ATIONAI LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDII NX* r \ %rf?/ | >& Noiasw jo Aivaan ivnoiivn 3Ni3i03w jo aivibii ivnoiivn inoiqiw jo Aivaan ivnoi lATIONAl LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDM 0 5 ^£1 * -^ s. i V INI3IQ3W jo Aivaan ivnoiivn JNniaiw jo Aivaan ivnoiivn 3Ni3ic-3w jo aivibii ivnoi a i%X! lATIONAl LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDIC z' * ini3ic-3w jo Aivaan ivnoiivn 3Ni3ia3w jo Aivian ivnoiivn iNOioiw jo aiviiii ivnoi 5 L NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDM NI3I03W JO AlViail IVNOIIVN iNISiaSW JO AIVIIII IVNOIIVN 3NI3I03W JO Aivaan IVNOI fw I ,..©?) ATIONAI LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDM /ViVO I /V^^N t /^fpV> 1 IVNOIIVN 3NI3I03W JO AIVIIII IVNOIIVN 3NI3IQ3W JO AIVIIII IVNOI \-£sy nidia aw jo Aiviai .■.»....,<,., .......,„...„.............io«.i I,.,;,/,,« N.D.aiW JO A.V.,1, TVNOI1VN ,N,3,a3* JO A.V,.,, TVNOI1VN ,N,3,03W JO AIVI.M ,7n0, ATIONAI LIBRARY OP MEDICINE NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDI NI3I01W JO ABVian TVN0.1VN 1NI3I01W JO AIVIBII IVNOIIVN 3N.3I03W JO AIYIIM tTnO. 4i ITIONAl LIBRARY OF MIDICINI NATIONAL LIBRARY OF MEDICINE NATIONAL LIBRARY OF MEDICI I3I01W JO AIVIIII IVNOIIVN 1NI3I01W JO AIVIIII IVNOIIVN 3NI3IQ3W JO AIVIIII IVNOII OBSERVATIONS OS CERTAIN parts 09 THE ANIMAL (ECONOMY, INCLUSIVE OP SEVERAL PAPERS FHOM THE PHILOSOPHICAL TRANSACTIONS, ETC. JOHN HUNTER, F. R. S. t5tB?ttit iOLOtes RICHARD OWEN, F.R.S., Fellow of the Linnean, Geological, and Zoological Societies of London. Corresponding Member of the Royal Academy of Sciences of Berlin; of the Royal Academy of Medicine and Philomathic Society of Paris; and of the Academy of Sciences of Philadelphia, Moscow, Erlangen, &.C. .^. _ , „ .. , Professor of Anatomy and Physiology, and Conservator of the* Museum crf-thr^yjri_4rf*teg»-0fc—._ Surgeons in London. ^ r '■ r 1 Ui . * Piflatrelirtita: / HAS WELL, BARRINGTON, AND HASWELL, 293 MARKET STREET. NEW ORLEANS: JOHN J. HASWELL & 00. 1841. »NNEX PHV5/0L06V mi TO SIR JOSEPH BANKS, Bart., PRESIDENT OF THE ROYAL SOCIETY, ETC., ETC. Dear Sir, As the following Observations were made in the course of those pursuits in which you have so warmly interested yourself, and promoted with the most friendly assistance, I should be wanting in gratitude were I not to address them to you, as a public testimony of the friendship and esteem with which I am, Dear Sir, Your obliged and Very humble Servant, JOHN HUNTER. Leicester Square, Nov. 9, 1786. ADVERTISEMENT To the lirst Edition of the Animal (Economy, 1786. The nine following papers have been read at the Royal Society, and published in the Philosophical Transactions; but in a work of so general a nature, and of which physio- logical inquiries make so small a part, the few facts and observations which I have given upon such subjects may probably be overlooked by those who are not members of that Society. That they may be more easily procured by students in medicine, and other readers, I have, by an ap- plication to the President and Council of the Royal So- ciety, obtained leave to reprint such of them as I consider to be connected with the principles and actions of the Ani- mal (Economy; and I have added such observations and remarks as have occurred to me since the time they were read before the Royal Society. 2 ADVERTISEMENT To the Second Edition of the Animal OZconomy, 1792. Eleven of the following papers have been read at the Royal Society, and published in the Philosophical Trans- actions ; but in a work of so general a nature, and of which physiological inquiries make so small a part, the few facts and observations which I have given upon such subjects may, probably, be overlooked by those who are not mem- bers of that Society. That they may be more easily pro- cured by students in medicine, and other readers, I have, by an application to the President and Council of the Royal Society, obtained leave to reprint them, in this work, as being connected with the principles and actions of the Animal (Economy; and I have added such observations and remarks as have occurred to me since the time they were read before the Royal Society. PREFACE. Always an admirer of the genius of Hunter, and of late years obliged by official duties to make frequent reference to his numerous and varied productions, especially to those which are scattered through different volumes of the Philosophical Transactions and other works, I have often felt the inconvenience that resulted from the absence of a uniform edition of the whole of the extant works of that great and original thinker. When, therefore, Mr. Palmer first communicated to me his design of publishing a new edition of Hunter's works, I heard with peculiar satisfaction his intention to include in the proposed collection every memoir of the author that could be found in print, and I gladly lent my assistance, which, however, the previous assiduous researches of Mr. Palmer rendered of little moment, towards completing a list of all the published essays or observations on various parts of the ' Animal (Economy' which had not before been included in the work so entitled. The proposal which Mr. Palmer at the same time made to me to edit this portion of the works of Hunter I declined, from a sense of the inadequacy of my powers to grapple with so vast a range of im- portant physiological subjects as the contemplated volume must necessarily embrace, and I sincerely hoped that Mr. Palmer would have found a coadjutor better qualified than myself to do justice to this portion of his most useful and praiseworthy undertaking. After a lapse of nearly two years Mr. Palmer again applied to me to revise the papers on the Animal (Economy, and I then acceded reluctantly to his request, led, by the sole motive of accele- rating the appearance of a much wished-for edition, to a task, to which I have since dedicated a great portion of my leisure hours, without the slightest expectation of profit or honour, the experiment having only served to convince me of the difficulty of adding the observations demanded by the progress of science to the text of Hunter in the spirit of its author, and a retrospect of my annota- tions leading me to suspect that often, with every wish to avoid it, I may have^tacitly implied an ignorance on the part of Hunter of facts'with which he was probably well acquainted, and to perceive that, in general, the addition of such details tends to overload and destroy the force of the original observations in the text. It is with much more satisfaction that I refer to the additions which have been made to the present edition of the Animal (Eco- nomy of the hitherto uncollected or unpublished writings of its original author. 8 HUNTER ON THE ANIMAL 03CONOMY. These consist of the following essays. From the Philosophical Transactions: ^ " On the Anatomy of the Siren or Amphibious Bipes (1766).' "On the Electric Organs of the Torpedo (1772)."^ "On the Electric Organs of the Gymnotus (1755)." "Experiments and Observations on Vegetables with respect to the power of producing Heat (1775)." "A case of Small-pox communicated by the Mother to the Foetus (1780)." " Anatomical Remarks on a New Marine Animal (1785)." "Observations on the Structure and (Economy of Whales (1787)." " On Bees (1792)." " On the Fibrous Structure of the Crystalline Lens (1793)." " On the Fossil Bones of the Caverns of Gailenreuth (17D4)." " Six Croonian Lectures read before the Royal Society by Hunter in the years 1776, 1777, 1779, 1780, 1781, and 1782," but with- drawn from publication by the Author. From the Medical Commentaries of Dr. William Hunter: " Experiments on Absorption by Veins." From the Transactions of a Society for the Promotion of Medical and Chirurgical Knowledge, vol. ii. (1794): " Description of the Human Uterus and Ovum in the first Month of Pregnancy." " Observations on the Growth of Bone." There is also added, "An Account of the Anatomy of the Jerboa," contributed by Hunter to the Appendix to Russel's History of Aleppo. And, lastly, " Descriptions of Five Marsupial Quadrupeds," from the Zoo- logical Appendix to White's Voyage to New South Wales. (1790.) In order to bring these different memoirs in juxtaposition with papers on analogous subjects in the original edition of the Animal (Economy, a slight alteration has been made in the arrangement of the different essays composing that work. Those which relate to generation are brought together at the beginning of the volume; then follow the observations on digestion, animal heat, and other physiological subjects; and lastly, the papers of a descriptive character, which refer more immediately to comparative anatomy and zoology. Thus for the first time are collected into one volume the physiological and anatomical stores, from which, in connexion with the materials composing his museum or destined for its illus- tration, an adequate idea may be formed of the nature of the "reat work in which Hunter had purposed to record the sum of hisVast experience. In the year 1786, when Hunter published a collection of his detached memoirs in the first edition of the Animal (Economy, he PREFACE. 9 observes, with reference to the subject of digestion, " I cannot at present spare sufficient time to give my opinions at large on this subject, with all the experiments and observations I have made upon it, but as soon as I have leisure I shall lay them before the public." And again, in describing the organ of hearing in fishes, he premises that he reserves a more complete investigation of this part of natural history " for a larger work on the structure of animals, which I one day hope to have it in my power to publish," and he states that ever since the year 1760 his researches have been continued in every part of the animal ceconomy. Hence instead of regarding the uncommon structures which he discovered in his dissections of different animals as individual peculiarities, he was enabled to advance beyond the anatomists of his own times, and view them from the same eminence to which subsequent induction has raised the observers of the present day : and referring to the series of preparations in his museum, he boldly states with reference to the structure of the organ of hearing in fish, that it is " only a link in the chain of varieties displayed in the formation of this organ of sense in different animals, descending from the most perfect to the most imperfect in a regular progression." The importance of these views, and the nature and amount of the knowledge which they indicated, could not be appreciated by the contemporaries of Hunter in the absence of a detailed exposi- tion of the evidences on which they were founded. It is no wonder, therefore, that we find his earlier eulogists sometimes founding his claims to scientific eminence on insecure grounds; some, for example, lauding him as the author of a theory of the organizing energy, which may be traced to the time of Aristotle, or as the originator of the doctrine of the vitality of the blood, which is supported with so much eloquence by Harvey and his immediate successors; while others, taking more definite grounds, have often unfortunately selecled as his discoveries precisely those subjects of Hunter's spe'cial researches in which he had but revived and ex- tended the ideas of his predecessors. Of this we have a striking example in the introductory observations on the character of Hun- ter contained in Sir Everard Home's Lectures on Comparative Anatomv, vol. i., p. 6, in which the independent function of the vesicular seminales and the determination of the organ of hearing in fishes are adduced as Hunterian discoveries. The true originators of these and of other ideas and facts which Hunter may have regarded as his discoveries, and which he doubtless did discover so far as independent and original research constitutes a claim to that honour, I have been careful to point out in every case where my reading has led me to detect in an older author a clear anticipation of Hunter. It cannot be doubted, however, that the ascription to Hunter by his friends and admirers, of facts and opinions to which he had no title as the original discoverer, must have contributed to lower his character in °the estimation of continental anatomists; whose 2* 10 HUNTER ON THE ANIMAL CECONOMY. acquaintance with the vast accumulation of facts in comparative anatomy due to the labours of the numerous cultivators of that sci- ence in the sixteenth and seventeenth centuries, easily enabled them to detect the weakness of such claims, without perhaps their possess- ing such a knowledge of Hunter's labours as to justly appreciate their scope and tendency, and to view them, as they deserve to be viewed, in the light of a first great attempt to arrange in one con- catenated system the diversified facts in comparative anatomy. Cuvier, for example, in his review of the progress of science in the latter half of the eighteenth century, a period which may be re- garded as a second revival of comparative anatomy and physiology, places Hunter in an inferior category of contributors to those sciences. After eulogizing the share which the erudite Haller took in demon- strating the importance of comparative anatomy to the advance- ment of physiolog}', and the corresponding effects which the labours of Daubenton and Pallas produced in establishing sounder ideas of the classification of animals, the historian of the natural sciences goes on to state : "John Hunter in England, the two Monros in Scotland, Camper in Holland, and Vicq D'Azyr in France, were the first who followed their footsteps. Camper," he observes, " cast, so to say, a passing glance of the eye of genius on a number of in- teresting objects, yet almost all his labours were but sketches. Vicq D'Azyr, with more assiduity, was arrested by a premature death in the midst of a brilliant career ; but their works inspired a general interest, which has ever since been on the increase." With reference to the nature or influence of the labours of Hunter, Cuvier is silent; he limits himself to an indication in a marginal note of the Treatise on the Teeth and " les autres ecrits de Hunter inseres en partie dans les Transactions Philosnphiques."* This was meting out but scanty justice to the author of the Treatise on the Blood and of the Observations on the Animal (Economy, which abound with so many general propositions in comparative anatomy and physiology. If, however, this opinion ot Cuvier be excusable under the circumstances under which it was written, it would be unpardonable not to appeal against it upon the evidence of the higher claims of Hunter afforded by the present edition of his works and by those manuscripts which have already appeared in the catalogue of his Physiological collection published by the Royal College of Surgeons. Had these manuscripts, expla- natory of the design of the Hunterian collection, been published before Cuvier wrote the work from which we have iust quoted that astonishing result of Hunter's labours might perhaps have claimed a passing notice from one whose statements all Eurooe now receives and all posterity will regard with confidence and respect. c tWJU " Les autres tents," the « other writings" of Hunter to whi h Cuv.er alludes, are indeed devoted rather to the development of * Histoire des Progress des Sciences Naturelles, depuis 1789, torn, i., p. 303 PREFACE. 11 general principles in physiology than to the detail of the anatomical observations upon which he founded them. Many of the facts ascertained in the course of his higher and more comprehensive inquiries, and incidentally alluded to in the narration, are however fully as interesting and important as those which other anatomists have sometimes thought worthy of being made the subjects of express monographs. But Hunter had higher aims than the reputation of a mere col- lector of facts in comparative anatomy; and this he not only felt but had expressed in an early period of his career. In a manu- script, copied by Mr. Clift, relating to a dissection of a turtle, he says, " The late Sir John Pringle, knowing of this dissection, often desired me to collect all my dissections of this animal, and send them to the Royal Society ; but the publishing of a description of a single animal, more especially a common one, has never been my wish." Howsoever we may regret this feeling, which has undoubtedly deprived the world of the results of much inestimable labour, and has operated in various ways disadvantageous^ to Hunter's own reputation, yet it indicates the expanded views of the man who en- tertained it. Had Hunter published seriatim his notes of the structures of the animals which ho dissected, these contributions to comparative anatomy would not only have vied with the labours of Daubenton as recorded in the Histoire Naturelle of Buffbn, or with the Compara- tive Dissections of Vicq d'Azyr which are inserted in the early volumes of the Encyclopedic Methodique and in the Mimoires de VAcadbmie Roy ale de France, but they would have exceeded them both together. It would be tedious to enumerate, name by name, the different species of animals whose organization was investigated and recorded by Hunter. Mr. Clift has evidence* that he left written descrip- tions, from autopsy, of the anatomy of the following Mammalia: Of Quadrumana . . 21 Species. Carnivora . 51 Rodentia 20 Edentata 5 Ruminantia . 15 Pachydermata 10 Cetacea 6 Marsupiata . 10 Birds . 84 Species. Reptiles 25 Fishes 19 Insects. 29 Species. Of other invertebrate animals, as mollusca, red-blooded worms, and radiata, upwards of twenty. From the titles of manuscripts, * See " Evidence before the Medical Committee of the House of Commons." 12 HUNTER ON THE ANIMAL (ECONOMY. therefore, it appears that Hunter possessed, at the period of his decease, original records of the dissections of three hundred and fifteen different species of animals. In addition to these, Hunter's preparations testify that he had dissected twenty-three species of mammalia, sixteen species of birds, fourteen species of reptiles, forty species of fishes, forty-two different mollusca, and about sixty species of articulate and radiate animals ; all species of animals of whose anatomy we have no evidence that he left written descriptions. So that by adding these undescnbed dissections to those of which we derive the evidence from the list of the manuscripts, and of which described dissections his anatomi- cal collection in like manner contains evidences in the dissected and preserved organs, there is proof that Hunter anatomized at least five hundred different species of animals, exclusive of repeated dissections of different individuals of the same species, besides the dissections of plants to a considerable amount. With respect to the rarer and less known invertebrate animals, Hunter was not content with merely recording their structure and displaying its leading peculiarities in preparations ; but he caused most elaborate and accurate drawings to be made from the recent dissections ; for which purpose he retained in his family many years an accomplished draughtsman, Mr. William Bell, better known as the author of two papers in the Philosophical Transactions, de- scriptive of the Sumatran Rhinoceros and the Ecan Bonna {Platax arthriticus, Cuv.). Several examples of these beautiful designs have already been published by the Council of the Royal College of Sur- geons in the illustrated catalogue of the Hunterian Museum: they relate to the anatomy of the Sepia and Solen, of the Ascidia and Salpa; they illustrate the circulation of the blood in the Crustacea and Anellida ; and the figure which Mr. Hunter has given of the circulation in the Chloeia capillata, a red-blooded worm, far sur- passes in beauty and detail any of those with which Cuvier illus- trates the memoir* dedicated to what he regarded to his latest breath as one of his most interesting discoveries. Hunter had also minutely investigated the anatomy of the cir- ri peds ;f but of his dissections of these, as of many other animals, it is to be lamented that the preparations and drawings are now the sole evidences. The illustrations of the anatomy of the Echinoder- mata, both of the spiny species and of the unarmed Holothuria, have never been surpassed either as to minuteness or accuracy; and, excepting the disputed article of the nervous system, little is added in the elaborate and well-known monograph of Tiedemann to the anatomy of the Holothuria as it is displayed by Hunter, t Now the anatomical labours of Daubenton were confined to that class of animals whose structure most nearly resembles man • he ♦ Bulletin de la Soc. Philomath., 1791, p. 146. + See Physiological Catalogue of the Hunterian Collection, vol. i n o« pi. IV. '* F* °' t Ibid., p. 251, pi. III. PREFACE. 13 describes the position and length and breadth and number of parts with most praiseworthy zoological precision, but never appears to raise his thoughts to the relations of the structures he detected with the habits of the species, or their adaptation to function. Hence he has been said to have made more discoveries of which he was unconscious than any other cultivator of comparative anatomy. Vicq d'Azyr, on the contrary, adorns his descriptions with many beautiful and philosophical views, but he did not carry his scalpel beyond the vertebrate series; while Hunter explored every modi- fication of animal structure, from man down to the polype. If Hunter surpassed his contemporaries in the value and amount of the materials which he collected in comparative anatomy, he rises far above them in the application of his facts. By a profound and unremitting meditation on the diversities of structure presented to his view, he derived more accurate notions than were current amongst his contemporaries of the parts essen- tial to the performance of the different functions, and every idea or doubt thus suggested he tested by the most varied, ingenious, and accurate experiments. "Many things," he observes, " arise out of investigation which were not at first conceived ; and even misfortunes in experiments have brought things to our knowledge that were not, and probably could not have been, previously conceived. On the other hand, I have often devised experiments by the fireside or in my carriage, and have also conceived the result; but when I tried the experi- ment the result was different, or I found the experiment could not be attended with all the circumstances that were suggested."* Few physiologists indeed, if any, have made more numerous, va- rious and conclusive experiments than Hunter. Yet he says, " I think it ma; ^e set down as an axiom that experiments should not be often repeated which merely tend to establish a principle already known and admitted, but that the next step should be the applica- tion of that principle to useful purposes."f By this series of labours of mind and hand, prosecuted uninter- ruptedly from year to year, Hunter at length came to establish a body of physiological doctrines, to the happy influence of which on the treatment of the various " ills that flesh is heir to," every cultivator of the healing science now bears grateful testimony. Most of the enlightened physiologists of this country have ac- knowledged the high merit and beneficial influence of Hunter's labours; but the general terms in which his merits have been ex- pressed have not availed in raising him from the secondary cate- gory of contributors to comparative anatomy, in which he has been classed by Cuvier, and from which some continental writers have lately been disposed to degrade him.J * Animal (Economy, p. 417 (the pages throughout refer to the present edition). t Ibid., p. 117. % See the Esquisse Wstorique sur VAnalomie Compares, prefixed to the French translation of the second edition of Carus's Comparative Anatomy, vol. i., p. xxx. 14 HUNTER ON THE ANIMAL CECONOMY. The present seems, therefore, to be a fitting? W0^ £ attempt to define the grounds for assigning a ^Je^m\lt. Hunter, considered as a physiologist and comparativean*tomist In this endeavour, however, to prove what Hunter was as a dis coverer, we must also fairly state what he was not. He has been spoken of as the originator of^the idea of a subtte imponderable principle operating in the fluids and solids of the organism, and causing the phenomena of life. B« " prin ciple, under various names and with various attributes, has been assigned as the cause of organization by Aristotle, Harvey, Willis, Cudworth, Grew, Van Helmont, and Stahl. . . \s both Harvey and Hunter had spent laborious lives in earnest inquiries and repeated dissections and experiments to ascertain relations between structure and function; as both had studied the changes which take place in the form and structure of animals from their embryo state to that of maturity ; and as both had care- fully traced the successive phaenomena which occur in the egg during incubation,—the similarity of their opinions on the nature and powers of the vital principle is correspondingly close. Both arrived at the conclusion, that an animating principle exists and operates in the ovum prior to the formation of any organ of the future animal. Both attributed the power by which the fecund egg resists putrefaction, while the unprolific one decomposes, to a principle of life, which Harvey more precisely terms the •« anima vegetiva."* Hunter, however, carries his researches a step further; he sub- mits the fecund egg to a low temperature, and ascertains a new property, of which Harvey was ignorant, a power, viz., of resist- ing cold: he also shows that when once frozen, and killed by cold, the dead impregnated egg yields to putrefaction like the unimpreg- nated one. Both physiologists observed that if the phaenomena of a vital principle were manifested in one part of the organization more than in another, it was in the blood. " For the blood,'"' says Harvey, "is the first formed, and is the primary animate particle of the em- bryo ; it is generated prior to the punctum saliens, before the first rudiment of the heart, and is endowed with the vital heat or princi- ple before it begins to move, and from it does pulsation commence. *"Plurimum itaque mecum ipse reputavi, qui fieret, ut ova improlifieagal- linae supposita, ab eodem calore extraneo corrumpantur, putrescant, et foetida evadant; ovis autem fcecundis idem non contingat." Harveii De Generations Jlnimalium Exercitatio 22. "Ovum itaque est corpus naturale virtute animali praeditum ; principio nempe motus, transmutationis, quietis, et conservationis." Exercit. 26. " Cum enim in ovo macula prius dilatelur, colliquamentum concoquatur et praeparetur, plurimaque alia (non sine providentia) ad pulli formationem et in- crementum instiluantur, antequam quidpiain pulli vel ipsa primogenita ejus particula appareat; quidni utique credamus calorem innatum animamque pulli vegetativam ante pullurn ipsum exsistere ?" Exercit. 57. PREFACE. in For the thing containing is made to be serviceable to the thing con- tained. " Nor is the blood therefore to be call the primogcnial part, be- cause that in and from it the organ of pulsation is derived, but also because the animal heat and vital principle are first implanted therein; and in it does life consist. For where heat and motion first begin, there also life doth first arise and last expire. "—Harvey, On Generation, pp. 274, 275. This explicit and beautiful enunciation of the preexistence of the blood to the machine by which it is mainly circulated, and of its endowment of life, fell barren from the pen of Harvey (if we except the brief practice of transfusion to which it gave rise), and was for- gotten, when Hunter resumed the inquiry. And why, it may be asked, was the doctrine of the vitality of the blood inoperative, as taught by Harvey? Because instead of establishing that doctrine by observations and experiments, from which alone it was suscep- tible of deriving further proof,—instead of applying the principle to the explanation of the phaenomena of disease, and to a modification and improvement of remedial measures, Harvey obscures and for- gets the conclusion of his cooler moments of observation, and, as the learned Barclay well observes, excited by the discovery which had extended his fame so widely over Europe, and had reflected such lustre on his name and country, he expatiates on the blood as something divine; he has recourse to hyperbole, and describes its properties in the extravagant language of romance. Hunter, on the contrary, carries a series of calm and philosophi- cal investigations on the vital properties of the blood to an extent which has never been surpassed; he examines it under every con- dition, both in the vessels and out of the vessels, during circulation and at rest, in health and in disease. He aims to establish the period in its formation at which it manifests the vital properties ; and he fully details the changes which it undergoes, and the phaeno- mena which supervene in the rest of the organism when these pro- perties are lost. Lastly, he tells us how the blood, by means of its vital properties, assists in the restoration of parts when injured or diseased. Hunter subjects the blood to both mechanical and chemical analy- sis, and endeavours to determine the characteristic properties of its dif- ferent constituents. It was not known in his time upon which of these constituents the act of coagulation depended. Hunter took advantage of a case in which the red globules subsided, as in some cases they do, more rapidly than usual, and skimming off the super- incumbent colourless fluid, found that the fibrin, as it is now termed, immediately coagulated and formed a colourless clot.* A subse- quent erroneous theory, which attributed the act of coagulation to the red globules, has recently been set aside by the application of an ingenious process for artificially separating the fibrin from the * Treatise on the Blood, &c, p. 32. 1C HUNTER ON THE ANIMAL CECONOMY. blood disks before coagulation takes place, and the opinions: of Hunter on this point ha?c been fully established by the experiments of Mailer. With respect to the serum, Hunter instituted a number of experiments and made many ingenious observations to determine the relative quantity of the coagulable to the uncoagulable part. His deductions as to the amount of nutrient albumen in the blood of animals of different ages, and under different circumstances, as re- gards exercise or rest, &c, formed, from observing the quantity ol gravy or uncoagulable serosity which different roasted meats afforded, is highly characteristic of his original and ever active mind. In seek- ing to determine the respective importance of the different constitu- ents of the blood, by the philosophical and most difficult inquiry into their respective periods of formation in the development of the embryo, Hunter made the interesting discovery that the vessels of the embryo of a red-blooded animal circulated in the first instance colourless blood, as in the invertebrate animals. " The red globules," he observes, " seem to be formed later in life than the other two constituents, for we see while the chick is in the egg the heart beating, and it then contains a transparent fluid before any red globules are formed, which fluid we may suppose to be the serum and the lymph."* I well remember the feelings of surprise with which I listened while at Paris in 1832 to a memoir read before the Academy of Sciences by MM. Delpech and Coste, the object of which was the announcement of the same fact as a novel and important discovery. The statement of the French observers was received with all the consideration which its importance justly merited, without its being suspected that our great physiologist had half a century before em- braced it, with all its legitimate deduction, in the extended circle of his investigations. In the same spirit in which he investigated the nature of the blood he also pursued his researches on the properties of the solids; he endeavours to determine the specific powers and vital phaenomena of the nervous system and of the stomach; he compares these im- portant parts of the animal body, with reference to the degree of energy with which their functions are manifested ; he considers the influence which they reciprocally exert in maintaining the vitality of the blood, and the relative dependence of the whole organism on the integrity of their vital powers. He also dwells at great length on the sympathies resulting from these mutual relations and de- pendencies. In all his physiological researches we may see that instead of dogmatising on the powers and virtues of an abstract essence, Hunter endeavours to analyse the vital forces peculiar to each organic element, and to classify, as it were, the phaenomena of which life consists. If we turn from Hunter's researches on life to his investigations * TreatiBe on the Blood, &c, p. 71. PREFACE. 17 on another equally difficult and recondite subject in general physio- logy, viz., Animal, or rather, Organic Heat, we see the same exer- cise of the powers of the same great and original mind. He first determines the relative extent to which the power of generating heat or resisting cold is enjoyed in the two grand divi- sions of organic nature, plants and animals: he next investigates the degree in which that power is possessed by different classes of animals; then the relation subsisting between that degree and the perfection and complexity of the organization with which the power is associated. lie anticipates some modern physiologists in determin- ing the different power of generating heat manifested by the same species at different periods of life, and advances a step further by considering the different powers of resisting cold which different parts of the same organized body possess in relation to their re- spective ages and periods of formation.* He lastly analyses, so to say, the different functions, to determine in what degree the pro- duction of heat depends on their exercise; and reciprocally, the in- fluence of the temperature of the body upon the active and healthy maintenance of their function. Throughout all this beautiful and justly celebrated inquiry we see the philosopher conscious of the extent of his powers, and of the kind of knowledge which the right exercise of those powers was adapted to acquire. We now here perceive a trace of a desire to establish a theory of the nature of animal heat in the abstract. Let any one compare the language of Harvey or of Willis, while expatiating on the calidum innalum, with the following just remark: " I shall not," says Hunter, " attempt to settle whether heat is a body or matter, or only a property of matter, which appears to me to be merely a difference in terms, for a property must belong to something."! It is precisely in the same spirit that he conducts his researches on life; and I would say, after a very careful study of the writings of Hunter, that of all physiologists he is one to whom a dogmatic theory of abstract life can least be attributed. But by those whose notions of Hunter's doctrines are founded solely on a perusal of the posthumous " Treatise on the Blood" he is liable to be misconceived, and in opinions expressed from that limited acquaintance with his writings to be misrepresented. With the just ideas which Hunter had acquired of the laws of vitality and organic heat he was enabled to explain many of the phaenomena of digestion more satisfactorily than had been done by his predecessors Spallanzani and Reaumur. The following is a fair example of the different views and ninds of knowledge which these experiments brought to the inquiry. Spallanzani had observed that digestion did not go on in rep- tiles below a certain temperature, he thought therefore that heat * P. 158. t P- 162. 3 18 HUNTER ON THE ANIMAL CECONOMY. was necessary to assist in the dissolving processes of the sto- mach; Hunter, referring to the same fact, shows that the influence here is not merely chemical, but that the heat operates by first raising the sensitive powers, these then transmit the stimulus to the respiratory and circulating functions, and lastly;to the motive and other actions and faculties, and that the digestive organs are necessarily excited to corresponding actions, in order to supply the waste occasioned by the working of the machine, which the heat has thus called into play. Hunter more accurately determined, and first applied and render- ed fruitful the fact which Grew incidentally mentions, viz., That it is the property of a living body or part to resist the action of the gastric juice ; and his celebrated paper "On the Digestion of the Stomach after Death," is a beautiful example of the application of his general view in physiology to the explanation of particular phaenomena. Of all his published writing, the paper on Digestion convey perhaps the best idea of the extent of Hunter's researches in Com- parative Anatomy, and of the soundness of his reasonings in General Physiology. Hunter's claims to the originality of observations which have been reproduced as new by late physiologists, I have pointed out in the notes to these and other memoirs; and have particularly endea- voured to define the merit of Hunter as a discoverer in reference to the absorbent system. Hunter's published writings on the Nervous System bear but a small proportion to the extent of his anatomical investigations on this subject, especially as they are manifested in the philosophical series of preparations in the Gallery of his collection, in which the nervous system is traced through its progressive stages of compli- cation, from the simple filaments of the entozoon and echinoderm, to the aggregated masses which distinguish the organization of man. The fibrous structure of the brain, the discovery of which, though due to Coiter as early as 1573, has sometimes been attributed to Reil and Gall, is displayed by Hunter in preparations made to show the fact (Nos. 1335, 1336), and is expressly mentioned in the description of the Anatomy of the Whale Tribe.* In treating of the comparative anatomy of the nervous system in his introductory observations to this division of his Collection^ Hunter rises to the following generalizations. He divides the ani- mals which have brains, or visible aggregations of the nervous sub- stance, into six classes, each characterized by a peculiar modifi- cation of the brain. The 'first class* has a brain in the form of a ring, through which passes the oesophagus, and from which the nerves arise, like radii from a centre. It consists of a pulpy substance, somewhat trans- parent, which is easily squeezed out when the brain is cut into. It r P. 373. + Physiological Catalogue, vol. iii., p. 4. PREFACE. 19 is not enclosed in hard parts, and is not defended from pressure or injuries more than any other internal part. The examples of this type in his Museum are selected from the gastropodous class of Mollusca. The same condition of the nervous system we now know, from the researches of Cuvier, to charac- terize the whole of a vast division of invertebrate animals, including, amongst the highest organized of that division, certain species,— the dibranchiate Cephalopods,—in which the character, as expressed by Hunter, is affected by the development of a cartilaginous cranium for the protection of the cerebral ring ; but ulterior researches have not led to any modification of Hunter's description of the typical form of the brain in the Molluscous sub-kingdom. In the 'second class ' the brain lies in the head of the animals ; it is a pulpy substance, somewhat transparent, which gives it a bluish cast; from its lower part go out two large nerves, one passes on each side of the oesophagus, and they then unite into one, form- ing a knot at their union; they disunite again, and so unite and disunite alternately through the whole length of the animal, at every union giving off the nerves as from the brain. This structure, Hunter says, he suspects to answer both the use of a medulla spinalis and the great intercostal nerve. The examples of the class of animals adduced by Hunter as being characterized by this essential form of the nervous system are the leech, earthworm, aphrodita, centipede, caterpillar, scorpion, and lobster. Subsequent researches have shown that it exists in the barnacles, or Cirripedia, which most zoologists now rank in the same primary division with the Anellides, Insects, Arachnidans, and Crustaceans. In the first class of animals in this neurological arrangement (for in enunciating general propositions respecting any given organ the comparative anatomist becomes involuntarily, as it were, a classi- ficator of animals as well as organs), Hunter observes, " we had the brain surrounded by soft parts only. In the second it was closely surrounded by soft parts, but these were surrounded by hard. In the 'third class' the brain has a case of hard parts for itself, called the skull." Now when Hunter made a brain relatively larger than in his first two classes—protected by a skull,—and continuous with a medulla spinalis extended down the back, and an endowment of the five senses,—the essential neurological characters of his third class of animals,—he erred in not applying them to his fourth, fifth, and sixth classes, as an attribute common to all, and one which dis- tinguished each alike from the two lower classes. The apprecia- tion of the great natural group characterized by a brain and spinal chord, situated on the dorsal aspect of the body, and protected by a vertebral case, was reserved for the sagacious penetration of Cuvier. However, in so far as Hunter limits his generalizations to the brain alone, he is consistent with himself, and exact in the differential 20 HUNTER ON THE ANIMAL OICONOMY. characters which he points out. The brain in fish, for example, or his ' third class,' is a very irregular mass, inconstant in its form and in the number of its parts ; still the " several parts which are similar to those in a superior class may be picked out;" the skull, more- over, is too large for the brain, and the interspace is filled by a cellular membrane, which Hunter compares to the arachnoid. In the 'fourth class,' the parts composing the brain " do not lie one upon another, but are very much detached and follow one another," in short, are characterized by their linear arrangement; a character, the accuracy of which, as applied to the Reptilia, has been confirmed by all subsequent experience. It is interesting to observe how Hunter determines the nature of these different de- tached masses. He says, " The two anterior consist of the cere- brum ; the two middle, I should suppose, of the nates and testes, which I take to be the middle lobes detached, because in the bird they are more underneath, not so much between the cerebrum and cerebellum ; the posterior is the cerebellum, consisting of one body entirely."* Every eminence, Hunter further observes, has a cavity or ventricle in it. The linear arrangement of the masses of the brain is common both to fishes and reptiles; but the relation of those masses to the skull, and their variable number and propor- tions, according to Hunter, distinguish the brain in fish. He further observes that in the crocodile the parts of the brain are more closely connected, and that the skull is more in contact with it, in which respect it comes nearer the bird than do any of the other amphibia. The brain in the 'fifth class,' or fowl, Hunter characterizes by its greater relative size, and the superposition of its component masses. In the ' sixth class,' or quadrupeds, the brain is in general larger than in the preceding, and the parts more compacted, the whole mass being brought into nearly a globular figure. " The nates and testes are four small bodies, with no visible cavities; are not seen externally, but lie at the posterior end of the third ventricle."t In the observations printed in the present volume on the branches of the fifth pair which are distributed to the nose and ear, we can- not fail to observe that Hunter had entered on that track of inquiry, and pereeived the governing principle or idea, which, more clearly appreciated and steadily retained by Sir Charles Bell, has since led to such important improvements in'this department of physiology. Hunter premises his description of the nerves which supply the organ of smelling by calling attention to the constancy which* per- vades the anatomical conditions of the nerves, and states in general his belief that particular nerves have particular functions, in relation to their differences of origin, union, and distribution ;J but this simple enunciation, without the proofs and illustrations of which it was susceptible, became unproductive of its proper results, and appears to have been subsequently lost sight of by Hunter himself, 1 phy on!i0gonal CataloSlie' ▼ol- »»•» P- 7. f Ibid., p. 10. PREFACE. 21 when speculating on the nerves as internuntiate conductors of a materia vitce diffusa. A knowledge of Hunter's opinions on the nervous system, derived only from the observations on that subject which occur in the Treatise on the Blood, might lead to the belief that he attributed to all the different nerves one common function ; but after perusing the distinct exposition of his views on this branch of physiology as recorded in the Animal CEconomy, it appears to me that Hunter needed only to have resorted to experiment in this, as he did so successfully in other fields of physiological inquiry, to have esta- blished the nature and degree of the functional differences of these nerves, of which he describes the anatomical conditions giving rise, as he supposes, to those differences. He limits himself, however, in his illustration of the grand propo- sition, by anatomical examples only. He shows that organs like the eye and nose, which are endowed by means of one nerve with a special sense, derive their ordinary sensation from a second nerve having a different origin. This nerve he determines, in the case of the eye and nose, to be the fifth pair. He says the same mode of reasoning is equally applicable to the organ of taste, and he traces the corresponding superadded nerve to the ear. Hunter further distinguishes the sensations of the stomach and of the glans penis as being peculiar, and shows that as these peculiar sensations reside in particular nerves, so at whatever part of the nerve the impression is made it always gives the same sensation as if affected at the common seat of the sensation of that peculiar nerve. In another place Hunter makes the ingenious remark that the nerves which are specially designed to receive peculiar impressions convey the ideas of such impressions to the brain, in whatever way they may be affected or stimulated. Thus he says, " A mechanical impression on the retina produces an impression of light; a blow on the ear the sensation of sound."* And later experiments have only extended this principle, by showing that whether the nerve be affected by mechanical, chemical, or electrical stimuli, it conveys the same sensation. Much importance has been attributed to these observations, on the supposition that they were new, and I have been induced to dwell thus long upon Hunter's contributions to the physiology of the nervous system, because in most of the recent works upon that subjec' he does not receive the credit which is due to him for having made them. The physiological discoveries of Bell, Magendie, Mayo, and Muller, have resulted from the combination of experiment with a philosophical consideration of the anatomical peculiarities of the nervous system. It was the neglect of experiment in this depart- ment of p'hysiology which rendered Hunter unable to account for ♦Lectures on Surgery, p. 56-7, of the'present edition, and Parkinson's Ilua- terian Reminiscences, p. 12. 3* 22 HUNTER ON THE ANIMAL 03C0N0MY. the peculiarities which equally struck his mind as being connected in an intimate degree with the functions of the nerves. Had Hunter combined experiment with dissection when he traced the lateral branch of the nervus vagus in the cod, the eel, and the gymnotus, and wondered " that a nerve should arise from the brain to be lost in common parts, while there was a medulla spinalis giving nerves to the same parts," this probably would not have remained to him, as he expresses it, " one of the inexplicable cir- cumstances of the nervous system."* Having been induced to 'dwell on the improved views which Hunter either established or suggested in different branches of physiology, I proceed next to advance a few instances of his dis- coveries in comparative anatomy, which, on the supposition that they were original, have contributed to add to the reputation of subsequent anatomists. 1. The organ of hearing in the sepia. The fact that this cepha- lopod possesses the organ in question is stated at p. 300 of the present edition of the Animal CEconomy, and it is said to differ from that of fishes. The discovery is attributed by Cuvier to Scarpa. 2. The semicircular canals of the Cetacea, described by Hunter in the paper on whales, a structure which Cuvier rightly states that Camper overlooked, but incorrectly claims the discovery as his own. 3. In the latest sketch of the history of comparative anatomy, prefixed to the French translation of Carus's Zootomie, John Hunter is introduced as the impudent self-appropriator of Camper's dis- covery of the air-cells in the bones of birds; and the historian of the science does not honour him with any further notice. Now the [acts with reference to this subject are as follows: Camper's account of the.air-cells in the bones of Birds was first published in the Dutch language in the year 1774, the same year in which Mr. Hunter's discovery was published in the Philosophical Transactions. The French memoir of Camper was not published till the year 1776, in the seventh volume of the Memoires Etrang. de VAcademie des Sciences de Paris. Hunter gives the date of his discovery as being in 1758; Camper his, in the year 1771. The numerous observations and experiments which their respec- tive memoirs detail are not such as could hastily be got up for an unworthy purpose ; but as both memoirs (which differ materially in their general scope and the mode in which the subject is treated) were published in the same year, the honour of the discovery may fairly be attributed to both their authors. I might dwell on the philosophical comparison which Hunter makes between the abdominal air-cells of the bird and those of reptiles and fishes had he not in this instance been anticipated by Harvey. Harvey, however, was not aware that the respiratory ♦ Animal (Economy, p. 412-13. PREFACE. 23 system was extended into the muscular interstices and the cavities of the bones; the honour of which discovery must be assigned to Hunter and Camper, without the necessity of supposing that either had borrowed from the other. The preparations in the Hunterian Collection and the Manuscript Catalogues show that Mr. Hunter had discovered the peritoneal canals or openings in the eel, salmon, and the cartilaginous fishes, in the crocodile, and the continuation of the same peritoneal canals into the corpus cavernosum penis in the tortoise and turtle. The latter have been recently rediscovered by MM. Isidore St. Hilaire and Martin St. Ange. Hunter's printed works, preparations, manuscripts and drawings contain proofs of his discovery of the circulation of the blood in insects, and of the peculiar diffused irregular and extended venous receptacles in these and the crustaceous animals, in the latter of which their existence remains unnoticed, even in the latest works on the subject. In the Treatise on the Blood* we have an opportunity of judging, by the accuracy of the general propositions which he enumerates on this subject, of the extent of Hunter's researches on the com- parative anatomy of the circulating system, and of the spirit in which he prosecuted the induction of particular facts. I cannot resist the quotation of the following passages which relate to the circulation in insects. "In the winged insects which have but one heart, as also but one circulation, there is this heart answering both purposes" (viz., the corporeal and the pulmonary circulations), p. 172. " Many of those which have one ventricle only have no auricle, such as insects ; but there are others which have both a ventricle and auricle, such as fish, the snail, and many shell-fish; some of the last class have indeed two auricles, with only one ventricle.—" The heart "is placed in what is called the chest in the quadruped, bird, amphibia, fish, and the aquatic and terrestrial insect, but not in what may be called the chest in the flying insect. " The chest in the aquatic insect seems best suited to contain the lungs and branchiae, and therefore the heart is placed there; but as thelungs of the flying insect are placed through the whole body of the heart is more diffused, extending through the whole length of the animal." p. 174. " Where the veins entering into the heart are small in comparison to the quantity of blood which is wanted in the ventricles, then we have an auricle; but when the veins near to the heart are large, there is no auricle, as in the lobster and generally in insects." p. 176. " In all animals which have an auricle and a ventricle, so far as I know, there is a bag (unattached) in which they are placed, called a pericardium ; but the insect tribe, whether aerial, aquatic, or ter- restrial, have none, their hearts being attached to the surrounding parts by the cellular membrane or some other mode of attachment. * § 5., p. 171 of the present edition. 24 HUNTER ON THE ANIMAL CECONOMY. The heart " gives to the blood its motion in most animals, and in all it sends the blood to the organs of respiration ; in the flying insect it sends the blood both to those organs and to the body at large, but in fish to those organs only, the body at large in them having no heart. In the amphibia there is an attempt towards a heart both for the lungs and body, but not two distinct hearts. In the bird and quadruped there is a distinct heart for each." And again, " With respect to its use, it is in the most simple kind of heart to propel the blood through the body immediately from the veins, which blood is to receive its purification in this passage when the lungs are disposed throughout the body as in the flying insect." p. 179. The researches of Cuvier led him to conceive that there was a generally diffused, but passive, or non-circulated condition of the blood, coexisting in insects with the distribution of the breathing organs through the whole body. Hunter, on the contrary, while he rightly appreciated that condition of the circulating system in insects which related to their peculiar respiration, viz., that the venous blood was diffused apparently through the cellular membrane, in the interstices of the fat, air-cells, and muscles, and that the veins in insects might be called in some measure the cellular membrane of the parts;* yet he well knew the relations of these diffused re- ceptacles of the venous blood to the dorsal heart, and the circulatory movement which was impressed upon the vital fluid by that organ. It is this remarkable error of Cuvier, with reference to the circula- tion in insects, that has given to the direct observations of the blood's motion by means of the microscope in the hands of Carus, Bowerbank, and other excellent observers, the character of a new discovery. Hunter first determined the bi-auricular structure of the heart in the batrachian caducibranchiate reptiles, which he included in the class Tricoilia of his classification of animals according to the structure of the heart. Hunter first discovered, by means of retrograde injections of the tuhuli uriniferi, that these essential partsof the kidney extended to the superficies of that gland, and were not confined to the medullary substance. Meckel, who saw while in London the beautiful pre- parations establishing this fact (Nos. 1202, 1203, 1214, 1215, 1235), described them on his return to Germany to Miiller,f who, in his repent elaborate work on the glands, acknowledges how important this observation was in establishing true notions of the structure of glands. Hunter extended his researches on the renal organ to the inver- tebrate classes, and shows " the kidney of the snail;" and the cor- rectness of this ascription to the so-called mucous gland has been recently established by the observations of Professors Jacobson and de Blainville. • See Physiological Catalogue, ii., p. 31 ; also the note at p. 221 vol iii of the present edition. ' ' 0,> "'•» 0I f De penitiori structural Glaadularum fol. p. 95. PREFACE. 25 I have selected a few facts from amongst the multitude which Hunter ascertained in the progress of those investigations, by which he sought in the simpler modifications of the structures in the lower animals the true uses of the different organs which are combined to form the complex frame of man. I might lastly allude to the extraordinary nature and extent of Hunter's labours in another track of physiological inquiry, viz., that which unfolds the laws of generation and animal development; but as the work confided to me by the Council of the Royal College of Surgeons, viz., the description of the series of preparations on these subjects, which include nearly one-half of Hunter's grand Physiological Collection, is still in progress, I defer the comparison of Hunter's labours in this field with those of his contemporaries until the whole body of the evidence of his discoveries can be laid before the public. The papers, however, which Hunter published in his lifetime, and which form the first part of the present volume, convey a most favourable idea of his views respecting this recondite branch of physiology. It is here that we find an attempt to explain congeni- tal defects by reference to the transitory structures or metamorpho- ses of foetal life. It was a question in the time of Hunter how it happened that the gut in the hernia congenita came to be in contact with the testes. Hunter solved the question, by direeting attention to the position of the testis in the abdomen, and to its relations to the other abdomi- nal viscera, and to the peritoneum, a few months, before the expi- ration of the term of foetal development. He watched the progress of the gland to the scrotum ; saw it carrying along with it a perito- neal pouch like the sac of an intestine, and thus demonstrated, that if the closure of that sac was prevented by the contemporaneous passage of a loop of intestine, it must remain a common receptacle, both of the part which had naturally, and the part which had pre- ternaturally, escaped from the abdomen. Hunter then goes on to show how the early and transitory con- dition of the tunica vaginalis in the human foetus, and also the still earlier abdominal position of the testes, are permanent structures in the lower mammalia. With respect to monstrosities in general, Hunter had drawn out a scheme for their classification, and had produced them by experi- ment. In the " Account of an extraordinary Pheasant" he states that every species of animal, and every part of an animal body, is subject to congenital malformation ; but he knew that such appear- ances were not attributable to a freak of Nature, or a matter of mere chance; for he observes that every species has a disposition to deviate from Nature in a manner peculiar to itself. It is this principle which forms the basis of the latest and most elaborate treatise on monsters,* a work which its author describes as being * Histoire des Anomalies de reorganization chez l'Homme et les Animaux, ou Traite" de Teratologic, par Isid. Geoffroy St. Hilaire: Paris, 8vo. 1832. 26 HUNTER ON THE ANIMAL CECONOMY. "the result of his having established by a great number of re- searches, that monsters are, like the beings called normal, sumect to constant rules." fa With respect to the cause or origin of monsters, Hunter reterred it to a condition of the original germ, or, as he expresses it, "each part of each species seems to have its monstrous form originally impressed upon it." In the introductory observations to his exten- sive collection of malformed foetuses and parts, he assigns the grounds for this hypothesis, and at the same time enunciates one of the most remarkable laws of aberrant formations. "I should imagine," he writes, " that monsters were formed monsters from their very first formation, for this reason, that all supernumerary parts are joined to their similar parts, as a head to a head, &c, &c." In proof of the important general principles, at a knowledge of which Hunter had arrived, I have elsewhere quoted this passage, together with the following remarkable one from Hunter's descrip- tions of his drawings illustrative of the development of the chick. " If we were capable of following the progress of increase of the number of the parts of the most perfect animal, as they first formed in succession from the very first, to its state of full perfection, we should probably be able to compare it with some one of the incom- plete animals themselves, of every order of animals in the creation, being at no stage different from some of those inferior orders; or in other words, if we were to take a series of animals from the more imperfect to the perfect, we should probably find an imperfect animal corresponding with some stage of the most perfect."* We may, I think, perceive, from the evident difficulty with which Hunter expresses the idea, that his mind was oppressed with both its novelty and vastness. Men's thoughts require to be familiar- ized with propositions of such generality before their exact limits and full application can be appreciated. Sufficient, however, has been adduced to prove the tendency of Hunter's labours, and that he possessed the highest qualifications as an investigator of Nature ; unwearied in induction, sagacious in grouping together analogous phaenomena, and ever striving to ascend from propositions of less to those of greater generality. Had the means and time been granted to Hunter to have made public the results of all his labours, or had his manuscripts enuncia- ting, or indicative of, so many general principles been fairly appre- ciated and given to the world, our teachers of anatomy would not now, after a lapse of half a century, have but begun to explain to their students those beautiful laws of animal development for the knowledge of which they are indebted to the labours of the profes- sors in the noble schools of physiology in Continental Europe, where teJ/Tl p {iu,ntenan. inquiries seems to have so long exclusively resided. But the period which has elapsed before those general laws began to be appreciated in the country where theV were first detected, affords perhaps, one of the strongest indications of the great advance which Hunter had made in physiological science * See preface to the Physiological Catalogue, vol. i. p., ii. PREFACE. 27 It would be a strange exception to the usual result of an exten- sive knowledge of comparative anatomy, combined with a tendency to express in general propositions new physiological and structural truths, if the possession and application of that knowledge with that tendency had so led to some corresponding advance towards a natural system of zoological classification. Accordingly we find the contemporaries of Hunter ascribing to him the highest ac- complishment which the zoologist can aspire to, that of discerning the natural affinities of a nondescript object; and this in terms and on occasions which seem to imply a general admission of his pos- session of such attainments. When the rare quadrupeds of Austra- lia were first brought to England, presenting, as they did, to the eye of the zoologist anomalies and peculiarities not less striking than those which perplexed the botantist in the plants from the same part of the world, it was to Hunter that they were referred. " There was no person," says Dr. Shaw, " to whom they could be given with so much propriety, he perhaps being most capable of examining accurately their structure, and making out their place in the scale of animals."* It may not be uninteresting to contrast the sketches of systems of zoological arrangement which Hunter has left, with the Linnaean method which prevailed in his time, and which continued to prevail until superseded by the labours of Cuvier, specially and unremit- tingly directed to that end. We have already seen that Hunter's attempts to enunciate general propositions respecting the nervous system led him to detect the condition characteristic of the mol- luscous sub-kingdom, and to speak of the animals with " the brain in the form of a ring, " &c, as a class. In still more definite terms he describes the condition of the nervous system which characterizes the articulate Invertebrata. With respect to that higher type of the nervous system, which is manifested in its aggregation into spinal and cerebral masses, we have seen that Hunter alludes to it as distinguishing only the class of fishes from his first and second classes, or the Molluscous and Articulate divisions as they are now termed ; and that he failed to perceive that all the other vertebrate classes were equally charac- terized by it. To Hunter, however, we must award the merit of having first obtained a perception of the distinct group formed by the higher organized vermes of Linnaeus, and their essential organ- ical character. Hunter had also investigated the structure of zoophytes, in which no annular brain can be detected ; he had conceived the idea of animals in which the nervous matter, or something analogous to it, a materia vita diffusa, was dispersed throughout the system. And we find another learned contem- porary of Hunter, in ascribing a diffused condition of the nervous matter to the Taeniae, bearing testimony that Hunter had entertained * Zoological Appendix to White's Voyage to New South Wales, p. 468 of the present work. 28 HUNTER ON THE ANIMAL CECONOMY. a similar opinion, and had applied that character of the nervous system to many of the lower tribes of animals.* The distribution of animals according to the nervous element ot their organization, is, however, but one of several attempts at classi- fication which Hunter made. The next scheme which we shall quote is one founded upon modifications of the generative function.! Hunter's first class, or Vivipara, corresponds with the Zootoka of Aristotle, and the Mammalia of Linnaeus ; these animals develop their young in the uterus, he says, from a mixture of male and female influence, and bring forth a living offspring. The second class, or Ooovivipara, is a subdivision of the Ootoka or Ovipara of Aristotle, and " hatch their young from an egg in the oviduct, as vipers, slow-worms, some lizards, newts, and the dog-fish." The third class includes the Ovipara, or " such animals as exclude their eggs, which are afterwards hatched out of the body ;" but this character, as Hunter justly observes, " takes in a wide field." Fourthly, he says, " We have animals which propagate by slips, and that in two different ways, one by a piece cut off, the other by branches growing, and these falling off', and producing a distinct animal." Hunter here rightly regards the fissiparous and gemni- parous modes of generation as modifications of the same reproduc- tive process which is characteristic of that lowest group of animals previously indicated by the molecular condition of the nervous system, and " where every other principle of the animal is diffused through the whole," a condition which in the animal kingdom seems essential to the possession of the property of fissiparous re- production, or to a division of the whole body with a continuance of the vital properties in the parts. Hunter seems, however, to have felt how unsatisfactorily and artificial was the classification founded on modes of generation, for he adds in the manuscript in which the above sketch is given, " Animals of any particular class have not one way only of propagating their species, excepting the more perfect, or first class according to hearts, for we have the second and even the third class aping the first, and attempting to be vivi- parous, as vipers, lizards, and some fishes, as the skate." He might have added examples of ovoviviparous animals, from the molluscous, articulate and radiate classes,—classes which in every other re- spect are most dissimilar. This idea of an arrangement of the animal kingdom from modifications of the generative function was afterwards carried out by Sir Everard Homeland applied by him to the definition of the narrower or subordinate groups. But as of all single characters the generative system affords the most, arbitrary and unnatural distinctions, and corresponds least with the modifi- ♦ See Carlisle, On the Structure and CEconomy of Taeniae, Linnaean Transac- tions, vol. ii. p. 253, and Treatise on the Blood, p. 116, of the present edition j See Introduction to the Physiological Catalogue, vol. iii., p. vi. i See his Syslema Itegni Animalis nunc primum ex ovi modificationibus vro- positum, Lectures on Comparative Anatomy, vol. iii., p. 535. H PREFACE. 29 cations of the rest of the organization, a classification of animals based upon it is least adapted to afford any of the conveniences of even an artificial system. In the Systema Naturce of Linnaeus the first of the characters by which the six classes of animals are distinguished is derived from modifications of the structure of the heart, as follows: " Mammalia, Cor biloculare^biauritum ; Aves, Cor biloculare, biauritum ; Amphybia, Cor uniloculare, uniauritum; Pisces, Cor uniloculare, uniauritum ; Insecta, Cor uniloculare, inauritum; Vermes, Cor uniloculare, inauritum." But Linnaeus combines the cardiac character with others derived from the nature of the blood, the condition of the respiratory organs, the structure of the mouth and generative organs, the nature of the integuments, &c. and thus makes an approach to a natural system of arrangement. Hunter, in his distribution of animals into different classes ac cording to the structure of the heart, uses the cardiac character singly, and produces a purely artificial arrangement; but his superior anatomical knowledge manifests itself in the accuracy with which he defines the condition of the circulating organ characteristic of the different groups. His first class includes the Mammalia and Aves of Linnaeus, and he proposes to call it Tetracoilia, the heart having four cavities, viz., two ventricles and two auricles. The second class, Tricoilia, includes those animals which have a heart with three cavities, viz., one ventricle and two auricles, and corresponds with the Amphibia of Linnaeus. The anatomical inac- curacy in the Linnaean character, although so early corrected by Hunter, long retained its ground in the systematic works of conti- nental naturalists, and continued to be erroneously applied to the Batrachian section of the Linnaean Amphibia until a very recent period.* * The two auricles were after the time of Linnaeus successively assigned in systematic works to the Chehnia and Sauria. Blumenbach long contiuued to assert that serpents, at least those of Germany, had but one auricle ; Cuvier al- lowed them two, but denied this higher structure of the heart to the Batrachia .• " lis n'ont au cceurqu'une seuleoreilletteet un seul ventricule." Regne Animal, ii., p. 101, edit. 1829. Meckel also ascribes this structure to the generality of the Batrachia: "Die Batrachier haben die einfachste Herzform. Das Herz besteht sehr allgemein nur aus einer Vorkaramer und einer Kammer." Vergl. .inat., band v., p. 215. The more complicated structure of the heart was, how- ever, truly described in the anourous Batrachia by Dr. John Davy in 1825; his observations Were confirmed by Prof. Weber in 1832; and in April, 1834, I communicated to the Zoological Society the result of a series of examinations of the hearts of the Batrachia, which proved that the whole order, including the perennibranchiate species, had distinct auricles for the pulmonic and systemic blood, since which time the tripartite structure of the heart has been universally assigned to the Batrachia. 30 HUNTER ON THE ANIMAL CECONOMY. The third class, or Dicoilia, includes those which Jave cavities in the heart, or one ventricle and one auricle, ian a oo of the gill-fish. The sharks and rays were included b> wuni« hi this class, but the diccelous or bipartite structure °£ the,ir,^a^P^e" sented no obstacle to their junction with the Amphibia in the Linnaean arrangement. . , , uQor4 Hunter's fourth class, or Monocoiha, characterized by a heart with but one cavity or ventricle, without an auricle, is restricted to insects of all kinds, i. e. to the articulate animals included by Hunter in his second class according to brains. . By Linneeus the character is applied to all invertebrate animals without exception. Hunter, with more truth, defines & fifth class of animals, by the name of Acardia, " whose stomach and heart are the same body, as in the blubber (Medusa) and polypus." But even with this improvement, the Cardiac arrangement of animals, as proposed by Hunter, is very incomplete. The whole division of the molluscous animals is left out of the system. This did not, however, arise from a want of the knowledge of the structure of the heart in those animals. Hunter well knew the complex condi- tion of the circulating organ in the cuttle-fish, a condition which, had he rigorously carried out his scheme of classification according to hearts, would have indicated a class above the mammalia, and to which the name of Heptacoilia might have been applied, since there are three distinct ventricles, one systemic and two pulmonic, and four auricles or venous sinuses in this and other dibranchiate cephalopods. In the snail and other gastropods Hunter had recog- nised a structure of the heart as complex and perfect as in fish, but having a different relation, both as regards function and position, to the respiratory organ.* In still lower Mollusca Hunter had detected the existence of two distinct auricles, with one ventricle ;f but his perception of the physiological relations of these different cavities prevented him from associating the mussel with the tortoise, on account of this tricoelous structure of the heart. We may thus perceive amidst the defects of this system of arrangement an evident advance towards a more natural distribution of animals, especially of the invertebrata, than that which was generally accepted at the period when Hunter wrote. We associate this progress with Hunter's superior knowledge of the organization and ceconomy of animals as its just and natural cause, and we proceed to adduce additional evidences of Hunter's attempts to frame a natural arrangement of animals. Perceiving that the modifications of the heart alone were inade- quate to the formation of a natural and symmetrical classification of animals, he next tested the efficiency of characters taken from conditions of the respiratory system, and proposed the following scheme: " The first class includes all those animals which have lungs with cells through the whole, and a diaphragm. ♦ On the Blood, vol. iii., p. 172. J Ibid., p. 172. PREFACE. 31 " The second class, all those which have their lungs attached to the ribs, so as to confine them to their place. " The third class, all those whose lungs come into the belly and are loose. " The fourth class, all those whose lungs are in their necks, called gills. " The fifth class, all those whose lungs are in their sides."* In this scheme we have most exact and concise characters of the four classes of vertebrate animals, as afforded by the breathing organs; and in this case Hunter was enabled by his profound anatomical knowledge to rise far above Linnaeus. In the Systemce Naturo?, the Mammalia and Aves, which corres- pond with Hunter's first and second classes, according to the organs of respiration, have both the same characters assigned to them, " pulmones respirantes reciproce," while the Amphibia, to which Hunter's third class corresponds, are said by Linnaeus to have " pulmones spirantes arbitrarie." Neither Hunter nor Linnaeus, however, arrived at the perception of that condition of the respira- tory organs which characterizes their first four classes in common, viz., that the breathing organs communicate with the mouth; nor am I aware that the Vertebrata have ever been distinguished in any system as oral breathers, in contradistinction to the Mollusca, which may be termed anal breathers, and to the Articulata, which respire by apertures or branchial organs arranged symmetrically at the sides of the body. We have thus traced Hunter in his character as a systematic zoologist through a series of attempts at the arrangement of the animal kingdom, in which, like the indefatigable Adanson in a sister science, considering each organ by itself, he formed, by pursuing its various modifications, a series of groups characterized by that organ alone ; and doing the same for another organ and another, thus constructed a collection of systems of arrangement, each arti- ficial, because each was founded upon the variations of a single as- sumed organ. It would, however, be doing injustice to Hunter to adduce the evidences of these attempts only. In that division of the animal kingdom where he had pushed his researches furthest, he aims to establish a more natural classification, by tracing the variations of all the important organs, and keeping in view the different value of each character; and thus he enunciates several general anatomical and physiological truths. The following are the characters which he assigns to the different classes of the animals now called Verte- brate. " The properties of the First Class, which includes both sea and land animals, are " Heart, made up of four cavities, essential. " Lungs, divided into small cells, and confined to a proper cavity, *" Physiological Catalogue, Introduction to the Third Volume, p. r. 32 HUNTER ON THE ANIMAL CECONOMY. the enlargement of which is the cause of respiration; essential, Respiration quick (and I believe this is the only class in wnicn it is so); essential. " Give suck; essential. . . " Parts of generation, made up of testes and one penis in trie male ■ the testes sometimes within and sometimes without the abdomen, but pass forwards. Clitoris, vagina, uterus or uteri, Fallopian tubes, and ovaria, in the female: all es- sential: " Kidneys, high up in the abdomen; circumstantial. " Organ of hearing, an external canal to the ear, membrana tympani concave externally,* a cochlea ; circumstantial. " The animals of this class are by much the most perfect, whether sea or land. There is a gradation from the land to the sea animals, viz., otter, seal, hippopotamus, whale. " The Second Class is confined to the Birds entirely. I do not know of any animal of this class but what has all the characteristics of the bird. They vary less in any of their parts than the first class.f " Lungs, attached to the ribs, that they may move with them: lungs perforated ; membranous bags in the abdomen that re- ceive air in respiration; something like a diaphragm. "Parts of generation, ova crustaceous; one oviduct; one penis, and that grooved; no bladder. Oviduct in the female, and penis with the vasa deferentia in the male, all open in the same cavity with the anus. " Liver, divided into two lobes ; cyst-hepatic ducts. " Organ of hearing, little external passage to the ear; membrana tympani convex externally, but one bone (ossiculum auditus); no cochlea. "Feathers; wings; two legs; long neck; bill; membrana nic- titans; bursa Fabricii. "There is none of this class that belong entirely to sea animals; but this class may be said to possess in some measure three elements, viz., air, earth, and water; but they live no more in the air than other animals, for it is only for their progres- sive motion. " In the Third Class we shall find some parts similar to the second. The third class may be divided into two, for they are not exactly alike, but one seems to partake of the second and third ; as it were, made up of both. The first division of the third class, then, is the Lizard and Serpent kind. They have " Heart, two auricles, one ventricle, two aortas which unite in the abdomen. * This appears to have been written before Mr. Hunter had dissected the organ of hearing in the whale. See p. 380, and note*. t So also Cuvier: " De toutes les classes d'animanx, celle des oiseaux est la mieux characterises, celle dont les especes se ressemblent le plus "—Ettme Anon., 1. p. 310. r ' ■"cs',ti PREFACE. 33 " Lungs, loose bags, which lie in the thorax and abdomen, only partially divided. No diaphragm. " Kidneys, in the lower part of the abdomen. No bladder.* " Parts of Generation, two penises, grooved,t which are in the tail. Some oviparous, eggs without shells; others viviparous, but not as the First Class. " Some have legs, others none; some a membrana tympani, which is convex outwardly, as the lizard; others none, as the snake. " The other part of this class, which may be termed the Fourth, or the Amphibious, are more closely allied to Fish than what the fish of the first class are.J These are the common amphibious animals, viz. frogs, turtles, efts, &c. This is also very similar to the two former, and is nearly, as it were, a mixture of both, yet the most essential parts belong, or are similar to the last. " Heart, two auricles, as in the Third; one ventricle, as in the Third ; aorta, as in the Third. " Lungs, as in the Third. " Kidneys, as in the Third. " Part of generations, one penis, as in the Second Class ; penis grooved, as in the Second and Third. Some oviparous, as the frog; others vivaparous as the salamander. " Organ of Hearing, some have a membrana tympani, as the frog ; others none, as the tortoise.^ " The Fourth or Fifth Class (according as the two preceding are regarded as subdivisions of one class, or as two distinct classes) consists of Fishes, and is very distinct from the former so far as I know." The manuscript from which the preceding remarkable passages are quoted, and which is printed entire in my Prefatory Observa- tions to the Third Volume of the Physiological Catalogue, contains no characters of the Class of Fishes, nor any relating to the Inver- tebrate Classes. It is in the definition of these latter classes, and in the determination of the wider divisions of the Invertebrata, which were equivalent to the entire vertebrate group, that Cuvier chiefly surpassed Hunter as a systematic zoologist. Yet, as I have before observed, Hunter rises above Linnaeus even in this depart- ment: he had seized the great character of the molluscous sub- kingdom afforded by the nervous system, and had well defined some of the subordinate groups, more especially that which Lamarck afterwards termed Tunicata, and which Cuvier denominates * This character is not applicable to the lizards; but the crocodile agrees with the serpents in having no urinary bladder. t The crocodile has but one. X «• «• Those of the first class which are shaped like fish, and live in water, as the Cetacea. § The turtles and tortoises, or Chelonian reptiles, as they are now termed, have a closer affinity to the lizards than to the Batrachia, or frogs and salamanders. 4* 34 HUNTER ON THE ANIMAL CECONOMY. " Aciphates sans Coquilles," but which Hunter, more correctly, termed " soft-shelled," having perceived the analogy of their ex- ternal elastic tunic to shell; and having detected, with admirable skill, the relations subsisting between the Ascidiae and Salpae in different individuals dissected by him, of which dissections there remain not only the preparations, but several beautiful designs, with the original descriptions.* Of Hunter's appreciation of the progression of affinities we have an example in his sketch of the transition from the terrestrial to the aquatic Mammalia; and I do not doubt that ere long zoologists will uniformly agree in the propriety of passing from the hippopo- tamus and its pachydermatous congeners to the dugong and the true Cetacea, instead of interposing the Ruminantia between the Pachy- dermata and Cetacea, as in the Cuvierian system. Of his mode of considering the affinities of two great and equal groups, Hunter has left the following specimen, which he quaintly designates " Of the similarity of the Fowl with the three-cavity- hearted gentry, called Amphibia." " The lungs of the fowl open into their air-cells or bags that are in the cavity of the belly. The lungs in the Amphibia are con- tinued into the belly, are cellular at the upper part, but in most, as the snake, become smooth bags at the lower end, as it were, answering the same purpose as the abdominal bags in the fowl. The cells of the lung-part are large. "No proper Diaphragm in either; but fowls have something similar to one.f " The Gall is green in both. " The Kidneys are placed in what may be called the pelvis; in both are conglomerated in a particular manner; have the ureter ramifying through their whole substance, and entering into the rectum. The urine is a chalky substance in many of both, and a kind of slime in others. *'• The Testes are situated in the abdomen in the male of both. " The Vasa deferentia enter the rectum in both. " The Penis is grooved in both. " Both oviparous. " Structure of Ear similar in both. " Heart very different. " These writings fully attest the enlarged views which Hunter en- tertained of comparative anatomy, and of its application not only to the establishment of sound theories of the functions and relative influences of the diffeernt organic systems in the animal body, but also of a natural distribution of different animals into classes ar- ranged according to their affinities. It is in this respect that he has more especially surpassed those of his countrymen who have immediately succeeded him in the same field of inquiry, and whose * See Plates 5, 6, and 7, vol. i. Physiological Catalogue. f See p. 196. PREFACE. 35 labours in comparative anatomy have not been productive of ade- quate results, chiefly from being restricted to the narrower channel of their physiological application. The museum of Hunter is the chief, but not the sole depository of the dissections by which he established the general principles to which we have alluded. Hunter had passed his thirtieth year before he had collected a single preparation for himself. All that he had made before that time were added to his brother's collection, which is now the orna- ment of the University of Glasgow. In commencing his indepen- dent labours, in anatomy, he conceived the idea of a collection, in which the illustrations of the human organization should form a part only of a general display of all the types and modifications of animal structure, and practically he was the first who reduced the scattered facts of comparative anatomy to a connected system. When Hunter had brought his museum to an approximate degree of perfection,* he then set apart certain days, in which he exhibited and explained to some chosen minds which could respond to the conceptions of his own, his great scheme, embracing the demon- stration of all the leading modifications of every organ of the ani- mal body, and of the different stages which each organ undergoes in its development, to fulfil the functions it is required to perform in the highest organisms. Amongst the enlightened men who enjoyed the inestimable advan- tage of listening to the explanations which the founder of the collec- tion gave of his own labours, and of their scope and tendency, were Camper, Poli, Scarpa, and the now venerable Blumenbach. Camper, as a contemporary, and in some respects a rival of Hunter, may have been less influenced in the general tenor and success of his investigations in comparative anatomy, by this cir- cumstance, than the last named and younger naturalists and physiolo- gists. We cannot but suppose that the spectacle of the organization of so many rare marine animals, beautifully displayed by so consummate a practical anatomist as Hunter, must have had a lasting influence on the mind of Poli; and it is not, perhaps, assuming too much to trace to this source the taste for anatomy and the stimulus to the indefatiga- ble and minute dissections, of the Mediterranean mollusca, and the magnificent illustrations of their organization, which have justly im- mortalized their author. In contemplating the gradational and connected series of the organs of animals, which Blumenbach must have witnessed for the first time in the museum of Hunter, that learned and accomplished physiologist was doubtless led vividly to appreciate the cumulative force with which comparative anatomy urges the onward progress of physiological science when all its scattered facts are concen- * In the year 1787. See Home's Lectures on Comparative Anatomy, vol. i. p. 7. and vol. i. p. 78 of the present edition of Hunter's Works. g6 HUNTER ON THE ANIMAL CECONOMY. trated into one orderly system. In his subsequent Pu^lic^;f. °nf the first systematic treatise of comparative anatomy tne eruimiun of Blumenbach supplied many of those links in the series ol animal structures which Hunter derived from Nature's original sources. In estimating therefore, the share which Hunter had in advancing comparative anatomy and physiology, his annual demonstrations of his collection to such individuals as we have instanced must not be overlooked. We may admit that while so vast a proportion of the stores of his experience lay buried in unpublished manuscripts, his strue station in the temple of Science could hardly be discerned; but, independently of these manuscripts, we cannot hesitate in allow- ing'that his published works, full of profound and original views, com- bined with the spectacle of his wonderful dissections, must have effected more than had been done by any previous author towards raising the science of comparative anatomy in the scale of human knowledge. Now, however, we have to estimate the scientific character of Hunter from more extended grounds. Enjoying the same privilege of consulting his museum, which the contemporaries of Hunter so highly esteemed, we also possess the advantage of studying it with the aid of those explanations of its scope and nature which its great founder had left with a view to ulterior publication. Thanks to the devotion of the last of Hunter's pupils to the memory of his great master, the evidences of Hunter's discoveries and labours, as recorded in his collections, are in a better state of preservation at this moment than they were nearly fifty years ago, when they first fell [to the care and charge of Mr. Clift. And here I embrace with pleasure the opportunity of expressing my grateful thanks to that gentleman for the kind aid which I have on every needful occasion received from him during the impression of the present work, and of recording my deep sense of the advantages which I have derived from a long intercourse with one whom I ever shall regard as the best of friends and worthiest of men. It is to the zeal and industry which induced Mr. Clift to tran- scribe portions of the Hunterian manuscripts, at a period when he little suspected their ultimate fate, that we owe our additional knowledge of the philosophical views which Hunter entertained of the application of anatomical facts, and of the general principles which he had deduced from them. As such of these extracts from the Hunterian Manuscripts as have been quoted in the present work have already been printed in the Catalogues of the Hunterian Col- lections published under the auspices of the Council of the Royal College of Surgeons, it is competent for any one to judge of the grounds on which I have endeavoured to show that Hunter, as a comparative anatomist, merits a higher, and altogether different station in science than has been awarded to him by Cuvier. Instead of viewing Hunter as one who had merely contributed a secondary proportion of detached facts to the general but unarranged PREFACE. 37 stock of materials in comparative anatomy, it appears to me that he marks a new epoch in its history, and that the historian of the natural sciences has just and sufficient grounds for regarding Hunter as the first of the moderns who treated of the organs of the animal body under their most general relations, and who pointed out the anatomical conditions which were characteristic of great groups or classes of animals : as one, in short, throughout whose works we meet with general propositions in comparative anatomy, the like of which exist not in the writings of any of his contemporaries or pre- decessors, save in those of Aristotle. RICHARD OWEN. November 15th, 1837. N.B. The Editor's Notes are distinguished from the Author's by being placed within brackets. CONTENTS. : Page Preface of the Editor ........7 1. Description of the Situation of the Testis in the foetus, with its descent into the Scrotum......41 2. Observations on the Glands situated between the Rectum and Bladder, called Vesiculae Seminales .... 58 3. Account of the Free-martin......70 4. Account of an extraordinary Pheasant .... 79 5. Experiments to determine the effect of extirpating one ovarium upon the number of Young produced . . . .85 6. Case of a young Woman who poisoned herself in the first month of Pregnancy, with a description of the Uterus . . 89 7. On the Structure of the Placenta.....93 8. Observations on the Placenta of the Monkey . . 103 9. Account of a Woman who had the Small-pox during Pregnancy, and who seemed to have communicated the same Disease to the Foetus.........105 10. Some Observations on Digestion r.....112 11. On the Digestion of the Stomach after Death . . 144 12. On a Secretion in the Crop of breeding Pigeons, for the nourish- ment of their Young ......149 13. Observations on the Gillaroo Trout, commonly called in Ireland the Gizzard Trout......, 151 14. Experiments and Observations on Animals with respect to the power of producing Heat . . . . . . 155 15. Experiments and Observations on Vegetables with respect to the power of producing Heat ...... 177 16. Proposals for the Recovery of Persons apparently drowned 185 17. Account of certain Receptacles of Air in Birds, which communi- cate with the Lungs and Eustachian Tube . . . 194 18. Description of the Nerves which supply the Organ of Smelling 204 19. Description of some Branches of the Fifth Pair of Nerves 209 20. Croonian Lecture on Muscular Motion, No. I. . 211 21. g?Do. Do. Do. Do. No. II. 238 22. Do. Do. Do. Do. No. III. 254 23. Do. Do. Do. Do. No. IV. 262 24. Do. Do. Do. Do. No. V. 265 25. Do. Do. Do. Do. No. VI. 277 40 HUNTER ON THE ANIMAL CECONOMY. Page. 26. On the Use of the Oblique Muscles . 282 27. On the Colour of the Pigmentum of the Eye in different a • i .... 285 Animals ...•••' 28. On the Crystalline Lens, or some Facts relative to the late Mr. John Hunter's Preparation for the Croonian Lecture . 292 29. Account of the Organ of Hearing in Fishes 297 30. Experiments on Absorption by Veins .... 303 31. Experiments and Observations on the Growth of Bones . 319 32. Observations tending to show that the Wolf, Jackal and Dog are all of the same species......323 33. Observations on the Structure and GSconomy of Whales . 334 34. Notes on the Anatomy of the Jerboa .... 391 35. Anatomical Description of the Amphibious Bipes of Ellis (Siren lacertani, Linn.) ... ... 392 36. On the Electric Property of the Torpedo ... 396 37. Anatomical Observations on the Torpedo . . . 404 38. Account of the Gymnotus electricus .... 408 39. Observations on Bees ...... 415 40. Anatomical Remarks on a New Marine Animal (Serpula gigan- tea, Pallas)........456 41. Observations on the Fossil Bones presented to the Royal Society by His Most Serene Highness the Margrave of Anspach 459 42. Descriptions of some Animals from New South Wales . 468 Of the Kangaroo (macropus major, Shaw) . . . 472 Of the Potoroo (Hypsiprymnus murinus, Illiger) . 474 Of the Hopoona Roo (Petaurus Taguanojles, Desmarest 475 Of the Wha Tapoua Roo (Phalangista Vulpina,\Geoffroy) 476 Of the Tapao Tafa (Phascogalepenicillata, Temminck) . 477 Of the Dingo (Canis Australasia) . 479 A TREATISE OK THE ANIMAL (ECONOMY. 1. A DESCRIPTION OF THE SITUATION OF THE TES- TIS IN THE FCETUS, WITH ITS DESCENT INTO THE SCROTUM. A discovery in any art not only enriches that with which it is im- mediately connected, but elucidates all those to which it has any re- lation. The knowledge of the construction of a human body is essential to medicine, therefore every improvement in anatomy must throw additional light on that branch of science. These im- provements strike more forcibly if they are on subjects quite new or little understood ; and this effect is well illustrated by the ad- vantages which pathology has derived from the discovery of the lymphatics being the absorbent system; and likewise by that case of hernia, where the intestine lies in contact with the testicle ; which has been perfectly explained by the discovery of the original seat of the testicle being in the abdomen. Several years before Haller's Opuscula Pathologica were pub- lished, my brother informed me, that in examining the contents of the abdomen of a child, stillborn, about the seventh or eighth month, he found both the testicles lying in that cavity, and mentioned the observation with some degree of surprise. By this we are enabled to account for a circumstance that sometimes happens in the scrotal hernia, as depending on the discovery that the testis is formed in the abdomen, and which we could never explain to our satisfaction till the publication of the Opuscula, to which Dr. Hunter alludes, (Commentaries, page 7*2,) in the following words: " In the latter end of the year 1755, when I first had the pleasure 5 42 HUNTER ON THE ANIMAL CECONOMY. of reading Baron Haller's observations On the Hernia Congenita, it struck my imagination! that the state of the testis in the foetus, and its descent from the abdomen into the scrotum, would explain several things concerning ruptures and the hydrocele, particularly that observation which Mr. Sharp had communicated to me, viz., that in ruptures the intestine is sometimes in contact, with the testis. I communicated my ideas upon this subject to my brother, and desired that he would take every opportunity of learning exactly the state of the testis before and after birth, and the state of ruptures in children. We were both convinced that the examination of those facts would answer our expectation, and both recollected having seen appearances in children that agreed with our supposition, but saw now that we had neglected making the proper use of them. ' " In the course of the winter my brother had several opportunities of dissecting foetuses of different ages, and of making some draw- ings of the parts; and all his observations agreed with the ideas I had formed of the nature of ruptures, and of the origin of the tunica vaginalis propria in the foetus. But till those observations were repeated to his satisfaction, and were sufficiently ascertained, he desired me not to mention the opinion in my lecture ; and therefore, when treating of the coats of the testis, and of the situation of the hernial sac, &c, I only put in this temporary caution, that I was then speaking of those things as they are commonly in adult bodies, and not as they are in the foetus: and at last, when I was conclud- ing my lectures for that season, in the end of April 1756, with a course of the chirurgical operations, I gave a very general account of my brother's observations, and showed both the drawing of fig. 2, which was then finished, and the subject from which it was made." The following observations on this subject were taken from my notes, and published by Dr. Hunter in his commentaries to which I have added some practical remarks. " Until the approach of birth, the testes of the fetus are lodged within the cavity of the abdomen, and may therefore be reckoned among the abdominal viscera. They are situated immediately below the kidneys, on the fore part of the psoas muscles, and by the side of the rectum, where this intestine is passing down into the * Alberti Halleri Opuscul. Patkolog., Lausan. 1755, 8vo., page 53, &c. f [Although Haller was in doubt as to the exact period of the descent of the testis, and in error as to the cause of that phenomenon, yet he accurately describes, in the original paper here alluded to, the original relations of the gland to the peritoneum and abdominal viscera, and the formation of the tunica vaginalis, and thus applies th& facts which he had discovered to the explanation of the disease he was considering. » Herniarum, ni fallor, congenitarum modus hinc elucescit, quogenerantur. Patulus est processus peritonei sub renibus positus, qui ex- pectat testem invitatque aperto ostio, atque eo deorsum ex solita lege pulso urgetur mque scrotum una descendit. Cum autem his in corporibus testis eodem cum mtestinis sacro omnino contineantur, nihil est singularis sive inexnectati, si ea in apertum saccum a levi vi depressa fuerint." (Opusc. Patholog., p 56 ) In th.s paper there are references to the older authors who had noticed the abdominal position of the testes in the fetus.] auuominai SITUATION OF THE TESTIS IN THE FCETUS. 43 cavity of the pelvis; for in the foetus, the rectum, which is much larger in proportion to the capacity of the pelvis than in the full- grown subject, lies before the vertebras lumborum as well as before the os sacrum. Indeed the case is pretty much the same with re- gard to all the contents of the pelvis; that is, their situation is much higher in the foetus than in the adult. The sigmoid flexure of the colon, part of the rectum, the greatest part of the bladder, the fundus uteri, the Fallopian tubes, &c, being placed in the foetus above the hollow of the pelvis in the common or great abdominal cavity. " While the testis remains in the abdomen its shape or figure is much the same as in the adult, and its position or attitude the same as when it is in the scrotum; that is, one end is placed up- wards, the other downwards ; one flat side is to the right, the other to the left; and one edge is turned backwards, the other forwards; and the vessels enter the posterior edge alike in both the foetus and adult. As the testis is not so immediately inclosed in the surround- ing parts while it is in the loins, its position may be a little variable, and the most natural seems to be when the anterior edge is turned directly forwards; but as the least touch of anything will throw that edge either to the right side or to the left, then the flat side of the testis will be turned forwards. It is attached to the psoas muscle all along its posterior edge, except just at its upper ex- tremity; and this attachment is formed by the peritoneum, which covers the testis and gives it a smooth surface, in the same manner as it envelopes the other loose abdominal viscera. " The epididymis lies along the outside of the posterior edge of the testis, as when in the scrotum, but is larger in proportion, and adheres backwards to the psoas. When the foetus is very young, the adhesion of the testis and epididymis to the psoas is very narrow, and then the testis is more loose, and more projecting; but as the foetus advances in months, the adhesion of the testis to the psoas becomes broader and tighter. " The vessels of the testis, like those of most parts of the body, commonly rise from the nearest larger trunks, viz., from the aorta and cava, or from the emulgents. "The artery generally rises from the fore part of the aorta, a little below the emulgent artery, and often from the emulgent itself, especially in the right side of the body, which may happen the rather, because the trunk of the aorta is more distant from the right testis than from the left. Sometimes, but much more rarely, the spermatic artery springs from the phrenic, or from that of the capsula renalis. Besides the artery which rises from the^aorta, or emulgent, &c, the testis receives one from the hypogastric artery, which is sometimes as large as the other. It runs upwards from its origin, passing close to the vas deferens in its way to the testis. The superior spermatic artery sometimes passes before the lower end of the kidney; and both these arteries run in a serpentine direction, making pretty large but gentle turnings. They are situ- 41 HUNTER ON THE ANIMAL CECONOMY. ated behind the peritoneum, and both run into the posterior edge of the testis, between the two reflected laminoe of that membrane, much in the same manner as the vessels pass to the intestines between the two reflected laminae of the mesocolon or mesentery. "The veins of the testis are analogous to its arteries, but com- monly change sides with the arteries respecting their origins irom the emulgents. The superior spermatic vein, to begin with its trunk, rises commonly in the following manner: on the right side, from the trunk of the vena cava, a little below the emulgent; and on the left side, from the left emulgent vein. The reason of this difference between the right and left spermatic vein, no doubt, is because the cava is not placed in the middle of the body; so that by the rule of ramification which is observed in most parts of the body, the cava is the nearest large vein of the right side, and the emulgent is the nearest large vein of the left side. But the differ- ence is inconsiderable; and accordingly we sometimes find the right spermatic vein coming from the right emulgent vein; and several other varieties are produced, which so far as I can observe, follow no precise rule. There is likewise a spermatic vein, which rises from the internal iliac, and runs up to the testis with the in- ferior spermatic artery. Both the spermatic veins run behind the peritoneum with their corresponding arteries, and go into the poste- rior edge of the testis, where they are lost in small branches. " The nerves of the testis, like, its blood-vessels, come from the nearest source; that is, from the abdominal plexuses of the inter- costal, especially the inferior mesenteric plexus. They run to the testis, accompanying its blood-vessels, and are dispersed with them through its substance. The testis, therefore, with respect to its nerves, may be reckoned an abdominal viscus ; and this observa- tion will hold good when applied to the full-grown subject; as well as to the fcetus; for those branches of the lumbar nerves which are commonly said to be sent to the testis, passing through the tendon of the external oblique muscle, in reality go not to the testis itself, but to its exterior coverings, and to the scrotum." p. 75. The testicle receiving its nerves from the plexuses of the inter- costal, accounts for the stomach and intestines sympathizing so readily with it and its particular sensation, and for the effects arising in the constitution upon its being injured. " The epididymis begins at the outer and posterior part of the upper end of the testis, immediately above the entrance of the blood- vessels, where it is thick, round, and united to the testis. As it passes down it becomes a little smaller and more flat, and is only attached backwards to the testis, or rather indeed to its vessels; for its anterior edge lies loose against the side of the testis forwards; and at its lower end it is again more firmly attached to the body of the testis, so that in the foetus there is a cavity or pouch formed between the middle part of the testis and the middle part of the epididymis, more considerable than is commonly observed in full-grown sub- jects. As the body grows, the epididymis adheres more closely to SITUATION OF THE TESTIS IN THE FCETUS. 45 the side of the testis; and its greatest part is made up of one con- voluted canal, which becomes larger in size and less convoluted towards the lower end, and at last is manifestly a single tube run- ning a little serpentine. That change happens at the lower end of the testis, and there the canal takes the name of vas deferens. " The vas deferens is a little convoluted or serpentine in its whole course, but is less so as it comes nearer to the bladder; instead of running upwards from the lower end of the testis, as it does when the testicle is in the scrotum, while that remains in the abdomen, it runs downwards and inwards in its whole course, so that it goes on almost in the direction of the epididymis, of which it is a continua- tion. It turns inwards from the lower end of the epididymis, under the lower end of the testis, and behind the upper end of a ligament or gubcrnaculum testis (which I shall presently describe); then it passes over the iliac vessels, and over the inside of the psoas muscle, somewhat higher than in adult bodies, and at last goes between the ureter and bladder towards the basis of the prostate gland." p. 77. In those animals where the testicles change their situation the cre- master muscle, which should be named musculus testis, has two very different positions in the fostus and in the adult, the first being the same as in those animals whose testicles remain through life in the cavity of the abdomen ; we must therefore conclude that the same purposes are answered by this muscle in the foetus as in those animals. The use of this muscle, when the testicle is in the scrotum, ap- pears to be evidently that of a suspensory; for I find this muscle is strong in proportion to the size of the testicle and pendulous situation in other animals. But what purpose it answers in the foetus, or in animals whose testicles remain in the abdomen, is not easily ima- gined, there being no apparent reason why such a muscle should exist.* The cremaster, or musculus testis, appears to be composed of the lower fibres of the obliquus internus and transversalis muscles in the foetus, turning upwards, and spreading upon the anterior surface of the gubernaculum, immediately under the peritoneum; it appears to be lost on the peritoneum, a little way from the testicle. This, although now inverted, is more evidently seen in adult subjects who have had a hydrocele or rupture; in such cases the muscle becomes stronger than usual, and its fibres can be traced spreading on the tunica vaginalis, and seem at last to be lost upon it, near to the lower end of the body of the testicle. The nerves which supply this muscle are probably branches from * [The cremaster does not in fact exist in the true testiconda, as the elephant, hyrax, seal, walrus, the Cetaceous and Monotrematous Mammalia; in these the testes are merely supported by their vessels and a fold of peritoneum analogous to the broad ligaments of the uterus and ovaries ; but when the cremaster is met with in apparent testiconda it is always in relation to a partial or temporary escape of the testis from the abdomen, as in bats and most insectivorous I eree, and in many of the Glires, as the rats, squirrels, beaver, porcupine, &c.J 46 HUNTER ON THE ANIMAL CECONOMY. the nerves of the obliquus internus and transversals muscles; for the same cause which throws the abdominal muscles into action produces a similar effect on the musculus testis; which circumstance appears to be most remarkable in the young subject. When we cough or act with the abdominal muscles, we find the testicles to be drawn up; the musculus testis and abdominal muscles taking on the same action from the same cause.f " At this time of life the testis is connected in a very particular manner with the parietes of the abdomen, at that place where in adult bodies the spermatic vessels pass out, and likewise with the scrotum. This connexion is by means of a substance which runs down from the lower end of the testis to the scrotum, and which at present I shall call the ligament, or gubernaculum testis, because it connects the testis with the scrotum, and seems to direct its course through the rings of the abdominal muscles. It is of a pyramidal form ; its large bulbous head is upwards, and fixed to the lower end of the testis and epididymis, and its lower and slender extremity is lost in the cellular membrane of the scrotum. The upper part of this ligament is within the abdomen, before the psoas, reaching from the testis to the groin, or to where the testicle is to pass out of the abdomen ; whence the ligament runs down into the scrotum, precisely in the same manner as the spermatic vessels pass down in adult bodies, and is there lost. The lower part of the round ligament of the uterus in a foetus very much resembles this ligament of the testis, and may be plainly traced down into the labium, where it is imperceptibly lost. That part of the ligamentum testis which is within the abdomen is covered by the peritoneum all round except at its posterior part, which is contiguous to the psoas, and connected with it by the reflected peritoneum and by the cellular membrane. It is hard to say what is the structure or com- position of this ligament; it is certainly vascular and fibrous, and the fibres run in the direction of the ligament itself, which is covered by the fibres of the cremaster or musculus testis, placed immediately behind the peritoneum. This circumstance is not easily ascertained in the human subject; but is very evident in other animals, more especially in those whose testicles remain in the cavity of the abdo- men after the animal is full grown. " In the hedgehog the testis continue through life to be lodged within the abdomen, in the same situation as in the human foetus; * [The first lumbar nerve, which gives many small branches to the transversalis abdominis, sends off a branch which, in conjunction with smaller branches from the second lumbar nerve, forms the'external spermatic nerve' from which the cremaster is supplied.] t [As the cremaster is supplied from common or spinal nerves, it is not sur- prising that it should in some cases, like the occipito-frontalis muscle, be under the control of the will. Mr. Marshall observes, in his work On Recruits, " Some individuals have the voluntary power of contracting and relaxing the cremaster muscle : others can elevate the testicle on one side but not on the other; and 1 have seen a few persons who could voluntarily raise a testicle, but had not the power ot letting it return into the scrotum."] SITUATION OF THE TESTIS IN THE FCETUS. 47 and they are fastened by the same kind of ligament to the inside of the parietes of the abdomen at the groin. Now in that animal I find that the lowermost fibres of the internal oblique muscle, which constitute the cremaster, are turned inwards at the place where the spermatic vessels come out in other animals, making a smooth edge or lip by their inversion, and that then they mount up on the liga- ment to the lower end of the testis.* Sometimes in the human body, and in many other animals, and very often in sheep, the testes do not descend from the cavity of the abdomen till late in life, or never at all. In the ram, when the testis is come down into the scrotum, the cremaster is a very strong muscle; and, though it be placed more inwards at its beginning, it passes down pretty much as it does in the human body, and is lost on the outside of the tunica vaginalis; but in the ram, whose testis still remains suspended in the abdominal cavity, I find that the cremaster still exists, though it is a weaker muscle; and instead of passing downwards, as in the former case, it turns inwards and upwards, and is lost in the peri- toneum that covers the ligament which attaches the testis to the parietes of the abdomen, which in this state of the animal is about an inch and a half in length. In the human foetus, while the testis is retained in the cavity of the abdomen, the cremaster is so slender that I cannot trace it to my own satisfaction, either turning up towards the testis or turning down towards the scrotum. Yet, from analogy, we may conclude that it passes up to the testicle; since in the adult we find it inserted or lost on the lower part of the tunica vaginalis, in the same manner as in the adult quadruped.t " The peritoneum, which covers the testis and its ligament or gubernaculum, is firmly united to the surfaces of these two bodies; but all around, to wit, on the kidney, the psoas, the iliacus, internus, and the lower part of the abdominal muscles, that membrane • [The apparent anomaly of this, as of almost every other natural structure, disappears when we attain the requisite amount of knowledge respecting the conditions under which it exists. The testes of the hedgehog, like those of the mole, (see p. G6,) are subject to remarkable periodical enlargement at the season of copulation, when they are drawn down by the cremaster to the external ring. In this situation they are favourably placed to be affected by the expulsive actions of the diiiphragm and abdominal muscles, by which they are eventually protruded and the cremasteric pouch is inverted. As the testes diminish in size their muscular covering contracts upon them and returns them into the abdomen.] f- [Uy such a p'e-arrangement of the relations of the cremaster to the testis the necessity for the latter to overcome in its passage outwards the resistance of the inferior fibres of the transversalis abdominis and obliquus internus is obviated. It cannot reasonably be doubted that the cremaster exists, as such, in the human foetus prior to the descent of the testis, since it is indubitably present and attached to an abdominal testis in animals where no mechanical cause could have operated to produce this disposition of the muscular fibres. Besides, the use of the cremaster as a supporler and compressor of the testis is obviously too important for such a connexion to have been allowed to result from ihe gland accidentally, as it were, pushing before it some opposing fibres of the abdominal muscles in its progress outwards, as Carus imagines. See his Comparative Anatomy, by Gore, vol. ii., p. 347.] 48 HUNTER ON THE ANIMAL CECONOMY. adheres very loosely to all the surfaces which it covers. Where the peritoneum is continued or reflected from the abdominal muscles to the ligament of the testis it passes first downwards a little way, as if going out of the abdomen, and then upwards, so as to cover more of the ligament than is within the cavity of the abdomen. At this place the peritoneum is very loose, thin in its substance, and of a tender gelatinous texture; but all around the passage of that liga- ment the peritoneum is considerably tighter, thicker, and of a more firm texture. When the abdominal muscles are pulled up so as to tighten and stretch the peritoneum this membrane remains loose at the passage of the ligament while it is braced or tight all around; and in that case the tight part forms a kind of border or edge around the loose double part of the peritoneum, where the testis is after- wards to pass. This loose part of the peritoneum, like the intro- suscepted gut, may, by drawing the testis upwards, be pulled up into the abdomen, and made tight, and then there is no appear- ance of an aperture or passage down towards the scrotum; but when the scrotum and ligament are drawn downwards, the loose doubled part of the peritoneum descends with the ligament, and then there is an aperture from the cavity of the abdomen all around the fore part of the ligament, which seems ready to receive the testis. This aperture becomes larger when the testis descends lower, as if the pyramidal or wedge-like ligament was first drawn down in order not only to direct but to make room for the testis which must follow it. In some foetuses I have found the aperture so large that I could push the testis into it as far as the tendon of the external oblique muscle. " From this original situation within the abdomen the testis after- wards descends to its destined station in the scrotum; but it becomes difficult to ascertain the precise time of this descent, as we hardly ever know the exact age of our subject. According to the observa- tions which I have made, it seems to happen sooner in some instances than in .others; but generally about the eighth month. In the seventh month I have commonly found the testis in the abdo- men ; and in the ninth I have as commonly found it in the upper part of the scrotum. The descent being thus early, and the passage being almost immediately closed, are the principal means of pre- venting the hernia congenita. " At the before-mentioned period the testis moves downwards till its lower extremity comes into contact with the lower part of the abdominal parietes: when the upper part of the ligament, which hitherto was within the abdomen, has sunk downwards, it lies in the passage from the abdomen to the scrotum, and in that which is afterwards to receive the testis. As the testicle passes out it in some degree inverts the situation of the ligament passing down beyond it; what was the anterior surface of the ligament while in the abdomen, now becoming posterior and composing the lower and anterior part of the tunica vaginalis, on which the musculus testis is lost, l his is more evident in those animals whose testicles SITUATION OF THE TESTIS IN THE FCETUS. 40 can readily be made to pass up from the scrotum to the abdomen. The place where the ligament is most confined, and where the testis meets with most obstruction in its descent, is the ring in the tendon of the external oblique muscle; and accordingly I think we see more men with one testis or both lodged immediately within the tendon of that muscle than who have one or both still included in the cavity of the abdomen, which I shall take notice of hereafter. " After the testis has got quite through the tendon of the external oblique muscle it may be considered as now in a way easily to acquire its determined station, though it commonly remains for some time by the side of the penis,*- and only by degrees descends to the bottom of the scrotum ; and when the testis has descended entirely into the scrotum its ligament is still connected with it, and lies immediately under it, but is shortened and compressed. " Having now given an account of the original situation of the testes, of the time of their descent from the abdomen, and of the route which they take in their passage to the scrotum, I shall in the next place describe the manner in which they carry down the peritoneum with them, and then explain how that membrane forms the tunica, vaginalis propria in common, and the sac of the hernia congenita in some bodies. " While the testis is descending, and even when it has passed into the scrotum, it is still covered by the peritoneum, exactly in the same manner as when within the abdomen, the spermatic vessels running down behind the peritoneum there as they did when the testis lay before the psoas muscle: that lamella of the peritoneum is united behind with the testis, the epididymis, and the spermatic vessels, as it was in the loins, and likewise with the vas deferens; but the testis is fixed posteriorly to the parts against which it rests, being unconnected and loose forwards, as while it remained in the abdomen. In coming down, the testis brings the peritoneum with it; and the elongation of that membrane, though in some circum- stances it be like a common hernial sac, yet in others is very dif- ferent. If we can imagine a common hernial sac reaching to the bottom of the scrotum, covered by the cremaster muscle; and that the posterior half of the sac covers and is united with the testis, epididymis, spermatic vessels, and vas deferens; and that the ante- rior half of the sac lies loose before all those parts, it will give a perfect idea of the state of the peritoneum, and of the testis when it comes first down into the scrotum. The testis therefore, in its descent, does not fall loose, like the intestine or epiploon, into the elongation of the peritoneum, but slides down from the loins, carry- ing the peritoneum with it; and both that and the peritoneum con- tinue to adhere, by the cellular membrane, to the parts behind them, as they did when in the loins. This is a circumstance which * [This is the permanent situation of the testis in the Quadrumana, in which also, as in the human foetus at the period above mentioned, the tunica vaginalis communicates with the abdominal cavity.] 6 50 HUNTER ON THE ANIMAL CECONOMY. I think may be easily understood, and yet that does not appear jo be the case; for I find students very generally puzzled wih it, imagining that when the testis comes first down it should be loose all round, like a piece of the gut or epiploon in a common hernia. The ductility of the peritoneum, and its very loose connexion by a slight cellular membrane to psoas muscle, and all the other parts around the testis, are circumstances which^ favour its elongation and descent into the scrotum with the testis." " This peculiarity of descent often takes place in some oi the intes- tines ; but can only happen in those which have adhesions to the loins. This I suspect is only to be met with in old ruptures, never happening at the first formation of the hernial sac, in which the intestine lies ; and, I should suppose, could only form very gradually. The caecum has sometimes been found to have descended into the scrotum, and to have brought along with it the adhesions through its whole course. The same thing has happened to the sigmoid flexure of the colon; and I have found the whole of it in the left side of the scrotum, with its adhesions brought down from the loins. Such hernia? cannot be reduced; and in case of strangulation, which may be brought on by a fresh portion of intestine coming down, are not to be treated in the common way : the sac should not be opened, but the stricture divided, and the newly protruded part reduced. " It is plain, from this description, that the cavity of the bag, or of the elongation of the peritoneum, which contains the testis in the scrotum, must at first communicate with the general cavity of the abdomen by an aperture at the inside of the groin. That aperture has exactly the appearance of a common hernial sac ; the spermatic vessels and vas deferens lie immediately behind it, and a probe passes readily through it from the general cavity of the abdomen down ;to the bottom of the scrotum. And if this process of the peritoneum be laid open through its whole length on the fore part, it will be plainly seen to be a continuation of the peritoneum: the testis and epididymis will appear at the lower part of it, and the spermatic vessels and the vas deferens will be found covered by the posterior part of the bag in their whole course from the groin to the testis. " Thus it is in the human body when the testis is recently come down: and thus it is, and continues to be through life, in every quadruped which I have examined where the testis is in the scrotum; but in the human body the communication between the sac and the cavity of the abdomen is soon cut off. Indeed I believe that the upper part of the sac naturally begins to contract as soon as the testis has passed through the muscles; which opinion is grounded on the following observation. In an instance where, from the age of the foetus and from every other mark, it was probable that the testis was very recently come down, and yet the upper part of the sac was very narrow, I pushed the testis upwards, in order to see if it could be returned. The attachments of the testis easily admitted of its ascent, and so did the aperture in the tendon SITUATION OF THE TESTIS IN THE FCETUS. 51 of the external oblique muscle ; but the orifice and upper end of the sac would not by any means admit of the testis being passed quite up into the abdomen. However this may be, the upper end of the sac certainly contracts and unites first, and is quite closed in a very short space of time, for it is seldom that any aperture remains in a child born at its full time; and this contraction and union is con- tinued downwards till it comes near the testicle, where this disposi- tion does not exist, leaving the lower part of the sac open or loose through life even in the human subject, and forming the tunica testis vaginalis propria, the common seat of a hydrocele. Many cases of hydrocele in children seem to prove that the progress of this contraction and union is downwards; for in them the water commonly extends higher up the chord than in the adult, except in those of a considerable size; yet in some children this union seems not to take place regularly, being interrupted in the middle, and producing a hydrocele of the chord which neither communicates with the abdomen nor tunica vaginalis testis. The contraction and obliteration of the passage appears to be a peculiar operation of Nature, depending upon steady and uniform principles, and not the consequence of inflammation nor of anything that is accidental; and therefore, if it is not accomplished at the proper time, the diffi- culty of bringing about a union of the parts is much greater, as is seen in children who have had the sac kept open by a turn of the intestine falling down in the scrotum immediately after the testis. This looks as if Nature, from being balked when she was in the humour to do her work, would not or could not so easily do it afterwards. I shall readily grant that what has been advanced here as a proof of the doctrine may be explained upon other principles; but this at least is certain, that the closing of the mouth and of the neck of the sac is peculiar to the human species ;* and we must suppose the final intention to be the prevention of ruptures, to which men are so much more liable than beasts from their erect state of body." In some cases the aperture of the sac is not entirely closed, allow- ing a fluid to pass down and form a hydrocele ; which fluid, upon pressure, can be squeezed back into the belly ; and instances of this kind sometimes giving the idea of a gut being protruded, make it difficult to determine the exact nature of the case. " What is the immediate cause of the descent of the testis from • [The chimpanzee, or African orang-utan (Simia Troglodytes, Blum.), which of all mammalia approximates most closely to the human structure, resembles man in the early obliterations of the canal which leads from the peritoneal cavity to the tunica vaginalis. In the Indian orang {Simia Satyrus, Linn.), on the con- trary, the canal of communication is free. This difference of structure relates doubtless to the different conditions of the lower extremities in these otherwise closely allied quadrumana : in the chimpanzee they are proportionally larger and stronger, the leg can be more extended on the thigh, and the hip-joint is strength- ened by a ligamentum teres; in the orang, on the contrary, the lower limbs are freely developed as organs of support, but have great extent of motion, the hip- joint being, like the shoulder-joint, without a round ligament.] 52 HUNTER ON THE ANIMAL CECONOMY. the loins to the scrotum ? It is evident that it cannot be the com- pressive force of respiration ; because the testis is commonly in the scrotum before the child has breathed, that is, the effect has been pro- duced before the supposed cause has existed. Is the testis pulled down by the cremaster muscle 1 I can hardly suppose that it is; because, if that was the case, I see no reason why it should not take place in the hedgehog, as well as in other quadrupeds ; and if the musculus testis had this power it could not bring it lower than the ring of the muscle. " Why do the testes take their blood-vessels from such distant trunks 1 Those physiologists who have puzzled themselves about the solution of this question have not considered that in the first formation of the body the testes are situated not in the scrotum but immediately below the kidneys; and that therefore it was very natural that their blood-vessels should rise nearly in the same manner as those of the kidneys, but a little lower.* The great length of the spermatic vessels in the adult body will no doubt occasion a more languid circulation, which we may suppose was the intention of nature. " The situation of the testis in the foetus may likewise account for the contrary directions of the epididymis and of the vas deferens in adult bodies, though these two in reality make only one excretory canal. In the foetus the epididymis begins at the upper end of the testis; and it is natural, considering it is an excretory tube, that it should run downwards. And it is as natural that the rest of the tube, which is called vas deferens, should turn inwards at the lower end of the testis, because that is its most direct course to the neck of the bladder. Thus we see that in the foetus the excre- tory duct is always passing downwards. But the testis is directed in its descent by the gubernaculum, which is firmly fixed to the lower parts of the testis and epididymis, and to the beginning of * [The singular course of the recurrent nerves results from a similar mechani- cal cause. At the period when the rudimentary larynx first derives its nerves from the par vagum, the head and trunk are not separated by a neck, the trachea is not formed, the heart is situated near the base of the cranium, and the branchial arteries given off from the bulb of the then single artery pass above the nerves in question. As the anterior extremities bud forth, the brachial plexuses are de- veloped and the neck begins to elongate; then the rings of the trachea are suc- cessively added, and the larynx, which before was close to the heart, is carried upward, and the recurrent nerves, restrained by their relations to the arteries, which are now converted into the subclavian on the right side, and aortic arch on the left, become proportionately elongated. The recurrent course of the branch of the dental nerve which supplies the pulp of the incisor in the porcupine and other Rodentia is explicable on a similar principle, the relative position of the pulp to the origin of its nerve being gradually changed by the growth of the jaw and extension of the tooth. See the preparation illustrating this fact in the Gallery of the Hunterian Museum, No. 357 b. It is scarcely necessary to observe that the above mechanical explanation of the course of the recurrent nerves leaves the question of the final cause as open as before. Mr. Hunter, after giving the physical cause of the course of the spermatic artery, next proceeds to inquire into the intention of Nature with re- ference to that peculiarity.] SITUATION OF THE TESTIS IN THE FCETUS. 53 the vas deferens, and thence must keep those parts invariably in their situation with respect to one another: and therefore in pro- portion as the testis descends the vas deferens must ascend from the lower end of the testis; and it must, from the passage through the abdominal muscles down to the testis, run parallel with the spermatic vessels. " The testis, its coats, and the spermatic chord are so often con- cerned in some of the most important diseases and operations of surgery, particularly in the bubonocele and hydrocele, that their structure has been examined and described by the surgeons, as well as by the anatomists, of every age. Yet the descriptions of the clearest and best writers upon the subject differ so much from one another, and many of them differ so much from what is obvious and demonstrable by dissection, as to render it difficult to account for such a variety of opinions. The very different state of the parts in the quadruped and in the human body, no doubt, must have occasioned error and confusion among the writers of more ancient times, when the parts of the human body were described from dissections and observations made principally upon brutes: and the structure of parts, which are peculiar to the foetus, having been imperfectly understood, we may suppose, has likewise con- tributed to cause perplexity and contradiction among authors. " Baron Haller, in his Opuscula Palhologica, has observed that in infants the intestine sometimes falls down into the scrotum after the testis, or along with it, and occasions what he calls the hernia congenita. In such a case the hernial sac is formed before the in- testine falls down, as that ingenious anatomist has observed. There are, besides, two circumstances peculiar to a rupture of this kind, the intestine being always in immediate contact with the testis, and there being no tunica vaginalis propria testis. The structure of the parts in a foetus explains in the most satisfactory manner both these circumstances, however extraordinary they must appear to a man who has only been accustomed to view the parts in subjects of a more advanced age; and indeed it is so clear that it needs no illus- tration. It should be observed, however, that the hernia congenita may happen not only by the intestine falling down to the testis before the aperture of the sac be shut up, but perhaps afterwards; for when the sac has been but recently closed it seems possible enough that violence may open it again. " It must likewise be obvious to every anatomist, who examines the state of the testis in children of different ages, that the mouth and neck only of the sac close up, and that the lower part of the sac remains loose around the testis, and makes the tunica vaginalis propria. Whence it is plain that this tunic was originally a part of the elongated peritoneum; and, as it is undoubtedly the seat of the true hydrocele, it is also plain that the hernia congenita and the true hydrocele cannot exist together in the same side of the scrotum. For when there is a hernia congenita there is no other cavity than 54 HUNTER ON THE ANIMAL CECONOMY. that of the hernial sac ; and that cavity communicates with the general cavity of the abdomen. " The observations contained in the two last paragraphs occurred to my brother upon reading Baron Haller's Opuscula 1 atho ogica, and gave rise to my inquiries upon this subject."—Medical Com- mentaries, part i., p. 83. Having explained the situation of the testicles in the foetus, and their descent, with the circumstances attending it, I shall next con- sider the cases in which the change takes place, in one or both testicles, later than the usual or natural time. And having re- marked the consequences of this descent at so late a period, I shall take notice of those instances in which the testicles never pass out of the abdomen. I have said that the early descent of the testicles, and closing of the mouth of the sac, by usually happening before birth, prevent likewise the descent of any part of the abdominal viscera; but when the testicles remain in their first situation beyond this period these advantages are lost; a part of the intestines or epiploon being, under these circumstances, liable to descend along with them. The first or natural process, in some instances, not having been begun, or having been interrupted before birth, it becomes afterwards very uncertain when the descent will be completed: yet I think the completion most frequently happens between the years of two and ten, while the person is young and growing, being seldom delayed beyond the age of puberty. It is not easy to ascertain the cause of this failure in the descent of the testicle; but I am inclined to suspect that the fault originates in the testicles themselves. This however is certain, that the tes- ticle which has completed its descent is the largest, which is more evident in the quadruped than in the human subject; as in these we can have an opportunity of examining the parts when we please, and can determine how small in comparison with the other that testicle is which has exceeded the usual time of coming down; it never descends so low as the other. The descent of that testicle is very slow which is not completed before birth, often requiring years for that purpose; and it some- times never reaches the scrotum, especially the lower part of it. There is oftener I believe an inequality in the situation of the two testicles than is commonly imagined, being seldom equally low in the scrotum; and I am of opinion that the lowest is the most vigorous, having taken the lead readily, and come to its place at once. The part where it meets with the greatest difficulty in its descent is in the division of the tendon of the external oblique muscle called the ring. How far an erect position of body, the action of the abdominal muscles, and the effect produced upon the contents of the abdomen in breathing may contribute mechanically to the descent of the testicles when the natural operations of the animal (economy have SITUATION OF THE TESTIS IN THE FCETUS. 55 failed, I will not pretend to decide; but when we see these com- bined actions producing an unnatural descent of a portion of intes- tine, we may conceive that they are likewise capable of contribu- ting to the descent of the testicle. When the testicle has remained in the cavity of the abdomen beyond the usual time, it is impossible to say whether the disposition for closing up the passage, after it has passed out, is in any degree lost or not; but when it comes down after birth, we can easily sup- pose a portion of intestine or epiploon is more likely to descend and prevent the closing of the mouth of the sac, than "before the child was born, when certain actions had not taken place. We should therefore watch this descent of the testicle, and endeavour, by art, to procure that union which the natural powers are either not dis- posed to perform, or are prevented from completing by the descent of other parts; but art should not be used too soon, nor till the testicle has got a little way below the ring. As this progress is very slow, especially when the testicle is creeping through the ring, a doubt often arises whether it is better entirely to prevent its passage, or to assist it by exercise or other means; and it would certainly be the best practice to assist it, if that could be done effectually and safely. When it has got upon the outside of the tendon it can in general be easily pushed up again into the abdomen ; and in these two situations it will sometimes play backwards and forwards for several years, without ever coming low enough to allow of the use of artificial means to hinder its descent, or to prevent a rupture. In this case it becomes difficult to determine what should be done; but, from what I have seen, I should be inclined to wait the descent, giving it every assistance in my power. Indeed, in all cases I would advise waiting with patience, for in most of those which I have seen, years have elapsed from the first appearance of the tes- ticle under the ring of the abdominal muscle before it has reached that situation in which we may safely apply a truss. I never have perceived that any inconvenience has arisen from waiting, and the danger, if there is any, may be in some degree avoided. I have always recommended moderate, not violent exercise. When the testicle has got some way below the ring, then the case is to be treated as an inguinal hernia, and a truss applied upon the ring; taking care that the testicle is not injured by it: but as this generally happens at too early a period for the patients themselves to be capable of attending to it, the surgeon who is employed should be very attentive, and those in whose immediate care they are, particularly watchful, that no inconvenience is produced by the truss. I have, however, known a rupture happen in a man thirty- years old, where the testicle had not even got into the ring. In such a case I think a truss should be immediately applied; for if it is thought advisable to prevent the testicle from coming down, a truss is equally adapted for that purpose, as for hindering the descent of an intestine where there is an hernial sac. It sometimes happens that one of the testicles remains in the 56 HUNTER ON THE ANIMAL CECONOMY. cavity of the abdomen through life, never acquiring the disposition to change its situation; therefore the person naturally concludes that he has only one testicle; and it can only be known that he had two by an examination of these parts after death; it is, however, possible that in some instances one may be wanting; but, it we are to reason from analogy, we must suppose this to be a very rare case; for it is a very common circumstance, that many quadrupeds have only one testicle in the scrotum ; and in such as are killed for food, and from that circumstance come more particularly under observation, if this peculiarity has been noticed, we in general find the other testicle in the cavity of the abdomen; though in some instances they are both found lying in that cavity. When one or both testicles remain through life in the belly, I believe that they are exceedingly imperfect, and probably incapable of performing their natural functions, and that this imperfection prevents the disposition for descent from taking place. That they are more defective than even those which are late in passing to the scrotum, is to be inferred from what is very evident in quadrupeds, the testicle that has reached the scrotum being in them considera- bly larger than the one which remains in the abdomen. It is probable that this peculiarity is a step towards the hermaphrodite, the testicle being seldom well formed. I have only seen one case in the human subject where both testicles continued in the abdo- men; this proved an exception to the above observation, since we are led to conclude that they were perfectly formed, as the persons had all the powers and passions of a man.* In such cases nothing is to be done by art, as it is not possible to give the testicles the stimulus of perfection, which I believe is necessary to make them assume the disposition requisite for their descent ;f and the ring of the external oblique muscle is perhaps less liable, in such instances, to allow a portion of intestine to push down, than where the testi- cles have passed through it; and such persons may probably be more secure from accidents of this kind than if they had been more perfectly formed. The testicle, in changing its situation, does not always preserve a proper course towards the scrotum, there being instances of its * [It seems remarkable, that with this experience Mr. Hunter should have formed, from inconclusive analogy, and promulgated an opinion tending to occasion so much unhappiness as that which attributes exceeding imperfection, and probable incapacity of performing their natural functions, to testes which in the human subject are retained within the abdomen. That there is nothing in such a situation which necessarily tends to impair their efficiency, is evident, f7om the number of animals in which they constantly form part of the abdominal viscera. And in those in which the testes naturally pass into a scrotum, their continuance in the abdomen, according to our author's own observation, is accompanied only with a difference of size or shape ; now we may readily sup- pose that this may influence the quantity, but not necessarily the quality of the secretion.] J t [The case described in the paper on the vesiculae seminales, p. CI, seems to offer an exception to this rule; the right testicle had passed through the external ring, although the vas deferens was impervious.] SITUATION OF THE TESTIS IN THE FCETUS. 57 taking another direction, and descending into the perinaeum. How this is brought about is difficult to say; it may possibly be occa- sioned by something unusual in the construction of the scrotum ; or, more probably, by a peculiarity in that of the perinaeum itself; for it is not easy to imagine how the testicle could make its way to the parts about the perinaeum if these were in a perfectly natural state. The first instance of this kind that occurred to me was the child of a shopkeeper in Oxford-street, which I visited, in company with Dr. Garthshore, about the year 1775; but what became of the patient afterwards I do not know. I have lately been consulted in a similar case, by Mr. Hunt, a surgeon, at Burford in Oxfordshire, whose apprehensions of what may be the consequences of a testicle remaining in the perinaeum appear to be well founded. The most effectual method of obviating these will probably be to support the testicle in a situation near the groin, by the application of a bandage that may hinder its descent into the perinaeum, by which the parts may be in time so consolidated as to retain it by the side of the scrotum. " Dear Sir, " I take the liberty of writing to you, in consequence of having met With a lusus naturae of a peculiar kind, in the son of a man in this neighbourhood. " The boy is about twelve months old: his right testicle is situated about an inch below the termination of the scrotum, and half an inch on the right side of the centre of the rapha perinaei. where a kind of pouch is formed of the common integuments, without the least rugous or scrotal appearance on its surface. It is perfectly detached from the scrotum ; nor can the testis or spermatic process be at any time felt in any part of the scrotum, though I can readily make the testis pass from its situation quite up into the groin ; but immedi- ately upon removing my hand the testis falls down into its pouch ; and I can trace the spermatic chord from the body of the testis up to the ring, running about a fourth of an inch on the right side of the scrotum. The scrotum on each side appears perfectly formed, and the left testis is in situ naturali. Now, sir, as I conceive this peculiar conformation maybe attended with great inconvenience to the child when he comes to ride on horseback, and on many other occasions, I beg leave to request your opinion upon it, with respect to what ought to be done to prevent accidents, which must, if left in its present situation, often occur. " Burford, Oxfordshire. [Signed] Thomas Hunt." 58 HUNTER ON THE ANIMAL CECONOMY. 2. OBSERVATIONS ON THE GLANDS SITUATED BE- TWEEN THE RECTUM AND BLADDER, CALLED VESICUL^E SEMINALES. Those bags, in the male of some animals, which are situated be- tween the bladder and rectum, and commonly called ' vesiculae semi- nales,' have been considered as reservoirs of the semen secreted by the testicles, in the same manner as the gall-bladder is supposed to be a reservoir of the bile. Physiologists must have been led to form this opinion from observing that in the human subject their ducts communicate with the vasa deferentia before their termination in the urethra. This communication was supposed to allow the semen, when not immediately wanted, to pass into the bags from the vasa deferentia by a species of regurgitation. But more accurate observations respecting their structure and contents in the human subject, and on corresponding parts in other animals supposed to answer a similar purpose, joined to the circumstance of their not being found in every class, induced me to conclude that this opinion was erroneous. To throw as much light upon this subject as possible I made a number of experiments, andavailed myself of every opportunity which offered of examining whatever could in any way elucidate the point; and, from what I have been able to collect, I think it will appear that they cannot be considered as reservoirs of the semen. To proceed regularly with my investigation, I shall begin by comparing the contents of these vesiculae with the semen as it is emitted from the penis of a living man. From which comparison it will appear that the two secretions are very different in their sensible properties of colour and smell; and although the semen which constitutes the first part of the emission is evidently different from the last, yet every part of it is unlike the mucus found in these vesiculae. The semen first discharged from the living body is of a bluish white colour, in consistence like cream, and similar to what is found in the vasa deferentia after death ; while that which follows is some- what like the common mucus of the nose, but less viscid. The semen becomes more fluid upon exposure to the air, particularly that first thrown out; which is the very reverse of what happens to secretions in general. The smell of the semen is mawkish and unpleasant, exactly resembling that of the farina of the Spanish chest- nut ; and to the taste, though at first insipid, it has so much punrrency as after some little time, to stimulate and excite a decree of heat bodv'isT^L BUt Jt flU!d COnt?eJ in these vesici^ in a dead body is of a brownish colour, and often varies in consistence in different parts of the bag, as if not well mixed. Its smel does nS resemble that of the semen, neither does it become more fluid by being exposed to the air. ' GLANDS CALLED VESICULA SEMINALES. 59 It may, however, be answered to this that the contents of the vesiculae are generally found in a putrid state, and have by that means undergone a change in their sensible properties. But the objection is readily obviated by comparing this fluid with that in the vasa deferentia as it comes from the testicles of the same dead body, between which there appears to be no resemblance. To be still more certain of the nature of what these vesiculae con- tain than was possible from the examination of bodies which had been dead some time, 1 took an opportunity of opening a man, im- mediately after his death, who had been killed by a cannon-ball. The fluid in the vesiculae was of a lighter colour than has usually been found in men who have been dead a considerable time; but it was not by any means like the semen either in colour or smell. In another man who died instantaneously, in consequence of falling from a considerable height, whose body I inspected soon after the accident, the contents of the vesiculae were of a lightish whey colour, having nothing of the smell of semen, and in so fluid a state as to run out on cutting into them. I have likewise examined with attention a mucus which some men discharge upon straining hard while at stool, or after throwing out the last drops of urine, an action which requires a considerable exertion of the parts. This discharge is generally called a seminal weakness, and is I believe commonly supposed to be the semen ;* but in all cases of this kind in which I have been consulted it nearly resembled the contents of the vesiculae in the dead body, though perhaps not quite of so deep a colour. 1 endeavoured in vain to persuade a gentleman who had this complaint that the discharge was not seminal, till by examining his own semen and comparing it with that mucus he was convinced of the difference. This gentleman had the power of emitting the semen in the same quan- tity as usual immediately after the mucus had been discharged, which is a further proof that this fluid is not semen.f In this country eunuchs seldom come under our examination; but we have sometimes opportunities of opening the bodies of those who have, in consequence of disease or accident, lost one or both testicles; and several subjects of this kind I have inspected after death. Persons who have had one testicle taken away will better illustrate the point in dispute than those who have been deprived of both. For it is to be presumed that such men have afterwards had connexion with women, and consequently had the action of emis- sion, which must have emptied the vesicula of the castrated side, if this had contained semen; and, as it could not be replenished, it should have been found empty after death. We have also in such cases an opportunity of making comparative observations between * Vide Treatise on the Venereal Disease, edit. 1st and 2d, p. 197. [vol. ii., p. 167 of the present edition.] { The discharge was truly supposed to be the contents of the vesicula?; and, it being imagined that these contained semen, according to this reasoning the discharge must be seminal. 60 HUNTER ON THE ANIMAL CECONOMY. the vesicula of the perfect and that of the imperfect side. In the eunuch such emissions never can happen, for the testicles being gone the natural and leading stimulus is lost; therefore, it in them the vesiculae were found full after death, it might be supposed to be the semen which they had received from the testicles before castra- tion that had remained there from the time of the operation; but castration being, ia such cases, usually performed on children, this circumstance should rather be considered as a proof that they secrete their own mucus. Yet it is probable the vesiculae will nei- ther be so large nor so full in eunuchs as in the perfect man; for I am of opinion that they are connected with generation, and that if the constitution is deprived of that power these bags will not grow to the full size. But where only one testicle is removed its loss does not in the least affect generation, therefore does not produce any change in the vesicula of that side from which the testicle is taken ; because the vesicula does not depend upon the testicle for its secretion, but upon the constitution, and on the person being capable of the act of generation: therefore as one testicle is suffi- cient to preserve manhood, it is of course capable of keeping up the action of both those glands. A man who had been under my care, in St. George's Hospital, for a venereal complaint, died there, and was discovered to have Jost his right testicle. From the cicatrix being hardly observable it must have been removed some considerable time before his death; and the complaint for which he was received into the hospital is a convincing proof that he had connexion with women after that period. I inspected the body in the presence of Mr. Hodges, the house- surgeon, and several of the pupils of the hospital. Upon dissecting out and examining the contents of the pelvis, with the penis and scrotum, I found that the vas deferens of the right side was smaller and firmer in its texture than the other, especially at that end next to the abdominal rings, near to the part which had been cut through in the operation. The cellular membrane surrounding the duct, on the right side, was not so loose as on the left; neither were the vessels which ramified on the right vesicula so full of blood. But upon opening the vesiculae, both appeared to be filled with the same kind of mucus, and similar to that which is found in other dead bodies ; the vesicula of the right side being rather larger than that on the left. Whatever, therefore, may be the real use of these vesiculae, we have a proof from this dissection that in the human subject they do not contain the semen. In a man who died in St. George's Hospital with a very large bubonocele, the testicle of the diseased side was discovered to have almost lost its natural texture, from the pressure of the hernial sac; and upon examining the testicle with attention there was no appear- ance of vas deferens till we came near the bladder, where it was almost as large as usual. The vesicula of that side was found to be as full as the other, and to contain the same kind of mucus. GLANDS CALLED VESICULA SEMINALES. 61 I extirpated the left testicle of a Frenchman, who was a married man, and died about a year afterwards, having been extremely ih for several months before his death. On examining the body, the vesiculae were both found nearly full, more especially that on the left side, which might be accidental; but the vas deferens of the left side, where it lies along this bag, and where it has a similar structure with the vesiculae, was likewise filled with the same kind of mucus; which I believe is always the case, whether the testicle has been removed or not. A young man, a coachman, with his left testicle much diseased, had it removed, at St. George's Hospital, by Mr. Walker, in August 1785; and in February 1786 he returned again to the hos- pital, on account of uncommon pains all over him. For these he requested to be put into the warm bath; but as he was going from the ward for that purpose, he dropped down almost imme- diately. The body was inspected, with a view to discover the cause of his death ; and, upon examination of the vesiculae, the bag of the left side was as full as that on the right, and the contents in both were exactly similar. In the winter 1788 another case oc- curred nearly resembling the above. In dissecting a male subject, in the year 1755, for a side view of the contents of the pelvis, I found a bag on the left side, lying con- tiguous to the peritonaeum, just on the side of the pelvis where the internal iliac vessels divide above the angle of reflection of the peritonaeum at the union of the bladder and rectum. The left vas deferens was seen passing on to this bag; and what is very singular, that of the right, or opposite side, crossed the bladder, near its union with the rectum, to join it. I traced the left vas deferens down to the testicle; but, on following the right through the ring of the external oblique muscle, I discovered that it terminated at once, about an inch from its passage out of the abdomen, in a blunt point, which was impervious. On examining the spermatic chord from this point to the testicle, I could not find any vas deferens ; but, by beginning at the testicle, and tracing the epididymis from its origin, about half-way along where it lies upon the body of the testicle, I perceived that it at first became straight, and soon after seemed to terminate in a point. The canal at this part was so large as to allow of being filled with quicksilver; which, however, did not pass far, so that a portion of the epididymis was wanting, and likewise the vas deferens for nearly the whole length of the spermatic chord of the right side. On the left side the vas deferens began where the epididymis commonly terminates, and there was a deficiency of nearly an inch of the extremity of the epididymis. I then dissected the bag above mentioned, which proved to be the two vesiculae; for, by blowing air from one vas deferens, I could only inflate half of it, and from the other vas deferens the other half. They contained the mucus commonly found in these bags ; but, upon the most accurate examination, I could neither discover 7 62 HUNTER ON THE ANIMAL CECONOMY. any duct leading from them to the prostate gland, nor the remains of one. «• It was evident in this subject that there was no communication between the vas deferens and epididymis, nor between these bags and the urethra. The caput gallinaginis had the common appear- ance, but there were no orifices to be found. The testicles were very sound, and the ducts from them to the epididymis were very manifest and contained semen.* . From these circumstances we have a presumptive prool that the semen can be absorbed in the body of the testicle and in the epididy- mis, and that the vesiculae secrete a mucus which they are capable of absorbing when it cannot be made use of. We may likewise infer from what has been said that the semen is not retained in re- servoirs after it is secreted, and kept there till it is used, but that it is secreted at the time in consequence of certain affections of the mind stimulating the testicles to this action; for we find that if lascivious ideas are excited in the mind, and the paroxysm is after- wards prevented from coming on, the testicles become painful and swelled from, we may suppose, the quantity of semen secreted, and the increased action of the vessels, which pain and swelling is re- moved immediately upon the paroxysm being brought on and the semen evacuated; but if that does not take place, the action of the vessels will still be kept up, and the pain in the testicle in general continue till the paroxysm and evacuation of the semen is brought on to render the act complete, without which a stop cannot be so quickly put to the action of the vessels that produce the secretion, nor the parts be allowed so easily to resume their natural state. There is at this time no sensation of any kind felt in the seat of the vesiculae seminales, which shows that the action is in the testicles, * As the semen, in consequence of this preternatural formation of parts, could not be conveyed to the urethra in the usual way, I conceived it possible that there might be another unnatural construction to make up for the deficiency in the vas deferens, and therefore examined it very carefully to see if there were no supernumerary vasa deferentia. I was led to do this more particularly from often finding parts resembling them where they could answer no kind of purpose. By a supernumerary vas deferens I mean a small duct which sometimes arises from the epididymis, and passes up the spermatic chord along with the vas deferens, commonly terminating in a blind end, near to which it is sometimes a little en- larged. I never found this duct go on to the urethra; but, in some instances, have seen it accompany the vas deferens as far as the brim of the pelvis. There is no absolute proof that this is a supernumerary vas deferens; but as we find the ducts of glands in general very subject to singularities, and that there are fre- quently supernumerary ducts; that there are often two ureters to one kidney, sometimes distinct from beginning to end ; at other times both arisinor from one pelvis. These ducts, arising from the epididymis, I am inclined from analogy to believe are of a nature similar to the double ureters. They resemble the vas deferens, as being continuations of some of the tubes of the epididymis; are eonvoluted where they come off from it; afterwards become a straight canal, and passing along with it for some way, they are then most commonly "obliterated. The idea of their being for the purpose of returning the superfluous semen to the circulation must certainly be erroneous, from their being so seldom met with, and so very seldom continued further than the brim of the pelvis. GLANDS CALLED VESICULA SEMINALES. 63 and in them alone. The pain in the testicles, in consequence of being filled with semen and of the action being incomplete, is some- times so considerable as to make it necessary to produce an evacua- tion of the semen to relieve the patient. It may be observed, in support of this opinion, that these bags are as full of mucus in bodies much emaciated, where the person has died from a lingering disease, as in those of the strong and robust, whose death has been occasioned by violence or acute dis- eases ; and they are nearly as full in the old as in the young; which, most probably, would not be the case if they contained semen. These facts, taken from the human subject, are, I think, sufficient to establish the opinion which I have laid down; but, for the satisfac- tion of others, I shall give such facts and observations as have oc- curred in my dissection of different animals as tend to clear up the point in question. These vesiculae are not similar either in shape or contents in any two genera* of animals which I have dissected; and they differ more in size, according to the bulk of the animal, than any other parts whose uses in different animals are supposed to correspond ; while the semen in most of those which I have examined may be said to be similar. The resemblance which obtains between these bags and the gall- bladder in the human subject by no means holds equally good when applied to other animals. In the horse they are like twof small urinary bladders, almost loose and pendulous, with a partial coat from the peritonaeum, under which there are two layers of muscular fibres; they are thicker in their coats at the fundus than any other part, and appear there to be glandular. Their openings into the urethra are very large, and although they open close to the vasa deferentia do not communicate with them. The septum between the two ducts is not continued on quite to the urethra, so that they cannot, in strict language, be said to enter that passage separately; but there is not length of common duct sufficient to admit of regur- gitation from the vasa deferentia into these bags. They are not of the same size in the gelding and in the stone-horse, being large in the last. Their contents in both are exactly similar, and nearly equal in quantity; but in no way resembling the semen emitted by the stone-horse in the coitus, or what is found in the vas deferens after death. In the boar these bags are extremely large, and divided into * [This term is here used in a more extended sense than in the present systems of natural history; but even as applied to the Linnaean genera the rule is affected by numerous exceptions of which a comparison of the vesiculte seminales of the ape with those of the human subject affords a striking example.] f [There is also in the horse a third'vesicula seminalis, of a similar structure to the two lateral ones, between which it is situated, and having, like them, no com- munication with the vasa deferentia. This want of correspondence therefore between the number of the vesiculae and that of the testes affords another argu- ment against their having the relations to each other which exist between the gall-bladder and liver.] 64 HUNTER ON THE ANIMAL CECONOMY. cells of a considerable size; or they may more properl) be said to form ramifications closely connected with one another,, and having a large canal or duct common to the whole. Ine ducts contain a whitish fluid, very unlike what is found in the vasa deferentia of the same animal, with which they have not the least communication.* . , L , , , In the rat the bags are large and flat, with serra ed edges, and lie some way within the abdomen, containing a thick ash-coloured mucus, nearly of the consistence of soft cheese; very different from what is found in the vasa deferentia of the same animal, with which they do not communicate. In the beaver the bags are convoluted ; their ducts have no com- munication with the vasa deferentia, but both the one and the other open on the verumontanum. ,. , • In the Guinea-pig they are composed of long cylindrical tubes, and lie in the cavity of the belly, are smooth on their external surface, and do not communicate with the vasa deferentia. They contain a thick, bluish, transparent substance, which is softest near the fundus, and becomes firmer towards the openings into the urethra, where it is as solid as common cheese. From this circumstance, and what is observed in the horse, the fundus appears to be the part that secretes this substance, which is very different in colour. and consistence from the contents of the vasa deferentia, and is often found in broken pieces in the urethra. To be more certain that the substance contained in these bags was not the secretion of the testicle, I extracted one of the testicles of a Guinea-pig; and six months afterwards gave it the female. As soon as the action of copulation was over (in which all the parts containing semen should naturally have emptied themselves) I killed the animal, and upon examination found the vesicula of the perfect side, and that of the side from which the testicle had been removed, both filled with a substance in every respect similar. It will scarcely be alleged that this substance had been contained in the bag before the extirpation of the testicle ; nor could it be semen, which must have been all thrown out in the previous connexion with the female. To ascertain that the contents of the vesiculae are not discharged into the vagina of the female with the semen in the act of emission, I killed a female Guinea-pig as soon as the male had left her, * [Tyson particularly notices the glandular structure of the vesiculre seminales in the peccari and boar, and was led by this circumstance to the same opinion respecting their nature and use as Mr. Hunter is endeavouring to establish by a more extensive and various induction in the present paper. "John van Horn," says Tyson, " would have a threefold matter of the seed : one from the testes, the second from the vesiculae seminales, and a third from the prostates. But this De Graaf strongly opposes; and will admit only that from the testes, which is trans- mitted to the vesiculae seminales, but not at all bred there. But in our subject, and so in some others, they being glandulous, they must therefore secrete some juice; which, in all likelihood, is some way serviceable, though not principally, in gener- ation."—Anatomy of the Mexico Musk-hog, Phil. Trans., vol. xiii. p. 370, 1683.] GLANDS CALLED VESICULA SEMINALES. 65 and examined with attention what was contained in the vagina and uterus; in neither could I find any of the mucus of the vesi- culae, which from its firmness must have been easily detected. In the hedgehog these bags are very large, being more than twice the size of the vesiculae in the human subject. Many animals have no such bags; and I believe they are want- ing in the greater part of that class which live chiefly upon animal food ; they are, however, to be found in some of them, and the hedgehog is an example.* There is no apparent difference in the testicles, vasa deferentia, or semen of the animals which have vesiculae and of those which have none; and the mode of copula- tion, as far as these bags can be concerned, is very similar in both. In birds, as far as I have yet observed, there is nothing analo- gous to these bags ; and yet there appears to be no difference between the mode of copulation of the drake and the bull or ram. It is very natural to suppose that if the vesiculae were reservoirs of semen they would be more necessary in birds, who have the power of repeating the act of copulation in an infinitely greater degree than quadrupeds; and indeed we find that in birds there are reser- voirs, which may account for this power; the vasa deferentia being enlarged just before they open into the rectum, probably to answer that intention. As birds have no urethra, some having merely a groove, as the drake and gander,f and many being even without a groove, as the common fowl, it was absolutely necessary there should be such a reservoir somewhere; and the necessity of this will appear more evidently by and by. What I have observed of the reservoir of birds is equally appli- cable to amphibious animals, and to that order of fish called rays. From the above observations I think we may fairly conclude that these vesiculae are not for the purpose of containing semen: the single circumstance of their ducts being united to those of the tes- ticles in the human subject not appearing sufficient to set aside the many facts which are contradictory to such an opinion. Having endeavoured to show that the function of these vesiculae has hitherto been misunderstood, the following cbservations will tend to prove that they are subservient to generation, though their particular use is not yet discovered; and,for the better understand- ing this part of the subject, I shall premise the following facts. Animals have their natural feelings raised or increased accord- ing to the perfection of the parts connected with such feelings; and the disposition for action is also in proportion to the slate of the * [The vesiculae seminales are wanting in all the Ferae with the exception of the lnsectivora ; also in the Ruminants, in the carnivorous Cetacea, and in all the Marsupiata; they are equally wanting in the insectivorous Monotremata, which of all mammiferous animals approximate most closely to the oviparous Vertebrata.] f [After repeated examination, we find the structure of the urethra in the drake to be as here described, viz., a groove, and not a complete canal, as represented by Sir Everard Home. See Phil. Trans. 1802, p. 361, pi. xii.] 7* 66 HUNTER ON THE ANIMAL CECONOMY parts and the excitement of such feelings. But, that these feelings may be duly excited, it is necessary that the animal and the parts should be healthv, in good condition, and in a certain degree of warmth suitable to that class to which the animal belongs. In the greatest part of the globe there is a difference in the warmth of the same district at different periods, constituting the seasons; and the cold in some of them is so considerable as to prevent those feelings or dispositions in animals from taking place, and to render them, for the time, unfit for the purposes of generation.* This is owing to the testicles becoming at this season small, and being there- fore unfit to give such dispositions, as is the case in very young animals. This fact is very obvious in birds, of which the sparrow may be produced as a proof. For if a cock-sparrow is killed in the winter, before the days have begun to lengthen, the testicle will be found very small; but if that organ is examined at different times in other sparrows, as the warmth of the weather increases, and if this examination is continued to the breeding-season, the difference in the size of the testicle will be very striking. This circumstance is not peculiar to birds, but is common, as far as I yet know, to all animals which have their seasons of copulation. In the buck we find the testicles are reduced to a very small size in the winter; and in the land-mouse, mole, &c, this diminution is still more remarkable. Animals, on the contrary, which are not in a state of nature have no such change taking place in their testicles; and, not being much affected by seasons, are consequently always in good condition, or in a state to which other animals that are left to themselves can only attain in the warmer season. Therefore in man, who is in the state we have last described, the testicles are nearly of the same size in winter as in summer ; and nearly, though not exactly, the same thing may be observed in the horse, ram, &c, these animals having their seasons in a certain degree. The variation above taken notice of is not confined to the testicles, but also extends to the parts which are connected with them. For in those animals that have their seasons for propagation the most distinctly marked, as the land-mouse, mole, &c, the vesiculae are hardly discernible in the winter, but in the spring are very large, varying in size in a manner similar to the testicle. It may, however, be alleged that the change in these bags might naturally be supposed to take place, even admitting them to be seminal reservoirs; but what happens to the prostate gland, which has never been supposed to contain semen, will take off the force of this objection, since in all the animals which have such a gland (and which have their season for propagation) it undergoes a similar change. In the mole the prostate gland in winter is hardly discernible, but in the spring becomes very large and is filled with mucus. * It is not required that the season for the copulation of different animate should be equally warm ; for the frog copulates in very cold weather, while the snake and lizard, which are also cold, sleeping animals, do not copulate till the season is warm. GLANDS CALLED VESICULAE SEMINALES. 07 From these observations it is reasonable to infer that the use of the vesiculae in the animal ceconomy must, in common with many other parts, be dependent upon the testicles. For the penis, urethra, and all the parts connected with them, are so far subservient to the testicles that I am persuaded few of them would have existed if there had been no testicles in the original construction of the body ;* and these would have been so formed as merely to assist in the ex- pulsion of the urine. To illustrate this opinion, let us observe what is the difference between these parts in the perfect male and in a male that has been deprived of the testicles when very young, at an age in which they have had no such influence upon the animal ceconomy as to affect the growth of the other parts. In the perfect male the penis is large ; the corpora cavernosaf being capable of dilatation. The corpus spongiosum is very vascular ;J that part of the canal which is called the bulb is considerably enlarged, form- ing a cavity; and the musculi acceleratores urina, as they are termed, are strong and healthy. In many animals which have a long penis, the muscular fibres are continued forwards to the end of it; and in others, though not extended so far, they are very large. On the contrary, in the castrated animal the penis is small, and not capable of much dilatation ; the corpus spongiosum is less vas- cular; the cavity at the bulb is a little larger than the canal of the urethra; and the muscles are white, small, and have a ligamentous * [The construction and functions of the penis in reptiles and those birds which possess the organ prove the correctness of this view; and very striking evidence of the exclusive relation of the penis to the functions of the testes is afforded by the discoveries in natural history which have been made since the time of Hunter. Thus, in those remarkable Australian quadrupeds, the Ornithorhynchus and Echidna, which form the passage from the mammiferous to the oviparous verte- brates, the penis, although perforated through its whole extent, does not carry off the urine, which escapes by the cloaca, but the urethra is destined solely for tne passage of the fecundating fluid during the time of the coitus.) f The cells of the corpora cavernosa are muscular, although no such appearance is to be observed in men ; for the penis in erection is not at all times equally distended. The penis in a cold day is not so large in erection as in a warm one; which, probably, arises from a kind of spasm that could not act upon it if it were not muscular. In the horse the parts composing the cells of the penis appear evidently muscular to the eye; and in a horse just killed they contract upon being stimu- lated.* X It may not be improper to observe, that the corpus spongiosum urethrae and glans penis are not spongy or cellular, but made up of a plexus of veins. This structure is discernible in the human subject, but much more distinctly seen in many animals, as the horse, &c. a [The disposition of the muscular fasciculi of this part is chiefly longitudinal, interlacing in an undulating manner with the transverse tendinous fibres. They are most numerous near the termination of the corpora cavernosa, and gradually diminish as they approach the origin. When examined with a high magnifying power the ultimate fibres of these fasciculi exhibit, but in a fainter degree, the transverse striae characteristic of the voluntary muscular fibre.] 68 HUNTER ON THE ANIMAL CECONOMY. appearance. The same observations are true, if applied to the eTerepSenTsnof the perfect male is of a ™ffi«en\ X^S erected, to reach to the further end of the vagina of the lemale. In the caslrated animal it is much shorter and erections having then become unnecessary, the parts which should project often adhere to the inside of the prepuce. The erectores muscles in the perfect male are strong enough to squeeze at once the blood out oi the crura into the body of the penis, so as to straighten and contract the urethra instantaneously, and the acceleratores urinae* have sufficient power to throw out the semen that is gradually accumu- lated at the bulb for ejection. The prostate gland.f Cowper's glands, and the glands along the urethra (of which the lacunae are the excretory ducts), are in the perfect male large and pulpy, secreting a considerable quantity of slimy mucus, which is salt to the taste; it is most probably for the purpose of lubricating those parts, and is only thrown out when in vigour for copulation : while in the castrated animal these are small, flabby, tough, and ligamentous, and have little secretion. From this account there appears to be an essential difference between the parts connected with generation of the perfect male, and those which remain in one that has been castrated, more especially if that operation had been performed while the animal was young. If it is objected that the same changes did not take place in the men from whom one testicle had been removed, it may be answered, that the operation was performed late in life: and one testicle being left, that was sufficient to carry on the necessary actions, and consequently to preserve the powers; therefore whatever parts * I shall call these muscles 'expulsores seminis,' as I apprehend their real use to be for the expulsion of that secretion : these muscles, likewise, throw out those drops of urine which are collected in the bulb from the last contractions of the bladder, and they have been, from this circumstance, named acceleratores urinae; but if a receptacle had not been necessary for the semen, those muscles had probably never existed, and the last drops of urine would have been thrown out by the action of the bladder and urethra, as in some measure is the case in the castrated animal. That the urethra has the power of contraction is evident upon the application of any stimulus, for 1 have seen the urethra refuse to allow an injection to pass on; and in that part where the injection stopped, a fulness was felt, which terminated at once: this contraction is most probably in the internal membrane; it also will often refuse the passage of a bougie. | The prostate gland is not common to all animals. It is wanting in the bull, buck, and most probably, I believe, in all ruminating animals. In this class the coats of the vesiculae are much thicker and more glandular, than in those which have prostate glands; it is therefore natural to suppose that the vesiculae answer nearly the same purposes as the prostate gland.a The prostate gland, and Cowper's glands, as well as the vesiculae, are wanting in birds, in the amphibious animals, and in those fish which have testicles, as all of the ray kind. a [The glands in Ruminants here termed 4 vesiculas,' are now regarded as a bifid prostate.] GLANDS CALLED VESICULAE SEMINALES. 69 had a connexion with these powers, would still have the stimulus of perfection given to them. The different appearance of the bulb and the muscles would seem to point out, in the perfect male, the enlargement of the bulb to be for the purpose of a receptacle for the semen ; for although I have denied the vesiculae to be reservoirs, yet, as it was necessary that the semen should be accumulated somewhere before ejection, I shall endeavour to prove, from the mode of copulation in the animals we are best acquainted with, that the bulb is intended for that purpose. Let us, therefore, give a short account of the different parts con- cerned in coition ; and by observing the dependence which they have upon one another, see how this proof will come out. The erection of the penis is produced by a stop being put to the returning blood, and this stoppage is so complete, that no mechani- cal pressure applied to the body of the penis can force the blood on into the veins. This erection answers two purposes; it gives size and strength to the penis, and it renders the canal of the urethra smaller. The corpus spongiosum of the urethra and the glans, which is only a continuation of it, are filled with blood from the same cause, but not so completely as the body of the penis, since from them it can be forced out into the veins by pressure.* This accu- mulation of blood in the corpus spongiosum diminishes the canal of the urethra so much, that any pressure upon one part of it will have a considerable effect upon the other ; not only by lessening its capa- city at the part pressed, but by forcing the blood forward, the parts beyond will be still more distended, and consequently the canal of * In April 1760, in the presence of Mr. Blount, I laid bare the penis of a dog, almost through its whole length ; traced the two veins that came from the glans (which in this animal makes the largest part of the penis), and separated them from the arteries by dissection, that I might be able to compress them at pleasure without affecting the arteries. I then compressed the two veins, and found that the glans and large bulb became full and extended ; but when I irritated the veins, in order to see if there was any power of contraction in them which might occasionally stop the return of the blood, no such appearance could be observed.a a [From this experiment, it is obvious that Hunter regarded the stoppage of the circulation through the veins as being produced by external compression. Douglas (Myographiae Comparatae Specimen, p. 9), had previously described the muscles which compress the vena dorsalis penis in the dog; and Cowper had more fully and particularly detailed the structure and actions of the muscles which have a corresponding office in the opossum, observing that "the muscles of the cavernous bodies of the penis of this creature, having no connexion with the os pubis, cannot apply the dorsum penis to the last-named bone, and compress the vein of the penis, whereby to retard the refluent blood and cause an erection, as we have observed in other creatures; but some large veins of the penis here take a different course, and pass through the middle parts of the bulb, and are only liable to compression made by the intumescence of the muscles' C C (mus- cles of the bulb) that inclose them. "Bui the chief agent in continuing the erection of the penis in this animal is the sphincter muscle of its anns, or rather cloaca; and not only the sphincter muscle of the cloaca of the male opossum, but that of the female also closely embraces the penis in coition, and effectually retard the refluent blood from its corpora cavernosa, by compressing the veins of the penis." (Phil. Trans., vol. xxiv. 1704, p. 1581.)] 70 HUNTER ON THE ANIMAL CECONOMY. the urethra be in that proportion diminished. The semen, in the time of copulation, in such animals as remain long in that act, is gradually squeezed along the vasa deferentia (as it is secreted) into the bulb; and when the testicles cease to secrete, the paroxysm, which is to finish the whole operation, comes on. The semen acting as a stimulus to the cavity of the bulb of the urethra, the muscles of that part of the canal are thrown into action; the fibres nearest the bladder, probably, act first, and those more forward in quick succession ; the semen is projected with some force; the blood in the bulb of the urethra is by the same action squeezed forward, but requiring a greater impulse to propel it, is rather later than the semen, on which it presses from behind; the corpus spongiosum being full of blood, acts almost as quick as undulation, in which it is assisted by the corresponding constriction of the urethra, and the semen is hurried along with a considerable velocity.* From the facts which I have stated respecting the organs of generation, the observations which I have made, and the series of actions which I have considered as taking place in the copulation of animals, I think the following inferences may be fairly drawn. That the bags, called vesiculae seminales, are not seminal reser- voirs, but glands secreting a peculiar mucus ; and that the bulb of the urethra is, properly speaking, the receptacle in which the semen is accumulated previous to ejection. Although it seems to have been proved that the vesiculae do not contain the semen, I have not been able to ascertain their particular use ; we may, however, be allowed upon the whole to conclude that they are, together with other parts, subservient to the purposes of generation. 3. ACCOUNT OF THE FREE-MARTIN. Generation, from a seed, requires the concurrence of two causes to give it perfection: the one to form the seed, the other to give it the principle of action.f * [Besides the functions here assigned to the bulb of the urethra, in relation to the reception and propulsion of the semen, we may also notice its uses in reference to the distention of the glans penis, of which Cowper, in his description of the male organs of the opossum above quoted, gives a remarkable example. He observes : " As the bulb of the urethra in man is framed for the use of the glans to keep it sufficiently distended when required, so it seems it is necessary to have' two of these bulbs inclosed with their particular muscles in this animal to main- ta™ .,™ turgescence of its double or forked glans when the penis is erected " (Phil Tram., vol. xxiv., 1704, p. 1585.)] «"«-«»•. f ^ may be necessary for some of my readers to have explained to them what 1 mean by a seed. I do suppose that the word seed was first applied to grain, or OF THE FREE-MARTIN. 71 The cause forming the seed is called the female, the other the male ; but those two causes in general make only a part of a whole animal, or are rather parts superadded to an animal. Probably these characteristics were first observed in such animals as had the female parts complete in one, and the male in the other; therefore the terms female and male have been applied to the whole animal, dividing them into two distinct sexes, and the parts which formed the one sex or the other were called the female or the male parts of generation. But, upon a more accurate knowledge of animals and of their parts of generation, these were found in many of the inferior tribes to be united in the same animal, which from possessing both has got the name of hermaphrodite. As the distinction of male or female parts is natural to most animals, as the union of them in the same animal is also natural to many, and as the separation of them is only a circumstance making no essential difference in the structure of the parts themselves, it be- comes no great effort or uncommon play in Nature sometimes to unite them in those animals in which they are commonly separated ; a circumstance we really find takes place in many animals of those orders in which such an union is unnatural. From this state of the case hermaphrodites may be divided into two kinds, the natural and unnatural. The natural hermaphrodite belongs to the inferior and more simple genera of animals of which there is a much greater number than of the more perfect; and as animals become more complicated, have more parts, and each part is more confined to its particular use, a separation of the two necessary powers for generation seems also to take place.* that which is always called seed in the vegetable; which seed is the part of such vegetables in which the matter of the young vegetable exists or is formed. The principle of arrangement in the farina, or male part, fitting the seed for action, being at first not known, a false analogy between the vegetable and animal was established, and the matter secreted by the testes was called the seed ; but, from the knowledge of the distinct sexes in the vegetable, it is well known that the seed is the female production in them, and that the principle of arrangement for action is from the male. The same operation and principles take place in many orders of animals, the female producing a seed in which is the matter fitted for the first arrangement of the organs of the animal, and which receives the principle of arrangement fitting them for action from the male. *■ [The animals in which the organs of the two sexes are naturally combined in the same individual are confined to the invertebrate division, and are most common in the molluscous and radiate classes. If the term hermaphrodite may be applied to those species which propagate without the concourse of the sexes, but in which no distinct male organ can be detected, as well as to those in whic.h both male and female organs are present in the same body, then there may be distinguished three kinds of hermaphroditism. First, the cryptandr oust, or in which the female or productive organs are alone developed. Ex. the accephalous mollusks, as the oyster, lamp-cockle, and ascidia; the cystic entozoa, echinoderms, acalephes, polyps, and sponges. Second, the heautandrous, or in which the male organs are developed, but so disposed as to fecundate the ova of the same individual. Ex. the cirripeds, the rotifers, the trernaiode and cestoid entozoa. Third, the allotriandrous, or in which the male organs are so disposed as not to 72 HUNTER ON THE ANIMAL CECONOMY. The unnatural hermaphrodite,* I believe, now and then occurs in every tribe of animals having distinct sexes, but is more in common in some than in others ;f and is to be met with, in all its gradations, fecundate the ova of the same body, but where the concourse of two individuals is required, notwithstanding the co-existence in each of the organs of the two sexes. Ex. the gastropodous mollusks, with the exception of the pectinibranchiate order, the class Annellida. , . ... ... All the other invertebrates, as the cephalopods and pectinibranchiate gastro- pods, the insects, arachnidans and crustaceans, the epizoa, and the nematoid entozoa, are, like the vertebrate classes, dioecious, or composed ot male and female individuals.] . . . * [The unnatural hermaphrodites may be divided into those in which the parts peculiar to the two sexes are blended together in different proportions, and the whole body participates of a neutral character, tending towards the male and female as the respective organs predominate, and into those in which the male and female organs occupy respectively separative halves of the body, and impress on each lateral moiety the characteristics of the sex. This latter and very singular kind of hermaphroditism has hitherto been found only in insects and crustaceans. In the Extracts from the Minute-Book of the Linnean Society, printed in the 14th Vol. of their Transactions, it is stated that Alex. MacLeay, Esq., Sec. L.S., exhibited a curious specimen showing that two Papiliones, referred to distinct families by Fabricius, are in reality the male and female of the same species. This specimen presented the forms and colours of both sexes, divided by a longi- tudinal line on the body: the right wings and side of the body being as in the male (Papilio Polycaon, Fabr.), and the left as in the female (Papilio Laodocus, Fabr.). In Loudon's Magazine of Natural History, (vol. iv. p. 434,) an experi- enced entomologist, Mr. J. O. Westwood, has given descriptions and figures, not only of dimidiate hermaphrodites, (the example is the Bombyx Penii) but also of quartered hermaphrodites : the latter singular condition is exemplified in a speci- men of the Bombyx castrensis, in which the right wing, left antenna, and left side of the abdomen are male; the left wing, right antenna, and right side of the abdomen are female; and again in a specimen of the stag-beetle (Lucanus Cervus), in which the left jaw and right elytrum are masculine, and the right jaw and left elytrum feminine. In most dimidiate hermaphrodites the left side is masculine; but an example of the contrary has been observed in Sphinx Populi. It is to be regretted that the condition of the internal organs of generation cannot be ascer- tained in the above singular examples ; but this deficiency is in some degree supplied by the results of Dr. Nicholl's dissection of a hermaphrodite lobster, {Phil. Trans., xxxvi., p. 290,) in which a testis was found on that side of the body which exhibited externally the male characteristics, and an ovarium on the opposite side.] f Quere: Is there ever, in the genera of animals that are natural hemaphrodites, a separation of the two parts forming distinct sexes? If there is, it may account for the distinction of sexes ever having happened.* a [The separation of the two sexual organs from one another in the same body occurs in many of that class of natural hermaphrodites which we have termed 'allotriandrous;' and there are many examples in the Hunterian collection showing the fact. What, therefore, Mr. Hunter seems here to refer to is a spon- taneous fission of the body in the interval separating the two sexual parts, so that one portion of the body shall contain the male and the other the female organs. Some annellides, as the Nais, exhibit the phenomenon of spontaneous fisVion, but the separation never occurs so as to divide the two sexual organs from one another, and appropriate one to each division; and were even such an occurrence to be supposed ever to take place, the application of the fact to explain the occur- rence of the distinct sexes in the naturally dioecious classes seems more worthy of a speculatist of the Lamarckian school than of a sober observer of Nature.] OF THE FREE-MARTIN. 73 from the distinct sex to the most exact combination of male and female organs. This, I fancy, happens most rarely in the human species, never having seen an instance. I can say the same of dogs* and cats, with which last, however, I am less acquainted; but in the horse, ass, sheep, and black cattle it is very frequent. There is one part common to both the male and female organs of generation in all animals which have the sexes distinct: in the one sex it is called the penis, in the other the clitoris ; its specific use in both is to continue, by its sensibility, the action excited in coition till the paroxysm alters the sensation. In the female it pro- bably answers no other purpose; but in the male it is more com- plicated, to adapt it for the purpose of conducting and expelling the semen that has been secreted in consequence of the actions so excited. Though the unnatural hermaphrodite be a mixture of both sexes, and may possess the parts peculiar to each in perfection, yet it cannot possess in perfection that part which is common to both. For as this common part is different in one sex from what it is in the other, and it is impossible for one animal to have both a penis and clitoris, the common part must of course partake of both sexes, and consequently render the hermaphrodite so far incomplete ; but these parts peculiar to each sex may be perfectly joined in the same animal, which will convey an idea of the truest hermaphro- dite.t Although it may not be necessary, to constitute an herma- phrodite, that the parts peculiar to the one sex should be blended with those of the other, in the same way that the penis is with the clitoris, yet this sometimes takes place in parts whose use in the distinct sexes is somewhat similar, the testicle and ovarium some- times forming one body, without the properties of either. This compounded part in those animals that have the testicle and ovarium differently situated is generally found in the place allotted for the ovarium; but in such animals as have the testicle and ova- rium in the same situation, as the bird tribe, the compound of the two, when it occurs, will also be found in that common situation. The parts of the female appropriated for the purpose of supplying the young with nourishment are variously placed in different ani- mals. In the horse, black cattle, sheep, and other graminivorous animals, their situation is between the hind legs; and this being also the place allotted for the testicles of the male of this tribe, and probably of all those in which the testicles come out of the cavity of the belly; in the hermaphrodite therefore, which has both these • [For an example of hermaphroditism in a dog, see Phil. Trans., lxxxix. p. 157.] r~f [In a recent work on hermaphroditism, by Geoffroy St. Hilaire, a mechanical reason is assigned for the non-existence of a penis and clitoris in the same indi- vidual, viz., because both parts arise from the same points of the pelvis: but in many animals neither the one nor the other has any bony attachment, and the explanation above given, founded on the similarity of their functions, is more philosophical and satisfactory.] 74 HUNTER ON THE ANIMAL CECONOMY. parts, the testicles must to a certain degree descend into the udder, though that cannot receive them so readily as the scrotum. The hermaphrodites which I have seen have always appeared externally and at first view to be females, from the penis being the part principally deficient, and there being an opening behind like the bearing in'the female; and as the testicles in such hermaphro- dites seldom come down, the udder is left to occupy its proper place. In animals the female of which is preserved for breeding only, as sheep, goats, pigs, &c, these are generally kept, from their being supposed to be females. Among horses such hermaphrodites are very frequent: 1 have seen several, but never dissected any. The most complete was one in which the testicles had come down out of the abdomen into the place where the udder should have been (viz., more forward than the scrotum), and, though not so pendulous as the scrotum in the perfect male of such animals, had all the appearance of an udder. There were also two distinct nipples, which, although they exist in the male, have no perfect form, being blended with the sheath or prepuce, of which there was none here. The external female parts were exactly similar to those of the perfect female; but instead of a common-sized clitoris, there was one about five or six inches long, which when erect pointed almost directly backwards. I procured a foal-ass, very similar in external appearance to the horse above-mentioned, and killed it to examine the parts. It had two nipples, but the testicles were not come down as in the above, owing perhaps to the animal's being yet too young. There was no penis passing round the pubis to the belly, as in the perfect male ass. The external female parts were similar to those of the she-ass. Within the entrance of the vagina was placed the clitoris; but much longer than that of a true female, it measuring about five inches. The vagina was pervious a little beyond the opening of the urethra into it, and from thence up to the fundus of the uterus there was no canal. The uterus was hollow at the fundus, or had a cavity in it, and then divided into two horns, which were also pervious. Beyond the termination of the two horns were placed the ovaria as in the true female; but I could not find the Fallopian tubes. From the broad ligaments, to the edges of which the horns of the uterus and ovaria are attached, there passed towards each groin a part similar to the round ligaments in the female, which were continued into the rings of the abdominal muscles; but with this difference, that there accompanied them a process or theca of the peritoneum, simi- lar to the tunica vaginalis communis in the male ass; and in these thecae were found the testicles, but I could not observe any vasa deferentia passing from them. Here then were found, in the same animal, the parts peculiar to each sex (although very imperfect), and that part which is common to both, but different in each, was a kind of medium of that difference. OF THE FREE-MARTIN. 75 Something similar to the above I have seen in sheep, goats, &c; but I shall not at present trouble the reader with a description of hermaphrodites in general, as it is a very extensive subject, admit- ting of great variety, which would make them appear a production of chance; whereas the intention of this account is to point out a circumstance which takes place in the production of hermaphro- dites in black cattle that appears to be almost an established prin- ciple in their propagation, and is perhaps peculiar to that species of animal. It is a fact known, and I believe almost universally understood, that when a cow brings forth two calves, and one of them a bull- calf and the other to appearance a cow, that the cow-calf is unfit for propagation, but the bull-calf grows up into a very proper bull. Such a cow-calf is called in this country a free-martin, and is commonly as well known among the farmers as either cow or bull. Although it will appear, from the description of this animal, that it is an hermaphrodite (being in no respect different from other herma- phrodites), yet I shall retain the term, free-martin, to distinguish the hermaphrodite produced in this way from those which resemble the hermaphrodite of other animals ; for I know that in black cattle such a deviation may be produced without the circumstance of twins : and even where there are twins, the one male the other a female, they may both have the organs of generation perfectly formed. But when I speak of those which are not twins, I shall call them hermaphrodites : the only circumstance worth our notice being a singularity in the mode of production of the free-martin, and its being, as far as I yet know, peculiar to black cattle. This calf has all the external marks of a cow-calf, similar to what was mentioned in the unnatural hermaphrodite, viz., the teats and the external female parts called by farmers the bearing; and when they are preserved by those who know the above fact, it is not for propagation, but for all the purposes of an ox or spayed heifer, viz., to yoke with the oxen and to fatten for the table. • It is known that they do not breed; they do not show the least inclination of the bull, nor does the bull ever take the least notice of them.f They very much resemble, in form, the ox or spayed heifer, being considerably larger than either the bull or the cow, having the horns very similar to the horns of an ox. The bellow of the free-martin is similar to that of an ox, having more resemblance to that of the cow than of the bull. Free-mar- tins are very much disposed to grow fat with good food. The flesh, like that of the ox or spayed heifer, is generally much finer in the fibre than either the bull or cow, is supposed to exceed that of the ox and heifer in delicacy of flavour, and bears a higher price at market. * I need hardly observe here, that if a cow has twins, and they are both bull- calves, that they are in every respect perfect bulls ; or if they are both cow-calves, they are perfect cows. f Vide Leslie on Husbandry, pp. 98, 99. 76 HUNTER ON THE ANIMAL CECONOMY. However, it seems that this is not universal, for I was lately informed by Charles Palmer, Esq., of Luckley in Berkshire, that a free-martin having been killed in his neighbourhood, from the general idea of its being better meat than common, every neigh- bour bespoke a piece, which turned out nearly as bad as bull-beef; worse, at least, than that of a cow. It is probable that circum- stance might arise from this animal having more the properties of a bull than the cow, as we shall see hereafter that they are some- times more the one than the other.* Although what I have advanced with respect to the production of free-martins be in general true, yet, by the assistance of Benja- min Way, Esq., of Denham, near Uxbridge, who knew my anxiety to ascertain this point, I was lately furnished with an instance which proves that it does not invariably hold good. One of his cows having produced twins, which were to appear- ance male and female, upon a supposition that the cow-calf was a free-martin, he obligingly offered either to give it me, or to keep it till it grew up, that we might determine the fact: as I conceived it to be a free-martin, and was to have the liberty of examining it after death, I desired that he would keep it; but, unfortunately, it died at about a month old. Upon examining the organs of generation, they appeared to be those of the female, and perfectly formed; but to make this more certain, I procured those of a common cow-calf, and comparing them together, found them exactly alike. This made us regret that the animal had not lived to an age that might have determined if it was capable of breeding; for the construction of the parts being to appearance perfect, is not sufficient of itself to stamp it a true or perfect female; as I can suppose that the parts being perfectly formed, but without the power of propagation, may constitute the most simple kind of hermaphrodite. It is, however, most probable that this was a perfect female, which is an excep- tion to the common rule; and I have been informed there are instances of such twins breeding.f If there are such deviations, as of twins being perfect male and female, why should there not be, on the other hand, an hermaphrodite produced singly, as in other animals 1 I had the examination of one which seemed, upon the * The Romans called the bull, taurus; they, however, talked of taurse in the feminine gender. And Stephen observes, that it was thought the Romans meant by taurae, barren cows, and called them by this name because they did not con- ceive. He also quotes a passage from Columella, lib. vi. cap. 22, "and like the turae, which occupy the place of fertile cows, should be rejected, or sent away." He likewise quotes Varro, De Re Rustica, lib. ii. cap. 5, "The cow which is barren is called taura." From which we may reasonably conjecture that the Romans had not the idea of the circumstances of their production. t [An instance of this nature is recorded in the fifth volume of Loudon's Magazine 0f Natural History, p..765. "Jos. Holroyd, Esq., of Withers, near Leeds, had a cow which calved twins, a bull-calf and a cow-calf. As popular opinion was against the cow-calf breeding, it had been considered a free-martin, Mr. Holroyd was determined to make an experiment of them, and reared them together. They copulated, and in due time the heifer brought forth a bull-calf and she regularly had calves for six or seven years afterwards."] OF THE FREE-MARTIN. 77 strictest inquiry, 1o have been a single calf; and I am the more inclined to think this true, from having found a number of her- maphrodites among black cattle, without the circumstances of their birth being ascertained. Hermaphrodites are to be met with in sheep; but, from the account given of them, I should suppose that they are not free- martins. I have seen several which were supposed to be her- maphrodites, but which were imperfect males, having the penis terminating in the perinaeum, the orifice of which appeared like the bearing in the female. Such are not naturally stimulated to put themselves in the position of the female when they void their urine, so that when it passes the surrounding parts are wetted by it, and being covered with wool, and retaining the urine, keeps them con- tinually moist, and gives the animal a strong smell. They are mentioned as both male and female. I believe it had never been even conjectured, notwithstanding all these peculiarities, what was the true nature of the free-martin; and from the singularity of the animal, and the account of its production, I was almost tempted to suppose the whole a vulgar error. Yet by the universality of the testimony in its favour, it ap- pearing to have some foundation, I eagerly sought for an oppor- tunity to see and examine them. I have succeeded in this inquiry, and have seen several, the first of which was one belonging to John Arbulhnot, Esq., of Mitcham, and was calved in his own farm. He was so obliging as to allow me to satisfy myself, first by permitting a drawing to be made of the animal while alive, which was executed by Mr. Gilpin, and afterwards to examine the parts when the animal died. At the time the drawing was made of Mr. Arbuthnot's free- martin, John Wells, Esq., of Bickley Farm.near Bromley in Kent, was present, and informed us that a cow of his had calved two calves, one of which was a bull-calf, and the other a cow-calf. I desired Mr. Arbuthnot to request Mr. Wells to keep them, or let me buy them of him ; but from his great desire of natural knowledge, he very readily consented to preserve both till the bull showed all the signs of a good bull; and when the free-martin was killed, he allowed me to inspect the parts. Of all the specimens which I have dissected, I shall only give the descriptions of the three which point out most distinctly the complete free-martin with the gradations towards the male and female. THE DESCRIPTION OF THE THREE FREE-MARTINS. Mr. Wright's Free-Martin, five years old. This animal had more the appearance and general character of the ox, or spayed heifer, than of either the bull or cow. The vagina terminated in a blind end, a little way beyond the opening 8* 78 HUNTER ON THE ANIMAL CECONOMY. of the urethra, from which the vagina and uterus were impervious. The uterus, at its extreme part, divided into two horns. At the termination of the horns were placed the testicles, instead oi the ovaria, as is the case in the female. The reasons why I call these bodies testicles, are the following. First, they were above twenty times larger than the ovaria of the cow, and nearly the size of the testicles of the bull, or rather of those of the ridgil, the bull whose testicles never come down. Secondly, the spermatic arteries were similar to those of the bull, especially of the ridgil. Thirdly, the cremaster muscle passed up from the rings of the abdominal muscles to the testicles, as it does in the ridgil.* There were the two bags placed behind, between the bladder and the uterus. Their ducts opened into the vagina, a very little way beyond the opening of the urethra; but there was nothing similar to the vasa deferentia. As the external parts had more of the cow than the bull, the clitoris, which may be reckoned an external part, was also similar to that of the cow, not at all in a middle state, between the penis of the bull and the clitoris of the cow, as I have described in the her- maphrodite horse. There were four teats: the glandular part of the udder was but small. This animal cannot be said to have been a mixture of all the parts of both sexes, for the clitoris had nothing similar to the penis in the male, and it was deficient in the female parts, by having nothing similar to the ovaria ; neither had the uterus a cavity. Mr. Arbuthnot's Free-Martin.^ The external parts were rather smaller than in the cow. The vagina passed on, as in the cow, to the opening of the urethra, and then it began to contract into a small canal, which passed on to the division of the uterus into the two horns, each horn passing along the edge of the broad ligament laterally towards the ovaria. At the termination of these horns were placed both the ovaria and the testicles ; they were nearly of the same size, and about as large as a small nutmeg. To the ovariaj I could not find any Fallopian tube. To the testicles were vasa deferentia, but they were imperfect. The left one did not reach near to the testicle; the right only came * Although I call these bodies testicles, for the reason given, yet they were only imitations of them, for when cut into they had nothing of the structure of the testicle; not being similar to anything in Nature, they had more the appear- ance of disease. From the seeming imperfection of the animal itself, it was not to be supposed that they should be testicles; for then the animal should have partaken of the bull, which it certainly did not. f This animal was seven years old ; had been often yoked with the oxen • at other times went with the cows and bull; but never showed anv desires'for either the one or the other. J *«>«co iui X [It is probable that these bodies were, as in the case previouslv noted re- mains of the corpora Wolffiana.] v y 0lea're OF AN EXTRAORDINARY PHEASANT. 79 close to it, but did not terminate in a body called the epididymis. They were both pervious, and opened into the vagina near the opening of the urethra. On the posterior, surface of the bladder, or between the uterus and bladder, were the two bags, called vesiculae seminales in the male, but much smaller than what they are in the bull; the ducts opened along with the vasa deferentia. This was more entitled to the name of hermaphrodite than the first or third, for it had a mixture of all the parts, though all were imperfect. Mr. Wells's Free-Martin. This animal was between three and four years old when killed; and had never been observed to show any signs of desire for the male, although it went constantly with one; and looked more like a heifer than free-martins usually do. The teats and udder were small compared with those of a heifer, but rather larger than in either of the former examples; the begin- ning of the vagina was similar to that of the cow, but soon ter- minated a little beyond the opening of the urethra, as in the first- described. The vagina and uterus, to external appearance, were continued, although not pervious, and the uterine part divided into two horns, at the end of which were the ovaria. I could not observe in this animal any other body which I could suppose to be the testicle. There was on the side of the uterus an interrupted vas deferens broken off in several places. Behind the bladder, or between that and the vagina, were the bags called vesiculae seminales, between which were the termina- tions of the two vasa deferentia. The ducts of the bags, and the vasa deferentia, opened as in the last instance. This could not be called an exact mixture of all the parts of both sexes, for here was no appearance of testicles. The female parts were imperfect, and there was the addition of part of the vasa deferentia, and the bags called vesiculae seminales. This circumstance of having no testicles, perhaps, was the reason why it had more the external appearance of a heifer than what they commonly have, and more than either of the two former. 4. AN ACCOUNT OF AN EXTRAORDINARY PHEASANT. Every deviation from that original form and structure which gives the distinguishing character to the productions of Nature, may not improperly be called monstrous. According to this 80 HUNTER ON THE ANIMAL CECONOMY. acceptation of the term, the variety of monsters will be almost infinite;* and, as far as my knowledge has extended, there is not a species of animal, nay, there is not a single part of an animal body, which is not subject to an extraordinary formation. Neither does this appear to be a matter of mere chance ; for it may be observed that every species has a disposition to deviate from Nature in a manner peculiar to itself.f It is likewise worthy of remark, that each species of animals is disposed to have nearly the same sort of defects, and to have certain supernumerary parts of the same kind: yet every part is not alike disposed to take on a * [Mr. Hunter attempted, notwithstanding, to reduce this variety of monsters to definite groups, and left the following outline of a classification of monsters, in an explanatory introduction to the extensive series of those objects in his collection: " 1. Monsters from preternatural situation of parts. " 2.-------------addition of parts. " 3.-------------deficiency of parts. " 4.-------------combined addition and deficiency of parts, as in herma- phroditical malformation." Licetus,a Huber,b and Malacarnec had proposed classifications of monsters prior to the time of Hunter, all of which are more or less tinctured with the superstitions of the times; thus, the tenth class in the system of Licetus is appro- priated to the offspring of the illicit intercourse of demons with women: the fifteenth of Malacarne contains the brutes with human members, &c. Blumen- bach, towards the end of the eighteenth century, published an arrangement of monsters which closely resembles that of Hunter; he, however, distinguishes, but without sufficient reason, unnatural hermaphrodites from monsters, and divides the latter into " 1. Monsters by an unnatural conformation of certain parts of the body,— Fabrica aliena. " 2.-----------transposition of parts,—Situs mutatus. " 3.-----------a deficiency of parts,—Monstraper defectum. " 4.-----------supernumerary parts,—Monstra per excessum.'1'' The study of the various congenital aberrations from the specific form presented in the different classes of the animal kingdom, has since been ably and success- fully pursued by Meckel, Geoffroy St. Hilaire, Otto, Breschet, Charuet, &c, the general results of whose labours may be found in the Histoire Generate et Particu- liere des Anomalies de V Organization chez /'Homme et les Animaux, ou Traitedt Teratologic, by Isid. Geoffroy Saint-Hilaire: 8vo, 1832.] f [The value of the principle here enunciated will be appreciated, when it is stated that it is the basis of the latest and most elaborate work on the subject of monsters. It is claimed for Geoffroy St. Hilaire as the most important of his deductions in Teratology, and the chief point in which his system differs from, and is superior to, those of his predecessors. " C'est de principes precisement inverses que mon pere a pris sur point de depart; et c'est aussi, comme cela devait etre a des resultats inverses qu'il est parvenu. Etablissant, par un grand nombre de recherches-, que les monstres sont, comme les etres dits normaux, soumis a des regies constantes, il est conduit aadmettre que la methode declassi- fication que les naturalistes emploient pour les seconds, peut etre appliquee avec succes aux premiers." Isid. Geoffroy St.-Hilaire, loc. cit., p. 99.] » Fortunius Licetus, Be Monstris, ex reccnsione G. Blasii: Amstelodami, 1665, 4to. i> Observationes nonnulhe de Monstris: 4to. Cassel, 1748. * " De' Mostri umani de' Caretteri fondamentali su cui ne se portrebbe stabilire la Classificazione," Mem. delta Soc. Ital., torn. ix. 4. OF AN EXTRAORDINARY PHEASANT. 81 great variety of forms; but each part of each species seems to have its monstrous form originally impressed upon it.* It is well known that many orders of animals have the two parts designed for the purpose of generation different in individuals of the same species, by which they are distinguished into male and female; but this is not the only mark of distinction, in the greatest part the male being distinguished from the female by various other marks. The varieties which are found in the parts of generation themselves I shall call the first or principal marks, being originally formed in them, and belonging equally to both sexes; all others depending upon these I shall call secondary, as not taking place till the first are becoming of use, and being principally, although not entirely, in the male. One of the most general marks is, the superior strength of make in the male ; and another circumstance, perhaps equally so, is this strength being directed to one part more than another, which part is that most immediately employed in fighting. This difference in external form is more particularly remarkable in the animals whose females are of a peaceable nature, as are the greatest number of those which feed on vegetables, and the marks to discriminate the sexes are in them very numerous. The males of almost every class of animals are probably disposed to fight, being, as I have observed, stronger than the females; and in many of these there are parts destined solely for that purpose, as the spurs in the cock, and the horns in the bull; and on that account the strength of the bull lies principally in his neck ; that of the cock in his limbs. In carnivorous animals, whose prey is often of a kind which requires strength to kill, we do not find such a difference in the form of the male and female, very little being discernible in the dog and bitch, in the he or she cat, or in the cock and hen of the eagle, f A difference, however, is often perceivable in the whole or in some part of their external covering; the mane of the lion distinguishing him from the lioness ; and the males of such animals as neither fight nor feed on flesh, being only distinguishable from the female by some peculiarity in the covering of their bodies, as the cock and hen in many birds. The male of the human species is distinguished * [In this principle Mr. Hunter is opposed to Geoffroy St.-Hilaire, who attri- buted the production (rordonnee) of monstrosities to the operation of exterior or mechanical causes at some period of foetal development. Defective formation in parts of a foetus has indeed been produced by destroying a portion of the respira- tory surface of an egg during incubation; but this result by no means affords adequate grounds for assigning as the sole cause of every malformation accidental adhesions between the foetus and its coverings. Mr. Hunter also made experi- ments with reference to monstrosities, and succeeded in effecting what, at first sight, seems the most difficult to produce, viz., the monsters by excess, of which several specimens of Lacerta, with a double tail (No. 2219—2223), afford exam- ples. It is evident, however, from the expression in the concluding paragraph of the text, that he regarded the cause of congenital malformation as existing in the primordial germ.] f [The difference in the size of the two sexes is sufficiently marked in most of the Raptorial birds; but it is the female which has the advantage in this respect.] 82 HUNTER ON THE ANIMAL CECONOMY. from the female both by his general strength and his covering, as also by a difference of voice. In these orders of animals whose sexes are distinct, we may not only observe the genital organs to be subject to mal-conformation, as in any other part of the animal, but that an attempt is sometimes made to unite the two organs in the same animal body, making what may be called an unnatural hermaphrodite. In producing the unnatural hermaphrodite the same laws seem to operate as in the mal-conformation of other parts of animals ; it being observable, that these deviations obtain through a whole species precisely in the same manner. I have already given an account of the free-martin, which exhibits a mixture of the two parts of generation in the same animal. It is my intention at present to extend my inquiry on this subject no further than what relates to the resemblance which one sex bears to another in those distinguishing properties which I term secondary; for we find that there is often a change of the natural properties of the female sex into those of the secondary of the male ; the female, in such cases, now and then assuming the secondary peculiarities of the male. It is to be observed, that some classes are more liable than others to this change, a singular example of which is to be the subject of the following pages. To bring the foregoing observations into one point of view, I here beg leave to remark, that in animals just born, or very young, there are no peculiarities to distinguish one sex from the other, ex- clusive of what relates to the organs of generation, which can only be in those who have external parts; and that towards the age of maturity the discriminating changes before mentioned begin to appear; the male then losing that resemblance he had to the female in various secondary properties ;* but that in all animals which are not of any distinct sex, called hermaphrodites, there is no such alteration taking place in their form when they arrive at that age. It is evidently the male which at this time in such respects recedes from the female, every female being at the age of maturity more like the young of the same species than the male is observed to be; and if the male is deprived of his testes when young, he retains more of the original youthful form, and therefore more resembles the female. From hence it might be supposed that the female character con- tains more truly the specific properties of the animal than the male; but the character of every animal is that which is marked by the roperties common to both sexes, which are found in a natural ermaphrodite, as in a snail, or in animals of neither sex, as the castrated male or spayed female. But where the sexes are separate, and the animals have two * Tjh'J- 'S "0t common t0 a11 animals of distinct sexes, for in fishes there is no great difference ; nor in many insects ; nor in dogs, as has been already observed- however, it is considerable in many quadrupeds, but appears to be most so in OF AN EXTRAORDINARY PHEASANT. 83 characters, the one cannot more than the other be called the true, as the real distinguishing marks of each particular species, as has been mentioned above, are those common to both sexes, and which are likewise in the unnatural hermaphrodite. That these properties give the distinct character of such animals is evident, for the cas- trated male and the spayed female have both the same common properties; and when I treated of the free-martin, which is a monstrous hermaphrodite, I observed that it was more like the ox than the cow or bull; so that the marks characteristic of the species which are found in the animal of a double sex are imitated by depriving the individual of certain sexual parts, in consequence of which it retains only the true properties of the species. They are curious facts in the natural history of animals, that by depriving either sex of the true parts of generation, they shall seem to approach each other in appearances, and acquire a resemblance to the unnatural hermaphrodite. In some species of animals that have the secondary properties we have mentioned, there is a deviation from the general rules, by the perfect female, with respect to the parts of generation, assuming more or less the secondary character of the male. This change does not appear to arise from any action produced at the first formation of the animal, and in this respect is similar to what takes place in the male; neither does it grow up with the animal as it does to a certain degree in the male, but seems to be one of those changes which happen at a particular period, similar to many common and natural phenomena: like to what is ob- served of the horns of the stag, which differ at different ages; or to the mane of the lion, which does not grow till after his fifth year, &,c* This change has been observed in some of the bird tribe, but principally in the common pheasant; and it has been observed by those who are conversant with this bird, when wild, that there every now and then appears a hen pheasant with the feathers of a cock: all, however, that they have described on the subject is, that this animal does not breed, and that its spurs do not grow. Some years ago one of these was sent to the late Dr. William Hunter, which I examined, and found it to have all the parts peculiar to the female of that bird. This specimen is still preserved in Dr. Hun- ter's museum. Dr. Pitcairn having received a pheasant of this kind from Sir Thomas Harris, showed it as a curiosity to Sir Joseph Banks and Dr. Solander. I happening to be then present, was desired to examine the bird, and the following was the result of my examination. I found the parts of generation to be truly female, they being as * [We have observed in the young African lions at the Zoological Gardens that the mane began to be distinctly developed at the third year, and was com- pleted at the fourth.] 84 HUNTER ON THE ANIMAL CECONOMY. perfect as in any hen pheasant that is not in the least prepared for laying eggs, and having both the ovary and oviduct. . As th? observations hitherto made have been principally upon birds found wild, little of their history can be known; but trorn what took place in a hen pheasant, in the possession of a lriend of Sir Joseph Banks, it appears probable that this change ol cha- racter takes place at an advanced period of the animal's hie, and does not grow up with it from the beginning. This lady, who had for some time bred pheasants, and paid particular attention to them, observed that one of the hens, after having produced several broods, moulted, when the succeeding feathers were those of a cock, and that this animal was never afterwards impregnated. Hence it is most probable that all the hen pheasants found wild, having the feathers of a cock, were formerly perfect hens, but have been changed by age, or perhaps by certain constitutional cir- cumstances.* Having bought some pheasants from a dealer in birds, among which were several hens, I perceived, the year after, that one of the hens did not lay, and that she began to change her feathers. The year following she had nearly the plumage of the cock, but less brilliant, especially on the head ; and it is more than probable that this was an old hen, nearly under circumstances similar to to those before described. Lady Tynte had a favourite pied pea-hen which had produced chickens eight several times; having moulted when about eleven years old, the lady and family were astonished by her displaying the feathers peculiar to the other sex, and appeared like a pied peacock. In this process the tail, which became like that of the cock, first made its appearance after moulting ; and in the following year, having moulted again, produced similar feathers. In the third year she did the same, and, in addition, had spurs resembling those of a cock. She never bred after this change in her plumage, and died in the following winter during the hard frost in the year 1775-6. This bird is now preserved in the museum of the late Sir Ashton Lever.f From what has been related of these three birds, we may con- * [The cause of the change in the plumage which Mr. Hunter here alludes to, has been proved by subsequent dissections to be effective and not uncommon. See the paper entitled ' On the change in the Plumage of some Hen-Pheasants,' by Wm. Yarrell, Esq., Phil. Trans. 1827, in which the author states, that "certain constitutional circumstances producing this change may, and do occur, at any period during the life of the fowl, and that they can be produced by artificial means."] t It might be supposed that this bird was really a cock which had been sub- stituted for the hen ; but the following facts put this matter beyond a doubt. First, there was no other pied pea-fowl in the country. Secondly, the hen had nobs on her toes, which were the same after her change. Thirdly, she was as small after the change as before, therefore too small for a cock. Fourthly, she was a favourite bird, and was generally fed by the lady, and used to come for her food, which 6he still continued to do after the change in the feathers. OF THE OVARIA. 85 elude, that this change is merely the effect of age, and obtains to a certain degree in every class of animals. We find something similar taking place even in the human species; for that increase of hair observable on the faces of many women in advanced life is an ap- proach towards the beard, which is one of the most distinguishing secondary properties of man. Thus we see the sexes which, at an early period, had little to distinguish them from each other, acquiring about the time of puberty secondary properties, which clearly characterize the male and female, the male at this time receding from the female, and as- suming the secondary properties of his sex. The female, at a much later time of life, when the powers of pro- pagation cease, loses many of her peculiar properties, and may be said, except from mere structure of parts, to be of no sex, even re- ceding from the original character of the animal, and approaching, in appearance, towards the male, or perhaps more properly towards the hermaphrodite. 5. AN EXPERIMENT TO DETERMINE THE EFFECT OF EXTIRPATING ONE OVARIUM UPON THE NUMBER OF YOUNG PRODUCED.* In all animals of distinct sex, the females, those of the Bird-kind excepted, have, I believe, two ovaria, and of course the oviducts are in pairs. By distinct sex I mean when the parts destined to the purposes of generation are of two kinds, each kind appropriated to an in- dividual of each species, distinguished by the appellation of male and female, and equally necessary to the propagation of the animal. The testicles, with their appendages, constitute the male; the ovaria, and their appendages, the female sex. As the ovaria are the organs which, on the part of the female, furnish what is necessary towards the production of the third, or young animal, and as females appear to have a limited portion of the middle stage of life allotted for that purpose, it becomes a question, whether those organs are worn out by repeated acts of propaga- tion ; or whether there is not a natural and constitutional period to that power on their part, even if such power has never been exerted ? If we consider this subject in every view, taking the human species as an example, we shall discover that circumstances, either local or constitutional, may be capable of extinguishing in the female the faculty of propagation. Thus we may observe when a woman begins to breed at an early period, as at fifteen, and has her children • [Originally published in the Philosophical Transactions, vol. Ixxvii., p. 233 ; read, March 22, 1787.] 9 86 HUNTER ON THE ANIMAL CECONOMY. fast, that she seldom breeds longer than the age of thirty or thirty- five; therefore we may suppose either that the parts are then worn out, or that the breeding constitution is over. If a woman begins later, as at twenty or twenty-five, she may continue to breed to the age of forty or more: and there are, now and then, instances of women who, not having conceived before, have had children as late in life as at fifty years or upwards. After that period few women breed, even though they should not have bred before; therefore there must be a natural period to the power of concep- tion. A similar stop to propagation may likewise take place in other classes of animals, probably in the female of every class, the period varying according to circumstances. But still we are not enabled to determine how far it depends on any particular property of the constitution, or of the ovarium alone. As the female, in most classes of animals, has two ovaria, I imagined that by removing one it might be possible to determine how far their actions were reciprocally influenced by each other, from the changes which by comparison might be observed to take place, either by the breeding-period being shortened, or perhaps, in those animals whose nature it is to bring forth more than one at a time, by the number produced at each birth being diminished. There are two views in which this subject may be considered. The first, that the ovaria, when properly employed, may be bodies determined and unalterable respecting the number of young to be produced. In this case we can readily imagine that, when one ovarium is removed, the other may be capable of producing its determined number in two different ways : one, when the remain- ing ovarium, not influenced by the loss of the other, will produce its allotted number, and in the same time; the other, when affected by the loss, yet the constitution demanding the same number of young each time of breeding, as if there were still two ovaria; it must furnish double the number it would have been required to supply had both been allowed to remain, but must consequently cease from the performance of its function in half the time. The second view of the subject is, by supposing that there is not originally any fixed number which the ovarium must produce, but that the number is increased or diminished according to circum- stances ; that it is rather the constitution at large that determines the number; and that if one ovarium is removed, the other will be called upon by the constitution to perform the operations of both, by which means the animal should produce with one ovarium the same number of young as would have been produced if both had remained. With an intention to ascertain those points as far as 1 could, I was led to make the following experiment; and for that purpose gave pigs a preference to any other animal, as being easily managed, producing several at a litter, and breeding perfectly well under the confinement necessary for experiments. I selected two females of the same colour and size, and likewise a boar-big, all of the same farrow; and, having removed an ovarium from one of OF THE OVARIA. 87 the females, I cut a slit in one ear to distinguish it from the other. They were well fed and kept warm, that there might be no impedi- ment to their breeding; and whenever they farrowed, their pigs' were taken away exactly at the same age. About the beginning of the year 1779 they both took the boar; the one which had been spayed earlier than the perfect female. The distance of time, however, was not great, and they continued breeding at nearly the same times. The spayed animal continued to breed till September 1783, when she was six years old, which was a space of more than four years. In that time she had eight farrows; but did not take the boar afterwards, and had in all seventy-six pigs. The perfect one continued breeding till Decem- ber 1785, when she was about eight years old, a period of almost six years, in which time she had thirteen farrows, and had in all one hundred and sixty-two pigs; after this time sh'e did not breed: I kept her till November 1786. I have here annexed a table of the different times of each farrow, with the number of pigs produced. Spayed Sow. Farrows. Number of you 1o" Time. 1 6 Dec. 1779. 2 8 July 1780. 3 6 Jan. 1781. 4 10 Aug. 1781. 5 10 Mar. 1782. 6 9 Sept. 1782. 7 14 May 1783. 8 13 Sept. 1783. 76 November following she was put to the boar, but brought no pigs. April 1784, she was again put to the boar, without effect, and never was observed to take the boar afterwards, although often with him. November 1784, she was killed. Perfect Sow. rows. Number of young. Time. 1 9 2 6 3 8 4 13 Dec. 1781. 5 10 June 1782. 6 16 Dec. 1782. 7 13 June 1783. 8 12 Oct. 1783. 87 Eleven pigs more than were produced by the spayed sow in her eight farrows. 88 HUNTER ON THE ANIMAL CECONOMY. Farrows. Number of 9 12 10 1(5 11 12 12 16 13 19 75 h she bred no more. The first eight farrows were The last five farrows were . The number from the spayed one . . 76 More than farrowed by the imperfect animal . . 86 It is observable that both sows rather increased in their number each time as they grew older, although not uniformly; the differ- ence between the first and last in both animals being considerable. From the above table we find that the sow with only one ovarium bred till she was six years old, from the latter end of 1779 till Sep- tember 1783, about four years, and in that time brought forth seventy-six pigs. The perfect animal bred till she was eight years of age ; and if conception depended on the ovari, we might have expected that she would bring forth double the number at each birth; or, if not, that she would continue breeding for double the time. We indeed find her producing ten more than double the number of the imperfect animal, although she had not double the number of farrows; but this may perhaps be explained by observing that the number of young increased as the female grew older, and the perfect sow continued to breed much longer than the other. From a circumstance mentioned in the course of this experiment it appears that the desire for the male continues after the power of breeding is exhausted in the female; and therefore does not alto- gether depend on the powers of the ovaria to propagate, although it may probably be influenced by the existence of such parts. If these observations should be considered as depending on a single experiment, from which alone it is not justifiable to draw conclusions, I have only to add that the difference in the number of pigs produced by each was greater than can be justly imputed to accident, and is a circumstance certainly in favour of the uni- versality of the principle I wished to ascertain.* From this experiment it seems most probable that the ovaria are * It may be thought by some that I should have repeated this experiment; but an annual expense of twenty pounds for ten years, and the necessary attention • to make the experiment complete, will be a sufficient reason for my not having done it. Time. Feb. 1784. June 1784. Dec. 1784. May 1785. Dec. 1785. 87 75 Total . 162 DESCRIPTION OF THE UTERUS, ETC. 89 from the beginning destined to produce a fixed number, beyond which they cannot go, although circumstances may tend to diminish that number; but that the constitution at large has no power of giving to one ovarium the power of propagating equal to both; for in the present experiment the animal with one ovarium produced ten pigs less than half the number brought forth by the sow with both ovaria. But that the constitution has so far a power of influ- encing one ovarium as to make it produce its number in a less time than would probably have been the case if both ovaria had been preserved, is to be inferred from the above-recited experiment. 6. THE CASE OF A YOUNG WOMAN WHO POISONED HERSELF IN THE FIRST MONTH OF HER PREG- NANCY. BY THOMAS OGLE, SURGEON, GREAT RUSSELL-STREET, BLOOMSBURY. To which is added, an Account of the Appearances after Death ; by the late John Hunter* Mary Hunt, servant to a gentleman in Charlotte-street, Bedford- square, twenty-five years of age, had for some time shown a par- tiality for one of the footmen in the same family. She became all at once exceedingly dejected, which was supposed to proceed from his neglecting her; and on Thursday, the 19th of April, at twelve o'clock at night, took half an ounce of white arsenic, and imme- diately afterwards drank a quart of wine; about one o'clock she had so much pain in her stomach as to be obliged to call for assistance. The symptoms were excruciating pain in the stomach, sick- ness, vomiting, excessive thirst, and a small tremulous pulse; these were followed by pain in the bowels, and several purging stools. She drank brandy and water, wine and water, and several quarts of plain water, to relieve the thirst and ease the pain. Some hours after taking the arsenic she became easier, expressed a desire to be left alone, being inclined to sleep, and remained several hours in a dosing or comatose state, from which she did not recover, and died about one o'clock on Friday, thirteen hours after taking the arsenic. Upon inspecting the body after death there were found the fol- lowing appearances. • [Originally published in the Transactions of a Society for the Improvement of Medical and Chirurgical Knowledge, vol. ii., p. 63. Communicated to the Society by Everard Home, and read August 5, 1794.] 90 HUNTER ON THE ANIMAL CECONOMY. In the cavity of the abdomen there was an WV™*™™0^* effects of slight inflammation on the peritoneal coat ot the small intestines. . , , . The stomach contained a greenish fluid, with a curdy substance in it, in all amounting to about twelve ounces. On the internal surface of the great curvature near the cardiac a portion of the villous coat, about the size of a crown-piece, was partly destroyed, and of a dark red colour, with a regularly defined edge, and some of the arsenic adhering to different parts of its surface. The rest of the stomach was in a natural state. This appearance in the stomach was an effect produced by the arsenic. The uterus was a little enlarged, and had the vessels unusually loaded with red blood. There was an uncommon quantity of blood in the vessels of the ovaria and Fallopian tubes, but principally in those of the ovarium, and morsus diaboli of the left side. The organs of generation being carefully removed, and both ovaria being slit open, there was found in the left a corpus luteum. It was evident, from this circumstance, that conception had taken place; which led to an inquiry respecting the last appearance of her menses, which appeared by the evidence of the family to have been little more than a month before her death. With the dread upon her mind of being with child, the usual period of menstruation had hardly elapsed without its appearing, which confirmed her suspicions, before she, in a fit of despair, put an end to her life. From this evidence, the period of conception could not exceed a month, and probably was much within that time. As it was interesting to have the parts accurately examined, to see what information might be acquired respecting the fcetus at so early a period, they were given to Mr. Hunter for that purpose, whose observations upon them are contained in the following account. The arteries of the uterus were injected, and the smaller vessels were filled to so great a degree of minuteness that the whole sur- face became extremely red. The cervix uteri and os tineas were of their natural size ; but the body, or that portion of the uterus next the fundus, was a little en- larged, and more prominent externally in the middle. The sper- matic vessels were also enlarged. On cutting into the substance of the uterus, it had more of a laminated structure than in the unimpregnated state; this appear- ance of lamellae appeared upon examination to be formed by veins somewhat enlarged, compressed and transversely divided. The uterus was unsually soft in texture, and terminated on the internal surface in a pulpy substance. The blood-vessels of the uterus passed into and ramified upon this pulpy substance, which was continued across at the cervix DESCRIPTION OF THE UTERUS, ETC. 91 uteri, so as to make the cavity of the uterus a circumscribed bag ; and at this part the pulpy substance was so thin as to resemble the retina. This cavity had a smooth but irregular internal surface, and the pulpy substance upon which it was formed was evidently blood coagulated and varied in its thickness in different parts. Upon a longitudinal section of the uterus, the posterior part of the coagulum, which was the thickest, was nearly half an inch; where it termi- nated towards the cervix it was pendulous and unattached. There were also several loose processes, all turned towards the cervix, one of them very thin, as broad as a silver penny, and only attached by one edge to the fundus near the opening of the right Fallopian tube. On slitting open the Fallopian tubes, the coagulum was found to pass some way into them, and to extend more than half an inch on the left side, which had the corpus luteum. The coagulum was thickest at the orifice of the tube, and there adhered to the inner surface for the eighth part of an inch; beyond which it became smaller and terminated in a point. In the left tube the coagulum was in two places coiled or folded upon itself, as if thrown back by the action of the tube. The portions of the coagulum at the orifices of the tubes were hollow. When the inner surface of the cavity of the uterus was examined with a magnifying glass it was found extremely vascular, and dotted with innumerable whitish spots too small to be seen by the naked eye. In the examination of this uterus and Fallopian tubes, as Mr. Hunter's chief object was the detection of the embryo, no precau- tion was omitted which could be devised to prevent it being over- looked or destroyed. The uterus was opened in a bason of clear water, the incision was conducted with great circumspection, and very slowly con- tinued, till the whole of the cavity was exposed. Every part of the internal surface was minutely examined with magnifying glasses; but in no situation was there anything resembling an embryo to be found. The presence of a corpus luteum, the enlargement of the uterus, the newly-formed vascular membrane, or decidua, lining the cavity, and the history of the case, sufficiently prove conception to have taken place; and the embryo being nowhere detected by an exa- mination so accurate and conducted by an anatomist so skilful in minute investigation, would induce a belief that the foetus had not been sufficiently advanced to take on a regular form. The appearances in the uterus, here described, the late Dr. Hunter, in his lectures, mentioned to have seen at a very early period after impregnation : so far they are not entirely new. The accuracy of the examination renders this case valuable, as it seems to enable us to decide a point hitherto not at all understood—that certain changes in the uterus not only take place previous to the 92 HUNTER ON THE ANIMAL CECONOMY. reception of the foetus, but that the foetus does not acquire a visible form for some time after these changes have been made.* * [The positive conclusions deduced from this case, viz., that certain changes take place in the uterus within one month after conception, have been confirmed by all those anatomists who have enjoyed similar opportunities of examining the uterine organs within the same period. These changes consist essentially in the effusion of fibrin or coagulable lymph from the villi of the lining membrane of the uterus, which villi also become much elongated and highly vascular; and minute vessels are continued from them into the effused lymph, forming loops or archea in that substance. This process is compared by Hunter, in the following paper, to the effusion of lymph consequent on the introduction of an extraneous living part into any of the cavities of the body; and Professor von Baer, in a recent elaborate description of the uterus of a female who drowned herself eight days after impregnation, makes the same comparison. Professor Weber, in an exami- nation of the uterus seven days after conception, also speaks of the great vascu- larity of its inner surface, and describes the villi as consisting of small cylinders placed perpendicularly to the inner surface of the uterus, united by a slimy mem. brane, and forming together a layer of a pale soft substance, from half a line to a line in thickness; whilst in some places the cylinder presented the length of from two to three lines. With respect to the negative results of Mr. Hunter's examination relative to the reception of the foetus in the uterus, and " its acquisition of a visible form," 1 suppose that the word ' foetus' is here used to express the product of generation, or ovum, especially as it is stated, that " in the examination of the uterus and Fallopian tubes Mr. Hunter's chief object was the detection of the 'embryo.'" Now if the product of generation were really expected to have been seen in that state of development which we understand by the terms embryo and foetus, its presence was most likely overlooked; since, from the analogy of the dog and rabbit, it most probably would have existed merely as a small pellucid vesicle or ovum, supposing that it had escaped from the ovarium; and it is to be regretted that the expression " there was found in the left 'ovarium' a corpus luteum " is all the evidence on that point which the present case affords. In the bitch, Von Baer has shown that the ova pass into the Fallopian tubes on the eight day after impregnation, and that when they reach the uterus they lie quite free in its cavity, are perfectly transparent, of a somewhat elongated form, and extremely delicate texture, and are from half a line to a third of a line in diameter. In the rabbit, the observations of De Graaf, of Prevost and Dumas, and of Coste, prove that the ova pass into the tubes the third (or, according to Coste, the second) day after impregnation; they reach the horns of the uterus on the fourth day, and are then about a line in diameter, in the form of pellucid bubbles, free and moveable. According to Home, the human ovum has reached the uterus on the eighth day after impregnation, when it is described as presenting an elliptical form, rather more than a line (£s% parts of an inch) in length, and ^£fl partsof an inch in breadth. It is composed of two membranes, of which the external is of consider- able thickness and consistence, very little transparent, quite smooth, and milk- white; the internal membrane or bag consist 'of a seemingly very thin, perfectly smooth, and glossy membrane, which seemed to have considerable strength.' This internal membrane contained a thick, slimy matter, like honey, and "two round corpuscles, apparently more opake, and of a yellowish tint," regarded as " the probable seat of the future heart and brain." On comparing the preceding account with the observations that have been made on the mammiferous ovum, it will be found that the nearest resemblance to the supposed human ovum obtains in that of the ornithorhynchus, at least in the texture ot the two membranes described, of which the external must be regarded as the chorion, the internal as the membrana vitelli. In the ornithorhynchus, as in the ovo-viviparous reptiles, the chorion is dense and unyielding ; but in the specimens ON THE STRUCTURE OF THE PLACENTA. 93 7. ON THE STRUCTURE OF THE PLACENTA. The connexion between the mother and foetus in the human sub- ject, has in every age, in which science has been cultivated, called forth the attention of the anatomist, the physiologist, and even the philosopher; but both that connexion, and the structure of the parts which form the connexion, were unknown till about the year 1754. The subject is certainly most interesting, and the discovery im- portant ; and it is my intention, in the following pages, to give such an account of it as I hope may be acceptable to the public ;* while, at the same time, I establish my own claim to the discovery. But that I may not seem to arrogate to myself more merit than I am entitled to, let me in justice to another person relate what follows. The late indefatigable Dr. MacKenzie, about the month of May, 1754, when assistant to Dr. Smellie, having procured the body of a pregnant woman, who died undelivered at the full term, had in- jected both the veins and arteries with particular success, the veins being filled with yellow, the arteries with red.f Having opened the abdomen, and exposed the uterus, he made an incision into the fore part, quite through its substance, and came which we examined, and which, as in Sir Everard Home's case, had been subjected to the action of spirit, the chorion was semitransparent. In those mammalia, however, which approximate the human species in the placental development of the foetus, the ovum, when it has been detected unattached in the uterus, has invariably presented a translucency and delicacy of its membranes, with which the structure of the human ovum, as described by Home, is totally at variance; and, from the tenor of the whole account, we believe the object to have been what Mr. Bauer, to whom its description and delineation were confided,1 declared it to resemble, viz., the egg of an insect. Rejecting, then, the description we have just been considering,—and its apo- cryphal character is rightly admitted by all physiologists of the present day, who have investigated the nature of the mammiferous ovum,—the determination of the period of the passage of the human ovum into the uterus after impregnation, and its condition and structure when first received into that cavity, still remain open to the researches of the physiologist.] * This paper was read at the Royal Society, but as the facts had before that time been given to the public, it was not published in the Philosophical Transac- tions. t Dr. MacKenzie being then an assistant to the late Dr. Smellie, the procuring and dissecting this woman without Dr. Smellie's knowledge was the cause of a separation between them, for the leading steps to such a discovery could not be kept a secret. The winter following Dr. MacKenzie began to teach midwifery in the Borough of Southwark. a " As the ovum was so extremely small as to admit of dispute whether it was one or not, I carried it immediately to Kew, to Mr. Bauer, who, after examining it, said it looked like the egg of an insect."—Phil. Trans., p. 255. Mr. Clift who laid open the uterus in question, and patiently scrutinized the whole of its cavity without perceiving any trace of an ovum, has always been of opinion that the one afterwards detected by Home was dropped from one of the numerous flesh-flies which were buzzing about at the time of the examination. 94 HUNTER ON THE ANIMAL CECONOMY. to what seemed to be an irregular mass of injected matter. The appearance being new he proceeded no further, and greatly obliged me, by desiring my attendance to examine parts, m which the appearances were so uncommon. The examination was made in his presence, and in the presence of several other gentlemen, whose names I have now forgotten ; but I have reason to believe that some are settled in this country, who I hope will have an oppor- tunitv of perusing this publication.* # I first raised, with great care, a part of the uterus from the irre- gular mass, and in doing this observed regular pieces of wax passing obliquely between it and the uterus, which broke off, leaving part attached to that mass; and on attentively examining the portions towards the uterus, they plainly appeared to be a continuation of the veins passing from it to this substance, which proved to be pla- centa. I likewise observed other vessels, about the size of a crow-quill, passing in the same manner, although not so obliquely ; these also broke upon separating the placenta and uterus, leaving a small portion on the surface of the placenta; and on examination they were disco- vered to be continuations of the arteries of the uterus. My next step was to trace these vessels into the substance of what appeared placenta, which was first attempted in a vein; but that soon lost the regular- ity of a vessel, by terminating at once upon the surface of the pla- centa in a very fine spongy substance, the interstices of which were filled writh the yellow injected matter. This termination being new, I repeated the same kind of examination on other veins, which al- ways led me to the same terminations, never entering the substance of the placenta in the form of a vessel. I then examined the arte- ries, tracing them in the same manner towards the placenta, and found that, having made a twist, or close spiral turn upon themselves, they were lost on its surface. On a more attentive view, I per- ceived that they terminated in the same way as the veins; for op- posite to the mouth of the artery the spongy substance of the pla- centa was readily distinguished with the red injection intermixed. Upon cutting into the placenta I discovered, in many places of its * If I should be so fortunate as to have this publication fall into any of those gentlemen's hands, I hope they will favour me with their opinion of my state of the facts, which led to the discovery. It may be suspected by some (but none I hope to whom I have the pleasure of being known,) that I am not doing Dr. MacKenzie justice, and am perhaps sup- pressing some part of that share of the discovery to which he is entitled. This idea (if ever it should arise), I may probably not be able to remove; but I hope it will also be seen that I myself have given rise to it; believing, if I had been so inclined, that I might have suppressed Dr. MacKenzie's name altogether without ever running the hazard of being detected. I was indeed so tenacious of my claim to the discovery, that I wrote this account in Dr. MacKenzie's lifetime, with a design to publish it; and often communicated my intentions to Dr. George Fordyce, who 1 knew was very intimate with the Doctor, in consequence of both teaching in the same place, and making many experiments together; therefore he is a kind of collateral witness, that what I now publish is the same account which I gave in Dr. MacKenzie's lifetime. ON THE STRUCTURE OF THE PLACENTA. 95 substance, yellow injection, in others red, and in many others these two colours mixed. The substance of the placenta, now filled with injection, had nothing of the vascular appearance, nor that of extra- vasation, but had a regularity in its form which showed it to be naturally of a cellular structure, fitted to be a reservoir for blood. I perceived, likewise, that the red injection of the arteries (which had been first injected), had passed out of the substance of the pla- centa into some of the veins leading from the placenta to the uterus, mixing itself with the yellow injection ; and that the spongy chorion, called the decidua by Dr. Hunter, was very vascular, its vessels going to and from the uterus, being filled with the different coloured injections. After having considered these appearances, it was not difficult for me to determine the real structure of the placenta and course of the blood in these parts: but the company, prejudiced in favour of former theories, combated my opinion ; and it was even disputed whether or not these curling arteries could carry red blood. After having dissected the uterus, with the placenta and membranes, and made the whole into preparations, tending to show the above facts, I returned home in the evening, and communicating what I had dis- covered to my brother, Dr. Hunter, who at first treated it and me with good-humoured raillery; but on going with me to Dr. Mac- Kenzie's he was soon convinced of the fact. Some of the parts were given to him, which he afterwards showed at his lectures, and probably they still remain in his collection. Soon after this time Dr. Hunter and I procured several placentas, to discover if after delivery, the termination of the veins and the curling arteries could be observed ; they were discernible almost in every one ; and by pushing a pipe into the placenta we could fill not only its whole substance, but also the vessels on that surface which was attached to the uterus, with injection. The facts being now ascertained and universally acknowledged, I consider myself as having a just claim to the discovery of the structure of the placenta, and its communication with the uterus, to- gether with the use arising from such structure and communication, and of having first demonstrated the vascularity of the spongy cho- rion. It is not necessary at present to enter into the various opinions which have been formed on this subject; because, whatever they were, they could not be just, the structure of the parts not being known : neither shall I endeavour to give a complete description of all the parts immediately connected with uterine gestation, but content myself with describing the structure of the placenta, as far as it has any relation to the uterus and child; and with explaining the connexion between the two ; leaving the reader to examine what has been said upon this subject by others, especially by Dr. Hunter, in that very accurate and elaborate work which he has published on the Gravid Uterus, in which he has minutely described and ac- curately delineated the parts, without mentioning the mode of dis- covery. 96 HUNTER ON THE ANIMAL CECONOMY. The necessary connexion subsisting in all animals between the mother and foetus, for the nourishment of the latter, as far as I know, takes place in two ways. In some it is continued, and subsists through the whole term of gestation ; in others the union is soon dis- solved ; but an apparatus is provided, which at once furnishes what is sufficient for the support of the animal till it comes forth. The first of these are the viviparous, the second the oviparous animals, both of which admit of great variety in the mode by which the same effect is produced.* In the first division is included the human species, which alone will engage our present attention. But before I describe this connexion, it may be necessary that the rea- der should understand my idea of generation : I shall therefore re- fer him to what I have said upon that subject in my account of the free-martin.f In the human species, the anatomical structure of the mother and embryo, relative to fcetation, being well known, it will only be neces- sary fully to describe the nature of the connexion between them, which is formed by the intermediate substance called placenta. For this purpose we must first consider the placenta as a common part; next, the uterus as belonging to the mother, yet having an immediate connexion with the placenta, from which the nourishment of the foetus is to be derived, which will lead us lastly to a consideration of those peculiarities of structure by means of which the foetus is to receive its nourishment, and which likewise constitutes its immediate commu- nication with the placenta. It is the structure of this intermediate substance, and its connexion with the child and the uterus of the mother, which have hitherto been so little understood, and without any accurate knowledge of which it was impossible any just idea could be formed of its functions. The placenta is a mass lying nearly in contact with the uterus; indeed it may in some degree be said to be in continuity with a part of its internal surface. On the side applied to the uterus the placenta is lobulated, having deep irregular fissures. It is probably, from this structure of the placenta, that the uterus has an intestine motion while in the time of uterine gestation, not an expulsive one; which those lobes of the placenta allow of; but all these lobes are united into one uniform surface on that surface next to the child, where its umbilical vessels ramify. When we cut into the placenta its whole sub- stance appears to be little else than a network, or spongy mass, through which the blood-vessels of the foetus ramify, and indeed seems to be principally formed by the ramifications of those vessels; it exhibits hardly any appearance of connecting membrane; but we cannot rea- dily suppose it to be without such a membrane, as there is so much * It may be remarked here, that the oviparous admit of being distinguished into two classes, one where the egg is hatched in the belly, as in the viper, which has been commonly called viviparous; the others, where the eggs have been first hud and then hatched, which is the class commonly called oviparous, such as all the bird tribe: and many others, as snakes, lizards, &c. f See page 70. ON THE STRUCTURE OF THE PLACENTA. 97 regularity in its texture. The cells, or interstices of each lobe, com- municate with one another, even much more freely than those of the cellular membrane in any other part of the body ; so that what- ever fluid will pass in at one part, readily diffuses itself through the whole mass of lobe; and all the cells of each lobe have a commu- nication at the common base. This structure of the placenta, and its reciprocal communication with the two bodies with which it is immediately connected, form the union between the mother and foetus for the support of the latter. Prior to the time I have mentioned above, anatomists seem to have been wholly unacquainted with the true structure of placenta. By notes taken from Dr. Hunter's lectures, in the winter 1755-6, it appears that he expressed himself in the following manner.* " The substance of the placenta is a fleshy mass, which seems to be formed entirely of the vessels of the umbilical rope." In another part, men- tioning the appearances when injected, he says : " and upon a slight putrefaction coming on, you will find the whole appearing like a mass of vessels :" then says," there is always a white uninjected substance between the vessels ; but whether lymphatics or what I cannot tell." This uninjected substance, mentioned by Dr. Hunter, is what forms the cellular structure. The placenta seems to be principally composed of the ramifica- tions of the vessels of the embryo, and may have been originally formed in consequence of those next to the uterus laying hold by a species of animal attraction of the coagulable lymph which lines the uterus. It might take place in a manner resembling what hap- pens when the root of a plant spreads on the surface of moist bodies, with this difference, that in the present instance the vessels form the substance through which they ramify, as in the case of granulations. At the time, or perhaps before, the female seed enters the uterus, coagulable lymph, from the blood of the mother, is thrown out every- where on its inner surface, either from the stimulus of impregnation taking place in the ovarium, or in consequence of the seed being ex- pelled from it. But I think the first the most probable supposition; for we find in extra-uterine cases that the decidua is formed in the uterus, although the ovum never enters it, which is a proof that it is produced by the stimulus of impregnation in the ovarium, and that it is prior to the entrance of the ovum into the uterus. When it has entered the uterus it attaches itself to that coagulable lymph, by which, being covered and immediately surrounded,! there is formed a soft pulpy membrane, the decidua, which I believe is peculiar to * These quotations were taken from Mr. Galhie's MS. of Dr. Hunter's lectures, <*ho is one of the gentlemen that favoured Dr. Hunter, upon a former occasion, with the use of his notes. See Dr. Hunter's Commentaries. t This is somewhat similar to another operation in the animal ceconomy. If an extraneous living part is introduced into any cavity it will be immediately in- closed with coagulable lymph. Thus we find worms inclosed, and hydatids, that have been detached, afterwards inclosed ; but in those cases this is a con- sequence of the pressure of the extraneous body, whereas in the uterus it is pre- paratory. 10 98 HUNTER ON THE ANIMAL CECONOMY. the human species and to monkeys, I never having found it in any other animal. That part which covers the seed or fcetus, where it is not immediately attached to the uterus, and likewise lorms a membrane, was discovered by Dr. Hunter, and is by him called decidua reflexa.* The whole of this coagulable lymph continues to be a living part for the time; the vessels of the uterus ramify upon it; and where the vessels of the fcetus form the placenta there the vessels of the uterus, after passing through the decidua, open into the cellular substance of the placenta, as before described. As this membrane lines the uterus and covers the seed, it is stretched out, and becomes thinner and thinner, as the uterus is distended by the foetus growing larger, especially that part of it, called decidua reflexa, which covers the fcetus; as there it cannot possibly acquire any new matter, except we could suppose that the foetus assisted in the formation of it. This membrane is most distinct where it covers the chorion; for where it covers the placenta it is blended with coagula in the great veins that pass obliquely through it, more especially all round the edge, where innumerable large veins come out; but the chorion and decidua can be easily distinguished from one another, the decidua being less elastic. From the description now given, I think we are justified in sup- posing the placenta to be formed entirely by the foetus, which is further confirmed by extra-uterine cases, and by the formation of the membrane in the egg, there being no living organic part to fur- nish them; and the decidua we must suppose to be a production of the mother : of both which the circumstance of the decidua passing between the placenta and uterus may be considered as an addi- tional proof. For if the vessels of the foetus branched into a part of the decidua, we might conceive the whole placenta to be formed from that exudation; the portion of it, where the vessels had rami- fied like the roots of a plant, becoming thicker than the rest, and forming the placenta. If that were the case, this membrana decidua, when traced from the parts distinct, and at a distance from the placenta, should be plainly seen passing into its substance all round at the edges, as a continuation of it. But the fact is quite otherwise; for the decidua can be distinctly traced between the placenta and uterus, hardly ever passing between the lobuli, the vessels of the fcetus never entering into it, and of course none of them ever coming in absolute contact with the uterus. But what may be considered as still a stronger proof that the decidua is fur- nished by the uterus is, that in cases of extra-uterine conception, where the fcetus is wholly in the ovarium or Fallopian tube, we find the uterus lined with the decidua, having taken on the uterine * The placenta is certainly a foetal part, and is formed on the inside of the spongy chorion, or decidua. How far the decidua reflexa is a uterine part I do not yet know ; if it is, then the ovum must be placed in a doubling of the coagu- lum, which forms the decidua; but if the ovum is attached to the inside of the decidua, then the decidua reflexa is belonging to the fcetus. ON THE STRUCTURE OF THE PLACENTA. 99 action; but no placenta, that being formed by the fcetus, and there- fore in the part which contained it. The vessels of the foetus adhering, by the intervention of the decidua, to a certain portion of the uterus when both are yet small, as the uterus increases in every part of its surface during the lime of uterine gestation, we must suppose that this surface of adhesion increases also; and that by the elongation of those vessels of the fcetus in every direction this substance should likewise be increased in every direction. This is in some degree the case, yet the placenta does not occupy so much of the enlarged surface of the uterus as one at first would expect. The vessels of the uterus in the time of the gestation are in- creased in size nearly in a proportion equal to the increased cir- cumference of the uterus, and consequently in a proportion much greater than the real increase of its substance. But when we reflect that the uterus ought not to be considered as hollow, but as a body nearly solid, on account of its contents, which derive support from this source, and that a much greater quantity of blood must neces- sarily pass than what is required for the support of the viscus itself, we cannot be at a loss to account for the greatly increased size of its vessels. The arteries which are not immediately employed in conveying nourishment to the uterus go on towards the placenta, and, pro- ceeding obliquely between it and the uterus, pass through the decidua without ramifying; just before they enter the placenta, after making two or three close spiral turns upon themselves, they open at once into its spongy substance without any diminution of size, and without passing beyond the surface, as above described. The intention of these spiral turns would appear to be that of diminishing the force of the circulation in the vessels as they ap- proach the spongy substance of the placenta, and is a mechanism calculated to lessen the quick motion of the blood in a part where a quick motion was not required. These curling arteries at this temination are in general about half the size of a crow's quill, and sometimes larger. The veins of the uterus appropriated to bring back the blood from the placenta commence from this spongy substance by such wide beginnings as are more than equal to the size of the veins themselves. These veins pass obliquely through the decidua to the uterus, enters its substance obliquely, and immediately communicate with the proper veins of the uterus. The area of these veins bears no proportion to their circumference, the veins being very much flattened. This structure of parts points out at once the nature of the blood's motion in the placenta; but as this is a fact but lately ascertained, a just idea may perhaps be conveyed by saying that it is similar, as far as we yet know, to the blood's motion through the cavernous substance of the penis. The blood, detached from the common circulation of the mother, 100 HUNTER ON THE ANIMAL CECONOMY. moves through the placenta of the foetus; and is then returned back into the course of the circulation of the mother, to pass on to the heart. This structure of the placenta, and its communication with the uterus, leads us a step further in our knowledge of the connexion between the mother and the foetus. The blood of the mother must pass freely into the substance of the placenta, and the placenta most probably will be constantly filled ; the turgidity of which will assist to squeeze the blood into the mouths of the veins of the uterus, that it may again pass into the common circulation of the mother; and as the interstices of the placenta are of much greater extent than the arteries which convey the blood, the motion of the blood in that part must be so much diminished as almost to approach to stagnation. So far and no further does the mother appear to be concerned in this connexion. The fcetus has a communication with the placenta of another kind. The arteries from the fcetus pass out to a considerable length, under the name of the umbilical arteries, and when they arrive at the placenta ramify upon its surface, sending into its sub- stance branches which pass through it, and divide into smaller and smaller, till at last they terminate in veins; these, uniting, become larger and larger, and end in one, which at last communicates with the proper circulation of the fcetus. This course of vessels, and the blood's motion in them, is similar to the course of the vessels and the motion of the blood in other parts of the body.* * [It is well known that the accuracy of this description has been disputed by several continental anatomists, and has especially been called in question in this country by Dr. Robert Lee, F.R.S., who, with a zeal becoming a sincere lover of truth, deemed it his duty to submit to the scientific world the results of a series of investigations, which he considered to be irreconeileable in some respects with the Hunterian descriptions. During the period in which Dr. Lee was examining, at the College of Surgeons, the Hunterian Preparations, illustrative of the struc- ture and connexions of the placenta, bis observations on the obscurity produced by apparently extravasated injection, led me to think of some less objectionable mode of demonstrating the vascular communication between the uterus and placenta, if it existed ; or of proving, more satisfactorily than the appearance pointed out by him in the Hunterian preparations seemed to do, that there was no such communication. This I proposed to do by dissecting the parts under water before disturbing them, either by throwing forcibly foreign matter into the vessels, or by separating the placenta from the uterus, to observe the appearances presented by the op- posed surfaces; a proceeding which, if done in the air, is liable to the objection of the possibility of having torn the vessels which were passing across, and the coats of which are acknowledged to be extremely delicate. For this purpose I was furnished by Dr. Lee with sections of an uninjected and naturally connected uterus and placenta, at the sixth month of uterine gestation, which I fixed under water in an apparatus used for dissecting mollusca, and com- menced the dissection from the outside, removing successively, and with great care, the layers of fibres, and tracing the veins as they passed deeper and deeper in the substance of the uterus in their course to the deciduous membrane ; in which situation, as the thinnest pellicle of membrane is rendered distinct by beino-sup- ported in the ambient fluid, I naturally expected to see the coats of the "veins ON THE STRUCTURE OF THE PLACENTA. 101 In addition to what I have said about the connexion between the mother and child in natural cases, it is necessary to observe, that continued into the deciduous membrane and placenta, and to be able to preserve the appearance in a preparation, if it actually existed in nature. Every vein, however, when traced to the inner surface of the uterus, appeared to terminate in an open mouth on that aspect; the peripheral portion of the coat of the vein, or that next the uterus, ending in a well-defined and smooth semicircular margin, the central part adhering to, and being continuous with, the decidua. In the course of this dissection I observed that where the veins of different planes communicated with each other, in the substance of the walls of the uterus, the central portion of the parietes of the superficial vein invariably projected in a semilunar form into the deeper-seated one ; and where .(as was frequently the case, and especially at the point of termination on the inner surface), two, or even three, of these wide venous channels communicated with a deeper sinus at the same point, the semilunar edges decussated each other so as to allow only a very small part of the deep-seated vein to be seen. It need scarcely be ob- served how admirably this structure is adapted to insure the arrest of the current of blood through these passages, upon the contraction of the muscular fibres with which they are everywhere immediately surrounded. On another portion of the same uterus and placenta, I commenced the exami- nation under water by turning off the placenta and deciduous membrane from the inner surface of the uterus. In this way the small tortuous uterine arteries which enter the deciduous membrane were readily distinguishable, though not nlJed with injected matter ; and, as it was an object to avoid unnecessary force in the process of separation, they were cut through, though they are easily torn from the decidua. But with respect to the veins, they invariably presented the same appearances as were noticed in the first dissection, terminating in open semicir- cular orifices, which are closed by the apposition of the deciduous membrane and placenta. This membrane is, however, thinner opposite these orifices than elsewhere, and in some places appeared to be wanting, or, adhering to the vein, was torn up with it; but in these cases the minute vessels of the placenta only appeared, and never any indication of a vascular trunk or cell commensurate with the size of the vein whose terminal aperture had been lifted up from the part. The above results of my examination of the impregnated uterus, which had been furnished to me by Dr. Lee, I communicated, as I had promised to do, to that gentleman. They appeared decisive of the fact that the veins of the uterus were*not continued as such across the decidua, to terminate in visible cells in the substance of the placenta; but whether the terminal orfices of the veins derived no returning blood from the interstices of the decidual laminae, was by no means certain. For my own part, having satisfied myself of the passage of the tortuous uterine arteries into the decidua, I undoubtedly considered the uterine venous sinuses as the most probable and natural channels by which the blood conveyed from the uterus by the tortuous arteries would return again to that body ; although I was unable to determine from this dissection how the blood was returned into the open mouths of the veins. „u„M«ka It must be admitted, that an impregnated uterus at the fifth month, where he vessels, which are very small, had been contracted by the spirit >n whichthe parts had been preserved, was not a very favourable subject for so delicate ^an investigation ; and I accordingly felt extremely desirous of repeating the dissec- ts on gravid uteri at a more advanced period. These opportunities do not, as s well known, frequently occur: about a year after I was, however, favoured by )r Lee with a large portion of a gravid uterus of a woman who died about he ninth month of gesfation, in which the uterine veins had been gently filled with red size injection. This preparation was submitted to theisame mooe odl3fcl»°n- ln tracing those veins which passed to the inner surface of *e J«eru8. "ear Ae middle of the placenta, the injection was seen to be continued from them into oblique, wide, but shallow channels, leading through the external decidua into the placental decidua, and had thence been diffused through the fine spongy 1 10* 102 HUNTER ON THE ANIMAL CECONOMY. though the uterus is appropriated for ihe support of the foetus, as best fitted for that purpose, yet it is not essential to its growth; as any other part in which the child may be situated, is capable ot receiving the same provisionary stimulus for supplying it with nourishment as the nterus ; and this, I believe, is peculiar to genera- tion. This prompts me to make the following observations upon the different situations of the foetus in extra-uterine cases, which are extraordinary, happen seldom, and when they do occur are often attended with so many hindrances to critical investigation, as hardly to allow of thorough or satisfactory information. Such cases are readily distinguished from natural ones by the uterus being found entire and empty ; and they may be divided into three different kinds, according to the situation of the foetus in the ovarium, Fallopian tube, or in the cavity of the abdomen. From a want of the appearances which usually attend the natural process, the investigation of extra-uterine cases is attended with considerable difficulty. For where uncommon actions have taken place, as well as in cases of disease, the natural texture of the parts cellular tissue which everywhere surrounds and supports the fcetal capillaries. On comparing these appearances with my first dissection, 1 perceived that the uterine vein, opposite the mouth of which I had supposed the decidua to be want- ing, and whose orifice was in contact with the capillaries of the placenta, was in reality one of the oblique decidual canals, returning the blood from the cellular substance of the placenta into the uterine vein, its continuity with which had been preserved. The continuation of the uterine veins into decidual canals was much more dis- tinct in those which terminated near the circumference of the placenta ; and here the irregular portions of injection, which filled the canals as far as the surface of the placenta, were evidently circumscribed, by distinct parietes, and not the result of confused extravasation: the injection from the decidual canals had passed into the large interlobular spaces, or maternal sinuses of the placenta, and thence had become diffused, generally for the extent of an inch, into the spongy or cellular texture of the placenta. The uterine arteries in this case had not been injected, but were easily trace- able passing through the external and placental decidua, as far as the internal surface of the latter, and apparently opening or being lost on the spongy surface of the placenta. With reference to preparations of vascular and cellular structures like the pla- centa, it is not easy to enforce conviction from the appearances they present, in consequence of the difficulty of distinguishing between natural and accidental extravasation. Having, however, carefully compared the Hunterian preparations with the results of my own examinations of the gravid uterus at the full period, I now believe they all fully bear out Mr. Hunter's general view, viz., that the maternal blood is diffused, by means of the tortuous arteries, into the spongy cellular sub- stance of the placenta, where it bathes the capillaries of the fcetal circulation, and is returned by the oblique decidual adventitious sinuses and channels into the orifices of the uterine veins. Thus the placental intercommunication between the foetus and mother, in the human subject and Quadrumana, is carried on by the contact of the fcetal capillaries with maternal extravasated blood ; while in the Ruminants, the mare, and the sow,a it takes place by the apposition of capillaries to cajXIlaries, and the two parts of the placenta, viz., fetal and maternal, can be separated. In the Ferae and Rodentia there appears to be an intermediate structure.] a [In the last two examples the placenta may be said to be diffused over nearly the whole surface of the chorion.] ON THE PLACENTA OF THE MONKEY. 103 is very much altered, and appears to be lost, not only by the parts themselves being enlarged, but from having a great deal of new matter superadded to them, by which they lose their natural dis-. tinctness, and become less fitted for examination than those which only have a relation to them, and which preserve their natural actions peculiar to that state. From these difficulties, and a want of accuracy in those who made the examination, it is not at present clear, with respect to many of the extra-uterine cases upon record, whether they were ovarian cases, Fallopian tube cases, or abdominal cases; when, if they had been acquainted with the principle in which they differ, nothing could have been more easy than to distinguish them. It is not difficult, perhaps, at the very first view, to distinguish an abdo- minal case from either of the two first: for if the ovaria and Fallo- pian tube are entire, natural, and can be well distinguished to be as those parts are when the circumstances are natural, then we may be sure it is an abdominal case. Appearances, however, may not in all cases be distinct; but the parts may adhere, or be other- wise rendered so obscure, that an abdominal case might be con- founded with either of the two first; therefore it is essential to have a characteristic difference established between the two first, and the third. The invariable difference between the two first, and the abdominal cases, will be in the vessels by which the child is nourished : for the arteries and veins belonging to the part in which the child is contained must be enlarged; which, being the increase of a natural part, will be readily ascertained, and the nature of the case as readily determined. We may lay it down as a principle, that when the spermatic artery and veins of either side are enlarged in an extra-uterine case, that the foetus is in the ovarium or Fallopian tube; since there are no other blood-vessels which supply these parts; and if any other system of vessels, as the mesenteric, are increased in size, while the spermatic are in a natural state, we may with equal certainty conclude the fcetus to be contained in the general cavity of the belly. As this becomes the great criterion, and as the situation and time will not always allow very nice in- vestigation on the spot, where the person employed has an oppor- tunity of taking away the parts concerned, I would advise his taking along with them the aorta and vena cava, cut through above the origins of the spermatic vessels. 8. OBSERVATIONS ON THE PLACENTA OF THE MONKEY. Monkeys always copulate backwards: this is performed some- times when the female is standing on all-fours; and at other times the male brings her between his thighs when he is sitting, holding her with his fore paws. 104 HUNTER ON THE ANIMAL CECONOMY. The female has her regular periods for the male, but she has commonly too much complaisance ever to refuse him. ± ney carry this still further, for they receive the male when with young, even when pretty far gone: at least this was the case with oneol which I am going to give an account. . A femafe monkey, belonging to Mr. Endersbay, in the summer 1782, had frequently taken the male. The keeper observed that after the 21st of June she became less lively than usual, although it was not suspected that she had conceived ; but some time after appearing to be bigger in the belly, it created a suspicion of her being with young. Great attention was paid to her, and great care was^aken of her. She went on gradually increasing in size ; and at last something was observed to move in her belly at particular times, and the motion could even be felt through the abdominal muscles. She became indolent,and did not like to leaporperform her usual feats of activity. Towards the latter part of the time they perceived the breast and nipple to have become rather fuller, and that a kind of water could be squeezed out at the nipple. Some time before she brought forth, she became red about the hips and posteriors, which redness extended to the inside of the thighs. It being now certain that she was with young, I desired that she might be particularly attended to when there were signs of ap- proaching delivery, both on her own account and that of the young one, and "requested the afterbirth might be carefully preserved, as that part would assist to ascertain the mode of uterine gestation. These directions were attentively followed; and when in labour it was observed that she had regular pains, that when the young one was in part come into the world, she assisted herself with her fore paws, and that it came with the hind parts first. This happened on the 15th of December 1782, in all about six months after con- ception ; and when she brought forth her young one it showed signs of life, but died immediately, owing probably to the unfavour- able mode of its being brought into the world. When delivered she took the young one up, and although it was dead clasped it to her breast. The afterbirth was preserved entire, and was perfectly fit for examination. It consisted of placenta, with the membranes and navel-string, which all very much resembled the corresponding parts in the human subject, as will now be described. The placenta had the appearance of being divided into two oblong bodies, united by their edges, each terminating in an obtuse point at the other end, which were of course at some little distance from one another. It is probable that these two points were placed towards the openings of the Fallopian tubes, where the uterus assumes a form resembling two obtuse horns. The two lobes above-mentioned were made up of smaller ones, united closely at their edges, which were more apparent and dis- tinct at some parts than at others. Some of these lobes were divided by fissures which seem to be derived from one centre, while OF A WOMAN WHO HAD THE SMALL-POX, ETC. 105 there were others near the edges passing in a different direction, in which fissures are placed veins or sinuses that receive the blood laterally from the lobes. The»substance of the placenta seems to be cellular, as in the human subject: this structure allows a com- munication to be kept up between different parts of each lobe, and the sinuses allowing of a communication between the different lobes of which the placenta is composed, the blood passes into the fissures before it enters the veins; in which respect it differs from the human placenta. The arteries from the uterus, on the surface of the placenta, were visible, but too small to be injected: I cannot therefore say how they terminated in the placenta. The principal veins arose in general from the fissures beginning from the surface, as in the human placenta ; but besides these, there were other small ones; all which, we may suppose, pass through the decidua and enter the substance of the uterus, most probably in the same way as in the human subject. The membranes are the amnios, the chorion, and the membrana decidua. These appear to be much the same as in the human, except that the decidua is considerably thicker, especially where it passes between the uterus and the placenta. The navel-string in the monkey is not proportionally so long as in the human, and is very much and very regularly twisted. There is no urachus, and of course no allantois; not even the small ligament that appears to be a drawing-in of the bladder at its attachment to the navel, the bladder here being rounded. 9. ACCOUNT OF A WOMAN WHO HAD THE SMALL- POX DURING PREGNANCY, AND WHO SEEMED TO HAVE COMMUNICATED THE SAME DISEASE TO THE FCETUS. BY JOHN HUNTER, ESQ., F.R.S.* Read January 17, 1780. Mr. Grant's Account. Ox the 5th of December, 1776, Mrs. Ford had been seized with shivering and the other common symptoms of fever, to which were added great difficulty of breathing and a very hard cough. Mr. Grant saw her on the 7th, and he took from her eight ounces of blood, and gave her a composition of the saline mixture with sper- maceti and magnesia every six hours. This had operated by the 8th two or three times very gently, when most of the complaints were relieved ; but the cough still shaking her violently, bleeding seemed necessary to be repeated, more particularly as she looked upon herself to be in the sixth • [Originally published in the Philosophical Transactions, vol. lxx., 1780.] 106 HUNTER ON THE ANIMAL CECONOMY. month of her pregnancy. The medicine was continued without the magnesia. In the evening (viz.. the 8th) the small-pox appeared, which proved of a mild kind, and moderate in quantity. Its progress was rather slower than might have been expected; but the woman passed through the disease in great spirits, sitting up the greatest part of the day during the whole time, and taking only a paregoric at night, and, as occasion required, a little magnesia; thus the symptoms were mitigated, and the cough at last became very little troublesome. On the 25th she complained of a pain in her side. Eight ounces of blood were taken away. The next day she was quite free from pain, and thought herself as well on the 27th as her particular situation would admit of; after which she was not visited by Mr. Grant till the 31st, when she was in labour. Mr. Wastall's Letter on the same subject. December 30, 1776, I was sent for to Mrs. Ford, a healthy woman, about twenty-two years of age, who was pregnant with her first child. She had come out of the country about three months before. Soon after her arrival in town she was seized with the small-pox, and had been under the care of Messrs. Hawkins and Grant, who have favoured me with the particulars here annexed. I called upon her in the afternoon, she complained of violent griping pains in her bowels, darting down to the pubes. On ex- amining, I found the os tineas a little dilated, with other symptoms of approaching labour. I sent her an anodyne spermaceti emulsion, and desired to be called if her pains increased. I was sent for. The labour advanced very slowly ; her pains were long and severe: she was delivered of a dead child with some difficulty. Observing an eruption all over the body of the child, and several of the pustules filled with matter, I examined them more particu- larly; and recollecting that Dr. Leake, in his Introductory Lecture to the Practice of Midwifery, had observed, that it might be neces- sary to inquire whether those adults who are said totally to escape the small-pox have not been previously affected with it in the womb, I sent a note to Dr. Leake, and likewise to Dr. Hunter, in hopes of ascertaining a fact hitherto much doubted. Dr. Leake came the same evening, and saw the child. Dr. Hunter came afterwards, with Mr. Cruickshank, and examined it; also Mr. John Hunter and Mr. Falconer; who all concurred with me, that the eruption on the child was the small-pox. Dr. Hunter thought the eruption so like the small-pox that he could hardly doubt; but said, that in all other cases of the same kind that he had met with, the child in utero had escaped the contagion. OF A WOMAN WHO HAD THE SMALL-POX, ETC. 107 From Mr. Grant's Notes. The eruption appeared on Mrs. Ford in the evening of the 8th of December, and she was delivered the 31st, that is, twenty-three days after the appearance of the eruptions. Reflections by Mr. John Hunter. The singularity of the above case, with all its circumstances, has inclined me to consider it with some attention. There can be no doubt that the mother had the small-pox, and that the eruption began to appear on the 8th of December; also, that it went through its regular stages, and that on the 31st, viz. twenty-three days after the first appearance of the eruption the woman was delivered of the child, who is the subject of this paper. Secondly, The distance of time when she had the small-pox before delivery, joined with the stage of the disease in the child when born, which probably was about the sixth or seventh day of the eruption, viz., about fifteen or sixteen days after the beginning of the eruption on the mother, perfectly agrees with the possibility of the infection's being caught from the mother. Thirdly, The external appearance of the pustules in the child was perfectly that of the small-pox, as must have appeared from tjie relation given in Mr. Wastall's letter. Most of the pustules were distinct, but some were blended or united at their base. The face had the greatest number, and these were in general the most in- distinct. They were somewhat flattened, with a dent in the middle.* So far were the leading circumstances and external appearances in favour of their being the variolous eruption ; but although these leading circumstances and external appearances were incontro- vertible, yet they were not an absolute proof of this being the genuine small-pox; therefore I must be allowed to consider this subject a little further, and see how far all the circumstances cor- respond or are similar to the true small-pox. In the small-pox we have a previous fever, in place of which, in the present case, we have no information but that of the mother's having had the small- pox within such a limited time as may favour the possibility of in- fection in the womb ; yet we may presume that the child must have had considerable fever preceding such an eruption, of whatsoever kind it was. In the small-pox the eruption goes through pretty regular stages in its progress and declension, which circumstances we know nothing of in the present case; but even this fever, the eruptions, and their • I endeavoured to take some matter upon the point of two lancets; but not having an opportunity of making an experiment myself, I gave them to two gen- tlemen, who, I imagine, were afraid of inoculating with them. 108 HUNTER ON THE ANIMAL CECONOMY. . 'progress, are not absolutely proofs that the disorder is the small-pox when it is caught in the common and natural way; and in proof of this assertion, it may be observed, that practitioners every now and then are mistaken. It may be asked, What is the true characteristic of the small-pox? That by which it differs from all other eruptions that we are ac- quainted with ? The most certain character of the small-pox that 1 know is, the formation of a slough, or a part becoming dead by the variolous inflammation ; a circumstance which hitherto, I be- lieve, has not been taken notice of. This was very evident in the arms of those who were inoculated in the old way, where the wounds were considerable, and were dressed every day; which mode of treatment kept them from scab- bing, by which means this process was easily observed ; but in the present method of inoculation it is hardly observable ; the sore being allowed to scab, the slough and scab unite and drop off together. The same indistinctness attends the eruptions on the skin; and in those patients who die of, or die while in, the disease, where we have an opportunity of examining them while the partis distinct, this slough is very evident. This slough is the cause of the pit after all is cicatrized ; for it is a real loss of substance of the surface of the cutis; and in pro- portion to this slough is the remaining depression. The chicken-pox comes the nearest in external appearance to the small-pox ; but it does not commonly produce a slough. As there is generally no loss of substance in this case, there can be no pit. But it sometimes happens, although but rarely, that there is a pit in consequence of chicken-pox; then ulceration has taken place on the surface of the cutis, a common thing in sores. In the present case, besides the leading circumstances mentioned in the case of the mother, corresponding with the appearances on the child, and the external appearances themselves, we have in the fullest sense the third and real or principal character of the small-pox, viz., the slough in every pustule ; from all which, I think, we may conclude, that the child had caught the small-pox in the womb; or at least a disease, the effects of which were similar to no other knowTn disease. In opening the bodies of those who had either died of, or died while under, the small-pox, I always examined carefully to see whether any internal cavity, such as the oesophagus, trachea, stomach, intestines, pleura, peritoneum, &c, had eruptions upon them or not; and never finding any in any of those cavities, I be- gan to suspect that either the skin itself was the only part of the body susceptible of such a stimulus, or that the skin was subject to some influence to which the other parts of the body were not sub- Uf'rZ ,7 i1 G h 3,?n? suscePtible of the variolous stimulus. It lrom the first cause, I then concluded it must be an original principle in the animal ceconomy. If from the second, I then sus- pected that external exposure was the cause; and I was thmore OF A WOMAN WHO HAD THE SMALL-POX, ETC. led into this idea, from finding that these eruptions often attack the mouth and throat, two exposed parts; add to which, that we gene- rally find the eruptions most on the exposed parts of the body, as the face, &o. With these ideas in my mind, I thought I saw the most favoura- ble opportunity of clearing up this point. I therefore very attentive- ly examined most of the internal cavities of this child; such as the peritoneum, pleura, trachea, inside of the oesophagus, stomach, in- testines, &c, but observed nothing uncommon. I have already observed, that in this child the face and extremities were the fullest similar to what happens in common ; from all which I may be allowed to draw this conclusion, that the skin is the principal part which is susceptible of the variolous stimulus, and is not affected by any external influence whatever. The communication of the small-pox to the child in the womb may be supposed to happen in two ways ; one by infection from the mother, as is supposed in the above case; the other, by the mother's having absorbed the small-pox matter from some other person, and the matter being carried to the child from the connexion between the two, which we may suppose done with or without first affecting the mother. Testimonies and opinions are various with respect to these two facts. Boerhaave seems to have been led by his experience to think that such infection was not communicable; for we find that he attended a lady, who having, in the sixth month of her pregnancy, had the confluent small-pox, brought forth at the regu- lar period a child, who showed not the least vestige of his mother's disease. His commentator, however, Van Swieten, supports a different opinion (see his Comment., vol. v.). He quotes a case from the Philosophical Transactions, vol. xxviii., No 337, p. 165, of a woman who, having just gone through a mild sort of small-pox, was, by means of a strong dose of purging physic, thrown into a miscarriage, and brought forth a dead female child, whose whole body was covered with variolous pustules full of ripe matter: but this history is founded only on the relation of a midwife to a clergyman, and therefore not absolutely to be depended upon as accurately stated; however, it is more than probable that there was a case as described, and that there were really eruptions on the skin of the child similar to the small-pox. Van Swieten likewise mentions what Mauriceau relates of him- self. This author testifies that he had often heard his father and mother say that the latter, when big with him, and very near her time of delivery, had a painful attendance on one of her children, who died of the small-pox on the seventh day of the eruption; and that on the day following the death of this child Mariceau came into the world, bringing with him five or six true pustules of the small-pox. It does not appear, however, from this recital whether or not Mauriceau passed through life free from any posterior infection ; 11 110 HUNTER ON THE ANIMAL CECONOMY. but admitting that this eruption of Mauriceau's was truly the small- pox, yet I should very much doubt his having caught it from the child who died of it : as it should seem that the pustules of Mauri- ceau were of the same date with those of the child who died. Van Swieten appeals to a more recent case, which had been reported to him by persons of great credit, and is recorded in the Philos. Trans, vol. xlvi., p. 235. " A woman big with child, having herself long ago had the small- pox, very assiduously nursed a maidservant during the whole pro- cess of this disease. At the proper time she brought a healthy female child, in whose skin Dr. Watson asserted that he discovered evident marks of the small-pox, which she must have gone through in the womb; and the same physician pronounced that this child would be free from future infection. After four years her brother was inoculated ; and Watson obtained permission of the parents to try the same experiment on the girl. The operation was performed on both children in the same manner, and the pus used in both cases was taken from the same patient. The event, however, was dif- ferent: for the boy had the regular eruption, and got well; but the girl's arm did not inflame nor suppurate. On the tenth day from the insertion of the matter she turned pale suddenly, was languid for two days, and afterwards was very well. In the neighbourhood of the incision there appeared a pustule, like those pustules that we sometimes observe in persons who, having had the disease, attend patients ill of the small-pox." In the Epistles of T. Bartholinus, Cent. II., p. 682, there is the following history : " A poor woman, aged thirty-eight years, preg- nant, and now near the time of delivery, was seized with the symp- toms of the small-pox, and had a very numerous eruption. In this state she was delivered of a child, as full of variolous pustules as herself. The child died soon after birth ; the mother three days afterwards." Van Swieten infers that the mother and the child were in this case infected at the same time; therefore, the child not infected by the mother. Dr. Mead asserts that when a woman in the small-pox suffers an abortion the fcetus is generally full of the contagion ; but that this does not happen always. This variety, he says, depends on the state of the mother's pustules when the child is born; that is, whether they are or are not in a state of purulence. Whence he has observed it sometimes to happen that on the second dav from the birth, or the third, or any day before the eighth, the disease caught from the mother shows itself in eruptions on the child. Dr. Mead here relates the history of a ladv of quality, of which this is the substance. A lady, in the seventh month of her preg- nancy, had the confluent small-pox, and on the eleventh day of the disease brought forth a son, having no signs of the disease on his body ; and she died on the fourteenth day. The infant having lived four days was seized with convulsions, and, the small-pox appearing, died. The doctor infers from hence that, the suppuration being in OF A WOMAN WHO HAD THE SMALL-POX, ETC. m some measure completed on the eleventh day, the mother's disease was communicated then to the fcetus, and made its appearance on the child after eight days. If there be no abortion, Dr. Mead pronounces that the child will ever be free from the disease, unless the birth should happen before the maturation of the pustules. He brings a case to prove that the fcetus in the womb may be infected by the contagion of which the mother does not partake. " A woman, who had long before suf- fered the small-pox, nursed her husband, under that disease, towards the end of her pregnancy; and was brought to bed at the due time. The child was dead, and covered all over with variolous pustules." With respect to the case quoted from Mauriceau, it has been proved by Sir George Baker (Med. Transact., vol. ii., p. 275), that Dr. Mead drew a conclusion from it directly contrary to the author's meaning. The negative opinion appears evidently to be supported by that history. Sir George Baker mentions in the same paper the case of two pregnant women who were inoculated at Hertford. They both had the small-pox favourably, and afterwards brought forth their children perfectly healthy at the usual time. Both these children, at the age of three years, were inoculated with effect. Sir George Baker likewise mentions a case which fell under the observation of Dr. Clarke of Epsom. " A woman towards the end of her pregnancy had the small-pox, from which she narrowly escaped. Five weeks after the crisis she was delivered of a healthy female child, who having numerous marks on her skin was judged by all who saw her to have undergone the same distemper before her birth. However, at the end of twelve months she had the small-pox in a very severe manner. Both the mother and child were lately living at Epsom." Since, then, we see that it is very probable that the small-pox may be caught from the mother when she is infected, it may be asked why does not this happen oftener? In answer to this we may suppose that this is not so ready a way as when the child is exposed to catch it after the birth, as we find too that a difference can be produced after birth; viz., inoculation is a much readier way of catching it than what is called the natural way. It may likewise be said that many women who are with child, and have the small- pox during pregnancy, do not recover ; therefore both mother and child die before the" disease can have time to produce eruptions upon the child. Finally, in many of those cases where the mother recovers, there is sometimes produced a miscarriage, which also hinders the infection from taking .place in the child. However, many women go through the whole disease, and the child shows no marks of the small-pox. Thus have I stated facts relative to the present subject, with some of the best authorities on both sides of the question; and shall now leave the reader to form his own judgment 112 HUNTER ON THE ANIMAL CECONOMY. 10. SOME OBSERVATIONS ON DIGESTION. The paper which I formerly presented to the Royal Society, " On the Stomach itself being digested after Death," was published in 1772, in the 62d volume of the Philosophical Transactions, and has attracted the attention of Spallanzani* and others. In the course of these my observations I shall make some remarks upon the experiments and opinions of these gentlemen, compare them with those of Reaumur,f and, having given some general facts of my own upon digestion, shall conclude by adding a copy of the above-mentioned paper, with the hope that others will take up the subject in a more enlarged point of view, and prosecute an inquiry which is of so much consequence in the investigation of the opera- tions of the animal ceconomy. I cannot at present spare sufficient time to give my opinions at large on this subject, with all the ex- periments and observations I have made upon it; but as soon as I have leisure I shall lay them before the public. To discover new parts has been a principal object in the re- searches of the young or practical anatomist; but the connexion, arrangement, mode of action, and uses of the whole, or of particular organs, have more commonly been reserved for the consideration of those whose views were extended further, and whose powers of reasoning had been enlarged by habits of observation and inquiry. Curious and speculative men have likewise made attempts in this way, but often without being sufficiently acquainted with the structure of the parts they were about to consider, and consequently ill informed respecting their relations and connexions with one another. Not contented to reason from those which were most obvious, which might have led to useful knowledge, they have been directed by what best suited their fancy, and have principally at- tempted the most obscure and intricate. Generation, or the mode of continuing the species, and digestion, or the means of preserv- ing the individual, have been with them the great objects of inquiry; yet it does not appear that they have been very successful. Al- though digestion, as being one of the most important operations of the animal ceconomy, and most obvious in its effects, supplies a number of facts to assist in ascertaining its powers, little has been hitherto made out towards investigating the various circumstances under which it is performed. The mode of dividing the food for the increase of its surface, in some animals, suggested one method of explaining the process of * [Spallanxani's observations on digestion appeared first in his work called Fisica Animate e Vegetabile, 12mo. 1782; a translation of which was published in London, with the title ' Dissertations relative to the Natural History of Animals and Vegetables,' in 1784.] f [" Sur la Digestion des Oiseaux," Mem de PAcad. des Sciences de Paris 1752 pp. 266—307, and pp. 461—495.] ' OBSERVATIONS ON DIGESTION. 113 digestion; and the secretion of a juice, which was supposed to have the power of converting vegetable and animal matter into a fluid proper for the purposes of nutrition, furnished another. Both these opinions have had their advocates; and while one party contended for a mechanical power, supposed to exist in the gizzard, the other had recourse to a chemical power, and considered fermentation as the great agent in digestion. They were, however, rather specula- tive philosophers than practical anatomists, and have frequently been misled with respect to the very facts and observations whose result was to decide the truth of their opinions. What, for instance, does it explain in digestion, that the force of the gizzard of a turkey is found equal to four hundred and seventy-three pounds? Does it afford a better solution of our doubts than we should derive from determining the force of the mill that grinds the wheat into flour 1 Or, on the other hand, will the most correct idea of fermentation enable us to account for the various phaenomena in the operation of digestion I But we can have no very high idea of experiments made by men who, for want of anatomical knowledge, have not been able to pursue their reasoning beyond the simple experiment itself. The great object should have been an endeavour to discover the universal agent in digestion; for the digestive organ is evidently constructed in a different manner in different animals. The me- chanical power for the division of the food is not universal ; and those gentlemen who consider this power in the gizzard as the im- mediate cause of digestion, forgot that the same effect was produced in other classes of animals with a different structure of stomach, by means of the grinding teeth. Thus, while the gizzard favoured the theory of the mechanical reasoner, that idea was again destroyed by the membranous structure of the stomach in many animals, which equally supplied the chemist with arguments in favour of the process of fermentation. It is more difficult than those gentlemen imagine, to acquire on this subject kiformation sufficiently accurate to be able to explain a process so complicated as that of digestion. There are in Nature's operations always two obvious extremes; and the mind of man eagerly adopts that which accords with some principle to which he is attached, and with which he is best acquainted, the inter- mediate connexions and gradations, as being less striking, not so forcibly affecting a superficial inquirer. It happens, unfortunately, that those who from the nature of their education are best qualified to investigate the intricacies, and im- prove our knowledge of the animal ceconomy, are compelled to get their living by the practice of a profession which is constant em- ployment. The only educated men who have leisure are those of the Church, some of whom we frequently find commencing philo- sophers and physiologists, though they have not had that kind of education which would best direct their pursuit. Experiments, it is true, may be made by men of this description; but these must 11* 114 HUNTER ON THE ANIMAL CECONOMY. neither be much complicated, nor have any immediate relation to those branches of knowledge with which they have had few oppor- tunities of being acquainted: at best, they will seldom go further than to explain a single fact. To look through a microscope and examine the red globules of blood, to view animalculae, and give a candid account of what they see, are points on which such inquirers may be allowed to indulge themselves ; but it is presumption in them to affect to reason of a science in which they can have but a very superficial knowledge, or to expect to throw light on subjects that they have not taken the previous steps to understand. It should be remembered that nothing in Nature stands alone; but that every art and science has a relation to some other art or science, and that it requires a knowledge of those others, as far as this connexion takes place, to enable us to become perfect in that which engages our particular attention. These strictures are applicable to all those who have made experiments to explain digestion. The effect of the mechanical powers being easily understood, those who considered digestion mechanically have in general explained them justly as far as they applied to the gizzard ; but their reasoning went no further, and they supposed these effects to be digestion. Those again who took it up chemically, being little acquainted with chemistry and totally ignorant of the principles of the animal oeconomy, have erroneously explained the operations of the animal machine as subject to the laws of chemistry. The first inquirers into digestion, struck only by the extremes of structure, the gizzard, and membranous stomach, paid no regard to the gradations leading from the one to the other ; which, if properly examined, would have materially assisted them to explain the functions of the stomach. Vallisneri, considering the power of the gizzard in one view only, imagined it would be as liable to be affected by the mechanical powers necessary for digestion as the grain which was to be digest- ed ; therefore supposed the existence of a solvent. But though Vallisneri is entitled to no merit from this idea, as the premises are false, yet this opinion of his set Reaumur to work, and has been the means of bringing several curious facts to light.* The experiments of Reaumur were first made with a view to confute that opinion, * [In this historical sketch, so rare in the writings of Hunter, of the opinions entertained by previous physiologists on the subject of digestion, the suggestion by Tyson of the existence and use of a solvent or corrodent fluid ought to have had a place. In his Anatomy of a Rattlesnake he observes, "The food, before it can prove aliment, must be comminuted, and broken into the smallest particles; which in these membranous stomachs I can't see how it can be performed but by corrosion. A principal menstruum in doing this I take to be that liquor which is discharged by the glands that are seated, in some, at the beginning of the throat, and are called salival,• or just above the stomach or gizzard of birds, and called the echinus.- or in others in the stomach itself, and called the glandulus coat, and such I take the inner coat of the stomach of our rattlesnake to be."— Philos. Trans., xiii. 1683, p. 33.] OBSERVATIONS ON DIGESTION. 115 and therefore birds having gizzards were adapted to his purpose. In this pursuit he only attended to such parts of the experiments as best accorded with his own opinion, yet carefully guarded against every possible accident that might affect their accuracy. Had trituration been the immediate cause of digestion, his experiments on the gizzards of birds were unnecessary; since it would have been sufficient to have examined the food after it had been masticated by the teeth of animals who have grinders, the teeth and gizzard answering one and the same purpose. But the circumstance of animals which masticate their food in their mouth having also a stomach, should have taught that there was something more in digestion than trituration. Reaumur's first experiments were made to ascertain the strength of the gizzard, with its effects, to prove that sharp cutting sub- tances when swallowed in no way injured its internal coat, and that the common food of the bird was not dissolved when guarded against its action. Yet, after all these proofs, he seems to doubt, and says, " Are we to conclude that grinding alone is sufficient to convert the grain and other aliment into a matter proper for the nutrition of the animal, without undergoing any other preparation? Several reasons seem to oppose this : trituration alone might reduce the grain into a flour; but flour alone is not chyle." " From the smell of the aliment (taken from the gizzards of birds) are we not led to conclude that it undergoes a fermentation? This smell may be said to arise from the liquor with which the aliment is mixed ; but is it likely that juices do not dispose to fermentation substances in which it is so easily excited? Fruit and flour, made into a paste, require little more than heat to make them ferment." From these experiments, made with a view to prove that digestion is carried on by trituration, Reaumur was led to suppose a solvent. But as there are some birds whose stomachs do no not seem suffi- ciently strong to have the power of trituration, he selected the buzzard as being of that kind, and the fittest for the subject of his experiments, from the circumstance of its throwing up whatever is solid and indigestible; therefore, without killing the bird, he could know the result, and repeat the experiment as often as he thought necessary. From the stomach in the buzzard being incapable of trituration, he concluded that a solvent was necessary for digestion; but, to preclude all mechanical effects of the stomach, in his experiments he employed tin tubes filled with meat, which, after the tubes had remained twenty-four hours in the stomach of the buzzard, was reduced to three-fourths of its size, was like threads, and was neither putrid, sour, nor volatile, but insipid. On this effect he made his remarks, which are very pertinent. In another experiment, which was still more accurate and conclusive, he was convinced of the action of a solvent. He then tried the soft bones of young animals, and found they were digested; and that though the hard bones were not acted on so readily, yet, by returning the same bones several times into the stomach, they were digested at last. 116 HUNTER ON THE ANIMAL CECONOMY. Reaumur was next anxious to know if such birds as were intended by Nature to live upon meat could also digest vegetables; but the result was not so satisfactory. He gave bread to his buz- zard, which upon being returned had the appearance of having been chewed. He next tried a piece of ripe pear, after having been twenty-four hours in the stomach, had lost some of its weight, and had the appearance of being boiled or baked ; and thence he concludes that its powers are too weak to digest vegetables so as to nourish the animal. To ascertain the nature of the liquor which had such powers, he tasted the jelly to which the meat and bone had been reduced, sup- posing that it must be well impregnated with this fluid; but he could only distinguish a bitter or a saltish taste. To have an opportunity of more certainly determining the nature of this solvent, he made his buzzard swallow small tuhes filled with sponge, which imbibed fifty grains of this liquor, having the same taste as the jelly, and changing blue paper to a red. He tried the effects of this liquor on meat out of the body, with comparative experiments in water; and after twenty-four hours the meat in the water was become putrid; but that in the liquor from the stomach was only softened, not dissolved. To see how far the analogy held good in membranous stomachs, he gave two bones to a dog, which being killed after twenty-six hours, they were found lessened in size, and become as soft as horn. He found that the stomach of the dog did not alter the shape of any of his tubes. He conveyed grass and hay, inelosed in tubes, into the stomachs of ruminating animals, which substances were not digested, but appeared as if macerated. Let us enumerate the experiments and facts made out by Reau- mur. The gizzard was not hurt by acting upon glass, which it ground to a powder. The stomach or gizzard had hardly any visible motion. The force of the gizzard was ascertained. The size of the stones found in the gizzard was in proportion to the size of the bird. The stomach of a buzzard digested bone, from which he con- cluded the gastric juice had a solvent power; but it did not digest bread, although it acted in a slight degree on fruit. He made experiments with the gastric juice. The juice in the ruminating animals' stomachs produced no effect on hay or grass when inclosed in tubes. Reaumur's experiments, although not complete, paved the way for future investigation; and Spallanzani, proceeding on the same ground, has not only confirmed them by his own, but has established several points not completely made out by Reaumur; for in some instances Reaumur gave up the point too soon, especially in the experiments respecting the buzzard's power of digesting vegetables. Reaumur not possessing general knowledge sufficient to direct him OBSERVATIONS ON DIGESTION. H7 in his pursuits, was necessarily confined to what he was most master of, the mere making experiments. Being neither an anato- mist nor a physiologist, he has not been perfectly just in his description of parts, having considered the crop and the oesophagus leading from it to the gizzard as two1 distinct stomachs; but this, however, is only to be set down as a piece of anatomical ignorance, not affecting the subject in the least. Spallanzani is also deficient in his anatomical knowledge ; yet it must be owned that his experi- ments, as far as they go, are in themselves conclusive; but like all mere experiment-makers, he is not satisfied even with those which are clear and decisive, but multiplies them most unnecessarily, without varying them to elucidate other and essential parts of the same subject. I think we may set it down as an axiom, that experiments should not be often repeated which tend merely to establish a principle already known and admitted; but that the next step should be, the application of that principle to useful pur- poses. If Spallanzani had employed half his time in this way, and had considered digestion under all the various states of the body and stomach, with all the varieties of food, both natural and artifi- cial, he had employed his time much better than in making experi- ments without end. The food of animals in general being composed either of vege- tables, animals, or both, and a solvent admitted as an agent in digestion, it only remained to prove, that the effect of the process of digestion was to produce from these various substances an animal matter, similar in all animals who live on such substances. But the application of principles requires more than simply the knowledge of the principle itself, and therefore those who cannot reason from analogy, or draw general conclusions from a few con- vincing facts, and who require to have every relative conclusion or inference proved by an experiment, must be pleased with Spallan- zani ; but he must tire even those whom he informs, and much more those who read his works in expectation of something new. To make comparative experiments upon the digestive power, the different animals destined for that purpose should be under similar circumstances as far as relates to digestion ; they should be equal in age, for the growing eat more than the full-grown, and of course digest faster; which point, therefore, can be best ascertained by selecting those in each class of animals which have attained their full growth. They should be equal in fatness, for this makes a very material difference in the powers of digestion in the same animal; and they should be equal in health, a circumstance which, of all others, probably makes the greatest difference in the powers of the stomach. In comparing animals of the same class, the atmosphere should likewise be of the same temperature; for the different classes of animals are variously affected by the same degree of heat. Experiments made upon snakes and lizards in the winter will differ greatly from those made in the summer, while similar experiments made on dogs will have nearly the same result 118 HUNTER ON THE ANIMAL CECONOMY. in both seasons. Nor will the powers of the stomach be found always equal in the same class. Sleeping animals of the quadruped kind, as hedgehogs, do not digest in the winter, but in the summer only ; therefore the conclusions to be drawn from experiments made respecting the digestive powers in the one, are not at all applicable to those made in the other season. Spallanzani observed that the snake digested food faster in June, when the heat was at 82° and 83°, than in April, when it was only 60°; from whence he concludes, that heat assists digestion; but this heat is not the immediate, but the remote cause of the increased power; heat having produced in the animal greater necessity for nourishment, and of course greater powers, gastric juice was secreted faster or in greater quantity. As a proof that heat does not act as an immediate, but only as a remote cause in assisting digestion, I shall mention the effect it pro- duced upon a hedgehog, the subject of Mr. Jenner's third experi- ment on the heat of that animal, related in another part of this work. " The hedgehog, while the heat of the stomach was at 30°, had neither desire for food, nor power of digesting it; but when in- creased by inflammation in the abdomen to 93°, the animal seized a toad which happened to be in the room, and, upon being offered some bread and milk, it immediately ate it. The heat roused up the actions of the animal ceconomy ; and the parts being unable to carry on these actions without being supplied with nourishment, the stomach was stimulated to digest, to afford them that supply." Spallanzani also mentions the slowness of digestion in serpents, and quotes Bomare, who gives an account of a serpent at Martinico, in whose stomach a chicken had remained for three months without being completely digested, the feathers still adhering to the skin.* The truth of this fact I should very much doubt, especially in so warm a climate as that of Martinico, where I must suppose the digestive powers to be constantly required; unless there is in Martinico, as in colder climates, a torpid season.f where the act of digestion is not necessary ; but in that case the serpent would hot have swallowed the chicken. At Belleisle, in the beginning of the winter 1761-2, I conveyed worms and pieces of meat down the throats of lizards when they were going into winter quarters, keeping them afterwards in a cool place. On opening them at different periods I always found the substances which 1 had introduced entire, and without any altera- tion : sometimes they were in the stomach ; at other times they had * Bomare, Diet. d'Hisloire Nat. f [This conjecture is true; the dry season in some tropical climes is that during which reptiles and insects retire to their hiding-places and become torpid ; they are awakened and called into activity by the showers of the rainy season. Tur ten,rec' a mammiferous animal of Madagascar and the Mauritius, re- sembling the hedgehog, also sleeps in a state of lethargy from April to Novem- ber, when the mean temperature exceeds our summer heat.] OBSERVATIONS ON DIGESTION. 119 passed into the intestine; and some of the lizards that were pre- served alive voided them towards the spring, with but very little alteration in their structure. So that digestion is regulated by the other actions of the body : warmth requires action suitable to that warmth ; the body requires nourishment suitable to that action; and the stomach being called upon, performs the office of digestion. Nothing can show more clearly that the secretion of the gastric juice is increased in proportion to the call for nourishment in the body, than what happened to Admiral Byron and Captains Cheap and Hamilton, when shipwrecked on the west coast of South Ame- rica, who, after suffering months of hunger and fatigue, were re- duced to skin and bone ; yet when they came to good living, Byron thus expresses himself: "He (viz., the governor) ordered a table to be spread for us, with cold ham and fowls, which only we three sat down to, and in a short time despatched more than ten men with common appetites would have done. It is amazing that our eating to that excess we had done, from the time we first got among these kind Indians, had not killed us ; we were never satisfied, and used to take all opportunities, for some months after, of filling our pockets when we were not seen, that we might get up two or three times in the night to cram ourselves. Captain Cheap used to de- clare that he was quite ashamed of himself." Spallanzani has made several attempts to prove what few will subscribe to, that stones in the gizzards of birds are of no use towards the breaking or grinding down the grain ; and that they are picked up without design. These stones have long been sup- posed to answer the purposes of trituration, and have been con- sidered as affording assistance to the stomach, in the manner of teeth, and of course as being necessary to the act of digestion. Spallanzani combats this opinion; but as stones are universally found in gizzards, and it was necessary to account for the mode of their being conveyed there, he attributes it to chance. But we find that the gizzards which have most occasion for them, and are most able to use them, are likewise best supplied with them : to corrobo- rate which facts may be added what we observed before, that in the larger gizzards are found the largest pebbles. In a turkey two hundred were found ; in a goose, a thousand; which could not de- pend entirely upon chance. In trying whether the stones were of service, Spallanzani introduced tubes, needles, and lancets into giz- zards in which there were but very few stones, yet found them broken. In this experiment these substances had been forty-eight hours in the gizzards; whereas in the former experiments, with the same kind of tubes, thirty-six hours was the longest time; in another, eighteen hours; and in another, the breaking of them was begun in less than two hours; therefore the experiments were not perfectly fair, as the times were not equal. What he thinks the most con- clusive is, that where he had taken care there should be no stones, the hard indigestible substances were acted upon much in the same 120 HUNTER ON THE ANIMAL CECONOMY. way as when there were stones; but in this experiment he does not give the time, which is very accurately stated in most of the others. He discovered that the inner surface of the stomach was not hurt by such substances; and indeed it is scarcely possible for the inner coat of the stomach of a fowl to be pierced by such as are even sharp-pointed, the quantity of its motion being so inconsiderable as hardly to make them pass through its inner coat. But the principal cause of their being harmless arises from the motion being lateral, and not pressing perpendicularly to the axis, one surface sliding in a contrary direction to the other, and that not in a straight, but in a circular direction, as will be explained hereafter. In considering the strength of the gizzard, and its probable effects when compared with the human stomach, it must appear that the gizzard is in itself very fit for trituration; we are not, however, to conclude that stones are entirely useless; for if we compare the strength of the muscles of the jaws of animals which masticate their food with those of birds which do not, we shall say that the parts are well calculated for the purpose of mastication ; yet we are not from thence to infer that the teeth in such jaws are useless, even although we have proof that the gums do the business when the teeth are gone. If stones are of use, which we may reasonably conclude they are, birds have an advantage over animals having teeth, so far as stones are always to be found, while the teeth are not renewed. Spallanzani concludes, " That we have at length a decision of the famous question concerning the use of these pebbles, so long agitated by authors ; it appearing that they are not at all necessary for the trituration of the firmest food, &c,;" but says, " He will, however, not deny that when put in motion by the gastric muscles, they are capable of producing some effects on the contents of the stomach." Now if we constantly find in an organ sub- stances which can only be subservient to the functions of that organ, should we deny them to be of any use because the part can to a certain degree do its office without them ? To account for pebbles being found in the gizzard, Spallanzani supposes the birds to have picked them up by chance, or not to have distinguished between their food and these stones. But it appears singular that only those which have gizzards should be so stupid; and he owns that Redi and himself found that birds died of hunger, yet without having picked up more stones than usual, which we might suppose they would have done if they had not had a choice, or could not have distinguished stones from the grain on which they feed. The stones assist in breaking the grain, and by separating its parts in the beginning of the process, and afterwards by rubbing off the surface already digested, allow the gastric juice to come more completely in contact with the whole. It has been said, that the motion of the gizzard is so small as OBSERVATIONS ON DIGESTION. 121 hardly to be observable, and that it cannot be felt by the hand. But as its cavity is very small, and must be capable of adapting itself to the quantity it contains (or it could not possibly grind), much motion is not necessary for the purposes of trituration: a swelling and collapsing, like the motion of the heart, would have no effect. The extent of motion in grindstones need not to be the tenth of an inch, if their motion is alternate and in contrary di- rections. But although the motion of the gizzard is hardly visible, yet we may be made very sensible of its action by putting the ear to the sides of a fowl while it is grinding its food, when the stones can be heard moving upon one another.* It may be remarked, that the motion of the whole intestinal canal, from the fauces to the anus, is naturally so slow, as not to be ex- cited into quick actions. The food passes slowly along the oeso- phagus ; and in a man, fluids which might be expected to act even by their own gravity, descend but slowly; yet 1 think we may be certain that the oesophagus has always a regular contraction, and that the lower parts must relax in progression as it contracts above; so that no position of the body makes any difference in this action. Upon exposing the stomach in living animals it does not appear much agitated or affected, even by being handled or otherwise irritated. The same thing may be observed in the whole track of intestines: and we find that when the fasces are expelled by the action of the gut alone, that the explusion is slow; the stomach and rectum, however, can be emptied at once ; but that is done by the abdominal and other muscles. We know that the action of vomiting is performed entirely by the diaphragm and abdominal muscles ; and we know that by the same action the contents of the rectum can be expelled. Neither is any other power required to empty the stomach in vomiting, these muscles being often capable of forcing the bowels themselves out of the abdomen, and of pro- ducing a rupture. It is not necessary the stomach itself should act violently to produce an evacuation of its contents ; nor is it even necessary it should act at all; for the lungs themselves do not act in the least when any extraneous matter is to be thrown up; and coughing is to the lungs what vomiting is to the stomach.f The * [Harvey makes a similar observation on birds of prey : u Falconibus, aquilis, aliisque avibus ex praeda viventibus, si aurem prope admoveris dum ventriculus jejunus est, manifestos intus strepitus, lapillorum illuc ingestorum, invicemque collisorum percipias."—Opera Omnia, 4to., p. 208. These investigations by means of the ear relative to the internal actions of animal bodies deserve a place in the history of auscultation.] f [The conclusion which Hunter deduces from philosophical and just analogies, with respect to the share performed by the stomach in the act of vomiting, has not been considered satisfactory, at least if we may judge from the experiments which have subsequently been made with a view to determine that point. But perhaps M. Majendie was not aware of what our illustrious physiologist had written on the subject, as he introduces his experiments to our notice as if the passive state of the stomach in vomiting had never before been suspected : " On a cru long-temps que le vomissement dependait de la contraction brusque et con- 12 122 HUNTER ON THE ANIMAL CECONOMY. muscles of respiration are the active part in emptying the lungs, and can act both naturally and preternaturally. The muscles of the thorax and abdomen do not act naturally on the contents ot the abdomen, but often act preternaturally, producing an evacua- tion from its viscera. There is this difference in the action of the parts in coughing and vomiting: the cough is performed by the proper muscles of respiration, which are those of expansion, supported by the abdo- minal, while the diaphragm is passive. Vomiting is performed by the abdominal muscles and diaphragm, while those of inspiration are supporting this action. In coughing the ribs are suddenly depressed, which diminishes the capacity of the thorax; and that the diaphragm may not be allowed to sink down and increase the capacity of the thorax, which would counteract the depressors of the ribs, the abdominal muscles at the same time act, which supports the diaphragm in its place, and probably may by this action assist in bringing down the ribs. To give as much force to this action as possible, the glottis is shut till the action is begun, and then the glottis open instan- taneously, which obliges the depressors of the ribs to begin the effort with their full action. The proper muscles of inspiration do not tire so soon in this action as the abdominal, for in violent coughing the muscles of the abdomen become sore. In vomiting these actions are reversed. The muscles of the cavity of the abdomen act, in which is to be included the diaphragm ; so that the capacity of the abdomen is lessened, and the action of the diaphragm rather raises the ribs; and there is also an attempt to raise them by their proper muscles, to make a kind of vacuum in the thorax, that the oesophagus may be rather opened than shut, while the glottis is shut so as to let no air enter the lungs. The muscles of the throat and fauces act to dilate the fauces, which is easily felt by the hand, making there a vacuum, or what is com- monly called a suction ; so that when all these actions take place together, the stomach is immediately emptied. In violent coughing we find that a kind of mixed action takes place; for although the diaphragm has not acted, yet the stomach is so much squeezed as to discharge its contents; and it affects the diaphragm, which is often thrown into action, and brings on vomit- ing at the same time; therefore violent coughing palls the stomach. There is reason to believe that the natural motion in all stomachs vulsive de l'estomac," &c; and then goes on to detail his notorious experiment on the dog, for whose stomach he substituted a pig's bladder; by which he proved, that when rilled with fluid and put into a situation to be pressed upon, the contents of the bladder would flow out. By dividing the phrenic nerves, and paralysing the diaphragm, Majendie also proved that the abdominal muscles alone were capable of producing vomiting ; and by another experiment, he satis- fied himself that the diaphragm alone was sufficient for that act when all the abdominal muscles had been dissected off, and the peritoneum left entire.] OBSERVATIONS ON DIGESTION. 123 is regular; and I am more inclined to be of this opinion from what takes place in the stomach of animals which are covered with hair, and which lick their own bodies, and of such as feed on whole animals which are likewise covered with hair. In the stomach of the calf, for instance, which licks its skin with its tongue, and swallows whatever is attached to the rough surface of that organ, balls of hair are often found; and on examining their surface the hairs in each hemisphere seem to arise from a centre, and to take the same direction, which is circular, corresponding to what would appear to be the axis of this motion, and resembling what we see in different parts of the skin of animals whose hair takes different turns. This regularity in the direction of the hair, in such balls, could not be produced if there was not a regular motion in the stomach. This motion is also proved in the dog; for I have seen a ball of this kind that had been thrown up from a dog's stomach, where the same regularity in the turns of the hair was very evident and complete. The same motion seems also to take place in the bird kind ; and of this the cuckoo is an example, which, in certain seasons living on caterpillars, some of which have hairs of a con- siderable length on their bodies, the ends of these are found sticking in the inner horny coat of the stomach or gizzard, while the hairs themselves are laid flat on its surface ; not in every direction, which would be the case if there was no regular motion, but all one way, arising from a central point placed in the middle of the horny part, and the appearance on the surface of both sides of the gizzard evidently corresponding.* These two facts prove, in my opinion, a regular circular motion taking place in the gizzard and mem- branous stomach, and therefore, most probably, something similar is carried on in stomachs of all the various kinds. Indeed this motion in the stomach is so considerable, that when there is no horny defence, we find the coats sometimes pierced by hard pointed substances. Thus, the cows which feed on the grass of bleeching- grounds have their stomachs, especially the second stuck full of pins ; and fish which prey upon and swallow other fish entire, often have their stomachs pierced by the bones. Spallanzani calls the inner coat cartilaginous, whereas, in fact, it is a horny substance, forming an inner cuticle, but differing in some respects from the common cuticle; this horny substance not only differs in structure from the common cuticle, but in its attachment, from cuticle, nails, and hoofs. The cutis where it is covered by such substances, has a vast number of villi on its surface, which pass into corresponding perforations in the cuticle; from this structure of parts, when the cuticle, nails, or hoofs are separated, their inner * [The appearance is so regular, that this hairy lining of the gizzard has been mistaken, for a natural peculiarity of the cuckoo. In one of these gizzards, which was exhibited at a meeting of the Zoological Society, I found the supposed gastric hairs under the microscope to present the complex structure characteristic of those of the larva of the tiger-moth (Arctia Caja). See Proceedings of the Zool. Soc. 1834, p. 9.] 124 HUNTER ON THE ANIMAL CECONOMY. surface appears to be full of small perforations, and the cutis from which they have been removed is villous; and these villi are more numerous in some parts than in others, where the sense oi touch is required to be delicate or acute. But the inner lining ol the gizzard is just the reverse, that surface of the horny substance which is in contact with the gizzard being villous, and when separated, the inner surface of the gizzard appearing perforated. These villi are either the last-formed parts of this horny substance, or are the fibres of which the horny coat is composed. It is probable that this horny substance takes the form of villi that it may be more firmly connected with the gizzard, in which acute sensation is not required. I may remark here, that the experiments made on the digestion of ruminating animals have been very deficient,* arising from this process in them being more complicated than in the stomachs of other animals, and requiring attention to be paid to certain circumstances, which cannot take place in stomachs of only one cavity. The circumstance mentioned by Spallanzani, of ruminating animals voiding the tubes by the anus, shows that the whole food is not necessarily returned into the mouth to be chewed a second time ; for if it were, the tubes would certainly come up likewise, and would as certainly be thrown out of their mouths as improper ' to be chewed, a circumstance which often really happened. But it was hardly necessary to make experiments to ascertain whether ruminating animals digested meat, when we know that in some cold countries the cattle are fed on dried fish, and most animals eat their own secundines: indeed the circumstance of animals living upon both animal and vegetable food might have taught us that the mode of digesting both (whatever it is) was the same; therefore all that was wanted must have been to discover that mode; except we could absurdly conceive that two different modes might take place in the same stomach at the same time. Spallanzani gives the opinion of authors respecting digestion; and so anxious is he to combat the idea of its being fermentation, that he will hardly allow that fermentation ever takes place in the stomach. That fermentation can go on in the stomach there is no doubt; but when that happens, it arises from the powers of digestion being defective. Milk, vegetables of all kinds, wine, and whatever has sugar in its composition, become much sooner sour in some stomachs than they would if left to undergo a spontaneous change out of the body; and even spirits in particular stomachs, almost immediately degenerate into a very strong acid. I am inclined to suppose that it is the sugar which is converted into spirit, and the spirit into acid ; consequently a glass of brandy, from being much stronger, because less diluted, most probably * [This deficiency has recently been supplied by M. Flourens, in an elaborate series of experiments made on living sheep, in which fistulous communications had been established between the external surface and the different cavities of the stomach. See Annales des Sciences Naturelles.'] OBSERVATIONS ON DIGESTION. 125 contains as much matter likely to become acid as half a pint of wine. In other substances, besides those mentioned above, the fermentative process (unless prevented by that of digestion) appears to begin sooner in the stomach than out of the body. All oily substances, particularly butter, very soon become rancid after being taken into the stomach; and this rancidity is the effect of the first process of the fermentation of oil. Mr. Sieffert has been able to restore rancid oils to their original sweetness, by adding to them their due quantity of fixed air;* the loss of which I consider as the first process in this fermentation, similar to what happens in the fermentation of animal and vegetable substances. Animal food does not so readily ferment in the stomach when combined with vegetables as when it is not; for the vegetables running more quickly into fermentation, preserve the meat from putrefaction. Put a piece of meat and some sugar, or bread, into water, and let them stand in a warm place; the bread and sugar will begin to ferment, the water will become sour, and the meat be preserved ; but the acid becoming weaker, as the fermentation advances towards the putrefactive, the meat at last begins to acquire the same putrid disposition.! Yet this last part of the process can- not, I think, take place in the stomach, as a succession of acids will be formed, by which the meat will be preserved sweet till it is digested ; the formation of this acid in the stomach, most probably, not preventing the digestion of those substances which are incapable of being rendered acid. Bread allowed to remain in the stomach of a dog for eight hours is so much changed that it will not run into the vinous fermentation, but when taken out and kept in a warm place becomes putrid; its putrefaction, however, is not so quick as a solution of meat that has been in the stomach for the same length of time. Similar effects are produced when milk and bread are the food administered; and perhaps the gastric juice, when in sufficient quantity, will always prevent the vinous fermentation. Spallanzani's next trials were to determine whether the gastric juice had the power of recovering meat already putrid: a fact which might have been proved by one experiment; for if very putrid meat is given to a dog, and the dog killed after some time, the meat will be found sweet, and all putrefaction at an end. Therefore his allowing fresh meat to continue a longer or shorter time in the stomach was immaterial, as it could not become putrid. It appears from the above facts that the stomach has not so much power in preventing the acetous fermentation in vegetables as in correcting the putrefactive disposition in animal substances. For although this cannot be certainly known in those who eat both * Physical and Chemical Essays, by Sir Tobern Bergman. f Of this Sir John Pringle was not aware in making his experiments on this subject. 12* 126 HUNTER ON THE ANIMAL CECONOMY. animal and vegetable food, yet it does not appear that the putre- faction of animal substances, where nothing else is eaten, takes place so quickly in the stomach as the change which is produced in vegetables; the acetous disposition is therefore either stronger than the putrefactive, or it more readily takes place: and indeed the living body shows this sufficiently; for we very often find an acid thrown up, but seldom or never anything putrefactive. It may be admitted as an axiom that two processes cannot go on at the same time in the same part of any substance; therefore neither vegetable nor animal substances can undergo their spon- taneous changes while in the act of being digested, it being a pro- cess superior in power to that of fermentation. But if the digestive power is not perfect, then the vinous and acetous fermentation will take place in the vegetable, and the putrefactive in the food of those animals which live wholly on flesh; although in the last I imagine but very seldom. The gastric juice, therefore, preserves vegetables from running into fermentation, and animal substances from putre- faction ; not from any antiseptic quality in the juice, but, by making them go through another process, preventing the spontaneous change from taking place. In the greater number of stomachs there is an acid, even although the animal has lived upon meat for many weeks; but as this is not always the case, we must suppose it is only formed occasionally. Whether the stomach has a power of immediately secreting this acid, or first secretes a sugar which afterwards becomes acid, is not easily ascertained;* but I should be inclined to suppose, from analogy, the last to be the case: animals in health seeming to have the power of secreting sugar; for we find it in the milk, and sometimes in the urine, in conse- quence of disease. Acid sometimes prevails in the stomach to so great a degree as to become a disease, attended with very disagree- able symptoms; the stomach converting all substances which have a tendency to become acid into that form. To ascertain whether there was an acid naturally in the stomach the most satisfactory mode was to examine the contents before the birth, when the diges- tive organs are perfect, and when no "acid could have been pro- duced by disease, or anything that had been swallowed. Ac- cordingly, in the slink-calf, near the full time, there was no acid found in the stomach, although the contents had the same coagulat- ing powers with those of animals who have sucked. As we find stomachs possessed of a power of dissolving the * [The singular case of the man with an external fistulous communication with the stomach, detailed by Mr. Beaumont, who has so ably availed himself of the circumstance to elucidate several obscure points in the process of digestion, has afforded the means of determining this question. The stomach in its empty and inactive state contains no gastric juice; but when mechanically stimulated, as by touching the inner surface with the bulb of a thermometer that secretion is immediately poured out, and manifests the usual acid properties. (Beaumont: " Experiments and Observations on the Gastric Juice, and on the Physiology of Digestion.")] 6 OBSERVATIONS ON DIGESTION. 127 whole substance of a bone, it is reasonable to suppose that its earth is destroyed by the acid ki the stomach. The stomach appears not only to be capable of generating an acid, but also to have the power of producing air: which last effect, I believe, arises from disease. It is not easy to account for the formation of this air; yet as the stomach is a reservoir for sub- stances disposed to ferment, it might reasonably be supposed to arise from the food going into that process. But this, in my opinion, will not account for the vast quantity of air frequently thrown up from the stomach, even where food has not been swal- lowed for a considerable time, and where digestion appeared to have been completed. For we must conclude this process to have been completed, if the food was not found to have disagreed with either stomach or bowels, and that the stools were good. When the gout falls on the stomach the quantity of air thrown up is often immense, and the same thing may be observed in some cases com- monly called nervous ; yet the process of digestion will not account for this formation of air, as no air is to be found in healthy stomachs ;* neither is it to be accounted for from a defect in digestion, as that would probably be productive of worse conse- quences. I am inclined to believe that the stomach has a power of forming air, or letting it loose, from the blood, by a kind of secretion. We cannot, however, bring any absolute proof of this taking place in the stomach, as it may in all cases be referred to a defect in digestion; but we have instances of air being found in other cavi- ties, where no secondary cause can be assigned. I have been informed of persons who have had air in the uterus or vagina, without having been sensible of it but by its escaping from them without their being able to prevent it; and who, from this circum- stance, have been kept in constant alarm lest it should make a noise in its passage, having no power to retard it as when it is contained in the rectum. This fact being so extraordinary made me somewhat incredulous, but rendered me more inquisitive, in the hope of being enabled to ascertain and account for it; and those of whom I have been led to inquire have always made the natural distinction between air passing from the vagina and by the anus: that from the anus they feel and can retain, but that in the vagina they cannot; nor are they aware of it till it passes. A woman, whom I attended with the late Sir John Pringle, informed us of this fact, but mentioned it only as a disagreeable thing. I was anxious to determine if there were any communication between the vagina and rectum, and was allowed to examine, but disco- vered nothing uncommon in the structure of these parts. She died some time after; and, being permitted to open the body, I found no disease either in the vagina or uterus. Since that time I have * In all my experiments on digestion, in dogs, I have never been able to detect any air in the cavity of the stomach. 128 HUNTER ON THE ANIMAL CECONOMY. had opportunities of inquiring of a number of women concerning this circumstance, and by three or four have been informed of the same fact, with all the circumstances above-mentioned. How far they are to be relied upon I will not pretend to determine. I have likewise found air in the cellular membrane in gunshot wounds, that had passed some way under the skin, without being able to account for its being there by any mechanical effect of the ball. That air is either formed from the blood, or let loose by some action of the vessels, both naturally and from disease, is an unde- niable fact. We find air formed in some fishes, to answer natural purposes; for in those whose air-bladders do not communicate externally (many of which there are) we must suppose it to have been formed there. We also find it in animals after death; and I have a piece of the intestine of a hog which has a number of air- bladders in it. Mr. Cavendish was so kind as to examine this air, and he found " it contained a little fixed air; and the remainder not at all inflammable, and almost completely phlogisticated." I have often seen such vesicles on the edges of the lungs; but these may be supposed to have been a kind of aneurismal air-cells filled from the trachea, and are circumscribed and impervious, so that in the state we find them they have no communication with the exter- nal air. In one instance I have discovered air in an abscess, which could not have been received from the external air, nor could it have arisen from putrefaction. The case is as follows: A lady, about forty years of age, had been afflicted with com- plaints in the bladder and parts connected with it. From the symp- toms, her disease was supposed by some to be the stone, though upon examination no stone was found ; and she had also an umbi- lical hernia, for which I had been consulted. She grew gradually worse, and from being lusty, became a thin woman. A small tumour appeared in the groin, and the skin over it became red, similar to an abscess when the matter is beginning to point exter- nally ; but before her death this subsided. A few days before she died I was desired to examine a swelling on the lower and right side of the belly, extending nearly from the navel to the spine of the ilium on the right side. It was tense, evidently contained air, and could be made to sound almost like a drum. It had come on within a few weeks, and I was puzzled to account for it, there being clearly no connexion between that tumour and the umbilical hernia. I was inclined to suppose it to be a ventral hernia, containing the cascum and part of the colon, filled with air; but as she had stools, as there were no symptoms of a strangulated gut nor any uneasi- ness in the bowels, as I could not make the air recede, but felt it as if confined to that part, I own I could form no conjecture what the case really was. The woman dying in a few days, I was permitted to examine the body. That I might not interfere with the tumour, or umbilical hernia, I made an opening into the abdomen on the right side of the linea alba, and on examining the cavity of the ab- domen, found everything natural, except a small portion of the epi- OBSERVATIONS ON DIGESTION. 129 ploon adhering to the inside of the navel; the parietes of the abdo- men corresponding with the tumour being in a natural state. On pressing the tumour by the hand, air was heard to make its escape; whether by the vagina or anus was at first doubtful; but on ex- amining with more attention, it was discovered to come from between the labia. I next opened the tumour externally, and let out the air, which was not in the least putrid, and was contained in a sac tolerably smooth on its inside, made up of compressed cel- lular membrane, the abdominal muscles and tendons forming the posterior surface, which extended as low as the inferior edge of Poupart's ligament. The contents of the abdomen were tolerably sound; but when I inspected the viscera contained in the pelvis, they were found adhering to each other; the bladder to the body of the uterus: the broad ligaments and ovaria to the uterus; and on examining these adhesions, I discovered a cavity between the bladder, uterus, and vagina, on the right side, something like an abscess. From the right side of this cavity there was a canal as- cending to the brim of the pelvis, in the course of the round liga- ment, as far as to the going out of the iliac vessels, which it seemed to accompany; and this canal, when it passed from behind Poupart's ligament, communicated with the tumour above men- tioned. I then endeavoured to discover if there were any com- munication between the rectum and the abscess, but could find none, the gut appearing to be quite sound. Having removed the whole contents of the pelvis, with the canal leading to Poupart's ligament, and the ligament itself, with such of the abdominal muscles as composed part of the sac, I found both the rectum and the vagina perfectly sound. The uterus had a polypus forming on its inside; neither the rectum nor uterus had any connexion with the abscess; but there was a small communication between the abscess and the bladder, that portion of the bladder which made part of the abscess being very much diseased. From this history of the appearances of the tumour before death, and the particular account I have given of the dissection, the reader may be able to draw his own conclusions relative to the origin of the air. It certainly appeared to have been formed in this bag; and it was only towards the latter end of her life that it could have made its escape into the cavity of the bladder, for it was not possible to squeeze the air out of the tumour when I first saw her; but just before death it became more flaccid. It could not be formed or let loose, in consequence of putrefaction, for the air itself was free from any smell; and although the cavity between the vagina and bladder had on its internal surface the irregular ulcerated appear- ance of an abscess, yet that on the abdomen had not, was tolerably smooth, and had rather the appearance of having been formed in consequence of some foreign matter accumulating there. This circumstance, of an animal having the power of forming air, or separating it from the juices by a kind of secretion, appears 130 HUNTER ON THE ANIMAL CECONOMY. at first view to be supported by the experiments of Dr. Ingen- housz.* The Doctor observed, that when we immerse our bodies " in a cold or warm bath," or " by plunging the hand and arm even in cold water," globules of air soon appear upon the skin ; and to be certain of the air coming from the body, he took all the necessary precautions to prevent the external air being carried into the water along with the body (which would certainly be a consequence if the body or part were immersed quickly, or when dried). But although his experiments seem to prove this opinion, yet I imagine there is a circumstance the Doctor did not attend to at the time, which renders them very fallacious; for he did not consider that water for the most part contains a great deal of air; therefore the globules of air might as readily come from the water as from the body, which makes it necessary to ascertain, by experiment, from whence the air comes which is attached to the body when immersed in water. Water takes up air in proportion to its coldness, until it loses the property of water, and becomes solid : upon this principle we may account for globules of air being found attached to the skin when a part of the body is immersed in water colder than itself; for when we immerse the whole body we increase the heat of the water, especially that next to the skin; and if we immerse only a part, as an arm, it being commonly in a smaller quantity of water, the water immediately surrounding it is also warmed. As a proof that it is the air from the water, and not from the surface of the body,f it matters not what the substance is that is immersed if it is but warmer than the water; for a piece of iron, heated to about 150°, immersed in water about 70°, will warm the water in contact with it so as to make it part with its air. This effect of heat is further proved by making another trial, with only this difference, that the iron be ten degrees colder than the water; in that case little or no air will be separated, and of course no bubbles observed. The bubbles of air do not appear to arise entirely from the degree of warmth of the water, but also in some measure from a solid body being immersed in it, that seems to have a power of attract- * Experiments upon Vegetables, proving their great power of purifying the common air, &c. t " Count de Milly, in the Berlin Transactions for the year 1777, published experiments to show that there is an excretion of air, or, as it is termed, ' an aerial transpiration,' from the whole surface of the human body while it remains in warm water; but Dr. Pearson found, on repeating these experiments, that there was no appearance of aerial bubbles on the surface of the cuticle durino bathing in warm water that had been previously boiled, so as to expel the air usually mixed and united to river and spring water. The human body, when immersed in the bath at Buxton, and kept at rest in it for some time, was covered with air-like bubbles; but these bubbles appeared in the same manner on any solid body whatever that was placed in it. It is therefore supposed that the attraction to the human body of the air, commonly suspended in water, especially when heated to the temperature of a warm-water bath, has been mistaken for an excretion of air from the cuticle." OBSERVATIONS ON DIGESTION. 131 ing the air, whose affinity to the water is now weakened by heat; for simply heating the water to the same degree will not separate the air, as we find that no bubbles are then produced. The power of attracting the air appears therefore in some sort to depend upon the solidity of the body immersed; at least bodies have a greater number of bubbles in proportion to their solidity ; for upon making comparative experiments between iron, stone, wood, and cork, the air separated from the water upon the surface of the iron and stone is in considerable quantity; that upon the wood very small, and scarcely any at all upon the cork. As these observations on the generation (or secretion) of air in cavities seemed to have a connexion with the present inquiry, I thought they might properly enough be introduced here ; but I shall content myself with having mentioned the circumstance, and pursue the subject of digestion. To determine with absolute certainty in what particular portion of the canal this important process of digestion is performed, is perhaps impossible; but there is the greatest reason to believe that it is principally carried on in the stomach, with a little variation in different animals. We may venture to affirm that it does not at all take place in the long and contracted oesophagus of the quadruped, the secretion of that part being a slimy mucus, possessed of no power similar to that of the gastric juice, but only intended to facilitate the passage of the food into the stomach. Neither has the mucus secreted in certain parts of the oesophagus of birds, as in the crop of those which have one, any digestive power; while, on the contrary, we find the lower end, which is extremely glandular, to be capable of secreting a juice with all the properties of the gastric ; and that passing into the cavity of the stomach becomes a substitute in this class of animals for the de- ficiency of the secretion of the stomach itself, which in some is lined with a horny substance, and in others with a cuticle. Even in birds the seat of digestion is chiefly in the stomach, the juice secreted in the lower part of the oesophagus passing into that cavity; and the mucus secreted by the other parts of the oesophagus, as in the crop of those which have one, has no such power. But if any digestible substance should be retained in the oesophagus, as may happen in many of those which swallow whole animals, digestion may even go on in its inferior portion. In the gull and heron, which take down snakes and fish entire, the tails may remain in the oesophagus till the head is digested in the stomach ; and in such cases the tail itself may be acted upon in that situation. As a further proof that digestion is carried on principally in the stomach, let us observe what happens to the yolk of an egg in the bird newly hatched. The yolk is not in the least consumed in the time of incubation, but appears to be reserved for the nourish- ment of the chick between the time of hatching, and its either being supplied with food by its parents, or being able to procure it for itself; for we find, that although the yolk passes into the gut at 132 HUNTER ON THE ANIMAL CECONOMY. some distance from the stomach, yet it is carried up to the stomach to be digested; and I have even seen it in the crop, being retained there till wanted. In those animals whose stomach consists of several cavities, the precise place where digestion is carried on has not been ascertained. I think, however, that in the ruminating class, in which it has four cavities, it may be set down as a fact that digestion goes on in the fourth, which is best proved by feeding the animal with a substance that does not require any kind of preparation for digestion, such as milk. If a calf be killed about half an hour after it has sucked its mother, we shall find the whole milk in the fourth cavity firmly coagulated, and formed into a ball, while the first, second, and third cavities contain only such food as requires mastication, or what other preparation is necessary to fit it for digestion. Such animals have the power of conveying the food from the oesophagus, either to the first or fourth cavity, according to the nature of the food; and for this purpose there is a groove leading directly from the oesophagus to the fourth stomach, which I suppose can be converted into a canal when wanted. It is possible that digestion may likewise be carried on in the duodenum, especially in its upper part, if either the intestine secretes the same juice with the stomach, or that some of the gastric juice and part of the food have passed into the intestine before it has been completely turned into chyle.* Although the stomach is the seat of digestion, it is not solely ap- propriated to that purpose; and in many animals these organs are not to be considered as only a digesting bag or bags, but in part as a reservoir for food. This is most remarkable in the ruminating animals, where the first stomach or bag is merely a reservoir, and in this respect analogous to a crop. It is the same in the porpus, and, I believe, in most animals of this class; although it cannot be supposed that those return the food who have not the power to masticate. In some animals which do not ruminate there is not the same necessity for distinct pouches, the stomach consisting either of one bag singly, or of stomach with appendages, as in the peccari. But the whole organ is not endowed with the property of secreting the gastric juice, there being a part whose structure is very different from that appropriated to digestion, and covered by * [This conjecture is eonfirmed by the observations of Tiedemann and Gmelin, who found that when any vegetable fecula passed the pylorus unaltered it was converted in the duodenum, as in the stomach, into sugar and amydine. Majendie attempted to subject this question to direct experiment, but failed from not having insured the continuance of the substance experimented on in the necessary situation. He found, on introducing a piece of raw flesh into the duodenum of a healthy dog, that in an hour it had been carried to the rectum : its weight was slightly diminished, but there was no other change than a discolora- tion of its surface. In another experiment he fixed a morsel of flesh in the small intestine with a thread; after the lapse of three hours it had lost about half its weight: the fibrin had been principally acted upon ; what was left was entirely cellular, and extremely foetid. See Precis Elementaire de Physiologie, ii. p. 114.] OBSERVATIONS ON DIGESTION. 133 a cuticle, as in the first, second, and third stomach of the ruminat- ing animals and in the first stomach of the porpus. The peccari, the common hog, and the rat, are likewise instances of this; and the same circumstance takes place, in a smaller degree, in the horse. This increase in the cavity of the stomach, beyond what is neces- sary for digestion alone, is peculiar to the animals that take in more food than is immediately wanted, or whose food is of a nature which requires a certain degree of preparation prior to digestion. The crop of the eagle, and perhaps the first stomach of the porpus, are of the first kind; the crop in the gallinaceous fowls, and the first stomach in ruminating animals, of the second.* It is the dis- position of such animals to fill these cavities ; and the quantity which they are capable of containing makes them seldomer require to be filled; it is probable, likewise, that it is the sensation excited by this fulness which gives satisfaction to the animal, and takes off the further desire for food, an effect similar to what is pro- duced in other animals from filling the stomach itself; and these having no such provision, are longer and oftener employed in pursuit of food. I should be apt to consider the power of the gastric juice to coagulate milk, and some other animal mucilages,t as a test of the stomach being the seat of digestion; for although milk may be coagulated by other substances, yet when found in that state in the stomach it is probably for the purpose of digestion, milk and many other natural substances requiring to be coagulated before they can be digested. I have found this coagulating power in the stomach of every animal that I have examined for that purpose, from the most perfect down to reptiles ;J and in the appendages which I have * [According to this difference in their functions, we find that the crop of the eagle is relatively smaller than that of the fowl, and the passage of its contents to the stomach is more direct and easy. The first stomach of the porpus is still smaller in comparison with the rumen of the sheep; and besides acting as a storehouse for the food, digestion goes on in it to a considerable extent. This is effected, not by secretion from its own parietes, which, as Hunter observes, are lined with a cuticle, but most probably by the gastric juice regurgitated into it from the second stomach, which is highly glandular. The flesh offish is found separated from the bones, and these in different stages of softening, in the first stomach ; indeed, the construction of the aperture of communication between the first and second stomachs of the porpus is such, that food can pass into the latter only in a very comminuted state.] f Milk is the substance commonly known to be coagulated by the gastric juice ; but I find that it has also the same power over the white of an egg. Give to a dog some raw egg, and kill him half an hour after he has swallowed it, the egg will be found coagulated in his stomach, as if boiled. The crystalline humour in the stomachs of fishes is likewise found coagulated. X [By " reptiles " there is reason to believe Mr. Hunter meant' creeping things,' as insects and worms. The ' Reptilia ' of modern naturalists he invariably calls by the Linnaean name 'Amphibia,' or by his own term, 'Tricoilia.' In the In- troduction to the Series of Digestive Organs, (Phys. Catalogue of the Hunterian Collection, vol. i.) he says, " In some reptiles the teeth are placed in the oesopha- gus," alluding to preparations of a Nereis ; and in a manuscript, published in 13 134 HUNTER ON THE ANIMAL CECONOMY. considered as only reservoirs preparatory to digestion, (as the first stomach in the ruminating animal, and the crop in birds,) 1 have discovered no such power. Yet it is not the digestive power which coagulates those substances, complete coagulation taking place even where digestion does not at all go on.* This is evident every day in children who suck, and who have diseased stomachs ; for we see them throw up the milk coagulated, and discharge it undigested by stool. A very remarkable instance occurred in a child that had lost entirely the power of digestion, yet the milk taken down came away strongly coagulated, some even as firm almost as cheese; which seems to show that the coagulating power is seldom wanting, although the other may. The gastric juice is a fluid somewhat transparent, and a little saltish or brackish to the taste; but whether this is essential or only accidental is not easily determined. Indeed there are very few of our secretions which have not some salt in them; it being found in the tears, the saliva, the secretion of the glans penis, of the glands of the urethra, and in the first and the last milk secreted in the udders of animals. I am not inclined to suppose that there is any acid in the gastric juice as a component or essential part of it, although an acid is very commonly discovered, even when no vegetable matter has been in- troduced into the stomach.f The acid may be increased in some the same volume of the Physiological Catalogue, there is proof that he experi- mented on an insect with especial reference to the seat of the digestive power. After detailing the peculiarities of the digestive organs in the flesh-fly (Musca vomitoria), he observes: " The bag belonging to the first-described canal is to be considered a craw or crop, viz., a reservoir for the food to be ready for digestion ; and as the abdomen contains almost every internal part of the animal, it is obliged to be situated in this cavity. That it is a reservoir for food I proved by experiment: I kept some of these flies fasting for some time: 1 then gave them milk, which they drank readily; and when I thought they had filled their bellies, I put them into spirits, which assisted in coagulating the milk wherever it might be. On opening the abdomen, I found this bag full of curd and whey, as also some in the stomach. I kept a fly for twelve hours without food, and then gave it milk, and killed it, and found no milk in the crop, but it had got through almost the whole tract of intestines : here the animal had immediate occasion for food, therefore the milk did not go into the crop. This experiment at the same time shows that, probably, every part of the intestines digest, for the stomach makes no distinct bag."] * [Or rather the digestive power may be equal to the coagulation, but not to the completion of the digestion of the coagulable substances.] f The only trial to which I ever put the gastric juice was with the 6yrup of violets, to ascertain if it was acid ; and in many of the trials the colour of the mixture was changed to red. But it is necessary, for the accuracy of the experi- ment which is to determine this fact, that the animal should not be fed upon vegetables for some time before the trial is made, these being liable in some de- gree to become sour; therefore it is hardly fair to make the experiment on the contents of the stomach of animals who live upon vegetables. In many trials of this kind we may be deceived, and led to suppose an alkali; for certain animal secretions being of a yellow cast, when such are mixed with the syrup of violets the mixture is changed to a green. The truth of the experiment may, however, be known by adding a little acid ; for if the green has been produced merely by OBSERVATIONS ON DIGESTION. 135 diseases, and in others the disposition to form it may be destroyed, which may be the reason why, by a kind of instinctive principle, many girls are fond of eating sour fruit and of drinking vinegar; while others, on the contrary, from a different cause, often eat chalk, lime, and other substances of that sort. But the acid not being always found, it is not yet determined on what occasions it is formed, or in what manner it is destroyed. The process of digestion differs from every other natural opera- tion in the change it produces on different bodies; yet it is by no means fermentation, though it may somewhat resemble it. For fermentation, a spontaneous process, is that natural succession of changes by which vegetable and animal matter is reduced to earth; therefore must be widely different from digestion, which converts both animal and vegetable substances into chyle, in the formation of which there cannot be a decomposition similar to fer- mentation. Digestion is likewise very different from chemical solution, which is only a union of bodies by elective attraction. But digestion is an assimilating process; and in this respect is somewhat similar in its action to that excited by morbid poisons. It is a species of generation, two substances making a third; but the curious cir- cumstance is its converting both vegetable and animal matter into the same kind of substance or compound, which no chemical pro- cess can effect. The chyle is compounded of the gastric juice a mechanical mixture, it will become immediately a scarlet, by being then a mix- ture of red and yellow ; but if the secretion is not only of a yellow colour, but of an alkaline nature, it will also continue green; and by adding a little more acid than what saturates the alkali the colour will then become orange.8 * [Various opinions have been entertained as to the acidity of the gastric juice. Spallanzani believed it to be a neutral fluid. Carminati could detect no acid in the gastric juice of carnivorous animals and mixed feeders, but found it to exist in that of vegetable feeders. (Uebtr die Xntur des Magensaftes, Wien, 1785.) Helm, who examined the gastric juice in a patient with a fistulous opening in the stomach, also states that it contains no sensible acid. (Zwei Krankengeschicten, Wien, 1803.) The same cause of error has probably operated in each of the pre- ceding cases, viz., not making a sufficient distinction between the ordinary mucous secretion of the stomach and tWe peculiar fluid which is poured out from the stimulus of the contact of food, or any innutritions substances. In the experi- ments of Tiedemann and Gmelin the ordinary secretion of the stomach in fasting horses and dogs was found to be almost neutral, or very slightly acid; but on stimulating the surface by means of stones, (by which any cause of error from a change of fermentable substances, as alluded to by Hunter, was avoided,) then the secretion manifested unequivocally the presence of acidity. Beaumont has more fully established the acidity of the gastric juice in the work before quoted. He observed in the man with gastric fistula that the gastric juice was poured out from numerous minute clear points or papillae. It is a clear inodorous fluid, with a somewhat salt and very marked acid taste, like that of thin mucilage which has been soured with muriatic acid. It dissolves in water, wine, and alcohol; slightly effervesces with alkali; decomposes slowly, and retards the decomposi- tion of animal matter. Saliva imparts to the gastric juice a blue colour and a frothy appearance. Chemical analysis shows the gastric juice to contain both the muriatic and acetic acids, alkaline phosphates, muriate of soda, magnesia, and lime, and an animal matter which is soluble in cold but not in hot water.] 136 HUNTER ON THE ANIMAL CECONOMY. and digestible substances when perfectly concerted j and it is pro- bable that the quantity of gastric juice may be nearly' equa 1 to that part of the food which is really changed int, chyle If so, it demonstrates the necessity of a very quick secretion to supp y a quantity so very considerable; but with this advantage, that it is not lost to the constitution. . , f The progress of the conversion of food into chyle may be otten seen mTe stomach of animals at different times after feeding. Fbhes at goorTsubjects on which to make observations for this oarooL as they swallow their food whole; and as that food is ^lPmonly fish and often too large to be completely admitted into ^stomach. As they do not masticate their food it is not adapted to theTavity of the stomach ; and therefore part of it is often found Wing in the oesophagus; a circumstance by which the comparative progress of digestion is rendered more obvious. It may also be well observed in the stomach of a dog, in which the whole quantity taken has been swallowed at once. In the great end the food will be but little altered; towards the middle, more; and towards the pylorus it will be similar to what is found in the duodenum.* . . , , From the structure of the stomach in ruminating animals they are badly adapted to assist our inquiries on this subject, because metallic balls, or whatever is swallowed in so nard and solid a form as to be unfit for digestion, requiring to be ruminated, will often be thrown out when returned into the mouth for that pur- pose; or it may lie a long time in the first stomach without being either thrown up or passed into the fourth, as I have frequently seen; therefore the chance of its getting into the fourth stomach in a proper time to fit it for the object of an experiment being very uncertain, no great light can be derived from trials made on animals of this class. Live or fresh vegetables, when taken into the stomach, are first killed, by which a flabbiness in their texture is produced, as if they had been boiled; and then they can be acted upon by the gastric juice. Meat appears to undergo no change as preparatory to digestion, but at once to submit to its union with the gastric juice ; for, after having been acted upon, it seems first to lose its texture, then be- comes cineritious in colour, next gelatinous, and last chyle. The first change made upon milk and some other secretions, as the yolk and white of an egg, is coagulation; after which the gastric juice begins to acquire a power of uniting with them. The first change which is produced on animal substances out of the body, either by being exposed to heat or by becoming spontane- * [The cardiac and pyloric portions of the stomach possess the digestive power in very different degrees, it being much more energetic in the latter. In the stomachs of Carnivora and Rodentia the two portions are commonly found divided by a constriction; and the same hour-glass contraction of the stomach is occasion- ally met with in the human subject. See Sir Everard Home, Phil. Trans. 1817, p. 347.] OBSERVATIONS ON DIGESTION. 137 ously putrid, is similar to the second of the three changes which takes place in digestion; and is only preparatory to the complete change, whether that be digestion or putrefaction. It appears from many experiments that the digested or animalized part, when carried into the intestine, is attracted by the villous coat, or clings to it as if entangled among the villi; while the excremen- titious part, such as bile, is found lying unconnected in the gut, as if separated from the other.* The food of animals in general consists of vegetable or animal substances; and vegetables seem intended to support one class, with a view to its being the food of another. Although there are classes of animals intended to subsist on each particular kind of food, yet they do not all invariably keep to the same kind in every stage of life, many being nourished by animal food when young that afterwards live on vegetables ; which circumstance will be more fully discussed while treating of the first food of pigeons. All stomachs do not equally digest the same substance, although it be their natural food. The caterpillar digests the expressed juice, but not the substance; while other animals are capable of dissolving nearly the whole. Some animals, as the common cattle, can feed on a variety of vegetables, although they may have a preference; but there are others that will hardly eat of more than one kind. Of this last sort are insects in general, and the silkworm will scarcely touch anything but mulberry leaves; but I believe those that live upon animal food are not so restricted in their choice. It is probable that all animal and vegetable substances are equally capable of being digested, if equally soft in their texture; but some being much firmer in that respect, and others also united with in- digestible matter, as the earth in bones, more strongly resist the powers of the gastric juice; therefore mastication and trituration become necessary to bring them to a similar consistence. But sub- stances may be rendered too soft, for a fluid is difficult of digestion ; and we may observe, that Nature having given us very few fluids as articles of food, to render these few fitter for the action of the digestive powers, a coagulating principle is provided to give them some degree of solidity.f It is not easy to assign a reason why * [In chylification, the alkaline principles of the bile combine with the acids which the chyme has received in its formation in the stomach, and the albumi- nous or chylous principles are developed and attracted by the villi; while the resinous parts of the bile, combined with the excrementitious particles of the chyme, are more or less completely separated. The most characteristic change which, according to Prout, takes place in the intestine is the conversion of part of the chyme into albumen, which happens even when no albuminous matter was originally contained in the food or formed in the stomach.} t The circumstance of the crystalline humour, which is solid, being coagulated prior to its being digested, renders it probable that all animal substances go through that process, and that the loss of texture which they undergo arises from coagulation.a a [This coagulation happens to all animal substances which contain albumen; but can hardly be considered, Dr. Prout observes, "to be essential to the subse- 13* 138 HUNTER ON THE ANIMAL CECONOMY. fluidity should be unfavourable to the process of digestion, more especially as it seems essential to those of fermentation and chemi- cal solution. The requisite degree of solidity I should suppose to be that of curd, or what is produced by the coagulation of animal mucilages, as of the white of an egg. But this is only supposition, founded on the idea that Nature's general principles are right, and all the corresponding parts adapted to one another, except when monstrous, either in form or action. Mastication is the effect of a mechanical power, produced by parts particularly provided for that purpose, which are of various kinds, fitted for that sort of food on which the animal is by Nature intended to live, and may be imitated with equal advantage by many other pieces of mechanism. The masticating powers are of three kinds. The first is that which merely fits the substance for deglutition, as in the lion and many other carnivorous animals; and which, in the ruminating tribe, renders the food fit to be swallowed, that it may undergo such preparation in the first stomach as is necessary before it is further masticated for digestion. The second is that which not only fits the food for deglutition, but exposes it to the action of the gastric juice, by breaking the shells or husks in which the nourishment is contained, and in which it would be defended from the powers of digestion. And the third is that which divides and bruises the food before it is received into the stomach ; which mastication is of con- siderable service, by producing a saving in food.* The husk of the seeds of plants, although a vegetable substance, appears to be indigestible in its natural state. Whether this arises from the nature of the husk itself, or from its compactness, I am not quite certain, but am inclined to suppose the last, as we find the cocoa, which is only a husk, to be digestible when ground to a powder and well boiled. We know likewise that cuticle, horn, hair, and feathers, although animal substances, are not affected, in the first instance, by the gastric juice; yet if reduced in Papin's digester to a jelly, that jelly can be acted upon in the stomach: we must therefore suppose that a certain natural degree of solidity in animal and vegetable substances renders them indigestible. This com- pactness in the husk seems to be intended to preserve, while under ground, the farinaceous part of the seed, in which the living principle is placed, the husk having probably no other power of resisting putrefaction than what arises from its texture ; but whatever may be the use of the husk, it must be connected with the vegetative process of the plant. The same purpose of preservation is pro- bably answered by the shells of all ova. Although husks are not capable of being dissolved in the gastric juice, they allow of transu- dation, and that the seed is in some degree affected by it is known quent process; for gelatin, a staminal alimentary principle, nearly resembling albumen in its composition, undergoes, under similar circumstances, no such solidifying change. (Br. Tr., p. 494.)] * [Blumenbach has we'll suggested that the vitality of the seeds is thus de- stroyed and they are made subject to the influence of the gastric juice.] OBSERVATIONS ON DIGESTION. 139 by its swelling in the stomach; yet it can only take up a certain proportion of it, and that not sufficient to convert it into chyle, the gastric juice having no power of action upon the husks themselves. Therefore we see grain of all kinds, when swallowed whole, pass through entire, though swelled ; and even the kernels of some nuts, as chestnuts, are not digestible when eaten raw. The essential oils of vegetables and animals are indigestible; but being soluble either in the gastric juice or chyle, they become medicinal, from their stimulating powers. The essential oil of vegetables, but more particularly that of animals, seems to pervade the very substance of those animals whose food contains much of this oil. Thus, we find sea-birds, whose constant food is fish, taste very strongly of fish ; and those who live on that kind of food only during certain times of the year, as the wild duck, have that taste only at such seasons. This fact is so well known that it was hardly necessary to put it to the test of an experiment; yet I took two ducks, and fed one with barley, the other with sprats, for about a month, and killed both at the same time : when they were dressed, the one fed wholly with sprats was hardly eatable, it tasted so strongly of fish. Although bones are in part composed of animal substance, and so far digestible, yet they require stronger powers to digest them than common meat, from the animal substance being guarded by the earth. Thus, the animal part of a bone is less easily soluble in an alkali than flesh, or than even the animal part when deprived of its earth by an acid ; nor will a bone, being guarded by the calcare- ous earth, submit to putrefaction so readily as meat; therefore animals which live upon others, and swallow them whole as the heron, digest bone with more ease than the crow or magpie, that are not accustomed to swallow bones, but commonly pick the flesh only. The degree of ease or difficulty with which substances are digested, will not only arise from "a difference in solidity, but from a difference in the structure of the parts themselves; brain, liver, muscle, and tendon, being digestible in the order here put down. There is not only a difference in the degree of facility with which the various kinds of natural food are digested, but these can also be made to undergo changes by art, which render them still more easy of digestion; for it appears from my experiments that boiled and roasted, and even putrid meat, is easier of digestion than raw, which, in the two first, may be supposed to arise from their juices being coagulated; but the same reason will not hold good with regard to the putrid.* A raw egg is thought more easy of diges- ♦ [From the various experiments instituted by Sir Astley Cooper on the diges- tibility of different substances, it appears that pork is more digestible than mutton, this than veal, while beef is the least digestible of any. In feeding dogs with determinate quantities of each, and opening them at the expiration of a given period, it happened that in some instances the pork and mutton had entirely dis- appeared, while the beef remained but little altered. Fish and cheese were also found to be very digestible substances. Potatoes were digestible in a less degree: 140 HUNTER ON THE ANIMAL CECONOMY. tion than an egg hard boiled, although the raw one must be coagu- lated in the stomach before it can be digested; and it has likewise been observed, that what is easy of digestion is one stomach will not be so in another; but such cases may probably arise from the stomach not being in a healthy state. In many animals the whole of the food does not appear to be digested, the substance in part being found in the fasces ; for if a dog is fed with tallow, his excrements will consist of a somewhat firm unctuous substance, so that the oil is only digested in part. The circumstance of some part of the food, though digestible, not being acted upon by the gastric juice, may arise from two causes: first, from many parts of vegetables being too firm in texture to be digested in the same time with the other food, and being therefore carried along in a crude state, together with the chyle, into the duodenum ; and secondly, from the stomach at the time being so much disordered as to digest imperfectly. We know that food may lie a considerable time in the stomach when it is diseased without being digested. Food has been retained in the stomach twenty-four hours, and thrown up without being in the least altered, the animal at the time not requiring nourishment: this often arises from disease, and is also the case with those which go to rest in the winter. The powers of digestion may in some instances be estimated by the appearance of the excrement, in which, if the food appears not to be much altered, we may conclude that digestion has had little or no influence on it. Thus, the excrement of a flea, that has lived on blood, is nearly, to appearance, pure blood, not having even lost its colour. Animals take food in proportion to the quantity of nourishment contained in it, of which the stomach appears, from instinct, to be capable of judging; and also in proportion to the powers they pos- sess of converting what they eat into chyle. A caterpillar, perhaps, eats more in proportion to its size than any other animal that lives on the same kind of food ; for not having the power of dissolving the vegetable, but only of extracting a juice or infusion from it, the bit of leaf comes away entire, coiled up and hardened ; but, by being put into water, unfolds like tea. There are few animals that do not eat flesh in some form or other, while there are many who do not eat vegetables at all; and therefore the difficulty to make the herbivorous eat meat is not so great as to make the carnivorous eat vegetables. Where there is an instinctive principle in an animal, directing it either to the one species of food or the other, the animal will certaintly die rather than break through of its own accord that natural law; but it may be made to violate every natural principle by artificial means. That the hawk tribe can be made to feed upon bread, I have known these thirty years; for to a tame kite I first gave fat, which it ate very readily; then tallow and butter; and afterwards small balls of Boiled veal was found to be two-thirds more digested than the same meat roasted, toe. Muscular tissue, skin, gristle, tendons, bone, were digestible in the order here set down.] ° OBSERVATIONS ON DIGESTION. 141 bread rolled in fat or butter, and by decreasing the fat gradually, it at last ate bread alone, and seemed to thrive as well as when fed with meat. This, however, produced a difference in the consistence of the excrements, for when it ate meat they were thin, and it had the power of throwing them to some distance ; but when it ate bread they became firmer in texture, and dropped like excrement of a common fowl. Spallanzani attempted, in vain, to make an eagle eat bread by itself; but by inclosing the bread in meat, so as to deceive the eagle, the bread was swallowed, and digested in the stomach. The excrements of animals we may suppose to be that part of the common food which is indigestible ; and as food is either animal or vegetable, and each different kind adapted to distinct classes of animals, it is natural to believe that the excrementitious part of each will be different; and where the animal feeds upon both, that the excrement will be of a mixed nature. Although this appears probable, it is only true in a certain degree; for the mode of diges- tion, and whether the animal has a caecum and colon, with their peculiar form, have all an influence in the changes which the food undergoes. Vegetable food produces more excrement than animal, and this according to the kind or parts of vegetables that are eaten. The woody parts and husks, which are indigestible, produce the most; the true farinaceous part the least: why there should be any at all from the farinaceous and animal substance, except what has eluded the action of the digestive organs, is not easily ac- counted for. All faeces have a tendency to putrefaction, but least in those animals which feed on vegetables. Indeed, the excrement from vegetable food alone could hardly ever become putrid if it was not mixed with the mucus of the intestines, and would even then be kept sweet by the tendency which undigested vegetables have to take on the vinous and acetous fermentation. But the fasces of those which live entirely on animal food in general very soon become putrid; and indeed often before they are voided ; but such animals are either without caecum or colon ; or if not, what they have is very short; so that the excrement not being long retained, has less time to become putrid. When the faeces stagnate so as to take on either the vinous or putrefactive fermentation, air is let loose, which will be according to the nature of the fermentation ; most probably, from the vegetable it will be fixed, and from the animal, inflammable air. The fasces of the greatest number of animals are tinged by the bile, which in some gives them a yellowish-green colour; in the bird they are generally green, but sometimes white, from being mixed with the urine. The fasces of the maggot appear to be loaded with bile; for besides being yellow, they are extremely bitter, which is known by eating the kernel of a nut that has a maggot in it. Some kinds of food, when not wholly digested, give a tinge to the faeces, as grass to the excrement of cows. 142 HUNTER ON THE ANIMAL CECONOMY. The animals which feed upon vegetables alone commonly have their fasces somewhat solid; but the degree will vary according to the state of the vegetable, whether green or dried ; and therefore the particular state of the faeces will depend on the nature of the indigestible part of the food, and must be different according to the digestive powers in different animals. An animal that feeds upon grass has the fasces much softer than when fed on the same kind of grass made into hay; and therefore the faeces of the herbivorous animals are softer in the summer than the winter; but green vege- table food does not produce soft faeces in all animals, for the cater- pillar, which lives upon the leaves of vegetables, has its fasces almost dry ; and we find in some ruminating animals, as sheep, that the difference in the fasces during summer and winter is incon- siderable. The quadrupeds and birds that live principally upon vegetables generally have their caeca large and the colon long, as we see in many of the ruminating animals. Some have the colon both long and large, as the horse and those of the rat tribe, which circumstance has considerable effects in allowing the fasces to become dry: in a few of the ruminating animals, and of the rat kind, they are formed into small portions. The faeces of quadrupeds living upon animal food are commonly soft, and in birds are fluid; but in such as live on both animals and vegetables, they are in consistence of a mixed nature, and will be more or less soft according to the food. If a dog is fed entirely on animal substance its faeces will be soft; if wholly on vegetable as on bread, they will become so hard as to be expelled with difficulty.* * [The following differences were found by Dr. Prout in the contents of the rectum of dogs which had been fed on Vegetable Food. Animal Food. Of a firm consistence, and of an olive Consisted of firm scybala, of a dark brown colour, inclining to yellow. Smell brown colour, inclining to chocolate. foetid and offensive. Did not coagulate Smell very foetid. Milk was coagulated milk. by the water in which it had been dif- fused. A. Water; quantity not ascertained. A. Water; quantity not ascertained. B. Combination or mixture of altered B. Combination or mixture of altered alimentary substances in much greater alimentary matters in much greater ex- excess than in the colon, with some cess than in either the colon or caecum, mucus; insoluble in acetic acid, and with some mucus; insoluble in acetic constituting the chief bulk of the faeces, acid, and constituting the chief bulk of the faeces. C. Albuminous matter, none. C. Albuminous matter, none. D. Biliary principle, partly changed D. Biliary principle more consider- to a perfect resin. able than in the vegetable faeces, and almost entirely changed to a perfectly resinous-like substance. E. Vegetable gluten? none; but con- E. Vegetable gluten? none;butcon- tained a principle soluble in acetic acid, tained a principle soluble in acetic acid, and precipitable very copiously by oxa- and precipitable very copiously in oxa- late of ammonia. late of ammonia. F. Insoluble residuum, consisting F. Insoluble residuum, consisting chiefly of vegetable fibres mixed with chiefly of hairs.] hairs. OBSERVATIONS ON DIGESTION. 143 Spallanzani made some experiments to prove that digestion is carried on after death; but they are not so conducted as to corres- pond with the appearances met with in the dead body where that process has taken place, and the coats of the stomach itself have been in part digested. An experiment, although it may be very well and accurately made so far as the experiment goes, if a close connexion is not preserved with the purpose for which it was made, the conclusions to be drawn from it cannot correspond with the in- tention. This is exactly the case with the experiments of Spallan- zani, which, although they prove that meat was digested in the stomach after the animal was killed (which no one doubted), yet are not at all calculated to show that the stomach itself may be digested. In fact, the mode in which they were managed rather tended to prevent that effect from taking place, for the gastric juice, by having substances introduced on which it could act, was less likely to affect the coats of the stomach. That the digestion was not carried on merely by the gastric juice secreted before the animal was apparently dead, is evident, from his own account, some of the food which had been introduced and digested being found in the duodenum, a thing that could not have happened if a cessation of the actions of life in the involuntary parts had taken place when visible life terminated. There had been an action, and most probably a secretion, in the stomach. The only experiment that can be made with any probability of a decided result, is to kill the animal while the stomach is empty, and observe what after- wards takes place. There are few stomachs that do not show, when examined after death, some of the inner villous coat destroyed, which may have been done by the gastric juice in the ducts of the glands which secrete it. Dr. Stevens in an inaugural dissertation on this subject, published at Edinburgh 1777, gives a number of experiments, some of which are well devised, to ascertain the substances that are easiest of digestion, a thing in fact more wanted than the cause of that pro- cess: but many of his experiments, more especially those on rumi- nating animals, were not made with sufficient accuracy. How the chopped hay and potherbs came to be so much changed in the first stomach of a ruminating animal I cannot conceive, as 1 have reason to believe it has not the least power of digesting, and should doubt very much that hay was capable of being wholly digested in any stomach. His experiment made on substances out of the body proves that the gastric juice is not able in all cases to prevent the vinous and acetous fermentation in vegetables, and is a circum- " stance which I believe often takes place in the living body when the stomach is weak. He seems to be in some apprehension for the safety of the stomach itself, from the action of so powerful a solvent as the gastric juice; but though inclined to suppose that the living powers of the animal may guard it against such effects, yet he is still disposed to fear that in all cases they may not be sufficient. The living power in the stomach must indeed be very weak to 144 HUNTER ON THE ANIMAL CECONOMY. admit of its being digested ; where that was likely to happen, I imagine the secretion of the gastric juice would be too defective to allow of the stomach being acted upon. Dr. Stevens gives two cases, with the dissections, to projfethat the livin" stomach has not always the power to resist the action of the gastric juice; but he has not made it clear that those very stomachs might not have been digested after death. The appear- ance of the edges of the hole should have been more particularly described; for if it took place before death it is probable it was owing to ulceration, which I have sometimes seen. Men should be very accurate in ascertaining the truth of facts before they advance them, especially when they tend either to overturn a received opinion or to establish a new one. As to the possibility of animals swal- lowed alive being digested, no fresh proofs are necessary, as we eat oysters everyday; but this does not prove that they are di- gested while alive. In his experiments made on ruminating animals and the dog, as the vegetables were not so readily digested as the meat, he concludes, " It is possible every species of animal has its peculiar gastric liquor, capable of dissolving certain substances only" which is certainly not true. Mr. Senebier relates some experiments made by Mr. Gosse upon himself, but which hardly contain anything except a curious con- jecture of Mr. Senebier's, " That distention of the stomach is the cause of the secretion of the gastric liquor." He mentions the sub- stances, both animal and vegetable, which are not digestible: then those difficult of digestion : afterwards, those easily digested; also what substances facilitate digestion, and what retard it. But if we are to judge of the truth of these facts from a detail of the experi- ments which he made to ascertain them, I am quite inclined to believe that the experiments have not been made with sufficient accuracy to be depended upon. 11. ON THE DIGESTION OF THE STOMACH AFTER DEATH. The following account of the stomach being digested after death was drawn up at the desire of the late Sir John Pringle, when he was President of the Royal Society; and the circumstance which led to it was as follows. I had opened, in his presence, the body of a patient who had been under his care, in which the stomach was found to be in part dissolved; a thing that appeared to him very accountable, there having been no previous symptom which could have led him to suspect any disease in the stomach. I took that opportunity of explaining to him my ideas respecting it; and that, having long been employed in making experiments on digestion, I had been induced to consider this as one of the facts which proved a converting power in the gastric juice. I mentioned my intention DIGESTION OF THE STOMACH AFTER DEATH. 145 of publishing the whole of my observations on digestion at some future period; but he desired me, in the meantime, to give this fact by itself, with my remarks; as it would prove that there is a sol- vent power existing in the stomach, and would be of use in the ex- amination of dead bodies.* An accurate knowledge of the appearances in animal bodies, where death has been the consequence of some violence while they were otherwise in health, ought certainly to be considered as neces- sary to qualify us to judge truly of the state of the body in those that die of diseases. An animal body undergoes changes after death; but it has never been sufficiently considered what those changes are, or how soon they may take place; yet till this be done it is impossible we can form an accurate judgment of the appear- ances which present themselves at the time of inspection. The diseases of an animal body (mortification excepted) are always connected with the living principle, and are not in the least similar to the changes which take place in the dead body: without a knowledge of this, an opinion drawn from dissections must always be very imperfect or very erroneous. Appearances which are in themselves natural may be mistaken for those of disease ; we may see diseased parts, and suppose them in a natural state; we may consider a circumstance to have existed before death which was really a consequence of it; or we may imagine it to be a natural change after death, when it was in fact a disease of the living body. It is easy to see, therefore, how a man in this state of igno- rance must blunder when he comes to connect the appearances in a dead body with the symptoms that were observed in life; and, indeed, all the advantage to be derived from opening dead bodies depends upon the judgment and sagacity with which this sort of comparison is made. There is a case of a mixed nature, which can neither be reckoned a process of the living body nor of the dead : it participates of both. inasmuch as its cause arises from life, and the effect cannot take place till after death. To render this more intelligible, it will be necessary to state some general ideas concerning this cause and effect. An animal substance, when joined with the living principle, can- not undergo any change in its properties but as an animal; this principle always acting and preserving the substance possessed of it from dissolution, and from being changed according to the natural changes which other substances undergo. * [The original paper is printed in the 62d volume of the Philosophical Trans- actions; and was read June 18th, 1772. It begins as follows: "An accurate knowledge of the appearances in animal bodies that die of a violent death, that is, in'perfect health, or in a sound state, ought to be considered as a necessary foundation forjudging of the state of the body in those that are diseased." The remainder of the essay is given in the 2d edition of the Animal CEconomy, with verbal alterations of the same kind and degree as are exemplified in the paragraph above quoted ; with tho omission of one sentence and a note, which are subjoined at the end of the paper.] 14 146 HUNTER ON THE ANIMAL CECONOMY. There are a great many powers in nature which the living prin- ciple does not enable the animal matter, with which it is combined, to resist, viz., the mechanical and most of the strongest chemical solvents. It renders it, however, capable of resisting the powers of fermentation, digestion, (and perhaps several others,) which are well known to act on this same matter, and entirely to decompose it, when deprived of the living principle. The number of powers which thus act differently on the living and dead animal substance not being ascertained, we shall only take notice of two, putrefac- tion and digestion, which do not affect this substance, unless when it is deprived of the living principle. Putrefaction is an effect which arises spontaneously; digestion is an effect of another principle, and shall here be considered a little more particularly. Animals, or parts of animals, possessed of the living principle, when taken into the stomach, are not in the least affected by the powers of that viscus so long as the animal principle remains. Hence it is that we find animals of various kinds not only can live in the stomach, but are even hatched and bred there; yet the moment that any of these lose the living principle, they become subject to the digestive powers of the stomach. If it were possible for a man's hand, for example, to be introduced into the stomach of a living animal, and kept there for some considerable time, it would be found that the dissolvent powers of the stomach could have no effect upon it; but if the same hand were separated from the body, and introduced into the same stomach, we should then find that the stomach could immediately act upon it. Indeed, if the first were not the case, the stomach itself ought to have been made of indigestible materials; for were not the living principle capable of preserving animal substances from being acted upon by the process of digestion, the stomach itself would be digested ; and accordingly we find that the stomach, which at one instant, that is, while possessed of the living principle, was capable of resisting the digestive powers which it contained, the next moment, viz., when deprived of the living principle, is itself capable of being digested, not only by the digestive powers of other stomachs, but even by the remains of that power which itself had of digesting other things. These observations lead us to account for an appearance which we often find in the stomachs of dead bodies ; and they at the same time throw considerable light upon the nature of digestion. The appearance we allude to is a dissolution of the stomach at its great extremity, in consequence of which there is frequently a considera- ble aperture made in that viscus. The edges of this opening appear to be half dissolved, very much like that kind of solution which fleshy parts undergo when half digested in a living stomach, or when acted upon by a caustic alkali, viz., pulpy, tender and ragged. In these cases the contents of the stomach are generally found loose in the cavity of the abdomen, about the spleen and diaphragm; and in many subjects the influence of this digestive power extends DIGESTION OF THE STOMACH AFTER DEATH. 147 much further than through the stomach. I have often found that, after the stomach had been dissolved at the usual place, its contents let loose had come into contact with the spleen and diaphragm, had dissolved the diaphragm quite through, and had partly affected the adjacent side of the spleen, so that what had been contained in the stomach was found in the cavity of the thorax, and had even affected the lungs to a small degree. There are very few dead bodies in which the stomach at its great end is not in some degree digested; and one who is acquainted with dissections can easily trace these gradations. To be sensible of this effect nothing more is necessary than to compare the inner surface of the great end of the stomach with any other part of its inner surface: the sound portions will appear soft, spongy, and granulated, and without distinct blood-vessels, opake and thick; while the others will appear smooth, thin, and more transparent; and the vessels will be seen ramifying in its substance, and upon squeezing the blood which they contain from the larger branches to the smaller, it will be found to pass out at the digested ends of the vessels, and to appear like drops on the inner surface. Though I have often seen such appearances, and supposed that they must have been seen by others, yet I was quite at a loss to account for them. At first I supposed them to have been produced during life, and was therefore inclined to look upon them as the cause of death, only that I never found they had any connexion with the patient's symptoms; but I was still more at a loss to account for them when I discovered they were most frequent in . those who died by sudden violence; a circumstance which made me suspect that the true cause was not guessed at.* At this time I was employed in making experiments upon digestion in different animals, all of which were killed at different times, after having been fed with various kinds of food : many of these were not opened immediately after death, and in some of them I found the above-described appearances in the stomach. The better to pursue my inquiry on the subject of digestion, I procured the stomachs of a vast variety of fishes, whose deaths are always violent, and who may be said to die in perfect health, with their stomachs usually * The first time that I had occasion to observe this appearance where death had been produced by violence, and where it could not therefore easily be sup- posed to be the effect of disease, was in a man who had his skull fractured by one blow of a poker. Just before this accident he had been in perfect health, and had taken a hearty supper of cold meat, cheese, bread, and ale. Upon opening the abdomen, I found that the stomach, though it still contained a good deal, was dissolved at its great end, and a considerable part of its contents lay loose in the general cavity of the belly; a circumstance which puzzled me very much. The second instance was in a man who died at St. George's Hospital, a few hours after receiving a blow on his head which fractured his skull. From these two cases, among various conjectures about so strange an appearance, I began to sus- pect it might be peculiar to cases of fractured skull, and therefore, whenever I had an opportunity, I examined the stomach of every person who died from that accident; but 1 found many of them which had not this appearance. I afterwards met with the same appearance in a man who had been hanged. 148 HUNTER ON THE ANIMAL CECONOMY. full. In them we can observe the progress of digestion most dis- tinctly, the shape of their stomachs being very favourable for that purpose. They likewise swallow their food whole, that is, without mastication,and swallow fish that are much larger than the digesting part of the stomach can contain ; therefore in many instances the part swallowed which was lodged in the digesting part of the sto- mach was found more or less dissolved, while that which remained in the oesophagus was perfectly sound ; and in many of these I saw the digesting part of the stomach itself reduced to the same dis- solved state as the digested part of the food. Being employed upon this subject, and therefore enabled to account more readily for appearances which had any connexion with it, and observing that the half-dissolved parts of the stomach were similar to the half-digested food, it immediately struck me that it was the process of digestion going on after death ; and that the stomach, being dead, was no longer capable of resisting the powers of that menstruum which itself had formed for the digestion of food.* These appearances of the stomach after death throw considerable light on the principles of digestion, and show that it neither depends on a mechanical power, nor contractions of the stomach, nor on heat, but something secreted in the coats of the stomach, and thrown into its cavity, which there animalizes the food, or assimilates it to the nature of the blood.f The power of the gastric juice is con- fined or limited to certain substances, generally of the vegetable and animal kingdoms; and although this menstruum is capable of acting independently of the stomach, yet it is indebted to that viscus. for its existence and continuance. * [Then follows in the original paper: " With this idea, I set about making experiments to produce these appearances at pleasure, which would have taught us how long the animal ought to live after feeding, and how long it should remain after death before it is opened ; and above all, to find out the method of producing the greatest digestive power in the living stomach: but this pursuit led me into an unbounded field."—Phil. Trans. (1772), p. 453.] f [In the original paper the following note here occurs: " In all the animals, whether carnivorous or not, upon which I made observations or experiments to discover whether or not there was an acid in the stomach (and I tried this in a great variety), I constantly found that there was an acid, but not a strong one, in the juices contained in that viscus in a natural state." The omission of this note both in the 1st and 2d editions of the Animal (Economy was probably a consequence of the doubt subsequently entertained by Hunter of the natural presence of an acid in the gastric juice; but as the existence of hydrochloric acid as an essential constituent of the animalizing secretion of the stomach is now satisfactorily determined, we have thought it proper to restore this record of the agreement of a great proportion of Hunter's experience with that of late observers on this subject.] SECRETION IN THE CROP OF BREEDING PIGEONS. 149 12. ON A SECRETION IN THE CROP OF BREEDING PIGEONS, FOR THE NOURISHMENT OF THEIR YOUNG. The nourishment of animals admits, perhaps, of as much variety in the mode by which it is to be performed as any circumstance connected with their ceconomy, whether we consider their numerous tribes, the different stages through which every animaL passes, or the food adapted to the support of each in their distinct conditions and situations. We are likewise to include in this view that endless variety in the means by which this food is procured, according to the class of the animal and the particular stage of its existence. If the food was the same through every period of the life of an animal; if every individual of a tribe lived on the same kind, and procured it by the same mode, our speculations would then admit of a regular arrangement. But when we see that the food adapted to one stage of an animal's life is rejected at another, and that animals of one class in some respects resemble those of another, by hardly having any food peculiar to themselves, the subject becomes so complicated that it is not surprising if we are at a loss to arrange the various modes by which animals are nourished. Animal life may not improperly be divided into three states or stages. The first comprehends the production of the animal and its growth in the fcetal state; the second commences when it emerges from that state by what is called the birth, yet for a certain time must, either mediately or immediately, depend on the parent for support; the third may be said to take place when the animal is fit and at liberty to act for itself. The first and third stages are perhaps common to all animals; but there are some classes, as fishes, spiders, &c, which seem to have no second stage, but pass directly from the first to what is the third in other animals. Of those requiring a second stage, the polypus and the viviparous animals continue to derive their nourishment immediately from the parent ? while the oviparous are for some time supported by a substance originally formed with them, and reserved for that purpose.* There is infinite variety in the means by which Nature provides * [The species of polypus to which Mr. Hunter here refers is most probably the freshwater gemmiparous hydra; but the period during which the young polype is growing at the expense of the parent seems rather to correspond to the first or foetal stage of existence than the second : when, again, the communication with the digestive sac of the parent is obliterated, the young polype derives its nourishment from without by the exercise of its tentacles, until it is finally cast off. The viviparous animals are the Mammalia, and the nourishment alluded to is the lacteal secretion. The nutritious substance with which the oviparous animals continue for a short period to be supported after their exclusion from the egg is the yolk, which has then passed into the abdomen, where it is finally absorbed.] 14* 150 HUNTER ON THE ANIMAL CECONOMY. for the support of the young in the second stage of animal life. In many insects it is effected by the female instinctively depositing the egg, or whatever contains the rudiments of the animal, in such a situation that, when hatched, it may be within reach of proper food; others, as thc'humble-bee and black-beetle • [Blatta],' collect a quantity of peculiar substance, which both serves as a nidus for the egg, and nourishment for the maggot, when the embryo arrives at that state. Most birds, and many of the bee-tribe, collect food for their young; when at a more advanced period the task of feed' ing them'is performed by both male and female, with an exception in the common bee, the young ones of which are not fed by either parent, but by the working-bees, which act the part of the nurse. There is likewise a number of animals capable of supplying im- mediately from their own bodies the nourishment proper for their offspring during this second stage, a mode of nourishment which has hitherto been supposed to be peculiar to that class of animals which Linnaeus calls Mammalia; nor has it, I imagine, been ever suspected to belong to any other. 1 have, however, in my inquiries concerning the various modes in which young animals are nourished, discovered that all of the dove kind are endowed with a similar power. The young pigeon, like the young quadruped, till it is capable of digesting the common food of its kind, is fed with a substance secreted for that purpose by the parent animal; not, as in the Mammalia, by the female alone, but also by the male, which, perhaps, furnishes this nutriment in a degree still more abundant. It is a common property of birds, that both male and female are equally employed in hatching, and in feeding their young in the secona stage; but this particular mode of nourishment, by means of a substance secreted in their own bodies, is peculiar to certain kinds, and is carried on in the crop. Besides the dove kind, I have some reason to suppose parrots to be endowed with the same faculty, as they have the power of throwing up the contents of the crop, and feeding one another. I have seen the cock parroquet regularly feed the hen, by first filling his own crop, and then supplying her from his beak. Parrots, maccaws, cockatoos, &c, when they are very fond of the person who feeds them, may likewise be observed to have the action of throwing up the food, and often do it. The cock pigeon, when he caresses the hen, performs the same kind of action as when he feeds his young; but I do not known if at this time he throws up anything from the crop. During incubation the coats of the crop in the pigeon are gradually enlarged and thickened, like what happens to the udder of females of the class Mammalia in the term of uterine gestation. On com- paring the state of the crop when the bird is not silting, with its appearance during incubation, the difference is very remarkable. In the first case it is thin and membranous j but by the time the young are about to be hatched, the whole, except what lies on the ON THE GILLAROO-TROUT. 151 trachea, becomes thicker, and takes on a glandular appearance, having its internal surface very irregular. It is likewise evidently more vascular than in its former state, that it may convey a quantity of blood sufficient for the secretion of the substance which is to nourish the young brood for some days after they are hatched. Whatever may be the consistence of this substance when just secreted, it most probably very soon coagulates into a granulated white curd, for in such form I have always found it in the crop; and if an old pigeon is killed just as the young ones are hatching, the crop will be found as above described, and in its cavity pieces of white curd, mixed with some of the common food of the pigeon, such as barley, beans, &c. If we allow either of the parents to feed the brood, the crop of the young pigeons when examined will be discovered to contain the same kind of curdled substance as that of the old ones, which passes from thence into the stomach, where it is to be digested. The young pigeon is fed for a little time with this substance only, as about the third day some of the common food is found mingled with it: as the pigeon grows older the proportion of com- mon food is increased ; so that by the time it is seven, eight, or nine days old, the secretion of the curd ceases in the old ones, and of course no more will be found in the crop of the young. It is a curious fact that the parent pigeon has at first a power to throw up this curd without any mixture of common food, although after- wards both are thrown up according to the proportion required for the young ones. I have called this substance curd, not as being literally so, but as resembling that more than anything I know; it may, however, have a greater resemblance to curd than we are perhaps aware of. for neither this secretion, nor curd from which the whey has been pressed, seems to contain any sugar, and do not run into the acetous fermentation. The property of coagulating is confined to the sub- stance itself, as it produces no such effect when mixed with milk. This secretion in the pigeon, like all other animal substances, becomes putrid by standing, though not so readily as either blood or meat, it resisting putrefaction for a considerable time; neither will curd much pressed become putrid so soon as either blood or meat. 13. OBSERVATIONS ON THE GILLAROO-TROUT, COM- MONLY CALLED IN IRELAND THE GIZZARD- TROUT.* One of the digestive organs of the gillaroo-trout being so very remarkable as to have given name to the fish, and to have been considered as its distinguishing characteristic, it is my intention to * [Originally published in the Philosophical Transactions, vol. lxiv. (1774.)] 152 HUNTER ON THE ANIMAL CECONOMY. inquire whether its resemblance to a gizzard be sufficiently strong to render the term of gizzard-trout a proper appellation, and what place its stomach ought to hold among the corresponding organs of other animals. For this purpose it will be necessary to state certain facts connected with the subject, and take a general view of the varieties which occur in the digestive organs in different animals. The food of animals may be divided into two kinds, what does, and what does not, require mastication to facilitate digestion. The flesh of animals is of the latter kind; but grain, and many other substances which serve for aliment, require a previous grinding or trituration, and therefore animals living on this kind of food are furnished with organs for that purpose. Granivorous quadrupeds have the two powers, for mastication and digestion, separate or distinct from one another; the first being executed by teeth, which serve as so many grindstones for reducing their food to smaller parts, before it is conveyed into the stomach for digestion; but the form of these teeth varies very considerably in different animals, although the food be the same. This grinding also fits it for deglu- tition ; for neither grain nor herbs could be swallowed without having first been masticated. When so prepared, it is, with regard to the digestive power, rendered similar to animal food; therefore in many of the granivorous the stomach resembles that of the carnivorous animals ; and whenever the stomach in the granivorous quadruped departs from this general rule, there is a peculiarity in the operations of digestion. Birds that live upon substances, for the digestion of which trituration is indispensably necessary, have the powers of mastication and digestion united in one part, the gizzard, which is particularly constructed for that purpose, but is more uniform in its construction than the teeth, varying only by being stronger or weaker in its powers; therefore the genius of birds exhibits less variety, respecting the organs relating to digestion, than the quadruped. In granivorous birds, therefore, one single organ answers both to the teeth and stomach of granivorous quadrupeds, and consequently the gizzard alone of birds will as clearly point out the food of the species as both teeth and stomach together, in those animals in which the two offices of mastication and digestion are not performed together in the same part. As it appears to be the difference of stomachs only that fits birds for their different kinds of food, as there is little difference in con- struction, excepting only in strength ; and as the food of the different species is of every kind, from the hardest grain to the softest animal matter, we may conclude that every gradation of the stomach is to be found among them, from the true gizzard, which is one extreme, to the mere membranous stomach, which is the other. In conse- quence of this, it must be as difficult to determine the exact limits of the two different modes of construction to which the names of gizzard and stomach specifically belong, as, in any other case, to distinguish proximate steps in the slow and imperceptible gradations of Nature. ON THE GILLAROO-TROUT. 153 The two extremes of true gizzard and membranous stomach are easily defined ; but they run so into each other, that the end of one and the beginning of the other is quite imperceptible. Similar gra- dations are observable in the food: the kinds suited to the two ex- tremes mixing together in different proportions adapted to the in- termediate states of stomach. A true gizzard is composed of two strong muscles, placed opposite and acting upon each other, like two broad grindstones. These muscles are joined together at their sides by a middle tendon, into which the muscular fibres are inserted, and which forms the nar- row anterior and posterior sides of the flat quadrangular cavity in which the grinding is performed. The upper end of this cavity is occupied by the termination of the oesophagus, and the beginning of the intestine. The lower end consists of a thin muscular ba»- con- necting the edges of the two muscles together. By these two more soft and flexible substances being thus inter- posed between the two strong grinding muscles a double advantage is gained; for whilst one gives an easy passage to the oesophagus and gut, when both act together they serve in some degree as a hinge, on which the two muscles may be said to move, by the mid- dle tendon allowing of a free motion of the grinding surfaces on each other, which is necessary for the comminution of food. The two flat lateral sides of the grinding cavity are lined with a thick horny substance, similar to a hard and thick cuticle; the nar- row anterior and posterior tendinous parts are also lined with a cu- ticle, but not so strong as the former; this horny substance is gra- dually lost at one end in a very thin cuticle, which lines the passages of the oesophagus and intestine for a little way, and at the other end is lost in the same manner in the membranous bag. The two large muscles may be considered as a pair of jaws, whose teeth are occasionally supplied, being small rough stones or pebbles which the animal swallows, which from the feeling of the tongue can distinguish such as are proper from those which are not, in- stantly dropping out of its mouth such as are smooth and otherwise unfit for the purpose. Some birds with gizzards have also a craw or crop, which serves as a reservoir, and for softening the grain; but as all of them have not this organ it is not to our present purpose. There are other animals, besides this class of birds, which mas- ticate their food in the stomach; but teeth are placed there by Nature; of this kind are crabs and lobsters. The gradation from gizzard to stomach is made by the muscular sides becoming weaker and weaker, and the food keeps pace with this change, varying gradually from vegetable to animal.* In one point of view, therefore, food may be considered as a first principle, with respect to which the digestive organs with their appendages * [The gizzards of birds which live on hard-coated coleopterous insects are stronger than those which have to digest soft pulpy fruits.] 154 HUNTER ON THE ANIMAL CECONOMY. act as but secondary parts, being adapted to and determined by the food as the primary object. We find then that in all granivorous animals there is an appa- ratus for the mastication of the food, although often differing in con- struction and situation ; but in true carnivorous animals, of what- ever tribe, mastication not being so necessary, they have no appa- ratus for that purpose. The teeth of such quadrupeds as are carni- vorous serve chiefly to procure food and prepare it for deglutition; the same thing is performed in the true carnivorous birds by their beak and talons, whose office it is to procure the aliment and fit.it for deglutition, corresponding in this respect with the teeth of the others. Applying this reasoning to fish, it seems, at first sight, as if there were no occasion in them for that variety of structure in the digestive organs as is found in the before-mentioned quadrupeds and birds, the food of fish being principally of one sort, namely animal; which, however, with regard to the digestive powers, is to be dis- tinguished into two kinds, viz., common soft and shell-fish. Such fish as live on the first kind have, like the carnivorous quadrupeds and birds, no apparatus for mastication, their teeth being intended merely for catching the food and fitting it to be swallowed. But the shells of the second kind of food render some degree of masti- cating power necessary to fit it for its passage either into the sto- mach or through the intestines; and accordingly we find in certain fish a structure suited to the purpose. Thus the mouth of the wolf-fish is almost paved with teeth, by means of which it can break shells to pieces and fit them for the oesophagus of the fish, and so effectually disengage the food from them, that though it lives upon such hard food, the stomach does not differ from that of other fish ; the organs of mastication and digestion, therefore, in this animal, exactly correspond to those of many gra- nivorous quadrupeds. Other fish, on the contrary, approach nearer to the structure of birds by having their.stomach furnished to a certain degree with a masticating power, which in many is very imperfect compared with the gizzards of fowls. Perhaps the difference is only what the dif- ference of food will properly allow ; as in fish which have this power, the food being still animal, and in general but imperfectly covered with the shell, it probably requires only to be broken, perhaps hardly that, for the mere purposes of digestion, as food is digested when introduced into the stomach in silver balls with only a few small ■holes, but it may be necessary to fit the shells for passing along the intestines after the fish is digested. In the Bulla lignaria of Linnaeus this apparatus is more perfect, consisting of two bones, which we must suppose capable of grinding hard shells ; but the food of gra- nivorous birds requires to be ground into a kind of meal. Of all the fish I have seen, the mullet is the most complete instance of this structure, its strong muscular stomach being evidently adapted, like the gizzard of birds, to the two offices of mastication and digestion. The stomach of the fish now before us holds the second place. ON ANIMALS PRODUCING HEAT. 155 But still neither of these stomachs can be justly ranked as gizzards, since they want some of the most essential characters, viz., a power and motion fitted for grinding, and the horny cuticle.* The stomach of the gillaroo-trout is, however, more globular than that of most fish, better adapted for small food, and endued with sufficient strength to break the shells of small shell-fish; which will probably be best done by having more than one in the stomach at a time, and also by taking pretty large and smooth stones into the stomach, which will answer the purpose of breaking, but not so well that of grinding, nor will they hurt the stomach, as they are smooth, when swallowed ; but this stomach can scarcely possess any power of grinding, as the whole cavity is lined with a fine villous coat, the internal surface of which appears everywhere to be digestive, and by no means fitted for mastication. The stomach of the common stream-trout is exactly of the same structure with that of the gillaroo ; but its coat not so thick by two thirds.f How far this difference in thickness of stomach is suffi- cient to form a distinct species, or barely a variety of the same, is only to be determined by experiment.^ The oesophagus in the trout is considerably longer and smaller than in many other classes of fish. The intesines are similar to those of the salmon, herring, sprat, &c. The pancreas is appendiculated. The teeth show them to be fish of prey. So far as we are led to determine by analogy, we must not con- sider the stomach of this fish as a gizzard, but as a true stomach. 14. EXPERIMENTS AND OBSERVATIONS ON ANIMALS, WITH RESPECT TO THE POWER OF PRODUCING HEAT.§ Some late ingenious experiments and observations, published in the Philosophical Transactions,!! upon a power which animals seem * [We have examined the gizzard of the mullet (Mugil Capito, Cuv.), and find that it is lined by a distinct layer of rough and easily separable cuticle.] f The common stream-trout swallows shell-fish, and also pretty large smooth stones, which serve as a kind of shell-breakers. X Viz., take some gillaroo-trout, male and female, and put them into water in which there are no trout, to see if they continue the same.* § [This Essay includes the greater part of two papers, one published with the title ' Experiments on Animals and Vegetables, with respect to the Power of pro- ducing Heat,' in the Philosophical Transactions, vol. lxv. (read June 22,1775) ; the other, 'On the Heat, &c, of Animals and Vegetables,' in the Philosophical Transactions, vol. lxviii. (read June 19, and Nov. 13, 1777.)] H [' Experiments and Observations in a heated Room,' by Charles Blagden, M.D., F.R.S., vol. lxv., p. 111.] a [They are considered to be varieties of the Salmo Fario, Linn., by the best modern naturalists: see Yarrell's • British Fishes,' vol. ii., p. 57.] 156 HUNTER ON THE ANIMAL CECONOMY. to possess of generating cold, induced me to look over my notes, containing some which I had made in the year 1766, indicating an opposite power in animals, whereby they are capable of resisting any external cold while alive, by generating within themselves a degree of heat sufficient to counteract it. Those experiments were not originally instituted with any expectation of the event which re- sulted from them, but for the purpose of satisfying myself whether an animal could retain life after being frozen, as has been confidently asserted both-of fishes and snakes. For that these, after being frozen, still retain so much of life as when thawed to resume their vital actions, is a fact so well attested that we are bound to believe it; and had my experiment succeeded, it was my intention to have tried the effects of freezing on living animals to a much greater degree than can ever happen accidentally. I mention these circumstances to account for what might other- wise be attributed to negligence and inattention, namely, the little nicety that was observed in measuring the precise degree of cold applied in the experiments. Accuracy in this particular was not aimed at, being of no consequence id the inquiry more immediately before me. The cold was first produced by means of ice and snow with sal ammoniac or sea-salt, to about the 10° of Fahrenheit's ther- mometer : ice was then mixed with spirit of nitre; but what degree of cold was thus produced I did not examine. This cold mixture was made in a tub surrounded with woollen cloths, and covered with the same, to prevent the effects of the heat of the atmosphere upon the mixture itself, and to preserve, as much as possible, a cold atmosphere within the vessel. Animal juices, as the blood, freeze at 25°, so that a piece of dead flesh could be frozen in an atmosphere cooled to that point. EXPERIMENTS. Experiment I. was made on two carp. These were put into a glass vessel with common river water, which was placed in the freezing mixture. The water not freezing fast enough, to hasten that effect as much cooled snow was added as to render the whole thick. The snow round the carp melting, we put in more fresh snow, which, melting also, was repeated several times, till we grew tired, and at last left them covered up in the yard to freeze by the joint operation of the surrounding mixture and the natural cold of the at- mosphere.* They were frozen at last, after having exhausted the whole powers of life in the production of heat. That this was really the case, could not be known tiil I had completed that part of the experiment for which the whole was begun, viz., the thawing of the * [This experiment is alluded to by Dr. Blagden, who observes, "The power of generating heat seems to attend life very universally. Not to mention other well-known experiments, Mr. Hunter found a carp preserve a coat of fluid water round him long after all the rest of the water in the vessel had been concealed bv a very strong freezing mixture."—Phil. Trans., lxv., p. 122.] S ON ANIMALS PRODUCING HEAT. 157 animals. It was done very gradually; but the animals did not, with flexibility, recover life ; and while in this cold, showed signs of great uneasiness by their violent motions. N.B. In some of these experiments, where air was made the conductor of the cold and heat, that the heat might be more readily carried offfrom the animal, a leaden vessel was used. It was small for the same reason ; and as it was necessary for the animal's respiration that the mouth of the vessel should communicate with the open air, it was made deep, that the cold of the atmosphere round the animal might not be diminished too quickly by the warmth of the open air, which would have spoiled it as a conductor. Experiment II. was upon a dormouse, the vessel in which it was confined being sunk in the cold mixture almost to its edge. The atmosphere round the animal soon cooled ; its breath froze as it came from the mouth ; a hoar-frost gathered on its whiskers, and on all the inside of the vessel, and the external points of the hair be- came covered with the same. While this was going on the animal showed signs of great uneasiness ; sometimes it would coil itself into a round form, to preserve its extremities and confine its heat; and finding that ineffectual, would then endeavour to make its escape.* Its motions became less violent by the sinking of the vital powers : its feet were at last frozen: but we were not able to keep up the cold a sufficient time to freeze the whole animal, the hair being so bad a conductor of heat that the consumption was not more than the animal powers were capable of supporting.! Experiment III. was made with another dormouse; and taught by the failure of the last experiment, I took care that the hair should not a second time be an obstruction to our success. Having, therefore, first made the animal wet all over, that its heat might be more rapidly carried off, it was put into a leaden vessel, and the whole placed in the cold mixture as before. The animal soon gave signs of feeling the cold, by repeated attempts to-make its escape; and the breath and water evaporating from its body being soon frozen, appeared like a hoar-frost on the sides of the vessel and on its whis- kers ; but while the vigour of life lasted it defied the approach of the cold. However, from the hair being wet, and thereby rendered a good conductor, there was a much greater consumption of heat than in the former experiment, which hastened on the diminution of the power of producing it. The animal dying, soon became stiff, and, upon being thawed, was found quite dead. Experiment IV. A toad being put into a vessel with water, at such a depth as not to cover its mouth, was placed in the mixture * This shows that cold carried to a great degree rather rouses than depresses the animal action : but it appears, from many circumstances and observations, that a certain degree of cold produces inactivity both in living and sensative principle, which will be further illustrated hereafter. | These experiments were made in presence of Dr. George Fordyce and Dr. Erwin, teacher of Chemistry at Glasgow, the latter of whom came in accidentally in the middle of our operations. 15 158 HUNTER ON THE ANIMAL CECONOMY. cooled to between 10° and 15°. The water froze so near to the body of the animal as quite to inclose it, but without destroying life; yet, though not frozen, it hardly ever recovered the use of its limbs. Experiment V. was with a snail, which froze very soon, in a cold between 10° and 13°. These two last experiments were made in the winter, when the living powers of the animals selected for the trial are very weak; they might have resisted the cold more strong- ly in the summer. Why the animals mentioned in the above ex- periments died before they were frozen, while those which are exposed to the atmosphere in very cold climates do not, is a point I shall not pretend to determine, not knowing the difference between the effects of a natural and an artificial cold. It may be accounted for by supposing that the natural cold in climates in which animals are found frozen is so intense as to produce congelation immediately, before the powers of life are exhausted; at least whether it is so or not is worthy of inquiry. It appears from the above experiments, first, That most proba- bly the animals were deprived of life before they were frozen; secondly, That there was an exertion or expense of animal power in resisting the effects of cold, proportioned to the necessity; thirdly, That this exertion was in proportion to the perfection of the animal and the natural heat proper to each species and to each age. This exertion might also perhaps depend in some degree on other cir- cumstances not hitherto observed; for from Experiments II. and III. upon dormice, I find that in the animals which are of a constitution to retain nearly the same heat in all temperatures of the air, it required the greatest cold I could produce to overcome this resisting power; while by Experiments IV. and V. on the toad and snail, whose natural heat is not always the same, but is altered very materially according to the external heat or cold, this power was exhausted in a degree of cold not exceeding 10° or 15°; and the snail being the most imperfect of the two, its powers of generating heat appeared to be much the weakest. That the imperfect animals will allow of a considerable variation in the temperature of heat and cold, is proved by the following ex- periments. The thermometer being at 45°, the ball was intro- duced by the mouth into the stomach of a frog, which had been exposed to the same cold. It rose to 49°. I then placed the frog in an atmosphere made warm by heated water, where I allowed it to stay twenty minutes; and upon introducing the thermometer into the stomach, it raised the quicksilver to 64°. To what decree the more imperfect animals are capable of being rendered hotter and colder at one time than another, I have not yet ascertained;* * [The snail (Cyclostomum thermale) which lives in the hot spring of Abano r ?nnSBpVt8 u°Ut wi£great activity, and propagates in water of tlietemperatore of 100° 1- ahrenheit. The Entozoa of warm-blooded animals become in a certain degree torpid in cold water, but revive and exhibit lively motions when placed in warm water of 95° Fahrenheit.] v ON ANIMALS PRODUCING HEAT. 159 but the torpidity of these animals in our winter is probably owing to the great change wrought in their temperature by the external heat and cold. The cold in their bodies is to such a degree as in a great measure to put a stop, while it lasts, to the vital functions: while in warmer climates no such effect is produced.* This variety (in the power of producing heat) not only takes place in animals of different orders, but in some degree in the same animal at different ages, even according to the different age of the parts in the same animal: a young animal requires more warmth than one full-grown ; and although an animal is equally old in all its original parts, yet, there are often new ones formed in consequence of disease; and we find that these new or young parts in animals are not so able to support life as the old, at least for some time: but as animals are of different ages, and the same animal is always growing older, and of course more and more perfect, they then be- come more capable of generating heat than when they were youngcr.f This, however, has its limitations, for after a certain period they again lose this power, and therefore require a less strongly conducting medium, or warm atmosphere. This power of generating heat seems to be a property in an animal while alive. In the more perfect animals it is to preserve a standard heat; and as they are most commonly in an atmosphere colder than themselves, they have most commonly occasion to exert it, and it is therefore a power only of opposition and resist- ance ; for it is not found to exert itself spontaneously and unpro- voked, but must always be excited by the energy of some external frigorific agent, or disease ; yet it is natural to such animals that this power should be called forth, as will be observed by and by. It does not depend on the motion of the blood, as some have sup- posed, because it likewise belongs to animals which have no circu- lation :J and the nose of a dog, which is always nearly of the same * [The Reptiles and many of the Invertebrate animals of tropical climates seek their hiding-places and fall into a state of lethargy during, the dry season, when the heat is most intense. A quadruped of Madagascar, the tenrec, which is nearly allied to our hedgehog, becomes lethargic at the dry season, when its in- sect food is inaccessible.] f [Young animals consume, in proportion, less oxygen than adults; conse- quently, a less proportion of carbonic acid is formed in the change of the arterial into the venous blood, and a less amount of heat is extricated. When exposed to cold they become torpid, lose their heat, and also their sensibility, in which latter circumstance, and in some other points, they differ considerably from the hybernaling animal in its state of lethargy.] X [An argument of this importance deserved to be stated with more circum- stance. Mr. Hunter does not say what the animals are which have no circu- lation. It is possible, however, that he was alluding to bees. But these insects we know enjoy a circulation, governed, as his own dissections show, by a dorsal heart. And insects manifest the power of generating heat above that of other invertebrate animals precisely in consequence of the greater activity of their loco- motive, respiratory, and sanguiferous functions. It is true, however, that mere motion of the blood is not a cause of animal heat, because the circulation goes on in the hybernaling animal when in its cold and lethargic state ; but the blood's motion is here inoperative as a cause of neat, because in torpidity no chemical 160 HUNTER ON THE ANIMAL CECONOMY. heat in all temperatures of the air, is well supplied with blood; al- though we must allow, where this power is greatest the circulation is the quickest. Neither can it be said to depend upon the nervous svstem, for it is found in animals that have no brain or nerves. However, it must be allowed that all that class which possess this power in the highest degree have the largest brain, although this power is not in the least in proportion to the quantity of brain in that class.f It is most probable that it arises from some other prin- ciple ; a principle so connected with life that it can, and does, act independently of circulation, sensation, and volition, and is that power which preserves and regulates the internal machine. This power of generating heat is in the highest perfection when the body is in health; and in many deviations from that state we find that its action is extremely uncertain and irregular, sometimes rising higher than the standard, and at other times falling much below it. Instances of this we have in different diseases, and even in the same disease, within very short intervals of time. A very remarkable one fell under my own observation, in a gentleman who was seized with an apoplectic fit; and while he lay insensible in bed, covered with blankets, I found that his whole body would, in an instant, become extremely cold in every part, continuing so for some time; and, as suddenly, would become extremely hot. While this was going on alternately there was no sensible altera- tion in his pulse for several hours.J. Being satisfied of the foregoing fact, that animals had a power of generating heat, I pursued the subject still further; not so much with a view to account for animal heat, as to observe the different phenomena, with the variations or difference in the heat in different change takes place in the blood during its passage through the capillaries, either of the systemic or pulmonic systems of vessels; it is only venous blood that is moving.] * [The temperature of the nose of a dog is lowered by the constant evaporation of the moisture excreted from its surface; when this secretion is checked in con- sequence of internal disease, then the nose soon grows hot; and the dryness and heat of this part, both in the dog and other animals, form a common symptom of< loss of health, as we have frequently had occasion to observe in the animals in the Zoological Gardens.] f [Although, from the experiments on vegetables subsequently given, it appears that vital heat is not dependent on a nervous system ; yet it has been shown that the production of heat in warm-blooded animals is modified by the nervous in- fluence. See the Physiological Researches, ' On the Influence of the Brain on the action of the Heart, and on the generation of Animal Heat,' by B. C. Brodie, F.R.S., Phil. Trans., vol. ci., p. 36; vol. cii., p. 380; also the experiments of Home and Mayo, Phil. Trans., vol. cxv., p. 7; and by Legallois, Annates de Chimie,t. iv. 1817.] X [Here ends the first paper in the 65th vol. of the Phil. Trans. The second communication commences as follows : "In the course of a variety of experiments on animals and vegetables, I have frequently observed that the result of experi- ments in the one has explained the ceconomy of the other, and pointed out some principle common to both ; I have therefore collected some experiments which relate to the heat and cold of those substances;" and then proceeds as in the text.] ON ANIMALS PRODUCING HEAT. 161 animals. In the course of my experiments, having found varia- tions in the degree of heat and cold in the same experiment, for which I could not account, I suspected that this might arise from some imperfection in the construction of the thermometer. I men- tioned to Mr. Ramsden my objections to the common construction of that instrument, and my ideas of one more perfect in its nature, and better adapted to the experiments in which I was engaged. He accordingly made me some very small thermometers, six or seven inches long, not above two-twelfths of an inch thick in the stem, having the external diameter of the ball very little larger than that of the stem, on which was marked the freezing point. The stem was embraced by a small ivory scale, so as to slide upon it easily, and retain any position. Upon the hollow surface of this scale were marked the degrees, which were seen through the stem. By these means the size of the thermometer was very much reduced, and it could be applied to soft bodies with much more ease and certainty, and in many cases in which the former ones could not be conveniently used; I therefore repeated with it such of my former experiments as had not at first proved satisfactory, and found the degrees of heat very different, not only from what I had expected, but also from what I had found by my former experi- ments with thermometers of the common construction. I have observed above, and find it supported by every experi- ment I have made on the heat and cold of animals, that the more perfect have the greater power of retaining a certain degree of heat, wliich may be called their standard heat, and allow of much less variation than the more imperfect animals ; however, it will appear from the three experiments which I am now going to relate, that many, if not all of the more perfect, are still incapable of keeping constantly to one degree, but may be altered from their standard heat either by external applications or disease. These variations are much greater below that standard than above it, the perfect animals having a greater power of resisting heat than cold, so that ihey are commonly near their ultimate heat. Indeed we do not want any other proof of a variation than our own feelings, being all sensible of heat and of cold, which sensations could not be pro- duced without an alteration really taking place in the parts affected; and that alteration could not take place if they did not become actually warmer or colder. I have often cooled my hands to such a decree that I could warm them by immersing them in water just pumped; therefore my hands were really colder than the pump- water. An increase of absolute heat must alter the texture or position of the parts, so as to produce the sensation which we call heat: and as that heat is diminished, the texture or position of the parts is altered in a contrary way, and, when carried to a certain degree, becomes the cause of the sensation of cold. Now these effects could not take place in cither case without an increase or decrease of ab- solute heat in the part; heat, therefore, in some one of its different 15* 1C2 HUNTER ON THE ANIMAL CECONOMY. degrees, must be present. . I shall not in this place attempt to settle whether heat is a body or matter, or only a property of matter, which appears to me to be merely a difference in terms; for a properly must belong to something. When heat is applied to the surface of the body the skin becomes in some degree heated accord- ing to the application, which may be carried so far as actually to burn the living parts : on the contrary, in a cold atmosphere a man's hand may become so cold as to lose that sensation altogether, and change it for pain. Absolute heat and cold may be carried so far as even to alter the structure of the parts upon which the actions of life depend. As animals being subject to variations in the degrees of heat and cold from external applications are of course, in this respect, affected in some measure like inanimate matter; and therefore, as parts are elongated or recede from the common mass, these effects more readily take place ; for instance, all projecting parts and extremities, more especially toes, fingers, noses, ears, combs of fowls, particu- larly of the cock, are more readily cooled, and are therefore most subject to be affected by cold. Animals are not only subject to an increase and decrease of heat, similar to inanimate matter, but the transition from one to the other (as far as they admit of it) is nearly as quick. I shall not, however, confine myself to sensation alone, as that is in some degree regulated by habit; for a habit of uni- formity in the application of heat and cold to an animal body renders it more sensible of the smallest variation in either; while by the habit of variety it will become, in a proportional degree, less sus- ceptible of all such sensations. This is proved every day, in cold weather, by people who are accustomed to clothe themselves warm. In them the least exposure to cold air, although the effect produced in the skin is perhaps not the hundredth part of a degree, imme- diately gives the sensation of cold, even through the thickest cover- ing ; those, on the contrary, who have been used to go thinly clothed, can bear the variation of some degrees without being sen- sible of it; of this the hands and feet afford an instance in point, ex- citing the sensation of cold when applied to another part of the body, without having before given to the mind an impression of cold existing in these parts themselves. The projecting parts and the extremities are those which admit of the greatest change in their degrees of beat and cold without materially affecting the • animal or even its sensations. I find that by heat or cold externally applied to such parts, the thermometer may be made to rise or fall; but not in an equal proportion as when applied to inanimate matter. Nor are the living parts cooled or heated in the same proportion, as appears from the application of the thermometerto the skin ; for the cuticle is to be considered as a dead covering, capable of re- ceiving greater degrees of heat and cold than the living parts un- derneath ; and as it might be suspected that the whole of the varia- tion was in this covering, to remove anv such doubt I made the following experiments. ON ANIMALS PRODUCING HEAT. 163 Experiment I. I placed the ball of the thermometer under my tongue where it was perfectly covered by all the surrounding parts; and having kept it there for some minutes, I found that it rose to 97° : yet it rose no higher by being continued there. I then took several pieces of ice, about the size of walnuts, and put them in the same situation, allowing them only to melt in part, that the appli- cation of cold might be better kept up, occasionally spitting out the water arising from the solution. Having continued this for ten minutes, I found, on introducing my thermometer, that it fell to 77°; so that the mouth at this part had lost 20° of heat. The ther- mometer gradually rose to 97° again; but did not in this experi- ment sink so low as it would have done in the hand, if a piece of ice had been held in it for the same length of time. Perhaps the surface under the tongue being surrounded with warm parts renders it next to an impossibility to cool it below that degree; but I rather sus- pect that such parts as the hand will allow of greater latitude in this respect, from having insensibly acquired the habit of varying the degree of cold, and becoming of course less susceptible of its im- pressions, and therefore less easily excited. As a further proof that the more perfect animals are capable of varying their heat in some measure according to the external heat applied, I shall adduce the following experiments made on the human subject. The mouth being a part so frequently in contact with the external atmosphere in the action of breathing, whatever is put into it may be supposed to be influenced by that atmosphere; this will always render an experiment made in that part, relative to heat and cold, somewhat uncertain. I imagined that the urethra would answer better, because, being an internal cavity, it can only be influenced by heat and cold applied to the external skin of the parts. I imagined also that, whatever effects the application of heat and cold might have, they would sooner take place in the urethra, as being a projecting part, than in any other part of the body; and therefore, if living animal substance was in any degree subject to the common laws of matter in this respect, the urethra would be readily affected. To determine this 1 procured a person who allowed me to make such experiments as I thought necessary. Experiment II. I introduced the ball of my thermometer into the urethra about an inch ; which having remained there about a minute, the quicksilver rose to 92°; at two inches it rose to 93°; at four inches to 94°; and when the ball had got as far as the bulb of the urethra, where it was surrounded by warm parts, the quick- silver rose to 97°. Experiment III. These parts being immersed for one minute in water, heated only to 65°, and the thermometer introduced about an inch and a half into the urethra, the quicksilver rose to 69°; which was repeated several times with the same result. To discover if there were any difference in the quickness of the transition of heat and cold in living and dead parts, and to determine if the extent to 164 HUNTER ON THE ANIMAL CECONOMY. which each would go were likewise different, I procured a dead penis, for the purpose of making the comparative experiments that follow ; being clearly of opinion that all such trials should be as similar as possible, except in those points where the difference (if there is any) makes the essential part of the experiment. Experiment IV. The heat of the penis of a living person, an inch and a half within the urethra, being found exactly 92°; and the dead one being heated to the same degree, I had both immersed in the same vessel, with the water at 50°, when, by introducing the thermometers several different times, I was able to note the comparative quickness with which they cooled from 92°, and ob- served that the dead cooled sooner by two or three minutes ; the living sunk the quicksilver to 58°, and the dead to 50°: the ther- mometer, although continued there some time longer, fell no lower. I repeated this experiment several times, with the same result; although at one time there was a small difference in the degrees of heat of the penis and also of the water; but the difference in the result was nearly proportional in all the three different trials, there- fore the same conclusions may be drawn from them. In these last experiments very little difference was observed between the cool- ing of a dead and of a living part; a circumstance which we cannot suppose to take place uniformly through the whole body, as in that case living animals would always be of the same degree of heat with the atmosphere in which they live. The subject of these experiments not choosing to have the part cooled lower than 53° or 54°, prevented my observing if the powers of generating heat were exerted to a greater degree when the heat was brought so low as to threaten destruction; but by some experiments on mice, which will be related hereafter, it will appear that the ani- mal powers are roused to exert themselves in this respect when necessary. Having found, from the above experiments, that parts of an animal were capable of being cooled below the common or natural heat, I proceeded to make others, with a view to ascertain if the same parts were capable of being made much hotter than the standard heat of animals. The experiments were made in the same manner as the former, only the water was now hotter than the natural heat of the animal. Experiment V. The natural heat of the parts being 92°, they were immersed for two minutes in water heated to 113°, and, the thermometer being introduced as before, the quicksilver rose to 100° and a half. This experiment I also repeated several times, but could not raise the heat of the penis beyond IOO50: this was probably owing to the person not being able at the time to bear the application of water warmer than 113°. By was of compari- son, I made Experiment VI. The living and dead parts being both immersed in water, gradually made warmer and warmer from 100° to 118°, and continued in that heat for some minutes, the dead part raised' ON ANIMALS PRODUCING HEAT. 165 the thermometer to 114°, while the living raised it no higher than 102$°. It was observed, by the person on whom the experiment was made, that after the parts had been in the water about a minute, the water did not feel hot, but on its being agitated it felt so hot that he could hardly bear it. Upon applying the thermometer to the sides of the living glans, the quicksilver immediately fell from 118° to about 104°, while it did not fall more than a degree when put close to the dead ; so that the living glans cooled the sur- rounding water to a certain distance.* Experiment VII. The heat of the rectum in the same man was 98° and a half exactly. In the second, third, fourth, fifth, and sixth experiments, an in- ternal cavity, which is both very vascular and sensible, was evidently influenced by external heat and cold, though only applied to the skin of the part; while in the seventh experiment another part of the same body, where external heat and cold could make little or no impression, was of the standard heat. Although it will appear, from experiment, that the rectum is not the warmest part of an animal, yet, in order to determine how far the heat could be increased by stimulating the constitution to a degree sufficient to quicken the pulse, I repeated the seventh experiment after the man had eaten a hearty supper and drank a bottle of wine, which in- creased the pulse from 73° to 87°, and yet the thermometer only rose to 98° and a half. Having formerly made experiments upon dormice during the sleeping season, with a view to see if there were any alteration in the animal ceconomy at that time, I found among my notes an ac- count of some which appear to our present purpose; but to be more certain of the accuracy of the former experiments, I repeated them with my new thermometer. Experiment VIII. In a room, in which the temperature of the air was between 50° and 60°, a small opening was made in the belly of a dormouse, of a sufficient size to admit the ball of my thermometer, which, being introduced into the belly at about the middle of that cavity, rose to 80°, and no higher. Experiment IX. The mouse was put into a cold atmosphere of 15° above 0, and left there for fifteen minutes; after which, the thermometer being introduced a second time, it rose to 85°. Experiment X. The mouse was again put into a cold atmosphere for fifteen minutes; and the thermometer being introduced, the quicksilver at first rose to 72° only, but graduallv came up to 83°, 84°, and 85°. Experiment XI. It was put a third time into the cold atmosphere, and allowed to stay there for thirty minutes: the lower part of the * This might furnish an useful hint respecting bathing in water, whether colder or warmer than the heat of the body : for if intended to be either colder or hotter, it will soon be of the same temperature with that of the body; therefore in a large bath the patient should move from place to place, and in a small one there should be a constant succession of water of the intended heat. 166 HUNTER ON THE ANIMAL CECONOMY. mouse, at the bottom of the dish, was almost frozen; the whole of the animal was numbed, and a good deal weakened. The ther- mometer being introduced, the heat was found to vary in different parts of the belly: in the pelvis, near the parts most exposed to the cold, it was as low as 62°; in the middle, among the intestines, about 70°; but near the diaphragm it rose to 80°, 82°, 84°, and 85°; so that in the middle of the body the heat had decreased 10u. Finding a variation in different parts of the same cavity in the same animal, I repeated the same experiments upon another dormouse. Experiment XII. Having brought a healthy dormouse, which had been asleep from the coldness of the atmosphere, into a room in which there was a fire (the atmosphere at 64°), I introduced the thermometer into its belly, nearly at the middle, between the thorax and pubis, and the quicksilver rose to 74° or 75°; turning the ball towards the diaphragm, it rose to 80°; and when I applied it to the liver, it rose to 81\°. Experiment XIII. The mouse being placed in an atmosphere at 20°, and left there half an hour, when taken out was very lively, even much more so than when put in. Introducing the thermometer into the lower part of the belly, the quicksilver rose to 91°; and upon turning it up to the liver to 93°. Experiment XIV. The animal being replaced in the cold atmo- sphere at 30° for an hour, the thermometer was again introduced into the belly; at the liver it rose to 93°; in the pelvis to 92°; the mouse continuing very lively. Experiment XV. It was again put back into an atmosphere, cooled to 19°, and left there an hour; the thermometer at the diaphragm was 87° ; in the pelvis 83°; but the animal was now less lively. Experiment XVI. Having been put into its cage, the thermo- meter being placed at the diaphragm, in two hours afterwards was at 93°. As I was unable to procure hedgehogs in the torpid state, to ascertain their heat during that period, I got my friend Mr. Jenner,* surgeon, at Berkeley, to make the same experiments on that animal, that I might compare them with those in the dormouse; and his account is as follows : " Experiment I. In the winter, the atmosphere at 44°, the heat of a torpid hedgehog, in the pelvis, was 45°, and at the diaphragm 48£°. "Experiment II. The atmosphere 26°, the heat of a torpid hedgehog, in the cavity of the abdomen, was reduced so low as 30°. " Experiment III. The same hedgehog was exposed to the cold atmosphere of 26° for two days, and the heat of the rectum was found to be 93°; the wound in the abdomen being now so small that it would not admit the thermometer. • [Afterwards Dr. Jenner, the discoverer of Vaccination.] ON ANIMALS PRODUCING HEAT. l(J7 " A comparative experiment was made with a puppy, the at- mosphere at 50°; the heat in the pelvis, as also at the diaphragm, was 102°. " In summer, the atmosphere at 78°, the heat of the hedgehog, in an active state, in the cavity of the abdomen, towards the pelvis, was 95°; at the diaphragm 97°." We find from these experiments, that the heat of the animal is increased under the circumstances of cold, whenever there are actions to be carried on for which heat is necessary. In the experiments on the first dormouse the heat of the animal was 80°, which is below the standard heat of the actions of that animal; and after being put into the cold mixture its heat was raised to 85°. In the second dormouse the heat was raised, by repeated experiments, from 75° to 93°. This question naturally occurs here : Was the increase of heat in the animals generated to resist the artificial cold produced by placing them in a cold atmo- sphere ? or was it owing to a wound having been made into the cavity of the abdomen, and an exertion of the animal powers being required to repair the injury, which exertion could not take place without the increased degree of heat 1 That it was in consequence of the wound, appears evident from the experiment made upon the second hedgehog; for in an atmosphere of 26° of heat it was in a very torpid state, and did not raise the thermometer higher than 30°; but after being wounded and put back into the cold, and kept there for two days, its heat in the rectum was 93°, and so far from being torpid, it was lively, and the bed in which it lay felt warm.* Why the heat of the dormouse should be so low as 80°, in an atmosphere of between 50° and 60°, is not easily accounted for, except as the effect of sleep. But I should very much suspect that sleep, simply considered, is out of the question, it being an effect that takes place in all degrees of heat and cold. In animals whose voluntary actions are suspended by cold, that appears to produce its effect by acting in a certain degree as a sedative, in consequence of which the animal faculties are proportionably weakened, though they still retain, even under such circumstances, the power of carrying on all the functions of life. Beyond this point cold seems to act as a stimulant, and rouses the animal powers to action for self-preservation. It is more than probable that most animals are in this predicament, and that there is a degree of cold corresponding with every particular order of animals, by which, when applied, the voluntary actions must be suspended. When a man is asleep he is colder than when awake; and I find in general that the difference is about one degree and a half; some- times less. But this difference in the degree of cold between sleep- ing and waking is not a cause of sleep, but an effect; for many diseases produce a much greater degree of cold in the animal * It is found, from experiments, that the heat of an inflamed part is nearly the greatest or standard heat of the animal, it appearing to be a part of the process of inflammation to raise the heat up to the standard. 168 HUNTER ON THE ANIMAL CECONOMY. without giving the least tendency to sleep ; therefore the inactivity of animals from cold must be different from sleep. Besides all the operations of perfect life, as digestion, sensation, &c, are going on in the time of natural sleep, at least in the perfect animals; but none of these operations are performed in the torpid state of animals.* To see if the result of these experiments upon dormice was pe- culiar to that species, I wished to repeat the same experiments upon common mice, for which purpose, in Experiment XVII. I made use of one strong and vigorous; and the atmosphere being at 60°, I introduced the thermometer into the abdomen ; the ball being at the diaphragm the quicksilver was raised to 90°, but at the pelvis only to 961°. Here there was a real difference of about 9° between the dor- mouse and the common, the dormouse only raising it to 80°, in two animals of the same size, in some degree of the same genus, and at the same season of the year, and the atmosphere of nearly the same temperature. Experiment XVIII. The same mouse was put into a cold atmo- sphere of 13° for an hour, and then the thermometer was introduced as before; but the animal had lost heat, for the quicksilver at the diaphragm was raised only to 83°, in the pelvis to 78°. Here the real heat of the animal was diminished 16° at the dia- phragm, and 18° in the pelvis, while in the dormouse it gained 5°, but lost upon a repetition. Experiment XIX. In order to determine whether an animal that is weakened has the same powers, with respect to preserving heat and cold, as one that is vigorous and strong, I weakened a mouse * [Some recent experiments of Dr. Marshall Hall confirm the accuracy of the distinction here drawn between sleep and torpidity, and also show that the ordinary sleep of hybernating warm-blooded animals differs from that of non- hybernating species, by inducing a more impaired state of the respiration, and a diminution of the power of evolving of heat. Although a consciousness or sen- sibility be lost, automatic susceptibility of impressions is remarkably perfect during torpidity. Dr. Hall states that the slightest touch applied to one of the spines of the torpid hedgehog immediately rouses it to draw a deep sonorous inspiration, which is its characteristic response to such disturbance while in that state. The merest shake induces few respirations in the hybernating bat. (Phil. Trans., 1832, p. 15.) So also with respect to circulation, this vital operation appears to be performed uninterruptedly, though slowly, during hybernation. M. Prunelle {Annates du Museum, torn, xviii., p. 28), found that the pulsations of the heart of a bat, which, while it is awake and active amount to 200 in a minute, are reduced to 50 or 55 when it is torpid. Dr. M. Hall, who succeeded, by an ingenious contrivance, in subjecting the wing of a torpid bat to microscopi- cal examination, found the circulation to be slow in the minute arteries and veins; but the beat of the heart was regular, and generally about twenty-eight times in a minute. {Ibid. p. 17.) The blood which is thus circulated is venous, the respi- ration being nearly, if not totally, suspended; and its propulsion in this state is explained on the augmented irritability of the muscular system, which is mani- fested by the double heart of the torpid mammal being stimulated to contract by carbonized blood, like the heart of the cold-blooded and slow-breathing batrachian reptile.] ON ANIMALS PRODUCING HEAT. 169 by fasting, and then introduced the ball of the thermometer into its belly ; the ball being at the diaphragm, the quicksilver rose to 97°; in the pelvis to 95°, being two degrees colder than the strong mouse. The.mouse being put into an atmosphere as cold as the other, and the thermometer again introduced, the quicksilver stood at 79° at the diaphragm, and 74° in the pelvis. In this experiment the heat at the diaphragm was diminished 18°, in the pelvis 21°. This greater diminution of heat in the second than in the first we may suppose proportional to the decreased power of the animal, arising from want of food. To determine how far different partsof other animals than those already mentioned were of different degrees of heat, I made the following experiments upon a healthy dog. Experiment XX. The ball of the thermometer being introduced two inches within the rectum, the quicksilver rose to lOOi0. The chest of the dog was then opened, and a wound made intQ the right ventricle of the heart; and immediately on the ball being introduced, the quicksilver rose to 101° exactly. A wound was next made some way into the substance of the liver, and the ball being intro- duced, the quicksilver rose to 1001°. It was next introduced into the cavity of the stomach, where it stood exactly at 101°. All these experiments were made within a few minutes. Experiment XXI. The thermometer was introduced into the rectum of an ox, and the quicksilver rose exactly to 99£°. Experiment XXII. This was also repeated upon a rabbit, and the quicksilver rose to 995°. From experiments on mice and upon the dog, it plainly appears that every part of an animal is not of the same degree of Jheat; and hence we may reasonably infer, that the heat of the vital parts of man is greater than either the mouth, rectum, or the urethra. To determine how far my idea was just, that the heat of animals varied in proportion to their degree of perfection, I made the fol- lowing experiments upon fowls, which I considered as one remove below what are commonly called quadrupeds. Experiment XXIII. I introduced the ball of the thermometer successively into the intestinum rectum of several hens, and found that the quicksilver rose as high as 103°, 103£°, and in one of them to 104°. Experiment XXIV. I made the same experiments on several cocks, and the result was the same. Experiment XXV. To determine if the heat of the hen was in- creased when she was prepared for incubation, I repeated the twenty-third experiment upon several sitting or clucking hens; in one the quicksilver rose to 104°, in another to 103$°, in a third to 103°, as in the twenty-third experiment. Experiment XXVI. I placed the ball of the thermometer under 16 170 HUNTER ON THE ANIMAL CECONOMY. the same hen, in whose rectum the quicksilver was raised to 101 , and found the heat as great as in the rectum. Experiment XXVII. Having taken some of the eggs from under the same hen, where the chick was about three parts formed, I broke a hole in the shell, and, introducing the ball of the ther. mometer, found that the quicksilver rose to 99£°. In some that were addled I found the heat not so high by two degrees; so that the life in the living egg assisted in some degree to support its own heat. Is the increase of three or four degrees of heat, which is the dif- ference found between the fowl and the quadruped, for the purpose of incubation 1 The heat in the eggs, which was caused and sup- ported by that of the fowls, was not above the standard of the quadrupeds ; and it would probably have been less if the heat of the hen had not been so great. Finding, from the above experiments, that fowls were some degrees warmer than that class commonly called quadrupeds (although certainly less perfect animals), I chose to continue the experiments upon the same principle, and made the following upon those of a still inferior order. The next remove from the fowl being what is commonly called the Amphibia. Experiment XXVIII. I introduced the thermometer into the stomach, and afterwards into the anus of a healthy viper, and the quicksilver rose from 58° (the heat of the atmosphere in which it was) to 68°; so that it was ten degrees warmer than the common atmosphere.* Experiment XXIX. Having ascertained the heat of the water in a pond, in which there were carp, to be 65§°, I took a carp out of this water, and having introduced the thermometer into its stomach, the quicksilver rose to 69°; so that the difference between the water and the fish was only 35°.f Experiment XXX. The heat of the atmosphere at 56; some earthworms were put into a glass vessel, and a thermometer being immersed among them, the quicksilver stood at 585°. This experiment was repeated ; the atmosphere at 55° : and the worms were found to be 57°. Experiment XXXI. The atmosphere at 54°; four black slugs * [The observations of Czermaek correspond with the above experiment. He found that the difference between the temperature of the animal and that of the surrounding medium was greater in serpents and lizards than in other reptiles. The temperature of a turtle {Chelonia Mydas) was 82° when the surrounding atmosphere was 84°. That of a frog was 48° when the surrounding water was 44°. That of a Proteus was 64°, the surrounding water being 56°.] f [Certain saltwater fishes, as the bonito and thunny, which have the gills supplied with nerves of unusual magnitude, and therefore probably enjoy a more energetic respiration, which have also a very powerful heart, and the quantity of red blood such as to give the muscles a dark red colour, manifest a higher degree of temperature than the white fishes of fresh water, on which Mr. Hunter experi- mented. Dr. John Davy found that the bonito had a temperature of 99° Fahren- heit when the surrounding medium was 80°.5. See Philos. Trans., 1835.] ON ANIMALS PRODUCING HEAT. 171 were put into a small vessel, and a thermometer immersed among them stood at 55i°. Experiment XXXII. The atmosphere at 56°; three leeches were put into a small glass vessel, and a thermometer immersed among them stood at 57°. This experiment was repeated ; the atmosphere at 54°; when the thermometer stood at 55^°. To see how far the colder animals had a power of preserving their standard heat when exposed to severe cold, I made the fol- lowing experiments. Experiment XXXIII. A viper, whose heat was 68°, was put into a pan, and the pan into a cold mixture of about 10°; after remain- ing there about ten minutes had its heat reduced to 37°. Being allowed to stay ten minutes longer, the mixture at 13°, its heat was reduced to 35.° It was continued ten minutes more in the mixture at 20, and its heat was reduced to 31°; nor did it sink lower, its tail beginning to freeze, and the animal now becoming very weak. It may be remarked, that it cooled much slower than many of the animals mentioned in the following experiments. The frog being in its structure more similar to the viper than to either the fowl or fish, I made the following experiments on that animal. Experiment XXXIV. I introduced the ball of the thermometer into its stomach, and the quicksilver stood at 44°. I then put the frog into a cold mixture, and the quicksilver sunk to 31°; the animal appeared almost dead, but recovered very soon: beyond this point it was not possible to lessen the heat without destroying the animal. But its decrease of heat was quicker than in the viper, although the mixture was nearly the same. The next experiments were made on fishes. Experiment XXXV. In an eel, the heat in the stomach, which at first was at 37°, sunk, after it had been some time in the cold mixture, to 31°. The animal at that time appeared dead, but was found to be alive the next day. Experiment XXXVI. In a snail, whose heat was at 44°, it sunk, after it had been put into the cold mixture, to 31°, and then the animal froze. Experiment XXXVII. Several leeches having been put into a bottle, and the bottle immersed in the cold mixture, the ball of the thermometer being placed in- the middle of them, the quicksilver sunk to 31°; and by continuing the immersion for a sufficient time to destroy life, the quicksilver rose to 32°, and then the leeches froze. In all these experiments the animals when thawed were found dead. Finding that animals of the imperfect classes will, without life being totally extinguished, admit of their heat being reduced to that point at which the dead solids and fluids freeze, but if sunk much below that, death must be the consequence, I wished therefore to be able to determine to what degree the heat of the animal could be raised. 172 HUNTER ON THE ANIMAL CECONOMY. Experiment XXXVIII. A healthy viper was placed in an atmo- sphere heated to 108°, and allowed to stay seven minutes; when the heat of the animal in the stomach and anus was found to be 92£°; beyond which it could not be raised in the above state of the atmosphere. The same experiment was made upon frogs, with nearly the same result. Experiment XXXIX. An eel, very weak, its heat at 44°, which was nearly that of the atmosphere, was put into water heated to 65°, for fifteen minutes; and, upon examination, it was found of the same degree of heat with the water. Experiment XL. A tench, whose heat was 41°, was put into water at 65°, and left there ten minutes; the ball of the thermome- ter being introduced both into the stomach and rectum, the quick- silver rose to 55°. These experiments were repeated with nearly the same result. To determine whether life had any power of resisting heat and cold in inferior classes of animals, I made comparative trials between living and dead ones. Experiment XL1. 1 took a living and a dead tench, and a living and a dead eel, and put them into warm water; they all received heat equally fast: and when they were exposed to cold, both the living and the dead admitted the cold likewise with equal quickness. I had long suspected that the principle of life was not wholly confined to animals, or animal substance endowed with visible organization and spontaneous motion; but supposed that the same principle might exist in animal substances, devoid of apparent organization and motion, when the power of preservation was simply required. I was led to this opinion about twenty years ago, when busied in making drawings of the growth of the chick in the process of incu- bation. I then observed, that whenever an egg was hatched, the yolk (which is not diminished in the time of incubation) was always perfectly sweet to the very last; and that the part of the albumen, which has not been expended on the growth of the animal, some days before hatching, was also perfectly sweet, although both were kept in a heat of 103° in the hen's egg for three weeks, and in the duck's for four; but I observed that if an egg was not hatched, that egg became putrid in nearly the same time with any other dead animal matter. To*, determine from other tests how far eggs possessed a living principle, I made the following experiments. Experiment XLII. After having placed an egg in a cold about 0, till it froze, I allowed it to thaw; by which process it was to be supposed the preserving powers of the egg must be destroyed. I then put this egg into the cold mixture, and with it one newly laid, and found the difference in freezing was seven minutes and a half, the fresh one so much longer time resisting the powers of cold. Experiment XLIII. A new laid egg being put into a cold atmo- ON ANIMALS PRODUCING HEAT. 173 sphere, fluctuating between 17° and 15°, took above half an hour to freeze; but when thawed and put into an atmosphere at 25°, it froze in half the time. This experiment was repeated frequently with nearly the same result. To ascertain the comparative degree of heat between a living and a dead egg, and also to determine whether a living egg be subject to the same laws with the more imperfect animals, I made the following experiments. Experiment XLIV. A fresh egg, and one which had been frozen and thawed, were put into the cold mixture at 15°: the thawed one soon came to 32°, and began to swell and congeal; the fresh one sunk to 29£°, and in twenty-five minutes later than the dead one it rose to 32°, and began to swell and freeze. In this experiment the effect on the fresh egg was similar to that produced on the frog, eel, snail, &c, where life allowing the heat to be diminished two or three degrees below the freezing point, afterwards resisted all further decrease; but the powers of life being expended by this exertion, the parts froze like any other dead animal matter. From these experiments it appears that a fresh egg has the power of resisting heat, cold, and putrefaction in a degree equal to many of the more imperfect animals; and it is more than probable this power arises from the same principle in both. From the circumstance of those imperfect animals (upon which I made my experiments) varying their heat so readily, we may conclude that heat is not so very essential to life in them as in the more perfect; although it be essential to many of the operations, or what may be called the secondary actions of life, such as digesting food* and propagating the species, both which, especially the last, requiring the greatest powers an animal can exert. The animals which we call imperfect being chiefly employed in the act of digestion, we may suppose their degree of heat to be only what that action requires ; it not being essentially necessary for the life of the animal that heat should ever rise so high in them as to call forth the powers necessary for the propagation of the species, f When- * How far this idea holds good with fishes, I am not certain. f The hedgehog may be called a truly torpid animal; and we find that its actual heat is diminished when the actions are not vigorous." From a general a [The experiments by which this important fact was established are those numbered I. and II., page 166. They were made after the publication of the original memoir in the Philosophical Transactions, in which the note consequently commences thus: " How far the animal heat is lowered in the more perfect animals, when these secondary actions are not necessary, as in the bat, hedgehog, bear, &c, I have not been able to determine, not having the opportunities of ex- amining these animals. Dormice are in a mixed state, between the voluntary, and involuntary, and we find the heat diminished when the actions are not vigor- ous; and, from a general review of this whole subject, it would appear that a certain degree of heat in the animal is necessary for digestion, and that necessary heat will be according to the nature of the animal."—Phil. Trans. 1778, p. 91. 16* 174 HUNTER ON THE ANIMAL CECONOMY. ever therefore these imperfect animals are exposed to a cold so great as to weaken their powers, and'disable them from performing the first of these secondary actions, they in some measure cease to be voluntary agents, and remain in a torpid state during that extreme degree of cold which always occurs during some part of the winter in the countries they inhabit; and the food of such animals not being in general produced in the cold season is a reason why this torpidity becomes in some measure necessary.* From the heat of such animals sinking to the freezing point, or even lower, and then becoming stationary, and the animal not being able to support life in a much greater degree of cold for any length of time, we see a reason why they should always endeavour to procure places of abode in the winter where the cold seldom sinks to that point. We find toads burrowing, frogs living under large stones, snails seeking shelter under stones and in holes, and fishes having recourse to deep water; the heat of all those places being generally above the freezing point even in our hardest frosts; which are however sometimes so severe as to kill many whose habitations are not well chosen. When the. frost is more intense and of longer standing than common, or in countries where the winters are always severe, there is generally snow on the ground, and the water freezes: the advantage arising from these two circumstances is great; the snow serving as a blanket to the earth, and the ice to the water, f review of this whole subject it would appear that a certain degree of heat in the animal is necessary for its various ceconomical operations, among which is di- gestion ; and that necessary heat will be according to the nature of the animal, and, probably, the nature of the operations to be performed. A frog will digest food when its heat is at 60°, but not when at 35° or 40° ; and it is very probable that, when the heat of the bear, hedgehog, dormouse, bat, &c, is reduced to 70°, 75°, or 80°, they lose their power of digestion; or rather that the body, in such a degree of cold, has no call upon the stomach. That animals in a certain degree of heat must always have food is further illustrated by the instance of bees. The construction of a bee is very similar to that of a fly, a wasp, &c. A fly and a wasp can allow their heat to diminish, as in the fish, snake, &c, without losing life, but a bee cannot; therefore a bee is obliged to keep up its heat as high as what we call its digestive heat, but not its propagating; for which purpose they provide against such cold as would deprive them even of their digestive heat, if they had not food to preserve it. * The torpidity induced by cold in hybernating animals is unlike that which is similarly induced in non-hybernating animals; in the former it is an action of preservation, in the latter one of destruction. See the paper before quoted, by Dr. Marshall Hall.] f Snow and ice are perhaps the worst conductors of heat of any substance yet known. In the first place, they never allow their own heat to rise above the freezing point, so that no heat can pass through ice or snow when at 32°, by which means they become an absolute barrier to all heat that is at or above that degree; hence the heat of the earth, or whatever substance they cover, is retained ; but they are conductors of heat below 32°. Perhaps that power decreases in pro- portion as the heat decreases under that point. In the winter 177G, a frost coming on, the surface of the ground was frozen ; but a considerable fall of snow fell, and continued several weeks : the heat of the atmosphere during the time was often at 15°; but so little did the frost affect the ON ANIMALS PRODUCING HEAT. 175 As all the experiments I ever made upon the freezing of animals (with a view to see if it were possible to restore the actions of life when thawed) were tried upon whole ones; as I never saw life return by thawing,* and wished to see how far parts were similar to the whole in this respect, it being asserted, and with some authority, that parts of a man may be frozen, and afterwards recover,—I made, for this purpose the following experiments upon an animal of the same class as ourselves. In January 1777, I mixed salt and ice till the cold was about 0; in the side of the vessel was a hole, through which I introduced the ear of a rabbit; and, to carry off the heat as fast as possible, it was held between two flat pieces of iron that went further into the mixture. That part of the ear projecting into the vessel became stiff, and when cut did not bleed ; the part divided by the scissors flying from between the blades like a hard chip. The ear having remained in the mixture nearly an hour, soon thawed when taken out, began to bleed, and became so very flaccid, as to double upon itself, from losing its natural elasticity. When out of the mixture nearly an hour, it became warm: and this warmth increasing to a considerable degree, it also began to thicken, in consequence of inflammation, while the other ear con- tinued in its usual degree of cold. The day following the frozen ear was still warm; and even two days after retained its heat and thickness, which continued for many days after. About a week after this, the mixture being the same as in the former experiment, I introduced the ears of the same rabbit through the hole, and froze them both: the sound one however froze first probably from its being considerably colder at the beginning. When withdrawn they soon thawed, both soon became warm, and the fresh ear thickened as the other had done before. Such a change in the parts does not always take place so quickly; ground underneath that the surface of the ground thawed, and the earth retained the heat of 34°, in which beans and peas will grow. The same thing took place in a pond where the water was frozen on the sur- face to a considerable thickness: a large quantityof snow having fallen, and co- vered the ice, the heat of the water was preserved ; the ice thawed, and the snow, at its under surface, was found mixed with the water. The heat of the water under the snow was at 35°, in which fishes lived very well. It would be an attempt worthy the attention of the public philosopher to investigate the cause of the heat of the earth, upon what principle it is pre- served, &c. * Vide Phil. Trans, for the year 1775, vol. lxv. part ii. p. 446.a a That animals, lower in in the scale than any which Hunter experimented on with this view, may, after having been frozen, recover life by thawing, is rendered at least highly probable from the following statement by Rudolphi. In his description of the Filaria capsularia, he observes, " Vermis vitae satis tenax est, ut per octiduum in frigida conservaverim, et Filarias in Harengis congelatis rigidas et glacie tectas frigida affusa reviviscere viderim." (Hist. Entoz., vol. ii., p. 62. 176 HUNTER ON THE ANIMAL CECONOMY. for on repeating the experiment on the ear of another rabbit till it became as hard as a board, it was found to be longer in thawing than in the former experiment, and much longer before it became warm ; in two hours, however, it had acquired some degree of warmth, and on the day following was hot and thickened. In the spring, 1776, I perceived that my cocks in the country had their combs smooth, with an even edge, and not so broad as formerly, appearing as if near one half of them bad been cut off. Having inquired into the cause of this, my servant told me that it had happened in that winter during the hard frost, he having then observed that the combs had in part dropped off, also that the comb of one cock had entirely separated: but this I did not see as by ac- cident he was burnt to death. I naturally imputed this effect to the combs having been frozen to so great a degree during the severe weather as to have the life of the part destroyed. To determine, therefore, by experiment, the solidity of this reasoning, I made the following experiment. I selected for the purpose a very large young cock, having a comb of considerable breadth, with deep serrated edges, the processes of which were full half an inch long. My attempts to freeze the sub- stance of the comb did not succeed ; for that, being thick and warm, resisted the effects of the cold, and only the serrated edges were frozen. The frozen parts became white and hard, and when I cut off a little bit did not bleed, nor did the animal show any signs of pain. I next immersed in the cold mixture one of his wattles, which was very broad and thin ; it froze very readily ; and upon thawing both the comb and wattle they became warm, but of a purple colour, having lost that transparency which remained in the other parts of the comb and in the other wattle. The wound in the comb now bled freely. Both comb and wattle recovered perfectly in about a month. The natural colour returned first nearest to the sound parts, in- creasing gradually till the whole had acquired a healthy appearance. There was a very material difference in the effect between those fowls, the serrated edges pf whose combs I suspected to have been frozen in the winter of 1775-6, for they must have dropped off. The only way in which I can account for this difference is, that in those fowls the parts were kept so long frozen that the unfrozen or active parts had time to inflame, and had brought about a separa- tion of the frozen parts, treating them exactly as dead, similar to a mortified part: and that before they thawed, the separation was so far completed as to deprive them of further support. As it is confidently asserted that fishes are often frozen, and again return to motion, and as I had never succeeded in any of my trials of the kind upon whole fishes, I made some experiments upon par- ticular parts, to which I was led by having found a material dif- ference in the result of experiments made upon the whole, and on parts of the more perfect animals. I froze the tail of a tench, as high as the anus, which became as ON THE HEAT OF VEGETABLES. 177 hard as a board : when thawed, that part was whiter than common ; and when it moved, the whole tail moved as one piece, and the ter- mination of the frozen part appeared like the joint on which it moved. On the same day I froze the tails of two gold fishes till they be- came as solid as a piece of wood. They were put into cold water to thaw, and appeared for some days to be very well; but that part of the tails which had been frozen had not the natural colour, and the fins of the tails became ragged. About three weeks after, a fur came all over the frozen parts; their tails became lighter, so that the fishes were suspended in the water perpendicularly; they had almost lost the power of motion ; and at last died. The water in which they were kept was New River water, shifted every day, and in quantity about ten gallons. I made similar experiments upon an order of animals still inferior, viz. common earth-worms. I first froze the whole of an earth-worm as a standard; when thawed it was perfectly dead. I then froze the anterior half of another earth-worm; but the whole died. I next froze the posterior half of an earth-worm; the anterior half continued alive, and separated itself from the dead part. From some of these experiments it appears that the more imper- fect animals are capable of having their heat and cold varied very considerably, but not according to the degree of heat or cold of the surrounding medium in which they can support life; for they can live in a cold considerably below the freezing point, and yet the living powers of the animal will not allow their heat to be diminished much beyond 32°. Whenever the surrounding cold brings them so low, the power of generating heat takes place; and if the cold is continued, the animals exert this power till life is destroyed; after which they freeze, and are immediately capable of admitting any degree of cold. 15. EXPERIMENTS AND OBSERVATIONS ON VEGE- TABLES, WITH RESPECT TO THE POWER OF PRODUCING HEAT.- To ascertain whether vegetables could be frozen, and afterwards retain all their properties when thawed, or had the same power of generating heat with animals, I made several experiments. Vege- table juices when squeezed out of a green plant, such as cabbage and spinage, froze in a cold of about 29°; and between 29° and 30° * [This paper includes those portions of the two communications to the Royal Society, On the Heat of Animals and Vegetables, which were omitted by Hunter in the ' Animal CEconomy.' See Phil. Trans., lxv., 1785, p. 450.] 178 HUNTER ON THE ANIMAL CECONOMY. thawed again, which is about 4° above the point at which the animal juices freeze and thaw. Experiment I. I took a young growing bean, about three inches long in the stalk, and put "it into the leaden vessel with common water, and then immersed the whole into the cold mixture. The water very soon froze all around it; however, the bean itself took up a longer time in freezing than the same quantity of water would have done; yet it did freeze, and was afterwards thawed and planted in the ground, but it soon withered. The same experi- ment was made upon the bulbous roots of tulips, and with the same success. Experiment II. A young Scotch fir, which had two complete shoots and a third growing, and which consequently was in its third year, was put into the cold mixture, which was between 15° and 17°. The last shoot froze with great difficulty, which appeared to be owing in some measure to the repulsion between the plant and the water. When thawed the young shoot was found flaccid. It was planted; the first and second shoot we found retained life, while the third, or growing shoot, withered. Experiment III. A young shoot of growing oats, with three leaves, had one of the leaves put into the cold mixture at 22°, and it soon was frozen. The roots were next put in, but did not freeze; and when put into the ground the whole grew, excepting the leaf which had been frozen. The same experiment was made upon the leaves and roots of a young bean, and attended with the same success. Experiment IV. A leaf taken from a growing bean was put into the cold mixture and frozen, and afterwards thawed, which'served as a standard. Another fresh leaf was taken and bent in the middle upon itself; a small shallow leaden vessel was put upon the top of the cold mixture, and the two leaves put upon its bottom; but one half of each leaf was not allowed to touch the vessel by the bend: the cold mixture was between 17° and 15°, and the atmo- sphere at 22°. The surfaces of the two leaves which were in con- tact with the lead were soon frozen in both; but those surfaces which rose at right angles, and were therefore only in contact with the cold atmosphere, did not freeze in equal times; the one that had gone through this process before froze much sooner than the fresh one. The above experiment was repeated when the cold mixture was at 25°, 24°, and the atmosphere nearly the same, and with the same success ; only the leaves were longer in freezing, especially the fresh leaf. Experiment V. The vegetable juices above-mentioned being frozen in the leaden vessel, the cold mixture at 28°, and the atmo- sphere the same, a growing fir-shoot was laid upon the surface, also a bean-leaf; and upon remaining there some minutes, they were found to have thawed the surface on which they lay. This I thought might arise from the greater warmth of these substances at the time of application ; but by moving the fir-shoot to another part, we had the same effect produced. ON THE HEAT OF VEGETABLES. 179 Experiment VI. A fresh leaf of a bean was exactly weighed ; it was then put into the cold atmosphere and frozen. In this state it was put back into the same scale, and allowed to thaw. No alteration in the weight was produced. From the foregoing experiments it appears, first, that plants, when in a state of actual vegetation, or even in such a state as to be capable of vegetating under certain circumstances, must be de- prived of their principle of vegetation before they Can be frozen. Secondly, vegetables have a power within themselves of producing or generating heat; but not always in proportion to the diminution of heat by application of cold, so as to retain at all times an uni- form degree of heat; for the internal temperature of vegetables is susceptible of variations to a much greater extent indeed than tha{ of the more imperfect animals, but still within certain limits : be- yond these limits the principle of vegetable, as of animal life, resists any further change. Thirdly, the heat of vegetables varies ac- cording to the temperature of the medium in which they are, which we discover by varying that temperature, and observing the heat of the vegetable. Fourthly, the expense of the vegetating powers in this case is proportioned to the necessity, and the whole vegetable powers may be exhausted in this way. Fifthly, this power is most probably in proportion to the perfection of the plant, the natural heat proper to each species, and the age of each individual. It may also perhaps depend, in some degree, on other circumstances not hitherto observed ; for in Experiment II. the old shoot did not lose its powers, while that which was young or growing did ; and in Experiments II. and III. we found that the young growing shoot of the fir was with great difficulty frozen at 15°, while a bean-leaf was easily frozen at 22°; and in experiment V. the young shoot of fir thawed the ice at 28° much faster than the leaf of the bean. Sixthly, it is probably by means of this principle that vegetables are adapted to different climates. Seventhly, that suspension of the functions of vegetable life, which takes place during the winter season, is probably owing to their being susceptible of such a great variation of internal temperature. Eighthly, the roots of vegetables are capable of resisting cold more than the stem or leaf; therefore, though the stem be killed by cold, the root may be preserved, as daily experience evinces. The texture of vegetables alters very much by the loss of life, especially those which are watery and yountr ; 'from being brittle and crisp, they become tough and flexi- ble. °The leaf of a bean when in full health is thick and mossy, repels water as if greasy, and will often break before it is consider- ably bent; but if it is killed slowly by cold, it will lose all these properties, becoming then pliable and flaccid : deprived of its power of repelling water, it is easily made wet, and appears like boiled greens. If killed quickly by being frozen immediately, it will re- main in the same state as when alive; but upon thawing, will im- mediately lose all its former texture. This is so remarkable, that it would induce one to believe that it lost considerably of its sub- 180 HUNTER ON THE ANIMAL CECONOMY. stance; but from Experiment VI. it is evident that it does not. The same thing happens to a plant when killed by electricity.* If a growing juicy plant receives a stroke of electricity sufficient to kill it, its leaves droop, and the whole becomes flexible. So far animal and vegetable life appear to be the same ; yet an animal and a vegetable differ in one very material circumstance, which it may be proper to take particular notice of in this place, as it shows itself with remarkable evidence in these experiments. An animal is equally old in all its parts, excepting where new part» are formed in consequence of diseases ; and we find that these new or young parts in animals, like the young shoots of vegetables, are not able to support life equally with the old ; but every plant has in it a series of ages. According to its years, it has parts of all the successive ages from its first formation; each part having power equal to its age, and each part, in this respect, being similar to ani- mals of so many different ages. Youth, in all cases, is a state of imperfection; for we find that few* animals that come into the world in winter live, unless they are particularly taken care of; and we may observe the same of vegetables. I found that a young plant was more easily killed than an old one; as also the youngest part of the same plant. fAs I had formerly, in making my experiments upon animals relative to heat and cold, made similar ones on vegetables, and had generally found a great similarity between them in these respects, I was led to pursue the subject on the same plan; but I was still further induced to continue my experiments upon vege- tables, as I imagined I saw a material difference between them in their power of supporting cold. From observations and the foregoing experiments, it plainly ap- pears that the living principle will not allow the heat of such animals to sink much lower than the freezing point, although the surround- ing atmosphere be much colder, and that in such a state they cannot support life long; but it may be observed, that most vege- tables of every country can sustain the cold of their climate. In very cold regions,asin the more northern partsof America, where the thermometer is often 50° below 0, where people's feet are known to freeze and their noses to drop off if great care be not taken, yet the spruce-fir, birch, juniper, &c, are not affected. Yet, that vegetables can be affected by cold, daily experience evinces; for the vegetables of every country are affected if the season be more than ordinarily cold for that country, and some more than others; for in the cold climates above mentioned the life of the vegetable is often obliged to give way to the cold of the country: a tree shall die by the cold ; then freeze and split into a great number of pieces; and in so doing produce considerable noise, giving loud cracks, which are often heard at a great distance. * To kill a whole plant by electricity, it is necessary to apply the conductor, or give a shock to every projecting part; for any part that is out of the line of direction will still retain life. t [See Phil. Trans.,lxviii., 1778, p. 38.] ON THE HEAT OF VEGETABLES. 181 In this country the same thing sometimes happens to exotics from warmer climates. A remarkable instance of this kind hap- pened this winter in His Majesty's garden at Kew. The Erica arborea, or tree-heath, a native of Spain and Portugal, which had kept its health extremely well against a garden wall for four or five years, though covered with a mat, was killed by the cold, and then, being frozen, split into innumerable pieces.* But the ques- tion is, Is every tree dead that is frozen ? I can only say, that in all the experiments I ever made upon trees and shrubs, whether in the growing or active state, or in the passive, that whole or part which was frozen was dead when thawed. The winter 1775-6 afforded a very favourable opportunity for making experiments relative to cold, which I carefully availed myself of. However, previous to that winter, I had made many experiments upon vegetables respecting their temperature, com- paratively with that of the atmosphere, and when they were in their different states of activity : I therefore examined them in different seasons, with a view to see what powers vegetables have. I shall relate these experiments in the order in which they were made. They were begun in the spring, the actions of life upon which growth depends being then upon the increase; and they were con- tinued till those actions were upon the decline, and also when all actions were at an end, but whilst the passive powers of life were still retained. The first were made on a walnut-tree, nine feet high in the stem, and seven feet in circumference in the middle. A hole was bored into it on the north side, five feet above the surface of the ground, eleven inches deep towards the centre of the tree, but obliquely upwards, to allow any sap, which might ooze through the wounded surface to run out. I then fitted to this part a box, about eight inches wide and five deep, and fastened it to the tree: the bottom of the box opened like a door with a hinge. I stuffed the box with wool, excepting the middle, opposite to the hole in the tree ; for this part Ivhad a plug of wool to stuff in, which, when the door was shut, inclosed the whole. The intention of this was to keep off, as much as possible, all immediate external influence either of heat or cold. The same thermometer with which I made my former experi- ments, seven inches and a half long, was sunk into a long feather of a peacock's tail, with a slit upon one side to show the degrees; * This must be owing to the sap in the tree freezing, and occupying a larger space when frozen than in a fluid state, similar to water; and that there is a sufficient quantity of sap in a tree newly killed, is proved by the vast quantity that flows out on wounding a tree. But what appeared most remarkable to me was, that in a walnut-tree, on which I made many of my experiments, I ob- served that more sap issued out in the winter than in the summer. In the sum- mer, a hole beintr bored, scarcely any came out, but in the winter it flowed out abundantly. 182 HUNTER ON THE ANIMAL CECONOMY. by this means the ball of the thermometer could be introduced into the bottom of the hole. Experiment 1. March 29. I began my experiments at six in the morning, the atmosphere at 57£°, the thermometer in the tree at 55°; when it was withdrawn the quicksilver sunk to 53, but soon rose to 57 J0.* This experiment was repeated three times with the same success. Here the tree was cooler than the atmosphere, when one should rather have expected to find it warmer, since it could not be sup- posed to have as yet lost its former day's heat. Exp. II. April 4th, half-past five in the evening. The tree at 56°, the atmosphere at 62°; the tree therefore still cooler than the atmosphere. Exp. III. April 5th. Wind in the north, a coldish day, six o'clock in the evening; the thermometer in the tree was at 55°, the atmosphere at 47°; the tree warmer than the atmosphere. Exp. IV. April 7th, a cold day, wind in the north, cloudy. At three in the afternoon the thermometer in the tree was at 42°, the atmosphere at 42° also. Exp. V. April 9th, a cold day, with snow, hail, and wind in the north-east. At six in the evening the thermometer in the tree at 45°, the atmosphere at 39°. Here the tree was warmer than the atmosphere, just as might have been expected. If these experiments prove anything, it is that there is no standard ; and probably these variations arose from some circumstance which had no immediate connexion with the internal powers of the tree; but it may also be supposed to have arisen from a power in the tree to produce or diminish heat, as some of them were in opposition to the atmosphere. After having endeavoured to find out the comparative heat between vegetables and the atmosphere when the vegetables were in action, I next made my experiments upon them when they were in the passive life. As the difference was very little when in their most active state, I could expect but very little when the powers of the plant were at rest. From experiment upon the more imperfect classes of animals it plainly appears, that although they do not resist the effects of extreme cold till they are brought to the freezing point, they then appear to have the power of resisting it, and of not allowing their cold to be brought much lower. To see how far vegetables are similar to those animals in this respect, I made several experiments: I however suspected them not to be similar, because such animals will die in a cold in which vegetables do live; I therefore supposed that there was some other principle. * The sinking of the quicksilver upon being withdrawn I imputed totheevapo- ating of the moisture of the fluid upon the ball. ON THE HEAT OF VEGETABLES. 183 I did not confine these experiments to the walnut-tree, but made similar ones on several trees of different kinds, as pines, yews, pop- lars, &c, to see what was the difference in different kinds of trees. The difference proved not to be great, not above a degree or two : however, this difference, although small, shows a principle in life, all other things being equal; for as the same experiments were made on a dead tree, which stood with its roots in the ground, similar to the living ones, they became more conclusive. In October I began the experiments upon the walnut-tree when its powers of action were on the decline, and when it was going into its passive life. Exp. VI. October 18th, at half-past six in the morning, the atmo- sphere at 51$°, the thermometer in the tree was at 553°; but, on withdrawing and exposing it for a few minutes in the common atmosphere, it fell to 5O50. Exp. VII. October 21st, seven o'clock in the morning, the atmo- sphere at 41°, the tree at 47°. Exp. VIII. October 21st, in the evening at five o'clock, the atmosphere at 51$°, the tree at 57°. Exp. IX. October 22d, at seven in the morning, the atmosphere at 42°, the tree at 48°. Exp. X. October 22d, one o'clock afternoon, the atmosphere at 51°, the tree at 53°. Exp. XL October 23d, in the evening of a wet day, the atmo- sphere at 46°, the tree at 48°. Exp. XII. October 28th, a dry day, the atmosphere at 45°, the tree at 46°. Exp. XIII. October 29th, a fine day, the atmosphere at 45°, the tree at 49°. Exp. XIV. November 2d, wind east, the atmosphere at 43°, the tree at 43°. Exp. XV. November 5th, wet day, the atmosphere at 43°, the tree at 45°. Exp. XVI. November 10th. Atmosphere at 49°, the tree at 55°. Exp. XVII. November 18th. Atmosphere at 42°, the tree at 44°. Exp. XVIII. November 20th, fine day, the atmosphere at 40°, the tree at 42°. Exp. XIX. December 2d. The atmosphere at 54°, the tree at 54°. In all these experiments, which were made at various times in the day, viz., in the morning, at noon, and in the evening, the tree was in some degree warmer than the atmosphere, excepting in one, when their temperatures were equal. For the sake of brevity, I have drawn up my other experiments (which were made on dif- ferent trees) into four tables, as they were made at four different degrees of heat of the atmosphere, including those made in the time of the very hard frost in the winter of 1775-6. They were as follows: 184 HUNTER ON THE ANIMAL CECONOMY. Table I. Atmosphere. Names. Height. Dia-meter. Heat. ft. in. ft. in. o f Carolina poplar..... 2 0 0 2 294 English poplar 4 0 0 2£ 294 Oriental plane 3 0 0 l£j 30 Occidental plane . 3 6 0 2 30 Carolina plane 1 0 0 1|; 30 Birch . 3 6 0 24 294 29 deg. < Scotch fir Cedar of Lebanon . Arbutus Arbor vitas Deciduous cypress Lacker varnish 3 6 2 2 2 6 2 8 3 0 3 6 0 4 0 44 0 34 0 34 0 24 0 2 284 284 30 29 30 30 t^Walnut-tree . 5 0 2 4 31 The old hole in the walnut tree, being full of sap, was frozen up but a new one was made. Table II. Dia- Atmosphere. Names. Height. meter. Heat. ft. in. in. 0 f Spruce fir..... 4 0 n 32 Scotch fir . 1 5A u 28 Silver fir . 3 11 2h 30 Weymouth fir . 4 6 n 30 27 deg. -> Yew 3 7 3 30 Holly 2 6 2 30 Plum-tree . 4 6 3 314 Dead cedar 3 11 3 29 ^.Ground under snow 0 3 deep. . . . 34 Table III. Atmosphere. Names. Heat. f Spruce fir .... 0 23 1 Scotch fir .... 23 | Silver fir .... 23 24 deg. -< Weymouth fir . 23 Yew 22 Holly..... 23 iJDead cedar .... 24 The same trees we mentioned when the thermometer was at 29°, in new holes made at the same height, and left some time pegged up till the heat produced by the gimlet was gone off; but in which, as they were moist from the sap, the heat could be very little, especially as the gimlet was not in the least heated by the opera- tion. OF PERSONS APPARENTLY DROWNED. Table IV. Atmosphere. Names. Heat. rCarolina poplar o 17 English poplar 17 Oriental plane 17 16 deg. ■< Occidental plane 17 Carolina plane 17 Birch .... 17 ^Scotch fir . . 16£ It will be necessary to observe, that the sap of the walnut-tree, which flowed out in great quantity, froze at 32°. I did not try to freeze the sap of the others. Now since the sap of a tree when taken out freezes at 32°; also, since the sap of a tree, when taken out of its proper canals, freezes when the heat of the tree is at 31°; and since the heat of the tree can be so low as 17°, without freezing; by what power are the juices of the tree, when in their proper canals, kept fluid in such a cold ? Is it the principle of vegetation ? Or is the sap inclosed in such a way as that the process of freezing cannot take place, which we find to be the case when water is confined in globular vessels? If so, its confinement must be very different from the confinement of moisture in dead vegetables ; but the circumstance of vegetables dying with the cold and then freezing appears to answer the last question. These, however, are questions which at present I shall not endeavour to solve. I have made several experiments upon the seeds of vegetables similar to those on the eggs of animals; but as inserting them would draw out this paper to too great a length, I will reserve them for another. 16. PROPOSALS FOR THE RECOVERY OF PERSONS APPARENTLY DROWNED.* Having been requested by a principal member of the society established for the recovery of persons apparently drowned to com- mit my thoughts on that subject to paper, I readily complied, hoping, that although I have had no opportunities of making actual experiments upon drowned persons, it might be in my power to throw some lights on a subject so closely connected with the inqui- ries which for many years have been my business and favourite amusement: I therefore collected together my observations and experiments relative to the loss and recovery of the actions of life, which I now offer to the public. The endeavour to recover per- * [From the Philosophical Transactions, vol. Ixvi.; read March 21, 1776.] 17* 1S6 HUNTER ON THE ANIMAL CECONOMY. sons apparently drowned is a new practice, and has furnished, as yet, few important and clear facts: our knowledge of the animal ceconomy is so imperfect, that I am afraid our reasoning from that alone must not be relied on in a question so interesting to the cause of humanity. But let us reason as well as wc can from the few data we have, and let every man bring forward, freely, the obser- vations he has made, that the subject thus fairly before the public may in time, by its united efforts, be more perfectly under- stood. I shall consider an animal apparently drowned as not dead, but that only a suspension of the actions of life has taken place. The difference between a suspension of the actions of life and absolute death is well illustrated by the common snail when drowning. If a snail is immersed in water and kept there, certain voluntary and instinctive actions take place; but after remaining a certain time covered by the water, all these actions cease. Hence the animal, being relaxed, naturally comes out of the shell in that state; its stomach is filled with water, and the body appears larger than natural, but without motion. These actions continue thus suspend- ed till either the cause of suspension be removed or some other stimulus shall bring the parts into action : but under such circum- stances life cannot be preserved for any considerable length of time; and when the stimulus which precedes death takes place, the whole animal is thrown into action, and in that contracted state, possibly, absolute death is produced. A state of relaxation should therefore (where an universal violence has not been committed), be considered as the criterion of life; and even in such cases should be for some time admitted as a probable reason for supposing life still to exist. If an animal appears so far dead as to have lost all the actions characteristic of life, yet a certain degree of action in all the parts will be produced when absolute death is taking place; and that animal, being still susceptible of stimulus, is recoverable if the proper stimulus could be applied. It is asserted that men have recovered the actions of life even after the contraction, in consequence of the stimulus which pre- cedes death, has taken place. If this be true, which I very much doubt, the stimulus must first produce relaxation, which is an action dependent on life. This is probably the case in the first appearances of death from all violent accidents, except those caused by lightning, electricity, an universal shock, a blow on the stomach, a violent affection of the mind, or some other modes by which absolute death may be instantaneously produced, which all appear to act in the same way, producing absolute and instant death. For in cases which have fallen under my observation, the concomitant circumstances have resembled those which attend death caused by lightning or electri- city, such as a total and instantaneous privation of sense and mo- tion without convulsions; consequently, no rigor of muscles having been produced, and the blood remaining uncoagulated, differing OF PERSONS APPARENTLY DROWNED. 187 entirely in these respects from what appears in persons deprived of sense and life by any injury done the brain. It seems only possible to account for this effect of a blow on the stomach, from the connexion subsisting between that viscus and every part of the body, at least with vital parts; the blow most probably causing instant death in that organ of which the death of the whole animal is the consequence.* When death takes place from violent affections of the mind, it must be referred to the universal influence which the mind has over the body. To ascertain when a body is deprived of life it is first necessary to know in what manner apparent death took place; whether in the common way, or from the vital actions being too long suspended. In either case stiffness of the muscles is probably the most certain and most evident proof of absolute death, since that arises from the stimulus immediately preceding death, having taken place. But if the privation of life is produced by any of the modes above men- tioned, which kill instantaneously and universally, the stimulus which produces stiffness is not allowed time to act, and the muscles are all left in a relaxed state. Yet this state of relaxation must not, on that account, be always considered as a proof of life still remaining. A degree of flaccidity in the eyeballs, which produces glassiness, is a certain mark of death ; but is, however, only a secondary mode of ascertaining it in those instances where the body becomes stiff; but may be the first mode where absolute death takes place instan- taneously ; and putrefaction will be the second ; while in the other cases putrefaction will be the third. That I may more fully explain my ideas upon this subject, it will be necessary to state some propositions. First; that so long as the animal retains the susceptibility of im- pression, though deprived of the action of life, it will, most probably, retain the power of action when impressed; therefore the action may frequently be suspended, and yet recoverable ; but when the susceptibility of impression is destroyed, the action ceases to be re- coverable. Secondly; it is jiecessary to mention, that I consider part of the living principle as inherent in the blood.j- Thirdly ; that the stomach sympathizes with" every part of an animal, and that * I should consider the situation of a person drowned to be similar to that of a person in a trance. In both the action of life is suspended without the power being destroyed ; but I am inclined to believe that a greater proportion of persons recover from trances than from drowning, because a trance is the natural effect of a disposition in the person to have the action of life suspended for a time; but drowning being produced by violence, the suspension will more frequently last for ever, unless the power of life is roused to action by some applications of art. t That the living principle is inherent in the blood is a doctrine which the nature of this account will not allow me to discuss ; thus much, however, it may be proper to say, that it is founded on the result of many observations and expe- riments. But it may be thought necessary I should here give a definition of what I call the living principle: so far, then, as I have used the term, I mean to express that principle which preserves the body from dissolution with or without action, and is the cause of all its actions. 1S8 HUNTER ON THE ANIMAL CECONOMY. every part sympathizes with the stomach ; therefore, whatever acts upon the stomach as a cordial, or rouses its natural and healthy actions, and whatever affects it so as to produce debility, has an immediate effect upon every part of the body. The last proposition I have to make is, that every part of the body sympathizes with the mind; for whatever affects the mind, the body is affected in pro- portion. These sympathies are strongest with the vital parts; but besides these universal sympathies between the stomach, the mind, and all parts of the body, there are peculiar sympathies, of which the heart, sympathizing immediately with the lungs, is an instance. If anything is received into the lungs which is a poison to animal life, such as inflammable air, volatile vitriolic acid, and many other well-known substances, the motion of the heart immediately ceases, even much sooner than if the trachea had been tied; and, from ex- periments, it appears that anything salutary to life, applied to the lungs, will restore the heart's action after it has been at rest some time. I shall divide violent deaths into three kinds ; first, where a stop is put only to the action of life in the animal, but without any irre- parable injury to a vital part, which action, if not restored in a certain time, will be irrecoverably lost. The length of that time is subject to considerable variation, depending on circumstances with which we are at present unacquainted. The second is, where an injury is done to a vital part, as by taking away blood till the powers of action are lost; or by a wound or pressure being made on the brain or spinal marrow while life remains in the solids suffi- cient for the preservation of the animal, if action could be restored to the vital parts. The third is, where absolute death instantly takes place in every part, as is often the case in strokes of lightning; in the common method of killing eels, by throwing them on some hard substance, in such manner as that the whole length of the animal shall receive the shock at the same instant; by a blow on the stomach; by violent affections of the mind; and by many diseases, in all which cases the muscjes remain flexible.* How far that may be strictly considered as a violent death which is caused by affections of the mind*, I will not pretend to say; but if it is to have a place in that class, it must be ranked with those which happen from lightning, and a blow on the stomach; and in most cases of persons drowned, I can easily conceive the mind to be so much affected prior to the immersion, and in the moment im- mediately succeeding it, as to make a material difference in the power of recovery. In many sudden deaths arising from violence, and even from disease, death shall take place so immediately that the muscles neither contract, nor does the blood coagulate. * On the other hand, when an eel is killed by chopping it into a number of pieces, the powers of life are by those means roused into action ; and as every part dies in that active state, every part is found stiff after death. This explains the custom of cutting fish into pieces while yet alive, in order to make them hard, usually known by the name of crimping. OF PER80NS APPARENTLY DROWNED. 169 The present consideration is, under which of the kinds of violent death drowning can be classed or arranged ? I am of opinion it will most commonly come under the first, and upon that ground I shall principally consider the subject, always supposing the body to remain flaccid. The loss of motion in drowning seems to arise from the loss of respiration, and the immediate effects which that has upon the other vital motions of the animal; except what may have arisen from the affections of the mind. The privation of breathing appears, how- ever, to be the first cause, and the heart's motion ceasing, to be the second or consequent; therefore most probably the restoration of breathing is all that is necessary to restore the heart's motion; for if sufficient life still exists to produce that effect, we may suppose every part equally ready to move the very instant in which the action of the heart takes place, their actions depending so much upon it. What makes it very probable, that in recovering persons drowned, the principal effect depends upon air being thrown into the lungs, is what happens at the birth of children, when too much time has intervened between the interruption of that life which is peculiar to the foetus and that which depends on breathing; they then lose altogether the disposition for this new life; and in such cases, there being a total suspension of the actions of life, the child remains to all appearance dead, and would certainly die if air were not thrown into its lungs, and by such means the first principle of action restored. To put this in a still clearer light, I will give the result of some experiments which I made in the year 1755 upon a dog. A pair of double bellows were provided, constructed in such a manner as by one action to throw fresh air into the lungs, and by another to suck out again the air which had been thrown in by the former, without mixing them together. The muzzle of these bellows was fixed into the trachea of a dog, and by working them he was kept perfectly alive. While this artificial breathing was going on I took off the sternum of the dog,and exposed the lungs and heart; the heart continued to act as before, only the frequency of its action was considerably increased. When I stopped the motion of the bellows the heart became gradually weaker, and less frequent in its contractions, till it entirely ceased to move. By renewing the action of the bellows the heart again began to move, at first very faintly, and with long intermissions ; but by continuing the artificial breathing, its motion became as frequent and as strong as at first. This process I repeated upon the same dog ten times, sometimes stopping for five, eight, or ten minutes, and observed that every time I left off working the bellows the heart became extremely turgid with blood, the blood in the left side becoming as dark as that in the right, which was not the case when the bellows were working. These situations of the animal appeared to me exactly similar to drowning. Death in persons drowned has been accounted for by supposing 190 HUNTER ON THE ANIMAL CECONOMY. that the blood, rendered unfit for the purposes of life by being de- prived of the action of the air in respiration, is sent in a vitiated state to the brain and other vital parts, by which means the nerves lose their effect upon the heart, and the heart in consequence its motion. This, however, I am fully convinced is false ; first, from the experiments on the dog, in which a large column of blood so vitiated (consisting of what had been propelled from the heart after respiration stopped, and might be supposed the cause of the heart ceasing to act, together with all that remained in the heart and pulmonary veins), was again pushed forward without any ill effect having been produced; and next, from the return to life of persons drowned and children still-born, which, were such a supposition true, could never happen, unless we imagine a change of the blood to take place in the brain, prior to the restoration of the heart's motion. This restoration must therefore depend immediately on the application of air to the lungs, and not on the effects which air has upon the blood, or that blood upon the vital parts. If the affections of the mind have had any share in the cessation of action in the heart, its motion will not be so easily restored as in other cases. In our attempts to recover those who have been drowned, it might therefore be proper to inquire if there had been time sufficient for the person to form any idea of his situation previous to his being plunged into the water, as it is not unlikely that the agitated state of mind might assist in killing him; and in such case I should very much doubt the probability of restoring him to life. In the history of those who have and who have not been recovered, could the difference be ascribed to any such cause, it might lead to something useful; as in those who have had an intention to destroy themselves, a great difference in the chance of recovery may arise, from the mind having been previously very much affected. It frequently happens, in the case of drowning, that assistance cannot be procured till a considerable time after the accident; every moment of this delay renders recovery more precarious, the chances of which are not only diminished in the parts where the first powers of action principally reside, but also in every other part of the body. In offering my sentiments on the method of treating persons who are apparently drowned, I shall say, first, what I would re- commend to have done ; secondly, what I would wish might be avoided. When assistance is called in soon after the immersion, perhaps blowing air into the lungs may be sufficient to effect a recovery;* but if a considerable time, as an hour, has been lost, it will seldom be sufficient, the heart in all probability having by that time lost its * Perhaps the dephlogisticated air described by Dr. Priestly (oxygen gas) may prove more efficacious than common air. It is easily procured, and may be preserved in bottles or bladders for that purpose. OF PERSONS APPARENTLY DROWNED. 191 intimate connexion with the lungs. It will in these cases, there- fore, be proper to apply, mixed with the air, such stimulating medi- cines as the vapour of volatile alkali, which may easily be done, by holding spirits of hartshorn in a cup under the receiver of the bel- lows. I would advise the air and volatile alkali to be thrown in by the nose rather than the mouth, as the last mode of administering, by producing sickness, is more likely to depress than rouse the living principle. It will be still better if it can be done by both nostrils, as applications of this kind to the olfactory nerves certainly rouse the living principle and put the muscles of respiration into action, and therefore are the more likely to excite the action of the heart: besides, that affections of these nerves are known to act more im- mediately on the living principle; since while a strong smell of very sweet flowers, as orange flowers, will in many cause fainting, the application of vinegar will as immediately restore the powers to action again. All perfumes in which there is some acid rather rouse than depress, as the sweet-brier, essence of lemon, &c. If, during the operation of the bellows, the larynx be gently pressed against the oesophagus and spine, it will prevent the stomach and in- testines being too much distended by the air, and leave room for the application of more effectual stimuli to those parts. This pressure, however, must be conducted with judgment and caution, so that the trachea and the aperture into the larynx may both be left per- fectly free. While this business is going on an assistant should prepare bedclothes, carefully brought to the proper degree of heat. I consider heat as congenial with the living principle; increasing the necessity of action, it increases action ; cold, on the other hand, lessens the necessity, and of course the action is diminished : to a due proportion of heat, therefore, the living principle owes its vigour; and, from observations and experiments, it appears to be a law of Nature in animal bodies, that the degree of external heat should bear a proportion to the quantity of life; when it is weak- ened, this proportion requires great accuracy in the adjustment, while greater powers of life allow a greater latitude.* I was led to make these observations bv attending to persons who are frost-bitten, the effect of cold in such cases being that of lessening the living principle. The powers of action remain as perfect as ever, but weakened, and heat is the only thing wanting to put these powers into action : yet that heat must at first be gradu- ally applied, and proportioned to the quantity of the living principle, which increasing, the degree of heat may likewise be increased. If this method is not observed, and too great a degree of heat is at first applied, the person or part loses entirely the living principle, and mortification ensues. Such a process invariably takes place * It is upon these principles that cold air is found of so much service to people who are reduced by disease, as the confluent small-pox and fevers, by diminish- ing heat in proportion to the diminution of life, or lessening the necessity of the body's producing its own cold. 192 HUNTER ON THE ANIMAL CECONOMY. with regard to men, and the same thing, I am convinced, happens to other animals. For if an eel is exposed to a degree of cold suffi- ciently intense to benumb it till the remains of life are scarcely per- ceptible, and still retained in a cold of about 40°, this small pro- portion of living principle will continue for a considerable time without diminution or increase; but if the animal is afterwards placed in a heat about 60°, after showing strong signs of returning life, it will die in a few minutes. Nor is this circumstance peculiar to the diminution of life by cold. The same phenomena take place in animals which have been very much reduced by hunger. If a lizard or snake, when it goes to its autumnal hiding-place, is not sufficiently fat, the living powers are, before the season per- mits it to come out, very considerably weakened; perhaps so much as not to admit of the animal being again restored. If animals in a torpid state are exposed to the sun's rays, or placed in any situa- tion which by its warmth would give vigour to those of the same kind possessed of a larger share of life, they will immediately show signs of increased life, but quickly sink under the experiment and die ; while others, reduced to the same degree of weakness, as far as appearances can discover, will live for many weeks, if kept in a degree of cold proportioned to the quantity of life they possess. I observed, many years ago, in some of the colder parts of this island, that'when intense cold had forced blackbirds or thrushes to take shelter in outhouses, such of them as had been caught, and were, from an ill-judged compassion, exposed to a considerable degree of warmth, died very soon. The reason of this I did not then understand; but I am now satisfied that it was owing, as in other instances, to the degree of heat being increased too suddenly for the proportion of life remaining in the animal. From these facts it appears that warmth causes a greater exertion of the living powers than cold; and that an animal in a weakly state may be obliged by it to exert a quantity of the action of life sufficient to destroy the very powers themselves.* The same effects probably take place even in perfect health; it appearing, from experiments made in a heated room, that a person in health, exposed to a great degree of heat, found the actions of life accele- rated so much as to produce at last faintness and debility.f If bedclothes are put over the drowned person, so as scarcely to touch him, steam of volatile alkali, or of warm balsams and essen- tial oils, may be so conveyed as to come in contact with many parts of his body; and it will certainly prove advantageous if the same kind of steams can be conveyed into the stomach, as that seat of universal sympathy will be roused by such means. This may be done by a hollow bougie and a syringe; but the operation should be performed with all possible expedition, because the instrument, by continuing in the mouth, may produce sickness, an * It is upon this principle that parts mortify in consequence of inflammation. } Vide Phil. Trans, for the year 1775, vol. lxv., p. 111. OF PERSONS APPARENTLY DROWNED. 193 effect I should choose to avoid, unless it is intended to produce the action of vomiting. Some of the stimulating substances, which are of a warm nature and have an immediate effect, as spirits of hartshorn, peppermint-water, juice of horse-radish, and many others which produce a more lasting stimulus in a fluid state, and are found to quicken the pulse of a man in health, as balsams and turpentines, may be thrown into the stomach; but the quantity must be small, as they have a tendency to produce sickness; for it may be imagined that what would produce debility, or lessen action when in health, would in opposite circumstances prevent actions from taking place. The application of steams and other substances should also be thrown up by the anus; and the process recom- mended under the first head of treatment should still be continued while that recommended under the second is putting in practice, the last being only an auxiliary to the first. The first, in many cases, may succeed alone; but the second without the first must, I think, always fail where the powers of life are considerably weakened. Motion may possibly be of service, it may at least be tried; but, as it has less effect than any other of the usually pre- scribed stimuli, it should be the last applied.* I would recommend to the operator the same care in regulating the application of every one of these methods as I did before in that of heat, as each may have the same property of entirely destroying the feeble action which they have excited, if administered in too great a proportion. Instead, therefore, of increasing and hastening the operations on the first signs of returning life being observed, as is usually done, I should wish them to be applied more gently and gradually, that their increase afterwards may be directed, as nearly as possible, in a degree proportioned to the powers as they arise. As the heart is commonly the last part that ceases to act, it is probably the first part that takes on the action of recovery. When it begins to move, I would advise lessening the application of air to the lungs, and enjoin those employed to observe with great attention when the muscles of respiration begin to act, that our endeavours may not interfere with their natural exertions, yet that we maybe still ready to assist. I would by all means discourage bloodletting, which I think weakens the animal principle and life itself, consequently lessens both the powers and dispositions to action; and I would advise being careful not to call forth any disposition that might depress, by introducing things into the stomach which ordinarily create nausea ; as that also will have a similar effect, except it can be carried so far as to excite the action of vomiting, by which the stomach could relieve itself. It will be prudent likewise to avoid •■ Electricity has been known to be of service, and should be tried when other methods have failed. It is probably the only method we have of immediately stimulating the heart; all other methods being more by sympathy. I have not mentioned injecting stimulating substances directly into the veins, though it might be supposed a proper expedient, because, in looking over my experiments on that subject, I found none where animal life received increase by that method. 18 194 HUNTER ON THE ANIMAL CECONOMY. administering by the anus anything that may be likely to produce an evacuation that way, every such evacuation tending to lessen the animal powers. I have purposely avoided speaking of the fumes of tobacco, which always produce sickness or purging, according as they are applied. Whoever is appointed for the purpose of recovering drowned persons should have an assistant well acquainted with the methods intended to be made use of; that while the one is going on with the first and most simple methods, the other may be preparing what else may be proper, so that no time may be lost between the opera- tions ; and this is the more necessary, as the first means recom- mended will, in all cases, assist the second ; and both together may often be attended with success, though each separately might have failed. A proper apparatus is also essentially necessary to the institu- tion : a description of which I here annex. First, a pair of bellows, so contrived, with two separate cavities, that by expanding them, when applied to the nostrils or mouth of a patient, one cavity may be filled with the common air, and the other with air sucked out from the lungs ; and by shutting them again, the common air may be thrown into the lungs, and that which is sucked out of the lungs be discharged into the room. The pipe of these should be flexible, in length a foot or a foot and a half, and at least, three eighths of an inch in width: as the artificial breathing may be continued by such means, while the other operations, except the application of the stimuli to the stomach, are going on ; which cannot conveniently be done if the nozzle of the bellows be introduced into the nose. The end next the nose should be double, and applied to both nos- trils. Secondly, a syringe, with a hollow bougie, or flexible catheter, of sufficient length to go into the stomach, and convey any stimu- lating matter into it, without affecting the lungs. Thirdly, a small pair of bellows, such as are commonly used in throwing fumes of tobacco up the anus, by which stimulating fluids or even fumes may be thrown in. I shall conclude this account by proposing that all who are em- ployed in this practice be particularly required to keep an accurate journal of the means used, and the degree of success attending them; whence we may be furnished with facts sufficient to enable us to draw conclusions, on which a certain practice may hereafter be established. 17. AN ACCOUNT OF CERTAIN RECEPTACLES OF AIR IN BIRDS, WHICH COMMUNICATE WITH THE LUNGS AND EUSTACHIAN TUBE. Since the account of these receptacles was read before the Royal Society, in the year 1774, I have, by the dissection of a number of birds, been able to make some additional observations relative to OF AIR-CELLS IN BIRDS. 195 the extent of the air-cells which communicate with the lungs in animals of this class. These latter observations were not, however, made in consequence of any regular design to investigate this sub- ject further, as to have established the principle seemed.all that was necessary; unless by general observations we could hope to throw more light on the final intention of this remarkable piece of mechanism. Before the period I have mentioned, the communication subsist- ing in birds, between the air-cells of the lungs and other cavities of the body, had not been clearly explained, nor even much attended to by anatomists or natural historians.* It is a singularity of structure peculiar to this tribe of animals; and on account of it cannot, I imagine, be unacceptable to the public. It is not my present intention to enter into minute descriptions of all the particular communications of this sort discoverable in birds by dissection, but only to mention such general facts as may serve to introduce the subject into natural history, and lead to an inquiry into the purposes which this structure was intended to answer. With this view I shall endeavour to give some idea of the con- struction of the lungs, and of the air-receptacles in birds, occasion- ally remarking the circumstances in which these principally differ from what is seen in other animals. The mechanism of the lungs in birds, which renders them fit for * [The continuation of the air-passages of the lungs into large membranous receptacles, situated in the abdominal cavity, was first discovered and described by Harvey (On Generation, 8vo., 1663, p. 7; Opera Omnia, 4to., 1766, p. 185). The abdominal air-cells of the ostrich are figured in Perault's Collection of Ana- tomical Memoirs of the French Academicians. Borelli, in explaining the causes of the greater specific levity of birds, observes, " Hoc patet, quia ossa avium fistulosa, valde excavata et subtilia sunt, ad instar radicum pennarum scapulae, costae et brachia partim carnosa sunt; pectus et abdomen amplas cavitates aere plenas habent; pennae tamen et plums levissimae sunt." (De Motu Animalium, 4to., 1685, p. 231, prop. 194.) Borelli appears, however, to have believed both the quills of the feathers and the hollow bones to have contained only a light marrow. The discovery that the bones of birds contained air was first published in the year 1771,—in England in the Philosophical Transactions of that year, which contained Mr. Hunter's ' Account,' &c, read before the Royal Society, February 27, 1774; and in Holland in the Verhandeling van Bataafsche Genoot- schte, Rotterdam, 1774, in which Camper's discovery of the same structure was first published. Camper transmitted, in the year 1773, an account of his re- searches on the air-bones of birds to the French Academy, which was published in the Mdmoires de Mathematiques et Physique, 4to., in 1776. Whilst, therefore, we may be willing to admit that Camper's Memoir was founded on an indepen- dent discovery, we must also conclude that the mass of valuable observations on the air-receptacles of birds, communicated to the Royal Society some months before the first publication of Camper's discovery in the Dutch language, was equally original. The French translator of Carus's Comparative Anatomy, in a prefatory sketch of the History of the Science, introduces John Hunter to the reader's notice as follows: "Le premier, il (Camper) a fait remarquer que les os longs du squelette des Oiseaux sont creuses de cavites dans lesquelles l'air a la facilite de s'introduire, parce qu'elles communiquent avec l'organe pulrno- naire, decouverte que Hunter eut l'impudeur de s'approprier quelques annees apres." (Jourdan's Carus, torn, i., p. xxxi.) Truly the ignorance of such an assertion can only be equalled by its impudence.); 196 HUNTER ON THE ANIMAL CECONOMY. conveying air to different parts of the body, consists principally in certain communications. It has been asserted that birds have no diaphragm ; but this opinion must have arisen either from a want of observation, or from too confined an idea of a diaphragm ; for there is a moderately strong, but thin and transparent membrane, covering the lower surface of the lungs, and adhering to them, that affords insertion to several thin muscles which arise from the inner surfaces of the ribs. The use of this part seems to be that of lessening the concavity of the lungs towards the abdomen at the time of inspiration, and thereby assisting to dilate the air-cells, for which reason it is to be considered as answering one main purpose of a diaphragm. Be- sides this attachment of the lungs to the diaphragm, they are also connected to the ribs, and to the sides of the vertebrae.* Such adhesions are peculiar to this tribe of animals, and are of singular use, nay, in fact are absolutely necessary in lungs like those of birds, out of which.it is intended the air should find a passage into other cavities. For if the lungs were loose in the cavity of ihe thorax, as is the case in many other animals, the cells of the lungs could not be expanded, either by the depression of the dia- phragm, or the elevation of the ribs; since the air rushing in to fill up the vacuum produced in the cavity of the chest by these actions would take the straight road from the trachea through the passages, and of consequence would expand no part of the lungs which lay out of that line, whereby respiration would be totally prevented, and an effect produced exactly similar to what happens in other animals when the lungs are so much wounded as to allow a free exit to the air in that part.f The cells in the bodies of birds which receive air from the lungs are to be found both in the soft parts and in the bones, and have no communication with the cavity of the common cellular membrane. Some of these air-bags are placed in the larger cavities, as in the abdomen; and others are so lodged in the interstices of muscles, blood-vessels, and nerves, about the breast, axilla, &c, as at first to give the appearance of the common connecting membrane. Some communicate immediately with one another, and all may be said to have a communication by means of the lungs. They are of very different sizes, as may best suit the particular circumstances of the parts in which they are placed. The bones which receive air are of two kinds; some, as the sternum, ribs, and vertebrae, having their internal substance divided into innumerable cells; whilst others,as the os humeri and os femoris, are hollowed out into one large canal, with sometimes a few bony columns running across at its extremities. Bones of this kind may be distinguished from those that do not receive air by several marks: first, by their less specific gravity; secondly, by being less vascular than the others, and therefore whiter; thirdly," by their containing * [See Harvey, on Generation, p. 6.] t [Ibid., p. 7.] OF AIR-CELLS IN BIRDS. 197 little or no oil, and consequently being more easily cleaned, and when cleaned, appearing much whiter than common bones; fourthly, by having no marrow, or even any bloody pulpy substance in their cells ; fifthly, by not being in general so hard and firm as other bones ;* and sixthly, by the passage that allows the air to enter the bones, which can be easily perceived. In the recent bone we may readily discover holes or openings not filled with any soft substance, as blood-vessels or nerves; several of these holes are placed together, near that end of the bone which is next to the trunk of the bird, and are distinguishable by having their external edges rounded off, which is not the case with the holes through which either nerves or blood- vessels pass into the substance of the bone. When birds break any of the bones which contain air, the surrounding parts often become emphysematous. There are openings in the lungs by which air is transmitted to the other parts; and the membrane or diaphragm above-mentioned is perforated in several places with holes of a considerable size, which admit of a free communication between the cells of the lungs and the abdomen, a circumstance which has been frequently noticed. To each of these perforations is joined a distinct membranous bag, extremely thin and transparent, which bags being afterwards con- tinued through the whole of the abdomen, and attached to the back and sides of that cavity, are kept firm in their proper situations, each receiving the air from their respective openings. There is no occasion to describe here all the bags, or their attachments, it being sufficient to have said that they extend over the whole abdomen. The lungs at the anterior part, contiguous to the sternum, have openings into certain membranous cells which lie upon the sides of the pericardium, and communicate with the cells of the sternum, At the superior part the lungs have a communication with the large cells of a loose network, through which the trachea, oesophagus. and great vessels pass as they are going to and from the heart. When these cells are distended with air, the size of that part where they lie is very considerably increased, and this enlargement is in general a mark of either the passion of anger or love. It-is plainly seen in the turkey-cock, the pouting-pigeon, &c, and is very visible in the breast of a goose when she cackles. These cells communi- cate with others in the axilla, under the large pectoral muscle, and in some birds are still further extended. In the pelican, for instance, the skin of the whole body, even to the tip of the wing, is united to the part underneath by means of these cells, which are equally formed ; and when the skin is removed, the two separated surfaces appear as if honeycombed. When the cells are distended the skin is removed to a considerable distance, by which means the volume * The bones of some birds are so soft that they can be squeezed together with the finger and thumb; the bones of the extremities, however, have very solid sides. 18* 198 HUNTER ON THE ANIMAL CECONOMY. is proportionally increased.* In most birds, I believe in all that fly, these axillary cells communicate with the cavity of the os humeri, by means of small openings in the hollow surface near the head of that bone; in some they are continued down the wing, communi- cating with the ulna and radius; in others they reach even as far as the pinions. The ostrich, however, is an exception. The posterior edge of the lungs (which lies on the sides of the spine, and projects backwards between the ribs,) communicates with the cells of the bodies of the vertebrae, with those of the ribs, the canal of the medulla spinalis, and the cells of the sacrum and other bones of the pelvis ; from which parts the air finds a passage into the cavity of the thigh-bone. This takes place in the greatest number of birds; but in some the air is even continued part of the way down the thighs. This account agrees with what we gene- rally find, though some birds have more, and some fewer of these communications; for, in the ostrich, no air gels into the os humeri, yet it enters into every other part, as before described, and in very large quantities. In the common fowl no air appears to enter any bone except the os humeri. The woodcock has no air-cells, either in the first bones of the wing or in the thigh-bones. On the other hand, in the pelican the air passes on to the ulna and radius, and into those bones which answer to the carpus and metacarpus of quadrupeds.! Thus the cells of the abdomen, those surrounding the pericardium, those situated at the lower and fore part of the neck and in the axilla, those in the cellular membrane under the pectoral muscles, as well as in that which unites the skin to the body, all communi- cate with the lungs, and are capable of being filled with air; and again, from them the cells of the sternum, ribs, vertebras of the back and loins, bones of the pelvis, the humeri, the ulna and radius, with the pinions and thigh-bones, can in many birds be furnished with air. It is not by the lungs alone that air is conveyed into the bones of birds, for the cells of the diploe between the two plates of the skull, in some birds, receive a considerable quantity of air by the Eusta- * [While inflating the air-cells of a gigantic crane {Ciconia Argala), in which bird they are continued along the wing, beneath the skin, as in the pelican, the wings became extended as the air-cells were filled. This phenomenon suggested to me a secondary use of the air-cells, which appears not to have been noticed, viz., to render mechanical assistance to the muscles of the wings, both by keep- ing the wing extended during the long hovering flight peculiar to this bird, and also by compressing and bracing the muscles, as is done by the fasciae of the ex- tremities in man.] f [In the hornbill the air is also extended into the phalanges of the toes, and in short into every bone in the skeleton; whilst in the penguin, on the other hand, the air-cells are confined, as in reptiles, to the thoracic abdominal cavity, and not a single bone of the skeleton is permeated by the atmospheric fluid. These birds present the two extremes of the condition of the respiratory apparatus described by Hunter in the present paper.] OF AIR-CELLS IN BIRDS. 199 chian tube.' Of this the owl is a remarkable instance. The lower jaw of some kinds is likewise supplied with air, and often by the same canal.f Some authors have considered the diploe in the cranium of a bird as a continuation of the mammillary process, and looked upon it as a circumstance peculiar to singing birds, which is not really true. These facts, which had been formerly observed, led me in the year 1758 to make several experiments upon the breathing of birds, that might prove the free communication between the lungs and the before-mentioned parts. First, I made an opening into the belly of a cock, and having in- troduced a silver canula, tied up the trachea. I found that the animal breathed by this opening, and might have lived; but by an inflammation in the bowels coming on, adhesions were produced, and the communication was cut off. I next cut the wing through the os humeri, in another fowl, and tying up the trachea, as in the cock, found that the air passed to and from the lungs by the canal in this bone. The same experi- ment was made with the os femoris of a young hawk, and was at- tended with a similar result. But the passage of air through the divided parts, in both these experiments, especially in the last, was attended with more difficulty than in the former one ; it was indeed so great as to render it impossible for the animal to live longer than evidently to prove that it breathed through the cut bone. I have made several preparations of these cells, by throwing into the trachea an injection, commonly called the corroding injection, * The only thing in other animals similar to this communication in birds, of the cells of bones with the external air, is that which takes place in the internal ear of quadrupeds, by means of the Eustachian tube.a f When I wrote this account to send it to the Royal Society, I did not then know by what means this was done; for in that I said, " but by what means I do not know;" that is, I did not know whether it was conveyed by the trachea, where it passes along the neck, or the Eustachian tube. Professor Camper, when he did me the honour to call upon me, was so obliging as to take some pains to show me, in the lower jaw of the hawk, the hole where the air entered, which makes me suspect he did not understand what I had written. For after having given the marks by which such openings were particularly distinguished, it will hardly be supposed I could say that 1 did not know the hole where the air entered.b a [Camper, besides citing the mastoid processes as an analogous structure ia the mammalia, also adduces the extensive sinuses containing air in the cranium of the elephant. The air-cavities of the diploe of the cranial bones in the porcupine are also remarkable for their extent.] b [In this note we have undesigned evidence that Hunter had never read the Memoir of Camper, or he would hardly have omitted to notice the error into which the Dutch anatomist falls with reference to the source whence the bones of the head derive their internal supply of air. Camper states that it is received by the meatus auditorii, believing that birds had no Eustachian tubes: "Pair entre dans le diploe du crane entier par les trous auditifs; car les oiseaux n'ont point de trompes d'Eustache comme les quadrupedes et les amphibies." {Mem. d& Mathcm. et de Physique, torn. vii. 1776, p. 334.)] 200 HUNTER ON THE ANIMAL CECONOMY. which first filled the air-cells of the lungs, then all the others, such as the cells in the abdomen, anterior and superior part of the chest, axilla, os humeri, cells of the back-bone and thigh ; and the whole being afterwards put into spirit of sea-salt, and corroded, the cast of injection came out entire. The singularity of these communications in birds put me upon considering what might be their final intention. At first I supposed it might be intended to assist the act of flying, that being the cir- cumstance which appears the most peculiar to birds; and it might be of service in that respect, I thought, by increasing the volume and strength with the same quantity of matter, wthout adding to the weight of the whole, which indeed would rather be diminished by the difference of specific gravity between the external and in- ternal air. This opinion was strengthened by discovering that the feathers of birds contained also a considerable quantity of air, in the very part which requires the greatest strength, and by the analogy which is observed between this mechanism in birds and what is discoverable in most kinds of fishes ; for these last have air contained within their bodies, which I believe is commonly supposed to lessen their specific gravity, although this does not appear so ne- cessary in fishes, which move in a much heavier element than birds.* * When we consider that the elevating and suspending apparatus is much smaller in fishes than in birds, we may reasonably conceive the air in them was intended as a kind of equilibrium between the fish and water; and that progres- sive motion was the only thing wanted in the actions of fishes. Were we to reason upon general principles alone, we should suppose that those fishes who have the largest air-bags should have their muscles of a greater specific gravity, and those fishes that have none should have the lightest flesh ; therefore that the flesh of the salmon and cod, which have an air-bag, should be heavier than that of the shark, which has none. But to know how far this, which appeared to be reasonable, was a fact, I made the following experiments: Experiment I. I took a portion of muscle of the shark, cod, and salmon, of the same weight in air; and first examined how far they occupied the same space, by immersing them in water, and observing the rise or fall of the water upon each of them being separately immersed in it. The shark occupied the smallest space, the salmon a little more, and the cod the largest. Experiment II. I then suspended the same three portions, upon a level, in a glass vessel filled with water about two feet high, and let them all go at the same instant, to see which would fall through the water in the shortest space of time. The shark got to the bottom first, the salmon next, and the cod last. It is necessary to observe that, in both these experiments, the difference in bulk and in the times of their falling was very little, but, however, sufficient to ascertain the fact for which the experiments were instituted. To see how far the muscular flesh of birds was specifically lighter than that of a quadruped, I repeated the above experiments upon a portion of a hind, of a pigeon, and of a sheep; but could discover no visible difference in their weight. It may be observed there are in common two situations of oil in fishes: in one it is diffused through the fish, as if the body had been steeped in it, as in the salmon, herring, &c. In the other it is found in the liver, as in all of the ray kind, cod, &c, and ingeneral those that have it in one part have none in the other; however, there' are some, although I believe but few, who have their oil in form of what may be called fat, viz., in flakes in the interstice of parts, as the sturgeon. The liver, in those of the ray kind, is large, and extended through OF AIR-CELLS IN BIRDS. 201 But when I found that the ostrich (which is not intended to fly) was amply provided with these cells; and that the common fowl, and many others of that class, which are endowed with the faculty of flying, were less liberally supplied ; when I saw that even the wood- cock, which flies and is supposed to be a bird of passage, was inferior in this respect to the ostrich, and that the bat differed not in structure from animals that do not fly ;* I was compelled, by so many con- tradictions to theory, to suppose that this singular mechanism might be intended for some other purpose. The next conjecture that offered was that these cells were to be considered as an appendage to the lungs; and to this I was led by the analogy observable between birds and amphibious animals. For although both in the bird and amphibious tribe, as the snake, viper, and many others, the lungs are continued down through the whole belly, in form of two bags,f and therefore appear to be larger than the lungs in any other animal, yet in all of them the quantity of surface exposed to the air is much less than in the quadruped; for the cells of the lungs in the bird are larger, and in the snake, &c. the upper part only can perform the office of respiration with any degree of effect, the lower having comparatively but few air-ves- sels. The air must pass through this upper part before it gets to the lower in inspiration, and must also repass in expiration, so that the respiratory surface has more air applied to it than what the lungs of themselves could contain. It is not however to be supposed that the air can be made to pass to and fro in bones as in parts which admit of contraction and dilatation; the purpose answered by these bony cells must therefore be different, and perhaps they should be considered as reservoirs of air.J There is in fact a great similarity the belly; therefore it might be supposed to lighten the body, from oil being lighter than water or the flesh ; but we have oil in the liver of the cod, and in the salmon and herring the oil is diffused through the whole: therefore I am afraid we are not yet acquainted with the full effect of the air-bladder in fishes. * [This is not absolutely true ; for it is a remarkable fact,—and one which gives additional probability to the hypothesis of Borelli as to the final intention of the air-cells of birds in diminishing the specific gravity for the facilitation of flight,—that in one genus of bats (Nycteris of modern naturalists) remarkable for their lofty and continued flight, air-cells are continued beneath the integument, which are inflated from the cheek-pouches. " The skin adheres to the body," says Bell, in his excellent article Cheiroptera (Cyclop, of Anatomy, p. 599), " only at certain points, where it is connected by means of a loose cellular mem- brane : it is therefore susceptible of being raised from the surface, on the back as well as on the under parts. These large spaces are filled with air at the will of the animal, by means of large cheek-pouches, which are pierced at the bottom, and thus communicate with the subcutaneous spaces just mentioned. When the animal, therefore, wishes to inflate its skin, it inspires, closes the nostrils, and then, contracting the cavity of the chest, the air is forced through the open- ings in the cheek-pouches under the skin, whence it is prevented from returning by means of a true sphincter, with which those openings are furnished, and by large valves on the neck and back. By this curious mechanism the bat has the power of so completely blowing up the spaces under the skin as to give the idea of a little balloon, furnished with wings, a head, and feet."] t [In most snakes the abdominal air-bag is single, but a rudiment of the second lung exists.] t It is not to be supposed that the air in the cells in birds will be changed 202 HUNTER ON THE ANIMAL CECONOMY. between birds and that class of animals called amphibia; and although a bird and a snake are not the same in the construction of the respiratory organs, yet the circumstance of the air passing in both beyond the lungs, into the cavity of the abdomen, naturally leads us to suppose that a structure so similar is designed in each to answer a similar purpose. This analogy is still further supported by the lungs in both consisting of large cells.* Now in amphibious animals the use of such a conformation of the lungs is evident, as it is in consequence of this structure that they require to breathe less frequently than others ; and in this respect it may in birds have some connexion with flying, as that motion might easily be imagined to render frequency of respiration inconvenient, and a reservoir of air would therefore become singularly useful. Although we are not to consider this structure in birds to be an extension of lungs, yet I can easily conceive this accumulation of air to be of great use in respiration. For it was observed before respecting the amphibia, that the air in its passage to from these cells must certainly have a considerable effect upon the blood in the lungs, by allowing a much greater quantity of air to pass in a given time than if there was no such construction of parts ;f and this opinion will not appear to be ill founded, if we consider that both in the bird and in the viper the surface of the lungs is small in comparison to what it is in many other animals which have not this extension of cavity. It is also a corroborating circumstance, that in the fowl, the air might have passed by a much readier way than through the lungs into all the cells about the breast, neck, axilla, wings, &c, as these could have been filled from the lower end of the trachea, upon which many of while flying; only accumulated and retained; not in the least influenced by either inspiration or expiration. It might be asked, Where is the stricture upon the air when flying, so as to keep the parts distended? Is it upon the outlets from the lungs, or is it at the glottis, as in the quadruped ? For we may observe that when an animal is using considerable exercise, it never either expands the lungs, nor makes a full expiration, giving the ribs and diaphragm as little extent of motion as possible, so that the body may be kept firm, which obliges it to breathe oftener; and as this quantity of air is not sufficient for the accelerated motion of the blood, the animal gets what is called out of breath, which is no more than the two not being proportioned; and when it rests, it breathes as quick and takes as long strokes as possible, to make up the loss. So that in exercise we probably breathe less air. * [The air-cells are smaller, and much more numerous in the lungs of birds than in the corresponding anterior or true respiratory portion of the lungs of rep- tiles. The analogy which Hunter here mentions, as also that between the ab- dominal air-receptacles of birds and the air-bladders of fishes, to which he previ- ously alludes, had not escaped the observation of Hervey, who says, " Quin etiam (quod tamen a nemine hactenus observatum memini) avium bronchia, siveasperae arteriae fines, in abdomen perforantur, aeremque inspiratum intra cavitates illarum membranarum recondunt. Quemadmodum pisces, et serpentes intra amplas vesicas in abdomine positas eundem altrahunt et reservant; eoquefacilius natare existimantur."—De Generatione Animalium, Ex. 111.] f It may, perhaps, occur to some, that the whole of these communicating cells are to be considered as extended lungs ; but I can hardly think that any air which gets beyond the vesiculated lungs themselves is capable of affecting the blood of the animal, as the other cavities into which it enters, whether of the soft parts or of the bones, appear to be very little vascular. OF AIR-CELLS IN BIRDS. 203 them lie. But the air must now take a roundabout passage both in its way ip and its way out, those openings being upon the exterior surface of the lungs. * We must not, however, give up the idea of such structure being of use in flying; for I believe we may set it down as a general rule, that in the birds of longest and highest flight, as eagles, this diffusion of air is extended further than in the others. This opinion is strengthened by comparing the structure above described with the respiratory organs in the flying insects, which are composed of cells diffused through the whole body; these are extended even into the head and down the extremities; while there is no such appearance in the insects that do not fly, as the spider; but why the pelican should be so amply provided Tcannot say, not knowing the natural history of that bird sufficiently to be able to judge of this point. Do they carry weights in the large fauces so great as to require such an increase of substance without increase of weight? How far this construction of the respiratory organs may assist birds in singing deserves investigation, as the vast continuance of song, between the breathings, in a canary-bird would appear to arise from it. This is a subject, however, which I shall not at present enter upon.* * [The objection offered by Hunter in the preceding note to the use of the air- cells as accessory organs of respiration, is weakened, if not removed, by the anatomical fact that the bronchiae open into them by such direct and wide apertures as to render it most probable that much of the air passes at once into the air-receptacles without having previously been'decomposed in the vesicles of the lungs. It may be concluded, therefore, that the respiratory function is heightened, in harmony with the increased energies of the circulating and locomotive powers in birds, by means of the extensive system of continuous air-receptacles above described, which operate both by effecting a change in the blood of the pulmonary circulation in the return of the air of the cells through the bronchial tubes, and also by the change which the blood undergoes in the capillaries of the systemic circulation, which are in contact with the air-receptacles. A second use of the air-receptacles in reference to the respiratory function arises out of the mechanical aid which they afford in the action of breathing. During inspiration the sternum of the bird is depressed or recedes from the spine, the angle between the vertebral and sternal ribs is made less acute, and the thoracic cavity proportionally enlarged ; the air then rushes into the lungs and into the thoracic air-receptacles, while those of the abdomen become flaccid; when the sternum is raised, or approximated towards the spine, part of the air is expelled from the lungs and thoracic cells by the trachea, and part driven into the thoracic receptacles, which are thus alternately enlarged and diminished with those of the thorax. Hence the lungs, notwithstanding their fixed con- dition, are subject to due compression through the medium of the contiguous air- receptacles, and are affected equally and regularly by every motion of the ster- num and ribs. A third use, and one which Hunter inclines to admit, is that of rendering the whole body specifically lighter, in relation to the peculiar actions of flight. A diminution of specific gravity must necessarily follow the desiccation of the marrow and other fluids in those spaces which are occupied with the air-cells, and by the rarefaction of the contained air by the heat of the body. In harmony with this view are the facts, not only that the quantity of air admitted into the system is in proportion to the general powers of flight, but also that in birds where the skeleton is only partially permeated by air, this is especially distributed to 204 HUNTER ON THE ANIMAL CECONOMY. 18. A DESCRIPTION OF THE NERVES WHICH SUPPLY THE ORGAN OF SMELLING. The nerves being in themselves perhaps the most difficult parts of an animal body to dissect, becomes a reason why we are still unacquainted with many of their minuter ramifications; yet if a knowledge of these, together with that of their origin, union, and reunion, is at all connected with their physiology, the more accu- rately they are investigated the more perfectly will the functions of the nerves be understood. I have no doubt, if their physiology was sufficiently known, that we should find the distribution and complication of nerves so imme- diately connected with their particular uses, as readily to explain many of those peculiarities for which it is now so difficult to account. What naturally leads to this opinion is, the origins and number of nerves being constantly the same, and particular nerves being invariably destined for particular parts, of which the fourth and sixth pair of nerves are remarkable instances. We may there- fore reasonably conclude, that to every part is allotted its particu- lar branch, and that however complicated the distribution may be, the complication is always regular. There are some nerves which have a peculiarity in their course, as the recurrent and chorda tympani; and others which are appro- priated to particular sensations, as those which go to four of the organs of sense, seeing, hearing, smelling, and tasting; and some parts of the body having peculiar sensations (as the stomach and penis), we may, without impropriety, include the fifth, or sense of feeling. This general uniformity in course, connexion, and distri- bution, will lead us to suppose that there may be some other pur- pose to be answered than mere mechanical convenience; and many of the variations which have been described in the dissec- tions of nerves, I believe to have arisen from the blunders of the anatomist, rather than from any irregularity in their number, mode of ramifying, course, distribution, or connexion* with each other. those members which are most employed in locomotion : thus it is admitted into the wing-bones of the owl, but not into the femur; while in the ostrich the air penetrates to the femur, but not the humerus or other bones of the wing. I have already alluded to the secondary use which the air-cells may afford to some large and long-winged bird, which, like the Argala, or the Frigate Bird, hover with a sailing motion for a long-continued period in the upper regions of the air, by diminishing the necessity for muscular exertion by the tendency of the distended air-cells to maintain the wings outstretched. Of the same adventitious character is the use finally suggested by Hunter to the air-receptacles, of contri- buting to sustain the song of birds, and to impart to it tone and strength. It is no just objection to this function that the air-cells exist in birds which are not endowed with the mechanism and power of song, since it is not pretended that this is the primary or exclusive office of the air-cells. The latest writer on the pneumaticity of birds, M. Jacquemin, has indeed reproduced this suggestion of Hunter's as a novel idea.] * Here it is to be understood I do not mean lateral connexion, such as two branches uniting into one chord and then dividing; or a branch going to a part, THE. NERVES OF THE ORGAN OF SMELLING. 205 We observe no such uniformity in vessels carrying fluids, but find particular purposes answered by varying their origin and dis- tribution : the pulmonary artery answers a very different purpose in the circulation of the blood from that of the aorta ; yet both arise from the same source, the heart. The course of the arteries is such as will convey the blood most conveniently, and therefore not necessarily uniform, it not being very material by what channel, provided the blood is conveyed,to the part; though in particular instances certain purposes may be answered by a peculiarity in origin and distribution, as happens in the testicle of quadrupeds. This observation respecting arteries is likewise applicable to veins, and still more to the absorbent vessels; in which last, regularity is even less essential than in the veins. Whoever, therefore, discovers a new artery, vein, or lymphatic, adds little to the stock of physiological knowledge; but he who discovers a new nerve, or furnishes a more accurate description of the distribution of those already known, affords us information in those points which are most likely to lead to an accurate knowledge of the nervous system; for if we consider how various are the origins of the nerves, although all arise from the brain, and how different the circumstances attending them, we must suppose a variety of uses to arise out of every peculiarity of structure.* Indeed, if we reflect on the actions arising immediately from the will and affections of the mind, we must see that the origin, con- nexion, and distribution of the nerves ought to be exact, as there either single or double, for still it is the same nerve; or whether a branch unites with another a little sooner or a little later, for still it is the same branch. Such effects may arise more from a variety in the shape of the bodies they belong to, than any variety in the nerves themselves.a *" [With reference to anatomical researches on the nervous system, Sir Charles Bell has observed: " Whilst the nerves are supposed to proceed from one great centre, to have the same structure and functions, and to be all sensible, and all of them to carry what has been vaguely called nervous power, these discoveries of new nerves and ganglia are worse than useless ; they increase the difficulty, and repel inquiry."—Exposition of the Natural System of the Nerves of the Human Body, 1824, p. 70. The different views entertained by Hunter on this subject doubtless arose from his belief that a variety of uses arose out of the various origins and other pecu- liarities of structure of the nerves. Hence he was led to trace the different nerves which are distributed to a single organ to their different origins, and to infer that the organ thereby received different sensitive endowments. It is this principle, in a more extended application from the nerves to their component filaments, so far as they have different origins, which forms the basis of the present improved doctrine of the nervous system. " The key to the natural system of the nerves," says Bell, " will be found in the simple proposition, that each filament or track of nervous matter has its peculiar endowment, independently of the others which are bound up along with it, and that it continues to have the same endowment throughout its whole length."—Ibid.] a [See the observations of Swan on the exceptions which occur in the uniformity of the anatomical conditions of the nervous system, in his excellent 'Demonstra- tion of the Nerves of the Human Body,' pp. 29, 30, 31.] 19 206 HUNTER ON THE ANIMAL CECONOMY. are parts whose actions immediately depend upon such circum- stances. The brain may be considered as having an intelligence with the body ; but no such intercourse subsists between the differ- ent parts of the body and the heart. In the summer of 1754, being much employed in dissecting the nerves passing out of the skull, I was, of course, led to trace many of their connexions with those from the medulla spinalis ; and was assisted bv Dr. Smith, then pursuing his studies in London.* The better to "trace these nerves through the foramina of the skull, I steeped the head in a weakened acid of sea-salt till the bones were rendered soft, and that the parts might be as firm as possible, and at the same time free from any tendency to putrefaction (it being summer), the acid was not diluted with water, but with spirit. When the bones were rendered soft, pursuing my intention, I dis- sected the first pair of nerves, and discovered their distribution ; and having made a preparation of the parts in which they were found, I immediately had drawings made from them, with a view to have presented the account to the Royal Society ; but other pursuits pre- vented it.f Engravings were afterwards made from these drawings, and the preparation was repeatedly shown by Dr. Hunter, in his courses of anatomy, who, at the same time, pointed out that altera- tion in the mode of reasoning upon those nerves which would naturally arise from this discovery. In this dissection I found several nerves, principally from the fifth pair, going to and lost upon the membrane of the nose ; but suppose that those have nothing to do with the sense of smelling, it being more than probable that what may be called organs of sense have particular nerves, whose mode of action is different from that of nerves producing common sensa- tion, and also different from one another, and that the nerves on which the peculiar functions of each of the organs of sense depend, are not supplied from different parts of the brain. The organfof sight has its peculiar nerve ; so has that of hearing; and probably that of smelling likewise; and, on the same principle, we may sup- * Dr. Smith was afterwards teacher in chemistry and anatomy in the university of Oxford ; is now Savilian professor of geometry, and lecturer in physiology. This account of the first pair of nerves, as also of the branches of the fifth, is taken from the original description written by him, and taken from my dissection when I was tracing them. f Dr. Scarpa, professor of anatomy at Pavia, while in London in 1782, ac- quainted me that he had dissected the ramifications of the olfactory nerves, and that on his return to Italy he meant to publish an account of them. At this time I showed him my drawings and engravings. I have lately been informed that he has published his account, but have not met with it: I have, however, seen one of his engravings, which was executed in London, and is very elegant. It only shows those on the septum narium, whose minuteness is rather carried further than the power of dissection, and the ramifications are more regular than we find them in Nature.a » [See Scarpa, Anatomicx Disquisitiones de Auditu et Olfactu, fol. 1789, and Anatomicarum Annotationum, Liber secundus De Organo olfactus prsecipuo, deque Nervis nasalibus interioribus e Pariquinto Nervorum cerebri, 4to., 1782.] THE NERVES OF THE ORGAN OF SMELLING. 207 pose the organ of taste to have a peculiar nerve. Although these organs of sense may likewise have nerves from different parts of the brain, yet it is most probable such nerves are only for the common sensations of the part, and other purposes answered by nerves. Thus we find nerves from different origins going to the parts composing the organ of sight, which are not at all concerned in the immediate act of vision; it is also probable, although not so demonstrable, that the parts composing the ear have nerves be- longing to them simply as a part of the body, and not as the organ of a particular sense: and if we carry this analogy to the nose, we shall find a nerve, which we may call the peculiar nerve of that sense : and the other nerves of this part, derived from other origins, only conveying common sensation, and we may suppose only in- tended for the common actions of the part. This mode of reasoning is equally applicable to the organ of taste; and if the opinion of peculiar nerves going to particular organs of sense be well founded, then the reason is evident why the nose, as a part of our body, should have nerves in common with other parts, besides its peculiar nerves ; and, as the membrane of the nose is of considerable extent, and has a great deal of common sensation, we may suppose the nerves sent to this part for that purpose will not be few in number. It is upon this principle the fifth pair of nerves may be supposed to supply the eye and nose in common with other parts ;* and upon the same principle, it is more than probable, that every nerve so affected as to communicate sensation, in whatever part of the nerve the impression is made, always gives the same sensation as if affected at the common seat of the sensation of that particular nerve.f * [Since the period when Hunter wrote this remarkable paper, in which the principle of different nerves having particular functions in relation to differences of origin and other anatomical conditions is so distinctly enuntiated, the attention of physiologists has been more especially called to the fact of the organs of sense being supplied by nerves from different sources, for the purpose of different en- dowments, by the experiments of Magendie. He divided the fifth pair of nerves within the cranium, and thus contributed to define more exactly than had before been done the importance of common sensation to the safety of some of the organs of sense, as the eye, and also the share which touch bears in the impressions received by the organs of special sense, as in that of smell. Physiological science does not perhaps afford a more striking example of the inferiority of mere experimental inquiry to that which is based on extensive anatomical induction, than the singular conclusions at which Magendie arrived after performing the experiment above alluded to. There are few physiologists, however, who do not adopt the conclusions of Hunter, that the organs of sense receive their endowments of ordinary sensation from the fifth pair, which is common to each, in preference to the well-known view originally adopted by Magendie. (See Journal de Pysiologie Exper., vol. iv., 169. " Le nerf olfactif est-il l'organe de l'odorat ?")] f I knew a gentleman who had the nerves which go to the glans penis com- pletely destroyed by mortification, almost as high as the union of the penis with the pubes; and at the edge of the old skin, at the root of the penis, where the nerves terminated, was the peculiar sensation of the glans penis; and the sensa- tion of the glans itself was now only common sensation; therefore the glans has 208 HUNTER ON THE ANIMAL CECONOMY. The first pair of nerves arriving at the part of its destination as soon as it escapes from the skull, and immediately ramifying, has rendered its distribution more obscure than that of the others, whose course to the part to which they are allotted is visible and to be traced. As the body of the nerve, while within the skull, is pulpy and composed of the brain itself, it easily breaks off at the very di- vision and exit of the small branches; it therefore becomes impos- sible to trace them, as we usually do other nerves; and they have by most physiologists been considered as never forming chords, but going on in their pulpy form to be distributed on the mernbrane of the nose, in a mode somewhat similar to that of the optic nerve, and to what is commonly supposed to take place with respect to the portio mollis of the seventh pair. Winslow has suggested an idea that the first pair forms chords ; but it is only as an assertion, and not having described them, that alone was not sufficient to alter the former mode of reasoning. Haller, who is to be considered as the latest anatomist and phy- siologist, who has published on the subject, on whom we can depead says, that" The first pair of nerves makes its way into the nose covered by the pia mater only, very little altered from what it was when within the cavity of the skull."* This shows that Haller rer tained the old idea concerning these nerves; but we shall find that they become firm chords immediately upon piercing the dura mater and cribriform plate of the ethmoid bone. The first pair, while within the skull, differs in some respects from all other nerves: firstly, it seems to be made up of a cortical and medullary substance ; while the others appear to consist of me- dullary alone; and secondly, it is different, in that it does not seem to be composed of fasciculi, and has but one covering from the pia mater investing the whole nerve, whereas other nerves appear to have a covering round each fasciculus; and this is probably the reason why the first pair is weaker while within the skull than the others. Its form is somewhat triangular, having three edges, from lying in a groove made by two convolutions of the brain. The course is forwards, a little upwards and inwards, and where it lies upon the cribriform plate of the ethmoid bone becomes somewhat larger, and divides into a grea,t many branches, like so many roots, answering to the number of holes in that plate, except one left for a branch of the fifth pair; but these divisions we cannot see, they being covered by the body of the nerve, which cannot be raised without breaking off the small branches at their origin. As the probably, different nerves, and those for common sensation may come through the body of the penis to the glans. A Serjeant of marines, who had lost the glans and the greater part of the body of the penis, upon being asked if he ever felt those sensations which are peculiar to the glans, declared, that upon rubbing the end of the stump, it gave him exactly the sensation which friction upon the glans produced, and was followed by an emission of the semen. * Elementa Physiologiae, vol. v., p. 151. OF SOME BRANCHES OF THE FIFTH PAIR OF NERVES. 209 branches of the nerve pass through this bone, they seem to take processes from the dura mater along with them, then becoming firm chords, similar to other nerves. These branches, after they have got through the bone, form themselves into two planes or divisions, one passing on the septum, the other on the turbinated bones. Those of the septum narium, in their passage to the nose, are first continued a little way down, in bony canals of the perpendicular lamella of the ethmoid bone, which holes become small grooves in that bone ; and those on the opposite side being more numerous and smaller, pass down through small holes that are on the inside plate of the ethmoid bone, which holes are likewise continued into grooves, for a little way, upon that plate. When the branches get upon the membrane of the nose, they subdivide into a great many smaller ones, which are somewhat flattened, and are only to be seen on that side of the membrane that adheres to the bones, not being visible at all on the other; so that the dissection of these nerves is no more than separating the membrane and bone from each other. They can hardly be dissected all round ; and the further they are traced upon the membrane the fainter they become, and growing smaller they sink deeper and deeper into the membrane to get on its outer surface, where we must suppose they terminate. Those upon the septum pass down a little radiated, and the branches, especially at the upper part, or at their first setting out, unite with one another. Those on the side next the antrum, when they have reached the membrane of the nose, in their course to the superior turbinated bone, form a very considerable network or plexus; and when they reach that bone, do not all go round its convex curvated pendulous edge to the concave side, but some passing through its substance get immediately upon it, which is the reason why we find so many holes in that bone. It is difficult to trace them further; but we have reason to suppose that they go through the inferior turbinated bone in the same manner, since we find similar holes. 19. A DESCRIPTION OF SOME BRANCHES OF THE FIFTH PAIR OF NERVES. In tracing the course of the olfactory nerves, I also discovered several branches of the fifth pair not commonly known, particularly two that were supposed to go to the membrane of the nose for the sense of smelling, but which only pass through that organ to their place of destination. The first is a small nerve from the first branch of the fifth pair; or, according to Winslow, the nervus ophthalmi- cus Willisii, which small nerve is called by Winslow the nasal. This branch, after having passed out of the skull into the orbit, re- enters the cranium through the foramen orbitariumanterius, and gets 19* 210 HUNTER ON THE ANIMAL CECONOMY. on the cribriform plate of the ethmoid bone; from thence it passes down through one of the anterior holes of the cribriform plate, and after having continued its course in a groove on the nasal process of the frontal bone, runs forward and downward in a similar groove on the inside of the os nasi; from thence getting on the outside of the cavity of the nose, it runs along the cartilaginous part of the ala, and near the extremity of the nose mounts up upon the tip of the ala, and then dipping down between the two alae, is lost on the anterior extremity of the cartilaginous septum. In its course it sends several small filaments into the alas. The second is a branch of the superior maxillary nerve; for that nerve, having passed through the foramen rotundum, divides and sends off several branches, one of which passing backwards and inwards, through the foramen commune, between the orbitar process of the palate, and the root of the ala of the sphenoid bone, gives a branch which gets into a fissure that seems to separate the root of the ala from the body of the sphenoid bone, where that bone makes the roof of the nose. This branch then passes along the under surface of the body of the sphenoid bone, in its way to the septum narium, and getting upon that part, passes along between its membranes and the bone : its course is downwards, and forwards towards the foramen incisivum, through which it passes and is lost in the gum behind the first dentes incisores, and on the membrane of the roof of the mouth at that part. There is another branch of the superior maxillary nerve, which comes off from a large branch that is going down to the mouth, uvula, &c, and this branch, with its division into two, has been described by Professor Meckel, of Berlin; but after tracing one of these into the portio dura, he pursued the search no further. This branch of the superior maxillary nerve passes back through the foramen pterygoideum, accompanies the carotid artery as it passes across the posterior edge of the foramen, and there divides into two branches; one of which passes down along with the carotid artery, through the basis of the skull, and proceeding in a direction con-. trary to the course of the artery, in contact with that branch of the cervical ganglion that passes up with the carotid artery to join the sixth pair, then joins the first cervical ganglion. The other branch decussates that artery on its upper surface, and getting upon the anterior side of the petrous portion of the temporal bone, enters a small hole near the bottom of that large one which affords a pas- sage to the seventh pair of nerves, joining the portio dura just where that nerve, making its first turn, passes along with it through what is called the aqueduct. This nerve, composed of portio dura, and the branch of the fifth pair, sends off, in the adult, the chorda tympani before its exit from the skull; and in the foetus immediately after. The termination of the branch, called chorda tympani, I shall not describe; yet I am almost certain it is not a branch of the seventh pair of nerves, but the last-deseibed branch from the fifth pair; for I think I have been able to separate this branch from the CROONIAN LECTURES ON MUSCULAR MOTION. 211 portio dura, and have found it lead to the chorda tympani; perhaps it is continued into it; but this is a point very difficult to determine, as the portio dura is a compact nerve, and not so fasciculated as some others are. However this may be, it is very reasonable to suppose that the chorda tympani is a branch of the fifth pair, as it goes to join another branch arising from the same trunk.* 20. CROONIAN LECTURE ON MUSCULAR MOTION, NO. I. FOR THE YEAR 1776. [Read before the Royal Society, by Mr. John Hunter, F.R.S.f] A self-moving power is such a phenomenon as must call up the attention of the thinking mind (while ignorant of the cause); and when that very mind is connected with this power it becomes still more interested. This power of motion was first discovered to be inherent in parts of an animal body of a certain construction, called muscles.J This construction appeared to be a composition of fibres, which were called muscular: and motion was supposed to be produced by these contracting in length, and all the varieties of motion in an animal * [This is a point which it is undoubtedly very difficult to decide by dissection of the parts in the human body. Cloquet, Hirzel, and Majendie describe the chorda tympani according to the supposition of Hunter. In the horse and calf, however, where the portio dura is less dense in its structure, the Vidian branch of the fifth may be distinctly seen crossing that nerve after penetrating its sheath, and separating into many filaments, with which filaments of the seventh nerve are blended, and a ganglion formed by the superaddition of gray matter; the chorda tympani is here continued partly from this ganglion, partly from the seventh or portio dura.] f [In Home's Account of the Life of John Hunter, prefixed to the treatise 'On the Blood, Inflammation, and Gunshot Wounds,'1794, p. xxviii., is the following passage: " Besides the papers which he presented to that learned body (the Royal Society), he (Mr. Hunter) read six Croonian Lectures upon the subject of mus- cular action, for the years 1776, 1777, 1779, 1780, 1781, 1782. In these Lec- tures he collected all his observations upon Muscles respecting their powers and effects, and the stimuli by which they are affected ; and to these he added com- parative observations upon the moving powers of Plants. These Lectures were not published in the Philosophical Transactions ; for they were withdrawn as soon as read, not being considered by the author as complete dissertations, but rather as materials for some future publication."] X [Both Aristotle and Hippocrates were ignorant of the function of the muscu- lar fibre: the important discovery that the animal motions were performed by the muscles is attributed to Lycus of Macedon, who wrote a voluminous work on Myology. It is certain that the use of the muscles was known to Herophilus, since he is quoted by Galen as having spoken of the happy disposition of the muscles for the movement of the limbs. To Herophilus belongs the honour of having first discovered in the nerves the organs of sensation and of voluntary motion.] 212 HUNTER ON THE ANIMAL CECONOMY. the most complicated, to be the result of the manner in which these fibres were disposed. It is no wonder, then, that the mode in which a muscular fibre produces motion has been esteemed an inquiry not unworthy the attention of the greatest philosophers, and has almost universally been one of the principal researches of the physiologist; especially when we consider that the substance, called muscular, alone con- stitutes the largest part of most animals; and indeed many are wholly composed of it. The inquiries into the nature of self-motion have been principally confined to animals; most probably from the power in them being more conspicuous, which almost prevented its being taken notice of in any other substance whatever. Inquiries into nature have, how- ever, become less confined, and experiments and observations have induced men to leave the beaten track of others, and take their ob- servations from nature herself; by which means a self-moving power has been observed and universally allowed in vegetables. And this principle, upon investigation, appears now to be as much a property in vegetables as in animals; and in such cases where the functions and uses are the same in both, it is perhaps as con- siderable in vegetables as animals. But where they are dissimilar in their actions, and the uses arising out of these actions are also different, it is reasonable to suppose the quantity of action will vary; and such difference must frequently occur in both animals and vegetables. In animals a considerable part of this motion is called muscular; in vegetables it has not yet got a name. The immediate cause of motion in all vegetables is most probably the same, and it is probably the same in all animals; but how far they are the same in both classes has not yet been determined. But I think it will appear, in the investigation of this subject, that vegetables and animals have actions evidently common to both, and that the causes of these actions are apparently the same in both: and most probably there is not an action in the vegetable which does not correspond or belong to the animal, although the mode of action in the parts may not be the same, or muscular, in both. There appear, however, to be actions in animals which are peculiar to them ; these make them more complicated, and in them another stimulus to action is superadded, evidently for that purpose.* * [The actions here alluded to are the voluntary, which are consequent upon an act of sensation, and are the result of a determination or stimulus derived from the brain. The action in the muscle produced by this stimulus is, how- ever, essentially the same as is produced by mechanical or chemical stimuli ap- plied to the muscle out of the body, or as takes place in the muscle involuntarily as in sleep, or when an animal is stimulated while in a state of hybernation, or immediately after decapitation. Instead therefore of saying that animals have actions of the moving powers peculiar to themselves, it is more correct to express, with reference to the volun- tary actions, that they have parts superadded, for the purpose of exciting the actions of the moving powers, which the vegetable has not, viz., the nerves. It is true that the actions of the moving powers of an animal, whether automatic CROONIAN LECTURES ON MUSCULAR MOTION. 213 All actions may be considered of two kinds, immediate and secondary. The first is an action of the part itself, having no relation to any- thing else ; as action in a muscle, or elasticity in a spring. The second may be divided into two kinds,—first, where this action has an effect upon some other part, or moves it, which is the ultimate effect, as the heart moving the blood by contracting,— secondly, where the action is applied to some other body adapted for a particular motion, which is to produce the ultimate effect, such as the muscles of a joint. We may in general observe, from what we know of motion or action in matter, that it is always preceded by something which we call the cause; and that the immediate cause is an irresistible impulse to action, which action becomes the effect. A body endowed with the power of self-motion is under the same influence of im- pulse as matter in general: it cannot move without an intermediate cause for its motion. Self-motion may be of three kinds in the more perfect animals. The first is where the motion is excited by a cause from within the animal itself, and is employed in the oeconomical operations and functions of the machine, and with the materials the machine is already in possession of, which are only made use of in the growth of parts, secretion of fluids, &c. The second is where motion is excited from an internal cause, and is employed in particular functions and operations, but where such materials used are out of the body; as in those excited in consequence of hunger and thirst, the passion between the sexes, &c. The third is where motion is excited by external stimuli, and where whole parts are put in mo- tion : as where the sight or voice of a person excites one to approach him; the application of a medicine which excites vomiting, &c. We can have no other idea of these motions in animals but that they are muscular: and as the two first of these actions exist in vegetables, it is natural to suppose that there is a similarity in the cause which produces the same final intention, although the same mode of action or a similar power is not made use of to pro- duce it. These immediate causes of action in an animal are called stimuli, and the capability in parts for action is termed irritability; but such a definition is too confined for the numerous actions excited in an animal body. The word stimulus is pretty well determined in its signification; it is an incitement to an action of a proper or salutary nature : but the calling a part capable of being stimulated an irritable part, weakens the idea of the stimulus being the cause of the action ; and indeed the expression of a part being irritated conveys a different meaning from what would be annexed to the effect produced by a or voluntary, are different from those which produce the motions of parts in vegetables, as explained in the notes, pp. 216, 222 ; but the observations in the text refer only to the voluntary actions.] 214 HUNTER ON THE ANIMAL CECONOMY. stimulus. I would therefore define a ' stimulus' to be the cause of an increased natural action ; and an ' irritation' to be the cause of an unnatural, disagreeable, or diseased action. Vegetables as well as animals have their motions produced by these causes, and are subject to the very same laws. A stimulus or excitement to actions of a salutary or proper kind is simple, and depends on the original mode of action, or the original laws of the vital ceconomy, and the action only changes in some degree as the properties of the matter which stimulates changes. An irritation or excitement to morbid action is according to the susceptibility of the body or part which is to be excited to action, and alters ac- cording to the power of the irritating matter, combined with the various susceptibilities of different animals and parts for irritation ; for different animals and parts have different modes and powers of receiving the same power of irritation. In the more perfect animals we have the senses, or parts so con- structed as to be impressed by the various properties of matter, and, as it were, adapted to these properties alone. These are con- nected together by the brain, or common sensorium, which is com- mon to the whole of the sensitive powers: to and from the brain pass the nerves, or conductors of sensation and voluntary stimulus. But as animals become more and more imperfect, the senses, or parts constructed so as to be impressed by the properties of matter, become fewer, and the common sensorium less perfect. There appear to be animals entirely deprived of these parts or senses, and consequently having neither brain nor nerves.* These senses give us intelligence of the various properties of matter, from whence we derive our acquired actions, and have been naturally led to suppose that there were no other causes of action in an animal body. The eye gives us at once the shape or limits, and the various effects of the reflection of light from bodies at a distance; the first of which could not be sufficiently effected by the sense of touch, and the second we could not have had the least idea of, the common powers of touch not being sufficiently acute. The ear is adapted to receive the vibrations of air, giving us intelligence of bodies at a distance. The nose is adapted for smelling, giving us the odorous proper- ties of the matter of which bodies at a distance are composed. The tongue is adapted to tasting, giving us a property in matter different from any discovered by the sense of touch. The sense of touch gives us a vast variety of information respecting the form, construction, density, &c, of bodies. In giving * [Mr. Hunter nevertheless appears subsequently to have believed that the animals here alluded to, the Acrila of modern naturalists, had something similar to the materials of the brain diffused through the body; and that every other principle or elementary tissue, as the muscular fibre, was diffused through the whole, making every part alike contractile and stimulable, as in the fresh-water polype, Hydra viridis.] CROONIAN LECTURES ON MUSCULAR MOTION. 215 us form and construction it is somewhat similar to the eye ; but it is obliged to run over the whole for this intelligence, whereas the eye takes in a larger scope of this intelligence at once. However, even the eye is obliged to do the same thing where the object is too large, or where it is examining minutely. None of these senses are affected by a stimulus or an irritant, although either the one or the other may be carried so far as to produce sensation. This, however, is not a necessary effect, unless the stimulus or irritant is the immediate object of sensation; as the stimulus of light to the eye, or the irritation of too much light to the eye. These organs of sense are parts constructed for sensation, and those animals that are endowed with all of them must be the most sensible; and those that are entirely deprived of them must be wholly insensible to every impression arising from the different modifications or external influence of matter. The animals which receive no intelligence from external objects have their actions arising out of immediate stimuli and irritants,* and their consequent sympathies, which last extend to the action beyond the part of impression. The perfect animals in some in- stances seem also to be under some general power or external influence, not referrible to any one sense or all of them taken together: it is a general observation that many animals go into shelter before a storm comes on, and before any of the particular senses can be effected. Many people are weather-wise, as it is vulgarly called, and, like the brutes, are sometimes previously apprised of the ensuing change. Many sleep soundest in a storm, especially when attended with thunder. The natural salutary actions, arising from stimuli, take place both in animals and vegetables, and may be divided into three kinds. The first kind of action, or self-motion, is employed simply in the ceconomical operations, by which means the immediate functions are carried on, and the necessary operations performed, with the materials the animal or vegetable is in possession of, such as growth, support, secretion, &c. The blood is disposed of by the actions of the vessels, according to their specific stimulus, producing all the above effects. The juices of a plant are disposed of according to the different actions of the sap-vessels, arising also from their spe- cific stimulus, which is different from that of blood-vessels, but equally produces growth: but a vine will grow twenty feet in one summer, while a whale probably does not grow so much in as many years.f The second kind of action is in pursuit of external influence, and arises from a compound of internal and external stimulus; it is ex- * [». e. Of stimuli which do not produce action through the medium of the brain.] f [The insensible organic contractility of Bichat corresponds with the kind of action which Hunter here defines.] 216 HUNTER ON THE ANIMAL CECONOMY. cited by the state of the animal or vegetable, which gives the stimu- lus of want, and, being completed by external stimulus, procures the proper supplies of nourishment. It produces motions of whole parts : thus we see the Hedysarum gyrans moving its lesser foliola. This is an action apparently similar to breathing in animals, though perhaps it does not answer the same purpose; yet there is an alternate motion in both. The cirriferous plants, or those bearing tendrils or claspers, requiring to be supported by other bodies, as the passion-flower, briony, vine, &c, stretch out their tendrils as it were at random, moving them slowly in various directions. They are to lay hold of any substance that may be within their reach that can support them, and when they come in contact with a body on that side where their power of motion is greatest they begin to bend in that direction, grasp it, and continue turning round it. We see motions of the same kind in the stems of the Plantce volubiles; some of these turn to the left, as the Lonicera, Humulus, &c.; some to the right, as the Clitoria, Convolvulus, &c. They are directed in this course by a lateral inclination, which takes place only on one side, they having little or no power of action on the other. Those which have one mode of action pursue that principally; but if prevented from doing it, their action then varies. In the vine and other plants the action of the tendrils is in different directions; and they may be seen at one time stretched out on one side of the stem, and in twenty-four hours' time on the opposite side ; and some time after in the direction of the stem itself, or in the very contrary di- rection. These actions arise equally from stimulus; it requires, however, different powers of action, arising from such stimulus, to produce these effects in different plants.* The random action of the polypus is of the same kind as those of plants. It elongates itself and throws out its tentacula, moving them in various direc- tions to catch food ; the use of this action to the animal, however, is immediate, and therefore quicker than those above described-! * [In the plants of the genus Cuscuta the tendrils will only twine around other living plants, which shows that the phenomena of climbing plants are not expli- cable simply by supposing that the inclination of the extremities of the tendrils or stems towards one side is a necessarily inherent law of their growth, but that it is, as Hunter regards it, an action dependent on stimulus, which, in the case of the Cuscuta, would seem to be a species of organic affinity.] f [In comparing the motions of a polype with those of a plant, the following difference must be borne in mind : the motions of a plant, like those of the parts of an animal after their communication with the brain has been cut off, are in- variably the result of external stimulus ; they follow, as it were mechanically, some appreciable change in the surrounding external circumstances or influences, —it may be alteration of temperature, difference of light, the application of a chemical or mechanical stimulus; or, in an animal, loss of blood, &c. But who- ever observes the actions of a living polype will see that although, for the most part, they may be traced to an external cause or stimulus, yet that one or more of the tentacula are occasionally extended or retracted without the slightest appre- ciable change in any of the external circumstances under which the animal exists. These motions evidently result from an internal impulse, and I would refer them to the presence, in the polype, of an organic element,—the nervous matter,—which CROONIAN LECTURES ON MUSCULAR MOTION. 217 The third kind of motion is from external stimulus, and consists principally of the motion of whole parts, which is not inconsiderable in vegetables, as in the Dioncea muscipula and Mimosa pudica is very evident; for the first, upon being touched, closes up, and as it were confines the stimulating cause; the second bends its leaves, from external stimulus. This kind of motion is very strongly illus- trated in the Tragopogon, Calendula pluvialis, and many other plants, which shut up their flowers either towards night or when rain comes on ; and in others of different genera which open in the evening, and shut up on the approach of the sun, as different species of the Convolvulus, Mirabilis, &c.; and in almost the whole class Diadelphia, which chiefly consists of the winged-leaved plants, which shut up their foliola towards night, not expanding them till morning, which is called by Linnaeus the sleep of plants; and in the motion of the footstalk of the leaf of an inverted plant, which twists so as to bring the surface of the leaf naturally uppermost to its natural position, which is remarkable in the vine, where there is evidently an apparatus for motion, although not a joint. These actions are similar to what arise in many animals from external stimulus, more especially those not endowed with sensa- tion, and also to the actions of many parts of animals which do not appear to be directed or stimulated by the brain and nerves; as the actions of a polypus, which has no brain, and the peristaltic motion of the intestines in the more perfect animals, which does not arise from the stimulus of the brain and nerves.* is wanting in the vegetable; even in that plant, which, from the energy of its excitability, has been erroneously called sensitive. There is also an essential difference in the nature of the motion itself of the Mimosa and Hydra. If we touch one of the feelers of the polype it recedes from the irritant by a true con- traction of the part within itself; which contraction appears to result from the injury experienced by that part of the nervous system which is disseminated through the feeler touched. In the case of the Sensitive plant there is nothing like that contraction of the part touched, but only an articular plication of the neighbouring part without any of the dimensions of the irritated leaf being altered.] * [The more just comparison of the motions of plants adduced in the text would be with those automatic actions of whole parts which take place in animals, but which result from the power possessed by the central axis of the nervous system, or any part of it, to transmit the action of an excitable nervous fibril to the ex- citing one with which that central axis or part brings it into communication: I apply the terms excitable and exciting to the nervous fibres with reference to their intermediate relation, as to the muscular fibre and the external stimulus to its contraction. The excitable fibres are those usually termed sensitive; the exciting fibres those usually termed motive. When the communication between the ex- citable nervous fibre and the brain is entire or uninterrupted, the latter may take cognizance of the excitement and sensation be produced. When the exciting nervous fibres of muscular motion are in connection with the brain, the will, through the brain, may excite them to action, and this act of the brain may be felt. The essential character, therefore, of the actions of the brain, whether as a recipient or transmitter of impressions, is consciousness of the action. But this property of consciousness is not possessed by the spinal chord, probably not by the medulla oblongata. Whenever, therefore, an impression received by an ex- citable nervous fibre is transmitted through the unconscious part of the central 20 218 HUNTER ON THE ANIMAL CECONOMY. The apparent difference in these actions would in many cases induce us at first to believe they were produced by different prin- ciples ; as in many species of the same genus of plants some open their flowers in the day, others at night (as in the Mesembryanthe- mum, or fig-marigold), similar to that which is the ceconomy of some animals, as in many species of the same genus of moths (Phalama, Linn.), some fly, seek their food, and procreate in the day; while others are inactive and fixed to one spot, without apparent motion, all day, but on the approach of night become all at once animated, fly abroad, seek their food, and procreate. These actions, are nevertheless, produced by one and the same cause. The owl and hawk are similar in their food, yet dissimilar in their times of catching it: hunger is the first stimulus, animal food is the second; light stimulates the one to motion, darkness the other.* The action, however, in-both arises from the same principle. These three kinds of motion in plants are influenced by various circumstances, and sometimes are all totally suspended-! This is axis to the exciting fibre of muscular motion, the latter phenomenon is unaccom- panied with consciousness or sensation. That the spinal chord, or any segment of it, possessed the power of transmitting an impression from an excitable to an exciting nervous fibre, has been known and admitted as a fundamental fact in physiology since the experiments of Whytt, Blane, and Mayo. To the latter physiologist we are more especially indebted for the most decisive experiments in proof, and the clearest enunciation, of this property of the central nervous axis. Recently the automatic animal motions resulting from this property have been grouped together more extensively than had before been done, and the morbid phe- nomena resulting from them ably traced out by Dr. M. Hall. But I cannot perceive the necessity of a distinct class of excitable nervous fibres for transmitting an impression to the motive fibre through the medium of the spinal chord and brain, and of another class of nervous fibres for transmitting an impression to the motive fibre through the medium of the spinal chord alone; still less can I perceive the necessity for one class of exciting or motive fibres for transmitting the stimulus to the muscular fibre from the brain and spinal chord, and of another and distinct class for transmitting a stimulus received from the spinal chord independently of the brain. It remains to be seen whether anatomy will establish the existence of these four classes of nervous fibres, which, so far as I understand Dr. Hall's hypothesis of the reflex function, are called in to account for the voluntary and automatic and muscular motions. There is not, however, a single phenomenon of automatic motion in parts supplied by spinal nerves which may not be accounted for on the demonstrated property of the central axis to transmit impressions from the excitable to the exciting nerves at any part where they are connected to it, inde- pendently of the rest: and I am at a loss to understand why impressions so received by the spinal chord should not also be transmitted to the brain (its continuity with that organ being uninterrupted), without the necessity of supposing a class of nervous fibres for conveying, in this case, the impressions to the spinal chord, distinct from a second class which are supposed to transmit to the motive fibres those impressions which are not afterwards propagated to the brain. It would appear from the text that Hunter supposed that the animal motions which are unaccompanied by consciousness were altogether independent of the nerves; but they can truly be stated to be only independent of the brain.] * It may be supposed that there is a physical cause for the one seeing only in the day, the other only at night; but it is having a much more enlarged idea of an animal to suppose that the senses are adapted to the first principle than the first principle to the senses. | Similar to drowned people. CROONIAN LECTURES ON MUSCULAR MOTION. 219 generally produced by cold, and shows them to be influenced by the seasons; often this cessation takes place when much weakened by transplanting, &c. I have kept a fir alive for three years with- out the least growth. The second and third kind of actions commonly take place only when the first kind of action is in full vigour, because the first must produce the only parts which are capable of the second and third; and these two last can only be of service to the first when it is in full force, nourishing the vegetable and performing the action of propagation. These actions are almost entirely suspended in some animals from cold, they being in this respect subject to seasons as well as plants. This is most remarkable in the simplest in their construc- tion, and becomes less and less so in the more complicated, they being better adapted to the various seasons. The first of these kinds of action is small and insensible, although its effects are great. The second is considerable in both vegetables and animals, but most so in animals. The third is almost peculiar to animals, as there are very few vegetables visibly affected by external stimulus, while all animals seem to be so. The variety of motions is greater in animals, and more purposes are answered by them, which constitutes the great difference between the actions of a vegetable and an animal; for those powers in an animal not only move themselves, but also other parts of the same body, which in many instances are so mechanically con- structed as to move common matter. A remarkable instance of this is the human hand; and it is by this means all our various operations on the matter of this globe are performed. The first kind of action appears to be stronger in its power, although less in quantity,* in vegetables than in animals; for a small vine was capable of sustaining and even of raising a column of sap 43 feet high,t while a horse's heart was only capable of sup- porting a column of blood 8 feet 9 inches high: both of which columns must have been supported by the action of the internal parts, for we must suppose the heart equal, or nearly so, to the strength or action of the other parts of the vascular system; and when we consider that the sap of the tallest tree must be supported and even raised from the root to the most distant branches, it must appear that the power of such vegetables far exceeds the power of any animal, and indeed it is such as the texture of a vegetable only can support. The power of supporting a leaf erect for a whole day is as great an effort of action as that of the elevator palpe- brarum muscle of the eye of an animal. If we consider the differences in the ceconomy and the mode of life of vegetables and animals, we shall find the increased quantity • I make a material difference between the power and the quantity of action. Some motions may be very small, yet act with great force; while others are of considerable extent, although very weak. f Vide Hale's Veg. Statics, vol. i., p. 112, Exp. 36. 220 HUNTER ON THE ANIMAL CECONOMY. of motion of the three kinds above mentioned, and the increased power of the third kind in animals are only adapting them to those differences. Locomotion, for the purposes of procuring nourishment, con- course of different individuals for the propagation of the species, and destruction of each other, are the chief differences in animals. This power, however, is not given to all animals, and those which are deprived of it have their motion confined to the procuring food and the propagation of their species,* Many of these, although with great impropriety, have been considered as vegetables. To see if the actions of plants were affected by a continuation of stimulus similar to those of animals, I made the following ex- periments. As I took for granted that the analogy could go no further than as it related to the actions produced by external stimuli, my ex- periments were only on such plants as exhibited actions of this kind. As those parts of plants which are capable of the second and third kinds of motion are in general small, as leaves, tendrils, flowers, &c, it is difficult to discover the mechanism upon which the motion depends: the sensitive plant is probably the best of this kind that we are as yet acquainted with. ' As the motion of the petioli is confined principally to one part, and that differing from the others in external appearance, which difference is its increased thickness and uniformity of surface, upon cutting the footstalk longitudinally, as also the stem on which it stands through its whole length, the following appearances may be observed:—f For the purpose of making my experiments I took three sensitive plants, having several others for any comparative experiments which might be thought necessary. I first pitched upon one leaf in each plant which was capable of the greatest motion of collaps- ing and erection; and behind each of these leaves a board was placed, on which was marked the greatest extent of the two motions, so that the leaf was like the index or radius of an arc. To have the greatest part of the day before me, I began my experiments at eight in the morning, while the leaves were in full expansion, and I continued them till four in the afternoon, as longer than this would not have been just, for they begin to collapse of themselves between five and six o'clock. * [The two sexes are also necessarily united in the same individual, as in all attached and pedicellate animals, from the Coralline to the Barnacle, and in many others of slow motions. See note, p. 71.] f [A blank in the manuscript here occurs, which leaves us ignorant as to the result of Hunter's examination of the structure of the irritable intumescence at the base of the leaf-stalks and stalklets of the Mimosa. With his usual sagacity, however, he rightly refers the motive power to this part, and it has been the subject of much diligent and minute investigation since these Croonian Lectures were read.] CROONIAN LECTURES ON MUSCULAR MOTION. 221 Comparative Trials of the Action and Relaxation of Three Sensitive Plants. The time. The point they fell to. The times they took to rise in. The point to which they rose 8 o'cl'k A.M 9£ A.M. 11 A.M. 12 Noon. 10 min. p.m 2 P.M. 3 P.M. 3$ P.M. To the lowest point,' and became sta- tionary. 'To the lowest point, \ but the second . lower down. C The second & third p } lower than lowest > f. point. ) Below lowest point. Below lowest point. 5 1st only below low- ( est point. Ditto. Below lowest point. No.l. Min. 51 77 40 30 60 45 45 15 No. 2, Min. 24 18 30 30 65 45 45 15 No. 3 Min 32 38 60 35 30 45 45 15 'The 1st and 3d rose to the highest point, the 2d not so high, and then became stationary. fThe 3d rose to the highest point, the ; 2d and 1st not so I high, and then be- L came stationary. ( All three rose to with in* a little of the ( highest point, and | there beeame sta- [_ tionary. S All three within a little \ of the highest point CThe 2d and 3d to < highest point, the ( 1st not so high. Ditto. S3d to highest point the 1st and 2d not so high. C 1st and 2d to highest < point, 3d not so ( high. From these experiments we may drkw the following conclusions: That there is no fixed time for the leaves of any of the plants to move through its course. That they are less affected as they become accustomed to the stimulus, but the power of collapsing is increased (although not in the same degree), so that they do not move through the same arc. That they require a stronger or quicker stimulus to produce motion after being some time accustomed to it, which was evi- dently seen in comparing these with others which had not been stimulated. It may also be observed that when these plants collapse in the evening they have nearly the same quantity of flexion as when roughly touched at noon; but if touched after they have collapsed from the effect of the evening, they become much more bent than by the same touch at noon. This would seem to arise from a dis- position to collapse in the evening, and a power of increasing that disposition and action when stimulated. 20* 222 HUNTER ON THE ANIMAL CECONOMY. Their collapsing more in the day, and erecting themselves less after a repetition of such actions, may assist in explaining the prin- ciple on which this depends. Relaxation in Vegetables. There is an action in plants which appears to be the contrary of expansion; it may be considered as a relaxation, or an action of those parts antagonising the others which acted through the day, or at other periods, and takes place at the time these other parts cease to act. This action has hitherto been considered as analogous to sleep in animals, whereas sleep is a total loss of the sensitive principle and all the actions dependent on volition for the time, and there- fore can onlytake place in animals endowed with sensation.* It is rather a defect in the animal than an action or the exertion of a principle. This action of relaxation is seen in the sensitive plant when the folioli close upwards and are kept bent by the power of action in the flexors, till light and some other of its attendants affect it, when the extensors begin to act, and this action of the flexors ceases. The footstalk dropping down favours the idea of simple relaxation ; but this only arises from the position of the plant, for if turned up- side down it still bends against its own gravity, f The one action is produced by the stimulus of light, the other by that of darkness; for if the sensitive plant is kept in a dark room it will keep bent, and perhaps as long as it lives * and if one part of the plant is kept in the dark and the other in the light, that in the dark will be bent, and continue so, while that in the light will ex- pand itself. Light and darkness become stimuli to the same plant, and have much more influence over vegetables than could at first be ima- gined. Many plants only grow through the day, others only grow after it is dark. Sympathy in Vegetables. Sympathy is the action of one part in consequence of an applica- tion being made to another part, or action in another part. This power of action is extended to few plants, and even in these appears to have little variation. It is evident in the sensitive plant; for if one of the little leaves be wounded at its termination it will collapse immediately, as also its fellow on the other side. This action runs through the whole of the rachis of the compound leaves, the leaves bending regularly in pairs. * The polypus does not sleep. f [The powers which produce the depression and elevation of the leaf-stalk operate in a manner precisely the reverse of the flexor and extensor muscles in animals, pushing the moving part from, instead of pulling it towards, the fixed point. See Mayo's Physiology, p. 9 et stq.] CROONIAN LECTURES ON MUSCULAR MOTION. 223 If it is a middle foliole that is wounded the same thing takes place ; they all collapse towards the foot-stalk, but seldom towards the extreme end of the leaf, and in a little time the rachis is inflected and the whole leaf drops at the trunk. It may be remarked that a small flexion takes place towards the tip; but this principally arises from a disposition in the folioles, for a middle one cannot collapse without pressing or folding a little on the one next to it towards the end of the leaf which stimulates it and makes it collapse. It is evident in the tendril of the vine, for these tendrils generally divide into two, near their ends: these two going out from the principal trunk in different directions, if one lays hold of any body and twines round it, the other immediately alters its direction and gradually approaches the same body till it comes in contact with it, and then bends round it and encircles it. This motion, however, is very slowly performed. Sympathy in plants is very slow in producing its actions ; the succession of stimuli in them being slow, the consequent actions must also move slowly along. Plants have but one mode of sympathy, which arises from stimulus. Animals with no brain or nerves have but one also. Those, however, endowed with sensation have three: they have one mode from stimulus, one from sensation,, and one compounded of both. Sympathy in animals, arising from stimulus only, is slow, as in plants ; but sympathy from sensation is often very quick. MOTION IN ANIMALS. Muscles would seem to act by vibration, although in a strong healthy man they are so short as not to be observed; yet if the muscles are made to act beyond their powers they plainly vibrate, but still more plainly in weak constitutions. The weaker a muscle is, the longer would seem to be the vibrations, for if a weak person holds anything out in his hand it shakes. In paralytic cases, whenever they are put to the smallest action, the vibration becomes very long, and the less the action the shorter the vibration. Fear also increases the vibration in proportion as it weakens the muscle.* ♦ [The first part of Dr. Wollaston's Croonian Lecture for 1809 is devoted to the illustration of an opinion on the nature of muscular motion, corresponding with that which Hunter has above enunciated. Dr. Wollaston, as is well-known, was led to infer that each act of contraction, apparently single, consisted in reality of a great number of contractions, repeated at short intervals, by reflecting on the sound perceived upon inserting the extremity of the finger into the ear. This sound, which resembles that of carriages at some distance passing rapidly over a pavement, is not perceived when the force applied to stop the ear is not muscular, unless the action of some distant muscle be communicated through some medium capable of conveying its vibrations. From experiment, associated. 224 HUNTER ON THE ANIMAL CECONOMY. The Causes of Action in Muscles. The actions of muscles have been hitherto attributed to the nerves as a cause; the mode of action of the nerves, however, not being known, most physiologists have thought themselves obliged either to make a new hypothesis, or support an old one; in all which they make it mechanical, depending either upon the motion of a fluid, or the vibration of a solid, or vapour ; but there is not a single known fact attending the nervous system which could either give rise to, or support, these hypotheses, except the distance between the seat of the will and a voluntary muscle; and they have conse- quently been such as few thinking men could adopt. As the brain and voluntary muscles are, with respect to our senses, in two different places, and are connected together by the nerves, it might be supposed there was some fluid in motion that would convey the impression to the mind, or the will of the mind to the voluntary muscles; but these informations are very probably the effects of sympathy. I am afraid we can go no further in the investigation of the cause of the action of muscles than by observing the phenomena which happen, and these all lead us to one cause of action. The visible external cause of the action of a muscle is called 'stimulus,' and it is reasonable to suppose that all causes of such action are similar. This, however, may admit of dispute, the heart certainly having no visible stimulus for its motion, except the being called upon, by the sympathy which subsists between the combined powers of the animal oeconomy, to, exert itself in their favour, which will not account for the heart's motion when removed from that connexion. The great question has hitherto been, whether a muscle is suscepti- ble of impression without the medium of a nerve, or whether a nerve is in all cases necessary to its being called into action; for a stimulus must either affect the nerve which affects the muscle, or the muscu- lar fibre itself must be susceptible of immediate impression from the stimulus. A muscle would appear to be capable of being affected in both ways, for many animals certainly exist without nerves, and plants are susceptible of stimulus where it must be immediate, they never having been supposed to have nerves.* It is also evident in ani- with the above observation, Dr. Wollaston concluded that the vibratory alterna- tions recur between twenty and thirty times in a second, varying in proportion to the degree of force exerted by the muscle ; the greatest number being estimated at thirty-five vibrations in a second, and the lowest at fifteen. The more obvious illustrations of this mode of muscular action, presented by the aged and infirm, are also adduced by Dr. Wollaston, who, without doubt, was quite unconscious ° * rVL°nC l°n PreYiously drawn by Hunter from the same phenomena.] [Ihose who admit that a muscle is susceptible of stimulus only through the medium of the nervous matter blended with its substance, do not scruple to ascribe CROONIAN LECTURES ON MUSCULAR MOTION. 225 mals with nerves that by stimulating a nerve the muscle to which it goes will be immediately thrown into action, the nerve becoming the immediate stimulant, so that a muscular fibre may be stimulated by a nerve as well as by any other impression. The modes of stimulating a muscle will be different according to the nature of the animal or of the muscle. In the more simple animals they will be few, increasing as the animal is more com- plicated. The first kind of stimulus is that common to all animals and vegetables, which regulates the internal machine, producing growth, preparing the parts of generation, &c, &c. The second is the internal stimulus, which respects external matter for the support and continuance of the first, as that pro- ducing breathing, hunger, the desire of propagating the species; all of which are common to vegetables as well as animals, and require the assistance of a third kind to complete the action. Vegetables are supposed with great reason to have an action analogous to breathing, for the same kind of air which kills animals which do breathe, certainly kills vegetables also.* Vegetables im- bibe nourishment, which action arises from the same stimulus as in animals. They also require the stimulus of certain operations to be performed upon them by external matter to enable them to propa- gate. This external matter is either some other part of the same plant, as in the Marchantia polymorphia calyce decemfido, which has the filaments almost constantly in motion striking the antherse.t nervous or sensitive globules to vegetables. But they here create the necessity which an undemonstrable organ is called in to supply. Now the more simple and philosophical mode of considering this question seems to be to examine whether the moving organs are stimulated in any new, distinct, and additional manner in those organized beings in which nerves have been detected; and if it be found that they all manifest spontaneous actions,—motions of parts independent of any external stimulus,—a phenomenon which has never been witnessed in any plant, then the next step would be to determine by experiment the relations subsisting between the new function and the superadded organ. The irritable fibre does not contract in a different manner when stimulated by the will than when stimu- lated mechanically out of the body; nerves, it is true, convey impressions which excite action, and are essential to the application of the voluntary stimulus, but not, therefore, to the muscular contraction. Hence, when we come to account for the cause of the spontaneous actions in animals in which no nerves have been detected, we are justified, by analogy, in attributing the spontaneous stimulus to the presence of undemonstrable nervous matter. But in the case of plants, if we attribute the contractions to anything but the irritability of the moving parts themselves, we must first hypothetically assume that nerves are necessary for the action, and then gratuitously infer their existence. This, however, only leads to a greater difficulty, to account, viz., for the non-existence of spontaneous motions in those organized beings to which nerves are, in the above theory, attributed.] • [As azote, hydrogen, or any gas deprived of carbon and oxygen ; for though vegetables in health and sunshine give out oxygen, they absorb that gas, and emit carbon, but in less proportion, during the night.] j" [In the barberry the filaments supporting the mature anther, when touched, bend towards the germen. In the tigor-lily the female part of the flower is endowed with irritability, and the style bends first to one stamen, then to another.] 226 HUNTER ON THE ANIMAL CECONOMY. The filaments of the flosculae of the thistle produce the same effect, or it is done by some foreign stimulus, as the wind, driving the pollen of the male plants against the germina of females.* Most animals perform these actions themselves, yet in both animals and vegetables a similar stimulus is necessary. The third kind of stimulus is from external or extraneous matter immediately applied to the part, which is also common to animals and vegetables. The fourth kind of stimulus arises from the nerves, which we may reckon twofold; one in consequence of the nerves being im- pressed by external matter, the other from their being impressed by the brain, or sensorium. This is peculiar to animals, many of them receiving intelligence from without, which becomes the regulator of their actions towards that matter which gives the intelligence. This leads us immediately to voluntary actions. The actions of muscles have hitherto only been considered by physiologists in the more perfect animals where this (the voluntary or nervous stimulus), is given,, which becomes a different cause of action from those found in other animals and vegetables. Those actions where the mind, being made sensible of them, may be considered as a cause, are called voluntary actions; and those actions over which the mind has no influence, and about which it is not in the least consulted, are called involuntary actions. The actions of the muscles which go on without the influence of the mind, but can be restrained, increased, or stopped by the mind, are called mixed. There #are also actions which may be allowed to arise from a peculiarity in the state of mind, but not dependent on the will: these are common to both the voluntary and involuntary muscles. Thus an involuntary muscle, as the heart, increases its strokes, and the voluntary muscles of the hands, legs, tongue, &c, tremble when the mind is agitated by anger, fear, &c. These four kinds of action not only appear to arise from different causes, but produce different phenomena. The first kind, or voluntary motions, last only for stated times, beyond which they cannot go, the muscles either losing the power altogether, or the mind becoming incapable of stimulating them ; by which means a cessation of action takes place, which indeed is necessary for the preservation of the animal. For these actions, too long continued, weaken, hurt or destroy the body ; and there- fore the mind which is under no restriction is thus prevented from continuing the action. We have this beautifully illustrated in some of the mixed motions : for where their involuntary motions are em- ployed for the preservation of the animal, as in breathing, they are constant; and where the stimulus of necessity does not constantly * The antherae of vegetables requires some motion to make them burst; some have not the power of producing this motion, but if the power is given they burst immediately. A blast of wind is often necessary, and in such plants, propagation does not go on well in a calm place. CROONIAN LECTURES ON MUSCULAR MOTION. 227 take place they rest, as in the stomach, levator palpebrarum, &c.; but if we voluntarily increase the actions of these they soon tire. The natural involuntary actions of muscles are such as never tire, while the voluntary always do; and we may observe that the muscles which are under the influence of both are never tired of their involuntary actions, while they are of their voluntary. This we might suppose was owing to this property being stamped upon them at first, and for very wise purposes; but it rather appears to be a property arising from the mode of impression, viz., not being impressed by the will, but probably acting from a general impression in the machine, viz., from general principles; whereas the voluntary actions are caused by a peculiar impression of the will, and the mus- cles are so constituted as to tire of that impression, or rather be- come incapable of acting, which gives the sensation called tired. But this is carried further, for in muscles that are entirely at the com- mand of the will, if they take on involuntary actions they never tire. For instance, Lord L——'s hands are almost perpetually in motion, and he never feels the sensation in them of being tired. When he is asleep his hands, &c, are perfectly at rest; but when he wakes, in a little time they begin to move. We tire of voluntary actions whether of voluntary parts or of parts that commonly act involuntarily, as the muscles of respiration. Tiring of action feels to the mind to be in the muscles themselves, but I imagine it must be in the mind, although it is referred to the muscles; for we cannot suppose that the mode of action of a mus- cle directed by the will is different from the mode of action when not directed by the will. This is not a tiring of the will itself, but probably a tiring of the action of the nerves of the will; and as the actions of these nerves is always referred to the part of their des- tination, the tiring is also referred there. The second kind are the involuntary actions, which are lasting, as the parts themselves : these are always fit for action ; and if they are inactive, it does not arise from the want of power in the part to act, but from a cessation of the stimulus, which cessation takes place whenever the action, from peculiar circumstances, is become un- necessary. Such actions are naturally so circumstanced as to be constantly wanted, being for the preservation of the animal, as the motion of the heart. The nerves are only to be considered as conductors carrying impressions from every part of the body to the brain, or carrying the command of the will to those muscles whose actions can only be employed about such external objects as can affect the mind ; but those parts whose actions are unknown to the mind appear not to be affected at all by the will. That the nerves are the principal agents between the mind and . the parts would appear from circumstances respecting their com- parative size; for all those parts which convey a strong sensation, or are intended to perform extraordinary voluntary actions, have large nerves; while those parts of animals which neither give intel- 228 HUNTER ON THE ANIMAL CECONOMY. ligence to the mind of their actions, nor are under the influence of the mind, have very small nerves. A stronger instance of this can- not be given than the electric organ of the torpedo, where the power of giving or restraining the shock depends upon the will: the actions are strong and violent, for he can soon exhaust himself by them; and the nerves which convey the power of the mind exceed, com- pared with the size of the animal, in bulk the nerves in any organ of any other known animal. It is a part whose actions, its growth excepted, depend entirely upon the will, having no power of action of its own; the communication between the will and the organ is large in the same manner as the communication between the senses in general and the brain is large. The voluntary muscles have large nerves to command the action of the muscle, which is independent of the will, although in some degree subservient to it; but they are not so large as those of the senses or electric organs, where they give the part its whole action. A nerve being cut going to a voluntary muscle, the muscle can- not obey the will, and thereby loses its voluntary actions; but it may be stimulated into action by immediate impression from other causes, as electricity. The voluntary and involuntary muscles having their quantity of motion in an inverted proportion to their quantity of nerves, is a strong argument against the nerves being the cause of muscular motion. If it is asked why the involuntary parts have nerves at all, the answer may be given that it is not for their common actions, but to keep up the connexion between the whole, for without them an animal would become two distinct machines, and one might be acting very contradictorily to the other; but by the intercourse between the will and voluntary parts, between the voluntary and involuntary, and also between these last and the mind, an universal and uniform agreement or regulation is kept up, which communi- cation produces one kind of sympathy. This connexion between the living principle and the sensitive produces a compound action, which becomes the cause of the instinctive principle in animals. Muscles are either employed upon the internal operations of the animal, as the heart, muscles of respiration, stomach, intestines, &c, or upon external matter for the support of both, as those of the extremities. The first of these are nearly of the same strength in the robust strong man and the small woman or man, if equally healthy; and it is right it should be so, for the small man has nearly the same resistance to cope with; but it is the others which constitute the strong or weak man. The power of muscles which are influenced by the will, although they have a common power of action with those independent of the will, sooner lose their powers than those which are wholly invo- luntary, as the heart, stomach, bladder, blood-vessels, &c, which CROONIAN LECTURES ON MUSCULAR MOTION. 229 would seem to show that the power of simple life lasts after the will is no more. We might naturally suppose that the voluntary muscles have nearly the same quantity of power of action as the involuntary; but upon considering several circumstances, we should rather con- ceive the contrary; for when we consider the power by which the colon of a horse propels such a load of solid contents, we can hardly conceive the power of any voluntary muscle of the same thickness equal to it. For, as voluntary motion arises from two causes, or has two causes of action, the moment one of these ceases, the power which remains is either not so strong originally as the whole power of the involuntary muscle which has only this princi- ple of action, or not so strong, from want of habit, not having been always employed as a principle of action in them. It is not clear to me but that every muscle has a sphinctorial power of contraction so as to bring them to the middle state. This we may see in the temporal muscles; for by opening the jaws the muscle sinks, and by leaving the jaw to itself, not acting with it in the least, the jaw rises and the muscle in part fills up, so that the jaw is suspended by the half action of the muscle ; however, this power may be much more in some muscles than others. The great variety of causes of muscular motion make it almost inexplicable: they may be said to be three,—the will, passions of the mind, and external stimuli. Those actions arising from the will and the mind appear to be most simple, because they are totally unintelligible; but those arising from external stimuli are either voluntary or involuntary, for a muscle that acts by the com- mand of the will at one time is also capable of being thrown into action by a particular state of mind or external stimulus. Those actions which arise from the will have reason and habit for their continuance; they are such as arise out of imitation, rea- soning, and all the powers collected by the senses. Those actions which arise from the mind belong mostly to the passions, which affect more muscles of the body than the will; perhaps there is not a muscular fibre in the whole animal machine but is at different times affected according to the different affections of the mind, every different state oS mind having its particular muscles to stimulate. Upon many of these occasions reason is introduced, which is provided by this state of mind to call in the assistance of other muscles, to act according to that state, either to bring about an increased action which will destroy itself, or to prevent the increase and continuance of those actions. From extraneous stimuli arise all our internal insensible actions, and these depend upon the principle of simple life, upon which depends also the action of medicines; and health is only the right action of such parts. Some muscles must be put upon the stretch, and they will con- tinue their action far beyond the easy point, or that which was so 21 230 HUNTER ON THE ANIMAL CECONOMY. before this action, as the stomach, intestines, and bladder. Others wait to be stretched, as the uterus; this, however, is not the cause of its contracting again, it is only putting it in a state to act when another cause takes place, as a miscarriage or fcetus at the full time. This is nearly opposite to the other, for what endeavours to empty or relax the uterus becomes the cause of its contraction, not what stretches it. Voluntary actions, when very violent, produce involuntary, as the cramp, from dancing, swimming, &c. We feel every involuntary action of a voluntary muscle, while we do not feel the voluntary, actions ; nor do we feel the actions of an involuntary muscle. When such actions are slight we only feel them as little convulsions, contractions in different parts of the body, called creeping in the flesh, or quivering in the eyelids ; but when these become violent, as in cramps or spasms, then the sensation is pain. Voluntary muscles, the stronger they are, the more they are at the command of the will; and the weaker they are the more they seem independent of the power of the will, and seem to be either at their own command, or at that of the nerve. Strong people are less subject to spasms than weak, w hich may perhaps arise from cus- tom ; the strong muscles being more healthy, are oftener in use, and therefore become more at the command of the will. Women, children, and sick men are subject to fits, for the reason just mentioned; perhaps also diseases of the uterus, for the same reason, are the cause of spasmodic complaints, it being very little at the command of the will, but of other circumstances; and from this disposition draws in other parts by consent, and so brings on general spasm. Voluntary muscles always become tired when long continued in the same action, which accounts for animals tiring sooner by being kept in one position than if allowed to move ; and we find a man can hardly stand five minutes in one position ; he never stands equally upon both legs, but upon one as a base, the other as a prop, so as to be able to shift his legs as they tire. Animals, also, by moving or producing alternate motions by their muscles, can go on for a considerable time, but their alternate motion must not be quick, as it always requires a certain time for muscles to regain the power which they lost in action, and if the alternate motion becomes quick and violent, it may tire sooner than constant motion. The voluntary actions of young animals are not so strong, and are much less lasting than those of middle age ; that strength they have they are not capable of employing for any great continuance without tiring, especially in actions where a considerable force is required. Thus we have young horses soon fatigued with labour, which the same horses will easily perform some years after. This ability in the older horse does not arise entirely from a naturally greater degree of strength, joined with a natural capability of continuance, CROONIAN LECTURES ON MUSCULAR MOTION. 231 but in some degree from an acquired strength from employment, and a capacity of endurance from the habit of action. This might be thought sufficient to account for the whole difference, but dealers in horses affirm that one of seven and one of four years old, having equally done no work, shall not be equal in their continuance of it. In riding they also give weight according to age, and the aged horse always carries the greatest weight, if other parts are equal.* When an animal is at its full strength is not easily ascertained, but it cannot be while growing ; it must have arrived at its full ex- tent, and perhaps it is even necessary to have been some time in that state. The involuntary actions are stronger before this period than after; this is perhaps necessary for the animal's growth. Besides the decrease in the size of a muscle from an atrophy, etc., and the restoration of them again to their natural size, which is disease and health, there is an increase which accompanies the whole body, till it arrives at its full size, when the whole seems to rest, except the muscles. How long the muscles continue in this full size is not easily ascer- tained, but when old age begins to come on, the muscles begin to decay; but not becoming pale and flabby, like a diseased muscle) but retaining their redness and sound appearance. A person grows thinner after a certain age, but not in proportion to the decrease of size of the muscles, for the interstices between the bundles of fibres, and also between the muscles themselves, are loaded with fat, and this takes place so constantly that an old man may be distinguished from a young one from only seeing the mus- cles, and the fat mixed with them. Muscles in old people lose their quantity of contraction, and the joints are therefore never moved to their full extent. This is the loss of only the extreme motion, which is weak, and therefore may be supposed to arise from weakness alone; but I do not think this effect is produced in young people from weakness. *■*» nld man stands with his knees, thighs, and all his joints bent, not beir * able to bring himself to the upright position. The ac.ions of the body that are both involuntary and voluntary are some of the most beautiful circumstances in the machine. I believe the muscles of respiration are the only perfect instances of it. The sphincters also have both ; but in them it would seem to be an involuntary continuation of an action which is voluntary. Fresh air was necessary for our existence, and it was therefore necessary that it should be regulated by some other principle than that of the will; for it is necessary when we sleep, and also when we will the contrary. Therefore our will has its limits of power over the involuntary actions, and the involuntary also have their limits over the actions of the will; each therefore can only go a certain length in opposition to the other. As all animals which breathe air are probably endowed with the • How accurate these gentlemen are I don't know. 232 HUNTER ON THE ANIMAL CECONOMY. power of forming sounds, and as air is in common necessary for such an effect, Nature has made this air answer the purpose of sound' as well as of life. For the purposes of life it was necessary the action should be kept pretty regularly constant, and therefore involuntary, because it required too much attention of the will to keep up the necessary action, and the will is not always in a state to attend to it; but for the purposes of sound it was necessary it should be at the command of the will, for sound is in some degree arbitrary: for although often attended or caused by a natural pro- pensity at the time, yet it can be avoided, as in crying. Vocal sounds, however, do not entirely interfere with inspiration and ex- piration ; it is performed by the last, which must have been preceded by the first, although not with the same ease. Many other actions of the body interfere with involuntary respi- ration ; all violent exertions of the body are a check upon it; but then in proportion to the intended exertion, the voluntary supersedes the involuntary, and they take in a proportionate quantity of air; but, both in sounds and exercise, if continued, the stimulus of neces- sity for a repetition of respiration takes'place, and the person is obliged to take in a fresh supply of air, which again answers the former purpose. The Colour of Muscles. Most parts of an animal body are white, and when they have any other colour it generally arises from some adventitious though necessary matter, as the pigment of the eye, which in many persons is black, in some green, in others white, &c.; also the pigment of the skin, which in many people is dusky in its colour. A muscle in all animals is in itself white, and its red colour found in living animals, and also immediately after death, arises from the blood ; for if a red muscle be steeped in water it will become white; or if the arteries of a part which has red muscles be injected with water till it returns by the veins, the muscles soon become white. A red muscle exposed to the air loses the Modena red, becoming florid. As the colour of muscles arises from the blood in their vessels, the muscles of every animal must have the same colour with the blood; if the blood is red, the muscle will be more or less so, according to its quantity; for in sick or unhealthy people they are pale. If the blood is of any other colour the muscle will be tinged with that colour, and also in proportion to the quantity of the blood. All muscles, however, have not the colour of the blood, for many animals having red blood have their muscles almost white; and even in the human body many muscles are much redder than others. The muscles of an arm or leg are much redder than those of the stomach or intestines; those of the face are much paler than the temporal or masseter, although nearly in the same situation. CROONIAN LECTURES ON MUSCULAR MOTION. 233 The muscles of quadrupeds are not equally red, there being a great difference between those of a hare and rabbit. The difference in the colour of muscles in the same animal, and in different animals of the same order, is very remarkable, but is equally to be observed in another order of animals, viz., fowls. The blood in fowls is red; there are few, however, in which some muscles are not much redder than others, and in some birds they shall be almost wholly red, as in the black cock, while in others they shall be nearly all pale, as in the turkey. The muscles of birds are more generally pale than those of quadrupeds, from their having a smaller proportion of red blood, and that blood being more partially distributed. The muscles in frogs, snakes, tortoises, &c, are generally pale, from their having a still smaller quantity of red blood, and that quantity more confined to the vital parts than in birds. The muscular parts in fish are generally white, although I believe they have all red blood, but in smaller quantity than even frogs and snakes, so that the motion of red blood in them is much confined in its extent, appearing to go no further than those parts which are essential to life. The mugcles of many animals of a still inferior order are gener- ally pale; the blood in them being not apparently of any colour, and in some almost transparent, as in the lobster, oyster, snail, &c.; and in this order of animals, if the blood is of any determined colour, it is generally so confined in its motion, not running minutely into parts, that they are hardly tinged with it, as in the slug, which is black, although the blood is of a milk white. The earth-worm, however, is an exception to these general observations on the more imperfect animals, for it has a great deal of red blood, which is seen through the whole body of the animal, from the external covering being pretty transparent. The red blood in a muscle is in proportion as the red blood in the animal is to the quantity of muscle; and also in proportion to the quantity of action in the muscle and the quantity of red blood taken together. The blood in the more perfect class of animals, as man and qua- drupeds, and in which class whales are a*lso included, is in greater quantity, and more loaded with red particles, than in other inferior orders;* therefore the muscles are in general redder, and the quantity of blood in this order of animals, and perhaps every other order in which they have red blood, is rendered greater by in- creasing the action of the muscles, the blood being driven or ex- tended further into those parts by their increased action. This happens commonly in voluntary muscles only ; the involuntary, * [From the numerous experiments of MM. Prevost and Dumas (Examen du Sang, Bibl. Uni. de Genev., t. xvii.), it would appear that the red globules and fibrin are most abundant in the blood of birds, in which respiration is most active and animal temperature highest.] 21* 234 HUNTER ON THE ANIMAL CECONOMY. being employed in uses at all times equally necessary, are even and constant in their action. Muscles much at rest are pale, as in animals just come into- the world, before the muscles have had much action, except the heart, which has been acting from the beginning; and all the muscles of a young animal, except the diaphragm, may be kept pale by keep- ing the animal in a state of rest,* for in that state the blood does not pass far into the muscle; but as the animal grows up, the muscles become redder and redder, especially if they are allowed action by the animal taking exercise, and nearly in proportion to that exercise. This, however, is not universally the case ; for the natural actions of a hare and rabbit are not very different, yet the muscles of a hare are very red, and those of a rabbit pale; whereas I do not believe it possible by rest alone to make a hare's pale, although by rest they will become proportionably paler, f This difference in animals so nearly allied would seem to arise from an original law in their nature; for although a hare may not have a greater quantity of motion in common, yet it is formed to be always in such a state as if it really had, that it may be con- stantly prepared to undergo such motion. The rabbit has no occa- sion for such a state of muscle, its sphere of action being much confined, and it is even not intended to run fast. In an inferior order of animals, where the quantity of red blood is not so great, and the destruction of voluntary action not nearly equal through the whole muscular mass, we find a great difference in the colour of muscles. A bird has two kinds of progressive motion, flying and walk- ing. Some principally fly, others walk,J and many perform both equally. In the walking bird the muscles of the leg are the reddest, as in the pheasant, partridge, and common fowl. In the flying bird the muscles of the wing are the reddest, as in the swallow and woodcock.§ In the frog, snake, turtle, alligator, &c, there is but little action, and the muscles are nearly equally employed through the whole animal except the heart; so that there is not that difference in colour in the muscles of the same .animal, or of any two of this order, although in many it may be observable. In fish we find a good deal of difference in the colour of muscles, and the heart, which is in constant action, is in them as red as any * This becomes a distinguishing mark between the hares of a barren mountain- ous country and a rich flat one. t Such is the method of preserving veal white, for the proportional quantity of red blood is not allowed to increase or go far from the heart. X Swimming in fowls I consider as walking, both being actions of the legs. § Epicures are sensible of this; therefore white veal, the leg of woodcocks, are delicious bits, and the feeders of domestic fowls indulge them.' They rob the appetite, however, to please the eye, the flavour generally being in the muscles of action. CROONIAN LECTURES ON MUSCULAR MOTION. 235 other animal.* The natural history of fish is very little known, but what variety there is we may attribute to the cause above mentioned-! The actions of the more inferior orders of animals we shall not at present enter into. From the above observations we may conclude that red blood, in those animals that have it, is of essential use to muscular con- traction. That the quantity of red blood brought to a muscle is of service in its action is plain; for a muscle become paralytic from an injury to the nerve, or an anchylosis in the joint preventing its having con- tracted for many years, is found white, small, and somewhat liga- mentous, retaining however a degree of transparency and gelatinous consistence, so that a muscle may become paralytic from too much rest alone. The wasting of a limb which is seen externally takes place prin- cipally in the muscles, more especially where they are paralytic from an anchylosed joint; in that case the muscles alone can be supposed to be affected, they alone being concerned in the motion ; but where it arises from a defect in the nervous system, that defect may be in all the nerves of the limb, and therefore all the parts may suffer alike. Swelling of Muscles. We may suppose that the blood is of great use in muscular con- traction ; for in violent and frequent actions of the muscles they swell and become considerably larger, not when in action only, but when relaxed immediately after the action, and will continue swelled for some time. This swelling does not come on till the muscle is tired of acting; this must be from a greater influx of blood at that time, or that the action does not let the blood pass so freely through the veins. It must be owing to something of this kind which happens to animals which use much violent exercise, and are killed during the action, that they are redder, fuller, and eat much tenderer, but do not keep so lono-. There is a material difference between a hare or deer that is shot and one run down by dogs. * [Most of the above facts, with their physiological inferences, were known to Grew, who alludes to them in the following digression while describing the digestive organs of the bird : " And as the strong and continual motion of all these muscles is taught, us from their structure, so likewise from their red colour, which, especially in the grinders" (the lateral muscles of the gizzard,) " is in- tense. Hence in a fish the muscles which move the fins are usually red although the rest of the flesh is very white ; and so the leg of a domestic fowl. Whereas the wings also of a wild fowl are of the same colour. So likewise the flesh of a driven calf, or of a hare, though that of a coney be white. And that which comes nearer, the heart in all creatures having the like continual motion is of a red colour."—Anatomy of Stomachs and Guts, fol., p. 41; 1681.] t [See note, p. 170.] 236 HUNTER ON THE ANIMAL CECONOMY. Muscles not only become really larger by acting, but also become larger in the time of acting, and for that time only, subsiding gradually after the action is over: this increase is in proportion to the violence of the action at the time, and appears to go on till they are tired, and is probably one cause of their being so. In order to ascertain this fact as much as possible, I made the following experiments. Immediately after getting up in the morn- ing, having used my arm as little as possible, I measured the circumference of my right arm across the belly of the biceps flexor, while in the relaxed state of all the muscles of this part, and found it measured ten inches and a half. I then bent the fore arm, in which action the biceps being contracted, I measured it again at the same place, and found it twelve inches one-eighth, so that this part of the arm had gained one inch and five-eighths. After having thus ascertained the size of the arm, both when all the muscles were relaxed, and also when contracted, I next worked an air-pump for about ten minutes with considerable violence, when my arm became quite tired. On repeating the above mensurations I found my arm in the relaxed state eleven inches and five-eighths, and in the bent state twelve inches and five- eighths ; so that the arm, by acting ten minutes, had acquired an increase of six-eighths of an inch in circumference even in the relaxed state of the muscles, and four-eighths in the contracted state. That the calf of the leg swells towards night is a common obser- vation; and 1 suppose it is principally owing to its having acted so much through the day. That the swelling in such cases is in the muscles themselves is evident from the stiffness felt in acting with tired muscles. What produces this temporary increase in the muscle 1 It is probable that an extravasation of fluids has taken place, and the weakness induced in the muscles in consequence of their having acted more than usual, and with greater force, is the cause of extravasation. Effects of Habit on Muscles. Muscles are capable of being improved and increased in different ways by exercise, or employing the muscle much in its natural functions. This improvement in action is most observable in the muscles of volition, as it is in consequence of the will that they become more familiar with the actions; and also they are more subjected to a variety of action, sometimes acting strongly, at others not at all. The stimulus of the will never loses its influence by habit or by becoming familiar, but these stimuli may be called arbitrary or accidental, foreign, &c. Muscles not only improve in one parti- cular, but in every respect whatever. CROONIAN LECTURES ON MUSCULAR MOTION. 237 One improvement voluntary muscles acquire from habit is the readiness with which they take up their own actions, the will fre- quently only having to set them a going; there are instances of people playing tunes without attending to the notes or even thinking of the tunes. From this facility of obeying the will in beginning actions, and of repeating actions they have been accustomed to, with the greatest variety of motions, in the voluntary muscles, particularly in man, and also from the frequent employment in any actions, muscles acquire a facility in obeying the mind in the performance of actions they had never tried before, going hand in hand with the mind ; for as the mind, when it sets the body to perform actions, acquires a facility in immediately employing the proper muscles, they obey directly, and this even in actions they never performed before. A man will learn one trade much more readily if he knows another, than if he knew no trade at all. The habit of acting in a muscle, especially when employed in considerable exertions, increases the necessity of becoming stronger, which necessity, acting as a stimulus upon the muscles, becomes a real cause of increase of size, which augments their strength. This effect is so evident, that painters and sculptors, as well as physiologists, have observed it. We have Charon and Vulcan always represented with large shoulders, brawny arms, and their lower extremities small, and apparently disproportioned. This effect is still more nicely marked by the difference between the right arm and the left; the right being generally employed in preference, and more particularly in great exertions, is therefore the largest and strongest. People who play much at tennis, where the ball is always struck with the right hand, have that arm much thicker and stronger than the left; therefore a man originally well- proportioned shall lose that proportion by being employed in any action that does not require the whole body. From these facts it must appear, that, if every animal was perfectly made, with respect to any standard proportion of its parts, that few would be allowed to grow to that standard, because few animals exert all their muscles equally, there being in most some circumstances in life which oblige them to exert one set of muscles more than another. This is probably more the case in man than in any other animal, and also in him less determined to any one set of muscles more than another; it, however, also takes place in animals, as there will be a considerable difference in the muscles of two birds' breasts of the same species, one being allowed to fly, and the other kept in a cage. The increase in the voluntary muscles appears not to be without limitation, and indeed if it was we might see them increase beyond conception. What principle sets bounds to this increase from ac- tion is not known; the circumstance of these muscles tiring may become a cause. 238 HUNTER ON THE ANIMAL CECONOMY. This increase is not confined to the voluntary muscles, for the in- voluntary, when obliged from any circumstance to act with un- common force, also enlarge, and become stronger, and in a much greater degree than the voluntary. The bladder has been found exceedingly thickened in its muscular coat where there are either strictures in the urethra or stones in the bladder, for in this last complaint, although it discharges the urine, yet it continues to act with more violence than usual, being irritated by the stone, which it cannot expel. I have seen it in- creased to three times its natural thickness.* Increase of thickness in the auricles and ventricles of the heart, in consequence of an aneurism in the arch of the aorta, is not un- common. The cremaster muscles I have seen very much enlarged in cases of hydrocele of long standing. In the increase of involuntary muscles there appear to be no limits: the power of increasing seems to be in proportion to the necessity, and as they do not tire there is no end to their power of acting. Whether this increase of the body of a muscle is a new addition of muscular fibres, or an increase in size of those already formed, is not easily determined, but I should be inclined to suppose the last. 21. CROONIAN LECTURE ON MUSCULAR MOTION, NO. II. [Read before the Royal Society in the year 1797, by John Hunter, F.R.S.] THE CONSTRUCTION OF THE ANIMAL MACHINE WITH THE MECHANICAL EFFECTS PRODUCED BY THE MUSCLES AS MECHA- NICAL POWERS. Mechanical arrangement of the Fibres of Muscles. The most simple mode of investigating an animal body is first to consider the matter of which it is composed. In this inquiry we shall find it more than probable that there is but one species of mat- ter which is peculiar to animals, and therefore I shall call it animal matter. The blood appears to be the most simple modification of this matter: it is the material from which all the solids are composed. The next modification, or what may be called the simplest organization, is a certain arrangement of this matter so as to pro- duce some action. This may be of two kinds: first, such an arrangement as may take place in any kind of matter, so as to produce elasticity. The second is such as is capable of producing * [Hunter has preserved many preparations in his Pathological Series illustra- tive of this fact, as Nos. 746, 752, 755, 758, 759, and 961, &c] CROONIAN LECTURES ON MUSCULAR MOTION. 239 a motion in itself, without the cause being mechanical as in elasti- city : this is the composing of a muscular fibre. A muscular fibre is one of the simplest constructions of an ac- tive solid, and it is these fibres which compose almost the whole of many animals. The muscles are the powers in an animal body, and are perhaps the most regular parts of the whole. They are apparently con- structed of fibres laid nearly parallel to one another; in some they are extended longitudinally from one end to the other of the muscle which they compose; in others their direction is oblique to the body of the muscle; this obliquity in some is regular from one end of the muscle to the other, while in other muscles the fibres lie in con- trary directions. In some a number of these oblique portions com- pose the muscle; the parallelism, however, in each portion is preserved. This parallelism is only found in some of those muscle whose fibres all tend to one point of action, and they are nearly of equal lengths in every part of such muscles; but where parts of a muscle produce different effects the fibres vary in length, suited to the quantity of motion admitted by the directions of the joints. The most simple muscle in an animal body is a bundle of fibres, distinct from end to end from all other portions, and having one determined use. The muscles which move the globe of the eye come the nearest to the idea of a distinct muscle; however, there are very few muscles in an animal body so unconnected with other muscles, which makes it difficult in many cases to say with cer- tainty what may be called a distinct muscle. If we take a view of what we call muscles in an animal body, the human for instance, we shall find that no definition can be given which will answer to them all. A muscle is said to be distinct if it is so at its insertion only, although it may be connected with others at its origin, as the extensor indicis proprius. A muscle is distinct, although connected with another at its insertion, if there is a difference in the use; or although connected at its origin with one muscle, and at its inser- tion with another; but where two portions of flesh are united at their insertion, both having the same use, they are considered as one muscle. So that it is the particular effect which is produced by a portion or portions of flesh which in general has made anato- mists either unite or divide them into separate muscles. This, however, has not been universally followed; for in some particular muscles, in which the origin is of considerable extent, and the insertion but small, each part of the muscle having the power of acting separately, and producing different effects accord- ing to the parts which act, (the joint admitting of a variety of motions,) these have generally been considered as one muscle; and in such muscles, when the whole acts, it produces one general effect, as in the pectoralis major muscle. Also those muscles in which the origin and insertion are of considerable extent, and pro- duce different motions of the same part, yet produce one general 240 HUNTER ON THE ANIMAL CECONOMY. effect when the whole acts, are considered as distinct muscles, as the trapezius, the broad muscles of the abdomen, &c. When a muscle has a number of insertions, and each portion moves a dis- tinct joint, while the whole mass, in the same action, moves all these joints, it is then considered as only one muscle. Of this kind is the longissimus dorsi, the use of which is to erect the whole spine; but its particular action (if it had any) could only be to move one or more joints, according to the number of portions in action. External Figure of Muscles. Muscles have various shapes and sizes; they are long, short, thick, round, flat. They have the fibres either in straight lines or in curved ones; they may be broad and thin, or hollowed and cir- cular, making rings; ail which varieties of size and shape are con- nected with their action and use, and have induced anatomists to give them different names, as teres major, latissimus dorsi, longus colli, palmaris brevis, sphincter oris, &c, rhomboides, deltoides, pyramidalis, &c, &c. The form and size of muscles are adapted to the uses in which they are employed ; and these in general arise from the nature of the parts or joints to be moved. In some muscles the position of the whole leads to the general direction of all its fibres ; but this does not always happen, being the case only in muscles of a more simple construction. A muscle, for example, lies between the os hyoides and the upper end of the sternum, which two points lying nearly in the same plane would lead one to presuppose the fibres of such a muscle to be rectilineal, which is really the case. The figure of the muscle often shows the motion of the joint which it moves, particularly if it is a simple motion. This is the case in the rectilineal muscles and those which are nearly so, or those which are radiated, as the pectoralis, diaphragm, &c. The different kinds of Muscles. Muscles are more or less complex, arising generally from the different dispositions of their fibres, which difference is owing to the manner of their arising and being inserted, more particularly the former; and hence we say, muscles are straight, broad, radiated, half-penniform, complete-penniform, and complex. The most simple muscle would be one whose fibres are in the direction of its body, or in a straight line between the two resisting points, and should be called rectilineal; but there is not in the human body a muscle truly rectilineal, and from what has been observed of the disposition of the muscles and their tendons, also of their origins, it is hardly possible to have one. The straight muscles have fewer fibres in proportion to their size than the oblique, therefore their powers are less; some are CROONIAN LECTURES ON MUSCULAR MOTION. 241 round, or nearly so ; others are flat and broad: some of these last are radiated. The half-penniform muscle, although nearly as simple as any in the body, appears to be the first stage towards combination. It is composed of a series of fibres, arising from a bone, tendon, or fascia, but more commonly a tendon, of which the insertion runs nearly parallel to the origin, representing a quill with one side of the feathers taken off. This disposition of fibres, from the mode of origin or general disposition of the bones and fascia above de- scribed, is almost as common as any in the body. The complete-penniform muscle is two half-penniform muscles joined together. The complex-muscle is several complete-penniform muscles united into one. There are many half-penniform and complex muscles in the hu- man body, but hardly one instance of a distinct complete-penniform muscle. In proportion to their combination their fibres are shorter, and a greater number in a given size, which must make them proportion- ally stronger. Situation of Muscles. Muscles which move bones, cartilages, &c, which are inflexible in themselves, generally lie upon them; for instance, the biceps flexor cubiti lies on the os humeri, the latissimus dorsi upon the back. Now the humerus and spine have little motion in themselves when these muscles have occasion to act. Muscles, however, lie some- times upon the axis of motion, the body of the muscle going ovei the joint. This is most remarkable in parts near the centre of the body, as in the muscles of the spine, and in those of the first joints, or setting on of the extremities. The necessity of this disposition will appear more evident when we consider the vast power which must often be brought into a small space. In the spine, for example, there is not surface sufficient in this chain of small bones for the origin and insertion of a sufficient quantity of muscle ; therefore the fixed point of the most superficial muscles is removed to a distant and broader base, and fhey pass over several joints to their different insertions, as the longissimus dorsi, sacro-lumbalis, &c. The same disposition is necessary in the first joints of the ex- tremities ; the extremities come out at once from the trunk, which is a broad or extended base for muscular attachment, so that the muscles are obliged to pass over the joint some way to find a sur- face for their insertion. Muscles in general lie in the direction of the parts they are to move; there are, however, exceptions to this where there is an irregularity in the motion of the joint, as in the motions of the head, shoulders, ribs, thighs, &c. 22 242 HUNTER ON THE ANIMAL CECONOMY. In those animals which have one great centre of motion, to which series of smaller ones are subordinate, as in man, the bodies of the muscles are in general nearer to the fixed point than to the moving one; and the muscular fibres often arise from the fixed point itself, without the interposition of a tendon; these muscles, however, do not come near to the moveable point, but are attached to it by a tendon, and frequently a very long one. This brings the body of the muscle, which is the heavy part, nearer to the centre or basis of the whole body, which is most able to support it; it also makes the part to be moved freer, more fit for motion, and better adapted for other purposes which may be required. Tendons and Fascia, and their Uses. In most machines constructed for motion by art, there is the machine itself, or all the different parts which are formed for mo- tion, so disposed as to make one part when moved become the cause of motion in another, communicating it to every part of the machine; and the moving power is superadded, and is not to be considered as being a part of any such machine. A horse, for instance, cannot be considered as a part of any machine which he moves, although he is essential to its motion. This is also the case in many parts of the more perfect animals where great variety of motion was necessary, parts being con- structed for the purpose of motion only, having no power within themselves, but this power is superadded or applied to them, as in the extremities of many animals; but there is no known animal so mechanically constructed in all its parts as to have the power dis- tinct from the parts to be acted upon in every part of its structure. There are in all animals parts constructed for motion which have the power of moving within themselves ; those in the more perfect animals are the heart, stomach, intestines, &c. In the more simple animals all the parts of the body are composed of materials with the power of motion, so that in them the machine and power are combined in one, as in the polypus, leech, worm, &c. In the parts of the compound animal constructed for motion each part is independent of another, so that one part may move, or have its motion complete, while all the other parts are at rest; but although the mechanical parts are so constructed as to have their motions independent, yet the simple effect is not always produced, for the powers are in many places so applied as for one power to move two, three, or more parts, as in the fingers. The same power has often a retrograde effect, moving the part which was its fixed point of motion. In an animal body the machine constructed for motion is com- posed of bones, cartilages, &c, and the unions of these form the places for motion, called joints. The construction of the bones at those parts which constitute the joints is only such as adapts them for motion on each other, not CROONIAN LECTURES ON MUSCULAR MOTION. 243 making them become themselves powers so as to move each other, as in the machines constructed by art. The bones and cartilages are confined or kept together by strong pliable substances called ligaments. There are also parts called tendons, which are the medium of union between the different parts of the machine and the powers. They have hitherto been considered as belonging to the powers; but I shall rather make them a part of the machine itself. A tendon is a peculiar substance, placed between some muscles or powers and the parts of the machine to be acted upon by such powers. It is composed of white fibres placed parallel to each other, forming a chord, which is extremely flexible, has no sensible elas- ticity, and is much smaller than the power to which it is attached. Its figure is in general a little rounded; sometimes, however, rather flattened, and in many situations it is broad and thin; in all cases it is extended between the body to be moved and the power. It is sometimes spread out in breadth, and is then called fascia: this form answers various purposes. Its fibres in some situations run pretty parallel, but in general they are interwoven. It has flexibility, strength, and convenience in size. The application of this substance is extremely extensive, complicated, and various. The parts adapted to motion in animal bodies, as bones, ten- dons, &c, are formed with greater nicety, and fitted for more exact motions in the more perfect animals, of which we have a striking instance in the human subject. The purposes which this substance, called tendinous, answers in the animal machine, are the following: First, it intervenes between the body to be moved and the power, to keep up the exact proportion necessary between them to pro- duce any determined motions, so that the length of the bones, or the distance between the joints or points of motion, the quantity of motion in the joint, and the quantity of contraction in the muscle, are proportioned to one another. But if this substance had been wanting, and the muscular fibres had extended the whole distance between many of those joints, the power of contraction in such a muscle would have been much too great, especially in the ex- tremities.* The tendon is used for this purpose principally where "" * [A most beautiful and forcible example of the use of tendon in limiting the length of a muscle to the extent of motion required to be produced in the part to be moved occurs in the sterno-thyroidei of the giraflTe. Had these muscles been continued fleshy as usual, from their origin, through the whole length of the neck, to their insertion, it is obvious that a great proportion of the muscular fibres would have been useless, because such a condition of the muscle would have been equal to have drawn down the larynx and os hyoides more than one third of the extent of the neck, which is neither required nor permitted by the mechanical attachments of the parts. The sterno thyroidei, therefore,"proceed from the head of the sternum, blended together in one fleshy fasciculus for about nine inches, and in a tendon which is continued for six inches ; this then divides and the muscles proceed again fleshy for about sixteen inches, when a second tendon intervenes 214 HUNTER ON THE ANIMAL CECONOMY. the fibres of the muscle run parallel to the direction of motion; for we shall find the tendons to which many muscles are attached longer than we could suppose necessary, from this reason singly. This, however, arises in them from the oblique manner in which the muscular fibres are placed, and the mode of their being attached to the tendon, as may be seen in the complete-penniform. Secondly, tendons and fascia are in many places substituted for bone, there not being a sufficient surface of bone for the attachment of all the muscles in an animal body; and, by being much smaller and thinner, they exclude the necessity of bone. Thirdly, tendons and fascias, from their flexibility, answer in many parts better than bone; for if a long process or thin lamella of bone had united the ends of the muscles to the principal bones to be moved, no motion could have been produced by the endeavour of such muscles. In many situations, where flexibility is not re- quired, they answer better than bone, from their yielding to external or internal pressure, which bone could not have done without being liable to be broken; as in those situations where they give attach- ment to two muscles, and where they cover many muscles, as in the forearm. The advantage arising from the flexibility of tendon and fascia is seen in its full extent by comparing the muscles of the more perfect animals with those of the oyster, lobster, or turtle, where many of them are attached to external shells, instead of fasciae. Flexibility also allows them to vary their direction, by which means they vary the motion of the parts, as in the tendon of the biceps flexor of the forearm winding round the head of the radius: the first action of the muscle (in some positions of the bone) gives it rotation upon its axis, the second bends it upon the os humeri. Similar actions are produced by the latissimus dorsi and teres major. Fourthly, fascias from their strength answer in many situations better than bone, for a lamella of bone of the same thickness would in many cases have been broken by the contraction of the muscle to which it was attached. Fifthly, it was necessary that some substance should be introduced as a medium between bones and muscles, to admit of the nicety of action and freedom of motion we find in many parts of the body, particularly in the fingers; which could not have taken place if the muscles had been continued from bone to bone. Where flexibility is not necessary, we find then that there is a continuation of bone, as in many birds, as in the leg of the turkey, in each between the preceding and the next fleshy portion, which is finally in- serted into the thyroid cartilage, and, by a continued fascia, into the os hyoides ; thus the quantity of contractile fibre is proportioned to the required extent of motion by intervening tendons ; the sterno-hyoidei being wanting, or their place supplied by the sterno-thyroidei, as in some other ruminants. The analogue of the omo-hyoideus is, in the same animal, adjusted to its office by a different and more simple modification ; its origin is removed from the shoulder-blade to the nearest point (the third cervical vertebra) from which it could act with the requisite force and extent upon the os hyoides.] CROONIAN LECTURES ON MUSCULAR MOTION. 245 partridge, &c, and through the whole body of most fishes; so that tendon is to be considered as a substitute for bone where that sub- stance would be improper. Physiologists, however, have given a very different idea of it, supposing it to be a continuation and con- densation of the muscular fibres; for which supposition there is no proof, even the smallest shadow of reason, either from analogy or from the parts themselves: it is therefore too absurd to deserve refutation. Besides the uses of fasciae above described, we find them in many parts of the body covering muscles, giving origin to them, binding down the belly of the muscle, and also binding down the tendon which is attached to it: this application of them is chiefly found in the extremities, particularly the forearm and leg. Where the fascia binds down the tendon at or near the joint it is called ' annular ligament/ which is in general little more than the fascia made strong; but where greater nicety in the motion of the parts is required we find annular bindings independent of the gen- eral fascia, as in the fingers and toes. These are to keep the ten- dons from having lateral motions, and where the joint makes an angle, to prevent their coming into straight lines, which would happen if not prevented by this annular ligament, and which would destroy the intention of the joint, as is evident in the fingers. Where the fascia covers twO muscles it is fixed to the tendon which lies between them, and generally covers their tendons. Where it covers a tendon it almost surrounds it, making a kind of theca, and is fixed to the bone along which the tendon passes. ' These circumstances only take place where muscles are placed at a considerable distance from the parts to be moved, and their tendons pass over more joints than one, as in the muscles of the forearm and leg, where the tendons go to the fingers and toes. Fascia is sometimes very thin, called membrana communis mus- culorum, covering superficial muscles, particularly the broad ones, as the obliqui externi, latissimus dorsi, pectoralis, &c, and on some of the deeper-seated broad muscles, but thinner and looser in its connexion with the muscles. It is never met with in this state on the round muscles. It would seem to be intended to connect the skin by its cellular membrane more closely to the muscles, by which means the skin may be in some measure moved by them. The fasche in some instances give insertion to muscles, as in the thigh, and to the broad abdominal muscles. Attachment of Muscles to Tendons. As the body of a muscle is much thicker than the tendon to which it is attached, the fibres of the one cannot be continued to the other in a straight line; therefore the end of the tendon is not joined to that of the muscle in one line, but by a tapering point or an irregular edge, to gain surface for the insertion of the muscular 22* 24G HUNTER ON THE ANIMAL CECONOMY. fibres, the oblique ending of a small body being capable of becoming equal to the less oblique ending of a thick one; but the direction of the tendon cannot be the same with the muscular fibres, but must be more or less oblique, so that an angle must be formed at their union, the muscular fibres being bent a little in towards the tendinous ones. This obliquity in the direction of most of the muscular fibres, and of their attachments at both ends when they have tendons at both origin and insertion, makes the muscle become gradually thicker from the body of the first tendon to the most distant point of that tendon; and if the middle part of the muscle is free from tendon, that part will be everywhere equal in size, or if the tendon at its insertion goes higher than at its origin, the part where these tendons are opposite and parallel to one another will also be equal in size, the body of the muscle from that part becoming gradually smaller upwards towards its origin, and downwards towards its insertion. From such disposition of fibres the bodies of most muscles are much longer than their component fibres, which produces in the same proportion a shorter complete tendon. This circumstance lessens the thickness of the bodies of such muscles, and also of their extremities, which gives to the muscle a curve in its outer line. The obliquity in the direction of the muscular fibres admits of there being a greater number, and lengthens the swell in the time of contraction, by which means the motion of the muscles in the cellular membrane becomes more free, the swell is smaller, and the smoothness of the whole body is preserved. The tendon at its origin is generally on one side, or surrounding the muscle, and the inserting tendon is on the opposite side, or next the centre of motion. Origin and Insertion of Muscles. In describing the origin and insertion of muscles the tendons are always included, and this is very necessary to be understood of the insertion, as it is the point of insertion which in some degree gives the use of the muscle. The origin of a muscle is in general the most fixed point, and the insertion the point where the greatest motion is produced ; in differ- ent muscles, however, these points are subject to variations, and on different occasions in the same muscle, most of them being capable of acting from either end. Some of these variations may be consi- dered as natural, and others as a force upon Nature. I shall call the variations natural where the effect is necessary in the natural movements of any part of the body, such as the exten- sors of the thigh, the glutaei, particularly the glutasus major, are commonly understood to produce; for these muscles, in the action of walking, when the leg is brought forwards or bent by the flexors, extend the body upon the thigh, by which action the body is brought CROONIAN LECTURES ON MUSCULAR MOTION. 247 forwards before and over the foot; also, after stooping or bending the body forwards, the glutacus muscle raises it; and these are as much the actions of this muscle as bringing the leg and thigh back upon the body. Some muscles are capable of performing similar inverted actions, although not commonly so employed as the recti abdominis, whose ordinary use is to bend the body upon the pelvis, but which some- times, however, bend the pelvis upon the body. Those which I call a force upon the natural effect of the muscle, or an inversion of the fixed point, are where the moving point is by art, or something foreign to the body made the fixed one, as the hand ; and the action of the muscles, instead of bringing the hand to the body, draws the body to the hand. In many animals, however, the effects of certain muscles are re- ciprocal, and these, therefore, cannot be said to have an origin and insertion, both the parts to which they are attached being equally moveable in themselves, and there being no power capable of keep- ing either the one or the other firm, as is very evident in animals where the two points of attachment, or parts to be moved, are similar or in pairs, as in the bivalve shell, where the motion in the two valves is equal. The origins of muscles are in general more simple than their in- sertions, nothing being wanted but a sufficient surface for attach- ment, which is generally required to be pretty extensive; and for this purpose there are various contrivances, which have given rise to particular names, for the various kinds of origins. The origin of a muscle is generally from an immoveable part with respect to the action of that muscle, and commonly from the most firm or solid parts of the body, as bones, cartilages, periosteum, tendons, and fascia; some muscles, however, arise from soft parts, as the lingualis, orbicularis oris, &c. The insertions of muscles are less simple, for as the insertion is to produce the various motions of the parts, and, as the construc- tion for motion is hardly the same in any two joints, more nicety and art is required; the insertions of muscles are commonly more determined than the origins. Few muscles are so situated as to arise from surfaces at right angles to the direction of their fibres, as they generally pass nearly in the same direction with the surface from which they arise, whe- ther bone, tendon, or fascia. They, therefore, take their origin from a part as they pass along it, which renders it very oblique, and produces the form of muscle called half-penniform. Some muscles, however, both arise from, and are inserted into, surfaces at right angles to the direction of their fibres, as many of the spine, &c. The insertions of muscles are more general than their origins, for they must be inserted into every'part of the body to be moved, and therefore we find them inserted into bones, cartilages, periosteum, tendons, fascia, and many of them into soft parts, as the skin, cel- lular membrane, the tongue, &c. 248 HUNTER ON THE ANIMAL CECONOMY. In describing muscles, they are never said to be inserted into, or to arise from, periosteum, but from the bone the periosteum covers, as it is upon the bone the effect is produced. Muscles never arise from, or are inserted into, capsular ligaments, for although in some few cases they seem to run into, or are at- tached to them, the effect is not immediately on the capsular liga- ment, but on the bone beyond it, and the ligament is strengthened at this part in proportion to the power of the muscle; so that in this case, as far as regards the mechanical effect, the ligament and tendon may be considered as one. Many tendons, in their course over joints, adhere to the liga- ments, and bring them along with them in the action of their muscles. This adhesion, however, is only to bring out a secondary use, to save the ligament from being bruised between the bones, which otherwise might have been the case. Many muscles besides these insertions give off fibres to the fasciae, which cover other muscles, as is evident from the lower edge of the pectoralis major, biceps flexor cubiti, semitendinosus, &c, but what is intended by it is difficult to determine. The origins of muscles are generally further from the centre of motion of the part to be moved than the insertion; remarkable in- stances of this are seen in the biceps flexor and triceps extensor of the forearm, and all the movers of the hand and fingers. This gives neatness to the parts to be moved ; but its principal use is to give velocity to the motion, with a small quantity of contraction; what it gains, however, in velocity, it loses in strength. That velocity is the intention is evident, for if the muscular fibres had been continued to the most distant end of the bone to be moved, the muscle must have been longer, and must have contracted more, to produce the same effect, which contraction must have taken a greater length of time.* Many muscles arise near to the centre of motion of the part to be moved, and are inserted at a considerable distance, as the del- toides. This also produces a great deal of motion in the part to be moved, with very little contraction of the muscle; for when the greatest quantity of motion is produced, the insertion has approached very little nearer the origin. This kind of insertion gives an advantage to the power of the muscle, which the other has not, viz., a much longer lever, and allows the muscles to communicate their strength to the moving parts more fully, although with less velocity; and being employed upon parts of considerable extent, as the arm and leg, and gener- ally upon the first joints of them, the effects upon the hand and foot are very considerable. In the formation of many parts of the body neatness is a prin- cipal object, as is visible, not only in the external form of the limb, but in the parts constructed for motion; as in the formation of the * [The extent of the space through v/hich the bone is moved is also greatly increased by this arrangement, in comparison with the extent to which the muscle itself contracts.] CROONIAN LECTURES ON MUSCULAR MOTION. 249 bones, and their situation with respect to one another, and the mode of removing the inserted tendon (when too close to the centre of motion to produce a sufficient effect) a little further off, by means of little moveable bones called patellae or sesamoid bones, as in the knee, first ioints of the thumb, and great toe : and where this con- struction would be clumsy and inconvenient, as in the fingers and lesser toes, the two tendons which are obliged to pass along these parts to their insertions at the second and third joints, are so dis- posed in their course, that the profundus, or one nearest to the bone, acts as a patella to the other, keeping it at a distance from the centre of motion equal to its own thickness; and the sublimis or upper one is obliged to split into two near its termination before it can be inserted into the second bone. The advantage gained by this construction is, that the tendon of the muscle employed in the greatest action is removed further from the centre of motion than it otherwise could be, and from which the other sustains no disad- vantage. Adaptation of Muscles to Joints. It is to be understood that the joints of an animal are fitted for motion, and that their form, with the application of the muscle or power, are, in a natural state, so adapted to each other that the power acts with the greatest advantage, and that any variation from the natural form or position of the joint weakens the effect of the power. This may be demonstrated in those who turn out their toes, as in a dancing-master, who, before he makes a leap, turns his toes forwards. Few joints in an animal body are confined to one motion, there- fore either a number of single muscles must be employed, or the direction of the muscular fibres, of the tendons, and of the inser- tions, must be so disposed that a few muscles may produce the different effects. Joints admitting of motion in only one direction come nearest to a simple joint: the joint of the elbow is perhaps as near this as any in most animals, as also the joint of the lower jaw in the car- niverous animals, and the fingers in most animals:* the muscles of such joints are tolerably simple in their structure, direction, and insertion. In the joints which admit of various or compound motions, the construction of the muscle, the course of its different fibres, the dis- position of the tendon in its course and insertion, produce a great variety of effects. This, indeed, was absolutely necessary in a number of animals, more especially those which have extremities, and particularly the human subject, in which there are more motions produced than separate muscles to perform them; nor was it possible, in the pre- sent construction of bones, &c, to have placed particular muscles * [In insects and Crustacea every joint of the extremities, save that which is between the limb and the body, is ginglymoid, and limited to motion in one plane.] 250 HUNTER ON THE ANIMAL CECONOMY. so as to perform all the motions, without interfering in the opposite actions. In the human subject the number of muscles exceeds that of any other animal; the motions in the joints, however, are still greater than can be accounted for by the increase in number of muscles, the difference in the construction of the muscles, as well as of the joints, producing this difference, which is so remarkable in the joint of the shoulder, the rotatory motion in the forearm, and the joint of the thigh. Instances of the different motions produced by the shape of muscles, their mode of application, and the disposal of tendons, are seen in the biceps flexor cubiti, latissimus dorsi, &c, passing some way round the bones into which they are inserted, so as to produce two very different motions in the parts; at one time they may move the part through some space, at another time upon its own axis. The muscles in the lower jaw in graminivorous animals give a remarkable instance of this, there being hardly any of them which do not perform more than one motion. The disposition of tendons will often give a different direction to the body moved from that of the muscle, arising from the tendon bending over some fixed point and taking another direction, which is beautifully illustrated in the trochlearis muscle of the eye, the body of it passing in the same direction as the straight muscle of the eyeball, while from the course of its tendon it counteracts the oblique, which passes in a different direction. The obturator internus of the thigh and circumflexus palati are both of this kind. The different positjpns of tendons shall make two muscles pro- duce the same effect in different ways, being inserted in the opposite sides of the same joint. The gastrocnemius, which is inserted into the heel behind the joint of the foot, pulls the heel up, which de- presses the toes. The tibialis posticus and peronei muscles, which pass in the same direction, and are inserted before the joint of the foot by means of their tendon passing round the joint, also pull the toes down, which raises the heel. Muscles, by the course and mode of insertion of their tendons, shall perform very differently a series of regular motions, bending some joints and extending others. Such are the uses of the lumbri- cales and interossei interni upon the fingers and toes: for their course is before the centre of motion in the first joint, but by wind- ing round the second bone they get upon the back of the fingers and extend the two last joints. These, by their situation and inser- tion, produce an effect which could not be performed by the other flexors or extensors of the same parts. From the various formations of joints, and the different positions and insertions of the muscles or powers, the greatest force of the power is required at different periods of the motion. In all those where the power is between the centre of motion and the resistance, the greatest action of the muscle is required at the beginning, as a smaller contraction of the muscle produces a greater effect at this time than afterwards, as in the deltoid. Where the power and weight are at the two ends and the fulcrum CROONIAN LECTURES ON MUSCULAR MOTION. 251 in the middle, as in the biceps extensor of the arm, or where the power and the fulcrum are at the two ends and the weight in the middle, as in the muscles of the tendo Achillis, the greatest force is required in the last part of the motion. Where there is no lever, but one body moving round a centre as a pulley, which is the case in the extensors of the knee-joint, the same force is required through the whole of the motion. We may observe that the ligaments of the joints are necessarily so constructed and placed with respect to their motion as to produce an effect analogous to that of a centre-pin in a plain circular joint, in all the various situations of the centre of motion. There are few levers of the first kind in the body, on account of the unevenness in the effects of muscular contraction upon them, arising from the variation taking place in the angle of insertion of the muscle; they are therefore introduced where that is compen- sated by some other circumstance in the action. The motion of the body upon the thigh is a lever of this kind, and is generally used in raising the body; but as the body becomes more and more bent it requires less power to overcome the power of gravity in the body, therefore the angle of insertion is becoming more and more in the same plane with the moving part. The same thing takes place in moving the heel. The angle of insertion can only have its effects vary when the insertion is some way from the centre of motion, and this only when in levers. When in levers of the first kind (which extend joints) the effect is gradually becoming less; as, for instance, the extensors of the forearm, which are inserted into the olecranon, because the angle is becoming less and less; but perhaps the velocity which the parts may commonly acquire make up this loss. When inserted into levers of the second kind they are gaining in their effect, the angle becoming greater, as in the flexors of the forearm. In the lever of the first kind the quantity of effect, according to the quantity of contraction, is becoming more and more as the angle becomes less. In the second it is becoming less and less as the angle becomes greater. Muscles going over more Joints than one. Many muscles, or their tendons, go over two joints while they only move one, and the joint which they do not move is often moving in a contrary direction, from the action of another muscle; this happens in the biceps flexor and extensor of the forearm, the flexors of the leg, &c. This disposition saves a great deal of mus- cular contraction; for by the biceps going over two joints while it is employed in bending the forearm upon the arm, the arm is bend- ing back upon the scapula, which last action would produce in some degree a flexion of the forearm, even if the biceps flexor did not contract at all, but only remained without relaxing. This arises from the motion of these joints going zigzag to one another. Muscles whose tendons pass over two joints keep the joint not to 252 HUNTER ON THE ANIMAL CECONOMY. be moved, firm; which is of great service, as when we bend the forearm by the biceps flexor, the two heads rising from the scapula, especially the long head which runs through the joint, keeps the joint of the shoulder firm. In this motion there are muscles acting on both sides of the joint. Had it not been for this purpose, the biceps flexor might as well have arisen from the head of the os humeri. Muscles often go over two, three, or four joints, and only move the third and fourth, as the flexors of the last joints of the fingers; but to prevent the first and second joints being moved by this action, the extensors of the intermediate joints are obliged to interfere and keep them from bending. Every joint has a certain quantity of motion, and the quantity of contraction of the muscles of that joint are adapted to that motion: we have therefore in joints of considerable motion long muscles, as those of the knee, and in joints with little motion we have short muscles, as those of the spine. Of the Strength of the Body as compounded. The strength of a part and the strength of the whole body is in proportion to the natural resistance, which arises either from some body to be propelled, as the blood, urine, &c, or from the position of our bodies, to overcome gravitation; for every muscle in the body is just able to move the part to which it is fixed with tolera- ble ease in the most difficult position, and any additional weight in that position will fatigue it, it being unable to support it any time. From this it would appear that the different parts of our bodies are not much stronger than can support their own motions with ease; and whatever motion the body can perform with ease, by exerting itself it can give it a considerable velocity, or support a greater weight for a continuance. If our muscles are capable of moving our bodies in every position, they must be able to move much more in some positions than others. If I can raise my body from the ground perpendicularly up when my feet are fixed upon the ground and my knees bent at right angles, I can support or raise a much greater weight when upright or nearly so. If a horse raise himself from the ground when his legs are bent, he can support a greater weight when erect or standing; and if loaded with no more than he can stand under upon three feet, he can walk with it. A leg also that can raise the quarter of a horse from the ground can move the parts of which it is constructed only with great velocity. If you load a man with no more than he can stand under upon one foot, he can walk with the load. A man can raise his whole body upon his hands, and therefore can move his hands with great velocity when they are put into motion without the body. The Effects arising from the different Constructions of Muscles. The straight narrow muscle, whose fibres run parallel, generally CROONIAN LECTURES ON MUSCULAR MOTION. 253 employs all its fibres, so that when it acts, the whole muscle is in action at the same time. The broad and radiated muscles do not always employ the whole of their fibres at the same time, each part often acting separately, like separate muscles ; they are capable of taking on an action at any one part, and of continuing from that part a succession of actions to any other part, or through the whole muscle; and they are capable, by an action of the whole muscle, of producing one general effect. The action of the lateral portions of such muscles affects the tendon somewhat similar to the complete-penniform; therefore the middle fibres must either be longer than the lateral, or have a great power of contraction, which will be better un- derstoood after the explanation of the action of the complete-penni- form. The temporal muscle is an exception to the rule of muscles being made radiated to produce a succession of actions; for whatever part of this muscle acts, nearly the same effect is produced ; such muscles, catteris paribus, produce effects proportioned to their length of fibres. These muscles have one advantage, which is, that their fibres are much longer than those of any other muscle whose body is of an equal length; they can therefore contract much more, and are always used in the more extensive motions. The half-penniform muscle is, I believe, similar in its action to the foregoing; for although the fibres are more oblique, the tendon is moveable laterally, so as to move nearly in the same line with the fibres. This kind of muscle is never used in extensive motions, except where there is considerable distance between the origin and insertion, to admit of sufficient length of fibres. Although there is hardly an instance of a complete-penniform muscle in the body, a e yet as all the complex penniform act upon the same principle, I shall explain the ef- fects in a supposed complete-penniform, and show that this disposition of fibres produces a greater effect than any of the foregoing. In the action of these muscles we sup- pose that the inserted tendon is always moved in the middle line, between the two origins of the muscle, and therefore the muscular fibres in this action do not lose their obliquity, as in the half-penniform, but have it increased, which produces a greater effect. Let A C and B C represent two fibres of a penniform muscle in their extended state, A and B being their origin, and C the point of insertion into the tendon C D. 23 D 254 HUNTER ON THE ANIMAL CECONOMY. Suppose these fibres contracted to the points E and F, it is evident that such contraction will bring the point of insertion from C to G, and that the motion of the tendon will be to the contraction of the muscle as C G is to C F or C E; for A G is equal to A E, and B G equal to B F, or A and B are the centres of the circles AGE andBGF. The advantage arising form this construction of muscle is great, as it allows of a great number of fibres in small bulk, and is there- fore used where strength is required. It is also used where the quantity of motion required is greater than the distance between the origin and insertion would admit of in any other construction of muscle. 22. CROONIAN LECTURE ON MUSCULAR MOTION, No. III. [Read before the Royal Society in the year 1779, by John Hunter, F.R.S.] Of the Effects of Muscles. In the spring of 1776 I had the honour of delivering to this Society the Croonian Lecture upon the self-moving power in animals seated in the muscles, in which I also made some observations on the analogy between this power in animals and a similar power in vegetables. I was then desired to prosecute this subject, and accordingly, in the winter following, I presented a paper, in which I considered the most remarkable circumstances relative to this power in animals, through which they are enabled to perform all their various mo- tions,—such as the arrangement of the fibres in the construction of all the muscles; the distinct muscles, their figure, kinds, and situation; the tendons, and fascia?, with their uses; the applications of muscles to tendons, their origin and insertion, and the fitness of them to the joints. It was here noticed that their effect in some cases is equal to their quantity of contraction ; in others not. The different quan- tity of contraction in the same length of fibres in different muscles was observed, and the effect arising from the different construction of muscles. As the muscles are, by their contraction, the cause, either im- mediate or remote, of every action in the animal, and as animals are so constructed as to produce evident mechanical effects, arising from an application or combination of the mechanical powers (the contraction of the muscles being the power or original cause), I shall now consider this mechanical application and its effects, with which I shall slightly compare the applications and effects of the mechanical powers as applied in machines which are the pro- ductions of art. Muscles are the first simple powers in an animal, by which all CROONIAN LECTURES ON MUSCULAR MOTION. 255 the mechanical effects are ultimately produced ; but an animal body is very differently constructed from that of a machine. A machine is composed of a series of parts, having a regular de- pendence on each other; and the power which produces motion is applied only at one end of these parts, although two, three, or more effects may ultimately be produced, which effects, notwith- standing, must therefore arise from the multiplication of the parts of the machine, and not from the increased number of powers. But an animal is composed of parts, each part, and each motion of each part, having its own moving power, capable of producing its immediate and remote effects independent of each other; so that in animals many effects may be going on at one and the same time, and each actuated by its own peculiar power, by which means an innumerable variety of effects arc carried on at the same time, and without the least confusion or interference with each other. A muscle, as to itself, may be considered in two lights, one re- specting its quantity of contraction, and the other its power, both of which produce considerable effects in the body, and each is employed according to circumstances. Every muscle in an animal body may be considered as a simple independent power; and if we attend to the effects that many animals are capable of producing, particularly the motion of fishes and the flight of birds, we shall see great reason to admire the immense velocity and great force with which their muscles are contracted; and if we compare the effects produced by the contraction of their muscles with the weight of each muscle and the part which is to move, it may lead us to conclude that there probably is not in nature a more active simple power than the contraction of the animal muscles. An animal is per- haps the only machine that has the power of overcoming its own gravity. In considering animal bodies in general in a mechanical light, we should first attend to the most simple mode of action in the animal, or the mode of action of the muscles in the most simple animal, and proceed from the most simple to the most compound or complicated, in which latter may be discovered applications and combinations of the several mechanical powers (which for beauty, simplicity, regularity, and aptness far excel all human applications), in order to produce the manifold effects of animal motion, and to accommodate the ultimate velocity or force at the same time to the particular effects to be produced, as well as to the simple power of contraction in the several muscles which act as first movers in producing that effect. In many animals the parts endowed with the first principles of motion, viz., the muscular fibres, are themselves formed in various shapes, so as to constitute complete animals of the most simple fibres; and even in the most complicated animal many distinct parts are composed of those moving powers, forming regular 256 HUNTER ON THE ANIMAL CECONOMY. bodies, called organs, commonly producing of themselves a vast variety of effects, by which means many of the numberless internal actions respecting the animal ceconomy are carried on; so that even in those more complicated animals we have the first organiza- tion formed of muscular fibres alone, in the same manner as in the more simple animals.* This would lead us to consider the effects of muscular contraction in very different views, viz., according to the various effects they are capable of producing in animals of all the various constructions and complications. In many of the more simple animals there is little else besides those formations or organizations composed of muscles. A polypus is little more than-a muscular bag, and by the contraction of its fibres in different parts, and in different directions at different times, the bag is changed into various forms and sizes. A worm seems a little more complicated: however it is in reality little more than a body formed of different parts, each of which is composed of muscle. A slug, a maggot, as also numberless tribes of sea-animals, come under the same description. But as animals emerge from this simplicity of construction, be- coming more and more complicated, having particular parts added, and those parts being composed of something besides mus- cle, and it also being necessary that these should move, and be so constructed as to direct, circumscribe, increase, or limit the motion, we find the muscular fibres of such animals collected into various portions and forms, in order to give all the different motions to these superadded parts which were taken notice of in the former lecture. Those additional parts are composed of more rigid matter than muscle, viz., bones, cartilages, &c, on which the muscles can have no other influence than by giving them motion. There are a number of those bones, cartilages, &c, in many animals, some having more, some fewer; and they are connected in such a way as to form between them intervals fit for motion, called joints: in most parts of the body there is a series of those bones and joints, as the spine, the extremities, &c. Many of these bones are so formed, and so placed and connected with one another, as to form levers (and those of all the various kinds), which direct and limit the motions, so as to produce a regu- larity in the whole. As the relative inclinations and positions of those several bones which are immediately connected and joined together are very various, it follows that there must be a variety in the angle of in- * [Hunter here compares the first-formed parts of the vertebrate embryo, derived from the mutually receding layers of the germinal membrane and the folding of those layers, with the simple homogeneous tissue of the hydra or other acrite animal. And, as he applies the term muscular to the contractile tissue of these animals, so he would also regard the homogeneous gelatinous parietes of the newly formed digestive eac of the embryo of the higher organized species as being in like manner endowed with contractility, and therefore ♦ formed of mus- cular fibres,' or contractile substance ♦ alone.' CROONIAN LECTURES ON MUSCULAR MOTION. 257 sertion of the several muscles, to accommodate them to the particular circumstance of each joint. And as those inclinations vary in the motions of the joint, so must the angle of insertion of the muscles which will produce a difference in the effects, both in the power and quantity of contraction. To this great variety of these levers and joints we have the mus- cles adapted. We may observe, that the more perfect the animal is, the more curiously these levers and joints are formed, the joints commonly consisting of compound curves (which is the most remarkable in the more perfect animals), by which means their own motions admit of greater variety. The human subject is a striking instance of this, having the joints more compounded, and the motions less limited, than in any other animal that I know, which circumstances require a greater variety of muscle, and the greater nicety in the adapting of each muscle to produce its peculiar motion. In the most perfect animals there are very few joints whose mo- tion is simple, or which are confined on all occasions to move in one direction ; for whatever may be their chief or ordinary motion, in many there is some other motion compounded with it; nor are there many joints which move upon one centre in all their motions, but they shift their centre as the curve varies.* These firm inflexible substances are kept together by soft, yield- ing yet sufficiently strong parts, called ligaments, which are neces- sarily so constructed and placed, with respect to the motion of the joint, as to produce an effect analogous to that of a centre pin in a plain circular joint, and in all the various situations of the centres of motion. I may be allowed to observe, previous to entering upon the mechanical motions produced by the muscles in an animal body, that, without external resistance, there would be no such thing as progressive motion in an animal; for although a muscle has the power of contraction in itself, and is capable of moving all its differ- ent parts upon itself, yet it cannot move any other part without having some fixed point to act from, which is the greatest point of resistance. There is in every animal, therefore, a fixed point from which the parts of the body take their principal motions. In the human body this fixed point seems to be in the joints of the thigh- bones ; which point, being in the middle of the body, must be com- mon to the extremities. We see, therefore, that the body either moves on the legs, or that the legs move on the body or trunk. Besides this, there are many fixed points, so that the body is to be looked upon as a chain of joints whose general centre of motion is in the joints of the thighs; but each has its fulcrum, or centre of motion, which is always on that side next to the first, or the general * A remarkable instance of this we have in the joint of the lower jaw in grami- nivorous animals. 23* 258 HUNTER ON THE ANIMAL CECONOMY. centre of motion of the whole, by which means the smaller moves upon the greater, the toe upon the foot, the foot upon the leg, the leg upon the thigh, and the thigh upon the body. The same in the arms, the wings of birds, the tails of fishes, the oars of a boat, &c. But those motions can be, and often are, inverted, so that the greater can be made to move upon the smaller; as, for instance, the body upon the thigh, the thigh upon the leg; or, in birds, the body upon the wing, &c.; but then the smaller must be so circum- stanced as to be the fixed point, which cannot be without external resistance. It is the inverted motions, then, which produce the progressive; but it is necessary, for the production of a succession of them, to bring in also the motion of smaller parts upon greater; the two kinds of motion are, therefore, acting alternately whenever the progressive motion is continued beyond the first action. The animals which move upon the earth have it for their point of resistance. Birds are supported and propelled in their flight by the resistance of the air ; and fishes, like boats, by the resistance of the water. The effects of muscular contraction may be divided into three kinds. The first is, where the effects are in those parts of the body which are principally composed of muscle : these simply vary their con- figuration without extending their power beyond themselves, as in the actions of many of the more imperfect tribes of animals, as the leech, polypus, &c, and in many parts of the more perfect animals, as the heart, stomach, intestines, bladder, and all the vascular system.* The second is where the effect is more extended and reaches beyond the muscles themselves to such adjoining parts as are either formed simply for motion, as bones, cartilages, &c, or whole parts of the body, such as an eye, a lip, the skin, &c. The third is where the effects are mixed, viz., partake of both the preceding, as in those produced by the muscles of the tongue, of respiration, of the abdomen, &c, where they both move parts and alter their configuration. The first and third kind of effects of muscles, when considered in the more perfect animals, are more connected with the internal ceconomy of the animal than with the mechanical application of the power of muscular contraction ; therefore in them it is the second which comes properly under consideration, as mechanical, since it produces visible mechanical effects upon parts formed for motion, and evidently calculated to vary the velocity from that of the first. The application of muscles in an animal body is either to pro- duce a quantity of motion equal to the quantity of contraction of the muscle; or, by the application of levers, to give a greater * [This is not exactly true of these viscera, for their contents ejected by the contraction of the surrounding fibres act upon the parts into which they are pro- pelled, as the bone moved by the muscle inserted into it also carries the part connected with it along with it in its motions.] CROONIAN LECTURES ON MUSCULAR MOTION. 259 motion than could be produced by the simple contraction of the muscle. This in general is not the case in machines composed by art; for in art the principal reason for the introduction of me- chanics is to acquire power in the effect, which obliges us to increase the velocity in the moving cause, as in levers and pulleys. However, this is not universal in machines; for some have it reversed, as the catapulta, the lock of a gun, and also in many machines where strength is not the object, but velocity in some par- ticular movements, as in watches, jacks, &c. Whether the effect of a given quantity of contraction in a muscle be or be not equal to that quantity depends upon the construction and disposition of the parts to be moved, or the form which the whole muscle is thrown into. Thus the effects of some muscles upon the parts are just equal to the contraction of the muscular fibres; such are those which simply draw parts to them, not vary- ing the position of the part moved from the right line, as many of the muscles of the larynx, the trapezius, rhomboideus, and all of the panniculus carnosus kind, as the muscles of the face, platysma myoides, and the muscles of the skin of animals. Another class, whose effects are always known, or are the same in all cases, are those muscles which produce their effects from the shape which the muscle 'is thrown into, for instance, a curve. Curved muscles are of two kinds, viz., those which are fixed at their ends, as the abdominal muscles, pharynx, &c, and those which are circular, as the sphincters, heart, and the whole vascular system. These muscles always reduce the circumference and, of course, the diameter of the circle, which they themselves compose, in proportion to their quantity of contraction; but the ultimate effect here is not in proportion to the quantity of contraction, but decreases as the squares of the diameters of such vessels. But most parts of the body are so mechanically formed, acting as levers, and the muscles so advantageously inserted, as to produce a much greater degree of velocity in the' motion of the part than is equal to the contraction of the muscle. But those mechanical applica- tions are so various that there are no two muscles which act with the same advantages, excepting those that are in pairs. On this application of muscles to levers depends the distinction between the absolute and apparent force of muscles, neither of which can possibly be ascertained with any degree of certainty. Every muscular fibre is capable of contracting with a given power, which power simply must be always its absolute force; but from the construction of parts to be moved, and the applica- tion of muscles to those parts, either an increased or decreased effect is produced. It is impossible to ascertain the absolute force of a muscle because there is no one known muscle in the body that we can throw into action separately, and independently of the collateral effects of others. And, if we could, there are many whose power could not be measured by any given quantity of resistance to be 260 HUNTER ON THE ANIMAL CECONOMY. overcome, so as to ascertain the power of contraction of that muscle, as, e. g., all those which simply pull bodies in a straight line : but, in those muscles which act upon the bones in the form of levers, if any could be made to act singly its power could easily be known. But whatever this power is it must be always the same; nothing can alter it excepting real weakness in the muscular fibres themselves. As we cannot separate and ascertain the absolute force of a single muscle, so it is impossible to find out the apparent force; and exactly for the same reasons that we cannot find out the abso- lute. The apparent force of circular muscles will be in a ratio proportionably to their diameters, and in those which are inserted into levers it will always be as the distance of the insertion of the muscle from the centre of motion, the angle of insertion, &c. But the relative force is not always the same, or it does not always act alone in the motion of the parts, for it is often joined with velocity, and then it may become vastly greater. But if not joined with velocity it will always be less than the absolute, as the length of lever in the resisting power is longer than in the acting one. The absolute force of a muscle will always be employed in the most simple action of the parts. The most simple action will be where a muscle passes in a straight line from some fixed point to a moveable one, and by its contraction simply pulls the moveable one towards the immoveable one, such as many of the muscles of the os hyoides, and in many other parts of the body. As the circular muscles are commonly employed in propelling bodies, and principally fluids, they will keep up an equal power upon the body to be expelled; for, the power increasing as the fluid decreases, it is capable of throwing out the same quantity in the same time.* I observed that the muscles, as moving powers in an animal, differ from the moving powers in a machine, the production of art, inasmuch as every part had its power adapted to the motion it is capable of, and therefore the motion of any one part did not depend entirely upon its own configuration and connexion with some other. Although this is in a great measure the truth, yet the motion in most parts is assisted by actions or the contrary in other parts, so that there is a kind of dependence and mutual assistance through the whole. This does not, however, arise from any mechanical construction, but from a connexion of the living principle in the powers of one part with those of another, which may be termed a species of intelligence. The motion of parts generally is the motion of a smaller upon a greater, and the greater becomes the fixed point upon which the * It may be asked, at what point of the contraction of a muscle has it the greatest power 1 Or, does it contract with the same force through the whole contraction ? CROONIAN LECTURES ON MUSCULAR MOTION. 261 smaller may be said to move; but we find that there are few mo- tions, however trifling, but what affect the greater part; therefore that this motion in the smaller part may be more effectual and an- swer the intended purpose, the greater part is either thrown into a counter-motion by its own muscles, or it is supported in its place by them, or it is thrown into the same action with the small part, so as to increase it. Hence the actions of these powers may be said to be of two kinds, immediate and secondary. The first is that which produces the immediate action of the part; the second produces the assistant, supporting, regulating actions, &c. For instance, when a man walks, it at first might appear that the only thing necessary to produce the ultimate effect was the motion of the two legs, the body being first thrown suffi- ciently forwards, so as always to require that motion of the legs to support the centre of gravity. But this is not sufficient; it is ne- cessary that the muscles of the trunk should act, and regulate the body so as to support the centre of gravity on all sides. If the right leg moves, the muscles of the left side of the trunk act to sup- port the whole on the left leg, and vice versd; so that the body plays upon the motion of the legs, by which means the legs have much less to do, and therefore can support it longer. In many of the actions of parts of the body other parts are kept immoveable, although they would appear to have nothing to do with any such actions. A man never performs any considerable action, even with any of the extremities, without the trunk being more or less affected, so as to favour the motion of the extremity. We find that we first make a full inspiration and that all the muscles of respiration act, also the muscles of the glottis, and of the soft palate, so as to confine the air which makes the trunk as rigid and firm as possible to support or sustain the actions and motion of the extremity. If an action takes place in an extremity, where a considerable effect is to be produced, which" can only be produced by a consi- derable velocity, then the whole body gives it assistance so far as it is possible for it to do. If a man throws a stone, or a blacksmith swings his sledge- hammer, the whole body humours the action, and the fixed point is thrown to a greater distance than the setting-on of the arm : the whole moves from the loins, or perhaps lower. Those secondary actions are brought in as auxiliaries, and an- swer two very important purposes: they increase the quantity of action when necessary, and they assist in easing the immediate action, so as to allow of a continuance of it, by which means ani- mals are capable of performing greater actions, with more ease, and a longer continuance. Muscles regulate the actions of others not only by their contrac- tion but by their relaxation, which last is a kind of negative action. When a man walks I have already observed that there are many muscles acting as secondary agents in the body, so as to assist the 262 HUNTER ON THE ANIMAL CECONOMY. immediate motions of the part to be moved; but, besides this, there are many of the same muscles that are gradually relaxing, so as to allow the alternate motions by imperceptible degrees to creep regu- larly into one another. Perhaps I cannot give a more striking idea of those primary and secondary actions, with the relaxations, which I have called nega- tive actions, than to present to the minds of those who have some knowledge of the subject what must be going on with the muscles of a man balancing himself on a slack or tight rope, when the first or immediate order of muscles are acting with their utmost force; where the secondary are assisting in the secondary actions of the body, and as it were playing into the hands of the first; where others again are relaxing in proportion as the first and second are acting ; and where the entirely relaxed are waiting the opportunity to act, when called upon by any change that shall take place in the position of the body, which in such circumstances is in a continued agitation. 23. CROONIAN LECTURE ON MUSCULAR MOTION, No. IV. [The manuscript of this Lecture appears not to have been among those which were accessible to Mr. Clift, and from his copies of which the Lectures in the present volume have, with his permission, been printed. Its absence may, however, be accounted for, from the fact that the substance of the Fourth Croonian Lecture was in- corporated by Hunter in his work 'On the Blood,' (see the Chapter on the Vascular System,) as is evident from the Abstract of the Lecture in the Archives of the Royal Society, the subjoined copy of which Abstract Mr. Palmer, with the permission of the President and Council, has obtained for the use of the present edition of Hunter's Works.] [The Croonian Lecture on Muscular Motion, by Mr. John Hunter, was read on the 25th of May and 1st of June, 1780.] "The construction and general application of muscles in the animal body having been discussed by our author in three former lectures, he now proceeds to treat of the action of muscles on the blood-vessels, an inquiry which, however essentially it may contri- bute to our better acquaintance with the animal ceconomy, has yet, it seems, till now been but little attended to, the existence of mus- cular fibres in the system of blood-vessels being by no means obvious. " Mr. H. finds it necessary previously to lay down some general principles concerning muscles, which he derives from their opera- tions in those parts of the animal where their uses are well un- derstood. CROONIAN LECTURES ON MUSCULAR MOTION. 263 " A muscle he defines such an arrangement of animal matter as, whilst it is endowed with life, is fitted for self-motion. This motion, he says, consists in the contraction of the muscular fibres, in which light he considers it as totally distinct from elasticity. And he ventures to assert that no part of an animal except the muscles is endowed with this power of self-motion. He acknowledges soon after that this power cannot be the sole effect of contraction, but that there must also be a power of relaxation, acting alternately, without which no effect could be produced. But even this relaxa- tion, he says, is not sufficient to produce any effect without a pre- vious elongation; and as no muscle is, as such, possessed of this power of elongation, he considers it as the effect of antagonists of some kind or other, or of what may be called the elongators of the muscles, and says, that it is not in all cases muscular, but some- times the effect of elasticity, and sometimes even of matter foreign to the body. This leads him to distinguish it into three kinds; the first, where it is immediately muscular, or when antagonist mus- cles act immediately upon each other; the second, when a muscle acts upon some other matter, and gives it the power of an antago- nist, as is the case in all those muscles that enter into the formation of canals or cavities, whose elongation is produced by other mus- cles, which have no immediate connexion with them, but which force them to an extension by propelling the contents of the canal, instances of which we find in the oesophagus, the intestines, and the bladder; and thirdly, when the elongation is owing to elastic sub- stances, which sometimes cooperate with, and sometimes resist the action of muscles; and of other powers, such as gravitation, velocity, &c. " The second section treats of the application of the muscular and elastic powers, where both indisputably act. The joint applica- tion of these two powers we are told is very common, though hitherto it has been but little noticed. Elasticity operates where constant or stationary action is wanted. Muscles are applied where occasional action is required; and where both effects are wanted both powers cooperate. This is illustrated by various examples, among the rest that of a bivalve, which has a muscle between the two shells, for the purpose of closing them, and an elastic ligament in the joint, which constantly tends to diverge them. " Another instance, much more to the present purpose, is that of the elastic cartilages and membranes of the trachea, and its branches, which maintain an equilibrium by counteracting the tendency the muscles of respiration have to contract that channel. " In most parts of the body the muscles are so well defined that their existence is evinced by merely viewing their structure and colour. But this is not always the case, and we especially find that in the blood-vessels no traces of muscles are distinguishable by mere inspection. " Here then other modes of information are requisite, and our author proposes two. The one is their effect when we see actions 264 HUNTER ON THE ANIMAL CECONOMY. that are in every respect muscular, although no muscle be distin- guishable by the eye ; and the other the change that takes place after death, when, as Mr. H. has observed, in many cases the power of contraction preponderates so as to stiffen all the muscular parts; and when, if the muscles thus contracted be afterwards stretched or put into what in the living body may be called its relaxed state, they remain thus relaxed without showing the least tendency to any further contraction. These circumstances mark the difference between muscular and elastic parts, since this latter power continues to act after death much in the same manner as it did during the life of an animal. " These two modes of information are next applied in the exami- nation of blood-vessels, which, our author previously observes, seldom bear any visible marks of muscular construction, and scarce ever admit of examining from their effects in the living body, on which account the second mode of information must be adopted as the likeliest to furnish some lights in this inquiry. He made a set of experiments on the blood-vessels of a dead horse, which were taken out so carefully as not to affect in the least either their texture or degree of contraction. They were examined both in their natural state and after they had been opened, and stretched different ways, by which means the different actions of the muscular and of the elastic powers become easily discernible. The following are the principal facts that resulted from this examination: "Every part of the vascular system is not equally endowed with muscles; the larger vessels, especially the arteries, being chiefly composed of elastic substances, whilst many parts of the smaller, or what are called the capillary vessels, appear to be almost entirely muscular. " In the middle-sized arteries two substances are visible to the eye, that towards the inner coat being evidently darker in colour, and of a structure somewhat different from the outward. The relative thickness of these coats differs as we recede from the heart, the interior becoming considerably thicker in proportion to the exterior ; whence it evidently follows that the external diameter of the duct is not to be inferred from its external thickness, this being always proportionably greater as the vessel diminishes in size. Both these coats are in some measure elastic, but the external is more so than the internal; whence it may be judged that it is the internal that is endowed with muscular properties. This indeed is confirmed by a variety of experiments, in which it was found that the inner surface after death was considerably more contracted than the outward, the latter being thrown into longitudinal corruga- tions, which could only be the effect of the greater transverse or circular contraction of the latter. " It has further been observed that this muscular contraction is chiefly in the transverse direction, and seldom if ever longitudinal. " The physiological application of these facts, especially to arte- ries, is briefly this. The muscular contraction being chiefly circu- CROONIAN LECTURES ON MUSCULAR MOTION. 265 lar, and tending to lessen the diameter of the vessel, the animal ceconomy would suffer greatly if in the larger arteries, where this contraction is greater in proportion as its diameter increases, some power did not counteract this tendency so as to maintain a middle state or equilibrium. Thus also when muscular parts are too much distended, which in large arteries will often happen on account of their vicinity to the heart, a similar power is requisite to contract it to its natural size or tone. In both cases the elastic power pro- duces the necessary effect, and it seems to follow hence that this power must always be proportionally greater in the larger vessels than in the smaller ones. " A Table, exhibiting at one view the results of the above-men- tioned experiments concludes this lecture."* 24. CROONIAN LECTURE ON MUSCULAR MOTION,No. V. FOR THE YEAR 1781. [Read before the Royal Society, June 14, by Mr. John Hunter, F.R.S.] Of the Contraction anU Relaxation of Muscular Fibres. Muscular motion differs from every other motion in matter; it is a motion taking place in the component parts of a muscle, and not a change of their relative situation. It is an uniform approxi- mation, and receding in all the parts; the size, construction, and connexion of these are as yet not known: it is similar, as far as we can discover by our senses, to elasticity; in both cases the motion is produced in the component parts, which we are as yet unac- quainted with, and only see the ultimate effect. For the better investigating this motion in muscles, we may divide the general motions in matter into four kinds. * [The irritability, or muscularity, of part of the coats of the artery contended for in the preceding lecture by Hunter, has since been demonstrated experi- mentally, first, by Dr. John Thompson of Edinburgh, and subsequently by many other physiologists; in whose experiments distinctcontraction of the small arteries was produced, not only by mechanical (Wilson Philip, Hastings, Kaltenbrunner) but by galvanical irritation. (See Wiedemeyer, Experimenla circa Statum San- guinis et Vasorum in Injlammatione, Monachii, 4to., 1826, and the Bibliography of the Vascular System, vol. iii., p. 226.) The muscular action is easily seen by dropping water colder than the atmosphere upon the capillaries in [the mesentery of a frog, which thereupon contract both longitudinally and transverse- ly, and after a little while resume their ordinary dimensions. Nevertheless the best chemists agree in classing the fibrous coat of arteries with the non- albuminous textures, as cellular tissue, cartilage, &c. The ultimate fibres of he middle coat, viewed microscopically, are smooth, branched, and anastomose reticular!y, like the fibres of involuntary muscles : they present a remarkably clear dark outline.] 24 266 HUNTER ON THE ANIMAL CECONOMY. The first is the motion of whole bodies by means of an external impulse, the vis inertia of the body being overcome. The second is the motion from attraction of one species of matter to itself or to another species, as wholes. Of this kind is gravitation, perhaps magnetism and electricity, probably also cohesion. The third kind of motion is from chemical attraction, where, besides the attraction of whole parts, there is an elective attraction between the particles of one kind of matter and those of another, as it were drawing them out from the general mass. This can only happen when suspended in a fluid or in the form of vapour, no other form admitting of the motion of particles among themselves. Repulsion produces a similar motion among the parts. The fourth kind of motion is muscular, arising most probably from construction, and a principle in action very different from the attractions in common matter. This action and the others are equally unintelligible, the general effect alone being evident to our senses. From the effect in muscular motion, we should be inclined to sup- pose that there is an approximation of the parts in one direction, which in the whole produces a visible contraction. It is natural to suppose that all muscular fibres act alike: that every fibre in every muscle when in action is under exactly the same circumstances: therefore whatever variety may appear in muscularaction, or difference between the action of different muscles, must depend upon the various causes and intentions of these actions. A muscle in action as it contracts becomes more dense or hard, and therefore iipi*iori we should suppose it becomes less, as we can form no adequate idea of the same substance becoming firmer or harder without either an approximation of its parts, or an addition of new matter introduced into all its parts, or a particular position of the constituent parts of a muscular fibre, so as to become im- moveable while in that position. One circumstance, however, which makes muscular fibres firmer when contracted in the living body is, their always overcoming some resistance in such contraction, which puts them more or less in the situation of a stretched cord. Take the unattached hairs which compose the strings of the bow of a fiddle, and they will feel pliant or soft; but when put upon the stretch they will feel much firmer. An elastic body also, as India rubber, feels much firmer while stretched than when con- tracted and at ease, by its natural elasticity. A muscular fibre, however, in the state of tension between the two points is little in- debted to this cause for its firmness, although it will increase the effect produced by the position of its component parts ; for a mus- cular fibre unattached is very much increased in hardness while contracted, as in crimped fish,* and in the flesh of all animals * [Sir Anthony Carlisle found that the contracted muscles in crimped fish had not only acquired a sensible rigidity, but also an increase of specific gravity. See his * Croonian Lecture for the year 1804,' Philos. Trans., 1805, p. 1.] CROONIAN LECTURES ON MUSCULAR MOTION. 267 allowed to die so gradually that the muscles, from the stimulus of death taking place, contract: but a muscle is as firm and as strong in all its degrees of contraction as it is in its full contraction, if not firmer and stronger than in its ultimate; therefore cannot be called contraction. It is its proximity of its parts arising from that attrac- tion, not from the proximity of such parts mechanically, but at- tractively. Many authors of authority, as well physiologists as others, have attempted to explain the contraction of a muscular fibre; but, however ingenious their opinions may be, none of them completely account for any one particular, relative to muscular contraction: I shall, however, mention them, with the objections to which they are liable. In the investigation of this subject the following apparent altera- tion in the figure of a muscular fibre has been principally attended to: When a muscle acts, it increases in thickness, and becomes visibly firmer in texture, therefore each component fibre of the mus- cle must be supposed to undergo the same change; and many ex- periments have been made to ascertain whether this increase of thickness in a muscular fibre is in proportion to its decrease in length, but hitherto without effect: probably the only method of ascertaining this fact is, to determine whether a muscle in the state of contraction is really increased or diminished in its bulk. Haller, in his Elements of Physiology, asks the following ques- tions: "Does a muscle really increase in bulk in its action? As a muscle, when it acts, becomes shorter, and swells, we may next ask, Do these two changes, contraction and dilatation, compensate each other? that is, Is there the same quantity of matter in it at both these periods ? Or does a muscle in action really lose in its size? or does it gain in bulk what it loses in length? Both sides of the question have had their advocates." Borelli, to find out whether a muscle really had an addition of new matter in its contracted state, and thereby became heavier, made the following experiment: He placed a naked man upon a table suspended upon a point, which supported it directly under his buttocks, in which situation he was perfectly balanced. He was then desired to act with the muscles of the lower extremities, but he still kept his balance, no change taking place in the equilibrium. (Borelli, vol. ii., p. 39.) This experiment was made most probably upon the supposition that some additional matter was to flow from the brain along the nerves, or from the heart along the vessels to the muscles of the extremities, so as to render the upper part lighter, and the lower part heavier. If it was to come from the brain, it was conceiving the supposed animal spirits to be heavier than air, of all of which we are wholly ignorant. The celebrated experiments of Goddard, Glisson, and Swam- merdam are quoted, to prove that muscles lose in their bulk while in action. They put a muscle or a whole limb into a glass vessel, 268 HUNTER ON THE ANIMAL CECONOMY. and filled it up with water; they then made all the muscles act at once ; or if a single muscle, they irritated the nerve, and made it contract, during which time they attended to the motion in the water, and its rising or falling was to determine whether the size of the muscle was increased or diminished. Swammerdam, in trying this experiment with a single muscle (the heart of a frog), saw the water sink in the contraction of that muscle, and rise in its relaxation. The result of this experiment has been very differently explained. Swammerdam himself doubted its being conclusive, believing the air might be compressed during the heart's action ; but we have no proof of the presence of air in a muscle in the simple state of air. Boerhaave and Sauvages accounted for the water descending by the blood being pressed out by the contraction of the muscle, which blood was returned into it by the relaxation, and raised the water. This certainly would be the'case in the experiment made upon a whole limb: for we know, from every day's experience, that in bleedings from the arm the blood is thrown out more forcibly while the muscles are in action : therefore there is less blood in the vessels of the limb when the muscles are contracted than in a state of relaxation, and of course the limb is less in bulk at that time than in the other : but when a single muscle or a whole animal is immersed in water, whatever loss the muscle has in its substance must be gained by the water, so that the whole can neither be diminished nor increased. Hambergerus tied a string round a man's arm, and found that during the action of the muscles it cut him ; he therefore thought that muscles in action were increased ; but the experiment only proved that it became thicker, which is generally allowed. It has been objected to such experiments, that if a person acts only with one set of muscles, their opponents become stretched or relaxed in proportion, keeping up an equilibrium in the part: as antagonizing muscles, however, never bear a just proportion to one another in strength, it follows, that if we act with the strongest set of muscles the limb will of course become thicker in the proportion that the strength of the acting muscles bears to the strength of the relaxing ones, and vice versa. To ascertain with as much precision as possible whether a muscle really alters in size or not when contracted, I repeated the experi- ments of Goddard, Glisson, and Swammerdam, but in such a way as to have little or no doubt what was the effect. I got a glass blown which contained almost a gallon; its mouth was about three inches over, to admit its receiving a pretty large muscle, and was fitted with a ground-glass stopper, which was water-tight, and a glass tube was fitted into this stopper, so as to communicate with the cavity of the glass, being at the same time water-tight. This apparatus could be filled with water, and have the water stand at any height in the tube which might be required, so as to give with CROONIAN LECTURES ON MUSCULAR MOTION. 269 great nicety the comparative size (should there be any difference), of a muscle when contracted and when relaxed, while immersed in it. The muscles best adapted for experiments of this kind are those which have no antagonists, for in that case the contraction of one muscle produces the elongation of the other. The muscle should be wholly detached, having neither origin nor insertion, as a muscle cut out of the body, or cut from its attachment, as in crimped fish : those muscles however are best which have no natural attachment, as the heart. In repeating such experiments it will be hardly possible to have the result of two exactly the same, for no two muscles will be equally relaxed at the beginning of the experiment, nor will any two muscles contract equally; but if there is one universal general effect taking place in all of them, that general effect be- comes the result of the experiment, and is what is to be at- tended to. Experiment 1. I killed a dog instantaneously, and took out the heart as expeditiously as possible, and put it into the glass filled with water, and immediately after putting in the stopper with the glass tube fixed in it. I now observed the height at which the water stood in the tube. The heart had so far lost its action as not to contract and relax alternately, having only the power of contraction from the stimulus of death, and when put into the water was perfectly relaxed. It was allowed to remain in the water some hours; and it was ob- served, that by its apparent loss of bulk it had contracted con- siderably ; and we also found that the water in the tube had fallen.* The next thing to be done was to ascertain how much the heart had lost in size, which was known by the quantity necessary to fill up the glass to the first height, which was sixteen grains. The size of the heart was equal to two ounces six drachms, and thirty-eight grains of water, that is, 1328 grains, so that the contracted state was to the relaxed as 82 to 83, or ^d part of the whole. Experiment 2. I took the heart of a sheep, whose size was equal to 13 ounces or 104 drachms of water; it lost in contraction 1 drachm; so that the contracted state was to the relaxed as nr*th part of the whole. Experiment 3. I took a live eel, which was gutted, to remove as much as possible everything not muscular, and then crimped, to destroy the attachment of most of the muscles. The eel was equal to 14 ounces and 133 grains, or 6853 grains of water, and it lost in contraction 39 grains, or j^th part of the whole.f * It is to be observed that the water was kept in the same degree of heat through the whole of the experiment. t [In the experiments above detailed Hunter drew his conclusions, as to the change of bulk in a muscle during contraction, from the effects observed in the level 21* 270 HUNTER ON THE ANIMAL CECONOMY. As this animal was composed of muscles, bones, &c, some allowance is to be made for these parts, which will account in some measure for the difference in the result between this and the hearts, although in the experiments on the hearts there is a con- siderable difference between the two, arising from the reasons above mentioned. It appears, however, upon the whole, lhat a muscle loses more of its length than it gains in thickness, unless the apparent difference arises from an universal approximation of all its parts. As a muscle loses in its general size by the contraction of the length of its fibres, we cannot suppose that contraction to arise from the introduction of additional matter into those fibres; therefore the opinions that a muscular fibre is a hollow tube from end to end, or a chain of cells of various shapes, either rhomboidalor circular, according to the ideas of the authors of such opinions, and these cells being filled with foreign matter, must fall to the ground ;* in- of the surrounding fluid, after the last contraction of the parlor ' rigor mortis.' In Mr. Mayo's well-known experiment, which is similar to the first of Hunter's, the ordinary contractions of the ventricles of a dog's heart, alternating with re- laxations of the same parts, produced no perceptible change in the level of the water in the tube.a In comparing the above experiments, one cannot fail to be struck with the period during which the muscular contractions of the dog's heart continued. But as Hunter killed his dog instantaneously, it was probably by some sudden concussion or injury to the brain, when the action of the heart would be arrested, and the last contraction only would be witnessed, notwithstanding the expedition with which it was taken out. In Mr. Mayo's experiment the dog was killed by hanging, and the ventricles of the heart continued alternately to contract and dilate for a considerable time. Baraolotti, Prevost and Uumas, who performed similar experiments on smaller portions of flesh, also found no change of level to take place in the surrounding fluid during the contraction of the muscle. Gruithuisen and Ermann,b on the contrary, observed, like Hunter, a slight change in the bulk of the muscle during contraction. Ermann introduced into a glass vessel the posterior half of an eel, the intestines being removed. A metal wire was inserted into the spinal marrow, and a second into the flesh, and these were directed so as to be brought into communication with the pole of a galvanic bat- tery. The vessel was then filled with water, so that a narrow tube, in which the apparatus ended above, was filled. In completing the chain, and during the con- traction of the muscles, the water fell in the tube four or five lines, and again rose to the opening, when the muscle relaxed. If, however, the muscular fibre, which is generally admitted to have increased in density, and, according to the experiments of Sir Anthony Carlisle, in specific gravity, during contraction, has really diminished in bulk, the difference is so trifling that we can hardly avail ourselves of it in elucidating the nature of mus- cular contraction.] * [It is now generally admitted by microscopical observers that the ultimate muscular fibre is solid. The voluntary muscular fibres (' secondary fibres' of Prevost and Dumas, 'ultimate fasciculi' of Muller,) in the vertebrate classes, and those of insects, arachnidans, crustaceans, and cirripeds, present a micro- scopical character which distinguishes them from every other animal tissue: it consists of close-set, parallel, transverse, or slightly oblique and sometimes slight- ly curved stria?. The fibres which present these striae are divisible into component fibriliae, which have a knotted or beaded structure; this I have myself observed a Anatomical and Physiological Commentaries, vol. i., p. 12. k [Gilbert's Annalsn, 40.] CROONIAN LECTURES ON MUSCULAR MOTION. deed, this idea of a muscular fibre being a chain of cells does not account for any one phenomenon attending muscular motion, and is directly contradicted by two circumstances attending muscular contraction: the first of these is the muscle becoming rather less than larger in its contraction, which is just contrary to what must have happened if the contraction had been owing to that cause; the second is, that a muscle is capable of contracting much more than one-third of its length, and indeed, as far as we yet know, having no limitation, which could not possibly happen if they were tubes capable of receiving foreign matter into their cavities; for according to that idea, a muscular fibre should become thicker in its contraction in proportion as the diameter of a sphere is greater than that of a cylinder of the same area, which would be an im- mense increase. Although a muscle becomes on the whole somewhat less in its contraction, and has its ends brought considerably nearer together, yet it cannot be called attraction, for there is nearly the same reason for supposing a lateral repulsion, as the muscle swells out laterally almost as much as it contracts in the other direction. I do suppose that a muscular fibre is not one uniform body from end to end, but is made up of parts, which may be called the com- ponent parts of a muscular fibre; and I am apt to suppose that a change takes place in the position of those parts, during contrac- tion, and this alteration diminishes the extent of those parts in one direction while it is increasing them in the other, although from the experiments it appears not to be in the same proportion; but what that alteration is I shall not pretend to determine.* in the human voluntary fibre, and in that of the mole-cricket. Some physiologists suppose that the transverse strise result from the lateral apposition of the knots on the parallel fibrillar. The muscular fibres of the mollnsca and radiata, and the involuntary muscular fibres of the vertebrata, with the exception of those developed in the vascular layer of the germ disc, as the fibres of the heart, do not present the striated character.] * [According to the observations of Hale3 {Hemostatics, p. 59), and of Prevost and Dumas (Magendie, Journal de Physiologie, iii., p. 301), the change in the muscular fibre, at the moment of contraction, is from a straight to a zigzag line : the observation has been generally made on the rectilinear parallel fibres of one of the thin abdominal muscles (the rectus) of a young frog, stimulated to contract while under the microscope; and the conclusion is admitted as an established fact in the most recent works on physiology. I have been led to doubt this fact, from observing the contraction of the muscular fibres in small Filarise (such as commonly infest the abdominal cavity of the cod), and more especially from observing ihe contraction of the retractor muscles of the tentacles of a species of Vcsicularia of Vanghan Thompson, a compound polype-like animal, which, under the guise of a Sertularia manifests a much higher type of organization. Here each separate fibre of the retractor muscles is seen with great distinctness, and is characterized by a single knot or swelling in the middle. In the act of retracting the tentacles the fibres become shorter and thicker, especially at the central knot, but do not fall out of the straight line. After the retraction has been effected, the fibres fall into a wavy or zigzag position: but this is characteristic of their state of relaxation under the circumstances which bring their two attached ex- tremities nearer each other. In like manner, in the parallel longitudinal fibres of the Fihr'.a, it is most evident that, at the moment of contraction, they become 272 HUNTER ON THE ANIMAL CECONOMY. Muscles have a disposition to throw themselves into wrinkles or corrugations when not in action, and when the position of the part moved by these muscles is such as allows the muscle to be in its shortest state, as in the biceps-flexor-cubiti after having bent the arm. If it is kept in that position by any other power, the biceps will leave acting and fall into wrinkles, adapting itself to the short distance between its origin and insertion; so that these wrinkles are a kind of substitute for the contraction that was in the muscle. The greatest strength in a muscle while in action is probably when it is half contracted, as we find that in all great exertions of muscular strength, where ultimate actions are to take place, the muscles employed are never allowed to relax their full relaxation, or contract to their full contraction. When a man walks with a heavy load his knees are a little bent, even of the leg he stands upon, which supports the whole while he is moving the other. The same thing takes places if he is weary; but if strong and full of activity his perpendicular joints may be kept pretty straight. The same thing also takes place in old people from the same cause; for as they become naturally weak, they become, like the strong, loaded with a heavy burden, therefore take on the same modes of action : the knees are never straightened, the back bent forwards, and all the parts that are constantly in the action of sup- port are all getting out of the perpendicular, in which perpendicular state, although they might be mechanically stronger, yet they are muscularly weaker, therefore get into that position in which the muscles can act with the greatest advantage. The relaxers, which become the sustainers of the muscles in action, never allow themselves to relax to their full extent while the contractors are carrying on the motion of a part, as it would produce weakness. The relaxation of muscles when contracted involuntarily, but from obnoxious stimuli, will not relax by the will; nothing but a counter-stimulus of necessity can, and even that with difficulty. For instance, if we attempt to breathe obnoxious air, or if anything touches the glottis, it immediately shuts, and it is out of the power of the will to relax it; but the stimlus of the necessity of breathing brings it to again. A muscle that has but one determined use, or rather a muscle that has but one point of orgin and one point of insertion, always acts wholly when put into action, so as to bring shorter and thicker, but do not alter their rectilinear position until the action has ceased, when they fall, like the parallel nervous chord, into zigzag folds, which continue until effaced by the restoration of the part to its usual length through the action of the exterior transverse fibres. On relating these observations to my friend Dr. Allen Thompson, he informed me that on repeating the experiment of Hales and Prevost on the frog, he had observed single fibres continuing in contraction, and being simply shortened, and not falling into the zigzag plicae; and he was led to suspect, from this and other appearances, that the zigzag arrangement was not produced till after the act of contraction had ceased.] CROONIAN LECTURES ON MUSCULAR MOTION. 273 about its effect on the part of insertion ; I believe never one part of the muscle only, or only a few of its fibres, but the whole. This is not the case with muscles whose origin is broad and its insertion narrow, whose insertion is broad and its origin broad, or whose origin is narrow and insertion broad. But in spasm in a muscle a very few fibres may be seen to act; in short, any number may act, as it is not motion of the part that is the intent of the action. Relaxation. Muscular fibres have a greater power of contraction than what is barely sufficient for the extent of the motion of the parts upon which they are designed to act. This is illustrated in the shell-fish called bivalve, for the muscle in that fish brings the two shells to- gether; but if one of the shells be broken, so as to allow of a nearer approximation of the two insertions of the muscle, we find that they arc brought nearer. It is also evident where the tendo- Achillis or patella is broken, for when that happens the fibres are allowed to contract to the full extent of their original contraction, and the parts heal in that position; in such cases the muscle is be- come shorter the whole length of its natural contraction, and the tendon is become so much longer; and in this case, if the muscle was not possessed of a greater power of contraction than was be- fore made use of, or did not acquire a greater power, no motion could now take place, whereas we find the ultimate quantity of motion produced. If the power of contraction was limited to the quantity produced in a straight muscle, the same kind of fibres, when forming sphincter muscles, could not answer the intended purposes, as a greater powrer of contraction is required. That the same length of fibre is not absolutely necessary to pro- duce in all cases the same effect, is strongly evinced, by the fibres of the gastrocnemius muscle in the African negro, being shorter than in the European, yet producing exactly the same quantity of motion in the joints which they move. This takes place univer- sally in the Africans, and now and then is met with in men of other nations. This difference in the length of muscular fibres is a principal reason of the difference in the outline of most men from one another; it is at least a secondary cause, and should be particularly attended to by painters and sculptors, as it is a distinguishing mark between original nations. The contraction of a muscular fibre is produced by the following causes: simple mechanical pressure, as touch, the pricking of a pin, &c.; simple impression on another part which acts upon this by sympathy. 274 HUNTER ON THE ANIMAL CECONOMY. It is also produced by properties of matter which are not me- chanical, as the essential oils, salts, acids, &c.; by affections of the mind and intentions of the will by means of the nerves; by the circumstances of the body itself at the time, as want, repletion, &c.; and even by death itself. An animal that dies so slowly as to allow the stimulus of death to be felt by its muscles, has those muscles so contracted as to become stiff; whether this contraction is equal to the greatest power of contraction of the same muscle, in such a position of the parts in the living body, I do not know. In order, however, to ascertain how much a common muscle contracts from the stimulus of death, I cut out a muscle from a horse just after it was killed, and found that in the action of death it had contracted one-third, and that the muscle so contracted had become one-fourth thicker in its diameter, a proportion I believe it would have kept in the living body; also the same muscle, when stretched, or when put into what in the living body may be called the relaxed state, did not again contract. The contraction of muscles from the stimulus of death is a stronger contraction than the attraction of cohesion of the muscles themselves; therefore when a muscle so contracted is attempted to be elongated it generally tears asunder: but this is not always the case, it only takes place under certain circumstances; it is with respect to the muscle itself in proportion to the power of con- traction of the muscle, for we find it takes place much oftener in those that die of violent deaths, especially when they die of strong convulsions ; it seldom or ever takes place in those which die of a disease of some standing, for in them the muscles have lost in some degree their absolute power of contraction; as also the disease may be such as has in some degree destroyed the stimulus of death upon the muscles, so that their contraction will be less, although their power may be pretty strong. It would appear from the above that muscular contraction is not simply an approximation of the parts of which a muscular fibre is composed. What the difference is in a muscular fibre between its relaxed state and the contracted, perhaps may never be known. Relaxation would appear to be a natural consequence of the con- traction having answered its end or fulfilled its purpose; or it may be supposed to have got rid of its stimulus by this action, the stimu- lus ceasing to have power when the action has taken place ; there- fore relaxation naturally occurs till excited to action by another sitmulus, of which it is susceptible. Relaxation might be supposed to be a simple cessation of action, but I think it is not; it appears to me to be a power as much de- pending on life as contraction ; for if it was simply a cessation of action, muscles would become relaxed that had contracted by the stimulus of death whenever absolute death took place, which is not the case; on the contrary, it takes probably as much force to CROONIAN LECTURES ON MUSCULAR MOTION. 275 overcome this contraction as the same muscles would have done when acting with all the power of the will in the living body. From the violence necessary for the elongation of a muscular fibre after death, it would appear that the position of the component parts of a fibre in any degree of contraction is such as requires force to alter or remove it, and, whatever that position is, it can be in part drawn out as if only in part contracted, or wholly drawn out; and in this operation of drawing out or relaxing a muscular fibre after death, we may observe there is a recoil or reaction in a certain degree when the elongating force is removed, becoming in this respect similar to elasticity. This recoil, however, is not extensive, although it takes place in every degree of relaxation, from the most contracted state to the almost totally relaxed state. I first observed this recoil in a man who died in convulsions in St. George's Hospital, from a fever, attended with delirium, which was brought on by a hurt on his arm, which inflamed considerably. A few hours after death his muscles were stiffer than usual, and extremely well marked through the skin, which induced me to make the following experiment on the relaxation of muscles. I laid bare the rectus muscle of the thigh, and separated it from the other mus- cles without stretching it; I then passed a thread behind it and inclosed the muscle, and cut the thread off where the ends met. Upon bending the knee the muscle was stretched, and I found that the ends of the thread were lapped over each other. Upon mea- suring the difference it was one-eighth of an inch diminished from what it was in the contracted state. I was much surprised by a considerable degree of contraction in the muscles, similar to elasticity, for they evidently contracted a good deal after being stretched. I suspected that this had arisen from some remains of life, and therefore waited till the next day, when the same thing happened. If, in stretching a contracted muscle after death, the fibres are not drawn out beyond this power of recoil, the whole contraction of the muscle (whatever quantity it is) continues the same; but if the muscle is drawn out further than this power of recoil, then the muscle becomes so far relaxed, but no further; for instance, if the recoil is the one-twelfth of an inch, and the muscle is only stretched so far, then the muscle will contract again one-twelfth of an inch; but if it is stretched one-sixth of an inch, then it will still only recoil one-twelfth, the other one-twelfth being the absolute relaxation of the muscle. From all that is mentioned above, I think it will appear that re- laxation of a muscular fibre depends upon life as much as the con- traction, neither the one nor the other being produced after death by any property in the muscle. The causes of relaxation are few ; the will is perhaps the princi- pal one, although not in all muscles. Emotion of the mind would appear to have a power of stopping the action of the heart, but is perhaps only hindering a new contraction. 276 HUNTER ON THE ANIMAL CECONOMY. The contraction and relaxation of a muscle are always adapting themselves to the motions of the parts on which they are to act, so that if a joint continues bent for sometime the muscle will retain it in that situation, and any extension of that joint will put the mus- cular fibres on the stretch. This is not, as has been supposed, a contraction of the tendon, but a contraction in the muscle, to adapt it to the remaining motion in the joint, this half contracted state becoming now the state of relaxation from which the muscle is in future to produce its action. The point of relaxation of a muscle, therefore, is always the extent of motion in the joint, and the quantity of contraction of a muscle is always equal to the full motion of the joint on which it acts, and if the joint loses part of its motion the muscle also loses a proportionable degree of contraction, so as still to be adapted to it. Muscles, however, so contracted, may be gradually stretched to their original length, and recover their original action, as the biceps- flexor-cubiti after inflammations, and abscesses in the arm. Muscles may be also stretched beyond their original length, and still retain their use, as those of the belly in dropsies. These circumstances prove that accidents to the body are pro- vided against in its construction ; for if the muscles remained in the half-bent state in the cases above mentioned, the length of muscle would be too great for the quantity of motion, and the first part of its action would produce no effect upon the joint. CROONIAN LECTURE ON MUSCULAR MOTION, No. VI. FOR THE YEAR 1782. [Read before the Royal Society June 13th, by Mr. John Hunter, F.R.S.] An inquiry how far, and in what instances, the density or firmness of a Muscle contributes to its strength. In comparative experiments respecting animals, where the actions of life are attempted to be imitated in the dead body, we should attend to every circumstance and see whether there is really any kind of similarity in the experiment. But, where life is absolutely necessary for the action, on one side, and the action is imitated only so far as regards the mechanical mode of performing it, the resem- blance between the vital action and the experiment is in reality very remote. To suppose that the action of a muscle should be equal, more or less, with its mechanical strength when dead is absurd, because they bear no analogy. The action of a muscle is as unlike its mechanical CROONIAN LECTURES ON MUSCULAR MOTION. resistance as the effects of the irritability of a living body upon impression is like the mechanical effects of the same impression; the mechanical effects being the same in the living as the dead. The action of a muscle is stronger than its mechanical resistance in the dead body; that is, its power of contraction is greater than the attraction of the cohesion of its fibres. These facts can only be ascertained by experiments on the power in the living body, opposing them with the resistance in the dead; but as a muscle is in very different states in contraction and relaxa- tion, even in the living body, and as the experiment is opposing contraction to the state of relaxation, the experiment is not con- clusive: it does not prove what it is meant to prove. The subject can and should be viewed in several lights. A muscle is first to be considered in two points of view; the relaxed state, where it is only united by the common attraction of cohesion of that muscle, and is probably as mechanically strong in the dead as the living; but they may be considered in the contracted state both in the dead and the living, for although a muscle does not con- tract after death, yet it often contracts in the act of dying; and death does not produce a relaxation, therefore it is to be presumed that the position of the parts of the muscle so contracted remains in the same state, and therefore such muscle affords an opportunity of making comparative experiments between it and one in the living body so contracted. How far the same muscles in the dead body, when fully con- tracted, could be relaxed by the same force as when in the living state, I do not know. It is certain that a muscle in health, and which feels the stimulus of death strongly, contracts with consider- able force, and requires a considerable power to overcome it; therefore the relaxation of a muscle, voluntarily contracted, must always be an act of the mind, or a cessation of action of the mind . upon that muscle. But when a muscle takes on an action without the mind, either in diseases, as the involuntary actions of voluntary muscles, or by the stimulus of death (the immediate cause of action being, I conceive, the same in both), then a relaxation from the mind cannot take place in either, because the mind had nothing to do with the first, and it did not exist in the second. So that those involuntary actions of voluntary muscles arise from a stimulus in- dependent of the will, and in those where it goes off it is because that stimulus can cease, and the part being alive a relaxation can ensue; whereas in death a relaxation cannot ensue, because a ces- sation of the stimulus cannot ensue, that cessation being an act of the living body. To oppose an experiment on muscles in the dead body with one in the living, the muscles should be always in similar states, for a muscle contracted is thicker than natural, and therefore stronger in its transverse direction; and if when in a contracted state the par- ticles of which it is composed are really brought nearer to each other, then it should be doubly strong, viz., in proportion to its in- 278 HUNTER ON THE ANIMAL CECONOMY. creased size and closer approximation of its particles. But as the state of a muscle in contraction is totally different from its natural state, or that slate which constitutes the natural structure of a muscle, no comparative experiments can be made which can explain anything. It is evident from observation, that in the construction of a muscular fibre it was not necessary that they should be all of equal density, for we find some fibres denser than others. We find this difference in the different tribes of animals; in some the fibres are extremely soft, while in others they are very firm. The firm fibre is found in the more perfect animals, called quad- rupeds, especially when full-grown; and this difference of density of muscular fibres would appear to be in a pretty regular gradation from the most imperfect to the most perfect, from the muscles of the medusa to those of the full-grown quadruped. We may also observe that the first rudiments of every animal are extremely soft, and even the rudiments of the more perfect are similar to the full-grown imperfect, and as they advance in growth they become firmer and firmer in texture. It may likewise be observed that there is a very considerable difference in the densities of the muscles in some of those animals that are of distinct sexes, the male (probably in most) having by much the densest muscles: and the muscles of the same animal, whether perfect or imperfect, are not of equal densities, some being denser than others. This arises from two causes,—one natural, growing up with the animal, the other acquired by frequent action. This difference in density of the muscular fibres in different ani- mals, and in the same animal at different ages, in different sexes of the same species, and even in the same sex, also the increased density arising from action, must answer some material purpose, and, from every observation, it would appear to produce strength or power in the contraction of the muscular fibre. From every circumstance attending muscular contraction, it is obvious that those muscles employed in, or intended for the strongest actions, are the firmest in texture of any animal body, at least from many circumstances it is natural to suppose so ; that they are the strongest would appear from the situation in which the firmest mus- cles are placed, for where the strongest actions are found in the living body, there we find the firmest muscles after death. There are two causes for this situation of the firm or strong muscles ; the first is an original or natural one, a principle in the animal ceconomy, depending upon the natural growth of the animal as much as the formation of a leg or any other part. The second is action. If we take a general view of the first or natural cause, we shall see from these general observations where we are to expect the strongest, and of course the hardest, muscles in any given animal whose mode of action is known. CROONIAN LECTURES ON MUSCULAR MOTION. 279 In animals which have progressive motion it will generally, if not always, be found that this action will be one of their greatest, because the parts intended for progressive motion bear a small proportion to the whole animal, which they are obliged to move ; whereas, every other part has its peculiar muscle, and the muscle is only obliged to move that one part, which is small in proportion to the others. Another action which many animals are endowed with, and which requires very considerable strength, is fighting; this is an action which always requires great powers in the muscles, because it is an action in a part which is to overcome the whole strength and weight of its antagonist, which is more than the natural weight of the same muscle, or the resistance of the same muscle,.orthe resist- ance of any muscle in the same body. Another partial cause of strength in some animals is for catching their prey, which is to overcome a resistance consider- ably beyond the motion of the part itself which is to perform the action. If such parts of animals as are adapted for progressive motion, for fighting, or for catching prey, require the greatest strength in the muscle adapted for such purposes, and if we find that such parts as are endowed with the firmest muscles are strongest, where all those purposes are united in the same part in any one animal, we must find there the greatest strength, and of course the firmest of all the muscles in the body, especially if every one of these actions is considerable or violent. Thus, then, we find the muscles in the arm of a lion where all these three purposes are performed, are extremely firm in texture, and we must suppose are also exceedingly strong. The muscles of the thigh of a fighting-cock are employed in fighting and progres- sive motion, and are extremely firm. The muscle which has the greatest resistance in an animal body to overcome is the heart, especially in quadrupeds, and this is perhaps the firmest in the body, being even firmer than those which have the above-mentioned resistances to overcome; but the firmness of this muscle may in some measure arise from its action, which I called the second cause of firmness. Some muscles in the more perfect animals are much firmer than others in the same animal; such is the muscle which draws the snail into its shell, and retains it there against almost any power that can be applied; also the muscle which shuts the two shells of the bivalve is very firm in its texture, and we know that itis exceed- ingly strong. A difference is sometimes found in firmness between the muscles of the male and female; this, however, is not universal, not taking place in fish; but in all animals where the males have a disposition to fight and the females not, or at least in a less degree, I believe the muscles of the male are much firmer than those of the female, and this in proportion as their disposition for fighting is greater; 280 HUNTER ON THE ANIMAL CECONOMY. therefore in beasts of prey, where the disposition to fight is nearly equal in the male and female, the difference in strength is not so remarkable as in many other animals, there being very little differ- ence between a male and female cat, a dog and bitch, a male and female hawk, &c; but the muscles appropriated for catching prey, and also for fighting, are much firmer than the other muscles in the same body allotted for common purposes, and according to our reasoning they must be much stronger. We find, however, in animals which do not catch prey, and where the male has a strong tendency to fight with the males of its own species, while the female has this disposition very little, if at all, that there is a very considerable difference in the strength of the same parts in the male and female while alive, and a similar difference in the firmness of their muscles after death. There is a considerable difference between the muscles of a bull and cow, and also between those of a cock and hen. Besides the general strength of the muscles of those males who fight, as they have parts which are intended for this purpose, we find that the muscles of those parts far exceed all their other mus- cles in firmness; as the muscles in the neck of the bull, and the legs of the cock, far exceed in firmness all the other muscles in the body, and exceed, therefore, in a much greater degree the muscles of the female. We may also observe, that all those muscles in the male imme- diately employed in fighting, although not intended for this action alone, having other actions which are common to the female, be- sides being firmer than those of the female, are very considerably increased in size; thus the muscles of the neck of the bull, and of the stone horse, those of the legs of the cock, &c, are much thicker and larger than in the female. The second cause of firmness in a muscle, and which contributes to its strength, is action, or what is commonly called exercise, and which has in general been considered as the principal cause of strength, size, and firmness. This may be called accidental, as it is not confined to any order of animals, or any one set of muscles ; it may, however, be observ- ed, that the muscles employed in progressive motion and the pur- poses above-mentioned, are more subject to this accidental cause of firmness than any other in the body, both from the natural ac- tions of the body, and also, being naturally firm and strong, from more readily being employed in violent actions. Thus we find the muscles employed in progressive motion are much firmer than any other muscles in the same animal, both from nature and action, except in those in the fighting males (who do not catch their food by violence), which are employed for that pur- pose, as in the neck of the bull. The heart of all animals partakes strongly of the two causes of firmness, and is perhaps the firmest muscle in the body. This firm- ness in the heart is very early in life, for in the small embryo the CROONIAN LECTURES ON MUSCULAR MOTION. 281 heart is a pretty firm manageable part, while every other muscular part of the animal is as tender as jelly. Constant action not only gives firmness to muscles, but increase of size. The epicure is no less sensible of the effects of these causes of firmness than the physiologist, and therefore prefers the inactive parts; and the leg of the woodcock, the breast of the partridge, pheasant, turkey, &c.,are held in high estimation. He even takes pains to diminish the effects which arise from exercise, &c, by feeding animals in such a way as to prevent them taking place.— Upon this principle house lamb, veal, &c, are made tender. How delicious to the sensualist must the flesh of the sloth be, if the ac- count of its motion being far exceeded by a snail is true! From the above account it must appear that muscles, in propor- tion as they are firm in texture, will be strong in action; it is at least demonstrable in the muscles of the same animal whose texture is different, and in similar muscles in the male and female of the same species, and we may reasonably suppose that it will hold good in different species; and therefore, when we find the muscles very firm in any one species, we may conclude that this species is stronger than any other species in which the muscles are tender and soft. This firmness in a muscular fibre we may suppose to arise from the density of its component parts, or those parts being closer to- gether, the uniting medium being less in quantity; this, however, it is perhaps impossible to determine exactly. That this idea may be better understood, I shall suppose that a part composed of dense parts (aggregated) at a given distance, will be firmer than a part composed of less firm parts at the same dis- tance ; and it is plain that a part composed of any given substance will be dense in proportion as the parts of that substance are near to each other. It may probably be similar to iron and steel; in the iron the parts or crystals which compose the mass are large, and perhaps not regular. In the steel they are small, and probably more regular in their figure, by which means they can adapt themselves better to each other, and still more so if tempered, according to the degree of temper, so that their crystals shall become still smaller, and of course the whole becomes harder. To ascertain whether the firm muscles really contained more matter, and were therefore specifically heavier than the soft, I made several experiments upon muscles of different densities. The ex- periments were made upon the same muscle of two animals of the same species whose muscles are of different densities, viz., the mus- cles of the neck of the ox and bull.* Nine ounces and a half of muscle from a bull's neck, and the * My reason for choosing those muscles in preference to others was, that they admit a greater degree of difference in firmness, and that they have no tendons intermixed, so as to give density from that cause. 25* 282 HUNTER ON THE ANIMAL CECONOMY. same quantity from that of an ox, were weighed in water, when the bull's was thirty-one grains heavier, which is about TTjth'* From this experiment it appears that there is some difference in weight between a firm muscle and one that is naturally soft or lax, although not great, not even so much as one might at first imagine, at least not so much as the apparent difference in density. As it appears, from the above observations, that with the same given size the firmer muscles are the strongest, it becomes a ques- tion why every muscle in the bodies of the more perfect animals, and in the young of such animals, as also the muscles of the more simple animals in general, should not all have been of this texture, which constitutes the greatest power of contraction 1 This is per- haps not yet to be fully answered. It certainly would have ren- dered many parts of the more perfect animals much smaller than what they now are, and would have had the same effect upon the whole body of the young of the more perfect animals, as also of the more simple animals universally; we must, however, suppose that it would have been attended with some inconveniences, although at present what these inconveniences would have been may not be perfectly understood. 26. THE USE OF THE OBLIQUE MUSCLES. Muscles are the active parts in an animal body, producing dif- ferent effects, according to the circumstances in' which they are placed; and the greater number of parts requiring a variety of motions, it became necessary to have a variety of muscles suited to such motions. The function of a muscle depends on the contraction of its fibres; and the most general effect produced by this contraction is to move some one part of the body upon another. But we may observe, that when motion in a part is performed by one set of muscles, there are other muscles employed in regulating that motion, as in most joints; and in a whole part, destined to a variety of motions, and composed of smaller parts, intended likewise to have their dis- tinct motions, we find muscles appropriated for the purpose of keeping some of those parts fixed in a particular position, while the whole part is to be moved by other muscles, according to the nature of the action to be performed. This will, perhaps, be best illustrated by attending to what takes place in the eye, considering it as part of the head. The eye being an organ of sense, which is to receive impressions from without,it was necessary it should be able to give its motions * [See note, p. 266.] THE USE OF THE OBLIQUE MUSCLES. 283 that kind of direction as would permit its being impressed by objects whether at rest or in motion, or moving from object to object; and it was also necessary that there should be a power capable of keeping the eye fixed upon an object when our body or head was in motion. For the better understanding this action of pointing the eye towards objects under the various circumstances of vision, it will be necessary to mention that the eye is furnished with muscles, some of which, in the quadruped, bird, amphibia, and fishes, are called straight, from their being placed in the direction of or parallel to the axis of the eye; and two, I believe, have always been named oblique. Of the straight, some animals have more than others. There are four straight muscles common to most animals; and those which have more have the additional muscles inserted immediately in the eyeball on its posterior surface, and surround- ing the optic nerve. The four straight muscles, which are common to all quadrupeds pass further forwards, and are rather inserted towards the anterior surface of the eye. For vision at large it was not only necessary that the eye should be capable of moving from object to object, or of following any object in motion, but also necessary that there should be a power to keep it fixed on any one object to which the mind might be attentive ; therefore the muscles are formed so as not only to be able to move the eye from object to object, but likewise to keep its point of vision fixed upon any particular one, while the eye is moving progressively with the head or body. This is the use of these muscles, when the parts from whence they arise are kept fixed respecting the objects the eye is pointed to ; but it is often neces- sary, while the eye is fixed upon a particular object, that the eye- ball and the head in which it is fixed should shift their situation respecting that object; and this would alter the direction of the eye, if the muscles had not the power of taking up an action that produces a contrary effect, that is, keeping the point of insertion of the muscles as the fixed point, by causing their fibres to contract according as the origins of the muscles vary their position respect- ing the object. From this mechanism we find these three modes of action produced : first, the eye moving from one fixed object to another; then the eye moving along with an object in motion; and, last, the eye keeping its axis to an object, although the whole eye, and the head, of which it makes a part, are in motion. From either of these motions taking place singly, or being combined, the eye is always kept towards its object. In the two first modes of action the origins of the muscles are fixed points respecting the object; and, in the last, the object becomes as it were the centre of motion, or fixed point, commanding the direction of the actions of the eye, as the north commands the direction of the needle, let the box in which it is placed be moved in what direction it may. These two first modes of action are performed by the straight muscles ; for the head being a fixed point, they are capable of moving the eye 284 HUNTER ON THE ANIMAL CECONOMY. up and down, from right to left, with all the intermediate motions, which, taken together, constitute a circular movement; or, when the eye is to become the fixed point, then the head itself performs the circular movement. Thence appears the necessity why the object, the axis of the eye, and the point of sensation, should all three be in the same straight line. But this does not take place in all movements of that whole of which the eye makes a part; for besides those which we have already taken notice of, the head is capable of a motion from shoulder to shoulder, the axis of which is through the axis of the two eyes, from the fore to the back part. It should be here observed, that for distinct vision the object must be fixed as respecting the pupil of the eye, and not in the least allowed to move over its surface.'' To prevent any progressive motion of the object over the retina of the eye, either from the mo- tion of the object itself, or of the head in some of the motions of that part, the straight muscles are provided as has been explained ; but the effects which would arise from some other motion of the head, as from shoulder to shoulder, cannot be corrected by the action of the straight muscles, therefore the oblique muscles are provided. Thus when we look at an object, and at the same time move our head to either shoulder, it is moving in the arch of a circle whose centre is the neck; and of course the eyes would have the same quantity of motion on this axis if the oblique muscles did not fix them upon the object. When the head is moved towards the right shoulder the superior oblique muscle of the right side acts and keeps the right eye fixed on the object; and a similar effect is produced upon the left eye by the action of its inferior oblique mus- cle: when the head moves in a contrary direction the other oblique muscles produce the same effect. This motion of the head may, however, be to a greater extent than can be counteracted by the action of the oblique muscles. Thus, for instance, while the head is on the left shoulder the eyes may be fixed upon an object, and continue looking at it while the head is moved to the right shoulder, which sweep of the head produces a greater effect upon the eye- balls than can be counteracted by the action of the oblique muscles; and in this case we find that the oblique muscles let go the eye, so that it immediately returns into its natural situation in the orbit. Whether this is performed by the natural elasticity of the parts, or * Optical writers seem to have been entirely ignorant of this ; for they not only suppose distinct vision compatible with the object having a motion over the different parts of the retina, but even explain the effects which would be produced by it on the mind of the observer. Keill makes the following observation : " Since optics teach us that every body which is visible has by means of the rays which proceed from that object its image painted on the bottom of the eye or retina, it follows that those objects will seern to be moved whose images are moved on the retina, that is, which pass over successively the different parts of the retina whilst the eye is supposed to be at rest; but those objects will be looked upon as being at rest whose images always occupy the same part of tha retina, that is, when the motion of those images are not perceived in the bottom of the eye."—Keill's Introduction to Natural Philosophy, p. 79. ON THE COLOUR OF THE PIGMENTUM OF THE EYE. 285 whether the antagonist oblique muscles take up the action and rein- state the eye, I do not know. If the head still continues its mo- tion in the same direction, then the same oblique muscles begin to act anew, and go on acting, so as to keep the eyes fixed on the object. As this motion of the head seldom takes place uncombined with its other motions, some of the straight and oblique muscles will be employed at the same time, according as the motions are more or less compounded. 27. ON THE COLOUR OF THE PIGMENTUM OF THE EYE IN DIFFERENT ANIMALS. In the eyes of all animals which I have examined there is a sub- stance approaching to the nature and appearance of a membrane, called the pigmentum, which lines the choroid coat, and is some- what similar to the rete mucosum which lies under the cuticle of the human body; and there is also some of the same kind of sub- stance diffused through the cellular membrane which unites the choroid with the sclerotic coat. My intention at present is only to communicate the observations I have made on this subject and its use, confining myself to the consideration of that kind of it which lines the tunica choroides of the class Mammalia, and of birds; in doing which I shall also take occasion to speak of the difference of colour occurring in animals of the same species. Although an ac- curate examination of the appearances of a similar substance in the eyes of some fishes might illustrate the subject, we cannot avail our- selves of that, as from not being sufficiently acquainted with the effects of light upon the eyes of that class of animals. The propagation or continuance of animals in their distinct classes is an established law of Nature, and in a general way is preserved with a tolerable degree of uniformity; but in the individuals of each species varieties are every day produced in colour, shape, size, and disposition. Some of these changes are permanent with respect to the propagation of the animal, becoming so far a part of its nature as to be continued in its offspring. Animals living in a free and natural state are subject to few deviations from their specific character; but nature is less uniform in its operations when influenced by culture.* Considerable varie- ties are produced under such circumstances, of which the most fre- * From the variations produced by culture it would appear that the animal is so susceptible of impression as to vary Nature's actions ; and this is even carried into propagation. VVhether this takes place at the very first union of the principles of the two parents, so as to derive its existence from both ; or whether it takes its formation from the mother, after the first formation of the embryo, are perhaps not easily determined. 286 HUNTER ON THE ANIMAL CECONOMY. quent are changes in the colour. These changes are always, I believe, from the dark to the lighter tints, and the alteration very gradual in certain species, requiring in the canary-bird several gene- rations; while in the crow, mouse, &c, it is completed in one. But this change is not always to white, though still approaching nearer to it in the young than in the parent, being sometimes to dun, at others to spotted, of all the various shades between the two extremes. This alteration in colour being constantly from dark to lighter, may we not reasonably infer that in all animals subject to such variation the darkest of the species should be reckoned nearest to the original; and that where there are specimens of a particular kind, entirely black, the whole have been originally black? Without this suppo- sition it will be impossible, on the principle I have stated, to account for individuals of any class being black. Every such variety may be considered as arising in the cultivated state of animals; but whether, if left to themselves, they would in time resume their ori- ginal appearance, I do not know.* The colour of the pigmentum of the eye always corresponds, I believe, with that of the hair and skin, especially if the animal be only of one colour, but is principally determined by the hair; and the most general colour is a very dark brown, approaching to black, from whence it had the name, nigrum pigmentum.f The colour differs in different classes of animals, often in the same class, and even in the same species. In the human it is most com- monly dark, in the ferret kind always light, and its difference of colour in the same species is evident from the variety observable in the eyes of different people. There is even a difference of colour in the same eye in many classes of animals, in all of the cat and dog kind, and perhaps in most part of the granivorous. In some it is partly black, and partly of the appearance of polished silver; and in many classes the variation from dark is of two colours: for in the cow, in sheep, deer, horses, and I believe in all animals feeding on grass, there are in the same eye certain portions of it white, and others of a fine green colour. The difference in colour of this pig- mentum in the eyes of different animals of the same species is very remarkable: in the human species it is of all the different shades between black and almost white, and the same variety is seen in rabbits, mice, crows, blackbirds, &c, but in these it is of one colour only in the same eye. Every species is, perhaps, subject to such variations; and some of these are so extraordinary as with pro- priety to be denominated monstrous.J * In vegetables, I believe, it invariably holds good that, however improved by culture, if neglected, they soon degenerate into their first state. | As the colour of this membrane corresponds with the colour of the skin and hair of the person, it is probable that the people among whom it first got the name were dark. X Perhaps the word monstrous is too strong, or not exactly just. It certainly may be laid down as one of the principles or laws of Nature to deviate under certain circumstances. It may also be observed, that it is neither necessary, nor does it follow that all deviations from the original must be a falling off; it appears ON THE COLOUR OF THE PIGMENTUM OF THE EYE. 287 The variation in the colour of the pigmentum in different species of animals seems to depend on a fixed law of Nature; but the varieties which are met with in the same species are much less constant, being merely different shades approaching to black or white. But the extraordinary circumstance is its being sometimes unusually lighter or darker in individuals of the same species; and this difference not seldom starting up in the young without any hereditary principle to account for it. The human species is a striking example of the colour of the pigmentum corresponding with that of the skin and hair; and though the skin and hair of one person differs very considerably from the skin and hair of another, yet it is not in so great a degree as in many animals. There are cattle perfectly while, white sheep, white dogs, white cats and rabbits ; but there are few of the human species that we can say are perfectly white. They rather pass from the black into the brown, red, and even light yellow; and we find this pigmen- tum, although only of one colour, varying through all the different corresponding shades. In the African negro, the blackness of whose hair and skin are great distinguishing characteristics, this pigmentum is also very black. In the mulatto, who has not the skin so dark as the African, but the hair nearly as black, this pig- mentum is of a shade not quite so deep ; yet still it does not approach so near to the middle tint as the skin, rather following the colour of the hair. In people of a swarthy complexion, as Indians, Turks, Tartars, Moors, &c, we find the hair always of a jet black, and this substance of a much darker brown than in those that are fair. In those of very dark complexions, and having very black hair, although descended from fair parents, the same thing holds good. There are few species of animals, or even individuals of a species, whose bodies are only of one colour. Crows and some others, are exceptions; but the greatest number are of two or more, being variously spotted or streaked either with different colours, or with shades of the same. Many species are constantly lighter in some parts of the body than in others; and, with a few exceptions, animals are generally lighter, as to colour, on the lower, or what may be called the foreparts, than on the upper or backparts. The fair man or woman may strictly be considered as a spotted or variegated animal. In many persons the hair of the head, eyebrows, eyelashes, beard, and hair on the pubes, all vary in colour. The hair of the three first may be called foetal, and are oftener all of the same than of a different colour; the two last are to be considered as adult hair, and are commonly alike in colour, which yet frequently varies from that of the foetus, which last is more liable to change its colour than the other ; and the change is generally that of growingdarker, especially on the head and the eyelashes.* This difference in the colour of just the contrary, therefore we may suppose that Nature is improving her works, or at least has established the principle of improvement in the body as well as in the mind. * The hair growing gray is not in the least to the present purpose. 288 HUNTER ON THE ANIMAL CECONOMY. the hair on different parts of the body is not so observable in those nations who are dark or swarthy, as in people inhabiting many of the northern climates. In animals which are variegated let us observe the colour of this pigmentum, and we shall find it regulated by some general principle, and corresponding with the colour of the eyelashes. The magpie, for instance, is nearly one-third, or fourth part white ; and the two colours, if blended, would make the compound gray; but the eye- lashes being black the pigmentum is black also. We sometimes meet with people whose skin and hair are very white and yet the iris is dark, which is a sign of a dark pigmentum ; but if we examine more carefully we shall also find that the eyelashes are dark, although the eyebrows may be the colour of the common hair. As the colour of the iris in the human species is probably a pre- sumptive, though not a certain sign of the colour of this pigmentum, we may be led to suppose that in those who have the iris in one eye different from that of the other, this substance will likewise differ; but this I cannot determine, never having examined the eyes of any person with such a peculiarity. It is not an uncommon circum- stance in some species of animals, the Angola cat seldom having the colour of the iris the same in both eyes. In people remarkably fair, whether they are of a race that is naturally so, or what may be called monstrous in respect to colour, as white ^Ethiopians, still we find this pigmentum following the colour of the skin and hair, being in some of a light brown, and in others almost white, according to the colour of the hair in such people. All foals are of the same colour, and whatever that may be, as they grow older it generally becomes lighter, therefore the pigmen- tum in them is almost always of the same colour, and does not seem to change with the hair. This change, however, is only in the hair, and not in the skin, the skin of a white or gray horse being as dark as the skin of a black one: yet there is a cream- coloured breed which has the skin of the same colour, whose foals are also of a cream-colour; and by inspecting the parts not covered with hair, such as the mouth, anus, sheath, &c, these, and the pigmentum of the eyes of such horses, are found of a cream-colour likewise. In the pigmentum of the rabbit kind there are all the degrees of dark and light, corresponding with the colour of the hair; yet there seem to be exceptions to this rule in some white rabbits with black eyes, and therefore with black pigmentum ; but in all such there is either a circle of black hair surrounding the eye or the eyelashes, and the skin forming the edge of the lid is als'o black. In many white cattle this is also observable ; and in that breed of dogs called Danes some have the hair surrounding one eye black, while the hair surrounding the other is white; and the iris of the one is often lighter than that of the other. This circumstance, of the iris of one eye being lighter in colour than that of the other, is a common thing ON THE COLOUR OF THE PIGMENTUM OF THE EYE. 289 in the human species; and sometimes only one half of the iris is light, without any difference in the colour of the eyelash or eye- brow. Whether this difference in the colour of the iris of the two eyes in the same animal is owing to the pigmentum being different in colour, I do not know, although I rather suspect it is something similar to the white iris in horses, which makes them what is called wall-eyed. The variation of colour appears most remarkable when a white starts up, either where the whole species is black, as in the crow or blackbird, or where only a certain part of the species is black (but permanently so), as a white child borne of black parents; and a perfectly whit-e child, whose hair is white, and who has the pig- mentum also white, though born of parents who are fair, should as much be considered as a play of Nature as the others. All these lusus naturae, such as the white negro, the pure white child of fair parents, the white crow, the white blackbird, white mice, &c, have likewise a white pigmentum corresponding with the colour of the hair, feathers, and skin. Besides the circumstance of animals of the same species differing from one another in colour, there are some distinct species which are, as far as we know, always of a light colour, and in them, too, this pigmentum is white : the animal I allude to is the ferret. When the pigmentum is of more than one colour in the same eye, the lighter portion is always placed at the bottom of the eye, in the shape of a half-moon, with the circular arch upward, the straight line or diameter passing almost horizontally across the lower edge of the optic nerve, so that the end of the nerve is within this lighter coloured part, which makes a kind of semicircular sweep above it. This shape is peculiar to the cat, lion, dog, and most of the carnivorous tribe; in the herbivorous the upper edge being irre- gular ; in the seal, however, the light part of this pigmentum is equally disposed all round the optic nerve, and is, on the whole, broader than it is commonly found in quadrupeds. How far this increase of surface is an approach towards the fish kind, in which it is wholly of this metallic white, I will not pretend to say, but it is probable, as the animal is to see in the water as well as in the air, that it may be formed circular, the better to correspond with the form of the eyelids, which open equally all around, which seems to accord with what is observable in fishes, they being without eyelids. The colour of the pigmentum, whether white or green, or both, has always a bright surface, appearing like polished metal, which appearance animal substance is very capable of taking on, as we see in hair, feathers, silk, &c. After having taken notice of the various colours of this pigmen- tum in different animals, both where permanent and where it ap- pears to be a play of Nature, let us next examine what effect it has upon vision in both cases, whether these effects are similar, or if one case illustrates the other. 26 290 HUNTER ON THE ANIMAL CECONOMY. It may be asserted as an undoubted fact, that the light which falls on the retina covering a white pigmentum has more effect than when it falls on the retina which covers a dark one; which is known by comparing the vision of those of the same species who have the pigmentum wholly dark with those who have it perfectly white; and something may be learned by a similar comparison of animals who have it only in different species, it being reasonable, from analogy, to suppose that some such effect is produced in the eye which is possessed of both. I shall first consider the effect produced when the white or light colour makes only part of the pigmentum. This will lead me to observe, that all animals having the pigmentum diversified, though they are capable of bearing as much light as others, and can see as perfectly when light is in an equal degree ; can likewise see very distinctly when the light is much less than will serve the purposes of animals having it wholly dark. May we not, therefore, ascribe this advantage to the pigmentum being partly white ? One might be almost tempted to suppose that such animals have a power of presenting the different parts of the eye to the light, accord- ing to the quantity of light required ; or of moving the crystalline humour higher or lower : but we are at present unacquainted with any power in the eye by which these actions can be performed. We may observe, that when a cat or dog looks at us in the twi- light the whole pupil is enlarged and illuminated, but in a full light there is no such appearance. It is plain there must be a reflexion of light from the bottom of the eye to produce the above effect, especially as the light reflected is always of the colour of the pig- mentum in such animals, which in the cow is of a light green. I shall secondly consider those animals which have the whole pigmentum of a white colour, whether it is accidental or natural, and that see much better in the dark, or with less light than those in which it is of a dark colour: of the first of these I shall take my instance from the human species; of the second the ferret will serve as an example. Those of the human species who have the pigmentum of a light colour see much better with a less degree of light than those who have it dark; and this in proportion to their fairness; for when the hair is quite white they cannot see at all in open day without knit- ting their eyebrows and keeping the eyelids almost shut. In many of these instances there is an universal glare of light from the pupil, tinged with a shade of red, which colour, most probably, arises from the blood in the vessels of the choroid coat. I have likewise observed that the pigmentum is thinnest when it is light, so that some of the light which is reflected from the point of vision would seem to be thrown all over the inner surface of the eye, which being white, or rather a reddish-white, the light appears to be again re- flected from side to side.* This seemed to be the case in a boy at * How far this is really the case I do not absolutely say ; for whatever light comes through the pupil must be reflected from the point of vision ; bull imagined I saw the light passing through the substance of the iris. ON THE COLOUR OF THE PIGMENTUM OF THE EYE. 291 Shepperton, when about three years of age, of whom I have a por- trait, to show that appearance. He is now about thirteen years of age:* the common light of the day is still too much for him; the twilight is less offensive. When in a room he turns his eyes from the window, and when made to expose his face to the light, or when out in the open air, he knits his eyebrows, half shuts his eye- lids, and bends his head forwards, or a little down; yet the light appears to be less obnoxious to him now than formerly, probably from habit. Such persons appear to be nearer-sighted than people in common, but I apprehend that appearance to arise from the position into which they throw the eyelids and eyebrows, which not only in a great degree excludes the light, making the object faint in proportion to the contraction of the pupil and shade made by the eyelids and eyebrows, but at the same time fits the eye to see near objects; for if we nearly close our eyelids and knit our eye- brows we can see a small object much nearer than if we did not perform such actions, and it will make above a foot difference in the focal distance of the eye. In many rabbits who have white eyelashes, and in white mice, the pigmentum is entirely white, which is likewise observable in a certain distinct species of animals, tho ferret, which we have ad- duced as an example of the pigmentum being naturally white; for these animals being intended to see in the dark, and their mode of life not exposing them to the light, they are liable to be affected by strong light to a greater degree than many others. If it is allowed as probable that in animals having the pigmentum diversified the object to be viewed is thrown upon the lighter coloured portion, how does it happen that such are able to bear the light better than those who have the pigmentum altogether of a light colour ? Perhaps it is not the illuminated object itself that is offensive to the retina, but that diffusion of light in the one kind of eye which does not happen in the other. Having stated the facts, and the general effect arising from the diversified pigmentum, let us consider the manner in which it is brought about, that such animals see better with little light than those which have the pigmentum wholly black. Let us then suppose the retina to be the organ of sight, and that by the rays which fall upon it being properly refracted it gives or conveys to the mind an idea of a distinct object, corresponding with the sensation of touch. This is the most common and simple man- ner in which vision is performed, and is that mode which takes place where the pigmentum is black, or nearly so, and where the greatest quantity of external light is required. The "retina, although somewhat opaque, is yet so transparent as to allow a considerable quantity of light to pass through it. For if this was not the case there could not be those differences in the appearance of the eye which I have been describing. The rays which pass through, we may suppose, do or do not give sensation * The period here alluded to is 1786, when the first edition of this work was published. 292 HUNTER ON THE ANIMAL CECONOMY. in their passage ; and we may also suppose that only those which strike against the retina are the cause of sensation: but this is not the present inquiry; the rays which pass through the retina are what I am alone to consider, which falling upon the pigmentum are there disposed of according to the reflecting powers of that sub- stance. If the pigmentum is black the rays will then be absorbed, and entirely lost, therefore in such eyes vision can receive no assistance from it, and consequently a considerable quantity of light is required to produce distinct vision ; but in those who have some part of this pigmentum white, we find that the rays of light which pass through the retina are reflected back again; and in this case it is not unnatural to suppose that the reflected rays, in their passage back, will strike against the retina, and increase the power of vision. It is evident that a considerable portion passes forwards through the retina, which, I suspect, is partly lost on the inner surface of the lateral and forepart of the eye, where the pigmentum is black, while the remainder passing through the pupil is again thrown on the object looked at. The next thing to be considered is, whether the shape of the eye is such as will throw the rays, which passed through the retina, back upon that membrane, in the same or nearly in the same place as that through which they originally came. The eye being a sphere, or approaching to that figure, makes it probable; but whether the curve is such as will reflect the rays exactly in the same direction is not so easily determined. If the curve be a true one, then the rays that are not obstructed in their return by the retina must pass forwards through the pupil, and, being refracted in their passage through the crystalline humour, will be sent out of the eye in the same lines in which they entered, and be thrown on the very object from whence they came; which seems to be in a great measure the case, if we may judge by the degree of illumination in the cat's eyes. If the rays reflected from the light part of the pigmentum should not, in their return, strike exactly on the same points in the retina, through which they first passed, yet if they are thrown nearly on the same place it will be sufficient, for we know that our sensations are not capable of conveying to the mind mathematical exactness. And the same circumstance will be a sufficient answer, should it be objected that the time lost in the passing and repassing of the rays may prevent distinct vision; for it is known that if an illumined body is made to move quickly in a circle, it will appear to the eye a circle of fire. 28. SOME FACTS RELATIVE TO THE LATE MR. JOHN HUNTER'S PREPARATION FOR THE CROONIAN LECTURE. BY EVERARD HOME, ESQ., F. R. S. [Read November 14,1793.] Mr. Hunter having announced to the Royal Society that he would make the structure of the crystalline humour of the eye the PREPARATION FOR THE CROONIAN LECTURE. 293 subject of the Croonian lecture for the present year, and having, un- fortunately for science, died before his observations on that subject were rendered complete, I feel it a duty I owe to his memory as well as to the Society, to state the facts respecting this humour with which he had acquainted me; and shall subjoin an unfinished letter from Mr. Hunter to Sir Joseph Banks on the same subject. It is now many years that Mr. Hunter has had an idea that the crystalline humour was enabled by its own internal actions to adjust itself, so as to adapt the eye to different distances; and when the Taenia hydatigend* first came under his observation as a living ani- mal, he was surprised to see the quantity of contraction that took place in a membrane devoid of muscular fibres, but made use of the facts in his investigation of the structure of the crystalline hu- mour of the eye. Some time after this, having occasion to dissect the eye of the cuttle-fish, which he had frequently done before, but not with exact- ly the same view, he discovered in the crystalline humour a struc- ture which corresponded with the idea he had formed of its actions in the human eye. He found it composed of laminae, whose ap- pearance was evidently fibrous for some depth from the external surface; but becoming less and less distinct, till at last this fibrous appearance was entirely lost, and the middle, or central part of the humour, was compact and transparent, without any visible laminae. From this structure it would appear that in the eye of the cuttle-fish the exterior parts of the humour are fibrous, the interior parts not; so that the central parts is a nucleus round which the fibrous cover- ings are placed. The preparations which demonstrate these facts will be laid before the Society.f As the structure of the crystalline humour in the cuttle-fish dif- fers in nothing from that of the same humour in other animals but in the distinctness of the fibrous appearance, Mr. Hunter was led to consider that the exterior part in all of them was similar, although no appearance of fibres could be demonstrated. What I have here explained I was acquainted with at the time I had the honour of giving the Croonian lecture, in which I ex- amined the different structures endowed with muscular action, and was desirous that Mr. Hunter would, either of himself or through me, communicate these observations to the Society; but this he declined doing till he had ascertained by experiment whether any muscular effect was really produced ; and the hope of being assisted by Mr. Ramsden made him, from time to time, put off making his experiments. In the course of this season he began his experiments, which were founded upon the analogy that ought to exist between this * [The hydatid commonly found in the abdominal cavity of the sheep,—Cysii- cercus tenuicollis, Rudolphi.] (■ [The Hunterian preparations demonstrating the peculiarities of the eye of the cuttle-fish are not fewer than twenty. See Physiological Catalogue, vol. iii., p. 140.]. 26* 294 HUNTER ON THE ANIMAL CECONOMY. humour, if muscular, and others of a similar structure, which led him to expect that they would be acted upon by the same stimuli: and having found that a certain degree of heat, applied through the medium of water, will excite muscular action after almost every other stimulus had failed, it was proposed to apply this to the crystalline humour, and ascertain its effects. The crystalline humour taken from animals recently killed must be considered as being still alive. Such humours were to be im- mersed in water of different temperatures, and placed in such a manner as to form the image of a lucid, well-defined object, by a proper apparatus for that purpose, so that any change of the place of that image from the stimulating effects of the warm water upon the humour would be readily ascertained. These were the experi- ments which Mr. Hunter had instituted and begun; but in which he had not made sufficient progress to enable him to draw any con- clusions. To Sir Joseph Banks, from Mr. Hunter. " Sir, " When I did myself the honour of giving in my claim to the dis- covery of the crystalline humour being muscular, and proposed to make it the subject of the Croonian lecture, I did not foresee that anything could prevent me from fulfilling my promise; but since that time, what with my state of health, which does not allow me to be very active, the hurry of official business on .account of the war, and my brother-in-law, Mr. Home, being employed on the medical staff", I have not had the power of repeating my experi- ments, and drawing out, to my satisfaction, the many conclusions which are the result of such a power in this humour. " The laws of optics are so well understood, and the knowledge of the eye, when considered as an optical instrument, has been rendered so perfect, that I do not consider myself capable of making any addition to it: but still there is a power in the eye by which it can adapt itself to different distances far too extensive for the simple mechanism of the parts to effect. This power writers upon this subject have been at great pains to investigate and explain. The motion of the crystalline humour forwards and backwards was asserted by some to be the cause, while others supposed in the eye a power to alter its shape, so as to shorten or lengthen its axis, which altered the distance between the crystalline humour and the point of impression ; but we should consider that a part of the eye is itself a refractor, and that if its shape be altered so as to remove the crystalline humour from the point of impression, in order to enable it to bring a distant object to its proper focus on the retina, this effect will be in some degree counteracted by the anterior part of the eye refracting more than before, by being rendered more convex. But we have, in fact, no power capable of producing this effect: for the straight muscles, so far from appearing to have this PREPARATION FOR THE CROONIAN LECTURE. 295 power, have been even supposed to flatten the eye, and shorten its axis; and it is very possible that the action of these muscles is such as tends to both effects; but, being in opposition to each other, the eye retains its shape, the insertion of these muscles being much more forwards than appears to be necessary for the simple motions of the eye. Further, when we consider that in many animals the shape of the eye is unalterable, as in all of the whale tribe, the sclerotic coat being above half an inch thick and composed of a strong tendinous substance ;—that in many fish this coat is com- posed of cartilage ; and in all birds the anterior part of it is (I be- lieve) composed of bone ;—from all these considerations, I saw no power that could adapt the eye to the various distances of which we find it capable in the human body, unless we suppose the crys- talline humour to be varied in figure, which can only be effected by a muscular action within itself. With this idea strongly im- pressed upon my mind, and finding that in many animals, when the crystalline humour was coagulated, it had a fibrous structure like muscles, I confess it seemed to me to confirm it; but as this might to others appear only conjecture, requiring some proof, I set about such experiments as were best adapted for that purpose. Knowing that in all violent deaths the muscles contract, I supposed the crys- talline humour, if muscular, would show signs of this effect; for which purpose I got the eyes of bullocks when removed from the sockets, the moment the animal was knocked down, and while he eyes were warm the humours were removed." Mr. Hunter had proceeded thus far in the account of his experi- ments, when he was suddenly, and very unexpectedly, carried off; and as he has left no notes upon this subject, I am unable to make any addition to the account I have already given. Mr. Hunter's laying claim to the discovery of a fibrous structure in the crystalline humour, which had been observed long before, and described by the accurate Leuwenhoek, may appear to require some explanation. The discovery of a fibrous appearance in that humour appertains to Leuwenhoek; but the discovery of an eye in which this structure of the crystalline humour was perfectly dis- tinct, and in which all the circumstances of course and situation could be determined, is due to Mr. Hunter:* and if it should be * [In this investigation by Hunter of the intimate structure of the crystalline lens we may perceive the continuation of the series of discoveries which, com- menced by Leuwenhoek, have, in the hands of Sir David Brewster, produced such unexpected results, and opened so interesting a field for philosophical ex- periment and teleological speculation with regard to this part of the mechanism of the instrument of vision. Notwithstanding the anatomical remarks of Hunter, the observation of Professor Blair (Edinburgh Transactions, vol. iii.), and the experiments of Young, Wol- laston, Wells, and Frauenhofer, we still find, even in very recent physiological works, a mere repetition of the simple statement of Paley that the lens consists of concentric layers, which gradually increase in density from the circumference to the centre; and, under the influence of an apt comparison, the principle of the construction of the lens is asserted to be the same as that of the compound or achromatic object-glass, and the invention of Dollond to be a repetition, though 296 HUNTER ON THE ANIMAL CECONOMY. lound, by future observation and experiments, that this structure, which is different from any that has hitherto been described, is ca- an imperfect one, of this the natural type and perfection of a dioptric instrument which is supposed to converge the rays of light into a focus without any dispersion of the rays, and consequently without the production of false colours round the image. Now the fact is that the image given by the eye is not perfect with regard to colours in its ordinary exercise : there is not only dispersion of the raya of light, but the quantity of dispersion has been measured, and the different focal lengths of the eye for red and violet lights have been accurately determined by Young and Frauenhofer; the latter philosopher, indeed, has found it necessary to correct the dispersion of the eye in the construction of his achromatic object- glasses. But to return to the structure of the crystalline lens,—this complex and beautiful part consists, according to Sir David Brewster, of innumerable fibres of nearly the same length, each of which tapers from its middle part to its two extremities, like the gores or gussets of a globe. In the lenses of some animals the extremities of all the fibres terminate in two opposite poles ; in others, in a line at each pole, the line at the posterior pole being at right angles to the line at the anterior pole, and all the fibres except a few being bent into the most beautiful curves of contrary flexure. In some lenses the fibres terminate in the lines of a rectangular cross at each pole, the line of the cross at one pole being inclined 45° to the lines at the other pole ; in others, the terminations of the fibres form more complicated figures. In the largest number of animals the arrange- ment of the fibres is the same at both poles; but in a few, such as the turtle, the fibres terminate in a different manner in the two surfaces of the lens. But the structure of each of the fibres is still more wonderful than their arrangement. The sides of each fibre are formed with teeth, like those of a watch-wheel, and the teeth of one fibre lock into those of the adjacent ones, apparently to strengthen them and give body to the frail morsel of transparent jelly into which they are so marvellously moulded. In the lens of a cod-fish, four-tenths of an inch in diameter, Sir D. Brewster calculates the number of fibres to be about five millions, and the number of teeth by which the fibres are bound together to be sixty-two thousand Jive hundred millions ,• and as every tooth has three surfaces, the number of touching surfaces will be one hundred and eighty-seven thousand Jive hundred millions ,■ and yet this little sphere of tender jelly is as transparent as a drop of the purest water, and allowa a beam of light to pass across these almost innumerable joints without obstruct- ing or reflecting a single ray ! With respect to the muscular theory of the lens, and its supposed power of adjusting the eye to vision at different distances, by an alteration of its own form or dimensions, ii is hardly necessary to state that these views have derived no support since the time of Hunter, and of Dr. Young, who also entertained the theory of the irritability of the crystalline fibres. It has, on the other hand, been shown, in the well-attested case of Henry Miles,* that the eye may retain its power of adjustment after the removal of the lens. The supposed function of the lens, as an achromatic instrument, has been de- duced from the structure which it presents in the human body, where the density of the fibrous layers diminishes from the centre to the surface : a structure of which the purpose is undoubtedly to correct spherical aberration: but the lenses of quadrupeds display three different structures of varying density, separated by neutral lines, in which lines a density decreasing outwards passes into a density increasing outwards. This structure is well displayed in the lens of the horse; and when the animal has attained a great age the densities of the central and superficial structures have become uniform throughout, while the middle one exhibits a varying density more strongly marked than in the young lens, and exhibiting by polarized light a brilliant yellow colour, like the most perfect films of regularly crystallized bodies. That these structures are intended to correct a See the Croonian Lecture, Phil. Trans., 1802, vol, xcii., p. 8» OF THE ORGAN OF HEARING IN FISHES. 297 pable of producing consequent actions and effects, sufficient to ex- plain the adjustment of the eye to different distances, it will not be considered as a small or unimportant discovery. The melancholy event which has deprived this learned Society of so valuable a member, and which has taken from me so able an instructor, so rare an example, and so inestimable a friend, is too recent to make any apology necessary for the shortness or incor- rectness of this account. I thought it due to the memory of my friend that no promise of his, however inadequate I feel myself to performance, should be left unfulfilled; and the circumstances of distress under which it has been drawn up will procure for me every indulgence from this learned Society. Everard Home. Leicester Square, Nov. 4, 1793. 29. AN ACCOUNT OF THE ORGAN OF HEARING IN FISHES.* Natural history, having ever been considered as worthy the attention of the curious philosopher, has in all ages kept pace with the other branches of knowledge; and as both arts and sciences have of late years been cultivated to a degree perhaps beyond spherical aberration or to improve vision cannot be doubted; but the principles are yet to be discovered on which that correction or improvement depends. Meanwhile it is the duty of the physiologist to set plainly before himself, and to offer fairly to his pupils these unexplained or residual phenomena of the theory of vision ; not to hide them beneath an easily comprehended but insufficient illustration. An achromatic lens, though highly desirable, indeed essential to the construction of a good telescope or microscope, is not therefore necessary in the eye : it is well known to be less adapted for the purposes of a camera obscura than a common lens; but the organ of vision has a much closer analogy to a camera obscura than to a telescope. In a telescope, if there be colour, or disper- sion of the object-glass, this must be greatly magnified by the eye-piece; and, what is still more essential, there is an eye behind the instrument which takes cognizance of those imperfections, and for whose sake they are endeavoured to be remedied. But there is no eye behind the retina to view in the same manner the image which is thrown upon that membrane. It is well-known that the retina is incapable of transmitting a distinct idea of any spectrum depicted upon it save of that which is situated in or near its axis; the colours of the lateral pencils cannot be seen, and hence it is of no importance whatever to render the image achromatic at a distance from the axis. When we wish to examine an ob- ject, or a part of an object, with minute attention, we direct to it the axis of the eye; and in order to obtain a sensible colourless vision in or near the axis achromatic compensation is not necessary. It is no doubt true that even in this axis there is a non-coincidence of the foci of the differently-coloured rays ; but owing to the shortness of the focal distance of the eye, and the low dispersive power of the humours, this non-coincidence of the different foci does no injury to our ordinary vision.] * [Originally communicated to the Royal Society, and printed in the Philoso- phical Transactions (vol. Ixxii., p. 379) for the year 1782.] 298 HUNTER ON THE ANIMAL CECONOMY. what was ever known before, we find that natural history has not been neglected. All the nations of Europe appear solicitous to encourage the study; and in this island it has been pursued with more philosophic ardour than was ever known in any country. It has become an object of pursuit to men possessed of affluent for- tune; which they have not only dedicated to the cultivation of this science, but have even risked their health and lives in exploring unknown regions to increase the sources of information, and in settling correspondences everywhere, so as to bring materials into this country that might render it the school of natural history. It is no wonder then that a spirit of inquiry is diffused through almost all ranks of men; and that those who cannot pursue it themselves, yet choosing at least to benefit by the industry of others, are eager to be informed of what is already known. These reflections have induced me to publish this short account of the organ of hearing in fishes; for, although the existence of such an organ is now known to many, it is still a subject of dispute with others whether they possess the sense or not.* Some time before I quitted my anatomical pursuits, in the year 1760,f and went with the army to Belleisle, I had discovered this * [Cuvier justly states that the structure of the organ of hearing was better known to some of the ancient anatomists in the class of fishes than even in the human subject. Casserius has given moderately good figures of the semi-circu- lar canals and the ossiculum auditus of the pike in his work entitled Pentestesion (p. 224), published in the year 1600. Steno, in the Acta Medica of Copenhagen for 1673, described the internal ear or the Squalus Mustelus, Linn., with tolera- ble exactness, although without figures. Klein, in his Missus Historise Piscium permovendae, printed in the year 1740, gives a detailed description and accurate figures of the ossicula of the ear of the pike, salmon, trout, umber, marene (Sulmo Maraena, L.), herring, cod, dorsch (Gudus callarius, L.), ling, pike-perch, perch, gremille, stickleback, turbot, sole, barbue {Pleuronectes Rhombus, L.), carp, barbel, and many other species of Cyprinus. In 1753, Etienne-Louis Geoffroy, a physician of Paris, presented to the Academy a memoir exprofesso on the organ of hearing in fishes; but this was not printed till the year 1778. He has described generally the ear of the eel, the cod, the pike, the carp, the gardon, (Cyprinus idus, Bio.), the flounder, and the perch ; but he errs in ascribing to certain holes in the cranium the office of a meatus auditorius externus, which they do not fulfil. The figures annexed to this memoir, Cuvier informs us, were mislaid and lost, and therefore they did not appear in the printed essay. The description of the ear of the rav was given by Geoffroy in a Memoir on the Ears of Reptiles, presented in 1752, and printed in 1755.] t [Camper's researches on this subject were made in the year 1761: they appeared first in the Haerlem Memoirs for 1762. He afterwards sent a more detailed memoir on the same subject to the Academy of Sciences of Pari9 in 1767, which was printed in the 4 liecueil des Savans Etrangers, t. vii.,' in 1774. He describes in detail the organ of hearing of the ray, the cod, the pike, and the lophius, with figures in his style, i. e., somewhat vague. He added but little to that which Geoffroy had advanced, except that he denied too generally the exter- nal canal, and that he speaks of an organ which he terms tensor bursx, which seems only to be an appendage, or rather a ligament, more distinct in the pike than in most other fishes. In the year 1773, in the 17th vol. of the Novi Commentarii of St. Petersburgh, OF THE ORGAN OF HEARING IN FISHES. 299 organ in fishes, and had the parts exposed and preserved in spirits. In some the canals were filled with coloured injection, which showed them to great advantage, and in others were so prepared as to fit them to be kept as dried preparations.* My researches, in that and in every other part of the animal ceconomy, have been continued ever since that time. I am still inclined to consider whatever is uncommon in the structure of this organ in fishes as only a link in the chain of varieties displayed in its formation in different animals, descending from the most perfect to the most imperfect, in a regular progression.! As in this age of investigation a hint that such an organ existed would be sufficient to excite a spirit of conjecture or inquiry, I was aware that there would not be wanting some men who, whether they only imagined the fact might be true, or really found it to be so, would be very ready to assume all the merit of the discovery to themselves. My attention was more strongly called to this point by hearing, in conversation, that some anatomists in France, Germany, and Italy, had discovered the organ of hearing in fishes, and intended to publish on the subject. I therefore thought that it would be only justice to myself to deliver to the Royal Society a short account of that organ, a discovery of which I had made more than twenty years before. This account I shall reprint here, without adding anything to what I had before written, reserving a more complete examination of this subject for a larger work, on the structure of animals, which I one day hope to have it in my power to publish. I do not intend to give a full account of this organ in any one fish, or of the varieties in different fishes, but only of the organ in general; those therefore who may wish to pursue this branch of the animal oeconomy will think it deficient perhaps in the descrip- Kolreuter gave some very precise and detailed descriptions and figures of the ear, in two species of sturgeon, the common one (Acipenser Sturio, Linn.), and the huso {Acipenser Huso, Linn.). Monro described, better than any of his predecessors or successors, the external ear of the Chondropterygii, in his Anatomy of Fishes, published in 1785. Scarpa denies the external communication in the ray, which Hunter correctly describes in the present memoir.] *I have injected these parts in other animals, both with wax and metals; which, the bone being afterwards corroded in spirit of sea-salt, make elegant casts of these canals. | The preparations to illustrate these facts* have been, ever since, shown in my collection, to both the curious of this country and foreigners. In showing whatever was new, or supposed to be new, the ears of fishes were always con- sidered by me as one important article.** » [He here alludes to the series of other organs in his collection analogous to those of the ear; and it is interesting to observe these incidental evidences of the philosophical tendency in Hunter to view the varieties of structure, which his numerous dissections displayed to him, as modifications of one type, or a graduated and connected chain of varieties.] b [See the Preparations in the Gallery of the Hunterian Museum, numbered from 1560 to 1574 inclusive.] 300 HUNTER ON THE ANIMAL CECONOMY. tive parts. If it was a difficult task to expose this organ in fishes I should perhaps be led to be more full in my description of it, but in fact there is nothing more easy. It may be proper just to observe here, that the class called Sepia has the organ of hearing, though somewhat differently constructed from what it is in fishes.* The organ of hearing in fishes is placed at the sides of the cavity which contains the brain, but the skull makes no part of it, as it does in the quadruped and the bird, the organ being a distinct and detached part. In some fishes, as in those of the ray kind, the organ is wholly surrounded by the parts composing the cavity of the skull; in others it is in part within the skull, or cavity which contains the brain, as in the salmon, cod, &c, the skull projecting laterally, and forming a cavity. The organ of hearing in fishes appears to increase in dimensions with the animal, and nearly in the same proportion, which is not the case with the quadruped, &c, the organs being in them nearly as large in the growing foetus as in the adult. Neither is its structure, by any degree, so complicated in fishes as in all those orders of animals which maybe reckoned superior, such as quadrupeds, birds, and amphibious animals; but there is a regular gradation from the first of these to fishes. It varies in different genera of fishes; but in all it consists of three curved tubes, which unite one with another ; this union forms in some only one canal, as in the cod, salmon, ling, &c, and in others a tolerably large cavity, as in the ray kind. In the jackf there is an oblong bag, or blind process, which is an addition to these canals, and communicates with them at their union. In the cod, &c, this union of the three tubes stands upon an ,oval cavity ; and in the jack there are two ; the additional cavities in these fishes appearing to answer the same purpose with the cavity J observed in the ray or cartilaginous fishes, which is at the union of the three canals. The whole organ is composed of a kind of cartilaginous substance, very hard or firm in some parts, and in some fishes crusted over with a thin bony lamella, to prevent it from collapsing; for as the skull does not form any part of these canals or cavities, they must be composed of a substance capable of keeping its form. * [This is the first announcement of the existence of an organ of hearing in the Cephalopoda. It differs from that of fishes in the absence of the semicircular canals, and exhibits a simpler stage of structure, consisting of a vestibule, with the nerve, fluid, sacculus, and ear-stone or otolithe. The low-organized Cyclos- tomous fishes manifest their character as transitional links between the inverte- brate animals in several partsof their structure, but more especially in the organ of hearing. The myxinehas a vestibule, with one canal extended from it. The lamprey shows a further stage of complication, in having two canals continued from the vestibule. All the osseous fishes have three semicircular canals, a9 described in the text; and the plagiostomous cartilaginous fishes, as the shark9 and rays, exhibit a higher type of structure, in having the internal ear inclosed within the parietes of the cranial cavity, and in the external communication or meatus which some of the species present.] f [Esox Lucius, L.] X {Sacculus veslibuli.] OF THE ORGAN OF HEARING IN FISHES. 301 Each tube describes more than a semicircle, resembling, in some sort, what we find in most other animals, but differing in the parts being distinct from the skull.* Two of the semicircular canals arc similar to one another, may be called a pair, and are placed perpendicularly; the third is not so long, and in some is placed horizontally, uniting as it were the other two at their ends or terminations. In the skate this is some- what different, the horizontal canal being united only to one of the perpendicular canals. The two semicircular canals, whose position is perpendicular, are united, forming one canal; at their other ex- tremities they have no connection with each other, but join the ho- rizontal one, near its entrance into the common cavity. Near the union of these canals they are swelled out into round bags * (ampullae),' and become much larger. In the ray kind all these canals terminate in one cavity, and in the cod in one canal, placed upon the additional cavity or cavities, in which there is a bone or bones. In some there are two bones ; and in the jack, which has two cavities, we find in one of them, (the accessory sacculus of the vestibule,)' two bones, and in the other • (the ordinary sacculus of the vestibule,)' one ; in the ray there is only a chalky substance.f In some fishes the external communication, or meatus, enters at the union of the two perpendicular canals, which is the case with all the ray kind, the external orifice being small, and placed on the upper flat surface of the head ; but it is not every genus or species of fishes that have the external opening.J The nerves of the ear pass outwards from the brain, and appear to terminate at once on the external surface of the enlarged part of the semicircular tubes above described.§ They do not appear to pass through these tubes so as to get on the inside, as is supposed to be the case in quadrupeds; I should therefore very much suspect * The turtle and the crocodile have a structure somewhat similar to this; and the intention is the same, for their skulls make no part of the organ. f This chalky substance is also found in the ears of amphibious animals.a X [Hunter had a drawing made of these orifices in the monk-fish (Squatina Angelus, Dum.), which has been engraved and published in the third volume of the Physiological Catalogue of the Hunterian Museum, pi. xxxiii. fig. 1, a.] § [The acoustic nerve comes off from the brain, nearly opposite the junction of the sacculus with the vestibule; it sends off from its upper part a filament to each of the semicircular canals: this filament penetrates the ampulla of the canal to which it appertains, and is there lost. Another division of the nerve goes to the vestibule, out by far the greatest part of it spreads out into a number of filaments which form a very beautiful apparatus, under the parietes of the sac which con- tains the large stone.] a [In these it is lodged in a small blind sac, communicating with the vestibule, and representing the cochlea in a rudimental state. In the ray also, the vestibule, after receiving the orifices of the semicircular canals, opens into a large oval sac, which gives off two appendages, one anterior, the other posterior; this sac is analogous to the rudimental cochlea in reptiles, as is also the sacculus vestibuli in the osseous fishes.] 27 302 HUNTER ON THE ANIMAL CECONOMY. that the lining of the tubes in the quadruped is not nerve, but a kind of internal periosteum. As it is evident that fishes possess the organ of hearing, it becomes unnecessary to make or relate any experiment made with living fishes, which only tends to prove this fact; but I will mention one experiment, to show that sounds affect them much, and is one of their guards, as it is in other animals. In the year 1762, when I was in Portugal, I observed in a nobleman's garden, near Lisbon, a small fish-pond full of different kinds of fish. The bottom was level with the ground, the pond having been made by forming a bank all round, and had a shrubbery close to it. Whilst I lay on the bank observing the fish swimming about, I desired a gentleman who was with me to take a loaded gun and fire it from behind the shrubs. The reason for desiring him to go behind the shrubs was, that there might not be the least reflexion of light. The moment the report was made the fish seemed to be all of one mind, for they vanished instantaneously, raising a cloud of mud from the bottom. In about five minutes afterwards they began to appear, and were seen swimming about as before. Mons. Geoffroi, who has written on this organ, considers the ray as in the class of reptiles, and with that idea has examined their organ of hearing. He is by no means clear in his description, so that it is almost impossible to follow him ; yet it is but doing him justice to allow that he has discovered what is analogous to the three semicircular canals in other animals, together with their union into one cavity. He mentions the chalky substance contained in that cavity, and also the nerves; but it is by no means clear that he was acquainted with the external opening which leads to these canals. He says, " The entrance of the organ of hearing (by which one would suppose he means the meatus auditorius externus) is not easily discovered;" but that which he describes does not corres- pond with the real situation of the external communication; we may therefore reasonably conclude that he is describing something else. He is not more clear in his mode of reasoning on the appli- cation of the parts to produce the sense of hearing. He observes that the organ of hearing is very imperfect in this species of animals, but supposes this to be compensated by the medium in which they live, and by which sound is conveyed to them, being more dense than that of the air, by which sound is communicated to animals living on the land; and of this idea he is certainly the author. Mons. Geoffroi cannot indeed be said to have given a perfect account of the organ of hearing in fishes, yet on the whole he should be considered as a discoverer; for though he only made his obser- vations on the ray, as belonging to the class of reptiles, yet as it may be properly considered of the fish kind, he has a just claim to that credit. Had 1 formerly been acquainted with this author's researches and pretensions, I should not have claimed that to which I had not a prior right: nor should I have held the discovery of the external communication alone, an object of consequence enough to induce me to dispute the honour with Mons. Geoffroi. OF ABSORPTION BY VEINS. 303 In looking over the works of the different authors who have treated of the organ of hearing in fishes, I find from a passage in Willoughby,* who published prior to Mons. Geoffroi, and indeed is quoted by him, that my claim, even to the discovery of the external opening, is not so strong as I believed it to be, as he mentions an external orifice in the skate contiguous to what he supposes the organ of hearing in that fish. If what he alludes to is really the external opening of the ear, it gives him a prior claim to the disco- very of that part of the organ, although from his account, he does not seem to have been acquainted with the organ itself; for, as in describing the external ear of the thornback, he has evidently mis- taken the nose of it, of which he gives a tolerably full account, it is very obvious that he was ignorant of the opening into the ear.f Although Professor Camper published an account of the organ of hearing in fishes so late as 1774, he did not seem at that time to have been acquainted with the external opening of the ear in the ray. After giving a description of the organ of hearing in the pike, he makes some general observations on the similarity of this organ in other fishes, but excepts the shark and ray.J This exception we might suppose alluded to the auditory canal, but further on he explains what is meant by this exception, and does not mention the external opening in the ray, from which we may fairly conclude that he was not acquainted with it.§ 30. OF ABSORPTION BY VEINS.|| [Or. Hunter introduces the account of his brother's experiments on this subject as follows.] In both my courses of the winter 1759-60, I went so far as to say, I believed that the red veins did not absorb; and gave my rea- * Willughbeii Historia Piscium, Oxonii 1686, lib. iii. cap. viii. f Lib. iii. cap. xiv. X " 11 est tres-vraisemblable que toutes les autres especes de poissons, tant malacopterygii qu' acanlhopterygii, aussi-bien que les branchiostegi & les chon- droplerygii d'Artedi, a l'exceplion des squales & des raies, ont l'organe de l'ouie construit a peu pres de la meme fatjon ; je n'excepte pas l'esturgeon, quoiqueM. Klein, ibid, ait donne la description du conduit auditif, page 19, figure A, Tab. 2. b; ce poisson e"tant rare parmi nous, je n'ai eu occasion de l'examiner qu'une seule fois sans avoir trouve ce conduit." Memoirs Etrangers de l'Academie des Sciences, 1774, torn. 6, page 190. § " Au contraire, les chiens de mer, lesga/etsdeRondelet & les poissons qu'il a de'crits, lib. XII.; les squalis d'Artedi & les raies, ont bien l'organe a peu pres de la meme composition, mais il est enferme dans une caisse tout osseuse ou cartilagineuse, ce qui ne fait pas une difference essentielle; ils entendent done comme le eglefins, les morues, les baudroyes & les brochets, en un mot comme tous les autres poissons non amphibies: M. Geoffroi s'est trompe en comparant leurs organes avec celui de reptiles, tels que la vipere, les lezards, &c. qui enten- dent le son comme les quad rupedes, les oiseaux & les amphibies aquatiques, savoir par le moyen de Pair & d'un tambour, comme j'ai dessein de le prouver dans une autre occasion." Memoires Etrangers de l'Academie des Sciences, 1774,torn. 6, page 190. || [Medical Commentaries, Part I., p. 39.] 304 HUNTER ON THE ANIMAL CECONOMY. sons for thinking so; and in different parts of my lectures I used to treat of the transudation and absorption of fluids in animal bodies in the following manner: " I have often considered with myself how the interstitial fluid gets into the smaller and greater cavities of our bodies; how the water of an anasarca, for instance, gets into the cellular membrane. The common opinion, I think, is, that there are everywhere exhalant arteries, which open and terminate on the superficies of such cavi- ties, and throw out the watery fluid which they contain. But for my own part, I cannot help believing that it is entirely by transuda- tion through the coats or sides of the vessels. My reasons for thinking so are these : "First, so far as I can find, all the arguments of the latest and best anatomists, taken from injecting the arterial system in dead and living bodies, only prove that a thin fluid passes readily from the arteries into the interstices of parts. They do not prove the existence of exhaling branches more than they prove transudation. " In the second place, the phenomena of injections, so far as I have been able to make observations, agree better with the notion of transudation than with that of exhaling arteries. I have had great experience" of injections, and I have made experiments with all sorts of fluids injected into the arteries and veins of dead bodies. I have always observed that subtile and penetrating fluids pass with ease from the arteries into the cavity of the intestines, and into the cellular membrane in any part of the body: such fluids are water, gum-water, whites of eggs strained, glue, isinglass dissolved in water or spirits, any fluid oil, melted butter or axunge, &c. But when these fluids were coloured with vermilion I always observed that none of the vermilion passed out of the arterial system but when there were manifest appearances of extravasation and rupture of the vessels: I never observed vermilion pass into the cavity of an intestine from the mesenteric arteries, without seeing a hundred ruptures and extravasations in the villi of the gut. All this looks as if the fluid oozed through the coats rather than was poured out by the branches of arteries. " In the third place, I have observed that the cellular membrane is not so immediately filled by injecting the arteries ; it requires some time, and I have plainly seen, when I have let an injected part lie by a little while, that the cellular membrane became gradually more loaded as the arterial system became more empty: a strong argument, in my mind, that it got out of the arteries by transudation. " In the fourth place, water and even red blood soaks through all our vessels and membranes in dead bodies; as you may see by steeping the apex of a heart well washed, or the convolution of a piece of fresh intestine in clear water; in both cases the water will become bloody. " But still it is said that in all these cases the fluids pass by fine exhaling vessels, though these vessels cannot be seen. To this I answer that if our interstitial fluid was of a strong marked colour, OF ABSORPTION BY VEINS. 305 we should then by dissection be able to observe whether it was poured out by small arteries, or whether it soaked through the natural pores in the coats of vessels. Now, very fortunately for us in this dispute, there is one such fluid in the body : it is the bile. Its colour is pretty deep, and very different from anything that lies near the gall-bladder. No man can have opened any number of bodies without allowing that the gall does pass through all the coats of the gall-bladder, and pervades the substance of the neighbouring parts, not by exhaling nor by inhaling vessels, but by manifest tran- sudation or soaking. " It might be asked, why the red blood does not transude through the vessels in living bodies; for I think it certainly does not. In answer to this it may be said that our fibres and vessels have per- haps some degree of tension and firmness in life which they lose with life; and it must be observed too, that in proportion as the blood purifies it becomes thinner; whence we see, in opening a putrid body, all the cavities more or less filled with a bloody water, and all distinction of colour in the muscles and cellular membrane quite lost. But what I suppose to be the principal reason that red blood does not transude through the vessels in living bodies is its glutinous quality, its thickness while it is equally mixed up with its coagulating part. That part coagulates as certainly as the blood stagnates even in living bodies ; and when the universal stagnation happens in death, this part of the blood collects itself into irregular polypi and coagulations all over the body, and the rest of the blood is no longer the thick viscid fluid it was before, but rather a bloody serum, that will ooze through all the vessels and membranes." Such were my notions of the source of our interstitial fluid. With regard to its absorption, I was of opinion that Nature had provided a system on purpose, viz., the lymphatics. I considered these vessels and the lacteals as an appendage to the venal system, by which the stores were brought in for supplying the circulation; and the glands and secretory vessels all over the body I considered as an appendage to the arterial system, by which the proper sepa- rations were made, and the redundancies thrown off. My only doubt was whether the veins did or did not absorb a certain quantity, especially in the intestines. From my own obser- vations on injections I should have concluded that they did not, and that there was no passage for liquors between an intestine and the mesenteric veins otherwise than by transudation. But authors of the best credit had given such arguments and experi-( ments in favour of absorption by veins, that I dared not, even in my own mind, determine the question. At this time my brother was deeply engaged in physiological inquiries, in making experiments on living animals, and in prose- cuting comparative anatomy with great accuracy and application. It is well known that I speak of him with moderation when I say so. He took the subject of absorption into his consideration, and 27* 306 HUNTER ON THE ANIMAL CECONOMY. from all his observations was inclined to believe that in the human body there was one, and but one, system of vessels for absorption. He knew so well that many things had been asserted by one person after another which were not true, that so many mistakes had been made from inattention, so many errors introduced from other causes, that he could easily suppose the veins might not perhaps absorb, after all the demonstrations that had been given of the fact; and therefore was determined to see how far this point could be cleared up by plain experiments and observations. With that intention he made the following experiments, in my presence and in the presence of a number of gentleman, who all of us assisted him, and made our own observations upon what passed before us. I shall quote the experiments from him, and can bear testimony to the fairness with which they were made and with which they are here related. " Animal First.—Experiment I. On the 3d of November, 1758,"* says he, " I opened the belly of a living dog. The intestines rushed out immediately. I exposed them fully; and we observed the lacteals filled with a white liquor at the upper part of the gut and mesentery ; but in those which came from the ileon and colon the liquor was transparent. " I tied up the mesenteric artery and vein that was going to about half a foot of intestine, and put a tight ligature upon the upper part of the intestine, including a little of the mesentery; then emptied that part of the gut by squeezing it downwards, and put a similar ligature upon the lower part of the gut. In the next place, I made a small hole in the upper end of this part of the gut, and by a funnel poured in some warm milk, and confined it by making a third ligature upon the gut close to this hole. These ligatures prevented the circulation of blood in this part of the bowel. Lastly, I punc- tured the vein beyond the ligature that had been made upon the mesenteric vessels, and by gently stroking with the end of the finger soon emptied it of its blood. "Experiment II. I immediately after this made the same experi- ment, and in the same manner, on a part of the intestine lower down, where the lacteals were filled with a transparent liquor. " In the first experiment the lacteals continued to be filled with a milky or white fluid: in the second, the lacteals, which before contained only a transparent lymph, were presently filled with white milk. " In both these experiments we could not observe that the least white fluid had got into the veins. After attending to these appear- ances a little while, I put all the bowels into the abdomen for some time, that the natural absorption might be assisted by the natural warmth; then took out and examined attentively the two parts of the gut and mesentery upon which the experiments had been made: * In presence of Doctors Clayton, Fordyce, and Michaelson, and Messrs. Blount, Jones, Churchill, and Richardson. OF ABSORPTION BY VEINS. 307 but the lacteals were still filled with milk, and there was not the least appearance of a white fluid in the veins; on the contrary, what little blood was in them was just as thick and as deep-coloured as in the other veins, and when squeezed out from them coagulated as the blood of other veins. • ' , "Experiment III. I tied up and filled another piece of the intes- tine with milk in the same manner, but did not make a ligature upon the mesenteric vessels, leaving a free circulation in the part. We looked very attentively at the colour of the blood in the vein of that part, both with our naked eyes and with glasses: we compared it with that in the artery and in the neighbouring veins, but could not observe that it was lighter-coloured, nor that it was milky, nor that there was any difference whatever. Experiment IV. Lastly, we took that part of the gut which was filled with milk in the first or second experiment, and squeezed and pressed it very gradually, in order to see whether any milk would by these means pass into the empty mesenteric veins. This we did gradually, with more and more force, till the gut at last burst; but still there was not the least appearance of anything milky in the veins. "Animal Second.—Experiment I. November 13, 1758,* I opened the abdomen of a living sheep, which had eat nothing for some days, and upon exposing the intestines and mesentery we observed the lacteals were visible, but contained only a transparent watery fluid. I made a hole in the intestine near the stomach, and by a funnel poured in some thin starch, coloured with indigo, so as to fill several convolutions ; then tied up the whole in the gut, and put all the bowels into the abdomen for some time. Upon taking them out after this we observed all the lacteals of that part filled with a fluid of a fine blue colour.f We thought at first that the * In presence of Doctors Wren, Fordyce, and Michaelson, and Messrs. Blount, Tickell, Churchill, Paterson, and Skeette. | [Martin Lister, in 1682, injected twelve ounces of the tincture of indigo into the small intestines of a living and fasting dog. At the time of the experiment there " was not the least appearance of lacteal veins in the mesentery :" after full three hours the mesentery was examined, and many lacteals were found of an azure colour; and some of the biggest of them being cut, a thick bluish chyle was seen to issue forth. (Phil. Trans., vol. xiii., p. 9.) The conclusion which Lister drew from this experiment with reference to the power of the lacteals to absorb extraneous matters along with the chyle, was opposed in his time by some writers, and it was stated " that people may be deceived with blue tinctures, for this is the natural colour of these lacteals when they are almost or altogether empty." See Phil. Trans., No. 275, October, 1701, p. 996. In order to try the value of this objection, Dr. Wm. Musgrave instituted the following experiments: " Feb. 1682-3. I injected into the jejunum of a dog, that had for a day before but little meat, about twelve ounces of a solution of indigo in fountain water, and after three hours, opening the dog a second time, I observed several of the lacteals of a bluish colour, which, upon stretching of the mesentery, did several times disappear, but was most easily discerned when the mesentery lay loose; an argument that the bluish colour was not properly of the vessel, but of the liquor contained in it. 44 A few days after this, repeating the experiment in another company, with the 308 HUNTER ON THE ANIMAL CECONOMY. blood in the veins of this part was of a darker colour, but on com- paring it carefully with that in the other veins it was manifestly the same. " Experiment II. I opened a vein upon this part of the mesen- tery, and catched a table spoonful of its blood. I set it by to con- geal and separate into its coagulum and serum. On the next day and the day after that I examined the colour of the serum, but it had not the least bluish cast. " Experiment III. I fixed an injecting pipe in an artery of the mesentery, where the intestine was filled with the blue starch, and tied up all communications both in the mesentery and intestine (as in Animal First, Exper. I.), but left the corresponding vein free; then I injected warm milk by the artery till it returned by the vein, and continued doing so till all the blood was washed away, and the vein returned a bright white milk. This was done with a viewr of seeing if the milk in the vein acquired any bluish cast, but there was no perceptible difference between the arterial and venal milk. " Experiment IV. After this I opened the vein with a lancet, and discharged most of the milk, then put a ligature upon both the artery and vein, and waited some time to see if they would fill, but they did not, nor did the remaining contents of the vein acquire the least bluish cast. Then I opened the gut at this part, but we solution of stone-blue in fountain water, and on a dog that had been kept fasting thirty-six hours, I saw several of the lacteals become of zperfect blue colour within very few minutes after the injection : for they appeared so before I could sew up the gut. At about the beginning of March following, having kept a spaniel fasting thirty-six hours, and then syringing a pint of a deep decoction of stone-blue with common water into one of the small guts, and after three hours opening the dog again, I saw many of the laeteals of a deep blue cofour. Several of them were cut, and afforded a blue liquor (some of the decoction), running forth on the mesentery. "After this I examined the ductus thoracicus (on which, together with other vessels near it, I had upon my return made a ligature), and saw the receptaculum chyli and that ductus of a bluish colour, not so blue indeed as the lacteals, from the solution mixing in and near the receptaculum with lympha, but much bluer than the ductus uses to be, or than the lymphatics under the liver (with which I compared it) were. I trusted not my own eyes in any one of these experiments, but in each of them had the company and assistance of several physicians, who all agreed with me as to the colouring of the lacteals." (Phil. Trans., No. 275, October, 1701.) The same objection, the force of which was invalidated by the experiments of Musgrave, has been in recent times urged against the experiments of Hunter, related in the text; but it is obvious that it cannot apply where care is taken to observe the colour or appearance of the empty or transparent lacteals before throw- ing the coloured fluid into the intestine, and to contrast that appearance of the lacteals with the colour which they present after the experiment has been per- formed. Now this precaution Hunter invariably adopted. With reference to the experiments on the lacteals recorded in the early numbers of the Philosophical Transactions, it may be observed that they differ from those of Hunter in the absence of observations and modifications which the latter physiologist combined with them, in order to test the share which the veins might take in the absorbing processes;—a question which does not appear to have occupied the attention of either Lister or Musgrave.] OF ABSORPTION BY VEINS. 309 could not observe any appearance of the milk having got into the cavity of the intestine. " Experiment V. I filled another part of the intestine with milk. All that we observed after doing this was, that the lacteals became fuller, though not of a white colour, and the veins remained of the same complexion. "Experiment VI. I fixed a pipe into the vein of the mesentery, and injected milk towards the intestine, to see if any would pass into the cavity of the gut; but presently innumerable extravasations happened, so that the experiment was'fruitless. tl Experiment VII. I fixed a pipe into an artery, and tied up the vein and all the communications; then injected milk for some time into the artery till the vein became quite turgid and tight; this was continued for some little time, and with as much force as we thought the vessels would bear without bursting; then we opened the intestine at that part, and there was no appearance of milk in its cavity. " Experiment VIII. I took a piece of the intestine that was quite empty and clean, and filled it with warm water. The returning blood in the vein of this part appeared not at all diluted or thinner than in the other veins. Then I tied up the artery and all the com- munications, and attended to the state of the vein for some time; it did not grow more turgid, nor did its blood become more watery, nor was there any appearance whatever of the water's having got into the veins. "The animal was quite alive all the time of our making these experimenls and observations, which lasted from one o'clock till half an hour after three. I chose a sheep rather than a dog, both because the animal was much larger, and therefore its mesenteric vessels were fitter for being easily injected, and besides, because it is much more patient and quiet. These advantages we were all sensible of when we made the experiments. " Animal Third.—June 22d, 1759. We repeated most of these experiments on another sheep, to see if the effect would be the same, but in this animal the viscera were diseased, inflamed, and thickened in most parts, so that the experiments were much less successful, less satisfactory, and conclusive. After injecting milk into the mesenteric artery for some time, and allowing it to return by the vein, we opened that part of the intestine which had been previously emptied, and found in it a watery fluid of a whitish cast, as if a few drops of milk had been mixed with it. " Animal Fourth.—In July, 1759,* I repeated most of the experi- ments related in article Animal Second, upon another sheep. The effect of all of them was so nearly the same that I need not be particular. " I shall only observe, that when the intestine was filled with starch-water and indigo, and milk injected by the artery till the * In presence of Doctors Macaulay, Ramsey, and Michaelson, and Messrs. Edwards and Tomlinson. 310 HUNTER ON THE ANIMAL CECONOMY. vein was washed clean of blood, and a ligature put upon the artery and vein, so as to leave them about half full of pure white milk, after waiting more than half an hour we could not observe that the vein was in the least more filled or turgid, nor had the milk in the veins acquired the least of a bluish cast, not even in the small veins upon the gut itself, where we should suppose the absorbed liquor must have been apparent if any had been taken up by the veins from the cavity of the intestine. "After the animal w'as dead I blowed into a mesenteric vein, and the air found a passage into the cavity of the gut; though in making the experiment when the animal was alive, I could not force the milk by injection from the vein into the gut. " Animal Fifth.—If any animal could be supposed a fitter subject for such experiments than a sheep, it would be an ass. He is not so large nor so strong but that he may be managed; he is patient in the greatest degree ; his mesentery and vessels being larger, it is so much more easy to fix injecting pipes, make ligatures, &c.; and, what is a very great advantage in making such experiments, his mesentery is very thin, without fat, so that the vessels are conspicuous and distinct. Hence it is easy to separate the artery from the vein, to fix pipes, to tie up anastomosing vessels by a needle, &c. " Therefore I got an ass, and on the 24th of August, 1759,* put him upon his back in an open garden, and tied him fast to four stakes drove into the ground, then opened his abdomen, &c. " Experiment I. I poured a solution of musk in warm water into a piece of the intestine, and confined it there by two ligatures. In doing this the animal struggled, and a little of the liquor was spilt upon the outside of the intestine and mesentery. "After wailing a little while, I opened with a lancet some lac- teals of this part, which were full of a watery fluid, and catched a little of their contents in a small spoon. Tt smelled strongly of the musk, and though it could hardly be doubted that the musk had been taken up from the intestine by absorption, yet as some of the musk-solution had been spilt upon the external surface of the parts, and as it was impossible to collect the lymph from the lacteals without resting the edge of the spoon upon the mesentery, the smell of the spoon might be owing to that circumstance. " After this I wiped a vein upon the mesentery very clean, and opened it with a lancet: a gentleman who had kept out of the way of the musk came immediately with a clean spoon, and filled it from the stream of blood without touching any part of the animal, and carried it directly off, but it had not the least smell of musk. " Experiment II. We poured some starch-water, made very blue with indigo, into a part of the gut in the same manner as in some of the former experiments, tied the vein and artery of this part, then punctured the vein close to the ligature, and pressed out almost * In presence of Doctors Macaulay and Michaelson, and of Messrs. Edwards, White, and Gee. OF ABSORPTION BY VEINS. 311 all the blood; then tied up the empty vein, and put all into the cavity of the belly for a quarter of an hour. After that we examined the part, found the lymphatics very turgid, as the fluid could not pass through them towards the thoracic duct on account of the ligatures made upon the mesenteric vessels; but we found the veins of this part empty, except indeed that a little blood had got into them from the neighbouring vessels, which, from the appearance, had evi- dently passed the ligatures tied round the ends of the gut, a circum- stance which it is very difficult to obviate. " Experiment III. I next repeated the Third Experiment of Ani- mal Second exactly in the same manner, and precisely with the same effect. " Experiment IV. Then I repeated the Fourth Experiment of Animal Second, and the effect was still the same. " N. B. It may not be amiss to observe that the lacteals continued to absorb the bluish liquor all this time, even at the part upon which this Fourth Experiment was made, where the nerves must necessarily have been tied up with the artery. " Experiment V. I squeezed a piece of the intestine so as to empty it as entirely as well might be, then tied up all the lateral com- munications of the vessels, and injected warm milk into the mesen- teric vein till it returned by the artery, and continued this operation for some time after all the blood was washed out. Then I opened that part of the intestine through its whole length, and found it quite empty. " I made this experiment again upon another part of the intestine, in the same manner, and exactly with the same success." Here is a new doctrine proposed in physiology, viz., that the red veins do not absorb in the human body. The fair inquirer after truth will be convinced, by the observations which occurred to me, that the common opinion, that they do absorb, is supported by some proofs that are at least doubtful or equivocal, and that the other opinion is not without plausibility; and he must allow that my brother's experiments render it highly probable. [In attempting to form a correct estimate of the merits of Mr Hunter as a discoverer in reference to the absorbent system, it becomes necessary, in the first place, to distinguish between the discovery of the vessels themselves, whether lacteals or lymphatics, and that of their functions and anatomical relations to the other parts of the vascular system. With respect to the Mammalia, it is scarcely necessary to observe that the existence of both lacteals and lymphatics had been determined in that class long before the time of Dr. William Hunter. The discovery of the lacteals by Asellius was first made publicly known in 1628 ; and that of the thoracic duct by Pecquet in 1651. In 1652 our countryman Joliff, having placed a ligature round the spermatic cord, saw, upon squeezing the testicle, that certain vessels, which he termed 4 vasa lymphatica,' became turgid ; he did not, however, 312 HUNTER ON THE ANIMAL CECONOMY. himself publish this observation, and it might never have seen the light, had not, in the meanwhile, the attention of the anatomical world been drawn to the lymphatic vessels by Bartholinus, an illustrious philosopher of Denmark, in 1651, and by Rudbeck, a Swede, and professor at Upsal, in 1652. In 1668, M. Louis de Bills appears to have traced lymphatic vessels from the 'jugular glanduls' of a dog to the thoracic duct. See Phil. Trans., iii. (1668), p. 791. But the lymphatic absorbents had never been distinguished as a system, either anatomically or physiologically, from the capillary vessels. Noquez, who of all anatomists before the Hunters, had dwelt more par- ticularly on the lymphatics, and who was cited by some of the contem- poraries of the Hunters as having anticipated them in this department of their anatomical labours, divided the lymphatics into four classes: one of these corresponded with the capillary blood-vessels of modern physiolo- gists ; a second, with the serous exhalant arteries ; a third, to the veins corresponding with these arteries, and to which Noquez gave the name of ' conduits absorbents,' until they became large enough to be sensible to the naked eye, and began to receive red blood. His fourth class of lymphatics includes the absorbent vessels of the Hunters, and were described by Noquez as ending in the receptaculum chyli, the thoracic duct, the vena cava, and the vena portarum. It is therefore obvious that the Hunterian doctrine of the absorbent sys- tem was in no way anticipated by Noquez, who appears to have been a mere compiler, undistinguished by any original research, and whose anatomical treatise was professedly an improvement upon Kcill's. With respect to the extension of our knowledge of the condition of the lymphatic system in the human subject, it appears that Mr. Hunter greatly contributed to this important branch of anatomy. Dr. Hunter describes one of his preparations, which showed the lymphatic vessels extending from the ham upwards to the thoracic duct, as well as the inguinal and lumbar glands, and the larger lacteals at the root of the mesentery, the receptaculum chyli, or what is so called, all finely filled with mercury. He acknowledges his brother's discovery in 1753 or 1754, that the lym- phatic glands, and the lymphatic vessels going from them, could be filled uniformly by pushing a pipe into their substance : and states it to have been Mr. Hunter's intention to have traced the lymphatic vessels all over the body, and to have given a complete description and figure of the whole absorbing system. This work was unfortunately arrested by a very indifferent state of health, the effect of too much application to anatomy, which obliged Mr. Hunter to be much in the country. It was afterwards, as is well known, ably accomplished by another ornament of the Hun- terian school, the celebrated Cruikshank. When the question of the office of the lymphatics first began to be agitated, one of the arguments against their being the exclusive agents of the absorbing processes was founded on their supposed absence in the oviparous vertebrata.* The discovery of this system of vessels in birds * [" Lacteal vessels have not as yet been certainly observed in birds, or in the more common fishes, nor in general in the animals called oviparous; and, from a considerable number of experiments I have made, I am convinced they want the lymphatics as well as the lacteal vessels." Monro, Observations Anatomical and Physiological, 8vo. Edinb., p. 57, 1758. OF ABSORPTION BY VEINS. 313 formed, therefore, no unimportant support to the views of Dr. William Hunter, and to this discovery Mr. Hunter is justly entitled. Mr. Hewson, who first published on the lymphatics of birds, and who discovered their lacteal absorbents, acknowledges that " it is but doing justice to the inge- nious Mr. John Hunter to mention here that these lymphatics in the necks of fowls were first discovered by him many years ago." (Phil. Trans., 1768, p. 220.) And it appears from Dr. Monro's reply to Mr. Hewson, that this discovery of Mr. Hunter's had been communicated to Dr. Cullen by Dr. George Fordyce, and had materially influenced Dr. Monro's opinions respecting the absorbent system. Mr. Hewson also informs us, that prior to his own publication on the Absorbent System of Amphibia, Mr. Hunter had discovered and demon- strated to him the chyle, and we must suppose the lacteal vessels, of a crocodile. • With respect to the absorbent system in fish, the discovery of this must be awarded to Mr. Hewson. As early as 1701 experiments had been instituted with a view to dis- cover the function of the lacteal vessels, indicated of old by Erasistratus, and rediscovered by Asellius. Martin Lister and Musgrave satisfied them- selves that coloured matter was taken up by these vessels which they termed lacteal veins, from the intestine.* Nevertheless, until the obser- vations and experiments of the Hunters, the lymphatics generally were believed by Haller and other physiologists to be simply continuations of capillary or lymphatic arteries, and they were supposed to have no other function than to carryback into the circulation the serum or lymph of the blood. Dr. William Hunter having observed that he could not inject the lymphatics from the arteries excepting the injection were extravasated in the cellular substance, but that he could readily inject the lymphatics both from the common cellular substance and that which assists in form- ing the parenchyma of the glands, as the testis, spleen, &c.; observing also that the course of the venereal poison, when introduced into the system, indicated that it was carried along by the lymphatics, affecting the inguinal glands when applied to the glans penis or prepuce, and in like manner affecting the glands of the armpits when applied to the hands, and the cervical glands when communicated by the lips; perceiving also the close analogy of the lymphatics to the lacteal absorbents, in their valvular structure and mode of termination ; he concluded from all these circumstances that they had an analogous function ; that they were not reflected capillary arteries, but originated from all the interstices and cavi- ties of the body, forming the absorbing vessels of the general system, as the lacteals were allowed to be of the alimentary canal. This doctrine was supported by the experiments of John Hunter given in the text, which were first published in 1762, while he was abroad with the army at Belleisle, by his brother, Dr. William Hunter, in the Medical Commentaries. It would seem, however, that Mr. Hunter did not consider these alone as sufficiently conclusive to be submitted to the public, since he left them in manuscript with his brother, who made use of them, four years afterwards, in the controversial essay with the Monros, while John ♦ [See Experiments for transmitting Blue-coloured Liquor into the Lacteals. Mus- grave, Phil. Trans., vol. xii. p. 996. Experiments for altering the Colour of the Chyle in the Lacteal Veins, by M. Lister, Phil. Trans., vol. xiii., p. 6. Powdered Blues pass into Lacteal Veins, ibid., vol. xxii., p. 819.] 28 314 HUNTER ON THE ANIMAL CECONOMY. was abroad with the army at Belleisle. They were unaccompanied by any additional proof or observations, but were considered by Dr. William Hunter as being decisive in depriving the veins of the power of absorb- ing altogether. Mr. Hunter, however, continued these experiments in other classes, as is shown in the following manuscript note in the posses- sion of Mr. Clift. 4' The experiments upon the bird, to ascertain whether the mesenteric veins absorbed or not, were nearly the same with those made upon the ass, in 1758, with musk, as also with spirits of wine ; and although in those researches I did not discover the lacteals in the bird, yet I discovered that the red veins in the mesentery in them most proba- bly did not absorb, because I never could find any of the liquors which had been thrown into the gut mixed with the blood of the veins of the mesentery ; and which I look upon as one of the first steps towards proving another system."- Subsequent experiments, especially those of Tiedemann and Gmelin, Meyer and Segalos, have shown that a power of absorption can- not be denied to the veins ; yet the admission of this power, (which must be granted on anatomical grounds to the veins of all invertebrate animals, and to some parts, probably, of the vertebrate, as the eye and the brain,) does not invalidate or diminish the credit due to those experiments and enlarged conceptions of the uses and anatomical relations of the lymphatics, by which the true function of these vessels was ascertained. I say the true function ; for though it be admitted that the veins absorb, yet every physiologist,*—with the exception of one who has held the sympathetic nerve to be no nerve, and who, in the nineteenth century, denied that rep- tiles and fishes had lymphatic vessels,—allows that absorption, and the effecting a certain change in the nature of the absorbed liquors are the only functions which the lymphatic vessels perform. I would here for the present willingly leave the subject, but that I feel it incumbent upon me, in regard to the character of an author whose works have exercised so great and salutary an influence over the surgical profes- sion, to show that the charge of imperfection and negligence* which has been cast upon the Hunterian experiments,—whose want of exactness, according to M. Majendie, can only be excused by the rude state in which the art of physiological experiment was at the period when they were made,—rests entirely on the culpable oversight of the accuser.. In relating one of his experiments, Mr. Hunter states : 44 Nov. 13, 1758, I opened the abdomen of a living sheep, which had eaten nothing for some days ; and upon exposing the intestines and mesentery we ob- served the lacteals were visible, but contained only a transparent watery fluid." Is it conceivable that any succeeding physiologist would have ventured, in his commentary on Mr. Hunter's experiments, to object to them, " be- * [" L'etat d'imperfection ou etait Part des experiences physiologiques a l'e"poque ou J. Hunter a fait celle-ci peut seul excuser ce celebre anatomiste de n'avoir pas senti combien il y manque de circonstances importantes pour que Ton puisse, en la suppo- santexacte, en tirer quelques consequences. En effet, pour que cette experience put etre de quelque utilite il faudrait savoir si I'animal etait a jeun lorsqu'on l'a ouvert, ou s'il etait dans le travail de la digestion; il aurait fallut examiner l'etat des lymphatiques au commencement de l'experience ; etaient-ilsou n'etaient-ils pas pleins de chyle," &c. And again," Hunter fait une fausse theorie sur Tune de fonctions les plus importantes de la vie, il l'etaie a peine de quelques experiences inexactes, et dans tous les cas insuffisantes."—Precis Eiementaire de Physiologie, (3me ed.) torn. ii. pp. 199, 201.] OF ABSORPTION BY VEINS. 315 cause the experimenter had neglected to notice whether the animal experi- mented on was full or fasting; or whether the lacteals were or were not distended with chyle ?" To give a colour to this objection, all reference to the experiment above quoted is avoided in the ' Precis Elementaire ;' but even in the very ex- periment of which M. Majendie gives a mutilated version, Mr. Hunter expressly premises that, " having exposed the intestines fully, he observed the lacteals filled with a white liquor at the upper part of the gut and me- sentery ; but in those that came from the ileon and colon the liquor was transparent." In the herbivorous quadruped, the sheep, in which Mr. Hunter employed starch as the menstruum of the indigo, the transparent watery nature of the contents of the lacteals was especially noted before the colouring ma- terial was thrown into the intestines: they were afterwards observed to be filled with a fluid of a fine blue colour. And yet M. Majendie (ibid., p. 210) would have us believe that no alteration had been observed; that the lacteals were of the same blue colour before the injection of the indigo and starch had been performed as after. Whether, however, the coloured matter had passed into the lacteals or not, it could not, by the most careful and varied experiments, be detected in the veins. Great precaution was taken to ascertain that fact. Since the natural colour of the blood rendered it difficult to perceive a change of hue, the contents of the veins were collected and suffered to coagulate, in the expectation of the serum manifesting the presence of the indigo; but it had not the least bluish tint. Warm milk was then made to circulate from the artery into the vein; and it might surely have been expected, especially if the doctrine of non- vital imbibition advocated by M. Majendie were true, to have then had a trace of the coloured contents of the intestine in the venal milk; but no such result took place. The experiment upon the ass, in which the odour of musk was pre- sent in the chyle, but not in the venous blood, is not referred to by M. Majendie. . .. , In making these comments it is by no means intended to uphold the infallibility of Mr. Hunter; but it may be safely averred that a candid and careful perusal of his experiments on absorption, recorded in the text, will not only exonerate him from any charge of haste or negligence, but must impress the unprejudiced reader with the conviction that those expe- periments have rarely been equalled and never excelled, either in the in- genuity and foresight manifested in their contrivance, in the skill and pre- caution against error displayed during their performance, in the fairness of the conclusions deduced from them, or in the minute accuracy and candour which pervade their narration. To prove the absorbent power of the lymphatics, however, is one thin* • that the veins are thereby deprived of the power of absorbing altogether is another; and it is in reference to this latter question that the experiments of M. Flandrin, recorded by M. Majendie, become interesting to the physiologist. But we may observe, en passant, that if M. Majendie and his collaborateur failed to obtain the same results as Hunter from similar experiments, other and as able experimenters in recent times have been more successful. Schroeder von der kolk, for example, filled a loop of intestine in a living dog with a solution of the ferro-prussiate of 316 HUNTER ON THE ANIMAL CECONOMY. potass, and included the distended loop between two ligatures. He then placed the loop and its contents in a solution of sulphate of iron. The blue compound, which could be formed by no other means except by the union of the two chemical fluids, was manifested in the lacteals alone, and not in the veins. (Mailer's Physiologic p. 229.) Viridet and Mattei also found that the chyle derived from yolk of egg was yellow, while that from food mixed with madder was red. It is allowed indeed by all physiologists, and even by M. Majendie, that the lacteals absorb the chyle. But various experiments seem to show that other fluids, and especially those of a poisonous nature, are taken up from the intestines by the veins. Such was the general result of the numerous experiments of Tiedemann and Gmelin.* Those related by Majendie are not, however, free from objection. He opened the abdomen of a dog; a loop of intestine was included between two ligatures and separated from the rest of the canal, all other connection between the intestine and the rest of the body was destroyed except a single mesenteric artery and vein. Two ounces of the decoction of nux vomica were then injected into the detached portion of gut. In six minutes the effects of the poison manifested themselves with the ordinary intensity. Great precaution was taken to obviate the doubt which any lacteals remaining attached to the coats of the vessel mighthave occasioned; but as this objection might still be urged, the following more conclusive experiment was performed : a limb of a dog was amputated with the ex- ception of a single artery and vein, which alone kept up the communica- tion between the limb and the trunk; upas poison was then inserted into the foot (enfonees dans lapatte). Its effects became evident in less than four minutes ; in less than ten the animal was dead. To avoid the objec- tion of invisible lymphatics in the tissue of the vessels, a segment of both artery and vein was removed, after having substituted a portion of quill, so that there remained no other communication between the limb and the animal excepting by the blood which circulated from one to the other. The poison introduced into the foot (introduit dans lapatte) produced its effects in about four minutes. What makes it so evident, adds M. Majendie, that the crural vein was the sole medium of introduction to the poison is this; that simple compression of this vessel arrested the deadly effects of the upas, which again immediately manifested themselves on a remission of the pressure.* Now, although the objection of lymphatics in the coats of the vessels is obviated in this experiment, yet its conclusiveness may be questioned on this ground, that the poison is applied to a wound where it can enter the circulating fluids by open and divided veins ; but this is by no means the condition which is understood in the theory of venous absorption, which relates only to an action attributed to the veins in their natural state, and through the medium of their organic pores. If this objection be invalidated by the experiment in which the decoction of nux vomica was applied to an entire mucous surface, as when injected into the intestine, yet this may be accounted for by the paralyzing effects of the narcotic upon the animal tissues with which it comes in contact: it may be objected that their vitality is destroyed, that inorganic imbibition then takes place, and that * [Versuche Uber die Wege auf welchem Substanzen aus dem Magen und Darm Kanal ins Blut gelangen.] f [Loc. cit., p. 255, 256.] OF ABSORPTION BY VEINS. 317 the poison thus passes into the cavity of the vessels, and is carried along the returning currents to the heart. But objections from the permeability of the tissue of a paralyzed vein are endeavoured to be overcome by the assertion that all absorption is the effect of non-vital imbibition, that it is a property which the living animal tissues possess in common with inorganic substances. Thus M. Fodera having repeated the experiment of M. Majendie and Segalas, in which the solution of nux vomica was injected into the intes- tine, afterwards incloses the same poisonous solution in a dead portion of intestine, inserts this into a loop of the intestines of a living animal, and from the effect produced by the transudation of the poison through the parietes of the dead intestine, and through the paralyzed surface of that of the animal experimented upon, draws a sweeping conclusion as to the nature of absorption in general. M. Majendie also rejects the theory of the vital actions of the absorbents, and strongly condemns the supposition of a selecting power in absorbent pores as gratuitous and unphilosophical. He threw into the thorax of a dog a solution of nux vomica, and he found that in proportion as the ob- stacles to a free circulation were increased, by distending the blood-vessels with warm water, the effects of the poison on the system were retarded. This experiment is of the same species as that by M. Segalas, who limit- ed the field of observation by confining the poison within a loop of intes- tine, and interrupted the venous current altogether by a ligature ; it is consequently less conclusive, though liable to the same objections. When M. Majendie removed the obstacles which he had imposed on the circula- tion by opening a vein and relieving the distended vessels, the imbibed solution of nux vomica rapidly produced its effects. Thus the ordinary laws of the living tissue being suspended by the application of a narcotic or other poison to them, and mechanical imbibition being thereby per- mitted,—or when similar poisons are directly applied to divided vessels; —it may be concluded, from the experiments above quoted, that whatever arrests the return of the empoisoned blood to the heart, whether atmo- spheric pressure, produced by the action of an exhausted cupping-glass, or by the direct pressure or ligature of the vein, or a general impediment to the circulation by a plethoric or artificial distension of vessels, will proportionately retard the deadly operations of the poison. M. Majendie has also shown that the rapidity of its action is increased by artificially diminishing the quantity of circulating fluids, and this observation is of great value in a practical point of view; but much is still wanting to sus- tain his conclusion that the ordinary and natural absorbent processes are arrested by a plethoric or distended state of the vessels, and vice versa. The experiments by which M. Majendie endeavours to support the theory of non-vital imbibition or capillary attraction as the immediate cause of absorption are these:—A saturated solution of nux vomica applied to the denuded vein of a living animal passes through the coats of that vein into the circulation and kills. The poison takes a longer time to soak through the coats of an artery ; but having done so produces the same deadly efleet. (Loc. cit., pp. 279, 280.) The nux vomica had certainly affected the system by transuding through the coats of the vessels, for its bitter taste could be detected in the blood which adhered to the inside of the coat of the paralysed vessels. Dead vessels and animal membranes exhibited the same permeability as those which M. Majendie 28* 318 HUNTER ON THE ANIMAL CECONOMY. imagines to have retained their vital properties unchanged after four or ten minutes' contact with the narcotic extract. Ink injected into the serous cavities of the body of a living animal stains the lining membrane and contiguous parts, (p. 282.) From these experiments the author concludes, " II me parait done hors de doute que tous les vaisseaux sanguins, arteriels et veineux, morts ou vivans, gros ou petits, presentent, dans leurs parois, une propriete physique propre a rendre parfaitement raison des principaux phenomenes de l'absorption."—Ibid. To be consistent in this application of the theory of physical imbibition to the actions of organized bodies, we ought to conclude, from observing the serum transuded after death into the pericardium, that such was the condition in the living state of the parts; and a physiologist could no longer infer from the different appearance of the parts in the immediate proximity of the gall-bladder, when examined in a living and dead animal, that the condition of the coats of that receptacle as to permeability must be influenced by the two states; and that the living tissue resists the percolation which the dead membrane readily allows. M. Majendie is, in fact, compelled by his theory to deny such difference ; 4' the bile," says he, " does transude through the coats of the living gall-bladder, but the sanguineous current which exists in the small vessels which form in great measure those parietes, carries it off in proportion as it transudes." Yet the same currents in the serous membranes, which at p. 258 he admits are more abundant in vessels than the mucous, have no such effect in preventing the passage of the ink, &c. But it is evident that he is himself not satisfied with his explanation, for in an account of one of the Hunterian experiments, in which means were adopted to ascertain whether water injected into the intestine of a living animal would be absorbed by the vein, M. Majendie observes that the vital action of the vein might be interrupted by the ligature of its cor- responding artery. Now this objection ought to have no weight if, as he supposes, the veins absorb by a property of simple inorganic imbibition with which their coats are endowed. But laying aside for a moment the consideration of experiments, in all of which the vital operations are more or less interrupted, and the parts in question forced into unnatural condi- tions, let us attentively consider those phaenomena of absorption which Nature plainly puts before our eyes. The chyle is known to contain globules of a definite size and form. It is admitted by M. Majendie that this fluid is exclusively taken up by the lacteal absorbents. The escape of the lacteal globules from the intestine could not be accounted for on the theory of imbibition or permeability of tissue; organic pores must be supposed to exist of a size adequate to their transmission. These pores have been described by Cruikshank as they were seen by himself and Dr. Wm. Hunter in the human subject; they have been witnessed by Majendie in a dog. But, says Majendie, it is unphilosophical, a mere physiological romance, to suppose that they can act in any way different from dead animal tissues ; physical imbibition, inorganic capillary attrac- tion is the only cause of the transmission of fluids through animal mem- branes that we are acquainted 'vith, &c. Yet these organized pores of the lacteal absorbents permit nothing to pass them, according to his own admission, except the chyle. Still it is contended that this must be a mechanical action, because lacteal absorption has been observed to go on in a dog for two hours after ON THE GROWTH OF BONES. 319 death ; but what does this prove but that the automatic or involuntary actions continue for a certain time after the sensorial power is lost,— after apparent death has ensued ? Thus the only natural absorbent process in the living body that we can reason upon from the evidence afforded by the nature of the substance absorbed, and the ascertained structure of the mechanism employed in its absorption, is totally at variance with the theory of non-vital imbibition as the cause of absorption, and can only be explained by a vital or organic endowment of the parts concerned, whether it be regarded as a power of selection or mutual attraction, or an action whose peculiar stimulus is the contact of chyle. The various phenomena of excretory absorption, as it may be termed, render the theory of the capillary attraction of the tissue, whether of veins or lymphatics, as their cause, equally unsatisfactory. A properly of dead matter cannot account for the rapid absorption of fat in disease ; or of the parts of muscles, &c, which, from some accident to a joint, have become useless ; or of alveoli of shed teeth ; or of the parts which in the progress of growth become inconveniently situated, as the first deposit of osseou3 matter in long bones ; or of parts which, at the conclusion of growth, are equally inconveniently situated in regard to some tumour or collection of matter, the discharge of which is salutary to the constitution, &c. A mere physical endowment of animal tissues ought always to be acting, and acting in but one way ; and we therefore conclude, with Hunter, that these various and partial operations of the lymphatics are affected by the vital actions of organic pores, in a manner analogous to that which de^ termines in the lacteals the exclusive absorption of chyle.] 31. EXPERIMENTS AND OBSERVATIONS ON THE GROWTH OF BONES, FROM THE PAPERS OF THE LATE MR. HUNTER. [Published by Mr. (afterwards Sir Everard) Home, in the Second Volume of the Trans- actions of a Society for the Improvement of Medical and Uhirurgical Knowledge.] Read October 4,1798. Mr. Hunter's Observations on the Growth of Bones have been mentioned in his lectures ever since the year 1772, the first year in which he gave lectures, and have been since adopted by the prin- cipal teachers of anatomy in London; it was therefore natural for me to suppose that they were generally known. In this, however, I find I have been mistaken, since the present Professor of Anatomy in Edinburgh, in a late publication, declares himself an advocate for the doctrine of Du Hamel; and from what he advances, it appears that he was not at all acquainted with Mr. Hunter's experiments upon this subject. Under these circumstances I lay before the Society Mr. Hunter's experiments and observations, that they may be made known to the public* * [This record contains little more than a brief notice of the general results of Mr. Hunter's Observations and Experiments on the Growth of Bone.] 320 HUNTER ON THE ANIMAL CECONOMY. It was some time anterior to the year 1772 that Mr. Hunter began to investigate this subject, and an account of the experiments and observations was given to me to copy in that year, as a part of his future lectures. Du Hamel had published a very ingenious theory upon the growth of bones, which he endeavoured to support by experiments tending to prove that bones grow by the extension of their parts. With this doctrine Mr. Hunter was not satisfied, and instituted experiments to determine the truth of Du Hamel's opinion. Mr. Hunter began his experiments by feeding animals with mad- der, which has a property of tinging with a red colour that part only of the bone which is added while the animal is confined to this particular food.* He fed two pigs with madder for a fortnight, and at the end of that period one of them was killed ; the bones, upon examination ex- ternally, had a red appearance; when sections were made of them, the exterior part was found to be principally coloured, and the in- terior was much less tinged. * [This effect of madder upon bone (first described in England by Belchier, Phil, Tr., vol. xxxix., 1736, p. 287), depends on the following chemical properties. The colouring principle of the Rubia Tinclorum has a strong affinity to phosphate of lime, which earth, if artificially precipitated from a solution of madder, carries down with it the colouring matter in a state of combination, which water does not disturb. The colouring principle of madder is hardly soluble in water, but is readily and abundantly soluble in albuminous fluids, and, consequently, when taken into the system as food, it is carried along, dissolved in the serum of the circulating blood, and is deposited, combined with the phosphate of lime, wherever that salt is separated from the blood to contribute to the increase or reparation of bone. There are still, however, some points connected with this subject to be deter- mined before the reasoning from experiments with madder on the growth of bone can have all the desirable exactness. Whether, e. g. the colouring principle of madder, after having been precipitated from the blood in combination with the phosphate of lime, remains in the bone until the particles of the earth are them- selves removed,—or whether the colouring matter may again be redissolved in the serum of the blood circulating through the substance of the bone,—are ques- tions not yet definitively settled ; but there is much reason for believing that the colouring matter may be removed without the earth with which it had been com- bined. Accordingly, although an inference may be safely drawn with respect to the part of a growing bone which receives the accessions of osseous substance, by observing the part which is coloured with madder, yet we cannot so certainly conclude that a superficial colourless layer, in an animal killed after remission of the madder, is a new deposit, since it may be the old, from which the madder has been removed, after having been redissolved in the serum. That the madder " tinges with a red colour that part only of the bone which is added," as is stated in the text, is an assertion, not only unsupported by any physio- logical reasoning, but directly in contradiction to Hunter's own statement, 44 that any part of a bone which is already formed is capable of being dyed with madder, though not so fast as the part that is forming." I may observe, incidentally, that the phaenomena under consideration throw light upon the chemical condition under which phosphate of lime is contained in the living body. Since the colouring principle of madder has no affinity for lime or calcium alone, it is clear that the phosphate of lime is not contained in the blood or the bones as phosphorus, oxygen, and calcium, but that it exists as a binary compound, and is mixed as phosphate of lime with the cartilage or animal basis of the bones.\ ON THE GROWTH OF BONES. 321 The other pig was allowed to live a fortnight longer, but had now no madder in its food ; it was then killed, and the exterior part of the bones was found of the natural colour, but the interior was red. He made many other experiments of the same kind upon the in- crease of the thickness of the neck and head of the thigh bone. From thence it appeared that the addition of new matter was made to the upper surface, and a proportional quantity of the old removed from the lower, so as to keep the neck of the same form, and re- latively in its place.* To ascertain that the cylindrical bones are not elongated, by new matter being interposed in the interstices of the old, he made the following experiment: he bored two holes in the tibia of a pig, one near the upper end, and the other near the lower; the space between the holes was exactly two inches : a small leaden shot was inserted into each hole. When the bone had been increased in its length by the growth of the animal, the pig was killed, and the space within the two shot was also exactly two inches. This experiment was repeated several times on different pigs, but the space between the two shot was never increased during the growth of the bone.f * [Amongst the original drawings of the bones coloured by madder in the Hunterian experiments, besides those of the thigh-bone referred to in the text, there are three which illustrate the mode and direction of increase of the lower jaw, showing that the new bone is deposited in greatest proportion on the upper and posterior part of the ascending ramus, by which the rest of the jaw is pushed forwards, while the bone is absorbed from the anterior part of the ramus, and thus the sockets of the posterior grinders are gradually brought into line, with a free space above for the teeth to come forth. This mode of growth, with absorption at the symphisis of the jaw, continues throughout life in the elephant, in which new grinders are thus brought forwards into use in uninterrupted succession. The preparations of bones coloured with madder in the Hunterian Collection are as follows. Nos. 190 to 201 inclusive, Physiological Series ; Nos. 742 to 751, Osteological Series.] t [Meckel has rightly observed (supposing the above to be a correct statement of Hunter's experiments on this point), that they are invalidated by the careful and numerous experiments of Duhamel, which prove that the middle portion of the long bones does increase in length, though in a less degree than the ex- tremities. It is not easy to understand how the unqualified assertion came to be published, since the preparation and record of an experiment confirmatory of those made by Duhamel are still preserved in the Hunterian Museum. The preparation (No. 188, Physiological Series), is the left tarso-metatarsal bone of a common fowl, exhibiting two perforations at equal distances, two thirds of a inch from the extremities of the bone. The original record of the experiment is preserved with the specimen. | | " "II " The two extreme lines are the present length of the bone from the head of the joint of the inner toe. The two inner lines are the length when cauterized. The outer dots are the present distance or the holes cauterized. The two inner dots are the distance of these holes when cauterized ; so that the bone between the two holes has grown about two-eighths of an inch, while the other parts have grown half an inch."—Physiological Catalogue, vol. i., p. 40. In another experiment, in which shots were inserted into the holes, the result was spoiled by the shots passing into the medullary cavity of the bone, while 322 HUNTER ON THE ANIMAL CECONOMY. Besides these experiments on the growth of bones, he made others, to determine the process of their exfoliation. He cauterized portions of bone in the same way in several different animals, so as to be able to examine the bones in the different stages of this process, and found that the earthy part of the living bone in contact with the dead portion was first absorbed ; afterwards the animal mucilage itself, so as to form a groove between the two, which became deeper and deeper, till the dead bone was entirely detached, the dead portion itself having undergone no change.* From these experiments he ascertained the changes which take place in bones during their growth, and the readiness with which the materials of bone are absorbed ; and from these facts, laid it down as an established principle, that the absorbents are the agents by means of which the bones, during their growth, are modelled as it were, and kept of the same shape. Bones, according to Mr. Hunter's doctrine, grow by two pro- cesses going on at the same time, and assisting each other; the ar- teries bring the supplies to the Lone for its increase ; the absorbents at the same time are employed in removing portions of the old bone, so as to give to the new proper form. By these means the bone becomes larger, without having any material change produced in its external shape.f the perforations became obliterated, as in Duhamel's experiment with the ring of wire, by the deposition of new bone from the periosteum. The shots being liberated from the osseous texture could no longer serve to indicate its growth. The subject of the experiment, the tarso-metatarsal bone of a fowl, is No. 188, Physiological Series. It is remarkable that there is not a single prepara- tion of the long bone of a pig, exhibiting the experiments with shot alluded to in the text. The notes of the experiments on the bones of fowls above mentioned are in the hand-writing of Mr. Wm. Bell, Mr. Hunter's talented artist and assist- ant, and must therefore have been written in or before the year 1789, when Mr. Bell left England for the East Indies.] * [See Preparations Nos. 197 to 204 inclusive, Pathological Series.] t [The difference between the Hunterian theory of the growth of bone and that of Duhamel will be readily appreciated by attending to the explanation given by Duhamel of the phaenomena which he observed during his investigations on this subject. Let us, for example, select from the number of his ingenious and in- structive experiments, that in which he placed a ring of silver wire round the middle of the shaft of the thigh-bone of a young pigeon ; and found at a subse- quent period the ring in the medullary cavity of the bone, instead of embracing the exterior of the shaft, where he had placed it. It need scarcely be observed that the Hunterian physiologist would explain these facts by stating that the arteries of the periosteum had deposited new bone on the external surface of the ring, while the absorbents had removed the old bone in contact with the internal surface of the ring, by which its relations to the osseous parietes of the femur became reversed. But this physiological view of the phaenomena, arising out of a knowledge of the powers and actions of great and important vascular systems in the frame, was wholly unsuspected by and unknown to the predecessors of Hunter. Duhamel explains the facts on mechanical principles; assuming that the bony layers of the shaft of the thigh-bone were expanded by the interposition of additional osseous matter, and that the layers were cut through in this process of expansion by the unyielding wire which he had placed around them. All his explanations bear the 6ame mechanical character, in which processes of growth are assumed which are negatived by observation; and they are frequently vitiated OF THE WOLF, JACKAL, AND DOG. 323 32. OBSERVATIONS TENDING TO SHOW THAT THE WOLF, JACKAL, AND DOG, ARE ALL OF THE SAME SPECIES. The true distinction between different species of animals must ultimately, as appears to me, be gathered from their incapacity of propagating with each other an offspring capable again of continu- ing itself by subsequent propagations : thus the horse and ass beget a mule capable of copulation, but incapable of begetting or pro- ducing offspring. If it be true that the mule has been known to breed, which must be allowed to be an extraordinary fact, it will by no means be sufficient to determine the horse and ass to be of the same species ; indeed, from the copulation of mules being very frequent, and the circumstance of their breeding very rare, I should rather attribute it to a degree of monstrosity in the organs of the mule which conceived, as not being a mixture of two different species, but merely those of either the mare or female ass. This is not so far-fetched an idea, when we consider that some true species produce monsters, which are a mixture of both sexes, and that many animals of distinct sex are incapable of breeding at all. If then we find Nature in its most perfect state deviating from general principles, why may it not happen likewise in the produc- tion of mules; so that sometimes a mule shall breed from the cir- cumstance of its being a monster respecting mules'? The time of uterine gestation being the same in all the varieties of every species of animals, it becomes a necessary circumstance towards determining a species. The affinity between the fox, wolf, jackal, and several varieties of the dog, in their external form and several of their properties, is so striking, that they appear to be only varieties of the same species. The fox would seem to be further removed from the dog than either the jackal or wolf, at least in disposition, being naturally a solitary animal, and neither so sociable respecting its own species or man; from which I should infer that it is only allied to the dog by being of the same genus. It is confidently asserted by many that the fox breeds with the dog; but this has not been accurately ascertained ; if it had, the inquiry would probably have been carried further; and once breeding, according to what we have said, does not con- stitute a species ; this, however, is a part I mean to investigate. I do not know if, in a wild state, there ever is in the same country a by overstrained analogies, as where, in explaining the process of union in a frac- tured bone, he compares the periosteum to the bark of trees. But the numerous experiments of Duhamel,* which are characterized by much precision and in- genuity, well merit the attention of the student of Physiology.] a [Sur le development et la crue des os. Memoires de l'Acad. des Sciences. Paris, 1742, p. 497 ; and 1743, p. 187.] 324 HUNTER ON THE ANIMAL CECONOMY. variety in any species of animal, but am inclined to think there never is; if so, as both wolves and foxes inhabited this country, they cannot then be of the same species. Wolves, as also jackals, are found in herds; and the jackal is so little afraid of the human species, that, like a dog, it comes into houses in search of food, more like a variety of the dog, the con- sequence of cultivation rather than of chance. It would appear to be much the most familiar of the two; for we shall find that in its readiness to copulate with the dog, and its familiarity with the dog afterwards, it is somewhat different from the wolf; however, this may depend on accident. The wolf being an animal well known in Europe, the part of the world where natural history is particu- larly cultivated, some pains have been taken to ascertain whether or not it wras of the same species with the dog; but I believe it has been hitherto considered as only belonging to the same genus. Accident often does as much for natural history as premeditated plans, especially when Nature is left to herself. The first instance of the dog and wrolf breeding in this country seems to have been about the year 1766. A Pomeranian bitch of Mr. Brookes's, in the New Road, was lined only once by a wolf, and brought forth a litter of nine healthy puppies. The veracity of Mr. Brookes is not to be doubted, respecting the bitch having been lined by a wolf; yet as it was possible she might have been lined by some common dog without his knowledge, the fact was not, in that, clearly made out; but it has since been ascertained that the dog and wolf will breed. One of the above-mentioned litter was presented to me by IV{r. Brooks, who likewise informed me that others had been pur- chased by different noblemen and gentlemen, and named Lord Clanbrassil as having bought a bitch puppy. I reserved mine for the purpose of experiment; and from observation it appeared that its actions were not truly those of a dog, having more quickness of attention to what passed, being more easily startled, as if particu- larly apprehensive of danger, quicker in transitions from one action to another, being not so ready to the call, and less docile. From ihese peculiarities it lost its life, having been stoned to death in the streets for a mad dog. Hearing that Lord Clanbrassil's bitch had bred, Sir Joseph Banks was so obliging as, at my request, to write to his Lordship, who sent the following account: " Sir, " About seventeen or eighteen years ago, the late Lord Mon- thermer and I happened to see a dog-wolf at Mr. Brookes's, who deals in animals, and lives in New Road. The animal was re- markably tame, and it struck us, for that reason, that a breed might be procured between him and a bitch. " We promised Mr. Brookes a good price for puppies if he suc- ceeded. In about a year a bitch produced nine, and Lord Mon- thermer bought one; and I had another, which was a bitch. Lord Monthermer's died of fits in about two years : mine lived longer, and OF THE WOLF, JACKAL, AND DOG. 325 had puppies only once. One I gave to Lord Pembroke, but what became of it I do not remember. It was granddaughter of the wolf by the dam, and got by a large pointer of mine. " It might be considered that Mr. Brookes's word was not suf- ficient proof that the puppies were really got by the wolf, but the appearance of the animals, so totally different from all others of the canine species, did not leave a doubt upon our minds; and I re- member Hans Stanley, who had adopted Buffon's opinion, was thoroughly convinced upon seeing mine. The animals had the shape of the wolf refined; the fur long, but almost as fine as that of the black fox. " I am afraid I have trespassed too much upon your time, and will only beg you will be assured nothing can give me more pleasure than any opportunity of assuring you how truly " I am, sir, &c. " Jan. 7,1787. " Clanbrassil." Upon the supposition that Mr. Brookes's bitch was not lined by a dog, but by the wolf, which I think we have no reason to doubt, the species of the wolf is ascertained; but choosing to trace this matter still further, and hearing that Lord Pembroke's bitch had likewise bred, I was desirous to know the truth of it; and as his lordship was in France I took the liberty of writing to Lord Herbert, and received the following answer : « Sir, Wilton House, Dec. 20, 1786. "The half-bred wolf-bitch you allude to was given, as I always understood, to Lord Pembroke by Lord Clanbrassil. She might, perhaps, have been bought at Brookes's by him. She had four litters, one of ten puppies, by a dog between a mastiff and a bull-dog. One of these was given to Dr. Eyre, at Wells in Somersetshire, and one to Mr. Bucket! at Stockbridge. The second litter was of nine puppies, some of which were sent to Ireland, but to whom I know not. This litter was by a different dog, but of the same breed as the first. The third litter was of eight puppies, by a large mastiff. Two of these were, 1 believe, sent to the present Duke of Queensberry. The fourth litter consisted of seven puppies, two of which were sent to M. Cerjat, a gentleman who now resides at Lausanne in Switzer- land, and is famous for breaking dogs remarkably well. These two puppies were, however, naturally so wild and unruly, that he found it impossible to break them. She died four years ago, and the following inscription was put over the place where she is buried in this garden, by Lord Pem- broke's orders: Here lies Lupa, whose grandmother was a wolf, whose father and grandfather were dogs, and whose mother was half wolf and half dog. She died on the 16th of October, 1782, aged 12 years. 29 326 HUNTER ON THE ANIMAL CECONOMY. " I am sorry it is not in my power to give you any better account; but if you think proper to write td Lord Pembroke, who is at Paris, I am convinced he will be very happy to give you any further in- formation. " I am, &c. " Herbert." Buffon, whose remarks in natural history are well known, made experiments to ascertain how far the wolf and dog were of the same species, but without success. He says, " A she-wolf, which I kept three years, although shut up very young, and along with a greyhound of the same age, in a spacious yard, could not Be brought to agree with it, nor endure it, even when she was in heat. She was the weakest, yet the most mischievous, provoking, attacking, and biting the dog, which at first only defended itself, but at last killed her." And in another part of his work he makes the following observation : " The dog, the wolf, the fox, and the jackall, form ,a genus, of which the different species are really so nearly allied to each other, and of which the individuals resemble each other so much, particularly by the internal structure and parts of generation, that it is difficult to conceive why they do not breed together."* This part of natural history lay dormant, till Mr. Gough, who sells birds and has a collection of animals on Holborn-hill, repeated the experiment on a wolf-bitch, which was very tame, and had all the actions of a dog under confinement. A dog is the most proper subject for comparison, as we have opportunities of being acquainted with its disposition and mode of expressing its sensations, which * In the Supplement to his Works he gives the following account which had been sent to him. " A very young she-wolf, brought up at the Marquis of Spon- tin's, at Namur, had a dog, of nearly the same age, kept with it as a companion. For two years they were at liberty, coming and going about the apartments, the kitchen, the stables, &c, lying under the table, and upon the feet of those who sat round it. They lived in the greatest familiarity. "The dog was a strong greyhound. The wolf was fed on milk for six months; after that, raw meat was given her, which she preferred to that which was dressed. When she ate no one durst approach her, but at other times people might do as they pleased, provided they did not use her ill. At first 6he made much of all the dogs which were brought to her, but afterwards she gave the preference to her old companion, and from that time she became very fierce if any strange dog ap- proached her. She was lined for the first time on the 25th of March ; this was frequently repeated while her heat continued, which was sixteen days; and she littered the 6th of June, at eight o'clock in the morning; the period of gestation was therefore seventy-three days at the most.a She brought forth four young ones of a blackish colour, some of whose feet, and a part of the breast, were white ; in this respect taking after the dog, which was black and white. From the time she littered she became surly, and set up her back at those who came near her; did not know her masters, and would even have killed the dog if it had been in her power." a This is a longer period than in the bitch by at least ten days, but as the ac- count was made from the first time of her being lined, and she was in heat for a fortnight, and lined in that time, it is very probable, if the time was known when she conceived, that it would prove to be the same period as in the dog. OF THE WOLF, JACKAL, AND DOG. 327 are most distinguishable in the motion of the ears and tail; such as pricking up the ears when anxious, wishing, or in expectation; depressing them when supplicant or in fear; raising the tail in anger or love, depressing it in fear, and moving it laterally in friendship ; and likewise in raising the hair on the back from many affections of the mind. This animal became in heat in the month of December 1785; and Mr. Gough having an idea of obtaining a breed from wild animals, as monkies, leopards, &c, he was desirous to have the wolf lined by some dog; but she would not allow any dog to come near her, probably from being always chained, and not accustomed to be with dogs. She was held, however, while a greyhound dog lined her, and they fastened together exactly like the dog and bitch. While in conjunction she remained pretty quiet, but when at liberty endeavoured to fly at the dog; yet in this way was twice lined. She conceived, and brought forth four young ones; and though the time she went with young was not exactly known, it was believed to be the same as in the bitch. Two of these puppies were like the dog in colour, who had large black spots on a white ground; another was of a black colour; the fourth of a kind of dun, and would probably have been like the mother.* She took great care of them, yet did not seem very anxious when one was taken from her by the keeper; nor did she seem afraid when strangers came into the room. Unfortunately these experi- ments were carried no further: one of the puppies being sold to a gentleman, who carried it to the East Indies ; and the other three, one of which I was to have had, were killed by a leopard. The same wolf was in heat in December 1786, and was lined several times by a dog. She pupped on the 24th of February 1787, and had six puppies, one of which, a bitch, I had, and kept it till it was in heat; but missed the opportunity of having her lined. That loss, however, wras made up by a wolf-bitch belonging to James Syrnmons, Esq., of Grosvenor-house, Milbank: the history of which is as follows: This female wolf had been in his possession some time, had been lined by a dog, and brought forth several puppies, which I saw in company with Sir Joseph Banks, soon after Mr. Gough's wolf, the subject of my former paper, had produced her litter; so that these puppies were nearly of the same age with mine. Mr. Syrnmons reared them all; but one only was a female, which more resembled the mother or wolf kind than any of the others. I communicated * [Here it may be observed, that, from the known disposition of varieties to revert to the original, it might have been expected, on the supposition that the wolf is the original of the dog, that the produce of the wolf and dog ought rather to have resembled the supposed original than the variety. In a litter lately ob- tained, in the Royal Menagerie at Berlin, from a white pointer and a she-wolf, two of the cubs resembled the common wolf-dog, but the third was like a pointer with hanging ears."] a [Lyell, Principles of Geology, vol. ii., p. 438, who cites Wiegmann for this fact.] 328 HUNTER ON THE ANIMAL CECONOMY. to Mr. Syrnmons my wish that we should endeavour to prove the fact of the wolf and dog being of the same species, by having either his female or mine lined by a dog. This he very readily Acceded to; and his bitch received the dog on the 16th, 17th, and 18th of December, 1788; and the 18th of February following she brought forth eight puppies, all of which she reared. If we reckon from the 16th of December, she went sixty-four days; but if we reckon from the 17th, the mean time, then it is sixty-three days, the usual time for a bitch to go with pup. These puppies are the second remove from the wolf and dog, and similar to that given by my Lord Clanbrassil to the Earl of Pembroke, which likewise bred again. (See Philosophical Transactions, vol. Ixxvii., p. 255.) It would have equally proved the same fact if she had been lined either by a wolf, a dog, or one of the males of her own litter.* It is remarkable that there seems to be only one time in the year in which impregnation is natural to the wolf, which is the month of December: for Mr. Gough's wolf has always been in heat in that month; so was that of Mr. Simmons. The time of heat in his of the half-breed (which is nearly of the same age with mine) corres- ponded likewise with that of the mother, and of those bred from Mr. Gough's wolf. OF THE JACKAL. This animal being so nearly allied to the dog, and only found wild like the wolf, I became desirous of ascertaining of what par- ticular species it was; and while pursuing the subject, I was in- formed that Captain Mears, of the Royal Bishop, East Indiaman, had brought home a bitch-jackal with young, which brought forth soon after his arrival; and that he had given the bitch-jackal and one puppy to Mr. Bailey, bird-merchant, in Piccadilly. I went to see them, and purchased the puppy, the subject of the following ex- periment, which wre found to have dispositions very similar to those of the half-bred wolf before-mentioned, which I had from Mr. Brookes. * [This assertion, that the fertility of a hybrid with an individual of a pure breed proves the fact of identity of two supposed distinct species equally with the production of offspring from the connection of hybrid with hybrid, cannot be admitted. To prove the identity of two supposed distinct species, granting that the fertility of the hybrids from the two to be the proof required, it should be shown that such hybrids are fertile inter se, and capable of propagating indefinitely an intermediate variety. Now this is precisely the fact which is wanting in the evidence adduced in the text. All that Hunter proves is that two species very nearly allied to each other will produce a hybrid offspring, and that the hybrid is again productive with an individual of the pure breed; but this only illustrates a general law by which the reversion of the hybrid to the pure breed is provided for; while, on the other hand, the intermixture of the distinct species is guarded against by the aversion of the individuals composing them to sexual union : an aversion which we see in the case of Mr. Gough's female wolf to have been only overcome by force.] OF THE WOLF, JACKAL, AND DOG. 329 To have a true history of this animal, I took the liberty of writing to Mr. Mears, who politely called upon me, and, at my request, sent me the particulars in a letter, of which the following is a copy: " Sir, " I had the honour of yours of the 15th instant; and with regard to the female-jackal, I can assure you that she took a small spaniel dog of mine on board my ship, the Royal Bishop. I had her, when a cub, at Bombay ; and a very short time before I arrived in England she got to heat, and enticed this small dog into the long- boat, where I saw them repeatedly fast together. I brought her to my house in the country, where she pupped six puppies, one of which you have seen. Mr. Plaw, at No. 90, Tottenham-court Road, has a dog-puppy, which will be at your service at any time you chuse to send for him, to make further experiments : I called on Mr. Plaw, and got his promise to let you have the dog. " I have the honour to be, sir, &c. "Wm. Mears. " No. 107, Hatton-street, 16th Jan. 1786. " P.S. I had the bitch on board fourteen months. " Having taken this puppy into the country, and chained it up near a mastiff-dog, they became very familiar, and seemingly fond of each other. When the bitch became first in heat I could not get a proper dog: but about the latter end of September, she being again in the same state, several dogs were procured and left with her.— They appeared indifferent about her, probably from being in a strange place; nor did she seem inclined to be familiar with them. One of them was a large dog, which might not perhaps be able to line her; but she was twice tied by a terrier on the 3d of Octo- ber. In a few weeks she was evidently bigger; and on the 30th of November, in all fifty-nine days, brought forth five puppies. A few days before this period she dug a hole in the ground, by the side of her kennel, in which she littered; and it was some time be- fore she would allow the puppies to stay in the kennel when put there. Some of these began to open their eyelids in about eight, others of them in nine days. Here then being an absolute proof of the jackal being a dog, and the wolf being equally made out to be of the same species, it now therefore becomes a question whether the wolf is from the jackal, or the jackal from the wolf (supposing them but one origin) 1 From the supposition that varieties become more tame in their nature than the originals, we should be led to believe the wolf to be the original, and that the jackal was a step towards civilization in that species of animal, and that therefore the jackal should be considered as a variety of the wolf. There are wolves of various kinds, each country having a kind peculiar to itself; but the jackals that I have seen have been more uniform in resemblance to each other, proba- bly because only to be found in one country, the East Indies. I am informed, however, that they vary in size. Whether the wolves 29* 330 HUNTER ON THE ANIMAL CECONOMY. of different countries are of one species, or some of them only of the same genus, I do not know; but I should rather suppose them to be all of one species. An argument with me in favour of this sup- position is, that if there were wolves of distinct species, we should have had by this time a great variety of every species of wolf, with the various dispositions arising from variation in other respects; and those varieties would now have been turned to very useful pur- poses, as in the case of the dog: for all the wolves we are yet ac- quainted with should have naturally the principle of cultivation in them (as much probably as any animal), as much at least as those wolves we now know by the name of dogs. The not having a civil- ized species with all the characteristics of the wolf is, indeed, with me a proof that they are all of the same species with the dog. If they are all of the same species with the dog, then the first variety that took place would be still in the character of a wolf, differing only in colour or some trivial circumstance, which could only arise from a difference in climate. The wolf is naturally, I believe, the inhabitant of cold climates, and little variety could take place while it remained in such a situation; but if the jackal was originally a wolf, which had strayed by accident more to the southward, a greater variation from the genuine character might be produced, the difference of climate, and perhaps of food, becoming causes of variety. By continuing to inhabit a warm climate, this circum- stance would in time lose part of its influence on the animal, and the.jackal would admit of little more variety. This, however, is a point not now to be determined, it being difficult (perhaps impossi- ble) to say where the wolf became jackal, or (what we call) dog; and, as dogs differ much from one another, what particular dog may be considered as the first remove; or whether the jackal is the intermediate link connecting the wolf and dog. In any case we may reckon three great varieties in this species, wolf, jackal, and dog; which again branch into their respective less obvious varieties. If the dog proves to be the wolf tamed, the jackal may probably be the dog returned to its'wild state; which leads to another curious question: Whether, as animals vary from climate, cultivation, or what may be called differences in mode of living, they would return to their genuine character if allowed to go wild again in the original country? To ascertain the original animal of a species, all the varieties of that species should be examined, to see how far they have the cha- racter of the genus, and what resemblance they bear to the other species of the genus; for it is natural to suppose that the original animal, or that which is nearest to it, will have more of the true character of the genus, and a stronger resemblance to the species nearest allied to it, than any of the other varieties of its own species. If we apply this to the dog, and consider the fox as a distinct species, which there is great reason to believe it is, that variety which has the greatest resemblance to the fox is to be looked upon as the original of all the others: which will prove to be the wolf. OF THE WOLF, JACKAL, AND DOG. 331 Another mode of considering this subject, which is, however, secondary to the above, is by supposing that all animals were at first wild ; and therefore that those animals which remain wild are the original stock ; and that when we find animals far removed from their originals in appearance the variation takes place in conse- quence of cultivation, yet so that we can still trace the gradation. What gives some force to this idea is, that where the dogs have been least cultivated, there they still retain most of their original character, or similarity to the wolf or the jackal, both in shape and disposition. The shepherd's dog, all over the world, has strongly the character of the wolf or jackal; so that but little difference is to be observed, except in size and hair. That of size may perhaps take place under a variety of circumstances ; but difference in hair is in general, although not always, influenced by climate. Thus the wolf has longer and softer hair than the jackal, because a more northern animal; while the jackal of the East, and the shepherd's dog in Portugal and Spain, have shorter and stronger hair than those of Germany or Kamtschatka, from inhabiting warmer climates. But when we consider their general shape, the character of countenance, the quick manner, with the pricked and erect ears, we must suppose them varieties of the same species. The smelling at the tail has been mentioned as characteristic of the dog; but I believe it is common to most animals, and only marks the male, for it is the most certain way the male has of knowing the female, and by another scent discovering whether the female is disposed to receive the male, which is perhaps the final intention. The Esquimaux dog, and that found among the Indians as far south as the Cherokees, the shepherd's dog in Germany, called Pomeranian, the shepherd's dog in Portugal and Spain, have all a strong similarity to the wolf and jackal. Buffon, on the origin of dogs, seems to have had nearly the same idea : for he says the shepherd's dog is the original stock from which the different kinds of dog have sprung. As the wolf turns out to be a dog, it seems astonishing that there was no account of dogs being found in America. But this I consi- der as a defect in the first history of that country, as there are wolves; and I must think, in spite of all that has been said to the contrary, that the Esquimaux and Indian dog is only a variety from a wolf of that country which had been tamed. Mr. Cameron, of Titchfield-street, who was many years among the Cherokees, and considerably to the westward of that country, observes that the dog found there much resembles the wolf, and that the natives consider it to be a species of tame wolf; but as we come-more among the Europeans who have settled there, the dogs are more of a mixed breed. Why the Cherokees should have had only this kind of dog transported among them, while every other part of America has the varieties of Europe, is not easily solved. The voice of animals is commonly characteristic of the species; but I should suppose it to be only characteristic of the original sne- 332 HUNTER ON THE ANIMAL CECONOMY. cies, and not always of the variety, and the supposition holds good in the dog species. Dogs may be said to have a natural voice and a variation, arising either from a variety having taken place in the species, or a kind of imitation. It would appear that the voice of the wolf and the jackal is very similar, being the natural voice, and is principally conveyed through the nose, and ex- actly resembling that noise in dogs which is a mark of longing or me- lancholy and also of fondness, but having no resemblance to the bark of the dog, which they do not perform. However, in catching a jackal, when the animal found it could not escape, it yelped like the dog, which is a kind of barking, and which is probably the natural sound. Barking is peculiar to certain varieties of the dog kind, and even of those that bark some do it less than others: the dogs in the South Sea Islands do not bark, our greyhound barks but little, while the mastiff and many of the smaller tribe, as spaniels, are particularly noisy in this way. There is reason to believe that the frequency of this noise may arise from imitation : for the dogs in the South Sea Islands learn to bark, the half-breed jackal barked, and so did the half-breed wolf, although but little; and others, as the hound, have a peculiar howl, by huntsmen called the tongue, which noise, and the barking also, are both made by opening the mouth. A variety in the voice, or some parts of the voice, in varie- ties of the same species, is not peculiar to the dog. It is a curious circumstance that variety not only takes place in colour and form, from the change of habits in the parents, but that the dispositions are also changed; and that the dispositions are most commonly changed in such a way as appears best adapted to the form of the animal. The change in the habits of the parent animal arise principally from its connection with the human kind, which has now succeeded in training dogs so as to fit them, both in body and mind, for almost every purpose of human ceconomy, as if man himself had formed them expressly with such intention, while at the same time he can only be considered as an occasional cause, for we may observe that all the males of the wolf kind are nearly the same, and so are likewise those of the jackal, having little or no variety in their dispositions. Those of the half-breed, and even those that are three removes, although tame, yet have not the docility of dogs, nor are they so immediately at the command of the human will; neither are they perfectly satisfied with an arti- ficial life, having when left to themselves a propensity to fall back into their original instinctive principles.* * [The range of deviation from the original type appears to be greater in the dog than in any other known species. Besides the well known and considerable differences in the quantity, colour, and texture of the hair, and in the size, form, and proportions of the body, in some individuals an additional false grinder ap- pears; and there is a race of dogs which have a supernumerary toe on the hind- foot, with the corresponding tarsal bones ;»—a variety analogous to the Dorking (or five-toed) fowl, and to the six-fingered families of the human race.] [Cuv. Disc. Prelim. Ossem. Fossiles, Ed. iv. torn, i., p. 205.] OF THE WOLF, JACKAL, AND DOG. 333 The following account from Mr. Jenner, of Berkeley, to whom I gave a second remove, viz., three parts dog, is very descriptive of this propensity: " The little jackal-bitch you gave me is grown a fine handsome animal; but she certainly does not possess the understanding of common dogs. She is easily lost when I take her out, and is quite inattentive to a whistle. She is more shy than a dog, and starts frequently when a quick motion is made before her. Of her inches she is uncommonly fleet, much more so than any dog I ever saw. She can turn a rabbit in the field ; she is fond of stealing away and lying about the adjacent meadows, where her favourite amuse- ment is hunting the field-mouse, which she catches in a particular manner." As animals are known to produce young which are different from themselves in colour, form, and dispositions, arising from what may be called the unnatural mode of life, it shows this curious power of accommodation in the animal oeconomy, that although education can produce no change in the colour, form, or disposition of the animal, yet it is capable of producing a principle which becomes so natural to the animal that it shall beget young different in colour* and form, and so altered in disposition as to be more easily trained up to the offices in which they have been usually employed, and having these dispositions suitable to such change of form. It also becomes a question, whether they would not go back again to their original state, if put into the situation of the original from whence they sprang; or acquire a form resembling the ori- ginal of that country where they are placed. I do not conceive that they must necessarily go back through the same changes; but I have some reason to suppose they would gradually return to a resemblance of that original.f And it would be difficult to prove whether, in many of the gradations, they are progressive or retro- grade. But this is a subject that requires particular attention and investigation, and upon which, I hope, some time or other, to be able to throw more light. * [This has recently been exemplified in the produce of a male and female Dingo, or wild dog of Australia, brought forth at the Zoological Gardens, and under circumstances which precluded the possibility of connection between the female and any other dog than the male with which she was kept confined. Two, out of the litter of five puppies brought forth, had the uniform red-brown colour of the parents, the rest were more or less pied, brown and white.] f [If the wolf were actually the original of the dog, it might have been expected that the Dingo of Australia, supposing it to have originated from some dog ac- cidentally introduced into that continent, would have been found reverted to its original condition, or as a wolf. But there appears to have been no further pro- gress towards the acquisition of the characters of the wolf, in this instance, than may be supposed, on the theory of reversion, to have taken place in the time of Cook. The existence of wild dogs which are not wolves, as the Dingo of Aus- tralia and the Dhole of India, which have either lost or have never acquired the cosnmon character of domestication, variety of colour, is itself a strong argumeut against the original of the domestic dog ever having been a wolf.] 334 HUNTER ON THE ANIMAL CECONOMY. 33. OBSERVATIONS ON THE STRUCTURE AND (ECO- NOMY OF WHALES. BY JOHN HUNTER, ESQ., F.R.S.* The animals which inhabit the sea are much less known to us than those found upon land ; and the oeconomy of those with which we are best acquainted is much less understood ; we are, therefore, too often obliged to reason from analogy where information fails, which must probably ever continue to be the case, from our unfit- ness to pursue our researches in the unfathomable waters. This unfitness does not arise from that part of our oeconomy on which life and its functions depend, for the tribe of animals which is to be the subject of this Paper has, in that respect, the same ceconomy as man, but from a difference in the mechanism by which our progressive motion is produced. The anatomy of the larger marine animals, when they are procured in a proper state, can be as well ascertained as that of any others, dead structure being readily investigated. But even such opportunities too seldom occur, because those animals are only to be found in distant seas, which no one explores in pursuit of natural history; neither can they be brought to us alive from thence, which prevents our receiving their bodies in a stale fit for dissection. As they cannot live in air, we are unable to procure them alive. Some of these aquatic animals yielding substances which have become articles of traffic, and in quantity sufficient to render them valuable as objects of profit, are sought after for that purpose; but gain being the primary view, the researches of the Naturalist are only considered as secondary points, if considered at all. At the best our opportunities of examining such animals do not often occur till the parts are in such a state as to defeat the purposes of accurate inquiry, and even these occasions are so rare as to prevent our being able to supply, by a second dissection, what was deficient in a first. The parts of such animals being formed on so large a scale, is another cause which prevents any great degree of accuracy in their examination, more especially when it is considered how very inconvenient for accurate dissections are barges, open fields, and such places as are fit to receive animals or parts of such vast bulk. As the opportunities of ascertaining the anatomical structure of large marine animals are generally accidental, I have availed myself as much as possible of all that have occurred; and, anxious to get more extensive information, engaged a surgeon, at a con- siderable expense, to make a voyage to Greenland, in one of the ships employed in the whale fishery, and furnished him with such necessaries as I thought might be requisite for examining and pre. * [Originally published in the Philosophical Transactions, vol. Ixxvii. 1787.] OBSERVATIONS ON THE STRUCTURE, ETC. 335 serving the more interesting parts, and with instructions for making general observations; but the only return I received for this expense was a piece of whale's skin, with some small animals sticking upon it. From the opportunities which I have had of examining different animals of this order, I have gained a tolera- bly accurate idea of the anatomical structure of some genera, and such a knowledge of the structure of particular parts of some others, as to enable me to ascertain the principles of their oeconomy. Those which I have had opportunities of examining were the following: Of the Delphinus Phocana, or Porpoise, I have had several, both male and female. Of the Grampus I have had two; one of them, (Delphinus Orca, Linn. Tab. XLIV.) twenty-four feet long, the belly of a white colour, which terminated at once, the sides and back being black; the other about eighteen feet long, the belly white, but less so than in the former, and shaded off into the dark colour of the back. Of the Delphinus Delphis, or Bottle-nose whale (Tab. XLVI.), I had one sent to me by Mr. Jenner, surgeon, at Berkeley. It was about eleven feet long. I have also had one twenty-one feet long, resembling this last in the shape of the head, but of a different genus, having only two teeth in the lower jaw (Tab. XLVIL); the belly was white, shaded off into the dark colour of the back. This species is described by Dale in his Antiquities of Harwich. The one which I examined must have been young, for I have a skull of the same kind nearly three times as large, which must have belonged to an animal thirty or forty feet long. Of the Balana rostrata of Fabricius I had one seventeen feet long. (Tab. XLVI1I.) The Balcena Mysticetus, or large Whalebone whale, the Physeter Macrocephalus, or Spermaceti whale, and the Monodon Monoceros, or Nar-whale, have also fallen under my inspection. Some of these I have had opportunities of examining with accuracy, while others I have only examined in part, the animals having been too long kept before I procured them to admit of more than a very superficial inspection.* * [Cuvier, in his masterly Chapter on existing Cetaceans (Ossem. Foss.,tom. v. pt. i.), divides the Balxnx or true whales, (cetaceans having the roof of the mouth furnished with baleen or whalebone), into those which have, and those which have not a dorsal fin. Of the latter he admits but one species, frequenting the northern latitudes, to be accurately defined, viz., the Balxna Mysticetus of Linnaeus, and which Hunter, from the relative size of its baleen-plates terms the ' large whalebone whale.' The species of Balxna found in the southern latitude differs, according to Cuvier, from the Bal. Mysticetus, in having all its cervical vertebra anchylosed, while in Bal. Mysticetus the five posterior cervical vertebrae remain detached; and in the number of ribs, which are thirteen pairs in the 336 HUNTER ON THE ANIMAL CECONOMY. From these circumstances it will be readily supposed that an accurate description of all the different species is not to be ex- pected ; but having acquired a general knowledge of the whole Bal. Mysticetus, and fifteen in the Bal. Australis.- there are also well-marked differences in the form of the skull in the two species. Of the fin-backed whales or Balxnopterx, Cuvier considers the existence of the species without ventral plicae, called gibbar or finfish, as reposing on more than doubtful authority : in the original figure by Martens (Voyage du Spiizberg, 1671), Cuvier supposes that the plicae were accidentally omitted, rather than absent in nature, since he finds that the 6kull of the so called gibbar, figured by Camper, and its skeleton figured by Albers {hones ad Anat., Comp. illustr.), are identical with those of the Rorquals or Balxnopterx with the skin of the throat and fore part of the abdomen disposed in longitudinal folds. Mr. Hunter had evi- dently never met with a specimen of the supposed gibbar, and, as he derived his observations from Nature alone, he did not contribute towards perpetuating the error of Martens, as most nomenclative naturalists and compilers had done up to his time, and continued to do until the publication of the works of Scoresby and Cuvier. The principal characters by which the Rorquals {Balxnopterx) differ from the Balxnx,aie the greater flatness of the head, the lower jaw projecting beyond the upper, the skin under the throat, chest, and anterior part of the abdomen longitu- dinally plicated and dilatable ; the short and hard baleen-plates, terminating in stiff and brittle bristles, a short and thick fin on the hinder region of the back. Of the Balxnopterx which frequent the northern latitudes three species have been admitted into the Zoologists' Catalogues, Balxnoptera Boops, Bal. musculus, Bal. rostrata. Cuvier submits these species to a criticism, severe, as usual, but just; he finds that no two of the species have ever been compared or seen by one naturalist, either together or at different periods : that the only appreciable differences he can gather from the best of their accounts resolve themselves into those of size or degrees of mutilation of the dorsal fin : and he asks, " Qui oseroit, d'apres l'observation d'individus vus isolement a de grandes distances de temps et de lieux, et par de personnes diverses, soutenir que ces differences ne venoient pas de l'age ?" Fabricius, however, assigns three rows of low ridges on the upper part of the head, extending forwards from the blow-holes, as a character distinguishing his Balxna Boops from Balxna rostrata: a more important dis- tinction is afforded by the number of vertebral. The Bal. musculus attains, according to Scoresby, the length of seventy or eighty feet ; the Bal. Boops of the same author that of forty-six feet. The Bal. rostrata of Fabricius is variously described as seventeen, twenty, and twenty- five feet in length. The young Rorqual dissected by Hunter was but seventeen feet long, and he accordingly refers it to the Bal. rostrata of Fabricius. In speaking of it he generally uses the term applied by Sibbald to the species of which this is sup- posed by Cuvier to be the young, viz., 'piked whale;' and sometimes from the relative size of the baleen plates, calls it 'small whalebone whale,' in contradis- tinction to the 'large whalebone whale,' or Balxna mysticetus,• not referring to the relative difference in the general bulk of the body, in which the ' small whale- bone whale' {Balxnoptera Boops, Cuv.) has the advantage, since it attains the length of from eighty to one hundred feet, while the 'large whalebone whale' was never seen by Scoresby to exceed the length of sixty feet, nor was ever re- ported to him to have been longer than sixty-seven feet. The whale described by Dale, in Taylor's Antiquities of Harwich (p. 411, {>!. xiv.), of which species Hunter dissected an individual, twenty-one feet in ength, is generally called by him the ' great bottle-nose whale,' in contradistinc- tion to the Delphinus tursio, which he calls also 'bottle-nose,' or 'small bottle- nose whale.' Dale's whale is distinguished chiefly by the presence of only two small teeth in the lower jaw, and a number of horny tooth-like projections from OBSERVATIONS ON THE STRUCTURE, ETC. 337 tribe from the different species which have come under my ex- amination, I have been enabled to form a tolerable idea, even of parts which I have only had the opportunity of seeing in a very cursory way. General observation would lead us to believe that the whole of this tribe constitutes one order of animals, which naturalists have subdivided into genera and species; but a deficiency in the knowledge of their oeconomy has prevented them from making these divisions with sufficient accuracy; and this is not surprising, since the genera and species are still in some measure undeter- mined, even in animals with which we are better acquainted. The animals of this order are in size the largest known, and probably, therefore, the fewest in number of all that live in water. Size, I believe, in those animals which feed upon others, is in an inverse proportion to the number of the smaller; but I believe this tribe varies more in that respect than any we know, viewing it from the whalebone whale, which is seventy or eighty feet long,* to the porpoise, that is five or six: however, if they differ as much among themselves as the salmon does from the sprat, there is not that comparative difference in size that would at first appear. The whalebone whale is, I believe, the largest; the spermaceti whale the next in size (the one which I examined, although not full grown, was about sixty feet long); the grampus, which is an exten- sive genus, is probably from twenty to fifty feet long; under this denomination there is a number of species. the roof of the mouth, which Cuvier conjectures may be the rudiments or ana- logues of the baleen of the true whales. This Cetacean is now considered the type of a new genus, called by Lacepede ' Hyperoodon,^ and the only well-ascer- tained species is generally designated, after its original describer, Dale, ' Hype- roodon Dulei.'' The individual described by Dale was fourteen feet in length. Another described by Chemnitz, which was captured at Spitzbergen, measured twenty-five feet. A female, which was taken with her young one, near Harfleur, in 1788, was twenty-three feet in length. Nevertheless, the skeleton of the Hunterian specimen manifests all the characters of immature age, in the separation of the epiphyses ; although it is to be observed that these parts are anchylosed less early in the Cetacea than in the land mammalia. The small bottle-nose whale of Hunter, is not the common dolphin, Delphinus delphis, L., as he supposed, but the Delphinus Tursio of Fabricius, as is shown by the skull and other parts which are preserved in the Hunterian Collection, as well as by the size of the specimen which Hunter describes. The Delphinus delphis is from six to seven feet in length, and has from forty-two to forty-seven teeth on each side of each jaw. The Delphinus Tursio attains the length often and eleven feet, and has from twenty-one to twenty-three teeth on each side of each jaw; which teeth are conical, but proportionally larger and more obtuse than in D. delphis.] * [This, as an average size, can only be attributed to the largest of the Balx- nopterx or fin-backed whales. The usual length of the largest cachalots (Physeter macrocephalus, Shaw,) taken in the South Seas is about sixty-feet; but this size refers only to the males, for there is a remarkable disproportion in the size of the two sexes in this species of Cetacean, the full-grown female of which rarely exceeds thirty-five feet. The difference is principally in the length of the jaws, which are twice as long in the male as in the female, reminding one of the sexual characters afforded by the mandibles in the Lucani or stag-beetles.] 30 338 HUNTER ON THE ANIMAL CECONOMY. From my want of knowledge of the different genera of this tribe of animals, an incorrectness in the application of the anatomical account to the proper genus may be the consequence; for when they are of a certain size they are brought to us as porpoises; when larger they are called grampus or fin-fish. A tolerably cor- rect anatomical description of each species, with an accurate drawing of the external form, would lead us to a knowledge of the different genera, and the species in each ; and, in order to forward so useful a work, I propose, at some future period, to lay before the Society descriptions and drawings of those which have come under my own observation. From some circumstances in their digestive organs we should be led to suppose that they were nearly allied to each other, and that there was not the same variety in this respect as in land animals. In the description of this order of animals I shall always keep in view their analogy to land animals, and to such as occasionally inhabit the water, as white bears, seals, manatees,* &c, with the differences that occur. This mode of referring them to other animals better known will assist the mind in understanding the pre- sent subject. It is not, however, intended in this paper to give a particular account of the structure of all the animals of this order which I have had an opportunity of examining: I propose at pre- sent chiefly to confine myself to general principles, giving the great outlines as far as I am acquainted with them, minuteness being only necessary in the investigation of particular parts. In my account I shall pay some attention to the relations of men who have given facts without knowing their causes, whenever I find that such facts can be explained upon true principles of the animal ceconomy, but no further. This order of animals has nothing peculiar to fish, except living in the same element, and being endowed with the same powers of progressive motion as those fish that are intended to move with a considerable velocity; for I believe that all that come to the sur- face of the water (which this order of animals must do) have con- siderable progressive motion; and this reasoning we may apply to birds, for those which soar very high have the greatest pro- gressive motion. Although inhabitants of the waters they belong to the same class as quadrupeds, breathing air, being furnished with lungs and all the other parts peculiar to the oeconomy of that class, and having warm blood ; for we make this general remark, that in the different classes of animals there is never any mixture of those * [The aquatic mammalia which Hunter includes under this name are associated by Cuvier, in consequence of the absence of hinder extremities, with the true Cetacea. They include the manatee of South America {Manaius), the dngong of the Indian Ocean and Red Sea (Halicore), and the manatee of the Arctic Seas (Rytina). They are all herbivorous, and differ in many anatomical particulars from the true cetacea, which are the subjects of Hunter's observations; connect- ing these mammalia with the quadrupeds of the Pachydermatous order.] OBSERVATIONS ON THE STRUCTURE, ETC. 339 parts which are essential to life, nor in their different mode of sensation.* I shall divide what is called the oeconomy of an animal: First, into those parts and actions which respect its internal functions, and on which life immediately depends, as growth, waste, repair, shifting or changing of parts, &c, the organs of respiration and secretion, in which we may include the powers of propagating the species. Secondly, into those parts and actions which respect external objects, and which are variously constructed, according to the kind of matter with which they are to be connected, whence they vary more than those of the first division. These are the parts for progressive motion, the organs of sense and the organs of diges- tion ; all of which either act upon, or are acted upon, by external matter. This variation from external causes in many instances influences the shape of the whole, or particular parts, even giving a peculiar form to some parts which belong to the first order of actions, as the heart, which in this tribe, in the seal, otter, &c, is flattened because the chest is flattened for the purpose of swimming. The contents of the abdomen are not only adapted to the external form ; but their direction in the cavity is, in some instances, regu- lated by it. The anterior extremities, or fins, although formed of distinct parts, in some degree similar to the anterior extremities of some quadrupeds, being composed of similar bones placed nearly in the same manner, yet are so formed and arranged as to fit them for progressive motion in the water only. The external form of this order of animals is such as fits them for dividing the water in progressive motion, and gives them power to produce that motion in the same manner as those fish which move with a considerable velocity. On account of their inhabiting the water, their external form is more uniform than in animals of the same class which live upon land; the surface of the earth on which the progressive motion of the quadruped is to be performed being various and irregular, while the water is always the same. The form of the head or anterior part of this order of animals is commonly a cone, or an inclined plane, except in the spermaceti whale, in which it terminates in a blunt surface. This form of head increases the surface of contact to the same volume of water which it removes, lessens the pressure, and is better calculated to bear the resistance of the water through which the animal is to pass; probably on this account the head is larger than in quadrupeds, having more the proportion observed in fish, and swelling out laterally at the * [That is, there is never any combination of the modifications of vital organs characteristic of two different classes of animals in the same species, as of a double heart of the mammal with the branchiae of a fish ; nor is the structure of the organ of hearing, or of any other sense characteristic of a higher class of vertebrata, ever combined with a modification of the vital organs peculiar to a lower class.] 310 HUNTER ON THE ANIMAL CECONOMY. articulation of the lower jaw. This may probably be for the better catching their prey, as they have no motion of the head on the body, and this distance between the articulations of the jaw is somewhat similar to the swallow, goat-sucker, bat, &c, which may also be accounted for from their catching their food in the same manner as fish ; and this is rendered still more probable, since the form of the mouth varies according as they have or have not teeth. There is, however, in the whale tribe more variety in the form of the head than of any other part, as in the whalebone, bottle-nose, and sper- maceti whales; though in this last it appears to owe its shape in some sort to the vast quantity of spermaceti lodged there, and not to be formed merely for the catching of its prey. From the mode of their progressive motion they have not the connexion between the head and body that is called the neck, as that would have pro- duced an inequality inconvenient to progressive motion. The body behind the fins or shoulders diminishes gradually to the spreading of the tail; but the part beyond the opening of the anus is to be considered as tail, although to appearance it is a continuation of the body. The body itself is flattened laterally, and I believe the back is much sharper than the belly. The projecting part, or tail, contains the power that produces progressive motion and moves the broad termination, the motion of which is similar to that of an oar in sculling a boat; it supersedes the necessity of posterior extremities, and allows of the proper shape for swimming. That the form may be preserved as much as pos- sible, we find that all the projecting parts found in land animals of the same class are either entirely wanting, as the external ear; are placed internally, as the testicles; or are spread along under the skin, as the udder. The tail is flattened horizontally, which is contrary to that fish,* this position of tail giving the direction to the animal in the pro- gressive motion of the body. I shall not pursue this circumstance further than to apply it to those purposes in the animal ceconomy for which this particular direction is intended. The two lateral fins, which are analogous to the anterior ex- tremities in the quadruped, are commonly small, varying however in size, and seem to serve as a kind of oars. To ascertain the use of the fin on the back is probably not so easy, as the large whalebone and spermaceti whales have it not; one should otherwise conceive it is intended to preserve the animal from turning. I believe, like most animals, they are of a lighter colour on their * [This difference in the position of the tail-fin relates chiefly to the difference between the whale and fish in the mode and amount of respiration; the warm- blooded whale requiring a frequent ascent to the surface of the water to breathe the air, which the horizontal tail enables it to do. In the air-breathing Ichthyo- saurus, the presence of a pair of horizontal flattened posterior paddles,°for direct- ing the snout to the surface of the water, enabled that extinct reptile to have lun signifying the hinder parts raised. Of this genus three or four species have been indicated. The skin and cranium of the individual described by Hunter, and figured in the Appendix to White's Voyage, are preserved in the Museum of the College of Surgeons. The skull agrees in size and form, as also the proportions of the stuffed skin, with the skeleton of the Hypsiprymnus murinus, given in Pander and D'Alton's ' Skelete der Beutelthiere,'1 tab. iii. We give the following admeasurements from the original specimen: ft. in. In. From the end of the nose to the vent . . . 13 0 Length of the tail.......0 8 7£ Length of the skull......0 3 3 Length of the foot......0 3 3 The Hypsiprymnus murinus of Illiger is the Hypsiprymnus White of Quoy and Gaimard, the Macropus minor of Shaw.] X [In the specimen here described, as in the rest of the genus, there are five toes on the fore foot, but the fifth is so small as scarcely to perferm any part of the office of a toe. DESCRIPTIONS OF SOME ANIMALS, ETC. 475 largest. From the nails on the two middle toes one would suppose that the animal burrowed. Their hind legs are long, and it is in their power to stand either on the whole foot, or on the toes only. On the hind legs are three toes, the middle one large, and the two side ones short ;* the tail is long. The hair on the body is rather thin ; it is of two kinds, a fur, and a long hair, which last becomes exterior from its length. The fur is the finest, and is composed of serpentine hairs; the long hair is stronger, and is also serpentine, for more than two-thirds of its length near to the skin, and termi- nates in a pretty strong pointed end, like the quill of a hedgehog ; it is of a brownish-gray colour, something like the brown or gray rabbit, with a tinge of a greenish-yellow. It has a pouch on the lower part of the belly ; the mouth opens forwards, and the cavity extends backwards to the pubis, where it terminates; on the abdominal surface of this pouch are four nipples or two pair, each pair placed very near the other.f The Hepoona Roo.% This animal is of the size of a small rabbit; it has a broad flat body; the head a good deal resembles that of the squirrel; the eyes are full, prominent, and large ; the ears broad and thin ; its legs short, and its tail very long. Between the fore and hind legs, on each side, is placed a* doubling of the skin of the side, which, when the legs are extended laterally, is as it were pulled out, forming a broad lateral wing or fin, and when the legs are made use of in walking, this skin, by its elasticity, is drawn close to the side of the animal, and forms a kind of ridge, on which the hair has a peculiar appearance. In this respect it is very similar to the flying squirrel of America. It has five toes, on each fore foot, with sharp nails. The hind- foot has also five toes, but differs considerably from the fore-foot; one of the toes may be called a thumb, having a broad nail, some- thing like that of the monkey or opossum. What answers to the fore and middle toes are united in one common covering, and ap- pear like one toe with two nails; this is somewhat similar to the kangaroo. The two other toes are in the common form ; these o * [There are four toes on this foot, as in the great kangaroo, but the two inner ones are so conjoined by a common sheath of integument as to act as but 0n<+3[The eenera Macropus and Hypsiprymnus are principally distinguished from the otheTmarsupialia anatomically by having a large stomach complicated with sacculi! produced as in the colon, by being puckered upon longitudinal ba±riL animal is the type of the genus Pteaurus, which is characterized by the following dental formula : incisors -J, molares spuria, _3, molares tubercu- 1 f U = 34 It is the largest known species, and is the Petaurus Taguanoides se,Ted in the Museum of the Royal College o^Surgeone.] 476 HUNTER ON THE ANIMAL CECONOMY. four nails are sharp, like those on the fore foot. This formation of the foot is well calculated for holding anything while it is moving its body or its fore foot to other parts ; a property belonging (pro- bably) to all animals which move from the hind parts, such as the monkey, mocock, mongoose, opossuin, parrot, leech, &c. Its hair is very thick and long, making a very fine fur, especially on the back. It is of a dark brown-gray on the upper part, a light white gray on the lower side of what may be termed the wing, and white on the under surface, from the neck to the parts adjacent to the anus. Wha Tapoua Roo.* This animal is about the size of a racoon, is of a dark gray colour on the back, becoming rather lighter on the sides, which terminates in a rich brown on the belly. The hair is of two kinds. a long hair and a kind of fur, and even the long hair at the roots is of the fur kind. The head is short, the eyes rather prominent; the ears broad, not peaked. The teeth resemble those of all the animals from that country I have hitherto seen. The incisors are not continued into the grinders by intermediate teeth, although there are two teeth in the intermediate space in the upper jaw, and one in the lower. The incisors are similar to those of the kangaroo, and six in number in the upper jaw, opposed by two in the lower, which have an oblique surface extending some distance from their edge, so as to increase the surface of contact. There are two cuspidati on each side in the upper jaw, and only one in the lower; five grinders on each side of each jaw, the first rather pointed, the others appear nearly of the same size, and quadrangular in their shape, with a hollow running across their base from the out- side to the inner, which is of some depth; and another which crosses it, but not so deep, dividing the grinding surface into four points. On the fore foot there are five toes, the inner the shortest, resembling, in a slight degree, a thumb. The hind foot resembles a hand, or that of the monkey and opossum, the great toe having no nail, and opposing the whole sole of the foot, which is bare. The nails on the other toes, both of the fore and hind foot, resemble in a small degree those of the cat, being broad and covered ; and the last bone of the toe has a projection on the under side, at the articulation. Each nail has, in some degree, a small sheath, covering its base when drawn up.t The tail is long, covered with * [This species is now called the vulpine opossum, or vulpine phalanger (Phalangista Vulpina,) and is the type of a genus of which the species are not confined to Australia, but some were known, as inhabitants of the Indian isles, to the older naturalists. The dental characters are described in the text.] f [In the hinder foot the two toes next the thumb are inclosed in a common sheath of integument as far as the ungual phalanx : this is the commencement of that peculiar degradation of the second and middle toe which is carried to so great an extreme in the kangaroos and potoroos. The term Phalangista was given to the genus in question in consequence of this binding together of the phalanges of two of the toes in the hind feet.] DESCRIPTIONS OF SOME ANIMALS, ETC. 477 long hair, except the under surface of that half towards the termi- nation, of the breadth of half an inch, becoming broader near the tip or termination: this surface is covered with a strong cuticle, and is adapted for laying hold. The Tapoa Tafa, or Tapha* This animal is the size of a rat, and has very much the appear- ance of the martin cat, but hardly so long in the body in proportion to its size. The head is flat forwards, and broad from side to side, especially between the eyes and ears; the nose is peaked, and pro- jecting beyond the teeth, which makes the upper jaw appear to be considerably longer than the lower; the eyes are pretty large; the ears are broad especially at their base, not becoming regularly nar- rower to a point,f nor with a very smooth edge, and having a small process on the concave or inner surface, near to the base. It has long whiskers from the sides of the cheeks, which begin forwards, near the nose, by small and short hairs, and become longer and stronger as they approach the eyes.J It has very much the hair of a rat, to which it is similar in colour; but near to the setting on of the tail it is of a lighter brown, forming a broad ring round it. The fore feet are shorter than the hind, but much in the same pro- portion as those of the rat; the hind feet are more flexible. There are five toes on the fore feet, the middle the largest, falling off on each side nearly equally; but the fore or inner toe is rather shortest; they are thin from side to side; the nails are pretty broad, laterally, and thin at their base; not very long, but sharp: the animal walks on its whole palm, on which there is no hair. The hind feet are pretty long, and have five toes; that which answers to our great toe is very short, and has no nail; the next is the longest in the whole, falling gradually off to the outer toe ; the shape of the hind toes is the same as in "the fore feet, as are likewise the nails; it walks nearly on the whole foot. The tail is long, and covered with long hair, but not all of the same colour. The teeth of this creature are different from any other animal yet known. The mouth is full of teeth; the lower jaw narrow, in comparison to the upper, more especially backwards, which allows of much broader grinders in this jaw than in the lower, and which occasions the grinders in the upper iaw to project considerably over those in the lower. In the middlei the cuspidati oppose one another; the upper piercers or holders go behind those of the lower; the second class of incisors in the lower jaw overtop those of the upper, while the two first in the lower go within, or behind those of the upper. In the upper * rTbk animal is the Phascogale penicillata of Temminck, {Monographies de ManZaloeTTttkDasyurus Tafa of Geoffroy, Dide/phis penicillata of Shaw.] nTemmTncPk describes the earsof Phascogale penicillata as being "arrondies nar le haut."—Loc. cit., p. 59.] P" [.■Les moustaches des levres sont place's plus pres des yeux que de nez. - Ibid.,] 478 HUNTER ON THE ANIMAL CECONOMY. jaw, before the holders ' (canines)', there are four teeth * (incisors)' on each side, three of which are pointed, the point standing on the inner surface; and the two in front are longer, standing more obliquely forwards, and appear to be appropriated for a particular use.* The holders * (canines)' are a little way behind the last fore teeth, to allow those of the lower jaw to come between ; they are pretty long. The cuspidati (spurious molares) on each side become longer and larger towards the grinders (true molares) ; they are points or cones placed on a broad base. There are four grinders on each side, the middle two the largest, the last the least; their base is a triangle, of the scalenus kind, or having one angle obtuse and two acute. Their base is composed of two surfaces, an inner and an outer, divided by processes or points; it is the inner that the grinders of the lower jaw oppose, when the mouth is regularly shut. The lower jaw has three fore teeth, or incisors, on each side, the first considerably the largest, projecting obliquely forwards: the other two of the same kind, but smaller; the last the smallest. The holder (canine) in this jaw is not so large as in the upper jaw, and close to the incisors. There are three cuspidati ' (false molares),f the middle one the largest, the last the least: these are cones standing on their base, but not on the middle, rather on the anterior side. There are four grinders, the two middle the largest, and rather quadrangular, each of which has a high point or cone on the outer edge, with a smaller, and three more diminutive on the inner edge. It is impossible to say critically what the various forms of these teeth are adapted for, from the general principles of teeth. In the * [This superiority of size of the two middle incisors of the two jaws is one of the characters which distinguish Phascogale from Dasyurus."] f [This is the second and most decisive distinguishing generic character between Phascogale and Dasyurus, the latter having only two false molars on each side of each jaw, instead of three. Had Fischer, Lesson, and other zoologists compared the description of the teeth in the text with that given by Temminck in his Monographies de Mammalugie,as characterizing his genus Phascogale, they could not have hesitated to refer the Tapoa tafa of Hunter to that genus, and the catalogues of mammalia need not have contained the imaginary species Dasyurus Tafa, which M. Temminck observes " n'a point eli vue depuis par aucun naturaliste," and which species Lesson suspects to be founded on the immature state of the spotted Dasyure (Dasyurus viverrinus). But neither observation nor analogy favour the idea of spots being acquired by age; on the contrary, the examples of the lion and the puma, which are spotted only when young, show that they are more likely to be lost. In the Hunterian collection the posterior half of the body of the individual described by Hunter is preserved, to show the marsupium and teats; these are eight in number, and arranged in a circle. The tail perfectly corresponds with the specimens of Phascogale penicillata, and with M. Temminck's description, being "couverte de poils assez courts a la base, tres-long, raides, et en pinceau vers la pointe " {loc. cit., p. 59) ; and the long hairs are black.] DESCRIPTIONS OF SOME ANIMALS, ETC. 479 front we have what may divide and tear off; behind those there are holders or destroyers; behind the latter, such as will assist in mashing, as the grinders of the lion, and other carnivorous animals; and last of all, grinders, to divide parts into smaller portions, as in the graminivorous tribe; the articulation of the jaw, in some degree, admits of all those motions. A Dingo, or Dog of New South Wales. This animal is a variety of the dog, and, like the shepherd's dog in most countries, approaches near to the original of the species, which is the wolf; but is not so large, and does not stand so high on its legs. The ears are short and erect, the tail rather bushy; the hair, which is of a reddish-dun colour, is long and thick, but straight. It is capable of barking, although not so readily as the European dog, is very ill-natured and vicious, and snarls, howls and moans like dogs in common. Whether this is the only dog in New South Wales, and whether they have it in a wild state, is not mentioned, but I should be inclined to believe they had no other, in which case it will constitute the wolf of that country; and that which is domesticated is only the wild dog tamed, without having yet produced a variety, as in some parts of America. THE END. 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