cfi 3 . A . 1*3. KING’S College LONDON T^w-J fjp$2 Tvw Library ti>wAto){ u-v. Ph /Vdiwr^ I ?72 20 12 41< 1 5 II II KINGS COLLEGE LONDON I Digitized by the Internet Archive in 2015 https://archive.org/details/b21307040 ^3. a. / u. ON THE INFLUENCE OF PHYSICAL AG ON LIFE, BY W. F. EDWARDS, M.D. F.R.S. member of the royal academy of sciences, and royal academy of MEDICINE OF PARIS, OF THE PHILOMATHIC SOCIETY OF THE SAME CITY, AND OF THE MEDICAL SOCIETY OF DUBLIN, ETC. CranSlatetJ from tlje dfrmclj, BY DR. HODGKIN AND DR. FISHER. TO WHICH ARE ADDED, IN THE APPENDIX, SOME OBSERVATIONS ON ELECTRICITY, BY DR. EDWARDS, M. POUILLET, AND LUKE HOWARD, F.R.S. ; ON ABSORPTION, AND THE USES OF THE SPLEEN, BY DR. HODGKIN ; ON THE MICROSCOPIC CHARACTERS OF THE ANIMAL TISSUES AND FLUIDS , BY J. J. LISTER, F.R.S. AND DR, HODGKIN ; AND SOME ■ NOTES TO THE WORK OF DR. EDWARDS. LONDON: PRINTED FOR S. H IG H LE Y, 32, FLEET AND WEBB STREET, MAZE POND, BOROUGH. 1832. 1 1 9S 3 nil LONDON : PRINTED BY STEWART AND CO OLD BAILEY. PREFACE. It does not appear necessary to say much to urge the importance of the investigation of the influence of a variety of physical agents on life, since it con- stitutes not only a most essential branch of phy- siology as a science, but is replete with practical points of vital importance and universal applica- tion ; seeing they are not less connected with the preservation of health, than with the cure of dis- ease. Many of the functions of life are con- fessedly veiled under an almost impenetrable ob- scurity. This indeed is so universally admitted, that the idea of reducing them to the rank of those phenomena which come within the province of physics (properly so called) or natural philosophy, and of applying to them those laws which we know to regulate operations in which inorganic or dead matter is concerned, is regarded as hopeless, and many physiologists, without reviving the auto- crateia of Stael, nevertheless refer to vitality with its vires conservatrices as so varying in its powers a 2 IV PREFACE. and operations, as to baffle every attempt to reduce to fixed principles many of those phenomena of which it is an element. We cannot be surprised at this when we consider the almost infinite variety which life presents in the wide range of the animal kingdom, and observe how these varieties are mul- tiplied by those presented by a single species, nay, by a single individual under various circumstances of age, season, and situation. We must not, how- ever, too hastily adopt the idea, that this subject is really one which presents inherent obstacles of insurmountable difficulty. Many subjects which at first appear to be involved in inextricable con- fusion and perplexity, become clear and intelli- gible when once the proper clue or explanation is furnished. Some minds are so happily constituted as to have a remarkable readiness in perceiving the relations which connect facts and observations, which to others appear not merely isolated, but absolutely contradictory. This appears to be par- ticularly the case with Dr. Edwards. The labours of his predecessors had accumulated a vast collec- tion of invaluable facts and observations, many of which seemed to be almost annihilated by their standing in direct opposition to others supported by equally valid and respectable authority ; the labours of Dr. Edwards have explained many of these discrepances. It may be ill becoming in me to anticipate the judgment of the reader, but I P R E F A C E . V cannot refrain from expressing my admiration ot the patient and clear induction with which the Doctor proceeds, step by step, through the great variety of subjects comprised in his work, so as to maintain the unity and connexion of the whole, and of the happy art with which he has both availed himself of the experiments and observa- tions of his predecessors, and supplied the breaks and deficiencies which he met with, by well con- trived simple and conclusive experiments of his own. It is at least presumptive evidence of the merit of the Doctor’s work, that different parts of it presented at separate times to the Academy of Sciences of Paris, obtained for their Author, al- though a foreigner, the honourable distinction of the physiological prize. It is certainly to be re- gretted, that our philosophical countryman has not himself exhibited his instructive work in an English dress, that our medical literature might have the credit of possessing it as an original ra- ther than as a translation. Translations are gene- rally inferior to original publications. In the pre- sent instance I have endeavoured to reduce the weight of this objection by submitting the trans- lation to the Author’s perusal, and he has kindly supplied me with some fresh matter, which will be found in the Appendix. Whilst I feel justi- fied in expressing jnyself as I have done with VI PREFACE, respect to the original work, to which I have to acknowledge the obligation of much important assistance in practice, I must confess myself very differently circumstanced with regard to the trans- lation. To suit the convenience of English students, who have in general neither time nor inclination for voluminous reading, Dr. Fisher and myself have laboured, as far as possible, to compress the work without omitting a single experiment or conclusion. This, however, has been no easy task, as Dr. Edwards’ own method of exposing the subjects of which he treats is in general too concise to admit of abbreviation, without incurring the risk of producing obscurity. I have thought it best, in publishing the transla- tion, to omit the copious tables, in which the Author has set forth- the individual results of his very nu- merous experiments, to enable the reader to con- firm the conclusions which he has deduced from them. These form a valuable addition to the ori- ginal work, but as I conceive that the majority of readers will rarely if ever refer to the tables, I have judged that to reprint them would consi- derably and needlessly increase the price of the book. Those who are engaged in similar re- searches with Dr. Edwards, and are desirous of referring to the tables, may easily consult them in the original work, since, as they are almost PREFACE. Vll purely numerical, they may be easily understood even by those who are unacquainted with the French language. The Appendix to the original work, relates to electricity in conjunction with the phenomena of life. It was furnished by Prevost and Dumas, and is principally devoted to their views respect- ing muscular contractions, on which subject I must confess myself under the necessity of dis- senting from those able physiologists. To the Appendix, in the translation, I have made some additions, in order to put the reader in posses- sion of subsequent researches regarding the re- lations between life and electricity ; yet it must be confessed, that this subject is still in a very imperfect state, and calls for further investiga- tion, which would doubtless well repay the la- bour of conducting it. Some other points relating to physical phseno- mena connected with life, are also briefly noticed in the Appendix, viz. : Dutrochet’s views re- specting endosmosis and exosmosis — those of Dr. Stephens, which have thrown most important light on the chemical changes produced in re- spiration and circulation, and the labours of other experimenters on the same subject. I have likewise reprinted, with some additions and alterations, my Thesis on Absorption, a short paper on the Uses of the Spleen, and the micro- Vlll PREFACE. scopic observations of my friend Joseph J. Lister and myself, in relation to the tissues and fluids of animals. The obvious relation which they bear to the objects of Dr. Edward’s work, will, I trust, be a sufficient apology for the introduction of them. The notes which are also given in the Appendix, are few and generally short. For the materials of the Appendix, I am greatly indebted to the kindness of my friends, and it gives me pleasure to embrace this opportunity of acknowledging my obligations in this respect to Sir Astley Cooper, Dr. Stephens, Dr. Marshall Hall, Dr. C. Thompson, my valued friend Luke Howard, C. Woodward and to my learned and accomplished friend A. R. Dusgate. I cannot conclude this preface without ex- pressing a hope, that the students and younger members of the profession may zealously pursue the investigation of the various interesting sub- jects which physiology presents, in the philoso- phical method of which Dr. Edwards has given so striking an example. CONTENTS Page Introduction 1 PART I. THE BATRACHIAN REPTILES. CHAP. I. — On Asphyxia 7 Sect. 1. — Comparative Influence of Air and Water upon the nervous and muscular Systems 9 Sect. 2. — Asphyxia in Water 11 Sect. 3. — Strangulation 11 Sect. 4. — Cutaneous Respiration 12 Sect. 5.' — Animals inclosed in solid Bodies 13 CHAP. II. — On the Influence of Tempera- ture 16' Sect. 1 . — Influence of the Seasons 18 CHAP. III. — On the Influence of the Air CONTAINED IN WATER 22 Sect. 1. — On the Effects of limited quantities of Water... 25 Sect. 2. — Stagnant Water renewed at intervals, ....... 26 X CONTENTS. Sect. 3. — Action of Aerated Water upon the Skin 27 Sect. 4. — Running Water 29 Sect. 5. — Limits of this Mode of Life 30 Sect. 6. — Combined Action of Water, Air, and Tempera- ture 32 CHAP. IV. — On the vivifying Action of the Atmosphere 35 Sect. 1. — Influence of Cutaneous Respiration 35 Sect. 2. — Influence of Pulmonary Respiration 38 CHAP. V. — The Influence of the Atmosphere on Perspiration 42 Sect. 1. — Loss by Perspiration in equal and successive Periods 42 Sect. 2. — Effect of Rest and of Motion in the Air .... 44 Sect. 3. — Respiration in Air of extreme Humidity .... 45 Sect. 4. — Perspiration in dry Air 46 Sect. 5. — Effects of Temperature 47 CHAP. VI. — Absorption and Perspiration .. 48 PART II. FISHES AND REPTILES. CHAP. I. — Tadpoles 51 CHAP. II.— Fishes 56 Sect. I. — Influence of Temperature on the Life of Fishes, in Water deprived of Air 56 CONTENTS. XI Sect. 2.— Influence of the Temperature of Aerated Wa- ter, in limited Quantities, in close Vessels.. 57 Sect. 3. — Influence of Temperature, and limited Quan- tities of Aerated Water, in contact with the Atmosphere 58 Sect. 4. — Respiration in the Air 59 Sect. 5. — Life of Fishes in the Air 59 CHAP. III.— Lizards, Serpents, and Tortoises 65 PART III. WARM-BLOODED ANIMALS. CHAP. I. — On the Heat of young Animals... 68 CHAP. II. — On the Heat of adult Animals.. 75 CHAP. III. — The Influence of the Seasons on the Production of Heat 81 CHAP. IV. — On Asphyxia 84 Sect. 1. — Influence of External Temperature 89 CHAP. V. — On Respiration in Youth and adult Age 91 CHAP. VI. — On the Influence of the Sea- sons upon Respiration 98 CHAP. VII. — On Perspiration, or Exhalation 103 Sect. 1. — Loss by Perspiration in equal and successive Periods 103 Sect. 2. — Influence of the Hygrometric State of the Air 107 Sect. 3. — Influence of the Motion and Rest of the Air. . 110 XU CONTENTS. PART IV. MAN AND VERTEBRAL ANIMALS. Page CHAP. I. — On the Modifications of Heat in Man, from Birth to adult Age. . 112 CHAP. II. — On the Influence of Cold on Mortality at different Periods of Life 117 CHAP. III. — Momentary Application of Cold 123 CHAP. IV. — Momentary Application of Heat 125 CHAP. V. — Influence of the Seasons in the Production of Heat 126 CHAP. VI.— Asphyxia 132 CHAP. VII. — On the Modifications of Respi- ration DEPENDING UPON SPECIES, Age, &c 141 CHAP. VIII. — Of the combined Action of Air and Temperature 145 CHAP. IX. — Effects of Temperature upon the Functions of Respiration and Circulation 151 CHAP. X. — Influence of the Respiratory Movements on the Production of Heat 157 CHAP. XI.— On Perspiration 162 Sect. 1. — Influence of Meals 164 Sect. 2.— Influence of Sleep 167 CONTENTS. Xlll Page Sect. 3. — Influence of the Hygrometric State of the Air.. 168 Sect. 4. — Influence of the Motion and Rest of the Air . . 169 Sect. 5. — Influence of Atmospheric Pressure 170 Sect. 6. — Perspiration by Evaporation and by Transuda- tion 171 Sect. 7. — On the Influence of Temperature 176 Sect. 8. — Cutaneous and Pulmonary Perspiration .... 178 Sect. 9. — Perspiration in Water 180 CHAP. XII. — Absorption in Water 181 CHAP. XIII. — Absorption in Humid Air 186 CHAP. XIV. — On Temperature 190 Sect. 1. — On the Degree of Heat which Man and other Animals can endure 190 Sect. 2. — On the Influence of Excessive Heat upon the Temperature of the Body 195 Sect. 3. — Comparison of the Losses by Perspiration in Dry Air, Humid Air, and Water, at Tem- peratures inferior to that of the Body .... 198 Sect. 4. — On the Influence of Evaporation upon the Tem- perature of the Body when exposed to an excessive Heat 200 Sect. 5. — On Cooling in different Media, at Tempera- tures, inferior to that of the Body 202 Sect. 6. — On Refrigeration in Air at Rest, and in Air in Motion 204 CHAP. XV. — On the In FLUENCE OF LlGHT UPON the Development of the Body. 206 XIV CONTENTS. CHAP. XVI. — On the Alterations in the Air from Respiration 212 Sect. 1. — Proportions of the Oxygen which disappears, and of the Carbonic Acid produced 216 Sect. 2. — On the Proportions of Azote in the Air inspired and expired 221 Sect. 3. — On the Exhalation and Absorption of Azote . . 225 Sect. 4. — On the Production of Carbonic Acid in Res- piration 2% Sect. 5. — General View of the Alterations of the Air in Respiration 242 CHAP. XV. — Applications 245 APPENDIX. On Electricity . By Prevost and Dumas 285 On Muscular Contractions produced by bringing a solid body into contact with a Nerve luitlwut a Galvanic Circuit. By Dr. Edwards 307 On Atmospheric Electricity . By M. Pouillet 316 Extract from an Essay on some of the P hcenomena of Atmo- spheric Electricity, By Luke Howard, F.R.S., Sfc. . . 320 Remarks on the same subject by the Editor, and Experi- ments and Observations by C. Woodward and P. Smith 325 De Absorbendi Functione. By Dr. Hodgkin 342 Further Remarks on the same subject, and Notices of the Papers of L. Franchini, Fiscinus and Seiler, Dr. Barry and Fodera 382 CONTENTS. XV On the Phenomena to which the Names Endosmosis and Exosjnosis have been qiven by H. Dutrochet 414 On the Mici-oscopic Characters of some of the Animal Fluids and Tissues. By J. J. Lister and Dr. Hodgkin .... 424 On the Uses of the Spleen. By Dr. Hodgkin 448 NOTES. On Asphyxia 463 On the same subject. By Dr. M. Hall 464 On the Proteus 464 On the Existence of Fish, Sfc. in Water of High Temperature 465 On Hybernating Animals 467 On the Temperature of Hybernating Animals and of Young Animals. By Dr. M. Hall 469 On the Views of Dr. M. Hall and Dr. Holland on this sub- ject 470 Original Experiments on the Effects of Heat and Cold. By Sir Astley Cooper 472 Experiments on the same subject, with reference to Resto- ration from suspended Animation. By Thomas Nun- nelly 475 Observations on the Influence of Temperature on the Mor- tality of Children. By Dr. M. Edwards and Dr. Villerme 476 On Cutaneous Absorption. By Dr. Corden Thompson .-. 476 Connexion of Rainy Seasons with Disease, exemplified in the Cases passing through an Hospital 479 On an Increase of the Weight of Atmospheric Air, noticed by Dr. Proul during the prevalence of Cholera 480 On the Changes effected in the Air by Respiration, with Notices of the Experiments of Dr. Stevens, S. D. Broughton, and Allen and Pepys 481 ERRATA. Page 9 line 8 from bottom for heart read hearts. 19 in note for preceding read succeeding. 24 line 9 from bottom for lugs read lungs. 245/or Chapter XV. read Chapter XVII. 331 line 10 from bottom/or hogs read dogs. 334 5 from bottom for F. Smith read P. Smith. 448 12 for contribution read contributor. The object of the present work is the examination of the effects of those agents by which we are surrounded, and whose influence is incessantly exerted upon us. They are called physical agents, as being the objects of that part of science which is denominated physics. They are to be distinguished from mechanical agents. These researches will relate to the Air in its several conditions of quantity, motion, or rest, density or rarity ; to Water in a liquid state, and in a state of vapour ; to Temperature, as modified both in degree and dura- tion ; to Light; and to Electricity. These agents operate simultaneously, and, in general, imperceptibly, on the animal economy. The impression produced is the result of their combined influence. Even when the intensity of any one of them is such, that we are enabled to distinguish the cause which is affecting us, it most frequently happens that the sensation alone is attended to, whilst the accompanying changes escape our notice. Hence, the most careful observation of phenomena, as presented by nature, cannot enable us to analyze the result of such combined actions, and to assign to each cause its peculiar effect, whilst those effects, which it is not in the province of sensation to detect, will re- main undiscovered. By means of experiments, we may, however, control external circumstances, and vary that B. 2 INTRODUCTION. of which we wish to appreciate the action; and thence, by observing the correspondence existing between such modi- fication, and the accompanying change which takes place in the animal economy, we may establish the relation of cause and effect. In order to derive advantage from this method, the intensity of the cause must be determined on the one hand, and the degree of effect on the other. In physics we may generally find means of accomplishing the first: the reader will judge how far I have succeeded with the second. I took, for the subjects of my experiments, various species of animals from all the four vertebrated classes, in order to give greater certainty to particular results, when an agent produced uniform effect on beings so differently con- stituted. Moreover, I hoped that the investigation of the very evident modifications, of which certain species are sus- ceptible, might lead to the discovery of similar modifica- tions in species in which they are too little marked to fix the attention in the first instance. I soon found the result to equal my expectation. In the detail of my researches I have adhered to the order in which they were conducted. I have divided the work into four parts. The first relates to the Batrachian Reptiles ; the second, to the other Cold-blooded Vertebrated Animals ; the third, to Warm-blooded Animals ; the fourth, to Man, and the other Vei’tebrated Animals.* In the outset of these inquiries I soon perceived that the science of electricity was too little advanced to supply me with the requisite means for placing the investigation of * I also made corresponding experiments with several families of invertebrated animals. M. Adoin,well known by his labours on the anatomy of insects, assisted me in conducting them. INTRODUCTION. 3 this on a par with that of other agents. The recent dis- covery of CErsted, by which the phenomena of electricity and magnetism are connected, 'forms, in conjunction with those of Ampere, and several other natural philosophers, a new epoch in the annals of this branch of science. The principles which they have established, and the instruments which they have invented for the appreciation of actions hitherto unknown, have furnished Prevost and Dumas with the means of making some very interesting researches on electricity, in connection with the animal economy. To their kindness I am indebted for the concise view of the present state of our knowledge on this subject, which is contained in the Appendix to this work. Tables are added, exhibiting the individual results of the principal experiments, in order that the reader may be better enabled to judge of the bases on which the con- clusions are founded. The examination of one fact always led me to that of another ; hence, the intimate connection between all the phenomena which I have detailed. The importance of the agent decided the point at which my researches were to commence. All the physical agents are indeed indis- pensable to the maintenance of life ; but as the air is that for which there is obviously the most pressing necessity, I began by examining the effects which result from the pri- vation of it. The choice of the animals for experiment followed as a consequence. Those which offered the widest scope for observation, with regard both to the duration of the phenomena, and to the facilities afforded for variation of the experiments, were the first to be examined, I therefore commenced with the family of the batrachians. They unite many other advantages, which render them peculiarly adapted to afford the first notions of the influence b 2 i 4 INTRODUCTION. of physical agents. As they participate in the qualities of reptiles and of fishes, the knowledge obtained from the study of them renders it the more easy to pass rapidly to the other cold-blooded vertebrals. The minutias of detail may be collected from the tables Avhenever the uniformity of the phenomena is obvious, whilst the attention is directed to the particular considera- tion of those instances which at first sight appear to be exceptions, the examination of which leads to further re- sults. The higher temperature of the mammalia and of birds, being the physiological fact which forms the strongest contrast between them and reptiles and fishes, I make it the first point to be considered in the study of warm- blooded animals ; and, regarding the development of heat as a function abstractedly, I endeavour to determine what are the variations to which it is subject, according to various circumstances with respect to organization on the one hand, and to external agents on the other. The results of this examination furnish the elements which enter into a great number of other phenomena, which are the subjects of sub- sequent researches. The commencement of the third part corresponds to the researches in the first, in which I examine the effects of the internal temperature on cold-blooded vertebral animals. I there make no allusion to the facts detailed in the pre- ceding parts, but confine myself in treating of warm- blooded animals to the independent consideration of them. It is only in the fourth part which relates to man, with the other vertebral animals, that I take an extended view of the phenomena, as well through the medium of the pre- viously detailed facts as of others, which serve as the com- plement to them, or lead to new considerations. It is this generalization which admits of our entering on the consi- INTRODUCTION. 5 deration of man. This is the end which I proposed to myself, and to which every thing that I have advanced leads and refers. The relations of the physical agents to the animal eco- nomy are infinite. It was necessary to make a selection. I have confined myself to those direct actions, which the present state of the physical sciences furnishes us with the means of appreciating, and to the examination of their combinations. In the choice of the circumstances, of which I sought to discover the influence, I have always been guided by the wish to establish principles capable of useful application. The agents which I have examined, having immediate relation to the nervous system, and to the organs of respir- ation, circulation, exhalation, and absorption, I have been led to the investigation of a great number of facts con- nected with hygeia and pathology, of which an idea will at once be formed, when it is considered that I have been particularly occupied with modifications dependent on con- stitution, and with the changes which constitution under- goes through the operation of external agents. The greater number of the facts which I have related, were first brought forward in various papers which I have read before the Royal Academy of Sciences of Paris, or presented to that body as subjects for the prize founded for the promotion of experimental physiology. # * Chap I. The part, On Asphyxia was read to the Academy of Sciences in 1817. and printed in the Annales de Physique et de Cliimie for the same year, Vol. 5. Chap. II. The first part, On the Influence of Temperature was read to the Academy in 1818, and published in the Annales de Phy- sique et de Chimie the same year, Yol. 8. Chap. III. The first part, On the Influence of Air, contained in 6 INTRODUCTION. I owe the acknowledgment of my obligations to my pupil M. Vavasseur, who assisted me in the course of my experiments. water, was read to the Academy in 1818, and inserted in the An- nales de Physique et de Chimie, Vol. 10. Chap. IV. The first part, On the Vivifying Influence of the At- mosphere— Chap. Y. First part, On the Influence of the Atmosphere on Transpiration — Chap. VI. First part, On Absorption and Transpiration in Water, — were read to the Academy of Sciences in 1819. These three chapters united to the second part with a short state- ment of the facts contained in the third, were presented to the con- cours for the prize of experimental physiology in 1819, and were crowned by the Royal Academy of Sciences, together with the work of M. Serres sur les V Osteogenic in 1820. Baron Cuvier gave an account of these memoirs in the Analysis of the Transactions of the Royal Academy of Sciences, published each year. The 1st and 2d sections of chap. 16. 4th part, are extracted from a paper which I read to the Academy, January 1821, On Respiration and the Influence of the Seasons on the Animal Economy ; and which, being presented to the concours, divided the prize for experimental physiology with M. Dutrocliet’s paper. On the Growth and Repro- duction of Vegetables. The 3d section, On the Exhalation and Absorption of Azote, Chap. 16, 4th part, was read to the Academy in 1823, and printed in the Annales de Physique et de Chimie, and in Magendie’s Jour- nal de Pliysiologie ; the 4th section, On the Production of Carbonic Acid in Respiration ; and the 5th section, A General View of the Changes in the Air in Respiration — were read to the Academy in the same year. It will be seen from several parts of this work that I did not originally intend here to treat of the changes of the air in respiration, this subject being designed for one of the parts of an- other work, On the Influence of the principal Chemical Agents. For reasons which I need not relate, I have concluded to publish these researches in this place, where they will serve as a supple- ment to those which precede them. PART I. THE BATRACHIAN REPTILES. CHAP. 1. ON ASPHYXIA. The action of Air in respiration, is one of the pheno- mena with the investigation of which physiology was the first engaged ; hut it has been one of the last to be studied with advantage. The solution of this question depended on another science which, until latter times, did not furnish the requisite light. When Priestley had discovered oxygen gas, and its pro- perty of converting dark into red blood, and when Lavoisier had laid the foundation of the new chemical theory, Good- win made the application of it to asphyxia, and demon- strated by accurate and skilfully combined experiments that the exclusion of air, by preventing the conversion of dark into red blood, is the cause of the death of animals. Bichat again took up the subject, and has published a treatise on as- phyxia, under the title of “ Researches on Life and Death.” Me took a wide view of the subject; and, by a beautiful train of experiments, endeavoured to determine the triple relation of the nervous, respiratory and circulatory systems. 8 ASPHYXIA. lie drew the conclusion, that venous blood penetrating the brain, causes its functions to cease, and that afterwards, the heart ceases to beat from the same cause. Legallois likewise treated of Asphyxia in his Researches on the Principle of Life, and made it appear that venous blood, acting on the spinal marrow, causes the movements of the heart to be stopped. It is to be observed, that these physiologists made their experiments almost exclusively on warm-blooded animals. The phenomena presented by cold-blooded animals merited particular attention. Spa- lanzani took them up in his Researches on the Relation which the Air bears to organized Beings, a work equally remarka- ble for the number and the importance of its facts. The alteration which the air undergoes from the organs, capa- ble of modifying it, was the principal object of his en- quiry. The relation between the three great functions, on which Bichat and Legallois have so much insisted, but little arrested his attention. At that time physiology had not made the progress which it has done since the labours of that celebrated experimental philosopher and naturalist ; and chemistry had not then perfected the process for the examination of gases. One of the philosophers, who has the most essentially contributed to this improvement, has also published a treatise on the respiration of fishes, which leaves nothing to be desired on this point.* The phenomena presented by cold-blooded animals are so wonderful, that it would seem impossible to bring them together with those exhibited by the other vertebrated ani- mals. It would not be believed, that they are united by a common chain, if the careful investigation of nature did not discover the uniformity of her laws. * Memoir e sur la Respiration des Poissons, by Humboldt and Provenpal, in the Memoirs of the Society of Arcueil. ASPHYXIA. 9 Sect. 1. — Comparative influence of Air and Water upon the nervous and muscular systems. Previous to our examination of the phenomena of as- phyxia, we shall first enquire whether the media in which it may take place have not a peculiar influence, independ- ent of that which is exerted over the lungs. Of these media, the most important are air and water. The singular power possessed by reptiles of living a considerable time after the excision of the heart, supplies us with the means of appreciating the respective influence of these media. By the removal of the heart the circulation of the blood, and, as a necessary consequence, respiration, are annihilated. A part of the blood escapes ; and that portion which remains may be regarded as a constituent part of the organs. The nervous and muscular system alone are left, and these are inseparably connected. If, after having cut out the hearts of reptiles, taking care to remove, also, the bulb of the aorta, an equal number be placed in air and in water, deprived of air, the difference in the duration of life, if any difference exist under these two circumstances, will indicate the respective influence of these media on the nervous and muscular systems, inde- pendently of that which it may exert on circulation and respiration. This experiment was performed on salaman- ders, frogs, and toads. I cut out the hearUof four salamanders of the species Triton, removing, also, the bulb of the aorta. I exposed two to the air, and immersed the two others in water of the same temperature, which had been deprived of air by boiling. In about four or five hours the salamanders in the water appeared dead ; but that life still existed was rendered evident, when they were moved or pinched. One died in eight hours, the other in nine. Those in the air. 10 ASPHYXIA. however, lived from twenty-four to twenty-six hours. These experiments were afterwards repeated with the same pre- cautions upon six other salamanders, and similar results were obtained. Consequently air, in comparison with water, has a superior vivifying influence upon the system of these animals, independently of its action by means of circulation and respiration. The heart and bulb of the aorta were removed from twelve frogs (R. esculenta and R. temporaria) six of which were placed in water, deprived of air, and six in air. Those in the water lived two hours, and those in the air three. Their activity which continued to be considerable, after the excision of the heart, decreased far more rapidly in the water than in air, and stimulation produced much less effect. The same experiment succeeds equally well upon toads. If a frog, thus deprived of its heart, and immersed in water, be drawn out and exposed to the air, at the moment when all signs of life have disappeared, it immediately begins to recover. If it be again plunged in water all ap- pearance of life instantly ceases ; and it may thus be made, several times alternately, to lose and recover its motion and sensibility. This confirms, in a striking man- ner, the vivifying effect of air, and the deleterious influence of water on the nervous system.* * Nasse has likewise shewn by experiment, that water has the effect of destroying the irritability of muscles, and has pointed out an application of this fact to some points of physiology and patho- logy. This property of water had already been noticed by Humboldt, and also by Pierson. Note of the Editor. # ASPHYXIA. 1 1 Sect. 2. — Asphyxia, in Water. In the preceding cases the functions of the nervous and muscular systems alone remained. In asphyxia, there is, in addition to these, the circulation of blood, which has been deprived of the influence of the air. I next attempted to ascertain the comparative duration of life under these two conditions, in order to discover the effect which the circu- lation of venous blood produces on the nervous system. With this view, frogs, whose hearts had been removed, and an equal number left entire, were placed in vessels containing water deprived of air. The result, in all cases, exhibited a marked difference, sometimes above twenty hours in favour of the latter. Similar results were ob- tained with toads and salamanders. The removal of the air in the lungs, by pressure or excision of the lungs them- selves occasions no difference in the effects. Hence the circulation, even of venous blood, is favourable to the action of the nervous and muscular systems, though incapable of maintaining life beyond a very limited period. Sect. 3. — Strangulation. It may be presumed, that the water which, from the experiments in sect. 1., was shewn to exert a deleterious influence upon the nervous system, may have prevented the circulation of venous blood from prolonging life so much as it would have done in a less noxious medium. I strangled six frogs, by tying, very tightly, with a pack- thread round the neck, a piece of bladder fitted very closely to the head, so as to exclude the air. In fact, the ligature was sufficiently tight to effect this of itself. At first the frogs were paralysed, but they afterwards, to a great degiec recovered, and lived from one to five days; while 12 A S P H Y X I A . the same number in water were dead in ten or twelve hours. The same experiment upon salamanders was at- tended with similar results. One of these animals lived twelve days, when the head became gangrenous ; it af- forded me an opportunity of making observations anala- gous to those of M. Dumeril, in his interesting experiments on a salamander, which survived decapitation a sufficient length of time for the neck to cicatrize. The phenomena in these cases being complicated with serious injury of the the nervous system, belong to a subsequent section. On comparing asphyxia by submersion with strangulation in the air, we see so marked a difference in the duration of life, as to lead to the inference, either that these animals can live for many days without any other action of the air than that which is exerted on the nervous system, or that that fluid acts also upon the blood through the skin. Sect. 4. — Cutaneous Respiration. Spallanzani concluded, from his investigation, that when the skin of these animals (frogs and other batrachians) is in contact with the air, carbonic acid is produced ; but he operated upon batrachians whose lungs had been cut out. In this case the blood from the wound, in contact with the air, must necessarily produce carbonic acid. To obviate this objection M. Chevillot and myself placed frogs, strangled with bladder and a ligature, as in the preceding experiment, in receivers containing atmospheric air. We took them out alive an hour or two after, and having ex- amined the air of the vessel, we found in it a sensible quantity of carbonic acid. Hence it follows, that the length of time which reptiles, in the state of strangulation, can live in air, must in part be referred to the action of that fluid upon the skin. ASPHYXIA. 13 I defer, for. the present, the consideration of the mode in which the carbonic acid was produced. Sect. 5. — Animals inclosed in solid Bodies. From the preceding facts and observations, it appears that animals asphyxiated under water perish sooner than the mere circulation of venous blood would cause them to do; while the life of those in air is prolonged by the influ- ence of that fluid exerted through the skin. If, therefore, the animals could be incased in a solid material, which should exert no deleterious influence on the nervous sys- tem, the influence of the venous blood would be free from both these complications. Numerous instances are re- corded of toads having been found in blocks of stone, and other similar situations, in which they must have re- mained, without extinction of life, for an incalculable length of time. But in these cases there was probably some crevice, forming a communication between the ex- ternal air and the cavity containing the animal.* In 1777 Herissant proved to the Academy of Sciences that toads could live eighteen months in boxes inclosed in plaster ; but as, even in this experiment, the animals were surrounded by the air in the boxes, it is not absolutely conclusive. 1 took, on the 24th of February 1817, five pasteboard boxes of three and a half inches diameter and two deep, and filled each of them with plaster, in which was imbed- ded a toad ; one of them was found alive on the nine- teenth day. The others were left for examination after a longer period. Similar experiments were tried upon sala- manders and frogs with the like results ; but these last do not live so long as the toads and salamanders. * We are inclined (o think that at least in some of these instances such communications must have been altogether impossible. 14 ASPHYXIA. The foregoing facts appear still more remarkable, on comparing the duration of life of some of those animals exposed to air, with that of others buried in solid bodies. Four frogs were exposed to the air in a dry bottle. At the same time, an equal number were placed in dry sand of the temperature of the atmosphere. I examined them every twenty-four hours. On the third day all those in the air were dead, except one, while all those buried in the sand, with one exception, were perfectly alive. The life of the animals inclosed in plaster or sand ap- pears to be preserved by the air having still sufficient access to them to exert its vivifying influence through the skin. The permeability of sand is evident. In order to ascertain how far plaster possessed the same property, I took an open tube, five inches long and five or six lines in diameter ; closed one extremity with plaster to the extent of about an inch, and took care to cover it outside. I let it dry and again put plaster over it, in order to - close the imperceptible openings which might exist in it. When the whole was sufficiently dry, the tube was filled, with mer- cury, and inverted over the same fluid : it was not long- before I perceived that the air penetrated and lowered the mercury. This experiment repeated several times had al- ways the same result, which shews that air freely pene- trates plaster. It might, however, have been the case, that the quantity of air which penetrates the plaster was insufficient to sup- port the life of these animals. I therefore inclosed frogs, salamanders, and toads in plaster, as in the preceding ex- periment, and placed some under water and others under mercury, to intercept the air, and found that they died almost as soon as when the water is in immediate contact with them. But it remains to be ascertained why the duration of ASPHYXIA. 15 the life of these animals is longer in the sand or plaster than in the air ? Frogs and salamanders waste rapidly in the air, and undergo desiccation. In the proportion that they waste, their motions are performed with increasing difficulty ; they move, however, until they have lost the quantity of water necessary to their existence. The pasteboard-boxes containing toads and salamanders, mentioned in p. 13, were opened at intervals of from six weeks to two months and a half from the commencement of those experiments. The animals were all dead, and in a state of complete desiccation. I observed the same of the fro^s which had died in the sand. Hence I concluded, O that in both cases death arose from the loss of the fluids by perspiration, and I presumed that the perspiration must be less in the plaster than in the air. This was afterwards proved by exposing some frogs to the air in dry vessels, and burying others in dry sand, and afterwards weighing them, at intervals of two, three, four, and five days, I uni- formly observed a greater loss in the air than in the sand. Comparative experiments were also made in air and plaster upon toads, and the difference was much more striking than in the sand. Hence the cause of the greater duration of life in sand or plaster than in air, is from the perspir- ation being more abundant in the air than in the solid substances. Under an exhausted receiver, in which the effects of rapid evaporation and absence of air are combined, death, as might be expected, takes place very speedily. Several experiments which I performed, in conjunction with M. Chevillot, on frogs and salamanders, demonstrate this fact. CHAPTER II. ON THE INFLUENCE OF TEMPERATURE. The facts detailed in the preceding chapter may be modified by various circumstances, which have not yet been considered. One of the most important of these is temperature. In the months of July and September, 1816. I made forty-two experiments on the submersion of frogs, in glasses containing two-tenths of a litre * of aerated water inverted over saucers. The mean temperature of the atmosphere was 15.°6 of the centigrade thermometer, or 60° of Fahrenheit in July, in September it was 14.°1 of the cent, or 58° of Fahr. the temperature of the water was from 17° cent, or 63° Fahr. to 15° cent, or 60° Fahr. The mean duration of life, or sensibility to ordinary stimuli was one hour and thirty- seven minutes in July, and one hour and forty-five minutes in September. At the same time I made the following experiments, in order that the only appreciable difference might be in the temperature. Spallanzani and some other naturalists had already observed, that frogs immersed in water lived longer in winter than in summer, but they had not investigated the subject. The temperature of the Seine water being 17° cent, or 63° Fahr. I cooled it by means of ice to 10° cent, or 50' Fahr., * A litre is equal to 176 pint, new measure. INFLUENCE OF TEMPERATURE. 17 and found that, of two frogs immersed in it, one lived 5h. 50' and the other 6h. 15'. When the water was re- duced to 0° cent, or 32° Fahr. eight frogs were introduced into it, and they lived from 6h. 7' to 8h. 18'. When, in- stead of cooling the water, its temperature was raised to 22° cent, or 72 Fahr., that of the air being 20° cent, or 68° Fahr., the frogs only lived from lh. 10' to 35'; when it was raised to 32° cent, or 90° Fahr. they died in from 32' to 12'; and when it was raised to 42° cent, or 108° Fahr., they scarcely lived a few seconds, and in no instance exceeded two minutes. Hence we may observe that as the temperature of the water is reduced, the duration of the life of the frogs im- mersed under it, is prolonged until at 32° Fahr., or 0° of the centigrade thermometer, it is more than tripled. On the other hand the elevation of the temperature produces a corresponding abbreviation of life, till, at 108° of Fahr. or 42° of the centigrade thermometer, death might almost be said to be immediate. It is worthy of remark that the de- gree of heat at which frogs cannot survive immersion in water, is about the natural temperature of warm-blooded animals. The temperature about zero appears then the most fa- vourable to the life of frogs plunged in water, but it must not be supposed that the prolongation of their life was oc- casioned by their becoming torpid. They are certainly less active at that temperature, but they perform the functions of voluntary motion and enjoy the use of their senses. On the other hand, the elevation of temperature is accompanied by a progressive and corresponding diminution in the dura- tion of life, and a proportional increase of agility. Analogous experiments on toads and salamanders pro- duced similar results. In warm climates, animals of this class may perhaps c 18 INFLUENCE OF TEMPERATURE. continue to live in water at 42° cent, or 108° Fahr., but since they would have full liberty of respiration, this fact, if proved, would not be an objection to the preceding ex- periments, which have reference to a state of asphyxia. The influence of temperature with freedom of respiration will be examined in the sequel. In reply to an objection which may be raised, that the speedy death of the frogs might be occasioned by the rapid transition from the temperature of 15° cent, or 60° Fahr. to that of 42° cent, or 108° Fahr., rather than to the eleva- tion of the latter, it may be observed that the transition was equally rapid in the descending scale. The considerations, to which the preceding researches conduct us, are by no means so simple as might at first be imagined. The influence of climates and seasons, the mode of life of these animals, the action of the air con- tained in the water, and the relation which it bears to tem- perature, and lastly the effect of habit are all accessory circumstances whose complicated elements exert their re- spective influences. Sect. 1. — Influence of the Seasons. It will be recollected that in the months of July and Sep- tember, the frogs lived from an hour to 2h. 27' in aerated water at 15° cent, or 60° Fahr. and at 17° cent, or 63° Fahr. On the 7th November, ten frogs similarly placed in water kept at the temperature of 17° cent, or 63° Fahr. lived from 2h. 5' to 5h. 35'. All the circumstances being the same in these cases, except the season, it is to this cause that the difference in the results must be referred. But in what way does the season produce this effect? Is it by means of temperature, or the intensity of light, or the weight of the atmosphere, or its hygrometric or electric INFLUENCE OF TEMPERATURE. 19 states, or its degree of motion or rest? Is any thing to be referred to changes in habits of the animals themselves? The influence of light and electricity must be left out of the question, until we can appreciate the degree of their in- tensity. The pressure of the atmosphere which exerts an influence by affecting perspiration may be disregarded’ since the difference of mean pressure in the two seasons in which the experiments were made was very inconsiderable.* The same may be said of the influence of the winds and of the hygrometric state of the air, since batrachians, though powerfully affected by these causes whilst living in the air, are wholly removed from their operation when immersed in water. The only circumstance, therefore, left for con- sideration is the influence of temperature, and as the water in which the animals were immersed was kept at the same degree in both the series of experiments, it is evident that the temperature of the atmosphere prevailing at the time could exert no influence upon the result. The case, how- ever, is different in regard to the temperature, during a cer- tain space of time previous to the experiment. The shallow waters which frogs inhabit, vary in temperature with the atmosphere and more or less approximate to it. The frogs submitted to the July experiments had been for the pre- ceding months under the influence of a mean temperature of 14°.8 cent, or 58 °.6 Fahr., and those made use of in September had experienced during August, the effect of a mean temperature of 15°.5 cent, or 60° Fahr. while the frogs subjected to the November experiments had been for the previous month exposed to a temperature of 7°.3 cent, or 45° Fahr. Hence results the remarkable fact, that these animals were able to live in the latter season twice as Iona* * The effects of variation in the rapidity of perspiration, and of diminished atmospheric pressure in accelerating' perspiration, are shewn in the preceding chapter. c 2 20 INFLUENCE OF TEMPERATURE, as in summer in water at the same temperature. Admitting this to be the uniform result, it necessarily supposes a con- siderable change in the constitution of these animals, which thus prolongs the duration of their existence in water. To ascertain the uniformity of this principle was the subject of the following experiments. On the 23d Nov. 1817, the air and water being at 10° cent, or 50° Fahr. and the mean temperature of the month being nearly the same ; five frogs were placed in water at the same degree. They lived from 5h. 10' to 1 lh. 40' ; the latter period being about double the duration of life of these animals in water at the same degree in summer. On the 22d Dec. the thermometer having been about 0° cent, or 32° Fahr. for twenty days, three frogs were put in water at 10° cent, or 50° Fahr. ; they lived from twenty to twenty- four hours. On the 23d Dec. the temperature being still 0° cent, or 32° Fahr. four frogs were placed in water at 0° cent, or 32° Fahr. the same apparatus being employed as in the preceding experiments. They lived from twenty- four to sixty hours. The experiments just related were frequently repeated with the same results, for two successive seasons, and can leave no doubt on the mind respecting, 1st, the in- fluence of the temperature of the water in which the animals were immersed, and 2d, the influence of the tem- perature of the air for some days previous to the experi- ment. When these causes are combined the effect is doubled. Hence, in the last-mentioned experiment the animals were placed in circumstances the most favourable to the prolongation of their life under water. The congela- tion of water fixes the limit of the descending scale. In a greater degree of cold, the conditions are altered, and belong to the question of asphyxia in solid bodies. Being desirous of ascertaining whether the influence INFLUENCE OF TEMPERATURE. 21 of previous temperature would extend itself to the case of batrachians immersed in water at a high temperature, I placed, on the 30th October, the mean temperature of the month having been 7° cent', or 45° Fahr., six frogs in water, kept at the temperature of 42° cent, or 107° 6' Fahr. the degree which proves instantly fatal to batra- chians in summer. But they lived about the same time as in the analogous experiments made in the summer, viz. from one to two minutes. I tried the same experiment on the 23d December, the temperature of the month having been near 0° cent, or 32° Fahr. and repeated it upon toads and salamanders with the same results. CHAPTER III. ON THE INFLUENCE OF THE AIR CONTAINED IN WATER. In entering on this subject, it will be necessary to direct our attention to the habits of the frog. Spallanzani, from observations made by himself in the neighbourhood of Pavia, states, that the frogs there leave the water in Oc- tober, and withdraw to the sand, in which they provide themselves with an aperture, called by the frog-catchers, il respiro della rana, the frog’s breathing hole. French naturalists, however, assert that frogs make their winter retreat in the water from October till spring ; and M. Bose, who has paid great attention to the habits of these animals, informs us that he has often found them under water during winter. But do they remain constantly in this situation ? or do they come occasionally to the surface for the purpose of respiration ? This is a question not easily decided by observation, for however narrowly we might watch them, we could scarcely be certain that they had not come to the surface without being observed. Be- sides, it has appeared, from one of the preceding experi- ments, that in winter they have lived in water for two days and a half. From direct observation, therefore, we can derive little assistance in our inquiry, whether frogs can during winter, dispense with respiration. The affirmative side of this question is somewhat supported by the fact, INFLUENCE OF AIR CONTAINED IN WATER. 23 that they are sometimes found alive in water which is covered with ice. But this is not decisive, unless it could also be ascertained how many days had elapsed since the formation of the ice, and whether it were free from any aperture. M. Bose has informed me, that he has seen, in winter, frogs quit the water for several days in succession, at a certain hour, and take breath for a short time on land. In the numerous experiments which I made in the win- ters of 1816 and 1817, on the asphyxia of frogs in a limited quantity of aerated water, they have never lived longer than two days and a half, even at the temperatures most likely to prolong their existence during their submersion. Spallanzani, in one instance, found a frog live eight days under water, varying in temperature from half a degree to a degree above zero, cent, and one to two degrees above 32° Fahr. ; he adds, that a more elevated temperature would inevitably occasion death in the course of a day. But during the season of the retirement of these animals, the temperature varies considerably. It may, perhaps, be supposed that frogs remain torpid during their hibernation. Torpor, however, does not ex- empt animals from the necessity of respiration ; but even admitting the contrary, it has been ascertained by the ob- servations of M. Bose and myself, that frogs, though less active in cold weather, are not torpid even at the tempera- ture of zero, cent, or 32° Fahr. Let us now proceed to investigate the influence of the air contained in the water. I am acquainted with one ex- periment only, which lias been made in reference to this subject. Spallanzani placed a frog in water, deprived of air, and another in a similar quantity of aerated water. The former was at the point of death in ten hours, but the latter not until twenty had elapsed. This insulated expe- 24 INFLUENCE OF THE riment, however, proves nothing, since the difference in the duration of life might have been occasioned by the different constitution of the individuals. The influence of the air contained in water, on the life of fishes, has been examined with great care by Spallan- zani, Sylvester, Humboldt, and Provencal; and their la- bours have brought to light some most interesting facts, in reference to the natural history of fishes, but the con- clusions .are applicable to this class of animals only, their gills being especially designed for receiving the influence of the air contained in water. To be amphibious in the strictest sense of the word, an animal ought to be capable of performing respiration both in the atmosphere and by means of the air contained in water; a double faculty, hitherto ascribed to no adult reptile, except the proteus and the siren. The axolotl, as Cuvier has shewn, has precisely the organization of the larva of the salamander. If these singular animals, which have been united to the family of batrachians, possess, like tadpoles, the faculty of breathing the air of the atmo- sphere, as well as that of water, they have also, like them, the double apparatus of lugs and gills. But, with these A # exceptions, the adult batrachians have only lungs, organs exclusively adapted to atmospheric respiration. There is nothing, therefore, which should lead us to conclude a priori, that they are capable of performing both func- tions. By the following experiments I have endeavoured to discover how far they are influenced by the air contained in water. AIR CONTAINED IN WATER. 25 Sect. 1. — On the Effects of limited quantities of Water. Several glasses, holding about five ounces and a half, and filled with water, deprived of air by boiling, and then cooled to the temperature of the atmosphere, were inverted over saucers containing about the same quantity of similar water. An equal number of similar glasses were filled with aerated water at the same temperature. At the same time a frog was introduced into each of these vessels, and the dura- tion of their respective lives carefully noticed. The result was in favour of the frogs placed in the aerated water, but it was not very decisive, showing only that the small quan- tity of water made use of did not contain so much air as to produce marked and uniform differences. We might safely, therefore, conclude, that though Humboldt and Provencal have shewn that boiling in open vessels is not sufficient entirely to deprive water of the air contained in it, and that the small quantity which remains is capable of exerting a marked influence upon fishes ; yet, that in this instance, no sensible influence could have been produced from this cause, in consequence of which I judged it un- necessary to have recourse to the method which they em- ployed for entirely banishing air from the water which they used. I next endeavoured to render the difference more strik- ing, by increasing the quantity of aerated water. On the 10th of November, the air being at ll°cent. or •52° Fahr., and the water at 13° cent, or 55° 4' Fahr. six glasses similar, to those used in the preceding experiments, 26 INFLUENCE OF THE were filled with aerated water, and inverted over the aper- ture perforated in the shelf of a pneumatic trough, contain- ing ninety-eight pints and a half of Seine water. A frog was placed in each glass. At the same time, the same number of frogs was put into similar glasses of boiled water of the same temperature, and inverted over saucers. The latter lived from three hours and forty minutes to five hours and thirty minutes; while those in the aerated water lived from six hours and forty-three minutes to ten hours and forty minutes. The result of these experiments, though satis- factorily shewing that aerated water has a decided in- fluence in prolonging the life of these animals, is yet far from proving that it is capable of doing so to an indefinite extent. Sect. 2. — Stagnant Water renewed at intervals. Although the want of organs specially constituted to act in the air contained in water, rendered it improbable that frogs could live in water like fishes, I thought I ought to leave nothing untried, in order to determine the in- fluence of aerated water upon their existence in that liquid. On the 4th of December, the temperature of the room being 6° cent, or 43° Fahr., a male frog of the species rana temporaria, was secured at the bottom of a glass vessel, holding seventeen pints and a half of Arcueil water, by means of a transverse wire grating. The next day the water was drawn off with a syphon till only a sufficient quantity was left to keep the animal covered, when the vessel was replenished with fresh water. This was repeated daily ; the frog not merely survived for eight days, the longest period for which Spallanzani had been able to keep A1U CONTAINED IN WATER. 27 a frog alive, in water at 1° or 0° 5., but continued to live to the 25th of February, that is, for more than two months and a half, during which period the temperature had varied from 0° cent, or 32° Fahr. to 11° cent, or 51° Fahr. An accidental neglect to renew the water occasioned the death of the animal. This experiment shows the remarkable fact, that frogs are really amphibious, since they can not only breathe the air of the atmosphere, but can also live exclusively by means of the air contained in water. Tadpoles, which are possessed of gills as well as lungs, can also live in water without coming to the surface; a fact which I proved by an experiment conducted in the same manner as that which has just been detailed. They cannot, however, live on land previous to the full development of their limbs. Sect. 3. — Action of aerated water upon the skin. Let us now inquire what is the organ through the me- dium of which the vivifying influence of the air contained in the water is exerted upon these animals. We shall first examine what foundation there may be for supposing that the water enters their lungs, which would, in this case, perform the functions of gills. Inspiration in frogs is per- formed by a kind of deglutition, and is accompanied by very evident movements of the throat, and of the soft parts under the lower jaw. When the animal is breathing in the atmosphere, their movements are repeated from forty to one hundred times in a minute. If it be plunged in water they immediately cease, and whatever be the length of time during which the submersion is continued, it is very seldom that any movement of deglutition can be observed. In the numerous experiments which I have made upon the 28 INFLUENCE OF THE asphyxia of’ frogs in aerated water, I have observed these movements in only a very few instances, and Spallanzani never perceived them. Humboldt observed that the fre- quency of the inspiration of a frog in a limited quantity of atmospheric air was diminished by the introduction of azote, and that the rarity of inspiration was proportioned to the quantity of azote introduced ; but neither azote, hydrogen, nor carbonic acid, has so strong a tendency to suspend inspiration as water. These experiments might be deemed sufficient to prove that it is not through the medium of the lungs that these animals receive the influence of the air contained in water. The importance of the fact, however, induced me to make a careful examination of the lungs of frogs, which had been previously immersed in water for a considerable time, and in no instance could I detect any water in them. This is likewise confirmed by the experience of Spallanzani. The air contained in water, therefore, does not act upon the lungs of the frogs which are immersed in it. Its action must consequently be referred to the skin, the only other organ in contact with the fluid. The question whether this action on the skin is analogous to that on the gills of fishes, and the investigation of the changes which these organs effect in the air, belong to a subsequent part of this work. It will be sufficient here to state, that during the time in which the life of the animal was maintained by aerated water, the arteries in the webs of the feet evidently contained florid blood. AIR CONTAINED IN WATER. ‘29 Sect. 4. — Running water. In the foregoing experiment, the water in which the frog was placed was at rest. Would life have been equally maintained in running water ? This query would certainly appear an idle one, had not Spallanzani been led to con- clude from his experiments, that the animals died sooner when submerged in running water, than in that which was at rest in vessels kept in his laboratory. On the 6th of November, a frog in a net to which a weight was attached, was sunk to the bottom of the Seine, at a part where there was about ten feet of water, and was retained in that situation. OnjLhe eleventh ? the net was drawn up, and the frog being found alive and well, was again similarly sunk. He was afterwards examined on the seventeenth, when he was found equally lively. At the very same season, frogs placed in vessels holding five ounces and a half of water which was left unchanged, .survived only a few hours. "'Water salamanders as well as frogs may have life sup- ported by the contact of aerated water with the skin. A crested salamander and a green salamander of Latreille, were confined by means of transverse septa of wire at the bottom of vessels, each containing four quarts of Arcueil water changed daily ; they lived about two months, and the latter died from neglect to change the water, on the same day that the frog mentioned above, suffered from the same cause. Both the above mentioned species of sala- mander bear submersion in water, at the temperature of zero, without becoming torpid. As conclusions deduced from experiments on frogs and water reptiles might not apply to the brown toad, which is altogether a land animal, an individual of this species was 30 INFLUENCE OF THE put into a neton the 6th of November, 1817, and sunk in the Seine. On the 17th he was still living; but he had made his escape when the net was again examined a month after. At the season of this experiment, brown toads as well as frogs survived only a few hours when confined under the surface of limited qualities of unchanged water. Sect. 5. — Limits of this Mode of Life. The faculty of living by means of air dissolved in water being shewn to belong to the three genera of batrachians, which were made the subject of the preceding experiments, it is important to know the conditions which influence this mode of life. Are these animals capable of it at all seasons? and what is the influence of temperature ? It might be supposed that when frogs quit their water retreats, they are no longer able to live under water, since at this season their constitution undergoes a remarkable change. They are in a state of the most lively excitation, and certain parts of their bodies become visibly altered : for example, the thumb of the male acquires a black colour, and a con- siderable increase of size. It is the period at which the species is propagated. In order to ascertain whether, at this time, frogs continued to retain the power of living- under water, one of these animals was tied by the leg, and secured at the bottom of a vessel, containing forty-nine pints of Arcueil water. He lived twenty days, during which time the water had been changed every twenty-four hours, and its temperature had never exceeded 10° cent, or 50° Fahr. Frogs, then, may live under water for a long- time after they are wont to quit it in the spring. Experi- ment further proved that they possess the same faculty in autumn. But is this mode of existence subjected to no limits ? Is AIR CONTAINED IN WATER. 31 it only necessary to attend to the quality of the aerated water ? Does temperature, which is productive of so great an influence when the water is limited in quantity, exercise none when the quantity is unlimited ? The frog before mentioned, immersed in aerated water, which was changed every twenty-four hours, died on the twentieth day, the temperature not being elevated above 10° cent, or 50° Fahr. This was in the spring of 1816. In October, 1817, a frog lived under water, in an earthen vessel, containing forty-nine pints, for eleven days. During this interval the temperature varied from 9° cent, or 48° Fahr. to 12° cent, or 53° 6' Fahr., and it was at the latter temperature when the animal died. These experiments induced me to attempt others, in order to determine whether so slight an elevation of temperature could affect the existence of these animals in aerated water, which was frequently changed. On the 12th of April l put a frog in a tub containing fifty -six litres (seven gallons and a half ) of Seine water, at 12° cent, or 53° 6' Fahr., and kept it at the bottom, by means of a packthread attached to a weight. I found it dead the next day. I repeated the same experiment for several successive days with the same result. The tempe- rature of the water had risen in this interval to 14° cent, or 57° Fahr. I repeated these experiments on toads and sala- manders, with the same result. In these experiments, the animals were kept in vessels containing water which was renewed every twenty-four hours. But would they experience the same fatal effect from this slight elevation of temperature, if they were kept under the water of ponds and rivers, so as not to be allowed to come to the surface to breathe? To solve this question I tried the following experiment : — On the 12th of April I put seven frogs and two toads into 32 INFLUENCE OF THE an osier basket, which was immersed in the Seine; the temperature of the river, at the surface, was 12° cent, or 53° 6' Fahr. On the 20th of the same month I drew them out, and of the seven frogs, four were dead, the two toads were still alive. The temperature continued at 12° cent, or 53° 6' Fahr. The running water was, therefore, much more favourable to the life of the frogs than the water in the vessels. Could this be attributed to a difference of tem- perature at the surface and bottom ? To decide this, I filled a bottle with water, and corked it, I then sunk it where I had placed the basket, at the depth of five feet and a half. J drew it out twenty-four hours afterwards, and found the temperature of the water which it contained exactly the same as that at the surface. The same experiment, re- peated several times in this month, gave the same result. Of the two" toads, one died on the 5th of May, the water at 16° cent, or 61° Fahr., the other on the 19th, the water at 17° cent, or 6-2° 6' Fahr. On the 13th of June one of the seven frogs was still living. During this interval of above two months, the temperature varied from 12° cent, or 53° 6' Fahr. to 22° cent, or 70° Fahr. In the first week more than half the frogs died, between 12° cent, or 53°. 6' Fahr. to 14° cent, or 57° Fahr. ; one only resisted the tem- perature of 22° cent, or 70° Fahr. Sect. 6. — Combined Action of Water, Air, and Tem- perature. In the life of frogs under water, there are then at least three conditions having a powerful influence on their exist- ence : — 1. the presence of air in the water; 2. the quan- tity, or the change of water ; and 3. its temperature. The relation of these three causes deserves particular notice. We have examined the first with great attention, CONTAINED IN WATER. 33 and have proved that the air in the water could maintain the life of batrachians immersed in that liquid. But how does the temperature act in this case ? Since the air is the principal condition for prolonging their existence, one might suppose that the elevation of temperature acts by diminish- ing the quantity of air. But Humboldt and Provencal, in their work on the Respiration of Fishes, have proved that the Seine water contained the same quantity of air, in the various analyses which they made of it, from the month of September to that of February. Now, its temperature varies in that interval, at least from 0° cent, or 32° Fahr. to 16° or 17° cent, or 61° or 62° Fahr., which last is higher than that at which the greater number of the frogs above mentioned died. Since it is the temperature, and not the quantity of air which varies, it is to the former that we must attribute the variation in the effects. The experiments related in the last chapter perfectly accord with those which have been just mentioned. By the former it was shewn, that when frogs are immersed in five ounces and a half of aerated water, the dura- tion of their life is inversely proportional to the eleva- tion of temperature from 0° to 42° cent, or 32° to 107°. 6 Fahr., at which point they die, almost suddenly ; and that through the whole range of this scale a small number of degrees is sufficient to produce a great difference in the duration of their life. It has now been shewn, that the air contained in the water has a contrary effect to the ele- vation of temperature. When they are immersed in about two gallons, changed every day, a temperature between 0° cent, or 32° Fahr., and 10° cent, or 50° Fahr. is not sufficiently high to counterbalance the vivifying effect of the air ; but when it rises to 10° or 12° cent, or 50° to 53° 6' Fahr., the former overcomes the latter, and the animals n 34 INFLUENCE OF AIR CONTAINED IN WATER. die, unless the quantity of air is increased. Now the quan- tity of air may be increased by furnishing, in a given time, a greater quantity of aerated water ; this was the cause of some of the frogs in running water resisting the tem- perature which would be fatal to them in the vessels with water changed only once in twenty-four hours. But the influence of the change of the water is very inconsiderable beyond certain limits ; for, as is well known, water contains but a small part of its bulk of air; and according to Hum- boldt, that of the Seine only -g^. These animals, then, have but one means of resisting the effects of temperature, and that is, by coming to the surface to breathe the air of the atmosphere, without which most frogs would die, in a tem- perature as low as 12° or 14° cent. 53°6. Fahr. or 57° Fahr. The small quantity of air contained in water under 10° cent, or 50° Fahr., which is sufficient to support the life of batrachians in that liquid, produces an extraordinary effect upon their mode of existence. The extreme activity of frogs is well known, and there is a striking contrast in this respect between them and toads ; but keeping them under aerated water destroys this characteristic. It does even more ; they become so sluggish in their movements as to resemble tortoises. The slightest noise, which in their state of liberty excites a panic among them, at that time makes no impression. Fight, which, on other occa- sions calls them so easily to the surface, no longer induces them to rise, when the temperature is sufficiently low. They have, however, the faculties of sense and motion ; but in air of the same 4emperature they are extremely lively. CHAPTER IV. ON THE VIVIFYING ACTION OF THE ATMOSPHERE. Sect. 1. — Influence of Cutaneous Respiration. In order to appreciate the influence of the atmosphere on the skin, it is necessary to suspend the action of the lungs, by intercepting the passage of the air to those organs. As the mouth of these animals, when they breathe, is necessarily shut, in order to introduce the air into the lungs by an act of deglutition, it has been thought that this mode of respiration could be suspended by keeping the mouth open. In order to determine, whether I could avail myself of this circumstance for the object which I had in view, I placed a piece of stick in the mouth of a frog to serve as a gag : it projected a little on each side ; and was fastened at its extremities by a thread which passed under the axillae. I tried this experiment on six frogs, which were placed under a glass, in a saucer; the edges of the glass were slightly raised to allow change of air, and a little water was also introduced into the saucer to supply the animal with the necessary degree of moisture. The tem- perature was then 24° cent, or 75° Fahr. In this state, five died the following day ; the sixth lived seven days. The state of constraint occasioned by the stick which kept the mouth open, and the slight compression of the limb by the thread could certainly not explain this rapidly fatal result. Respiration was evidently checked, but it was n 2 36 ON THE VIVIFYING ACTION not entirely suspended. The movements of deglutition, al- though less frequent, still took place; the flanks at inter- vals contracted. These indications of respiration were suffi- cient to destroy my confidence in the experiment for the accuracy of which, a perfect suspension of the communica- tion between the lungs and the atmosphere was absolutely necessary. A ligature passed behind the head can be sufficiently tightened to completely intercept the passage of the air. I in this manner applied a ligature to six frogs, and took particular care to use the most rigid compression, and tied the ligature several times, so as altogether to exclude the atmospheric air. The temperature was 12° cent, or 53°.6 Fahr. in the room, and 6° cent, or 43° Fahr. out of doors. I placed the animals on wet sand. They lived a considerable time, one of them for twenty days. These animals would have died in the space of from one to three days, if I had placed them in five ounces and a half of water, as I proved at the same season in this and the preceding years. The influence of the atmosphere on the skin must then have been considerable, in order to obviate the effects of stran- gulation for so long a time. It may be here mentioned that the more rapid termination of life in the former experiment in which respiration was only imperfectly suspended, than in the present, is fully ex- plained by the higher temperature to which they were ex- posed. The important influence of this circumstance has already been shown. The violent operation, however, inflicted in this last ex- periment must have tended to shorten life ; and conse- quently to set limits to the beneficial influence of the at- mosphere upon their skin. I, therefore, determined upon other more effective means of accomplishing my purpose; this was no less than the absolute removal of the lungs OF THE ATMOSPHERE. 37 which may be done by a very slight incision, and with the loss of very little blood. I performed this extirpation in the middle of December, 1818, on three frogs of mode- rate size. They did not appear to suffer much, and pre- sented, after the operation, the same activity as those which had not been touched. I placed them upon moist sand. The temperature of the room was 7° cent, or 45° Fabr., and it rose to 12° cent, or 53°. 6' Falir. on the 17th Jan. 1819. Two died at this time, having lived thirty- three days, and the third on the 24th, having lived forty. If we now call to mind the long duration of the life of these animals under aerated water which was continually renewed, and which acts only on the skin, we shall be in- clined to query, since air dissolved in water serves so well to maintain their life without the aid of their lungs, ought not they to find still greater resources in the atmosphere itself, if we only furnish them with sufficient moisture ? To answer this in the affirmative would be a mere as- sumption. The comparative influence of the atmosphere and of aerated water is so little understood, that we can- not say why fishes live better in aerated water than in air. Yet the knowledge of this would be of considerable physiological interest. I wished to determine whether the operation itself, in the preceding experiment, did not tend to shorten life. With this view, on the 4th March 1819, I cut out the lungs of six frogs, and closed the incision by a suture. They were placed in a basket with six other frogs, which had not been mutilated, and immersed in the water of the Seine, which was then at 4° cent, or 39°.G, but in the space of a week, it progressively rose to 9° cent, or 48° Fahr. The greater number of the frogs without lungs died before the others ; but at the end of the experiment, one of the frogs deprived of lungs was found alive, with the only sur- . 38 ON T1IE VJVIFYING ACTION vivor of those which possessed them. The season being unfavourable to the life of these animals under water, ter- minated the experiment on the 15th of March. These frogs were in every respect similarly circum- stanced, with the single exception of the operation ; I therefore, felt myself warranted to conclude, from the re- sult of this experiment, that since the greater part of the . frogs which had undergone the operation died before those which had not, the operation must have also contributed to terminate the lives of those which were placed in the at- mosphere, in the preceding experiment. Hence it may not have shewn the utmost duration of life in the batrachians, maintained by the influence of the air exerted on the skin alone, but for the present we admit the limit which it has given us, and proceed to further considerations respecting the action of the air. Sect. 2. — Influence of Pulmonary Respiration. We have now to resolve the converse of the question con- sidered in the last section, viz. would these animals live if permitted to breathe by the lungs alone, the atmosphere being altogether excluded from contact with the skin ? A frog was placed in a glass containing five ounces and a half of water. A wooden cover at the surface of the water prevented him from coming out, and an opening which was made in it gave him liberty to breathe the atmospheric air. The liquid, which he dirtied in a few hours, was changed every day. The temperature was 12° cent, or 53° 6' Fahr. and it was as high as 24° cent, or 75° Fahr. at the latter period of the experiment. This frog lived three months and a half, with no other nourish- ment than the small quantity of water in which it was immersed. In this situation, the animal has no other OF THE ATMOSPHERE. 39 direct communication with the atmosphere than by the lungs. Through the medium of the water, he can, it is true, receive the influence of the small quantity of air con- tained in this liquid ; but we have seen in former experi- ments that where these animals were immersed in the same quantity of aerated water without being allowed to breathe at the surface, this quantity of air did not sensibly prolong their existence. Still, however, there is some room to doubt, whether this small quantity, which under other circumstances, might be safely overlooked, may not be useful in this instance and contribute to aid the action of the lungs. The application of a coating to the surface of the body* naturally suggests itself as a ready method of cutting off the influence of the air on the skin ; but the moisture and continued secretion of the skin, renders it nearly or quite impracticable. The removal of the skin does not get rid of the difficulty, because none of the batrachians long sur- vive this severe operation, which is rather surprising, when we consider how much mutilation they are capable of en- during. Oil would answer the purpose of excluding the air if it were free from objection in other respects. If it be sub- stituted for water in the glasses with floating covers, as in the preceding experiments, the frogs die in a short space of time. The experiment was tried on ten frogs, six of them lived seven or eight hours, the other four died the following day. The temperature was at 21° cent, or 70° Fahr. as in the experiments with water. It was also found that this substance has a deleterious action on the skin. Some frogs were placed in glasses containing five ounces and a half of oil, and others in the same quantity of water, and not allowed to breathe. Those in the oil made extraordinary movements, and even many attempts 40 ON THE VIVIFYING ACTION at vomiting ; however they lived equally long in both liquids. If, in these two cases, instead of suppressing re- spiration it be left free, the difference becomes considerable. Water, which contains or absorbs a little air, has a ten- dency the reverse of that of the oil, and pulmonary respira- tion with this feeble assistance in the one case, and slight obstacle in the other, is found sufficient or insufficient to support life. If then we could confine these animals, in their relation to the atmosphere, to pulmonary respira- tion alone, they would be as it were, on the limits of life and death. This consideration induced me to inquire if there were not other animals of the same family, to the support of whose life pulmonary respiration would not be suffici- ent, notwithstanding the influence of the small quantity of air contained in the water. Tree-frogs are animals of this family ; they differ from common frogs and toads in having a little cushion at the end of their toes, which en- ables them to climb perpendicularly on trees, and even on smooth and flat walls. The species submitted to the ex- periment is that which is the most common in France. I made use of the same apparatus as in the preceding ex- periment, with the addition of a small but loose net, fixed over the opening in the floating cover. The frog put- ting its head under the net, breathed in the atmosphere without being able to escape from the water which sur- rounded him. Eight of these animals in succession were submitted to this experiment in the space of five days; the temperature varied from 17° cent, or 62° Fahr. to 20° cent.- or/680 Fahr. ; there was in each glass only about five ounces and a half of water, which was changed several times a day. They did not live, however, beyond three or four days. Hence it is evident that pulmonary respiration is not 41 or THE ATMOSPHERE. «* * sufficient to support the life of tree-frogs without being accompanied by the atmospheric influence upon the skin. The case is the same with the rana obstetricans, on which the experiment was also tried, and we may conclude that the observation applies to all the batrachians. I put seventeen frogs into a vessel containing seven pints of Seine water permitting them to breathe at the surface ; the temperature was the same as in the preceding experi- ments. Four days after, seven of them died. I repeated this experiment on twenty frogs placed in the same cir- cumstances, adopting the precaution of changing the water every day ; nine died in the space of three days ; while others, which were placed in glasses with five ounces and a half of water, all lived. The difference depended on the depth of the water. In the glasses, being supported by the bottom, they breathe ad libitum, but in vessels contain- ing seven pints, and having a foot in depth, although they may support themselves for some little time at the surface, yet, after having expelled a certain quantity of air from the lungs, their specific gravity being increased, sends them to the bottom, and they rise and sink alternately, till these intermissions of respiration, uncompensated by the action of well aerated water on the skin, puts an end to their existence. We may therefore conclude, that frogs would die in deep waters, if they could not occasionally come to the bank, or find support from time to time on other J f rj CHAPTER V. THE INFLUENCE OF THE ATMOSPHERE ON PERSPIRATION. The first very perceptible change which animals ex- perience when placed in the atmosphere, consists in a diminution of weight, from a vapour which is exhaled from, or a liquid which transudes through their skin, or escapes from the pulmonary surface, and is known under the name of sensible and insensible perspiration. It is this loss of weight that wre are now to appreciate, as well as its variations, according to certain circumstances. Sect. 1. — Loss by Perspiration in equal and successive Periods. We shall first inquire, What is the relative quantity of perspiration in equal and successive periods ? Is it vari- able or uniform? Or, if variable, does it increase or di- minish according to any fixed law ? It was very necessary to make this preliminary enquiry, in order to ascertain the rate of the loss by perspiration, influenced only by changes depending on the animal itself, and consequently avoid confounding these variations with those which depend on external agents. With a view to determine the relation of the losses of weight sustained in equal times, 1 weighed a frog from INFLUENCE OF T1IE ATMOSIMIEltE, &C. 43 hour to hour in air, which appeared calm, the temperature was carefully noted, and remained sensibly the same during the course of the experiment. In comparing the successive losses of weight, a remarkable fluctuation was observed. The variations were very considerable, in some cases amounting to double or triple quantities in equal times ; they were usually alternate, without, however, pre- senting equality in their increments and decrements. Repeated experiments proved that this phenomenon was not confined to an individual case, but appeared even in the different genera of the family which were examined. This irregularity not depending on any error in the mode of experimenting, supposes the action of various influential causes, which do not remain constant in the course of the experiment. This induced me to give a longer period to the duration of the experiments, and in weighing the animals at intervals of two hours, I found a marked ten- dency to diminution in the quantities lost in equal times. On comparing them afterwards at intervals of three hours, the tendency becomes indubitable ; three hours in most cases proved sufficient to render the diminution constant; but in a few instances, intervals of nine hours were neces- sary to arrive at such a result. This difference, doubtless, depends on a change in the state of the animal. Now the most remarkable change in its state is the progressive diminution of the mass of its fluids ; and in proportion as this is reduced by previous perspiration, ought the subsequent losses from this cause to be less considerable. In observing the degree of rapi- dity with which the loss by perspiration takes place, it deserves particular notice, that in the intervals of time employed in the experiments just related, the loss in the first period was often great in proportion to that in the subsequent periods, and that in these succeeding intervals 44 INFLUENCE OF THE ATMOSPHERE its rapidity progressively lessened. Taking the animal at the point of saturation at the commencement of the experi- ment, it may be said that it loses by perspiration less and less in proportion as it removes from this point. Hence it is obvious, that for a number of experiments to agree in these results, attention must be paid to the condition of the animals in respect of saturation. If we compare the weight of the animals, and the perspiration, without refer- ence to their state as to saturation, we shall obtain not only very different, but even contradictory results. We shall have to return to this subject in the sequel. Sect. 2. — Effect of Rest and of Motion in the Air. The fluctuations in the amount of loss by perspiration as observed from hour to hour, did not arise from any cir- cumstance dependent on the life of the animal, nor even on its peculiar organization, since they are found to take place in pieces of charcoal soaked in water, and exposed to the influence of spontaneous evaporation, under the same cir- cumstances, with respect to the atmosphere, as the frogs. We must, therefore, have recourse to external agents, to account for the variation. It is well known that the at- mosphere, even when it appears to us perfectly calm, is really sufficiently agitated to exercise a perceptible in- fluence on evaporation. We are, then, naturally led to ex- amine into the extent of that influence on the perspiration of animals. For this purpose I hung some frogs in the draft of an open window, and placed an equal number in the same room at another window which was shut. The animals exposed to the open window lost at least the double, and, according to the intensity of the wind, the triple, and quadruple of what was lost by those which were placed in the interior of the room. It was also found, that on sus- ON PERSPIRATION. 45 pending these animals in vessels, with a wide mouth, to allow the perspiration to dissipate itself freely in the at- mosphere, the hourly fluctuations either ceased altogether, or were very inconsiderable. Sect. 3. — Respiration in Air of extreme Humidity. We now come to examine the results arising from the hygrometric state of the atmosphere ; and in the first place to consider the question, whether perspiration can take place in air saturated with moisture ? To arrive at the solution of this question, it was of course necessary to remove, as much as possible, the influ- ence of the motion of the air, and all other disturbing- causes. With this view the animal was suspended in a glass vessel, inverted over water; which vessel had been ascertained, by experiment, to be sufficiently large to obvi- ate any effect from the alteration of the air by respiration on the duration of its life. The experiments were often repeated, the intervals of weighing were varied considerably, and a diminution of weight was uniformly observed. It is true, that the che- mical changes in the air, occasioned by respiration, would occasion a diminution of weight, in case of this loss not being repaired ; but particular experiments on the extent of the respiration of these animals, proved that the slight de- duction which this cause requires, leaves a greater loss, which can only be attributed to perspiration. It is true, that these animals have a temperature of their own, though it differs in general, but very little indeed, from that of the bodies which surround them ; and this may have a slight influence on perspiration in damp air. But it is the fact rather than its cause which I am here seeking, and we may conclude, that air saturated with moisture does 46 INFLUENCE OF THE ATMOSPHERE not prevent perspiration, though it reduces it to its mini- mum, relatively to all the other causes which we have hitherto examined. Sect. 4. — Perspiration in dry Air. The effects of air as dry as could be procured were after- wards compared with those of air saturated with moisture. Several causes prevented the air of the vessel from attain- ing the point of extreme dryness ; in the first place, the necessity of commencing the experiment on perspiration at the same time with the drying of the air in a close vessel, in order to obviate the passing of the animal through the mercury into a vessel containing air previously dried ; which circumstance might occasion such an increase of weight as to destroy the effect of the experiments ; add to this, the perspiration of the animal, which, in air perfectly dry, changes the hygrometric state of this fluid. An hygrometer placed in the vessel with the animal, and a good quantity of quick lime, marked the degree of dry- ness of the air. On the whole, the effects of calm air pro- gressively dried during the course of the experiment, was very remarkable. In the same space of time, all other cir- cumstances being the same, the perspiration in dry air was from five to ten times greater than in extreme humidity, according to the degree of dryness and the duration of the experiment. If we compare the influence of the hygrome- tric state of the air with that resulting from its motion, we shall find, that the agitation of the air, provided it is not at the point of extreme moisture, may increase the perspir- ation, as considerably as a drier air in a state of rest. ON PERSPIRATION. 47 Sect. 5. — Effects of Temperature. In order to appreciate the effects of mere temperature, it was of course necessary to reduce to a minimum the influ- ence of the two preceding causes. Hence, the experiments made with a view to this object, were performed in a still atmosphere saturated with moisture. I compared the influence of temperature between 0° and 40° cent, or 32° and 104° Fabr., which are the limits com- patible with life, and nearly those of the atmosphere itself. The general tendency of a rise of temperature was to equalise the losses in equal times, or in other words to di- minish the decrements in the quantities lost. As to the relative influence of different degrees of tem- perature upon the quantity of perspiration itself, it is much less than would have been anticipated. During five hours the quantity perspired at 20° cent, or 68° Fahr., was scarcely twice what it was at 0° cent, or 32° Fahr. ; that at 40° cent, or 104° Fahr. is seven times greater than that at 0° cent, or 32° Fahr. ; which resembles the effects obtained from a dry and still, compared with a humid atmosphere. CHAPTER VI. ABSORPTION AND PERSPIRATION. The present question is, how is the weight of the body- influenced by the contact of water with its external sur- face ? To render this as sensible as possible in the case of frogs, they were first placed in air, until they had under- gone evident loss by perspiration, with the expectation, that if they absorbed water this absorption would be more strongly marked, according as they were removed from the point of saturation, which was found to be the fact. These animals, having previously lost a considerable portion of their weight by perspiration, and being afterwards put in water of the same temperature as the air, increased in weight, while the absorption of the fluid was rendered evi- dent, by the sensible diminution of its quantity in the vessel in which the animals were placed. But to what extent does this absorption take place ? what is its rate of progress and what its limit? what ensues when this limit is reached, if the animal be still kept in contact with the water, a condition to which all these animals may be exposed, and of which it is important to know the influence? It results from the experiments which I made, that if perspiration in the atmosphere be not car- ried too far, water will be absorbed, until the loss incurred thereby shall be repaired. It does not, however, always cease at that point ; it may, indeed, go far beyond it, be- ABSORPTION AND PRESPIRATION. 49 fore it arrives at the point of saturation. The quantities absorbed in equal times, like those lost by perspiration in the atmosphere, diminish progressively, provided the tem- perature is not very high. This diminution is likewise more rapid, according as the animals approach the point of saturation. It appears, also, that the time required to repair by absorption the loss occasioned by perspiration, is shorter than the time during which the same loss is incurred. A question still remains. When the body has arrived at the point of saturation, does its weight remain stationary, or undergo any further variation ? In seeking for the so- lution of this question, I found that after the body has arrived at its point of saturation, there are alternate stages of diminution and of increase, but the increments do not pass beyond the point of saturation, at which the diminu- tion commences. This circumstance is explained by the fact, that in addition to the aqueous fluid exhaled from the skin, a portion of solid matter is also excreted. The loss occasioned by these excretions are at first compensated by the absorption of the water ; but after some time a real and progressive diminution is observed to take place. It is evident, from what has already been stated, that when one of these animals is placed in water, the weight of his body will increase or diminish according as either of the opposing functions of absorption and transudation predominates over the other. It is interesting to determine what is the influence of temperature upon the relations of these functions. It appeared from experiments, that at 0°. cent. or. 32° Fahrenheit, the absorption predominates over the loss of weight ; while at 30° cent, or 86° Fahr. the losses are greater than the increase by absorption. It was also observed that elevation of temperature in water had a marked tendency to augment the animal excretions ; E 50 ABSORPTION AND PERSPIRATION. from which we seem authorized to conclude that an ana- logous effect would be produced upon perspiration in the air. On the other hand, the motion of the air, exercising little, if any chemical agency, would have less influence than temperature upon the excretion of animal materials, and consequently contribute more to the production of the aqueous portion of perspirable matter. The effects of dryness and moisture would also seem to have less influence than temperature on the loss of the animal matters. PART IT. FISHES AND REPTILES. CHAPTER I. TADPOLES. In treating of the family of the Batrachians, the first stage of their lives, during which they have a peculiar form and distinct functions, has been slightly passed over. And since their mode of life at this period, in many re- spects, resembles that of fishes, I have reserved the exa- mination of it until I should come to treat of this class of cold-blooded animals. The most important peculiarity of tadpoles is not that which depends on their external con- formation, the absence of limbs, and the presence of a tail ; but that which results from their possessing two kinds of respiratory organs, lungs and gills. Tadpoles unite, in regard to respiration, the functions of reptiles with those of fishes; their use of them varies not only according to their deve- lopment, but also according to their physical conditions, under the influence of which we are now about to consider them. The tadpole has, in common with the adult animal, the power of supporting life through the medium of the skin, by means of the air contained in water. It has e 2 52 TADPOLES. already been shewn that the limits of temperature in which the adult animals are able to exist, are 32° and 50° F. or 0°. and 10° cent., and that beyond the higher limit, the greater part were obliged to have recourse to atmospheric respiration ; but tadpoles having an additional organ, by which they are enabled to avail themselves, in a higher degree, of the vivifying influence of the air contained in water, ought, one would imagine, to support, under water, a much greater elevation of temperature, without having recourse to the external air. That this is actually the case, is shewnby experiments, in which they were kept a long time in vessels with the water occasionally changed, and in running water, at the temperature of 25° cent, or 77° Fahr. The most important point in our enquiries respecting tad- poles, is the influence which physical agents may exert on their transformation. The action of these agents on the form of animals, is one of the most curious questions in physiology. One of the conditions which is best known, is the necessity of aliment for the development of forms. This is the reason that when we wish to hasten the metamorphosis of tadpoles, we take care to mix with the water in which they are kept a small quantity of nutritious substances, and to change the liquid, that the decomposition of these materials may not prove fatal to them. On the other hand, their transform- ation is retarded, when the supply of nourishment is scanty. Temperature is another condition, the influence of which is generally known. We are aware that tadpoles change in warm seasons : but it is a fact not so generally known, that in our climate a great many are not changed the same year. This happens to those which are produced late in the summer. The subsequent temperature not being sufficiently high, they pass the winter in the state of larva, and do not quit it until the return of warm weather. These TADPOLES. 53 are the only influences which have been hitherto ascer- tained with regard to the developement of these animals. There is another which I have endeavoured to determine, and to which I have been led by my experiments on the adults: it is, the effect which atmospheric, compared with aquatic respiration, exercises on the form of these animals in their earliest age. The difference which these two modes of respiration occasioned. in the activity of the adult animal, induced me to conceive, that limiting the tadpole to aquatic respiration would tend to continue its original form. With this view I procured a tin box, divided into twelve compartments, each of which was numbered and pierced with holes, so that the water might readily pass through the box. A tadpole, (which had been previously weighed) was put into each compartment, and the box was then placed in the river Seine, some feet below the surface. A larger nurnbei was at the same time put into an earthen vessel,/- taining about four gallons of Seine water, which was changed every day. These tadpoles were at liberty to rise to the surface and respire air, and they soon went through their metamorphosis. Of the twelve placed in the box under water ten preserved their form, without any progress in their transformation, although some had doubled, and others trebled their weight. It should be observed, that at the timer when the experiment was begun, the tadpoles had acquired the size at which the change is about to take place. Two only were transformed, and this very much later than those which, in the earthen vessel, had the liberty of respiration in air. The want of atmospheric respiration appeared here to have a marked influence, but we had not the means of accurately informing ourselves of one very influential cir- cumstance, that is, the supply of nourishment. In the river the water is renewed incessantly ; and frequently ve- 54 TADPOLES. getable and animal substances must necessarily be more abundant in it, than in the water of a vessel which is changed only every twenty-four hours. Notwithstanding this difference in favour of the tadpoles deprived of atmo- spheric respiration, it had influence upon two only; the other ten underwent no change. It would appear to result from these facts, that the young animals, with double respiration, would retain their original form under water, if their nutriment were not too abundant, and the temperature were not too high ; and that the difference of atmospheric respiration alone, joined to these circumstances, would determine the trans- formation. This conclusion, at first, appeared to me to be strictly correct ; but there was an element which I had not taken into account ; namely, the absence of light : for the tad- poles, which were in the tin box, were deprived of light as well as of atmospheric air. For the present, we will rest satisfied with the conclusion that, under these two priva- tions, tadpoles are retarded in their transformation ; but we shall return to the subject in another part of this work, in which the influence of light is considered. There are three remarkable animals, which have a strong affinity to tadpoles, and have been considered as belonging to the family of batrachians, these are the axolotl, the siren, and the proteus. We are indebted to Cuvier for some valuable investigations respecting the structure of these animals. According to him, the axolotl has the anatomical characters of the larva of the salamander ; and the siren and proteus are species of different genera from each other. In the proteus, the lungs, he says, are little more than ru- dimentary. These animals are all furnished with a double respiratory apparatus, lungs and gills ; but the pulmonary organ of the proteus is, as we have said, in an imperfect TADPOLES. 55 state. It is possible, that the result of the preceding re- searches might be applicable to these animals. It would be desirable to ascertain the effect of the united influence of increased nourishment, elevation of temperature, aerial respiration, and the presence of light, on the axolotl, and the siren ; and to examine whether the exercise of the lungs, by a frequent use of atmospheric respiration at the surface of the water, would not tend to suppress the bran- chiae, as happens to the young batrachians, when tempera- ture and nutrition are favorable. It may be remarked, that the proteus has been always found placed in those conditions as to temperature, darkness, and respiration, in which the branchiae remain. In fact, it inhabits the sub- terranean waters of the lakes of Carniola, in which it can- not perform atmospheric respiration, and where the tem- perature is, perhaps, sufficiently low to preserve the bran- chiae. The last point of view under which it remains to examine tadpoles, relates to their existence in air : but this subject being intimately connected with the life of fishes in the air, will be examined when I treat of that class of animals. 06 CHAPTER II. FISHES. The labours of Spallanzani, of Sylvestre, and of Humboldt and Provencal, have made us more accurately acquainted with the physiology of fishes than with that of any other cold-blooded animals. I shall not attempt to detail the result of their researches, most of which are foreign to my present subject. I have only to consider fishes in relation to those points which bear on the phenomena already pre- sented to us by the batrachian reptiles. I shall first examine the influence of temperature. Sect. 1. — Influence of Temperature on the Life of Fishes, in Water deprived of Air. To arrive at a correct result, we must ficrst reduce the cir- cumstances of the experiment to their greatest simplicity. For this reason I shall commence by enquiring into the effect of temperature on fishes in water deprived of air. Comparative experiments were made on individuals of the same species, and with as close a resemblance as possible, at temperatures varying from 0° cent, or 32° F. to 40° cent, or 104° Fahr. The result was, that at the higher limit death was speedy as with the batrachians, and the duration of FISHES. 57 life progressively augmented in proportion as the tempera- ture was diminished to the lower limit. It is here seen that the effect of temperature (excluding all other influ- ences) is altogether analogous to what has been observed in the batrachians ; that the limits of the shortest and longest duration of life in the batrachians and fishes placed in water deprived of air, are alike in both ; and that in the same range of temperature, from 0° cent, or 32° F. to 40° cent, or 104°Fahi\, the duration of their life goes on augment- ing or diminishing, according as the temperature falls or rises between these extremes. In regard to the differences which fishes of the same species present at the same degrees of temperature between these limits, size has a marked influence, the smallest as well as the youngest are those which are the least capable of bearing an elevation of temperature. However different may be the duration of the life of small fishes at low tem- peratures, at 40° cent, or 104 Fahr. it is almost uniform in all. They scarcely ever live more than two minutes ; but the larger fishes are able to survive several minutes longer. % Sect. 2. — Influence of the Temperature of Aerated Water, in limited Quantities, in close Vessels. On varying, in a series of experiments, the temperature and quantities of aerated water, it appears, 1st, That the duration of life goes on increasing with an increase of the quantity of aerated water, the tempera- ture remaining the same. 2. That the same result takes place when, the quantity of water remaining the same, we lower the temperature. 3. That the duration of life remains the same, when , within certain limits, we increase or diminish, at the same time, both the temperature, and the quantity of aerated water. 58 I'ISHES. Sect. 3. — Influence of Temperature, and limited Quantities of Aerated Water, in contact with the Atmosphere. Sylvestre has ascertained that a limited quantity of aerated water, in which a fish is placed, absorbs the air in contact with its surface. It evidently follows from this fact, that the life of the animal, in a limited quantity of water, will, cccteris paribus, be the longer, the more fully the absorption of air by the water compensates for that which the animal consumes in the water. Add to this, that the fish, when free, is able to derive directly from the atmo- sphere fresh supplies of air, according to its wants. Let us now see the influence of temperature under these circumstances. Take for example a bleak (cyprinus albur- nus). If we put it into a vessel with a large mouth, con- taining five ounces and a half of aerated water at 20° cent, or 68° F. in summer, it dies within a few hours : but when the temperature is lowered to 10° or 12° cent., or 50° or 53° F., and is kept at that degree, the animal lives until its secretions are so abundant as to corrupt the water. If, to remedy this inconvenience, we merely renew the water every twenty-four hours, the animal lives in it almost inde- finitely. This is exactly what we have seen to take place with the batrachians. Between 0° cent, or 32 Fahr. and 10° or 12° cent, or 50" or 53° Fahr. they live an indefinite time in aerated water, provided it be renewed sufficiently often ; but they die for the most part as soon as the temperature rises above this limit. Let us now examine the general result of these facts, not- withstanding the different conditions in which the animals are placed. The more the temperature is raised beyond certain limits, the greater is the degree of the influence of the air required for the support of life. This influence, FISHES. 59 without reference to other causes, will be great in propor- tion to the quantity of this fluid. Here, however, there are limits depending on the organization of the animal. Sect. 4. — Respiration in the Air. As yet we have only considered the respiration of fishes in water: their respiration in air deserves particular atten- tion. When a fish, in a given quantity of aerated water, has reduced the proportion of air until its respiration has become difficult, it rises to the surface and takes in air from the atmosphere. In order to show that atmospheric re- spiration has an influence on the life of fishes, Sylvestre placed a diaphragm at the surface of the water, to prevent the fishes from taking air directly from the atmosphere. He observed that in this case fishes die sooner than when they had access to the atmosphere, which proves that they can breathe air, and that this mode of respiration tends to prolong their life in water. Sect. 5. — Life of Fishes in the Air. We now proceed to the examination of a new circum- stance in respect to the life of these animals; viz. their existence in the atmosphere. This, as regards the influence of physical agents, is the most obscure point in the life of fishes. It is also a condition in which they present phe- nomena which do not appear in any way to accord with those presented by animals breathing air. When we take a fish out of the water, we see it, according to its species, die in a few minutes, or in a few hours. It is not then surprising that fishes should have been considered inca- pable of living by atmospheric respiration, and that this should have been attributed to the greater density of the air existing as atmosphere, compared with that contained in solution in water. Air does, undoubtedly, act differently 60 FISHES. according to its density, on living beings. It is also true that the greater part of vertebrated animals quickly perish from the opposite transition, by passing from the atmosphere into aerated water ; but in this case it is evident, that they die because they have not sufficient air; and we might suppose that fishes die in the atmosphere because they have too much. Having already stated the proofs by which Sylvestre has shewn the influence which the respi- ration of air exerts in prolonging the life of fishes in water, I may proceed with these animals as with others in the examination of the changes which they undergo by ex- posure to the atmosphere. A chub, (cyprinus jeses) and a gudgeon, (cyprinus gobio) were first wiped, then weighed, and exposed to the air. Their gills continued to beat until death. The sur- face of their bodies gradually dried, and at the time of their death they were stiff, and dry. On weighing them again, I found that they had lost by perspiration, the one, one-fifteenth, and the other, one-fourteenth of its weight. This result is nearly the mean of experiments made on other species. Having in our researches on the batrachians seen the in- fluence of loss by perspiration from exposure to air, we shall now apply it to the case of fishes. To simplify the examination of this subject, let us here consider, as we have done in our researches on the batrachians, the losses by perspiration, as solely at the expence of the water con- tained in the animal. Capacity of saturation with water implies the quantity of this liquid which an animal is able to contain, between the point of greatest repletion, or satu- ration, and that of the greatest inanition, compared with the weight of its body. The means of carrying the body to the point of saturation when it is capable of absorbing- water, is to place it in that fluid, until the increase in FISHES. 61 weight has arrived at its maximum. This is exactly the condition in which fishes are found in their natural state, and on removing them from the water in which they live, we may regard them as saturated with this liquid, pro- vided they are in a state to absorb it. Now we shall take for the measure of their capacity of saturation with water, as we have hitherto done in regard to the batrachians, the loss which they experience by perspiration before death ; and we see it is sufficient to ensure the death of fishes, that they lose the fourteenth or fifteenth part of their weight. If this loss appear too inconsiderable for us to ascribe the death of these animals to it, let us compare this result with those which we obtained in our researches on the batrachians. They were not given in the preceding- chapter, that they might be reserved for this occasion. It has been shewn that the point of saturation with water, in the case of batrachians, depends on the state of their nu- trition, and that it may vary within very considerable limits. Now the losses which they undergo by perspiration vary in the same manner. In conditions favourable to nu- trition, their capacity of saturation may equal the third of their weight ; but, in unfavourable conditions, it is so small, that the least appreciable loss is sufficient to cause death. On applying these results to fishes, whose capacity for water is small compared to that of batrachians, we shall see that the loss which they experience by evaporation is enough to cause their death in air. But the phenomena relative to this subject are not always so simple; they may be very complicated : one might be led to believe that at- mospheric respiration would keep fishes alive if we could devise means for obviating their loss of weight by evapo- ration. With this view, a fish which had been wiped and then weighed, was suspended in a limited quantity of aerated water, so that it had its head and gills above the 62 FISH KS. surface ; it died in nine hours and twenty-one minutes. On then weighing it again, it appears that it had not sen- sibly diminished in weight, but on the contrary had slightly increased. This result would appear to be inde- pendent of the cause we have before assigned for the death of fishes, where the whole body is exposed to the action of the atmosphere. But before enquiring into the influence of a new cause which may be added to the first, let us more attentively examine the complicated case in which fishes are found in the circumstances of the experiment last related. The body is plunged in water, but the head and gills are exposed. On one hand absorption takes place in the water, on the other, perspiration in the air. The ab- sorption by the body plunged in water is proved by the slight increase of weight which takes place during the ex- periment, and the loss by perspiration from the part ex- posed to the air is demonstrated by the preceding experi- ments. Now it is evident, that the organ of respiration, which is exposed to the atmosphere, cannot continue its functions unless the losses by perspiration are repaired. It is true the rest of the body absorbs, and that, on the whole, it does not lose any of its weight ; but this condition is not sufficient for the continuance of respiration. It is also ne- cessary that the distribution of the fluid absorbed by the trunk, should be such, that the gills and muscles which move them should receive a proportion of it capable of re- pairing the loss which those organs experience by perspi- ration. Presuming it possible that this equilibrium might not take place, I made the following experiment to enquire into the relations of partial and simultaneous perspiration and absorption. I placed some fishes in the opposite position to that of the fish employed in the last experiment, that is, with the head and gills in water of the same quality and quantity, and the trunk, suspended in the air FISH ES. G3 by a thread passed through the end of the tail. They lived in this state many days. I weighed them after that inter- val, and discovered that there was evidently, in this case, a slight increase of weight. But the drying of the surface of the part of the trunk exposed to the air was as marked as in the case where these animals were entirely exposed to the atmosphere, and where they died after a considerable diminution in weight. It is therefore evident that the fluid absorbed by the gills was not distributed to the rest of the body in a proportion sufficient to repair, in all parts of the trunk, the loss which it had sustained by perspiration in air. The following fact, relative to the physical conditions of fishes in air, is important in the consideration of the principal causes of their death when so placed. Some fishes, when exposed to the air, soon cease to move their gills, although they continue to live pretty long afterwards ; but they die much sooner than those of the same species whose gills beat to the last. Suspecting that this difference in the duration of life proceeded from the interception of the air, I remedied it by raising the gills by a small peg placed be- neath them. The branchiee were thus exposed to the air. This change of condition, in relation to the atmosphere, proved sufficient to protract life as long as in those cases in which the respiratory movements were continued spon- taneously. The effect of thus raising the gills is so con- siderable, that if the gills of a fish, out of water, have quickly ceased to beat, we may, by its means, restore, for a while, their spontaneous action, and even do so for several times in succession. We see, therefore, that the life of fishes in the atmosphere, depends on several conditions ; of which the principal are, temperature, the capacity of sa- turation with water, the corresponding loss by perspiration from the trunk and gills, the quickness of this loss, the ac- tion of the muscles which move the gills, and the use 64 FISHES. which they make of their muscles to avail themselves of the action of the air upon the gills. In short, they come under the general law, relative to the influence of the atmo- sphere on the life of vertebrated animals. As fishes seem to form an exception to this law, I have thought it neces- sary to shew that they are so only in appearance. What has been here stated relative to the life of fishes in the at- mosphere, is equally applicable to tadpoles, placed in the same circumstances. They die from the quantity of water which they lose by perspiration, and although their capa- city of saturation is, at least, equal to that of frogs, since it varies between one-third and one-fourth of their weight, yet, as their size is very small, and their perspiration rapid, on account of the delicacy of their skin, they soon lose that proportion of water, and in the experiments which I made, I found that thev did not live more than four hours. u G5 CHAPTER III. LIZARDS, SERPENTS, AND TORTOISES. The cold-blooded animals which remain to be examined are the families of lizards, serpents, and tortoises ; in other words, the saurian, the ophidian, and the chelonian reptiles. The species employed in my experiments were the grey lizard, the ring-adder, and the rat-tailed and the mud tortoises, which served as types of their differ- ent families. The external covering of all these cold- blooded animals like that of the batrachians, receives a vivifying influence from the contact of the atmosphere, and thus concurs with the pulmonary respiration to support their existence, as connected with the influence of the air. The isolated influence of pulmonary respiration in lizards, serpents, and tortoises, presents the same differences as in the batrachians, i. e. in summer it is sufficient with some, and insufficient with others for the continuance of life. The families to which pulmonary respiration is in general sufficient are serpents, and tortoises. In lizards, on the con- trary, it does not, in summer, suffice to maintain life. The same experiments were made on these animals, as on the tree-frog, and the ream obsletricans, and with the same re- sult : but it was much more remarkable, in as much as their skin being scaly, would certainly not induce us to presume that the action of the air on that organ was so necessary for the preservation of their life. If we enquire into the general cause of these differences in the batrachians and F GG LIZARDS, ADDERS AND TORTOISES. other reptiles, we find it in the varied proportions of the lungs. I have proved that among the species submitted to this kind of experiment, those in whom pulmonary respira- tion is sufficient are the frog, and the brown toad, and that of Uoesel ; these are precisely the species in which the lungs are proportionally the largest. Now, as it has been shown by multiplied experiments that pulmonary respiration alone was scarcely sufficient in summer to maintain the life of these animals, and that it required only slight obstruc- tions to occasion their death, it follows that inferiority in the extent of the lungs, in other species, would produce the same effect when they are limited to pulmonary respiration. We see the same circumstance giving rise to the same re- sult in other reptiles. Tortoises and serpents are similarly circumstanced with the frog and common toad : pulmonary respiration alone appears sufficient for them, but lizards die in summer in a few hours if we confine them to pulmonary respiration, and suppress the vivifying action of the atmo- sphere on the skin. There is a marked difference in the proportionate extent of their lungs, and those of serpents and tortoises. We see then that, as respects the action of the atmosphere, the general results are the same with all cold-blooded animals. The modifications of the vivifying action of the atmosphere on the external surface of the body, all reduce themselves, on taking the phenomena in a general point of view, to the physical conditions of the ex- ternal covering. The same may be said of the physical agents which we have examined with reference to perspira- tion. We shall therefore consider the influence of the ex- ternal covering as respects its porosity and thickness, in relation both to the vivifying influence of the atmosphere, and to perspiration. We have geen that the batrachians can live in solid coverings surrounding them on all sides, provided these coverings are so porous as to admit a suffi- LIZARDS, ADDERS, AND TORTOISES. 67 cient quantity of air. I showed that these animals lived a long time in plaster exposed to the air, notwithstanding the thickness of the covering; but in pursuing these re- searches, 1 afterwards discovered that the quantity of air which they receive through plaster, is only under certain circumstances, sufficient for the maintenance of life. It is evident that through these coverings the proportion of air which they receive in a given time, is less than when the skin is exposed. For this reason they cannot live under running aerated water, when enclosed in solid bodies, although they do so very well without such a covering. In the same way, lizards, serpents, and tortoises, in the ex- periments which I have made on this subject, were unable, on account of the thickness of their natural coverings, to live under running aerated water. The same cause has an equal influence on perspiration. We have seen, in the first chapter, that when the animals are surrounded by a solid covering, they perspire much less than when the bare skin is exposed to the air. In like manner lizards, serpents, and tortoises, on account of the scales with which they are covered, perspire much less than the batrachians. From these differences dependent on the coverings of the body, arises the variety which we observe in the duration of the life of these animals when deprived of nourishment. This diversity depends on the rapidity or slowness of per- spiration, as is proved by the numerous and varied experi- ments which I have made on the duration of the life of batrachians, under different circumstances with respect to perspiration, among which the effect of solid coverings was the most remarkable. The influence of temperature on the duration of life in lizards, serpents, and tortoises, is analo- gous to that which I hav that in this circumstance, as in others, we have judged of life by external acts only, and not by the feeble motions which go on within, when these have ceased. Hence it follows, that children in whom respiration may be limited by engorgement of the lungs, will, all other cir- cumstances being the same, be less in danger than adults, when communication with the atmosphere may be limited in like manner and to the same degree ; and as the disturb- ance of the system, marked by the acceleration of respira- tion, circulation, &c., is so much the greater as the want of air is more pressing, the symptoms of pneumonia will be more intense in adults, in cases in which the relative extent of disease is equally limited. The facts formerly detailed prove, that the principal characteristic which distinguishes warm-blooded animals, at different periods, from their birth to adult age, is derived from their power of producing heat. We have also shewn the connexion between this power, and that of supporting the total privation of air. It is the same with limited re- spiration. As we have shewn, that adults may differ much in their power of developing heat, we may conclude, that applications. 275 they differ also in their power of supporting diminished re- spiration. XXV. These considerations lead us farther. I fan in- dividual is affected with pneumonia, so far as to endanger his life by diminished communication with the air, the most urgent indication is to employ the best means to bring back his constitution to that state which would enable him to support this limited respiration. Now, although this has not been kept in view, in the treatment at all times adopted in this disease, the indication has, however, been fulfilled. In whatever manner the blood contributes to the production of heat, we cannot doubt that it does exercise a considerable influence over it. A small abstraction of blood cannot in this case produce a sensible effect, but a sufficient evacua- tion could not fail to diminish the power of producing heat ; and keep it within the limits compatible with life. The more serious the case, the greater ought to be the abstrac- tion of blood. XXVI. The present state of our knowledge respecting the blood, presents new views which are intimately con- nected with physiology and pathology. MM. Prevost and Dumas, who have analyzed the blood of a great number of species of the cold-blooded vertebrata, and of warm-blooded animals, have found, that the proportion of water was the greatest in the cold-blooded vertebrata, less in mammalia, and at the minimum in birds ; or, reciprocally, that the re- lative number of globules (particles) increased in the order of the preceding classes. It is evident, that if we could change the proportion between the water and the globules, (particles) we should have another means tending to ap- proximate the constitution of the mammalia to that of the cold-blooded vertebrata. t 2 276 APPLICATIONS. Suppose that we have recourse to the injection of water to effect this change, it will then be found, by what we have formerly established respecting absorption, within what narrow limits this change will be confined. In the experiments upon animals, the best adapted for manifesting the effects of the absorption of water, we saw that there was a point of saturation which they do not pass so long as their constitution does not experience certain changes, however multiplied and prolonged may be the contact of the water with the absorbing surface. The point of saturation at which absorption ceases, is determined by the maximum of liquid which the body can contain in the natural state. Let us now suppose, that the body is at its point of sa- turation, absorption will cease only for the moment; for the body will rapidly recede from the point of saturation, by the losses which perspiration continually occasions, without mentioning other excretions. Absorption will take place in consequence, as we have shewn elsewhere. The body will then tend to maintain itself at the point of saturation ; but it will not maintain itself exactly at it: — it will undergo fluctuations dependent on excretion and absorption, and so long as food repairs the losses of animal matter, the injection of water, however abundant, will have little effect upon the proportion of this fluid to the globules (particles) of blood. If strict abstinence is observed, as in acute diseases, the losses of animal matter not being repaired, the proportion of globules necessarily diminishes, but this change is too slow for the most severe cases. The most prompt and most efficacious means of effecting this change, consists in the abstraction of blood. Bleed- ing, at first affects only the quantity of blood, and not the proportion of its constituent parts ; but the depletion, ac- APPLICATIONS. 277 cording to its extent, lias removed the body from its point of saturation ; absorption is increased in consequence, and is then principally operating upon the water in contact with the absorbing surfaces. The body may thus be restored to its original weight, or very nearly so. It follows, that the number of globules being diminished by the abstraction of blood, and absorption supplying this loss by water, which brings scarcely anything with it but the materials which it holds in solution, the proportions of the blood in relation to the water and the globules may change very rapidly, and to a great extent compatibly with life. If these deductions should leave any doubt respecting the justness of the conclusion, it may be removed by direct observation. Prevost and Dumas have proved, that the blood drawn at a suitable interval, after previous bleeding, presents a diminution in the proportion of globules. I refer those who wish further to examine the subject, to the memoir read by Magendie in 1820, on the mechanism of absorption in animals with red and warm blood, ( Journal cle P/17/siologie, tom. 1.) and also to Fodera’s Experimental Researches on Absorption and Exhalation. When it is considered, that the cold-blooded vertebrata differ from warm-blooded animals, not only in their power of supporting limited respiration, but also in their resistance to a multitude of other deleterious influences, it will be ac- knowledged, that the plan of treatment which tends to pro- duce an approximation to their constitution, in individuals of superior classes, within the limits which their organiza- tion admits, would put, them also, in the most favourable conditions for escaping the same causes of destruction. XXVII. We have seen, by the comparison of the blood of different species, and the action of some means adapted to modify this fluid in a determinate manner, how this 278 A PP LI CATIONS. change can be effected. But this change has limits which depend not only on the proportions of water and of globules, but also on the nature of those globules themselves. They differ, as we have already pointed out, from the researches of Prevostand Dumas, according to classes and species, by their form and their dimensions. No means with which we are acquainted can effect alterations of this kind ; and even, if we had them at our controul, their employment might, perhaps, be not salutary, but fatal. These physi- ologists have, indeed, been able to restore life and health to animals, which appeared deprived of them through loss of blood, by infusing into them blood having globules of the same kind. But when they endeavoured to produce the same effect with blood, the globules of which were of a different kind, they succeeded so much the worse, as the form and dimensions of these globules were further removed from those of the globules of the blood of the individual sub- jected to the experiment, and in cases of extreme difference, although at first they re-animated the animal, they caused horrible convulsions, quickly followed by death. XXVIII. There are other characters, besides the dimen- sions and the form of the globules, which have intimate re- lations with the mode of vitality. They are derived in the first place, from the apparent change which the globules undergo in their colour ; a change common to all the verte- brata. The globules are composed of a central white nucleus, and of an envelope of a red colour* ; which alone undergoes that modification which makes the particles pass from a dull red to a bright vermillion ; and according to the shade, they exert upon the phenomena of life an action no less powerful than that which is derived from their form and * See the correction of this view in the additional matter subjoined to the Appendix. 1 applications. 279 dimensions. Their communication with the air determines the extent of this change. A great number of facts record- ed in this work are referable to it, some immediately, others in a more remote manner, and they lead to the determi- nation of other facts which the state of science places within reach ; such especially as those which I have given relat- ing to the alterations of air from respiration in Part IV. Chap. XVI. As these facts lead us to consider the oxygen which dis- appears in respiration as really absorbed, we should now follow its traces in the system, and establish the nature of its combinations and of its actions. Here commences a new order of researches. The same is the case with the azote absorbed in the act of respiration, and the sources from whence the exhalation of this gas and of carbonic acid is derived : it is also the limit prescribed to this work ; but I cannot terminate without pointing out how this order of researches necessarily connects itself with the recent dis- coveries on the composition of the blood, and the action of the nervous system. XXIX. We have considered the composition of the blood only in relation to the water and globules ; but these are not its only constituents. It is known that the limpid por- tion is not pure water,- it contains in solution, among other substances, albumen, salts, &c., and forms what is called serum. It is sufficient to draw blood from a living animal and analyse it by the known means, to find there several of these substances and determine their proportions. But if we confined ourselves to this method, we should not discover other constituent parts, the knowledge of which throws a great light, not only on the composition of this fluid, but also on the secretory functions. The differences which had 280 AT’ PLICATIONS. been observed between the immediate constituents of the blood, and those of several other fluids in the system, had caused them to be attributed to a different orio-in. Thus, urea, the characteristic principle of urine, not being found in the blood by known methods, it had been concluded, with much apparent reason, that it did not exist in it, and that it owed its formation to the kidneys. This opinion has been universally adopted since the discovery of urea. Pre- vost and Dumas thought, that this secretion might be re- garded in two different lights, either the one which I have just mentioned, or the following. They discovered the means of deciding the question. They supposed that the kidneys, instead of forming urea with the materials derived from the blood, might give passage to it according as the blood fur- nished them with this principle already formed. In this case, it would be found in so small a quantity in the blood drawn from the animal in the natural state, that it could not be recognized by the ordinary means of chemical ana- lysis ; but these means would be sufficient, if, on the sup- position that the kidneys give passage to this principle, this passage were arrested. The extirpation of the kidneys, with the necessary precautions, must fulfil this indication, and then the urea, accumulating in the blood, would be- come manifest by the ordinary methods of analysis. They thus discovered in the urea a new principle in the blood which they found in great quantity, and made us acquainted with one of the principal secretions of the body in a new point of view. The fact just mentioned relates to the state of health ; but there are others which constitute new relations between the composition of the blood in the state of disease, and the secretions which depend upon it. Children are subject to a disease characterized by induration of the cellular tissue. Chevreul, on analyzing the fluid secreted by this tissue, APPLICATIONS. 281 found that it contained a substance which coagulates whilst cold. He has also recognized its existence in the blood of the same patients, and this in great proportion. It is the same with the colouring matter of jaundice which frequently accompanies this disease. Thus, morbid secretions are connected with the constitution of the blood, by the co- existence of the same principles in this and in the other fluids. XXX. These relations will doubtless be multiplied. Since a great number of the immediate principles of the organs and of the secretions, must now be referred to the blood, it is natural to inquire how they come to make part of it. It is known that the digestive system furnishes a great number of them ; but the origin of all of them cannot be referred to that source. Although the course which is taken by the oxygen which disappears in respiration has not been discovered, it is a necessary consequence of the absorption of any substance, that it passes in a greater or less proportion into the blood. Here then is evidently one source of the changes in this fluid, which may give rise to some of the immediate prin- ciples which constitute it. It remains for further researches to determine them. Enquiries of this nature appear in- timately connected with the study of the nervous influence, especially since the labours of Dr. Wilson Philip have made us acquainted with the share taken by the nervous system, in converting the food carried into the stomach into chyle. The accuracy of the Doctor’s researches have been verified by the experiments of Breschet, Vavasseur, and of my bro- 1 her Henry Edwards. ( Arch . gen. de Med. Aout, 1823, p. 485.) XXXI. We find, in the changes which the blood can 282 APPLICATIONS. undergo as to its composition, a fertile source of the changes in the mode of vitality. It would appear at first, that it is only through this medium that we can act on the nervous system, in order to modify its action so as to change the constitution of individuals ; on account of the extent in which this fluid can vary, and of the apparent immutability of the nervous system in its form and structure. It is evident, that the dimensions and proportions of that system have limits assigned by nature to the modifications which their vitality can undergo; it is, however, sus- ceptible of considerable changes, not discernible by in- spection, but which manifest themselves by the actions which result from them, and which do not arise from the influence of the blood. Such effects may, as we have formerly proved, be produced by temperature, by light, elec- tricity, and a number of other influences by contact, to say nothing of moral causes. It is this which I have had in view in speaking of the special action of the air on the system, and which I have designated vivifying influence. It is thus that the impression of the air serves to reanimate a life almost extinguished in the case of appa- rent death, and here man has an advantage over all warm-blooded animals, even the hybernating. Their skin, covered with hair or feathers, is less accessible to the air; and I have never seen an adult individual which, after the cessation of all external motion by submersion in water, has been recalled to life by exposure to the air. Man, on the contrary, whose skin is bare, delicate, and sensible, may be re-animated by the action of the air, when he ap- pears to have lost, under water, sense and motion. We have shown elsewhere, that new-born children, when deprived of air, would not give signs of life during so long a space of time as young mammalia of the same age, which are born with closed eyes ; they will, however AIR FROM RESPIRATION. 283 more easily recover from apparent death, because their skin is adapted to receive a stronger impression from the air. We have have seen how fatal heat is in cases of asphyxia, and of very confined respiration. Now, when the action of the air is reduced to the effects which it produces upon con- tact with the skin, its influence is the weakest possible, and at first it cannot easily be conceived what advantage can be derived from the application of heat. If that application be of long duration it will be fatal ; in some cases it may be useful, if it is of short duration. When an animal is plunged in water, at the temperature of 40° cent, or 104°Fahr., its motions, are much more forcible, but less numerous than at inferior temperatures. There are circumstances, then, in which heat may be momentarily applied in order to excite the movements of the chest. The immersion of a great part of the body in warm water, is frequently an efficacious means of re-animating a child just born without signs of life. As soon as motion is produced, or if it be slow in manifesting itself, it will be right to abandon a method, the prolonged use of which, would be fatal. We must, therefore, look upon the vivifying influence of the air in two points of view, its direct action on the nervous system by contact ; and its action on the blood by the changes which it produces in it. In like manner, the vitality of individuals may be modified by a number of other causes which act immediately, either on the nervous system, or on the blood. Many facts mentioned in this work, are examples of both modes of action. f - * V . ' I APPENDIX. ON ELECTRICITY. In relation to the animal economy, the phenomena of electri- city may be divided into two classes : one comprehending the actions of the external fluid upon the body of the animal, and the other the electrical influences which he exercises upon himself. We shall examine, in the first place, the effects produced by tension, or the state of a body when charged with elec- tricity. If a man, or other animal, be placed upon an insu- lated stool, and put in communication with a body charged with free electricity: from the moment of contact he will give the signs which answer the presence of that species of electricity. We shall now proceed to the effects which result from the passage of a single species of electricity through a con- ductor interposed between the source which furnishes the fluid, and the common reservoir in which it is going to lose itself. The molecules of which it is composed will tend to separate, on account of the repulsive action which they acquire while charging themselves with a similar electricity. Were this influence to become sufficiently powerful to over- 286 APPENDIX. come the force of aggregation which holds the molecules together, the body would be reduced to powder. This property may be applied without difficulty to phy- siological phenomena, and explains them in a manner which leaves little to be desired. If an electric spark be passed through a small drop of blood, the particles which it contains, will be seen instantly to assume the appearance of raspberries, which indicates the partial separation of the elementary globules of which they are formed. If the same experiment be tried upon a liquid containing spermatic or infusory animals, a similar effect will be observed, and these various beings will instantly lose the spontaneous motion with which they were endowed. In all these cases, the disorganization seems to consist merely in the forced separation of the organic globules of which the tissue is composed. But if the same trial be made upon bodies com- posed of various heterogeneous tissues', it is manifest, that the strongest action will be received by the portions best adapted for transmitting the electric fluid. In a vertebrated animal, it will therefore be the nervous tissue which will suffer the most from the effects of an electric shock, and if its intensity be such, that if the globules which compose the nervous fibres shall be disjoined, all the functions of that system will be instantly destroyed, and life will be irrecoverably lost. Such is the effect of a stroke of light- ning, and such are the general symptoms which manifest themselves in man, and other animals, which have been struck in this manner. No experiments have, indeed, as yet been made calculated to show the nature of the disor- ganization undergone by the brain and its dependencies on such occasions, but it is very well known, that muscular irritability diappears at the very moment at which life is destroyed by an electric shock, while it is preserved long after death from other causes. It is also observed in ani- APPENDIX. 287 raals struck by lightning, that their blood does not coagu- late, as in most other cases after death, but remains fluid, or at least presents only a few inconsiderable clots. There is another kind of influence which deserves still more attention, since it appears, that it is to it that the re- action, which the body of an animal is capable of exerting on itself, are to be referred. In 1789, Galvani observed by chance, that a metallic circle, composed of two heterogeneous metals, placed in contact on one hand with the muscles, and on the other with the nerves, instantaneously produces contractions of the muscular structure comprehended in this circuit. The physical explanation of this fact was furnished by Volta, who demonstrated, that two conductors in contact, become charged with opposite electricities, and that when they are united by a third body, capable of transmitting the electric fluid, a current is established within, owing to the neutra- lization of the fluid collected in the metals. It is this cur- rent which determines muscular convulsion, when the nerve of a muscle serves as a conductor, and sensation, when one of the cerebral nerves is employed, as in the experiments of Galvani and in others, equally remarkable, which are related in the more ancient work of Sultzer, entitled Theorie du P/aisir. Let us more clearly examine each of these properties, and we shall see to what order of phsenomena, we are now enabled to refer them. It is well known to physiologists, that the integrity of the division of a nerve which supplies a muscle, and the free circulation of the blood through the vessels which are distributed to it, must be considered as the necessary con- ditions of the contractile power. Anatomists are aware that the muscles present con- siderable analogy in all the animals in which they can be 288 APPEN mx. observed with sufficient plainness. They are bundles of fibres, soft, flexible, yielding, and of very various lengths. A cellular tissue of great delicacy unites them together, and their extremities lose themselves in the common mass, or attach themselves to tendons, which form the medium of connection between the muscle and the parts which it is designed to move. The manner in which their fibres are grouped is very various, but the muscular tissue appears to be strictly the same in all cases. Its colour is white, and if in warm-blooded animals it appears red, this must be at- tributed to the fluid which bathes it. We shall subdivide the muscular fibre into three orders. We shall call tertiary fibres, those muscular filaments which are found on cutting the muscle longitudinally : we shall call secondary, those ob- tained by the subdivision of the former : they are very well marked, inasmuch, as it is impossible to subject them to any mechanical alteration without arriving at the primary fibre, which the labors of Home, those of Henry Edwards, and our own, have made known in a very satisfactory manner. Henry Edwards found the elementary fibre the same in all animals and at all ages, and formed, in all cases, of a series of globules of the same diameter. From the combination of a bundle of primary fibres, result the secondary fibres, upon which our attention must be fixed, inasmuch, as the contractile movements are effected by their means. When they are examined with a magnifying power of 300 diameters, they exhibit themselves frequently in a very peculiar manner, which might lead into error respecting their real composition. They are seen like cylinders, crossed by a considerable number of little sinuous lines placed at the regular distance of the 300th part of a mil- limetre. This appearance seems owing to the membranous sheath in which they are invested, and is not found in secondary fibres which have been cut or torn. It disappears APPENDIX. 289 likewise in certain states of illumination, when the true muscular structure becomes manifest, and appears com- posed of a considerable number of small elementary threads placed parallel or nearly so. If a muscle be taken sufficiently thin to be examined as a transparent object, without its being necessary to divide it, it will be seen that it results from the combination of a certain number of secondary fibres placed sometimes with little order, one beside another, parallel, or nearly so, and often grouped so as to produce the muscular bundles which are conspicuous in thick muscles. These are held together by an adipose cellular tissue, and are traversed in various directions by vessels and nerves which seem to pervade the muscle, without having any easily observable connexions with it. We cannot now enter into the history of the cir- culation peculiar to these organs, and shall therefore only observe, that if there exists a material communication be- tween the muscular fibres and the bloodvessels, it can only be conceived on the supposition of transudation taking place through the coats of the vessels. The passage from the arteries to the veins is easily traced, and does not pre- sent the extreme division which would be indispensable to the nutrition of the organ, if it took place as it is generally imagined. Let us now examine these muscular bundles, independ- ently of the accessory organs, and with a very weak magni- fying power, to obviate all objections to which the use of the microscope is liable. If the muscle be at rest, we merely see a number of straight parallel fibres, which are very flexible and so disposed as easily to change their position with the least motion of the muscle. When this appearance has become familiar to the eye., we can appreciate the changes which are effected at the moment of contraction. For this purpose, we take a muscle u 290 APPENDIX. recent and thin, the sterno-pubic muscle of the frog, for example. We place it under the microscope, and submit it to galvanic influence by means of a very simple arrange- ment, described in our Essay upon Spermatic Animalcula. As soon as the current is established, the muscle contracts and presents a most remarkable appearance. The parallel fibres which compose it are suddenly bent zigzag, and present a great number of regular undulations. If the current be interrupted, the organ resumes its original appearance, and bends again when it is re-established. It is even easy, when the muscle is strong and irritable, to repeat the experiment a number of times. In general, however, the muscle must be renewed after two or three trials. The precision and instantaneousness of these changes render this phenomenon one of the most curious in physi- ology. On examining it with attention it will be perceived, that the flexions take place at determinate points, and do not change their position, which seems to indicate, that it is occasioned by the momentary attraction of these points to each other. In all the muscles the same peculiarity is discovered. Warm as well as cold-blooded animals exhibit, it; and birds as well as mammifera. It is also perceived without diffi- culty in the muscles of the stomach, the intestines, the heart, the bladder, the uterus, &c. On the surface of the secondary fibres, and in the inner part of the angle which they form, when contracted, may be remarked wrinkles or folds, owing evidently to the forced bending to which they have been subjected. This appear- ance is frequently very well marked ; in other cases it is, less so. This arises only from the energy of the contraction. When it is weak, the angle is obtuse, and the fibre does not undergo sufficient flexion to occasion these wrinkles ; but if it becomes more acute, the inner part of the bundle APPENDIX. 291 must necessarily be compressed, and thus form wrinkles. It is even probable, that this cause limits the energy of the contractions, and prevents them from passing a certain angle. At least, it is certain, that in the muscles ol loco- motion, we have never been able to produce contractions oc- casion i no- angles so acute as .50°. The fibres of the intestinal muscles, however, frequently exhibit themselves at angles even more acute. But, in the first place, the summits of the angles are sensiblymoredistantthan in theothermuscles,and in the next, their secondary fibres are thinner, and are dis- played over a larger surface. It will readily be conceived, there- fore, that they are in a situation altogether peculiar, and that each fibre contracts, as it were, independently of the others, and without being constrained by the surrounding bundles. Having observed the phaenomena just described, it was essential to determine all their conditions. It was possible, that the muscular fibre might have undergone other changes besides those which we had perceived, and that, on this supposition, it might undergo a variation in bulk. Ancient anatomists, and among them Borelli, had believed, that the bulk of the muscle was sensibly augmented at the moment of contraction. This opinion, which was not founded upon any measurement, was overturned by Glisson. He caused the arm of a man in the state of rest to be immersed in a bucket filled with water, and he thought he perceived a lower- ing of the surface as soon as the muscles came into play. This experiment was repeated with more care by Carlisle, who uniformly arrived at the contrary result. More judi- cious observers have, however, perceived, that these ex- periments were deceptive, since no allowance was made for the alterations in the skin, and sub-cutaneous cellular tissue, when compressed by the muscular effort. Blanc pursued a method similar to that of Carlisle ; but he took the precaution to make use of a compact muscular mass, u 2 292 APPENDIX. and placed in the vessel a piece of an eel, which he stimu- lated by means of a pointed metallic wire. This method having shewn him no alteration in the level of the liquid, he inferred from it, the equality of volume in the two states of the muscles. But before him, and without his know- ledge, Barzoletti, by a much more elegant experiment, had arrived at precisely the same conclusion. He suspended in a bottle, the posterior part of a frog, filled the bottle with water, and closed it with a cork, through which was passed a narrow graduated tube. He then found the muscle to contract by the stimulus of galvanism, and in no case could he observe the least variation in the column which the tube contained. The apparatus which we employed did not differ, in its principal conditions, from that of Barzoletti ; though we made use of larger masses of muscle, and not having per- ceived any disturbance of the level, we also came to the same conclusion as Blanc and Barzoletti. The experiments just related were sufficient to show, that the muscle underwent no alteration, except in the direction of its fibres. Great importance being thus given to the examination of the sinuosities which the muscular fibres describe, we were induced to devote some attention to this subject. a b c d e f o n m g q r t v y APPENDIX. 293 On one of the muscles of the leg or a frog being placed under the microscope, and made to contract by means of the pile, we held over it, in several places, the broken lines as above, and carefully compared them with the natural sinuo- sities, making use of both eyes. We afterwards completed the triangles by means of the dotted lines and took the fol- lowing measures. Length of the lines. Distance of the points. a o — 10mm. ab — 17mm. ob — 10 cd — 16 c n — 10 ef — 16 nd — 10 gq — 42 e m — 10 ry - 39 mf — 11 Total 130 gh — 10 hi — 10 ik — 11 kl — 11 lp — 12 st — 11 tu — 12 u v — 12 vx — 10-5 xy - 12 Total 172-5 If we suppose the 16 lines in the above table to form a series, we shall have 172-5 for the distance of the points, a and y, when the fibre is straight, and only 130, when it is contracted. This indicates, a shortening of 0'23 in the fibre. 294 APPEN I)T X. But it was1 possible to assure ourselves directly of the truth of this fact, by taking the same muscle and measur- ing it with care, in the two states of relaxation and con- traction. For this purpose, as soon as we had taken the muscle from the body of the animal, we placed it under the microscope, to ascertain that its fibres were quite straight, and then measured its length by means of a pair of com- passes. We afterwards stimulated it to contraction by the current of a weak pile, and took a new measure whilst it was in that state. 25mm. Contracted 17mm. 20 15 25 18 20 15 90 65 By this method the diminution was found to be 023. We may then conclude, that the flexion of the fibre repre- sents in reality the quantity by which it is shortened, which proves, that the change which it has undergone, is refera- ble to direction only. This consideration is so much the more important, as many facts commonly known prove to us the elasticity of muscular fibre, and there might be some reason for sup- posing, that that property was concerned in the phenome- non of contraction. We shall now detail what we know with precision on the subject. Living muscle, abandoned to itself, always assumes the regular state in which we sub- jected it to examination ; but, when its two extremities are fixed, and the distance of the points of attachment is in- creased, the fibre lengthens in virtue of its elasticity, as APPENDIX. 295 shewn by old experimenters, who have endeavoured to es- timate the weight necessary to produce its rupture. It is evident, that this action is of an opposite nature to that which produces contraction, and which it ought to resist in its effects ; at least, we are authorized to think so after the following experiments. We took female frogs a short time before spawning. Their abdomen was very much distended by the eggs, and the sterno-pubic muscles must have yielded to the increase of bulk and become lengthened. We separated these muscles from the cellular tissue, and from the other parts of the abdominal parietes. We de- termined their lengths, and then we cut one of their ex- tremities. At that very instant they underwent a remark- able shortening : but on examining them with the micro- scope, we ascertained that that phenomenon was not accom- panied by any flexion of the fibre, and that it consequently differed from its ordinary contraction. Being afterwards subjected to galvanic influence, the same muscles further diminished in length, presenting the usual sinuosities. We shall here give the numerical proportions, which express the conditions of these two phenomena. Muscle in its place 45mm. Cut 34mm. Contracted 22mm. 49 36 25 51 37 27 145 107 74 These numbers are nearly in the proportion of 30 — 20 — 15; in other words, a muscle, whose strong contractions are equal to a quarter of its length only, may be brought, by means of continued traction to the distension expressed by the pro- portion 2 : 3, without undergoing any alteration in its con- tractile power. 296 APPEN UlX. When vve reason upon this fact, a view is presented to the mind, which altogether destroys the objection which might be drawn from certain cases of extraordinary con- tractions, apparently difficult to be reconciled w'ith our theory. In fact, the stomach, the intestines, and the bladder, exhibit to us variations of volume, which are almost incredible; and, although, their muscular structure is such, that it is easy to explain why their contractile power pro- duces results much more powerful than those, the intensity of which we have measured in the mucles of locomotion, it is no less true, that they would be much less than they are, if the elasticity of their fibres did not act an important part in that phenomenon. The explanation of the facts becomes very easy if we make use of the twro following principles : 1. The muscles are elastic, and consequently capable of beino- lengthened under the influence of traction exerted at their point of attachment; 2. Their contractile power may act in all cases; but it probably increases in force as it ap- proaches to the natural state of the muscle. It results from these two properties, that the stomach and intestine, for example, may be greatly distended by the pressure of ali- mentary matters. If in such circumstances, any stimulus is made to act upon them, they will undergo successive contractions, which will gradually follow the foreign bodies included in their cavity, until atlength they attain their point of rest. Their muscularfibres were straight while they were distended, they are so still in this latter state. This power of extension is much facilitated by the secondary fibres of these muscles being very thin and very long. They are dis- posed nearly on the same plan, and are united by means of a very loose cellular tissue. These various circumstances permit them to be easily separated ; they do so in fact when the organ is stretched, and if this trial is carried too far. APPENDIX. 297 rupture takes place, and that in the intervals between the muscular fibres. The contraction of these organs differs then entirely from that of the muscles of locomotion. The latter are fixed in an invariable manner at their extremities, and can scarcely undergo more than a single contraction, or, if they undergo a certain number, they are alternate, and always bring back the organ to the same point. In the abdominal viscera, on the contrary, it is by means of a series of contractions that the muscles gain the point of rest. Let us now examine the connexions which exist between the phenomena just adverted to and the nervous system. It is well known that a muscle contracts, 1. When its nerve communicates freely with the brain, and there exists in that organ the will to produce a contraction; 2. When the nerve is pinched, after its connexions with the brain have been destroyed ; 3. When the current from a galvanic pile is passed through it ; 4. When it is touched with active chemical stimuli, such as concentrated mineral acids, chlorurets of antimony, bismuth, &c. ; 5. When placed in contact with a hot body. Since it is evident that the pre- sence of the brain is not necessary to the exercise of the contractile power, we shall at once set it aside, and pass on to the examination of the contractions determined by means of the pile. If one of the poles of a galvanic pile be placed in contact with the nerve, and the other in communication with the muscle, the latter undergoes contractions. In order that we may form a distinct idea of the course of the galvanic fluid in this experiment, it is necessary to study more closely the relations which exist between these two organs. The nerves present to the naked eye, a satin-like appear- ance, which was first particularly described by Fontana. 298 APPENDIX. It is particularly sensible in the nerves of the cat, the rab- bit, the guinea-pig, and the frog. When they are examined with a power magnifying from 10 to 15 diameters only, alternate lines of light and dark are seen, which forcibly suggest the idea of a spiral coil situated beneath the neur- elema. After a series of varied experiments, we were con- vinced that this appearance, like that of the tendinous tissues, was owing to a little pleating of the fibres of the neurelema, which loses its transparency in some parts, and preserves it in others. This would merit little attention, did it not present a very certain criterion for recognizing the little nervous threads, and render them easily distin- guishable from the blood-vessels or lymphatics. If the neurelema of a nerve be divided, and the nerve be then spread out under water, it is seen to be composed of a great number of very small parallel fibres, which appear to be continuous throughout the length of the nerve ; at least, they are no where seen to divide or unite. Their filaments are flat, and composed of pure elementary fibres, placed nearly on the same plane, which gives them the appearance of ribbons. These fibres are formed of globules, and pre- sent a remarkable circumstance, namely, that the two outer are the most distinct. The middle series can be seen only occasionally, doubtless because the pressure which they undergo effaces the line of demarcation of the globules com- posing them. The number of these secondary nervous fibres is very considerable as the following calculation will shew, although the data of the observation may not be admitted as rigorously correct. Let us suppose, that each elementary nervous fibre occupies in the section of the nerve, of a square millimeter, we shall have 90,000 for every square millimeter. But we know that the secondary fibres include four elementary fibres, there must then be 22,500 in the same APPENDIX. 299 space, or about 1 6,000 for a cylindrical nerve of a millimeter in diameter, such as the crural nerve of a frog, for example. If a nerve be examined at its entrance into a muscle, and followed attentively, it will be seen to ramify in a man- ner which at first appears not to be very regular, except that there is a tendency in the branches to direct themselves perpendicularly to the muscular fibres. This observation may be easily made upon all muscles, such as those of the ox, cat, &c. ; but it requires in this case precautions regard- ing light, which render it painful and fatiguing. It is on the contrary, very easy to discern it in the thin muscles of the frog, on account of their transparency. After having thus followed one of the nervous branches as far as ob- servation with the naked eye and the lens will permit, it be- comes easy to fix the point at which we mus stop, and to continue the examination assisted by higher magnifying powers. As the nerve arrives at its ultimate ramifications, it widens, and its secondary fibres separate and display themselves, precisely as when it has been stripped of its neurelema. This little nervous trunk then presents the appearance of a fibrous cloth, from which some threads are occasionally seen to shoot into the muscle, perpendicularly to its own fibres. Sometimes there are two nervous trunks, parallel to the fibres of the muscle, which proceed at some distance from one another, and mutually send across little threads, which are seen to pass through the muscular space which separates them, cutting it at right angles. Some- times the nervous trunk is itself pressed close to the fibres of the muscle, and the threads which it furnishes spread out, preserving this direction, run through the organ, and return on themselves, forming a loop. But in all cases, it is observed, 1st, that the extreme nervous ramifications are parallel to each other, and perpendicular to the fibres of the 300 AI’PENDIX. muscles ; and 2ndly, that they return into the trunk which has furnished them, or anastomose with a neighbouring trunk. But, in all cases, it appears very certain that they have no termination, and that their relations are the same as those of the blood-vessels. Now, let a galvanic stream be passed through a muscle examined in this manner, and it will be seen, that the summits of the angles precisely correspond to the passage of these nervous filaments. Be- fore admitting this fact, we subjected it to all the verifica- tions that we could think of, and it was only after having repeated and varied our experiments in every possible way, that we considered ourselves warranted to adopt it. All preparations do not succeed, but in the delicate muscles of the lower jaw of the frog were found the best specimens that could be discovered. It becomes then very probable, that the nerves approach, and thus determine the phenomenon of contraction. Now, what is the cause which forces them to advance towards each other? It is impossible here not to recognize the ap- plication of the beautiful law discovered by M. Ampere. It remains to investigate how far it is applicable. If two streams attract each other, when they go in the same direction, it will be enough to suppose, that the nerve transmits the galvanic fluid more easily, and in more con- siderable quantity than the muscular stratum itself, (which is quite in accordance with experiment,) in order to form a clear idea of the phenomenon in question. Indeed, if we interpose a muscle between the poles of a pile, it will be found to be traversed by the fluid, but in an unequal man- ner, on account of the better conducting power of the nerve. The branches of this being parallel, will reciprocally attract each other, and will thus determine the flexion of the fibre, and the shortening of the muscle. Admitting the correctness of this opinion, it will easily appendix. 301 be conceived, that the living muscle is really a galvanometer, and the short distance between the conducting branches on the one hand, and their tenuity on the other, unite in giving it an extraordinary sensibility. We shall now consider it in this point of view, and compare the phsenomena of mus- cular contraction with the experiments on the moving power of electricity, with which natural philosophy has of late years been enriched. The beautiful experiments of the Italian philosophers upon muscular contraction, produced by the contact of heterogeneous matters, are generally known, and we have now increasingly strong grounds for believing, that these motions are owing to the passage of a small galvanic stream. But admist all these results, it will be remarked, as Humboldt has clearly shewn, that the contractions manifest themselves at the moment when the communication between the nerve and the muscle is etablished, by means of a single metal. This is generally explained, by supposing that the metal and the muscle become placed in opposite states of electricity, and that the neutralization of the two fluids is effected through the nerve. If to each end of Schweigger’s galvanometer be fitted similar plates of platina, and if around one of them be fixed some ounces of muscle, recently taken from a living animal, and if they are then plunged into blood or water, slightly impregnated with salt, the magnetic needle will deviate, and the stream will go from the metal to the muscle. It appears then, that the view which has been adopted is accordant with experiment, and we might regard this method as an excellent means of comparison between Shweigger’s galvanometer and the frog. In fact, if we arm the muscle and nerves of the animal with portions of the wire, which forms the galvanometer, and then bring 302 APPEN DIX. the two ends of the apparatus in contact with the armatures, the contractions will be strong- and frequent. The needle, however, in the majority of cases, will not change its posi- tion ; and if, sometimes, slight oscillations are thought to be perceptible, they only serve still further to prove the want of sensibility of the instrument. The animal, with exquisite sensibility, indicates all the electric currents which influence the galvanometer, as for example, the action of an incandescent metal upon a cold one, that of an alkali upon an acid, and that of twrn oxidable wires, unequally immersed in an acid. It is very certain, however, that if we did not possess the galvanometer, it would be impossible to present an exact analysis of these various phenomena, since the frog does not indicate the the direction of the current. We easily perceive, in all that has been adduced, the power of the electric fluid in producing muscular contrac- tions, and we know, from other experiments, that it is indispensable, that that fluid should be in motion. If a frog, prepared and insulated, be brought near the charged plate of an electrophorus, the nerves, like all other light bodies, will be strongly attracted. The frog will give very marked signs of free electricity ; but the attractions will manifest themselves, only at the moment when the spark is taken. Thus, every time that the galvanic current passes through a living muscle, the contractions of that organ betray its passage. We have now to show, that in all cases, where contractions are produced, there also exists a develop- ment of electricity. For this purpose, let two similar platina wires be fitted to the ends of the branches of the galvanometer ; let one of them be plunged in the muscles of the frog, and the nerves of the animal be touched with the other, heated to redness. APPENDIX. 303 The contractions will be strong, and the deviation of the needle very sensible. Both these phenomena will be pro- duced, but with less intensity, if the heated metal be ap- plied to the muscles. Let a platina cup, filled with nitric acid, be now substi- tuted for one of the wires, and fix to the other a fragment of nerve, muscle, or brain; at each contact the needle will deviate, and the stream will proceed from the acid to the animal matter. Similar effects may be obtained with chlo- ruret of antimony. With regard to pressure or pricking, which are only modi- fications of the same thing, we have not been able, in this kind of experiments, to detect the electricity which they must excite; but the beautiful discoveries of Becquerel leave no room for doubt on this point; and the difficulties which we have experienced depend on circumstances which render modifications in the apparatus necessary. Besides, we ascertained, by experiment, that by the slightest pressure, two living animal substances acquire opposite states of electricity. It is sufficient for two insu- lated persons to touch hands, and then withdraw from the contact, to develop an excess of electricity sufficient to affect the electroscope of Caulomb. It is proper to remark, that the greater part of these effects are not connected with the existence of life, but it is very evident, that when death has affected the organs which are submitted to this kind of action, the conducting- power of the nerves may have been essentially modified. It is even possible, that that may be the only circumstance which determines the irritability of the muscles, without which, it would not always produce the approximation of their nervous branches. The arrangement of the tissues is so delicate, that when matter abandoned to itself is with- drawn from the power which had organized it, it must, in a 304 APPENDIX. short time, lose the properties with which it had been en- dowed. It may be supposed, that this hypothesis is not appli- cable to all the circumstances of contraction ; but the results recorded in our memoir, and which may be obtained with great facility, readily shew that it is. The insulation of the nervous fibres, is produced by the abundant fatty matter, for the discovery of which, we are indebted to Vauquelin. It surrounds each of the fibres, and does not permit the electric fluid to pass from one to the other. Besides this arrangement, which exists in the interior of the nerve, under the neurelema, there is always, round the nervous trunk itself, and external to its covering another bed of fat, which exhibits itself in its most minute ramifi- cations. It will be obvious, that by means of these pro- visions, the electric fluid, which has arrived in the nerve, cannot deviate to take a different route. Hitherto we have rather regarded the effects resulting from an extraneous action upon the animal economy. It now remains to shew, that there are internal phenomena, the result of the reaction of one organ upon the neighbour- ing organs, which may also receive some light from known physical facts. The fluid with which the sanguineous system is filled, contains pure caustic soda, in sufficient quantity to impart to it manifest alkaline properties. Now, the greater part of the materials separated from the blood by the secreting organs, differ from it entirely in this respect. Some, as the bile and the saliva, are alkaline also; but they contain, in proportion to the quantity of animal matter, a much larger quantity of soda than is found in the blood. Others, as milk, and chyme, are, on the contrary, acid, and owe this property to the presence of the lactic, phosphoric, APPENDIX. 305 and other acids, which arc also met with in the blood, but are naturalized by alkaline bases. Lastly, the urine and sweat, in the state of health, present themselves under two different conditions. They are generally acid, but sometimes neutral. What is called sweat, in the ordinary acceptation of the word, is always acid; but the liquid, which is continually, evaporating from the skin, as well as the water which ac- companies the air as it issues from the lungs, is found, when collected, to be neither acid nor alkaline, and their analysis shews only a small proportion of animal matter, accom- panied by some traces of alkaline hydrochlorates. The urine is always acid in health ; but this character is scarcely apparent, if the individual has drunk a large quantity of water some hours before. If we seek among the facts known in chemistry, for an explanation of this difference between the constitution of the blood, and that of the fluids secreted from it, we may soon be convinced, that the action of the voltaic pile, is the only one which approaches to it. Moreover, it appears pos- sible, artificially to imitate the principal conditions of the secretions, and to separate from the blood, by means of the pile, a liquid resembling milk, and from the food itself, a material resembling chyme. We recommend this subject to the attention of medical men, inasmuch as they may find in it some valuable hints respecting the use of various medicines. Many of these act too evidently on the secretory functions, and too plainly disturb their equilibrium, for us not to ascribe their action in a great degree to this peculiar effect. We need merely mention, mercury for the bile and saliva, and diuretics for the urinary functions. W e cannot conclude this chapter without remarking, that if muscular motion and the secretions may be re- garded as owing to electrical movements, the production of x 306 APPENDIX. animal heat can only be suitably explained in the same manner; for it is known to electricians, that the conducting wire acquires considerable heat during the action of the pile. M. de la Rive, the learned Professor of Chemistry at Geneva, was the first to seize the happy idea of referring the phenomena of animal heat to electric agency. 307 ON MUSCULAR CONTRACTIONS PRODUCED BY BRINGING A SOLID BODY INTO CONTACT WITH A NERVE WITHOUT A GALVANIC CIRCUIT. BY DR. EDWARDS. Read before the Royal Academy of Sciences, MAY, 1825. The experiments of galvanic or muscular contraction ex- cited an interest in the scientific world, which gave rise to many important researches. It seemed that a new epoch in physiology had commenced. This was really the case, not merely as regards the singular character oi the newly discovered phenomena, but with respect to the fundamental results to which they led. The creation of a new branch of natural philosophy, was another and not less remarkable consequence. Physiologists, who at first had hoped for too much, were too soon discouraged. From the close of the last century, when Humboldt’s celebrated work on Galvanism made its appearance, up to a very recent period, but little attention was directed to researches of this kind. It was natural that attention should again be excited by the new impulse given to this branch of science by Professor CErsted, nor could the researches of Becquerel, which have so greatly increased our knowledge of this subject, fail to revive the hope, that electricity might be satisfactorily called in to explain some of the phenomena exhibited by animal life. Accordingly, Prevost and Dumas shortly after, laid before the Academy of Sciences, a memoir, which called forth a very lively in- terest. They described the terminations of nerves, and ex- hibited their relation to the muscular fibre, in a manner which introduced perfectly new ideas on the subject of x 2 308 APPENDIX. muscular contraction. Their proofs are grounded on the evidence of the senses, and the testimony of several of the members of the Academy confirms the accuracy of their observations. (Their views are given in the preceding Appendix, to which it is sufficient to refer, more particu- larly to page 302, et seq., where they endeavour to shew, that in all cases in which muscular contractions are in- duced by external excitation, there also exists a develop- ment of electricity.) This fact, is very much in favour of the opinions advanced by these physiologists, that the mus- cular contractions thus excited, depend upon the electricity developed by the action of these stimuli. There is, indeed, the simultaneous production of electricity, and of muscular contraction, but the question may be asked — is it by virtue of this production of electricity, that the contractions take place ? Though it is well known that electricity, provided it be in sufficient quantity and applied in a particular manner, gives rise to muscular contractions, we do not know whether the fluid, disengaged by the three modes of excitation al- luded to, is in the conditions necessary to produce such contractions. Being occupied with some researches on the nervous sys- tem, I had occasion to examine a mode of mechanical excitation, which appeared to have been previously neg- lected, and which led me to some observations which bear on the question above stated. The procedure consists in passing a solid body along a nerve, in the same manner in which we pass a magnet along a bar of steel which we wish to magnetize. In doing so, the object is not to act by pressure, although, more or less must be exercised in every form of contact, but rather to touch various contiguous portions successively, and we have it always in our power to bear as lightly as we please. A 1> P E N D I X . 309 In order to pass the exciter along a certain portion of nerve, it is necessary that the nerve should be supported and kept more or less lense. These conditions are fulfilled when a portion of nerve is simply laid bare, while its con- nexions, superiorly with the rest of the nervous system, and inferiorly with the muscles to which it is directed, are left unimpaired. Expose the entire sacral portion of the sciatic nerves of a frog, by removing the skin and muscle which cover them. Take off the skin from the lower limbs, in order to see the \ contractions of the muscles, and pass under the nerve a slip of oiled silk to bring them better into view, and also to make them even with the sacrum. We have then by this preliminary step, an animal, whose sciatic nerve can be both better seen and touched, and in whose lower extremities, the slightest muscular contraction cannot take place without being visible. In order to cut off voluntary movements, which would interfere with and derange the experiment, the spinal marrow should be di- vided immediately below the head. Having the animal thus prepared, touch the sciatic nerve in the before-mentioned manner, with a slender rod of silver. The muscles of the corresponding limb will be thrown into contractions, and such will continue to be the result when- ever this treatment is repeated, however delicate the con- tact. The exciter is to be drawn along the whole extent of the denuded nerve, which will be from a quarter to a third of an inch in length. Contractions are also produced by rods of various other metals, such as copper, zinc, lead, iron, gold, tin, and platina. I took care to employ metals of the utmost purity, in which state I was supplied with them by the essayers of the mint. It is not necessary that the rod should be metallic ; I succeeded with glass or horn. 310 APPENDIX. To produce muscular contractions, it is sufficient that the nerve be touched with any solid body in the manner above related. This method of producing contractions, by successively touching contiguous points of a small extent of nerve, em- ploying only a single body which has no connexion with the muscles of the leg, appeared to afford a favourable opportunity for examining the principle of this excitation ; that is say, of ascertaining whether it causes contractions through the intervention of an agent altogether unknown to us, or whether it does so by means of electricity, mechani- cally excited. My first researches were directed to discover, whether any difference of action resulted from the use of different exciting substances, whilst all the other conditions re- mained sensibly the same : I plainly saw that iron and zinc produced far less vigorous contractions than other metals, but I was unable to establish in a satisfactory manner, the scale of gradation. I could not even hope to do so, for variations in the state of the animal, occasioned differences in the contractions, under the influence of the same exciter, as great, or perhaps greater, than those which depended- on the nature of the metals employed. I was satisfied with having ascertained, that these ex- citers sensibly differed among themselves, and gave up the idea of a scale, which the subject would hardly admit ofi and which, moreover, would not directly lead to the object which I had in view. The question in fact, as before stated, was to determine whether in the preceding experiments, the muscular con- tractions were occasioned by an agent altogether unknown to us, or whether they were effected by electricity, which is developed every time one body exerts a mechanical action on another. APPEN D1X. 31 1 If electricity produced by the contact of the exciter with the nerve, were really the cause of the contractions, we might by greatly diminishing the quantity of electricity in the nerve, either sensibly diminish, or altogether suspend, muscular contractions. Now, these effects may be pro- duced by varying the conducting power of the substance placed under the nerve. Thus, when the nerve maintains its natural relations, it rests on muscle, which is an excel- lent conductor of electricity. If, whilst the nerve is so situated, it be acted upon by a given quantity of electric fluid, this will be divided between the nerve and the mus- cle, and thus there will be a diminution of the excitation of the nerve, and of the intensity of the phenomena resulting from it. If, on the contrary, we place under the nerve which we wish to excite, a non-conducting body, the whole of the electricity will be concentrated upon the nerve, and we shall obtain from the fluid the full effect which we are desirous of producing. This precaution is had recourse to in galvanic experiments, when it is wished to excite muscu- lar contractions by very small quantities of electricity ; such for instance, as are produced by the contact of two metals. To ascertain the respective influence of the insulation, and non-insulation of the nerve, the comparison must not be made without giving attention to the state of the ani- mal. If the animal be very fresh and excitable, the contrac- tions will, in both cases, be so strong that the difference will not be perceptible : for no conclusions can be drawn from the comparison, if motion takes place in the limb, under circumstances the most unfavourable, since we should then be commencing almost where gradation ceases. On this account, it is proper to wait till the animal is so ol-i APPENDIX. far exhausted, that no muscular contractions, sufficient to move the limb, can be excited by the action of two metals on the nerve whilst it is resting on muscle. We may thus obtain the simple contraction of the muscle without loco- motion, or even suffer muscular contraction to cease. If, in this state of things we place a non-conducting body, as a piece of glass or oiled silk, under the nerve, and then establish the circuit by means of two different metals, we immediately cause the agitation of the limb. This fact, and the principle on which it depends, being well established, the next step was to ascertain, whether in the preceding experiments, in which the nerve was touched with only one body, and no circuit was formed, the muscular contractions were to be referred to the action of the same cause. It will be remembered, that a slip of oiled silk was placed under the portion of denuded nerve. A comparison was now to be made between an animal so prepared, and another in which the nerves, instead of being insulated, reposed on the subjacent flesh. I made use of small rods, with which I easily excited contractions, when I drew them from above to below, along the portion of de- nuded nerve, which was supported by the oiled silk ; but I was unable to excite them when I passed them along the nerve of the other animal, in which they were not insu- lated. Frequent repetitions assured me, that the want of effect did not depend on difference in the degree of con- tact ; I tried the experiment on many animals of the same species, lest there might be anything in individual pecu- liarity. As in the one case the nerves were brought farther into view, and kept somewhat tense and even with the sacrum, by means of the slip of oiled silk, whilst in the other they had no such support, I restored the parity of position, by placing under the unsupported nerves, a portion APPENDIX. 313 of muscle, corresponding to the slip of oiled silk, as well in size as mode of insertion, and still was unable to produce contractions by treating the uninsulated nerve, whatever was the material of the rod employed as the exciter. The difference was rendered still more striking, when instead of making the comparison between two individuals, it was made upon the same animal. After having in vain at- tempted to produce contractions by contact of a nerve rest- ing upon muscle, I found that they might still be induced, if the oiled silk were had recourse to, and I was able to command their alternate appearance and disappearance, by using sometimes a non-conductor, and at others, a con- ductor for the support of the nerve. The manipulations which cannot be avoided, in making these trials, exhaust the nerve if they are too often re- peated. The difference is here as marked as possible. So decided a contrast as this was not necessary ; a less, would have sufficed, provided it were really manifest. The reason is not obvious, why contractions should not sometimes be produced when the nerve is not insulated, since in galvanic experiments, the quantity of electricity, elicited by the con- tact of two metals, will or will not produce contractions, according to the state of vitality of the animal, which not merely differs in different individuals, but varies in the same individual at different moments. This extreme of contrast in the effects, at first very satisfactory, as more strongly exhibiting the influence of the respective states, and throwing light on the nature of the cause, seemed, on a closer view, to prove too much, by uniformly exhibiting the same difference. I wished to be able sometimes to produce contractions by touching the uninsulated nerve, as happens in ordinary 314 A P I? E N 1) I X . galvanic experiments, in which the contact of two metals is employed, though they might be expected to be less marked than in the latter case, since my method of excita- tion was one of inferior energy. I at length succeeded in this point. In observing the difference of effect in touch- ing an insulated nerve, more or less rapidly, I discovered that contractions were the most constantly produced by a quick and light touch. Having found that I produced contractions more easily by increasing the rapidity of the taction, I made trial on an animal whose nerve was not insulated, and frequently ob- tained slight contractions. In the preceding experiments, choice has been made of the extremes from amongst the good and the bad conductors, suitable to be placed under the nerves, for it is necessary that they should lie on a soft material, in order not to be irritated, and compressed between two hard bodies. Thus, the slip of muscle, and the piece of oiled silk, are both soft and flexible, but the one is the best conductor, and the other the best calculated to insulate ; they, therefore, offer the most favourable conditions for obtaining distinctly, marked, but opposite results. Notwithstanding the diffi- N • culty of obtaining appreciable differences, when employing substances of intermediate properties, I did not restrict myself to the two before-mentioned. Having prepared a frog, in the manner already described, I placed under the sciatic nerves, a piece of the skin of the animal, and under those of another, I introduced a slip of moistened paper, and perceived a marked difference ; when, in the same manner, and with moderate quickness, I alternately touch- ed the nerves, first of the one, and then of the other. The frog, whose sciatic nerves were supported by the piece of skin, remained motionless, whilst the same degree of tac- APPENDIX. 315 tion applied to the nerve, resting on moistened paper, pro- duced contractions of the muscles. To find out whether the difference of effect was referable to the different con- ducting power of the slips placed under the nerves, I in- stituted by means of galvanic experiments, in which I employed two metals, a comparison between the conduct- ing power of the skin of the frog, and that of the moistened paper, and ascertained that they differed essentially. The frog’s skin conducted much better than the moisten- ed paper, which is but an imperfect conductor. It is need- less to enter into the detail of these experiments, M. de Humboldt having already established the fact, that the conducting power of animal substances, is superior to that of vegetable matter in its recent state, and having shewn that this difference does not depend on the water which they contain, but on the nature of the organized structures themselves. These experiments are easily conducted ; they are founded on well known principles, and they appear sa- tisfactorily to prove that, cseteris paribus, the muscular, contractions, produced by the contact of a solid body with a nerve, are much less considerable, or even wholly ab- sent, when the nerve, instead of being insulated, is in communication with a good conductor, and it would seem to follow as a legitimate conclusion, that these contractions are dependent on electricity. 31G ON ATMOSPHERIC ELECTRICITY. BY M. POUILLET. Various theories have been formed by meteorologists to ac- count for the electricity sensibly present in the atmosphere. Of these, Volta’s was, perhaps, the only plausible one. That philosopher was induced to believe, that bodies, in passing from one state to another, undergo a change in their electric condition, and supposed that the electricity lost in storms, was constantly being renewed by that pro- duced by evaporation perpetually going on from the surface, as well of the land as of the water. The recent and interesting researches of Pouillet, were instituted, not merely to ascertain the truth of the Italian Professor’s hypothesis ; he was also desirous of discovering the efficacy of another cause, which he believed to be of no small importance in the production of electricity, and of bringing to proof a theory of his own, relative to the dis- tribution and accumulation of this principle in the atmo- sphere. Numerous and various experiments have brought him to the conclusion, that the mere passage [of a body, from the solid form to a state of vapour, is unaccompanied by the development of electricity, that the result is similar, when vapour is condensed into the liquid, or solid form. He conceived that Volta, though too accurate an observer to be mistaken as to the fact of the presence of electricity in his experiments, was, nevertheless, deceived as to the cause of its production, by the formation of carbonic acid, which mixed with the vapour of water, and complicated his experiments. In 1782, Volta, Lavoisier, and Laplace, shewed, that electricity was developed during chemical action, but as APPENDIX. 317 experiments relating to this point, are liable to afford dif- ferent and contradictory results, from slight differences of circumstances, the question has been regarded as undecided. It became, on this account, an object of special attention with M. Pouillet. He finds that in the combustion of charcoal, there is an unequivocal production of electricity, that the acid produced is in the positive state, whilst the charcoal always becomes negative. It is necessary, in order uniformly to obtain the same result, that the combustion should take place only at the upper part of the piece of charcoal, and by no means extend over the whole of it ; otherwise the contact, both of the charcoal and of the car- bonic acid, with the plate of metal destined to receive the electricity, will render the experiment irregular. To dis- cover whether the electricity, rendered evident in the pre- ceding experiment, was to be attributed to chemical action, or to the conversion of the charcoal from the solid to the gaseous, he examined the flame produced by the combus- tion of hydrogen. The external part of the flame con- stantly exhibits vitreous, and the interior resinous elec- tricity. Thus, by the act of combustion, the combustible becomes electrified negatively, and the body which is ac- tually burning, becomes positively electrified, whilst a trans- fer of electricity is taking place between the molecules, which are combining, and those which are about to do so. This fact is supported by a great number of experiments on the combustion of phosphorus, sulphur, the metals, alkohol, ether, fat substances, and vegetable matter. As plants during vegegation exert a chemical action on the atmosphere, sometimes converting its oxygen into car bonic acid, and at others, decomposing the carbonic acid already existing in it, the idea suggested itself, that if electricity were developed in the process of vegetation, their very extensive operation would warrant one in attri- 318 APPENDIX. buting to them a considerable portion of the electricity of the atmosphere. To investigate this subject, Pouillet examined the vege- tation of seeds in an insulated situation, having a condenser connected with the soil. Till the germs appeared at the surface, no signs of electricity could be detected, but as vegetation advanced, it became very evident. For the success of this experiment, it is necessary that the air should be in a state of considerable dryness; when this does not happen to be the case, the apartment must be ar- tificially dried by quick lime or some absorbent. It is obvious, that the soil could not acquire one electric state, without the opposite state, in a corresponding degree being communicated to the atmosphere. If, then, a languid vegetation, on a surface of five or six square feet, be capable of producing very decided effects, may we not reasonably conclude, that the influence of the same cause, operating over a large portion of the surface of the earth, is fully adequate to the production of many of the phenomena, which we observe.. A second memoir, by the same author, carries this subject still further, and exhibits other causes besides the process of vegetation, which contribute to supply the atmosphere with electricity. In the first memoir he had shewn, that when two bodies combine, electricity is developed ; in the second he proves, that similar phenomena attend the sepa- ration of bodies which were previously combined, and he applies this fact to the numerous instances of decomposition which nature is spontaneously producing on the surface of our terraqueous globe. Pouillet, in his experiments connected with this inquiry, employed two processes — the first resembles that adopted by Saussure, in his experiments on evaporation, and consists in connecting one of the disks of the condenser with the APPENDIX. 319 heated vessel, in which the subject of the experiment is to be placed. By the other process, the heated vessel is dis- pensed with, and he makes use of one of Fresnel’s large lenses, to heat the body whilst it rests on a plate of platina. It should be remarked, that when vessels of copper, iron, or of other materials, on which the substance under exami- nation can act chemically are employed, the result will be a complication of effect, by which the phasnomenawill some- times be heightened, and at others neutralized. The results of these experiments are, 1. That by mere evaporation, whether rapid or short, no signs of electricity are produced. 2. That evaporation from an alkaline solution, however recent, whether it be of soda, potass, baryta, or strontian, leaves the alkali electrified positively. 3. That when other solutions, either saline or acid, are employed, evaporation leaves the body which was combined with the water, electrified negatively. Of the numerous saline solutions which were essayed, that of muriate of soda was naturally the one which excited the greatest interest. It formed no exception to the rule. Hence it can hardly be doubted, that evaporation from the surface of the sea forms one of the most important sources of atmospheric elec- tricity. Even lakes and rivers must have their influence, since their waters are never perfectly pure. 320 EXTRACT FROM AN ESSAY ON SOME OF THE PHENOMENA OF ATMOSPHERIC ELECTRICITY. BY LUKE HOWARD, F.R.S., &c. Read before the Askesiun Society in 1800. From an attentive examination of Read’s observations, I have been able to deduce the following general results. 1. The positive electricity common to fair weather often disappears, and yields to a negative state before rain. 2. In general the rain that first falls after a depression of the barometer is negative. O' . 3. Above 40 cases of rain in 100 give negative electricity, although the state of the atmosphere is positive before and afterwards. 4. Positive rain in a positive atmosphere occurs more rarely; perhaps 15 times in 100. 5. Snow and hail unmixed with rain are positive almost without exception. 6. Nearly 40 cases of rain in 100 affected the apparatus with both kinds of electricity ; sometimes with an interval in which no rain fell, so that a positive shower was suc- ceeded by a negative, and vice versa; at others the two kinds alternately took place during the same shower, and it should seem with a space of non-electric rain between them. The regularity with which the latter phenomena some- times occurred, seem to furnish a clue for explaining some of the preceding cases, and indeed for constructing a hy- pothesis of local rain. I shall submit to the consideration 9 HibUrheS by S.l/u/A/ey. 32. J7eet Street . Octr IS32. APPENDIX. 321 of the Society my conjectures, in the confidence of their meeting with a candid examination, and on this account I ought to add, that the latter part of my investigation of Read’s Journal has been performed with this supposed clue in my hands ; that I have met with some facts to which it is not applicable, and am, therefore, willing to distrust its guidance, except on those points were it applies directly to the phenomena. The members may do well to compare what I shall advance with the Journal at large, since ob- jections may occur to them which escaped me. Let fig. 1. represent the area on which a local shower falls a. being a certain portion in the centre in which the rain is charged positive; b. b. a surrounding portion in which the positive charge terminates, and which may be considered as occupied by non-electric rain; c. c. the re- mainder of the area surrounding the two former portions, and occupied by a negative charge, which also extends into the surrounding atmosphere, e. e. to a distance propor- tioned to the intensity of the central positive charge. The non-electric boundary of the negative charge is represented by the line, d.d. d.d. Without this line, the atmosphere is supposed positive as usual when free from clouds. In a shower so constituted, the electric signs obtained by obser- vations made in a single and fixed station, (as Read’s were,) would be subject to the following variations. 1. The central area remaining the whole time over the instrument, the observation would be positive ; and 2. The circumferential area doing the same, it would be negative. Many cases in Read will be thus explained, and it is favourable to the hypothesis, that the positive observations are to the negative nearly as 1 to 3 ; but, on the other hand, this does not account for the fact of several showers being negative in succession, nor for the relation Y 322 A PPEN DIX. which seems to obtain between depressions of the barometer and negative rain. 3. The rain beginning with the central area over the instrument, and ending with the circumferential, the obser- vation would be first positive, then negative after an inter- mission of the electric signs. 4. The circumference being first examined, and the rain ceasing by expenditure during the charge from the centre ; the order would be the reverse of 3. 5. The cloud passing over in the zenith of the appara- tus, and the latter describing under it the line f. f., all the appearances would agree with those cases in which a shower commencing with negative electricity, shews itself to be positive in the middle and terminates as it began, with negative. 6. But the line which the apparatus may be considered as describing under the cloud, in consequence of irregu- larities either in the motion or form of the latter, may re- semble the curve, g. f. ; and after having entered the shower or commenced within it, may pass and repass the non-electric boundary several times during its continuance. It may also happen to commence or to terminate in the latter. This will serve to explain some of the most irregu- lar cases in the Journal. 7. It frequently happens, that the apparatus is charged in consequence of rain falling at such a distance, that not even the skirts of the shower come over it. This is par- ticularly the case in thunder storms, and the phsenomena are such as ought to take place, according to the hypothesis, when the centre of the mass of clouds and rain (which elec- trically considered form one aggregate) passes at a certain distance from and parallel to the line, f. k., on which we now suppose the apparatus to be. The latter then loses its positive charge at i., and presently acquires a negative, which APPENDIX. 323 becomes more intense as the rod enters further into the ne- gative area, and dies away as it quits it, till at k. it be- comes extinct. 8. If the station of the observer, during a thunderstorm, happened to be in any part of the circle, d. d. d. d., he might be unable, if the time devoted to the observation were short, to obtain any signs whatsoever from his apparatus, although he might both see and hear the successive discharges in the horizon. I have witnessed such an occurrence myself, and I sus- pect that what Read has noted under June 22, 1790, is from the same cause. The centre of the storm in this case, appears to have been about Salisbury, distant 80 miles. When we consider the elevation which was necessary to render even the extremity of this storm visible at Knights- bridge, we shall not find this distance too great for the semidiameter of the total area in which its effects might be sensible with a good instrument. To some of the cases these explanations seem clearly appli- cable; in others there is room for correction by future observa- tions, which would be far the most instructive if conducted in concert, by several persons at different stations, within the compass of a few square miles. It will be readily seen, that I have made the accumulation of positive electricity in a certain portion of the atmosphere, the basis of the whole system. The remainder follows as a necessary consequence from the known laws of electricity. But the production of positive electricity is not necessarily confined to the centre of an aggregate of clouds, nor its effects to a lateral direction only. Cases may occur in which one extremity of the ag- gregate may be positive, and the other in consequence, negative ; there may be positive electricity in a certain stra- tum of the atmosphere, and from hence may result v 2 a ne- 324 A PPEN D1X. gative counter-charge in a contiguous stratum above or below. In continued rain such a distribution most pro- bably obtains, but we must have more observations to be able to prove it. Our present object is to shew how a local shower is organized, and if possible to trace its immediate origin to electrical causes ; for it is in vain that the principles of chemistry alone are appealed to in this case. Let us see therefore how it happens, that the centre of a shower is often strongly positive. The clouds originate from vapour, which is first formed in contact with the earth. It is not therefore then electrified, except the surface on which it is formed be at the time super-induced. But the latter is the proper effect of impending clouds, and although a truly electrised vapour may be thus formed, and being condensed, may constitute a part of the system of clouds in a thunder storm, yet our present enquiry goes further: we want to account for the super-inducing charge. It would be a difficult undertaking to ascertain by expe- riment the electrical state of vapour, and of the surface on which it originates in the natural process. Experiments have been made on insulated substances at high tempera- tures, the results of which, even if more conclusive, would be quite inapplicable to this case. I shall therefore offer some conjectures on the origin of atmospheric electricity, which will in the first instance proceed on the supposition that vapour is originally non-electrised. A body in order to be charged must be first insulated, and the charge will continue during perfect insulation, but the latter seems unattainable. There is always a small degree of conduct- ing power in the very atmosphere when at the maximum of dryness, and this is greatly augmented by what is called moisture, by which I understand, diffused and suspended (not elastic and gaseous) water. We can scarcely imagine a body more perfectly insulated APPENDIX. 325 than the first particle of water which, separating from va- pour that has ascended into the higher atmosphere, begins to obey the law of gravity. There are two sources from whence such a particle may obtain an electric charge, viz., the surrounding air, and the vapour out of which it was formed, and which may, though in itself non-electrified, afford to the water, now reduced many hundred-fold in vo- lume, a real positive charge. Appearances, likewise, are much in favour of the opinion, that the precipitation of water in the higher atmosphere is sometimes effected by a double affinity, in which electric air and gaseous water are mutually decomposed, the former seizing the caloric, the latter the electric fluid. At all events we are certain of the fact, that clouds are insulated and charged conductors. Franklin supposed, that clouds arising from the sea were positive, those from the land negative, and that their rencounters in the air were the cause of thunder storms. Kirwan, and others, go a little further, and say, that a positive cloud (become such in the way I have stated) may affect another with a negative state by its approach, and thus attract it to form rain. But all these explanations fall short of the phse- nomena. Had this been all the process, we should have known nothing of the electricity of rain, for a negative and positive cloud would unite in those proportions only, which should form non-electric rain. * * * * The reader who may be curious further to pursue these highly interesting meteorological considerations, is referred to a new edition of Luke Howard’s work on the Climate of London, now in the press, and in which will be found the whole of the paper of which the preceding is an extract, together with much new and important matter on collateral subjects. I have been induced to give the preceding extracts, from 326 APPENDIX. the idea that they may tend to throw some light on the very interesting, but still imperfectly understood subject of the influence of electricity upon vital phenomena. The observations of Prevost and Dumas, contained in the Appendix, relate to the supposed operations of electri- city, as an agent in some of the functions carried on within the body, and more especially in conjunction with muscu- lar contraction. The views which they contain are ex- tremely ingenious and interesting, but I must confess my- self unable fully to adopt them. The experiments and operations of Pouillet, respecting the development of electricity by the process of vegetation, led me to conclude, that a similar development must take place in the production of carbonic acid by the respiration of animals, and also by the vinous fermentation of fluids. My attempts to demonstrate the correctness of this sus- picion have not yet been successful. I hope hereafter to pursue the enquiry, and in the mean time I shall relate a few facts which seem to bear on the subject. It has long been observed that individuals of highly sensitive consti- tutions are concious of uneasiness, sometimes amounting to absolute pain, or the disturbance of function during the existence of a thunder storm ; this is by no means neces- sarily connected with fear, or other mental emotions, pro- duced by the loud sound and vivid light, or any other phenomenon cognizable to our senses. The influence of which I am speaking is frequently felt before the storm has commenced, and has occasionally been experienced by in- dividuals so far removed from the skirts of the storm, as not to be conscious of its existence at the time, except by the intimations afforded through the symptoms in question. Such cases seem to be analogous to the instance alluded to in the paper of Luke Howard, in which Read’s appa- A P P E N D 1 X . 327 ratus, set up at Knightsbridge, for the examination of aerial electricity, was influenced by a storm supposed to have passed over Salisbury. Persons who watch the habits of leeches, have frequently remarked their peculiar agitation when the electric state of the air is disturbed by storms, and it is believed by persons accustomed to the rearing of poultry, that storms sometimes have an injurious, and even a fatal influence upon eggs undergoing incubation. It is a generally admitted fact, that liquors undergoing the vinous fermentation, suffer a great disturbance in this process during the existence of a thunder storm. These facts taken together, led me to question, whether the negatively induced electricity may not have a tendency to disturb the production of carbonic acid, which Pouillet has shewn to escape in a negatively electric state. We have as yet but few well-conducted and satisfactory observations, respecting the influence of an artificially dis- turbed electric state upon living organized beings. Some observations have been made with reference to vegetable physiology, and as this may often be appealed to for as- sistance, in our attempts to elucidate the more difficult subject of the physiology of animals, it may not be amiss briefly to relate them. With respect to dead animal and vegetable matter, the experiments of electricians completely tally with what has been observed to be the effect of the electric disturbance of the atmosphere. The observations of Achard of Berlin support this assertion. They are briefly noticed in the Encycloptedia Metropolitana, from which the following- short statement is extracted. It is a well known observation, that after a storm, flesh, either raw or boiled, acquires a putrid smell, which, in the latter, is particularly acid. It is known, also, that grain 328 APPENDIX. suffered to ferment for the purposes of brewing or distilling, undergoes, during stormy weather, very sudden and per- ceptible changes. On such occasions, it is often extremely difficult to observe where the first degree of fermentation ceases. It passes so speedily that the second degree, or the acetous fermentation, takes place before one is aware of it. To ascertain, therefore, whether the electric matter, which, during stormy weather, is so abundant in the atmosphere, has any share in these phsenomena, the following experi- ments were made. A piece of raw beef was cut into three parts. One of these parts was electrified positively for ten hours without any shock ; a second was electrified negatively for a similar time ; and the third was not electrified at all. The three pieces were left in the same apartment, exposed to the same degree of heat. When examined next day, both the pieces which had been electrified appeared to be tender, but were free from the least bad smell. On the fourth day, the elec- trified flesh had an intolerably foetid smell, and that which had not been electrified began to smell a little. M. Achard repeated these experiments with boiled veal. That which was electrified had, the next day, an acid smell, and an unpleasant taste ; but that which had not been elec- trified, continued sweet for three days, and only on the fourth day began to have an acid smell. Several birds were killed by electric shocks, and others were deprived of life, by sticking a needle through their heads, and then placing all in the same temperature, they were covered with glass receivers in order to preserve them from insects. Observing the- gradual progress of corrup- tion in both sets, M. Achard plainly perceived, that it took place much sooner, and advanced more rapidly in those killed by electric shocks, than in those deprived of life by '•"V 'X. 'A APPENDIX. 329 the needle. In those also, to which a stronger shock had been given, the degree of corruption was far greater than in the others. Van Marum made a similar observation with respect to the rapid decomposition of eels, which had been killed by electricity. It clearly follows from these experiments, that electricity accelerates corruption, and that the putrefaction of flesh after a storm, must be ascribed solely to the more abundant accumulation of the electric matter at that time. M. Achard saw that this was the case in regard to several persons killed by lightning. The body of a farmer, who lost his life in this manner, between five and six o’clock in the evening, emitted next morning a very perceptible foetid smell, which in the evening was totally insupportable. Having stated these effects of electricity on dead vege- table and animal matter, which are sufficient to shew its power in modifying and accelerating chemical changes* we may now inquire after what is known of its influence when life is present. We shall commence with vegetables, in which the direct physical effects are less complicated, from their not being mixed up with what may be regarded as its moral effect on a highly sensitive nervous system. It is well known that trees may be killed by lightning, but in these instances there is so much violence and de- struction of texture, that we can draw no conclusion from them as to the influence of electricity. Cavallo, though he disputes the correctness of the statements of some elec- tricians, with respect to the influence of electricity on plants, has shewn that the balsamina impatiens is killed by shocks which are too slight to impair the structure. A branch of this plant died the day after receiving the shock — the branches of other plants survived longer. A laurel branch 330 APPEN UIX. VanMarum and Naitfne confirm the deleterious effects of electric shocks, shewing that they kill some plants and pre- vent slips from taking root and budding. If electricity in the form of shocks has the power of de- stroying vegetable life, we may reasonably presume, that a less violent application of this agent' would produce some sensible modifying effect. The first experiments upon the application of electricity to living vegetables, appear to have been made by Mainbry, in Edinburgh, in the year 1746. In the autumn of that year, he subjected two myr- tles to gentle electric action during one month, and ob- served that they subsequently put forth leaves earlier than similar trees which had not been electrified. The Abbe Nollet, Jallabert, Boze, Menon, Dr. Carmoy, the Abbes D’Ormoy and Bartholon, maintain the power of electricity as a stimulant to vegetables ; the last named experimenter, in particular, has been extremely zealous in this enquiry. He regarded electricity as a most powerful stimulant to ve- getation, and recommended its practical application in hor- ticulture, for which purpose he contrived an apparatus, called electro-vegetometer, with which he employed artifi- cial excitation. He proposed the direction of atmospheric electricity to the same object, and believed that he pro- duced some good effect by watering plants with water charged with electricity. Although there can be little doubt, that the Abbe’s enthusiasm in his subject led his imagination to the over-straining of facts, yet it is by no means improbable, that there is more truth in his observa- tions than Cavallo and Ingenhouse are disposed to admit. It has been asserted, that plants grow with encreased vigour in the neighbourhood of thunder rods. It might have been supposed, that if plants in general are influenced by elec- tricity, those plants which offer the most striking proofs of sensibility would be the most signally excited by it. Van APPENDIX. 331 Mamin was, therefore, led to try its effects on the mimosa ptidica, and on the hedysarum gy rails > but he could not detect that their movements were positively affected by it. It will be well to bear this fact in mind, when considering the motions of animals and vegetables. The fatal effects which violent discharges of electricity produce on animal life, are more notorious than in the case of vegetables. Scarcely a summer passes without nu- merous instances occurring in which man and other animals are killed by lightning. The discharge of an ordinary bat- tery is sufficient to kill insects and worms, and the shock from a tolerably large one will kill mice. It is truly sur- prising to see how instantaneously some of the lower ani- mals, which are remarkably tenacious of life, are completely deprived of it by the electric shock. I once discharged a battery of considerable size through a common earth-worm, which would in all probability have shewn signs of life long after minute division. Its death was as sudden as the shock, and the semi-transparent substance of the animal was changed like albumen which has been exposed to heat. The artificial accumulation of electricity in batteries of very large size, has been found sufficient to kill not only- rabbits, but even large and vigorous hogs, a fact which was completely proved by my friend Charles Woodward in the presence of Dr. Scudamore. It may now be interesting to notice some of the pheno- mena induced by electricity, within those limits which are compatible with life. With the hope that this short expo- sition may tend to assist, either in the extension or appli- cation of our present knowledge of the subject, I shall endeavour to class these phenomena under the following heads. 332, APPliNDIX. Electric tension — its effects on the system generally — difference of the positive and negative charge — its effects on particular functions, such as circulation, exhalation, and secretion and respiration — the effects of the transmission of shocks — of a continuous stream — sparks — aura — appli- cation. It is well known, that that state of the atmosphere which is unfavourable to electrical experiments from its being ad- verse to the insulation, and consequently to the electric tension of bodies, is also ungrateful and oppressive to our feelings; and that precisely the opposite effect is ex- perienced in clear and frosty weather, and in other states of the atmosphere which facilitate the working of electri- cal machines. We might regard these as coincident, rather than connected facts, if it had not been observed that an artificial repletion with electric fluid produced a similar effect in exhilarating the spirits, a fact for which, with many others here related, I am indebted to my friend Charles Woodward of Islington, a gentleman who has long and successfully devoted his attention to electricity. This fact conducts us to the enquiry, whether there is any difference, as far as the influence on the animal eco- nomy is concerned, between a positive and a negative charge. Here, I regret to say, that I have very little of a decisive character to bring forward, yet I may state on the same valuable authority which I have just given, that a negative charge continued for about half-an-hour, has caused an unequivocal perception of languor and oppression. Do we not find an obvious parallel to this experiment in the power- fully oppressive and sometimes distressing influence of which highly sensitive individuals are conscious on the approach of a thunder storm, or during the prevalence of a north-east wind, which is characterized as peculiarly un- APPEN DIX. 333 healthy and productive of a sensation of dryness and cold, unaccompanied by a corresponding depression of the ther- mometer? It was shewn, in the preceding article on Atmo- spheric Electricity by Luke Howard, that a highly electri- fied thundercloud is surrounded to a considerable extent by atmosphere which is in a negative or neutral state. The north-east and east winds are often in a similar condition. Except in cases of the transmission of a strong electric current through some part of the nervous system, which produces an instantaneous disagreeable, or even fatal effect, it would seem that a considerable portion of time is neces- sary for the production of anything like a sensible effect from disturbance of the electric equilibrium. Leeches, as I before observed, are said to be highly susceptible to very slight alterations in this respect. I was, therefore, led to enquire what would be the result of a great, but sudden and transient encrease of their electric tension. I was careful to avoid subjecting their bodies to the direct effect of a spark or shock. I placed several active healthy leeches in a glass vessel containing water, which being thus insulated, I kept for a little while strongly electrified positively, but without producing any sensible effect. Precisely the same result attended a negative charge. I next tried what would be the effect of converting the vessel containing water into a Leyden jar, by applying a partial coating of tin-foil out- side. Having given a moderate charge, I suddenly restored the equilibrium by discharging the jar, but I could not perceive any unequivocal appearance of uneasiness in the leeches, which remained perfectly healthy for several days, after which they were no longer watched. Although the statements which are made respecting the effects of increased electric tension upon the circulation at first appear contradictory, a little consideration will satisfyus, that these decrepancies are analogous to such as attend the 334 APPENDIX. application of other stimulants. Walker and Carpue have both recorded, that the blood flows more freely from an opened vein when the patient is electrified. The force of the circulation must, therefore, have been increased. Ca- vallo was assured by an experienced medical electrician, that in a diseased state of body, an evident acceleration of the pulse is often observed to result from the application of electricity. Van Marum took considerable pains to inves- tigate this point. Eleven persons were selected, and the experiment was repeated four times upon each, both with positive and negative electricity. These persons were placed in a room which was at such a distance from the machine, that they could not hear the noise it made in turn- ing ; they were insulated, and the pulse of each was felt when the machine was in motion, as well as when it was at rest, (which last circumstance was unknown to them,) and the beats were counted by a good observer, provided with an excellent watch. In some cases a few more beats were observed, but, on the whole, there was no important acce- leration. In general, however, there was great irregularity in the pulse, both during the time the persons were electri- fied, and during the time the machine was at rest. There can be little doubt, but that the individuals who were the subject of this experiment, were much influenced by mental emotion, and it seems very probable, that the interruption in the application of the electric influence, con- tributed to vitiate the result. The following observations on this subject were commu- nicated to Charles Woodward, Esq., by his friend F. Smith of Fordham, and are confirmed by his own experience. The pulsations were carefully watched before electrifica- tion. The electric influence was passed through each per- son without sparks, and continued fifteen minutes, after appendix. 335 which, while the fluid was still passing through them, the pulsations were again noticed. Patient. Pulse at first. Reduced to 1 80 75 2 64 51 3 90 76 4 66 61 5 70 60 6 74 62 7 65 58 8 100 90 These individuals were all males. Electrification for less than ten minutes did not in gene- ral appear to affect the pulse. It may be imagined, that in the subject of this experi- ment, the previous apprehension had raised the pulse, which subsided when they were quietly placed on the stool. This objection appears to be met by two case.s of ague, in which the pulse was soon reduced by electricity thirty beats per minute during the paroxysm. As one of these instances occurred in the electrician’s own person, it cannot be supposed that the pulse had been raised by trepida- tion. When the Abbe Nollet had shewn, that the evaporation of volatile bodies is promoted by an electric charge, it be- came a matter of curiosity, whether it had any influence on the insensible perspiration of animals. Many experi- ments were made which seemed to prove, that that func- tion was increased whilst the animals were electrified. Van Marum, who afterwards undertook to examine this question, came to a different conclusion. 336- appendix. For the purpose of ascertaining the increase of insensible perspiration, lie employed a very delicate balance; one scale of which was insulated by means of a silk cord. On this scale he placed a boy, eight years of age, connected with the conductor; and the balance was brought to a state of equilibrium. He then ascertained the loss of weight sustained in half an hour, before the boy was elec- trified, and found it to amount to 280 grains. By a simi- lar experiment on another occasion, the loss of weight, before being electrified, was 330; and after exposure to electricity only 310. A girl of seven years old lost, before being electrified, 180; and when electrified, 165 grains. A boy of eight years and a half lost, before being electri- fied, 430; and when electrified, 290 grains. Another of nine years unelectrified, 170; electrified, 240. As the last boy was exceedingly quiet during the experiment, it was thought that the increase was the consequence of elec- tricity ; on this account he was several times subjected to the experiment, and the results were: in the unelectrified state, 550 ; in the electrified, 390, 300, 270, 550, and 420. If we consider these experiments of Van Marum, in con- junction with the light thrown on the subject of perspira- tion, by the observations of Dr. Edwards, given in this volume, we shall have no difficulty in perceiving, that they by no means warrant the inference, that increased electric tension is unfavourable to perspiration. It will be remem- bered, that it was proved by Dr. Edwards’s experiments, that the loss by perspiration in a given period, progressively diminishes as the body perspiring recedes from the point of saturation. Circumstances may for a time produce appa- rently contradictory results, which, when investigated, ra- ther confirm than invalidate the principle. It can scarcely be doubted, that electricity promotes evaporation from the A I* PEN nix. 337 surface of inanimate bodies, but it must still be regarded as an undecided question, in what manner it effects the insensible perspiration of animals. From facts recorded by medical electricians, it appears that some secretions are promoted by electricity, but it has been found, both in Germany and in this country, that the excessive secretion of urine in diabetes has been repressed by electricity applied in the form of galvanism to the loins. The function of absorption appears, in some cases, to be salutarily excited by electricity. It has been successfully applied to tumours, with a view to promote their dispersion. In one case, which occurred to Philip Smith of Fordham, sixteen applications of electricity, employed for another object, had the gratifying effect of removing a chronic hydropic affection. Even ovarian dropsy, than which no variety is regarded as less under the controul of medical means, seems, in some in- stances, to have yielded to its influence. Although there is no function more important to life, or more intimately connected with other functions than respiration, and none which possesses so decidedly chemical a character, and consequently bears so obvious a relation to the changes of inorganic matter, to which electrical phenomena are acces- sary or concomitant ; yet, we are still perfectly in the dark as to the relations which may exist between this function and electricity. I have already mentioned this subject as one which I have in vain wished to investigate, and, there- fore, have little to offer respecting it. There is, however, one circumstance which I may mention, not only because it tends to shew that a connection between respiration and electricity is not purely imaginative, but because it may serve as a hint for one of the modes in which the enquiry may be pursued. It has been asserted, that hens hatch their eggs after a shorter period of incubation, when they and their nest have been insulated and kept in a state of z 33S APPENDIX. state of increased electric tension. Now the only function by which the eggs are in relation with surrounding objects, is that of respiration, carried on by the vascular membrane within the shell, through the pores of which the atmo- spheric influence is exerted. The passage of the electric influence is probably pro- ductive of no less important effects on the animal economy, than increased tension. In some instances their effects may be combined. The sensation produced by the electric shock, is the most notorious and perceptible effect which electricity produces in the system, yet it is so transient, that except in those cases in which it has been of sufficient force to be injurious to life, it is generally limited to the inappreciably short interval occupied by the discharge. The rapid succession of sparks received at one part of the body, and given off at another, the individual being insulated for the purpose, is an approximation to a continued current of electric influence, and though much milder than the shock, as far as the feelings are concerned, exerts a much more powerful influence on the system and is of far greater ser- vice as a medical application. This is still more strikingly the case, when the sparks, whether given or taken, are re- duced to a very small size, though encreased in number by bringing the metallic ball nearly into contact with the per- son, a thin piece of flannel alone intervening between it and the skin. It is in this form that the electric current has been long and very successfully employed in a variety of maladies by C. Woodward. The electric aura affords the means of applying a yet more equable and continuous current, the effects of which appear to be proportionately superior, notwithstanding they are even less perceptible to the senses. The reality of this influence is confirmed by phenomena connected with dead inorganic matter, as well as by its effects on parts of the appendix. 339 living system. All attempts to make the compass deviate from the magnetic meridian by means of common electri- city, as CErsted had done by galvanism, had been unsuc- cessful, until C. Woodward conceived the idea of applying electricity in the form of aura to the wire destined to pro- duce the deviation. This plan he found completely answer, and repeatedly exhibited it some time before Dr. Wollaston, by whom the fact has been announced, appears to have had his attention arrested by it. The hand of a lad had been long permanently and powerfully clenched in consequence of a blow from a hammer. Every mode of treatment com- pletely failed, until the electric aura was applied, which effected a perfect cure.* The transmission of the electric influence seems to act directly upon the nervous system of animals. I have al- ready alluded to the sensation which it excites, and which is manifestly to be referred to the nervous system. Defects in the senses of feeling, seeing, and hearing, and distressing neuralgias, have been relieved by its influence on that sys- tem. Through the medium of the nerves, the electric cur- rent acts powerfully on the muscular system. This is most conspicuously seen in recently dead or expiring animals, but it is also evident in many cases of paralyzed limbs. Some of the phenomena connected with this part of the subject are so striking, that it is by no means surprising that some physiologists should have regarded the natural influence of the nerves in the production of muscular motion, as of an electric character. Porret, Prochaska, Dr. Wollaston, and others, have endeavoured to shew by analogy, that secre- tion is effected by an electric current. Dr. Young has proposed a similar theory. Drs. Wilson Phillip and Hast- ings have laboured to prove, that the fatal effects of the * See a cast of this contracted hand in the Museum of Guy’s Hospital. z 2 340 Al'PEN D1X, division of the eighth pair of nerves depend on the con- sequent interruption to secretion, which the application of electricity to the divided nerves will in a great degree re- store and maintain. Dr. Milne Edwards opposes this view, and contends that an equally advantageous effect is pro- duced by the mere mechanical excitation of the divided nerves. The following fact is of no less practical importance than physiological interest. I am informed by my friend C. Woodward, that it is an essential rule in the application of electricity to medical purposes, that the current should pass in the direction from the trunk to the extremity of the affected limb. In this way it often affords prompt relief ; but if the current be reversed, the evil is aggravated. The experiments which I have next to relate appear so truly wonderful that, but for the good authority by which they are supported, I should feel unwilling to give them a place here. The remarkable results which accompanied them can scarcely be explained as coincidences, and they appear to open the way to new and important inquiries ; but nu- merous observations and experiments must be made before we can be warranted in drawing any certain conclusions on the subject. P. Smith of Fordham, to whose experiments I have already alluded, having relieved numerous patients, labouring under gout, rheumatism, and other painful affec- tions, was induced to try the effects of electricity upon in- termittent fevers. He intended to employ it as the cold stage was coming on, but his first patient having mistaken the time of the accession of the fit, he did not apply it until the hot stage had commenced : he insulated the man, and caused him to receive sparks at the epigastric region, while he took them from him along the course of the spine ; the pulse was speedily reduced thirty beats per minute. The APPENDIX. 341 next patient was electrified on the coining on of the chill, which it immediately checked ; nevertheless the hot stage ensued, when electricity was again applied, and, as in the former case, it reduced the pulse thirty beats there was no return of the paroxysm, but the application of electricity was repeated for some days. Another case of ague, which had lasted four months, and obstinately resisted bark, arsenic, and other medicines, was quickly cured by a few applications to electricity. The most extraordinary circum- stance remains to be mentioned. P. Smith himself had held the ball, with which he took sparks from his first patient, during the hot stage. In the same evening, he found himself unwell; but had no suspicion of the nature of his complaint, until the recurrence of the paroxysm con- vinced him that he had become the subject of ague. He allowed these to recur to the seventh time, before he at- tempted the cure by electricity, which was speedily effected, being the second case already alluded to. As he. had never been the subject of ague, and had not been more than usually exposed to causes calculated to give rise to it, he felt persuaded that it had been communicated to him by elec- tricity from his former patient. In order to ascertain this, he was desirous of trying ex- periments on some persons labouring under a disease which was inflammatory, but not considered infectious ; he, there- fore, had one of his men vaccinated. On the seventh day, the man was placed on the insulating stool, and connected with the positive conductor; a small incision was made with a lancet in the pustule, and an incision was also made in the arm of a lad with a new lancet ; a wire four inches long was passed through a glass tube, one end of which touched the pustule on the man’s arm, and the other the incision on the boy’s arm — the electrification was continued for eight minutes, when the boy was removed. His arm was 342 APPENDIX. daily examined, and it was found, that he was as com- pletely vaccinated by electricity as any person could be by the usual mode. My friend afterwards endeavoured to communicate the virus to two girls, by passing the electri- cal fluid from the pustule on the boy’s arm, who had been vaccinated by electricity, to incisions made in theirs. For three days the medical gentleman supposed it had taken effect; but, on the fourth day, all appearances of vaccina- tion died away. These girls were, however, afterwards vaccinated in the usual way in four places, two of which died away, and the other two took but very slightly. My friend Charles Woodward afterwards repeated this experi- ment upon an infant, the child of one of his friends, but with this difference, that he did not allow the conducting wire to come in contact with the child’s arm. The electric fluid was consequently transmitted in the form of small sparks. The disturbance which these produced, though trivial, prevented the application from being prolonged for the full time, which my friend would have wished ; inflam- mation however succeeded, and, until the sixth day, was such as to induce the medical attendant to believe, that the vaccination had been complete; from that day, however, the pustule died away. Circumstances, which it is wholly foreign to this work to relate, interrupted the continuance of the research. The facts already related have come to my knowledge at too late a period to allow of my pursuing the investigation; but I trust, it will not long continue neglected. D1SSERTATI0 PHYSIOLOGICA INAUGURALIS DE ABSORBENDI FUNCTIONE; QUAM EX AVGTORITATE ORNATI "VIRI, D. GEORGH BAIRD, ACADEMIAE EDINBURGENAE PRAEFECIT; NECK ON AMPLISSIMI SENATUS ACADEMIC! CONSENSU , ET NOBILISSIMAE FACULTATIS MEDICAE DECIIETO; PRO GRADU DOCTORIS, SUMMISQUE IN MEDICINA HONORIBUS AC PRIVILEGIIS RITE ET LEGITIME CONSEQUENDIS ; EltUDITOEUM EXAMINI SUBJICIT THOMAS HODGKIN, ANGLUS, SOC1ETATIS REGIAE MEDICAE EDINENSIS, ET PIIYSICAE GUYENS1S SOCIUS. “ To Si ottojq iyivtro roiovrov, iav iTTLXtipyvyg ZtjTeiv dvairrSryrog, (pui- paSr/ay icai ri)g 1X. ■ 353 l Hie, et in sequentibus excerptis non tantura actionem, sed instrumenta quoque indicat. “ Kai yap ai ifiXtfltg,, ai he ti]q vp^vog, Kai rwv ivTtpiov, tig a ^vXXtytTai ra airia, nai ra 7 rora, intiSciv SrtppavSi) raura, eAkoucti to XtnroTaTOV, ko.1 to vyporaTOv, to Se tt a^urarov avTtov KUToXtintTai, Kai (vtTai KOirpog, tv toIulv ivrtpoiai rottxt k arw.” Item “ Etai e k al ano rijg KoiXpg, (f>Xtfitg, iiva to criopa, ncipnoXXai re icat TruvTo’iai , St’ uiv i) Tpoipp tv Tip trivpuTt 'ipytrai Dubi- tare non possumus quin Ekasistratus vasa chylifera vi- disset quum dixerit — “ ’Ev yap Tip SiaiptioSai to intyaa- Tpiov, apa Tip irtpiTOvaup, Kara to pttrtVTtpiov apTppiag iS?tv Eort traipivg, ini piv rwv vtioSpXijJV ipiipivv, yciXaKTog ■\ / 7 T/*i)ptig. Nee magis haec vasa Herophilum, quanquam il- lorum finem non intellexit latuisse videntur, ut sequentibus Galen i verbis apparet. “ Iljowrov piv yap, navTl Tip ptatvTtpup ipXtfiag inoipatv 1%'iag civaKtipivag avTip, tt} 5pt\pu Tutv ivTtpivv, pi) ntpaiovptvag tig to pnap * uig yap teat H poifnXog tXtyev, tig aStvivSr} Tiva crivpaTa TtXtvTivaiv avTag ai ipXtfitg, Tuiv aXXiov enraoiov ini Tag nvXag avaiptpopt- viov. — Galenus quoque corpus absorbere docuit, et ab- sorbendi functionem in quadam attractione consistere exis- timavit. Cuti etiam hanc facultatem tribuit, dicit enim — “ "Qcrnsp, Stct twv tig to Sippa ntpaivopivivv oTopaTivv, sk- Kpivivm piv tL,io 7rav oaov ciTpioStg Kai KanvaiStg ntp'iTTwpa, ptTaXapfiavovm Se tig iavTag, Etc row npiiyovTog ppag atpog, oiiK oXiypv polpav' teat tovt taTi to npog lnnoKpaTOvg Xtyoptvov wg etc nvovv Kai tlanvovv ianv oXov to aiopa.” — Arterias quidem illam aliquanto habere suspicavit “ 'Arpov piv ovv txpvaai, teat nvtvpa teat Xtnrov alpa, Kara ralg Siaa- Tuaug sXkhv ai aprrjptat, rov tc ara rr)v k oiXiav Kat ra tVTtpa ntpityoptvov \vpbv, p ov$i bXwg p navTanam ovvtnitrnuiv- rai fipaxu.*” In saeculis ignorantiae quae postea secuta sunt medicina et physiologia cum aliis scientiis communis ruinae parti- cipes fuerunt. Harum reliquiae ab Arabibus conservatae, potius quam excultae fuisse videntur. Solebant medici Arabes ad cutem admotis medicamentis uti, cum vel urinam, aut vomitum excitare, vel ventrem movere, vel su- dores elicere vellent. Nec ita fecissent nisi cutem sorbere existimassent. Illos tamen ad hanc medendi rationem _ * In nostris diebus, opinio huic simillima, a Cl. Prociiaska esse renovata videtur. — Vid. cap. viii. A A 354 APPENDIX. iatralepticorum exemplo adductos fuisse verisimillimum reor. Reviviscenlibus tandem scientiis, anatomia cultoribus non caruit. Anno molxiii Eustachius ductuni tboracicum primus invenit, sed nescius illius naturae, venam albam thoracis nominavit. Anno mdcxxii Asseli.ius, Italus, vasa chyli- fera diu ante ab Herophilo et Erasistrato visa, sed parum cognita, animadvertit. Hie vero vivis animalibus dissectis, ista vasa acerrime scrutatus est, et eorum func- tionem, chyli scilicet absorptionem, sagacissime assecutus. Ea tamen in liomine oculis cernere, ut cupiebat, nunquam ipsi datum est. Hoc autem contigit feliciori Veslingio, qui etiam in ductum thoracicum vasa chylifera secutus est primus. Post chylifera vasa ab Assellio deprehensa vi- ginti octo circiter annis, lymphifera, Olaus Rudbeck Suecus invenit. Cu.m illo tamen de hoc honore certant et Jo li v i u s Anglus, anatomicus peritissimus, Danusque Bartholinus. Post hos alii anatomici haec vasa scrutati sunt, et eorum actionem conjectarunt. At tandem Gulielmus Hunter, lymphifera et chylifera vasa non nisi unum esse et integrum vasorum ordinem, per universum corpus ex- tensum, et ubique absorbendi functione praeditum com- periit. Hujus egregii physiologi discipulis Heuson et Cruickshank, horum vasorum in corpore humano dispo- sitionis scientiam praecipue debemus. Heuson quoque et J. Hunter haec vasa in avibus, in animalibus amphi- biis, et in piscibus primi invenerunt, et exploraverunt, nisi forsitan Bartholin us in pisce Diodonte, ex familia Gym- nodontium, Cuvieri, eorum vestigia prius aspexerit. Nec tacendum est Alexandrum Monro secundum, qui tunc temporis in hac urbe florebat, et anatomiam comparativam magno fructu excolebat Gulielmi Hunter et discipu- lorum observationes, non multo post, iterasse. Quinetiam cum illis de primae inventionis laude certavit, quam tamen hac contentione, non adeptus fuisse videtur. Dum haec de vasis chyliferis et lymphiferis agerentur, insignes physiologi Harvey, H.etK. Boerhaave, Swam- merdam, Haller et alii veterum opinionem de ab- sorbendi facultate in venis insita, et ratione, et experimentis probare susceperunt. Proinde orta est veterum fautores inter et sectatores G. Hunter notabilis controversia, de qua etiamnum sub judice lis est. A J* HEN 1)1 X. 355 Priusquam hanc controversiam ineamus, non omninb erit inutile, organa, functioni a nobis investigandae subservientia paulisper conternplari. Minimi taraen meo proposito con- venit ; nec res ipsa postulat, ut longam et completam de- scriptionem anatomicam luc proferam. Primb igitur de venis loquar. Haec vasa non aliter ac arteriae, quas et numero, et capacitate longe superant, ex duabus membranis constant, atque etiam ut aliis vasis, sic et illis circumdatur involucrum ex membrana cellulosh. Tunicae venosae, arteriosis sunt longe tenuiores, et distentu faciliores, sed et eaedem validiores, ut testatus est Win- tringham. Membrana interna tenuis, laevis, et glabra omni circuitus sanguinis apparatui, ut alii dicunt com- munis est, at alii venis dextroque cordi esse peculiarem vo- lunt. Externa, sive propria, ex fibris non circularibus, ut in arteriis, sed potius in longum dispositis constare reputa- tur, ita saltern visum est celeberrimo Bichat ; declarat tamen Macendie se nunquam hanc dispositionem reperire potuisse. Non desunt qui et arteriis, et venis, tres membranas, et vim muscularem tribuunt, at licet Hunter, Blumen- bach, Richerand, Monro, alter, et tertius, et multi alii ita docuerint, horum vasorum functio et compositio prohi- bent, ne earn opinionem amplectar. Veruntamen nec irritabilitate, nec sese contrahendi fa- cultate, venae penitus carere videntur. Bichat enim, qui venis istas facultates vix concedit, et miro quodam errore resiliendi vim illis omnino denegat, venarum contractiones se bis terve animadvertisse contitetur. Chaussier, Ma- gendie, et Adelon, has facultates in venis inesse ne- gant. Beclard autem, rectius, ut opinor, vim vitalem sese contrahendi, neque vero magnam, venis concedit, non tamen reticendum est venas cavas, ubi dextrae auriculae committuntur, et ex ea non nullas musculosas fibras ac- cipere videntur, ibidem irritabilitate manifesto non carere. Imo etiam decedente vita, in hac parte quae revera ulti- mum moriens vocari potest, irritabilitas sese postremum ostendit, et mirabiles contractiones perficiuntur, ut amicus meus vir acutissimus R. Knox M.D. praecisis squalorum thoracibus, saepius et iterum conspexit. Haec vasa, vena portae et quibusdam aliis exceptis, val- vulis ex membrana interiore constantibus muniuntur. Ubi minores venae in majores sese effundunt, valvulae plerum- que reperiri possunt, at in cursu vasorum nulla certa ra- a a 2 356 A PPEMU1X. tione ponuntur. Hae valvulae interdum arctiores sunt quatn ut officio fungantur, id quod Bichat, venae disten- tioni solummodo attribuit: longe autem verisirailius est, in talibus exeraplis conformationem esse peculiarem. Atque haec vetus sententia a Magendie et aliis hodie promulo-a- tur. Extremae venae ea sunt tenuitate, ut vix (ac ne vix quidem) illas persequi possiraus. Illarum tarnen investi- gatio ad nostram rem maximb pertinet. Docent, Soemm erin g et Prochask a extremas arterias in quaque corporis textura peculiari ratione distribui, sed quonam modo sanguis ex illis in venas transeat, videre non datur. Bichat Inc posuit peculiarem vasorum ordinera, quam systeme capillaire nominavit. At, me judice, ita innovando adeo non bonam distinctionem fecit, ut potius duos, ad minimum, vasorum ordines confudisse videatur. Antiquiores Anatomici structuram specialem, arteriis et venis intermediam imaginati sunt. Verum ex quo tem- pore Malpighi, Leeuwenhoek, Cowper, et Spal- lanzani venas arteriis continuatas ostenderunt, atque quotidianis fere experimentis venas ex arteriis injectas ma- terias accipere demonstratum est ; haec opinio suos fautores amisit. Ita sane quarundam venarum initia ostenduntur, at nequaquam exinde sequitur, alias venas non aliter originem ducere. Recentius autem Prochaska, structu- ram vasis carentem existere strenue contendit, illius tamen sententia non veterum opinionem omnino renovat, ab ilia enim non nihil discrepat. Quinetiam Chaussier et Adelon, structuram extremis vasis interpositam non reji- ciunt, neque tamen jam confirmatam habent. Venae quoque a variis intends superficiebus, et etiam a solidis corporis texturis, ut e. g. a musculis, apertis osculis inci- pere, a nonnullis reputantur, sic testatus est Kaaw Boer- haave aquam, vel ceram per haemorrhoidales venas in- jectam, in intestinorum cava exire. Narrat etiam Meckel se venas in pelvi sitas, ceram aut aerem in vesiculas semi- nales, vel in vesicam injiciendo, sine partium laesione implevisse. Et sic quoque Haller se gluten piscarium, caeruleo colore tinctum, in pericardium et in cerebri ven- triculos non semel impulisse testatur. Leiberkuhn ma- teriam in venas injectam, ex intestinorum villis defluere animadvertit. Vidit etiam aeraper venas immissum, mem- branam cehulosam pervadere. Mag en die quoque haec contirmat, quibusdam experi- APPEN 1) 1 X . 357 mentis ad venas cordis spectantibus. Talibus autem in ex- periments Ckuickshank partium structuram laesam fuisse existimavit. Item Fordyce, haec venarum ostiola in vivo corpore existere posse non cred id it. Quanquam vero haec experimenta mihi non sic rejicienda videantur, nostra tamen refert recordari illius rutv 'En.Trtipt.Kiov sen- tentiae, nobis a Celso traditae, scilicet “ non quicquam esse stultius, quam quale quidque vivo homine est, tale existimare esse moriente, imo jam mortuo.” Multa enim longe aliter in viva ac in mortua structura se habent. Si haec sententia confirmatione egeret, experimenta ab Alexandro Humboldt viro omnigena scientia ornato, et a clarissimo Professore Beclard in cutem facta memo- rare possem. llle, microscopio tricenties et duodecies millies et qua- dringenties formam augente, cutem externam exploravit, sed nequaquam potuit poros detegere; hie eandem cutem altae hydragyri columnae subjecit, metallum verb nullo pacto exudavit. Ast in vivo homine, ut omnibus notum est, sudor facile, et interdum magna copia cutem permeat. Solus igitur vitae Calor ille vias, et caeca relaxat Spiramenta. Sunt quoque et alia experimenta ad nostram rem quam maxi me spectantia, atque hanc sententiam abunde confir- mantia. Joannes Hunter in pluribus tentaminibus materias per venas in intestina impellere, et vice versa, venas ab intestinis implere frustra conatus est. Mortuo tamen animali, per venas meseraicas intestinurn inflavit. Aliae venarum origines ab Anatomicis enumerantur, ut ex folliculis, ex glandulis, et ex structura quae erectile tissue vocatur. Verum illas specialiter tractare minime hie opus est. Venis igitur relictis, jam ad alterum vasorum ordinem, vasorum scilicet absorbentium vulgo dictorum, pergamus. Cum haec vasa contemplamur, quaedam illis cum venis communia, quaedam autem propria videmus. Vasorum absorbentium pellucidae tunicae, venosis tunicis tenuitate praestant, quibus tamen firmitate non cedunt. Sicut venae, ex duabus membranis constant, ut Nuck primus demonstravit.. Interior membrana venarum interiori con- tinua, huic non dissimilis videtur, ac pariter valvulis ejus- dem generis, sed multb frequentioribus, munitur, ex- terior, secundum Cruickshank, Magendie, Sheldon, 358 APPENDIX. Goodlad, et alios fibrosa est. Hanc autem structuram Bichat detegere non potuit. Haller, Crujckshank, Monro, Goodlad, multique alii vim muscularem vasis absorbendibus attribuunt. Alii autem istam facultatem in illis existere omnino ne- gant. Bichat nullas oculis percipiendas contractiones ab illis effici credidit. Non tamen omnino negavit illas, darti in more, posse sese contrahere. Permulti, quos inter numerandus est, Cel. Blumenbach, licet vim muscu- larem rejiciant, sese contrahendi facultatem in his vasis insitam admittunt. Professores Tiedmann et Gmelin ductum thoracicum ex aeris contactu, vel ex affixo liga- mento se contrahere saep& conspexerunt. Non dubito quin hae contractiones sint ejusdem generis ac contrac- tiones a Doctore Parry in detectis arteriis observatae, quasque tonicitati (parce verbo) adscripsit. Nihil, magis quam glandulae, per quas in quibusdam corporis partibus transeunt, haec vasa ab omnibus aliis distinguit. Rarius, sed aliquando tamen, vasculum hujus ordinis per totum suum cursum cum nulla glandula committi- tur, id quod Hewson in lymphifero vase ex pollice pedis proveniente, Cruickshank in lumbis, et Magendie in equis observavit. Usque adhuc, harum glandularum struc- tura, et usus non satis comperta sunt. Notatu quoque dignum est, vasa absorbentia, etsi magno in numero concurrant, nusquam ampla fieri. Ipse etiam ductus thoracicus, inferiores ramulos capacitate saepe non multo superat. Pariter atque ostiola, quibus minores venae in majores sese effundunt, valvulis muniuntur, sic etiam ubi haec vasa cum venis se committunt, valvulae inveniuntur. Dubitari non potest, quin in plerisque exemplis pars maxima chyli et lymphae, per ductus thoracicos dextrum et sinistrum, in venas subclavianas sese effundat. In multis de anatomia libris hae solae terminationes describun- tur. Quinetiam Haller et Cruickshank alias non existere contenderunt, et hanc sententiam participant Lieutaud, Hewson, Portal et Soemmering. Haec autem vasa prae aliis, quod ad distributionem attinet variant, et multa ab aliis anatomicis exempla prolata sunt, quae satis superque demonstrant vasa, quae absorbentia dicuntur multimodis cum venis rubris conjungi. Mascagni quoque, qui tales communicationes impug- APPENDIX. 339 nat, eas tamen in mesenterio, etsi rari>, invenit. M Eckel saepe, in venas hydrargyrum injecit per vasa absorbentia. Astley P. Cooper, Baronettus, eodem modo hydrar- gyrum in venam portae impulit: idem quoque fecerunt Rosen, Walericus, Lobstein, Lindner, et Tied- mann, et Gmelin. Docet Magendie lympham ex si- nistro capitis latere provenientem, non raro per ductum proprium, in venam subclavianam transmitti. Abernethy vasa lymphifera efferentia a glandulis in venam prosecutus est. Vidi et ipse vas lymphiferum ex pulmone ortum, cum vena sine pari committi. In equo meus amicus B. Clark receptaculum chyli sese in venam quandam lumborum elfundentem invenit. Denique ductus thoracicus a Duveiiney, Astley Cooper, Dupuytren, et Flandrin in bestiis saepis- sime ligatus est. Hoc experimento, plures necatae sunt, aliae autem vitam conservaverunt, at in his, ut Dupuy- tren demonstravit, aliae viae patebant, quibus lympha ad cor usque pervenire posset. Quod ad horum vasorum radices extremas attinet, nullo pacto faciliores assecutu sunt, quam vena-rum origines. Chylifera vasa, etiam ab Assellio, ex interna superfi- cie intestinorum oriri existimata sunt. Bartholin us, Nuck, Cowper, Senac, Bergerus et Ferri er, lym- phifera arteriis esse continuata rati sunt. Malpighi vero haec a folliculis tantummodo oriri voluit. Haller, G. et J. Hunter, Cruickshank, Meckel, et plerique alii physiologi vasa lymphifera ab omnibus internis superfi- ciebus oriri docent. Professori autem Meckel cum his superficiebus non tam facile, quam venae, communicare videbantur, et experimenta, quaenuperius instituitRiBEs, ad eandem opinionem ducunt. Incipiunt quoque ex glandularum ductibus, ut e. g. ex ductibus f'ellis, ex tubulis lactiferis, nec non viis urinariis. Ad hanc sententiam ac- cedunt, Hambergerus, Ferrier, Haller, Cruick- shank, Desgenettes, Soemmering, Beclard et alii. Postremo ab omni corporis parte nascuntur, et Bartiio- lini sententia de communicatione arterias inter et ab- sorbentia vasa, nonnullis experimentis confirmari vide- tur. Affirmant enim Haller et Cruickshank materies in arterias injectas, in lymphifera penetrare, et cum illis con- sentit Magendie. At contra hujusmodi origines strenhe contendit Monro 360 APl’KN DIX. secundus. Beclard etiam se de his communicationibus etiamnum dubitare confessus est. Cum venis quoque tales communicationes, a Vieussenio olim creditas, Meckel, et Ribes existere demonstrarunt. In foetu, Cruickshank vasa lymphifera per venam umbilicalem implevit. Hae omnes origines ab effectu monstratae esse videntur, at ipsa oscula e 406 APPENDIX. garding imbibition, and transudation, as phenomena that do not take place in organized beings until life is extinct, we may regard them, when variously modified, as concerned in most of the essential functions of life. Ihe difficulty of admitting a power of selection possessed by different sets of vessels is very much done away with, and our ideas respecting the molicular changes attendant on nutrition, secretion, and absorption simplified ; when, in- stead of referring them to supposed and imaginary mouths, or extremities of vessels, we may regard them as taking place through the sides of the most minute vessels throughout their course. The difficulty respecting the removal of solid parts, is in particular very much removed. I have repeated in my Thesis, with reference to this point, the remark of Bichat ; that entire decomposition takes place prior to absorption, in consequence of which, they may pass into the circulation in a fluid form. May we not conceive the solid parts of the body, such for example, as the most minute fibrillse of muscles, nerves, cellular membrane, &c., which the most powerful microscopes can place within the limits of our vision, and the more amorphous elements of some of what are called parenchymatous structures, con- stantly, as it were, washed by the fluids just transuding from, or about to enter the minute vessels which pervade them, and giving up to them those elements which are to be thrown off from the system, and receiving others which are to be deposited in their place. The continual succes- sion of new parts will therefore depend, as I have already suggested, not only on the joint operation of depositing and absorbing vessels, but also on the nature of those particles which they are destined to reinforce or succeed. See p.377. I am aware here that I have been tempted into a mere speculation, and I ask the reader’s excuse for intruding it on his attention. Whatever be the precise mode in which A 1‘PENUIX, 407 the vessels influence the fluids they contain, or by which they are surrounded, and whatever be the changes taking- place in those minute structures, to the support of which these vessels and their fluids are subservient, it is manifest that they are liable to various influences and changes, very distinct from anything which takes place in materials not possessed of life. Physiologists, almost by common consent, point to the nervous system as the medium through which this mysterious influence is conveyed. Notwithstanding the very important advances which have been made in the phy- siology of the nervous system, it is still the department in which most remains to be done. Justice seems to require, that I should not omit this opportunity of mentioning the laborious, but neglected and almost unknown work of Bel- lingeri, who appears in part, at least, to have anticipated our ingenious and meritorious countryman. Sir C. Bell, in the distinction which he has made between the respective functions of particular nerves. He plainly distinguished that portion of the fifth pair which does not belong to the semilunar ganglion from that which does so, and pointed out the former as a nerve of motion, as Palletta had previously done. He also described the seventh pair as supplying motive influence to the same parts which re- ceive the ramifications of those branches of the fifth, which proceed from the semilunar ganglion ; but as he makes the seventh pair subservient to the functions of animal life, he did not separate the motive from the sentient nerves. See the Inaugural Dissertation of C. F. J. Bellingeri, published at Turin in 1818. For the knowledge and use of this extraordinary thesis, I am indebted to my friend S. D. Broughton. With reference to this interesting subject, I cannot for- bear to mention another circumstance, to which I can offer my personal testimony, and which, I trust, will contribute 408 A 1‘ l> E’N 1) 1 X . to allay the jealousy that has been excited in the minds of some. — I passed the winter of 1821-22, in Paris, and was frequently present at the meetings of the Institute. On one of these occasions, I had the pleasure of hearing some of the experiments and inductions of our distin- guished countryman, related by Professor Magendie, who passed a just encomium on their author, and admitted the importance of the views which they opened. It can hardly excite surprise, that when this act of justice had been per- formed, the distinguished physiologist of Paris should him- self enter the promising field that was laid open to him, and that his skilful hands should have collected some of the fruits, without abstracting, as has been too gratuitously suspected, from the labours of his predecessor. Although most important steps have been taken in the physiology of the nervous system, not only in the estab- lishment of the distinction between the nerves of sensation, and the nerves of motion, but also in the improvement of our knowledge of the anatomy of the brain, and the approach to the determination of the functions of several of its parts, which we owe to Dr. Foville, Flourens, Desmoulins, Ma- gendie, Mayo, and others ; yet, there are several points respecting which, we still continue in almost perfect igno- rance. This is particularly the case with the part which the nerves are supposed to perform in secretion, and other vital phenomena of a chemical character. This influence, whether real or merely imaginary, we may designate, for the sake of convenience, by the term, chemical influence of the nerves. Many distinguished philosophers and phy- siologists have adopted the idea, that this influence is iden- tical with galvanism. Dr. Young says, “ We may imagine that at the subdivision of a minute artery, a nervous fila- ment pierces it on one side, and afi'ords a pole positively electrical, and another opposite filament, a negative pole.” appen mx. 409 Rolando, who was disposed to dispute the palm of merit with Sir Charles Bell and Magendie, as a successful inves- tigator of the nervous system, attached considerable im- portance to his having represented the cerebellum as a sort of electromotor, and formed a theory for the explanation of the nervous influences, upon the basis of electricity. Dr. Wilson Philip has particularly distinguished himself, as a staunch advocate for the electric character of the nervous agency. Nevertheless, if we except the experiments which have been adduced by the last mentioned author, we shall find that we have little more than a shrewd suspicion, sanc- tioned by high authority, for the adoption of the theory. The observations of Dr. Philip, as well as those of Prevost and Dumas, whohave trodden in nearly the same path, havebeen called in question, or attempted to be variously explained away. Hence, it may not be amiss briefly to examine what is actually known, and distinct from conjecture, in con- nexion with the subject. It is by no means easy, effectually to separate even a part of the body so completely from the influence of the nervous system, as to render the experiment conclusive in this respect, without at the same time so com- pletely interfering with the circulation, as entirely to viti- ate the experiment by its complexity. A considerable por- tion of the body and limbs may be completely paralyzed, as to sensation and motion, and considerable wasting may take place, in consequence of the want of activity of the mus- cles, and an inferior supply of blood. The process of nu- trition is nevertheless carried on, and a certain degree of irritability remains, as shown by the paralyzed part being- still susceptible of the influence of various agents — blisters will rise, and eruptions and ulcers may form, and also heal. Moieover, when this kind of paralysis has been most com- pletely produced by the division of the spinal marrow, or ol nerves near their origin, the effects of active poisons ap- 410 APPENDIX. plied to wounds in the part are not intercepted, although it has been shown by the experiments of Dr. Addison and J. Morgan, already noticed, that the operation of the poison, is not to be ascribed to its introduction into the circulation. To explain this difficulty, recourse has been had to branches of nerves derived from the sympathetic system, and sup- posed to accompany the branches of the vascular system. Still, however, nothing is known of these branches, and we have no direct experiments to throw any certain light on their functions. The observation respecting the influence of these nerves on the function of absorption, founded on the experiments of John Hunter, and others, offered at p. 371 of the Thesis, may, perhaps, be regarded as an approach to an experimental inquiry into the subject. The intestines being solely supplied by nerves of the sym- pathetic system, and the facilities which they offer for the division or the ligature of these nerves, render them rather peculiarly adapted for this investigation. Though no posi- tive conclusions can be drawn without the assistance of a greater number and variety of experiments, yet those which have been adverted to, seem, at least, to indicate the pro- bability, that the vessels, when unassisted by the nervous influence, lose much of their power of selection. Numerous experiments have been made upon the division of the eighth pair of nerves, with the hope of obtaining some light on the subject of nervous influence. But although these nerves offer some manifest advantages for experiment, from their size and distinctness, and the readiness with which they can be divided, with comparatively little injury to other parts, and the character and importance of the functions of those parts to which they are distributed, yet it ap- pears to me, that they are liable to some decided objec- tions. It is evident that they have so complex an origin, that it is impossible to say, whether, at the point at which appendix. 411 division is to be made, the fibrillae belong more to the motive, or the sentient nerves. The gangliform enlarge- ment, which is sometimes very evident at the upper part, would seem to place them amongst the sentient nerves, and favour the suspicion as to their function, noticed at p. 350. On the other hand, this nerve did not appear in the experiments of my friend, S. D. Broughton, to be possessed of sensibility; and the experiments of Drs. Wilson Philip and Hastings, and those of Dr. Milne Edwards, and others, exhibit this nerve as acting by virtue of an influence directed from the brain to the branches, and in this res- pect more allied to the motive, than to the sentient nerves. Dr. Holland, although an opponent to the views of Dr. Philip, at least, agrees with him in this respect, and re- gards this nerve as communicating an influence to the lungs, by which the circulation of the blood through them is pro- moted. The disturbance of respiration, and digestion, ac- companied by an accumulation of mucus in the lungs, and the alteration of the secretions of the stomach, which suc- ceed the division of the eighth pair of nerves, he regards as secondary to the interruption of the circulation through the lungs, which is a direct effect of the division. The destruc- tion of different parts of the brain, and spinal marrow, does not appear to have thrown any certain light on the influence which the nerves exert upon the circulation through the capillaries, in which their chemical agency is chiefly ex- erted. It appears evident, that this destruction produces a disturbance in this part of the circulation ; but the expe- riments of Dr. Marshall Hall have shewn, that the same effect is produced by the sudden destruction of other parts; as for example, the stomach. This interesting fact, as well as the operation of poisons inserted into a wound, seems to point at a kind of sympathy, or consent of parts, with which we are at present wholly unacquainted. 412 APPENDIX. Dr. Foville has recently advanced some highly inter- esting observations and speculations, concerning the joint agency of the extreme branches of vessels and nerves, which have been greatly admired by some of the ablest physiologists in France, and which will, I hope, before long be laid before the public. Page 378. That the production of black matter is pro- moted by the retardation, or stasis of blood in the ves- sels, as suggested in the Thesis, appears to be strongly confirmed by the effects of inflammation. It not unfre- quently leaves the small vessels of the part affected, dis- tended with blood, after the activity of the circulation through them has ceased ; this is strikingly the case with the mucous membrane of the alimentary canal, in which the production of black matter from this cause is by no means unfrequent. In some instances we may notice the different shades of colour which attend the transition from red or purple to black. This colour, and various shades connected with it, have been regarded by some distinguished foreign pathologists as evidences of the existence of chronic inflammation, I would rather regard them as proofs that in- flammation had subsided. Though it is not my intention to pursue this pathological subject further in this volume, I wish to correct an error into which I have been led, in re- presenting this black pigment as a frequent occurrence in the spleen. Though I made this statement in consequence of my own personal observation in dissecting-rooms, the numerous opportunities which I have since had of the inspection of recent subjects, have convinced me that, except to a limited and partial extent, the deposition of this pigment in the spleen, is by no means common. Although I retain unchanged the opinion, that the black matter of the lungs is generally produced in the system itself by the alteration of the blood, in opposition to APPENDIX. 413 the view of Dr. Pierson, who ascribed it to inhaled car- bonaceous matter, I cannot omit to notice a fact which has been since observed by my friend, Dr. Gregory of Edin- burgh. He found the lungs of a patient, who had been long- engaged as a coal-miner, unusually loaded with black mat- ter. A specimen of this matter was subjected to a careful analysis by Dr. Christison, the result of which rendered it almost certain, that the black matter was in part, at least, composed of minute particles of coal. Page 380. That the circulation of the blood is promoted by the way in which it is disposed of in the extreme vessels, is a view which I am still disposed to entertain. It seems to receive the support of analogy from the observations of Dutrochet, respecting the motion of the sap in the roots, and branches of vegetables. 414 APPENDIX. OF THE PHENOMENA TO WHICH THE NAMES ENDOSMOSIS AND EXOSMOStS HAVE BEEN GIVEN BY H. DUTROCHET. Since the publication of some of the preceding views re- specting transudation and inhibition by Magendie and Fo- dera, the subject has been very carefully investigated by Dutrochet, who, in examining the transmission of dif- ferent fluids through different kinds of thin and slightly porous septa, has thrown much light on the phsenomena attending this transmission, and exhibited what appears to him to be a new physical force distihct from ordinary capillary attraction, electric agency, and hydrostatic pres- sure ; to the movements resulting from this force, he gives the names of endosmosis or exosmosis, according to the direction. Whether this force be altogether distinct and sui generis, or a modification of some principle, with which we are already partially acquainted, it seems to operate very generally throughout living and dead, and organic as well as inorganic matter, and as an agent intimately con- nected with some vital phsenomena, it must not be wholly passed over in this volume. If we take a membranous sac or cavity, as for example, the ccecum of a fowl, or the air- bladder of a fish, and having put a small quantity of fresh milk into it, and secured the mouth by a ligature, we shall find on immersing this sac in water, that in the course of a few hours it will become quite full, and eventually turgid. This turgidity is not permanent, and after a few hours more have elapsed, the sac will again be flaccid. If the sac be now opened, it will be found to contain curdled and putrid milk ; if the sac be cleansed from this offensive substance, and again partially filled with APPENDIX. 415 milk and immersed in water, we shall find a repetition of the phenomena, but the sac will neither become so turgid nor so long remain full as in the first instance ; this may be repeated several times, but with diminish- ed effect. It does not make any sensible difference to the experiment, whether the sac be inverted or not, or whether the mucous or peritoneal coat be removed. If in- stead of milk some other fluid be employed, similar phe- nomena may be observed, but by no means in the same degree in all ; in fact, very striking differences may be observed, depending on the nature of the fluids within and without the sac, as well as upon the texture through which they have to pass. All these points have been carefully investigated by Dutrochet. In this enquiry, instead of a fowl’s ccecum, or fish’s bladder, he employed an instru- ment, to which he has given the name of an endosmometer, which it will be necessary briefly to describe. It con- sists of a cylindrical tube of glass, to which is fitted at one extremity, a sort of moveable funnel, or cupola, having such a rim, or lip, as will admit of a firm attach- ment of the membrane, or other material, by which this aperture is to be closed, and though the transmission of endosmosis and exosmosis is to be examined, the other extremity of the tube is left open, and a graduated scale is applied to the tube itself : the fluid of which the power of producing endosmosis is to be tried, is placed in the reservoir formed by the closed funnel, after which the tube is applied and the funnel immersed in water. If endosmosis take place, the fluid will rise in the tube above the level of the water surrounding the reservoir, and the amount of this elevation may be read off from the graduated scale. In this way Dutrochet discovered a very considerable difference in the power of different fluids in inducing endosmosis, ^ and it appeared that in general this power was greater in dense 416 APPENDIX. than in thin fluids. Solutions of sugar and of gum arabic possessed this power in a very remarkable degree ; the for- mer, when of the strength of one part sugar to three of water, producing an elevation in a column of quicksilver of 258 millimeters, or 45 inches 9 lines, French ; and the latter, when of the same strength, an elevation of more than 28 inches. Saline and alkaline solutions have also considerable endosmodic power. Dutrochet, at one time, conceived that the acids were unfriendly to en- dosmosis, or rather that they produced exosmosis, and he was in consequence induced to attribute the phsenomena of this kind of transmission to electric, or galvanic agency; and this opinion seemed to be strengthened by the results of various experiments, which he instituted to endeavour to ascertain the fact. Further experiments led him to abandon the idea of electric agency, and he dis- covered moreover, that most of the acids really possess some power of producing endosmosis ; sulphuric acid how- ever continued to form a marked exception. Dutrochet likewise tried many of the animal fluids be- sides milk, and he found that they also possessed con- siderable energy in producing endosmosis, until, as in the cases of the milk in the preceding experiments, they had become putrescent. In this state he found that all the ani- mal fluids were opposed to endosmosis. By varying his experiments and employing other fluids free from animal matter, but containing sulphurated hydrogen, as for ex- ample, the hydro-sulphuret of ammonia, he discovered that this principle, like sulphuric acid, is decidedly opposed to endosmosis ; but he states, that we are at present com- pletely ignorant of the mode in which these two principles, the only known sedatives of endosmosis, act. In observing the differences in the phcenomena of endosmosis presented by different fluids, there are two points to which Dutrochet A1M>EN D 1 X . 417 turns his attention, viz., the force and the rapidity of endos- mosis, both of which may be made the subject of actual measurement. The rapidity he appreciated by the number of millemeters through which the fluid in the tube ascended in successive hours. In order to estimate the strength, he employs an endosmometer of a form somewhat different from that before described. It is constituted on the same principle as the apparatus by which Hales estimated the force exerted in raising the sap of the vine. The reservoir of this endosmometer is similar to that used in the former experiments ; but the tube is bent so as to form a syphon with its convexity upwards ; the descending leg of this syphon fits one of the legs of another, which has its con- vexity downwards. Mercury is put into this second syphon, and the force of endosmosis being exerted on the quick- silver in one leg, produces a corresponding elevation on the mercury in the other, when it may be read off on a gra- duated scale. By trying the rapidity and force of endos- mosis on different fluids, by the use of these instruments, Dutrochet found, as might have been anticipated, that those fluids which acted with the greatest rapidity, likewise acted with the greatest force ; and he also found, that the power of endosmosis, in these two respects, increased with the specific gravity of the fluids; provided that we estimate this only by its excess above the specific gravity of water. The following are some of the most remarkable differ- ences depending on the nature of the substance through which the transmission takes place. It may be seen from the experiments performed on milk, and the intestines of a fowl, that at each successive repetition of the experiment with fresh milk, but the same portion of intestine, the amount of endosmosis continued progressively to decrease : this appeared to depend upon decomposition taking place in the membranes themselves, by which they became infil- E E 418 APPENDIX. trated with a fluid, containing one of the principles which has been already remarked to be negative of endosmosis. Conducted by this fact, Dutrochet was led to the ob- servation, that the transmission of fluid through a septum, by the influence of endosmosis, was very materially in- fluenced by the fluid with which it happened to be per- vaded. When the septum was dry, and the pores conse- quently filled with air, endosmosis was obstructed. This obstruction was removed as soon as the septum was satu- rated with water, and it became greatly increased, when, instead of water, a fluid favourable to endosmosis, such as a solution of sugar, or gum, occupied the pores of the sep- tum. Various materials, besides the membranous parts of animals and vegetables, were employed to close the funnel of the endosmometer, such as very thin plates of sand-stone, plaster of Paris, lime-stone, burnt slate, and the biscuit of earthenware ; with some of these substances, the endos- mosis was carried on with considerable energy, whilst with others, it seemed totally inactive: this evidently did not depend on the mere porosity of the material employed, and satisfactorily showed that the phenomena of endosmosis must not be confounded with capillary attraction ; very little, if any, endosmosis was observed to take place through plates of sand-stone, whether the most porous, or the least porous were employed, but the presence of a little ferrugi- nous matter in one of the specimens was observed to favour it. To ascertain, that in instances in which endosmosis took place, there did not exist a physical impediment to the transmission of fluids, Dutrochet tried them both with the pressure of a column of fluid, and with the galvanic cur- rent, and in these cases he observed transmission to take place. The septa of lime-stone, though sufficiently porous to allow the passage of fluids and to exert a capillary attrac- tion upon them, were found to be extremely unfriendly to A PPEND1X. 419 endosmosis ; but those of burnt slate, and baked clays, though but little promising, were observed to exhibit, endosmosis, strongly. In some of these experiments it was remarked, that after the endosmosis had been carried on with considerable ac- tivity in several trials with the same septum, a diminution in the transmission took place, indicating that some impe- diment had interposed itself; this was discovered to pro- ceed from an accumulation of the gum, sugar, or other principle in solution upon the surface of the plate or sep- tum. As respects the fluid, in which the reservoir of the endos- mometer is immersed, it would seem, that there is no fluid more favourable to endosmosis, and at the same time so con- venient for experiment, as pure water. The examination of this fluid, after it had been for some time employed, afforded convincing evidence of a very curious fact. Not- withstanding the copious and forcible transmission of water through the septum, occasioning in some instances an elevation of several inches in the tube, there is likewise, at the same time, a transmission of fluid in an opposite direc- tion; thus, if a solution of muriate of soda be employed in the endosmometer, it will not be long before traces of this salt will be found in the water surrounding the reservoir of the instrument. Dutrochet has been remarkably ingenious and happy in the application which he has made of the principle of en- dosmosis and exosmosis, to the explanation of many cu- rious points of vegetable physiology. The cause of the motion of the sap, which has led to so much interesting- investigation and controversy, he attributes, in a great mea- sure, to a structure situated near the junction of the root and the stalk, in the minute cells of which, a powerful en- dosmosis is exerted. The peculiar firinness which forms so e e 2 « 420 APPEN DIX. striking a distinctive character between a fresh and a living leaf, or other vegetable tissue, and the permanent flaccidity of that which is dead, he designates by the term turgid state, and refers it to endosmosis filling the cells of the ve- getable structure, and induced by the nature of the fluid in these cells. Hence, a faded, but still living plant, is rapidly restored by immersion in water, and this experiment may be repeated until the death of the plant, has allowed such an alteration of the fluid remaining in the cells, that endosmo- sis is no longer provoked. Even when this condition has been arrived at, Dutrochet has succeeded in procuring an artificial turgid state, by causing the cells to imbibe solu- tions favourable to endosmosis. The forcible ejection of the juice from the fruit of the elaterium is referred, by Dutro- chet, to the progressive operation of endosmosis, in con- junction with a peculiar arrangement of the cells, of which the substance of the fruit is composed. Many curious spe- culations have been formed respecting the cause which de- termines the direction of the roots and the stalks of plants. That which has been offered by Dutrochet, is, perhaps, the happiest application of endosmosis, which he has yet pointed out. From a difference in the arrangement of the cellular structure in the stalks and the roots, it seems to follow as an inevitable consequence, that the turgid state induced by endosmosis, will cause the first to form a curl with its concavity upwards, and the latter with its concavity downwards, until the one has acquired an ascending, and the other a descending direction. Dutrochet thinks’ that the same principle of motion may be applied to the explanation of the curious phe- nomena presented by the balsamina impatiens, the hadysarum givans, and the mimosa puclica ; but in the movements of this last especially, we are at fault for another yet unex- plained power by which the movements are called info APPENDIX. 421 play, even supposing that endosmosis is, in some way, im- mediately concerned in producing the temporary turgidity of the cellular organs, placed at the angles formed by the moving joints of the plant. But if, as Dutrochet very can- didly admits, something be wanted in the explanation of the movements of the sensitive plant, this difficulty is much more strongly felt in the movements performed by animal life. Their nature and rapidity seem completely at va- riance with any explanation founded on endosmosis ; they are opposed by the experiments of Blanc, Burzoletti and Pre- vost. and Dumas, upon muscles in action, and by the most careful and minute microscopic observation of the elemen- tary fibre, in which nothing approaching to the vesicular, or cellular structure, imagined by Dutrochet, can be dis- covered. I am far from believing, that endosmosis and exos- mosis, are not actively concerned in many of the phse- nomena of animal life ; but in applying them, we must be extremely careful not to ascribe too much to them, to the neglect of other forces, which nature employs in living ani- mals to restrain and modify their influence. I have had occasion to notice a similar error into which, I apprehend, both Magendie and Fodera have been led, with reference to the phenomena of transudation and imbibition. It is doubtless extremely difficult to decide, how much may cor- rectly be attributed to any of the different forces which take a part in the various and complicated operations of animal life, and it is only as a conjecture, that I notice the following instances, in which it seems probable, that the principle pointed out by Dutrochet may be concerned. When we consider the great increase in the quantity of urine, which takes place in conjunction with the production of sugar, in those who are labouring under diabetes, and consider the strong power of endosmosis, which Dutrochet ascribes to APPENDIX. sugar, may we not attribute the accumulation of a part of the superabundant fluid to this cause, and even suspect, that not in the kidneys alone, but throughout the urinary apparatus, endosmosis may add to the bulk of secreted urine? This idea, as respects the bladder at least, has, prior to the publication of Dutrochet’s views, had the sanction of some distinguished physiologists, who have con- tended, that even in the healthy state, much of the fluid passed from the bladder is so collected. Some proof that the excessive quantity of the secreted urine is influenced by the presence of sugar, is afforded by the fact, that if by strict exclusion of vegetable matter, the production of sugar may be suspended for a time, the quantity of fluid evacuated will exhibit a corresponding diminution, notwithstanding that the disposition to the complaint remains unabated. Another instance in which the operation of endosmosis will, perhaps, be more readily admitted, since the structures concerned are adventitious, and, consequently, less perfectly organized, is furnished by the enormous cysts, which are not unfrequently formed in or near to the ovaries, constituting what is generally called, ovarian dropsy. As these cysts are furnished with no special glandular apparatus, it is not unreasonable to refer the production of the fluid which they contain, to the whole internal surface ; although, for reasons which I have endeavoured to explain in a short essay on the anatomical character of some adventitious structures, and which, I need not here repeat, it is very probable that the produc- tion of fluid is not equally rapid from every part. The short space of time in which some of the largest of these sacs are refilled, after the operation of paracentesis, is no less remarkable than the character of the fluid so produced. It is well known that these fluids are copiously charged with a nnico-albuminous substance, which, like sugar, must. A I>PEN1>1X. 423 on Dutrochet’s principles, be greatly favourable to endos- mosis. If endosmosis be admitted to take a part in those func- tions, in which there is a high degree of life and organiza- tion, it must be admitted, a fortiori, in other instances, in which organization is greatly inferior, and life nearly or quite extinct. Hence, I apprehend, we may be allowed to have recourse to its assistance to explain the changes which take place in structures which appear to be devoid of or- ganization, or which having lost the life and organization which they once possessed, are yet still retained in the system. The copious impregnation of such substances with earthy salts, constituting what are termed petrefac- tions, examples of which are met with in old tubercles of the lungs, in the mesenteric glands, in the coats of arteries, and in various other situations, may, I believe, be referred to this principle. 424 A L> l> UN 01 X. ON THE MICROSCOPIC CHARACTERS OF SOME OF THE ANIMAL FLUIDS AND TISSUES. BY J. J. LISTER AND DR. HODGKIN. The researches of Prevost and Dumas, respecting the microscopic appearances of the blood, are alluded to in the work of Dr. Edwards. The very superior compound achro- matic microscopes of my friend J. J. Lister, who has devoted much of his leisure time to the cultivation of this branch of optics, have enabled him and myself to correct some of the illusions into which the indefatigable physiologists of Geneva, to whom I have alluded, were unwittingly led by the imperfection of their instruments. Hence, it appears, that there would be an obvious advantage in reprinting in this work, with some few additions, the observations which have already been published in the Annals of Philosophy, and in the Catalogue to the Anatomical Museum of Guy’s Hospital. Any approaches towards a more accurate knowledge of the intimate structure of organized beings, may reasonably be looked to as collateral aids to our acquaintance with the influence of physical agents on life. Very soon after the invention of the microscope, it was ascertained, that the blood, instead of being homogeneous, consisted of a fluid with coloured particles suspended in it. This discovery is attributed to Malpighi ; but it does not appear that his inquiries into this subject were pushed to any great extent. APPF.N nix. 425 Observations similar in their result, but far more numerous and minute, were made nearly at the same time by Levven- hoeck, apparently without any connexion with those of Mal- pighi. This indefatigable Micographer, describes the coloured particles of the blood as circular, or spherical, while at rest, but elliptical when in motion. Those of fish, he states to be flat and elliptical ; and he remarked, that in the fluids of some insects, the particles were of a green colour. He believed rather than demonstrated, that each globule of the blood was composed of six subordinate globules. For a considerable time the opinions of Lewenhoeck were generallyreceived, and physiologists and micographers, amongst whom we may notice Fontana, taught that the particles of the blood were globular. Haller in one part of his works concurs in this opinion, but doubts their form being susceptible of change from mo- tion. In another place, he describes the red particles of the blood as flattened, and compares them to lentils. Senac has taken the same view of them. De la Torre, who employed in his observations single globules of glass possessed of very high power, but defec- tive in point of clearness, recognized the flattened form of the particles, but mistaking the shaded spot in their centres for a perforation, he described them as rings. He believed them to be jointed, and to break regularly into seven pieces. De la Torre was soon followed by Hewson, who, together with improved instruments, brought a large stock of inge- nuity and perseverance into the inquiry. To obviate the confused view, which the large proportion of the particles in undiluted blood is very apt to produce, he introduced the plan of mixing it with fresh serum, 42G APPENDIX. being well aware of the change of form produced by the addition of water. lie states that if, after this change is effected, a drop or two of a neutral solution be added before the burst- ing of the vesicles, the flat figure will be restored. He found no central particles in the blood of the splenic vein. Without entering into the numerous and in many respects accurate observations of Hewson, since we shall have occa- sion to refer to them in a subsequent part of this paper, it will be sufficient to recall to memory the results which he drew, as to the nature and figure of the particles. He satisfactorily shewed that they are not globular, but flattened, as well when circulating in the vessels of the living animal, as when drawn from the body ; and he also proved the fallacy of De la Torre’s views with respect to a central perforation. He believed the dark central spot to be a solid particle, contained in a flat red vesicle, whose middle only it occu- pied, and whose edges were hollow and either empty, or filled with a subtile fluid. He observed the flattened vesicles to become spherical, by the addition of water, and at the same time to be contracted in their diameters. He states, that the middle particle may be seen to fall from side to side in the hollow vesicle like a pea in a bladder, or sometimes to stick to one part of the vesicle. The middle particles are less easily soluble than the flat vesicles which contain them, and a little time after the proper quantity of water being added they disappear, leaving the middle par- ticles which appear to be very small. He states them to be larger in the immature young, than in the perfect animal. He likewise observed them to be of the same form, when APPENDIX. 427 circulating in the vessels during life, as when escaped from them, and denies that they alter from resistance during cir- culation. This view of the structure of the particles, was founded on the examination of the blood of the skate of the larger size, and elongated form, of which he was perfectly aware* He admits, that it is more difficult to gain a sight of these appearances in the blood of man, but tells us that he had, notwithstanding, distinctly done so with the help of bright and clear day-light. Falconar, by whom Hewson’s Observations were repeated and published; and also Dr. Wells, entertained similar views respecting the figure of the particles of the blood. Cavallo believed, that they consisted of double spheres. The concise but pertinent observations of Dr. Young, claim particular attention and respect. The particles of the blood of the skate, from their superior size, are con- sidered by him, as they had been by Hew son, as the best suited for the commencement of the investigation. He describes them as exhibiting an oval and flattened form, and containing a nucleus generally round, but some- times a little irregular, which occupies a nearly permanent position in the centre of the particle. It often remains distinctly visible, while the oval part is scarcely perceptible, and as the portion of blood dries, becomes evidently pro- minent. This nucleus is about the size of an entire par- ticle of the human blood, the whole oval being about twice as wide, and not quite three times as long. The nucleus is very transparent, and forms a distinct image of any large object which intercepts a part of the light by which it is seen, but exhibits no inequalities of light and shade that could lead to any mistake respecting its form. Having given these remarks respecting the particles in the blood of the skate, he proceeds to those of human blood, 428 APPEN D1X. of which he says, that if placed under similar circumstances in the field of the microscope, near the confine of light and shade ; although they are little if at all less transparent, one immediately sees on the disk an annular shade, which is most marked on the side of the centre on which the mar- ginal part appears the brightest, and consequently, indi- cates a depression in the centre ; but the Doctor was not quite decided, whether this apparent depression might not depend on some internal variation in the respective density of the particle. He thought the axes about ■§- or l of the diameters, but the particles never appeared to him to be “ as flat as a guinea.” He never observed a prominence on the outline of the particles of human blood, but he remarked, that when they had been kept for some time in water, and a little solution of salt was added, their form and structure are more easily examined, and that they appear to resemble a soft substance with a denser nucleus, not altogether unlike the crystalline lens with the vitreous humour as seen from behind ; but with respect to a central particle detached within a vesicle, like a pea in a bladder, he is satisfied that Hewson was completely mistaken. The colouring matter, according to the Doctor’s view, does not appear to be a mere superficial layer, but imbues the substance of the par- ticle from which water extracts it, and occasions such a loss of specific gravity that they remain suspended instead of sinking in that fluid. In this state they easily escape ob- servation, which circumstance, together with their passage through filtering paper, has led to the monstrous assertion that they are soluble in water. When they have been long- kept in water, and even after putrefaction has taken place, they do not appear to become constituent parts of an homo- geneous fluid. In the memoirs of Sir E. Home and Bauer relating to APPENDIX. 429 the subject before us, we find the globular figure of the blood again maintained. The colouring matter appeared to them not to be con- tained in the particles, but rather to envelop them. They describe it as separating very readily, and flowing from all parts at the same instant. “ To examine them,” say they, “ in their coloured state, a very small quantity of blood must be examined at once, and this must be spread as thinly as possible that the moisture may instantly evaporate, they then remain of their full size and colour, perfectly spherical. They seem to consider the flattened form as the effect of a change which takes place after death ; for Bauer observes, in opposition to the assertion of Hewson, that in the skate, the particles during life are of the form of an egg, but that almost immediately after death they are flattened. If the quantity of blood under examination be sufficiently large to retain its moisture only half a minute, the colour- ing matter in a few seconds begins to separate and form a circle round the globules. If the blood be diluted with water, the separation is instantaneous. They give the diameter of the globule, enveloped in its colouring matter, as ttVo> and when deprived of it, as yoTo- Elsewhere they state the proportion of the colouring matter to the globule to be as three to one. They describe the globules, when separated from the colouring matter, as being mu- tually attracted and coalescing with some disposition to linear arrangement, which is not the case so long as the coloured envelope remains attached ; they further describe globules in pus, in muscular fibre, and in the substance of the brain, identical in point of size with the uncoloured globules of the blood. The more recent and extended researches of Prevost and Dumas tend in some respects to confirm the opinions of 430 APPENDIX. Hewson, while- in others they more nearly coincide with those of Sir E. Home and Bauer. They represent the particles of the blood as circular in all the mammalia, and elliptical in birds, reptiles, and fishes, but flattened in all, though a little prominent at the cen- tre. Their size is uniform in the same animal, but differs in different species, from of a millimetre in the salaman- der, to in the callitriche, or in the goat. They regard them as consisting of a central colourless globule of one uniform size, -3^ of a millimetre, in all classes of animals, like those of chyle, milk, and pus, and inclosed, as before stated by Hewson, in a coloured membraneous vesicle, on which depends the difference in the form and size of the particles. In those animals whose blood has elliptical particles, the nucleus appears also elliptical until muriatic acid is added, by which they conclude, that the surrounding matter is dis- solved and removed. The nucleus has then the same ap- pearance as that of the mammifera. By repeated examination of the blood whilst in the course of circulation, these physiologists satisfied them- selves that the particles possess the same size and form whilst in the vessels, as they do when recently drawn from the body. They deny that they perform a movement of rotation on the centres ; but in describing the effect pro- duced on the form of the particles from occasional resistance which they meet with, they confirm the remark of Lewen- hoeck as to the elongation of the particles during circula- tion. In our examination of the particles of the blood, we have in vain looked for the globular form attributed to them, not only by the older authors, Leeuwenhoeck, Fon- tana, and Haller, hut still more recently by Sir Everard Home and Bauer. Our observations are also at variance APPENDIX. 431 with the opinion long since formed by Iiewson, that these particles consisted of a central globule inclosed in a vesicle composed of the coloured part, and which, though refuted by Dr. Young, has since, in a modified form, been revived by Sir Everard Home and Bauer in this country, and by Prevost and Dumas on the Continent. We have never been able to perceive the separation of the colouring matter, which our countrymen have described as taking place in a few seconds after the particles have escaped from the body ; nor can we with Prevost and Dumas, consider the particles as prominent in the centre. The particles of the blood must unquestionably be classed amongst the objects most difficult to examine with the microscope ; partly from the variations of form to which their yielding structure renders them liable, but still more from their being transparent and composed of a substance which, as Dr. Young has remarked, is probably not uniform in its refractive power. These causes of error we have endeavoured to counteract by varying the mode of observation. We have viewed the particles both wet and dry, both as opaque and as transpa- rent objects, under great varieties of power and light, and we lay no stress on observations which have not been confirmed by frequent repetition. To us the particles of human blood appear to consist of circular flattened transparent cakes, which, when seen singly, appear to be nearly or quite colourless. Their edges are rounded, and being the thickest part, occasion a depres- sion in the middle, which exists on both surfaces. This form perfectly agrees with the accurate observations of Dr. Young, that on the disks of the particles there is an annular shade, which is darkest on that side of the centre on which the margin is brightest. Though the Doctor drew the obvious conclusion that the disks were concave, he does not 432 APPENDIX. consider the fact as demonstrated ; since the appearance might be produced by a difference in the refractive power of different parts of the corpuscle. This objection we think completely met; 1 st. By their transmitting the erect image of any opaque body placed between them and the light, precisely as a concave lens would do. 2dly. By the appearance presented by the particles when viewed dry, as opaque bodies. When illuminated by the whole of a Leiberkuhn, the entire margin is enlightened, and in most of the particles there is besides a broad inner ring of considerable brightness ; whilst the centre, and the space between the two rings, is completely dark. On half the Leiberkuhn being covered, the rings are reduced to semicircles, the outer one being opposite to the light side, and the inner to the darkened side of the speculum. 3dly. When fluid blood having been placed between two slips of glass, a single particle happens to be at right angles to the surfaces of the glass, so as to be seen in profile, the two concave surfaces are visible at the same time,* or alter- nately, but more distinctly, if the particle slightly va- cillates. The concavity of the disks is, however, extremely trifling ; and under particular circumstances, in a few of the particles, the surface is to all appearance quite flat. Notwithstanding the great uniformity in the size of the particles of the blood, so long as they retain, unimpaired, the form which they possess on escaping from the body, their real magnitude lias been so variously estimated, that we judged it worth while to attempt a new measurement. In doing so, we adopted a method somewhat different from * This happens notwithstanding the interposition of the edge, when the centre of the particle is accurately in focus, owing to the large pencil of light admitted by the object glass. appendix. 433 those hitherto employed. A camera lucida is adapted to the eye-piece of the microscope in such a manner that the distance of the paper being ascertained, the object may be drawn on a known scale. Tracings of several of the images being made, they were applied to, and compaied with, the images of other particles until their accuracy was established. The diameter of the particles obtained in this manner may be pretty correctly stated at an inc^- The following measurements by former observers are given for the sake of comparison. Jurine Jurine in a 2d measurement . . -x ^ Bauer vtW Wollaston TihsTS Young thtW Kater tztVo Ditto • • * "e'oV'o Prevost and Dumas ToVe The thickness of the particles, which is perhaps not so uni- form as the diameter of the disks, is on an average to this latter dimension as 1 to 4.5 The form and size of the particles of the blood of other animals have frequently been compared with those of man. Many observations were made for this purpose by Hewson ; but while some of them appear tolerably accurate, others are decidedly far from the truth. Those which have recently been made by Prevost and Dumas, are the most extensive and complete which as yet exist. Our attention having- been chiefly taken up with the blood of man, we have not as yet carried our investigation of that of other animals so far as we design doing ; we have, however, examined the F F 434 APPEN DIX. blood in all the classes of vertebrated animals, and in dif- ferent species of most of t^em. Our observations com- pletely accord with those of Prevost and Dumas, as to the particles having a circular form in the mammalia, and an elliptical one in the other three classes. There are varieties both in the size and proportion of the particles in different species. Thus for example, in the pig and rabbit, the par- ticles have a less diameter, but a greater thickness than in man. We have hitherto invariably found the elliptical particles larger than the circular, but they are propor- tionably thinner. In birds, the particles are much more numerous, but smaller than in either reptiles or fishes. There are numerous interesting phaenomena which pre- sent themselves when the particles lose their integrity and assume new forms. Changes of this description are occa- sioned by the spontaneous decomposition which the blood undergoes a longer or shorter time after its escape from the body, by mechanical violence, and by the addition of va- rious substances, which appear to exert a chemical action on the matter of which the particles are composed. To these appearances we have been induced to devote the more attention, from their seeming calculated to throw some light on the composition and structure of the particles. We were also desirous of not hastily or rashly denying the existence of those colourless central globules which have been strongly insisted on by Sir Everard Home and Bauer, and by Prevost and Dumas, and which have been regarded not merely by themselves, but by other distinguished and intelligent physiologists, as constituting by their varied combination the different organic tissues. The separation and detection of these globules is stated to be facilitated by some of the means which effect the changes to which I have alluded ; but, as I have already stated, we have in vain looked for these globules. APPEN DIX. 435 After blood taken from the living body has been kept a sufficient length of time for an alteration in the form of the particles to commence, and this according to circumstances will be from a very few hours to one or more days, the first change which we have noticed is a notched or jagged ap- pearance of the edge of a few of the particles. The number so modified continues to increase : some of the particles lose their flattened form, and appear to be contracted into a more compact figure ; but their outline continues to appear irregular and notched, and their surfaces seem mammillated. Hewson and Falconar appear to have accurately noticed this change, and have compared the particles in this state to little mulberries. When more time has elapsed, most of the particles lose this irregularity of surface and assume a more or less perfectly globular form, and reflect the image of an interposed opaque body as a convex lens would do. Some of the particles resist these changes much more obsti- nately than others. If a small quantity of blood be placed between two pieces of glass, which are afterwards pressed together with some force, several of the particles, however recent the blood, will be materially altered. The smooth circular outline is lost, and as in the former case, they appear notched. A few seem to be considerably extended by the compression. When the surface of the particles has in this way been broken into, the ruptured part exhibits an adhe- sive property capable of gluing it to another particle or to the surface of the glass ; but the particles in their natural state, seem to be nearly void of adhesiveness. There is scarcely any fluid except serum which can be mixed with the blood without more or less altering the form of its particles, probably in consequence of some chemical change. In this general result our observations accord with those of Hewson and Falconar, whose experiments of F F 2 -136 A r P E N D I X . this kind were very numerous. We differ from them, how- ever, in a few particulars. There is no fluid which, when mixed with the blood, produces a more remarkable and sud- den alteration in the appearance of the particles than water does. With a rapidity which, in spite of every precaution, the eye almost invariably in vain attempts to follow, they change their flattened for a globular form, which from the brightness and distinctness of the images which they reflect as convex lenses, must be nearly perfect. Contrary to Sir Everard Home’s remark, that the par- ticles in their perfect and entire state are not disposed to arrangement, it is in this state only that wTe have found them run into combinations, which they assume with con- siderable regularity. In order to observe this tendency of the particles, a small quantity of blood should be placed between two slips of glass. In this way the attraction exerted by one of the pieces of glass, counteracts that of the other, and the mutual action of the particles on each other is not interfered with, as is necessarily the case when only one slip is employed. When the blood of man, or of any other animal having circular particles, is examined in this manner, considerable agitation is at first seen to take place amongst the particles ; but as this subsides they apply themselves to each other by their broad surfaces, and form piles or rouleaux which are sometimes of considerable length. These rouleaux often again combine amongst themselves, the end of one being attached to the side of another, producing at times very curious ramifications. When blood containing elliptical particles is examined in the same manner, it exhibits a not less remarkable but very different mode of arrangement. Though they are applied to each other by some part of their broad sides, they are not so completely matched one to another, as is the case APPENDIX. 437 with circular particles ; and instead of placing themselves at right angles to the glass, with their edges presented to its surface, they are generally seen nearly parallel to it, one particle partially overlaying another, and their long di- ameters being nearly in the same line. In the blood of the toad or frog the lines thus formed are subjected to a kind of secondary combination, in which several assume to them- selves a common centre, whence they diverge in radii. It is by no means rare to see several of these foci in the field of the microscope at one time. The particles at these points appear crowded, confused, and misshapen. This tendency to arrangement is perhaps not to be wholly attributed to the ordinary attraction existing between the particles of matter, but is probably to a greater or less degree dependent on life; since we have not only observed that the aggregating energy is of different force in the blood of different individuals, but that in the blood of the same individual it becomes more feeble the longer it has been removed from the body. At the same time, we are very far from believing that these or any other mode of aggregation which the particles of the blood may be observed to assume, ought to be regarded as at all analogous to the process which nature employs in the formation of the different tissues. I some years ago briefly stated this opinion, which I was induced to form a priori* ; but I may now appeal to facts in support of it. Besides the particles above described, and which are evidently very important and essential constituents of the blood, other particles, much smaller and much less nu- merous, may occasionally be observed in the blood. They are circular, and perhaps globular, but we have not made them the subject of much examination. ' See '■ Thesis IX. 461 besides having little opportunity for doing so, I conceived that, by availing myself of the experiments of others, of men of the highest celebrity, no imputation could arise of facts having been warped to suit theory, which, by the theorist, may sometimes be innocently done ; and further, the performance, of these experiments would be necessarily attended with a degree of cruelty, which would render them alike painful to myself to undertake, and to others to hear detailed. Thomas Hodgkin. Edinburgh, 4th month (April) 1821. » / NOTES. PART I. CHAPTER I. Page 11. — In confirmation of the opinion advanced by Dr. Edwards, that venous blood, though greatly inferior to arterial, still contributes to produce the action of the nervous and muscular systems, may be adduced the extraordinary facts with which the epidemic cholera has familiarized us. We have seen indi- viduals, whose dark and blue colour has attested the general circulation of venous blood, exercising, though with a certain degree of habitude, the intellectual and locomotive faculties. Page 13. — Although in Dr. Edwards’ experiments on the duration of the life of frogs inclosed in plaster, the animals do not appear in any instance to have sur- vived more than six weeks ; we are not on this account bound to discredit the state- ment of H6rissant, who kept them alive eighteen months, in boxes inclosed in plaster. My friend — Hodgson of Birmingham, has informed me, they have been kept alive for three years inclosed in globular masses of plaster, but that to effect this, it will be necessary to keep them in a cellar at a low temperature. I believe it is his intention to publish these, and some other interesting facts pointed out by a deceased friend of his. Page 37. — The fact, that fishes cannot live in water deprived of air, and yet speedily die when removed from the water and exposed to the direct and unmixed influence of the atmosphere, is probably in some respects analagous to what oc- curs in the mammalia, who, though they cannot survive many minutes, when removed from the vivifying influence of the oxygen, nevertheless require that it 464 NOTES. be diluted with a large proportion of nitrogen, or hydrogen, and are soon cut off when restricted to an atmosphere of pure oxygen. I shall have occasion to ad- vert to the experiments of Broughton on this subject in a subsequent note. The following is a note by Dr. Marshall Hall. * The results of the experiments detailed in this interesting chapter, do not appear to be all phaenomena of the same kind. It is plain that death is the result of asphyxia within certain limits of tempera- ture. But as we approach that of 42° cent. (107° 6' Fahr.) the animal is doubt- less destroyed, not by asphyxia, but by the positive action of this elevated tem- perature upon the nervous and muscular systems ; the nerves are deprived of their peculiar properties and the muscles become perfectly rigid. The facts, however, together with those of chap. 2. sect. 1. p. 18, and that quoted from Legallois, p. 148, demonstrate, that exposure to a low temperature, both previous and immediate, enables the animal tribes to bear the privation of air better than exposure to a higher one. What is the rationale of this fact 1 Mr. Edwards does not offer a conjecture upon the point. It is probable, that it depends upon augmented irritability. The effect of exposure to cold, when the temperature of the animal falls, appears to be, in a general point of view and within certain limits, diminished respiration and augmented irritability. The experiments detailed, pp. 19 and the following, appear incomplete. It was found, that the temperature of 42° cent. (107° 6' Fahr.) was alike immedi- ately fatal to the bactrachiae in summer and in winter ; but as the experiments were first performed in the months of July and September, it was a question not only whether the temperature of 42° cent. (107° 6' Fahr.) would be equally promptly fatal in November, but whether a lower temperature would not have been so. It is probable, that all temperatures which reduce that of an animal, without destroying life, raise its irritability and lower its respiration, and render it, at once, less capable of bearing any increased stimulus, as that of heat, and more capable of bearing diminished stimulus, as the privation of air, or of food. This will probably be found a general law of the animal economy, equally applicable to the warm-blooded and cold-blooded animals. It is illustrated and confirmed by the fact quoted from Legallois, p. 148 ; and by the histories of persons or animals buried in the snow.* PART II. CHAPTER I. Page 55. — I visited the Magdalen grotto, near Adelsberg, in 1824, and ob- tained some of the protei from the subterranean pools which exist in it. Only NOTES. 465 a part of the floor of the cavern was then occupied with water, and these animals might have enjoyed atmospheric respiration had they inclined to do so, to at least an equal degree with those which Dr. Edwards kept in an earthen vessel exposed to the air. They were, however, deprived of the benefit of light. CHAPTER II. Page 56. — I have been furnished with the following authorities for fishes being able to live in water at very high temperature, by my excellent and accomplished friend A. R. Dusgate of Paris, from which it would appear, that in a state of nature, fish not only live, but thrive in a temperature beyond the limit which they were able to endure in Dr. Edwards’ experiments : may not this difference be in part referred to the influence of habit 1 Saussure, speaking of the hot springs of Aise in Savoy, says, “ I have frequently examined the temperature of these waters at different seasons, and have always found it very nearly alike, viz. from 35 in that of Souffre, and from 36J to 36-jt, in that of St. Paul. Notwith- standing the heat of these waters, living animals are found in the basins which receive them. I saw in them eels, rotifera and infusoria, in 1790. I discovered in them two new species of tremelles possessing spontaneous motion, of which a description may be seen in the ‘ Journal de Physique’ for 1790, p. 401.” See Saussure, Voyage dans les Alps, vol. vii. pp. 18 and 1168. Neufchatel edition in 8vo. Sonnerat states, that in the island of Lugon, one of the Manillas, there is a hot spring, of which the temperature was so high as to raise Reaumur’s ther- mometer to the degree of 60, equal to 86*25 cent, or 187*25 of Fahr. Accord- ing to his account, one could not put one’s hand in it, yet he distinctly saw fish which did not appear to be at all incommoded by the heat ; and small plants, the agnus castus, flourishing in it. — Journal de Physique de Rosier, April 1774, p. 256. See also Rees’s Cyclopaedia and Pinkerton’s Geography. The sparus Desfontaines of Lacepede — the chromis of Cuvier, was found by Desfontaines in the hot waters of Cafsa in Barbary, in which Reaumur’s ther- mometer rose to 30 degrees. — See the article ‘ Spares’ by Bose, Dictionaire d’His- toire Naturelle, Deterville’s edition, vol. xxxi. p. 550. My friend likewise received the same statement from the Professor’s own mouth. The following extract is from Bruce. “ At Feriana, the ancient Thala, are baths of warm water without the town : — in these there were a number of fish, about four inches in length, not unlike gudgeons. Upon trying the heat by the ther- mometer, I remember to have been much surprised, that they could have existed, or even not been boiled, by continuing so long in the heat of this medium. In opposition to the account of the hot springs at Manilla, given by Sonnerat, must be placed that of Dr. Abel, who accompanied Lord Amherst in his embassy to China. In his narrative of the journey, he notices visiting those springs, and remarks, that “ Sonnerat has stated, and his statement has been copied by other authors, that a species of fish lives in these springs. It is scarcely necessary to II II 466 NOTES. observe, that I was unable to verify this observation. All the animals which I saw there, and I saw two, a small snake and a frog, were not only dead, but boiled;” but he adds, “ a plant vegetates in them, and in this respect my ex- perience partially accords with his. 1 found a small plant, apparently a species of arenaria, vegetating in a soil that raised the thermometer, plunged amongst its roots, to 110 degrees on the side of the spring, which was 120 degrees.” — Fourth edit. London, 1818, pp. 246-249. (It will scarcely escape the attention of the reader, that Dr. Abel’s account does not positively disprove that of Sonne- rat. Though he appears only to have seen two dead animals, which probably came there accidentally, it is still not impossible, that other species, under the influence of habit, may support the temperature of some parts of the fountain.) Shaw, after enumerating the thermal waters of Barbary, adds, “ The ain el houle (fish fountain) and the springs of Cafsa and Tozer, nourish a number of small fishes of the mullet and perch kind.” — Shaw’s Travels in Barbary, folio edition, Oxford, 1738, p. 231. The late lamented Baron Cuvier, whilst engaged in publishing his great work on fishes, was reminded of these observations by my friend, and in consequence wrote to M. Marc6scheau, the French vice-consul at Tunis, who, not only con- firmed the fact in his reply, but sent him two long-tailed fresh-water turtles, from a basin of water at Utica, of which the water is at the temperature of 36 degrees of Reaumur, or 113 of Fahr. The vice-consul also sent some fishes from the hot waters of Cafsa and Tozer, which proved to be chromis or spari Desfontuines of Lacepede. These waters were said to be as warm as 62 degrees of Reaumur. Breislak in his Institutions Geologiques, has an article on this subject. Amongst other facts, to those above noticed, he adds, that Dunbar and Hunter, in their journey made in 1804, along the Washila or Ouachita, a river of Louisiana, observed above Fort Meiro, on the frontiers of the United States, springs of the temperature of 40 degrees to 50 degrees of Reaumur, or 122 to 145 Fahr., in which were not only growing conferva, and herbaceous plants, but also shrubs and trees. They likewise found in them bivalve molusca. Lamark, in his Histoire des Animaux sans Vertebres, states, that the paladina muriatica is found in Italy and in France, especially in the south, inhabiting in fresh water, and has been met with in water of the temperature of 34 degrees Reaumur, 109 Fahr. To these instances presented by nature, of animal and vegetable life, maintai ned at high temperatures, my friend Dusgate adds the following extract from an ar- ticle by Bose, in the Dictionnaire d’Histoire Naturelle, tom. xxxi. p. 551. "The facts mentioned by Sonnerat, and other travellers, induced Broussonnet to make some experiments on the degree of heat which our river fish are capable of endur- ing. I have no detail of the result of his observations, although 1 took a part in them ; but many species lived for several days in water, which was so hot that 1 could not bear my hand in it for a single minute.” NOTES. 467 I have not brought forward these curious facts, with the intention of disputing the general accuracy of the limits of high temperature assigned by Dr. Edwards, as consistent with the life of fishes. As exceptions to it, they may be apparent rather than real, since it is by no means impossible, that the heat of that part of the water in which the fishes were seen, might not be exactly the same as that in which the thermometer was placed. Tf they cannot in this manner be ex- plained away, they afford a very legitimate object for further enquiry. The fol- lowing fact is quite compatible with the limit given by Dr. Edwards, but it is interesting as shewing, that a very considerable degree of warmth is not only sup- ported, but very congenial to some species of fish. It is well known, that in manufacturing districts, where there is an inadequate supply of cold water for the condensation of the steam employed in the engines, recourse is had to what are called engine dams or ponds, into which the water from the steam-engine is thrown for the purpose of being cooled ; in these dams, the average temperature of which is about 80 degrees, it is common to keep gold-fish, the ciprinus aureus ; and it is a notorious fact, that they multiply in these situations much more rapidly than in ponds of lower temperature exposed to the variations of the climate. Three pair of this species were put into one of these dams, where they increased so ra- pidly, that at the end of three years, their progeny, which were accidentally poi- soned by verdigris mixed with the refuse tallow from the engine, were taken out by wheelbarrows-full. Gold-fish are by no means useless inhabitants of these dams — they consume the refuse grease which would otherwise impede the cool- ing of the water by accumulating on its surface. It is not improbable, that this unusual supply of aliment may co-operate with increase of temperature in pro- moting the fecundity of the fishes. My friend, Charles May, of Ampthill, to whom I am indebted for the fact just related, has communicated to me another fact in proof of the high temperature which vegetable life is sometimes capable of enduring. —John Daulby, brother to the curator at the Botanic Garden, at Liver- pool, brought from Iceland, a short time since, a species of Chara, which he found flowering and producing seed in one of the hot springs of that island, in which he states, that he boiled an egg in four minutes. PART HI. CHAPTER II. The remarks of Dr. Edwards, respecting the hybernating mammalia, induced me to query, whether there might not be some species amongst the class of birds possessed of a similar constitution, as respects the influence of temperature. The migrating birds, which quit this country on the approach of cold weather, seemed the most likely to be of this description. The season was far advanced, and swallows had for the most part left the country, when this idea occurred to me. Through the kindness of a friend I obtained two individuals, which cuabled me to perform the following experiment : — H II 2 468 NOTES. With a small and very delicate thermometer, I ascertained the temperature of the swallows to be 106° Fahr., that of the laboratory in which the experiment was performed, being nearly 70°. One of the birds was then placed in a deep glass vessel, immersed in a mixture of ice and salt. Although the bird remained quiet, its respiration soon became greatly accelerated, and its temperature, in somewhat less than an hour, was reduced about 20 degrees. It is not easy sa- tisfactorily to ascertain the temperature of so small animal as a swallow. In this instance the temperature was examined with a small thermometer, carefully placed under the wing, which was kept applied to the side. Although the extra- ordinary powers of flight possessed by swallows, and other migrating birds, gene- rally enables them to avoid that degree of cold, which their constitutions are not calculated to resist ; it is extremely probable, that if they survived detention in this country, after the setting in of cold weather, they would fall into a state of torpor. The brumal retreat of swallows, has long been a subject of speculation and controversy, and numerous anecdotes of their having been found in a state of torpor, are related by those who maintain the opinion that they do not quit the countiy, but retire to various places of concealment during the winter. Some of these statements may rest on questionable authority, but I am convinced that others are too well attested to admit of rejection. As an example of this kind, I might cite the following incident which occurred to my friend, James Browell of Guy’s Hospital. I will relate it in his own words : — “ I will endeavour to give you as clear an account as I can of the circumstances relating to the habits of the swallow, which came under my notice at a period of life not very prone to philosophise on things seen. The impression on my mind is very vivid, though the distance of time is half a century. “ Residing with my parents in Hampshire, so near the sea that the high tides reached the walls of the house, after morning school, I was occupied in the boyish play of throwing up a ball in the back yard, which fell into a butt placed for re- ceiving the rain water from the roof of the house. It was in the winter, though not a wet time, as the cask was only half full. On my getting up to the edge of the water cask, and leaning over into it, sweeping my hand round in search of the ball, my hand touched the bung cloth, a little under the water, and I felt something which induced me to move it, and found it, on examination, to be a bird in a torpid state, perfectly wet and to appearance inanimate. Whether I had heard any thing said on the subject, or what is not very probable at about nine years of age, had read about it, I cannot recollect ; but I remember well, leaving the ball and taking my prize to the kitchen fire, which after drying and warming, I had succeeded in restoring to perfect animation my bird ; when my mother found me there, and it was time for me to go to school ; my entreaties to be allowed to complete my restoration were not attended to, and I received orders to let the bird fly when it could, and it was put opposite an open window, facing the sun, and on my return from school, no trace of my protegee could be found.” NOTES. 469 Dr. Marshall Hall has obliged me by furnishing me with his remarks respecting the subjects of this PART. They are in- cluded between asterisks. CHAPTER I. III. IV. V. and VI. * This interesting series of experiments, admits of a ready association and expla- nation, by a reference to the law, that the quantity of respiration is inversely as the degree of irritability, and the facts, that the activity of the animal is directly as the former, and that its tenacity of life under the privation of air, food, and other stimuli, is directly as the latter. The very young animal has a lower respiration, and a higher irritability than the adult. It has less power of evolving heat, and greater power of bearing the privation of air. The adult animal has a higher respiration, and a lower irritability. It has greater activity, and less tenacity of life, under the privation of air and food. The animal which maintains a steady given temperature, has a higher respi- ration, and a lower irritability, in winter than in summer. Animals, which do not maintain their temperature, have a lower respiration, and a 'higher irritability, in winter and summer. When the cold induces the state of torpor, these phae- nomena are observed in a still more marked degree, and the animal bears asphyxia, and the privation of food, with comparative impunity. The fact quoted from Legallois, p. 148, and the case of animals buried under the snow, already no- ticed, are sufficient proofs of this fact. CHAPTER II. It appears to me that the case of the young animal, is incorrectly compared with that of the hibernating animal. The former lose their heat whenever they are exposed singly to the influence of the atmosphere, even in moderate temperatures. The hibernating animal, on the contrary, maintains its temperature unimpaired, even when the thermometer is pretty low. Besides this remarkable difference, there is another which has not, I believe, been pointed out. It is that sleep invariably intervenes, in the hibernating ani- mal, between its power of maintaining its temperature, and the order of phe- nomena, of which the loss of temperature constitutes one, and one so remark- able. I cannot, therefore, agree with the inferences of this Chapter, and of p. 155. Under ordinary circumstances, the hibernating animal maintains its own tem- perature. It has, therefore, the full power of evolving heat. The loss of this power is an induced condition, not hitherto noticed, and is observed in the or- dinary sleep of these, and, indeed, of all animals, only in a less degree, than in true lethargy, or hibernation. It is further obvious, that a due distinction is not made between hibernation, and the torpor which may be induced by cold in any animal, and especially the 470 NOTES. young. Legallois commits this oversight. (See p. 148, and the (EuvresdeLagal- lois, tom. i. 282.) The first condition is preservative, the second destructive of life* To the objections of Dr. Marshall Hall, already given in his own words, may be added those of Dr. Holland, respecting the temperature of young animals. The Doctors agree in this respect — that they regard the inferior power of resisting the influence of exposure to cold, which hibernating mammalia, and very young individuals of the class of birds, and mammalia, generally possess, as not indi- cative of a constant inferiority iu the power of producing warmth ; since under different circumstances, and a higher temperature, their animal heat exceeds that of the ordinary temperature of the atmosphere, as much, or more than is known to be the case, with those adult mammalia which possess the strongest power of resisting cold. Dr. Holland found the mean temperature of forty infants, aged from one day to eighteen months, to exceed that of the same number of adults, by 1 §°. Twelve children possessed a temperature of 100° to 103 j-°, whilst in no instance did the temperature of adults exceed, and in one instance only did it reach 100°. The solitary observation made by myself on swallows, shows the high temperature which they are capable of raising themselves, in con- junction with a very feeble power of maintaining it. I do not consider that the objections of either of the physiologists, whom I have mentioned, undervalue the credit or importance of Dr. Edwards’s observations on the relations which young and hibernating animals bear to external temperature. Without disturbing the practical inferences to be drawn from what has been stated by Dr. Edwards, they are of great value in themselves, not only by correcting one of his deductions, but as leading us some steps in advance into the inquiry concerning the physical and vital conditions, concerned in regulating the phaenomena in question. Dr. Hall considers that a different degree of irritability, possessed by young animals, by hibernating mammalia, and in some degree even by other adult mammalia, which have been exposed to the continued heat of the summer season, is the constant associate of their inferior power of resisting external cold, t I confess that I am much disposed to adopt this view, which, so far from ar- resting the progress of inquiry by interposing the mysterious agency of the nervous system as an insuperable obstacle, ought rather to assist our investigation con- cerning the functions of that system. Dr. Holland, in his experimental inquiries into the laws of life, takes a different view of the subject. He, as well as Dr. Hall, has ably pointed out the fallacy of some of the conclusions of Dr. Wilson Phillip, and others, with reference to the agency of the nervous system ; but I cannot help suspecting, that he has carried his objections somewhat too far, and thereby been led to regard the functions he has examined, as more independent of t See two papers in the Philosophical Transactions on Hybernation and on the Inverse Ratio which subsists between Irritability and Respiration, by Dr. Marshall Hall, 1832. NOTES. 471 the nervous system than is really the case. Be this as it may, the view which he has taken has had one important influence on his investigations. It has led him to pay a very careful and undivided attention to the varied conditions of the circu- lation and respiration, functions, which certainly stand in the closest relation to the production of animal heat. Ur. Holland lays it down as an axiom, on which he strongly insists, and which he makes the basis of several other principles, which it is his object to establish, that animal heat is in the inverse ratio to the quantity of blood exposed to oxygen in the lungs ; and he opposes the opinion of Dr. Edwards, that it is in the direct ratio to the quantity of oxygen consumed. Dr. Holland insists on the opposite effect produced by inspiration and expiration. The latter tends to expel blood from the thorax, and to oppose its return thither, consequently, when the force of the ex- pirations predominates over that of the inspirations, the quantity of blood in the lungs is diminished, and the production of animal heat is increased with the di- minished proportion which the blood bears to the inspired air. He illustrates this by various kinds of exercise, by the effects of the exhilarating passions, and of some diseases. He is obliged, however, to admit the acceleration of the circulation, by which the mass of blood is brought more rapidly and frequently under the in- fluence of inspiration, to be one of the causes of the increase of temperature. A predominance of inspirations, he represents as producing precisely the op- posite effect. It increases the quantity of blood in the lungs, and, consequently, its proportion to the inspired air. Hence it is followed by a manifest reduction of temperature. The depressing passions, bodily inactivity, and various diseases productive of congestion of blood in the lungs, but more especially asthma, are adduced as illustrations of this point of the Doctor’s views. He attributes the diminution of the production of heat, occasioned by a sudden, or temporary ex- posure to cold, to be owing to the altered condition of the circulation — the sur- face of the body becomes pale, because the capillaries cease to be filled with blood — the internal organs are loaded at their expence, and the blood in the lungs bears a larger proportion to the inspired air. Though he differs from Dr. Edwards in regarding their young animals as capable, under favourable circum- stances, of raising their temperature to as high, or even a higher degree than that of adults, he of course admits their inferior power of maintaining it, in spite of ex- posure to cold, and attributes this to the difference in the character of the circulation at different periods of life ; that of the young animal, is what he calls external, the blood sent to the surface bearing a larger proportion to that with which the internal parts are supplied, than is the case with the adult, whose circulation possesses, what the Doctor calls the internal character ; this change he attributes to the successive development of particular organs. In the young animal, at birth, the internal organs present their minimum of activity, digestion calls an encreased quantity of blood to the chylo-poietic viscera — the lungs continue to receive an increasing quantity of blood as the thoracic viscera are developed under the in- fluence of respiration and exercise. The exercise of the functions of the brain 472 NOTES. makes a demand in that direction, and the last additional demand is made as the period of puberty takes place by the development of the sexual organs. The habits and passions of the young animal concur with its organization to give the external character to its circulation, whilst those of the adult concur with the or- ganic changes which it has undergone, in producing the preponderance of the internal circulation. It is to these differences, which I have briefly sketched, that Dr. Holland refers the inferior power which the young, compared with the adult animal, possesses, of resisting cold. When cold has constringed the vessels of the surface, a larger quantity of blood is thrown upon the internal organs, which receive it, with a less proportionate capacity of vessels, than in the adult. The proportion which the blood in the lungs bears to the inspired air is increased, and the production of heat, according to the Doctor’s hypothesis, is diminished as a consequence. Adult animals in summer have a circulation of a more external and juvenile character than in winter ; hence their power of producing heat is liable to a similar reduction by the application of cold. Dr. Holland brings for- ward several interesting facts, and employs considerable ingenuity of reasoning to support of his views, and to exhibit the importance of their application ; they do not, however, appear to contain the whole truth. Why does the vigorous adult maintain the ruddy colour of his well-injected skin in a temperature, in which the infant would be pale and benumbed with cold! Dr. Holland himself remarks, that the greater vigour of the adult enables him to resist cold better than the in- fant. The reader is left to form his own opinion of what this vigour consists, and I confess, that I think this is to be found in the different condition of the nervous system, which Dr. Holland appears not to take into account in his investigation of the calorific process. I must return to his objection to Dr. Edwards’s view regarding the produc- tion of heat, when we shall have to consider the changes of the air effected by respiration. [The following experiments , which the kindness of Sir As t ley Cooper has allowed me to extract from amongst several re- corded in one of his Memorandum Books, dated 1790, anti- cipate and corroborate some of the observations of Dr. Ed- wards. — They have not to my knowledge been hitherto pub- lished.] Experiment I A young puppy was immersed in warm water, at about 120°Fahr. for one minute and a half. It struggled violently, and during the latter part of this time threw out the air from its lungs. It then remained still for another minute and a half, when its struggles were renewed, at which time it voided its excrement. These efforts were soon over. After remaining still for three minutes, it was put into another vessel containing water of the same tem- perature. In this it gasped twice or thrice. In ten minutes after its first immer- sion 1 opened it — a slight undulation was observable at the lower part of the NOTES. 473 right auricle of the heart, and there was some motion in the intestinal canal. The action of both ceased in about a minute, and could not be reproduced by the irritation of touching and piercing it. Thus, then, the action of the heart was destroyed eleven minutes after its first immersion. Experiment II. — A puppy, of the same age as the last, was immersed in water, at about 56°Fahr. For one minute and a half its voluntary motions con- tinued violent — it expired the air from the lungs, and then was quiet. At the end of another minute and a half its struggles were renewed. Its excretions passed off. For two or three minutes after it continued to gasp. It was then thrown into another vessel containing water of the same heat. It gasped at the end of every minute, and ten minutes after its first immersion it was opened. The heart acted vigorously, and there was strong peristaltic motion in the intes- tines. The action of the heart continued strong for nineteen minutes after it was opened, when it began to undulate — it undulated for four minutes, when all ac- tion ceased. At the end of twenty-nine minutes, then, the heart of this animal acted as strongly as that of the first, which died in ten minutes. Experiment III.— A puppy was immersed in water heated to 90° of Fahr. for a minute and a half. It continued to struggle violently another minute and a half — it remained motionless — when it began to struggle again, and for half a minute continued to do so. At the end of ten minutes it was opened. The lower part of the right auricle undulated, and continued to do so seventeen minutes after it was opened, when no motion could be produced by the stimulus of vinegar, or by the irritation of pricking it. Experiment IV. — A puppy of the same age was immersed in cold water. The first minute and a half it struggled. It remained quiet for one minute and a half, then struggled again. It continued to struggle at the fourth and fifth mi- nute for one quarter of a minute. At the tenth minute it was opened. The heart contracted strongly in every part, and the intestines moved. Eighteen minutes after opening the animal, the heart contracted more strongly than that of the third experiment did at first, and it continued to undulate six minutes after ; so that it acted twenty-four minutes from the opening of the chest. Experiment V. — A kitten was put into cold water, and after about two mi- nutes ceased to struggle. For some minutes after it had convulsive motions. Twelve minutes after it was immersed, its abdomen and thorax were opened. The heart was contracting, and the intestines moving. The heart continued to do so for half-an-hour. Experiment VI. — A kitten was immersed in water heated to 100° Fahr. Its efforts seemed rather more violent than those of the other in the fifth experiment. Its convulsions were sooner discontinued. Twelve minutes after its immersion it was opened no action could be observed, either in the heart or intestines, nor could it be produced by stimuli or irritation. Experiment VII. A snake was opened after having been immersed in rec- tified spirits of wine in order to destroy it. It coiled itself up, became rigid, and 474 NOTES. was supposed to be dead. In opening it, it shewed some voluntary power, and its heart was found beating strongly. It was put into a vessel of cold water, and the action of the heart became languid and slow. It was then thrown into water heated to about 80°Fahr. — the action of the heart became quick and vigorous, and it began to move freely in the vessel, recovering its voluntary motions, al- though its body was opened. It was then returned into cold water — its volun- tary power lessened, and its heart acted less frequently and vigorously. Experiment VIII. — The atmosphere being at 61 F ahr., a thermometer was introduced into the belly of a viper, and it stood at 76°. Experiment IX. — Water was heated to 99J0Fahr. A viper was plunged in and kept there ten minutes. The thermometer stood in its belly at 92°, but soon fell. Experiment X. — A viper was exposed to air heated to 102° Fahr., and kept there fifteen minutes. The thermometer stood in its belly at 96°. Experiment XI. — A viper was exposed to air at 34° Fahr. It became torpid in a considerable degree — it was retained in this stupefaction fifteen minutes. The thermometer stood in its belly at 42°. Nitre and muriate of ammonia, in equal parts, were used to produce this degree of cold. From these last experi- ments it appears, that the viper is subject to great changes of its temperature by the surrounding atmosphere, which corroborates the idea of Dr. Crawford, — “ for these reptiles have their blood but very partially heated ; hence their power of re- sisting high and low degrees of heat must be weak.” Experiment XII. — I put a kitten six weeks old into water, which I kept at 32 Fahr. by putting in it small pieces of ice. Its mouth was above water. It died at the end of sixteen minutes. During almost the whole of the first five minutes it laid quiet in the water, but its nose, lips, and gums, which were pre- viously pallid, soon after immersion, became of a beautiful vermillion colour. It struggled violently during the second five minutes. Between the tenth and sixteenth minutes it laid quietly. It breathed first quickly, then laboriously, and lastly at long intervals, when it died. Upon introducing a thermometer, imme- diately after the last breath, into the chest, it stood at 52°. The heart did not act. The blood was of a florid red in the left side of the heart. The peristaltic motion of the bowels still continued. When touched, the heart acted ; but was quite motionles, unless thus stimulated. An hour and thirty-five minutes after its apparent death, I poured warm water at 90° or 100° into the chest. The heart began to act, and continued to do so for more than two hours; therefore, four hours after the chest had been laid open. The blood in the mesentery was very florid. Another experiment, almost in every respect similar, is related as tided upon a puppy a month old. It survived twice as long. Its temperature was less re- duced, and its heart continued to act longer. Its lips, nose, and toes, became of a florid colour. NOTES. 475 A few experiments on the immersion of kittens seven days old in water of different temperature. Made 28th August, 1832. By T. Nunnelly. With water pumped up from the well at 57° Fahr. No. 1. Struggled hard for a minute, when it apparently became insensible and passed the feces ; it exspired frequently and made violent attempts to inspire. Some involuntary motion was continued for two minutes and a half, when it was taken out, wiped dry, and placed before the fire at a temperature of about 80 ; it heated immediately and quickly recovered. No. 2. Allowed to remain in the water four minutes ; the effects were the same as in No. 1, except that it did not completely recover so soon. No. 3. Allowed to remain under the water for five minutes ; during the last minute the involuntary motion was very slight, when taken out, breathed, and recovered in fifteen minutes. No. 4. Allowed to remain under water for six minutes ; this kitten did not breathe for thirty seconds after being taken out, and was half an hour before completely recovering. No. 5. Allowed to remain under water for ten minutes ; for seven minutes and a half some very feeble involuntary motion could be seen, but not more than three minutes after the fifth minute. When taken out it was apparently quite dead. I opened the trachsea, and continued artificial respiration for ten minutes before it made any effort to respire, which for half an hour was very feeble ; for an hour it lay in a comatose state, after which it gradually recovered, and in four hours looked much as the other kittens. 1 allowed it to live for two days, when 1 destroyed it, as of course it was unable to suck owing to the opening in the trachrea. With water at 100° Fahr. No. 1,2, 3. Effects much the same as with water at a temperature of 57°F. No. 4. Remained under water six minutes ; this kitten recovered, but was a longer time than that with the water at 57°, and lay for an hour as though asleep without moving, unless disturbed. No. 5. Allowed to remain under water for ten minutes ; motion was per- ceived for a longer time than in the similar experiment with water at 57°, viz. for nine minutes. When taken out it was quite dead. Dry heat was applied, the trachaea opened, and artificial respiration continued for an hour without success. Water at 120° Fahr. No. 1. Allowed to remain under the water for five minutes ; it struggled hard as the others did for a minute, and involuntary motion could be seen for four minutes. When taken out, it was quite dead, and although precisely the same means weie adopted as with the other cases, they were without success. 476 NOTES. In all the kittens that recovered, in proportion to the time they had been under water, was the breathing at the first slow, it then became exceedingly quick and short, and it was some time before they regained their ordinary temperatures, quite as long, or rather longer, after the warm medium, as after the colder. Thomas Nunnelly. PART IV. CHAPTER II. Since the publication of Dr. Edwards’s observations respecting the heat of young animals, some interesting researches have been made by his brother, Dr. Milne Edwards, in conjunction with Dr. Villerme. They not only prove the inferiority of the infant’s power of resisting cold, but show in a forcible and striking manner, the great practical importance of bearing this fact in mind. It is the custom in France to convey infants, within a few hours of their birth, to the office of the mayor of the quarter in which the nativity took place, in order that the birth may be re- gistered, and the child become posssessed of its civil rights. A careful compa- rison of the register of births, with the register of deaths, furnished statistical ob- servations on so large a scale, that there can be no room to doubt the correctness of the results. It appeared that the proportion of deaths, within a very limited period after birth, compared with the total births, was much greater in winter than in summer, and that this difference of proportion, was much greater in the northern and colder departments, than in the southern and warmer. The details of this investigation are recorded in a paper which the Doctors have presented to the Institute. They have since continued the inquiry, and the following extract from a letter which I have received from Dr. Milne Edwards, will show the accord- ance of their results. ‘ ‘ In order to ascertain in a more positive manner than before, whether the mor- tality of new born children is increased by their being carried to the maire im- mediately after birth, we obtained from the minister of the interior, necessary orders to have the tables of mortality of infants made in a certain number of parishes, where the inhabitants are scattered over a larger surface of ground ; and in others, where they are, on the contrary, agglomerated around the maire. It appeared evident to us, that if our opinion was correct, the increase of mortality during winters, must be much greater in the former parishes than in the latter, and such is, indeed, the result actually afforded by our tables.” CHAPTER IX. I have received the following letter on the subject of cutaneous absorption, of which Dr. Edwards is a decided advocate, and, although, it combats the Doc- tor’s opinions, I am induced to publish it, not only because the author, Dr. Cordon Thompson of Sheffield, is an extremely well-informed physician, tho- NOTES. 477 roughly versed in physiological reasoning and experiment, on which account his opinion is entitled to respect ; but also, because it affords me an opportunity of meeting similar objections, which maybe urged by others, against the conclusions maintained by Dr. Edwards, upon this subject. “ At the commencement of his observations on cutaneous absorption, Dr. Ed- wards states, that from comparative essays made in air and water, Seguin thought himself justified in concluding, that the latter fluid was not absorbed. But, he continues, ‘ the result of these experiments admits of being viewed in a different light, when we consider certain facts relative to the animal creation.’ 4 We have seen,’ he observes, 4 that the batrachia are capable of imbibing, by their ex- ternal surface, a considerable quantity of water, which passes into the system at large. In such animals, as well as in man, the skin is bare, a condition highly favourable to absorption. The human skin, it is true, from the nature of its cuticle, is less fitted for performing this function, though it continues to exercise it in a high degree.’ Such is the language of Dr. Edwards. Now, in the first place, I cannot, for a moment, admit the correctness of the analogy, here as- sumed, betwixt the exterior surface of the batrachia, and that of man. The former approaches the nature of mucous membrane, the absorbing faculties of which, no one for a moment questions ; but, the latter, is essentially modified by the dry superjacent cuticle, which, even the Doctor confesses, is less fitted for for absorbing. To infer from mere analogy, that because the one takes up sub- stances, therefore the other does, is in reality to take for granted, the very thing which ought to be proved. The analogy, in fine, is incomplete ; the anatomical elements of comparison are not the same in each case ; neither are the functions of the structures in question the same. Pursuing, however, a similar, and I should say, illusive mode of argument, we are told that it becomes impossible to entertain further doubts on the subject, when we witness what occurs in animals, the teguments of which, appear the least susceptible of transmitting fluids. Lizards, for example, possess, as all know, a hard scaly exterior, which should seem an effectual barrier to the passage of an aqueous fluid. Yet, could this be proved to take place, our author imagined he would be justified in concluding a fortiori, that a similar transmission exists in the human integuments. Hence, for the pur- pose of determining that point, he confined an animal of this description in water, in such a way, that the tail, posterior, extremities, and corresponding parts of the body, were alone immersed. The lizard, moreover, in order to excite the activity of the absorbents, had been previously kept in air for a few days ; its weight being thus somewhat diminished, any subsequent increase would be ren- dered more notable. At different intervals of time the animal was weighed ; and the weight gradually augmented until the loss it had previously sustained was restored. At this stage, the experiment was stopped, the Doctor being satisfied with its result. I cannot, however, help thinking, that he has overlooked several very important considerations ; considerations, which, to me, at least, seem alto- gether to invalidate the conclusions drawn from this trial. In the first place, whe- 478 NOTES. ther absorption by the skin do, or do not, exist, that by the lungs eannnot for a moment be doubted; neither can it be doubted, that it is of a most active and energetic description. Now, here we have an animal confined mid-way in water, in a glass tube, and surrounded therefore by a highly moist atmosphere, and yet no notice whatever taken of pulmonary absorption ! This omission of itself is fatal to the accuracy of the experiment. But, again ; if we revert to the nature of the integuments, such an experiment, we shall see, is not calculated to set- tle the point in question. The exterior covering of the body is an inorganic pro- duction, and like similar substances, capable of mechanical imbibition, after con- tinued maceration in a fluid. This is very easily observed in those parts of the body where the cuticle is thick, as in the hands and feet. When thus saturated , it becomes white and wrinkled. In like manner, the inorganic tegument of the lizard would doubtless absorb a portion of water, after considerable maceration in that fluid, and thus the weight of the animal be increased, totally independent of any absorption, into the interior of the system. Here, then, is another source of fallacy. But, let us even suppose, after continued maceration of the integu- ments in water, and after having thus been saturated, that eventually a portion of the fluid finds its way into the system, would such an experiment warrant us in concluding, that under any ordinary natural circumstances, any such thing as cutaneous absorption exists ? Surely not ; and I apprehend we shall find it to be a frequent and radical error with experimentalists, to conduct their experi- ments under highly unnatural circumstances, and to assign the result, thus ob- tained, as a natural and ordinary function of the animal economy. “ If we except Seguin, whose admirable experiments on this subject most phy- siologists are well acquainted with. Dr. Edwards does not notice any other writers, or the facts which they adduce, in disproof of the doctrine which he maintains. Seguin himself, indeed, obtains but a cursory glance; nor are his experiments in any way refuted. Having established the existence of cutaneous absorption, as he conceives, by the evidence already mentioned, Dr. Edwards next proceeds to institute, what may be called, tare and tret computations, relative to the gain or loss sustained by the body when immersed in water. And here again the ca- pital oversight is committted, of neglecting to take pulmonary absorption into the estimate. It is needless, therefore, to follow him in his observations on this part of the subject. On the whole, the evidence from which Dr. Edwards seems to infer the existence of cutaneous absorption, is either loose and vague on the one hand, or manifestly fallacious on the other. The doctrine may be true ; but the reasons here produced, are insufficient to substantiate it.” The principal objection advanced by Dr. Thompson, appears to rest on the experiments of Seguin, and on the impediment, which he conceives, the epidermis must oppose to absorption from the surface of the body. There can, indeed, be no question as to the reality of the obstacle, but it is by no means evident, that it is insurmountable. On the contrary, I think it most reasonable to infer, that if this absorption, or imbibition, can take place through the dense and less per- NOTES. 479 vious coverings of many reptiles, it must, notwithstanding Dr. Thompson’s objection, be admitted in the case of the human epidermis. There is an obvious difficulty in bringing this question to the test of direct experiment, arising from the fact, that exhalation, or transmission outwards, is unquestionably taking place, and in general to a greater degree than we can even suspect it to take place in the opposite direction. This very objection, however, furnishes us by analogy, with one of the best arguments in favour of cutaneous absorption, since we have the authority of several investigators, and more especially of Fodera and Dutrochet, to prove that imbibition, and transudation, are reciprocal and simultaneous. Dr. Thompson points to pulmonary absorption, as the cause to which the sup- posed effects of cutaneous absorption ought to be ascribed. Many experiments, but especially those of Meyer and Magendie, leave no room to doubt the activity of the pulmonary absorption ; but, except under very extraordinary circumstances, it does not seem probable that it can be exerted to any considerable extent, ex- cept upon the secretions of the mucous membrane itself. It cannot, therefore, be assigned as the inlet to any perceptible accession to the system. The fact, that the expired air is much more charged with watery vapour, than that which is inspired, tends to the same conclusion. If Dr. Edwards has omitted, as Dr. Thompson remarks, to notice the statements of several authors, who have called in question the reality of cutaneous absorption, he has likewise omitted to claim the support of many who have sanctioned it, amongst whom might be mentioned several of those who have written on the subject of diabetes. Connection of rainy seasons with disease, exemplified in the cases passing through an hospital. There fell at the Havannah, in seven years, 603f French inches of rain, viz. in 1821, 131f inches ; in 1822, 53^ inches ; in 1823, 100 inches ; in 1824, 79^ inches; in 1825, 97 inches; in 1826, 74 inches; in 1827, 683; inches. The distribution per month, was as follows : — average for January, 4f inches ; for February, 3 inches ; for March, 3^ inches ; for April, 2^ inches ; for May, 9J inches ; for June, 23| inches ; for July, 5| inches ; for August, 6J inches ; for September, 1 Of inches; for October, 10 \ inches; for November, 4f inches ; for December, If inches. From a corresponding table of 4028 sick, who passed through the Hospital, in the course of seven years, it appears, that the months in which the sick exceeded the monthly mean in number, were those from May to October inclusive, in which, (with two exceptions) the rain was above the general monthly average of seven inches. And the two exceptions lying between months which had rain in excess, and following the highest amount of rain, (in June,) seem to be ac- counted for on the principle, that disease may be continued by infection, after the atmospherical predisposing causes lxftve ceased to operate. Again, the years in which the rain was above the annual mean of 76J inches, are mostly those in which the sick exceeded the average annual number of 575 cases. 480 NOTES. In both accounts the temperature is not to be left out of the question. The an- nual mean, being 25‘6° cent. ; that of the winter, is 21,8° ; of the summer, 28‘5°. The number of sick in seven years is, on an average for the winter, 218 ; for the summer, 357. Yet it is not probable that heat alone, without the mois- ture, would cause such a difference, but rather, that the summer would in that case be the more healthy season. — Translated and abridged (with a remark an- nexed by L. Howard) from Bibliotheque Universelle, 16me annee, p. 33. Although it can scarcely be supposed, that any slight addition to the weight and pressure of the atmosphere can have any sensible effect on the animal eco- nomy, seeing, that not only changes of this description frequently accompany vicissitudes in the weather, without leading to any obvious consequences, and that by ascending to considerable heights and by descending into mines, we may greatly increase the extent of such changes with perfect impunity ; yet, I cannot omit to notice a recent observation of Dr. Prout’s, which seems to indicate, that even a slight increase in the weight of the atmosphere, may be the concomitant, if not the cause, of a highly deleterious influence. Dr. Prout had, foryears, been in the habit of carefully examining the weight of the atmosphere, when, on the breaking out of cholera, he noticed a slight, but sensible increase of its weight, which maintained itself with constancy for six weeks, when circumstances oc- curred to suspend the Doctor’s observations. He does not attribute any morbid influence to the mere increase of weight of the atmosphere, but rather regards this as the consequence of a deleterious and heavy gaseous principle, diffused through the lower regions of the atmosphere. For a detailed account of Dr. Prout’s ex- periments and opinions upon this subject, the reader is referred to his paper, which is about to appear in the transactions of the British Association. Those who descend to a considerable depth in diving bells, are subjected to the greatest atmospheric pressure to which it is easy for man to expose himself ; but its effect is necessarily complicated with that of the deterioration, and want of motion of the air. Notwithstanding these combined sources of inconvenience, it is well known, that workmen may continue their operations, during several hours of the day, at a depth of many feet. From personal experience of the effects of this situation, during about half-an-hour, I may state, that the only painful sensa- tion is that occasioned by the pressure on the membrane of the tympanum, which is felt on first descending ; but soon ceases, when the equilibrium between the in- terior and exterior of the body is restored. The blood is very much driven from the surface of the body, producing in general extreme paleness. When the su- perficial capillaries are not emptied, which I observed to be the case with one individual, who had, what is styled a fixed colour in his face, they become com- pletely livid. According to the theory of Dr. Holland, the production of heat ought to be reduced nearly to its minimum, since the proportion of the blood in the lungs to that of the inspired oxygen must be great. The heat, however, be- comes oppressive. It seems by no means improbable, that increased pressure of the atmosphere may be one of the causes requiring the exercise of the function, Sch I have ascribed to the spleen. NOTES. 481 CHAPTER XVI. In considering the observations of Dr. Edwards on the changes of the air in respiration, there are two points which appear to be particularly interesting and worthy of attention. The experimenters who have succeeded him had arrived at different conclusions, more especially with respect to the consumption of oxygen, and the alterations in the quantity of nitrogen. As these differences could not be attributed to errors of observation, they tended to render the subject more complex and puzzling, until Dr. Edwards, by instituting a series of experiments, continued through the different seasons of the year, at once confirmed and ex- plained the discrepancies of his predecessors, and made a valuable discovery res- pecting the influence of climate and season . The other point to which 1 have alluded, refers to the part of the body in which the changes in the respired air are effected. It had been a subject of question, whether the carbonic acid expired, was not formed immediately in the lungs, by the combination of the oxygen of the atmo- sphere with the carbon of the venous blood. According to another view, it was supposed that whilst a portion of the oxygen of the atmosphere was taken up by the blood, and carried with it in its circulation, and at the same time carbonic acid was thrown off from the lungs, having been previously taken up in the course of the circulation. Dr. Edwards appears to have settled this question, which seemed previously to be nearly balanced, by confirming the latter view. We have, therefore, in the function of respiration, not only a striking instance of the transu- dation, and imbibition of the gases through the membrane, but also of their simultaneous passage in different directions. In both of these respects, Dr. Ed- wards has anticipated Fodera and Dutrochet, whose observations have further elucidated them, and pointed out analogous phenomena in other parts and func- tions. Since the publication of Dr. Edwards’s work, some further experiments on respiration have been performed by those careful and accurate operators, my friend William Allen, and his associate, W. H. Pepys ; and others of equal interest, by my friend S. Broughton. Before I notice the facts, which these ex- perimenters have either confirmed or added, it appears necessary that I should notice the discoveries and views of Dr. Stevens, which throw the most important light on the process of respiration. These views were not the offspring of specu- lation, which he has sought to confirm by subsequent experiments, but they forced themselves upon him, whilst he was investigating the changes of the blood, and the phenomena of fever ; and it seems necessary that I should remavk, to set aside any prejudice which may exist in the mind of the reader, that the Doctor’s physiological observations respecting respiration, stand upon their own distinct merits, and are by no means compromised by his pathological and therapeutical doctrines. In order to keep the subjects distinct, I purposely refrain from offer- ing an opinion respecting the last mentioned points ; yet, I cannot withhold the expression of my admiration of the zeal, perseverance, and self-devotion, with which the Doctor has pursued his investigations respecting them, under the most I I 482 NOTES. V arduous, and, perhaps, perilous circumstances. One of the most, striking facts which the Doctor lias brought into notice, is the powerful attraction which exists between oxygen and carbonic acid. It was so fully admitted amongst chemists, that carbon in carbonic acid is united with its maximum dose of oxygen, that the idea of attraction between carbonic acid and oxygen was rejected from a priori reasoning by several able chemists, to whom the Doctor mentioned the subject. The fact, however, is clearly proved by the experiments of Dr. Stevens. If a receiver filled with carbonic acid, and closed by a piece of bladder firmly tied over it, be exposed to the atmospheric air, the carbonic acid, notwithstanding its superior specific gravity, rapidly escapes, and does so without the exchange of an equivalent portion of atmospheric air; the bladder is consequently forcibly de- pressed into the receiver. If the converse of this experiment be tried, and the re- ceiver, containing atmospheric air be tied over with a piece of bladder, or thin leather, and then be immersed in carbonic acid, this gas will so abundantly pe- netrate the membrane, and enter the receiver, as to endanger its bursting. Dr. Stevens had repeated opportunities of verifying these facts, during a stay which he made at Saratoga, in the United States ; the springs at which place liberate a large quantity of carbonic acid. In the high rocks it often collects in considerable quantity and purity, and experiments on dogs and rabbits are often made for the entertainment of strangers, as at the Grotto del Cane, near Naples. This rock stands by itself in a low valley, through which there run two currents of water, the one fresh and superficial, the other beneath, and charged with salts and carbonic acid. A current of this water rises to some height in a cavity of the high rock, which appears to have been formed by a deposition of earthy salts from the water. It has a conical figure, the base of which, is below the surface of the ground, is about nine feet in diameter. It rises about five feet from the ground, where it is truncated, and presents an aperture a foot in diameter. The cavity of this rock is conical, like its external figure — the water appears formerly to have overflowed the summit, but it now rises in general only about two feet above the ground. In the three feet above, the liberated carbonic acid collects, but it varies very much, both in quantity and purity, notwithstanding the sides of the rock are thick and impervious, and the superior specific gravity of the gas, which is con- stantly liberated in large quantity. The removal of the carbonic acid appears to be effected by virtue of that attraction, which Dr. Stevens has pointed out as exist- ing between it, and the oxygen of the atmosphere. When the air is somewhat agitated by wind, a taper will burn in the cavity of the rock, almost as low as the surface of the water ; but when the air is calm, the taper is extinguished much nearer the top of the rock. By luting a large funnel over the aperture, so as to exclude the influence of the air, the rock became filled with carbonic acid, which the Doctor collected for his experiments, at the mouth of the funnel. Dr. Stevens took advantage of the facilities afforded by this rock, to multiply and vary his ex- periments, the results of which, were not only perfectly satisfactory to himself, but to many individuals to whom he exhibited them. This attraction, which the NOTES. 483 Doctor has pointed out, is not only to be regarded as an important agent in the function of respiration, but throws considerable light on the constitution of the atmosphere, since it accounts for carbonic acid, notwithstanding its greater spe- cific gravity being found in equal proportions at every elevation to which we can ascend, instead of being collected at or near the surface of the earth. Experiments similar to those of Dr. Stevens, and attended with the same re- sults, have been published in an American Journal, byDrs. Faust and Mitchell, who have anticipated Dr. Stevens, in committing them to the press, without mak- ing any allusion to his discovery, although there can be but little doubt but they were in a degree acquainted with it, as the Doctor himself had related the re- sult of his previous experiments, not only to other professional individuals in the United States, but even to the very editor of the Journal in which the American papers were first published. It is stated also, that this gentleman took a part in Dr. Mitchell’s experiments. Dr. Stevens formed his views, respecting the attrac- tion of the atmosphere for carbonic acid, and committed them to paper, in 1827, at which time, he resided in the West Indies. In 1828, they were mentioned, or shewn in manuscript, to several persons in this country : and in France, which the Doctor visited in 1829, more than one chemical philosopher was disposed to dispute the existence of such an attraction — Dr. Edwards himself was amongst this number. Dr. Stevens went to the United States in 1830, in the seventh month (July). The American experiments commenced soon after, and were published be- fore the end of the year. The reader, I trust, will allow the excellence of the principle, suurn cuique, to be a sufficient apology for the introduction of this statement. Although this mutual influence, between carbonic acid and oxygen, may not now be doubted, yet different views may be entertained respecting its nature. The views and discoveries of Dalton, respecting the admixture of gases and va- pours, appear to bear the closest relation to this subject, but they do not seem to be adequate for the explanation of all the phaenomena. Although the particles of a particular gas, or vapour, may repel each other, yet allow those of a different gas, or vapour, to come between them, and thus allow, what Dr. Mitchell styles, the penetrativeness of one and the elasticity of another gas, to promote their inter- mixture ; yet, it is not very evident, that this theory can explain their energetic union, when a membranous septum has been interposed between them, and still less, why carbonic acid should be so much more powerfully brought into ad- mixture with oxygen, than with nitrogen, or hydrogen, which are much rarer gases. It has been supposed, that the phaenomena pointed out by Dr. Stevens, are of the same nature with those which Dutrochet has described under the terms, endosmosis and exosmosis, but unless we are to regard every instance, in which one fluid diffuses itself through another, or passes through a porous body, as an in- stance of endosmosis, or exosmosis, an idea which Dutrochet himself would rc- i i 2 484 NOTES. ject — there is, notwithstanding, some analogy — a striking difference between the phamomena in the cases of endosmosis related by Dutrochet ; the intervening septum performs a very important part in influencing the movement of the fluids. This is most strikingly exemplified in Ihe application which he makes of his prin- ciple to the circulation of the sap in the roots and branches of plants. In the phamomena pointed out by Dr. Stevens, the impulse resides in the gases them- selves, and all we can say respecting the septum interposed between, is, that it does not prevent their union. Although Dr. Stevens informs us, that Dr. Edwards offered some objections to his views, respecting the removal of carbonic acid from venous blood in the lungs, by virtue of an attraction for that acid, inherent in the inspired air ; yet, I must confess, that after a careful consideration of the subject, the views of Dr. Stevens, instead of militating against the observations of Dr. Edwards, are in the most satisfactory accordance with them. In order to understand the application of the attraction pointed out by Dr. Ste- vens to the function of respiration, it will be necessary to be aware of a few facts relating to the blood ; some of these were more or less known prior to the expe- riments of Dr. Stevens, but he has the merit of greatly extending, as well as ap- plying them. All acids impart a dark colour to the blood. With respect to most acids this colour remains, although the added acid be afterwards saturated. Car- bonic acid forms an exception, for on the removal of this aerial acid the blood re- sumes its bright and arterial colour. Alkalies, like acids, darken the colour of the blood, but salts produce a bright and Vermillion colour, when added to the colour- ing matter of the blood. The alkaline carbonates require particular notice. Theacid is so feebly held by the base, that in some respects they conduct themselves as al- kalies, and in particular, will restore the blue colour to reddened litmus. Dr. Stevens believes that this circumstance has led some chemists of great celebrity, to admit the presence of free alkali in the blood, whilst he takes an opposite view, and believes that in venous blood at least, there is a superabundance of free car- bonic acid, which, however, is soon removed by exposure to the air. This opinion seems to be confirmed by the fact, that if water, holding carbonate of soda, and carbonic acid in solution be added to the blood, a deep and venous hue is pro- duced. After a short exposure to the air the carbonic acid is removed, as Dr. Stevens believes, by the attraction already noticed, and the blood is reddened by the carbonate of soda, the influence of which, is no longer controuled by the re- dundant acid. The recently separated serum of venous blood has no effect on turmeric paper, although it has after a little exposure to the air. There are many other phenomena connected with the blood which Dr. Stevens has noticed ; for these, I must refer the reader to the Doctor’s own interestingwork. Those which I have already mentioned, will suffice to enable us to appreciate the light which the Doctor has thrown on the function of respiration. I must, how- ever, take the liberty of remarking, with respect to the curious phainomena he observed with the help of a powerful solar microscope, that I believe some fallacy NOTES. 485 attends them, in consequence of the heat unavoidably applied to the object, brought into the field of the instrument in bright daylight. It will, I am sure, be under- stood, that I am not invalidating the Doctor’s evidence, when 1 ascribe many of the globular appearances which came under his view, to the disengagement of gases effected by the heat in question. The best compound achromatic micro- scopes, not only possess a superior power, but are exempt from the objections which I am now urging against the solar microscope. The account given in this volume of the microscopic appearances of the blood, as seen through a compound microscope of the highest quality, does not coincide with the description given by Dr. Stevens. The explanation which I have offered, will, I believe, satis- factorily account for the difference. Though I do not regard the microscopic phenomena, described by Dr. Stevens, as affording a correct view of the struc- ture of the blood, I am not disposed to reject them, but rather to query, whether they may not lead to some curious observations in the disengagement of gases from fluids. To return to the subject of respiration. The views of Dr. Stevens accord with the opinions of those who reject the idea of the formation of carbonic acid as taking place in the lungs, by the immediate union of the oxygen of the atmosphere with the carbon contained in the venous blood. We have seen that Dr. Edwards is of this number, inasmuch, as he believes, the formation of carbonic acid to take place throughout the body. Dr. Stevens, however, does not regard the air as passively receiving the carbonic acid as it is liberated from the blood, which had not only held it in solution, but actually imbibed it. He considers that it is ac- tively removed by the attraction existing between oxygen and carbonic acid, which overcomes the weaker, attraction by which the acid was united with the blood. When the blood has lost its carbonic acid, it presents the bright Vermil- lion tint which naturally belongs to its colouring matter, and salts, when com- bined. When the venous blood gives up its carbonic acid, it receives in exchange, a portion of the inspired air, which is chiefly at the expence of the oxygen. The proportion of this gas, abstracted from the inspired air, being very nearly, and often exactly, the same as that of the carbonic acid added to it. Dr. Edwards has pointed out the circumstances under which the quantities differ. We must not, however, suppose that it is only carbonic acid which is exhaled, or oxygen which is received by the blood and lungs. The experiments of Allen and Pepys, as well as those of Dr. Edwards, have proved that there is an interchange of other gaseous principles. The reddened and oxygenated blood having returned to the heart, is diffused over the system, imparting animal heat in proportion to the quantity of oxygen which it gives up for the production of carbonic acid. It receives this carbonic acid in exchange for the oxygen which it has lost, and is darkened by its presence, which counteracts the effects of its salts. This, I be- lieve to be a concise sketch of Dr. Stevens’s theory of respiration ; it is far from clashing with Dr. Edwards’s observation respecting the disengagement of car- bonic acid ; it seems, on the contrary, satisfactorily to account for cutaneous 486 NOTES. respiration, since, wherever the atmosphere is exposed to a vascular part, its oxygen must promote the separation of carbonic acid from the venous blood. If we apply this view to the respiration of animals who live in water, and admit that the oxygen dissolved in that fluid, separates carbonic acid from their venous blood, we have another argument in favour of an actual attraction existing bo- tween oxygen and carbonic acid, since the discoveries of John Dalton, and the penetrativeness of Dr. Mitchell, are quite inapplicable to the subject. The experiments of Allen and Pepys to determine the changes produced in the air by respiration, which have been made subsequent to the publication of Dr. Edwards’ work, are a continuation of their former researches, and were made solely on the respiration of birds. These enquirers conducted their experiments in the same method as that which they had formerly employed, and in no instance compromised the life or health of the animal. The birds were placed in a small glass chamber, which received its supply of air from one gasometer and parted with it into another at certain intervals. The most careful analysis was made, both of the gas supplied to the animal, and of that which it had respired ; every calculation being made which the state of the barometer and thermometer, and the volume of air existing in the receiver containing the bird, and the tubes leading to it, could require ; their results may be stated as follow : — After one hour and twelve minutes respiration, the amount of gasses employed being originally oxygen azote carb add. Cubic inches . .245*59 61*41 There remained 195*61 9011 21*27 shewing a loss of 28*71 of oxygen beyond the volume converted into carbonic acid, and a gain of 28*70 of azote. The head and other parts of the pigeon in which the state of its vessels could be seen, were of a bright red. In a similar experiment which lasted one hour and ten minutes, 24*74 cubic inches of car- bonic acid were produced, besides which, 21*75 of oxygen were lost. In atmo- spheric air, 35*80 cubic inches of carbonic acid were produced in sixty-nine minutes. In a mixture of oxygen and hydrogen with a portion of azote, a pigeon in the course of twenty-six minutes, produced 17*62 cubic inches of carbonic acid ; 35*48 of hydrogen were lost, and 35*23 of azote were added. Allen and Pepys were not acquainted with the researches of Dr. Edwards, and as they inclined to the belief, that the volume of oxygen lost was replaced by an equal volume of carbonic acid, their delicate and accurate experiments form a valuable confirmation and supplement to those of the Doctor. The experiments of S. D. Broughton, relate to the same subject, but were performed in a somewhat different manner, and supply us with new and valuable facts. He placed a variety of animals in receivers of considerable capacity compared with their bulk ; he filled them with different gases, in which he allowed the animals to remain until they were nearly or quite dead, when he examined their state and that of the gas remaining in the receiver. His most important and numerous experi- ments relate to the respiration of oxygen. He found, as Allen and Pepys had NOTES. 487 done, that animals at first bear this kind of respiration with apparent impunity, that the pure oxygen at first acts as a stimulus, and that all the parts of the body in which the state of the vessels can be seen are injected with bright arterial blood. Though this florid colour continues, the powers of the animal progres- sively sink, he falls into a state of suspended animation, and inevitably dies in the couise of a few hours if suffered to remain in the gas ; and even if taken out alive, the injury which he has received may be fatal. This effect is not to be ascribed to the deterioration of the air in the receiver, as in the case of an animal dying in a given quantity of atmospheric air. The remaining oxygen is still sufficiently pure to support the vivid combustion of iron-wire, and to produce a repetition of effects on a second and third animal similar to those described as occurring with the first. The animal is found to have all its sanguiferous vessels filled with bright arterial blood, and its temperature is found to have fallen several degrees, even when taken out before life is extinct. The fatal effects of the respiration of pure oxygen gas are con- firmed by the experiments of Sir H. Davy, and by those of Drs. Prout and Ma- gendie. The blood is observed quickly to coagulate after the respiration of this gas. S. D. Broughton tried the effects of the gaseous oxide of nitrogen, com- monly known as the exhilarating gas ; this can be respired longer than other gases, yet death takes place sooner than in pure oxygen. The blood continues fluid and thin. He found animals die very quickly in sulphuretted hydrogen ; indeed it is impossible to conceive death more instantaneous than that which I have myself seen take place in a sparrow, which Professor Thenard introduced into this gas. This effect of sulphuretted hydrogen, appears to have been known to the ancients long before chemistry existed as a science, as may be inferred from the expression, graveolens aornus, employed by Virgil, as well as from some remarks of Pliny, respecting a fountain not far from Rome. He found carbonic oxide, though a fatal gas, to be less promptly so than sulphuretted hydrogen ; and it is worthy of remark, that the interior of animals killed by it, was not only gorged with venous blood, but seemed unusually hot. The results of the preceding experiments, together with some others detailed in this volume, suggest the following observations : — We have seen that Dr. Holland has objected to the theory maintained by Dr. Edwards, that the amount of animal heat is in proportion to the consumption of oxygen, and endeavours to substitute in its place, that it is in the inverse ratio of the quantity of the blood to the inspired air. It is evident from Dr. Edwards’s own words, that by the consumption of oxygen, he means its conversion into carbonic acid, since he admits the absorption of this gas during summer, when even adult animals are considered by him, to lose a part of their power of pro- ducing heat. The researches of Broughton have shewn, that when animals inspire this gas in its pure state, they sink in temperature ; and the experiments of Allen and Pepys have shewn, that a larger quantity of this gas is consumed than is replaced by 488 NOTES. carbonic acid, the production of which, is diminished. It is also remarked, that those external parts, in which we can observe the state of the circulation, become manifestly injected ; hence we must have that condition of the circulation, which Dr. Holland regards as the most favourable for the production of animal heat ; yet we have seen that the results alluded to oppose this conclusion. I am in- clined to believe, that the production of animal heat bears a close and necessary relation to thp quantity of carbonic acid produced. I agree so far with Dr. Hol- land as to believe, that when the lungs are greatly loaded with blood, the changes in it effected by the air are impeded, and that the temperature may sink ; but this I conceive to be the consequence of the diminished production of carbonic acid. On the other hand, the effects of pure oxygen evince a striking difference between animal heat, and that of ordinary combustion. The carbonic acid by which the blood is darkened, is strikingly removed ; but contrary to what one would have suspected, a priori, its further production is impeded : hence, not only the diminution of temperature, but also, the universal redness of the blood. It has been shewn by some of the experiments of Sir Astley Cooper already re- lated, that immersion in ice-cold water, had the effect of inducing a singularly bright arterial colour in those parts in which the blood is collected. This effect, like that of animals dying in oxygen gas, was more to be ascribed to the sus- pended carbonization, than to the increased decarbonization of the blood. Without attempting to draw any express conclusions from the experiments of Dr. Edwards, with reference to temperature, season, and age, beyond those which the Doctor has himself offered, I cannot refrain from remarking, that there is no part of the Doctor’s work which possesses greater practical importance and utility. In conjunction with the researches of Dr. Curry of Liverpool, they will afford the most valuable assistance in the regulation of clothing, of exposure to the open air, of confinement within doors, and of the application of the various forms of baths. v I’lllNTED BY STEWAKT AND CO., OLD BAILEY. s ' I ♦