceive to have been controlled under the circumstances in which the living body is placed; nor does there seem any sufficient reason for calling in the intervention of an occult principle to explain that, to the solution of which by known causes, every fresh advance in chemical knowledge seems to bring us into closer approximation." " It is now cer- tain that the same simple laws of composition pervade the whole creation ; and that, if the organic chemist only takes the requisite pre- cautions to avoid resolving into their ultimate elements the proximate principles upon which he operates, the results of his analysis will show that they were combined precisely according to the same plan as the elements of the mineral bodies are known to be." BIBLIOGRAPHY. Besides the systematic Trea- tises on physiological science by Haller, Cullen, Blumenbach, Dumas, Richerand, Treviranus, Ru- dolph, Magendie, Bostock, Tiedemann, Mayo, Ade- lon, Burdach, Alison, Roget, Fletcher, Dunglison, Arnold, Miiller, Carpenter, and others, the fol- lowing, among the almost innumerable writings on the subject, may be advantageously consulted. Aristotle, Opera. Cicero, Qusst. Tusc. lib. i. Idem, DC nat. deorum. Lucretius, De rerum na- turd. Bacon, Historia vitas et mortis. Harvey, 160 NORMAL ANATOMY OF THE LIVER. De generatione animalium, Lond. 1651. Glisson, De vita naturali, Lond. 1672. Stahl, De vita, Halle, 1701. De Gorter, De actione viventium particular;, Amstel. 1748. Hoffman, Dissertatio vitae animalis, Halle, 1731. Bonnet, sur les corps organises, Amst. 1776. Brown, Elementa medi- cine, Edinb. 1780. Priestley, On matter and spirit, Birm. 1782. Hunter, On the animal economy, Lond. 1786. Darwin, Zoonomia, Lond. 1794. Cu- vier, Le9ons d' anat. comp., Paris, 1799. Bichat, Sur la vie et la mort, Paris, 1802. Oken, Abriss