i■ • it*.. :vtii ... ARMY MEDICAL LIBRARY FOUNDED 1836 r * WASHINGTON, D.C I PROSPECTUS OF A SERIES OF NEW WORKS, ENTITLED THE AMERICAN LIBRARY OF HISTORY; NOW PUBLISHING BY COLLINS & HANNAY and W. E. DEAN. Of all the numberless improvements which distinguish our age, there is none more remarkable, and more widely beneficial in its influence, than the introduction of a cheap popular literature for the use of those whose occupations or means deny them access to the larger and more expensive works which alone were thought worthy, but a short time ago, of the labours of the closet or the honours of the press. Among the high merits of the most enlightened statesman of his generation, is noted the creation of this valuable instrument of moral and intellectual ad- vancement; and the name of Brougham is associated in some manner with more than half of the publications which, at reduced prices, are now finding their way into houses in which the luxury of reading was, but a few years before, confined to a single book, or entirely un- known. In America, the advantages of such a literature must be strik- ingly apparent when we reflect that the only recognized distinction among us is the distinction of merit, and the only inferiority of the lowest orders, is an inferiority of knowledge occasioned by the diffi- culty or the impossibility of its attainment. Within a very recent period efforts have been made by enterprising publishers to reproduce here, for the benefit of their countrymen, the works of English writers in this new and most useful department of letters. To these efforts the public have corresponded in such a man- ner as to testify their full appreciation of the service, and of the intrin- sic excellence of the design. The " Family Library,'' the ''Cabinet Cyclopaedia," the "The Cabinet of History," with several others de- vised to the same end, and in the same spirit, have vindicated by their success the efficacy and the merit of the plan : and if the public spirited projectors in this country have in some measure reaped the fruit of their risk and their labour, they have but received the just reward of a public benefaction. Yet with all the excellences of the many works now offered to the world, with the laudable desire to extend among the poor and the young the advantages of education and knowledge, it appeared to the Proprietors that something still remained to be done; something without which the contemplated work of improvement could never be complete. The tone of even liberal writers in England cannot be ex- pected to come up to that standard which in the United States would be required to harmonize with the character of our institutions ; but it is a fact, which will not be denied, that of those very writers, whose literary eminence entitles them to a reprint in this country, the greater A number are of that class who inculcate opinions and doctrines the re- verse of those which, as Americans, we should desire our children to imbibe. It cannot be desirable that the early notions of those who will derive their principal stock of general knowledge from publica- tions of this kind, should receive them coloured with the prejudices of writers who have grown up in the midst of institutions, habits, and prepossessions opposed to those which the interests of this republic require in its citizens, or that their sentiments in regard to great poli- tical and moral revolutions should be shaped by the opinions of men who have formed their own conceptions of things on the data present- ed to them by the history of the old world, and who are unwilling or unable to concede their due authority to the influence of American his- tory, American manners, and American institutions. To supply the desideratum, which the best collections have thus left, iu our cheap and popular literature, the Proprietors have embarked in their present enterprise; and they offer their series, " The American Library of History," with a full conviction, that if the execution ol the several works shall merit the public approbation, they will not fail to receive that patronage upon which the success of their experiment must depend. The peculiar characteristics of this publication will make themselves manifest in its name ; and the Proprietors conceive that they have already sufficiently justified, in their reasons set fortn above, the admission of American productions alone into their collec- tion. In confining themselves to Historical subjects exclusively, they also believe that they are best consulting the wants and wishes of the community, inasmuch as all the publications of this kind which have preceded theirs, have been miscellaneous in their nature, and have no- thing in their character to constitute a series, with the exception of the uniformity of their outward appearance. By the means now proposed, it is obvious that works which are not calculated to promote the ends of general knowledge will not by any accident find a place in their list; and that when their series shall have embraced the history of nations, or when it 3hall, in other words, have come to constitute a cheap and popular universal history, it will be brought to a termination. The lives of individuals, as being too limited in their bearings, will not be considered as possessing historical value, unless their history be the his- tory of their times. Indeed, it must be evident, that if the biography of individuals can be admitted, the series cannot be brought to a close until the life of every illustrious character shall have had its separate tribute. The life of Wickliffe, of Alexander the Great, of Mahomet, of Buonaparte, is history; the- lives of Nelson and Belisarius, are me- moir and biography. In regard to their plan, the Proprietors need only observe in conclu- sion, that it will be their aim to furnish, in the works which they are now about to offer to the Public, an historical library, sufficiently de- tailed for all the purposes of the general reader, and in a form suffi- ciently attractive to engage his interest and secure his attention. The numbers already in preparation are: A History of the Turkish Empire in Europe ; A History of Florence ; A History of the Northern Nations of Europe; and A History of Persia ; upon which some of the ablest writers of our country have employed their pens. The editorial department of the publication is entrusted to the charge of Lorenzo L. da Ponte, Professor of Italian Literature in the University of the City of JVeio.York, from whom the Proprietors feel confident in assuring the Public it will meet with a faithful atten- tion and assiduous care. ELEMENTS ^ PHYSIOLOGY: A. RICHERAND, PROFESSOR OP THE FACULTY OF MEDICINE OF PARIS, MEMBER OF THE ACADEMIES OF VIENNA, PETERSBURGH, MADRID, TURIN, &Cj Stanslatett from the iFrencft By G. J. M. D E L Y S, M D. FIFTH EDITION. CAREFULLY REVISED AFTER THE NINTH AND LATEST FRENCH EDITION, AND SUPPLIED WITH NOTES AND A COPIOUS APPENDIX, JAMES COPLAND, M.D. LECTURER ON PHYSIOLOGY, PRINCIPLES OF PATHOLOGY, AND THE NATURE AND TREATMENT OF DISEASES ; CONSULTING PHYSICIAN TO QUEEN CHARLOTTE'S LYING-IN HOSPITAL ; SENIOR PHYSICIAN TO THE ROYAL INFIRMARY FOR CHILDREN ; MEMBER OF THE ROYAL COLLEGE OF PHYSICIANS, LONDON, &C. SECOND EDITION. NEW-YORK: W. E. DEAN, PRINTER, 70 FRANKFORT-STREET. COLLINS AND HANNAY ; COLLINS AND CO. J SAMUEL WOOD AND SONS J AND GRIGG AND ELLIOTT, PHILADELPHIA. 18^3. >. TO HALL1DAY L1DDERDALE, M.D. MEMBER OP THE ROYAL COLLEGE OF PHYSICIANS, LONDON, &C, THIS REVISED EDITION, THE NOTES, AND THE APPENDIX, AS AN ACKNOWLEDGMENT OF HIS PRIVATE AND PUBLIC WORTH, OF HIS PROFESSIONAL AND SCIENTIFIC ATTAINMENTS, AS WELL AS A SMALL TESTIMONY OF GRATEFUL RECOLLECTIONS OF HIS VARIOUS ACTS OF KINDNESS, &re venpetttulls Knacrflirt* BY THE EDITOR. dsi 7 Q i PREFACE TO THE PRESENT EDITION OF THE TRANSLATION, AND OF THE EDITOR'S NOTES AND APPENDIX. The Editor has endeavoured to revise the present edition, as care- fully as was in his power, after the latest French edition. He has been anxious to get rid, as far as he could, of the foreign idiom and obscurities which he found in the translation ; and he has introduced whatever new matter could conveniently be added to the body of the Work. He has made considerable additions to his Annotations, as well those which accompany the author's text, as those which form the Appendix. In order that the Work should not be too bulky, the Editor has enlarged the page much beyond the size of that of former editions. He has generally refrained from adducing in his Notes old or obsolete opinions, in order that he should have sufficient space wherein to discuss modern doctrines, and to state his own views. The former edition of the Editor's Notes contained opinions which he is not aware to have seen previously published, and which, indeed, were opposed to those generally believed in, even by the latest obser- vers and writers. Many of these opinions have since received con- firmation in the researches and writings of various continental phy- siologists. The reader will find them discussed as fully as the limits of the Notes could admit. The Editor, however, has still hopes of being able to bestow upon them these illustrations, and to give them that degree of developement, which they still require, and to consider them in their relations to the nature and treatment of diseases. This, however, cannot be satisfactorily performed on an occasion like the present, but must be made the object of a separate undertaking. 1, Bulstrode Street, Welbeck-Street, Cavendish Square, 9th May, 1829. THE EDITOR'S PREFACE TO THE FIRST EDITION OF HIS NOTES AND APPENDIX. The Author of the Notes to this Edition of the English translation of M. Richerand's Elements of Physiology has endeavoured to give a full, but concise account of the opinions recently offered on some of the topics embraced by the Work. He has not, however, confined himself to the bare detail of the views of others—he has frequently stated his own opinions. In doing this he has been as concise as the nature of his subjects would allow him. The office of an Annotator has not permitted him to bestow that copiousness of illustration on his own views which many may consi- der them to require : this will be attended to on another occasion. In the meanwhile, in whatever manner his opinions may be received, he will not shrink from a fair discussion of them ; he will always re- spect, and endeavour to profit by, a candid examination of them ; and he will espouse them no longer than he is perfectly convinced that they are founded on a correct interpretation of the operations of the animal economy. 1, Bulstrode Street, 5th June, 1824. THE TRANSLATOR'S PREFACE. It is a singular fact, that in this country, which has given birth to some of the most import* ant discoveries in physiology, there should not have been produced a single elementary of systematic work on the subject. Those only have written on physiology who had discove- ries to make known, and to these they have, in general, confined their publications. The consequence has been, that there are, in the English language, many works in different de- partments and on single points of physiological inquiry, and that our miscellaneous scien- tific publications, the transactions of societies, and periodical works of inferior importance, are stored with much valuable matter, both of new facts and original speculation : but till this is brought together, from the various quarters where it lies scattered, into some more comprehensive form, it is not truly within the reach of those to whom it would furnish an important part of their professional knowledge; nor, indeed, until it possesses some syste- matic work, embracing all that is known of the subject, can the country itself exhibit its claims on the scientific world for the service it has done to physiology. Such a work, however, which should fairly represent the state of physiology as it at pre- sent exists in Europe, was perhaps scarcely to be expected ; for though it should contain no discovery, it would be, if rightly executed, a work of great magnitude, and requiring quali- ties which do not often go together. The industry requisite for collecting materials from so great a number of writers in different languages—the judgment and profound knowledge of the subject necessary in the selection—the acuteness required in arriving at the truth, where the variety of opinions is so great,—are qualities rare in themselves, and still more rarely combined. The genius which inspired to the great English physiologists the important dis- coveries that have immortalised such names as Harvey, Hunter, Monro, seems as if it had unfitted them for the more laborious and ungracious task of compiling and arranging the dis- coveries of others. How seldom may we expect to meet with such a combination of genius and indefatigable industry as was seen in the great Haller; yet without a certain degree, at least, of the same qualities, no writer can pretend to tread in his footsteps. It is probable, too, that the great work itself of Haller, at the same time that it best illus- trates the importance of the undertaking and its dirfipulty, must be considered as having long remained, by its excellence, an impediment to the production of a similar succeeding work. Haller was fifty years engaged in the most ardent study of physiology : his work, besides all that he himself, the great leader in physiological discovery, and also the most exten- sive discoverer, wished to give to the world, of his own, contained all that was known on the subject at the time it appeared. As it was written, too, in the Latin language, it found a ready access to every school of medicine, and was every where received by the profession as, at once, the most authentic record of the facts of physiology, and the most luminous exposi- tion of the principles of the science. We cannot wonder, therefore, that while Haller had exclusive possession of physiology, no other writer should have attempted any work on the same subject, even for some time after his death, while the additions to the mass of know- ledge were not sufficient to effect any important change in the science. Now, however, enough has been added to change, in many important respects, the face of the science, and to demand systematic arrangement. Of late years, accordingly, several works, composed with this view, have appeared on the continent; amongst which may be mentioned those of Blumenbach, Bichat, Dr. Dumas of Montpellier, and JVi. Richerand. This priority in the systematic, arrangement of our knowledge does not, however, at all imply that the progress of physiology abroad has been more rapid than in this country. It would be difficult to say where it is furthest advanced. If a comparative view were to be given of the science, as it exists in Britain and on the continent, it would rather appear that a different excellence has been attained on either side, accompanied, of course, by different defects. In Britain, it might be shewn that it is founded on sounder principles, and more freed from the doctrines of the older physiologists, who were rather given to invent explana- tions of the phenomena of nature, than to seek them in the laborious investigation of her operations. The physiologists of this country have studied with intelligent, patient, and zea.ous research, the facts of physiology ; they have distinguished themselves in this, as in Vlll TRANSLATOR'S PREFACE. the other sciences, by an anxiety for exactness of knowledge. The continental physio- logists are fond of theory; an adherence even to the old theories characterises, very remark- ably, the works of the most modern foreign writers on medicine and surgery, influencing even the practice of the profession in a very unfavourable manner. But this spirit of theo- rising—this anxiety to extend individual facts into general principles, is as essential to the progress of the science, as that zeal in the acquisition of knowledge which prepares its ma- terials. They carry this spirit to excess ; but which is the most dangerous error to science I will not pretend to determine—that impatient activity of mind, which, in its eagerness to theorise, will not wait for fulness of knowledge,—or that over distrust of theory, which is not judicious caution, but timidity, or indolence, or a real want of intellectual disposition to high philosophic speculation. The same comparison would shew a superiority in another respect, in the physiologists of this country—that they have made further progress in pathological physiology. They have applied themselves more to the study of nature under disease, investigating both the disorder- ed functions and the altered structure of disease, and seeking to understand, and successful- ly availing themselves of, the powers of renovation and substitution, which are provided in the body for injuries of its original organisation ; drawing, in short, from physiology a light to the intelligence and practice of their art. The continental physiologists, on the other hand, have rather endeavoured to bring light from other sciences to physiology. And though here, too, their speculations have borne the same character of precipitancy, there is no doubt iheir labours in this department have been attended with considerable success; and that while many of their applications and analogies have passed away from the public mind al- most as soon as they were before it, much still remains that will be permanently received as convincing illustration, from the sciences of inanimate matter, of the processes of living nature.* This different direction of the spirit of inquiry in different countries, has probably been fa- vourable to the rapid progress of the science. Yet something has been lost to it by what was not at all a necessary consequence of such a division of labour, a disregard of each other's pursuits and acquisitions. Both here and abroad, we have every day discoveries brought forward by writers, who are very legitimate discoverers, if real ignorance of the previous knowledge of others entitle to the name of originality. These imagined discoveries are pro- secuted with infinite zeal, and much good labour is lost to physiology, in bringing facts to light that were well established in the world before these authors were born- The Work now given to the public can scarcely be offered as a remedy, as far as this country is con- cerned, of the inconvenience; for though it contains a good summary of the knowledge and opinions of modern physiologists, arid does very fairly represent the present state of the sci- ence on the continent, those who really desire to possess themselves of what has been done there will be aware that they must undertake a much more laborious study, and seek for the information they want, in most cases, at its original sources. This work, I believe, will be chiefly useful for the purpose which was designed by the au- thor,—as an elementary book for students. There is not, as I have said, one English ele- mentary work on physiology; scarcely, indeed, on any part of our professional knowledge. Whether it be that there is more literary industry abroad, or that in the institutions for medi- cal education the public teachers are. more separated from their profession and devoted to the duties of instruction, it is certain that in all departments of professional study they have dis- tinguished themselves by the number and ability of their elementary works; and in the sci- ence of physiology in particular, the English student who is desirous ,of engaging in it will find himself at a loss for a guide, among the names that have done honour to science at home, and compelled to seek assistance in his pursuit from the writers of other countries. An eloquent modern writer on anatomy complains that too much attention is now bestow- ed on physiology, while anatomy, on which sound physiology ought to rest, is neglected. That anatomy ought to be made the ground-work of all medical education, and that a tho- rough knowledge of the structure of the human body ought to precede the study of its func- tions, is indisputable ; nor does the truth of this opinion appear to be denied by any one in the present day: and, accordingly, anatomy appears every where to be cultivated with ardour. In all places of medical education, the number, both of teachers and students of anatomy, is increased in much greater proportion than in any other department of professional study. Dissection is now considered as essential in the study of anatomy, and almost a new system of minute surgical anatomy has been instituted within a few years. * It was in the contemplation of the transla- compensation to himself for the unsatisfactory tor, when he undertook this Work, to have en- labour of translation. It is not till towards the gaged, in some degree, in the comparison of close of the work, of which the translation and which he has here spoken. He intended to an- printing have been unavoidably going on to- nex to it, in the form of an Appendix, a compa- gather, that he finds the time to which it was of rative view of the opinions entertained in this importance to the publisher to fix the publica- country, and on the continent, on many inter- tion, does not allow him to complete his original esting points of physiology, which might serve intention. the purpose of notes to the work, and be some translator's preface. IX There appears no reason, then, to complain that anatomy has been neglected ; and if there were, it is not to physiology the neglect could be imputed. The number of teachers of ana- tomy, of medicine, and surgery, is more than four times what it was half a century ago, but the number of teachers ofphysiology remains nearly the same. Physiology is either not taught at all, or forms a very insignificant part of a course of anatomy. A professed course of physiology is, at present, scarcely delivered any where out of the metropolis; and even there, only one lecturer is found to undertake such a course. It is not true that in this country physiology absorbs too much of the attention of students, and interferes with more important studies ; it may rather be said to be too little attended to as a branch of instruction: it is omitted until the engagements of the profession leave no time for the prosecution of a labo- rious study; and it is, in the end, neglected altogether. If physiology, if the knowledge of the healthy functions, be necessary to him whose object in life is to understand the functions of the body in disease, it is of consequence that physiology be more generally studied, that it be considered more as an essential object of professional education, that our public teach- ers bestow on it a greater share of their attention. Let it not be objected to the public teaching of physiology, that it may be learnt from books as well as from lectures. The objection, if valid, would be equally applicable to most of the other departments of professional study, the objects of which do not admit of ocu- lar demonstration ; yet no one objects to lectures on medicine, materia medica, &c. This study, however, does require the frequent illustration of anatomy, of drawings, of preparations, and even of experiments, which are within the reach of few. The study of physiology in books alone is dry and uninteresting to the young student, and will never be prosecuted with ardour. It seems too much to rely on the capacity for solitary study of young minds j and, at all events, the study of physiology, as of any other science, by a number of young men under one teacher, will be more ardent, from the frequency of discussion and experi- ment, than if carried on by each separately. To study physiology with any effect, the stu- dent should have access to public lectures on the subject, in which he will see experiments and preparations, besides such dissections in human and comparative anatomy as may be re- quired to illustrate the doctrines he hears : he will then be qualified to turn his private stu- dies to account, and will pursue them with interest. Haller, who may justly be termed the father of physiology, was himself a distinguished lecturer, and his mode of instruction may be safely followed. He was a pupil of the cele- brated Boerhaave, and when he himself became a public teacher, the doctrines of that great man had possession of the schools: these doctrines he tells us, in his preface to the Primae Lineae Physiologiae, he continued to teach for twenty-four years, using the work of his illus- trious teacher, as he calls him, for his text-book; but finding that since the time of Boer- haave many improvements and discoveries had been made in the science, he thought it right to substitute an elementary work of his own, containing the more recent discoveries; and this work he addressed to his class. Physiology is improving, and new discoveries are daily added to the store of knowledge already in our possession. If all these scattered materials were brought together, a work might be grounded on them of the highest value to the public teacher who has to communicate instruction, and to the student who has to meditate, in pri- vate and at leisure, on the knowledge that has been rapidly communicated to him in a public lecture. This object is, as was already observed, in part fulfilled by the work of M. Rich- erand, though incompletely as far as respects this country, as it does not embrace sufficient- ly the state of the science in Britain. Birmingham, Sept. 14, 1812. THE AUTHOR'S ADVERTISEMENT TO THE FIFTH EDITION. In preparing for the press this Fifth Edition of his Work, the Author has carefully revised and corrected it, in all its parts, so as to render it more worthy of the success it has already obtained. The additions which have been made will be found not to consist of idle dis- courses or frivolous hypotheses. The ground-work and the order are the same, the Author has merely added to the mass of facts,—supported, by additional proofs, the opinions which he had advanced,—and developed those parts of his subject, which, from being explained in too concise a manner, might be involved in some degree of obscurity. Among the variety of opinions which criticism, oftener unjust than enlightened, has pro- nounced,, in judging this Work, there is one which requires to be refuted, because it proceeds from an erroneous idea of what an elementary work should be. The Author, it has been said, ought to have contented himself with giving a view of the present state of the science, without any additions of his own; and he should have abstained from inserting new opinions, which, until they had received the sanction of the learned world, ought not to have been introduced into an elementary work. This objection may be answered by considering that modern physiology being, in some measure, a new and regenerated science, there will be found, in treating of it to its full extent, many deficiencies to be filled up, and many doctrines evidently erroneous for which truths are to be substituted, which it is of importance to dis- cover. Lavoisier, in his Elements of Chemistry, set forth, in a methodical order, truths which he himself had discovered : he introduced original ideas, not such as owe an appear- ance of originality to minute explanation of what is already known, or to a general want of erudition, too prevalent in the present day. One of his most illustrious colleagues, in des- cribing the state of the science, has likewise given a history of his discoveries and labours, and men of the soundest judgment ascribe the astonishing progress of chemistry, in a great measure, to the favourable circumstance of our possessing elementary works written, by the most distinguished chemists. The present work has been translated in England, in Spain, in Italy, in Germany, and men of merit have not disdained the task. Since the publication of the Fourth Edition of this Work, Professor Sprengell has published his Institutes of Physiology.* The date of that new work, and the well-deserved reputation of its author, entitle it to be considered as a faithful account of the state of physiological science in Germany. In that work the reader will be astonished to find it stated that every thing in the human body is governed by polar influence and by the laws of antagonism ; that man is in a state of positive electricity ; that his body is formed chiefly of oxygen; while the female body is in a state of negative electricity, with a superabundant quantity of hydrogen in the composition of its solids and fluids. Thus, by the premature application of a few facts borrowed from the physico-che- mical sciences, the learned of Germany have thrown back physiology into the uncertainty of conjectures and hypotheses. On the other hand, Gall, by his anatomical discoveries on the organisation of the brain and nerves; and a few other physiologists, by their experiments on living animals, have been usefully employed in advancing the progress of physiology. The Author has been anxious to increase the value of this new edition bv adding to it the result of their observation*. * Inttitutiones Physiologic^. Amstelod. 1809, 2 voL 8vo. PREFACE TO THE FIRST EDITION* These Elements of Physiology, which contain an abstract of the doctrines I have taught for several years past in my public lectures, are written on the model of the small work on Physiology of the great and immortal Haller, {Prima: Linear Physiologic). I am far, how- ever, from presuming to say that I have equalled the merit of a work which, as is remarked by a man of the highest ability.t when it appeared, gave a new aspect to the science, and commanded universal approbation. If these new Elements of Physiology deserve any pre- ference over that work, the honour is not due to the Author, but to the times in which he writes, enriched by the progress of the physical sciences, with a multitude of data and re- sults that may be said to have rendered Physiology altogether a new science. It will be easily perceived that the plan I have adopted differs essentially from that follow- ed by several respectable physicians : and that the treatises on Physiology, most lately pub- lished, resemble the present only in their title. In combining a great number of facts, in adding to those already known the result of my own observation and experience, and in con- necting them, by a method that should unite accuracy and simplicity, I have had it in view to keep a due measure between those elementary works whose conciseness approaches to obscurity and dryness, and those in which the authors, omitting no detail and exhausting in a manner their subject, seem to have written only for those who have leisure or inclination for the profoundest study. Should any conceive that the present undertaking is above the capacity of my age, I will say, even at the risk of a paradox, that young men are perhaps fittest to compose ele- mentary works, because the difficulties they have encountered in the study are yet fresh in their memory, as well as the steps which they have taken to overcome them; and further, because their recent experience points out to them the defects and advantages of the differ- ent methods of other instructors :t so that he who in the shortest space of time has carried to the greatest extent his own acquisition of sound knowledge, will, in some respects, be the best guide to his successors in the difficult and perplexing paths of elementary study. In the composition of the work I have borne constantly in mind the necessity of sacri- ficing elegance to clearness, which I know to be the most important merit of an elementary treatise. Further, I have throughout followed, I believe, the same arrangement in the succes- sion of the subjects, and applied to the science of living man the principle of the associa- tion of ideas; a principle so well developed by CondiUac, in his Treatise on the Art of Writing, and to which that philosopher has shewn that all the rules of the art are to be re- ferred. Notwithstanding the rigorous law to which I have subjected myself, I have, after the example of the ancients, and, among the moderns, of Bordeu, and of several other fhysicians and physiologists of equal celebrity, thought myself justified in employing, when felt it necessary, metaphorical expressions; because, as has been justly observed by a wri- ter who has been, in our own times, an honour to her sex, if conciseness do not consist in the art of reducing the number of words, still less does it consist in depriving language of imagery. The conciseness which is to be envied is that of Tacitus, at once eloquent and * Published in 1801. ferences."—Vicq-D'Azyr. f " When Haller published his Prima Linece J " The best order in which truth can be set Physiologic, which he valued most of all his forth, is that in which it might naturally have works, a considerable sensation was excited in been discovered ; for the surest method of in- the schools. In works on the same subject, it structing others, is to lead them along the path was customary to find long dissertations, almost which we ourselves have followed in our own always void of proof, extraordinary opinions, instruction. In this way we shall seem not so or brilliant fictions. It was matter of wonder, much to lay before them our own knowledge, that in Haller's work there should be found only as to set themselves on the search and discovery numerous facts, precise details, and direct in- of unknown truths,"—Condillac. Xll PREFACE. energetic; and, far from any fear that imagery should injure that justly-admired compression of style, figurative expressions are, indeed, those which comprise in fewest words the greatest sum of ideas.* Those who insist on meeting, in a work on Physiology, with a romance instead of the history of the animal economy, will, no doubt, reproach me with having entirely neglected a great number of hypotheses, ingenious or absurd, on the uses of organs; with having omitted, for example, while speaking of the spleen, to mention the opinion which considers that viscus as the seat of mirth and laughter; with having said nothing of the opinion of those authors who conceive it to maintain, by counterpoising the liver, the equilibrium of the two hypochondria ; nor even of the doctrine of the ancients, who ascribed to it the ex- cretion of the atrabilis, &«. To recall such errors for the sake of elaborate refutation, would be wasting much precious time in idle discussions, and possessing, as Bacon calls it, the art of making one question bring forth a thousand, by answers more and more unsatisfactory. I have chosen to forego all such vain parade, from a clear conviction, that works of merit are as often distinguished by some things that are not to be found in them, as by those they do contain. Several authors, in treating of the science of man, have indulged themselves in frequent excursion into the vast field of accessory sciences, and have, without necessity, incorporated in their works whole chapters on air, on sound, on light, and other subjects which belong to the department of natural philosophy and chemistry. Haller himself is not entirely free from blame, for having discredited Physiology by this borrowed display. I have introduced only such general ideas of the subject as were absolutely necessary to render my own intel- ligible, and were, indeed, too closely connected with it to admit of separation. One of the principal faults of writers on Physiology is, that they are apt to fall into fre- quent repetitions ; and that fault is often owing to the difficulty of settling satisfactorily the limits of actions which are mutually connected and dependent among themselves, and run- ning into each other, like those that are carried on in the animal economy. "In composition, one should avoid prolixity, because it is fatiguing to the mind; digres- sions, because they divert the attention ; frequent divisions and subdivisions, because they are perplexing; and repetitions, because they are oppressive. What has been once said, and in its proper place, is clearer than if several times repeated elsewhere.''t In following these precepts, and they cannot be too much attended to, one may, it is true, incur the risk of being thought superficial by superficial readers, who form their opinion of a work from the perusal of a single chapter; but a most ample compensation will be found in the opinion of those who choose to be thoroughly acquainted with a work before they pass on it their final judgment. After having stated in what spirit this work has been written, I may say something of the motives which have led to its publication. I would mention, in the first place, the advantage which, it might be expected, would accrue to the science, and to those who are engaged in its pursuit;- and, in the next place, the satisfaction which study has in store for him who bestows on it the time he can snatch from the laborious practice of our art. In his short intervals of leisure from public instruction and from professional duty, left to himself and his own thoughts, in the silence of study, and in the calm of meditation, he looks down with an eye of pity on those who drag on, through the lowest intrigues, a despicable existence, and finds his consolations against the endless vexations that are prepared for him by super- cilious ignorance and jealous mediocrity. r * De la Literature, considiree dans ses rap-. t CondiUac, Essai sur I'Origine des Con- ports avec les Institutions Societies, par Madame noissances ffumaines, second© partie, sec. ii, de Stael Holstein, tome ii. chap. iv. ANALYTICAL TABLE CONTENTS. Page Dedication iii Preface by the Editor v -------■— to the First Edition of his Notes and Appendix vi ------by the Translator vii ------by the Author x ---------to the First Edition xi Preliminary Discourse. — Physiology— the sience of life. Definition of life, 1. Sect. I. Of natural beings.—They are inor- ganic or organised—the former are simple or complex ; the latter always complex, and distin- guished into vegetable and animal. Reciprocal dependence of all these beings, 1. Sect. II. Of the elements of bodies. — The elements of bodies. Their number forty-four ; but it is probable that several appear to us sim- ple, from the imperfection of our means of ana- lysis, 2. Sect. III. Differences between organised and inorganised bodies. — Differences between or- ganised and inorganised bodies, 3. Homoge- neousness of the latter ; complex nature of the former ; necessary co-existence of fluids and solids in all organised and fliving beings ; sim- plicity of inanimate matter ; complex nature and tendency to decomposition of organised bodies, 4. Sect. IV. Differences between animals and plants. — Differences between animals and plants, 5. The great distance between the mi- neral and vegetable kingdom ; a considerable approximation, on the contrary, between ani- mals and plants, 6. Of all the characters which mark the differences between these substances, the most remarkable is the presence of an ali- mentary tube, which is found in every animal from man down to the polypus, 6. In all ani- mals, nutrition is performed by two surfaces, especially by the internal; the alimentary canal is the most essential part of their body, 7. It retains life longer than any other part; experi- ments disproving Haller's opinion on this sub- ject, 7. Sect. V. Of life.—Consists of a number of phenomena proportioned to the complication of the organisation, 8. Simple in plants, in which its actions are limited to nutrition and reproduction, 8. Of life in the polypus ; this animal consisting merely of a sentient and con- tractile pulp, shaped into an alimentary cavity, 9. Of life in worms, 9. In crustaceous ani- mals, its apparatus more perfect, 10. Of life in cold-blooded animals, 10. In warm-blooded ani- mals and in man, 11. General view of the hu- man organisation, 11. Of the elementary fibre, 13. Dependence of life on the oxidation of the blood in the lungs, and on the distribution of this vivified blood throughout the organs, 14. Sect. VI. Of the vital properties, sensibility and contractility. — Those two properties not possessed in an equal degree by all living bodies, 14. Modifications of sensibility in dif- ferent organs, 17. Observations on the con- tractility of serous membranes, 18. Caloricity, 19. Laws of sensibility, 20. Influence of sleep, of climate, of the seasons, of the age, &c. on the vital properties, 22-24. Sect. VII. Of sympathies.—Of sympathy, 24.—Diseases arising from association ; syner- gies, 26. Sect. VIII. Of habit. — Of habit, 27. It uniformly lessens physical sensibility, 28. A curious fact, shewing the effects of habit, 28. Habit impairs the sensitive power, but improves the judgment, 29. Sect. IX. Of the vital principle.—The vital principle not a being existing by itself, and in- dependently of the actions by which it mani- fests itself, 31. A perpetual struggle in organis- ed bodies between the laws of the vital prin- ciple and those of universal nature, 32. The vital principle resists the laws of chemistry, of physics, and mechanics, 32. There takes place, however, in the animal economy, chemical, physical, and mechanical phenomena, but they are always modified by the vital principle, 32. Influence of the stature on the energy of the vital powers and even on longevity, 33: Vis medicatrix naturae, 34. Theory of inflammation, 35. Analogy between the turgescence of an inflamed part and of one in a state of erection, as the penis, &c. 36. Indirectly tonic influence of cold, 37. Sect. X. Of the system of the great sym- pathetic nerves.—These nerves are to be con- sidered as connecting the organs of the func- tions of assimilation, as the cerebral nerves unite that of the external functions, 37. They are the only nerves found in several animals without vertebra?, 38. They arise from all the vertebral nerves, from which they receive fila- ments, as well as from the fifth and sixth cere- bral pairs, 38. Ganglions of the sympathetic nerves ; the semi-lunar ganglion the principal, 38. The great sympathetics render the internal organs independent of the will, 39. Pathologi- cal relations of the great spmpathetic, 41. Sect. XI. Of the relations of physiology to several other sciences.—The relation of physio- logy to physics, chemistry, and mechanics, 41. Connexion of physiology with human and com- parative anatomy, 43-45. Its connexion with medicine, 46. Sect. XII. Classification of the vital func- tions.—The best division of the vital functions is that which was first pointed out by Aristotle, adopted by Buffon, and completely developed by Grimaud, 47. Modifications of which this xiv CONTENTS. division is susceptible ; preservative functions of the individual or of the species, 48. These two great divisions further divided into two orders, 48. Other classifications of the func- tions, 48. Why man is subject to more diseases than other animals, 50. Of the arrangement of this work, 52. The voice is a natural connexion between the pre- servative functions of the individual and those of the species, 53. The history of the ages and temperaments, and of the varieties of the human species ; the account of death and putre- faction forms a separate appendix, 53. Table of the classification of the functions, as adopted in this work, 54. FIRST CLASS. FUNCTIONS SUBSERVIENT TO THE PRE- SERVATION OF THE INDIVIDUAL. ORDER FIRST. FUNCTIONS OF ASSIMILATION. , CHAPTER I. On digestion. Definition of this function, 57. General con- siderations on the digestive apparatus 57. Con- nexion between the nature of the aliment and the extent of the digestive tube, 57. Of ali- ments, 58. The nutrient principle obtained from the aliment, by our organs, is always the same, 59. Of the nature of the alimentary principle, 59. Differences of regimen, accord- ing to the climate, 60. Of hunger, 62. Of thirst, 64. Mastication, 65. Action of the lips, of the cheeks, of the tongue, of the teeth, of the jaws, 65-67. The salivary solution, 67. Deglutition, its mechanism, 69. Deglutition of fluids and of gaseous substances, 70. Of the abdomen, 70. Of digestion in the stomach, 71. Different systems of digestion ; of con- coction, fermentation, 72. Of putrefaction, 73. Of trituration ; of digestion in granivorous fowls, 74. Of maceration, 75. Phenomena of rumination, 75. Of the gastric juices, 76. Its source, its quantity, and solvent qualities, 76, 77. Digestion chiefly consists in the solution of the aliment in this fluid, 78. Singular case of a fistula of the stomach, 80. Chemical con- stitution of chyme, 81. Action of the stomach, 82. Functions of the pylorus, 82. Of nervous influence in digestion, 84. Of vomiting, 85. Digestion in the duodenum, 86. Analysis of chyme taken from the duodenum, 87. Of the bile and its secretory organs, 87. Circulation of the blood in the liver, 88. Uses of the spleen, 89. Of the pancreas and pancreatic juice, 90. Separation of the alimentary matter into two substances, the one chylous, the other excre- raentitious, 91. Of the action in the small in- testines, 92. The uses of their curvatures and valvular conniventes ; of the peristaltic motion, 92. Of digestion in the great intestines, 93. Uses of the appendicula vermiformis of the cae- cum, 94. Of the evacuation of the faeces, 94. Intestinal gases, 95. » Of the secretion and excretion of the urine, 96. Of the calibre of the renal arteries, struc- ture of the kidneys, 96. Action of the kidneys and ureters, 98. Accumulation of the urine within the bladder, 99. In what manner it is expelled, 100. Physical qualities of the urine, 102. Chemical analysis of this fluid, urea, 102. Its retention produces urinous fever, 103. Ex« periments on the effects attending retention of urine by tying the ureters in living animals, 103. Urea, 104. Occasional changes in the urine, 105. Urinary calculi, 106. why most frequent in cold and damp climates, 107. CHAPTER II. Of absorption. Absorption takes place in every part of the body, both on its surface and in its internal parts, 107. Absorption more or less active in different circumstances, 107. Its activity is very slight on the external surface, except where the skin is thin and the epidermis moist, 107. Absorbing mouths, 110. Their mode of ac- tion in absorption, 110. Of the lymphatics, 111. Their innumerable anastomoses, from the union of which there is formed a mesh-work envelop- ing the whole body, 111. Pathological infer- ences, 112. Of the conglobate glands, 113. Their action, 113. Circulation of the lymph, 113. Morbid states of the absorbent system, 114. Observa- tions on cancer, 115. Of the thoracic duct, 115. Of the physical and chemical properties of the lymph, 116. CHAPTER. III. Of the circulation. Definition and general idea of this function! 118. Of the structure and action of the heart, 118; uses of the pericardium, 119. Connexion between the bulk of the heart and strength and courage, 119. Singular case of communication between the two ventricles, 120. Structure of the heart, 121. Action of the heart in circula- tion, 122. Decurtation and pulsation of the heart every time the ventricles contract, 124. The quantity of blood which these cavities send out along the arteries, 124. Action of the arteries, 125 ; their arrange- ment and anastomoses, 125. Of the structure of the arteries, the force and contractility of their different coats, 126. Dilatation of the ar- teries, 129. Of the pulse and its varieties, 130 Velocity of the circulation along the arteries, 131. Of the capillary vessels, 132. Those which convey a colourless fluid, 132. Of the manner in which the blood flows along these vessels, 133. Terminations of the arterial system, 134. Functions and conditions of the capillaries, 134. Of the action of the veins, 135. Proportion of the arterial to the venous blood ; difference of arrangement and structure between the ar- teries and veins, 136. Of the use of the valves of the veins, 137. Of the use of the vena azygos, 138. Gradual increase of velocity in the venous circulation, 138. Reflux of the blood in the great venous trunks, 138. Theory of the circulation, 139. Of the systemic cir- culation, 139. Partial circulations in the midst of the general circulation, 140. Of the pul- monary circulation, 140. Of the two divisions, venous and arterial, of the circle of circulation, 140. Organs situated on the two points of in- tersection of this great circle, 141. CHAPTER IV. Of respiration. Of all the changes which the blood under- CONTENTS. XV goes, in penetrating through the organs placed in the course of the circulation, the most re- markable are those it receives from respiration, 141. Differences of arterial and venous blood, 142. Of the atmosphere, 142. Mechanism by which respiration is performed, 144. Motions of the ribs, 145. Action of the respiratory muscles, 145. Difficult respiration, 147. Of inspiration, 147. Of expiration, 147. State of the lungs during inspiration, 147. Of the pul- monary vessels, 148. Structure of the lungs, 148. Use of the bronchial arteries, 148. Pul- monary inflammations, 149. Absorbents of the lungs, 149. Changes on the air and on the blood by respiration, 150. Vitality of the lungs, 153. Respiration of certain animals, 153. Division or ligature of the eighth pair of nerves, 154. Of animal heat, 155. Animal heat is inde- pendent of the media in which animated beings live, 155. The heat of the animal body thirty- two degrees, 156. The lungs not the only parts in which caloric is disengaged, 156. Caloric evolved, to a certain degree, in all organs receiving arterial blood, 157. Cutaneous eva- poration the most powerful means of lowering the temperature, 158. It does not explain, how- ever, why the animal temperature remains the same, in a medium hotter than the body ; case of a man said to be incombustible, 159. Causes enabling the body to resist cold, 160. Effects of cold, 160. Source of animal heat, 161. Phenomena of the circulation of the blood through the lungs, 161. Pulmonary exhalation, 162. Of asphyxia, from drowning and from strangulation, 163. From noxious gases and from intoxication, 164. From obstruction of the glottis ; of-the asphyxia of new-born child- ren, 165. Of several phenomena of respiration, as sigh- ing, yawning, sneezing, coughing, hiccup, and laughter, 165. Cutaneous perspiration, 167. Its connexion with the other functions, 167. Its quantity, 168. Of the sweat, 168. Of the for- mation of carbonic acid gas on the surface of the skin, 169. Of the use3 of the cutaneous perspiration, 169. CHAPTER V. Of the secretions. Classification of the animal fluids, 170. Che- mical classification of the fluids by Fourcroy, the best, 170. Other classifications, 170. Of the blood, 171. The constituent parts of the blood, 171. Of the ultimate elements of the blood, 172. Of the changes in the blood, 173. Of the transfusion of blood, 175. Of the secretions, 176. Of arterial exhala- tion, 176. Of follicular secretion, 177. Secre- tions of conglomerate glands, 177. Accidental secretions, 178. Of nervous influence on se- cretion, 179. Of the secretion of synovia, &c. 180. State of the circulation during secretion, 181. Influence of the brain and of the mind on the secretions, 182. Quantity of fluids se- creted, 183. Of other secreting parts, 183. Of the secretion of adeps, 184. Circumstances which increase or lessen its secretion, 184. Of the use of the fat, 185. Of the secretion of the marrow, 186. Insensibility of the medullary membrane, 187. CHAPTER VI. Of nutrition. Nutrition is the complement of assimilation, 187. Period of the complete renovation of the body, 188. Process of nutrition, 188 ; from ar- terial blood only, 189. Substances capable of yielding nutrition, 189. Difference of vegeta- ble and animal substances, 189. New products, 189. Changes produced in alimentary sub- stances, 190. Of the emunctories, 191. Ge- neral view of the functions of nutrition, 192. Man enjoys sensation in its greatest perfection, 193. SECOND ORDER. FUNCTIONS WHICH TEND TO THE PRE- SERVATION OF THE INDIVIDUAL, BY ESTABLISHINGHIS RELATIONS WITH THE BEINGS THAT SURROUND HIM. CHAPTER. VII. Of sensations. Of light and of colours, 194. Organ of sight, 195. Formed of three distinct parts, 195. Use of the eye-lids, eye-lashes, and lachrymal ducts, 195. Eye-ball, its structure, 198. Chemical analysis of the different parts of the eye, 199. Mechanism and phenomena of vision, 201. Structure and motions of the iris, 202. Re- fraction of the rays of light by the membranes, 203, and by the fluids of the eye ; inversion of object on the retina ; point of distinct vision, 203. Defects of vision, 204. Developement of the eyes and their motions, 205. Errors of vision, 206. Its difference in different animals, 206. Of sound, 207. Organ of hearing, 209. Structure of the ear, and mechanism of hearing, 209. Differences in animals, 210. Pathologi- cal physiology of hearing, 211. Of odours, 212. Organ of smell, 213. Sen- sation of smell, 213. Of flavours, 214. Of taste 215. Of the tastes of different substances ; or- gan of taste, 215. In different animals, 215. Uses of the nerves of the tongue, 216. Gal- vanic experiments on this subject, 216. Of touch, 217. Its certainty and errors, 217. Of the integuments, 218. Of the nails, 221. Of the hair, 222. The sense of touch, 224. Of the hand, 224. Touch in different animals, 225. Of the nerves, 226. Of their origin in sen- sible parts, 226. Of their structure, 226. Opi- nion of Reil on this subject, 226. Of the man- ner they arise from each other, 227. Distribu- tion of the nerves into four different kinds, 227. Of their termination in the brain, 228. Of their comparative size in different animals, and in man at different ages, 228. Of the spinal chord and its functions, 229. 230. Of the coverings of the brain, 230. Me- chanism of the bones of the skull and face, 231. Uses of the sphenoid, 231. Rounded form of the skull, 233. Uses of the dura ma- ter, of the arachnoid, and the pia mater, 234. Size of the brain, 235. Form of the head, 235. Connexion with the intellectual powers, 236. Structure of the brain, 236. Nerves crossing^ 237. Divergent and convergent fibres, 237*. Cerebral circulation, 238. Arterial blood re- tarded, 239. Jugular veins, 240. Connexion of the action of the brain and heart, 240. Theory of syncope, 241. Motion of the brain, 243. Experiments shewing the cause of the brain's motion, 246. Actions of the nerves and XVI CONTENTS. brain, 249. Principle of motion and sensation, 251. Different intellectual functions of differ ent parts of the brain, 251. Not yet perfectly understood, 252. Analysis of the understanding, 252. Sources of our ideas, 253. Peiception, 253. Reasoning and instinct, 254. Generation of the faculties, 254. Sensation, perception, attention, memory, imagination, association of ideas, comparison, judgment, reasoning, 254. Influence of signs on the faculties of thought, 256. Analysis of ideas, by Tracey, 258. Derangements of the mind, 258. Mania, 259. Idiocy, 260. Of the passions, 261. State of the intellec- tual powers connected with them, 261. Effects on the animal economy, 262. Of sleep and waking, 263. Repose of the functions which connect us with surrounding objects ; condition of the functions of assimilation during sleep, 264. Proximate causes of sleep, 266. Of dreams and somnambulism, 267. Animals are also sub- ject to dreams, 268. CHAPTER VIII. Of voluntary motions. This chapter treats only of voluntary mo- tions, whose organs may be distinguished into active and passive (the bones, and the muscles), 269. Structure and properties of muscular fi- bres, 269. Of the tendons and aponeuroses, 271. Phenomena of muscular contraction de- termined by an act of the will, 271. A sound state of the nerves, arteries, and veins be- longing to a muscle, necessary to its action, 272. Theory of this action, 272. Preponde- tance of the flexor muscles over the extensors, 273. This preponderance varies, according to the age, and'the state of health or disease, 275. Pathological physiology of muscular action, 275. Of the power of the muscles ; it bears a proportion to the number of their fibres, 276. The degree of dccurtation of which they are capable is proportioned to the length of their fibres, 277. Direction of the motions perform- ed by the action of the muscles, 278. Of the fixed point or fulcrum in muscular action, 278. Of muscular flesh, 279. Galvanism, 280. Volta's apparatus or gal- vanic pile, 283. Effects of galvanism" in the treatment of disease, 285. General view of the osseous system, 286. Of the vertebral column ; it forms the most essential part of the skeleton, 287. Difference ot the stature at different times of the day, 288. Of the lower limbs, 289. Structure of the bones, 289. Uses of the periosteum and of the marrow, 291. Theory of necrosis, 291. Of the articulations, 292. Of the articulating car- tilages, 292. Of the synovia, 293. Theory of anchyloses, 294. Of animal mechanics ; of standing, 295.. Of the centre of gravity, 295. Tendency of the body to faff, 296. Standing is performed by an effort of the extensor muscles, 296. Reasons why it is impossible for a new-born child to stand, 296. Man is the only animal that can stand upright, 299. Of falls, 302. Of standing on one foot, 302. A degree of separation of the feet necessary in standing, 302. Of kneel- ing ; of sitting; of the recumbent posture, 303. Of lying on the sides, 303. Of the prone and supine postures, 304. The different modes of the recumbent posture have a reference to "the degrees of facility of respiratibn and to [the period of life, 305. Recumbent posture, on an Inclined plane, necessary, especially to olef people, 305. Of motions of progression ; of walking, 306. Of walking up or down an in- clined surface, 307. Mechanism of the arti- culation between the leg and foot, 308. Of running, 309. Of leaping, 310. Leaping is per- formed by the sudden extension of the lower extremities, previously inastate of flexion, 311. Of the vertical and oblique leap, 312. Of swim- ming ; man swims with difficulty, 312. Swim- ming natural and easy to fishes ; its mechanism, 313. Of flying, 313. The structure of the body in birds is favourable to this action ; how performed, 314. Of crawling, 315. All the phe- nomena of animal mechanics may be referred to the theory of the lever of the third kind, 315. Partial motions performed by the upper extre- mities, 317. Of climbing ; of pushing, 317. Of throwing a projectile, 318. Partial motions, as signs expressive of ideas, 319. Of gestures. and attitudes, 319. CHAPTER IX. Of voice and speech. Definition of the voice and of speech ; cir- cumstances necessary to the formation of the voice ; its organs, 319. Opinions of Ferrein and Bodart, on the uses of the glottis, 320. The larynx is at once a wind and a stringed instrument, 321. Of the power of the voice ; of speech ; man alone is capable of speech, 322. Of the vowels and consonants, 323. Of song and music, 323. Of stammering, burr, and dumbness, 324. Instruction of the deaf and dumb, 324. Ventriloquism, 325". SECOND CLASS. FUNCTIONS SUBSERVIENT TO THE PRE- SERVATION OF THE SPECIES. FIRST ORDER. those generative functions which apper- tain to both sexes. CHAPTER X. Of generation. Differences of the sexes, 329. Case in which the sexual organs did not exist, 329. Hermaphrodism is never met with in the human species, 330. Of generation in-mam, 331. Manr in the exercise of the functions of generation, not under the control of the seasons, 331. Of the.organs of generation in man, 332. Of the female organs of generation, 333. Of the signs- of virginity, 334. Of the functions of the generative organs, 335. Of erection, 335. Of the human semenj 336. Of the ovaria, 338. Of the impregnation of the ovum, 338. Of barrenness, 339. Sys- tems of generation, 340. SECOND ORDER. FUNCTIONS EXCLUSIVELY BELONGING TO THE. FEMALE. CHAPTER XI. Of the foetus, parturition, and lactation. Gestation, 342. Of the foetus and its cover- ings, 344. Of the developement of its organs, 344. Of the circulation of the blood in the fcetus, 345. Of the placenta, 346. The um- CONTENTS. xvii bilical chord, 348. Mode of existence of the foetus, 349. Morbid affections to which it is subject while in the womb, 350. Of monsters, 350. Their different kinds, and the causes which produce them, 351. History of a re- markable case, 351. Of the chorion ; of the amnion and liquor amnii, 352. Of the allantois and urachus, 353. Of the natural term of gestation, 353. Of parturition, 354. Of the mechanism of parturi- tion, 355. Of twins, 356. The number of male children born exceeds that of female, 357. Of superfoetations, 357. Of suckling, 357. Sym- pathy between the uterus and mammae^; struc- ture of the latter, 358. The milk appears not to be brought to the breasts by the lymphatics, 359. Chemical qualities of the milk, 360. Connexion between the new-born child and the mother, 361. Imperfect developement of the foetal lungs, 362. CHAPTER XII. Containing the history of the ages, the tempera- ments, and the varieties of the human species ; of death and putrefaction. Of infancy, 362. Of dentition, 363. Ossi- fication, 364. Phenomena of puberty, 365. Connexion between the developement of the sexual organs and the voice, 365. Of men- struation, 365. Of the cause of menstruation, 366. Of the cessation of this evacuation, 367, Of manhood, 367. Of temperaments and idiosyncrasies, 368. Of the sanguine temperament, 368. Of the mus- cular or athletic temperament, 369. Of the bilious temperament, produced by an increased energy of the hepatic system, joined to consi- derable activity of the sanguineous system, 370. Of the melancholy temperament, 371. Lym- phatic temperament, 373. Nervous tempera- ment, 374. Mixed and acquired temperaments, 374. Influence of climate on temperaments, 375. Varieties of the human species, 376. Euro- pean Arab race, 376. Mogul, 377. Hyper- borean, 377. Negro, 377. Moral characteris- tics of the different races, 378. Giants and dwarfs, 378. Of old age and decrepitude, 379. Decay, 379. Death, 381. Gradual extinction of bodily and mental powers, in the reversed order of their production, 381. Period of death, 382. Probabilities of human life, 383. Returns of longevity in Great Britain, 384. Putrefaction, 385. APPENDIX, CONTAINING ADDITIONAL NOTES AND DISQUISITIONS, By THE EDITOR. ADDITIONAL NOTES TO THE PRELIMINARY DISCOURSE. Of life (Note A), 1.—Life, although connect- ed with organisation, is not a function of or- ganisation, 1. The arguments used by the or- ganists shewn to be inconclusive, &c. 1. Ofthenervous system, in the lower animals (Note B), 2.—This system exists in all animals, 2. Its organisation more perfect, and its parts more complicated, as we ascend the scale of animal creation, 3. Of the primary solids and compound textures of the body (Note C), 3.—Meckel's opinion re- specting the elementary tissues, 3. Opinions of Pfaff and of Meyer, 3. The Editor's division of the primary solids, 4. The divisions of Chaussier and of Bichat, 4. The divisions of the animal textures adopted by Dupuytren and Be- clard, 4. By Meckel and De Blainville, 4. By Professor Meyer, 4. The analytical division of the various tex- tures of the body proposed by the Editor, 4 : 1 Complex, or associated structures, 4 ; 2, Parti- cular textures, 4 ; 3, General systems, 5 ; 4, Elementary solids or fibres, 5. A synthetical table of the Editor's classification of the ani- mal textures, 5. Simple tissues, as enume- rated by Dr. Craigie, 5. Of sensibility and contractility (Note D), 5.— Of sensibility, and its various states or modes, 6. Active sensibility, 6. Passive sensibility, 6. Organic sensibility, 6. The states or modes of organic sensibility, 6. Contractility, 7. Insensible organic contrac- tility, 7. Sensible organic contractility, or irritability, 7. Cerebral contractility, or the contractions occasioned by the will, 7. Sensi- bility and contractility contrasted, 7. Of sympathy (Note E), 7.—Sympathies divid- ed into direct and reflex, 7. The ganglial nerves, in their direct ramifications, and in their course along the blood-vessels, the chief agents of sympathy, 7. Organic sympathies, in which the vital energy evinces various modifications in degree and distribution, 8. Illustrations, 8. Or- ganic sympathies, in which, in addition to va- rious modifications in degree and distribution, the vital manifestations suffer a change in kind, 8. Illustrations, 9. Of habit (Note F), 9.—Modifications in the effects of habit on the voluntary and involun- tary organs, 9. Of inflammation (Note G), 9. — The first change inducing the phenomena of inflamma- tion commences in the fibriles of the organic nerves, 10. Phenomena of inflammation, 10 : 1, Uneasy sensation, 10 ; 2, Redness, 11 ; 3, Increased animal heat, 11. Turgescence of the capillaries, and consequently of the inflam- ed part, 11. XVlll CONTENTS. Of the ganglial or great sympathetic system of nerves (Note H), 12.—This system exists in every individual of the animal creation, 12. The other orders of nerves proceed from this system, 12. The ganglial nerves differ in or- ganisation, distribution, and function, from the other nerves, 12. They form an original and distinct system, 13. Proofs of the independence of the ganglial system of nerves, 13. Of the parts supplied by the ganglial nerves, 13. In- fluence of the ganglial nerves on the circulating system, 13. The subordinate ganglia bestow a modified vital influence on the organs which they supply with nerves, 13. The relations of the ganglial nerves with the heart and arteries, 14. Influence of the ganglial system on the blood, 14. Influence of this system on the se- creting organs and secretions, 14. Influence of this system on the portal circulation, and functions of the'liver, 14. Influence of this system on animalisation and nutrition, 14. In- fluence of the ganglial system in the produc- tion of animal heat, 14. The reciprocating in- fluences of this system on the cerebro-spinal nervous system, and of this latter on the former, 15. Modified vital functions of distinct ganglia and plexuses, 16. ADDITIONAL NOTES TO THE CHAP- TER ON DIGESTION. Of some collateral phenomena of digestion (Notes I and K), 16, 18.—The effects of long- protracted abstinence illustrated by a singular case, 16. Opinions of M. Lallemand respect- ing digestion in the stomach, 18. Opinions of the Editor respecting digestion, 18. Of human rumination, 18. Its nature and causes, 19. Of the influence of the pueumo-gastric nerves on digestion, 20. The conclusions drawn by M.M. Breschet, Edwards, and Vavasseur, from their experiments, 20. Reflections by the Edi- tor, 20. Conclusions of the Editor as to the influence of the nerves in digestion, and as to the operation of galvanism, 21. Of vomiting (Note L), 21.—The opinion of Magendie on this subject controverted, 21. Opinions of the Editor respecting it, 21. Of the intimate structure and functions of the liver (Note M), 22.—The researches of M. Mappes on the structure of the liver, 22. Func- tion of the granular structure of the organ, 23. The assimilating function of the liver maintained by the Editor, 23. The assimilat- ing and secreting processes of the organ ne- cessarily related to each other, 23. Source of the vital actions of the liver, 23. Of the vary- ing characters and properties of bile, 23. Of the uses of bile, 24. Opinions of Mr. Brodie and of Dr. Prout as to the bile, 24. Of the gall-bladder and cystic bile, 25. Opinion of Dr. Steams, 25. Of the structure and functions of the spleen (Note N), 25.—Opinions of-various authors as to its functions adduced, 25. Researches into the structure of the spleen, 26. Inquiries of Beclard, Home, Schmidt, Tiedemann, Gmelin, and others, as to its structure and functions, 26, 27. The nervous connexions of the organ, 27. The influence of various agents on the spleen, 27. Functions of the small and large intestines (Note O), 27.—Of the structure of the mucous surface of the digestive tube, 27. Of the vil- losities, 27. Of the functions of the digestive mucous surface, 27. Of the digestive process in the intestines, 28. Is not a chemical, but a vital process, 28. Of the functions of the C83- cura, 28. The opinion of Viridet confirmed by Tiedemann and Gmelin, 28. Physiological pathology of the caecum, 28. The function of faecation, 29. Of the functions of the kidneys (Note P), 29.—Results of experiments performed by MM. Dumas, Prevost, and Legulas, 29. Of the pro- duction of urea, 30. Pathological relations of the states of the urine, 30. ADDITIONAL NOTES TO THE CHAP- TER ON ABSORPTION. Of absorption (Note Q), 30.— Of absorption from the digestive canal, 30. The results of Tiedemann's and Gmelin's researches, 31. Of the passage of chyle into the vena portas, 31. Results of experiments, 31. Experiments of MM. Seiler and Ficinus, 31. Inferences of the Editor, 31. Of absorption in the lungs, 31. Opinions of Professor Meyer of Bonn, 31. Of the manner in which absorption is performed, 32. Opinions of Magendie, 32. Investiga- tions of MM. Segalas and Fodera, 32. Their opinions, 32. Of transudation and imbibition, 33. The veins and absorbents only absorb, 34. Ceitain substances seem to be absorbed chiefly by the veins, 34. The rapidity of absorption, 34. Inferences of the Editor, 34. The re- searches of Drs. Lawrence and Coates, 35. Their experiments re.ferred to, 35. Opinions of Dr. Barry as to the agency of atmospheric pressure in absorption, 36. The Editor's views as to absorption of foreign substances into the blood, and as to the opera- tion of medicines in this way, 36. Inferences by him as to various points connected with absorption, overlooked by physiologists, 37. ADDITIONAL NOTES TO THE CHAP- TER ON THE CIRCULATION. Of the action of the heart and arteries (Note* R), 37.—Of the nerves of the heart, 37. The actions of the heart are chiefly dependent upon the ganglial nerves, 37. Indirect influence of the cerebro-spinal nervous nerves system on the actions of the heart, 38. Of the active dilatation of the heart, 38. Of the arteries 38. Their connexion with the ganglial system of nerves, 38. Of the ac- tion of the arteries in the circulation, 38. Opi- nions of Magendie, Home, Hastings, and others, 38. Inferences of the Editor, 38. Of the functions of the capillaries (Note S), 39.—Division of the capillary vessels, 39. Of subordinate capillary vessels, 39. Opinions of Drs. Alard and Hutchinson, 39. Of the veins (Note T), 40.—Of the commence- ment of the veins, 40. Of the functions of veins, 40. Influences by which the veins circu- late their contents, 40. Absorbing function of the veins, 40. Assimilating function of the veins, 40. Of the functions of the portal veins, 40. ADDITIONAL NOTES TO THE CHAP- TER ON RESPIRATION. ,^P-f tft1 mecflanism of the respiratory organs (N°te U), 41.—Of the structure of the lungs, 41. Magendie's description of the cellules of the lungs, 41. The description of the bronchia and air-cells, given by M. Reisseisen, 41. Of the actions of the glottis, 41. Of the state of CONTENTS. XIX the lungs during respiration, 41. Opinions of Dr. Carson, 42. Experiments of Dr. D. Wil- liams, 42. Of the effects of respiration on the venous circulation, 42. The experiments of Haller, Lamure, Lorry, Cloquet, and Bourdon, referred to, 42. The inferences of M. Magendie, 42, The experiments and opinions of Dr. Barry, 42. Inferences of Dr. Arnott, and the Editor, re- specting the opinions of Drs. Barry and Carson, 42. Dr. Williams's inferences as to the effects of suspended respiration on the circulation, 43. Of the changes induced on the air and the blood by respiration (Note W), 43.—Of the production of carbonic acid during respiration, 43. Opi- nions of the Editor, 43. The experiments of Drs. Edwards, Murray, Prout, Fyfe, &c, re- ferred to, 43. Influence of temperature and other causes, in the production of carbonic acid during respiration, 44. Results of the Editor's researches, 44. Is the carbonic acid formed within, or external to, the vessels ? 44. Inferences of the Editor, 44. Of the absorption and ex- halation of azote during respiration, 44. The experiments of Dr. Edwards on this point re- ferred to, 44. Of pulmonary transpiration 45. Experiments of Magendie and of the Editor on this topic referred to, 45. Of the assimilating function of the lungs, 45. The influence of respiration on the genera* tion of animal heat, 45. Of the production of animal heat, 45. The preparatory changes take place in the lungs, 45. The ganglial nervous influence a chief agent in the generation of animal heat, 45. The state of the blood modifies the degree of heat, 45. Animal heat is a vital secretion, rather than a chemical phenomenon, 45. Of the cutaneous function (Note Z), 46.—Of insensible transpiration, 46. Of the influence of states of the air in promoting the cutaneous function, 46. Opinions of Dr. Edwards, 46. Of the sweat, or sensible exhalation, 46. The skin is a respiratory organ, 46. Proofs, 46. The skin is an eliminating organ, 46. ADDITIONAL NOTES TO THE CHAP- TERS ON THE SECRETIONS AND NUTRITION. Of the fluids (Notes A A), 47.—Of the clas- sifications of the fluids, 47. Classification of Adelon, 47. The absorbed fluids, 47. The nutritive fluids, 47. The secreted fluids, 47. The recrementitial fluids, 47. The excrementi- tial fluids, 47. Humours secreted by follicular glands, 47. Secretions of glandular organs, 48. Of the states of the various secretions, 48. Editor's opinion as to their being endowed, to a certain extent, with an emanation of vitality, which, for a time, resists the changes which they are disposed to enter into, 48. Of the blood (Notes B B), 48.—Of the small or colourless globules of the blood, 48. Re- sults of the roiscroscopic observations of Home and Bauer, 48. Of MM. Prevost and Dumas, 48. Of the red globules, 48. Of the coagulation of the blood, and on its vitality, 49. Results of the researches and ob- servations of the Editor on these subjects, 49. The motion of the particles of the blood, 49. The vitality of the blood derived from the ves- sels containing it, and the organs in which it circulates, 49. Vitality first manifested, in an obscure manner, in the chyle, 49. Coagulation proceeds from the loss of the vital emanation with which the blood was endowed when in the vessels, and from the presence of the air, 49. Coagulation of arterial blood, 49. Circum- stances influencing the coagulation of the blood, 49. Of the formation and source of the fibrin, 49. Circumstances influencing the state and appearances of the coagulum, 50. The state of the coagulum is chiefly owing to the state of the vital influence of the system generally, modified by the condition of the blood itself at the time, 50. The lower the vital action, the quicker the coagulation, but the looser will be the'coagulum, 50. The state of the coagulum shewn to be dependent upon the vital influence, 50. The subject illustrated, by referring to various diseases of an opposite character, 50. Various pathological inferences, 50. Of the transfusion of blood, and the injection of various foreign matters into it, 51. Experi- ments of MM. Prevost and Dumas referred to, 51. The practical success of Dr. Blundell with transfusion, 51. Of secretion and exhalation (Notes C C), 51. —Of the mechanism by which these functions are performed, 51. As to the existence of dis- tinct secreting capillaries, or of pores, &c, 51. Of the influence of the ganglial nerves in se- cretion, 52. Of nutrition (Notes D D), 52.—Of the me- chanisms, of nutrition, 52. Opinions of Mas- cagni, Bichat, and Prochaska, on this point, 52. Inferences deduced by the Editor, 52. The subject illustrated, by reference to nutrition in the lower classes of animals, 52. The gan- glial nerves shewn to be instrumental in nutri- tion, 53. Nutrition essentially a vital action, 53. ADDITIONAL NOTES TO THE CHAP- TER ON SENSATIONS. Of the decussation of the optic nerves, and mo. tions of the eye (Notes E E), 54.—Decussation of the optic nerves, 54. Inferences of Trevi- ranus and Magendie, 54. Of the motions of the eyes ; opinions of Mr. C. Bell, 54. Of the connexion of the fifth pair of nerves with the function of vision, 54. Case recorded by M. Serres, illustrating this con- nexion, 54. Of the adaptation of the lens to distinct vision, 55. The inferences of Professor Mile on this subject, 55. Of the nerves chiefly concerned in the sense of smell (Notes F F), 55.—Opinions of various authors respecting the nerves Concerned in the sense of smell, 55. Inferences of the Editor, 56. Of the formation of the spinal chord and brain (Notes G G), 56.—The formation of the spinal marrow, according to the observations of Gall, Tiedemann, Wenzel, Doellinger, Carus, and the Editor, 56. The Editor's opinion that the spinal chord is produced from the ganglial sys- tem of nerves, 56. The developement of the chord at the various periods of fcetal life, 56. Of the formation of the brain, 58. Researches of Tiedemann, 58. Developement of the brain at the different epochs of foetal existence, 58. The relative weights of the cerebrum, of the cerebellum, and of the whole brain, at the va- rious epochs of existence, 59. Of the cephalo-spinal fluid, 59. M. Magem die's inferences respecting its uses, 59. XX CONTENTS. Of the functions of the cerebrospinal system of nerves (Notes G G), 60.—General view of the nervous system through the different class- es of animals, 60. The rudiments of a nervous system, 60. Its progressive developement as we ascend the scale of animals, 60. Opinions of Home, Saint Hilaire, De Blainville, and Schultze, on the protection which the skeleton gives to the nervous system, 61. Of the functions of distinct parts of the cerebro-spinal order of- the nervous system, 61. The results of the researches of M. Flourens, 61. Functions of the hemispheres, 61. Of the cerebellum, 62. Of the tubercula quadrige- mina, 62. Conclusions from the experiments of M. Flourens, 62. The results of experiments by M. Rolando, 63. Inferences of M. Flourens, 63. Of the distinct functions of the anterior and posterior columns of the spinal marrow, 63. Opinions and experiments of Bell and Magen- die, 63. Opinion of M. Ollivicr, 63. Opinion of Dr. Spurzheim, and of the Editor, 64. Ex- periments of Dr. Bellingeri, 64. Experiments of M. Schcepf referred to, 65. Of the respiratory order of nerves, 65. The researches of Bell, Shaw, Mayo, and Brough- ton, into the functions of this order of nerves, 65. Inferences of the Editor, 65. Principle observed in the origin of the cerebro-spinal nerves, 66. General remarks on the different parts com- posing the nervous system, 66. Divisions pro- posed of the nervous system, 66. The functions of distinct nerves not yet assigned with suffi- cient precision, 66. The functions of nerves vary according to the nature of the organs they supply, 67. Many nerves seem concerned in more than one function, 67. The opinions of Johnstone, Bichat, Soemmering, and Reil, re- specting the ganglial nerves referred to, 67. Opinions of the Editor, 67. Of the pheiwmena of mind, as manifested through the instrumentality of a perfect nervous system (Notes H H), 67.—The slow progress of the science of mind, 67. Difficulty of the subject, 67. Causes of the slow progress of our knowledge respecting it, 68. Impeded by the doctrine of materialism, 68. The doctrine of materialism combated, 68. Dr. Brown quot- ed, 68. The materialists have falsely assigned the opinions of Gassendi to Locke, 69. The writings of various metaphysicians referred to, 68, 69. ■ Basis of a classification of the phenomena of mind proposed by the Editor, 69. Table of the Editor's arrangement of the manifestations of mind, 69. Instinctive feelings and emotions, 69. Instinctive feelings which tend to preserve the individual, 69. Instinctive feelings which tend to perpetuate the species, 69. Other in- stinctive emotions of mind, 69. Intellectual powers or states of mind, 69. Powers of con- sciousness, 69. Powers of intellection, 69. Ideas of reflection, arising from the exercise of the former powers, 69. Moral affections of mind, 70. Reflections on the above classification, 70. Consciousness accompanies all present mental manifestations; but it is more intimately related to certain states of mind, 70. Instinctive affec- tions of mind inquired into, 70. Man is pos- sessed of various instinctive or innate emotions and affections of mind, beyond those evinced by the lower animals, 70. The opinions of Locke, Berkeley, Hume, and CondiUac, as to the instinctive feelings, denied, 70. An analytical classification ofthe phenomena of mind, according to the views of the late Dr. Thomas Brown, 70. External affections of mind, 70. Internal affections of mind, 70. In- tellectual states of mind, 70. Emotions of mind, 71. Of the doctrines of Gall, 72. Dr. Gall's sum- mary of his doctrine, 72. Of dreaming, 72. Of the formation and developement of the mus- cular textures, and of the source of irritability (Notes 11), 72.—Researches of Dr. Isenflamm, 72. Results of microscopic observations of the muscular fibre, 73. Relations of the muscular fibres with the nervous tissue, 73. Source of irritability, 73. Inferences of the Editor, 73. The nerves of volition merely convey a stimu- lus to parts already possessed of the faculty of contraction, 73. The opinion thrown out, that the voluntary and other nerves originate in the structures which they supply, 74. Of galvanic electricity (Notes K K), 74.—The researches of Davy, Wollaston, Biot, Coulcomb, Poisson, Oersted, and Becquerel, referred to, 74. Electricity results from two distinct fluids, 74. Mode of their existence on the surface of the earth, 74. The classes of phenomena which they produce in their electro-motive ca- pacity, 74. The circulation of the electricities, or their electro-motive state, gives rise to the phenomena of galvanism, 74. General law established by M. Biot, 75. Law as to the at- traction existing between the electric fluid and material substances, 75. Relation of chemical affinity to galvanic electricity, 75. Gravitation and repulsion depend upon the electricities, 75. Late discovery by Mr. Brown, of motion existing in all organic and inorganic matter, re- ferred to vitality in the former, and the electri- city in the latter, 75. The relation of the elec- trical states with light, 75. The polarisation of matter depends upon the electricities, 75. Con- nexion between the electrical agencies and magnetical attractions, 76. Opinion of the Editor, that all the pl^nomena of the inorganised world, and of the solar sys- tems (as attraction, gravitation, affinity, com- bustion, crystallisation, magnetism, light, and heat), may be explained by means of the ageney of the two universally diffused electricities, 76. .The electro-motive energy cannot, however, account for all the vital phenomena, 76. The opinions of Sprengel, Reil, Piochaska, Philip, Lenhossek, &c, referred to, and controverted, 76. Influence of the electro-motive energy upon living bodies and textures referred to and illus- trated, 77. Experiments of Ritter, Ure, and Philip, referred to, 77. Criticisms by the Edi- tor, 77. The opinion that life is identical with galvanism, noticed and rebutted, 77. Observa- tions of Dr. Pring as to this topic, referred to and quoted, 77. Of ossification (NotesL L),78.—Observations of MM. Beclard and Serres, 78. Progress of ossification at the different epochs of foetal life 78, 79. Of voice (Notes M M), 79.—Office of the muscles of the larynx in the production of voice, 79. Of ventriloquism, 79. Explanations of Dr. Good and M. Magendie, 79. Of the generative organs and their functions (Notes N N), 79. Of the male organs of gene- ration, 79. Of the structure of the penis, 80. Of the nervous influence upon the circulation CONTENTS. xxi of the organ, 79. Of the function of the vesi- culas seminaies, 80. Of the spermatic animal- culas, 80. Of the female organs of generation, 80. Of the nerves supplying the female generative or- gans, 80. Description of Tiedemann, &c. 80. These nerves enlarge during gestation, 80. Of impregnation, 80. Opinions of authors, 80. Ovarian foetation, and cases of referred to, 81. The venereal desire exists prevous to the developement of the ovaria and testes, 81 ; and continues after the disappearance of the menses, 81. Conception may take place even although the female may be indifferent during the vene- real congress, 81. Experiments of Dr. Blun- dell referred to, 81. The presence of corpora lutea cannot be relied upon as a proof that im- pregnation had taken place, 81. Impregnation cannot take place unless the semen comes in contact with the rudiments, 81. Of superfoetation, 82. Cases of, referred to, 82. Of the developement of the textures and organs of the foetus (Notes O 6), 82.—The early state of the embryo, 82. Progressive developement, 82. Early appearance of the rudiments of a nervous system, 82. First appearance of the intestinal canal, 82. The progressive phases through which the human embryo passes during the early epochs of foetal existence, 82. These correspond to the different stages of organisa- tion observed as we ascend the scale of animal creation, 83. Developement of the nervous system of the foetus, 83. This system seems to be formed from the circumference, the nerves advancing from the organs which they supply towards centres, which become more fully developed as the em- bryo advances, 83. Of the developement of the heart, 83. Ob- servations of M. Meckel, 83. Of the develope- ment of the pulmonary organs, 83. Researches o/ Meckel, 84. Of the circulation of the placenta, 84. Ex- periments of M. Gaspard, 84. Proofs that the foetal blood is fabricated by the foetus itself, chiefly from the nutritious juices furnished to the placenta, 84. By what organs is the san- guifying process of the foetus performed ? 84. The question answered, 84. Opinions of M. Geoffrey St. Hilaire and Dr. R. Lee, 84. The sanguifying process of the liver of the foetus intimately connected with a secreting function, 84. Respiration of the foetus, 85. Means by which the requisite changes are effected in the foetal blood, 85. Opinions of Mueller and Saint Hilaire, 85. Of the varieties of the human species (Notes P P), 85.—The classification of Cuvier pre- ferred to those of other authors, 85. The Cau- casian variety, 85. Mongolian variety, 85. The Negro variety, 85. Of the Malays and the Papuas, 85. The American tribes, 85. Of the mortality of females at the change of life (Note Q Q), 86.—Results of M. Benois- ton^de ChateauneuPs inquiries, 86. APPENDIX, No. II. THE CHEMICAL CONSTITUTION OF THE SOLIDS AND FLUIDS OF THE HUMAN BODY. I. Simple substances entering into the constitu tion of the different animal principles or consti- tuents of the human body, 86. II. Animal constituents or principles, 86. — Gelatine, 86. Albumen, 86. Fibrin, 86. Co- louring matter of the blood, 86. Urea, 86. Mu- cus, 86. Osmazome, 87. Picromel, 87. Sugar of milk, 87. Fixed oils, 87. Acids, 87. III. Individual textures and fluids of the hu- man body, 87. Constituents of the bones and teeth, 87. Of the enamel of the teeth, 87. Of tophus, 88. Of the marrow of bones, 88. Of cartilages, 88. Of the synovia, 88, Synovia of the horse and elephant, 89. Composition of the periosteum, 89. Of the ligaments, 89. Of the membranes, 89. Chemical constitution of the integuments, 89. Of the cutis vera, 89. Of the rete mu- cosum, 89. The epidermis, 89. Of the hair, 89. Constitution of the muscular flesh, 89. Of the heart, 89. Of ossific deposits in muscular flesh, 89. Constituents of the brain and nerves, 89. Of the medulla oblongata, 90. Of the nerves, 90. Of the greasy substance of the brain, 90. Of the white medullary matter, 90. Of the lymph found in the ventricles of the brain, 90. Of concretions found in the brain, 90. Constituents of mucus, 90. Of the saliva, 90. Of salivary calculi, 90. Of the tartar of the teeth, 90. Of the lachrymal fluid, 90. Constituents of the gastric juice, 90. Of the lymph, 90. Of the chyle, 90. Chyle of the horse, 90. Of the dog, 90. Constituents of the blood, 91. Of the serum, 91. Of the cruor or clot, 91. Of the foetal blood, 91. Of diseased blood, 91. Constituents of milk, 91. Of the curd, 92. Of the cream, 92. Of the whey, 92. Of fer- mented milk and whey, 92. Peculiarities of human milk, 92. Constituents of bile, 92. Of biliary calculi, 92. Cerumen of the ears, 92. Of the tears, 92. Of the sweat, 92. Constituents of'urine, 93. Of the urine in various diseases, 93. Of the semen," 93-. Off the human ova, 93. Of the amniotic fluid, 93. Constituents of pus, 93. Of expectorated matter, 93. Liquor of the pericardium, 93. Liquor of dropsy, 93. Fluid from blisters, 94. Composition of human farces, 94. Gases ex-j- isting in the intestinal canal, 94. In the sto- mach, 94. In the small intestines, 94. In the large intestines, 94. PRELIMINARY DISCOURSE. Physiology* is the science of life. The term life is applied to an ag- gregate of phenomena, which manifest themselves in succession, for_ a limited time, in organised bodies. Combustion is likewise only a combina- tion of phenomena ; oxygen unites with the substance which is burning, caloric is disengaged from it; affinity is the cause of these chemical phe- nomena, as attraction is the cause of the phenomena of astronomy, and in the same manner as the sensibility and contractility of living and organised bodies are the primary causes of all the phenomena which such bodies exhibit—phenomena which, in their union and aggregate succession, con- stitute life. The false notions which have been entertained on the subject of life, and the vague definitions which have been given of it, are to be accounted for, by considering that physiologists, instead of regarding life as a simple re- sult, have mistaken it for the properties of life. These last are causes : the first is merely an effect, more or less complex ; and, as the spring of a watch, or rather the elasticity of that spring, determines, by the mere ac- tion of the wheels, the motion of the hands, and all the phenomena of which the machine is capable ; so the vital properties acting by the organs pro- duce all those effects, which in their combination constitute life."j" These effects are more or less numerous, according to the number of the organs : they become more rapid, too, in their succession, and life more active with the increase of energy in the vital properties, precisely as the motions of a watch become more complicated, stronger, or quicker, according to the greater tension of the spring, or the increased number of the wheels. Sen- sibility and contractility are to be ranked among primary causes, of whose existence and laws we acquire a knowledge from observation, but whose essence eludes our investigation,^ and will probably remain for ever be- yond its reach. Sect. I.—OF NATURAL BEINGS. The vast domain of nature is divided between two classes of beinga. Inorganic beings, possessing merely the common properties of matter ; or- ganic and living beings, obeying particular laws, though subjected to the general laws which regulate the universe. Each of these two grand di- visions is naturally divided into two classes : we meet with inorganic bodies under the form of elementary substances, simple and not capable of analysis, or else under the form of mixed substances, compound, and admitting of decomposition. Thus, too, organised beings exist under two very different forms of life, which distinguish them into vegetables and animals. * Anatomy is the science of organization. of other parts of natural philosophy. The che- t See Appendix, Note A. mist, who explains all his combinations by % It would be wrong to infer, from our ig- referring them to the principle of affinity, and norance of the nature of the vital properties, the astronomer, who finds in attraction the that physiology is an uncertain science. Its cause that rules the universe, are absolutely certainty, in that point of view, is equal to that ignorant of the nature of those properties. 2 OF the elements of bodies. The first general conception with which we ought to enter upon this comprehensive study of nature is, the mutual dependence of those beings, which, in their co-ordinate whole, compose the system of nature—a de- pendence which requires for each the simultaneous, existence of all. Thus a vegetable derives its nourishment from inorganic bodies * and alters their inert° substance, which is unfit for the food of animals, unless it has pre- viously undergone the influence of vegetable life. Sect. II.—OF THE ELEMENTS OF BODIES. Another consideration, of equal importance with the former, is, the con- vertibility of all those substances so different from one another, and their capacity of being reduced to a small number of simple substances, called elements. The ancient doctrine of Aristotle, relative to the four elements, still prevailed in the schools, with a few modifications which it had received from the chemists, when the " pneumatists"| demonstrated, by their beau- tiful experiments, that three, at least, of these pretended principles of bo- dies,—air, water, and earth,—far from being simple substances, were evidently formed by the union and combination of several others; that atmospherical air, for example, far from being a homogeneous fluid, was composed of many different gases, and that in its purest state it contains at least two very distinct principles—oxygen and azote; that water is a compound of oxygen and hydrogen, and that earth contains clay, lime, silex, &c. We have seen added, in the present day, to the number of the elements or simple substances, several which were notf considered as such at the time when our natural philosophers, misled by erroneous metaphysical doctrines, had created out of their imaginations beings of the existence of which they could find no proof. There is every reason to believe, that the number of substances not admitting of decomposition, limited at present to fifty-one, without embracing the imponderable bodies, may hereafter be increased or diminished by the discovery of new principles in simple sub- stances, or of new elements in compound bodies, which have hitherto eluded the investigation of chemists. Whatever may be the success of their inquiries, of which it is impossible to foresee the results or to fix the limits, there is reason to believe that it will ever be denied us to arrive at a knowledge of the true elements of bodies, and that many of those sub- stances, which the imperfection of our means of decomposition or analysis obliges us to consider as such, are frequently compound substances, and subject to their laws. After what has been stated on the elements or constituent principles of substances, let us now see in what manner the combination of these ele- * Mikbel, in his Treatise on Vegetable Anatomy and Physiology, observes, " that plants have the power of deriving nourishment from inorganic matter, which is not the case with animals who feed on animals and vege- tables, or on both, but are never nourished on earths, salts, and airs." Richerand has adopt- ed the plausible opinion of Mirbel. Farther inquiry might, however, have shewn them that " earths and salts" furnish as little direct nourishment to plants as to animals. Indeed, it may be observed, that the vegetable king- dom derives the chief part of its food from dead animal and vegetable matters, which, al- though they contain both " earths and salts," cannot be either ranked under these substan- ces, nor even classed with them.—J. C. t This is the name given to the school of modern chemistry, because it originated from the discoveries made relative to the nature of air and elastic fluids. It must be acknowledg- ed, to the credit of metaphysics, that the old errors were forsaken, only at the period when chemists were thoroughly convinced of this truth, that every idea is obtained through the medium of the senses, and that nothing is to be admitted beyond what they demonstrate in actual experiment. CHARACTERISTICS OF ORGANISED BODIES. 3 ments gives existence to all beings, and what are the general differences existing among the great classes into which they are divided. Sect. III.—DIFFERENCES BETWEEN ORGANISED AND INORGANISED BODIES. Much attention has been bestowed of late on the difference which exists between organised and inorganised bodies. The latter have been observed to be very different from those which are endowed with life, in the homo- geneous nature of their substance, in the complete independence of their molecules, each of which, according to the observation of Kant, has in itself causes to account for its peculiar mode of existence, in that power of resisting decomposition which they owe to the simplicity of their structure, and in the absence of those peculiar powers which free organic bodies from the absolute dominion of physical laws. The multiplicity, the vola- tility of their elements, the necessary union of fluids and solids, the nutrition and development from the diffusive combination, while the growth of inan- imate bodies takes place from the mere juxta-position of particles, the origin of living bodies in generation, their destruction in death,—such are the cha- racters which distinguish organised beings from inorganised substances. We are about to enter into a detail of those characters, to appreciate all their differences ; for knowledge is to be acquired only by comparison, and the greater our accuracy in comparing, the more precise and extensive will be the knowledge we obtain. Several modern authors have proved, that it is impossible to obtain an accurate idea of life, except by comparing those bodies which are endowed with it with those in which life has never exist- ed, or has ceased to exist. This comparison, I hope, will be fruitful in interesting results, and will furnish several useful considerations imme- diately applicable to the knowledge of man. The first remarkable difference between organised and inorganised bo- dies is to be found in the homogeneousness of the latter, and the compound nature of the former. Let a block of marble be broken ; each piece will be perfectly similar to the rest; there will be no differences among them, but such as relate to size or shape. Break down the fragments ; each grain will contain particles of carbonate of lime, which will be throughout the same. On the other hand, the division of a vegetable or an animal shews parts heterogeneous or dissimilar. In different parts there will be found muscles, bones, arteries, blossoms, leaves, bark, pith, &c. ( Organised beings cannot live or exist in their natural condition, unless solids and liquids enter at once into their composition. The co-existence of these two elements is necessary ; and living bodies always contain a liquid mass more or less considerable, and incessantly agitated by the mo- tion of the solid and living parts. It is, in fact, impossible to conceive life existing without a complicated combination of solids and fluids ; and with- out admitting in the former the faculty of being affected by impressions from the latter, and the power of acting in consequence of those impres- sions. The water which penetrates into mineral substances does not form a necessary part of them ; and one cannot adduce in proof of the existence of liquids in that class of substancesKthe water of crystallisation, though intimately combined, and rendered solid in the crystallised substances. These inorganic and homogeneous substances, formed of particles simi- lar to one another, when resolved by decomposition into their last elements, possess a great implicity of inward nature, Among them are ranked all 4 CHARACTERISTICS OF organised BODIES. the substances which do not admit of analysis; the mineral compounds are often binary, as the greater part of saline substances; sometimes they are ternary, but seldom quaternary ; while the most simple vegetable con- tains at least three constituent principles, oxygen, hydrogen, and carbon ; and no being possessed of life consists of less than four, oxygen, hydrogen, carbon, and azote. In the degree of composition, nature appears, there- fore, to rise in gradations, from the mineral to the vegetable, and from the latter to the animal kingdom. The complicated nature of the latter, the multiplicity of their elements, account for their tendency to alteration. Minerals are not subject to change, unless they are acted upon by external causes. Endowed with a vis inertiae, they continue in one condition with- out change. The state of organised bodies is incessantly varying. Their internal parts contain an active laboratory, in which a number of instru- ments are constantly transforming into their own substance nutritious par- ticles. Besides that tendency to alteration in living animals and vege- tables, when deprived of life they become decomposed by a process of fer- mentation which begins in their internal parts, and by which their nature is changed in proportion to the complication of their structure, and the greater number and volatility of their constituent principles. All the parts of a living body, whether of an animal or a vegetable, have a natural tendency to a common object, the preservation of the indi- vidual and of the species : each of the organs, though provided for a pe- culiar action, concurs in this object; and life in general, or life properly so called, is the result of that series of concurring and harmonic actions. On the contrary, each part of an inorganic mass is independent of the other parts, to which it is united only by the force or affinity of aggregation. When such a part is separated from the rest, it maintains all its charac- teristic properties, and differs only by its size from the mass to which it no longer belongs. Among animals and vegetables, all the individuals of the same class appear to have been formed after the same model; their parts are equal in number, and resemble each other in colour ; their differences are slight and evanescent. The forms peculiar to organised beings are, therefore, inva- riably determined ; and when nature departs from them, she never does so to such a degree as in the shapes of minerals. The veins of mines are never precisely alike, as the leaves of vegetables or the limbs of animals. Crystals, formed from similar substances, assume very different shape's, equally distinct and precise. Carbonate of lime, for example, assumes, according to circumstances, the shape of a rhomboid, that of a six-sided regular prism, that of a solid, terminated by twelve scaleni triangles, that of a different dodecahedron with pentagonal faces, &c, as may be seen at large in the writings of tiaiiy. A powerful inward cause seems to arrange the constituent parts of ani- mal and vegetable bodies by a determinate rule, in such a manner that they shall present a surface more or less completely rounded. Minerals often take their form from external bodies ; and when an especial force as- signs it to them, as in crystals, their surfaces are flat and angular. When the crystallisation is disturbed, and the molecules of the crystals are driven tumultuously together, the geometrical form is impaired; the parts are rounded which would have been terminated by angles, if a slow and tran- quil crystallisation had allowed of regular aggregation ; and, as M. Haiiy has remarked, these waving outlines, these roundings, so frequent in vege- tables and plants, where they belong to beauty of form, are, in minerals CHARACTERISTICS OF ANIMAL BODIES. 5 indication of defects. True beauty, in these beings, is characterised by the straight line ; and it is on good grounds that Rome de Lisle* has said of this sort of line, that it seems to have an especial determination to the mineral kingdom. Amongst all the characteristics which distinguish the two great divi- sions of natural bodies, the most absolute and the most palpable is that which is drawn from the manner of growth and of nourishment. Inorganic bodies grow only by accretion, that is, by the accession of new layers to their surface ; whilst the organic, in virtue of its vital powers, receives into intimate combination, and is penetrated and pervaded by, the substance it assimilates to itself. In animals and plants, nutrition is the effect of an internal mechanism ; their growth is a development from within. In minerals, on the contrary, growth cannot claim the name of development: it goes on externally, by successive addition of new layers ; it is the same being, assuming other dimensions, whilst the organic body is renewed in its growth. Living bodies spring from a germ, which at first was part of another being, from which it detaches itself for the sake of its own development and growth. From the first, they are already aggregates. Inorganic bodies have no germ: they are made up of distinct parts brought to- gether ; they have no birth; but a multitude of molecules, collecting into one, compose masses of various bulk and figure. Organised bodies alone can die; all have a duration, determined by their own nature ; and this duration is not, like that of minerals, propor- tioned to the bulk and density: for if man has not the life of the oak, whose substance much exceeds his in density, neither does he equal the life of many animals, such as fishes, whose flesh is of inferior consistence to his own : and he lives longer than the large quadrupeds, though his bulk is less. The parts, also, of a living body, are developed and strength- ened by exercise: a muscle or an organ, instead of being wasted by re- peated action, increases in bulk, whilst friction and use destroy inorganised substances. Spontaneous motion is proper to living bodies, but inorganised matter evinces only communicated movements. Finally, inorganic are essentially distinguished from organic bodies by the want of these peculiar powers or properties*of living nature; powers which uphold the equilibrium of the whole system of nature, as I shall explain more at large when I have considered the differences that mark the two divisions of the organic kingdom, vegetables and animals. Sect. IV.—DIFFERENCES BETWEEN VEGETABLES AND ANIMALS. These are much fewer, less absolute, and therefore more difficult to es- tablish. There is, in fact, very little difference between a zoophyte and a plant; and there is a much wider distance in their internal economy, between man, who stands at the height of the animal scale, and the polvpus on its lowest line, than between the polypus and a plant. There lies be- tween organised and inorganic bodies a space, which is not to be filled up by figured stones, nor by lithophytes, nor by crystals, in which some natu- ralists have thought they saw a beginning of organisation : whilst, at the extremity of the animal chain, are found beings, fixed, like plants, on the spot of their birth, sensitive and contractile, like the sensitive and some * Cristallographie, torn. i. p. 94, 6 CHARACTERISTICS OF ANIMAL BODIES. other plants, and reproduced like them from slips. Yet we are able to state some differences sufficiently marked, to assign to the vegetable kind a character of their own, which will not suit the individuals of either of the other kingdoms. Their nature, more complex than that of minerals, is less so than that of animals : the proportion of the solids to the liquids is greater than in these last: accordingly they retain, long after death, their form and bulk, only that they grow lighter. The solids are, in man, nearly a sixth of the whole body: his carcass, decomposed by putrefaction, remains a little earth, and a light skeleton, when the ground and the air have drawn from it all its juices. A tree, on the contrary, is more than three parts of its substance solid wood. It has been dead for ages ; and yet in our build- ings it preserves its form and size, though, by drying, it has lost a little of its weight. Their constituent principles, as they are less in number, are also less diffusable. In fact, azote, which is predominant in animal substances, is a gaseous and volatile principle; whilst carbon, the base of vegetable sub- stance, is fixed and solid. This circumstance, added to the smaller quan- tity of their liquids, explains the long duration, after death, of vegetable substances. But of all the characteristics which have been employed in establishing the limits of animal and vegetable nature, there is one quite sufficient to distinguish these two great classes of beings ; but which has not been al- lowed the-weight it deserves. The zoophyte, who, fixed in his rocky habitation, cannot change his place, confined to partial movements, which certain plants are possessed of, who, besides, has not that sensitive unity so remarkable in man, and in the animals who nearest resemble him in their organisation; the zoophyte, whose name indicates an animal plant, is totally separated from all beings of the vegetable kingdom, by the existence of a cavity, in which alimen- tary digestion is carried on,—a cavity, by the surface of which is an ab- sorption, an imbibition, far more active than that which takes place by the external surface of the body. From this shapeless animal, up to man, nutrition is effected by two surfaces, and especially the internal; whilst in the plant, nutrition, or rather the absorption of nutritive principles, is only by the external surface* Every animal may be considered, in extreme abstraction, as a nutritive tube, open at the extremities ;■(* the whole existence of the polypus seems reduced to the act of nutrition, as its whole substance is employed in the formation of an alimentary tube, of which the soft parietes, extremely sensible and contractile, are busied in appropriating to themselves, by a sort of absorption, the substances which are brought into it. From the worm up to man, the alimentary canal is a long tube, open at the-extremi- ties" * at first only of the length of the body of the animal, not bent at all in passing from the head to the tail, and carried on towards the mouth and towards the anus, with the external covering of the body ; but soon re- * This most prominent characteristic of sons, torn. i. There may be brought against animal organisation was first pointed out by this principle, the instance of some zoophytes Boerhaave ; and afterwards insisted on by Dr. such as sponges, &c. ; but do these bodies' Alston of Edinburgh; and recently by Dr. A. really belong to the animal kingdom ? and T. Thomson, in his excellent work on the Ele- should not we be warranted in rejecting them ments of Botany.—/. C. by the want of the alimentary cavity, the es- t Lacepede, Histoire Naturelle des Pois- sential characteristic of animal existence ? CHARACTERISTICS OF ANIMAL BODIES. 7 turning upon itself, and stretching out into length far beyond that of the body which contains it. I It is in the thickness of the parietes of this animated tube, betwixt the mucous membrane that lines it inwardly, and the skin with which this membrane is continuous, thai, all the organs are placed, which serve for the transmission and elaboration of fluids, together with the nerves, the mus- cles, in short, all that serves for the carrying on of life. As we rise from the white-blooded animals to the red and cold-blooded, from these to the warm- blooded, and from these to man, we see a progressive multiplication of the organs that are contained within the thickness of the parietes of the canal:—if we follow, on the other hand, the descending scale, we see this structure gradually simplified, till we arrive at last at the polypus, and find in it only the essential part of animal existence. The simplicity of its or- ganisation is such, that it may be turned inside out, and the external be made the internal surface; the phenomena of nutrition, which are the whole life of the animal, go on, from the close analogy between the two surfaces ; unlike to man and the greater part of animals, in whom the skin and the mucous membranes, though growing into each other, though linked by close sympathies, are far from possessing a complete analogy of structure, or a capacity for the interchange of functions. Man, then, and the whole animal kind, carry about within themselves the supply of their subsistence ; and absorption, by an inward surface, is their distinguishing characteristic. It is inaccurate to ascribe to Boerhaave the comparison of the digestive system of animals to the soil in which plants suck up the juices that feed them, and the chylous vessels to real in- ternal roots. I find the same thought well expressed in the work on hu- mours, which, justly or falsely, bears the name of Hippocrates: Quemad- modum terra arboribus, ita animalibus ventriculus. The digestive tube, that essential part of every animal, is the part of which the existence and action are the most independent of the concur- rence of the other organs, and to which the properties of life seem to ad- here, if one may say so, with most force, Haller,* who has made so many and such interesting inquiries into the contractile power of the muscular organs, examining them under the twofold relation of their irritability, as it is more or less lively, or more or less lasting, looks on the heart as the one in which these two conditions are found in the highest combination. He gives the second place to the intestines, the stomach, the bladder, the ute- rus, and the diaphragm ; and, after these, all the muscles under the com- mand of the will. I had at first admitted, with every other writer, this classification of the contractile parts; but more than a hundred experi- ments on living animals have satisfied me that the intestines are ahvays the last part in which the traces of life may be discovered. Whatever may be the sort of death by which they are destroyed, peristaltic motions, un- dulations, are still continued in this canal, while the heart has already ceased to beat, and the rest of the body is all an inanimate mass. M. Ju- rine has already observed on the pulex monoculus, that, of all the parts of the body of this little white-blooded animal, the intestines were the last to die."!" * Opera Minora, 3 vols. 4to. blowing of pure air into the lungs, the means •f- If the intestinal tube be the ultimum mo- that ought next to be attended to is the injec- riens, if it be the last organ in which life lin- tion of acrid and irritating clysters thrown in gers and goes out, it is to it we ought to direct, with force. The large intestines are connect- in preference, the stimulants that are capable ed with the diaphragm by a close sympathy, of recalling it in case of asphyxia. After the as is proved by the phenomena of foecal eva- 8 OF LIFE. Sect. V—OF LIFE* After having thus laid down, between organic bodies and organised liv- ing beings, and again between animal and vegetable nature, a line of de- marcation that cannot be mistaken, let us endeavour to exalt ourselves to the conception of Life ; and, for accuracy of thought, let us, in some sort, analyse it, by studying it in all the beings of nature that are endowed with it. In this study, of which I may be allowed to state, in advance, the re- sults, we shall see life composed at first of a small number of phenomena, simple as the apparatus to which it is given in charge ; but soon extending itself as its organs or instruments are multiplied, and as the whole organic machine becomes more complex ; the properties which characterise it and bear witness of its presence, at first obscure, becoming more and more ma- nifest, increasing in number as in development and energy ; the field of ex- istence enlarging, as from the lower beings we re-ascend to man, who, of all, is the most perfect: and observe, that by this time of perfection, it is simply meant that the living beings to which we apply it, possessed of more means, present also more numerous results, and multiply the acts of their existence: for in this wonderful order of the universe every being is perfect in itself, each being is constructed most favourably for the purpose it is to fulfil; and all is equally admirable, in living and animated nature, from the lowest vegetation to the sublimity of thought. What does this plant present to us that springs up, and grows, and dies every year ? A being whose existence is limited to the phenomena of nu- trition and reproduction: a machine constructed of a multitude of vessels, straight or winding capillary tubes, through which the sap is filtrated, and other juices necessary to vegetation; these vegetable liquors ascend, ge- nerally, from the roots, where their materials are taken in, to the summit, where what remains from nutrition is evaporated by the leaves, and what the plant could not assimilate to itself is thrown off in transudation. Two properties direct the action of this small number of functions : a latent and faint sensibility, in virtue of which each vessel, every part of the plant, is affected in its own way by the fluids with which it is in contact: a con- tractility as little apparent, though the results prove irrefragably its ex- istence ; a contractility, in virtue of which the vessels, sensible to the im- pression of liquids, close or dilate themselves, to effect their transmission and elaboration. The organs allotted to reproduction animate, for a mo- ment, this exhibition: more sensible, more irritable, they are visibly in action : the stamina or male organs bow themselves over the female or- gan, the pistils, shake on the stigma their fertilising dust, then straighten, retire from it, and die with the flower, which is succeeded by the seed or fruit. This plant, divided into many parts, which are set in the earth with suit- able precautions, is reproduced and multiplied by slips, which proves that these parts are little enough dependent on each other; that each of them contains the set of organs necessary to life, and can exist alone. The dif- ferent parts of a plant can live separately, because life in its simpler organs and properties is diffused more equably, more uniformly, than in animals like man, and its phenomena are connected in a less strict and absolute de- cuation: the irritation of them is the surest part that is forsaken by life. means of accelerating it; and this irritation is * See Appendix, Note A. the easier, as the alimentary canal is the last OF LIFE. 9 pcndence. I myself have witnessed a very curious fact, which confirms what I have said.* A vine, trained against the eastern wall of a forge, shot into the building a few branches. These branches, which entered by straight enough passages, were covered with leaves in the middle of the hardest winters ; and this premature but partial vegetation went through all its periods, and was already in flower when the part that remained with- out was beginning to bud with the spring. If we pass from the plant to the polypus, which forms the last link of the animal chain, we find a tube of soft substance, sensible and contractile in all its parts, a life and an organisation at least as simple as that of the plant. The vessels which carry the liquids, the contractile fibres, the tra- chea? which give access to the atmospheric air, are no longer distinctly to be traced in this almost homogeneous substance. There is no organ espe- cially allotted to the reproduction of the kind. Moisture oozes from the in- ternal surface of the tube, softens and digests the aliments which it finds there; the whole mass draws in nourishment from it; the tube then spon- taneously contracts, and casts out the residue of digestion. The mutual independence of parts is absolute and perfect: cut the creature into many pieces, it is reproduced in every piece ; for each becomes a new polypus, organised and living, like that to which it originally belonged. These gem- miparous animals enjoy, in a higher degree than plants, the faculties of feel- ing and of self-motion; their substance dilates, and lengthens, and con- tracts, according' to the impressions they receive. Nevertheless, these spontaneous movements do not suppose, any more than those of the mi- mosa, the existence of reflection and will; like those of a muscle detach- ed from the thigh of a frog and exposed to galvanic excitation, they spring from an impression which does not extend beyond the part that feels it, and in which sensibility and contractility are blended and lost in each other. From this first degree of the animal scale, let us now ascend to worms. We have no longer a mere animated pulp shaped into an alimentary tube: parcels of contractile or muscular fibres ; a vessel divided by several con- strictions into a series of vesicles, which empty themselves into one an- other by a movement of contraction that begins from the head, or the entrance of the alimentary canal, and proceeds towards the tail, which an- swers to the anus; a vessel from which, in all probability, are sent out lateral ramifications; a spinal marrowf equally knotted, or composed of a * Vegetable life compared in its means and of plants. Like those of the human body, they in its results to the life of animals, would are much less dangerous when their surface throw the greatest light on many phenomena is smooth than when their edges are hacked, which it is still difficult for us to conceive and torn, or bruised. Trees felled with the saw to explain. The treatment of disease in plants, will hardly shoot up from the stool, which al- for which as much would be gained by these ways furnishes a better growth when an axe inquiries, is almost entirely surgical. When, has been employed. The saw lacerates the to make vegetation more fruitful, the gardener vegetable texture ; and its violent and distress- prunes a luxuriant branch ; when the peasants ing action on the fibres, extending towards the of the Ceivennes, as M. Chaptal has observed, roots, affects, more or less, the organisation hum the inside of their chestnut trees to stop The uneven surface of a tree felled in this the progress of a destructive caries; when manner holds wet, as injurious to the trunk, the actual cautery is applied to the really icho- which it rots, as a too great quantity of pus, rous and foul ulcers of many trees, &c, it is which bathes constantly the surface of a wound, to the organs of inward life (or that which car- checks the process of granulation, and resists ries on the process of assimilation), the only cicatrisation. life of vegetables, that surgery is applied ; t This class of animals cannot be consider- whilo, on the contrary, in man and animals, it ed to possess a spinal marrow. The series of is to the derangement of the external organs gangkons which they exhibit is merely the that the remedy is directed. I shall conclude vertebral ganglia of the sympathetic nerve.— this note with an observation on the wounds /. C. 2 10 Of LIFE. chain of ganglions,* stigmas, and trachea, analogous to the respiratory organs of plants, and, in some, even gills : all shews clearly an organisa- tion further advanced, and more perfect: sensibility and contractility arc more distinct; the motions are no longer absolutely automatic ; there are some which seem to suppose choice. The worm, too, may be divided into many pieces ; each will become a separate and perfect worm, a head and tail growing to each ;| but this division has its term, beyond which there is no longer complete regeneration. It cannot, therefore, be pushed so far as in the polypi. The substance of the worm being formed of elements more dissimilar, it may be that too small a portion does not contain all that is necessary to constitute the animal. The crustaceous tribes, and among them the lobster, discover a more complex apparatus of organisation. Here you will find distinct muscles, an external articulated skeleton, of which the separate parts are movable upon each other, distinct nerves, a spinal marrow with bulgings, but, above all, a brain and a heart. These two organs, though imperfect, as- sign the animal to an order much above that of worms. The first becomes the seat of a sort of intelligence ; and the lobster acts evidently under im- pulses of will, when, attracted by a smell, it pursues a distant prey, or when it flies a danger discovered to it by its eyes. There are viscera ac- companying the intestinal tube, which give out to it liquids that concur in alimentary digestion. Sensibility and contractility present each two shades: in fact, the parts of the animal are obedient to the internal stimuli, feel the impression of fluids, and contract to impel them ; on the other hand, by its nerves and locomotive muscles, the lobster places itself in connexion with the objects that surround it. The phenomena of life are linked together by a strict necessity: it is no longer possible to separate the creature into two parts, of which each may continue to live ; there are but few parts you may cut off without, injury, while you spare the central foci of life. So, if you take off a claw, you observe soon a little granu- lation, which swells and is developed, and which, soft at first, is soon clothed in a calcareous covering like that which encloses the rest of its body. This partial regeneration is frequently to be seen. If from white-blooded animals we go on to the red and cold-blooded*, such as fishes and reptiles, we see this power of reproduction becoming more and more limited, and life more involved in organisation. In fact, if you cut off a part of the body of a fish, the tail of a serpent, or the foot of a frog, the separated parts are either not supplied at all, or very imperfectly reproduced. All these creatures maintain, with the medium in which they live, relations of more strict dependence. Gills in these, lungs in others, are added to a heart, nor are less essential to life. However, the action of these chief organs is not so frequent, nor of momentary necessity for the continuance of Hfe. The serpent passes long winters, torpid with cold, in holes where he has no air, without breathing, without any motion of life and in all appearance dead. These creatures, like all reptiles, are able to breathe only at long intervals, and to suspend, for a time, the admission of ah, without risking their existence. Here, the vital powers are distinct and strong, and differ from those of the more perfect animals, and of man, by very slight shades : the heart and the vessels of the fish feel and act within him without his consciousness. Further, he has senses, nerves, and a » Appendix, Note B. collection during our endeavours to remova t This may be observed in several of the them from the body. intestinal wormj. It ought to be kept in re- ELEMENTS OF ANIMAL BODIES. 11 brain, from which he has intimation of whatever can affect him ; muscles and hard parts, by the action of which he moves and changes his place, adapting himself to the relations that subsist between the substances around him and his own peculiar mode of existence. We are come, at last, to the red and warm-blooded animals, at the head of which are the mammifersE and man. They are entirely alike, save some slight differences in the less essential organs. There is none that has not the vertebral column, four limbs, a brain which fills exactly the cavity of the skull, a spinal marrow, nerves of two sorts, five senses, muscles partly obedient to the will, partly independent in their action: add to these, a long digestive tube coiled upon itself, furnished at its mouth with agents of saliva and mastication; vessels and lymphatic glands, arteries and veins, a heart with two auricles and two ventricles, lobular lungs, which must act inces- santly in impregnating the blood that passes through them with the vital part of the atmosphere * if which fail, life is suspended or gone. None of their organs live but while they partake in the general action of the sys- tem, and while they are under the influence of the heart: all die, irrecover- ably, when they are parted from the body of the animal, and are in no way replaced, whatever some physiologists may have said on pretended regene- ration of the nerves and some other parts. Every thing that is important to life is to be found in these animals; and as the most essential organs are within, and concealed in deep cavities, a celebrated naturalist was correct in saying, that all animals are essentially the same, and that their differences are in their external parts, and chiefly to be observed in their coverings and in their extremities. The human body, consisting of a collection of liquids and solids, contains of the former about five-sixths of its weight. This proportion of the liquids to the solids, may, at first sight, appear to you beyond the truth : but con- sider the excessive decrease of size of a dried limb ; the gluteus maximus, for example, becomes, by drying, no thicker than a sheet of paper. The liquids, which constitute the greatest weight of the body, exist before the solids ; for the embryo, which is at first in a gelatinous slate, may be con- sidered as fluid: besides, it is from a liquid that all the organs receive their nourishment and repair their wastes. The solids, formed from the liquids, return to their former state, when, having for a sufficient length of time formed a part of the animal, they become decomposed by the nutritive pro- cess. Even from this slight view of the subject, fluidity is seen to be essential to living matter, since the solids are uniformly formed from the fluids, and eventually return to their former state. Solidity is, then, only a transient condition and an accidental state of organised and living matter ; and this circumstance affords to the humoral pathologists ample opportunities of embarrassing their opponents with many objections not easily answered. The simplest"living bodies, as the infusoria, polypi, &c. are only found in water; so that we may justly say, with M. Lamarck, that it is exclusively in this fluid that the animal kingdom has derived its origin. Water forms the principal part, and the principal vehicle of all the animal fluids ; it con- tains saline substances in a state of solution, and even animal matter itself is found in it fluid, and that in three different conditions, under the form of gelatine, of albumine, or fibrine. The first of these substances, solidified, forms the basis of all the organs of a white colour, to which the ancients gave the name of spermatic organs, such as the tendons, the aponeurosis, the cellular tissue, and the membranes. Albumine exists in abundance in * See Chapter on Respiration. 12 ARRANGEMENT OF THE ANIMAL TEXTURES. almost all the humours : the fibrine of the blood is the cement which is employed in repairing the waste of a system of organs, which, in point of bulk, hold the first rank among the constituent parts of the human body— I mean the muscular system. The chemists suspect, and not without rea- son, that the animal matter passes successively through the different states of gelatine, albumine, and fibrine ; that these different changes depend upon the progressive animalisation of the animal matter, which is at first gelatinous, a hydrocarbonous oxyde, containing no azote, and acidifiablc by fermentation, becomes more closely combined with oxygen, takes up azote, so as to become albumen, capable of putrefaction ; and finally is converted into fibrine by a super-addition of the same principles. The solid parts are formed into different systems, to each of which is intrusted the exercise of a function of a certain degree of importance. Limit- ing the term organic apparatus, or system, to a combination of parts which concur in the same uses, we reckon ten, viz. the digestive apparatus, con- sisting essentially of the canal which extends from the mouth to the anus ; the absorbent, or lymphatic system which is formed of the vessels or glands of that name; the circulatory system, which consists of an union of the heart, the veins, the arteries, and the capillary vessels ; the respiratory, or pulmonary system; the glandular, or secretory system ; the sensitive sys- tem, including the organs of sense, the brain, and spinal marrow ; the mus- cular system, or that of motion, including not only the muscles, but their tendons and aponeuroses ; the osseous system, including the appendages of the bones, the cartilages, the ligaments, and the synovial capsules ; the vocal system ; and the sexual or generative system, different in the two sexes. Each of these organic systems contains in its structure several simple tis- sues, or " similar parts," as the ancients called them. These tissues, in man, may be enumerated as follow: cellular tissue, nervous tissue, muscular tissue, besides that horny substance which constitutes the basis of the epider- mis, the nails, and the hair.* These four substances maybe considered as real organic elements, since, with our means of analysis, we never can succeed in converting any one of these substances into another. The cerebral pulp is not convertible into a horny substance, into cellular substance, or into muscular fibre ; neither can any one of these tissues ever be converted into cerebral pulp. The bones, the cartilages, the ligaments, the tendons, the aponeuroses, may, by * One of the oldest divisions of the primary of muscular fibres derive their peculiar cha- textures of the body, and one which nearly racters and functions from the accession of the coincides with that given by the author, ac- fibrilae of voluntary nerves to the ganglial and knowledges three tissues only, viz. the cellular, cellular textures. If this position be allowed nervous, and muscular. This arrangement has the involuntary muscular fibres will appear to been adopted by the majority of physiologists result from the combination of the cellular sub- since the time of Haller. It may be shewn, stance with the ganglial nerves only • the vo- that all the textures and organs of the body re- luntary, from the union of the cellular with both suit either from the various distribution of the ganglial and cerebral matters composing these primary tissues, or from the cellular only, the extremities of their ramifications, the mus- in consequence of a greater condensation of cular fibre varying -its character and pheno- its substance, or approximation of the mole- mena according as more or less of either kind cules of matter entering into its constitution, of nervous substance enters into its composi- and owing to a deposition of earthy substance tion. An intimate view of the mode of distri- between its interstices, as in the bones. It bution which characterises both classes of may, however, be a matter of doubt, whether nerves, as well as various other considerations the muscular texture does not arise from the support this opinion, which is calculated to union of the cellular tissue with the nervous form the basis of plausible explanations of substance ; the former combining with the many of the most important appearances and fibrite of the organic or ganglial nerves to functions of the different kinds of muscular form the muscular fibres generally, whether texture.—/. C. involuntary or voluntary; while the latter class ARRANGEMENT OP THE ANIMAL TEXTURES, ia long maceration, be converted into cellular substance. Muscular fibres are not subject to that alteration, nor is the nervous or cerebral pulp : the horny substance also resists that change. Every thing, therefore, leads us to acknowledge these four constituent principles in our organs. The primitive or simple tissues, variously modified and combined in dif- ferent quantities and in various proportions, constitute the substance of our organs. Their pumber is much more considerable, according to BicMt, whose happiest conception was this analysis of the human organisation. This physiologist reckoned in the human economy no fewer than twenty- one general or generating tissues* But it is evident that this analysis is carried too far ; that the tissues of which the skin and the hair are formed are exactly of the same nature, are analogous in their properties, and are nourished in a similar manner ; that the cellular tissue is the common basis of the osseous, cartilaginous, mucous, serous, synovial, dermoid, &c. It must be confessed, that this separate consideration of each organic tissue has furnished him with new ideas, ingenious analogies, and useful results; and that his " Anatomie Generale," in which those researches are contained, is his chief title to glory. That glory would be complete, if, in that book, and yet more in his other works, he had done his predeces- sors, as well as his contemporaries, the justice they had a right to expect from him. The simple or elementary fibre, about which so much has been written, may be considered as the philosopher's stone of physiologists.! In vain has Haller himself, in his pursuit of his chimera, told us, that the elemen- tary fibre is to the physiologist what the line is to the geometer, and that, as all figures are formed from the latter, so are all the tissues formed from this fibre. Fibra enim physiologo id est quod linea geometry, ex qud nempd figivrce omnes oriuntur. The mathematical line is imaginary, and a mere abstraction of the mind ; while the elementary fibre is allowed a material or physical existence. Nothing, therefore, can make us admit the exist- * The following classification of the prima- ry and compound textures nearly coincides 1. Cellular. 2. Nervous..........ganglial with that recommended by Dupuytren and Magendie:— \ Cerebral. 3. Muscular.........\ vJlun "ar^?' i Arterial, 4. Vascular..........\ Venous, Lymphatic. 5. Osseous. 6. Fibrous }F (D Fibrous, ibro-Cartilaginous, Dermoid. 7. Erectile. 8. Mucous. 9. Serous. •> 10. Synovial. 11. Glandular. ^12. Epidermous, or Corneous.—J. C. t Almost every physiologist who has writ- and fluids of the human body can be reduced ten on animal organisation has proposed a new to two elementary substances, jhe one formed arrangement of the primary textures. We will by globules, the other by a coagulable matter only take notice of the two following :—Wal- which, either alone or united to the former, ther considered the different organs and com- constitutes the living fluids, if it be in the li- pound textures to result from the cellular or quid state, and gives rise to the solid tissues, membranous, the vascular or fibrous, and from when it assumes the concrete form. See Ap- the nervous. J. F. Meckel founds his classi- pendix, Note C, for a more detailed account fication of organic substances on microscopic of the opinion of this eminent anatomist.— researches. He is of opinion that the solids /. C. 14 OP THE VITAL PROPERTIES. ence of a simple, elementary, or primitive fibre, since our senses shew us, in the human organisation, four very distinct materials. Each of these four substances, of which our solids are formed, and the principles of which, as we have seen above, are contained in the fluids, may be chemically resolved into azote, oxygen, hydrogen, and carbon. To these four chemical elements of our textures may be added phospho- rus, sulphur, lime, iron, and some other substances which are not so con- stantly present in the fluids and solids as those enumerated. Shall we also mention, as constituents of the animal economy, certain substances which are not subjected to the laws which ponderable bodies evince, and which are made known to us chiefly by their effects, such as caloric, light, and electricity, of which magnetism and galvanism are the effects 1 Among the organs, whether single or combined in systems, which enter into the human organisation, there are some whose action is so essential to life, that with the cessation of that action life at once becomes extinct. These primary systems, whose action regulates that of all secondary sys- tems, are as numerous in man as in the other warm-blooded animals. None of them can act unless the heart sends into the brain a certain quantity of blood, vivified by the contact of atmospherical air in the pulmonary tissue. Every serious wound of the brain or heart, every lasting interruption to the access of blood into the former of these organs, is invariably attended with death. The oxydation of the blood, and its distribution into all the organs, is consequently the principal phenomenon on which the life of man and of the most perfect beings depends. Sect. VI.—OF THE VITAL PROPERTIES ; SENSIBILITY AND CONTRACTILITY.* By sensibility is meant that faculty of living organs which renders them capable of receiving, from the contact of other bodies, an impression, stronger or fainter, that alters the order of their motions, increases or di- minishes their activity, suspends or directs them. Contractility is that other property by which parts excited, that is, in which sensibility has been called into action, contract or dilate; in a word, act and execute mo- tions. In the same manner, as we have not always a consciousness of the impressions received by our organs, and as, for example, no sensation in- forms us of the stimulating impression by which the blood calls the heart into action ; so it is by reflection only that we are induced to admit the ex- istence of certain motions; of those, for instance, by which the humours, when they have reached the smallest vessels, become incorporated into the tissue of our organs.| These motions, to make use of an ingenious com- parison, resemble those of the hour-hand compared with the second-hand of a watch. The hour-hand appears motionless, and yet in twelve hours it describes the whole circumference of the dial-plate, round which the other hand moves in one minute, with a motion that is visible. In considering life through the great series of beings that possess it, we have seen that those in which it is most limited, or rather, in which it con- sists of the least number of actions and phenomena,—vegetables, for in- stance, and animals like the polypus, which have no brain, no distinct ner- vous system,—are at once endowed with sensibility and contractility in all * See Appendix, Note D. the explanation of the properties, sensibility t If the suggestions offered in the note at and contractility, and the relations which they p. 12, respecting the constitution of the dif- hold with the circle of vital functions would be ferent kinds of muscular fibres, were adopted, • more apparent and better understood.—/. C. OP SENSIBILITY. 15 their parts. All living beings, all the organs which enter into their com- position, are impregnated, if we may be allowed the expression, with these two faculties necessarily co-existing, and which shew themselves by in- ternal and nutritive motions, obscure, indeed, and to be distinguished only by their effects. These two faculties appear to exist in the degree abso- lutely required for enabling the fluids that pervade all the parts of a living body to induce the action by which these parts are to assimilate such fluids. It is clear that the two properties of feeling and of motion are in- dispensable to all parts of the body. They are properties universally dif- fused through organised and living matter; but they exist without possess- ing any peculiar organ or instrument of action. Were it not for these two faculties, how would the different parts act on the blood, or on the fluid which supplies its place, so as to obtain from it the materials subservient to nutrition, and the different secretions 1 These faculties are therefore given to every thing that has life — to animals, to vegetables, to man in his wak- ing hours, or in his most profound sleep, to the foetus, to the child that is born, to the organs of the assimilating functions, and to those which con- nect us with surrounding beings. Both these faculties, obscure and in- separable, preside over the circulation of the blood, of the fluids, and, in short, over all the phenomena of nutrition. Though this kind of sensibility is always latent or concealed, it is other- wise with regard to contractility, which may be sensible or otherwise. The bone, which takes up the phosphate of lime, to which it owes its solidity, exerts that action without our being aware of its taking place, except by its effect; but the heart which feels the presence of the blood, without any consciousness on pur part of such sensation, exerts motions that are easily perceptible, but over which we have no control, either to suspend qr ac- celerate them. Vital properties in so weak a degree would not have been sufficient to the existence of mr0> and of the animals which resemble him,—obliged to keep up multifarious intercourse with every thing that surrounds them ; thus they enjoy a very superior kind of sensibility, by means of which the impressions which affect some of their organs are perceived, judged, and compared. This mode of sensibility might be more properly called percep- tibility, or the faculty of accounting to oneself for the emotions which are experienced. It requires a centre to which the impressions may be refer- red, and therefore it exists only in the animals which, like man, havea brain, or some organ in its stead ; so that the zoophytes and vegetables wanting that organ are equally destitute of this faculty. The polypi, and some plants, as the sensitive, perform, nevertheless, certain spontaneous motions, which seem to indicate the existence of volition, and consequent- ly of perceptibility. But these motions are the result of an impression which does not extend beyond the part in which it is experienced, and in which sensibility and contractility are blended. The almost latent sensibility of certain parts of the body cannot be ab- solutely compared to that of vegetables, since those organs, whose sensi- bility is so imperfect, manifest in disease a percipient sensibility, which shews itself by acute pain; and it is even sufficient to change the stimulus to which they are accustomed to determine the occurrence of this pheno- menon. Thus the stomach, on the parietes of which the food does not in health produce any perceptible impression, becomes the seat of very dis- tinct sensation, and of dreadful pain, when a small quantity of poisonous matter is introduced into it, In like manner, we are not conscious of the 16 OF SENSIBILITY AND CONTRACTILITY. impressions excited in the parietej of the bladder or rectum by the collec- tion of urine or foecal substances, except when their contents have be- come sufficiently irritating by their presence to excite in a certain degree those irritable and sensient cavities, and to transform their obscure into a very distinct sensibility. Is there not reason to suspect, that our uncon- sciousness in health of the impressions made on our organs by the fluids which they contain, depends on our being accustomed to the sensations which they incessantly excite 1 so that there remains but a confused per- ception, which in time disappears ; and may we not, under that point of view, compare all these organs to those of sight, hearing, smelling, tast- ing, and touching, that are no longer irritable by stimulants, to which they have long been habituated 1 Two systems of organs, very different in their uses and in their quali- ties, enter into the composition of the human body ; they are as two living and united machines,—the one, formed by the organs of sense, the nerves, the brain, the muscles, and the bones, serves to maintain its connexion with external objects ; the other, destined to internal life, consists in the diges- tive tube, and the organs of absorption, circulation, respiration, and secre- tion. The organs of generation in the two sexes form a separate class, which, as far as relates to the vital properties, partakes of the nature of the other two. By the organs of sense, and the nerves which form a communication between these organs and the brain, we are enabled to perceive, or to feel, the impressions made on us by external objects: the brain, the true seat of that relative sensibility, which might very justly be termed perceptibility, or the perceptive power (Pott), when excited by these impressions, is able to irra- diate into the'muscles the principle of motion, and to indfice the exertion of their contractility. This property, which is under the direction of the will, manifests itself by the sudden decurtation of a muscle, which swells, hard- ens, and determines the motion of those parts of the skeleton to which it is attached. The nerves and the brain are essentially thForgans of these two properties ; a division of the former is attended with a loss of sentiment and voluntary motion in the parts to which they are distributed. The other kind of sensibility is, on the contrary, quite independent of the pre- sence of nerves; it exists in all organs, although all do not receive ner- vous filaments. It might even be asserted, that the cerebral nerves are not at all essential to the life of nutrition ; the bones, the arteries, the carti- lages, and several other tissues, in whicn no nerves are seen to enter, are nourished equally well with the organs in which they exist in considerable number; the muscles themselves will carry on their own internal econo- my, notwithstanding the division of their nerves ; only, deprived of those means of communication with the brain, they can no longer receive from it the principle of voluntary contraction ; instead of that sudden, energetic, and lasting decurtation, which the will determines in them, they become merely capable of those quiverings called palpitations. The anatomist who studies the nerves with a view to ascertain their ter- mination, finds them all arising from the brain and spinal marrow, and pro- ceeding, by a longer or shorter course, to the organs of motion or of sensa- tion : let him take his scalpel and dissect one of our limbs, the thigh, for instance ; he will see the cords parting into numerous threads, most of which disappear in the thickness of the muscles ; whilst others, after creep- ing for a time about the cellular tissue, which joins the skin to the aponeu- rosis, end on the inward surface of the skin, of which they compose the OF SENSIBILITY AND CONTRACTILITY. 17 texture, and expand into sentient papillae on its surface. The bones, the cartilages, the ligaments, the arteries, and the veins, all those parts whose action is not under the control of the will, are without them.* Neverthe- less, all those parts which, in their natural state, send no perceptible im- pressions to the brain, which, when once insulated, may be tied and cut, without any sign of pain from the animal, and whose action the will does not control, are yet endued with a sensibility'and a contractility, which en- able them, after their own manner, to feel and to act, to recognise in the fluids that moisten them what is suited to their nourishment, and to sepa- rate that recrementitious part which has suitably affected their particular mode of sensibility."f In confining our attention, then, to the consideration of a single limb, we may easily satisfy ourselves of the existence of two modes of feeling, as of two sorts of motion ; a sensibility, in virtue of which certain parts can send up to the brain the impressions they receive, to be there objects of con- sciousness ; and another sensibility belonging to all organs, without excep- tion, and all that some of them possess, which is sufficient for the exercise of the functions of nutrition, and by means of which they are evolved, and are kept up in their natural state ; two kinds of contractility, appropriated to the two different kinds of sensibility :—the one, in virtue of which the muscles, obedient to the will, exercise the contractions which it determines ; the other, independent of the will, manifests itself by actions, of which we have no intimation, any more than of the impressions by which they are determined. The distinction being fairly laid down between sensibility and contracti- lity, it is easy to understand the origin of the endless disputes of Haller and his followers, about the parts of the body, in man and animals, which are endowed with sensibility and irritability.! All the organs to which that learned physiologist has denied these properties, as bones, tendons, mem- branes, cartilages, and cellular membranes, &c. possess only that latent sensibility, and that obscure contractility, common to all living beings, and without.which it is impossible to conceive life to exist. In a state of .health, they are utterly incapable of transmitting to the brain perceptible impres- sions, and of receiving from it the principle of manifest and sensible mo- tion. It has likewisebeen a matter of much dispute, whether sensibility and contractility are qualities of nerves, if these parts are their only instru- ments, and if their destruction is attended with a loss of these two vital properties in the parts to which they are transmitted. We may answer in the affirmative, as far as relates to the sensibility of perception and the vo- luntary motion which is entirely subservient to it; but that the existence of nerves is not at all necessary to the exercise of the sensibility and contrac- tility which are indispensable to the assimilation of nutrition. * Are destitute, or at least nearly so, of that belong to the other class, the cerebro- voluntary nerves.—/. C. spinal, may be inferred to exist in an organ t All these parts may be considered to pos- more or less abundantly, or to be entirely ab- sess ganglial nerves ; for as these nerves sent from it, according to the nature of the may be demonstrated on the more considera- phenomena which that organ presents. See bie trunks of arteries, even in the extremities, the Chapters on the Circulation, Sen- they may be supposed to accompany these sation, and Motion.—J. C. vessels to their most minute ramifications and % If the constitution of the muscular fibre, extremities, and to bestow on them those as formerly alluded to, be considered maturely, manifestations which these parts of the vas- the source of irritability, and its various de- cular system evince. Such, then, being the grees of intensity, with the relation which it constitution and connexion of the arterial and holds to sensibility, and the other modes of capillary vessels, no texture which possesses action which the animal textures evince, will these vessels can be considered to be des- become more apparent.—/. C. titute of this class of nerves. Those nerves 18 OF SENSIBILITY AND CONTRACTILITY, No part of the living body is absolutely insensible, but that sensibility of every organ is so modified that it is not affected by the same stimuli. Thus, the eye is insensible to sound, and the ear to light. A solution of tartar emetic causes no disagreeable impression to the conjunctiva ; taken into the stomach, it excites convulsive motions ; while an acid from which the stomach does not suffer, proves a cause of irritation to the conjunctiva, and brings on a violent inflammation of the eye. In the same manner, purgatives pass along the stomach without producing any effect on that viscus, but they stimulate the alimentary canal. Cantharides have a spe- cific action on the bladder, and mercury on the salivary glands. Each part feels, lives, moves, after its own way ; in each, the vital properties ap- pear under such shades and modifications, that they may be looked upon as so many separate members of the same family, concurring in one en- deavour, working for a common end, consentienlia omnia. (Hipp.) The faculty of assigning a cause to the sensations, and that of moving by volition, which man possesses in common with all animals formed with a distinct nervous centre, are essentially bound together. For, suppose a living being, furnished with locomotive organs, but without sensation, plac- ed in the midst of bodies that every moment endanger its existence, with- out any means of distinguishing them, it will hasten its own destruction. If perceptibility could, on the other hand, exist independently of motion, how dreadful would be the fate of such sentient beings, similar to the fabu- lous Hamadryads, who, immovably fixed in the trees of our forests, receiv- ed, without any power to shun them, ail the blows inflicted on their rustic abode. Dreams place us sometimes in situations which give us a just idea of their condition. A certain danger threatens our existence ; an enor- mous rock seems to detach itself, to roll and precipitate itself on our frail machine ; a frightful monster seems to pursue us, and opens a yawning mouth to ingulf us. We struggle to escape this imaginary danger, to avoid or to repel it; but an irresistible and unknown power, a mighty hand, paralyses our efforts, and keeps us rooted to the spot: it is a situation of horror and despair, and we awaken overwhelmed with the uneasiness which we have suffered. As there is no part that does not feel in a manner peculiar to itself, so there is no one that does not act, move, or contract, in a manner peculiar to itself; and the parts which have been found without a power of motion analogous to muscular contractility, have remained in that state of immo- bility only for want of a stimulus fitted to their peculiar nature. Some phy- siologists say they have excited a distinct quivering in the mesentery of a frog and of a cat, by touching them after they had been previously moisten- ed with alcohol, or muriatic acid. In the operation for sarcocele* I have often perceived that, while with my left hand I supported the tumour, and with a scalpel in the right divid- ed the spermatic chord, the tunica vaginalis shewed oscillatory contrac- tions. It visibly contracts in the operation for hydrocele. The injection of an irritating fluid determines evident motions in the tunica vaginalis. The osseous tissue, notwithstanding the phosphate of lime with which it is en- crusted, is susceptible of a contraction, whose effects, though slow, are ne- vertheless undeniable. After teeth have been shed or extracted, the edges * The contraction of the membrane, formed the same muscle corrugate the skin of the by the expansion of the cremaster muscle, has scrotum when this part is exposed to cold, and doubtless assisted in rendering more distinct draw up the testicles towards the inguinal the appearance in question. This effect must rings. The contractility of the skin of the he particularly distinct at the moment of divid- scrotum has but little influence in producing ing the spermatic chord. The contractions of this effect. W SENSIBILITY AND CONTRACTILITY. 19 eF the alveolar processes become thinned from contraction, and the alveo- lar cavities disappear. These facts appear to me to prove, still better than all the experiments performed on living animals (experiments of which, by the by, the results ought not-too confidently to be applied to the economy of man), what one should think of the, assertions of Haller and his follow- ers, on the insensibility and inirritability of the serous membranes, and of the organs of a structure analogous to theirs. We shall, at present, say nothing of the porosity, of the divisibility, of the elasticity, and other properties, which are common to living bodies and inanimate substances. These properties are never possessed hi their whole extent and in all their purity, if that expression may be allowed. Their results are always influenced by the vital power, which constantly modifies the effects which seem to depend most immediately upon a physical, chemical, or mechanical cause, or upon any other agent whatsoever. When life no longer is present, the organisation is the source of the physi- cal properties exhibited by our organs, and which may be denominated the properties of the tissues. It is owing to the organisation that a part exhi- bits the property of elasticity, and retracts and hardens when submitted to the action of fire. The extensibility proceeding from distension, traction, or the application of an analogous force, is dependent upon the organisa- tion, and should not be confounded with the truly vital extensibility which is so manifest in certain organs, as the penis and the clitoris. When ex- cited, they become turgid and dilated by the afflux of humours ; but that effect does not depend on a peculiar property distinct from sensibility and contractility. These parts dilate, their tissue stretches under the action of these two properties, which would occasion the same phenomenon in all other parts if their structure were similar. The same applies to caloricity, or that power inherent in all living beings of maintaining the same degree of heat in varying temperatures.* In consequence of which property, the human body preserves its tempera- ture of from thirty to forty degrees (of Reaumur's scale) under the frozen climate of the polar regions, as well as in the burning atmosphere of the torrid zone. It is by the exercise of sensibility and of contractility, that is, by the exercise of the functions over which these vital powers preside, that the body resists the equally destructive influence of excessive heat and cold. If one were to admit caloricity as one of the vital properties, because, according to Professor Chaussier, that power of preserving a uniform warmth is a very remarkable phenomenon, one might be led to suppose a distinct cause or a peculiar property to operate in producing other phe- nomena of no less importance. Barthez and Professor Dumas have fallen into the same error ; the for- mer, in wishing to establish the existence of a power of permanent situa- tion in the molecules of muscular fibres; the latter, in adding to sensibility and contractility a third property, which he terms the power of vital re- sistance. Living muscles are torn with much more difficulty than when dead, because the contractility which these organs possess in the highest degree is incessantly tending to preserve^the contact of the molecules, the series of which forms the muscular fibre, and even to draw them into closer connexion. This fact, which is brought forward as a proof of the existence of a peculiar power, is easily explained on the principle of con- tractility. r * See the notes on the subject of animal heat contained in the Chapter on Respira- tion. 20 OF SENSIBILITY AND CONTRACTILITY. Organised and living bodies resist putrefaction from the very circum- stance of their being endowed with life. The continual motion of the fluids, the re-action of the solids on the fluids, the successive and continual renovation of the latter by the reception of new chyle, their constant puri- fication by means of the secretions through which the products animalis- ed in excess are parted with, such are the causes which prevent the putre- factive action from taking place in bodies endowed with life, notwithstand- ing the multiplicity and the volatility of their elements. Their preserva- tion is therefore a secondary effect, and depending on the exercise of the functions regulated by sensibility and contractility. Nature is distinguish- ed for deriving a multitude of effects from a very small number of causes ; it, therefore, shews a very imperfect acquaintance with her laws, to assign a separate cause to each fact. The separation of the chyle which takes place in the duodenum, from the admixture of the bile with the alimentary substance, the vivification of the blood by respiration, the secretion of the fluids in the conglobate glands, nutrition in the organs, are so many acts of the living economy to which one might feel disposed to assign distinct causes; but these chemico- vital processes are so subordinate to sensibility and contractility, that they are met with only in organs endowed with these two properties, and they take place in a degree more or less perfect according to the condition of these properties in the organs in which they occur. We have stated that there exist two great modifications of sensibility and contractility ; that sensibility is divided into percipient sensibility and latent sensibility ; that contractility is at times voluntary, at others invohtn- tary, and that the latter may be perceivable or insensible. ' Perceiving. (Cerebral, nervous, animal sensibili- ty, perceptibility.) With consciousness of impressions, or percepti- bility; it requires a peculiar apparatus. Latent. {Nutritive, organic sensibility.) Without consciousness of impressions, or ge- neral sensibility, common to every thing that has life ; it has no peculiar organ, and is found universally diffused in living parts, ani- mal or vegetable.* f Voluntary and sentient, subordinate to percepti- I bility. Contractility. -J. Involuntary and insensible, corresponding to la- tent sensibility. Tonicity. (, Involuntary and sentient The cause of this last modification of contractility appears to depend on the peculiar organisation of the system of the great sympathetic nerves. From these nerves, the heart, the digestive canal, &c. seem to receive the power of exerting sensible contraction ; an effect produced by the direct application of a stimulus, and over which volition has no control, as will be stated in speaking gf those nerves. Sensibility and contractility offer a vast number of differences the prin- cipal of which depend on the age. the sex, the regimen, the climate the state of waking or of sleep, of health or of sickness, on the relative de- velopment of the lymphatic, cellular, or adipose systems, and on the prc« pprtions which exist between the nervous and muscular systems. * See Note at page 18. Sensibility. ^ OF SENSIBILITY AND CONTRACTILITY. 21 In the first place, the principle of sensibility and of contractility may in its action be likened to a fluid flowing from any source whatsoever, which is consumed, repaired, and drained by use, re-supplied, or exhausted, equal- ly distributed, or occasionally concentrated on certain organs. Secondly. Sensibility, like contractility, is very considerable at the in- stant of birth, and seems to diminish more or less rapidly till death. Thirdly. The liveliness and frequency of impressions wear it out very early. It, in a manner, repairs itself, that is, recovers its original delicacy, when the sentient organs have been long at rest. Thus, an epicure, whose taste has grown dull with high living, will recover all its accuracy, if, du- ring several months, instead of spiced ragouts and spirituous liquors, he lives on dry bread and plain water. In like manner, contractility becomes exhausted in the muscles which are too long employed, and it is recovered during the repose of sleep. Fourthly. The following is an instance of the manner in which sensi- bility becomes concentrated in one organ, and appears to forsake the others: when the venereal excitement is in its highest degree, animals under its influence receive blows and stings without pain. Domestic animals in that condition are often ill treated, without appearing to feel what is done to them. If the hind legs of the toad are cut off, at the time that he is holding the female firmly embraced, and is pouring his prolific seminal fluid on the ova which are issuing at her anus, he does not lose his hold, he seems insensible to every other sensation ; as a man who is taken up with one thought, and absorbed in reflection, is scarcely diverted from it by any means that can be employed. When, during the influence of satyria- sis, the vital power is carried to excess in the penis, patients have been known (as we are told by Aetius) to cut off both their testicles, without suffering the pain usually attending so severe an operation. It is by this law of sensibility that we are to explain the observation of Hippocrates, that two parts of the body cannot be in pain at the same time. If two pains come on at once, the more violent prevents the slighter from being felt. Duobus doloribus, simul orientibus, non eodem in loco, vehementior obscu- rat alterum. In cases of scrofulous swellings, the parts are observed to in- flame, to become painful, and suppuration occurs but rarely in every part at once, if the case is serious and attended with acute pain. The germ of a disease, or of a slighter affection, may sometimes remain dormant under a greater pain. I was once overturned in a carriage, from the awkward- ness of the coachman, the windows were broken, and my wrists sprained. The right wrist, which had suffered most, swelled first; I emploj'ed the proper treatment, and when, at the end of a week, the swelling and pain had almost completely ceased, and the right hand was beginning to recover its suppleness and flexibility, the left wrist swelled, and, in its turn, became pained ; two complaints, if they may be called such, appeared in succes- sion, and separately went through their regular course* The perfection of one sense is never obtained but at the expense of an- other ; the blind, who bestow more attention on the sensations communi- cated by the sense of touch and of hearing, often astonish us by the deli- cacy of these organs ; so that, as has, been observed, those who, to im- prove the human voice, have dared to mutilate their fellow-creatures, by depriving them of the organs of generation, might have bethought them- * John Hunter maintains, from theory, the gether, the diseases themselves must be vica position that no two different fevers can take rious. And he verifies his reasonings from ex place at the same time in the constitution ; perience, But that if the two causes of disease exist to- 22 OF SENSIBILITY AND CONTRACTILITY. selves of putting out their eyes, to render them more sensible to the sweet impressions of harmony. Fifthly. During sound sleep, the exercise of the percipient faculty, and that of voluntary contractility, are entirely suspended. In that state, it seems as if some covering were thrown over the sentient extremities. We know how hard the hearing becomes, how dull the senses of smell and of taste, how dim the sight, a cloud spreading before the eyes, the mo- ment we are fallen asleep. Vir guidam, exquisitissima sensibilitale prcedilus, semiconsopitus coibat; huic, ut si velamento levi glans obductus fuisset, sensus voluptatis referebatur. Sixthly. Sensibility is more lively, and more easily excited, in the in- habitants of warm climates than in those of northern regions. What a prodigious difference there is in that respect between the native of Germany and of the southern provinces of France. Travellers tell us, that there are in the neighbourhood of the poles natives so little endowed with sensi- bility, that they feel no pain from the deepest wounds. The inhabitants of the coast of North America, if we may believe the testimony of Dixon and Vancouver, thrust sharp nails and pieces of glass into the soles of their feet without feeling the slightest uneasiness. On the contrary, the slightest prick from a thorn, for instance, in the foot, is in the strongest African frequently followed by convulsions and locked jaw. The impres- sion of the air is alone sufficient to produce the same accident in the negro children in the colonies, the greater number of whom die of locked jaw a few days after birth. Montesquieu* very justly observed this difference which exists in the sensibility of the southern and northern nations, and he says of the latter, that " if you would tickle, you must flay them." Now, as the imagina- tion is always proportioned to the sensibility, all the arts that are cultivated and brought to perfection only by the exercise of that faculty, will flourish with difficulty near the icy~polar regions, unless the powerful influence of climate be counteracted by well-directed moral and physical causes. Man is of all beings the one that most powerfully resists the influence of external causes ; and although the influence of climate is sufficient to modify his external appearance, so as to lead to a division of the species into several distinct varieties or kinds, this superficial impression is very different from the great alterations to which other beings are exposed from the mere change of climate. Man is every where indigenous, and exists in all climates ; while the plants and animals of the equator languish and die when conveyed to the polar regions. From the flexibility of his na- ture, man enjoys the power of adapting himself to the most opposite situa- tions, of establishing between them and himself relations compatible with the preservation of life. Nevertheless, it is not without difficulty that man undergoes these changes, and accustoms himself to new impressions. The periodical return of the seasons determines that of certain derange- ments to which the animal economy is subject. The same diseases mani- fest themselves under the influence of the same temperature, and, to use * This philosopher has borrowed from the ble to the establishment of tyranny. Hippo- father of physic one of his most brilliant and crates had said of the Asiatics, that their be- paradoxical opinions. In his conception, ing less warlike than the Europeans depended warm climates are the seats of despotism, and on the difference of climate, and likewise on the cold, the seat of liberty. This error is the despotic form of their government. And completely refuted in the profound and phi- he observes, that men who do not enjoy their losophical work of Volney on Egypt and natural rights, but whose affections are con- Syria. He shews that what Montesquieu has trolled by masters, cannot feel the bold pas- said of cold climates applies to mountainous sion of war.—See Chap. XI. on the Varieties regions, while a champaign is more favoura- of the Human Species. OF SENSIBILITY AND CONTRACTILITY. 23 an ingenious comparison, resemble those birds of passage which visit us at stated seasons of the year. Thus, hemorrhages and eruptive affections come on with the return of the spring; summer comes attended by bilious fevers ; autumn brings on a return of dysenteric affections ; and winter abounds in inflammations of the lungs and other parts. The influence of climate on the human body does not shew itself merely in occasioning epidemic diseases, the consideration of which leads to the establishing what physicians call medical constitutions : this influence operates on man in health, as well as in sickness ; and to say nothing of the alterations which our moral nature experiences from the tendency to love, rendered more impetuous with the return of spring, or of the melancholy to which nervous people are often subject towards the end of autumn, when the trees are shedding their leaves, the increase of> growth is particularly re- markable at the time of the first growth of plants, as was observed again and again by a friend of mine, physician to a large seminary. Seventhly. Sensibility is greater in women and children, their nerves* are likewise larger and softer, in proportion to the other parts of the body. In general, the principle of sensibility seems to decrease in proportion as it has contributed to the development of the acts of life; and the power of being impressed by external objects diminishes gradually with age, so that there is a period of decrepid old age at which death appears a neces- sary consequence of the complete exhaustion of that principle. In short, as I have said in describing the progress of death, at its approach sensi- bility shews increase of activity and liveliness, as if its quantity required to be completely exhausted before the termination of existence, or as if the organs made a last effort to cling to life. Eighthly. The development of the cellular and adipose substance diminishes the energy of sensibility ; the extremities of the nerves being more covered, and therefore not so immediately applied to the objects, the impressions which are felt are more obscure. The fat operates on the nerves as wool would do on vibrating chords, if wrapped round them, to fix them, to prevent their quiverings, and stop their vibrations. Very nervous women are very thin ; persons of much sensibility have seldom much embonpoint. Swine, in which the nerves are covered by a thick layer of fat, are the most insensible of all animals. The suscepti- bility of the nerves may be diminished, and their sensibility blunted by pressure. The application of a bandage firmly rolled round the body and limbs of an hysterical woman, will diminish the violence of her fits. In dressing wounds affected with what is called the hospital gangrene, I have often relieved the pain by desiring an assistant to apply firm pressure above the sore. Ninthly. There exists between the force of the muscles and the sensi- bility of the nerves, between the sensible energy and the force of contrac- tion, a constant opposition, so that the most vigorous athletes, whose mus- cles are capable of the most prodigious efforts and of the most powerful contractions, are but slightly affected by impressions, and are with difficulty roused into action, as we have explained in giving a history of the nervous and muscular temperaments, which are characterised by this difference. Hence, man has more sensibility than the quadrupeds, although his nerves are smaller than theirs, which seem destined to set the muscles in action, and to serve as nerves of motion rather than of sensation. There is no muscular fibre, however minute, in which we are not obliged to admit the existence of a small nervous filament, to which it probably * Their, voluntary nerves, 24 OF SYMPATHY. Sftv rtlP T °f contracting- Contractility, at least voluntary contrac- pnt7ni T aPpef t0 be inherent in the muscular fibre, nor independ- 2 ^^^rves, through the medium of which the will determines the action of the muscles ; and if these last organs, when insulated, contract on me direct application of a stimulus, is there not reason to suspect that tnis stimulus acts on that portion of nerves which remains in the muscle after it has been insulated, and which is intimately united to its fibres % 1 he animals which have no distinct nervous system possess at once in all their parts sensibility and contractility; these two properties become blended in the organs, as well as in the phenomena of life, and can be perceived separate only by a pure abstraction of the mind, which considers in succession the impression produced on these beings, and the motion of their substance, which is an immediate consequence of that impression* Sensibility and contractility being always present in living animal bodies, some authors have conceived it more natural to combine them under the common appellation of excitability. This one term has been even consider- ed sufficient to designate the whole of the vital properties. But in embrac- ing these properties by this abridged expression, Brown, far from having simplified the study of them, has only increased the obscurity in which they are veiled. In health, as well as in disease, sensibility and contrac- tility do not appear constantly to obey the same laws : action and repose produce not similar effects on them. The sensibility of the eye is enliven- ed and repaired by the absence of impressions ; but a muscle condemned to repose becomes paralytic. The physiologist who wishes to ascertain the causes of sensibility and contractility is as absurd as the person who endeavours to account for the weight, elasticity, and other secondary properties of matter. These two vital principals are only found in organised bodies: their existence is related to a certain arrangement of parts, which has been conveniently called or-; ganisation ; but it suffices not that a body should be organised in order that it should enjoy sensibility and contractility—that it should live. Death often supervenes without the organisation having evinced any derangement. A certain commixture or amalgamation of electricity, or of some other imponderable agent, with organised matter,, is most probably indispensable to life. But what are the conditions or states of this amalgamation 1 We will not enter any farther into a consideration of the laws and phe- nomena of the vital properties, for fear of being led into useless repetitions when we come to the history of the functions over which they preside. We will conclude what relates to them by presenting the two most impor- tant features of their history, I mean sympathy and habit. Sect. VII.—OF SYMPATHY. There exist among all the parts of the living body intimate relations ; all correspond to each other, and carry on a reciprocal intercourse of sen- sations and affections. These links which unite together all the organs, by establishing a wonderful concurrence and a perfect harmony among all the actions that take place in the animal economy, are known under the name of sympathies. The nature of this phenomenon is yet unknown ; we know not why, when a part is irritated, another very distant part par- takes in that irritation, or even contracts: we do not even understand what are the instruments of sympathy, that is, what are the organs which connect two parts in such a manner, that when one feels or acts the other * See the notes on Sensibility and Contractility in Appendix, Note D. OF SYMPATHY, 25 is affected. But though beyond explanation, sympathy is not the less im- portant in the economy of living beings ; and these connexions between remote parts constitute one of the most remarkable differences between those beings and inorganic bodies. They are the most characteristic phe- nomena of vitality. Nothing similar is observable in dead or inanimate nature, in which all things are connected together only by palpable and material links ; here the chain is invisible, the connexion evident, the cause occult, and the effect apparent. Whytt has clearly shewn that the nerves cannot be considered as the exclusive instruments of sympathy,* since several muscles of a limb, which receive filaments from the same nerve, do not sympathise together, while there may be a close and manifest relation between two parts, of which the nerves have no immediate connexion, since each nervous fila- ment having one of its extremities terminating in the brain, the other, in the part to which it is sent, remains distinct from those of the same trunk, and does not communicate with them. Sympathies may be distinguished into different kinds. In the first place, two organs which execute similar functions :—the kidneys, may supply each other's office. When the uterus is in a state of pregnancy, the breasts participate in its condition, and there is determined into them a flow of humours necessary to the secretion which is to take place. Secondly: the continuity of membranes is a powerful source of sympa- thy. The presence of worms in the bowels determines an uneasy pruritus around the nostrils. When there is a stone in the bladder, a certain degree of itching is felt at the extremity of the glans penis. The secretion of se- veral fluids is determined in the same manner; thus the presence of food in the mouth brings at the extremity of the parotid duct an irritation which ex- tends to the parotid glands, calls them into action, and increases their secre- tion. Thirdly : if the pituitary membrane is irritated, the diaphragm with which it has no immediate organic connexion, nervous, vascular, or mem- branous, contracts and occasions sneezing. Is not this sympathy one of those which Haller ascribed to a re-action of the sensorium commune ? If the impression produced on the olfactory nerves by snuff is too powerful, the uneasy sensation is transmitted to the brain, which determines towards the diaphragm a quantity of the principle of motion sufficient to enable that muscle suddenly to contract the dimensions of the chest, so as to expel a column of air, that may detach from the pituitary membrane the substances that are a cause of uneasiness to it. Fourthly : does not the principle of life seem to control at pleasure the phenomena of sympa- thy ? The rectum, when irritated by the presence of the excrements, contracts ; which cause determines the accessory and simultaneous action of the diaphragm and abdominal muscles ? Does this connexion de- pend on organic communications ? Why, then, is not the sympathy re- ciprocal, and why does not the rectum contract when the diaphragm is ir- ritated 1 Fifthly : can the repeated habit of the same motions explain the harmony which is observed in the symmetrical organs 1 Why, when our sight is directed to an object placed laterally, does the rectus externus of the eye on that side act at the same time as the rectus externus of the other eye ? The indispensable utility of this phenomenon, in keeping a paral- * The nerves of voluntary motion certainly of the gan«*ial class of nerves. See the cannot be supposed to be the instruments of notes on the chapter which treats of " the sympathy ; but no valid argument can be ad- System of the great Sympathetic Nerves"—r- duced against the opinion which refers the /. C. sympathies to the distribution and connexions 4 2fJ OF SYMPATHY. wum axis of vision'is very obvious ! buFwho can assign the cause 1 Why are rotatory motions, in different directions, performed with so much difficulty by the arm and leg of the same side of the body ? Can it be called a just idea of the innumerable varieties of this phenomenon and of its frequent anomalies, to say, with Rega, that there are sympathies of action or of contractility {consensus actionum), sympathies of sensibility {consensus passionum). All these difficulties render it pardonable in Whytt to have considered the soul as the sole cause of sympathy, which was, in fact, a modest avowal of the difficulty of explaining the subject. We are not justified in considering sympathy as an anomalous action, as an aberration of the vital power* Can it be said that the natural order of sensibility and irri- tability is inverted in the sympathetic erection of the clitoris and of the nip- ple, or in the turgescence of the breasts, determined by the gravid state of the uterus 1 It is by means of sympathy that all the organs concur in the same end, and yield each other mutual assistance. It affords us the means of ex- plaining how an affection, at first local or limited in its extent, spreads and extends to all the systems; it is thus that every morbid process is carried on. The diseases termed general, always originate, through the medium of association, in the insulated affection of an organ or a system of organs. In fact, the affections which appear to vis most complex in the num- ber, the variety, and the dissimilarity of their symptoms, consist of only one, or of a small number of primitive or essential elements ; all the rest are accessory, and depend on numerous sympathies of the affected or- gan, with the other organs of the animal economy. Thus, if the sto- mach is the seat of irritation, from foulness of its contents, pains of all kinds come on, but especially in the head and limbs, with a burning heat, nausea, loss of appetite, anxiety ; and these symptoms constitute a disease, which appears to affect the whole system. To go on with the same illustration, the stomach, when oppressed by ir- ritating substances, contracts spontaneously to get rid of them. The uni- versal disturbance which their presence occasions, seems directed towards the same end, as if the suffering organ called upon all the others to assist in relieving it. These synergies, or aggregate motions, tending to one end, and arising out of the laws of sympathy, constitute the diseases termed general, as well as the greater part of those which are called local. It is by means of them, and through these kinds of organic insurrections, if we may be per- mitted to use this term, which perfectly expresses our meaning, that na- ture struggles with advantage, and rids herself of the morbific principle, or of the cause of the disease ; and the art of exciting and directing these actions furnishes the materials of the most important doctrines of the practice of medicine. I have used the terms excite and direct; for it is * Sympathy may be considered to be that the cerebral nerves and to the reaction of the state of an organ or texture which holds a sensorium, as when the Schneiderian mem- certain relation to the condition characterising brane is irritated, the diaphragm is affected in another organ or texture, in health or in dis- consequence of the excitement conveyed to ease : or, it may be viewed as a certain re- the brain, and thence to this muscle by means lative state of the vital power as it exists in of its voluntary nerves. The latter class takes separate organs or textures ; as when one part place independently of the sensorium, and is excited, another participates fn the change, arises from the ramification and distribution and evinces a similar feeling, motion, or func- of the ganglial nerves, especially those which tion. are sent to the vascular system. For the Sympathies may be classed into the reflex elucidation of this subject, see Appendix, and direct. The former may be referred to Note E.—J. C. OF HABIT. 27 necessary at times to increase, at others to diminish, their intensity and force, and on some occasions to excite them, when nature, overwhelmed under disease, is almost incapable of reaction. This last circumstance be- longs to the diseases of the most dangerous kind, if we include those in which the efforts of nature, though marked by a certain degree of energy, are without connexion or consent, and frustrated by their want of cohe- rence. The character of these affections was first well expressed by Selle, who substituted for the term malignant, which used to be applied to them without any precise meaning, that of ataxic, which points out very correct- ly the want of order, and the irregular succession of their symptoms* A knowledge of sympathies is of the highest importance in the practice of medicine.f When we wish to avert an irritation fixed in a diseased organ, experience and observation prove that it is on the organ which bears to it the closest sympathetic connexions that it is useful to apply medicines intended to excite counter-irritation. This might perhaps be the fittest place to inquire into the nature of those concealed relations which draw men together, and of those aversions which prevent their union ; to discover the causes of those secret impulses which lead two beings towards each other, and force them to yield to an irresistible propensity. We might inquire into the reason of antipathy ; and, in a word, establish the complete theory of moral sentiments and af- fections. Such an undertaking is greatly above our strength; and, be- sides, does not absolutely belong to our subject. It would require a con- siderable time; and whoever should undertake it, would be in consider- able danger of losing his way at every step in the extensive field of con- jectures. Sect. VIII.—OF HABIT. It is easier to feel the meaning of this term than to define it. Habit, however, may be said to consist in the frequent repetition of certain acts, of certain motions, in which the whole body participates, or only some of its parts. The most remarkable effect of habit is to weaken, after a time, the sensibility of organs. J Thus, a catheter introduced along the urethra, and allowed to remain there, causes, during the first day, rather sharp pain; on the second day it feels less uneasy ; on the third day it is only trouble- some ; and on the fourth the patient scarcely feels it. The use of snuff at first increases the secretion of mucus in the nose; but if continued a certain time, it ceases to affect the pituitary membrane, and the secretion would diminish considerably but for the practice of increasing daily the quantity of that acrid powder : the presence of a canula in the nasal duct, after the operation for fistula lachrymalis, increases at first the mucous secretion of that canal; but in proportion as it becomes accustomed to the extraneous body, the secretion returns to its natural condition. * Symptomata nervosa, nee inter se, neque % The influence of habit is chiefly percepti- tausis manifestis respondentia. . Ordo tert. ble on the organs of sense and voluntary mo- ataxia?, C. G. Selle. Rudimenta Pyretologise tion. Methodicae. Habit produces very different effects upon f This information may be obtained by con- separate parts of the animal economy, ac- sulting the works of the ancients, and espe- cording as they are altogether removed from cially of Hippocrates, who appears to have the influence of the will, or as they are more felt all the importance of this subject. Among or less, or entirely, subjected to it ; the effects the moderns, Vanhelmont, Baglivi, Rcga, of habit, for instance, on our voluntary organs, Whytt, Hunter, Barthez, and Bichut, have differ very much from those which result from collected on this topic a great number of its operation on the viscera of organic life. facts obtained from experiments on animals, See Appendix, Note F.—J. C. and especially from observations on diseases, 28 OF HABIT. It is only by our sensations that we are aware of our existence. Life, to make use of the figurative language of system, of a modern writer, consists in the action of stimuli on the vital powers. {Tola vita, quanta est, consistit in stimulo et vi vitali.—Brown.) Sentient beings feel a continual necessity of renewed emotions; all their actions tend to the obtaining agreeable or disagreeable sensations: for, in the absence of other sensa- tions, pain is sometimes attended with enjoyment. Those who have ex- hausted every kind of enjoyment, and who have had no pleasures ungrati- fied, are led to suicide from a weariness of life : who can live, when all power of feeling is gone ? The following is the most extraordinary and remarkable instance known of the manner in which habit, and a frequent repetition of the same impres- sions, wear out by degrees the sensibility of organs:—A shepherd, about the age of fifteen, became addicted to onanism, and to such a degree as to practise it seven or eight times in a day. Emission became at last so diffi- cult, that he would strive for an hour, and then discharge only a few drops of blood. At the age of six-and-twenty, his hand became insufficient; all he could do, was to keep the penis in a continual state of priapism. He then bethought himself of tickling the internal part of his urethra, by means of a bit of wood six inches long; and he would spend in that occupation several hours, while tending his flock in the solitude of the mountains. By a con- tinuation of this titillation for sixteen years, the canal of the urethra be- came hard, callous, and insensible. The piece of wood then became as ineffectual as his hand. At last, after much fruitless effort, G-----one day in despair drew from his pocket a blunt knife, and made an incision into his glans along the course of the urethra: this operation, which woukl have been painful to any one else, was in him attended with a sensation of pleasure, followed by a copious emission. He had recourse to his new discovery every time his desires returned. When, after an incision into the cavernous bodies, the blood flowed profusely, he stopped the haemor- rhage by applying around the penis a pretty tight ligature. At last, after repeating the same process perhaps a thousand times, he ended in split- ting his penis into two equal parts, from the meatus urinarius to the scrotum, very near to the symphysis pubis. When he had got so far, un- able to carry his incision any farther, and again reduced to new privations, he had recourse to a piece of" wood shorter than the former : he introduced it into what remained of the urethra, and exciting at pleasure the extremi- ties of the ejaculatory ducts, he provoked easily the discharge of semen. He continued this about ten years : after that long space of time, he one day introduced his bit of wood so carelessly, that it slipped from his finders and dropped into the bladder. Excruciating pain and serious symptoms came on. The patient was conveyed to the hospital at Narbonne. The surgeon, surprised at the sight of two penes of ordinary size, both capable of erection, and in that stage diverging on both sides, and seeing besides from the scars and from the callous edges of the division, that this confor- mation was not congenial, obliged the patient to give him an account of his life, which he did, with the details which have been related. This wretch was cut as for the stone, recovered of the operation ; but died three months after, of an abscess in the right side of the chest, his phthisical state having been evidently brought on by the practice of onanism carried on nearly forty years.* * The habit of suffering renders us, in the end, insensible to pain • but every thing in this world is balanced-; and if habit lightens our evils by * Chopart, Maladies des Voies Urinaires, tome ii. OF HABlf. 29 blunting sensibility, it, on the other hand, drains the source of our sweetest enjoyments. Pleasure and pain—these two extremes of sensation, in a manner approximate to each other, and become indifferent to him who is accustomed to them. Hence arises inconstancy, or rather, that insatiable desire of varying the objects of our inclinations, that imperious want of new emotions ; hence we possess with indifference what we pursued with the utmost ardour and perseverance, and even cease to be impressed by those charms which once held us captivated. A striking instance of the powerful influence of habit on the action of organs is afforded by that criminal who, we are told by Sanctorius, was taken ill on being removed from a noisome dungeon, and did not recover till he was replaced in the impure air to which he-had been long accustomed. Mithridates, that formidable rival of the Roman power, dreading to be taken alive by his enemies, tried in vain to put an end to his life by taking large doses of the most subtle poisons, because he had long inured himself to their action.* It has, therefore, been justly said of habit, that it is a second nature, whose laws ought to be respected. The organs of generation in women, in consequence of their lively sensi- bility, are in an especial manner submitted to the powerful influence of habit. The womb, after a miscarriage, has a tendency to a renewal of the same occurrence when the same period of pregnancy recurs ; so that the greatest precautions are necessary to prevent abortion in women who are subject to it, when they have reached the month in which they before mis- carried. May not death be considered as a natural consequence of the laws of sensibility? Life, depending on the continual excitement of the living solids by the fluids which moisten them, ceases, because the parts endowed with sensibility and contractility, after long habitude of the impressions of those fluids, lose their capacity of feeling them. Their action, gradually extinguished, would perhaps revive, if the energy of the stimulating power were increased. A knowledge of the power of habit is a useful guide in the application of remedies, the greater part of which operate in the cure of diseases, only by modifying sensibility. A wound in which lint has kept up the degree of inflammation necessary to cicatrisation, becomes insensible to that applica- tion, the parts become spongy and soft, and the cure is protracted. The lint should then be covered with an irritating powder, and the pledgets soaked in an active fluid : one may safely increase the doses of a medicine which has been long employed. Thus, in the treatment of the venereal disease by mercurials, the dose is to be gradually increased : with the same view, Frederick Hoffman recommended, in the treatment of chronic diseases, that the remedies should be suspended for a time and then resumed, lest the system should get accustomed to them, and their influence be lost. The same motive should lead one to vary the treatment, and to employ, in suc- cession, those medicines to which nearly the same qualities are assigned, for each of them call forth the sensibility in a peculiar manner. The ner- vous system may be compared to an earth abounding in various juices, and for a full display of whose fecundity it is necessary that the husbandman commit to it the germs of various plants. It is very remarkable, that habit, or the frequent repetition of the same act, which uniformly, under all circumstances and in all organs, blunts * In some very rare cases, habit produces vomiting in themselves, that the twentieth a quite contrary effect. Cullen states, that part of a grain of tartar emetic was sufficient he knew persons so accustomed to excite to excite a convulsive action of the stomach. 30 OF HABIT. physical sensibility, should improve the intellect,* and increase the facility and activity of execution of all the operations of the understanding, or of the actions which depend on them. " Habit impairs the sensitive power, aud improves the judgment." Bich&t was therefore incorrect, when, in his distinction of the organs which are subservient to the functions of assimila- tion, from those which serve to keep up our relation with the surrounding objects, he maintained, that the sensibility of the latter becomes more ex- quisite, while the sensibility of the former becomes impaired from habit. But can a painter, because he judges more correctly than the ignorant of the beauties of a picture, be said to see it better ? Surely not; for he may, with a sight far less penetrating and more infirm, form a more accu- rate analysis, from the habit which he has acquired, and judge with a great deal more promptitude and certainty, of the several parts and of the whole ; just as the practised ear of the musician seizes, in a piece of mu- sic, and during the most rapid execution, the expression and the value of all the notes and tones. The error has arisen, from its being forgotten, that, correctly speaking, it is not the eyes that see, or the ears that hear ; that the impressions produced by the sounds on these organs are but the occasional cause of the sensation, or of the perception of which the brain is the exclusive seat. Which has the more delicate sense of hearing, the North American savage, who hears the noise of the step of his enemies at distances that astonishes us; or the artist who does not hear a person speak- ing at the distance of fifty$)aces from him, but who directs with judgment all the operations of a great orchestra, and who distinguishes skilfully the effect of each part % Bring down to a frugal Pythagorean regimen one of our modern epi- cures : his palate, exhausted of its sensibility by the most savoury dishes, by ardent liquors, and the most exquisite ragouts, will discover no taste in dry bread. Let him, however, live on bread, if he can, for some time ; it will soon appear to him to have a grateful taste, as it does to those who make it their principal article of food, or who take it only with substances which have not a very distinct taste. Although, with the sense of smell, that of taste furnishes us only with ideas the most directly connected with our preservation, those which most turn upon the wants of our animal na- ture ; although we retain with difficulty the impressions of these senses, and that, to enable us to retain them, they must be often repeated ;—the epicure had so carefully analysed them, that he. had attained to the discern- ment of the faintest differences of taste, all those delicacies of sensation, which, as Montesquieu said, are lost to us vulgar eaters. The motions, under the direction of the will, acquire, by the precision of the determinations, the same aptness, facility, and readiness ; and the dancer, who surprises us with his agility, has reflected, more than might be imagined, on the very complicated steps of which a ballet is composed. Morbid sensibility is equally under the influence of habit. I have always observed, that discharges from the urethra become less painful from their frequency. There is nothing, down to disease itself, that is not made lighter by habit, as has been well observed by the old man of Cos. It remains then demonstrated, even as a general thesis, that habit, or the frequent repetition of the same acts, whilst it regularly reduces physi- cal sensibility, improves intelligence, and gives facility and promptness to all the motions that are under the direction of the will. * As soon as an act fails to excite our nature : as sensation ceases, reflection corn- sensations, in an inordinate degree at least, mences; an enquisite state of the former is scl- the reasoning powers proceed to analyse its dom compatible with a sound judgment.—J.C. OF THE VITAL PRINCIPLE. 31 Sect. IX.—OF THE THE VITAL PRINCIPLE* The words vital principle, vital force, &c. do not express a being existing1 by itself, and independently of the actions by which it is manifested : it must be used only as an abridged formula, which serves to mark the total of the powers that animate living bodies, and distinguishes them from inert matter. So that whenever, in the course of this section, I shall use these terms, or any equivalent, it is to be taken as if I had said, the aggregate of the properties and laws that regulate the animal economy. This expla- nation is become indispensable, now .that several writers, realising a mere abstraction, have spoken of the vital principle as of something very dis- tinct from the body, as of a being altogether separable, which they have invested with feeling, and thought, and even deliberate intentions. From the furthest antiquity, the many and striking differences of living and inorganic bodies, have led some philosophers to conceive in the for- mer a principle of particular actions, a force which maintains the harmony of their functions, and directs them all to a common end, the preservation of individuals and of the species. This simple and luminous doctrine has remained, even to our own days, only modified in its passage through many years : and no one now disputes the existence of a principle of life, which subjects the beings that enjoy it to a system of laws different from those which inanimate beings obey ; a force which might be characterised as withdrawing the bodies it animates from the absolute dominion of chemical affinities, which would else, from the multiplicity of their elements, act on them with great power; and as maintaining them in a nearly equal tem- perature, whatever may be that of the atmosphere. Its essence is not in preserving the aggregation of constituent molecules, but in drawing to it other molecules, which, by assimilation to the organs it prevades, replace those that are carried off in daily waste, and serve for their nourishment and growth. All the phenomena that are to be observed in the living human body might be brought as proofs of the principle which animates it. The ac- tions of the digestive organs on its food ; the absorption, by the chylous vessels, of its nutritious parts ; the circulation of these nutritious juices through the sanguineous system ; the changes they undergo in their pas- sage though the lungs and the secretory glands ; the impressibility by out- ward objects; the power of approaching or avoiding them ; in a word, all the functions that are carried on throughout the animal economy, proclaim its existence. • But it is customary to take a proof of it yet more direct from the properties with which the organs of these functions are endowed. We have examined these properties, and we have seen that each of them presents us with at least two great modifications ; that the last discovers three, which are, voluntary contractility, contractility involuntary and in- sensible, Stahl's tonic motion ; and lastly, contractility involuntary and sen- sible, as that of the heart and the intestines. If it is useful to analyse in order to know, it is of equal importance not to multiply causes, from misconceiving the nature of effects. And if, on the one hand, the multitude of the phenomena of life inclines us to the belief of many causes to produce them ; the unfailing harmony that pervades all the actions, their mutual connexions and reciprocal dependencies, point * See Appendix, Note A. 32 OT THE VITAL PRINCIPLE. much more decisively to a sole agent, as causing, directing, and controlling these phenomena. The hypothesis of the vital principle is to the philosophy of living be- ings what attraction is to astronomy. To calculate the revolutions of the planets, this science is compelled to recognise a force, which draws them constantly towards the sun, and constrains their tendency to fly from it, within the measured distance of those ellipses which they describe around that common centre of light and heat, which dispenses to them, as they roll, the precious germs of life and of fertility. We are about to speak of this force, to which all the powers that animate each separate organ join themselves, and in which all the vital powers are blended ; but under the declaration, for the second time, oftusing the term only in a metaphorical sense. Without this precaution, I might lead you into all the false reason- ings which those have fallen into who have assigned to it a real and sepa- rate existence. The vital power is in perpetual strife with the powers that govern inani- mate bodies. The laws of individual nature are, according to the saying of antiquity, for ever struggling against those of universal nature : and life, which is only this contest prolonged, in favour altogether of the vital powers during health, but with uncertain issue in disease, is at an end the moment in which the bodies endowed with it fall again into the system of lifeless being. This constant opposition of vital to physical laws, both mechanical and chemical, does not withdraw altogether living bodies from the control of these laws. There are effects always going on in the living being, chemical, physical, and mechanical: only these effects are constant- ly influenced, modified, and altered by the powers of life* Why, when we stand up, are not all the humours carried down to the lower parts, by the force of gravitation 1 The vital power resists the com- pletion of this hydrostatic phenomenon, and neutralises this tendency of the fluids, the more successfully as the individual is more robust and vigo- rous. If it is one enfeebled by previous disease, the propensity will be but imperfectly repressed : the feet, after a certain time, swell; and this cede- matous swelling can be ascribed only to the insufficient energy of the vital powers, which determine the distribution of the fluids, &c. When a tumbler throws himself backwards, the blood does not flow al- together to his head, though this is become the lowest part: yet the natu- ral tendency of fluids downwards is not altogether overcome, it is only di- minished ; for if he preserve long the same attitude, the struggle of the hydraulic and vital powers becomes unequal; the former prevail; they accumulate the blood upon the brain, and the man dies. The following experiment proves incontestably what has just been said of the power of resistance, which, in the human body, more or less, effec- tually counterbalances the force of physical laws. I applied bags filled with very hot sand along the leg and foot of a man whose artery had been tied by two ligatures, in the hollow of the ham, for popliteal aneurism. Not only the limb was not chilled, which is what happens when the course of the blood is intercepted, but the extremity thus covered acquired a heat much above the ordinary temperature of the body. The same apparatus applied to the sound leg did not produce this excess of heat certainly, be- cause the fulness of hfe in that limb resisted the physical action. * In proof of this may be adduced the ob- ing between 86° and 100° of Fahrenheit, in- servation long since made by Dr. Alexander, eludes the usual standard of human heat.—. that the range of temperature most favourable J. C. to the putrefaction of dead animal matter, be- OF THE VITAL PRINCIPLE. 33 The vital principle seems to act with the greater energy as the sphere of its activity is narrowed ; which has led Pliny to say, that it was chief- ly in the smallest things that Nature has shewn the fulness of her power* The circulation is quicker, the pulse more frequent, the determinations more prompt, in men of short stature. Such was the great Alexander : never did man of colossal make display great activity of imagination : none of them have glowed with the fire of genius. Slow in their actions, moderate in their desires, they obey without murmuring the will that go- verns them, and seem made for slavery. Agrippa (says Omilius Probus, in his History of Augustus) advised that they should disband the-Spanish guard, and that, in its room, Caesar should choose one of German, " wot- ting well, that in these large bodies there was little of coverte malice, and yet lesse of subtiltie, and that it was a people more minded to be ruled than to rule." To judge soundly of the remarkable difference which inequality of stature brings into the character, compare extremes ; set against a Colossus a little man of diminutive stature.; granting, nevertheless, to this last full and vigorous health. You may guess that he is talkative, stirring, always in action, always changing his place ; one would say that he is labouring to recover in time what he has lost in space. The probable reason of this difference in the vital activity, following the difference of stature, arises from the relative bulk of the primary organs of life. The heart, the vis- cera of digestion, &c. are of nearly the same bulk in all men : in all, the great cavities are nearly of the same extent, and it is principally in the length of the lower limbs that the difference of stature will be found to he. It is easily conceivable, that the viscera supplying the same quantity of nutritious juices to a smaller bulk, that the heart giving the same impulse to blood which is to traverse a shorter course, all the functions will be exe- cuted with greater rapidity and energy. By an obvious consequence, the diseases of little men have a more acute character ; they are more vehement, and tend more rapidly to their crisis.f They have in them something of the velocity, I would even say the in- stability, of morbid reaction during infancy. There is nothing, even to the duration of life, on which the differences of stature have not some in- fluence. With this suspicion, and some curiosity to ascertain its justness, I have made inquiries in the hospitals where people in advanced life are taken in, and I found them, for the most part, occupied by old men above the middle size ; so that reasoning and observation concur in shewing that, all things else being equal, those of superior stature have a grounded hope of prolonging their life beyond the ordinary term. I have observed, with many others, that the whole body unfailingly re ceives an increase of vigour from the amputation of a limb. Frequently, after the loss of a part of the body, you will see a manifest change take place in the temperament; those that were weak, even before the disease which brings on the necessity of the operation, becoming robust; affec-i tions, chronic from debility, such as scrofula, tabes mesenterica, dissipated ; and glandular swellings resolved ;—phenomena which indicate a very remarkable increase in the actions of all the organs. J * Nusquam magis quam hi minimis tota est gan never takes place but at the expense of Natvra. Hist. Nat. lib. ii. cap. 2. those about it, of which it draws off the juices. t The acute diseases of tropical coun- Aristotle observes, that the lower extremities tries, especially fever, prove more fatal to are most always dry and Wasted in those who short men, or those of middle size, than to the are of ardent temperament, or in habits of tall.__/. c. frequent venery. Hippocrates relates (in his t The extraordinary development of an or- work De cere, locis, et aquis, Foe's : fol. 293), 5 34 OF THE VITAL PRINCIPLE. The parts most remote from the centre of circulation are, in general, less alive than those which are nearer. Wounds of the legs and feet are more liable to ulcerate, because, besides the circulation of the fluids, which the slightest weakness greatly retards in them, their life is too feeble for their wounds to go quickly through their periods, and readily cicatrise. The toes freeze first, when we remain too long exposed to severe cold : it is in them, too, that the mortification begins, which sometimes attacks a limb after the ligature of its vessels. Thus, although we may say that the principle of life-is not seated in any part of our being, that it animates every system of organs, every separate organ, every living molecule, that it endows them with different properties, and assigns to them, in some sort, specific characters, it must be confessed that there are in the living body some parts more alive, from which all the others seem to derive motion and life. We have already seen, that these central organs, these foci of vitality, in whose life that of the whole body is involved, diminish gradually in number in the animal kinds as they are more removed from man; whilst the fewer they are, the more they are spread out over the body ; so that life is more generally diffused, and its phenomena less rigorously and strictly connected, as we descend in the scale of being, from the red and warm-blooded, to the red and cold-blooded animals, from these to the mollusca, the Crustacea, worms and insects, to the polypus, who forms the extreme link of the animal chain ; and, last- ly, to plants, of which not a few, like the zoophytes, so similar to them in many respects, are endowed with the remarkable property of reproduction by slips, which implies, that each part contains the aggregate of organs necessary to life, and can exist aloae. The vital principle has by some been confounded with the rational soul; but others have distinguished it from that emanation of Divinity, to which, as much as to the perfection of his organisation, man owes his superiority to all the animal kinds. What bond unites the material principle, which receives impressions and transmits them to the intelligence, which feels, per- ceives, examines, compares, judges, and reasons on them 1- Were man one, says Hippocrates, did his material principle make up his whole nature, pleasure and pain would be as nothing to him, he would be without sensa- tion ; for how could he account to himself for impressions? Si unus esset homo, non doleret, quia non sciret unde doleret. Here we stand on the confines of physiology and metaphysics : let us beware of setting foot in the dim paths that are before us : the torch of observation would yield but ineffec- tual light, too faint to dispel the thick darkness that lies over them. The vital power is merely the vis medicatrix natures, more powerful than the physician in the cure of many diseases ; the art of the physician con- sisting, in most cases, in awakening or directing the action of that power. When a thorn is thrust into a part endowed with sensibility, a sharp pain is felt, the fluids rush in abundance to the part, it becomes red and swollen ; all the vital powers are excited, the sensibility becomes more acute, the contractility greater, and the temperature rises. Does not this increase of vital energy in the injured part, this process which takes place arcund the substance that is the cause of the disorder, those means which are pro- that the Scythian women seared their right breast, that the arm on that side might grow in size and strength. Galen speaks of ath- letes, who, in his time, kept the sexual organs in the most entire inaction,—that, withered, shrunk, and perished, in some sort, by this absolute repose, they might not draw off the nutritious juices from the sole nourishment of the muscular organs. A young man who has several times carried off the prize by running at the public fetes, abstains from venery for some months before entering the lists, in per- fect certainty of victory after this privation. THEORY OF INFLAMMATION. 35 vided to expel it, indicate the existence of a preserving principle, incessant- ly watching over the harmony of the functions, and struggling against all the powers that may tend to interrupt its exercise, or to annihilate the vital motion 1 Theory of inflammation*—Inflammation may, I believe, be defined, the increase of vital properties in the parts which it affects. Sensibility becomes more acute in the part so affected, its contractility greater; and from that increase of sensibility and action arise all the sjmiptoms characteristic of inflammation. Thus the pain, the swelling, the redness, the heat, and the difference in the state of the secretions, denote in the part a more energetic and active vitality. Those who have objected to the definition which I have given of inflam- mation, have evidently mistaken the functions of the organs for their pro- perties. It is very true, that inflammation of the eye is attended with loss of sight: but that circumstance depends on the opacity of the transparent parts, which should transmit the luminous rays to the retina. The sight is prevented by a mechanical obstacle; but the sensibility of the organ is augmented to such a degree, that the faintest light reaching the bottom of the eye through the transparent cornea dimmed by the congestion of the vessels, causes in it intolerable pain. On this principle, darkness is uni versally recommended to patients affected with ophthalmia. In like man- ner, when a muscle is inflamed, the action of the fibre, its decurtation, is prevented by the congestion in the cellular membrane, which covers it, and fills its interstices. The cause preventing contraction, or the exercise of contractility, is mechanical, and. may be compared to that which, in an in- flamed lung, opposes the admission of air and the passage of the blood from the right to the left side of the heart. Can any one call in question the in- crease of vital action in peripneumony ? 1 am, therefore, of opinion, that the above definition is better than that proposed by Bichat in his Jlnatomie Generate,—a work of later date than the first edition of these Elements of Physiology, and in which he makes inflammation to consist in the increase of those vital properties which he terms insensible. All the parts of the human body, with the exception of the epidermis and its different productions, as the nails and the hair, appear capable of in- flammation. One might include among these ""epidermoid" parts, certain dry and slender tendons, as those of the flexors of the fingers, which when pricked, lacerated, and irritated in a thousand ways, are insensible to pain, and remain uninjured in the midst of a whitlow, though attended with suppuration of all the neighbouring soft parts ; and when exposed to the air, they exfoliate instead of granulating. Organisation is so indistinct in all these parts, life so feeble and languid, that they remain insensible to the impression of all those causes which might tend to increase its activity. The degree of sensibility in a part, the number and size of the nerves and vessels which are sent into it, determine the degree of its aptitude to in- flammation ; thus, the bones and cartilages inflame with considerable difficulty. When one of these parts is laid bare, the first effect of irri- tation to which it is exposed, is a softening of its substance. When a bone is laid bare it becomes cartilaginous and softens, in consequence of the absorption of the phosphate of lime which fills up the interstices of its tissue ; and it is only after this kind of incarnation that fleshy granulations begin to spout, as may be observed on the extremities of bones after ampu- tation. The difficulty with which inflammation is set up in the harder parts of the body explains why, before the twelfth or fifteenth day after a * See Appendix, Note G. 36 THEORY OF INFLAMMATION. fracture, it is of little consequence towards union of the bone that the frac- tured ends should be placed in apposition ; not that it is right to wait so long before applying the proper bandages, which are indispensable from the first, to prevent the pain and laceration occasioned by the displaced bone. The blood is determined, from all quarters, towards the irritated and pain- ful part, which swells and assumes a red colour from the presence of that fluid. The swelling would be unlimited, if, at the same time that the arte- ries increase in power and calibre to occasion that determination, the veins and lymphatics did not acquire a corresponding energy, to enable them to relieve the part of the fluids which have accumulated in it, and which irri- tation is constantly determining to it. The power of irritability and con- tractility increases with sensibility; the circulation is more rapid in the inflamed part; the pulsations of the capillary vessels are manifest. The part is likewise hotter ; because in a given time there passes through its tissue more arterial blood, from which a larger quantity of caloric is disen- gaged, and the continued effects of the pulmonary respiration are better marked in it than in any other organ. It forms no part of our intention to treat of the varieties of inflammation: they depend principally on the structure of the organ which is affected, on the violence and rapidity of the symptoms, and on its effects.* Is not the turgescence of an inflamed part occasioned in the same man- ner as in parts subject to erection, as the corpora cavernosa of the penis and of the clitoris, the nipples, the iris, &c. ? In erection of the penis, as in inflammation, there is an irritation, a determination of fluids to the part, an increase of sensibility and contractility ; yet its condition is not that of inflammation. Nature has so disposed the organisation of these parts, that they can sustain, without injury, those instantaneous augmentations of vital energy necessary to the exercise of the functions performed by the organs to which they belong. As in inflammation, these congestions dis- appear when the cause of irritation has ceased to act; thus, the pupil di- lates because the iris recedes when the eye is no longer exposed to the rays of a vivid light. The penis returns to its naturally flaccid and soft state when no irritation operates to determine to it the fluids, whose presence, as long as the erection lasts, is easily explained by the continuance of the ir- ritation, without its being necessary to have recourse to mechanical ex- planations to account for that phenomenon. When the irritation which produces the vital turgescence of the penis, or iris, is carried too far, or con- tinues too long, the natural congestion becomes morbid. It is well known that priapism is frequently attended with mortification of the penis ; and that the too long continued action of light on the eye brings on inflamma- tion of that organ. The preceding observations on inflammation shew that an acquaintance with its phenomena is useful, even in a physiological view. The vital pro- cesses, which in some organs take place in so obscure a manner that they are imperceptible, acquire in inflammation a character of rapidity and inten- sity, which renders it much easier to observe and recognise them. Con- sidered in a general and abstract point of view, and merely with a reference to its object, inflammation may be considered as a means employed by na- ture to repel the influence of noxious agents, which, when introduced with- in the body, or on its surface, she has no power of resisting but by a more active development of the powers which animate it. * They depend also upon the causes which fluences operating on his frame either pre- produced them, on the habit and constitution vious to or during the progress of the inflam- pf the patient, and the endemic or epidemic in- matory disease.—/. C. 6F THE GREAT SYMPATHETIC NERVES. 37 During the severe winter of 1793, the chemist Pelletier repeated the celebrated experiment of freezing mercury, and obtained a solid ball in the bulb of a barometer, which he had for a long while kept immersed in the midst of a quantity of ice, continually moistened with nitric acid. When the metal had attained a completely solid state, he drew the ball from the bulb, and placed it on his hand. The heat of the part, joined to that of the atmosphere, soon restored the quicksilver to its fluid state : at the same instant he experienced in his hand so intolerable a degree of cold, that he was obliged to drop the quicksilver instantly. There soon came on, in the painful and chilled part, a phlegmonous inflammation, which was cured by resolution. Quicksilver, in a solid state, is one of the coldest bodies in na- ture : how very rapidly the caloric must have been carried off in this case, and how deep the impression must have been in.the palm of the hand, doubly affected by the cold,and by the vital re-action, which terminated in inflammation ! I have produced a similar effect, by endeavouring to melt a piece of ice in my hand, during the heat of summer." In this experiment, the impression of cold is soon succeeded by a sensation of acute pain, and extraordinary throbbings in the hand and fore-arm. When the two hands are afterwards compared, that which held the piece of ice is ex- tremely red, from .the congestion of blood in the cutaneous capillary tis* sue, and is very different in its appearance from that which was not the subject of experiment. Analogous facts, if seriously considered, should induce the followers of Brown to apply to the effects of cold the distinction which he applied to debility, of direct and indirect. They would have no difficulty in ascer- taining, that, in its medical application, that negative state of caloric which is directly debilitating, may, nevertheless, by the re-action which it excites, be considered as an indirect tonic. SECT. X.—OF THE SYSTEM OF THE GREAT SYMPA, THETIC NERVES* The great sympathetic nerves are to be considered as the bond destined to unite the organs of the nutritive functions, by whose action man grows, is evolved, and incessantly repairs the continual waste attending the vital motions. They form a nervous system, very distinct from the system of the cerebral nerves; and, as the latter are the instruments of the functions by which we hold intercourse with external objects, the great sympathetic nerves supply motion and life to the organs of the inward, assimilating, or nutritive functions. In animals without vertebra?, may not the nervous system, which floats in the great cavities, with the viscera which they contain, be considered as consisting entirely of the great sympathetics ?f These nerves are princi- * See Appendix, Note H. ly vertebral ganglia, without the cceliac ganglia t Treviranus, in his Biologie, considers of mammalia and birds ; in the acephalous the knotted chord found in the abdomen of molluscae there are the latter, without the for- insects and worms to be the vertebral ganglia mer ; in the cuttle-fish and snails there are of the sympathetic nerve. That it cannot be single ganglia of both kinds. All these ani- considered a spinal chord is evident. Its si- mals have no spinal marrow ; fishes and rep- tuation shews sufficiently the difference. The tiles have one, and also vertebral ganglia ; but molluscae, and many animals removed a little the cceliac is not fully developed in them as in above this class in the scale of creation, pos- birds and mammalia. sess merely single ganglia, from which pro- These remarks convey the sum of the ob- ceed fibrilae to the different organs. The servations made by those who have inquired great sympathetic nerve is the most general into the subject: how, therefore, can the gan- and the most original of all the nerves. Its glial class of nerves be considered to arise characters are, however, modified in different from the cerebral and vertebral masses ?— classes. In worms and insects there are mere- /. C. 38 OF THE GREAT SYMPATHETIC NERVES. pally distributed to the organs of inward life, whose activity in those ani- mals seems to grow in proportion as their external senses, and their faculty of locomotion, are imperfect. If the great sympathetics exist in all the animals which have a distinct nervous system, do they not, in an especial manner, contain the principle of vegetable life, essential to the existence of every organised body possessing the power of digestion, absorption, circu- lation, secretion, and nutrition 1 Finally, is it not probable, that in man the system of the sympathetic nerves has a very great share in occasioning a number of diseases ; and that the impressions with which patients are af- fected, are to be referred to their numerous ganglions, while the brain is ex- clusively the seat of intellect and thought 1* These suggestions will, doubtless, be answered in the affirmative, if one considers the origin, the distribution, and the peculiar structure of these nerves, the acute sensibility of their branches, as well as the disorders at- tending their injury. Extended along the vertebral column, from the base of the skull to the lower part of the sacrum, these great nerves, in some measure parasitic, do not arise from the branches supplied them by the fifth and sixth pairs aris- ing from each side of the brain: they live, and are nourished, as it were, at the expense of all the nerves of the spinal marrow, from which they re- ceive branches, so that there is not one of them from which one can say that the great sympathetics arise exclusively-. The numerous ganglions which are distributed along their course, divide them into so many small systems, from which arise the nerves of the organs nearest to them. Amid these bulgings, considered by several physiologists as so many little brains, in which is performed the elaboration of the fluid which they trans- mit to the nerves, no one is of more importance than the semi-lunar gan- glion, situated behind the organs which occupy the epigastric region ; and from which those nerves originate which are distributed to the greater part of the viscera of the abdomen. It is to the region occupied by that gan- glion, in which the great sympathetic nerves unite, and which may be con- sidered as the centre of the system formed by their union, that we refer all our agreeable sensations ; there it is that we feel, in sadness, a constriction which is commonly referred to the heart. Thence, in the sad emotions of the soul, seem to originate those painful irradiations which trouble and dis- order the exercise of all the functions."f The numerous filaments of the great sympathetic nerves are finer, they are not of the same whitish colour, nor of the same consistence as the fila- ments of the cerebral nerves. On that account, they are less easily dis- sected, J the nervous fibrilse are less distinct, their reddish chords are moist- er, and they appear formed of a more homogeneous substance: their membraneous coverings are less considerable. They are likewise endow- ed with a more acute and more delicate sensibility. Every one knows the danger attending wounds of the mesentery, a membraneous duplicature, * These opinions on the uses of the great of its crura. sympathetic nerves, are explained in my essay % One of the best modes of dissecting them, on the connexion of life with the circulation, is to macerate the part in which we wish to This essay was published before any thing trace their ramifications, during two or three that has appeared on the same subject. Con- days in water ; then place it for a short time suit the " Memoires de la Societe Medicale in a very dilute acid, or warm spirits, or in oil pour l'an vn," of turpentine. The filaments of these nerves -f Consult, on the subject of the epigastric may be then traced more distinctly. Other centre, Van Helmont, who calls it the Ar- processes, which are complex, are requisite to chorus ; Buffon, Bordeu, Barthez, and Lacaze, the dissection of the minuter ramifications, who give it the name of the phrenic centre, be- especially those which supply the blood-veg- cause they ascribe to the diaphragm what be- sels.—/. C. longs to the nervous ganglions placed in front OF THE GREAT SYMPATHETIC NERVES. 39 in itself insensible; but containing such numerous nerves destined to the intestinal tube, that the most pointed instrument can scarcely wound the mesentery without injuring some of their branches. The pain attending affections of the great sympathetic nerves is of a very peculiar kind ; it leads directly to the extinction of the vital power. It is a well-known fact, that a bruise of the testicles overpowers, in a moment, the strongest man. Every one knows, that patients who die of a strangulated hernia, of vol- vulus, or of any other affection of the same kind, die in the most distressing anguish ; their heart feels oppressed, and they are tormented with constant vomiting. Intestinal and nephritic colics are attended with the same sort of pain : that attending injection of the tunica vaginalis, in hydrocele, is of the same kind. And one expects a favourable event of the operation only in those cases in which the patient has felt pain along the spermatic chord, in the course of the spermatic nerves, which arise, as it is well known, from the renal plexus. In three cases of wounds of the abdomen, I was led by the nature of the pain which the patients suffered to prognosticate that the wounds had penetrated : the event justified my prognostic. In all these affections of the great sympathetic nerves, the pulse is frequent and hard, the face is covered with a cold sweat, the features are sunk; all the symptoms are alarming, and soon terminate fatally. The use of the system of the great sympathetic nerves is, not merely to establish a closer connexion and a greater union between all the organs which perform the functions of assimilation, but likewise to free those parts from the influence of the will,—a power of the mind so fickle and so vary- ing, that life would be in constant danger, if we had it in our power to stop or suspend the exercise of the functions with which it is essentially con- nected. If we consider what are the organs to which the functions of assimila- tion are intrusted, and which receive their nervous influence from the great sympathetic nerves, we shall find that the action of the greater number is wholly independent of the control of the will.* The heart, the stomach, the intestinal canal, &c. do not obey the will, and seem to possess a more insulated and more independent existence, and to act and rest without any influence on our part. Some of these organs, as the bladder, the rec- tum, and the muscles of respiration, which do not receive their nerves ex- clusively from the great sympathetics, are obedient to the will, and receive from the brain the principle of motion; the former from the branches which the sacral nerves send to the hypogastric plexuses; the diaphragm from the nerves which it receives from the fifth and sixth cervical pairs. The great sympathetic nerves supply the diaphragm, the rectum, and bladder, only with nerves of sensation. This provision was a very neces- sary one, for if, as is the case with the heart and the intestines, these parts had received their nerves of motion from the great sympathetics, their ac- tion would have been independent of the will, as is the case with all the parts which these nerves supply with motion. The bladder and rectum, placed at the extremities of the digestive apparatus, and destined to serve as reservoirs to the excrementitious residue of our solid and liquid aliments, * All those parts which receive their nerves follow the course of the branches of the inter- com ganglions are equally independent. Pro- nal carotid, and like them are sent to the base fessor Chaussier thinks, that the upper fila- of the brain, beyond which they cannot be ments of the great sympathetic nerves as- traced. I have myself observed in dissection cend alon°r the internal carotid, and join the these filaments around the branches of the spheno-palatine and lenticular ganglions. M. internal carotid artery, but I had always con- Kibes thinks he has ascertained by dissection sidered them to be formed of cellular sub- that several very long and slender filaments stance. 40 OF THE GREAT SYMPATHETIC NERVES. would have been constantly evacuating their contents as fast as the sub* stances which are destined to be retained within them for some time reach- ed their cavity. On the other hand, if the diaphragm had received its nerves of motion from the great sympathetics, respiration would have ceased to be a volun- tary function, of which we might at pleasure accelerate, slacken, or even completely suspend the action. To prove that the act of respiration is under the control of the will, we may have recourse to analogy, and ad- duce the instance of reptiles, as lizards, frogs, serpents, salamanders, and toads, which are cold-blooded animals, and in which this function is mani- festly voluntary. We may further mention those slaves, who, we are told by Galen, put themselves to death when summoned before their execution- ers or judges. According to that physiologist, and others, they choaked themselves, by swallowing their Jongue. But it is sufficient to know how the muscles that bind down the tongue are situated, and the degree of mo- tion which they allow, to see how little ground there is for that opinion. The action of the brain would, in that case, have been no longer necessary to the maintenance of life; in an animal without a brain, respiration would have continued, and the circulation would not have been interrupted. I he death of that viscus would not have been attended with the sudden death of all the rest. . The nerves which arise from the spinal marrow, and which give to the diaphragm the power of contraction—a power which that muscle loses suddenly if these nerves be tied—appear to me the chief links which unite the internal assimilating, or nutritive functions, to those which keep up the relation of the animal with external objects. Without this bond of union, the series of vital phenomena would have been less close, and their depend- ence less necessary. Had it not been for the necessity that the diaphragm should receive from the brain, by means of the phrenic nerves, the princi- ple which determines its contractions, acephalous animals, which are born without that organ, might continue to live as they did before birth, when the organs of nutritive life received blood which had undergone, in the lungs of the mother, the changes necessary to life. But where the bond which united them to the mother is destroyed, obliged themselves to produce in their fluids the necessary changes, by the inhalation of the vivifying prin- ciple contained in the atmosphere, they no longer can obey that necessity ; the organs of respiration are deficient in the principle which should excite them. When an internal inflammation is of small extent * and is seated in a part in which there are not many nerves, and whose tissue yields easily to the humours which irritation determines into it, the whole morbid action takes place in the affected part, and the general order of the functions is not sensibly deranged. But when inflammation takes place in a part endow- ed with much sensibility, or of a close texture, as the fingers and toes, then fever comes on, because a sympathy in the morbid action takes place be- tween the diseased part and the rest of the system. This diffusion of the * A thousand pustules in the small-pox oc- casion only a moderate degree of fever, if they are at a distance from each other ; but if the disease is confluent, that is, if the pustules are close together, and run into each other, the fe- ver becomes considerable, and the patient's life is endangered. The fleshy granulations which sprout in abundance from an ulcerated surface, are so many small phlegmons unac- companied by a febrile state ; but if brought close to each other by irritation, that condition will not fail to ensue. Vaccination is not, in the greater number of cases, attended by the slightest febrile action, if, as I always have done, the punctures are made at a certain dis- tance from each other, so that the inflamma- tory areolae may not run into each other. RELATIONS OF PHYSIOLOGY. 41 local action almost infallibly takes place when inflammation occurs in one of the organs of the assimilating functions. This effect may be consider- ed as uniform, though Morgagni mentions several instances of inflamma- tion of the liver, marked by no peculiar symptoms. A knowledge of the great sympathetic nerves accounts for this difference. When an external part is affected with inflammation, the irritation which it suffers is, by means of its nerves, propagated to the brain, which by a fe-action,* called by Vicq-d'Azyr (who on this subject has only developed the opinions of Van Helmont) internal nervous action, transmits that irrita- tion to the heart, to the organs of respiration, of digestion, and of secretion. in which the phenomena, denoting a febrile state, are principally evolved, When, on the contrary, the heart, the lungs, or any other internal organ, is affected with acute inflammation, all the viscera partake in the derange- ment with which any one of them is affected, and without the intervention of the brain. They are all intimately connected by the filaments which they receive from the great sympathetic nerves ; and by means of that nervous system, which is in an especial manner appropriated to them, they carry on a more intimate intercourse of sensations and affections. Besides, the derangement of the important functions intrusted to the diseased or- gans, is necessarily attended with proportionate changes in all the acts of the animal economy, in the same manner, no doubt, as the defect of one wheel interrupts or disturbs the mechanism of the whole machine. There exists in the stomach a union of the cerebral and sympathetic nerves, which explains the manifest dependency of this viscus on the brain ; a dependency so marked, that every strong affection of the soul, every vio- lent agitation of the mind, weakens, or even totally suspends, the action of digestion in the stomach. " This combination of cerebral and sympathetic nerves likewise accounts for various phenomena connected with disease, and for the operation of several remedies in removing it."| Sect. XL—OF THE RELATIONS OF PHYSIOLOGY TO SE- VERAL OTHER SCIENCES. It would be entertaining a very incorrect notion of the science of living man, to imagine, with some authors, that it solely consists in the applica- tion of the laws of natural philosophy to the explanation of the phenome- na of the animal economy. Physiology is an independent science, resting upon truths of its own, which it draws from the observation of those ac- tions which, in their aggregate succession and connexion, constitute life. It is enriched, it is true, with facts furnished to it by natural philosophy, chemistry, and mathematics ; but what it has borrowed from these is ac- cessory merely, and does not form an essential part of the edifice of the science. Thus, the better to understand the mechanism of hearing and vision, physiology borrows, from acoustics and optics, elementary notions on sound and light; and in order to obtain a more correct knowledge of the nature of our solids and fluids, and of the manner in which animal * The cerebral re-action appears to be in no measure necessaiy to the induction of symp- tomatic fever : it may, however, contribute to ils continuance. The irritation appears to be propagated to the heart in consequence of the numerous connexions which this organ holds, by means of the ganglial nerves, with the other viscera, and owing to the continuous re- ticulation of these nerves upon the arterial system from the heart to the capillary termi- nations of the vessels. See the Appendix, Note H, for further observations on this sub- ject.—/. C. ■f See the observations on the functions of the Stomach, and on the influence of the eight pair of nerves in Digestion, in the Appendix, Notes K and L. 6 42 RELATIONS OF PHVS10L0GV. substances are constantly passing from the one to the other of these two conditions, physiology calls in the aid of chemistry. Thus, geometry and mechanism furnish it"with the means of better understanding the advan- tageous form of the organs, and the perfection of their structure* Where the natural philosopher stops, the physician commences. Ubi desinit phy- sicus, ibi incipit medicus, was well said by Aristotle. No study carries along with it a more lively interest than that of the ad- mirable relations existing between the conformation of our parts and the external objects to which they are applied. These relations are calculated with such precision, and laid down with such accuracy, that the organs of sense and of motion, considered in this point of view, may be regarded as the model of the most ingenious productions of art. So true it is, in the words of the great physician of Pergamus, that nature did every thing before art, and better.f At the beginning of the last century, geometrical physicians, deceived by an appearance of rigid precision, attempted to explain every thing by the calibre of vessels, their length, their curvatures, the compound ratio of the action of solids, and the impulse of fluids. Hence were formed theo- ries so very imperfect, that, as we shall see, in treating of several points of physiology, and especially of the force with which the heart acts, not one of those who proposed them coincides with those who have since followed their track. However, it does not admit of a doubt, that there occur, in the animal machine, effects which are referable to the laws of hydraulics. The brain, for example, required a large and constant supply of arterial blood, vivified by recent circulation through the lungs; but the too rapid and abrupt access of that fluid in the brain might have disordered its struc- ture. Nature, therefore, has, as we shall mention in the article of the cerebral circulation, employed all the hydraulic resources in her power, to break the force with which the blood enters the brain, and to slacken its course. Has man ever applied the laws of hydraulics in a more felicitous man- ner than nature, in the rete mirabile formed at the base of the brain by the carotids of quadrupeds ?—an arrangement truly remarkable, without which the blood conveyed to the brain by those arteries, impelled by a force superior to that of the human heart, and not having to overcome the re- sistance of its own gravity, would infallibly have occasioned a disorgani- sation of that organ, whose consistence is so soft. As to the application which is allowable of mathematical sciences, it may be said, that, as in physiology, but little is absolutely certain,^ and much merely probable, we can reckon only on probabilities, and seek our elements in facts deduced from observation or experience ; facts which, when collected and multiplied to a certain degree, lead to results of equal value with truths absolutely demonstrated. * A knowledge of mathematics, and of the tempore sit, et in operibus magis sapiens quam whole circle of natural philosophy, including ars.—Galenus de Usu Parlium, hb. vii. cap. more especially chemistry and natural history, 13. and, in a more particular manner, human and It was from observing the manner in which comparative anatomy, is requisite to the sue- nature prevents the diffusion of light in the cessful study of physiology. This last branch globe of the eye, that Euler was led to the im- of knowledge, although independent of, some provement of his astronomical telescopes. of these, is yet more easily acquired, and its t This is to be understood as applying only difficulties are better explained, by a previous to the causes of the phenomena, and not to the acquaintance with all of them. Pathology and phenomena themselves; for physiology is per- t.ie treatment of diseases, also, reflect a light haps richer than any other science, in facts upon physiology which they first derive from unquestionable, and easily ascertained by ob- this productive source.—J. C. servation. f Qudndoquidem natura, ut arbitror, et prior RELATIONS OF PHYSIOLOGY. 41 The phenomena presented by living bodies vary incessantly in their ac- tivity, their intensity, and their velocity. How can mathematical formulae apply to such variable elements ? As well might you enclose in a frail vessel, hermetically sealed, a fluid subject to expansion, and of variable bulk. The motions of progression in man and in the animals afford, nevertheless, sufficiently correct applications of calculation. Calculation may likewise be applied with advantage to the measurement of the results of our different secretions, to ascertain the quantity of air or of aliment in- troduced into our organs, &c. Among the principal causes which have retarded, in a considerable de- gree, the progress of physiology, may be enumerated the mistake of those who have endeavoured to explain all the phenomena of living bodies by a single science, as chemistry, hydraulics, &c, while the union of all these sciences will not account for the sum of these phenomena. The abuse, however, of these sciences sliould not be a reason for setting them aside altogether. The facts obtained from natural philosophy, chemistry, me- chanics, and geometry, are so many means applicable to the solution of the great problem of the vital economy ; a solution which, though as yet undiscovered, should not be considered as unattainable, and to which we shall approach the nearer as we attempt it with a greater number of data. But it cannot be too often repeated, that he alone can hope for that honour who, in the application of the laws of natural philosophy to living bodies, will take into account the powers inherent in organised nature, which con- trol, with supreme influence, all the acts of life, and modify the results that appear most to depend on the laws by which inorganic bodies are go- verned. Anatomy and physiology are united by such close relations, that it has been an opinion with some that they are absolutely inseparable. If phy- siology, say they, has for its object a knowledge of the functions carried on by our organs, how is one to understand their mechanism, without knowing the instruments by which they are performed 1 One might as well attempt to explain the manner in which the hand of a watch per- forms the circle of its diurnal revolution, without understanding the springs and numerous wheels which set it in motion. Haller is the first who es- tablished the connexion between anatomy and physiology, and who illus- trated it in his great work. Since Haller, a great number of anatomists, and among them Soemmering * in a work recently published, have combin- ed, as much as possible, these two sciences ; the latter, in treating sepa- rately of each system of organs, explains what is best known of their uses and properties. However ciose the connexion between anatomy and physiology, they have, nevertheless, appeared perfectly distinct to the greater number of au- thors, and we have several valuable works on anatomy, of which physi- ology occupies but a small part. This manner of embracing the two sci- ences appears to me attended with the greatest advantage : in fact, if the insulated description of organs suffices to the physiologist who wishes to study their functions, that method is attended with the disadvantage of furnishing few truly useful views in the practice of operative surgery. To render the knowledge of the human body more especially applicable to the practice of surgery, it is necessary not only to consider separately the different parts, but likewise to view them in their connexion, and to determine precisely their relations. The anatomist, who knows that the principal artery of the thigh is the crural ; that, continued under the name * J. Ch. Soemmering, de Corporis Humani Fabrica, 6 vols. 8vo. 1804. 44 RELATIONS OF PHYSIOLOGY. of popliteal, it passes behind the knee in its way to the leg; that in its course it supplies with branches different parts of the limb ; even though he knew perfectly the names, the number of these branches, the varieties to which they are subject, the parts to which they are distributed, would, nevertheless, possess a knowledge of that branch of the system, almost useless in the treatment of the diseases with which it may be affected. The situation of the artery, its direction, the parts which surround it, its precise relations to each of them, its superficial or deep-seated course, &c. are the only circumstances from which he can derive any advantage. He who, in this point of view, cultivates anatomy, may be compared to the chemist: in the same manner as the latter is never better acquainted with a substance than when he is able to decompose it, and to reproduce it from a combination of its parts; so the anatomist is well acquainted with the body of man only when, having studied separately and with the greatest care each of his organs, and each of the systems formed by the collection of a certain number of similar organs, he is able to assign to each of them its place, to determine its relations, and the proportions which it bears in the structure of any one of our limbs. The study of the latter is much more difficult and extensive than that of the former; for, the chemist who decomposes and recompounds a well-known substance,— phosphate of lime, for instance,—attains only to the knowledge of its con- stituent principles and respective proportions: the phenomena of situation altogether escape him. The anatomist, on the other hand, who knows that such a part is composed of bones, of muscles, of nerves, of vessels, must know not only every one of these parts, and their relative bulk, but the exact place in which they are to be found. Anatomy, pursued in this spirit, offers a field of wide extent: it is the art which Leibnitz called the analysis of situation, analysis situs ; and the knowledge of it is too important not to require a separate place among the departments of medical knowledge. I will not pass over the motives that are alleged for combining anatomy and physiology in one course of in- struction. Anatomy, confined to the mere description of the organs, is too dry and fatiguing ; physiology throws over it interest and variety ; it helps to ensure the attention of the hearers, who will retain more permanently what they have listened to with pleasure. Would not one think that phy- siological details were, for an audience, what is contrived for a sick and froward child, in the honey that is rubbed on the edge of the cup, to dis- guise the bitterness of the draught that is to recall him to health 1 In combining two objects, of which one has no interest but that of usefulness, whilst the other is engaging as well, the attention will be not merely divided, but altogether distracted ; and the mind of those who read or listen will skim over dry details, to seize with avidity what furnishes more to its activity of intelligence. Anatomy is to physiology what geography is to history. General considerations on the situation, the size, the form, the relations, the structure of the organ, are an indispensable preparation to the perfect understanding of its functions : accordingly, you shall find much anatomy in physiological treatises, as you find much geographical detail in faithful historians. I have said enough, I trust, to escape the reproach of not having filled my book with anatomical descriptions from the multitude of excellent works we possess on the anatomy of the human body. Let us now in- quire what relation physiology bears to comparative anatomy. If a machine can be perfectly known only after taking it to pieces, down to its simplest elements ; if the whole mechanism of its performance can RELATIONS OF PHYSIOLOGY. 45 be conceived only by examining separately the action of each different part composing it, comparative anatomy,—by aid of which we may study, in the great chain composing the various classes of the animal kingdom, the separate action of each organ, appreciate its absolute or relative im- portance, consider it at first insulated and reduced, so to speak, to its own powers, in order to determine what part it bears in the carrying on of a function,—comparative anatomy is of absolute necessity to him who would make great progress in the knowledge of man: it may be looked upon as a sort of analytical method of study, by means of which we more complete- ly attain to the knowledge of ourselves. In order to conceive rightly the operations of the human intellect, and explain the generation of the faculties of the soul, metaphysicians have imagined a statue, into which they have infused a gradual animation, by investing it, one by one, with our organs of sensation. Now nature has realised, in some sort, this dream of philosophy. There are animals to which she has entirely denied the organs of sight and hearing: in some, taste and smell seem to have no separate existence from touch ; in others, she has exercised a sort of analysis on a system of parts which all concur in one function. It is thus, that in some animals, divesting the organ of hearing of the accessories allotted to collect, transmit, and modify the rays of sound, she has reduced it to a simple cavity, filled with a gelatinous fluid, in which float the extremities of the acoustic nerve, alone fitted to receive the impression of sound ; a fact which overthrows all the hypo- theses that had ascribed this sensation to other parts of the auditory appa- ' ratus. Of all the physical sciences, comparative anatomy is that which fur- nishes the most useful facts to physiology * Like physiology, it is con- cerned with organised living beings ; there is, therefore, no need of watch- ing against the false applications, so often made from the sciences, whose objects are matter inorganic and dead, or which study, in living beings, only the general properties of matter. Haller was so well aware of the utility of introducing this science into physiology, that he has brought together the greater part of the facts known in his time on the anatomy of animals, at the head of each chapter of his immortal work. This general consideration of living and animated beings, so well adapted to unveiling the secret of our organisation, has this further advantage, that it enlarges the sphere of ideas of him who applies to it. Let him who aspires to that largeness of conception, so requisite in medicine, where facts are so multiplied and various, explanations so contradictory, and rules of conduct so unfixed, cast a general glance on this great division of organised beings, of which many, in their physical structure, so nearly resemble man, —he will see the sovereign Architect of the world distributing to all the elements of life and activity, giving to some a less power of motion, to others more ; so that, formed all on one model, they seem only the infi- nitely varied but gradual shades of the same form, if forms have shades like colours; never passing abruptly from one to another, but rising or falling by gentle and due degrees, covering the interval that separates two different beings with many species that serve as a transition! from one to * "The extensive examination of various tive, respiratory, generative, or other processes structures," Mr. Lawrence very justly ob- of man, and will review the successive stages serves, " is not only a necessary ground-work of its progress, will find that comparative an- for the edifice of general physiology, but it has atomy has rendered us the most essential as- thrown great light on the organisation and sistance."—/. C. functions of the human frame. Whoever will + The conception of a scale of being, which, reflect on our present knowledge of the diges- as was said by C. Bonnet, connecting all the 46 RELATIONS OF PHYSIOLOGY. the other, and which present a continuous series of advancement or degra- dation ; organisation being constantly simplified in descending from man to the inferior creatures, but rising in complexity in re-a&cending from those animals to man, who is the most complex being in nature, and was justly considered by ancient philosophy as the master-piece of the Creator. If the intimate structure of our organs totally eludes our investigation, it is that the finest and most delicate of their constituent parts are of such minute dimensions that our senses have no hold on them. It is then well to have recourse to analogy, and to study the organisation of animals that exhibit the same organs on a larger scale. Thus the cellular texture of the lungs, which cannot be distinctly shewn in man, on account of the extreme minuteness of the smallest bronchia?, may be satisfactorily seen in the vesicu- lar lungs of salamanders and frogs. In like manner, the scales which cover the bodies of fishes and reptiles, or the legs of birds, give us a just idea of the structure of the epidermis, and of the arrangement of its small scales, which lie over each other, in a part of their surface. The human structure being more complicated, must produce effects more numerous, and results more varied and more difficult to understand. In commencing the study of the animal organisation by that of man, we do not therefore follow the analytic method ; we do not proceed from what is simple to what is more complex. It would perhaps be an easier and a more natural way of arriving at a solution of the grand and difficult prob- lem of the animal economy, to begin by explaining its most simple terms; to rise by degrees from plants to vegetating animals, as polypi; from these to white-blooded animals ; then to fishes and reptiles ; from the latter to warm-blooded animals; and, lastly, to man himself, placed at the head of that long series of being, whose existence becomes complicated in propor- tion as they approach him. The study of every part of natural history, and especially of compara- tive anatomy, cannot fail, therefore, to prove of infinite advantage to the physiologist; a truth well expressed by the eloquent M. de Buffon,* who says, that if there existed no animals, the nature of man would be still more incomprehensible. I shall say nothing of the well-known relations of physiology to medi- cal science, of which it is justly considered as the base or support. Medi- cine, called by some the art of healing, by others, more properly, the art of treating diseases, may be defined the art of preserving health, of curing diseases, or of rendering them more supportable ; medicine, in all its parts, is enlightened by physiology, and cannot have a surer guide. Owing to a neglect of this auspicious guide, therapeutics and materia medica long re- mained involved in a mist of conjectures and hypotheses. Physicians worlds, embracing all the spheres, should ex- getable productions; and if this undertaking, tend from the atom to the most exalted of che- in the hand3 of men the most able to bring it rubim, is noble and interesting. Without car- to a successful termination, left any thing de- rying it so high or so low, if we confine it to fective, would not that imperfection be an in- the natural beings with which we are well ac- dication of the existence of other worlds, or of quainted, and which can be brought under ob- lands yet unknown on the -globe we inhabit • servation, it will be seen, that the idea is not undiscovered regions, where those animals so chimerical as some writers of most respect- and plants, and minerals, would be found which able authority have supposed it. The plan were wanting to fill up the gaps in the immense traced by C. Bonnet is evidently defective; series of co-ordinate existence ? we find in it beings set beside each other, that Demonstratum fuit et hoc, nullam rem contra- have but faint lines of resemblance, or alto- rias, vel omnind, multum differentes, qualitates gether illusive. The present state of the na- recipere posse, nisi per medias prius iter fecerit. tural sciences would allow of its being better —Galenus de Usu Partium, lib. iv. cap. 12. done: one might try at least for all bodies * Histoire Nat. torn. v. 12mo. p. 241. Dis- what Jussieu has executed with regard to ve- cours sur la Nature des Animaux. CLASSIFICATION OF THE FUNCTIONS. 47 should never for a moment forget, that as a great number* of diseases con- sist in a derangement of the vital functions, all their efforts should tend to bring back sensibility and contractility to their natural condition ; that the best classification of diseases and of medicines is that which is founded on a judicious distinction of the vital powers. With this view it is that M. Alibert, in his elements of materia medica, classes medicines according to their effects on sensibility or contractility, and according to the organs on which their action is particularly exerted. Sect. XII.—CLASSIFICATION OF THE VITAL FUNCTIONS. After having treated separately of the vital powers or faculties, nothing is easier than to arrange, in a clear and methodical order, the functions car- ried on by the organs which these powers call into action. The term function might be defined means of existence. This definition would be the more just, as life is only the exercise of these functions, and as it ceases when any one of the more important can no longer be carried on. From not distinguishing the faculties from the functions, which are merely the acts of the faculties or powers, several modern divisions, though far prefer- able to the old classification of the functions into vital, animal, and natural, are, nevertheless, deficient in accuracy and simplicity. Thus, Vicq-d'Azyr, in the classification of the phenomena of physiology, inserted in the dis- course which he has prefixed to his work on anatomy, mistakes the cause for the effect, and places sensibility and irritability among the functions; and commits another mistake, by ranking ossification among the latter, which is but a peculiar mode of nutrition, belonging to parts of a hard structure. The best method of classing the actions which are performed in the liv- ing human body is, doubtless, that by which they are distributed and ar- ranged according to the object which they fulfil. Aristotle, Buffon, and especially Grimaud, have laid on that base the foundation of a method which we shall adopt, with the modifications which we are about to mention. Aristotle and Buffon had observed, that among the acts of the living eco- nomy, some were common to all beings that have life, to plants and animals during sleep and in waking, while others seemed to belong exclu- sively to man, and to the animals which more or less resemble him. Of these two modes of existence, the one vegetative, the other animal, the for- mer appeared to them the more essential, as being more diffused, and con- sisting merely in the assimilation of nutritive molecules in the nutrition absolutely necessary to the preservation of the living being, f who, as his substance is incessantly wasting, would soon cease to exist, if these con- tinual losses were not always repaired by the act of nutrition. Grimaud, Professor of Physiology at Montpellier, too soon lost to the science which he cultivated as a philosopher, truly deserving that name, adopted this simple and luminous division, developed it better than had been done before him, and uniformly followed it in his lectures and in his works.J The division of the functions into internal, which he likewise * All diseases consist in physical derange- Prole'gomenes, torn. i. ments, as solutions of continuity, displace- + Nam anima nutritiva etiam aliis inest, et ments ; organic alterations, as polypi, aneu- prima et maxima communis facultas animce, se- risms, and other affections resulting from or- cundum quam omnibus vivere inest.—Aeistot. ganic affection and alteration of structure; de Anim. lib. ii. cap. 4. vital lesions, as sthenic, asthenic, ataxic disor- J In his MS. lectures on physiology, he ders, asphyxia, &c.—See Nosographie et The- seems to feel a complacency in that division rapeutique ChirurgkaUs, 5° edit. Paris, 1821; which he had in a manner appropriated to him. 4S CLASSIFICATION OF THE FUNCTIONS. calls digestive, and into external or-locomotive, lately brought forward under the name of organic and animal,—the former of which terms is quite inaccurate and defective, since it leads to a belief that the auimal life or that of relation is not confided to organs, and that the vital instruments are solely employed on internal life or of nutrition {JVIotus assimilationis, Bacon ; Bias alterativum, Van Helmont)—this division does not comprehend the whole of the phenomena, and does not embrace the sum of the functions which are performed in the animal economy. In fact, there are not found in the two great classes which it establishes, the acts by which animals and vegetables reproduce and perpetuate themselves, and immortalise the du- ration of their species. All the functions destined to the preservation of the species are not included ; they merely relate to the functions subservient to the preservation of individuals. I have, therefore, thought it right to include under two general classes: 1, the functions which tend to the preservation of the individual, and en- able him to enjoy an isolated mode of existence ; 2, the functions which belong to the preservation of the species, functions without which man might exist, as we see in eunuchs, but without which the human species would soon perish, from a loss of the power of reproduction. In laying down these two great divisions, I have merely considered the object and end which each function has to fulfil. Among the functions which are employed in the preservation of the in- dividual, some fulfil this office by assimilating to his own substance the food with which he is nourished ; the others, by establishing, in a manner suit- ed to his existence, his relations with the beings which surround him. The fuctions destined to the preservation c-f the species, may likewise be divided into two classes. Those of the first class require the concourse of two sexes ; they constitute generation, properly so called : those of the second order, ^exclusively belong to the female, who, after conception, is alone destined to bear, to nourish, to bring into the world, and suckle the new being, the result of conception.* The internal, assimilating, or nutritive functions concur in the same end, and all serve to the elaboration of the nutritive matter. The aliment once admitted into the body is subjected to the action of the digestive organs, which separate its nutritive parts ; the absorbents take it up, and convey it into the mass of fluids ; the circulatory system conveys it to all the parts of the body, and makes it flow towards the organs ; the lungs and the se- cretory glands supply it with certain elements, and deprive it of others, alter, modify, and animalise it: in fine, nutrition, which may be considered self, by his happy illustrations of it, and by the the organs of sense, that he adapts himself to changes which he had introduced into it. In those objects, that he places himself in a man- every lecture, I might almost say in every ner suited to the mode of their activity," &c. page, he returns to this division, explains it, * The classification of the functions which dilates, and comments upon it. " The func- Richerand has adopted, with a slight modifica- tions," says he, "may be divided into two tion, from Grimaud, nearly agrees with the " great classes ; some are formed in the inte- one more generally followed by the best mo- " rior of the body, and exclusively belong to dern physiologists, Sprengel arranges them " it; others take place outwardly, and belong into the vegetative, the sensiferous, and the ge- " to external objects," &c. The digestive nerative. Cuvier forms but two classes, the power presides, in his opinion, over the inter- vital and animal. Magendie and Adelon divide nal functions, whose object is nutrition ; the them into functions of relation, functions ofnu- locomotive power directs the external func- trition, and functions of generation. Lenhossek, tions. " It is by means of the organs of sense professor of anatomy and physiology in the that the animal enlarges his existence, that he university of Vienna, classes the functions applies and distributes it to the surrounding into those of organic life, of sensiferous or ani- objects, and takes cognizance of the qualities mal life, and those belonging to generation. in those objects which concern him ; it is by Dr. Bostock admits only two classes, the con- means of the muscles essentially obedient te tractile and sensitive.—/. C. CLASSIFICATION OF THE FUNCTIONS. 49 a« the complement of assimilating functions, whose object it is to provide for the maintenance and growth of the organs, applies to them this animalised substance, assimilated by successive acts, when it has become quite similar to them. Several, however, of these functions serve at once to preserve and to de- stroy : absorption, which takes up extraneous molecules, to be employed in the growth of the organs, takes up equally the organic molecules which are detached by motion, friction, heat, and all the other physical, chemical, and vital causes : the action of the heart and of the blood-vessels sends these fragments, together with the parts truly recrementitious, towards the lungs, which, at the same time that they bring about a combination of the nutritive parts with the oxygen of the atmosphere, separate from the blood the mate- rials which can no longer be employed in nourishing the organs ; the same power propels them towards the secretory glands, which not only purify what is liquid, by separating from it that which cannot without danger remain in the animal economy, but which likewise elaborate or prepare peculiar fluids, some of which are results of the act of nutrition, are employed in that act, and impart to the substances on which it is performed a certain de- gree of animalisation (as to the bile and saliva), while the others seem to be intermediate states, which the nutritive particles of the food are obliged to undergo, before complete animalisation ; such are the serous fluids and the fat. It might perhaps seem more in conformity to the order of nature, to have combined the account of respiration with that of the circulation, by treating of the course of the venous blood, after the action of the absorbent vessels, with which the veins have so much analogy ;—then to have treated of the phenomena of respiration, or of the conversion of the venous blood into arte- rial, and of the course of the latter into all the parts of the body by the ac- tion of the heart and arteries ; but the advantage which would be obtained from a method so contrary to the common practice, which is to consider sepa- rately the functions of circulation and respiration, appeared to me too unim- portant to justify its adoption. The external or relative functions, equally connected by their common des- tination, associate the individual to every thing that surrounds him : the sen- sations, by warning him of the presence of objects which may be useful or injurious to him ; motion, by enabling him to approach or avoid such object?, according as he perceives relations of advantage or disadvantage, according as the opposite sensations of pain or pleasure result from his action on them, or from theirs on him. In fine, voice and speech give him communication with beings enjoying the same means of communication, and that without a necessity of motion. The brain is the principal organ of these functions, as the system of circulation is the centre of the assimilating functions. All the impressions received by the organs of sense are transmitted to the brain, and from the brain determinations arise, as well as the voluntary motions and the voice. The sanguineous system receives the molecules destined to nutrition, and those which are to be thrown out of the body. The sensitive and circula- tory systems are the only systems provided with a centre (the brain and the heart), which extend to all parts of the body, by emanations originating from that organ, or terminating in it (the nerves, the arteries, and veins): and as the motions and the voice depend on sensation, and are immediately connected with it as necessary results, so respiration, secretion, and nutrition, are, in a manner, but consequences of the circulation which distributes the blood to all the organs, in order that these may produce on it various changes, which con- stitute respiration, secretion, and nutrition. They are, if I may anticipate what 50 CLASSIFICATION OF THE FUNCTIONS. is to come hereafter, only different kinds of secretion that take place at the expense of the different principles contained in the blood. The circulation, which holds the functions of nutrition in a kind of depen- dence, subjects the brain, which is the principal organ of the external func- tions, to an influence still more immediate and indispensable. The muscu- lar motions are not less under its influence. It is the first function that is appa- rent in the embryo, whose evolution it brings about: in natural death, of all the functions, it is the last to cease. These reasons justify Haller for having placed the circulation in the first order, and for having begun by its history his great work on physiologj\ I enter into this digression only to expose the absurdity of the claims of some authors, who, because they have varied the me- thodical order of the functions, broken the series, or made the slightest chan- ges,—for example, by placing the history of the functions of smell and taste before the account of the internal or nutritive functions,—think they have totally changed the aspect of the science : pitiful sophists, who accumulate subtleties instead of facts and ideas. In warm and red-blooded animals, the nutritive functions, digestion, absorp- tion, circulation, respiration, the secretions, and digestion, are performed as in man, and in that respect there exist between them very slight differences : nay, in some animals, these functions are performed with much more energy. Thus several animals digest substances on which our own organs produce no effect, and others (birds) have a more rapid circulation, a more active nu- trition, and evolve more heat. But not one of them is as well provided with organs to keep up intercourse, as a living being, with the surrounding objects. In no one animal are the senses possessed of the same degree of perfection ; the eagle, whose sight is so piercing, has a very dull sense of touch, taste, and smell. The dog, whose smell is exquisite, has a very ordinary extent of sight: in him the taste and touch are equally imperfect—his touch, in the perfection of which no animal comes up to man, has not been improved in delicacy, at the expense of the other senses. The sight, the hearing, the taste and smell, preserve a great delicacy, when their sensibility has not been impaired by injudicious or too frequent impressions. The sensitive centre is in no one better developed, and fitter to direct safely the use of the organs of motion. No other animal can articulate vocal sounds, so as to acquire speech. This greater extension of life in man, from the number and perfection of his organs, makes him liable to many more diseases than the other animals. It is with the human body as with those machines, which become more liable to be deranged, by increasing the number of their wheels, with a view of obtaining more extensive or more varied effects. All organised bodies are possessed of assimilating functions ; but as assi- milation requires means varying in number and power, according to the na- ture of the being which performs it. The series of assimilating phenomena commences in the plant by absorption, since it draws immediately from the earth, the juices which it is to appropriate to itself. Its absorbing system at the same time performs the functions of a circulatory organ, or rather the circulation does not exist in plants ; and the direct and progressive motion of the sap, which ascends from the root towards the branches, and sometimes in a retrograde course from the branches towards the roots, cannot be com- pared to the circulation of the fluids which takes place in man, and in the animals which most resemble him, by means of a system of vessels which every moment bring back the fluids to the same spot, and convey them over the whole body, by-making them describe a complete circle, frequently even a double rotation, (animals with a single or double circulation, that is, whose CLASSIFICATION OF THE FUNCTIONS. 51 heart has one or two ventricles). Plants breathe after their own manner, and produce a change in the atmospherical air, by depriving it of its carbonic acid gas, thexesult of combustion and of animal respiration : so that, by a truly admirable reciprocity, plants which decompose carbonic acid, and allow ozygen to exhale, continually purify the air, which combustion and animal respiration are incessantly contaminating.* The functions preservative of the species are common to animals and plants. The organs by which these functions are performed, when compar- ed in these two kingdoms of nature, offer a resemblance which has struck all naturalists, and has led them to observe, that of all the acts of vegetable life, no one is more analogous to the animal economy than that by which fecunda- tion is effected. I shall not here explain the general characters of the two orders of func- tions which are subservient to the preservation of the species : the differences which belong to them are pointed out in several parts of this work.f I shall merely observe, with the authors who have considered them generally, that they are in an inverse ratio to each other ; so that, in proportion as the activity of the assimilating functions increases, that of the external functions is abated. Grimaud has, in the most complete manner, illustrated this idea of the constant opposition which exists between those two series of actions, over which, in the opinion of that physician, there preside two powers, which he calls locomotive and digestive. It is in no kind of animals more distinct than in the carnivorous, which possess organs of sense of the greatest de- licacy, together with muscles capable of prodigious efforts, and yet powers of assimilation so feeble that their food cannot be digested, unless it be com- posed of materials analogous in composition to their own organs.i Too much importance should not be attached to this classification ; like all other divisions, it is purely hypothetical. All is connected together, all is co-ordinate in the animal economy ; the functions are linked together, and de- pend on one another, and are performed simultaneously ; all represent a cir- cle of which it is not possible to mark the beginning or the end. In circulum abeunt (Hippocrates). In man, while awake, digestion, absorption, circula- tion, respiration, secretion, nutrition, sensation, motion, voice, and even gene- ration, may be performed at the same time; but whoever, in the study of the animal economy, should bestow his attention on this simultaneous exertion of the functions, would acquire but a very confused knowledge of them.§ * This opinion originated with Priestley, and condition may require, they partially absorb the was generally adopted, in opposition to the ex- carbonic acid from the air, convert it to their perience of his contemporary, the celebrated use, decompose it, and emit the oxygen which Scheele. More modern physiologists, espe- results from the decomposition, especially when cially Ellis, Gilby, and TT de Saussure, have they are exposed to the sun's rays. The illus- shewn, by well-conducted experiments, that all tration of this subject belongs to vegetable phy- plants, whether growing in absolute darkness, siology.—/. C. in the shade, or when not exposed to the direct t Especially in the account of living beings, rays of the sun, " are constantly removing a Sect. V. of the Preliminary Discourse, articles quantity of oxygen from the atmosphere, and sleep and foztus. It is impossible at present to substituting an equal volume of carbonic acid." go over all these distinctions, without entering Thus far these philosophers nearly agree. They into useless and disagreeable repetitions. differ, however, very widely respecting the % In carnivorous animals the power of diges- manner in which this change is effected. Ellis tion is exceedingly weak, but their muscles are supposes that the leaves, flowers, fruits, stems, very powerful. This relative force of the mus- and roots of plants emit carbonaceous matter, cles was necessary in carnivorous animals, as which combines with the oxygen of the sur- they live by depredations and slaughter, as their rounding air. Gilby and Saussure are of opi- instinct, in unison with their organisation, sets nion that the oxygen is absorbed by the respira- them constantly at war with every thing that lory organs, and that the carbonic acid is form- has life, and as their subsistence depends on ed within the plant. their being victorious in their battles to which Although vegetables, under the ordinary cir- nature incessantly calls them.—Grimaud, first cumstances of their growth, consume oxygen Memoir on Nutrition. during respiration, and disengage carbonic acid, (j The division which I lay down is not to be yet, according as their situation and particular strictly adopted, and as being absolutely true, 52 CLASSIFICATION OF THE FUNCTIONS. By becoming familiar with these abstractions, one might soon mistake them for realities, and even go the length of seeing two distinct lives in the same in- dividual ; one would be apt to assign, as the character of internal life, that it is carried on by organs independent of the will, although this faculty of the mind presides over the phenomena of respiration, of mastication, and of the ex- pulsion of the urine and faeces ; one might consider life as intrusted to un- symmetrical organs, although the heart, the lungs, and the kidneys, are evi- dently symmetrical; and might fancy it to exist in the foetus, which neither breathes nor digests, &c. Nothing in the animal economy, said Galen, is ru^d^by invariable laws, or can be.subject to the same accurate results and calculations as an inanimate machine. (Nil est in corpore viventi plant since- rum. Galen.) Thus respiration, which connects the external and assimilat- ing functions, furnishes the blood with the principle which is to keep up the action of the brain, and to excite muscular contractions. On the other hand, the motion of the muscles is of use in the distribution of the humours, and concurs in the phenomena of assimilation. The brain, by means of the eighth pair of nerves, holds influence over the stomach. The sensations of taste and smell seem to preside in an especial manner over the choice of food and of air, and to belong rather to the digestive and respiratory functions than to those of the intellect or of thought. We have seen in this kind of general introduction of the study of physiolo- gy what idea is to be formed of that science as well as of life, the study of which is its object; into how many classes the beings in nature may be di- vided, and into how many elements they are resolvable; what differences exist between inorganised and organised and living bodies, between plants and animals ; how life is complicated, modified, and extended, in the immense series of beings which are endowed with it, from the plant to man ; and in further particularising the object under our consideration, we have examined what are the organs which, by their union, form the human machine ; what powers govern the exercise of their functions. Then we have laid down the fundamental laws of sensibility and contractility ; we have spoken of sym- pathies and habits ; of the internal nervous apparatus, which unites, collects, and systematises the organs of the assimilating functions ; we have endea- voured to determine from facts the existence of the cause which subjects living beings to a set of laws very different from those which inorganic mat- ter obeys. The knowledge of these laws is the light which is to guide us in the application to physiology of the accessory sciences. Finally, in the arrangement of the objects which this science considers, I have adopted a more simple and natural division than any hitherto employed. > I shall close this Preliminary Discourse by saying a few words on the order adopted in the distribution of the chapters. I might have begun by a view of the external functions, as well as of those of assimilation or nutri- tion, of sensation, or of digestion. I have given preference to the functions of assimilation, because of all others they are the most essential to existence, and their exercise is never interrupted from the instant in which the embryo begins to live till death. In beginning with an account of them, we imitate It is a mere hypothesis, to be attended to only dations so insensible and so adjusted, as to leave in so far as it assists in arranging one's ideas no space for us to lay down the lines of separa- in a more orderly manner. For every arrange- tion or demarcation, which we may choose to ment, even when arbitrary, is useful in laying draw. All our methods of classing and arrang- before us a great number of ideas, and in there- ing the productions of nature are mere abstrac- by facilitating the comparison that is to be in- tionsof the mind, which does riot consider things stituted among them. All the acts of Nature as they really are, but which attends to certain are so connected, and are linked together in so qualities, and neglects or rejects all the rest.— close a union, and she passes from the one to Grimaud, Lectures on Physiology. the other by such uniform motions, and by gra- CLASSIFICATION OF THE FUNCTIONS. 53 nature, therefore, who imparts to man this mode of existence before she has connected him with outward objects, and who does not deprive him of it until the organs of sense, of motion, and of the voice, have completely ceased to act. As to the course which has been followed in the arrangement of the func- tions that belong to the same order, or which concur in the same end, it was too wrell laid down by nature to allow us to depart from it. 1 have thought it right that the consideration of the voice should immediately precede that of generation, in order that the arrangement might, at a glance, shew the connexion which exists between their phenomena. Several animals use their voice only during the season of love: the birds which sing at all times, have, during that period, a more powerful and sonorous voice. When man be- comes capable of reproduction, his vocal organs suddenly become evolved, as though nature had wished to inform him that it is through them he is to express his desires to the gentle being who may sympathise in them. The voice, therefore, serves as a natural connexion between the external functions and those which are employed in the preservation of the human species. The voice, which leads so naturally from the functions which establish our external relations to those whose end is the preservation of the species, is still more intimately connected with motion. It is, in a manner, the complement of the phenomena of locomotion ; by means of it our communication with external objects is rendered easier, more prompt, and more extensive : it de- pends on muscular action, and is the result of voluntary motion. Finally, these motions sometimes supply the place of speech—in pantomime, for ex- ample ; and in the greater number of cases the language of action concurs in adding to its effect. Every thing, therefore, justifies me in placing this function after motion, in separating it from respiration, with which every other author has joined it, without considering that the relation between the voice and respiration is purely anatomical, and can therefore in no wise ap- ply to physiology. I have placed after generation an abridged account of life and death, in which will be found whatever did not belong to any of the preceding divisions. The necessity of this Appendix, containing the history of the different pe- riods of life, that of the temperaments and varieties of the human species, that of death and putrefaction, arises from the impossibility of introducing into the particular history of the functions these general phenomena in which they all participate. CLASS I. FUNCTIONS WHICH TEN? TO THE PRESERVATION 0*" THE INDIVIDUAL. (^Individual I- ery moderate in the use of fluids. She had always taken considerable exercise on foot, and even up to the period at which we saw her, she resorted to it as much as the great bulk of her body could permit. The secret, however, of her increasing ohesity was disclosed, when she mentioned her insatiable desire for refined su- gar, which she almost hourly made use of, fre- quently to the extent of one pound weight daily. She considered it her chief article of diet. She reckoned the average quantity which she used at about three-fourths of a pound in the day. Tea or coffee was taken by her sweetened in the usual way. She ate the sugar in the solid state, and unaccompanied with any other article of diet; the finest sort only was relished. Her digestive functions were in a perfect condi- tion ; neither cardialgia, acidity, nor flatulence, were complained of. Her teeth were sound. She found her corpulence supervene to a spare habit of body, some time after the practice of eating sugar was acquired. She thought that the obesity increased with the increase in the quantity of sugar which she consumed. The habit had become so confirmed, at the time when we saw her, that she conceived it to be quite impossible to relinquish it.—/. C. * The inhabitants of warm climates, who are subjected, in consequence of the nature of the situation in which they live, to a moist and miasmatous atmosphere, generally adapt their vegetable diet, as much as may be in their power, to the circumstances in which they are placed. They endeavour, by adding a large proportion of the stimulant and tonic seeds of plants to their aliments, to counteract the de- bilitating and septic influence of the air which they breathe, and of other sedative causes of disease to which they are more or less exposed. Hot spices are their chief condiments, and even prophylactics : without the use of these their very aliments would become a source of dis- ease ; the various kinds of parasitical animals which prey on man would abound to the most loathsome degree, and they would be continually the subject of dysentery, and the other maladies which imperfect or itnproper nourishment, and an unwholesome climate, induce. The hot spices are, to individuals so circumstanced, more requisite than salt is to the inhabitants of temperate or cold climates, who live chiefly on animal food.—/. C. OF DIGESTION.--KINDS OF FOOD. 61 happy consequence of the climate. Northern nations, on the contrary, are voracious from instinct and necessity. They swallow enormous quantities of food, and prefer those substances which in digestion produce the most heat. Obliged to struggle incessantly against the action of cold, which tends to be- numb the vital powers, to suspend every organic motion, their life is but a continual act of resistance to external influences. Let us not reproach them with their voracity and their avidity for ardent spirits and fermented liquors. Those nations that inhabit the confines of the habitable world, in which man is scarcely able to withstand the severity of the climate, the inhabitants of Kamtschatka, the Samoiedes, live on fish that, in the heaps in which they are piled up, have already undergone a certain degree of putrefactive fermen- tation. Does not the use of a food so acrid and heating, that in our climate it would inevitably be attended with a febrile action, prove plainly the neces- sity of balancing, by a vigorous inward excitement, the debilitating influence of powers that are operating from without 1 The abuse of spirituous liquors is fatal to the European transported to the burning climate of the West In- dies ; yet the Russian drinks spirituous liquors with a sort of impunity, and lives on to an advanced age, amidst excesses under which an inhabitant of the south of Europe would sink. This influence of climate affects alike the regimen of man in health and that of man in sickness ; and it has been justly observed of medicine, that it ought to vary according to the places in which it is practised. Barley, ptisan, honey, and a few other substances, the greater part obtained from the vege- table kingdom, sufficed to Hippocrates in the treatment of diseases ; his the- rapeutic treatment was, in almost every case, soothing and refreshing. Phy- sicians who practise in a climate such as that of Greece, may imitate this simplicity of the father of physic. Opium, bark, wine, spirits, aromatics, and the most active cordials are, on the other hand, the medicines suited to the inhabitants of the North. The English physicians use, freely and without risk, these medicines, which elsewhere would be attended with the utmost danger. Simple aqueous drinks promote digestion,* by facilitating the solution of the solids, by serving as a vehicle to their divided parts; and when rendered active by saline or other substances, as spirituous liquors are by alcohol, they are further useful in stimulating the organs and exciting their action. The least compound drinks are possessed, in different degrees, of this dou- ble property of dissolving solid aliments and of stimulating the digestive or- gans. The purest water is rendered stimulating by the air and by the salts which it contains in different proportions ; and to the want of that stimulating quality is to be attributed the difficult digestion of distilled water. The drinks best suited to the wants of the animal economy are those in which the stimulating principles are blended in due proportions with the water which holds them in solution. But almost all the fluids which we drink contain a certain proportion of nutritious particles. Wine, for example, ^ contains these nutritive particles in greater quantity, as it is the produce of a warmer climate, and as saccharine matter predominates in its composi- tion. Thus, Spanish wines are in themselves nourishing, and are perhaps fitter to satisfy hunger than to allay thirst; while the acidulous Rhenish wines, which are merely thirst-allying, scarcely contain any cordial quali- ty. Between the two extremes are the French wines, which possess, in a * Simple fluids promote this process only in too great a degree the gastric juice, and to when they are taken in small quantity, and when over-distend the stomach, especially during thirst indicates the propriety of resorting to meals, they evidently letard digestion.—/. C. them. If they are used so largely as to dilute 62 OF HUNGER AND THIRST. nearly equal degree, the treble advantage of diluting the fluids, of stimulat- ing the organs, and of furnishing to the animal economy materials of nutri- tion. IV. Of hunger and thirst.—By the words hunger and thirst are meant two sensations, which warn us of the necessity of repairing the loss which our body is continually undergoing from the action of the vital principle. Their nature, as is well observed by M. Gall, is not better known than that of thought. Let us endeavour to explain the phenomena by which they are attended. The effects of a protracted abstinence are, a diminution of the weight of the body—a diminution which becomes sensible in the course of twenty-four hours,—a wasting of the body from the loss of fat, discoloration of the fluids, especially the blood, loss of strength, excessive sensibility, sleeplessness,- with painful sensations in the epigastric region.* Death from inanition is most easily brought on in those who are young and robust. Thus, the unfortunate father, whose horrible story has been narrat- ed by Dante, condemned to die of hunger, and shut up with his children in a dark dungeon, died the last, on the eighth day, after having witnessed, in the convulsions of rage and despair, the death of his four sons, unhappy victims of the most execrable vengeance ever recorded in the history of man. Haller has related, in his great work on physiology, several instances of prolonged abstinence: if we are to give credit to these accounts, some of which are deficient in the degree of authenticity required to warrant belief, persons have been known to pass eighteen months, two, three, four, five, six, seven, and even ten years, without taking any nourishment. In the Memoirs of the Edinburgh Society is found the history of a woman who lived on whey only for fifty years. The subjects of these cases are mostly weak, infirm women, living in obscurity and inaction, and in whom life, nearly extinct, just shewed itself in an almost insensible pulse, and an unfrequent and indistinct respira- tion. It is a fact well worthy of observation, that the muscles and viscera of some of them, when examined after death, shone with a light evidently phosphoric.f Can it be that phosphorus is the result of the lowest degree of animalisation 1 It may be easily conceived, that living in a manner on their own substance, the fluids in such persons have been frequently subject- ed to the causes which produce assimilation and animalisation, and have un« dergone the greatest alteration of which they are capable. The proximate cause of hunger has by some been conceived to depend on the friction of the nervous papillae of the empty stomach on each other ; by others it has been imputed to the irritation produced on its parietes by the ac- cumulation of the gastric juice. It has been thought to depend on the lassi- tude attending the permanent contraction of the muscular fibres of the sto- mach, and on the compression and creasing of the nerves during that per- manent constriction ; on the dragging down of the diaphragm by the liver and spleen, when the stomach and intestines, being empty, cease to support those viscera,—a dragging which is the greater, as a new mode of circula- tion takes place in the viscera, which are supplied with blood by the cceliac artery, and while the stomach receives less blood, the spleen and liver increase n weight and size, because their supply is increased. J * See Appendix, Note I. or that it is a sensation connected with the \ Nitidissima viscera sunt animalium fame contracted state of this organ and the corruga- enectorum, et argentei fibrarum fasciculi.—Hal- tion of its internal membrane. It is not un- LBE, Elem. Phys. torn. vi. p. 183. likely that both causes may contribute to the \ The most prevalent opinions respecting the production of this sensation, in consequence of proximate causes of hunger are, that it is owing the impression which they may make on the to the action of the gastric juice on the stomach, sentient extremities of these cerebro-spinal OF HUNGER. 63 Those who maintain that hunger depends on the friction of the parietes of the stomach against each other, when brought together in an empty state, adduce the example of serpents, whose stomach is purely membranous, and who endure hunger a long time; while fowls, whose powerful and muscular stomach is able to contract strongly on itself, endure it with difficulty. But, to say nothing of the great difference of vitality in the organs of a bird and of a reptile, the stomach which continues closing on itself as it is emptied, may contract to such a degree as scarcely to equal in size a small intestine, without its following, as a necessary consequence, that the parietes which are in contact should exert on each other any friction on which the sensation of hunger may depend. In fact, the presence of food is necessary to determine an action of the parietes of the stomach; and as long as it is empty, there is nothing to call forth such action. Those who think that hunger is mechanically produced by the weight of the spleen and liver, that keeps pulling down the diaphragm, which the empty stomach no longer bears up, observe, that it may be appeased for a time, by supporting the abdominal viscera by means of a wide girdle ; that hunger ceases as soon as the stomach is full, before the food can have yielded to it any materials of nutrition. On this hypothesis, which is purely mecha- nical, as that which explains hunger by the irritation of the gastric juice, by the lassitude of the contracted muscles, by the compression of the nerves,— how shall we explain the fact, that when the hour of a meal is over, hunger ceases for a time ? Ought not hunger, on the contrary, to be considered as a nervous sensation which exists in the stomach, is communicated by sympathy to all the other parts, and, keeping up an active and continuous excitement in the organ in which it is principally seated, determines into it the fluids from all parts % This phenomenon, like all those which depend on nervous influ- ence is governed by the laws of habit, by the influence of sleep, and of the passions of the mind, whose power is so great, that literary men, absorbed in meditation and thought, have been known entirely to forget that they re- quired food. Every thing which awakens the sensibility of the stomach, in a direct or sympathetic manner, increases the appetite and occasions hunger.' Thus, bulimia depends sometimes on the irritation of a tape-worm in the organs of digestion. The application of cold to the skin, by increasing from sympathy the action of the stomach, has been known to occasion/ames canina, of which several instances are related by Plutarch (Life of Brutus). Ardent spirits and highly seasoned food excite the appetite, even when the stomach is over-filled. Whatever, on the contrary, blunts or renders less acute the sensi- bility of the stomach, renders more endurable or suspends the sensation of hun- ger. Thus, we are told by travellers, that the Turkish dervises and the Indian faquirs endure long fasts, because they are in the habit of using opium, and lull, in a manner, by this narcotic, the sensibility of the stomach. Tepid and nerves, which reinforce the vital operations of hours, and further to increase the appetite by the stomach. The state of the absorbent ves- more exercise than usual. At the end of this sels, and the irritation which the gastric fluid time he was very hungry ; but, instead of eat- induces on the extremities of those vessels dur- ing, excited vomiting by drinking warm water ing an empty state of this viscus, ought also to and irritating the fauces. The water returned be taken into consideration in our speculations mixed only with a ropy fluid, such as the gastric respecting the origin of this sensation. fluid is described to be by Spallanzani, or as I The following experiment of Dr. W. Philip, have myself obtained it from the stomach of a detailed in his excellent work on indigestion, crow. After this operation, not only all desire appears to confirm the opinion that the influence to eat was removed, but a degree of disgust of the gastric juice on the stomach is, in some was excited by seeing others eat. He, how- way or other, productive of the sense of hun- ever, was prevailed upon to take a little milk ger. and bread, which in a very short time ran into " A person in good health was prevailed up- the acetous fermentation, indicated by flatu- on to abstain from eating for more than twenty lencc and acid eructations."—/. C. 64 OF THIRST relaxing drinks impair the appetite ; the use of opiates suspends suddeoly the action of the stomach. V. Of thirst.—The blood, deprived of its serosity by insensible perspiration and by internal exhalation, requires incessant dilution, by the admixture of aqueous parts, to lessen its acrimony; and as the serosity is incessantly ex- hausting itself, the necessity for repairing that loss is ever urgent * The calls of thirst are still more absolute than those of hunger, and it is much less patiently endured. If it be not satisfied, the blood and the fluids which are formed from it become more and more stimulating, from the concentration of the saline and other substances which they contain. The general irritation gives rise to an acute fever, with heat and parching of the fauces, which in- flame, and may even become gangrenous, as happens in some cases of hy- drophobia. English sailors, who were becalmed, had exhausted all their stock of fresh water, and were at a distance from land ; not a drop of rain had for a long while cooled the atmosphere: after having borne, for some time, the agonies of thirst, further increased by the use of salt provisions, they resolved to drink their own urine. This fluid, though very disgusting, allayed their thirst; but at the end of a few days it became so thick and acrid, that they were incapable of swallowing a mouthful of it. Reduced to despair, they expected a speedy death, when they fell in with a ship which restored them to hope and life. Thirst is increased every time that the aqueous secretions are increased; thus, it becomes distressing to a dropsical patient, in whom the fluids are determined towards the seat of effusion. It is excessive in diabetes, and in proportion to the increased quantity of urine. In fever it is increased from the effect of perspiration, or because in some of these affections, for example in bilious fevers, the blood seems to become more acrid. Hence the advantage of cooling, diluting, and refreshing drinks, administered co- piously, with a view to correct the temporary acrimony occasioned by the absence of a great quantity of the serous parts of the blood, and to lessen the over-excitement of a fluid become too stimulating. The use of aqueous drink is not the most effectual method of allaying thirst. A traveller, exposed to the scorching heat of summer, finds it advan- tageous to mix spirits with plain water, which alone does not stimulate suf- ficiently the mucous and salivary glands, whose secretion moistens the inside of the mouth and pharynx, and covers these surfaces with the substance best * As hunger seems to depend upon a certain condition of, or impression made upon, the nerves distributed to the stomach, so thirst ap- pears to arise from an altered state of the fluids, which state modifies the functions of the ves- sels, diminishes, or otherwise alters, the condi- tion of the fluids secreted in the mouth and fauces, and which impresses the nerves of sen- sation, in these situations, in such a manner as to give rise to the phenomenon under considera- tion. As the sense of thirst is induced by a state of the circulating fluids which would become hurtful to the system were it to continue for any considerable period, so this sensation is to be regarded in the light of a watchful guardian, which both points out that state, and the only way in which it can be removed. The superabundance of saline or stimulating substances in the blood is readily indicated hy the sensation induced in the mouth and fauces, which are the first parts to evince the delete- rious effects of these substances upon the ani- mal economy : hence the state of these organs is an important index to the condition of the circulating fluids, and of the whole system, in a number of diseases. Those physiologists who refer the operations of the living body to a galvanic process, carried on by the nervous system on the fluids contain- ed in the vascular, especially in the capillaries, assign, as the proximate cause of thirst, a de- ficiency of oxygen, and an abundance of the inflammable materials amongst those elements which constitute the fluids circulating at the time in which the sensation is induced, {Oxy- genii autem defectum, et phlogisticorum abundan- tiam sitim adducere.) This, or a similar opi- nion, is entertained by Sprengel, Prochaska, Burdach, and Lenhosseck. The arguments which these systematic writers on physiology adduce, as well as the experiments of Dr. Philip, in support of the theory which ascribes the vital phenomena to galvanic processes tak- ing place in the system, deserve to be calmly considered before they are designated to be either visionary or untenable.—J. C. OF MASTICATION. 65 Calculated to suspend, at least for a time, the erethism on which thirst appears to depend. VI. Of mastication*—The organs employed in the mastication of the food are the lips, the jaws, and the teeth: with these are furnished the mus- cles by which they are moved, and those which form the parietes of the mouth. The motions of the lips are extremely varied, and depend on the single or combined action of their muscles, by which the greater part of the face is covered, and which may be enumerated as follows : Elevators of the upper lip (caninus, incisivus, levatores communes labiorum et myrtiformes.) De- pressors of the under lip (triangularis labiorum, quadratics gence). Abductors (buccinator, zygomaticus major et minor, plalysma-myoides). Constrictors (or- bicularis oris). . VII.—The motions of the upper jaw are so confined, that some have de- nied that it has any motion: it, nevertheless, rises a little when the lower jaw descends; but it is principally by the depression of the latter that the mouth is opened. The muscles at the back of the neck, and that part of the digastric muscle nearest the mastoid process, produce a slight elevation of the upper jaw, which moves with the whole head, to the bones of which it is firmly united. This connexion of the upper jaw with the bones of the head renders this jaw less movable in man than in the greater number of animals, in which, freed from the enormous weight of the skull, it stretches out in front of that cavity, over the lower jaw. As we follow downwards the scale of animal existence, the motions of the upper jaw are seen to increase the further we descend from the human species ; it is equal to that of the lower jaw in the reptiles, and in several fishes ; hence the enormous dimen- sions of the mouth of the crocodile and shark ; hence serpents frequently swallow a prey of a bulk greater than their own, and would be suffocated, but for the power they possess of suspending respiration for a long time, and of waiting patiently till the gastric juice dissolves the food as it is swallowed. In the act of mastication the upper jaw may be considered as an anvil, on which the lower jaw strikes as a movable hammer ; and the motions of the under jaw, the pressure it exerts, and its efforts, would soon have disturbed the connexion of the different bones of which the face is formed, if this un- steady edifice, merely formed of bones in juxta-position, or united by sutures, were not supported, and did not transmit to the skull, the double effort which presses on it from below upwards, and pushes it out laterally. Six vertical columns, the ascending apophyses of the superior maxillary bones,-the orbitar processes of the malar bones, and the vertical processes of the palate bones, support and transmit the effort which takes place in the first direction, while the zygomatic processes forcibly press the bones of the face against each other, and powerfully resist separation outwardly or laterally. The lower jaw falls by its own weight when its elevators are relaxed ; the ex- ternal pterygoid muscles, and those attached to the os hyoides, complete this motion, the centre of which is not in the articulation of the jaw to the tem- poral bones, but corresponds to a line that should cross the coronoid processes a little above the angles of the jaw. It is around this axis that, in falling, the lower jaw performs a motion of rotation, by which its condyles are turned forwards, while its angles are carried backwards. In children, the coronoid processes standing off at a smaller distance from the body of the bone, of which they have nearly the same direction, the centre of motion is always in * The following operations are comprehend- duodenum ; 6, the action of the small intes- ed under the process of digestion, namely, 1, tines ; 7, the function of the cascum ; 8, the mastication ; 2, insalivation ; 3, deglutition; 4, action of the colon ; 9, the expulsion of the the action of the stomach ; 5, the action of the faeces.—/. C. 9 66 of Mastication. the glenoid cavities, which the condyles never quit, however much the jaW may be depressed. By this arrangement, nature has guarded against dis- location, which would have been frequent at an early period of life from cry- ing, during which the jaw is depressed beyond measure, or when, not know- ing the just proportion between the capacity of the mouth and the size of the bodies they would put into it, children endeavour to introduce those which Jt cannot receive. The lower jaw forms a double bended lever of the third kind, in which the power represented by the temporal masseter and internal pterygoid muscles lies between the fulcrum and the resistance, at a smaller or greater distance from the chin. The mode of articulation of the jaw to the temporal bones allows ft only a motion upwards and downwards, in which the teeth of both jaws meet like the blades of scissors, and a lateral motion, in which the teeth glide on each other, producing a friction well calculated to grind the food, which in the first part of the act of mastication was torn or divided. VIH.—In carnivorous animals, the levator muscles of the under jaw, espe- cially the temporals and masseters, are prodigiously large and powerful. In them the coronoid processes, to which the temporal muscles are attached, are very prominent; the condyles are received into a very deep cavity; while in herbivorous animals, on the contrary, they are less strong and bulky, and the pterygoid muscles, by whose action the lateral or grinding motion is per- formed, are stronger and more marked. The glenoid cavities are also in them wide but shallow, so that they allow the condyles to move freely on thei* surface. The comparative power of the levator and abductor muscles of the lower jaw may be easily appreciated by viewing the temporal and zygo- matic fossa?. Their depth is always in an inverse ratio, and proportioned to the bulk of the muscles which they contain. In carnivorous animals, the zygomatic arch, to which the masseter is attached, is depressed, and seems to have yielded to the effort of the muscle. In the point of view which we have just taken, man holds a middle station between carnivorous animals and those which feed on vegetable substances ; nothing, however, determines his nature better than the composition of his dental arches. IX.—The small white and hard bones which form the dental arches, are not alike in all the animals whose jaws are furnished with them. All have not, as man, three kinds of teeth. The laniary* teeth are not to be met with in the numerous class of rodentia. Some are without incisors ; the former appear more fitted to tear fibrous tissues which offer much resistance. In carnivorous animals they are likewise very long, and bent like curved pincers. The grinders are principally employed in grinding substances previously di- * After the example of several naturalists, 1 have thought it right to give that name to the canine teeth; in the first place, because their principal use being to lacerate or tear fibrous tissues, it is fit that they should have a name from their manner of acting on the food, as is the case with the incisors and molares ; in the second place, because the word canine may lead to an erroneous conception, by inducing a be- lief that this kind of tooth belongs only to one kind of carnivorous animals, while they are stronger and more distinct in the lion, the ti- ger, &c. Such an explanation is indispensable, at a period when every body aspires to the easy glo- ry of introducing innovations in language. The invention of words is, however, in the opinion of a celebrated female writer, a decided symp- tom of barrenness of ideas. The teeth differ essentially from the other bones ; 1st, by the acute sensibility with which they are endowed; 2dly, by the nerves which may be traced into them, while they seem to be wanting in every other part of the osseous sys- tem ; 3dly, by the mode of distribution of the blood-vessels : these penetrate into them at an aperture which is seen at the extremity of their root, and they expand in the mucous membrane contained in the tooth, and which forms the most essential part of the bone ; 4thly, by their not undergoing any change from exposure to the air, a property which they owe to the enamel that covers them externally. It has been said with justice, that nature, in sheathing the tooth with this covering, has imitated the process of tempering, by means of which we harden the edge of steel or iron tools. BAT.1VAP.T SOLUTION. 67 vided by the laniary teeth, which tear them, or by the incisors, which, in meeting as the blades of scissors, fairly cut them through; the latter, of which each jaw contains four, acting only on bodies which present but a slight resistance, are placed at the extremity of the maxillary lever. The grinders are brought nearer to the fulcrum, and it is on them that the great stress of mastication rests. If we wish to crush a very hard substance, we instinctively place it between the last large grinders, and by thus shortening considerably the lever between the resistance and the fulcrum, we improve on the lever of the third kind, which, though most employed in the animal economy, acts the most unfavourably. The laniary teeth have very long fangs, which lying deeply buried in the alveolar processes, give them a de- gree of firmness to enable them to act powerfully, without a danger of being loosened from their situation. The enamel which covers the teeth preserves the substance of the bone exposed to the contact of the air from the injurious effects which would not fail to result from direct exposure; and as enamel is much harder than bone, it enables the teeth to break the hardest bodies without injury. The concen- trated acids soften this substance, and occasion a painful affection of the teeth. The sensibility possessed by these bones is seated in the mucous membrane which lines their inward cavity, through which are distributed the vessels and nerves that enter by openings at their roots. This membrane is the seat of a great number of diseases, to which the teeth are subject. The enamel, incessantly worn by repeated friction, grows and repairs its waste. The alve- olar processes-which receive the fangs of the teeth firmly embrace them, and all of them being exactly conical in form, every point of these small cavities, and not merely their lower part at which the nerves and vessels enter, supports the pressure which is applied to these bones. When, from accidental causes, or in the progress of age, the teeth are gone, their alveoli first contract, and then disappear; the gums, a reddish and dense membranous substance, which connects the teeth to the sockets, harden and become callous over iheir thinned edges. Old men, who have lost all their teeth, masticate but imperfectly ; and this circumstance is one of the causes of their slow diges- tion, as the gastric juice acts with difficulty on food whose particles are not sufficiently divided. X. Salivary solution.—The above mechanical trituration is not the only change which the food undergoes in the mouth. Subjected to the action of the organs of mastication, which overcome the force of cohesion of its mole- cules, it is at the same time imbued with the saliva. This fluid, secreted by the glands placed in the vicinity of the mouth, is poured in considerable quantity into that cavity during mastication. The saliva is a transparent and viscous fluid, formed of about four parts of water and one of albumen, in which are dissolved phosphates of soda, of lime, and of ammonia, as well as a small quantity of muriate of soda: like all other albuminous fluids, it froths when agitated, by absorbing oxygen, for which it appears to have a strong affinity. Its affinity for oxygen is such, that one may oxydise gold and silver, by triturating in saliva thin leaves of those metals, which are of such difficult oxydisement. The irritation occasioned by the presence or the desire of food, excites the salivary glands ; they swell and become so. many centres of fluxion, towards which the humours flow abundantly.* Bordeu first called the attention of * The intimate sympathy or consent of ac- cess of digestion and all the operations of se- tion that exists between the functions of the sto- cretion and nutrition, is strongly evinced by the mach and the salivary apparatus, by means of following fact. An individual, in an attempt to the nerves which chiefly preside over the pro- commit suicide, divided the oesophagus to a con- 68 SALIVARY SOLUTION. physiologists to the great number of nerves and vessels received by the paro* tid, maxillary, and sublingual glands, from the carotid, maxillary, and lingual arteries, from the portio dura of the seventh pair of nerves, from the lingual nerve of the fifth pair, which penetrate their substance, or pass over a portion of their surface. This great number of vessels and nerves is, proportioned to the quantity of saliva which is secreted, and this is estimated at about six ounces during the average time of a meal. It flows in greater quantity when the food that is used is acrid and stimulating : it mixes with the mucus, copiously secreted with the mucous, buccal, labial, palatine, and lingual glands, and with the serous fluid exhaled by the exhalent arteries of the mouth. The saliva moistens, imbues, and dissolves the ball formed by the aliment, brings together its divided molecules, and produces on them the first change. There can be no doubt that the saliva, mixing with the food by the motion of the jaws, absorbs oxygen, and unites to the alimentary sub- stances a quantity of that gas fit to bring about the changes which they are ultimately destined to undergo* XI.—The muscular parietes of the mouth are, during mastication, in per- petual action. The tongue presses on the food, in every direction, and brings it under the teeth; the muscles of the cheek, especially the buccinator, against which the food is pressed, force it back again under the teeth, that it may be siderable extent. During the endeavours to up oxygen without a portion of nitrogen, or of preserve his existence, food was conveyed into common air. If any quantity of the latter be the stomach by means of a tube. As soon as mixed with it during the insalivation of the food, the aliments were received into this viscus, the an evident source is disclosed from which nitro- salivary secretion became abundant, although gen may be conveyed into the circulating fluids, the process of mastication was not, of course, in addition to that portion of it which is derived attempted.—J. C. from the ordinary aliments. * The specific gravity of saliva is l-0038. It The affinity which the saliva has for oxygen, mixes with water only by trituration, has a and the readiness with which it gives out this strong affinity for oxygen, absorbs it readily substance to other bodies, explains the reason from the air, and gives it out again to other bo- why gold or silver triturated with it is oxydised ; dies. Whether it possesses any affinity for ni- and why mercury soon disappears when triturat- trogen, has not been shewn; nor has the ab- ed with saliva. Hence, also, the reason why sorption of oxygen by this fluid, during the pro- the application of saliva to sores is an useful cess of mastication, been sufficiently attended remedy, and one to which the lower animals have to in our speculations respecting the process of a constant recourse.—J. C. digestion. We can hardly suppose that it takes The constituents of saliva, according to Berzelius, are as follow :— Water.......................9929 Peculiar animal matter (precipitated by acet. plumbi), mucus of Bostock 29 Mucusf—albumen of Bostock and Thompson.......... 1-4 Alkaline muriates................... 1-7 Lactate of soda and animal matter.............. 0'9 Pure soda...................... 02 _________________ 10000 + The mucous or albuminous portion has all peculiar substance which adheres to the teeth, the characters of albumen. On incineration, and gives origin to the tartar that surrounds its ashes contain a considerable portion of phos- them. This deposition, according to Berzelius, phate of lime, although none of that salt can be is composed of detected in it before the incineration. It is thi3 Earthy phosphates...............79-0 Undecomposed mucus..............J2-5 Peculiar salivary matter.............TO Animal matter soluble in mur. acid..........7-5 1000 It cannot be doubted, that, like the other ani- stinate venereal disease impregnated with oxalic mal flnids, the constitution of this is liable to acid. changes from disease. It is, however, a sub- The concretions which sometimes form in the ject which has excited little attention among salivary ducts chiefly consist of phosphate of chemists and physiologists. Brugnatelli found lime in coagulated albumen.—/. C. the saliva of a patient labouring wider an ob- OF DEGLUTITION. 69 duly triturated. When the food has been sufficiently divided, and imbued with saliva, the tip of the tongue is carried to every part of the mouth, and the food is collected on its upper surface. The food having been thus com- pletely gathered together, the tongue presses it against the roof of the mouth, and turning its tip upwards and backwards, at the same time that its base is depressed, there is offered to the food an inclined plane, over which the tongue presses it from before backwards, to make it clear the isthmus of the fauces, and to thrust it into the oesophagus. In this course of the food along the pharynx and into the oesophagus, consists deglutition, a function which is assisted by the co-operation of several organs whose mechanism is rather complicated. XII. Deglutition.—In the process of deglutition, the mouth closes by the approximation of both jaws ; at the same time, the submaxillary muscles, the digaslrici, the genio-hyoidei, the mylo-hyoidei, &c. elevate the larynx and pharynx, by drawing down the os hyoides towards the lower jaw, which is fixed by its levator muscles. The hyoglossus muscle, at the same time that it elevates the os hyoides, depresses and carries backwards the base of the tongue. Then the epiglottis, situated between these two parts, which are brought together, is pushed downwards and backwards by the base of the tongue, which lays it over the opening of the larynx. The alimentary mass, pressed between the palate and the upper surface of the tongue, slides on the inclined plane formed by the latter, and pressed by its tip, which bends back, clears the isthmus of the fauces. The mucous substance which exudes from the surface of amygdalae further facilitates the passage of the food. When the food has thus dropped into the pharynx, the larynx, which had risen, and had come forward, and which in that motion had drawn the pha- rynx along with it, descends and falls backwards. This last organ, stimu- lated by the presence of uie food, contracts, and would in part send it back in a retrograde direction, by the nasal fossa, if the velum palati, elevated by the action of the levatores palati, stretched transversely by the tensores palati, was not applied to their posterior apertures, and towards the openings of the Eustachian tubes. Sometimes this obstacle is overcome, and the food returns, in part, by the nostrils. This happens, when, during the act of deglutition, we attempt either to laugh or speak. At such times, the air, expelled from the lungs with a certain degree of force, elevates the epiglottis, and meeting the alimentary mass, pushes it back towards the nostrils through which it is to pass. The isthmus faucium is closed against the return of the food into the mouth, by the swelling of the base of the tongue, raised by the action of the constrictor faucium, and of the constrictor pharyngis superior, which are smalrmuscles contained in the thickness of the pillars of the velum. The alimentary mass is directed towards the oesophagus, and is thrust in- to that canal by the peristaltic contractions of the pharynx, which may be considered as the narrow part of a funnel-like tube. The solid food passes behind the aperture of the larynx, which is accurately covered over by the epiglottis.* The liquids flow along the sides of that opening, in two chan- nels easily distinguished. They are always of a more difficult deglutition than the solids ; the molecules of a fluid have an incessant tendency to se- parate from one another ; and to prevent this separation, the organs are ob- liged to use greater exertion, and to embrace with more precision the sub- * During deglutition the glottis is accurately this. The fact, however, has been demonstrated closed, as well as protracted by the epiglottis, to Magendie and others, who have seen the epi- so as to prevent the entrance or irritation of fo- glottis completely destroyed by disease, without reign substances. Attention to the phenomena either deglutition or speech being impaired.— of respiration and deglutition, particularly as /. C. connected the one with the other, will prove 70 OF THE ABDOMINAL CAVITY. stance that is swallowed. Thus, it is observed in those cases in which de- glutition is prevented by some organic affection pf the oesophagus, that the patients, though they have the power of swallowing solid food, find it diffi- cult to swallow a few drops of a liquid, and are tortured with thirst, though they haVe still the power of satisfying their hunger. The deglutition of air and of gaseous substances is still more difficult than that of liquids, because these elastic fluids are much less coercible, and it re- quires considerable practice to transmit a mouthful of air into the stomach. M. Gosse, of Geneva, had acquired that power from repeated experience, and he made use of it to induce vomiting at pleasure, and by the application of that faculty to the interests of science, he ascertained the digestibility of the articles of food in most common use. The food descends into the oesophagus, propelled by the contractions of that musculo-membranous duct situated along the vertebral column, from the pharynx to the stomach. Mucus is secreted, in considerable quantity, by the membrane which lines the inner part of the oesophagus, it sheathes the substances which pass along it, and renders their passage more free. The longitudinal folds of the inner membrane allow the oesophagus to dilate ; nevertheless, when it is stretched beyond measure, severe pain is experienced, occasioned, no doubt, by the distension of the nervous plexuses, formed by the nerves of the eighth pair, which embrace the oesophagus, as they course along its sides.—I purposely avoid speaking of the weight of the food, as one of the causes which enable it to pass along the oesophagus. Although, in man as in quadrupeds, that weight is no obstacle to deglutition, it favours that function in so slight a degree, that the diminution of muscular contrac- tility at the approach of death is sufficient altogether to prevent it. The act of drinking is then attended with a noise of unfavourable omen. This noise consists in a gurgling of the fluid, which has a tendency to get into the larynx, whose opening is not covered over by the epiglottis ; and if it be in- sisted upon that the patient shall swallow some ptisan, the deglutition of which is impracticable, it flows into the trachea, and the patient dies of suf- focation. XIII. Of the abdomen*—Before inquiring any farther into the phenomena of digestion, let us shortly attend to the cavity which contains its principal organs. The abdomen is almost entirely filled by the digestive apparatus, of which the urinary passages form a part ; its size, and the structure of its parietes, are evidently adapted to the functions of that apparatus. The ca- pacity of the abdomen exceeds that of the other two great cavities ; its dimensions are not invariably fixed, as those of the skull, whose size is de- termined by the extent of its osseous and inelastic parietes. They are like- wise more varying than those of the chest, because the degree of dilatation of which the latter is susceptible, is limited by the extent of motion of which the ribs and sternum are capable. The abdomen, on the contrary, enlarges in a sort of indefinite manner, by the yielding of its soft and extensible parietes. * It is requisite, in physiology as well as in from their situation under the cartilages of the medical practice, to have an artificial division false ribs. The middle region occupies about of the abdominal cavity, in order to point out four inches above and below the umbilicus. Its the exact and relative situations of the viscera middle portion is called the umbilical, and its which it contains. With this view it has been lateral parts the loins or lumbar regions. The usually divided into three regions, called the under division of the abdominal cavity corn- upper, middle, and under region : each of these mences where the former one terminates, or at is subdivided into three others. The upper re- a line drawn between the superior and anterior gion begins at the ensiform cartilage, and ex- spinous processes of the ossa ilii, and forms, in tends downwards to about four inches from the the middle, the hypogastrium, or bottom of the umbilicus ; the middle of it is termed the epigas- belly ; and at the sides, the iliac regions.—/. C. trium, and the two lateral portions hypochondria, THE FUNCTIONS OF THE STOMACH. 71 In some cases of ascites, the abdomen has been known to contain as much as eighty pints of liquid, and yet death has not followed as a consequence of so enormous an accumulation ; while by reason of the delicate texture of the brain, of the exact fulness of the skull, and especially of the inflexibility of its parietes, the slightest effusions within that cavity are attended with so much danger ; while the collection of a few pints of fluid within the chest occasions suffocation. This vast capacity of the abdomen, capable of being" easily increased, was required in a cavity whose viscera, for the most part hollow, and admitting of dilatation, contain substances varying in quantity, and from which are disengaged gases occupying a considerable space. What a difference is there not in the capacity of the abdomen of animals, according to the quality of the food on which they feed ! Compare the slender body of the tiger, of the leopard, and of all carnivorous animals, with the heavy mass of the elephant, of the ox, and of all animals that wholly or principally live on vegetable food. In the child, who digests a considerable quantity of food for the purposes of growth and development, the abdomen is much more capacious than in the adult or the old man. In the child, the ensiform carti- lage is situated opposite to the body of the eighth or ninth dorsal vertebra. In old men, it descends to the tenth or even the eleventh ; so that the capacity of the abdomen decreases with the want of food and with the activity of digestion. The internal organs of the body are incessantly called into action by dif- ferent causes and excited to different motions. The action of the arterial system tends to raise the cerebral mass, and to impart to it motions of eleva- tion and depression. The motion of the ribs brings about the expansion and the compression of the pulmonary tissue.; the heart, which adheres to the diaphragm, drawn down by that muscle when it descends, strikes against the parietes of the chest every time its ventricles contract. The abdominal viscera are not less agitated by the motions of respiration ; they experience from the diaphragm and from the abdominal muscles a perpetual action and re-action, by means of which the circulation of the fluids in their vessels is pro- moted, the course of the food in the alimentary canal is accelerated, the ac- tivity of digestion increased, and several excretions, as of the urine and fae- ces performed. XIV. Of Digestion in the Stomach*—The food which is taken into the stomach accumulates gradually within its cavity, and separates its parietes, which are always in contact with each other when it is empty. The sto- mach, in that mechanical distension by the food, yields without re-acting. It is not, however, absolutely passive ; its parietes apply themselves by a gene- ral contraction, by a kind of tonic motion, to the food which lies within it; and to this action of the whole stomach, the ancients gave the name of peris- tole.^ As the stomach dilates, its great curvature is thrust forward, the two folds of the omentum recede from each other, receive it between them, and embrace its outer and dilated part. In man, the principal use of this fold of the peritoneum appears to be to facilitate the dilatation of the stomachr which expands chiefly at its forepart, as may be observed by inflating it in a dead body. As this viscus becomes distended with air, the two folds of the omen- * See Appendix, Note K. stomach, and is continued to the duodenum; t In order to explain correctly the functions the second, or middle stratum, which is the thick- of the stomach, either in their healthy or disor- est, is composed of fibres that have an oblique dered state, the conformation of the muscular direction, and which, surrounding the stomach, coat requires to be pointed out. This tunic is decussate one another ; the third, or interior composed of three strata : the first, or the ex- stratum, consists entirely of circular fibres, terior, consists of longitudinal fibres, proceed- which extend from one curvature of this viscus ing from the oesophagus along the axis of the to the other,—/. C. 72 OF CHYMIFACTlONi turn apply themselves to its surface, and if this membrane is pierced with a pin, at the distance of an inch from its great curvature, the pin is observed to get nearer to this curvature ; but the upper portion of the omentum can alone be employed in this use, and the whole of this membranous fold is ne- ver entirely occupied by the stomach. Shall we say with Galen, that the omentum guards the intestines against cold, and preserves in them a gentle warmth necessary to digestion ; or, shall we admit the opinion of those who maintain that it answers the purpose of a fluid, filling up spaces, and lessen- ing the effect of friction and pressure from the anterior parietes of the abdo- men ; or, shall we assert with others, that the use of the omentum is to allow the blood to flow into it, when the stomach, in a state of contraction, is in- capable of receiving it % May not the blood which flows so slowly in its long and slender vessels, acquire some oleaginous quality which renders it fitter to supply the materials of bile ?* The stomach likewise stretches, though in a less distinct manner, towards its lesser curvature ; and the laminae of the gastro-hepatic omentum are se- parated from each other, as those of the omentum majus. Such is the uti- lity of the gastro-hepatic omentum, which may be considered as a necessary result of the manner in which the peritoneum is disposed in relation to the viscera of the abdomen. This membrane, extending from the stomach to the liver, so as to cover it, could not fill the space which separates those or- gans, were it not for a kind of membraneous communication that connects them, and in which are contained the vessels and nerves, that, from the lesser curvature, or the posterior edge of the stomach, course towards the concave surface of the liver. The gastro-hepatic epiploon may, besides, by the sepa- ration of the two laminae of which it is formed, favour the dilatation of the he- patic vein, which is situated, as well as the vessels, the nerves, and the excre- tory ducts of the liver, in the thickness of its right border. The stomach has ever been considered as the principal organ of digestion, yet its function in that process is but secondary and preparatory : it is not in the stomach that the principal and most essential phenomenon of digestion takes place,—I mean the separation of the nutritive from the excremen- titious part of the food. The food when received into the stomach, is prepar- ed for this separation which is soon to be performed, it becomes fluid, and un- dergoes a material alteration ; it is converted into a soft and homogeneous paste, known under the name of chyme. What is the agent that brings about this change ? or, in other words, in what does digestion in the stomach consist ? As it is frequently necessary to clear a spot on which one means to build, we will bring forward and refute the hypotheses that have been successively broached to explain the mechanism of digestion. They may be enumerated as follows : concoction, fermentation, putrefaction, trituration, and maceration, of the food taken into the cavity of the stomach. XV.—The first of these opinions was that of the ancients and of the father of physic; but, by the term concoction, Hippocrates did not mean a phenomenon similar to that which takes place when food is put into a vessel and exposed to the influence of heat. The temperature of the stomach, which does not exceed that of the rest of the body (32 degrees of Reaumur's * The omentum seems to lubricate the in- and increased action of the latter, during respi- testines by means of its adipose halitus, and to ration and muscular exertion, from impeding or aid in facilitating the continual movements of injuring the functions of the former. It hke- the intestines. It also appears to assist in the wise obviates, during disease, the adhesion of reciprocal motion which takes place between the intestines to the peritoneum covering the the digestive tube and the anterior abdominal abdominal parietes, and the consequent impedi- parietes, especially in preventing the natural ment to the operations of the prima? viae.—J. C OF GHYMIFACTIOtf* 73 scale), would be insufficient. Cold-blooded animal chge* £^ ^» warm-blooded; and, as Van Helmont observes, febrile heat impairs instead Of increasing the powers of digestion. In the language of the ^cients con coction means the alteration, the maturation, the animalisation of ahmenta y substances, assimilated to our nature by the changes which they undergo m the cavity of the stomach. It is, however, a verified fact, hattknatur heat of the stomach promotes and facilitates those changes ^ fxP«" ments of Spallanzani on artificial digestion shew that the gutnc ju ce is no of more efficacy than plain water in softening and dissolving ^mentaiy sub stances when the heat is below seven degrees (of Reaumur s scale , that its activity, on the contrary, is greatly increased when the heat is ten, twenty, thirty, or forty degrees above the freezing point. The digestion in the cold- blooded animals is, besides, slower than in the hot-blooded XVI—The abettors of the theory of fermentation admit, that the food taken into the stomach undergoes an inward and spontaneous motion,^in virtue of which it forms new combinations, and, as the process of fermentation^pro- moted by adding to the substance that is undergoing the change a certain quantity of the same which has already undergone the process, some ha ^e supposed that there continually exists in the stomach a leavef'f™P'a^f cording to Van Helmont, by a subtile acid * and consisting, in the opmion 0f othersfof a small quantity of the food that remains from the forme digestion. But, independently of the circumstance that the stomach empties itself com- pletely, and presents no appearance of leaven when examined a few Ws after digestion, substances undergoing fermentation require to be kept perfect- ly at relt, whereas the food is exposed to the oscillatory circulations and to the peristaltic contractions of the stomach and this viscus is shaken by the pulsaPtfonl of the neighbouring arteries ; it is besides ^5^^^™^ by the act of respiration. In fermentation gases are "th" J^^™."£ cated, neither of which circumstances takes place when the stomach is not °1tri^however, be stated, in support of the opinion that accounts for digestion oA the principle of fermentation, that we can der ye ?™nshment only from substances capable of undergoing fermentation, and tha the sub- stances which have undergone the panaiy and saccharine feimentation aie more easily digested and in less time. This imperceptible fermentation, if it Sy take pface, must bear a greater analogy to these two lajtP^c^ to those which are called vinous and acetous fermentation, butctiefl yto the acid fermentation: indeed, matters received into the stomach;J«m^ome somewhat acid, and milk is frequently curdled ■ ^^^^m^^ markable in the stomach of herbivorous animals. The internal memtuane 7tSi stomach of a calf preserves for several months "s property of curdling- milk, and is thus used in the making of cheese. According to Reaumi, he internal membrane of the stomach of the domestic fowlpos- sesses similar virtues. Food insufficiently digested ? ^^ £sutaLJ. cannot therefore be doubted that acid properties are develoPed/nnStuhbpS^?enS subjected to the action of the stomach ; a circumstance opposed to the notion that digestion is connected with the putrid fermentation. XVII.-There have been physiologists, however from the time of Phs- tonicus the disciple of Praxagoras, who maintain that digestion is, in fact [he consequence P0f putrefaction. But not only is ammonia not disengaged . See a™»«. Note K "S^^^^S^^^ lis^r tt ^S^f^^^A t^AheUic See on this sublet the Ar- 1824, and of Tiedemann and Gmelin in their pendix, Notes K.-/. C. 74 OT CHVMIFACTTOIT during that process, but our digestive organs have the power, as will be seen presently, of.retarding, or of suspending, the putrefaction of the substances which are submitted to their action. In serpents, which, in consequence of the great power of dilatation of the oesophagus, and from the power of holding asunder their jaws, both of which are movable nearly in an equal degree, frequently swallow larger animals than themselves, and take several days to digest them,—that part of the animal which is exposed to the action of the stomach is observed to be perfectly fresh, and dissolved to a certain extent, while the part which remains out, exhibits signs of incipient putrefaction. In fine, notwithstanding the heat and moisture of the stomach, the food does not remain in it long enough to allow putrefaction to come on, even though every thing else should favour that process. Animals which have by chance swallowed putrescent animal substances, either reject them by vomiting, or, as Spallanzani has observed in some birds, deprive them of their putridity. XVIII.—The system of fermentation was invented by the chemists ; theot of trituration by the mechanical philosophers, who compare the* changes which substances undergo in a mortar from the action of the pestle, to the changes which the food undergoes in the stomach. But how different is the triturating action of a pestle, which crushes a substance softer than itself against a resisting surface, to the gentle and peristaltic action of the fibres of the stomach, on the substances which it contains ! Trituration, which is a mechanical effect, does not alter the nature of the substanee exposed to its action ; but the food is decomposed, and no longer the same substance after it has remained some time in the stomach. As this evidently absurd hypo- thesis has long been held in high estimation, it will not be improper to spend a little time in the refutation of the proofs which are adduced in its support. The manner in which digestion is brought about in birds whose stomach is muscular, and especially in the gallinaceous fowls, is the most specious argument adduced by the abettors of mechanical digestion. Those granivo- rous birds all have a double stomach ; the first is called the crop, its sides are thin, and almost entirely membranous ; a fluid is abundantly effused on its inner surface, the seeds on which they feed get softened, and undergo a kind of preliminary maceration in the crop, after which they are more easily ground by the gizzard, which is a truly muscular stomach, that fulfils the office of organs of mastication, almost entirely deficient in that class of animals. The gizzard acts so powerfully that it crushes the solid substances exposed to its action, reduces into dust balls of glass and crystal, flattens tubes of fin, breaks pieces of metal, and, what is much more extraordinary, breaks, with impunity, the points of the sharpest needles and lancets. Its internal part is lined with a thick semicartilaginous membrane, incrusted with a number of small stones and gravel, taken in with the food of those birds. The turkey cock is, of all other fowls, that in which this structure is most apparent; besides the small pebbles which line its inner membrane, its cavity contains, almost in all cases, a number of them. The rubbing together of these hard substances, exposed along with the seeds among which they are mixed, to the action of the stomach, may assist in breaking them down. The pieces of iron and the pebbles which the ostrich swallows, some of which Valisnieri met with in the stomach of that bird, are destined to the same use. But this mechanical division which the gizzard performs in the absence of organs of mastication, does not constitute digestion ; the food, softened and divided by the action of the crop and of the gizzard, passes inio the duodenum, and, exposed in that intestine to the action of the biliary juices, undergoes within it the changes most essential to the act of digestion. The singular structure of the lobster's stomach is not more favourable to OF CHYIvlIFACTIOtf. 75 the hypothesis of trituration. In that crustaceous animal the stomach ig furnished with a real mandibular apparatus, destined to break down the food. There are found in it, besides, at certain times of the year, two roundish concretions on each side, under its internal membrane. These concretions, improperly termed crabs' eyes, consist of carbonate of lime joined to a small quantity of gelatinous animal matter; they disappear when, after the annual shedding of the shell, the external covering, at first membranous, becomes solid from the deposition of the calcareous matter of which they are formed. The very great difference between the stomach of these animals and that ■of man, ^ought to have precluded every idea of comparing them together. Spailanzani has justly observed, that in regard to the muscular power of the parietes of the stomach, animals might be divided into three classes, the most numerous of which consists of those creatures whose stomach is almost entirely membranous, and furnished with a muscular coat of very little thickness. In this class are contained man, quadrupeds, birds of prey, rep- tiles, and fishes. Notwithstanding the weakness of that muscular coat, Pitcairn, by a misapplied calculation, has estimated its power at 12,951 pounds ] he reckons at 248,335 pounds that of the diaphragm and of the ab- dominal muscles which act on the stomach and compress it in the alternate motions of respiration. What does so exaggerated a calculation prove, ex- cept, as Garat observes, that this vain shew of axioms, definitions, scholia, and corollaries, with which works not belonging to mathematics have been disfigured, have served only to protect vague, confused, and false notions, under the cover of imposing and respected forms f One need only introduce one's hand into the abdomen of a living animal, or a finger into a wound of the stomach, to ascertain that the force of that viscus on its contents does not exceed a few ounces. XIX.—The learned and indefatigable Haller thought that the food was merely softened and diluted by the gastric juice. This maceration was, in his opinion, promoted and accelerated by the warmth of the part, by the in- cipient putrefaction, by the gentle but continual motions which the alimentary substance undergoes. Maceration, in time, overcomes the force of cohesion of the most solid substances ; but by dilution it never changes their nature, Haller rested on the experiments of Albums on the conversion of membra- nous tissues into mucilage by protracted maceration. In ruminating animals the cavity of the stomach is divided into four parts, which open into one another, and of which the three first communicate with the oesophagus. When the grass, after imperfect trituration by the organs of mastication, whose power is inconsiderable, has reached the paunch, which is the first and largest of the four stomachs, it undergoes a real mace- ration, together with an incipient acid fermentation. The contractions of the stomach propel, the food, in small quantities at a time, into the bonnet, which is smaller and more muscular than the paunch; it coils on itself, covers with. mucus the already softened food, then forms it into a ball, which rises into the mouth by a truly antiperistaltic motion of the cesophagus. The alimentary bolus, after having been chewed over again by the animal, which seems to enjoy that process, descends along the cesophagus into the third stomach, called the manyplus, on account of the large and numerous folds of its inner membrane. From this cavity the food enters into the abomasum, in which the stomachic digestion is completed. Such is the mechanism ©f ru mination, a function peculiar to animals that have four stomachs; they do not, how- ever, ruminate at all periods of their life. The sucking lamb does not rumi- nate ; the half-digested milk does not pass along the paunch or the bonnet, which are useless, but at once descends into the third stomach. Some men 76 OF THE GASTRIC JUICES. have been capable of a kind of rumination; the alimentary ball, after de- scending into the stomach, shortly after rose into the mouth, to be there chewed a second time, and to be anew imbued with saliva. Conrad Peyer has made this morbid phenomenon the subject of a dissertation, entitled Me- ricologia, sive de Ritminantibus.* This fourfold division of the stomach, so favourable to Haller's theory, is observed only in ruminating animals. But though animals are in general monogastric, as man, that is, provided with only one stomach, this viscus of- fers a number of varieties, the most remarkable of which refer to the relative facility which the food meets in remaining within its cavity. The insertion of the cesophagus is nearer to its left extremity, and the great fundus of that viscus is smaller, as animals feed more exclusively on flesh, which is a sub- stance of remarkably easy decomposition, and not requiring for its digestion a long stay in the stomach. In herbivorous quadrupeds, which do not rumi- nate, this great fundus forms nearly one half, sometimes even the greater part, of the stomach, as the oesophagus enters into it very near the pylorus. In some, as in the hog, the stomach is divided into two parts by a circular contraction. The food which is received into the great fundus of the stomach may remain longer in that viscus, as this part of its cavity lies out of the course of the aliment. XX. Of the gastric juices.—Of all the organs, the stomach probably re- ceives, in proportion to its bulk, the greatest number of blood-vessels; in its membrano-muscular parietes, which are little more than the twelfth part of an inch in thickness, there is distributed the coronary artery of the stomach, entirely destined to that organ, the pyloric and the right gastro-epiploic, given off by the hepatic artery, the arteries, breves, and the left gastro-epiploic, branches of the splenic artery. The greater part of the blood, therefore, which passes from the aorta to the cceliac artery goes to the stomach; for though of the arteries into which that trunk is divided, the coronary of the stomach is the least, the arteries of the liver and spleen send to the stomach several pretty considerable branches before entering the viscera to which they are more particularly allotted. One need only observe the great dis- proportion between the stomach and the quantity of blood which it receives, to conclude that this fluid is not merely subservient to its nutrition, but is des- tined to furnish the materials of some secretion. The secretion in question is that of the gastric juice, which is most abun- dantly supplied by arterial exhalation from the internal surface of the sto- mach ; it is most active at the instant when the food received within its cavi- ty excites irritation, transforms it into a centre of fluxion, towards which the fluids flow from all directions. The state of fulness of the stomach favours the afflux of the fluids into the vessels, as, in consequence of the extension of its parietes, previously collapsed, the vessels are no longer bent and creas- ed. The arteries of the stomach, of the spleen and liver, arising from a common trunk, it may be easily understood how, when the stomach is emp- ty, little blood enters into it in that state of contraction; how, at the same time, the spleen, which is less compressed, and the liver, must receive a larger supply of blood, and again a smaller quantity when the stomach is full. The gastric juice, the result of arterial exhalation, mixes with the mucus poured out by the mucous follicles of the internal membrane of the stomach. This mixture renders it viscous and ropy, like the saliva, to which, in man, the gastric juice bears a great analogy. It is very difficult to obtain it pure, bo as to analyse it j and even if, by long fasting, the stomach should be de- * See Appendix, Notes K. OF THE GASTRIC JUICES. 77 prived of the alimentary residue which might affect its purity, one could not prevent it being mixed with a certain quantity of liquid bile, which always flows back through the pyloric orifice, turns yellow the inner surface of the stomach in the neighbourhood of that orifice, and even imparts a certain de- gree of bitterness to the gastric juice. The passage of the bile from the duo- denum into the stomach cannot be looked upon as morbid ; it occurs in the most perfect health,—which has led to a well-founded opinion, that a small quantity of the biliary fluid is a useful stimulus to the stomach. This opi- nion is confirmed by an observation of Vesalius, who relates, that he found the ductus communis choledochus opening into the stomach in the body of a convict noted for his voracious appetite. It is further confirmed by what is observed in birds of prey, in the pike, &c, which digest easily and with great rapidity, because the termination into the duodenum of the ductus communis choledochus being very near to the pylorus, the bile easily ascends into the stomach, and is always found there in considerable quantity. To obtain some of this gastric juice, it is necessary either to open a living animal under the influence of hunger, or to oblige a night bird of prey, as an owl, to swallow small sponges fastened to a long thread. When the sponge has remained for a short time in the stomach, it is withdrawn soaked with gastric juice, of which the secretion has been promoted by its presence in the stomach. The gastric juice, in its natural state, is neither acid nor alkaline; it does not turn red or green vegetable blue colours. Its most remarkable quality is, its singularly powerful solvent faculty ; the hardest bones cannot withstand its action ; it acts on those on which the dog feeds ; it combines with all their organised and gelatinous parts, reduces them to a calcareous residue, form- ing those excrementitious substances so absurdly called album Grtecum by the older chemists. The solvent energy of the gastric juice is in inverse ratio of the muscular strength of the parietes of the stomach; and in those animals in which the parietes of that viscus are very thin and almost entire- ly membranous, it has most power and activity. In the numerous class of zoophytes it alone suffices to effect decomposition of the food, always more prompt when accompanied by warmth of the atmosphere, as was observed by Du Trembley in the polypi, which in summer dissolve in twelve hours what in colder weather it would take three days to digest. In the actinia, and in the holothuria, the gastric juice destroys even the shells of the mus- cles which they swallow. Are we not all acquainted with the peculiar fla- vour of oysters, how much they tend to whet the appetite ? This sensation depends less on the salt water contained in the shell than on the gastric juice which acts on the tongue, which softens its tissue, and quickens its sensibili- ty. This mucous substance, when received into the stomach, promotes the digestion of the food which is afterwards taken into it, for the oyster itself is very little nutritious, and is used rather as a condiment than as affording nourishment. The gastric juice not only pervades and dissolves the food received into the stomach, but it unites and intimately combines with it, completely alters its nature, and changes its composition. The gastric juice acts in a manner peculiar to itself on the food exposed to its action, and, far from inducing a beginning of putrefaction, suspends, on the contrary, and corrects putrescen- cy. This antiseptic quality of the gastric juice suggested the practice of moistening ulcers with it to accelerate their cure; and the experiments made at Geneva and in Italy have, it is said, been fully successful. I have made similar experiments with saliva, which, there is every reason to consider, is very similar to the gastric juice ; and I have seen old and foul ulcers assume 78 OF THE GASTRIC JUICE3. a better appearance, the granulations become healthy, and the affection ra- pidly advance towards a cure, from the use of that irritating fluid. I had under my care an obstinate sore on the inner ankle of the left leg of an adult: notwitstanding the external application of powdered bark, and of compresses soaked in the most detergent fluids, this sore was improving very slowly, when I bethought myself of moistening it every morning with my saliva, the secretion of which was increased by the hideous aspect of the sore. From that time the patient evidently mended, and his wound contracting daily, at last became completely cicatrised, However powerful the efficacy of the gastric juice to dissolve the alimen- tary substances, it does not direct against the coats of the stomach its active solvent faculty. These parietes, endowed with life, powerfully resist solu- tion. The lumbrici, so tender and delicate, for the same reason, can exist within it, without being in the least affected by it; and such is this power of vital resistance, that the polypus rejects unhurt its arms, when it happens to swallow them among its food* But when the stomach and the other organs have lost their vitality, its parietes yield to the solvent power of the juices which it may contain, they become softened, and even in part destroy- ed, if we may believe Hunter, who found its inner membrane digested in several points in the body of a criminal, who, for some time before his execu- tion, had been prevailed upon, in consideration of a sum of money, to abstain from food.| * It had been thought that no animal could live on the flesh of its own kind, and this cir- cumstance was explained on the same principle ; but to refute it, we need only quote the instance of cannibals and of several tribes of carnivorous animals, who, in the absence of other prey, de- vour one another. t The following case of solution of the sto- mach after death came under the observation of Professor Haviland. The subject was a young man, whose body was opened twelve hours after death; and the stomach, on being examined af- ter its removal from the body, presented the fol- lowing appearances :—The mucous membrane seemed more red and vascular than usual throughout its whole extent, and here and there were small spots of what seemed to be exlrava- sated blood, lying beneath the mucous coat, as they could not be washed off, nor removed by the edge of the scalpel. There were two holes in the stomach; the larger very near to the car- diac end of the small curvature, and on the pos- terior surface ; this was more than an inch in length, and about half an inch in breadth. The other, not far from the former, and likewise upon the posterior surface, was about the size of a sixpence. The edges of these holes were smooth, well defined, and slightly elevated. The coats of the stomach were thin in many other spots, and in one part nothing was left but the peritoneum, the mucous and muscular coats being entirely destroyed. There was a hole in the diaphragm through the muscular por- tion, where it is of considerable thickness, large enough to admit the end of the finger. There was no appearance of ulceration or of pus ad- hering to the edges of this perforation of the diaphragm. Dr. Haviland concludes, that, ow- ing to the activity of the solvent power of the gastric juice, it sometimes not only corrodes the parietes of the stomach, but even the thick muscle of the diaghragm, and that within the space of twelve hours after death, as was exem- plified in this case.—Transactions of the Cam- bridge Philosophical Society, vol. i. pait ii. 1822. Hunter's view of this subject has been dis- puted, to the present day, by several eminent pathologists, and by the author, in a sentence added to the above paragraph in the last edition, from which this edition of the translation is re- vised ; but Dr. Philip's observations are quali- fied to prove it in a very satisfactory manner to those who yet require convincing arguments. On opening the abdomen of rabbits which had been killed immediately after having eaten, and which were allowed to lie undisturbed for some time before the examination, he has found " the great end of the stomach soft, eaten through, sometimes altogether consumed, the food being only covered by the peritoneum, or lying quite bare for the space of an inch and a half in diame- ter ; and part of the contiguous intestines in the last case also consumed, while the cabbage, which the animal had just taken, lay in the cen- tre of the stomach unchanged, if we except the alteration which had taken place in the external parts of the mass it had formed, in consequence of imbibing gastric fluid-from the half-digested food in contact with it." The following are Dr. Philip's observations : —" We sometimes found the great end of the stomach dissolved within an hour and a half af- ter death. It was more frequently found so when the animal had lain dead for many hours. This effect does not always ensue, however long it has lain dead. It seems only to take place when there happens to be a greater than usual supply of gastric fluid: for we always ob- served it most apt to happen when the animal had eaten voraciously. " Why it should take place without the food being digested, is evident from what has been said. Soon after death, the motions of the sto- mach, which are constantly carrying on towards the pylorus the most digested food, cease. Thus, the food which lies next to the surface of the OF THE GASTRIC JUICES. 79 The gastric juice is capable, even after death, of dissolving food introduced into the stomach by a wound made into it, provided the animal still preserves some degree of animal heat. It acts on vegetable and animal substances tri- turated and put into a small vessel, such as those under which Spallanzani, in his experiments on artificial digestion, kept up a moderate heat. Let us not, however, consider as the same this solution of the food in the gastric juice out of the stomach, and that which occurs in digestion within the organ. Every thing tends to shew that the stomach ought not to be considered as a chemical vessel, in which there takes place a mixture giving rise to new com- binations. The tying, dividing, or rather removing, a portion of the nerves of the eighth pair,* the use of narcotics and of opium, intense thought, every powerful affection of the mind, trouble, or even gaiety, entirely suspend diges- tion in the stomach, which cannot take place independently of nervous influ- ence. Yet this nervous influence may possibly not concur directlyand of itself to stomachic digestion ; it is, perhaps, merely relative to the secretion of the gastric juice, which the ligature or division of the nerves, the action of nar- cotics, or of other substances, may impede, alter, or even completely sus- pend. It is now pretty generally admitted, that digestion in the stomach consists in the solution of the food in the gastric juice.f This powerful solvent pene- trates, in every direction, the alimentary mass, removes from one another, or divides its molecules, combines with it, alters its inward composition, and im- stomach becoming fully saturated with gastric stomach, with headach. fluid, neutralises no more, and no new food be- Seven days afterwards, the bulb of a fhermo- ing presented to it, it necessarily acts on the meter was carefully introduced through the fis- stomach itself, now deprived of life, and, on this tulous opening into the stomach, after fasting account, as Mr. Hunter justly observes, equally for a considerable time, and in a few minutes subject to its action with other dead animal the mercury rose to 100° of F. An ounce of matter. It is remarkable that the gastric fluid pure gastric juice was withdrawn, by means of of the rabbit, which in its natural state refuses a gum elastic tube, and poured into a glass ves- animal food, should so completely digest its sel capable of holding three ounces, in which a own stomach as not to leave a trace of the parts small piece of salted beef was placed. The ves- acted on. I never saw the stomach eaten sel was surrounded by water, at the tempera- through, except in the large end; in other parts, ture of 100° F., and preserved at that height by its internal membrane is sometimes injured."— means of a sand-bath. At the end of forty mi- /. C. nutes the surface of the beef was evidently act- * See the Appendix, Note K, for the results ed upon. After fifty minutes, solution was be- of the most recent researches into this subject, coming very apparent, and after two hours the —J. C. cellular texture of the beef was completely dis- t Dr. Beaumont published, in the American solved, and the muscular fibres separated and! Medical Recorder for January 1828, some in- floating in the turbid fluid in the form of ex- teresting experiments made by him upon a young tremely fine short and white filaments. After man with a fistulous opening into the stomach, five hours, the solution was nearly complete ; He first introduced into this viscus, through the and at the termination of the ninth hour, the opening, and attached by means of a silk thread, whole was dissolved. The gastric fluid which, small pieces of the following substances, the when removed from the stomach, was clear and quantity of each being about forty grains : a limpid, was now slightly frothy, thickened, and piece of highly seasoned beef a la mode, lean of more opaque ; and when allowed to stand for a salted beefraw, lean fresh beef also raw, salted few minutes, deposited a sediment of a flesh bacon raw, boiled beef, bread, and cauliflower, colour. At the end of two hours the bread, cauliflower, At the same time that the above experiment boiled beef, and the bacon, were completely di- was being performed with the gastric fluid out gested, and had separated from the thread : the of the stomach, a piece of salted beef, of the other substances were scarcely altered ; these same weight and form, was introduced through were returned into the stomach ; and, after two the fistulous opening into the stomach, and, at hours, the patient complained of pain in the epi- the end of two hours, it had undergone piecise- gastrium, with nausea. They were withdrawn ly the same change as that which was placed at the end of five hours from the time of their in the glass vessel, and was completely detach- first introduction, scarcely more altered than cd from the thread by which it was held; so when removed previously. The liquids of the that there was an end to further observation re- stomach had an acrid and rancid flavour, and the specting it. subject of the experiment complained previous The above experiments fully illustrate the to the removal of the above substances of gene- accuracy of the opinion stated above.—J. C. ral debility, nausea, oppression and pain at the 80 OF DIGESTION. parts to it qualities very different from those which it possessed before the mix' ture. If, in fact, a mouthful of wine or of food is rejected a few minutes after being swallowed, the smell, the flavour, all the sensible and chemical quali- ties of such substances are so completely altered that they can scarcely be re- cognised ; the vinous substances turned, to a certain degree, sour, are no long- er capable of the acetous fermentation. The energy of the solvent power of the gastric juice, perhaps over-rated by some physiologists, is sufficient to dis- solve and reduce into a pulp the hardest bones on which some animals feed. It is highly probable that its chemical composition varies at different times ; that it is acid, alkaline, or saponaceous, according to the nature of the food. Although the gastric juice be the most powerful agent of digestion, its solvent power requires to be aided by several secondary causes, as warmth, which seems to increase, and, in a manner, to concentrate itself in the epigastric region, as long as the stomach is engaged in digestion ; a sort of inward fer- mentation which cannot be, strictly speaking, compared to the decomposition which substances subject to putrefaction and acescency undergo. The gen- tle and peristalic action of the muscular fibres of the stomach, which press, in every direction, on the alimentary substance, performs on it a slight tritura- tion, while the moisture of the stomach softens and macerates the food before it is dissolved; one might therefore say, that the process of digestion is at once chemical, mechanical, and vital ; in that case, the authors of the theo- ries that have been broached have been wrong, in ascribing to only one cause, such as heat, fermentation, putrefaction, trituration, maceration, and the ac- tion of the gastric juice, a process which is the result of a concurrence of these causes united. The food remains in the stomach during a longer or shorter space of lime, according as, by its nature, it yields more or less readily to the changes which it has to undergo. Gosse, of Geneva, ascertained, by experiments performed on himself, that the animal and vegetable fibre, concrete albumen, white and tendinous parts, paste containing fat or butter, substances which have either not undergone fermentation, or which do not readily undergo that process, remain longer in the stomach, offer more resistance to the gastric juice, than the gelatinous parts of animals or vegetables, fermented bread, &c.; that the latter required but an hour for their complete solution, while the former were scarcely dissolved at the end of several hours. XXI.—The following case throws some light on the mechanism and im- portance of the action of the stomach in digestion. The patient was a wo- man, whom I had frequent opportunities of examining at the Hopital de la Charite, at Paris, in the clinical wards of professor Corvisart, in which she died on the 8th Nivfise, of the year 10, after six months stay in the hospital. A fistulous opening, of an oval form, an inch and a half in length, and up- wards of an inch in breadth, situated at the lower part of the chest, at the upper and left side of the epigastric region, afforded an opportunity of view- ing the inner part of the stomach, which, when empty of food, appeared of a vermilion colour, was covered with mucus, its surface wrinkled over with folds, about half an inch deep, and enabled one to distingush the vermicular undulations of these folds, and of all the parts which were in sight. The patient, who was then forty-seven years of age, had this fistula since she was in her thirty-eighth year. Eighteen years before, she had fallen on the threshold of a door, the blow had struck against her epigastric region. The place remained affected with pain, and she became incapable of walking or of sitting otherwise than bent forward, and to the left side. At the end of this long interval, a phlegmonous and oblong tumour appeared on the injured spot: during the nausea and vomiting which supervened, the tumour broke, OF DIGESTION. 31 and there escaped at the wound left by this rupture, two pints of a fluid which the patient had just swallowed. From that time, the fistula, which at first would scarcely have admitted the tip of the little finger, increased daily ; at first it allowed only the fluids to pass, but on the eighth day, the solid food came away freely, and continued to do so till she died. When admitted into the hospital she ate as much as three women of her age, she voided about a pint of urine, and went to stool only once in three days. Her faeces were yel- lowish, dry, rounded, and weighed more than a pound. Her pulse was very feeble and extremely slow, its pulsation scarcely exceeding forty-five or forty- six beats in a minute. Three or four hours after a meal, an irresistible desire obliged her to take off the lint and compresses with which she covered the fis- tulous opening, and to give vent to the food which her stomach might happen to contain : it came out rapidly, and there escaped at the same time, and with a noise, a certain quantity of gases. The food thus evacuated exhaled an in- sipid smell, was neither acid nor alkaline ; for the chymous and grayish-co- loured pulp into which it was reduced, when suspended in a certain quantity of distilled water, did not affect vegetable blues. The digestion of the food was far from being always complete; sometimes, however, the smell of wine could not be recognised, and the bread formed a viscid, thick, and soft sub- stance, pretty similar to fibrine newly precipitated by the acetous acid, and it floated in a tenacious liquid of the colour of common broth* it follows, from the experiments performed at the Ecole de Medecine on these half-digested substances, and on the same before their admission in- the stomach, that the changes which they undergo consist in the increase of gelatine, in the formation of a substance which has the appearance of fibrine, without having all its qualities, and in a greater proportion of muriate and phosphate of soda, as well as of phosphate of lime. This patient was unable to sleep till she had emptied her stomach, which she cleared by swallowing a pint of infusion of chamomile. In the morning there was seen in the empty stomach a small quantity of a ropy frothy fluid, like saliva. It did not turn vegetable blues to a green or red colour, was not homogeneous, but exhibited particles of some degree of consistence, among the more fluid parts, and even albuminous flakes completely opaque. The * Dr. Prout has made several experiments in order to ascertain the chemical composition of the chyme, from which he obtained the follow- ing results:— No. 1. Chyme of a dog fed on vegetable food when assisted by a gentle heat. No. 2. Chyme of a dog fed on animal food.— This was more thick and viscid than No. 1, and its colour was more inclining to red. Spec. grav. 1*022. It shewed no traces of a free acid, —Composed of a semifluid, opaque, yellowish or alkali, nor did it coagulate milk, even when white part, containing another portion of similar assisted by the most favourable circumstances, colour, but of firmer consistence, mixed with it. On being subjected to analysis, these two Spec. grav. 1 056. It shewed no traces of a free specimens of chyme were found to consist of acid, or alkali, but coagulated milk completely A. Water.........••••.■ B. Gastric principle, or mucus united with ali-"| mentary matters, and apparently constitut-1 ing the chyme properly so called, mixed ( with excrementitious matter. . . . • ) C Albuminous matter, chiefly fibrin .... D. Biliary principle ........•• E. Vegetable gluten ......•■■• F. Saline matters........... G. Insoluble residuum......... F. The saline matters were obtained by incineration, and consisted chiefly of the muriates, sul- phates, and phosphates.—/. C. 1. Chyme from Vegetable Food. -. Chyme from Animal Food. 86-5 80' 6 158 1-6 5 ■7 •2 1-3 1-7 •7 ■5 100- 100- 62 Off THE PYLORUS. experiments performed on this fluid shewed that it bore a considerable ana* logy to saliva, which, however, is rather more liable to putrefaction. The vermicular motion by which the stomach cleared itself of its contents, took place in two different but not in opposite directions, the one pressing tho food towards the fistulous opening, the other towards the pylorus, through which the smaller quantity was allowed to pass. On opening the body, it was found that the fistula extended from the carti- lage of the seventh left rib, as high as the osseous termination of the sixth ; its edges were rounded, and from three to four Knes in thickness ; they were covered with a thin moist skin, of a red colour, and similar to that of the lips. The peritoneal coat of the stomach adhered so firmly to the peritoneum lining the fore part of the abdomen around the opening, that the line of adhesion could not be observed. The opening was in the anterior part of the sto- mach, at the union of the two-thirds on the left side, with the third on the right of that viscus ; that is, about eight fingers' breadth from its greater ex- tremity, and only four from the pylorus. It extended from the greater to the lesser curvature. In other respects it was the only organic affection of that viscus. It should be stated, that for several years the patient had been thin and emaciated, and had led a languid hfe, which was terminated by a colliqua- tive diarrhoea. She seemed to be supported only by the small quantity of food which passed through the pylorus into the duodenum, where it received the influence of the bile, whose action on the chyme is, as we shall presently state, absolutely essential to the separation of the nutritious parts. Not that there was any thing to prevent the absorbents of the stomach from taking up a certain quantity of nutritious particles, but that small quantity of food, in an imperfect condition, was of very little service in imparting nourishment; and in that respect she was in similar circumstances to patients who are affected with obstruction of the pylorus, and reject the greater part of their food, when, digestion being over, this contracted opening can no longer allow any food to pass. XXII.—While the alimentary solution is going on, the two openings of the stomach remain perfectly closed ; no gas disengaged from the food es- capes along the cesophagus, except when digestion is imperfect. A si ransparent laminae be laid on one another, the red colour becomes darker, in proportion a3 a greater number are brought together. * The arterial divisions which may be dis- still further, when they are become so minute cerned by the aid of anatomy do not exceed as not to be discernible without the help of ths .eighteen or twenty ; nevertheless, they divide most powerful microscope. OF THE CAPILLARY CIRCULATION 188 Let irritation, from whatever cause, determine the blood to flow into the serous capillary vessels in greater quantity, and with more force; these ves- sels will become apparent, the organs in whose structure they circulate will acquire a red colour, more or less deep; thus, the conjunctiva, the pleura, the peritonaeum, the cartilages, the ligaments, &c. which naturally are whit- ish or transparent, become red when affected with inflammation, either from the increased impetus of the circulation, which forces and accumulates into the capillary vessels a greater number of red globules, or that the sensibility of these small vessels is impaired by inflammation, so that they admit glo- bules which they formerly rejected. Some capillary vessels transmit blood at all times, and uniformly exhibit a red colour: this is the case with the capillary vessels of the spleen, of the corpora cavernosa of the penis, of the bulb and corpus spongiosum of the urethea ; the same applies to the capillaries of the muscles of the mucous membranes: there are, however, very few of those organs in which the whole portion of the capillary tube, between the termination of the artery and the origin of the vein, is filled with red blood. There is almost always a division in the tortuous line described by the capillary, and within this space the blood cannot be detected of its usual colour.* The number of the capillary vessels, as well as that of the arteries, to which the former are as auxiliaries, is much more considerable in the secre- tory organs than in those in which life carries on only the process of nutri- tion. It is on that account that the bones, the tendons, the ligaments, the cartilages, contain so much smaller a quantity of blood than the mucous and serous membranes and the skin. The capillary vessels are, however, very numerous in the muscles, which owe that colour to the great quantity of blood they contain ; but, as we shall point out when we come to speak of motion, this fluid appears to form an essential element in muscular con- traction ; it is, therefore, not to be wondered that these organs should have a greater number of capillary vessels sent to them, since these vessels do not supply them merely with molecules to carry on nutrition, and to repair the waste of the part, but impart to them the principle of their frequent contrac- tion : the quantity of them is so considerable in all these parts, employed in the twofold offices of nutrition and secretion, that Ruysch penetrated with his injections the whole thickness of their substance, to such a degree, that the organs which he had prepared were only a wonderful and inextricable net- work of capillary vessels, extremely minute. On these anatomical prepara- tions, made with an art hitherto unrivalled, Ruysch grounded his hypothesis relative to the intimate structure of the body, in which he imagined all was capillary tubes,—an hypothesis which has obtained the most favourable re- ception, and has reigned during more than a century in the schools. It is enough to reflect a moment on their uses, to conceive that the number of them must be really prodigious. As long as the blood is enclosed within the arteries, and flows under the control of the heart, it fulfils no purpose, either of nutrition or secretion. To make it subservient to these great func- tions, it must be diffused through the very tissue of the organs, by means of the capillary divisions ; these little vessels exist, then, in every part where any organised molecules are found united, since the particle formed by their assemblage must,-at least, find in the juices which they bring to it the mate- rials of its reparation. Entering, in greater or less proportion, into the or- * There is every reason for concluding that portion of the blood when performing their capillary vessels exist, which, running between healthy functions ; but which may, in a state of some of the terminations of the arteries and the inflammation, admit also the red particles of commencement of veins, admit only the serous this fluid to flow along them.—J. C. 134 THR ANASTOMOSES OF CAril.HRIF*. ganisation of all the tissues, the -capillaries receive certain modifications from the organs of which they are an integral part; modifications which enable them to deposit the serous part of the blood on the surface of the se- rous membranes, admit the transudation of the fat into the cells of the cellu- lar tissue, furnish the urine to the kidneys, and the liver with the materials of the bile : in a word, suffer to escape through the porosities with which their parietes are pierced, the principles which the blood has to furnish to every organ. It is by these lateral porosities, and not by extremities open on all the sur- faces, and in all the points of the organs, that the capillaries transpire, in some sort, the elements of nutrition and of the various secretions.* Mas- cagni was aware that Nature, skilful in deducing many effects from few causes, has not deviated, in the construction of the system of circulation, from the invariable laws of her ordinary simplicity ; but the lateral pores of the capillaries,—which are sufficient for the explanation of all the phenomena ascribed to the exhaling mouths of the arteries, and to the pretended con- tinuity of these vessels with the excretory ducts of the organs, &c.—are not openings like the pores common to all matter ; each of them may be con- sidered as an orifice, sensible, and especially contractile, of differing size, according to the state of the strength or of the vital powers. The size, then, of these capillary pores is subject to frequent variations ; and this is the ex- planation given of the formation of scorbutic ecchymoses, of petechiae, and of passive or relaxed haemorrhages. In all these affections, contractility being really diminished, the pores of the capillaries enlarge, and suffer the red bjood to transude through their relaxed mouths. This phenomenon takes place, not only under the skin, and on the various mucous surfaces ; it is ob- served also in the very tissue of the organs. It is thus that I have often seen, on opening the bodies of those that had died of scurvy in its last stage, the muscles of the leg filled with blood. This sort of interior haemorrhage con- verts the muscles into a kind of pulp, and the extravasated blood itself under- goes a beginning of decomposition. The bones themselves are liable to these scorbutic, bloody infiltrations. I had an opportunity of ascertaining this in the Hospital of St. Louis, at the same time that I learnt the difficulty of procuring a durable skeleton from such bodies. The greatest number die in a very advanced stage of the disease, and the bones dissolve in maceration, or rot in a very little time. The capillary vessels, whether the blood flow through them red or colour- less, are not a system of vessels distinct from that of the arteries and from that of the veins ; they belong essentially to these two orders of vessels. Those which, ramifying in the tissue of the skin or of the serous membranes, suffer the serum of the blood to transude, are not more entitled to the name of exhalant system, which some authors have given them. To consider as distinct and insulated systems, separate parts of a system of organs, is to encumber science with a crowd of divisions, as false as they are useless. LXI.—The sanguineous capillaries anastomose, and form, like the lym- phatic capillaries, a net-work that envelopes all the organs. Their frequent communications do not allow obstructions to take place, and to produce in- flammation, as Boerhaave thought, and as was long taught on the authority of that celebrated physician. Haller, Spallanzani, all the microscopic obser- vers, have perceived threads of blood flowing in the capillaries, offering them- selves at the various inosculations of these vessels, and have seen them flow back, when they were not admitted, to seek other easier entrances. * See Appendix, Note S, for observations on the Functions of the Capillary System, and ob Nutrition. OF THE VEINS. 135 I will not heap up in this place superfluous arguments against the theory of the Leyden professor, rejected at its birth by the physicians of Montpelier, absolutely refuted, and now universally given up. Irritation alone keeps the blood in the inflamed part; for when death, which puts an end to all irrita- tions, and relaxes all spasms, (mors spasmos solvit. Hipp.) when, I say, death comes on, all slight inflammations are dissipated; and whenever they have not been sufficiently intense to induce transudation of the blood through the pa- rietes of the capillaries into the areola of the organic tissues, the blood flows back into the large vessels, and there is no trace of it left. It is thus that erysipelas of the skin disappears, that the pleura preserves its transparency, in individuals affected before death with sharp pains in the side. If to this we add our ignorance of the real organisation of the nervous system, of the con- ditions absolutely required of the brain and nerves for the maintenance of hfe, we shall cease to be surprised that the opening of bodies has taught us no more on the real seat of disease; and we shall confess with Morgagni, who, however, employed with great success this means of improving the art of healing, that there are numberless diseases, of which, after death, no trace is left, and for the fatal termination of which we are unable to account. Contractility and sensibility exist in a much higher degree in the capillary and serous vessels than in the veins and arteries. Life must needs be more active in the former ; for, the motion given to the blood by the contractions of the heart being exhausted, this fluid, no longer in the sphere of action of that organ, can circulate but from the influence of the action of the vessels themselves. The termination of the arteries into veins is the only well-ascertained termi- nation of those vessels ; it may be seen, by the help of the microscope, in cold- blooded animals, in frogs and salamanders. In some fish we may, even with the naked eye, observe frequent and considerable inosculations between the arteries and veins. In man, however, and in other warm-blooded animals, these communications take place only at the extremities of the two systems of vessels. In this case the arteries terminate sometimes in capillary vessels, carrying serous fluid, such as the vessels of the sclerotic coat; these vessels, become small veins, whose calibre gradually increases, until they admit red globules in sufficient number to reflect that colour. At other times the artery and vein are continuous, without the intervention of that extremely minute subdivision : the red blood then passes readily and immediately from the ar- tery into the vein. It will be shewn, in speaking of secretion, that the continuation of the arte- ries into the excretory ducts of the conglomerate glands, and their termination in exhaling orifices, cannot be admitted ; and that the presence of small pores in the sides of the minute arteries and veins would afford an explanation of the phenomena on which the belief of this termination of the arteries rests. There exists no parenchyma,'no spongy tissue, between the extremities of the arteries and the origin of the veins, with, perhaps, the exception of the substance of the cavernous bodies of the penis and of the clitoris, of the bulb and spongy part of the urethra,* the retiform plexus which surrounds the ori- fice of the vagina, and perhaps also the tissue of the spleen ; though the ex- periments of anatomists (Mascagni and Lobstein) seem to prove that in these organs the arteries and veins are immediately continuous.| LXII. Of the distribution and action of the veins.%—These vessels, whose function it is to carry back to the heart the blood which the arteries have sent to all the organs, are much more numerous than the arteries themselves. It * See the chapter on the Organs of Genera- t See Appendix, Note T. tion. t See Appendix, Note N. 136 OF THE VEINS. is observed, in fact, that arteries of a middle size, aa those of the leg and fore arm, have each two corresponding veins, whose calibre at least equals theirs, and that there is, besides, a set of superficial veins, lying between the skin which covers the limbs, and the aponeuroses which envelop the muscles: these have.no corresponding arteries. The space which the venous blood occupies is, therefore, much greater than that taken up by the blood in the arteries. Hence, also, it is estimated, that of twenty-eight or thirty pounds of this fluid, making about a fifth part of the whole weight of the body in an adult man, nine parts are present in the veins, and only four in the arteries. In this calculation, one should consider as arterial the blood contained in the pulmonary veins and in the left cavities of the heart, while that which fills the cavities in the right side of the heart and the pulmonary artery, is truly venous, and has every character of such blood. Although the veins generally accompany the arteries, and are united to them by a common sheath of cellular membrane, this disposition of parts is not without exceptions. The veins which bring back the blood from the liver, do not, in any respect, follow the course of the branches of the hepatic artery; the sinuses of the brain are very different in their arrangement from the cerebral arteries ; the veins of the bones, which are particularly nume- rous, and of a much greater calibre than the arteries of the same parts, from the slow circulation of the blood along them, do not generally follow the direction of the arteries, and arise singly from the substance of the bone, with the exception of those in the middle canal, and which pass through the nutritious foramen of the bone. The veins are not only more numerous than the arteries, but they are likewise more capacious, and dilate more readily : this structure was necessary, on account of the slowness with which the blood circulates, and of the readiness with which it stagnates, when the slight- est obstacle impedes its circulation* The force which carries on the circu- lation of the blood along the arteries is so great, that Nature seems not to have availed herself of the mechanical advantages which might have fa- cilitated its flow. On the other hand, the power which determines the pro- gression of the venous blood is so feeble, that she has sedulously removed every obstacle which might have impeded its course. And as the relation of the minute to the larger branches, and of these to the trunk, is the same as in the arteries,—two branches uniting to form a vein of greater calibre than each separate vessel, but smaller than the two taken together,—the blood flows along a space which becomes narrower .the nearer it approach- es the heart ; the rapidity of its course must, therefore, be progressively in- creased. The veins are almost straight in their course ; at least, they are much less tortuous than the arteries. The force which makes the blood flow along them is consequently not taken up in straightening these curves ; the anas-' tomoses are likewise more frequent ; and, as the flow of the blood might have been intercepted in the deep-seated veins of the limbs, when the mus- cles, among which these vessels lie during contraction, compress them by their enlargement and induration, they communicate freely with the super- ficial veins, towards which the blood is carried, and flows the more readily, as they are not liable to be compressed. It is observed, and is to be ac- * The arteries contain, at all times, nearly nique, applied to it by Professor Pinel), only when the same quantity of blood. The veins are al- the venou3 congestion becoming excessive, the ways the seat of plethora, because the blood blood passes with difficulty from the arteries stagnates in them more readily; and this con- into the veins. The heart and the arteries then dition brings on inflammatory fever (consisting struggle, with considerable effort, to rid them- merely in an increased action of the vascular selves of the fluid which oppresses them, &c. svstem, as 1* expressed by the term angeiote- OF THE VENOUS CIRCULATION 137 counted for on the same principle, that the superficial veins are very large and distinct "among the lower orders, who are employed in laborious occu- pations, requiring an almost continual exertion of their limbs. Lastly, the internal part of the veins, like that of the lymphatics, is furnished with val- vular folds, formed by the duplicature of their epidermoid coat. These valves, which are seldom single, and almost always in pairs, are not found in the minute veins, nor in the great trunks, nor in the veins which bring back the blood from the viscera in the great cavities. These valves in falling close completely the canal of the vessel, destroy the continuity of the column of blood returning to the heart, divide it into smaller columns, as numerous as the intervals between the valves, and the height of which is determined by the distance between these folds. So that the power which carries onward the venous blood, and which would be inca- pable of propelling the whole mass, acts advantageously on each of the small portions into which it is divided. LXIII.—It has been thought that the principal cause which makes the blood flow into the veins, is the combined action of the heart and arteries ; but the impulse from those organs is lost in the system of capillary vessels, and does not extend to the veins. The specific action of their own parietes, aided by auxiliary means, such as the motion of the neighbouring arteries, is sufficient to carry the blood on to the heart.* These parietes, which are much thinner than those of the arteries, are con- tained, like theirs, in a sheath common to all the vessels. Three coats, like- wise, enter into their structure ; the middle, or fibrous coat, is not very dis- tinct, and consists merely of a few longitudinal reddish fibres, which can be distinguished only in the larger veins near the heart. In some of the larger quadrupeds, as in the ox, these fibres form distinct fasciculi, and their muscu-. larity is much more manifest. The internal coat, which is more extensible than that of the arteries, and equally thin, adheres more closely to the other coats. The cellular coat, which connects it to the middle one, is less abundant; hence phosphate of lime is seldom deposited into it, as happens to the arteries, which frequently become ossified as we advance in years. This internal coat is merely a con- tinuation of that which lines the cavities of the heart; and as the origin of the inner coat of the arteries is the same, there exists a non-interrupted con- tinuity in the membrane which lines all the canals of the circulation. The inner coat forms the only essential part of the venous system ; it alone con- stitutes the veins within the bones, the sinuses of the dura mater, the hepatic veins, in a word, all the veins which are so firmly attached externally to the neighbouring parts, that the blood flows along them as along inert tubes, their parietes being almost completely incapable of contracting. The veins in their passage through muscles, are, like the arteries, guarded by aponeurotic rings, than which none is more remarkable than that belong- ing to the aperture in the diaphragm, which transmits the ascending cava from the abdomen into the thorax. This vessel is, therefore, not compressed by the contraction of that muscle in inspiration. LXIV.—As the inferior cava passes through the lower edge of the liver, whether along a deep fissure, or in a real canal in the parenchymatous sub- stance of that viscus, the course of the blood must be impeded, when, from congestion of the parenchyma, the vessel is, in some sort, strangulated. Obstruction of the liver, which is of such frequent occurrence, would have * It would perhaps be more just to assign parietes, and by the active dilatation of the the cause of the flow of blood in the veins to the heart. See Appendix, Note T,—/. C. vis d tergo, assisted by the action of their own 18 138 OF THE VENOUS CIRCULATION. been attended with fatal consequences, by preventing the return of the blood from the inferior parts, along the ascending cava, if this great venous trunk did not keep up, by means of the vena azygos, an open and free communica- tion with the descending or superior cava. -The use of this anastomosis of the two great veins, is evidently to facilitate the passage of the blood from the one of these vessels into the other, when either, especially the lower, does not readily evacuate its contents into the right auricle. On this account, the ve- na azygos is capable of considerable dilatation, and is entirely without valves. In the body of a man opened this day in my presence, and whose liver was twice as large as in health, I Observed that the vena azygos, which was dis- tended with blood, was of the size of the little finger : the terminations down- wards of this vessel, in the right renal vein, and above in the superior cava, were most distinct; and by compressing it from above downward, or from below upward, the blood flowed into the one or other of these vessels. As the causes which determine the circulation of the venous blood com- municate to it an impulse which is far from rapid; and as this fluid meets with only trifling obstacles, and such as are easily overcome, the pressure against the parietes of the veins is very inconsiderable ; and these vessels do not pulsate as the arteries. There is observed, however, near the heart an undulatory motion, which the blood communicates to the parietes of the ves- sels. These kinds of alternate pulsations depend on the rapidity with which the blood, whose course is progressively accelerated, flows towards the heart, and on the reflux of the blood during the contraction of the right auricle. The contraction of this cavity forces back the blood into the veins which open into it; this retrograde course is manifest in the superior cava, and is the more readily occasioned, as the orifice of this vein is not furnished with any valve that might prevent it. It does not, however, extend very far towards the brain, the blood having to ascend against its own weight, and the jugulars admitting of considerable dilatation. This regurgitation is still more marked in the inferior cava, the orifice of which is but imperfectly closed by the valve of Eustachius; it is felt in the abdominal veins, and extends even to the ex- ternal iliacs, according to the testimony of Haller. LX V.—The orifice of the great coronary vein being exactly covered over by its valve, the blood does not return into the tissue of the heart, which, being a contractile organ, would have had its irritability impaired by the presence of venous blood. It is of consequence to observe, that this reflux never extends to the veins which bring back the blood from the muscles, and that it is never felt in the veins of the limbs which are furnished internally with valvular folds. The case is very different between our organs of motion and these secretory glands : towards these latter the blood is required to be sent back, so as to be the longer exposed to their action ; whereas venous blood dimi- nishes and even destroys muscular irritability, and is truly oppressive to the organs of motion, as may be ascertained by injecting some in the arteries of a living animal, or else by tying the veins, so as to prevent its return, or by observing what happens when the course of the blood is interrupted, either by applying firm ligatures round the limbs, or by wearing confined clothes. I am satisfied, that it was from observing the oscillatory undulations of the venous blood in the great vessels, that the ancients were led to the opinions they entertained on the course of the blood, which they compared to the Eu- ripus, whose waves were represented by the poets as uncertain in their course, and in currents running in contrary directions. The internal veins in which thi3 reflux is observed shew this motion of the blood most distinctly of any ; their sides, which are thin and semi-transparent, not being, as in other parts, surrounded by an adipose cellular tissue. To OF THE GENERAL CIRCULATION, 139 give a complete notion of the doctrine of the ancients on the subject of the circulation, it will merely be necessary to add to the above idea the opinion which they entertained, that the chyle taken up by the meseraic veins was carried to the liver, in which its sanguification was effected ; and lastly, that the arteries were filled with vital spirit, and contained only a, few drops of blood, which passed through small holes, that Galen says, perforate the sep- tum of the ventricles. The blood, however, continually urged on by the columns which follow each other in succession, by the action of the veins whose parietes become gradually stronger, and by the compression which these vessels experience from the viscera during the motions of respiration, reaches the heart, and enters the auricles with the greater facility, as the orifices of the cavae not being directly opposed to each other, the columns of blood which they con- vey do not meet^ and do not oppose each other. LXVI. Of the general or systemic circulation.—The blood continually carried to all parts of the body by the arteries, returns, therefore, to the heart, by a motion which can never be interrupted without considerable dan- ger of life. We know that the circulation is thus effected, from the direction of the valves of the heart, of the arteries and veins, by what happens when these vessels are opened, compressed, or tied, or when a fluid is injected into them. When an artery is wounded, the blood comes from the part of the vessel nearest the heart; it comes, on the contrary, from towards the extremities, if it is a vein that has been opened. By compressing or tying an artery, the course of the blood is suspended below the ligature, and the vessel swells above. The veins, on the contrary, when tied or compressed, dilate below. Lastly, when an acid fluid is injected into a vein, the blood is seen to coagulate in the direction of the heart. By the help of the micro- scope, we may see in the semi-transparent vessels of frogs and other cold- blooded animals, the blood flowing from the heart into the arteries^ and from these into the veins, which return it to the heart. It was on the strength of these convincing proofs, that William Harvey established, towards the middle of the sixteenth century, the theory of the circulation of the blood. Its mechanism had been rather guessed at, than understood, by several au- thors ; Servetus and Cesalpine appear to have been acquainted with it; but no one has more clearly explained it than the English physiologist, who is justly considered the author of that immortal discovery. LXVII The theory of Harvey, such "as it is laid down in his work, en- titled, De sanguinis circuitu exercitationes anatomica, does not appear to me entirely admissible. He considers the heart as the only agent which sets the blood in motion, and does not take into account the action of the veins and arteries, which he considers as completely inert tubes; while every thing tends to prove that the arteries and veins assist the motion of the blood,* by an action peculiar to themselves. He admits, that the blood flows in every part of the circulatory system with an uniform degree of speed ; an opinion so manifestly contradicted by reasoning and experience, which prove that the velocity of its course diminishes, the greater its dis- tance from the heart, from the influence of a great number of circumstances, which it would be useless to repeat (LVII). This doctrine has yet, how- ever, several abettors ; and among the moderns, Spallanzani has endeavoured to support it, by a number of experiments so contradictory, that one is sur- prised that so judicious a physiologist should have collected them to esta- blish a theory completely refuted by several of them. Nothing, for example, contradicts it more fully, than the continuation of the flow of the blood, in * See Appendix, Notes A, B, S, T. 140 OF THE PTTLMONAKT CIRCULATION the vessels of frogs and salamanders, after the heart of, these reptiles has been torn out: there are, besides, animals which, not possessed of that cen- tral organ, have, nevertheless, vessels along which the blood flows, and which contract and dilate by alternate motions. If the mere force of the heart propelled the blood to every part, the course of this fluid ought, at intervals, to be suspended : its circulation, at least, ought to be slackened when the ventricles cease to contract; but as the contraction of the arteries corresponds to the relaxation of the ventricles, these two powers, whose action alternates, are continually employed in propelling the blood along its innumerable channels. Besides the general circulation, of which the laws and phenomena have just been mentioned, each part may be said to have its peculiar mode of cir- culation, more or less rapid, according to the arrangement and structure of its vessels. Each of these individual circulations forms a part of the ma- chinery included in the great circle of the general circulation, and in which the course of the blood takes place in a different manner, may be accelerated or retarded, without affecting the general circulation. Thus, the circulation in the brain is modified from that of the lungs ; and this latter, from the cir- culation of the abdominal viscera, the venous blood of which, destined to furnish the materials of the bile, flows much more slowly than that of other parts. These modifications, affecting the velocity of the circulatory motion of the blood, account for the difference of its qualities in different organs: all these differences form a part of the plan of nature, and it is not difficult to understand their utility. LXVIII. Of the pulmonary or lesser circulation.—In what has been said of the circulation, no separate mention has been made of the course of the blood through the lungs, called by-authors the lesser or pulmonary circula- tion. The vascular system of the lungs, with the addition even of the cavities of the heart which belong to it, does not represent a complete circle ; it is only a segment, or rather an arch, of the great circle of general circula- tion. The blood, in going along that great circle, meets with the organs, situated like so many points of intersection in the course of the vessel, which form that circle. To render still more simple the idea which is to be entertained on the sub- ject, one may reduce these intersections to two principal ones ; the one cor- responding to the lungs, the other to the rest of the body ; the veins, the right cavities of the heart, and the pulmonary artery with its divisions, form- ing one half of the circle ; the pulmonary veins, the left cavities of the heart, the aorta with all its branches, representing the other half. The capillary vessels of the lungs form one of the points of intersection, and the capillaries of all the other organs represent the other point of intersection, by uniting together the arteries and veins of the whole body, in the same manner as those of the lungs establish a communication between the veins and arteries of these organs. This division of the system of circulation into two parts, in one of which there circulates a dark venous blood, while the other contains red or arterial blood, is at once more simple and more accurate. As was already stated, in the history of the circulation, its organs are, in an especial manner, des- tined to the mechanical act of conveying the fluids . the changes, the alte- rations which the blood undergoes in passing through the organs, are effected only at the moment when, in penetrating into their tissue, it passes into the cajpillary vessels which are distributed into them. The columns of blood are OF RESPIRATION 141 then sufficiently minute to be operated upon by the vital action ; till then, the columns of blood are too large, and resist, by their bulk, if one may so speak, any decomposition. It is, therefore, in the capillary vessels that the blood undergoes its essential changes, and from them it deposits its nutritious ele- ments ; and to understand how the nutritious.lymph, which is carried by the thoracic duct into the left subclavian vein, experiences, in its course along the sanguiferous system, the changes whickare to assimilate it to our own sub- stance, it is necessary to follow it, along the venous blood with which it unites, into the heart, through the right half of which it passes in its way to the lungs, there to combine with the atmospherical air, from which we are per- petually deriving another aliment indispensable to life ; then, to examine how, when modified and conveyed with the red blood from the lungs to the whole body, it serves to the secretions, and supplies nourishment to the different structures of the frame. In considering, in this manner, the circulation of the blood, with a reference to the changes which it undergoes in the organs through which it passes in describing that circle, we shall find that this fluid, already combined with the lymph and chyle, parts, in the lungs, with some of its principles, at the same time that it becomes impregnated with the vital portion of the atmosphere, which suddenly changes its colour and other qualities. The blood will then be seen to flow into all the parts which it stimulates, to keep up their energy, to awaken their action, and furnish them the materials of the fluids which they secrete, or the molecules by which they grow or are repaired ; so that, in supplying thus the different organs, the blood loses all the qualities which it had acquired by the union of the chyle and of the vital air, parts with the principles to which it owed its colour, and again becomes dark, to be repaired anew by combining with the lymph, and by the absorption of the vital part of the atmospheric air :* this constitutes the principal phenomenon of the function which will be considered in our next chapter. CHAPTER IV. OF RESPIRATION LXIX. The Purposes of this Function.—LXX Of the Atmosphere.—LXXI. The Mechanism of the Respiratory Organs.—LXXII. Actions of the Respiratory Muscles.—LXX1II. Of Inspi- ration and Expiration.—LXXIV. State of the Lungs during Inspiration.—LXXV. Of the Pul- monary Vessels.—LXX VI. Changes induced on the Blood and in the Air by Respiration.— LXXVII. Of the nervous Influence in the function of Respiration.—LXX VIII. and LXXIX Of Animal Heat.—LXXX. and LXXXI. Of the Causes enabling the Body to resist Increase or Diminution of Temperature.—LXXXII. Source of Animal Heat.—LXXXIII. The Pul- monary Circulation, and Changes induced upon the Chyle received into the Venous Blood.— LXXXIV. Of Pulmonary Exhalation.—LXXXV. Of Asphyxia.—LXXXVI. Of Sighing, Sobbing, Yawning, Sneezing, Coughing, Hiccup, Laughing, &c.—LXXXVII. Of the Cuta- neous Perspiration. LXIX.—Of the different changes which the blood undergoes in the different organs, none are more essential or more remarkable than those it receives from the air which during respiration is alternately received into the lunga and expelled from them. The blood which the veins convey to the heart, and which the right ventricle transmits to the lungs, is of a dark colour, and heavy ; its temperature is only thirty degrees (Reaumur) ; if laid by, it coa- gulates slowly, and there is separated from it a considerable quantity of serum. * See the Note on Respiration, in the Appendix, for a different opinion. 142 or THE ATMOSPHERE The blood which is brought by the pulmonary veins to the left side of the heart, and which is conveyed to all parts of the body by means of the arteries, is, on the contrary, of a florid red colour ; it is spumous, lighter, and warmer by two degrees. It likewise coagulates more readily, and contains a smaller quantity of serum. All these differences, which are so easily distinguished, depend on the changes which it has undergone, by being in contact with the atmospherical air. LXX. Of the atmosphere.—The mass of air which surrounds the globe, and to which we give the name of atmosphere, bears on all bodies with a pres- sure proportioned to their surface. That of man* bears a weight of air amounting to about thirty-six thousand pounds. Moreover, one of its con- stituent principles is absolutely necessary to the keeping up of life, of which it is a principal agent. The variations in the weight of the atmosphere have, in general, but little influence on the exercise of the functions ; nevertheless, when, by ascending the tops of very high mountains, man rises several thousand fathoms above the level of the sea, the remarkable diminution of the weight of the air pro- duces a very sensible effect. Respiration becomes laborious and panting, the pulse is quickened, and there is felt an universal uneasiness joined to ex- cessive weakness, and haemorrhages come on : these symptoms are occasion- ed both by the diminished pressure of the air and by the smaller quantity of oxygen contained in a rarer atmosphere. — (Saussure, Voyage au Mont-Blanc.) The human body resists, without any effort, the atmospherical pressure, because it is applied at all times, and in every/direction.f But if a part of its surface ceases for a moment to be under its influence, it swells, the fluids are determined to it in considerable quantity, the integuments become exces- sively distended, so as to be in danger of bursting; such are the phenomena which attend the application of cupping glasses. The pressure of the air on the surface of the globe is necessary to the ex- istence of bodies in the condition in which we see them. Several very vola- tile fluids, as alcohol and ether, would become gaseous under a less pressure of the atmosphere ; water would boil under eighty degrees of temperature (Reaumur's scale); solid bodies themselves might become fluid. In a word, a considerable diminution in the weight of the atmosphere would have abso- lutely the same effect as raising its temperature to a very great height, which, changing the face of the universe, would convert all liquids into elastic fluids, and would, doubtless, melt all solid bodies. The variations in the weight of the atmosphere, distinguishable by the barometer, are of very little importance to the physiologist, and, I might even add, to the physician, notwithstanding the minute attention with which some writers note the state of the barometer, of the thermometer and hygrometer and of the electrical state of the atmosphere, in giving an account of a dis- ease or of an experiment, on which the above circumstances have no appa- rent or certain influence. The atmosphere, like every other fluid, has a per- petual tendency to a state of equilibrium ; hence the rush of air into the lungs, or into other situations, in which its quantity is diminished by the com- binations which it forms, or by the effects of heat, which renders it lighter by rarefaction Xhe same principle explain? the formation of the trade and other winds. * The surface of the body is estimated it functions, as particularly respiration and venous fifteen or sixteen square feet, in a man of middle circulation, to which lattei, according tp the ex- »"e' . periments of Dr. Curson and Dr. Barry, it ap- t The pressure of tne atmosphere is even ne- pears to contribute. See on this subject the eessary to the due performance of some of our Notes on Respiration, in the Appendix__/. C. CONSTITUTION OF THE ATMOSPHERE. 143 The atmospherical air combines with water and dissolves it, as the latter dissolves saline substances. In this consists the process of evaporation. The air becomes saturated with water, in the same manner as water becomes sa- turated with salt, to such a degree as to be incapable of holding a greater quantity in solution. As its temperature rises, its solvent power increases, and the latter diminishes as it grows cold ; variations of temperature produce the same effect on solutions of salts in liquids. The formation of all the aqueous meteors depends on the different conditions of the solvent powers of the atmosphere ; when considerable, the atmosphere is warm and dry, and the air serene ; clouds form when it is saturated ; dews, fogs, and rain, are the consequence of a diminution of its solvent power, as snow'and hail of a degree of cold which precipitates the fluid. The different degprees of drvness or moisture, marked by the hygrometer, only sensibly affect the human body when it has been exposed for a considerable time to its influence. Chemically considered, the atmospherical air, which was long regarded as & simple body, is composed of about 21 of oxygen, 79 of azote, by measure, and of -01 or 02 of carbonic acid. The carbonic acid is the more abundant as the air is less pure. This part of natural philosophy, which is called eudio- metry, or the measurement of the purity of the air, is far from accomplishing what its name indicates, and has disappointed the hopes which had been entertained on the subjeet. Eudiometrical instruments can inform us only of the proportion of oxygen contained in the atmosphere ; now, its salubrity, its fitness for respiration, is not in proportion to the quantity of oxygen. The volatilised remains of putrid animal or vegetable substances, and various mephitic gases, combine with it and affect its purity. In the comparative analysis of air procured on the Alps and in the marshes of Lombardy, there was found in each the same quantity of oxygen ; and yet, those who breathe the former enjoy robust health, while the inhabitants of the marshy plains of Lombardy are carried off by epidemic diseases, are pale, emaciated, and habitually lead a languid existence. Though at least "20 parts of oxygen are necessary to render the air fit for respiration, the proportion may be diminished to seven or eight parts in the hundred ; but in such cases the breathing is laborious, panting, and attended with a sense of suffocation; in short, asphyxia comes on even while the air still contains a certain quantity of oxygen, of which the lungs cannot entirely deprive it. Whenever a numbor of persons are collected in a confined place, in which the air cannot be easily renewed, the quantity of oxygen diminishes ra- pidly, while that of carbonic acid increases. The latter, in consequence of its specific gravity, sinks to the lowest part, and strikes with death every living being which it envelopes. When two lighted candles of different lengths are placed under the same bell, the shorter candle goes out first, because the car- bonic acid formed during combustion sinks to the most depending part. For the same reason, the pit is the most unhealthy part of a playhouse, when a great number of people, after remaining in it for several hours, have deprived the air of a considerable portion of its oxygen. Persons collected together and enclosed in a small space, injure each other, not only by depriving the atmosphere of its respirable element, but particu- larly by altering its composition, by the combination of all the substances ex- haled from their bodies. These volatilised animal emanations become putrid while in the atmosphere, and conveyed to the lungs during respiration, be- come the germ of the most fatal diseases. It is in this manner that the gaol and hospital fever, so fatal to almost ail whom it attacks, arises and spreads. A dry and temperate air, containing 21 of oxygen and 79 of azote, and free of other gases or other volatilised substances, is the fittest for respiration. In 144 MECHANISM OF THE THORAX. certain cases of disease, however, this function is most freely performed in a less pure air. Thus, patients labouring under pulmonary consumption, pre- fer the thick and damp air of low situations to the sharp and dry air of moun- tains ; nervous women prefer that in which horn, feathers, or other animal substances are burning. An atmosphere highly electrical, at the approach of a storm, renders respiration very laborious, in some cases of asthma. In short, the qualities of the air must be suited to the condition of the vital power in the lungs, as those of the food to the sensibility of the stomach. Being obliged, on this subject, to content myself with the ungracious office of compiler, I hasten to bring -this article to a close, and to refer the reader for a fuller account of the air, considered in its physical and chemical relations, to the works of MM. Fourcroy, Hauy, Brisson, Thenard, &c.; and to that of M. Guyton Morveau, on the method of purifying the air, when from diffe- rent combinations it is become unfit for respiration. LXXI. The mechanism of the respiratory organs.—In man, and in all warm- blooded animals, with a heart containing two auricles and two ventricles, the blood which has been conveyed to all the organs by the arteries, and which has been brought back by the veins to the heart, cannot return to it without having previously passed through the lungs, which are viscera destined to the transmission of air, of a spungy texture, and through which the blood must, of necessity, circulate, to get from the right to the left cavities of the heart. This course of the blood constitutes the pulmonary, or lesser circulation : it does not exist in some cold-blooded animals. In reptiles, for instance, the heart has but one auricle and one ventricle ; the pulmonary artery in them arises from the aorta, and conveys but a small proportion of the blood ; hence, the habitual temperature of these animals is much lower than that of man. For the same reason, too, there exists so small a difference between their ve- nous and arterial blood ; the quantity of fluid vivified by exposure to the air in the pulmonary tissue being too small to effect, by its union with the gene- ral mass, a material change on its qualities. Mayow has given the most accurate notion of the respiratory organ by comparing it to a pair of bellows, containing an empty bladder, the neck of which, by being adapted to that of the bellows, should admit air on drawing asunder its sides. The air, in fact, enters the lungs only when the chest di- lates and enlarges, by the separation of its parietes. The agents of respira- tion are, therefore, the muscles which move the parietes of the chest1, these parietes are formed of osseous and soft parts, in such a manner as to possess a solidity proportioned to the importance of the organs which the chest con- tains, besides a capacity of motion required to carry on the functions intrusted to them.* To carry on respiration, which may be defined the alternate ingress of air into the lungs and its egress from those organs, it is necessary that the dimen- sions of the chest should be enlarged (this active dilatation of the cavity of the chest is called inspiration), and that it should contract to expel the air which it had received during the first process. This second action is called expiration ; it is always of shorter duration than the former, its agents are more mechanical, and the muscles have much less influence upon it. The parietes of the chest are formed, at the back part, by the vertebral column, at the fore part by the sternum, and on the sides by the ribs, which are osseo-cartilaginous arches, situated obliquely between the vertebral co- lumn, which is fixed, and becomes the point of support of their motions, and the sternum which is somewhat movable—the spaces between the ribs are filled by muscular planes of inconsiderable thickness, consisting of the inter- * See Affkndix, Note U, for remarks on the Mechanism of the Respiratory O) girts. ACTION OF THE RESPIRATORY MUSCLES. 145 nal and external intercostal muscles, the fibres of which lie in opposite di- rections. Besides, several muscles cover the outer part of the thorax, and pass from the ribs to the neighbouring bones ; as the subclavian muscles, the great and lesser pectorals, the serrati, the latissimi dorsi, the scaleni, the lon- gissimi dorsi, the sacro-lumbales, and the serrati minores, posteriores, and infe- riores. But of all the muscles which form the anterior, posterior, and lateral parietes of the chest, the most important is the diaphragm, a fleshy and tendi- nous partition, lying horizontally between the chest and the abdomen, which it divides from each other; it is attached to the eartilages of the false ribs, and to the lumbar vertebrae, and has three openings to transmit the cesophagus and the vessels which pass from the abdomen to the chest, or from the latter into the abdomen. In health, the chest dilates only by the descent of the diaphragm. The curved fibres of that muscle, straightened in contraction, descend towards the abdomen, and compress the viscera. The descent of the viscera thrusts for- ward the anterior parietes of that cavity, and these recede, when, on expira- tion taking place after inspiration, the diaphragm, now relaxed, rises, pressed upward by the abdominal viscera, compressed themselves by the large mus- cles of the abdomen. But when it is necessary to take into the chest a great quantity of air, it is not sufficient that it should be enlarged merely by the de- scent of the diaphragm—it is required besides, that its dimensions should be increased in every direction. The intercostal muscles then contract, and tend to bring together the ribs between which they are situated. The intercostal spaces, however, become wider, especially at their anterior part; for, when- ever lines falling obliquely on a vertical line change their direction, approach- ing to a right angle, the intermediate spaces receive the greater increase, as the lines, more oblique at first, become at last more nearly horizontal. Be- sides, as the ribs are curved in the course of their length in two directions, and both in the direction of their faces and edgewise, the convexity of the first cur- vature is outwards, and the ribs recede to a distance from the axis of the chest, whose cavity is enlarged transversely ; while the second curvature (in the direction of their edge) being increased by a real twisting of these bones, and which reaches to the cartilaginous parts, the sternum is heaved forward and upward, so that the posterior extremity of the ribs is removed from their sternal end. But as the ribs are not all equally movable,—as the first is almost al- ways invariably fixed, and as the others are movable in proportion to their length,—the sternum is tilted in such a way that the lowermost extremity is thrust forward. The diameter of the chest from the fore to the back part in- creases, therefore, as well as the transverse diameter. This increase of di- mensions has been estimated at two inches to each of these diameters ; the dimensions of the vertical diameter, which are regulated by the depression of the diaphragm, are much greater. LXXII. Action of the respiratory muscles.—Professor Sabatier, in his me- moir on the motion of the ribs, and on the action of the intercostal muscles, maintains, that during the action of inspiration, the upper ribs alone rise, that the lower ribs descend and slightly close on the chest, while the middle ribs project outwardly ; and that in expiration, the former set of ribs descend, that the latter start a little outwardly, and that the middle set encroach on the ca- vity of the chest. The learned professor adds, that the cartilaginous articu- lating surfaces, by which the ribs are connected to the transverse processes of the vertebras, appear to him to favour these different motions, as the direction of the articulations of the upper ribs is upward, and that of the lower down- ward; but, on considering the subject with attention, it will be seen, that the sur- faces by which the transverse processes of the vertebras are articulated to the 19 146 ACTION OF THE RESPIRATORY MUSCLES. tuberosities of the ribs, are turned directly forward in the greatest number, while some of the lower ribs are, at the same time, directed slightly upward. If we examine the action of the bones of the chest during inspiration, in a very thin person,—for example, in phthisical patients, whose bones are covered with little else than skin,—we shall find, that all the ribs rise, and are carried somewhat outwardly. It is not easy to conceive how the intercostal muscles, which Professor Sabatier considers as the agents of respiration. should elevate the upper ribs and depress the lower. The diaphragm, whose circumference is inserted in the latter, might, by its contraction, produce this effect; but as the intercostals have their fixed point of action in the upper ribs, they oppose and neutralise this effort, and all the ribs are elevated at once. If this were not the case, the ribs ought to be depressed whenever the intercostals contract, since the lowermost, fixed by the diaphragm, would be- come the fixed point on which all the others should move. As the fibres of the external and internal intercostal muscles are in direct opposition to each other,—those of the former set of muscles having an oblique direction, from above downward, and from behind forward, and crossing the fibres of the other set, whose obliquity is in a different direction,—several physiologists have thought that these muscles were opposed to each other ; that the internal intercostal muscles brought together the ribs after they had been separated by the external intercostals, the one set being muscles of expi- ration, while the other set contracted during inspiration. It is well known with what pertinacity Hamberger, in other respects a physiologist of considerable merit, defended this erroneous opinion in his dis- pute with Haller: it is now, however, ascertained, that all the intercostal muscles concur in dilating the chest, and that they ought to be ranked among the agents of inspiration, because the unequal capacity of motion in the ribs prevents the internal intercostals, the lower insertion of which is nearer to the articulation of these bones to the vertebrae, from depressing the upper ribs. Of the very conclusive experiments by which Haller under- took to refute the arguments of his adversary, I shall relate only that which is performed by stripping the parietes of the chest in a living animal of all the muscles which cover it, and by removing, in different parts of the thorax, some of the external intercostal muscles. The internal intercostals are then seen to contract during inspiration, together with the remaining external in- tercostals. These muscles, therefore, have a common action, and are not in opposition to each other. The same experiment serves to prove the increased dimensions of the space between the ribs. On holding one's finger between two of the ribs, it feels less confined, when, during inspiration, these bones rise and thrust forward the sternum. This question being at rest, although in the pursuit of science one should inquire how things are effected, and not wherefore they come to pass, we feel naturally desirous to know what purpose is answered by the different direction of the fibres of the two sets of intercostal muscles ; and with what view Nature has departed from her wonted simplicity, in giving to their fibres opposite directions. In answer to this I may observe, that the action of powers applied obliquely to a lever being decomposed in consequence of that obliquity, a part of the action of the external intercostals would tend to draw the ribs towards the vertebral column, which could not happen with- out forcing back the sternum, if the internal intercostals did not tend to bring forward the ribs at the same time that they elevate them ; so that these two muscular planes, united in their action of raising the ribs, antagonise and reciprocally neutralise each other, in the effort by which they tend to draw them in different directions. OF INSPIRATION AND EXPIRATION, 147 To this advantage of mutually correcting the effects that would result from their respective obliquity, may be added the benefit arising from a tex- ture capable of a greater resistance : it is clearly obvious, that a tissue whose threads cross each other, is firmer than one in which all the threads, merely in juxta-position, or united by means of another substance, should all lie in the same direction. Hence Nature has adopted this arrangement in the for- mation of the muscular planes constituting the anterior and lateral parietes of the abdomen, without which the abdominal viscera would frequently have formed herniary tumours, by separating the fibres and getting engaged be- tween them. In this respect we may compare the tissue of the abdominal parietes,—in which the fibres of the external and internal oblique muscles, which cross each other, are themselves crossed by the fibres of the transver- sales,—to the tissue of those stuffs whose threads cross each other, or rather to wicker-work, to which basket-makers give so much strength by inter- weaving the osier in a variety of directions. LXXIII. Of inspiration and expiration.—When from any cause respiration becomes difficult, and the diaphragm is prevented from descending towards the abdomen, or the motion of inspiration in any way impeded, the intercos- tals are not alone employed in dilating the chest, but are assisted by several other auxiliary muscles ; the scaleni, the subclavii, the pectorals, the serrati magni, and the latissimi dorsi, by contracting, elevate the ribs, and increase, in more directions than one, the diameter of the chest. The fixed point of these muscles then becomes their movable point, the cervical column, the clavicle, the scapula, and the humerus, being kept fixed by other powers, which it is unnecessary to enumerate. Whoever witnesses a fit of convul- sive asthma, or of a suffocating cough, will readily understand the import- ance and action of these auxiliary muscles. Inspiration is truly a state of action, an effort of contractile organs, which must cease when these are relaxed. The expiration which follows is pas- sive, and assisted by very few muscles, depending chiefly on the re-action of the elastic parts which enter into the structure of the parietes of the chest. We have seen that the cartilages of the ribs are pretty considerably twisted, so as to carry outward and downward their upper edge : when the cause which occasions this twisting ceases to act, these parts return to their natural condition, and bring back the sternum towards the vertebral column, towards which the ribs descend from their weight. ' The diaphragm is forced towards the chest by the abdominal viscera, which are compressed by the broad mus- cles of the abdomen. In every effort of expiration, as in cough and vomiting, these muscles re- act, not merely by their own elasticity, but they besides contract and tend to approach towards the vertebral column, by pressing upwards the abdominal viscera towards the chest. The triangularis sterni, the subcostales, and the serratus inferior pesticus, may likewise be ranked among the agents of expi- ration ; but they appear to be seldom employed, and to be too slender and weak to contribute much to the contraction of the chest. LXXtV. State of the lungs during inspiration.—When the chest enlarges, the lungs dilate and follow its parietes as these recede from each other. These two viscera, soft, spongy, and of less specific gravity than water, covered by the pleura, which is reflected over them, are always in contact with the portion of that membrane which lines the cavity of the thorax ; no air is interposed between their surfaces (which are habitually moistened by a serous fluid exuding from the pleura) and that membrane, as may be seen by opening under water the body of a living animal, when no air will be seen to escape. As the lungs dilate their vessels expand, and the blood cir- 148 OF THE PULMONARY* VESSELS. culates through them more freely : the air contained in the innumerable cells of their tissue becomes rarified, in proportion as the space in which it is cOrt- tained is enlarged. Besides, the warmth communicated to it by the surround- ing parts, enables it, in a very imperfect manner, to resist the pressure of the atmosphere, rushing through the nostrils and mouth into the lungs, by the opening in the larynx, which is always previous except during de- glutition. LXXV. Of the pulmonary vessels.—The pulmonary tissue into which the air is thus drawn every time the capacity of the chest is increased, does not consist merely of air-vessels, which are but branches, of different sizes, of the two principal divisions of the trachea, but is formed, likewise, by the lobular tissue into which these canals deposit the air; it contains, also, a great quan- tity of lymphatics and blood-vessels, of glands and nerves. Cellular tissue unites together all these parts, and forms them into two masses, covered over by the pleura, and of nearly the same bulk ;* suspended in the chest from the bronchia and trachea, and every where in contact with the parietes of the cavities of the chest, except towards their root, at which they receive all their nerves and vessels. The pulmonary artery arises from the base of the right ventricle, and di- vides into two arteries, one to each lung. On reaching the substance of the lungs, these arteries divide into as many branches as there are principal lobes. From these branches there arise others, which again subdivide into lesser ones, until they become capillary, and continuous with the radicles of the pulmonary veins. These vessels, formed from the extremities of the artery, unite into trunks, which progressively enlarging, emerge from the lungs, and open, four in num- ber, into the left auricle. Besides these large vessels, by means of which the cavities in both sides of the heart communicate together, the lungs receive from the aorta two or three arteries called bronchial arteries: these penetrate into their tissue, where they follow the direction of the other vessels, and ter- minate in the bronchial veins, which open in the superior cava, not far from its termination into the right auricle. These bronchial vessels are sufficient for the nourishment of the pulmonary organ, which, in reality, is not near so bulky as it appears, as may be ascertained by examining the lungs after all the air has been extracted from them, by means of an air-pump applied to the trachea. Physiologists, for the most part, consider the bronchial arteries as the nu- tritious vessels of the lungs. They assert, that as the blood which flows along the branches of the pulmonary artery resembles venous blood, it is un- fit for the nutrition of the lungs, and that it was necessary that these organs should be supplied by arteries arising from the aorta, and containing blood analogous to that which is sent to every part of the body. But though it be admitted that this venous blood, brought from every part of the body and sent into the lungs by their principal artery, may not be fit to maintain the organ in its natural economy, this blood is fit for that use, when, after being made hot, spumous, and florid, by the absorption of the atmospherical oxygen t it returns by the pulmonary veins into the left cavities of the heart. Some have thought, that the blood which flows in the bronchial vessels exposed to the action of the air, like the portion of this fluid which traverses the pulmonary system, loses nothing of its arterial qualities, and that, poured by the bronchial veins into the superior or descending vena cava, it was a necessary stimulus for the right cavities of the heart, of which blood entirely * It is well known that the right lung is three principal lobes, while the latter ha-s only larger than the left, and that it is divided into two of the Pulmonary vessels. 149 dark and venous would not have awakened the contractility. But even, if the experiments of Goodwin had not proved that the parietes of these cavities have a sensibility relative to dark blood, by virtue of which this stimulus is sufficient to determine their contraction, the action of the heart does not de- pend as closely as has been said on the impression of the blood on its sub- stance, since it contracts, though empty, and prolongs its contractions to re- lieve itself of the black blood which fills it, when an animal dies of asphyxia. Boerhaave, who admitted one sort of peripneumony depending on the ob- struction of the bronchial vessels, whilst another, according to the same wri- ter, depends on the obstruction of the pulmonary vessels, seems to justify, in some measure, the reproach, exaggerated, unquestionably, which some au- thors have thrown out against anatomy of having rather retarded than acce- lerated the progress of the Hippocratic practice of medicine. The anatomical analysis of the lungs, or the distinction of the tissues which enter into their composition, furnishes juster ideas of the difference of the inflammations by which they may be attacked. It has been seen, that of these pulmonary phlegmasia?, the commonest and least serious consists in inflammation of the mucous membrane which lines the air passages, whilst the real peripneumo- ny has its seat in the parenchyma of the organ, which it converts into a hard and compact mass. It is this state that anatomists have long designated by the name of hepatisation, because, in fact, the substance of the lung has ac- quired the hardness, the weight, and something of the appearance, of the liver. The same anatomical researches have shewn that pleurisy consists.in inflam- mation of the pleura and of the surface of the lung, an inflammation which sometimes leaves no trace, but which oftener exhibits, on the opening of bo- dies, the pleura thickened and opaque, covered with a layer of coagulable lymph, whitish, more or less thick, or even adhering to the lung.* There arise from the surface and from the internal substance of the lungs, a prodigious number of absorbents, which may be divided into superficial and deep-seated. The latter accompany the bronchial tubes, and penetrate into the substance of the glandular bodies situated where those air-vessels divide, but collected in greatest number towards the root of the lungs, and at the an- gle formed by the bifurcation of the trachea. These bronchial glands, belong- ing to the lymphatic system, do not differ from the glands of the same kind, and are remarkable only by their number, their size, and their habitually darkish colour. The absorbents of the lungs, after ramifying in these glands, terminate in the upper part of the thoracic duct, at the distance of a few inches from its termination into the subclavian vein. Lastly, the lungs, though en- dowed with a very imperfect degree of sensibility, have a pretty considerable number of nerves furnished by the great sympathetic, and especially by the eighth pair. * These adhesions of the lung to the pleura tention, in the same way as in simple wounds costalis are so common, that the old anatomists immediately united. There is no organ that considered them as a natural disposition, and abounds more than the lungs in facts important called them ligaments of the lungs. It has been to morbid anatomy. The variety of appearances believed till now, that these adhesions arose they exhibit on the opening of bodies, is almost from the organisation of a substance transuding innumerable ; and to give one instance, the from, the two surfaces. Numerous dissections pleura appears after pleurisy in five perfectly have convinced me, that in all the points where distinct conditions : 1st, in its natural state, they are met with, the pleura has disappeared ; when the disease being incipient and slight, the that it is decomposed ; and that whether it be at resolution is effected at the moment of death; the surface of the lungs, or within the ribs and 2dly, when it is red, thickened, and opaque; their muscles, it is produced by the act of in- 3dly, when it is covered with coagulable lymph; flammation ; that it is become cellular, by the 4thly, when it adheres ; 5thly, when, in conse- thinning of its tissue and the separation of its quence of chronic inflammation, hydrothorax lamina-. The pleura thus reduced to cellular has taken place, &c. &c. tissue, the adhesion is produced by the first in- 150 CHANGES PRODUCED BY RESPIRATION". It was long believed, on the authority of Willis, that the aerial tissue of the lungs is vesicular, that each ramification of the bronchia terminated in their substance, in the form of a small ampullula ; but at present most anatomists adopt the opinion of Helvetius. According to him, every air-vessel terminates in a small lobe, or kind of sponge fitted for.the reception of air, and formed of a number of cells communicating together. These lobes, united by cellular tissue, form larger lobes, and these together form the mass of the lungs. The tissue that connects together the different lobes is very different from that in which the ramifications of the bronchia terminate : air never pene- trates into it, except when the tissue of the air-cells is ruptured. On such oc- casions, which are not of rare occurrence, on account of the excessive thinness of the lamina? of the air-cells of that tissue, the lung loses its form, and be- comes emphysematous. Haller estimates at about the thousandth part of an inch the thickness of the parietes of the air-cells ; and as the extreme rami- fications of the pulmonary vessels are distributed on these parietes, the blood is almost in immediate contact with the air. There can be no doubt that the oxygen of the atmosphere acts on the blood, under such circumstances, since it alters its qualities, and communicates to it a florid red colour, when enclosed in a pig's bladder, and placed under a vessel filled with oxygen gas. LXXVI. Changes produced in the air and blood by respiration.—Every time the chest dilates, in an adult, there enter into the lungs between thirty and forty cubic inches of atmospherical air,* consisting, when pure, of seventy-nine parts in the hundred of azote, twenty-one of oxygen, and a fractional part of carbonic acid.f When the air has been exposed, for a few moments, in the pulmonary tis- sue, it is expelled by the effort of expiration; but it is diminished in quantity, and is reduced to thirty-eight inches. Its composition is no longer the same ; it contains, it is true, "79 parts of azote, but the vital portion fit for respiration, the oxygen, has undergone a great diminution ; its proportion is only -14 : oarbonic acid forms the remaining '07, and there are sometimes found one or two parts of hydrogen. It is, besides, affected by the addition of an aqueous vapour, which is condensed in cold weather, as it escapes at the mouth and nostrils. It is called the humour of the pulmonary transpiration. These changes, compared to those which the blood experiences in passing through the lungs, clearly shew a reciprocal action of this fluid and of the oxygen of the atmosphere. The dark venous blood which coagulates slowly, and which then disengages a considerable quantity of serum, abounding in hydrogen and carbon, and of a temperature of only thirty degrees, yields its hydrogen * Some physiologists think that the quantity chest. Keill injected water into the cheat of a of air inspired, is much less considerable. Pro- dead body. Lastly it has been proposed to in- fessor Gregory, of Edinburgh, states, in his ject the bronchial tubes, and the lobular tissue public lectures, that scarely two inches of air into which they terminate, with fusible metal enter into the lungs at each inspiration. It consisting of eight parts of pewter, five of lead' may be proved, however, that this calculation is three of bismuth, to which may be added one of inaccurate, either by drawing a full inspiration, mercury. as was done by Mayow, at the expense of a cer- Menzies calculates the quantity of air admit- tain quantity of air contained in a bladder, or ted into the lungs at each respiration, at 43 cu- by breathing into a vessel connected with a bic inches; Sir H. Davy estimates it at about pneumatic apparatus the air taken in by draw- 17; Messrs. Allen and Pepys at 16£; and Good- ing a deep inspiration. Or else one may inflate win and Abernethy at 12 only. There can be the lungs of a dead body, by adapting to the no doubt that the estimate of Menzies is too trachea a stop-cock, connected with a curved high for the natural state of the respiration ; but tube to receive the air, under a vessel of the the quantity of air received at such inspiration same apparatus. Various means have been em- must necessarily vary very much, according to ployed to measure the capacity of the chest, the size and conformation of the individual. Boerhaave placed a man in a tub containing t See Appendix, Note W, for observations water above his shoulders ; he then made him on the changes induced on the air, and on the take a deep inspiration, and measured the height blood, by respiration. at which the fluid rose from the dilatation of the ON THE VENOUS BLOOD. 151 and carbon to the oxygen of the atmosphere, to form carbonic acid and the pulmonary vapour; and as oxygen cannot enter into these new combinations without parting with a portion of the caloric which keeps it in a state of gas, the blood acquires this warmth, which is disengaged the more readily, accord- ing to the ingenious experiments of Crawford, as, by parting with its hydro- gen and carbon, its capacity for caloric increases in the proportion of 10 : 11-5. In parting with its carbon, which, by uniting with oxygen, forms the car- bonic acid that is thrown out during expiration, the blood loses its dark and nearly purple colour, and becomes of a florid red, and its consistence increases, from the escape of its hydrogen and of its aqueous parts. Besides, as it ab- sorbs a certain quantity of oxygen, it becomes spumous and light; its con- erescibility and plasticity increase, and on coagulating, there is separated from it a smaller quantity of serum. After parting with its hydrogen and carbon, and combining with oxygen and caloric, in its passage through the lungs, the blood, which is become arterial, parts with these two principles, in proportion as, in receding from the heart, it forms new combinations, and is converted into oxides of hydrogen and carbon, which, on receiving an additional quantity of oxygen, are changed into water and carbonic acid, when, on being carried along with the venous blood into the pulmonary tissue, they are exposed to the influence of the at- mospherical air. The arterial blood becomes venous by yielding its oxygen, when any cause whatever suspends or slackens its course, as is proved by the following experiment of John Hunter. He tied the carotid artery of a dog with liga- tures placed at the distance of about four inches from each other : the blood contained in the portion of artery included between the two ligatures, on laying open this part of the vessel at the end of a few hours, was found coa- gulated, and as dark as that in the veins. The blood contained in an aneu- rismal sac,' and which is frequently found in a fluid state, when the internal coats of the artery are but lately ruptured, becomes venous after remaining in it some time. The changes, however, which the blood undergoes in its course through the arterial system, are not very remarkable, owing to the rapidity with which it flows along those vessels : there is less difference be- tween the blood contained in an artery near the heart and that contained in an artery at a distance from that organ, than in the blood taken from the veins near their extremities and from the great trunks which deposit it into the right auricle. The blood in the small veins resembles arterial blood; and frequently, in a very copious bleeding, the colour of the blood, which, at first, is very dark, gradually becomes less so, till, towards the end of the bleed- ing, it shews nearly the same qualities as the arterial ; a phenomenon which, as is well observed by the English writer already quoted, depends on the more easy and rapid flow of the blood of the arteries into the veins, in consequence of the evacuation of the venous system. This observation is a complete refutation of the assertion of Bellini, who maintains, that when a vein is wounded, the blood which comes from it forms a double current, which flows out at the wound. The above opinion is maintained by highly distin- guished physiologists, as Haller and Spallanzani, who support it by experi- ments performed on the vessels of cold-blooded animals, or on veins without valves. In bleeding at the bend of the arm, the blood cannot come from that part of the vessel which is above the wound; the valves oppose insuperable obstacles to its retrograde flow : hence it is very easy to distinguish the red blood which comes from the lower extremity of the vein from that which flows from the upper end, and which is poured into the vessel by the veins which open into it, between the puncture and the nearest valve. 152 THEORY OF RESPIRATION. In its course to the parts among which the arteries are distributed, the blood, vivified in its passage through the lungs, and fitted, as M. Fourcroy says, for a new life, loses its oxygen and caloric. Its capacity for the latter diminishes in proportion as the oxygen, by combining with hydrogen and carbon, restores it to the venous state. This theory of the process by which the blood parts with its oxygen in its progress along the blood vessels, is rendered still more probable by recent dis- coveries on the nature of the diamond. This substance is the only pure car- bon, and that which is called so by chemists is an oxide of carbon, which owes its dark colour to the oxygen with which it is combined. Before these experiments, it was not easy to determine the particular condition of the car- bon which exists so plentifully in venous blood. No precise calculation has yet been made of the quantity of oxygen ab- sorbed by the venous blood, nor of the quantity employed in the combustion of hydrogen and carbon in the lungs, so as to form water and carbonic acid* Is the carbon in venous blood merely combined with oxygen, or is it united with hydrogen, so as to form carburetted hydrogen 1 It appears to me more probable, that the oxygen which is absorbed by combining with hydrogen in every part of the body produces the water which dilutes the venous blood, renders it more fluid and richer in serum than arterial blood, while, by its union with carbon, it forms an oxide that gives to the blood the dark colour which is one of its most remarkable characters. On reaching the lungs, which are real secretory organs, the water is exhaled, dissolved in the air, and forms the pulmonary transpiration ; the oxide of carbon, completely de- composed by an additional quantity of oxygen, constitutes carbonic acid, which gives to the air that is expired the power of forming a precipitate in lime water. The absorption of oxygen by the venous blood explains how the pheno- mena of respiration are continued into every part^ of the body, and produce the warmth uniformly diffused over all our organs. In proportion as the blood parts with its caloric, for which its affinity diminishes as it becomes venous, the parts which give out their hydrogen and carbon combine with it. If the lungs were the only organs in which caloric might be disengaged, the temperature of those viscera ought considerably to exceed that of other parts : experience, however, shews that the temperature of the lungs is not sensibly more elevated. This theory of respiration, for which we are entirely indebted to modern chemistry, is contradicted by no one phenomenon. The greater the extent and capacity of the lungs, the more frequent is respiration, and the greater the warmth and vivacity of animals. Birds, whose lungs extend into the abdomen by various membranous sacs, and whose bones are hollow and com- municate with the lungs, consume a great deal of oxygen, either on account of the magnitude of this respiratory apparatus, or from their frequent, and, at times, hurried respiration. On that account, the habitual temperature of their body exceeds that of man and mammiferous animals. In reptiles, on the contrary, whose vesicular lungs admit but a very small quantity of blood, and present to the atmosphere a surface of very limited extent, and in which respiration is performed with intervals of longer duration, the body is at a temperature which, naturally, never rises above seven or eight degrees. * Instead of saying that the venous blood ab- and absorbs a portion of oxygen, with a very sorbs oxygen, it will approach nearer the state variable proportion of az_ote. For a full view of of our knowledge to believe, that the venous the latest opinions on this subject, see Appbn- blood both gives off its carbon, which combines dix, Note W.—J. C. in the lungs with the oxygen of the inspired air, VITAL INFLUENCE OF THE LUNGS. 153 LXXVII. Of the vital influence of the lungs in the function of respiration.— Though the temperature or warmth of the body is generally proportioned to the extent of respiration, to the quantity of blood exposed in a given time to the action of the atmospherical air, it may be higher or lower, according to the degree of the vital energy of the lungs. These organs should not be considered as mere chemical receivers ; they act On the air, digest it, as the ancients said, and combine it with the blood, by a power which is peculiar to them.* If it were otherwise, there would be nothing to prevent a dead body from being restored to life, by inflating with oxygen its pulmonary tissue. The ancients alluded to this action of the lungs on the air we breathe, by calling that air the pabulum vita. Its digestion was, they thought, effected in the lungs, in the same manner as the digestion in the stomach of other aliments less essential to life, and whose privation may be borne for a certain time, while life is endangered when the aeriform nutriment ceases to be fur- nished to the lungs for the short space of a few minutes. In proof of the vitality of the lungs, and of the share which they have in producing the changes which the blood undergoes in passing through them, I may mention the experiment which proves that an animal placed under a vessel filled with oxygen, and breathing that gas in a pure state, consumes no more of it than if it was received into the chest mixed with other gases unfit for respiration. A guinea-pig placed under a vessel full of vital air, and of known capacity, will live four times longer than if the ves- sel contained atmospherical air. No remarkable difference is at first perceived in the act of respiration, but if the animal remains long immersed in the oxygen, his respiration becomes more frequent, his circulation more rapid, and all the vital functions are executed with more energy. The lungs se- parate, by a power inherent in themselves, the two atmospherical gases, and this process is effected by a pretty considerable power; for oxygen, in its combination with the blood, is with difficulty separated from azote. In fact, the blood, though in thin layers, becomes dark when exposed to the atmo- spherical air. It is observed, that the purity of the air contained in the receiver is the more readily affected, as the animal placed under it is younger, more robust, and as his lungs are more capacious. Hence birds, whose lungs are very large, contaminate a considerable quantity of air, and consume more quickly its re- spirable part. A frog, on the contrary, will remain a considerable time in the same quantity of air, without depriving it of its oxygen. The vesicular lungs of that reptile, as well as of all oviparous quadrupeds, are much more irritable than those of warm-blooded animals ; they appear to contract at the will of the animal. The frog is without a diaphragm, at- tracts the air into its lungs by swallowing it by a real process of deglutition, as was proved by Professor Rafu, of Copenhagen, who killed those animals by holding their jaws asunder for a» certain time. They reject the air by a contraction of the lungs, in the same manner as in man the bladder empties itself of urine. In birds, whose diaphragm is equally membranous, and contains several openings to transmit the air into the pulmonary appendices, the parietes of the thorax are likewise more movable than in man and quadrupeds. Their pectoral muscles are more powerful, their ribs contain a joint situated in the middle of those arches which are completely ossified in that class of animals : and those two portions move on each other, forming, at their point of union, angles more or less acute, according to the distance of the sternum from the vertebral column. * Sec Appendix, Note W -20 154 VITAL INFLUENCE OF THE LU.NOS A numerous class of cold red-blooded animals, viz. fishes, have no lungs ; the gills, which supply their place, are small penniform lamina1, generally four in number, situated on each side, at the posterior and lateral part of the head, covered over by a movable lid, to which naturalists give the name of operculum. The water which the animal swallows, passes, when it chooses, through the parietes of the pharynx, which contain several pretty consider- able openings, is spread over the gills and the pulmonary vessels which are distributed in them, then escapes at the auricular apertures, when the animal closes its mouth and raises the opercula. It is not known whether the water is decomposed and yields its oxygen to the blood which circulates in the gillsr or whether the small quantity of air that is dissolved in the water, alone serves to vivify the pulmonary blood. The latter opinion seems the most pro- bable, if it be considered that a fish may be suffocated by closing accurately the vessel of water in which it is enclosed. The same result might, I con- ceive, be obtained, by placing the vessel under the receiver of an air-pump, so as entirely to exhaust it. Respiration, which is completely under the influence of the brain, as far as relates to its mechanism, is less dependent upon it in regard to the action of the lungs on the blood, and the combination of this fluid and of its carbo- naceous elements with oxygen, which is the essential object of that function. The nerves, however, have gome influence on the changes which the blood experiences in the lungs during respiration, as well as on the various secre- tions, in the formation of which, according to Bordeu, they are of first-rate importance. M. Dupuytren ascertained by his experiments, that the divi- sion of the cervical portion of the eighth pair of nerves did not sensibly affect respiration; but the animal died with all the symptoms of asphyxia when this nerve was divided on both sides. Death took place in the course of a few minutes, when the experiment was performed on horses. Other animals did not die so soon after; dogs, for instance, have been known to live several days after the experiment. By interrupting the communication between the lungs and the brain, we paralyse the former of these organs, and it ceases to convert the venous into arterial blood.* This fluid, conveyed by the pul- monary artery, continues of a dark colour when brought to the left cavities of the heart; the arteries convey the blood without its having received its vivifying principle, in passing through the lungs, which are paralysed by having their nerves tied or divided. It is easy to conceive that all organs, for want of the stimulus which determines their action, carry on their functions imperfectly, and at last cease to act. The animal heat is likewise lowered a few degreesl as was ascertained by the above-mentioned physician, who thinks he has established as a fact, that the ligature of the nerves of the lungs does not destroy, but weakens the vital power, which enables them to take up the oxygen, and to give out the carbonic acid. The brain, therefore, possesses a double influence over the function of respiration ; on the one hand, it directs its mechanism by means of the nerves which it sends to the dia- phragm and to the intercostal muscles ; and on the other hand, it is through the nerves which arise from the brain, that the lungs have the power of con- verting dark blood into arterial blood, which is the principal phenomenon of respiration* Experiments performed on the same subject by Dr. Legallois, subsequent to those I have just related, tend to throw some degree of uncertainty on their results. Dr. Legallois repeated these experiments publicly, in my pre- * By dividing these nerves (the eighth pair) renewal of the air,—but we do not directly in- we paralyse the muscles of respiration, and oc- jure the vital functions of the lungs themselves ca$ion a species of asphyxia. We prevent the —J. C. OF ANIMAL HEAT. 155 sence, and at the society of the Ecole de M<;decine of Paris. After dividing the two nerves of the eighth pair, in a guinea-pig, and after having by that process brought on a state of asphyxia, he restored life and motion to the ani- mal by opening the trachea at its anterior part. The blood of the carotids, which from red had become dark the moment the nerves were divided, as- sumes a brighter colour as soon as respiration is restored, and the animal lives several days after the experiment. Whence does this difference arise % ■does the division of the eighth pair bring on asphyxia, by occasioning spas- modic constriction of the glottis, and by impeding or even completely ob- structing, the admission of the atmospherical air 1* LXXVIII. Of animal heat.—The human body, which is habitually of a temperature of between thirty-two and thirty-four degrees of Reaumur's thermometer, f" preserves the same degree of warmth under the frozen climate of the polar region, as well as under the burning atmosphere of the torrid zone, during the most severe winters and the hottest summers. Nay, further, the experiments of Blagden and Fordyce in England, and of Duhamel and Tillet in France, shew, that the human body is capable of enduring a degree of heat sufficient to bake animal substances. The fellows of the Academy of Scien- ces saw two girls enter into an oven in which fruits and animal substances were being baked ; Reaumur's thermometer, which they took in with them, stood at 150 degrees ; they remained several minutes in the oven without suf- fering any inconvenience. All living bodies have a temperature peculiar to themselves, and independent of that of the atmosphere. The sap of plants does not freeze, when the ther- mometer stands only at a few degrees below zero ; on placing the bulb of a „ thermometer in a hole in the trunk of a tree during winter, the fluid sensibly rises. Now, three circumstances remain to be investigated : in the first place, what produces in living bodies this inherent and independent temperature ? In the second place, how do these bodies resist the admission of a greater de- gree of heat than that which is natural to them? What prevents calorie, which has a perpetual tendency to a state of equilibrium, from passing into a body surrounded by a burning atmosphere ? Lastly, how does a body which resists the influence of heat, withstand equally the destructive influence of an excessive degree of cold ? J LXXIX.—Caloric, in a latent state, or in combination with bodies, is dis- engaged from them, whenever they assume a different state; when, from a gaseous form they become liquid ; or when from being liquid they become solid. Now, living bodies are a kind of laboratory, in which all these chan- ges are perpetually going on ; the blood which circulates in every part of the human frame is constantly receiving supplies of fresh materials; from the thoracic duct, which pours into it the chyle, abounding in nutritious particles ; from respiration, which imparts to it an aeriform principle, obtained from the atmosphere ; and even, in some cases, from cutaneous absorption, through which different elements are received into it. All these different substances carrying along with them into the blood a certain quantity of caloric, which is combined with them, and which is disengaged during the changes which they undergo, from the influence of the action of the organs, and gives out its caloric to the parts among which it is disengaged. Of all the principles in the blood which have the power of communicating heat to the organs, none furnishes a greater quantity than oxygen, which, during respiration, combines with the blood in the lungs. Gaseous substances, it is well known, contain most combined caloric ; their state of elastic fluidity is entirely owing * Sec Appendix, Note W. % See the remarks in Appendix, Note Y, ! Between 96 and 98 of Fahrenheit. on the production of Animal Heat, 15G OF A MIMA I. MEAT. to the accumulation of that principle, and they part with it, when from any cause whatever they become liquid. It is on that account that the heat of bodies is greater, the more they have the power of impregnating their fluids with a considerable quantity of oxygen from the atmosphere. For the same reason, as was already observed, in animals that have cellular lungs, and a heart with two ventricles, the blood is of the same temperature as in man ; and such animals belong, as well as man, to the great class of warm red- blooded animals ; a class in which birds occupy the first plaGe, from the vast extent of their lungs, which reach into the abdomen, and communicate with the principal bones of the skeleton. The capacity of the pulmonary organ of birds is not the only cause why their temperature is eight or ten degrees higher than that of man : this increase of temperature depends, likewise, on the greater frequency of their respiration, and on the velocity of their pulse ; on the quickness and multiplicity of their motions, and on the vital activity which animates them. In reptiles, which have vesicular lungs, and a heart with a single ventricle, whose respiration is slow, and performed at distant intervals, the blood, though red, is of very inferior temperature to that of man. They have, from that circumstance, been called cold red-blooded animals : this numerous class includes fishes, which possess an organ supplying but imperfectly the office of lungs. In fishes, the heart, which has but a single ventricle, sends, it is true, to the gills (the organ supplying the place of lungs is so called) the whole of the blood ; that fluid, however, is but imperfectly vivified in the gills, on account of the small quantity of air which can be taken in during the act of respiration. Lastly, in white-blooded animals and in plants, the combinations with the air being more difficult, the vital energy less marked, the temperature differs only by a few degrees from that of the atmosphere, and they do not endure heat or cold so well as the* more perfect animals. The lungs, as was before observed, consuming only a certain quantity of air, there is no increase of temperature, however great the quantity of oxygen contained in the atmosphere that is breathed ; as a man who should take a double quantity of aliment could not receive more nourishment than if he contented himself with the quantity of food proportioned to his wants ; for, as the digestive organs can extract only a certain quantity of chyle, the quantity of recrementitious matter would only be greater, if more than the due quantity of food were received into the stomach. Hence the common saying, that nourishment comes from what we digest, and not from what we eat. The pulmonary organ may, however, act on the air with different degrees of power in robbing it of its oxygen ; and when the body becomes of an icy coldness, in certain nervous and convulsive affections, this cold may depend as much on the atony of the lungs, and on the spasmodic condition of the chest, which, dilating with difficulty, does not admit the air readily, as on the 6pasm and general insensibility of the organs, which allow the blood to pass without affecting its component parts. It would be curious to ascertain, whether or no the air expired from the lungs of a cataleptic is deprived of less oxygen, is less impaired in purity, and contains a smaller quantity of car- bonic acid, than the breath of a sound active adult. Perhaps it would be found, that in catalepsy, and other similar affections, the blood does not part with its hydrogen and carbon, that it retains its colouring principles and the different materials of the urine, which is voided in a colourless and limpid state, insipid and without smell, and in the condition of a mere serosity. The temperature of the body is not only produced by the pulmonary and circulatory combinations, it is besides developed in several organs, in which of animal Heat. 157 fluid or gaseous substances become solid, by parting with a portion of their caloric. Thus, digestion, particularly of certain kinds of food* is an abun- dant source of caloric ; the skin, which is habitually in contact with the atmosphere, decomposes it, and deprives it of its caloric. Lastly, caloric is produced and evolved in all parts whose molecules, affected by a double mO' tion, in consequence of which they are incessantly being formed and decom- posed, by changing their condition and consistence, absorb or disengage more or less caloric. The great activity of the power of assimilation in children is, no doubt, the cause of the habitually high temperature at that period of life.* The'temperature of the body is not only one or two degrees higher at that period of life, but young people, after death, preserve, for a longer period, the remains of vital heat ; or rather, as tonicity does not so soon forsake the capillary vessels, life departing reluctantly, the combinations from which caloric is evolved continue some time, even after it is extinct. For the .same reason, the bodies of persons that have died suddenly retain their warmth long, while an icy coldness seizes those who have died of a lingering disease, from the slow, gradual, and total abolition of the powers of life. Calorification, or the disengaging of animal heat, like nutrition, takes place at all times, and may be considered as belonging to all organs. It was of the utmost consequence that the internal temperature of the human body should be nearly the same at all times. For, let us for one moment suppose, that the temperature of the blood should rise to fifty degrees of Reaumur's thermometer, its albuminous parts would suddenly coagulate, obstruct all the vessels, interrupt the circulation, and destroy life. When, therefore, from an increased activity of the nutritive combinations, a greater quantity of heat is disengaged, the animal economy parts with it, and it is taken up in greater quantity by the surrounding bodies. This accounts for the equality of the temperature of the internal parts of the body in old people and in children, notwithstanding the difference of their temperature externally. The differ- ence consists in this, that where most caloric is produced most is given out, and though the blood and urine in old people, as well as in the young, are at thirty-two degrees, what a difference is there not between the .hot and pene- trating perspiration which is poured in abundance from the child, and the dryness and coldness of the skin in old people ! between the sweet and warm breath of the former, and the frozen breath of the latter % Hence the opinion so generally received, and of such antiquity, that old people are benefited by cohabiting with the young. Thus we are told, that David had a young virgin brought to him, that he might lie with her, and get heat in his limbs that were stiffened with years.f If it be true, that in the very act of nutrition, which converts our fluids in- to solids, there is disengaged a considerable quantity of caloric, the motion of nutritive decomposition, by which our solids are converted into liquids, must cause an equal quantity of heat to be absorbed. The objection is a very strong one, and not easily got over : it may be answered by observing, that all living bodies, from the instant of their formation, contain a certain quantity * Considering the temperature of the body well as these, seems equally to tesult from the to be under the influence of that part of the ner- influence of these nerves upon the vessels to vous system which is distributed to the blood- which they are distributed.—J. C. vessels, as pointed out in the note on this sub- t The ancients appeared to have some idea ject in the Appendix, the reason will appear of what the moderns would do well to attend to evident, why animal warmth is greater in young more than they have done, if, indeed, they have and robust subjects, than in the old and debili- attended to it at all, namely, the beneficial in- tated. Indeed, the temperature holds a close fluence of the application of animal warmth to relation with the other changes which take place the system when its vital influence is either Ian- in the different textures of the body ; and it, as guid or sinking.—/. C. 158 OF ANIMAL HEAT. of caloric, which they retain, so that this double process of acquiring heat and parting with it, the unavoidable result of nutritive composition and de- composition, merely keeps up an equilibrium, and maintains the same degree of temperature. The blood, which becomes saturated with oxygen in the capillaries of the lungs, parts with that principle, and disengages its caloric throughout the capillary vessels of the whole body, of which' each organ must set free a greater -quantity, in proportion to the activity of the living principle, and to the rapidity of the circulation. The parts through which the greatest num- ber of vessels circulates, perhaps, give out most caloric, and communicate a portion of it to the organs which receive but a small quantity of blood, as the bones, the cartilages, &c. It is easy to understand why an inflamed part, through which the blood circulates with more rapidity, and whose sen- sibility and contractility are much increased, is manifestly hotter to the feel of the patient and of the physician, though, as was observed by John Hunter, a thermometer applied to the inflamed part shews a scarcely perceptible in- crease of temperature. He injected into the rectum of a dog, and into the vagina of an ass, a strong solution of oxymuriate of mercury. Acute inflam- mation came on, the swollen mucous membrane formed, externally, a con- siderable projection. Blood flowed from the torn capillaries, yet the thermo- meter rose very slightly, only one degree of Fahrenheit. But however slight that increase of heat in the inflamed part, it is very sensibly felt, on account of the extreme sensibility of the organ, whose vital properties are all increased. The liveliness of impressions being proportionate to the degree of the power of sensation, one need not wonder that the patient should experience a sense of burning heat in a part in which the thermometer indicates no increase of temperature, or in which it cannot be perceived even by the touch. I have just felt a young man's hand that is swollen from chilblains ; though the pain which he feels in it seems to him to be occasioned by an accumulation of caloric, his hand is colder than mine, which is of the same degree of warmth as the rest of my body, and in which I have no peculiar sensation. It may, therefore, be laid down as an axiom, that the real or thermometrical increase of heat is inconsiderable in inflammation, but that it is intensely felt in consequence of the increase of sensibility.* What is the reason that, during the cold fit of a febrile paroxysm, a sensa- tion of excessive cold is felt in a part in which no diminution of heat can be discovered by the touch 1 Whence comes the burning heat which attends inflammatory fever (causus) % What is the cause of the difference of the sensations attending the heat of erysipelas, bilious fevers, and phlegmon, &c. ? These various sensations are owing to the different modifications of sensibility in these different diseases. Should this explanation appear unsatisfactory, let it be recollected, that however accurate may be the calculations that have been made on the subject of caloric, or of the matter of heat, the existence of caloric itself is hypothetical, and that it is not known whether caloric is a body, or whether heat is merely a property of matter. LXXX. Of the causes enabling the body to resist increased temperature.—If we now inquire into the causes which enable the body to resist the admission of a degree of heat superior to that which habitually belongs to it, we shall be compelled to admit a power in all living bodies, by means of which they repel an increase of heat, and retain the same temperature. Cutaneous perspiration, it is true, acts very powerfully in lowering the temperature • and as this evaporation increases with the temperature, it should seem as if * For some remarks on the Influence of the Nervous Svstcm in the production of Animal Heat, see Appendix, Note Y. OF ANIMAL HEAT, 159 this function sufficed to moderate the heat of the body, and to restore the equilibrium. It is a fact known since the time of Cullen * that the evaporation of fluids, or their solution in the air, is the most powerful means of cooling bodies, and that the mercury in the bulb of a thermometer may be frozen merely by moistening it with aether, spirits of wine, or any other volatile substance, and then exposing it to a dry and warm air. This method is equally suc- cessful in its application to the human body, and the hands may be cooled to such a degree as to feel benumbed, by being frequently wetted with a spirituous fluid, and by being moved in a dry and renewed air. But though cutaneous perspiration operates in a somewhat similar manner, and though it may be ranked among the means which nature employs to preserve the animal temperature in a nearly uniform state, it must, however, be confessed, that it is not the only way in which this object is accomplished, and that it does not satisfactorily account for this phenomenon; for, the evaporation of the fluids contained in dead animal substances does not prevent their being roasted on the application of heat; and besides, fishes and frogs have been known to live and retain their temperature in mineral waters nearly of a boiling heat."j" I thought it right to repeat these experiments, and with this view, I placed living frogs in a vessel containing water at fifty degrees of temperature, and on taking them out, at the end of ten minutes, I ascertained that they were not so hot as the liquid, nor as pieces of flesh which had been put into it at the same time. We cannot admit the opinion of Grimaud, that living bodies have the power of producing cold ; for as cold is merely the absence of heat, one cannot allow a positive existence to a negative being. Habit has a remarkable influence on the faculty which the body possesses of bearing a degree of heat much exceeding that which is natural to it. Cooks handle burning coals with impunity ; workmen employed in forges leave the mark of their feet on the burning and liquid metal at the moment when it becomes solid by cooling. Many, no doubt, recollect the too famous instance of a Spaniard, who became so general a subject of conversation in Paris : this young man, in making his way through a house on fire, per- ceived that the heat was less inconvenient to him than he had imagined. He applied himself to bear, with impunity, the action of fire, and was enabled to touch with his tongue a spatula heated red hot, and to apply the soles of his feet and the palms of his hands on a red hot iron, or on the surface of boil- ing oil. Nothing can equal the absurdity and the exaggeration of the stories that were told of this man, except the ignorance and the want of veracity of those who invented them. The following is a correct statement of the feats of this man, who was represented as incombustible and insensible. He passes rapidly along the surface of his tongue, which is covered with saliva, a red-hot spatula, the action of which seems merely to dry it,, by bringing on an evaporation of the fluids with which it is covered. After carrying the spa- tula from the base to the tip of his tongue, he brings it back- again into his mouth, and-applies it to his palate, to which it communicates a part of its heat, at the same time that it becomes moistened with saliva. This man having, in a public exhibition, carried on too long the application of the spatula, * This celebrated physician made this dis- fluids, and of some other means of producing covery about forty years ago, which has thrown cold,"^ by Dr. W. Cullen. much light on several physico-chemical pheno- t See Sonnerat's "Voyage to the East In- mena, and he published it in a dissertation, en- dies." titled, " Of the cold produced by evaporating 160 OF ANIMAL HEAT. the caustic effects of its heat shewed themselves ; the epidermis was de- tached, and found coiled, like the outer covering of an onion, in the cloth which he used to wipe his mouth. He does not dip his hands and feet in boiling oil, he merely applies to the surface of the fluid his palms and his soles, and he repeats this frequently, with only a short interval between each application. When the experiment is carried on for a certain length of time, there is emitted a smell of burnt horn. No one has yet observed, that though this man's hands are not callous, the palms of these, and the soles of his feet, are cushioned with fat. A thick layer of fat, which is a bad conductor of heat, separates the skin from the subjacent aponeuroses and nerves : this circumstance, to a certain degree, accounts for his imperfect sensibility. His pulse, during those experiments, was about a hundred and twenty ; the perspiration evidently increased, and sometimes copious. Every part of his body possesses the ordinary degree of sensibility, may be destroyed by the protracted application of caustic substances, and would be consumed by fire, if applied for a sufficient length of time ; and nitric acid would infallibly de- stroy his tongue, if he took any into his mouth, as it has been said he did. This man, therefore, in no one respect departs from the known laws of the animal economy, but, on the contrary, affords an additional proof of the in- fluence of habit on our organs* LXXXI. Causes enabling the body to resist cold.—Before bringing to a con- clusion this article on animal heat, it remains for me to explain how the body resists cold, and preserves its temperature in the midst of a frozen atmosphere. This cannot be accomplished without an increase of activity in the organs ; it is only by augmenting the sum of the combinations by which caloric is dis- engaged, that we can succeed in making up for the loss of that principle so necessary to our existence. What is the reason that in cold wTeather diges- tion is more active, (Hieme verb ventres sunt calidiores, Hipp.) the pulse strong- er and more frequent, and the vital energy greater ? It is because heat comes from the same source, and is produced by the same mechanism, as the nutrition of the organs ; and that its evolution may go on increasing, it is necessary that the secretions, nutrition, in a word, all the vital functions, should increase in the same proportion. Observe, for a moment, a man who is exposed to a moderate degree of cold ; he feels more activity, more strength, and is more nimble ; he walks and exerts himself, the most violent exertions do not appear to him laborious, he struggles against the disadvantages of the debilitating influence ; and pro- vided the cold is not excessive, and the body tolerably vigorous, there is disengaged within himself a sufficient quantity of caloric to make up for the loss of that which is carried off by the air and the surrounding bodies. These general effects of cold are not disproved by what happens, when only a part of the body is exposed to it. Supposing the temperature a few degrees below zero, there is felt, at first, a sensation of cold much more inconvenient, cateris paribus, than if it acted on a more extensive surface. The spot on which the cold air acts becomes affected with a painful sense of pricking, reddens, then inflames ; and in this case, inflammation is evidently the result of a salutary effort of nature, which determines into the inflamed part an excess of the vital principle, so that the quantity of heat that is disengaged may correspond to that which has been abstracted. The effort of this conserva- tory principle is more marked than if the whole surface of the body were at once exposed to cold, because, acting wholly on a limited point, of small ex- tent, it operates with more intensity. * Theie is every reason to believe that these previously applied to the parts about to be ex- feats are performed by means of a composition posed to the high tempciature.—J. C. SANGUIFYING FUNCTION OF THE LUNGS. 161 Beyond a certain degree, however, nature in vain struggles against cold ; if severe, and if the creature exposed to it have not the power of sufficient re- action, the part becomes purple and benumbed from the loss of its caloric, vitality ceases, and it mortifies; and if the whole body is equally exposed to the influence of cold, the person is benumbed, feels a stiffening of his limbs, stammers, and, overpowered by an irresistible propensity, yields to a sleep which inevitably ends in death. By yielding thus to the illusive sweets of a perfidious sleep, many travellers have perished, after losing their way, in the mountains of the old and of the new world. Thus, two thousand soldiers of Charles the Twelfth's army perished, during a siege, in the severe winter of 1790. To resist the effects of cold, a certain degree of strength and vigour is there- fore necessary ; it is consequently very injudicious to recommend the cold bath to very young children, to delicate and nervous women, to persons whose constitution is not capable of a sufficient re-action. The evil attending the injudicious use of this remedy in the cases that have just been enumerated, justifies the apparently singular terms in which Galen expressed himself: " Let the Germans (says this first of physiologists), let the Sarmatians. those northern nations as barbarous as bears and lions, plunge their children in frozen water; what I write is not intended for them." On the other hand, if it be recollected that there is within us a power of re- action which increases with use, that motion strengthens our organs, it will be readily understood that cold acts as a tonic, whenever it is not applied to such a degree as to extinguish the vital power. The.manner in which enlightened physicians have, at all times, prescribed the cold bath, shews that they were acquainted with this tonic effect, depend- ing, not on the application of cold, which in itself is debilitating, but on the re-action which it occasions. Hence, along with the cold bath, they are in the habit of recommending exercise, a generous wine, bark, nutritious food, and an analeptic regimen, calculated to excite a salutary re-action. LXXXII. Source of animal heal.—Animal heat is, therefore, produced by the combinations of our fluids and solids in the process of nutrition ; it is a function common to all the organs, for, as they all nourish themselves, so they all disengage, more or less, the caloric combined with the substances which they apply to their nutrition. , Though we are without precise information respecting the manner in which a living body resists the admission of a degree of heat exceeding that which is natural to it, one may consider cutaneous exhalation, which is increased by the use of heating substances, as the most powerful means employed by na- ture to get rid of the excess of heat, and to restore the equilibrium. Lastly, the body resists cold, because the organs being rendered more ac- tive by cold, there is disengaged a quantity of caloric equal to that which is carried off by the air, or ~by the other substances with which the body hap- pens to be in contact.* LXXXIII. Sanguifying function of the lungs.—The rapidity of the circu- lation of the blood through the lungs, is equal to the velocity with which it flows in the other organs. For if, on the one hand, the parietes of the right ventricle and of the pulmonary artery are weaker and thinner than those of * The animal economy resists a moderate operation. The effects of cold differ not only degree of cold, and is even strengthened by it, according to its degree, but also according to owing to the re-action of the vital influence, the duration of exposure to it, to the state of the If, however, the degree of cold be either abso- nervous system previous to, or during the ex- lutely or relatively great, the energy of the sys- posure, and to the general condition of the body tern is entirely overwhelmed by its sedative at the time.—/. C. 21 162 OF PULMONARY EXHALATION. the left ventricle and aorta, the lungs, from their soft, easily dilated, and spongy texture, are the most easily penetrated by fluids of all our organs. The right ventricle sends into the lungs a quantity of blood equal to that which each contraction of the left ventricle propels into the aorta, and it is not necessary to adopt the opinion of M. Kruger, that each contraction of the heart propels into the lungs, and into the rest of the body, an equal quantity of blood ; for, in that case, the circulation would have been much slower, the length of the lungs being much shorter than the whole body. Nor need we say, with Boerhaave, that this circulation is much more rapid, because the same quantity of blood returns by the extremities of the pulmonary artery, and of all the other arteries of the body. The extension of the pulmonary tissue, and the straightening of its vessels, are, no doubt, favourable to the circulation of the blood, but if the admission of air did not answer a different purpose, the circulation would not be indispen- sably necessary. The blood flows from the right into the left cavities of the heart, notwithstanding the collapse of the lungs, and the creases of their ves- sels. The air which penetrates, at all times, into the lungs, supports their tissue and the vessels which are distributed to it; so that, even during expi- ration, the vessels are much less creased than has been imagined by several physiologists. But the changes produced by the contact of the atmosphere, renovate this fluid, and fit it to re-excite and keep up the action of all the or- gans which require to be stimulated by arterial blood. If you make a living animal breathe de-oxygenated air, the blood undergoes no change by its pul- monary circulation; the left cavities of the heart are no longer duly irritated by this fluid, which preserves all its venous qualities; their action becomes languid, and with it that of all the organs ; and in a little while it ceases al- together. It is revived by introducing pure air, through a tube fitted to the trachea; all the parts seem to awake out of a sort of lethargic sleep, in which they are again immersed by depriving the lungs anew of the vital air. The chyle, mixed in great quantity with the venous blood, undergoes, in its passage through the heart and the sanguineous system, a more violent agitation: its molecules are struck together, break on each other, and, thus attenuated, become more perfectly intermingled : in its passage through the lungs, a great part of this recrementitious fluid is deposited by a sort of inter- nal perspiration, in the parenchymatous substance of these viscera. Oxydat- ed by the contact of the air, and re-absorbed by a multitude of lymphatic or inhalant vessels, it is carried into the bronchial glands, which are found black- ened by what it there deposits of carbonic and fuliginous matter. Purified by this elaboration, it returns into the thoracic duct, which pours it into the sub- clavian vein, whence it soon returns to the lungs, to be there anew sub- jected to the action of the atmosphere; so that there is effected, through these organs, a real lymphatic circulation, of which the object is to bring the chyle to a higher degree of animalisation. LXXXIV. Of pulmonary exhalation.—It will be remembered that one of the great differences between the blood of the arteries and that of the veins consists in the great quantity of serum found in this last. It is in the lungs that the separation of this aqueous part takes place and that its proportion is reduced, whether it be that oxygen gives albumen and gelatine a greater ten- dency to concrete, or that the serum, formed by the fixation of oxygen ' throughout the whole extent of the circulatory system, exhales from the arteries, and thus furnishes the matter of pulmonary exhalation. It is scarce- ly possible to admit the combination of oxygen with the hydrogen of the ve- nous blood, and that water is thus formed from its elements, as happens when storms are gathering in the high regions of the atmosphere. If a similar pro- ASPHYXIA FROM DROWNING. 163 cess can be carried on in the lungs without producing deflagration and the various phenomena attending the production of aqueous meteors, it is pro- bable that it furnishes but a small part of the exhalation ; and that this hu- mour, analogous to the serum of the blood, exhales, completely formed, from the arterial capillaries ramified in the bronchia and the lobular tissue of the lungs. It is believed that the quantity of the pulmonary exhalation is equal to that of the cutaneous exhalation (four pounds in twenty-four hours). These two secretions are supplemental to one another; when much water passes off by the pulmonary exhalation, the cutaneous is less, and vice versa. . . The surface from which the pulmonary exhalation is given out, is equal, if not superior, in extent to that of the skin ; exhalation and absorption are^ at once carried on from that surface, many nerves are distributed to it, and are almost exposed in the tissue of the membranes, which are extremely thin. Are the miasmata, with which the atmosphere is sometimes loaded, absorbed by the lymphatics, which, it is well known, have the power of taking up gaseous substances ; or do they merely produce on the nervous and sensible membranes of the bronchia, and of the lobular tissue, the impression whence the diseases of which they are the germ arise 1 A part of the caloric which is disengaged in the combinations which oxygen undergoes in the lungs, is taken up in dissolving and reducing into vapour the pulmonary exhalation, which is the more abundant according as respiration is more complete. Pulmonary exhalation should be carefully dis- tinguished from the mucous matter secreted within the bronchia and trachea, and which is thrown up by a forcible expiration, and forms the matter which we expectorate. LXXXV. Of asphyxia*—-The term asphyxia, though merely indicating a want of pulse, is applied to any kind of apparent death occasioned by an external cause, and suspending respiration, as submersion, strangulation, the diminution of oxygen in the air inhaled, &c. The only difference between real death and asphyxia is, that in this last state the principle of life may yet be re-animated, whilst in the other it is completely extinct. Asphyxia takes place in drowning, because the lungs, deprived of air, no longer impart to the blood which passes through them the qualities essential to the support of life. The water does not find its way into these viscera ; the spasmodic closing of the glottis prevents its getting into the trachea and its branches. Yet there is found a small quantity in the bronchia after drowning, always frothy, because air has mixed with it, in the struggles which precede asphyxia. If the body remaining under water, the spasmo- dic state of the glottis ceases, water passes into the trachea and fills the lungs. The anatomical examination of a drowned body shews the lungs collapsed, and in the state of expiration ; the right cavities of the heart, the venous trunks which terminate in them, and, generally, all the veins, are gorged with blood,f whilst the left cavities and the arteries are almost entirely empty. Life ceases in this kind of asphyxia, because the heart has sent to the dif- ferent organs, and especially to the lungs, no blood that is not deficient in the qualities necessary to their action ; and, perhaps, also, because the venous blood that is accumulated in the tissues, affects them by its oppressive and deadly influence. On that account, the best way of restoring the drowned to life is to blow pure air into their lungs. This is done by means of bellows adapted to a canula introduced into the nostril; if a proper apparatus can- * See Appendix, Note W. quently injected with dark blood; the very deli- t Hence the dark and livid colour of the skin cate veins of the brain are considerably dilated, and conjunctiva. This last membrane is fre- and this viscus is distended with venous blood. 164 ASPHYXIA FROM HANGING AND INEBRIATION. not be procured, one might blow with his mouth into that of the drowned person, or into his nostrils, by means of a tube ; but air so expired, having already undergone the process of respiration, contains a much smaller quan- tity of oxygen, and is much less fitted to excite the action of the heart. 1 here remain several other less efficacious remedies, such as friction, broncho- tomy, glysters, fumigations and suppositories, stimulating errhines, and es- pecially ammonia ; stimulants taken into the mouth and stomach, the appli- cation of fire, bleeding, the bath, electricity, and galvanism. The redness and lividity of the face in persons who are hanged, had led to the opinion, that death, in such cases, was from apoplexy; but it appears that in the asphyxia from strangulation, as in that from drowning, death is caused by the interception of the air. To prove this, Gregory performed the following experiment: he opened the trachea of a dog, and passed a noose round his neck, above the wound. The animal, though hanged, con- tinued to live and to breathe ; the air entered and came out alternately, at the small opening: he died when the constriction was applied below the wound. A respectable surgeon, who served in the Austrian army, assured me, that he had saved the life of a soldier, by performing upon him the opera- tion of laryngotomy a few hours before his execution. Persons who are hanged may die, however, from dislocation of the cer- vical vertebrae, and from the injury done at the same time to the spinal marrow. Louis, it is well known, ascertained, that of the two executioners in Lyons and Paris, the one despatched the criminals he executed by dislocat- ing the head at its articulation with the neck, while the other executioner destroyed them by inducing asphyxia. Of the different mephitic gases unfit for respiration, some appear to bring on asphyxia, merely by depriving the lungs of the vital air necessary to the support of life, while others evidently affect the organs and the blood which fills them, by their poisonous and deleterious influence. One may mention, among the former, carbonic acid : in the asphyxia oc- casioned by this gas, and which, of all others, is the most frequent, the blood preserves its fluidity, the limbs their suppleness, and the body its natural warmth, or even a greater degree of warmth, for some hours after death ; for, this kind of asphyxia occurring always in a very hot situation, the body, deprived of life, admits an excess of caloric, such as would have been re- sisted if the vital power had not been suspended. However, in this asphyxia, as in the preceding, the lungs remain uninjured; the right cavities of the heart and the venous system are gorged with a dark but fluid blood. In the asphyxia, on the other hand, that is occasioned by sulphuretted or phos- phuretted hydrogen, &c, or by certain vapours whose nature is not well understood, and which escape from privies, or from vaults in which a number of dead bodies undergo putrefaction; there are frequently found in the lungs dark and gangrenous marks, and death seems the effect of a poison which is the more active, as its particles, exceedingly divided and in a gaseous state are more insinuating, and affect, throughout its-whole extent, the nervous and sensible surface of the lungs. Inebriation seldom goes the length of bringing on asphyxia; it most com- monly produces a stupor readily distinguished from the affection treated of in this article, by the perceptible, though obscure pulse, and by the motions of respiration, though these are rare and distinct. On this account, M. Pinel in his Nomographic Philosophique, has placed inebriation, and the different kinds of asphyxia, in two separate genera of the class neuroses. It is con- ceivable, however, that the muscular irritability may be so far impaired by the OF SIGHING, SOBBING, YAWNING, &C. 165 use of spirituous liquors, that the heart and diaphragm might lose the power of contraction, which would bring on complete asphyxia. The glottis, through which the atmospherical air passes in its way to the lungs, is so small, that it may be readily obstructed, when the epiglottis rising at the moment of deglutition, the substance that is swallowed stops at the orifice of the larynx: a grape seed may produce this effect; and it was in this manner, we are told, that Anacreon, that lovely poet of the graces and of voluptuousness, came by his death. Gilbert, the poet, died in the same way, after a long and painful agony. A great eater, in the midst of a feast went into an adjoining room, and did not return, to the great surprise of all the guests. He was found stretched on the floor, without any sign of life. Help, given by ignorant people, was of no use. On opening the body, a piece of mutton was found fixed in the larynx, and completely stopping the passage of the air. Sometimes a child is born, and shews no signs of life. When it is proba- ble, from the circumstances of the delivery, that there has been no organic injury decidedly mortal, it must be considered as a case of asphyxia from weakness; and all means employed that are recommended in such cases, especially blowing in air into the lungs, by means of a tube introduced into the mouth or nostrils. It is thus that the Prophet Elisha restored to life the son of the Shunamite, as we are informed in the second book of Kings, chap- ter the fourth. LXXXVI. Of certain phenomena of respiration, as sighing, sobbing, yawning, sneezing, coughing, hiccup, laughing, fyc.—When the imagination is strongly impressed with any object, when the vital functions are languid, the vital principle seems to forsake all the organs, to concentrate itself on those which partake most in the affection of the mind. When a lover, in the midst of an agreeable reverie, sighs deeply, and at intervals, a physiologist perceives in that expression of desire, nothing but a long and deep inspiration, which, by fully distending the lungs, enables the blood collected in the right cavities of the heart to flow readily into the left cavities of that organ. This deep in- spiration, which is frequently accompanied by groans, becomes necessary, as the motion of respiration, rendered progressively slower, are no longer suffi- cient to dilate the pulmonary tissue. Sobbing differs from sighing merely in this, that though the expiration is long, it is interrupted, that is, divided into distinct periods. Yawning is effected in the same manner ; it is the certain sign of ennui,— a disagreeable affection, which, to use the expression of Brown, may be con- sidered as debilitating, or asthenic. The fatigued inspiratory muscles have some difficulty in dilating the chest, the contracted lungs are not easily pene- trated by the blood which stagnates in the right cavities of the heart, and produces an uneasy sensation, which is put an end to by a long and deep in- spiration ; the admission of a considerable quantity of air is facilitated by opening the mouth widely by the separation of both jaws. One yawns at the approach of sleep, because the agents of inspiration, being gradually de- bilitated, require to be roused at intervals. One is, likewise, apt to yawn on waking, that the muscles of the chest may be set for respiration, which is al- ways slower and deeper during sleep. It is for the same reason that all ani- mals yawn on waking, that the muscles may be prepared for the contrac- tions which the motions of respiration require. The crowing of the cock, and the flapping of his wings, seem to answer the same purpose. It is in consequence of the same necessity, that the numerous tribes of birds in our groves, on the rising of the sun, warble, and fill the air with harmonious 166 OF RESPIRATION DURING MUSCULAR ACTIONS. sounds. A poet then fancies he hears the joyous hymn by which the fea- thered throngs greet the return of the god of light. . While gaping lasts, the perception of sounds is less distinct; the air, as it enters the mouth, rushes along the Eustachian tubes into the tympanum, and the membrane is acted upon in a different direction. The recollection ot the relief attending the deep inspirations which constitute gaping, the recol- lection of the grateful sensation which follows the oppression that was felt before, involuntarily leads us to repeat this act whenever we see any one ^Sneezing consists in a violent and forcible expiration, during which the air, expelled with considerable rapidity, strikes against the tortuous nasal pas- sages, and occasions a remarkable noise. The irritation of the pituitary membrane determines, by sympathy, this truly convulsive effort of the pecto- ral muscles, and particularly of the diaphragm, ,,.«,, Coughing bears a considerable resemblance to sneezing, and differs trom it only in the shorter period of duration, and the greater frequency of the expi- rations ; and, as in sneezing, the air sweeps along the surface of the pituita- ry membrane, and clears it of the mucus which may be lying upon it, so the air when we cough, carries along with it the mucus contained in the bron- chia, in the trachea, and which we spit up. The violent cough at the be- ginning of a pulmonary catarrh, the sneezing which attends coryza, shew that the functions of the animal economy are not directed by an intelligent principle for such an archseus could not mistake, in such a manner the means of putting a stop to the disease, and would not call forth actions which, instead of removing the irritation and inflammation aheady existing, can only aggravate them. . Laughing is but a succession of very short and very frequent expirations. In hiccup the air is forcibly inspired, enters the larynx with difficulty, on ac- count of the spasmodic constriction of the glottis ; it is then expelled rapidly, and striking against the sides of that aperture, occasions the particular noise I Shall, on another occasion, explain the mechanism of sucking, of panting, and of the efforts by which the muscles of the thorax fix the parietes of that cavity, so that it may serve as a fixed point of the other muscles of the trunk and of the limbs. ... , , Respiration is besides employed in the formation of the voice; but the voice, and the different modifications of which it is capable, will form the sub- ject of a separate chapter.* * The author has neglected to notice the state thereby greatly increased because the trunk of of respiration during the more active voluntary the body is thus rendered immovable in respect motions Muscular exertion, especially when of its individual parts, the muscles arise from considerable is preceded by a full inspiration, fixed points, and consequently wield the limbs immediately upon which the glottis is firmly with their full energy. Haller appears to be closed and the abdominal muscles contracted, correct, in concluding that, under a state of ui- At this moment the diaphragm is relaxed; but creased action of the muscles, the flow of blood the complete closure of the glottis, and contrac- becomes greater towards the head: the nervous tion of the abdominal muscles engaged in respi- energy is increased, by means of this augment- ration, furnish a fixed basis of action to the mus- ed flow, and supplied so as to keep up the mus- cles employed in great exertions. At the same cular action for a longer period than otherwise time that the glottis is closed, the muscles of would be the case. During violent exertions, the face participate in the action, in consequence also, the return of blood from the brain is in some of being supplied with branches of the respira- degree impeded. tory order of nerves, (see the Notes in the Ap- The physiological state of muscular actions, PENDix on the different Orders and Functions as they are related to the mechanical function of the Voluntary System of Nerves), and the of respiration, is very happily described by iaws are forcibly pressed together. By this ac- Shakespeare, where he makes the fifth Henry tion of the muscles engaged in respiration, the encourage his soldiers at the siege of Har- chest is rendered capacious, the circulation fleur:— through the lungs facilitated, and the strength OF THE CUTANEOUS PERSPIRATION. 167 LXXXVII. Of cutaneous perspiration.—An abundant vapour is continual- ly exhaling from the whole surface of the body, and is called the insensible perspiration, when in a state of gas in the air which holds it in solution, it then eludes our sight; it is called sweat, when in greater quantity and in a liquid form. Sweat differs, therefore, from insensible perspiration, only by the condition in which it appears ; and it is sufficient for its production, that the air should be incapable of reducing it into vapour, whether from an in- creased secretion by the skin, or from the dampness and consequent diminish- ed solvent powers of the atmosphere. The insensible perspiration is con- stantly escaping through the innumerable pores in the parietes of the minute arteries of the integuments ; it oozes in the interstices of the scales of the skin ; the air which immediately surrounds our body becomes saturated with it, and carries it off as soon as it is renewed. There is the greatest resemblance between the cutaneous perspiration and the pulmonary exhala- tion ; both are mere arterial exhalations ; and the mucous membrane which lines the canals along which the air is transmitted, is a mere prolongation of the skin into those organs and into the digestive tube. The surface from which the cutaneous perspiration is exhaled, is not quite so considerable as that from which the pulmonary exhalation arises, since it is reckoned at only fifteen square feet in a man of middle size. These two secretions are sup- plementary to each other; the increase of the one is generally attended with a sensible diminution of the other ; lastly, the mucous membrane of the in- testinal canal, besides secreting mucus, exhales likewise a fluid which in- creases much in quantity when the cutaneous perspiration is languid,—as is proved by the serous diarrhoeas so frequently occasioned by a suppressed perspiration. It must be owned, however, that notwithstanding those ana- logies of structure and function in the skin and mucous membranes, there exists perhaps a still more intimate connexion between its action and that of the organs which secrete the urine : it has always been observed, that when this last fluid is'scanty, there is a greater cutaneous perspiration, and vice versa. If we examine with a microscope the naked body, exposed during sum- mer to the rays of a burning sun, it appears surrounded with a cloud of- steam, which becomes invisible at a little distance from the surface. And if the body is placed before a white wall, it is easy to distinguish the shadow of that emanation. We may likewise satisfy ourselves of the existence of the cutaneous perspiration, by the following experiment: hold the tip of the finger at the distance of the twelfth part of an inch from a looking-glass, or any other highly polished surface, its surface will soon be dimmed by a vapour condensed in very small drops, which disappear on removing the finger. One may, in this manner, ascertain that the cutaneous perspiration varies in quantity in different parts of the surface of the body ; for, on plac- ing the back of the hand before a looking-glass, the latter will be covered by no vapour. No function of the animal economy has been the subject of more investi- gation, nor has any excited the attention of more accurate and indefatigable physicians, than the secretion now under consideration. From the time of Sanctorius, who, in the beginning of the seventeenth century, published in his immortal work, Medicina Slalica, the result of experiments carried on for " Stiffen the sinews, summon up the blood, In vomiting also, and in the action of expel- ****** ling the faeces and contents of the bladder, the Now set tlie teeth, and stretch the nostrils wide ; thoracic and abdominal muscles of respiration Hold hard the breath, and bend up every spiiit are brought into action, and the glottis closed.— To his fdl height." /. C. 168 OF THE CUTANEOUS PERSPIRATION. thirty years, with a patience which very few will imitate,—to that of Lavoi- sier, who, jointly with Seguin, aided by the resources of the improved state of chemistry, instituted an examination of the insensible perspiration,—we find engaged in this inquiry, Dodart, who,, in 1668, communicated to the Academy of Sciences, which had been founded but a short time, the result of his observations at Paris, under a climate different from that of Venice, where Sanctorius lived :—Keill, Robinson, and Rye, who repeated the same experiments in England and Ireland :—Linnings, who performed his in South Carolina ; and several physiologists of no less merit, as Gorter, Hartmann, Arbuthnot, Takenius, Winslow, Haller, &e, who all aimed at ascertaining, with more precision than had been done by Sanctorius the variations in the cutaneous perspiration, according to the climate, the season of the year, the age, the sex, the state of health or disease, the hour of the day, and the quantity of other secretions. According to Sanctorius, of eight pounds of solid and liquid aliments taken in twenty-four hours, five were carried off by the perspiration, and only three in excrement and urine. Haller conceives this calculation to be exag- gerated ; Dodart, however, carried it still further, and maintained that the relation of the perspiration to the solid excrements was as seven to one. In France, and in temperate climates, the quantity of the cutaneous per- spiration and of the urine is nearly the same ; it may be estimated at be- tween two and four pounds in the twenty-four hours. We perspire most in summer, and void most urine in winter. The perspiration, like every other secretion, is in smaller quantity during sleep than while we are awake ; in old age than during infancy ; in weak persons, and in damp weather, than under the opposite circumstances. The perspiration may be said to be in a compound ratio of the force with which the heart propels the blood into the minute capillary arteries, of the vital energy of the cutaneous organ, and of the solvent powers of the at- mosphere. The strongest and most robust men perspire most.; some parts of the skin perspire more than others, as the palms of the hands, the soles of the feet, the arm-pits, &c. When the air is warm, dry, and frequently renewed, cutaneous perspiration is greater, and the necessity of taking liquid aliment is more urgent, and more frequently experienced : in summer, as every body knows, a profuse perspiration is brought on by passing from the heat of the sun into the shade; and on no occasion is a copious sweat more easily brought on, than by taking exercise in summer, when, on the approach of a storm, the atmosphere, containing a small quantity of vapours, and warm from the rays of the sun, which shews itself now and then, sur- rounded by the clouds, is little capable of dissolving the insensible perspira- tion. The skin may be covered with sweat, without any increase of the cu- taneous perspiration ; this may happen from dampness in the air, or from its being imperfectly renewed. It must be owned, however, that sweating is more frequently occasioned by an increase of the insensible perspiration, and that the warmth of the bed which excites it, acts by increasing the power of the organs of circulation, and the energy of the cutaneous system. The body is weakened by sweating, which is seldom the case with the insensible perspiration. A profuse sweat is attended with a very speedy exhaustion • thus, in hectic fever, in the suelte (sudor anglicus,) and other affections equally dangerous, it is the cause of a wasting almost universally fatal. The matter of the insensible perspiration, and of the sweat, is,- in great measure, aqueous. Like the urine, it holds in solution several salts| also the volatilised recrementitious matter of animal substances, sometimes even acids OF THE CUTANEOUS PERSPIRATION. 169 as in the case in which Berthollet detected the phosphoric acid in children affected with worms, in pregnant women, in nurses, from whom there ex- hales an odour manifestly acid. It may contain ammonia, and, on certain occasions, the smell enables us to discover that alkali in the sweat or per- spiration. The air which constantly surrounds our body does not merely dissolve the aqueous vapour which arises from it; but several physiologists very reasonably conjecture, that the ozygen of the atmosphere may combine with the carbon of the blood brought to the skin by the numerous vessels which are sent to it, and likewise with the gelatine forming the substance of the rete mucosum of Malpighi. The experiments of Jurine, of Tingry, and of several other naturalists, shew that carbonic acid is constantly formed on the surface of the skin, so that the skin may be considered as a supplementary organ to that of re- spiration ; and in that point of view, one may compare to it the mucous membranes which are in contact.with the atmospherical air in the nasal fossae, and in the intestinal canal which they line. The cutaneous perspiration is, likewise, as was before mentioned, a power- ful means of cooling the body, and of keeping it, while living, in a uniform temperature. The water which is exhaled from the whole surface of the body, carries off from it, in passing into vapour, a considerable quantity of caloric ; and it is observed, that every thing which increases the production of caloric gives rise to a proportionate increase of the cutaneous perspiration, and of the pulmonary exhalation ; so that a constant equilibrium being kept up between its production and escape, the animal warmth always remains nearly the same*. To conclude, the extremities of the nerves of our organs of sensation are all moistened by a fluid varying in quantity, and which maintains them in a softened state, favourable to the exercise of their functions. It was likewise necessary that the membrane in which the sense of touch resides should be habitually kept moist by a fluid that should penetrate it throughout: this use of the insensible perspiration is not less important than the preceding, on which physiologists have bestowed most attention. * If transpiration be restrained or stopped, have supposed that they have seen, when the and if the causes productive of heat act with in- air of a room is saturated with humidity, and tensity, it would appear that the temperature of rendered very warm, that the human body ex- the surface of the body rises some degrees ; posed to this atmosphere acquires a higher tem- hence the reason that the heat is so distressing perature than is natural to it; the cutaneous and in those diseases which are characterised by pulmonary transpiration either being altogether diminished transpiration, and in which the dry- arrested, or imperfectly performed. For farther ncss of the skin is so remarkable, as erysipelas, observations on this subject, see Appendix, erythema, &c. MM. Berger and Delaroche Note Z.—/. C. 22 170 OF THE ANIMAL FLUIDS. CHAFFER V. OF THE SECRETIONS. LXXXVIII. Of the Animal Fluids.—LXXXIX. Of the Blood.—XC. Of the constituent Parts of the Blood.—XCI. Of the ultimate Elements of the Blood.—XCII. Of the Changes in the Blood.—XCIII. Of the Transfusion of Blood.—XCIV. Of the Secretions.—XCV. Of Arte- rial Exhalation or Transudation.—XCVI. Of Secretion from Glandular Follicles.—XCVII. Of the Secretions of Conglomerate Glands.—XC VIII. Of Accidental Secretions.—XCIX. Of Nervous Influence on Secretion.—C. Of the Secretion of Synovia, &c.—CI. Of the State of the Circulation in Secreting Organs.—CII. Of other Glands.—CHI. Of the Secretion of Adeps. —CIV. Of the Use of the Fat—CV. Of the Secretion of the Marrow. LXXXVIII. Of the animal fluids.—The animal fluids were formerly divided into recrementitious, excrementitious, and excremento-recrementitious: this division, founded on the uses to which the fluids are subservient, is preferable to any that has since been adopted, and in which they are ranked according to theii nature. The first class remain in the body, and are employed in its nutrition and growth ; such as the chyle, the blood, the serosity which lubricates the sur- fece of the pleura, of the peritonaeum, and of the other membranes of the same kind. The second kind are ejected from our body, and cannot remain long within it without danger ; such as the urine, the matter of insensible perspiration and of sweat. Lastly, those of the third class partake of the nature of the two preceding, and are in pait rejected, while another part is retained and employed in the support and growth of the organ ; this is the case with the saliva, the bile, the mucus of the intestines, &c. If one affect- ed to be very minutely scrupulous, one might consider all the animal fluids as recremento-excrementitious. The chyle and the blood, which are, so very nutritious, contain an abundance of heterogeneous and excrementitious parts ; the ttrine, which of all our fluids is that which may, with most propriety, be termed such, contains likewise aqueous parts, which, while it remains in the bladder, the lymphatics absorb and carry into the mass of the fluids. Of all the modern divisions, Fourcroy's is the best; Vicq-d'Azyr acknow- ledged its superiority over that proposed by Haller in his Physiology. Four- eroy admits six classes of fluids : 1st, those which hold salts in solution, as the sweat and urine,—he gives the name of saline to such fluids ; 2d, in- flammable oily fluids, all possessing a certain degree of consistence and con- crescibility, as fat, and the cerumen of the ears, &c.; 3d, the saponaceous fluids, as the bile and milk; 4th, the mucous fluids, as those which lubricate the internal coat of the intestinal canal; 5th, the albuminous fluids, among which one may rank the serum of the blood; 6th, the fibrinous fluids, con- taining fibrina, as the fluid last mentioned.* - In proportion as we advance in our knowledge of animal chemistry, the defects of these divisions become more and more evident. In short, the ani- mal fluids are so compound, that there is not one which does not, at once, * Berzelius distinguishes the fluids formed ter division acids predominate : the excretory from the blood into secretions, properly so called, fluids embrace the urine, the cutaneous and and excretions, or those which are directly dis- pulmonary transpiration, and the milk. Ma- charged from the body. The former are destin- gendie divides the secretions into exhalations, ed to perform a farther office in the animal eco- follicular secretions, and glandular secretions. nomy—all of these are alkaline ; they are the See Appendix, Note AA, for farther observa- bile, the saliva, and the fluid, which is secreted tions on this subject.—/. C. on. the mucous and serous surfaces. In the lat- ' Ol' THE BLOOD. 171 belong to several of these classes, and whose prevailing element is not some- times exceeded in quantity by materials which commonly form but a small part of them. LXXXIX. Of the blood.—The blood is the reservoir and the common source of the fluids ; these do not exist in the blood, with the qualities which characterise them, unless, after having been previously formed by the secre- tory organs, they have been absorbed by the lymphatics, and conveyed, with the chyle and lymph, into the circulatory system. Let us shortly attend to its nature, although this belongs more especially to the department of che- mistry. The blood is red in man and in all warm-blooded animals, and even in some whose temperature is not very different from that of the atmosphere, as in fishes and reptiles. This colour, of a deeper or lighter shade, accord- ing as the blood is drawn from an artery or a vein, varies in its degree of in- tensity according to the state of health or weakness. It is of a deep red in strong and active persons, pale and colourless in dropsical patients, and when- ever the health is weak. By its colour, one may judge of all its other qualities. Its viscidity is greater, its saline taste more marked, its peculiar smell stronger, when its colour is deep. This colour is produced by a pro- digious number of globular molecules, which move and float in an aqueous and very liquid fluid. When the blood is pale, the number of these mole- cules diminishes : they seem to be dissolved in cachexia. Does the microscope, which affords the only method of perceiving them, enable one to determine their bulk and their figure 1 Sir E. Home considers the red particles to be T „Vo of an inch in diameter. Leeuwenhoek, who brought forward the idea of their being.so minute, by his calculation that they were one millionth part of an inch in size, thought them spherical. Hewson says they are annular, and have an opening in their centre. Others compare them to a flattened lentil, with a dark spot in the middle. They are solid, and formed by a nucleus or red point, covered over by a membranous vesicle, which appears to be readily formed and destroyed* XC. The constituent parts of the blood.—The blood, when no longer in the course of the circulation, and on being received into a vessel, parts with its caloric, and exhales at the same time a po'werful smell, a gas to which, according to some physiologists, (Moscati, Rosa, &c.) it owes its vital pro- perties, and the absence of which is attended with a loss of its vitality ; so that its analysis cannot furnish facts applicable to the explanation of the phenomena of health and disease. This odour, extremely strong in carni- vorous animals, is very distinguishable in man, especially in arterial blood. I remember retaining it a whole day in my throat, after removing the dres- sings, and suppressing a haemorrhage occasioned by a relaxation of the ligatures, a week after the operation for popliteal aneurism. Unless the blood is prevented by agitation from coagulating as it cools, its consistence increases, and on being laid by, it separates into two very different parts, the one aque- ous, more or less red, heavier than common water, and evidently saltish; this is called the serum, consisting of water, in which are dissolved albumen, gelatine, soda, phosphates and muriates of soda, nitrate of potash, and mu- riate of lime. Serum, though bearing some analogy to the albumen of egg, differs from it, in forming, on coagulating, a less solid and less homogeneous mass. The albumen is evidently mixed with a portion of transparent gelatine, not coagu- lable by heat. Albumen has so great an attraction for oxygen, that it is fair to presume that the serum absorbs oxygen and combines with it, through the very thin parietes of the air-cells of the lungs, and that it gives to arte- * See the Appendix, Note B B. 172 Or TIIL r.I.EMF.NTS OF THE BLOOD rial blood that spumous appearance which is one of its distinguishing cha- racters. This oxidisement, and the fixation of the caloric which accompanies it, equally increase its consistence. It does not, however, coagulate, because it is kept in perpetual motion by the circulatory action, and is diluted by a sufficient quantity of wrater ; because the animal temperature, which never exceeds thirty-two or thirty-four degrees, cannot give a solid form to albumen, which coagulates only at fifty degrees of Reaumur's thermometer ; and lastly, because as serum contains a certain quantity of uncombined soda, which enables it to turn green vegetable blues, this alkali concurs in keeping the albumen in a dissolved state, which it renders fluid when it has been co- agulated by the acids, by heat, or by alcohol. Amid the serum, and on its surface, there floats a red cake, spongy and solid (insula rubra), which, by repeated washing, may be separated into two very distinct parts. The one is the cruor, or the colouring matter, which mixes with the water; it is a more highly oxygenated and more concresciblc albumen than that of the serum ; it holds in solution soda, as well as phos- phate of iron, with an excess of iron.* The other is a solid and fibrous sub- stance, which, after being repeatedly washed, has the appearance of felt, the filaments of which cross each other, are extensible, and very elastic. This third part of the blood is called flbrina; it is very similar in its nature to muscular fibre, and, like it, gives out, on distillation, a considerable quantity of carbonate of ammonia. Fibrina does not exist in the blood in a solid form, but in a state of solution, and combined with the other constituent parts of the fluid, as is indicated by the appropriate expression of liquid flesh (chair coulante), first used by Bordeu in speaking of the blood. XCI. Of the ultimate elements of the blood.—If the blood be exposed to the action of fire, if it be calcined and reduced to powder, and if this pul- verised substance be exposed to a magnet, the presence of iron will be mani- festly seen by the magnetic attraction. Authors do not agree in their ac- counts of the quantity of iron contained in the blood. Menghini says there is one part in the hundred ; others that it is in the proportion of 1 to 303 ; so that it is probable that this constituent principle of the blood, like all the materials of our fluids, may vary in quantity according to different circum- stances. Blumenbach justly observes, that iron is found only in calcined blood ; that none is to be found if it be slowly dried. This peculiarity is no longer surprising, since M. Fourcroy has shewn that iron existed in the blood, in combination with the phosphoric acid, and formed with that acid a phosphate of iron, with an excess of its base. This salt becomes decomposed by cal- cination, the iron is set free, and is acted upon by the magnet. Physiologists attribute the colour of the blood to the presence of the oxide of iron in that fluid. * It is a more oxygenated and a more coagu- lable albumen than that of the serum. The co- louring part of the blood, when incinerated, af- ter giving off a considerable quantity of ammo- nia during the combustion, leaves ashes which, according to Berzelius, are only a hundredth part of its weight, and which contain 55 parts of the oxide of iron, 8J of the phosphate of lime, a little of magnesia, 17J parts oS lime, and 10§ of carbonic acid. The oxide of iron is neither found in the ashes of the coagulable part of the serum, nor in those of the fibrine. Berzelius, however, further informs us, that the serum, al- though able to dissolve a small portion of the oxides of iron, but not of its phosphates, does not acquire a red colour by this weak solution, and that he has neither detected iron nor lime in the entire blood, although both are so abun- dant in its ashes. He therefore concludes, that the blood contains the elements only of the phosphate of iron, and of lime and magnesia, and of the carbonate of lime, united very diffe- rently from their combination in these salts. Nor is it unlikely that these salts are formed during incineration, from the presence of the elements of their respective bases, the other elements being furnished during incineration. The existence of iron in the colouring particles of the blood, and its absence from the serum, have been confirmed by the recent experiments of several chemists on the continent.—/. C. OF THE CHANGES IN THE BLOOD. 173 It has been the received opinion, that the red colour of the blood is owing to the presence of phosphate of iron, which being conveyed of a white co- lour into the blood, along with the chyle, meets with the pure soda, by which it is dissolved^ and from which it receives its colour ; the colour of the blood is likewise owing to the oxidisement of the metallic portion, which is in very considerable quantity in that salt. This solution of the phosphate of iron by soda, the oxidisement of the excess of iron, and the absorption of oxygen by albumen, constitute, in an especial manner, hematosis or sanguification, which is principally carried on in the lungs. This opinion of Fourcroy respecting the source whence the blood acquires its red colour, has, since his time, been adopted by some, and combated by other, physiologists. It is now entirely abandoned, because it is known that the colouring part of this fluid may be obtained separately, and entirely exempt from iron. This colouring portion of the blood, according to M. Vauquelin, does not change its colour when tested with gallic acid,—a farther proof that it contains no iron.* The respective proportion of the three parts into which the blood separates spontaneously, varies considerably. The serum constitutes about one-half or three-fourths of the fluid ; the colouring matter and fibrina are in inverse ratio of the serum ; and it is observed, that the more brilliant and red the colour of the blood, the greater the proportion of the fibrous part. The pale, aqueous, and colourless blood of a dropsical patient contains very little fibrina. In putrid or adynamic fever, in which bleeding, as is universally known, is improper, I have sometimes seen the blood containing but a small portion of fibrina, and very slow of coagulating ; its texture seemed to suffer from the affection under which the muscular organs were evidently labour- ing. In inflammatory diseases, on the contrary, the plastic power of the blood is augmented, the fibrina is in greater quantity, even the albumen coagulates spontaneously, and forms a crust above the serum, which is al- ways in smaller quantity.f XCII. Of the changes in the blood. — The fluids not only undergo changes in their composition, in their qualities and nature, when the action of the solids is itself altered, but even the absorbent system may introduce into the mass of our fluids heterogeneous principles, evidently the cause of several diseases. In this manner, all contagions spread, the virus of small-pox, of syphilis, of the plague, &c. Thus, in time, the habitual use of the same aliment produces in our fluids a crasis or peculiar constitution, which has on organised solids an influence acting even on the mind. A purely vegetable diet conveys into the blood, according to Pvthagoras, bland and mild principles : this fluid excites the organs in a moderate degree, and this check over the physical excitement facilitates the observance of the laws of temperance, the original source of all virtues. These observations of ancient philosophy on the influence of regimen have, doubtless, led their authors to exaggerated inferences ; but they should not be considered as altogether unsupported. The carnivorous species are marked by their strength, their courage, and their ferocity ; savages who live by hunting, and who feed on raw, bloody, and palpitating flesh, are the most ferocious of * Since the time of Fourcroy, chemists have acid in the proportion of two cfibic inches of differed widely respecting the presence of iron the gas for each ounce of blood. This acid dis- in the red particles of the blood. The recent engages itself immediately when a portion of researches, however, of some continental in- the warm blood is placed in an air-pump. Dr. quirers seem to have settled the question in the Davy has, however, recently contended that the affirmative. See Appendix, Note B B.—J. C. blood contains little or no carbonic acid. See t According to Mr. Brande and Sir E. Home, Appendix, Note B B, for farther remarks re- both venous and arterial blood contain carbonic specting the Blood. 174 OF T4IE CHANGES IN THE BLOOD men ; and in our own country, in the midst of those scenes of horror which we have witnessed, and from which we have suffered, it was observed that butchers were foremost in the massacres, and in all the acts of atrocity and barbarity. I know that this fact, which was uniformly noticed, has been explained by saying that the habit of slaying animals had familiarised them to shed human blood. But though I do not deny the existence of this moral cause, which certainly operates, I think I may add to it as a physical cause, the daily and plentiful use of animal food, and the breathing an air filled with emanations of the same kind, which contributes to their embonpoint, which is sometimes excessive. As the plasticity and concrescibility of the blood are diminished in as- thenic diseases, or of debility, as putrid fevers and scurvy, two causes may be assigned for the haemorrhages which come on in those diseases, viz. the relaxed state of the vessels, and the dissolution of the blood. In scurvy the tissue of the capillaries is relaxed, its meshes enlarged, red blood passes into them, transudes through their parietes, and forms scorbutic spots. I have sometimes seen those ecchymoses or sanguineous cutaneous transudations extend under the skin of the whole of one lower extremity. Petechia?, in putrid fever, are formed in the same manner, and depend, likewise, on the relaxation of the minute vessels, and on the greater fluidity of the blood, whose molecules are less coherent, and more readily separated from each other. In the summer of the year 1801 I amputated the arm of an old man of sixty, on account of a corroding and varicose ulcer, which for thirty years had occupied a part of the fore arm, and extended to the elbow. All who were present at this operation observed that the blood which flowed from the arteries was not nearly so red as that from the arteries of a young man, whose thigh had just been taken off on account of a scrofulous caries of the leg ; that the venous blood was entirely dissolved, purple, and similar to a weak dye of logwood. The blood did not coagulate like that of the young man ; it became fluid, and was converted into a serum, containing a few colourless clots. Those who have endeavoured to find in the changes undergone by the blood and the other fluids, the cause of all diseases, have fallen into as serious blunders as the determined solidists, who maintain that all diseases arise from a deranged condition of the solids, and that every change in the condi- tion of the fluids in a consequence of that derangement. The believers in the humoral pathology have certainly gone too far ; they have admitted that the animal fluids might be acid, alkalescent, or acrimonious, while we have no proof whatever that they ever do undergo such changes. The solidists have, likewise, gone much beyond the truth, in saying that every primitive change in the condition of the fluids is imaginary, and that the doctrine *of humoral pathology is without foundation. Stahl relates* that the blood of a young woman, who was bled during a fit of epilepsy, was absolutely coa- gulated, as if that fluid had partaken in the rigidity affecting the muscular organs. Some authors say they have met with the same appearance ; I have, however, never been able to discover any sensible difference between the blood Of an epileptic patient and of any other person of the same con- stitution, of the same age, and living on the same regimen ; and it should be considered, that to make a just comparison of our fluids, it is necessary that every thing should be alike in ,the persons from whom they are taken, with the exception of the difference of which we are to judge. In fact, the blood has not the same appearance, and does not coagulate in the same man- * Theoria Medica Vera, p. 678. OF THE TRANSFUSION OF BLOOD. 175 ner, when taken from a child, a woman, or an old man ; from a man who lives abstemiously, or from one who lives on a full diet. After enumerating the changes which the blood undergoes, one might speak of those which affect the fluids that are formed from it, one might at- tend to the greenish, leek colour, and sometimes even darkish appearance of the bile, which is not always of the same degree of bitterness ; the limpid state of the urine, which is voided colourless, without smell or flavour, after a fright, or during the convulsive fits of hysterical women ; the foetid smell and the viscidity of the saliva, when the salivary glands are under mercurial influence ; the milky state of the serum which lubricates the parietes of the abdomen, and of the viscera which it contains after inflammation of the peritonaeum ; changes which almost universally depend on a derangement of action in the secretory organ, and sometimes, likewise, on the general con- dition of the fluids ; for a gland cannot secrete a fluid endowed with the qualities which peculiarly belong to it, unless the blood furnish it with the materials of secretion, and unless it be in a state to bring about a due com- bination of their particles. When we come to the article of accidental se- cretions, we shall speak of some of those disorders of the fluids depending on a depraved condition of the secretory organs* XCT1I. Of the transfusion of blood.—In the midst of the disputes to which the discovery of the circulation gave rise, some physicians conceived the idea of renovating completely the whole mass of the fluids in persons in whom they might be vitiated, by filling their vessels with the blood of an animal, or of a person in good health. Richard Lower, known by his work on the heart, first practised it on dogs, in 1665. Two years afterwards, transfusion was performed at Paris on men : it excited the greatest expectations : it was thought that by this process, called transfusive surgery (chirurgie transfusiore), all remedies would be superseded ; that henceforth, to cure the most serious and inveterate diseases, it would be necessary merely to transfuse the blood of a strong and healthy man into the veins of the diseased ; nay, they went so far as actually to imagine they might realise the fabulous fountain of Jouvence ; they expected no less than to restore youthful vigour to the old, by infusing into them the blood of the young, and thus to perpetuate life. All these brilliant chimeras soon vanished ; some underwent the experiment without any remarkable effects from it, others were affected with the most violent delirium ; a lad of fifteen lost his senses, after suffering two months from the most violent fever. The legislative authority at last interfered, and prohibited those dangerous experiments. The experiments on the subject of the transfusion of blood were repeated, but without success, at the Academy of Sciences. Perault opposed this new method, and shewed that it was very difficult for one animal to exist on the blood of another ; that this fluid, though apparently the same in animals of the same age, was as different from it as the features of their face, their temper, &c.; that an extraneous fluid was thus introduced, which convey- ing to the organs an irritation to which they were not accustomed, must dis- order their action in various ways ; that if, as an objection to what he had said, they should bring forward what takes place in grafting, in which the sap of one tree nourishes another of a different kind, he would answer,— that vegetation does not depend on so complicated or on so delicate a mecha- nism as the nutrition of animals ; that a hut may be formed of all kinds of stones taken at random, but that to build a palace stones must be designedly * For additional remarks on the changes ob- dition of the Blood, see Appendix, Note B B. served, under various circumstances, in the con- —/. C. 176 OF THE ARTERIAL EXHALATION. shaped for the purpose, so that a stone destined for an arch will not do for a wall, or even for another arch * It would be easy, by means of a curved tube, to transfuse the arterial blood of an animal, from a wound in its carotid artery, into the saphena vein of a man, into the internal jugular, or into some of the cutaneous veins of the fore arm ; but it is to be presumed, from experiments on living animals, that it would be very difficult to transfuse blood into the arteries,—as these vessels, filled with blood during life, do not yield to a greater distension. The capil- laries, in which the arteries terminate, become corrugated, and refuse to transmit a fluid which does not act upon them according to their wonted sen- sibility. Such was the result of the experiments of Professor Buniva : he observed in a living calf, that the vessels did not transmit freely the fluid which was forced into them till the instant when the animal was killed, by dividing the upper part of the spinal marrow. Attempts have been made to turn to useful purposes these experiments on transfusion, by limiting the process to the injecting of medicinal substances into the veins. It is singular, that the moment a fluid is injected into the veins of an animal, it endeavours to perform motions of deglutition, as if the substance had been taken in at the mouth. All these attempts have been too few in number, and are not sufficiently authenticated, to justify their application to the human subject. But there is every reason to believe, that, eVen with the utmost care, the life of those who should submit to them would be endangered ; so that it is at once humane and prudent to abstain from them."f" XCIV. Of the secretions.—It has been said in too general a way, that the organs receive from the blood conveyed to them by the arteries, the materials of the fluids which they separate from it. We have seen that the liver is a remarkable exception to this general rule. One is, therefore, justified in saying that the elements of our fluids may be furnished by vessels of every kind, to the organs in which such fluids may be elaborated. The term secretion, whatever its etymology may be, denotes that function by which an organ separates from the blood the materials of a substance which does not exist in that fluid with its characteristic qualities. By the term secretion, one should not, therefore, understand the mere sepa- ration of a fluid existing before the action of the organ by which it is prepared. XCV. Of arterial exhalation.—The differences between the secreted fluids are evidently connected with those of the organs employed in their formation. Thus, the arterial exhalation which takes place throughout the whole ex- tent of the internal surfaces maintains their contiguity, throws out an albumi- nous serosity, which is merely the serum of the blood slightly changed by the feeble action of a very simple organisation. The analysis of the fluid of dropsy, which is merely the serosity constantly transuding from the surface of the serous membranes, as the pleura and peritonaeum, shews, that it bears the strongest resemblance to the serum of the blood, and that it differs from it only in the varying proportions of albumen and of the different salts which it holds in solution. This first kind of secretion, this perspiratory transudation, would seem to be a mere filtration, through the pores of the arteries, of a fluid already formed in the blood. There is, however, besides, an inherent action in the membranes whose surface it continually lubricates. If it were not for this action, the serum would remain united to the other constituent parts of the fluidl which is in too much motion, and at too high a temperature, to allow of a sponta- neous separation. The term exhalation, which is applied to this secretion, * Academic ltoyale des Sciences, p. 37. marks on transfusion, and on the injection of t See Appendix, Note B B, for some re- medicinal substances into the veins.—/. C. SECRETIONS OF CONGLOMERATE GLANDS. 177 gives an incorrect idea of it; for exhalation, which is a purely physical phe- nomenon, and requiring the presence of air to dissolve the fluid that is ex- haling, cannot take place from surfaces that are in absolute contact, and be- tween which there is no interval. The character of this mode of secretion is the absence of any intermediate substance between the vasa afferentia and the excretory ducts ; the minute arteries and veins which enter into the structure of the membranes, being at once both the one and the other. The fluid secreted by the serous membranes, though bearing a consider- able analogy to the serum of the blood, differs from it, however, by being animalized in a greater degree. The most important function of these or- gans is, therefore, that they concur in the common process of assimilation : the office,, which has long been assigned to them, of facilitating the motion of the organs which they envelope,'by lubricating their surface, will appear to be of very secondary importance, if it be considered, that respiration is not im- peded by adhesions between the lungs and the pleura, and that, besides, the brain, which, when the cranium is whole, is completely motionless, is entirely surrounded by a serous membrane. XCVI. Of secretion from glandular follicles.—Next in order to the sejrous transudation, which requires a very simple organisation, comes the secretion which takes place in the cryptae, in the glandular follicles, and in the mu- cous lacunae. Each of these small glands, contained within the membranes lining the digestive canal, the air tubes, and the urinary passages, and the collection of which forms the amygdake, the arytaenoid glands, &c. may be compared to a small bottle, with a round bottom and a very short neck: the membranous parietes of these vesicular cryptae receive a considerable num- ber of vessels and nerves. The peculiar action of the parietes of these dif- ferent parts determines the secretion of the mucus furnished by those glands. These mucous fluids, less liquid and more viscid than the serosity which is the product of the first mode of secretion, contain more albumen and a greater number of salts, differ still more from the serum of the blood, are more ani- malised, and are of a more excrementitious nature. The bottom of these utricular glandulae is turned towards the parts to which the mucous membranes adhere ; and their mouth or neck opens on the free or unattached surface of those membranes. These kinds of excre- tory ducts, which are wider or narrower, and always very short, sometimes unite, run into each other, and open within the cavities. These common orifices, at which several mucous glands empty themselves, are easily seen on the amygdalae, towards the mucous lacunas of the rectum and of the urethra, at the base of the tongue, &c. The albuminous fluid, which is poured within those glandular cryptae, remains some time within the cavity, and becomes thicker, from the absorption of its more fluid parts; for there are, likewise, lymphatics within the texture of their parietes. When the sur- faces on which they are situated require to be moistened, this small pouch contracts and throws up the fluid with which it is filled. The secretion and excretion are promoted by the irritation which the presence of the air, of the aliment, or of the urine, occasions, by the compression exerted by those substances, and, lastly, by the peristaltic contractions of the muscular planes to which the mucous membranes adhere throughout the whole extent of the digestive tube. XCVII. Secretions of conglomerate glands.—Those fluids which differ much from the blood, require for their secretion organs of a more complicated na- ture ; such organs are called conglomerate glands, to distinguish them from the lymphatic glands, which have been termed conglobate. Those glands constitute the viscera, and are formed by a number of nerves and vessels of 23 178 OF THE SECRETIONS. all kinds, arranged in fasciculi, and united by cellular membrane. A mem- brane peculiar to the organs, or supplied by those which line the cavities in which they are contained, covers their outer part, and insulates them from the neighbouring organs. The intimate arrangement of the different parts which form the secretory glands, the disposition of the arteries, of the veins and nerves, and the man- ner in which the lymphatic and excretory ducts arise from them, has given rise to endless discussions, and formed the basis of former physiological theo- ries. What follows may be considered as a correct abstract of what is known on the subject. The respective arrangement of- the similar parts (parties similaires*) which enter into the structure of the glands, and which form their proper substance, or parenchyma,! is different in each of them : this explains their differences in the double relation of their properties and their uses. The arteries are not, as Ruysch thought, immediately continuous with the excretory ducts, nor are there immediate glands between those vessels, as Malpighi conceived. It seems more probable that each gland has its own peculiar cellular or parenchymatous tissue, in the areolae of which the arteries pour the materials Of the fluid which the gland prepares, in virtue of a power which is inherent to it, and which is its distinguishing character. The lymphatics and the excretory ducts arise from the parietes of those cells, and these two kinds of vessels absorb ; the one set, the secreted fluid, which they carry to the reser- voirs in which it accumulates ; while the other set take up that part of the fluid on which the organ has not completed its action—in other words, the residue of secretion. XCVIII. Of accidental secretions.—If one wished to extend the idea at- tached to the term secretion, one might say that every thing in the living economy is performed by means of the secretions. What is digestion but the separation or secretion of the chylous or nutritive parts of aliments from their faecal or excrementitious portion 1 Do not the absorbents concur in this se- cretion ? May they not be considered as the excretory ducts of the digestive organs, which act on the aliment in the same manner as a secretory gland acts on the blood that contains the materials of the fluid to be elaborated? Respiration, as we have already seen, is but a double secretion which the lungs perform, on the one hand, of the oxygen contained in the atmospherical air ; and, on the other hand, of the hydrogen and carbon, of the water, and of the other heterogeneous principles contained in venous blood ; and, as will be shewn in the ensuing chapter, nutrition is but a peculiar mode of se- cretion, which is different in every organ. It is, therefore, only after a series of very delicate and very complicated separations and analyses, that the organs are enabled to make extraneous substances undergo such a change of composition as to render them fit for their growth and reparation. There is every reason to believe, that the phenomena of sensation and of motion, by means of which man keeps up with surrounding objects the rela- tions necessary to his existence, are the result of the secretions of which the blood furnishes the materials prepared by the brain, by the nerves, by the * "By parties similaires, the author means the readily distinguish the substance of the liver simple elementary tissues. See the Prelimi- from that of the salivary glands, depend on the nary Discourse. existence of a peculiar tissue in each organ? t Do the different appearances of the sub- This question cannot be answered in the pre- stance of glandular bodies depend on the diffe- sent state of anatomy. The opinion, however, rent manner in which the similar parts cross which supposes the different nature of the glands each other, and on their different proportions in to depend on the different proportions of those each kind of gland? or do these differences of constituent parts in each of them, appears the colour, of density, by means of which we so most probable OF THE SECRETIONS 179 muscles, &c. A plant separates from the earth, in which its roots are buried. the juices that it requires ; these juices constitute the sap, which, after being filtered through a multitude of canals, supplies the different secretions, whose products are leaves, blossoms, and fruits, with gums, essential oils, and acids. All organised bodies are, therefore, so many laboratories, in which numerous instruments spontaneously perform various compositions, decompositions, syn- theses, analyses, which may be considered as so many secretions from the common fluid. If we confine ourselves in our view of the subject, and limit our attention to man, the principal and almost the sole object of our study, we shall see that the different secretions that may take place in him are extremely nu* raerous and varied, and that a change in the condition of one of his organs is sufficient to enable it to secrete a new fluid. Hence inflammation in any gland is sufficient to alter the secretion of the organ that is affected. A portion of adipose tissue, on being affected with inflammation, shall secrete, instead of fat, a whitish fluid, known by the name of pus ; the pituitary membrane, when inflamed, furnishes a mucus more fluid and more abundant, and which, hy degrees, returns to its natural state, in proportion as the coryza goes off; the serous membranes, as the pleura and the peritonaeum, will allow a greater quantity of serum of a more albuminous quality, sometimes even coagulable lymph, to exude. At other times, inflammation causes an adhesion of their contiguous surfaces, and as the inflammatory state varies in intensity, the accidental secretion will likewise vary as to its qualities ; thus, the phlegmo- nous inflammation, which should furnish, on terminating in suppuration, a whitish fluid, thick, consistent, and almost without smell, will give out, if the process is not sufficiently active, a serous pus, colourless, and without con- sistence, &c. For the same reason, the blood-vessels of the uterus pour out in some women a dark-coloured blood, while in others they give out a mere serosity, very slightly, if at all, tinged with blood. The menstrual discharge in women is the product of a real secretion of the arterial capillaries of the uterus, in the same manner as those vessels in the pituitary membrane, the membrane which lines the bronchia, the stomach, the intestines, the bladder, &c. pour out blood abundantly, or allow its transu- dation, when irritation is determined to those parts ; as in haemorrhage from the nose, in bleeding from the lungs, or from the stomach, when the vessels are not ruptured by external violence. Apoplexy itself, whether sanguineous or serous, may, in several instances, be ranked amongst those secretory evacuations, the quality of which varies according to the energy of the capillaries which produce it. On opening dead bodies, one frequently meets with a collection of blood in the ventricles of the brain in persons who have died from apoplexy ; yet the most careful examination does not enable one to detect the slightest laceration or rupture in the veins, or in the arteries within the skull. XCIX. Of nervous influence on secretion.—The nerves, of which there is always a certain number in the structure of the secretory organs, and which are principally branches of the great sympathetic* nerves, terminating in various ways in their substance, give to each of them a peculiar sensibility, by means of which they discover, in the blood which the vessels bring to them, the materials of the fluid they are destined to secrete, and these they appropriate to themselves by a real selection. Besides, the nerves communi- * They are likewise given off in great num- vical nerves, a number of nerves that will appear bers from the cerebral; thus, the salivary glands very great, if the bulk of those glands is consi- receive from the seventh pair, from the maxilla- dered.—/. C ry nerve, from the fifth pair, and from the cer- 180 OF THE SECRETIONS cate to them a peculiar mode of activity, the exercise of which makes those separated elements undergo a peculiar composition, and bestows on the fluid which is the product of it, specific qualities, always bearing a certain relation to the mode of action of which it is the result. Thus, the liver seizes the materials of the bile contained in the blood of the vena portae, elaborates, combines those materials, and converts them into bile,—an animal fluid, dis- tinguishable by peculiar characteristic properties, subject to certain variations, according as the blood contains, in different proportions, the elements of which it is formed ; and according as the gland is more or less disposed to retain them, and blend them together. The qualities of the bile, depending on a concurrence of all these circumstances, must present as many differences as the blood which contains its elements, and the liver, may present varieties, with regard to the composition of the former, and to the activity of the lat- ter. Hence the many changes in the qualities of the fluid, the slightest of which, not affecting the health, escape observation ; while those changes which are greater, and which disorder the natural order of the functions, shew themselves in diseases of which they may be considered as the effect, and at other times as the cause. These changes in the condition of the bile (and what is now said applies to almost all the secretions of the animal economy), are never carried so far as to make the bile lose all its distinguish- ing characters ; it never takes on the qualities belonging to another fluid, it never resembles semen, urine, or saliva. The secretory glands do not carry on an uninterrupted action ; almost all of them are subject to alternate action and repose ; all, as Bordeu observed, sleep or waken when irritation affects them or their neighbouring parts, and determines their immediate or sympathic action. Thus, the saliva is more plentifully secreted during mastication, and the gastric juice is poured within the stomach only while digestion is going on ; when the stomach is emptied of food, the secretion ceases, and is renewed when the presence of food again excites a sufficient degree of irritation. The bile flows more abundantly, and the gall-bladder frees itself more readily of that which it contains, while the duodenum is filled by the chymous mass. When a secretory organ is in action, it determines the motion of the parts in its vicinity, or, as Bordeu expresses it, within its atmosphere. A part is said to belong to the department of- a certain gland, when it partakes in the motion affecting the latter during the process of secretion, or when it is em- ployed in functions subservient to that of the gland : these departments are of different extent, according to the importance of the action of the gland. Thus, one may say that the spleen, and most of the viscera of the abdomen, are of the department of the liver, since they receive from it the blood on which they are to act. The liver is also comprised in the sphere of activity of the duodenum, since the distension of that intestine irritates it, and deter- mines a more copious flow of its fluids, and a more abundant secretion of bile. C. Of the secretion of synovia, SfC.—The blood which is sent to a secretory gland, before reaching it, undergoes preparatory changes, which dispose it to furnish the materials of the fluid that is to be separated from it. We have seen, in treating of digestion, how the blood which the vena portae sends to the liver is fitted for the secretion of bile. There can be no doubt that the portion of blood which is carried to the testicles, by the long, slender, and tortuous spermatic arteries, undergoes changes which bring it nearer to the seminal fluid. The rapidity with which the blood flows into an organ, the length, the diameter, the direction, the angles of its vessels, the arrangement of their OF THE SECRETIONS. 181 extreme ramifications, which may be stellated, as in the liver—in fasciculi, as in the spleen—convoluted, as in the testicles, &c, are circumstances which should be taken into account in the study of each secretion, since all have some influence on the nature of the fluid secreted, and on the manner in which the secretion is effected. The fluid which lubricates the whole extent of the movable surfaces by which the bones of the skeleton are articulated together, is not exclusively prepared by the membranous capsules which envelope the articulations. A number of reddish-coloured cellular substances, placed in their vicinity, co- operate in the secretion. Though these parts, which were long considered as synovial glands, do not completely resemble the conglomerate glands, and although no glandular bodies nor excretory ducts can be demonstrated in them, they cannot, however, but be considered as fulfilling, to a certain degree, the same functions ; and one must admit that they are of some utility in the secretion of the synovia. They are always met with, and their extent and bulk are always proportioned to the extent of the auricular surfaces, and to the frequency of motion in the joints near which they are situated. They are found in all animals ; pale and light coloured in those which have been long at rest; red, highly vascular, and bearing the marks of a kind of inflammatory diathesis, in those which have been compelled to violent exer- cise, as the oxen which are brought to Paris from distant provinces, and the wild animals which have been hunted. In anchylosis they are less red, and of greater consistence, than in a healthy state. When, from the irritation attending friction, the fluids are determined to- wards an articulation which is in motion, do they not then, by passing through those glandulo-cellular bodies, undergo a peculiar modification, which renders them fitter for the secretion of synovia 1 This would not be the only instance in the human body of parts whose action is but secondary, and connected with that of other organs principally engaged in a secretion whose materials are contained in the blood which passes through them. It will be urged, no doubt, that this preparatory apparatus is not met with in the neighbourhood of the great cavities : but ij should be recollected, that the chemical compo- sition and the uses of the synovia are not precisely the same as those of the fluids secreted by the pleura or the peritonaeum ; and that, besides, the ana- logy between two objects does not constitute their identity. The human mind, being naturally indolent, loves to discover analogies that support it in its weakness, and that may save it the trouble of seeking points of difference. I am aware that, to prove that the mechanism of the synovial secretion, which exactly resembles that of the fluid which moistens the inside of the great cavities, and requires, like it, but a simple membranous apparatus, it is customary to repeat, in every possible way, that Nature is scanty in her means, and lavish in her results ; that she produces from the same cause a variety of different effects, &c. ; but, without pointing out the manifest ab- surdity of admitting metaphysical arguments in the natural sciences, is it not much more reasonable to acknowledge, with philosophers, that the primitive cause may vary in many ways, and that its innumerable modifications, whence arise the difference in the effects, exceed the limited powers of our understanding ? CI. Of the state of the circulation and nervous influence in secreting parts.—- When a gland is irritated it becomes a centre of fluxion, towards which the fluids are determined from every part ; it swells, hardens, contracts, is in a kind of state of erection, bends on itself, and acts on the blood conveyed by its vessels. Secretion, depending on the peculiar and inherent power of the glandular organ, is promoted by the slight motion which it receives from the 182 OF THE SECRETIONS neighbouring muscles The gentle pressure of those parts on the glandular organs is sufficient to keep up their excitement, and to assist in the separa- tion and excretion of the fluid. Bordeu, in his excellent work on the glands and on their action, has shewn that it is not in consequence of the compres- sion which is produced on them by the neighbouring muscles, that they part with the fluid they have prepared ; and that physiologists were there- fore very much in the wrong in saying that the excretion of a fluid consisted merely in its expression, and in comparing, under that point of view, the glands to sponges soaked with a fluid which they give out on being squeezed. The excretory ducts of organs absorb or reject the secreted fluid according as it affects their inhalant mouths : these canals partake in the convulsive state of the gland, undergo a degree of erection, and contract on the fluid to expel it. Thus, the saliva starts from the parotid duct at the sight, or on the recollection, of food that has been longed for ; thus, the vesiculae seminales and the urethra (for the reservoirs in which the fluids lie some time before being expelled may be considered as forming a part of the excretory ducts), contract, become straighter, and lengthen themselves, to force .to a distance the spermatic fluid. The thin and transparent ureters of fowls have been seen to contract on the urine, which, in these animals, concretes on the slightest stagnation. After remaining a certain length of time in that state of excitement, the glands relax, their tissue collapses, the juices cease to be conveyed to it as plentifully, they fall into a state of repose or sleep, which restores their sensi- bility, exhausted by too much action. It it well known that a gland over- stimulated, becomes, like any other part, insensible to the stimulus, the con- tinued application of which parches and exhausts it. From what has just been said relative to the mechanism of the secretions, it will be seen that this function may be divided into three very distinct periods ; 1st, that of irritation, characterised by the growth of the vital pro- perties, and by the more copious accession of the fluids, the necessary conse- quence of that excitement ; 2dly, the action of the gland, that is, its secre- tion, properly so called ; 3d, and lastly, the action by which the organ parts with the fluid which it has prepared : this is the last process,—it is called excretion, and is promoted by the action of the neighbouring parts. The determination of fluids to the part, the secretion and excretion succeed each other ; they are preceded by the excitement, which is the primary cause of all the subsequent phenomena. The circulation is at first excited, more blood is sent into the part, and penetrates into the tissue of the gland. Dr. Murat has had occasion to open a considerable number of old men, who died at the Bicetre, and who were known to be great smokers of tobacco. He uni- formly observed that their parotid glands, continually called into action by that habit, were larger than in those who were not given to it, and that they were remarkably red, in consequence of the blood with which they were constantly injected. What is the office of the nerves in the act of secretion ? what share has the nervous influence in the elaboration of the fluids furnished by the glan- dular organs ? All the glands which receive their nerves from the system of animal life, such as the lachrymal and salivary glands, appear, in certain cases, to receive from the brain the secretory excitation. The influence of the imagination is sufficient to determine it; thus, we shed involuntary tears when the mind is taken up with painful thoughts ; and the mouth fills with saliva on the recollection of a grateful meal* In such cases, the influence * These glands, viz. the lachrymal and sali- glions and from the nerves of voluntary motion : vary, receive nerves both from the nearest gan- the former set of nerves most probably enables OF THE SECRETIONS. 183 of the nerves on the process of secretion is indisputable ; it is not so, however, with the conglomerate glands that receive their nerves from the great sym- pathetics. The secretion of the kidneys, of the liver, and of the pancreas, appears less influenced by affections of the mind ; the brain, besides, has no immediate connexion with these glands; their nerves are almost entirely given off by the great sympathetics ; the kidneys, in particular, receive no nerves from the brain or from the spinal marrow ; hence the secretion of urine seems, more than any other, to be independent of the nervous influence* This great number of secretory organs, constantly engaged in separating various secretions from the mass of the fluids, would soon exhaust it, if the calculations of physiologists of the amount of what a gland is capable of secreting, were not manifestly exaggerated. In fact, if we admit with Haller, that the mucous glands of the intestinal canal secrete in twenty-four hours eight pounds of mucus ; that, in the same space of time, the kidneys secrete four pounds of urine ; that the same quantity is lost by the insen- sible perspiration, and again as much by the pulmonary exhalation ; there will be lost, daily, twenty pounds of fluids, almost entirely excrementitious ; for we do not include in that calculation the bile, the tears, nor the saliva and pancreatic fluid, which, in part, return into the blood after being sepa- rated from it; nor the serum, which moistens the internal surfaces, and which is purely recrementitious. This exaggeration in the calculation of the fluids which are daily ^poured out by the different emunctories, is to be attributed to the circumstance of having taken the maximum of each secretion, without considering that they mutually supply each other ; so that when less urine is voided, the quantity of perspiration is greater, and vice versd. It is very well known, that a violent diarrhoea is frequently the consequence of sudden cold applied to the skin ; the fluids, at once repelled towards the intestinal canal, having to pass through the mucous glands, whose action is greatly increased.f CII. Of other glands.—It has been customary to enumerate among the glands certain bodies which have truly a glandular appearance, but the uses of which are yet unknown. Thus, the thyroid and thymus glands, which are parenchymatous organs, destitute of excretory ducts, though receiving them to perform their ordinary functions, the fluids which that organ secretes ? A close in- latter excites or reinforces these functions vestigation of the structure of the secreting vis- whenever the mind is under certain impressions, cera and surfaces shews that their blood-vessels, —/. C. which bear a close relation to the extent of * Although these organs are not directly in- function which such viscera individually per- fluenced by the cerebral and spinal nerves, it form, are more liberally supplied with this class cannot be satisfactorily denied that the ganglial of nerves than the vessels of any other of the nerves, which are so abundantly distributed to animal textures : indeed, every important se- the blood-vessels supplying these organs, be- creting gland has a distinct ganglion, or plexus stow on these vessels that peculiar influence of these nerves, surrounding the blood-vessels which determines the nature and quantity of the which belong to it, but more especially the ar- secretion ; for how can we suppose the capilla- teries; and some of these organs have both a ry tubes, through which the blood flows, to be large plexus of nerves and a ganglion, whence able to secrete a peculiar fluid of themselves, their nerves are exclusively derived, and which without resorting to the position that the nerves, appears to be entirely devoted to the functions which so abundantly supply the ramifications of of the viscus whose blood-vessels they so plen- the blood-vessels, and the substance of the se- tifully supply. See, on this subject, the Ap- creting organs, actually influence, and, through pendix, Notes H, A A, and those on Digestion. the medium of those vessels, even produce, the —/. C. secretions in question ? ATe not these nerves t An increased flow of urine takes place in requisite to the vital actions of the viscera which most persons during the first cold of autumn; they supply ? Do we know an animal that does and cold suddenly applied to the surface of the not possess them as a most essential part of its body, by checking the perspiration, often in- organisation ? And can we suppose that they creases exhalation into the cellular textures and are distributed in so abundant a manner to the on the serous membranes, thus inducing drop- vessels of a secreting organ, without performing sies. a most requisite part in the production of the 184 OF THE SECRETION OF FAT. many vessels and some nerves, do not appear to secrete any fluid. But may not the blood which is conveyed so plentifully to the thyroid gland, undergo, nevertheless, certain changes, though we may not be able to discover what they are 1 Besides, may not the lymphatics perform the office of excretory ducts, and convey back again immediately into the mass of the blood the fluid which has undergone changes in the glandular body 1 The capsulae renales are in the same condition : they have, however, in addition, an inter- nal reservoir, a kind of lacuna, whose parietes are smeared with a viscid and brown coloured substance secreted by the capsule, and which, doubtless, is conveyed into the mass of the blood by the lymphatics arising from the pari- etes of its internal cavity. CHI. Of the secretion of adeps within the cellular tissue.—This soft tissue, which is diffused over the whole body, and affords a covering to all our organs, is of use not merely in separating them from one another, and in connecting together the different parts ; it is, besides, the secretory organ of the adipose substance, a semi-concrete oily animal matter, which is found in almost every part of the body, deposited in its innumerable cells. The membranous parietes of these small cellular cavities are supplied by numerous minute ar- teries, in which the adeps is separated ; it is conveyed by its specific light weight to the circumference of the column of blood in the vessels, and trans- udes through the pores in their parietes. Its quantity and consistence vary in different parts of the body, and in different persons : there is situated below the skin a thick layer of cellular substance (pannicule grassieux) ; it is found in considerable quantity between the interstices of the muscles, along the blood-vessels, near the articulations, and in the vicinity of certain organs, as the eyes, the kidneys, and the breasts. That which fills the .bottom of the orbit, and which surrounds the eye-ball, is softish and almost fluid ; that which envelopes the kidneys and the great joint, is, on the contrary, of the consistence of suet. Between these two extremes there are many grada- tions ; and it may be said that the animal oil in question is not exactly the same in any two different parts of the body. The high temperature of the human body maintains it in a state of semi-fluidity, as may be observed in surgical operations. In some parts it is even absolutely fluid ; but its nature is then observed to be greatly changed, it no longer contains any oily substance, and differs but little from a mere aqueous gelatine. Thus, the fluid in the cellular tissue of the eye-lids, of the scrotum, die, has been considered by several physiologists as positively different from fat. It may not be amiss to observe, that the laminae of the cellular tissue in such circumstances yield more readily to ex- tension, present a greater surface, form membranous expansions, and cir- cumscribe cells of a considerable size, so that the differences in the secretion perfectly coincide with the difference of structure. It may further be ob- served, that the functions of the eye-lids and of the penis required that they should not contain any fat. Considerable deformity, when the person grew fat, would have been the consequence of the increased bulk of these parts • and besides, the folds of the skin would not have that free motion which their functions require. No real adeps is ever found within the skull, and the utility of this condition is very obvious. To how many dangers would not life have been exposed, if a fluid so varying in quantity, and the amount of which may be trebled in a very short space of time, had been deposited in a cavity accurately filled by an organ which is affected by the slightest compression ? In an adult male, of moderate embonpoint, the proportion of adeps is about one-twentieth of the weight of the whole body ; it is greater in pro- OF THE USES OF THE FAT. 185 portion in children and in females, for its quantity is always relative to the energy of the functions of assimilation. When digestion and absorption are performed with great activity, fat accumulates within the cellular substance: and if it be considered that it is but imperfectly animalised ; that it bears the most striking analogy to the oils extracted from plants ; that it contains very little azote and much hydrogen and carbon, like all other oily substances, since, on distillation, it is decomposed, and yields water and carbonic acid, with a very small quantity of ammonia ; that its proportions are very vari- able, and may be considerably increased or diminished, without manifestly impairing the order of the functions ; that animals that spend a great part of their life without eating, seem to exist during their torpid state on the fat which they have previously accumulated in certain parts of the body ;*—> one will be led to think that the state of fat is to a portion of the nutritive matter, extracted from the food, a kind of intermediate state through which it has to pass before it can be assimilated to the animal whose waste it is destined to repair. Animals that live on grain and vegetables are always fatter than those which live exclusively on flesh. Their fat is consistent and firm, while that of carnivorous animals is almost completely fluid. A corpulent man on having his diet suddenly reduced, sensibly becomes thinner in a very short time ; the bulk and weight of his body diminishes from the absorption of the fat which supplies the deficient quantity of blood. Adeps may, therefore, be considered as a substance in reserve, by means of which, notwithstanding the small quantity of food and its want of nutritious qualities, Nature finds wherewith to repair the daily waste. CIV. Of the use of the fat.—The use of adeps is not, as has been stated, on the authority of Macquer, to absorb the acids that are formed in the animal economy ; that which is obtained from it by distillation (the sebaceous acid) is a new product, formed by the combination of the oxygen of the atmosphere with the hydrogen, the carbon, and the small quantity of azote which it contains. The small quantity of this last substance nearly constitutes it a vegetable acid. Fat has a considerable affinity for oxygen, and by combin- ing with it turns rancid, after remaining some time exposed to the air. It deprives metallic oxides of a part of their oxygen, and likewise, on being triturated with metallic substances, promotes their oxidisement. In propor- tion as it absorbs oxygen its density increases ; thus, oils become concrete by combining with oxygen, and fat acquires a consistence almost equal to that of wax, which is itself a fatty substance highly oxidised. Besides the principal use we have assigned to adeps, and according to which the cellular system may be looked upon as a vast reservoir, in which there is deposited a considerable quantity of nutritive and semi-animalised matter, this fluid answers several purposes of secondary utility. It preserves the body in its natural temperature, being, as well as the tissue of the cells in which it is contained, a very bad conductor of heat. Persons who are ex- cessively corpulent, scarcely feel the most severe cold ; and the animals which inhabit northern climates, besides being clothed in a thick fur, are likewise provided with a considerable quantity of fat. The fishes of the frozen seas, the animals which seldom go far from the polar regions, and all kinds of whales, are covered with fat, and have also a considerable quantity within their bodies. By its unctuous qualities, fat promotes muscular contraction, * Marmots and dormice become prodigiously the abdomen, in which the epiploon forms masses fat during the autumn; they then take to their of a considerable size. When, in the spring, holes, sind live in them during the six winter their torpor ceases, and they awaken from then? months .on the fat which is accumulated in all sleep, they are, for the most part, exceedingly their organs. There is most fat collected in emaciated. 24 186 OF THE SECRETION OF THE MARROW. the motion of the different organs, and the free motion on each other of the different surfaces; it stretches and supports the skin, fills vacuities, and gives to our limbs those rounded outlines, those elegant and graceful forms, pecu- liar to the female body. Lastly, it envelopes and covers over the extremities of the nerves, diminishes their susceptibility, which is always in an inverse ratio of the embonpoint,—a circumstance that induced a physician of merit to say, that the nervous tree, planted in the adipose and cellular substance, suf- fers when, from the collapse and removal of that tissue, its branches are ex- posed in an unprotected state to the action of external causes, as injurious to them as the rays of the sun to a plant torn from its native soil. It is, in fact, observed, that nervous people are exceedingly thin, and have an excessive degree of sensibility. Too much fat, however, is as injurious as too small a quantity of it. I have seen several persons whose obesity was such that, be- sides being completely incapable of taking the slightest exercise, they were in great danger of suffocation. Respiration in such persons is, at times, in- terrupted by deep sighs; and their heart, probably overloaded with fat, ex- pels with difficulty the blood within its cavities. CV.—According to modern chemists the use of fat is to take from the sys- tem a part of its hydrogen. When the lungs or liver are diseased, when re- spiration or the biliary secretion does not carry out of the system a sufficient quantity of that oily and inflammable principle, fat forms in a greater propor- tion. They appeal to the result of the experiment of shutting up a goose, whose liver is to be fattened, in a confined cage, placed in a hot and dark situa- tion, and in gorging it with paste, of which it eats the more greedily, as being unable to stir, it gratifies its inclination to action by exerting the organs of di- gestion. Notwithstanding this quantity of food, the bird becomes emaciated, is affected with a kind of marasmus, its liver softens, grows fatter, more oily, and attains an enormous size. This experiment, and many other facts, prove that the secretions from which analogous products are formed, may mutually supply each other: but can we admit the chemical theory of the use of fat, when we recollect, that frequently, in the most corpulent persons, respiration and the secretion of the bile are performed with great freedom and with no difficulty ; while the diffi- cult respiration attending pulmonary consumption, and the difficult flow of the bile from an obstruction of the liver, are always accompanied with com- plete marasmus 1 Whatever moderates the activity of the circulatory system, tends to bring on adipose plethora. Thus, an inactive state of the mind and body, profuse bleedings, castration, sometimes induce obesity; an affection in which the cellular tissue appears affected with atony, and undergoes an actual adipose infiltration, somewhat analogous to that which gives rise to tumours called steatomatous. If the energy of the heart and arteries is too great, emaciation is always the consequence ; when, on the contrary, the sanguineous system is languid, there is formed a gelatinous fat, and the embonpoint is a mere state of bloatedness. This incompletely formed fluid, which distends the parts in persons of a leucophlegmatic habit, is but an imperfect kind of fat; it resembles the mar- row or the medullary juice, which is a very liquid fat, whose consistence di- minishes when animals become lean. Enclosed within the cells of the osse- ous tissue, in cavities whose sides cannot collapse, and whose dimensions must always remain the same, the marrow, of which they are never free, is of different degrees of density ; and what authors say of its diminished quanti- ty, must be understood as applying to the diminution of its consistence. CVI. Of the secretion of the marrow.—The secretion of the marrow is, like OF NUTRITION. 187 that of the fat, a mere arterial transudation: it is performed by the medullary membrane, which is thin, transparent, and cellular, lines the inside of the cen- tral cavity of the long bones, and extends over all the cells of that spongy substance. The medullary membrane, when in a healthy state, does not give any marks of relative sensibility. In all the amputations I have per- formed, and they have not been few, in all the operations of the same kind, at which I have been present, whatever the bone was, whether it was divided near a joint or in the middle of its body, I never knew the patient complain of pain, provided the limb was well supported by the assistants, and provided no jerk was given by the operator himself. In that operation, the pain occa- sioned by the division of the skin and of the nerves overcomes every other pain ; and I have always seen patients, impressed with the popular prejudice, and expecting anxiously the division of the bone, feel quite free from pain as soon as the saw had begun to work. Nay, several, after expressing by their cries the most acute pain, taking advantage of the kind of ease which follows the division of the flesh, raise their head, and look on while the bone is being sawn through; at once actors and spectators in this last partnf a painful and bloody operation. Yet the medullary membrane, the injury of which is attended with no pain while in a healthy state, becomes the seat of the most exquisite sensi- bility in the pains in the bones which mark the last stages of the venereal disease ; in the kind of conversion into flesh of the solid bone, known by the name of spina ventosa, as will be mentioned in speaking of the uses of the marrow, in the chapter on the Organs of Motion and on their Ac- tion.* CHAPTER VI. OF NUTRITION. CVII. Nutrition the end of the assimilating Processes.—CVIII. and CIX. Of the Process of Nutrition.—CX. Substances capable of yielding Nutriment.—CXI. Changes produced in ali- mentary Substances.—CXII. The ultimate result. CVII.—All the functions which we have hitherto made the object of our study,—digestion, by which the alimentary substances received within the body are deprived of their nutritive parts ; absorption, which conveys that recrementitious extract into the mass of the fluids ; the circulation, by which it is carried to the parts wherein it is to undergo different changes ;—diges- tion, circulation, absorption, respiration, and the secretions, are but prelimi- nary acts, preparatory to the more essential function treated of in this chap- ter, and the consideration of which terminates the history of the phenomena of assimilation. Nutrition may be considered as the complement of the functions of assi- milation. The aliment, altered in its qualities by a series of decompositions, animalised, and rendered similar to the substance of the being which it is to nourish, is applied to the organs whose waste it is to repair ; and this identi- fication of the nutritive matter to our organs, which take it up and appro- priate it to themselves, constitutes nutrition. Thus there is accomplished a real conversion of the aliment into our own substance. * For some further remarks on Secretion, sec Appendix, Note C C.—/. C. 188 OF NUTRITION. There is incessantly going on a waste of the integrant particles of the living body, which a multiplicity of circumstances tend to carry away from it: several of its organs are constantly engaged in separating from it the fluids containing the recrementitious materials of its substance, worn by the combined action of the air and of caloric, by inward friction, and by a pulsa- tory motion that detaches its particles. Analogous, therefore, to the vessel of the Argonauts, so often repaired in the course of a long and perilous navigation, that on her return no part of her former materials remained, an animal is incessantly undergoing decaj', and if examined at two different periods of its duration, does not contain one of the same molecules. The experiment performed with madder, which dyes red the bones of animals among whose food it is mixed, proves, most unquestionably, this incessant decomposition of animated and living matter. One has only to interrupt, for a sufficient length of time, the use of that plant, to make the uniformly red colour assumed by the bones completely disap- pear. Now, if the hardest and most solid parts, which are best calculated to resist decay, are undergoing a perpetual motion of decomposition and of regeneration, there can be no doubt that this motion must be far"more rapid in those whose power of cohesion is much inferior—for example, in the fluids. Attempts have been made to determine the period at which the body is completely renovated ; it has been said, that, an interval of seven years was required for one set of molecules to disappear and be replaced by others ; but this change must go on more rapidly in childhood and in youth. It must be slower at a mature age, and must require a considerable time at a very advanced period of life, when all the parts of the body become, in a re- markable degree, fixed and firm in their consistence, while the vital powers become more languid. There can be no doubt, that the sex, the habit, the climate in which we live, the profession we follow, our mode of life, and a variety of other circumstances, accelerate or retard it; so that it is impossi- ble to fix, with any degree of certainty, its absolute duration. C VIII. Of the process of nutrition.—The parts of our body, in proportion as they undergo decay, are repaired only by means of homogeneous par- ticles exactly like themselves ; were it otherwise, their nature, which always remains the same, would be undergoing perpetual changes. When, in consequence of the successive changes which it has undergone from the action of the organs of digestion, of absorption, of the circulation, of respiration, and of secretion, the nutritive matter is animalised or assimi- lated to the body which it is to nourish, the parts which it moistens retain it and incorporate it to their own, substance. This nutritive identification is not performed alike in the brain, in the muscles, in the bones, &c. Each of them appropriates to itself, by a real process of secretion, whatever it meets with fitted for its nature in the fluids conveyed to it by the different kinds of vessels, but especially by the arteries ; it leaves unaffected the remaining heterogeneous particles. A bone is a secretory organ, around which phos- phate of lime is deposited ; the lymphatic vessels which, in the process of nutrition, perform the office of excretory ducts, remove that saline substance, when it has lain sufficiently long in the cells of its tissue. The same hap- pens to the muscles with regard to fibrina, and to albumen with regard to the brain ; every part appropriates to itself, and converts into a solid form, those fluids which are of the same nature, in virtue of a power of which the term affinity of aggregation, used in chemistry, gives an idea, and of which it is perhaps the emblem.*. * Assimilation takes place in a more perfect all its relations. See AprENnix, Note D D.— manner when the vital influence is complete in J. C. OF NUTRITION. 189 The nutrition of a part requires that it should be possessed of sensibility and motion ; by tying the arteries and nerves of a part, it cannot be nourish- ed, nor can it live. The blood which flows along the veins, the fluid con- veyed by the absorbents, contain, in a smaller proportion than arterial blood, vivifying and reparatory particles. It is even commonly thought, that the lymph and venous blood contain no directly nutritive particles. As to the share which the nerves take in the process of nutrition, that is not yet com- pletely determined. A limb that is paralysed, by the division or tying of its nerves, or by any other affection, sometimes retains its original size and plumpness ;* most frequently, however, though perhaps for want of mo- tion, it becomes parched, emaciated, and shrinks in a remarkable degree. CIX.—We should be enabled to understand the process of nutrition, if, afte* having accurately determined the difference of composition between our food and the substance itself of our organs, we could see how each function robs the aliments of their qualities, to assimilate them to our own bodies; and what share each function takes in the transmutation of the nutritive particles into our own substance. To illustrate this point, suppose a man to live exclu- sively on vegetable substances, which, in fact, form the basis of our food : on whatever part of the plant he may live, whether on the stem, on the leaves, on the blossoms, on the seeds, or on the root, carbon, hydrogen, and oxygen, enter into the composition of these vegetable substances, which, by a com- plete analysis, may all be resolved into water and carbonic acid. To these three constituent principles there is frequently united a small quantity of azote, of salts, and of other materials, in different proportions. If, then, we examine the nature of the organs in this man, whose food is entirely vegeta- ble, it will be found that they are different in their Composition, and far more animalised than that kind of food ; that azote predominates, though the vegetable substance contains none or only a very small quantity ; that new products, undistinguishable in the aliments, exist in considerable quantity in the body which is fed on them, and appear produced by the very act of nu- trition. The essence of this function is, therefore, to make the nutritive matter undergo a more advanced state of composition, to deprive it of a portion of its carbon and of its hydrogen, to make azote -predominate, and to produce several substances which did not exist in it before. All living bodies seem to possess the faculty of composing and decomposing the sub- stances by means of- which they are maintained, and to form new products ; but they possess it in various degrees of energy. The sea-weed, from the ashes of which soda is obtained, on being sown in a box of soil in which there is not a single particle of that alkali, and watered with distilled water, will no longer contain it, as if it had grown on the sea shore, in the midst of marshes constantly inundated by salt and brackish water, t Living bodies, then, are real laboratories, in which there are carried on * This and various other considerations equal degree when watered with distilled as evince that nutrition is not essentially depend- with sea-water. This, I apprehend, is the au- ent upon the voluntary nerves, but upon that thor's meaning, though the text is somewhat class of nerves (the ganglial), which is chiefly obscure, and would almost lead one to believe ramified on the blood-vessels. See the above he meant, that no alkali whatever can be obtain- Note in the Appendix.—/. C. ed from the sea plant under the circumstances f I am unacquainted with the details of the he states : " L'algue marine, dont les cendres experiment referred to by the author ; he quotes fournissent la soude, semee dans une caisse it, I conceive, to shew that the power which, pleine d'un terreau qui ne contient pas un seul he says, is common to all living bodies, of pro- atome de cet alkali, arrosee avec l'eau distillee, ducing a substance not supplied to them from ne le fournit plus, comme si elle avoit pris sa without, is not possessed, in the same degree, croissance au milieu des marais toujouis inondes by all bodies endowed with life; since the sea- par leurs caux saumatres et muriatiques."— T. weed here alluded to does not possess it in an 190 OF NUTRITION. combinations and decompositions which art cannot imitate ; bodies that ap- pear to us simple, as soda and silex, seem to be formed by the union of their constituent particles ; while other bodies, whose composition we do not un- derstand, undergo an irresistible decomposition : hence, methinks, one may infer, that the power of nature in the composition and decomposition of bodies far exceeds that of chemistry. Straw and cereal plants contain a considerable quantity of silex, even when the earth in which they grow has been carefully deprived of its silicious par- ticles. Oats, particularly, contain a large quantity of that verifiable earth; the ashes obtained by burning its seed, on being analysed by means of the nitric acid, were found by M. Vauquelin to contain tWo or" Pure s^ex m&\s~ soluble in that acid, and 0-393 of phosphate of lime dissolved in it. The excrements of a hen fed for ten days on oats only, on being calcined and analysed by the same chemist, produced twice as much phosphate and carbonate of lime as was contained in the oats, with a small deficiency in the quantity of silex, which might have been employed in furnishing the excess of calcareous matter; a transmutation depending on the absorption of an unknown principle, to the amount of nearly five times its own weight* CX. Substances capable of yielding nutriment.—A substance, to be fit for our nourishment, should be capable of decomposition and fermentation ; that is, capable of undergoing an inward and spontaneous change, so that its elements and relations may be altered. This spontaneous susceptibility of decomposition excludes from the class of aliments whatever is not organised and is not a part of a living body ; thus, mineral substances absolutely re- sist the action of our organs, and are not convertible into their own sub- stance. The common principle extracted from alimentary substances, how- ever varied they may be, the aliment, as Hippocrates terms it, is, most proba- bly, a compound highly subject to decomposition and fermentation ; this is likewise the opinion of all those who have endeavoured to determine its na- ture. Lorry thinks it a mucous substance; Cullen says it is saccharine ; Professor Halle considers it as an hydro-carbonous oxide, which differs from the oxalic acid only in containing a smaller quantity of oxygen. It is evident that these three opinions are very much alike, since oxygen, carbon, and hy- drogen, combined in different proportions, form the "mucous saccharine sub- stances and the base of the oxalic acid. On analysing the animal substance, by means of the nitric acid, it is reduced to this last base by depriving it of a considerable quantity of azote, which constitutes its most remarkable cha- racter. But whence comes this enormous quantity of azote ? How happens it that the flesh of a man living exclusively on vegetables contains as much azote and ammonia, and is as putrescent, as that of a man living on animal food 1 Respiration does not introduce a single particle of azote into our fluids: this gas comes out of the lungs as it entered ; the oxygen alone is diminish- ed in quantity.| Might not one suspect that this element of animal sub- stances is a product of the vital action, and that, instead of receiving it from our aliments, we form it within ourselves, by an act that is hypher-chemical, that is, which chemistry cannot imitate ?J * See the Annates de Chimie, and the Sys- quantity of oxygen.—Philosophical Transac- trme des Connaissances Chimiques de Fourcroy, tions, 1809. But this arises from the azote al- tom. x. p. 72. ready absorbed by the blood from the air; for t See Appendix, Notes W and D D. the recent experiments of M. Edwards demon- t The experiments of Messrs. Allen and Pe- strate that azote is absorbed by the blood in the pys prove, that when an animal is made to lungs, and thence given out during respiration. breathe pure oxygen, the blood disengages a See Les Agens Physiques sur la Vie, par M. certain quantity of azote, and absorbs an equal Edwards, 1824.—J. C. OF NUTRITION. 191 CXI. Changes produced in alimentary substances.—It has been maintained, that the hydro-carbonous oxide combines, in the stomach and intestinal canal, with oxygen, whether this principle has entered with the aliments into the digestive tube, or whether it is furnished by the decomposition of the fluids within that cavity. The intestinal fluids extricate azote, which combines with the alimentary mass, and occupies the place of the carbon, which the oxygen has taken from it, to form carbonic acid. On reaching the lungs, and being again exposed to the action of the oxygen of the atmosphere, this gas robs it of a portion of its carbon, and as it disengages the azote of the venous blood, it brings about a new combination of that principle with the chyle. Lastly, propelled with the blood to the surface of the skin, the atmospherical oxygen disengages its carbon and completes its azotisation. The cutaneous Organ is perhaps to the lymphatic system, what the pulmonary organ is to the sanguineous system. The animalisation of the animal substance is therefore effected principally by the loss of its carbon, which is replaced by the excess of azote in the - animal fluids. These maintain themselves, in this manner, in a due tempe- rament ; for, continually parting with the carbonous principle in the intesti- nal, pulmonary, and cutaneous combinations, they would be over-animalised, if an additional quantity of chyle did not seize the azote, which is in excess. Still, this theory does not account for the formation of the phosphoric salts, of the adipocire, and a variety of other products : but, without adopting it to the full, one may presume, from the experiments and facts on which it rests, that the oxygen of the atmospherical air is one of the most powerful agents employed by nature in the transformation of the aliments we live upon into our substance. How are those animals nourished which live solely on mere animalised flesh ; that is, containing a greater quantity of azote, and a greater propor- tion of ammonia, than their own substance ? In such a case, the assimila- tion of the aliments consists in their disanimalisation, either by the co-operation of all the organs, or by the sole action of the digestive organs, by the com- bination of the gastric juice with the other fluids. The constituent elements entering into the composition of our organs, whether coming from the exterior, or formed by the vital power itself, are thrown out of our body by the different emunctories, and cease to form a part of it, after remaining within it for a limited time. The urine carries along with it an enormous quantity of azote ; the lungs and the liver rid us of the carbon and of the hydrogen ; the oxygen, of which eighty-five part3 in the hundred enter into the composition of water, is evacuated by means of the aqueous secretions, which carry off, in a state of solution, the saline and other soluble principles. Among those salts there is one but little soluble, and which, nevertheless, is of primary consequence among the constituent principles of the animal economy. Phosphate of lime, in fact, forms the base of several organs ; it almost entirely forms the osseous system at an advanced period of life ; all the white organs, all our fluids, contain a remarkable quantity of that sub- stance, of which the economy rids itself by a kind of dry secretion. The outer covering is, in all animals, the emunctory destined for that purpose : the annual moulting of birds, the fall of the hair of quadrupeds, the renovation of the scales of fishes and reptiles, carry off every year a considerable quan- tity of calcareous phosphate. Man is subject to the same laws, with this difference, that the annual desquamation of the epidermis is not under the absolute influence of the seasons, as in the brute creation. The human epi- dermis is renewed annually, as well as the hair on the head and on the body ; 192 OF NUTRITION. but this change is brought about gradually, and is not completed in a season : it does not take place in the spring, as in most animals, nor in autumn with the fall of the leaf, though at these two periods the hair falls off m greatest quantity, and the desquamation of the cuticule is most active. These two phenomena last throughout the whole year, as in southern climates the fall of the leaves and the renovation of vegetation are continually going on. As will be mentioned, in speaking of the functions of generation, man living in a state of society, and enjoying all the advantages of civilisation, is not as much under the influence of the seasons as the inferior animals. One cannot, however, but observe, that the successive shedding and renewing of the epidermoid parts, as the cuticle, the nails, and the hair, are among the most effective means which nature possesses of parting with the phosphate of lime, so abundant in all animals, and which, nevertheless, is so insoluble, and consequently so unfit to be carried out of the system along with the ex- crementitious fluids. This effect is very remarkable, on the termination of several diseases, in the salutary renovation of the solids and fluids which takes place during convalescence. The hair ceases to grow on the bald head of an old man ; his perspiration diminishes. May not this be the cause of the great quantity of calcareous salts, of the ossification of the vessels, of the induration of the membranes ? CXII. What is the ultimate result presented to us by this series of func- tions, linked together, growing out of one another, and all acting on the matter of nutrition, from the moment it is received within the body, till it is applied to the growth and reparation of its organs 1* It shews us man living within himself, unremittingly employed in converting into his own substance hetero- geneous substances, and reduced to an existence purely vegetative, inferior even to the greater part of organised beings in his powers of assimilation. But how high is he not placed above them all in the exercise of those func- tions we are now about to contemplate,—functions which raise him above his own nature, which enlarge the sphere of his existence, wrhich serve him to provide for all his wants, and to keep up, with all nature, those manifold relations which subject her to his empire ! j * Intimately connected with the considera- tion of nutrition is that of reproduction. This phenomenon takes place to a very limited ex- tent indeed in the more perfect animals ; but as we descend in the scale of creation, we find that the destruction of a member or part of the body of an animal is, after a time, followed by a partial or entire reproduction of the Qart de- stroyed ; and amongst the lowest class of ani- mals, even a portion only of the body becomes a perfect animal, and presents the specific cha- racters of the parent. In this respect, the phe- nomena of animal life, as we descend through its gradations, approach those of vegetable ex- istence. t For further observations on Nutrition, see Appendix, Notes S and C C. OF SENSATIONS, 193 ^ccoittr #vtrn\ FUNCTIONS WHICH TEND TO THE PRESERVATION OF THE INDIVIDUAL, BY ESTABLISHING HIS RELATIONS WITH THE BEINGS THAT SURROUND HIM. CHAPTER VII. OF SENSATIONS. civiISOfSeth0ef Ghfe of the Eye, &C-CXV1II M^^^,;^; CXIX. Of the Organ of Light in the lower Animals.—CXX. Of Sound—CXX.I. Uttheur gan and MechaniL of Helring.-CXXII .Pathological Physiology£nH^ffv)C™Ii: 5f Odours.-CXXIV. Of the Organ of SmelL-CXXV. Of the Sensat™0*™™?-. CXXV1. OfFlavours.-CXXVII. and OXXVIII. Of^|fen»e,°A N,1i7 PXXXII and Sense of Touch.-CXXX. Of the Integuments.-CXXXI. Of the Nails^OXXXH. and CXXXIII. Of the Hair of the Headanlof other parts.-CXXXIV and CXXg• W the Sensations conveyed by Touch, and of its States m different parts °f,^f ££^£g£j£ ^LI^S^^RSlde«.-CLIV. Of.?«r^^T^VmV!&S^i Reasoning—CLV. Of spoken Signs or Words—CLVI. to CLV111. Ul the uisoraers 01 thought-CLIX.Of SlePeP and Waking.-CLX. Of Dreams and Somnambulism. CXIII —We have already seen how the human body, essentially changeable and perishable, maintains itself in its natural economy, carries on its growth, and supplies its decay, by assimilating to its own substance principles that are yielded to it by the food it digests, and by the air it breathes. I shall now proceed to examine by what organs man is enabled to keep up, with all na- ture the relations on which his existence depends; by what means he is made aware of the presence of objects which concern him, what means he possesses to fit his connexion with them to his welfare, to draw them towards him or to repel them, to approach or to avoid and escape them, as he perceives in them danger, or the promise of enjoyment. Man possesses, in all its plenitude, this new mode of existence, which is denied to vegetable nature. Of all animals, it is he that receives impressions the most crowded and various, that is most filled with sensations, and that employs them with the most powerful combination, as the materials of thought, and the sources of intelligence ; he is the best organised for feeling the action of all beings around him, and re-acting on them in his turn. In the study which we are about to undertake we shall see many instruments placed on the limits of existence, on the surface of, the living being ready to receive every impression ; conductors, stretching from these instruments to one common centre, to which all is carried ; conductors through which this central organ regulates the actions, which now transport the whole body from one place to another (locomotion) ; now merely change the relative 25 194 OF LIGHT. situation of its parts (partial motion); and at other times produce in the organs certain dispositions, of which speech and language, in their various forms, are the result. If we are thoroughly to understand the mechanism of this action of out- ward objects on our body, we must follow the natural succession of the phe- nomena of sensation ; studying first the bodies which produce the sensitive impression, examining next the organs that receive it, and next the conduc- tors which transmit it to a particular centre, whose office is perception. To take the sense of sight, for instance, we can never understand how it is that light procures us the knowledge of certain qualities of bodies, if we have not learnt the laws to which that fluid was subjected, if we know nothing of the conformation of the eyes, of the nerves by which those organs communicate with the brain, and of the brain itself, whither all sensations, or rather the mo- tions in which they consist, are ultimately carried. CXIV. Of light.—At this day, the greater part of natural philosophers consider it as a fluid impalpable, from its exceeding tenuity. Many believe it to be only a modification of caloric, or of the matter of heat; and this last opinion has received much plausibility from the late observations of Herschel.* I shall not examine whether, as Descartes and his followers imagine, light, consisting of globular molecules, exists of itself, uniformly diffused through space ; or as Newton has taught us to believe, it be but an emanation of the sun and fixed stars, which throw off from their whole surface a part of their substance, without ever exhausting themselves by this continual efflux ; it is enough for us to know, 1st, That the rays of this fluid move with such velocity, that light passes in a second through a distance of seventy two thou- sand leagues, since, according to the calculation of Roemer, and the tables of Cassini, it traverses in something less than eight minutes the thirty-three millions of leagues that separate us from the sun ; 2dly, That light is called direct, when it passes from the luminous body to the eye without meeting any obstacle ; reflected, when it is thrown back to that organ by an opaque body ; refracted, when its direction has been changed by passing from one transparent medium to another of different density. 3dly, That the rays of light are re- flected at an angle equal to that of incidence ; that a ray passing through a transparent body, is more strongly refracted as the body is more convex on the surface, denser, or of more combustible elements. It was from this last observation, that Newton conjectured the combustibility of the diamond, and the existence of a combustible principle in water, since placed beyond doubt, by the beautiful experiments of modern chemistry. 4thly, That a ray of light refracted by a glass prism, is decomposed into seven rays, red, orange, yellow, green, blue, indigo, and violet. Each of these rays is less refrangible as it is nearer to the red. This ray is, of all, that which strikes the eye with the greatest force, and produces on the retina the liveliest impressions. The eagerness of savages for stuffs of this colour is well known. Among almost all nations it has dyed the mantle of kings : it is the most brilliant and splen- did of all: there are animals whose eyes seem scarcely to sustain it: I have seen maniacs whose madness, after a long suspension, never failed to break out at the sight of a red cloth, or of one clothed in that colour. Green is, * This celebrated astronomer has published and towards the red ray, so that it would re- in the Philosophical Transactions of the Royal ceive any rays yet less refrangible, rises highes Society for 1800, a series of experiments, which than when it is placed in that colour : from which shew that the different coloured rays heat in dif- Herschel concludes that rays are given out by ferent degrees the bodies on which they fall, and the sun, too little refrangible to produce the sen- that the red ray, which is the least refrangible, sation of light, and of colours, but which pro- gives also the greatest heat. duce the sensation of heat. The thermometer placed out of the spectrum. OF THE SENSE OF SIGHT 195 on the contrary, the softest of colours, the most permanently grateful, that which least fatigues the eyes, and on which they will longest and most wil- lingly repose. Accordingly, nature has been profuse of green, in the colour- ing of all plants ; she has dyed, in some sort, of this colour the greater part of the surface of the globe. When the eyes bear uneasily the glare of too strong a light, glasses of this colour are used to soften the impression, which slightly tinge with their own hue all the objects seen through them. 5thly, The violet ray, last in the scale, of which the middle place is filled by the green, is of all the weakest, the most refrangible. Of all colours, violet has the least lustre ; forms shew to less advantage under it, their prominences are lost • painters accordingly make but little use of it. When an enlightened body reflects all the rays, the sensations they might separately produce blend into the sensation of white ; if it reflects a few, it appears differently coloured ac- cording to the rays it repels : finally, if all be absorbed, the sensation of black is produced, which is merely the negation of all colour. A black body is wrapped in utter darkness, and is visible only by the lustre of those that sur- round it Lastly, That from every point in the surface of a luminous or en- lightened body there issue a multitude of rays, diverging according to their distance, with a proportionate diminution of their effect; so that the rays from each visible point of the body form a cone, of which the summit is at that point, and the base the surface, of the eye on which they fall. CXV. Sense of sight.—The eyes, the seat of this sense, are so placed as to command a great extent of objects at once, and enclosed in two osseous cavities, known by the name of orbits. The base of these cavities is forwards, and shaped obliquely outwards; so that their outward side not being so long as the others, the ball of the eye, supported on that side only by soft parts, may be directed outwards, and take cognisance of objects placed to a side, without it being necessary, at the same time, to turn the' head. In proportion as we descend from man in the scale of animated beings, the shape of the base of the orbits becomes more and more oblique; the eyes cease to be directed forward ; in short, the external side of the socket disappears, and the sight is entirely directed outward ; and, as the physiognomy derives its principal character from the eyes, its expression is absolutely changed. In certain ani- mals very fleet in running, such as the hare, the lateral situation of the or- gans of vision prevents the animals from seeing small objects placed directly before them ; hence those animals, when closely pursued, are so easily caught in the snares which are laid for them. The organ of sight consists of three essentially distinct parts. The one set intended to protect the eye-ball, to screen it, at times, from the influence of light, and to maintain it in the conditions necessary to the exercise of its functions : these parts are the eye-brows, the eye-lids, and the lachrymal ap- paratus, and they serve as appendages of the organ. The eye-ball itself con- tains two parts, answering very different purposes; the one, formed by nearly the whole globe, is a real optical instrument, placed immediately in front of the retina, and destined to produce on the luminous rays those changes which are indispensable in the mechanism of vision ; the other, formed by the medullary expansion of the optic nerve, is the immediate organ of that function. It is the retina which alone is affected by the impression of light, and set in motion by the contact of that very subtle fluid: This impression, this motion, this sensation, is transmitted to the cerebral organ by the optic nerve, the expansion of which forms the retina. CXVI. Of the eye-brows, the eye-lids, and the lachrymal apparatus (tutamina oculi, Haller). The more or less dark colour of the hairs of the eye-brows renders that projection very well adapted to diminish the effect of too vivid a 196 OF THE EYES, EYELIDS, &C light, by absorbing a part of its rays. The eye-brows answer this'purposc the more completely, from being more projecting, and from the darker colour of the hairs which cover them ; hence we depress the eye-brows, by knitting them transversely, in passing from the dark into a place strongly illuminated, which causes an uneasy sensation to the organ of sight. Hence, likewise, the custom that prevails with some southern nations, whose eye-brows are shaded by thicker and darker hairs, to blacken them, that they may still better answer the purpose for which they are intended. The eye-lids are two movable curtains placed before the eyes, which they alternately cover and uncover. It was requisite that they should be on the stretch, and yet capable of free motion ; now, both these ends are obtained by the tarsal cartilages, which are situated along the whole of their free edges, and of the muscles which enter into their structure. The cellular tissue which unites the thin and delicate skin of the eye-lids to the muscular fibres, contains, instead of a consistent fat, which would have impeded its motion, a gelatinous lymph, which, when in excess, constitutes oedema Of the eye-lids. The tissue of the eye-lids is not absolutely opaque, since, even when strongly drawn together, and completely covering the globe of the eye, one may still discern through their texture light from darkness. On that account, light may be considered as one of the causes of awakening, and it is of consequence to keep in the dark patients fatigued by want of sleep. The principal use of the eye-lids is to shade the eyes from the continual impression of light. Like all the other organs, the eyes require to recruit themselves by repose ; and they had not been able to enjoy it, if the inces- sant impression of the luminous rays had continually excited their sensibility. The removal of the eye-lids* is attended with loss of sleep. The fluids are determined to the affected organ, which suffers from incessant irritation. The eyes inflame, the inflammation spreads towards the brain, and the patient expires in the most dreadful agony. Thanks to an advanced state of civili- sation, these barbarous tortures have long been abolished ; but what hap- pens, when, from ectropium of one or other of the eye-lids, a small portion of the sclerotic coat or cornea remains uncovered, proves the indispensable necessity of those parts. The spot exposed to the continued action of the air and of the light becomes irritated and inflamed, and there comes on an ophthalmia, which can be cured only by bringing together, by means of a surgical operation, the divided edges of the opening which is the cause of the affection. From the movable edges of both eye-lids there arise short curved hairs, of the same colour as those of the eye-brows ; they are called eye-lashes, and are intended to prevent insects, or other very light substances floating in the atmosphere, from gettiner between the eye-ball and the eye- lids.! The anterior part of the eye, thus defended against external injuries, is continually moistened by the tears. The organ which secretes this fluid is a small gland, situate in a depression at the anterior and external part of the arch of the orbit, imbedded in fat, and supplied with pretty considerable ves- sels and nerves in proportion to its bulk, and pouring the fluid it secretes, by means of seven or eight ducts which open on the internal surface of the upper eye-hd, by capillary orifices directed downward and inward. The tears are a muco-serous fluid, rather heavier than distilled water, saltish, changing to a green colour vegetable blues, and containing soda, muriate * A mode of punishment in use amongst the luminous rays, and thus clnmr.isli the hurtful ef- ancients, especially Ihe Carthaginians. fects of too strong a light.— J. C t 1 hey also absorb and intercept some of the OF THE TEARS. 197 and carbonate of soda, and a very small quantity of phosphate of soda and of lime* In ophthalmia, the irritation of the conjunctiva, transmitted by sympathy to the lachrymal gland, not only augments the quantity of its secretion, but appears likewise to alter the qualities of the fluid that is secreted. The tears, which in those cases flow in such profusion, bring on a sense of burn- ing heat in the inflamed part. Do they not, perhaps, contain a greater quan- tity of the fixed alkali than in the ordinary state of the parts ? and may not the painful sensation depend as much on the increased proportion of soda in the tears, as on the greater sensibility of the conjunctiva 1 This last membrane is merely a fold of the skin, which is exceedingly thin, covers the posterior surface of the eye-lids, and is then reflected over the an- terior part of the eye, which it thus unites to the eye-lids. From the whole extent of its surface there oozes an albuminous serosity, which mingles with the tears, and adds to their quantity."! The tears are equably diffused over the globe of the eye by the alternate motions of the palpebrae ; .they prevent the effects of friction, and save the organ of sight from being dried at that part which is exposed to the air. The air dissolves, and carries off in evaporation, a part of the lachrymal fluid. This evaporation of the tears is proved by the weeping, to which those in whom that secretion is very profuse are subject, whenever the at- mospherical air, from being damp, does not carry off a sufficient quantity of the fluid. The unctuous and oily fluid secreted by the Meibomian glands, smears the loose edge of the palpebrse, prevents the tears from falling on the cheek, and answers the same purpose as the greasy substance with which one anoints the edges of a vessel filled above its level, to prevent the over- flowing of the contained fluid. The greatest part of the tears, however, flow from without inward and towards the inner canthus of the eye ; they take that direction in conse- quence of the natural slope of the movable edge of the palpebrse, of the triangular groove, which is formed behind the line of union of their edges, whose round and convex surfaces touch each other only in a point; and this course of the tears is likewise promoted by the action of the palpebral por- tions of the orbicularis palpebrarum, whose fibres, having their fixed point at the inner angle of the orbit where the tendon is inserted, always draw inward their external commissure. On reaching the internal angle of the palpebrae, the tears accumulate in the locus lachrymalis, a small space formed between the edges of the palpebrae kept separated from each other by the caruncula lachrymalis. This last sub- stance, long considered by the ancients as the secretory organ of the tears, is merely a collection of mucous cryptas, covered over by a loose fold of the conjunctiva. These follicles, alike in nature to the Meibomian glands, se- crete, like them, an unctuous substance, which smears the movable edges * The saline parts amount only to about 0-01 name of conjunctiva, over the transparent cor- of the whole. The mucus contained in the nea, to which it adheres so firmly that it is not tears has the property of absorbing oxygen from easily separated from it. In some animals that the atmosphere, and of becoming thick and have no palpebras, the skin is continued, of the viscid, and of a yellow colour. The ciicum- same thickness, over the fore part of the eye. stance of their acquiring new properties from The conjunctiva (if, however, this portion of the absorption of oxygen explains the changes the skin deserves that name) when opaque, ren- which take place in the tears in some diseases ders the globe of the eye, in other respects im- of the eye. See the Chapter in the Appendix, perfect, absolutely useless. This is observed on the Chemical Constitution of the Textures in the kind of eel called, in books of natural his- and Secietions, &c.—/. C. tory, murena ccecilia: the gastrobranchus ccecus t There is no opening in the skin at the part is blind from the same circumstance.—{Riche- which corresponds to the globe of the eye ; it rand). M. Ribes is of opinion that it terminates is exceedingly thin, and is continued, under the at the circumference of the cornea. 198 OF THE GLOBE OF THE EYE. of the palpebral, near the internal commissure. The edges of the eye-lida in this situation require a thicker coating, as the tears accumulated in that spot have no where a greater tendency to flow on the cheek. Near the union of the inner sixth of the free edge of the palpebral with the remaining five-sixths, at the outer part, where their internal, straight, or horizontal portion unites with the curved part, there are situated two small tubercles, at the top of each of which there is a minute orifice. These are the puncta lachrymalia, and they are called superior and inferior, according to the palpebrse to which they belong. Iu the dead body the puncta do not appear tubercular, the small bulgings, produced doubtless by a state of or- gasm and of vital erection, collapse at the approach of death. These small apertures, directed inward and backward, are incessantly immersed in the accumulated tears, absorb them, and convey them into the lachrymal sac by means of the lachrymal ducts, of which they are the external orifices. The absorption of the tears, and their flow into a membranous reservoir lodged in the groove formed by the os unguis, do not depend on the capillary attraction of the lachrymal ducts ; each of them, endowed with a peculiar vital action, takes up, by a real process of suction, the tears accumulated in the lacus lachrymalis, and determines their flow into the sac. The weight of the fluid, the effort of the columns which succeed each other, co-operate with the ac- tion of the parietes of the duct. The flow of the tears is further facilitated by the compression and slight concussions attending the contractions of the palpebral fibres of the orbicularis, behind which the lachrymal ducts are situated. The vitality of the puncta lachrymalia and of the ducts is readily dis- covered when we attempt to introduce into them Anel's syringe or Mejean's stylet, to remove slight obstructions of the lachrymal passages. In a child now under my care for a mucous obstruction of the nasal duct, I can see the puncta lachrymalia contract, when the extremity of the syphon does not at once enter the canal. One is then obliged to wait, before it can be introduc- ed, for a cessation of the spasmodic contraction, which lasts but a few mo- ments. The tears which flow into the lachrymal sac by the common orifice of the united puncta lachrymalia, never accumulate within it, except in case of morbid obstruction ; they, in that case at once enter into the nasal duct, which is a continuation of it, and fall into the nasal fossas below the anterior part of the inferior turbinated bones of these cavities. There they unite with the mucus of the nose, increase its quantity, render it more fluid, and change its composition. The use of the tears is to protect the eye-ball against the irritating impression of the immediate contact of the atmosphere. They at the same time favour the sliding of the palpebrse, lessen the friction in those parts and in the eye-ball, and thus promote their motion. CXVII. Of the globe of the eye.—The eye-ball, as was already observed, may be considered as a dioptrical instrument, placed before the retina, whose office it is to refract the luminous rays, and to collect them into one fasciculus, that may strike a single point of the nervous membrane exclusively calcu- lated to feel its impression. An outer, membranous, hard, and consistent covering supports all its parts. Within the first membrane, called the scle- rotic, hes the choroid, a darkish coat, which lines the inside of the sclerotic, and forms the eye into a real camera obscura.^ At the anterior part of the * Gmelin (Schweigger's Journ. vol. x. p. 507) like clay ; is insoluble in water, alcohol, ether, made an interesting set of experiments in order oils, lime-water, and distilled vinegar. It dis- to determine the composition of the black pig- solves in potash and ammonia when assisted by ment which lines the choroid coat of the eye. heat, and is again precipitated by acids. Suf- " Its colour," he informs us, " is blackish- phuric acid dissolves it, and changes its colour brown; it is tasteless and adheres to the tongue to reddish-brown. When distilled, it yields OF THE HUMOURS OF THE EYE, 199 globe there is a circular opening in the sclerotic, in which the transparent cornea is inserted. At about the distance of a twelfth part of an inch from this convex segment, received in the anterior aperture of the sclerotica, lies the iris, a membranous partition, placed perpendicularly, and containing a round opening (the pupil), which dilates or contracts, according to the state of dilatation or contraction of the iris. At the distance of about half a line from the back part of the iris, towards the union of the anterior fourth of the globe of the eye with the posterior three-fourths, opposite to the opening of the pupil, there is situated a lenticu- lar body, enclosed in a membranous capsule, immovably fixed in its situation by adhering to the capsule of the vitreous humour. Behind the crystalline lens the posterior three-fourths of the cavity of the eye contain a viscid transparent humour, enclosed in the cells of a remark- ably fine capsule, called hyaloid. This vitreous humour forms about two- thirds of a sphere, from which the anterior segment had been taken out; the pulpous expansion of the optic nerve, the retina, is spread out on its sur- face so as to be concentrical to the choroid and sclerotic coats. The eye-ball being nearly spherical, the length of its different diameters differs but little. The diameter of the eye, from the fore to the back part, is between ten and eleven lines; the transverse and vertical diameters are somewhat shorter. Within the space measured by the diameter from the fore to the back part, there are, situated, taking them in their order from the fore part, the cornea; the aqueous humour contained in the anterior chamber the iris, and its central opening or pupil; the aqueous humour of the poste rior chamber; the crystalline lens, surrounded by the ciliary processes : then the vitreous humour in its capsule ; and behind those transparent parts of the eye, through which the luminous rays pass in approaching to a per- pendicular, are the retinae, which receive the impression ; the choroid, whose black point absorbs the rays that pass through the thin and transparent retina; and the sclerotic, in which there is an opening for the passage of the optics nerve to the globe of the eye. The Cornea, contained in the anterior aperture of the sclerotica, like the glass of a watch-case within its frame, is about the third of a line in thickness ; it forms at the fore-part of the eye the segment of a smaller sphere, behind it lies the aqueous humour, which fills what are called the chambers of the eye ; these form spaces, divided into anterior and posterior ; the former, which is the larger of the two, bounded by the cornea at the fore part, and by the iris at the back part; the latter, which is smaller, and separates the crystal- line humour from the iris, the posterior part of which, covered by a black pigment, is called the uvea* The specific gravity of the aqueous humour water, a brown oil, and carbonate of ammonia, ing; for, the expansion of fluids on their freez- It gives out at the same time carburetted hydro- ing being proportioned to their bulk, the vitre- gen, carbonic oxide, azotic and oxygen gases, ous humour, which freezes at the same time as The coal remaining in the retort consists almost the aqueous, must prevent its retrograde flow entirely of charcoal." Mich. Mondini (Osser- through the pupil. Lastly, the uvea or poste- vaz. sull nero pigmento dell' occhio, &c.) con- nor part of the iris is covered with a black point tends that the dark colour of this pigment is which is easily detached from it: now, if the owing to the presence in it of the oxide of iron, anterior part of the crystalline lens had 'been in —J- C- . immediate contact with it, it would have been * Some anatomists have doubted the exist- soiled by some of this colouring matter, which ence of the posterior chamber of the eye ; but would have tarnished its natural transparency, to be convinced of its existence, one need but indispensable to perfect vision. It is, therefore* to freeze an eye, when there will be found a undeniable, that there does exist a posterior piece of ice between the crystalline lens and chamber, which is to the anterior in the propor- the uvea. The formation of this icicle is not tion of two to five, and containing about two- owing to the admission, through the opening of fifths of the aqueous humour, the whole of which the pupil, of the aqueous humour, which, Tike is estimated at five grains, and that the iris all other fluids, expands considerably on freez- forms a loose partition between the two portions 200 OF THE SEAT OF VISION. does not much exceed that of distilled water; some have even thought it less ; it is albuminous, and holds in solution several saline substances.* The crystalline, enclosed in its membranous and transparent capsule, is a lenticu- lar body, rather solid than fluid ; its consistence is particularly great towards its centre ; it there forms a kind of nucleus, around which are several con- centric layers, whose density diminishes as they approach the surface, where the external layers, truly fluid, form what Morgagni considered as a peculiar liquid, on which the lens might be nourished by a kind of imbibition. This body, composed of two segments of unequal convexity, about two lines in thickness at its centre, consists of an albuminous substance coagulable by heat and alcohol. Extremely minute arteries, given off by the central artery of Zinn, pass through the vitreous humour, and bring to it the materials of its growth and reparation.f The vitreous humour, so called from its resemblance to melted glass, is less dense than the crystalline, and more so than the vitreous, and is in considera- ble quantity in the human eye: it appears to be secreted by the minute arte- ries which are distributed to the parietes of the membrane of the vitreous humour; it is heavier than common water, somewhat albuminous and saltish. J The sclerotica is a fibrous membrane, to which the tendons that move the globe of the eye are attached; it supports all the parts of that organ, and these collapse and decay whenever the continuity of its external covering is destroyed. The use of the choroid is not so much to afford a covering to the other parts, as to present a dark surface, destined to absorb the luminous rays, when they have produced on the retina a sufficient impression. If it were not for the choroid, the light would be reflected ; after having impinged on the nervous membrane, its rays would cross, and produce only indistinct of the aqueous humour in which the dark pig- at a temperature of 60. From, various recent ment of the uvea is insoluble. The aqueous experiments it appears to be water slightly im- humour appears to be the product of arterial ex- pregnated with—1st, Albumen; 2d, Gelatine; halation ; it is soon re-produced, as we see after 3d, Muriate of soda. Its constituents, accord- the operation for cataract. ing to the analysis of Berzelius, are :— * Theaqueous humour.—Specific gravity T090 Water..................98'10 Albumen.................a trace. Muriates and lactates.............l-]5 Soda, with animal matter soluble only in water .... -75 10000—J. C. t The crystalline lens.—Its specific gravity lated by heat, and gives a copious precipitate is riOO. When fresh it has little taste. It with tannin, both before and after the coagula- putrefies very rapidly. It is almost completely tion. Its composion, according to the analysis soluble in water. The solution is partly coagu- of Berzelius, is as follows :— Water..................58'0 Peculiar matter...............35-g Muriates, lactates, and animal matter soluble in alcohol . 2-4 Animal matter soluble only in water with some phosphates 1'3 Portions of the remaining insoluble cellular membranes . 2'4 1000 The peculiar matter of the lens possesses all free lactic acid. (Ann. of Phil. vol. xi. p. 385.) the chemical characters of the colouring matter —/. C. of the blood, except colour. When burnt it % The vitreous humour possesses- the same leaves a little ash, containing a very small por- properties as the aqueous ; even its specific gra- tion of iron. When its solution in water is coa- vity is the same, or only a very little greater. gulated by boiling, the liquid in which the coa- Its constituents, according the analysis of Ber- gulum was formed reddens litmus, containing zelius, are :— Water..................9840 Albumen................. -16 Muriates and lactates.............1-42 Soda, with animal matter soluble only in water .... -02 10000.—J. C. OF THE MECHANISM OF VISION. 201 eensations. Mariotte thought that the choroid was the immediate seat of vision, and that the retina was only its epidermis. This hypothesis would never have obtained so much celebrity, if, besides the objections that analogy might have furnished against it, there had been adduced, in opposition to it, the fact observed in fishes, in which the choroid is separated from the retina by a glandular body, opaque, and incapable of transmitting the luminous rays. The retina loses its form as soon as it is separated from the vitreous humour, or from the choroid coat, between which it is spread out as a very thin capsule, so soft as to be almost fluid. A number of blood-vessels, from the central artery of .Zinn, are distributed on the nervous substance of the retina, and give it a slight pink colour. Ought we, with Boerhaave, to attribute to aneurismal or varicose enlargements of those small vessels, the spots which are seen in objects, in the disease to which Mattre Jean gave the name of imaginations ? In order to form the retina, the optic nerve (which proceeds to the globe of the eye, by piercing the sclerotica, to which the covering given to that nerve by the dura mater is connected) penetrates through a very thin membrane, perforated by a number of small holes ; and, closing the opening left for the nerve, and which belongs as much to the choroid as to the sclerotic coats, it then spreads out to furnish the expansion which lines the concavity of the choroid, and covers over the convex surface of the vitreous humour.* The whole extent of the retina, which is equally nervous and sentient, may receive the impression of the luminous rays; though this faculty has, by several philosophers, been exclusively assigned to its central part, called the optical axis, or porus opticus. This central part is easily recognised in man by a yellow spot discovered by Soemmering; in the middle of this spot, situated at the outer side of the entrance of the optic nerve into the globe of the eye, there is seen a. dark spot, and a slight depression, the use of which is not understood. This peculiar structure is met with only in the eye of man and of monkeys.f CXIX. Mechanism and phenomena of vision.—The rays of light passing from any point of an enlightened object form a cone, of which the apex an- swers to the point of the object, and of which the base covers the anterior part of the cornea. All the rays, more diverging, which fall without the area of the cornea on the eye-brows, the eye-lids, and the sclerotica, are lost to vision. Those which strike the mirror of the eye pass through it, under a refraction proportioned to the density of the cornea, which much exceeds that of the atmosphere, and to the convexity of that membrane ; approaching the perpendicular, they now pass through the aqueous humour, less dense, and fall upon the membrane called the iris. All those that fall upon this membrane are reflected, and shew its colour different in different persons, and * The optic nerves differ very remarkably the body struck with the paralysis,—it is on the from the other cerebral pairs, both in their thick- opposite side that the pupil is dilated ; and this ness, and in the delicacy of their substance, pathological phenomenon, which is easily prov- which appears to be an immediate continuation ed in persons who have experienced a paralytic of the medullary fibres of the brain, to which seizure, seems to be one of the best proofs the meninges furnish one common envelope, which can be opposed to those who suppose and not a distinct membranous canal for each that the optic nerves, where they approach each fibre. other, experience an approximation of their The nerves of vision cross each other before fibres only. It may be farther argued, in sup- the cella turcica, in a manner similar to the pri- port of the actual decussation of these nerves, mitive crossing, which their roots, as well as that the wasted optic nerve of an eye that has those of the other nerves, undergo in the sub- been for some time in a state of atrophy, can be stance of the brain. These double decussations traced towards the opposite lobe of the brain; may be said to neutralise each other ; and, con- and that an evident crossing of the optic nerves sequently, each optic nerve may be considered may be observed in many of the class of fishes. to arise primarily from the hemisphere corre- —J. C. sponding to the eye which it supplies. In hemi- + See Appendix, Note E E. plcgia, the affected eye is not on that side of 26 202 OF THE STRUCTURE AND MOTlOHs OF THE 1R14. apparently depending on the organic texture, and on the particular and very diversified arrangement of the nerves, of the vessels, and cellular tissue, which enter into its structure. None but the most central traverse the pnpil and serve to sight. These will pass that opening, in greater or less number, as it is more or less dilated. Now, the pupil is enlarged or diminished by the contraction or expansion of the iris. The motions of this membrane depend entirely on the manner in which light affects the retina. The iris itself is in- sensible to the impression of the rays of light, as Fontana has proved, who always found it immovable when he directed on it alone the luminous rays. When the retina is disagreeably affected by the lustre of too strong a light, the pupil contracts, to give passage only to a smaller number of rays : it dilates, on the contrary, in gloom, to admit enough to make the requisite im- pression on the retina. To explain the motions of the iris, it is not necessary to admit that mus- cular fibres enter into its structure ;* it is enough to know its vascular, * Some anatomists contend, and we think justly, that two sets of muscular fibres enter in- to the structure of the iris ; the one radiant, and the other orbicular. Amongst those who have lately argued in support of this position, we may mention M. Maunoir of Geneva, and M. Ed- wards. Some anatomists consider the iris to be a tissue sui generis ; whilst others rank it among the erectile structures. It appears to us, that those who deny muscularity to this part, do so in consequence of a mistaken idea, which seems to be too generally adopted, viz. that no part is »eally muscular but that which possesses fibres of a similar appearance to those which perform the function of voluntary motion. It should, however, be kept in recollection, that involuntary muscles—those fibrous textures which receive only nerves proceeding from the ganglia, which are not supplied with voluntary nerves, and which are consequently not direct- ly influenced by the will—differ very essentially from voluntary muscles in their structure. In- deed muscular textures vary not only in their functions,'but even in their external characters, according as they are more or less plentifully supplied with either class of nerves—the cere- bral or ganglial. The structure also of muscu- lar parts, especially those which are removed from the influence of volition, has some relation to the kinds of irritants by which they are de- signed to be influenced by Nature. Thus, the eye being formed with an intimate relation to the functions which it has to perform, and to the external influences which act on it, possesses in the structure of its iris a muscular texture of peculiar delicacy ; and hence it.is more sensi- ble to the irritations which accompany, and are subservient to, the right performance of this im- portant animal function. If the structure of the iris, the number of the soft and delicate nervous fibrils which proceed to it from the lenticular ganglion p.nd the nasal branch of the fifth pair, and the connexion which they form with the retina in their couise, be kept in view, we shall readily be able to com- prehend the procession of phenomena which lead to the motions of the iris. It is not im- probable, that the nervous fibrils proceeding from the ganglion to the iris, form, with the ca- pillary arteries which supply its cellular tex- ture, that particular organisation which may be considered as muscular; or, in other words, that these ganglial nerves terminating conjunctly with capillary lamifications in the delicate cel- lular substance of the iris, constitute by such a disposition its particular structure, and enable it to perfoim its peculiar functions. Hence it will be seen, that impressions made upon the retina, (in the sensible state of that nervous ex- pansion, and in proportion to the extent of its sensibility), and transmitted to the Iris, hy means of the connexion which exists between the retina and the nerves supplying the iris, cause a contraction of its circular fibres: as soon as such impressions cease, these fibres re- lax, and the comparative action in the circular and radiated fibres, giving rise to certain states of pupil, is relative to the conditions of the ner- vous system, and the extent to which the irrita- tion proceeds along the axis of the nerves and vessels, and affects cither set of fibres. According to this view of the subject, com- pression of the brain, or an insensible state of the optic nerve, is followed by expansion of the pupil, because the impression requisite to con- traction of the orbicular fibres cannot be made, unless occasionally to a small extent, owing to the loss of sensibility; and, consequently, the greater tonic power of the antagonist (the ra- diated) fibres predominates in preserving a per" manently dilated state of the pupil. The pupil is also dilated in weak children, and in those afflicted with worms, conformably to what is generally observed in the animal economy, namely, that all orbicular muscles, when no ad- joining irritation exists, evince a greater 01 If se degree of relaxation as the vital energies are more or less diminished. It would appear that, in a debilitated state of the system, the nervous influence proceeding from the lenticular gan- glion is insufficient to the purpose of exciting fully the orbicular fibres of the iris; and at the same time the retina perhaps possesses that low degree of sensibility to the irritation of light which is followed by an inadequate effect upoa the nerves supplying the iris. Indeed, it seems, under the circumstances just referred to, where irritation generally is present in the abdominal viscera, that nervous influence is secreted in the brain and parts adjoining in an insnfficieat manner, and consequently tne diminished ac- tivity of the cerebral and ganglial nerves sup- plying the various structures of the eye is the result. When, however, irritation exists in the OP THB PHENOMENA OF VISION. 203 spongy, and nervous texture ; the irritation of the retina sympathetically transmitted to the iris determines a more copious afflux of humours ; its tissue dilates and stretches, the circumference of the pupil is pushed towards the axis of this opening, which becomes contracted by this vital expansion of the membranous tissue. When the irritating cause ceases to act, by our passing from light into darkness, the humours flow back into the neighbouring vessels, the membrane of the iris returns upon itself, and the pupil enlarges the more as the darkness is greater. The rays admitted by the pupil pass through the aqueous humour of the posterior chamber, and soon meet the crystalline, which powerfully refracts them, both from its density and its lenticular form. Brought towards the perpendicular by this body, they pass on towards the retina through the vitre- ous humour, less dense, and which preserves, without increasing it, the re- fraction produced by the crystalline lens. The rays, gathered into one, strike on a single point of the retina, and produce the impression which gives us the idea of certain properties of the body which reflects them. As the retina embraces the vitreous humour, it presents a very extensive surface to the con- tact of the rays, which enables us to behold at once a great diversity of ob- jects variously situated towards us, even when we or these objects change our relative situation*. The luminous ravs refracted by the transparent parts of the eye, form therefore in the interior of the organ a cone, of which the base covers the cornea, and applies to that of the external luminous cone, whilst its apex is on some point of the retina. It is conceived, gene- rally, that the luminous cones, issuing from all points of the object beheld, cross in their passage through the eye, so that the object is imaged on the retina reversed. Admitting this opinion, established on a physical experi- ment, we have to inquire why we see objects upright, whilst their image is reversed on the retina ? The best explanation we possess of this phe- nomenon we owe to the philosopher Berkeley, who proposed it in his Eng- lish work, entitled Theory of Vision, §c. In his opinion, there is no need of the touch to correct this error into which sight ought to betray us. As we refer all our sensations to ourselves, the uprightness of the object is only relative, and its inversion really exists at the bottom of the eye. By the point of distinct vision is understood the distance at which we can read a book of which the characters are of middling size, or distinguish any other object equally small. This distance is not confined withiavery narrow limits, since we can read the same book at six inches from the eye, or at five or six times the distance. This faculty of the eyes to adapt themselves to the distance and the smallness of objects, cannot depend, as has been fondly re- peated, on the lengthening or shortening of the globe of the eye by the mus- cles that move it. Its four recti muscles are not, in any case, capable of compressing it on its sides, nor of lengthening it by altering its spherical form : their simultaneous action can only sink the ball in its socket, flatten it from the fore to the back part, diminish its depth, and make the refraction brain, or when an increase of the circulation oc- absorb these rays. Does any intimate combi- curs in that organ, without overwhelming its nation take place between the nervous pulp and powers, accompanied with or preceded by de- the light, which may give rise to that sensation bility, the pupil contracts, or even remains con- which follows a violent compression of the globe traded; because, in consequence of such irri- of the eye in an obscure situation ? The spots tation or increase of circulation in the brain and which are observable, after having had the eye connected parts, the sensibility and nervous ac- fixed for a considerable time on certain colour- tivity are heightened.—/. C. ed objects, do they arise from this sort of an im- * The rays of light may be said to penetrate pregnation of the retina, or rather of a portion or traverse the demi-transparent tissue of the of it with the rays of light ?—or, as is more ge- rctina, and, as it were, to search through the nerally believed, has the sensibility of the retina nervous pulp when they arrive at the choroid become partially increased or diminished by the coat, which is designed in a great measure to circumstance of inaction or of exercise ? 204 OF THE PHENOMENA OF VISION. consequently less powerful when objects are very distant or very small: this last effect even might be disputed. The eye, which moves and rests on the adipose cushion that fills the bottom of the socket, is never strongly enough pressed to lose its spherical figure, which, of all the forms that bodies can be invested in, is that which, by its especial nature, best resists alteration. The extremities of the ciliary processes, which surround the circumference of the crystalline lens, cannot act on this transparent lens, compress, nor move it; for these little membranous folds, of which the aggregate composes the ir- radiated disk, known under the name of corpus ciliare, possessing no sort of contractile power, are incapable of moving the crystalline lens, with which their extremities, lying in simple contiguity, have no adherence, and which, besides, is immovably fixed in the depression it occupies by the adhesions of its capsule with the membrane of the vitreous humour. The various de- grees of contraction or dilatation of which the eye-ball is susceptible, afford a much more satisfactory explanation of this physiological problem. The rays of light which come from a very near object are very divergent : the eye would want the refracting power necessary to collect them into one, if the pupil, contracting by the enlargement of the iris, did not throw oft* the more divergent rays, or those which form the circumference of the luminous cone. Then those which form the centre of the cone, and which need but a much smaller refraction for their reunion on a single point of the retina, are alone admitted by the narrowed opening. When, on the contrary, we look at a distant object from which rays are given out, already very convergent, and which need but a small refraction to bring them towards the perpendicu- lar, we dilate the pupil, in order to admit the more diverging rays, which, when collected, will give the image of the object. In this respect very small bodies are on the same footing as those at a great distance. Though the image of every object is traced at the same time in both our eyes, we have but one sensation, because the two sensations are in harmony and are blended, and serve only, one aiding the other, to make the impres- sion stronger and more durable. It has long been observed, that sight is more precise and correct when we use only one eye ; and Jurine thinks that the power of the two eyes united exceeds only by one-thirteenth that of a single eye. The correspondence of affection requires the direction of the optical axes on the same objects ; and, be that direction ever so little dis- turbed, we see really double, which is what happens in squinting. If the eyes are too powerfully refractive, either by the too great convexity of the cornea and the crystalline, the greater density of the humours, or the excessive depth of the ball, the rays of light, too soon reunited, diverge anew, fall scattering on the retina, and yield only a confused sensation. In this defect of sight, called myopia, the eye distinguishes only very near ob- jects, giving out rays of such extreme divergence as to require a very power- ful refractor. In presbytia, on the other hand, the cornea too much flattened, the crystalline little convex, or set too deeply, the humours too scanty, are the cause that the rays are not yet collected when they fall upon the retina, so that none but very distant objects are distinctly seen, because the very* convergent rays they give out have no need of much refraction. Myopia is sometimes the effect of the habit which some children get of looking very close at objects which catch their attention. The pupil then becomes accustomed to great constriction, and dilates afterwards with diffi- culty. It is obvious, that to correct this vicious disposition, you must shew the child distant objects which will strongly engage his curiosity, and keep him at some distance from every thing he looks at. * The author means '•' scarcely divergent."— T. OF THE PHENOMENA Of VISION. 205 The sensibility of the retina on some occasions rises to such excess that the eye can scarcely bear the impression of the faintest light. Nyctalopes, such is the name given to those affected with this disorder, distinguish objects amidst the deepest darkness : a few rays are sufficient to impress their organ. It is related that an English gentleman, shut up in a dark dungeon, came gradually to distinguish all it contained : when he returned to the light of day, of which he had in some sort lost the habit, he could not endure its splendour ; the edges of the pupil, before extremely dilated, became con- tracted to such a degree as entirel}' to efface the opening. When, on the other hand, the retina has little sensibility, strong daylight is requisite to sight. This injury of vision, known by the name of hemera- lopia* maybe considered as the first step of total paralysis of the optic nerve, or gutta serena. It may arise from any thing that can impair the sensibility of the retina. Saint-Yves relates, in his work on diseases of the eyes, many cases of hemeralopia. The subjects were chiefly workmen employed at the Hotel des Mqnnoies, in melting the metals. The inhabitants of the northern regions, where the earth is covered with snow great part of the year, become at an early age hemeralopes. Both contract this weakness from their eyes being habitually fatigued by the splendour of too strong a light. Finally, in order to the completion of the mechanism of vision, it is re- quisite that all parts of the eye be under certain conditions, the want of which is more or less troublesome. It is especially necessary that the mem- branes and the humours which the rays of light are to pass through should be perfectly transparent. Thus, specks of the cornea, the closing of the pupil by the preservation of the membrane which stops that opening during the first months of the life of the foetus ; cataract, an affection which consists in the opacity of the crystalline lens or its capsule ; the glaucoma, or defect of transparency, in the vitreous humour,—weaken or altogether destroy sight, by impeding the passage of the rays to the retina. This membrane itself must be of tempered sensibility to be suitably affected by the contact of the rays of light. The choroid, the concavity of which it fills, must pre- sent a coating black enough to absorb the rays that pass through it. It is to the sensible decay of the dye of the choroid in advancing years, as much as to the collapsing induration and discolouring of different parts of the eye, and the impaired sensibility of the retina from long use, that we ascribe the confusion and weakness of sight in old people. The extreme delicacy of the eyes of the Albinos proves equally the necessity of the absorption of light by the black coating which covers the choroid. Of all the organs of sense, the eyes are those which are the most deve- loped in a new-born child ;—they have then nearly the bulk which they are to retain during life. Hence it happens, that the countenance of children, whose eyes are proportionably larger, is seldom disagreeable, because it is chiefly in these organs that physiognomy seeks expression. Might we not say, that if Nature sooner completes the organ of sight, it is because the changes which it produces on the rays of light arising purely from a physical necessity, the perfection of the instrument was required for the exercise of the sense % The eyes are not immovable in the place they occupy. Drawn into very * I give to the words nyctalopia and hemera- night.; and hemeralopia, one in which it is lost lopia the same meaning as all other writers during the day. It is accordingly in this sense down to Scarpa, who have published treatises that they arc used by the father of physic. I on diseases of the eyes. This acceptation is, owe this remark to Dr. Roussille Chamseru, however, a grammatical error; since, of the two who has carefully verified the text of Hippo- terms, nyctalopia, in its Greek roots, signifies crates, in the MSS. of the Imperial Library. an affection wnich takes away sight during the 206 OF VISION IN THE LOWER ANIMALS. various motions, by four recti muscles and two oblique, they direct themselves towards all objects of which we wish to take cognizance : and it is observ- ed, that there is, between the muscles which move the two eyes, such a cor- respondence of action, that these organs turn at once the same way, and are directed at once towards the same object, in such a manner that the visual axes are exactly parallel. It sometimes happens" that this harmony of mo- tion is disturbed, and thence squinting,—an affection which, depending almost always on the unequal force of the muscles of the eye, may be distinguished into as many species as there are muscles which can draw the globe of the eye into their direction, when from any cause they become possessed of a predominating power. Buffon has further assigned as a cause of squinting, the different aptitude of the eyes to be affected by light. According to this celebrated naturalist, it may happen, that one of the eyes being originally of greater sensibility, the child will close the weaker to use the stronger, which is yet strengthened by exercise, whilst repose still weakens the one that re- mains in inaction. The examination of a great many young people who had fallen under military conscription, and claimed exemption on the score of infirmities, has shewn me that squinting is constantly connected with the unequal power of the eyes. Constantly, the inactive eye is the weakest, being almost useless ; and it was quite a matter of necessity that the di- verging globe should be thus neutralised, else the image it would have sent to the brain, different from that which the sound eye gives, would have in- troduced confusion into the visual functions. The squinting eye, being in- active, falls by degrees into that state of debility, from default of exercise, which Brown has so well called indirect debility. The sense of sight appears to me much rather to deserve the name which J. J. Rousseau has given to that of smell, of sense of the imagination. Like that brilliant faculty of the soul, the sight, which furnishes us with ideas so rich and varied, is liable to betray us into many errors. It may be doubted whether it gives the notion of distance, since the boy couched by Cheselden conceived every thing he saw to touch his eye. It exposes us to false judg- ments on the form and size of objects ; since, agreeably to the laws of optics, a square tower seen at a distance appears to us round ; very lofty trees seen also very far off, seem no taller than the shurbs near us ; a body moving with great rapidity appears to us motionless, &c. It is from the touch that we gain the correction of these errors, which CondiUac, in his treatise on sensa- tion, has perhaps exaggerated. CXX. Of the organ of sight in the lower animals.—The organ of sight in different animals varies according to the medium in which they live ; thus, in birds which fly in the higher regions of the air, there is an additional and very remarkable eye-lid : this is particularly the case with the eagle, which is thus enabled to look at the sun ; and with night-birds, whose very delicate eye it seems to protect from the effects of two strong a light. In birds, like- wise, there is a copious secretion of tears, the medium in which they live causing a considerable evaporation. The greater part of fishes, on the con- trary, have no movable eye-lid, and their eyes are not moistened by tears, as the water in which they are immersed answers the same purpose. In some fishes, however, the eyes are smeared with an unctuous substance calculated to prevent the action of the water on the organ. The globe of the eye in birds is remarkable for the convexity of the cornea, which is sometimes a complete hemisphere ; hence it possesses a considerable power of refraction. This power of refraction appears to be very weak in fishes, the forepart of their eyes being very much flattened ; but the water in which they live made it unnecessary that they should have an aqueous OF SOUND. 207 humour, for the density of this fluid being nearly the same as that of water, it would not have produced any refraction ; besides, being in sea-fish of in- ferior density to that of salt water, it would have broken the rays of light by making them diverge from the perpendicular. In fact, the refractive power of a medium is never but a relative quantity ; the degree of refraction is not determined by the density of the medium, but by the difference of density between it and the medium that is next to it. To make up for the flatness of the cornea occasioned by the small quantity, or even by the absence, of aqueous humour, fishes have a very dense and spherical crystalline humour, the spherical part of which forms a part of a small sphere. The eyes of birds, whose cornea is thrust out by a very copious aqueous humour, possess, in consequence of the presence of this fluid, a very consider- able power of refraction ; the air, in its higher regions, owing to its extreme rarefaction, being but little calculated to approximate the rays of light. The pupil admits of greater dilatation in the cat, in the owl, in night-birds, and in general in all animals that see in the dark. The sensibility of the retina is, likewise, greater in those animals ; several of them appear incom- moded by the light of day, and never pursue their prey but in the most ob- scure darkness. The crystalline humour of several aquatic fowls, as the cormorant, is spherical like that of fishes ; and this is not, as will be mentioned hereafter, the only peculiarity of structure in this kind of amphibious animals. Lastly, the choroid of some animals, more easily separated into two distinct laminse than that of man, presents, at the bottom of the eye, instead of a darkish, uniformly diffused coating, a pretty extensive spot of various colours, and in some it is most beautiful and brilliant. It is not easy to say what is the use of this coloured spot, known by the name of tapetum. The rays of light reflected by this opaque substance, in passing through the eye, cross those which are entering at the same time; they must, conse- quently, prevent distinct vision, or at least impair the impression, in a man- ner which it is impossible to determine. It has been said, that the lower animals, provided with less perfect and often less numerous senses than those of man, must have different ideas of the universe : is it not likewise probable, that in consequence of the indistinct vision occasioned by the reflection from the tapetum, they may entertain erroneous and exaggerated notions of the power of man? And notwithstanding the power granted to man by the Creator over the lower animals, as we are told in the book of Genesis, is it probable that those which Nature has gifted with prodigious strength, or with offensive weapons, would obey the lord of the creation, if they saw him in his feeble and destitute condition,—in a word, such as he is 1 The head of insects with numerous eyes is joined to their body, and moves along with it: their existence is, besides, so frail, that it was requisite that Nature should furnish them abundantly with the means of seeing those ob- jects which may be injurious to them. We shall not enter any farther into these remarks relative to the differences in the organ of sight in the various kinds of animals : more ample details on this subject belong, in an especial manner, to comparative anatomy.* CXXI. Of sound.—Sound is not, like light, a body having a distinct existence; we give the name of sound to a sensation which we experience whenever the vibrations of aft elastic body strike our ears. All bodies are capable of producing it, provided their molecules are susceptible of a certain degree of re-action and resistance. When a sonorous body is struck, its in- tegrant particles experience a sudden concussion, are displaced, and oscillate * For some further remarks on the Organ and Sense of Vision, see Appendix, Note E E. 208 OF SOUND. with more or less rapidity. This tremulous motion is communicated to the bodies applied to its surface : if we lay our hand on a bell that has been struck by its clapper, we feel a certain degree of this trembling. The air, which envelopes the sonorous body, receives and transmits its vibrations with the more effect from being more elastic. Hence it is observed that, caleris paribus, the voice is heard at a greater distance in winter, when the air is dry and condensed by the cold. The sonorous rays are merely series of particles of air, along which the vibration is transmitted from the sonorous body to the ear which perceives the noise occasioned by its percussion. These molecules participate in the vibrations which are communicated to them ; they change their form and situation in proportion as they are nearer to the body that is struck, and vice versa.; for, sound becomes weaker in proportion to the increase of distance. But this oscillatory motion of the aerial molecules should be well distinguished from that by which the atmosphere, agitated by the winds, is transported and changes its situation. And in the same manner as the balance of a pen- dulum moves incessantly within the same limits, so this oscillatory motion affects the molecules of the air within the space which they occupy, so that they move to and fro during the presence or the absence of the vibration. The atmospherical air, when set in motion in a considerable mass at a time, produces no sound, unless in its course it meets with a body which vibrates from the percussion which it experiences. The force of sound depends entirely on the extent of the vibrations expe- rienced by the molecules of the sonorous body. In a large bell struck violent- ly, the agitation of the molecules is such that they are transmitted to consider- able distances, and that the form of the body is evidently changed by it. Acute or grave sounds are produced by the greater or smaller number of vi- brations in a given time, and the vibrations will be more numerous the small- er the length and diameter of the body. Two catgut strings, of the same length and thickness, and with an equal degree of tension, will vibrate an equal number of times in a given period, and produce the same sound. This, in music, is called unison. If one of the strings is shortened by one-half, it vibrates as often again as the other, and gives out a sound more acute, or higher by one octave. The same result may be obtained by reducing the string one-half of its original thickness, without taking from its length. The vibrations will, in the same manner, be accelerated by giving a greater degree of tension to the sonorous cord. The difference of the sounds produced by a bass, a harp, or any other stringed instrument, depends on the unequal tension, length, and size of the strings. This division of the elementary sound is an act of the understanding, which distinguishes, in a noise apparently monotonous, innumerable varieties and shades, expressed by signs of convention. But in the same manner as light, refracted by a prism, presents innumerable intermediate shades between the seven primitiye colours, and as the transition is gradual from one to the other of these colours ; so the division of the primitive sound into seven tones, expressed by notes, is not absolute, and there are a number of interme- diate sounds which augment or diminish their value, &c. Sound has, therefore, been analysed as well as light: the use of the ear with regard to sound corresponds to that of the prism with regard to light; and the modifications of which sound is capable are as numerous and as va- rious as the shades between the primitive colours. Sound is propagated with less velocity than light. The report of a can- non fired at a distance is heard only a moment after the eye has perceived the flash of the explosion. Its rays diverge and are reflected, like those of light, OF THE ORGAN OF HEARtfrd 200 when they meet with an obstacle at an angle equal to that of incidence. The force of sound, like that of light, may be increased, by collecting and concentrating its rays. The sonorous rays which strike a hard and elastio body, when reflected by it, impart to it a vibratory motion, giving rise to a secondary sound, which increases the force of the primitive sound. When these secondary sounds, produced by the percussion of a body at a certain distance, reach the ear, they give rise to what is called an echo. Who is unacquainted with the ingenious allegory by which its nature is ex- pressed in ancient mythology, in which echo was called daughter of the air and earth ? CXXI1. Of the organ and mechanism of hearing.—The organ of hearing in man consists of three very distinct parts; the one, placed externally, is intended to collect and to transmit the sonorous rays which are modified in passing along an intermediate cavity, between the external and internal ear. It is within the cavities of this third part of the organ, excavated in the sub- stance of the petrous portion of the bone, that the nerve destined to the per- ception of sound, exclusively resides. The external ear and the meatus auditorius externus may be compared to an acoustic trumpet, the broad part of which, represented by the concha, collects the sonorous rays, which are afterwards transmitted along the contracted part, represented by the meatus externus. The concha contains several prominences separated by corre- sponding depressions ; its concave part is not wholly turned outward ; in those who have not laid their ears flat against the side of the head by tight bandages, it is turned slightly forward, and this arrangement, favourable to the collection of sound, is particularly remarkable in savages, whose hearing, it is well known, is remarkably delicate. The base of the concha consists of a fibro-cartilaginous substance, thin, elastic, calculated to reflect sounds, and to increase their strength and intensity by.the vibrations to which it is liable. This cartilage is covered by a very thin skin, under which no fat is collected that could impair its elasticity : these prominences are connected together by small muscles, which may relax it by drawing the projections together, and thus place it in unison with the acute or grave sounds. These small muscles within the external ear, as the musculi helicis major and minor, the tragicus and anti-tragicus, and the transversus auris, are like the muscles on the outer part of the ear, stronger and more developed in timid animals with long ears. In the hare the fibre of these muscles are more distinctly marked ; their action is most apparent in'this feeble and fearful animal, which has no resource but in flight against the dangers which incessantly threaten its existence, and which required that it should receive early intimation of the approach of danger : hence hares have the power of making their ears assume various forms, of shaping them into more advantageous trumpets, of moving them in every direction, of directing them towards the quarter from which the noise proceeds, so as to meet the sounds and collect the slightest. The form of the external ear is not sufficiently advantageous in man, whatever Boerhaave may have said to the contrary, to enable all the sono- rous rays, which in striking against it are reflected at an angle equal to that of their incidence, to be directed towards the meatus auditorius externus. TJnited for the most part into a single fasciculus, and directed towards the cOncha, they penetrate into the meatus auditorius externus, and the tremu- lous motions which they excite in its osso-cartilaginous parietes contribute to increase their force. On reaching the bottom of the meatus, they strike against the membrana tympani, a thin and transparent septum, stretched be- tween the bottom of the meatus, and the cavity in which the small bones of the ear are lodged. These small bones form a chain of bone which cross- 27 210 OF THE SENSE OF HEARING. es the tympanum from without inward, and which, extends from the mem*' brana tympani to that which connects the base of the stapes to the edge of the fenestra ovalis. An elastic air, continually renewed by the Eustachian tube, fills the cavity of the tympanum ; small muscles attached to the malleus and stapes move these bones, or relax the membranes to which they are attached, and thus institute a due relation between the organ of hearing and the sounds which strike it. It will be easily conceived, that the relaxation of the membrana tympani, effected by the action of the anterior muscle of the malleus, must weaken acute sounds ; while the tension of the same membrane, by the in- ternal muscles of the same bone, must increase the force of the grave sounds* In the same manner as the eye, by the contraction or dilatation of the pupil, accommodates itself to the light, so as to admit a greater or smaller number of its rays, according to the impression which they produce, so by the relax- ation or tension of the membrane of the tympanum, or of the fenestra ovalis, the ear reduces or increases the strength of sounds, whose violence would affect its sensibility in a painful manner, or whose impression would be insuf- ficient. The iris and the muscles of the stapes and of the malleus are, therefore, the regulators of the auditory and visual impression ; there is as close a sympathetic connexion between these muscles and the auditory nerve as between the iris and the retina. The air which fills the tympanum is the true vehicle of sound ; this air diffuses itself over the mastoid cells, the use of which is to augment the dimensions of the tympanum, and the force and extent of the vibrations which the air experiences within it. These vibrations, transmitted by the membrana tympani, are communicated to those membranes which cover the fenestra ovalis and the fenestra rotunda ; then, by means of these, to the fluid which fills the different cavities of the internal ear, and in which lie the soft and delicate filaments of the auditory nerve, or of the portio mollis of the seventh pair. The agitation of the fluid affects these nerves, and determines the sensa- tion of grave or acute sounds, according as they are slower or more rapid. It appears that the diversity of sounds should rather be attributed to the more or less rapid oscillations, and to the undulations of the lymph of Co- tunni, than to the impressions on filaments of different lengths of the auditory nerve. These nervous filaments are too soft and too slender to be traced to their extreme terminations. It is, however, probable, that the various forms of the internal ear (the semicircular canals, the vestibule, and the cochlea), have something to do with the diversity of sounds. It must also be observed, that the cavities of the ear are contained in a bony part, harder than any other substance of the same kind, and well fitted to maintain, or even to augment by the re-action of which it is capable, the force of the sonorous rays.* The essential part of the organ of hearing, that which appears exclusively employed in receiving the sensation of sounds, is, doubtless, that which exists in all animals endowed with the faculty of hearing. This part is the soft pulp of the auditory nerve, floating in the midst of a gelatinous fluid, con- tained in a thin and elastic membranous cavity. It is found in all animals, from man to the sepia. In no animal lower in the scale of animation has an organ of hearing been met with, although some of these inferior animals do not seem to be absolutely destitute of that organ. This gelatinous pulp * If the cavities of the internal ear were her- violent agitation of tnis fluid does not amount radically sealed, it may be conceived that the to such a height, for it may flow towards the violent undulations of the lymph of Cotunni internal surfaces of the cranium by means of would injure the nervous pulp; but the most the two small conduits named aqueducts.—J. C. OF THE SENSE OF HEARING. 211 is in the lobster contained in a hard and horny covering. In animals of a higher order its internal part is divided into various bony cavities. In birds there is interposed a cavity between that which contains the nerve of hearing and the outer part of the head ; in man and in quadrupeds the organ of hear- ing is very complicated ; it is enclosed in an osseous cavity, extremely hard, situated at a considerable depth, and separated from the outer part of the head by a cavity and a canal, along which the sonorous rays are transmitted^ after having been collected into fasciculi by trumpets situated on the outside. This kind of natural analysis of the organ of hearing is well calculated to give accurate notions of the nature and importance of the functions fulfilled by each of its parts. But in the investigation of the uses and of the relative importance of the auditory apparatus, morbid anatomy furnishes data of an equal value with those obtained from comparative anatomy. CXXIII. Pathological physiology of hearing.—The external ear may be removed with impunity in man, and even in animals in which its form is more advantageous : the hearing is at first impaired, but at the end of a few days recovers its wonted delicacy. The entire obliteration of the meatus auditorius externus is attended with complete deafness. It is not essentially necessary for the mechanism of hearing that the membrana tympani should be whole ; persons in whom it has been accidentally ruptured can force out smoke at their ears without losing the power of hearing; it may be con- ceived, however, that if, instead of having merely a small opening that would not prevent its receiving the impression of the sonorous rays, nor its being acted upon by the handle of the malleus, the membrana tympani were >almost entirely destroyed, deafness would be the almost unavoidable conse- quence.* If, owing to the obstruction of the Eustachian tube, the air in the tympanum is not renewed, it loses its elasticity, and combines with the mu- cus within the tympanum. The cavity of the tympanum is then in the same condition as an exhausted receiver, in which the sonorous rays are transmitted with difficulty. It has been thought that the use of the Eusta- chian tube was, not only to renew the air contained in the tympanum, but also to transmit the sonorous rays into that cavity. In listening attentively, we slightly open our mouth ; in order, it is said, that the sound may pass from this cavity into the pharynx, and thence reach the organ of hearing. This explanation is far from satisfactory ; for the obliteration of the meatus auditorius externus is attended with complete deafness, which would not hap- pen if the Eustachian tubes transmitted the sonorous rays. When a man listens attentively, and with his mouth open, the condyles of the lower jaw, situated in front of the external auditory meatus, being depressed and brought forward, the openings are evidently enlarged, as may be ascertained by put- ting the little finger into one's ear, at the moment of depressing the lower jaw.f The luxation of the small bones of the ear, or even their complete destruction, does not occasion deafness ; the only consequence is, a confusion in the perception of sounds. When, however, the stapes, the base of which rests on the greatest part of the fenestra ovalis, or when the thin membrane * We find that a temporary obstruction of the + The open 3tate of the mouth in an attentive Eustachian tube in guttural angina is sufficient listener, by no means proves that the sonorous to occasion a considerable degree of deafness, rays are introduced along the Eustachian tube. In such a case the inflammation of the mucous Indeed, if such were the case, the aerial pulsa- niembrane of the pharynx extends itself to that tions arriving by this tube would strike the which lines the tube, of which it is a continua- tympanum in an opposite direction to those that tion; and the effects that the inflammation pro- are admitted by the external passage, and thus duces on the function of the organ are propor- render the hearing confused. The purpose, tionate to the extent to which it advances in therefore, which the Eustachian tube performs the different departments of the internal ear.— is nothing more than to allow the renewal of /. C. the air within the tympanum.—J. C. 212 OF ODOURS. which closes the fenestra ovalis, or when that which closes the fenestra rev tunda, is destroyed, deafness takes place in consequence of the escape of tlie fluid which fills the cavities in which the auditory nerve is distributed. The existence of this fluid appears essential to the mechanism of hear- ing ; either from its keeping the nerves in the soft and moist state required for the purpose of sensation, or from its transmitting to them the undulatory motion with which it is agitated. The deafness of old people, which, according to authors, depends on the impaired sensibility of the nerves, whose excitability has been exhausted by impressions too frequently repeated, appears sometimes to be occasioned by a deficiency of this humour, and by the want of moisture in the internal ca- vities of the ear. During the severe winter of 1798, professor Pinel opened, at the Hospital of Saltpetriere, the skulls of several women who died at a very advanced age, and who had been deaf for several years. The cavities of the internal ear were found quite empty ; they contained an icicle in younger subjects who had possessed the power of hearing. Deafness may likewise be produced by a palsy of the portio mollis of the seventh pair, or by a morbid condition of the part of the brain from which this nerve arises. The mechanical explanation applied by Willis to the anomalous affections of the organ of hearing, is inadmissible,—those in which that organ is sensible only to the impression of weak or strong sounds acting together or separately. This author relates the case of a woman who could not hear unless a great noise was made near her, either by beating a drum or by ringing a bell, be- cause, says he, under such circumstances these loud noises determine in the membrana tympani, which he supposes in a state of relaxation, the degree of tension required to enable it to vibrate under the impression of weaker sounds. This membrane, to present greater resistance, must be put on the stretch by the internal muscle of the malleus, or by its own contraction. The total absence of muscular fibres in the membrana tympani in man, ren- ders very doubtful this spontaneous contraction. Mr. Home, however, has just ascertained that the membrana tympani of the elephant is muscular and contractile. Admitting all these suppositions, we only substitute one diffi- culty for another, and it remains to be shewn, why the more powerful sounds merely increase the tone of the membrana tympani; why they do not be- come objects of perception of the organ of hearing, though they might be expected to render us insensible to the perception of weaker sounds. CXXIV. Of odours.—Chemists have long thought that the odoriferous parts of bodies formed a peculiar principle, distinct from all the other substan- ces entering into their composition ; they gave it the name of aroma. M. Fourcroy, however, has clearly shewn, that this pretended element consisted merely of minute particles of bodies, detached by heat and dissolved in the at- mosphere, which becomes loaded with them, and conveys them to the olfac- tory organs. According to this theory, all bodies are odoriferous, since ca- loric may sublimate some of the particles of those which are least volatile. Linnaeus and Lorry had endeavoured to class odours according to the sensa- tions which they produce ;* M. Fourcroy has been guided by the chemical *■ Linnaeus admits seven classes of odours: 7th, nauseous, as that of gourds, melons, eucum- lst class, ambrosiac odours, those of the rose bers, and, in general, all cucurbitaceous plants. and of musk belong to this class,—they are cha- Lorry admits only five kinds of odours, cam- racterised by their tenacity; 2d, fragrant,—for phorated, narcotic, ethereal, volatile-acid, and al- example, the lily, the saffron, and the jasmine,— kaline. they fly off readily ; 3<}, aromatic, as the smell M. Fourcroy admits the mucous aroma belong- of the laurel; 4th, aliaceous, approaching to that ing to plants, improperly termed inodorous. of garlic; 5th, fetid, as that of valerian and Oily and fugacious, oily and volatile, acid ana) fungi; 6th, virous, as of poppies and opium; hydro-sulphureous. OF THE SENSE OF SMELL. 213 nature of substances : but, however advantageous this last classification may be, it is difficult to include in it the infinite variety of odours which ex- hale from substances of all kinds ; and it is perhaps as difficult to arrange them in classes, as the bodies from which they are produced. This being laid down on the nature of odours, it is next explained why the atmosphere becomes loaded with the greater quantity, the warmer and the more moist it is. We know that in a flower-garden the air is at no time more loaded with fragrant odours, and the smell is never the source of greater en- joyment, than in the morning, when the dew is evaporating by the rays of the sun. It is, likewise, easily understood why the most pungent smells generally evaporate very readily, as aether, alcohol, the spirituous tinctures, and essential volatile oils. CXXV. Of the organ of smell.—The nasal fossae, within which this organ is situated, are two cavities in the depth of the face, and extending backward into other cavities, called frontal, ethmoideal, sphenoideal, palatine, and maxillary sinuses. A pretty thick mucous membrane, always moist, and in the tissue of which the olfactory nerves and a considerable number of other nerves and vessels are distributed, lines the nostrils, and extends into the sinuses which com- municate with them and covers their parietes throughout their windings and prominences. This membrane, called pituitary, is soft and fungous, and is the organ which secretes the mucus«of the nose ; it is thicker over the tur- binated bones which lie within the olfactory cavities ; it grows thinner and firmer in the different sinuses. The smell appears more delicate in proportion as the nasal fossa; are more capacious, and the pituitary membrane covers a greater space. The soft and moist condition of the membrane is likewise essentially necessary to the perfection of this sense. In the dog, and in all animals which have a very exquisite sense of smell, the frontal, ethmoideal, sphenoidal, palatine, and maxillary sinuses, are prodigiously capacious, and the parietes of the skull are in great measure hollowed by these different parts of the olfactory ap- paratus ; the turbinated bones are likewise very prominent in them, and the grooves between them very deep ; lastly, the nerves of the first pair are large in proportion. Among the animals possessed of great delicacy of smell, few are more remarkable than the hog. This impure animal, accustomed to live in the most offensive smells and in the most disgusting filth, has, however, so very nice a smell, that it can detect certain roots, though buried in the earth at a considerable depth. In some countries this quality is turned to advantage, and swine are employed in looking for truffles. The animal is taken to those places where they are suspected to be, turns up the earth in which they are buried, and would feed on them greedily, if the herdsman, satisfied with this indication, did not drive them away from this substance intended for more delicate palates. CXXVI. Of the sensation of odours.—Do the nerves of the first pair alone give to the pituitary membrane the power of receiving the impression of smell, and do the numerous filaments of the fifth pair merely impart to it the general sensibility belonging to other parts 1 This question appears to require an answer in the affirmative. The pituitary membrane, in fact, possesses two modes of sensibility perfectly distinct, since the one of the two may be almost completely destroyed, and the other considerably increased. Thus, in violent catarrh, the sensibility of the part, as far as relates to the touch, is very acute, since the pituitary membrane is affected with pain ; while the patient is insensible to the strongest smells. It seems probable, that the olfactory nerves do not extend into the sinuses, 214 OF FLAVOURS. and that these improve the sense of smell merely by retaining, for a longer space of time, a considerable mass of air, loaded with odoriferous particles. I have known detergent injections, strongly scented, thrown into the antrum Highmorianum by a fistula in the alveolar processes, produce no sensation of smell. A phial filled with spirituous liquor having been applied to a fistula in the frontal sinuses, gave no impression to the patient. The true seat of the sense of smell is at the most elevated part of the n:strils, which the nose covers over in the form of a capital. There the pituitary membrane is moister, receives into its tissue the numerous filaments of the first pair of nerves, which, arising by two roots from the anterior lobe of the brain, and from the fissure which separates it from the posterior lobe, passes from the cranium, through the openings of the cribriform plate of the ethmoid bone, and ter- minates by the expansion of its filaments forming a kind of parenchymatous tissue, not easily distinguished from that of the membrane. The olfactory papillae would soon be destroyed by the contact of the atmospherical air, if they were not covered over by the mucus of the nose. The use of this mucus is, not merely to preserve the extremities of the nerves in a sentient state, by preventing them from becoming dry, but likewise to lessen the too strong impression that would arise from the immediate contact of the odori- ferous particles. It perhaps even combines with the odours, and these af- fect the olfactory organs only when dissolved in mucus, as the food in saliva. As the air is the vehicle of odours, .these affect the pituitary membrane only when we inhale it into the nostrils. Hence, when any odour is grate- ful to us, we take in short and frequent inspirations, that the whole of the air which is received into the lungs may pass through the nasal fossae. We, on the contrary, breathe through the mouth, or we suspend respiration alto- gether, when smells are disagreeable to us. The sense of smell, like all the other senses, is readily impressed in child- ren, though the nasal fossa? are in them much contracted, and though the sinuses are not yet formed. The general increase of sensibility at this period of hfe makes up for the imperfect state of the organisation, and it is in this respect with the nasal fossa? as with the auditory apparatus, of which an important part, the meatus externus, is then not completely evolved. Tho sense of smell is perfected by the loss of some of the other senses ;—every body, for example, knows the history of the blind man whom that organ enabled to judge of the continence of his daughter,—it becomes blunted by the application of strong and pungent odours. Thus, snuff changes the quality of the mucus secreted by the membrane of the nose, alters its tissue, dries its nerves, and in the course of time impairs their sensibility. The shortness of the distance between the origin of the olfactory nerves in the brain, and their termination in the nasal fossae, render very prompt and easy the transmission of the impressions which they experience. This vicinity to the brain induces us to apply to those nerves those stimulants calculated to rouse the sensibility when life is suspended, as in fainting and asphyxia. The sympathetic connexions between the pituitary membrane and the diaphragm account for the good effects of sternutatories, in cases of apparent death.* CXXVII. Of flavours.—Flavours are no less varied and no less numerous than odours, and it is as difficult to reduce them to general classes connected by analogies and including the whole.j Besides, there exists no element of * For some remarks on the Organ and Sense Linnaaus. Acid, sweet, bitter, acrid, saltish, al. of Smell, see Appendix, Notes F F.—J. C. kaline, vinous, spirituous, aromatic, and acerb, ■f This has been attempted, though with in- were the terms employed by those physicians to different success, by Boerhaave, Haller, and express the general characters of flavours. OF THE SENSE OF TASTE. 215 flavour, any more than an odoriferous principle. The flavour of fruits alters as they ripen, and appears to depend on the inward composition of bodies on their peculiar nature, rather than on the form of their molecules , since cry- stals of the same figure, but belonging to different salts, do not produce simi- lar sensations. To affect the organ of taste, a body should be soluble at the ordinary temperature of the saliva ; all insoluble substances are insipid ; and one might apply to the organ of taste this celebrated axiom in chemistry, corpora non agunt nisi soluta. If there is a complete absence of saliva, and if the body that is chewed is altogether without moisture, it will affect the parched tongue only by its tactile, and not at all by its gustatory, qualities. The substances which have most flavour are those which yield most readily to chemical combinations and decompositions, as acids, alkalies, and neutral salts. When, in affections of the digestive organs, the tongue is covered with a mucous or whitish fur, or of a yellowish or bilious colour, we have only incorrect ideas of flavours ; the thinner or thicker coating prevents the im- mediate contact of the sapid particles ; when they act, besides, on the ner- vous papillae, the impression which they produce is lost in that occasioned by the morbid contents of the stomach ; hence every aliment appears bitter while the bilious disposition exists, and insipid in those diseases in which the mucous elements prevail. CXXVIII. Of the sense of taste.—No sense is so much akin to that of the touch, or resembles it more. The surface of the organ of taste differs from the common integuments only in this respect, that the chorion the mu- cous body, and the epidermis which envelop the fleshy part of the tongue are softer, thinner, and receive a greater quantity of nerves and vessels and are habitually moistened by the saliva, and by the mucus secreted by the mucous glands contained in their substance. These mucous cryptae, and the nerves of the cutaneous covering of the tongue, raise the very thin epi- dermis which covers its upper surface, and form a number of papillae dis- tinguished by their form into fungous, conical, and villous. With the excep- tion of the first kind, these small prominences are formed by the extremities of nerves, surrounding a plexus of capillary blood-vessels, which give to these papillae the power of becoming turgid and prominent, and of bein*- affected with a kind of erection when we eat highly-seasoned food or when we long for a savoury dish. The fungous papilla? are mostly situated at the remotest part of the upper surface of the tongue, towards its root, where it forms a part of the isthmus faucium. The pressure with which they are affected by the alimentary bolus, in its passage from the mouth into the pharynx, squeezes out the mucus which lubricates the edges of the aperture and serves to promote its passage : these mucous follicles fulfil, in this re- spect, the same office as the amygdalae. The upper surface of the tongue is the seat of taste ; it is undeniable however, that the lips, the gums, the membrane lining the arch of the palate' and the velum palati* may be affected by the impression of certain flavours' It is observed m the different animals, that the organ of taste is more per- fect according as the nerves of the tongue are larger, its skin thinner and The flavour of any substance appears chiefly ed by Scarpa, after arising from the sranelion of to arise from the odoriferous particles which es- Mekel, and going for a pFe tv^onsidSle dis cane from it, during the process of mastication tance into the nfsal fo£» terminatesin thl and deglutition, through tne posterior narcs, and thick and rugous portion of the palatine mem affect the olfactory nerves fn that situation.- brane situated behindX? upperPinc4ors"and 'Especially the anterior.part of the palatine ^Itomact.6 ^ °f ** t0ngUe * ™ *** **" membrane. The naso-palatine nerve, discover- 216 OF THE SENSE OF TASTE. moister, its tissue more flexible, its surface more extensive, its motions easier and more varied. Hence, the bone in the tongue of birds, by diminishing its flexibility ; the osseous scales of the swan's tongue, by reducing the extent of the sentient surface ; the adhesion of the tongue to the jaws in frogs, in the salamander, and in the crocodile, by preventing freedom of motion,— render, in these animals, the sense of taste duller, and less calculated to feel the impression of sapid bodies, than in man and the other mammiferous ani- mals. Man would, probably, excel all the other animals in delicacy of taste, if he did not at an early period impair its sensibility by strong drinks, and by the use of spices, and of all the luxuries that are daily brought to our tables. The quadrupeds, whose tongue is covered by a rougher skin, discover better than we can, by the sense of taste, poisonous or noxious substances. We know that in the great variety of plants which cover the face of the earth, herbivorous animals select a certain number suited to their nature, and uni- formly reject those which would be injurious to them. CXXIX.—Is the lingual branch of the fifth pair of nerves, alone subser- vient to the sense of taste 'I Are not the ninth pair (almost wholly distribut- ed in the tissue of the tongue), and the glossopharyngeal branch of the eighth, likewise subservient to this function 1 Most anatomists, since Galen, have thought that the eighth and ninth pair supplied the tongue* with its nerves of motion, and that it received from the fifth its nerves of sensation. Several filaments, however, of the great hypoglossal nerve may be traced into the nervous papillae of the tongue. This nerve is larger than the lingual, and is more exclusively distributed to this organ than the fifth pair, to which the other nerve belongs. Hevermann states, that he knew a case in which the sense of taste was lost from the division of the nerve of the ninth pair, in removing a scirrhous gland. This case, however, appears to me a very suspicious one. The patient might still have tasted, by means of the lingual nerve, and the sense would only have been weakened. The division of one of the nerves of the ninth pair could render insensible only that half of the tongue to which it is distributed, the other half would continue fully to pos- sess the faculty of taste. The application of metals to the different nervous filaments distributed to the tongue, ought to inform us of their different uses, if, as Humboldt sus- pects, the galvanic excitement of the nerves of motion alone produces con- tractions. To ascertain the truth of this conjecture, I placed a plate of zinc within the skull, under the trunk of the nerve of the fifth pair, in a dog that had been killed a few minutes before, and that still retained its warmth : the muscles of the tongue, under which a piece of silver was placed, quivered very slightly ; those of the forehead and temples in contact with the same metal experienced very sensible contractions whenever a communication was made by means of an iron rod. This experiment shewed that the lingual branch of this nerve was almost solely subservient to the sensation of taste,— which agrees with the opinion of most physiologists; and the same inference may be drawn from the anatomical knowledge of the situation of this nerve, which almost entirely terminates in the papilla? of the membrane of the tongue, and sends very few filaments to the muscles of that organ. But though the galvanic irritation applied to the hypoglossal nerve affected the whole tongue in a convulsive manner, I did not think myself justified to infer that this nerve was solely destined to perform its motions : as this nervous trunk might, in this part of the body, as it does in others, contain filaments both of sensation and motion. The tongue, though an azygous organ, is composed of parts completely symmetrical; there are on each side four muscles, (stylo, kyo, genio-glossal, OF THE ORGAN OF TOUCH. 217 and lingual); three nerves, (lingual, glossopharyngeal, and hypoglossal) ; a ranine artery and vein ; and a set of lymphatic vessels precisely alike. All these parts, by their union, form a fleshy body of a close texture, and not easily unravelled, similar to that of the ventricles of the heart, endowed with a considerable degree of mobility, in consequence of the numerous vessels and nerves entering into its substance.* If we compare their number and size with the small bulk of the organ, it will be readily understood, that as no part of the body can execute more frequent, more extensive, and more varied motions, so no one receives more vessels and nerves. A middle line separates and marks the limits of the two halves of .the tongue, which, anatomically and physiologically considered, appears formed of two distinct organs in juxta-position. This independence of the two parts of the tongue is confirmed by the phenomena of disease : in hemiplegia, the side of the tongue corresponding to the half of the body that is paralysed, loses likewise the power of motion ; the other retains its mobility, and draws the tongue towards that side. In carcinoma of the tongue, one side remains unaffected by the disease which destroys the other half: lastly, the arteries and nerves of the left side rarely anastomose with those on the right; injections forced along one of the ra- nine arteries, fill only the corresponding half of the organ, &c. CXXX. Of the organ of touch.—No part of the surface of our body is exposed to receive the touch of a foreign body, without our being speedily informed of it. If the organs of sight, of hearing, of smell, and of taste, occupy only limited spaces,—touch resides in all the other parts, and effec- tually watches over our preservation. The touch, distributed over the whole surface, appears to be the elementary sense, and all the others are only modi- fications of it, accommodated to certain properties of bodies. All that is not light, sound, smell, or flavour, is appreciated by the touch, which thus in- structs us in the greater part of the qualities of bodies which it concerns us to know, as their temperature, their consistence, their state of dryness or hu- midity, their figure, their size, their distance, &c. It corrects the errors of the sight, and of all the other senses, of which it may justly be called the regulator ; and it furnishes us with the most exact and distinct ideas. The touch, of which some authors have sought to consecrate the excel- lence, by giving it the name of the geometrical sense, is not, however, safe from all mistake. ^Whilst it is employed on the geometrical properties derived from space, and that it appreciates the length, the breadth, the thickness, the form of bodies,—it transmits to the intellect rigorous and mathematical re- sults ; but the ideas we acquire by its means, on the temperature of bodies, are far from being equally precise. For, if you have just touched ice, ano- ther body colder than yours will appear warm. It is for this reason that sub- * Haller concluded that the tongue possesses were its movements, when cut across after its irritability. Blumenbach has lately determined separation, that its motions might be compared the point by direct experiment. He caused the to those of the tail of a mutilated snake. The tongue of a four-year-old ox, which had been same phenomenon was remarkable in the divid- killed in the usual way, to be cut out while the ed tongues of other animals, on the application animal wa3 yet warm, and at the same time the of mechanical or chemical stimuli; and also in heartj in order that he might compare the oscil- that of a boy, which had been bit off during a latory motions of both viscera ; and when they violent fit of epilepsy. were excited at the same time by mechanical From this, it would appear that the account stimuli, the tongue appeared to survive the which Ovid gives of the cruel deed of Tereus heart by more than seven minutes; and so vivid is nearly correct:— -------------" Compressam forcipe linguam Abstulit ense fero. Radix micat ultima linguae, Ipsa jacet, terrasque tremens immurmurat atras, Utque salire solet mutilata) cauda colubra?, Palpitat, et moriens dominac vestigia qu;rrit."—Mriamcr. VI.—J. C. 2* 218 OF THE INTEGUMENTS terraneous places appear warm to us during winter. They have kept their temperature whilst all things else have changed theirs ; and as we judge of the heat of an object by its relation not only to our own, but also to that of other bodies, and of the air about ue, we find the same places warm which had appeared cold to us in the middle of summer. The densest bodies being the best conductors of heat,* marble, metals, &c, appear colder to us than they really are, because they carry it off so rapidly. Marble and metals, when polished, appear still colder, because as they touch the skin in many more points at once, they effect this abstraction more effec- tually. Every one.knows the experiment of placing a little ball between the two fingers crossed, and producing the sensation of two different balls. CXXXI. Of the integuments.—The general covering of the whole body is the organ of touch, which resides in the skin properly so called. The cel- lular tissue, which connects together all our parts, forms over the whole body a layer, varying in thickness, which covers it in every part: it is called pan- niculus adiposus. As it approaches the surface, its lamina? are more condensed, are in more immediate contact with each other, and are no longer separated by adeps. It is by the closer juxta-position of the lamina? of the cellular tis- sue that the skin or dermis is formed,—a dense and elastic membrane, into which numerous vessels, of all kinds, are distributed, and into which so great a quantity of nerves terminate, that the ancients did not hesitate to consider the skin as purely nervous. In certain parts of the body a very thin muscular plane separates the skin from the panniculus adiposus. This kind of panniculus carnosus en- velopes, almost entirely, the body of some animals ; its contractions wrinkle their skin covered with hairs, these rise, vibrate, and thus are cleared of the dust and dirt which may have gathered on them. It is by means of a cuta- neous muscle, of very complex structure, that the hedge-hog is enabled to coil himself up, and to present to his enemy a surface studded with sharp points : only a few scattered rudiments of an analogous structure are to be met with in the human body; the occipito-frontalis, the corrugator supercilii, several muscles of the face, the platysma myoides, the pahnaris cutaneus, may be considered as forming part of this muscle. We may even include the cremaster, whose expanded fibres, surrounded by the dartos, have misled some anatomists to such a degree that they have admitted the existence of a muscular texture in the latter. These fibres of the cremaster produce distinct motions in the skin of the scrotum, wrinkle it in a transverse direction, and at the same time bring up the testicles. The platysma myoides acts likewise on the skin of the neck : lastly, the occipito-frontalis in some men performs so distinct a motion of the hairy scalp, as to throw off a hat, a cap, or any other covering that may be on the head. One may compare to the panniculus carnosus, the muscular coat of the digestive tube situated through- out its whole length below the mucous membrane, which is merely a pro- longation of the skin modified and softened. r But if in man the subcutaneous muscle, from its imperfect state, answers purposes only of secondary importance, the layer of cellular adipose sub- * Woolly substances, &c. all felts, of which as well as heat, will pass with ease. It is by the crossing hairs confine, in some sort, a great thus confining a certain mass of air that snow quantity ofair, a fluid which, from its gaseous keeps the soil it covers in a mild temperature, state, is a very bad conductor of heat, retain and preserves plants from the injury of exces- heat well; and, being of equal thickness, a stuff sive cold ;—a physical truth which is found of fine wool, of which the hairs are more sepa- figuratively expressed in the words of the rated and the tissue softer, will be warmer than Psalmist, " Et dedit illi nivem tanquam vestimen- a stuff of coarse wool, of which the threads, too turn." close, form a dense body, through which cold, OF THE INTEGUMENT? 219 stance, extended under the skin, gives to the latter its tension, its whiteness, its polish, its suppleness, favours its applying itself to tangible objects, and thus renders the touch more delicate. Too hard or wrinkled a skin would have applied itself in a very incomplete manner to bodies of a small size, and would not readily have accommodated itself to the small irregularities of those of inconsiderable bulk. Hence, the pulp of the fingers, which is the seat of a more delicate touch, is furnished with a kind of adipose cushion supported by the nails, ready to be applied to polished surfaces, and to dis- cover the slightest asperities. I have observed the sense of touch to be very imperfect in men wasted by marasmus, and whose hard, dry, and wrinkled akin adheres, in certain situations, to the subjacent parts. The chemical analysis of the cutaneous tissue shews that it does not ex- actly resemble that of the cellular and membranous tissue ; it is gelatino- fibrous, and, with regard to its structure and to its share of contractility, it occupies a medium between the cellular tissues and the muscular flesh* There arise from the surface of the skin innumerable small papillae, fungous. conical, pointed, obtuse, and variously shaped, in the different parts of the body. These papillae are merely the pulpous extremities of the nerves which terminate into them, and around which there are distributed vascular tissues, of the utmost minuteness. The papilla? of the skin, which are more distinct in the fingers and lips than elsewhere, swell when irritated, and elevate in a manner the epidermis ; and this kind of erection, which is use- ful when we wish to touch a substance with great precision, may be excited by friction, or by moderate heat. The nervous or sentient surface of the skin is covered with a mucous coat- ing, colourless in Europeans—blackened, from the effects of light, among the natives of southern climates ; of a gelatinous nature, destined to main- tain the papillae in that state of moisture and softness favourable to the sense of touch. This mucilaginous layer, known under the name of rele mucosum of Malpighi, seems to contain the principle which causes the variety of co- lour in the skin of different nations, as will be observed in speaking of the varieties of the human species. The reticular state of the rete mucosum may be explained in two ways : a thin and gelatinous layer, extended on the papillar surface of the skin, is perforated at each nervous papilla, and if it were possible to coagulate or to detach this coating, we should have a real sieve or reticulated mesh-work, with a perforation at every point, corresponding to a cutaneous papilla. The sanguineous and lymphatic capillaries which surround the nervous papilla?, form, besides, by their connexions, a net-work, the meshes of which are very minute, and adhere to the epidermis by a multitude of small vascular fila- ments, that insinuate themselves between the scales of this last envelope, and terminate in exhaling or absorbing pores, according as they belong to the arterial capillaries or to the lymphatic absorbents. It is sufficient, indeed, to remove gently the scales of the epidermis, in order to bare their orifices, and procure the absorption of any virus. It is the net-work of Malpighi, or rather this assemblage of interlaced capillary vessels below the epidermis, which appears to be the seat of the primary phenomena in the majority of cutaneous inflammations and eruptive diseases. The skin would be unable to perform its functions, if an outer, thin, and transparent membrane, the epidermis, did not prevent it from being over-dried. This superficial covering is quite insensible ; no nerves, and no vessels of any kind, are found in it; and even in the present state of the science, we * See the chapter in the Appendix, on the Chemical Constitution of the Animal Textures tnd Spcretions 220 UF THE CUTANEOUS TISSUES. do not understand how it is formed, or how it repairs and reproduces itself when destroyed. The most minute researches on its structure merely shew the existence of an infinite number of lamellae, overlapping each other, like the tiles of a roof. This imbrication of the epidermoid lamellae is very obvious in fishes and reptiles ; the scaly skin of which is merely an epidermis whose parts are much more coarsely shaped. It was observed (XLII.) in the account of absorption, how much friction facilitates the absorption of substances applied to the surface of the skin, by raising the scales of the epidermis so as to expose the orifices of the absorb- ents, whose activity it in other respects increases. Haller conceives that the epidermis is formed by the drying up of the outer layers of the rete mucosum. Morgagni thinks it is formed by the in- duration of the skin, in consequence of the pressure of the atmosphere. In objection to these hypotheses, one may inquire how it happens, that by the time the foetus, immersed in the liquor amnii, has attained its third month, it is covered with such an envelope.* Pressure renders the skin hard and cal- lous, increases considerably its thickness, as we see in the soles of the feet and in the palms of the hands of persons engaged in laborious employments. The epidermis reproduces itself with an incredible rapidity, after falling off in scales, after erysipelas or herpetic eruptions; or, when removed in large flakes by blistering, it is renewed in the course of a very few days. The cuticle, together with the hairs and nails, which may be considered as pro- ductions of the same substance, are the only parts in man that are capable of reproducing themselves. The hairs and the horns of quadrupeds, the feathers of birds, the calcareous matter of the lobster and of several molusca, the shell of the turtle, the solid sheaths of a number of insects, possess, as well as the epidermis, this singular property. In other respects the chemi- cal structure of all these parts is the same ; they all contain a considerable proportion of phosphate of lime, withstand decomposition, and give out a considerable quantity of ammonia on being exposed to heat. The use of the epidermis is to cover the nervous papilla?, in which the faculty of the touch essentially resides, to moderate the too vivid impression that would have been produced by an immediate contact, and to prevent the air from drying the skin or from impairing its sensibility. This dessication of the cutaneous tissue is further prevented, and its sup- pleness maintained, by an oily substance which exudes through its pores, and is apparently secreted by the cutaneous exhalants. This unctuous liniment should not be mistaken for that which is furnished by the sebaceous glands in certain situations, as around the nostrils, in the hollow of the arm-pits, and in the groins. This adipose substance with which the skin is anointed, is abundant and fetid in some persons, especially in those of a bilious tempera- ment, with red hair. It is likewise more copious in the African negroes, as if Nature had been anxious to guard against the too rapid dessication, by the burning atmosphere of tropical climates. This use of the oil of the skin is likewise answered by the tallow, the fat, and the disgusting substances with which the Caffres and the Hottentots anoint their body, in the manner de- scribed under the name of tatooing by the travellers! who have penetrated into the interior of the burning regions of Africa. * The epidermis seems to be formed from a which covers the egg. The epidermis may, certain dry secretion, of which the skin is the therefore, be considered as a kind of excremen- organ. The exhalants, with which the dermal tal tissue—as a residue or product of nutrition tissue is abundantly supplied, allow a viscus thrown on the surface of the body, and forming and albuminous fluid to escape, which contains a useful and requisite protection to the econo- a great proportion of phosphate of lime ; thus my of organized beings. an envelope is formed analogous to the shell + Among others, Kolben, Description du Cap OF THE NAILS 221 The ancients had a somewhat similar practice ; and the anointing with oil, so frequently used in ancient Rome, answered the same purpose of soften- ing the skin, of preventing its becoming dry or chapped* The pomatums employed at the present day at the toilet possess the same advantages. The continual transudation of this animal oil renders it necessary, occasionally, to clean the skin by bathing ; the water removes the dust and the other im- purities which may be attached to its surface by the fluid which lubricates it. It is this humour wheh soils our linen, and obliges us so frequently to renew that in immediate contact with the skin, and which makes the water collect in drops when we come out of the bath, &c. Though the parts in which there is found the greatest quantity of sub- cutaneous fat are not always the most oily, and though one cannot consider this secretion as. a mere nitration of this adeps through the tissue of the skin ; corpulence has, however, a manifest influence on its quantity. I know several very corpulent persons in whom it appears to be evacuated by per- spiration, on their being heated by the slightest exertion. They all grease their linen in less than twenty-four hours. An excess of the oily matter of perspiration is injurious, by preventing the evacuation of the perspiration, and its solution in the atmosphere. We all know how, after the epidermis has been removed, the slightest contact is painful ; that of the air is sufficient to bring on a painful inflam- mation of the skin, exposed by the application of a blister. The epidermis, as was likewise mentioned in speaking of the absorption, placed on the limits of the animal economy, and in a manner inorganic, serves to prevent hetero- geneous substances from being too readily admitted into the body, and, at the same time, it lessens the too vivid action of external objects on our organs. All organised and living bodies are furnished with this covering ; and in all, in the seed of a plant, in its stem, and on the surface of the body in man and animals, it bears to the skin the greatest analogy of function and nature. Incorruptibility-is in a manner its essence, and is its peculiar character; and in tombs, which contain merely the dust of the skeleton, it is not uncommon to find whole, and in a state to be readily distinguished, the thickened epider- mis that forms the sole of the foot, and especially the heel. However, this incorruptibility is possessed, as well as others of the qualities of the skin, by the nails and the hairs, which may be considered as its appendages. CXXXII. Of the nails.—The nails are, in fact, only a part of the epider- mis ; they are continuous with it, and after death fall off along with it. They are thicker and harder; like it they are inorganic and lamellated ; they grow rapidly from their root towards their free extremity ; they reproduce them- selves rapidly, and acquire several inches in length, when the part beyond the ends of the fingers and toes has not been removed ; as is the case with the Indian fakirs. In this state of development they bend over the tips of the fingers and toes, and impair the sense of touch, whose free enjoyment is preferable to any advantages which savages can derive from their long and crooked nails, in defending themselves, or in attacking animals, or tearing to pieces those which they have killed in hunting. The nails are quite insen- sible, and the reason that so much pain is felt when the nails run into the flesh, and that the operation of tearing them out, which is sometimes neces- sary, is so painful, is, that the nerves over which the nail grows are more or less injured when it grows in a wrong direction. The pain from the growing de Bonne-Esperance. Sparrmann, Voyage au who, on being asked by Augustus how he came Cap de Bonne-Espirance et chez les Hottentots, to live so long, said he owed his long life to the Vaillant, Voyage dans Vlnterieur de VAfrique. use of wine inwardly, and to that of oil outward- * The reply of the old soldier is well known, ly : intus vino, extus oleo. 222 OF THE HAin of the nails into the quick, is no proof of their being sentient; any more than the growth of corns proves the sensibility of the epidermis, of which they are but thickened parts, become hard and callous by pressure, and which, con- fined in tight shoes, press painfully on the nerves below. The nail itself may acquire a considerable degree of thickness ; I have seen that of the great toe nearly half an inch thick. The use of the nails is to support the tips of the fingers, when they are applied to unyielding substances ; they likewise concur in improving the mechanism of the touch.* CXXXIII. Of the hair on the head and other parts of the body.—These parts are treated of in the present instance, only in consequence of their connexion with the epidermis ; as, far from improving the touch, they interfere with it, or at least render it less delicate. The skin in man is more bare than that of other animals; it is likewise least covered with insensible parts that might blunt the sense of touch. In almost all mammiferous animals the whole body is covered with hair ; only a small part of the human body has any hair on it, and that in too small a quantity, and of too delicate a texture, to interfere with the touch. Some men, however, have a very hairy skin, and I have seen several who, when naked, looked as if covered over with the skin of an animal, so great was the quantity of hair over the whole body, of which no part was bare but a small portion of the face, the palms of the hands, and the soles of the feet. This extraordinary growth of hair is in general a sure sign of vigour and strength. In childhood, there is no hair except on the head, the rest of the body is covered with down. Women have no beard, and there is in them a smaller quantity of hair in the arm-pits and on the parts of generation, and scarcely any on the limbs and trunk. But as though the matter which should provide for the growth of the hair were wholly applied to the hairy scalp, it is observed, that the hair of their head is longer and in greater quantity. The colour of the hair varies from white to jet black ; and, as will be mentioned in speaking of the temperaments and of the varieties of the hu- man species, this difference of colour is a test by which we judge of those varieties. The colour of the hairs enables us to judge of their thickness: Withof, who, with a truly German patience, was at the pains to count how many hairs were contained in the space of a square inch, states, in his dis- sertation on the human hair, that there are five hundred and seventy two black hairs, six hundred and eight chestnut, and seven hundred and ninety light coloured ; so that the diameter of a hair, which is between the three and seven hundredth part of an inph, is least in light hair, and these are the finer the lighter their shade. It is likewise observed, that men of a bilious constitution, with dark hair, and inhabiting warm climates, have more hair in other parts of the body, and that it is coarser and more greasy. In whatever part of the body hairs may grow, they are every where of the same structure, they all arise from a vesicular bulb in the adipose cellular tissue : from this bulb, containing a gelatinous lymph, on which the hair * The toe-nails are favourable to the laying fore part of the foot into several distinct and Ae foot to the surface on which the body is sup- separate parts, serves to enable us to stand ported ; they likewise improve the sense of more firmly, and facilitates the action of walk- touch in this part. The use of the feet is not ing. I have seen several soldiers who lost, merely to support the weight of the body; they from severe cold, the extremities of their feet, are also intended to guide us in feeling for the in crossing the Alps which separate France plane on which we are to rest them, to enable from Italy. Those who had lost only their toes, us to judge of the solidity, of the temperatuie, did not walk so steadily, and frequently fell in and of the inequalities of the ground on which treading on uneven ground. Those who had we tread. They, therefore, required rather a lost one half of their feet were obliged to use delicate sense of touch. The division of the crutches. OF THE HAIR. 223 seems to be nourished, the latter, at first divided into two or three filaments which constitute a kind of root, comes out in a single trunk, passes through the skin and epidermis, receiving from the latter a sheath that covers it to its extremity, which terminates in a point. A hair may therefore be considered as an epidermoid tube, filled with a peculiar kind of marrow. This spongy stem, which forms the centre of a hair, is a more essential part of it than the sheath supplied by the epidermis. Along this spongy and cellular filament, the animal oil of the hair and the juices on which it is repaired flow. Though we see, in some animals, vascu- lar branches and very small nervous filaments directed towards the root of certain kinds of hair, and lost in it, as is the case with the long and stiff whiskers of some of the quadrupeds,—it is impossible to say, whether in man the hair or its* bulbs receives vessels and nerves. Is the human hair nourished by the imbibition of the gelatinous fluid contained in its bulb, or is it nourished on the fat in which the latter is imbedded ? Are vessels distri- buted along their axis, from the root to the extremity % In favour of this opinion, it was usual to mention the bleeding from the hair when cut, in the disease called plica Polonica. But this disease, lately observed in Poland by the French physicians, appeared to them a mere entangling of hair, in con- sequence of the filth of the Poles, and of their habit of keeping their head constantly covered with a woollen cap. The hairy scalp remains perfectly sound beneath the entangled hair, and the only way to cure the complaint is to cut off the hair. Fourcroy* thinks that each hair has several short branches that stand off from it, which, according to the explanation given by Monge, favour the matting of the hairs that are to be converted into tissues, by the process called felting. CXXXIV.—Among the most remarkable qualities of the hair one may take notice of the manner in which it is affected by damp air, which, by re- laxing its substance, increases its length. It is on that account that hairs are used for the construction of the best hygrometers. Nor must we omit either the readiness with which they grow and are reproduced, even after being plucked out by the roots, as I have often seen after the cure of tinea by a painful method: nor their insulating property with respect to the electric fluid, of which they are very bad conductors; a remarkable property, viewed with reference to the conjectured nature of the nervous fluid. The hairs possess no power of spontaneous motion by which they can rise on the head, when the soul shudders with horror or fear ; but they do bristle at those times, by the contraction of the occipito-frontalis, which, inti- mately adhering to the hairy scalp, carries it along in all its motions. They appear totally without sensibility ; nevertheless, the passions have over them such influence that the heads of young people have turned white the night before execution. The Revolution, which produced in abundance the extremes of human suffering, furnished many authentic instances of persons that grew hoary in the space of a few days. In this premature hoari- ness, is the hair dried up, as in old people, when it seems to die for want of moisture and its natural juices ? The following fact seems to shew that they are the excretory organ of some principle, the retention of which might be of very injurious consequence. A chartreux, who every month had his head shaved, according to the rule of his order, quitting it at its destruction, went into the army, and let his hair grow. After a few months, he was attacked with excruciating headaches, which nothing relieved. At last, some one advised him to resume his old * Systime des Connoissances Chimiques, tome ix. p. 263 224 OF THE SENSE OF TOUCH habit, and to have his head frequently shaved ; the headaches went off, and never returned. We know, says Grimaud,* that there are nervous headaches, which give way to frequent cropping the hair :—when it is kept close cut, the more ac- tive growth that takes place sets in motion stagnating juices. A friend of Valsalva, as Morgagni f relates, dispelled a maniacal affection, by having the head of the patient shaved ; Casimir Medicus cured obstinate gonorrhoea, by the frequent shaving of the parts of generation. The hairs partake of the inalterability, the almost indestructibility of the epidermis. Like it, they burn with a fizzing, and give out in abundance a fetid ammoniacal oil. The ashes that remain from burning them contain much phosphate of lime.J The horns of mammifera?, the feathers of birds, give out the same smell in burning, and yield the same products as the hair on the head and other parts ; which has led to the saying that these last were a sort of horny substance, drawn out like wire. Acids, but especially alkalies, dissolve them : accordingly, all nations that cut the beard, first soften it, by rubbing it with alkaline and soapy solutions. Is the use of the hair to evacuate the superabundant nutritious matter % The epoch of puberty and of the termination of growth, is that in which it first springs, in many parts of the body which were before without it. They are, at the same time, the emunctory by which nature gets rid of the phos- phate of lime, which is the residue of the work of nutrition. The hairs of quadrupeds, whose, urine abounds less in phosphoric salts than that of man, seem especially to fulfil this destination. The hairs have some analogy with the fat, which has not yet been ascertained. They are often found acciden- tally developed in the fatty tumours known under the name of steatomas. Finally, they have uses relative to the parts on which they grow. CXXXV. Of the sense of touch, SfC—-The faculty of taking cognizance of tangible qualities belongs to all parts of the cutaneous organ. We have only to apply a substance to any part of the surface of our body, to acquire the idea of its temperature, of its dryness or moisture, of its weight, its con- sistence, and even its particular figure. But nO part is better fitted to acquire exact notions on all these properties, than the hand, which has ever been con- sidered as the especial organ of touch. The great number of bones that form its structure, make it susceptible of very various motion, by which it changes its form, adapts itself to the inequalities of the surfaces of bodies, and exactly embraces them: this apt conformation is particularly manifest at the extremities of the fingers. Their anterior part, which is endued with the most delicate feeling, receives, from the medium and cubital nerves, branch- es of some size, which end in rounded extremities, close, and surrounded with a cellular tissue. The part of the fingers which is called their pulp, is sup- ported by the nails ; vessels in great number are spread through this nervo- cellular tissue, and moisten it with abundant juices, that keep up its supple- ness. When perspiration is increased, it breaks out in small drops over this extremity of the fingers, along the hollow of the concentric lines with which the epidermis is furrowed. It has been attempted to explain the pleasure we feel in touching rounded and smooth surfaces, by shewing that the reciprocal configuration of the hand and of the body to which it is applied, is such, that they touch in the greatest number of points possible. The delicacy of the touch is kept up by the fineness of the epidermis: it increases by education, which has more power over this sense than over any of the others. It is known with what * Second Memoir on Nutrition, p. 49. % See the Chapter in the Appendix, on the t Dc Sedibus et Causi.-; Epist. 8. No. 7. Chemical Constitution of the Textures, &c OF THE SENSE OF TOLCH. 225 eagerness a child, allowed the free use of his limbs, stretches his lit lie hands to all the objects within his reach, what pleasure he seems to take in touch- ing them in all their parts, and running over all their surfaces. Blind men have been known to distinguish by touch the different colours, and even their different shades. As the difference of colour depends on the disposition, the arrangement, and number of the little inequalities which roughen the surface of bodies that appear the most polished, and fit them to reflect such or such a ray of light, absorbing all the others, one does not refuse to believe facts of this kind, related by Boyle, and other natural philosophers. Some parts appear endowed with a peculiar touch; such are the lips, whose tissue swells and spreads out under a voluptuous contact; a vital tur- gescence, explicable without the supposition of a spongy tissue in their struc- ture,1—such are tliose organs which Buffon considers as the seat of a sixth sense. In most animals, the lips, and especially the lower one, without feathers, scales, or hair, are the organ of a sort of touch, imperfect at best. When the domestic quadrupeds, such as the horse, the dog, the ox, &c. want to judge of the tangible qualities of bodies, you will see them apply to it the end of their nose, the only part where the external covering is without hair ; the fleshy appendages of certain birds, and many fish ; the antenna? of but- terflies, always set near the opening of the mouth, answer the same purpose. The tail of the beaver, the trunk of the elephant, are, in like manner, the parts of their body where touch is most delicate. Observe that the perfection of the organ of touch insures to these two animals a degree of intelligence allot- ted to no other quadruped, and becomes, perhaps, the principle of their socia- bility. The books of travellers and naturalists swarm with facts attesting the wonderful sagacity of the elephant. Some Indian philosophers have gone the length of allowing him an immortal soul. If birds, notwithstanding the prodigious activity of their life of nutrition, are yet of such confined in- telligence, so little susceptible of durable attachment, so restive to education, is not the cause to be assigned to their imperfection of touch ? In vain the heart sends towards all their organs, with more force and velocity than in any other animal, a warmer blood, and endued more remarkably with all the qualities which characterise arterial blood ; in vain is their digestion rapid, their muscular power lively and capable of long-continued motion, and certain of their senses, as those of sight and hearing, happily disposed ;—touch being almost nothing with them, as also the greater number of impressions belong- ing to this sense, which informs us of the greater part of the properties of bodies, the circle of their ideas must be extremely narrow, and their habits and manners much more remote than those of quadrupeds from the habits and manners of man. CXXXVI.—Of all the senses the touch is the most generally diffused among animals. All possess it,—from man, who in the perfection of this sense excels all vertebral animals, to the polypus, who, confined to the sense of touch only, has it in such delicacy, that he appears, to use a happy ex- pression of M. Dumeril, to feel even light. The skin of man is more deli- cate, fuller of nerves than that of the other marnmiferEe; its surface is co- vered only by the epidermis, insensible indeed, but so thin that it does not in- tercept sensation, whilst the hairs which cover so thickly the body of quad- rupeds, the feathers which clothe that of birds, quite deaden it. The hand of man, that admirable instrument of his intelligence, of which the structure has appeared to some philosophers* to explain sufficiently his superiority over all living species ; the hand of man naked, and divided into many movable * Sec the work of Galen, de Usu Partium, cap. iv. v. vi.; and Buffon, Hisloire Naturelle, torn. iv. et v. 12mo. 29 226 OF THE STRUCTURE OF SERVES. parts, capable of changing every moment.its form, of exactly embracing the surface of bodies, is much fitter for ascertaining their tangible qualities than the foot of the quadruped, enclosed in a horny substance, or than that of the bird, covered with scales too thick not to blunt all sensation. CXXXVII. Of the nerves.—These whitish cords, which arise from the base of the brain and from the medulla oblongata, are distributed to all parts of the body, and give them at once the power of moving and feeling. In this analysis of the functions of the nervous system, the most natural order is to consider them merely as conductors of the power of sensation. We shall then see in what manner they transmit the principle of motion to the organs by which it is performed. The nerves arise* from all sentient parts, by ex- tremities that are in general soft and pulpy, but not alike in all in consistence and form; and it is to these varieties of arrangement and.structure, that the varieties of sensation in the different organs are to be referred. One may say, that there exists in the organs of sense a certain relation between the softness of the nervous extremity and the nature of the bodies which produce an impression upon it. Thus, the almost fluid state of the retina bears an evident relation to the subtilty of light. The contact of this fluid could not produce a sufficient impression unless the sentient part were capable of being set in motion by the slightest impression. The portio mol- lis of the seventh pair, wholly deprived of its solid covering, and reduced to its medullary pulp, readily partakes in the sonorous motions transmitted to it by the fluid, in the midst of which its filaments are immersed. The nerves of smell and of taste are more exposed than the nervous papillae of the skin which are employed in receiving the impressions produced by the coarser properties of bodies, &c. From their origin the nerves ascend towards the medulla oblongata and the spinal marrow, in a line nearly straight, and seldom tortuous, as most of the vessels. When they have reached these parts they terminate in them, and are lost in their substance, as will be mentioned in speaking of the struc- ture of these nervous cords. CXXXVIII. Sb-ucture of nerves.—Every nerve is formed of a great num- ber of filaments, extremely delicate, and which have two extremities, the one in the brain, and the other from the part into which they terminate, or from which they originate. Each of these nervous fibres, however minute, is composed of a membranous tube, which is a production of the pia mater. Within the parietes of this tube there are distributed innumerable vessels of extreme minuteness ; it is filled within with a whitish marrow, a kind of pulp, which Riel states he insulated from the small canal containing it, by concret- ing it by means of the nitric acid, which dissolves the membranous sheath, and leaves uncovered the medullary pulp, forming the essential part or basis of the nervous filament. The same physiologist discovered by a different process the internal structure of each nervous fibrilla : he dissolved the whi- tish or pulpy part by a long-continued solution in alkaline ley, and he. suc- ceeded thus in separating it from the membranous tube which enclosed it, and which was emptied. The membranous sheath is of cellular structure, and is remarkable only by its consistence, and by the very considerable num- * In considering the nerves as conductors of the brain; for it is from the centre to the cir- sensation, it is correct to say, that they arise cumference that the principle of motion is trans- from sentient parts, since it is the extremity mitted to the muscles called by Cullen moving most distant from the brain which experiences extremities of the nerves. Some anatomists have the sensitive impression that is propagated to the thought it a doubtful point, whether the nerves organ itself along the course of the nerve. In arise from the brain and spinal marrow, or whe- attending, on the contiary, to the phenomena of ther these parts are formed by the union of the motion, the nerves are considered to arise from nerves. OF THE DISTRIBUTION OF NERVES. 227 ber of vessels of all kinds that are distributed to its parietes ; it ceases to co- ver the nerves near their two extremities, and protects them only along their course. Each nervous fibre, thus formed of two very distinct parts, joins other fibres of a perfectly similar structure, to form a nervous filament enveloped in a common sheath of cellular tissue. These filaments by their union form small ramifications, and these progressively larger branches, and lastly trunks, wrapped in a common covering of cellular tissue; then other envelopes to each fasciculus of filamenis, and lastly, a sheath to each individual filament. When nervous cords are of a certain size, veins and arteries of a pretty consi- derable calibre may be seen to insinuate themselves between the bundles of fibres of which they are composed ; these vessels then divide, after penetrating among them, and furnish the capillary ramifications which are distributed to the parietes of the sheath common to each filament. These small vessels, ac- cording to Reil, allow the nervous substance to exhale into each membranous tube ; this likewise becomes the secretory organ of the medulla, with which it is filled. CXXXIX. Distribution of nerves.—The nervous filaments unite, or are separated from one another, but do not run into each other. The divisions of the nerves are different from those of the arteries, and their mode of junc- tion does not admit of being compared to that of the veins. It is, in the first instance, a mere separation; in the second, an approximation of filaments which had been separated, and which, though united in common sheaths, have, nevertheless, each a proper covering, are merely in juxta-position, and perfectly distinct. If that were not the case, one could not say that each fibre has one extremity in the brain, and the other in some one point of the body; nor could one conceive how the impressions which several sentient extremities receive at once, reach the brain without running into each other; nor in what manner the principle of motion could be directed towards a single muscle receiving its nerves from the same trunk as the other muscles of the iimb. We may admit the existence of four kinds of nerves : 1st, those having double roots, as the spinal nerves, the sub-occipital, and the trigeminal or the fifth pair of cranial nerves,—one of these roots being subservient to volun- tary motion, whilst the other is a conductor of sensibility, as the anterior and posterior roots of the spinal nerves ; 2dly, nerves having a single root or origin, as the first, second, third, fourth, sixth, the portio mollis of the seventh, and the ninth pairs,—nerves which are exclusively subservient either to sensation, as the olfactory, optic, and auditory nerves, or to the mo- tion of the muscles which they supply, as the third, fourth, sixth, and ninth pairs ; 3dly, the respiratory nerves, which have been called by Mr. Bell also the superadded, and which consist in the portio dura of the seventh pair, the eighth or pneuinogastric, which may be considered as the centre of this class of nerves, the glasso-pharyngian, the spinal or accessory of Willis, and the diaphragmatic or external thoracic : all these nerves proceed from the lateral columns of the superior portion of the medulla oblongata, and are destined to preside over the organs concerned in respiration ; 4thly, the sympathetic order of nerves, which communicate with all the spinal nerves. It is by thus distributing the nerves in four divisions, that we are enabled to form an accurate conception of the particular functions of this very com- plicated and difficult part of the animal economy, and to ascertain that sen- sation and motion have, in the first and second classes, peculiar and distinct agents, whilst the third and fourth divisions serve to associate, by more or less intimate connexions, the most important functions of our economy. The. 223 OF THE DISTRIEVTION OF NERVES earlier anatomists seem to have had some idea of this important distinction, since they applied the terms of middle and little sympathetics to the eighth pair, and the portio dura of the seventh. In general, the nerves divide from each other, and unite at an angle more or less acute, and equally favourable to the circulation of a fluid, from the circumference to the centre, and from the centre to the circumference. The structure of the nerves is different according to their situation. Thus, the medullary fibres of the optic nerve are not provided with membranous coverings, the pia mater alone furnishing a sheath to the cord formed by the union of these filaments ; the dura mater adds a second coat to it on its leav- ing the skull. This coat, belonging likewise to the whole nerve, is not con- tinued over it after it has entered the eye-ball, and is lost in the sclerotica. A minute artery passes through the centre of the optic nerve, and then divid- ing, forms a rete mirabile, which supports the medullary pulp of the retina. The nerves which pass along osseous canals, as the Vidian nerve of the fifth pair, are not provided with a cellular covering, and their consistence is .al- ways greater than that of the nerves which are surrounded by soft parts. CXL.—On reaching the brain, the medulla oblongata, or the spinal mar- row, every nervous filament, as was already mentioned, parts with its mem- branous covering, which is lost in the pia mater, or immediate covering of these central parts of the brain. The medullary or white part of the brain is continued into their substance, which may be considered as principally formed by the assemblage of these nervous extremities, which it is difficult to distinguish in its tissue, from its want of- consistence. It has long been known, that the origin of the nerves is not the spot at which they are de- tached from the brain, that they sink into the substance of this viscus, in which their fibres cross each other, so that those on the right pass to the left, and viceversd. Soemmering thought that the roots of the nerves, especially of the nerves of the organs of sense, reached to the prominences in the pa- rietes of the ventricles of the brain, and that their furthest extremity was moistened by the serosity which keeps these inward surfaces in contact. It has likewise long been thought, that the cerebral extremities or the nerves all joined in a fixed point of the brain, and that to this central point all sen- sations were carried, and that from it all the"determinations producing volun- tary motion arose. But the inquiries of Gall on the structure of the brain and nervous system have completely overset these various hypotheses. The sninal marrow and the nerves, in the different animals furnished with them, are larger in proportion to the brain, according as the animal is more distant from man in the scale of animation. In carnivorous animals the pro- digious developement of the muscles required nerves of motion of a propor- tionate size ; hence in them the cerebral mass, compared to the nerves and spinal marrow, is very inconsiderable. It is observed that there exists the same relation in men of an athletic disposition ; the whole nervous power seems employed in moving their large muscles ; and the nerves, though very small in proportion to the rest of the body, are, however, very large, if com- pared to the cerebral organ. In children, in women, and in individuals pos- sessed of much sensibility, the nerves are very large in proportion to the other parts of the body ; they decrease in size and shrink in persons advanc- ed in years ; the cellular tissue which surrounds them becomes more consis- tent, adheres to them more closely, and there exists a certain analogy be- tween the nerves of old men, enveloped by that yellowish tissue which makes their dissection laborious, and the branches of an old tree covered over by a destructive moss. As the uses of the nerves cannot be explained independently of those of the brain, I shall now go on to consider this important viscus. OF THE SPINAL CORD. 229 CXLI. Of the spinal cord and its functions.—This part of the nervous sys- tem ought no more to be called the spinal prolongation of the encephalon, as it has been by some writers, than it ought to be named the spinal marrow ; both designations are equally erroneous. It is independent of the encephalic organ. As the central portion of the nervous system, it is to be found in many animals which possess no brain, and its volume is not proportionate to that of this organ. The ox, horse, and sheep, for example, which have smaller brains than man, have a much larger spinal cord. It is found in acephalous foetuses, where the brain never existed. This latter orga'n ap- pears to be superadded to it, and that only in the perfect animals, its propor- tionate'size being always in an inverse ratio to the spinal cord. This part of the nervous system cannot, therefore, be considered as a production from the brain, and as formed by a collection of nerves which successively detach themselves from it. Its volume does not gradually diminish, owing to the nerves which it sends off; and instead of presenting the characters of a cord, which gradually decreases in thickness as it advances from the brain, it consists of a set of knots, bulbs, or separate prominences, equal in number to the pairs of nerves which arise from it. Finally, the spinal marrow is formed in the foetus before either cerebellum or cerebrum ; these organs pro- ceeding from it, and not it from them. About the second month of the foetal existence, the first epoch at which the brain can be rendered apparent by the action of alcohol, this organ is uncommonly small in proportion to the size of the spinal marrow, and arises evidently from a prolongation of the pyramidal eminences and the corpora olivaria. The different parts of the encephalic mass are gradually formed by the successive developement of the corpora pyramidalia, and it is only towards the end of gestation that the hemispheres are fully formed* The special functions that may be assigned to the spinal cord are different from those performed by the brain. In the spinal marrow resides the source of all the movements, both voluntary and involuntary, that are performed by the animal economy : it presides over those of the heart, of all the mus- cles of the interior life, as well as over those of the locomotive apparatus ; and while the brain, reserved for the most noble and most important func- tions, seems exclusively charged with the operations of intelligence and thought, the spinal marrow holds under its"controul all the contractile organs, and it is by its influence that all their contractions are executed.f Thomas Bartholin had already acknowledged that the brain was more particularly the organ of sensation, and the spinal marrow that of motion.J He was equally sensible, that the best way of proceeding in the dissection of the brain, was to advance from the base to the vertex, and not from the sum- mit to the base, as was the custom until our own times. If we take a view of the graduated scale of the animal creation, says Dr. Gall, in his Researches on the Nervous System, &c. the sensible substance, which is merely a gelatinous pulp in the polypus, gradually becomes dis- posed into nervous filaments and cords in the more perfect animals. In or- der to establish a more extended intercourse with the external world, Nature has added more complex organs, according as the relations of the species with the surrounding creation become more numerous : it is thus that, by the successive addition of new organs, and the perfection of others, that the animal creation is elevated to man himself. * See Appendix, Note G G. vero medulla? ad cerebrum admodum exiguum ; t See Appendix, Note G G. cujus rei causa est, quod pisces motu magis % " Et id quidem manifestius fit inspicienti- quam sensu utantur, ac sic ad sensum plus con- bus anatomen piscium; ibi cnim medullae caput ferat cerebrum vel cortex, ad motum plus me- et cauda insignis est magnitudinis ; processus dulla ipsa."—Anatomia. 230 OF THE COVERINGS OF THE BRAIN. The brain, a simple tubercle added to the anterior extremity of the spinal marrow, of which it seems to be nothing else than an accessory part, an ap- pendix, in the insects, because amongst them it is. but little larger-that one of their numerous ganglions, becomes more complex and more .perfect in the higher animals : in the fishes it but little exceeds the spinal cord ; whilst in the mammalia it possesses the same parts as in man, it is disposed neaily in the same form ; but in no animal is the double appearance of diverging and converging fibres, better developed than in him ; in no other animal is the brain properly so called, that is to say, the superior part of the encephalon, or the hemispheres, possessed of a greater volume in proportion to the size of the animal.* The brain proper seems to be the seat of the nobler functions of intelligence; whilst in the cerebellum,.the medulla oblongata, and the spinal cord, appear to reside those faculties and manifestations that are com- mon to us and the lower animals. The nervous system ought not, therefore, to be compared to a tree, the trunk of which, represented by the spinal marrow, has its roots in the brain, and expands its branches through all parts of the body ; but ought rather to be considered as a net-work, whose threads communicate with each other, separate, re-unite, and join several masses or dilatations of greater or less size ; these masses or ganglions ought to be viewed as being the centres of commu- nication. The brain should not be considered as a ganglion, or even as a collection of ganglions, as the common ganglion of the nerves of the cranium, as some physiologists have done": the nerves which detach themselves from its base, or from the medulla oblongata, have their origins distinct from its substance. Their volume has no relation to its bulk, but is proportionate to the perfection of the different senses in the various species of animals ; thus, the olfactory nerve, which is very large in the mole, is small in the eagle ; while the optic nerve is, on the contrary, largely developed in the latter. The spinal marrow may be considered as a series of ganglions, communi- cating with each other and with the brain.f These ganglions are of a size proportioned to that of the nerves which originate from them. It is owing to this that the spinal marrow is thicker towards the inferior part of the cervical and dorsal regions than in other portions of its length. Can the vertebral column be compared to a galvanic pile, of which the spinal cord is the con- ductor, and of which the brain and the parts of generation form the two ex- tremities, occupying, and as if constituting, the two extremities of this kind of electro-motive apparatus ? Observation establishes, it may be said, a sort of antagonism between these two organs. Is there any analogous opposition existing between the cerebral nervous system and that which forms the grand sympathetic nerves 1 We have formerly remarked, more than once, how ill- founded this attempt at identifying the vital phenomena with those of electri- city appears to us. The communication of the spinal marrow with the brain is established by the medium of a double bundle of fibres, which, crossing each other, form the corpora pyramidalia, and direct themselves towards the brain, where we shall find them again, when the structure of this viscus comes under consideration. CXLII. Of the coverings of the brain.—If it be true that one may judge of the importance of an organ by the care which Nature has taken to protect it from external injury, no organ will appear of greater importance than the brain, for no one appears to have been protected with greater care. The substance of this viscus has so little consistence, that the slightest injury would have altered its structure, and deranged its action ; hence it is powerfully * See Appendix, Note G G. t See Appendix, Note G G. OF THE COVERINGS OF THE BRAIN. 231 guarded by several envelopes, the most solid of which is the bony case in which it is contained. No part of anatomy is better understood than that of the many bones which, by their union, form the different parts of the human head. Every thing that relates to the place they occupy, to their respective size, to their projections and depressions, to the cavities whose parietes they form—every thing that relates to their internal structure, to the different proportions of their compo- nent parts, to the aggregation of some of these substances in certain points of their extent,—has been described by several modern anatomists with an accuracy which it would not be easy to surpass. Several, however, have not sufficiently appreciated the direct influence of their mode of union on the purposes which they are destined to fulfil; no one has insisted sufficiently on the manner in which they all concur to a principal object,—the preservation of the organs enclosed within the skull. Hunauld, in a memoir inserted among those of the Academy of Sciences for the year 1730, was the first that endeavoured to account for the arrange- ment of the articulating surfaces of the bones of the skull. After laying down a few principles on the theory of arches, and after shewing, that the difference of extent of their concave and convex surfaces renders it necessary that the parts of which they are formed should be shaped obliquely, he explains the advantages of the squamous articulation between the temporal and parietal bones. When the arch of the cranium is loaded with a-very heavy burthen, the temporal bones prevent the parietals on which the effort is immediately ap- plied from being forced inwardly, or from being separated-outwardly. Hu- nauld very aptly compares them to buttresses, which are to the parietal bones of the same use as walls to the arches which they support. Bordeu* endeavoured to apply to the bones of the face the principles by which Hunauld has been guided in his investigation with regard to those of the skull. According to Bordeu, the greater part of the bones of the upper jaw, but particularly the superior maxillary bones, resist the effort of the lower jaw, which, by acting on the upper dpntal arch, has a perpetual tendency to force upward, or to separate outwardly, the bones in which the teeth of that jaw are inserted. As the greatest stress of the effort determines them up- ward, it is likewise in that direction that the bones of the upper jaw rest most powerfully on those of the skull. The author concludes this very ingenious memoir, by proposing to physiologists the solution of the following problem : " When a man supports a great weight on his head, and holds at the same time any thing very firmly between his teeth, which is the bone of the head that is most acted upon % which supports the weight of the whole machine 1" The body of the sphenoid, and especially its posterior half, appears to me to be the central point on which the united efforts of the bones of the skull and of the face act, in the case supposed by Bordeu. The sphenoid is connected with all the other bones of the skull; it is im- mediately connected with several of the bones of the face, as with the malar bones, with the palatine bones, with the vomer, and sometimes with the su- perior maxillary bones. These bones of the face, in the case in question, alone support the lower jaw against the upper. The ethmoid bone, the ossa unguis, and the inferior turbinated bones, are thin and frail, and serve merely to form the nasal fossae, of which they increase the windings, and do not de- serve to be attended to in this investigation. The vomer may, it is true, com- municate to the ethmoid, in an inferior degree, a part of the effort; for the an- terior part of its upper edge is articulated with the perpendicular lamella? of * Acadimie des Sciences, Mimoircs prisentes par les Savans Etrangers, torn. iii. 232 OF THE COVERINGS OF THE BRAIN. that bone; but this quantity is very small, as the vomer is thin, and transmits it almost wholly to the body of the sphenoid, with the lower face of which it is articulated. The effort exerted on the bones of the upper jaw is transmitted, by means of the nasal processes of the upper maxillary bones, by the ovbitar and zygo- matic processes of the malar bones, and by the upper edge of the palate bones and of the vomer, to the frontal, to the temporal, and sphenoidal bones. If we wish to determine what becomes of the greater part of the effort transmitted to the frontal bone by the maxillary and malar bones, we may observe, in the first place, that it is articulated with the sphenoid bone by the whole of its lower edge, which is bevelled at its inner part, so that it is cover- ed by the ake minores of the os sphenoides, which is shaped obliquely at the outer part of the bone. The frontal bone is articulated, besides, with the lat- ter and inferior parts of its upper edge. The remainder of this upper part is united to the anterior edge of the parietal bones, which, by means of a slope in a different direction, rest on the middle part of this edge, while the frontal bone is applied to them laterally. This bone, which the effort tends to force upward and backward, cannot yield to this double impulse ; for, on the one hand, its mode of articulation with the anterior edge of the ala? minores of the sphenoidal bone, and the in- ternal part of the anterior edge of the parietal bones, resist this tendency up- ward, while the resistance from the latter prevents them being forced back- ward. That share of the effort which affects the parietal bones follows the curved line described by these bones, and extends along that formed by the occipital, and thus reaches the posterior face of the body of the sphenoid bone. • . The portion directly transmitted to the anterior and inferior face of this bone by the ossa palati and by the vomer, is inconsiderable, and proportioned to their thinness. The anterior half of the body of the sphenoid bone, hollowed by the sphenoidal sinus, would have been incapable of supporting greater pressure. Lastly, the situation of the body, placed between the dental arches, in front of the place occupied by the ossa palati, explains why this transmis- sion is chiefly effected by the upper maxillary bones.. The above is the manner in which the effort exerted from below upward, by the lower on the upper jaw, is carried to the anterior, posterior, and inferior faces of the body of the sphenoid bone. The temporal bones, which are affected by it in a very slight degree, by means of the zygomatic processes of the malar bones, support the greater weight of the effort acting from above downward, or from the arch of the skufl towards its base. The weight laid on the head tends to depress or to separate the parietal bones, which resist the pressure, in consequence of the support afforded them by the temporals. These transmit the effort to the lateral and posterior parts of the body of the sphenoid, by means of the ala? majores of that bone, which are articulated, along the whole extent of their external edge, and along the posterior fourth of their internal edge, with the temporals. Besides, the upper extremity of the ala? majores is sloped on the inner part of the bone, that it may be articulated with the anterior and infe- rior angles of the parietal bones, and answer the same purpose to them as the squamous portion of the temporals. The lateral and posterior parts of the body of the sphenoid support, there- fore almost the whole effort of the pressure applied to the parietal bones. It is communicated to them by the ala? majores, which receive it themselves, either directly at the anterior and inferior angles of this bone, or through the medium of the temporals. The small portion of the effort transmitted by the OF THE COVERINGS OF THE BRAIN. 238 latter to the occipital follows the curved line of this bone, and is felt on the posterior face of the body of the sphenoid. To the effort resulting from the pressure exerted by the body on the summit of the head, one should add that occasioned by the contraction of the mus- cles which elevate the lower jaw. These tend to depress the temporal, the malar, and sphenoid bones ; and in this action they employ a power equal to that by which' they raise the lower jaw, and press it firmly against the upper. The effort exerted from the arch to the base of the skull depends, therefore, on two very different causes : the portion resulting from the action of the elevators of the lower jaw is equal to the effort exerted from below upward by this bone. After what has been stated, it would be useless to say any thing further of the manner in which the effort is transmitted : we may merely observe, that the least powerful of these muscles, the internal ptery- goid, tends to draw the sphenoid downward, and prevents this bone, fixed like a wedge, with its base turned upward,from being disengaged by the effort applied to it by the bones between which it is situated. The posterior, anterior, inferior, and lateral faces of the sphenoid bone sup- port, therefore^ the whole effort of the bones of the skull and face, on one another, when, the top of the head being loaded with a heavy burden, one presses at the same time something very firmly between the dental arches. The anterior part of the body .of the bone, containing the sphenoidal sinus, is thin and very frail; the posterior ^part corresponding to the cella turcica, is alone capable of resisting the effort which I believe it is destined to sustain ;* hence it is at this point that ossification begins ; and this con- firms the observation of Kerkringius, that the spot at which bones begin to ossify is that on which they have to bear the greatest effort; thus the ala? majores, by means of which the greatest part of the efforts that the body of the sphenoid has to support, arise from the lateral parts of its posterior half, by an origin of considerable size, and which is further increased by the base of the pterygoid processes which arise from its lower part. The shocks which the cranium has often to endure are chiefly experienced towards its base, where its parietes are thickest, and offer the greatest resist- ance. This transmission of the shock to the. base explains wherefore, in wounds or injuries of the head, fractures often take place in the base, whilst the rest of the skull, even at the 'place of the external injury, preserv- ed its integrity. I have in this inquiry purposely avoided mentioning the support which the head receives from the vertebral column, and which, in the case under con- sideration, is of use merely in preventing it from yielding to the law of gravi- tation. If the bones of the skull and of the face had pressed, during the effort which they sustain, on the circumference of the foramen magnum, this aperture would have been incapable of increasing its dimensions, and this would have been attended with the most serious inconveniences. The name given by the ancients to the bone whose principal use has just' been explained, is composed of sphenos, which means a wedge, and eidos, which signifies resemblance ; and would lead one to think that they were not ignorant of its uses. From its situation, at the middle and inferior part of * The sphenpidal sinus is prolonged, it is sidered as forming a part of that bone, from true, into this posterior part of the body of the which it cannot be detached. The cranium of bone, in persons far advanced in years ; but the an old man, in this respect, resembles that of parietes of this portion of its cavity are of con- several quadrupeds, in which the union of the siderable thickness. The anterior part of the sphenoid to the occipital bone takes place so hasilary process of the occipital bone is then early, that these two bones might well be con- firmlv united to the sphenoid, and may be con- sidered as forming but one. 30 234 OF THE COVERINGS OF THE BRAIfl. the skull, and from its various connexions with the bones which form this os- seous case, it is to them of the same use as the key-stone of arches, with regard to the different parts of which they are formed. The numerous con- nexions required for this purpose, account for its strange and irregular form, and for the different shapes of its articular surfaces, and the great number of its projections, which render the demonstration of this bone so complicated, and a knowledge of it so difficult. It is more advantageous, with regard to the brain, that the skull should be formed of several bones, than if it had consisted of a single bone. It resists more effectually the blows it receives, their effect being lessened in passing from one bone to the other, and being interrupted in the obscure motions which they may experience at their sutures ; its rounded form increases like- wise its power of resistance. This force would be equal, in every point of the parietes of the cranium, if the form of that cavity were completely spherical, and if the thickness of its parietes were, in every part of it, the same. In that case, no fractures by contre coup could occur,—a kind of lesion occa- sioned by the unequal resistance of the bones of the head to the force applied to their surface. The pericranium, the hairy scalp, the muscles which cover it, and the great quantity of hair on its surface, serve, besides, to defend the brain, and are well calculated to break the force of blows applied to the cranium. In addition to this hard and unyielding case, there lies over the brain a treble membranous covering, formed by the dura mater, which owes -its name to the erroneous opinion, according to which it was supposed to form all the other membranes of the body; it is further covered by the tunica arachnoidea, so called from the extreme minuteness of its tissue ; and by the pia mater, which adheres firmly to the substance of the brain. The dura mater lines not only the inside of the skull and of the vertebral canal, which may be considered as a prolongation of it, but likewise pene- trates between the different parts of the cerebral mass, supports them in the different positions of the head, and prevents mutual compression. Thus, the greatest of its folds, the falx, stretched between the crysta galli of the ethmoid bone, and the inner protuberance of the occipital bone, prevents the two hemispheres of the brain, between which it lies, from compressing each other, when the body is on the side, and maintains on the other hand the tentorium cerebelli in the state of tension necessary to enable it to support the weight of the posterior lobes of the brain. This second fold of the dura mater is of a semicircular form, and separates .the portion of the skull which contains the brain from that in which the ceiebellum is situated. It is kept in a state of tension by the falx cerebri, on which it also exerts the same action : it does not present an horizontal plane to the portion of brain which lies upon it, but one that slopes in every direction towards the parietes of the skull, to which it transmits most of the weight which it has to support. The tentorium cerebelli, which thus divides the internal cavity of the skull into two parts of unequal dimensions, is bony in some animals that move by bounding and with rapid action : this is the case with the cat, which can, without being stunned, take leaps from a considerable height. By means of this complete partition, the two portions of the brain are prevented from pressing on each other, in the violent concussions which they experience. The tunica arachnoides, according to Bonn* who was thoroughly ac- quainted with its structure, and who has given a very beautiful plate of it, is the secretory organ of the serum which moistens the internal surface * Ditsertatio de Continuationibus Membranarum. Lugdun. Bat. 4to, 1763. ■I2E OF THE BRAIN. 235 of the dura mater, a fibrous membrane which serves as a periosteum to the bones it lines.* CXLIII. Of the size of the brain.] —Of all animals, man has the most capacious skull in proportion to his face ; and as the bulk of the brain is al- ways of a size proportioned to that of the osseous case which contains it, the brain is also most bulky in man. This difference of size between the ora- nium and face may be taken as the measure of the.human understanding and of the instinct of the lower animals : the stupidity and ferocity of the latter are greater according as the proportions of these two parts of their skull vary from those of the human head. To express this difference of size, Camper imagined- a vertical line, drawn from the forehead to the chin, and perpendicular to another drawn in the di- rection of the base of the skull. He has called the first of these lines facial, the second palatine or mental. It is easy to understand, that as the projection of the forehead is determined by the size of the skull, the larger it is the more the angle at which the facial line meets that from the base of the skull must be obtuse. In a well-formed European head, the facial line meets the palatine at an angle nearly straight (of between 80 and 90 degrees). When the angle is quite straight, and the line which measures the height of the face is completely vertical, the head is of the most beautiful form possible ; it approaches most to that conventional degree of perfection which is termed ideal beauty. If the facial line slopes backward, it forms with the palatine line an angle more or less acute ; and projecting forward, the inclination in- creases, and the sinus of the angle is shorter. If from man we pass to mon- keys, then to quadrupeds, to birds, reptiles, and fishes, we find this line slope more and more, and at last become almost parallel to the mental, as in rep- tiles, and in fishes with flat heads. If, on the contrary, we ascend from man to the gods, whose images have been transmitted to us by the ancients, we find the facial line to incline in a different direction : the angle then enlarges and becomes more or less obtuse. From this inclination forward of the facial line there results an air of grandeur and majesty, a projecting forehead, indi- cating a voluminous brain and a divine intellect. To obtain with precision, by this means, the respective dimensions of the skull and face, one must measure, not only the outside, but likewise draw the tangents on the internal surfaces, after dividing the head vertically. There are, in fact, animals in which the sinuses of the frontal bone are so large that a considerable portion of the parietes of the skull is protruded by their cells. Thus, in the dog, in the elephant, in the owl, &c. the apparent size* of the skull exceeds greatly its real capacity. J The relative size of the head, and consequently the proportionate bulk of the brain,' is inconsiderable in very tall and muscular subjects : this fact will be confirmed by observing the proportions of antique statues. In all those which represent heroes or athletes,gifted with a prodigious bodily power, the head is very small in proportion to the rest of the body. In the statues of Hercules, the head scarcely equals in size the top of the shoulder. The statues alone of the king of the gods present the singular combination of an enormous head resting on limbs of a proportionate size : but the Greek * Analogous to the serous membranes which line the cavities of the body, the arachnoid is a shut sac, whose internal surface is every where in contact with itself, while its external surface adheres to the two other meninges. The sero- sity which exudes from the internal surface of the arachnoid differs from that which escapes from the other serous membranes, owing to the almost entire absence of albumen from the for- mer. The exhalation that takes place from this membrane appears to be the source of a more limpid and dilute effusion, even in disease, than that which is observed in the other serous cavi- ries.—J. C. t See Appendix, Note G G. X See Appendix, Notes G G. 236 STRUCTURE OF THE BRAIN. artists have transgressed the laws of nature only in favour of the god that rules over her, as if a vast brain had been necessary to one whose intellect carries him, at a glance, over the whole universe. The relatively small di- mensions of the head in athletes depend on this circumstance, that in such men the excessive development of the organs of motion gives to the body, and especially to the limbs, an enormous size ; while the head, covered by few muscles, remains very small. Soemmering has stated, that the head in women is larger than in men, and that their brain is heavier ; but it must be recollected, that this great anatomist obtained this result by examining two bodies, male and female, of the same length. Now, the absolute size being the same, the proportionate magnitude was not so, and he was wrong in comparing the head, the skull, and brain of a very tall woman to that of a very short man. It has long been believed that there exists a connexion between the bulk of the cerebral mass and the energy of the intellectual faculties. It has been thought that, in general, men whose mind is most capacious, whose genius is most capable of bold conceptions, had a large head supported on a short neck. The exceptions to this general rule have been so numerous, that many have doubted its truth : should it then be absolutely rejected 1 and will it be allowed to be wholly without foundation, when we consider that man, the only rational being out of so great a number, and some of which bear to him a considerable resemblance both as to organisation and structure, is like- wise the only animal in which the brain, properly so called, is largest in pro- portion to the cerebellum, to the spinal marrow, to the nerves, and to the other parts of the body ? Why may it not be with the brain as with the other organs, which fulfil their functions the better from being more com- pletely developed ? It should be recollected, in this comparison of the brain and of the intellectual powers, that several causes may give to this viscus an unnatural degree of enlargement. Thus, in subjects of a leucophlegma- tic temperament, the tardy ossification of the bones of the skull causes the brain, gorged with aqueous fluids,* to acquire a considerable size, without its containing a greater quantity of real medullary substance. Hence it is ob- served, that men of this temperament are.most frequently unfit for mental exertion, and rarely succeed in undertakings that require activity and perse- verance.* CXLIV. Structure of the cerebral mass.—What we know of the brain serves only to shew us that we are ignorant of much more. All that we know of it consists of tolerably exact notions of its external conformation, its colour, its density, and of the different substances that enter into its compo- sition • but the knowledge of its intimate structure is yet a mystery, which will not be so soon unveiled to us. The brain, properly called, is divided by a longitudinal furrow into two lobes of equal bulk. Gunzius, however, ima- gined°that he found the right lobe, or hemisphere, a little larger than the left: but even were this fact as certain as it is doubtful, we could not thereby ex- plain the predominant force of the right side of the body ; since the nerves which are distributed to this side rise from the left lobe of the brain, in the substance of which all the roots of-these cords cross. This fact of the cross- ing of the nerves at their origin is proved by a multitude of pathological observations, in which the injury of a lobe is always found to bring on para- lysis, convulsion, or some other symptomatic affection, on the opposite side of the body,—unless you choose to explain this phenomenon by admitting a necessary equilibrium in the action of the two lobes—an equilibrium, the dis- * See, in the article on Temperaments, an sation on the moral disposition and on the in. account of the influence of the physical organi- tellectual faculties. STRUCTURE OF THE BRAIN. 237 turbance of which is the occasion that the sound lobe, acting with more force, compresses the origin of the nerves on its side, and determines paralysis. May not the want of judgment, the unevenness of humour and character, depend on the want of harmony between the two corresponding halves of the cerebral mass % In order to disclose, better than had before been done, the structure of the brain, M. Gall began his dissection at the lower part: examining, in the first place, the anterior part of the prolongation, known under the name of Cau- da of the medulla oblongata, he finds the two pyramidieal eminences. If you part the two edges of the median line below the furrow which separates the two pyramids, you see distinctly the crossing of three or four cords, or fasciculi of nerves, which, consisting of many filaments, tend obliquely from right to left, and vice versa. This crossing of nervous fibres, which is not found in any other part of the Drain, had Been observed by several anatomists:. it is not known how it came to be forgotten ; so that the most exact and latest among them, Boyer for instance, says that the crossing of the nerves cannot be proved by anatomy. These nervous cords, traced upwards, en- large, strengthen, and, forming pyramidieal eminences, ascend towards the tuber annulare. Having reached the ganglion, the fibres strike into it, and are lost in a mass of pulpy or grayish substance, of the same nature as that which, under the name of cortical substance, covers the two lobes of the brain. This grayish pulp, distributed in various parts, may be considered, agreeably to the views of M. Gall, who calls it the matrix of the nerves, as the source from which the medullary fibres take their origin. These ascend- ing fibres cross other transverse fibres, which, on either side, proceed from the crura of the cerebellum, enlarged and multiplied by means of their passage through the gray substance which is found in the tuber annulare : they rise from it at its upper part in two fasciculi, which compose nearly the whole of the crura cerebri. The interior of these crura contains a eertain quantity of gray substance, which is what nourishes, the nervous fibre. On reaching the ventricles, these peduncles, or rather the two fasciculi of fibres which form them, meet with large ganglions, full of gray substance : they have long been called thalami optici, though they do not give origin to the optic nerves. There the fibres are sensibly enlarged, and they pass from the tha- lami optici into new ganglions. These are the corpora striata ; and the stria? which are apparent on cutting these pyriform masses of gray substance are only the same fibres, which, enlarged, multiplied, and radiated, spread out in the manner of a fan towards the lobes of the brain, where, after forming by their expansion a whitish and fibrous substance, they terminate at the outer part of that viscus,w forming its convolutions, all covered with the substance in which are terminated in like manner the extremities of the diverging fibres. From this gray substance proceed converging fibres, tending from all parts of the periphery to the centre of the brain, where they unite to form the di£ ferent commissures, .the corpus callosum, and other productions destined to facilitate the communication of the two hemispheres* The exterior of the brain may, therefore, be considered as a vast nervous membrane, formed by the gray substance. To have a due conception of its extent, it must be understood that the convolutions of the brain are a sort of duplicatures, susceptible of extension by the unfolding of two contiguous me- dullary laminae which form its base. The exterior surface of the brain, by means of this unfolding, offers then some relation to the skin,—a vast nervous expanse every where covered by a sort of pulpy substance, known by the name of the rete mucosum of Malpighi. M. Gall compares this cutaneous * See Appendix, Notes G G, 238 CIRCULATION IN THE BRAIN. pulp to the cineritious substance which forms the outer part of the brain; and, I must confess, it is not every one that will admit the analogy. However, true it is that the brain consists principally of a mass of ganglions,—that it produces neither the elongated medulla nor the spinal marrow,—that this last may be considered as a series of ganglions united together,—that the vertebral nerves arise from* Jhe grayish pulp of_ which the spinal marrow is full, as is best seen in animals without a brain, but not the less provided with a spinal marrow, or series of ganglions, from which the nerves arise,—and that the ganglions, or rather the gray substance which they always shew, produce the nervous fibres, and thicken the nervous cords that pass through them. That is the only use that can be assigned to these parts of the nervous system ; for if they were meant to withdraw from the dominion of the will the parts in which they are found, why do not the ganglions of the vertebral nerves fulfil the same function? All these nerves communicate by reciprocal anastomoses. These communications in man are equivalent to a real con- tinuity. In truth, the brain acts upon the nerves that proceed from the spinal marrow as if this were one of its productions, and all the nervous fibres spread through the different organs had an extremity terminating in this viscus: One thing well worthy of attention, and on which no anatomist has dwelt, is, that the brain of the foetus, and of the child just born, appears to consist almost entirely of a cineritious pulp, to such a degree that the medullary substance is with difficulty perceived in it. Would it be absurd to believe, that the medullary part of the brain does not take its perfect organisation till after birth, by the development of the fasciculi of medullary fibres in the midst of these masses of cineritious substance, which must be considered as the common source from which the nerves have their origin ; or, to use the language of Gall, as the uterus which gives them birth. The almost total inactivity, the passive state of the brain in the foetus, makes unnecessary there the existence of. the medullary apparatus, to which the most important operations of intelligence seem intrusted. Its first rudiments are found in the foetus at its full time. That fibro-medullary apparatus will be strengthened by the exercise of thought, as the muscles are seen to enlarge and perfect their growth by the effect of muscular action.* CXLV. .Circulation in the brain.—I have said that the blood, in its circular course, does not traverse the different parts of the body with uniform velo- city^—that there are partial circulations in the midst of the general circula- tion. In no organ are the laws to which this function is subjected more re- markably modified than in the brain. There is none which receives, in pro- portion to its bulk, larger arteries and more in number. The internal carotid and vertebral arteries, as we may satisfy ourselves frofn the calculations of Haller, carry thither a great portion of the whole quantity of blood that flows along the aorta (from a third to a half). The blood which goes to the brain, said" Boerhaave, is more aeratedthan that which is distributed to the other parts : the observation is not without foundation. Though the blood which the contractions of the left ventricle * See the Appendix, Notes G G, where the reader will find some observations by the Edi- tor, on the development of the spinal cord and bia'in, and on the functions of the cerebro-spinal nervous system in man and the lower animals. The views contained in that part of our Appen- dix were published in the former edition of our Notes, before the publication of the work of M. Serres, which soon afterwards appeared, and fully confirmed them. We think it right thus to allude to the circumstance, as some physio- logical writers have taken occasion to quote M. Serres as the originator of these views, without reference to the earlier publication of similar opinions in this country,—opinions which had been long entertained, and frequently discussed by us with anatomists and physiologists, both in this country and on the continent, before their publication.—J. C. CIRCULATION IN THE BRAIN. 239 Bend into the vessels arising from the arch of the aorta does not undergo at the place of this curvature a mechanical separation, carrying its lighter parts towards the head ; it is not less true that this blood, just passing from the contact of the air in the lungs, possesses, in the highest degree, all the pecu- liar qualities of arterial blood. So great a quantity of light, red, frothy blood, impregnated with caloric and oxygen, coming upon the brain with all the force it has received from the action of the heart, would unavoidably have deranged its soft and delicate structure, if Na&ure had not multiplied precau- tions to weaken its impulse. • The fluid, compelled to ascend against its own weight, loses, from that cause alone, a part of its motion. The vertical column must strike against the angular curvature which the*internal carotid makes in its passage along the osseous canal of the petrous portion of the temporal bone ; and as this curvature, supported by hard parts, cannot straighten itself, the column of blood is violently broken, and turned out of its first direction with considerable loss of velocity. The artery immersed in the blood of the cavernous sinus, as it comes out from the carotid canal, is very easily dilated. Finally, the branches into which it parts on reaching the base of the brain have coats exceedingly thin, and so weak that they collapse when they are empty like those of the veins. This weakness of the cerebral arteries explains their frequent ruptures, when the heart sends the blood into them too violently; and it is thus that the greater part of sanguineous apoplexies are occasioned, many of which, how- ever, take effect without rupture, and by the mere transudation of blood through the coats of the arteries. These vessels, like the branches arising from their divisions, are lodged in the depressions with which the base of the brain is furrowed, and do not enter its substance till they are reduced to a state of ex- treme tehuity, by the further divisions they undergo in the tissue of the pia mater. Notwithstanding the proximity of the brain to the heart, the blood reaches it, then, with an exceedingly slackened motion ; it returns, on the contrary, with a motion progressively accelerated. The position of the veins at the upper part of the brain, between its convex surface and the hollow of the skull, causes these vessels, gently compressed by the alternate motions of rising and falling of the cerebral mass, to disgorge their contents readily into the mem- branous reservoirs of the dura mater, known by the name of sinuses. These, all communicating together, offer to this fluid a sufficiently large receptacle, from which it passes- into the great jugular vein, which is to carry it again into the general course of the circulation. Not only is the calibre of this vein considerable, but its coats too, of little thiekness, are veiy extensible: so much so, that it acquires by injection a calibre superior to that of the vena? cavge. The flowing of the blood is favoured by its own weight, which makes a retro- grade course very difficult.* Thus, to sum up all that is peculiar in the ce- rebral circulation, the brain receives in great quantity a blood abounding in oxygen; the fluid finds in its course thither many obstacles which impede and slacken its impulse, whilst all, on the contrary, favour its return, and pre- vent venous congestion."j" Let me observe, to conclude what I have to say on the circulation of the brain, that that of the eye is nearly allied to it, since the ophthalmic artery is given out by the internal carotid, and the ophthalmic * In preventing this reflux, there is no use valvular folds, and insufficient to stop the canal, of valves, which the jugular vein is entirely in that great augmentation of its dimensions. without. It is sufficiently prevented by the di- f The transverse anastomoses of the arteries rection in which the blood flows, and the exten- at the base of the brain are very proper for dis- sibility of its coats. This great size which the tributing the blood in equal quantity to all parts vein can acquire would have made useless the of this viscus. 240 ACTION OF THE BRAIN. vein empties itself into the cavernous sinus of the dura mater. Accordingly, the redness of the conjunctiva, the prominence, the brightness, the moistnesa of the eyes, indicate a stronger determination of the blood towards the brain. Thus, the eyes are animated at the approach of apoplexy, in the transport of a burning fever, and during delirium, which is a dangerous symptom of ma- lignant or ataxic fevers. On this connexion of the vessels of the eye and brain depends the lividity of the conjunctiva, whose veins, injected with a dark- coloured blood, indicate the fulness of the brain in the generality of cases of suffocation. • CXLVI. Of the connexion between the action of the brain and that of the heart. —It is possible, as was done by Galen, to tie both carotids in a living animal without its appearing sensibly affected by*it; but if, as has never yet been done, both the vertebral arteries are tied, the animal drops instantly, and dies at the end of a few seconds. To perform jhis experiment, it is necessary, af- ter tying the carotid arteries of a dog, to remove the soft parts which cover the side of the neck ; then with needles, bent in a semicircular form, passed into the "flesh along the sides of the articulation of the cervical vertebra1, to apply ligatures to the arteries which ascend along their transverse processes. The same effect, viz. the speedy death of the animal, is produced by lying the ascending aorta in an herbivorous quadruped. , These experiments, which have been repeated a number of times, decided- ly prove the necessity of the action of the heart on the brain in preserving life. But how does, this action operate ? Is it merely mechanical ? Does it consist solely in the gentle pressure which the arteries of the brain exert on the sub- stance of this viscus, or is it merely to the intercepted arterial blood which the contractions of the heart determine towards the brain, that death is to be attributed 1 The latter opinion seems to me the most probable; for if, the moment the vertebrals have been tied, the carotids are laid open, and: the pipe of a syringe adapted to them, and any fluid whatever is'then injected with a moderate degree of force,, and at nearly the same intervals as those of the cir- culation, the animal will not be restored to life. The heart and brain are, therefore, united to each other by the strictest .connexion ; the continual access of the blood flowing along the arteries of the head is, indeed, absolutely necessary to the preservation of life ; if inter- cepted for one moment, the animal is .infallibly destroyed. The energy of the brain appears, in general, to bear a relation to the quan- tity of arterial blood which it receives. I know a literary man who, in the ardour of composition, exhibits all the symptoms of a kind of brain fever. His face becomes red and animated, his eyes sparkling ; the carotids pulsate vio- lently ; the jugular veins are swollen ; every thing indicates that the blood i.s carried to the brain with an impetus, and in a quantity, proportioned to its de- gree of excitement. It is, indeed, only during this kind of erection of the ce- rebral organ, that his ideas flow without effort, and that his fruitful imagina- tion traces, at pleasure, the most beautiful descriptions. Nothing is so fa-. vourable to this condition as remaining long in a recumbent posture : in this horizontal posture, the determination of the fluids towards the head is the more easy, as the limbs, which are perfectly quiescent, do not divert its course. He can bring on this state by fixing his attention steadfastly on one object. May not the brain, which is the seat of this intellectual action, be considered as a centre of fluxion ; and may not the stimulus of the mind be compared, as to its effects, to any other stimulus, chemical or mechanical 1 A young man of a sanguineous temperament, subject to inflammatory fe- vers, which always terminate by a profuse bleeding at the nose, experiences, during the febrile paroxysms, a remarkable increase of his intellectual powers, THEORY OF STNCOPE. 241 and of the activity of his imagination. Authors had already observed, that in certain febrile affections patients of very ordinary powers of mind would sometimes rise to ideas which in a state of health would have exceeded the limits of their conception. May we not adduce these facts in opposition to the theory of a celebrated physician, who considers a diminution of the ener- gy of the brain to be the essential character of fever 1 It is well known that the difference of the length of the neck, and, conse- quently, the greater or lesser degree of vicinity of the heart and brain, give a tolerably just measure of the intellect of man, and of the instinct of the lower animals; the disproportionate length of the neck has ever been considered as the emblem of stupidity. In the actual state of our knowledge, is it possible to determine in what manner arterial blood acts on the brain ? Are oxygen or caloric, of which it is the vehicle, separated from it by this viscus, so as to become the principle of sensation and emotion ? or do they merely preserve it in the degree of con- sistence necessary to the exercise of its functions ? What is to be thought of the opinion of those chemists who consider the brain as a mere albuminous mass, concreted by oxygen, and of a consistence varying in different persons, according to the age, the sex, or the state of health or disease ? Any answer that one might give to these premature questions would be but a simple con- jecture, to which it would be difficult to assign any degree of probability.* CXLVTI. Of the theory of syncope.—If we consider the action of the heart on the brain, we are naturally led to admit its necessity to the maintenance of life,, and to deduce from its momentary suspension the theory of syncope. Several authors have attempted to explain the manner in which their-proxi- mate cause operates ; but as not one of them has gone upon facts ascertain- ed by experience, their explanations do not all agree with what is learnt from observing the phenomena of these diseases. To satisfy oneself that the momentary cessation of the action of the heart and the brain is the immediate cause of syncope, one need but read with at- tention the chapter which Cullen, in his work on the practice of physic, has devoted to the consideration of this kind of affection. It will be readily un- derstood, that their occasional causes, the varieties of which determine their different kinds, exist in the heart or great blood-vessels, or act on the epi- gastric centre, and affect the brain only in a secondary manner. Thus, the * The connexion which exists between the passing either, 1st,* through the auriculo-ventri- functions of the heart and those of the brain are cular opening; 2d, the aortic orifice ; 3d, along not only manifest in their healthy relations, but the aorta,—necessarily produces a stagnation also in their disordered actions. Portal, Briche- and congestion, 1st, in the pulmonary veins; teau, and Testa, iiad pointed out this connexion 2d, in the pulmonary artery ; 3d, in the right in the diseases of these organs ; and, more re- side of the heart. The effect of this is to retard cently, Dr. Craigie has contended for its import- or impede veiy remarkably the return of the ance, although some contemporary pathologists blood from the cerebral veins, and consecutively have denied its existence. This pathologist, either to distend them, to rupture them, or to after stating his experience on the subject, draws occasion an effusion of the serous part of the the following inferences from it:— blood, as we find in other examples of obstruct- " 1st, It is quite obvious that several mala- ed venous circulation."—(Edin. Med. Jour. No. dies of the heart, such as ossification of the left 74.)—Dr. Craigie has, however, omitted to men- side, or of the artery connected with it; ossi- tion the influence of active enlargement of the fication of the neutral valve ; of the semi-lunar left side of the heart in producing apoplexy, valves ; aretation of the apertures, either auri- owing to the increased impulse or determina- culo-ventricular or aortic ;—have a tendency to tion of blood which is thus prodifced, and to terminate in extravasation within the cranium, which the brain is most obnoxious. This, and producing apoplexy, paralysis, or a comatose every other form of connexion of disease of the state terminating in death. heart with apoplexy, can only be viewed as oc- " 2d, It is by no means difficult to see how casional occurrences ; the former states being these effects in the cerebral organ result from by no means necessarily followed by the latter. an irregular and disordered action of the heart. —J. C. The difficulty which the blood experiences in 31 242 THEORV OF SYNCOPE. kinds of syncope occasioned by aneurismal dilatations of the heart and great vessels, by polypous concretions formed in these passages, by ossification of their parietes or of their valves, evidently depend on the extreme debility, or on the entire cessation of the action of the heart and arteries. Their parietes, ossified dilated, adhering to the neighbouring parts, or compressed by anv fluid whatever, no longer act on the blood with sufficient force ; or else this fluid is interrupted in its progress by some obstacle within its canal, as a po- lypous concretion, an ossified and immovable valve. Cullen very justly term- ed these, idiopathic or cardiac syncopes. To the above may be added plethoric syncope, depending on a congestion of blood in the cavities of the heart: the contractions of this organ become more frequent, it struggles to part with this excess of blood, which is injurious to the performance of its functions; but to this unusual excitement, by which the contractility of its fibres is exhausted, there succeeds a kind of paralysis, necessarily accompanied by syncope. One may, likewise, include the fainting attending copious blood-letting : the rapid detraction of a certain quantity of the vivifying principle deprives the heart of the stimulus necessary to keep up its action. The same effect is produced by drawing off the water contained in the abdomen in ascites : a considerable number of vessels cease to be compressed ; the blood which they before refused to transmit is sent to them in profusion ; the quantity sent to the brain by the heart is lessened in the same proportion, and becomes in- sufficient for its excitement. Among the syncopes called idiopathic, one may enumerate those occuring in the last stage of the scurvy, the principal character of which is an excessive debility of the muscles employed in the vital functions and in voluntary motion. Lastly, we may add asphyxia from strangulation, from drowning, and from the gases unfit for respiration ; affec- tions in which the blood being deprived of the principle which enables it to determine the contractions of the heart, the circulation becomes interrupted. If the blood loses, by slow degrees, its stimulating qualities, the action of the heart, gradually weakened, impels towards the brain a bloed which, by its qualities, partakes of the nature of venous blood, and which, like it, cannot preserve the natural economy of the brain. It was thought, that by injecting a few bubbles of air into the jugular vein of a dogr one might occasion in the animal immediate syncope, and that it was even sufficient to deprive it of life ; but the late experiments of M. Nysten have proved, that the atmo- spherical air produces these bad effects only when injected in a quantity suf- ficient to distend in excess the cavities of /the heart, or when, by being inject- ed into the arteries, it compresses the brain. When injected only in a small quantity, the gas dissolved in the venous blood is conveyed along with it to the'lungs, and is thence exhaled in respiration. A second class of occasional causes consists of tjiose which, by acting on the. epigastric centre, determine by sympathy a cessation of the pulsations of the heart, and the syncope necessarily attending this cessation. Such are the violent emotions of the soul,—terror, an excess of joy, an irresistible aversion to certain kinds of food, the dread which is felt on the unexpected sight of an object, the disagreeable impression occasioned by certain odours, &c. In all these cases, there is felt in the region of the diaphragm an inward sen- sation of a certain degree of emotion. From the solar plexus of the great sympathetic nerve, which, according to the general opinion, is considered aa the seat of this sensation, its effects extend to the other abdominal and tho- racic plexuses. The heart, the greater part of whose nerves arise from the great sympathetic, is particularly affected by this sensation. Its action is at times merely disturbed by it, and at others wholly suspended. The pulse be- MOTIONS OF THE BRAIN. 243 comes insensible, the countenance pale, the extremities cold, and syncope en- sues. This is the course of things when a narcotic or poisonous substance has been taken into the stomach; when this viscus is much debilitated in consequence of long fasting, or when it contains indigestible substances; in cholic, and in hysterical affections. This last class of occasional causes does not act directly, and produces syn- ' cope only at a distant period ; but the result is always the same. It happens in all these cases, that as the arteries of the head no longer receive as much blood as in health, the brain falls into a kind of collapse, which occasions a momentary cessation of the intellectual faculties, of the vital functions, and of voluntary motion. Morgagni, in treating of diseases according to their anatomical order, ranks lypothymia among the affections of the chest, because the viscera contained in that cavity shew marks of organic affection in persons who, during life, were subject to frequent fainting. The compression of the brain, by a fluid effused on the dura mater, in wounds of the head, does not produce real syncope, but rather a state of stu- por. All causes acting in this manner on the brain produce comatose, and even apoplectic affections. When a man, on being exasperated, falls into a violent and sudden fit of passion, his face becomes flushed, and he is affected with vertigo and fainting. There is no loss of colour, no loss of pulse ; the latter, on the contrary, generally beats with more force. This is not syncope, but the first stage of apoplexy, occasioned by the mechanical pressure on the- brain, towards which the blood is carried suddenly and in too great a quantity. I might support this theory of syncope by additional proofs drawn from the circumstances which favour the action of the causes giving rise to affections of this kind. For instance, syncope comes on almost always when we are in either an erect or sitting attitude, and in such a case it is right to lay the patient in an horizontal posture. Patients debilitated by long diseases faint the moment they attempt to rise, and recover on returning to the recumbent posture. Now, how are we to explain this effect of standing, in persons in whom the mass of humours is much impoverished, and whose organic ac- tion is extremely languid, unless by the greater difficulty to the return of the blood from the more depending parts, and on the difficulty in ascending of that which the contractions of the heart send- towards the head 1 The phenomena of the circulation are, under such circumstances, more subject to the laws of hydraulics than when the body is in a state of health ; the living solid yields more easily to the laws of physics and mechanics ; and, ac- . cording to the sublime idea of the father of physic, our individual nature approaches more nearly to universal nature. CXLVIII. Of the motions of the brain.—Are the alternate motions of ele- vation and depression seen, when the brain is exposed, exclusively isochro- nous to the pulsations of the heart and arteries, or do they correspond at the same time to those of respiration ? Such is the physiological problem of which I am about to attempt the solution. Those authors who admit the existence of motions in the dura mater do not agree as to the cause which produces them. Some, and among others, Willis and Baglivi, thought they had discovered muscular fibres, and ascribed these motions to their action : others, as Fallopius and Bauhinus, attributed these motions to the pulsations of the arteries of that membrane. The dura mater possesses no contractile power; its firm adhesion to the inside of the skull would, besides, prevent any such motion. The motion observed in this membrane is not occasioned by the action of its vessels ; for, as Lorry 244 MOTIONS OF THE BRAIN. observes, the arteries of the stomach, of the intestines, and of the bladder, do not communicate any motion to the parietes of these hollow viscera, and yet, in number and size, they at least equal the meningeal arteries. ^ The motion' observed in-the dura mater is communicated to it by the cere- bral mass which this membrane covers ; and this opinion of Galen, adopted by the greater number of anatomists, has been placed beyond a doubt by the experiments of Schlitting, of Lamure, Haller, and Vicq-d' Azyr. They have all observed, that on removing the dura mater, the brain continued to rise and fall; and, with the exception of Schlitting, they agreed that the brain, absolutely passive, received from its vessel the motions in which the dura mater partook ; but are these motions communicated by the arteries or by the cerebral veins, and by the sinuses in which these terminate ? or,, in other words, are they isochronous to the beats of the pulse, or to the con- traction and successive dilatation of the chest, during respiration ? Galen, in his treatise on this function, says, that the air admitted into the pulmonary organ distends the diaphragm, and is conveyed along the ver- tebral canal into the skull. According to this writer, the brain rises during the enlargement of the chest, and it sinks, on the contrary, when the parietes of this cavity are brought nearer to it's axis. Schlitting, in a memoir pre- sented to the Academy of Sciences, towards the middle of the last century, maintains that these motions take place in a different order, the elevation of the brain corresponding to expiration, and its depression to inspiration. Con- ceiving that he has determined this fact by a sufficient number of experi- ments, he does not enter into any explanation, and concludes his inquiry by asking whether the motions of the brain are occasioned by the afflux of air or of bloOd towards that organ. Haller and Lamure attempted to answer this difficulty. They both per- formed a number of experiments on living animals, acknowledged the fact observed by Schlitting, and explained it in the following manner : as well as this last anatomist, Lamure believed that there is a vacuum between the dura and pia mater, by means of which the motions of the brain might al- ways be performed. The existence of such a vacuum is disproved by the close contact of the membranes between which it is supposed to exist. During expiration, continues Lamure, the parietes of the chest close on themselves, and'lessen the extent of this cavity. The lungs, pressed in every direction, collapse ; the curvature of their vessels increases, and the blood flows along them with difficulty. The heart and great vessels thus compressed, the blood earned by the upper vena cava to the right auricle cannot be freely poured into this cavity, which empties itself with difficulty into the right ventricle, whose blood is unable to penetrate through the pul- monary tissue. On the other hand, as the lungs compress the vena cava, a regurgitation takes place of the blood Which it was conveying to the heart ; forced back along the jugulars and vertebrals, it distends these vessels, the sinus of the dura mater which empty themselves into them, and the veins of the brain which terminate into these sinuses. Their distension accounts for the elevation of the cerebral mass,—an elevation soon followed by de- pression, when, on inspiration succeeding expiration and on the lungs dilating, the blood which fills the right cavities of the heart can freely penetrate into the pulmonary substance, and make way for that which the vena cava is bringing from the superior parts of the body. Haller considered this reflux as very difficult, the blood having to rise against its own gravity ; and he admitted Lamure's explanations only in the forcible acts of respiration, as in coughing, laughing, and sneezing. He maintained that, in a state of health, there is to be observed during expiration, MOTIONS OF THE BRAIN. 245 a mere stagnation of the blood in the vessels which bring it from the internal parts of the skull. He further admits, on the testimony of a great number of authors, another order of motions depending on the pulsations of its arte- ries ; so that, according to Flaller, the cerebral mass is incessantly affected by motions, some of which depend on respiration, while the others are quite independent of it. Lastly, according to Vicq-d'Azyr, the brain, on being exposed, presents a double motion, or rather two kinds-of motion, from without; the one from the arteries, and which is least remarkable,—the other from the alternate motions of respiration. CXLIX. This opposition between authors of. reputation, and whose theo- ries have in general been adopted, induced me to repeat the experiments which each of them brings in support of his own opinion, and to perform further experiments on this subject. My investigation soon convinced me, that these authors had given a statement of their opinions, and not of the fact itself. Indeed, the alternate motions of elevation and depression observed in the brain, are isochronous to the systole and diastole of the arteries at its base. The elevation of the brain corresponds to the dilatation of these vessels, its depression to their contractions. The process of respiration has nothing to do with this phenomenon ; and even admitting the stagnation of the re- gurgitation of the blood in the jugular veins, the arrangement of the veins within the skull is such, that this stagnation or reflux could not produce alter- nate motions of the cerebral mass. The brain receives its arteries from the carotids and vertebrals, after they have entered the skull, the former along the carotid canals, the latter through the foramen magnum of the occipital bone. It would be useless to describe their numerous divisions, their frequent anastomoses, the arterial circle, or rather polygon, formed by these anastomoses, and by means of which the carotid and vertebral* arteries communicate together, by the side of the sella turcica. Haller-has given a very correct view, and an excellent description of this part.* The account of the internal carotid artery published by that great anatomist is, according to Vicq-d'Azyr, a chef-d'a?uvre of learning and precision ; the same encomium might be bestowed on the latter, who gave a superb drawing of the same part. I shall content myself with observing, that the principal arterial trunks going to the brain are situated at the base of this viscus; that the branches into which these trunks divide, and the subdivisions of these branches, are likewise lodged at its base in a number of depressions ; and that, in the last plaee, the arteries of the brain do not pene- trate into its substance till after they have undergone in the tissue of the pia mater, which appears completely vascular, very minute subdivisions. The vessels which return the portion of blood which has not been employed in the nutrition and growth of the brain, are, on the contrary, situated towards its upper part, between its convex surface and the arch of the cranium : each convolution contains a great vein which opens into the superior'longitudinal sinus. The vena Galeni, which deposits into the sinus the blood brought from the choroid plexus ; small veins which open into the cavernous sinuses ; others, likewise very minute, which, passing through the foramina in the ala? majores of the sphenoid bone, contribute to form the venous plexus of the zygomatic fossa,—are the only exceptions to this general rule. This being laid down on the arrangement of the arteries and veins, let us examine what will be the effect of their action with regard to this viscus. The contractions of the heart propel the blood into the arterial tubes, which experience, especially at the place of their curvatures, a manifest displace- * Fasciculi anatomici, f. vii. tab. ii. 246 CAUSE OF THE BRAIn's MOTION. ment at the time of their dilatation. All the arteries situated at the base of the brain experience both these effects at once. Their united efforts com- municate to it a motion of elevation succeeded by depression, when, by their contraction, they re-act on the blood which fills them. These motions take place only as long as the skull remains entire ; this cavity is too accurately filled, and there is no void space between the mem- branes of the brain. Lorry, who, with good reason, denied the existence of such a space, committed an equally serious anatomical mistake in asserting, that as no.motion could take place, on account of the state of fulness of the skull, it was effected in the ventricles, which he considers as real cavities ; but which, as Haller has shewn, are, when in a natural state, merely sur- faces in contact. No motion actually takes place, except in those cases in which there is a loss of substance in the parietes of the skull. It is easy to conceive, however, that the brain, which is soft and of weak consistence, yields to the gentle pressure of its arterial vessels. Does not this continued action of the heart on the brain explain, in a satisfactory man- ner, the remarkable sympathy between those two organs, linked by such close connexions 1 It is, besides, of very manifest utility, and connected with the return of the blood distributed to the cerebral mass and to its enve- lopes. The veins which bring it back, alternately compressed against the arch of the skull, empty themselves more easily into the sinuses of the dura mater, towards which their course is retrograde, and unfavourable to the cir- culation of the blood which they pour into them. , When any thing impedes the free passage of the blood through the lungs, it stagnates in the right cavities of the heart; the superior vena cava, the internal jugulars, and consequently the sinuses Of the dura mater, and the veins of the brain which terminate in them, are gradually distended ; and if this dilatation were carried to a certain degree/the veins of the brain, placed between it and the arch of the skull, would tend to depress it towards the base of that cavity. If this dilatation, at first sight, were carried beyond the extensibility of these vessels, their rupture would occasion fatal effusions. It is in this manner that some authors have explained sanguineous apoplexy. - It will be objected, perhaps, that many of the sinuses of the dura mater are at the base of the skull; and that consequently their dilatatiori must tend ta raise the cerebral mass. But the greater part of these sinuses are connected only with the cerebel- lum and the medulla oblongata, of which it has not yet been possible to as- certain the motions. These sinuses are almost all lodged in the edges of the falx and of the tentorium cerebelli. The cavernous sinus in which the oph- thalmic vein disgorges itself, the communicating sinuses which allow the blood of one of these sinuses to pass into the other, are too insignificant to produce a raising of the cerebral mass. Lastly, the resistance of their pari- etes, formed chiefly by the dura mater, must set strait bounds to their dilata- tion ; the spongy tissue which fills the interior of the cavernous sinuses makes this dilatation and the reflux of the blood still more difficult. CL. Experiments shelving the cause of the brain's motion.—It is not enough to prove, by reasons drawn from the disposition of parts, that the motions of the brain are communicated to it by the collection of arteries at its base ; the fact must yet be established upon observation, and placed beyond doubt by positive experiments. The following are what I have attempted for this purpose:— A. I have first repeated the observation of some authors, and ascertained, as they did, that the pulsations felt on placing the finger on the fontanels of the skulls of new-born infants, correspond perfectly to the beatings of the heart and arteries. CAUSE OF THE BRAIN's MOTION. 247 B. A patient trepanned for fracture, with effusion on the dura mater, ena- bled me to see the brain alternately rising and falling. The rising corre- sponded with the diastole, the falling with the systole of the arteries. C. Two dogs, trepanned, exhibited the same phenomenon, in the same re- lation to.the dilatation and contraction of the arteries. D. I removed carefully the areh of the skull from the body of an adult. The dura mater, disengaged from its adhesions to the bones which it lines, was preserved perfectly untouched. I afterwards laid bare the main carotids, and injected them with water. At every stroke of the piston the brain shewed a very sensible motion of rising, especially .when the injection was forced at once along the two carotids. E. I injected the internal jugular veins,—the cerebral mass remained mo- tionless ; the veins of the brain only, and'the sinuses of the dura mater, were dilated. The injection having been kept up for some time, there resulted from it a slight swelling of the brain : when driven with more force, some of the veins burst, and the liquor flowed out. The same injection being made with water strongly reddened, the surface of the brain became coloured with an intense red. To see clearly this effect, you ought, after removing the arch of the skull, to divide on each side the dura mater, on a level with the circu- lar incision of the skull, then turn back the flaps towards the upper longitu- dinal sinus. F. The internal jugular veins having been laid open while the injection was forced along the main carotids, each time the piston was pushed forward the venous blood flowed with the greatest impetus ; a clear proof of the manifest influence of the motions of the brain on the course of the blood in its veins, and in the sinuses of the dura mater. This experiment had been already performed by other anatomists, and amongst others by Ruysch, with a view of proving the immediate communication between the arteries and ^ veins. This communication, which is at present universally acknowledged, may be proved by other facts. This one is evidently any thing but conclusive. G. In a trepanned dog, I tied successively the two carotids. The motions of the brain abated, but did not cease. The anastomoses of the vertebrals with the branches of the carotids account for this phenomenon. H. I took a rabbit, a gentle creature, easy to confine, and very well adapt- ed for difficult experiments : after laying bare the brain, and observing that its motions were simultaneous to the beats of the heart, I tied the trunk of the ascending aorta : the moment the blood ceased rising to the head, the brain ceased moving, and the animal died. I. The tying of the internal jugular veins did not stop the motion of the brain; but its veins dilated, and its surface, bared by the removal of a flap of the dura mater, was sensibly redder than in the natural state. The dog be- came affected with stupor, and expired in convulsions. The opening of these veins did not hinfler the continuance of the motions ; they grew fainter only when the animal was weakened by loss of blood. K. The opening of the superior longitudinal sinus, the only one that could easily be opened, did not weaken the motions of the brain. It is observed that the blood flows out more freely from it during the elevation. L. The compression of the thorax on human bodies produces but a slight reflux in the jugular veins, especially if, during this compression, the trunk is kept raised. The reflux is greater when the trunk is laid flat. These experiments might be varied and multiplied : if4 for instance, the in- jection were thrown at once along the vertebral arteries and the internal caro- tids ; but those I have stated are sufficient for my purpose. Since the first publication of this inquiry, in the Memoirs of the Medical 248 MOTION OF THE BRAIN. Society,* I have had many opportunities of repeating the observations and experiments, which serve as a foundation to the theory there detailed. Among the facts which confirm this theory, there is one that appears to me worth stating : it would be sufficient by itself, if it were possible to establish a theory on the observation of a single fact. A woman, about fifty years of age, had an extensive carious affection of the skull; the left parietal bone was destroy- ed in the greatest part of its extent, and left uncovered a pretty considerable portion of the dura mater. Nothing was easier than to ascertain the exist- ence of a complete correspondence between the motions of the brain and the beats of the pulse. 1 desired the patient to cough, and to suspend her respi- ration suddenly ; the motions continued in the same relation to each other : when she coughed, the head was shaken, and the general concussion, in which the brain partook, might have been mistaken by a prejudiced observer for the proper motions of that organ, and depending on the reflux of blood in the veins. In experiments on dogs, the same motion takes place when the animal barks^ but it is easy to perceive, that the concussion affecting the brain ia experienced by the whole body, and that the effort of expiration in barking causes a concussion more or less violent. The patient mentioned in the preceding observation died about a month af- ter I came to the Hospital of St. Louis, in which she had been for a consider- able length of time. On opening the body, the left lobe of the brain was found softened and in a kind of putrid state ; the ichor,-which was formed in considerable quantity, flowed outwardly, by a fistulous opening in the dura mater, whose tissue was rather thickened. CLI.—The slight consistence of the brain, which Lorry considers as fa- vourable to the communication of the motion which its arteries impart to it, appears tome to be against this transmission. In fact, the dilated vessels not being able to depress the base of the skull on which they rest, make their effort against the cerebral mass, and'raise it the more easily (the arch of the skull being removed) from its presenting a certain resistance. If the brain were too soft, the artery would merely swell into it, and would not lift it. To satisfy oneself of this truth, one need only observe what happens when the posterior part of the knee rests on a pillow, or on any Thing of the same sort; then, the motions which the popliteal artery impresses on the limb are but httle apparent, but they become v,ery visible if the ham rests On any thing that offers a certain resistance, as on the knee of the opposite side, for instance ; then the arterj', which cannot depress it, exerts its whole action in raising the lower extremity, which it does the more easily from acting against a bony, resisting, and hard.part. This experiment completely invalidates the opinion of Lorry. The want of analogy will not be objected ; it will not be said that the brain is heavier than the lower extremity, nor that the sum of the calibres of the internal carotid and the vertebral arteries is not greater than that of the popliteal artery. This continual tendency of the brain to rise, produces in the end, on the bones of the skull which resist this motion, very marked effects. Thus, the interior surface of these bones, smooth in early life, becomes furrowed with depressions, the deeper as we advance in age. The digital depressions and the mammillary processes, corresponding to the convolutions and windings of the brain, are very evidently the result of its action on the enclosing parietes. Sometimes it happens, that at a very advanced age the bones of the skull are so thinned by this internal action, that the pulsations of the brain become per- ceptible through the hairy scalp. * Memoires de la Societe" Medicale de Paris, troisieme annee, torn. iii. p. 197, et suiv. MOTION OF THE BRAIN> 249 No doubt the same cause hastens the destruction of the skull by the fur> gous tumours of the dura mater. The effort from expansion of the tumour, which developes itself, is further added, and makes the waste of the bones more rapid. At the end of a few months the tumour projects outwardly, with pulsations plainly simultaneous to the beatings of the pulse, as Louis observes in a memoir inserted among those of the Academy of Surgery. I have shewn (CXLIX.) that the disposition of the veins of the brain and of the sinuses of the dura mater was adverse to the action ascribed to them on this viscus. Experiment (E, L) shews that the stagnation of the blood, or even its regurgitation,' could produce only a slow and gradual distension of the sinuses of the dura mater and veins terminating in it, with a slight turgescence of the cerebral mass, if the cause producing the stagnation of the blood or its reflux, prolomred its action to a partial destruction of the skull. Lastly, the alternate motions of the brain, said to correspond to those of respiration, ought to be to the beats of the pulse in the ordinary ratio of 1 to 5. On the contrary, it is easy to satisfy oneself that these motions are in an in- verse ratio, and perfectly simultaneous to the pulsations of the heart and ar- teries. The results of the experiments I have stated in that memoir, compared to those obtained by justly celebrated inquirers, are too remarkably different not to have induced me to make some attempt at investigating the cause of our disagreement. For that purpose I thought it necessary to examine scrupu- lously all the circumstances. The work of Lamure contains anatomical errors, which throw suspicions upon his accuracy. Haller did not himself make the experiments of which he speaks in treating of the influence of respiration on the circulation of ve- nous blood. This article is drawn from a thesis defended at Gottingen by one of his disciples. Lastly, Vicq-d'Azyr attempted no confirming experi- ment, and seems to have had in view only the reconciling all opinions. No one of these anatomists has distinguished the motions of elevation im- pressed on the cerebral mass by the impulse of its arteries, from the swelling of the sinuses of the dura mater, of the veins distributed to it, and from the tumefaction of the brain which may be caused by difficult respiration. This mistake would be the more easy, as animals tortured by the knife of the ana- tomist breathe painfully, convulsively, and at shorter intervals than in their natural state. Schlitting, the first author of these experiments, appears es- pecially to have confounded the motion of rising, the real displacement of the brain, with the turgescence of this viscus. At every expiration, he says, I have seen the brain rise,.that is to say, swell, and at every inspiration I have seen it fall, that is to say, collapse. " Toties animadverti perspicui, in omni expiratione cerebrum waiver sum ascen- der e, id est inlumescere; atque in qudvis inspiratione illud descendere, id est detu- mescere." We may therefore consider as a truth, strictly demonstrated by observation, experiment, and reasoning, the following proposition :— The motions observable in the brain, when laid bare, are imparted to it solely by the pulsations of the arteries at its base, and are perfectly simultaneous to the pulsa- tions of these vessels: further, the reflux and stagnation of the venous blood are able to sioell its substance. CLII. Action of the nerves and brain.—It is undoubtedly, as Vicq-d'Azyr has said, by a motion of some sort that the nerves act. Setting out from this simple idea, one may admit several kinds of nervous motions, the one operat- ing from the circumference to the centre—(it is the motion of sensation which 32 250 ACTION OF THE NERVES, &C. we are about more particularly to study in this paragraph)—the other acting: from the centre to the circumference ; and this motion, produced by the will, determines the action of the muscular organs, &c. In what manner are the impressions produced on the senses by the bodies which surround us, transmitted, along the nerves, to the brain ? Is it through the intervention of a very subtle fluid ? or can the nerves, as has been stated1 by some physiologists, be considered as vibrating cords 'I This last idea is so absurd, that one cannot help wondering it should so long have been in vogue. A cord, that it may vibrate, must be in a state of tension along the whole of its length, and fixed at both extremities. The nerves are not in a state of tension : their extremities, in no degree fixed, approach towards each other or recede, according to the difference of position, the tension, the turgescence,, the fulness or collapse of parts, and vary constantly in their distance from each other. Besides, the nervous cords, situated between pulps at their ori- gin and at their termination, cannot be extended between these two points. The nervous fibre is'the softest, the least elastic of all the animal fibres : when a nerve is divided, its two extremities, far from receding by contracting, pro- ject, on the contrary, beyond each other; the point of section shews a num- ber of small granulations of medullary and nervous substance, which flows through its minute membranous canals. Surrounded by parts to which they are, to a certain degree, united, the nerves could not vibrate. Lastly, admit- ting the possibility of their being capable of vibrating, the vibration of a sin- gle filament ought to bring on that of all the rest, and carry confusion and dis- order in every motion and sensation. It is much more probable that the nerves act by means of a subtle, invisible-,. and impalpable fluid, to which the ancients gave the name of animal spirits i this fluid, unknown in its nature, and to be judged of only by its effects, must be wonderfully subtle, since it eludes all our means of investigation. Does it entirely proceed from the brain, or is it equally secreted by the membranous envelopes of each nervous filament ? (Neurilimes, Reil.) To say the truth,. one can bring no other proof of the existence of a nervous fluid, but the facili- ty with which, by means of it, we are enabled to explain the various pheno- mena of sensation. This proof, however, may not appear completely satis- factory to those who are very strict, and who do not consider as proved what is merely probable. Among the constituent principles of the atmosphere there are generally diffused several fluids, such as the magnetic and electric fluids. Might not these fluids, on entering with the air into the lungs, combine with the arterial blood, and be conveyed, by means of itT to the brain or to the other organs t Does not the vital action impart to them new qualities, by making them un- dergo unknown combinations 1 Do caloric and oxygen enter into these combinations which endow fluids with a certain vitality, and produce on them important changes, and which are not understood ?* Have not these con- jectures acquired a certain degree of probability, since the analogy of gal- vanism to electricity, at first supposed by the author of this discovery, has been confirmed by the very curious experiments of Volta, repeated, com- mented, and explained by all the natural phylosophers of the present day in Europe ?| The actim of the nervous fluid takes place from the extremity of nerves to- * Were it not for these changes, electricity, magnetism, and galvanism, would suffice to re- store life to an animal recently dead. + Galvanism, as yet, has not realised the ex- pectations of physiologists. Chemistry has de- rived the greatest advantages from it. It is, at present, with MM. Davy, Thenard, and Gay- Lussac, the most powerful agent in the analysi» of certain bodies. JUNCTIONS OF THE BRAIN. 251 Wards the brain, so as to produce the phenomena of sensation; for when the nerves are tied, the parts below the ligature lose the power of sensation ; while, as will be seen in the proper place, this action is propagated from the brain towards the nervous extremities, and from the centre to the circumference, in producing motions of every kind. This double current, in contrary directions, may take place in the same nerves, and it is not necessary to arrange the nerves into two classes of sensation and of motion. All the impressions received by the organs of sense and by the sentient ex- tremities of nerves, are transmitted to the cerebral mass. The brain is, therefore, the centre of animal life ; all sensations are carried to it; it is the spring of all voluntary motion : this centre is to the functions of relation as the heart to the functions of nutrition. One may say of the brain as of the heart, omnibus dot et ab omnibus accipit,—it receives from all, and gives to all.* The medullary mass enclosed in the cranium appears to be formed of two apparatuses of a different nature. In the parts lodged at the base of the cranium, and which have received from anatomists the name of medidla ob- longata, especially resides the nervous energy which presides over muscular motions. According to recent experiments, the principle of inspiratory mo- tion should have its seat in that part of the medulla oblongata whence pro- ceed the eighth pair of nerves. The superior portions of the medullary mass seem to be especially destined to the exercise of intelligence. No part of these superposed, and, I may say, superadded organs, is more fully developed than in man. There is.no animal who has so voluminous hemispheres as he, covering not only as they do all the rest of the encephalic mass, but also elevating and pushing before them the anterior portion of the cranium which surmounts the face, or rather which forms its frontal region. This anterior developement of the brain seems so truly characteristic of the human species, that certain philosophers have not hesitated to place in it the faculty by which man forms abstract ideas of the Divinity. There, according to the theory of Gall, is lodged the organ of theosophy. But in what manner, or by what means does the will act, in producing the various movements ? What ties connect the sensations with the powers of volition ? These ques- tions are unanswerable in the present state of our knowledge ; and the chief desiderata of this department of physiological science are yet to be supplied, namely, to determine, in a precise manner, the functions which belong to the different portions of the brain and of its central apparatus ; likewise, whe- ther the nervous energy proceeds from the nerves themselves, is inherent in their structures, and is the result of their action ; or are they only the simple conductors and distributors of it from the sources at which they de- rive their origin ? The existence of a centre, to which all the sensations are carried, and from which all motions spring, is necessary to the unity of a thinking being, and to the harmony of the. intellectual functions. But is this seat of the principle of motion and of sensation circumscribed within the narrow limits of a mathematical point % or rather should it not be considered as diffused over nearly the whole brain ? The latter appears to me the more probable opi- nion : were it otherwise, what could be the use of those divisions of the or- gan into several internal cavities ? what could be the use of those prominen- ces, all varying in their form ; and of the arrangement of the two substances which enter into their structure 1 We may conjecture, with considerable probability, that each perception, each class of ideas, each faculty, is assigned to some peculiar part of the brain. It is, indeed, impossible to determine the * See Appendix, Notes H H. 252 Or THE UNDERSTANDING. peculiar functions of each part of the organ ; to say what purpose is sewed by the ventricles, what is the use of the commissures, what takes place in the peduncles ; but it is impossible to study ■ an arrangement of such combi- nation and to believe that it is without design, and that this division of the cerebral mass into so many parts, so distinct, and of such various forms, is not relative to the different function which each has to fill in the process of thought. That ingenious comparison, mentioned in the panegyric of Mery, by Fontenelle, is very applicable to the brain. "We anatomists," he once said to me, " are like the porters in Paris, Avho are acquainted with the narrowest and most distant streets, but who know nothing of what takes place in the houses." What, then, are we to think of the system of Gall, and of his divi- sion of the outside of the skull into several compartments, which, according to the depression or projection of the osseous case, indicate the absence or the presence of certain faculties, moral or intellectual ? I cannot help thinking, that this physiological doctrine of the functions of the brain, resting on too few well-observed facts, is frivolous ; while his anatomical discoveries on the anatomy of this organ, and on the nervous system, are of the highest import- ance and well founded. CL1II. Analysis of the understanding.—In vain were the organs of sense laid open to all impressions of surrounding objects ; in vain were their nerves fitted for their transmission : these impressions were to us as if they had never been, were there not provided a seat of consciousness in the biain ; for it is there that every sensation is felt. Light, and sound, and odour, and taste, are not felt in the organs they impress ; it is the sensitive centre that sees, and hears, and smells, and tastes. You have only to interrupt, by compression of the nerves, the communication between the organs and the brain, and all consciousness of the impressions of objects, all sensation is suspended. The torturing pains of a whitlow cease if you bind the arm so strongly as to compress the nerve which carries the sensation to the brain. A living animal under experiments suffers nothing from the most cruel laceration, if you have first cut the nerves of the parts on which you are operating. To conclude, the organs of sense, and the nerves which communicate between them and the brain, shall have suffered no injury, shall be in a perfect state for receiving and transmitting the sensitive impression, yet no phenomena of sensation can take place if the brain be diseased —when it is compressed, for instance, by a collection of fluid, or by a splinter from the skull in a wound of the head. This organ is, therefore, the immediate instrument of sensa- tions, of which impressions made on the others are only the occasional causes. This modification of sensibility, which serves to establish the rela- tions of the living being with objects without, would be correctly denominated cerebral sensibility ; but that, even in animals without brain, or distinct ner- vous system, it is very manifest. The sensibility in virtue of which the polypus dilates his cavity for the admission of his prey, and contracts itself to retain it, is in fact quite distinct from that sensibility of nutrition by which its substance is enabled to take to itself nutritious juices. The brain, as Cabanis has well expressed it, acts upon the impression transmitted by the nerves, as the stomach upon the aliments it receives by the cesophagus : it does, in its own way, digest them : set in motion by the impulse it receives, it begins to re-act; and that re-action is the percep- tive sensation, or perception. From that moment the impression becomes an idea, it enters as an element into thought, and becomes subject to the various combinations that are necessary to the phenomena of understanding.* » I ought to observe, that the terms thought and understanding are, in my opinion, synony- SOURCES OF IDEAS. 253 CLIV. Sources of our ideas. — Our sensations are nothing but modifications Of our being ; they are not qualities of the objects : no body has colour to the blind from birth : the rose has lost its most precious quality to him who has lost his smell ; he knows it from the anemone only by its colour, its figure, &c. We perceive nothing but within ourselves. It is only by habit, only by applying different senses to the examination of the same object, that we are at last able to separate it from our own existence ; to conceive of it as distinct from ourselves, and from the other bodies with which we are ac- quainted ; in a word, to refer to outward objects the sensations that take place within ourselves. Our ideas come to us only by the senses ; there are none innate, as was imagined till the time of Locke, who has allotted to the refutation of this error a large part of his valuable work on the Human Un- derstanding.* The child that opens its eyes to the light is prepared for the acquisition of ideas by this merely, that it is provided with an organic apparatus susceptible of impressions from the objects that surround it. The brain pre-exists the ideas, as the eye the sensations of sight. Every where the existence of the organ precedes the exercise of its functions. It is thus as impossible to conceive thought without a brain as vision without the organ destined to receive the impression of light. It is inaccurate, however, to compare, as some philosophers have done, the brain of a child new-born to a blank tablet, on which are to be figured all the future acts of his intelligence. If sensation came only from without, if the external senses were the only organs that could send impressions to the cerebral centre—the understanding, at the moment of birth, had indeed been nothing, and the comparison of its organ to a sheet of white paper, cr to a slab of Parian marble, on which not a character was drawn, had been perfectly correct. But we are compelled to acknowledge, with Cabanis, two sources of ideas quite distinct from each other, the external senses and the internal organs. These inward sensations, springing from functions that are carrying on within us, are the cause of those instinctive determinations by which the new-born child seizes the nipple of its mother, and sucks the milk by a very complicated process ; which directs the young of animals the mo- ment after birth, and sometimes in the very act of birth, while the limbs are yet engaged in the vagina, to seize upon the dug of their dam. . Instinct, ^.s the author just quoted has very correctly observed, springs from impressions received by the interior organs, whilst reasoning is the produce of external sensations ; and the etymology of the word instinct, composed of two Greek words, signifying " to prick," and " within," agrees with the meaning we as- sign to it. These two parts of the understanding, reason and instinct, unite and blend together to produce the intellectual system, and the various determinations of mental action. But the part that each bears in the generation of ideas is very different in animals, whose grosser external senses allow instinct to pre- dominate, and in man, in whom the perfection of these senses and,the art of signs, which perpetuate the transient thought, augment the power of reason while they enfeeble instinct. It is easy to conceive that the brain, assailed by a crowd of impressions from without, will regard less attentively, and therefore suffer to escape, the greater part of those that result from internal excitation. Instinct is more vigorous in savage man, and its relative per- mous ; both are alike an abridged expression of our ideas, and upon the manner in which he has the whole of the operations of the sensitive cen- been misunderstood, or his opinions miscon- tre. strued, and even perverted, by several modern * See the Appendix, Notes H H, for some writers.—/. C. remarks upon Locke's account of tho origin of 254 OF PERCEPTION, &C. fection is his compensation for the advantages which superior reason brings to man in civilisation. The moral and intellectual system of the individual, considered at different periods of life, owes more to internal sensation the less it is advanced ; for instinct declines as reason is strengthened and enlarged. Thus, though all the phenomena of understanding have their source in physical sensibility, this sensibility being set in action by two sorts of impres- sions, the brain of an infant just born has already the consciousness of those which spring from the internal motion, and it is from these impressions that it executes certain spontaneous movements, of which Locke and his followers could find no explanation : accordingly, the partisans of innate ideas looked upon them as the strongest confirmation of their system. But these ideas, anterior to all action of outward objects on the senses, are simple, few, and extending to a very small number of wants : the child is but a few hours old, and already it expresses a multitude of sensations that throng upon it from the instant of its birth—sensations which have passed to the brain, combined themselves there, and entered into the action of the will with a ve- locity which equals, if it does not surpass, that of light. It is only after laying down between the sources of our knowledge a very exact line of demarcation,—after scrupulously distinguishing the rational from the instinctive determinations,—acknowledging that age, sex, tempera- ment, health, disease, climate, and habit, which modify our physical organi- sation, must, by a secondary effect, modify these last,—that we can possibty understand the diversity of humours, of opinions, of characters, and of ge- nius. He who has well appreciated the effect on the judgment and reason of the sensations that spring from the habitual state of the internal organs, fees easily the origin of those everlasting disputes on the distinction between the sensitive and the rational soul; why some philosophers have believed man solicited for ever by a good or an evil genius—spirits which they have personified under the names of Oromazes and Arimanes, betwixt whom they imagined eternal war ; the contest of the soul with the senses, of the spirit with the flesh, of the concupiscent and irascible with the intellectual princi- ple,—that contradiction which St. Paul laboured under, when he said, in his epistle to the Romans, that his members were in open war with his reason. These phenomena which suggest the conception of a two-fold being (homo duplex, Buffon) are nothing but a necessary strife betwixt the determinations of instinct and the determinations of reason—between the often times impe- rious wants of the organic nature, and-the judgment which keeps them under, or deliberates on the means of satisfying them without offending received ideas of fitness, of duty, of religion, &e* CLV. Of perception, attention, memory, imagination, reasoning, tyc.—A being absolutely destitute of sensitive organs would possess only the existence of vegetation : if one sense -were added, he would not yet possess understanding, because, as CondiUac has shewn, the impressions produced on this only sense would not admit of comparison ; it would end in an inward feeling, a per- ception of existence, and he would believe the things which affected him to be a part of his being. The fundamental truth, so completely made out by modern metaphysicians, is found distinctly stated in the writings of Aristotle ;| and there is room for surprise that that father of philosophy should have merely recognised it, without conforming to its doctrines ; but still more that it should have been for so many ages disregarded by his successors. So ab- solutely is sensation the source of all our knowledge, that even the measure * For some remarks on Instinct, see AprEN- sensu :—Nisi intellectus ipse, as Leibnitz has dix, Notes H H. very justly added. See Appendix, Notes H H. + Nil est in intellectu quod non prius fuerit in OF ATTENTION, &C< 255 of understanding is according to the number and perfection of the organs of sense ; and that by successively depriving the intelligent being of them, we should lower at each step his intellectual nature; whilst the addition of a new sense to those we now possess, might lead us to a' multitude of un- known sensations and ideas, would disclose to us in the beings we are con- cerned with a vast variety of new relations, and would greatly enlarge the sphere of our intelligence. The impression produced on any organ by the action of an outward body does not constitute sensation ; it is further requisite that the impression be transmitted to the brain, that it be there perceived, that is, felt by that organ j the sensation then becomes perception, and this first modification supposes, as is apparent, a central organ, to which the impressions on the organs of sense may be carried. The cerebral fibres are more or less disturbed by the sensa- tions sent to them at once from all the organs of sense; and we should ac- quire but confused notions of the bodies from which they proceed, if one strong- er perception did not silence as it were the rest, and fix the attention. In this concentration of the soul upon a single object, the brain is feebly stirred by many sensations that leave no trace ; it is thus that after the attentive perusal of a book, we have lost the sensations that were produced by the different co- lour of the paper and the letters. When a sensation is of short duration, our knowledge of it is so slight that soon there remains no remembrance of it. It is thus that we do not perceive every time we wink that we pass from light to darkness, and from darkness to light. If we fix our attention on this sensation, it affects us more perma- nently. After occupying oneself for a given time with a number of things, with but moderate attention to each—after reading, for instance, a novel, full of events, each of which in its turn has interested lis, we finish it without be- ing tired of it, and are surprised at the time it has taken up. It is because successive and light impressions have effaced one another, till we have for- gotten all but some of the principal actions. Time ought then to appear to us to have passed rapidly ; for; as Locke has well said, in his Essay on the Human Understanding, " We conceive the succession of times only by that of our thoughts." This faculty of occupying oneself long and exclusively with the same idea, of concentrating all the intellectual faculties on one object, of bestowing on the contemplation of it alone a lively and well-supported attention, is found in greater or less strength in different minds ; and some philosophers appear to me to have explained, very plausibly, the different capacity of different minds and the various degrees of instruction of which we are capable, by the degree of attention we are able to give to the objects of our studies. Who, more than the man of genius, pauses on the examination of a single idea, considers it with more profound reflection, under more aspects and rela- tions, bestows on it, in short, more entire attention. Attention is to be considered as an act of the will, which keeps the organ to one sensation, or prepares it for that sensation so as to receive it more deep- ly. To look is to see with attention; to listen is to hear attentively; the smell, the taste, in the same way, are fixed upon an odour or a flavour, so as to receive from them the fullest impression. In all these cases the sensation may be involuntary, but the attention by which it is heightened is an act of the will. This distinction has already been well laid down with regard to the feeling, which is only the touch exerted under the direction of the will. According to the strength or faintness of the impression that a sensation or an idea (which is but a sensation operated upon b}' the cerebral organ) has produced on the fibres of that organ, will be the liveliness and permanence of 258 OF LANGUAGE. the recollection. Thus, we may have reminiscence of it or recall faintly that we have been so affected ; or memory, which is a representation of the object with some of its characteristic attributes, as colour, bulk, &c. The pains thatappear to be felt in limbs which we have lost have not their place in the part that is left; the brain is not deceived when it refers to the foot the sufferings of which the cause is in the stump, after the amputation of the leg or thigh. I have at this moment before me the case of a woman and of a young man, whose leg and thigh I took off for scrufulous caries, of many years standing, and incurable by any other means. The wound from the operation is completely cicatrised. The stump has not more sensibility than any other part covered by integuments, since it may be handled without pain ; and yet, both at intervals, and especially when the atmosphere is high- ly electrified, complain of pains in the limbs which they have lost some months ago: they recognise them, by certain characters, for those of their disease. They, like all perceptions, are manifestly given in charge to the memorj', which reproduces them when the cerebral organ repeats the action once oc- casioned by the impressions of the disease. Finally, if the brain is easy of excitation, and at the same time faithful in preserving the impressions it has received, it wTill possess the power of bring- ing up ideas with all their connected and collateral notions—of reproducing them, in some sort, by recalling the entire object, whilst memory presents us with a few of its qualities only. This creative faculty is called imagination. If it sometimes produces monsters, it is that the brain, by its power of asso- ciating, connecting, combining ideas, reproduces them in an order not accord- ing to nature, gathers them under capricious associations, and gives occasion to many erroneous judgments. When the mind brings together two ideas, when it compares them and de- termines on their analogy, it judges. A certain number of judgments, in se- ries, forms a reasoning. To reason, then, is only to judge of the relations that exist among the ideas with which the senses supply us, or which are produc- ed by imagination. It is with the faculties of the soul as with those of the body ; when called into full exertion, the intellectual organ gains vigour ; it languishes in too long repose. If we exercise certain faculties only, they are greatly developed, to the prejudice of the rest. It is thus that by the study of mathematics soundness of judgment and precision of reasoning are acquired, to the extinc- tion of imagination, which never rises to great strength without injury to the judging and reasoning powers. The descriptive sciences employ especially the memory, and it is seldom that they much enlarge the minds of those who study them exclusively. CLVI. Of spoken signs or language.—CondiUac has immortalised his name by being the first to discover, and by demonstrating irrefragably, that signs are as necessary to the formation as to the expression of ideas ; that language is not less useful for thinking than for speaking ; that if we could not attach the notions once acquired to received signs, they would remain always un- connected and incomplete, since we should have no power to associate and compare them, and to determine their relations. It is the imperfection or the total want of signs for fixing their ideas, that makes the infancy of the lower animals perpetual. It is this that makes it impossible for them to transmit to another generation, or even to communicate one with another, the acquisi- tions of individual experience, which experience is indeed, by the same cause, restrained within very narrow limits, and confined to a few simple notions— a few ideas, resting merely on its wants and on its powers. If there were not signs to preserve ideas and to connect them, memory would be nothing: all OF LANGUAGE. 257 impressions would be effaced soon after they were felt, all collections of ideas would be dissolved as soon as formed (if they could be formed at all); our ignorance would be indefinitely prolonged, and we should reach old age with a mind still in its infancy. When we reflect on a subject, it is not directly on the ideas, but on the words expressing them, that the mind operates ; we should never have the idea of numbers if we had not assigned distinct names to numbers, whether single or collected. Locke speaks of some Americans who had no idea of the number thousand, because the words of their language expressed nothing beyond the number twenty. La Condamine informs us, in his narrative, that there are some who count only to three, and the word they employ to express the number is so complicatedy of a pronunciation so long and difficult, that, as CondiUac observed, it is not surprising that, having begun with a method so inconvenient, they have not been able to advance any farther. " Deny," says this writer, " to a superior mind the use of letters, how much of knowledge you put out of his reach, which an ordinary capacity will attain to without difficulty. Go on, and take from him the use of speech, the lot of the dumb will shew you how narrow are the limits within which you confine him. Finally, take from him the use of all sorts of signs, let him be unable to find the least sign for the most ordinary thought, and you have an idiot."* We are made'acquainted by travellers with certain tribes, so backward in the art of expressing their ideas by signs, that they seem to serve as a link between civilised nations and certain species of animals whose instinct has been perfected by education. One'might even assert, that there is less dis- tance, in respect to intelligence, from man in that extreme abasement to the higher animals, than there is .to a man of superior genius, such as Bacon, Newton, or Voltaire. In another part of the same work, after having demonstrated that lan- guages are real analytic methods—that the sciences may be reduced to well- constructed languages, he shews how powerful is their influence in the cul- tivation of the mind. • But he shall spe&k himself with that clearness of ex- pression which is the characteristic and the charm of his writings. " Lan- guages are like the ciphers of the'geometricians ; they present new views to the mind, and expand it as they are brought nearer to perfection. The dis- coveries of Newton had been prepared for him by the signs that had been al- * ready contrived and the methods of calculations that had been invented. If he had arisen sooner he might have been a great man to his own age, but he would not have been the admiration of ours. It is the same in other depart- ments." The most scanty languages have been formed in the most barren countries. The savage who strays along the desert shores of New Zealand needs but few signs to distinguish the small number of objects that habitually impress his senses ; the sky, the earth, the sea, fire, shells, the fish that form his chief food, the quadrupeds, and the vegetables, which are but few in number under this severe climate, are all that he has to name and to know: accordingly, his vocabulary is very small; it has been given to us by" travellers in the compass of a few pages. A copious language, one capable of expressing a great variety of objects, of sensations, and of ideas, supposes high civilisation in the people among whom it is spoken. You hear complaints of the per- petual recurrence of the same expressions, the same thoughts, the same ima- ges in the poetry of Ossian; but living amidst the barren rocks of Scotland, the bards could not speak of things of which nothing on the soil they inhabit- ed could supply them with the idea. The monotony of their language was * Essai sur l'Origine des Connoissances Humaines, sec. 4. 33 258 DISORDERS OF THOUGHT involved in that of their impressions, always produced by rocks, mists, winds, the billows of the ireful ocean, the gloomy heath, and the silent pine, &c. The repetition of the same expressions in the Scriptures, shews that civilisa- tion had not made the same progress among the Hebrews as among the Greeks and Romans. The connexion there is between the genius of a lan- guage and the character of the people that speak it; the influence of climate, of government, and of manners, on language ; the reason why the great wri- ters in every department appear together at the very time in which a lan- guage reaches its perfection and maturitj', &c.;—these are problems that suggest themselves, and would well merit our endeavours to obtain solution, did not the investigation manifestly lead beyond the limits of our inquiry. Though CondiUac has said repeatedly in his works, that all the operations of the soul are merely sensation variously transformed, and that all its facul- ties are included in the single one of sense, his analysis of thought leaves still much doubt and uncertainty on the real character .and relative importance of each of her faculties. The merit of dispersing the mist which covered this part of metaphysics remained for M. de Tracy. His Elements of Ideology,* leave nothing to be wished for on this subject. I shall extract some of its main results, referring the reader for the rest to the work. To think is only to feel; and to feel is, for us,- the same as to exist; for it is byssensation we know of our existence. Ideas or perceptions are either sen- sations, properly so called, or recollections, or relations which we perceive ; or, lastly, the desire that is occasioned in us by these relations. The faculty of thought, therefore, falls into the natural subdivision of sensibility, properly termed memory, judgment^ and will.- To feel, properly speaking, is to be conscious of an impression ; to remember, is to be sensible of the remembrance of a past impression ; to judge, is to feel relations among our perceptions ; lastly, to will, is to desire something. Of these four elements, sensations, re- collections, judgments, and desires, are formed all com pound.ideas. Attention is but an act of the will; comparison cannot be separated from judgment, since we cannot compare two objects without judging them; reasoning is only a repetition of the act of judging; to reflect, to imagine, is to compose ideas, analysable into sensations, recollections, judgments, and desires. This ' sort of imagination, which is only certain and faithful memory, ought not to be distinguished from it. Finally, want, uneasiness, inquietude, desire, passions, . In sitting, the weight of the body bearing on the tuberosities of the ischia, there is much less effort required than in standing on the feet. The base of support is much larger ; and when the back leans, almost all the extensor muscles employed in standing are in action. CLXXXVI. Of the recumbent posture. Decubitus.—All the authors who, like Borelli, have treated professedly of the animal mechanism ; all the physi- ologists, Who, like Haller, have set forth in some detail the mechanism of standing and of progression, have completely passed over the consideration of the human body in repose, left to its own weight, in lying on an horizontal plane. The intention of the following observations is to fill up this gap. Let us consider, at setting out, that lying on an horizontal plane is the only pos- ture in which all the locomotive muscles recover the principle of their con- tractility, exhausted by exertion. Standing, without motion, has only the appearance of repose; and the unremitted contractions it requires, fatigue the muscular organs more than the alternate contractions by which the va- rious motions of progression are carried into effect. The human body, stretched -on an horizontal plane^ reposes in four posi- tions—as it lies on the back, the belly, or one or other of the sides. The Latin tongue expresses the first two situations by the terms supine and prone * It has no particular word for lying upon the side."]" Lying upon the right side is the most ordinary posture of sleep, in which we rest most pleasantly, and longest together. There are very few, except under constraint of some faulty organisation, who lie on the other side. This depends on two causes': when the body lies on the left side, the liver, a bulky viscus, very heavy, and ill steadied in the right hypochondrium, presses'with all its weight on the stomach, and draws down the diaphragm ; thence ensues an uneasiness, which hinders long continuance of sleep, or disturbs it with distressing dreams ; then the human stomach presents a canal, in which the course of its contents is obliquely directed from above downwards, and from left to right: the right or pyloric orifice of the stomach is much less raised than its left or cardiac orifice. Lying on the right side favours, therefore, the.descent of aliments, which, to pass into the intestines, are not obliged to ascend against their own weight, as they must in lying on the left * Cubitus supinus, Plin. Cubitus pronus,' t Pextro vel laevo latere cubare ; cubitus in Cic. Cubare in faciem, Juven. Supinus vel latus. Plin. pronus jacere. 304 OF RECUMBENT POSTURES side. These two anatomical causes exert their influence on tlie generality of men ; and if there are any who fall into the habit of lying on the left, one may safely conjecture some vicious organisation, or some accidental cause, that determines them, as by instinct, to this posture. Let us suppose an effusion of blood, water, or pus, in the sac of the pleura of the right side. The patient lies on this side, that the weight of his body may not oppose the dilatation of the sound side of the chest. The parietes of this cavity are not equally distant from its axis ; the pressure of the body on the plane of support prevents the separation of the ribs, whether as a me- chanical hindrance to the displacement of these bones, or in numbing the contractility of the muscles of inspiration, all being more or less compressed. Now, as the healthy lung must supply the place of the diseased, nothing could be more in the way than to produce, on that side, by a bad posture, a constraint equal to that occasioned by disease on the other. It has long been imagined, and it is taught still, that in thoracic effusions, patients lie on the side of the effusion to hinder the effused fluid from pres- sing on the mediastinum, and pushing it against the opposite lung, of which it will constrain the developement. The following experiments shew clearly enough the error of such a supposition :— . • I have several times produced artificial hydrothorax by injecting the chests of several bodies with water, through a wound in one of the sides. This experiment can be made only on bodies in which the lungs are free from adhesion Par Jnu*y Dugowr, truth as eloquence, by Thomas, in the last edi- 2YoL18mo. tion of his Essaisurles Ekges. t Vie de Sixte Quint, 2 vol. in 12mo. || Mimoirea de Gourville. % See his character, drawn with as much OF THE TEMPERAMENTS. 371 tinguished by it are subject, involve, in fact, either as their principal charac- teristic, as accessary circumstances, or as complication, the derangement ot the action of the hepatic organs, joined to changes of composition in the bile. Among the remedies directed against this sort of diseases, evacuants, and especially emetics, are the best. . If all the characteristics assigned to the bilious temperament are earned to the highest degree of intensity, and to this state is added great susceptibili- ty,—men are irascible, impetuous, violent on the slightest occasions, fcucn Homer describes Achilles and some others of his heroes. CCXXXIV. Of the melancholic temperament.—When to the bilious tem- perament is added diseased obstruction of any one of the organs of the ab- domen, or derangement of the functions of the nervous system, so that the vital functions are feebly or irregularly performed, the skin takes a deeper hue, the looks become uneasy and gloomy, the bowels sluggish, all the ex- cretions difficult, the pulse hard and habitually contracted. The general un- easiness affects the mind ; the imagination becomes gloomy, the disposition suspicious. The exceedingly multiplied varieties of this temperament, call- ed by the ancients the melancholic; the diversity of accidents that may bring it on, such as hereditary disease, long grief, excessive study, the abuse of pleasures, &c. justify the opinion which Clerc has proposed in his natural history of man in a state of disease, where he considers the melancholic temperament less as a primitive and natural constitution, than as a diseased affection hereditary or acquired: The characters of Lewis XI. and ribenus leave nothing wanting for the moral determination of this temperament. Read, in the Memoirs of Philip de Commines, and in the Annals of Tacitus, the history of these two tyrants, fearful, perfidious, mistrustful, suspicious, seek- ing solitude by instinct, and polluting it by all the acts of the most savage atrocity and the most ungoverned debauch. Distrust and fearfulness, joined to all the disorders of imagination, compose the moral character of this tem- perament. The passage in which Tacitus paints the artful conduct of Tiberius, when he refuses the empire offered him after the death of Augus- tus, may be given as the most perfect model of it.* As Professor Pinel very justly observes, in his treatise on insanity, the his- tory of men celebrated in the sciences, letters, and arts, has shewn us the melancholic under a different light: endowed with exquisite feeling and the finest perception, devoured with an ardent enthusiasm for the beautiful, capa- ble of realising it in rich conceptions, living with men in a state of reserve bor- dering upon distrust, analysing with care all their actions, catching in sen- timent its most delicate shades, but ready in unfavourable interpretations, and seeing all things through the dingy glass of melancholy. It is extremely difficult to delineate this temperament in a general or abstract manner. Though the ground-work of the picture remains always the same, its numerous circumstances give room for an infinite number of variations. It is better, therefore, to have recourse to the lives of illustrious men who have exhibited it in all its force. Tasso, Pascal, J. J. Rousseau, Gilbert, Zim- merman, are remarkable, among many others, and deserve by their just cele- brity, to fix our consideration. The first, born in the genial climate of Italy- proscribed and unhappy from his childhood—author, at twenty-two years old of the finest epic poem the moderns can boast of—was seized, in the midst of the enjoyments of premature glory, with the most violent and most in- auspicious love for the sister of the Duke of Ferrara, at whose court he lived—an extravagant passion/which was the pretext for the most cruel per- secutions, and which followed him to his death : this took place towards the * Versa inde ad Tiberiumpreces, <$c— Corn. Tacit. Annal. lib. 1. 372 OF THE TEMPERAMENTS. liJlW^'n°f thf Provi"cJal Le,Uers and °f the Thoughts, enjoying, meKnrbol'v JtTfT cfleb^ alm^ on quitting childhood was led To melancholy, not, like him, by the crosses of unhappy love, but by a violent and overpowering terror, which left in his imagination the sight oL gulf for ever open at his side-an illusion which left him only at his death, eight years after the accident* ' 6 No one, perhaps, has ever shewn the melancholic temperament in a higher degree of energy than the philosopher of Geneva. To be convinced of it, it is enough to read with attention certain passages of his immortal works, and especially the two last parts of his Confessions, and the Reveries in the Solitary Walker: tormented with continual distrusts and fears, his fruitful imagination represented to him all men as enemies. If you believe him, the whole human race is in league to do him mischief- " kings and nations have conspired together against the son of a poor watchmaker ,•" children and invalids are brought in to execute these dreadful plots. But let us leave him to speak lor himself, the most eloquent and the most unfortunate man of the eigh- teenth century. « Here then I am, alone upon the earth, without brother, neighbour, friend, without society but myself: the most, sociable and the most loving of men has been proscribed by them with unanimous consent." This is the beginning of the first walk ; further on he adds, " Could I believe that 1 should be held, without the smallest doubt, for a monster, a poisoner, an assassin ; that I should become the horror of the human race, and the game of the rabble ; that all the salutation of those that passed by me would be to spit upon me ; that a whole generation would amuse itself, with unani- mous consent, in burying me alive?" It is idle to multiply quotations in speaking of the works of a philosopher who, in spite of his errors, will for ever be the delight of all those who love to read and to think. The history of J. J. Rousseau, like that of all the melancholies who have distinguished themselves in literature, shews us genius struggling with mis- fortune ; a strong soul lodged in a feeble body; at first gentle, affectionate open, and tender, but soured by the sense of an unhappy condition, and of the injustice of men. Till the time when, impelled by the desire of fame Rousseau sprang forward in the career of letters, we see him endowed with a sanguine temperament, acting with all the qualities belonging to it • oentle loving, generous, feeling, though inconstant, his fertile imagination "shews him nothing but gay images, and in this illusion of happiness he lives on agreeable, chimeras ; but gradually undeceived by the hard lessons of expe- rience—afflicted m the depth of his heart, with his own wretchedness and the wrongs of his fellow-creatures,—his bodily vigour wastes and decays, with it his moral nature changes, and he may be referred to as the mos striking proof of the reciprocal influence of the moral on the physical, and *he physical on the moral part of our bemg.f His history is a proof, beyond s^Sdjzr^^sx Ssr?^ ble the solution of the folloS^fffim £X tertcl^Z^V™^*' ThomaS' d'Alem" gous to that with which ComlilKnchi'dM his dv of it °' v '' u^ *!"> ^ ; and the sUl" Lrk on the origin of human knowT^ot ^ ^ulfen cXnu'piS^T^r TH* HM(\r' The physical man being given to del,-™,;,,, th. fi„ j , 'a t8V nel' Halle> who ha™ mod - AarniZldext^ofhJc^^^^ tirTlT^t ^ anCient 6 tem- perament, like the nervous affections which are the result of it, has never shewn itself but among societies brought to that state of civilisation in which man is the farthest possible from nature. The Roman ladies became subject to nervous affections only in consequence of those depraved manners which marked the decline of the empire. These affections were extremely common in France during the eighteenth century, and in the times preceding the fall of the monarchy. Of that epoch are the works of Wylt, Raulin, Lorry, Pomme, &c. on nervous affections. Tronchin, a Genevese physician, acquir- ed great wealth and reputation by the treatment of these diseases. His whole secret consisted in exercising to fatigue women habitually inactive, keeping up their strength at the same time by simple, healthy, and plentiful food. The two most remarkable men of the eighteenth century, Voltaire and the great Frederick, may be given as instances of the nervous tempera- ment ' and the history of their brilliant and agitated life shews sufficiently how much the circumstances in which they lived contributed to develope their native dispositions. I shall finish this article on temperaments by observing, that in truth we bring with us into the world these particular dispositions of body; but that OF THE TEMPERAMENTS. 875 from education, manner of life, climate, acquired habits, they are altered or altogether changed. Further, it is exceedingly rare to find individuals who shew in their purity the characteristics assigned to the different tempera- ments : the descriptions given are drawn from an assemblage of individuals much resembling one another. Their characters are pure abstractions, which it is difficult to realise, because all men are at once sanguine and lymphatic, &c. In this instance, physiologists have imitated the artist, who united in the image of the goddess of beauty a thousand perfections, which he saw separate in the most beautiful women of Greece.* It is an observation, that the sanguine constitution is directly opposed to the melancholic, and never combines with it; that it is the same with the bilious and lymphatic : though it may happen that a man, sanguine in youth, shall become melancholic after a lapse of time ; for, as I have said before, man never remains such as he came from the hands of Nature: fashioned by all that surrounds him, his physical qualities, at different periods of his life, are as much changed as his character. Of all the causes that can modify the constitution of man, and which will even change completely the nature of his original dispositions, there is none more powerful than the long-continued action of air, water, and residence, as the father of medicine has said. Climate, in fact, exerts upon the tempera- ment the most marked influence. Thus, the bilious temperament is that of the greater part of the inhabitants of southern countries; the sanguine that of the nations of the north; the lymphatic constitution reigns, on the con- trary, in cold and moist countries like Holland. We have seen in what man- ner the athletic, melancholic, and nervous temperament grows out of our habits of life; let us now endeavour to appreciate the power of climate over the constitution of the greater part of mankind. It is known that the influence of heat in the production of bilious diseases is such, that after having been extremely prevalent during the summer, they disappear, or at least become much less frequent, in the autumn. A notable increase of perspiration never takes place without a proportional diminution in the quantity of the secretions with which the ahmentary mucous surfaces are moistened. Now, when the gastric and intestinal juices are less abun- dant, the bile, being mixed with a smaller quantity of these fluids, irritates more the intestinal surfaces ; the digestive powers languish, and there is an approaching disposition to meningo-gastric fevers. The same influences, con- tinued during the whole year in hot countries, must necessarily increase, with the activity of the biliary system, its power over the other parts of the economy; and thus establish a predominance of the bilious constitution through both health and disease. As for the sanguine temperament, so generally met with among northern nations, it is the necessary consequence of the continual and very energetic re-action of the powers of circulation, against the effects of external cold. It is only by the constant activity of the heart and vessels that calorification can be effected with the necessary vigour. Now, the effects of this redoubled action are the same to the organs of circulation as to the muscles under the influence of volition; in both, exertion increases the power of the organs ex- erted. The diseases of the nations of the north, analogous to their tempera- ment, have, for the most part, their seat in the system of sanguineous ves- sels : their character is eminently inflammatory. Lastly, the lymphatic state of nations living under a moist climate is nothing more surprising than the aqueous nature of plants, and small density * It is thus that, in the arts of imitation, the features, now from the union of qualities which ideal grows up—now from the exaggeration of nature has produced separate. 878 VARIETIES OP THE HUMAN SPECIES. of the wood in trees growing under the influence of a foggy air. Animal bodies, like plants, absorb by their surfaces, and become gorged with hu- mours, the excess of which always produces a remarkable slackening of ac- tivity in the organic motions. The temperament of which the character is the predominance of one or- gan or system of organs, departs from that ideal state where all the powers are reciprocally balanced, so as to exhibit in the living economy a perfect equilibrium. This latter state, which has, perhaps, never been found but in the imaginations of physiologists, and which was called by the ancients the temperate temperament, (temperamentum temperatum) being taken as the type of health, it follows that this temperament is already a step made to- wards disease. Yet the action of the predominant system is not in such ex- cess as to destroy all equilibrium, and impede the action of life : but let the constitutional dispositions be much increased, the disease is begun ; and thi3 transition takes place in the conversion of the lymphatic temperament into scrofula.* In the scrofulous constitution there is at once activity of the ab- sorbing mouths, great facility of absorption, inertness of the vessels and lymphatic glands, weakness of the absorbents, and consequently a thicken- ing and stagnation of the liquids absorbed. The same thing is seen in the lymphatic temperament, characterised by the activity of the inhaling mouths, and the debility of the lymphatic system, as Professor Cabanis was aware,! when he refuted the opinion of those who ascribe the lymphatic tempera- ment to the excess of activity in the absorbent system, though the only part of this system really quickened is that which immediately performs absorp- tion, whilst the rest is in a state of perfect atony. CCXXXVIl. Varieties of the human species.—The power of producing, by copulation, individuals which are alike, is considered by naturalists as the most certain test for fixing the species in red and warm-blood animals. This power of self-perpetuation, by a constant succession of similar beings, is found in all the races composing the human species, however different in colour, structure, and manner of life. Men, then, are but one species ; and the dif- ference that appears in them, according to the region of" the globe they in- habit, can only constitute varieties or races. 1 admit, with M. Lacepede, the worthy continuator of Buffon, four principal races of the human species, which I shall call, like him, the European Arab, the Mongid, the Negro, and the Hyperborean. We might add a fifth, the American, were it not most pro- bable that the new continent is peopled by inhabitants, who, coming from the old, either by land in the austral hemisphere, or along the immense archipe- lago of the Pacific Ocean, have been altered by the influence of that climate, and the yet virgin soil, so that they are to be regarded less as a distinct race than a simple variety.J There is, in truth, this difference between varieties and races, — that in these lasts there are implied modifications more profound, more essential dif- ferences, changes not confined to the surface, but extending to the verv struc- ture of the body ; whereas to make a variety, nothing more is needed than the superficial influence of climate on the integuments, which it colours, and on the hairs, which it makes longer or shorter, lank or curled, hard or soft. An Abyssinian, scorched by the heat of an almost tropical sky, is as black as the negro under the equator ; yet they are by no means of one race, since * See Nosographie Vhirurgicale, tome i. for planations of the grossest mechanism. the history of scrofulous ulcere, from which this f Of the R« lations of the Physical and Moral paragraph is taken entire. The author in that Man, by G. Cabanis, .Senator, Professor in the work has aimed at introducing physiology into Schoofof Medicine in Paris, &c. surgery, till then exclusively abandoned to ex- + t?'.-c Aite.M'ix. Notes P P. VARIETIES OF THE HUMAN SPECIES. 377 the Abyssinian, a negro only in colour, resembles the European in the cast of his face, and the proportions of all his parts. The characteristics of the European Arab race, which takes in the inhabit- ants, not of Europe only, but of Egypt also, Arabia, Syria, Barbary, and Ethiopia, are an oval or almost oval face, in the vertical direction, a long nose, a prominent skull, long and commonly lank hair, a skin more or less white. These fundamental characteristics are no where more decided than in the north of Europe. The inhabitants of Sweden, Finland, and Poland, give the prototype of the race: their stature is tall, their skin of perfect whiteness, their hair long, lank, and of a light colour ; the iris generally bluish. The Russians, the English, the Danes, the Germans, are already removed somewhat from this primordial type : the colour of their skin is of less pure white, their hair of a deeper hue. The French seem to stand mid- way betwixt the nations of the north and those of the south of Europe. Their skin is shaded with a deeper dye, their hair less straight, and more of a chestnut and brown colour. The Spaniards, the Italians, the Greeks, the European Turks, and the Portuguese, are browner, their hair in general black. Lastly, the Arabs, the Moors, and the Abyssinians, have hair in some measure black and crisp, the skin tawny ; and might serve for the step from the European Arab to the Negro race, which is, however, distin- guished from them by the flatness of the forehead, the smallness of the skull, the slope of the line measuring the height of the face, the thickness of the lips, the projection of the malar bones : and further, by a darker skin, thick- er, greasy, and, as it were, oily,—as well as by shorter, finer, curly, and woolly hair. The Mongol race has the forehead flat, the skull jutting but little, the eyes looking rather obliquely outwards ; the cheeks are prominent, and the oval of the face, instead of extending from the forehead to the chin, is drawn between the two malar bones. The Chinese, the Tartars, the inhabitants of the Peninsula, of the Ganges, and of the other countries of India, of Tonquin, Cochin-china, Japan, of the kingdom of Siam, &c. compose this race, which is more numerous than all the others, apparently more ancient, and which is spread over a greater extent of surface than the European Arab race, and yet greater than the Negro race, since it reaches from the fortieth to the sixtieth parallel of latitude, occupying an arc of the meridian of nearly 75° ; whilst that which measures the countries of the European race is only of 50°, and the Negro race lying under the equator, between the tropics of Cancer and of Capricorn, is bounded within the limits of an arc of from 30° to 35°.* The Hyperborean race, situated in the north of the two continents, in the neighbourhood of the polar circles, composed of the Laplanders, the Ostiaks, the Samoiedes, and the Greenlanders, is characterised by a flat face, a squat body, and a very short stature. This degraded portion of the human species evidently derives from the climate its distinctive characteristics. Striving for ever with the inclemency of a severe climate, and the destructive action of an icy temperature, Nature, fettered in her motions, and shrunk in her dimen- sions, can produce only beings whose physical imperfections explain their al- most barbarous condition. The small progress of the Negroes in the study of the sciences and in civi- lisation ; their decided taste and singular aptitude for all the arts which re- quire more taste and dexterity than understanding and reflection, as dancing, music, fencing, &c. ; the figure of the head, which is midway between that of the European and the ourang-outang ; j" the existence of the intermaxilla- * Lacepede, Giographie Zoologique. seems owing, as I have already said, to the t The black colour of the skin m Negroes .scorching of the gelatine, which is the base of 48 a7S varieties op the human species. ry bones at an age when with us the traces of their separation are complete*- ly effaced; the high situation and small developement of the calf of the leg ; —iave been arguments more specious than solid to those who have endea- voured to abase this portion of the human species, in order to justify an ini- quitous traffic and a cruel tyranny—reproaches of civilised men, which they must wipe off by other means than a presumptuous assertion of their own dig- nity, or a proud insult on the native character of those whom they themselves have cast into degradation. Without admitting this belief, which owes its origin to a thirst for riches, we cannot help acknowledging that the differences of organisation draw af- ter them a striking inequality in the developement of the moral and intellec- tual faculties. This truth would appear in its full light, if, after summarily indicating, as I have just done, the physical characteristics of the races of men, I could unfold their moral differences as real, and not less markedj by opposing the activity, the versatility, the restlessness, of the European, to the indolence, the phlegm, the patience of the Asiatic ; examining what is the power or the character of nations, the fertility of soil, serenity of sky, mild- ness of climate ; shewing by what catenation of physical and moral causes the empire of custom is so powerful over the people of the East that we find in India and China the same laws, manners, and religion, which prevailed there long before our era; inquiring by what singularity, well worthy the meditation of philosophers and politicians, these laws, this worship, and these manners, have undergone no change amidst the revolutions which have so often taken place among those nations, many times conquered by the warlike Tartars ; shewing how, by the irresistible ascendancy of wisdom and know- ledge, ignorant and ferocious conquerors have adopted the usages of the na- tions they have subjugated ; and proving that the stationary condition of the sciences and arts among those who, so long before ourselves, were in posses- sion of the advantages of civilised society, is derived not so much from the imperfection of their organisation, as from the degrading yoke of a religion loaded with absurd practices, and which makes knowledge the exclusive birthright of a privileged cast.* But such an undertaking, besides exceed- ing the limits I have prescribed myself, does not belong directly to my sub- ject. The Albinoes of Africa, the Cagois of the Pyrenees, and the Cretins of the Valais, cannot be given as varieties of the human species. They are infirm, feeble, degraded beings, incapable of reproducing an existence which has fallen to them in the midst of a healthy, vigorous, and robust population. We are not to believe what some travellers have written on the existence of tribes of giants that have appeared on the Magellanic coast. The Pata- gonians, concerning whose stature there is so little agreement in relations, are the rete mucosum of Malpighi. This colour, acquired in a long succession of ages, perpetuat- ed and transmitted by generation, is become one of the characteristic features of the Negro race. M. Volney, in a work which should be a model to all travellers, grounds on the face of the blacks a conjecture as ingenious as it is probable. He observes, that it exhibits precise- ly that state of contraction which our face takes when it is struck by light, and a strong rever- beration of heat; then, says this philosophical traveller, the cheek-bones rise, the brow and the eye-lids contract, and the lips project. Must not this contraction of the movable part have in- fluenced, in course of time, the hard parts, and even moulded the structure of the bones ?— Voyage en Syrie et en Egypte, torn. L p. 70, sixieme edition. * We must assign further, as a main cause of the want of progress of the Indians and Chi- nese in the arts and sciences sprung from civi- lisation, the imperfection of their alphabet, which, being composed of a multitude of cha- racters, does not, like ours, represent sounds, but ideas. It belongs not to our subject to shew how much signs so defective must confine the sphere, and fetter the combinations, of the mind. See, concerning the religion of the Brahmins and the Indian customs, Raynal's Philosophical History ; the Asiatic Researches ; Institutes of Menu, Edin. Review, xxxii.; Ward's View of the History of the Hindoos; Halked's Code of Gentoo Laws ; Colebrooke's Digest of Hindoo Law. OLD AGE AND DECAY. 379 men very well formed, and whose height does not exceed ours more than nine or ten inches. The Laplanders, whose stature is the smallest, are as much below as the Patagonians are above ; it does not exceed from four feet to four and a half. In the midst of ourselves, individuals reach, from time to time, a stature sufficient to entitle them to the name of giants; whilst others, shrunk in all their proportions, are a renewal of the pigmies. Such was Be be, the dwarf of Stanislaus, king of Poland ; Goliah, spoken of in the book of Kings, (ch. xvii. v. 4.); the king Og, (Deut. ch. hi. v. 2); and many others, whose stature varies from six to ten feet high. CCXXX VIII. Of old age and decrepitude.—The human body, which, from the twentieth year of life, ceases to grow in height, increases in every dimen- sion during the twenty succeeding years. After this period, far from growing, it begins to decay, and loses daily a part of its strength. The decay proceeds at the same rate as the growth, and is not more rapid ; since man requires from thirty to forty years in reaching to his full growth, and takes about tlie same time in his progress to the grave, provided no accident hurries him to an untimely end* The whole bulk of the body diminishes,! the cellular tissue becomes collapsed, and the skin wrinkled, especially that of the forehead and face The hairs of the head and over the rest of the body turn gray, then white ; the organic action becomes languid ; the fluids become more disposed to putrefaction (Hunter); hence, at this period of life, all diseases of debility are more frequent, and attended with greater danger. Decay succeeds old age. The sensibility of the organs is blunted ; the physical and intellectual faculties undergo a gradual decay ; man ceases to be impressed in the same manner by surrounding bodies. His judgments are incorrect, because self-love preventing him from being aware of the changes which he has undergone, he is more disposed to ascribe to an universal de- generacy the difference which exists between the sensations which he now Experiences and those which he experienced irihis youtf'. (^" W™ acti). The digestion is bad, the pulse weak and slow ; the absorption diffi- cult from the almost complete obliteration of the lymphatics and he indura- tion of the conglobate glands, the languid secretion and imperfect nutrition The old man is°slow in all his actions and stiff in all his motions ; his hair falls off, his teeth drop from their sockets ; the cartilages ossify the bones grow irregularly and become anchylosed, their internal cavity enlarges jail fheorcrani wasle; and the muscular fibres are indurated and ngid. The bones become heavier, from the gradual accumulation of phosphate of lime; andff, on Te conLry, those of The skull, as is justly observed by Scemmer, * The du^tion of ■* ~**£^* ^t^^^S^^^^ that of the growth. A dog ceases to grow at uie h f ; 1 j formed, the the end of two or three years and 1 esonly ten ^XrtioTofYhem int0 thatgparticular sub, or twelve ; man, whose growth requires a space « » game ^ rf ^ of from twenty to thirty years attains^o the age stance „ m ^ dominance of ninety or a hundred. J>sh"V™ »f™£ ThTs ncrease of bulk, owing to the augmenta- centuries, their developement requiring a con f™™™^^ 0/ fat> in%erS0ns advanced siderable number of years. f f b • favourable to the free + The diminution of the entire bulk of the ir^»te>^ar^°™ rjousg functions. for certain body of aged persons frequently gives place to ^f^* £«» « thecausft of ^ increased energy of the system being ™^'^ £*?" *"„£,„ of fat goes on increasing. This suf- complete assimilation of the nutritive mat en ate, secreton^w g ^J ^ drogen and carbon in the blood which these ves- 380 OLD AGE AND DECAY. ing, become lighter, it is that they are in a manner worn out by the continued motions of the brain on their internal surface. The ossification of some of the cartilages,—for example, of those of the ribs and vertebra,—is productive of remarkable effects. The ribs becoming soldered in a manner to the sternum, perform very imperfectly their natural motions, (LX.XI.) which contribute to the enlargement of the chest. This cavity dilating less fully, the pulmonary combinations, which are the abun- dant sources of animal heat, take place in a less effectual manner; and this, joined to a want of tone and energy in the lungs and in all the organs, low- ers the temperature of old people, as was observed by the father of physic ;* a circumstance, however, which has been denied by De Haen. Those fibro-cartilaginous lamina?, with oblique fibres crossing each other, which unite so firmly the bodies of the vertebrae, become indurated, dried, and shrivelled, sink under the weight of the body, and do not recover their former thickness, so that the stature is really reduced ; besides, the weakened condi- tion of the muscles which raise the trunk makes the weight of the viscera bend forward the vertebral column, whose different parts may remain fixed in this attitude, so that the whole column, consisting of twenty-four vertebrae, may come to consist of only seven or eight distinct bones. It should not be imagined, however, that all the soft parts become more compact, for several, as Haller observes, (the muscles, for instance), become softer,! and seem, in losing a part of their vital properties, to draw towards a speedy dissolution ; not that death is entirely owing to the accumulation of phosphate of lime, which enters into the composition of all the organs, converts into ossific mat- ter the whole osseous system, and interrupts the action of the animal ma- chine. If this ossific matter invade every part of the animal system, it is be- cause the digestive powers, gradually weakened, cease to affect in a suitable manner the alimentary substances. The exuberance of calcareous salts is, therefore, not so much the cause as the effect of the successive destruction of the vital powers. The slowness, the rigidity, and the difficulty of moving, do not depend so much as is thought on the induration of^the ligaments and other fibrous or- gans : these ligaments become softened and relaxed to a considerable degree so that luxation is more easily performed after death in old people. In them likewise, organs which in youth have a degree of consistency, become flac- cid and soft: this is the case with the heart, which is found collapsed in old people, its cavities remaining entire, while in young persons and in adults their parietes are firm and not in close contact. The brain becomes harder and firmer, and less soluble in alkalies • its albumen appears more completely oxidised than in younger subjects-'im- pressions are less easily made, and the motions necessary to the operations of the understanding are performed with difficulty. Hence, in decrepitude man returns, as far as relates to his intellectual faculties, to a state of second chddhood, limited to certain recollections, which are at first confused, and in the end completely lost: incapable of judgment or will, or of new impres- sions, sleep resumes its influence ; reduced to a mere vegetative existence he sleeps the greatest part of the day, and wakens only to satisfy his physi- cal wants and to take food, which he digests very imperfectly; for in the first place, the want of teeth prevents his being able to divide sufficiently the different substances ; and, in the next place, the supply of saliva, of gastric * '• Senibus autem modicus est calor » * * * mortis oportet ponere ; nam ex defectu irritabi fngidum est emm ipsorum corpus."—Hippocr. litatis, plurimi in senibus muscuh languent Aph. xiy. sect. 2. . .... .. mollesque pendent."—Elementa Physiol, torn! f " Non ergo in sola ngiditate causam semi vm. 4to. lib. 30. OP DEATH. S8l B.hd intestinal juices, is almost interrupted ; the bile and other fluids are less active, and the intestinal tube is without energy. Universal rigidity will be admitted as one of the principal causes of death, if it be considered that wo- men, in whom the organs are naturally softer, are longer in reaching that state, are more retentive of life than men, and generally live to a greater age. The body, therefore, dies slowly and by degrees, says the eloquent M. de Buffon ; life gradually becomes extinguished, and death is but the last term of this series of degrees, the last shade of life. CCXXXIX. Of death.—Long, in fact, before the close of life, man loses the power of reproduction ; and in the course of the agony which serves as a passage between life and death, the organs of sense first become insensible to all sorts of impressions ; the eyes grow dim, the cornea fades, the eye-lids close, the voice becomes extinct, the limbs and the trunk motionless; yet the circulation and respiration continue to be carried on, but at last cease, first in the vessels furthest from the heart, and then gradually in the vessels nearest that organ. Respiration, gradually slackened, being entirely sus- pended after a strong expiration,* the lungs no longer transmit the blood which the veins bring from every quarter to the heart. This fluid stagnates in the right cavities of the heart, and these die last, (ultimum moriens) ; and distended by the blood which collects within them, they attain a capacity exceeding greatly that of the left cavities, which are, to a certain degree, emptied. Such is the course of natural death : the brain ceases to receive from the weakened heart a sufficient quantity of blood to keep up sensibility ; there remains still some degree of contractility in the respiratory muscles ; it is soon exhausted, however, and the circulatory motion of the blood ceases with the life of all the organs, of which this fluid is one of the principal movers. As to accidental death, it is always determined by the cessation of the action of the heart and brain ; for the death of the lungs occasions that of the whole body only by preventing the action of the heart, by interrupting its influence on the encephalic organ. In natural death, therefore, life be- comes extinguished from the circumference to the centre; in accidental death, on the contrary, the centre is affected before the extremities. Bich&t, in his work entitled, " Recherches sur la Vie et la Mort," has given a very complete account of the manner in which the organs of the animal economy cease to act in articulo mortis ; but, like all the authors who went before him, he has limited his inquiries to certain functions. No one has at- tempted to extend them to the phenomena of the action of the brain, nor has any one traced the order in which the various faculties of thought and of sensation vanish. I shall endeavour faithfully to mention the results of seve- ral hundred observations of my own on this subject. The close of life is marked by phenomena similar to those with which it be- gan. The circulation first manifested itself, and ceases last. The right auricle is the part first seen to pulsate in the embryo, and in death is the last to retain its motion. The phenomena of nutrition, to which the foetal existence is almost entirely limited, continue even when the organs destined to establish a relation with the beings that surround us have long been sunk into a slum- ber from which they are never to be roused. The. following is the order in which the intellectual faculties cease and are decomposed."j" Reason, the exclusive attribute of man, first forsakes him. * Does this last and powerful expiration, often attended by sighing, depend on the spas- modic contraction of the muscles of expiration ; or rather docs it not depend on the re-action of the elastic parts which form the chest—a re-ac- tion which suddenly ceases to be counterbalanc- ed by the vital properties ? t I need not inform the reader that I am not 882 OP THE PERIOD OF DEATH. He begins by losing the faculty of associating judgments, and then of com- paring, of bringing together, and of connecting, a number of ideas, so as to judge of their relations. The patient is then said to have lost his conscious- ness, or to be delirious. This delirium has generally for its subject the ideas that are most familiar to the patient, and his prevailing passion is easily re- cognised. The miser talks in the most indiscreet manner of his hidden trea- sures, the unbeliever dies haunted by religious apprehensions. Sweet recol- lections of a distant native land, then it' is that ye return with your all-power- ful energy and delight! After reasoning and judgment, the faculty of associating ideas is next com- pletely destroyed. The same occurs in fainting, as I once experienced in myself. I was conversing with one of my friends, when I felt an insuper- able difficulty in associating two ideas, from the comparison of which I wish- ed to form a judgment. Yet syncope was not complete; I still preserved memory and the faculty of feeling. I could distinctly hear those about me say, " he is fainting," and exert themselves to relieve me from this condition, which was not without enjoyment. The memory then fails. The patient who, during the early part of his de- lirium, recognised the persons about him, no longer knows his nearest and most intimate friends. At last he ceases to feel, but his senses vanish in succession and in a de- terminate order: the taste and smell cease to give any sign of existence ; the eyes become obscured by a dark and gloomy cloud ; the ear is yet sen- sible to sound and noise; and no doubt it was on this account that the ancients, to ascertain that death had really taken place, were in the habit of calling loudly to the deceased. A dying man, though no longer capable of smelling, tasting, hearing, and seeing, still retains the sense of touch : he tosses about in his bed, moves his arms in various directions, and is perpetually changing his posture ; he per- forms, as was already said, motions similar to those of the fcetus within the mother's womb. CCXL. Of the period of death.—This period is nearly the same with all men: whether they live near the poles or under the equator, whether they live exclusively on animal or vegetable substances, whether they lead an ac- tive life, or consume their existence in disgraceful sloth,—few live beyond a hundred years. There are, however, cases of men who have lived far beyond that period, as, for example, those mentioned in the Philosophical Transactions, one of whom lived to a hundred and sixty-five. Few men, however, attain a hundred years, and death, even when na- tural, overtakes us from the age of seventy-five to a hundred. Difference of climate, though producing little difference in the duration of life, has, however, a remarkable influence on rapidity of growth. Puberty, manhood, and old age, come on much sooner in warm climates than in north- ern countries ; but this premature developement, which shortens the dura- tion of the periods of life, augments in the same proportion that of old age. It is, however, difficult to say at what precise period old age begins. Is it towards the fortieth year, when the body begins to decrease and to decay % Can the change of the colour of the hair be considered as the certain sign of old age 1 We daily see young men with gray hair. May we determine here speaking of the, immortal soul, of that di- intellectual faculties common to man, and to vine emanation which outlives matter, and those animate which, like him, are provided which, freed from our perishable part, returns with a brain. to the Almighty. I am speaking merely of the PROBABILITIES OF HUMAN LIFE. 383 its accession by the cessation of the functions of generation and the incapa- city of reproduction 1 Fecundity, whose term is so easily determined in wo- man by the cessation of the menses, is in man very equivocal; the emission of the seminal fluid is an uncertain sign, from the difficulty of distinguishing the mucus of the vesiculae seminales and of the prostate from the truly pro- lific semen. Erection is likewise a sign not to be relied upon : this state maybe occasioned by sympathetic irritation, by the compression of the blad- der distended with urine on the vesiculae seminales. It is more difficult than is imagined to determine from observation the period at which, in the human species, the male is entirely deprived of the power of generation ; and it may be said that, in establishing the period of from forty-five to fifty-five as the beginning of old age in our climate, there will be found men arrived at that state before having reached that age ; as, on the other hand, others will be found after the age of fifty-five with all the characters of manhood. The climacterical period of sixty-three is the decided and confirmed period of old age. Whatever regimen may have been followed, man at that age is truly old, and cannot but be aware of it. CCXLI. Of the probabilities of human life.—Man dies at all ages ; and if the duration of his life surpass that of the lower animals, the great number of diseases to which he is liable renders it much more uncertain, and is the cause why a much smaller number arrive at the natural term of existence. It has been attempted to discover what are the probabilities of life, that is, to ascer- tain from observation how long a man may expect to live who has already reached a determinate age. From late accurate observations of the age at which a number of persons have died, and from a comparison of the deaths with the births, it has been ascertained, that about one-fourth of the children that are born die within the first eleven months of life ; one-third under twen- ty-three months ; and one-half before they reach the eighth year. Two- thirds of mankind die before the thirty-ninth year, and three-fourths before the fifty-first; so that, as Buffon observes, of nine children that are born, only one arrives at the age of seventy-three ; of thirty, only one lives to the age of eighty; while out of two hundred and ninety-one, one only lives to the age of ninety ; and, in the last place, out of eleven thousand nine hundred and ninety-six, only one drags on a languid existence to the age of a hundred years. The mean term of life is, according to the same author, eight years in a new-born child. As the child grows older his existence becomes more se- cure, and after the first year he may reasonably be expected to live to the age of thirty-three. Life becomes gradually firmer up to the age of seven, when the child, after going through the dangers of dentition, will probably live forty-two years and three months. After this period, the sum of pro- babilities, which had gradually increased, undergoes a progressive decrease ; so that a child of fourteen cannot expect to live beyond thirty-seven years and five months ; a man of thirty, twenty-eight years more ; and, m the last place, a man of eighty-four, one year only. From the eighty-fifth to the ninetieth year, probabilities remain stationary, but after this period, existence is most precarious, and is painfully carried on to the end. Such is the result of observation, and of calculations on the different degrees of probability of human*life, by Halley, Graunt, Kersboom, Wargentin, Simson, Deparcieux, Dupre de St. Maur, Buffon, d'Alembert, Barthez, and M. Mourgues, who has just published his observations, collected at Montpelier in the course Of a great number of years, and with the most scrupulous accuracy.* * From the observations made duiing more duration of human life has experienced an in- recent periods, it would appear that the mean crease of nearly five years in the greater num.- 3S4 PROBABILITIES OF HUMAN LIFE. I should enter more fully into this subject, but that it belongs rather to the department of political economy than to that of physiology. Do the calculations on the probabilities of human life present results appli- cable to the generality of cases, and is the mean duration of existence nearly the same with all men, in all countries and climates 1 The shepherd of the Pyrenees, who lives happy in the innocence of a pastoral life, breathing the pure air of his mountains,—is he, in this respect, subject to the same laws as the inhabitant of populous cities, exposed to the inconveniences attend- ing numerous collections of men; inconveniences which, viewed in a philo- sophical point of view, or which, being greatly over-rated, have so often fur- nished a text to the meditations of philosophy, and to the idle declamations of oratory 1* Does life experience a progressive diminution in proportion to the duration of the world ; and to say nothing of the time preceding the flood, when, ac- cording to the Book of Genesis, men lived several hundred years, did the men of former times five longer than those of our own 1 This is very im- ber of .European countries. This may be in some measure owing to the introduction of vac- cination, but perhaps the chief causes may be found in the progress of science and civilisa- tion, giving rise to a general improvement in the habits of life, particularly with regard to ventilation and cleanliness; to better nabita- tions; a more ample supply of food, clothing, and fuel; greater sobriety; a more general cul- tivation of the soil, and consequent removal of the sources of several diseases ; to improved management of children ; and to the advanced state of medical knowledge. The same causes that conduce to longevity must of course increase the population of a country. The suppression of monastic celibacy, and the more equal distribution of landed pro- perty, consequent on the revolution in France, have tended to increase the population of that country, notwithstanding the destructive wars in which she has been engaged.—J. C. * In order to answer these questions in a satisfactory manner, it would be necessary to have tables of mortality kept with care in the different countries and climates of the globe. The religions and superstitions of the East, of all Africa, and of a great part of America, op- pose invincible obstacles to thege researches, independently of those resulting from the state of civilisation, and the policy of the various go- vernments of these countries. Judging, how- ever, from the results already before us, the northern kingdoms of Europe appear to be those in which mankind enjoy the longest tenn of ex- istence. The tables of mortality of the empire of Russia for the year 1811, gave, in 828,561 individuals deceased belonging to the Greek church, 947 who had reached a hundred years and upwards; amongst whom were 83 of 115 years of age, 51 of 120, 21 of 125, 7 of 130, 1 of 135, and another who had reached 140. According to the abstract of the population returns of Great Britain in 1821, the number of individuals in England, aged from 90 to 100 years, was 990 in every 20,000; and of those aged 100 and upwards, 34 : the general morta- lity was 1 in 57. In Scotland, those aged from 90 to 100 was 1413; and 100 and upwanls, 1-903 in every 20,000. In Wales, the number of persons aged from 90 to 100 was 17-97 ; and of those aged 100 and upwards, 50 in 20,000: the mortality was 1 in -69. The maximum longevity was found to be in Scotland, in the shire of Ross and Cromarty. Here the proportion of individuals aged from 90 to 100 was 3439 to the 20,000; and of those aged 100 and upwards, 9-22. In the shires of Inverness and Argyle, the proportion of persons aged from 90 to 100 were 34*49 and 2984, re- spectively, to 20,000. In 1811, the population of Scotland was 1,865,900 ; in 1821 it was 2,135,300. The first actual enumeration of the inhabit- ants of England and Wales was made in 1801, and gave a population of 9,168,000, and a mor- tality of 1 in 448. The second was made in 1811, and gave a population of 10,502,900, and a mortality of 1 in 50. The third and last, which took place in 1821, has given an enume- ration of 12,218,500, and a mortality of 1 in 58. It appears from these returns, that the healthi- est counties in England and Wales are Pem- broke, Sussex, Cornwall, Cardigan, and Mon- mouth, the mortality in these being 1 in about 71; and that the least salubrious are Middlesex, Kent, Surry, and Warwick, the mortality being in these 1 in about 50. It is not easy to explain altogether the difference in salubrity in the dif- ferent counties. Locality is, doubtless, an im- portant agent. Cities and large manufacturing towns modify greatly the ratio of mortality in a particular district. This is well illustrated with respect to London. In 1700, the annual morta- lity of this city was 1 in 25 ; in 1750, 1 in 21 ; in 1821 and the four preceding years, 1 in 35; in 1810, 1 in 38; and in 1821, 1 in 40. It. must be evident, that the increase or dimi- nution of the population of a district, as well as the mean term of life in it, must depend upon the nature of the climate and soil, its mean ele- vation and temperature, the state of its civilisa- tion and cultivation, pursuits of its inhabitants, and means of subsistence. The government and religion of a country also exert no inconsi- derable control on the mean duration of human life, and inciease of its population. Together w ith these already ment ioned, many other causes of a moral and physical nature may be adduced, as influencing in no slight degree the extent of population, and the salubrity of a district or country.—J. C OF PUTREFACTION. 365 probable : among the Egyptians, the Hebrews, the Greeks, and Romans, there were very few instances of persons living to the age of a hundred years, and instances of longevity are perhaps more frequent among the moderns. The art of providing for the wants of life making daily progress, it is very probable, that far from being shortened, the term of human life may be length- ened a certain number of years beyond its ordinary duration. This idea is, it is true, contrary to the commonly received opinion of the progressive de- pravity of mankind in all ages ; but the golden age never existed but in the imagination of poets, and the daily complaints of morose old age have their origin in motives easily understood by the physiologist. He whose sentiment is blunted by a long course of years, is affected in a very different manner by surrounding objects. As to the old man, flowers have lost their scent and beauty, fruits no longer retain their flavour ; the whole of nature seems dull and colourless. But the cause of all these changes is within himself; every thing else remains as it was. Always equally fruitful, Nature exposes every thing to the action of her inexhaustible crucible, maintains every thing in a state of everlasting youth, and preserves a freshness ever renewed. Indivi- duals die, species are renovated; life every where arises in the midst of death. The materials of organised bodies enter into new combinations, and serve in forming new beings, when hfe ceasing to animate those to which they belong- ed, putrefaction seizes upon them and effects their destruction. CCXLII. Of putrefaction.—Here the history of life ought to terminate : if, however, it be considered that the changes which bodies experience after death throw a considerable light on its means, its ends, and its nature, there will be an obvious necessity for shortly inquiring into the different phenomena which accompany the decomposition of animal substances. And this inves- tigation appears to me to belong to the department of physiology, until the aspect of the body ceases to recall the idea of its former state, and until the last lineaments of organisation are completely effaced. As soon as life for- sakes our organs, they become subject to the laws of physics operating on substances that are not organised. An inward motion takes place within their substance, and their molecules have the greater tendency to become separated from one another as their composition is more advanced. Chemistry informs us, that the tendency to decomposition of bodies is in direct ratio to the num- ber of their elements ; and that a dead animal body is capable of remaining unchanged, in proportion as its composition is more simple, and its constitu- ent principles less numerous and less volatile. Before putrefaction can come on in the human body, it must be entirely deprived of life, for the vital influence is most powerfully antiseptic; and one might say that life is a continual struggle against the laws of physics and chemistry. This vital resistance, alluded to by the ancients when they said that the laws of the microcosm were in perpetual opposition to those of the universal world, and that these in the end prevailed—this power which is in a state of perpetual re-action, manifests itself in fife : the latter, considering only the results, might therefore be defined as follows—the resistance opposed by organic bodies to the causes incessantly tending to their destruction. By attend- ing to all these phenomena, it will be seen that all of them tend to one end— the preservation of the body, and that they obtain it by keeping up a perpe- tual struggle with the laws which govern inorganic substances. It might appear singular that death should furnish a just idea of life, did we not know that it is by comparing that we are enabled to distinguish, to judge, and to arrive at knowledge. Putrefaction takes place and is completed only in substances deprived of life. A mortified limb loses its vitality before putrefaction comes on; and if Nature preserve sufficient energy to resist this destructive process, she draws, 49 386 OF PUTREFACTION. by a line of inflammation, the separation between the dead and the living part. Life and putrefaction are, therefore, two absolutely contradictory ideas; an I when, in some diseases, there is observed a tendency in the solids and fluids to spontaneous decomposition, this tendency to putrefaction should not be mistaken for putrefaction itself. Several conditions are required to enable putrefaction to affect the human body after death. In the first place, a mild temperature, that is, above ten de- grees of Reaumur's thermometer ; in the next place, a certain degree of mois- ture ; and lastly, the presence of air. This last condition, however, is not so necessary as the two former, since substances undergo putrefaction in a va- cuum, though more slowly. The air consequently promotes a decomposition only by carrying off the element, which rises in vapours. On the other hand, an icy cold, or a degree of heat approaching to boiling, prevents it; the for- mer by condensing the parts ; the second by depriving them of moisture, the complete absence of which accounts for the preservation of the Egyptian mummies. The phenomena of putrefaction, resulting from a series of peculiar attrac- tions, are modified in various ways according to the nature of the animal substances which are subjected to it, to the media in which it takes place, to the different degrees of moisture and temperature, and even according to its different periods*. Notwithstanding these innumerable varieties, one may say, that all exhale a certain cadaverous smell, are softened, increase in bulk, acquire heat, change colour, assume a greenish, then a livid and dark-brown colour : there are, at the same time, disengaged a great number of gaseous substances, of which ammonia is the most remarkable, either from its quan- tity, or from being given out by animal substances from the moment when decomposition begins to the period of the most complete dissolution. This gas produces the pungent and putrid smell which exhales from dead bodies. Towards the termination of putrefaction, there 13 disengaged carbonic acid gas, which, combining with ammonia, forms a fixed and crystallisable salt. Besides these products, there are given out sulphuretted and phosphoretted hydrogen, azoter carbonic acid, and all the gaseous matters that may be produced by their respective combinations. In the last place, animal sub- stances, when reduced to a residue containing oils and salts of different kinds, form a mould, from which plants draw the principles of a luxuriant and vigo- rous vegetation. The bones, those least alterable parts of the organised ma- chine, in time become dried by the slow combustion of their fibrous part, and by the evaporation of their medullary juices. At last, reduced to an earthy skeleton, they crumble into dust, and this dust is dissipated on opening the tombs in which they were laid. Thus, in course of time, is effaced all that could recall the idea of our physical existence. Putrefaction, considered in a philosophical point of view, is but a means employed by nature to restore our organs, deprived of life, to a more simple composition, in order that their elements may be applied to new creations (circulus aterni motiis*). Nothing, therefore, is better proved, than the me- tempsychosis of matter ;f which warrants the belief that this religious dog- ma, like most of the fabulous worships and imaginations of antiquity, is but a veil ingeniously thrown by philosophy between nature and the ignorant. * Becchee, Physiea subterranea. store to the inexhaustible fund of Nature those + Matter is eternal in this sense, that the elements which she lends without ever parting molecules of bodies merely pass from the one with fhem. into the other ; they survive the destruction, or Mancupio nulli datur, omnibus usu.—Luoret rather the dissolution, of organic and inorganic lib. iii. beings, when the former, ceasing to live, re- APPENDIX: JAMES COPLAND, M. D. &c ADDITIONAL NOTES TO THE PRELIM1MARY DISCOURSE. OF LIFE. there subjected to our experience, they endea- vour to get rid of the difficulty by denominating (Note A. See pp. 1, 8, 31,139.) them vital; thus tacitly admitting the very prin- ciple, in the place of which such insufficient Physiologists are divided into those admit- properties are attempted to be substituted; and, ting a principle of life, 'and those attributing after all, without the smallest success in pre- the vital phenomena to organisation solely — venting a recurrence to this principle, of which the latter class contending that life presupposes all these properties, admitting their existence, organisation, the former that organisation pre- are nothing else than the results : for, however supposes the presence of life. An attentive we may denominate them, we merely substitute consideration of the phenomena presented by expressions which (if they convey any mean- the whole range of organised bodies, and a fair ing) imply only the existence of certain effects contrast instituted between these and the or operations which are inferior agents or in- changes which inanimate matter exhibits, will struments, under the control of vitality, in the readily convince the mind unbiassed by precon- production of the organic phenomena. ceived notions which of the two doctrines to From this view, therefore, of the subject, it prefer. appears that the argument used against the ex- Those who contend that life is the result of istence of a vital principle is rather verbal than organisation ought to explain in what manner real. The organists cannot even prove the the organisation itself took place ; they should basis of their doctrine, for they cannot shew shew the means employed to produce the dis- that organisation came into existence before position of parts, which they conceive requisite the effects which they impute to it; and while to give rise to vital phenomena. If they deny they bestow properties and qualities on orga- the primary influence of a vital power associat- nised matter similar to those imputed to a vital ed with the particles of matter, let them explain principle, and different from those which cha- by what other agency the different atoms can racterise inorganised matter, although they can- assume organic actions. All effects must have not point out the difference otherwise than by a cause, and it is better to assign one according calling them vital, they virtually admit the ex- to which difficulties may be accounted for, than istence of the principle against which they con- to contend for the efficiency of properties or tend: for what principle in nature, we would powers of the existence of which we have no ask, can be shewn to exist, or how can its ex- evidence, and which, even granting them to istence be rationally inferred, but by certain exist, can only be considered as inferior agents, properties and qualities which are peculiar to or peculiar manifestations of a vital principle. itself, and which, moreover, as respects this With respect to this class of physiologists, it principle, are dissimilar and greatly superior to, may be remarked generally ;—1st. That expla- and indeed hold a controlling influence over, nations of organisation which admit not of the all the other properties of matter with which primary and controlling influence of vitality, we are acquainted ? however applicable they may seem to those who Such, therefore, being the case, we are justi- look only at the gross relations of things, can- fied in recurring to the belief in a vital princi- not satisfactorily account for the origin and pie, which, allied to matter, controls its changes nature of the phenomena to which they relate ; and forms, and to which principle the laws and for, however terms may be substituted, or illus- affinities of matter are entirely subject, when- trations multiplied, the changes which continu- ever they are embraced within its sphere of ally take place in living bodies cannot be ex- action. By means of this superior principle, plained by means of the laws and affinities we are enabled to explain the phenomena of which characterise the combinations of inorga- the organised creation and of the human eco- nised matter. nomy ; but without reference to it we are lost 2d. In order to explain the phenomena which in the mazes of vague hypothesis and ground- are more justly ascribed to a vital principle, the less supposition. supporters of the doctrine of organism have re- It has been objected to the existence of this course to the substitution of properties, occult principle, that we cannot demonstrate it to the qualities, impulses, and motions; and when re- senses in any form unconnected with matter. quired to shew wherein these qualities, impul- But we are not contending for the existence of ses, and properties, are different from those a principle which is material, according to the which we observe in organised matter, and arc received notions respecting matter, otherwise A 2 Al'PENDIX there would be at once an end of the argument. It is, therefore, no evidence of the non-existence of this principle, that it does not become visi- ble to our senses in an uncombined form: it is, however, sufficiently demonstrable by its ef- fects, in alliance with matter, in which state it presents proofs of its existence equal to those from which we infer the existence of matter itself. , .. From these, and many other considerations that might be adduced, we conclude that life is a first principle in nature; that it exists in vari- ous degrees of energy, and in diversified condi- tions and forms, throughout her domains ; and that these diversified states of vital existence are continued, as far as the operation of extra- neous causes will admit, by a specific process, which gives rise to the production of similar beings by means of ova and germs. It will be perceived, that the generation by which vegetable and animal bodies are perpetu- ated involves the belief that the ova or germs convey an emanation from the parent of a spe- cific portion of vitality. As, however, we can form no just, concep- tions of such a principle but by its effects, and as we have no experience of these effects un- connected with matter, so we are warranted in the conclusion, that the vital influence is asso- ciated with the molecules of matter forming the impregnating secretions and the sensible 'bulk of the ovum. This is its lowest state of activi- ty or energy ; and its influence is chiefly mani- fested, under such circumstances, in preserving the elements of matter with which it is asso- ciated from entering into the combinations to which the chemical affinities of these elements dispose them. The hibernation of animals present this prin- ciple also in its lowest degree of activity : m either case, and indeed under every circum- stance, it is acted upon and excited to an ex- alted state of existence by most of the active agents in nature. The electric fluid, heat, and other powers, have this effect, while some ap- pear to produce a contrary impression. The manner in which several of the active asrents of inorganic nature thus influence the energy of the vital principle, appears to have been the chief reason why these powers have been substituted for vitality itself. We have stated that the manifestations ot this principle throughout the vegetable and ani- mal kingdoms present considerable difference in degree. Its character in the vegetable crea- tion is more uniform, and its phenomena more simple We perceive in this kingdom, under circumstances which furnish the usual stimuli, that the vital operations of digestion, circula- tion respiration, and assimilation, go forward. As soon, however, as the exciting causes are withdrawn, this principle subsides to a state of less activity ; and the integrity of such organs and textures as are necessary to the growth and propagation of the species, is merely pre- served by its influence until a returning im- pulse excites its energies. As we advance in the scale of the animal creation, the operations of this principle be- come more distinct and numerous, and the me- chanism provided for the performance of them more manifest and complex. As they are per- formed in man and in the more perfect animals, may be gathered from the body of the work and the notes which follow. OF THE NERVOUS SYSTEM IN THE LOWER ANIMALS. (Note B. See pp. 10, 139.) The lowest order of animals, as the polypi, &c. has usually been considered to be destitute of a nervous system. This, however, is not the case. If we look narrowly into the stiuc- ture of the lower animals, we shall find that even the lowest offers traces of a nervous sys- tem ; and as we rise through the scale of the animal creation, we shall find this system be- coming more and more perfect in its state ot existence, and presenting appearances of per- fection in proportion to the number and extent of functions which the animal is capable of ex- erting. Even the polypus, the lowest of the animal kingdom, seems to possess a nervous system in the simplest state of existence. 11 this apparently homogeneous animal be examin- ed with a powerful microscope, numerous glo- bules, entirely resembling those seen in the nervous system, appear disseminated through- out its structure. As a result of this simplici- ty of conformation, it presents no perfect mani- festation of sensibility and contractility. It is not constituted of separate textures and organs, destined to perform specific purposes ; and, con- sequently, as no relation or bond of union is requisite between its parts, as in those animals which have particular organs or structures exe- cuting particular offices ; and as each of its in- dividual parts performs the functions of the whole animal,—so its nervous system is dis- seminated throughout its structure, without be- ing arranged into cords of communication or eentres of reinforcement, as in those animals which, endowed with distinct organs and per- fect functions, possess both. As we rise in the scale, on the contrary, we perceive in the more perfect, and in the highest animals, the intimate texture of the nervous system, arranged so as to form communicating cords between organs which are distantly sepa- rated from each other; and not only are they provided with these, but each viscus frequently possesses, in addition, a separate nervous cen- tre, on which the functions performed by that viscus depend: whilst the former arrangement is calculated to preserve a reciprocity of action — a mutual dependence of parts and of func- tions, the latter generates a vital influence mo- dified in kind and in degree to the part which it actuates ; which influence, in conjunction with what the organ may receive from a common centre, and what may be generated in the nerves of its own structure, is exerted in the production of the functions of which the con- formation of the organ is but ihe mechanical instrument. Thus the vital influence is fur- nished to the different viscera in proportion to, and suitably with the nature of, its expenditure in the more complex and more complete exer- tion of the operations which each of them is destined to fulfil. Respecting this subject? therefore, the fol- lowing propositions may be stated'.— That ac- cording to our own observations, as well as those of Prochaska, the Wenzels, Bauer, and Edwards, corpuscles or globules, entirely simi- lar to those of which the nervous system is com- posed, are found disseminated, without any re- gular order, throughout the apparently homoge- OF THE ELEMENTART lOLlDi 3 neous structure of the lowest order of the animal kingdom : that, as we rise in our observations through the scale of animals, we perceive this dissemination of the nervous corpuscles exist- ing only in the mucous structures ; and, as the animal presents separate organs destined to the vital operations, so these nervous corpuscles are disposed into cords of communication, and we observe a distinct nervous mass or masses, each organ possessing in addition — the higher that we ascend in the scale more especially — a detached but dependent nervous mass or gan- glion of reinforcement, which varies in form, appearance, and connexion with other organs, or with other parts of the same system, accord- ing to the functions which it is destined to ac- tuate.— See the notes on Generation, and on the Developement of the Textures of the Body, for some farther remarks illustrative of this sub- ject. OF THE PRIMARY SOLIDS AND COM- POUND TEXTURES OF THE BODY. (.Note C. See p. 13.) The intimate or elementary constitution of the animal textures has long engaged the at- tention of anatomists and physiologists. As researches respecting this subject can only be prosecuted by means of the microscope, the re- sults must, therefore, be received with some degree of reservation, unless they coincide with the observations of former inquirers, or be con- firmed by subsequent observers. From amongst those who have engaged in this species of in- vestigation, J. F. Meckel is entitled to much confidence, on account of his talents and indus- try ; and the results of his labours claim parti- cular notice, as they confirm much that has been recorded by former observers. According to the views of this physiologist, the solids and fluids of the human body may be reduced to two elementary substances: the one is formed of globules, the other of a coagulable matter, which, either alone or united to the for- mer, constitutes the living fluids when it is in the liquid state, and gives rise to the solid tis- sues when it assumes the concrete form. The globules present, in their nature and aspect, differences which are relative to the situations in which they are examined. They appear in the blood flattened, and composed of a central part which is solid, and of an exterior portion which is hollow and vesicular. Those found in the kidneys are smaller than those of the 3pleen, and the globules of the liver are still smaller; those contained in the substance of the nerves present a less volume than those ob- served in the blood. Globules exist not, according to Meckel, in the proper structure of the cellular tissue, of fibrous and cartilaginous parts, and of the bones. On the contrary, they abound in nerves and muscles, and determine their nature and colour. Some of the fluids, also, as the urine, contain no globules, whilst they are abundant in the blood, in the chyle, the lymph, milk, &c. During the first period of conception, the * Journ. CompUm. des Scien. Mid. Nov. 1821. i It should be kept in recollection, that fibre is used as signifying an elementary animal •ubstance ;—tistue indicates a certain arrange- mucous and homogeneous mass which consti- tutes the embryo contains no globules ; it is not until a more advanced period that it is compos- ed of two substances, the one fluid the other solid. These two elements seem to influence the form of the fibres and plates in which ani- mal substances are disposed. The laminated tissues arise almost exclusively from the fluid matter. • The fibrous tissues may also be pro- duced from this matter alone, as in the tendons, &c.; they are, however, more frequently form- ed from the union of the globules with the con- cretive fluid, as may be observed in the nervous and muscular textures. These observations of Meckel respecting ani- mal organisation, it ought to be noticed, bear a near resemblance to the opinion entertained by Pfaff, who considered the elementary tissues to be formed from a series of molecules and glo- bules, and to be different according to the pre- sence and^ influence of the latter form of mat- ter. The' idea of an animal fluid, capable of concretion, is analogous to the opinion of the ancients respecting the substance denominated by them gluten. It is the cellular tissue, accord- ing to Meckel, which represents that substance ; and, in fact, he regards this tissue as a species of concrete fluid, possessed of the properties already indicated. It must, in our opinion, be admitted, that the theory of Meckel possesses claims to a favour- able notice. It is the result of observations which accord with those of others; it is also simple, and is easily to be reconciled with the phenomena which living textures present. Dr. Meyer, of Bonn,* also considers that two kinds only of elementary textures exist in ani- mal bodies. The one is, according to him, com- posed chiefly of capillary vessels, and is formed from the assemblage of these vessels ; under it he arranges cellular, serous, fibrous, and mu- cous tissues : the other possesses a proper and peculiar parenchyma, composed of globules, or of an organic pulp ; such are the glands, the bones, muscles, nerves, the brain and spinal cord. The first set of organs is a continuation, in his opinion, of the vascular system ; while the second, on the contrary, is farther removed from such a connexion. Foreign substances introduced into the circulation pass immediate- ly, and with rapidity, into the former texture3 ; while they either fail altogether in penetrating, or insinuate themselves much more slowly, and after quite a different manner, into the paren chyma of the latter organs. The one class seems to appertain in general to the system of secre- tion ; the other class of textures neither secrete from their own individual influence, nor can they of themselves add to their nutrition. The first appears to be nourished by the immediate, rapid, and continual access of the fluid part of the blood ; the second by a slow and periodic deposition, and conversion into their proper substance, of the sanguineous globules of the blood, by means of the influence of the vascu- lar extremities upon the blood which they con- tain. The primary solids, or rather the elementaryt fibres of the human body, and of the higher ment of the former—a peculiar structure of parts ;—and organ signifies a compound or com- plex part which performs functions peculiar to itself 4 APPENDIX. classes of animals, cannot be considered v\ ith propriety to be more than three—the cellular or laminar, the muscular, and the nervous. 1st. The cellular fibre is the most essential to animal existence, and is found in every in- dividual of this kingdom. It consists of an as- semblage of minute lamina? and delicate fila- ments. It is neither sensible nor irritable, and is chiefly composed of a nearly concrete gela- tine. 2d. The muscular fibre is not so generally distributed throughout the animal kingdom as the former, for it is not found in the zoophytes. 3d. The nervous or medullary fibre. The nature of this tissue has been the subject of much in- vestigation. M. de Blainville thinks that it originates in the muscular fibre, as this latter takes' it origin in the cellular substance. To these fibres Professor Chaussier has add- ed a fourth, namely, the albugineous fibre, which is satiny, white, and very strong ; and is neither sensible nor irritable. The majority of anatomists, however, consider it as merely a very condensed variety of the cellular fibre. These fibres may be called the first order of solids, as they serve to form all the other tis- sues and organs of the body. The cellular substance, for instance, is spread out and con- densed into membranes, or rolled up in the form of vessels ; muscular fibres also assume the form of membranes, concur in the formation of vessels, and constitute muscles ; nervous fibres produce the nerves, &c. Finally, those pri- mary solids associate in various forms, and give rise to the compound solids, as the bones, the glands, &c.; and even to those of a more com- plex nature, as several of the thoracic and ab- dominal viscera. Indeed, every species of solid has for its base cellular substance, which is penetrated by nerves and vessels. The viscera, for example, are of this nature, having, more- over, membraneous envelopes. The bones al- so consist of a similar texture, and of a deposi- tion of phosphate of lime in their cellular sub- stance.* Those primary solids, or most simple anato- mical constituents, which we have just now particularised, associate in various forms, giv- ing rise to compound solids or tissues, which are characterised not only by their form and nature, but also by the functions which they perform. , These animal textures or compound solids were first arranged with any degree of accu- racy by Biehat ; and however successful future researches into their ultimate nature may be, or whatever classifications may be proposed by future inquirers, he is still entitled to the ho- nour of having introduced a philosophical analy- sis into anatomical and physiological science. The arrangement of the tissues which this great man adopted is as follows. The exhalent, absorbent, cellular, arterial, venous, nervous of animal life, nervous of organic life, osseous, me- dullary, cartilaginous, fibro-cartilaginous, fibrous, muscular of animal life, musadar of organic life, mucous, serous, synovial, glandular, dermoid, epi- dermoid, and corneous or pilous, systems. The exhalent, absorbent, cellular, arterial, venous, and nervous systems, he considered as being * See Adelon's Physiology, vol. i. p. 108. t Andt. Generate, p. 100, et seq. % Manual of Descriptive, General, and Pa- thological Anatomy, vol. i. p. 22, et seq. the frame-work of the body, and as generating the other structures, which he denominated the compound tissues. M. Dupuytren has lately proposed another classification, possessing some advantages over that of Bichat. He has reduced the number of textures or systems to twelve, viz.—the cellular ; the vascular, subdivided into arterial, venoUs, and lymphatic ; the nervous, divided into tha< of the ganglions and of the brain ; the osseous, the cartilaginous ; the fibrous, comprehending the fibrous proper, the fibro-cartilaginous, ana the dermoid ; the muscular of voluntary and in- voluntary motion ; the erectile ; the mucous ; the serous ; the corneous, embracing the pilous and epidermoid tissues ; and the parenchyma- tous, forming the viscera, and including glan- dular structures. M. Beclardf admits but ten systems : the cellular and adipose, the serous and synovial, the tegumentary surfaces, comprehending the skin and mucous membranes ; the vascular, the glandular, the ligamentous, the osseous, the car- tilaginous, the muscular, and the nervous. J. F. Meckel}: also admits but ten animal structures : the cellular or mucous, the vascular, the nervous, the osseous, the cartilaginous, the fibrous, the fibro-cartilaginous, the muscular, the serous, and the dermoid. M. de Blainville^ considers that the animal structures amount to sixteen, of which nine are produced from the cellular fibre, three from the muscular fibre, and four from the nervous fibre. In the first division he arranges the der- moid, mucous, fibrous, cartilaginous, osseous, se- rous, synovial, arterial, and venous (embracing the lymphatics) systems. Under the second di- vision he places the sub-dermoid or voluntary muscular system, the sub-mucous or involuntary muscular system, and the heart. To the third division'he assigns the pulpy ganglial system, the non-pulpy ganglial system, the nervous sys- tem of animal life, and the nervous' system of or- ganic life. Professor Mayer has recently adopted a clas- sification of the animal textures or compound solids, founded on his views respecting the ele- mentary fibres or primary solids. He recog- nises only eight systems, viz. 1st, the lamellated tissue ; 2d, the cellulo-filamentous tissue ; 3d, the fibrous system ; 4th, the cartilaginous tissue; 5th, the osseous tissue ; 6th, the muscular fibre ; 7th, the glandular structure ; and 8th, the ner- vous tissue. || The arrangement of solids which we would propose is nearly the same as that given by us at another place.IT Proceeding analytically, we would divide the compound solids of the body into four classes, viz. complex structures, parti- cular textures, general systems, and elementary fibres or solids. I. Complex or Associated Structures. —1st the digestive organs ; 2d, organs of absorp- tion and circulation; 3d, of respiration and assimi- lation ; 4th, organs of secretion and excretion ; 5th, organs of motion and of sensation ; and 6th, or- gans of generation. II. Particular Textures.—This class in- cludes, 1st, the mucous textures ; 2d, serous tex- tures ; 3d, the fibrous textures, embracing the § Princip. d1 Anat. Comp. t. i. p. 13, et seq. II Bibliotheque Germanique, No. viii. t. 2. IT London Medical Repository for July 1823. OF THE COMPOUND SOLIDS. 5 fibrous, the fibro-cartilaginous, and the dermoid; 4th, the cartilaginous textures ; 5th, the osseous textures ; 6th, the erectile textures ; 7th, the glandular textures, including the parenchyma of the viscera ; 8th, the corneous textures, embrac- ing A, the pilous, and D, the epidermoid tex- tures. III. General Systems.—Under this class we would arrange, 1st, the cellular system ; 2d, the nervous system, which comprehends two orders, viz. A, the involuntary or ganglial order of nerves, or the system of the great sympa- thetic, and B, the voluntary order of nerves ; 3d, the muscular system, which also embraces two Orders, A, the involuntary order of muscular fibres, B, the voluntary order of muscular fi- bres ; 4th, the vascular system : this system has four orders, viz. A, the arterial order of vessels ; B, the capillary order ; C, the venous order ; D, the absorbent vessels, including a, the lymphatics, and 6, the lacteals. IV. Elementary Solids or Fibres.—1st, the cellular fibre ; 2d, the muscular fibre; and 3d, nervous corpuscles and fibres. Proceeding synthetically, we may arrange all the solids of which the animal body is compos- ed after the following manner:— class i. elementary animal solids; The cellular fibre. The nervous fibre. The muscular fibre. CLASS II. SECONDARY OR COM- POUND ANIMAL SOLIDS. Order I. General Systems. The cellular system. The nervous system. Including the adipose A. The involuntary or tissue. ganglial order of nerves, or system of the great sym- pathetic. B. The voluntary or- der of nerves. The muscular system. " The vascular system. A. Involuntary muscles. A. Arterial vessels. B. Voluntary muscles. B. Venous vessels. C. Absorbents. a. Lymphatic ab- sorbents. b. Lacteal absorb- , ents. Order II. Particular Textures. Mucous textures. Serous textures. Erectile textures. Fibrous textures. A. The fibrous. B. Fibro-serous mem- branes. C. Fibro-cartilaginous tex- tures. D. The dermoid textures. * Elements of General and Pathological Anatomy, Edinburgh, 1828. •f In the account given by Dr. Craigie of the various arrangements of the animal textures proposed by anatomists, he has quoted the one Glandular textures. Corneous texture. ^Cartilaginous textures. A. The epidermoid. Osseous textures. B. The pilous. CLASS III. ASSOCIATED OR COM- PLEX ANIMAL STRUCTURES. Order I. Organs of Nutrition. Digestive organs. Organs of absorption and cir- Organs of respi- culation. ration andassi- Organs of secretion and ex- milation. cretion. Order II. Organs of Relation. Organs of sensation. Organs of voluntary motion. Order III. Organs of Reproduction. Organs of generation in both sexes. Dr. Craigie* has lately given a different enu- meration of the simple tissues, which he de- scribes in the following order:—filamentous or cellular tissue, including cellular and adipose membrane, artery and vein, with the capillary and erectile vessels; lymphatic vessel and gland; nerve, plexus, and ganglion ; brain; muscle ; white fibrous system, including liga- ment, periosteum, and fascia ; yellow fibrous system, including the yellow ligaments ; bone and tooth ; gristle or cartilage ; fibro-cartilage ; skin; mucous membrane ; serous membrane ; synovial membrane ; compound membranes, as the fibro-mucous and fibro-serous ; and the pe- culiar matter which forms the glandular or- gans.! OF SENSIBILITY AND CONTRAC- TILITY. (Note D. See p. 14.) Sensibility. — The phenomena classed by the author under this property of animal life, at p. 14 and 15, are evidently referrible only to or- ganic contractility, with which all classes of animals are endowed, and which, in the lowest orders and in some vegetables, assume the ap- pearance of sensibility. In these, however, we have no reason to infer the presence of sensi- bility, merely because they contract under the influence of a stimulus ; for the contraction may take place without the existence of this property, from the effect produced by the stimu- lus upon the organisation of the contracting part. Indeed, we cannot suppose that sensibi- lity is present where the parts generally observ- ed to be instrumental in its production are not found to exist: a sensation cannot be supposed to be produced where there neither is an organi- sation suitable to receive, a channel to convey, nor an organ to perceive an impression. We should, therefore, limit this term to those phe- nomena which the author arranges under that of perceptibility. proposed by us in the first edition of our notes, but, by mistake, has attributed it to M. Riche- rand, whose classification is in every respect different, if indeed it may be considered as an attempt, at classification at all. 6 APPENDIX With this limitation, sensibility may be called the function of sensation, and a property pecu-' liar to the animal kingdom. The sensations are derived through the medium of the senses and of the nerves, which are distributed to cer- tain parts of the body, and which communicate with the encephalic centre. On this centre the existence of sensibility chiefly depends ; the ramification of its nerves, or the subordinate portions of it, being also parts of the apparatus requisite, but not giving rise to this property. As we ascend in the scale of creation, and as we perceive the senses and the organs of voli- tion in more intimate relation with this nervous mass—the encephalon,— so we find sensibility becoming more perfect, until in man it reaches an extent greatly surpassing that in which we observe it in any other animal. In man, and perhaps in the more perfect ani- mals, the modes of sensibility seem to vary. These modes may, however, be divided into two conditions, as they are more or less active ; namely, conscious or active sensibility, and in- conscious or passive sensibility : the former re- lates to those impressions, either from within or from without, which give rise to perceptions or ideas; the latter to those that are frequently produced upon the senses and upon the ramifi- cations of the cerebal nerves, and, owing either to habit or the want of due attention to them, are not perceived by the mind. In this latter mode of sensibility, the organ receiving, and the channel conveying the impression, perform their offices ; but the mind either is not, at the time when the impression is made, in a state to receive it, or receives it so imperfectly, from its weakness oj its transient nature, as not to give rise to consciousness. This mode does not necessarily imply a difference in the degree of sensibility, but the condition in which this pro- perty exists, owing either to its being more ex- cited by other impressions, or to its being ex- hausted at the time when the impression is made. This condition is one to which the high- est manifestations of sensibility as well as the lowest may be occasionally subject: it is, how- ever, merely a relative mode of this property; and the relation subsists extirely between the state of the cerebral organ which perceives, and the force and duration of the impression made upon the organ of sense. Thus, when the sen- sibility is actively occupied with a particular object, and an impression is made at the same time upon a different organ from that through which the perception with which the mind is engaged was conveyed, the second impression may affect the senses in an evident manner, and even so as to influence volition, yet we may be unconscious of its operation, and no active perception may result from it. If, however, the second impression be stronger or more vivid than the first, or if, from various other circum- stances, it should excite the cerebral functions, active sensibility or consciousness is the result. As sensibility, according to this view of the subject, is, in it3 active state, a term merely ex- pressive of consciousness in the wide range of this very generally diffused faculty of the ner- vous system; and as this faculty is evidently dependent upon this system, especially on that more complex part of it which holds relation with surrounding objects; and, also, as we have no reason to attribute the possession of this part of the nervous system to the very lowest orders of animals, particularly to the class radiata,— sa we roust conclude that, although ' sensibility is a property of animal life, its high- er grades are not possessed by all animals. It may be also stated, that active sensibility, being considered as expressive of the consciousness of the whole class of sensations, and of all the intellectual and moral ( perations, varies in its extent throughout the animal kingdom, accord- ing as those manifestations are more or less numerous and perfect. How far the passive mode of sensibility, or that unattended by con- sciousness, may be a property of the lowest orders of animals, is difficult to say. We may, however, infer, that as this condition of sensi- bility may take place without an active exer- tion of this property in the highest animals, so it may result from a less perfect endowment of sensibility in the lower; and as this mode may require a less complex apparatus for its produc- tion, inasmuch as its relations are more simple, so it may be possessed by animals whose or- ganisation and manifestations do not permit us to conclude that they are capable of evincing sen- sibility in its more perfect and active conditions. The relations which this form or mode of sen- sibility holds with the numerous instincts of animals, must be evident to all who consider thd subject. The relations, however, which evi- dently subsist between that form of sensibility called organic sensibility by Bichat, and the animal instincts, are much more numerous, more intimate, and more apparent. Organic sensibility refers to those sensations which are produced in different degrees of in- tensity, owing to the existence of certain con- ditions of those viscera which are immediately subservient, to the preservation of the individual and the species—to nutrition and reproduction, and which are not immediately subjected to the influence of volition. The conditions of the parts exciting sensibility are very various, and are the result of irritations arising from the pre- sence of a stimulus, of unnatural actions super- vening in particular systems or textures, and of the deficiency of that stimulus or influence to which particular viscera have become accus- tomed. Many of the changes preceding this class of sensations seem to interest, in the first instance, the ganglial class of nerves ; but, owing to the intimate relation subsisting be- tween thi3 part of the nervous system and the voluntary or sentient part, the impression or change is propagated to the brain. This is the only essential difference which exists between this and the other forms of sensibility. It is the brain which perceives in them all; and al- though stimuli, or the defect of stimuli, may give rise to certain phenomena possessing the characters of the higher manifestions of this property in the organs appropriated to the pre- servation of the organic system, independently of the sensorium,— consciousness, or the more perfect form of sensibility, cannot form part of the results. Organic sensibility may be active or passive —it may or it may not be attended with consci- ousness ; and even the unconscious mode of it may indirectly impel to action, or give rise to many of the manifestations or instincts which characterise the lower animals, owing to the ganglial centres, either from their organisation or connexions, or from both, performing a great- er extent of function than usually falls to their share. If, therefore, the passive form of organic sensibility may propel to action without con- or CONTRACTIUTT—SYMPATHT 7 ■ciousness, or the sensorial sensibility being excited, in these animals, we may also account in the same manner for many of the instinctive functions being performed when we cannot trace them to the influence of a cerebral organ. Of all the conditions of sensibility, the active organic form is the least under the control of the mental powers. It also, in all its modes of existence, more intimately interests the exist- ence of the individual than the other forms of sensibility,—organic sensibility involves a feel- ing in all its active manifestations instinctive of life or death. From this it will be readily seen how close a connexion exists between organic sensibility and the animal instincts : it does not belong to our plan to trace the connexion in all its rela- tions. Of sensibility generally we may observe that, in the human species, it is very variable; in Bome persons it is very much exalted, in others very obtuse. It is vivid in early life and in youth ; after the age of manhood it gradually diminishes; as old age advances, it decreases rapidly; and in persons who have attained a greater age, it.is present in the lowest grade in which we find it in the species. Contractility is essentially a vital phenome- non, and is the result of a change in the rela- tive position of the molecules composing the solids of a living body. This property may be divided into the following grades, commencing with the lowest, it being the most generally, diffused throughout nature :— 1. ■Insensible organic contractility, or that Usually denominated tone or tonicity. This grade of contractility is not confined to the animal kingdom ; it is a property of vegetables, and of animals not possessed of a heart. It is diffused throughout the tissues. The vascular system possesses it in the most eminent degree ; and it may be viewed as the result of the vital in- fluence with which the structures are endow- ed : it is more or less perfect as the vital energy is perfect, and it disappears with the extinction of this principle. It is a property of the tis- sues and of the vessels, which is more or less exerted in all the vital operations — in the cir- culation, the secretions, nutrition,-and absorp- tion. The ganglial or organic class of nerves seems to be instrumental in its production and preservation in the animal kingdom. 2. Sensible organic contractility ox irritability is that inherent property of contraction which exists in all muscular and in some other tex- tures. It is excited by the application of a variety of irritants. It seems to depend upon the ultimate distribution of the nervous sub- stance to these parts, and chiefly upon the nerves proceeding from the ganglia. Both these species of organic contractility seem to result from one species of influence, with which animal bodies are endowed — they are the proximate result of vitality, and merely differ from each other owing to the intimate structure of the parts in which they are seated, and to the extent to which each of the parts evincing their presence is supplied with gan- lial ramifications. 3. Cerebral contractility is the contraction oc- casioned by the will in voluntary muscles. It takes place only in such musculai parts as have nerves proceeding from the encephalon, or rather from the medulla oblongata and spinal chord, terminating in their structure, and Is the result of this conformation and connexion with theas large nervous masses. The fiist and second species of contractility result from the ganglial distributions and ia- fluence, the third from the superaddition of the nerves of voluntary motion. Whilst, therefore, sensibility, in its more per- fect grades, is the function of the sensations, is chiefly confined to certain parts and textures of the body, and is dependent upon the part of the nervous system of which the encephalon is the centre, contractility exists throughout the whole animal structures, although in different grades, and is, with the exception of the third species or grade of its existence, entirely inde- pendent of sensibility and volition ; — contrac- tility is a general expression of life, sensibility of the higher functions only of this principle. OF SYMPATHY. (Note E. See pp. 24—28.) Baglivi attributed the sympathies to mem- branous connexion ; Bordeu to the cellular tis- sue ; Willis and Vieusens to the agency of the nerves ; and Whitt and Broussais chiefly to the brain. Rega divided the sympathies into those of sensibility and those of contractility—a divi- sion which has much to recommend it. Bichat offered some very excellent observations on the relations subsisting between them and the dif- ferent parts of the nervous system , but, al- though these observations were calculated to lead to a more correct arrangement of the sympathies than had been formerly offered, it has not come to our knowledge that any has appeared founded on a better basis than that indicated in the observations of Bichat. In the note at p. 26, we suggested that the sympathies should be arranged into the reflex and the direct; the former arising through the instrumentality of the sensorium, the latter tak- ing place independently of it, through the means of the ganglial nerves, and chiefly of those which are distributed to the blood-vessels, and which form communicating chords between the viscera: With a view to the illustration of the latter class of sympathies, viz. those which are direot, and chiefly consist of the sympathetic actions of organic life, we shall offer a few remarks. When it is considered, that the ganglial nerves alone supply the blood-vessels and the secreting organs and surfaces ; that they ac- company these vessels to the utmost limits of their ramifications ; that they communicate very freely with each other, and with their chief centre, the semilunar ganglion ; that they give rise to numerous plexuses, which render the connexion between them still more intimate; and that they hold a close relation with the rest of the nervous system, through means of com- municating nerves ;—the mutual dependence of action between the chief organs of the body, in health and in disease, may be easily explain- ed. If, moreover, it be granted that the most important vital phenomena, as digestion, assi- milation, circulation, secretion, animal heat, generation, &c. (see the Note on the functions of the ganglial system,)—in short, that life itself, with all those manifestations of it now particu- larised, and which have been usually called 8 APPENDIX. organic, results from the influence exerted by this part of the nervous system, through the in- strumentality of the vessels upon the fluid they contain, and in some measure reciprocally by this fluid upon these nerves ramified in the pa- i-ietes of the vessels, and upon the ganglia themselves, through which it must of course cir- culate,— the agency of this system in the pro- duction of the class of sympathies under con- sideration must be evident. From this view of the subject, and from taking into account the modifying operation of similar textures, the re- lated action of various organs, and, under cer- tain circumstances, the combined influence and jre-action of the sensorium, the numerous rela- tions and connexions of healthy function and of disordered action may be more satisfactorily traced. When one organ or system of parts is excited to increased action, or when its operations are diminished or obstructed, we perceive all the other parts of the system which communicate with it through the medium of the ganglial system, experiencing a modification of their functions, — the action of one or more organs * When the natural functions of one organ are simply excited, without being diseased, the functions of other organs with which it holds communication, by means of the ganglial nerves, undergoes a relative degree of change, — for the excitement of a viscus is merely an exaltation of its vitality; and, as we exalt the vital actions in one or more departments of the entire series, we diminish them throughout the rest in an equal proportion; the excitement be- ing frequently greater or less in some parts, and the diminution more or less confined to others. If, for the sake of illustration, we suppose the vital energies of the system to be equal to 50 ; and, through meaas of the organic or ganglial nerves to~be distributed as follows ;—to the sto- mach and intestines, 7 ; to the heart, vascular system^ and lungs, 8 ; to the brain and volun- tary nerves, 7; to the liver, spleen, and pan- creas, 6; to the generative organs, 3; to the urinary apparatus, 4; to the surface of the body, 3 ; to the rest of the body, 11 ; we may consider that it is duly proportioned. But if, owing to the application of certain excitants to one or more organs, as to the stomach and in- testines, we exalt the proportion bestowed on these to 13, we shall consequently find the brain and voluntary nerves possessing only 5; the heart, vessels, and lungs 7 ; the urinary organs 3 ; the surface of the body 2 ; and the rest of the body experiencing the loss of the remain- ing one. If, again, we excite the vital forces distributed to the heart and vaseular system until they amount to 16, we shall have a febrile condition of the system in its simplest form, and all the other organs will suffer a diminution in proportion: the stomach will only equal 4, and so on in proportion. But the vital forces of the heart and blood-vessels may equal 16; and, owing to the arteries of the brain experi- encing an undue proportion of this increase, this organ may at the same time equal 10 ; or, instead of this increase falling to the lot of the cerebral vessels, those of other viscera may be similarly augmented, whilst those of the re- maining organs may be proportionally dimi- nished : in such cases we have a less simple rc- having always an evident relation to the kind and degree of action going on in the other. In these cases the relation is sufficiently manifest; but the kind and degree of it may vary very greatly between different organs. And the re- lations may be of the following sorts, as the vital energies distributed throughout the system are affected in degree or in kind, or in both ways at the same time. I. Organic sympathies, in which the vital energy of the system evinces various modifications in de- gree and distribution, but in which it is not chang- ed in kind. 1. Related actions may be characterised by a due proportion or a healthy degree of the vital forces of the whole system; but, owing to t>he application of an exciting cause to one organ or part, or to two or three organs, these forces may be greatly increased in them; as, however, the healthy, or medium quantity of the vital forces of the body is not supposed to be exceed- ed, there consequently must be a diminution of these forces throughout the other parts of the system,* in proportion to the increase in the ex- cited organs. suit; but, nevertheless, the increase of the cir- culating functions is followed by an equal di- minution of the secreting. Viewing the sym- pathetic connexion of function in another direc- tion, we shall suppose that the excited state of vital action takes place in secreting organs : in this case the nutritive and other animal opera- tions are diminished in an equal degree-. Or we shall suppose that the excitement commeji- ces in the capillaries, of an organ, from the presence of an irritating cause ; that, owing to these vessels being supplied with ramifications of the same order of nerves which supply the heart and vascular system generally, the excite- ment extends more or less throughout this sys- tem ; and that, in consequence of the continui- ty of this order of nerves, and their very fre- quent reticulations and inosculations, not only do the heart and arteries experience the excite- ment produced at a part of the extreme circum- ference, but the whole body suffers a relative degree of derangement, and hence evinces all the phenomena of sympathetic fever. Thus, the capillaries of a particular organ are excit- ed ; the excitement extends more or less gene- rally throughout the vascular series, and the nutritive and secreting functions are diminish- ed in pioportion as the actions of the heart and arteries are increased. Many collateral views of this subject may be adduced, and many of its.connexions traced, as well as various modi- fying influences, both in and out of the body, appreciated — all tending to establish the posi- tion, that it is chiefly to the ganglial nerves wc ought to attribute the manifold phenomena of related action which we observe in the animal economy. At this place we have only consi- dered one of the genera belonging to this class of sympathies, namely, that which comprehends the most simple of the related actions — those which supervene in the system without an in- crease or diminution of the whole amount of the vital energies with which the body is en- dowed. The other kinds of related function have been pointed out in the above arrange- ment of this class of sympathies, and we can- not farther allude to" them here ; indeed, it would be much beyond our limits to consider OF OUGANlC SVMPATMV. 9 In this order of sympathies there are three relations to be observed, which actually more or less obtain and constitute the essence of the subject, or the actual condition of the animal functions under consideration; 1st,the relation may respect the increased actions subsisting in two or more organs ; 2d, it may be viewed between the increased functions of one part and the diminished functions of another; and 3d, it may regard the diminished functions ob- served in those parts which do not participate in the excitement; the relation being most im- mediate in the first, and least so in the third of these forms. 2. The sympathetic or related actions may be attended with a diminution of the sum of the vital energies throughout the system. In this case the different relations pointed out above may nevertheless exist, or one or Iwo of them only may be remarkable ; the chief diffe- rence here being that the sympathies of this order are generally induced by agents, which, while they diminish the entire sum of vital ener- gy, act more decidedly upon particular organs or systems of parts. 3. The sympathetic operations may be cha- racterised by a somewhat greater amount of the vital energies of the whole body-. In this order of sympathies the three relations particularis- ed above also subsist; for although the entire sum of vital actions may be greater than what is usually bestowed on the system, it may be so much increased in some oigans -is to be greatly diminished in others. This condition of functional sympathy seldom continues long, until it subsides to the first, or, from exhaustion of the vital energies, to the second order just now particularised. II. Organic sympathies in which, in. addition to various modifications in degree and distribution, the vital energy of the system suffers a change in its kind. 1. Svmpathetic actions in which the general amount of the vital forces is natural in degree, but vitiated or modified in kind, the relation be- ing evident—1st, mutually between those func- tions which are increased; 2d, between the ac- tions which are augmented and those which are diminished ; and 3d, between those only which are diminished. . 2. Sympathies in which the entire sum of vital energy is both reduced in degree and modified in kind ; the relation between its distribution in the various organs being the same as just now pointed out. 3. Sympathies in which the amount of the whole vital energy is both heightened in degree and modified in kind. In this order, the distri- bution and the relations to which such distribu- tion gives rise are the same as already adduc- ed. . , . The application of this classification, and ot the views whiclv it embraces, to medicine, must appear evident. OF HABIT. (Xote F. See p. 27.) In the note at p. 27, we have said that the effects of habit upon our voluntary organs are fully the different kinds of sympathy in their manifold relations; we have illustrated one more particularly, because of its importance, very different from those which result from its influence on the viscera of organic life. This difference is, however, chiefly in degree ; for as sensibility, there is every reason to suppose, from its most vivid state of existence, until it merges in contractility, and in its various modes of manifestation, differs chiefly in degree, and as it is bestowed in some one mode and degree to all the organs of the body, although it be more particularly limited to one of their tissues, and also as the influence of habit is chiefly ex- erted upon the sensibility of the system,— so it follows that it modifies more or less all the ani- mal and organic functions, although it acts in the most manifest manner on those organs which are in the closest relation with the sen- sorium or functions of the brain. Thus the stimulus which excites the action of the sen- sorium produces a much less intense effect by repetition ; but the repeated employment of the same food, or of the same purgative, does not materially less excite the action of the viscera to which they are respectively applied. As the influence of habit, therefore, is chiefly on the sensibility of the system, so it follows, that when the organic sensibility of the involuntary organs is repeatedly excited, it. is then that the diminished effects of the excitant upon them are most manifest—that the more the sensibili- ty of our organ is called forth, the more is the influence of habit remarkable. Those stimuli, however, which act chiefly and the most exclu- sively on the contractility of the textures> and those organs whose actions principally consist in the exertion of this principle of life, have their operations the least impaired by repeated employment; indeed, in many instances those organs have their functions increased and ren- dered more perfect by frequent exerti which it is necessary to searches on the circulation :— advert, is the question as to the active dilata: " 1. That neither the larger nor the smaller tion ofthe heart — a function of this viscus arteries present any trace of irritability. much insisted on by Hamberger, and more re- " 2. That they are dilated during the heart's cently by Carson and others. We doubt not systole. that it actually exists, to some extent, in all ani- "3. That they are capable of contracting mals provided with a perfect heart; but we do themselves w^h sufficient force on the blood not believe that it takes place with great energy, they'contain, so as to propel it into the veins. If the dilatation, however, of the heart were a " 4. That the blood in the arteries is not al- mere result of a relaxation of its fibres, its cavi- ternately at rest and in motion ; but that it is, ties could not be so quickly and perfectly filled on the contrary, in a continued succedaneous by the mechanical pressure of the blood direct- (by little jets) motion in the trunks and rami- ed towards them, as we observe that they are ; fications, and uniform in. the smallest ramifica- and dilatation would be only the consequence tions and divisions. of this pressure, and be proportionate to it. " 5. That the contraction of the left ventricle But this is not the case ; for, as far as we could of the heart, and the elasticity of the larger judge from observing the circulation in fishes, and smaller arteries, furnish a satisfactory me- the dilatation seems to precede the flow of chajiical reason for these phenomena. blood, the latter appearing as a consequence of " 6. That the contraction of the heart and the former. arteries has a considerable influence on the Allowing, therefore", that the dilatation of the course of the blood through the veins." cavities of the heart takes place to a certain We cannot concur in these conclusions, espe- extent — an extent which it is difficult fully to cially in the sweeping inference which forms determine, but which we consider much less M. Magendie's fifth proposition ; and we might, than that contended for by Hamberger and Car- were it consistent with our limits, point out son,—one of the causes of the flow of blood in -vartous fallacies in his experiments, to some of the large veins will be apparent. which, indeed, all experiments on living sub- The heart is perfectly insensible in its natifral jects are more or less liable, viz. the unnatural state. This was satisfactorily shewn in an position of the animal during their performance, operation performed by M. Richerand in 1813, and more particularly as respects the operations wherein he divided the ribs, and removed a por- of the part immediately its subject. If M. Ma- rion of scirrhous pleura, thus allowing the peri- gendie limits the process to the mechanical cardium to be exposed. The patient was per- means indicated above, we would ask, how he fectly insensible of any impression when M. accounts for the influence of mental emotions Richerand touched this organ, although the in determining the action of the vessels in par- pericardium, the part through which it was ticular parts of the body ? How the diversified handled, is evidently the most sensible part of influences of numerous external agents on the it during disease: in a state of inflammation circulation can be explained ? Wherefore so its organic sensibility becomes indistinctly and very opposite effects are produced upon the obscurely developed. arteries when one extremity is placed in a pail * Willis divided the eighth pair of nerves in the neck with a view of paralysing the action of the heart, but death did not supervene until some hours, and, in some cases, not until seve- ral days, after the operation. In the experiments of M. Legallois and Dr. Phillips, destruction of the brain and spinal marrow did not necessarily and immediately put a stop to the action of this viscus, although, as should be expected, it was greatly influenced by the privation of a neces- sary and an accustomed influence. . In experi- ments which we performed on several species of fishes, the actions of the heart continued long after the destruction of the cerebro-spinai masses, and frequently for a short time after it was removed from the body. Lastly, foetuses have been born, in which the action of the heart and circulation were perfect, although they wanted both brain and spinal chord ; and many of the lower classes of animals have continued to live for a very considerable time after decapi- tation. f See pp. 30, 31. OF THE FUNCTIONS Of THE CAPILLARIES. 39 Pt ice, and another in a pail of warm water ? How can he reconcile his conclusions with the Very satisfactory experiments performed by Sir Everard Home, Dr. Hastings, and others ? and how can he account for the determinations of blood to particular parts, whilst a diminished quantity is sent to other situations ?—if he dis- card the predominating or vital power which the vessels themselves, and especially their smaller ramifications, possess in virtue ofthe particular structure already noticed. We readi- ly grant that the larger branches of arteries evince littla or no contractile action, particu- larly in their natural state ; but we contend that it increases as we advance towards the ex- treme capillaries, the action of which derives the blood to them in larger proportion, and thus increases both the mechanical and vital proper- ties of the larger branches supplying them. We allow that the properties for which M. Magendie contends have an actual place in the process of arterial circulation ; but they are not the only ones ; they are insufficient of them- selves to accomplish the purposes which he as- signs to them ; and, moreover, they are secon- dary to, and controlled by, a superior influence. From these observations it.may be perceived that the arteries act in the process of the cir- culation, not by means of a contractile action similar to what is performed by the heart ; nor yet by means of elasticity only ; but by an or- ganic or vital operation, which is nearly imper- ceptible in the larger arterial branches, but which increases as we advance to the extreme capillaries ; whilst, on the contrary, the elastic or mechanical properties augment as we pro- ceed in the opposite direction. OF THE FUNCTIONS OF THE CAPIL- LARIES. (Note S. Seep. 134.) This class of vessels may be divided into two orders, performing distinct functions :—1st, Those capillary vessels between the termina- tions of the aortic arteries and the commence- ment of the veins of the body ; and 2d, Those between the termination of the pulmonary ar- teries and veins of the same name. The first of these orders is disposed, in different propor- tions, to the compound solids of the body ; the second is distributed on the surface of the air- cells of the lungs only, In the one are perform- ed changes which render the blood unfit for the purposes of the animal economy ; in the other takes place an elaborative process of an oppo- site nature. In the first are produced those or- ganic functions which relate more directly to the nourishment of the frame, as digestion, secretion, and nutrition ; in the second, those preparatory operations on the blood which en-' able the sensible and contractile textures ofthe body to perform their offices. Without the ac- complishment of the latter, the former could not be petformed ; for as the formei depends upon the vital influence distributed to the capillaries and to their respective organs, as well as upon its state.in the sources whence it is'derived, so does this influence itself depend upon the operations, which take place in the latter order of capillaries. The importance, therefore, of these operations in the animal economy must be manifest, as well as the intimate bond which unites them throughout the frame : without the performance of the one class of functions, the other could not be discharged. This part of the circulation, the most inter- esting, perhaps, of any to the physiologist and pathologist, without being independent of the heart's action, is the least under its control; the functions of the capillary vessels continuing to a certain extent, even after the heart has ceased to contract. And, as has been shewn by some experiments* performed in this country, in France, and in America,' these actions are not limited, even then, to the mere circulation of the fluid which they contain ; for under this particular circumstance, they may also per- form, for a short time, the functions of absorp- tion and secretion. These phenomena may be readily explained when we consider two circumstances :—1st, The source whence the capillaries derive their functions ; and 2d, the kind of death which the animal experiences, and the order in which the different organs cease to act^ We cannot enter here further into this topic ; we have pointed out the way, those who are interested in it will be able to pursue it ; those who are not, would profit little from a lengthened explanation. Before we leave this subject we may notice an opinion which has been entertained among the most eminent physiologists. This relates to the existence of subordinate sets of minute and colourless arterial capillaries, each devoted to a particular function ; namely, one to nutri- tion, another to secretion, and a third and prin- cipal set to the transmission of the red blood, which, in consequence of the functions of the former two, have become possessed of venous properties. The first and second of these sets are considered to be pellucid in their natural state, and, although they cannot be satisfac- torily demonstrated in this state, their existence seems to be rendered probable, if not proved, by many of the phenomena of disease, and by artificial injections. Dr. Alard has lately contended for the exist- ence of a similar set of colpurless vessels con- nected in the same manner with the veins ; and that whilst those of the arteries carry the fluids intended for the nutrition of the textures, for the secretions and exhalation,—these belonging to the veins perform the functions of absorp- tion. Some of these latter vessels, whose open mouths are present every where, in the most intimate textures of the organs, as well as on the surfaces of the great cavities, are supposed by Dr. Alard to terminate in the pa- rietes of the adjacent veins ; while others unite and form the trunks which are generally known by the name of absorbents. The discovery of Dr. Fohmann, of Heidelberg, of a communica- tion of the lymphatics of the intestines with the mesenteric veins in some animals, concurs to support the proposition of Dr. Alard. On this subject Dr. Hutchinson, whose physiological knowledge is of the first order, has justly ob- served :—The view of Alard,—that supposing the existence of minute pellucid vessels spring- ing-from the parietes of the small arteries ; dis- tributed to every part of the body ; conveying different fluids, and producing different effects, accoiding as their vital properties are modified ; having corresponding vessels-, which spring * See pp. 37, 38. 40 ATPENDIX, from the most intimate texture of the organs and surfaces of the great cavities, and unite in larger tubes, forming in some instances long continuous canals, denominated absorbents, in others running to be inserted into veins, — is one which is qualified to explain, more plausi- bly than any other, the mechanism of the dis- tribution of the fluids for the purposes of the organic functions ; and is, besides, capable of obviating the difficulties which have been pre- sented by the diversity of the results-of the ex- periments of Hunter, Magendie, Brodie, and others, relative to the mechanism of absorption. * OF THE VEINS. % (Note T. See pp. 135, 137, 139.) 1. As to the precise way in which the veins commence, opinions have been various. At the place where the capillaries change from arteries into veins, there appears to be no reason to sup- pose the existence of either interspace, or vehi- cular or spongy structure. The inflected canal of the artery seems to be continuous with the vein. Whilst, however, this conformation is allowed by nearly all, some consider, with Mr. Ribes, that the veins have another commence- ment in addition to this ; and that a certain pro- portion of their radicles commence in open mouths or in the pores or»areolae of the lami- nous tissues, and in the substance of the or- gans. Others" also suppose, with M. Alard,f that some of their roots commence in pellucid lymphatic absorbents. The structure of the erectile tissues, as the penis, the clitoris, the spleen, &c. seems to support the opinion of M. Ribes, (which is also that of M. Meckel,) who farther supposes that one cause of the difference of the appearance and functions of organs may be ascribed to the extent to which the veins originate in the par- ticular manner for which he contends. The views of M. Alard derive their chief support from the phenomena connected with absorption ; but, although they appear proba- ble, they cannot be fully demonstrated. The veins receive but a small proportion of nerves, and these are chiefly from the ganglia. The nerves supplying the pulmonary veins come principally from the anterior pulmonary plexus. 2. The functions of the veins are, — 1st, to bring back the blood from the capillaries to the heart ; 2d, to receive and assist in the assimi- lation of the fluids, which are absorbed by the lacteals and absorbents ; and 3d, in certain si- tuations, and under certain circumstances, to co-operate in the function of absorption. The first of these operations is performed by means of the vital action with which the veins are endowed, assisted by the vis d tergo pro- .---------w~ * See the Note on Absorption. Admitting fully the justness of Dr. Hutchin- son's remarks, we must observe, that the exist- ence of the sets of capillaries here contended for by Dr. Alard is not proved demonstratively. Indeed, we possess this species of proof in fa- vour only of one set of capillaries, — namely, those which constitute the termination of the arteries and commencement of veins. We know that secretion, nutrition, and absorption, are functions of capillary vessels. This has always been granted, from the time of Hippo- crates ; but there have been various instru- ceeding from the vital action of the capilliirie8( —by the contraction of the surrounding mus- cles viewed in connexion with the direction of valves, with which they are provided, — by the pressure of the atmosphere upon the surfaces ofthe body, — and by the active dilatation of the cavities of the thorax and heart, which draws the blood into the large venous trunks and auri- cles. The third action of the veins, or venous ab- sorption, seems to be proved by the researches already detailed. J The venous radicles, either immediately or mediately, seize the absorbed materials, and convey them into the current of the circulation. This seems to be a vital or organic action, which is probably assisted, in some parts of the body, and under certain cir- cumstances, by the physical property of imbibi- tion, or capillary attraction, which all animal textures evince in a greater or less degree, even during life, according to the penetrating properties of the substances absorbed. It should, however, be recollected, that this physical pro- perty is a very subordinate one to vitality, i* entirely under its control, and takes place very imperfectly when this influence is jn full vigour. The second function of this class of vessels is the admixture of the absorbed vessels, and the assimilation of them. The former or me- chanical part of this function is performed gene- rally throughout the body, although it takes place to a greater extent in some instances than in others, as in those viscera in which the blood circulates more immediately after it has received the chyle and lymph from the lacteal absorbents and thoracic duct. Hence it chiefly takes place in the heart itself, and in the liver and lungs. The latter part of-this function, the assimilation and animalisation of the absorb- ed matters, is essentially a vital action, and appears to us to result from the vital influence derived from the nerves with which the blood- vessels are provided. Supposing this position to be correct, we should expect that the vessels in which this process takes place would be mot t abundantly supplied with those nerves whence we consider the assimilating influence to proceed. Now this is actually the case ; the blood which is carried into the portal veins contains a larger proportion of absorbed and imperfectly assimilated materials- than the blood in any other organ ; and this particular order of veins, whose office it is to assimilate them, and to eliminate the effete elements from the circu- lating fluid, is provided with a much greater number of ganglial nerves than any other part of the venous system ; and, indeed, even more than the arteries in some situations. This par- ticular set of veins, therefore, performs a dou- ble function, viz. of assimilation, and of secre- .tion ; in the latter action, however, it may only ments allotted to the process ; some physiolo- gists insist, with Dr. Alard, upon the existence of subordinate sets of capillaries allotted to each function ; whilst others contend, wilh M. Richerand, that they take place through the medium "of lateral pores in those capillaries which communicate directly between the ar- teries and veins. These veins will come un- der consideration in the notes in this Appendix on Secretion and Nutrition. t See the preceding Note. X See Absorption, in the Appendix. MECHANISM OF THE RESPIRATORY ORGANS. 41 participate with the hepatic artery ; for, as the hepatic vein returns the blood of both the vena portae and the artery, the biliary secretion may, probably, not take place until the terminating capillaries of both have given rise to the radi- cles of the vein. Assimilation goes on in the next degree of activity in the lungs, and more or less partially m other organs of the body. OF THE MECHANISM OF THE RE- SPIRATORY ORGANS. (Note U. See pp. 144, et seq.) I. Of the structure of the lungs.—According to the observations of M. Magendie, the cellules of the lungs do not appear to be arranged in a methodical manner, nor to have membranous parietes. With respect to the non-existence of the latter, we think that he was betrayed into error by the method of investigation which he adopted.* These cellules seemed to him to be formed solely by the minutest and last rami- fications of the pulmonary artery ; by the radi- cules of the veins of the same name, which are a continuation of the former ; and lastly, by the numerous anastomoses of all these vessels. These cellules are separated.into many distinct lobules, in each of which the cellules communi- cate among themselves ; while between the lobules there is no communication. The number of cellules is in an inverse ratio to the age of the subject ; consequently, the older the person, the larger is each cellula, or, what comes to the same thing, the fewer are the cellulae. It follows, therefore, that the lungs become specifically lighter as we advance in life ; and in support of the correctness of this inference, M. M. states that he found, by actual experi- ment, that, in equal volumes, a portion of the lungs of -a man at seventy was fourteen times specifically lighter than that of a child a few days old. The most accurate description of the bron- chia and air-cells of the lungs is given by Reis- seisen.f He states, 1st. That the ramifications of the bronchia are more and more numerous as they decrease in diameter ; and that the ulti- mate twigs end in close bulbous extremities, or air-cells, and that these cells do not commu- nicate with each other directly, but only through the medium of the extreme twigs, of which they are the terminations. 2d. That these ra- mifications and cells, as proved by Malpighi, have no communication with the surrounding cellular substance. 3d. That these ramifica- tions and cells consist, 1st, of mucous membrane; 2d, of a coat of elastic white fibres, on which the elastic properties of the bronchial ramification depend ; 3d, of muscular fibres, placed trans- veisely, relatively to the course of these canals. 4th. That the ramifications of the bronchial and pulmonary arteries freely anastomose both in * He partially filled the lungs by insufflation after their removal from the subject, and allowed them to dry. When quite dry, he found this sort of preparation to be nearly transparent, and readily cut into thin slices with a knife. f F. D. Reisseisen, M.D., Strasburg. Uber den bau der Lungen, eine von der Kbniglichen Academic dct Wissenskaften zu Berlin gekronte Pnisschrift. Berlin, 1822. the air-passages and in the surface of the lungs» and that the bronchial arteries chiefly run direct to the pulmonary veins. 5th. That the air- passages and blood-vessels of the lungs are most abundantly supplied with nerves from the par vagum, whose conjunctions with the sym- pathetic take place externally to the lungs. 11. Of the action of the glottis.—M. Bourdon J considers that the glottis performs the following functions, in addition to those which are re- quisite to the formation of the voice. 1. That-it is the glottis which suspends rr- spiratioa during considerable efforts, in oppos- ing by its closure the escape of the v\\i contain- ed in the lungs. 2. Without the glottis, the action of the ab- dominal muscles would be constantly employed in producing respiration : neither compression of the viscera, nor flexure of the trunk, could be produced. 3. There exists a real consensus of action be- tween the glottis and the abdominal muscles, and, through this medium, between the glottis and the different reservoirs, the bladder, the rectum, the stomach, and the uterus. 4. The glottis does not confine its - action to the production of the voice ; but by the aid of the sympathetic connexions which unite it to the abdominal muscles, charged to concur in, if not to preside over, important functions, it excites the greatest influence on those functions themselves. 5. Lastly, in the different efforts there is a tendency to expiration, to the production of which the closure of the glottis is an obstacle. III. Of the state of the lungs during respira- tion.— According to Dr. Carson, a principal part of the mechanical operation of respiiation is performed i>y the lungs themselves, and as follows :— After premising": that the substance of the lungs is possessed oT elastic properties, and is kept in a state of distension after birth by atmospheric pressure,$ Dr. C. considers that, during inspiration, the intercostal muscles raising and drawing out the ribs, and the dia- phragm contracting and descending, create a tendency td vacuum in the thoracic cavities, by enlarging their capacity : but this vacuum is prevented by the rushing of the air into the lungs, the pressure of the air overcoming the elasticity of the organ, and causing it to fill the enlarged thorax. Inspiiation is thus effected* But the diaphragm and intercostal muscles hav- ing enlarged the thorax, and ceasing to act, the substance of the lungs is enabled to exert its elasticity, recovers its dimensions, and thus expels the additional volume of air just inspired, the passive, respiratory muscles following the collapsing lungs, owing to the atmospheric pres- sure in the external surface of the trunk. Ex- piration is thus produced. Dr. Carson seems to err in imputing the function entirely to the causes now stated, and explaining expiration by means of the elasti- city of the lungs only. The elastic property of X Recherches sur le Mtchanisme de la Respira- tion, fyc. Paris, 1820. ij As admitted by Haller and other physiolo- gists, and as shewn by experiments on various animals, and by puncturing the walls of the thorax ; when the lungs, if healthy, always col- lapse, the atmospheric pressure within and w ith- out the lungs being then balanced. 42 APPEND'*. the organ Certainly exists to a small extent, and performs its part in the operation ; but to us it seems to be merely apart, and that a small one ; for the muscular Contraction ofthe bronchia, as instanced by Haller and Reisseisen, have evi- dently a share in producing the phenomenon, as well as the elasticity of the cartilages, and the contractions of the abdominal muscles, as contended for by those who explained the me- chanism of the function before the time of Dr. Carson. It should, however, be stated, that the cartilages of the ribs are liable to ossification, and that the abdominal muscles are nearly pas- sive, unless during forced expirations, when the lungs are emptied to the utmost. The experiments and opinions of Dr. Carson have had the effect of directing the attention of physiologists to the state of the lungs them- selves during "respiration, and under the various influences to which they are usually subjected either by accident, by operations, or by disease. Dr. Carson had inferred from his experiments, that it is possible to collapse one of the lungs, and to retain it in that state ad libitum, by keep- ing open the communication between the cavity of the chest and the external ah ; and further, that upon allowing the opening to close, the lung, in a given time, will recover its wonted function, — thereby rendering it practicable, when conceived necessary, to place the opposite lung under the like discipline. In order to ex- amine the stability of these inferences, Dr. David Williams, of Liverpool, instituted several experiments, in the presence of Dr. Trail and others, which contradict some of the chief posi- tions held by Dr. Carson. After detailing his experiments, Dr. Williams draws the following conclusions from them :— 1. That a lung will not collapse from exposure to the atmosphere as long as respiration is car- ried on by the opposite one, and the auxiliary respiratory powers are not restrained. 2. That a lung possesses for a time, indepen- dently of the influence of the diaphragm and intercostal muscles, if respiration is carried on by the opposite lung, a peculiar motive power, the sources of which I do not pretend to ex- plain. 3. That a sound lung soon regains its full power of expansion, when the pressure of the exterior air is removed. 4. That air freely and uninterruptedly admit- ted into both cavities of the chest simultane- ously, through tubes of a certain calibre, will not collapse the lungs, if the auxiliary respira- tory organs are unrestrained. 5. That air admitted into both the cavities of the chest (of a middle-sized dog) simultaneous- ly through apertures of an -inch and better in length in the intercostal spaces, will not col- lapse the lungs, provided the animal is allowed unconfined the use of his respiratory organs. 6. That a sound lung never fills the bag of the pleura. IV Of the effects of respiration on the circula- tion of the blood, especially through the veins.— The experiments of Haller, Lamure, and Lorry, and subsequently those of Cloquet and Bour- don, have shewn, 1. That, during inspiiation, the blood of the vena cava, superior and inferior, is drawn to- wards the heart. 2. That, during expiration, the blood, is, on the contrary,- driven in the same vein* toward* the viscera. 3. That the arterial blood is also driven to- wards the viscera at the time of expiration. 4. That the alternate motions of the brain- are owing to the changes caused by respiration in the flow of blood. 5. That all these changes are but little mark- ed in ordinary respiration ; but that they be- come very evident in full respirations, and parti cularly so during great efforts. 6. Lastly, that during great efforts the glottis is firmly closed, the air contained in the lungs is compressed, as well as all the pectoral and abdomirral viscera. In order to ascertain the precise effects pro- duced by respiration on the venous circulation, M. Magendie instituted a set of experiments from which he draws the inferences, that respi- ration modifies the venous circulation ;—1st, by the influence which it exerts on the course of the arterial blood ; — 2d, by its direct action on the current of blood in the veins. That in pro- found respirations and violent efforts, the circu- lation appears nearly suspended. The six propositions given above, seem to convey a brief and correct statement of facts. The inferences of M. Magendie are perhaps carried a little too far. The pressure of the at- mosphere upon the surfaces of the body, and the actions of respiration, have been adduced by Dr. Carson and Dr. Barry to explain the phenomena of the venous circulation, and what- ever suctive action the heart may exert. That the atmospheric pressure remaining constant on the body generally, while it is slightly diminish- ed about the heart, during inspiration, produces a small disturbance of the uniformity of the venous current near the chest, has always been admitted, as just stated; but that this circum- stance is productive of effects such as Dr. Carson and Dr. Barry impute to it, cannot be allowed. Dr, Barry considers that, in conse- quence of the enlarged state of the thoracic parietes during inspiration, and tendency to a vacuum, the pericardium is drawn out, and with it the parietes of the venous sinuses of the heart, and the large veins, just before they open into these situations. Hence the blood during every inspiration rushes, into these parts, which become the reservoir from whence the cavities of the heart are replenished; and the suctive influence thus occasioned in consequence of the pressure of the air being thus taken off this part of the vascular circle, being the cause of both the progression of the blood in the veins, and of absorption. That some slight influence of the kind now stated may he occasioned by the violent and forced respirations observed in the living ani- mals on which Dr. Barry performed his experi- ments, we will not dispute ; but we believe that, during the healthy and usual state of re- spiration, httle or no effect upon the circulation beyond what was already admitted, is actually produced; for we believe that no such tendency to vacuum is ordinarily occasioned in a heilthy state of the lungs, and whilst, from the pres- sure of the air within them, they are enabled to follow the motions of the respiratory appa- ratus. Upon this subject, the remarks of Dr. Arnott, in his valuable work,* seem to us, upon the - Elements of Physics, or Natural Philosophy, General and Medical, (Sec. By Neil Arnott, MP-, &c. London, 1827. p. 528. OF THE FUNCTIONS OF THE LUNGS. 43 whole, correct, although even here various con- comitant relations are overlooked. This author states it to be " a physical impossibility, that a sucking action of the heart or chest can be a cause of the blood's motion along the veins. 1st. The veins are pliant tubes, free to collapse, and no pump can lift liquid through such. 2d. The suction power of the chest in healthy re- spiration is too weak to lift liquid even one inch through tubes of any kind." In respect of the first proposition, we grant its accuracy upon the main; but it should, in justice to the exact state of the case, be re- membered, that the parietes of the veins are so intimately connected to the parts surrounding them, as to furnish a mechanical resistance to collapse from a slight suctive influence, and that hence such influence may be productive of a slight or partial effect, especially when the vessels are kept full at the time of its operating by other causes, as the vis a tergo, and the vital influence of the system, which latter has been too much kept out of view, both, by Dr. Barry and by Dr. Arnott. As to the second proposi- tion, we do not dispute its accuracy. ' There are various circumstances which mili- tate against the hypothesis of Dr. BarVy, be- sides the fundamental one now alluded to, such as the circulation and absorption in the foetus, the circulation in the vena portae, and the circu- lation in animals not possessing one distinct respiratory cavity. V. Of the effects of suspended respiration on the circulatitm. — From the experiments which were made by Dr. Williams, of Liverpool, on this subject, he deduces the following corolla- ries :— T. The blood is obstructed in its passage through the lungs, on suspension of respiration, while its circulation through the other parts of the body continues. 2. The obstruction of the blood in the lungs, on suspension of respiration, is not occasioned by a mechanical cause. This is proved by the flow of blood through the lungs being suddenly arrested, without any subsidence of-this organ, while the circulation was carried on vigorously through the other parts of the body, in the ex- periments detailed by the author. 3. The obstruction of blood in the lungs, on suspension of respiration, arises from the de- privation of pure atmospheric air. 4. The blood which is found post mortem in the left auricle and ventricle is the remnant after the last systole, and the subsequent drain- ing of the pulmonary veins. 5. The obstruction of blood in the lungs on suspension of respiration, is one ofthe principal causes of the vacuity after death of the system circulating arterial blood. 6. The immediate cause of the cessation of the action of the heart is a privation of its na- tural stimulus, arising from the obstruction of the blood in the lungs.* OF THE CHANGES INDUCED ON THE AIR AND THE BLOOD BY RESPIRA- TION. (Notes W. See pp. 150—158, 163, 201.) 1 Of the production of carbonic acid during respiration.—The experiments of Mr. Ellis and others have led physiologists to conclude, that oxygen is not absorbed by the blood in the lungs from the air during respiration, but that the blood gives off its superabundant carbon from the surface of the air-cells, and the car- bonic acid is thus formed in the lungs them- sgI vgs. This mode of accounting for the changes in- duced upon the air and upon the blood during respiration, has been very generally adopted in this country ; while the former mode of explain- ing the process (that which is given in the text) has still been received, with various modifica- tions, on the continent. It appears to us that the production of car- bonic acid gas by the respiratory function has been ascribed too exclusively to one of the above processes ; and that it has been too ge- nerally viewed as altogether a chemical pheno- menon. When the theory of the absorption of oxygen was dismissed, in favour of that which contended for the discharge of carbon from the blood, either in its pure state, or in that of a hydrate, no participation in the process by which the carbonic acid is formed, was allowed to the previously received opinion: however, it still appears a matter of doubt how far either function predominates ; for we are inclined to think that both operations go on simultaneously, and that, whilst a portion of the carbonic acid gas is given out from the blood, already formed, it is accompanied with another portion of free carbon, or an oxide of carbon, or even with a hydrate of the same substance, which combines with an additional quantity of oxygen in the lungs, and thus forms the whole of the carbonic acid in question; and that, at the same time, a portion of oxygen is absorbed which combines with the carbon in the blood, and there gene- rates the carbonic acid gas, or the oxide of car- bon, which forms a part of the matters discharg- ed from the blood in the lungs. These pro-' cesses may vary, and either may predominate, according to the state of the vital influence at the time, under whose control they are imme- diately and completely placed. This view of the phenomenon in question seems to be fully supported by the experiments of Dr. Edwards, of Paris. They prove that the carbonic acid gas does not form instanta- neously in the lungs through the action of the respired air; but that it appears to be secreted to a considerable extent from the blood in the respiratory organs. As to the quantity of this gas which is form- ed during respiration, different physiologists have estimated it differently. Godwin con- sidered that for every 100 cubic inches of at- mosphere respired, there were given off 10 or 11 of carbonic acid. Menzies, from experi- ments made with much accuracy, found the quantity of carbonic acid to be about 5 in the 100. Dr. Murray considered it to vary from 6 to 65. Sir H. Davy from 3-95 to 45. Messrs. Allen and Pepys from 35 to 95. They esti- mated the mean at about 8. Dr. Prout found it to be about 345. Dr. Fyfe about 8 5. The discrepancies which are remarkable in these results of the experiments performed by these^ physiologists, doubtless arose, in a great mea-' sure, from the different proportions of this gas produced by different individuals, according to the state and developement of the lungs, and. • Annals of Philosophy, Sept. 1823, 44 APPENDIX. according to the particular circumstances of the individual at the time of the experiment. The influence which the state of the individu- al exerts upon the function was first shewn by the experiments of Dr. Prout and Dr. Fyfe. They proved that the carbonic acid gas formed during respiration is liable to be very materially affected in its quantity in the same individual, by various' circumstances. It was formed in a minimum quantity during the night; and the maximum quantity, which was generally pro- duced about noon, exceeded the minimum about one-fifth of the whole. The passions of the mind were found to have a great influence over its production; the depressing passions dimi- nishing its quantity, and those of an opposite nature the reverse; exercise, when moderate, appeared to increase in some measure the quan- tity, but fatigue diminished it. The greatest decrease experienced was from the use of alco- hol and vinous liquors, especially when they were taken upon an empty stomach. In short, whatever diminished the powers of life, as low diet, mercurial irritation, &c. appeared, from the experiments of Dr. Prout and Dr. Fyfe, to have the effect of diminishing the quantity of the carbonic acid. Dr. Crawford found the quantity of this gas was much diminished when respiration was performed in a high temperature ; and Lavoisier and Seguin confirmed his observation. Nearly similar results to theirs were obtained from some experiments which we performed in 1815 ; and from the data thus obtained, we endeavour- ed* to account for several of the most import- ant diseases to which the inhabitants of warm countries are liable. Similar experiments were afterwards performed in an intertropical cli- mate, where we found the diminution of the quantity of carbonic acid to be considerably greater than that which our experiments in an artificial temperature of equal elevation had furnished. This seems to be accounted for by the depressing influence upon the nervous sys- tem which the atmosphere, loaded with moisture and malaria, may be reasonably expected to produce. We also attribute a share of this dis- crepancy to the increased function of the skin, which evidently co-operates in hot climates with the lungs, and performs a subordinate re- spiratory function. In some comparative ex- periments made by us on that occasion, both on our own respiration, and on the respiration of a negro having a chest of about equal capacity, we found that the quantity of carbonic acid formed during respiration, in a given time, was much greater in our case than in that of the negro ; and that the carbonic acid formed upon the cutaneous surface of his body exceeded that formed on ours in about the proportion of 3 to 2. We shall not pursue this particular topic farther at this place, as we propose con- sidering it more at length on a future occasion. Reverting to the question, whether the car- bonic acid is formed within the vessels or with- out them, — we must remark, that the evidence on the subject is very contradictory. The ex- periments of Dr. Edwards, already referred to, shew that the former process exists, at least to some extent; and it is farther supported by the fact,.established by Berzelius, that bluod, espe- cially its colouring part, not only absorbs oxy- gen very quickly, but it also retains some part of the carbonic acid thereby produced ; but whether or no this absorption will take place through the parietes of the capillaries, is the point at issue. The evidence for the absorption of oxygen through the capillary parietes, is, however, nearly on a par with that for the ex- cretion ofthe carbon ; if the vessels will permit the transmission of the one, they may allow the transit of the other. Those who contend for the passage of the carbon from the vessels, and who, consequent- ly, consider that the carbonic acid is formed ex- ternally as respects the vessels, support their opinion by the experiments of Mr. Ellis, who first promulgated the doctrine. His experiments were, however, performed out of the body, and under circumstances which entirely excluded the operation ofthe vital influence ofthe lungs, and of the system generally. The most conclusive experiments in favour of this opinion are those performed by MM. Magendie and Orfila. They found that phos- phorus, dissolved in oil, and injected into the jugular vein of a dog, was expelled by the mouth and nostrils in the form of copious va- pours of phosphorous acid; which could hardly have been the case if the phosphorous acid had been formed within the vessels, as in this case it would have remained in solution in the blood, it not being a volatile substance. It might, therefore, be supposed that the phosphorus was. excreted in a state of minute division from the vessels of the lungs, and meeting in this state with the oxygen of the atmosphere, formed the phosphorous acid in question. If this reason- ing be admitted with respect to phosphorus, it may be extended to the carbon contained in the venous blood. From the contradictory evidence on the sub- ject ; from the nature of that evidence ; from the experiments of Dr. Edwards; from various analogies that might be adduced, could our limits permit, from the conformation of the lungs, and the extent of their excreting and absorbing functions, as evinced by experiments; and lastly, from the consideration that, although respiration takes place frequently, yet a very large portion of air remains for a considerable time in the chest, thereby allowing the vitality of the lungs themselves to be exerted upon the air contained in them, — we eonclude that this organ may act in both the ways contended for ; and that, whether it act in one manner or the other, more or less partially, the process is a vital one, and whatever chemical laws may be employed in it are under the control of the vital influence of the organ, and modified by the ever-varying condition of this influence. II. Of the absorption and exhalation of azote during respiration. — Another subject of much interest, connected with the respiratory func- tion, is that which immediately relates to the absorption in the lungs of a portion of the azote contained in the respired air. On this point, also, the results of experiments have been vari- ous, and opinions respecting them equally so. Dr. Edwards, 6f Paris, who is well known as a very able and intelligent physiologist, con- cludes, from different experiments, and from the circumstance of the opposite results which they give, — some indicating a diminution of the azote of the air, others an increase of it dur- ing respiration, — that this gas is absorbed into * These views wete contained in a Latin thesis written at Edinburgh in 1815. OF THE PRODUCTION OF ANIMAL HEAT. 45 the circulation, and afterwards discharged from it; and that each of these actions is regulated by the constitution, habit, and circumstances of the individual, and by the influences to which he may be subjected ; the absorption being to a small extent, while the exhalation is consider- able, and vice versa. Independently of the satisfactory nature of the experiments whence Dr. Edwards has drawn his inferences, there are many collateral proofs that may be brought to their support, derived from the manifestations of the animal economy in health and in disease ; and we have little doubt, that not only azote, but that other gases, even those whose presence in.the respir- ed air are accidental, may be also absorbed into, and discharged from, the circulation, in a great- er or less quantity, according to the varying state of the vital energies of the system. III. Of pulmonary transpiration..—The mucous membrane of the lungs gives off a considerable portion of the watery secretion, which is carried out of the lungs, in the form of vapour, by the respired air. This perspiration equally takes place when the animal breathes a gas contain- ing neither oxygen, hydrogen, nor azote ; it therefore does not result from the combination in the lungs of the hydrogen contained in the blood with the respired air; but is strictly an aqueous vapour, slightly charged with animal matter, and is the production of a vital trans- piration or secretion. It has not been determined whether or no it be produced from the bronchial or from the pul- monary arteries. The question is difficult to decide, as an injection thrown into either set of arteries arrives on the surface of the air-cells. Pulmonary transpiration may contain, like secretions, foreign matters which have been conveyed into the circulation ; the lungs acting as an organ eliminating them from the system. This has been shewn by some experiments of M. Magendie ; and also in experiments which we performed, especially one, in which ten diachms of the oil of turpentine were chiefly discharged by the lungs from the circulation in the state of vapour, within twenty-four hours.* The large quantity of the turpentine vapour evolved from the lungs on that occasion, leads us to suppose that transpiration takes place prin- cipally from the venous blood, about the time when the changes are effected in it by respira- tion. This experiment also seems to support the doctrine of the evolution of carbon from the blood. IV. Of the assimilating function of the lungs. —The extent of the function of the lungs has been a matter of doubt. Their principal office, namely, that of changing venous into arterial blood, has always been admitted, although the nature of the process has been disputed. Many physiologists have, in addition to this, attribut- ed to them an assimilating influence which is exerted chiefly upon the absorbed chyle and lymph which the venous blood contains. This opinion appears correct. But the process is purely a vital one. If the opinion of Dr. Ed- wards respecting the absorption and exhalation of azote be correct, this substance may be in- strumental in the process. A third function has been referred to this organ, viz. the formation of animal heat. But however intimately related it «may be with the * For the particulars of these experiments, respiratory process, it cannot be considered a function of the lungs. It must, nevertheless, be allowed, that the changes induced upon the blood during respiration are preparatory to the evolution of animal heat; and although we con- tend that this heat is immediately the result of a manifestation of the vital influence of the ganglial system of nerves, exerted upon the blood contained in the vessels to which these nerves are distributed, yet it must be admitted, that the respiratory processes are necessary to its production, inasmuch as they produce on the blood a change of properties, which are re- quisite to excite this system, and as this fluid, when thus changed, contains the materials ne- cessary to, or is otherwise in a suitable condi- tion for, the manifestation of the influence which that part of this system of nerves that is distributed to the blood-vessels exerts. OF THE PRODUCTION OF ANIMAL HEAT. (Note Y. See pp. 155, 158.) It is not necessary to add at this place much to what is contained in the text, and to what we have said at page 15, and towards the conclu- sion of the preceding note. It will there be perceived that we have attributed the production of animal heat to the vital influence exerted by that part of the ganglial system distributed to the arteries on the blood which they circulate. Preparatory changes, however, take place in the lungs, which are necessary to the'exertion of this influence, and to the evolution of heat; but as it was contended that those changes are more of a vital than of a chemical nature, so it is considered that the production of heat is more the result of the influence which the soft nerves supplying the vessels exert upon the blood, than of the change in the capacity for caloric \vhich the blood itself experiences in its passage into the venous state. The difference of capacity which actually exists between venous and arterial blood is not sufficient, ac- cording to the experiments of Dr. Davy, to form the basis of the chemical theory formerly re- ceived ; but the difference which actually does exist may be concerned in a subordinate man- ner in the process. Conformably with the opinion that was first maintained on an occasion already alluded to, page 15, we infer that the various causes which modify the production of animal heat act, 1st, immediately upon the organic system of nerves themselves, changing the condition of their influence ; 2d, upon the blood, altering the nature and composition of this fluid, and thereby rendering it unfit for producing the requisite excitement of this system of nerves, and less capable of the changes which the influ- ence of these nerves produces upon its consti- tuent parts ; 3d, immediately through the cere- bro-spinal system, modifying the influence which this system imparts to the ganglial. These different ways in which the vital influ ence, exerted by this system of nerves in the production of animal heat, is modified, might have been illustrated by the results of experi- ments, and by reference to facts in comparative physidlogy and in pathology, if we could have admitted of so great an extension of our limits. the Medical and Physical Journal, vol. xlvi. 46 APPENDIX. From what we have said, it will be perceived, that we view the production of animal heat more in the light of a vital secretion than of a chemical phenomenon ; and that, like the other secretions and nutrition, it proceeds from, or is controlled by, the vital influence of the ganglial system of nerves, and is co-ordinate with the vital manifestations of the whole body. OF THE CUTANEOUS FUNCTION. (Notes Z. See p. 169.) I. Cutaneous exhalation, or insensible transpi- ration.—In transpiration there appears to betvvo actions,—a physical one, consisting of the eva- poration in the air of the fluid parts of the body ; and a vital action, giving rise to an ex- crementitial exhalation, of which the skin is the organ. This view of the subject is justly contended for by Dr. Edwards ; but we think he has refined in an unnecessary manner in ex- plaining it. The cutaneous exhalation is doubt- less an organic function, of which the skin is the organ ; but we conceive that the skin must first perform its office before the physical action can take place to any considerable extent: in short, that as transpiration is performed, the physical law, evaporation, operates, and that both go on, the latter as a consequence of the former, pari passu, until an increase of the tran- spiration on the one hand, and an uncommonly dry state of the atmosphere on the other, give us different results. When the former takes place, we perceive the formation of sweat, or the transpiration becomes sensible : when the latter exists, then the phenomenon for which Dr. Edwards and some others have argued, as constituting one of the actions into which this function may be divided, really supervenes to some extent. Thus we have witnessed, during the Harmattan wind, which occasionally blows on the west coast of Africa, and which is re- markable for its dryness, evaporation going on so rapidly as to give rise to very inconvenient sensations, and even to serious disorders of the parts which are usually exposed to the air. In this case the evaporation exceeds the mere solution of the transpired fluid in the surround- ing atmosphere ; and the parts of the body which are subjected to its operation have a por- tion of the fluids sent to the surface carried off by it, in addition to what is exhaled by the natural and organic action of the vessels of the skin. The cutaneous exhalation contains a portion of the carbonic and lactic acids, and sometimes minute portions of urea and uric acid ; and, ac-, cording to our experiments, these are more abundant in negroes and the dark-skinned races than in Europeans. II. Of the sweat, or sensible exhalation. — When we said that, if the production of the halitus, or insensible tianspiration from the skin, exceed the evaporation of it in the atmo- sphere, sweat is formed, we stated the source of this fluid. It is, therefore, produced from the same Vessels as the insensible perspiration. But although this is the case with respect to their source, there is some difference between the nature or chemical constitution of the sen- sible and insensible cutaneous exhalations/ * The experiments which were made in or- der to ascertain this, from the want of the means and proper facilities, we're not performed upon The former is generally less charged with car- bonic acid than the latter, but it abounds more with the salts usually excreted from the sys- tem. A careful view of the functions of the skin throughout the different classes of animals leads us to conclude, that it performs operations which hold an intermediate place between those of respiration and elimination,—that it partakes of the character of a respiratory and of an elimi- nating organ. 1. It is a respiratory organ. — This is shewn by the circumstance of this function being per- formed in the lowest orders of animals on the external surface of their bodies only ; by the developement of the' organs of respiration in the different orders ; and by the gradual perfec- tion at which the respiratory organ arrives in ascending the scale of animal creation. In the higher animals the respiratory apparatus be- comes more and more distinct, and the function depending upon it more and more limited to ap- propriate organs ; however, the same type which characterises the lower orders, and is most remarkable in them, is still preserved throughout the whole series of the animal scale, although it becomes gradually, and nearly, but not altogether, lost. Thus in man the lungs perform the chief respiratory process; but, even in him, the respiratory function of the skin is remarkable. Carbonic acid gas is pro- duced from the cutaneous surface, transpiration also takes place there ; and this respiratory act of the skin becomes more and more remarkable under circumstances which diminish or partial- ly obstruct the respiratory process of the lungs. Thus we found that the quantity of carbonic acid gas formed in the lungs in a given time, and in the same individual, was about one-third less in a hot climate than in a cold one ; this was about the average result of our experi- ments : whilst we observed that the respiratory function of the skin, both as respects the quan- tity of the insensible transpiration and the for- mation of carbonic gas, was very remarkably increased.* In a negro, as far as we could infer from experiments performed on a single limb, the respiratory function of the external surface of the body was much greater, and the quantity of carbonic acid formed in his lungs much less, than in our own case, although our size and weight were equal. Hence we were led to infer, that in this race of the human species the skin perforins a much greater sup- plementary function to that of the lungs, than in the inhabitants of cold or temperate climates. In two cases that came under ourobseivation, in which the lungs were partly destroyed from an imposthume, and the side of the chest was consequently contracted, the cutaneous func- tions were afterwards very remarkably increas- ed. Were it consistent with the limits of these notes, many facts illustrative of this particular function of the skin, as it respects the inhabit ants of cold, temperate, and hot climates, might be adduced. 2. The shin is an eliminating organ.—M. Ri- cherand has so fully illustrated this function of the skin, and contrasted it with that performed by the kidneys, that it is unnecessary to say any thing respecting it at this place. The che- the whole body,—they were made only upon a single limb ; but the results were very decisive and remarkable. OF THE FLUIDS. 4? Hf»ioa\ analysis of the perspired fluid, given in Ine next chapter of the Appendix, will shew to what extent it performs an eliminating office. OF THE FLUIDS. (Notes A A. See pp. 170—183.) In addition to the classifications ofthe fluids, noticed in the Note at page 232, we may men- tion that adopted by M. Chaussier. He divides the fluids into five classes : those produced by the digestive process, the chyme and the chyle ; the circulating fluids, the lymph and the blood; the exhaled or perspired humours ; the follicu- lar humours ; and the glandular humours. M. Adelon,* the able and eminent pupil of M. Chaussier, has proposed another classifica- tion, which possesses some advantages over those which have preceded it. It is also simpler and more natural. He divides the organic fluids into those of absorption, the fluid specially nu- tritive, and the secreted humours. 1. The absorbed fluids are the chyle, the lymph, and the venous blood. These are taken up and conveyed by the lymphatic and venous class of vessels, and ultimately become assimi- lated with, and indeed concur to form the fluid specifically nutritive. Thus the chyle, after a longer or shorter course, mingles with the lymph, both are poured into the venous blood, and when they arrive at the organs of respiration, they become perfectly united, being converted into the nutritive fluid by the functions of those organs. 2. The fluid especially nutritive.—The three fluids constituting the first class being changed in the respiratory organs into that which can alone nourish the body, thus constitute the se- cond class, which, in its turn, furnishes the materials of all those embraced by the third. The second class is, therefore, the arterial blood only, which, being fully perfected in the lungs by the action of the atmospheric air, and cir- circulated throughout the body, furnishes the materials of nutrition and secretion, and sti- mulates and contributes to preserve the func- tions of the living solids, and, in conjunction with these solids,t produces the calorification of the animal system. 3. The secreted humours.—This class may be divided into three orders, according to the forms of the secreting organs which produce them ; namely, into exhaled or perspired fluids, fohicu- lar humours, and glandular humours. A. Exhaled or perspired humours.—These are numerous, are produced in the form of vapour, and they differ from one another in their physi- cal and chemical properties, and in the purposes which they fulfil in the animal economy. They are, moreover, distinguished into those which are taken up by lymphatic or venous absorption, and carried back into the torrent of the circula- tion, and into those which are entirely thrown out of the body ; the former being usually de- nominated recrementitial, the latter excrementi- tial, from these circumstances. The recrementitial fluids are all produced in cavities or in situations that have no external outlet. The following enumeration includes all the fluids appertaining to this genus :—1. Serous fluids, as those which are exhaled on the sur- * PhysMogie de V Homme, par N. P. Adelon, D. M. P. &c. vol. i. t By living solids is here meant all sensitive face of the arachnoid, of the pleura, of the peri- cardium, the peritonaeum, and the tunica vagi- nalis.—2. The synovia.—3. The serosity of lu- minxms tissues.—4. The fat formed in the adi- pose tissue.—5. The marrow, or medullary juice. —6. The colouring humour of the skin, placed under the epidermis.—7. The colouring humours of the iris, of the uvea, and of the choroid.—8. The three humours of the eye—the aqueous, crys- talline, and vitreous.—9, The lymph of Cotug- no.—10. The humour of the lymphatic glands, a gelatino-albuminous fluid, existing in the spongy tissue of these organs.—11. and lastly, the fluid perspired on the internal surface of all the ves- sels, the existence of which may be doubted, as it is next to impossible to demonstrate its existence. In addition to the perspired tecre- mentitial fluids, may be added those which exist in the human ovum, viz. the amniotic fluid, the water of the chorion, which exists between the chorion and amnios only during the early months of pregnancy ; and the water of the umbilical vesicle, which may be compared to the yolk of an egg, and which some physiologists believe destined to nourish the embryo before the de- velopement of the placenta. The excrementitial perspired fluids are all thrown off from the external surface of the bo- dy, and from the mucous membranes, which have a communication externally by means of the natural outlets, and which may therefore . be considered as merely forming parts of the external surface.—1. Those fluids which perspire from the skin, as the cutaneous insensible per- spiration, and the humour constituting the sweat. —2. The fluids perspired from the respiratory ap- paratus ; these differ somewhat in different si- tuations, as in the nasal cavities, in the trachea, and bronchia.—3. The humours exhaled on the surface of the digestive canal.—4. Those hu- mours exhaled on the internal surface of the urt- nary apparatus, viz. on the internal surface of the ureters, the bladder, and urethra.—5. The fluids exhaled from the genital organs, namely, from the internal surface of the vesiculae semi- nales and ejaculatory conduits, in the male, and from the uterus and vagina in females (the men- strual flux and the lochia). B. The secreted follicular fluids are those form- ed by a particular secreting organ called folli- cular. They are all excrementitial, and con- sequently are formed on, and eliminated from, the two external surfaces of the body, the skin and mucous membranes. They consist of,—1. The sebaceous humour of the skin.—2. The ceru- men ; the humours of Meibomius.—3. The hu- mour of the carunculalachrymalis.—4. Thehu- mour secreted at the base of the glans penis in the male, and on the surface of the vulva in the female. The humours secreted by the follicles in the mucous surfaces are generally charac- terised by the generic term mucus. They are distinguished into the mucus of the respiratory organs, the mucus of the digestive apparatus, of the urinary apparatus, and of the genital or- gans. The humours formed by the prostate, and , by the glands of Cowper, compound and glandi- form follicles, are usually referred to the last mentioned in this enumeration. The fluid se- creted by the tonsils is, generally classed with those of the digestive organs. and irritable parts,—all those which are influ- enced by an irritating cause. 4S APFENDI*. C. Lastly—The secreted glandular humours are the production of glandular organs. They are.—1. The lachrymal fluid.—2. The salivary fluid.—3. The pancreatic humours.—4. The bile. —5. The urine.—6. The semen ; and 7. The milk. It may be remarked generally, with respect to the humours, that the degrees of fluidity which belong to them vary greatly from a state of gas or of vapour to that of semi-fluidity ; they have, moreover, all the physical conditions constituting a fluid body. Their fluidity, how- ever, does not result from the general forces of matter, but from those of life. Indeed, the vital influence modifies their physical form of exist- ence, in a more or less marked manner, as long as they continue subjected to its operation. From this source also they are imbued with a certain influence, the presence of which is in- dicated by the continuance, for a time, of the specific characters of each. This influence, be- ing no longer renewed when they are removed from the body, soon becomes dissipated, and the secretion which, while within the sphere of the animal system, and for a short time afterwards, possessed an emanation of the vital influence sufficient to give it certain characters, and to preserve it from the chemical changes to which its constituents are naturally prone, at last falls into a state of dissolution, as unequivocal as that evinced by the textures of the body. In confirmation of this view, we need only refer , the physiologist and pathologist to the compara- tive condition of the more perfectly elaborated secretions immediately after their formation and excretion, and after periods of various du- ration have elapsed from the time-of their dis- charge from the body. Finally, we may remark, that the fluids, be- ing composed of molecules moving with faci- lity on each other, cannot, as the solids, be trac- ed to constituents of an elementary nature. They can only become the subject of micro- scopic research in our endeavours to trace the nature of their constitution ; by this means we can merely learn that they are generally com- posed of globules, swimming in a fluid sub- stance ; and whatever be the fluid employed, we perceive only globules suspended in an amorphous liquid. It should, however, be re- marked, that, as we find in some solids merely a concrete amorphous substance containing no globules,—as in the cellular tissue for example, —so we perceive some fluids destitute of glo- bules, and formed only of an amorphous sub- stance, whjch is perfectly fluid. In other solids and fluids, on the contrary, we find both globules and an amorphous matter, which is concrete * See on this subject Physiologie del'Homme, par N. P. Adelon, vol. i. p. 116. + Phil. Trans, for 1820. X The microscopic observation of the blood satisfied these gentlemen that this liquid, dur- ing life, was nothing else than the serum, hold- ing in suspension small, regular, and insoluble corpuscles. Those are uniformly composed of a central, colourless spheroid, and of a species cf membranous bag, of a red colour, surround- ing this spheroid, from which it is easily separ- able after death. The central body is white, transparent, of a spherical form in animals with circular particles, of an ovoid form in those with elliptical particles. Its diameter is constant in the first, but it varies very perceptibly in the in the former, and liquid in the other. But these globules vary greatly, both in solids and in fluids, and even in the same part, according to age : those of the blood, for instance, are composed of a solid central part, and of an ex- ternal envelope which is coloured ; those of the chyle appear to be the same as the central part of the former, without its coloured envelope ; those of the muscular fibre seem to be the same as those of the blood ; those of the brain and nerves are smaller than the foregoing ; and those of the kidneys are smaller than those of the spleen. During the first epoch of conception, the globules are not visible ; they, however, soon form and become more and more distinct.* OF THE BLOOD. (Notes B B. See pp. 171—177.) I. Of the small or colourless globules of the blood.—The researches of Sir Everard Home and Mr. Bauerf seem to lead to the following conclusions respecting these globules. 1. That the milk-like fluid, the produce of digestion (chyle), which is found in the lacteal vessels and glands, contains an infinite number of white globules, chiefly of a minute size. 2. These newly discovered minute globules are ^-fa-^ part of an inch in diameter. 3. That the chyle contains also some white globules, of the size of the red globules of the blood. 4. Mr. Bauer supposes that the full-sized glo- bules acquire their form in the lacteal glands. 5. Sir Everard Home considers that the glo- bules of the blood receive their red hue in the vessels of the lungs. 6. That lymph or fibrine, whether taken from an inflamed surface, from the buff of what is commonly called inflamed blood, or from the slowly formed layers of aneurismal tumours, consists of innumerable white globules, much smaller than those which constitute the red glo- bules of the blood, and similar to those minute globules already described. 7. That those small globules constitute the substance thrown out in inflammation. 8. That they are held in solution in the se- rum, and consequently are only brought into view in the act of coagulation. 9. "That these globules, as well as those which subsequently receive the red colour, are the pro- duce of digestion, and are formed in the pyloric portion of the stomach and in the duodenum, surrounded by a glairy mucus, which is met with in these parts. MM. Prevost and Dumasf agree with Sir second. It manifests also a great disposition to assume-aggregates or ranges, in the form of a string of beads. The coloured portion appears to be a kind of jelly, easily divisible, but insoluble in water, from which it may always be separated by re- pose. It is likewise transparent, but much less so than the central corpuscle ; and the fragments arising from its division are not susceptible of regular aggregation. As the attraction, which keeps the red substance fixed round the white globules, ceases at the same time with the move- ment of the liquid, these globules can then obey the force which tends to unite them, and to form a net-work, in whose meshes the liberat- ed red colouring matter gets enclosed, and thus Or THE COAGULATION OF THE BLOOD. 49 Eretard Home as to the form and structure of the globules of the blood ; but they do not ad- mit with him that the red globules undergo a rapid change after they escape from the vessel, or that the colouring matter which envelopes the central spherical body separates from the lobule so soon as thirty seconds after the blood as issued from the vein. They, however, agree with him in saying, that these central spheres (the smaller globules) unite themselves in filaments, which differ in no respect from the muscular fibre. They observed also small glo- bules in the milk, in pus, and in the chyle; and they consider that those of the former fluids have been, and these of the latter are to be, sur- rounded by the colouring matter of the blood. MM. Prevost and Dumas found the globules of the blood to be circular in all the mammalia; and in their size to vary in different animals : they are smallest in the goat. The globules are elliptical in birds, and they vary considerably in size in this class of ani- mals. This variation is chiefly in the great axis of the globules. They are elliptical also in all cold-blooded animals. II. Of the coagulation of the blood, and on its vitality.—On the part of the subject before us we cannot enter minutely. We will merely state, as briefly as we can, those inferences at which we have arrived, after a careful examin- ation of the phenomenon itself, under various circumstances, and of the different opinions en- tertained respecting it, 1. According to our own observations, as well as those of Treviranus and Kolk, whose re- searches on this subject have been extended and faithful, the particles or globules of the blood possess a rotatory motion during life, and this motion continues until the phenomenon of coagulation takes place. 2. We conceive that this motion of the glo- bules is the cause of the blood's fluidity. 3. That the motion of the globules of the blood is the consequence of the vital influence emanating from the ganglial nerves distributed in the parietes of the vessels in which they cir- culate, and endowing them with vitality. (See pp. 14, 15.) 4. We therefore infer that the blood possesses vital properties, but that these properties are derived from, and depending upon, the vital con- ditions of the vessels in which, and the organs through which, it circulates ; that it is not tJ^ source of vitality, although manifesting a **eci- procative vital influence; and the paanifesta- tions of vital properties may be *-aced in the chyle, or originate there, proceeding from the admixture of the secretions contributing to its to produce the phenomenon of coagulation. If the coagulum be exposed to a stream of water, the colouring matter is washed away, while the aggregate formed by the white globules remains in the form of filaments, in which may be re- cognised, by means of the microscope, the as- pect and structure of the muscular fibre,- Three animal substances ought, therefore, to fix our attention : these are, the albumen of the blood, the white globule, and the colouring mat- ter which envelopes-this. With respect to the colouring particles of the blood, these chemists suppose that it is formed of an animal substance in combination with a peroxide of iron. The I'olourless globules they considered to be coagu- formation, and from the vessels and organ* through which it circulates in" its course into the current of the blood,— vitality thus begin- ning to manifest itself, in its lowest grades, with the formation, in the chyle, of the central globules of the blood. 5. That the cause of the coagulation of the blood is not to be found in external agencies, but in the loss of that emanation (proceeding from the organic nerves distributed to the coats of the vessels) of the vital influence with which the globules are endowed. 6. That the presence of the air, especially of the oxygenous portion of it, promotes this phe- nomenon. 7. That when coagulation commences at any point of a mass of blood, it is rapidly propagat- ed throughout the whole : this may arise from the cause being co-ordinate, or nearly so, throughout the whole. 8. Neither the heat of the body, nor the strength of the circulation, are causes of the blood's fluidity: they are both results of the same cause, viz. the vital energy of the ves- sels, and vital endowment of the globules of the blood ; both are co-ordinate, and both, as well as the phenomena of coagulation, are de- pendent on this source. 9. That coagulation occurs sooner in venous than in arterial blood ; and that coagulation of arterial blood is .still longer delayed if it be prevented from leaving the arteries. 10. That coagulation takes place the sooner after the blood is removed from the vital sphere of the system, the weaker the vital energy to which it was subjected whilst circulating in the system. 11. That the weaker the vital energy, and, consequently, the quicker the coagulation, the more lax is the coagulum which is formed. 12. That, on the same principle, coagulation is more slow, and the coagulum more firm, ac- cording as the vital influence of the vessels is more energetic. 13. That the quantity of globules modifies these results; a large proportion also of these globules indicates great energy, and vice versa. 14. That, &> the central globules retain their coloured envelopes during their circulation in the blp^d-vessels, and lose them soon after re- moval beyond the sphere of the vital influence of these vessels, and as this is a part, and in- deed the first part, of the act of coagulation, so we consider that it is in consequence of the vitality emanating from the interior of the ves- sels into the blood, that the coloured envelopes of the central globules continue to surround 'hem ; and, consequently, that the separation of lated albumen. They have examined the pro- portion which the white corpuscles and red mat- ter together bear to the rest of the blood, in a great variety of animals; and they find them most abundant in birds, next in the mammalia, especially the carnivorous mammalia ; and they are least plentiful in cold-blooded animals. In man they constitute about one hundred and twenty-nine parts by weight per thousand. They are more abundant in arterial than in ve- nous blood ; one thousand parts of the arterial blood of the sheep, dog, and cat, contain ten parts more of these particles than blood taken from the veins. The serum is identical in both 50 APPENDIX the envelope from the central globule is the re- sult of the loss of the chief portion of that vitality which proceeds from the containing blood-vessels ; and as this loss of vitality may be reasonably supposed to be quickest where it has been originally the least, therefore the sepa- ration of the envelopes and the coagulation will be the quicker, the weaker the vital energy, and vice versa,; and the coagulum will be the more lax. 15. That the loss of the vitality emanating from the vessels, and consequently the loss of their envelopes, disposes the central globules to attract each other ; and that in the exertion of this contraction they dispose themselves into reticulated fibres, which entangle the colouring matter and a portion of the serum, and thus the clot is formed. 16. It would appear that the central globules continue to retain, in the fibres which they form in the act of coagulation, a small portion of the vital emanation with which they were endow- ed ; inasmuch as the fibrous part of the coagu- lum evinces phenomena approaching to those denominated irritable ; and that it is the loss of the chief part of the vitality, and not the whole of it, which occasions the separation of the coloured envelopes from the central globules. 17. That the firmness of the coagulum, and the irritable phenomena evinced by its fibrous part, are proportionate in degree to the vital energies with which the vessels are endowed by the ganglial nerves distributed in them, and to the emanation which the globules themselves derive from this source. 18. That the vital emanation, proceeding from the ganglial nerves distributed in the ves- sels, affecting the globules in this manner, and giving rise to these phenomena, has been the cause of, and has countenanced, the hypothesis of the vitality of the blood, — a vitality which does not belong to it independently of these nerves, and of the vessels and organs through which it circulates, which it possesses in a di- minished degree, and which is an emanation from a different source (Prop. 3), which source is efficient in the formation of the blood itself, and bestows on it, through the medium of the vessels containing it, the chief properties which this fluid evinces in health and in disease__ (See Prop. 4, p. 49.) 19. That when the vitality of the system, especially that of the blood-vessels, is greatly diminished,.as in purpura haemorrhagica, scurvy, and in other diseases, coagulation either does not at all take place, or it takes place very quickly, and the coagulum is weak, lax, and re- sembling cruor. Under such circumstances, the envelopes separate rapidly from the central globules, because the vitality of the vessels is scarcely sufficient to continue them in connex- ion even when circulating through the vessels themselves ; coagulation takes place quickly, because the motion impressed upon the globules by the vital energy of the vessels, owing to the defect of this energy, is soon lost, and because the separation of the envelopes from the globules takes place almost instantly; and the coagu- lum which is formed is weak, or it does not * This appearance of the blood has generally been observed by us in cases of disease charac- terised by unusual frequency of the heart's con- tractions, accompanied by g-reat loss of vascular form at all, because the vitality of the globule* is insufficient to dispose to an energetic attrac- tion, or even to any attraction between the cen- tral globules. 20. In various diseases, especially in those which are malignant and infectious, when tho vitality of the system is much exhausted, a3 in the advanced stages of typhoid and adynamic fevers, in the true infectious puerperal fever, and puerperal mania, in the worst forms of ery- sipelas and diffusive inflammation of the cellu- lar structures, and in several other diseases, particularly when epidemic, or occurring in hos- pitals, the air of which is vitiated by crowding of the sick, and the decomposition of the dis- charges and secretions, as in lying-in hospitals, —the blood taken from a vein will often not separate into a distinct coagulum and serous fluid, but will assume the appearance of a straw-coloured gelly, at the bottom of which gelly the red envelopes of the vessels will be found forming a loose, reddish brown or blackisk stratum. In such cases, the blood, participat- ing in the deficiency of the vital energy of the body, and being also, perhaps, deranged from the admixture of hurtful materials with it, which are not duly eliminated by the various emunc- tories, evinces the lowest grades of vital en- dowment ; the attraction between the globules of the blood being so weak as not to give rise to the exclusion of the watery parts, and per- miting the envelopes of the globules to sepa- rate speedily, and to form a loose and unadher- ing stratum over the bottom of the vessel.* 21. Opposite phenomena to the above, result from the increased eneigy of the vital functions generally, particularly of the vascular system, and of the functions of the nerves which supply it. 22. If this were a suitable place, various other morbid states of the blood, arising both from deficient vital energy and consequent in- activity of the functions of those organs which are the emunctories of the vascular system, and from the introduction of hurtful emanations and ingredients into the circulation, and occur- ring in the course of numerous diseases, espe- cially such as are epidemic and febrile, might be adduced. 23. We may infer as a corollary, that the ap- pearances which the blood exhibits have al- ways an intimate relation to the vital conditions <* the system, and to the state of excitement whiti) the heart and blood-vessels present; and that the Huffy coat is merely one of the mani- festations finished by the blood, indicating re- action of the powers of life, or excitement of the vascular system. We believe that the blood participates in the vitality of the body through the hipdium of the vessels and organs in which it circulates ; that according to the degree or condition of this vital endowment, coagulation and the coagulum are modified in their pheno- mena and appearances, and the production of the buffy coat promoted or altogether prevented ; and that the blood gradually acquires its vital endowment from the time that the secretions mix with the more soluble portions of the chyme and form the nutritious chyle, which also gene- tone, and vital resistance of the system gene- rally. The blood-letting in such cases has al ways been very hurtful. i'»F SL.JRETION AND EXHALATION. 51 "•uiy presents the phenomena of coagulation, although in a less degree. III. Of transfusion of blood, and injection of foreign matters into it. — MM. Prevost and Du- mas* found that, after bleeding an animal until all organic actions ceased, and injecting, with- in a few minutes afterwards; the warm blood taken from another of the same species, until a quantity equal to that taken away was restored, the animal gradually revived and took nourish- ment, and perfectly recovered if the operation was well performed. If, however, the blood injected was taken from an animal of a different species, possessing globules of the same form, but different in di- mensions, the animal was very imperfectly re- vived, and could be rarely preserved beyond six days. The pulse became in these frequent, the temperature fell remarkably, if not artificially preserved, while the respiration retained its na- tural frequency. Immediately after the ope- ration the dejections became mucous and bloody, and preserved that character until death. If blood with circular globules was injected into the veins of a bird, the animal generally died, before the operation was completed, in very violent and rapid nervous convulsions. Transfusion of blood from the cow or sheep into the veins of the cat or rabbit, was followed by the recovery of the animal in a number of cases. The blood of the sheep excited in the mallard duck the most violent and rapid convulsions, which were immediately followed by death, as was observed to follow the injection of the first syringeful in land-birds. | OF SECRETION AND EXHALATION. (Notes CC. See pp. 180—187.) Opinions have been various respecting the mechanism provided for the performance of ex- halation and secretion. One class of physiolo- gists contends for a separate order of very mi- nute capillaries, proceeding from those carrying red blood, which they call exhalent or secretory capillaries, and devoted to these functions, (see p. 39.) Belonging to this class we may reckon Haller, Hewson, Soemmering, Bichat, Chaus- sier, Alard, &c. As these vessels cannot be demonstrated, their existence is denied by Mas- cagni, Prochaska, Richerand, Magendie, and others, who argue, that these functions take place in the sanguineous capillaries, through the medium of organic lateral pores. The fact appears to be, that the evidence for a separate set of capillaries is equal to that for the exist- ence of organic pores in the capillaries carry- ing red blood; it is not easy to demonstrate the * Bibliotheque Univcrs. Juillet 1821. t Since MM. Prevost and Dumas have thus recalled the attention of the profession to the subject of transfusion, the operation has been performed successfully by Dr. Blundell and others in this country, in cases of excessive uterine haemorrhage ; and under favourable cir- cumstances it promises to be of decided utility. The experiments and observations of various physiologists and pathologists have also shewn that much advantage win be obtained, and a more energetic effect produced, by injecting im- mediately into the current of the circulation presence of either; whilst both the one and the other may prove a sufficient medium through which the processes will go on, under the influ- ence with which the capillary vessels are en- dowed. The existence and efficacy of this in- fluence is sufficiently manifest, although the more minute instruments, by means of which it operates, cannot be satisfactorily demonstrated to our senses. In respect of secretion, the state of opinions and of our knowledge as to the manner in which it takes place, or rather the mechanism provided for its performance, is similar to what we have shewn to exist on the subject of absorption and on that of the minute capillaries. In stating the opinions on these subjects, and those lately espoused by M. Alard, we gave the views of those who contend for the existence of minute lymphatics running into the venous capillaries, in a similar manner to that in which exhalent vessels are supposed, as stated above, to pro- ceed from the arterial capillaries. But the lat- ter set of vessels has been as little seen as the former. This, however, in a matter of this na- ture, is not a sufficient proof against their ex- istence. Some physiologists, on the other hand, contend that exhalation and secretion take place through means of pores analogous to those which are supposed to be instrumental in the phenomena of absorption ; and that the process is entirely one of transudation. But the same objection may be offered against the existence of pores as to that of the exhalents or secreting capillaries in question. We believe that the precise way in which ex- halation and secretion take place cannot be rea- dily demonstrated to the senses, — that the one apparatus may explain the process as well as the other,—that secretion as well as absorption are not mechanical processes, although there are apparatuses, or subordinate instruments, provided for their performance,— and that they are essentially vital operations, and under the control of the vital influence with which the capillaries themselves, and the organs to which they belong, are endowed. As to the question of pores, it must be grant- ed, that the solids of the body, and the parietes of the vessels, are all porous ; it is only with respect to the extent and magnitude of the pores that the question can be entertained. Those who contend for the existence of sepa- rate and subordinate sets of capillary vessels, cannot deny the existence of pores ; for if they do not exist both on the surfaces and in the tex- tures whence these capillaries are supposed to originate, how could they obtain the fluids cir- culating in them? On the other hand, those who contend for the existence and functions of pores, cannot deny the existence of minute absorbents various medicinal substances, than when such substances are exhibited in the usual way. The results of this mode of treatment shew that a large proportion of medicinal agents act in a similar manner when injected into the blood, as when exhibited through the medium of the di- gestive organs — the quantity, however, in the former case requiring to be much smaller; and, moreover, it has been shewn also, that when ac- tive substances are thus introduced at once into the blood, they produce the specific effects usual- ly observed to proceed/rom their use in the com mon modes of exhibition. 52 APPENDIX. or lymphatics ; for they can be demonstrated to a certain extent as respects the minuter ramifi- cations, and in a satisfactory manner as regards tke more considerable branches. It appears to us that both species of organisation exist to a greater or less extent in different textures and secreting organs. We refer our readers to our notes at p. 183, for some remarks on the fact, that each secret- ing viscus is supplied with a distinct ganglion, plexus, or both; that these preside over the se- creting function ; and that the functions of some of these ganglia are influenced by the opera- tions of the cerebro-spmal system ; as, for ex- arriple, the secretion of the lachrymal gland is increased by the influence which the nerves of this latter system convey to the ganglion that supplies it, and is the chief source of its functions. OF NUTRITION. (Notes DD. See pp. 189—192; and Note S, p. 39.) As we have already seen, in the Notes on the Capillary System and on Secretion, the func- tion of nutrition has been explained by one class of physiologists by supposing the existence of nutritive capillaries, and by another by means of organic pores, with which they endow the capillary vessels circulating red blood, and to which they commit the exhalent, secreting, and nutritive functions. The first of these hypo- theses supposes that nutrition takes place in minute colourless vessels, which proceed in a more or less tortuous direction from the arterial capillaries, absorption proceeding through the medium of a similar set of colourless vessels continuous with the former, which run into the venous capillaries, and thus the nutritious mole- cules are always circulating within colourless capillaries, which, with the nerves and larger capillaries, constitute the basis of the different textures. Mascagni supposes that the arterial capilla- ries, at the point where they change into veins, are provided with exhalent pores, both for the purposes of secretion arid nutrition; and that there every where exists the orifices of minute absorbent vessels, commencing in the latter de- scription of pores, in order to take up the nutri- tive molecules. The elementary tissues con- sist, in his opinion, of this particular class of absorbent vessels, which contain the molecules as long as they are a part of the textures, and which, by their union, form the most simple membranes. These hypotheses do not differ very material- ly. Both contend for the existence of very fine capillaries, which attract the nutritive mole- cules, and contain them in a state of progressive circulation, as long as they form constituents of the textures; these molecules being after- wards carried onward in succession into the branches of the absorbent lymphatics and into the veins. In the first of these hypotheses, the nutritious particles are supposed to circulate in the finest of the vessels proceeding from the arterial capillaries ; in the second, the process is ascribed to the most minute radicles of the absorbents ; but both agree in considering the molecules constituting the mass of the textures to be contained in colourless vessels, and to be in a state of continual circulation. The opinion ot Bichat on this subject is *">ruf what different. According to him, each mole cule of those constituting the textures of the body is "placed between the orifices of two ves- sels: one, a nutritive exhalent orifice, which has deposited the molecule ; the other a nutri- tive absorbent orifice, about to absorb it. Prochaska, who conceives that the arterial capillaries are continued directly into veins, considers that nutrition takes place in conse- quence of the porosity of the capillaries, and of the general permeability ofthe substances con- stituting the mass of the structures. M. Riche- rand espouses a similar opinion ; but he seems to allow an organic property to the pores which he ascribes to the capillary vessels. Opinions respecting the mechanism of nu- trition, or the manner in which it takes place, can only be theoretical. We have not the means of demonstrating the existence or non- existence of either the one or the other mode of organisation contended for: each may of ilult be sufficient to explain the phenomenon, as far as respects the apparatus required for the pro- cess, but it is only the apparatus. The function itself is purely a vital one. It presents us with a continual motion, of a double nature—a con- tinual attraction and decomposition of material molecules. In the most simple animals, as the polypus, these processes go forward without any previous preparatory function : the animal im- bibes, in a direct manner, similar molecules of matter to those of which it is itself formed from the surrounding medium, and again exhales them in a manner equally direct. In these there are no vessels destined for the purpose of cir- culation and nutrition, yet they present the phe- nomenon of irritability; and on examination with a microscope, their structure appears al- most homogeneous, with the exception of glo- bules entirely similar to those which are observ- ed in the ganglial nerves of the higher animals. As these are the chief marks of internal organi- sation which can be detected in the very lowest of the animal kingdom, and as we must con- ceive that the organisation must be instrument- al in the nutrition and operations of animal bodies, and as, moreover, we perceive that the perfection of the organisation or material ap- paratus is commensurate with, and has an evi- dent relation to, the extent of the vital opera- tions which it performs, — so it seems reason- able to suppose that this organisation, which is the only one that is detected in the very lowest of animals, is the chief and indeed only instru- ment of the limited function which they per- form ; and that, as a similar .but more perfect organisation presides over the nutritive function of the highest animals, so this presides over that ofthe lowest, without the assistance of the complicated capillary apparatus assigned by some physiologists to them; and if a distinct set of subordinate capillary vessels be not re- quisite to the nutritive function in the lowest class of animals, we may allow that this func- tion takes place in the highest classes, under the dominion of the more perfect nervous orga- nisation to which we have assigned it, without the existence of the complicated capillary ap- paratus for which some contend. Concluding, therefore, that as the nervous globules demonstrable in the very lowest animals are the only .internal organisation which they evince, that organisation must have a determi- nate object or function, which it performs under OF NUT*UTION. 53 the control of the vitality with which it is allied, and which all animals possess ; and that nutri- tion and irritability are the only organic actions which these animals perform,—so it must inevi- tably follow, that these actions result from the vital influence allied to the particular organisa- tion in question ; and that the nervous globules constituting the only marks of internal organi- sation possessed by these animals, attract from the surrounding media, in consequence of the vitality with which the globules are endowed, these molecules of matter corresponding to those forming the structure of the animal, which come within the sphere of their influ- ence, and retain them for an indefinite time, unassisted by either exhalent or absorbent ves- sels. Now, as the same type, especially as re- spects the nutritive functions, may be observed throughout the whole animal creation, and as we can trace nervous chords, formed of globules similar to those already ascribed to the lower, and indeed to all animals, throughout almost the whole of their bodies,—is it not reasonable to suppose that similar globules exist in all the simple textures in a more diffused form—that the globules constituting the organic or gan- glial system of nerves become more disseminat- ed amongst the molecules of the textures in the course of their distribution with the capillary ves- ' sels, and of their more direct ramifications and terminations in the textures themselves ? If this be granted,—and it scarcely can be denied, for it has been demonstrated in different orders of animals—and as it has been shewn that these nervous globules are present, in a more or less organised form, throughout the whole animal creation—it may consequently be inferred, that the same function which we have aseribed to them in the lowest animals should be extended to them in the highest. This is conformable to the laws characterising the animal economy. As we have contended in another place, (p. 13, et seq.) conformably with this opinion, that the ganglial nerves, in some one or other of their forms of existence, are present throughout every part of the body, that they preside over digestion, nutrition, secretion, &c. and are more nearly allied than any other .texture with the vital influence which the body exhibits,—so we now conclude, that the globules constituting the ganglial system, being allied with vitality, and being distributed in different forms of con- nexion to the various textures of the body, ex- ert, in consequence of the vital influence with which they are endowed, a vital attraction on those molecules of matter which come within the sphere of their influence; that the force of this attraction, and the manner in which the material molecules are arranged in order to form the different textures of the body, result in a great measure from the influence proceeding from the form, the number, or the condition of these globules in the textures which it is their office to perpetuate ; and that the chief office of the digestive, the respiratory, the animalising, and the circulating processes, is to present the materials, whence the different textures are preserved and nourished in a fit state for the exertion of this vital attraction; and that the principal operation performed by the capillary vessels is to convey these materials within the sphere of this attraction; and, so that this is performed, it matters but little whether or no these vessels accomplish it by means of subor- dinate nutritive capillaries, destined to the cir- culation or deposition of the nutritious mole- cules, or by means of organic pores, with which their parietes may be provided. But, whilst we suppose that the function of nutrition may thus take' place in consequence of a vital attraction, resulting in the manner which we have explained, and exerted exterior to and independently of the vessels, and whilst we consider this explanation to be supported by the nutritive actions of the lowest animals ; yet we would by no means exclude the influence of that part of the ganglial nerves distributed to the capillaries from a part in the operation, more especially in the higher classes of animals. Indeed, it seems difficult to suppose which of those in the higher animals—namely, whether the nervous globules distributed to the simple textures, and placed beyond the capillaries, or those constituting the nervous fibrilae which surround them,—are most efficient in the nutri- tive process. An intimate view of the subject would suggest, that in man and the more per- fect animals the latter organisation is the more active of the two in the operation in question ; and that the capillary vessels, in consequence of the ultimate nervous structure which sur- rounds them, and of the vital influence which this structure exerts, secrete from the fluid cir- culating in them certain materials in a similar manner to that in which they perform the other secretions in secreting organs, and by means either of appropriate vessels or pores. As it has been shewn that the blood consists of minute globules, or corpuscles, surrounded by a coloured envelope circulating in a mass of fluid, and that the simple solids of the body are constituted of similar corpuscles, in a state of intimate or vital attraction, to those of the blood, when they are separated frpm their en- velopes,—so it may be inferred, that a part of the function, which the ultimate distribution of the ganglial nerves performs on the capillary vessels, is to secrete similar corpuscles, from the blood circulating in these vessels, to those of which the texture is formed in which the operation takes place ; and that this having been accomplished, the vital attraction is preserved by means either of the influence with which these corpuscles are endowed, as a consequence of the previous process of animalisation which they have undergone, or of the influence exert- ed upon them after they leave the vessels by the nervous globules and fibrilae disseminated in the textures, or perhaps by both species of vital action, either the one or the other acting more or less partially, according to the nature of the particular texture in which the process takes place, and according to inappreciable and fortuitous causes. Hence it will be perceived that nutrition is essentially a vital operation, that it is placed under the control of the extreme ramifications of a particular system, to which we have refer- red all the vegetative or organic operations which characterise the animal kingdom ; that it is performed in all animals, except the very lowest, through the medium of circulating or- gans, and in the highest as a consequence of certain preparatory processes ; that it requires in man and in the higher animals a capillary circulation for its performance, but that neither of the capillary apparatuses which have been contended for is sufficient of itself to perform this function, although the most simple appara- tus, whilst under the dominion of the vital in- 54 APPENDIX fluence of that particular structure which we find every where disseminated where there is life, is all that is requisite as the material in- strument of the process;—and lastly, and as a consequence of the foregoing position, that nu- trition is modified, controlled, increased, or even annihilated, either generally or in particular parts of the body, by the state of the vital influ- ence allied to the material organisation, to which we have already imputed it, according as this particular organisation in its centres and ramifications throughout the animal frame is generally or locally affected. OF THE DECUSSATION OF THE OP- TIC NERVES, AND MOTIONS OF THE EYES, &c. &c. (Notes EE. See pp. 201—206.) I. Decussation of the optic nerves.—Vicq d'Azyr found, on examining with a microscope a horizontal section of the optic nerves of the human subject, after it had been hardened in alchohol, that the medullary fibres occupying the exterior side of the optic nerve proceed in a direct manner from the optic thalamus to the eye of the same side, and that the place of union presents a homogeneous tissue. The Wenzels came nearly to the same conclusion from their observations ; but remarked, in addi- tion, that while the fibres of the exterior side of the nerve go immediately to the eye of the same side, those fibres placed in its interior side are directed obliquely towards the other nerve, without, however, any crossing of fibres being manifest at the point where the junction of both nerves takes place. M. Treviranus has, in a great measure, con- firmed these observations on the male simia aygula. The nerves and brain were left during some months in alcohol, and afterwards kept some time in caustic potash to soften them. Having thus prepared them, he submitted them to a careful dissection, when he made out, with the aid of a microscope, that the external fibres of the upper side of each were continued from their cerebral extremity to that in the eye, with- out uniting themselves to those of the other side ; whilst, on the contrary, the internal and inferior fibres of one nerve went to the other side, and united with the fibres of the opposite nerve. It was difficult to determine whether any of the fibres actually passed from one side to the other. He thought, however* that some of the fibres did so. The internal fibres, thus interlacing together, were evidently more nu- merous than the external fibres which ran to the eye without uniting with those of the oppo- site nerve.* M. Magendie infers from his ex- periments that the decussation of the optic nerves is complete, t II. Of the motions of the eye, p. 206.—Mr. Charles Bell has lately examined the motions of the eye, in illustration of the uses of the muscles of the orbit; and has shewn, in the _, first place, that there are motions performed by this organ not hitherto noticed. Every time the eyelids descend to cover the transparent part of the eye, the eyeball ascends, or suffers * Journal Complementaire, Oct. 1823. f See his compendium of Physiology, 2d edition. a revolving motion. If this were not the c\ne the surface of the eye would not be moistened, nor freed from offensive particles. He has proved, in the next place, that during sleep the eyeball is turned up, and the cornea lodges se- cure and moistened by the tears, under cover of the upper eyelid. He considers that these mo- tions are rapid and insensible, and that they are provided for the safe-guard of the eye. The other motions are voluntary, and for the purpose of directing the eye to objects. Mr. Bell next examined the actions of the muscles of the eyeball, and distinguished them, as usual, into the straight and oblique muscles. It has been supposed, hitherto, that both these classes of muscles were voluntary ; some de- scribing the oblique as coadjutors of the recti muscles, and others as opponents to the recti; but Mr. Bell has viewed the oblique as provided for the insensible motions of the eyeball, and the recti for those motions which are directed by the will, and of which we are conscious. Mr. B. has also proceeded to shew, that the consciousness of the action of the recti mus- cles gives us the conception of the place or re- lation of objects ; and has endeavoured to prove, by observation and experiment, that the actions of the straight muscles are inseparably connect- ed with the activity of the retina, that is, with the enjoyment of vision ; but that the moment the vision is unexercised, the eyeball is given up to the operation of the oblique muscles, and the pupil is consequently drawn up under the eyelid. " Hence the eyes are elevated in sleep, in faintness, and on the approach of death; and that distortion which we compas- sionate as the expression of agony, is the con- sequence merely of approaching insensibili- ty.":): III. Of the connexion of the fifth pair of nerves with the function of vision.—The branches ofthe fifth pair of nerves are evidently related to the functions of sensation and touch in respect of the parts to which they are ramified. In a few of the lower animals in which the optic nerve is wanting, the first branch of the trige- minal nerve seems to be so intimately connect- ed with the sense of vision, as to be entitled to be considered as the chief nerve of this organ, and the one on which the sensation depends. It seems also, both from experiment and patho- logical observation, to be subservient in the higher animals to the perfection of the sense of vision; and it supplies in an especial manner some of the parts of the organ, particularly the iris, most intimately associated in function with the retina. The fifth pair of nerves seems to establish a kind of relation between the senses of sight, smell, taste, and hearing, by means of the filaments proceeding from its three princi- pal branches to the most important parts of the organs of these senses; and whilst it contri- butes to their perfection generally, it is particu- larly concerned in the production of the sense of taste. It is not A special or principal nerve of sight, nor of smell, nor of hearing, in man, but it performs an accessary part, and renders these senses more perfect. M. Serres6 records a case of disease con- firmatory of these views, which occurred in an X Annals of Philosophy, May 1823. t) Archives Gintrales de Me'decine, Aoiil 1824. OF THE NERVES OF THE 8ENSE OF SMELL. 55 epileptic patient in the hospital la PitiA. The patient had lost the sight of the right eye, and the senses of taste and smell of the same side ; hearing also was nearly lost in the right ear. Upon dissection, the fifth pair on the right side, at its origin, was converted into a yellowish gelly-like substance, and wasted to less than two-thirds the size of the nerve on the opposite side. The ganglion was also yellowish and diseased. The muscular fibres of the affected nerve seemed healthy : mastication was not observed to have been affected. When the first branch of the fifth pair is in- jured, or its functions impeded or destroyed, either by experiments, by accidents, or disease, the more important parts of the eye become in- flamed or otherwise diseased, sometimes to an extent sufficient to destroy the organ. IV. Of the adaptation of the lens to distinct vision.—The majority of physiologists have considered adaptation of the crystalline lens to the objects observed as a matter of fact. Hal- ler, however, seemed to have entertained a dif- ferent opinion, and to have denied that any adaptation of the lens obtains. This opinion has recently been ably supported by the reason- ing of Dr. Milligan, the learned translator of M. Magendie's Compendium of Physiology. Dr. Milligan states, that " the. human eye is a camera obscura, and, like it, receives the image of every object accurately at every distance." But although we have no satisfactory proof that any adjustment of the lens actually takes place, yet we conceive that some adaptation of the eye, particularly as respects the motions of the iris, and the resulting effects upon the cornea, may be observed. On this subject, the most exact and conclusive observations which have hitherto been adduced have been made by Jean Mile, professor of physiology-in the University of Warsaw.* The inferences at which he has arrived are as follow :— 1. The eye does not see with the same dis- tinctness objects at all distances, but only when placed within a certain distance. 2. This does not proceed fiom external causes, such as the diminution of the optic angle, and the obscura- tion of the object by the intermediate air ; for to see clearly, and to see distinctly an object, are not identical. 3. The causes of distinct vision a$e internal, and situated in the eye it- self ; they are two in number, one disposes the eye for continuous distinct vision, the other for transient distinct vision of objects at different distances ; but neither of them can act but within certain limits. 4. These limits are greater for the presbyote than for the myope. 5. These faculties both depend upon the action of the iris, which acts at the same time in two ways to produce two effects ; first, the contrac- tion of its aperture, and secondly, the flexion of the cornea; the alteration in the size of the pupil being only visible. 6. The adjustment of the eye for continuous distinct vision of ob- jects contained within certain limits depends not upon the greater density ofthe vitreous hu- mour at the bottom of the eye than towards the lens ; 7, but is owing to the disfraction ot the rays of light near the edge of the aperture of * De la Cause qui dispose l'CEil pour voir distinctement les objects places a differentes distances.— Traduit du Polonais. Journal de Physiologic, torn vi. pp. 166, 179, et seq. the iris, in consequence of which there are formed, by a single external luminous point, several foci instead of one, ranged successively in a line of a certain length, so that the object may change its distance within certain limits, and yet one of its foci shall always fall on the bottom of the eye. 8. This focal length is in- versely as the magnitude of the pupil. 9. The circumference of indistinct objects appears ra- diated, and to the phenomenon of confusion are added the motion and multiplication of the im- age when the edges of bodies are brought near the side of the fasciculus of rays which enter the eye ; besides, the prismatic colours also ap- pear. 10. All these phenomena, which are ob- served in an eye performing its functions, may be produced by an apparatus the structure of which resembles that of the eye, and even by a common lens, substituting for the motions of the iris diaphragms or screens of different sizes. 11. The nature of all these phenomena proves, that disfraction is their common origin, and they may constitute a separate kind of optical illu- sions, proceeding from disfraction. 12. The second cause which disposes the eye for the momentaneous distinct vision of objects, de- pends neither upon the action of the external muscles of the eye, nor the advancement of the bottom of the eye, nor in change of form or po- sition of the crystalline lens ; but appears to be owing rather to the change of curvature of the cornea by the contraction of the iris, which takes place when the eye adjusts itself to see very near objects, as is proved by the simulta- neous approximation of the pupil. OF THE NERVES CHIEFLY CON- CERNED IN THE SENSE OF SMELL. (Note FF. See p. 214.) The first pair of nerves is chiefly distributed to those parts of the nasal apparatus which are principally concerned in this function; namely, the olfactory or pituitary membrane, particular- ly at the upper parts of the nasal cavities, and where it covers the spongy and convoluted bones. The nasal branches of the fifth pair are distributed rather to the accessary parts of the organ, than to the pituitary membrane itself; they form a circle around the expansions of the olfactory nerves, in the same manner as the ciliary nerves around the retina. The first pair of nerves generally presents a size and deve- lopement in proportion to the energy of smell, in the more perfect animals; whilst, on the other hand, it must be conceded, that the fifth pair is the chief nerve of smell in fishes and the cetacea. It was formerly doubted by Mery,t that the first pair of nerves are actually the nerves of smell; and recently M. MagendieJ has revived these doubts, and appealed to ex- periments in justification of them. That the first pair are most intimately connected with . the function of smell, seems proved by the fol- lowing facts : LoderiJ found the olfactory nerves destroyed in a man who was entirely deprived of the sense of smell. A similar fact came un- t Brunet, Progres de la Medecine, 1697. X Journ. de Physiol. Exper. torn. iv. p. 169. () Observatio Tumoris Scirrhosi inbasi Crami reperti. Jena?, 1779. 56 APPENDIX. der the observation of Oppert ;* and Ceruttit relates the ease of a man who had never enjoy- ed the sense, and in whom, upon dissection, the olfactory nerves were ascertained to have been entirely wanting. It should not, however, be concealed, that Mery adduced equally conclusive facts, in proof of the second branch of the fifth pair being the chief nerve of this sense. He opened the heads of three persons who had experienced no defect of the sense of smell, and in whom the first pair of nerves was changed, so as appa- rently to have been incapable of performing their functions. In our speculations respecting the sense of smell, it should be recollected that, in order that this function may be duly performed, the pitui- sary membrane must be constantly moistened oy a fluid mucous secretion. This secretion requires a continued supply of nervous influence to promote it, under the coustant evaporation it ts experiencing by the currents of air passing aver it; and such influence we conceive to pro- ceed chiefly from the first pair of nerves; these lerves performing, perhaps, in addition, the office of transmitting the impression made upon the pituitary membrane to the brain, or being assisted in this part of their functions by the second branch of the fifth pair; and, perhaps, this latter nerve may become the chief medium of the sensation in those cases where the first pair of nerves has been injured or destroyed. It should be recollected, that impressions made upon the organ of smell, owing to the odoriferous particles having in some measure combined with the mucus covering the pituitary membrane, will continue for some short time after they have been made, and that they pow- erfully affect the state of the brain and of the nervous system, and even also influence the amorous propensities, and the states of the genital organs. OF THE FORMATION OF THE SPINAL MARROW AND BRAIN. (Note GG. See pp. 229, 235—238.) I. Of the formation of the spinal marrow.— The researches of MM. Gall, Tiedemann, the Wenzels, Doellinger, Carus, and Desmoulins, have furnished us with much interesting infor- mation on this subject, and which, as far as we are enabled to judge from some observations made by ourselves, seems to be, upon the whole, extremely correct. The soft and gelatinous state of the embryo * Dissertatio de Vitiis Nervorum organicis. Berlin, 1815. t Beschreibung der Pathologischen, rd are more especially concerned in the per- formance of particular functions, yet that their functions are not strictly limited to distinct por- tions of the chord; and that the spinal chord is not a mere conductor of sensation and voluntary motion, but that it also aids in maintaining the vital energies of those parts to which its nerves are distributed. On this subject we find the opinions of Dr. Spurzheimt are agreeable to our own. Hfe con- ceives that the muscles or instruments of mo- tion acquire their power ih part through the in- fluence of their nerves, whilst the will to make the muscles act resides in the brain. The experiments instituted by Dr. Bellin- geri,| and detailedin a memoir read before the Royal Academy of Sciences at Turin, in Fe- bruary 1824, do not tend to throw any new light upon this interesting subject. They con- firm the idea of separate nerves of sensation and motion in the spinal chord ; but they fur- ther accord motion to the nerves that issue from the dorsal roots. His inferences are, 1st, that the posterior roots of the lumbar and sacral nerves produce the motions of extension in the lower extremities ; 2d, that the posterior roots alone preside over sensation ; 3d, that the ante- rior roots produce the motions of flexion in the sacral extremities, and do not aid in perceiving external impressions; 4th, that the*posterior bundles of the spinal chord preside over the motions of extension ofthe inferior extremities, and have no connexion with perceptions of touch; 5th, that the white substance of the spinal chord, and the nervous fibres that arise from it, are appropriated to motion ; and 6th, that under the direction of the brain, and through the channel of the spinal chord and nerves,-the moving principle to the muscles. M. Flourens, as we have shewn, views this organ as the regu- lator and balancer of the muscular contractions. M. Magendie regards it as requisite to the pro- duction of motion forwards : and Mr. C. Bell, MM. Fodera, Foville, and Pinel-Grandchamp, are of opinion that it is the seat of sensibility. t The Anatomy of the Brain, with a General View oftfie Nervous System. By G. Spurzheim, M.D., &c. Lond. 1826. X Bulletin des Sciences Midicales, Juin 1825. OP THE RESPIRATORV NERVES. 65 the. gray substance of the chord, and the ner- vous fibres that spring from it, belong to sensa- tion. In opposition to the last inferences here stat- ed, namely, that the spinal nerves may be di- vided into those which come from the white, and those which proceed from the gray, sub- stance of the chord, it may be contended, that these nerves are universally implanted into the gray substance of the chord. Upon the whole, therefore, although we may grant that the co- lumns of the spinal chord seem concerned to a certain extent in the performance of distinct Junctions, yet we conceive that these functions have not yet been appropriated with sufficient precision to the different parts of the chord and origins of its nerves, and that this subject stands much in need of further investigation. W hilst the above remarks were passing through the press, M. Schoepfs experiments on the different parts of the cerebro-spinal ner- vous system were made known to us. These experiments shew the justice of our remarks, whilst they, upon the whole, confirm the results of those performed by M. Rolando,* M. Flou- rens, and Dr. Bellingeri: they are in opposition, however, to many of the inferences at which Mr. Bell and M. Magendie have arrived. They shew, moreover, that volition is entirely to be referred to the cerebral lobes ; that slight irrita- tion of the medulla oblongata produces convul- sions, and afterwards paralysis of the same side ; that more severe lesions of this part im- mediately arrest the movements of the respira- tory organs ; that the posterior as well as the anterior columns of the spinal chord, and the anterior as well as the posterior roots of the spinal nerves, are concerned in the function of voluntary motion ; and that the sense of touch or sensibility belongs neither to the one nor the other. + IV. Of the respiratory order of nerves, cf-c.— Ail animals that possess a perfect cerebro-spi- nal system have an intermediate order of nerves which connect the vegetative functions of the ganglial system with the functions of the ence- phalon. This order of nerves has lately been very satisfactorily examined into, both as re- spects their distribution and functions, by Mr. Charles Bell. On investigating the minute structure of the nerves which, both in man and in the lower animals, arise from the spinal marrow by dou- ble roots, and those which proceed from the medulla oblongata, by single origins, to the or- gans of respiration, and those parts of the face and trunk which evince an intimate relation with this important function, Mr. Bell perceiv- ed that their texture and mode of distribution were very different. This circumstance led him to consider that two distinct orders of nerves must exist, independently of the sym- pathetic ; the one simple and uniform, the other irregular and complex in proportion to the com- plexity of the organisation. The former he has called original or symmetrical, the latter super- added or irregtdar. In the superadded class of nerves, which are chiefly devoted to the func- tion of respiration, Mr. Bell arranges, 1st, the * Saggio sopra la vera Struttura del Cervello, c sopra le Funzioni del Sistema Nervoso. Edit. 2d. vol. ii. p. 298, et seq. t Annali t'niversali di Mr.dicina. Milanr>. par vagum ; 2d, the portio dura ; 3d, the spinal accessory ; 4th, the phrenic ; 5th, the external respiratory nerves, &c. " The nerves," this physiologist states, " on which the associated actions of respiration depend, and which have been proved to belong to this system, by direct experiment, and the induction from anatomy, arise very nearly together. Their origins are not in a bundle of fasciculus, but in a line or series, and form a distinct column of the spinal marrow. Behind the corpus olivare, and ante- rior to that process which descends from the cerebellum, the corpus reshforme, a convex slip of medullary matter, may be observed ; and this convexity, or fasciculus, or virga, may be traced down the spinal marrow, betwixt the sulci which give rise to the anterior and pos- terior roots of the spinal nerves. This portion of medullary matter is narrow above where the pons Varolii overhangs it. It expands as it de- scends ; opposite to the lower part of the corpus olivare it has reached its utmost convexity, after which it contracts a little, and is continued down the lateral part of the spinal marrow." From this track of medullary matter on tlie side of the medulla oblongata, arise in succes- sion from above downwards the portio dura, the glosso-pharyngeus, the par vagum, the nervus ac- cessorius, the phrenic, and the external respirato- ry. These superadded nerves are comparative- ly but little sensible ; they do not arise by dou- ble roots, as the symmetrical do ; they have no ganglia on their origins ; and while the other voluntary nerves have large, free, and round filaments, they have a close, loose texture, re- sembling a minute plexus. " These are the nerves which give the appearance of confusion to the dissection, because they cross the others, and go to parts already plentifully supplied from the symmetrical system." From these anatomical investigations, and from experiments made in order to ascertain the exact functions of this order of nerves, Mr. Bell and Mr. Shaw have drawn some import- ant inferences :—1st, They consider that the portio dura of the seventh pair "produces all those motions of the nostrils, lips, or face gene- rally, which accord with the motions of the chest in respiration. When cut, the face is deprived of its consent with the lungs, and all expression of emotion. 2d, The par vagum as- sociates the larynx, the lungs, the heart, and the stomach, with the muscular apparatus of re- spiration. 3d, The spinal accessory controls and directs the operations of the muscles of the neck and shoulder, in the offices of respira- tion. 4th, The phrenic nerve has its functions sufficiently characterised in the name of inter- nal respiratory, which Mr. Bell has assigned it. 5th, The glosso-pharyngeal nerve, &c. ; and 6th, The external respiratory nerve, perform the functions which those parts, to which they are distributed, have in connexion with the ope- rations of respiration." Mr. Mayof subsequently investigated the functions of these nerves, and added much to our knowledge of them. He has shewn that the portio dura of the seventh nerve, and the ganglionless portion of the fifth, are simply Luglio 1808. X See this author's very able work, entitled "Outlines of Human Physiology." Second edition. London, 1829. Pp. 334—36. 66 APPENDIX. voluntary nerves td parts which receive sen- tient nerves from the larger or ganglionic por- tion of the fifth, and that this portion of the fifth is exclusively sentient. Mr. Broughton has also demonstrated that the portio dura of the seventh nerve, and the par vagum, are strictly nerves of motion ; and he has further proved that they are entirely un- concerned in the function of sensation.* It will be perceived, from some observations offered by us at p. 21, that we consider that the ganglionic portion of the fifth nerve is not only a sentient nerve, but that it also is engaged in the functions of secretion, exerted by the parts which it supplies, namely, the lachrymal secretion, the secretion of mucus in the nares, and the secretions of the mouth. As far as reliance may be placed upon a sin- gle experiment lately performed by ourselves, we conceive that Mr. Broughton is perfectly correct in considering the par vagum as a nerve of motion only ; and that it is in no way con- cerned in endowing the parts to which it is ramified with sensibility. We consider that the sensibility evinced by those parts is bestow- ed upon them chiefly by the visceral-ganglial nerves, which nerves are also concerned in the production of the secretions of the mucous surfaces covering the organs whose motions the par vagum actuates. As far as our own observation enables us to form an opinion, we believe that the par vagum influences the pro- cess of digestion chiefly by being concerned in the motions of the muscular coats of the stomach, thereby changing the position of its contents in respect of the villous surface, and propelling the digested portions towards the pylorus. The secreting functions of the vil- lous surface, we believe chiefly to depend upon the ganglial nerves distributed to this organ. We further consider, that the complete division of the par vagum has impeded, or, to a certain extent, arrested, the process of digestion, owing to the acting of the muscular coats of the stomach having been thereby interrupted. V. Principle observed in the origin of the cere- bro-spinal nerves.—Mr. Mayo believes " that nerves of motion take their rise from the same region or segment with those sentient nerves which transmit the impressions by which their action is usually regulated. The correctness of this remark, as it respects the spinal nerves, will not be disputed. It is owing to this cir- cumstance, that if in an animal just killed, the spinal chord be divided in the neck and in the back, on irritating the integument of either foot, that foot is retracted as promptly and to the same extent as if the spinal chord and medulla oblongata were entire. " We observe, that the smaller portion ofthe fifth rises from the upper part ofthe medulla oblongata, close upon the greater portion ; and we recollect, that the sense of pressure upon the teeth and gums, and of muscular exertion attending it, depends upon the latter, the mus- cular effort itself upon the former. " We observe, that the largo root of the fifth and the portio dura rise together; and we re- collect that the delicate sense of touch upon the eye and eyelids depends upon the first, and the action of the orbicularis palpebrarum on the se- * Medical and Physical Journal for June 1823, p. 46.1. cond ; that the sense of touch in the nostrils do^ pends upon the first, and the action of the mus- cles of the nostrils upon the second ; that feel- ing in the lips depends upon the first, and the action of the muscles of the lips upon the se- cond ; and, finally, that the sensation of those muscles, which the second sets in action, de- pends upon the first. " We observe, that the portio dura rises near the portio mollis; and we recollect, that the motions of the ear depend upon the former, and the sense of hearing upon the latter."t These observations seem to us both correct and interesting; although this principle will not apply to every nerve of the body, as the au- thor has candidly admitted. VI. General remarks on the different parts composing the nervous system.—From what we have already advanced respecting the functions of the ganglial system of nerves, and from what has also been said respecting the other parts of the nervous system, it may be inferred that the nerves present a modified state of conformation and distribution, according to the functions which they perform. This view of the subject is confirmed not only by an attentive examin- ation of the diffeventnerves ofthe human body, but also by a comparative investigation of this part of the animal economy throughout the dif- ferent classes of animals. In some of the lower orders, the organisation of the nervous system is intermediate between that of the visceral- ganglial nerves and that of the spinal nerves ; and we accordingly find that nerves proceeding from the same ganglion supply both their diges- tive and locomotive organs. As we rise in the animal scale, nerves of an appropriate or dis- tinct organisation and mode of distribution sup- ply particular organs, and discharge specific functions. It was not until the time of Winslow that this principle in the animal economy seems to have been sufficiently recognised. He first distinguished between the ganglial nerves and those of the cerebro-spinal system. This divi- sion was afterwards adopted by Johnstone, Bichat, and some other anatomists. But a more attentive examination will shew, that the ner- vous systems may be still further divided. The ganglial system of nerves may, we conceive,. be subdivided,—1st, into the ganglial nerves supplying the viscera ; and 2dly, into the gan- glial nerves of association, or those which com- municate between the first division, or visceral nerves, and the cerebro-spinal nervous system. This latter system may be subdivided into, 1st, the brain proper; 2d, the cerebellum; 3d, the medulla oblongata and spinal chord; 4th, the nerves of sensation; and 5th, the nerves of motion. Although it seems evident, from the experi- ments of Mr. Bell, Mr. Magendie, Mr. Mayo, Mr. Broughton, and Dr. Bellingeri, that the nerves perform distinct functions, yet we con- ceive that those functions have not been assign- ed with sufficient precision to their respective nerves. Indeed, the imperfect state of our knowledge has not allowed this to be done in a way at all accordant with well-ascertained phe- nomena. Many of the nerves, also, seem to perform more functions than one : thus the ophthalmic branch of the trigeminal nerve sup- f Outlines of Human Physiology. By H. Mayo, F. R. S., &c. 2d Edit. Pp. 343, 344. OF THE PHENOMENA OF MIND. 67 plies the lachrymal gland, and presides over its secreting functions ; filaments proceeding from the same branch supply the iris, ate instrumen- tal in its motions, and seem to preserve the eye in a fit state for the performance of its delicate functions : the nasal portion of the nerve seems to be concerned in both the secretions and sen- sations of the organ ; and the third branch of the same nerve appears to perform similar offi- ces in respect of the organ of taste. We know that some of the ganglial nerves of the thorax and abdomen are chiefly instrumental in the production ofthe insensible motions of the con- tractile organs which these cavities contain, whilst others of these nerves preside chiefly over the functions of the secreting viscera. Yet these nerves, whether those engaged in endowing contractile organs with the power of motion, or those presiding over the functions of secretion and sanguification, &c. also possess the faculty of conveying sensations, and are evidently possessed of variously modified sensi- bilities. How far these latter properties de- pend upon the associating ganglial nerves, or those which communicate between the cerebro- spinalsystem* and thevisceral ganglial system,t our researches have not enabled us to deter- mine : but, from the examinations we have alrea- dy made, we conceive that this associating order of nerves performs a very important part in conveying to the visceral-ganglial system of nerves the nervous energy of the spinal chord and medulla oblongata, in connecting the func- tions of the different nervous masses, and in transmitting the peculiar sensations excited in any of the viscera of organic life to the brain. In the first edition of these Notes we stated fully our opinions as to the functions which the ganglial system of nerves performs in the ani- mal economy. These opinions were mistaken by one or two writers who soon afterwards no- ticed them, and who confounded them with the opinions which had been entertained respecting these nerves by Drevious writers, especially with those of Bichat. His opinions respecting them were, in many respects, the same as those espoused by Soemmering and by Reil ; and whoever has attentively read the "Anatomie Generate," and the writings of the German anatomists, previous to perusing the note on the functions of ganglial nerves, at p. 12, et seq., will perceive in what we have differed from, or agreed with them ; and how much far- ther our inferences have been carried than those at which these great physiologists had arrived.^ OF THE PHENOMENA OF MIND AS MANIFESTED THROUGH THE IN- STRUMENTALITY OF A PERFECT NERVOUS SYSTEM. (Notes H H. See pp. 251—261.) The manifestations of mind have engaged the researches of some of the most acute inquirers who have " interrogated nature" during the last half century. Their progress, however, in this very interesting and difficult field, has not been equal to the growing zeal with which it has been cultivated. This want of success is, in our opinion, much less to be imputed to the indi- viduals who have engaged in the inquiry, than to the obstacles which beset a subject that in- volves the mysterious union of mind with mat- ter, and which holds relations with both of the most intimate nature, and under aspects of ap- parently the most contradictory character. The operations of a system possessing so ex- tended a connexion between the intellectual fa- culties on the one hand, and the corporeal func- tions on the other, and reciprocally receiving and communicating influence during health and disease, cannot be accurately traced, even in the more evident phenomena, without a consi- derable degree of patient observation and re- search. There, however, exist many subtle relations, which require a still more laborious demonstration ; and which, when admitted, are explained with greater difficulty and doubt. These have always afforded materials for va- rious and conflicting hypotheses, which, while they have saved us from secure and happy ignorance, have roused us to a more eager search after truth. Notwithstanding the num- ber of theories that have consequently abound- ed, and the impulse they have given to hu- man intellect, many humiliating considera- tions must obtrude themselves, when we medi- tate upon the conclusions to which some of them have led, and upon the slow progress that » The nervous system of sensation, voli- tion, and of the mental manifestations. t The neivous system of organic or vegeta- tive life. , . . T , _ t We may remark, by the way, that John- stone, Bichat, Soemmering, and Red, conceiv- ed that the ganglia of the great sympathetic in- terrupt the reciprocal influence of the cerebro- spinal nervous system, and the viscera ot t£e large cavities. Now, this is evidently not the fact, because this nerve, through the means ot its various connexions, actually conveys sensa- tions and impressions, made upon these viscera, both in health and in disease, to the brain, as well as transmits the energies of the brain ana soinal chord of the perfect animals, to reinforce the appropriate functions of the viscei al-gan- Llial nerves. Besides, if we examine the or- ganisation of those nerves which are now prov- fft„be chiefly engaged in the function of sen- sion we shan find that they all possess a soft texture, and have ganglial enlargements near their origins ; so that ganglia do not interrupt the functions of sensation, although they may modify the sensation, and are perhaps adapted to the conveyance of certain impressions in preference to others; and we may, moreover, add, that ganglia are chiefly important in inter- rupting the transmission of volition, and of the impressions, passions, and affections of the mind, to the viscera more immediately related with life, and thus preventing the bad conse- quences which would result from the dominion of the cerebro-spinal nervous system over the vicera of organic life. Indeed, we perceive, that when a nerve presents a soft consistence, and is connected with a ganglion, it is not a nerve of volition, or the medium through which the will changes the condition or position of a part, although it may be a nerve of sensation, and performing either this function alone, or that of secretion, or some other action in addi- tion. 68 APPENDIX lias been made towards advancing our know - ledge respecting the cerebral functions in rela- tion both to the mental and corporeal manifesta- tions. How little has been added to the strictly physiological department of this subject, to what may be found in the writings of Galen ! and what has the science of mind gained, du- ring so many centuries, from the contending followers of Plato, Aristotle, and Epicurus, be- yond the dawn of reason which had already ap- peared in their discordant theories ? It certainly cannot be wondered at, that hu- man intellect has wandered upon an ocean of uncertainty respecting its own operations, and those corporeal functions with which it holds so intimate a connexion, when it is considered, that until the end of the last century but little care was taken to collect and arrange a requi- site number of facts, and to direct the mind to a careful observation and analysis of the extent and nature of its faculties. Until our own times, how little anxiety have the majority of philosophers shewn to ascertain the stability and connexion of the data upon which they founded their doctrines; and which often led, from the neglect of that precaution, to conclu- sions irreconcilable with common sense and the experience of our senses ! The philosophy of Bacon, which, in this coun- try at least, has extended its influence to the science of mind, promises to advance this de- partment of human knowledge ; and by teach- ing the necessity of attending with more preci- sion to the relations of our various mental emotions, to the objects of our consciousness, and to the origin and history of our ideas, whether those which are derived from our senses or from 1 eflection, to guide our speculations through an inductive chain to conclusions more correct, and certainly more ennobling, as they regard human nature, than many that have been adopted in modern times. The metaphysical system of Kant has tended in no small degree to retard this advancement throughout a great part of the continent; and, although it is indebted to Cudworth for its b'et- * See Note A of this Appendix. t Since the above remarks were first publish- ed by us (in 1822), the doctrine of materialism has been ably opposed by Dr. Barclay, (An In- quiry into the Opinions, Ancient and Modern, concerning Life and Organisation. By John Barclay, M.D. &c. &c.) and by Dr.* Thomas Brown, in his Lectures, which have been re- cently printed. "In whatever manner, there- fore," it has been argued by the latter able me- taphysician, " the materialist may profess to consider thought as material, it is equally evi- dent, that this system is irreconcilable with our very notion of thought. In saying that it is material, he says nothing, unless he means that it has those properties which we regard as es- sential to matter; for, without this belief, he might as well predicate of it any barbarous term that is absolutely unintelligible, or rather might predicate of it such a barbarous term with more philosophic accuracy; since, in the one case, we should merely not know what was asserted— in the other case we should conceive erroneous- ly that properties were affirmed of the principle of thought, which were not intended to be af- firmed of it. Matter is that which resists com- pression, and is divisible. Mind is that which ter parts, it appears to have given a wrong im- pulse to the science of mind ; and thus nave arisen the mystifications of Fichte and of Schelling, now so generally adopted over Ger- many ; and which, most probably, will enjoy as short a dominion as that of their predecessor. It has been urged by all the favourers of Epi- cureanism, and by many of the followers of Gassendi and Hobbes,—but more especially by Priestly, Buffon, Darwin, Maupertius, Blumen- bach, Cabanis, Lawrence, and by others of the modern French school of materialism,—that, as the manifestations of mind are never met with, unless connected with a brain, or are suspend- ed by compression of this organ, so the pheno- mena generally attributed to it are the result of the organisation of the nervous fabric. All these philosophers do not distinctly enunciate this proposition ; but the general tendency of their doctrines leads to its adoption. That any combination of the molecules of matter can produce the various powers of mind, is a para- dox which they generally evade, but cannot ex- plain. If this principle proceed from certain as- sociations of organic particles, why is not some probable opinion respecting this process given ? Does our experience respecting the mutual in- fluence of either the elements or the aggregate of matter furnish us with resulting phenomena, that can in any degree approach to the lowest manifestations of either vitality* or mind ? If it be derived from the combination of these par- ticles, or from the operation of certain of their products upon each other, is it possible to con- ceive that matter, in such a state, possesses qualities, of which the elements or even the in- dividual atoms are divested ? If, on the other hand, properties necessary to the generation of the mental faculties be conceded to every parti- cle entering into the formation of the encepha- lon, how can the idea of the subdivision of the powers of mind, to such an extent as matter, be admitted ? Can the supposition be for a mo- ment entertained, that every molecule of this admirable organ has a fractional part of mind connected with it? t Many of the materialists, feels, remembers, compares, desires. In saying of mind that it is matter, then, we must mean, if we mean any thing, that the principle which thinks is hard and divisible ; and that it will be not more absurd to talk of the twentieth part of an affirmation, or the quarter of a hope, of the top of a remembrance, and the north and east corners of a comparison, than of the twentieth part of a pound, or of the different points of the compass, in reference to any part of the globe of which we may be speaking. The true an- swer to the statement of the materialist, the answer which we feel in our hearts, on the very expression of the plurality and divisibility of feeling, is, that it assumes what, far from ad- mitting, we cannot even understand ; and that, with every effort of attention which we can give to our mental analysis, we are as incapable of forming any conception of what is meant by a quarter of a doubt, or the half of a belief, as forming to ourselves an image of a circle with- out a central point, or of a square without a single angle." (See Lectures on the Philosophy of the Human Mind. By the late Thomas Brown, M.D., Professor of Moral Philosophy in the University of Edinburgh. 8vo. Edinburgh, 1828. pp. 646.) CLASSIFICATION 0*' THE STATES OF MIND. C9 in order to account for the operations of this principle, had recourse to so many suppositions respecting the nature and endowments of mat- ter, either in respect of its elements or aggre- gate, as were tantamount to a negative admis- sion of the agency of life ; with this notable difference, however, that they required the ope- ration of more numerous agents, instead ofthe more philosophical doctrine that referred them to states of this first and noblest constituent of °nr nature. The genius of Leibnitz saw the difficulty that stood in the way of pure material- ism, and in order to give his passive atoms ac- tivity, and origin to the mental phenomena, he had recourse to the ivrcXcvetai, or spirits, of Aris- totle. * The French physiologists, with Cabanis at their head, adopted the doctrine of organism ; and in order to supply the want of a foundation to their structure, they seized with avidity upon the opinions of Gassendi respecting the origin of our ideas. Their theory still required sup- port ; and in order that it might receive such from a name looked to with deference throughout Europe, they unjustly imputed to Locke doc- trines which were derived from the two cele- brated opponents of Descartes already mention- ed. Much of the credit which this system ac- quired in France and in the north of Germany, arose also from the neglect with which that class of our ideas derived from reflection was uni- formly treated. The writings of Locke, Cud- worth, Price, and others, directed attention to this highest principle of our nature, and, in fiart, gave origin to the system of Kant; which, ike the physiology of Gall and Spurzheim, pro- mulgated so soon after the philosophy of their countryman, was indebted to some acknow- ledged truths, mixed up with many assumptions, for the partial credit which it has obtained. In- deed, the doctrines of these systematists are more closely allied than has been generally sup- posed ; and it is not unlikely that the opinions of Gall were, in a great measure, derived from the Critique of Pure Reason. How far these systems, especially that of Gall, may lead to Spinozism, we cannot here inquire. We would recommend the writings of Cudworth, Price, Reid, Stewart, Barclay, and Brown, especially those of the three last-named authors* to those who are inclined to satisfy themselves more fully as to the arguments which may be adduced in proof of the independent existence of mind, and who wish to guard against the seductions to Phyrronism contained in the writings of Mon- taigne, Beikeley, and Hume. Our remarks on this very extensive subject, were we to pursue it further, could only be cur- sory, and therefore would necessarily appear to many both desultory and unsatisfactory. We shall merely, therefore, offer a classification of the manifestations of mind, commencing with the lowest, or those most extensively dissemi- nated throughout the animal kingdom, and pro- ceeding to the highest or more perfect facul- ties. CLASS I. Instinctive Feelings and Emo- tions.—(Strong and immediate Incentives to Action. ORDER I. Instinctive fecliyigs which tend to preserve the In- dividual. 1. The Sensations. 2. Vo- litions or Desires. 3. The Appetite for Food and Drink. 4. The Desire of preserving the Animal Warmth. 5. The Desire of Re- pose. 6. Desire of Place. 7. Desire of continued Existence. 8. Desire of Pleasure, and Dread of Pain. Order II. Instinctive Feelings which tend to perpetuate the Species. 1. The Appetite for Pro- creation. 2. Parental and filial Affection. 3. Desire of Society. 4. Social Affection, giving rise to mutual support. Order III. Instructive Emotions of Mind, tending to pro- mote the chief Objects of our Existence; (and, with the former orders of this class, entering more or less as ingre- dients into all the Intellectual and Mo- ral Manifestations of Mind.) 1. Gratitude. 2. Anger. 3. Pride, Humility. 4. Gladness, Regret, Sadness. 5. Wonder, Desire of Novelty, Mental Languor. 6. Beauty and Deformi- ty. 7. Sublimity and Ludicrousness. 8. Sympathy. 9. Love and Hate. 10. Love of Approbation. 11. Desire of Knowledge. 12. Desire of Pow- er. CLASS II. Intellectual Powers, or States of Mind. Order I. Powers of Consciousness, or the simpler Intel- lectual States of. Mind. 1. Perception. 2. Atten- tion. 3. Conception. 4. Memory. ORDER II. Powers of Intellection, or the more Active Intel- lectual States of Mind. 1. Association of Ideas. 2. Abstraction. 3. Ima- gination. 4. Judg- ment or Reasoning. Order III. Ideas of Reflection, spring- ing from the Exercise ofthe former Orders of Powers. (Rational In- centives to action.) 1. Mental Identity. 2. Time. 3. Power. 4. Truth, Causation. 5. Right and Wrong. 6. Exist- ence of a Deity. 7. Immortality of the Soul. 70 APPENDIX. CLASS III. Moral Affections of Mind, cular states of mind, is also the concomitant of (Fn which our Instinc- all our present mental emotions and manifesta- tive Feelings and Emo- tions : it is the present state of mental existence, tions, as well as our whatever that state may be; it indicates the Intellectual Powers, mind's unity and the mind's identity : hence it are frequently more or has attended on all our mental feelings, actions, less engaged, and and passions ; does attend them ; and w ill at- which are deliberate, tend those which shall take place at a future pe- rational, and often riod. strong incentives to Of the instinctive principles of mind, which action.) we have made the first, because the mostgene- 1. Duty, Rectitude, Virtue, rally diffused, class, and especially of the first Merit and Demerit, and second orders placed under it, we shall mere- with all our moral Ob- ly remark, that they guide the operations of ani- ligations, Emotions, mals in a uniform manner; that similar instinc- and Desires, in our tive actions and feelings manifest themselves various relations to uniformly in all the individuals belonging to the society, &c. 2 Re- same species; that they lead to determinate ligious Obligations, ends with unerring certainty, prior to all experi- &c. 3. Duties we ence ; and that they are far superior, as incen- owe ourselves, and lives to action, to all the manifestations of rea- which tend to promote son of which the lower animals are possessed. our Intellectual and Even in man, the instinctive feelings when in- Moral Excellence and dulged in, and strengthened by habit, become too Happiness, &c. powerful for our reason ; and although man is It will be perceived that the third order of characterised by his reason being superior to ideas into which we have here arranged the in- his instinctive emotions, yet the latter not in- tellectual powers, are chiefly derived from re- frequently obtain the ascendancy, when their flection, or from the mind itself.* dictates are blindly followed, and when the in- The above arrangement exhibits merely a tellectual and moral principles of our minds general outline of the phenomena of the human have not been duly cultivated. The instincts mind. It does not contain every collateral or of the lower animals are scarely ever controlled -subordinate affection, particularly several of by the manifestations of reason which they those which belong to the first and third classes, evince ; although a few exceptions to this occa- into which we have divided the mental manifes- sionally appear in respect of a few animals tations. It may be remarked generally, that which have been domesticated with man. sensation, and volition or desire, are the most Our limits will not permit us to controvert widely diffused throughout the animal kingdom, the opinions of Locke, Berkeley, Hume, and of all the states of mind ; and that although we CondiUac, who denied the existence of any in- have assigned perception, attention, memory, stinctive feelings in the human mind ; — but it and conception, more especially to conscious- is evident, from a careful analysis of the diffe- ness, we consider that this state of mind is not rent phenomena of mind, that, in addition to distinct in itself, but the concomitant of these the instinctive feelings we possess in common end all the other manifestations of the human with the lower animals, we are originally en- mrnd. Perception is a sensation of which we dowed with various mental emotions of a higher are presently conscious. Memory is the sug- nature than those which they manifest, and gestion of sensations of which we were former- which, independently of the ideas we acquire ly conscious, and of whose present suggestion by means of reflection, and the numerous class we are now conscious. Conscientiousness is of our moral emotions, desires, and duties, the attendant on both attention and conception, evince that we possess a somewhat differently in a similar manner as in respect of the other constituted, as well as a more advanced state of two mental states ; for attention is continued or mind. Of this kind are those instinctive emo- repeated perceptions, and conception is only a tions which we have arranged in the third order more definite act of memory, proceeding from of the first class of the above classification of the influence of volition or desire upon our pre- the mental powers, as well as the whole of our sent or our former sensations. Consciousness, moral affections.t although thus intimately related to these parti- The doctrines of Gall.—The anatomy of the * See on this subject the writings of Dugald Stewart; the published Lectures of Dr. Brown ; Dr. Barclay on Life and Organisation; Dr. Prichard on the Nervous System ; and the Lon- don Medical Repository, vols. xvii. and xviii. t We subjoin the following analysis of the physiology of mind, according to the very able and original views of Dr. Thomas Brown, whose early death must be a matter of regret to all lovers of metaphysical inquiries and of the belles letters. CLASS I. External Affections of Mind; arising from the presence of objects ex- ternal to the mind itself. Order I. Simple External Affections of Mind. The Sensations derived by the Organs of Smell, Taste, Hearing, Seeing, Touch, Muscular Action, Pleasure, Pain, &c. Order II. Complex External Affections of Mind. Sensation accompanied by simple Sug- gestion, is Perception. Perception with Desire, is Attention. CLASS II. Internal Affections of Mind; proceeding from previous Change in the States of the Mind itself, in consequence of the Laws of Thought and Feeling. Order I. Intellectual States of Mind. Genus I. Simple Suggestion. (Association.) Primary Laws of.—1. Resemblance. THE DOCTRINES OF GALL. 71 hervous system has been greatly indebted to this very indefatigable and eminent inquirer; and to whatever credit his doctrines may be found entitled, it cannot be denied that the sci- ence of mind has already been somewhat bene- fited, although indirectly, by the opinions he has promulgated, and which have at least been ingeniously supported by his followers. As to the doctrines themselves, we will not give any opinion : if we were inclined to do so, what we could offer respecting them would not be favour- able to them in all their details, although we might admit that some of their fundamental principles seem based on truth. The favourers of craniology appeal to facts, assert that it is eminently a science of observation and rational induction, and call upon those who oppose it to make themselves acquainted with its principles and details, and then observe and judge for themselves. This seems candid and rational; but, unfortunately, when their advice is follow- ed, and facts are observed which militate against their theory, they endeavour to rid them- selves of the difficulty by asserting that the observer is mistaken, and unacquainted with its principles,—thus virtually denying that any one 2. Contrast. 3. Nearness in Place or Time. Secondary or Modifying Laws of.— 1. Duration ofthe original Sen- sation. 2. The Liveliness of the Sensation. 3. The Repetition or Renewal of the Sensation. 4. The Recentness or Remote- ness of the Feeling. 5. The Feeling having co-existed but little with other Feelings, or only with one or two Feelings. 6. They vary according to origin- al Constitutional Differences. 7. According to Differences of Temporary Emotion. 8. Ac- cording to Changes produced in the State of the Body. 9. Ac- cording to general Tendencies produced by prior Habits. Forms of Simple Suggestion. A. Conception, merely a more spe- cial Suggestion. B. Memory is merely Suggestion combined with the Feeling of a Relation of Priority to our pre- sent Consciousness. a. Memory combined with Desire is Recollection. C. Imagination. a. A Mode of simple Suggestion, or a momentary grouping of Images, independently of Choice or Desire. b. Groups of simple Suggestion in union with Desire, or Con- ception following Conception at Desire. D. Habit, or the frequent Repeti- tion of any Action or Train of Suggestions. a. As producing a greater Tenden- cy to Actions or Trains of Suggestion. b. As occasioning greater Facility and Excellence in those par- ticular Actions. Genus II. Relative Suggestion. Species I. Co-existent Relative Sug- gestion, or Relations of Co-ex- istence. A. In respect of Po- sition. B. In respect of Re- semblance or Difference. C. Of Degree. D. Of Proportion. E. Of Comprehensiveness, or the Relation of a Whole to its separate Parts. Species II. Successive Relative Sug- gestions, or Relations of Suc- cession, or Relations involving the Notion of Priority and Sub- sequence. A. Casual Relations of Succession. B. Invariable Antecedence or Consequence. Forms of Relative Suggestion. A. Judgment. B. Reasoning. C. Abstraction. Order II. Emotions of Mind. When excited by External Objects, are excited only indirectly and through the Medium of Sensation. They differ from the Intellectual State of Mind by the peculiar Vividness of Feeling accompanying them. Genus I. Immediate Emotions. Species I. Immediate Emotions in- volving no Moral Affection. A. Cheerfulness, Melancholy. B. Wonder, Novelty, &c.; Lan- guor, from the same Succession of unvaried Feelings. C. Beau- ty, and its reverse. D. Sub- limity and its opposite, Ludi- crousness. Species II. Immediate Emotions, in which Moral Feeling is neces- sarily involved. A. Feelings dis- tinctive of Vice and Virtue. B. Emotions of Love and Hate. C. Sympathy with the Happi- ness and Sorrow of others. D. Pride and Humility. Genus II. Retrospective Emotions. Species 1. As they relate to Others. A. Anger, Gratitude. Species II. Having direct reference to ourselves. A. Simple Regret and Glad- ness, arising from Events we cannot control. B. Moral Re- gret and Gladness, arising from our own Actions. Genus III. Prospective Emotions ; com- prehending all our Desires and Fears. Wish, Hope, Expectation, Confidence, are different Forms of Desire. Species I. Desire of continued Exist- ence. 2. Desire of Pleasure. 3. Desire of Society. 4. De- sire of Knowledge. 5. Desire of Power. A. Direct Power, as Ambition. B. Indirect Pow- er, as Avarice. 7. Desire of the Affection of those around us. 8. Desire of Glory. 9. Desire of the Happiness of Others. 10. Desire of the Un- happiness of those we hate. 72 APPtfiDlX. can be acquainted with their doctrines unless he be likewise a convert to a belief in them. When, however, pressed by facts which seem inesistible, they have so many ways of eluding the difficulty between their ideas respecting the activity and volume of the particular organ in question, or the developement and activity of controlling, of opposing, and of co-operating organs, that there is an end of all argument. The numerous treatises which have appeared upon this subject render it unnecessary for us to enter more particularly into details respect- ing it. We should, however, be guilty of a neglect of duty were we to refrain from recom- mending to the perusal of the candid and inqui- sitive reader the last and greatest work of the celebrated originator of the doctrine in ques- tion.* We have seldom been more interested than we were by the perusal of this work, al- though it failed of converting us to a belief of the doctrines which it inculcated. In order to give the reader an idea of the opi- nions of this able author in as succinct a man- ner as possible, we need only quote the follow- ing condensed translation contained in the learn- ed notes of Dr. Elliotson, one of the most learn- ed and indefatigable supporters of craniology in this country. " The exact situation of the organs can be learnt from drawings or marked heads only. I shall, therefore, confine myself to remarking: —1st, That the organs of the faculties or quali- ties common to man and brutes are placed in parts of the brain common to man and brutes, —at the inferior-posterior, the posterior-inferior, aad inferior-anterior parts of the brain ; v. c. of the instinct of propagation, the love of offspring, the instinct of self-defence, of appropriating, of stratagem, &c. 2dly, Those which belong to man exclusively, and form the barrier between man and brutes, and placed in parts of the brain not possessed by brutes, viz. the anterior-supe- rior and superior of the front; v. c. of compara- tive sagacity, causuality, wit, poetic talent, and the disposition to religious feelings. 3dly, The more indispensable a quality or faculty, the nearer are its organs placed to the base of the brain or median line. The first and most indis- pensable, the instinct of propagation, lies near- est the base ; that of love of offspring follows. The organ ofthe sense of localities is more in- dispensable than that of the sense of tones or numbers; accordingly, the former is situated nearer the median line than the two latter. 4thly, The organs of the fundamental qualities and faculties which mutually assist each other, are placed near to each other; v. c. the love of propagation and of offspring, of self-defence and the instinct to destroy life, of tones and of num- bers. 5thly, The organs of analogous funda- mental qualities and faculties are equally placed near each other; v. c. the organs of the relations of places, colours, tones, and numbers, are placed in the same line, as well as the organs of the superior faculties, and the organs of the inferior propensities.-!" Of Dreaming.—Mr. A. Carmichael has lately adopted and illustrated the theory of dreaming proposed by Dr. Spurzheim, that dreams are caused by certain isolated portions or organs of * Sur les Fonctions du Cerveau. Par F. J. Gall. torn. 1, 8vo. Paris, 1825. f Gall sur les Fonctions du Cerveau, torn. iii. the brain continuing awake, while the remain- der of it is in a temporary paralysis from sleep. " According to this view", the particular dream will be fashioned by the part or parts which are not under the dominion of sleep; and the irra- tionality of our sleeping thoughts is accounted lor by one or more parts or organs thus acting without co-operation or correction from the other parts of the encephalon." Mr. C. enumerates no fewer than seven diffe- rent states of sleeping and waking '•—When the entire brain and nervous system are buried in sleep, — then there is a total exemption from dreaming. 2. When some of the mental organs are awake and all the senses are asleep, — then dreams occur, and seem to be realities. 3. When the above condition exists, and the nerves of voluntary motion are also in a state of wake- fulness,—then may occur the rare phenomenon of somnambulism. 4. When one of the senses is awake, with some of the mental organs,—then we may be conscious, during our dream, of its illusory nature. 4. When some of the mental organs are asleep, and two or more senses awake, — then we can attend to external impressions, and notice the gradual departure of our slum- bers. 6. When we are totally awake, and in full possession of our faculties and powers. 7. When, under these circumstances, we are so occupied with mental operations as not to attend to the impressions of external objects ; and then our revery deludes us like a dream. OF TPIE FORMATION AND DEVE- LOPEMENT OF THE MUSCULAR STRUCTURE, AND OF THE SOURCE OF IRRITABILITY. (Note 11. See pp. 270—273, 280.) In the very lowest orders of animals, a mus- cular structure does not exist in a distinct state. Their partial movements are performed by means of the cellular tissue of which they are composed. In the lowest ofthe series possess- ing a muscular texture, it moves only the inte- guments to which it is attached, and of w-hich it even forms a part. In all animals possessed of a heart the muscular tissue constitutes an important part. In all the vertebrated animals a small number only of the muscles are attach- ed to the mucous surfaces, to the skin and its appendages ; whilst the greatest proportion is connected with the skeleton, for the purposes of progression. According to the researches of Dr. Isenflamm, of Dorpat, into the progressive developement of the muscular structure in the human foetus, this tissue is formed from the mucous and gela- tinous fluid of which the embryo is at first com- posed. From this mucous fluid the involuntary mus- cles are first developed, and afterwaids the voluntary. During the first three months the voluntary muscles present the appearance of viscous layers, with a slight yellowish tint. At the end of the third month the tendons make their appearance. During the fourth and fifth months the muscles become redder, more fibrous, p. 208 et seq.: and Dr. Elliotson's Notes to his Translation of Blumenbach's Physiology, p. 209. OF THE SOUnCE Mi more easily to be distinguished from their tendons. In the sixth month, although very soft, they are still more perfect. At the full term of utero-gestation the muscles are fontoed but they are pale, yet vasciUar: they are soft, ana their bulk much greater in proportion to the tendinous and aponeurotic substances than in the adult. As age advances, the voluntary muscles be- come redder and more fully developed; and to- wards the decline of life, more rigid, less capable ot quick and extensive contraction, and com- paratively of less bulk than their aponeurotic and tendinous connexions. The microscopic observations of Mr. Bauer, Sir Everard Home, MM. Prevost, Dumas, and i cu Seem t0 prove that tne ultimate mus- cular fibre is composed of corpuscles (arranged like a string of beads) in every respect similar to those in the centre of the red globules of the blood. However, to obtain a correct idea of the ultimate conformation of the muscular fibre, re- searches ought to be made with this view on the raw and unprepared muscle; for the action of heat, of alcohol, and acids, evidently produces changes in the fibre, and coagulates the albu- men which enters into its composition. The voluntary nerves dip into the texture of the voluntary muscles at different points, and divide into numerous minute fibriles, which ab- ruptly escape demonstration. This sudden manner of disappearing is owing to the extreme fibriles having become soft and diaphanous, and deprived of their proper envelopes, so that their medullary substance is diffused, as it were, into the mucous tissue, connecting the muscular fibres. The cerebro-spinal nerves, although they are numerous and large in the voluntary muscles, disappear in the manner just pointed out, long before their divisions become sufficiently nume- rous to be distributed to each muscular fibre. This being the case, how can the action of these nerves on all the fibres be explained ? They cannot be the direct cause of the muscular con- traction, but must act in producing it through the medium of another and a more general con- formation. What this formation appears to us to be, we will now endeavour briefly to shew. It has been stated that all the involuntary muscles are supplied with the ganglial or soft nerves only ; that they surround the arteries throughout their ramifications, and consequently are thus present in the voluntary muscles and in all vascular parts; that the voluutary nerves themselves, whether we trace the process of their formation in the human embryo, or observe them in the lower orders of animals, seem to originate from the ganglial, the cerebro-spinal masses being the perfection of the nervous con- formation, and the last part of it which- becomes completely developed ; and that the cerebro- spinal nerves are destined to the performance of functions distinct from those u> which the * We have perceived, as the above sheet was passing through the press, that the identical opinions which have been insisted upon by us, both in the former edition of these Notes, and in several numbers of the Medical Repository for 1822, respecting the functions ofthe ganglial nerves, have been recently espoused by M. Ade- lon in his System of Physitflogy. Our opinions on these subjects will be fbtiha stated succinctly in the copious notes coaltained at pp. 12—16 >r inniTABiMTT. 73 other and more generally diffused class is allot- ted. As irritability is present in parts which do not icceive voluntary nerves, and in animals which do not possess this part of the nervous system, this property cannot be attributed to it. To what other species of organisation can we refer this property > We find it, in the more perfect animals, chiefly displayed by the mus- cular structure. Is it from this circumstance an attribute of muscular parts, and the pure result of their conformation f One class of physiolo- gists answer this question in the affirmative. But irritability is displayed by the lowest orders of the animal creation, wherein a muscular structure cannot be detected, even in the parts themselves which furnish the phenomenon; therefore, although a property of the muscular fibre, it is neither altogother restricted to it, nor is it strictly the result ofthe organisation ofthe fibre itself. We must, consequently, refer this property to a conformation still more general than the muscular tissue, both as respects the whole scale of the animal creation and the or- ganisation of individual species; allowing, at the same time, that a particular structure is re- quisite to the full and perfect developement of this property, but that this structure depends upon a different source than itself for the pro- perty which it displays.* Having arrived at "the conclusion, that irrita- bility, although a property of muscular parts, is not the result of muscular organisation, but is derived from a different and more general sys- tem, supplying the muscular structure as well as other structures, we must next inquire what this system is. It has been already inferred, from various considerations, that the ganglial class of nerves is distributed in different pro- portions to the various textures and organs of the body; that these nerves are similarly dis- tributed throughout all the individuals com- posing the animal kingdom ; that in some of its orders they constitute the only nervous system which the animal possesses : it has also been de- monstrated that this class of nerves, in a more or less perfect state of organisation, is present wherever irritability is manifested; that these nerves are the most generally diffused of any of the animal tissues ; that no other structure ex- ists but this which can be shewn to be present in every species of irritable parts, in all orders of animals ; and, consequently, that to no other source but this can the property of irritability be assigned. Having inferred that this muscular fibre is only the instalment of contraction in its more perfect condition,—that it performs this function in consequence of a certain conformation, and owing to that conformation being endowed by means of another still more generally diffused than itself,—and that this property is derived from the ganglkl or soft nerves, which proceed, either directly or as an envelope to the arteries, to all the tissues of the body,—we are led fai- and p. 15 ofthe present impression, and without the smallest addition to, or alteration from, what is to be found in the first edition of this Appen- dix, which was published in the beginning of 1824. For M. Adelon's observations on these subjects, we refer to his Physiologic de VHomme, tome iv. (the first edition of which appeared at the commencement of 1825,) seconde edition, p. 146, er sea. Paris, 1829. 74 APPEirmx. ther to infer that the cerebro-spinal nerves are distributed to muscular parts for specific pur- poses, but that these parts do not derive their innate properties from these latter nerves—these nerves merely excite them, or rather are con- ductors of a Btrmulusacting on properties which proceed from a different source. We have con- tended that these properties are not innate, or the consequence of the conformation ofthe mus- eular fibre itself; but are derived from- a con- formation still more general, which surrounds or is otherwise connected with the muscular fibriles, and that this more general conformation is the ramifications of the ganglial! crass of nerves. Conceiving, therefore, that these nerves in their state of ultimate distribution and dis- semination in the texture of the muscle, whether in the form of unarranged globules, or of minute and variously arranged fibriles resulting from the regular distribution of these globules, are the chief source of the property evinced by mus- cular parts of every denomination, we further' conclude that the voluntary or cerebro-spinal nerves do not produce their specific effects on the muscular fibres, owing to a nervous fibrile being ramified to each muscular fibrile, for this does not take place; nor do these effects pro- teed from the direct influence of these nerves upon the muscular fibrile, for the muscular fibre derives its property or faculty of contraction from a source different from itself and from the voluntary nerves which occasionally excite its contractions ; but thatthese nerves seem to act directly upon the ultimate distribution of the ganglial nerves of the muscle, which latter nerves bestow on it the faculty of, or the dispo- sition to, active contraction, on the application of a stimulus, which faculty all muscular parts possess,—the former class of nerves conveying to some of these parts only the natural stimulus which induces contraction, or which excites the active exertion of this faculty bestowed on these parts from a different source, namely, from the ganglial system. The mode of termination which the voluntary nerves observe in muscular parts, also favours the opinion which we have now given. These nerves terminate, as we have already noticed, in such a manner as leads us to infer, that they become, in the textures which they supply, gradually identified, as it were, or amalgamated, with the ultimate distri- butions of the ganglial nerves : and the history of the embryo, and the progressive develope ment of the nervous system in the lower ani- mals, dispose us to believe that the voluntary nerves originate in the textures which they sup- ply ; that they proceed from the ganglial sys- tem ; and that their larger branches, the spi- nal marrow, and encephalon, are successively formed.* * See the Note on the developement of the nervous system of the human foetus, contained in the Appendix, also the Note at p. 270. •j- The galvanic or electro-motive apparatus may be considered, " as producing, by the mu- tual contact of the heterogeneous bodies which compose it, a developement of electricity, which is propagated and distributed through its inte- rior, by means of the conductors interposed be- tween its metallic elements (plates). If we form a communication between its two poles, the discharge which follows, overturning the state of electrical equilibrium, in the series of bodies super-imposed on each other," (and forra- OF GALVANIC ELECTRlCITr. (Note K K. See pp. 885,286.) The phenomena of electricity have been long known to- philosophers; but science has been chiefly indebted, in our own times, to the re- searches "of Davy, Woollaston, Biot, Coulomb, Poisson, Oersted, and Becquerel, for a know- ledge of the laws by which it is characterised. The observations and experiments of these suc- cessful1 inquirers appear fully to warrant the con- clusion, that this very active agent of nature re- sults from t wodistinct fluids universally diffused through every species of matter. During their circulation, in their electro-motive capacity, through the corpuscles of matter forming the crust of this planet, they accumulate in the it free and uncombined state upon its externa? surface, in consequence of the imperfectly conducting property of the enveloping atmo- sphere. The electricities " are thus confined on the superficies of the globe, and indeed of all bo- dies placed on its exterior,' not merely by the non-conducting faculty of the air, but also by * species of mechanical pressure which the air exercises." Hence arise the electrical pheno- mena which so frequently become the objects ot observation. In elevated situations, hi experiments where the density of the air is exhausted and the aerial particles rendered fewer in number, and in other favourable circumstances of the atmosphere, as in its humid state, the electric power emanates with rapidity ftom the electrised ball. Such is the mode of existence of this fluid upon the surface of the earth. But there also exists a continual condensation ofthe electrical agencies in the substance of the different mat- ters composing the crust of this planet; and the galvanic, chemical, and other-phenomena, clear- ly shew that although snch condensation ofthe electricities takes place under particular cir- cumstances of mayer, yet a continuous circula- tion of it is also evident under other relations. This, indeed, is observed to occur during every manifestation of the galvanic influence. Such then being the case, and as it is now generally believed that the circulation of the electricities through the atoms of matter, or the electro-motive state, as it has with propriety been called, gives rise to the phenomena of galvanism,! which, within these few years, has led to the most splendid discoveries in the phy- sical world,—is it not reasonable to suppose that similar operations to those with which galvanic experiments make us acquainted, are continu- ally taking place in the elements of nature T As it has been shewn that every species of mat- ing the voltaic pile,) "causes them to be re- charged, according to the conditions of this equilibrium, either at the expense of the ground,. or by the decomposition of their natural elec- tricities. The repetition, then, of such dis- charges, or rather their continuation, must oc- casion in the apparatus a continued electric current, the energy and the quantity of which depend as well on the magnitude and the nature of the metallic elements in contact with each other, as on the greater or less facility which the conducting parts of the apparatus present to the transmission of electricity."—Biot. OF GALVANIC ELECTRICITY. 75 ter possesses a certain proportion of the elec- tricities, may it not be allowed that, under cir- cumstances similar to those with which experi- ment and observation make us acquainted, a continuous current of the different electricities is produced, tlie rapidity and sensible effects of which vary according to the accidental disposi- tion and situation of the different material bodies, and their natural states of electricity. This opinion is calculated to account for many of the changes which are continually taking place on the face of our globe; and although many may not feel inclined to consider these fluids as the chief agents, no one can deny them a share, in producing the effects which are so frequently observed upon its surface. The laws of electricity, whether they have been observed in connexion with its free and uncombined state, or in its form of continuous circulation, as displayed in the various galvanic processes, have been lately veiy closely marked and reduced even to precise calculation. From among these we may adopt the following gene- ral law, which has been clearly established by M. Biot, namely, that "each ofthe two electrical principle* is a fluid, whose particles, perfectly movable, mutually repel each other, and attract those of the other principle, with forces reciprocal as the square of the distance. Also, at equal dis- tances the attractive power is equal to the repul- sive." . This therefore being an established law which characterises the actions of these fluids, is it not reasonable to explain the material phenome- na of the universe by its assistance, especially when such an explanation may be conducted in accordance with the known laws of matter, and supported by the conviction that the atoms of every material substance possess certain elec- trical states ? . Another very important law, which regards the electric fluids chiefly with respect to the atoms of matter with which they are associated, must not be overlooked, viz. "that a mutual at- traction exists between the electric fluid and all material substances, when they are in their na- tural state of electricity." But this is a mere extension of the former law as regards the con- nexion of these fluids with the atoms of mat- ter, and is entirely the result of the electrical in- fluence with which these atoms are endowed, as we can have no idea of matter devoid of its nntuial electricity. ,,- L 1 Proceeding, therefore, upon the established laws of electricity, and upon these which, it is presumed, the particles of matter obey, it may be concluded, that the cohesion which exists between the atoms of unorganised substances results from the attraction existing between the opposite electricities. Whether we conceive the particles of matter to exist innately, endow- ed with certain electrical states, or surrounded with one or other of these fluids, according to their reciprocal affinity, still the attraction be- tween the atoms of matter must be equally the result of opposite states of this universally dit- But it may be contended, that as the particles of matter mutually repel each other, they there- fore are either altogether devoid of any kind of electrical influence, or are endowed with the property of mutual repulsion, which they exert notwithstanding the electrical agency. But thi3 objection is by no means valid ; for it may be shewn that, even granting them to possess the property of mutual repulsion, the supposition is favourable to the theory, and serves, more- over, to account for the varied phenomena to which the different particles of matter and the electrical fluids give rise. As, however, we have just supposed that the attraction of matter results from the atoms be- ing endowed with the opposite state of elec- tricity, it is as reasonable to suppose that an opposite condition to attraction must take place when homogeneous particles, or those possess- ing the same kind of electrical energy, are brought within the sphere of action. From this consideration we are led to the con- clusion, that attraction and repulsion between the particles of matter arise as a necessary consequence of the electrical states of these particles. The various anomalies or peculiar conditions of material substances can be easily supposed to result from certain degrees of elec- trical saturation, or neutralisation, to which these substances are subjected. From the consideration of corpuscular attrac- tion and repulsion, tl»e transition to chemical affinity becomes evident. . It may be shewn by direct experiment, that repulsion can be produced between two bodies, by giving one of them an electrical state difle- rent from that which it naturally possesses, that is, by bringing it artificially into a conditicn similar to the other; so chemical attraction be- tween two bodies may be increased by exalting the energy of the electrical states which thiy naturally possess. ■>. c ., , As chemical affinities are the result of attrac- tion or repulsion between the particles of matter, owing to their electrical conditions, so these affinities will be simple or compound, according to the electric states of the different materials which are brought into mutual action, and ac- cording to the various energies of these states. Having endeavoured to establish the propo- sition of different material atoms possessing different electrical states, both as regards the negative or positive modes of existence of this agent, and as respects the energy of each mode ; and having considered such relations sufficient to account for the phenomena of repulsion and gravitation,—it becomes unnecessary to point the application of the doctrine to the various chemical changes which take place. However, that such changes actually do occur, after the manner which d priori reasoning would lead us to expect, is a genetal inference which presents very few exceptions. But our knowledge re- meeting the abstract state of those substances which present the presumed exceptions, is as vet so very imperfect, that no conclusive argu- ment can be adduced that their chemical com- bination is not the result of the electrical states of their atoms, or of these fluids during their continuous circulation through them The excitement of electricity by means ot • The celebrated botanist Mr. Brown has latelv ascertained that the molecules of both organised and inorganised matter are in a con- stant state of motion. May not this motion be, in the former class of bodies the consequence ofthe electrical states of these particles, for which states we have contended above>,-or, in other words, a sensible phenomenon of theirelec 70 appendix:. friction, by compression, by the fusion of in- flammable bodies, by evaporation, by the disen- gagement of gas, by the disruption of a solid body, by the conUet of dissimilar substances, and lastly by chemical decomposition—all combine in establishing the intimate connexion for which we contend. Whenever bodies, brought by artificial means into high states of opposite electricity, are al- lowed to restore the electricity, heat and light are the consequences. (Davy.) These effects take place in the same maimer if performed in a vacuum. The light thus pro- duced appears, from the experiments which have been related, to tie of the same nature with the solar beam, and to be divisible into the prismatic colours. The light exhibited by phosphorescent bodies, and by matter under its various conditions, gives similar results. There- fore, from taking a survey of the electrical phe- nomena, of those displayed by chemical com- binations, and of other manifestations of na- ture, we are inclined to adopt the belief that light and caloric (as they exist in the solar rays, and as they are otherwise produced) are the re- sult of the combination and neutralisation of the opposite electricities, whether taking place in a direct manner and in their free state of ex- istence, or through the medium of the particles of matter which they endow^; light being more or less perfect according as the neutralisation is more or less complete, and the caloric result- ing from the intensity of their action. Before leaving the consideration of the ac- tion of the electric fluids upon each other and upon the molecules of matter, it is necessary to remark respecting a property which the mole- cules of matter appear to possess under certain circumstances, of arranging themselves in de- finite directions ;—this has generally been call- ed the polarisation of matter—a phenomenon observed in the crystallisation of numerous substances, and in different chemical actions. The polarisation of the atoms of matter seems to result from the electrical states which they acquire from the electricities circulating around them, and to arise from a property with which the electricities are themselves endowed, or from their mutual action independently of their connexion with the molecules of matter. Ac- cording to this view of the subject, we should be led to expect, that the electricities, as they exist in the solar beam, unconnected with mat- ter, would give rise to the phenomenon of po- larisation, in a similar manner as when their ac- tion is exerted through the medium of tlie atoms of matter: this conclusion is supported by the experiments of Dr. Brewster, Biot, and others, on the polarisation of light. The intimate connexion which exists between the electrical agencies and the magnetical at- tractions, is a subject which has lately interest- ed scientific inquirers throughout Europe. It tro-motive conditions ? The motion presented by organised liodies must doubtless be ascribed to their vitality,and its concomitant changes. Mo- tion in dead organised bodies is to be referred to the chemical changes which took place, when these changes are no longer restrained from su- pervening by the controlling influence of life,— which changes, as argued (or above, are merely the results of electro-motive agencies. • In the annual oration delivered to the Mo- would almost seem, from their observations, that manifestations of the magnetic power re- sult from the electrised state of the atoms of the magnet, and their consequent polarisation ; and from the continuous ciiculation of the elec- tric fluids either through its substance or upon its surface.* Since the discovery of Galvani, several phy- siologists have attempted to explain the phe- nomena of ihe animal world by imputing the functions of the nervous system to the electro- motive energy, generated or developed by tlie cerebro-spinal masses. Amongst those who have espoused this opinion, we may mention Sprcngcl, Reil, Prochaska, Wilson Philip, Lenhossek, <&c. There can be no doubt that the electricities circulate through animal bodies in different conditions, and giTe rise to subordi- nate offices in the animal economy, under the superior dominion of a vital influence ; and, moreover, that they (or one of them at least) are a stimulus to this influence. The experiments of the physiologists just named, especially those of Dr. Philip, shew this, but nothing more than this. They refer to the electrical apparatus which certain fishes possess, and the power they have of giving electrical shocks, in farther proof of the justness of their inference : but it may be asked, if the nervous influence be the same as electricity, why should these animals possess an apparatus distinct from the nervous system, and under its control, for the production of the electrical phenomena ? The existence of this apparatus confirms the proposi- tion we have just now stated; and its office is evidently that of accumulating within itself, in consequence of the vital function with which it is endowed, the electricities circulating in the body, so that they may be discharged ac- cording to the wants of the animal: but the electricities which the animal thus accumu- lates and discharges, cannot be said, from the evidence which we as yet possess on the sub- ject, to be identical with its nervous influence, nor with the vitality of its system, moie than oxygen, nitrogen, hydrogen, or any other fluid constantly present in, circulating through, and combining with the constituents of the body, may be considered to be the source of its numerous manifestations. The one fluid may accumulate in the system as well as the other, by means of the vital operations of the organ in which the accumulation takes place, and it may be again discharged in consequence either of an operation determined by the nervous in- fluence, or of some other process, and, in fact, we find such a phenomenon actually taking place ; but are we to infer on that account, that either the one or the other of these fluids constitutes the vitality of the system, or even that they are the source of vitality, when it can only be shewn to be a single function from amongst the many which the animal exhibits ? We find thatclcc- dical Society of London in March 1822, we en- deavoured to shew that the phenomena of at- traction or gravitation, chemical affinity, com- bustion, crystallisation, magnetism, light and heat, (both as they exist in the solar rays, and as they ate otherwise produced), in short, that all the phenomena of the inorganised world and of the solar systems, may be explained by means of the agency of two universally diffused elec- tricities. OF OALV1NIO ELECTRICITY. 77 trictty is accumulated in, and discharged from, the electrical apparatus of some fishes ; and we also perceive that oxygen and nitrogen are, in like manner, accumulated in, and discharged from, the swimming bladders of other fishes ; but these circumstances do not warrant us to infer that electricity is the nervous influence of the former, any more than that oxygen is the nervous influence of the latter; or that the vi- tality of the one is electricity, of the other it is oxygen. But, although the agency of the electricities has been extended farther, as respects the ani- mal kingdom, by some physiologists, than well- ascertained facts can warrant, it must be allow- ed, from the evidence which has been adduced, that, they give rise to very important phenomena when they are brought to operate on some of the animal textures. It is these effects, or rather the stimulus which electricity imparts to the sensible and contractile parts of the body, that constitute the chief physiological relations of electricity, and give a degree of plausibility to the doctrines of those who consider that all the animal functions are discharged by the electricities in their electro-motive condition. These circumstances require that we should no- tice at farther length the effects of this agent on the animal system.* "According to Ritter, the electricity of the positive pole augments, while the negative di- minishes, the actions of life. Tumefaction of parts is produced by the former, depression by the latter. The pulse of the hand, he says, held a few minutes in contact with the positive pole, is strengthened ; that ofthe one in contact with the negative is enfeebled: the former is accom- panied with a sense of heat, the latter with a feeling of coldness. Objects appear to a posi- tively electrified eye, larger, brighter, and led ; while to one negatively electrified they seem smaller, less distinct, and bluish,—colours indi- cating opposite extremes of the prismatic spec- trum." An electrical practitioner referred to by Dr. Ure, from whom the above paragraph is quoted, considers that his experience in the application of this agent in disease warrants him in refer- ring its operation to three distinct heads : " first, the form of radii, when projected from a point positively electrified ; secondly, that of a star, or the negative fire concentrated on a brass ball; thirdly, the Leyden explosion." The first acts, he considers, as a sedative; the second as a stimulant; and the last has a deobstruent operation. Dr. Ure has found that the negative pole of a voltaic battery gives more poignant sensations than the positive. The experiments of Dr. Philip with voltaic electricity have led him to infer that the ner- * Amongst the living tissues, the nervous is the best conductor of electricity ; therefore when anelectrical current is established through the body, it is transmitted by this texture. If the electrical current consists only of one of the electricities, the molecules composing the nervous texture tend to propel each other, or to disunite ; and if the electrical action is very intense, they are actually decomposed, and con- founded with the fatty matter which isolates the nervous fibres ; all the functions of the nerves are instantly destroyed, the irritability of the muscles dissipated, and life is immediately ter- vous influence is nothing else than this agent. This proposition has .already been noticed, and it will be again referred to ; we shall only ob- serve at this place, that his experiments appear to shew the extent to which the electro-motive agency, transmitted through their voluntary nerves, may prove a stimulus to particular or- gans, and enable them to perforin their functions when these functions have been impeded by the removal of a natural and requisite stimulus. We have at another place endeavoured to shew that the functions which Dr. Philip has imputed to the cerebro-spinal nerves are actually derived from another source ; that the operations of these nerves (with the exception of the nerves of sense) are chiefly confined to the transmission of the cerebro-spinal influence, which is the natural stimulus to the vital endowment that the organs receive from a different system—the ganglial; but that this stimulus cannot be considered to be galvanism, merely because galvanism is a stimulus, and acts in a manner which we have every reason to suppose other stimuli would act, if they were capable of being transmitted through, and be present in, every part of the body on which they are disposed to operate. It is the particular constitution of this agent, its properties, and its relations with the solids and fluids of the body, that give rise to its active operation, and to phenomena liable to be con- founded with those of the nervous system, or even with those of life itself. What we have just now adduced has a strict- er reference to the opinions of those who con- sider that the nervous influence and galvanism are the same ; we shall now refer more particu- larly to the notion of the identity of this agent and life itself; and here we cannot do better than quote the very acute, conclusive, and un answerable observations of Dr. Pringt on this subject. " We observe that electricity is re- lated with life, and acts upon it; this is no proof of identity. We observe also that elec- tricity will substitute in some instances the properties derived from a nervous centre; in this respect there is an identical property com- mon to it and life, which is also possessed by many other substances. We observe also, that the formation of heat, and the faculty of gene- rating electricity, belong to animals, and are dependent upon their life. The faculty of ge- nerating electricity in animals does not prove that electricity is even a constituent part of their life ; it proves that it is a phenomenon of their life ; but that it is a part of it, is no more to be concluded on this account, than that urine or mucus, &e. is a part of life, because these are also products of it. " We have made out, then, only one point of resemblance between lite and electricity, which minated. These effects are frequently witness- ed from lightning. They are not confined, however, to the nervous and inusculat systems, all the soft parts are more or less affected ; the blood does not coagulate, owing to the dissipa- tion of the vital influence giving rise to the phenomenon of coagulation (see p. 50); and all tissues fall quickly into a state of putrefac- tion. t Principles of Pathology. We recommend the physiologist to study closely the physio- logical and pathological writings of this most acute and philosophical writer. 73 APPENDIX. is, that electricity will in some cases substitute a property otherwise derived from a nervous centre ; which property, applied to the stomach, will aid digestion, in which respect it has not yet been found that more common stimuli re- semble it: applied to the voluntary muscles, it will produce their contraction ; and in this re- spect the property is a common one to many other substances, which no one ever thought of identifying with life. But even the properties which are said to depend upon a nervous centre are not all of them substituted by electricity, which will stimulate muscular contraction, like many other substances, but, like those substan- ces also, it is incapable of conferring sensibili- ty ; or if electrical influence ever excites sen- sation in paralytic limbs, it is only because their sensibility is not totally extinct, and will therefore admit of sensation under the applica- tion of this, or of any other stimulus of a pow- erful kind. " We have seen that electricity can do a very little which is also done by life ; there is then analogy in one property, hut to be the same identity, there must be analogy in all; or to ap- proach to such identity, there must be at least a general analogy. The living principle main- tains itself by assimilation from exposure to its elements; electricity is not capable of main- taining itself from its elements, but must he produced from them. Muscular power in the animal system is related with mind, and direct- ed by volition ; we have no evidence that mind, pr volition independently of the properties which distinguish the living state, can so ally itself with electricity. Animal life confers sensibility on structures ; electricity can mere- ly excite sensation in common with chemical and mechanical stimuli. The organic life pro- duces from a common material, arranges, and renovates, in the muscular system, the parti- cles which compose muscle; in the tendons, those of tendon; in the membranes, those of membrane; in the bones, the constituents of these structures; and of all others, with all their circumstances, however diversified. Now if electricity were capable of doing all this, there would then be established only a general resemblance with life ; analogies would after- wards be sought for, corresponding with those powers exhibited by the relation of properties of life in different seats, and more especially among the phenomena of disease. But until the pretensions of electricity to an identity with life shall be established by rather a more exten- sive analogy, it is superfluous to inquire how far the phenomena of electricity resemble those of dyspepsia, diarrhoea, consumption, abscess, or gout. If, perchance, electricity should be endowed with the properties engaged in these phenomena, it will be greatly indebted to its friends for bestowing upon it attributes which it has never displayed. In the mean time, it is to he wished that experimentalists will go on mul- tiplying their facte, and that they will abstain from reasoning upon them : they will not, how- ever, err to any great extent in this way, if they will take the trouble to remember that so far as things are proved to be alike, they are alike ; and where they are not proved to be alike, it is possible that they may be different. " The identity of Hfe and electricity or gal- vanism has been inferred, as appears from the preceding account, from very slender premises; but the arguments just considered are among the best that have been proposed in favour of the sameness of the two principles, or substan- ces, if they are substances." OF OSSIFICATION. (Note L L. See pp. 290,391.) The bones are at first of a mucous or gela- tinous consistence in the embryo. They next become cartilaginous, and some of them fibro- cartilaginous ; they are lastly perfectly ossified. At the early period of the embryal state the bones gradually increase, without any apparent division into separate parts. The cartilaginous bones, or the temporary cartilages, do not ap- pear before two months have elapsed from the period of conception, and then this process to- wards ossification only commences in those bones, or in the parts of bones, which are ossi- fied at a later period. It appears doubtful whe ther or not those bones which ossify the first, or those parts of bones in which the process takes place at an early period, pass through an inter- mediate or cartilaginous state. It seems most probable, from the observations of MM. Beclard and Serres, that in them the ossific deposit is made in the first or mucous state of their exist- ence ; whilst, in those bones which are perfect- ed at a remoter period, the cartilaginous or in- termediate state which they assume is rather a provisional function than a state of ossification —a temporary condition of structure, for the purpose of performing the offices of bone, and not a requisite antecedent to the ossific pro- cess. . . , Ossification commences successively in the different bones, from about a month after im- pregnation, in those which are the first formed, until ten or twelve years after birth, in those which ossify at a later period ; and in certain subordinate parts of bones, the ossific process does not commence until the fifteenth or eigh- teenth year. The clavicle and maxillary bones are amongst the first developed ; the sternum, the bones of the pelvis, and those of the ex- tremities, are the latest. It may be considered as a general proposition, that those bones which are nearest the nervous and sanguineous cen- tres are the first to be formed, as if their more immediate developement were required to pro- tect these important systems : hence we per- ceive that the vertebrae and ribs ossify at an ear. ly period. At the end of the first month ossification commences in the clavicle, and successively in the inferior maxilla, in the femur, tibia, hume- rus, superior maxilla, and bones of the fore- arm, where it begins about the thirty-fifth day. About the fortieth day this process commences in the fibula, scapulum, the palatine bones ; and during the following days, in the occipital and frontal bones, in the arches of the first verte- bras, and in their sides, in the sphenoid, the zygomatic apophysis, the phalanges of the fin- gers, the bodies of the vertebrae, the nasal and zygomatic bones, the ilium, the metacarpal bones, the condyles of the occipital bones, in the squamous portion of the temporal bone, the parietal, and in the vomer: in all these, ossi- fication begins about the middle of the seventh week. In the course of the same week it ap- pears also in the orbitar process of the sphenoid ; and, about the end of the week, in the metatar- sal bones and phalanges of the fingers and toes. OF VOICE—VENTRILOQUISM. 79 During the ten following days it begins in the first sacral vertebra, and around the tympa- num. During the subsequent weeks and months it commences in the bones of the ear, in the pu- bis, in the processes of many of the already- mentioned bones, in the small bones of the ex- tremities, &c. Ossification does not always result, as we have already noticed, from the transformation of cartilage into bone. The diaphysis of the long bones, and the centre of the large bones, which are amongst those first formed, pass im- mediately from a mucous to an osseous state. The other parts of this structure have an inter- mediate cartilaginous condition: and it is in these parts that the successive stages of ossi- fication may be best observed. The cartilage which, for a longer or shorter period, supplies the place of bone, becomes at first hollowed into irregular cavities, afterwards into canals lined with a vascular membrane and filled by a mucilaginous and viscid liquid ; these canals become red, the cartilage now as- sumes an opaque appearance, and ossification commences towards its centre. The first point of ossification is alwa3-s in the centre of the cartilage, and never at its surface. This point is surrounded by a reddish cartilage, and that part which is nearest it is opaque and pierced with canals still fartherthan the opacity reaches. The osseous point augments progressively by means of additions on its surface, as well as by an interstitial deposit in its substance. The cartilage gradually becomes hollowed by cavi- ties and canals, lined by a vascular sheath, di- minishes as the ossification extends, and disap- pears altogether when the process is complet- ed. With respect to the state in which the osse- ous matter is formed, we are inclined to agree with M. Beclard in the opinion, that the earthy matter is deposited in a fluid condition, and at the same time with animal matter, in the or- ganised tissue which secretes it. Its subse- quent solidification arises either from the depo- sition of a larger proportion of earthy matter, or from the absorption of the vehicle which gives it the fluid condition ; or fiom the joint opera- tion of both these causes. OF VOICE. (Note M M. See p. 320.) The cricoid cartilage, which supports the two arytenoid cartilages, is not immovable at the inferior part of the larynx. The trachea, to which it is attached by its inferior margin, yields and elongates itself in order to allow it motion. The muscles of the larynx do not contribute to the production of the voice solely by means of the action which they exercise on the sides of the glottis ; several of them, and particularly the thyro-arytenoids, may be con- sidered as forming a part of the parietes of this opening. These small muscles give rise to acute sounds, by drawing closer the two aryte- noid cartilages, and when in a state of contrac- tion they also seem susceptible of a vibratory motion, varying in degree according to the de- gree of contraction: by the assistance, there- fore, of the muscular fibres covering its sides, the glottis is susceptible of vibrations analo- gous to that of the lips applied to the opening of a French horn. The production of sound is owing to the action of the muscles of the larynx on its cartilages during expiration ; and what- ever impedes the functions of the nerves ac- tuating these muscles, puts a stop to the utter' ance of sound. Of Ventriloquism,(p. 325.)—Various attempts have been made to explain the manner in which the ventriloquist is enabled to modify his articu- lations into the semblance of distinct voices. Dr. Good considers ventriloquism " to be an imitative art, founded in a close attention to* the almost infinite variety of tones, articula- tions, and inflexions, which the glottis is capa- ble of producing in its own region alone, where long and dexterously practised upon; and a skilful modification of these vocal sounds, thus limited to the glottis, into mimic speech, pass- ed for the most part, and whenever necessary, through the cavity of the nostrils, instead of through the mouth." He farther supposes that " some peculiarity in the structure of the' glot tis, and particularly in respect to its muscles and cartilages," is requisite to carry this art to perfection. The explanation which Magendie offers on this subject appears to us to be more correct, although perhaps not sufficiently so. This physiologist asserts that ventriloquism consists in certain modifications of sounds or speech, produced by a larynx of the common formation, with a strict attention to the diffe- rent effects of sound thrown at different dis- tances, and through different modes of con- veyance. We cannot agree with Dr. Good, that the ventriloquist performs articulation by means of the larynx only, although we may concede some share in the process to this or- gan ; nor can it be granted that any " addition to the muscular organism of the glottis" is en- joyed by those who have perfectly acquired thi» imitative art. OF THE GENERATIVE ORGANS, AND THEIR FUNCTIONS. (Notes N N. See pp. 333,335,' 338—344.) I. Of the male organs of generation.—The cellular structure of the corpora cavernosa pe- nis, according to the microscopic examinations- of M. Bauer, appears to be made up of an in- finite number of thin membranous plates, ex- ceedingly elastic, so connected together as to form a trellis-work, the edge of which is firmly attached to the strong elastic ligamentous sub- stance which surrounds the whole, and also forms the septum pectiniforme. This substance has an admixture of mnscular fibres. The cell6 are generally larger, or rather the trellis-work is more loose, in the middle portion of each corpus cavernosum. Arterial ramifications are supported by this reticular structure, and they are distributed every where throughout the cavernous part of this organ. In the usual state of the penis, the blood is not poured into the cells, but re- turns by the veins, and it remains flaccid ; but when a person is under the influence of parti- cular impressions, the minute arterial branches, which before had their orifices closed, now have their action suddenly increased, and pour from their open mouths the blood into these cells, so as to overcome the elastic power that un- der ordinary circumstances keeps them col- lapsed. The corpus spongiosum penis appears, from 80 APPENDIX, the observations of th? same physiologist, to consist of the same kind of structure as that observed in the corpora cavernosa, but on a less scale. Its structure is also more regular throughout; without, however, having any mus- cular fibres mixed with the trellis-work, these being confined to the outer surface of the inner membrane of the urethra. The erection of this part is supposed to take place after the same manner as that of the corpora cavernosa, namely, from a vital expansion taking place in the extremities of the arterial capillaries, and thus allowing the blood to flow from them into the cells of both structures. We may state, moreover, that the arteries of the penis are surrounded by a larger proportion of nerves than in most of the other tissues of the body. The veins form very numerous an- astomoses. It is the division, on dissection, of these numerous veins, and of their numerous roots, anastomoses, and plexuses, which, in the opinion of M. Beclard, gives the appearance of cells, the existence of which he denies. Erec- tion of this texture is the result of the influence of the nerves upon the arteries and veins be- longing to it. By this influence the action of the arteries is increased, whilst the diameter of the veins returning the blood is diminished by the tonic contractility which these nerves exert on the coats of the veins. P. 333.—The vesiculae seminales may, under particular circumstances, more likely to occur in the human species than in the lower animals, be employed as reservoirs; although their ordi- nary use may be to secrete a fluid which, mixing with the semen in coitu, may render the act more perfect, and more likely, therefore, to pro- duce fecundation. P. 336 —MM. Prevost and Dumas have both examined the spermatic animalculie. They seem to vary in form in different animals, and to be the product of a real secretion. These physiologists conclude, — " 1st, that spermatic animalculae have nothing in common with infu- sory ones,'except in their microscopic size ; 2d, that they are produced in the testes alone, but do not appear in these organs till the age of puberty ; and 3d, that they seem to be the active principle or agent of the semen." II. Of the female organs of generation. P. 335. — The uterus, the ovaria, and the Fallopian tubes, receive their nerves from the abdominal portion of the trisplanchnic nerves, branches of which unite variously with each other, and form six plexuses. The first, which M. Tiede- mann calls spermatic, or the plexus common to the ovaria and tubes, is situated on the anterior surface of the abdominal aorta, and on the origin of the internal spermatic artery. It is formed of a number of branches which come from the renal ganglia. Its filaments descend, surround- ing the arteries of the ovaria, between the mem- branes which form the broad ligaments of the uterus, and arrive at the ovaria and tubes, in which they are ramified ; a few filaments reach the fundus of the uterus. The second plexus, which is the largest, M. Tiedemann calls the superior lumbar plexus, or common uterine. It is formed of branches which proceed from the superior lumbar and rend gan- glions ; and is placed on the body of the fifth lumbar vertebra, and on the promontory of the sacrum, between the iliac arteries. On its entrance into the pelvic basin, it divides itself into two considerable plexuses, which M. T. calls the hypogastric or lateral uterine plexUsd. These are placed on the trunks of the iliac arte- ries, and anastomose with the firnt and second sacral ganglions. A gieat many filaments pro- ceed from these plexuses, forming a reticulum around the arteries of the uterus, v ith the rami- fications of which they penetrate into the texture of the organ, chiefly its posterior and lateral aspects. Several branches proceed from the superior lateral or hypogastric plexus to the vagina, at the point of its union with the neck of the uterus, and there unite with the anterior branches of the third and fourth sacral nerves, and form a large plexus, which M. Tiedemann calls the inferior lateral hypogastric, and which interweaves with and embraces small ganglia. This gniigliform plexus gives origin to a great many branches, chiefly to the vagina, to tho uterus, and also to the bladder and rectum. These nerves, as well as those belonging to the other plexuses, always closely embrace the arteries in the form of a net-work. It appears, therefore, that the womb and itH appendages are surrounded by important ner- vous plexuses. These nerves are soft, small, reddish-gray, and in every respect similar to the other portions of the great sympathetic nerves. Of their appearance and character \vs have had several opportunities of satisfying ourselves, when making researches respecting this grand organic system ; and wc can beai testimony to the correctness of the observations of M. Tiedemann. M. Tiedemann states, that the number and size ofthe uterine nerves vary according to tho age of the female ; that they are small and ap- parently few in girls — laige and numerous m adults—and very small in old women. He has observed another fact, confirmatory of their functions, which indeed was previously noticed by Dr. W. Hunter and Professor Chaussier, that these nerves become larger and more nu- merous during gestation,—a fact which we have verified on several occasions. III. Of impregnation. P. 339 — Several opi- nions have been entertained respecting the im- pregnating process. Some physiologists sup- pose that the actual contact of the ovum arid semen are requisite ; others that the aura semi- nalis is all that is requisite. Of the former class of physiologists, some suppose that the semen is absorbed into the uterus, where the ovum, having descended through the Fallopian tubes, meets it; others consider that the semen is con- veyed by a peristaltic-like action of the vagina, uterus, and tubes, to the ovarium, — and they adduce in support of their opinion the occur- rence of extra-uterine foetatiun ; a third party belonging to this class conceives that the semen is conveyed to the ovum itself, in its situation in the ovarium, by means of absorption, through a set of vessels allotted to this specific purp(vw». Dr. Dewees, of Philadelphia, has argued strenu- ously for this last doctrine ; it has also been adopted by other physiologists ; and it seems to have received support from the labours of Dr. Gartner, of Copenhagen, who has discovered, in some animals, a duct leading from the ovary to the vagina. The occurrence of ovarian foeta- tion wherein the foetus is lodged within the en- veloping membrane of the ovarium, can be most satisfactorily explained by mean* of this doc- trine. Two cases of this description have late- ly been detailed by Dr. Granville and Mr. Pain- OP IMPREGNATION, &C. SI Jcr. It must, however, be allowed, that the alter class of physiologists, or those who con- tend for the impregnating influence of the aura seminalis, have it in their power to adduce strong arguments in behalf of their opinion. It has even been asserted, very recently, by some continental physiologists, that the impregnating power of the aura seminalis may be proved by experiment performed on rabbits, in the follow- ing manner : — Let the semen be received in a cup, over which is to be immediately placed an inverted funnel; and let the apex of this funnel be introduced into the vagina. If this experi- ment be performed immediately after the semi- nal emission, they say that impregnation will be the result. It has been argued, that the venereal desire is present in neither sex before the developement ofthe testes and ovaria. This, however, is not the case. The venereal appetite makes it.< ap- pearance in both girls and boys long before the generative organs are developed. It has been frequently observed in them both, in temperate climates, as early as the sixth or seventh year. It has also been supposed, that the venereal appetite disappears soon after the menses have ceased to flow ; this also is not the case, With respect to the assertion, that the vene- real orgasm on the part ofthe female is necessary to impregnation, we may observe, that although it may be requisite in some females, it is by no means so in others ; for many women conceive who are indifferent during the venereal con- gress ; there are others who conceive, notwith- standing their successful endeavours to sup- press their orgasm ; and some are impregnated, when, owing to disease, as procidentia uteri, &c. they cannot be supposed to enjoy much pleasure from the act.* Dr. Blundell found, in his experiments, that when only one of the uteri of a rabbit was di- vided, or rendered impervious at its neck, or when the passage to both was obstructed by tying the vagina, and afterwards freely admitted to the male, that the obstructed uterus, or uteri, did not become impregnated ; but he found, in those whose vagina was tied, that, notwithstand- ing, the ovaries, Fallopian tubes, and womb, were excited by coition ; and in those who ad- mitted the male frequently, the abdomen acquir- ed a large size, and in some cases exceeded the bulk of mature gestation. These enlargements arose from an accumulation of a humour in the womb, which, at a temperature below boiling, formed albuminous concretions. In its appear- ance it was various, but generally fluid, pale, and turbid. In those who had only one. uterus obstructed, the sound one became filled with foetuses, and the barren one with the humour described. The formation of the lutea, the de- velopement of the womb, and the repeated ac- cumulations of fluid, in consequence of coition, in these experiments, seem to indicate the de- scent of the rudimental material. Thus, although the passage to the uterus was completely interrupted, the tubes were excited by the venereal orgasm, they really conveyed the rudiments to the womb,and these rudiments engendered the watery accumulations there, in the abortive attempts at generation. This ap- pears to confirm the supposition, and indeed to establish it, that even in viviparous animals, generation may be carried to a certain extent, although the access of the semen to the rudi- ments is interrupted : under these circum- stances, the young animal cannot be formed, it is true, but corpora lutea may be generated, the womb may be developed, and the rudiments may even be transferred to the uterine cavity by the play of the Fallopian tubes. This opi- nion receives countenance from the generation of oviparous animals, in most of whom the rudi- ments may be discharged, independently of pre- ceding impregnation.! Dr. Blundell supposes that the vagina and womb perform a peristaltic motion, from the sti- mulus of the semen, both in the human subject and lower animals; and that this motion con- veys the semen to the rudiments. From these experiments it would appear, that the presence of corpora lutea cannot be relied upon as a proof that impregnation had taken place. There is evidence that they may be pro- duced even independently of the sexual inter- course, from the mere excitement of desire in a high degree. Dr. Blundell has in his posses- sion a preparation of the ovaria of a young woman who died of chorea, under seventeen years of age, in which the hymen was un- broken, and nearly closed the entrance of the vagina. In these ovaries the corpora lutea are no fewer than four — two rather obscure, the other two perfectly distinct. As Dr. Blunder's experiments go to prove that impregnation cannot take place without the semen coming in contact with the rudiments, he therefore supposes, that when the ovary lodges either in the tubes, the peritoneal cavity, or in the ovary itself, and there impregnated, that the semen must be conveyed to those situations. Or, that the rudiments in their descent meet the semen in its ascent, and that the transfer of the * Sir Everard Home (Phil. Trans. 1818,) Mates that corpora lutea are never met with before puberty. They are formed in the loose structure of the ovarium previous to, and in- dependent of, sexual intercourse ; and when they have fulfilled their office of forming ova, they are afterwards removed, by absorption, whether the ova be impregnated or not. It seems that the ovum too, with its amnion and chorion, is formed in the virgin after puberty. This was found to be the case in a woman of twenty years of age, who had a perfect hymen. " The Fallopian tube ol that side was fuller than the opposite. The fimbria; were spread out, and unusually vascular." We know that animals part with their eggs whether there be sexual intercourse or not; and this is done with such force during coition, that the cavity of the corpus luteum is absolutely inverted, so that the ovum is exposed completely to the emission of the male. Extravasation of blood follows the rupture of the ovum frequently to so great a degree, that blood occasionally passes out through the vagina. In nine months after im- pregnation the corpus luteum is nearly absorb- ed, but a new one is usually found in a state of forwardness in the other ovarium. All prepara- tions of corpora lutea, which are made from women who have died in child-bed, belong, in Sir E.'s opinion, to ova which were to succeed, not to the ovum of the child which had been born. t Med. Chirug. Trans, vol. x. m APPENDIX. semen beyond the womb may be the cause of extra-uterine pregnancy. IV. Of Superfcetation.—M. de Bouillon* has adduced an instance of superfcetation in a negress. At the end of her pregnancy she was delivered of two male children, full-grown, and of the same proportions, but the one a negro and the other a mulatto. The mother, after a long resistance, confessed that she had connex- ion the same evening with a white and a negro. Similar instances have lately been detailed in the American journals, of which we shall only instance the following:—A white woman, near Philadelphia, is said by Dr. Dewees to have been delivered of twins, one of whom was per- fectly white, the other black. The latter of these had all the characteristics of the, African, whilst the former was delicate, fair-skinned, light-haired, and blue-eyed. Similar cases have been detailed by Dr. Elliotson, and Drs. Norton and Stearns, of New-York. Superfcetation, in our opinion, can only take place under circumstances similar to those which produced it in the foregoing instances : —in them, it would seem, that there had been connexion with different individuals within a short space of time. We conceive that, when the decidua is thrown out, and the ovum has formed its connexions, superfoetation is then impossible, unless in the case of a double uterus. OF THE DEVELOPEMENT OF THE TEXTURES AND ORGANS OF THE FCETUS. (Note 0 O. See pp. 344—353.) It was our intention to have illustrated this subject at considerable length ; but we have so far exceeded our limits, that we must now be brief. 1. Of the developement of the foetus.—At first the embryo appears to be only a semi-liquid vesicle, and to consist of minute globules dis- seminated through a more fluid medium, which presents an oval or spheroid form.f As the embryo advances, the proportion of solid matter increases, and continues to increase to the ter- mination of the life of the individual. The first stage of its existence resembles that of the polypus; and the globules which may be ob- served in its otherwise homogeneous texture closely resemble those which are observed in the nervous system. At first the embryo is colourless; it afterwards presents a gradual developement of colour, and at last a coloured fluid may be discerned. From a state of orga- nisation consisting merely of disseminated glo- bules — fibres, membranes, and vessels, come successively into existence. The organs, as we * Bulletin de la Faculte et de la Societe de Medicine, No. 3. + Mr. Bauer says that he has detected the human ovum on the eighth day from coition. It consisted of two membranes: the external one open throughout its length, but with its edges turned inwards, like the shells of the genus voluta ; the internal membrane pointed at one end, and obtuse at the other, slightly contracted in the middle, and containing a slimy fluid and two vesicles. X It would appear, that, in the process of the have already said, arc not formed at once; tfj-f are gradually developed. Even particular sys- tems do not assume at once their form of or- ganisation, but are developed by degrees, and run through the same stages of organisation as may be remarked in the animal scale. This is particularly remarkable as respects the deve- lopement of the nervous system.^ — See tho note on this subject, p. 60.) The exterior form of the foetus seems to be assumed before its tissues attain any consider- able degree of consistence. The glandular viscera are at first formed in isolated parts. The globules of the nervous system first ap- pear1 ; these become united into chords and gan- glia. The vessels commence in isolated vesi- cles, which become elongated, and connected in regular series. The intestinal tube seems to be the viscus which first presents a definite conformation, ft is at first straight, and after- wards it curves forwards, and i« embraced by the umbilical chord : it thus forms an angle, and descends into the abdominal cavity, which is open at its anterior aspect, and apparently con- tinuous with the short and imperfectly develop- ed chord. This turn of the intestinal canal, and its retention in the chord, seems to form the umbilical vesicle ; and the subsequent strangu- lation of the intestine, by the constriction and elongation of the chord, first gives rise to an isolated appearance of this vesicle ; subse- quently, to its entire disappearance ; and lastly, to the separation of the intestines ; the vermi- form appendix remaining as a type of the ori- ginal conformation. About the same time that the intestinal tube curves into the umbilical chord, the urinary bladder seems to be also prolonged into the chord, between the chorion and amnion, forming the allantois and urachus, the former of which disappears as the foetus is developed and the chord lengthened, the urachus only remaining at the time of birth, shewing the nature and type of the original conformation, and the communica- tion formerly existing between the allantois and bladder. We have already said, that all the.phases through which the human embryo passes until its conformation is perfected, correspond with the different stages of permanent organisation which characterise the animal scale. Since these observations were first published by us, we perceive that a similar opinion has been en- tertained by J. F. Meckel, and adopted by M. Beclard in his excellent work on General Ana- tomy. Many proofs may be adduced in support of this doctrine : so evident indeed is the analo- gy, that a very close parallel may be drawn between the stages of developement through which the human fcetus passes, and the degrees of animal organisation. rowth of the embryo even of man, during the rst days of its existence the nervous system can only be traced as it exists in the polypi; its globules seem dispersed through the embryal structure: as the ovum advances, the ganglial branches, and the ganglia themselves, make their appearance, the nerves of sensation and voluntary motion, the spinal chord, and the brain, being successively formed. See the remarks on the Developement of the Nervous System. OP THE DEVELOPEMENT OF THE NERVOUS SYSTEM. 83 TThe human embryo is at first an imperfectly formed vesicle : such are the polypi and others of the zoophyta. At a remoter period it consists of a small vermiform body, without a distinct feead or limbs: such are the echinodermata and the annelides. At a still later period its limbs are equally developed, and its tail is prominent: such are the quadrupeds. As respects the nervous system, the ganglial or vital nerves first appear with the ganglions : such is the nervous structure of the inverte- brated animals. As the embryo advances, the ganglial nerves give rise to two thin strips of medullary matter, in the situation of the spinal •canal,-these increase, coalesce, form the spinal and cervical marrow (medulla oblongata), and the tubercles of the latter, whence are produced the brain and cerebellum : we observe the same conformation in reptiles, fishes, &c. The human foetus is remarkable for the ra- pidity with which it runs through the early grades of the scale of organisation. It is this circumstance that renders the early changes which it experiences so difficult to be recog- nised. 11. Of the developement of the n ervous system.— Viewing the nervous system throughout the numerous classes of animals, and tracing the process of its formation from the embryo up to the period of perfect foetal existence in the per- fect animals, especially in man, we are led to infer that this system is not originally formed from the centre towards the circumference, but that the origin of its ramifications commences in the mucous or cellular tissue, when the em- bryo is yet but in an apparently homogeneous state ; and that as the textures become, in the process of foetal growth, more and more deve- loped, so the globules composing the nervous system, and chiefly those of the ganglial system of nerves, are arranged into chords of communi- cation, chiefly in the course of the vessels, for the purpose of preserving a connexion between the organs, and reinforcing each ofthe textures with the influence which they generate in their perfect state of developement. As the process of foetal growth proceeds, the nervous ramifica- tions advance towards centres, which vary in their characters according to the species of the animal; in those which are more perfect, those centres are numerous, and almost each differs in a more or less sensible manner from the other, both as to appearance and function. At an early period of foetal life the ganglial ramifications and centres are first formed,-and afterwards the ramifications and centres of the voluntary nerves. In the more perfect ani mals, even that part of the nervous system which is general throughout the animal creation, and which the lowest orders of it possess, is the first formed; and that part which is destined to perform the highest functions, and which the perfect animalsonly possess, is produced the last. III. Of the developement ofthe heart and lungs. —J. F. Meckel has concluded from his obser- vations, 1st, The heart is relatively larger, the younger the embryo. For in his observations he found, at the first period at which the heart could be distinguished, that it filled completely the thoracic cavity. 2d, The heart is more symmetrical with re- spect to situation and form, soon after its for- mation, than at a more remote period. 3d, The form of the heart undergoes various changes during the growth-of the foetus. A. The proportion between the arterial and venous portions of the heart is not always the same. The auricles surpass the ventricles in capacity, in proportion as the embryo is younger. B. The relative volume of the two sides of the heart is not always the same at all periods. In the adult the right side always more or less exceeds the left; but in very young embryos the two ventricles are equally capacious, but that of the right side increases rapidly. The right auricle surpasses the left in size in the fcetus, and it is only by degrees that the left becomes equal to the right. C. The right ventricle is unquestionably smaller than the left at first. D. The thickness of the parietes of the heart is much more considerable at first. The two halves of the heart equally present this differ- ence, but the right ventricle always appears a little thicker than the left. This is, however, less, the younger the foetus. E. The two ventricles communicate with each other at an early period, and, according to all appearances, continue to do so until the end of the second month, by means of an opening in their interior aspects, situated at their base, and immediately beneath the origin of the great ves- sels. F. The interior disposition of the auricles with respect to their communication, either with one another, or with the venous trunks, undergoes considerable changes. These turn chiefly on the form and size of the oval hole, the situation of the orifice ofthe vena cava'inferior, the situation, the form, the extent, and relations ofthe valve of Eustachius, and that ofthe fora- men ovale. Here M. Meckel's researches con- firm those of Sebatier and Wolff. 4th, The disposition of the aorta and of the pulmonary artery offers several considerable changes in succession, of which the following are the chief:— A. At first there exists only an aorta. A pul- monary artery is fonned at a remoter period, It is not until after the seventh week that the pulmonary artery begins to appear, and then it is only a second aortic trunk, as yet without branches—a right aorta, proceeding in the di- rection of the lungs, which are very distant, and extremely small. The disposition of the large arteries at this period (seventh week) nearly resembles what it continues to be, in reptiles, during the whole life of the animal. B. It is in the course of the eighth week only, that the branches of the pulmonary artery can be discovered. They are then much smaller, when compared to the trunk of the artery and to the arterial canal, the younger the embryo. At five months they become equal to this canal, and afterwards they surpass it, frequently so far, that when the foetus has completed the ninth month, each principal branch of the pul- monary artery is as large as it is, or even larger. The venous canal presents similar appear- ances. It is during the first periods of the ex- istence of the foetus that it offers, proportion- ally, the greatest amplitude. All the obser- vations which M. Meckel has made, confirm the law, which is the more important, as it throws considerable lighton the functions of this canal. Indeed it is probable that this conformation is only the remains of a disposition which may be seen at the epoch when the liver has not come into existence, when the vena porta and the 84 APPENDIX. vena cava inferior form but one trunk, as the pulmonary artery forms, at the early stage of its existence, only one with the aorta. This conjecture respecting the origin of the venous canal is confirmed by the organisation of the acephalous class of animals, in which the veins ofthe intestinal canal, and consequently the vena porta, also open immediately into the vena cava inferior. 5th, The lungs are not formed until a more advanced period. In man, manifest traces of them cannot be seen before the sixth or seventh week. Then they advance beneath the heart, at the two sides of the inferior extremity of the pectoral portion of the aorta. At the period of their appearance, and even for some time afterwards, they are so small, in proportion to the heart and the other organs, that it requires the greatest attention in following their progressive developement, to be convinced that they are in reality the rudiments of the respiratory organ. At first the lungs closely approach one an- other : they are flat and of a whitish colour. Their surface is perfectly united ; but on their external border may be observed, at an early period, indentations, which are the traces of tha approaching separation of the lobes, notwith- standing that these lobes are not yet in exist- ence. At a farther advanced period the lobes appear to be composed of lobules. These latter are at first larger and much less numerous, in proportion, than at subsequent periods, but they separate by degrees into others much smaller. At the period when they are first observed, they are as much more apparent, and as much less intimately united, by cellular tissue, as the em- bryo itself is younger. 6th, As the lungs become developed, in the reptiles and leeches, in the form of an empty sac, it is natural to suppose that their production in animals of a higher order takes place accord- ing to the same manner and law. M. Meckel endeavoured to ascertain whether or no this was actually the case. But, under whatever aspect he viewed the lungs at the early stages of their formation, even with the assistance of the microscope, he always found the slices which were removed from them completely so- lid : if they are really so during this epoch, it would seem as if they had some analogy of structure with the branchiae of fishes. 7th, The branches of the pulmonary artery, which proceed from the right or pulmonary aor- ta, are at first certainly wanting. It must therefore be admitted, that at this epoch their places are supplied by the bronchial arteries, especially by the inferior, since the lungs are at first placed low in the inferior part of. the chest. Moreover, this depending situation of the re- spiratory oigan, at the commencement of its de- velopement, is remarkable under two points of view:— A. Since, amongst reptiles, and many ofthe mammiferi, the lungs are placed much lower than in man, and below the heart, in every re- spect like the fishes, the swimming bladder is placed below this organ. * D. F. Lavagna concludes that the menstrual blood differs from common blood only in con- taining no fibrin ; also, that the blood in the um- bilical arteries ofthe funis contains scarcely any fibrin, whilst that in the umbilical vein forms a tenacious jelly: hence he infers that the blood B. Because it seems that the lungs and lh« thymus gland correspond in their functions, the developement of the one being in direct propor- tion to the decrease of tho other. J. F. Meckel concludes from the researches of which we have given an abridged outline, that the general results confirm it to be a grand law of the animal economy, that the emhrvo, from the instant of its formation until that of its maturity, rises successively through many inferior grades of organisation, and that the principal monstrosities of the heart and large blood-vessels depend upon these organs being arrested at some one grade or degree of orga- nisation, instead of following the progress of the others towards perfection. IV. Of the circulation of the placenta and nutri- tion of the fcetus.—There are abundant facts to prove that the circulation of the foetus is inde- pendent of that of the mother ; that the blood of the former flows from the umbilical arteries into the vein of the same name, and not from the uterine arteries into that vein; that the foetal blood is fabricated by the foetus itself from the juices furnished by the mother to the placenta, and absorbed by the radicles of the umbilical vein; and, consequently, that the fcetus does not receive one drop ready formed from this or- gan.* In proof of the correctness of this opinion, we may refer to the experiments performed by M. Gaspard,t in order to ascertain this point; to the formation of the blood in the impregnated egg on the second or third day after incubation ; and to the fact that, in the numerous tribe of oviparous animals, the foetuses are insulated from the mother, and are the real manufacturers of their own blood. Admitting, therefore, that the frfitus is the fabricator of its own blood, from the nutritive juices derived from the placenta, by what or- gans, it may be asked, is the sanguifying pro- cess performed ? The great size of the liver during foetal existence, the early formation of this viscus, and the large quantity of blood which is conveyed to it by the umbilical vein, would suggest it as the chief organ of sanguification. We have already referred} a sanguifying func- tion to the liver as well as to the lungs, during extra-uterine life, and we believe that this func- tion, which cannot be performed by the lungs during foetal existence, is chiefly accomplished by the liver. Some authors conceive, particu- larly M. Geoffroy St. Hilaire and Dr. R. Lee, that the blood circulating in the liver of the foe- tus supplies an abundant bilious secretion, of a mild or albuminous character, which, when poured into the alimentary canal, and mixed with the mucous secretion of the bowels, is there digested and converted into chyle, and carried into the foetal circulation for its nourish- ment. This opinion seems very probable. The sanguifying process of the liver appears to us intimately connected with a secreting function, the former in a great measure depending upon the latter; or, in other words, the secretions performed by this organ being the elimination of matters from the blood, the discharge of which acquires fibrin in the circulation in the placenta, which it parts with in its passage through the foetus.—Annali di Medicina di Milano, No. 17. + Journ. de Physiol. Experiment. No. 3. X See Appendix, Note M. p. 22. OF THE VARIETIES OF is necessary to the perfect state of sanguifica- tion. It should, however, be recollected that a very large part of the bile secreted during extra- uterine life is actually recrementitious; and wherefore may it not be altogether so during the comparatively short period of foetal exist- ence? Other peculiarities of the foetus are adduced in the different sections of thi3 Note; but on these, and various other subjects,—many of which we could not even enter upon,—our limits have obliged us to be extremely brief. V. Respiration of the foetus.—The thymus gland appears to assist the placenta, the liver, and the secretion of fat, in the respiration of the foetus, or rather in purifying the blood of the foetus. It seems to form a nidus for the recep- tion of those elements of the blood, carbon and hydrogen, which are secreted in a state ap- proaching to fat, and which, if too abundant in this fluid, would endanger the existence of the foetus. These materials on the commencement of active respiration are again absorbed, to be discharged from the economy by the lungs, liver, or intestinal canal. The thymus gland in the human foetus, in the ninth month, generally weighs from 160 to 180 grains; at twenty-eight years of age, only 90 grains. In the calf it weighs sixteen ounces, in the cow nine ounces. " Etenim placenta, hepar, adipis aucta secretio rcspirationi, sed aliud alio modo, inserviunt. Quae naturae institutio, ut in foetu organon alte- rurn alterius vices obtinere possit, pulcherrima et prajstantissima; quo fit, ut fcetus vita non- dum autonomica, a noxiis quibuscunque mo- mentis, quae vim in ipsum habere possunt, tue- atur conserveturque, donee ex asylo matris in lu- cem aeremque editus vim innatam exerceat. " Vena umbilicalis illo principio (oxygenio) gra- vida partim in hepar, partim in venam cavam in- ferioremsanguinemreducit a partibus phlogisti- cisliberatum. Itaque vena cava inferior, postquam sanguinis partem ex venaumbilicaliet venishepa- ticis excepit, prater sanguinem oxydatum, veno- sum quoque sanguinem ex corporis partibus redu- cemcontinei, cujustamen pars satis magna, san- guis lienalisacmeseraicus.inhe.pate jam carbone relicto, mera existit. Quoniam vero vena cava inferior prima vitae foetalis parte magis in sinis- trum quam in dextrum cordis atrium aperitur, sanguis autem venae cavae superioris, nil minus quam oxygenium ducens ex dextro cordis atrio per arteriam pulmonalem, hinc per ductum Bo- tallicum, dernum, postquam jam arteriae superi- orum partium ex aorta excreverunt, in ipsam perfunditur;—sequitur caput atque extremitates superiores sanguinem magis oxydatum, seu, si mavis, dephlogisticatum, in atrio sinistra ventri- culoque congestum, accipere;—aortam vero des- cendentem sanguinem ex vena cava supenori phlogisticum nee oxydatum in abdomen atque extremitates inferiores perducere, quo fit, ut su- periores corporis partes, exeeptis pulmonibus, qui sanguinem ex vena cava superiori yenientem venosum accipiunt, primo graviditatis tempore magis vigeant polleantque." P. 215. " Placenta oxygenium afferente, hepate car- bonium submovente, qua? functiones in adulto in uno pulmone conjuctae sunt."* P. 21G. * Joannis Mueller de Respirations Foetus Com- mmUtio Physiehgica, in Academia Bontssicd THE HUMAN SPECIES. 85 M. Geoffrey St. Hilaire, proceeding on the- principle that there cannot be organisation with- out the combination of a nutritious fluid, nor yet assimilation without oxygenation or pre- vious respiration, endeavours to shew :__1st That a respirable gas is present in the amniotic fluid, as shewn by the experiments of MM. Chevreuil and Lassaigne ; 2, That the foetus^ by means of its pores, as by so many tracheas, in the same manner as aquatic insects, is ena- bled to consume the air contained in tlie sur- rounding fluid, owing to the air being thus brought in contact with the venous blood which, fills the capillaries of the skin; 3d, That the contraction of the womb and of the abdominal muscles keeps up a certain degree of pressure, which is as requisite to the perfect performance of this process as to the ordinary act of respira- tion, t OF THE VARIETIES OF THE HUMAN SPECIES. (Notes P P. See p. 376.) Buffon, Blumenbach, Prichard, Gavoty and Touluzan, Cuvier, and others, have proposed classifications ofthe varieties ofthe human spe- cies : of these we prefer that of Cuvier. The following is an outline of it:— 1st, The fair, or Caucasian variety ; 2d, the yellow, or Mongolian ; 3d, the negro, or Ethi- opian. 1st, Caucasian. Characters.— The beautiful form of the head, the variable shades of com- plexion, and colour of the hair. Principal Branches.—1. The Syrian, whence have proceeded the Assyrians, the Chaldeans, the Arabs, Phoenicians, Jews, the Abyssinians, Arabian colonies, and ancient Egyptians. 2. The Indian, German, or Pelasgic branch was early subdivided into the Sanscrit, the Pelasgi, the Teutonic, and Slavonian. 3. The Scy- thian or Tartarian branch. 2d, Mongolian. Characters.—Prominent cheek-bones ; flat visage ; narrow and oblique eyes; straight and black hair; scanty beard, and olive complexion. Its civilisation has al- ways remained stationary. 3d,' The Negro. Characters.—Black com- plexion ; woolly hair; compressed cranium, and flattish nose. " It is very difficult to refer the Malays, or the Papuas, to any one of the three great varieties of mankind already described. It is a question, however, whether the former people can be ac- curately distinguished from their neighbours on either side ; the Caucasian Hindoos on the one, and the Mongolian Chinese on the other. " The Americans themselves have not yet been properly referred to either of the other races, nor have they characters precise and con- stant enough to constitute a fourth variety. Their copper-coloured complexion is not suffi- cient. The black lank hair and scanty beard would seem to approximate them to the Mon- goles, if their well-defined features and prominent noses did not oppose such a classification: their Rhenanaprcemioornata. Lipsim, 1823. P. 159. t Rev. Med. Dec. 1823. 86 APPENDIX. languages we likewise «s rmramerable as their tribes, and no mutual analogy has yet been as- certained between them, nor any affinity with the dialects of the ancient world."* We are inclined to infer that America was peopled by the Mongoles from Asia; and that, subsequently, it had been visited by Phoenician navigators, the greater part of whom settled in it, particularly in Mexico ; and that the imper feet navigation of that era prevented many of the adventurers, if not all of them, from re- turning. OF THE MORTALITY OF FEMALES AT THE CHANGE OF LIFE. (Note Q',Q. See p. 383.) From the bills of mortality of both sexes, col- lected in Provence, Switzerland, Paris, Berlin, Sweden, and Peteisburgh, it would seem, 1st, that from 30 to 70, no other increase takes place in the mortality of females than what naturally results from the progress of age -, 2d, that at all periods of the life of man, from 30 to 70, a greater mortality occurs than in women, but especially from 40 to 50.| APPENDIX, No. II. CHEMICAL CONSTITUTION OF THE SOLIDS AND FLUIDS OF THE HU- MAN BODY, I. Simple Substances entering into the Constitution op the different Ani- mal Principles or Constituents of the Human Body. The follow ing simple substances are variously combined, in order to produce the constituent parts of the body :— ] Azote. 8 Soda (-Sodium). 2 Carbon. 9 Potass (Potassium). 3 Hydrogen. 10 Muriatic Acid. 4 Oxygen. 11 Magnesia (Magnesium). 5 Phosphorus. 12 Silica. 6 Lime. 13 Iron. 7 Sulphur. H Manganese. Of these, magnesia and silica may be con- sidered as foreign bodies, they being seldom found, and in exceeding small quantities. 1 he principal elementary ingredients are the nrst six • animal substances may be considered as chiefly composed of them. The first four con- stitute almost entirely the soft parts, and the other two form the basis of the hard parts. II. Animal Constituents or Principles. I Gelatin consists of carbon, 4788; hy- drogen, 2720; oxygen, 2720; azote, 1700; or of 15, 14, 6, 2 atoms respectively,—con- tained in skin, bone, tendons, &c— Test, Tan- nin. II. Albumen.—Corrosive sublimate detects __L_ part the weight of the water containing UU°Comp.: Carbon, 52-883; oxygen, 23872; hydrogen, 7540; azote, 15705, in 100 parts. Dr. Prout found it to consist of 15 atoms of car- bon, 6 of oxygen, 14 hydrogen, 2 azote, accord- ing to the analysis quoted. j III. Fibrin varies in its species in the differ- ent classes of animals. Comp. : Carbon, 53360; oxygen, 19685; hydrogen, 7-021; azote, 19934. Consists of carb. 18 atoms, oxyg. 5,hydrog. 14, IV. Colouring Matter of the Blood.— Berzelius found it possessed of nearly the same properties as fibrin. It is soluble in water at a low temperature, and in all the acids except the muriatic: contains iron.t V. Urea or Nephrin, soluble in water and in alcohol. Precipitated in pearly crystals by nitric acids and oxalic acid. Dissolved by a solution of potass or soda. Constituents ac- cording to Dr. Prout:— Oxvgen .. 39-5^1 2 atoms Hydrog. 025 666 Azote..... 32-5 \ 1 ---- Carbon . 075 2000 Carbon ... 147 f 1 ---- Oxygen 100 2666 Hydrog... 133) 1 ---- Azote.... 1-75 4666 100~ 3-75 100 Gelatin is insoluble in cold water, albumen is insoluble in hot, and fibrin is insoluble in both cold and hot. The constituents of these three bodies, and of nephrin, according to the best analysis of them hitherto made, are as follow :— Carbon. Oxy. Hydro. Azote. atoms 15........6..........14.........2 ---- 17........6..........13.........2 ---- 18........5..........14.........3 ---- 1........1.......... 2......... 1 The colouring matter of the blood approaches albumen in many of its properties ; but it seems entirely destitute of azote. VI. Mucus.—Insoluble in water, transparent when evaporated to dryness, and, like gum, so- luble in the acids. Not soluble in Alcohol or ether—does not coagulate by heat—nor is pre- Gelatin Albumen Fibrin Nephrin * Griffiith's Trans, of the Regne Animal. t M Benoiston de Chateauneuf on the Mor- tality of Females from 40 to 50 years of age. Paris, 1822. X Berzelius, vol. iii. Med. Chirurg. Trans. CONSTITUENTS OF BONE, &C. g7 cipitated by corrosive sublimate or by galls. Is precipitated by the acetates of lead, arid by nit. argenti. Found in the epidermis, in nails, feathers, &c.* VII. Osmazome is, probably, only an altered state of fibrin. Soluble in water and alcohol- does not gelatinise. Precipitated by nit. argen- ti, nit. hydrarg., and acet. and nit. of lead. VIII. Picromel.—Found principally in bile ; resembles inspissated bile in its appearance; soluble in water and in alcohol:— 5 atoms Carbon ....... 3"75..........5453 1 ---- Hydrogen....... 125.......... 182 3 ---- Oxygen .......3-000..........4365.t IX. Sugar of Milk, according to Berzelius, consists of oxygen, 53359 ; carbon, 39474; hydrogen, 71674 Dr. Thomson gives the table of the atomic analysis as follows :— 4 atoms Oxygen ............4 ............484 5 ---- Carbon .............375............454 4 ---- Hydrogen.........050........... 62 8-25 1000 X. Oils are fixed.—Fat—Cholesterine.—The former is composed of oxygen, hydrogen, and carbon. The latter, according to Saussure, con- sists of 84068 of carbon, 12672 of hydrogen, and 3914 of oxygen ; and differs little from the other fixed animal oils, excepting that it con- tains more carbon and less oxygen than they. XL Acids. — The acids found constituting and ready formed in animal bodies, are the fol- lowing :— 1 Phosphoric. 6 Uric. 11 Acetic. 2 Sulphuric. §7 Rosacic. 12 Malic. 3 Muriatic. 8 Amniotic. 13 Lactic. 4 Carbonic. 9 Oxalic. 14 Silica. 5 Benzoic. 10 Formic. It may be remarked, that the whole of the soft parts of animals consists chiefly of albu- men, fibrin, and oils ; and the hard parts of phos- phate of lime. The other animal principles are only in small quantities, and in particular tex- tures. The oils seldom enter into the structure of the organs of animals; they serve rather to lubricate the different parts, and fill up inter- stices. III. Individual Textures and Fluids of this Human Body (formed of two or mouz OF THE FOREGOING CONSTITUENTS). The Constituents of the Bones and Teeth of some of the Mammalia, according to the Analysea of Berzelius and other Chemists. • Substances analysed. Cartilage, with the water of crystallisa-tion of the earthy salts and gelatin. *£ W ~ '—-CO ° a B tB-5 a o o ts a o ■s s v« O o t o S 'S *ed o (+* O 3 a a E o C bo s •*-o o rt «'5* t a Human bones recently dried . . . 33-3 1-2 11-3 51-4 2- 116 Bullock's bones recently dried . . 33-3 245 385 55-45 29 205 Osseous parts of human teeth . . 280 1-4 53 61-95 21 1-25 Osseous parts of bullock's teeth . 310 24 1-38 57-46 569 207 The enamel of human teeth.... 20 8-0 853 3-2 1-5 The enamel of bullock's teeth . . 3-56 1-4 71 810 4-2 30 251 * Bostock, in Nicholson's Journal, vol. xi. p. t' Dr. Thomson, An. Ph. vol. xiv. p. 69. &c. X Annals of Philos. vol. v. p. 266. $ Forms the lateritious sediment in levers, 83 APPENDIX. The compact and cellular substances of human bones are, according to Berzelius, of tho same composition. Substances submitted to analysis. bo J5 '■£ o Pepys. 200 040 60 10 The roots of the teeth . . . 280 580 40 10 The emanel of teeth . . . 780 60 16 The spine softened by ) disease .-.....J " 79-75 082 4-7 13-6 113 V Bostock. Fourcroy and Vauquelin could not discover the fluate of calcium either in the enamel of the teeth or in recent ivory. Boiling water extracts slowly the cartilage of bone in the form of gelatin. Cold hydrochloric acid dissolves the salts which have lime for their base, leaving nearly altogether untouched the whole of the cartilage. Ammonia precipi- tates the phosphate of lime from its solution in warm hydrochloric acid : the phosphate of lime, however, thus obtained, is accompanied with a considerable proportion of gelatin. Bones submitted to dry distillation, give gelatin, and, as a residue, the carbon of bones, which is a compound of animal charcoal and the salts, with potash for their base : exposed to the air, the charcoal of bones passes into the state of ashes. Tophus, found in the articulations of the arm, consists of animal matter, with traces of adi- pocire, 562 ; carbonate, phosphate, and hydro- chlorate of potash, 32; carbonate of lime, with traces of the carbonate of magnesia, 12*5 ; phosphate of lime, 28-1. Another specimen contained animal matter, with unctuous and fatty matter, and a little soda, 730 ; carbonate of lime, 10; phosphate of lime, 17.* The concretions found in persons subject to the gout are composed of the urate of ammo- The marrow of bones. — The medulla of the cylindrical bones of the bullock contain, mem- branes and vessels, 1; fat, 96; a reddish se- rum, 3. The medulla of the lower part of the radius, and of the tibia, contains a very liquid fat, and neither coloured vessels nor membranes. The diploe of the extremities of the long bones contain fatty matter and a reddish scrum, in very variable proportions. The vertebrae of the dorsal column contain a deep brown serum, partly concrete, soluble in water, and rarely a trace of fat.f The cartilages dissolve in water kept for a considerable time at the boiling point, and form a jelly. The synovia ofthe human subject consists of a yellowish fat, albumen, which constitutes its chief ingredient, an uncoagulable animal mat- ter, soda, chlorate of potassium and of sodium ; and the ashes furnish carbonate and phosphate of lirae.§ The synovia of the articulations of the kners of a man was found to consist of a flocculcnt substance, which coagulated at the temperature of boiling water, and was precipitated by the chlorate of mercury. || Gout appears to change, in some degree, the secretion in the joints affected. Dr. Wollaston, Dr. Pearson,.and Mr. Tennant, found the chalk- stones formed in this disease composed of urate of soda. Fourcroy has confirmed ttiis analysis ; «■ John, Ecrits Chim. torn. v. p. 104. t Wollaston. X Berzelius, Nouv. Journ. de Gehl. torn. u. 287. § Lassaigne and Boisscl, Joum. de Pharm. torn. viii. p. 30C. || Bostock. CONSTITUENTS OF MUSCLE, RRAIN, NERVE, &C. 89 ■**.e therefore conjectures that synovia contains uric acid.* Synovia of a horse.—A. From an articulation which was in a healthy state : soluble albumen, 6-4; animal matter, which did not become con- crete with the carbonate and the hydrochlorate of soda, 06; phosphate of lime, 015 ; traces of an ammoniacal salt, and of phosphate of soda; water, 9-28. — B. From a joint anchylosed in consequence of a wound: insoluble, fibrous albumen; soluble albumen; free phosphoric acid ; the same salts as mentioned above.t Synovia of an elephant. — Reddish, filamen- tous, of a slightly saline and insipid taste; when warmed or heated by mineral acids it coa- gulated. It contained a soluble albumen of animal matter precipitated by tannin, and which did not become concrete in a small quantity ; soda and hydrochlorate of potash-t The periosteum approaches the chemical pro- perties of cartilage, and yields a small propor- tion of gelatin. The ligaments resist for a very long time the action of boiling water, but dissolve at last, in part, like gelatin. The membranes, as the serous (the pia-mater, arachnoid, pericardium, pleura, peritonaeum, &c.) and the skin, dissolve in boiling water, and pass to the state of gelatin. Integument.— Cutis vera—formed of fibres interwoven like a felt. It yields little gelatin on maceration in cold water ; by long boiling in water it becomes gelatinous, and dissolves completely, and by evaporation it becomes glue. Hence it appears to be a peculiar modification of gelatin. By tannin, and the extractive of oak-bark combining with it, leather is formed. Rete mucosum — "is a mucous membrane, situated between the cutis vera and the epider- mis. The black colour of negroes is said to depend upon a black pigment situated in this substance; but it seems to us to be situated in the inner or flocculent surface ofthe epidermis. Chlorine deprives it of its black colour, and renders it yellow. A negro, by keeping his foot for some time in water impregnated with that gas, deprived it of its colour, and rendered it nearly white ; but in a few days the black colour returned again with its former intensi- ty.^ This experiment was first made by Dr. Beddoes on the fingers of a negro."H The epidermis possesses the same properties as horn. The internal surface of the epidermis seems to be the seat of the black colour of the negro, and not the rete mucosum. The human epidermis consists of fatty matter, 0-5 ; animal matters soluble in water, 50 ; concrete albumen, 93 to 95; lactic acid, lactate, phosphate, and hydrochlorate of potash, sulphate, and phos- phate of lime, an ammoniacal salt, and traces of iron, l.f The nails of the fingers and toes pre- sent an analogous constitution. Human Hair may be regarded as fine tubes ot a substance similar in all its properties to horn, covered by a white adipocire, (probably furnish- ed by the sebaceous glands of the scalp, and filled with an oily matter, which is either of a greenish black colour, red, yellow, or nearly colourless, according as the hair is black, red, yellow, or white. The ashes of human hair is composed of the hydrochlorate of soda; of the carbonate, sulphate, and phosphate of lime, (and the phosphate of magnesia in that which is white) a considerable portion of silica, oxide of iron in a very marked proportion in black hair, but scarcely to be recognised in that which is white ; and a very small quantity of the oxide of manganese. The sulphur, which is undoubtedly combined in the organisation ofthe corneous or horny substance, is found more abundantly in the red and light-coloured hair than in the black. The Muscular Flesh.—The muscular sub- stance is probably composed of very little more than fibrin, traversed by cellular tissue contain- ing fat, by the aponeuroses and tendons, by ves- sels containing blood, by lymphatics containing lymph, and by nerves. It is, however, very probable that osmazome, lactic acid, the hydro- chlorate and phosphate of soda, and the phos- phate of lime, particularly belong to muscular flesh, although they are also found in the blood. Cold water extracts of the muscular substance ,the red colouring matter of the blood, the albu- men, the osmazome, and the salts of the blood : boiling water takes up the cellular tissue reduc- ed to gelatin, and the fat which swims on its surface ; the residuum consists of fibrin, a little altered by the boiling, and which yields the phosphate of lime by incineration. The mus- cular substance of beef gives, by incineration, more lime than that of veal.** According to Berzelius, the muscular texture contains fibrin, vessels, and nerves, 158 ; cellu- lar substance, P3 ; albumen, 22 ; osmazome, with the lactate and hydrochlorate of soda, 1-8 ; mucous matter, 0-15; phosphate of soda, 0-9 ; phosphate of lime, containing a portion of albu- men, 00-8 ; water and loss, 77-17. Bullock's heart. — Osmazome, 757 ; albumen and cruor,' 276 ; fibrin, with vessels, nerves, cellular tissue, fat, and phosphate of lime, 1819; an ammoniacal salt and a free acid, in an inde- terminate quantity; lactate of potash, 019; phosphate of potash, 0-15 ; chloruret of potas- sium, 012 ; water, 77-04. ft An ossification found in the human heart. — It contained a cartilaginous matter and phosphate of lime in nearly equal proportions, with a little carbonate of lime.ft An ossification found in the veins of the human uterus.—Membranous substance and phosphate of lime, in nearly equal quantities, with a little of the carbonate of lime and traces of the hydro- chlorates.v§ Brain and Nerves. — The hemispheres of the human brain: a reddish-brown liquid fat, leaving phosphoric acid by combustion, 07 ; a white fat, becoming blacker by fusion, and giv- ing rise to much phosphoric acid by combustion, 4-53 ; phosphorus contained in these fatty sub- stances, 1-5; osmazome, 1-12; albumen, 7-0; ■" Fourcroy, torn. ix. p. 224. + John. Ecrits Chim. torn. vi. p. 146. X Vauquelin, Ann. de Chim. et de Phys. vi. . 309. > The human cerebellum gave the same re- Medulla oblongata and spinnl chord have the same constituent principles, but they contain more of the fatty matter, and less albumen, osmazome, and water. The nerves of the human subject contain less ot the liquid and crystallisable kinds of fatty matter, but more of the fatty substance which resembles adipocire, and much more albumen than the brain.* The gray substance of the brain of a calf: albumen insoluble in water, 10-0; an unctuous mcrystalhsable fat, osmazome, phosphate of ammonia, phosphate of soda, phosphate of lime, phosphate of magnesia, hydrochlorate of soda, and traces of iron, 150 to 100; water, 75 to 80. The white substance of the brain of a calf contained more fatty matter than the gray ; it presented traces of silica. The cerebellum of the calf gave the same products as the cineri- tious substance. The optic thalami, the medulla oblongata, spinal marrow, and the nerves of the calf, gave results similar to those furnished by the whito substance of the brain, excepting that they con- tained more albumen, and less water. The brain of a bullock contained also phos- Pha'? °f ammonia, a more solid albumen, a reddish-coloured fat, and a crystallisable fat. The composition of the brain of the stag Was similar.f The lymph found in the ventricles of the human brain : gelatin (osmazome ?), 09 ; mucus (sali- vary matter?),0-3 ; albumen, 0-6 ; hydrochlorate of soda, and a little of the phosphate of soda. 1-5; water, 96-5 ; loss, 0-24 A soft concretion found encysted in the cere- bral pulp of a subject who was afflicted with mental alienation : white grease, C ; semi-con- crete albumen, 170; cartilaginous substance, insoluble in potash, 18-0; salts, with ammonia, potash, soda, and lime for their base, about 20 ; water, 57.v See the note at pp. 199 and 200, for the com- position of the humours and textures of the eye. The pigmentum nigrum is mixed with mucus. Mucus.—The nasal mucus of the human sub- ject contains :—mucus, 5'33; albumen and sali- vary matter, with a trace of phosphate of soda, 0-35; osmazome, with lactate of soda, 03; soda, 009 ; hydrochlorate of potash and of soda, 0-56; water, 93-37.H The mucus of the trachea, according to Berzelius, is similar in its compo- sition. Saliva has a strong affinity for oxygen, ab- sorbs it readily from the air, and gives it out again to other bodies. The human saliva con- sists of—salivary matter, 0-29 ; mucus, 014; osmazome, with lactate of soda, 0-09; soda, 0-02; hydrochlorate of potash and hydrochlo- rate of soda, 0-17; water, 9929.1T * Vauquelin, Ann. de Chim. Ixxxi. p. 37. t John, Ecrits Chim. torn. iv. p. 249 • torn v p. 162. X Haldat, Ann. de Chim. ex. p. 175. § John, Ecrits Chim. torn. v. p. 102. || Berzelius, Fourcroy, and Vauquelin. Salivary calculi arc formed of a membranous substance, containing phosphate of lime. The tartar ofthe teiili.—Mucus, 125 ; saliva- ry matter, 1-0 ; animal matter, soluble in hy- drochloric acid, 7-5 ; phosphate of lime and phosphite of magnesia, 790.** The Lachrymal Fluid.—Animal matter, soda, hydrochlorate and phosphate of soda, and phosphate of lime, 10; water, 99-0. The cal- culi of the lachrymal gland are formed of the phosphate of lime, j f The Gastric Juice.—The gastric juice ejected by vomiting, after fasting for some time, resembled, according to Montegre, the saliva ; it contained flocculi of mucus, and underwent putrefaction as rapidly as the saliva ; but some- times it was acid, and then it did not undergo putrefaction. Lymph.—The liquor found in the thoracic duct of animals which have not taken nourish- ment for twenty hours, is as limpid as water, does not affect the vegetable colours, and does not coagulate cither by heat or by acids ; it be- comes slightly turbid from alcohol, leaves a very small residuum when submitted to evaporation, and consequently appears to contain but very little matter, and only a small quantity of the hydrochlorate of soda. The lymph of a horse taken from the thoracic duct towards the inguinal region and meso-co- lon, was of a greenish yellow, translucid, and concreted in twelve minutes into a clear gela- tin ; the coagulum, which hardly amounted to tJt> was similar to fibrin, the fluid contained about 0-04 of albumen, muriate of soda, with a little soda and phosphate of soda.JJ Chyle.—The chyle taken from the thoracic duct of a dog, three hours after a vegetable diet, resembled clear milk, and deposited a reddish- white coagulum: this coagulum, which had the appearance of fibrin, was to the serum at first in the proportion of 48 to 100; but after being left longer to itself it increased considerably. The specific weight of the serum was T018 ; it did not coagulate at the temperature of boiling wa- ter, but became turbid; after some weeks it be- came a little sour, without undergoing putrefac- tion : in 100 parts it contained from 48 to 7-3 of solid matter, which consisted of 0-9 of soluble albumen and salts; it contained neither gela- tine, nor phosphate of lime, nor any ammoniacal salt. The chyle of a dog, collected three hours af- ter having eaten meat, had the appearance of cream: its coagulum, a little red, was to the serum at first as 46-5 to 100, but this quantity diminished gradually: the serum became much more turbid by heat, and by the addition of acids, than that produced from vegetable food; it underwent putrefaction in three days ; it de- posited, when allowed to stand, a white and greasy cream, and furnished from 7 to 95 per cent, of solid matter, consisting of soluble albu- men, without any gelatin. Brande observed a substance analogous to the sugar of milk in the serum.9^ if Berzelius, Bostock, Thomson, John. ** Berzelius. tt Vauquelin. XX Reuss and Emmert, Journ. de Scherer torn. v. p. 681. v$ Marcet, Vauquelin, Brande, &c. CONSTITUENTS OP THE BLOOD, &C. 91 VhyU, when drawn from the thoracic duct, about five hours after the animal has taken food, is an opaque liquid, of a white colour ; without smell, and having a slightly acid taste, accom- panied by a perceptible sweetness. The pre- sence of a free alkali is indicated. About ten minutes after it is -drawn from the animal it coagulates into a stiff jelly, which fn the course of twenty-four hours gradually separates into two parts, producing a firm contracted coagu- lum, surrounded by a colourless fluid." 1st. " The coagulum, as appears, from the experiments of Vauquelin,* is an intermediate substance between albumen and fibrin. He con- siders it albumen on its way to assume the na- ture of fibrin. It is not so stiff nor of so fibrous a tex.t.ure as fibrin ; it is more easily acted on and dissolved by caustic alkalies ; it is insolu- ble in alcohol and ether, readily dissolved by sulphuric acid, very dilute ; nitric acid converts it into adipocire. When burnt, it leaves a char- coal containing common salt, phosphate of lime, and gives traces of iron."t 2d. The liquid portion separates albumen on boiling, and contains sugar and a very small portion of a fatty matter, similar to that found in brain. The same salts as in other animal fluids. Blood.—Taste slightly saline, smell pecu- liar, specific gravity L0527. As soon as the vital influence of the vessels ceases to act on the blood, it separates into the coagulum or cru- or, and serum. The common proportion is one part of cruor to three of serum. The proportion, however, varies from 12 to 14. If the sepa- ration of fibrin, giving rise to the coagulation, takes place in repose, the fibrin entangles the red particles of the blood; but if the blood be kept in motion, the red particles escape into the serum, and the fibrin is separated into threads. 1st. Serum.—Possesses the taste and smell ofthe blood; specific gravity is about 1-0287. Berzelius found that the serum of human blood was composed as follows :—water, 905-00; albumen, 80-00; muriates of potash and soda, 6-00 ; lactate of soda, with animal matter, 4-00 ; soda, phosphate of soda, with animal matter, 410; loss, 0-90=1000-00.t " Dr. Marcet found the constituents of serum as follows :—water, 900-00 ; albumen, 86-80 ; muriates of potash and soda, 660; muco-ex- tractive matter, 400; sub-carbonate of soda, 1-65; sulphate of potash, 035; earthy phos- phates, 0-60=1000."§ " The muco-extractive matter was, doubtless, impure lactate of soda." " Berzelius is of opinion, that the sulphate of potash, and the earthy phosphates which were found by Dr. Marcet in the ashes of serum, were formed du- ring the incineration ; for phosphorus, sulphur, and the basis of lime and magnesia, exist.^ ac- cording to him, as constituents of albumen." " Gelatin was considered as a constituent of serum until Dr. Bostock and Professor Berzelius proved that the opinion of its existence in blood was not well founded." 2. The cruor, or the clot.—Specific gravity about 1245. Is separated into two portions by ablution in water. 1st, a white, solid, elastic substance, which has all the properties of fibrin; 2d, the portion held in solution by the water is the colouring matter, with a portion of se- rum. " Berzelius and Brande have shewn that this clot is a compound of fibrin, albumen, and co- louring matter of blood. According to the ana- lysis of Berzelius, it consists of—colouring mat- ter, 64 ; fibrin and albumen, 36=100." " When the colouring matter is incinerated, about one-third of a per cent of oxide of iron may be extracted from its ashes. This portion of iron is a constituent of the colouring matter, and perhaps the cause of its red cokmr.H But in what way it is united to the albuminous por- tion of the colouring matter, remains unknown. When incinerated, the colouring matter leaves •g*y~th of its weight of ashes, consisting, accord- ing to the analysis of Berzelius (which appears to be the most to be depended on), of the fol- lowing ingredients :—oxide of iron, 500 ; sub- phosphate of iron, 7-5 ; phosphate of lime, with traces of magnesia, 6-0 ; pure lime, 20'0 : car- bonic acid and loss, 16'5=lO0O." Berzelius is of opinion that none of these bo- dies existed in the colouring matter ; but merely their bases, iron, phosphorus, calcium, &c.; and that they are formed during the incineration. " The albumen of blood leaves the same quan- tity of ashes as the colouring matter; but these ashes contain no traces of iron." " Dr. Gordon has made it appear probable, that during the coagulation of blood a little heat is evolved."IT Rouelle has obtained nearly the same ingre- dients, only in different proportions, from the blood of a great variety of animals. Fcetal blood.—" Fourcroy made some experi- ments on the blood of the foetus. He found that it differed from the blood of the adult in three things :—1st, Its colouring matter is darker, and seems to be more abundant. 2d, It contains no fibrin, but probably a greater,proportion of gela- tin (?) than blood of adults. 3d, It contains no phosphoric acid."** Diseased blood.—1st. " Deyeux and Parmen- tierft ascertained that the buffy coat consists of the fibrin. The cruor, deprived of this sub- stance, is much softer than usual, and almost totally soluble in water. 2. " The blood drawn from several patients labouring under sea scurvy, afforded scarcely any remarkable properties to these chemists^ except a peculiar smell, and an albumen which' was net so easily coagulated as usual." 3. The blood of patients in putrid fevers gave no sensible alteration in its properties to the ex- aminations of these chemists. 4. " The blood of diabetic patients : the se- rum of the blood, according to the experiments of Dobson and Rollo, assumes the appearance of whey. Dr. Wollaston has shewn that it con- tains no perceptible quantity of sugar, even when the urine is loaded with it." Milk separates into cream, curd, and whey. 1st, Cream is composed of a peculiar oil, curd, and serum. Cream of the specific gravity of 1-0244, was analysed by Berzelius, who found it composed of—butter, 4'5 ; cheese, 3-5; whey, 920=1000. * Ann. de Chim. xxxi. p. 113. + Thomson. X Annals of Philosophy, vol. ii. p. 202. t) Medico.-Ohirurg. Soc. Trans, vol. ii. p. 376. II Thorn, vol. iv. p. 492. «[ Annals of Philosophy, vol. iv. p. 139. ** Four., Ann. de Chim. torn. vn. p. 162. tt Journ. de Phys. torn. xliv. p. 454. 92 APPENDIX. 2d. Curd may be precipitated by rennet, or Carbon.....59-7^1 the acids: alkalies dissolve it easily. The Oxygen .... 11409 constituents of curd, according to the analysis Hydrogen .... 7-42!) of Gay Lusac and Thenard, are as follows:— Azote ..... 21-381=100000' 7 atoms Carbon 1 — Oxyg'en 5 — Hydro. 1 — Azote Dr. Thomson's application of this analysis to the atomic theory. By doubling the \ 14 atoms Carbon 8625 100-00 ( number of atoms, | 2 it may be compared [ 10 with gelatin, albu- [ 2 men,1 and fibrin- I — ;28 Oxygen — Hydrog. — Azote 105 20 125 35 1725 Proust has found in cheese an acidy whichhe calls the cascic acid, to which he ascribes seve- ral of the peculiar properties of cheese. * The coagulation of curd probably depends upon the same cause as that of albumen^ 3. Whey still possesses some curd :• on eva- poration it deposits crystals of sugar of milk. Towards the end ofthe evaporation,- some crys- Water..........92875 Curd, with a little cream . . , . 28-00 Sugar of milk........35"00 Muriate of potash....... 1'70 Phosphate of potash ...... 025 Lactic acid, acetate of potash, with ) q.qq a trace of lactate of iron . . . ) Earthy phosphates.......030 100000 It has been ascertained that milk is incapable of being converted into wkie till it has become sour; after this, nothing is necessary but to place it in the proper temperature ; the fermen- tation begins of its own accord, and continues till the formation of wine be completed.6 A great quantity of carbonic acid is extricated du- ring the fermentation of milk.|| Milk is fer- mented and kept for many months, or even years, in the Orkney and Shetland Islands ; but, along with a small portion of alcohol which is formed, the acidity is considerable. The ingredients of the milk of most animals are nearly the same ; the proportion only differs. The human milk differs from cow's milk— 1st, in containing a much smaller quantity of curd : 2d, its oil is so intimately combined with its curd, that it does not yield butter; 3d, it contains rather more sugar of milk. Parmentier and Deyeux ascertained that the quantity of curd in woman's milk increases in proportion to the time after delivery.f None of the methods by which cow's milk is coagulated succeed in producing the coagula- tion ofthe human milk.** Bile (hnman).—The following is the analy- sis of bile, according to Berzelius : water, 908-4; picromel, 800; albumen, aO ; soda, 4-1; phos- phate of lime, 0T ; common salt, 34; phos- phate of soda, with some lime, 10= 1000. Biliary calculi are formed either entirely of cholesterine, or they also contain a yellow con- crete mucus, picromel, and rarely phosphate of tals of muriate of potash and of muriate of soda make their appearance.t According to Scheele it contains also a little phosphate of lime.J Fourcroy and Vauquelin, Thenard, Bouillon, la Grange, and Berzelius, have analysed whey. The latter chemist gives the following as the? ingredients of milk deprived of its cream :— Milk may be made to afford a liquor re- sembling wine or beer, from which alcohol may be separated by distillation. The Tar- tars obtained all their spirituous liquors from mare's milk. lime or carbonate of lime. These latter ingre- dients frequently almost entirely replace the cholesterine.ft Cerumen of the Ear.—Vauquelin considers it composed of the following substances. lstr Albumen. 2d, An inspissated oil. 3d, A colouring matter :—1th, Soda. 5th, Phosphate of lime.J J Tears.—According to the analysis of Four- croy and Vauquelin,§§tbey are composed of the following ingredients :—1st, Water. 2d, Mu- cus. 3d, Muriate of soda. 4th, Soda. 5th, Phosphate of lime. 6th, Phosphate of soda. " The saline parts amount only to about 0-01 of the whole. The mucus contained in the tears has the property of absorbing oxygen gradually from the atmosphere, and of becoming thick and viscid, and of a yellow colour. This property of acquiring new qualities from the absorption of oxygen, explains the changes which take place in tears in some diseases ofthe eye." Sweat contains salivary mucus, osmazome, lactic acid, lactate of soda, and hydrochlorate of potass and soda.|||| Thenard found it composed of an animal sub- stance analogous to gelatin, acetic acid, hydro- chlorate of soda, phosphate of lime, phosphate of iron, and water. According to Dr. Anselmino,1[Tf the sweat consists of 002 of calcareous salts ; 021 of ani- mal matter with the sulphates ; 0-48 of osma- zome, and the chlorurets of soda and of lime ; and of 0'29 parts of osmazome, combined with the acetates and free acetic acid-. * Journ. de Phys. lxiv. p. 107. t Parmentier, Journ. de Phys. xxxviii. p. 417. X Scheele, vol. ii. p. 61. § Parmentier, Journ. de Phys. xxxviii. p. 365. || Scheele, vol. ii. p. 66. •f Journ. de Phys. torn, xxxviii. p. 422. ** Clarke, Irish Trans, vol. ii. p. 175. ft Gren. Orfila, XX Fourcroy, torn. rx. p: 373. §$ Journ.de Phys. torn, xxxix. p. 236. IIH Berzelius. %% Zeitschrift filr die Physiologic von Fr. Tiedemann, 14-0 luble residue........5 Liquor of blisters.—The analysis of Macque- ronj gives it nearly the same constituents as the serum of the blood: from 200 parts he ob- tained—albumen, 36; muriate of soda, 4 ; car- bonate of soda, 2; phosphate of lime, 2 ; wa- ter, 156=200. Human F^ces.—Their colour seems to de- pend upon the bile mixed with the food in the digestive canal: when too light, it is supposed to denote a deficiency of bile ; when too dark, there is thought to be a redundancy of that se- cretion. The following table shews the analy- sis of Berzelius:—§ (a) The salts, their relative proportions. Carbonate of soda........35 Muriate of soda.........4 Sulphate of soda........'^ Amm. phosphate of magnesia .... 2 Phosphate of lime........4 100-0, Gases existins in the Intestinal Ca- nal.—These maybe ascribed to three sources : 1st, from the common air swallowed with food; 2d, from the decomposition of the intestinal con- tents ; and 3d, from the occasional secretion of gas from the mucous surface of the tube. The gases from the first source are found chiefly in the superior portions of the canal; those from the second source in the lower part; and those from the third are by no means limited 1. Gases in the Stotnach. Oxygenf..........1100 Carbonic acid........14-00 Hydrogen..........3'55 Azote...........7P45 10000 in their situation. It is reasonable to suppose that a large proportion of the azote and carbonic acid is derived from this last source. From the experiments of Magendie and Chev- reul, who examined, very soon after death, the gaseous contents of the stomach and intestines of four criminals executed at Paris, the follow- ing appear to be the proportions and the rela- tive quantities in the different portions of the canal:—1| 2. Gases in the small Intestines.** Oxygen .... 0000 0000 000 Carb. acid . . . 2439 4000 250 Hydrogen . . . 5553 51 15 84 Azote.....2008 88 0 666 10000 10000 1000 3. Gases in the large Intestines. Carbonic acid......-.......4350......... 700 Hydrogen and carburetted hydrogen......54-7.........116 Azote................51-03 = 10000 184 = 10000 4. Gases in tlie Cmcum. Carbonic acid.........12-5 Hydrogen..........7-5 Carburetted hydrogen......12'5 Azote............67'5 1000 5. Gases in the Rectum. Carbonic acid........42 86 Carburetted hydrogen.....11-18 Azote...........4596 100 00 * Nicholson's Journ. vol. xiv. p. 145. + Ann. of Phil. vol. xvi. p. 151. 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