NRLF 
 
THE 
 
 PHYSIOLOGY OF MM; 
 
 DESIGNED TO REPRESENT 
 
 THE EXISTING STATE OF PHYSIOLOGICAL 
 SCIENCE, 
 
 AS APPLIED 
 
 TO THE FUNCTIONS OF THE HUMAN BODY. 
 
 BY 
 
 AUSTIN FLINT, JR., I.D., 
 
 PROFESSOR OP PHYSIOLOGY AND MICROSCOPY IX THE BELLEVUE HOSPITAL MEDICAL COLLEGE, 
 
 NEW YORK, AND IN THE LONG ISLAND COLLEGE HOSPITAL J FELLOW OF THE NEW 
 
 YORK ACADEMY OF MEDICINE, MICROSCOPIST TO BELLEVUE HOSPITAL. 
 
 INTRODUCTION; THE BLOOD; CIRCULATION; 
 RESPIRATION". 
 
 NEW YORK: 
 D. APPLETON AND COMPANY, 
 
 90, 92 & 94 GRAND STREET. 
 1870. 
 
 PO .^ 
 
 
 
ENTERED, according to Act of Congress, in the year 1865, by 
 
 D. APPLETON & CO., 
 
 In the Clerk's Office of the District Court of the United States for the Southern District 
 
 Fork. 
 
/. 
 
 TO 
 
 CHARLES ROBIN, 
 
 THE FIKST PROFE8SOB OF HISTOLOGY IN THE FACULTY OF MEDICINE OF PABIS, 
 
 AS A TOKEN OF APPEECIATION OF THE 
 NUMEEOUS OEIGINAL EESEAEOHES AND DISCOVEEIES, 
 
 PAETIOULAELY IN 
 
 HISTOLOGY AND PHYSIOLOGICAL CHEMISTEY, 
 
 BTZ "WHICH HE HAS CONTEIBTJTED SO LAEGELY TO BEING THE SCIENCE OP 
 PHYSIOLOGY TO ITS PEESENT CONDITION, 
 
 AND IN 
 
 GEATEFUL EEMEMBEANOE OF MANY ACTS OF FEIENDSHIP, 
 THIS WOEK IS INSCEIBED BY 
 
 THE AUTHOR. 
 
P E E F A O E. 
 
 IN entering upon the labor incident to the preparation 
 of a work purporting to treat comprehensively of the physi- 
 ology of man, the author appreciated the magnitude of the 
 undertaking ; and the special study which it necessarily de- 
 manded has not diminished that diffidence with which a 
 student of any of the natural sciences puts forward a book 
 which he hopes may add somewhat to existing knowledge, 
 or fairly represent what is known in any particular depart- 
 ment. In assuming so grave a responsibility, the author 
 should be actuated by a sense of peculiar fitness for his task, 
 as well as a conviction that literature demands such a work 
 as he proposes to write. Without assuming these good and 
 sufficient reasons, the author of the present volume pleads an 
 earnest desire to advance the science of physiology and facili- 
 tate its study ; and he indulges the hope that he may be in- 
 strumental in making the student and practitioner of medi- 
 cine better acquainted with what must be conceded to be the 
 basis of true pathology, and interest, to some extent, the gen- 
 eral reader in the all-important subject of human physiology. 
 
 The plan of the present work involves a consideration of 
 
PEEFACE. 
 
 pure hum an physiology, and will embrace physiological 
 chemistry and the anatomy of the tissues and organs of the 
 body, only so far as necessary for the elucidation of the func- 
 tions of the organism. Though, undoubtedly, the chemistry 
 and general anatomy of the tissues and organs strictly belong 
 to physiology, they present many points which have no bear- 
 ing, that we are as yet able to comprehend, upon the func- 
 tions. In the present condition of the science, a considera- 
 tion of these would only encumber and obscure the history 
 of the physiological processes. While it is undoubtedly true 
 that every advance in physiological chemistry or histology 
 will have its bearing, sooner or later, upon physiology, it is 
 evident that discoveries in these departments must be multi- 
 plied and coordinated before their relations to the functions 
 can be fully appreciated. Until then they are specially inter- 
 esting only in a chemical and anatomical point of view. In 
 the same way every discovery in physiology, no matter how 
 unimportant it may at first appear in a practical point of 
 view, will eventually have its bearing upon practical medi- 
 cine, surgery, or obstetrics ; yet it will not find its way into 
 works on those subjects until its relations become apparent. 
 
 As an introduction to the study of physiology proper, a 
 certain amount of knowledge of physiological chemistry is 
 indispensable. It is in this direction that we are to look for 
 advances which will enable us to comprehend the processes 
 of nutrition, the end and object of all the vegetative functions 
 of the body. The introduction, then, is devoted to physiolog- 
 ical chemistry. No attempt has been made to treat of this 
 subject exhaustively, or to include a consideration of all the 
 proximate principles which have been isolated and studied. 
 As the general properties and relations of the different classes 
 
PREFACE. 7 
 
 of proximate principles are by far the most important to us as 
 physiologists, these have been specially dwelt upon, and 
 their relations to nutrition followed out as completely as 
 possible, with our present knowledge. A consideration of 
 the excrementitious proximate principles, being connected 
 exclusively with excretion, has been deferred, to be taken up 
 in connection with that function. 
 
 In treating of physiology proper, it has been the design 
 of the author to present what is actually known regarding 
 the functions of the body ; and in order to facilitate^ their 
 study, he has generally commenced the consideration of in- 
 dividual functions with a sketch of the physiological anat- 
 omy of the parts. This is the natural point of departure in 
 the thorough investigation of any special function. 
 
 The science of physiology dates from the earliest periods 
 in the history of medicine; and certain important physio- 
 logical facts were demonstrated experimentally hundreds of 
 years ago. "While the author has regarded purely historical 
 considerations, and discussions of mere theoretical questions, 
 as unprofitable, he has attempted to give due credit to those 
 who, by their experiments and observations, have contributed 
 to bring the science to its present condition. With this view, 
 he has procured and consulted, as far as possible, accounts of 
 original investigations ; but from the poverty in physiologi- 
 cal works of the public libraries to which he has had access, 
 it has been necessary to depend to a certain extent on the 
 exhaustive treatises on physiology published in other coun 
 tries. Though, undoubtedly, he has been unable in all in- 
 stances to give due credit to every observer, this has been 
 attempted as far as possible. 
 
 It is an undoubted fact that nearly all the important 
 
8 PREFACE. 
 
 developments in physiology have been the result of experi 
 ments upon living animals, by vivisections or otherwise, or 
 accurate experimental observations upon the human subject. 
 The great extension of this method of study is the cause of 
 the rapid advances the science is making at the present day. 
 For some years the author has f>een in the habit of employ- 
 ing vivisections in public teaching, and in this way has fre- 
 quently verified the observations of the earlier as well as the 
 more modern physiologists. A frequent repetition of experi- 
 ments has often enabled him to reconcile the discordant results 
 of the observations of others ; and following out new questions 
 which have presented themselves in the constant observa- 
 tion of the living organs, he has advanced some original 
 views regarding certain of the functions. A new method is 
 likewise presented for the analysis of the blood with reference 
 to its organic constituents. 
 
 The plan of publication of the present work is one which 
 is novel in this country, but which has been adopted abroad, 
 particularly in France, in almost all elaborate treatises on phys- 
 iology. It is to be issued in separate parts, each, however, 
 forming a distinct treatise devoted to natural subdivisions of 
 the subject. The volume now issued embraces an Introduc- 
 tion, the Blood, Circulation, and Respiration. The remain- 
 ing volumes, three in number, will be issued yearly until the 
 work is finished, and will likewise be severally complete in 
 themselves. Simple and well-known anatomical and physi- 
 ological points have not been illustrated by engravings, 
 which have only been introduced where they seemed neces- 
 sary to elucidate the text. 
 
 NEW YORK, October, 1865. 
 
CONTENTS. 
 
 INTRODUCTION. 
 
 General considerations Vital properties of organized structures Proximate 
 principles Inorganic principles Organic non-nitrogenized principles Or- 
 ganic nitrogenized principles, Page 13 
 
 CHAPTER I. 
 
 THE BLOOD. 
 
 General considerations Transfusion Quantity Physical characters Opacity 
 Temperature Specific gravity Color Anatomical elements of the blood 
 Eed corpuscles Chemical characters of red corpuscles Development of red 
 corpuscles Formation of red corpuscles Leucocytes, or white corpuscles 
 Development of leucocytes, , . 95 
 
 CHAPTER II. 
 
 COMPOSITION OP THE BLOOD. 
 
 General considerations Methods of quantitative analysis Fibrin Corpuscles 
 Albumen Inorganic constituents Sugar Fatty emulsion Coloring matter 
 of the serum Urea and the urates Cholesterine Creatine Creatinine, 127 
 
 CHAPTER III. 
 
 COAGULATION OP THE BLOOD. 
 
 General considerations Characters of the clot Characters of the serum Coagu- 
 lating principle in the blood Circumstances which modify coagulation Co- 
 agulation of the blood hi the organism Spontaneous arrest of hemorrhage 
 Cause of coagulation of the blood Summary of the properties and functions 
 of the blood, .142 
 
10 CONTENTS. 
 
 CHAPTER IY. 
 
 CIRCULATION OF THE BLOOD. 
 
 Discovery of the circulation Physiological anatomy of the heart Valves of the 
 heart Movements of the heart Impulse of the heart Succession of move- 
 ments of the heart Force of the heart Action of the valves Sounds of the 
 heart Cause of the sounds of the heartj .... Page 170 
 
 CHAPTER V. 
 
 FREQUENCY OF THE HEAET's ACTION. 
 
 Frequency of the heart's action Influence of age Influence of digestion Influ- 
 ence of posture and muscular exertion Influence of exercise Influence of 
 temperature Influence of respiration on the action of the heart Cause of 
 the rhythmical contractions of the heart Influence of the nervous system on 
 the heart Division of the pneumogastrics Galvanization of the pneumogas- 
 trics Causes of the arrest of action of the heart Blows upon the epigas- 
 trium, . .211 
 
 CHAPTER VI. 
 
 CIRCULATION OF THE BLOOD IN THE ARTERIES. 
 
 Physiological anatomy of the arteries Course of blood in the arteries Elasticity 
 of the arteries Contractility of the arteries Locomotion of the arteries and 
 production of the pulse Form of the pulse Sphygmograph Pressure of 
 blood in the arteries Hemodynamometer Cardiometer Differential cardio- 
 meter Pressure in different parts of the arterial system Influence of respi 
 ration on the arterial pressure Effects of hemorrhage Rapidity of the -cur- 
 rent of blood in the arteries Instruments for measuring the rapidity of the 
 arterial circulation Variations in rapidity with the action of the heart Ra- 
 pidity hi different parts of the arterial system Arterial murmurs, . . 240 
 
 CHAPTER VII. 
 
 CIRCULATION OF THE BLOOD IN THE CAPILLARIES. 
 
 Distinction between capillaries and the smallest arteries and veins Physiological 
 anatomy of the capillaries Peculiarities of distribution Capacity of the 
 capillary system Course of blood in the capillaries Phenomena of the 
 capillary circulation Rapidity of the capillary circulation Relations' of the 
 capillary circulation to respiration Causes of the capillary circulation In- 
 fluence of temperature on the capillary circulation Influence of direct irrita- 
 tion on the capillary circulation, . . . . . . . 278 
 
CONTENTS. 11 
 
 CHAPTEE VIII. 
 
 CIRCULATION OP THE BLOOD IN THE VEINS. 
 
 Physiological anatomy of the veins Strength of the coats of the veins Valves 
 of the veins Course of the blood in the veins Pressure of blood in the 
 veins Rapidity of the venous circulation Causes of the venous circulation 
 Influence of muscular contraction Air in the veins Function of the valves 
 Yenous anastomoses Conditions which impede the venous circulation Re- 
 gurgitant venous pulse, Page 301 
 
 CHAPTER IX. 
 
 PECULIARITIES OF THE CIRCULATION IN DIFFERENT PARTS OF THE SYSTEM. 
 
 Circulation in the cranial cavity Circulation hi erectile tissues Derivative circu- 
 lation Pulmonary circulation General rapidity of the circulation Time re- 
 quired for the passage through the heart of all the blood in the organism 
 Relations of the general rapidity of the circulation to the frequency of the 
 heart's action Phenomena hi the circulatory system after death, . . 332 
 
 CHAPTER X. 
 
 RESPIRATION. 
 
 General considerations Physiological anatomy of the respiratory organs Respi- 
 ratory movements of the larynx Epiglottis Trachea and bronchial tubes 
 Parenchyma of the lungs Carbonaceous matter in the lungs Movements of 
 respiration Inspiration Muscles of inspiration Action of the diaphragm 
 Action of the scaleni Intercostal muscles Levatores costarum Auxiliary 
 muscles of inspiration, 353 
 
 CHAPTER XI. 
 
 MOVEMENTS OF EXPIRATION. 
 
 Influence of the elasticity of the pulmonary structure and walls of the chest 
 Muscles of expiration Internal intercostals Infra-costales Triangularis ster- 
 ni Action of the abdominal muscles in expiration Types of respiration 
 Abdominal type Inferior costal type Superior costal type Frequency of the 
 respiratory movements Relations of inspiration and expiration to each other 
 The respiratory sounds Coughing Sneezing Sighing Yawning Laugh- 
 ing Sobbing Hiccough Capacity of the lungs and the quantity of air 
 changed in the respiratory acts Residual air Reserve air Tidal, or breathing 
 air Complemental air Extreme breathing capacity Relations in volume of 
 the expired to the inspired air Diffusion of air in the lungs, . . . 382 
 
12 CONTENTS. 
 
 CHAPTER XII. 
 
 CHANGES WHICH THE AIE UNDERGOES IN RESPIRATION. 
 
 General considerations Discovery of carbonic acid Discovery of oxygen Com- 
 position of the air Consumption of oxygen Influence of temperature In- 
 fluence of sleep Influence of an increased proportion of oxygen in the atmos- 
 phere Temperature of the expired air inhalation of carbonic acid Influence 
 of age Influence of sex Influence of digestion Influence of diet Influence 
 of sleep Influence of muscular activity Influence of moisture and tem- 
 perature Influence of seasons Relations between the quantity of oxygen 
 consumed and the quantity of carbonic acid exhaled Exhalation of watery 
 vapor Exhalation of ammonia Exhalation of organic matter Exhalation 
 of nitrogen, Page 409 
 
 CHAPTER XIII. 
 
 CHANGES OF THE BLOOD IN RESPIRATION. 
 
 Difference in color between arterial and venous blood Comparison of the gases 
 in venous and arterial blood Observations of Magnus Analysis of the blood 
 for gases Relative quantities of oxygen and carbonic acid in venous and ar- 
 terial blood Nitrogen of the blood Condition of the gases in the blood 
 Mechanism of the interchange of gases between the blood and the air in 
 the lungs General differences in the composition of arterial and venous 
 blood, 452 
 
 CHAPTER XIV. 
 
 RELATIONS OP RESPIRATION TO NUTRITION, ETC. 
 
 Views of physiologists anterior to the time of Lavoisier Relations of the con- 
 sumption of oxygen to nutrition Relations of the exhalation of carbonic acid 
 to nutrition Essential processes of respiration The respiratory sense, or 
 want on the part of the system which induces the respiratory movements 
 Location of the respiratory sense in the general system Sense of suffocation 
 Respiratory efforts before birth Cutaneous respiration Asphyxia, . 472 
 
PHYSIOLOGY OF MAN. 
 
 INTRODUCTION. 
 
 General considerations Vital properties of organized structures Proximate prin- 
 ciples Inorganic principles Organic non-nitrogenized principles Organic 
 nitrogenized principles. 
 
 THE epoch of purely speculative reasoning, without the 
 basis of established facts sufficient to justify any connected 
 theories, belongs to the remote history of Natural Science. 
 The ideas of the great philosophers of ancient times, who 
 studied Nature by what may be called the intuitive method, 
 have been gradually giving place to doctrines based on the 
 observation and investigation of phenomena. Ages of obser- 
 vation and generalization of facts by the greatest intellects 
 have put us but little beyond the threshold of the great 
 domain of Science. But we have learned enough to know 
 that all Nature is regulated by immutable laws. Students 
 of her divine mysteries should be more than content if per- 
 mitted to discover some of the truths, the development of 
 which marks the scientific advancement of each succeeding 
 age, though they may seem an insignificant portion of what 
 is to be learned. It is only by accurate observation and 
 generalization of a sufficient number of phenomena, that the 
 laws of Nature are to be discovered. They are the creation 
 
14 INTRODUCTION. 
 
 of an infinite wisdom which never errs. We cannot hope to 
 arrive at a knowledge of them by pure reasoning; or by 
 assuming that they are in accordance with definite principles, 
 too often the offspring of our own limited intellects. Never- 
 theless, it is a physiological attribute of the human mind to 
 desire to press on in advance of observation, and to form 
 theories, which may or may not be carried out by the suc- 
 ceeding development of actual knowledge. Theories which 
 are not built upon false or imperfectly observed phenomena, 
 are the pioneers of actual discovery. When theoretical pre- 
 conceptions are justified and corrected by original observa- 
 tions and experiments, with the brain to conceive and the 
 will to execute, man, in thus working out the great problems 
 of Nature, is fulfilling one of the highest purposes of his 
 existence. 
 
 With the few facts which were at first known, the 
 ancient speculative philosophy professed to embrace the 
 whole of natural science ; but as discoveries were made in 
 different departments, a division of labor became necessary. 
 We now find different classes of scientific men, each working 
 in a particular sphere ; as in the lower zoological divisions, 
 a single organ performs all the varied functions of nutrition, 
 while in the higher orders, when the processes of life are 
 more intricate and complicated, the system is divided up 
 into elaborately-organized parts, each of which has an allotted 
 office. 
 
 From the time of Galen may be said to date, as distinct 
 from astronomy, chemistry (or rather alchemy), physics, &c., 
 the science which is now called PHYSIOLOGY. 
 
 Physiology, from its etymology, signifies the science of 
 Nature ; but in the sense in which the term is now used, it 
 may be defined to be the science of life. More elaborate defi- 
 nitions have been given, but they only qualify and explain the 
 meaning of what we know as life. 
 
 A natural division of physiology is into animal and 
 vegetable; and again, into the physiology of the inferior 
 
GENERAL CONSIDERATIONS. 15 
 
 animals as compared with man, or comparative physiology, 
 and the PHYSIOLOGY OF MAN. The latter, which is the sub- 
 ject of the present work, is peculiarly interesting to the 
 physician, as the basis of all accurate knowledge of the 
 science of medicine. 
 
 In the early history of physiological science, the develop- 
 ment of anatomy necessarily gave us much information con- 
 cerning the functions of the body ; and we now have to 
 acknowledge our continual indebtedness to anatomical inves- 
 tigations, particularly those made with the aid of the micro- 
 scope, for important advancements in physiology. In treating 
 of the subject, it is impossible to neglect what is most appro- 
 priately called the physiological anatomy of parts, a knowl- 
 edge of which alone enables us, oftentimes, to comprehend 
 their functions. For example, we can scarcely conceive how 
 the anatomy of the circulatory system could be clearly under- 
 stood without giving us a knowledge of its physiology. 
 
 Chemistry, also, when the components of the body are 
 studied in such a way as not to destroy their properties as 
 organic compounds, has a most important bearing on the 
 advancement of physiology. As a striking example of this, 
 we may take the discovery of the properties of the gases of 
 the air and their relations to the blood by Lavoisier, which 
 gave us the first definite ideas regarding the essential phe- 
 nomena of respiration. We are now largely indebted to 
 modern physiological chemistry for a knowledge of many of 
 the essential phenomena of life, and look to a further develop- 
 ment of this* science for an elucidation of many important, 
 but still obscure, questions connected with nutrition. 
 
 Certain physiological functions are in exact accordance 
 with established physical laws ; which are competent, for 
 example, to explain the refraction in the structures of the 
 eye, or the conduction of vibrations in the ear. Physical 
 laws are involved in most of the phenomena of life, but are 
 generally more or less modified by the peculiar properties of 
 organized bodies. 
 
16 INTRODUCTION. 
 
 Many of the phenomena of life are made clear by a 
 comparison of the physiology of man with that of the infe- 
 rior animals, which is often simpler and more easily investi- 
 gated. 
 
 As physiology is the natural and only correct basis of 
 pathology, we frequently derive important information as 
 to the functions of parts by studying the effects of disease, 
 by which their functions are modified or abolished. The 
 experiments thus performed by Nature on the human system 
 are frequently more instructive than those which we make 
 on the inferior animals. 
 
 As the complement to anatomy, human and comparative, 
 organic chemistry, and pathology, we have as the most pre- 
 cious and fruitful means of physiological investigation, direct 
 observation of the phenomena of life in man and the inferior 
 animals, and experiments on animals by vivisections. The 
 present condition of physiology is a testimony of the incal- 
 culable value of this method of study. "Were it consistent 
 with our plan to follow out the general development of the 
 science from an historical point of view, we should find the 
 names of Harvey, Aselli, Haller, Hales, Spallanzani, Ed- 
 wards, Bichat, Bell, Majendie, and a host of others, bearing 
 witness by their works to the value of vivisections in physio- 
 logical investigations ; to say nothing of the great observers 
 of the present day, who are constantly adding to our knowl- 
 edge. The field would be sterile indeed were it not for 
 experiments on living animals ; and the loss to the science 
 which has for its object the alleviation of the sufferings of 
 mankind, would have been incalculable, had physiologists 
 been unwilling, from false motives of humanity, to inflict 
 pain upon the lower animals, which is to a certain extent 
 unavoidable in experimentation. 
 
 Physiological literature, in the great Elementa Physiolo- 
 gioB of Haller, which belonged to a past generation, and 
 the elaborate systematic works of Berard, 1 Longet, Miiller, 
 
 1 Berard did not live to complete his great work on physiology. He died 
 
GENERAL CONSIDERATIONS. IT 
 
 and other experimentalists of the present generation, fur- 
 nishes abundant proof that the faculty of observation and the 
 power of generalization are not necessarily inconsistent with 
 each other. 
 
 It would be futile to attempt to point out all the difficul- 
 ties and sources of error in experimentation on living animals. 
 These must be overcome by the physiologist after he has 
 become practically acquainted with them. It must be borne 
 in mind, however, that we are interrogating Nature ; and 
 our sole aim must be to put our questions intelligently and 
 interpret the answers correctly. She does not unfold her 
 mysteries to the careless and inconsiderate observer. An 
 accident may lead the reflecting student to frame a particular 
 set of experiments, for the explanation of an unexpected 
 phenomenon ; but we should go to work with an idea of what 
 we wish to know, always ready to correct or abandon our 
 most cherished preconceived notions if we find they are not 
 in accordance with facts. Experiments should not be isolat- 
 ed. A golden opportunity is thrown away if we stop short 
 of the end in a legitimate series of investigations ; for none 
 are better fitted to go through the later steps of a natural 
 series of experiments than they who have conceived and 
 executed the first. 
 
 With the many varying conditions of the system which 
 inevitably occur in living animals, it is almost unnecessary to 
 add that an important observation should be repeatedly con- 
 firmed, and the answer to our experimental inquiries obtained, 
 if possible, in different ways. It must be remembered that 
 Nature never contradicts herself, and has no exceptions. 
 Her laws are invariable ; and if experiments are apparently 
 contradictory, we must look for differences in the conditions 
 
 shortly after he had commenced the publication of the fourth volume in 1855. The 
 prolegomenes, and the sections on digestion, absorption, the blood, respiration, 
 and circulation, are perhaps the most candid, exhaustive, and best considered 
 essays on these subjects in any language. Science suffered a great loss when 
 the author was thus cut off in the midst of his labors. 
 2 
 
18 INTRODUCTION. 
 
 under which the observations were made. It would be 
 always possible to reconcile discordant results of observations, 
 were we able to entirely appreciate the conditions under 
 which they were made. For this reason, a practical physiolo- 
 gist, if entirely unbiassed, is most competent to judge of, and 
 assimilate, the observations of others. 
 
 Vital Properties of Organized Structures. In com- 
 mencing the study of physiology, we should have some idea 
 of the physiological chemistry of the body, comprehending 
 fully, in the first place, what is meant by life, or the vital 
 properties of the tissues. 
 
 The tissues which are endowed with vitality are in a 
 state of continual metamorphosis, more or less active accord- 
 ing to their degree of organization. They are constantly 
 undergoing transformation into what are known as effete 
 matters and have the property of appropriating, in the great 
 majority of instances from the blood, material for their re- 
 generation. In other words, under proper conditions, living 
 tissues have the property of self-regeneration. This constant 
 waste, or physiological disintegration, is known under the 
 name of destructive assimilation, and its products are called 
 excretions. The power of self-regeneration is called nutrition. 
 
 This property affects all the constituents of the body 
 without exception. We shall see that physiological chemis- 
 try divides the constituents of the organism into organic and 
 inorganic principles ; the latter being identical with princi- 
 ples found in the inorganic world. Inorganic principles, in 
 the living body, are always in union with organic principles ; 
 they are regularly thrown off with the products of their de- 
 structive assimilation, and are supplied to the parts, as a 
 necessity of nutrition. They never exist in their crystalline 
 form, in which they so commonly occur in the inorganic 
 kingdom. 1 Every part of the body either is, or has been, 
 
 * There is a single exception to this law in the crystals of carbonate of lime 
 which are found in the internal ear, constituting the otoconies or otoliths. 
 
THE PROPERTIES OF ORGANIZED STRUCTURES. 19 
 
 endowed with life. Some are desquamated and reproduced, 
 like the nails, hair, or epidermis ; some are worn away and 
 not reproduced, like the enamel of the teeth ; but they are 
 all subject to vital laws in their formation, and the exceptions 
 to the law that each tissue has the property of self-regenera- 
 tion are very few. 
 
 The power of self-regeneration of organized tissues does 
 not exist indefinitely. After a time the tissues fail to appro- 
 priate enough organic matter to entirely supply the waste ; 
 they gradually degenerate, and finally die, as a necessary 
 condition of their existence. The activity of the regenerat- 
 ing powers seems to depend on the proportion of organic 
 matter which the tissues contain. In childhood, when, as a 
 condition of growth, the nutrition is greater than the waste, 
 the organic matter of the tissues is in excess. In old age 
 calcareous deposits are frequent, and the inorganic matter 
 in all parts is in excess, until finally the organs become inca- 
 pable of performing their functions. 
 
 The properties above mentioned serve to distinguish 
 organized living bodies from those not endowed with life. 
 Man, in the general properties of his tissues and organs, 
 does not differ from the higher classes of the inferior animals, 
 as the mammalia. Their tissues are as highly organized, 
 and the various functions connected with nutrition, such as 
 secretion, digestion, circulation, respiration, etc., are essen- 
 tially the same. In some instances, as in the digestive func- 
 tion of some of the herbivora, the process is even more 
 elaborate than in the human subject. For this reason, 
 with proper precautions, we can apply without hesitation 
 most experiments on the mammalia to the physiology of 
 man. 
 
 To the development of the great centre of the nervous 
 system, man owes his preeminence in the animal scale. In 
 the w T ords of Longet: "In his psychical relations, but in 
 these only, man can constitute a distinct kingdom. Physi- 
 ology has specially in view the acts which assimilate man to 
 
20 INTRODUCTION. 
 
 animals ; it belongs to psychology to study and make known 
 the faculties which separate him from them." 1 
 
 Even without accidents, physiological death is a necessity 
 of existence ; but nature has provided, as one of the most im- 
 portant attributes of organization, a means by which organ- 
 ized bodies may be perpetuatedjhrough all ages. In the fully- 
 developed organism are produced two kinds of organic ele- 
 ments, the male and the female. These, when brought in 
 contact with each other under proper conditions, are capable 
 of being developed into a new being, similar in organization 
 to, and designed to take the place of^ the one which is to pass 
 away. These new beings are generated in sufficient number 
 to insure the perpetuation of the species. 
 
 The excrementitious products of the body during life, and 
 the body itself after death, changed by the peculiar process 
 of putrefaction, are returned to the earth and to the air, and 
 contribute to the nutrition of the vegetable kingdom. The 
 vegetables, in their turn, are consumed in the nutrition of 
 animals. All the elements necessary to nutrition, except 
 oxygen, are taken into the alimentary canal as food. Our 
 food consists either of vegetables, or the flesh of animals that 
 are nourished by vegetables. 
 
 PROXIMATE PRINCIPLES. 
 
 From the preceding general remarks, it is evident that 
 physiology, to be systematically and properly studied, must 
 be connected with physiological anatomy and chemistry. 
 The physiological anatomy of special organs and systems 
 naturally precedes the consideration of their functions ; and in 
 treating of the functions of other parts, more especially the 
 nutritive and excrementitious fluids and the secretions, we 
 are unavoidably led to consider fully their chemical constitu- 
 tion. There are, however, certain constituents of the body, 
 
 1 LONGET, TraitS dc Physiologic, Paris, 1861, tome i., p. xxviii. 
 
PROXIMATE PRINCIPLES. 21 
 
 a full consideration of which, in connection with special 
 functions, would be out of place, as well as many points in 
 physiological chemistry, showing the relations of the different 
 elements to nutrition, etc. ; hence is desirable, as an intro- 
 duction to physiology proper, a brief review of the prox- 
 imate principles of the economy. In this introduction it is 
 not proposed to treat exhaustively of physiological chemistry. 
 Such principles as will demand, from their connection with 
 special functions, extended consideration in another place, 
 are omitted or simply alluded to, as well as some which have 
 a very unimportant or obscure function. 
 
 If we were to study the constitution of the body from a 
 purely chemical point of view, it would be divided into 
 elementary substances, or those which are absolutely incapa- 
 ble of further subdivision. In this way we should lose all 
 distinction between organic matters and those which enter 
 indifferently into the composition of all bodies in Nature, 
 whether inert or endowed with vital properties. After 
 having thus ascertained the ultimate constitution of the 
 organism, we have learned all that is possible by this method ; 
 for we are already familiar with the properties and be- 
 havior of elementary matter, as obtained from the inorganic . 
 kingdom. 
 
 In physiological chemistry this method is inadmissible. 
 The substances which are presented for our study in the 
 living organism are endowed with vital properties. Their 
 ultimate composition is of little consequence compared with 
 a knowledge of the laws which regulate their behavior, not 
 as elements, but as constituents of an elaborate vital organi- 
 
 ' O 
 
 zation. 
 
 We can separate from the organism of animals substances 
 of a peculiar nature which are never found in the inorganic 
 world. These demand our special consideration. If we 
 attempt to study them by the ordinary chemical processes of 
 analysis, they are destroyed and lose their properties as 
 organic principles. 
 
22 INTEODTJCTION. 
 
 Combined with these organic principles we always have 
 a certain proportion of inorganic matters which may, it is 
 true, be separated from them easily, and apparently without 
 decomposition, but which are, notwithstanding, necessary to 
 the peculiar properties by which we recognize organic sub- 
 stances. Their physiological union is so intimate that they 
 may justly be considered as organic, though originating in 
 the inorganic kingdom. 
 
 Chemistry recognizes fifty-nine elementary substances, of 
 which some fifteen or eighteen enter into the constitution of 
 the human body ; but as physiologists, we must make a 
 division of the body into component principles, without 
 reference to the elementary substances themselves, but with 
 a view to the form and condition of their existence in the 
 organism. As we have seen that the distinguishing properties 
 of organic principles are destroyed when they are reduced to 
 their ultimate elements, it is evident that many or most of 
 the principles into which the body is divided physiologically 
 are compound substances. 
 
 From this point of view, the organism may be said to be 
 composed of Immediate or Proximate Principles. 
 
 A Proximate Principle may be defined to be a substance 
 extracted from the l>ody, which cannot be further subdivided 
 without chemical decomposition and loss of its characteristic 
 properties. 
 
 According to Robin and Yerdeil, there exist from eighty- 
 five to ninety distinct proximate principles in the human 
 body. 1 
 
 The distinction between proximate principles and chem- 
 ical elements is apparent from the definition above given. 
 To illustrate this difference, however, we may take the fol- 
 lowing example. Chloride of sodium is an important proxi- 
 mate principle, and is composed of the chemical elements 
 chlorine and sodium. As chloride of sodium, it has certain 
 
 1 ROBIN and VERDEIL, Chimie Anatomique et Physiologique, Paris, 1853, 
 tome L, p. 128. 
 
PKOXIMATE PKINCIPLES. 
 
 properties, and is endowed with certain functions in the econ- 
 omy, which are, of course, entirely different from the proper- 
 ties of chlorine or sodium ; the latter especially being only 
 obtained in a state of chemical purity by a difficult and elab- 
 orate process of manipulation. As physiologists we have 
 nothing to do with the properties of chlorine, or the rare 
 metal sodium ; we only wish to know as much as possible 
 about the functions of these two bodies united to form com- 
 mon salt. Again, fibrin, a proximate principle found in the 
 blood, may be reduced by chemical manipulations to a cer- 
 tain number of atoms of carbon, hydrogen, oxygen, nitrogen, 
 and sulphur. But a knowledge of even the exact proportions 
 of these ingredients would be of no practical benefit, if we 
 were unacquainted with the general properties of fibrin and 
 its uses in the economy. Salt cannot be subdivided into 
 chlorine and sodium, nor fibrin into its elements, without. 
 chemical decomposition and loss of characteristic proper- 
 ties / but both of these substances can be extracted from the 
 body in the condition in which they exist in the organism, 
 and are therefore proximate principles. 
 
 A constituent of the body may be at the same time a 
 chemical element and a proximate principle. An example 
 of this is the free oxygen in solution in the blood. This 
 enjoys, in the body, the properties of free oxygen, and may 
 be extracted from the blood by mere displacement with an- 
 other gas, or by the air-pump ; a process quite different from 
 the elaborate chemical manipulation which would be neces- 
 sary to obtain oxygen by decomp'osition of fibrin, albumen, 
 or any compound principle. 
 
 The principles which compose the body, with the excep- 
 tion of excrementitious substances, exist in our food ; this 
 being the only way in which material is supplied for the con- 
 tinual repair which is characteristic of living tissues. They 
 are all introduced from without. Certain principles, such as 
 water and the inorganic salts, are merely transitory in the in- 
 terior of the body, and are discharged in the same form in 
 
24 INTRODUCTION. 
 
 which they enter. Others are consumed in the process of 
 repair, and after having performed their functions, are thrown 
 off as effete matters. Examples of the latter are fibrin 
 and albumen, which are transformed first into the sub- 
 stance of the tissues, and then into urea, creatine, choleste- 
 rine, and other excrementitious matters, which are the re- 
 sult of the breaking down or wearing out of the tissues. 
 Finally, there are certain principles, the sugars and fats for 
 example, which have an important connection with the pro- 
 cess of nutrition, and disappear in the system, but whose 
 transformations we have not as yet been able to follow. 
 These, besides being taken in as food, are manufactured by 
 certain organs, and appear de novo in the economy. 
 
 Division of Proximate Principles. In the division ol 
 proximate principles, we shall follow, with slight modifica- 
 tions, the classification of Robin and Verdeil. With refer- 
 ence solely to anatomical and physiological chemistry, the 
 classification of these authors cannot be improved; but in 
 treating of the whole subject of physiology, it will be conven- 
 ient to take up certain of the elements in connection with the 
 functions in which they play an important part. Oxygen 
 and carbonic acid, for example, will be fully considered in 
 connection with respiration ; urea and cholesterine with ex- 
 cretion, &c. Again, there are some whose function is appa- 
 rently of so little importance, or so obscure, that, while they 
 may be interesting in a chemical point of view, merely as 
 constituents of the body, it is not worth while to treat of 
 them in connection with physiology. 
 
 The two great divisions of proximate principles which we 
 propose, comprise : 
 
 FIRST. Substances which enter into the normal con- 
 stitution of the organized tissues, and those constituents of 
 the fluids which are used in nutrition. 
 
PROXIMATE PEmCIPLES. 25 
 
 SECOND. Substances which are the result of the wearing 
 out of the tissues, and are not used in nutrition? 
 
 The first division, which is the only one that will be taken 
 up in this connection, may be subdivided, according to the 
 classification of Robin and Yerdeil, into three classes. 
 
 1. Inorganic Substances. This class is of inorganic ori- 
 gin, definite chemical composition, and crygtallizable. The 
 substances forming it are all introduced from without, and are 
 all discharged from the body in the same form in which they 
 entered. They never exist alone, but are always combined 
 with the organic principles, to form the organized fluids or 
 solids. This union is " atom-to-atom," and so intimate that 
 they are taken up with the organic elements, as the latter are 
 worn out and become effete, and are discharged from the 
 body, though themselves unchanged. To supply the place 
 of the principles thus thrown off,- a fresh quantity is depos- 
 ited in the process of nutrition. They give to the various 
 organs important properties ; and, though identical with sub- 
 stances in the inorganic world, in the interior of the body 
 they behave as organic substances. They require no special 
 preparation for absorption, but are soluble and taken in un- 
 changed. They are received into the body in about the same 
 proportion at all periods of life, but their discharge is nota- 
 bly diminished in old age ; giving rise to calcareous incrusta- 
 tions and deposits, and a considerable increase in the calca- 
 reous matter entering into the composition of the tissues. 
 As examples of this class we may cite water, chloride of so- 
 dium, the carbonates, sulphates, phosphates, and other inor- 
 ganic salts. 
 
 2. Organic Non-Nitrogenized Substances. This class of 
 
 1 This division is composed of excrementitious matters, which will be fully 
 considered when treating of excretion. It is included in the second class of prox- 
 imate principles by Robin and Verclcil. 
 
26 INTEODUCTION. 
 
 proximate principles is of organic origin, definite chemical 
 composition, and crystallizable. With the exception of the 
 salts peculiar to the bile, which will be considered when we 
 come to treat of that fluid, pneumic acid, and one or two 
 unimportant principles, they are distinguished by being com- 
 posed of three elements, Carbon, Hydrogen, and Oxygen. 
 As they thus contain hydrogen and carbon, to the exclusion 
 of all other elements, except the almost universal principle, 
 oxygen, they are frequently spoken of as Hydro-carbons. 
 They are distinguished from other organic substances by the 
 absence of nitrogen, which has given them the name of Non- 
 nitrogenized or Non-azotized substances. They are intro- 
 duced into the body as food, and are manufactured in the 
 economy by special organs ; but, unlike principles of the first 
 class, with the exception of sugar and fat, which are dis- 
 charged in the milk during lactation, are never discharged 
 from the body in health. The principles of this class play 
 an important part in development and nutrition. One of 
 them, sugar, appears very early in foetal life, formed first by 
 the placenta, and afterwards by the liver ; its formation by 
 the latter organ continuing during life. Fat is a necessary 
 element of food, and is also formed in the interior of the 
 body. The exact influence which these substances have on 
 development and nutrition is not known, but experiments 
 and observation have shown that this influence is important. 
 Many physiologists are of the opinion that principles of this 
 class undergo direct oxidation or combustion in the lungs, and 
 have the exclusive office of keeping up the animal tempera- 
 ture. At one time, indeed, they were generally spoken of as 
 calorific elements ; but in the present condition of science this 
 exclusive view is not tenable ; and we shall see, when treating 
 of the subject of animal heat, that its production cannot be 
 referred entirely to combustion of the hydro-carbons. The 
 sugars and fats, lactic acid and the lactates, pneumic acid and 
 the pneumates, the fatty acids and their combinations, consti- 
 tute the most important principles of this class. 
 
PKOX1MATE PRINCIPLES. 27 
 
 3. Organic Nitrogenized Su'bsta/n^ces. This class of prox- 
 imate principles is of organic origin, indefinite chemical com- 
 position, and non-crystallizable. Substances forming this 
 class are apparently the only principles which are endowed 
 with vital properties, taking materials for their regeneration 
 from the nutritive fluids, and appropriating them to form 
 part of their own substance. Considered from this point 
 of view, they are different from any thing which is met with 
 out of the living body. They are all, in the body, in a state 
 of continual change, wearing out and becoming effete, when 
 they are transformed into excrementitious substances, which 
 constitute the second grand division of proximate principles. 
 The process of repair in this instance is not the same as in 
 inorganic substances, which enter and are discharged from 
 the body without undergoing any change. The analogous 
 substances which exist in food, undergo a very elaborate prep- 
 aration, by digestion, before they can even be absorbed by 
 the blood-vessels ; and still another change takes J)lace 
 when they are appropriated by the various tissues. They 
 exist in all the solids, semi-solids, and fluids of the body, 
 never alone, but always combined with inorganic substances. 
 As a peculiarity of chemical constitution, they all contain 
 nitrogen, which has given them the name of Nitrogenized or 
 Azotized principles. As before intimated, they give to the 
 tissues and fluids their vital properties. In studying their 
 properties more fully, we shall see that they are by far the 
 most important elements in the organism. The elaborate 
 preparation which they require for absorption involves the 
 most important part of the function of digestion. Their ab- 
 solute integrity is necessary to the operation of the essential 
 functions of many tissues, as muscular contraction, or con- 
 duction of nervous force. An exact knowledge of all the 
 transformations which take place in their regeneration and the 
 process by which they are converted into effete or excremen- 
 titious matters, would enable us to comprehend nutrition, 
 which is the essence of physiology ; but as yet we know little 
 
28 INTRODUCTION. 
 
 of these changes, and consider ourselves fortunate in under- 
 standing a few of the laws which regulate them. As exam- 
 ples of principles of this class we may cite musculine, os- 
 teine, fibrin, albumen, and caseine. 
 
 INOEGANIC PRINCIPLES. 
 
 The number of principles of this class, now well estab- 
 lished as existing in the human body, is twenty-one. 1 All 
 substances which at any time exist in the body are proximate 
 principles ; but some are found in small quantities, are not 
 always present, and apparently have no very important func- 
 tion. These will be passed over rapidly, as well as those 
 which are so intimately connected with some important func- 
 tion as to render their full consideration in connection with 
 that function indispensable. The following is a list of the 
 inorganic principles, excluding those which are excrementi- 
 tious,' and one or two which are not yet well established : 
 
 Table of Inorganic Principles. 
 
 Proximate Principle. Where Found. 
 
 ' Oxygen. Lungs and Blood. 
 
 Hydrogen. Gases of Stomach and Colon. 
 
 Nitrogen. Lungs, Intestinal Gases, and Blood. 
 
 Carburetted Hydrogen. Lungs (expired air), Intestines. 
 
 [_ Sulphuretted Hydrogen. Lungs (expired air), Intestines. 
 
 Water. Universal. 
 
 Chloride of Sodium. Universal, except the enamel. 
 
 Chloride of Potassium. Muscles, Liver, Milk, Chyle, Blood, Mu- 
 
 cus, Saliva, Bile, Gastric Juice, Ce- 
 phalo-rachidian Fluid, and Urine. 
 
 1 Robin and Verdeil give twenty-nine ; but of these, three (acid phosphate of 
 soda, acid phosphate of lime, and ammonio-magnesian phosphate) are found only 
 in the urine, and may be considered as coming under the head of excrements, 
 with carbonic acid, which is one of the most important excretions ; one (bicar- 
 bonate of lime) is abnormal ; one (bicarbonate of potassa) is found only in cer- 
 tain of the inferior animals ; and two (carbonate and bicarbonate of ammonia) 
 are doubtful. 
 
INOKGANIC PRINCIPLES. GASES. 
 
 29 
 
 Proximate Principle. 
 Phosphate of Lime (basic). 
 Carbonate of Lime. 
 
 Carbonate of Soda. 
 
 Carbonate of Potassa. 
 Phosphate of Magnesia. 
 Phosphate of Soda (neutral). 
 Phosphate of Potassa. 
 Sulphate of Soda. 
 
 Sulphate of Potassa. 
 Sulphate of Lime. 
 Hydrochlorate of Ammonia. 
 Carbonate of Magnesia. 
 
 Bicarbonate of Soda. 
 
 Where Found. 
 
 Universal. 
 
 Bones, Teeth, Cartilage, Internal Ear, 
 Blood, Sebaceous Matter, and some- 
 times Urine. 
 
 Blood, Bone, Saliva, Lymph, Cepholo- 
 rachidian Fluid, and Urine. 
 
 Blood, Bone, Lymph, and Urine. 
 
 Universal. 
 
 Universal. 
 
 Universal. 
 
 Universal, except Milk, Bile, and Gastric 
 Juice. 
 
 Same as Sulphate of Soda. 
 
 Blood and Feces. 
 
 Gastric Juice, Saliva, Tears, and Urine. 
 
 A trace in the Blood and Sebaceous 
 matter. 
 
 Blood (Liebig). 
 
 The Gases. 
 
 The gases (oxygen, hydrogen, nitrogen, carburetted hy- 
 drogen, sulphuretted hydrogen) 1 exist both in a gaseous state, 
 and in solution in some of the fluids of the body. Oxygen 
 plays a most important part in the function of respiration ; 
 but the office of the others is by no means so essential. Ni- 
 trogen seems to be formed by the system in small quantity, is 
 taken up by the blood and exhaled by the lungs ; except dur- 
 ing inanition, when the blood absorbs a little from the in- 
 spired air. It exists in greatest quantity in the intestinal 
 canal. The carburetted and sulphuretted hydrogen, with 
 pure hydrogen, are found in minute quantities in the expired 
 air, and are also found in a gaseous state in the alimentary 
 canal. From the offensive nature of the contents of the 
 large intestine, we would suspect the presence of sulphuretted 
 hydrogen in considerable quantity ; but actual analysis has 
 shown that the gas contained in the stomach and intestines, 
 
 1 Carbonic acid is here omitted, and will be treated of under the head of res- 
 piration. 
 
30 INTRODUCTION. 
 
 large as well as small, is composed chiefly of nitrogen, with 
 hydrogen and carburetted hydrogen in about equal propor- 
 tion, five to eleven parts per hundred, and but a trace of sul- 
 phuretted hydrogen. With the exception then of oxygen 
 and carbonic acid, the latter being an excretion, the gases do 
 not hold an important place among the proximate principles. 
 At all events, their function, whether it be important or not, 
 is but little understood. 
 
 Water, HO. 
 
 "Water is by far the most important of the inorganic prin- 
 ciples. 1 It is present at all periods of life, existing even in 
 the ovum. It exists in all parts of the body ; in the fluids, 
 some of which, as the lachrymal fluid and perspiration, con- 
 tain little else, and in the hardest structures, as the bones, or 
 the enamel of the teeth. 
 
 In the solids and semi-solids it does not exist as water, 
 but enters into their structure, assuming the consistence 
 by which they are characterized. For example, we have 
 water in the bones, teeth, and even in the enamel, not con- 
 tained in the interstices of their structure, as in a sponge, 
 but incorporated into the substance of the tissue. In these 
 situations it is essentially water of composition. During the 
 process of nutrition, water is deposited in the tissues with the 
 other nutritive principles, as we have it incorporated in the 
 substance of certain inorganic compounds in the process of 
 crystallization, when it is known in chemistry as water of 
 crystallisation. In the interior of the body, water is thus 
 incorporated in the substance of organic matters, which are 
 
 1 In comparing principles which are essential to nutrition and to life, it is im- 
 possible to say that one is absolutely more important than another ; still, writers 
 are in the habit of making a distinction in the importance of necessary constit- 
 uents of the body, chiefly with reference to their quantity and the extent of their 
 distribution. When we come to organic principles, we shall see that these are 
 manifestly the most important constituents of the living body, as giving to the 
 tissues their vital properties. 
 
WATER. 31 
 
 of indefinite chemical composition, and non-crystallizal)le, 
 and we have no reason to be surprised, as physiologists, to 
 find it entering into their composition in indefinite propor- 
 tions, assuming the form and consistence of the organic sub- 
 stance. Our definition of a proximate principle is : " a sub- 
 stance extracted from the body, which cannot be further 
 subdivided without chemical decomposition," The union 
 of water with the organic principles is chemical ; and though 
 feeble, is not more so than the chemical union of elements 
 in some compounds found in the inorganic world. The bi- 
 carbonates, for example, are formed by a union of two equiv- 
 alents of carbonic acid with one of the base ; but the second 
 atom of carbonic acid is in so feeble a condition of union, that 
 it is set free when the compound is placed under the receiver 
 of an air-pump. It might be objected that water is combined 
 with organic substances in an indefinite quantity, while the 
 carbonic acid is present in definite proportion ; but it must be 
 remembered that indefinite proportions of all the constituents 
 are characteristic of organic substances ; and that the quantity 
 of water existing, within certain limits, in indefinite propor- 
 tions, only obeys the law which regulates the components 
 which are universally recognized as existing in a state of 
 chemical union. The only difference between water and the 
 other constituents of an organic compound, is that the former 
 is extracted with facility ; as one atom of carbonic acid is 
 extracted from the bicarbonates more easily than the other. 
 Studying the organism as physiologists, we must consider 
 water as an integral constituent of the tissues, and not as 
 merely absorbed by them. 
 
 All the organized structures contain a certain proportion of 
 water, and this is necessary to the performance of all or any of 
 their functions. If a normal muscle be considered as a con- 
 tracting organ, and a nerve as a conducting organ, or albu- 
 men as a nutritious element, we must consider, as one of their 
 constituents, water. It is necessary to the proper form, consist- 
 ence, and function of these and all organized structures. In 
 analysis of organic matters, when water is lost or driven off 
 
32 INTRODUCTION. 
 
 in our manipulations, the principle is not brought near a state 
 of chemical purity, but is essentially and radically changed. 
 
 The quantity of water which each organic substance con- 
 tains is important / and it is provided that this quantity, 
 though indefinite, shall not exceed or fall below certain lim- 
 its. The truth of this proposition is made evident from the 
 following facts : In the first place, all organs and tissues must 
 contain a tolerably definite quantity of water to give them 
 proper consistence. The evils of too great a proportion of 
 water in the system, and consequently a diminution of solid 
 elements, are well known to the practical physician. Gen- 
 eral muscular debility, loss of appetite, dropsies, and various 
 other indications of imperfect nutrition, are among the re- 
 sults of such a condition ; while a deficiency of water is im- 
 mediately made known by the sensation of thirst, which 
 leads to its introduction from without. 
 
 The fact that water never exists in any of the fluids, semi- 
 solids, or solids, without being combined with inorganic salts, 
 and especially chloride of sodium, is one reason why its pro- 
 portion in various situations is to a certain extent constant. 
 The presence of these salts influences, in the semi-solids at 
 least, the quantity of water entering into their composition, 
 and consequently regulates their consistence. A very simple 
 experiment shows this with reference to the chloride of 
 sodium. If a piece of muscle be placed in a strong solution 
 of common salt, as in salting meat, it becomes harder, and 
 loses a portion of its water of composition ; while exposed 
 to the action of pure water, it absorbs a certain quantity and 
 becomes softer. The nutrient fluid of the muscles during 
 life contaiiiS water with just enough saline matter to pre- 
 serve their normal consistence. This action of saline matters 
 is even more apparent in the case of the blood corpuscles. 
 If pure water be added to the blood, these bodies swell up 
 and are finally dissolved ; while if we add a strong solu- 
 tion of salt, they lose water, and become shrunken and 
 corrugated ; but their natural form and consistence can 
 be restored, even after they have been completely dried, by 
 
WATEE. 33 
 
 adding water containing -about the proportion of salt which 
 exists in the plasma. 
 
 It seems clear, then, that water is a necessary element of 
 all tissues, and is especially important to the proper constitu- 
 tion of organic nitrogenized substances ; that it enters into 
 the constitution of these substances, not as pure water, but 
 always in connection with certain inorganic salts ; that its 
 proportion is confined within certain limits ; and that the 
 quantity in which it exists, in organic nitrogenized substances 
 particularly, is regulated by the quantity of salts which en- 
 ter, with it, into the constitution of these substances. 
 
 The quantities of water which can be driven off by a mod- 
 erate temperature (212 Fahr.) from the different fluids and 
 tissues of the body, vary of course very considerably, ac- 
 cording to the consistence of the parts. The following is a 
 list of the quantities in the most important fluids and solids : 
 
 Table of Quantity of Water. 
 
 Parts per 1,000. 
 In Enamel of the Teeth. . 2 
 
 1 
 
 a 
 
 Epithelial Desquamation 37 
 
 Teeth 100 
 
 Bones 130 
 
 ' Tendons (Burdach) 500 
 
 Articular Cartilages 550 
 
 Skin (AVeinholt) 575 
 
 Liver (Frommherz and Gugert) 618 
 
 Muscles of Man (Bibra) 725 
 
 Ligaments (Chevreul) 768 
 
 Mean of Blood of Man (Becquerel and Rodier) 780 
 
 " Milk of Human Female (Simon) 887 
 
 " Chyle of Man (Rees) 904 
 
 " Bile 905 
 
 " Urine 933 
 
 " Human Lymph (Tiedemann and Gmelin) 960 
 
 " Human Saliva (Mitscherlich) 983 
 
 " Gastric Juice 984 
 
 " Perspiration 986 
 
 " Tears 990 
 
 " Pulmonary Vapor 997 
 
 1 This table is made of selections from the table of Robin and Verdeil taken 
 from various authors. 
 3 
 
34 INTRODUCTION. 
 
 Function of Water. After what has been stated re- 
 specting the condition in which water exists in the body, 
 there remains but little to say concerning its function. As 
 a constituent of organized tissues, it gives to cartilage its 
 elasticity, to tendons their pliability and toughness ; it is 
 necessary to the peculiar pow^r of resistance of the bones, 
 and, as we have already seen, it is necessary to the proper 
 consistence of all parts of the body. It has other important 
 functions as a solvent. Soluble articles of food are intro- 
 duced in solution in water. The excrementitious matters, 
 which are generally soluble in water, are dissolved by it in 
 the blood, carried to the organs of excretion, and discharged 
 in a watery solution from the body. 
 
 Origin and Discharge of Water. It is evident that the 
 great proportion of water is introduced from without in the 
 fluids, and in the watery constituents of all kinds of food ; 
 but the theoretical views of some physiologists with regard 
 to the hydrocarbons and their combustion, led to the supposi- 
 tion that water is also formed in the body by a direct union 
 of oxygen and hydrogen. The true way of determining this 
 point is to estimate all the water introduced into the organism, 
 and compare this quantity with that which is discharged. The 
 latter estimate, however, presents very great difficulties. As 
 water is continually given off in the form of vapor from the 
 skin, and in the expired air, the quantities thus discharged 
 are subject to great variations, dependent upon exercise, tem- 
 perature, the state of the atmosphere, etc., and even if con- 
 stant could be estimated with great difficulty. Experiments 
 on this point have been undertaken by Sanctorius, Barral, 
 Boussingault, and others; but they are not sufficiently com- 
 plete to settle the question. 
 
 In the present state of our knowledge, we can only say 
 that water is introduced with the fluid and solid elements of 
 food, by the stomach, and that it escapes by the urine, feces, 
 lungs, and skin. There is no direct evidence that any is pro- 
 
CHLORIDE OF SODIUM. oO 
 
 duced in the interior of the body. In the issue of water by 
 the kidneys and skin, it has long been observed that, in point 
 of activity, these two ermmctories bear a certain relation to 
 each other. When the skin is inactive, as in cold weather, 
 the kidneys discharge a large quantity of water ; when the 
 skin is active, the quantity of water discharged by the kid- 
 neys is diminished. Certain therapeutical agents, also, can 
 be made to act as diaphoretics by combining other measures 
 which favor cutaneous action ; or as diuretics, by employing 
 measures to diminish the action of the skin. 
 
 Chloride of Sodium (Common Salt), !N"aCl. 
 
 Chloride of sodium is next in importance, as an inorganic 
 proximate principle, to water. It is found in the body at all 
 periods of life, existing, like water, in the ovum. It exists in all 
 the fluids and solids of the body, with the single exception of 
 the enamel of the teeth. In the fluids, it seems to be simply 
 in a state of solution, and can be recognized by the ordinary 
 tests ; in this respect we may class together the chlorides of 
 sodium and potassium. 
 
 The quantity of chloride of sodium in the entire body 
 has never been estimated ; nor, indeed, has any accurate esti- 
 mate been made of the quantity contained in the various tis- 
 sues ; for all the chlorides are generally estimated together. 
 It exists in greatest proportion in the fluids, giving to some 
 of them, as the tears and perspiration, a distinctly saline 
 taste. The following table gives an idea of the quantity 
 which has been found in some of the most important of the 
 fluids and solids : 
 
 Table of Quantity of Chloride of Sodium. 
 
 Parts per 1,000. 
 
 In Blood, Human (Lehmann) 4-210 
 
 " Chyle (Lehmann) 6-310 
 
 " Lymph (Nasse) 4-120 
 
 " Milk, Human (Lehmann) 0-870 
 
36 INTRODUCTION. 
 
 Parts per 1,000. 
 
 In Saliva, Human (Lehmann) 1-530 
 
 " Perspiration, Human (mean of three analyses, Piutti). . . . 3-433 
 
 " Urine (maximum) \ ( 7'280 
 
 " " (medium).. [ Valentin. < 4.610 
 
 " " (minimum)) ( 2-400 
 
 " Fecal Matters (Berzelius) 3-010 
 
 
 
 Function of Chloride of Sodium. The function of this 
 principle is undoubtedly important, but is not yet fully un- 
 derstood. It does not seem to enter into the substance of 
 the organized solids and semi-solids as an important and es- 
 sential element, but apparently exercises its chief function in 
 the fluids. It certainly determines, to a great extent, the 
 quantities of exudations, regulates absorption, and serves to 
 maintain the albuminoids, especially those contained in the 
 blood, in a state of fluidity. Albumen is coagulated by heat 
 with much greater difficulty in a solution of chloride of so- 
 dium than when mixed with pure water. A strong solution 
 of common salt is capable of dissolving casein, or of prevent- 
 ing the coagulation of fibrin. We have already alluded to 
 the fact that it is the chloride of sodium particularly which 
 regulates the quantity of water entering into the composition 
 of the blood corpuscles, thereby preserving their form and 
 consistence ; and that it seems to perform an analogous func- 
 tion with reference to the other semi-solids of the body. 
 "With regard to the general function of this substance, the 
 following proposition of Liebig is adopted by Robin and Yer- 
 deil, and a little reflection will show that it is sustained, as 
 far as we know, by the facts : 
 
 " Common salt is intermediate in certain general pro- 
 cesses^ and does not participate ~by its elements in the forma- 
 tion of organs" 
 
 In the first place, the fluids of the body are generally in- 
 termediate in their functions, containing nutritious elements, 
 which are destined to be appropriated by the tissues and organs, 
 and worn-out elements, which are to be separated from the body. 
 In the blood and chyle chloride of sodium is found in greatest 
 
CHLORIDE OF SODIUM. 37 
 
 abundance. When the nutrition of organs takes place, which 
 consists in the fixation of new proximate principles, chloride 
 of sodium is not deposited in any considerable quantity, but 
 seems to regulate the general process, at least to a certain 
 extent. In all civilized countries salt is used extensively as 
 a condiment, and it undoubtedly facilitates digestion by ren- 
 dering the food more savory, and increasing the flow of the 
 digestive fluids ; here, likewise, acting simply as an interme- 
 diate agent. There is nothing more general among men and 
 animals than this desire for common salt. The carnivora 
 crave it, and obtain it in the blood of animals ; the herbivora 
 frequent " salt licks " and places where it is found, and relish 
 it when mixed with their food ; while by man its use is 
 almost universal. In the domestic herbivora the effect of 
 a deprivation of this article is very marked, and has been 
 made the subject of some very interesting experiments by 
 Boussingault. This observer experimented upon two lots 
 of bullocks, of three each, all of them, at the time the ob- 
 servations were commenced, being perfectly healthy and in 
 fine condition. One of these lots he deprived entirely of salt, 
 excepting what was contained in their fodder, while the other 
 was supplied with the usual quantity. No marked difference 
 in the two lots was noticed until between five and six months, 
 when the difference in general appearance was very distinct. 
 The animals receiving salt retained their fine appearance, 
 while the others, though not diminished in flesh, were not as 
 sleek and fine. At the end of a year the difference was very 
 marked. The hides of those which had been deprived of salt 
 were rough and ragged, their appearance listless and inani- 
 mate, contrasting strongly with the sleek appearance and 
 vivacious disposition of the others. 1 The experiments of 
 Boussingault are the most conclusive that have ever been 
 instituted with regard to the influence of chloride of sodium 
 
 1 BOUSSINGAULT, Memoir es de Chimie Agricole et de Physiologie, Paris, 1854, 
 p. 271 et seq. 
 
38 INTRODUCTION. 
 
 upon nutrition. They indicate a certain deficiency in the 
 nutrition of animals deprived of it, but not any considerable 
 loss of weight. Before these observations were made, Dailly 
 made upon twenty sheep analogous experiments, which were 
 continued for three months. At the end of that time the 
 lot which received salt presented a considerable excess of 
 weight (about 22f Ibs.) over the others. 1 
 
 It is a significant fact that the quantity of chloride of so- 
 dium existing in the blood is not subject to variation, but 
 that an excess introduced with the food is thrown off by the 
 kidneys. The quantity in the urine, then, bears a relation to 
 the quantity introduced as food, but the proportion in the 
 blood is constant. This is another fact in favor of the view 
 that the presence of a definite quantity of common salt in 
 the circulating fluid is essential to the proper performance of 
 the general function of nutrition. 
 
 Origin and Discharge of Chloride of /Sodium. This 
 substance is always introduced with food in the condition 
 in which it is found in the body. It is contained in the sub- 
 stance of all kinds of food, animal and vegetable ; but in the 
 herbivora and in man, this source is not sufficient to supply 
 the wants of the system, and it is introduced, therefore, as 
 salt. The quantity which is discharged from the body has 
 been estimated by Barral 2 to be somewhat less than the 
 quantity introduced, about one-fifth disappearing ; but these 
 estimates are not exactly accurate, for the amount thrown off 
 in perspiration has never been directly ascertained. It exists 
 in the blood in connection with the phosphate of potassa, and 
 a certain amount is lost in a double decomposition which 
 takes place between these two salts, resulting in the forma- 
 tion of chloride of potassium and phosphate of soda. It also 
 is supposed to furnish the soda to all the salts which have a 
 
 1 LONGET, Traite de Physiologic, tome i., p. 76. 
 
 2 Cited by KOBIN and YERDEIL. Chimie Anatomique et Physiologique, Paris, 
 1853, tome ii., p. 193. 
 
CHLOEIDE OF POTASSIUM. 39 
 
 soda base, and a certain quantity, therefore, disappears in this 
 way. 
 
 Existing, as it does, in all the solids and fluids of the 
 body, it is discharged in all the excretions, being thrown off 
 in the urine, feces, perspiration, and mucus. 
 
 Chloride of Potassium, KC1. 
 
 Chloride of potassium, though not as important a proxi- 
 mate principle as the chloride of sodium, nor so generally 
 distributed in the economy, seems to have an analogous 
 function. It is found in the Muscles, Liver, Milk, Chyle, 
 Blood, Mucus, Saliva, Bile, Gastric Juice, Cephalo-Rachidian 
 Fluid, and Urine. It is exceedingly soluble, and in these 
 situations exists in solution in the fluids. 
 
 Its quantity in these situations has not been accurately 
 ascertained, as it has generally been estimated together with 
 the chloride of sodium. In the muscles, it exists, however, 
 in a larger proportion than common salt. In cow's milk, 
 Berzelins 1 has found 1'7 pts. per 1,000 ; Pfaff and Schwartz, 
 1*35 per 1,000 in cow's milk, and 0*3 per 1,000 in human 
 milk. 2 
 
 Of the function of this principle, little remains to be said 
 after what has been stated with regard to the chloride of 
 sodium. Their functions are probably identical, though the 
 latter, from its greater quantity in the fluids, and its univer- 
 sal distribution, is by far the more important. 
 
 Origin and Discharge of Chloride of Potassium. This 
 substance has two sources ; one in the food, existing, as it 
 does, in muscular tissue, milk, etc., and the other in a chem- 
 ical reaction between the phosphate of potassa and the 
 chloride of sodium, forming the chloride of potassium and 
 
 1 SIMON, Chemistry of Man, American edit., p. 342. 
 
 2 ROBIN and YERDEIL, op. cit., tome ii., p. 205. 
 
40 INTRODUCTION. 
 
 the phosphate of soda. That this decomposition takes place 
 in the body, is evident from the fact that the ingestion of a 
 considerable quantity of common salt has been found, in the 
 sheep, to increase the quantity of chloride of potassium in 
 the urine, without having any influence on the amount of 
 chloride of sodium. The chloride of potassium is discharged 
 from the body in the urine and mucus. 
 
 Phosphate of Lime, 3 CaO, PO 6 . 
 
 Phosphate of Lirne is found in all the solids and fluids of 
 the body. As it is always united, in the solids, with organic 
 substances as an important element of constitution, it is 
 hardly second in importance to water. It differs in its func- 
 tions so essentially from the chlorides of sodium and potas- 
 sium, that they are hardly to be compared. It is insoluble 
 in water, but held in solution in the fluids of the body by 
 virtue of free carbonic acid, the bicarbonates, and the chlo- 
 ride of sodium. In the solids and semi-solids, the condition 
 of its existence is the same as that of water ; i. e. it is incor- 
 porated, particle to particle, with the organic substance char- 
 acteristic of the tissue, and is one of its essential elements 
 of composition. Nothing need be added here as to this mode 
 of union in the body of organic and inorganic substances, 
 after what has been said under the head of water. 
 
 The following table 1 gives the relative quantity of phos- 
 phate of lime in various situations : 
 
 Table of Quantity of Phosphate of Lime. 
 
 Parts per 1,000. 
 
 In Arterial Blood, ) p iale and March&1 ( 0-790 
 
 " Venous Blood, ) ( 0-760 
 
 " Milk, Human (Pfaff and Schwartz) 2-500 
 
 " Saliva (Wright) O'GOO 
 
 1 Selections from the table of Robin and Verdeil, op. cit. 
 
PHOSPHATE OF LIME. 41 
 
 Parts per 1,000. 
 
 In Urine (proportion to weight of ash, Fleitmann) 25*700 
 
 " Excrements (Berzelius) 40'000 
 
 " Bone (Lassaigne) 400- 
 
 Vertebra of a rachitic patient (Bostock) 136' 
 
 Teeth of Infant one day old. ^| C 510- 
 
 Teeth of Adult 610- 
 
 Teeth, at eighty-one years.. f Lag saignej 6fi() . 
 
 Enamel of Teeth I I 885' 
 
 By this table it is seen that the phosphate of lime exists in 
 very small quantity in the fluids, but is abundant in the 
 solids. In the latter the quantity is in proportion to the 
 hardness of the structure, the quantity in enamel being, 
 for example, more than twice that in bone. The variations 
 in quantity with age are very considerable. In the teeth 
 of an infant one day old, Lassaigne found 510 parts per 
 1,000; in the teeth of an adult, 610 parts; and in the teeth 
 of an old man of eighty-one years, 660 parts. This increase 
 in the calcareous elements of the bones, teeth, etc., in old age 
 
 j / j o 
 
 is very marked ; and in extreme old age they are deposited in 
 considerable quantity in situations where there existed but a 
 small proportion in adult life. The system seems to grad- 
 ually lose the property of appropriating to itself organic mat- 
 ters ; and though articles of food are digested as well as ever, 
 the power of assimilation by the tissues is diminished. The 
 bones become brittle, and fractures, therefore, are common at 
 this period of life, when dislocations are almost unknown. 
 Inasmuch as the real efficiency of organs depends on organic 
 matters, the system actually wears out, and this progressive 
 change finally unfits the various parts for the performance of 
 their functions. An individual, if he escapes accidents and 
 dies, as we term it, of old age, passes away thus by a simple 
 wearing out of his organism. 
 
 function of Phosphate of Lime. This substance, as be- 
 fore remarked, enters largely into the constitution of the 
 solids of the body. In the bones its function is most appa- 
 
42 INTRODUCTION. 
 
 rent. Its existence, in suitable proportion, is necessary to the 
 mechanical office of these parts, giving them their power of 
 resistance, without rendering them too brittle. It is more 
 abundant in the bones of the lower extremities, which 
 have to sustain the weight of the body, than in those of the 
 upper extremities ; and in the ribs, which are elastic rather 
 than resisting, it exists in less quantity than in the bones of 
 the arm. 
 
 The necessity of a proper proportion of phosphate of lime 
 in the bones is made evident by cases of disease. In rachi- 
 tis, where, as is seen by the table, its quantity is very much 
 diminished, the bones are unable to sustain the weight of the 
 body, and become deformed. Finally, when the phosphate of 
 lime is deposited, they retain their distorted shape. The 
 phosphate of lime may be extracted from the bones by ma- 
 ceration in dilute hydrochloric acid,. which dissolves it, leav- 
 ing only the organic substance. Bones treated in this way, 
 though they retain their form, become very pliable ; and a 
 long slender one, like the fibula, may be actually tied into 
 a knot. 
 
 Origin and Discharge of Phosphate of Lime. The ori- 
 gin of this principle is exclusively from the external world. 
 It enters into the constitution of our food, and is discharged 
 with the feces, urine, and other matters thrown off by the 
 body. Its quantity in the urine is exceedingly variable. Le- 
 canu found from O437 to 29*250 grains thrown off by the 
 kidneys during the twenty-four hours. 1 
 
 Carbonate of Lime, CaO, CO 2 . 
 
 Carbonate of lime exists in the Bones, Teeth, Cartilage, In- 
 ternal Ear, Blood, Sebaceous Matter, and sometimes in the 
 Urine. It exists as a normal constituent in the urine of some 
 herbivora, but not in the carnivora, nor in man. It is most 
 
 1 LEHMANN, Physiological Chemistry, American Edition, vol. ii., p. 161. 
 
CARBONATE OF LIME. 4:3 
 
 appropriately considered immediately after the phosphate of 
 lime, because it is the salt next in importance in the consti- 
 tution of the bones and teeth. In these structures it exists 
 intimately combined with the organic matter, under the same 
 conditions as the phosphates, and has analogous functions. 
 In the fluids it exists in small quantity, and is held in solu- 
 tion by virtue of free carbonic acid and the chloride of po- 
 tassium. 
 
 The carbonate of lime is the only example of an inor- 
 ganic proximate principle existing uncombined, and in a 
 crystalline form, in the body. In the internal ear it is found 
 in this form, and has a function connected with audition. 
 
 According to Robin and Verdeil, it is possible that in 
 chemical analyses a certain quantity may come from a 
 decomposition by calcination of those salts of lime which 
 contain a combustible acid. 1 These authors give a table 
 of the quantity of this substance in various of the solids 
 and fluids of the body, from which we make the following 
 selections : 
 
 Table of Quantity of Carbonate of Lime. 
 
 Parts per 1,000. 
 
 In Bone, Human (Berzelius) 113-00 
 
 " " " (Marchand) 102-00 
 
 " " " (Lassalgne) 76-00 
 
 " Teeth of Infant one day old \ t ... 140*00 
 
 " Teeth of Adult j- Lassaigne ) . . . 100-00 
 
 " Teeth of Old Man, eighty-one years ) (,. . . lO'OO 
 
 " Urine of Horse (Boussingault). 10-82 
 
 Origin and Discharge of Carbonate of Lime. Carbonate 
 of lime is introduced into the body with our food, held in so- 
 lution in water by the carbonic acid, Which is always present 
 in small quantity. It is also formed in the body, particularly 
 in the herbivora, by a decomposition of the tartrates, ma- 
 
 1 Op. cifc, vol. ii., p. 247. 
 
44: INTRODUCTION. 
 
 lates, citrates, and acetates of lime contained in the food. 
 These salts, meeting with carbonic acid, are decomposed, and 
 the carbonate of lime is formed. It is probable that in the 
 human subject some of it is changed into the phosphate of 
 lime, and in this form is discharged in the urine ; but when 
 and how this change takes pla^e has not been definitely as- 
 certained. 
 
 Carbonate of Soda, NaO, CO 2 + 10 HO. 
 
 Carbonate of soda is found in the blood and saliva, giv- 
 ing to these fluids their alkalinity ; in the urine of the hu- 
 man subject, when it is alkaline without being ammoniacal ; 
 in the urine of the herbivora ; in the lymph, cephalo-rachid- 
 ian fluid, and bone. The analyses of chemists with regard 
 to this substance are very contradictory, on account of its 
 formation during the process of incineration ; but there is no 
 doubt that it is found in the above situations. The follow- 
 ing table gives the quantities which have been found in some 
 of the fluids and solids : 
 
 Table of Quantity of Carbonate of Soda. 
 
 Parts per 1,000. 
 
 In Blood of the Ox (Marcet) 1-62 
 
 " Lymph (Nasse). 0'56 
 
 " Cephalo-rachidian Fluid (Lassaigne) 0*60 
 
 " Compact Tissue of Tibia in Male of 38 years (Valentin) 2 '00 
 " Spongy Tissue of the same (Valentin) 0-70 
 
 Function of Carbonate of Soda. This substance has a 
 tendency to maintain the fluidity of the fibrin and albumen of 
 the blood, and assists in preserving the form and consistence 
 of the blood corpuscles. Its function with regard to nutri- 
 tion is rather accessory, like that of chloride of sodium, than 
 essential, like the phosphate of lime in the constitution of 
 certain structures. 
 
MAGNESIA, ETC. 45 
 
 Origin and Discharge of Carbonate of Soda. This sub- 
 stance is not introduced into the body as carbonate of soda, 
 but is formed, as is the carbonate of lime in part, by a de- 
 composition of the malates, tartrates, etc., which exist in 
 fruits. It is discharged occasionally in the urine of the hu- 
 man subject, and a great part of it is decomposed in the 
 lungs by the action of pneumic acid, setting free carbonic 
 acid, which is discharged in the expired air. 
 
 Carbonate of Potassa, KO, C0 2 . 
 
 This salt exists particularly in herbivorous animals. It 
 is found in the human subject when subjected to a vegetable 
 diet. Under the heads of function, origin, and discharge, 
 what has been said with regard to the carbonate of soda will 
 apply to the carbonate of potash. 
 
 Carbonate of Magnesia, MgO, C0 2 HO, and Bicarbonate of 
 Soda, NaO, CO 3 + HO, C(V 
 
 It is most convenient to take up these two salts in con- 
 nection with the other carbonates, though they are put at the 
 end of the list of inorganic substances, as the least important. 
 We know very little about them, chemically or physiologi- 
 cally. Traces of carbonate of magnesia have been found 
 in the blood of man, and it exists normally in considerable 
 quantity in the urine of herbivora. In the human subject 
 it is discharged in the sebaceous matter. 
 
 Liebig has merely indicated the presence of bicarbonate 
 of soda in the blood. 
 
 Phosphate of Magnesia, 3 MgO, PO 5 + 7 HO ; Phosphate 
 of Soda (neutral), 3 NaO, PO 5 ; and Phosphate of Potassa, 
 2 KO, P0 6 . 
 
 1 Formula of Graham, op. cit., p. 389. 
 
46 INTRODUCTION. 
 
 These salts are found in all the fluids and solids of the 
 body, though not existing in a very large proportion, com- 
 pared with the phosphate of lime, which we have already 
 considered. In their relations to organized structures, they 
 are analogous to the phosphate of lime ; entering into the 
 composition of the tissues, and existing there in a state of 
 intimate combination. They are all taken into the body 
 with food, especially by the carnivora, in the fluids of which 
 they are found in much greater abundance than the carbo- 
 nates ; which latter, as we have already seen, are in great 
 part the result of the decomposition by carbonic acid of the 
 malates, tartrates," oxalates, etc. 
 
 With respect to their functions, we can only say that, 
 with the phosphate of lime, they go to form, and are neces- 
 sary constituents of, the organized structures. 
 
 They are discharged from the body in the urine and 
 feces. 
 
 Sulphate of Soda, ISTaO, SO 3 + 10 HO ; Sulphate of 
 Potassa, KO, SO 3 ; Sulphate of Lime, CaO, SO 3 + 2 HO. 
 
 The sulphate of soda and the sulphate of potassa a,re 
 identical in their situation, and apparently in their functions. 
 They are found in all the fluids and solids of the body, ex- 
 cepting milk, bile, and gastric juice. Their origin in the 
 body is from the food, in which they are contained in small 
 quantity, and they are discharged in the urine. Their chief 
 function appears to be in the blood, where they tend to pre- 
 serve the fluidity of the fibrin and albumen, and the form 
 and consistence of the blood corpuscles. 
 
 The sulphate of lime is found in the blood and feces. It 
 is introduced into the body in solution in the water which is 
 used as drink, and is discharged in the feces. 
 
 Its function is not understood, and is probably not very 
 important. 
 
SUMMARY OF INOKGANIC PRINCIPLES. 47 
 
 Hydrochlorate of Ammonia, 2sH 3 , HC1. 
 
 This substance has simply been indicated by chemists as 
 existing in the gastric juice of ruminants, the saliva, tears, 
 and urine. Some chemists make a rearrangement of its par- 
 ticles, calling it chloride of ammonium, when instead of 
 ]N"H 3 , HC1, it would be NH 4 C1; but as the ammonium is 
 hypothetical, the name we have used seems more appropriate. 
 
 It is discharged in the urine, in which it exists, according 
 to Simon, 1 in the proportion of 0*41 parts per 1,000. Its 
 origin and function are unknown. 
 
 Summary. A review of the functions of the individual 
 inorganic constituents of the body, excluding the gases, will 
 show that they may be divided into two groups : one, which 
 is composed of those substances, existing particularly in the 
 solids and semi-solids, which are in a condition of molecular 
 union with organic substances, merge their identity, as it 
 were, into them, and become necessary constituents of the 
 tissues / and the other, composed of substances which rather 
 regulate, by their influence in endosmosis, or otherwise, the 
 nutritive processes^ do not seem to be indispensable constituents 
 of the tissues, lut have rather an accessory office to perform 
 in the function of nutrition. 
 
 At the head of the first group we may place water ; the 
 absence of which involves destruction of the properties of 
 the tissues, and even of the organic elements. 
 
 At the head of the second group we may place common 
 salt ; which is absolutely necessary to the functions of nutri- 
 tion, though it does not seem to form an indispensable ele- 
 ment of the tissues. 
 
 The first group, as we should naturally expect, forms a 
 considerable proportion of the body, and the articles compo- 
 sing it are discharged in small quantity ; as in the case of 
 
 1 SIMON, Animal Chemistry, with Reference to the Physiology and Pathology 
 of Man, Philadelphia, 1846, p. 403. 
 
4:8 INTRODUCTION. 
 
 water, which composes two-thirds of the entire organism, and 
 yet only about four and a half pounds are discharged daily 
 from the skin and lungs, and in the urine and feces. 
 
 The second group enters and is discharged from the body 
 in considerable quantity, and very little remains in the or- 
 ganism; as common salt, which exists in the urine in a 
 greater proportion than in any of the solids or other fluids. 
 
 The following are the inorganic substances which are ap- 
 parently indispensable to the constitution of organized tissues : 
 
 Water. 
 
 Basic Phosphate of Lime. 
 Carbonate of Lime. 
 Phosphate of Magnesia. 
 
 " u Soda, 
 " " Potassa. 
 
 The following are those which appear to have an accessory 
 office in nutrition : 
 
 Chloride of Sodium. 
 
 " " Potassium. 
 Carbonate of Soda. 
 Bicarbonate of Soda. 
 Carbonate of Potassa. 
 
 " " Magnesia. 
 Sulphate of Soda. 
 
 " Potassa. 
 
 The remaining two principles, sulphate of lime and hy- 
 drochlorate of ammonia, are so obscure in their function that 
 they cannot be definitely put in either of the above groups. 
 
 ORGANIC NON-NITROGENIZED PRINCIPLES. 
 
 (Hydro- Carbons.} 
 
 The principles of this class differ widely from inorganic 
 substances In the first place, they have a different origin, 
 
STJGAKS. 49 
 
 being formed exclusively in animal or vegetable bodies. They 
 are of definite chemical composition, and crystallizable. The 
 most important groups of this class, i. e. the sugars and fats, are 
 composed of carbon, hydrogen, and oxygen, whence they are 
 sometimes called Hydro-Carbons. They are distinguished 
 from another class of organic substances by the fact that 
 they do not contain nitrogen ; which has given them the 
 name of Non-nitrogenized Principles. They are in part 
 introduced into the body as food, and in part formed in the 
 economy by special organs. In the former instance, they 
 undergo an elaborate preparation by digestion before they 
 become part of the organism, differing in this respect from 
 the inorganic principles, which are absorbed unchanged 
 With the exception of butter and the sugar of milk, they are 
 never discharged from the body in health, but disappear in 
 the processes of nutrition. In this respect, also, they differ 
 from the inorganic principles, all of which are discharged 
 from the body, most of them in the condition in which they 
 entered. 
 
 The most important principles of this class may be divided 
 into two great groups, the Sugars and the Fats ; in addition 
 to which we have, lactic acid and the lactates, pneumic acid, 
 pneumate of soda, the fatty acids and their combinations, 
 and certain organic salts which are found in the bile. 
 
 The varieties of sugar with which we are most familiar, 
 of which cane sugar may be taken as the type, are not 
 found in the animal body, but belong to the vegetable 
 kingdom. These, which form an important element of 
 food, must . be modified by digestion before they become 
 proximate principles. For a long time it was supposed 
 that sugar was an exclusively vegetable production and 
 consumed by animals ; but late experiments, especially those 
 of Bernard, have shown that sugar is constantly produced by 
 animals, presenting, in this instance, marked differences from 
 4 
 
50 INTRODUCTION. 
 
 the vegetable varieties. Yegetable sugar taken as food is 
 changed so as to resemble animal sugar, before it is absorbed. 
 In considering, then, the proximate principles of the body, we 
 have only to do with the animal sugars. 
 
 There are two varieties of sugar manufactured in the 
 economy. The first is constantly formed by the liver, and is 
 found in this organ and the blood which circulates between 
 it and the lungs. This variety is called Liver Sugar / and, as 
 it appears in the urine of diabetics, is sometimes known un- 
 der the name of diabetic sugar. The second variety is only 
 present in the organism during lactation. It exists in the 
 milk, and is called Milk Sugar. We have also sugar resulting 
 from the transformation by digestion of cane sugar and starch, 
 which is called Glucose. This resembles the liver sugar very 
 closely, and is, indeed, identical with it in composition, but 
 differs from it in the fact that it ferments less easily. 
 
 The presence of sugar in the economy seems to be a ne- 
 cessity of existence. It, or starch which is readily converted 
 into glucose, constitutes an important and necessary element 
 of food. In early life large quantities are taken in with the 
 milk. This, however, does not seem to be sufficient to supply 
 the wants of the system, and we have it continually manufac- 
 tured in the interior of the body ; but once formed, or intro- 
 duced from without, it undergoes some transformation innutri- 
 tion, and is never discharged in health. Sugar is exceedingly 
 soluble, and in the economy, exists in solution in the blood. 
 Here it forms a union with the chloride of sodium, which 
 masks, to a certain extent, some of its characteristic proper- 
 ties, such as the peculiar taste by which it is so readily 
 .recognized. 
 
 Composition and Properties. The sugars are composed 
 of carbon, hydrogen, and oxygen ; and it is noticeable that the 
 hydrogen and oxygen always exist in equal proportions, or 
 in the proportions which form water ; a peculiarity affording 
 an explanation of the transformation of one variety of sugar 
 
SUGAES. 51 
 
 into another, which is effected in some instances with great 
 facility. 
 
 Simon 1 gives the following composition of the animal 
 sugars in a crystalline form : 
 
 Liver Sugar and Glucose, C I2 H 14 O U . 
 Milk Sugar, C 12 H 12 O 12 . 
 
 On exposing either of these varieties of sugar to a dry 
 heat, two atoms of water of crystallization are driven off, 
 leaving the formula for liver sugar, C 12 H 12 O 12 , and for milk 
 sugar, C 12 H 10 O 10 . From the relative composition of these 
 varieties of sugar, it is seen that the addition of two atoms 
 of hydrogen and oxygen, or water, to milk sugar, will trans- 
 form it into glucose. This change actually takes place in 
 digestion. The digestive fluids act also upon cane sugar 
 (C 12 H u O n ) and starch (C 12 H ]0 O 10 ), transforming them into 
 glucose. 
 
 Animal sugars are distinguished from cane sugar by 
 their different behavior in the presence of acids and alkalis. 
 Cane sugar is converted into the animal variety by boiling 
 for a few seconds with a dilute mineral acid, and is unaffected 
 by boiling with an alkali; while the animal sugars are not 
 affected by acids, and are transformed into a dark-brown 
 substance, melassic acid, by boiling with an alkali. 
 
 If .a solution of sugar be mixed with a little fresh yeast 
 and kept for a few hours at a temperature of from 80 to 
 100 Fahr., a peculiar change takes place which is called fer- 
 mentation. The sugar is decomposed into carbonic acid gas, 
 which rises to the top in bubbles, and alcohol, which remains 
 in the liquid. Some ferments, especially organic matters in 
 process of decomposition, when they exist in a saccharine 
 solution, have the property of inducing a change of the sugar 
 into lactic acid (C 6 H O 6 ), giving rise to what is called the 
 lactic-acid fermentation. This process is peculiarly interest- 
 
 1 SIMON'S Chemistry of Man, Philadelphia, 1846. 
 
52 INTRODUCTION. 
 
 ing in a physiological point of view, from the fact that much 
 of the sugar which disappears in the economy is now thought 
 to undergo this change. 
 
 A clear solution of sugar has a peculiar effect upon polar- 
 ized light, being possessed of what is called a rotatory power. 
 If a ray of polarized light be gassed through a tube contain- 
 ing simple water, its direction is unchanged ; but if a saccha- 
 rine solution be substituted, it is found to possess what is 
 called molecular activity, and turns the ray to the right. The 
 amount of deviation, which can easily be measured by an 
 instrument constructed for this purpose by Biot and Soleil, 
 called a polarimeter, indicates the quantity of sugar in the solu- 
 tion. The instrument above mentioned is sometimes used 
 for quantitative analysis. 
 
 Tests for Sugar. Eeliable tests for determining the 
 presence of sugar in the animal tissues and fluids are useful 
 to the practical physician as well as the physiologist; for 
 this substance frequently occurs in the urine, as a pathological 
 condition, when it is essential to ascertain the fact of its 
 presence, even if no attempt be made to determine its quan- 
 tity. For this purpose a number of tests have been devised, 
 which are most of them reliable and simple of application. 
 
 Moords, or the Potash Test. This test depends on the 
 conversion of the animal sugars into melassic acid by boiling 
 with a caustic alkali. It is employed in the following way : 
 To a small portion of the suspected liquid in a test tube we 
 add a little caustic potash in solution, and boil the mixture. 
 If sugar be present, a brownish color will be produced, its 
 intensity depending upon the quantity of sugar. This test 
 is applicable only to glucose, grape sugar, and the animal 
 varieties. 
 
 Trommels Test. This is one of the most delicate and 
 convenient tests for sugar. It is employed in the following 
 
SUGARS. 53 
 
 way : To the suspected liquid in a test tube, we add one or 
 two drops of a moderately strong solution of sulphate of 
 copper, and render the mixture distinctly alkaline by the 
 addition of caustic potash in solution. On the addition of 
 the alkali the mixture will assume a distinctly blue color, 
 especially marked if sugar be present. On the application 
 of heat, if sugar be -present, a little before the liquid reaches 
 the boiling point, a yellowish or reddish precipitate will 
 begin to show itself in the upper part of the test tube, which 
 as the heat continues will gradually extend through the whole 
 of the liquid. If no sugar be present, the liquid will retain 
 its clear blue color, unless the boiling be prolonged, when a 
 black precipitate of the black oxide of copper is likely to 
 appear. In this test, before the heat is applied, the copper 
 is in the form of the sulphate of a protoxide (CuO, SO 3 ), 
 which is soluble; but on boiling in an alkaline solution, 
 the sugar becomes oxidized, is transformed into an acid, 
 the nature of which is not well determined, and the copper, 
 losing an equivalent of oxygen, becomes reduced to the con- 
 dition of a sub-oxide (Cu 2 O), which has a reddish or yellow- 
 ish color, and is insoluble. This is the way in which the test 
 is generally employed. Trommer recommended (1841), with 
 special reference to examination of urine, to first add the 
 solution of potash, then filter, and then add the solution of 
 copper. If sugar be present, a reduction of the sub-oxide will 
 take place spontaneously in a few hours, or may be produced 
 immediately by boiling. This removes certain sources of 
 obscurity in examining the urine, which result from a pre- 
 cipitate produced by the simple action of the potash, and not 
 dependent on the presence of sugar. 
 
 If care be taken to employ the following simple precau- 
 tions in the application of this test, it will be found the most 
 reliable and simple of any that are in use for qualitative 
 analysis. 
 
 The solution to be examined must be clear. A clear 
 extract of the blood, muscles, or liver, is easily made in the 
 
54: INTRODUCTION. 
 
 following way : The blood, or tissue, finely divided, is boiled 
 with a little water and sulphate of soda. In a few moments 
 the organic and coloring matters will become coagulated, 
 when it is to be thrown on a filter, and a clear extract will 
 pass through. This extract will contain sulphate of soda, 
 which is very soluble in hot watgr, but this does not interfere 
 with the application of the test. The same result may be 
 obtained by boiling with animal charcoal, enough being 
 added to make a thin paste, and filtering ; a process, how- 
 ever, which is more tedious and has no advantages over the 
 one just described. 
 
 In testing the urine, a light flocculent precipitate will 
 generally be obtained, though no sugar be present. "With 
 a little experience this may be distinguished from the 
 deposit of sub-oxide of copper, by the fact that it is less 
 highly colored, and appears in flakes after it finally settles 
 to the bottom of the test tube, of a light grayish color ; 
 while the sub-oxide of copper settles to the bottom in the 
 form of a heavy red powder. If there be any doubt as to 
 the nature of the reaction, the urine may be purified in va- 
 rious ways before testing. A very simple, and perhaps the 
 best method, is to make a paste with animal charcoal and 
 filter. Robin recommends the following process: "To be 
 certain of the presence of glucose, we free it (the liquid) from 
 all reducing matters ; 1st, adding to the urine an excess of 
 the neutral acetate of lead, then filtering ; 2d, adding to this 
 clear filtered liquid, ammonia, until it is slightly alkaline, 
 and filtering. We can then treat the second liquid with the 
 reagents ; and if it precipitates, it is certain that there is sugar 
 in the urine." : Another method is to evaporate the urine to 
 the consistence of a syrup, extract this with alcohol, drive 
 off the alcohol by evaporation, and dissolve the residue in 
 water; when if sugar be present it will respond to the test. 
 
 1 Didionnaire de Medecine, etc., de P. H. NYSTEN, par E. LITTRE et CH. ROBIN, 
 Paris, 1858. " Sucre." 
 
SUGAES. 55 
 
 It is a curious fact that sugar added to healthy urine, even 
 in large quantity, will not respond to Trommer's test, on 
 account of organic matters, which interfere with the reduc- 
 tion of the copper. The cause of this interference we do not 
 understand ; but in diabetes, the organic substances, whatever 
 they may be, are not present, or at least do not interfere with 
 the application of tests for sugar. 
 
 Another precaution to be adopted is to add a small quan- 
 tity, two or three drops only, of the solution of sulphate of 
 copper, especially if we suspect the sugar to be present in 
 small quantity ; for if too much be added, a portion only of 
 the oxide of copper will be reduced, and that which remains, 
 by its blue color, may obscure the reaction. 
 
 Ban^eswiWs Test. For those engaged in physiological 
 investigations, when it is desired to roughly estimate the 
 quantity of sugar in any clear extract, and when the test is 
 to be employed very -frequently, Barreswill's solution is con- 
 venient. This is simply a solution of tartrate of copper and 
 caustic potash. The reaction with this fluid is precisely the 
 same as in Trommer's test. It has seemed to me, if there be 
 any difference, that the reduction takes place more promptly 
 with the sulphate of copper, but that the tartrate will detect 
 a smaller quantity of sugar. The advantage of Barreswill's 
 test is, that but a single fluid is to be added to the suspected 
 solution. The only disadvantage is, that the solution is liable 
 to alteration if kept more than a few days or weeks. After 
 standing for a certain time, a yellowish sediment is deposited, 
 and the fluid will no longer reduce in the presence of sugar. 
 Its properties may be renewed by adding a little potash and 
 iiltering ; but in delicate observations, it is always better to 
 use a solution which has not undergone alteration. 
 
 In employing this test, we add to the suspected fluid 
 enough of the solution to give the whole a distinctly blue 
 color, and boil ; if sugar be present, we have a reduction of 
 the yellowish sub-oxide of copper as in Trommer's test. 
 
56 INTRODUCTION. 
 
 The solution may be prepared according to the following 
 formula, reduced to grains from the formula given by' Ber- 
 nard : 1 
 
 Of bitartrate of potash, 3 vi. gr. xxiij. 
 
 Of crystallized carbonate of soda, 3 v. gr. ix. 
 
 Dissolve in vss. of water ^ add to the solution 3 iij. gr. 
 li. of sulphate of copper, and boil ; allow the mixture to 
 cool and add 3 v. gr. ix. of potash dissolved in 5 iv. of water. 
 Add water till the whole measures 3 xvii. 
 
 Maumen&s Test. B'6ttger*s Test. The first of these 
 tests is employed by saturating strips of some woollen tissue, 
 such as flannel, with a strong solution of bichloride of tin, 
 and drying. One of these strips is moistened with the sus- 
 pected liquid, and dried quickly by the heat of a fire or lamp. 
 If sugar be present, the strips will assume a brownish or black 
 tint. 
 
 Bottger's test depends upon the reduction of a salt of bis- 
 muth, analogous to the. reduction of the copper in Trommer's 
 test. It is employed in the following way : We add to the 
 suspected liquid a few drops of a weak solution of the nitrate 
 of bismuth in nitric acid, render the whole alkaline by the 
 addition of a solution of carbonate of soda, and boil for three 
 or four minutes. If sugar be present, the bismuth will be 
 reduced, and form a dark precipitate. Neither of these tests 
 presents any advantage over Trommer's test, which is the one 
 most generally employed. 
 
 Fermentation Test. With the exception of actual ex- 
 traction, this is the most certain test for sugar, and should 
 always be employed when the other tests leave any doubt 
 with regard to its presence. It depends on a property of 
 sugar whereby it is decomposed into alcohol and carbonic 
 acid in the presence of certain ferments, at a moderately ele- 
 vated temperature. The test is applicable to all varieties of 
 
 1 BERNARD, Lemons de Physiologic Expirimcntalc, Paris, 1855, p. 34. 
 
6UGAKS. 67 
 
 sugar; but it must be remembered that milk sugar fer- 
 ments slowly and with difficulty. In its application, all that 
 is necessary is to add a few drops of fresh yeast, and keep 
 the suspected liquid for a few hours at a temperature of from 
 80 to 100 Fahr. The mixture should be placed in some appa- 
 ratus by which the gas which forms may be collected and an- 
 alyzed. To effect this, we may fill a large test tube and in vert it 
 in a small shallow vessel ; or if there be but a small quantity of 
 liquid, we may use a very simple and convenient apparatus 
 described by Bernard. This is simply a large test tube fitted 
 with a good cork, perforated to allow the passage of a small 
 tube which extends to the bottom. This tube may be turned 
 up at the lower end, and bent above so as to permit the 
 escape of the liquid as the gas is formed. The whole is com- 
 pletely filled with the suspected solution, to which have been 
 added a few drops of fresh yeast, and kept at a temperature 
 of 80 to 100 Fahr. If sugar be present, bubbles of gas will 
 soon begin to appear, which will collect at the top and force 
 a portion of the liquid out by the small tube. If no gas has 
 appeared at the end of four or six hours, it is certain that no 
 sugar is present. This test is conclusive, if proper care be 
 taken in its application ; and to insure accuracy, it is well to 
 test the yeast with a saccharine solution to demonstrate its 
 activity, and test it also with pure water, to be sure that it 
 contains no sugar. "We may then demonstrate that the gas 
 produced is carbonic acid by removing the cork and inserting 
 a lighted taper, which will be immediately extinguished, or 
 passing it into another vessel and agitating with lime-water, 
 which will be rendered milky by the formation of the insolu- 
 ble carbonate of lime. The alcohol remains in the liquid, 
 from which it may be separated by careful distillation. 
 
 Measures for demonstrating the composition of the gas 
 and the presence of alcohol in the liquid are by no means 
 necessary in the ordinary application of the test. The dis- 
 tinct formation of gas in the liquid is generally sufficient 
 evidence of the presence of sugar. 
 
58 INTRODUCTION. 
 
 Torulce. Another test of the presence of sugar is the 
 growth of the Torulce cerevisice. After diabetic urine has 
 stood for some time at a moderate temperature, a delicate 
 scum will form upon the surface, which, on microscopic 
 examination, will be found to consist of a vegetable growth, 
 presenting a number of oval joints irregularly connected. 
 These are called Torulce. After a time they break up and 
 fall to the bottom of the vessel, as minute oval spores. This 
 appearance is observed even when a small quantity of sugar 
 is present. 
 
 Yarious modes of procedure have been described for the 
 determination of the quantities of sugar. In general terms 
 it may be stated that the copiousness of the precipitate in 
 Trommer's test, and the amount of gas evolved in the fer- 
 mentation test, give some idea of the quantity of sugar 
 present. For directions for accurate quantitative analysis the 
 reader is referred to works on organic chemistry. 
 
 Origin and Functions of Sugar. Sugar is an important 
 element of food at all periods of life. In the young child it 
 is introduced , in considerable quantity with the milk." In 
 the adult it is introduced partly in the form of cane sugar, 
 but mostly in the form of starch, which is converted into 
 sugar in the process of digestion. With the exception of 
 milk sugar, which is present only during lactation, all the 
 sugar in the body exists in a form resembling glucose, into 
 which milk sugar, cane sugar, and starch are all converted, 
 either before they are absorbed, or as they pass through the 
 liver. In addition to these external sources of sugar, it is 
 continually manufactured in the economy by the liver, 
 whence it is taken up by the blood passing through this 
 organ. It disappears from the blood in its passage through 
 the lungs. Sugar is found then in the economy con- 
 stantly, in the substance of the liver, in the blood coming 
 from the liver, and in the blood of the right side of the 
 heart; and after the ingestion of saccharine or amylaceous 
 
STJGAKS. 59 
 
 articles of food, in the blood of the portal vein. It is not 
 found in other organs, nor does it normally exist in the 
 arterial blood. 
 
 During the first three or four months of foetal life sugar 
 is formed by the placenta, and exists in all the fluids of the 
 foetus, in greater quantity even than after birth. At the 
 third or fourth month the liver begins to take on this func- 
 tion, which is gradually lost by the placenta. The constant 
 production of this principle in the economy, even in the 
 early months of foetal life, is significant of the importance of 
 its function. 
 
 The function of sugar and its mode of disappearance in 
 the economy are not yet well understood. Its early forma- 
 tion in large quantity, when the processes of nutrition are 
 most active, seems to point to an important office in the 
 performance of this general function. Its presence is un- 
 doubtedly necessary at all periods of life ; for its formation 
 never ceases in health. Bernard has attempted to show that 
 its presence in the animal fluids favors cell development, but 
 has hardly succeeded in establishing this fully. 1 
 
 It has been claimed that the sugars and fats are for the 
 purpose of keeping up the animal temperature, and are 
 oxidized or undergo combustion in the lungs. This view 
 was afterwards modified by Liebig and others, who supposed 
 that the oxidation takes place in the general system. This 
 theory will be discussed more fully in the chapter on animal 
 heat. Here we can only say that, while there are many cir- 
 cumstances which, taken by themselves, might lead to such 
 a conclusion, the production of heat in the body is closely 
 connected with the general process of nutrition, of which the 
 disappearance of oxygen and formation of carbonic acid are 
 but a single one of many important changes. "We have not yet 
 sufficient ground for the supposition that the substances under 
 consideration are directly and exclusively acted upon by oxy- 
 
 1 BERNARD, Lemons de Physiologic Uxperimcntale, Paris, 1855, p. 247 et seq. 
 
60 INTRODUCTION. 
 
 gen in the organism. The term calorific elements, which 
 is sometimes applied to them, cannot therefore be accepted. 
 When we endeavor to substitute for this theory a definite ex- 
 planation of the uses of sugar in the economy, we find our- 
 selves at a loss ; but it must be remembered that we are yet far 
 from having a complete knowledge of the functions of the 
 body, particularly those connected with the intimate pro- 
 cesses of nutrition. 
 
 In the present state of science, we are only justified in 
 saying that sugar is important in the process of development 
 and nutrition, at all periods of life. The precise way in 
 which it influences these processes is not fully understood. 
 
 Sugar disappears from the blood in its passage through 
 the lungs, in great part, probably, by conversion into lactic 
 acid. This change has been demonstrated in the blood of a 
 diabetic patient ; all the sugar contained in the blood being 
 thus changed in less than twenty minutes. 1 
 
 Sugar is never discharged from the body in health, with 
 the single exception of the sugar of milk in the female during 
 lactation. Under certain diseased conditions of the system 
 its production by the liver is exaggerated, so that a certain 
 quantity passes through the lungs, exists in the arterial blood, 
 and appears in the urine, constituting the very serious affec- 
 tion, called diabetes mellitus. 
 
 Fats. 
 
 Fatty or oily matters exist in both the animal and 
 vegetable kingdoms. Those which are most interesting to 
 us as physiologists are the varieties found in animals, which 
 constitute an important group of proximate principles. Both 
 vegetable and animal fats are important elements of food. 
 
 In the animal economy fat exists in three varieties, which 
 are called, respectively, Oleine, Margarine, and Stearins. 
 In certain situations are found some of the fatty acids and 
 
 1 ROBIN and YERDEIL, Chimie Anatomique, tome ii., p. 553. 
 
FATS. 61 
 
 their combinations, but they exist in minute quantity, and 
 their function is comparatively unimportant. 
 
 Composition and Properties. In their ultimate composi- 
 tion, fats bear a certain resemblance to the sugars. Like 
 them they are composed of carbon, hydrogen, and oxygen ; 
 but the two latter elements do not exist, as in sugar, in the 
 proportions to form water. From this difference we should 
 be led to suspect, what is really the fact, that the different 
 varieties of fat are not mutually convertible. 
 
 The fat which exists in the body is a mixture of the three 
 varieties above mentioned, and is found in the ordinary adi- 
 pose tissue, and in the substance of certain tissues in the 
 form of minute globules or granules. It is not found in any 
 great quantity in the blood, except after digestion of a full 
 meal. It exists in the chyle in a state of extremely minute 
 subdivision and suspension. It exists in the milk, also in a 
 state of minute subdivision, but presenting some slight differ- 
 ences from the ordinary fatty matter of the economy. 
 
 Robin and Yerdeil give, as the ultimate composition of 
 Stearine, C 71 H 70 O 8 . The other varieties are separated from 
 their union with each other with great difficulty, and have 
 not yet been obtained in a state of sufficient purity for ulti- 
 mate analysis. The reaction of all the varieties of fat is 
 neutral. 
 
 Fat, in greater or less quantity, is found in all the tissues 
 of the body, with the exception of the substance of the bones, 
 the teeth, and the elastic and inelastic fibrous tissue. It 
 always consists of a mixture of the three varieties in varying 
 proportions, but, with one or two exceptions, is never com- 
 bined with any other of the proximate principles. In the 
 adipose tissue proper, it is enclosed in little cells which are 
 called the adipose vesicles. In all other situations it is in the 
 form of microscopic globules or granules. As it is thus dis- 
 tinct from other elements, it may be always recognized in the 
 organism by the naked eye or the microscope. In the ner- 
 
62 INTRODUCTION. 
 
 vous matter there exists a phosphorized fat, the composition 
 and properties of which are not very well understood, in 
 union with organic matter. A minute quantity of fat exists 
 in combination with the organic matter of the blood corpus- 
 cles. 
 
 The fats are insoluble in waier and in the animal fluids, 
 with the exception perhaps of the bile, which holds a small 
 quantity in solution by virtue of its saponaceous constituents. 
 They are all very soluble in ether and hot alcohol, and but 
 slightly soluble in cold alcohol. The varieties which are solid 
 at the temperature of the body, stearin e and margarine, are 
 easily dissolved by oleine, which is liquid. 
 
 The most marked distinction between the varieties of fat 
 is in their consistence. Oleine is liquid at the temperature 
 of the body, and even at the freezing point of water. Mar- 
 garine is liquid at or above the temperature of 118, and 
 stearine at the temperature of 143 Fahr. The difference in 
 the consistence of adipose tissue of different animals depends 
 upon the relative proportion of the various kinds of fat. 
 
 Saponification. When fat is boiled for a certain time 
 with an alkali, in the presence of water, it undergoes a pecu- 
 liar decomposition which is called saponification. A portion 
 of the water is appropriated, and the fat is converted into 
 glycerine and an acid. The acid is called oleic, margaric, 
 or stearic acid, as it is formed from oleine, margarine, or 
 stearine. In this process the glycerine remains uncombined, 
 and the acid unites with the alkali to form what is commonly 
 known as a soap. 
 
 This kind of decomposition is called saponin'cation by a 
 base ; but technically, saponification is regarded as any pro- 
 cess by which a fat is decomposed into its acid and glycerine. 
 This may be effected by passing the vapor of water through 
 fat which has been raised to a temperature of 572 Fahr. The 
 action of the strong acids is also to decompose fat. "When a 
 small quantity of acid is used, it unites with the glycerine ; 
 
FATS. 63 
 
 I 
 
 when a large quantity is used, it unites with the fatty acid. 
 The process of formation of glycerine and fatty acids in- 
 volves the fixation of a certain quantity of water ; so that 
 the combined weights of the glycerine and acid exceed that 
 of the fat originally employed. 1 It is thought by some that 
 this acidification of fat takes place to a certain extent in di- 
 gestion ; however this may be, it is not an essential part of 
 the digestive process. 
 
 Emulsion. When liquid fat is violently shaken up with 
 water, it is minutely subdivided, and an opaque milky mix- 
 ture is the result. But this is momentary,' the two liquids 
 separating almost immediately from each other when they 
 are no longer agitated. There are certain fluids, however, 
 which have the property of holding fat permanently in a 
 state of minute subdivision and suspension, forming what is 
 called an emulsion. Out of the body, mucilaginous fluids 
 and white of egg have this property. In the body, we find 
 as examples of emulsions the chyle, which is formed by the 
 action of the pancreatic juice upon the fatty elements of 
 food, and milk, which is composed of butter held in suspen- 
 sion by the water and caseine. The property of forming 
 emulsions with certain liquids is one of the most interesting 
 attributes of the fats, as it is in this form only that it can 
 find its way from the alimentary canal into the general 
 system. 
 
 Origin and Functions of Fat. One source of fat in the 
 economy is the food. It constitutes an important article of 
 diet, existing in animal food in the form of adipose tissue, 
 and mingled to a certain extent with the muscular tissue. 
 Yegetable oil also is quite a common article of food. When 
 introduced in the form of adipose tissue, the fat is freed from 
 its vesicles by the action of the gastric juice, is generally 
 
 1 REGNAULT, Cours filementaire de Chimie, Paris, 1853, tome iv., p. 414. 
 
O INTRODUCTION. 
 
 melted at the temperature of the body, and floats in the form 
 of oil on the alimentary mass. It passes then into the smal] 
 intestines unchanged, is emulsified by the pancreatic juice, 
 and absorbed by the lacteals. A small quantity of fat is 
 absorbed by the radicles of the portal vein. After a full 
 meal, the blood of a carnivorous animal frequently contains 
 enough fatty emulsion to form a thick white pelicle on cooling. 
 
 The question as to the possibility of the formation of fat 
 in the organism may be now considered as definitely settled. 
 It has been shown by Liebig, Boussingault, and others, that 
 in young animals especially, the fat in the body cannot all be 
 accounted for by that which has been taken in as food added 
 to that which the body contained at birth. The experiments 
 of Boussingault, 1 on this point, on young pigs, are very con- 
 clusive, and demonstrate that fat must be produced some- 
 where in the organism. Bernard 2 has shown that an emul- 
 sive substance, which he regards as fat in combination with 
 organic nitrogenized matters, is produced by the liver, and 
 is taken up by the blood of the hepatic vein. He believes 
 that it is produced at the expense of the amylaceous or sac- 
 charine elements of food. 
 
 It is very certain that the generation or deposition of 
 fat in the body may be influenced very considerably by 
 diet, and the conditions of the system. This is daily exem- 
 plified in the inferior animals, and is true, though it is not 
 perhaps as universal, in the human subject. It has been 
 found that a diet consisting largely of fatty, amylaceous, and 
 saccharine principles favors the accumulation of fat, while 
 an exclusively nitrogenized diet is unfavorable to it, and will 
 produce emaciation, if rigidly followed. Muscular activity, 
 it is well known, is unfavorable to the accumulation of fat ; 
 which may account in a measure for its greater relative quan- 
 tity in the female. In some individuals, especially when its ac- 
 
 1 BOUSSINGAULT, Chimie Agricole, Paris, 1854. 
 
 8 BERNARD, Lemons de Physiologic Experimentale, Paris, 1855, p. 154 et seq. 
 
FATS. 65 
 
 cumulation is excessive, there is an hereditary tendency to fat. 
 Organs which are in process of atrophy from disease, or other 
 causes, are apt to be the seat of a deposit of fatty granules ; 
 as the muscular fibres, which, in many diseases character- 
 ized by rapid emaciation, are found to be the seat of fatty 
 degeneration. 
 
 There are certain situations where fat never exists, as in 
 the eyelids and scrotum ; and others where it is always found, 
 even in extreme emaciation, as in the orbit and around the 
 kidneys. Ordinarily, fat is pretty well distributed through- 
 out the body, having a tendency to accumulate, however, 
 beneath the skin, and in the omentum, where its presence is 
 least likely to interfere w T ith the function of parts, and where 
 it serves to maintain the uniform temperature of the body, 
 and particularly of the delicate abdominal organs. 
 
 The average relative quantity of fat in the human body 
 has been calculated by Burdach to be five parts per hundred. 
 In the body of a man weighing 176 pounds, he found 8'8 
 pounds of fat. 1 
 
 In certain parts fat has an important mechanical func- 
 tion. It serves as a soft bed for delicate organs, as the eye 
 and kidney. It is a bad conductor, and thus prevents the 
 loss of heat by the organism. This is very important in 
 some warm-blooded animals, as the whale, in which the loss 
 of heat would be very great were it not for the immensely 
 thick layer of fat just beneath the skin. It is important in 
 filling up the interstices between the muscles, bones, ves,- 
 sels, &c. 
 
 Fat, like sugar, has undoubtedly an important office in 
 connection with the general processes of development and nit- 
 trition. We have not yet arrived at an accurate knowledge 
 of the changes which it undergoes as it is used up by the 
 economy ; for with the single exception of butter in the milk, 
 
 1 BURDACH, Traite de Physiologic, Paris, 1837, tome viii., p. 80. Translated-' 
 from the German by Jourdan. 
 
bO INTRODUCTION. 
 
 it is never discharged from the body in health. We have 
 already alluded to the view that the sugars and fats are 
 respiratory or calorific elements, which undergo oxidation 
 in respiration, and are immediately concerned in the produc- 
 tion of animal heat. One of the arguments in favor of this 
 function of fat has been that ip. cold climates, where there is 
 a greater demand for the generation of heat by the system, 
 fat is a more common and more abundant article of diet. 
 This is undoubtedly true, but other principles are consumed 
 in greater quantity, and the general process of nutrition, of 
 which the production of heat is but a single phenomenon, is 
 intensified. There is not sufficient ground for supposing that 
 fat has any such exclusive function. Its office is connected 
 with the general process of nutrition ; and its various trans- 
 formations in connection with this function, we have as yet 
 been unable to follow. 
 
 Fatty Acids and Soaps. In addition to the fatty sub- 
 stances just described, the following fatty acids, free, and 
 united with bases to form soaps, have been found in the blood : 
 
 Oleic Add (C 36 H 33 O 3 HO), 
 Margaric Acid (C 34 H 33 O 3 HO) 
 Oleate of Soda, 
 Mar gar ate of Soda. 
 
 Oleic and margaric acids have been detected in minute 
 quantities in a free state in the blood and bile. Their 
 function is unknown. The oleate and margarate of soda are 
 found in small quantity in the blood, bile, and lymph. They 
 serve to hold in solution the small quantity of the fatty acids 
 and fats which exists in these fluids. The function of all 
 these substances is comparatively unimportant. In the blood 
 of the ox, Robin and Yerdeil have found a small quantity of 
 ;Stearic acid and the stearate of soda. 
 
 Odorous Principles. It is well known that the perspira- 
 
, ODOROT76 PRINCIPLES. 67 
 
 tion of certain parts, as the axilla and sometimes the feet, has 
 a distinct odor. This is supposed to be due to combinations 
 of volatile fatty acids with soda and potassa. Most of the 
 inferior animals have a distinctive odor, which may generally 
 be readily recognized, and is always strongly developed in 
 the blood by the addition of sulphuric acid. Barreul gives 
 the following conclusions as the result of an extended series 
 of observations on this subject : 
 
 "1. That the blood of every species of animal contains 
 a principle peculiar to each one. 2. This principle, which 
 is very volatile, has an odor like that of the perspiration. 
 
 3. The volatile principle is in a state of combination in the 
 blood, and while this combination exists it is not appreciable. 
 
 4. When this combination is destroyed, the principle of the 
 blood becomes volatile, and from that time it is not only 
 possible, but very easy to recognize the ' animal to which it 
 belongs. 5. In each species of animal the odorous principle 
 is manifested with greater intensity in the male than in the 
 female. 6. The combination of this odorous principle is in 
 a state of solution in the blood which permits it to be devel- 
 oped either in the blood entire, in the defibrinated blood, or 
 in the serum. 7. Of all the means employed for setting free 
 the odorous principle of the blood, concentrated sulphuric 
 acid is that which succeeds the best. It suffices to add one- 
 third or one-half of the volume of blood employed, and a few 
 drops of blood is sufficient." 1 
 
 Lactic Acid Pneumic Acid Pneumate of Soda. 
 
 Lactic acid may be formed by what is called the lactic acid 
 fermentation of sugars, particularly sugar of milk. This kind 
 of action is induced by the presence of certain organic fer- 
 ments, or by organic nitrogenized matter in process of de- 
 composition. This principle does not exist, as was at one 
 
 1 ROBIN and VEKDIEL, op. cit., tome iiL, p. 90. 
 
68 INTRODUCTION. 
 
 time supposed, in fresh milk, but only after it has become 
 sour. Its composition (C G H 5 O 5 + HO) assimilates it to the 
 sugars, and indicates how it may be formed theoretically from 
 them by transposition of their atoms ; milk sugar having for 
 its composition 12 H 12 O 12 , which is also the formula for an- 
 hydrous glucose. 
 
 It is a constant constituent of the gastric juice, and is 
 indispensable to the digestive properties of this secretion. 
 
 Lactic acid has been demonstrated by Liebig in the 
 juice of muscular tissue. 1 
 
 Sources and Function. This principle may be formed, in 
 minute quantity, in the intestines, from the saccharine and 
 amylaceous articles of food ; but it is in greatest part pro- 
 duced in the economy as an element of secretion. It is 
 thought that a great portion of the sugar which passes in the 
 blood from the liver to the lungs is converted into lactic acid. 
 If this be the case, it unites with bases and is almost imme- 
 diately decomposed and lost. Lactates in the blood are very 
 readily converted into carbonates, as has been shown by the 
 experiments of Lehmann, 2 who took into the stomach half an 
 ounce of dry lactate of soda, and ' in thirteen minutes his 
 urine had an alkaline reaction from the presence of carbon- 
 ates. Alkalinity of the urine from this cause is often pro- 
 duced by the ingestion of combinations of the vegetable acids 
 in fruits, etc. 
 
 The most marked function of lactic acid is in the gastric 
 juice, and will be considered under the head of digestion. 
 
 Pneumic Acid and Pneumate of Soda. Pneumic acid 
 was discovered and extracted from the tissue of the lungs by 
 Yerdeil in 1851. 3 Its ultimate composition is not given. 
 According to this author, it exists in the lungs of the mam- 
 
 1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, voL i., p. 90. 
 
 2 Ibid, p. 97. 
 
 8 ROBIN and VERDEIL, op. cit., tome il, p. 466. 
 
ORGANIC PRINCIPLES. C9 
 
 malia at all periods of life. He extracted about three-fourths 
 of a grain from the perfectly healthy lungs of a female who 
 was guillotined. It has not been found in other situations. 
 
 Its function is connected with respiration. The carbon- 
 ates and bicarbonates of the blood, in passing through the 
 lungs, are in part decomposed by pneumic acid, a certain 
 portion of the carbonic acid in the expired air being evolved 
 in this way. 
 
 Pneumate of Soda is produced by the action of pneumic 
 acid upon the carbonates of soda in the blood, and is found 
 in the blood which passes through the lungs. It is not dis- 
 charged from the body, undergoing in the system some 
 transformation with which we are unacquainted*. 
 
 ORGANIC NITROGENIZED PRINCIPLES. 
 
 Principles of this class differ essentially from all the other 
 constituents of the body. They are the only elements en- 
 dowed with what are called vital properties, and upon them 
 depend all the phenomena which characterize living struc- 
 tures. This important fact cannot be too fully insisted upon. 
 
 All the vital phenomena which take place in the lody 
 depend primarily upon organic nitrogenized principles, which 
 are the only elements in the organism endowed with life. 
 
 By a tissue or fluid endowed with life is meant : 
 
 A combination of proximate principles which has the prop- 
 erty, under certain conditions, of appropriating materials for 
 its nourishment and regenerating itself , to repair the continual 
 destruction or waste to which all living ~bodies are subject. 
 
 This, which is the great process of NUTRITION, is going 
 on from the beginning to the end of life ; its phenomena 
 are distinct from those which take place in inert com- 
 pounds, and are called vital. Take, for example, the nutri- 
 tive processes which take place in the muscles or the bones. 
 In common with all pails of the body, these tissues arc 
 continually undergoing waste. The circumstances under 
 
TO INTRODUCTION. 
 
 which they can supply this waste, or regenerate themselves by 
 the appropriation of suitable materials, involve contact with 
 the circulating blood. They take materials from this fluid and 
 change them into their own substance. This process takes 
 place only in living bodies, and is unknown in the inorganic 
 kingdom. As it is the great cliaracteristic of life, its accom- 
 plishment being the end and object of all the functions of 
 the organism, the study of these organic principles is mani- 
 festly of the greatest importance. We shall find that their 
 properties are peculiar to themselves, and their chemical study 
 must necessarily be eminently physiological. To arrive at 
 any definite idea of their properties, the methods of study 
 which have been generally employed by chemists must be 
 discarded, as by these they are reduced to inorganic ele- 
 ments, and treated simply as combinations of inert sub- 
 stances. They must be studied as nearly as possible in the 
 condition in which they exist in the body ; which is neces- 
 sarily the condition in which they are capable of manifesting 
 their characteristic vital phenomena. 
 
 These principles are found in all the fluids, semi-solids, 
 and solids of the body, except the excrementitious fluids. 1 
 The nutritive fluids contain several. In each tissue an or- 
 ganic principle is found which presents certain peculiarities 
 more or less distinctive. They are all formed in the or- 
 ganism, and, with the exception of the milk, a little mucus, 
 desquamated epidermis and epithelium, and an almost inap- 
 preciable quantity exhaled by the lungs and skin, are never 
 discharged unchanged from the body, in health. They 
 assunie the consistence of the part in which they are found ; 
 being, therefore, fluid, semi-solid, and solid. They constitute 
 by far the greater part of the organism ; but their quantity 
 in the whole body has never been accurately estimated. 
 Their reaction is neutral. As a peculiarity of chemical com- 
 position, they all contain nitrogen ; whence they are called 
 
 1 The excrementitious fluids contain coloring matters, which Robin and Verdeil 
 put in this class, but which do not seem to be endowed with vital properties. 
 
OEGAJSTIC PRINCIPLES. 71 
 
 Nitrogenized Principles. They all closely resemble one of 
 the most important and certainly the most carefully studied 
 of their number, namely, albumen ; whence they are some- 
 times called Albuminoids. They were regarded by Mulder 
 as compounds of a theoretical radical or base which he 
 called Proteine, and after this chemist are sometimes called 
 Proteine com/pounds. 
 
 Composition and Properties. 1. Studied, as they gener- 
 ally have been, from a purely chemical point of view, they 
 are regarded by many as solid substances in solution in the 
 fluids, in a condition approximating to this in the semi-solids, 
 and of course as solid in the solids, like the bones and teeth. 
 This view is erroneous, as we shall see that some are natu- 
 rally fluid, some are semi-solid, and some are solid. In this 
 condition they have been found to consist of Carbon, Hydro- 
 gen, Oxygen, Nitrogen, with sometimes a little Sulphur and 
 Phosphorus. The coloring matters contain in addition a 
 small proportion of Iron. By ultimate analysis they have been 
 found to be of indefinite chemical composition* which, indeed, 
 we would be led to expect from the state of continual change 
 in which they exist in the body. By the method em- 
 ployed in arriving at their ultimate composition, even before 
 analysis, they are completely destroyed as organic principles 
 by desiccation, and rendered incapable of exhibiting any of 
 their characteristic properties. The composition of their 
 dry residue only is thus given, while in reality they all con- 
 tain more or less water, which enters into their composition, 
 and deprived of which they cannot be called organic sub- 
 stances. The proportion of water is to some extent variable, 
 but confined within tolerably narrow limits. 2 
 
 2. The organic principles never exist alone, but always in 
 
 1 ROBIN and VERDEIL, op. cit., tome iii., p. 147. 
 
 2 For a further discussion of this important subject, see an article by the author 
 in the American Journal of the Medical Sciences, October, 1863, On the Organic 
 Nitrogenized Principles of the Body, ivith a New Method for their Estimation in 
 tfie Blood. 
 
INTRODUCTION. 
 
 combination with inorganic substances, which, though per- 
 haps not absolutely necessary to the properties by which they 
 are recognized out of the body, are essential in the perform- 
 ance of their vital functions in the economy. Under these cir- 
 cumstances the organic and inorganic principles are so closely 
 united, that the latter may be. said to acquire, by virtue of 
 this union, vital properties. Though unaltered, the inorganic 
 are discharged with the worn-out organic substances, and, 
 combined with fresh organic matter, are deposited in the 
 tissues in the process of regeneration. 
 
 3. The organic principles which are naturally fluid may 
 be coagulated, but under no circumstances do they assume a 
 definite or crystalline form. We should be led to expect this 
 from the fact that they have no absolutely fixed composition. 
 When the liquids of this class are thus solidified, they are 
 not precipitated from a solution, but are made to assume 
 a new form, still retaining their water of composition. 
 When exposed to evaporation, whether they be fluid or semi- 
 solid, their water may be driven off, and they are said to be 
 desiccated. They can be made to assume their water of 
 composition again by simple contact, as they have in a high 
 degree the property of Tiygrometmcity . Both these properties 
 are peculiar to organic substances. 
 
 4. When exposed to a very elevated temperature, that 
 which has been considered by chemists as the organic sub- 
 stance . proper is volatilized and driven off, leaving the inor- 
 ganic substances, which always enter into its composition. 
 
 5. In their natural condition, the organic principles have 
 no very distinct odor ; but when exposed for some time to a 
 moderate heat, certain odorous or empyreumatic substances 
 are produced. This change is peculiar to organic matters, 
 and takes place in the process of cooking. When these ele- 
 ments are used as food, this process serves a useful purpose, 
 rendering them more agreeable to the taste, and facilitating 
 their digestion. 
 
 6. One of the great distinctive properties of organic prin- 
 
ORGANIC PRINCIPLES. 73 
 
 ciples, out of the body, is putrefaction. In contact with 
 the air, at a moderate temperature, they undergo decompo- 
 sition into carbonic, lactic, and butyric acids, and ammonia. 
 When this change has once commenced, it has been found 
 by "Wurtz to continue in a vacuum. 1 Putrefaction is a 
 process peculiar to organic substances. By it they are 
 transformed into substances which are used in the nutrition 
 of vegetables ; and as vegetables are eventually consumed by 
 animals, the animal matter is not lost, but returns again 
 through this channel, so that the two kingdoms are continu- 
 ally interchanging elements. Organic matters in putrefac- 
 tion are capable of setting up the same process in other 
 articles of this class by simple contact, neither giving up nor 
 taking away any chemical elements. They are then called 
 ferments, and this action is said to be catalytic. As before 
 remarked, this constitutes one of the most important charac- 
 teristics of organic matters ; one, indeed, which enables us 
 to recognize them when they exist in quantities too minute for 
 chemical analysis, as in exhalations from the pulmonary and 
 cutaneous surfaces. 
 
 Proteine. In 1838, just after the promulgation of the 
 theory of vegetable organic radicals by Liebig and Dumas, 
 Mulder attempted to show that the organic animal substan- 
 ces were all compounds of a radical which he called Prote- 
 ine. This theory was pretty generally received, and gave to 
 organic matters the name of Proteine Compounds, by which 
 they are sometimes known. He treated albumen, fibrin, and 
 ca seine with alcohol and ether to remove the fats, and with 
 hydrochloric acid to remove inorganic salts ; dissolved them, 
 thus purified, in a solution of potash, and precipitated with 
 acetic acid a substance said to possess always the same char- 
 acters, which he called proteine ; and which, by union with a 
 certain quantity of sulphur and phosphorus, was capable 
 of forming fibrin, albumen, and caseine. But the analyses 
 
 1 Cited by ROBIN and VERDEIL, op, cit. : tome Hi., p. 142. 
 
74 INTRODUCTION. 
 
 of different chemists have shown that proteine itself has an 
 indefinite chemical composition, hardly any two formulae 
 being the same. It is essentially an artificial product ; and 
 with the views we have taken of the composition of organic 
 substances, there is not the slightest reason to suppose that 
 it plays the part of a base or radical for a group of definite 
 compounds. It is not a distinct chemical substance, for 
 its composition is indefinite ; nor a proximate principle, for it 
 is produced artificially and by decomposition. We must 
 therefore reject the theory that it serves as the radical of a 
 definite series, and discard the name of Proteine Compounds, 
 as applied to organic principles. 
 
 Catalysis. Catalysis, or catalytic action, is a name given 
 to a certain process which we do not as yet understand. The 
 word was introduced by Berzelius in 1835, and applied to 
 certain actions or affinities brought into play in inorganic 
 bodies by the mere presence of another substance, the latter 
 not undergoing any chemical alteration. It is now applied 
 to all chemical changes which are induced by the simple 
 presence of any substance, like the particular class of sub- 
 stances called ferments, in which the substance inducing this 
 action undergoes no chemical change. Fermentation, which 
 was considered in treating of sugar, is an example of catalysis ; 
 the sugar being decomposed into carbonic acid and alcohol from 
 the fact of the mere presence of yeast, which has nothing to 
 do, chemically, with the process. Putrefaction, which we 
 have just considered, is an example of catalysis ; for a small 
 quantity of any animal substance in a state of putrefaction 
 is capable, ~by its presence, of setting up the same process in 
 other principles of this class. Nutrition, and to a certain ex- 
 tent digestion, are examples of catalysis ; for in the repair 
 of the system, certain materials are taken from the blood by 
 the tissues, and by the latter changed into different sub- 
 stances, as musculine for the muscles, osteine for the bones, 
 etc. ; and in digestion, the organic elements which are dissolved 
 
ORGANIC PRINCIPLES. 75 
 
 are changed by the presence of certain organic substances in 
 the digestive fluids. Any process set up by the mere presence 
 of substances, which themselves undergo no chemical change, 
 or the transformation of one variety of organic matter into 
 another from the mere fact of contact, is called catalysis. 
 
 The general properties we have mentioned are possessed 
 by all organic principles ; which, indeed, differ from each other 
 very little in their general characters, and even in ultimate 
 composition. Those which go to form the tissues are endowed 
 with identical vital properties. Robin and Yerdeil give seven- 
 teen distinct substances belonging to this class, of which four 
 are coloring matters. 1 But three of these principles have been 
 carefully studied with reference to their ultimate composition ; 
 but their composition, which is indefinite, and not necessary 
 to their vital properties, is of little physiological interest. 
 The number of equivalents of the various ultimate elements 
 is entirely arbitrary, as these principles enter into no definite 
 combinations. 
 
 Table of Organic Principles. 
 
 Name. Where Found. 
 
 'Fibrin (C M8 H M6 M X 4 oS a ) , .Blood, Chyle, Lymph. 
 
 ( Blood, Chyle, Lymph, 
 Albumen WW>.N.A) j Seros u ics , ant. 
 
 Albuminose Chyme, Blood. 
 
 Caseine (C 288 H 228 PO N 36 S 2 ) Milk. 
 
 Mucosine Mucus. 
 
 Pancreatine Pancreatic Juice. 
 
 ^Pepsin Gastric Juice. 
 
 Globuline Blood Globules. 
 
 Musculine Muscles. 
 
 Osteine Bone. 
 
 o 
 
 Cartilagine Cartilage. 
 
 Elasticine Elastic Jissue. 
 
 Keratine Nails, Hair, Epidermis. 
 
 . Crystalline Crystalline Lens. 
 
 1 These authors do not consider that pepsin has been fully established as a 
 distinct proximate principle. Its distinctive properties seem to be sufficiently 
 well marked, and it has therefore been included in the list. 
 
76 INTKODUCTION. 
 
 Name. Where Found. 
 
 60 
 
 . HEematine ...... " f Coloring Matter of Blood. 
 
 *** ....... AU contain Iron 
 
 3 os Bihverdme ...... Bile. 
 
 [Urrosacine ...... J ^ " " Urine. 
 
 fibrin. 
 
 Fibrin is found in the Wood, lymph, and chyle. In 
 the first-named fluid it exists in considerable quantity, but 
 in the last two it is much less abundant. Its quantity has 
 been estimated by chemists in all the above-mentioned fluids, 
 but the analyses which are generally given represent dried 
 fibrin, and give us no definite idea of its quantity in the form 
 in which it naturally exists. The quantity of fibrin in the 
 blood, estimated by the author by a process in which it is 
 not exposed to desiccation, is between 8 and 9 parts per 
 1000. 1 This proportion is undoubtedly quite variable within 
 the limits of health. According to Becquerel and Eodier, 2 its 
 quantity is considerably increased during gestation, and is 
 greater in adults than in very young or very old persons. 
 As a general rule, it is more abundant in arterial than in 
 venous blood, and is often entirely absent from the blood of the 
 hepatic and renal veins. No constant difference in quantity 
 has been established in the sexes, and its proportion appears 
 to bear no definite relation to the vigor of the individual. 
 
 It appears in the blood at about the fifteenth day of intra- 
 uterine life, and exists constantly from that time. 
 
 The composition of fibrin is given in the table. It con- 
 tains carbon, hydrogen, oxygen, nitrogen, and a little sulphur. 
 The proportion of these substances, however, is indefinite, 
 and the formula, like that of all the principles of this class, 
 is entirely arbitrary, as it enters into no definite combina- 
 tions, and consequently has no combining equivalent. Its 
 ultimate composition is comparatively unimportant, for it 
 
 1 See article in Am. Jour., loc. cit. Though the ordinary methods of analysis 
 do not give the real quantities of fibrin, they give important results with regard to 
 the comparative quantities in different situations. 
 
 2 BECQUEREL and RODIEK, Traite de Chimie Pathologique, p. 101 et scq. 
 
ORGANIC PRINCIPLES. 77 
 
 gives us no indication of the properties by which it is recog- 
 nized, nor of its functions ; and, indeed, has been found to 
 differ little, if at all, from the composition of masculine or 
 albumen, the properties of which are very different. 
 
 Fibrin may be easily extracted from the fluids in which 
 it exists. Perhaps the best mode of procedure is to whip 
 the fluid, freshly drawn, with a bundle of twigs or broom 
 corn. In this way the fibrin may be quickly and completely 
 separated. It is then freed from foreign matters, such as 
 blood-corpuscles, by washing under a stream of water, at the 
 same time kneading with the fingers. 
 
 Fibrin is not, as is supposed by many, a solid substance 
 in solution in the liquids in which it is found. It is naturally 
 liquid and mingled with the watery elements. After coagu- 
 lation it contains a certain proportion of water, capable, it is 
 true, of being driven off by evaporation, but nevertheless 
 water of composition, deprived of which it loses the prop- 
 erties by which we recognize it as fibrin. 
 
 Properties of Fibrin. The striking peculiarity by which 
 fibrin is recognized is its spontaneous coagulability. All the 
 fluids in which it is contained, when drawn from the body or 
 placed under abnormal conditions, become more or less 
 coagulated, and their coagulating principle is called fibrin. 
 It is this substance, therefore, which gives to the blood its 
 peculiar and important property of coagulability. The con- 
 dition under which fibrin coagulates seems to be that of stasis. 
 Whenever it is drawn from the body, or in the vessels, when 
 circulation becomes arrested, it assumes, after a variable time, 
 a semi-solid consistence. The cause of this remarkable phe- 
 nomenon was obscure until the essay of Eichardson on the 
 " Cause of the Coagulation of the Blood" appeared in 1856. 
 By a series of carefully conducted experiments, this observer 
 demonstrated that the blood contains a small quantity of free 
 ammonia, which has the power of maintaining the fibrin in its 
 liquid condition. This ammonia is being continually devel- 
 
78 INTRODUCTION. 
 
 oped in the system, is taken up by the circulating blood and 
 exhaled by the lungs. When the circulation is arrested in any 
 part, of course the blood takes up no more ammonia ; and as 
 that which it contained is gradually exhaled through the 
 tissues, arrest of the circulation in any part for a certain time 
 is followed by coagulation o/ the fibrin. When blood is 
 drawn from the vessels, the exhalation of ammonia is rapid, 
 and coagulation takes place very readily. Some other chem- 
 ical substances, such as the carbonate of soda, have the 
 power of maintaining the fluidity of the fibrin. 
 
 Fibrin does not coagulate into a homogeneous mass, but 
 forms minute microscopic filaments, or fibrils, which after- 
 wards contract for ten or twelve hours, so that the clot at 
 the end of that time is much smaller than immediately after 
 coagulation. 
 
 We recognize only as fibrin that liquid organic principle 
 which coagulates whenever removed from its natural con- 
 dition. By coagulation its form only is changed, not its 
 weight, and we must consider, therefore, the water which is 
 contained in the coagulated mass as water of composition. 
 
 Pure coagulated fibrin is a grayish-white substance, com- 
 posed of microscopic fibrils, and possessing considerable 
 strength and elasticity. It is insoluble in water and in the 
 serum of the blood, but dissolves slowly in solutions of caustic 
 alkalis. It swells, assumes a jelly-like consistence, and is 
 finally partially dissolved in a very feeble mixture of hydro- 
 chloric acid and water. Like all principles of this class, it 
 decomposes at a moderate temperature in contact with the 
 air and moisture. 
 
 Organization of Fibrin. The question of the organiza- 
 tion of accidentally effused and coagulated fibrin has occupied 
 the attention of pathologists a great deal, and some are of 
 opinion that it is capable of becoming part of the organized 
 living structure. This supposition had its origin in an 
 assumed identity between fibrin and reparative lymph, or, 
 
ORGANIC PRINCIPLES. 79 
 
 as it is sometimes called, coagulable lymph, which repairs losses 
 of tissue. As the process of repair of parts after destruction 
 must be considered as analogous to, and almost identical with, 
 ordinary nutrition, the above question, which is so important 
 in pathology, is one of great physiological interest. 
 
 The conditions under which the organization of fibrin has 
 been assumed to have taken place, are in clots remaining 
 after vascular extravasations, and fibrinous exudations upon 
 inflamed surfaces. The most important information is to be 
 derived from a study of the anatomical characters of such 
 effusions. By the microscope, and all means of investigation 
 which are at our command, it is impossible to distinguish in 
 these effusions any thing but fibrin. There are no blood- 
 vessels, nerves, nor any anatomical elements which would 
 lead us to suppose them capable of self-regeneration, that 
 distinctive property of all organized tissues; and, in addi- 
 tion, these are never developed. The changes which these 
 effusions undergo are retrograde in their character ; and the 
 fibrin, if it be not absorbed, remains as a foreign substance. 
 The fibrillation which takes place is by no means an evidence 
 of even commencing organization; for in effusions into the 
 tissues it soon disappears, and if the effusion be not too large, 
 the mass breaks down and is finally absorbed. When, on 
 the other hand, effusion of organizable lymph takes place, 
 the process is very different. It is elaborated, indeed, rather 
 than effused; first appearing as a homogeneous fluid, in 
 which fibro-plastic nuclei, then fibres, are developed, and in 
 some instances blood-vessels, lymphatics, and nerves. Ac- 
 cording to Robin, plastic lymph does not even contain fibrin ; 1 
 much less are the two identical. The process of organization 
 is slow and gradual, and in no case does it take place from 
 the blood, or elements of the blood, suddenly or accidentally 
 effused. 
 
 There can be no doubt that effused and coagulated 
 
 1 Dictionnaire de NTSTEN, par KOBIN et LITTRE, Paris, 1858. " Lymph Plas- 
 tique." 
 
80 INTRODUCTION. 
 
 fibrin is incapable of organization ; and it may be further 
 stated as a general law that no single proximate principle, 
 nor mere mechanical mixture of proximate principles, effused 
 into any part of the l>ody, ever acts in any other way than as 
 a foreign substance. 
 
 In certain instances of morbid action, effusions take place, 
 either on the surfaces of membranes, or between two opposing 
 surfaces, attaching them to each other by bridles or adhe- 
 sions, which actually become organized. This occurs most 
 frequently in serous membranes, and the structure thus 
 formed is entirely different from coagulated fibrin, which has 
 no connection with the parts, except that of contiguity. Both 
 of these formations have been included in the term, false 
 membranes ; but Robin makes a very proper distinction be- 
 tween them, calling the one, which is merely coagulated 
 fibrin, like the membrane of croup, false membranes, or 
 pseudo-membranes / and the others membranes of new forma- 
 tion, or neo-meinbranes. The former consist simply of the 
 fibrin, which nature has been unable to remove by absorption ; 
 and the latter, of regularly elaborated anatomical elements, 
 endowed with the properties of self-regeneration common 
 to all organized structures. 
 
 Origin and Function of Fibrin. The fibrin of the blood 
 has its direct origin, in part at least, from the albumen, by 
 the catalytic transformation which so often takes place in 
 principles of this class. It has been noticed that when fibrin 
 is increased in the blood, albumen is diminished. In some 
 experiments presented to the Society of Biology of Paris by 
 Dr. Brown-Sequard, it was shown that defibrinated blood 
 injected into the arteries of a criminal just after death, on 
 being returned by the veins, coagulated, and presented a 
 notable quantity of fibrin. 1 The remote origin of fibrin is 
 from the organic nitrogenized elements of food ; which, after 
 having undergone the catalytic changes incident to digestion, 
 
 1 ROBIN and VERDEIL, op. Y M tome iii., p. 269. 
 
ORGANIC PRINCIPLES. 81 
 
 are absorbed and transformed into albumen. As albumen 
 exists in the lymph and chyle, it is probable that in these 
 fluids fibrin is produced in the same way as in the blood. 
 
 A very important office of fibrin is to give coagula- 
 bility to the blood. This will be taken up more fully here- 
 after. At present we need only say that by virtue of this 
 property spontaneous arrest of hemorrhage after division or 
 rupture of small vessels is effected. In its natural liquid 
 condition, in intimate union with albumen and certain inor- 
 ganic matters which cannot be separated from it without 
 incineration, fibrin constitutes one of the two peculiar organic 
 principles of the plasma of the blood. It is brought in con- 
 tact with the tissues in the capillary vessels, and probably 
 takes part in the catalytic changes which constitute nutrition, 
 being transformed into the peculiar organic element of each 
 part. In this way it disappears forever as fibrin, and is only 
 discharged from the body after the tissue has undergone the 
 transformations which result in excrementitious products. 
 
 Simon, Lehmann, Bernard, and others have noticed the 
 remarkable fact that the blood of the hepatic and renal veins 
 generally contains no fibrin. The liver and kidneys seem to 
 have the power of destroying this principle. Its transfor- 
 mations in these organs we have not been able to follow. 
 
 Albumen. 
 
 Albumen is found in the blood, lymph, chyle, intermus- 
 cular fluid, secretions of serous membranes, and in small 
 quantity in the milk. It is most abundant in the blood, 
 constituting the most important organic constituent of the 
 plasma. Its proportion has been estimated in the various 
 situations in which it is found, but, as in the case of fibrin, 
 this has been done after complete desiccation, and the results 
 thus obtained are far from representing the real quantities. 
 In some analyses designed to give the quantity of moist albu- 
 men in the blood, we have found a proportion in a healthy 
 specimen of 329*82 parts per 1000. The proportion will 
 6, 
 
82 INTRODUCTION. 
 
 undoubtedly be found to vary considerably within the limits 
 of health, and, as a rule, it bears an inverse ratio to the quan- 
 tity of fibrin. "No constant difference in the quantity of 
 albumen in the sexes has been established. The quantity is 
 greater in the well-nourished and vigorous, than in anemic 
 and feeble subjects. 
 
 Albumen is found in the organism at all periods of life, 
 existing even in the ovum. 
 
 In ultimate composition albumen has been found by 
 chemists to differ very little, if at all, from fibrin. Like the 
 other principles of this class, the proportions of its ultimate 
 elements are indefinite. 
 
 Albumen may be extracted from the fluids in which it is 
 contained by simple coagulation. The most convenient 
 method of separating it is to add to the liquid a quantity of 
 absolute alcohol, and immediately filter. In operating upon 
 the serum, we have found that about twice its volume of 
 alcohol will coagulate all the albumen. It may then be 
 collected on a filter, and its weight will represent the propor- 
 tion of this principle in its natural condition. 
 
 Like fibrin, albumen is naturally fluid, and in this con- 
 dition and this condition only forms the important organic 
 principle of the fluids in which it is contained. 
 
 Properties of Albumen. Liquid albumen has certain 
 properties which serve to distinguish it from other principles 
 of the same class. In a neutral mixture it is coagulated com- 
 pletely by a temperature of 167 Fahr. The same result fol- 
 lows the addition of the strong mineral acids, alcohol, and some 
 of the metallic salts. It is distinguished from caseine by 
 the fact that it is not coagulated by the vegetable acids. 
 Coagulated albumen is a grayish- white substance, always com- 
 bined with inorganic matter, which cannot be separated with- 
 out incineration, insoluble in water, but soluble in a weak solu- 
 tion of a caustic alkali. In an alkaline solution it is no longer 
 coagulable by heat. Becqnerel has found that albumen has 
 
ORGANIC PRINCIPLES. 83 
 
 the property of deviating the plane of polarization to the 
 left. He has employed a polarizing apparatus like the one 
 used by Biot in the examination for sugar, for the purpose 
 of estimating the quantity of albumen in a watery mixture, 
 and found that "each minute of deviation corresponds to 
 18 decigrammes (29*77 grains) of dried albumen in 1,000 
 cubic centimetres (1*76 pints) of water." 1 This instrument he 
 calls an albuminimeter. A current of galvanism passed 
 through a mixture containing albumen produces coagulation, 
 whicli has been attributed to a decomposition of certain salts 
 which are combined with it and maintain its fluidity. 
 
 Some organic principles almost identical with albumen 
 in chemical reactions, are found to possess very different 
 vital properties. One of these is the organic principle of 
 the gastric juice, which, like albumen, is coagulable by 
 heat, alcohol, and the metallic salts, but exerts a peculiar 
 and distinctive action in the digestion of certain articles of 
 food. 
 
 Tests for Albumen. As a pathological condition, albu- 
 men sometimes exists in the urine, and it becomes important 
 clinically to be able to determine this fact by the application 
 of tests. These require certain precautions for their suc- 
 cessful application. They depend upon its property of 
 coagulation. 
 
 If a solution containing albumen be exposed to heat 
 in a test tube, as the temperature rises a slight cloudiness 
 or opacity in the upper part of the liquid occurs, which 
 gradually extends through the whole mass, until, at a 
 temperature of about 167, a precipitate more or less abun- 
 dant is produced, which is entirely insoluble. If albumen be 
 very abundant, the whole mass may become solidified, and 
 we may have all shades between this and the slight opacity 
 produced by a very minute quantity. In the latter case 
 
 1 BECQUEREL and RODIER, Traite de Chimie Pathologiqice, Paris, 1854, p. 53. 
 
84 INTRODUCTION. 
 
 coagulation is not complete until the liquid has been brought 
 to the boiling point. It must be remembered, however, that 
 albumen is not coagulated by heat in an alkaline solution. 
 In testing the urine for albumen by heat, if the liquid be 
 alkaline it must be neutralized with a little acetic acid ; other- 
 wise there will be no coagulation, even if albumen be present 
 in abundance. There may also arise a source of error from 
 the precipitation by heat of an excess of earthy phosphates. 
 This precipitate is distinguished from albumen by the fact 
 that it is dissolved by a few drops of hydrochloric acid, while 
 coagulated albumen is not changed. Coagulated albumen 
 in urine is redissolved by the addition of a little potash, 
 which has no effect upon an opacity produced by the 
 phosphates. 
 
 Another test is the addition to the suspected solution of 
 a strong mineral acid ; when, if albumen be present, coagu- 
 lation will take place. There is only one source of error in 
 the application of this test to the urine. If the urates be 
 present in very large quantity, we may have a deposit of 
 uric acid, giving an opacity something like that produced 
 by coagulated albumen. This error may be avoided by 
 adding an excess of nitric acid, which will clear up the mix- 
 ture if the deposit be due to the presence of urates, but has 
 no effect upon albumen. In such a case, also, no turbidity 
 is produced by heat. "When uric acid is deposited, the 
 turbidity makes its appearance more slowly than when albu- 
 men is present Various acid mixtures have been proposed 
 as tests for albumen, but they seem to possess no advan- 
 tages over nitric acid, which is the one most generally em- 
 ployed. 
 
 The tests by heat and nitric acid are sufficient to deter- 
 mine the presence or absence of albumen in any clear 
 fluid, if applied with the precautions above indicated. We 
 may employ, however, coagulation by alcohol, or the albu- 
 minimeter of Eecquerel ; but the latter, like the saccharom- 
 eter of Biot and Soleil, is little used on account of the 
 
ORGANIC PRINCIPLES. 85 
 
 expense of the instrument, and a certain dexterity which, is 
 necessary for its exact application. 
 
 Origin and Function of Albumen. The albumen of the 
 blood has its origin from a catalytic transformation of the 
 products of digestion of the albuminoid elements of food. 
 It forms the great organic nutrient element of the blood. As 
 we have already seen, it seems to be used in the formation 
 of the fibrin. In nutrition, it undergoes catalytic transfor- 
 mations which result in the peculiar organic principles of the 
 various tissues. In the circulating blood there seems to be 
 a union of the fibrin and albumen which is necessary to the 
 nutritive properties of the latter. Bernard has shown 1 that 
 the albumen of white of egg injected into the veins of an 
 animal is incapable of assimilation, and is therefore rejected 
 by the kidneys. The same result follows the injection of 
 fresh serum, even from an animal of the same species ; but 
 the blood itself, containing both albumen and fibrin, can be 
 injected without the appearance of albumen in the urine, show- 
 ing that in this state it is capable of being used in nutrition. 
 
 In the passage of the blood through the liver, it has been 
 found that a small quantity of albumen disappears ; but, as 
 in the case of fibrin, we have not been able to follow its 
 transformations. With the exception of the minute quantity 
 which is discharged in the milk during lactation, albumen is 
 never discharged from the body in health. After being 
 appropriated by the tissues in the process of nutrition, it 
 undergoes changes in the wearing out of the system, which 
 convert it into excrementitious matter. 
 
 Albuminose. 
 
 This principle is intermediate between the organic nitro- 
 genized elements of food and the albumen of the blood. It 
 is found in the blood in very small quantity after digestion, 
 
 1 BERNARD, Lemons sur les Proprietes Physiologiques et les Alterations Pa* 
 thologiquto den Liquidcs de VOrganisme, Paris, 1859, tome i., p. 467. 
 
86 INTRODUCTION. 
 
 almost immediately undergoing transformation into albu- 
 men. It is also contained in the stomach and small intestines 
 during digestion. It is naturally fluid, like albumen and 
 fibrin. 
 
 In its behavior to reagents, albuminose presents certain 
 differences from albumen. It. is coagulated by alcohol and 
 many metallic salts, but is not coagulable by heat, and only 
 imperfectly by nitric acid. It is coagulated by a small quan- 
 tity of acetic acid, but the coagulum is dissolved in an excess 
 of this agent, the latter peculiarity distinguishing it from 
 caseine, which is coagulated by acetic acid in any quantity. 
 Mialhe states that albuminose is more endosmotic, or passes 
 through membranes with much greater facility than albumen, 
 which he says is absolutely non-endosmotic. This property 
 favors its introduction into the blood. 
 
 Albuminose has its origin from the organic nitrogenized 
 elements of food, which are not only liquefied by the diges- 
 tive fluids, but undergo a catalytic transformation into this 
 substance. By virtue of its endosmotic properties, it passes 
 into the blood-vessels, and is there converted into albumen. 
 Mialhe, who first described this substance under the name 
 of albuminose, has shown that, injected into the veins of an 
 animal, it becomes assimilated, and does not pass away in 
 the urine. 1 
 
 Caseine. 
 
 This organic principle is peculiar to the milk, and there- 
 fore exists in the body only during lactation. Like fibrin 
 and albumen, it is naturally fluid. 
 
 Caseine may be easily extracted by the following process, 
 which is recommended by Robin and Yerdeil. 2 " "We add 
 to the milk a few drops of acetic acid, which precipitates the 
 caseine accompanied by the fats. The coagulum separated 
 
 1 MIALHE, Chimie Appliquee d la Physiologic, Paris, 1856, p. 125. 
 
 2 Op. cit., tome iii., p. 341. 
 
OEGANIC PEINCIPLES. 87 
 
 from the liquid, then washed, is redissolved in a solution of 
 carbonate of soda ; this solution separates from the fat which 
 floats on the top, and can be completely removed at the end 
 of twelve hours of repose. The liquid thus freed from fat is 
 acidified by a few drops of hydrochloric acid, and the caseine 
 is precipitated perfectly pure." Obtained by this process, it 
 is perfectly white, and insoluble in water, resembling pot 
 cheese. 
 
 Caseine has certain marked properties by which it is dis- 
 tinguished from albumen. It is not coagulable by heat; 
 is coagulable by the feeble vegetable, as well as the mineral 
 acids, and by rennet. This latter substance is obtained from 
 the fourth stomach, or abomasus, of sucking ruminating ani- 
 mals, and is the milk almost reduced to caseine, and mixed 
 with the gastric fluids. It is salted and dried, and in this con- 
 dition used in making cheese. Added to the milk in the pro- 
 portion of fifteen to twenty grains to a quart, it produces com- 
 plete coagulation. According to Robin and Yerdeil, caseine 
 is precipitated by the metallic salts, with which it forms com- 
 binations not to be distinguished from like combinations of 
 albumen. 1 It is a curious fact that caseine is sometimes 
 coagulated almost instantly during thunder storms. This 
 phenomenon we cannot fully explain; but the immediate 
 cause of the coagulation is the transformation of some of the 
 sugar of milk into lactic acid. Caseine retains its fluidity 
 in the milk by union with the carbonate of soda ; and when 
 coagulated spontaneously, it may be restored to its liquid 
 condition by the addition of this salt, which does not render 
 the fluid alkaline, "but seems to enter into combination with 
 the organic substance. 
 
 Caseine has its origin in the albumen of the blood, by a 
 catalytic process which takes place in the mammary glands. 
 In its liquid condition it constitutes the important organic 
 element of the milk. It is taken into the stomach of the 
 
 1 Loe. tit. 
 
88 INTRODUCTION. 
 
 infant, converted into albuminose, which it resembles very 
 closely, and absorbed by the blood, where it is converted into 
 fibrin and albumen, and contributes to the nutrition of the 
 system. At this period it constitutes almost the only nitro- 
 genized element of food. It is the only proximate principle 
 of this class, with the exception of a little mucosine and the 
 coloring matter of the urine and bile, which is discharged 
 from the body in health. 
 
 Pancreatine. 
 
 This is the organic principle peculiar to the pancreatic 
 juice. Bernard was the first to describe its properties, both 
 chemical and physiological. 1 Before the appearance of his 
 admirable monogragh on the pancreas it was confounded with 
 albumen; but we shall see that it possesses properties by 
 which it may be distinguished as readily as caseine. 
 
 Pancreatine exists in the pancreatic juice in large quan- 
 tity. It is naturally fluid, but very viscid. It is coagulated 
 by heat, the strong acids, and alcohol, but is unaffected by 
 the feeble vegetable acids. It is distinguished from albumen 
 by the fact that it is completely coagulated by an excess of 
 sulphate of magnesia. Its distinctive physiological character 
 is its powerful digestive action upon certain elements of food, 
 and its property of forming an instantaneous, complete, and 
 very fine emulsion with liquid fats. 
 
 Pancreatine has its origin from the albumen of the blood 
 by a catalytic change which takes place in the pancreas. It 
 gives to the pancreatic juice its digestive properties. , 
 
 Pepsin. 
 
 Pepsin is the organic principle of the gastric juice. It 
 is hardly to be distinguished from albumen, except by its phys- 
 iological action in digestion. The principle which has been 
 extracted by various processes from the mucous membrane 
 
 'BERNARD, Hemoire sur le Pancreas* Paris, 1858. 
 
ORGANIC PRINCIPLES. 89 
 
 of the stomach, particularly after commencing putrefaction, 
 cannot be regarded as pure pepsin. It is undoubtedly neces- 
 sary to the digestive action of the gastric juice, which loses 
 its physiological properties when this substance has been 
 coagulated by heat and separated by filtration. Its properties 
 will be more fully considered under the head of digestion, 
 
 Mucosine. 
 
 This is the organic principle of the general secretion 
 of mucous membranes, presenting, however, some differ- 
 ences in different situations. In its general properties it 
 closely resembles albumen ; indeed, what is generally taken 
 as the type of pure albumen, the white of egg, should strictly 
 be called mucosine, as it is the secretion of the mucous mem- 
 brane of the Fallopian tubes, and almost identical with some 
 specimens of pure mucus, such as the secretion at the neck 
 of the uterus during gestation. It is imperfectly coagulated 
 by heat, but is thrown down by strong acids and the metal- 
 lic salts. It is formed from the blood by the mucous follicles ; 
 and, as a small quantity is discharged from the body, forms 
 one exception to the general law that organic nitrogenized 
 principles are never discharged from the body in health. 
 
 Semi-solid or Solid Principles. 
 
 Most of the liquid elements which we have just considered 
 have been found to be connected, directly or indirectly, with 
 the nutrition of the body. Those which we now have to 
 consider are all directly formed from the organic principles 
 of the blood, and constitute the organic portion of the econ- 
 omy. Here is found to be the final destination of fibrin and al- 
 bumen in nutrition ; for the organic principles constitute the 
 vital elements of all the tissues, and are nourished exclusively 
 by these elements of the blood. We include here the blood 
 corpuscles, which must be regarded as organized bodies, 
 nourished like any of the tissues. The following are the prin- 
 
90 INTRODUCTION. * 
 
 ciples in this group which are well established, and have been 
 studied to a greater or less extent : 
 
 * 
 
 Globuline, 
 
 Crystalline, 
 
 Musculyne, 
 
 Osteine, 
 
 Cartilagine, 
 
 ElastiGine, 
 
 Keratine. 
 
 Gldbuline. This is a semi-solid organic principle, con- 
 stituting the greater portion of the blood corpuscles. It is 
 soluble in water, from which it is coagulated by a tempera- 
 ture a little below the boiling point. Excepting that when 
 mixed with water it requires a much higher temperature 
 for its coagulation, it has nearly the same properties as 
 albumen. 
 
 Like the rest of these principles, it exists in a state of 
 intimate molecular union with inorganic elements; but, 
 exceptionally in this case, is united with a small quantity of 
 fat. In this condition it goes to form the organized structure 
 of the blood corpuscles. 
 
 Crystalline. This is a semi-solid organic principle, 
 peculiar to the crystalline lens. It presents most of the 
 characters of globuline, but is coagulated at a little lower 
 temperature, though higher than is required to coagulate 
 albumen. 
 
 Musculine. This semi-solid organic principle is peculiar 
 to the muscular tissue. It is immediately dissolved at the 
 ordinary temperature by a mixture of ten parts of water with 
 one of hydrochloric acid. It may be precipitated from this 
 solution by neutralizing the acid, and the precipitate is re- 
 dissolved by an alkali. It is always united with a consider- 
 
OEGANIC PEINCIPLES. 91 
 
 able quantity of inorganic salts, in which the phosphates 
 predominate. 
 
 Musculine, in combination with inorganic substances, 
 goes to form the muscles ; but in addition, is interesting as 
 being by far the most important and abundant nitrogenized 
 element of food. It is the great source of the fibrin and 
 albumen of the blood of man and of the carnivorous animals. 
 
 Osteine. This organic principle, naturally solid, is pecu- 
 liar to the bones. If the earthy matter of bone be dissolved 
 out with dilute hydrochloric acid, the residue is nearly pure 
 osteine. By boiling with water it is transformed into gelatine^ 
 a soluble substance differing in many respects from osteine. 
 According to the experiments of Magendie, fresh bones 
 possess considerable nutritive power, which is entirely de- 
 stroyed by prolonged boiling. It enters into combination 
 with large quantities of earthy salts, to form the bones. 
 
 Cartilagine. This principle holds the same relation to 
 cartilage as osteine does to bone. By prolonged boiling it 
 is transformed into a substance resembling gelatine, called 
 by Miiller chondrine. This presents many points of difference 
 from gelatine, which renders it probable that the transfor- 
 mation of cartilage into bone, does not merely consist in the 
 deposition of calcareous matter, but also the substitution of a 
 new organic principle. 
 
 JElasticine. This is the organic principle of the yellow 
 elastic tissue and the investing membrane of the muscular 
 fibres. According to Robin and Yerdeil it is slowly dissolved 
 by sulphuric, nitric, and hydrochloric acids, and these solu- 
 tions, diluted with water, are not precipitated by alkalis. It 
 is possessed of great strength and elasticity. 
 
 Keratine. This is an organic principle, found in the nails 
 and hair, about which we know very little. It differs from 
 
92 INTRODUCTION. 
 
 the other principles in the fact that it is not dissolved, but 
 decomposed by potash, giving off ammoniacal vapor. 
 
 Coloring Matters. 
 
 These substances have beii classed with the organic 
 nitrogenized principles, from the fact that they contain ni- 
 trogen ; but they do not seem to be endowed with the vital 
 properties which characterize this class, with the exception 
 perhaps of hematine and melanine. As a peculiarity of 
 chemical constitution, they all contain iron, which is molec- 
 ularly united with their other elements. The following are 
 the principles of this group : 
 
 Hcematine, 
 Melanine^ 
 JBiliverdine, 
 Urrosacine. 
 
 Hcematine. This is the red coloring matter of the blood, 
 and exists, intimately united with globuline, in the blood 
 corpuscles. The iron which it contains can be readily dem- 
 onstrated, even in a single drop of blood, by the following 
 process : To a small quantity of blood in a watch-glass we 
 add a drop of nitric acid, then evaporate slowly over a lamp, 
 when fumes of nitrous acid are driven off, the iron takes 
 oxygen and is converted into a per-oxide. If we then add a 
 drop of the sulpho-cyanide of potassium, we produce the 
 characteristic red color of the sulpho-cyanide of iron. Sep- 
 arated from the blood, hsematine is soluble in ether and boil- 
 ing alcohol, but insoluble in water and in acids. 
 
 "We do not exactly understand the mode of formation of 
 haematine, but pathology teaches us that it is an essential 
 principle of the blood. In certain cases of anaemia, when 
 there is extreme pallor and consequently deficiency of hema- 
 tine, the administration of iron in any form induces the for- 
 mation of this substance, restores the normal constitution of 
 
COLORING MATTEES. 93 
 
 the circulating fluid, and relieves the general effects of the 
 deficiency of coloring matter; an effect which cannot be 
 produced by the most nutritious articles of food. Hsematine 
 is probably destroyed in the organism, and furnishes material 
 for the formation of the other coloring matters. 
 
 Melanine. This substance resembles hsematine, contain- 
 ing, however, a smaller proportion of iron. It is of a brown- 
 ish color, and is found in all parts of the body where pigment 
 exists ; such as the choroid, iris, hair, or epidermis. It exists 
 in the form of granulations, either free or enclosed in epithe- 
 lial cells. In all probability it is formed by a transformation 
 of'hematine. 
 
 Biliverdine. This is a greenish-yellow coloring matter 
 peculiar to the bile. Extracted from the bile, it is insoluble 
 in -water, but soluble in alcohol or ether. It contains iron in 
 nearly the same proportion as haematine. 
 
 Biliverdine is formed from haematine, enters into the con- 
 stitution of the bile, is discharged into the small intestine, 
 and, after undergoing certain modifications, is discharged 
 from the body in the feces. 
 
 Urrosacine. This is the principle which gives the amber 
 color to the urine. After extraction, it is insoluble in water, 
 but soluble in alcohol or ether. It exists in the urine in very 
 small quantity, and is formed in the kidney, in all probability 
 at the expense of the haematine. Urrosacine and biliverdine 
 are the two coloring matters discharged from the body. 
 
 Summary. A review of the individual properties of the 
 organic nitrogenized principles shows great differences in their 
 physiological, and very slight differences in their purely 
 chemical characters. It is a fact too apparent to require 
 argument, that their chemical history is of little importance 
 compared to a study of their vital properties. In fact re- 
 searches into their ultimate composition, with the excep- 
 
94: INTRODUCTION. 
 
 tion that they have shown them all to contain nitrogen, are 
 almost without value. Without exception they are all in a 
 state of intimate molecular union with inorganic matter, and 
 in this union inorganic compounds become endowed with 
 life ; that is, the inorganic parts of the body, as the calcareous 
 elements of bone, taken up ty the blood with the worn-out 
 organic principles and undergoing constant waste, are capa- 
 ble of self-regeneration. 
 
 The vitality thus imparted to inorganic matters, and the 
 fact that neither the organic nor inorganic elements are alone 
 capable of engaging in the phenomena of life, cannot le too 
 fully insisted upon. Both are taken into the body as food, 
 are digested, assimilated, and finally discharged, always in 
 combination; the organic principles changed, and converted 
 into excrementitious substances, and the inorganic principles 
 unchanged. 
 
 The readiness with which the organic principles are con- 
 verted one into the other by catalysis must also be appre- 
 ciated, as well as the constant operation of this process in 
 all the phenomena of life. Even albumen, taken in as food, 
 must be converted into albuminose, and again into albumen, 
 before it is capable of building up the tissues ; and all the 
 nitrogenized articles of food are converted into the same sub- 
 stance, regenerating the blood, and through it the body. 
 
 In the economy we find two great divisions of organic 
 elements : one, which, is nutritive, and the other, which 
 forms the great part of the tissues. By simple contact, the 
 plastic, or nutritive, principles are mysteriously converted 
 into the varied elements of the organism, and take w r ith them 
 the inorganic elements necessary to the proper constitution 
 of the parts. 
 
 It is only with a just appreciation of these general princi- 
 ples that we are able to study intelligently the special functions 
 of respiration, circulation, digestion, absorption, secretion and 
 excretion, which are all tributary to the complicated function 
 of nutrition. 
 
CHAPTEE I. 
 
 THE BLOOD. 
 
 General considerations Transfusion Quantity Physical characters Opacity- 
 Temperature Specific gravity Color Anatomical elements of the blood 
 Eed corpuscles Chemical characters of red corpuscles Development of red 
 corpuscles Formation of red corpuscles Leucocytes, or white corpuscles 
 Development of leucocytes. 
 
 IN all ages, even before physiology became known as a dis 
 tinct science, the importance of the blood in the animal 
 economy has been recognized ; and with the progress of 
 knowledge this great nutritive fluid has been shown to be 
 more and more intimately connected with the phenomena of 
 life. It is now known to be the most abundant and highly 
 organized of the animal fluids; providing materials for the 
 regeneration of all parts, without exception, receiving the 
 products of their waste and conveying them to proper organs, 
 by which they are removed from the system. These processes, 
 on the one hand, require constant regeneration of its constit- 
 uents, and on the other, constant purification by the removal 
 of effete matters. As it has been found desirable to preface 
 our study of general physiology with a history of proximate 
 principles, showing the chemical and vital properties of 
 what maybe considered as the permanent constituents of the 
 body, so before considering individual functions, all of which 
 bear finally on the great process of nutrition, we should 
 have an accurate knowledge of the anatomy and chemistry 
 
96 THE BLOOD. 
 
 of what is most appropriately called the great nutritive fluid. 
 It has been said that all parts are dependent on the blood for 
 nourishment. Those tissues in which the processes of nutri- 
 tion are active are supplied with blood by vessels ; but some 
 less highly organized, like the epidermis, hair, cartilage, etc., 
 which are sometimes called ^xtra-vascular because they are 
 not penetrated by blood-vessels, are none the less dependent 
 upon the fluid under consideration; imbibing, as they do, 
 nourishment from the blood of adjacent parts. 
 
 It must be remembered that in nutrition the tissues 
 are active, selecting, appropriating, and modifying material 
 which is simply furnished by the blood ; and as the real vital 
 force which governs these processes resides in the tissues, ten- 
 dencies of the system, such as the tubercular, scrofulous, or 
 cancerous diatheses, which lead to disordered nutrition, must 
 have their seat in the solids, and not in the circulating fluid. 
 The first cause of these conditions may lie in a disordered 
 state of the blood, from bad nourishment, from the introduc- 
 tion of poisons, such as malaria, or the emanations from per- 
 sons affected with contagious diseases, and under some cir- 
 cumstances the elimination of these poisons may be effected 
 through the blood ; but when they exist in the blood, they 
 either become fixed in the system, or are thrown off. We 
 must regard most of the morbid actions which are dependent 
 on diathesis, as the result of a vice in the tissue itself, not the 
 blood with which it is supplied. It is none the less essential 
 to health, however, that the blood should have its proper 
 constitution. 
 
 The final importance of the blood in the processes of 
 nutrition is evident ; and in animals in which nutrition is 
 active, death is the immediate result of its abstraction in large 
 quantity. Its immediate importance to life can be beauti- 
 fully demonstrated by experiments upon inferior animals. 
 If we take a small dog, introduce a canula through the right 
 jugular vein into the right side of the heart, adapt to it a 
 syringe, and suddenly withdraw a great part of the blood 
 
TRANSFUSION. 97 
 
 from the circulation, immediate suspension of all the vital 
 processes is the result. If we then return the blood to the 
 system, the animal is as suddenly revived. 1 To perform this 
 experiment satisfactorily, we must accurately adjust the ca- 
 pacity of the syringe to the size of the animal. Carefully 
 performed, it is very striking. 
 
 Trcwsfusion. Certain causes, one of which is diminution 
 in the force of the heart after copious hemorrhage, prevent the 
 escape of all the blood from the body, even after division of 
 the largest arteries ; but after the arrest of the vital functions 
 which follows copious discharges of this fluid, life may be re- 
 stored by the injection into the vessels of the same blood, or 
 the fresh blood of another animal of the same species. This 
 observation, which was first made on the inferior animals, 
 has been applied to the human subject ; and it has been as- 
 certained that in patients sinking under hemorrhage, the in- 
 troduction of even a few ounces of fresh blood will restore 
 the vital forces for a time, and sometimes permanently. The 
 operation of transfusion, which consists in the introduction 
 of the blood of one individual into the vessels of another,, 
 was performed upon animals in the middle of the seven- 
 teenth century, and was soon after attempted in the human 
 subject. So great was the enthusiasm with which some re- 
 garded these experiments, that it was even thought possible 
 to effect a renewal of youth by the introduction of young 
 blood into the veins of old persons ; and it was also proposed 
 to cure certain diseases, such as insanity, by an actual renewal 
 of the circulating fluid. These ideas were not without ap- 
 parent foundation. It was stated in 1667, that a dog, old and 
 deaf, had his hearing improved and was apparently rejuve- 
 nated by transfusion of blood from a young animal. A year 
 later Denys and Emmerets published the case of a maniac 
 who was restored to health by the transfusion of eight ounces 
 
 1 BERNARD, Lemons sur les Liquides de V Organisme, tome i., p. 44. 
 
 7 
 
98 THE BLOOD. 
 
 of blood from a calf; and another case was reported of a man 
 who was cured of leprosy by the same means. But a reac- 
 tion followed. The case of insanity, which was apparently 
 cured, suffered a relapse, and the patient died during a 
 third attempt at transfusion. 1 It is almost unnecessary to 
 say that these extravagant ^expectations were not realized. 
 In fact some operations were followed by such disastrous con- 
 sequences, that the practice w r as forbidden by law in Paris in 
 1668, and soon fell into disuse. 
 
 Transfusion, with more reasonable applications, was re- 
 vived in the early part of this century (1818) by Blundell, 
 who, with others, demonstrated its occasional efficacy in des- 
 perate hemorrhage, and in the last stages of some diseases, 
 especially cholera. There are now quite a number of cases on 
 record where life has been saved by this means ; and often- 
 times, when the result has not been so happy, the fatal event 
 has been considerably delayed. In a case which occurred at 
 'New Orleans, when the system was prostrated by an obscure 
 affection and life became nearly extinct, about seven ounces 
 of blood in all were transfused in three operations, within two 
 hours, with the palpable effect of prolonging life for from 
 twelve to sixteen hours.' Berard had collected from various 
 sources thirteen observations of hemorrhage, which w r ould have 
 been fatal, in which life was permanently restored by the 
 injection of a few ounces of healthy human blood. In all 
 but two of these cases the hemorrhage was uterine. 3 
 
 1 Philosophical Transactions, London, 1668, p. 710, et seq. 
 
 * In this case the patient suffered extreme prostration after the delivery of a 
 seven and a half months' child. This continued for a few days, and at the time 
 of transfusion, the pulse was 140 and very feeble ; respirations six to eight per 
 minute ; nostrils compressed at each inspiration ; surface cool ; countenance Hip- 
 pocratic, and the coma so profound that the patient could not be aroused. After 
 each transfusion the lips became more florid, the nostrils dilated in inspiration, 
 and the surface became warmer. The patient lived twenty-four hours after the 
 first operation. The blood was taken from the arm of a healthy male and trans- 
 fused immediately into the median cephalic vein. 
 
 3 BERARD, Cours de Physiologic, Paris, 1851, tome iii., p. 219, et scq. 
 
TEANSFUSION. 99 
 
 Since this time a great many experiments on transfusion 
 in animals have been performed, with very interesting results. 
 Prevost and Dumas l have shown, that while an animal may 
 be restored after hemorrhage by the transfusion of defibrinated 
 blood, no such effect follows the introduction of the serum ; 
 showing that the vivifying influence in all probability resides 
 in the corpuscles. These observers have also shown, that 
 though an animal may be temporarily revived by the injection 
 of defibrinated blood from an animal of a different species, 
 death follows the operation in a few days. 3 Brown-Sequard 
 has shown that in parts detached from the body, after nervous 
 and muscular irritability have disappeared, these properties 
 may be restored for a time by the injection of fresh blood. 3 
 lie also reports a curious experiment in which blood was 
 passed from a living dog into the carotid of a dog just dead 
 from peritonitis. The animal was so far revived as to sustain 
 himself on his feet, wag his tail, etc., and died a second time, 
 twelve and a half hours after. In this experiment insufflation 
 was employed in addition to the transfusion. 4 
 
 It may then be considered established, that in animals, 
 after hemorrhage, life may be restored by injecting the blood, 
 defibrinated or not, of an animal of the same species, pro- 
 vided it be introduced slowly, without admixture with air, 
 and not in too great quantity. If, however, the blood of an 
 animal of a different species be used, life will be restored but 
 for a short time. Death occurs after the transfusion of blood 
 in this instance, only when the animal receiving it is exsan- 
 guine, and the blood of an animal of a different species is 
 substituted. If the animal be not exsanguine, a little blood 
 can be superadcled to the mass from an animal of different 
 species without this result, as is shown by the experiments 
 
 1 BERARD, op. tit., tome iii., p. 219. 
 
 2 MILNE-EDWARDS, Lemons sur la Physiologic el VAnatomie Comparee, tome i., 
 p. 322 et seq. 
 
 3 Journal de la Physiologic, tome i., p. 106. 
 
 4 Ibid., p. 668. 
 
100 THE BLOOD. 
 
 already alluded to, of transfusion of the blood of a calf into 
 the veins of a man. 
 
 In the human subject, especially after hemorrhage, the 
 vital powers are sometimes restored by careful transfusion 
 of human blood, with the above precautions; remembering 
 that a very small quantity, three or four ounces, will some- 
 times be sufficient. 
 
 Quantity of Blood. The determination of the entire 
 quantity of blood contained in the body is a question of great 
 interest, and has long engaged the attention of physiologists, 
 without, however, absolutely definite results. Among those 
 who have experimented on this point, may be mentioned 
 Allen-Moulins, Herbst, Fried. Hoffmann, Yalentin, Blake, 
 Lehmann and "Weber, and Yierordt. 1 The fact that the 
 labors of these eminent observers have been so far unsuccess- 
 ful in determining definitely the entire quantity of blood, 
 shows the difficulties which are to be overcome before the 
 question can be entirely settled. The chief difficulty lies in 
 the fact that all the blood is not discharged from the body 
 on division of the largest vessels, as after decapitation ; and 
 no perfectly accurate means have been devised for estimating 
 the quantity which must always remain in the vessels. The 
 estimates of experimenters present the following wide differ- 
 ences. Allen-Moulins, who was one of the first to study this 
 question, estimates the quantity of blood at one-twentieth 
 the weight of the entire body. The estimate of Herbst is a 
 little higher. Hoffmann estimates the quantity at one-fifth 
 the weight of the body. These observers estimated the quan- 
 tity remaining in the system after opening the vessels, by 
 mere conjecture. Yalentin was the first who attempted to 
 overcome this difficulty by experiment. For this purpose 
 
 1 The reader is referred to the works of Longet (Physiologic, Paris, 1861, 
 tome L, p. 705 et seg.) and Milne-Edwards (Physiologie, Paris, 1857, tome i., p. 
 308 et seq.\ for a more extended account of the various experiments which have 
 been made with a view of determining the entire quantity of blood in the body. 
 
QUANTITY OF BLOOD. 101 
 
 he employed the following process. He took first a small 
 quantity of blood from an animal for purposes of comparison ; 
 then injected into the vessels a known quantity of a saline solu- 
 tion, and taking another specimen of blood some time after, 
 he ascertained by evaporation the proportion of water which 
 it contained, compared with the proportion in the first speci- 
 men. He reasoned that the excess of water in the second 
 specimen over the first would give the proportion of the water 
 introduced, to the whole mass of blood; and as the entire 
 quantity of water introduced is known, the entire quantity 
 of blood could be deduced therefrom. Suppose, for example, 
 that the excess of water in the second specimen should be 
 one part to ten of the blood, it would show that one part of 
 water had been mixed with ten of the blood ; and if we 
 had injected in all five ounces of water, we would have the 
 whole quantity of blood ten times that, or fifty ounces. 
 
 This method is open to the objection that it is impossi- 
 ble to take note of the processes of imbibition and exhalation 
 which are constantly in operation. Taking it for what it is 
 worth, the estimates, applied to the human subject, give the 
 weight of blood as -ff^ that of the body. 
 
 Blake estimated the quantity of blood by an analogous 
 process, injecting a known quantity of sulphate of alumina 
 into the vessels, estimating its proportion in a specimen of 
 blood, and from that deducing the entire quantity. He gives 
 the proportion of blood in dogs as from one-ninth to one- 
 third the weight of the body. The objection we have men- 
 tioned applies also to these experiments. 
 
 The following process, which is, perhaps, least open to 
 sources of error, was employed by Lehmann and Weber, and 
 applied directly to the human subject, in the case of two 
 decapitated criminals. These observers estimated the blood 
 remaining in the body after decapitation, by injecting the 
 vessels with water until it came through nearly colorless. 
 It was carefully collected, evaporated to dryness, and the dry 
 residue assumed to represent a certain quantity of blood ; the 
 
102 THE BLOOD. 
 
 proportion of dry residue to a definite quantity of blood 
 having been previously ascertained. If we could be certain 
 that only the solid matter of the blood was thus removed, the 
 estimate would be tolerably accurate. As it is, we may con- 
 sider it as approximating very nearly to the truth. We quote 
 the following account of these observations : 
 
 " My friend, Ed. Weber, determined, with my coopera- 
 tion, the weights of two criminals both before and after their 
 decapitation. The quantity of blood which escaped from the 
 body was determined in the following manner : Water was 
 injected into the vessels of the trunk and head, until the fluid 
 escaping from the veins had only a pale red or yellow color ; 
 the quantity of the blood remaining in the body \vas then 
 calculated, by instituting a comparison between the solid 
 residue of this pale-red aqueous fluid, and that of the blood 
 which first escaped. By way of illustration, I subjoin the 
 results yielded by one of the experiments. The living body 
 of one of the criminals weighed 60,140 grammes (132*7 
 pounds), and the same body after decapitation 54,600 gram- 
 mes; consequently 5,540 grammes of blood had escaped. 
 28*560 grammes of this blood yielded 5*36 grammes of solid 
 residue ; 60*5 grammes of sanguineous water collected after 
 the injection, contained 3*724 grammes of solid substances ; 
 6,050 grammes of the sanguineous 'water that returned from 
 the veins were collected, and these contained 37*24 grammes 
 of solid residue, which corresponds to 1,980 grammes of 
 blood ; consequently, the body contained 7,520 grammes 
 (16*59 pounds), 5,540 escaping in the act of decapitation, and 
 1,980 remaining in the body ; hence, the weight of the whole 
 blood was to that of the body nearly in the ratio of 1:8. 
 The other experiment yielded a precisely similar result. 
 
 " It cannot be assumed that such experiments as these 
 possess extreme accuracy, but they appear to have the advan- 
 tage of giving in this manner the minimum of the blood con- 
 tained in the body of an adult man ; for although some solid 
 substances, not belonging to the blood, may be taken up by 
 
QUANTITY OF BLOOD. 103 
 
 the water from the parenchyma of the organs permeated with 
 capillary vessels, the excess thus obtained is so completely 
 counteracted by the deficiency caused by the retention of 
 some blood in the capillaries, and in part by transudation, 
 that our estimate of the quantity of blood contained in the 
 human body may be considered as slightly below the actual 
 quantity." * 
 
 In extreme obesity, the weight of the blood would not 
 bear a natural ratio to that of the body ; but from the data 
 which we have at our command, we may state the proportion 
 in a well-formed man to be about 1 to 8, or the whole quantity 
 of blood at from 16 to 20 pounds avoirdupois. The quantity 
 of blood undoubtedly varies in the same individual in differ- 
 ent conditions of the system ; and these variations are fully 
 as important, in a physiological point of view, as the entire 
 quantity. 
 
 Prolonged abstinence has a notable effect in diminishing 
 the mass of blood, as indicated by the small quantity which 
 can be removed from the body, under these circumstances, 
 with impunity. It has been experimentally demonstrated 2 
 that the entire quantity of blood is considerably increased 
 during digestion. Bernard drew from a rabbit weighing about 
 2-J- Ibs., during digestion, over 10 J- ounces of blood without 
 producing death ; .while he found that the removal of half 
 that quantity from an animal of the same size, fasting, was 
 followed by death. In Burdach, 3 we find a case reported by 
 "Wrisberg, of a female criminal, very plethoric, from whom 
 21 Ibs. Tf ounces of blood flowed after decapitation. As the 
 relations of the quantity of blood to the digestive function 
 are so important, it is unfortunate that in the observations 
 of Lehmann and Weber, the conditions of the system in this 
 
 1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. i., p. 638. The 
 weights of the body and the entire quantity of blood have been reduced from 
 grammes to pounds avoirdupois. 
 
 2 BERNARD, Liquidcs de V Organisme, tome i., p. 419. 
 8 Op. tit., tome vi., p. 119. 
 
104: THE BLOOD. 
 
 respect were not noted ; a circumstance which would have 
 added materially to their value. 
 
 It is thus evident that the quantity of blood in the body 
 is considerably increased during digestion ; but as to the 
 extent of this increase, we cannot yet form any definite idea. 
 It is only shown that there is a very marked difference in 
 the effects of hemorrhage in" animals, during digestion and 
 fasting. 
 
 The reaction of the blood, which has been determined 
 after the globules have separated so as to allow the applica- 
 tion of test paper to the clear plasma, has been found to be 
 uniformly alkaline. 
 
 Physical Characters of the Blood. 
 
 Opacity. One of the first physical characters of the blood 
 which attract our attention is its opacity. This depends 
 upon the fact that it is not a homogeneous fluid, but com- 
 posed of two distinct elements : a clear plasma, and corpus- 
 cles, which are nearly as transparent, but which have a dif- 
 ferent refractive power. If both of these elements had the 
 same refractive power, the mixture would present no obstacle 
 to the passage of light ; but as it is, the rays, which are bent 
 or refracted in passing from the air through the plasma, are 
 again refracted when they enter the corpuscles, and again 
 when they pass from the corpuscles to the plasma, so that 
 they are lost, even in a thin layer of the fluid. This loss of 
 light in a mechanical mixture of two transparent liquids of 
 unequal refractive power can be demonstrated by the fol- 
 lowing simple experiment. If to a little chloroform, col- 
 ored red, clear water be added in a test-tube, these liquids 
 remain distinct from each other, and are both transparent ; 
 but if we agitate them, violently, the chloroform is tempo- 
 rarily subdivided into globules and mixed with the water ; 
 and as they refract light differently, the mixture is opaque. 
 
 Odor. The blood has a faint but characteristic odor. This 
 
PHYSICAL CHAKACTEBS. 105 
 
 may be developed more strongly by the addition of a few 
 drops of sulphuric acid, when an odor, peculiar to the animal 
 whose blood we are examining, becomes very distinct. 
 
 Temperature. The temperature of the blood is generally 
 given as 98 to 100 Fahr., but recent experiments have 
 shown that it varies considerably in different parts of the 
 circulatory system, independently of exposure to the refrig- 
 erating influence of the atmosphere. By the use of very 
 delicate registering thermometers, Bernard has succeeded in 
 establishing the following facts with regard to the temperature 
 in various parts of the circulatory system in dogs and sheep : 
 
 1. The blood is warmer in the right than in the left cav- 
 ities of the heart. 
 
 2. It is warmer in the arteries than in the veins, with a 
 few exceptions. 
 
 3. It is generally warmer in the portal vein than in the 
 abdominal aorta, independently of the digestive act. 
 
 4. It is constantly warmer in the hepatic than in the 
 portal veins. 
 
 He found the highest temperature in the blood of the 
 hepatic vein, where it ranged from 101 to 107. In the 
 aorta it ranged from 99 to 105. 
 
 We may assume, then, in general terms, that the tem- 
 perature of the blood in the deeper vessels is from 100 to 
 107 Fahrenheit. 1 
 
 Specific Gravity of the Blood. According to Becquerel 
 and Eodier, who, perhaps, are as high authority as any on 
 this subject, the specific gravity of defibrinated blood is from 
 1055 to 1063. 2 It is somewhat less in the female than in 
 the male. 
 
 1 These facts were taken from the lectures of Bernard, " Sur les Liquides de 
 V Organisme," Paris, 1859, in two volumes. The first volume is devoted to th<J 
 blood, and the subject of temperature is very thoroughly investigated. 
 
 2 BECQUEREL aud RODIER, Traite de Chimie Pathologique, Paris, 1854. 
 
106 THE BLOOD. 
 
 Color of the Blood. The color of the blood is due to the 
 corpuscles. In the arterial system it is uniformly red. In 
 the veins it is dark blue and sometimes almost black. This 
 difference in color between the blood in the arterial and in 
 the venous system, was a matter of controversy at the time 
 
 of Harvey. By the discoverer of the circulation, the differ- 
 
 j / 
 
 ence, which is now universally known and admitted, as re- 
 gards most of the veins, was supposed to be merely accidental, 
 and dependent on external causes. Fifty years later, Lower 1 
 demonstrated the change of color in the blood as it passes 
 through the lungs, and associated it with the true cause, vis., 
 the absorption of oxygen. The color in the veins, however, 
 is not constant. Many years ago, John Hunter observed, in 
 a case of syncope, that the blood drawn by venesection was 
 bright red ; 2 and more recently Bernard has demonstrated 
 that in some veins the blood is nearly, if not quite, as red as 
 in the arterial system. The color of the venous blood de- 
 pends upon the condition of the organ or part from which it 
 is returned. The red color was first noticed by Bernard in 
 the renal veins, where it contrasts very strongly with the 
 black blood in the vena cava. He afterwards observed that 
 the redness only existed during the functional activity of the 
 kidneys ; and when, from any cause, the secretion of urine 
 was arrested, the blood became dark. He was led from this 
 observation to examine the venous blood from other glands ; 
 and directing his attention to those which he was able to 
 examine during their functional activity, particularly the 
 salivary glands, found the blood red in the veins during 
 secretion, but becoming dark as soon as secretion was arrested. 
 These observations may be easily verified by opening the 
 abdomen of a living animal so as to expose the emulgent 
 veins, introducing a canula into the ureter so as to be able 
 to note the flow or arrest of the urine. As long as the urine 
 
 1 LOWER, Tractatus de Corde item de Motu & Oolore Sanguinis, Amstelodami, 
 1669, p. 180. 
 
 a The Works of John Hunter, Philadelphia, 1840, vol. iii., p. 93. 
 
PHYSICAL CHAEACTEES. 107 
 
 continues to flow, the blood in these vessels will be bright 
 red ; but when secretion becomes arrested, as it soon does 
 after exposure of the organs, it presents no difference from 
 the blood in the vena cava. In the sub-maxillary gland, by 
 the galvanization of a certain nerve, which he calls the motor- 
 nerve of the gland, Bernard has been able to produce secre- 
 tion, and by the galvanization of another nerve, to arrest it ; 
 in this way changing at will the color of . the blood in the 
 vein. It has been found by the same observer that division 
 of the sympathetic in the neck, which dilates the vessels and 
 increases the supply of blood to one side of the head, produces 
 a red color of the blood in the jugular. He has also found 
 that paralysis of a member by division of the nerve has the 
 same effect on the blood returning by the veins. ' 
 
 The explanation of these facts is evident when we reflect 
 upon the "reasons why the blood is red in the arteries and 
 dark in the veins. Its color depends upon the corpuscles ; 
 and as the blood passes through the lungs it loses carbonic 
 acid and gains oxygen, changing from black to red. In its 
 passage through the capillaries of the system, in the ordinary 
 processes of nutrition, it loses oxygen and gains carbonic acid, 
 changing from red to black. During the intervals of secre- 
 tion, the glands % have just enough blood sent to them for their 
 nutrition, and the ordinary interchange of gases takes place, 
 with the consequent change of color ; but during their func- 
 tional activity, the blood is supplied in greatly increased 
 quantity, in order to furnish the watery elements of the 
 secretions. Under these circumstances it does not lose 
 oxygen and gain carbonic acid in any great quantity, as has 
 been demonstrated by actual analysis, 2 and consequently 
 experiences no change in color. "When filaments of the sym- 
 pathetic are divided, the vessels going to the part are dilated, 
 and the supply of blood is increased to such an extent, that a 
 
 1 BERNARD, op. cii. 
 
 2 Unpublished lectures delivered by Bernard in the College of France during 
 the summer of 1861. 
 
108 
 
 THE BLOOD. 
 
 certain proportion passes through without parting with its 
 oxygen, a fact which has also been demonstrated by analysis, 
 and consequently retains its red color. The explanation in 
 cases of syncope is probably the same ; though this is merely 
 a supposition. Even during secretion, a certain quantity of 
 carbonic acid is formed in the gland, which, according to 
 Bernard, is carried off in solution in the secreted fluid. 1 
 
 It may be stated in general terms that the color of the 
 blood in the arteries is bright red ; and in the ordinary veins, 
 like the cutaneous or muscular, it is dark blue, almost black. 
 It is red in the veins coming from glands during secretion, and 
 dark during the intervals of secretion. 
 
 Anatomical Elements of the Blood. 
 
 In 1661, the celebrated anatomist, Malpighi, in examining 
 the blood of the hedgehog with the feeble and imperfect 
 lenses at his command, discovered little floating particles 
 which he mistook for granules of fat, but which were the 
 blood-corpuscles. He did not extend his observations in 
 this direction; but a few years later (1673), Leeuwen- 
 hoek, by the aid of simple lenses of his own construction, 
 varying in magnifying power from 40 to 160 diameters, first 
 saw the corpuscles of human blood, which he minutely 
 described in a paper published in the Philosophical Trans- 
 actions, in 1674. To him is generally ascribed the honor of 
 the discovery of the blood-corpuscles. About a century later, 
 William Hewson 2 described another kind of corpuscles in 
 the blood, which are much less abundant than the red, and 
 which are now known under the name of white globules, or 
 as they have lately been called by Robin, leucocytes. 
 
 Without following the progress of microscopic investiga- 
 
 1 BERNARD, op. cit., tome i., p. 346. 
 
 2 The Works of William Hewson, F. R. S., Sydenham Society edition, London, 
 1846. 
 
ANATOMICAL ELEMENTS. 109 
 
 tions into the constitution of the blood, it may be stated 
 that it is now known to be composed of a clear fluid, the 
 Plasma, or liquor sanguinis, holding certain corpuscles in 
 suspension. These corpuscles are 
 
 1. Red Corpuscles; by far the most abundant, constituting 
 about one-half of the mass of blood. 
 
 2. Leucocytes, or White Corpuscles ; much less abundant, 
 existing only in the proportion of one to several hundred red 
 corpuscles. 
 
 3. Granules / exceedingly minute, called, by Milne- 
 Edwards, globulins, and by Kolliker, elementary granules. 
 These are few in number, and are undoubtedly fatty particles 
 from the chyle. They are to be regarded as accidental con- 
 stituents of the blood. 
 
 Red Corpuscles. These little bodies give to the blood its 
 red color and its opacity. They are true organized structures, 
 containing organic-nitrogenized and inorganic elements molec- 
 ularly united, and, as an exception to the general rule, a lit- 
 tle fatty matter in union with their organic principle. Like 
 other organized structures, they are constantly undergoing 
 decay, and are capable of self-regeneration. They constitute 
 about one-half the mass of blood, and, according to the obser- 
 vations of all who have investigated this subject, are more 
 abundant in the male than in the female ; this constituting, 
 perhaps, the only constant difference in the composition of 
 the blood in the sexes. 
 
 The form of the blood-corpuscles is peculiar. They are 
 flattened, bi-concave, circular disks, with a thickness of from 
 one-fourth to one-third of their diameter. Their edges are 
 rounded, and the thin central portion occupies about one-half 
 of their diameter. Their consistence is not much greater 
 than that of the plasma. They are very elastic, and if de- 
 formed by pressure, immediately resume their original shape 
 when the pressure is removed. Their specific gravity is some- 
 what greater than that of the plasma. 
 
110 THE BLOOD. 
 
 The peculiar form of the blood-corpuscles gives them a 
 very characteristic appearance under the microscope. "When 
 examined with a magnifying power of from 300 to 500 
 diameters, those which present their flat surfaces have a 
 shaded centre, when the edges are in focus. Before we were 
 in possession of the perfect instruments now used in micro- 
 scopic investigation, this spot was supposed to be a nucleus 
 having a constitution different from the rest of the corpuscle. 
 Now this is understood to be an optical effect, the result of 
 the form of the corpuscle; their bi-concavity rendering it im- 
 possible for the centre and edges to be exactly in focus at 
 the same instant, so that when the edges are in focus the 
 centre is dark, and when the centre is bright the edges are 
 shaded. 
 
 As the blood-corpuscles are examined by the microscope 
 by transmitted light, they are quite transparent, and of a 
 pale amber color. It is only when they are collected in 
 masses that they present the red tint characteristic of blood 
 as it appears to the naked eye. This yellow or amber tint is 
 characteristic. A pretty good idea of it may be obtained by 
 largely diluting blood in a test tube and holding it between 
 the eye and the light. 
 
 In examining blood under the microscope, the corpuscles 
 are seen in many different positions ; some flat, some on their 
 edges, etc. This assists us in recognizing their peculiar 
 form. 
 
 It has been observed by microscopists that the blood- 
 corpuscles have a remarkable tendency to arrange themselves 
 in rows like rouleaux of coin. This has attracted universal 
 attention, and for a long time was not satisfactorily explained. 
 Robin has lately given us what seems to be the true explana- 
 tion of this phenomenon. 1 This observer has shown that 
 
 1 ROBIN, Sur quelques Points de VAnatomie et de la Physiologic dcs Globulea 
 Rouges du Sang. Journal de la Physiologic de VHomme et des Animaux, 
 Paris, 1858, tome L, p. 295. 
 
BED CORPUSCLES. Ill 
 
 shortly after removal from the vessels, there exudes from the 
 corpuscles an adhesive substance which smears their surface 
 and causes them to stick together. Of course the tendency 
 is to adhere by their flat surfaces. In examining a specimen 
 of blood under the microscope, the presence of this adhesive 
 exudation may be demonstrated by employing firm and 
 gradual pressure on the glass cover, when the adherent cor- 
 puscles may be separated in some instances, and with oblique 
 light we can sometimes see a little transparent filament be- 
 tween them, which draws them together, as it were, when 
 the pressure is removed. This phenomenon is due to a post 
 mortem change, but it occurs so soon, that it presents itself in 
 nearly every specimen of fresh blood which we examine, and 
 is therefore mentioned in connection with the normal charac- 
 ters of the blood-corpuscles. 
 
 Dimensions. The diameter of the blood-corpuscles has a 
 more than ordinary anatomical interest ; for, varying perhaps 
 less in size than in other anatomical elements, they are rather 
 taken as the standard by w^hich we form an idea of the size 
 of other microscopic objects. The diameter usually given is 
 ^jVo- f an inch. The exact measurement given by Robin is 
 .0073 of a millimetre 1 .or ^^ T of an inch. It is stated by 
 some authors that the size of the corpuscles is very variable, 
 even in a single specimen of blood. I have repeatedly 
 measured them with the eye-piece micrometer of Cachet, 
 and found a diameter of -g^Vo- of an inch. Yery few are to 
 be found which vary from this measurement. Kolliker, who 
 gives their average diameter as -g^Vo- of an inch, states that 
 " at least ninety-five out of every hundred corpuscles are of 
 the same size." 2 
 
 "We cannot leave the subject of the size of the blood-cor- 
 puscles without a notice of the measurements in the blood of 
 
 1 Loc. at. 
 
 * KOLLIKER, Manual of Microscopic Anatomy, London, 1860, p. 619, 
 
112 THE BLOOD. 
 
 different animals. This point is interesting from the fact 
 that it is often an important question to determine whether a 
 given specimen of blood be from the human subject or one 
 of the inferior animals. Comparative measurements also 
 have an interest on account of a relation which seems to 
 exist in the animal scale between the size of the blood-cor- 
 puscles, and muscular activity. In all the mammalia, with 
 the exception of the camel and lama, in which they are oval, 
 the blood-corpuscles have the same anatomical characters as 
 in the human subject ; the only difference is in size. In only 
 two animals, the elephant and sloth, are they larger than in 
 ?nan ; in all others they are smaller, or of nearly the same 
 diameter. By reference to the table it will be seen that in 
 some animals the corpuscles are very much smaller than in 
 man ; and by accurate measurement, we are enabled to dis- 
 tinguish their blood from the blood of the human subject. 
 But in forming an opinion on this subject, it must be remem- 
 bered that there is some variation in the size of the corpuscles 
 of the same animal. We can easily distinguish the blood of 
 the human subject, or of the mammals generally, from that 
 of birds, fishes, or reptiles ; for in these classes of animals the 
 corpuscles are oval and contain a granular nucleus. 
 
 Milne-Edwards has attempted to show, by a comparison 
 of the diameter of the blood-corpuscles in different species, 
 that their dimensions are in inverse ratio to the muscular 
 activity of the animal. 1 Reference to the table will show 
 that this relation holds good to a certain extent, while there 
 certainly exists none between the size of the corpuscle and 
 the size of the animal. In deer, which are remarkable for 
 their muscular activity, the corpuscles are very small, 5 oV^ 
 of an inch ; while in the sloth they are ^sV o-, and in the ape, 
 which is comparatively inactive, ^Vo- But, on the other 
 hand, in the dog, which is quite active, we have a corpuscle 
 
 1 MILNE-EDWARDS, Legons sur la Physiologic et PAnatomie Comparee, 
 tome i., p. 57 et seg. 
 
BED COKPUSCLES. 113 
 
 of -3 jV o- f an inch, and in the ox, which is certainly not so 
 active, the diameter of the corpuscle is J^TT of an i ncn - 
 Though this relation between the size of the blood-corpuscles 
 and muscular activity is not invariable, it is certain that the 
 higher we go in the great classes of animals, the smaller the 
 blood-corpuscle becomes ; the largest being found in the lowest 
 orders of reptiles, and the smallest in the mammalia. In the 
 blood of the invertebrates, with a few exceptions, 1 we find no 
 colored corpuscles. 
 
 Table of Measurements of Red Corpuscles. 
 
 This table is taken from the table of Mr. Gulliver, published in the Sydenham 
 edition of Hewson's Works, page 237. Nearly five hundred measurement were 
 made by Mr. Gulliver ; and of these, one hundred of the most important have been 
 selected. It will be observed that the diameter of the human blood-corpuscle is 
 greater than that generally given. It must be borne in mind that all these meas- 
 urements are mere approximations ; but as such they are useful, as showing the 
 relations of the corpuscles in different animals, and enabling us to distinguish 
 the blood of the human subject from that of some of the inferior animals ; 
 a question which is often of vital importance. The measurements are all given 
 in fractions of an English inch ; and in making the selections, the common names 
 of the animals have been substituted for the technical names given in the original. 
 
 Diameter. 
 
 
 MAMMALS. 
 
 Corpuscles Circular. 
 
 Diameter. D 
 , ,1 n "Whale 
 
 Chimpanzee, . 
 Ourang-Outang, 
 Black Monkey, 
 Bed Monkey, 
 Cape Baboon, 
 
 infra- Hog, . 
 WST Indian Elephant, . 
 guVo Indian Ehinoceros, . 
 ir/97 Horse, .... 
 
 Brown Baboon, 
 Dog-faced Baboon, 
 Lazy Monkey, . 
 
 . . TrtVir Stag, .... 
 mnrr Fallow Deer, . 
 TeVx Virginia Deer, 
 
 4 6 
 4T5T5 
 
 1 Note sur V Existence de Globules de Sang colores chez plusieurs d'animanx in- 
 vcrtebres. Par le Docteur CH. ROUGET. Journal de la Physiologic, &c., Paris, 
 1859, tome ii., p. 660. In this article Dr. Rouget cites a number of invertebrate 
 animals, in the blood of which he has found corpuscular elements. This is op 
 posed to the general idea that corpuscles exist only in the blood of the verte- 
 brates. 
 
 8 
 
114 
 
 THE BLOOD. 
 
 Diameter. 
 
 Diameter. 
 
 Bat, nVr Giraffe, . 
 
 Long-eared Bat, . . ^5- Antelope, 
 
 Mole, ffof Gazelle, .... ? -^- 
 
 Hedgehog, . . . ^3- Goat, .... -^Vg- 
 
 Badger, .... -yfav Sheep, 
 
 Polar Bear, . . . ^ w Ox, ... 
 
 Brown Bear of Europe, . ^VF Buffalo, .... ffo-s 
 
 Black Bear of K America, -3-5^- Musk Deer of Java, . TS&TX 
 
 Eacoon, .... ^-gVo- Flying Squirrel, . . -5-^- 
 
 Dog, . . . . . -s^ Eed Squirrel, . . To Vo- 
 
 Fox, ^TVr Black Squirrel, . . -5-5^ 
 
 Jackal, .... mmr Gray Squirrel, . . ^^ 
 
 Wolf, -jrsVo- Marmot, . 
 
 Striped Hyena, . . . ^Vr Brown Eat, . 
 
 Spotted Hyena, . . . -g-gVir Black Eat, 
 
 Cat, jiVi" Mouse, .... -g-fay 
 
 Lion, yfay Water Eat, . . . -j T Vir 
 
 Tiger, .... j^rr Porcupine, . . . ^^r 
 
 Leopard, .... ^o- Beaver, .... -5-^ 
 
 Panther, .... ^Vs- Guinea Pig, . . . -g^V* 
 
 Ferret, 4-T5T Rabbit, . . . ^Vr 
 
 Weasel, . . . . 4^0-5- Two-toed Sloth, . . ^^ 
 
 Polecat, . . . . 4-rVr Opossum, . . . ^y 
 
 Otter, .... -g^Vs* Kangaroo, . . . -g^V? 
 
 L. diam. S. diam. 
 
 Seal, -g^Vr Dromedary (oval), -g^Vr Wn 
 
 Porpoise, .... ?fa Camel (oval), 
 
 BIRDS. 
 
 Corpuscles Oval. 
 
 Long Short 
 Diameter. Diameter. 
 
 Eagle (ring-tailed), 
 
 Owl, 
 
 Jay, 
 
 Eaven, . 
 
 Starling, 
 
 Wren, 
 
 Sparrow, 
 
 Woodpecker, . 
 
 Swallow, 
 
 Stork, . 
 
 3-rVr 
 
 TTTT 
 2-T5T 
 
 irA-ir 
 
 Pigeon, 
 
 Turtle-dove, 
 
 Peacock, 
 
 Cock, . 
 
 Turkey, 
 
 Guinea-fowl, 
 
 Quail, 
 
 Goose, . 
 
 Swan, 
 
 Long Short 
 Diam'r. Diam'r. 
 
 '2 oo 5" STST 
 1835" ^589 
 2102' 
 
 Tijnr 
 
 '18 Off ttTZ 
 TT3T 1T2~? 
 
BED CORPUSCLES. 115 
 
 REPTILES. 
 
 Corpuscles Oval. 
 
 Long Short Long Short 
 
 Diam'r. Diam'r. Diam'r. Diam'r. 
 
 Green turtle, . . -j-^i rswz Lizard, 
 Land tortoise, . -^^ TZTS Viper, . 
 
 AMPHIBIA. 
 
 Corpuscles Oval. 
 
 Long Short Long Short 
 
 Diam'r. Diam'r. Diam'r. Diam'r. 
 
 Toad . . 
 
 FISHES. 
 
 Corpuscles Oval. 
 
 Long Short Long Short 
 
 Diam'r. Diam'r. Diam'r. 'Diam'r. 
 
 Perch, . . . TnjViF 2-gVr Pike > innnr 
 Carp, . . . 1 nVr ^Vir Eel. . . . 
 
 Post-mortem Changes of Blood-Corpuscles. In examining 
 the fresh blood under the microscope, after the specimen has 
 been under observation a short time, the corpuscles assume a 
 peculiar appearance, from the development on their surface 
 of very minute rounded projections, like the granules of a 
 raspberry; indeed they are said by the French to become 
 framboisees, which expresses the appearance very well. A 
 little later, when they have become desiccated to a certain 
 extent, they .present a shrunken appearance, and their edges 
 become serrated. Under these circumstances, their original 
 form may be restored by adding to the specimen a liquid of 
 the density of the serum. "When they have been completely 
 dried, as in blood spilled upon clothing or a floor, months 
 or even years after, they can be made to assume their char- 
 acteristic form by being carefully moistened with an appro- 
 priate fluid. This property is taken advantage of in exami- 
 nations of old spots supposed to be blood ; and if the manipu- 
 
116 THE BLOOD. 
 
 lations be carefully conducted, the corpuscles may be recog- 
 nized without difficulty by the microscope. 1 
 
 If pure water be added to a specimen of blood under the 
 microscope, the corpuscles will first swell up, become spher- 
 ical, and are finally lost to view by solution. The same effect 
 follows almost instantaneously on the addition of acetic acid. 
 
 Structure. The structure of the blood-corpuscles is very 
 simple. They are perfectly homogeneous, presenting, in 
 their normal condition, no nuclei nor granules, and are not 
 provided with an investing membrane. A great deal has 
 been said by anatomists concerning this latter point, and 
 many are of the opinion that they are cellular in their struc- 
 ture, being composed of a membrane, with viscid, semi-fluid 
 contents. Without going fully into the discussion of this 
 point, it may be stated that few have assumed actually to 
 demonstrate this membrane; but they hate, for the most 
 part, inferred its existence from the fact of the swelling, and 
 as they term it, bursting on the addition of water ; and par- 
 ticularly, as it seems to me, to make the blood-corpuscles 
 obey the theoretical laws of cell-development and nutrition 
 laid down by Schwann. Their great elasticity, the persist- 
 ence with which they preserve their bi-concave form, and 
 their general appearance, would rather favor the idea that 
 they are homogeneous bodies of a definite shape, than that 
 they have a cell-wall with semi-fluid contents ; especially as 
 the existence of a membrane has been interred rather than 
 demonstrated. Their mode of nutrition is like that of any 
 other anatomical elements. They are continually bathed in 
 a nutritive fluid, the plasma, and as fast as their substance 
 becomes worn out and effete, new material is supplied. In 
 this way they undergo the same changes as other anatomical 
 elements. When destroyed, or removed from the body in 
 
 1 For full directions for the examination of blood stains, the reader is referred 
 to an article on the medico-legal examination of spots of blood by Robin, in the 
 Buffalo Medical Journal, 1857-'58. Vol. xiii., p. 555 
 
BED COEPUSCLES. 117 
 
 hemorrhages, new corpuscles are gradually developed, until 
 their quantity reaches the normal standard. Thus in the 
 anemia which follows considerable loss of blood, the color 
 gradually returns with the development of the corpuscles. 
 
 Chemical Characters. In all chemical analyses of the 
 blood-corpuscles, the proportions of dried constituents only 
 are given. As we have seen in treating of organic-nitrogen- 
 ized elements, such estimates give no idea of the actual pro- 
 portions of the organic constituents of fluids or tissues. We 
 must consider the corpuscles as organized bodies, consisting 
 almost entirely of globuline, with which are combined a 
 small quantity of hsematine, or coloring matter, fat, and cer- 
 tain inorganic salts, from which it cannot be separated with- 
 out decomposition. The chemical characters of globuline 
 have already been considered. 1 The iron which the blood 
 contains is regarded as existing in the hsematine. Its pres- 
 ence can readily be demonstrated in a single drop of blood 
 by adding nitric acid and evaporating, which reduces it to 
 the condition of a per-oxide, when a red color is produced on 
 the addition of the sulpho-cyanide of potassium. The iron 
 is molecularly united with the other constituents, probably 
 as iron, and not as an oxide, as has been supposed by some. 2 
 The fat which is found in the corpuscles forms an exception 
 to the general law regulating the condition of this principle 
 in the tissues, namely, that it is always uncombined with 
 
 1 Vide page 90. 
 
 2 Crystals have long been observed in blood under certain circumstances. 
 Sir Everhard Home first observed them in the clots of aneurismal sacs in 1830. 
 Since then they have been described by Scherer, Virchow, and others, and by 
 many are supposed to be pure hsematine, or the normal coloring matter of the red 
 corpuscles. Robin and Yerdeil, who have studied them very closely, do not con- 
 sider these crystals as constituting a proximate principle, but as formed by an 
 alteration of the hsematine, consisting in the substitution of water for the iron. 
 By careful analysis, these observers have failed to detect any iron entering into 
 their composition. They are treated of in their " Chimie Anatomique," under 
 Hcernatoidine. Op. tit., tome iii., pp. 376 and 430, and Kysterfs Dictionary, 
 1858. Hcemato'idine. 
 
118 
 
 THE BLOOD. 
 
 other principles, existing as adipose tissue or in granules. 
 Here it is molecularly united with the other elements. 
 
 In accordance with the invariable law, that the organic 
 nitrogenized elements of the body are combined with inor- 
 ganic principles, we find entering into the composition of the 
 blood-corpuscles certain inorganic salts. These all exist in 
 the plasma in about the same proportions as in the cor- 
 puscles. In short, as we shall see when we take up the com- 
 position of the entire blood, the corpuscles differ from the 
 plasma only in the fact that they contain coloring matter and 
 globuline, instead of fibrin and albumen, and that the fat is 
 united with the organic matter instead of being in distinct 
 granules. In all other respects their composition is nearly 
 identical. "We can thus appreciate how favorable their con- 
 stitution and situation are for their nutrition at the expense 
 of elements furnished by the plasma. 1 
 
 Development of the Blood-Corpuscles. Yery early in the 
 development of the ovum the blood-vessels appear, consti- 
 
 1 Lehmann gives the following table showing the comparative composition of 
 the corpuscles and plasma ; the organic matters being desiccated. 
 1000 parts of Blood-Corpuscles 
 
 contain : 
 
 Water, 
 
 Solid constituents, 312-00 
 
 Specific Gravity, 1.0885. 
 
 Hematine, 16-75 
 
 Globuline and cell-membrane, 282-22 
 
 Fat, 2-31 
 
 Extractive matters, 2-60 
 
 Mineral substances (without iron), 812 
 
 Chlorine, 1-680 
 
 Sulphuric Acid 0-066 
 
 Phosphoric Acid, 1'134 
 
 Potassium, 3-328 
 
 Sodium, 1-052 
 
 Oxygen, 0-667 
 
 Phosphate of Lime, 0-114 
 
 Phosphate of Magnesia, 0-073 
 
 1000 parts of Liquor Sanguinis 
 contain : 
 
 Water, 902-90 
 
 Solid constituents, 97-10 
 
 Specific gravity, 1-028 
 
 Fibrin, 4-05 
 
 Albumen, 7S-84 
 
 Fat, 1-72 
 
 Extractive matters, 3'94 
 
 Mineral substances, 8 - 55 
 
 Chlorine, 3'664 
 
 Sulphuric Acid, 0-115 
 
 Phosphoric Acid, 0-191 
 
 Potassium, . 
 Sodium, 
 
 0-323 
 
 Oxygen, 0403 
 
 Phosphate of Lime, 0-311 
 
 Phosphate of Magnesia, 0-222 
 
 Physiological Chemistry. Philadelphia, 1855 ; vol. i., p. 546. 
 
RED CORPUSCLES. 119 
 
 tuting what is called the area yasculosa. At first the vessels 
 are filled with a colorless fluid, which soon becomes yellow, 
 and when the embryo is about one-tenth of an inch in length, 
 becomes red, and the corpuscles make their appearance. From 
 this time until the sixth to the eighth week, they are from 
 30 to 100 per cent, larger than in the adult. Most of them 
 are circular, but some are ovoid, and a few are globular. At 
 this period, nearly all of them are provided with a nucleus ; 
 but from the first, there are some in which this is wanting. 
 The nucleus is from TT i jnr to -g^Vo of an inch in diameter, 
 globular, granular, and insoluble in water and acetic acid. 
 As development advances, these nucleated corpuscles are 
 gradually lost ; but even at the fourth month we may still 
 see a few remaining. After this time they present no ana- 
 tomical differences from the blood-corpuscles in the adult. 
 
 In many works on physiology and microscopic anatomy, 
 we find accounts of the development of the red corpuscles 
 from the colorless corpuscles^ or leucocytes, which are sup- 
 posed to become disintegrated, their particles becoming de- 
 veloped into red corpuscles ; but there seems to be no suffi- 
 cient evidence that such a process takes place. The red 
 corpuscles appear before the leucocytes are formed ; 1 and it 
 is only the fact that the two varieties coexist in the blood- 
 vessels which has given rise to such a theory.' It is most 
 reasonable to consider that the red corpuscles are formed by 
 a true genesis in the sanguineous blastema. We can offer 
 no satisfactory explanation of the process by which the tissues 
 are formed from their blastema, nor can we explain the way 
 in which the blood-corpuscles, which are true anatomical 
 elements, take their origin. There is furthermore no suffi- 
 cient evidence that any particular organ or organs have the 
 function of producing the blood-corpuscles. Hewson sup- 
 posed that they were formed in the spleen. Kolliker is of 
 the opinion that they are destroyed in the spleen. It ia 
 
 1 LONGET, Traite de Physiologic, tome i., p. 715. 
 
120 THE BLOOD. 
 
 regarded by some as a necessity that there should be an organ 
 for the destruction of the corpuscles, and one for their forma- 
 tion. Regarding them, as wo certainly must, as organized 
 bodies which are essential anatomical elements of the blood, 
 it is difficult to imagine what reasons, based on their function, 
 should lead physiologists to geek so persistently after an 
 organ for their destruction. The hypothesis that they are 
 used in the formation of pigment seems hardly sufficient to 
 account for this. 
 
 In the present state of our science, the following seem to 
 be the most rational views with regard to the development 
 and nutrition of the blood-corpuscles : 
 
 1. At their first appearance in the ovum, they are formed 
 by no special organs, for no special organs exist at that time, 
 but appear by genesis in the sanguineous blastema. 
 
 2. When fully formed, they are regularly organized ana- 
 tomical elements, subject to the same laws of gradual molec- 
 ular waste and repair as any of the tissues. 
 
 3. They are generated de novo in the adult, when dimin- 
 ished in quantity by hemorrhage or otherwise, and under 
 these circumstances they are probably formed in the liquor 
 sanguinis by the same process by which they take their origin 
 in the ovum. 
 
 Function of the Blood- Corpuscles. Though the fibrin 
 and albumen of the plasma of the blood are essential to 
 nutrition, the red corpuscles are the parts most immediately 
 necessary to life. We have already seen, in treating of trans- 
 fusion, that life may be restored to an animal in which the 
 functions have been suspended from hemorrhage, by the in- 
 troduction of fresh blood ; and while it is not necessary that 
 this blood should contain fibrin, it has been shown by the 
 experiments of Provost and Dumas and others, that the 
 introduction of serum, without the corpuscles, has no resto- 
 rative effect. When all the arteries leading to a part are 
 ligated, the tissues lose their properties of contractility, sen- 
 
LEUCOCYTES, OR WHITE CORPUSCLES. 121 
 
 sibility, &c., which may be restored, however, by supplying 
 it again with the vivifying fluid. We shall see when we 
 come to treat of the function of Respiration, that one great 
 distinction between the corpuscular and fluid elements of the 
 blood, is the great capacity which the former have for absorb- 
 ing gases. Direct observations have shown that blood will ab- 
 sorb ten to thirteen times as much oxygen as an equal bulk 
 of water. This is dependent almost entirely on the presence 
 of the red corpuscles. 1 As all the tissues are continually 
 absorbing oxygen and giving off carbonic acid, a property 
 which is immediately essential to a continuance of vitality, 
 a great function of the corpuscles is to carry this principle to 
 all parts of the body. In the present state of our knowledge, 
 this is the only well-defined function which can be attributed 
 to the red corpuscles, and it undoubtedly is the principal one. 
 They have an affinity, though not so great, for carbonic acid, 
 which, after the blood has circulated in the capillaries of the 
 system, takes the place of the oxygen. In some experiments 
 performed a few years ago on the effects of hemorrhage 
 and the location of the " besoin de respirer" it w r as shown 
 that one of the results of removal of blood from the system, 
 was a condition of asphyxia, dependent upon the absence of 
 these respiratory elements. 2 The following may then be 
 stated as the principal function of the red corpuscles of the 
 blood : 
 
 They are respiratory organs ; taking up the greater part 
 of the oxygen which is absorbed by the blood in its passage 
 through the lungs, and conveying it to the tissues, where it 
 is given up, and its place supplied by carbonic acid. 
 
 Leucocytes ) or White Corpuscles of the Blood. In addition 
 to the red corpuscles of the blood, this fluid always contains 
 a number of colorless bodies, globular in form, in the sub- 
 
 1 ROBIN and VERDEIL, op. cit., tome ii., p. 32. 
 
 3 See an article by the Author in the American Journal of the Medical Sciences, 
 October, 1861. 
 
122 THE BLOOD. 
 
 stance of which are embedded a greater or less number of 
 minute granules. These have been called by Robin, Leucocytes. 
 This name seems more appropriate than that of white or 
 colorless blood-corpnscles, inasmuch as they are not peculiar 
 to the blood, but are found in the lymph, chyle, pus, and 
 various other fluids, in which ^iey were formerly known by 
 different names. All who have been in the habit of exam- 
 ining the animal fluids microscopically, must have noticed 
 the great similarity existing between the corpuscular ele- 
 ments found in the above-mentioned situations. As mi- 
 croscopes have been improved, and as investigations have 
 become more exact, the varieties of corpuscles have been 
 narrowed down. Now it is pretty generally acknowledged 
 that the corpuscles found in mucus and pus are identical ; 
 also that there is no difference between* the white corpuscles 
 found in the lymph, chyle, and blood ; and finally, the recent 
 investigations of Robin have shown that all of these bodies, 
 which were formerly supposed to present marked distinctive 
 characters, belong to the same class, presenting but slight 
 differences in different situations. The description which 
 will be given of the Avhite corpuscles of the blood, and the 
 effects of reagents upon them, will answer, in the main, for 
 all that are grouped under the name of Leucocytes. 1 
 
 Leucocytes are normally found in the Blood, Lymph, 
 Chyle, Semen, Colostrum, and Yitreous Humor. Patholog- 
 ically they are found in the secretion of mucous membranes, 
 after the slightest irritation, and in inflammatory products, 
 when they are called pus-corpuscles. 
 
 In examining a specimen of blood with the microscope, 
 we immediately notice the marked difference between the 
 leucocytes and red corpuscles. The former are globular, 
 with a smooth surface, but rendered somewhat opaque by 
 
 1 For a full account of the Anatomy and Physiology of these bodies, the reader 
 is referred to an elaborate article on this subject by Robin in the Journal de la 
 Physiologic, tome ii., p. 41, and the article "Leucocyte" in Nysten's Dictionary, 
 Paris, 1858. 
 
OK WHITE CORPUSCLES. 123 
 
 the presence of more or less granular matter, white, and 
 larger than the red corpuscles. 
 
 In examining the circulation under the microscope, we 
 are struck with the adhesive character of the leucocytes as 
 compared with the red corpuscles. The latter circulate with 
 wonderful rapidity in the centre of the vessel, while the 
 leucocytes have a tendency to adhere to the sides, moving 
 along slowly, and occasionally remaining for a time entirely 
 stationary, until they are swept along by a change in the 
 direction or force of the current. 
 
 Their size varies somewhat, even in any one fluid, 
 as the blood. Their average diameter may be stated as 
 g-gJy-g- of an inch. It is in pus, where they exist in greatest 
 abundance, that their microscopic characters may be studied 
 with greatest advantage. In this fluid, after it is discharged, 
 the corpuscles sometimes present remarkable deformities. 
 They become polygonal in shape, and sometimes ovoid ; oc- 
 casionally presenting projections from their surface, which 
 give them a stellate appearance. These alterations, how- 
 ever, are only temporary ; and after from twelve to twenty- 
 four hours, they resume their globular shape. On the addi- 
 tion of acetic acid they swell up, become transparent with a 
 delicate outline, and present in their interior one, two, three, 
 or even four rounded nuclear bodies generally collected in a 
 mass. This is rather to be considered as a coagulation of a 
 
 O 
 
 portion of the corpuscle, than a nucleus brought out by the 
 action of the acid, which renders the corpuscle transparent ; 
 though in some it is seen through the granules without the 
 addition of any reagent. This appearance is produced, 
 though more slowly, by the addition of water. 
 
 Leucocytes vary considerably in their external characters 
 in different situations. Sometimes they are very pale and 
 almost without granulations, while at others they are filled 
 with fatty granules, and are not rendered clear by acetic 
 acid. As a rule, they increase in size and become granular 
 when confined in the tissues. In colostrum, when they are 
 
124 THE BLOOD. 
 
 called colostrum corpuscles, they generally undergo this 
 change. 1 As the result of inflammatory action, when they 
 are sometimes called inflammatory or exudation-corpuscles, 
 leucocytes frequently become much hypertrophied, and are 
 filled with fatty granules. They always retain, however, 
 general characters by which they may be recognized. 
 
 Development of Leucocytes. These corpuscles appear 
 in the blood-vessels very early in foetal life, before the lym- 
 phatics can be demonstrated. They arise in the same way 
 as the red corpuscles, by genesis from materials existing in 
 the vessels. They appear in lymphatics, before w r e come to 
 the lymphatic glands, and in the foetus anterior to the devel- 
 opment of the spleen, and also on the surface of mucous 
 membranes ; so they cannot be considered as produced exclu- 
 sively by these glands, as has been supposed. There is no 
 organ nor class of organs in the body specially charged 
 w T ith their formation ; and though frequently a result of in- 
 flammation, this process is by no means necessary for their 
 production. Robin 2 has carefully noted the phenomena of 
 their development in recent wounds. The first exudation 
 consists of clear fluid, with a few red corpuscles ; then a 
 finely granular blastema. In from a quarter of an hour to an 
 hour, pale transparent globules, -g-^oir to -g-gVo of an inch in 
 diameter, make their appearance, which soon become finely 
 granular, and present the ordinary appearance of leucocytes. 
 They are thus developed, like other anatomical elements, by 
 
 1 Colostrum is the discharge from the mammary glands, occurring during the 
 first few days after delivery, which precedes the full establishment of the lacteal 
 secretion. It is a serous fluid, rather clear, which presents, on microscopical 
 examination, a few milk-globules, large drops of oil, rounded masses of small 
 fatty granules, and enlarged and granular leucocytes, called colostrum- corpuscles, 
 as well as those which have undergone no alteration. These gradually disappear, 
 as the secretion is established, and their place is supplied by the milk-globules. 
 (See Colostrum, Nysten's Dictionary, by Littre and Robin ; Paris, 1858.) 
 
 8 Loc. cit. 
 
OB WHITE CORPUSCLES. 125 
 
 organization of the necessary elements furnished by a blas- 
 tema, and not by the action of any special organ or organs. 
 
 The quantity of leucocytes compared to the red corpuscles 
 can only be given approximately. It has been estimated by 
 counting under the microscope the red corpuscles and 
 leucocytes contained in a certain space. Moleschott 1 gives 
 the proportion as 1 : 335 ; others at from 1 : 300 to 1 : 500. 
 It has been found by Dr. E. Hirt, of Zittau, whose obser- 
 vations have been confirmed by others, that the relative 
 quantity of leucocytes is much increased during diges- 
 tion. He found in one individual a proportion of 1 : 
 1800 before breakfast; an hour after breakfast, which he 
 took at 8 o'clock, 1 : TOO ; between 11 and 1 o'clock, 1 : 1500 ; 
 after dining at 1 o'clock, 1 : 400 ; two hours after, 1 : 1475 ; 
 after supper at 8 P. M., 1:550; at 11 J P. M., 1 : 1200. 2 The 
 leucocytes are much lighter than the red corpuscles, and when 
 the blood coagulates slowly, are frequently found forming a 
 layer on the surface of the clot, which is called the " buffy 
 coat." 
 
 Numerous observers, among whom may be mentioned 
 Donne, Kolliker, Gray, and Hirt, 3 have noticed a great in- 
 crease in the number of leucocytes in the blood coming from 
 the spleen, and have supposed that they are chiefly manufac- 
 tured in this organ. It is inconsistent with the mode of 
 development of these corpuscles to suppose that any special 
 organ is exclusively engaged in their production ; and their 
 persistence in animals after extirpation of the spleen shows 
 that they are developed in other situations. 
 
 The function of the leucocytes is not understood. The 
 supposition that they break down and become nuclei for the 
 development of red corpuscles, which at one time obtained, 
 is a pure hypothesis, and has no basis in fact. 
 
 1 KOLLIKER, Manual of Microscopic Anatomy, London, 1860, p. 521. 
 
 2 MILNE-EDWARDS, Lecons our la Physiologic et V Anatomic Comparec^ tome 
 i., p. 350. 
 
 3 Ibid., p. 353. 
 
126 THE BLOOD. 
 
 Elementary Corpuscles. Little granules are found in the 
 blood, especially during digestion, which, as they were 
 supposed to take part in the formation of the white corpuscles, 
 have been called elementary granules or corpuscles. They 
 are little fatty particles of the chyle which come from the 
 thoracic duct, and are not positively known to have any con- 
 nection with the formation of the other corpuscular elements 
 of the blood. 
 
CHAPTER II. 
 
 COMPOSITION OF THE BLOOD. 
 
 General considerations Methods of quantitative analysis Fibrin Corpuscles 
 Albumen Inorganic constituents Sugar Fatty emulsion Coloring matter 
 of the serum Urea and the Urates Cholesterine Creatine Creatinine. 
 
 ASSUMING, as we certainly must, that the blood furnishes 
 material for the nourishment of all the tissues and organs, we 
 expect to find entering into its composition all the proximate 
 principles existing in the body which undergo no change in 
 nutrition, like the inorganic principles, and organic matters 
 which are capable of being converted into the organic ele- 
 ments of every tissue. Furthermore, as the products of waste 
 are all taken up by the blood before their final elimination, 
 these also should enter into its composition. With these 
 great principles in our minds, it is unnecessary to insist upon 
 the importance of accurate proximate analyses of the circu- 
 lating fluid. It is not many years that our knowledge of 
 the laws of nutrition and destructive assimilation have enabled 
 us to appreciate the full importance of the blood ; but it has 
 been so palpable that this fluid is necessary to life, that the 
 older physiologists made numberless futile attempts to obtain 
 some clear idea of its composition. "We have only to go 
 back to the beginning of the present century to find the first 
 analyses of the blood which were attended with any degree 
 of success. In 1808, Berzelius analyzed the serum of the 
 
128 THE BLOOD. 
 
 human blood, indicating certain proportions of albumen, 
 lactate of soda, muriate of soda, etc. ; lie was followed by 
 Marcet in 1811, by whom his observations were confirmed. 
 In 1823, Provost and Dumas published their elaborate re- 
 searches into the composition of the blood, which seemed to 
 give an impulse to investigations in this direction, and were 
 soon followed by the analyses of Andral and Gavarret, Leh- 
 mann, Simon, Becquerel and Rodier, Denis, and a host of 
 others, whose labors have made us comprehend some of the 
 most important laws which regulate the general processes of 
 nutrition. 
 
 Notwithstanding the immense amount of labor bestowed 
 by the most eminent chemists of the day upon the quantita- 
 tive analysis of the blood, and the great physiological interest 
 attaching to every advance in our knowledge in this direction, 
 the difficulties in the way are so great, that even now there 
 are no analyses which give the exact quantities of each of its 
 inorganic constituents. This is owing to the great difficulty 
 in the analysis of any fluid in which inorganic and or- 
 ganic principles are so closely united ; for there is no more 
 delicate problem in analytical chemistry than the determina- 
 tion of the presence and quantities of inorganic substances 
 united with organic matter. Of the animal fluids which are 
 easily obtained, the blood, from the large proportion of differ- 
 ent organic principles which enter into its composition, presents 
 the greatest difficulties to the analytical chemist. Another 
 difficulty presents itself in the necessity of & proximate, and not 
 an ultimate analysis. It is not sufficient to give the amount 
 of certain chemical elements which the blood contains ; we 
 must ascertain the amount of these elements in the state of 
 union with each other to form proximate principles. 
 
 Analyses have shown that the constituents of the blood 
 may be divided into : 
 
 1. Inorganic Constituents. These exist in a state of inti- 
 mate and molecular union with the organic-nitrogenized ele- 
 
COMPOSITION OF THE BLOOD. 129 
 
 ments. Their presence is indicated by the appropriate tests 
 applied to the residue of the blood after incineration, which 
 show the well-known reactions of the chlorides, sulphates, 
 phosphates, and carbonates, with sodium, potassium, lime, 
 magnesia, and iron. In addition we have certain gases 
 (oxygen, nitrogen, and carbonic acid), which may be extracted 
 by the air-pump or by displacement. 
 
 2. Organic, Non-nitrogenized, Constituents. These are 
 the sugars and fats ; which are separated from the other ele- 
 ments without much difficulty, and may be recognized by 
 their peculiar properties. 
 
 3. Organic, Nitrogenized Constituents. These constitute 
 the greater part of the blood, and are inseparably connected, 
 in their functions, and as a condition of existence, with the 
 inorganic principles. They may be extracted by processes 
 already described in treating of fibrin, albumen, and globu- 
 line, and recognized by their peculiar properties. 
 
 Most of the constituents of the blood are found both in 
 the corpuscles and plasma. It is difficult to determine the 
 different constituents of these two parts of the blood. It has 
 been shown, however, by Schmidt, of Dorpat, that the phos- 
 phorized fats are more abundant in the globules, while the 
 fatty acids are more abundant in the plasma. The salts with 
 a potash base have been found by the same observer to exist 
 almost entirely in the corpuscles, and the soda salts are four 
 times more abundant in the plasma than in the corpuscles/ 
 All the iron exists in the red corpuscles. 
 
 The proportions of the various constituents of the blood 
 are subject to certain variations. These points, with their 
 relations to the tissues in the processes of nutrition, have 
 been so fully taken up in the consideration of Proximate 
 Principles, that they do not demand special notice in this 
 
 1 MILNE-EDWARDS, Le$ons sur la Physiologic, etc., tome i., p. 225. 
 9 
 
ISO THE BLOOD. 
 
 connection. In addition to the nutritive principles, we have 
 entering into the composition of the blood, urea, cholesterine, 
 urate of soda, creatine, creatinine, and other substances, the 
 characters of which are not yet fully determined, belonging 
 to the class of JExcrementitious Principles. Their considera- 
 tion comes more appropriately*under the head of Excretion, 
 and they will be fully taken up in the chapter devoted to 
 that subject. Though a knowledge of the exact proportions 
 of the various elements of the blood is not necessary in order 
 to appreciate the relations of this fluid to the tissues, the 
 great interest which is attached to this line of investigation, 
 and the important advantages which we may look for in the 
 future from extended inquiry in this direction, lead us to 
 discuss at some length the methods which have been employ- 
 ed by physiological chemists in quantitative analyses, with 
 some of the results which have already been obtained. 
 
 Quantitative Analysis of the Blood. 
 
 The methods which have been, and are now, commonly 
 employed for quantitative analysis of the blood vary very 
 little from the process recommended by Provost and Dumas 
 in 1823. They are based upon the supposition that the 
 organic constituents, fibrin and albumen, are solid substances 
 in solution in the watery elements, and that all the water of 
 the blood is to be attributed to the serum. As we have shown 
 in treating of organic substances that this view of their con- 
 dition in the fluids is erroneous, and that the desiccated ma- 
 terials obtained from the blood do not represent the real 
 quantities of its organic elements, a new method of analysis, 
 based on the view that these principles are naturally fluid, 
 seems necessary. The same process has been employed for 
 the estimation of the proportion of corpuscles. Here the 
 error is too manifest to require discussion. It is evident that 
 the blood-corpuscles are semi-solid bodies which become 
 altered by desiccation ; and an estimate which does not give 
 
QUANTITATIVE ANALYSIS. 131 
 
 their weight in their natural moist condition, gives us no idea 
 of their real proportion. So apparent has this been to phy- 
 siological chemists, that attempts have been made by Denis, 
 Schmidt, Yierordt, Figuier, and others to estimate the moist 
 corpuscles; but in attempting to attain extreme accuracy, 
 these observers have almost entirely failed, and their ideas of 
 the real proportion of the corpuscles are merely conjectural. 
 These remarks only apply to researches into the organic 
 constituents of the blood. The analyses with reference to the 
 inorganic elements, though they have not yet shown us the 
 exact proportion of each one of them, are of course accurate 
 as far as they go. 
 
 The various processes for analysis of the blood now em- 
 ployed by chemists do not differ very much. As one of the 
 best, we may take that recommended by Becquerel and Ro- 
 dier, who are perhaps as high authority on this subject as 
 any. Their process, which we give in its essential particulars, 
 has an advantage over most others in simplicity. 
 
 Two specimens of blood are taken and carefully weighed ; 
 one of them is defibrinated, the fibrin collected, dried, and 
 weighed, which gives the proportion of fibrin. The other 
 is set aside to coagulate. A known weight of the defibrinated 
 blood is then evaporated to dryness, and the proportion of 
 dry residue carefully estimated. The residue is then calci- 
 nated to give the proportions of inorganic constituents, which 
 remain after the organic matters have become volatilized. 
 After the blood set aside to coagulate has separated into clot 
 and serum, a definite quantity of the serum is evaporated to 
 dryness and the residue estimated. As the dry residue of the 
 defibrinated blood contains the solid matters of the serum + 
 the dried corpuscles the proportion per 1,000 parts of the 
 solid matters of the defibrinated blood the proportion per 
 1,000 parts of the solid matters of the serum, would give the 
 proportion of corpuscles. 
 
 We thus have obtained the proportions of water, of inor- 
 ganic matter, of corpuscles, and of fibrin. The next step is 
 
132 THE BLOOD. 
 
 to estimate the albumen, fatty, and extractive matter. For 
 this purpose we desiccate a known quantity of serum, care- 
 fully pulverize the dry residue, and treat it repeatedly with 
 boiling water till it has washed out all soluble matters. 
 These are undetermined extractive matters, and free salts 
 in solution in the serum. Tke residue, thus treated with 
 boiling water, is desiccated and treated several times with 
 boiling alcohol, which dissolves all the fatty substances. The 
 insoluble residue is then dried and weighed, and represents 
 pure albumen, which, it will be remembered, is not affected 
 by boiling water or alcohol. The loss after treating with 
 boiling alcohol gives the quantity of fatty matters. The pro- 
 portions of inorganic matters are obtained by analysis of the 
 residue after incineration. It is unnecessary to describe 
 the complicated and difficult manipulations involved in this 
 process. 1 
 
 1 The above is condensed from BECQUEREL and RODIER, " Traite de Chimie 
 Pathologique appliquee d la Medecine Pratique" Paris, 1854, page 21 et seq. As 
 the result of analyses of the blood of twenty-two healthy persons, they give the 
 following table, page 86. The list of inorganic salts is taken from pages 65, 66, 
 and 67. 
 
 DENSITY OF THE BLOOD 1060 
 
 COMPOSITION. 
 
 Water 781-600 
 
 Globules 135-000 
 
 Albumen 70-000 
 
 Fibrin . . . . 2-500 
 
 Seroline 0-025 
 
 Cholesterine . 0*125 
 
 Oleate, margarate, and stearate of soda 1-400 
 
 Chlorides of sodium, potassium, and magnesium 3-500 
 
 Carbonate of soda... 
 
 Free soda 
 
 Sulphate of s'oda 
 
 Phosphate of soda... 
 
 (Carbonate of soda most abundant) .... 2'COO 
 
 Carbonate of potassa .... 
 
 Sulphate " 
 
 Phosphate " .... 
 Sulphate of magnesia. . . . 
 
 Phosphate of lime j t\ar\ 
 
 Phosphate of magnesia . . j " 
 
 Iron 0-550 
 
 Undetermined extractive matters 2*450 
 
 1,000-000 
 
QUANTITATIVE ANALYSIS. 133 
 
 The above process is perhaps as simple and reliable as 
 any ; but of course each chemist has some slight modifica- 
 tions. By some the globules are estimated by drying the clot 
 after coagulation and deducting the weight of the fibrin. 
 Some recommend to expose the fibrin after desiccation to in- 
 cineration, and deduct the weight of the residue of inorganic 
 matter. All of the processes, however, are materially the 
 same, and differ but little from that employed by Provost and 
 Dumas. As before remarked, the results, as regards the fatty 
 and inorganic constituents of the blood, are as accurate as 
 possible with our present means of investigation ; and the 
 comparative results, in analyses of the blood for fibrin, albu- 
 men, and corpuscles in health and disease, which have crowned 
 the labors of Andral and Gavarret, Becquerel and Rodier, 
 and a number of others, are of permanent value. But a 
 glance at the process, and the quantities given for the fibrin, 
 albumen, and corpuscles, indicate that the whole is inconsist- 
 ent with our ideas of the condition under which these sub- 
 stances exist in the body. Microscopic examination shows 
 that at least one-half the mass of the blood consists of cor- 
 puscles, while analysis gives only 135 parts per 1,000. The 
 fibrin of the blood is sufficient to entangle, as it coagulates, 
 all the corpuscles, and with them form the clot ; yet we are 
 told that its proportion is 2*5 parts per 1,000. We boil the 
 serum, the albumen changes from a fluid to a semi-solid con- 
 dition, and the whole mass is solidified ; yet the estimate of 
 its proportion is 70 parts per 1,000. The fact is that these 
 estimates give us only the dry residue of the organic princi- 
 ples ; and to form an idea of their actual proportion, we should 
 estimate them, if possible, with their water of composition, 
 and united with the inorganic salts, which cannot be separated 
 from them without incineration and consequent destruction. 
 
 With this end in view, and for want of a better process, we 
 may employ the following mode of analysis, which is easy of 
 application, and sufficiently accurate for all practical purposes. 1 
 
 1 See an article by the author, on The Organic Nilrogenized Principles of the 
 
134 THE BLOOD. 
 
 The blood to be analyzed is taken from the arm, and re- 
 ceived into two carefully weighed vessels. The quantity in 
 each vessel may be from two to four ounces. One of the 
 specimens is immediately whipped with a small bundle of 
 broom-corn, previously moistened and weighed, so as to col- 
 lect the fibrin ; and after the fibrin is completely coagulated, 
 the whole is carefully weighed, deducting the weights of the 
 vessel and broom-corn, which gives the weight of the specimen 
 of blood used. The other specimen is set aside to coagulate. 
 
 The first specimen is used in the estimation of the fibrin 
 and corpuscles ; the second is set aside to coagulate, and is 
 used to estimate the albumen. It is important to cover the 
 vessels as soon as the blood is drawn, for, as has been demon- 
 strated by Becquerel and Rodier, blood exposed to the air 
 loses weight rapidly by evaporation. 1 
 
 We now pass the first specimen of blood through a fine 
 sieve to collect any fibrin that may not have become attached 
 to the wisp, strip the fibrin from the wisp, and wash it under 
 a stream of water. This may be done very rapidly if we 
 cause the water to flow through a small strainer, by which it 
 is broken up into a number of little streams, and knead the 
 fibrin with the fingers, doing this over a sieve so as to catch 
 any particles that may become detached. In this way it 
 may be freed from the corpuscles in five or ten minutes. The 
 fibrin is then freed from most of the adherent moisture by 
 bibulous paper, and weighed as soon as possible. By the 
 following formula we estimate the proportion per 1,000 parts 
 of blood : 
 
 Weight of blood used : Weight of fibrin : : 1,000 : Fi- 
 brin per 1,000. 
 
 The next step is to estimate the corpuscles. For this pur- 
 pose a portion of the defibrinated blood, which is carefully 
 
 Body, with a New Method for their Estimation in the Blood, American Journal 
 of the Medical Sciences, October, 1863. 
 1 Op.cit., p. 31. 
 
QUANTITATIVE ANALYSIS. 135 
 
 weighed, is mixed with twice its volume of a saturated solu- 
 tion of sulphate of soda, and thrown upon a filter which has 
 been carefully weighed and moistened with distilled water, 
 and also, just before receiving the mixture of blood and 
 sulphate of soda, with the saline solution. The fluid which 
 passes through should be about the color of the serum ; if a 
 few corpusles pass at first, the liquid should be poured back 
 until it becomes clear. The funnel is then covered, and the 
 fluid allowed to separate, the blood-corpuscles being retained 
 on the filter. The filter and funnel are then plunged several 
 times into a vessel of boiling water, by which all the sulphate 
 of soda which remains is washed out, and the corpuscles are 
 coagulated without changing in weight. The funnel should 
 be again covered and the water allowed to drip from the 
 filter, after which it is weighed, deducting the weight of the 
 moist filter previously obtained, which gives us the weight 
 of the corpuscles. We obtain the proportion of corpuscles 
 to 1,000 parts of blood by the following formula : 
 
 Defibrinated blood used : Corpuscles : : Defibrinated 
 blood per 1,000 : Corpuscles per 1,000. 
 
 The next step is to estimate the quantity of albumen in 
 the serum, and thence its proportion in the blood. Fo'r this 
 purpose we first ascertain the quantity of serum in 1,000 
 parts of blood, which is done by subtracting the sum of the 
 fibrin and corpuscles per 1,000 from 1,000. Having done this, 
 and waited ten or twelve hours for specimen "No. 2 to sepa- 
 rate completely into clot and serum, we take a small quan- 
 tity of the serum, about half an ounce, weigh it carefully, 
 and add suddenly twice its volume of absolute alcohol. The 
 albumen will be thrown down in a grumous mass, and the 
 whole is thrown upon a filter, Avhich has been previously 
 moistened with alcohol and weighed. The funnel is imme- 
 diately covered, and the fluid separates from the albumen 
 very rapidly. "We ascertain that no fluid albumen passes 
 through the filter by testing the fluid with nitric acid. After 
 
136 THE BLOOD. 
 
 the filter has ceased to drip, it is weighed, and the weight of 
 the albumen ascertained by deducting the weight of the filter. 
 The proportion of albumen to 1,000 parts of blood is obtained 
 by the following formula : 
 
 Serum used : Albumen : : Serum per 1,000 : Albumen 
 per 1,000. 
 
 The above process, which has been described in detail in 
 the hope that it may be employed by others in analysis of 
 the blood for its organic constituents, has at least the advan- 
 tage of simplicity and facility of application. As regards 
 accuracy, having repeatedly made analyses of different por- 
 tions of the same fluid with almost identical results, it has 
 seemed sufficiently exact for all practical purposes. As an 
 example we may mention an analysis of two equal portions of 
 defibrinated blood (34*20 grammes) for corpuscles ; one speci- 
 men gave 16*4:0, and the other 16*43 grammes. This part of the 
 process would seem more open to the objection of inaccuracy 
 than any, yet the difference of the result in the two analyses is 
 so slight that it may be disregarded. Repeated examinations 
 of different specimens of the same serum for albumen were 
 followed by identical results. 1 While the exceeding accu- 
 racy which is desired by chemists, and is necessary in many 
 analyses, is not attainable in such examinations as these, it is 
 not even desirable ; for as physiologists we must see that 
 even an approximation of the proportions of the organic 
 matters, as they really exist, is better than the most accu- 
 rate estimate of their dry residue. In taking the weights, 
 the only point is to do it rapidly and avoid loss by evapo- 
 ration. If this be borne in mind, and care be taken in differ- 
 ent examinations to weigh the principles at the same stage 
 of the operation, the simplicity of the process should make it 
 valuable in comparative analyses of the blood in different 
 conditions of the system. 
 
 In estimating the proportion of fibrin, the ordinary 
 
 1 American Journal of the Medical Sciences, loc. cit. 
 
QUANTITATIVE ANALYSIS. 137 
 
 method is followed, with the exception that the weight of the 
 moist fibrin is taken instead of the dry residue. 
 
 In estimating the corpuscles, after a number of trials, the 
 process recommended by Figuier was adopted, with a similar 
 modification. Figuier dried the corpuscles after separating 
 them from the serum by filtration, taking advantage of the 
 property of sulphate of soda, which retains them on the filter. 
 He employed this method to separate the corpuscles com- 
 pletely, and investigate their chemical constitution. 1 
 
 In estimating the albumen, the object was, as in the case 
 of the other principles, to obtain it as nearly as possible in its 
 natural condition, simply changing its form from fluid to 
 semi-solid, without adding any thing which would decompose 
 it, or unite with it. For this purpose absolute alcohol seemed 
 better than heat, nitric acid, the galvanic current, or any other 
 agents by which it is coagulated. 
 
 If the different organic principles be incinerated, the ash 
 will present the characteristic reactions of the chlorides, sul- 
 phates, phosphates, etc., inorganic principles, which, as we 
 have already seen, cannot be separated from the organic con- 
 stituents of the body without destruction of the latter. 
 
 The blood of a healthy male, set. 27 years, weight 170 
 pounds, who had never suffered from disease, taken from the 
 arm at 1 p. M., the last meal having been taken at 8 A. M., 
 furnished the proportions of organic constituents given in the 
 following table. To complete the table, the proportions of 
 inorganic principles, fats, etc., were taken from the analyses 
 of Becquerel and Rodier, to which reference has already been 
 made. The proportion of water is estimated by subtracting 
 the sum of the solid and semi-solid constituents from the 
 entire weight of the blood. 2 
 
 1 Sur une Method* nouvelle pour V Analyse du Sang, et sur la Constitution 
 chimique des Globules mnguins. Par M. L. FIGUIER. (Ann. de Chim. et de Phys., 
 1844, 3 m serie, tome xi., p. 506.) 
 
 2 Further details of experiments on this subject are contained in the article, to 
 which reference has been made, in the ' American Journal," October, 1 863. 
 
138 THE BLOOD. 
 
 Composition of the 
 
 Water 154-870 
 
 Corpuscles , . . . 495-590 
 
 Albumen 329-820 
 
 Fibrin 8'820 
 
 Seroline(?) 0'025 
 
 Cholesterine 0-125 
 
 Oleate, margarate, and stearate of soda. . .T 1*400 
 
 Chloride of sodium, ) 
 
 potassium (a trace), f 
 
 Carbonate of soda 
 
 Free soda 
 
 Sulphate of soda 
 
 ^OMteoflSSia:. \ ( Carbonate of soda most abundant), 
 Sulphate of potassa... 
 Phosphate of potassa. 
 Sulphate of magnesia. 
 
 Phosphate of lime 
 
 Phosphate of magnesia. 
 
 Iron 0*550 
 
 Undetermined extractive matters 2-450 
 
 0-350 
 
 1,000-000 
 
 There exist in the blood certain well-determined principles 
 not given in the above table, some of which have great physio- 
 logical importance ; and it is to be expected that further 
 investigations will reveal others, among what are now called 
 extractive matters, an acquaintance with which will mate- 
 rially advance our pathological, as well as our physiological 
 knowledge of this fluid. The developments of the last few 
 years with regard to urea and cholesterine lead us to look 
 for the discovery of new principles, variations from the nor- 
 mal proportions of which will, perhaps, be found to constitute 
 important pathological conditions. In both a physiological 
 and pathological point of view, there is much to be done in 
 this line of investigation. 
 
 Aside from the gases^ we are now acquainted with the 
 
 1 For purposes of comparison, the fibrin, albumen, and corpuscles were desic- 
 cated and weighed, giving the following proportions of dry residue : 
 Fibrin, 2-50 parts per 1,000 of fresh blood. 
 
 Albumen, 71 '5 3 do. do. 
 
 Corpuscles, 125*00 do. do. 
 
QUANTITATIVE ANALYSIS. 139 
 
 following additional principles in the blood, which are either 
 constant or temporary constituents : Sugar, Fatty Emulsion, a 
 Coloring Matter peculiar to the serum, Urea, Uric Acid in 
 combination, Cholesterine, Creatine, and Creatinine. 
 
 Sugar. Bernard ' showed in 1848 that sugar always exists 
 in the blood of the hepatic veins and the right side of the 
 heart. It is manufactured by the liver, and disappears in the 
 lungs. When its production is most active, as in full diges- 
 tion, it may exist in small quantity in the arterial blood. 
 Ordinarily it is only to be found in the blood between the 
 liver and the lungs, except when it exists in the blood of the 
 portal vein, after the ingestion of saccharine or starchy 
 matters. 
 
 Fatty Emulsion. After a full meal with an abundance 
 of fat, the blood contains a considerable proportion of fatty 
 emulsion. Bernard 2 has shown, also, that the blood of the 
 hepatic veins contains an emulsive substance which is 
 formed by the liver. "We have already seen that the blood 
 corpuscles contain a certain proportion of fatty matter in a 
 state of molecular union with the organic nitrogenized prin- 
 ciples. 
 
 Coloring Matter of the Serum. The serum has a yellowish 
 color, more or less intense, which is dependent upon a pecu- 
 liar coloring matter. This has never been isolated, but is 
 thought by some to be identical with the coloring matter of 
 the bile, 3 a supposition, however, which does not seem very 
 probable. 
 
 1 Recherches sur une Nouvelle Fonction du Fole considers comme Organe 
 Producteur de Mature Sucree chez THomme et les Animauz. These. Paris, 
 1853. 
 
 2 See page 64. 
 
 3 BECQUEREL and RODIER, .Recherches sur la Composition du Sang dans 
 Tetat de Sante et dans Vetat de Maladie, Paris, 1844. 
 
140 THE BLOOD. 
 
 Urea and the Urates. In 1821 Prevost and Dumas l 
 discovered urea in the blood of auimals from which the 
 kidneys had been removed ; which was the first experimental 
 demonstration that this principle is formed in the system and 
 eliminated by, not manufactured in, the kidneys. It was 
 demonstrated in healthy blood* by Marchand, 2 in 1838, and 
 since then has been recognized as one of its normal constit- 
 uents, though existing in very minute quantity. These 
 observations have been confirmed by numerous French, Ger- 
 man, and English physiologists. The urate of soda also exists 
 in small quantity in the blood, and possibly the hippurate of 
 soda. The reason why the proportion of these principles is 
 so small, is that they are eliminated by the proper organs as 
 soon as formed. 
 
 Cholesterine. This substance was demonstrated in the 
 blood by Denis in 1830. 3 It is now known to exist in this 
 fluid in considerable quantity. It is most abundant in the 
 blood coming from the nervous centres, where it is produced 
 in great part, and is diminished in the passage of the blood 
 through the liver/ 
 
 A substance was described by Boudet in 1833, in the 
 blood, which he called Seroline. Its existence in the blood 
 is problematical. 6 
 
 Creatine and Creatinine. Yerdeil and Marcet have de- 
 monstrated the presence of these substances in the blood.' 
 Their proportion is very small, and has not been determined. 
 They undoubtedly have the same relation to the system as 
 urea and cholesterine. 
 
 1 Annales de Chimie et de Physique, 1821, tome xviii., p. 280. 
 a Annales des Sciences Naturelles, 1838, 2me serie, tome x., p. 46. 
 
 3 ROBIN and VERDEIL, op. cit., tome iii., page 63. 
 
 4 See an article by the author on a New Excretory Function of the Liver, 
 American Journal of the Medical Sciences, October, 1862. 
 
 6 Ibid. 
 
 6 ROBIN and VERDEIL, Chimie Anatomique, tome ii., pp. 480 and 439 
 
QUANTITATIVE ANALYSIS. 141 
 
 A consideration of abnormal or accidental constituents of 
 the blood, such as poisonous or medicinal substances, does 
 not belong to its physiological history. It is hardly necessary 
 to mention certain substances, the existenc^ of which is 
 doubtful, such as lactic acid, copper, magnesia, etc. 
 
CHAPTEE III. 
 
 COAGULATION OF THE BLOOD. 
 
 General considerations Characters of the clot Characters of the serum Coagu- 
 lating principle in the blood Circumstances which modify coagulation Co- 
 agulation of the blood in the organism Spontaneous arrest of hemorrhage 
 Cause of coagulation of the blood Summary of the properties and functions 
 of the blood. 
 
 THE remarkable property in the blood of spontaneous 
 coagulation has been commonly recognized as far back as 
 we can look into the history of physiology ; and since the 
 immortal discovery of Harvey, which naturally gave an im- 
 pulse to investigations into the properties of the circulating 
 fluid, there have been few subjects connected with the physi- 
 ologj- of the blood which have excited more universal interest. 
 At first, the ideas with regard to the cause of this phenom- 
 enon were entirely speculative. The first definite experi- 
 ments on record were performed by Malpighi and published 
 in 1666. He was followed by Borelli, Euysch, and a host of 
 others who hold conspicuous places in the history of our 
 science; among whom may be mentioned Hunter, Hewson, 
 Miiller, Thackrah, J. Davy, Magendie, Nasse, and Dumas. 
 While much labor has been expended on this subject, the final 
 cause of coagulation cannot even now be said to be settled 
 beyond question. 
 
 The blood retains its fluidity while it remains in the 
 vessels, and circulation is not interfered with. It is then co^- 
 
COAGULATION OF THE BLOOD. 143 
 
 posed, as we have seen, of clear plasma, holding corpuscles in 
 suspension ; but these little bodies do not differ much from 
 the plasma, either in consistence or specific gravity, and give 
 to the fluid only a slight degree of viscidity. Shortly after 
 the circulation is interrupted, or after blood is drawn from 
 the vessels, it coagulates or " sets" into a jelly-like mass. In 
 a few hours we find that contraction has taken place, and a 
 clear, straw-colored fluid has been expressed, the blood thus 
 separating into a solid portion, the crassamentum or clot, and 
 a liquid, which is called serum. The serum contains all the 
 elements of the blood except the red corpuscles and fibrin, 
 which together form the clot. Coagulation takes place in 
 the blood of all animals, commencing a variable time after 
 its removal from the vessels. In the human subject, accord- 
 ing to Nasse, 1 when the blood is received into a moderately 
 deep, smooth vessel, the phenomena of coagulation present 
 themselves in the following order : 
 
 First, a gelatinous pellicle forms on the surface, which 
 occurs in from 1 minute and 45 seconds to 6 minutes ; 
 in from 2 to 7 minutes a gelatinous layer lias formed 
 on the sides of the vessel ; the whole mass becomes of 
 a jelly-like consistence in from 7 to 16 minutes. Contrac- 
 tion then begins, and if we watch the surface of the clot we 
 will see little drops of clear serum making their appearance. 
 This fluid increases in quantity, and in from 10 to 12 hours 
 separation is complete. The clot, which is heavier, sinks to 
 the bottom of the vessel, unless it contain bubbles of gas, or 
 the surface be very concave. In most of the warm-blooded 
 animals the blood coagulates more rapidly than in man. It 
 is particularly rapid in the class of birds, in some of which 
 it takes place almost instantaneously. Observations have 
 shown that coagulation is more rapid in arterial than in 
 venous blood. In the former the proportion of fibrin is 
 notably greater. 
 
 1 MILNE-EDWARDS, Lcfons sur la Physiologic, etc., tome i., p. 125. 
 
144 
 
 THE BLOOD. 
 
 The relative proportions of the serum and clot are very 
 variable, unless we include in our estimate of the serum that 
 portion which is retained between the meshes of the clot. 1 
 As the clot is composed of corpuscles and fibrin, and as these 
 in their moist state represent in general terms about one-half 
 of the blood (see table, page 198), it may be stated that after 
 coagulation, the actual proportions of the clot and serum 
 are about equal. If we take simply the serum which 
 separates spontaneously, we have a large quantity when 
 the clot is densely contracted, and a very small quantity when 
 it is loose and soft.' 
 
 Characters of the Clot. On removing the clot, after the 
 separation of the serum is complete, it presents a gelatinous 
 consistence, and is more or less firm, according to the degree 
 of contraction which has taken place. As a general rule, 
 when coagulation lias been rapid, the clot is soft and but 
 slightly contracted. When, on the other hand, coagulation 
 has been slow, it contracts for a long time, and is much 
 denser. When coagulation is slow, the clot frequently pre- 
 sents what is known as the cupped appearance, having a con- 
 cave surface, a phenomenon which merely depends on the 
 extent of its contraction. It also presents a marked differ- 
 
 1 It is estimated by Milne-Edwards that the clot retains, in most instances, 
 one-fifth of the entire volume of serum. Lemons sur la Physiologic, etc., tome L, 
 p. 124. 
 
 a According to Thackrah the following are the periods required for the coagu- 
 lation of the blood in some of the inferior animals : 
 
 Horse, Blood coagulates in from 5 to 13 minutes. 
 
 Ox, 
 
 Dog, 
 
 Sheep, 
 
 Hog, 
 
 Babbit, 
 
 Lamb, 
 
 Duck, 
 
 Fowl, 
 
 Pigeon, 
 
 12 
 3 
 H 
 
 H 
 H 
 
 i 
 
 2 
 
 almost instantaneously. 
 
CHAEACTEE8 OF THE CLOT. 145 
 
 ence in color at its superior portion. The blood having re- 
 mained fluid for some time, the red corpuscles settle, by virtue 
 of their greater weight, leaving a colorless layer on the top. 
 This is the buify coat so frequently spoken of by authors. 
 The buffed and cupped appearance of the clot has been sup- 
 posed to indicate an inflammatory condition of the circulating 
 fluid; inasmuch as the quantity of fibrin is generally in- 
 creased in inflammation, and the greater the quantity of 
 fibrin the more rapid is the gravitation of the red corpuscles. 
 Though this frequently presents itself in the blood drawn in 
 inflammations, it is by no means pathognomonic of this con- 
 dition, and is liable to occur whenever coagulation is slow, or 
 retarded by artificial means. It is always present in the 
 blood of the horse. Examined microscopically, the buffy 
 coat presents fibrils of coagulated fibrin with some of the 
 white corpuscles of the blood. On removing a clot of ve- 
 nous blood from the serum, the upper surface is florid from 
 contact with the air, while the rest of it is dark ; and on 
 making a section, if the coagulation has not been too rapid, 
 the gravitation of the red corpuscles is apparent. The sec- 
 tion, which is at first almost black, soon becomes red from 
 contact with the atmosphere. The clot from arterial blood 
 has a dark-red color. If the clot be cut into small pieces, it 
 will undergo further contraction, and express a part of the 
 contained serum. If the clot be washed under a stream of 
 water, at the same time kneading it with the fingers, we may 
 remove almost all the red corpuscles, leaving the meshes of 
 fibrin, which, on microscopic examination, will present the 
 fibrillated appearance to which we have already referred. 
 This is a method sometimes employed for the extraction of 
 the fibrin. It was in this way that fibrin was isolated by 
 Malpighi ; who made the first experiments which rendered 
 it probable that coagulation of the blood depended upon this 
 principle. In a few days, as the result of putrefaction, the 
 clot softens, mixes with the serum, and the blood regains its 
 fluidity. 
 
 10 
 
14:6 THE BLOOD. 
 
 Characters of the Serum. After coagulation, if the seruin 
 be carefully removed, it is found to be a fluid of a color 
 varying from a light amber to quite a deep, but clear, red. 
 This depends upon a peculiar coloring matter, distinct from 
 hematine, but which has never been isolated. The specific 
 gravity of the serum is some^diat less than that of the entire 
 mass of blood; being, according to Becquerel and Rodier, 
 about 1,028.' It contains all the principles found in the 
 plasma, or liquor sanguinis, with the exception of the fibrin. 
 It can hardly be called a physiological fluid, as it is formed 
 only after coagulation of the blood, and never exists isolated 
 in the body. The effusions which are commonly called 
 serum, though they resemble this fluid in some particulars, 
 are not identical with it, being formed by a process of transu- 
 dation rather than separation of the blood, as in coagulation. 
 "We have already seen that, in the body, fibrin and albumen 
 are in combination, and that the organic principle of the 
 serum (albumen) when injected into the vessels of a living 
 animal does not become assimilated, but is rejected by the 
 kidneys. The serum must not, therefore, be confounded with 
 the plasma or liquor sanguinis, which is the natural clear 
 portion of the blood. 
 
 Coagulating Principle in the Blood. Acquainted, as 
 we are, with the properties of fibrin, it is evident that this 
 principle is the agent which produces coagulation of the blood. 
 In fact, whatever coagulates spontaneously is called fibrin, 
 and whatever requires some agent to produce this change of 
 consistence is called by another name. But before the prop- 
 erties of fibrin were fully understood, the question of the 
 coagulating principle was a matter of much discussion. 3 
 Malpighi was probably the first to isolate this principle; 
 
 1 Op. tit., p. 86. 
 
 9 An admirable historical review of the theories and discoveries relating to 
 the properties of fibrin and the coagulation of the blood is to be found in Mr. 
 Gulliver's introduction to the Sydenham edition of the works of William Hewson, 
 London, 1846, p. 25 el seq. 
 
COAGULATING PRINCIPLE IN THE BLOOD. 14:7 
 
 which he did by washing the clot in a stream of water, which 
 removed the corpuscles and left a whitish fibrous network. 
 His experiments are set forth in an article in which he at- 
 tempted to show that the so-called polypi of the heart were 
 formed of fibrin, though it was not then called by that name. 
 These observations were soon confirmed by others, and finally 
 Ruysch extracted fibrin from his own blood and the blood 
 of the pig by whipping with a bundle of twigs, and thereby 
 prevented its coagulation. This is the method now most com- 
 monly employed for the separation of fibrin. It then became a 
 question whether this substance existed as a fluid in the> liquor 
 sanguinis, or was furnished by the corpuscles after the re- 
 moval of blood from the vessels. This was decided by Hew- 
 son, whose simple and conclusive experiments, published in 
 1YY1, leave no doubt that coagulation of the blood is due to 
 fibrin, and that this principle is entirely distinct from, and 
 independent of, the corpuscles. This observer, taking advan- 
 tage of the property possessed by certain saline substances of 
 preventing the coagulation of the blood, was the first to sepa- 
 rate the liquor sanguinis from the corpuscles. He mixed 
 fresh blood with a little sulphate of soda, which prevented 
 coagulation, and after the mixture had been allowed to stand 
 for a time, the corpuscles gravitated to the bottom of the ves- 
 sel. The clear fluid was then decanted, and diluted with 
 twice its quantity of water, when the fibrin became coagu- 
 lated. 1 Another experiment is still more conclusive ; and as 
 the credit of having first separated the corpuscles from the 
 plasma and demonstrated the coagulability of the latter is by 
 some ascribed to Miiller, we will give it in the author's own 
 words : 
 
 " Immediately after killing a dog, I tied up his jugular 
 veins near the sternum, and hung his head over the edge of 
 the table, so that the parts of the veins where the ligatures 
 were might be higher than his head. I looked at the veins 
 
 1 The Works of William Hewson, F. R. S., Sydenham edition, p. 12. 
 
148 THE BLOOD. 
 
 from time to time, and observed that they became trans- 
 parent at their upper part, the red particles subsiding. I 
 then made a ligature upon one vein, so as to divide the trans- 
 parent from the red portion of the blood ; and opening the 
 vein, [ let out the transparent portion, which was still fluid, 
 but coagulated soon after. On pressing this coagulum, I 
 found it contained a little serum. The other vein I did not 
 open till after the blood was congealed, and then I found the 
 upper part of the coagulum whitish like the crust in pleuritic 
 blood." l 
 
 Nothing could more conclusively demonstrate that coag- 
 ulation of the blood depends upon a coagulating principle 
 existing in the liquor sanguinis, than this simple experiment. 
 It also beautifully illustrates the formation of the buify-coat. 
 
 The facts thus demonstrated by Hewson were confirmed 
 by Miiller in 1832. He succeeded in separating the plasma 
 from the corpuscles in the blood of the frog by simple filtra- 
 tion ; first diluting it with a saccharine solution. "The great 
 size of the corpuscles in this animal prevents their passage 
 through a filter, and the clear fluid which is thus separated 
 soon forms a colorless coagulum. 2 
 
 From these observations it is evident that the coagulation 
 of the blood is due to the presence of fibrin in the liquor san- 
 guinis. Coagulation of this principle first causes the whole 
 mass of blood to assume a gelatinous consistence ; and by 
 virtue of its contractile properties it soon expresses the serum, 
 but the red corpuscles are retained. One of the causes which 
 operate to retain the corpuscles in the clot is the adhesive 
 matter which covers their surface after they escape from the 
 vessels, which produces the arrangement in rows like piles 
 of coin, which we have already noted under the head of 
 microscopic appearances. This undoubtedly prevents those 
 
 1 The Works of William Hewson, F. R. S., Sydenham edition, p. 32. 
 3 J. MUELLER, Manuel de Physiologic, trad, par Jourdan, Paris, 1851, tome i., 
 p. 96. 
 
CIRCUMSTANCES WHICH MODIFY COAGULATION. 149 
 
 which are near the surface from escaping from the clot during 
 its contraction. 
 
 Circumstances which modify Coagulation out of the Body. 
 
 The conditions which modify coagulation of the blood 
 have been closely studied by Ilewson, Davy, Thackrah, Robin 
 and Yerdeil, and others. They are, in brief, the following : 
 
 Blood flowing slowly from a small orifice is more rapidly 
 coagulated than when it flows in a full stream from a large 
 orifice. If it be received into a shallow vessel, it coagulates 
 much more rapidly than when received into a deep vessel. 
 If the vessel be rough, coagulation is more rapid than if it 
 be smooth and polished. If the blood, as it flows, be received 
 on a cloth or a bundle of twigs, it coagulates almost instan- 
 taneously. In short, it appears that all circumstances which 
 favor exposure of the blood to the air, hasten its coagulation. 
 The blood will coagulate more rapidly in a vacuum . than in 
 the air. 
 
 Coagulation of the blood is prevented by rapid freezing, 
 but afterwards takes place when the fluid is carefully thaw- 
 ed. Between 32 and 140 Fahr., elevation of temperature 
 increases the rapidity of coagulation. 1 Experiments are 
 impracticable above 140, as we are- then likely to have 
 coagulation of the albumen. According to Hichardson, agi- 
 tation of the blood in closed vessels retards, and in open 
 vessels hastens coagulation. 2 
 
 Yarious chemical substances retard or prevent coagula- 
 tion. Among them we may mention : solutions of potash 
 and of soda; carbonate of soda; carbonate of ammonia; 
 carbonate of potash ; ammonia ; sulphate of soda. In the 
 menstrual flow the blood is kept fluid by mixture with the 
 abundant secretions of the vaginal mucous membrane. 
 
 1 RICHARDSON, The Cause of the Coagulation of the Blood. Astley Cooper 
 Prize Essay for 1856, p. 140 et seq. 
 
 2 Ibid., p. 228. 
 
150 THE BLOOD. 
 
 Coagulation of the Blood in the Organism. 
 
 The blood coagulates in the vessels after death, though 
 less rapidly than when removed from the body. As a gen- 
 eral proposition it may be stated that this takes place in from 
 twelve to twenty-four hours after circulation has" ceased. 
 Under these circumstances it is found chiefly in the venous 
 system, as the arteries are generally emptied by post mortem . 
 contraction of their muscular coat. Coagula are found, how- 
 ever, in the left side of the heart and in the aorta, but they 
 are much smaller than those found in the right side of the 
 heart and the large veins. These coagula present the general 
 characters we have already described. They are frequently 
 covered by a soft whitish film, analogous to the buffy coat, 
 and are dark in their interior. 
 
 It was supposed by John Hunter that coagulation of the 
 blood did not take place in animals killed by ]ightning } 
 hydrocyanic acid, or prolonged muscular exertion, as when 
 hunted to death ; but it appears from the observations 
 of others that this view is not correct. J. Davy reports a 
 case of death by lightning where a loose coagulum was found 
 in the heart twenty-four hours after. In this case decompo- 
 sition was very far advanced, and it is probable that the 
 coagula had become less firm from that cause. His obser- 
 vations also show that coagulation occurs after poisoning by 
 hydrocyanic acid, and in animals hunted to death. 1 
 
 Coagulation in different parts of the vascular system is 
 by no means unusual during life. In the heart we sometimes 
 find coagula which bear evidence of having existed for some 
 time before death. These were called polypi by some of the 
 older writers, and are often formed of fibrin almost free from 
 red corpuscles. They generally occur when death is very 
 gradual, and the circulation continues for some time with 
 
 1 DR. JOHN DAYY, Researches Physiological and Anatomical, vol. ii., p. 70 
 si *e. 
 
COAGULATION IN THE ORGANISM. 151 
 
 greatly diminished activity. It is probable that a small 
 coagulum is first formed, from which the corpuscles are 
 washed away by the current of blood; that this becomes 
 larger by farther depositions, until we have large vermicular 
 masses of fibrin, attached, in some instances, to the chordae 
 tendinese. Clots formed in this way may be distinguished from 
 those formed after death by their whitish color, dense consist- 
 ence, and the closeness with which they adhere to the walls 
 of the heart. Cases have been reported by Richardson and 
 others, where concretions of this kind extended from the' 
 cavities of the heart far into the large vessels. It is also 
 stated by Richardson 1 that they sometimes become partly 
 organized, and connected with the tissue of the heart ; but 
 we have seen that accidental deposits of a proximate prin- 
 ciple, like fibrin, never become transformed into organized 
 structures. 
 
 We need only enumerate some of the other circumstances 
 under which the blood coagulates in the vessels, as this sub- 
 ject belongs rather to pathology than to physiology. Coag- 
 ulation may be said, in general terms, to occur as a con- 
 dition of stasis. When a ligature is applied to an artery, 
 the vessel becomes filled with a coagulum up to the site of 
 the first branch which is given off, whatever be its situation. 
 In applying the ligature, the delicate inner coat is ruptured, 
 and the shreds, which curl up in the interior of the vessel, 
 soon become covered with a layer of coagulated blood, which 
 thickens until the whole vessel is filled. In cases in which 
 the flow of blood becomes arrested, or very much retarded, 
 as in varicose veins of the extremities, the enlarged veins in 
 hemorrhoids, etc., these vessels may become obliterated by the 
 formation of a clot. In some aneurisms, the retardation of 
 the blood-current produces spontaneous cure by the deposi- 
 tion of successive layers of fibrin next the walls of the dilated 
 vessel. A knowledge of this fact has been made use of in 
 the treatment of aneurism by compression of the artery which 
 
 1 Op, tit. 
 
152 THE BLOOD. 
 
 supplies it with blood. Many cases are on record, where this 
 has been continued for a number of hours, and a cure 
 effected. 
 
 Bodies projecting into the caliber of a blood-vessel soon 
 become coated with a layer of fibrin. Rough concretions 
 about the orifices of the heart* frequently induce the depo- 
 sition of little masses of fibrin, which sometimes become 
 detached, and are carried to various parts of the circulatory 
 system, as the lungs or brain, plugging up one or more of the 
 smaller vessels. These masses have been called by Yirchow, 
 emboli, and have been traced by him, in some instances, from 
 the heart to the situations above mentioned. The experiment 
 has been made of passing a thread through a small artery, 
 allowing it to remain for a few hours, when it is found 
 coated with a layer of coagulated fibrin. 
 
 Blood generally coagulates when it is effused into the 
 areolar tissue, or any of the cavities of the body ; though, 
 effused into the serous cavities, the tunica vaginalis for exam- 
 ple, it has been known to remain fluid for days and even 
 weeks, and coagulate when let out by an incision. In the 
 Graafian follicles, after the discharge of the ovum, we gener- 
 ally have the cavity filled with blood, which forms a clot, 
 and is slowly removed by the process of absorption. 
 
 Coagulation thus takes place in the vessels as the result 
 of stasis, or very great retardation of the circulation, and in 
 the tissues or cavities of the body, whenever it is accidentally 
 effused. In the latter case, it is generally removed in the 
 course of time by absorption. This takes place in the fol- 
 lowing way : First, we have disappearance of the red cor- 
 puscles, or decoloration of the clot, and the fibrin is then 
 the only element which remains. This becomes reduced 
 from a fibrillated to a granular condition, softens, finally be- 
 comes amorphous, and is absorbed; though when the size 
 of the clot is considerable, this may occupy weeks, and even 
 months, and may never be completely effected. Effused in 
 this manner, the constituents of the blood act as foreign 
 
SPONTANEOUS ARREST OF HEMORRHAGE. 153 
 
 bodies ; the corpuscles cease to be organized anatomical 
 elements capable of self-regeneration, break down, and are 
 absorbed. The fibrin which remains undergoes the same 
 process ; the stages through which it passes being always 
 those of decay, and not of development. In other words, it 
 is incapable of organization. 
 
 Office of the Coagulation of the Blood in Arresting 
 Hemorrhage. The property of the blood under consideration 
 has a most important office in the arrest of hemorrhage. 
 The effect of an absence or great diminution of the coagu- 
 lability of the circulating fluid is exemplified in instances 
 of what is called the hemorrhagic diathesis ; a condition in 
 which slight wounds are apt to be followed by alarming, 
 and it may be fatal, hemorrhage. This condition of the 
 blood is not characterized by any symptoms excepting the 
 obstinate flow of blood from slight wounds, and may con- 
 tinue for years. In a case which came under the observation 
 of the author a few years since, excision of the tonsils was 
 followed by bleeding, which continued for several days, and 
 was arrested with great difficulty. On inquiry it was 
 ascertained that the patient, a young man about twenty 
 years of age, in other respects perfectly healthy, had been 
 subject from early life to persistent hemorrhage from slight 
 wounds. In reviewing the functions of fibrin, we find that 
 apparently its most important office is in the arrest of hem- 
 orrhage. The degree of coagulability of the blood depends 
 on the quantity of fibrin, but its proportion has not been 
 shown to bear any definite relation to the vigor of the indi- 
 vidual, nor to the processes of nutrition generally. The 
 necessary and constant variations in the organic elements of 
 the blood, which are the result of insufficient alimentation, 
 exhausting discharges, or diseases characterized by impover- 
 ishment of this fluid, are observed in the albumen and red 
 corpuscles, and not in the fibrin. By this it must not be 
 understood that the quantity of fibrin is not variable. 'It has 
 
154: THE BLOOD. 
 
 been found, for example, by Andral and Gavarret to be pretty 
 generally increased in the phlegm asise ; but it bears no rela- 
 tion to the richness of the blood. Its proportion is not in- 
 creased always in plethora and diminished in anemia ; and 
 in fact it has been found by Nasse to be increased in animals 
 suffering from hunger. 1 After l^emorrhage, which diminishes 
 the corpuscles and albumen, the fibrin is generally increased ; 
 so that the fact of loss of blood, diminishing the force of the 
 heart and increasing the tendency to coagulation, has an in- 
 fluence in the arrest of the flow. 
 
 Circumstances which accelerate coagulation have a ten- 
 dency to arrest hemorrhage. It is well known that exposure 
 of a bleeding surface to the air has this effect. The way in 
 which the vessel is divided has an important influence. A 
 clean cut will bleed more freely than a ragged laceration. In 
 division of large vessels this difference is sometimes marked. 
 Cases are on record where the arm has been torn off at the 
 shoulder-joint, and yet the hemorrhage was, for a time, spon- 
 taneously arrested ; while we know that division of an artery 
 of smaller size, if it be cut across, would be fatal if left to 
 itself. Under these circumstances the internal coat is torn in 
 shreds, which retract, their curled ends projecting into the 
 caliber of the vessel, and have the same effect on the coagu- 
 lation of blood as a bundle of twigs. In laceration of such a 
 large vessel as the axillary artery, the arrest cannot be per- 
 manent, for as soon as the system recovers from the shock, 
 the contractions of the heart will force out the coagulated 
 blood which has closed the opening. 
 
 In our study of the functions of the body we shall con- 
 tinually see evidences that Nature, not content with simply 
 providing for the ordinary wants of the system, has made 
 provision for extraordinary occurrences and accidents. A 
 striking example of this is the function of fibrin. All the 
 ordinary operations of the body go on perfectly well in a 
 
 1 KOBIN and YERDEIL, Chimie Anatomique, tome iii., p. 205. 
 
SPONTANEOUS ARREST OF HEMORRHAGE. 155 
 
 person affected with the hemorrhagic diathesis, in whose blood 
 the fibrin is wanting ; and, as we have already seen in treat- 
 ing of transfusion, the vivifying effects of defibrinated blood 
 are equal to those of blood which contains all its constituents ; 
 yet it is provided that in hemorrhage the blood solidifies and 
 closes the opening in the vessels, if they be not too large. 
 She often makes attempts to cure aneurisms, or hemorrhoids, 
 by the same process ; and hence does not obliterate the vessels 
 by an organized substance, which would be capable of self- 
 regeneration and always remain as part of the body, but 
 throws out a temporary plug, which is destined to be re- 
 moved, partially, if not completely, by absorption. The pro- 
 cess of coagulation of the fibrin of the blood is essentially 
 different from that of gradual effusion of plastic lymph by 
 which injuries are repaired. Individuals suffering under the 
 hemorrhagic diathesis, are not deprived of the power of 
 repairing injuries by means of plastic exudations from the 
 blood, though the blood contains no fibrin, and hemorrhage 
 is not arrested until the process of repair has closed the 
 openings in the vessels, or we have closed them by the effect 
 of our styptics. We likewise see that in the lower animals 
 who have not the means of artificially arresting hemorrhage, 
 its spontaneous arrest is more effectually provided for by a 
 more rapid coagulation of the blood. 
 
 From the foregoing considerations it is evident that the 
 remarkable phenomenon of coagulation of the blood, which 
 has so much engaged the attention of physiologists, has rather 
 a mechanical than a vital function ; for its chief office is in the 
 arrest of hemorrhage. Coagulation never takes place in the 
 organism, unless the blood be in an abnormal condition with 
 respect to circulation. Here its operations are mainly con- 
 servative ; but as almost all conservative processes are some- 
 times perverted, clots in the body may be productive of injury, 
 as in the instances of cerebral apoplexy, clots in the heart 
 occurring before death, the detachment of emboli, etc. 
 
156 THE BLOOD. 
 
 Cause of the Coagulation of the Blood. Though the phe- 
 nomena of coagulation, and the circumstances which modify 
 it, especially as occurring in the organism, are of more prac- 
 tical importance than any thing else, the study of these 
 phenomena naturally leads us to inquire into the reason why 
 fibrin thus changes its form. When we say that this prin- 
 ciple is endowed with the property of spontaneous coagula- 
 bility, we do not express what is strictly the fact. It remains 
 fluid until it is placed in abnormal conditions, when, without 
 the application of heat, or any chemical reagents, it coag- 
 ulates ; but so long as it remains in the circulating blood, 
 lymph, or chyle, coagulation does not take place. This 
 property, which has been so long recognized, has been the 
 subject of many speculations as to its cause, and some experi- 
 ments ; but until the last few years the experiments have done 
 nothing but familiarize us with the actual phenomena which 
 take place, and left the cause, as before, entirely a matter of 
 speculation. Under these circumstances it will not be found 
 very profitable to discuss the old theories on the subject. 
 Our object in the historical review of physiological questions 
 is to show the gradual development of truth, as facts have 
 been accumulated by different observers, which those last in 
 the field have been able to coordinate, rather than to exhume 
 hypotheses which have fallen before actual observation. On 
 no subject have hypotheses been more vague and unsatis- 
 factory, and more readily disproved by experiment, than 
 with regard to the cause of coagulation of the fibrin. The 
 idea that exposure to the air is the cause of coagulation, 
 which was held by Hewson, is disproved by the simple fact 
 that coagulation takes place in a vacuum. The vital theory 
 of Hunter, which was adopted by most physiologists of his 
 time, is too indefinite for discussion at the present day, and 
 really expresses utter want of knowledge on the subject. 
 The theory that motion is the cause of the fluidity of fibrin 
 in the body, is disproved by the fact that violent agitation of 
 the blood out of the body does not prevent coagulation. 
 
CAUSE OF COAGULATION OF THE BLOOD. 157 
 
 On the other hand, we are not justified, with Eobin and 
 Yerdeil, in abandoning the subject with the assertion that 
 it is " as vain to seek after the cause of this fact as to inquire 
 why fibrin exists, why sulphate of copper is blue, etc." ; ! 
 assuming that fibrin coagulates merely because it has the 
 property of coagulation, as albumen is coagulated by heat, 
 or ca seine by acetic acid. An extension of this method in 
 physiology would put an end to all generalization, restricting 
 the operations of the intellect to the mere observation of 
 phenomena. 
 
 Circulating in the organism, the plasma contains, molec- 
 ularly united with each other and uniformly distributed in 
 the fluid, fibrin, albumen, salts, and volatile substances. 
 Albumen retains its fluidity out of the body, until heat or 
 some coagulating agent is applied ; but by employing a 
 current of galvanism, which we know changes the condition 
 of the inorganic substances in the serum, something is taken 
 away which causes albumen to coagulate, or which, when it 
 existed unchanged, retained albumen in its fluid condition. 
 Is it not possible that the blood while circulating may contain 
 a substance capable of keeping fibrin fluid, the evolution of 
 which out of the body is the cause of coagulation ? We are 
 particularly led to ask this question, as we are acquainted 
 with many substances which possess this property when added 
 to blood drawn from the vessels ; such as carbonate of soda, 
 ammonia, etc. This idea forms a fit basis for experimental 
 inquiry, by a study of the substances evolved by the blood 
 during coagulation in the form of vapor. If it be objected 
 that no coagulation takes place in the vessels, while an op- 
 portunity for volatilization is constantly presented in the 
 lungs in normal circulation, it must be remembered that the 
 blood is continually washing out, as it were, in the course of 
 circulation, matters formed in the various parts of the organ- 
 ism ; and substances which are continually discharged by the 
 lungs, skin, kidneys, etc., are necessarily as continually taken 
 
 1 ROBIN ana VERDEIL, op. cit., tome iii., p. 210. 
 
158 THE BLOOD. 
 
 up by the blood in the system. From this point of view it 
 does not seem entirely unprofitable to look after the cause of 
 the coagulation of the blood. It was with such an idea as 
 this that almost the first definite experiments which we have 
 on the cause of coagulation, were performed. These consti- 
 tute the basis of the Astley Cooper prize essay for 1856, and 
 if they be not sufficient to convince all physiologists, must 
 be acknowledged to settle many points with reference to the 
 question under consideration. Dr. Richardson has here given 
 us the only definite and probable explanation of this phenom- 
 enon that has ever been presented. 1 
 
 The views of Richardson, and the experiments on which 
 they are based, are briefly the following : 
 
 Taking as a point of departure the fact, which, as we have 
 already seen, is sufficiently proven, that all circumstances 
 which facilitate the separation of volatile elements from the 
 blood hasten coagulation, Richardson attempted to show 
 that the volatile substances which thus escape, if retained, or 
 if made to pass through blood, will retard or arrest coagulation. 
 His experiments on the prevention of exhalation are very 
 satisfactory. The jugular vein is laid bare ; a portion of it, 
 filled with blood, is included between two ligatures, then 
 separated from the body and drawn under mercury in a U 
 tube, the vein being allowed to remain in the bend of the 
 tube for from nine to twenty-four hours. At the end of this 
 time it is removed, the blood let out, and exposed to the air. 
 In a number of experiments he found the blood entirely fluid 
 when drawn from the vein immediately after removal from 
 beneath the mercury, while it coagulated firmly in a few 
 minutes after exposure to the air. 2 This simple experiment 
 we have repeated with the same result. It shows conclusively 
 that coagulation of the blood is not a consequence of simple 
 rest, or lowering of temperature, and that it is not kept fluid 
 in the organism by any vital influence. 
 
 1 RICHARDSON, The Cause of the Coagulation of the Blood, London, 1858. 
 a Ibid., p. 204 et seq. 
 
CAUSE OF COAGULATION OF THE BLOOD. 159 
 
 The next experiments, which bear directly on the subject 
 under consideration, were made with reference to the impor- 
 tant question, whether the volatile substances escaping from 
 coagulating blood, if passed through fresh blood, would have 
 the effect of retarding or preventing coagulation. The ex- 
 periments on this point are likewise conclusive. The appa- 
 ratus which is used consists of two wide-mouthed bottles, 
 capable of holding about two ounces, and a Wolffe's bottle 
 capable of holding about three pounds. The small bot- 
 tles, fitted with perforated corks, are half filled, and the 
 large bottle nearly filled, with fresh blood. A tube con- 
 nected with a small bellows is introduced into one of the 
 small bottles, passing nearly to the bottom, while a second 
 perforation in the cork is fitted with a short tube which 
 simply allows the escape of air or vapor. The latter is con- 
 nected with a tube passing nearly to the bottom of the Wolffe's 
 bottle through one of the necks, while the other is fitted with 
 a short tube to permit the escape of the vapor. The vapor 
 is then made to pass through the blood in the third bottle by 
 a long tube reaching to the bottom. If air be now gently 
 forced through the apparatus by the bellows, the vapor from 
 the mass of blood (about two pounds is used) in the large 
 bottle will pass through the third, which contains but an 
 ounce of blood. In an experiment of this kind performed by 
 Richardson, " the blood through which the air was first passed 
 coagulated in two minutes ; that in the Wolffe's bottle coagu- 
 lated in three minutes ; while the blood in the third bottle, 
 which for a time received a full charge of the vapor, retained 
 its red color and its fluidity for eight minutes and a half; as 
 long, in fact, as any vapor could be sent through it. When 
 the vapor failed, and air only began to circulate, this blood 
 coagulated feebly, the fibrin separating and floating on the 
 top." 1 
 
 These experiments apparently have but one explanation. 
 As the blood when drawn from the body may sometimes be 
 
 1 Op. cit., p. 268. 
 
160 THE BLOOD. 
 
 kept fluid by preventing the escape of volatile substances, 
 and the vapor of coagulating blood forced through another 
 specimen of blood prevents coagulation so long as it continues 
 to pass, something is given oif from the blood which, when 
 contained in this fluid, has the power of retaining fibrin in 
 its fluid state. Having gone tkus far in the investigation, 
 the next point is to subject the vapor of blood to analysis, 
 and ascertain, if possible, what substance or substances it 
 contains which, when retained in the blood, or introduced, 
 have the power of keeping it fluid. 
 
 This was the next step in .Richardson's investigations. 
 He found that blood-vapor contained, among other things, 
 ammonia. This lie detected by passing blood-vapor through 
 hydrochloric acid and afterwards testing it with the per- 
 chloride of platinum, forming the ammonio-chloride of plati- 
 num. He also obtained crystals of the chloride of ammo- 
 nium, by allowing the vapor to pass over a glass slide moist- 
 ened with hydrochloric acid. He demonstrated in this way 
 the presence of ammonia in the exhalation from the blood of 
 the human subject, as well as the inferior animals. He also 
 demonstrated by numerous experiments that ammonia mixed 
 with blood, or the vapor passed through it, will prevent coag- 
 ulation ; while the passage of air and the various gases has 
 the effect of hastening, rather than retarding this process. 
 It was further demonstrated that ammonia is constantly dis- 
 charged by the organism, particularly by the lungs ; and, of 
 course, must be as constantly produced in the tissues, and 
 taken tip by the blood in the course of the circulation. 1 
 
 The points above enumerated certainly seem to be ex- 
 
 1 In the discussion of Richardson's views, we have attempted to connect the 
 great experimental links in his chain of evidence. His admirable and laborious 
 treatise contains details of 399 experiments ; and though a summary is given at 
 the end of each chapter, and a summary at the conclusion, much labor is necessary 
 on the part of the reader to separate those which are important from the great 
 mass of minor facts, and appreciate the proofs of the doctrines advanced. This, 
 as it seems to me, has had the effect of causing the views of Dr. Richardson to 
 receive far less attention at the hands of physiologists than they really merit. 
 
CAUSE OF COAGULATION OF THE BLOOD. 161 
 
 perimentally proven. The experiments cited show conclu- 
 sively that as blood coagulates, out of the body, a vapor is 
 given off which contains some substance capable of preserv- 
 ing the fluidity of the fibrin ; and that ammonia, which is a 
 constituent of this vapor, has this property. But the rigid 
 requirements of our science render it necessary, in order to 
 establish the fact that the evolution of ammonia is the sole 
 and constant cause of coagulation, to show how ammonia is 
 given off under all the varied circumstances under which 
 coagulation of the blood is known to take place. In other 
 words, it must be demonstrated that the evolution of ammo- 
 nia in coagulation is not a coincidence, occurring, it may be, 
 pretty generally, but a necessity. The fact that ammonia 
 added to blood prevents coagulation is not sufficient evidence 
 of this ; for, as we have seen, other substances, such as carbon- 
 ate of soda, have the same effect. 
 
 Are there any circumstances under which coagulation of 
 blood takes place, where ammonia is not, and cannot be, 
 given off? There are observations which seem to answer 
 this question in the affirmative; and it becomes necessary 
 now to carefully study, with reference to this point, all the 
 varied conditions under which the blood will coagulate. 
 
 The view that coagulation of the blood is due to the 
 evolution of ammonia explains perfectly how this process is 
 hastened by exposure to air, by a moderately high tempera- 
 ture, by a vacuum, by the blood flowing slowly in a small 
 stream, and in brief, the various circumstances which modify 
 coagulation out of the ~body. Its evolution from the blood 
 by the lungs is not incompatible with the fact of the fluidity 
 of the blood in the body, for it is taken up from the tissues 
 as fast as it is eliminated. Some instances, however, of 
 coagulation m the ~body, and some experiments on coagulation 
 out of the body, when, as is thought, ammonia is not and 
 cannot be evolved, seem opposed to the view advanced by 
 Richardson. 
 
 It is easy to understand, adopting the views of Eichard- 
 11 
 
162 THE BLOOD. 
 
 son, why the blood coagulates in the body after death. Under 
 the circumstances in which it is then placed, the escape of 
 volatile substances, though retarded, is evidently not pre- 
 vented. Thus when the body is opened shortly after death, 
 we may find the blood perfectly fluid, coagulating, however, 
 shortly after it is removed from the vessels and exposed to 
 the air. During life, when circulation is arrested or much 
 retarded, the blood will coagulate ; but here there is the same 
 opportunity presented for the escape of volatile matter. As 
 ammonia is undoubtedly received by the blood in the course 
 of circulation, arrest of circulation in any part of the vascular 
 system prevents the blood therein contained from receiving 
 its constant supply. As it has been shown that out of the 
 body the evolution of ammonia always accompanies coagu- 
 lation, we must infer simply that coagulation in the body, 
 under the above-mentioned circumstances, is attended with 
 the evolution of this principle, for the conditions here do not 
 admit of direct experimentation,, situated as the blood is in 
 the midst of tissues, from which volatile substances are also 
 evolved. It is not proper, however, to shut our eyes to the 
 fact that blood effused into the tissues and into the cavities, 
 during life, has been known to remain fluid for days and 
 even weeks, when there are no circumstances which we can 
 appreciate as modifying or preventing the gradual evolution 
 of ammonia. But we know that there are many animal 
 products, such as the vaginal mucus, etc., which prevent 
 coagulation ; and in these instances, which are not very fre- 
 quent, it has not been shown that some influence of this kind 
 was not brought to bear on the process. It is a curious fact, 
 also, that leech-drawn blood remains fluid in the body of the 
 animal. Richardson has verified this fact, but says that he 
 can offer no satisfactory explanation. He observed also that 
 the blood flowing from the leech-bite presented the same 
 persistent fluidity, which explains the well-known fact that 
 the insignificant wound gives rise to considerable hemorrhage. 
 On. this point he has made the following curious experiment : 
 
CAUSE OF COAGULATION OF THE BLOOD. 163 
 
 " After the leech was removed from the arm, the wound 
 it had produced continued to give out blood very freely. I 
 caught the blood thus flowing at different intervals, allowing 
 it to trickle into teaspoons of the same size and shape. The 
 results were curious. The blood which was received into the 
 first spoon, and which was collected immediately after the 
 removal of the leech, was dark, and showed the same feeble- 
 ness of coagulation as the blood taken from the leech itself. 
 Another portion of blood, received into a second spoon five 
 minutes later, coagulated in twenty-five minutes with mod- 
 erate firmness. A third portion of blood, caught ten min- 
 utes later still, coagulated in eight minutes ; while at the 
 end of half an hour the blood which still flowed from the 
 wound coagulated firmly, and in fine red clots, in two min- 
 utes. Ultimately the blood coagulated as it slowly oozed 
 from the wound, so that the wound itself was sealed up." 1 
 
 The existence of projections into the caliber of vessels, 
 or, as was done by Simon, the passage of a fine thread through 
 an artery or vein, will determine the formation of a small 
 coagulum upon the foreign substance, while the circulation 
 is neither interrupted nor retarded. These facts demand 
 explanation, but all we can say with regard to them is, that 
 in the present state of our knowledge explanation is difficult, 
 if not impossible. As before remarked, the process, under 
 these circumstances, cannot be subjected to direct experiment, 
 as in the case of the blood coagulating out of the body. 
 
 Since the publication of Hichardson's essay, various 
 experiments on coagulation out of the body have been made 
 which are claimed to disprove his views. Dr. John Davy 
 has reported some experiments on the coagulation of blood 
 in the common fowl, in which he attempts to show that the 
 process is not attended with the evolution of ammonia, and 
 furthermore, that ammonia mixed with the blood will not 
 prevent coagulation.' 2 It is well known that the blood of 
 
 1 Op. dt., p. 207. 
 
 3 JOHN DAVY, M.D., Physiological Researches, London, 1863, p. 384 et seq. 
 
164 THE BLOOD. 
 
 birds is remarkable for the rapidity of its coagulation, and is 
 therefore not so well adapted to experiments relative to the 
 circumstances which attend this process as the blood of 
 animals in which coagulation is less rapid. The experiments 
 referred to are imperfect, and no attempt is made to invali- 
 date the accuracy of the observations of Richardson on the 
 blood of mammals and the human subject 
 
 The most recent experiments on this subject are by Jo- 
 seph Lister, published in a lecture on " Coagulation of the 
 Blood," in the u London Lancet," February, 1864. The view 
 entertained by Mr. Lister is, that the blood is kept fluid in 
 the organism by its contact with living parts ; and that all 
 other contact, especially that of inorganic bodies, produces a 
 tendency in this fluid to coagulate. The power of retaining 
 the fluidity of the blood he supposes to reside particularly in 
 the coats of the blood-vessels, but he further says : " I think it 
 probable, though not yet proved, that all living tissues have 
 these properties with reference to the blood." l The ammonia 
 theory he considers entirely fallacious, and ascribes coagula- 
 tion either to the contact of animal tissues after death, when 
 their vital property of maintaining the fluidity of the blood 
 slowly disappears, or the contact of ordinary matter. 2 
 
 Various experiments are cited in support of the view thus 
 briefly given. In one of them, the author, by an ingenious 
 mechanism, draws the blood into an apparatus consisting of 
 a tube in which it is eifectually secluded from the air, and 
 which allows the fluid to be stirred with a little wire which 
 is provided with projecting spokes. In one experiment the 
 tube was filled with blood, which did not come in contact 
 with the air, and the blood stirred with the wire. In thirty- 
 seven minutes the wire was removed and found enveloped in 
 a mass of clot. In another experiment, "Receiving blood 
 from the throat of a bullock into two similar wide-mouthed 
 
 1 London Lancet, American republication, Feb. 1864, p. 91. 
 
 2 This view, as stated by Mr. Lister, was entertained by Astley Cooper, Thack- 
 rah, Briicke, and others. 
 
CAUSE OF COAGULATION OF THE BLOOD. 165 
 
 bottles, I immediately stirred one of them with a clean ivory 
 rod for ten seconds very gently, so as to avoid the introduc- 
 tion of any air, and then left both undisturbed. At the end 
 of a certain number of minutes, I found that, while the blood 
 which had not been disturbed could be poured out as a fluid, 
 with the exception of a thin layer of clot on the surface and 
 an incrustation on the interior of the vessel, the blood in the 
 other vessel, which had been stirred for so brief a period, was 
 already a solid mass." 3 
 
 Other experiments are brought forward, modifications of 
 the one already mentioned as performed by Simon, showing 
 that incrustations will form on the surface of foreign sub- 
 stances introduced into the vessels ; and that after death their 
 introduction will induce coagulation in the entire vessel much 
 sooner than it would otherwise have taken place. 
 
 The idea of simple contact with living tissues preventing 
 coagulation hardly merits discussion. It is well known that 
 coagulation frequently takes place during life, almost always 
 following arrest of the circulation. After division of the ves- 
 sels, the blood, in contact with living parts, performs its con- 
 servative function in the arrest of hemorrhage. There is cer- 
 tainly something very curious in the effect of the contact of 
 foreign substances, and the experiments on this point are very 
 striking. Why is it that a coagulum forms upon a fine thread 
 or a needle passed through a vessel ; or on the wire with which 
 the blood in Mr. Lister's apparatus was stirred, though there 
 was no exposure to the air ? And why did the blood, which 
 was only gently stirred for a few seconds with a. smooth ivory 
 rod, coagulate so much more rapidly than that which was 
 undisturbed ? 
 
 These are questions which we must acknowledge our 
 inability to answer. The phenomena cannot be satisfactorily 
 explained by the supposition that ammonia is evolved ; but 
 on the other hand, this is not a sufficient reason for rejecting 
 the fact, experimentally demonstrated, that, out of the or- 
 
 1 Op. cit., p. 83. 
 
166 THE BLOOD. 
 
 ganism, ammonia, a substance capable of maintaining the 
 fluidity of the fibrin, is given off from coagulating blood. 
 We may suppose that ammonia separates itself from one 
 portion of the blood, and is retained in another. An experi- 
 ment by Richardson gives color to this supposition, for in 
 one experiment 011 the passage of blood-vapor through blood, 
 he found that the lower part coagulated while the upper part 
 remained fluid; and on examination, ascertained, in expla- 
 nation of this, that the tube which carried the vapor into the 
 blood did not extend to the bottom of the vessel. 1 
 
 The effect of foreign bodies on coagulation is not more 
 inexplicable than the operation of inert substances in certain 
 chemical processes ; as the action of the oxide of manganese 
 in the formation of oxygen from the chlorate of potash ; or, 
 to take a process more like the one under consideration, the 
 formation of crystals on threads and projections in vessels, or 
 the escape of electricity from points. Examples of this kind 
 in the organic world are numerous, and we are content to 
 say that these facts are entirely beyond explanation, in the 
 present state of our knowledge. "We should hardly be sur- 
 prised, then, at our inability to explain the tendency which 
 the presence of foreign bodies has to induce the deposition of 
 so coagulable a substance as fibrin. The theory that coagu- 
 lation of the blood is always, or even generally, due to the 
 contact of foreign substances, or tissues which have lost their 
 vital properties and act as foreign substances, must be rejected 
 as opposed to experiment and observation. When, as hap- 
 pens in the interior of the body, the blood coagulates under 
 circumstances when the process will not admit of direct 
 experimentation as far as the evolution of volatile substances 
 is concerned, the best we can do is to apply, as far as possible, 
 the facts which are proven with regard to coagulation out of 
 the body, when the phenomena can be minutely studied. 
 Here, at least in the human subject and in mammals, it 
 seems demonstrated to be due to the evolution of ammonia. 
 
 1 Op. cit., p. 269. 
 
SUMMARY OF PEOPEETIES AND FUNCTIONS. 167 
 
 Summary of the Properties and Functions of the Blood. 
 
 The blood, constituting as nearly as can be estimated one- 
 eighth of the weight of the body, is the great nutritive fluid ; 
 its presence being necessary to life, and its normal constitution 
 and circulation essential to the performance of all the func- 
 tions. 
 
 Anatomically ', its most important elements are a clear 
 plasma and the red corpuscles, these existing in about equal 
 proportions. The corpuscles are intimately connected with 
 the function of respiration. Their chief office seems to be to 
 carry oxygen from the lungs to the tissues. Their presence 
 is immediately essential to life, and their normal proportion 
 essential to health. They are organized anatomical elements, 
 capable of self-regeneration from principles contained in the 
 plasma. They contain all the principles which exist in the 
 plasma, with the difference that the fibrin and albumen of 
 the latter are replaced by globuline, and a coloring matter, 
 hematine, is superadded. The plasma seems to be the part 
 chiefly employed in the nourishment of the tissues, some of 
 which, as cartilage, do not receive any of the corpuscular 
 elements of the blood. 
 
 Chemically, the plasma contains all the elements which 
 are necessary for the regeneration of all parts of the body. 
 These are continually being used up in nutrition, but are 
 replaced by the absorption of articles of food after they have 
 undergone the preparation of digestion. In the deposition 
 of new matter in the regeneration of the tissues, the organic 
 and inorganic constituents of the plasma are deposited to- 
 gether ; the inorganic elements of the tissues receiving, as it 
 were, the vital properties of self-regeneration, which we sup- 
 pose to reside particularly in organic principles, from the 
 fact of their molecular union with these organic principles. 
 
 Of the organic constituents, albumen constitutes by far 
 the greater proportion, and is the one chiefly used in the- 
 
168 THE BLOOD. 
 
 nutrition of the organic nitrogen ized elements of the tissues. 
 Its diminution in the blood to any considerable extent de- 
 termines defective nutrition. It is proJbable that all the other 
 organic nitrogenized principles are formed from it. 
 
 In the blood, part of the albumen is transformed into 
 fibrin, which exists in small quantity, and does not appear 
 to bear any relation to nutrition. Its peculiar property of 
 spontaneous coagulation gives it a most important conser- 
 vative function in the arrest of hemorrhage. Ammonia, which 
 is contained in the blood, has the property of maintaining its 
 fluidity ; but on exposure to air, or in rupture of vessels, we 
 have an escape of ammonia, and the fibrin by its coagulation 
 reduces the whole mass of blood to a semi-solid consistence. 
 The proportion of fibrin in the blood bears no relation to the 
 function of nutrition. Its occasional absence only induces 
 obstinate hemorrhage on the division of vessels, even of very 
 small size. 
 
 Fat, which exists in small quantity in the blood, and sugar, 
 which exists only in certain parts of the circulatory system, 
 disappear .in the organism in a way which is not at present 
 understood. They are concerned in, and necessary to, the 
 processes of nutrition ; but the exact nature of their function 
 is unknown. 
 
 The inorganic constituents of the body are found in vary- 
 ing proportions in the plasma, and have varied functions. 
 Their presence tends to preserve the proper constitution of 
 the corpuscles, which are dissolved and lost in pure water. 
 
 The water which does not enter into the constitution of 
 the albumen and fibrin serves to hold the various salts in 
 solution, and cannot vary much in quantity from a certain 
 standard. 
 
 Some of the inorganic salts, the chlorides particularly, 
 seem to regulate, to a certain extent, the processes of nutri- 
 tion, are found most abundantly in the fluids, and apparently 
 do not form a very essential portion of the tissues themselves. 
 A tendency to an excess in the blood is relieved by discharge 
 
SUMMARY OF PROPERTIES AND FUNCTIONS. 169 
 
 from the system, and a diminution is accompanied by certain 
 indefinite disorders in the general processes of nutrition. 
 
 The alkaline carbonates have a tendency to preserve the 
 fluidity of the fibrin. 
 
 Some of the inorganic salts, such as \ho, phosphate of lime, 
 are important elements entering into the constitution of the 
 various tissues. They are most abundant in the solids and 
 semi-solids of the body ; and when their introduction with 
 food is prevented, we have certain definite changes in the 
 constitution of some of the tissues, as softening of the bones 
 in animals deprived of the phosphate of lime. 
 
 As already remarked, the inorganic principles are neces- 
 sary to, and participate in the performance of the vital func- 
 tions of organic principles. 
 
 In addition to these elements, the blood contains large 
 quantities of carbonic acid, which is eliminated by the lungs, 
 and small quantities of other excrementitious matters, such as 
 urea, the urates, cholesterine, creatine, creatinine, and am- 
 monia (which is perhaps an excretion), their proportion being 
 kept down by their constant removal by the proper eliminat- 
 ing organs. Their increase in the blood from any cause 
 produces toxic efiects, which, as regards some, urea and cho- 
 lesterine for example, are easily recognized. 
 
CHAPTEK IV. 
 
 CIRCULATION OF THE BLOOD. 
 
 Discovery of the circulation Physiological anatomy of the heart Valves of the 
 heart Movements of the heart Impulse of the heart Succession of move- 
 ments of the heart Force of the heart Action of the valves Sounds of the 
 heart Cause of the sounds of the heart. 
 
 HARVEY discovered the circulation of the blood in 1616, 
 taught it in his public lectures in 1619, and in 1628 published 
 the " Exercitatio Anatomica de Motu Cordis et Sanguinis 
 in Animalibus" It is justly said by Flourens, in his ele- 
 gant little work on the discovery of the circulation, that 
 from this discovery dates the epoch of modern physiology, 
 when tradition began to give place to observation. "When 
 we reflect that it is through the medium of the blood that 
 all the processes of life take place ; that all tissues are nour- 
 ished by it, and all fluids formed from it ; that it gives fresh 
 material to every part, and takes away that which is worn 
 out ; that it carries oxygen to every part of the system, and 
 gives to each structure its vital properties ; we can form some 
 idea of the state of physiology before anything was known 
 of the circulation. This momentous discovery, from the 
 isolated facts bearing upon it which were observed by nu- 
 merous anatomists, to its grand culmination with Harvey, so 
 fully illustrates the gradual development of most great phy- 
 siological truths, that it does not seem out of place to begin 
 our study of the circulation with a rapid sketch of its history. 
 
DISCOVERY OF THE CIRCULATION. 171 
 
 The facts bearing upon the circulation which were devel- 
 oped before the time of Harvey were chiefly of an anatomical 
 character. Hippocrates and his contemporaries distinguished 
 two kinds of vessels, arteries and veins ; but they regarded 
 the former as air-bearing tubes, as their name implies, in 
 communication with the trachea. Galen, by a few simple 
 experiments upon living animals, demonstrated the error of 
 this view. He showed that blood issued from divided arte- 
 ries, and demonstrated its presence in a portion of one of 
 these vessels included between two ligatures in a living ani- 
 mal. His ideas, however, of the mode of communication 
 between the arteries and veins were entirely erroneous, be- 
 lieving, as he did, in the existence of numerous small orifices 
 between the ventricles. 
 
 In 1553, Michael Servetus, who is generally regarded as 
 the discoverer of the passage of the blood through the lungs, 
 or the pulmonary circulation, described in "a work on theology 
 the course of the blood through the lungs, from the right to 
 the left side of the heart. This description, complete as it 
 is, was merely incidental to the development of a theory with 
 regard to the formation of the soul, and the development of 
 what were called animal and vital spirits (spiritus). The 
 same year, by order of Calvin, Servetus was burned alive at 
 Geneva, and nearly every copy of his work was committed to 
 the flames. But one or two copies of this work are now in 
 existence. One is in the library of the Institute of France, 
 and bears evidence, in some pages which are partially burned, 
 of the fate which it so narrowly escaped. 1 
 
 A few years later, Columbo, professor of anatomy at 
 Padua, and Cesalpinus, of Pisa, also described the passage of 
 the blood through the lungs, though probably without any 
 knowledge of what had been written by Servetus. To Cesal- 
 pinus is attributed the first use of the expression, circulation 
 
 1 The physiological portion of the Christianismi Restitutio of SERVETUS has 
 been extracted from the original by FLOURENS, and is published in his little work 
 entitled Histoire de la Decouverte de la Circulation du Sang, Paris, 1854. 
 
172 CIRCULATION. 
 
 of the Uood. He also remarked that after ligature or com- 
 pression of veins, the swelling is always below the point of 
 obstruction. These ideas, the importance of which is evi- 
 dent now that we understand the circulation, passed into 
 oblivion. They were unknown to investigators during the 
 succeeding century, and were onljP brought to light after the 
 discoveries of Harvey had become widely disseminated. 
 From this point of view they can hardly be called discoveries, 
 taking no place in science, and their authors not considering 
 them definite enough, or of sufficient importance, to be fully 
 insisted upon. 
 
 A great discovery, preparatory to that of the circulation, 
 was made by Fabricius ab Aquapendente, professor at Padua, 
 who, in the words of Flourens, had a double glory: "He 
 discovered the valves of the veins, and he was the master of 
 Harvey." Yalves had been described by Etienne in the 
 portal vein, by Cananius in the azygos vein, and Eustachi 
 had discovered the valve which bears his name and the 
 valves of the coronary veins ; but to Fabricius is generally 
 ascribed the honor of the discovery of the valvular system in 
 the veins. 1 This was demonstrated to Harvey at Padua, 
 though Fabricius does not appear to have had any definite 
 idea of their function. It is possible that this anatomical 
 fact may have directed the mind of Harvey in his first spec- 
 ulations on the circulation. Shortly after his return from 
 Padua in 1602, he advanced beyond the study of inanimate 
 parts by dissections, and investigated animated nature by 
 
 1 BERARD, ( Cours de Physiologic, tome iv., p. 34) quotes a passage from 
 Piccolomini, an Italian anatomist, in which the valves of the veins are mentioned : 
 " *- * * quod est, in mediis venis reconditas esse innumerabiles pene valvas, 
 quemadmtidum in orificiis vasorum cordis. Jfce venarum valvce maxime con- 
 spicuce sunt in divisione ramorum vence cavce" (Anatomicce Prcdectiones, Romce, 
 1586, p. 412). It is the assertion, undoubtedly made in good faith, in the great 
 work of Fabricius, that the valves had never before been seen, which has led many 
 physiologists to regard him as the discoverer ; especially when this fact is taken 
 in connection with their demonstration by Fabricius to Harvey, to whom is due 
 the sole credit of having pointed out their function. 
 
DISCOVERY OF THE CIRCULATION. 
 
 means of vivisections. As is evident when we consider the 
 state of science at that time, anatomists had long been 
 preparing the way for the discovery of the circulation, though 
 they knew little of the functions of the parts they described. 
 The conformation of the heart and vessels, and even the 
 arrangement of the valves of the veins, did not lead them to 
 suspect the course of the blood ; but a few well conceived 
 experiments on living animals have made it appear so sim- 
 ple, that we now wonder it remained unknown so long. 
 Furthermore, these experiments made it evident that there 
 was a communication at the periphery between the arteries 
 and the veins. 
 
 In the work of Harvey are described, first, the move- 
 ments of the heart, which he exposed and studied in living 
 animals. He describes minutely all the phenomena which 
 accompany its action; its diastole, when it is filled with 
 blood, and its systole, when the fibres of which the ventricles 
 are composed contract simultaneously, and " by an admirable 
 adjustment all the internal surfaces are drawn together, as 
 if with cords, and so is the charge of blood expelled with 
 force." From the description of the action of the ventricles, 
 he passes to the auricles, and shows how these, by their con- 
 m traction, fill the ventricles with blood. By experiments 
 upon serpents and fishes, he proved that the blood, fills the 
 heart from the veins, and is sent out into the arteries. Ex- 
 posing the heart and great vessels in these animals, he applied 
 a ligature to the veins, which had the effect of cutting off 
 the supply from the heart so that it became pale and flaccid ; 
 and by removing the ligature the blood could be seen flowing 
 into the organ. When, on the contrary, a ligature was 
 applied to the artery, the heart became unusually distended, 
 which continued as long as the obstruction remained. "When 
 the ligature was removed, the heart soon returned to its 
 normal condition. 1 
 
 The descriptions given by Harvey were the result of nu- 
 
 1 The Works of William Harvey, M. D. Sydenham Edition, p. 53. 
 
174: CIRCULATION. 
 
 merous experiments upon living animals ; exposing the heart 
 of cold-blooded animals, in which the movements are com- 
 paratively slow; studying also the action of this organ in 
 warm-blooded animals,- after its movements had become 
 enfeebled. As we shall see when we come to describe the 
 movements of the heart, nothing can exceed the simplicity 
 and accuracy of the descriptions of Harvey, which are uni- 
 versally acknowledged to be correct in almost every par- 
 ticular. 
 
 Harvey completed his description of the circulation, by 
 experiments showing the course of the blood in the arteries 
 and veins, and the uses of the valves of the veins. These 
 experiments are models of simplicity and pertinence. First, 
 he showed that a ligature tightly applied to a limb prevented 
 the blood from entering the artery and arrested pulsation. 
 The ligature then relaxed, and applied with moderate tight- 
 ness so as to compress only the superficial veins, allowed the 
 blood to pass into the part by the arteries, but prevented its 
 return by the veins, which consequently became excessively 
 congested. The ligature being removed, the veins soon 
 emptied themselves, and the member regained its ordinary 
 appearance. 1 
 
 He observed the " knots" in the veins of the arm when a 
 ligature is applied, as for phlebotomy, and showed that the 
 space between these knots, which are formed by the valves, 
 could be emptied of blood by pressing toward the heart, and 
 would not fill itself while the finger was kept at the lower 
 extremity. It was impossible, by pressure with the fingers, 
 to force the blood back through one of the valves. 3 
 
 By such simple, yet irresistibly conclusive experiments, 
 was completed the chain of evidence establishing the 
 fact of the circulation of the blood. Truly is it said that 
 here commenced an epoch in the study of physiology ; for 
 then the scientific world began to emancipate itself from the 
 ideas of the ancients, which had held despotic sway for two 
 
 1 Op. cit. t p. 55 et seq. 9 Ibid., p. 65. 
 
DISCOVERY OF THE CIRCULATION. 175 
 
 centuries, and study Nature for themselves by means of 
 experiments. 
 
 Though Harvey described so perfectly the course of the 
 blood, and left not a shadow of doubt as to the communica- 
 tion between the arteries and veins, it was left to others to 
 actually see the blood in movement and follow it from one 
 system of vessels to the other. In 1661, Malpighi saw the 
 blood circulating in the vessels of the lung of a living frog, 
 in examining it with magnifying glasses ; and a little later, 
 Leeuwenhoek saw the circulation in the wing of the bat. 
 The great discovery was then completed. 
 
 Enough has been said in the preceding historical sketch 
 to give a general idea of the course of the great nutritive 
 fluid, and the natural anatomical and physiological divisions 
 of the circulatory system. There is a constant flow from the 
 central organ to all the tissues and organs of the body, and a 
 constant return of the blood after it has passed through 
 these parts. But before the blood, which has thus been 
 brought back, is fit to return again to the system, it must pass 
 through the lungs and undergo the changes which constitute 
 the process of Respiration. In some animals, like fishes, the 
 same force sends the blood through the gills, and from them 
 through the system. In others, like the reptiles, a mixture 
 of aerated and non-aerated blood takes place in the heart, 
 and the general system never receives blood that has been 
 fully arterialized. But in man and all warm-blooded ani- 
 mals, the organism demands blood that has been fully purified 
 and oxygenated by its passage through the lungs, and here 
 we find the first great and complete divisions of the circula- 
 tion into the pulmonary and systemic, or, as they have been 
 called, the lesser and greater circulation. The heart in this 
 instance is double; having a right and left side which are 
 entirely distinct from each other. The right heart receives 
 the blood as it is brought from the system by the veins, and 
 sends it to the lungs ; the left heart receives the blood from 
 
176 CIECULATIOK". 
 
 the lungs and sends it to the system. 1 It must be borne in 
 mind, however, that though the two sides of the heart are 
 distinct from each other, their action is simultaneous ; and in 
 studying the motions of this organ, we will find that the 
 blood is sent simultaneously from the right side to the lungs, 
 and from the left side to the system*. It will not be necessary, 
 therefore, to separate the two circulations in our study of 
 their mechanism; for the simultaneous action of both sides 
 of the heart enables us to study its functions as a single 
 organ, and the constitution and operations of the two kinds 
 of vessels do riot present any material differences. 
 
 For convenience of study, the circulatory system may be 
 divided into heart and vessels, the latter being of three 
 kinds : the arteries, which carry blood from the heart to the 
 system ; the capillaries, which distribute the blood more or 
 less abundantly in different parts of the system ; and the 
 veins, which return the blood from the system to the heart. 
 The function of each of these divisions may be considered 
 separately. 
 
 Action of the Heart. 
 
 Physiological Anatomy of the Heart. The heart of the 
 human subject is a pear-shaped, muscular organ, situated 
 in the thoracic cavity, with its base about in the median 
 line, and its apex at the fifth intercostal space, midway be- 
 tween the median line and a perpendicular dropped through 
 the left nipple. Its weight is from 8 to 10 ounces in the 
 female, and from 10 to 12 ounces in the male. It has four 
 distinct cavities : a right and a left auricle, and a right and 
 a left ventricle. Of these, the ventricles are the more capa- 
 cious. The heart is held in place, or may be said to be 
 attached, by the great vessels, to the posterior wall of the 
 thorax, while the apex is free and capable of a certain degree 
 
 1 In some animals, as the dugong, the division between the two sides of the 
 heart is very marked. The heart is really double, having two points, the two 
 sides joined together only at the base. 
 
PHYSIOLOGICAL ANATOMY OF THE HEAKT. 177 
 
 of motion. The whole organ is enveloped in a fibrous sac 
 called the pericardium, lined by a serous membrane which is 
 attached to the great vessels at the base and reflected over its 
 surface. This sac is lubricated by a drachm or two of fluid, so 
 that the movements are normally accomplished without any 
 friction. The serous pericardium does not present any differ 
 ences from serous membranes in other situations. The cav 
 ities of the heart are lined by a smooth membrane, called the 
 endocardium, which is continuous with the lining membrane 
 of the blood-vessels. 
 
 The right auricle receives the blood from the venae cavse 
 and empties it into the right ventricle. The auricle presents 
 a principal cavity or sinus, as it is called, with a little appen- 
 dix, called, from its resemblance to the ear of a dog, the 
 auricular appendix. It has two large openings for the vena 
 cava ascendens and the vena cava descendens, with a small 
 opening for the coronary vein, which brings the blood from 
 the substance of the heart itself. It has, also, another large 
 opening, called the auriculo-ventricular opening, by which 
 the blood flows into the ventricle. The walls of this cavity 
 are quite thin as compared with the ventricles, measuring 
 about one line. They are constituted of muscular fibres 
 which are arranged in two layers ; one of which, the external, 
 is common to both auricles, and the other, the internal, is 
 proper to each. These muscular fibres, though involuntary 
 in their action, belong to the striped, or what is termed vol- 
 untary, variety, and are similar in structure to the fibres of 
 the ventricles. The fibres of the auricles are much fewer 
 than those of the ventricles. Some of them are looped, arising 
 from a cartilaginous ritfg which separates the auricles and 
 ventricles, and passing over the auricles ; and others are cir- 
 cular, surrounding the auricular appendages and the openings 
 of the veins, extending, also, a short distance along the course 
 of these vessels. One or two valvular folds are found at the 
 orifice of the coronary vein, preventing a reflux of blood ; but 
 there are no valves at the orifices of the venae cava3. 
 12 
 
178 CIRCULATION. 
 
 The left auricle receives the blood which comes from the 
 lungs by the pulmonary veins. It does not differ materially 
 in its anatomy from the right. It is a little smaller, and its 
 walls are thicker, measuring about a line and a half. It has 
 four openings by which it receives the blood from the four pul- 
 monary veins. These openings are not provided with valves. 
 Like the right auricle, it has a large opening by which the 
 blood flows into the left ventricle. The arrangement of the 
 muscular fibres is essentially the same as in the right auricle. 
 
 In adult life the cavities of the auricles are entirely 
 distinct from each other. Before birth they communicate 
 by a large opening, the foramen ovale, and the orifice of 
 the inferior vena cava is provided with a membranous fold, 
 the Eustachian valve, which serves to direct the blood from 
 the lower part of the body through this foramen into the 
 left auricle. After birth the foramen ovale is closed, and the 
 Eustachian valve gradually disappears. 
 
 The ventricles, in the human subject and in warm-blooded 
 animals, constitute the bulk of the heart. They have a ca- 
 pacity somewhat greater than that of the auricles, and are 
 provided with thick muscular walls. It is by the powerful 
 action of this portion of the heart that the blood is forced, on 
 the one hand, to the lungs and back to the left side, and on 
 the other, through the entire system of the greater circulation 
 to the right side. It was supposed by Legallois 1 that the 
 capacity of the right ventricle was considerably greater than 
 the left, while the more recent observations of Bouillaud 2 on 
 the human heart seem to show that there is no great differ- 
 ence between the two sides in this regard. The most recent 
 and conclusive observations on this subject are those of Hif- 
 felsheim and Robin. 3 In these experiments the cavities 
 were filled with an injection of wax, and the estimates 
 
 1 LEGALLOIS, (Euvres, Paris, 1824, tome i., p. 331. 
 
 2 J. BODILLAUD, Traitc Clinique dcs Maladies du Cceur, precede de Recherches 
 nouvelles sur V Anatomic et la Physiologic de cette Organe, Paris, 1841, tome i., p. 54. 
 
 3 Journal de I 1 Anatomic et de la Physiologic, Paris, juillet, 1864, p. 413. 
 
PHYSIOLOGICAL ANATOMY OF THE HEAET. 179 
 
 made by calculating the amount of liquid displaced by the 
 moulds of the different cavities. Care was taken to make 
 the injection in animals before cadaveric rigidity set in, or 
 after it had passed away in the human subject. The com- 
 parative results obtained by these observers are the most 
 interesting, for the cavities were undoubtedly distended by 
 the injection to their extreme capacity, and contained more 
 than they ever do during life. They found the capacity of 
 the right auricle from -J to -| greater than that of the left. 
 The capacity of the right ventricle was from T 1 to ^ greater 
 than that of the left, but more frequently there was less dis- 
 parity between the two ventricles than between the auricles. 
 The capacity of each ventricle exceeded that of the corre- 
 sponding auricle by from J to -J. Nine times out of ten, this 
 predominance of the ventricle was more marked on the left 
 side. The absolute capacity of the left ventricle, according 
 to these observations, is from 143 to 212 cubic centimeters, 
 which is about 4*8 to 7 ounces. This is much greater than 
 most estimates, which place the capacity of the various cavi- 
 ties, moderately distended, at about 2 ounces. The estimates 
 of Yolkmann and Yalentin are about equal to those we have 
 cited. 
 
 In spite of the disparity in the extreme capacity of the 
 various cavities, the quantity of blood which enters the cav- 
 ities is necessarily equal to that which is expelled. This. is given 
 in the "Cyclopaedia of Anatomy and Physiology" (vol. ii., 
 p. 585) as a little more than two ounces. There are no means 
 of estimating with exactness the quantity of blood discharged 
 with each ventricular contraction ; and we find the question 
 rather avoided in works on physiology. All we can say is, 
 that from observation on the heart during its action, it never 
 seems to contain much more than half the quantity in all its 
 cavities that it does when fully distended by injection ; but 
 it is the right cavities which are most dilatable, and prob- 
 ably the ordinary quantity of blood in the left ventricle is 
 within one-fifth or one-sixth of its extreme capacity. 
 
180 CIRCULATION. 
 
 The cavities of the ventricles are triangular or conoidal ; 
 the right being broader and shorter than the left, which ex- 
 tends to the apex. The inner surface of both cavities is 
 marked by peculiar ridges and papillae, which are called the 
 columnce carnece. Some of these are mere fleshy ridges pro- 
 jecting into the cavity ; others aVe columns attached by each 
 extremity and free at the central portion ; and others are 
 papillae giving origin to the chordae tendinece^ which are at- 
 tached to the free edges of the auriculo-ventricular valves. 
 These fleshy columns interlace in every direction, and give 
 the inner surface of the cavities a reticulated appearance. 
 This arrangement evidently facilitates the complete emptying 
 of the ventricles during their contraction. 
 
 The walls of the left ventricle are uniformly much thicker 
 than the right. Bouillaud found the average thickness of 
 the right ventricle at the base to be 2J- lines, and the thick- 
 ness of the left ventricle at the corresponding part 7 lines. 
 
 The arrangement of the muscular fibres constituting the 
 walls of the ventricles is more regular than in the auricles, 
 and their course enables us to explain some of the phenom- 
 ena which accompany the heart's action. The direction of 
 the fibres cannot be well made out unless the heart has been 
 boiled for a number of hours, when part of the intermus- 
 cular tissue is dissolved out, and the fibres can be easily sep- 
 arated and followed. Without going into a minute descrip- 
 tion of their direction, it is sufficient to state, in this con- 
 nection, that they present two principal layers: a super- 
 ficial layer common to both ventricles, and a deep layer 
 proper to each. The superficial fibres pass obliquely from 
 right to left from the base to the apex; here they take a 
 spiral course, become deep, and pass into the interior of the 
 organ to form the columnse carnese. These fibres envelop 
 both ventricles. They may be said to arise from cartilaginous 
 rings which surround the auriculo-ventricular orifices. The 
 external surface of the heart is marked by a little groove 
 which indicates the division between the two ventricles. 
 
VALVES OF THE HEART. 
 
 The deep fibres are circular, or transverse, and surround 
 eacli ventricle separately. 
 
 The muscular tissue of the heart is of a 
 deep red color, and resembles, in its gross 
 characters, the tissue of ordinary voluntary 
 muscles ; but, as already intimated, it pre- 
 sents certain peculiarities in its minute anat- 
 onfy. The fibres are considerably smaller 
 and more granular than those of ordinary 
 muscles. They are, moreover, connected with 
 each other by short inosculating branches, 
 while in the voluntary muscles each fibre runs 
 
 . . . . i -i Anastomosing: muscu- 
 
 irom its origin to its insertion enveloped in la ^ fibres fro^ the nu - 
 
 r man heart. (After Kol- 
 
 its proper sheath, or sarcolemma. In the ker -> 
 heart the fibres have no sarcolemma. 1 These peculiarities, 
 particularly the inosculation of the fibres, favor the contrac- 
 tion of the ventricular walls in every direction, and the complete 
 expulsion of the contents of the cavities with every systole. 
 
 Each ventricle has two orifices : one by which it receives 
 the blood from the auricle, and the other by which the blood 
 passes from the right side to the lungs, and from the left side 
 to the system. All of these openings are provided with valves, 
 which are so arranged as to allow the blood to pass in but 
 one direction. 
 
 Tricuspid Valve. This valve is situated at the right 
 auriculo-ventricular opening. It has three curtains, formed 
 of a thin but resisting membrane, which are attached around 
 the opening. The free borders are .attached to the chordae 
 tendineae, some of which arise from the papillae on the inner 
 surface of the ventricle, and others directly from the walls of 
 
 1 ROBIN states (Dictionnaire de Medecine, etc., de P. H. Nysten, onzieme edition 
 par E. Littre et Ch. Robin. Coeur.) that the fibres of the heart have no sarco- 
 lemma, which I believe to be the fact, though Kolliker (Manual of Microscopic 
 Anatomy, London, 1860, p. 477) says : " Their sarcolemma is very deh'cate, or even 
 may not be demonstrable at all, except by the aid of reagents." 
 
182 CIRCULATION. 
 
 the ventricle. When the organ is empty, these curtains are 
 applied to the walls of the ventricle, leaving the auriculo- 
 ventricular opening free ; but when the ventricle is com- 
 pletely filled, and the fibres contract, they are forced up, their 
 free edges become applied to each other, and the opening is 
 closed. 
 
 Pulmonw Valves. These valves, also called the semi- 
 lunar or sigmoid valves of the right side, are situated at the 
 orifice of the pulmonary artery. They are strong membra- 
 nous pouches, with their convexities, when closed, looking 
 towards the ventricle. They are attached around the orifice 
 of the pulmonary artery, and are applied very nearly to the 
 walls of the vessel when the blood passes in from the ven- 
 tricle ; but at other times their free edges meet in the centre, 
 forming an effectual barrier to regurgitation. In the centre 
 of the free edge of each valve is a little corpuscle called the 
 corpuscle of Arantius / and just above these points of attach- 
 ment, the artery presents three little dilatations, or sinuses, 
 called the sinuses of Valsalva. The corpuscles of Arantius 
 have been supposed to facilitate the closure of the valves by 
 slightly removing them from the walls of the vessel, so that 
 the blood may get behind them. This, however, is probably 
 not their function. They aid in the adaptation of the valves 
 to each other, and the effectual closure of the orifice. 
 
 Mitral Valve. : This valve, sometimes called the bicuspid, 
 is situated at the left auriculo-ventricular orifice. It is called 
 mitral from its resemblance, when open, to a bishop's mitre. 
 It is attached to the edges of the opening, and its free borders 
 are held in place when closed by the chordae tendinese of the 
 left side. It presents no material difference from the tri- 
 cuspid valve, with the exception that it is divided into two 
 curtains instead of three. 
 
 Aortic Valves. These valves, also called the semilunar 
 
MOVEMENTS OF THE HEAKT. 183 
 
 or sigmoid valves of the left side, present no difference from 
 the valves at the orifice of the pulmonary artery. They are 
 situated at the aortic orifice. 
 
 The physiological anatomy of the tricuspid and mitral 
 valves may be studied, by cutting away the auricles so as to 
 expose the auriculo-ventricular openings, introducing a pipe 
 into the pulmonary artery and aorta, after destroying the 
 semilunar valves, and then forcing water into the ventricles 
 by a syringe or from a hydrant. In this way the play of the 
 valves will be beautifully exhibited. 
 
 We can study the action of the semilunar valves, by 
 cutting away enough of the ventricles to expose them, and 
 forcing water into the vessels. These experiments give an 
 idea of the immense strength of the valves; for they can 
 hardly be ruptured by a force which is not sufficient to rup- 
 ture the vessels themselves. 
 
 Movements of the Heart. 
 
 In studying the phenomena which accompany the action 
 of the heart, we shall follow the course of the blood, begin- 
 ning with it as it flows from the vessels into the auricles. 
 The dilatation of the cavities of the heart is called the diastole, 
 and their contraction the systole. When these terms are 
 used without any qualification, they are understood as refer- 
 ring to the ventricles ; but they are also applied to the action 
 of the auricles, as the auricular diastole or systole, which, as 
 we shall see, is distinct from the action of the ventricles. 
 
 A complete revolution, so to speak, of the heart consists 
 in the filling and emptying of all its cavities, during which 
 they experience an alternation of repose and activity. As 
 these phenomena occupy, in many warm-blooded animals,- a 
 period of time less than one second, it will be appreciated 
 that the most careful study is necessary in order to ascertain 
 their exact relations to each other. When the heart is ex- 
 posed in a living animal, the most prominent phenomenon 
 
184 CIRCULATION. 
 
 is the alternate contraction and relaxation of the ventricles ; 
 but this is only one of the operations of the organ. In any 
 of the class of mammals the anatomy and action of the vas- 
 cular system are to all intents and purposes the same as in 
 the human subject ; and though the exposure of the heart by 
 opening the chest modifies somewhat the force and frequency 
 of its pulsations, the various phenomena follow each other 
 in their natural order, and present essentially their normal 
 characters. The operation of exposure of the heart may be 
 performed on a living animal without any great difficulty ; 
 and if we simply take care to keep up artificial respiration, 
 the action of the heart will continue for a considerable time. 1 
 We may keep the animal quiet by the administration of 
 ether, or by poisoning with woorara, the latter agent acting 
 upon the motor nerves, but having no effect upon the heart. 
 Having opened the chest, we see the heart enveloped in its 
 pericardium, regularly performing its functions ; and on 
 slitting up and removing this covering, the various parts are 
 completely exposed. The right ventricle and auricle, and" 
 a portion of the left ventricle, can be seen without disturbing 
 the position of the parts; but the greater part of the left 
 auricle is concealed. As both auricles and ventricles act- 
 together, the parts of the heart which are exposed are suffi- 
 cient for purposes of study. 
 
 Action of the Auricles. Excepting the short time occu- 
 pied in the contraction of the auricles, these cavities are con- 
 tinually receiving blood on the right side from the system, 
 by the venae cavse, and on the left side from the lungs, by 
 the pulmonary veins. This continues until their cavities are 
 completely filled, the blood coming in by a steady current ; 
 and during the repose of the heart, the blood is also flowing 
 
 1 For a full description of the operations for exposing the heart in living ani- 
 mals, the reader is referred to an article by the author in the American Journal 
 of the Medical Sciences, October, 1861, entitled Experimental Researches on points 
 connected with the Action of the Heart and with Respiration. 
 
MOVEMENTS OF THE HEART. 185 
 
 through the patent auriculo-ventricular orifices into the ven- 
 tricles. When the auricles have become fully distended, they 
 contract quickly and with considerable power ^(the auricular 
 systole), and force the blood into the ventricles, effecting the 
 complete diastole of these cavities. During this contraction, 
 the blood not only ceases to flow in from the veins, but some 
 of it is regurgitated, as the orifices by which the vessels open 
 into the auricles are not provided with valves. The size of 
 the auriculo- ventricular orifices is one reason why the greater 
 portion of the blood is made to pass into the ventricles ; and 
 furthermore, during the auricular systole, the muscular fibres 
 which are arranged around the orifices of the veins constrict 
 them to a certain extent, which tends to diminish the reflux of 
 blood. There can be no doubt that some regurgitation takes 
 place from the auricles into the veins, but this prevents the 
 possibility of over-distention of the ventricles. 
 
 It has been shown by experiments that the systole of the 
 auricles is not immediately necessary to the performance of 
 the circulation. M. Marey, 1 in a recent work on the circu- 
 lation, cites an experiment of Chauveau in which the con- 
 tractility of the auricles was temporarily exhausted by pro- 
 longed irritation ; nevertheless the ventricles continued to act 
 and keep up the circulation. 
 
 Action of the Ventricles. Immediately following the 
 contraction of the auricles, which has the effect of producing 
 complete distention of the ventricles, we have the contraction 
 of the ventricles. This is the chief active operation performed 
 by the heart, and is generally spoken of as the systole. As 
 we should expect from the great thickness of the muscular 
 walls, the contraction of the ventricles is very much more 
 powerful than that of the auricles. By their action, the blood 
 is forced from the right side to the lungs by the pulmonary 
 artery, and from the left side to the system by the aorta. 
 Kegurgitation into the auricles is effectually prevented by the 
 
 1 MAREY, Circulation du Sang, Paris, 1863, p. 36. 
 
186 CIRCULATION. 
 
 closure of the tricuspid and mitral valves. This act accom- 
 plished, the heart has a period of repose, the blood flowing 
 into the auricles, and from them into the ventricles, until the 
 auricles are filled, and another contraction takes place. 
 
 Locomotion of the Heart. Jhe position of the heart after 
 death, or during the repose of the organ, is with its base di- 
 rected slightly to the right, and its apex to the left side of 
 the body ; but with each ventricular systole, it raises itself 
 up, the apex is sent forward, and moved a little from left to 
 right. The movement from left to right is a necessary con- 
 sequence of the course of the superficial fibres. The fibres 
 on the anterior surface of the organ are longer than those on 
 the posterior surface, and pass from the base, which is com- 
 paratively fixed, to the apex, which is movable. From this 
 anatomical arrangement the heart is moved upwards and 
 forwards. Their course, from the base to the apex, is from 
 right to left ; and as they shorten, the apex is of necessity 
 slightly moved from left to right. 
 
 The locomotion of the entire heart forwards was observed 
 by Harvey in the case of the son of the Viscount Montgom- 
 ery. "The young man, aged about nineteen years, suffered a 
 severe injury to the chest, resulting in an abscess, which on 
 cicatrization left an opening into which Harvey could intro- 
 duce three fingers and the thumb. This opening was directly 
 over the apex of the heart. The action of the portion of the 
 heart thus exposed is described by Harvey in the following 
 words : 
 
 "We also particularly observed the movements of the 
 heart, viz. : that in the diastole it was retracted and with- 
 drawn; whilst in the systole it emerged and protruded; 
 and the systole of the heart took place at the moment the 
 diastole or pulse in the wrist was perceived. To conclude, the 
 heart struck the walls of the chest, and became prominent at 
 the time it bounded upward and underwent contraction on 
 itself." 1 
 
 1 HARVEY, op. cit., p. 384. 
 
MOVEMENTS OF THE HEAKT. 187 
 
 The locomotion of the heart takes place in the direction 
 of its axis, and is due to the sudden distention of the great 
 vessels at its base. These vessels are eminently elastic, and 
 as they receive the charge of blood from the ventricles, be- 
 come enlarged in every direction, and consequently project 
 the entire organ against the walls of the chest. This 
 movement is somewhat aided by the recoil of the ventricles 
 as they discharge their contents. The displacement of the 
 heart during its systole has long been observed in vivisec- 
 tions, and may be demonstrated in any of the mammals. 
 The most interesting observations on this point are those of 
 Chauveau and Faivre, which were made upon a monkey. 
 In this animal, in which the position of the heart is very 
 much the same as in the human subject, the locomotion of 
 the organ was fully established. 1 
 
 Twisting of the Heart. The spiral course of the super- 
 ficial fibres would lead us to look for another phenomenon 
 accompanying its contraction, namely, twisting. If we 
 attentively watch the apex of the heart, especially when its 
 action has become a little retarded, there is a palpable twist- 
 ing of the point upon itself from left to right with the systole, 
 and an untwisting with the diastole. 
 
 Hardening of the Heart. If the heart of a living ani- 
 mal be grasped by the hand, it will be observed that at each 
 systole it becomes hardened. The fact that it is composed 
 almost exclusively of fibres resembling very closely those of 
 the voluntary muscles, explains this phenomenon. Like any 
 other muscle, during contraction it is sensibly hardened. 
 
 Shortening and Elongation of the Heart. The foregoing 
 phenomena are admitted by all writers on physiology, .and 
 
 1 Nbuvelles Rccherches experimentales sur les Mouvements et les Bruits nor- 
 maux du Coeur, envisages au point de vue de la Physiologie Medicate. Par A. 
 CHAUVEAU et J. FAIVRE, Paris, 1856, p. 24. 
 
188 CIRCULATION. 
 
 can easily be observed ; but the change in length of the heart 
 during its systole has been, and is now, a matter of discussion. 
 All who have studied the heart in action have observed 
 changes in length during contraction and relaxation ; but the 
 contemporaries of Harvey were divided as to the periods in 
 the heart's action which are Attended with elongation and 
 shortening. Harvey himself is not absolutely definite on this 
 point. In one passage he says, in describing the systole, 
 " that it is everywhere contracted, but especially towards the 
 sides, so that it looks narrower, relatively longer ', more drawn 
 together." ' In his description of the case of the Yiscount 
 Montgomery, who suffered from ectopia cordis, he states that 
 during the systole, the heart " emerged and protruded." * Ye- 
 salius, Riolan, Fontana, and some others, contended for elon- 
 gation during the systole; but Haller, Steno, Lancisi, and 
 Bassuel contended that it shortened. The view generally 
 entertained at the present day is that the heart becomes 
 shorter during its systole; but there are some eminent au- 
 thorities who hold an opposite opinion. Among the latter 
 may be mentioned Drs. Pennock and Moore, who made a 
 great number of experiments on the action of the heart in 
 sheep and young calves. These experiments were made in 
 Philadelphia in 1839, and it was apparently demonstrated 
 that the heart elongated to such a marked degree, that the 
 distance could be measured with a shoemaker's rule. In one 
 experiment (a ewe one year old), the elongation was a quarter 
 of an inch. 3 Of all the writers of systematic works on phy- 
 siology, Prof. Dalton is the only one, as far as we know, who 
 accepts this view. 4 The experiments of this observer appa- 
 
 1 HARVEY'S Works, published by the Sydenham Society, p. 21. 
 
 3 Ibid., p. 384. 
 
 8 HOPE, on the Heart. American Edition by PENNOCK, Philadelphia, 1846, 
 p. 59. 
 
 4 DALTON, A Treatise on Human Physiology, Philadelphia, 1864, third edition, 
 pp. 275, 276. The heart of the eel is said by Haller to elongate during its 
 ventricular systole, though this is denied by Fontana (Memoires de Haller* Lau- 
 
MOVEMENTS OF THE HEART. 189 
 
 rently confirm those of Drs. Pennock and Moore. Some 
 experiments made by the author a few years ago, published 
 in the "American Journal of Medical Sciences," Oct. 1861, 
 had apparently the same result. There is no doubt that the 
 point of the heart is protruded during the ventricular systole, 
 as the experiments referred to conclusively prove ; but the 
 author was led by the perusal of recent experiments by Chau- 
 veau and Faivre, to recognize the fact that this protrusion is 
 probably due to other causes than the elongation of the ven- 
 tricles, and that during the systole the ventricles are short- 
 ened. The experiment cited by these eminent physiologists 
 is very simple and conclusive. It is made by suddenly 
 cutting the heart out of a warm-blooded animal, and watch- 
 ing the phenomena which accompany the few regular con- 
 tractions which follow. They found that the ventricles 
 invariably shortened during the systole. This could easily 
 be appreciated by the eye, but more readily if the point 
 of the organ were brought just in contact with a plane 
 surface at right angles, when at each contraction it is 
 unmistakably observed to recede. 1 This experiment we 
 have lately repeated before the class of the Bellevue Hos- 
 pital Medical College, and have satisfied ourselves of its 
 accuracy. A large Newfoundland pup, about nine months 
 old, was poisoned with woorara, artificial respiration was 
 kept up, and the heart exposed. After showing the protru- 
 sion of the point and the apparent elongation while in the 
 
 sanne, 1760, tome iii., p. 224) ; but in experimenting on the organ after excision, 
 the position in which it is held is important. If, for example, we take the heart 
 of a turtle between the thumb and finger and hold it with the point upwards, the 
 ventricle is so thin and flabby that it will become flattened during the intervals 
 of contraction, and the point will be considerably elevated at each systole ; but if 
 we reverse the position and allow the point to hang down, it will be drawn up and 
 the ventricle will shorten with the systole. 
 
 1 CHAUVEAU ET FAIVRE, op. cit., p. 14. These observers show the shorten 
 ing of the heart during its systole by holding it by the great vessels with the point 
 down. It is more free from sources of error to observe the phenomena as the 
 heart lies on a flat surface. 
 
190 CIRCULATION. 
 
 chest, the organ was rapidly removed, placed upon th table, 
 and confined by two long needles passed through the base, 
 pinning it to the wood. It contracted for one or two min- 
 utes; and at each systole, the ventricles were manifestly 
 shortened. The point was then placed against an upright, 
 and it receded with each systole about an eighth of an inch. 
 This phenomenon was apparent to all present. 
 
 In another experiment, performed a few weeks later, the 
 heart, which had been exposed in the same way, was exam- 
 ined in situ by pinning it with two needles to a thin board 
 passed under the organ. The presence of these needles did 
 not seem to interfere with the heart's action, and at each 
 ventricular systole the point evidently approached the base. 
 To render this absolutely certain, a knife was fixed in the 
 wood at right angles to and touching the point during the 
 diastole, and a small silver tube was introduced through the 
 walls into the left ventricle. At each contraction, a jet of 
 blood spurted out through the tube, and the point of the heart 
 receded from the knife about an eighth of an inch. The 
 animal experimented upon was a dog a little above the me- 
 dium size. 
 
 These simple experiments demonstrate that, in the dog 
 at least, the ventricles shorten during their systole. The 
 arrangement of the muscular fibres is too nearly identical in 
 the heart of the warm-blooded animals to leave room for 
 doubt that it also shortens in the human subject. 
 
 The error which has arisen in this respect, and which 
 obtained in our former experiments, is due to the locomotion 
 and protrusion of the entire organ, so as to make the point 
 strike against the chest. A little reflection indicates the 
 mechanism of this phenomenon. . During the intervals of 
 contraction, the great vessels, particularly the aorta and pul- 
 monary artery, which attach the base of the heart to the pos- 
 terior wall of the thorax, are filled, but not distended, with 
 blood ; at each systole, however, these vessels are distended 
 to their utmost capacity ; their elastic coats permit of con- 
 
IMPULSE OF THE HEAKT. 191 
 
 siderable enlargement, as can be seen in the living animal, 
 and this enlargement, taking place in every direction, pushes 
 the whole organ forward. We have also considerable loco- 
 motion of the heart from recoil. It is for this reason that, 
 observing the heart in situ, the ventricles seem to elongate, 
 and an instrument applied to it apparently indicates removal 
 of the apex from the base. It is only when we examine the 
 heart firmly fixed, or contracting after it is removed from the 
 body, that we can appreciate the actual changes which occur 
 in the length of the ventricles. 1 
 
 In addition to these marked changes in form, position, 
 etc., which the heart undergoes during its action, we observe, 
 on careful examination, that the surface of the ventricles 
 becomes marked with slight longitudinal ridges during the 
 systole. This was not observed by Harvey, but is men- 
 tioned by Haller. 2 
 
 Impulse of the Heart. Each movement of the heart pro- 
 duces an impulse, which can be readily felt and sometimes 
 seen, in the fifth intercostal space, a little to the left of the 
 median line. Yivisections have demonstrated that the impulse 
 is synchronous with the contraction of the ventricles. If 
 the hand be introduced into the chest of a living animal, and 
 the finger placed between the point of the heart and the 
 walls of the thorax, every time we have a hardening of the 
 point the finger will be pressed against the side. If the im- 
 pulse of the heart be felt while the linger is on the pulse, it is 
 evident that the heart strikes against the thorax at the time of 
 the distention of the arterial system. The impulse is due to 
 the locomotion of the ventricles. In the words of Harvey, 
 
 1 The observations of Fontana on the shortening of the heart are very con- 
 clusive. He constructed a little instrument consisting of two vertical rules, slid- 
 ing on a horizontal bar like a shoemaker's measure, one of which was applied to 
 the base, and the other just grazed the apex. He estimated the shortening of the 
 heart in a lamb at about two Paris lines (Mem. de Haller, tome iii., p. 225). 
 
 a Elementa Physiologies, vol. i., p. 389. 
 
192 CIRCULATION. 
 
 " the heart is erected, and rises upwards to a point, so that at 
 this time it strikes against the breast and the pulse is felt ex- 
 ternally." 1 In the case of the son of the Yiscount Mont- 
 gomery, already referred to, Harvey gives a most graphic de- 
 scription of the manner in which the heart is " retracted and 
 withdrawn " during the diastole, and " emerged and protrud- 
 ed " during the systole. 
 
 Succession of the Movements of the Seart. We have al- 
 ready followed, in a general way, the course of the blood 
 through the heart, and the successive action of the various 
 parts ; but we have yet to consider these points more in de 
 tail, and ascertain if possible the relative periods of activity 
 and repose in each portion of the organ. 
 
 The great points in the succession of movements are read- 
 ily observed in the hearts of cold-blooded animals, where the 
 pulsations are very slow. In examining the heart of the frog, 
 turtle, or alligator, the alternations of repose and activity are 
 very strongly marked. During the intervals of contraction, 
 the whole heart is flaccid, and the ventricle is comparative- 
 ly pale ; we then see the auricles slowly filling with blood ; 
 when they have become fully distended, they contract and 
 fill the ventricle, which in those animals is single ; the ven- 
 tricle immediately contracts, its action following upon the 
 contraction of the auricles as if it were propagated from 
 them. When the heart is filled with blood, it has a dark red 
 color, which contrasts strongly with its appearance after the 
 systole. This operation may occupy from ten to twenty sec- 
 onds, giving an abundance of time for observation. The' 
 case is different, however, with the warm-blooded animals, in 
 which the anatomy of the heart is nearly the same as in man. 
 Here a normal revolution may occupy less than a second, and 
 it is evident that the varied phenomena we have just men- 
 tioned are followed with the utmost difficulty. In spite of 
 this rapidity of action, it can be seen that a rapid contraction 
 
 1 Op. dt. 
 
SUCCESSION OF MOVEMENTS OF THE HEAKT. 193 
 
 
 
 of the auricles precedes the ventricular systole, and that the 
 latter is synchronous with the impulse. 
 
 Various estimates have been made of the relative time 
 occupied by the auricular and ventricular contractions. This 
 interesting point has been carefully studied by MM. Chau- 
 veau and Faivre, by auscultating the heart exposed in a living 
 animal, and establishing, by the touch, the relations between 
 the contractions of its different parts and the heart sounds. 
 These observers made a great number of experiments upon 
 horses and dogs, in which the pulse was not more accelerated 
 than the pulse of the human subject. As the result of these 
 observations, the following numbers are given as representing 
 the rhythm of the movements of the heart in man : Auricular 
 systole, 6 ; Ventricular systole, 10 ; Diastole, 8. 1 Though this 
 estimate is perhaps better than any we had before, it is evi- 
 dent from the way in which it was arrived at that it can be 
 nothing more than an approximation ; for it is impossible to 
 estimate accurately, by the stethoscope and the touch, opera- 
 tions which follow each other with such rapidity. 
 
 This question has been at last definitely settled by the 
 late observations of Marey, who has constructed some very 
 ingenious instruments for registering the form and frequency 
 of the pulse. He devised a series of most interesting experi- 
 ments, in which he was enabled to register simultaneously 
 the pulsations of the different divisions of the heart, and has 
 succeeded in establishing a definite relation between the con- 
 tractions of the auricles and ventricles. The method of M. 
 Marey enables us to determine, to a small fraction of a sec- 
 ond, the duration of the contraction of each of the divisions 
 of the heart. 
 
 The method of transmitting the movement from the heart 
 to a registering apparatus is very simple. It consists of two 
 little elastic bags connected together by an elastic tube, the 
 whole closed and filled with air. A pressure, like the pres- 
 
 1 CIIAUVEAU et FAIVRE, op. tit., p. 18. These authors represent the rhythm 
 by musical notes, which have been reduced to the numbers given above. 
 13 
 
194: CIRCULATION. 
 
 sure of the fingers, upon one of these bags produces, of course, 
 an instantaneous and corresponding dilatation of the other. If 
 we suppose one of these bags to be introduced into one of the 
 cavities of the heart, and the other placed under a small le- 
 ver, so arranged on a pivot as to be sensible to the slightest 
 impression, it is evident that a*ny compression of the bag in 
 the heart would produce a corresponding change in volume 
 in the other, which would be indicated by a movement of 
 the lever. M. Marey has arranged the lever with its short 
 arm on the elastic bag, and the long arm, provided with a 
 pen, moving against a roll of paper which passes along at a 
 uniform rate. When the lever is at rest and the paper set 
 in motion, the pen will make a horizontal mark ; but when 
 the lever ascends and descends, a corresponding trace will be 
 made, and the duration of any movement can readily be es- 
 timated by calculating the rapidity of the motion of the 
 paper. The bag which receives the impression is called by 
 Marey the initial bag, and the other, which is connected with 
 the lever, is called the terminal bag. The former may be 
 modified in form with reference to the situation in which it 
 is to be placed. 
 
 The experiments of M. Marey, with reference to the rela- 
 tions between the systole of the auricles, the systole of the 
 ventricles, and the impulse of the heart, were performed upon 
 horses in the following way : 
 
 A sound is introduced into the right side of the heart 
 through the jugular vein, an operation which is performed 
 with certainty and ease. 1 This sound is provided with two 
 initial bags, one of which is lodged in the right auricle, while 
 
 1 Catheterization of the cavities of the heart, especially upon the right side, is 
 an operation familiar to physiologists. With a double canula, such as is described 
 by Marey (p. 61), of the requisite dimensions and with the proper curves, it must 
 be easy to lodge the bags respectively in the auricle and ventricle ; especially in 
 an animal of large size like the horse. A tube is easily introduced into the right 
 side of the heart, in the dog, through the external jugular. M. Marey gives full 
 details of every step of the operation, and there can be no doubt of the facility and 
 accuracy with which it may be performed. 
 
SUCCESSION OF MOVEMENTS OF THE HEART. 
 
 195 
 
 the other passes into the ventricle. The bags are connected 
 with distinct tubes which pass one within the other, and are 
 connected by elastic tubing with the registering apparatus. 
 At each systole of the heart the bags in its cavities are com- 
 pressed, and produce corresponding movements of the levers, 
 which may be registered simultaneously. 
 
 To register the impulse of the heart, an incision- is made 
 over the point where the apex beat is felt, through the skin 
 
 FIG. 2. 
 
 Figure representing the " cardiographe " of Marey. "The instrument is composed 
 of two principal elements: A E, the registering apparatus, and AS, the sphygmo- 
 graphic apparatus, that is to say, which receives, transmits, and amplifies the 
 movements which are to be studied. " The compression exerted upon the hag c, 
 which is placed over the apex of the heart "between the intercostal muscles, is con- 
 ducted hy the tube t c, which is filled with air, to the first lever. The compression 
 exerted upon the bags o and , in the double sound, is conducted by the tubes to 
 and tv to the two remaining levers. The movements of the levers are registered 
 simultaneously by the cylinders AE. (MAREY, Sur la circulation du sang, Paris, 
 1863, p. 54.) ' 
 
 and external intercostal muscle. A little bag, stretched over 
 two metallic buttons separated by a central rod, is then care- 
 fully secured in the cavity thus formed, and connected by an 
 
196 CIRCULATION. 
 
 elastic tube with the registering apparatus. All the tubes 
 are provided with stop-cocks, so that each initial bag may be 
 made to communicate with its lever at will. "When the oper- 
 ation is concluded, and the sound firmly secured in place by 
 a ligature around the vein, the animal experiences no incon- 
 venience, is able to walk about, eat, &c., and there is every 
 evidence that the circulation is not interfered with. The 
 cylinders which carry the paper destined to receive the traces 
 are arranged to move by clock-work at a given rate. The 
 paper may also be ruled in lines, the distances between which 
 represent certain fractions of a second. 
 
 Fig. 2, taken from the work of Marey, represents the 
 apparatus reduced to one-sixth of its actual size. Two of 
 the levers are connected with the double sound for the right 
 auricle and ventricle, and one is connected with the bag des- 
 tined to receive the impulse of the heart. 
 
 In an experiment upon a horse, every thing being care- 
 fully arranged in the way indicated, the clock-work was set 
 in motion, and the movements of the three levers produced 
 traces upon the paper which were interpreted as follows : 
 
 1. The paper was ruled so that each division represented 
 one-tenth of a second. The traces formed by the three levers 
 indicated four revolutions of the heart. The first revolution 
 occupied l^ sec., the second 1-^- sec., the third 1 T V sec., and 
 the fourth 1 sec. 
 
 2. The auricular systole, as marked by the first lever, 
 immediately preceded the ventricular systole, and occupied 
 about two-tenths of a second. The elevation of the lever 
 indicated that it was much more feeble than ihe ventricular 
 systole, and sudden in its character ; the contraction, when 
 it had arrived at the maximum, being immediately fol- 
 lowed by relaxation. 
 
 3. The ventricular systole, as marked by the second lever, 
 followed immediately the auricular systole, and occupied 
 about four-tenths of a second. The almost vertical direc- 
 tion of the trace, and the degree of elevation, showed that it 
 
FORCE OF THE HEART. 197 
 
 was sudden and powerful in its character. The abrupt de- 
 scent of the lever showed that the relaxation was almost in- 
 stantaneous. 
 
 4. The impulse of the heart, as marked by the third lever, 
 was shown to be absolutely synchronous with the ventricular 
 systole. 1 
 
 Condensing the general results obtained by Marey, which 
 are of course subject to a certain amount of variation, we 
 have, dividing the action of the heart into ten equal parts, 
 three distinct periods, which occur in the following order : 
 
 Auricular Systole. -This occupies two- tenths of the heart's 
 action. It is feeble compared with the ventricular systole, 
 and relaxation immediately follows the contraction. 
 
 Ventricular Systole. This occupies four-tenths of the 
 heart's action. The contraction is powerful, and the relaxa- 
 tion sudden. It is absolutely synchronous with the impulse 
 of the heart. 
 
 Diastole. This occupies four-tenths of the heart's action. 
 
 Force of the Heart. There are few points in physiology 
 on which opinions have been more widely divergent, than on 
 the question of the force employed by the heart at each con- 
 traction. Borelli, who was the first to give a definite esti- 
 mate of this force, put it at 180,000 pounds ; while the calcu- 
 lations of Keill give only 5 ounces. 2 These estimates, how- 
 ever, were made on purely theoretical grounds. Borelli esti- 
 mated the force employed by the deltoid in sustaining a given 
 weight held at arm's length, and formed his estimate of the 
 
 1 MAREY, op. cit., p. 68 et seq. I have preferred to give the general signifi- 
 cance of the three traces obtained by Marey, rather than reproduce the traces 
 themselves, which present certain minor characters which might confuse the read- 
 er. Nothing could be more distinct than the illustration of the particular points 
 above enumerated ; and there can be no other opinion than that these observa- 
 tions settle the question of the rhythm of the heart's action in the animals on, 
 which the experiments v/ere performed. 
 
 2 JAMES KEILL, M.D., Essays on Several Parts of the Animal (Economy, Lon- 
 don, 1717, pp. 87, 91. 
 
198 CIRCULATION. 
 
 power of the heart by comparing the weight of the organ 
 with that of the deltoid. Keill made his estimate from a 
 calculation of the rapidity of the current of blood in the 
 arteries. Hales was the first to investigate the question ex- 
 perimentally, by the application of the cardiometer. He 
 showed that the pressure of blood in the aorta could be meas- 
 ured by the height to which the fluid would rise in a tube 
 connected with that vessel, and estimated the force of the 
 left ventricle by multiplying the pressure in the aorta by the 
 area of the internal surface of the ventricle. The cardiometer 
 has undergone various improvements and modifications, but 
 this is the principle which is so extensively made use of at 
 the present day, in estimating the pressure of the blood in 
 different parts of the circulatory system. First we have the 
 improvement of Poiseuille, who substituted a U tube partly 
 filled with mercury, for the long straight tube of Hales ; and 
 then the -various forms of cardiometers constructed by Magen- 
 die, Bernard, Marey, and others, which will be more fully 
 discussed in connection with the arterial circulation. These 
 instruments have been made use of by Marey, with very 
 good results, in investigating the relative force exerted by 
 the different divisions of the heart. 
 
 Hales estimates, from experiments upon living animals, 
 the height to which the blood would rise in a tube connected 
 with the aorta of the human subject, at 7 feet 6 inches, and 
 gives the area of the left ventricle as 15 square inches. From 
 this he estimates the force of the left ventricle at 51*5 pounds. 1 
 
 Though this estimate is only an approximation, it seems 
 based on more reasonable data than any other. 
 
 The apparatus of Marey for registering the contrac- 
 tions of the different cavities of the heart enabled him to as- 
 certain, also, the comparative force of the two ventricles and 
 the right auricle ; the situation of the left auricle as yet pre- 
 cluding the possibility of introducing a sound into its cavity. 
 
 1 STEPHEN HALES, B.D., F.K.S., &c., Statical Essays : Containing Hwmastaticks, 
 &c., London, 1733. Vol. II., p. 40. 
 
ACTION OF THE VALVES. 199 
 
 By first subjecting the bags to known degrees of pressure, 
 the degree of elevation of a lever may be graduated so as to 
 represent the degrees of the cardiometer. In analyzing traces 
 made by the left ventricle, right ventricle, and right auricle, 
 in the horse, Marey found that, as a general rule, the 
 comparative force of the right and left ventricles is as 1 to 3. 1 
 The force of the right auricle is comparatively insignifi- 
 cant, being in one case, as compared with the right* ventricle, 
 only as 1 to 10. 
 
 Action of the Valves. "We have already indicated the 
 course of the blood through the cavities of the heart, and it 
 has been apparent that the necessities of the circulation de- 
 mand some arrangement by which the current shall always 
 be in one direction. The anatomy of the valves which guard 
 the orifices of the ventricles gives an idea of their function ; but 
 we have yet to consider the precise mechanism by which they 
 are opened and closed, and the way in which regurgitation is 
 prevented. 
 
 In man and the warm-blooded animals, there are no 
 valves at the orifices by which the veins open into the auri- 
 cles. As has already been seen, compared with the ventri- 
 cles, the force of the auricles is insignificant ; and it has 
 furthermore been shown by experiment that the ventricles 
 may be filled with blood, and the circulation continue, when 
 the auricles are entirely passive. Though their orifices are 
 not provided with valves, the circular arrangement of the 
 fibres about the veins is such, that during the contraction 
 of the auricles the openings are materially narrowed, and re- 
 gurgitation cannot take place to any great extent. The force 
 of the blood flowing into the auricles likewise offers an obsta- 
 cle to its return. There is really no valvular apparatus which 
 operates to prevent regurgitation from the heart into the 
 veins ; for the valvular folds which are so numerous in the 
 
 1 MAREY, op. cit., p. 104. 
 
200 CIRCULATION. 
 
 general venous system, and particularly in the veins of the 
 extremities, do not exist in the vense cavse. 
 
 The continuous flow of blood from the veins into the 
 auricles, the feeble character of their contractions, the ar- 
 rangement of the fibres around the orifices of the vessels, and 
 the great size of the auriculo- ventricular openings, are condi- 
 tions which provide sufficiently well for the flow of blood into 
 the ventricles. 
 
 Auricula - Ventricular Valves. After the ventricles have 
 become completely distended by the auricular systole, they 
 take on their contraction ; which, it will be remembered, is 
 very many times more powerful than the contraction of the 
 auricles. They have to force open the valves which close the 
 orifices of the pulmonary artery and aorta, and empty their 
 contents into these vessels. To accomplish this, at the moment 
 of the ventricular systole, there is an instantaneous and com- 
 plete closure of the auriculo-ventricular valves, leaving but 
 one opening through which the blood can pass. That these 
 valves close at the moment of contraction of the ventricles is 
 demonstrated by the experiments of Chauveau and Faivre, 
 who introduced the finger through an opening into the auri- 
 cle, and actually felt the valves close at the instant of the ven- 
 tricular systole. 1 
 
 This tactile demonstration, and the fact that the first 
 sound of the heart, which is produced in great part by the 
 closure of the auriculo-ventricular valves, is absolutely syn- 
 chronous with the ventricular systole, leave no doubt as to 
 the mechanism of the closure of these valves. 
 
 It is probable that as the blood flows into the ventricles 
 the valves are slightly floated out, but they are not closed un- 
 til the ventricles contract. A German physiologist, Baum- 
 garten," has attempted to show that the valves are closed by 
 the contraction of the auricles, basing this opinion upon the 
 fact that when the auricles are cut away, and fluid is poured 
 
 1 Op. cit., p. 21. a MILNE-EDWARDS, op. cit., tome iv., p. 31. 
 
ACTION OF THE VALVES. 201 
 
 through the auriculo-ventricular opening, the valves are 
 floated up, and finally closed when the ventricle is completely 
 filled. This experiment we have repeated and found to be 
 correct ; but in this way we are far from fulfilling the natu- 
 ral conditions of the circulation. In the natural action of the 
 heart, the blood flows from the auricles in a large stream, 
 which opens the valves and applies them to the walls of the 
 ventricles. This is quite different from the action of a small 
 stream, which may insinuate itself between the lips of the 
 valves, and force them up by reacting from the ventricle. If 
 the semilunar valves be exposed, and the artery closed, a 
 stream of water poured from the ventricles will close the 
 valves ; and yet we could hardly say that in the natural course 
 of the circulation the valves at the arterial orifices are closed 
 by the ventricular systole. 
 
 These experiments do not throw any doubt upon the fact 
 that the auriculo-ventricular valves are closed by the pressure 
 of blood against them during the ventricular systole. 
 
 If a bullock's heart be prepared by cutting away the auri- 
 cles so as to expose the mitral and tricuspid valves, securing 
 the nozzles of a double syringe in the pulmonary artery and 
 aorta, after having destroyed the semilunar valves, and if 
 fluid be injected simultaneously into both ventricles, the play 
 of the valves will be exhibited. The mitral valve effectually 
 prevents the passage of the fluid, its edges being so accurately 
 approximated that not a drop passes between them ; but when 
 the pressure is considerable, a certain quantity of fluid passes 
 the tricuspid valve. There is, indeed, a certain amount of 
 insufficiency at the right auriculo-ventricular orifice, which 
 does not exist on the opposite side. 
 
 This fact was first pointed out by Mr. T. W. King, 1 and is 
 called by him the " safety-valve function of the right ven- 
 tride" The advantage of this slight insufficiency is apparent 
 on a little reflection. The right ventricle sen ds its blood to the 
 
 1 KING, An Essay on the Safety-valve Functions of the Eight Ventricle of the 
 Human Heart. Guy's Hospital Reports, 1837, vol. ii., p. 104. 
 
202 CIRCULATION. 
 
 lungs, where, in order to facilitate the respiratory processes, 
 the walls of the capillaries are very thin. The lungs them- 
 Belves are exceedingly delicate, and an effusion of blood, or 
 considerable congestion, would be liable to be followed by 
 serious consequences. To prevent this, the right ventricle is 
 not permitted to exert all its "force, under all circumstances, 
 upon the blood going into the pulmonary artery ; but when 
 the action of the heart is exaggerated from any cause, the 
 lungs are relieved by a slight regurgitation, which takes 
 place through the tricuspid valve. The lungs are still further 
 protected by the sufficiency of the mitral valve, which pro- 
 vides that no regurgitation shall take place into their substance 
 from the left heart. In the systemic circulation the capilla- 
 ries are'less delicate ; extravasation of blood would not be 
 followed by any serious results, and the circulating fluid is 
 made to pass through a considerable extent of the elastic 
 vessels, before it begins to be distributed in the tissues. It is 
 evident that on the left side there is no necessity for such a 
 provision, and it does not exist. 
 
 Aortic and Pulmonic Valves. The action of the semi- 
 lunar valves is nearly the same upon both sides. In the in- 
 tervals of the ventricular contractions, they are closed, and 
 prevent regurgitation of blood into the ventricles. The sys- 
 tole, however, overcomes the resistance of these valves, and 
 forces the contents of the ventricles into the arteries. During 
 this time the valves are applied, or nearly applied, to the 
 walls of the vessel ; but as soon as the ventricles cease their 
 contraction, the constant pressure of the blood, which, as we 
 shall see hereafter, is very great, instantaneously closes the 
 openings. 
 
 The action of the semilunar valves can be seen by cutting 
 away a portion of the ventricles in the heart of a large ani- 
 mal, securing the nozzles of a double syringe in the aorta and 
 pulmonary artery, and forcing water into the vessels. In 
 performing this experiment, it will be noticed that while the 
 
SOUNDS OF THE HEAKT. 203 
 
 aortic semilunar valves oppose the passage of the liquid so 
 effectually that the aorta may be ruptured before the valves 
 will give way, a considerable degree of insufficiency exists, 
 under a high pressure, at the orifice of the pulmonary artery. 
 There is at this orifice a safety-valve function as important 
 as that ascribed by King to the tricuspid valve. It is evi- 
 dent that the slight insufficiency at the pulmonic orifice may 
 be even more directly important in protecting the lungs than 
 the insufficiency of the tricuspid valve. The difference in 
 the sufficiency of the semilunar valves on the two sides is 
 fully as marked as between the auriculo-ventricular valves, 
 and it is surprising that since the observations of King, this 
 fact has not attracted the attention of physiologists. 1 
 
 It is probable that the corpuscles of Arantius, which 
 are situated in the middle of each valvular curtain, assist in 
 the accurate closure of the orifice. The sinuses of Yalsalva, 
 situated in the artery behind the valves, are regarded as facil- 
 itating the closure of the valves by allowing the blood to pass 
 easily behind them. 
 
 Sounds of the Heart. If the ear be applied to the prse- 
 cordial region, it will be found that the action of the heart is 
 accompanied by certain sounds. A careful study of these 
 sounds, and their modifications in disease, has enabled the 
 practical physician to distinguish, to a certain extent, the 
 conditions of the heart. This increases the purely physiologi- 
 cal interest which attaches to the audible manifestations of 
 the action of the great central organ of the circulation. 
 
 The appreciable phenomena which attend the heart's 
 action are connected with the systole of the ventricles. It is 
 this which produces the impulse against the walls of the 
 thorax, and, as we shall see further on, the dilatation of the 
 arterial system, called the pulse. It is natural, therefore, in 
 
 1 This observation was first made, and the fact publicly demonstrated, in 
 the course on physiology at the Bellevue Hospital Medical College, session of 
 1864-'65. 
 
204: CIRCULATION. 
 
 studying these phenomena, to take the systole as a point of 
 departure, instead of the action of the auricles, which we 
 cannot appreciate without vivisections ; and the sounds, 
 which are two in number, have been called first and second, 
 with reference to the systole. 
 
 The first sound is absolutely synchronous with the apex 
 beat. The second sound follows the first without any appre- 
 ciable interval. Between the second and first sounds there 
 is an interval of silence. 
 
 Some writers have attempted to represent the sounds of 
 the heart, and their relations to each other, by certain sylla- 
 bles, as, "lull-dup or lull-tub ;" 1 but it seems unnecessary to 
 attempt to make a comparison, which can only be appre- 
 ciated by one who is practically acquainted with the heart- 
 sounds, when the sounds themselves can be so easily studied. 
 
 Both sounds are generally heard with distinctness over 
 any part of the prsecordia. The first sound is heard with its 
 maximum of intensity over the body of the heart, a little 
 below and within the nipple, between the fourth and fifth 
 ribs, and is propagated with greatest facility downwards, 
 towards the apex. The second sound is heard with its max- 
 imum of intensity at the base of the heart, between the nipple 
 and the sternum, about the locality of the third rib, and is 
 propagated upwards, along the course of the great vessels. 
 
 The rhythm of the sounds bears a certain relation to the 
 rhythm of the heart's action, which we have already dis- 
 cussed ; the difference being, that we here regard the heart's 
 action as commencing with the systole of the ventricles, while 
 in following the action of different parts of the organ, we 
 followed the course of the blood, and commenced with the 
 systole of the auricles. Laennec, the father of auscultation, 
 was the first to direct special attention to the rhythm of these 
 sounds, though they had been recognized by Harvey, who 
 compared them to the sounds made by the passage of fluids 
 
 1 C. J. B. WILLIAMS, in Dunglison's Human Physiology. Philadelphia, 1856, 
 voL L, p. 393. 
 
SOUNDS OF THE HEART. 205 
 
 along the oesophagus of a horse when drinking. 1 He divides 
 a single revolution of the heart into four parts : the first two 
 parts are occupied by the first sound ; the third part by the 
 second sound ; and in the fourth part there is no sound. 2 
 He regards the second sound as following immediately after 
 the first. Some authors have described a " short silence " as 
 occurring after the first sound, and a " long silence " after 
 the second. The short silence, if appreciable at all, is so 
 indistinct that it may practically be disregarded. 
 
 Attempts have been made to improve upon this division 
 of Laennec, by dividing the heart's action into three equal 
 parts, as is done by M. Beau ; 3 the first being occupied by 
 the first sound, the second by the second sound, and the third, 
 silence. This hardly needs discussion. M. Beau bases this 
 division upon a theory of the production of the sounds which, 
 though pretty generally discussed by physiologists, is, as far 
 as we have seen, adopted by none, and is so entirely opposed 
 to facts that it hardly demands comment. It is evident to 
 any one who has heard the sounds of the heart, that the first 
 is longer than the second. 
 
 Most physiologists regard the duration of the first sound 
 as a little less than two-fourths of the heart's action, and the 
 second sound as a little more than one-fourth. When we 
 come to consider the mechanism of the production of the two 
 sounds, we shall see that if our views on that point be correct, 
 the first sound should occupy the period of the ventricular 
 systole, or four-tenths of the heart's action, the second sound 
 about three-tenths, and the repose three-tenths. 
 * The first sound is relatively dull, low in pitch, and made 
 up of two elements : one, a valvular element, in which it 
 resembles in character the second sound; the other, an ele- 
 ment which is due to the action of the heart as a muscle. 
 It has been ascertained that all muscular contraction is at- 
 
 1 Op. dt, p. 32. 
 
 9 LAENNEC, Traite de V Auxcuttatian, Mediate, Paris, 1837, tome in., p. 48. 
 3 BEAU, Traite expcrimentale et clinique d 1 Auscultation, Paris. 1856, p. 228. 
 
206 CIKCULATIOK". 
 
 tended with a certain sound. To this is added an impulsion 
 element, which is produced by the striking of the heart against 
 the walls of the thorax. 
 
 The second sound is relatively sharp, high in pitch, and 
 has but one clear, element, which we have already alluded to 
 as valvular. 
 
 Cause of the Sounds of the Heart. There is now 
 scarcely any difference of opinion respecting the cause of the 
 second sound of the heart. The experiments of Rouanet, 
 published in 1832, settled beyond a doubt that it was due to 
 a closure of the aortic and pulmonary semilunar valves. In 
 his essay upon this subject, Bouanet acknowledges his indebt- 
 edness, for the first suggestion of this explanation, to Mr 
 Carswell, who was at that time prosecuting his studies in 
 Paris. 1 
 
 The experiments by which this is demonstrated are as 
 simple as they are conclusive. First we have the experi- 
 ments of Rouanet, who imitated the second sound by produ- 
 cing sudden closure of the aortic valves by a column of water. 
 We then have the experiments, even more conclusive, of the 
 British Commission, in which the semilunar valves were 
 caught up by curved hooks introduced through the vessels 
 of a living animal, the ass, with the result of abolishing the 
 second sound, and substituting for it a hissing murmur. 
 When the instruments were withdrawn, and the valves per- 
 mitted to resume their action, the normal sound returned. 3 
 
 It is unnecessary to discuss the various theories which 
 have been advanced to explain the second sound, as it is now, 
 generally acknowledged to he due to the sudden closure of the 
 
 1 Cydop&dia of Anatomy and Physiology, vol. ii., p. 617. In this article, we 
 find Dr. Elliott, of Carlisle, alluded to as having stated in his thesis, published in 
 1831, " that the second sound of the heart is dependent upon the rush of blood 
 from the auricles into the ventricles during their diastole, and also upon the sud- 
 den flapping inward of the sigmoid valves at the origin of the large arteries by the 
 refluent blood." 
 8 Ibid., p. 618. 
 
CAUSE OF THE SOUNDS OF THE HEART. 207 
 
 semilunar valves at the orifices of the aorta and pulmonary 
 artery. We remark, however, that the sound is heard with 
 its maximum of intensity over the site of these valves, and is 
 propagated along the great vessels, to which they are attach- 
 ed. It also occurs precisely at the time of their closure ; i. e., 
 immediately following the ventricular systole. 
 
 The cause of the first sound of the heart has not, until 
 within a few years, been as well understood. It was maintain- 
 ed by Rouanet, that this sound was produced by the sudden 
 closure of the auriculo- ventricular valves ', but the situation 
 of these valves rendered it difficult to demonstrate this by 
 actual experiment. We have already seen, that while the 
 second sound is purely valvular in its character, the first 
 sound is composed of a certain number of different elements ; 
 but auscultatory experiments have been made by which all 
 but the valvular element are eliminated, and the character 
 of the first sound made to resemble that of the second. Con- 
 clusive observations on this point were made a few years ago 
 by Dr. Flint, constituting part of an essay which received 
 the prize of the American Medical Association in 1858. 1 
 
 The following facts were developed in this essay : 
 
 1. If a folded handkerchief be placed between the stetho- 
 scope and integument, the first sound is divested of some of 
 its most distinctive features. It loses the quality of impul- 
 sion, and presents a well-marked valvular quality. 
 
 2. In many instances, when the stethoscope is applied to 
 the praecordia, while the subject is in a recumbent posture, and 
 the heart by force of gravity is removed from the anterior 
 wall of the thorax, the first sound becomes purely valvular 
 in character, and as short as the second. 
 
 3. When the stethoscope is applied to the chest a little 
 distance from the point where the first sound is heard with 
 its maximum of intensity, it will present only its valvular 
 element. 
 
 1 AUSTIN FLINT, Prize Essay on the Heart-Sounds in Health and Disease. 
 Transactions of the American Medical Association, 1858. 
 
208 CIRCULATION. 
 
 These facts, to which we may add the modifications of 
 the first sound in disease, so as to leave only the valvular ele- 
 ment, taken in connection with the fact that the first sound 
 occurs when the ventricles contract, and necessarily accom- 
 panies the closure of the auriculo-ventricular valves, show 
 pretty conclusively that these valves produce at least a cer- 
 tain element of the sound. In further support of this opinion, 
 we have the fact that the first sound is heard with its maxi- 
 mum of intensity over the site of the valves, and is propa- 
 gated downwards along the ventricles, to which the valves 
 are attached. 
 
 Actual experiments are not wanting to confirm the above 
 view. Chauveau andFaivre 1 have succeeded in abolishing 
 the first sound by the introduction of a wire ring through a 
 little opening in the auricle into the auriculo-ventricular ori- 
 fice, so arranged as to prevent the closure of the valves. 
 When this is done, the first sound is lost ; but on taking it out 
 of the opening, the sound returns. These observers also 
 abolished the first sound by introducing a small curved 
 tenotomy-knife through the auriculo-ventricular orifice, and 
 dividing the chordae tendinese. In this experiment a loud rush- 
 ing murmur took the place of the sound. We have already 
 alluded to the experiment of introducing the finger through 
 an opening in the auricle ; if this be done, and the heart be 
 auscultated at the same time, the valves will be felt striking 
 against the finger in unison with the first sound. 
 
 The above observations and experiments settle beyond 
 question the fact that the closure of the auriculo-ventricular 
 valves produces one element of the first sound. 
 
 The other elements which enter into the composition of 
 the first sound are not as prominent as the one we have just 
 considered, though they serve to give it its prolonged and 
 " booming " character. These elements are, a sound like that 
 produced by any large muscle during its contraction, called 
 
 1 Op. cit., pp. 30 and 81. 
 
CAUSE OF THE SOUNDS OF THE HEART. 209 
 
 by some the muscular murmur, and the sound produced by 
 the impulse of the heart against the walls of the chest. 
 
 The muscular sound has been recognized by Wollaston, 
 Laennec, and others, and by Laennec was supposed to be 
 the sole cause of the first sound of the heart. This observer 
 attributed the first sound to the muscular action of the ven- 
 tricles, and the second to the action of the auricles. There 
 can be no doubt but that this is one of the elements of the first 
 sound ; and it is this which gives it its prolonged character, 
 when the stethoscope is applied over the body of the organ, 
 as the sound produced in muscles continues during the whole 
 period of their contraction. Admitting this to be an element 
 of the first sound, we can understand how its duration must 
 necessarily coincide with the ventricular systole. We can 
 appreciate, also, how all but the valvular element is eliminated 
 when the stethoscope is moved from the body of the heart, 
 the muscular sound not being propagated as completely as 
 the sound made by the closure of the valves. 
 
 The impulse of the heart against the walls of the thorax 
 also contributes to produce the first sound. This is demon- 
 strated by noting the difference in the sound when the sub- 
 ject is lying upon the back, and when he is upright ; or by 
 interposing any soft substance between the stethoscope and 
 the chest, or by auscultating the heart after the sternum has been 
 removed. Under these circumstances the first sound loses its 
 booming character, retaining, however, the muscular element, 
 when the instrument is applied to the exposed organ. It was 
 thought by Magendie that the shock of the heart against the 
 chest was the sole cause of the first sound. 1 This observer 
 maintained that when the sternum is removed in a living ani- 
 mal, the first sound cannot be heard over the heart. This, 
 however, is not the fact ; and though the element of impul- 
 sion enters into the composition of the first sound, the view 
 that it is the sole cause of this sound is not tenable. 
 
 The first sound of the heart is complex. It is pro 
 
 1 MILNE-EDWARDS, Lemons sur la Physiologic, etc., tome iv., p. 3S. 
 14 
 
210 CIRCULATION. 
 
 duced by the sudden closure of the auriculo-ventricular 
 valves at the beginning of the ventricular systole ; to which 
 are superadded the muscular sound, due to the contraction 
 of the muscular fibres of the heart, and the impulsion sound 
 due to the shock of the organ against the walls of the thorax. 
 
 The second sound is simple. It is produced by the sud- 
 den closure of the aortic and pulmonary semilunar valves, 
 immediately following the ventricular systole. 
 
 It is of the greatest importance, with reference to pathol- 
 ogy, to have a clear idea of the currents of blood through the 
 heart, with their exact relation to the sounds and intervals. 
 
 At the commencement of the first sound, the blood is 
 forcibly thrown from, the ventricles into the pulmonary 
 artery on the right side and the aorta on the left, and the 
 auriculo-ventricular valves are suddenly closed. During the 
 entire period occupied by this sound, the blood is flowing 
 rapidly through the arterial orifices, and the auricles are re- 
 ceiving blood slowly from the vense cavse and the pulmonary 
 veins. 
 
 "While the second sound is produced, the ventricles hav- 
 ing become suddenly relaxed, the recoil of the arterial walls, 
 acting upon the column of blood, immediately closes the 
 semilunar valves upon the two sides. The auricles continue 
 to dilate, and the ventricles are slowly receiving blood. 
 
 Immediately following the second sound, during the first 
 part of the interval the auricles become fully dilated ; and 
 in the last part of the interval immediately preceding the 
 first sound, the auricles contract, and the ventricles are fully 
 dilated. This completes a single revolution of the heart. 
 
CHAPTER Y. 
 
 FREQUENCY OF THE HEARTS ACTION. 
 
 Frequency of the heart's action Influence of age Influence of digestion Influ- 
 ence of posture and muscular exertion Influence of exercise Influence of 
 temperature Influence of respiration on the action of the heart Cause of 
 the rhythmical contractions of the heart Influence of the nervous system on 
 the heart Division of the pneumogastrics Galvanization of the pneumogas- 
 trics Causes of the arrest of action of the heart Blows upon the epigas- 
 trium. 
 
 Frequency of the Heart's Action. Physicians have al- 
 ways attached the greatest importance to the frequency of 
 the action of the heart, as one of the great indications of the 
 general condition of the system. The variations which are 
 met with in health, dependent upon age, sex, muscular activ- 
 ity, the condition of the digestive system, etc., point to the 
 fact that the action of the heart is closely allied to the various 
 functions of the economy, and readily sympathizes with their 
 derangements. As each ventricular systole is followed by 
 an expansion of the arteries which is readily appreciated by 
 the touch, it is more convenient to study the succession of 
 these movements by exploring the vessels, than by examina- 
 tion of the heart itself. Leaving out certain of the qualities 
 of the pulse, this becomes an exact criterion of the acts of the 
 heart. 
 
 The number of pulsations of the heart is not far from 
 seventy per minute in an adult male, and from six to ten 
 
212 CIRCULATION. 
 
 more in the female. 1 There are individual cases where the 
 pulse is normally much slower or more frequent than this, a 
 fact which must be remembered when examining the pulse 
 in disease. It is said that the pulse of Napoleon I. was only 
 forty per minute. Dr. Dun^lison mentions a case which 
 came under his own observation, in which the pulse was on 
 an average thirty-six per minute. The same author states 
 that the pulse of Sir William Congreve w T as never below one 
 hundred and twenty-eight per minute, in health. 2 It is by 
 no means unfrequent to find a healthy pulse of a hundred or 
 more per minute. 
 
 Influence of Age and Sex. In both the male and female, 
 observers have constantly found a great difference in the rapidi- 
 ty of the heart's action at different periods of life. The observa- 
 tions of Dr. Guy on this point are very numerous, and were 
 made with the utmost care with regard to the conditions of the 
 system, at the time the pulse was taken, in each case. All were 
 taken at the same hour, and with the subject in a sitting posture. 
 
 Dr. Guy found the pulsations of the heart in the foetus 
 to be pretty uniformly 140 per minute. At birth the pulse 
 is 136. It gradually diminishes during the first year to about 
 128. The second year the diminution is quite rapid, the 
 tables of Dr. Guy giving 107 as the mean frequency at two 
 years of age. After the second year, the frequency progres- 
 sively diminishes until adult life, when it is at its minimum, 
 which is about 70 per minute. It is a common, but erro- 
 neous, impression that the pulse diminishes in frequency in 
 old age. On the contrary, numerous observations show that 
 at the latter periods of life the movements of the heart be- 
 come slightly accelerated, ranging from 75 to 80. 
 
 During early life there is no marked and constant differ- 
 
 1 Most of the facts which will be referred to with regard to the frequency of 
 the pulse are taken from the article of Dr. Guy (Pulse) in Todd's Cyclopaedia of 
 Anatomy and Physiology. 
 
 a Human Physiology. Philadelphia, 1856, vol. i., p. 445. 
 
FREQUENCY OF THE HEART ? 8 ACTION. 213 
 
 ence in the rapidity of the pulse in the sexes ; but towards 
 the age of puberty, the development of the sexual peculiarities 
 is accompanied with an acceleration of the heart's action in 
 the female, which continues even into old age. The differ- 
 ence at different ages is shown in the following table, com- 
 piled by Milne-Edwards from the observations of Dr. Guy : ; 
 
 AGES. MALES. FEMALES. 
 
 Average Pulsations. Average Pulsations. 
 
 From 2 to 7 years . . 97 .... 98 
 
 8 
 
 14 
 21 
 28 
 35 
 42 
 
 14 " .84 94 
 
 21 " .. 76 .... 82 
 
 28 " . . . 73 . . . . .80 
 
 35 " . . 70 . ' . . . 78 
 
 42 " . 68 . . 78 
 
 49 " .. 70 .... 77 
 
 " 49 " 56 " . .67 76 
 
 " 56 " 63 " . . 68 . . . 77 
 
 " 63 " 70 " . .70 78 
 
 " 70 " 77 u . . 67 . . . . 81 
 
 " 77 " 84 " . .71 82 
 
 Influence of Digestion. The condition of the digestive 
 system has a marked influence on the rapidity of the pulse. 
 According to observations cited by Milne-Edwards, 2 there is 
 an increase in the pulse of from five to ten beats per minute 
 after each meal. Prolonged fasting diminishes its frequency 
 from twelve to fourteen beats. Alcohol first diminishes, and 
 afterwards accelerates, the pulse. Coffee is said by the same 
 author to accelerate the pulse in a marked degree. It has 
 been ascertained that the pulse is accelerated to a greater 
 degree by animal than by vegetable food. These variations 
 have long been recognized by physiologists. 
 
 Influence of Posture and Muscular Exertion. It has 
 been observed that attitude has a very marked influence upon, 
 the rapidity of the action of the heart. Experiments of a 
 
 1 Le$ons sur la Pkysiologie, tome iv., p. 62. 
 
 2 Loc. cit. 
 
214: CIRCULATION. 
 
 very interesting character have been made by Dr. Guy and 
 others, with a view to determine the difference in the pulse 
 in different postures. In the male, there is a difference of 
 about ten beats between standing and sitting, and fifteen 
 beats between standing and the recumbent posture. In the . 
 female, the variations with p^ition are not so great. The 
 average given by Dr. Guy is, for the male : . standing, 81 ; 
 sitting, 71 ; lying, 66 ; for the female : standing, 91 ; sitting, 
 84 ; lying, 80. This is given as the average of a large num- 
 ber of observations. There were a few instances, however, 
 in which there was scarcely any variation with posture, and 
 some in which the variation was much greater than the 
 average. In the inverted posture, the pulse was found to be 
 reduced about fifteen beats. 
 
 The question at once suggests itself whether the accelera- 
 tion of the pulse in sitting and standing may not be due, in 
 some measure, to the muscular effort required in making the 
 change of posture. This is answered by the further experi- 
 ments of Dr. Guy, in which the subjects were placed on a 
 revolving board, and the posture changed without any mus- 
 cular effort. The same results as those cited above were 
 obtained in these experiments ; showing that the difference 
 is due to the position of the body alone. In a single obser- 
 vation, Dr. Guy found the pulse, standing, to be 89 ; lying, 
 77; difference, 12. With the posture changed without any 
 muscular effort, the results were : standing, 87 ; lying, 74 ; 
 difference, 13. 
 
 Various theoretical explanations of these variations have 
 been offered by physiologists; but Dr. Guy seems to have 
 settled experimentally that the acceleration is due to, the mus- 
 cular effort required to maintain the body in the sitting and 
 standing positions. The following are the results of experi- 
 ments which bear conclusively on this point, in which it is 
 shown that when the body is carefully supported in the erect 
 or sitting posture, so as to be maintained without muscular 
 effort, the pulse is less frequent than when the subject is 
 
FBEQUENCY OF THE HEAET's ACTION. 215 
 
 standing; and furthermore that the pulse is accelerated, in 
 the recumbent posture, when the body is only partially sup- 
 ported : 
 
 "1. Difference between the pulse in the erect posture, 
 without support, and leaning in the same posture, in an 
 average of twelve experiments on the writer, 12 beats; and 
 on an average of eight experiments on other healthy males, 
 8 beats. 
 
 " 2. Difference in the frequency of the pulse in the recum- 
 bent posture, the body fully supported, and partially sup- 
 ported, 14 beats, on an average of five experiments. 
 
 " 3. Sitting posture (mean often experiments on the writer), 
 back supported, 80 ; unsupported, 87 ; difference, 7 beats. 
 
 " 4. Sitting posture with the legs raised at right angles with 
 the body (average of twenty experiments on the w r riter), back 
 unsupported, 86; supported, 68; difference, 18 beats. An 
 average of fifteen experiments of the same kind on other 
 healthy males gave the following numbers : "back unsupport- 
 ed, 80 ; supported, 68 ; a difference of 12 beats." 1 
 
 Influence of Exercise. It is a fact generally appreciated 
 that muscular exertion increases the frequency of the pul- 
 sations of the heart ; and the experiments just cited show 
 that the difference in rapidity, which is by some attributed 
 to change in posture (some positions, it is fancied, offering 
 fewer obstacles to the current of blood than others), is in 
 reality due to muscular exertion. Every one knows that the 
 action of the heart is much more rapid after violent exertion, 
 such as running, lifting, etc. Experiments on this point 
 date from quite a remote period. Bryan Robinson, who 
 published a treatise on the "Animal Economy" in 1734, 
 
 1 TODD'S Cyclopedia of Anatomy and Physiology, vol. iv., p. 188. There is 
 an apparent contradiction between these results, and results of the experiments 
 with the " revolving board." It is probable, however, that the subjects experi- 
 mented upon with the board were simply placed in the erect posture without 
 muscular effort, but maintained themselves in position without any aid. 
 
CIRCULATION. 
 
 states, as the result of observation, that a man in the recum 
 bent position has 64 pulsations per minute ; after a slow walk, 
 78 ; after walking a league and a half in an hour, 100 ; and 
 140 to 150 after running with all his might. 1 This general 
 statement, which has been repeatedly verified, shows the 
 powerful influence of the muscuiar system on the heart. The 
 fact is so familiar that it need not be further dwelt upon. 
 
 The influence of sleep upon the action of the heart reduces 
 itself almost entirely to the proposition, that during this con- 
 dition, we have an entire absence of muscular effort, and 
 consequently the number of beats is less than when the in- 
 dividual is aroused. It has been found that there is no differ- 
 ence in the pulse between sleep and perfect quiet in the 
 recumbent posture. This fact obtains in the adult male ; but 
 it is said by Quetelet that there is a marked difference in 
 females and young children, the pulse being always slower 
 during sleep. 2 
 
 Influence of Temperature. The influence of extremes of 
 temperature upon the heart is very decided. The pulse may 
 be doubled by remaining a very few minutes exposed to ex- 
 treme heat. Bence Jones and Dickinson have ascertained 
 that the pulse may be very much reduced in frequency, for 
 a short time, by the cold douche. 3 It has also been remarked 
 that the pulse is habitually more rapid in warm than in cold 
 climates. 
 
 Though many circumstances materially affect the rapidi- 
 ty of the heart's action, they do not complicate, to any great 
 extent, our examinations of the pulse in disease. In cases 
 which present considerable febrile movement, the patient is 
 generally in the recumbent posture. The variations induced 
 by violent exercise are easily recognized, while those depend- 
 ent upon temperature, the condition of the digestive system, 
 etc., are so slight that they may practically be disregarded. 
 
 1 MILNE-EDWARDS, Lemons sur la Physiologic, tome iv., p. 68. 
 
 2 Ibid. 
 
 3 Journal de la Physiologic, 1858, tome i., p. 72. 
 
INFLUENCE OF RESPIRATION ON THE HEART. 217 
 
 It is necessary to bear in mma, however, the variations which 
 exist in the sexes, and at different periods of life, as well as 
 the possibility of individual peculiarities, when the action of 
 the heart may be extraordinarily rapid or slow. 
 
 Influence of Respiration upon the Action of the Hea/rt. 
 The relations between the functions of circulation and respi- 
 ration are very intimate. One function cannot go on without 
 the other. If circulation be arrested, the muscles, being no 
 longer supplied with fresh blood, soon lose their contractile 
 power, and respiration ceases. We shall also find that circu- 
 lation is impossible if respiration be permanently arrested. 
 When respiration is imperfectly performed, the action of the 
 heart is slow and labored. All physicians are familiar with 
 the slow, full pulse, indicating labored action of the heart, 
 which occurs in profound coma. The effects of arrest of 
 respiration are marked in all parts of the circulatory system, 
 arteries, capillaries, and veins ; but the disturbances thus pro- 
 duced all react upon the heart, and the modifications which 
 take place in the action of this organ are of the greatest in- 
 terest and importance. 
 
 If the heart be exposed in a living animal, and artificial 
 respiration be kept up, though the pulsations are increased in 
 frequency and diminished in force, after a time they become 
 perfectly regular, and continue thus as long as air is ade- 
 quately supplied to the lungs. Under these circumstances 
 we have the respiration entirely at our command, and can 
 study the effects of its arrest upon the heart with the greatest 
 facility. If we arrest respiration, we observe the following 
 changes in the action of the heart : 
 
 For a few seconds pulsations go on as usual ; but in about 
 a minute they begin to diminish in frequency. At the same 
 time the heart becomes engorged with blood, a condition 
 which rapidly increases. For a time its contractions are 
 competent to discharge the entire contents of the left ventri- 
 cle into the arterial system, and a cardiometer applied to an 
 
218 CIRCULATION. 
 
 artery will indicate a great increase in the pressure of blood, 
 and a corresponding increase in the movements of the mer- 
 cury will be noted at each action of the heart ; indicating 
 that the organ is acting with an abnormal vigor. If respira- 
 tion be still discontinued, the engorgement becomes intense, 
 the heart at each diastole being distended to its utmost capa- 
 city. It now becomes incapable of emptying itself; the con- 
 tractions become very unfrequent, perhaps three or four in a 
 minute, and are progressively enfeebled. The organ is dark, 
 almost black, owing to the circulation of venous blood in its 
 substance. If respiration be not resumed, this distention 
 continues, the contractions become less frequent and more 
 feeble, and in a few minutes entirely cease. 
 
 The arrest of. the action of the heart, under these circum- 
 stances, is chiefly mechanical. The UD aerated blood passes 
 with difficulty through the capillaries of the system, and as 
 the heart is constantly at work, the arteries become immensely 
 distended. This is proven by the great increase in the arte- 
 rial pressure, while these vessels are full of black blood. If 
 we now closely examine the heart and great vessels, we are 
 able to note distinctly the order in which they become dis- 
 tended. These phenomena were particularly noticed and de- 
 scribed by Prof. Dalton, and they demonstrate conclusively 
 that in asphyxia the obstruction to the circulation commences, 
 not in the lungs, as is commonly supposed, but in the capil- 
 laries of the system, and is propagated backwards to the heart 
 through the arteries. 
 
 " The obstacle to the passage of venous blood through the 
 capillaries, therefore, is partial, not complete. But it is still 
 sufficient to produce an immediate backward engorgement of 
 the arterial system. Then the aorta becomes distended at its 
 origin, and the left ventricle and left auricle in succession, 
 being unable to relieve themselves of blood through the arte- 
 rial system, become distended in 1 a similar manner. During 
 this time the same kijid of engorgement takes place in the pul- 
 monary artery and the right cavities of the heart ; though 
 
INFLUENCE OF RESPIRATION ON THE HEAKT. 219 
 
 the distention of the pulmonary artery is never so excessive 
 as that of the aorta, either because there is less obstacle to 
 the passage of venous blood through the lungs than through 
 the general capillaries, or because the injecting force of the 
 riffht ventricle is less than that of the left, or because less 
 
 O ' 
 
 blood is supplied by the capillaries to the veins, and by the 
 veins to the right side of the heart. In either case the prin- 
 cipal accumulation is certainly in the arterial system." 1 
 
 The distention of the heart in asphyxia is therefore due to 
 the fact that uhaerated blood cannot circulate in the systemic 
 capillaries. "When thus distended, its muscular fibres become 
 paralyzed, like any muscle after a severe strain. 
 
 If respiration be resumed at any time before the heart's 
 action has entirely ceased, the organ in a few moments re- 
 sumes its normal function. "We first notice a change from 
 the dusky hue it has assumed to a vivid red, which is owing 
 to the circulation of arterial blood in its capillaries. The 
 distention then becomes gradually relieved, and for a few 
 moments the pulsations are abnormally frequent. If we now 
 open an artery, it will be found to contain red blood. An in- 
 strument applied to an artery will show a diminution of 
 arterial pressure and force of the heart's action, if the arrest 
 of respiration has been carried only far enough to moderately 
 distend the heart ; or an increase in the pressure and force of 
 the heart, if its action has been nearly arrested. A few mo- 
 ments of regular insufflation will cause the pulsations to re- 
 sume their normal character and frequency. 
 
 In the human subject, the effects of temporary or perma- 
 nent arrest of respiration on the heart, are undoubtedly the 
 same as those observed in experiments upon the warm-blood- 
 ed animals. In the same way, also, it is possible to restore 
 the normal action of the organ, if respiration be not too long 
 suspended, by the regular introduction of fresh air into the 
 lungs. The numerous examples of animation restored by 
 
 1 D ALTON, Lectures on the Physiology of the Circulation, published in the 
 Buffalo Medical Journal and New York Review, Lecture III., April, 1860. 
 
220 CIRCULATION. 
 
 artificial respiration, in drowning, etc., particularly by what 
 is known as the Marshall Hall method, are evidence of this 
 fact. In cases of asphyxia, those measures by which artificial 
 respiration is most effectually maintained have been found 
 most efficient. 
 
 Certain individuals have the power of temporarily arrest- 
 ing the action of the heart by a voluntary suspension of res- 
 piration. The most remarkable case of this kind on record 
 is that of Colonel Townshend, which is quoted in many 
 works on physiology. 1 Col. T. was said to be able to arrest 
 respiration and the action of the heart so completely as to 
 simulate death. "When in this condition, the pulse was not 
 perceptible at the wrist nor over the prsecordia, a mirror held 
 before the mouth was not tarnished, and he was to all ap- 
 pearances dead. On one occasion, in the presence of several 
 medical gentlemen, he remained in this condition for half an 
 hour ; afterwards the functions of respiration and circulation 
 becoming gradually reestablished. This, to say the least, is a 
 very remarkable case, but is credited by many physiologists. 
 
 Cause of the Rhythmical Contractions of the Heart. 
 
 The phenomena attending the action of the heart pre- 
 sent few difficulties in their investigation, compared with the 
 study of the cause of the regular contractions and relaxations, 
 which commence early in foetal development, to terminate 
 only with life. This interesting question has long engaged 
 the attention of physiologists, and has been the subject of 
 numerous experiments and speculations. It would be idle 
 to follow the various theories which have been offered to 
 account for this constant movement, except as a subject of 
 purely historical interest ; for many of them are based upon 
 a very imperfect knowledge of the phenomena of the circu- 
 
 1 DUNGLISON, Human Physiology, Philadelphia, 1856. Eighth edition, vol. i., 
 p. 405. 
 
CAUSE OF THE RHYTHMICAL CONTRACTIONS OF THE HEAKT, 221 
 
 lation, and have fallen to the ground, as science has advanced. 
 At the present day, though we are perhaps as far as ever 
 from a knowledge of the actual cause of the regular move- 
 ments, we are pretty'well acquainted with the various condi- 
 tions which modify and regulate them, and have arrived at a 
 limit of knowledge which there seems little prospect of ex- 
 ceeding. The enthusiastic dreamers of past ages hoped to 
 discover the seat of the soul and arrive at the principle of 
 life, but we are as much in the dark as were they with regard 
 to the cause of the various vital phenomena. We know, for 
 example, how to induce contraction in a living muscle, or 
 one which is just separated from the organism and has not 
 yet lost what we call its vital properties y \)Mi we must confess 
 our utter ignorance when we ask ourselves why it acts 
 in response to a stimulus. The wonderful advances we 
 have made in chemistry and microscopic anatomy do not 
 disclose the vital principle ; and when we come to examine 
 the various conditions under which the heart will continue 
 its contractions, we are arrested by the impossibility of fathom- 
 ing the mystery of the cause of contraction. The heart is, 
 anatomically, very much like the voluntary muscles ; but it 
 has a constant function to perform, and will act without any 
 palpable excitation, while the latter, which have an occa- 
 sional function, act only under the influence of a natural 
 stimulus like the nervous force, or artificial irritation. 
 The movements of the heart are not the only examples of, 
 what seems to be, spontaneous action. The ciliated epithe- 
 lium is in motion from the beginning to the end of life, and 
 will continue for a certain time even after the cells are de- 
 tached from the organism. This motion cannot be explained, 
 unless we call it an explanation to say that it is dependent 
 on vital properties. 
 
 But if we are yet ignorant of the absolute cause of the 
 rhythmical contraction of the heart, we are pretty well ac- 
 quainted with the influences which render its action regular, 
 powerful, and sufficient for the purposes of the economy. It 
 
222 CIRCULATION. 
 
 will facilitate our comprehension of this, to compare this 
 action with that of the ordinary voluntary muscles. 
 
 In the first place, every one knows that the action of the 
 heart is involuntary. We can neither arrest, retard, nor 
 accelerate its pulsations by a direct effort of the will. In this 
 statement we of course except those examples of arrest by 
 the stoppage of respiration, or acceleration by violent exer- 
 cise, etc. In this respect the heart differs from certain mus- 
 cles, like the muscles of respiration, which act involuntarily, 
 it is true, but whose action may be temporarily arrested or 
 accelerated by a direct voluntary effort. 
 
 The last-mentioned fact gives us the precise difference 
 between the heart and all other striped muscles. All of 
 them, in order to contract, must receive a stimulus, either 
 natural or artificial. The natural stimulus comes from the 
 nervous centres, and is conducted by the nerves. If the nerves 
 going to any of the respiratory muscles, for example, be 
 divided, the muscle is paralyzed, and will not contract with- 
 out some kind of irritation. Connection with the nervous 
 system does not seem necessary to the action of the heart, for 
 it will contract, especially in the cold-blooded animals, some 
 time after its removal from the body. 
 
 When a muscle has been removed from the body, and is 
 subjected to a stimulus, such as galvanism, mechanical or 
 chemical irritation, it is thrown into contraction ; but if care- 
 fully protected from irritation, will remain quiescent. Con- 
 traction in this instance is evidently produced by the appli- 
 cation of the stimulus ; but the question arises, Why does the 
 muscle thus respond to stimulation ? This is a question which 
 it is impossible to answer satisfactorily, but one concerning 
 which our ideas, since the time of Haller, have assumed a 
 definite form. This great physiologist called the property 
 which causes the muscle thus to contract, irritability which 
 is nothing more nor less than an unexplained property in- 
 herent in the muscle, and continuing as long as it retain^ its 
 absolute physical and chemical integrity. More than a hun- 
 
CAUSE OF THE RHYTHMICAL CONTRACTIONS OF THE HEART. 223 
 
 dred years ago, Haller described certain tissues of the body 
 which possessed this "irritability," such as the muscles, 
 stomach, bladder, etc., and the different degrees of irritability 
 with which each one was endowed. 1 He applied this theory 
 to the action of the heart, which he considered as the part 
 endowed with irritability to the highest degree. His theory 
 of the action of the heart was that its rhythmical contraction 
 depended upon the irritability inherent in its muscular fibres. 
 He was far from denying the various influences which modi- 
 fied this action, but regarded its actual power of contraction 
 as independent. It will be interesting to review some of the 
 facts which were established by Haller, and by numerous 
 physiologists who have since investigated this subject, and 
 see how far this view of the independence of the contractile 
 power of the heart accords with the present state of our 
 knowledge. 
 
 Experiments have shown that the heart will pulsate for a 
 time when removed from all connection with other parts of 
 the organism. 2 In the cold-blooded animals, in which the 
 irritability of the tissues remains for some time after death, 
 this is particularly marked. It is not the blood in the cavi- 
 ties of the heart which causes it to contract, for it will pul- 
 sate when its cavities have been 'emptied. It is not the con- 
 
 1 HALLER, Memoires sur la Nature Sensible et Irritable des Parties du Corps 
 Animal, Lausanne, 1756, tome i. These views with regard to the cause of the 
 action of the heart were first advanced by Haller in 1739 in commentaries on the 
 " Institutes " of Boerhaave (Mem. de HALLER, p. 87). 
 
 2 Numerous instances of contractions of the heart in cold-blooded animals con- 
 tinuing for a very long time after excision, are on record. Dr. Dunglison, in his 
 work on Physiology (op. cit., vol. i., p. 408), mentions several instances where the 
 heart pulsated for from ten to twenty-four hours after removal from the body. 
 The most remarkable examples of this prolonged action were in the heart of the 
 sturgeon. In one instance, in an experiment on a large alligator, we found the heart 
 pulsating, in situ, twenty-eight hours after the animal had been killed by the injec- 
 tion of a solution of woorara. The heart was then excised, and continued to 
 beat during a long series of experiments, until it was arrested by powerful compres- 
 sion with the hand, after it had been filled with water and the vessels tied. 
 
224: CIRCULATION. 
 
 tact of the air, for the heart will pulsate in a vacuum. 1 The 
 heart does not receive its irritability from the nervous sys- 
 tem, for, when removed from the body, it has no connection 
 with the nervous system ; and it is not probable that it re- 
 ceives any influence from sympathetic ganglia which have 
 lately been discovered in its substance, for detached portions 
 of the heart will pulsate, and the contractions of the organ 
 will continue in animals poisoned with woorara, which is 
 known to paralyze the motor system of nerves. 
 
 It is unnecessary to refer to the various experiments 
 which have demonstrated the independence of the contrac- 
 tions of the heart. They are of such a simple nature that they 
 may be verified by any one who will take the trouble to ex- 
 cise the heart of a frog or turtle, place it under a small bell- 
 glass so that it will not be subject to possible irritation from 
 currents of air, and watch its pulsations. In such an observa- 
 tion as this, it is evident that for a certain time contractions, 
 more or less regular, will take place ; and the experiments 
 referred to above show that they take place without any ex- 
 ternal influence. In short, it is evident that the muscular 
 fibres of the heart possess an irritability, by virtue of which 
 they will contract intermittently for a time, though no stim- 
 ulus ~be applied; as ordinary striped muscular fibres have an 
 irritability, by virtue of which they will respond, for a time, 
 to the application of a stimulus. 
 
 It is manifestly necessary that the action of the heart 
 should be constant, regular, and powerful ; and when we say 
 that the irritability inherent in its muscular tissue is such 
 that it will contract for a time without any external stimulus, 
 we by no means assume that this is the cause of its physiolog- 
 ical action. It is only an important and incontestable prop- 
 erty of the muscular fibres of the heart, and its regular action 
 is dependent upon other circumstances. 
 
 In the first place, we have to inquire what makes the ac- 
 tion of the heart constant. The answer to this is, that the 
 
 1 JOHN REID, in Cyclopaedia of Anatomy and Physiology, vol. ii., p. 611. 
 
CAUSE OF THE RHYTHMICAL CONTRACTIONS OF THE HEART. 225 
 
 changes of nutrition, by which, through the blood circulating 
 in its substance, the waste of its tissue is constantly supplied, 
 preserves the integrity of the fibres, and keeps them, conse- 
 quently, in a condition to contract. This is true, likewise, 
 of the ordinary striped muscular fibres. If the supply of 
 blood be cut off from the substance of the heart, especially in 
 the warm-blooded animals, the organ soon loses its irritabil- 
 ity. This was beautifully shown by the experiments of 
 Erichsen. This observer, after exposing the heart in a warm- 
 blooded animal and keeping up artificial respiration, ligated 
 the coronary arteries, thus cutting off the greatest part of the 
 supply of blood to the muscular fibres. He found, as the 
 mean of six experiments, that the heart ceased pulsating, 
 though artificial respiration w r as continued, in 23^ minutes. 
 After the pulsations had ceased, they could be restored by 
 removing the ligatures and allowing the blood to circulate 
 again in the substance of the heart. 1 The same is true of the 
 irritability of ordinary muscles, as has been lately shown by 
 the experiments of Dr. Brown-Sequard, though the continu- 
 ous action of the heart undoubtedly causes these phenomena 
 to be more marked and rapid. If we take a muscle which 
 has just lost its irritability and will no longer respond to the 
 most powerful stimulus, and inject fresh blood by the artery 
 supplying it, the irritability w r ill be immediately restored. 8 
 
 In the second place, the regular and powerful contraction 
 of the Jieart is provided foi* l>y the circulation of the blood 
 through its cavities. Though the heart, removed from the 
 body, will contract for a time without a stimulus, it can be 
 made to contract during the intervals of repose by an irri- 
 tant, such as the point of a needle, or a feeble current of gal- 
 vanism. For a certain time after the heart has ceased to 
 contract spontaneously, contractions may be induced in this 
 way. This can easily be demonstrated in the heart of any 
 
 1 London Medical Gazette, July 8, 1842. - 
 
 8 BROWN-SEQUARD, Proprietes et Usages du sang rouge et du sang noir,. 
 Journal de la Physiologic, 1858, tome i., p. 95 et seq. 
 15 
 
226 CIRCULATION. 
 
 animal, warm or cold-blooded. This irritability, which is 
 manifested, under these circumstances, in precisely the same 
 way as in ordinary muscles, is different in degree in different 
 parts of the organ. Haller and others have shown that it is 
 greater in the cavities than on the surface ; for long after ir- 
 ritation applied to the exterior*fails to excite contraction, the 
 organ will respond to a stimulus applied to its interior. The 
 experiments of Haller also show that fluids in the cavities of 
 the heart have a remarkable influence in exciting and keep- 
 ing up its contractions. This observation is of much interest, 
 as showing conclusively that the presence of blood is neces- 
 sary to the natural and regular action of the heart. "We 
 quote one of the experiments on this point performed upon a 
 cat: 
 
 -x- # * T^ superior vena cava having been divid- 
 ed, and the inferior ligated, and the pulmonary artery opened, 
 and the right ventricle emptied by a sufficient compression, 
 and the aorta ligated, all with promptitude, I saw the right 
 auricle repose first, the right ventricle continued to beat for 
 some time in unison with the left ventricle, and its walls de- 
 scended toward the middle line of the heart : but this ven- 
 tricle did not delay to lose its movement the first. As for 
 the other ventricle, which could no longer empty itself into 
 the aorta, it was filled with blood, and its movement contin- 
 ued for four hours. * * * 
 
 This experiment was confirmed by numerous others. It 
 will be observed that one side of the heart was made to cease 
 its pulsations, while the other side continued to contract, by 
 simply removing the blood from its interior ; which conclu- 
 sively proves that, though the heart may act for a time in- 
 dependently, the presence of blood in its cavities is a stim- 
 ulus capable of prolonging its regular pulsations. Schiff has 
 gone still further, and succeeded in restoring the pulsations 
 in the heart of a frog, which had ceased after it had been 
 
 1 HALLER, Memoircs sur la Nature Irritable et Sensible des Parties, etc., tome 
 i., p. 363. 
 
CAUSE OF THE RHYTHMICAL CONTRACTIONS OF THE HEART. 227 
 
 emptied, by introducing a few drops of blood into the au- 
 ricle. 1 Our own experiments upon the hearts of alligators 
 and turtles show that when removed from the body and 
 emptied of blood, the pulsations are feeble, rapid, and irreg- 
 ular ; but that when filled with blood, the valves being de- 
 stroyed so as to allow free passage in both directions between 
 the auricles and ventricle, the contractions become powerful 
 and regular. In these experiments, when water was intro- 
 duced instead of blood, the pulsations became more regular 
 but were more frequent and not as powerful as when blood 
 was used. 2 These experiments show also that the action of 
 the heart may be affected by the character, particularly the 
 density, of the fluid which passes through it, which may ex- 
 plain its rapid and feeble action in anemia. 
 
 It seems w r ell established that the heart, though capable 
 of independent action, is excited to contraction by the blood 
 as it passes through its cavities. A glance at the succession 
 of its movements, particularly in the cold-blooded animals, 
 where they are so slow that the phenomena can be easily ob- 
 served, will show how these contractions are induced. If we 
 look at the organ as it is in action, we see first a disten- 
 tion of the auricle ; this is immediately followed by a con- 
 traction filling the ventricle, which in its turn contracts. 
 Undoubtedly the tension of the fibres, as well as the contact 
 of blood in its interior, acts as a stimulus ; and as all the 
 fibres of each cavity are put on the stretch at the same in- 
 stant, they contract simultaneously. The necessary regular 
 distentionof each cavity thus produces rhythmical and forcible 
 contractions ; and the mere fact that the action of the heart 
 alternately empties and dilates its cavities, insures regular 
 pulsations as long as blood is supplied, and no disturbing in- 
 fluences are in operation. 
 
 The muscular fibres of the heart are endowed with 
 
 1 MILNE-EDWARDS, op. cit., tome iv., p. 126. 
 
 2 Action of tlie Heart and Respiration, American Journal of the Medical 
 Sciences, Oct. 1861. 
 
228 CIRCULATION. 
 
 an inherent property, called irritability, by virtue of which 
 they will contract for a certain time without the application 
 of a stimulus. Irritability, manifested in this way, continues 
 so long as, by the processes of nutrition, the fibres are main- 
 tained in their integrity. The muscular tissue, however, may 
 be thrown into contraction, dufing the intervals of repose, by 
 the application of a stimulus, a property which is enjoyed 
 by all muscular fibres. The irritability manifested in this 
 way is much more marked in the interior than on the exterior 
 of the organ. Blood in contact with the lining membrane of 
 the heart acts as a stimulus in a remarkable degree, and is 
 even capable of restoring irritability after it has become ex- 
 tinct. The passage of blood through the heart is the natural 
 stimulus of the organ, and may be said to be the cause of 
 its regular pulsations, though it by no means endows the 
 fibres with their contractile properties. 
 
 Influence of the Nervous System on the Heart. 
 
 The movements of the heart, as we have seen, are not 
 directly under the control of the will ; and observations on 
 the human subject, as well as on living animals, have shown 
 that the organ is devoid of general sensibility. The latter 
 fact was demonstrated in the most satisfactory manner by Har- 
 vey in the case of the Yiscount Montgomery. In this case 
 the heart was exposed ; and Harvey found that it could be 
 touched and handled without even the knowledge of the sub- 
 ject. This has been verified in other instances in the human 
 subject. Its physiological movements are capable of being 
 influenced in a remarkable degree through the nervous sys- 
 tem, notwithstanding this insensibility, and in spite of the 
 fact that the muscular fibres composing it are capable of 
 contraction when removed from all connection with the 
 body, and that the regular pulsations can be kept up for a 
 long time "by the mere passage of blood through its cavities. 
 The influence thus exerted is so great, that some eminent au- 
 
INFLUENCE OF THE NEEVOTJS SYSTEM ON THE HEART. 229 
 
 thorities held the opinion that the cause of the irritability of 
 the organ was derived from the nerves. One of the most 
 distinguished advocates of this opinion was Legallois. This 
 observer arrested the action of the heart of the rabbit by sud- 
 denly destroying the spinal cord, from which he drew the 
 conclusion that the heart derived its contractile power from 
 the cerebro-spinal system. 1 The experiments which we have 
 already cited, showing the continuance of the heart's action 
 after excision, disprove this so completely, that it was not 
 thought worth while to discuss this view while treating of 
 the cause of its rhythmical contraction. The same may be 
 said with regard to the experiments of Brachet, in which he 
 endeavored to prove that the contractility of the heart is de- 
 rived from the cardiac plexus of the sympathetic system of 
 nerves. The fact that the heart does not depend for its con- 
 tractility upon external nervous influence may be regarded 
 as long since definitely settled ; but within a few years the 
 discovery in its substance of ganglia belonging to the sympa- 
 thetic system has revived, to some extent, the view that its 
 irritability is derived from nerves. 
 
 It is not necessary to follow out all the experiments which 
 combine to demonstrate the incorrectness of this view. Ber- 
 nard, by a series of admirably conceived experiments upon 
 the effects of the woorara poison, has succeeded in demon- 
 strating the distinction between muscular and nervous irri- 
 tability. 2 In an animal killed with this remarkable poison, 
 the functions of the motor nerves are entirely abolished ; so 
 that galvanization, or other irritation, does not produce the 
 slightest effect. Yet the muscles retain their irritability, and 
 if artificial respiration be kept up, the circulation will con- 
 tinue for a long time. The heart, by this means, seems to 
 be isolated from the nervous system as completely as if it were 
 excised; and galvanization of the pneumogastric nerves in 
 
 1 LEGALLOIS, (Euvres, tome i., p. 97. 
 
 BERNARD, Lemons sur les Effete des Substances Toxiques el Medicamen femes, 
 Paris, 1857. 
 
230 CIRCULATION. 
 
 the neck, which, in a living animal, will immediately arrest 
 its action, has no effect. On the other hand, poisoning by 
 the sulpho-cyanide of potassium destroys the muscular irrita- 
 bility, and leaves the nerves intact. By these experiments, 
 which we have frequently repeated, we can completely sep- 
 arate the nervous from the rSuscular irritability, and show 
 their entire independence of each other ; and there is every 
 reason to suppose that the heart, like the other muscles, does 
 not derive its contractility from any other system. 
 
 It is evident, however, that the heart is often powerfully 
 influenced through the nerves. Sudden and violent emotions 
 will occasionally arrest its action, and have been known to 
 produce death. Palpitations are to be accounted for in the 
 same way. Some of the modifications which we have already 
 considered, depending on exercise, digestion, etc., are effected 
 through the nerves ; and it is through this system that the 
 heart, and all the important organs of the body, are made to 
 a certain extent mutually dependent. It becomes interesting, 
 and highly important, then, to study their influences, and 
 follow out, as clearly as possible, the action of the nerves 
 which are distributed to the heart. 
 
 The anatomical connections of the heart with the nervous 
 centres are mainly through the sympathetic and the pneu- 
 mogastric nerves. We can study the influence of these nerves 
 to most advantage in two ways : first, by dividing them and 
 watching the effect of depriving the heart of their influence ; 
 and second, by exciting them by means of a feeble current 
 of galvanism. It is well known that in an animal just killed 
 the " nervous force " may be closely imitated by galvanism, 
 which is better than any other means of stimulation, as it 
 does not affect the integrity of the nerves, and the amount 
 of the irritation may be easily regulated. 1 
 
 1 We shall not discuss the effects upon the heart of sudden destruction of the 
 great nervous centres. It has been shown that the heart becomes arrested when 
 the brain is crushed, as by a blow with a hammer, when the medulla oblongata or 
 the spinal cord is suddenly destroyed ; and even the crushing of a foot, in the frog. 
 
DIVISION OF THE PNEUMOGASTRIC8. 231 
 
 Experiments on the influence of the sympathetic nerves 
 upon the heart are not quite as satisfactory as we might 
 desire. Brachet asserts that the action of the heart is imme- 
 diately arrested by destroying the cardiac plexus. 1 With 
 regard to this observation, we must take into account the 
 difficulty of making the operation, and the disturbance of the 
 heart consequent upon the necessary manipulations ; circum- 
 stances which take away much of its value. It has been 
 shown pretty conclusively, however, that stimulation of the 
 sympathetic in the neck has the effect of accelerating the 
 pulsations of the heart. 2 The extreme difficulty of dividing 
 all the branches of the sympathetic going to the organ leaves 
 a doubt as to whether such an operation would definitely 
 abridge its action. 
 
 We have next to consider the influence of the pneumo- 
 gastrics upon the heart. Experiments on these nerves are 
 made with greater facility than on the nerves of the sympa- 
 thetic system, and the results are much more satisfactory. 
 Like all the cerebro-spinal nerves, the influence generated 
 in the nervous centre from which they take their origin 
 is conducted along the nerve, and manifested at its distribu- 
 tion. When they are divided, we may be sure that, as far 
 as they are concerned, all the organs which they supply 
 are cut off from nervous influence ; and when galvanized in 
 their course, we imitate or exaggerate the influence sent from 
 the nervous centre. 
 
 The invariable effect on the heart of division of the pneu- 
 mogastric nerves in the neck is an increase in the frequency, 
 and diminution in the force, of its pulsations. One or two 
 
 has been known to produce this effect. In fine, this may be done by any exten- 
 sive injury to the nervous system ; but this fact does not teach us much with 
 regard to the physiological influences of the nerves. For example, while crush- 
 ing of the brain arrests the heart, the brain may be removed from a living animal, 
 and the heart will beat for days. Experiments upon the influence of the medulla 
 oblongata and spinal cord are by no means satisfactory. 
 
 1 Cyclopaedia of Anatomy and Physiology, vol. ii., p. 612. 
 
 3 MILNE-EDWARDS, Physiologic, tomeiv., p. 156, note. 
 
232 CIRCULATION. 
 
 writers have denied this fact, but it is confirmed bj the testi- 
 mony of nearly all experimenters. To anticipate a little in 
 the history of the pneumogastric nerves, it may be stated that 
 while they are exclusively sensitive at their origin, they receive 
 after having emerged from the cranial cavity a number of 
 filaments from various motor tierves. That they influence 
 certain muscles, is shown by their paralysis after division of 
 the nerves in the neck; as, for example, the arrest of the 
 movements of the glottis. 
 
 Having this double property of motion and sensation, and 
 being distributed in part to an organ composed almost exclu- 
 sively of muscular fibres, which, as we have seen, is not en- 
 dowed with general sensibility, we should expect that their 
 section would arrest, or at least diminish, the frequency of 
 the heart's action. "What explanation, then, can we offer for 
 the fact that this seems actually to excite the movements 
 of the heart? We will be better prepared to answer this 
 question after we have studied the effects of galvanization of 
 the nerves in a living animal, or one in which the action of 
 the heart is kept up by artificial respiration. 
 
 Numerous experiments have been made with reference to 
 the effects on the heart of galvanic currents, both feeble and 
 powerful, passed through the pneumogastrics before division, 
 of currents passed through the upper and lower extremities 
 after division, etc., a full detail of which belongs properly to 
 the physiological history of the nervous system. In this con- 
 nection, a few of these facts only need be stated. 
 
 It has been shown by repeated experiments, which we 
 have frequently confirmed, that a moderately powerful cur- 
 rent of galvanism passed through both pneumogastrics will 
 arrest the action of the heart, and that the organ will cease 
 its contractions as long as the current is continued. This 
 experiment has been performed upon living animals, both 
 with and without exposure of the heart. The arrest is not 
 due to violent and continued contraction of the muscular 
 fibres ; on the contrary, the heart is relaxed, its ventricles are 
 
GALVANIZATION OF THE PNEUMOGASTKICS. 233 
 
 flaccid, and its fibres are for the time paralyzed. The ques- 
 tion then arises whether this action is directly exerted on the 
 heart through the nerves, or whether an influence is conveyed 
 to the nervous centre, and transmitted to the heart in another 
 way. This is settled by the experiment of dividing the 
 nerves and galvanizing alternately the extremities connected 
 with the heart and those connected with the nervous centres. 
 It has been ascertained that galvanization of the extremities 
 connected with the heart arrests its action, while galvaniza- 
 tion of the central extremities has no such effect. Another 
 interesting fact also shows that the influence exerted upon 
 the heart is through the motor filaments of the pneumogas- 
 trics. It has been shown by Bernard, in a very curious series 
 of experiments which we will not fully discuss in this connec- 
 tion, that the woorara poison paralyzes only the motor nerves, 
 leaving the sensory nerves intact. If we expose the heart 
 and pneumogastric nerves in a warm-blooded animal poi- 
 soned with this agent, and continue the pulsations by keep- 
 ing up artificial respiration, we find that the most powerful 
 current of galvanism passed through the pneumogastrics has 
 no effect upon the heart. The effect of a feeble current of 
 galvanism upon the motor nerves is so like the operation of 
 the natural stimulus, or nervous force, that for a time many 
 physiologists regarded the two forces as identical. Though 
 this view is not received at the present day, it is an admitted 
 fact that by galvanism we imitate in the closest manner the 
 natural action of the motor nerves, and this has become a 
 most valuable means of investigation into the physiology of 
 the nervous system. 
 
 Though galvanization of the pneumogastrics arrests the 
 action of the heart in nearly all animals, there are some in 
 which this does not take place, as in birds ; a fact which is 
 stated by Bernard, 1 but for which he offers no explanation. 
 In some experiments instituted on this subject a few years 
 
 1 BERNARD, Physiologic et Pathologie du Systeme J!Wv<?wa;,Paris, 1858, tome iL, 
 p. 394. 
 
234 CIRCULATION. 
 
 ago on alligators, we noticed a singular peculiarity which 
 throws some light on the question we are now considering. 
 Desiring to demonstrate to the class at the New Orleans 
 School of Medicine the action of the heart in this animal, an 
 alligator six feet in length was poisoned with woorara, and 
 the heart exposed. The animal came under the influence of 
 the poison in about thirty minutes, when the dissection was 
 commenced, and was quite dead when the heart was exposed. 
 The pneumogastrics were then exposed and galvanized, with 
 the effect of promptly arresting the action of the heart. This 
 observation was verified in another experiment. "We were 
 at first at a loss to account for the absence of effect of the 
 woorara on the motor filaments of the pneumogastric nerves ; 
 but on reflection thought it might be due to slow absorption of 
 the poison in so large a cold-blooded animal. With a view 
 of ascertaining whether there is any difference in the prompt- 
 ness with which different nerves in the body are affected by 
 this agent, we made the following experiment upon a dog. 
 The animal was brought under the influence of ether, and 
 the heart, the pneumogastrics, and the sciatic nerve were 
 exposed. Galvanization of the sciatic produced muscular 
 contraction, and of the pneumogastrics arrested the heart 
 promptly. A grain of woorara, dissolved in water, was then 
 injected under the skin of the thigh. One hour after the 
 injection of the woorara, the sciatic was found insensible to 
 galvanism, but the heart could be arrested by galvanization 
 of the pneumogastrics, though it required a powerful current. 
 A weaker current diminished the frequency, and increased 
 the force, of its pulsations. 1 In this experiment, the opera- 
 tion of opening the chest undoubtedly diminished the activity 
 of absorption of the poison, and consequently retarded its ef- 
 fects upon the nervous system. Taken in connection with 
 
 1 This increase in the 'force of the heart, which accompanied the diminution in 
 the frequency of its pulsations, consequent upon feeble galvanization of the pneu- 
 mogastrics, was constantly observed in many experiments. The force of the pul- 
 sations was measured by the cardiometer. 
 
GALVANIZATION OF THE PNEUMOGASTRICS. 235 
 
 the observations on alligators, it shows that the motor nerves 
 are not all affected at the same time, and that the pneumo- 
 gastrics resist the action of this peculiar poison after the 
 motor nerves generally are paralyzed. This shows a conser- 
 vative provision of Nature which guards particularly the im- 
 portant influence exerted by these nerves upon the heart. 1 
 
 Our knowledge of the inherent properties of the muscular 
 fibres of the heart, and the effects of the passage of blood 
 through its cavities, which together are competent to keep 
 up for a time regular pulsations without the intervention of 
 the nervous system, taken in connection with the facts just 
 stated, concerning the influence of section or galvanization 
 of the pneumogastric nerves, enables us to comprehend pretty 
 well the influence of these nerves on the heart. They un- 
 doubtedly perform the important function of regulating the 
 force and frequency of its pulsations. 
 
 Hardly any reflection is necessary to convince us of the 
 importance of such a function, and how it must of necessity 
 be accomplished through the pneumogastrics. It is impor- 
 tant, of course, that the heart should act at all times with 
 nearly the same force and frequency. We have seen that 
 the inherent properties of its fibres are competent to make it 
 contract, and the necessary intermittent dilitation of its cavi- 
 ties makes these contractions assume a certain regularity ; 
 but the quantity and density of the blood are subject to very 
 considerable variations within the limits of health, which, 
 without some regulating influence, would undoubtedly cause 
 variations in the heart's action, so considerable as to be inju- 
 rious. This is shown by the comparatively inefficient and 
 palpitating action of the heart when the pneumogastrics are 
 divided. These nerves convey to the heart a constant influ- 
 ence, which we may compare to the insensible tonicity im- 
 parted to voluntary muscles by the general motor system. 
 
 1 For details of these experiments the reader is referred to an article by the 
 author, on the Action of the Heart and Respiration, in The American Journal of 
 Medical Sciences, Oct., 1861. 
 
236 CIRCULATION. 
 
 For we know that when a set of muscles on one side is par- 
 alyzed, as in facial palsy, their tonicity is lost, they become 
 flaccid, and the muscles on the other side, without any effort 
 of the will, distort the features. 
 
 "We can imitate an exaggeration of this force by a feeble 
 current of galvanism, which makes the pulsations of the heart 
 less frequent and more powerful ; or exaggerate it still more 
 by a more powerful current, which arrests the action of the 
 heart altogether. 
 
 Phenomena are not wanting in the human subject which 
 verify these views. Causes which operate through the 
 nervous system frequently produce palpitation and irregular 
 action of the heart. Cases are not uncommon in which pal- 
 pitation habitually occurs after a full meal. There are in- 
 stances on record of immediate death from arrest of the 
 heart's action from fright, anger, grief, or other severe men- 
 tal emotions. Syncope from these causes is by no means un- 
 common. In the latter instance, when the heart resumes its 
 functions, the nervous shock carried along the pneumogastrics 
 is only sufficient to arrest its action temporarily. When 
 death takes place, the shock is so great that the heart never 
 recovers from its effects. 1 
 
 Summary of certain Causes of Arrest of the Action of the 
 ^ c Heart. 
 
 In warm-blooded animals, the heart's action speedily 
 ceases after it is deprived of its natural stimulus, the blood. 
 It is not from experiments on the inferior animals alone that 
 we derive proof of this fact. It is well known that in profuse 
 hemorrhage in the human subject, the contractions of the 
 
 1 An explanation of the influence of the pneumogastric nerves on the heart, 
 very like the one we have given, is made by Longet (Traite de Physiologic, 
 Paris, 1861, tome i., p. 785); but this author assumes that the pneumogastrics 
 and 'the sympathetic have an antagonistic action, the former moderating, and the 
 latter accelerating the heart's action. 
 
CAUSES OF ARREST OF THE ACTION OF THE HEART. 237 
 
 heart are progressively enfeebled, and, when the loss of blood 
 has proceeded to a certain extent, are permanently arrested. 
 Cases of transfusion after hemorrhage show that when blood 
 is introduced, the heart may be made to resume its pulsa- 
 tions. The same result takes place in death by asthenia ; and 
 cases are on record where life has been prolonged, as in hem- 
 orrhage, by transfusion of even a small quantity of healthy 
 blood. These facts have been demonstrated on the inferior 
 animals by experiments already cited. The experiment of 
 Haller, in which the action of the right side of the heart of a 
 cat was arrested by emptying it of blood, while the left side, 
 which was filled with blood, coDtinued to pulsate, showed 
 that the absence of blood in its cavities is competent of itself 
 to arrest the heart. The experiments of Erichsen, who par- 
 alyzed the heart by ligating the coronary arteries, and Schiff, 
 who produced a local paralysis by ligating the vessel going to 
 the right ventricle, show that the heart may also be arrested 
 by. cutting off the circulation of blood in its substance. Both 
 of these causes must operate in arrest of the heart's action 
 in hemorrhage. 
 
 The mechanical causes of arrest of the heart's action are 
 of considerable pathological importance. The heart, in 
 common with other muscles, may be paralyzed by sufficient 
 mechanical injury. A violent blow upon the deltoid paralyzes 
 the arm ; a severe strain will paralyze the muscles of an 
 extremity ; in the same way excessive distention of the cav- 
 ities of the heart will arrest its pulsations. This is shown by 
 arrest of the circulation in asphyxia. "We have already seen, 
 that under these circumstances the heart is incapable of 
 forcing the unaerated blood through the systemic capillaries ; 
 it finally becomes enormously strained and distended, and 
 consequently paralyzed. The same result follows the appli- 
 cation of a ligature to the aorta. This effect may be pro- 
 duced, also, in the cold-blooded animals, in which, if the 
 heart be left undisturbed, the pulsations will continue for a 
 long time. The following experiment illustrating this point 
 
238 CIRCULATION. 
 
 was performed upon the heart of an alligator six feet in 
 length : 
 
 The animal was poisoned with woorara, and twenty-eight 
 hours after death the heart, which had been exposed and left 
 in situ, was pulsating regularly. It was then removed from 
 the body, and after some experiments on the comparative 
 force, etc., of the pulsations, when empty, and when filled 
 with blood, was filled with water, the valves having been 
 destroyed so as to allow free passage of the fluid through the 
 cavities, and the vessels ligated. " TJie ventricles, still filled 
 with water confined in their cavity, were then firmly com- 
 pressed with the hand, so as to subject the muscular fibres to 
 powerful compression. From that time the heart entirely 
 ceased its contractions, and became hard, like a muscle in a 
 state of cadaveric rigidity." ] 
 
 This experiment shows how completely and promptly the 
 heart, even of a cold-blooded animal, may be arrested in its 
 action by mechanical injury. 
 
 Cases of death from distention of the heart are not infre- 
 quent in practice. It is well established that the form of 
 organic disease which most frequently leads to sudden death 
 is that in which the heart is liable to great distention. "We 
 refer to disease at the aortic orifice. In other lesions, there 
 is not this tendency ; but when the aortic orifice is contracted, 
 or the valves are insufficient, any great disturbance of the 
 circulation will cause the heart to become engorged, which is 
 liable to produce a fatal result. 
 
 Most persons are practically familiar with the distress- 
 ing sense of suffocation which frequently follows a blow 
 upon the epigastrium. A few cases are on record of instan- 
 taneous death following a comparatively slight blow in this 
 region. We had an opportunity in the winter of 1854-'55 of 
 witnessing an autopsy in a case of this kind. A young 
 mulatto man, employed as a waiter at the Louisville Hotel, 
 received a blow in the epigastrium, while frolicking, which 
 
 1 American Journal, Oct. 1861, p. 352. 
 
CAUSES OF ARREST OF THE ACTION OF THE HEART. 239 
 
 produced instantaneous death. On post-mortem examination 
 no lesion was discovered. Though these cases are rare, they 
 are well known, and the effects are generally attributed to 
 injury of the solar plexus. The distress is precisely what 
 would occur from sudden arrest of the heart's action ; for it 
 is the blood charged with oxygen and sent by the heart to 
 the system, which supplies the wants of the tissues, and not 
 the simple entrance of air into the lungs; and arrest of the 
 circulation of arterial blood, from any cause, produces suffo- 
 cation as completely as though the trachea were ligated. 
 This fact is clearly proven by experiments in the article re- 
 ferred to above. It is a question whether the arrest of the 
 heart, if this be the pathological condition, be due to concus- 
 sion of the nervous centre, or to the direct effects of the blow 
 upon the organ itself. Our present data do not enable us to 
 answer this question definitely, but rather incline us to the 
 opinion that in such accidents the symptoms are due to direct 
 injury of the heart. An additional argument in favor of this 
 view is founded on our knowledge of the mode of operation 
 of the sympathetic system. The effects of stimulation or 
 irritation of this system are not instantaneously manifested, 
 as is the case in the cerebro-spinal system, but are developed 
 slowly and gradually. 
 
 As far as we have been able to learn by experiment, the 
 nervous influences which arrest the action of the heart oper- 
 ate through the pneumogastrics. As we have just seen, we 
 can closely imitate this action by galvanism. The causes of 
 arrest in this way are numerous. Among them may be men- 
 tioned, sudden and severe bodily pain and severe mental 
 emotions. With the exceptions of arrest of the heart from 
 loss of blood and from distention, from, whatever cause it may 
 occur, stoppage of the heart takes place through the nervous 
 system. It may be temporary, as in syncope, or it may be 
 permanent ; examples of which, though rare, are sufficiently 
 well authenticated. 
 
CHAPTEE VI. 
 
 CIRCULATION OF THE BLOOD IN THE ARTERIES. 
 
 Physiological anatomy of the arteries Course of blood in the arteries Elasticity 
 of the arteries Contractility of the arteries Locomotion of the arteries and 
 production of the pulse Form of the pulse Sphygmograph Pressure of 
 blood in the arteries Hemodynamometer Cardiometer Differential cardio- 
 meter Pressure in different parts of the arterial system Influence of respi- 
 ration on the arterial pressure Effects of hemorrhage Rapidity of the cur- 
 rent of blood in the arteries Instruments for measuring the rapidity of the 
 arterial circulation Variations in rapidity with the action of the heart Ra- 
 pidity in different parts of the arterial system Arterial murmurs. 
 
 IN man and in all animals possessed of a double heart, 
 each contraction of this organ forces a charge of blood from 
 the right ventricle into the pulmonary artery, and from the 
 left ventricle into the aorta. We have seen how the valves 
 which guard the orifices of these vessels effectually prevent 
 regurgitation during the intervals of contraction. There is, 
 therefore, but one direction in which the blood can flow in 
 obedience to this intermittent force ; and the fact that in the 
 smallest arteries there is an acceleration in the current coin- 
 cident with each contraction of the heart, which disappears 
 when the action of the heart is arrested, shows that the ven- 
 tricular systole is the prime cause of the arterial circulation. 
 
 This part of the physiology of the circulation is not as 
 simple as we might at first be led to suppose. The arteries 
 have the important function of supplying nutritive matter to 
 all the tissues, of furnishing to the glands materials out of 
 
PHYSIOLOGICAL ANATOMY OF THE AKTEEIES. 241 
 
 which the secretions are formed, and in short are the avenues 
 of supply to every part of the organism. The supply of 
 blood regulates, to a considerable extent, the process of nu- 
 trition, and has an important bearing on the general and 
 special functions. The physiological processes necessarily 
 demand considerable modifications in the quantity of arterial 
 blood which is furnished to parts at different times. For ex- 
 ample, during secretion, the glands require twice or three 
 times as much blood as in the intervals. of .their action. The 
 force of the heart, we have seen, varies but little within the 
 limits of health, and the conditions necessary to the proper 
 distribution of blood in the economy are regulated almost 
 exclusively by the arterial system. These vessels are not in- 
 ert tubes, but are endowed with elasticity, by which the cir- 
 culation is considerably facilitated, and with contractility, by 
 which the supply to any part may be modified, independent- 
 ly of the action of the heart. Sudden flushes or pallor of the 
 countenance are examples of the facility with which this may 
 be effected. It is evident, therefore, that the properties of 
 the coats of the arteries are of great physiological importance. 
 We will then commence the study of this division of the cir- 
 culatory system with a consideration of its physiological 
 anatomy. 
 
 Physiological Anatomy of the Arteries. 
 
 The vessels which carry the venous blood to the lungs 
 are branches of a great trunk which takes its origin from the 
 right ventricle. They do not differ in structure from the 
 vessels which carry the blood to the general system, except 
 in the fact that their coats are somewhat thinner and more dis- 
 tensible. The aorta, branches and ramifications of which sup- 
 ply all parts of the body, is given off from the left ventricle. 
 Just at the origin, behind the semilunar valves, the aorta has 
 three sacculated pouches, called the sinuses of Yalsalva. Be- 
 yond this point the vessels are cylindrical. As we recede 
 16 
 
242 CIRCULATION. 
 
 from the heart, the arteries branch, divide, and subdivide, 
 until they are reduced to microscopic size. The branches^ 
 with the exception of the intercostal arteries, which make 
 nearly a right angle with the thoracic aorta, are given oft' 
 at an acute . angle. As a rule, the arteries are nearly 
 straight, taking the shortest course to the parts which they 
 supply with blood ; and while the branches progressively di- 
 minish in size, but few are given off between the great trunk 
 and the minute vessels which empty into the capillary sys- 
 tem. Haller counted but twenty branches of the mesenteric 
 artery between the aorta and the capillaries .of the intestines. 1 
 So long as a vessel gives off no branches, its caliber does not 
 progressively diminish ; as the common carotids, which are 
 as large at their bifurcation as they are at their origin. 
 There are one or two instances in which vessels, though giv- 
 ing off numerous branches in their course, do not diminish 
 in size for some distance ; as the aorta, which is as large at 
 the point of division into the iliacs, as it is in the chest ; and 
 the vertebral arteries, which do not diminish in caliber until 
 they enter the foramen magnum. 2 "With these exceptions, as 
 we recede from the heart, the caliber of the vessels progres- 
 si vely diminishes. 
 
 It has long been remarked that the combined caliber of 
 the branches of an arterial trunk is much greater than that of 
 the main vessel ; so that the arterial system, as it branches, 
 increases in capacity. 
 
 The arrangement of the arteries is such that the requisite 
 supply, of blood is sent to all parts of the economy by the 
 shortest course, and with the least expenditure of force from 
 the heart. Generally the vessels are so situated as not to be 
 exposed to pressure and consequent interruption of the cur- 
 rent of blood ; but in certain situations, as about some of the 
 joints, there is necessarily some liability to occasional com- 
 
 1 Cyclopaedia of Anatomy and Physiology, vol. i., p. 220 ; and HALLER, Ele- 
 menta Physiologice, tomus i., sec. i., 17. 
 
 2 Ibid. 
 
PHYSIOLOGICAL ANATOMY OF THE ARTERIES. 243 
 
 pressiori. In some situations, also, as in the vessels going to 
 the brain, particularly in some inferior animals, it is neces- 
 sary to moderate the force of the blood current, on account 
 of the delicate structure of the organs in which they are dis- 
 tributed. Here Nature makes a provision in the shape of 
 anastomoses ; by which, on the one hand, compression of a 
 vessel simply diverts, and does not arrest, the current of 
 blood, and on the other hand, the current is rendered more 
 equable and the force of the heart moderated. 
 
 The arteries are provided with membranous sheaths, of 
 greater or less strength, as the vessels are situated in parts 
 more or less exposed to disturbing influences or accidents. 
 
 Researches into the minute anatomy of the arteries have 
 shown that they are possessed of three pretty well marked 
 coats. As these vary very considerably in arteries of different 
 sizes, in their description, it is convenient to divide the ves- 
 sels into three classes. 
 
 1. The largest arteries in which are included all that are 
 larger than the carotids and common iliacs. 
 
 2. The arteries of medium size ; that is, between the 
 carotids and iliacs and the smallest. 
 
 3. The smallest arteries / or those less than ^ to -^ of an 
 inch in diameter. 1 
 
 The largest arteries are endowed with great strength and 
 elasticity. Their external coat is composed of white or in- 
 elastic fibrous tissue. According to Kolliker, this coat is no 
 thicker in the largest vessels than in some of the vessels of 
 medium size. In some medium-sized vessels it is actually 
 thicker than in the aorta. This is the only coat which is 
 vascular. 
 
 The middle coat, on which the thickness of the vessel de- 
 
 1 This is essentially the division made by Kolliker (Manual of Human Micro- 
 scopic Anatomy, London, 1860, p. 485). Some anatomists make five or even 
 more coats to the arteries. The three coats are pretty well marked, each pos- 
 sessing distinctive properties. The numerous coats which are sometimes given, 
 are, many of them, simple layers of the same tissue. The division into three coats 
 is more simple and physiological. 
 
244 
 
 pends, is composed chiefly of the yellow elastic tissue. This 
 tissue is disposed in numerous layers. First we have a thin 
 layer of ramifying elastic fibres, and then a number of layers 
 of elastic membrane, with numerous oval longitudinal open- 
 ings, which has given it the name of the " fenestrated mem- 
 brane." According to Kolliker, between the layers of this 
 membrane are found a few unstriped or involuntary muscu- 
 lar fibres, but Robin states that muscular fibres are only found 
 in arteries of medium size. 1 ' Muscular fibres, if they exist at 
 all in the largest arteries, are very few, and of little physio- 
 logical importance. . The middle coat of the largest arteries 
 gives them their yellowish hue, and the elasticity for which 
 they are so remarkable. 
 
 The internal coat of the largest arteries does not differ 
 materially from the lining membrane of the rest of the 
 arterial system. It is identical in structure with the endo- 
 cardium, the membrane lining the cavities of the heart, and 
 is continued through the entire vascular system. It is a thin 
 homogeneous membrane, covered with a layer of elongated 
 epithelial scales, with oval nuclei, their long diameter fol- 
 lowing the direction of the vessel. 
 
 The arteries of medium size possess considerable strength, 
 some elasticity, and very great contractility. In the outer 
 and inner coats we do not distinguish any great difference 
 between them and the largest arteries, even in thickness. 
 The essential difference in the anatomy of these vessels is 
 found in the middle coat. Here we have a continuation of 
 the elastic elements found in the largest vessels, but rela- 
 tively diminished in thickness, and mingled with the fusiform 
 involuntary muscular fibres, arranged at right angles to the 
 course of the vessel. These fibres are found in the inner 
 layers of the middle coat, and, according to Robin, only in 
 arteries smaller than the carotids and primitive iliacs. In 
 arteries of medium size, like the femoral, profunda femoris, 
 radial, or ulnar, they exist in numerous 'layers. There is no 
 
 1 ROBIN, in Nysten's Dictlonnaire de Medecine, 1858. Artere. 
 
PHYSIOLOGICAL ANATOMY OF THE ARTERIES. 24:5 
 
 distinct division, as regards the middle coat, between the 
 largest arteries and those of medium size. As we recede from 
 the heart, muscular fibres gradually make their appearance 
 between the elastic layers, progressively increasing in quan- 
 tity, while the elastic element is diminished. 
 
 In the smallest arteries the external coat is thin, and dis- 
 appears just before the vessels empty into the capillary sys- 
 tem ; so that the very, smallest arterioles have only the inner 
 coat and a layer of muscular fibres. 
 
 The middle coat is composed of circular muscular fibres, 
 without any admixture of elastic elements. In vessels ^ 
 of an inch in diameter, we have two or three layers of fibres; 
 but as we near the capillaries, and as the vessels lose the ex- 
 ternal fibrous coat, these fibres have but a single layer. 1 
 
 The internal coat presents no difference from the coat in 
 other vessels, with the exception that the epithelium is less 
 distinctly marked, and is lost near the capillaries ; the mem- 
 brane being studded with longitudinal oval nuclei. 
 
 A tolerably rich plexus of vessels is found in the external 
 coats of the arteries. These are called the vasa vasorum, and 
 come from the adjacent arterioles, having no direct connec- 
 tion with the vessel on which they are distributed. A few 
 vessels penetrate the external layers of the middle coat, but 
 none are ever found in the internal coat. 
 
 Nervous filaments, principally from the sympathetic sys- 
 tem, accompany the arteries, in all probability, to their re- 
 motest ramifications : though they have not yet been demon- 
 strated in the smallest arterioles. These are not distributed 
 in the walls of the large vessels, but rather follow them in 
 their course ; their filaments of distribution being found in 
 those vessels in which the muscular element of the middle 
 coat predominates. When we come to treat of the physiology 
 of the organic system of nerves, we shall see that the " vaso- 
 
 1 The structure of the smallest arteries can be beautifully exhibited in fresh 
 microscopic preparations of the pia mater, in which the various points to which 
 we have alluded can be easily studied. 
 
24:6 CIRCULATION. 
 
 motor " nerves play an important part in regulating the 
 function of nutrition. 
 
 Course of the Eldod In the Arteries. At every pulsation 
 of the heart, all the blood contained in the ventricles, except- 
 ing, perhaps, a few drops, is forced into the great vessels. 
 We have already studied the valvular arrangement by which 
 the blood, once forced into these vessels, is prevented from 
 returning into the ventricles during the diastole. The sketch 
 we have given of the anatomy of the arteries has prepared us 
 for a complexity of phenomena in the circulation in these 
 vessels, which would not obtain if they were simple, inelastic 
 tubes. In this case the intermittent force of the heart would 
 be felt equally in all the vessels, and the arterial circulation 
 would be subject to no modifications which did not come 
 from the action of the central organ. As it is, the blood is 
 received from the heart into vessels endowed, not only with 
 great elasticity, but with contractility. The elasticity, which 
 is the prominent property of the largest arteries, moderates 
 the intermittency of the heart's action, providing a continuous 
 supply to the parts ; while the contractility of the smallest 
 arteries is capable of increasing or diminishing the supply in 
 any part, as may be required in the various functions. 
 
 Elasticity of the Arteries. This property, particularly 
 marked in large vessels, has long been recognized. If, for 
 example, we forcibly distend the aorta with water, it may be 
 dilated to more than double its ordinary capacity, and will 
 resume its original size and form as soon as the pressure is 
 removed. This simple experiment teaches us, that if the 
 force of the heart be sufficient to distend the great vessels, 
 their elasticity during the intervals of its action must be 
 continually forcing the blood toward the periphery. The 
 fact that the arteries are distended at each systole is abun- 
 dantly proven by actual experiment; though the immense 
 capacity of the arterial system, compared with the small 
 
ELASTICITY OF THE ARTERIES. 247 
 
 charge of blood which enters at each pulsation, renders the 
 actual distention of the vessels less than we should be led to 
 expect from the force of the heart's contraction. The most 
 satisfactory experiments on this subject are those of Poiseu- 
 ille. 1 This observer illustrated the dilatation of the arteries 
 in the following way : Having exposed a considerable extent 
 of the primitive carotid in a horse, he enclosed a portion in a 
 tin tube filled with water and connected with a small upright 
 graduated tube of glass. The openings around the artery, as 
 it passed in and out of the apparatus, being carefully sealed 
 with tallow, it is evident that any dilatation of the vessel 
 would be indicated by an elevation of the water in the grad- 
 uated tube. This experiment invariably showed a marked 
 dilatation of the artery with each contraction of the heart. 
 
 " We remark that the dilatation is not very considerable ; 
 thus it is not easy to recognize it by simple inspection, in an 
 artery of even the caliber of that which occupies us, after we 
 have it exposed." 2 
 
 It being fully established that the arteries are dilated with 
 each ventricular systole, it becomes important to study the 
 influence of their elasticity upon the current of blood. Divi- 
 sion of an artery in a living animal exhibits one of the im- 
 portant phenomena due to the elastic and yielding character 
 of its walls. We observe, even in vessels of considerable 
 size, as the carotid or femoral, that the flow of blood is not 
 intermittent, but remittent. With each ventricular .systole 
 there is a sudden and marked impulse ; but during the inter- 
 vals of contraction, the blood continues to flow with consid- 
 erable force. As we recede from the heart, the impulse 
 becomes less and less marked ; but it is not entirely lost, even 
 in the smallest vessels, the flow becoming constant only in 
 the capillary system. That the force of the heart is abso- 
 lutely intermittent, is shown by the following experiment : 
 
 1 POISEUILLE, Recherclies sur I 1 Action des Artfrres dans la Circulation Arte- 
 rielle. Journal de Physiologic, Paris, 1829, tome ix., p. 44. 
 
 2 Ibid., p. 48. 
 
248 i CIRCULATION. 
 
 If the organ be' exposed in a living animal, and a canula be 
 introduced through the walls into one of the ventricles, we 
 have a powerful jet at each systole, but no blood is discharged 
 during the diastole. The same absolute intermittency of the 
 current will be seen if the aorta be divided. It is evident 
 that we must look to the arferies themselves for the force 
 which produces a flow of blood in the intervals of the heart's 
 action. The conversion of the intermittent current in the 
 largest vessels into a nearly constant flow in the smallest 
 arterioles is effected by the physical property of elas- 
 ticity. This may be illustrated in any elastic tube of 
 sufficient length. If we connect with a syringe a series of 
 rubber tubes progressively diminishing in caliber, and dis- 
 charging by a very small orifice, and inject water in an in- 
 termittent current, if the apparatus be properly adjusted, 
 the fluid will be discharged at the end of the tube in a 
 continuous stream. Nearer the syringe, the stream will 
 be remittent; and directly at the point of connection' of 
 the syringe with the tube, the stream will be intermittent. 
 The intermittent impulse may be said, in this case, to be 
 progressively absorbed by the elastic walls of the tube. Each 
 impulse first distends that portion of the tube nearest to it, 
 and further on, the distention is diminished, until it becomes 
 inappreciable. If the syringe be connected with two tubes, 
 one elastic and the other inelastic, the current will be either 
 remittent or continuous in the one, and intermittent in the 
 other. 
 
 This modification of the impulse of the heart has great 
 physiological importance; for it is evidently essential that 
 the current of blood, as it flows into the delicate capillary 
 vessels, should not be alternately intermitted, and impelled 
 with the full power of the ventricle. After all, it is in the 
 capillaries that the blood performs its functions, and here we 
 should have a constant supply of the fluid in proper quantity 
 and in proper condition to meet the nutritive requirements 
 of the parts. 
 
ELASTICITY OF THE ARTERIES. 249 
 
 The elasticity of the arteries favors the flow of the blood 
 toward the capillaries by a mechanism which is easily un- 
 derstood. The blood discharged from the heart distends the 
 elastic vessel, which reacts, after the distending force ceases 
 to operate, and compresses its fluid contents. This reaction 
 would have a tendency to force the blood in two directions, 
 were it not for an instantaneous closure of the valves, which 
 makes regurgitation impossible. The influence then can only 
 be exerted in the direction of the periphery ; and, if we can 
 imagine as divided an action which is propagated with such 
 rapidity, the reaction of that portion of the vessel immedi- 
 ately distended by the heart, distends a portion farther on, 
 which in its turn distends another portion, and so the wave 
 passes along until the blood is discharged into the capillaries. 
 In this way we can see that in vessels removed a sufficient 
 distance from the heart, the force exerted on the blood by 
 the reaction of the elastic walls is competent to produce a 
 very considerable current during the intervals of the heart's 
 contraction. 
 
 This theoretical view is fully carried out by the following 
 simple and conclusive experiment of M. Marey. He con- 
 nected two tubes of equal size, one of rubber and the other 
 of glass, with the stop-cock of a large vase filled with water. 
 The elastic tube was provided with a valve near the stop- 
 cock, which prevented the reflux of fluid, and both were 
 fitted with tips of equal caliber. When, by alternately opening 
 and closing the stop-cock, water was allowed to flow into these 
 tubes in an intermittent stream, it was found that a greater 
 quantity was discharged by the elastic tube ; but an equal 
 quantity was discharged by both tubes when the stop-cock 
 was left open, and the fluid allowed to pass in a continuous 
 stream. 1 
 
 This simple experiment shows that not only does the elas- 
 ticity of the arteries convert the intermittent current in the 
 largest vessels into a current more and more nearly contin- 
 
 1 MAREY, Circulation du Sang^ Paris, 1863, pp. 128, 131. 
 
250 CIRCULATION. 
 
 nous as we approach the periphery, but that when reflux is 
 prevented, as it is by the semilunar valves, the resiliency of 
 the arteries assists the circulation. 
 
 Contractility of the Arteries. It is a fully established 
 anatomical fact that the medium-sized and smallest arteries 
 contain contractile or muscular elements ; and it is also a 
 fact, proven by actual experiment, that as a consequence of 
 the condition of these fibres, the vessels undergo considerable 
 variation in their caliber. The opinions of the older physi- 
 ologists on this question have only an historical interest, and 
 will not, therefore, be discussed. Among the more recent 
 investigations on this subject, we have the experiments of Cl. 
 Bernard and Schiif, which have been repeatedly confirmed, 
 showing that through the nervous system the muscular coats 
 of arteries may be readily made to contract or become re- 
 laxed. If the sympathetic be divided in the neck of a rab- 
 bit, in a very few minutes the arteries of the ear on that side 
 are notably dilated. If the divided extremity of the nerve 
 be feebly galvanized, the vessels soon take on contraction, and 
 may become smaller than on the opposite side. These expe- 
 riments demonstrate, in the most conclusive manner, the con- 
 tractile properties of the small arteries, and give us an idea 
 how the supply of blood to any particular part may be regu- 
 lated. The vessels may be most effectually excited through 
 the nervous system ; and it is on account of the difficulty in 
 producing marked results by direct irritation, that the older 
 physiologists were divided on the subject of their " irrita- 
 bility." 
 
 The contractility of the arteries has great physiological 
 importance. As their function is simply to supply blood to 
 the various tissues and organs, it is evident that w r hen the 
 vessels going to any particular part are dilated, the supply 
 of blood is necessarily increased. This is particularly impor 
 tant in the glands, which, during the intervals of secretion, 
 receive a comparatively small quantity of blood. Bernard 
 
CONTEACTILITY OF THE AETEEIES. 251 
 
 has shown, by a beautiful series of experiments, which will 
 be more particularly alluded to on the subject of secretion, 
 that galvanization of what he calls the motor nerve of a 
 gland dilates the vessels, largely increases the supply* of blood, 
 and induces secretion ; while galvanization of the sympathetic 
 filaments contracts the vessels, diminishes the supply of blood, 
 and arrests secretion. The pallor of parts exposed to cold, 
 and the flush produced by heat, are due, on the one hand, to 
 contraction, and on the other to dilatation of the small arter- 
 ies. Pallor and blushing from mental emotions are examples 
 of the same kind of action. 
 
 The ulterior eifects on nutrition, which result from dila- 
 tation of the vessels of a part, are of great interest. When the 
 supply of blood is much increased, as in section of the 
 sympathetic in the neck, nutrition is exaggerated, and the 
 temperature is raised beyond that of the rest of the body. 
 
 The idea, which at one time obtained, that the arteries 
 were the seat of rhythmical contractions, which had a favor- 
 able influence on the current of blood, is entirely erroneous. 1 
 It is hardly necessary to repeat that the prime cause of 
 the arterial circulation is the force of the ventricles. We 
 have seen that the elasticity of the arteries produces a flow 
 during the intervals of the heart's action, and the question 
 now arises whether the force thus exerted is simply a re- 
 turn of the force required to expand the vessels, which has 
 been borrowed, as it were, from the heart, or is something 
 superadded to the force of the heart. The experiment of 
 Marey, already alluded to, settles this question. "When 
 water was forced in an intermittent current into two tubes, 
 one elastic and the other inelastic, but discharging by open- 
 ings of equal size, by far the greater quantity was discharged 
 by the elastic tube. A little reflection will show how the 
 
 1 Schiff has noticed rhythmical contractions in the superficial arteries of the 
 ear in the rabbit, and some other animals; but this phenomenon is excep- 
 tional, and the movements do not appear to favor the current of blood. 
 (MILNE-EDWARDS, Physiologic tome, iv., p. 217.) 
 
252 CTECULATIOK". 
 
 action of the elastic arteries must actually assist the circula- 
 tion. The resiliency of the vessels is continually pressing their 
 contents toward the periphery, as regurgitation is rendered 
 impossible by the action of the semilunar valves. The dila- 
 tation of the vessels with each systole, of course, admits an 
 increased quantity of blood ; *and it has been experimentally 
 demonstrated, that the same intermittent force exerted on 
 an inelastic tube, will discharge a less quantity of liquid 
 from openings of equal caliber. 
 
 Superadded, then, to the force of the heart, we must 
 recognize, as a cause influencing the flow of blood in the 
 arteries, the resiliency of the vessels, especially those of large 
 size. 
 
 Thus it will be seen that the arteries are constantly kept 
 distended with blood by the heart, and by virtue of their 
 elasticity and the progressive increase in the capacity of this 
 system as they branch, the powerful contractions of the cen- 
 tral organ only serve to keep up an equable current in the 
 capillaries. The small vessels, by virtue of their contractile 
 walls, regulate the distribution of the blood ; acting as the 
 guards or sentinels of the process of nutrition, and, in fact, 
 all the numerous functions in which the blood is concerned. 
 Obeying the commands transmitted through the sympathetic 
 nervous system, they allow the passage to every part of the 
 proper quantity of the nutritive fluid at the proper time. 
 
 Locomotion of the Arteries and Production of the Pulse. 
 At each contraction of the heart, the arteries are increased in 
 length, and many of them undergo a considerable locomo- 
 tion. This may be readily observed in vessels which are 
 tortuous in their course, and is frequently very marked in the 
 temporal artery in old persons. The elongation may also be 
 seen if we watch attentively the point where an artery bifur- 
 cates, as at the division of the common carotid. It is simply 
 the mechanical effect of sudden distention ; which, while it 
 
PRODUCTION OF THE PULSE. 253 
 
 increases the caliber of the vessel, causes an elongation 
 even more marked. 
 
 TKe linger placed over an exposed artery, or one which 
 lies near the surface, experiences a sensation at every beat 
 of the heart, as though the vessel were striking against it. 
 This has long been observed, and is called the pulse. Ordi- 
 narily it is appreciated when the current of blood can be 
 subjected to a certain amount of obstruction, as in the radial, 
 which can readily be compressed against the bone. In an 
 artery imbedded in soft parts, which yield to pressure, the 
 actual dilatation of the vessel being very slight, pulsation is 
 felt with difficulty, if at all. When obstruction is complete, 
 as in ligation of a vessel, the pulsation above the point of 
 ligature is very marked, and can be readily appreciated by 
 the eye. The explanation of this exaggeration of the move- 
 ment is the following : JSTormally, the blood passes freely 
 through the arteries, and produces, in the smaller vessels, 
 very little movement or dilatation ; but when the current is 
 obstructed, as_by ligation, or even compression with the 
 finger, the force of the heart is not sent through the vessel to 
 the periphery, but is arrested, and therefore becomes more 
 marked and easily appreciated. In vessels which have be- 
 come undilatable and incompressible from calcareous deposit, 
 the pulse cannot be felt. The character of the pulse in- 
 dicates,, to a certain extent, the condition of the heart and 
 vessels. We have spoken, when treating of the heart, of 
 the varying rapidity of the pulse, as it is a record of the 
 rapidity of the action of this organ ; but it remains for us 
 to consider the mechanism of its production, and its various 
 characters. 
 
 Under ordinary circumstances, the pulse may be felt in 
 all arteries which are exposed to investigation ; and as it is 
 due to the movement of the blood in the vessels, the prime 
 cause of its production is the contraction of the left ventriqle. 
 The late very interesting experiments of M. Marey have 
 shown that the impulse given to the blood by the heart is 
 
254 CIRCULATION. 
 
 not felt in all the vessels at the same instant. By ingenious 
 contrivances, which will be described further on, this observer 
 has succeeded in registering simultaneously the impulse of 
 the heart, the pulse of the aorta, and the pulse of the femoral 
 artery. He has thus ascertained that the contraction of the 
 ventricle is anterior to the pulsation of the aorta, and the 
 pulsation of the aorta precedes the pulse in the femoral. 1 
 This only confirms the views of other physiologists, particu- 
 larly Weber, who described this progressive retardation of 
 the pulse as we recede from the heart, estimating the differ- 
 ence between the ventricular systole and the pulsation of the 
 artery in the foot, at one-seventh of a second. 8 The observa- 
 tions of M. Marey are particularly referred to as being the 
 most conclusive. 
 
 It is evident from what we know of the variations which 
 occur in the force of the heart's action, the quantity of blood 
 in the vessels, and from the changes which may take place in 
 the caliber of the arteries, that the character of the pulse 
 must be subject to numerous variations. Many of these may 
 be appreciated simply by the sense of touch. We find wri- 
 ters treating of the soft and compressible pulse, the hard 
 pulse, the wiry pulse, the thready pulse, etc., as indicating 
 various conditions of the circulatory system. The character 
 of the pulse, aside from its frequency, has always been re- 
 garded as of great importance in disease ; and the variations 
 w 7 hich occur in health form a most interesting subject for 
 physiological inquiry. 
 
 Form of the Pulse. It is evident that few of the charac- 
 ters of a pulsation, occupying as it does but a seventieth 
 part of a minute, can be ascertained by the sense of touch 
 
 1 MAREY, Circulation du Sang, p. 197. In an article published in the 
 Journal de la Physiologic, 1859, tome ii., p. 267, Marey took ground against 
 the" progressive retardation of the pulse in arteries removed from the heart ; but 
 in his last work the fact is admitted, and seems proven beyond a doubt. 
 
 a MILNE-EDWARDS, Physiologic, tome iv., p. 188. 
 
FORM OF THE PULSE. 255 
 
 alone. This fact lias been appreciated by physiologists ; and 
 within the last few years, in order to accurately study-this 
 important subject, instruments for registering the impulse 
 felt by the arterial system have been constructed, to enable 
 us to accurately analyze the dilatation or movements of the 
 vessels. The idea of such an instrument was probably sug- 
 gested by the following simple observation : When the legs 
 are crossed, with one knee over the other, the beating of the 
 popliteal artery will produce a marked movement in the foot. 
 If we could apply to an artery a lever provided with a mark- 
 ing point in contact with a slip of paper moving at a definite 
 rate, this point would register the movements of the vessel, 
 and its changes in caliber. The first physiologist who put 
 this in practice was Yierordt, who constructed quite a com- 
 plex instrument, so arranged that the impulse from an acces- 
 sible artery, like the radial, was conveyed to a lever, which 
 marked the movement upon a revolving cylinder of paper. 
 This instrument was called a " sphygmograph." The traces 
 made by it were perfectly regular, and simply marked the 
 extremes of dilatation, exaggerated, of course, by the length 
 of the lever, and the number of pulsations in a given time. 
 The latter can, of course, be easily estimated by more simple 
 means ; and as the former did* not convey any very definite 
 physiological idea, the apparatus was regarded rather as a 
 curiosity than an instrument for accurate research. 
 
 The principle on which the instrument of Vierordt was 
 constructed was correct, and it only remained to construct 
 one which would be easy, of application, and produce a 
 trace representing the shades of dilatation and contraction 
 of the vessels, in order to lead to important practical results. . 
 These indispensable conditions are fully realized in the 
 sphygmogragh of M. Marey, to whose researches on the cir- 
 culation we have repeatedly referred. The instrument sim- 
 ply amplifies the changes in the caliber of the vessel, without 
 deforming them ; and though its application is, perhaps, not so 
 easy as to make it generally useful in practice, in the hands 
 
256 
 
 CIRCULATION. 
 
 of Marey it has given us a definite knowledge of the physio- 
 logical character of the pulse, and its modifications in certain 
 
 FIG. 3. 
 
 Sphygmograph of Marey. The apparatus is securely fixed on the forearm, so that the 
 spring under the screw V is directly over the radial artery. The movements of the 
 pulse are transmitted to the long and light wooden lever L, and registered upon the 
 surface P, which is moved at a known rate by the clock-work H. The apparatus is so 
 adjusted that the movements of the vessel are accurately amplified and registered by 
 the extreme point of the lever. (MABEY, Recherches, etc. Journal de la jihysiologie, 
 Paris, 1860, tome iii., p. 244.) 
 
 diseases ; information which is exceedingly desirable, and 
 could not be arrived at by other means of investigation. In 
 short, its mechanism is so accurate that, when skilfully used, 
 it gives on paper the actual "form of the pulse? 
 
 FIG. 4. 
 
 Trace of Vierordt (Ibid.). 
 
 This instrument, applied to the radial artery, gives a 
 trace very different from that obtained by Yierordt, which 
 
FORM OF THE PULSE. 257 
 
 was simply a series of regular elevations and depressions. 
 A comparison of the traces obtained by these two observers 
 gives an idea of the defects which have been remedied by 
 Marey ; for it is 'evident that the dilatation and contraction of 
 
 TIG. 5. 
 
 Trace of Marey. Portions of four traces taken in different conditions of the pulse (Ibid.) 
 
 the arteries cannot be as regular and simple as would be in- 
 ferred merely from the trace made by the instrument of 
 Yierordt. 
 
 Analyzing the traces of Marey, we see that there is a 
 dilatation following the systole of the heart, marked by an 
 elevation of the lever, more or less sudden, as indicated by 
 the angle of the trace, and of greater or less amplitude. The 
 dilatation, having arrived at its maximum, is followed by 
 contraction ; which may be slow and regular, or may be, and 
 generally is, interrupted by a second and slighter upward 
 movement of the lever. This second impulse varies very 
 much in amplitude. In some rare instances it is nearly as 
 marked as the first, and may be appreciated by the finger, 
 giving the sensation of a double pulse following each con- 
 traction of the heart. This is called the dicrotic pulse. 
 
 As a rule, the first dilatation of the vessel is sudden, and 
 indicated by an almost vertical line ; this is followed by a 
 slow reaction, indicated by a gradual descent of the trace, 
 which is not, however, absolutely regular, but marked by a 
 slight elevation indicating a second impulse. 
 
 The amplitude of the trace, or the distance between the 
 highest and lowest points marked by the lever, depends upon 
 the amount of constant tension of the vessels. Marey has 
 found that the amplitude is in an inverse ratio to the tension ; 
 which is very easily understood, for when the arteries are little 
 distended, the force of the heart must be more marked in its 
 17 
 
258 CIRCULATION. 
 
 effects than when the pressure of blood in them is very great. 
 Any circumstance which facilitates the flow of blood from 
 the arteries into the capillaries, will, of course, relieve the 
 tension of the arterial system, lessen the obstacle to the force 
 of the heart, and increase the amplitude of the pulsation ; 
 and vice versa. In support of this view, Marey has found 
 that cold applied to the surface of the body, contracting, as 
 it does, the smallest arteries, increases the arterial tension 
 and diminishes the amplitude of the pulsation ; while a mod- 
 erate elevation of temperature produces an opposite effect. 
 
 In nearly all the traces given by Marey ,. the descent of 
 the lever indicates more or less oscillation of the mass of blood. 
 The physical properties of the larger arteries render this 
 inevitable. As they yield to the distending influence of the 
 heart, reaction occurs after this force is taken off, and, if the 
 distention be very great, gives a second impulse to the blood. 
 This is quite marked, unless the tension of the arterial system 
 be so great as to offer too much resistence. One of the most 
 favorable conditions for the manifestation of dicrotism is 
 diminished tension, which is always found coexisting with a 
 very marked exhibition of this phenomenon. 
 
 The delicate instrument employed by Marey enabled him 
 to accurately determine and register these various phenomena, 
 by observations on arteries of the human subject and animals ; 
 and by means of an ingeniously constructed " schema" rep- 
 resenting the arterial system by elastic tubes, and the left ven- 
 tricle by an elastic bag, provided with valves, acting as a syr- 
 inge, he satisfactorily established the conditions of tension, 
 etc., necessary to their production. In this schema, the regis- 
 tering apparatus, simpler in construction than the sphygmo- 
 graph, could be applied to the tubes with more accuracy 
 and ease. 
 
 He demonstrated, by experiments with this system of 
 tubes, that the amplitude of the pulsations, the force of the 
 central organ being the same, is greatest when the tubes are 
 moderately distended, or the tension of fluid is low, and vice 
 
FOKM OF THE PULSE. 259 
 
 versa. He demonstrated, also, that a low tension favors 
 dicrotism. In this latter observation he diminished the ten- 
 sion by enlarging the orifices by which the fluid is discharged 
 from the tubes, imitating the dilatation of the small vessels, 
 by which the tension is diminished in the arterial system. 
 He also demonstrated that an important and essential element 
 in the production of dicrotism, is the tendency to oscillation 
 of the fluid in the vessels, between the contractions of the 
 heart. This can only occur in fluid which has a certain 
 weight, and acquires a velocity from the impulse; for 
 when air was introduced into the apparatus, dicrotism could 
 not be produced under any circumstances, as the fluid did 
 not possess weight enough to oscillate between the impulses. 
 Water produced a well-marked dicrotic impulse under favor- 
 able circumstances; and with mercury, the oscillations made 
 two, three, or more distinct impulses. 
 
 By these experiments he proved that the blood oscillates 
 in the vessels, if this movement be not suppressed by too great 
 pressure, or tension. This oscillation gives the successive 
 rebounds that are marked in the descending line of the 
 pulse, and is capable, in some rare instances, when the arte- 
 rial tension is very slight, of producing a second rebound of 
 sufficient force to be appreciated by the finger. 1 
 
 1 In treating of the form of the pulse, of course including dicrotism, from a 
 purely physiological point of view, we have given an analysis of the physiological 
 portion of the late work of MAREY (Physiologic Medicate de la Circulation du 
 Sang, Paris, 1863). To portions of this work relating to the action of the heart, 
 sounds, etc., we have already referred. As is evident from our sketch of the 
 instruments for registering the pulse, the author referred to is the only one who 
 has produced a trace correctly representing the shades of locomotion and dilatation 
 of the arteries ; and by his brilliant and ingenious experiments, which cannot be 
 too highly praised, he has settled many important points, and given a precious 
 means of investigation to other physiologists. He has opened a new field for 
 study of the pathological changes in the form of the pulse; but before we 
 can advance far in this direction, we must become familiar with all the modi- 
 fications which occur in health, an end which as yet is by no means fully attained. 
 The construction of a sphygmograph was a problem of great delicacy, and a 
 certain amount of practical experience with the instrument has convinced us of 
 
260 CIRCULATION. 
 
 "Without treating of the variations in the character of the 
 pulse in disease, due to the action of the muscular coat, we 
 will consider some of the external modifying influences which 
 come within the range of physiology. The smallest vessels 
 and those of medium size possess to an eminent degree what 
 is called tonicity, or the property of maintaining a certain 
 continued amount of contraction. This contraction is antag- 
 onistic to the distending force of the blood, as is shown by 
 opening a portion of an artery included between two ligatures, 
 in a living animal, when the contents will be forcibly dis- 
 charged and the caliber of that portion of the vessel very 
 much diminished. Too great distention of the vessels by 
 the pressure of blood seems to be prevented by this constant 
 action of the muscular coat; and thus the conditions are 
 maintained which give the pulse the character we have just 
 described. 
 
 By excessive and continued heat, the muscular tissue of the 
 arteries may be dilated so as to offer less resistance to the 
 distending force of the heart. Under these circumstances, 
 the pulse, as felt by the finger, will be found to be larger and 
 softer than normal. Cold, either general or local, has a pre- 
 cisely opposite effect ; the arteries become contracted, and 
 the pulse assumes a harder and more wiry character. Usually, 
 prolonged contraction of the arteries is followed by relaxation, 
 as is seen in the full pulse and glow of the surface which 
 accompany reaction after exposure to cold. 
 
 It has been found, also, that there is a considerable differ- 
 
 the accuracy of results to be obtained when it is used with skill and care ; but the 
 very perfection and nicety of the instrument present almost insurmountable 
 difficulties in the way of its use by the general practitioner. Results, regarding 
 the amplitude of pulsations especially, should be received with great caution, from 
 the extreme difficulty of adjusting the lever so as to give the maximum of the 
 impulse. It does not appear, however, how these drawbacks to the general use 
 of the instrument can be obviated; for its construction leaves nothing to be 
 desired, and the delicacy of its adjustment, like that of a fine balance, is indis- 
 pensable. In the hands of Marey, its results, we conceive, are to be fully ao 
 cepted. 
 
AKTEKIAL PRESSURE. 261 
 
 ence in the caliber of the arteries at different periods of the 
 day. The diameter of the radial has been found very much 
 greater in the evening than in the morning, 1 producing, 
 naturally, a variation in the character of the pulse. "We 
 learn from these physiological variations, how in disease, 
 when they become more considerable, they may give 
 important information with regard to the condition of the 
 system. 
 
 Pressure of Blood in the Arteries. 
 
 The reaction of the elastic walls of the arteries during the 
 intervals of the heart's action gives rise to a certain amount 
 of constant pressure, by which the blood is continually forced 
 toward the capillaries. The discharge of blood into the ca- 
 pillaries has a constant tendency to diminish this pressure ; 
 but the contractions of the left ventricle, by forcing repeated 
 charges of blood into the arteries, have a compensating ac- 
 tion. By the equilibrium between these two agencies, a 
 certain degree of tension is maintained in the arteries, which 
 is called the arterial pressure. 
 
 The first experiments with regard to the extent of the 
 arterial pressure were made by Hales an English physiolo- 
 gist, more than a hundred years ago. 2 This observer, adapt- 
 ing a long glass tube to the artery of a living animal, ascer- 
 tained the height of the column of blood which could be 
 sustained by the arterial pressure. In some experiments on 
 the carotid of the horse, the blood mounted to the height of 
 from eight to ten feet. Hales was not fully acquainted with 
 the influences capable of modifying the arterial pressure, and 
 his estimates of the normal tension in these vessels were not 
 entirely correct. It is now ascertained that the pressure in 
 the arteries will sustain a column of about six feet of water, 
 or six inches of mercury, and is subject to considerable vari- 
 
 1 MILNE-EDWARDS, op. tit., tome iv., p. 222. 
 
 2 HALES, Statical Essays, London, 1733, vol. ii., HcemastaticJcs. 
 
262 
 
 CIRCULATION". 
 
 Fi?. 6. 
 
 ations, depending upon the condition of the heart and ves- 
 sels, the quantity of blood, respiration, muscular exercise, etc. 
 All experiments on the arterial pressure are made on the 
 principle of the experiment of Hales, which, with reference 
 simply to the constant pressure in the arteries, is as useful as 
 those of later date, and mue*h more striking. The only in- 
 convenience is in the manipulation of the long tube, but this 
 may be avoided by setting it in a strip of wood, when it can 
 be easily handled. If a large artery, as the carotid, be ex- 
 posed in a living animal, and 
 a metallic point, connected with 
 a vertical tube of small caliber 
 and from seven to eight feet 
 long by a bit of elastic tubing, 
 be secured in the vessel, the 
 blood will rise to the height of 
 about six feet, and remain at 
 this point almost stationary, 
 indicating by a slight pulsatile 
 .movement the action of the 
 heart. On carefully watching 
 the level in the tube, in addi- 
 tion to the rapid oscillation co- 
 incident with the pulse, another 
 oscillation will be observed, 
 which is less frequent, and 
 which corresponds with the 
 movements of respiration. The 
 pressure, as indicated by an 
 
 llaemodynamometer of Poiseuille, modified elevation of the fluid, IS sliffllt- 
 by Ludwig, Spongier, and Valentin. The IT.' 
 
 1 ly increased during expira- 
 and diminished 
 
 tion, 
 
 during 
 
 instrument is connected with the vessel 
 V V, in such a manner that the circula- 
 tion is not interrupted. The elevation of 
 the mercury in the branch B C indicates 
 the amount of pressure. (BECLAKD, Phy- inspiration 
 tiologie, Paris, 1859, p. 204.) 
 
 1 In all these experiments on the arterial or cardiac pressure, it is necessary 
 to fill part of the tube, or whatever apparatus we may use, with a solution of car- 
 bonate of soda, in order to prevent coagulation of the blood as it passes out of 
 the vessels. 
 
AKTEEIAL PEESSUEE. 
 
 263 
 
 The experiment with the long tube gives us the best idea 
 of the arterial pressure, which will be found to vary from five 
 and a half to six feet of blood, Fi s- 7 - 
 
 or a few inches more of water. 
 The oscillations produced by 
 the contractions of the heart are 
 not very marked, on account of 
 the immense friction in so long 
 a tube ; but this is favorable to 
 the study of the constant press- 
 ure in the arteries. It has been 
 found that the estimates above 
 given do not vary very much 
 in animals of different sizes. 
 Bernard found the pressure in 
 the carotid of a horse little 
 more than in the dog or rab- 
 bit. In the larger animals it 
 is the force of the heart which 
 is increased, and not to any 
 considerable extent the con- 
 stant pressure in the vessels. 1 ' 
 
 The experiments of Hales 
 were made with a view of cal- 
 
 Section of the cardiometer of Magendie, as 
 modified by Bernard. A strong glass bottle 
 is perforated at each side, and fitted with an 
 iron tube, with an opening, T, by which the 
 mercury enters. One end of the iron tube 
 is closed, and the other is bent upwards and 
 connected with the graduated glass tube T', 
 Avhich has a caliber of from f 5 to of an inch. 
 The bottle is filled with mercnry until it 
 rises to n' in the tube which is marked O. 
 The cork is perforated by the tube , which 
 
 and were not directed particu- 
 larly to the conditions and va- 
 riations of the arterial pressure. 
 It is only since the experiments 
 performed by Poiseuille with 
 the iKKinodynamometer^ in 1828, 
 that we have any reliable data 
 on this latter point. 8 Poiseuille's instrument for measuring 
 the force of the blood is a simple graduated U tube, half 
 
 is connected by a rubber tube with the point 
 C, which is introduced into the vessel. 
 (BERNARD, Liquides de POrganisme, Paris, 
 1859, tome i., p. 167.) 
 
 1 BERNARD, lAquides de V 'Organismc, Paris, 1859, tome i., p. 172. 
 
 a POISEUILLE, Recherche* sur la Force du Cceur Aortique, Paris, 1828. 
 
264 
 
 CIRCULATION. 
 
 Fig. 8. 
 
 filled with mercury, with one arm bent at a right angle, so 
 that it can easily be connected with the artery. The press- 
 ure of the blood is indicated by a depression in the level of 
 the mercury on one side, and a corresponding elevation on 
 the other. 
 
 This instrument is gene^lly considered as possessing 
 
 great advantages 
 over the long glass 
 tube; but for esti- 
 mating simply the 
 arterial pressure, it 
 is much less useful, 
 as it is more sensi- 
 tive to the impulse 
 of the heart. For 
 the study of the 
 cardiac pressure, it 
 has the disadvan- 
 tage, in the first 
 place, of consider- 
 able friction ; and 
 again, the weight 
 of the column of 
 mercury produces 
 an extent of oscilla- 
 tion by its mere im- 
 petus, greater than 
 that which would 
 actually represent 
 the force of the 
 heart. 1 
 
 An important 
 improvement in 
 
 Compensating Instrument of Marey. 
 
 1 Ludwig devised a means of registering the oscillation in the hoemody- 
 namometer of Poiseuille. He used a U tube of considerable size, and placed a 
 Coat on the surface of the mercury, to which a pencil was attached The point 
 
AKTEKIAL PRESSURE. 265 
 
 the hsemodynamometer was made by Magendie. This ap- 
 paratus, the cardiometer^ in which Bernard has made some 
 important modifications, is the one now generally used. It 
 consists of a small but thick glass bottle, with a fine graduated 
 glass tube about twelve inches in length, communicating 
 with it, either through the stopper, or by an orifice in the side. 
 The stopper is pierced by a bent tube which is to be connected 
 with the blood-vessel. The bottle is filled with mercury so 
 that it will rise in the tube to a point which is marked zero. 
 It is evident that the amount of pressure on the mercury in 
 the bottle will be indicated by an elevation in the graduated 
 tube ; and, moreover, from the fineness of the column in the 
 tube, we avoid some of the inconveniences which are due to 
 the weight of mercury in the hemodynamometer, and also 
 have less friction. 
 
 This instrument is appropriately called the cardiometer, 
 as it indicates most accurately, by the extreme elevation of 
 the mercury, the force of the heart ; but it is not as perfect 
 in its indications of the mean arterial pressure, as in the ab- 
 rupt descent of the mercury during the diastole of the heart, 
 the impetus causes the level to fall considerably below the 
 real standard of the constant pressure. Marey has succeeded 
 in correcting this difficulty in what he calls the " compensat- 
 ing " instrument ; which is constructed on the following prin- 
 ciple : Instead of a simple glass tube which communicates 
 with the mercury in the bottle, as in Magendie's cardiometer, 
 he has two tubes : one of which is like the one already describ- 
 ed, and represents oscillations produced by the heart ; the 
 other is larger, and has at the lower part a constriction of 
 the caliber which is there reduced to capillary fineness. This 
 tube is designed to give the mean arterial pressure. The 
 
 of the pencil, brought in contact with a revolving cylinder covered with paper, 
 produced a trace of the oscillations. By analysis of this trace he arrived at the 
 mean pressure in the arteries. This instrument was called the kymographion. It 
 has never been much used in investigation, and is entirely superseded by the car* 
 diometer of the present day. 
 
266 CIRCULATION. 
 
 constriction in the tube offers such, an obstacle to the rise of 
 the mercury that the intermittent action of the heart is not 
 felt, the mercury rising slowly to a certain level, which is con- 
 stant, and varies only with the constant pressure in the vessels. 
 
 We have only an approximative idea of the average press- 
 ure in the arterial system in thfc human subject, deduced from 
 experiments on animals. It has already been stated to be 
 equal to about six feet of water, or six inches of mercury. 
 
 The most interesting questions connected with this sub- 
 ject are : the comparative pressure in different parts of the 
 arterial system, the influences which modify the arterial press- 
 ure, and its influence on the pulse. These points have all 
 been pretty fully investigated by experiments on animals, and 
 on systems of elastic tubes arranged to represent the vessels. 
 
 Pressure in Different Parts of the Arterial System. 
 The experiments of Hales, Poiseuille, Bernard, and others, 
 seem to show that the constant arterial pressure does not vary 
 in arteries of different sizes. These physiologists have ex- 
 perimented particularly on the carotid and crural, and have 
 found the pressure in these two vessels about the same. 
 From their experiments, they conclude that the force is 
 equal in all parts of the arterial system. The experiments of 
 Yolkmann, however, have shown that this conclusion has been 
 too hasty. With the registering apparatus of Ludwig, he has 
 taken the pressure in the carotid and metatarsal arteries, and 
 has always found a considerable difference in favor of the 
 former. 1 In an experiment on a dog, he found the pressure 
 
 1 For comparing the pressure in different vessels and in different animals, 
 Bernard has devised an instrument which he calls the differentialhcemodynamo- 
 meter. It consists of a graduated U tube so arranged that both amis may be 
 simultaneously connected with separate vessels. If the pressure be equal in the 
 two vessels with which it is connected, the level of the mercury will not be affect- 
 ed ; but an inequah'ty of pressure will be marked by a depression of the mercury 
 in the arm corresponding to the vessel in which the pressure is the more power- 
 ful. With this instrument, Bernard assumes to have demonstrated that the con- 
 stant pressure is equal in all parts o the arterial system, the force of the heart, 
 
ARTERIAL PRESSURE. 267 
 
 equal to 172 millimetres in the carotid, and 165 mm. in the 
 metatarsal. In an experiment on a calf, the pressure was 116 
 mm. in the carotid, and 89 mm. in the metatarsal ; and in a 
 rabbit, 91 mm. in the carotid, and 86 mm. in the crural. 1 
 
 These experiments, which seem to have been performed 
 with great care, show that the pressure is not absolutely the 
 same in all parts of the arterial system ; that it is greatest in 
 the arteries nearest the heart, and gradually diminishes as 
 we near the capillaries. The difference is very slight, almost 
 inappreciable, until we come to vessels of very small size ; 
 but here the pressure is directly influenced by the discharge 
 of blood into the capillaries. 
 
 The cause of this diminution of pressure in the smallest 
 vessels is the proximity of the great outlet of the arteries, the 
 capillary system ; for, as we shall see further on, the flow into 
 the capillaries has a constant tendency to diminish the press- 
 ure in the arteries. It is obvious that this influence can only 
 be felt in a very marked degree in the vessels of smallest size. 2 
 
 Influence of JBespiration. It is easy to see, in studying 
 the arterial pressure with any of the instruments we have 
 described, that there is a marked increase with expiration, 
 and a diminution with inspiration. The fact that expiration 
 will increase the force of the jet of blood from a divided 
 artery has long been observed, and accords perfectly with the 
 above statement. 
 
 only, diminishing in the smaller vessels. The instrument by no means possesses 
 the delicacy of the apparatus used by Yolkmann, in giving the mean pressure. 
 (Liquides de V Organisme, tome i., p. 209 et seq.) 
 
 1 MILNE-EDWARDS, op. tit., tome iv., p. 234. 
 
 2 This view is fully sustained by physical laws. If fluid be discharged from a 
 reservoir by a long horizontal tube of uniform caliber, the pressure, as indicated 
 by vertical tubes at different points, will be found to diminish regularly from the 
 height of the fluid in the reservoir to the orifice of discharge. An instrument of 
 this kind, which is called a piezometer, shows the apparent physical necessity 
 of a progressive diminution in pressure in the arterial system, as we pass from the 
 heart to the capillaries. 
 
268 CmCULATTON. 
 
 In tranquil respiration, the influence upon the flow of 
 blood is due simply to the mechanical action of the thorax. 
 "With every inspiration the air-cells are enlarged, as well as 
 the blood-vessels of the lungs ; the air rushes in through the 
 trachea, and the movement of the blood in the veins near the 
 chest is accelerated. At the same time the blood in the arteries 
 is somewhat retarded in its flow from the thorax, or at least 
 does not feel the expulsive influence which follows with the act 
 of expiration. The mean of the arterial pressure at that time 
 is at its minimum. With the expiratory act, the air is ex- 
 pelled by compression of the lungs, the flow of blood into the 
 thorax by the veins is retarded to a certain extent, while the 
 flow of blood into the arteries is favored. This is strikingly 
 exhibited in the augmented force, with expiration, in the jet 
 from a divided artery. Under these circumstances the arte- 
 rial pressure is at its maximum. 
 
 In perfectly tranquil respiration, the changes due to in- 
 spiration and expiration are very slight, marked by a differ- 
 ence of not more than half an inch to an inch in the car- 
 diometer. "When the respiratory movements are exaggerated, 
 the oscillations are very much more marked. 
 
 Interruption of respiration is followed by a very great in- 
 crease in the arterial pressure. This is due, not to causes 
 within the chest, but to obstruction to the circulation in the 
 capillaries. We are already aware of the influence which 
 the flow of blood into the capillaries is constantly exerting 
 upon the arterial pressure. This tendency to diminish the 
 quantity of blood in the arteries, and consequently the 
 pressure, is constantly counteracted by the blood sent into 
 the arteries by the contractions of the heart. In interruption 
 of the respiratory function, the non-aerated blood passes into 
 the arteries, but refuses to pass through the capillaries ; and 
 as a consequence, the arteries are abnormally distended, and 
 the arterial pressure is enormously increased. If respiration 
 be permanently arrested, the arterial pressure becomes, after 
 a time, diminished below the normal standard, and ultimate- 
 
AKTEEIAL PEESSUEE. 2(19 
 
 ly abolished, on account of the stoppage of the action of the 
 heart. If respiration be resumed before the heart has become 
 arrested, the pressure soon returns to its normal standard. 
 
 Muscular effort considerably increases the arterial press- 
 ure. This is due to two causes. In the first place, the chest 
 is generally compressed, favoring the flow of blood into the 
 great vessels. In the second place, muscular exertion pro- 
 duces a certain amount of obstruction to the discharge of 
 blood from the arteries into the capillaries. Numerous ex- 
 periments upon animals have shown a great increase in press- 
 ure in the struggles which occur during severe operations. 
 Bernard has shown that galvanization of the sympathetic in 
 the neck and irritation of some of the cerebro-spinal nerves 
 increase the arterial pressure, probably from their effects on 
 the muscular coats of some of the arteries, causing them to 
 contract, and thereby diminishing the total capacity of the 
 arterial system. 1 
 
 Effects of Hemorrhage. Diminution in the quantity of 
 blood has a remarkable effect upon the arterial pressure. If, 
 in connecting the instrument with the arteries, we allow even 
 one or two jets of blood to escape, the pressure will be found 
 diminished perhaps one-half, or even more. It is hardly neces- 
 sary to discuss the mechanism of the effect of the loss of blood 
 on the tension of the vessels, but it is wonderful how soon the 
 pressure in the arteries regains its normal standard after it has 
 been lowered by hemorrhage. As it depends upon the quan- 
 tity of blood, as soon as the vessels absorb the serosities in suf- 
 ficient quantity to repair the loss, the pressure is increased. 
 This takes place in a very short time, if the loss of blood be 
 not too great. 
 
 Experiments on the arterial pressure with the cardiometer 
 have verified the fact stated in treating of the form of the pulse, 
 namely, that the pressure in the vessels bears an inverse ratio 
 to the distention produced by the contractions of the heart. 
 
 1 BERNARD, Liquides de VOrganisme, Paris, 1859, tome i., p. 241, et seq. 
 
270 CIRCULATION. 
 
 In the cardiometer, the mean height of the mercury indicates 
 the constant, or arterial, pressure, and the oscillations, the 
 distention produced by the heart. It is found that when the 
 pressure is great, the extent of oscillation is small, and vice. 
 versa. It will be remembered that the researches of Marey 
 demonstrated that an increase of the arterial pressure dimin- 
 ishes the amplitude of the pulsations, as indicated by the 
 sphygmograph, and that the amplitude is very great when 
 the pressure is slight. 
 
 It is also true, as a general rule, that the force of the heart, 
 as indicated by the cardiometer, bears an inverse ratio to the 
 frequency of its pulsations. 
 
 Summary. The arterial pressure, due to the distention 
 of the arteries, and the reaction of their elastic walls contin- 
 ually forcing the blood toward the capillaries, is equal to 
 about six feet of water or six inches of mercury. It is in- 
 creased by any thing which favors the flow of blood into the 
 great vessels, like the expiratory act, or by any thing which 
 obstructs the flow from the arterioles into the capillaries, 
 like muscular effort, contraction of the muscular coat of the 
 smallest arteries, or non-aeration of the blood. It is dimin- 
 ished by any considerable diminution in the quantity of the 
 circulating fluid, or by any thing which facilitates the passage 
 of blood through the capillaries. 
 
 Rapidity of the Current of Blood in the Arteries. 
 
 Though this is not a question of great physiological im- 
 portance, it is a point of some interest. It has long engaged 
 the attention of physiologists, and has lately been made the 
 subject of some curious and ingenious experiments. Passing 
 over the speculations and calculations from imperfect physi- 
 cal data of the older physiologists, which led to no definite 
 results, we find the first experiments on this subject made by 
 Yolkmann, with an instrument called the hemodromometer. 
 This apparatus consists of a U tube, graduated, and so ar- 
 
RAPIDITY OF THE ARTERIAL CIRCULATION. 271 
 
 ranged that when the instrument is connected with the artery 
 of a living animal, the current may be instantaneously di- 
 rected through the graduated tube, and by a stop-watch, the 
 length of time occupied in passing from one extremity to 
 the other accurately measured. Observations with this in- 
 strument, on the rapidity of the circulation in the carotid of 
 the dog and horse, show that the blood moves at the rate of 
 from 10 to 13 inches per second. The rapidity is diminish- 
 ed in the smaller vessels, being but 2*2 inches per second in 
 the metatarsal artery of a horse, and 10 inches in the carotid. 1 
 
 The results thus obtained cannot be received as absolutely 
 exact. The blood is diverted from its natural course, and 
 must experience a certain diminution in velocity from the 
 curves in the tubes. It is also evident that the normal cur- 
 rent is not uniform ; that it is much more rapid immediately 
 after the systole of the heart, than during the diastole ; and, 
 as has been demonstrated by Marey, the blood in the arteries 
 undergoes a certain oscillation. The experiments of Vblk- 
 inann give an approximative idea of the mean rapidity, it is 
 true, but they are far from exhibiting the natural current, with 
 the variations corresponding to the movements of the heart. 
 
 A few years later (1858), an instrument was devised by 
 Yierordt, which seemed to embody the right principle, but 
 it was not sufficiently sensitive to accomplish all that was de- 
 
 1 The experiments of Volkmann and Huttenheim, published in 1846, are re- 
 ferred to, and the instrument described and delineated, in most works on physiol- 
 ogy. When the instrument is first connected with the artery, the blood passes 
 through a straight tube, and is not deviated from its course. The current is 
 diverted into the graduated U tube by two stop-cocks which are arranged so that 
 they may be turned simultaneously. Before it is applied, the apparatus is filled 
 with warm water, so as to prevent the entrance of air into the vessels. 
 
 The following are the results obtained by Volkmann in experiments on dogs 
 and horses : 
 
 In the dog, carotid . . . . 10 '7 inches per second. 
 
 do. do. .... 13 u " " 
 
 In the horse, carotid 10 " " " 
 
 do. raetatarsal artery . . 2-2. " " " 
 
 LONGET, Traite de Physiologic, Paris, 1861, tome L, p. 848. 
 
272 CIRCULATION. 
 
 sired. It consisted of a little square box made of glass, with 
 an opening at each, end, by which it was to be connected with 
 the artery. This is filled with water, and contains a pendu- 
 lum, which is struck by the current of blood. The deviations 
 of the pendulum are marked on a scale. After this has 
 been applied to an artery, and the extent of movement of 
 the pendulum noted, it is removed from the vessel and con- 
 nected with an elastic tube, in which a current of water is 
 made to pass with a degree of rapidity which will produce 
 the same deviation as occurred when the instrument was con- 
 nected with the blood-vessel. The rapidity of the current in. 
 this tube may be easily calculated by receiving the fluid in a 
 graduated vessel, and noting the time occupied in discharg- 
 ing a given quantity. By this means we ascertain the 
 rapidity of the current of blood. By means of a needle 
 attached to the pendulum, the oscillations could be regis- 
 tered on a revolving cylinder of paper, and the mean velocity 
 taken. 
 
 With this instrument, Yierordt estimated the mean velo- 
 city of blood in the carotid at 10*2 inches per second. Chau- 
 veau, who invented an instrument which we will describe 
 presently, found the instrument of Yierordt not sufficiently 
 sensitive, and requiring so much care and precaution in its 
 use as to essentially diminish the value of its results. 
 
 The best instrument for measuring the rapidity of the 
 circulation in the arteries was devised by Chauveau, of the 
 Yeterinary School at Lyons. 1 This will give, by calcula- 
 tion, the actual rapidity of the circulation ; and, what is more 
 interesting, it marks accurately the rapid variations in velo- 
 city, with reference to the heart's action. 
 
 The instrument to be applied to the carotid of the 
 horse consists of a thin brass tube, about 1J inch in length, 
 and of the diameter of the artery (about f of an inch), which is 
 
 1 MM. A. CHAUYEAU, G. BERTOLUS et L. LAROYENNE, Vitesse de la Circulation 
 dam les Arteres du Cheval. Journal de la Physiologic, Paris, 1860, tome iii., 
 p. 695. 
 
RAPIDITY OF THE AKTEKIAL CIRCULATION. 
 
 273 
 
 Fig. 9. 
 
 provided with an 
 oblong longitudi- 
 nal opening, or 
 window, near the 
 middle,' about two 
 lines long and one 
 line wide. A 
 piece of thin vul- 
 canized rubber is 
 wound around the 
 tube, and firmly 
 tied, so as to cov- 
 er this opening. 
 Through a trans- 
 verse slit in the 
 rubber is intro- 
 duced a very light 
 
 metallic needle,Chauveau's instrument for measuring the rapidity of the flow of 
 i ITT/? blood in the arteries. The instrument viewed in face a, the 
 
 an men and a nail tube to be fixed in the vessel; &, the dial which marks the ex- 
 -i , -i T n , tent of movement of the needle d ; *, a lateral tube for the 
 
 111 length, aild fiat- attachment of a cardiometer, if desired. 
 
 tened at its lower part. This is made to project about half 
 way into the caliber of the tube. A flat semicircular piece 
 of metal, divided into an arbitrary scale, is attached to the 
 tube, to indicate the deviations of the point of the needle. 
 
 The apparatus is introduced carefully into the carotid of 
 a horse, by making a slit in the vessel, introducing first one 
 end of the tube, directed toward the heart, then allowing a 
 little blood to enter the instrument, so as to expel the air, 
 and, when full, introducing the other end, securing the whole 
 by ligatures above and below. 
 
 When the circulation is arrested, the needle should be 
 vertical, or mark zero on the scale. "When the flow is estab- 
 lished, a deviation of the needle occurs, which varies in extent 
 with the rapidity of the current. 
 
 Having removed all pressure from the vessel, so as to al- 
 low the current to resume its normal character, the deviations 
 18 
 
274: CIRCULATION. 
 
 of the needle are carefully noted, as they occur with the sys- 
 tole of the heart, with the diastole, etc. After withdrawing 
 the instrument, it is applied to a tube of the size of the ar- 
 tery, and we measure the rapidity of the current required to 
 carry the needle to the points noted, which may be done by 
 the same calculation used in graduating the apparatus of 
 Yierordt. 1 
 
 This instrument is on the same principle as the one con- 
 structed by Yierordt, but in sensitiveness and accuracy is 
 much superior. In the hands of Chauveau, the results, par- 
 ticularly those with regard to variations in the rapidity of 
 the current, are very interesting. 
 
 Rapidity of the Current in the Carotid. It has been 
 found that three currents, with different degrees of rapidity, 
 may be distinguished in the carotid : 
 
 1. At each ventricular systole, we have, as the average 
 of the experiments of Chauveau, the blood moving in the 
 carotids at the rate of twenty -^ inches per second. After 
 this the rapidity quickly diminishes, the needle returning 
 quite or nearly to zero, which would indicate complete 
 arrest. 
 
 2. Immediately succeeding the ventricular systole, we have, 
 a second impulse given to the blood, which is synchronous 
 with the closure of the semilunar valves, the blood moving 
 at the rate of eight -^ inches per second. This Chauveau 
 calls the dicrotic impulse. 
 
 3. After the dicrotic impulse, the rapidity of the current 
 gradually diminishes, until, just before the systole of the 
 heart, it becomes almost nil. The average rate after the di- 
 crotic impulse is five -f$ inches per second. 
 
 These experiments give us, for the tirst time, correct no- 
 tions of the rapidity and variations of the flow of blood in 
 the larger vessels ; and it is seen that they correspond in a 
 
 1 In graduating the apparatus, Chauveau uses warm water. It would be 
 more accurate to use defibrinated blood, or a fluid of equal density. 
 
RAPIDITY OF THE ARTERIAL CIRCULATION, 275 
 
 remarkable degree with the experiments of Marej on the 
 form, of the pulse. Marey showed that there is a marked os- 
 cillation of the blood in the vessels, due to a reaction of their 
 elastic walls, following the first violent distention by the 
 heart ; that at the time of closure of the semilunar valves, the 
 arteries experience a second, or dicrotic, distention, much less 
 than the first ; and following this, there is a gradual decline 
 in the distention until the minimum is reached. Chauveau 
 shows by experiments with his instrument, that correspond- 
 ing to the first dilatation of the vessels, the blood moves with 
 immense rapidity ; following this, the current suddenly be- 
 comes nearly arrested ; this is followed by a second accelera- 
 tion in the current, less than the first; and following this we 
 have a gradual decline in the rapidity to the time of the next 
 pulsation. 
 
 Rapidity in Different Parts of the Arterial System. 
 From the fact that the arterial system increases in capacity 
 as we recede from the heart, we should expect to find a cor- 
 responding diminution in the rapidity of the flow of blood. 
 There are, however, many circumstances, aside from simple 
 increase in the capacity of the vessels, which undoubtedly 
 modify the blood current, and render inexact any calculations 
 on purely physical principles ; such as the tension of the 
 blood, the conditions of contraction or relaxation of the 
 smallest arteries, etc. It is therefore necessary to have re- 
 course to actual experiment to arrive at any definite results 
 on this point. The experiments of Volkmann showed a great 
 difference in the rapidity of the current in the carotid and 
 metatarsal arteries, the average being 10 inches per second 
 in the carotid, to 2*2 inches in the metatarsal. The same 
 difference, though not quite as marked, was found by Chau- 
 veau between the carotid and the facial. 
 
 The last-named observer also noted an important modifi- 
 cation in the character of the current in the smaller vessels. 
 As we recede from the central organ, the systolic impulse 
 
276 CIRCULATION. 
 
 becomes rapidly diminished, being reduced in one experiment 
 about two-thirds ; the dicrotic impulse becomes very feeble or 
 even abolished ; but the constant flow is very much increased 
 in rapidity. This fact coincides with the ideas already ad- 
 vanced, with regard to the gradual conversion, by virtue of 
 the elasticity of, the vessels, of the impulse of the heart into, 
 first, a remittent, and, in the very smallest arteries, a nearly 
 constant current. 
 
 The rapidity of the flow in any artery must be subject to 
 constant modifications due to the condition of the arterioles 
 which are supplied by it. When these little vessels are di- 
 lated, the artery of course empties itself with greater facility, 
 and the rapidity is increased. Thus the rapidity bears a re- 
 lation to the arterial pressure ; as, independently of a dimi- 
 nution in the entire quantity of the circulating fluid, varia- 
 tions in the pressure depend chiefly on causes which facili- 
 tate or retard the flow of blood into the capillaries. A good 
 example of enlargement of the capillaries of a particular part, 
 is in mastication, when the salivary glands are brought into 
 activity, and the quantity of blood which they receive is 
 greatly increased. Chauveau found an immense increase in 
 the rapidity of the flow in the carotid of a horse during mas- 
 tication. The enlargement of the vessels of the glands during 
 their function has been conclusively proven by the experi- 
 ments of Bernard. 
 
 It must be remembered that in all parts of the arterial 
 system the rapidity of the current of blood is constantly liable 
 to increase from dilatation of the small vessels, and diminution 
 from their contraction. 
 
 Arterial Murmurs. 
 
 In the largest vessels, we can frequently hear with the 
 stethoscope the sounds conducted from, the heart. In addi- 
 tion, we can hear, in all except the smallest vessels, a pecu- 
 liar blowing sound, called the fyruit de souffle, which is 
 
AETERIAL MURMURS. 277 
 
 produced by the pressure of the end of the instrument on the 
 artery. The following is the mechanism of the production 
 of this sound : The pressure of the instrument produces a 
 constriction in the vessel, and more or loss obstruction to the 
 current of blood. As the blood flows from this constricted por- 
 tion into that just beyond, where of course the vessel is rela- 
 tively larger and the current is somewhat retarded, the rela- 
 tively small and forcible stream produces an unusual and 
 irregular current, which is accompanied by a certain sound. 
 It has been proven by the experiments of Chauveau and 
 Marey with elastic tubes, that this sound is always produced 
 when any part of the apparatus is dilated so that the fluid 
 passes from the tube into a sort of sac. In this way aneuris- 
 mal murmurs are accounted for. The sounds which are 
 heard in the arteries, and are not dependent upon compres- 
 sion with the stethoscope, depend upon conditions, the con- 
 sideration of which belongs to pathology. 
 
CHAPTEE VII. 
 
 CIRCULATION OF THE BLOOD IN THE CAPILLAEIES. 
 
 Distinction between capillaries and the smallest arteries and veins Physiological 
 anatomy of the capillaries Peculiarities of distribution Capacity of the 
 capillary system Course of blood in the capillaries Phenomena of the 
 capillary circulation Rapidity of the capillary circulation Relations of the 
 capillary circulation to respiration Causes of the capillary circulation In- 
 fluence of temperature on the capillary circulation Influence of direct irrita- 
 tion on the capillary circulation. 
 
 BEFOBE entering upon the study of the capillary circu- 
 lation, let us define what we mean by the capillary vessels, 
 as distinguished from the smallest arteries and veins. From 
 a strictly physiological point of view, the capillaries should 
 be regarded as commencing at the point where the blood is 
 brought near enough to the tissues, to enable them to sep- 
 arate the elements necessary for their regeneration, and give 
 up the products of their physiological decay. With our 
 present knowledge, it is impossible to assign any limit where 
 the vessels cease to be simple carriers of blood ; and it does 
 not seem probable that it will ever be known to what part of 
 the vascular system the processes of nutrition are exclusively 
 confined. The divisions of the blood-vessels must be, to a 
 certain extent, arbitrarily defined, and we should feel at lib- 
 erty to adopt the views of any reliable observer with regard 
 to the kind of vessels which are to be considered as capilla- 
 ries. The most simple, and what seems to be the most phys- 
 
PHYSIOLOGICAL ANATOMY OF THE CAPILLARIES. 279 
 
 iological view, is that the capillaries are the vessels which 
 have but a single, homogeneous tunic ; for in these the blood 
 is brought in closest proximity to the tissues. Vessels which 
 are provided, in addition, with a muscular, or muscular and 
 fibrous coats, are to be regarded as either small arteries, or 
 venous radicles. This view is favored by the character of 
 the currents of blood, as seen in microscopic observations on 
 the circulation in transparent parts. Here an impulse is 
 observed with each contraction of the heart, until we come 
 to vessels which have but a single coat, and are so narrow as 
 to allow the passage of but a single line of blood-corpuscles. 
 
 Physiological Anatomy of the Capillaries. If the arteries 
 be followed out to their minutest ramifications, they will be 
 found progressively diminishing in size as they branch, and 
 their coats, especially the muscular, becoming thinner and 
 thinner, until at last they present an internal structureless 
 coat, provided with oval longitudinal nuclei ; a middle coat 
 formed of but a single layer of circular muscular fibres, the 
 oval nuclei of which are at right angles to the nuclei of the 
 internal coat ; and an external coat composed of a very thin 
 layer of longitudinal fibres of the white inelastic tissue. Kobin 
 calls these the third variety of capillary vessels ; but they are 
 large, -j-J-Q- to -g-J-g- of an inch in diameter, become smaller as 
 they branch, and undoubtedly possess the property of con- 
 tractility, which is particularly marked in the arterial system. 
 Following the course of the vessels, when they are reduced in 
 size to about -g-J-Q- of an inch, the external fibrous coat is lost, 
 and the vessel then presents only the internal structureless 
 coat, and the single layer of muscular fibres. These are 
 called by Kobin, capillaries of the second variety. They 
 become smaller as they branch, and finally lose the muscular 
 coat, and have then but the single amorphous tunic, with its 
 longitudinal nuclei. These, the capillaries of the first variety 
 of Robin, 1 we shall consider as the true capillary vessels. 
 
 1 Didionnaire de Medecine, etc., Paris, 1858 (Capillaire). This division of the 
 
280 CIRCULATION. 
 
 The true capillary vessels present the following charac- 
 teristics : 
 
 1. Simplicity of Structure. They have but the single 
 amorphous coat, from -g-yJor to TirVoT f an i ncn thick, the 
 continuation of the lining membrane of the larger vessels ; 
 not provided with an epithelial lining, but presenting, im- 
 bedded in its thickness, a number of oval nuclei with their 
 long diameters in the direction of the axis of the vessel. 
 
 2. Small Diameter of the Vessels. -^Their diameter is gen- 
 erally as small or smaller than that of the blood-corpuscles ; 
 so that these bodies always move in a single line, and must 
 become deformed in passing through the smallest vessels ; 
 recovering their natural shape, however, when they pass into 
 vessels of larger size. The capillaries are smallest in the 
 nervous and muscular tissue, retina, and patches of Peyer, 
 where they have a diameter of from -g^Vo- to ^^ of an inch. 
 In the mucous layer of the skin, and in the mucous mem- 
 branes, they are from ^Vo- t -nVir f an ^ ncn ^ n diameter. 
 They are largest in the glands and bones, where they are from 
 g^ to -joVu f an i nc h i n diameter. 1 These measurements 
 indicate the size of the vessel, and not its caliber. Taking 
 .out the thickness of their walls, it is only the very largest of 
 them which will admit of the passage of a blood-disk without 
 ,a change in its form. 
 
 3. Peculiarities of Distribution. Unlike the arteries, 
 which grow smaller as they branch, and simply carry blood 
 by the shortest course to the parts, and the veins, which be- 
 come larger as we follow the course of the blood by union 
 with each other, the capillaries form a true plexus of vessels 
 of nearly uniform diameter, branching and inosculating in 
 
 capillaries into three varieties, the first with a homogeneous coat, the second with 
 the addition of the muscular coat, and the third with the muscular and fibrous 
 coat, was made by Henle, and is, perhaps, the one most generally adopted. Kol- 
 liker gives the division we have adopted, regarding as true capillaries only those 
 vessels which have a single coat. The others he calls "vessels of transition." 
 1 KOLLIKER, Manual of Human Microscopic Anatomy, London, 1860, p. 500, 
 
PHYSIOLOGICAL ANATOMY OF THE CAPILLARIES. 281 
 
 every direction, distributing blood to the parts, as their phys- 
 iological necessities demand. This inosculation is peculiar 
 to these vessels, and the plexus is rich in the tissues, as a gen- 
 eral rule, in proportion to the activity of their nutrition. 
 Though their arrangement presents certain differences in 
 different organs, the capillary vessels have everywhere the 
 same general characteristics, the most prominent of which 
 are uniform diameter and absence of any positive direction. 
 
 The network thus formed is very rich in the substance 
 of the glands, and in the organs of absorption ; but the ves- 
 sels are only distended with blood during the physiological 
 activity of these parts. In the lungs the meshes are partic- 
 ularly close. In other parts the vessels are not so abundant, 
 presenting great variations in different tissues. In the mus- 
 cles and nerves, in which nutrition is very active, the supply 
 is much more abundant than in other parts, like nbro-serous 
 membranes, tendons, etc., whose functions are rather passive. 1 
 In none of the tissues do we find capillaries penetrating the 
 anatomical elements, as the ultimate muscular or nervous 
 fibres. Some tissues receive no blood, at least they contain 
 no vessels which are capable of carrying red blood, and are 
 nourished by imbibition of the nutrient plasma of the circu- 
 lating fluid. Examples of these, which are called extra-vas- 
 cular, are cartilage, nails, hair, etc. 
 
 The foregoing anatomical sketch gives an idea of how 
 near the blood is brought to the tissues in the capillary sys- 
 tem, and how, once conveyed there by the arteries, and the 
 supply regulated by the action of the muscular coat of the 
 smaller vessels, the blood is distributed for the purposes of 
 nutrition, secretion, absorption, exhalation, or whatever func- 
 
 1 The arrangement of the capillaries in different tissues and organs has gen- 
 erally been ascertained by minute injections. In studying injected preparations, 
 however, it must be borne in mind that when injected, the elastic and yielding 
 vessels are distended to their extreme capacity, and the capillaries, therefore, 
 occupy a space much greater than is natural. In injections of the liver, for ex- 
 ampJe, the capillaries seem to constitute the bulk of the organ, and we are at a 
 'oss to understand how the cells, ducts, etc., find place between their meshes. 
 
282 CIRCULATION. 
 
 tion the part has to perform. This will be still more appa- 
 rent when we come to consider the course of the blood in the 
 capillaries, and the immense capacity of this system, as com- 
 pared with the arteries or veins. 
 
 The capacity of the capillary system is immense. It is 
 only necessary to consider the prodigious vascularity of the 
 skin, mucous membranes, or muscles, to realize this fact. In 
 injections of these parts, it seems, on microscopic examination, 
 as though they contained nothing but capillaries. In prepa- 
 rations of this kind, the elastic and yielding coats of the capil- 
 laries are distended to their utmost limit. Under some cir- 
 cumstances, in health, they are much distended with blood, 
 as the mucous lining of the alimentary canal during diges- 
 tion, the whole surface presenting a vivid red color, indicat- 
 ing the great richness of the capillary plexus. Various 
 estimates of the capacity of the capillary, as compared with 
 the arterial system, have been made, but they are simply ap- 
 proximative, and there seems to be no means by which an 
 estimate, with any pretentious to accuracy, can be formed. 
 The various estimates which are given are founded upon cal- 
 culations from microscopic examinations of the rapidity of 
 the capillary circulation, as compared with the arteries. In 
 this way Bonders estimates the entire capacity of the capil- 
 lary system as 500, and Yierordt as 800 times that of the 
 arterial system. It must be evident to any one who has 
 witnessed the capillary circulation under the microscope, that 
 the conditions under which the animal under examination is 
 placed are liable to interfere with the current of blood ; and 
 the periodical congestion of certain parts, the fugitive flushes 
 of the skin, the condition of the smallest arteries induced by 
 changes of temperature, exercise, etc., make it evident that 
 the current of blood is liable to great variations. It is impos- 
 sible to strictly apply to the capillary circulation in the vari- 
 ous parts of the human subject, observations on the wing of a 
 bat, or the mesentery of a cat. We must consider, then, 
 
COURSE OF BLOOD IN THE CAPILLARIES. 283 
 
 these estimates as mere suppositions ; and they are given for 
 what they are worth. 
 
 With the older physiologists, the contractility of the capil- 
 laries was a subject of discussion. Some went so far as to 
 suppose that these little vessels were the seat of rhythmical 
 contractions which materially assisted the flow of the blood. In 
 microscopic examinations, irritation or stimulation is seen to 
 produce contraction of the smallest arteries ; but there is no 
 evidence that the capillaries, which have a single amorphous 
 coat, have any such property. They undergo, while under 
 observation, considerable alterations in caliber; but this is 
 due, in all probability, to differences in the pressure of blood 
 in their interior. The capillaries can only be considered as 
 endowed with elasticity, which enables them to react upon 
 their contents, when there is any diminution in pressure. In 
 the vascular system, contractility disappears with the muscu- 
 lar fibre- cells which form the middle coat of the arterioles. 
 
 Course of the Blood in the Capillaries. 
 
 The phenomena of the capillary circulation are only ob- 
 servable with the aid of the microscope. It was not granted 
 to the discoverer of the circulation to see the blood moving 
 through the capillaries, and he never knew the exact mode 
 of communication between the arteries and veins. After it 
 was pretty generally acknowledged that the blood did pass 
 from the arteries to the veins, it was disputed whether it 
 passed in an intermediate system of vessels, or became dif- 
 fused in the substance of the tissues, like a river flowing 
 between numberless little islands, to be collected by the ve- 
 nous radicles and conveyed to the heart. Accurate micro- 
 scopic investigations have now demonstrated the existence, 
 and given us a clear idea of the anatomy, of the interme- 
 diate vessels. In 1661, the celebrated anatomist, Malpighi, 
 first saw the movement of the blood in the capillaries, in the 
 lungs of a frog. Since that time, physiologists have studied 
 
284: CIRCULATION. 
 
 the circulation in various transparent parts in the inferior 
 animals, as the web of the frog's foot, the tongue of the frog, 
 the lungs of the frog and of the water-newt, tile mesentery of 
 very young rats or mice, the wing of the bat, etc. The most 
 convenient situation is the tongue or the web of the frog. 
 Here may be studied, not only the movement of the 
 blood in the true capillaries, but the circulation in the small- 
 est arteries and veins ; the variations in caliber of these ves- 
 sels, especially the arterioles, by the action of their muscular 
 tunic; and indeed the action of vessels of considerable 
 size. This has been a most valuable means of studying the 
 circulation in the capillaries, as contrasted with the small 
 arteries and veins ; the only one, indeed, which could give us 
 any definite idea of the action of these vessels. 
 
 Before taking up the causes of the capillary circulation, 
 and the various physical or vital laws which are involved, we 
 will describe the phenomena which are observed with the aid 
 of the microscope. 
 
 Phenomena of the Capillary Circulation. The magnifi- 
 cent spectacle of the capillary circulation, first observed by 
 Malpighi, in the lungs, and afterwards by Leeuwenhoek, 
 Spallanzani, Haller, Cowper, and others, in other parts, has 
 ever since been the delight of the physiologist. "We see 
 the great arterial rivers, in which the blood flows with won- 
 derful rapidity, branching and subdividing, until the blood is 
 brought to the superb network of fine capillaries, where the 
 corpuscles dart along one by one ; the fluid being then col- 
 lected by the veins, and carried in great currents to the heart. 
 This exhibition, to the student of Nature, is of inexpressible 
 grandeur; and our admiration is not diminished when we 
 come to study the phenomena in detail. "We find here a 
 subject as interesting as was the action of the heart when first 
 seen by Harvey, involving some of the most important phe- 
 nomena of the circulation. It can be seen how the arterioles 
 regulate the supply of blood to the tissues ; how the blood 
 
PHENOMENA OF THE CAPILLARY CIRCULATION. 285 
 
 distributes itself by the capillaries ; and finally, having per- 
 formed its office, how it is collected and carried off by the 
 veins. 1 
 
 In studying the circulation under the microscope, the an- 
 atomical division of the blood into corpuscles and a clear 
 plasma is observed. This is peculiarly evident in cold-blood- 
 ed animals, the corpuscles being comparatively large, and 
 floating in a plasma which forms a distinct layer next the 
 walls of the vessel. The white corpuscles, which are much 
 fewer than the red, are generally found in the layer of 
 plasma. 
 
 In vessels of considerable si^e, as well as the capillaries, 
 the corpuscles, occupying the central portion, move with 
 much greater rapidity than the rest of the blood, leaving a 
 layer of clear plasma at the sides, which is nearly immovable. 
 This curious phenomenon is in obedience to a physical law 
 regulating the passage of liquids through capillary tubes for 
 which they have an attraction, such as exists, for example, 
 between the blood and the vessels. In tubes reduced to a 
 diameter approximating to that of the capillaries, the attractive 
 force exerted by their walls upon a liquid, causing it to enter 
 
 1 Various methods of preparing the animal for examination have been em- 
 ployed. The one we have found most convenient, in examining the circulation 
 in the frog, is to break up the medulla with a needle, an operation which does not 
 interfere with the circulation, and attach the animal by pins to a thin piece of 
 cork, stretching the web over an orifice hi the cork, to allow the passage of light, 
 and securing it with phis through the toes. The membrane is then moistened with 
 water, and covered with thin glass, and if the general surface be kept moist, the 
 circulation may be studied for hours. (See " Phenomena of the Capillary Circula- 
 tion," an inaugural thesis, by the author, American Journal of the Medical Sciences, 
 July, 1857.) By gently inflating the lungs with a small blow-pipe, securing them 
 by a ligature passed around the larynx beneath the mucous membrane, and open- 
 ing the chest, the circulation may be examined in this situation. It may be stu- 
 died in the tongue (which presents a magnificent view of the circulation as well as 
 the nerves and muscular fibres) by drawing it out of the mouth, and spreading it 
 into a thin sheet, securing it with pins. The circulation may be studied in the 
 mesentery of a small warm-blooded animal, like the mouse, by fixing it upon the 
 frog-plate, opening the abdomen, and drawing out the membrane ; but not as 
 well or as conveniently as in the tongue or web of the frog. 
 
2 86 CIRCULATION. 
 
 the tube to a certain distance, called capillary attraction, be- 
 comes an obstacle to the passage of fluid in obedience to 
 pressure. Of course, as the diameter of the tube is reduced, 
 this force becomes relatively increased, for a larger propor- 
 tion of the liquid contents is brought in contact with it. 
 When we come to the smallest arteries and veins, and still 
 more the capillaries, the capillary attraction is sufficient to 
 produce the immovable layer, called the " still layer " by 
 many physiologists, and the liquid only moves in the central 
 portion. The plasma occupies the position next the walls of 
 the vessels, for it is this portion of the blood which is capable 
 of wetting the tubes. The transparent layer was observed 
 by Malpighi, Haller, and all who have described the capillary 
 circulation. Poiseuille recognized its true relation to the 
 blood -current, and explained the phenomenon of the still 
 layer by physical laws, which had been previously established 
 with regard to the flow of liquids in tubes of the diameter of 
 from J T to -J- of an inch, but which he had succeeded in apply- 
 ing to tubes of the diameter of the capillaries. 1 
 
 A red corpuscle occasionally becomes involved in the still 
 layer, when it moves slowly, turning over and over, or even 
 remains stationary for a time, until it is taken up again and 
 carried along with the central current. A few white corpus- 
 cles are constantly seen in this layer. They move along 
 slowly, and apparently have a tendency to 'adhere to the 
 walls of the vessel. This is due to the adhesive character of 
 the surface of the white corpuscles as compared with the red, 
 which can easily be observed in examining a drop of blood 
 between glass surfaces, the red corpuscles moving about with 
 great facility, while the white have a tendency to adhere. 
 
 Great differences exist in the character of the flow of 
 blood in the three varieties of vessels which are under obser- 
 vation. In the arterioles, which may be distinguished from 
 the capillaries by their size and the presence of the muscular 
 
 1 POISEUILLE, JRecherches sur les Causes du Mouvement du Sang dans Us Vais- 
 seaux Capillaires, p. 144 et seq. 
 
PHENOMENA OF THE CAPILLARY CIRCULATION. 287 
 
 and fibrous coats, the movement is distinctly remittent, even 
 in their most minute ramifications. The blood moves in 
 them with much greater rapidity than in either the capil- 
 laries or \ 7 eins. They become smaller as they branch, and 
 carry the blood always in the direction of the capillaries. 
 The veins, which are relatively larger than the arteries, carry 
 the blood more slowly, and in a continuous stream, from the 
 capillaries toward the heart. In both these vessels the cur- 
 rent is frequently so rapid, that the form of the corpuscles 
 cannot be distinguished. Only a portion of the white cor- 
 puscles occupy the still layer, the rest being carried on in the 
 central current. 
 
 The circulation in the true capillaries is sui generis. Here 
 the blood is distributed in every direction, in vessels of nearly 
 uniform diameter. The vessels are generally so small as to 
 admit but a single row of corpuscles, which move almost like 
 beings endowed with volition. In a single vessel, a line of 
 corpuscles may be seen moving in one direction at one mo- 
 ment, and a few moments after taking a directly opposite 
 course. Spall anzani, in one of his observations, describes the 
 following phenomenon. Two single rows of corpuscles, pass- 
 ing in two capillary vessels of equal size, were directed to- 
 ward a third capillary vessel, formed by the union of the two 
 others, which would itself admit but a single corpuscle. The 
 corpuscles in one of these vessels seemed to hold back until 
 those from the other had passed in, when they followed in their 
 turn. 1 When the circulation is natural, the movement in 
 the capillaries is always quite slow compared with the move- 
 ment in the arterioles, and is continuous. Here, at last, the 
 impulse of the heart is lost. The corpuscles do not neces 
 sarily circulate in all the capillaries which are in the field ot 
 view. Certain vessels may not receive a corpuscle for some 
 time, but after a while one or two corpuscles become engaged 
 in them, and a current is finally established. Many inter- 
 esting little points are noticed in examining the circulation 
 
 1 SPALLANZANI, Experiences sur la Circulation Paris, 1808, p. 177. 
 
288 CIRCULATION. 
 
 for a length of time. A corpuscle is frequently seen caught 
 at the angle where a vessel divides into two, remaining fixed 
 for a time, distorted and bent by the force of the current. 
 It soon becomes released, and, as it enters the vessel, regains 
 its original form. In some of the vessels of smallest size, the 
 corpuscles are slightly deformed as they pass through. 
 
 The scene is changed with every different part which is 
 examined. In the tongue, in addition to the arterioles and 
 venules, with the rich network of capillaries, dark-bordered 
 nerve-fibres, striated muscular fibres, and pavement epithe- 
 lium can be distinguished. In the lungs, the view is very 
 beautiful. Large, polygonal air-cells are observed, bounded 
 by capillary vessels, in which the corpuscles move with ex- 
 treme rapidity. It has been observed that the larger vessels 
 are crowded to their utmost capacity with corpuscles, leaving 
 no still layer next the walls, such as is seen in the circulation 
 in other situations. 
 
 When the circulation has been for a long time under 
 observation, as the animal becomes enfeebled, very interest- 
 ing changes in the character of the flow of blood take place. 
 The continuous stream in the smallest vessels diminishes 
 in rapidity, and after a while, when the contractions of the 
 heart have become infrequent and feeble, the blood is nearly 
 arrested, even in the smallest capillaries, during the intervals 
 of the heart's action, and the current becomes remittent. 
 As the central organ becomes more and more enfeebled, the 
 circulation becomes intermittent ; the blood receiving an 
 impulse from each contraction, but remaining stationary 
 during the intervals. At this time, the corpuscles cease to 
 occupy exclusively the central portion of the vessels, and the 
 clear layer of plasma next their walls, which was ob- 
 served in the normal circulation, is no longer apparent. 
 Following this, there is actual oscillation in the capillaries. 
 At each contraction of the heart, the blood is forced onwards 
 a little distance, but almost immediately returns to about its 
 former position. This phenomenon has long been observed, 
 
RAPIDITY OF THE CAPILLARY CIRCULATION. 289 
 
 and is explained in the following way : As the heart has 
 become enfeebled, the contractions are so infrequent and in- 
 effectual, that during their intervals the constant flow in the 
 capillaries is entirely arrested ; for the arterial pressure, which 
 is its immediate cause, and which is maintained by the suc- 
 cessive charges of blood sent into the arteries at each ventric- 
 ular systole, is lost. But as the blood is contained in a con- 
 nected system of closed tubes, the feeble impulse of the heart 
 is propagated through the vessels and produces a slight im- 
 pulse, even in the smallest capillaries, which dilates them 
 and forces the fluid a little distance. As soon, however, as 
 the heart ceases to contract, the current is arrested, and the 
 blood, meeting with a certain amount of obstniction from the 
 fluid in the small veins, which are still further removed from 
 the heart, is made to return to its former position. 
 
 This phenomenon continues for a short time only, for the 
 heart soon loses its contractility, and the circulation in all the 
 vessels is permanently arrested. 
 
 Rapidity of the Capillary Circulation. The circulation 
 in the capillaries of a part is subject to such great variations, 
 and the differences in different situations are so considerable, 
 that it is impossible to give any definite rate which will 
 represent the rapidity of the capillary circulation. It is for 
 this reason that it has been found impracticable to estimate 
 the capacity of the capillary, as compared with the arterial, 
 system. The rapidity of the flow of blood is by no means 
 as great as it appears in microscopic examinations; being, 
 of course, exaggerated in proportion to the magnifying power 
 employed. It is, nevertheless, to microscopic investigations 
 that we are indebted for the scanty information we possess 
 on this subject. The estimates which have been made by 
 various observers refer generally to cold-blooded animals, and 
 have been arrived at by simply calculating the time occupied 
 by a blood-corpuscle in passing over a certain distance. Hales, 
 who was the first to investigate this question, estimated that 
 19 
 
290 CIRCULATION. 
 
 in the frog a corpuscle moved at the rate of an inch in ninety 
 seconds. 1 The estimates of Weber and Yalentin are con- 
 ' siderably higher, being about -fa f an i ncn P er second. 
 Yolkmann calculated the rapidity in the mesentery of the 
 dog, which would approximate more nearly to the human 
 subject, and found it to be aftout -fa of an inch per second. 3 
 Yierordt made a number of curious observations upon him- 
 self, by which he professed to be able to estimate the rapidity 
 of the circulation in the little vessels of the eye. He states 
 that when the eye is fatigued, and sometimes when the ner- 
 vous system is disordered, compression of the globe in a cer- 
 tain way will enable one to see a current like that in a capil- 
 lary plexus. This he believes to be the capillary circulation, 
 and by certain calculations he formed an estimate of its rapid- 
 ity, putting it at from -fa to -fa of an inch. The latter figure 
 accords pretty nearly with the observations of Yolkmann 
 upon the dog. 3 How far these observations are to be relied 
 upon it is impossible to say. Certainly no great importance 
 would be attached to them if they did not, in their results, 
 approximate to the estimates of Yolkmann, which probably 
 represent, more nearly than any, the rapidity in the capil- 
 laries of the human subject. 
 
 After what has been said of the variations in the capillary 
 circulation, it is evident that the foregoing estimates are by 
 no means to be considered exact. 
 
 delations of the Capillary Circulation to Respiration. - 
 In treating of the influence of respiration upon the action of 
 the heart, the arterial pressure, pulse, etc., it has already 
 been stated that non-aerated blood cannot circulate freely in 
 the capillaries. Yarious ideas with regard to the effects of 
 asphyxia upon the circulation have been advanced, which 
 will be again discussed in connection with respiration. The 
 
 1 Statical Essays, containing Hcemastaticks, London, 1733, p. 68. 
 
 a MILNE-EDWARDS, Lemons sur la Physiologic, Paris, 1859, tome iv., p. 286. 
 
 'Ibid. 
 
RELATIONS TO KESPIKATION. 291 
 
 fact is evident, that arrest of respiration produces arrest of 
 circulation. This is ordinarily attributed to an impediment 
 to the passage of blood through the lungs, when they no 
 longer contain the proper quantity of oxygen. This view is 
 entirely theoretical, and has been disproved by experiments 
 dating more than half a century ago. In 1789, Goodwyn 
 advanced the theory that, in asphyxia, the blood passes 
 through the lungs, but is incapable of exciting contractions 
 in the left ventricle. 1 Bichat, in his celebrated essay " Sur 
 la Vie et la Mort" 1805, proved by experiment that black 
 blood passes through the lungs in asphyxia, and is found in 
 the arteries. His theory was that non-aerated blood, circu- 
 lating in the capillaries of the nervous centres, arrests their 
 function, thus acting indirectly upon the circulation ; and 
 that finally the heart itself is paralyzed by the circulation of 
 black blood in its substance. 
 
 Dr. John Keid, in an article " On the Cessation of the 
 Yital Actions in Asphyxia," a describes an experiment in which 
 a hemodynamometer applied to the femoral artery of a dog 
 indicated increase in the arterial pressure during the first 
 moments of asphyxia, followed finally by a depression in the 
 mercury. He found a corresponding diminution in the 
 pressure in the vein of the opposite side. " This was so un- 
 looked for at first sight so inexplicable, and so much at 
 variance with my preconceived notions on the subject," says 
 the author, "that I was strongly inclined to believe there 
 must be some source of fallacy ; but after repeating the ex- 
 periment more than twenty times, and invariably with the 
 same results, I was at last compelled to admit its accuracy." 
 This he surmises is due to " an impediment to the passage of 
 the venous blood through the capillaries of the systemic cir- 
 culation." In his conclusions at the end of the article, how- 
 
 1 P. BERARD, Cours de Physiologic fait d la Faculte de Medecine de Paris, 
 1851, tome iii., p. 444. 
 
 a JOHN REID, M. D., Physiological, Anatomical, and Pathological Researches, 
 Edinburgh, 1848, p. 26. (Article extracted from the Edinburgh Medical and 
 Surgical Journal, April, 1841.) 
 
CIRCULATION. 
 
 ever, he takes no account of the results of this experiment, 
 which point conclusively to arrest of blood in the capillary 
 system, and the conclusions with regard to the effect of as- 
 phyxia upon the circulation are substantially those of Bichat. 
 
 The immediate effects of asphyxia upon the circulation 
 are referable to the general capillary system. This fact was 
 demonstrated by experiments on the frog published in 1857. * 
 In these experiments, the medulla oblongata was broken 
 up, and the web of the foot submitted to microscopic exam- 
 ination. This operation does not interfere with the circula- 
 tion, which may be observed for hours without difficulty. 
 The cutaneous surface was then coated with collodion, care 
 only being taken to avoid the web under observation. The 
 effect on the circulation was immediate. It instantly be- 
 came less rapid, until, at the expiration of twenty minutes, 
 it had entirely ceased. The entire coating of collodion was 
 then instantly peeled off. Quite a rapid circulation imme- 
 diately commenced, but it soon began to decline, and in 
 twenty minutes had almost ceased. In another observation, 
 the coating of collodion was applied without destroying the 
 medulla. The circulation was affected in the same manner 
 as before, and ceased in twenty-five minutes. 
 
 These experiments, taken in connection with observations 
 on the influence of asphyxia upon the arterial pressure, con- 
 clusively show that non-aerated blood cannot circulate freely 
 in the systemic capillaries. 2 Yenous blood, however, can be 
 forced through them with a syringe, and even in asphyxia it 
 filters slowly through, and if air be admitted to the lungs 
 before the heart has lost its contractility, the circulation's 
 restored. 
 
 Eb differences in the capillary circulation have been no- 
 
 1 See article by the author, entitled "Phenomena of the Capillary Circula- 
 tion," American Journal of the Medical Sciences, July, 1857. 
 
 2 In these experiments, ether had previously been freely applied to the surface 
 to render it certain that the effects on the circulation were not the result of this 
 ingredient of the collodion. 
 
CAUSES OF THE CAPILLARY CIRCULATION. 293 
 
 ticed accompanying the ordinary acts of inspiration and 
 expiration. 
 
 Causes of the Capillary Circulation. The contractions 
 of the left ventricle are evidently capable of giving an im- 
 pulse to the blood in the smallest arterioles, for a marked ac- 
 celeration of the current accompanying each systole can be 
 distinguished in all but the true capillaries. It has also been 
 shown by experiments after death, that blood can be forced 
 through the capillary system and returned by the veins by a 
 force less than that exerted by the heart. This, however, 
 cannot rigidly be applied to the natural circulation, as the 
 smallest arteries are endowed during life with contractility, 
 which is. capable of modifying the blood current. 1 Dr. 
 Sharpey adapted a syringe, with a hemodynamometer at- 
 tached, to the aorta of a dog just killed, and found that fresh 
 defibrinated blood could be made to pass through the double 
 capillary systems of the intestines and liver, by a pressure of 
 three and a half inches of mercury. It spurted out at the 
 vein in a full jet under a pressure of five inches. In this ob- 
 servation, the aorta was tied just above the renal arteries. 
 The same pressure, the ligature being removed, forced the 
 blood through the capillaries of the inferior extremities. 2 
 This is much less than the arterial pressure, which is equal 
 to from five and a half to six inches of mercury. 
 
 It is thus seen that the pressure in the arteries which 
 forces the blood toward the capillaries is competent, unless 
 opposed by excessive contraction of the arterioles, not only to 
 cause the blood to circulate in these vessels, but to return it to 
 the heart by the veins. This fact is so evident, that it is un- 
 
 1 As showing the difference between the vessels immediately after death, and 
 after they have lost all their vital properties, we may refer to an observation of 
 Berard (op. cit., p. 776), in which he found it impossible to inject, with a solidifi- 
 able fluid, parts of the body immediately after amputation. Water passed with 
 facility, but alcohol or vinegar could not be forced through. 
 
 2 TODD and BOWMAN, The Physiological Anatomy and Physiology of Man, 
 Philadelphia, 1857, p. 678. 
 
294: CIRCULATION. 
 
 necessary to discuss the views of Bichat, and some others, 
 who supposed that the action of the heart had no effect upon 
 the capillary circulation. It must be admitted that this is its 
 prime cause ; and the only questions to be considered are, 
 first, whether there be any reason why the force of the heart 
 should not operate on the blood in the capillaries, and 
 second, whether there be any force in these vessels which 
 is superadded to the action of the heart. 
 
 The first of these questions is answered by microscopic 
 observations on the circulation. A distinct impulse, follow- 
 ing each ventricular systole, is observed in the smallest ar- 
 teries. The blood flows from them directly and freely into 
 the capillaries ; and there is not the slightest ground for the 
 supposition that the force is not propagated to this system of 
 vessels. 
 
 Various writers have supposed the existence of a " capil- 
 lary power," which they have regarded as of greater or less 
 importance in producing the capillary circulation. The 
 views of some are purely theoretical, but others base their 
 opinion on microscopic observations. These views do not 
 demand an extended discussion. There is a force in opera- 
 tion, the action of the heart, which is capable of producing 
 the capillary circulation ; and there is nothing in the phenom- 
 ena of the circulation in these vessels, which is inconsistent 
 with its* full operation. Under these circumstances, it is 
 unphilosophical to invoke the aid of the currents produced 
 in capillary tubes in which liquids of different characters are 
 brought ID contact, or a " capillary power " dependent upon 
 a vital nutritive attraction between the tissues and the blood, 
 unless we do it on the basis of phenomena observed in the 
 capillaries when the action of the heart is suppressed. 
 When the heart ceases its action, movements in the 
 capillaries are sometimes due to the contractions of the ar- 
 teries, a property which has already been fully considered. 
 Movements which have been observed in membranes de- 
 tached from the body are due to the mere emptying of the 
 
CAUSES OF THE CAPILLARY CIRCULATION. 295 
 
 divided vessels or simple gravitation. It must be remem- 
 bered that in microscopic examinations, the movements which 
 are observed are immensely exaggerated by the magnifying 
 power, and we receive, at first sight, an erroneous idea of 
 their rapidity. The movements of the blood in detached 
 membranes, due merely to gravity, have been so satisfactorily 
 explained by the experiments of Poiseuille, that it is deemed 
 unnecessary to refer to the observations of those who have 
 attributed this phenomenon to other causes. 1 
 
 Dr. Dowler, of New Orleans, made some experiments on 
 the circulation in patients dead with yellow fever, in which 
 he found that the blood would flow in a tolerably full stream 
 from a punctured vein a few minutes after death. This he 
 attributes to an independent action of the capillaries, which 
 continues for a time after the action of the heart has 
 ceased. 3 These observations are met by the following experi- 
 ment performed years before by Magendie. 3 A ligature was 
 passed around the thigh of a dog, leaving only the crural 
 artery and vein. A ligature was then applied to the vein, 
 and a small opening made below it in the vessel, from which 
 the blood escaped in a jet. On compressing the artery, the 
 flow of blood was not immediately arrested in the vein, but 
 continued to gradually diminish in force until it stopped after 
 a few moments. On examining the artery below the point 
 of compression, it was found contracted, and completely 
 emptied of blood, while the vein was full below the punc- 
 ture. The pressure being removed from the artery, the blood 
 commenced to flow from the vein, and a jet was soon estab- 
 lished as before. When the artery was slightly compressed, 
 so as to allow the passage of a small quantity of blood, not 
 enough to distend the vessel, the blood flowed from the vein, 
 but no longer in a jet. This experiment shows that when 
 
 1 POISEUILLE, Recherches sur les Causes du Mouvement du Sang dans les Vats- 
 seaux Capillaires, 1835, p. 127. 
 
 3 DUNGLISON, Human Physiology, Philadelphia, 1851, vol. i., p. 420 
 
 3 MAGENDIE, Precis filementaire de Physiologic, Paris, 1836, tome ii., p. 390. 
 
296 CIRCULATION. 
 
 an artery supplying a part with blood is removed from the 
 influence of the heart, the vessel will contract and force its 
 contents into the vein. This affords the most rational expla- 
 nation of the phenomena observed by Dr. Dowler. When 
 the blood is allowed to enter slowly, so as not to distend the 
 vessel, though it be supplied *to the capillary system, it does 
 not there undergo any propelling influence, competent, at any 
 time, to increase the rapidity of the flow from the vein. 
 
 Physiologists who, like Bichat, 1 have been unable to 
 explain the local variations in the capillary circulation with- 
 out the intervention of a force resident in these vessels or the 
 surrounding tissues, have not appreciated the action of the 
 arterioles. These little vessels are endowed to an eminent 
 degree with contractility and, by the contractions and re- 
 laxations of their muscular walls, regulate the supply of blood 
 to the capillaries of individual parts. Their action is com- 
 petent to produce all the variations which are observed in the 
 capillary circulation. 
 
 It is evident, then, that the arterial pressure, which is 
 itself derived from the action of the heart, is competent to 
 produce the circulation of the blood, as we observe it, with 
 all its variations, in the capillary vessels ; that there is no 
 evidence of the intervention of any other force, but, on the 
 contrary, microscopic observations and experiments on the 
 arteries and veins, thus far, show that there is no other force 
 in operation. 2 
 
 1 Loc. cit. 
 
 2 It has been asserted that there is a circulation of the blood in the area vas- 
 culosa, the first blood-vessels that are developed, before the heart is formed ; but 
 there are no definite and reliable observations which show that there is any regular 
 movement of the blood, which can be likened to the circulation. as it is observed 
 after the development of the heart, anterior to the appearance of a contractile 
 central organ. Another example of what is supposed to be circulation without 
 the intervention of the heart is in cases of acardiac foetuses. Monsters without a 
 heart, which have undergone considerable development and which present systems 
 of arteries, capillaries, and veins, have been described. All of these, however, 
 are accompanied by a twin, in which the development of the circulatory system is 
 
INFLUENCE OF TEMPERATURE. 297 
 
 Influence of Temperature on the Capillary Circulation. 
 Within moderate limits, a low temperature, induced by local 
 applications, has been found to diminish the quantity of blood 
 sent to the capillaries, and retard the circulation; while a 
 high temperature increases the supply of blood and acceler- 
 ates its current. The mechanism of this is beautifully shown 
 by the experiments of Poiseuille. This observer found that 
 when a piece of ice was applied to the web of a frog's foot, 
 the mesentery of a small warm-blooded animal, or any part 
 in which the capillary circulation can be observed, the quan- 
 tity of corpuscles circulating in the arterioles became very 
 much diminished, " those which carried two or three rows 
 of corpuscles giving passage to but a single row." The cir- 
 culation in the capillaries first became slower, and then en- 
 tirely ceased in parts. On removing the ice, in a very few 
 minutes the circulation regained its former characters. 
 
 If, on the other hand, the part be covered with water at 
 104 , the rapidity of the current in the capillaries is so much 
 
 perfect. The most remarkable case of this kind is one reported by Dr. Houston 
 in the Dublin Journal of Medical Science (1836, vol. x., p. 204). In this case 
 there was a perfect twin, but two distinct cords and sets of membranes. Dr. 
 Houston supposed that the circulation in this monster was carried on by " capil- 
 lary power " alone. In these cases, as has been shown by Astley Cooper and 
 Lallemand (Edinburgh Medical and Surgical Journal, 1844, vol. Ixii., p. 156 et 
 seq.\ there is a free anastomosis of the vessels of the two foetuses in the placenta. 
 Some have supposed, from the fact that the veins of the monster are not provided 
 with valves, that in it the circulation is from the veins to the arteries, or is inverted. 
 It is not exactly clear how the circulation is carried on in an acardiac foetus. Un- 
 doubtedly the heart of one child may influence the circulation in the umbilical 
 vessels of the other, in cases of twins ; for Lallemand has observed (loc. cit.\ after 
 the birth of one child, the cord having been divided, a regular pulsatile flow from 
 the placental extremity of the cord, as from a divided artery ; but we find on 
 careful examination of the case reported by Dr. Houston, and an article on the 
 case by Dr. G. Calvert Holland (Edinburgh Med. and Surg. Journal, loc. cit.\ no 
 sufficient evidence that the circulation was carried on by any " capillary power." 
 Not being able to regard as facts these grounds, on which some have based their 
 belief in the existence of a force in the circulation which is independent of the 
 heart's action, we have abstained from their discussion in treating of the causes 
 of the capillary circulation. 
 
298 CIRCULATION. 
 
 increased, that we can hardly distinguish the form of the 
 corpuscles. 1 
 
 Influence of Direct Irritation upon the Capillary Circu- 
 lation. Experimental researches on the effects of direct irri- 
 tation of the capillaries, in parts where the circulation can 
 be observed microscopically, have been quite numerous since 
 Thompson studied the effects of saline solutions on the web 
 of the frog's foot in 1 813.' The most noticeable papers on 
 this subject are those of Dr. Wilson Philip 3 and Mr. Wharton 
 Jones. 4 The latter paper, which received the Astley Cooper 
 prize for 1850, is based on very extended and carefully 
 conducted observations, in which the author, by means of 
 various irritants, succeeded in producing very curious and 
 interesting phenomena, which he regarded as inflammatory. 
 It is not our object to discuss the nature of inflammation, or 
 to treat of the changes in the character of the capillary circu- 
 lation which are supposed to attend this condition, as this 
 subject is eminently pathological ; but it must be remember- 
 ed, in considering the effects of direct irritation on the capil- 
 lary circulation, that the phenomena thus observed in cold- 
 blooded animals cannot be taken as absolutely representing 
 the characters of inflammation in the human subject. When 
 an irritation is applied to a transparent part, the phenomena 
 observed may be due to many causes, as the direct effects 
 upon the contractile elements of the blood-vessels, the reflex 
 action through the nervous system, and the direct influence 
 of the application upon the constitution of the blood. Saline 
 or other fluids are competent to modify, to a very consider- 
 able extent, the composition of the blood, separated from it 
 only by the thin, permeable -walls of the vessels ; and the 
 
 1 POISEUILLE, op. c'd., p. 158 ei seq. 
 
 2 THOMPSON, Lectures on Inflammation, Edinburgh, 1818. 
 8 Medico- Chirurgical Transactions, 1823, vol. xii. 
 
 4 Guy's Hospital Reports, vol. vii., 1851, On the State of the Blood and tJie 
 Blood-vessels in Inflammation, ascertained by Experiments, Injections, and Obser- 
 vations by the Microscope, by T. WHARTON JONES, F. R. & 
 
INFLUENCE OF IRRITATION. 299 
 
 phenomena which follow their application are necessarily 
 very complex. The process of inflammation is by no means 
 completely understood, but it is pretty generally acknowl- 
 edged to be a modification of nutrition, in a way that we are 
 as yet ignorant of. We are hardly prepared to admit that 
 this modification, whatever it may be, can be induced under 
 our very eyes, simply by the application of irritants. With 
 these views, microscopic researches on the " state of the blood 
 and blood-vessels in inflammation " do not assume the im- 
 portance which is attributed to them by many authors. 
 
 Keeping this in mind, we may state the following as a 
 summary of the phenomena which have been observed in 
 the capillary circulation, as the result of irritation applied to 
 transparent parts : 
 
 The application of the irritant is immediately followed by 
 constriction of the arterioles, and diminution in the rapidity 
 of the current in them as well as in the capillaries. 
 
 This constriction of the vessels is but momentary, if a 
 powerful irritant, like a very strong solution of salt, be used. 
 It is followed by a dilatation of the vessels, and an increase in 
 the rapidity of the circulation. 
 
 Soon after the vessels have become dilated, the rapidity 
 of the circulation is progressively diminished, until oscillation 
 of the blood in the vessels takes place, which occurs when 
 the circulation is about to cease. This oscillation finally 
 gives place to complete stagnation. The vessels become 
 crowded with blood, so that the transparent layer next 
 their walls is no longer observed. In this condition, it has 
 been often noticed that the proportion of colorless corpuscles 
 is increased. 
 
 Following the contraction and subsequent dilatation of the 
 vessels, there is stasis, and engorgement of the parts which 
 have been exposed to irritation. If the irritation be discon- 
 tinued, this condition is gradually relieved, and the blood re- 
 sumes its normal current. 
 
 In inflammation, as it is observed in the conjunctiva and 
 
300 CIRCULATION. 
 
 other vascular parts, there is unquestionably congestion of the 
 vessels ; but there is no positive evidence of stagnation of 
 blood in the parts as a constant occurrence. The circula- 
 tion seems, indeed, to be more active than in health. With 
 regard to the microscopic phenomena just mentioned, the 
 contraction of the arterioles is'simply the effect of a stimulus 
 upon their muscular coats ; and dilatation takes place prob- 
 ably in consequence of the excessive contraction, for it has 
 been shown that this condition of the muscular fibres is pretty 
 constantly followed by unusual relaxation. It has never yet 
 been determined how far the stasis of the blood is due to an 
 osmotic action of solutions employed in observations of this 
 kind. 
 
CHAPTEK VIII. 
 
 CIRCULATION OF THE BLOOD IN THE VEINS. 
 
 Physiological anatomy of the veins Strength of the coats of the veins Valves 
 of the veins Course of the blood in the veins Pressure of blood in the 
 veins Rapidity of the venous circulation Causes of the venous circulation 
 Influence of muscular contraction Air in the veins Function of the valves 
 Venous anastomoses Conditions which impede the venous circulation Re- 
 gurgitant venous pulse. 
 
 Physiological Anatomy of the Veins. The blood, dis- 
 tributed to the capillaries of all the tissues and organs by the 
 arteries, is collected from these parts in the veins and carried 
 back to the heart. In studying the anatomy of the capillary 
 system, or in observing the passage of the blood from the 
 capillaries to larger vessels, in parts of the living organism 
 which can be submitted to microscopic examination, it is 
 seen that the capillaries, vessels of nearly uniform diameter 
 and anastomosing in every direction, give origin, so to speak, 
 to a system of vessels, which, by union with others as we fol- 
 low their course, become larger and larger, and carry the 
 blood away in a uniform current. These are called the 
 venules, or venous radicles. They are the peripheral radicles 
 of the numerous vessels which transport the blood, after it 
 has served the purposes of nutrition or secretion, to the cen- 
 tral organ. 
 
 The venous system may be considered, in general terms, 
 as divided into two sets of vessels : one, which is deep, and 
 
CIRCULATION. 
 
 situated in proximity to the arteries ; and the other, which 
 is superficial, and receives for the most part the blood from 
 the cutaneous surface. The entire capacity of these vessels, 
 as compared with the arteries, is very great. As a general 
 rule, each vein when fully distended is larger than its adja- 
 cent artery. Many arteries are accompanied by two veins, 
 as the arteries of the extremities; while certain of them, like 
 the brachial or spermatic, have more than two. Added to 
 these is the superficial system of veins which have no corre- 
 sponding arteries. It is true that some arteries have no cor- 
 responding veins, but examples of this kind are not sufficient- 
 ly numerous to diminish, in any marked degree, the great 
 preponderance of the veins, both in number and volume. It 
 is impossible to give an accurate estimate of the extreme ca- 
 pacity of the veins as compared with the arteries ; but from 
 the best information we have, it is several times greater. 
 Borelli estimated that the capacity of the veins was, to the 
 capacity of the arteries, as 4 to 1 ; and Haller, as 2J to 1. 
 The proportion is very variable in different parts of the body. 
 In some situations the capacity of the veins and arteries is 
 about equal ; while in others, as in the pia mater, according 
 to the researches of Hirschfeld, the veins will contain six 
 times as much as the arteries. 1 
 
 In attempting to compare the quantity of blood normally 
 circulating in the veins, with that contained in the arteries, 
 such variations in the venous system at different times and 
 in different parts, both in the quantity of blood, rapidity of 
 circulation, pressure, etc., are found, that a definite estimate 
 is impossible. It would be unphilosophical to attempt an 
 approximate comparison, as the variations in the venous cir- 
 culation constitute one of its greatest and most important 
 physiological peculiarities, which must be fully appreciated 
 in order to form a just idea of the function of the veins. 
 
 1 BERARD, Cours de Physiologic, Paris, 1855, tome iv., p. Y. The circulation 
 in the erectile tissues will be separately considered, and no account is now taken 
 of the relative capacity of veins and arteries in them. 
 
PHYSIOLOGICAL ANATOMY OF THE VEINS. 303 
 
 The arteries are always full, and their tension is subject to 
 comparatively slight variations. Following the blood into 
 the capillaries, there are the immense variations in the circu- 
 lation with varying physiological conditions of the parts, 
 which we have already noted. As should naturally be ex- 
 pected, the condition of the veins varies with the changes in 
 the capillaries, from which the blood is taken. In addition 
 to this, there are independent variations, as in the erectile 
 tissues, in the veins of the alimentary canal during absorp- 
 tion, in veins subject to pressure, etc. 
 
 Following the veins in their course, it is observed that 
 anastomoses with each other form the rule and not the 
 exception, as in the arteries. There are always a number of 
 channels by which the blood may be returned from a part ; 
 and if one vessel be obstructed from any cause, the current 
 is simply diverted into another. The veins do not present a 
 true anastomosing plexus, such as exists in the capillary sys- 
 tem, but simply an arrangement by which the blood can 
 easily find its way back to the heart, and by which the ves- 
 sels may accommodate themselves to the immense variations 
 in the quantity of fluid contents to which they are liable. 
 This, with the peculiar valvular arrangement in all but the 
 veins of the cavities, provides against obstruction to the flow 
 of blood through, as well as from, the capillaries, in which 
 it seems essential to the proper nutrition and function of 
 parts, that the quantity and course of the blood should be 
 regulated exclusively through the arterial system. Special 
 allusion to the different venous anastomoses belongs to de- 
 scriptive anatomy. Physiologically, the communication be- 
 tween the different veins is such that the blood can always 
 find a way to the heart, and once fairly out of the capillaries, 
 it cannot react and influence the circulation of fresh blood in 
 the tissues. 
 
 Collected in this way from all parts of the body, the blood 
 is returned to the right auricle, from the head and upper 
 extremities, by the superior vena cava, from the trunk and 
 
304: CIRCULATION. 
 
 lower extremities, by the inferior yena cava, and from the 
 substance of the heart, by the coronary veins. 
 
 Structure and Properties of the Veins. The structure of 
 the veins is somewhat more complex and difficult of study than 
 that of the arteries. Their walls, which are always much 
 thinner than the walls of the arteries, may be divided into 
 quite a number of layers ; but for convenience of physiologi- 
 cal description, we shall regard them as presenting three dis- 
 tinct coats. These have properties which are tolerably distinc- 
 tive, though not as much so as the three coats of the arteries. 
 
 The internal coat is a continuation of the single coat of 
 the capillaries and the internal coat of the arteries. It is a 
 simple, homogeneous membrane, somewhat thinner than in 
 the arteries, lined by a delicate layer of epithelium. 
 
 The middle coat is divided by some into two layers : an 
 internal layer, which is composed chiefly of longitudinal 
 fibres ; and an external layer, in which the fibres have a cir- 
 cular direction. These two layers are intimately adherent, 
 and are quite closely attached to the internal coat. The 
 longitudinal fibres are composed of the white fibrous tissue 
 mingled with a large number of the smallest variety of the 
 elastic fibres. This layer contains a large number of capil- 
 lary vessels (vasa vasorum). The circular fibres are com- 
 posed of the elastic tissue, some of the same variety as found 
 in the longitudinal layer, some of medium size, and some in 
 the form of the " fenestrated membrane." In addition, there 
 are white inelastic fibres interlacing in every direction and 
 mingled with capillary blood-vessels, and the unstriped or 
 involuntary muscular fibres, which are always circular in 
 their direction. The muscular fibres are relatively much 
 less numerous than in the arterial system. They are most 
 abundant in the superficial veins. 
 
 The external coat is generally composed simply of the 
 white fibrous tissue, like the corresponding coat of the arte- 
 ries. In the largest veins, particularly those of the abdominal 
 
STRUCTURE OF THE VEINS. 305 
 
 cavity, this .coat contains a layer of longitudinal unstriped 
 muscular fibres. In the veins near the heart, are found a few 
 striated fibres, which are continued on to the veins from the 
 auricles. In some of the inferior animals, as the turtle, these 
 fibres are quite thick, and pulsation of the veins in the imme- 
 diate vicinity of the heart is very marked. 
 
 In nearly all veins, the external coat is several times 
 thicker than the internal. This is most marked in the larger 
 veins, in which the middle coat, particularly the layer of 
 muscular fibres, is very slightly developed. 
 
 In what are called the venous sinuses, and in the veins 
 which pass through bony tissue, we have only the internal 
 coat, to which are superadded a few longitudinal fibres, the 
 whole closely attached to the surrounding parts. As exam- 
 ples of this, may be mentioned the sinuses of the dura mater, 
 and the veins of the large bones of the skull. In the first in- 
 stance, there is little more than the internal coat of the vein 
 firmly attached to the surrounding layers of the dura mater. 
 In the second instance, the same thin membrane is adherent 
 to bony canals formed by a layer of compact tissue. The 
 veins are much more closely adherent to the surrounding tis- 
 sues than the arteries, particularly when they pass between 
 layers of aponeurosis. This fact has been pointed out by 
 Berard 1 as very general, and is one to which he attaches 
 considerable physiological importance. He considers that 
 this arrangement serves to keep the veins open and give 
 them additional strength. 
 
 The above peculiarities in the anatomy of the veins indi- 
 cate considerable differences in their properties, as compared 
 with the arteries. When a vein is cut across, its walls fall 
 together, if not supported by adhesions to surrounding tis- 
 sues, so that its caliber is nearly or quite obliterated. The 
 yellow elastic tissue, which gives to the larger arteries their 
 great thickness, is very scanty in the veins, and the thin- 
 walls collapse when not sustained by liquid in the interior of 
 
 2 Op. cit., tome iv., p. 9. 
 20 
 
306 CIRCULATION. 
 
 the vessels. Whenever the veins remain open after section, 
 it is on account of their attachment to surrounding tissues, 
 and is not due to the walls of the vessels themselves. 
 
 Though with much thinner and apparently much weaker 
 walls, the veins, as a rule, will resist a greater pressure than 
 the arteries. Observations on the relative strength of the 
 arteries and veins were made by Hales, 1 but the most ex- 
 tended experiments on the subject were made by Clifton 
 Wintringham, in 1740. 3 This observer ascertained that the 
 inferior vena cava of a sheep, just above the opening of 
 the renal veins, was ruptured by a pressure of 176 pounds, 
 while the aorta at a corresponding point yielded to a pressure 
 of 158 pounds. The strength of the portal vein was even 
 greater, supporting a pressure of nearly 5 atmospheres, bear- 
 ing a relation to the vena cava of 6 to 5 ; yet these vessels 
 had hardly one-fifth the thickness of the arteries. In the 
 lower extremities in the human subject, the veins are much 
 thicker and stronger than in other situations, a provision 
 against the increased pressure to which they are habitually 
 subjected in the upright posture. Wintringham noticed one 
 singular exception to the general rule just given. In the 
 vessels of the glands, and of the spleen, the strength of the 
 arteries was much greater than that of the veins. The splenic 
 vein gave way under a pressure of little more than one atmos- 
 phere, while the artery supported a pressure of more than 
 six atmospheres. 
 
 A little reflection on the influences to which the venous 
 and arterial circulation are subject will enable us to under- 
 stand the physiological importance of the great difference in 
 the tenacity of the two varieties of vessels. It is true that in 
 the arterial system the constant pressure is greater than in 
 
 1 Statical Essays, vol. ii., p. 154 et seq. These observations are not very sat- 
 isfactory. In a case where the strength of the carotid and jugular were com- 
 pared, in a mare, the carotid sustained the greater pressure ; but it is stated that 
 the jugular had been weakened by repeated venesections. 
 
 2 BERARD, op. cit., tome iv., p. 24 et seq. 
 
PKOPEETIE8 OF THE VEINS. 307 
 
 the veins ; but it is nearly the same in all the vessels, and 
 the immense extent of the outlet into the capillaries provides 
 against any very great increase in pressure, so long as the 
 blood is in a condition which enables it to pass into the ca- 
 pillaries. The muscular fibres of the left ventricle have but 
 a limited power, and when the pressure in the arteries is 
 such, as it sometimes is in asphyxia, as to close the aortic 
 valves so firmly that the force of the ventricle will not open 
 them, it cannot be increased. At the same time it is being 
 gradually relieved by the capillaries, through which the blood 
 slowly filters, even when completely unaerated. With the 
 veins it is different. The blood has a comparatively restrict- 
 ed outlet at the heart, and is received by the capillaries from 
 all parts of the system. The vessels are provided with nu- 
 merous valves, which render a general backward action im- 
 possible. Thus, restricted portions of the venous system, 
 from pressure in the vessels, increase of fluid from absorption, 
 accumulation by force of gravity, and other causes, may be 
 subjected to great and sudden variations in pressure. The 
 great strength of these vessels enables them ordinarily to 
 suffer these variations without injury ; though varicose veins 
 in various parts present examples of the effects of repeated 
 and continued distention. 
 
 The veins possess a considerable degree of elasticity, 
 though this property is not as marked as it is in the arteries. 
 If we include between two ligatures a portion of a vein dis- 
 tended with blood, and make a small opening in the vessel, 
 the blood will be ejected with some force, and the vessel be- 
 comes very much reduced in caliber. 
 
 It has been proven by direct experiment that the veins 
 are endowed with that peculiar contractility which is char- 
 acteristic of the action of the unstriped muscular fibres. On 
 the application of galvanic or mechanical excitation, they 
 contract slowly and gradually, the contraction being followed 
 by a correspondingly gradual relaxation. There is never any 
 rhythmical or peristaltic movement in the veins, which is 
 
308 CIRCULATION. 
 
 competent to assist the circulation. 1 The only regular move- 
 ments which occur are seen in the vessels in immediate prox- 
 imity to the right auricle, which are provided with a few 
 fibres similar to those which exist in the walls of the heart. 
 
 Nerves, chiefly from the sympathetic system, have been 
 demonstrated in the walls of the larger veins, but have not 
 been followed out to the smaller ramifications. 
 
 Valves of the Veins. The discovery of the valves of the 
 veins has already been alluded to in connection with the his- 
 tory of the discovery of the circulation. They had undoubt- 
 edly been observed in various parts of the venous system by 
 Cananius, and found very generally distributed throughout 
 this system by Piccolomini, the last named anatomist having 
 published an account of them in 1586 ; but Fabricius, the 
 greatest anatomist of his day, had the good fortune to dem- 
 onstrate them to his illustrious pupil William Harvey, 
 whose immortal discovery indicated their physiological im- 
 portance. Being ignorant of the observations of his prede- 
 cessors on this subject, Fabricius announced himself as their 
 discoverer, and is generally so regarded. In all parts of the 
 venous system, except, in general terms, in the abdominal, 
 thoracic, and cerebral cavities, there exist little membranous 
 semilunar folds, resembling the aortic and pulmonic valves of 
 the heart. When distended, the convexities of these valves 
 look toward the periphery. In the great majority of instances 
 the valves exist in pairs, but are occasionally found in groups 
 of three. They are formed of the delicate lining membrane 
 of the veins, with the internal or longitudinal layer of the 
 middle coat. Some transverse fibres are found around the 
 base of the valves, and a few muscular fibres have been 
 
 1 This statement applies particularly to the human subject. Schiff has noticed 
 rhythmical contractions of the veins in the ear of a rabbit (LONGET, Traite de 
 Physiologic, Paris, 1861, tome i., p. 876), and Mr. Wharton Jones has observed 
 the same phenomenon in the wing of the bat (TODD and BOWMAN, Physiological 
 Anatomy, Am. ed. 1857, p. 703, note). There is no evidence that this is general, 
 or that it has any influence in favor of the circulation. 
 
VALVES OF THE VEINS. 300 
 
 traced into their folds. There exists, also, a fibrous ring fol- 
 lowing the line of attachment of the valvular curtains to the 
 vein, which renders the vessel much stronger and less dilata- 
 ble here than in the spaces between the valves. The valves 
 are by far the most numerous in the veins of the lower ex- 
 tremities. They are generally situated just below the point 
 where a small vein empties into one of larger size, so that the 
 blood, as it passes in, finds an immediate obstacle to passage 
 in the wrong direction. The situation of the valves may be 
 readily observed in any of the superficial veins. If the flow 
 of blood be obstructed, little knots will be formed in the con- 
 gested vessels, which indicate the position and action of the 
 valves. The simple experiment of Harvey, already referred 
 to, presents a striking illustration of the action of the valves. 
 When the vein is thus congested and knotted, if the finger be 
 pressed along the vessel in the direction of the blood current, a 
 portion situated between two valves may be emptied of blood ; 
 but it is impossible to empty any portion of the vessel by 
 pressing the blood in the opposite direction. On slitting 
 open a vein, we observe the shape, attachment, and extreme 
 delicacy of structure of the valves. When the vessel is 
 empty, or when fluid moves toward the heart, they are closely 
 applied to the walls ; but if liquid or air be forced in the 
 opposite direction, they^ project into its caliber, and by the 
 application of their free edges to each other, effectually pre- 
 vent any backward current. Fabricius noted the following 
 peculiarity in the arrangement of the valves. When closed, 
 the application of their free edges forms a line which runs 
 across the vessel ; it is found that in successive sets of valves 
 these lines are at right angles to each other, so that if in one 
 set, this line has a direction from before backwards, in the 
 sets above and below the lines run from side to side. 
 
 There are certain exceptions to the general proposition 
 that the veins of the great cavities are not provided with 
 valves. Yalves are found in the portal system of some of 
 the inferior animals, as the horse. They do not exist, how- 
 
310 CrRCULATTOK". 
 
 ever, in this situation in the human subject. Generally, in 
 following out the branches of the inferior vena cava, no 
 valves are found until we come to the crural vein ; but occa- 
 sionally there is a double valve at the origin of the external 
 iliac. In some of the inferior animals, there exists constantly 
 a single valvular fold in the vena cava at the openings of the 
 hepatic, and one at the opening of the renal vein. This is 
 not constant in the human subject. 1 Valves are found in the 
 spermatic, but not in the ovarian veins. A single valvular 
 fold has been described by Dr. J. H. Brinton, at the opening 
 of the right spermatic into the vena cava. 8 There are two 
 valves in the azygos vein near its opening into the superior 
 vena cava. There is a single valve at the orifice of the 
 coronary vein. There are no valves at the openings of the 
 brachio-cephalic into the superior vena cava ; but there is a 
 strong double valve at the point where the internal jugular 
 opens into the brachio-cephalic. Between this point and the 
 capillaries of the brain, the vessels are entirely deprived of 
 valves, except in very- rare instances, when one or two are 
 found in the course of the jugular. 
 
 In addition to the double, or more rarely triple, valves 
 which have just been described, there is another variety, 
 found in certain parts, at the point where a tributary vein 
 opens into a main trunk. This consists of a single fold which 
 is attached to the smaller vessel, but 'projects into the larger. 
 Its action is to prevent regurgitation, by the same mechanism 
 as the ileo-csecal valve prevents the passage of matter from 
 the large into the small intestine. These vajves are much 
 less numerous than the first variety. 
 
 1 Dr. Crisp, of England, has described valves in the splenic veins in some of 
 the inferior animals. In one of the mesenteric veins of the reindeer, he showed 
 forty-two pairs of valves (New York Medical Journal, April, 1865, p. 67). 
 
 a Description of a Valve at the Termination of the Right Spermatic Vein 
 in the Vena Cava, with Remarks on its Relations to Varicocele. By JOHN H. 
 BRINTON, M. D. American Journal of the Medical Sciences, July, 1856. The 
 presence of this valve, according to Dr. Brinton, explains the more frequent oc- 
 currence of varicocele on the right side. 
 
COURSE OF THE BLOOD IN THE VEINS. 311 
 
 The veins form a system which is adapted to the re- 
 turn of blood to the heart in a comparatively slow and 
 unequal current. Distention of certain portions is pro- 
 vided for ; and the vessels are so protected with valves, 
 that whatever influences the current must favor its flow in 
 the direction of the heart. It is a system which is cal- 
 culated to receive the blood from the parts after it has 
 become unfit for nutrition, and pass it in the requisite 
 quantity to the lungs, through the right side of the heart, 
 for regeneration. 
 
 Course of the Blood in the Veins. The experiments of 
 Hales and Sharpey, showing that defibrinated blood can be 
 made to pass from the arteries into the capillaries and out at 
 the veins by a pressure less than that which exists in the 
 arterial system, and the observations of Magendie upon the 
 circulation in the leg of a living dog, showing that ligation 
 of the artery arrests the flow in the vein, points which have 
 already been fully discussed in treating of the causes of the 
 capillary circulation, have established, beyond question, the 
 fact that the force exerted by the left ventricle is sufficient to 
 account for the venous circulation. The heart must be con- 
 sidered the prime cause of all movement in these vessels. 
 Regarding this as definitely ascertained, there remain to con- 
 sider, in the study of the course of the blood in the veins, the 
 character of the current, the influence of the vessels them- 
 selves, and the question of the existence of forces which may 
 assist the vis a tergo from the heart, and circumstances which 
 may interfere with the flow of blood. 
 
 As a rule, in the normal circulation, the flow of blood in 
 the veins is continuous. The intermittent impulse of the 
 heart, which progressively diminishes as we recede from this 
 organ, but is still felt even in the smallest arteries, is lost, as 
 we have seen, in the capillaries. Here, for the first time, the 
 blood moves in a constant current ; and as the pressure in the 
 arteries is continually supplying fresh blood, that which has 
 
312 CIRCULATION. 
 
 circulated in the capillaries is forced into the venous radicles 
 in a steady stream. As the supply to the capillaries of differ- 
 ent parts is regulated by the action of the small arteries, and 
 as this supply is subject to great variations, there must neces- 
 sarily be corresponding variations in the intensity of the 
 current in the veins, and the quantity of blood which these 
 vessels receive. As we should anticipate, then, the venous 
 circulation is subject to very great variations arising from ir- 
 regularity in the supply of blood, aside from any action of 
 the vessels themselves, or any external disturbing influences. 
 A great variation in the venous current is observed in the 
 veins which collect the blood from the intestinal canal. 
 During the intervals of digestion, these vessels carry a com- 
 paratively small quantity of blood; but during digestion, 
 they are laden with the fluids received by absorption, and the 
 quantity is immensely increased. 
 
 It often happens that a vein becomes obstructed from 
 some cause which is entirely physiological, as the action of 
 muscles. The immense number of veins, as compared with 
 the arteries, and their free communications with each other, 
 provide that the current, under these circumstances, is sim- 
 ply diverted, passing to the heart by another channel. When 
 any part of the venous system is distended, the vessels react 
 on the blood, and exert a certain influence on the current, 
 always pressing it toward the heart, for the valves oppose the 
 flow in the opposite direction. 
 
 The intermittent action of the heart, which pervades the 
 whole arterial system, is generally absorbed, as it were, in 
 the passage of the blood through the capillaries ; but when 
 the arterioles of any part are very much relaxed, the impulse 
 of the central organ may extend to the veins. Bernard has 
 shown this in the most striking manner, in his well-known 
 experiments on the circulation in the glands. 1 When the 
 glands are in physiological activity, the quantity of blood 
 
 1 BERNARD, Liquides de V Organisme, Paris, tome i., p. 301 ; and Journal de 
 tAnatomie ct de la Physiologic, Septembre, 1864, p. 507 et seq. 
 
COURSE OF THE BLOOD W THE VEINS. 313 
 
 which they receive is very much increased. It is then fur- 
 nished to supply material for the secretion, and not exclu- 
 sively for nutrition. If the vein be opened at such a time, it 
 is found that the blood has not lost its arterial character, that 
 the quantity which escapes is much increased, and the flow 
 is in an intermittent jet, as from a divided artery. This is 
 due to the relaxed condition of the arterioles of the part, and 
 the phenomenon thus observed is the true venous pulse. 
 "What thus, occurs in a restricted portion of the circulatory 
 system may take place in all the veins, though in a less 
 marked degree. Physicians have frequently noticed, after 
 the blood has been flowing for some time, in the operation of 
 venesection, that the color changes from black to red, and 
 the stream becomes intermittent, often leading the operator 
 to fear that he has pricked the artery. In all probability 
 the phenomenon is due to the relaxation of the arterioles, as 
 one of the effects of abstraction of blood, producing the 
 same condition that has been noted in some of the glands 
 during their functional activity. The hypothesis that it is 
 due to an impulse from the adjacent artery is not admissible. 
 Except in the veins near the heart, any pulsation which oc- 
 curs is to be attributed to the force of the heart, transmitted 
 with unusual facility through the capillary system. A nearly 
 uniform current, however, is the rule, and a marked pulsation 
 the rare exception. Mr. T. "W. King, in an article on the 
 " Safety-Yalve of the Human Heart," * discussing the forces 
 which concur to produce the venous circulation, mentions 
 the fact that in some individuals, after a full meal, pulsation 
 can be observed in the veins of the hand or the median veins 
 of the forehead. This phenomenon is very delicate, and, to 
 make it more apparent, he employed a thread of black seal- 
 ing wax about two inches long, which was fixed across the 
 vein of the back of the hand with a little tallow, so as to 
 make a long and excessively light lever, capable of indicating 
 a very slight movement in the vessel. In this way he dem- 
 
 1 Guy's Hospital Reports, 1837. 
 
314 CIRCULATION. 
 
 onstrated pulsation in the veins of the hand, and also in 
 the arm, foot, and leg. These movements are very slight,, 
 and are generally only appreciable by some such delicate 
 means of investigation. This is a strong argument in oppo- 
 sition to the opinion of those who regard the action of the 
 heart as inoperative in the veins. In certain cases of disease, 
 Mr. King has noted very marked pulsation in the veins of 
 the back of the hand, and other vessels far removed from 
 the heart. 
 
 Pressure of Blood in the Veins. The pressure in the 
 veins is always much less than in the arteries. It is exceed- 
 ingly variable in different parts of the venous system, and in 
 the same part at different times. As a rule, it is in inverse 
 ratio to the arterial pressure. Whatever favors the passage 
 of blood from the arteries into the capillaries has a tendency 
 to diminish the arterial pressure ; and, as it increases the 
 quantity of blood which passes into the veins, must increase 
 the venous pressure. The great capacity of the venous sys- 
 tem, its numerous anastomoses, the presence of valves which 
 may shut off a portion from the rest, are circumstances which 
 involve great variations in pressure in different vessels. It 
 has been ascertained by Yolkmann, and this has been con- 
 firmed by others, that as a rule the pressure is diminished as 
 we pass from the periphery toward the heart. In an obser- 
 vation on the calf, he found that with a pressure of about 6'5 
 inches of mercury in the carotid, the pressure in the meta- 
 tarsal vein was 1*1 inch, and but O36 in the jugular. 1 The 
 pressure is, of course, subject to certain variations. Muscular 
 effort has a marked influence on the force of the circulation 
 in certain veins, and, consequently, in these vessels produces 
 an elevation in the pressure. As the reduced pressure in the 
 veins is due in a measure to the great relative capacity of 
 the venous system, and the free communications between the 
 vessels, it would seem that if it were possible to reduce the 
 
 1 MILNE-EDWARDS, Lepons sur la Physiologic, Paris, 1859, tome iv., p. 329. 
 
CAUSES OF THE VENOUS CIRCULATION. 315 
 
 capacity of the veins in a part, and force all the blood to 
 pass to the heart by a single vessel corresponding to the ar- 
 tery, the pressure in this vessel should be greatly increased. 
 Poiseuille has shown this to be the fact by the experiment of 
 ligating all the veins coming from a part, except one, which 
 had the volume of the artery by which the blood was sup- 
 plied, forcing all the blood to return by this single channel. 
 This being done, he found the pressure in the vein immensely 
 increased, becoming nearly equal to that in the artery. 1 
 
 Rapidity of the Venous Circulation. It is impossible to 
 fix upon any definite rate as representing the rapidity of the 
 current of blood in the veins. It will be seen that various 
 circumstances are capable of increasing very considerably the 
 rapidity of the flow in certain veins, and that under certain con- 
 ditions the current in some parts of the venous system is very 
 much retarded. Undoubtedly the general movement of blood 
 in the veins is very much slower than in the arteries, from 
 the fact that the quantity of blood is greater. If it be as- 
 sumed that the quantity of blood in the veins is double that 
 contained in the arteries, the general average of the current 
 would be diminished one-half. As we near the heart, how- 
 ever, the flow becomes more uniform, and progressively in- 
 creases in rapidity. 
 
 As the effect of the heart's action upon the venous circu- 
 lation is subject to so many modifying influences through the 
 small arteries and capillaries, and as there are other forces 
 influencing the current, which are by no means uniform in 
 their action, with our present knowledge, estimates of the 
 general rapidity of the venous circulation, or the variations 
 in different vessels, would be founded on mere speculations. 
 
 Causes of the Venous Circulation. 
 
 In the veins, the blood is farthest removed from the influ- 
 ence of the contractions of the left ventricle ; and though 
 
 1 BERARD, Cows de Physiologic, Paris, 1855, tome iv., p. 21. 
 
316 CIRCULATION. 
 
 these are felt, there are many other causes which combine to 
 carry on the circulation, and many influences by which it is 
 retarded or obstructed. 
 
 The great and uniform force which operates on the circu- 
 lation in these vessels is the vis a tergo. We have repeatedly 
 referred to the entire adequacy of the arterial pressure, prop- 
 agated through the capillaries, to account for the movement of 
 blood in the veins, provided there be no very great obstacles 
 to the current. There are no facts which lead us to doubt the 
 operation of this force as the prime cause of the venous circula- 
 tion ; and the only question which arises is whether there be 
 any force exerted in the capillaries themselves which is super- 
 added to the force of the heart. In discussing the capillary 
 circulation, there has been found no direct proof of the exist- 
 ence of a distinct " capillary power " influencing the move- 
 ment of blood in these vessels ; and consequently all the vis 
 a tergo operating on the circulation in the veins must be 
 attributed to the action of the left ventricle. 
 
 The other forces which concur to produce movement of 
 blood in the veins are : 
 
 1. Muscular action, by which many of the veins are at 
 times compressed, thus forcing the blood toward the heart, 
 regurgitation being prevented by the action of the valves. 
 
 2. A suction force exerted by the action of the thorax in 
 respiration; operating, however, only on the veins in the 
 immediate neighborhood of the chest. 
 
 3. A possible influence in the contraction of the coats of 
 the vessels themselves. This is marked in the veins near the 
 heart, in some of the inferior animals. 
 
 4. The force of gravity, which operates only on vessels 
 which carry blood from above downward to the heart ; and 
 a little suction force which may be exerted upon the blood in 
 a small vein as it passes into a larger vessel in which the 
 current is more rapid. 
 
 The obstacles to the venous circulation are: Pressure 
 sufficient to obliterate the caliber of a vessel, when, from the 
 
CAUSES OF THE VENOUS CIRCULATION. 317 
 
 free communication with other vessels, the current is simply 
 diverted into another channel ; the expulsive efforts of res- 
 piration ; the contractions of the right side of the heart ; and 
 the force of gravity, which operates, in the erect posture, on 
 the current in all excepting the veins of the head, neck, and 
 parts of the trunk above the heart. 
 
 Influence of Muscular Contraction. That the action of 
 muscles has a considerable influence on the current of blood 
 in the veins situated between them, and in their substance, has 
 long been recognized. It is exemplified in the operation of 
 venesection, when it is well known that the jet from the vein 
 may be very much increased in force by contraction of the 
 muscles below the opening. This action is so marked, that 
 the parts of the venous system which are situated in the sub- 
 stance of muscles have been compared by Chassaignac to a 
 sponge full of liquid, vigorously pressed by the hand. 1 It 
 must always, be remembered, however, that though the 
 muscles are capable of acting on the blood contained in veins 
 in their substance with great vigor, the heart is fully capable 
 of producing the venous circulation without their aid ; a fact 
 which is exemplified in a striking manner in the venous cir- 
 culation in paralyzed parts. 
 
 It has been shown by actual observations with the hemo- 
 dynamometer, that muscular action is capable of immensely 
 increasing the pressure in certain veins. The first definite 
 experiments on this subject were made by Magendie, who 
 showed a pressure of over two inches of mercury produced 
 by a general muscular contraction, on the passage of a gal- 
 vanic current from a needle plunged into the cervical region 
 of the spinal marrow to one fixed in the muscles of the thigh. 2 
 The experiments of Bernard have shown this more accurately. 
 This physiologist found that the pressure in the jugular of a 
 horse, in repose, was 1-4 inch ; but the action of the muscles in 
 
 1 BERARD, op. tit., tome iv., p. 57. 
 
 9 MAGENDIE, Phenomena Physiques dela Vie, Paris, 1842, tome iii, p. 163. 
 
31 8 CIRCULATION. 
 
 raising the head increased it to a little more than five inches, 
 or nearly four times. 1 These observations show at once the 
 great variations in the venous current, and the important 
 influence of muscular contraction on the circulation. 
 
 In order that contractions of muscles shall assist the 
 venous circulation, two things are necessary : 
 
 1. The contraction must be intermittent. This is always 
 the case in the voluntary muscles. It is a view entertained 
 by many that each muscular fibre relaxes immediately after 
 its contraction, which is instantaneous, and that a certain 
 period of repose is necessary before it can contract again. 
 However this may be, it is well known that all active mus- 
 cular contraction, as distinguished from the efforts necessary 
 to maintain the body in certain ordinary positions, is inter- 
 mittent, and not very prolonged. Thus the veins, which are 
 partly emptied by the compression, are filled again during 
 the repose of the muscle. 
 
 2. There should be no possibility of a retrograde move- 
 ment of the blood. This condition is fulfilled by the action 
 of the valves. Anatomical researches have shown that these 
 valves are most abundant in veins situated in the substance 
 of or between the muscles, and that they do not exist in the 
 veins of the cavities, which are not subject to the same kind 
 of compression. It is thus that the blood is prevented from 
 passing backward toward the capillary system ; and when 
 the caliber of a vein is reduced by compression, part of its 
 contents must be forced toward the heart. This action of 
 the valves constitutes their most important function. 
 
 Milne-Edwards alludes to an important physiological 
 bearing of the acceleration of the venous circulation by con- 
 tractions of muscles, on their nutrition. 2 It is apparently 
 necessary that the supply of blood should be increased in a 
 muscle, in proportion to and during its activity ; for at that 
 
 1 BERNARD, Lemons sur la Physiologic et la Pathologie du Sysleme Nerveux^ 
 Paris, 1858, tome i., p. 285. 
 
 * Lefons sur la Physiologic, tome iv., p. 310. 
 
CAUSES OF THE VENOUS CIRCULATION. 319 
 
 time its destructive assimilation is undoubtedly augmented, 
 and there is an increased demand on the blood to supply the 
 waste. It is apparently a provision of Nature that the ac- 
 tivity of a muscle, facilitating the passage of blood in its 
 veins, and consequently its flow from the capillaries, induces 
 an increased supply of the nutrient fluid. As the develop- 
 ment of tissues is generally in proportion to their vascularity, 
 this may account for the increase in the development of 
 muscles, which is the invariable result of continued exercise. 
 
 Force of Aspiration from the Thorax. During the act 
 of inspiration, the enlargement of the thorax, by depression 
 of the diaphragm and elevation of the ribs, affects the move- 
 ments of fluids in all the tubes in its vicinity. The air rushes 
 in by the trachea and expands the lungs, so that they follow 
 the movements of the thoracic walls. The flow of blood into 
 the great arteries is somewhat retarded, as is indicated by 
 the diminution in the arterial pressure ; and finally, the blood 
 in the great veins passes to the heart with greater facility, 
 and in increased quantity. This last-mentioned phenomenon 
 can be easily observed, when the veins are prominent, in pro- 
 found or violent inspiration. The veins at the lower part of 
 the neck are then seen to empty themselves of blood during 
 the inspiration, and become distended during expiration, 
 producing a sort of pulsation which is synchronous with res- 
 piration. This can always be observed after exposure of the 
 jugular in the lower part of the neck in an inferior animal. 
 After this operation, if we cause the animal to make violent 
 respiratory efforts, the vein will be 'almost emptied and col- 
 lapsed with inspiration, and turgid with expiration. The 
 movements of the veins near the thorax have long been ob- 
 served and described with tolerable accuracy. By the fol- 
 lowing simple yet conclusive experiment, the regular action 
 of the suction force was demonstrated by Magendie. Having 
 introduced a gum-elastic sound into the jugular vein of a dog, 
 and passed it down to the right auricle, he saw " that the 
 
320 CIRCULATION. 
 
 blood flowed from the extremity of the sound only in the 
 moment of expiration. We obtain results entirely analogous 
 if we introduce the sound into the crural vein, directing it 
 toward the abdomen." l As several contractions of the right 
 auricle occur between two acts of respiration, it is shown by 
 this experiment that, during inspiration, the suction force is 
 sufficient to counterbalance the contractions of the auricle, 
 which would otherwise force a certain quantity of blood 
 through the soiind, as it does during expiration ; for then we 
 have a jet synchronous with the beats of the heart. Cathe- 
 terization of the right side of the heart is now quite a common 
 experiment ; and we have frequently observed the variations 
 in the flow of blood from a sound introduced through the 
 jugular, which were mentioned by Magendie. The suction 
 force is still more strikingly exhibited in this operation by 
 the entrance of air, which is frequently draw r n into the heart 
 during a violent inspiration. 
 
 The influence of aspiration on the circulation in the veins 
 was still more minutely studied in 1825 by Barry, whose 
 most important experiments have been repeated, with some 
 modifications, by Poiseuille. Barry introduced through the 
 jugular of a horse a bent tube of glass, one extremity being 
 passed into the right cavities of the heart, or the vena cava, 
 and the other into a vessel containing a colored liquid. He 
 found that with each act of inspiration the liquid mounted 
 up in the tube, demonstrating the operation of a notable suc- 
 tion force. The observations and experiments of Barry were 
 made on quite an extended scale, but many of his conclusions 
 were not entirely warranted. He studied, for example, the 
 effect of preventing the entrance of air into the chest by the 
 trachea, and found that this increased the suction force very 
 considerably, as indicated by the greater elevation of liquid 
 in the tube with each inspiratory effort ; but he supposed 
 
 1 MAGENDIE, Influences des Mouvements de la Poitrine et des Efforts sur la Cir- 
 culation du Sang. Journal de Physiologic Experimentale, Paris, 1821, tome i. ; 
 p. 136. 
 
CAUSES OF THE VENOUS CIRCULATION. 321 
 
 that this force from the thorax was felt in the entire venous 
 system, an opinion which, as we shall see, the most simple 
 observations have shown to be entirely erroneous. 1 As this 
 force is not felt throughout the whole of the venous system, 
 it becomes a question of interest to determine how far its in- 
 fluence extends, and why it is restricted to certain vessels. 
 Like the action of the muscular system on certain veins, it is 
 simply superadded to the force of the heart, the latter being 
 entirely competent to keep up the venous circulation. A 
 proof that it is not essential is seen in the fact that the circu- 
 lation is effected in animals which do not inspire, but swallow 
 their air, 2 and in the foetus, before any movements of respi- 
 ration take place. 
 
 Direct observations on the jugulars show conclusively that 
 the influence of inspiration cannot be felt much beyond these 
 vessels. They are seen to collapse with each inspiratory act, 
 a condition which limits this influence to the veins near the 
 heart. The flaccidity of the walls of the veins will not permit 
 the extended action of any suction force. If a portion of a vein 
 removed from the body be attached to the nozzle of a syringe, 
 and we attempt to draw a liquid through it, though the suc- 
 tion force be applied very gently, when the vessel has any 
 considerable length, its walls will be drawn together. In the 
 circulation, the veins are moderately distended with blood by 
 the vis a tergo, and, to a certain extent, supported by con- 
 nections with surrounding tissues, so that the force of aspira- 
 tion is felt farther than in any experiment on vessels re- 
 moved from the body. The blood, as it approaches the 
 thorax, impelled by other forces, is considerably accelerated 
 in its flow ; but it is seen by direct observation, that beyond 
 
 1 BARRY, Recherches Experimentales sur les Causes du Mouvement du Sang dans 
 les Vdnes, Paris, 1825, p. 12 et &eq. 
 
 2 In many animals that take the air into the lungs by an act like that of de- 
 glutition, there are regular pulsations in the veins near the heart, which are quite 
 abundantly provided with muscular fibres like those found in the heart. It is a 
 question whether this does not take the place of the suction force from the chest,, 
 which operates in other animals. 
 
 21 
 
322 CIRCULATION. 
 
 a certain point, and that very near the chest, ordinary aspi- 
 ration has no influence, and violent efforts rather retard than 
 favor the current. 
 
 In the liver, the influence of inspiration becomes a very 
 important element in the production of the circulation. 
 This organ presents a vascular 'arrangement which is excep- 
 tional. The blood, distributed by the arteries in a capillary 
 plexus in the mucous membrane of the alimentary canal and 
 in the spleen, instead of being returned directly to the heart 
 by the veins, is collected into the portal vein, carried to the 
 liver, and there distributed in a second set of capillary vessels. 
 It is then collected in the hepatic veins, and carried by the 
 vena cava to the heart. This double capillary plexus be- 
 tween the left and right sides of the heart has been cited as 
 an argument against the fact that the left ventricle is capable 
 of sending the blood through the entire circuit of the vascu- 
 lar system. The three hepatic veins open into the inferior 
 vena cava near the point where it passes the diaphragm, 
 where the force of aspiration from the thorax would mate- 
 rially assist the current of blood. On following these vessels 
 into the substance of the liver, it is found that their walls are 
 so firmly adherent to the tissue of the organ, that, when cut 
 across, they remain patulous ; and it is evident that they re- 
 main open under all conditions. The thorax can therefore 
 exert a powerful influence upon the hepatic circulation; 
 for it is only the flacci-dity of the walls of the vessels which 
 prevents this influence from operating throughout the entire 
 venous system. 
 
 Though this must be a very important element in the 
 production of the circulation in the liver, the fact that the 
 blood circulates in this organ in the foetus before any move- 
 ments of the thorax take place, shows' that it is not absolute- 
 ly essential. All of the influences which we have thus far 
 considered are merely supplementary to the action of the 
 great central organ of the circulation. 
 
 A further proof, if any were needed, of the suction force 
 
AIR IN THE VEINS. 323 
 
 of inspiration is found in an accident which is not infrequent 
 in surgical operations in the lower part of the neck. "When 
 the veins in this situation are kept open by a tumor, or by 
 induration of the surrounding tissues, an inspiratory effort 
 has occasionally been followed by the entrance of air into the 
 circulation ; an accident which is liable to lead to the gravest 
 results. This occurs only when a divided vein is kept patu- 
 lous ; and the accident proves both the influence of inspira- 
 tion on liquids in the veins near the chest, and its restriction 
 to the vessels in this particular situation by the flaccidity of 
 their walls. The conditions under which this occurs may be 
 imitated in the lower animals by introducing a tube through 
 the vein into the thorax; when, with a violent act of inspi- 
 ration, air will be drawn in, and the curious and startling 
 effects upon the circulation may be observed. 
 
 A full discussion of the subject of air in the veins, which 
 is of great pathological interest, does not belong to the domain 
 of physiology. The blood is capable of dissolving a certain 
 quantity of atmospheric air ; and a small quantity, very grad- 
 ually introduced into a vein, can be disposed of in this way. 
 When, however, a considerable quantity suddenly finds its 
 way into the venous system, the patient, or animal, experi- 
 ences a sense of mortal distress, and almost immediately falls 
 into a state of insensibility. A peculiar whistling sound is 
 heard when the air passes in ; and if the ear be applied to the 
 chest, we distinguish the labored efforts of the heart, accom- 
 panied by a loud churning sound. On opening the chest 
 after death, the right cavities of the heart are invariably 
 found distended with air and blood ; the blood being frothy 
 and florid. Generally the left side of the heart is nearly or 
 quite empty. 
 
 The production of death from air in the veins is purely 
 mechanical. The air, finding its way to the right ventricle, 
 is mixed with the blood in the form of minute bubbles, and 
 passed into the pulmonary artery. Once in this vessel, it is 
 impossible for it to pass through the capillaries of the lungs, 
 
324: CIRCULATION. 
 
 and death by suffocation is the inevitable result, if the quan- 
 tity of air be large. It is because no blood can pass through 
 the lungs, that the left cavities of the heart are usually found 
 empty. 
 
 Certain cases of entrance ef air into the veins in surgical 
 operations, though presenting the most alarming immediate 
 symptoms, have terminated in recovery. In these instances, 
 the quantity of air is not sufficient to completely block up 
 the pulmonary capillaries, and it is gradually absorbed by 
 the blood. 
 
 Air injected into the arteries produces no such serious ef- 
 fects as air in the veins. It is arrested in the capillaries of 
 certain parts, and in the course of time is absorbed without 
 having produced any injury. 
 
 Aside from the pressure exerted by the contraction of 
 muscles, and the force of aspiration from the thorax, the in- 
 fluences which assist the venous circulation are very slight. 
 As far as the action of the coats of the vessels themselves is 
 concerned, their contraction, it must be remembered, is slow 
 and gradual, like the contraction of the arteries ; and it is 
 hardly possible that in the general venous system it should 
 operate at all on the blood-current, beyond the simple influ- 
 ence of the reduction of the caliber of the vessel. There is 
 a slight contraction in the vense cavse, in the immediate 
 proximity of the heart, which is very much more extended 
 in many of the lower vertebrate animals, and may be men- 
 tioned as having an influence, very insignificant it is true, 
 on the flow of blood from the great veins. 
 
 In the veins which pass from above downwards, the force 
 of gravity favors the flow of blood. This is seen by the tur- 
 gescence of the veins of the neck and face, when the head is 
 kept for a short time below the level of the heart. If the 
 arm be elevated above the head, the veins of the back of the 
 hand will be much reduced in size, from the greater facility 
 with which the blood passes to the heart ; while they are 
 
FUNCTION OF THE VALVES. 325 
 
 distended when the hand is allowed to hang by the side, and 
 the blood has to mount up against the force of gravity. 
 
 In the extreme irregularity in the rapidity of the circula- 
 tion in different veins, it must frequently happen that a ves- 
 sel empties its blood into another of larger size, in which the 
 current is more rapid. In such an instance, as a physical 
 necessity, the more rapid current in the larger vessel exerts 
 a certain suction force on the fluid in the vessel which 
 joins with it. 
 
 Function of the Valves. 
 
 With our present knowledge, it is difficult to compre- 
 hend how any anatomist could have accurately described 
 the valves of the veins, and yet be ignorant of their function; 
 and the fact that their use was not understood before the 
 description of the circulation by Harvey, shows the greatness 
 of this as a discovery, and the shallow character of any pre- 
 tence that men of science had any idea of the motion of the 
 blood before his time. 
 
 With our present knowledge of the course of the blood, 
 it is evident that the great function of the valves is in pre- 
 senting an obstacle to the reflux of blood toward the capil- 
 lary system ; and it only remains to study the conditions 
 under which they are brought into action. 
 
 There are two distinct conditions under which the valves 
 of the veins may be closed. One of them is the arrest of cir- 
 culation, from any cause, in veins *in which the blood has to 
 mount against the force of gravity ; and the other, compres- 
 sion of veins, from any cause (generally from muscular con- 
 traction) which tends to force the blood from the vessels 
 compressed into others, when the valves offer an obstruction 
 to a flow toward the capillaries, and necessitate a current in 
 the direction of the heart. 
 
 In the first of these conditions, the valves are antagonistic 
 to the force of gravity, and, when the caliber of any vessel is 
 
326 CIRCULATION. 
 
 temporarily obliterated, aid in directing the current into an- 
 astomotic vessels. It is but rarely, however, that they act 
 thus in opposition to the force of gravity ; and it is only 
 when many of the veins of a part are simultaneously com- 
 pressed that they aid in diverting the current. When a sin- 
 gle vein is obstructed, it is not probable that the valves are 
 necessary to divert the current into other vessels, for this 
 would take place in obedience to the vis a tergo / but when 
 many veins are obstructed in a dependent part, and the 
 avenues to the heart become insufficient, the numerous 
 valves divide the columns of blood, so that the pressure is 
 equally distributed through the extent of the vessels. For it 
 must be remembered, the strength of the walls diminishes as 
 we pass from the larger veins to the periphery, and the small- 
 est vessels, which, were it not for the valves, would be sub- 
 jected to the greatest amount of pressure, are least calculated 
 to bear distention. This is but an occasional function which 
 the valves are called upon to perform ; and it is evident that 
 their influence is only to prevent the weight of the entire 
 column of blood, in vessels thus obstructed, from operating 
 on the smallest veins and the capillaries. It cannot make 
 the labor of the heart, when the blood is again put in mo- 
 tion, any less than if the column were undivided, as this 
 organ must have sufficient power to open successively each 
 set of valves, when, of course, they cease to have any influ- 
 ence whatsoever. 
 
 It is in connection with the intermittent compression of 
 the veins that the valves haVe their principal and almost con- 
 stant function. Their situation alone would lead to this sup- 
 position. They are found in greatest numbers throughout 
 the muscular system, having been demonstrated by Sappey 
 in the smallest venules. They are also found in the upper 
 parts of the body, where they certainly do not operate against 
 the force of gravity, while they do not exist in the cavities, 
 where the venous trunks are not subject to compression. It 
 has already been made sufficiently evident that the action of 
 
FUNCTION OF THE VALVES. 327 
 
 muscles seconds most powerfully the contractions of the 
 heart. The vis a tergo from the heart is, doubtless, generally 
 sufficient to turn this influence of muscular compression from 
 the capillary system, and the valves of the veins are open ; 
 but they stand ready, nevertheless, to oppose any tendency 
 to regurgitation. 
 
 In the action of muscles, the skin is frequently stretched 
 over the part, and the cutaneous veins are somewhat com- 
 pressed. This may be seen in the hand, by letting it hang 
 by the side until the veins become somewhat swollen, and 
 then contracting the muscles, when the skin will become 
 tense and the veins very much less prominent. Here the 
 valves have an important action. The compression of the 
 veins is much greater in the substance of and between the 
 muscles than in the skin ; but the blood is forced from the 
 muscles into the skin, and the valves act to prevent it from 
 taking a retrograde course. The fact that the contraction of 
 muscles forces blood into the veins of the skin may be seen 
 by surrounding the upper part of the forearm with a moder- 
 ately tight ligature, which will distend the cutaneous veins 
 below. If we now contract the muscles vigorously, the veins 
 below will become sensibly more distended and knotted; 
 showing, at once, the passage of blood into the skin, and the 
 action of the valves. 
 
 When a vein is distended by the injection of air, or a 
 liquid, forced against the valves, it is observed that at the 
 point where the convex borders of the valves are attached, 
 the vessel is not dilated as much as at other parts. This is 
 due to the fact that the valves are bordered with a fibrous 
 ring, which strengthens the vessel, and prevents distention at 
 that point, which would separate the free borders of the valves 
 and render them insufficient. 
 
 A full consideration of the venous anastomoses belongs to 
 descriptive anatomy. Suffice it to say, in this connection, that 
 they are very numerous, and provide for a return of the blood 
 to the heart by a number of channels. The azygos vein, the 
 
328 CIRCULATION. 
 
 veins of the spinal canal, and veins in the walls of the abdo- 
 men and thorax, connect the inferior with the superior vena 
 cava Even the portal vein has lately been shown to have 
 its communications with the general venous system. Thus, 
 in all parts of the organism, temporary compression of a vein 
 only diverts the current into some other vessel, and permanent 
 obliteration of a vein produces enlargement of communicating 
 branches, which soon become sufficient to meet all the require- 
 ments of the circulation. 
 
 Conditions which impede the Venous Circulation. 
 
 Influence of Expiration. The influence of expiration on 
 the circulation in the veins near the thorax, is directly oppo- 
 site to that of inspiration. As the act of inspiration has a 
 tendency to draw the blood from these vessels into the chest, 
 the act of expiration has a tendency to force the blood out 
 from the vessels of the thorax, as the air is forced out by the 
 trachea, and opposes a flow in the opposite direction. The 
 effect of prolonged and violent expiratory efforts is very 
 marked ; being followed by deep congestion of the veins of 
 the face and neck, and a sense of fulness in the head, which 
 may become very distressing. The opposition to the venous 
 current generally extends only to vessels in the immediate 
 vicinity of the thorax, or, it may be stated in general terms, 
 to those veins in which the flow of blood is assisted by the 
 movements of inspiration ; but, while the inspiratory influence 
 is absolutely confined to a very restricted circuit of vessels, 
 the obstructive influence of very violent and prolonged expi- 
 ration may be extended very much further, as is seen when 
 the vessels of the neck, face, and conjunctiva become con- 
 gested in prolonged vocal efforts, blowing, etc. 
 
 The mechanism of this is not w r hat we might at first be 
 led to suppose ; namely, a mere reflux from the large trunks 
 of the thoracic cavity. "Were this the case, it would be ne- 
 cessary to assume an insufficiency of certain valves, which 
 
KEGUKGITANT VENOUS PULSE. 329 
 
 does not exist. In extreme congestion, reflux of blood may 
 take place to a certain extent in the external jugular, for this 
 vessel has but two valves, which are not competent to pre- 
 vent regurgitation ; ' but the chief cause of congestion is 
 due, not to regurgitation, but to accumulation from the pe- 
 riphery, and an obstruction to the flow of blood into the great 
 
 It is in the internal jugular that the influence of expiration 
 is most important, both from the great size of the vessel in the 
 human subject, as compared with the other vessels, and from 
 the importance and delicacy of the parts from which it collects 
 the blood. At the opening of this vessel into the innominate 
 vein, is a pair of strong and perfect valves, which effectually 
 close the orifice when there is a tendency to regurgitation. 
 These valves have attracted much attention among physiolo- 
 gists, since the discovery of the circulation has made it evi- 
 dent how important they might be in protecting the brain 
 from reflux of blood. When the act of expiration arrests the 
 onward flow in the veins near the thorax, these valves are 
 closed, and effectually protect the brain from congestion by 
 regurgitation. The blood accumulates behind the valves, but 
 the free communication of the internal jugular with the 
 other veins of the neck relieves the brain from congestion, 
 unless the effort be extraordinarily violent and prolonged. 
 
 The above remarks with regard to the influence of expira- 
 tion are applicable to vocal efforts, violent coughing or sneez- 
 ing, or any violent muscular efforts, such as straining, in 
 which the glottis is closed. 
 
 .Regurgitant Venous Pulse. In the inferior animals, like 
 the dog, if the external jugular be exposed, a distention of 
 the vessel is seen to accompany each expiratory act. This is 
 sometimes observed in the human subject, when respiration 
 is exaggerated, and has been called improperly the venous 
 pulse. There is no sufficient obstacle to the regurgitation of 
 
 1 GRAY, Descriptive Anatomy, Philadelphia, 1859, p. 404. 
 
330 CIRCULATION. 
 
 blood from the thorax into the external jugular, and distinct 
 pulsations, synchronous with the movements of respiration, 
 may be produced in this way. 
 
 In some forms of cardiac disease affecting the right side, 
 a pulsation, synchronous with, the heart's action, has also 
 been noticed. This is always confined to the jugular, and 
 must not be connected with the slight pulsations which 
 sometimes occur in the veins of the extremities. It is due to 
 a regurgitant impulse from the right side of the heart ; and 
 generally, to the action of the right ventricle, propagated into 
 the veins on account of pathological insufficiency of the tri- 
 cuspid valves. Two distinct pulsations accompanying each 
 act of the heart have been occasionally observed: one im- 
 mediately preceding, and the other coincidiDg with, the ven- 
 tricular systole. In a case of this kind, post-mortem examin- 
 ation revealed contraction of the right auriculo-ventricular 
 orifice, as well as insufficiency of the tricuspid valves. 1 The 
 relation of the pulsation of the jugular to the action of the 
 heart showed that the first impulse was produced by the con- 
 traction of the right auricle, and the second by the contrac- 
 tion of the right ventricle. 
 
 It is evident that there are various other circumstances 
 which may impede the venous circulation. Accidental 
 compression may temporarily arrest the flow in any par- 
 ticular vein. "When the whole volume of blood is materi- 
 ally increased, as after a full meal, with copious ingestion of 
 liquids, the additional quantity of blood accumulates chiefly 
 in the venous system, and proportionately diminishes the ra- 
 pidity of the venous circulation. 
 
 The force of gravity also has an important influence. It 
 is much more difficult for the blood to mount from below up 
 to the heart, than to flow downwards from the head and 
 neck. The action of this is seen if comparison be made be- 
 tween the circulation in the arm elevated above the head 
 and hanging by the side. In the one case the veins are read 
 
 1 FLINT, Diseases of the Heart, Philadelphia, 1859, p. 147. 
 
KEGUKGITANT VENOUS PULSE. 331 
 
 ily emptied, and contain but little blood ; and in the other 
 the circulation is more difficult, and the vessels are moderate- 
 ly distended. The walls of the veins are thickest, and the 
 valves most numerous, in parts of the body which are habit- 
 ually dependent. The influence of gravity is exemplified in 
 the production of varicose veins in the lower extremities. 
 This disease is frequently induced by occupations which re- 
 quire constant standing ; but the exercise of walking, aiding 
 the venous circulation, as it does, by the muscular effort, has 
 no such tendency. 
 
CHAPTER IX. 
 
 PECULIARITIES OF THE CIRCULATION IN DIFFERENT PARTS OF 
 THE SYSTEM. 
 
 Circulation in the cranial cavity Circulation in erectile tissues Derivative circu- 
 lation Pulmonary circulation General rapidity of the circulation Time re- 
 quired for the passage through the heart of all the blood in the organism 
 Relations of the general rapidity of the circulation to the frequency of the 
 heart's action Phenomena in the circulatory system after death. 
 
 Circulation in the Cranial Cavity. In the encephalic 
 cavity, there are certain peculiarities in the anatomy of some 
 of the vessels, with exceptional conditions of the blood, as re- 
 gards atmospheric pressure, which have been considered ca- 
 pable of essentially modifying the circulation. In the adult, 
 the cranium is a closed, air-tight box, containing the incom- 
 pressible cerebral substance, and blood ; conditions which are 
 widely different from those presented in other parts of the 
 system. On this account, some have gone so far as to con- 
 sider any change in the quantity of circulating fluid in the 
 brain, a physical impossibility. 1 Pathological facts in oppo- 
 
 1 A number of years ago, there was considerable interest excited in the dis- 
 cussion of the possibility of an increase or diminution in the quantity of blood in 
 the brain under any circumstances. Monro, Abercrombie, and Dr. Kellie sup- 
 posed the quantity of blood in the brain to be invariable; Dr. Kellie assuming to 
 have proved this position by experiments which showed (according to his conclu- 
 sions at least) no diminution in the quantity of blood in the brain in animals 
 killed by hemorrhage, and no increase in the quantity in animals killed by a liga- 
 ture around the neck. He made other observations on this subject which it is un- 
 
CIRCULATION IN THE CRANIUM. 333 
 
 sition to such a view are so numerous and well established, 
 that the question does not demand extended discussion. It 
 is well known, that in certain cases the vessels of the brain 
 and its membranes are found engorged with blood, and in 
 others containing a comparatively small quantity ; but it is 
 nevertheless true that there are anatomical peculiarities in 
 these parts, the effects of which on the circulation present 
 important and interesting points for study. 
 
 In the brain, the venous passages which correspond to the 
 great veins of other parts, are sinuses between the folds of 
 the dura mater, and are but slightly dilatable. In the per- 
 fectly consolidated adult head, the blood is not subjected to 
 atmospheric pressure as in other parts, and the semi-solids 
 and liquids which compose the encephalic mass cannot in- 
 crease in size in congestion, and dimmish in anemia. Not- 
 withstanding these conditions, the undoubted fact remains 
 that examinations of the vessels of the brain after death show 
 great differences in the quantity of blood which they contain. 
 The question then arises as to what is displaced to make 
 room for the blood in congestion, and what supplies the 
 place of the blood in anemia. 
 
 An anatomical peculiarity, which has not yet been con- 
 sidered, offers an explanation of these phenomena. Magen- 
 die has shown by observations on living animals, confirmed 
 by dissections of the human body, that between the pia mater 
 and the arachnoid of the brain and spinal cord there exists a 
 
 necessary to enumerate. These experiments were fully reviewed by Dr. George 
 Burrows, who shows by his quotations from Dr. Kellie that they proved nothing 
 of the kind. Dr. B. repeated the experiments on rabbits, and demonstrated that 
 great variations exist in the quantity of blood in the brain, when the animals are 
 killed in different ways. He showed that the blood-vessels are engorged when the 
 head is left dependent for a number of hours, and that they contain but little 
 blood when it is elevated. Certain of Kellie's experiments, cited by Dr. Burrows, 
 show that the difference is in the conclusions, and not in the experimental 
 facts. For a full discussion of this subject, the reader is referred to the work 
 of Dr. Burrows on Disorders of the Cerebral Circulation, &c. (American reprint), 
 Philadelphia, 1848. 
 
334 CIRCULATION. 
 
 liquid, the cephalo-rachidian fluid, which is capable of pass- 
 ing from the surface of the brain to the spinal canal, and 
 communicates with the fluid in the ventricles. 1 This he has 
 conclusively demonstrated to be situated, not between the 
 layers of the arachnoid, as was supposed by Bichat, but be- 
 tween the inner layer of this membrane and the pia mater. 
 The communication between the cranial cavity and frhe spinal 
 canal is very free. This was demonstrated by exposing the 
 dura mater of the brain and of the cord, making an opening 
 in the membranes of the cord, so as to allow the liquid to 
 escape (which it does in quite a forcible jet), when pressure 
 on the membranes of the brain not only accelerated the flow, 
 but pressed out a quantity of the liquid after all that would 
 escape spontaneously had been evacuated. 
 
 It is easy to see one of the physiological uses of this liquid. 
 When the pressure of blood in the arteries leading to the 
 brain is increased, or when there is an obstacle to its return 
 by the veins, more or less congestion takes place, and the 
 blood forces the liquid from the cranial into the spinal cavity ; 
 the reverse taking place when the supply of blood to the brain 
 is diminished. The functions of all highly organized and 
 vascular parts seem to require certain variations in the sup- 
 ply of blood ; and there is no reason to suppose that the 
 brain, in its varied conditions of activity and repose, is any 
 exception to this general rule, though the physiological con- 
 ditions of its vascularity are not easily studied. 
 
 In some late experiments by Mr. Durham on the physi- 
 ology of sleep, the comparative vascularity of the meninges 
 of the brain at different times has been studied in animals, by 
 removing a portion of the skull with a trephine, and supply- 
 ing its place by a watch-glass cemented to the edges of the 
 bone with Canada balsam. In these experiments, the author 
 demonstrates that the vessels are much more congested dur- 
 
 1 MAGENDIE, Journal de Physiologic, 1825, tome v., p. 27 et seg., and 1827, 
 tome vii., p. 66 et seq. Sur un Liquide gut se trouve dans le Crane et le Canal 
 Vertibral de VHomme et des Animaux Mammiferes. 
 
CIRCULATION IN THE CRANIUM. 335 
 
 ing the activity of the brain, than during the suspension of 
 its functions in sleep. The blood-vessels of the meninges 
 were exposed freely to view by the operation, and were ex- 
 amined by the microscope, with a low power, as well as with 
 the naked eye. 1 Dr. Hammond has lately published an in- 
 teresting paper on sleep and insomnia, in which the obser- 
 vations of Mr. Durham are fully confirmed, leaving no doubt 
 that the vessels within the cranial cavity are subject to con- 
 siderable physiological variations in tension. These obser- 
 vations were published in 1865, 2 though they were made 
 before the article of Mr. Durham appeared. 
 
 Physiologists, even before the time of Haller, had noticed 
 alternate movements of expansion and contraction in the 
 brain, connected with the acts of respiration. 'This is ob- 
 served in children before the fontanels are closed, and in 
 the adult when the brain is exposed by an injury or a 
 surgical operation. The movements are, an expansion with 
 the act of expiration, which, in violent efforts, is sometimes 
 so considerable as to produce protrusion, and contraction 
 with inspiration. Magendie also studied these movements, 
 which he explained in the following way : 3 With the act of 
 expiration, the flow of blood in the arteries is favored, and 
 the current in the veins is retarded. If the effort be violent, 
 the valve at the opening of the internal jugular may be 
 closed. This act would produce an expansion of the brain, 
 not from reflux by the veins, but from the fact that the flow 
 into the chest is impeded, and the blood, while passing in 
 more freely by the arteries, is momentarily confined. With 
 inspiration, the flow into the thorax is materially aided, and 
 the brain is in some degree relieved of this expanding force. 
 
 1 ARTHUR E. DURHAM, The Physiology of Sleep. Guy's Hospital Reports, 1860, 
 p. 149. 
 
 2 War. A. HAMMOMD, M.D., On Sleep and Insomnia. New York Medical Jour- 
 nal, 1865, vol. i., Nos. 2 and 3. 
 
 8 Journal de Physiologic, tome i., p. 132. De F Influence des Mouvements de la 
 Poitrine et des Efforts sur la Circulation du Sang. 
 
336 CIRCULATION. 
 
 Kobin has lately noted a peculiarity in the small vessels 
 of the brain, spinal cord, and pia mater, which is curious, but 
 the physiological function of which is not yet apparent. 1 
 These vessels are surrounded by a thin, amorphous sheath, 
 which has a diameter of from j-^j- to -^^ of an inch greater 
 than that of the vessel itself. Between this and the blood- 
 vessel is a transparent liquid. This structure, which has 
 been observed in no other part of the circulatory system, is 
 regarded by its discoverer as the commencement of the lym- 
 phatics of the nervous centres. What effect this disposition 
 of the vessels may have upon the facility with which they 
 may become dilated or contracted, it is difficult to determine. 
 
 Circulation in Erectile Tissues. In the organs of gener- 
 ation in both sexes there exists a tissue which is subject to 
 great increase in volume and rigidity, when in a state of what 
 is called erection. The parts in which the erectile tissue ex- 
 ists are, in the male, the corpora cavernosa of the penis, the 
 corpora spongiosa, with the glans penis ; and in the female, 
 the corpora cavernosa of the clitoris, the gland of the clitoris, 
 and the bulb of the vestibule. In addition, Kouget has lately 
 demonstrated the presence of true erectile tissue in the body 
 of the uterus, and in a bulb annexed to the ovary of the hu- 
 man female, but states that it is not found in the inferior 
 animals. He has shown by injections that the uterus is 
 capable of erection like the penis. 2 In some other parts, 
 such as the nipple and the mucous membrane of the 
 vagina, which are sometimes described as erectile, the pecu- 
 liar vascular arrangement which is characteristic of true 
 erectile tissues is not found. In the nipple, the hardness 
 which follows gentle stimulation is simply the result of con- 
 traction of the smooth muscular fibres with which this part 
 
 1 ROBIN, Sur une Tunigue Appartenante cnpropre aux Capillaires Encephalo- 
 Rachidiens. Journal de la Physiologic, etc., Oct. 1859, tome ii., p. 543. 
 
 3 ROUGET, JRecherches sur les Organes Erectiles de la Femme, etc. Journal 
 de la Physiologic, Paris, 1858, tome L, pp. 320, 479, 735. 
 
ERECTILE TISSUES. 337 
 
 is largely supplied, and is analogous to the elevations in the 
 follicles of the skin from the same cause, in what is called 
 goose-flesh. In the vagina, congestion may occur, as in other 
 mucous membranes, but there is no proper erection. 
 
 The vascular arrangement in erectile organs, of which the 
 penis may be taken as the type, is peculiar to them, and not 
 found in any other part of the circulatory system. Taking 
 the penis as an example, the arteries, which have an unusually 
 thick muscular coat, after they have entered the organ, do not 
 simply branch and divide dichotomously, as in most other 
 parts, but send off large numbers of arborescent branches, 
 which immediately become tortuous, and are distributed in 
 the cavernous and spongy bodies in numerous anastomosing 
 vessels, with but a single thin homogeneous coat, like the true 
 capillaries. These vessels are larger, even, than the arterioles 
 which supply them with blood, some having a diameter 
 of from -^ to ^ of an inch. 1 The cavernous bodies have an 
 external investment of strong fibrous tissue of considerable 
 elasticity, which sends bands, or trabeculse, into the interior, 
 by which it is divided up into cells. The trabeculse are com- 
 posed of fibrous tissue mixed with a large number of smooth 
 muscular fibres. These cells lodge the blood-vessels, which 
 ramify in the tortuous manner already indicated, and finally 
 terminate in the veins. 2 The anatomy of the corpora spon- 
 giosa is essentially the same ; the only difference being that 
 the fibrous envelope and the trabeculse are more delicate, 
 and the cells are of smaller size. 
 
 Without going fully into the mechanism of erection, 
 which comes more properly under the head of generation, it 
 may be stated in general terms that during sexual excite- 
 
 1 ROBIN, Observations sur la Constitution du Tissu Erectile, Paris, 1865. 
 
 2 J. Miiller professed to have discovered a peculiarity in the arteries of erectile 
 tissues consisting in arborescent diverticula from the main vessel, with blind ex- 
 tremities. These he called the helicine arteries. (Manuel de Physiologic. Trad. 
 parJourdan, Paris, 1851, tome i., p. 181.) Rouget in his admirable article (loc. 
 cit.) has gone over the experiments of Miiller, and shown conclusively that the 
 so-called helicine arteries do not exist ; and that the appearances described by 
 Miiller are due to imperfect filling of the vessels by the injection. 
 
 22 
 
338 CIRCULATION. 
 
 ment, or when erection occurs from any cause, the thick mus- 
 cular walls of the arteries of supply relax, and allow the ar- 
 terial pressure to distend the capacious vessels lodged in the 
 cells of the cavernous and spongy bodies. This produces the 
 characteristic change in the volume and position of the organ. 
 It is evident that erection depends upon the peculiar arrange- 
 ment of the blood-vessels, and is not simply a congestion, 
 such as could occur in any vascular part. During erection, 
 there is not a stasis of blood ; but if it continue for any length 
 of time, the quantity which passes out of the part by the 
 veins must be equal to that which passes in by the arteries. 
 If return by the veins were prevented, gangrene would inev- 
 itably supervene, an occurrence which sometimes takes place 
 when the root of the penis has become constricted, and is not 
 speedily relieved. Erection may be produced in the dead 
 body, by preventing reflux by the veins, and filling the ves- 
 sels contained in the cells of the cavernous and spongy bodies 
 by injection. It has been shown by Miiller that the penis 
 may be made rigid by an injection at a pressure about equal 
 to the pressure of blood in the arteries. 1 
 
 The mechanism of erection of the clitoris, and other 
 erectile parts, is essentially the same as in the penis. It is 
 seen that in this condition, circulation is by no means arrested ; 
 and the tortuous vessels are filled with blood by an enlarge- 
 ment in the caliber of the small arteries of supply. 
 
 Ronget has shown that the body of the uterus possesses an 
 erectile tissue as perfect as that of the penis ; and that after 
 death the organ may be made to change its form and posi 
 tion by injecting the vessels, when it increases in size about 
 one-half, rising up, and becoming rigid and erect in the cavity 
 of the pelvis. 2 
 
 This relaxation of the muscular coats of the arteries only 
 exists for a time; tonic contraction occurs, the supply of 
 blood is diminished, and the organ returns to its ordinary 
 condition. 
 
 1 J. MULLER, op. cit., tome i., p. 182. 2 ROUGET, op. cit., pp. 338, 339. 
 
DERIVATIVE CIRCULATION. 330 
 
 Under stimulation, the muscular fibres in the covering 
 and trabeculse of the corpora cavernosa and spongiosa may 
 contract, force the blood from the parts, and produce a cer- 
 tain amount of rigidity, with diminution in size. This is 
 frequently seen under the influence of cold, which is a pow- 
 erful excitant of the unstriped muscular fibres. 
 
 Derivative Circulation. In some parts of the circulatory 
 system, there exists a direct communication between the arte- 
 ries and the veins, so that all the blood does not necessarily 
 pass through the minute vessels which have been described 
 as true capillaries. This peculiarity has been closely studied 
 by M.Sucquet,who was first led to investigate the subject by 
 noticing that by injecting a very small quantity of fluid, en- 
 tirely insufficient to fill all the capillaries of a member, it was 
 returned by certain of the veins. On using a black, solidifi- 
 able injection, he found that there were certain parts of the 
 upper and lower extremities and the head which became 
 colored by the injection, while other parts were not pene- 
 trated. Following this out by dissection, he showed that, in 
 the upper extremity, the skin of the fingers and part of the 
 palm of the hand, and the skin over the olecranon, is provided 
 with vessels of considerable size, which allowed the fluid in- 
 jected by the axillary artery to pass directly into some of 
 the veins, while in other parts the veins were entirely empty. 
 Extending his researches to the lower extremity, he found 
 analogous communications between the vessels in the knee, 
 toes, and parts of the sole of the foot. He also found com- 
 munications in the nose, cheeks, lips, forehead, and ends of 
 the ears, parts which are particularly liable to changes in color 
 from congestion of vessels. 1 
 
 1 J. P. SUCQUET, De la Circulation du Sang dans les Membres et dans la Tete 
 de rilomme, Paris, 1860, p. 55. Though all the physiological deductions in this 
 memoir do not seem justifiable, the anatomical facts are undoubted. The prepa- 
 rations have been examined by a commission, of which M. Robin was a member, 
 which confirmed the statements of M. Sucquet. (Oral communication from M. 
 Robin.) 
 
34:0 CIRCULATION. 
 
 It is evident that, under certain circumstances, a larger 
 quantity of blood than usual may pass through these parts 
 without necessarily penetrating the true capillaries and thus 
 exerting a modifying influence upon nutrition. The changes 
 which are liable to occur in* the quantity of blood, in the 
 force of the heart's action, etc., may thus take place without 
 disturbing the circulation in the capillaries, a provision which 
 the functions of the parts would seem to demand. 1 
 
 Pulmonary Circulation. The vascular system of the 
 lungs merits the name, which is frequently applied to it, of 
 the lesser circulation. The right side of the heart acts simul- 
 taneously with the left, but is entirely distinct from it, and its 
 muscular walls are very much less powerful. The pulmo- 
 nary artery has thinner and more distensible coats than the 
 aorta, and distributes its blood to a single system of capil- 
 laries, which are located very near the heart. We have seen 
 that the orifice of the pulmonary artery is provided with 
 valves which prevent regurgitation into the ventricle. In 
 the substance of the lungs, the pulmonary artery is broken 
 up into capillaries, most of them just large enough to allow 
 the passage of the blood-corpuscles in a single row. These 
 vessels are provided with a single coat, and form a very close 
 network surrounding the air-cells. From the capillaries, the 
 blood is collected by the pulmonary veins, and conveyed to 
 
 1 Before the publication of the researches of Suquet, Todd and Bowman men- 
 tioned the possibility of direct communications between the arteries and veins in 
 many parts of the body, and the probable existence of such communications in 
 some of the bones. 
 
 "It is not improbable that further research may detect a direct communication 
 between arteries and veins, even in tissues, the greatest part of which is furnished 
 with a true capillary plexus. In the cancellated structure of bone, and the diploe 
 of the cranial bones, it seems highly probable that the arteries communicate im- 
 mediately with the veins at many points. Mr. Paget (Lectures on Inflammation) 
 describes a direct communication between the arteries and veins of the wing of 
 the bat, without any intermediate capillary plexus." TODD and BOWMAN, Physi- 
 ological Anatomy and Physiology of Man, American edition, Philadelphia, 1857, 
 p. 662. 
 
PULMONARY CIRCULATION. 34:1 
 
 the left auricle. There is no great disparity between the ar- 
 teries and veins of the pulmonary system as regards capacity. 
 The pulmonary veins in the human subject are not provided 
 with valves. 
 
 The blood in its passage through the lungs does not meet 
 with the resistance which is presented in the systemic circu- 
 lation. This fact we have often noticed in injecting defibrin- 
 ated blood through the lungs of an animal just killed. We 
 have also observed that an injection passes through the lungs 
 as easily when they are collapsed as when they are inflated. 
 The anatomy of the circulatory system in the lungs and of 
 the right side of the heart shows that the blood must pass 
 through these organs with comparative ease. The power of 
 the right ventricle is evidently less than half that of the left, 
 and the pulmonary artery will sustain a much less pressure 
 than the aorta. 
 
 The two sides of the heart act simultaneously ; and while 
 the blood is sent by the left ventricle to the system, it is sent 
 by the right ventricle to the lungs. Some physiologists have 
 endeavored to measure the pressure of blood in the pulmo- 
 nary artery. The only experiments which have not involved 
 opening the thoracic cavity, w an operation which must inter- 
 fere materially with the pressure of blood in the pulmonary 
 artery, as it does with the general arterial pressure, are those 
 of Chauveau and Faivre. 1 These observers measured the 
 pressure by connecting a cardiometer with a trocar intro- 
 duced into the pulmonary artery of a living horse, through 
 one of the intercostal spaces, and found it to be about one- 
 third as great as the pressure in the aorta ; an estimate which 
 corresponds pretty nearly with the comparative power of the 
 two ventricles, as deduced from the thickness of their muscu- 
 lar walls. 
 
 Anatomy teaches us that the capillaries of the lungs have 
 exceedingly delicate walls ; and it is evident that rupture of 
 these vessels from excessive action of the heart would lead to 
 
 1 LONGET, Traite de Physiologic, Paris, 1861, tome i., pp. 886, 887. 
 
34:2 CIRCULATION. 
 
 grave results. It has already been noted that on the right 
 side the lungs are protected bj an insufficiency of the auri- 
 culo-ventricular valves, which does not exist on the left side, 
 allowing of a certain degree of regurgitation when the heart 
 is acting with unusual force, and thus relieving, to a certain 
 extent, the pulmonary system. This was pointed out by Mr. 
 King of London, and called the safety-valve function of the 
 right ventricle. 1 We have noticed, in the heart of the ox, a like 
 disparity between the aortic and pulmonic semilunar valves. 
 If these be exposed on both sides by cutting away portions of 
 the ventricles, and a current of liquid be forced against them 
 through the vessels, the aortic valves will be found to entire- 
 ly prevent the passage of the liquid, even under very great 
 pressure, while the pulmonic valves permit regurgitation un- 
 der a very inconsiderable pressure. A little reflection will 
 make it evident that when the heart is acting with undue 
 force it is quite as important to relieve the lungs by a certain 
 amount of regurgitation from the pulmonary artery, as by 
 insufficiency of the tricuspid valves. This insufficiency is 
 important, both at the auriculo-ventricular and pulmonic ori- 
 fices, in protecting the delicate structure of the lungs from 
 the variations in force to which the action of both ventricles 
 is constantly liable. 
 
 On microscopic examination of the circulation in the 
 lower animals, as the frog, the movement of blood in the ca- 
 pillaries of the lungs does not present any differences from the 
 capillary circulation in other parts ; except that the vessels 
 seem more crowded with corpuscles, and there is no " still 
 layer " next their walls. 
 
 There are no forces of any moment which are superadded 
 to the action of the right ventricle, in the production of the 
 arterial, capillary, or venous circulation in the lungs; but 
 there are certain conditions which may obstruct the flow of 
 blood through these parts. We have already noted the effect 
 of introduction of air into the veins, in blocking up the capil- 
 
 4 Guy's Hospital Reports, 1837. 
 
GENERAL RAPIDITY. 343 
 
 laries of the lungs, and preventing the passage of blood. It 
 is a view pretty generally entertained, that in asphyxia the 
 non-aeration of the blood obstructs the pulmonary circula- 
 tion. We have already considered this subject rather fully 
 in treating of the general effects of arrest of respiration on 
 the circulation. The celebrated experiments of Bichat dem- 
 onstrated the passage of black blood through the lungs in as- 
 phyxia, and its presence in the arterial system. The experi- 
 ments of Dalton and others have shown that in this condi- 
 tion, the obstruction to the circulation occurs first in the sys- 
 temic capillaries, and the distention is propagated backward 
 through the great vessels and left cavities of the heart to the 
 right side. When the heart is exposed in a living animal, 
 and artificial respiration is kept up, arrest of respiration 
 produces engorgement and labored action of both sides. 
 There are no observations which show that increase of press- 
 ure in the pulmonary artery is the first and immediate result 
 of asphyxia. It is true, that after death the right side of the 
 heart is engorged ; but it is well known, from observations 
 after death, and experiments on living animals, 1 that the 
 tonic contraction of the arteries is competent to empty the 
 blood into the veins ; and the facts just stated regarding the 
 insufficiency of the pulmonic semilunar valves explain how 
 the right side of the heart may become engorged as the result 
 of obstruction to the blood-current in the left side. Estab- 
 lished facts seem to show that asphyxia does not ^primarily 
 affect the pulmonary circulation ; but that it is possible for 
 venous blood to pass through the lungs without undergoing 
 arterialization. 
 
 General Rapidity of the Circulation. 
 
 Several questions of considerable physiological interest 
 
 arise in connection with the general rapidity of the circulation : 
 
 1. It would be interesting to determine, if possible, what 
 
 1 See experiments by MAGENDIE on the causes of the circulation in the veins. 
 Precis fiUmenlaire de Physiologic, Paris, 1833, tome ii., p. 391. 
 
344 CIRCULATION. 
 
 length of time is occupied by the blood in its passage 
 through the entire circuit of both the lesser and greater 
 circulations. 
 
 2. What is the time required for the passage of the entire 
 mass of blood through the heart ? 
 
 3. "What influence has the number of pulsations of the 
 heart on the general rapidity of the circulation ? 
 
 The first of these questions is the one which has been 
 most satisfactorily answered by experiments on living ani- 
 mals. In 1827, Hering, 1 a German physiologist, performed 
 the experiment of injecting into the jugular vein of a living 
 animal a harmless substance, which could be easily recog- 
 nized by its chemical reactions, and noted the time which 
 elapsed before it could be detected in the blood of the vein of 
 the opposite side. This gave the first correct idea of the rapid- 
 ity of the circulation ; for though the older physiologists, such 
 as Haller, Hales, and Keill, had studied the subject, their esti- 
 mates were founded on calculations which had no accurate 
 basis, and gave very different results. The experiment of 
 Hering is often roughly performed as a physiological demon- 
 stration ; and we have thus had frequent occasions to verify, 
 in a general way, its accuracy. If, for example, we expose 
 both jugulars of a dog, inject into one a solution of ferro-cy- 
 anide of potassium in water, and draw a specimen of blood 
 from the other with as little loss of time as possible, it will 
 be found, that in twenty or thirty seconds after the injection, 
 the salt has had time to pass from the jugular to the right 
 heart, thence to the lungs and left heart, from this through 
 the capillaries of the head and face back to the jugular on 
 the opposite side. Its presence can be determined by the 
 distinct blue color produced on the addition of the perchlo- 
 ride of iron to the serum, if the specimen be allowed to 
 stand, or a clear extract of the blood may be made by boiling 
 with a little sulphate of soda and filtering, treating the color- 
 less liquid thus obtained with the salt of iron. 
 
 1 MILNE-EDWARDS, Lemons sur la Physiologie, tome iv., p. 362, note, 
 
GENERAL BAPEDITY. 345 
 
 The experiments of Hering were evidently conducted with 
 great care and accuracy. He drew the blood at intervals of 
 five seconds after the commencement of the injection, and 
 thus, by repeated observations, ascertained pretty nearly the 
 rapidity of a circuit of blood in the animals on which he ex- 
 perimented. Others have taken up these investigations, and 
 introduced some modifications in the manipulations. Yier- 
 ordt collected the blood as it flowed, in little vessels fixed on 
 a disk revolving at a known rate, which gave a little more 
 exactness to the observations ; * but the method is essentially 
 the same as that employed by Hering, and the results obtain- 
 ed by these two observers nearly correspond. 
 
 The length of time occupied by a portion of blood in 
 making a complete circuit of the vascular system, in the hu- 
 man subject, is only to be deduced from observations on the 
 inferior animals ; but before this application is made, it will 
 be well to examine the objections, if any exist, to the experi- 
 mental procedure above described. 
 
 The only objection which could be made is, that a saline 
 solution, introduced into the torrent of the circulation, would 
 have a tendency to diffuse itself throughout the whole mass 
 of blood, it might be, with considerable rapidity ; and that 
 this fact is opposed to the proposition that the salt, when de- 
 tected in a specimen of blood drawn from a given vessel, is 
 simply carried there by the force of the blood-current. This 
 objection to the observations of Hering has been made by 
 Matteucci, and is considered by him as fatal to their accu- 
 racy. 5 It certainly is an element which should be taken into 
 account; but from the definite data which have been ob- 
 tained concerning the rapidity of the arterial circulation, and 
 the inferences which are unavoidable with regard to the ra- 
 pidity of the venous circulation, it would seem that the saline 
 solution must be carried on by the mere rapidity of the arte- 
 rial flow to the capillaries, which are very short, taken up 
 
 1 MILNE-EDWARDS, loc. cit. 
 
 3 MATTEUCCI, Phenomenes Physiques dcs Corps Vivants, p. 326 et scq. 
 
346 CIRCULATION. 
 
 from them, and carried on by the veins, and thus through the 
 entire circuit, l>efore it has had time to diffuse itself suffi- 
 ciently to interfere with the observation. It is not apparent 
 how this objection can be overcome, for a substance must be 
 used which will mix with the blood, otherwise it could not 
 pass through the capillaries. The objection made by Mat- 
 teucci, especially as it does not appear how the difficulty can 
 be obviated, seems an unnecessary refinement ; for the ques- 
 tion itself is not one of vital importance, on which depends 
 an important physiological principle, but simply one to 
 which a tolerably close approximation of the exact truth is a 
 sufficient answer. It is interesting to know that the varied 
 and complicated actions which we have been studying effect 
 a single complete circuit of the. blood in about half a min- 
 ute ; but it makes no great difference whether it be four or 
 five seconds more or less. In this statement, we must not be 
 understood as denying the value of the closest possible accu- 
 racy in physiological investigations ; but it is evident that 
 this accuracy is important in proportion to the importance 
 of the question, in itself, and in its physiological relations. 
 
 There seems no reason why, with the above restrictions, 
 the results obtained by Hering should not be accepted, and 
 their application, as far as possible, made to the human 
 subject. 
 
 Hering found that the rapidity of the circulation in dif- 
 ferent animals was in inverse ratio to their size, and in direct 
 ratio to the rapidity of the action of the heart. 
 
 The following are the mean results in certain of the do- 
 mestic animals, taking the course from jugular to jugular, 
 when the blood passes through the lungs and through the 
 capillaries of the face and head : 
 
 In the Horse, the circulation is accomplished in 27'3 seconds. 
 " Dog, " " 16-2 " 
 
 " Goat, " 12-8 " 
 
 " Rabbit, " " 6-9 "' 
 
 1 MILNE-EDWARDS, loc. cit. Vierordt found the mean rapidity in the horse 
 
GENERAL RAPIDITY. 347 
 
 Applying these results to the human subject, taking 
 into account the size of the body and the rapidity of the 
 heart's action, the duration of the circuit from one jugular 
 to the other is estimated at 21*4 seconds, and the general 
 average through the entire system, at 23 seconds. This is 
 simply approximative ; but the results in the inferior ani- 
 mals may be received as very nearly, if not entirely, 
 accurate. 
 
 An estimate of the time required for the passage of the 
 whole mass of blood through the heart is even less definite 
 than the estimate of the general rapidity of the circulation. 
 To arrive at any satisfactory result, it is necessary to know the 
 entire quantity of blood in the body, and the exact quantity 
 which passes through the heart at each pulsation. If we 
 divide the whole mass of blood by the quantity discharged 
 from the heart with each systole of the ventricles, we ascer- 
 tain the number of pulsations required for the passage of the 
 whole mass of blood through the heart ; and, knowing the 
 number of beats per minute, can ascertain the length of time 
 thus occupied. 
 
 The objection to this kind of estimate is the inaccuracy 
 of the data respecting the quantity of blood in the system, 
 and the quantity which passes through the heart with each 
 pulsation. Nevertheless, an estimate can be made, which, 
 if it be not entirely accurate, cannot be very far from the 
 truth. 
 
 The entire quantity of blood, according to estimates 
 which seem to be based on the most reliable data, is about 
 one-eighth the weight of the body, or eighteen pounds in a 
 man weighing one hundred and forty-four. The quantity 
 discharged at each ventricular systole is estimated by Yalen- 
 tin at five ounces, and by Yolkmann at six ounces. 1 In 
 
 to be 28*8 seconds. In experimenting on the crural vein, this observer found 
 that the circulation in the lower extremities, probably from the greater length of 
 the vessels, occupied from one to three seconds more than in the head. 
 
 1 TODD and BOWMAN, Physiological Anatomy, American edition, 1857, p. 704. 
 
348 CIRCULATION. 
 
 treating of the capacity of the different cavities of the heart, 
 it has been noted that the left ventricle, when fully distend- 
 ed, contains from five to seven ounces. Assuming that at 
 each systole the left ventricle discharges all its blood, except 
 perhaps a few drops, and that tins quantity in an ordinary- 
 sized man is five ounces (for in the estimates of Robin and 
 Hiffelsheim, the cavities were fully distended, and contained 
 more than under the ordinary conditions of the circulation), it 
 would require fifty-eight pulsations for the passage through 
 the heart of the entire mass of blood. Assuming the pulsa- 
 tions to be seventy-two per minute, this would occupy about 
 forty-eight seconds. 
 
 We have given elsewhere the opinions of various physiol- 
 ogists on the quantity of blood in the body, and the capacity 
 of the cardiac cavities, and shall not discuss the discordant 
 views on the " duration of the circulation," as each is based 
 on different opinions regarding the two essential questions in 
 the problem. As the quantity of blood in the body is sub- 
 ject to certain physiological variations, there should be cor- 
 responding variations in the duration of the circulation, 
 which it is unnecessary to take up fully in this connection. 
 
 The almost instantaneous action of certain poisons, which 
 must act through the blood, confirms our ideas with regard 
 to the rapidity of the circulation. The intervals between the 
 introduction of some agents (strychnine for example) into the 
 circulation, and the characteristic effects on the system, have 
 been carefully noted by Blake, 1 whose observations coincide 
 pretty closely in their results with the experiments of 
 Hering. 
 
 The relation of the rapidity of the circulation to the fre- 
 quency of the heart's action is a question of considerable in- 
 terest, which was not neglected in the experiments of He- 
 ring. It is evident that if the charge of blood sent into the 
 arteries be the same, or nearly the same, under all circuin- 
 
 1 Edinburgh Med. and Surgical Journal, 1840, vol. liii., p. 35, and 1841, voL 
 Ivi., p. 412. 
 
GENERAL EAPIDITr. 349 
 
 stances, any increase in the number of pulsations of the heart 
 would produce a corresponding acceleration of the general 
 current of blood. But this is a proposition which cannot be 
 taken for granted; and there are many facts which favor 
 a contrary opinion. It may be enunciated as a general rule, 
 that when the acts of the heart increase in frequency, they 
 diminish in force ; which renders it probable that the ven- 
 tricle is most completely distended and emptied when its ac- 
 tion is moderately slow. When, however, the pulse is very 
 much accelerated, the increased number of pulsations of the 
 heart might be sufficient to overbalance the diminished force 
 of each act, and increase the rapidity of the circulation. 
 
 Hering has settled these questions experimentally. His 
 observations were made on horses by increasing the frequen- 
 cy of the pulse, on the one hand, physiologically, by exercise, 
 and on the other hand, pathologically, by inducing inflamma- 
 tory action. He found, in the first instance, that in a horse, with 
 the heart beating at the rate of 36 per minute, with 8 respi- 
 ratory acts, ferro-cyanide of potassium injected into the jugu- 
 lar appeared in the vessel on the opposite side after an inter- 
 val of from 20 to 25 seconds. By exercise, the number of 
 pulsations was raised to 100 per minute, and the rapidity 
 of the circulation was from 15 to 20 seconds. The observa- 
 tions were made with an interval of 24 hours. The same 
 results were obtained in other experiments. 1 Here there is 
 a considerable increase in the rapidity of the circulation fol- 
 . lowing a physiological increase in the number of beats of the 
 heart ; but the value of each beat is materially diminished ; 
 otherwise the rapidity of the current would be increased 
 about three times, as the pulse became three times as frequent. 
 In its tranquil action, with the pulse at 36, the heart con- 
 tracted thirteen times during one circuit of blood ; while it 
 required twenty-nine pulsations to send the blood over the 
 same course, after exercise, with the pulse at 100 ; showing a 
 
 MILNE-EDWARDS, Lemons sur la Physiologic, tome ir., p. 371, note. 
 
350 CIRCULATION. 
 
 diminution in the value of the ventricular systole of more 
 than one-half. 
 
 In animals suffering under inflammatory fever, either 
 spontaneous or produced by irritants, the same observer 
 found a diminution in the rapidity of the circulation, accom- 
 panying acceleration of the pulse. In one observation, in- 
 flammation was produced in the horse by the injection of 
 ammonia into the pericardium. At the commencement of the 
 experiment, the pulse was from Y2 to 84: per minute, and the 
 duration of the circulation about 25 seconds. The next day, 
 with the pulse at 90, the circulation was accomplished in 
 from 35 to 40 seconds ; and the day following, with the pulse 
 at 100, the rapidity of the circulation was diminished to from 
 40 to 45 seconds. 
 
 If we are justified in applying these observations to the 
 human subject (and there is no reason why this should not 
 be done), it is shown that when the pulse is accelerated in 
 disease, the value of the contractions of the heart, as rep- 
 resented by the quantity of blood discharged, bears an 
 inverse ratio to their number; and is so much diminished 
 as absolutely to produce a current of less rapidity than 
 normal. 
 
 "With regard to the relations between the rapidity of the 
 heart's action and the general rapidity of the circulation, the 
 following conclusions may be given as the result of experi- 
 mental inquiry : 
 
 1. In physiological increase in the number of beats of the 
 hear^ as the result of exercise, for example, the general circu- 
 lation is somewhat increased in rapidity, though not in pro- 
 portion to the increase in the pulse. 
 
 2. In pathological increase of the hearts action, as in 
 febrile movement, the rapidity of the general circulation is 
 generally diminished, it may be, to a very great extent. 
 
 3. Whenever the number of beats of the heart is consider- 
 ably increased from any cause, the quantity of Hood dis- 
 charged at each ventricular systole is very much diminished, 
 
CIRCULATION AFTER DEATH. 351 
 
 either from lack of complete distention, or from imperfect 
 emptying of the cavities. 1 
 
 Phenomena in the Circulatory System after Death. -We 
 do not believe that any one has proven the existence of a 
 force in the capillaries or the tissues (capillary power) which 
 materially assists the circulation during life, or produces any 
 movement immediately after death; and shall not discuss 
 further the extraordinary post-mortem phenomena of circu- 
 lation, particularly those which have been observed by Dr. 
 Dowler in subjects dead of yellow fever. 1 But nearly every 
 autopsy shows that after death the blood does not remain 
 equally distributed in the arteries, capillaries, and veins. 
 Influenced by gravitation, it accumulates in and discolors the 
 most dependent parts of the body. The arteries are always 
 found empty, and all the blood in the body accumulates in 
 the venous system and capillaries ; a fact which was observed 
 by the ancients, and gave rise to the belief that the arteries, 
 as their name implies, were air-bearing tubes. 
 
 This phenomenon has long engaged the attention of phys- 
 iologists, who have attempted to explain it by various 
 theories. Without discussing the views on this subject an- 
 terior to our knowledge of the great contractile power of the 
 arteries as compared with other vessels, we may cite the ex- 
 periment of Magendie, already referred to, 2 as offering a 
 satisfactory explanation. If the artery and vein of a limb be 
 exposed in a living animal, and all the other vessels be tied, 
 compression of the artery does not immediately arrest the 
 current in the vein, but the blood will continue to flow until 
 the artery is entirely emptied. The artery, when relieved 
 
 1 These great variations in the value of the ventricular systole, amounting 
 even, in the experiment on the healthy animal, to a diminution of one-half, as the 
 result of exercise, show the uncertainty of the basis of those estimates with regard 
 to the time required for the entire mass of blood to pass through the heart, which 
 are calculated from the entire quantity of blood, the quantity discharged from the 
 heart at each pulsation, and the number of pulsations per minute. 
 
 2 See page 295. 
 
352 CIRCULATION. 
 
 from the distending force of the heart, reacts on its contents 
 by virtue of its contractile coat, and completely empties itself 
 of blood. An action similar to this takes place after death 
 throughout the entire arterial system. The vessels react on 
 their contents, and gradually ^force all the blood into and 
 through the capillaries, which are very short, to the veins, 
 which are capacious, distensible, and but slightly contractile. 
 This begins immediately after death, while the irritability of 
 the muscular coat of the arteries remains, and is seconded by 
 the subsequent cadaveric rigidity, which affects all the in- 
 voluntary, as well as the voluntary muscular fibres. Once in 
 the venous system, the blood cannot return on account of the 
 valves. Thus after death the blood is found in the veins and 
 capillaries of dependent parts of the body. 
 
CHAPTEE X. 
 
 RESPIRATION. 
 
 General considerations Physiological anatomy of the respiratory organs Respi- 
 ratory movements of the larynx Epiglottis Trachea and bronchial tubes 
 Parenchyma of the lungs Carbonaceous matter in the lungs Movements of 
 respiration Inspiration Muscles of inspiration Action of the diaphragm 
 Action of the scaleni Intercostal muscles Levatores costarum Auxiliary 
 muscles of inspiration. 
 
 THE characters of the blood are by no* means identical in 
 the great divisions of the vascular system ; but thus far, phys- 
 iologists have been able to investigate only the differences 
 which exist between arterial and venous blood ; for the capil- 
 laries are so short, communicating directly with the arteries 
 on the one side and the veins on the other, that it has been 
 impossible to obtain a specimen of blood which can be said 
 to belong to this system. In the capillaries, however, the 
 nutritive fluid, which is identical in all parts of the arterial 
 system, undergoes a remarkable change, rendering it unfit 
 for nutrition. It is then known as venous blood; and, 
 as we have seen, the only office of the veins is to carry it 
 back to the right side of the heart, to be sent to the lungs, 
 where it loses the vitiating materials it has collected in the 
 tissues, takes in a fresh supply of the vivifying oxygen, and 
 goes to the left or systemic heart, again prepared for nutri- 
 tion. As the processes of nutrition vary in different parts of 
 the organism, necessarily, there are corresponding variations 
 23 
 
354 
 
 RESPIRATION. 
 
 in the composition of the blood throughout the venous 
 system. 
 
 The important principles which are given off by the 
 lungs are exhaled from the blood ; and the gas which disap- 
 pears from the air is absorbed by the blood, mainly by its 
 corpuscular elements. 
 
 A proper supply of oxygen is indispensable to nutrition, 
 and even to the comparatively mechanical process of circula- 
 tion ; but it is no less necessary to the vital processes that 
 carbonic acid, which the blood acquires in the tissues, should 
 be given off. 
 
 Respiration may 1)6 defined to 1)6 the process by which 
 the system receives oxygen, and is relieved of carbonic acid. 
 
 As it is almost exclusively through the blood that the 
 tissues and organs are supplied with oxygen, and as the 
 blood receives and exhales most of the carbonic acid, the re- 
 spiratory process may be said to consist chiefly in the change 
 of venous into arterial blood. But experiments have demon- 
 strated that the tissues themselves, detached from the body 
 and placed in an atmosphere of oxygen, will absorb this gas 
 and exhale carbonic acid. 1 Under these circumstances, they 
 certainly respire, and it is evident, therefore, that in this 
 process the intervention of the blood is not an absolute 
 necessity. 
 
 The tide of air in the lungs does not constitute respiration, 
 as we now understand it. These organs only serve to facili- 
 tate the introduction of air into the blood, and the exhalation 
 of carbonic acid. If the system be drained of blood, or if the 
 blood be rendered incapable of interchanging its gases with 
 the air, respiration ceases, and all the phenomena of asphyxia 
 are presented, though air be introduced into the lungs with 
 
 1 G. Liebig demonstrated that the muscles of the frog, separated from the 
 body and carefully freed from blood, will continue to absorb oxygen and exhale 
 carbonic acid as long as they retain their irritability. (LEHMANN, Physiological 
 Chemistry, Philadelphia, 1855, vol. ii., pp. 247, 474.) 
 
GENERAL CONSIDERATIONS. 355 
 
 the utmost regularity. It must be remembered that the es- 
 sential processes of respiration take place in all the tissues 
 and organs of the system, and not in the lungs. Respiration 
 is a process similar to what are known as the processes of 
 nutrition ; and although it is much more active and uniform, 
 as far as its products are concerned, than the ordinary nutri- 
 tive acts, it is inseparably connected with, and strictly a part 
 of the general process. As in the nutrition of the substance 
 of tissues, certain principles of the blood, fibrin and albu- 
 men, for example, united with inorganic principles, are used 
 up, transformed into the tissue itself, finally changed into 
 excrementious products, such as urea or cholesterine, and dis- 
 charged from the body, so the oxygen of the blood is appro- 
 priated, and carbonic acid, which is an excrementitious prod- 
 uct, produced whenever tissues are worn out and regener- 
 ated. There is a necessary and inseparable connection be- 
 tween all these processes ; and they must be considered, not 
 as distinct functions, but as different parts of the one great 
 function of nutrition. As we are as yet unable to follow out 
 all the changes which take place between the appropriation 
 of nutritive materials from the blood, and the production of 
 effete or excrementitious substances, it is impossible to say 
 precisely how the oxygen is used by the tissues, and how the 
 carbonic acid is produced. We only know that more or less 
 oxygen is necessary to the nutrition of all tissues, in all ani- 
 mals, high or low in the scale, and that they produce a cer- 
 tain quantity of carbonic acid. The fact that oxygen is con- 
 sumed with much greater rapidity than any other nutritive 
 principle, and that the production of carbonic acid is corre- 
 spondingly active, as compared with other effete products, 
 points pretty conclusively to a connection between the ab- 
 sorption of the one principle and the production of the other. 
 In asphyxia, indeed, it is difficult to say which destroys 
 life, the absence of oxygen or the accumulation of carbonic 
 acid. 
 
 In some of the lowest of the inferior animals, there is 
 
356 RESPIRATION. 
 
 no special respiratory organ, the interchange of gases being 
 effected through the general surface. Higher in the animal 
 scale, special organs are found, which are called gills, when 
 the animals live under water and respire the air which is in 
 solution in the water, and lung^ when the air is introduced 
 in its gaseous form. 1 Animals possessed of lungs have a tol- 
 erably perfect circulatory apparatus, so that the blood is 
 made to pass continually through the respiratory organs. In 
 the human subject and warm-blooded animals generally, the 
 lungs are very complex, and present an immense surface 
 by which the blood is exposed to the air, only separated from 
 it by a delicate permeable membrane. These animals are 
 likewise provided with a special heart, which has the duty of 
 carrying on the pulmonary circulation. Though respiration 
 is carried on to some extent by the general surface, the lungs 
 are the important and essential organs in which the inter 
 change of gases takes place. 
 
 The essential conditions for respiration in animals which 
 have a circulating nutritive fluid are : air and Nood, sepa- 
 rated by a membrane which will allow the passage of gases. 
 The effete products of respiration in the blood pass out and 
 vitiate the air. The air is deprived of a certain portion of its 
 oxygen, which passes into the blood, to be conveyed to 
 the tissues. Thus the air must be changed to supply fresh 
 oxygen and get rid of the carbonic acid. The rapidity of 
 this change is in proportion to the nutritive activity of the 
 animal and the rapidity of the circulation of the blood. 2 
 
 1 Insects have no lungs ; but the air is disseminated throughout the organism 
 by a system of air-bearing tubes (true arteries), or tracheas, and is probably ap- 
 propriated directly by the tissues, without the intervention of the blood. 
 
 2 The manner in which this change of air is effected in the different classes of 
 animals constitutes one of the most interesting subjects in comparative physiology. 
 Its study has shown how, as we pass from the lower to the higher orders of ani- 
 mals, and the functions become more active, a division of labor takes place. 
 Functions which in the lowest animals have no special organs, one part, as the 
 integument or alimentary track, performing many offices, in the higher classes 
 are assigned to special organs, which are brought to a high condition of develop- 
 
ANATOMY OF THE RESPIRATORY ORGANS. 357 
 
 In treating in detail of the function of respiration, it will 
 be convenient to make the following division of the subject: 
 
 1. The mechanical phenomena of respiration ; or the pro- 
 cesses by which the fresh air is introduced into the lungs 
 (inspiration), and the vitiated air is expelled (expiration). 
 
 2. The changes which the air undergoes in respiration. 
 
 3. The changes which the blood undergoes in respiration. 
 
 4. The relations of the consumption of oxygen and the 
 production of carbonic acid to the general process of nutri- 
 tion. 
 
 5. The respiratory sense ; a want, on the part of the sys- 
 tem, which induces the respiratory acts (besoin de respirer}. 
 
 6. Cutaneous respiration. 
 
 7. Asphyxia. 
 
 The study of these questions will be facilitated by a brief 
 consideration of some points in the anatomy of the respira- 
 tory organs. 
 
 Physiological Anatomy of the Respiratory Organs. 
 
 Passing backward from the mouth to the pharynx, two 
 openings present themselves: one, posteriorly, which leads to 
 the oesophagus, and one, anteriorly, the opening of the larynx, 
 which is the commencement of the passages devoted exclu- 
 sively to respiration. The construction of the oesophagus and 
 the air-tubes is entirely different. The oesophagus is flaccid, 
 and destined to receive and convey to the stomach the ar- 
 ticles of food which are introduced by the constrictions of the 
 muscles above. The trachea and its ramifications are exclu- 
 sively for the passage of air, which is taken in by a suction 
 force produced by the enlargement of the thorax. The act 
 of inhalation requires that the tubes should be kept open by 
 
 ment. The perfection of organization in the higher animals seems to consist in 
 the multiplication of organs, for the more efficient performance of the various 
 functions. 
 
358 RESPIRATION. 
 
 walls sufficiently rigid to resist the external pressure of the 
 air. 
 
 Commencing with the larynx, it is seen that the cartilages 
 of which it is composed are sufficiently rigid and unyield- 
 ing to resist the pressure produced by any inspiratory 
 effort. Across its superior opening are the yocal cords, 
 which are four in number, and have a direction from before 
 backwards. The two superior are called the false vocal 
 cords, because they are not concerned in the production of 
 the voice. The two inferior are the true vocal cords. They are 
 ligamentous bands covered by folds of mucous membrane, 
 which is quite thick on the superior cords, and very thin and 
 delicate on the inferior. Anteriorly, they are attached to a 
 fixed point between the thyroid cartilages, and posteriorly, 
 to the movable arytenoid cartilages. Air is admitted to the 
 trachea through an opening between the cords, which is 
 called the rima glottidis. Little muscles, arising from the 
 thyroid and cricoid, and attached to the arytenoid cartilages, 
 are capable of separating and approximating the points 
 to which the vocal cords are attached posteriorly, so as to 
 open and close the rima glottidis. 
 
 If the glottis be exposed in a living animal, certain regu- 
 lar movements are presented which are synchronous with the 
 acts of respiration. The larynx is widely opened at each in- 
 spiration by the action of the muscles referred to above, so 
 that the air has a free entrance to the trachea. At the ter- 
 mination of the inspiratory act, these muscles are relaxed, 
 the vocal cords fall together by their own elasticity, and in 
 expiration, the chink of the glottis returns to the condition 
 of a narrow slit. These respiratory movements of the glottis 
 are constant, and essential to the introduction of air in 
 proper quantity to the lungs. The expulsion of air from the 
 lungs is rather a passive process, and tends in itself to sepa- 
 rate the vocal cords ; but inspiration, which is active and 
 more violent, were it not for the movements of the glottis, 
 would have a tendency to draw the vocal cords together. 
 
EESPDRATOBY MOVEMENTS OF THE GLOTTIS. 359 
 
 The muscles which, are engaged in producing these move- 
 ments are animated by the inferior laryngeal branches of 
 the pneumogastric nerves. If these nerves be divided, the 
 movements of the glottis are arrested, and respiration is 
 very seriously interfered with. This is particularly marked 
 in young animals, in which the walls of the larynx are com- 
 paratively yielding, when the operation is frequently followed 
 by immediate death from suffocation. The movements of 
 the glottis enable us to understand how foreign bodies of 
 considerable size are sometimes accidentally introduced into 
 the air-passages. 
 
 The respiratory movements of the larynx are entirely dis- 
 tinct from those engaged in the production of the voice, and 
 are simply for the purpose of facilitating the entrance of air 
 in inspiration. 
 
 Attached to the anterior portion of the larynx is the epi- 
 glottis ; a little leaf-shaped lamella of fibro-cartilage, which, 
 during ordinary respiration, projects upward, and lies against 
 the posterior portion of the tongue. During the act of de- 
 glutition, respiration is momentarily interrupted, and the air- 
 passages are protected by the tongue, which presses backward 
 carrying the epiglottis before it, completely closing the open- 
 ing of the larynx. Physiologists have questioned whether 
 the epiglottis be necessary for the complete protection of the 
 air-passages ; and, repeating the experiments of Magendie, it 
 has been frequently removed from the lower animals without 
 apparently interfering with the proper deglutition of solids 
 or liquids. We have been satisfied from actual experiment 
 that a dog will swallow liquids and solids immediately after 
 the ablation of the epiglottis, without allowing any to pass 
 into the trachea ; but it becomes a question whether this ex- 
 periment can be absolutely applied to the human subject. 
 In a case of entire loss of the epiglottis, which was observed 
 in the Bellevne Hospital, the patient experienced slight 
 difficulty in swallowing, from the passage of little parti- 
 cles into the larynx, which produced cough. Tljis- case 
 
360 RESPIRATION. 
 
 seemed to show that the presence of the epiglottis, in the 
 human subject at least, is necessary to the complete protec- 
 tion of the air-passages in deglutition. 1 
 
 Passing down the neck from the larynx toward the lungs, 
 is a tube, from four to four an$ a half inches in length, and 
 about three-quarters of an inch in diameter, which is called 
 the trachea. It is provided with cartilaginous rings, from 
 sixteen to twenty in number, which partially surround the 
 tube, leaving about one-third of its posterior portion occupied 
 by fibrous tissue, mixed with a certain number of unstriped 
 muscular fibres. Passing into the chest, the trachea divides 
 into the two primitive bronchi; the right being shorter, 
 larger, and more horizontal than the left. These tubes, pro- 
 vided, like the trachea, with imperfect cartilaginous rings, 
 enter the lungs, divide and subdivide, until the minute rami- 
 fications of the bronchial tree open directly into the air-cells. 
 After penetrating the lungs, the cartilages become irregular, 
 and are in the form of angular plates, which are so disposed 
 as to completely encircle the tubes. In tubes of very small 
 size, these plates are less numerous than in the larger bronchi, 
 until in tubes of a less diameter than -^ of an inch, they are 
 lost altogether. 
 
 The walls of the trachea and bronchial tubes are com- 
 posed of two distinct membranes : an external membrane, 
 between the layers of which the cartilages are situated, and a 
 lining mucous membrane. The external membrane is com- 
 posed of inelastic and elastic fibrous tissue. Posteriorly, in 
 the space not covered by cartilaginous rings, these fibres are 
 mixed with a certain number of unstriped or involuntary 
 muscular fibres, which exist in two layers : a thick internal 
 layer, in which the fibres are transverse, and a thinner longi- 
 tudinal layer, which is external. This collection of muscular 
 fibres is sometimes called the trachealis muscle. Throughout 
 
 1 This remarkable case, in which the epiglottis had sloughed entirely away 
 leaving the parts completely cicatrized, as demonstrated by a laryngOscopic exam- 
 ination, will be given in eztenso in connection with the subject of deglutition. 
 
PARENCHYMA OF THE LUNGS. 361 
 
 the entire system of bronchial tubes, there are circular fasciculi 
 of muscular fibres lying just beneath the mucous membrane, 
 with a number of longitudinal elastic fibres. The character 
 of the bronchi abruptly changes in tubes less than -^ of an 
 inch in diameter. They lose the cartilaginous rings, and the 
 external and the mucous membranes become so closely united 
 that they can no longer be separated by dissection. The 
 circular muscular fibres continue down to the air-cells. The 
 mucous membrane is smooth, covered by ciliated epithelium, 
 the movements of the ciliae being always from within out- 
 ward, and it is provided with numerous mucous glands. These 
 glands are of the racemose variety, and in the larynx are of 
 considerable size. In the trachea and bronchi, racemose 
 glands exist in the membrane on the posterior surface of 
 the tubes ; but anteriorly are small follicles, terminating in 
 a single, and sometimes a double, blind extremity. These 
 follicles are lost in tubes less than -g 1 -^ of an inch in diameter. 
 It is the anatomy of the parenchyma of the lungs which 
 possesses the most physiological interest, for here the essential 
 processes of respiration take place. When moderately in- 
 flated, the lungs have the appearance of irregular cones, with 
 rounded apices, and concave bases resting upon the diaphragm. 
 They fill all of the cavity of the chest which is not occupied 
 by the heart and great vessels, and are completely separated 
 from each other by the mediastinum. In the human subject, 
 the lungs are not attached to the thoracic walls, but are 
 closely applied to them, each covered by a reflection of the 
 serous membrane which lines the cavity on the corresponding 
 side. They thus necessarily follow the movements of ex- 
 pansion and contraction of the thorax. Deep fissures divide 
 the right lung into three lobes, and the left lung into two. 
 The surface of the lungs is divided into irregularly polygonal 
 spaces, from J of an inch to an inch in diameter, which mark 
 what are sometimes called the pulmonary lobules, though 
 this term is incorrect, as each of these divisions includes 
 quite a number of the true lobules. 
 
362 
 
 "RESPIRATION. 
 
 Following out the bronchial tubes from the diameter of 
 fa of an inch, the smallest, which are from yfo to fa of an 
 inch in diameter, open into a collection of oblong vesicles, 
 K g. 10. which are the air- 
 
 cells. Each collec- 
 tion of vesicles con- 
 stitutes one of the 
 true pulmonary lo- 
 bules, and is from 
 fa to fa of an inch 
 in diameter. After 
 entering the lobule, 
 the tube forms a sort 
 of tortuous central 
 canal, sending off 
 branches which ter- 
 minate in groups of 
 from eight to fifteen 
 pulmonary cells. 
 The cells are a little 
 deeper than they are 
 wide, and have a 
 rounded blind ex- 
 tremity. Some are 
 smooth, but many 
 
 (After Eobin.) are mar k e d by little 
 
 circular constrictions, or rugse. In the healthy lung of the 
 adult, after death, they measure from -^ to T |o- or fa of an 
 inch in diameter, but are capable of very great distention. 
 The smallest cells are in the deep portions of the lungs, and 
 the largest are situated near the surface. By sections of lung 
 inflated and dried, Magendie demonstrated, a number of 
 years ago, that there is a considerable variation in the size 
 of the cells at different periods of life ; that the smallest 
 cells are found in young children, and that they progres- 
 
 Mould of a terminal bronchus and a group of air-cells 
 moderately distended by injection, from the human subject. 
 
PARENCHYMA OF THE LUNGS. 363 
 
 sively increase in size with age. 1 The air-cells are sur- 
 rounded by a great number of elastic fibres, which do not 
 form distinct bundles for each cell, but anastomose freely 
 with each other, so that the same fibres belong to two or 
 more. This structure is peculiar to the parenchyma of the 
 lungs, and gives these organs their great distensibility and 
 elasticity, properties which play an important part in ex- 
 pelling the air from the chest, as a consequence simply of 
 cessation of the action of the inspiratory muscles. Inter- 
 woven with these elastic fibres is the richest plexus of 
 capillary blood-vessels found in the economy. The vessels 
 are larger than the capillaries in other situations, and the 
 plexus is so close that the spaces between them are narrower 
 than the vessels themselves. When distended, the blood-ves- 
 sels form the greater part of the walls of the cells. 
 
 There is some difference of opinion among anatomists with 
 regard to the lining of the air-cells. Some are of the opinion, 
 with Rainey and Mandl, that the mucous membrane, and 
 even the epithelium, cease in the small bronchial tubes, and 
 the blood-vessels in the cells are uncovered. The presence of 
 pavement epithelium has been demonstrated, however, in the 
 cells, but the scales are detached soon after death, and cannot 
 always be observed. All who contend for the existence of a 
 mucous membrane admit that it is of excessive tenuity. 
 Robin, Kolliker, and others have demonstrated in the air- 
 cells very thin scales of pavement epithelium, from -g-^L-o- * 
 jroVo f an i ncn i* 1 diameter, which are applied directly to the 
 walls of the blood-vessels. 2 The epithelium here does not 
 seem to be regularly desquamated, as in other situations. 
 Examination of injected specimens shows that the blood-ves- 
 sels are so situated between the cells, that the blood in the 
 greater part of their circumference is exposed to the action 
 of the air. 
 
 1 MAGENDIE, Memoire sur la /Structure du Poumon de THomme. Journal de 
 Physiologic, 1821, tome i., p. V8. 
 
 a KOLLIKER, Manual of Human Microscopic Anatomy, London, 1860, p. 387 ; 
 and POUCHET, Histologie Humaine, Paris, 1864, p. 286. 
 
364: RESPIRATION. 
 
 The entire mass of venous blood is distributed in the lungs 
 by the pulmonary artery for the purposes of aeration. Arte- 
 rial blood is conveyed to these organs by the bronchial arte- 
 ries, which ramify and subdivide on the bronchial tubes, and 
 follow their course into the lyings, for the nourishment of 
 these parts. It is possible that the tissue of the lungs may 
 receive some nourishment from the blood conveyed there by 
 the pulmonary artery ; but as this vessel does not send any 
 branches to the bronchial tubes, it is undoubtedly the bron- 
 chial arteries which supply the material for their nutrition 
 and the secretion of the mucous glands. This is one of the 
 anatomical reasons why inflammatory conditions of the bron- 
 chial tubes do not extend to the parenchyma of the lungs, and 
 vice versa. 
 
 The foregoing anatomical sketch shows the admirable 
 adaptation of the trachea and bronchial tubes to the pas- 
 sage of the air by inspiration to the deep portions of the 
 lungs, and the favorable conditions which it there meets with 
 for an interchange of the elements of the air and blood. It 
 is also evident, from the enormous number of air-cells, that 
 the respiratory surface must be immense. 1 
 
 Carbonaceous Matter in the Lungs. The lungs of most 
 of the inferior animals and the human subject, in early life, 
 have a uniform rose tint ; but in the adult, and particularly 
 in old age, they contain a greater or less quantity of black 
 matter, which may exist in little masses, deposited here and 
 there in the pulmonary structure, or forming lines on the 
 
 1 Hales estimated the combined surface of the air-cells at 289 square feet 
 (Statical Essays, voL i., p. 242) ; Keill at 21,906 square inches (Essays on Several 
 Parts of the Animal (Economy,}). 122); and Lieberkiihn at 1,500 square feet 
 (DUNGLISON'S Human Physiology, 1856, vol. i., p. 278). There are not sufficient 
 data on this point for us to form any thing like a reliable estimate. It is 
 simply evident that the extent of surface must be very great. In passing from 
 the lower to the higher orders of animals, it is seen that Nature provides for 
 the necessity of an increase in the activity of the respiratory process, by a 
 ished size and a multiplication of the air-cells. 
 
CARBONACEOUS MATTER IN THE LUNGS. 365 
 
 surface of the organs. The deposit is generally most abun- 
 dant at the summit of the lungs. This matter also exists in 
 the lymphatic glands connected with the pulmonary struc- 
 ture, which are sometimes called the u bronchial glands." 
 The nature of this deposit has been the subject of consider- 
 able discussion. Some have supposed that it was connected 
 with melanotic deposits, and consisted of ordinary pigmentary 
 matter ; but chemical investigations have now pretty conclu- 
 sively demonstrated that it is nothing more nor less than 
 carbon. It exists in great abundance in the lungs of miners, 
 who inhale great quantities of carbonaceous particles, and of 
 those who are much exposed to the inhalation of smoke. 
 These facts, taken in connection with its absence in young 
 persons and the inferior animals, and its small quantity, even 
 in old age, in those who inhabit villages and are not exposed 
 to a smoky atmosphere, point to its introduction from with- 
 out. The subject has been most completely and ably inves- 
 tigated by Robin, w r ho has come to the conclusion that the 
 matter is really carbon ; that it is introduced in fine particles 
 in the inspired air, and that, once in the lungs, it penetrates 
 the tissue, not by absorption, but by mechanical action, until it 
 finds its way beneath the pleura and into the intercellular 
 substance. From the fact that carbon is insoluble, its penetra- 
 tion must be mechanical ; and, when found in the lymphatic- 
 glands, it is carried there by the absorbent vessels. When 
 it has penetrated the substance of the tissues, it can no more 
 be removed than the tattooing beneath the skin ; indeed, the 
 deposition in the lungs may be compared very aptly to the 
 process of tattooing. 
 
 The mechanism of its introduction is the following : The 
 little sharp, almost microscopic, particles are inhaled and 
 come in contact with the delicate walls of the air-cells, in 
 which they are imbedded under a certain pressure. "When 
 any part is subject to pressure, it is well known that it gives 
 way by absorption, the pressure facilitating the removal of 
 worn-out matter, but interfering with the deposition of new 
 
366 RESPIRATION. 
 
 material. These particles thus penetrate the lung substance, 
 from which they can never be removed. They may find 
 their way into the lymphatic vessels, but become fixed in the 
 lymphatic glands, in which the quantity is always propor- 
 tionate to that which exists in ihe lungs. It has been shown 
 that the particles introduced under the skin in tattooing may 
 also be taken up by the lymphatics, but are arrested and 
 fixed in the glands. 1 
 
 There is no ground for the hypothesis that the carbona- 
 ceous matter of the lungs and bronchial glands is deposited 
 as a residue of combustion of the hydrocarbons, in the process 
 of respiration. 
 
 Movements of Respiration. 
 
 In man and the warm-blooded animals' generally, the 
 lungs attain their greatest degree of development, the sur- 
 face which is exposed to the atmosphere is relatively great- 
 est, and it is in these organs that nearly all of the process of 
 interchange of gases takes place. In all animals of this class, 
 inspiration takes place as a consequence of enlargement of 
 the thoracic cavity, and the entrance of a quantity of air 
 through the respiratory passages corresponding to the in- 
 creased capacity of the lungs. In the mammalia, the chest is 
 enlarged by the action of muscles; and in ordinary respi- 
 ration, inspiration is an active process, while expiration is 
 comparatively passive. In many birds, the chest is com- 
 pressed by muscular action in expiration, and inspiration is 
 effected in a measure by elastic ligaments. In both classes, 
 the air is drawn into the chest to supply the space produced 
 by its enlargement. In some of the lower orders of animals 
 which have no ribs or sternum, or in which the thorax is 
 immovable and there exists no division between its cavity 
 and the abdomen, the air is forced into the lungs by an act 
 like deglutition. In these animals (frogs, lizards, turtles, 
 
 1 The results of the investigations of Kobin are to be found in the Chimic 
 Anatomique, by ROBIN and YERDEIL, tome iii., p. 505 et seq. 
 
INSPIRATION. 367 
 
 etc.) the respiratory acts are very infrequent ; and in some, 
 the oxidation of the blood is more effectually performed by 
 the general surface than by the lungs. 
 
 A glance at the physiological anatomy of the thorax in 
 the human subject makes it evident that the action of certain 
 muscles will considerably increase its capacity. In the first 
 place, the diaphragm mounts up into its cavity in the form 
 of a vaulted arch. By contraction of its fibres, it is brought 
 nearer a plane, and thus the vertical diameter of the thorax 
 is increased. The walls of the thorax are formed by the 
 dorsal vertebrae and ribs posteriorly, by the upper ten ribs 
 laterally, and by the sternum and costal cartilages anteriorly. 
 The direction of the ribs, their mode of connection with the 
 sternum by the costal cartilages, and their articulation with 
 the vertebral column, are such that by their movements the 
 antero-posterior and transverse diameters of the chest may be 
 considerably modified. 
 
 Inspiration. 
 
 The ribs are somewhat twisted upon themselves, and have 
 a general direction forwards and downwards. The first 
 rib is nearly horizontal, but the obliquity progressive- 
 ly increases from the upper to the lower parts of the 
 chest. They are articulated with the bodies of the vertebrae, 
 so as to allow of considerable motion. The upper seven ribs 
 are attached by the costal cartilages to the sternum, these 
 cartilages running upwards and inwards. The cartilages of 
 the eighth, ninth, and tenth ribs are joined to the cartilage 
 of the seventh. The eleventh and twelfth are floating ribs, 
 and are only attached to the vertebrae. 
 
 It may be stated in general terms that inspiration is effect- 
 ed by descent of the diaphragm and elevation of the ribs ; 
 and expiration by elevation of the diaphragm and descent 
 of the ribs. 
 
 Arising severally from the lower border of each rib, and 
 
368 RESPIRATION. 
 
 attached to the upper border of the rib below, are the eleven ex- 
 ternal intercostal muscles, the fibres of which have an oblique 
 direction from above downwards and forwards. Attached to 
 the inner borders of the ribs are the internal intercostals, which 
 have a direction from above Downwards and backwards, at 
 right angles to the fibres of the external intercostals. There 
 are also a number of muscles attached to the thorax and spine, 
 thorax and head, upper part of humerus, etc., which are 
 capable of elevating either the entire chest or the ribs. 
 These must act as muscles of inspiration when the attach- 
 ments to the thorax become the movable points. Some of 
 them are called into action during ordinary respiration; 
 others act as auxiliaries when respiration is a little exagger- 
 ated, as after exercise, and are called ordinary auxiliaries ; 
 while others, which ordinarily have a different function, 
 are only brought into play when respiration is excessively 
 difficult, and are called extraordinary auxiliaries. 
 
 The following are the principal muscles concerned in in- 
 spiration : 
 
 Muscles of Inspiration. 
 
 ORDINARY RESPIRATION. 
 
 Muscle. Attachments. 
 
 Diaphragm Circumference of lower border of thorax. 
 
 Scalenus Anticus Transverse processes of third, fourth, 
 
 fifth, and sixth cervical vertebrae 
 
 tubercle of first rib. 
 
 Scalenus Medius Transverse processes of six lower cervi- 
 cal vertebrae upper surface of first 
 
 rib. 
 
 Scalenus Posticus Transverse processes of lower two or 
 
 three cervical vertebras outer sur- 
 face of second rib. 
 
 External Intercostals Outer borders of the ribs. 
 
 Sternal portion of Internal Intercostals . .Borders of the costal cartilages. 
 
 Twelve Levatores Costarum Transverse processes of dorsal vertebrae 
 
 ribs, between the tubercles and 
 
 angles. 
 
ACTION OF THE DIAPHRAGM. 369 
 
 Ordinary Auxiliaries. 
 
 Muscle. Attachments. 
 
 Serratus Posticus Superior Ligaraentum nuchae, spinous processes 
 
 of last cervival and upper two or threo 
 
 dorsal vertebrae upper borders of 
 
 second, third, fourth, and fifth ribs 
 just beyond the angles. 
 
 Stemo-mastoideus Upper part of sternum mastoid pro- 
 cess of temporal bone. 
 
 Extraordinary Auxiliaries. 
 
 Levator Anguli Scapulse .Transverse processes of upper three or 
 
 four cervical vertebrae posterior 
 
 border of superior angle of the scapula. 
 
 Trapezius (superior portion) Ligamentum nuchse and seventh cervical 
 
 vertebra the upper border of the 
 
 spine of the scapula. 
 
 Pectoralis Minor Coracoid process of scapula anterior 
 
 surface and upper margins of third, 
 fourth, and fifth ribs near the cartilages. 
 
 Pectoralis Major (inferior portion) Bicipital groove of humerus costal 
 
 cartilages and lower part of the ster- 
 num. 
 
 Serratus Magnus Inner margin of posterior border of scap- 
 ula external surface and upper bor- 
 der of upper eight ribs. 
 
 Action of the Diaphragm. The descriptive and general 
 anatomy of the diaphragm gives a pretty correct idea of its 
 functions in respiration. It arises, anteriorly, from the inner 
 surface of the ensiform cartilage, laterally, from the inner 
 surface of the lower borders of the costal cartilages and the 
 six or seven inferior ribs, passes over the quadratus lumborum 
 by the external arcuate ligament, and the psoas magnus by 
 the internal arcuate ligament, and has two tendinous slips of 
 origin, called crurse of the diaphragm, from the bodies of the 
 second, third, and fourth lumbar vertebrae and the interverte- 
 bral cartilages on the right side, and the second and third lum- 
 bar vertebrae and the intervertebral cartilages on the left side. 
 From this origin, which extends around the lower circumfer- 
 24 
 
370 RESPIRATION. 
 
 ence of the thorax, it mounts up into the cavity of the chest, 
 forming a vaulted arch or dome, with its concavity toward 
 the abdomen and its convexity toward the lungs. In the cen - 
 tral portion there is a tendon of considerable size, and shaped 
 something like the club on a^ playing card, with middle, 
 right, and left leaflets. The remainder of the organ is com- 
 posed of radiating fibres of the striped or voluntary muscular 
 tissue. The oesophagus, aorta, and inferior vena cava pass 
 through the diaphragm from the thoracic to the abdominal 
 cavity, by three openings. 
 
 The opening for the oesophagus is surrounded by muscular 
 fibres, by which it is partially closed when the diaphragm 
 contracts in inspiration, as the fibres simply surround the 
 tube, and none are attached to it. 
 
 The orifice for the aorta is bounded by the bone and 
 aponeurosis posteriorly, and in front by a fibrous band to 
 which the muscular fibres are attached; so that their con- 
 traction has rather a tendency to increase, than diminish, the 
 caliber of the vessel. 
 
 The orifice for the vena cava is surrounded entirely by 
 tendinous structure, and contraction of the diaphragm, though 
 it might render the form of the orifice more nearly circular, 
 can have no effect upon its caliber. 
 
 The action of the diaphragm can be easily studied in the 
 inferior animals by vivisections. If the abdomen of a cat, 
 which, from the conformation of the parts, is well adapted to 
 this experiment, be largely opened, we can observe the descent 
 of the tendinous portion, and the contraction of the muscular 
 fibres. The action of this muscle may be rendered more 
 apparent by compressing the walls of the chest with the hands, 
 so as to interfere somewhat with the movements of the ribs. 
 In ordinary respiration, the 'descent of the diaphragm and 
 its approximation to a plane is the chief phenomenon ob- 
 served; but. as there is a slight resistance to the depres- 
 sion of the central tendon, it is probable that there is also a 
 slight elevation of the inferior ribs, the diaphragm assisting, 
 
ACTION OF THE DIAPHKAGM. 371 
 
 in a limited degree it is true, the action of the external 
 intercostals. 
 
 The phenomena referable to the abdomen, which coincide 
 with the descent of the diaphragm, can easily be observed 
 in the human subject. As the diaphragm is depressed, 
 it necessarily pushes the viscera before it, and inspiration 
 is therefore accompanied by protrusion of the abdomen. 
 This may be rendered very marked by a forced or deep in- 
 spiration. 
 
 The action of the diaphragm maybe illustrated by a very 
 simple yet striking experiment. In an animal just killed, 
 after opening the abdomen, if we take hold of the structures 
 which are attached to the central tendon, and make traction, 
 we imitate, in a rough way, the movements of the diaphragm 
 in respiration, and the air will pass into the lungs, sometimes 
 with a distinctly audible sound. 
 
 The effects of the action of the diaphragm upon the size 
 of its orifices are chiefly limited to the oesophageal opening. 
 The anatomy of the parts is such that contraction of the 
 muscular fibres has a tendency to close this orifice. When 
 we come to treat of the digestive system, we shall see that this 
 is auxiliary to the action of the muscular walls of the oeso- 
 phagus itself, by which the cardiac opening of the stomach 
 is regularly closed during inspiration. This may become 
 important when the stomach is much distended ; for descent 
 of the diaphragm compresses all the abdominal organs, and 
 might otherwise cause regurgitation of a portion of its con- 
 tents. 
 
 The contractions of the diaphragm are animated almost 
 exclusively, if not exclusively, by the phrenic nerve ; a nerve 
 which, having the office of supplying the most important 
 respiratory muscle, derives its filaments from a number of 
 sources. It arises from the third and fourth cervical nerves, 
 receiving a branch from the fifth, and sometimes from the 
 sixth ; it passes through the chest, penetrates the diaphragm, 
 and is distributed to its under surface. This nerve was the 
 
372 RESPIRATION. 
 
 subject of numerous experiments by the earlier physiologists, 
 who were greatly interested in the minutiaa of the action of 
 the diaphragm, and other muscles, in respiration. Its gal- 
 vanization produces convulsive contractions of the diaphragm, 
 and its section paralyzes the muscle almost completely. It 
 was noticed by Lower, that after section of both phrenic 
 nerves the movements of the abdomen were reversed, and it 
 became retracted in inspiration. 1 This is explained and illus- 
 trated by voluntary suspension of the action of the diaphragm, 
 and exaggeration of the costal movements. As the ribs are 
 raised, the atmospheric pressure causes the diaphragm to 
 mount up into the cavity of the thorax, and of course the 
 abdominal organs follow. 
 
 From the great increase in the capacity of the chest pro- 
 duced by the action of the diaphragm, and its constant and 
 universal action in respiration, it must be regarded as by far 
 the most important and efficient of the muscles of inspiration. 
 
 Hiccough, sobbing, laughing, and crying are produced 
 mainly by the action of the diaphragm, particularly hic- 
 cough and sobbing, which are produced by spasmodic con- 
 tractions of this muscle, generally beyond the control of the 
 will. 
 
 Action of the Muscles which elevate the JRibs. /Scalene 
 Muscles. In ordinary respiration, the ribs and the entire 
 chest are elevated by the combined action of a number of 
 muscles. The three scalene muscles are attached to the cervi- 
 cal vertebrae and the first and second ribs. These muscles, 
 which act particularly upon the first rib, must elevate with 
 it, in inspiration, the rest of the thorax. The articulation of 
 the first rib with the vertebral column is very movable, but 
 it is joined to the sternum by a very short cartilage, whicli 
 allows of very little movement, so that its elevation necessa- 
 rily carries with it the sternum. This movement increases 
 both the transverse and antero-posterior diameters of the 
 
 1 BERARD, Cours de Physiologic, Paris, 1851, tome iii., p. 245. 
 
ACTION OF THE SCALENI. 373 
 
 thorax, from the mode of articulation and direction of the 
 ribs, which are somewhat rotated as well as rendered more 
 horizontal. 
 
 Perhaps there is no set of muscular actions to which as 
 much observation and speculation have been devoted as those 
 concerned in respiration ; and the actions of the muscles 
 which are attached to the thorax are so complex and difficult 
 of observation, that the views of physiologists concerning 
 them are still somewhat conflicting. While some adopt the 
 opinion of Haller, 1 that the first rib is almost fixed and im- 
 movable, others contend, as did Magendie, that it is the 
 most movable of all. 2 With regard to this point there can 
 now, it seems, be no doubt. By putting the thumb and fin- 
 ger on either side of thp neck over the scaleni, we can dis- 
 tinctly feel these muscles contract with every tolerably deep 
 inspiration (a movement which Magendie proposed to call 
 the respiratory pulse, loo. tit.) ; and it is further evident 
 that though in the male, in ordinary respiration, the sternum 
 is almost motionless, in the female, and in the male, in deep 
 inspirations, the sternum is considerably elevated and pro- 
 jected, particularly at its lower part. This latter movement 
 increases the antero-posterior diameter of the thorax, and can 
 be measured with an appropriate instrument. The elevation 
 of the sternum is necessitated by its close and almost im- 
 movable connection, through its short cartilage, with the 
 first rib. 
 
 The action of the scaleni, while it is inconsiderable in 
 ordinary respiration in the male, in all cases renders the first 
 rib practically a fixed point, from which those intercostal 
 muscles which raise the ribs can act. 
 
 Intercostal Muscles. Concerning the mechanism of the 
 action of these muscles, there is great difference of opinion 
 among physiologists ; so much, indeed, that the author of a 
 
 1 Elementa Physiologies, Lausanne, 1761, tomus iii., p. 23. 
 
 2 Precis filementaire de Physiologic, tome ii., p. 317. 
 
374 RESPIRATION. 
 
 late elaborate work assumes that the question is still left in 
 considerable uncertainty. 1 The most elaborate researches on 
 this point are those of Beau and Maissiat (Archives Generates 
 de Medecine, 1843), and Sibson (Philosophical Transactions, 
 1846). The latter seem to settle the question of the mode of 
 action of the intercostals, and explain satisfactorily certain 
 points which even now are not generally appreciated. 2 
 
 Let us first note the changes which take place in the 
 direction of the ribs, and their relation to each other, in 
 inspiration, before considering the way in which these move- 
 ments are produced. 
 
 In the dorsal region, the spinal column forms an arch 
 with its concavity toward the chest, and the ribs increase in 
 length progressively, from above downwards, to the deepest 
 portion of the arch, where they are longest, and then become 
 progressively shorter. " During inspiration the ribs approach 
 to or recede from each other according to the part of the arch 
 with which they articulate ; the four superior ribs approach 
 each other anteriorly and recede from each other posteriorly ; 
 the fourth and fifth 'ribs, and the intermediate set (sixth, 
 seventh, and eighth), move further apart to a moderate, the 
 diaphragmatic set (four inferior), to a great extent. The upper 
 edge of each of these ribs glides toward the vertebrae in rela- 
 tion to the lower edge of the rib above, with the exception of 
 the lowest rib, which is stationary." 3 
 
 These movements, accurately and admirably described 
 by Sibson, and illustrated by drawings of the chest, empty, 
 
 1 LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 629. 
 
 a Sibson's article is the most complete ever published upon the mechanism of 
 respiration. The action of the respiratory muscles was observed in vivisections, 
 and the mechanism by which the capacity of the thorax is modified is illustrated 
 in the most ingenious manner by mechanical contrivances, representing the posi- 
 tion, etc., of the ribs, and their movements. By dilating the chest after death, 
 also, he shows the change which takes place in the direction of the ribs and the 
 consequent shortening of certain muscles, which, he assumes, must act as muscles 
 of inspiration, a fact which he has taken care to verify by vivisections. 
 8 SIBSON, op. cit. t p. 529. 
 
INTEECOSTAL MUSCLES. 
 
 375 
 
 Dorsal Eegion. 
 Expiration. Inspiration. 
 
 Anterior Eegion of the Thorax. 
 Inspiration. Expiration. 
 
 FIG. 14. 
 
 Inspiration. 
 
376 KESPIRA.TION. 
 
 as in expiration, and distended with air, increase the antero 
 posterior and transverse diameters of the thorax. As the 
 ribs are elevated and become more nearly horizontal, they 
 must push forward the lower portion of the sternum. Their 
 configuration and mode of artioulation with the vertebrae are 
 such, that they cannot be elevated without undergoing a con- 
 siderable rotation, by which the concavity looking directly 
 toward the lungs is increased, and with it the lateral diameter 
 of the chest. All the intercostal spaces posteriorly are widen- 
 ed in inspiration. 
 
 These points are clearly illustrated in the accompanying 
 diagrams. 1 
 
 The ribs are elevated by the action of the external inter- 
 costals, the sternal portion of the internal intercostals, and 
 the levatores costarum. 
 
 The external intercostals are situated between the ribs 
 only, and are wanting in the region of the costal cartilages. 
 As the vertebral extremities of the ribs are the pivots on 
 which these levers move, and the sternal extremities are 
 movable, the direction of the fibres of the intercostals, from 
 above downwards and forwards, renders elevation of the ribs 
 a necessity of their contraction ; if it can be assumed that the 
 first rib is fixed, or at least does not move downwards. The 
 scalene muscles elevate the first rib in ordinary inspiration ; 
 and in deep inspiration, this takes place to such an extent as 
 to palpably carry with it the sternum and the lower ribs. 
 Theoretically, then, the external intercostals can do nothing 
 but render the ribs more nearly horizontal. The action of 
 these muscles has, however, been the subject of considerable 
 controversy, on theoretical grounds. We shall discuss the 
 question chiefly from an experimental point of view. 
 
 If the external intercostals be exposed in a living animal, 
 the dog for example, in which the costal type of respiration 
 is very marked, close observation cannot fail to convince any 
 one that these muscles enter into action in inspiration. This 
 
 1 SIBSON, loc. cit 
 
INTEECOSTAL MUSCLES. 377 
 
 fact has been observed by Sibson and many other physiolo- 
 gists. If attention be now directed to the sternal portion of 
 the internal intercostals, situated between the costal cartilages, 
 their fibres having a direction from above downwards and 
 backwards, it is equally evident that they enter into action 
 with inspiration. By artificially inflating the lungs after 
 death, Sibson confirmed these observations, and showed that 
 when the lungs are filled with air, the fibres of these muscles 
 are shortened. In inspiration the ribs are all separated pos- 
 teriorly ; but laterally and anteriorly, some are separated (all 
 below the fourth), and some are approximated (all above the 
 fourth). Thus all the interspaces, excepting the anterior por- 
 tion of the upper three, are widened in inspiration. Sibson 
 lias shown by inflation of the chest, that though the ribs are 
 separated from each other, the attachments of the intercostals 
 are approximated. The ribs, from an excessively oblique 
 position, are rendered nearly horizontal; and consequently 
 the inferior attachments of the intercostals are brought nearer 
 the spinal column, while the superior attachments on the 
 upper borders of the ribs are slightly removed from it. Thus 
 these muscles are shortened. If, by separating and elevating 
 the ribs, the muscles are shortened, shortening of the muscles 
 will elevate and separate the ribs. In the three superior 
 interspaces, the constant direction of the ribs is nearly hori- 
 zontal, and the course of the intercostal fibres is not as oblique 
 as in those situated between the lower ribs. These spaces are 
 narrowed in inspiration. The muscles between the costal 
 cartilages have a direction opposite to that of the external 
 intercostals, and act upon the ribs from the sternum, as the 
 others do from the spinal column. The superior interspace 
 is narrowed, and the remainder are widened, in inspiration. 
 
 The probable explanation of the great difference of opin- 
 ion with regard to the action of the intercostals is the diffi- 
 culty of comprehending, at the first blush, that the contrac- 
 tion of muscles situated between the ribs can separate them 
 from each other ; a phenomenon which is easily understood 
 
378 RESPIRATION. 
 
 after a careful consideration of the relative position of the 
 parts. 
 
 Xevatores Costarum. The action of these muscles cannot 
 be mistaken. They have imnaovable points of origin, the 
 transverse processes of twelve vertebrae from the last cervical 
 to the eleventh dorsal, and, spreading ont like a fan, are at- 
 tached to the upper edges of the ribs between the tubercles 
 and the angles. In inspiration they contract and assist in the 
 elevation of the ribs. They are more developed in man than 
 in the inferior animals. 
 
 Auxiliary Muscles of Inspiration. The muscles which 
 have just been considered are competent to increase the ca- 
 pacity of the thorax sufficiently in ordinary respiration ; there 
 are certain muscles, however, which are attached to the ches* 
 and the upper part of the spinal column, or upper extremities, 
 which may act in inspiration, though ordinarily the chest is 
 the fixed point, and they move the head, neck, or arms. 
 These muscles are brought into action when the movements 
 of respiration are exaggerated. When this exaggeration is 
 but slight and physiological, as after exercise, certain of them 
 (ordinary auxiliaries) act for a time, until the tranquillity of 
 the movements is restored. But when there is obstruction 
 in the respiratory passages, or when respiration is excessively 
 difficult from any cause, threatening suffocation, all the 
 muscles which can by any possibility raise the chest are 
 brought into action. The principal ones are put down in the 
 table under the head of extraordinary auxiliaries. Most of 
 these muscles can voluntarily be brought into play to raise 
 the chest, and the mechanism of their action can in this way 
 be demonstrated. 
 
 Serratus Posticus Superior. This muscle arises from the 
 ligamentum nuchse, the spinous processes of the last cervical 
 and upper two or three dorsal vertebras, its fibres passing 
 
AUXILIARY MUSCLES OF mSPIEATION. 379 
 
 obliquely downwards and outwards, to be attached to the 
 upper borders of the second, third, fourth, and fifth ribs just 
 beyond their angles. By reversing its action, as we have re- 
 versed the description of its origin and insertions, it is capable 
 of increasing the capacity of the thorax. Sibson has seen 
 this muscle contract in inspiration, in the dog and the ass. 1 
 
 Sterno-mastoideus. That portion of the muscle which is 
 attached to the mastoid process of the temporal bone and the 
 sternum, when the head is fixed, is capable of acting as a 
 muscle of inspiration. It does not act in ordinary respira- 
 tion, but its contractions can be readily observed whenever 
 respiration is hurried or exaggerated. 
 
 The following muscles, as a rule, only act as muscles of 
 inspiration when respiration is exceedingly difficult or la- 
 bored. In certain cases of capillary bronchitis, for example, 
 the anxious expression of the countenance betrays the sense 
 of impending suffocation ; the head is thrown back and fixed, 
 the shoulders are braced, and every available muscle is 
 brought into action to raise the walls of the thorax. 2 
 
 Levator Anguli Scapulae and Superior Portion of the 
 Trapezius. Movements of the scapula have often been ob- 
 served in very labored respiration. Its elevation during in- 
 spiration is chiefly effected by the levator angnli scapulae 
 and the upper portion of the trapezius. The former arises 
 from the transverse processes of the upper three or four cer- 
 vical vertebrae, and is inserted into the posterior border of 
 the scapula below the angle. It is a thick flat muscle, and 
 when the neck is the fixed point, assists in the elevation of 
 the thorax by raising the scapula. The trapezius is a broad 
 flat muscle arising from the occipital protuberance, part of 
 the superior curved line of the occipital bone, the ligamentum 
 
 1 Op. tit., p. 521. 
 
 2 Under these circumstances, some muscles which we have not thought it ne- 
 cessary to enumerate may act indirectly as muscles of inspiration. 
 
380 RESPIRATION. 
 
 michae, and the spinous processes of the last cervical and all 
 the dorsal vertebrae, to be inserted into the upper border of 
 the spine of the scapula. Acting from its attachments to the 
 occiput, the ligamentum nuchse, the last cervical vertebra, 
 and perhaps one or two of the. dorsal vertebrae, this muscle 
 may elevate the scapula and assist in inspiration. 
 
 Pectoralls Minor and Inferior Portion of the Pectoralis 
 Major. These muscles act together to raise the ribs in diffi- 
 cult respiration. The pectoralis minor is the more efficient. 
 Tracing it from its attachment to the coracoid process of the 
 scapula, its fibres pass downwards and forwards to be attached 
 by three indigitations to the external surface and upper mar- 
 gins of the third, fourth, and fifth ribs, just posterior to the 
 cartilages. With the coracoid process as the fixed point, this 
 muscle is capable of powerfully assisting in the elevation of 
 the ribs. That portion of the pectoralis major which is at- 
 tached to the lower part of the sternum and costal cartilages 
 is capable of acting from its insertion into the bicipital 
 groove of the humerus, when the shoulders are fixed, in con- 
 cert with the pectoralis minor. In great dyspnoea, it is fre- 
 quently observed that the shoulders are braced, the pectorals 
 acting most vigorously to raise the walls of the chest. 
 
 Serratus Magnus. This is a broad thin muscle covering a 
 great portion of the lateral walls of the thorax. Attached to the 
 inner margin of the posterior border of the scapula, its fibres 
 pass forwards and downwards, and are attached to the exter- 
 nal surface and upper borders of the eight superior ribs. 
 Acting from the scapula, this muscle is capable of assisting 
 the pectorals in raising the ribs, and becomes a powerful aux- 
 iliary in difficult inspiration. 
 
 We have thus considered the functions of the principal 
 inspiratory muscles, without taking up those which have an 
 insignificant or undetermined action. In many animals the 
 nares are considerably distended in inspiration; and in the 
 
AUXILIARY MUSCLES OF INSPIRATION. 381 
 
 horse, winch does not respire by the mouth, these movements 
 are as essential to life as are the respiratory movements of the 
 larynx. In man, as a rule, the nares undergo no movement 
 unless respiration be somewhat exaggerated. In very diffi- 
 cult respiration the mouth is opened at each inspiratory act. 
 "We have not thought it necessary to treat of the action of 
 those muscles which serve to fix the head, neck, or shoulders 
 in dyspnoea. 
 
 The division into muscles of ordinary inspiration, ordi- 
 nary auxiliaries, and extraordinary auxiliaries, must not be 
 taken as absolute. In the male, in ordinary respiration, the 
 diaphragm, intercostals, and levatores costarum are the great 
 inspiratory muscles, and the action of the scaleni, with the 
 consequent elevation of the sternum, is commonly very slight, 
 or perhaps wanting. In the female, the movements of the 
 upper parts of the chest are very marked, and the scaleni, the 
 serratus posticus superior, and sometimes the sterno-mastoid, 
 are brought into action in ordinary respiration. In the vari- 
 ous types of respiration, the action of the muscles engaged in 
 ordinary respiration necessarily presents considerable varia- 
 tions. 
 
CHAPTER XI. 
 
 MOVEMENTS OF EXPIRATION. 
 
 Influence of the elasticity of the pulmonary structure and walls of the chest- 
 Muscles of expiration Internal intercostals Infra-costales Triangularis ster- 
 ni Action of the abdominal muscles in expiration Types of respiration 
 Abdominal type Inferior costal type Superior costal type Frequency of the 
 respiratory movements Relations of inspiration and expiration to each other 
 The respiratory sounds Coughing Sneezing Sighing Yawning Laugh- 
 ing Sobbing Hiccough Capacity of the lungs and the quantity of air 
 changed in the respiratory acts Residual air Reserve air Tidal, or breathing 
 air Complemental air Extreme breathing capacity Relations in volume of 
 the expired to the inspired air Diffusion of air in the lungs. 
 
 THE air is expelled from the lungs, in ordinary expiration, 
 by a simple and comparatively passive process. The lungs 
 contain a great number of elastic fibres surrounding the air- 
 cells and the smallest ramifications of the bronchial tubes, 
 which give them great elasticity. "We can form an idea of 
 the extent of elasticity of these organs, by simply removing 
 them from the chest, when they collapse and become many 
 times smaller than the cavity which they before completely 
 filled. The thoracic walls are also very elastic, particularly 
 in young persons. After the muscles which increase the 
 capacity of the thorax cease their action, the elasticity of the 
 costal cartilages and the tonicity of muscles which have been 
 put on the stretch, will restore the chest to what we may call 
 its passive dimensions. This elasticity is likewise capable of 
 acting as an inspiratory force when the chest has been com- 
 
EXPIRATION. 383 
 
 pressed in any way. There are also certain muscles, the 
 action of which is to draw the ribs downward, and which, in 
 tranquil respiration, are antagonistic to those which elevate 
 the ribs. Aside from this, many operations, such as speak- 
 ing, blowing, singing, etc., require powerful, prolonged, or 
 complicated acts of expiration, in which numerous muscles 
 are brought into play. 
 
 Expiration may be considered as depending upon two 
 causes : 
 
 1. The passive influence of the elasticity of the lungs and 
 the thoracic walls. 
 
 2. The action of certain muscles, which either diminish 
 the transverse and antero-posterior diameters of the chest by 
 depressing the ribs and sternum, or the vertical diameter by 
 pressing up the abdominal viscera behind the diaphragm. 
 
 Influence of the Elasticity of the Pulmonary Structure 
 and Walls of the Chest. It is easy to understand the in- 
 fluence of the elasticity of the pulmonary structure in expi- 
 ration. From the collapse of the lungs when openings are 
 made in the chest, it is seen that even after the most complete 
 expiration, these organs have a tendency to expel part of their 
 gaseous contents, which cannot be fully satisfied until the 
 chest is opened. They remain partially distended, from the 
 impossibility of collapse of the thoracic walls beyond a certain 
 point ; and by virtue of their elasticity, they exert a suction 
 force upon the floor of the thorax, the diaphragm, causing it 
 to form a vaulted arch or dome above the level of the lower 
 circumference of the chest. When the lungs are collapsed, 
 the diaphragm hangs loosely between the abdominal and 
 thoracic cavities. In inspiration and in expiration, then, the 
 relations between the lungs and diaphragm are reversed. In 
 inspiration, the descending diaphragm exerts a suction force 
 on the lungs, drawing them down ; in expiration, the elastic 
 lungs exert a suction force upon the diaphragm drawing it 
 up. This antagonism is one of the causes of the great power 
 
384 RESPIRATION. 
 
 of the diaphragm as an inspiratoiy muscle. Carson, in 1820, 1 
 was the first to note the relation of the elasticity of the lungs 
 to the expulsion of air. Introducing a IT tube partly filled 
 with water into the trachea of an animal just killed, and 
 securing it by a ligature, this ^bserver noted a considerable 
 pressure on opening the chest ; equal in the calf, sheep, or 
 dog to a column of water of from 12 to 18 inches, and in the 
 cat or rabbit, from 6 to 10 inches. 2 
 
 The elasticity of the lungs operates chiefly upon the dia- 
 phragm in reducing the capacity of the chest ; for the walls 
 of the thorax, by virtue of their own elasticity, have a reac- 
 tion which succeeds the movements produced by the inspi- 
 ratory muscles. A simple experiment, which we have often 
 performed in public demonstrations, illustrates the chief ex- 
 piratory influence of the elasticity of the lungs. If, in an 
 animal just killed, we open the abdomen, seize hold of the 
 vena cava as it passes through the diaphragm, and make 
 traction, we imitate the action of this muscle sufficiently to 
 produce at times an audible inspiration ; on loosing our hold, 
 we have expiration, as it is in a measure accomplished in 
 natural respiration, by virtue of the resiliency of the lungs, 
 carrying the diaphragm up into the thorax. 
 
 Though this is the main action of the lungs themselves 
 in expiration, their relations to the walls of the thorax are 
 important. By virtue of their elasticity, they assist the pas- 
 sive collapse of the chest. When they lose this property to 
 any considerable extent, as in vesicular emphysema, they 
 offer a notable resistance to the contraction of the thorax ; so 
 much, indeed, that in old cases of this disease the movements 
 are much restricted, and the chest presents a characteristic 
 
 1 Philosophical Transactions, 1820. 
 
 2 If, after noting the elevation in the liquid due to the elasticity of the lungs, 
 these organs be stimulated by means of a current of galvanism, the liquid will 
 gradually rise, in obedience to the contractions of the muscular elements of the 
 bronchial tubes. This slow contraction, characteristic of the non-striated muscu- 
 lar fibres, does not intervene in the physiological phenomena of expiration, but 
 the action of these fibres is important in certain cases of disease. 
 
EXPIRATION. 385 
 
 rounded and distended appearance. In some of these cases 
 the elasticity of the lungs is so far lost, that when the chest 
 is opened after death, they are actually protruded, instead of 
 collapsed. 1 
 
 Little more need be said concerning the passive move- 
 ments of the thoracic walls. When the action of the inspi- 
 ratory muscles ceases, the ribs regain their oblique direction, 
 the intercostal spaces are narrowed, and the sternum, if it 
 have been elevated and drawn forward, falls back to its place 
 by the simple elasticity of the parts. 
 
 Action of Muscles in Expiration. The following are the 
 principal muscles concerned in expiration : 
 
 Muscles of Expiration. 
 
 ORDINAEY RESPIRATION. 
 
 Muscle. Attachments. 
 
 Osseous portion of Internal Intercostals. .Inner borders of the ribs. 
 
 Infra-costales Inner surfaces of the ribs. 
 
 Triangularis Sterni Ensiform cartilage, lower borders of 
 
 sternum, lower three or four costal 
 
 cartilages cartilages of the second, 
 
 third, fourth, and fifth ribs. 
 
 1 In old cases of emphysema, the chest generally becomes rounded and dis- 
 tended, presenting constantly the appearance which it has in forced inspiration. 
 This is explained in the following way : Emphysema is generally preceded and 
 accompanied by a difficulty in respiration, from some cause which is more or less 
 constant. This gives rise to frequent violent movements of inspiration, when the 
 lungs and chest are distended to their utmost capacity. In this condition, expi- 
 ration is difficult, and the chest collapses but imperfectly. Gradually, as the per- 
 manent dilatation of the air-cells gains ground, the lungs lose their elasticity, and 
 offer considerable resistance to the collapse of the thoracic walls. But difficult 
 breathing, and consequent violent elevation of the ribs, becomes more and more 
 frequent; the chest is constantly dilated, the lungs following, of course, but refus- 
 ing to collapse in expiration, until the chest becomes permanently distended. In 
 this condition, the lungs press downward, as well as laterally, and the movements 
 of the diaphragm are considerably restricted. 
 25 
 
386 RESPIRATION. 
 
 Auxiliaries. 
 
 Attachments. 
 
 Obliquus Externus External surface and inferior borders of 
 
 eight inferior ribs the anterior 
 
 Half of the crest of the ileum, Pou- 
 part's ligament, linea alba. 
 
 Obliquus Internus Outer half of Poupart's ligament, ante- 
 rior two-thirds of the crest of the 
 
 ileum, lumbar fascia cartilages of 
 
 four inferior ribs, lineal alba, crest of 
 the pubis, pectineal line. 
 
 Transversalis Outer third of Poupart's ligament, ante- 
 rior two-thirds of the crest of the 
 ileum, lumbar vertebrae, inner sur- 
 face of cartilages of six inferior ribs 
 
 crest of the pubis, pectineal line, 
 
 linea alba. 
 
 Sacro-lumbalis Sacrum angles of the six inferior 
 
 ribs. 
 
 Internal Intercostals. The internal intercostals have dif- 
 ferent functions in different parts of the thorax. They are 
 attached to the inner borders of the ribs and costal cartilages. 
 Between the ribs they are covered by the external intercos- 
 tals, but .between the costal cartilages are simply covered 
 by aponeurosis. Their direction is from above downwards 
 and backwards, at right angles to the external intercostals. 
 The function of that portion of the internal intercostals situ- 
 ated between the costal cartilages has already been noted. 
 They assist the external intercostals in elevating the ribs in 
 inspiration. Between the ribs these muscles are directly an- 
 tagonistic to the external intercostals. They are more nearly 
 at right angles to the ribs, particularly in that portion of the 
 thorax where the obliquity of the ribs is greatest. The ob- 
 servations of Sibson have shown that they are elongated 
 when the chest is distended, and shortened when the chest is 
 collapsed. This fact, taken in connection with experiments 
 on living animals, shows that they are muscles of expiration. 
 Their contraction tends to depress the ribs, and consequentlv 
 
INFKA-COSTALES TRIANGULAKIS STEENI. 387 
 
 to diminisli the capacity of the chest. If we bring an ani- 
 mal, a dog for example, completely under the influence of 
 ether, expose the walls of the chest, dissect off the fascia from 
 some of the external intercostals, then remove carefully a 
 portion of one or two of these muscles so as to expose the 
 fibres of the -internal intercostals, it is not difficult, on close 
 examination, to observe the antagonism between the two sets 
 of muscles ; one being brought into action in inspiration and 
 the other in expiration. 
 
 Infra-costales. These muscles, situated at the posterior 
 part of the thorax, are variable in size and number. They 
 are most common at the lower part of the chest. Their 
 fibres arise from the inner surface of one rib to be inserted 
 into the inner surface of the first, second, or third rib below. 
 The fibres follow the direction of the internal intercostals, 
 and acting from their lower attachments, their contractions 
 assist these muscles in drawing down the ribs. 
 
 Triangularis Sterni. There has never been any doubt 
 concerning the expiratory function of the triangularis sterni. 
 From its origin, the ensiform cartilage, lower borders of the 
 sternum, and lower three or four costal cartilages, it acts 
 upon the cartilages of the second, third, fourth, and fifth ribs, 
 to which it is attached, drawing them downwards, and thus 
 diminishing the capacity of the chest. 
 
 The above-mentioned muscles are called into action in 
 ordinary tranquil respiration, and their sole function is to 
 diminish the capacity of the chest. In labored or difficult 
 expiration, and in the acts of blowing, phonation, etc., other 
 muscles, which are called auxiliaries, play a more or less 
 important part. These muscles all enter into the formation 
 of the walls of the abdomen, and their general action in 
 expiration is to press the abdominal viscera and diaphragm 
 into the thorax, and diminish its vertical diameter. Their 
 action is voluntary ; and by an effort of the will it may be 
 
388 RESPIKATION. 
 
 opposed more or less by the diaphragm, by which means the 
 duration or intensity of the expiratory act is regulated. 
 They are also attached to the ribs or costal cartilages, and 
 while they press up the diaphragm, depress the ribs, and 
 thus diminish the antero-postemr and transverse diameters 
 of the chest. In this action they may be opposed by the 
 voluntary action of the muscles which raise the ribs, also 
 for the purpose of regulating the character of the expiratory 
 act. The importance of this kind of action in declamation, 
 singing, blowing, etc., is evident; and the skill exhibited by 
 vocalists and performers on wind instruments shows how 
 delicately this may be regulated by practice. 
 
 In labored respiration in disease, and in the hurried 
 respiration after violent exercise, the auxiliary muscles of ex- 
 piration, as well as of inspiration, are called into action to a 
 considerable extent. 
 
 Obliquus Externus. This muscle, in connection with the 
 obliquus internus and transversalis, is efficient in forced or 
 labored expiration, by pressing the abdominal viscera 
 against the diaphragm. Its fibres run obliquely from above 
 downwards and forwards. Acting from its attachments to 
 the linea alba, crest of the ileum, and Poupart's ligament, by 
 its attachment to the eight inferior ribs, it draws the ribs 
 downwards. 
 
 ObliquiCs Internus. This muscle also acts in forced expi- 
 ration by compressing the abdominal viscera. The direction 
 of its fibres is from below upwards and forwards. Acting 
 from its attachments to the crest of the ileum, Poupart's lig- 
 ament, and the lumbar fascia, by its attachments to the carti- 
 lages of the four inferior ribs, it draws them downwards. 
 The direction of the fibres of this muscle is the same as that 
 of the internal intercostals. By its action the ribs are drawn 
 inwards as well as downwards. 
 
 Transversalis. The expiratory action of this muscle is 
 mainly in compressing the abdominal viscera. 
 
TYPES OF RESPIRATION. 389 
 
 Sacro-lwnbalis. This muscle is situated at the posterior 
 portion of the abdomen and thorax. Its fibres pass from its 
 origin at the sacrum, upwards and a little outwards, to be 
 inserted into the six inferior ribs at their angles. In expira- 
 tion it draws the ribs downwards, acting as an antagonist to 
 the lower levatores costarum. 
 
 There are some other muscles which may be brought into 
 action in forced expiration, assisting in the depression of the 
 ribs ; such as the serratus posticus inferior, the superior fibres 
 of the serratus magnus, the inferior portion of the trapezius ; 
 but their function is unimportant. 1 
 
 Types of Respiration. In the expansive movements of 
 the chest, though all the muscles which have been classed as 
 ordinary inspiratory muscles are brought into action to a 
 greater or less extent, the fact that certain sets may act in a 
 more marked manner than others has led physiologists to 
 recognize different types of respiration. Following Beau 
 and Maissiat, three types are generally given in works on 
 physiology : 2 
 
 1. The Abdominal type. In this, the action of the dia- 
 phragm, and the consequent movements of the abdomen, are 
 most prominent. 
 
 2. The' Inferior Costal type. In this, the action of the 
 muscles which expand the lower part of the thorax, from 
 the seventh rib inclusive, is most prominent. 
 
 3. The Superior Costal type. In this, the action of the 
 muscles which dilate the thorax above the seventh rib, and 
 which elevate the entire chest, is most prominent. 
 
 1 It is uncertain whether the straight muscles of the abdomen are ever con- 
 cerned hi expiration. From their situation, it might be supposed that they would 
 have some action in the more violent phenomena of expiration, such as sneezing, 
 toughing, crying, etc. ; but Beau and Maissiat, who have investigated these ques- 
 tions very carefully, state that in dogs they have never seen these muscles act, 
 even in the most violent efforts. (Archives Generates^ 4th series, vol. iii.) 
 
 8 Loc. cit. 
 
390 RESPIRATION. 
 
 The abdominal type is most marked in children under 
 the age of three years, irrespective of sex. In them, respira- 
 tion is carried on almost exclusively by the diaphragm. 
 
 At a variable period after birth, a difference in the types 
 of respiration in the sexes begins to show itself. In the male 
 the abdominal, conjoined with th inferior costal type, is pre- 
 dominant, and continues thus through life. In the female the 
 inferior costal type is insignificant, and the superior costal 
 type predominates. Observers differ in their statements of 
 the period when this distinction in the sexes becomes appa- 
 rent. Haller states that he observed a difference in children 
 less than a year old. Beau and Maissiat state that after the 
 age of three years the superior costal type begins to be marked 
 in the female. Sibson states that no great difference is ob- 
 servable before the age of ten or twelve years. 1 Without 
 discussing the nice question as to the exact age when this 
 difference in the sexes first makes its appearance, it may be 
 stated in general terms, that shortly before the age of pu- 
 berty, in the female, the superior costal type becomes more 
 marked, and soon predominates ; while in the male, respira- 
 tion continues to be carried on mainly by the diaphragm and 
 lower part of the chest. 
 
 The cause of the excessive movements of the upper part 
 of the chest in the female has been the subject of considerable 
 discussion. It is evident that it is not due to the mode of 
 dress now so general in civilized countries, which confines the 
 lower part of the chest, and would render movements of ex- 
 pansion somewhat difficult, for the same phenomenon is ob- 
 served in young girls, and others who have never made use 
 of such appliances. But there is evidently a physiological 
 condition, the enlargement of the uterus in gestation, which 
 at certain times would nearly arrest all respiratory move- 
 ments, excepting those of the upper part of the chest. The 
 peculiar mode of respiration in the female is a provision of 
 Nature against the mechanical difficulties which would other- 
 
 1 LONGET, Traite de Physiologie, Paris, 1861, tome i., p. 617- 
 
FREQUENCY OF RESPIRATORY MOVEMENTS. 391 
 
 wise follow the physiological enlargement of the uterus. In 
 pathology it is observed that, in consequence of this peculiar- 
 ity, females are able to carry, without great inconvenience, 
 immense quantities of water in the abdominal cavity ; while 
 a much smaller quantity, in the male, produces great distress 
 from difficulty of breathing. 1 
 
 Frequency of the Respiratory Movements. In counting 
 the respiratory acts, it is desirable that the subject be uncon- 
 scious of the observation, otherwise their normal character is 
 apt to be disturbed. Of all who have written on this sub- 
 ject, Hutchinson presents the most numerous and convincing 
 collection of facts. This observer ascertained the number of 
 respiratory acts per minute, in the sitting posture, in 1,897 
 males. The results of his observations, with reference to fre- 
 quency, are given in the following table : a 
 
 Bespirations per minute. Number of cases. 
 From 9 to 16 79 
 
 16 239 
 
 17 105 
 
 18 195 
 
 19 74 
 
 20 561 
 
 21 129 
 
 22 143 
 
 23 42 
 
 24 243 
 
 24 to 40 87 
 
 Though this table shows considerable variation in differ- 
 ent individuals, the great majority (1,Y31) breathed from six- 
 teen to twenty-four times per minute. Nearly a third 
 breathed twenty times per minute, a number which may be 
 taken as the average. 
 
 1 Modifications of the types of respiration by disease are frequently very 
 marked. In peritonitis, when movements of the diaphragm would be productive 
 of excessive pain, the abdominal type may be wholly suppressed. In the early 
 stages of acute pleurisy, the affected side may become nearly or quite motionless. 
 
 a Cyclopaedia of Anatomy and Physiology, vol. iv., part ii., p. 1085. 
 
392 RESPIRATION. 
 
 The relations of the respiratory acts to the pulse are quite 
 constant in health. It has been shown by Hutchinson that 
 the proportion in the great majority of instances is one re- 
 spiratory act to every four pulsations of the heart. The same 
 proportion generally obtains when the pulse is accelerated in 
 disease, except when the pulmonary organs are involved. 
 
 Age has an influence on the frequency of the respiratory 
 acts, corresponding with what we have already noted with 
 regard to the pulsations of the heart. 
 
 Quetelet gives the following as the results of observations 
 on 300 males : 
 
 44 respirations per minute soon after birth ; 
 
 26, at the age of five years ; 
 
 20, at the age of fifteen to twenty years ; 
 
 19, at the age of twenty to twenty-five years ; 
 
 16, about the thirtieth year ; 
 
 18, from thirty to fifty years. 
 
 The influence of sex is not marked in very young chil- 
 dren. The same observer noted no difference between males 
 and females at birth ; but in young women the respirations 
 are a little less frequent than in young men of the same 
 
 The various physiological conditions which have been 
 noted as affecting the pulse have a corresponding influence 
 on respiration. In sleep the number of respiratory acts is 
 diminished about twenty per cent (Quetelet). Muscular ef- 
 fort accelerates the respiration pari passu with the move- 
 ments of the heart. 
 
 Relations of Inspiration and Expiration to each other. 
 The Respiratory Sounds. In ordinary respiration, inspira- 
 tion is produced by the action of muscles, and expiration, in 
 greatest part, by the passive reaction of the elastic walls of 
 the thorax and the lungs. The inspiratory and expiratory 
 acts do not immediately follow each other. Commencing 
 
 1 MILNE-EDWARDS, Lemons de Physiologic, tome ii., pp. 482, 483. 
 
RELATIONS OF INSPIRATION AND EXPIRATION. 393 
 
 with inspiration, it is found that this act maintains about the 
 same intensity from its commencement to its termination; 
 there is then a very brief interval, when expiration follows, 
 which has its maximum of intensity at the commencement 
 of the act, and gradually dies away. 1 Between the acts of ex- 
 piration and inspiration is an interval, somewhat longer than 
 that which occurs after inspiration. 
 
 The duration of expiration is generally somewhat greater 
 than that of inspiration, though they may be nearly, or in 
 some instances quite, equal. 
 
 After from five to eight ordinary respiratory acts, one 
 generally occurs which is rather more profound than the rest, 
 and by which the air in the lungs is more effectually changed. 
 The temporary arrest of the acts of respiration in all violent 
 muscular efforts, in straining, in parturition, etc., is familiar 
 to all. 
 
 Ordinarily respiration is not accompanied by any sound 
 which can be heard without applying the ear directly, or by 
 the intervention of a stethoscope, to the respiratory organs ; 
 excepting when the mouth is closed, and breathing is carried 
 on exclusively through the nasal passages, when a soft, 
 breezy murmur accompanies both acts. If the mouth be 
 sufficiently opened to admit the free passage of air, no sound 
 is to be heard in health. In sleep, the respirations are un- 
 usually profound ; and if the mouth be closed, the sound is 
 rather more intense than usual. 
 
 Snoring, a peculiar sound, more or less marked, which 
 sometimes accompanies the respiratory acts during sleep, oc- 
 curs when the air passes through both the mouth and the 
 nose. It is more marked in inspiration, sometimes accom- 
 panying both acts, and sometimes not heard in expiration. 
 It is not necessary to describe the characters of a sound so 
 
 1 la listening to the respiratory murmur over the substance of the lungs, the 
 expiratory follows the inspiratory sound without an interval (see p. 395). The 
 interval between the acts of inspiration and expiration is only appreciated as the 
 air passes in and out at the mouth. 
 
394: EESPIEATION. 
 
 familiar. Snoring is an idiosyncrasy with many individuals, 
 though those who do not snore habitually may do so when 
 the system is unusually exhausted and relaxed. It only oc- 
 curs when the mouth is open, and the sound is produced by 
 a vibration, and sort of flapping, of the velum pendulum pa- 
 lati between the two currents of air from the mouth and 
 nose, together with a vibration in the column of air itself. 
 
 The auscultatory phenomena which accompany the act of 
 respiration have been made the subject of special experimen- 
 tal observations by Dr. Flint, who, from carefully recorded 
 examinations of a large number of healthy persons, has ar- 
 rived at the following conclusions : 1 
 
 Applying the stethoscope over the larynx or trachea, a 
 sound is heard, of a distinctly and purely tubular character, 
 accompanying both acts of respiration. In inspiration, " it 
 attains its maximum of intensity quickly after the develop- 
 ment of the sound, and maintains the same intensity to the 
 close of the act, when the sound abruptly ends, as if sudden- 
 ly cut off." After a brief interval, the sound of expiration 
 follows. This is also tubular in quality ; it soon attains its 
 maximum of intensity, but, unlike the sound of inspiration, 
 gradually dies away and is lost imperceptibly. It is seen 
 that these phenomena correspond with the nature of the two 
 acts of respiration. 
 
 Sounds approximating in character to the foregoing are 
 heard over the bronchial tubes before they penetrate the 
 lungs. 
 
 Over the substance of the lungs, a sound may be heard 
 entirely different in its character from that heard over the 
 larynx, trachea, or bronchial tubes. In inspiration, the sound 
 is much less intense than over the trachea, and has a breezy, 
 expansive, or what is called in auscultation a vesicular char- 
 acter. It is much lower in pitch than the tracheal sound. It 
 
 1 FLINT, Physical Exploration and Diagnosis of Diseases affecting the Respi- 
 ratory Organs, Philadelphia, 1856, p. 137 et seq. We give but a brief summary 
 of these results, which are specially applied to auscultation iu disease. 
 
COUGHING, SNEEZING, ETC. 395 
 
 is continuous, and rather increases in intensity from its com- 
 mencement to its termination; ending abruptly, like the 
 tracheal inspiratory sound. The sound is produced in part 
 by the movement of air in the small bronchial tubes, but 
 chiefly by the expansion of the innumerable air-cells of the 
 lungs. It is followed, without an interval, by the sound of 
 expiration, which is shorter, one-fifth to one-fourth as long, 
 lower in pitch, and very much less intense. A sound is not 
 always heard in expiration. In fifteen examinations record- 
 ed by Dr. Flint, five presented no expiratory sound. 
 
 The variations in the intensity of the respiratory sounds 
 in different individuals are very considerable. As a rule 
 they are more intense in young persons; which has given 
 rise to the term puerile respiration, when the sounds are 
 exaggerated in parts of the lung, in certain cases of disease. 
 The sounds are generally more intense in females than in 
 males, particularly in the upper regions of the thorax. 
 
 It is difficult by any description or comparison to convey 
 an accurate idea of the character of the sounds heard over 
 the lungs and air-passages ; and it is superfluous to make the 
 attempt, when they can be so easily studied in the living 
 subject. 
 
 Coughing^ /Sneezing, Sighing, Yawning, Laughing, Sobbing, 
 and Hiccough. 
 
 These peculiar acts demand a few words of explanation. 
 
 Coughing and sneezing are generally involuntary acts, 
 produced by irritation in the air-tubes or nasal passages ; 
 though cough is often voluntary. In both of these acts there 
 is first a deep inspiration, followed by convulsive action of 
 the expiratory muscles, by which the air is violently expelled 
 with a characteristic sound, in the one case by the mouth, 
 and in the other by the mouth and nares. Foreign bodies 
 lodged in the air-passages are frequently expelled in violent 
 fits of coughing. In hypersecretion of the bronchial mucous 
 
396 RESPIRATION. 
 
 membrane, the accumulated mucus is carried by the act 
 of coughing either to the mouth, or well into the larynx, 
 whence it is expelled by the act of expectoration. When 
 either of these acts is the result of irritation, either from a 
 foreign substance or secretions, it may be modified or partly 
 smothered by the will, but is not completely under control. 
 The exquisite sensibility of the mucous membrane at 
 the summit of the air-passages, under most circumstances, 
 protects them from the entrance of foreign matter, both 
 liquid and solid ; for the slightest impression received by the 
 membrane gives rise to a violent and involuntary cough, by 
 which the offending matter is removed. The glottis is also 
 spasmodically closed. 
 
 In sighing, a prolonged and deep inspiration is followed 
 by a rapid and generally audible expiration. This occurs, as 
 a general rule, once in every five to eight respiratory acts, 
 for the purpose of changing the air in the lungs more com- 
 pletely, and is due to an exaggeration of the cause which 
 gives rise to the ordinary acts of respiration. "When due 
 to depressing emotions, it has the same cause ; for at such 
 times, respiration is less effectually performed. Yawning 
 is an analogous process, but differs from sighing in the 
 fact that it is involuntary, and cannot be produced by an 
 effort of the will. It is characterized by a wide opening of 
 the mouth, and a very profound inspiration. Yawning is 
 generally assumed to be an evidence of fatigue, but it often 
 occurs from a sort of contagion. When not the result of 
 imitation, it has the same exciting cause as sighing, viz., defi- 
 cient oxygenation of the blood, and is followed by a sense of 
 satisfaction, which shows that it meets some decided want on 
 the part of the system. 
 
 Laughing and sobbing, though expressing opposite condi- 
 tions, are produced by very much the same mechanism. 
 The characteristic sounds accompanying these acts are the 
 result of short, rapid, and convulsive movements of the dia- 
 phragm, accompanied by contractions of the muscles of the 
 
CAPACITY OF THE LUNGS. 397 
 
 face, which produce the expressions characteristic of hilarity 
 or grief. Though to a certain extent under the control of 
 the will, they are mostly involuntary. Yiolent and convul- 
 sive laughter may be excited in many individuals by titilla- 
 tion of certain portions of the surface of the body. Laugh- 
 ter and sometimes sobbing, like yawning, may be the result 
 of involuntary imitation. 
 
 Hiccough is a peculiar modification of the act of inspira- 
 tion, to which it is exclusively confined. It is produced by 
 a sudden, convulsive, and entirely involuntary contraction of 
 the diaphragm, accompanied by a spasmodic constriction of 
 the glottis. The contraction of the diaphragm is more exten- 
 sive than in laughing and sobbing, and occurs only once in 
 four or five respiratory acts. The causes which give rise to 
 hiccough are numerous, and many of them are referable to 
 the digestive system. Among these may be mentioned the 
 rapid ingestion of a quantity of dry food, or of effervescing or 
 alcoholic drinks. It occurs frequently in cases of disease. 
 
 Capacity of the Lungs, and the Quantity of Air changed in 
 the Respiratory Acts. 
 
 Several points of considerable physiological interest arise 
 in this connection. It is evident from the simple experiment 
 of opening the chest, when the elastic lungs collapse and ex- 
 pel a certain quantity of air which cannot be removed while 
 the lungs are in situ, that a part of the gaseous contents of 
 these organs necessarily remains after the most complete and 
 forcible expiration. After an ordinary expiration, there is a 
 certain quantity of air in the lungs which can be expelled by 
 a forced expiration. In ordinary respiration, a comparatively 
 small volume of air is introduced with inspiration, which is 
 expelled by the succeeding expiration. 1 By the extreme action 
 
 1 Experiments have shown that a certain volume of air is lost in the lungs, 
 the expired air being a little less in volume than the quantity inspired (from Vu 
 to o 1 ^). This is not taken into account in this connection. 
 
RESPIRATION. 
 
 of all the inspiratory muscles in a forced inspiration, a sup- 
 plemental quantity of air may be introduced into the lungs, 
 which then contain much more than they ever do in ordi- 
 nary respiration. For convenience, many physiologists have 
 adopted the following names, which are applied to these 
 various volumes of air : 
 
 1. Residual Air / that which is not, and cannot be, ex- 
 pelled by a forced expiration. 
 
 2. Reserve Air ; that which remains after an ordinary 
 expiration, deducting the residual air. 
 
 3. Tidal, or ordinary Breathing Air / that which is 
 changed by the ordinary acts of inspiration and expiration. 
 
 4. Complemented Air / the excess over the ordinary 
 breathing air, which may be introduced by a forcible inspi- 
 ration. 
 
 The questions relating to the above divisions of the re- 
 spired air have been made the subject of numerous investiga- 
 tions ; but though at first it might seem, easy to determine all 
 of them by a sufficient number of experiments, the necessary 
 observations are attended with considerable difficulty, and the 
 sources of error are numerous. In measuring the air changed 
 in ordinary breathing, it has been found that the acts of res- 
 piration are so easily influenced by the mind, and it is so 
 difficult to experiment on any individual without his knowl- 
 edge, that the results of many good observers are not to be 
 relied upon. This is one of the most important of the ques- 
 tions under consideration. The difficulties in the way of 
 estimating with accuracy the residual, reserve, or comple- 
 mental volumes, will readily suggest themselves. The ob- 
 servations on these points, which may be taken as the most 
 definite and exact, are those of Herbst of Gottingen, and 
 Hutchinson of England. 1 Those of the last-named observer 
 
 1 A summary of the observations of Herbst, made in 1828, is to be found in the 
 Archives Generates de Medecine, tome xxi., p. 412. The observations of Hutch- 
 
RESERVE AIR. 399 
 
 are exceedingly elaborate, and were made on an immense 
 number of subjects of both sexes, and of all ages and occupa- 
 tions. They are generally accepted by physiologists as the 
 most extended and accurate. 
 
 Residual Air. Perhaps there is not one of the questions 
 under consideration more difficult to answer definitely than 
 that of the quantity of air which remains in the lungs after a 
 forced expiration ; but fortunately it is not one of any great 
 practical importance. The residual air remains in the lungs 
 as a physical necessity. The lungs are always, in health, in 
 contact with the walls of the thorax ; and when this cavity 
 is reduced to its smallest dimensions, it is impossible that 
 any more air should be expelled. The volume which thus 
 remains has been variously estimated at from 40 cubic inches 
 (Fontana) to 220 cubic inches (Jurin). Dr. Hutchinson, who 
 has carefully considered this point, estimates the residual 
 volume at about 100 cubic inches, but states that it varies 
 very considerably in different individuals. Taking every 
 thing into consideration, we may assume this estimate to be 
 as nearly correct as any. It is certain that the lungs of a 
 man of ordinary size, at their minimum of distention, contain 
 more than 40 cubic inches of air ; and from measurements 
 of the capacity of the thorax, deducting the estimated space 
 occupied by the heart and vessels and the parenchyma of 
 the lungs, it is shown that the residual air cannot amount to 
 any thing like 200 cubic inches. 1 
 
 There is no special division of the function of res- 
 piration connected with the residual air. It remains in 
 the lungs merely as a physical necessity, and its volume 
 must not be taken into account in considering the volumes 
 
 inson are contained in extemo in the Cyclopcedia of Anatomy and Physiology, vol. 
 iv., part 1, article Thorax. 
 
 1 Hutchinson found the mean absolute capacity of the thorax to be 312 cubic 
 inches. He allows 100 cubic inches for the heart and blood-vessels, and 100 for 
 the parenchyma of the lungs, leaving about 100 for the residual volume Op. cit., 
 p. 1067. 
 
400 RESPIRATION. 
 
 which are changed in any of the operations connected with 
 breathing. 
 
 Air. This name is appropriately given to the 
 volume of air which may be expelled and changed by a vol- 
 untary effort, but which remains in the lungs, added to the 
 residual air, after an ordinary act of expiration. It may be 
 estimated, without any reference to the residual air, by for- 
 cibly expelling air from the lungs, after an ordinary expira- 
 tion. The average volume is 100 cubic inches. 1 
 
 The reserve air is changed whenever we experience a 
 necessity for a more complete renovation of the contents of 
 the lungs than ordinary. It is encroached upon in the unu- 
 sually profound inspiration and expiration which occur every 
 five or six acts. It is used in certain prolonged vocal efforts, 
 in blowing, etc. 
 
 Added to the residual air, it constitutes the minimum 
 capacity of the lungs in ordinary respiration. As it is con- 
 tinually receiving watery vapor and carbonic acid, it is always 
 more or less vitiated ; and when reen forced by the breathing 
 air, which enters with inspiration, is continually in circulation, 
 in obedience to the law of the diffusion of gases. Those who 
 are in the habit of arresting respiration for a time, as the 
 pearl-diver, learn to change the reserve air as completely as 
 possible by several forcible acts, and then fill the lungs with 
 fresh air. In this way they are enabled to suspend the re- 
 spiratory acts for from one to two minutes without inconven- 
 ience. The introduction of the fresh air with each inspira- 
 tion, and the constant diffusion which is going on, and by 
 which the proper quantity of oxygen finds its way to the air- 
 cells, gives, in ordinary breathing, a composition to the air 
 in the deepest portions of the lungs which insures a constant 
 aeration of the blood. The slight difference in the rapidity 
 of oxidation between inspiration and expiration is only suffi- 
 cient to give rise to the involuntary reflex acts of respiration, 
 
 1 HUTCHINSON, IOC. df. 
 
COMPLEMENTAL AIR. 401 
 
 and is not sufficiently marked to produce any sensation, such 
 as is experienced when respiration is in the slightest degree 
 interrupted. 
 
 Tidal, or Ordinary Breathing Air. The volume of 
 air which is changed in the ordinary acts of respiration is 
 subject to immense physiological variations, and the respira- 
 tory movements, as regards intensity, are so easily influenced 
 by the mind, that great care is necessary to avoid error in 
 estimating the volume of ordinary breathing air. The esti- 
 mates of Herbst and of Hutchinson are the results of very 
 extended observations made with great care, and are gener- 
 ally acknowledged to be as nearly accurate as possible. As 
 a mean of these observations, it has been found that the 
 average volume of breathing air, in a man of ordinary stat- 
 ure, is 20 cubic inches. According to Hutchinson, in perfect 
 repose, when the respiratory movements are hardly percep- 
 tible, not more than from 7 to 12 cubic inches are changed ; 
 while, under excitement, he has seen the volume increased to 
 77 cubic inches. Of course the latter is temporary. 1 Herbst 
 noted that the breathing volume is constantly increased in 
 proportion to the stature of the individual, and bears no defi- 
 nite relation to the apparent capacity of the chest. 
 
 Complemental Air. The thorax may be so enlarged by 
 an extreme voluntary inspiratory effort, as to contain a quan- 
 tity of air much larger than after an ordinary inspiration. 
 The additional volume of air thus taken in may be estimated 
 by measuring all the air which can be expelled from the 
 lungs after the most profound inspiration, and deducting the 
 sum of the reserve air and breathing air. This quantity has 
 been found by Hutchinson to vary in different individuals, 
 bearing a close relation to stature. The mean complemental 
 volume is 110 cubic inches. 
 
 The complemental air is drawn upon whenever an effort 
 
 1 We have not thought it worth while to enumerate the varied estimates found 
 in works on physiology, which are not based on extended experimental inquiry 
 * 26 
 
402 RESPIRATION. 
 
 is made which requires a temporary arrest of respiration. 
 Brief and violent muscular exertion is generally preceded by 
 a profound inspiration. In sleep, as the volume of breathing 
 air is somewhat increased, the complemental air is encroached 
 upon. A part or the whole of the complemental air is also 
 used in certain vocal efforts, in blowing, in yawning, in the 
 deep inspiration which precedes sneezing, in straining, etc. 
 
 Summary. In a healthy male of medium stature, the 
 residual air, which cannot be expelled from the lungs, 
 amounts to about 100 cubic inches. 
 
 The reserve air, which can be expelled, but which is not 
 changed in ordinary respiration, amounts to about 100 cubic 
 inches. 
 
 The tidal air, which is changed in ordinary respiration, 
 amounts to about 20 cubic inches. 
 
 The complemental air, which may be taken into the 
 lungs after the completion of an ordinary act of inspiration, 
 amounts to about 110 cubic inches. 1 
 
 1 In Robin's Journal de V Anatomic et de la Physiologie, Sept. 1864, p. 523 
 et seg.j we find an article by Dr. Nestor Grehant, on the physical phenomena 
 of respiration in man, which contains some novel and interesting observations on 
 the capacity of the lungs, volume of breathing air, etc. The volumes of air are 
 estimated by a process which is exceedingly ingenious, and apparently accurate ; 
 but the number of observations is very small compared with those of Hutchinson, 
 and in estimating the capacity of the lungs, he does not take into consideration 
 the very decided influence of stature. The method employed is essentially the 
 following : 
 
 It having been demonstrated by Regnault and Reiset that hydrogen intro- 
 duced into the lungs is not absorbed by the blood, the author, taking advantage 
 of the well-known property of gases, by which they form a uniform mixture when 
 brought hi contact with each other, caused the subjects of his experiments to re- 
 spire a measured volume of hydrogen often enough to make the mixture uniform, 
 and estimates, by analysis of the expired air, the quantity which remains in the 
 lungs, which is necessarily represented by the volume of hydrogen lost. He as- 
 certained by experiments that five respirations of the gas caused a perfect 
 mixture. 
 
 By this method he estimates the normal capacity of the lungs after an ordi- 
 nary expiration (the sum of the residual and reserve air), at from 133*65 to 191*51 
 cubic inches, in men between 17 and 30 years of age (p. 554). 
 
EXTREME BREATHING CAPACITY. 403 
 
 Extreme Breathing Capacity. By the extreme breathing 
 capacity is meant the volume of air which can be expelled 
 from the lungs by the most forcible expiration, after the most 
 profound inspiration. This has been called by Dr. Hutchin- 
 son the vital capacity r , as signifying "the volume of air 
 which can be displaced by living movements." Its volume 
 is equal to the sum of the reserve air, the breathing air, and 
 the complemental air, and represents the extreme capacity 
 of the chest, deducting the residual air. Its physiological 
 interest is due to the fact that it can readily .be determined 
 by an appropriate apparatus, the spirometer, 1 and compari- 
 sons can thus be made between different individuals, both 
 healthy and diseased. The number of observations on this 
 point made by Dr. Hutchinson is enormous, amounting in 
 all to little short of five thousand. 
 
 The extreme breathing capacity in health is subject to 
 variations which have been shown to bear a very close rela- 
 tion to the stature of the individual. Hutchinson com- 
 mences with the proposition that in a man of medium height 
 (5 feet 8 inches\ it is equal to two hundred and thirty cubic 
 inches. He has shown that the extreme breathing capacity 
 is constant in the same individual, and that it is not to be 
 increased by habit or practice. 
 
 The most striking result of the experiments of Dr. 
 Hutchinson, with regard to the modifications of the vital ca- 
 
 The tidal or breathing air, he estimates at 30 cubic inches. 
 
 The observations of Dr. Grehant are as yet so few in number that we prefer 
 to adhere to the results of the greatly extended observations of Hutchinson ; 
 though the new method is very ingenious, and further experiments will probably 
 lead to important results. 
 
 1 The spirometer consists of a vessel containing water, out of which a receiver 
 is raised by breathing into it through a tube ; the height to which the receiver is 
 raised indicating the volume of the vital capacity (Cyclop, of Anat. and Phys., 
 vol. iv., part 2, p. 1068). In all the observations of Dr. Hutchinson, he has taken 
 care to see that the level of the water was the same in the receiver and the reser- 
 voir, and to carefully correct the volumes of air for temperature. All observa- 
 tions were made with the subject erect, and every thing carefully avoided which 
 could interfere with the free action of the respiratory muscles. 
 
404 
 
 RESPIRATION. 
 
 pacity, is that it bears a definite relation to stature, without 
 being affected in a very marked degree by weight, or the 
 circumference of the chest. This is especially remarkable, as 
 it is well known that height does not depend so much upon 
 the length of the body, as the length of the lower extremities. 
 
 It has been ascertained that for every inch in height, 'be- 
 tween five and six feet, the extreme breathing capacity is in- 
 creased eight cubic inches. 
 
 The following table shows the mean results of the im- 
 mense number of observations on which this conclusion is 
 based : l 
 
 Progression of the Vital Capacity Volume with the Stature. 
 
 
 si 
 
 Joo en 
 
 1 
 
 
 g* o 2 
 
 o 2 
 
 **"* *-* 
 
 Height. 
 
 s| 
 
 5|| 
 
 |H 
 
 
 
 
 o 
 
 ^fi 
 
 6 feet inches ) K ? , , . , 
 r o " V inch. 
 
 1st result 
 
 175-0 
 
 3d result. 
 
 176-0 
 
 174-0 
 
 5 4 [ 5 " 3 " 
 
 188-5 
 
 191-0 
 
 190-0 
 
 5 4 [K K 
 
 5 6 f 5 
 
 206-0 
 
 207-0 
 
 206-0 
 
 S fi ) 
 
 
 
 
 5 s k-:.-.i" 
 
 222-0 
 
 228-0 
 
 222-0 
 
 50 i 
 
 
 
 
 L K M Q " 
 5 10 " f. 
 
 237-5 
 
 241-0 
 
 238-0 
 
 5 10 " Is 11 
 
 6 " j" 5 
 
 254-5 
 
 258-0 
 
 254-0 
 
 Mean of all Heights. . . . 
 
 214-0 
 
 217-0 
 
 214-0 
 
 
 
 
 
 Age has an influence, though less marked than stature, 
 upon the extreme breathing capacity. As the result of 4,800 
 
 1 Op. cit., p. 1072. The increase in breathing capacity, pari passu witn an 
 increase in height, was mentioned by Herbst (loc. cit.\ but Hutchinson was the 
 first to make any extended observations, and give any definite information on 
 this point. 
 
EXTREME BREATHING CAPACITY. 405 
 
 observations (males), it was ascertained that the volume in- 
 creases with age up to the thirtieth year, and progressively 
 decreases, with tolerable regularity, from the thirtieth to the 
 sixtieth year. 
 
 These figures, though necessarily subject to certain indi- 
 vidual variations, may be taken as the basis for examinations 
 of the extreme breathing capacity in disease, which frequently 
 give important information. Of course, the breathing capa- 
 city is modified by any abnormal condition which interferes 
 with the mobility of the thorax, or the dilatability of the 
 lungs. Of all diseased conditions, phthisis pulmonalis is the 
 most interesting in this connection. With regard to the 
 significance of the variations in this disease, Dr. Hutchinson 
 has arrived at the following conclusions : 
 
 " It has been found that ten cubic inches below the due 
 quantity, i. e., 220 instead of 230' inches, need not excite 
 alarm ; but there is a point of deficiency in the breathing 
 volume at which it is difficult to say whether it is merely 
 one of those physiological differences dependent on a certain 
 irregularity in all such observations, or deficiency indicative 
 of disease. A deficiency of 16 per cent, is suspicious. A 
 man below 55 years of age breathing 193 cubic inches instead 
 of 230 cubic inches, unless he is excessively fat, is probably 
 the subject of disease. 
 
 " In phthisis pulmonalis the deficiency may amount to 
 90 per cent., and yet life be maintained. The vital capacity 
 volume is likewise a measure of improvement. A phthisical 
 patient may improve so as to gain 40 upon 220 cubic inches." 
 
 Herbst has shown l that the extreme breathing capacity 
 is diminished by obesity ; that it is proportionally less in 
 females than in males, and in children than in adults. 
 
 Relations in Volume of the Expired to the Inspired Air. 
 A certain proportion of the inspired air is lost in respira- 
 tion, so that the air expired is always a little less in volume 
 
406 RESPIRATION. 
 
 than that which is taken into the lungs. All the older ex- 
 perimenters, except Magendie, were agreed upon this point. 
 The loss was put by Davy at -fa, and by Cuvier at -^ of the 
 amount of air introduced. 1 Observations on this point, to be 
 exact, must include a considerable number of respiratory 
 acts ; and from the difficulty of continuing respiration in a 
 perfectly regular and normal manner, when the attention is di- 
 rected to that function, the most accurate results may prob- 
 ably be obtained from experiments on animals. Despretz a 
 caused six young rabbits to respire for two hours in a con- 
 fined space containing 299 cubic inches of air, and ascertained 
 that the volume had diminished 61 cubic inches, or a little 
 more than one-fiftieth. "We may take the approximations of 
 Davy and Cuvier, as applied to the human subject, as nearly 
 correct, and assume that in the lungs, from -fa to -^ of the 
 inspired air is lost. 
 
 Diffusion of Air in the Lungs. When it is considered 
 that with each inspiration but about twenty cubic inches of 
 fresh air is introduced, sufficient only to fill the trachea and 
 larger bronchial tubes, it is evident that some forces must act 
 by which this fresh air finds its way into the air-cells, and the 
 vitiated air is brought into the larger tubes, to be expelled 
 with the succeeding expiration. The expired air may be- 
 come so charged with noxious gases, by holding the breath 
 for a few seconds, that when collected in a receiver under 
 water, it is incapable of supporting combustion. 
 
 The interchange between the fresh air in the upper portions 
 of the respiratory apparatus and the air in the deeper parts 
 of the lungs is constantly going on, in obedience to the well- 
 known law of the diffusion of gases, aided by the active cur- 
 rents or impulses produced by the alternate movements of 
 the chest. When two gases, or mixtures of gases, of different 
 densities are brought in contact with each other, they diffuse 
 
 1 BERABD, Cours de Physiologic, Paris, 1851, tome iii., p. 338, 
 3 Idem. 
 
DIFFUSION OF AEB IN THE LUNGS. 407 
 
 or mingle with great rapidity, until, if undisturbed, the whole 
 mass has a uniform density and composition. This has been 
 shown to take place between very light and very heavy gases 
 in opposition to the laws of gravity, and even when two res- 
 ervoirs are connected by a small tube many feet in length, 
 though then it proceeds quite slowly. In the respiratory ap- 
 paratus, at the termination of inspiration, the atmospheric 
 air, composed of a mixture of oxygen and nitrogen, is intro- 
 duced into the tubes with a considerable impetus, and is 
 brought into contact with the gas in the lungs, which is 
 much heavier, as it contains a considerable quantity of car- 
 bonic acid. Diffusion then takes place, aided by the elastic 
 lungs, which are gradually forcing the gaseous contents out 
 of the cells, until a certain portion of the air loaded with 
 carbonic acid finds its way to the larger tubes, to be thrown 
 off in expiration, its place being supplied by the fresh air. 
 
 In obedience to the law established by Graham, that the 
 diffusibility of gases is inversely proportionate to the square 
 root of their densities, the penetration of atmospheric air, 
 which is the lighter gas, to the deep portions of the lungs 
 would take place with greater rapidity than the ascent of the 
 air charged with carbonic acid ; so that 81 parts of carbonic 
 acid should be replaced by 95 of oxygen. 1 It is found, in- 
 deed, that the volume of carbonic acid exhaled is always less 
 than the volume of oxygen absorbed. 
 
 This diffusion is constantly going on, so that the air in 
 the pulmonary vesicles, where the interchange of gases with 
 the blood takes place, maintains a pretty uniform composi- 
 tion. The process of aeration of the blood, therefore, has 
 none of that intermittent character which attends the me- 
 chanical processes of respiration, which would undoubtedly 
 occur if the entire gaseous contents of the lungs were changed 
 with every act. 
 
 There is no evidence sufficiently definite to show that the 
 muscular fibres in the bronchial tubes, which are of the un- 
 
 3 Cyclopaedia of Anatomy and Physiology, vol. iv., part 1, p. 362, 
 
408 RESPIRATION. 
 
 striped variety, and slow and gradual in their contraction, 
 have any thing to do with the diffusion of gases in the lungs ; 
 nor is it probable that any marked influence is exerted by 
 the movements of the cilioe which cover the mucous mem- 
 brane. 
 
CHAPTEK XII. 
 
 CHANGES WHICH THE AIR UNDERGOES IN RESPIRATION. 
 
 General considerations Discovery of carbonic acid Discovery of oxygen Com- 
 position of the air Consumption of oxygen Influence of temperature In- 
 fluence of sleep Influence of an increased proportion of oxygen in the atmos- 
 phere Temperature of the expired air Exhalation of carbonic acid Influence 
 of age Influence of sex Influence of digestion Influence of diet Influence 
 of sleep Influence of muscular activity Influence of moisture and tem- 
 perature Influence of seasons Relations between the quantity of oxygeii 
 consumed and the quantity of carbonic acid exhaled Exhalation of watery 
 vapor Exhalation of ammonia Exhalation of organic matter Exhalation 
 of nitrogen. 
 
 FROM the allusions which have already been made to the 
 general process of respiration, it is apparent, that before the 
 discovery of the nature of the gases which compose the air 
 and those which are exhaled from the lungs, it was impossible 
 for physiologists to have any correct ideas of the nature of 
 this important function. It is not surprising that the ancients, 
 observing the regular introduction of air into the lungs, and 
 noting the fact that the air is generally much cooler than the 
 body, supposed the great object of respiration to be the cool- 
 ing of the blood. It is also evident that no definite knowl- 
 edge of any of the processes of respiration could exist prior 
 to the discovery of the circulation of the blood. 
 
 Though it is foreign to our purpose to treat historically 
 of the theories concerning any of the functions of the body, 
 the facts relating to changes in the respired air, which from 
 
410 KESPEBATION. 
 
 time to time have been developed, bear so close a relation to 
 discoveries of the properties of certain gases, particularly 
 carbonic acid and oxygen, that it seems desirable to give at 
 least a rapid sketch of these discoveries, and follow the ad- 
 vances in our knowledge of thg processes of respiration, with 
 which they are necessarily connected. 1 
 
 In the latter part of the fifteenth century, Leonardo da 
 Yinci, the great painter, mathematician, and naturalist, made 
 a discovery which conclusively proved the fallacy of the idea 
 that the air simply cooled the blood in respiration. He dis- 
 covered that fire consumed the air, and that animals could 
 not live in a medium which was incapable of supporting 
 combustion. This is the first statement in the history of 
 science which points to the fact that the function of the air 
 in respiration depends on its composition, and not on its 
 physical properties. 
 
 About the middle of the seventeenth century, Yan Hel- 
 mont discovered some of the properties of what is now known 
 as carbonic acid gas. He showed that a gas, the result of 
 fermentation, or of the combustion of carbon, and formed by 
 the action of vinegar on certain carbonates, was incapable of 
 supporting combustion or maintaining animal life. He rec- 
 ognized this as the gas which is found in the lower part of 
 the celebrated Grotto del Cane, near Naples, into which a man 
 may enter with impunity, but which will asphyxiate a small 
 animal, as it is brought under the influence of the lower strata. 
 
 A few years later (1670), Boyle, the founder of the Royal 
 Society of London, by some experiments published in the 
 Philosophical Transactions, attempted to show that air was 
 necessary to the life of all animals, even those which live 
 under water. In a remarkable paper entitled /Suspicions 
 about some Hidden Qualities of the Air, he pointed to the 
 
 1 The reader is referred to the elaborate "work of MILNE-EDWARDS (Legons sur 
 la Physiologic, tome i., p. 375 et seq.) for a complete and highly interesting history 
 of the physiology of respiration, from which we have taken most of the historical 
 facts to which reference will be made. 
 
CHANGES IN THE AIR IN RESPIRATION. 411 
 
 probable existence of some unknown vital substance in the 
 atmosphere. A few years later it was demonstrated by Ber- 
 noulli, that the existence of aquatic animals depends upon 
 air held in solution in the water. About this time Robert 
 Hooke performed his celebrated experiment of exposing the 
 lungs of a living animal, and maintaining the vital processes 
 by artificial respiration. He demonstrated that asphyxia 
 occurred when he ceased to change the air in the lungs, 
 though these organs were allowed to remain distended. 
 
 Fracassati also showed that the red color of the upper 
 surface of a clot of blood was due to its exposure to the air ; 
 and Lower, examining the blood before and after its passage 
 through the lungs, in artificial respiration, showed that the 
 red color of arterial blood depends on the renewal of the 
 atmosphere. 
 
 In 1667, Mayow published his work on Eespiration, in 
 which he advanced the view that the air contained a princi- 
 ple, capable of supporting combustion, which is absorbed in 
 respiration, changes venous into arterial blood, and is the 
 cause of the heat which is developed in animal bodies. 1 The 
 importance of this discovery was not appreciated by the phys- 
 iologists of that day ; and it was more than a century before 
 it received its appropriate place in science. 
 
 In 1757, Joseph Black, of Glasgow, isolated and studied 
 carbonic acid, which he called fixed air. He recognized this 
 gas in the expired air, by passing the breath through lime- 
 
 1 We find the following passage in an analysis of the work of MAYOW on Res 
 piration, published in the Philosophical Transactions, 1668, p. 833 : 
 
 " The author * * * delivers his thoughts on the use of Respiration, waving 
 those opinions, that would have respiration either to cool the heart, or make the 
 Bloud pass through the Lungs out of the right ventricle of the heart to the left, 
 or to reduce the thicker venal blood into thinner and finer parts ; and affirming, 
 That there is something in the Air, absolutely necessary to life, which is conveyed 
 into the Bloud; which, whatever it be, being exhausted, the rest of the air is 
 made useless, and no more fit for Respiration. Where yet he doth not exclude 
 this use, That with the expelled Air, the vapors also, steaming out of the Bloud, 
 are thrown out together." 
 
412 RESPIRATION. 
 
 water. It is evident that this was the gas which was ob- 
 served so many years before by Yan Helmont. 
 
 In 1775, Priestley discovered that the air is composed of 
 oxygen and nitrogen, though he did not make use of these 
 names; and a few years latei^ showed that air which has 
 been vitiated by the respiration of animals is consumed by 
 vegetables, which return the elements necessary to the life of 
 animals. In a paper published in the Philosophical Transac- 
 tions for 1776, he proved that the change in the color of the 
 blood in the lungs is due to the absorption of the newly 
 discovered oxygen ; and showed, furthermore, that the inter- 
 change of gases between the air and the blood can take place 
 through membranes, as readily as when the two fluids are 
 brought directly in contact with each other. 1 
 
 The discoveries above enumerated, though all bearing on 
 the great question, were simply isolated facts, and failed to 
 develop any definite idea of the changes of the air and blood 
 in respiration. The application of these facts was made by 
 the great chemist Lavoisier ; who was the first to employ the 
 delicate balance in chemical investigation, and whose obser- 
 vations mark the beginning of an accurate knowledge of the 
 function of respiration. With the balance, Lavoisier showed 
 the nature of the oxides of the metals ; he discovered that 
 carbonic acid is formed by a union of carbon and oxygen ; 
 and, noting the consumption of oxygen and the production 
 of carbonic acid in respiration, advanced, for the first time, 
 the view that the one was employed in the production of the 
 
 1 BERARD attributes the discovery of oxygen to Bayen (op. cit., tome iii., p. 
 328). It is true that Bayen in 1774 evolved oxygen by heating the red oxide of 
 mercury, but he simply saw a gas given off, the nature and properties of which he 
 did not describe. Priestley first published his discovery of oxygen, with a descrip- 
 tion of certain of its important properties, in the same year; and because he thus 
 described properties which distinguish this from every other gas, to Priestley is 
 generally, and justly, ascribed the honor of its discovery. Scheele, in Sweden, 
 obtained and described oxygen (" the air of fire ") shortly after it had been ob- 
 tained by Priestley, without the knowledge that his discovery had been anticipated. 
 His work was published in 1777. 
 
COMPOSITION OF THE ADJ. 413 
 
 other. Though, as should naturally be expected, the doc- 
 trines of this great observer have been modified with the 
 advances in science, he developed facts which will stand for- 
 ever, and which have served as the starting point of all 
 our knowledge on this subject. From that time physiol- 
 ogists began to look on respiration as consisting in the appro- 
 priation of oxygen and the exhalation of carbonic acid; 
 and now the seat of this process is only changed from the 
 lungs to the tissues. From the limited knowledge of the 
 intimate phenomena of nutrition which obtained in his day, 
 Lavoisier could not be expected to entertain any other view 
 than that the carbonic acid produced was the result of the 
 direct union of oxygen with carbon in the blood. It is only 
 since investigations have made manifest the great complexity 
 of the processes of nutrition, that some are unwilling to be- 
 lieve that carbonic acid is produced in as simple a way as 
 it appeared to Lavoisier. 1 
 
 Composition of the Air. Pure atmospheric air is a 
 mechanical mixture of 79*19 parts of nitrogen with 20'81 
 parts of oxygen (Dumas and Boussingault). 2 It contains in 
 addition a very small quantity of carbonic acid, about one 
 part in 2,000 by volume, and traces of ammonia. The air 
 is never free from moisture, which is very variable in quan- 
 tity, being generally more abundant at a high than at a low 
 temperature. In 1840, Schonbein discovered in the air a pecu- 
 liar odorous principle called ozone, which he conceived to be a 
 compound of oxygen and hydrogen (HO 3 ), but which is now 
 pretty well shown to be an allotropic form of oxygen. The 
 
 1 The applications of the discoveries of Lavoisier to the production of animal 
 heat will be taken up in connection with that phenomenon. 
 
 a Some chemists suppose that the oxygen and nitrogen in the air are in a con- 
 dition of feeble chemical combination. However that may be, it is certain that 
 in respiration it is the oxygen which is absorbed by the blood, and which carries 
 on the function. The nitrogen seems to act simply as a diluent, thus providing 
 that the blood in the lungs shall be exposed to but a certain quantity of the re- 
 spiratory principle. 
 
4:14: RESPIRATION. 
 
 oxygen which is obtained by decomposing water by the Yol- 
 taic pile is in this condition. It exists in very small quantity 
 in the air, and plays no part in the function of respiration. 
 Its chief interest has been in a theoretical connection with 
 epidemic diseases. 1 Floating ii the atmosphere are a num- 
 ber of excessively minute organic bodies. Yarious odor- 
 ous and other gaseous matter may be present as accidental 
 constituents. 
 
 In considering the function of respiration, it is not neces- 
 sary to take account of any of the constituents of the atmos- 
 phere, except oxygen and nitrogen ; the others being either 
 inconstant, or existing in excessively minute quantity. It 
 is necessary to the regular performance of the function that 
 the air should contain about four parts of nitrogen to one of 
 oxygen, and have about the density which exists on the gen- 
 eral surface of the globe. When the density is very much 
 increased, as in mines, respiration is somewhat, though not 
 gravely, disturbed. By exposure to a rarefied atmosphere, as 
 in the ascent of high mountains or in aerial voyages, respira- 
 tion may be very seriously interfered with, from the fact that 
 less oxygen than usual is presented to the respiratory surface, 
 and the reduced atmospheric pressure diminishes the capa- 
 city of the blood for holding gases in solution. 
 
 Magendie and Bernard, in experimenting on the minimum 
 proportion of oxygen in the air which is capable of sustaining 
 life, found that a rabbit, confined under a bell-glass with an 
 arrangement for removing the carbonic acid and water ex- 
 
 1 Ozone may be formed bypassing electric discharges through the ordinary at- 
 mosphere, or through oxygen. Its proportion in the air is supposed to be much 
 increased in storms which are accompanied by electric phenomena. Schonbein 
 exposed animals to the action of this substance. A dog, confined for an hour in 
 a bell-glass, into which ozone was passed, died, though it was estimated that he 
 absorbed only about *03 of a grain. An examination showed the lungs in a con- 
 dition of acute inflammation. M. de la Kive, who has also experimented upon 
 it, compares its action on the respiratory organs to that of chlorine (BERNARD, 
 JLefOns sur les Effete des /Substances Toxiques et Medicamenteuses, Paris, 1857, p. 
 150). 
 
COMPOSITION OF THE AIR. 415 
 
 haled, as fast as they were produced, died of asphyxia when 
 the quantity of oxygen became reduced to from 3 to 5 per 
 cent. 1 
 
 Following Lavoisier, the Abbe Spallanzani, 2 by researches 
 on a great number of animals of all classes, demonstrated the 
 universal necessity of air, either in a gaseous condition or in 
 solution in liquids, throughout the animal kingdom. 
 
 A few experiments are on record in which the human 
 subject and animals have been made to respire for a time 
 pure oxygen. Though this is the gas which is essential in 
 ordinary respiration, the process being carried on about as 
 well in a mixture of oxygen with hydrogen as with nitrogen, 
 the functions do not seem to be much altered when the pure 
 gas is taken into the lungs. Some authors state that its pro- 
 longed inhalation exaggerates the function for a time, and 
 that inflammation of the lungs and death follow its pro- 
 longed use ; while the experiments of others show that it is 
 harmless. Allen and Pepys confined animals for twenty- 
 four hours in an atmosphere of pure oxygen, without any 
 notable results ; 3 but, as is justly remarked by Longet, these 
 experiments do not show that it would be possible to respire 
 unmixed oxygen indefinitely without inconvenience. As it 
 exists in the air, oxygen is undoubtedly in the best form for 
 the permanent maintenance of the respiratory function. 
 The blood seems to have a certain capacity for the absorp- 
 tion of oxygen, which is not increased when the pure gas is 
 presented. 
 
 The only other gas which has the power of maintaining 
 respiration, even for a time, is nitrous oxide. This is ab- 
 sorbed by the blood-corpuscles with great avidity, and for a 
 time produces an exaggeration of the vital processes, with 
 delirium, etc. properties which have given it the common 
 
 1 BERNARD, op. cit., p. 115. 
 
 a SPALLANZANI, Memoires sur la Respiration, traduits en Fran$ais cFapres son 
 manuscrit in'edit, 1803. 
 
 * LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 458. 
 
416 RESPIRATION. 
 
 name of the " laughing gas " ; but this condition is followed 
 by anaesthesia, and finally asphyxia, probably because the 
 gas has such an affinity for the blood-corpuscles as to re- 
 main to a certain extent fixed, interfering with the inter- 
 change of gases which is essential to life. Notwithstanding 
 this, experimenters have confined rabbits and other animals 
 in an atmosphere of nitrous oxide for a number of hours. 
 In all cases they became asphyxiated, but in some instances 
 were restored on being brought again into the atmosphere. 1 
 
 Other gases which may be introduced into the lungs 
 either produce asphyxia, negatively, from the fact that they 
 are not absorbed by the blood and are incapable of carrying 
 on respiration, like hydrogen or nitrogen, or positively, by a 
 poisonous effect on the system. The most important of the 
 gases which act as poisons are, carbonic oxide, sulphuretted 
 hydrogen, and arseniuretted hydrogen. It is somewhat un- 
 certain whether carbonic acid exerts its deleterious influence 
 as a poison, or as merely taking the place of the oxygen in 
 the blood-corpuscles. It is easily displaced from the blood 
 by oxygen, and therefore does not seem to possess the prop- 
 erties of a poison, like carbonic oxide, and some other gases, 
 which become fixed in the blood, and are not readily dis- 
 placed when fresh air is introduced into the lungs. 
 
 Consumption of Oxygen. The determination of the 
 quantity of oxygen which is removed from the air by the 
 process of respiration is a question of great physiological in- 
 terest, and one which engaged largely the attention of La- 
 voisier and those who have followed in his line of observa- 
 tion. On this point there is an accumulated mass of 
 observations which are comparatively unimportant, from the 
 fact that they were made before the means of analysis of the 
 gases were as perfect as they now are. Though many of the 
 results obtained by the older experimenters are interesting 
 and instructive, as showing the comparative quantities of 
 
 1 LONGET, op. dt., tome i., p. 460. 
 
CONSUMPTION OF OXYGEN. 417 
 
 i 
 
 oxygen consumed under various physiological conditions, they 
 are not to be compared with the more recent observations, 
 particularly those of Kegnault and Eeiset, Valentin and Brun- 
 ner, Dumas, Andral and Gavarret, Scharling, and Edward 
 Smith, with regard to the absolute quantity of oxygen made 
 use of in respiration. In the observations of Regnault and 
 Reiset, the animal to be experimented upon was enclosed in 
 a receiver filled with air, a measured quantity of oxygen 
 was introduced as fast as it was consumed by respiration, and 
 the carbonic acid was constantly removed and carefully esti- 
 mated. In most of the experiments, the confinement did not 
 appear to interfere with the functions of the animal, which 
 ate and drank in the apparatus, and was in as good condition 
 at the termination as at the beginning of the observation. 
 This method is infinitely more accurate than that of simply 
 causing an animal to breathe in a confined space, when the 
 consumption of oxygen and accumulation of carbonic acid 
 and other matters must interfere more or less with the proper 
 performance of the respiratory function. This is known as 
 the direct method of investigating the changes in the air pro- 
 duced by respiration. As employed by Regnault and Reiset, 
 it is only adapted to experiments on animals of small size. 
 These give but an approximative idea of the processes as they 
 take place in the human subject, as it is natural to suppose 
 that the relative quantities of gases consumed and produced 
 in respiration vary in different orders of animals-. 1 
 
 1 In Robin's Journal de TAnatomie et de la Physiologic, July, 1864, tome i., 
 p. 429, we find an analysis of researches on respiration by Dr. Max Pettenkofer, in 
 which the conditions for accurate observations on the human subject seem to be 
 fulfilled. Dr. Pettenkofer has constructed a chamber large enough to admit aman t 
 and allow perfect freedom of motion, eating, sleeping, etc., into which air is con- 
 stantly introduced in definite quantity, and from which the products of respiration 
 are constantly removed, and estimated. An incomplete series of observations is- 
 published, which has particular reference to the products of respiration. Thus 
 far the subject of consumption of oxygen has not been considered. Extended ob- 
 servations by Dr. Pettenkofer will undoubtedly settle many disputed questions 
 regarding the changes of the air in respiration. This method was adapted to the 
 27 
 
418 EESPEBATION. 
 
 The indirect method was first employed by Boussingault, 
 but was particularly directed to the exhalation of carbonic 
 acid. This observer experimented upon large animals, such 
 as the horse or cow, in the following way : Having first care- 
 fully regulated the diet, so that there was no change in weight 
 during the experiments, he carefully weighed all that was 
 introduced as food and drink, and all that was discharged 
 as urine and feces. The excess in the quantity introduced, 
 over that discharged in the way above mentioned, represents, 
 necessarily, the amount lost by the skin and lungs. By a 
 quantitative comparison of the elementary constituents of the 
 food and excrements, tolerably accurate results were arrived 
 at ; though it must be admitted that this method would be 
 considered of little value, did the results not correspond pretty 
 closely with those obtained by direct analysis. 1 
 
 Estimates of the absolute quantities of oxygen consumed, 
 or of carbonic acid produced, which are based on analyses of 
 the inspired and expired air, calculations from the aver- 
 age quantity of air changed with each respiratory act, and 
 the average number of respirations per minute, are by no 
 means as reliable as analyses showing the actual changes 
 in the air, like those of Eegnault and Keiset, provided the 
 physiological conditions be fulfilled. When there is so much 
 multiplication and calculation, a very slight and perhaps 
 unavoidable inaccuracy in the quantities consumed or pro 
 duced in a single respiration will make an immense error 
 in the estimate for a day, or even an hour. 
 
 Bearing all these sources of error in mind, from the ex- 
 periments of Yalentin and Brunner, Dumas, and others, a suf- 
 ficiently accurate approximation of the proportion of oxygen 
 consumed by the human subject may be formed. The air, 
 
 human subject on a small scale in 1843, by Scharling, but there was no arrange- 
 ment for estimating the quantity of oxygen furnished (MILNE-EDWARDS, Physi- 
 ologic, tome ii., p. 498, note.) 
 
 1 BOUSSINGAULT, Memoires de Chimie Agricole et de Physiologic, Paris, 1854, 
 pp. 1-12. 
 
CONSUMPTION OF OXYGEN. 419 
 
 which contains, when inspired, 20*81 parts of oxygen per 
 100, is found on expiration to contain but about 16 parts 
 per 100. In other words, the volume of oxygen absorbed in 
 the lungs is five per cent, or -^ of the volume of air in- 
 spired. 1 
 
 It is interesting and useful to extend this estimate as far 
 as possible to the quantity of oxygen absorbed in a definite 
 time ; for the regulation of the supply of oxygen where many 
 persons are assembled, as in public buildings, hospitals, 
 etc., is a question of great practical importance. Assuming 
 that the average respirations per minute are 18, and that 
 with each act 20 cubic inches of air are changed, 15 cubic 
 feet of oxygen are consumed in the twenty-four hours, which 
 represents 300 cubic feet of pure air. This is the minimum 
 quantity of air which is actually used, making no allowance 
 for the increase in the intensity of the respiratory processes, 
 which is liable to occur from various causes. To meet all the 
 respiratory exigencies of the system, in hospitals, prisons, etc., 
 it has been found necessary to allow at least 800 cubic feet 
 of air for each person, unless the situation is such that the air 
 is changed with unusual frequency; for, beside the actual 
 loss of oxygen in the respired air, constant emanations from 
 both the pulmonary and cutaneous surfaces are taking place, 
 which should be removed. In some institutions as much as 
 2,500 cubic feet of air is allowed to each person. 2 ^ 
 
 The quantity of oxygen consumed is subject to great 
 variations, depending upon temperature, the condition of the 
 digestive system, muscular activity, etc. The following con- 
 clusions, the results of the observations of Lavoisier and Se- 
 guin, give at a glance the variations from the above-men- 
 tioned causes : 3 
 
 1 MILNE-EDWARDS, Phyxiologie, tome ii., p. 510. 
 
 2 TODD and BOWMAN, Physiological Anatomy and Physiology of Man, Phila- 
 delphia, 1857, p. 728. 
 
 8 Taken from LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 526. 
 Though the absolute quantities obtained by Lavoisier and Seguin are not so rp- 
 liable as those obtained by later observers, yet the accurate employment of the 
 
420 RESPIRATION. 
 
 " 1. A man, in repose sad fasting, with an external tem- 
 perature of 90 Fahr., consumes 1,465 cubic inches of oxygen 
 per hour. 
 
 " 2. A man, in repose and fasting, with an external tem- 
 perature of 59 Fahr., consume^ 1,627 cubic inches of oxygen 
 per hour. 
 
 " 3. A man, during digestion, consumes 2,300 cubic 
 inches of oxygen per hour. 
 
 " 4. A man, fasting, while he accomplishes the labor ne- 
 cessary to raise, in fifteen minutes, a weight of 7*343 kil. 
 (about 16 Ib. 3 oz. av.) to the height of 656 feet, consumes 
 3,874 cubic inches of oxygen per hour. 
 
 " 5. A man, during digestion, accomplishing the labor 
 necessary to raise, in fifteen minutes, a weight of 7*343 kil. 
 (about 16 Ib. 3 oz. av.) to the height of 700 feet, consumes 
 5,568 cubic inches of oxygen per hour." 
 
 Influence of Temperature. All who have experimented 
 on the influence of temperature upon the consumption of 
 oxygen, in the warm-blooded animals and in the human sub- 
 ject, have noted a marked increase at low temperatures. 
 Cold-blooded animals always suffer a depression of the vital 
 processes at low temperatures, with a corresponding diminu- 
 tion in the quantity of oxygen consumed, until they finally 
 become torpid. 
 
 Immediately after birth, the consumption of oxygen in 
 the warm-blooded animals is relatively very slight. Buffon * 
 and Legallois 2 have shown that just after birth, dogs and 
 other animals will live for half an hour or more under water ; 
 and cases are on record where life has been restored in newly- 
 born children after seven, and, it has been stated, after twenty- 
 three hours of asphyxia. During the first periods of exist- 
 ence, the condition of the newly-born approximates to that of a 
 
 best means of investigation at their command leads us to place every confidence 
 in the comparative results. 
 
 1 MILNE-EDWARDS, Physiologic, tome ii., p. 559. 
 
 2 LEGALLOIS, (Euvres, Paris, 1824, tome i., p. 67. 
 
INFLUENCE OF TEMPEKATUKE. 421 
 
 cold-blooded animal. The lungs are relatively very small, and 
 it is some time before they fully assume their function. The 
 muscular movements are hardly more than is necessary to take 
 the small amount of nourishment consumed at that period, and 
 nearly all of the time is passed in sleep. There is also very 
 little power of resistance to low temperature. Though accu- 
 rate researches regarding the comparative quantities of oxy- 
 gen in the venous and arterial blood of the foetus are wanting, 
 it has been frequently observed that the difference in color is 
 not as marked as it is after pulmonary respiration becomes 
 established. The direct researches of "W". F. Edwards have 
 shown that the absolute consumption of oxygen by very 
 young animals is very small ; * and the observations of Lcgal- 
 lois on rabbits, made every five days during the first month 
 of existence, show a rapidly increasing demand for this prin- 
 ciple with age. 2 
 
 Regnault and Reiset have shown that the consumption 
 of oxygen is greater in lean than in very fat animals, pro- 
 vided they be in perfect health. They have also shown that 
 the consumption is much greater in carnivorous than in 
 herbivorous animals; and in animals of different sizes, is 
 relatively very much greater in those which are very small. 
 In very small birds, such as the sparrow, the proportional 
 quantity of oxygen absorbed was ten times greater than in 
 the fowl. 3 
 
 In sleep, the quantity of oxygen consumed is considerably 
 
 1 De ^Influence des Agens Physiques sur la Vie, Paris, 1824, p. 178 et seq. 
 
 2 Loc. oil. In his experiments on rabbits, Legallois found that immmediately 
 after birth they would live for fifteen minutes deprived of air. "In asphyxiating 
 rabbits of different ages, for example, every five days, from the moment of birth 
 to the age of one month, it was constantly observed that the duration of sensa- 
 tion, of voluntary motion, in a word, the signs of life, always diminished in pro- 
 portion as the animals advanced in age. Thus, in a rabbit newly born, sensation 
 and voluntary movements were not extinct until the end of about fifteen minutes 
 of asphyxia, while they were extinct in less than two minutes in a rabbit of the 
 age of thirty days." Pp. 57, 58. 
 
 * Loc. cit. 
 
422 RESPIRATION. 
 
 diminished ; and in hibernation is so small, that Spallanzani 
 could not detect any difference in the composition of the air 
 in which a marmot, in a state of torpor, had remained for 
 three hours. 1 In experiments on a marmot in hibernation, 
 Regnault and Reiset observed % reduction in the quantity of 
 oxygen consumed to about -^ of the normal standard. 2 
 
 It has been shown by experiments, that the consumption 
 of oxygen bears a pretty constant ratio to the production of 
 carbonic acid ; and as the observations on the influence of 
 sex, number of respiratory acts, etc. on the activity of the 
 respiratory processes, have been made chiefly with reference 
 to the carbonic acid exhaled, we will consider these influences 
 in connection with the products of respiration. 
 
 Experiments on the effect of increasing the proportion of 
 oxygen in the air have led to varied results in the hands of 
 different observers. Regnault and Reiset, whose observa- 
 tions on this point are generally accepted, did not discover 
 any increase in the consumption of oxygen when this gas was 
 largely in excess. 
 
 The results of confining an animal in an atmosphere com- 
 posed of 21 parts of oxygen and 79 parts of hydrogen are 
 very curious and instructive. "When hydrogen is thus sub- 
 stituted for the nitrogen of the air, the consumption of oxygen 
 is largely increased. Regnault and Reiset attribute this to 
 the superior refrigerating power of the hydrogen ; but a more 
 rational explanation would seem to be in its superior diffusi- 
 bility. Hydrogen is the most diffusible of all gases; and 
 when introduced into the lungs in the place 6f the nitrogen 
 of the air, the vitiated air, charged with carbonic acid, is 
 undoubtedly more readily removed from the deep portions 
 of the lungs, giving place to the mixture of hydrogen and 
 oxygen ; and it is probably for this reason that the quantity 
 of oxygen consumed is increased. It is probable that the 
 
 1 SPALLANZANI, Memoires sur la Respiration, traduites par SENEBIER, Geneve, 
 1803, p. 334. 
 
 2 Op. cit., p. 442. 
 
INFLUENCE OF TEMPERATURE. 423 
 
 nitrogen of the air plays an important part in the phenomena 
 of respiration by virtue of its degree of diffusibility. 
 
 In view of the great variations in the consumption of 
 oxygen dependent on different physiological conditions, such 
 as digestion, exercise, temperature, etc., it is impossible to fix 
 upon any number which will represent, even approximative^, 
 the average quantity consumed per hour. The estimate 
 arrived at by Longet, 1 from a comparison of the results ob- 
 tained by different reliable observers, is perhaps as near the 
 truth as possible. This estimate puts the hourly consumption 
 at from 1,220 to 1,525 cubic inches, " in an adult male, during 
 repose and in normal conditions of health and temperature." 
 
 In passing through the lungs, the air, beside losing a 
 proportion of its oxygen, undergoes the following changes : 
 
 1. Increase in temperature. 
 
 2. Gain of carbonic acid. 
 
 3. Gain of watery vapor. 
 
 4. Gain of ammonia. 
 
 5. Gain of a small quantity of organic matter. 
 
 6. Gain, and occasionally loss, of nitrogen. 
 
 The elevation in temperature of the air which has passed 
 through the lungs has been carefully observed by Dr. Gre- 
 hant. 2 He found that with an external temperature of 72, 
 respiring 17 times per minute, the air taken in by the nares 
 and expired by the mouth, through an apparatus containing 
 a thermometer carefully protected from external influences, 
 marked a temperature of 95*4. Taking in the air by the 
 mouth, the temperature of the expired air was 93. At the 
 commencement of the expiration, Dr. Grehant noted a tem- 
 perature of 94. After a prolonged expiration, the temper- 
 ature was 96. In these observations the temperature taken 
 beneath the tongue was 98. 
 
 1 Op. cit., p. 531. 
 
 2 GREHANT, Rcchcrclws Physiques sur la -Respiration de VHomme. Journal d< 
 FAnatomie et de la Physiologic, 1864, tome i, p. 546. 
 
4:24 RESPIRATION. 
 
 Valentin had previously made experiments on this point, 
 and put the temperature of the expired air a little higher, 
 i. <?., about 99, with an external temperature of 68. He 
 also showed that the temperature of the surrounding atmos- 
 phere exerted an important influence on the temperature of 
 the expired air. In an observation made in winter, with an 
 external temperature of 18, the temperature of the expired 
 air was only 85'S . 1 
 
 Exhalation of Carbonic Acid. The production of car- 
 bonic acid in the respiratory process is as universal as the 
 consumption of oxygen. Experiments have shown that all 
 animals during life exhale this principle, as well as all tis- 
 sues, so long as they retain their irritability. This takes 
 place, not only when the animals or tissues are placed in an 
 atmosphere of oxygen, or common air, but, as was observed 
 by Spallanzani, 2 in an atmosphere of pure nitrogen or hydro- 
 gen. This fact has since been noted by "W. F. Edwards, J. 
 Miiller, G. Liebig, and others. 
 
 The study of the exhalation of carbonic acid presents sev- 
 eral problems of great physiological interest : 
 
 1. What is the absolute quantity of carbonic acid exhaled 
 by the lungs in a given time 1 
 
 2. What are the variations in the exhalation of this prin- 
 ciple due to physiological influences ? 
 
 3. What is the relation between the quantity of carbonic 
 acid produced and the quantity of oxygen consumed ? 
 
 On account of the variations in the quantities of carbonic 
 acid exhaled at different periods of the day, and particularly 
 the great influence of the rapidity of the respiratory move- 
 ments, it is exceedingly difficult to fix upon any number 
 which will represent the average proportion of this gas con- 
 tained in the expired air. The same influences were found 
 affecting the consumption of oxygen ; and the same difficulties 
 
 1 GREHANT, Rtcherches Physiques sur la Respiration de V Homme. Journal de 
 PAnatomie et de la Physiologic, 1864, tome i., p. 545. 
 3 Op. dt., p. 343. 
 
EXHALATION OF CARBONIC ACID. 425 
 
 were experienced in forming an estimate of the proportion 
 of this gas consumed. As we assumed, after a comparison 
 of the results obtained by different observers, that the vol- 
 ume of oxygen consumed is about five per cent, of the entire 
 volume of air, it may be stated as an approximation, that in 
 the intervals of digestion, in repose, and under normal con- 
 ditions as regards the frequency of the pulse and respiration, 
 the volume of carbonic acid exhaled is about four per cent, 
 of the volume of the expired air. 1 As the volume of the oxy- 
 gen which enters into the composition of a definite quantity of 
 carbonic acid is precisely equal to the volume of the car- 
 bonic acid, it is seen that a certain quantity of oxygen disap- 
 pears in respiration, and is not represented in the carbonic 
 acid exhaled. 
 
 There are great differences in the proportion of carbonic 
 acid in the expired air, depending upon the time during 
 which the air has remained in the lungs. This interesting 
 point has been studied by Yierordt, in a series of 94 experi- 
 ments made upon his own person, with the following results : 2 
 
 " When the respirations are frequent, the quantity of car- 
 bonic acid expelled at each expiration is much less than in a 
 slow expiration ; but the quantity of carbonic acid produced 
 during a given time by frequent respirations is greater than 
 that which is thrown off by slow expirations." 3 
 
 The air which escapes during the first period of an expi- 
 ration is naturally less rich in carbonic acid than that which 
 is last expelled and comes directly from the deeper portions 
 of the lungs. Dividing, as nearly as possible, the expiration 
 into two equal parts, Yierordt found, as the mean of twenty- 
 
 1 MILNE-EDWARDS, Physiologic, tome ii., p. 507. This approximation is taken 
 from the observations of Valentin and Brunner, Dalton, Prout, Apjohn, Coathupe, 
 Horn, and Vierordt. The experiments of Vierordt are, perhaps, entitled to the 
 most credit, as he has studied very carefully the influence of the frequency of res- 
 piration upon the quantity of carbonic acid exhaled. 
 
 a Cited in MILNE-EDWARDS, Physiologic, tome ii., p 574, and BERARD, Cours 
 do Physiologic, tome iii., p. 349. 
 
 s BERARD, loc. cit. 
 
426 RESPIRATION. 
 
 one experiments, a percentage of 3 '72 in the first part of the 
 expiration, and 5*44 in the second part. 1 
 
 Temporary arrest of the respiratory movements, as we 
 should expect, has a marked influence in increasing the pro- 
 portion of carbonic acid in the ^xpired air ; though the abso- 
 lute quantity exhaled in a given time is diminished. In a 
 number of experiments on his own person, Vierordt ascer- 
 tained that the percentage of carbonic acid becomes uniform 
 in all parts of the respiratory organs, after holding the 
 breath for 40 seconds. Holding the breath after an ordinary 
 inspiration for 20 seconds, the percentage of carbonic acid 
 in the expired air was increased 1*73 over the normal stand- 
 ard ; but the absolute quantity exhaled was diminished by 
 2'642 cubic inches. After taking the deepest possible inspi- 
 ration, and holding the breath for 100 seconds, the percent- 
 age w r as increased 3*08 above the normal standard ; but the 
 absolute quantity was diminished more than 14 cubic inches. 2 
 Allen and Pepys state that air which has passed 9 or 10 times 
 through the lungs contains 9*5 per cent, of carbonic acid. 3 - 
 
 Yierordt gives the following formula as representing the 
 influence of the frequency of the respirations on the produc- 
 tion of carbonic acid : Taking 2'5 parts per hundred as rep- 
 resenting the constant value of the gas exhaled by the blood, 
 the increase over this proportion in the expired air is in 
 exact ratio to the duration in the contact of the air and 
 blood. This, though it may hold good in many instances, 
 seems rather an excessive refinement. 4 
 
 1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. ii., p. 439. 
 
 2 Cyclopaedia of Anatomy and Physiology, vol. iv., part 1, p. 352. 
 
 3 Ibid. 
 
 4 The following table gives at a glance the most important results of these 
 experiments : 
 
 Proportion of Carbonic Acid. Number of Respirations per Minute. 
 
 5-7 per 100 parts of air 6 
 
 41 " " " 12 
 
 3-3 " " " 24 
 
 2-9 ' " " 48 
 
 2-T " " " 96 
 
EXHALATION OF CAKBONIC ACID. 427 
 
 The absolute quantity of carbonic acid exhaled in a given 
 time is a more important subject of inquiry than the propor- 
 tion contained in the expired air ; for the latter is constant- 
 ly varying with every modification in the number and ex- 
 tent of the respiratory acts, and the volume of breathing 
 air is subject to great fluctuations, and is very difficult of 
 determination. The direct method, in which the actual 
 products of respiration are collected and/ estimated, has led 
 to very important results, which have been confirmed to a 
 certain extent by Boussingault, Barral, and others who have 
 employed the indirect method. It is by the direct method, 
 in the hands of Regnault and Reiset, Andral and Gavarret, 
 and more recently Dr. Edward Smith, that we have learned 
 so much regarding the physiological variations in the prod- 
 ucts of respiration ; one of the most important considerations 
 connected with the subject. 
 
 Among the most reliable observations on the quantity of 
 carbonic acid exhaled by the human subject in a definite 
 time, and the variations to which it is subject, are those of 
 Andral and Gavarret, 1 and Dr. Edward Smith. 8 The obser- 
 vations of Lavoisier and Seguin, Prout, Davy, Dumas, Allen 
 and Pepys, Scharling, and others, have none of them seemed 
 to fulfil the necessary experimental conditions so completely; 
 Schaiiing's method was to enclose his subject in a tight box, 
 with a capacity of about 27 cubic feet, to which air was con- 
 stantly supplied; but the observations were comparatively 
 few, being made on only six persons. In his observations, 
 the quantities of gas exhaled must have been considerably 
 modified by the elevation of temperature and exhalation of 
 moisture in so small a space. 3 The mental condition of the 
 
 1 Recherches sur la Quantite d'Acide Carbonique exhale par les Poumons dan* 
 VEspece Humaine. Annalesde Chimie etde Physique, 3meserie,tomeviii.,p. 129. 
 
 a EDWARD SMITH, Experimental Inquiries into the Chemical and other Phenom- 
 ena of Respiration, and their Modifications by various Physical Agencies (Phi- 
 losophical Transactions, 1859, p. 681) ; and On the Action of Foods upon the 
 Respiration during the Primary Processes of Digestion (Ibid., p. 715). 
 
 3 Annales de Chim. et de Phys., tome viii., p. 488. Scharling recognized the 
 
428 RESPIRATION. 
 
 subject of an experiment has an influence upon the products 
 of respiration, and the function is sometimes modified from 
 the mere fact that an experiment is being performed ; an in- 
 fluence which Scharling did not fail to recognize, but which 
 frequently cannot be guarded against. 
 
 The observations of Andral and Gavarret were made on 
 sixty-two persons of both sexes and different ages, and under 
 absolutely identical conditions as regards digestion, time of 
 the day, barometric pressure, and temperature. The prod- 
 ucts of respiration were collected in the following way : 
 A thin mask of copper covering the face, and large enough 
 to contain an entire expiration, was fitted to the face by 
 its edges, which were provided with India-rubber, so as to 
 make it air-tight. At the upper part was a plate of glass for 
 the admission of light, and at the lower part an opening, 
 which allowed the entrance of air, but was provided with a 
 valve preventing its escape. By another opening the mask 
 was connected by a rubber tube with three glass balloons, ca- 
 pable of holding 8,544 cubic inches, in which a vacuum was 
 previously established. With the mask fixed upon the face, 
 and a stop-cock opened, connected with the balloons, so as to 
 graduate the current of air, the subject respires freely in the 
 current which comes from the exterior into the receivers. In 
 this way, though the quantity of air respired is not measured, 
 the vacuum in the receivers draws in the products of respira- 
 tion. The current will continue for from 8 to 13 minutes, 
 and is so regulated that the air is respired but once. The 
 quantity of carbonic acid in the receivers represents the 
 quantity produced during the time that the experiment has 
 been going on. 
 
 By carefully fulfilling all the physiological conditions, 
 
 necessity of guarding against the influence of elevation of temperature and accu- 
 mulation of moisture, and attempted to remove the latter by introducing a vessel 
 of sulphuric acid. His greatest difficulty was in the analyses of the air. Though 
 the results obtained are valuable, the process cannot claim the accuracy attained 
 by Andral and Gavarret. 
 
EXHALATION OF CAKBONIC ACID. 429 
 
 regulating the number of respirations, as far as possible, to 
 the normal standard, different observations on the same sub- 
 ject, at different times, under the same conditions, were at- 
 tended with results so nearly identical, as to give every con- 
 fidence in the accuracy of the process. But even then, these 
 observers recognized such immense variations in the exhala- 
 tion of carbonic acid with the constantly varying physiologi- 
 cal conditions, that they did not feel justified in taking their 
 observations as the basis for calculations of the entire quantity 
 exhaled in the twenty-four hours. 
 
 The results of these observations on the male, between the 
 ages of sixteen and thirty, between 1 and 2 P.M., under iden- 
 tical conditions of the digestive and muscular systems, each 
 experiment lasting from eight to thirteen minutes, showed an 
 exhalation of about 1,220 cubic inches of carbonic acid per 
 hour. 
 
 Dr. Edward Smith, 1 in his elaborate paper on the phe- 
 nomena of respiration, employed a very rigorous method for 
 the estimation of the carbonic acid exhaled. He used a 
 mask, fitting closely to the face, which covered only the air- 
 passages. The air was admitted after being measured by 
 passing through an ordinary dry gas-meter. The expired 
 air was passed through a drying apparatus, and the carbonic 
 acid absorbed by a solution of potash, arranged in a number 
 of layers, so as to present a surface of about 700 square inches, 
 and carefully weighed. This apparatus was capable of col- 
 lecting all the carbonic acid exhaled in an hour. The esti- 
 mate was made for 18 waking hours and 6 hours of sleep. 
 The observations for the 18 hours were made on four persons, 
 namely : Dr. Smith, set. 38 years, weighing 196 pounds, 6 
 feet high, with a vital capacity of 280 cubic inches ; Mr. 
 Moul, set. 48 years, 5 feet 9J inches high, 175 pounds 
 weight ; Dr. Murie, set. 26 years, 5 feet 7 inches high, 133 
 pounds weight, vital capacity 250 cubic inches ; Prof. Frank- 
 land, set. 33 years, 5 feet 10J inches high, and 136 pounds 
 
 1 Loc. tit. 
 
430 RESPIRATION. 
 
 weight. Breakfast was taken at 8J- A.M., dinner at 1J, tea at 
 
 5 J, and supper at 8J P.M. The observations occupied ten min- 
 utes, and were made every hour and half-hour for 18 hours. 
 The average for the 18 hours gave 20,082 cubic inches of 
 carbonic acid for the whole peiiod. Observations during the 
 
 6 hours of sleep showed a total exhalation of 4,126 cubic 
 inches. This, added to the quantity exhaled during the day, 
 gives as the total exhalation in the twenty-four hours, during 
 complete repose, 24,208 cubic inches (about 14-24 cubic feet), 
 containing 7*144 oz. av. of carbon. 1 
 
 Considering the great variations in the exhalation of car- 
 bonic acid, this estimate can be nothing more than an ap- 
 proximation. One of the great modifying influences is mus- 
 cular exertion, by which the production of carbonic acid is 
 largely increased. This would indicate a larger quantity 
 during ordinary conditions of exercise, and a much larger 
 quantity in the laboring classes. Dr. Smith gives the fol- 
 lowing approximate estimates of these differences : 2 
 
 In quietude 7'144 oz. av. of carbon. 
 
 Non-laborious class 8'68 " " 
 
 Laborious class ll'T 
 
 In studying the variations in the exhalation of carbonic 
 acid, important information has been derived from experi- 
 ments by many observers on the inferior animals, as well as 
 from the observations of Dumas, Prout, Scharling, and others 
 on the human subject. The principal conditions which 
 influence the exhalation of this principle are : 
 
 Age and sex ; activity or repose of the digestive system ; 
 form of diet ; sleep ; muscular activity ; fatigue ; moisture, 
 and surrounding temperature ; season of the year. 
 
 1 Op. cit., p. 692. In these calculations there is a slight arithmetical error; 
 but it makes a difference of only 40 cubic inches of gas in the estimate for the 24 
 hours. In the original paper, the quantity is given by weight. We have re- 
 duced it to cubic inches, assuming that 100 cubic inches of gas weigh 47 26 grains. 
 
 a Op. cit., p. 693. 
 
INFLUENCE OF AGE. 431 
 
 Influence of Age. In treating of the consumption of 
 oxygen, it was stated that during the first few days of extra- 
 uterine existence, the demand for oxygen on the part of the 
 system is very slight. At this period there is a correspond- 
 ingly feeble exhalation of carbonic acid. It is well known 
 that during the first hours and days after birth the new 
 being has little power of generating heat, needs constant 
 protection from changes in temperature, and the volun- 
 tary movements are very imperfect. During the first few 
 days, indeed, the infant does little more than sleep and take 
 the small quantity of colostrum which is furnished by the 
 mammary glands of the mother. "While the animal functions 
 are so imperfectly developed, and until the nourishment be- 
 comes more abundant and the child begins to increase rapidly 
 in weight, the quantity of carbonic acid exhaled is very small. 
 
 After the respiratory function becomes fully established, 
 it is probable, from the greater number of respiratory move- 
 ments in early life, that the production of carbonic acid, in 
 proportion to the weight of the body, is greater in infancy 
 than in adult life. Direct observations, however, are wanting 
 on this point. 
 
 The observations of Andral and G-avarret 1 show the com- 
 parative exhalation of carbonic acid in the male, from the age 
 of twelve to eighty-two, and give the results of a single obser- 
 vation at the age of one hundred and two years. They show 
 an increase in the absolute quantity exhaled from the age of 
 twelve to thirty-two ; a slight diminution from thirty-two to 
 sixty ; and a considerable diminution from sixty to eighty- 
 two. These results are given in the following table : 
 
 Carbonic acid exhaled per hour. 
 
 In boys from twelve to sixteen years 915 cubic inches. 
 
 In young men from seventeen to nineteen years 1,220 " " 
 
 In men from twenty-five to thirty-two years 1,343 " " 
 
 In men from thirty-two to sixty years 1,220 " " 
 
 In men from sixty-three to eighty-two years 933 " " 
 
 In an old man of one hundred and two years 671 " ** 
 
 1 Loc. cit. 
 
432 EESPIEATION. 
 
 Taking into consideration the increase in the weight of 
 the body with age, it is evident that the respiratory activity 
 is much greater in youth than in adult life. Andral and 
 Gavarret do not give the weight of the subjects of their 
 observations, but as the weight generally does not diminish 
 after maturity, there can be no doubt that there is a rapid 
 diminution in the relative quantity of carbonic acid produced 
 in old age. 
 
 Scharling, in a series of observations on a boy nine years 
 of age, weighing 48*5 pounds, an adult of twenty-eight, and 
 one of thirty-five years, the latter weighing 163*6 pounds, 
 showed that the respiratory activity in the child was nearly 
 twice as great, in proportion to his weight, as the average in 
 the adults. 1 It is seen from the observations of Andral and 
 Gavarret, that the absolute increase in the exhalation of car- 
 bonic acid from childhood to adnlt life is very slight in com- 
 parison with the natural increase in the weight of the body ; 
 showing that, proportionately, the exhalation of carbonic acid 
 is greater in early life. 
 
 Influence of Sex. All observers have found a marked 
 difference between the sexes, in favor of the male, in the 
 proportion of carbonic acid exhaled. Andral and Gavarret 
 noted an absolute difference of about forty-five cubic inches 
 per hour, but did not take into consideration the difference 
 in the weight of the body. Scharling, taking the proportion 
 exhaled to the weight of the body, noted a marked difference 
 in favor of the male. 
 
 The difference in the degree of muscular activity in the 
 sexes is sufficient to account for the greater evolution of car- 
 bonic acid in the male, for this principle is exhaled in pro- 
 
 1 SCHARLING, Recherches sur la Quantite d'Acide Carbomque expire par VHomme. 
 Annales de Chimie et de Physique, 3me serie, tome viii., p. 486. 
 
 Taking the proportion of carbonic acid exhaled per hour to the weight, in 
 the man 28 years of age, as 1, in the man 35 years of age the proportion was 1'14, 
 and in the boy 9 years of age, 2'07. P. 489. 
 
INFLUENCE OF DIGESTION. 433 
 
 portion to the muscular development of the individual ; but 
 there is an important difference connected with the variations 
 with age, which depends upon the condition of the generative 
 system of the female. 
 
 The absolute increase in the evolution of carbonic acid 
 with age in the female is arrested at the time of puberty, 
 and remains stationary during the entire menstrual period, 
 provided the menstrual now occur with regularity. During 
 this time, the average exhalation per hour is 714 cubic inches. 
 After the cessation of the menses, the quantity gradually 
 increases, until at the age of sixty it amounts to 915 cubic 
 inches per hour. From the age of sixty to eighty-two, the 
 quantity diminishes to 793, and finally to 670 cubic inches. 
 
 When the menses are suppressed, there is an increase in 
 the exhalation of carbonic acid, which continues until the flow 
 becomes reestablished. In a case of pregnancy the exhalation 
 was increased to about 885 cubic inches. 1 
 
 Influence of Digestion. Almost all observers agree that 
 the exhalation of carbonic acid is increased during digestion. 
 Lavoisier and Seguin found that in repose and fasting, the 
 quantity exhaled per hour was 1,210 cubic inches ; which was 
 raised to 1,800 and 1,900 during digestion. 3 Numerous ex- 
 periments on animals have confirmed this statement. A very 
 interesting series of observations on this point was made by 
 Yierordt upon his own person. Taking his dinner at from 
 12*30 to 1 P. M., having noted the frequency of the pulse 
 and respirations and the exhalation of carbonic acid at 12, 
 he found at 2 p. M. the pulse and respirations increased in 
 frequency, the volume of expired air augmented, and that 
 the carbonic acid exhaled had increased from 15*77 to 18'22 
 cubic inches per minute. In order to ascertain that this 
 
 1 The above facts, showing the peculiar influence of the condition of the genera- 
 tive organs in the female, are among the most important results of the observa- 
 tions of Andral and Gavarret. Loc. cit. 
 
 a Cyclopaedia of Anatomy and Physiology, vol. iv., part i., pp. 346, 347. 
 28 
 
434 RESPIRATION. 
 
 variation did not depend upon the time of day, inde- 
 pendently of the digestive process, he made a comparison at 
 12 M., at 1 and at 2 p. M., without taking food, which showed 
 no notable variation, either in the pulse, number of respira- 
 tions, volume of expired air, .or quantity of carbonic acid 
 exhaled. 1 
 
 It is unnecessary to cite other observations on this point, 
 unless we mention those of Prout and Coathupe, which 
 seemed to show a diminution in the exhalation of carbonic 
 acid during digestion. Dr. John Reid, in the Cyclopaedia 
 of Anatomy and Physiology r , points out the source of error 
 in these observations. 2 Prout did not estimate the actual 
 quantity of gas exhaled, but only its proportion in the ex- 
 pired air ; and it has been demonstrated that in digestion the 
 volume of the expirations is notably increased. Coathupe, 
 in the observations on his own person, took a pint of wine 
 with his dinner. As it has been shown by experiment that 
 alcohol has the effect of rapidly reducing the exhalation of 
 carbonic acid, this observation does not represent the simple 
 influence of digestion. 
 
 There can be no doubt, then, that the exhalation of car- 
 bonic acid is notably increased during the functional activity 
 of the digestive system. 
 
 The effect of inanition is to gradually diminish the exha- 
 lation of carbonic acid. This fact was long since demon- 
 strated by Spallanzani on caterpillars, and Marchand on 
 frogs; but observations on the warm-blooded animals are 
 more applicable to the human subject. Bidder and Schmidt 
 noted the daily production of carbonic acid in a cat which 
 was subjected to eighteen days of inanition, at the end of 
 which time it died. The quantity diminished gradually from 
 day to day, until just before death it was reduced a little 
 more than one-half. Dr. Smith 8 noted in his own person 
 
 1 Cyclopaedia, of Anatomy and Physiology, vol. iv., part i., pp. 346, 347. 
 
 2 Ibid., article Respiration. 
 
 3 Op. dt., p. 696. 
 
INFLUENCE OF DIET. 435 
 
 the influence of a fast of twenty-seven hours. There was a 
 marked diminution in the quantity of air respired, in the 
 quantity of vapor exhaled, in the number of respirations, and 
 in the rapidity of the pulse. The exhalation of carbonic acid 
 was diminished one-fourth. An interesting point in this 
 observation was the fact that the quantity was as small four 
 and a half hours after eating, as at the end of the twenty- 
 seven hours. " An increase of carbonic acid in the absence 
 of food, at or near the period when it is usually increased by 
 food," was also noted in the experiment of Dr. Smith. 
 
 Influence of Diet. Regnault and Reiset, in their experi- 
 ments on animals, studied the effect of different kinds of diet 
 upon the relations of the quantity of oxygen absorbed to the 
 carbonic acid exhaled. About the only conclusive and ex- 
 tended series of investigations on the influence of diet upon 
 the absolute quantity of carbonic acid exhaled are those 
 of Dr. Smith. This observer made a large number of 
 experiments on the influence of various kinds of food, and 
 extended his inquiries into the influence of certain beverages, 
 such as tea, coffee, cocoa, malt and fermented liquors. 1 We 
 have already fully described the method employed in these 
 experiments, and the conclusions, which are of great interest 
 and importance, are very exact and reliable. 
 
 Dr. Smith divides food into two classes, one which in- 
 creases the exhalation of carbonic acid, which he calls respi- 
 ratory excitants, and the other, which diminishes the exhala- 
 tion, which he calls non-exciters. 
 
 The following are the results of a large number of care- 
 fully conducted observations upon four persons : 
 
 " The excito-respiratory are nitrogeneous food, milk and 
 its components, sugars, rum, beer, stout, the cereals, and 
 potato. 
 
 " The non-exciters are starch, fat, certain alcoholic corn- 
 
 1 On the Action of Foods on the Respiration during the Primary Processes of 
 Digestion. 'Philosophical Transactions, 1859, p. 715 
 
4:36 . KESPIEATIOK. 
 
 pounds, the volatile elements of wines and spirits, and coffee 
 leaves. 
 
 " Kespiratory excitants have a temporary action ; but the 
 action of most of them commences very quickly, and attains 
 its maximum within one hour* 
 
 " The most powerful respiratory excitants are tea and 
 sugar ; then coffee, rum, milk, cocoa, ales, and chicory ; then 
 casein and gluten, and lastly, gelatin and albumen. The 
 amount of action was not in uniform proportion to their 
 quantity. Compound aliments, as the cereals, containing 
 several of these substances, have an action greater than that 
 of any of their elements. 
 
 " Most respiratory excitants, as tea, coffee, gluten, and 
 casein, cause an increase in the evolution of carbon greater 
 than the quantity which they supply, whilst others, as sugar, 
 supply more than they evolve in this excess, that is, above 
 the basis. No substance containing a large amount of car- 
 bon evolves more than a small portion of that carbon in the 
 temporary action occurring above the basis line, and hence 
 a large portion remains unaccounted for by these experi- 
 ments." 
 
 The comparative observations of Dr. Smith upon the four 
 persons who were the subjects of experiment demonstrated 
 one .very important fact : namely, that the action of different 
 kinds of food upon respiration is modified by idiosyncrasies, 
 and the tastes of different individuals. For example, in ex- 
 periments on his own person, certain articles which were 
 agreeable to him excited the exhalation of carbonic acid ; but 
 in experimenting with the same articles upon Mr. Moul, to 
 whom they were distasteful, he found the respiratory action 
 diminished. 
 
 Quite a number of observers have noted the influence of 
 alcohol upon the products of respiration ; but the results of 
 experiments have not been entirely uniform. Prout ob- 
 served a constant diminution in the quantity of carbonic acid 
 exhaled, under the influence of alcohol. This has been confirm 
 
INFLUENCE OF DIET. 437 
 
 ed by the observations of Horn, Yierordt, and many others ; but 
 Hervier and Saint-Lager assert that the use of alcohol increases 
 the exhalation of carbonic acid. 1 In the experiments of Prout, 
 a small quantity of wine taken fasting caused the proportion 
 of carbonic acid in the expired air to fall immediately from 
 4 to 3 parts per 100. During the four hours following, it 
 oscillated between 3*40, 3*10, and 3. The administration of 
 a second dose, followed by some symptoms of intoxication, 
 diminished the proportion to 2*70 per 100. Dr. Fyfe, of 
 Edinburgh, showed that the depressing .effects of an alcoholic 
 excess were continued into the following day. 2 Dr. Ham- 
 mond, in an elaborate and excellent paper on the effects of 
 alcohol and tobacco on the human system, observed a dimin- 
 ished exhalation of carbonic acid following the ingestion of 
 twelve drachms of alcohol daily for five days, both when the 
 system was kept at the normal standard of weight, etc., by 
 the ingestion of the habitual quantity of food, when the 
 weight was diminished by an insufficient diet, and when the 
 weight was increased by an excessive diet. 3 
 
 The observations of Dr. Smith, which were all made 
 fasting, show a certain variation in the effects of different al- 
 coholic beverages. His results are briefly the following : 
 
 " Brandy, whiskey, and gin, and particularly the latter, 
 almost always lessened the respiratory changes recorded, 
 whilst rum as commonly increased them. Rum and milk 
 had a very pronounced and persistent action, and there was 
 no effect on the sensorium. Ale and porter always increased 
 them, whilst sherry wine lessened the quantity of air in- 
 spired, but slightly increased the carbonic acid evolved. 
 
 1 MILNE-EDWARDS, Physiologic, Paris, 1857, tome ii., p. 535. 
 
 2 Ibid. Prout took cognizance only of the proportion of carbonic acid in the 
 expired air, and not of the absolute quantity exhaled in a given time. 
 
 s WM. A. HAMMOND, M. D., The Physiological Effects of Alcohol and Tobacco 
 upon the Human System. Physiological Memoirs, Philadelphia, 1863. In this 
 valuable paper the author considers the general influence of alcohol and tobacco 
 on nutrition, as indicated by the production of urea, carbonic acid, and other ex- 
 crementitious principles, and the variations in the weight of the body. 
 
438 RESPIRATION. 
 
 " The volatile elements of alcohol, gin, rum, sherry, and 
 port-wine, when inhaled, lessened the quantity of carbonic 
 acid exhaled, and usually lessened the quantity of air inhaled. 
 The effect of fine old port-wine was very decided and uni- 
 form ; and it is known thatwines and spirits improve in 
 aroma and become weaker in alcohol by age. The excito- 
 respiratory action of rum is probably not due to its volatile 
 elements." 1 
 
 From these facts, it would seem that the most constant 
 effect of alcohol, and alcoholic liquors, such as wines and 
 spirits, is to diminish the exhalation of carbonic acid. This 
 effect is almost instantaneous, when the articles are taken 
 into the stomach fasting ; and when taken with the meals, 
 the increase in carbonic acid which habitually accompanies 
 the process of digestion is materially lessened. Rum, which 
 Dr. Smith found to be a respiratory excitant, is an exception 
 to this rule. Malt liquors seem to increase the exhalation of 
 carbonic acid. With regard to alcohol itself, Dr. Smith 
 says : " The action of pure alcohol was much more to increase 
 than to lessen the respiratory changes, and sometimes the 
 former effect was well pronounced." a 
 
 Regarding as one of the great sources of carbonic acid 
 the development of this principle in the tissues, whence it is 
 taken up by the blood, Dr. Smith attributes the grateful and 
 soothing influence of tea, coffee, eau sucree, and the other 
 beverages which he classes as respiratory excitants, to their 
 action in facilitating the removal of this principle from the 
 system. The presence of carbonic acid in the tissues and 
 in the blood produces a sense of malaise, or depression, 
 which we should suppose would be relieved by any thing 
 which facilitates its elimination. It is undoubtedly this in- 
 definite sense of discomfort which induces the act of sighing, 
 by which the air in the lungs is more effectually renovated. 
 This view is sustained by the fact that intellectual fatigue 
 and mental emotions diminish the exhalation of carbonic acid. 
 
 1 Op. cit., p. 731. 2 Loc. tit. 
 
INFLUENCE OF MUSCULAR ACTIVITY. 439 
 
 Apjohn cites an instance in which the proportion of carbonic 
 acid in the expirations was reduced to 2*9 parts per 100 under 
 the influence of mental depression. 1 
 
 Dr. Hammond could not determine any modification in the 
 exhalation of carbonic acid under the influence of tobacco. 2 
 
 Influence of Sleep. All who have directed attention to 
 the influence of sleep upon the respiratory products have 
 noted a marked diminution in the exhalation of carbonic 
 acid ; but we again recur to the experiments of Dr. Smith 
 for exact information on this point. Dr. Smith estimated 
 the quantity of carbonic acid exhaled during six hours of 
 sleep, at night, at 4,126 cubic inches. According to this 
 observer, the quantity during the night is to the quantity 
 during the day, in complete repose, as 10 is to 18. During 
 a light sleep, the exhalation was 10*32, and during profound 
 sleep, 9'52 cubic inches per minute. 
 
 We have alluded to the great diminution in the quantity 
 of oxygen consumed in hibernating animals, while in a torpid 
 condition. Regnault and Reiset found that a marmot in 
 hibernation consumed only ^ of the oxygen which he used 
 in his active condition. In the same animal they noted an 
 exhalation of carbonic acid equal to but little more than half 
 the weight of oxygen absorbed ; so that in this condition the 
 diminution in the exhalation of carbonic acid is proportion- 
 ately even greater than in the consumption of oxygen. 3 
 
 Influence of Muscular Activity. All observers, except 
 Prout, 4 agree that there is a considerable increase in the 
 
 1 MILNE-EDWARDS, Physiologic, tome ii., p. 535. 
 a Op. cit. 
 
 1 REGNAULT ET REISET, Annales de Chimie et de Physique, 3me serie, tome 
 xxvi., p. 446. The marmot consumed in five days 13,088 grammes of oxygen, 
 raid exhaled 7,1Y4 grammes of carbonic acid. 
 
 4 Prout only noted the proportion of carbonic acid in the expired air ; and as 
 exercise has the effect of immediately and largely increasing the number of respi- 
 
440 RESPIRATION. 
 
 exhalation of carbonic acid during and immediately follow- 
 ing muscular exercise. In insects, Mr. Newport has found 
 that a greater quantity is sometimes exhaled in an hour of 
 violent agitation, than in twenty-four hours of repose. In a 
 drone, the exhalation in twentytfour hours was O30 of a cubic 
 inch, and during violent muscular exertion the exhalation 
 in one hour was O34:. 1 Lavoisier recognized the great in- 
 fluence of muscular activity upon the respiratory changes. 
 In treating of the consumption of oxygen, we have quoted 
 his observations on the relative quantities of air vitiated in 
 repose and activity. 
 
 Yierordt, in a number of observations on the human 
 subject, ascertained that moderate exercise increased the 
 average quantity of air respired per minute by nearly nineteen 
 cubic inches, and that there was an increase of 1*197 cubic 
 inches per minute in the absolute quantity of carbonic acid 
 exhaled. 2 
 
 The following results of the experiments of Dr. Edward 
 Smith on this subject are very definite and satisfactory : 
 
 In walking at the rate of two miles an hour, the exhala- 
 tion of carbonic acid during one hour was equal to the quan- 
 tity produced during If hour of repose, with food, and 2J 
 hours of repose, without food. 
 
 "Walking at the rate of three miles per hour, one hour 
 was equal to 2J hours with, and 3 j- hours without food. 
 
 One hour's labor at the tread-wheel, while actually work- 
 ing the wheel, was equal to 4^ hours of rest with food, and 6 
 hours without food. 3 
 
 The various observers we have cited have remarked that 
 
 ratory movements and the quantity of air passing through the lungs, and as we 
 have seen the quantity of carbonic acid in the expired air is increased in propor- 
 tion to the length of time that the air remains in the lungs, we can easily see the 
 source of error in his observations. 
 
 * MILNE-EDWARDS, Physiologic, tome ii., p. 530. 
 
 2 Cyclopaedia of Anatomy and Physiology, vol. iv., part i., p. 348. 
 
 ' Op. cit., p. 713. 
 
INFLUENCE OF MOISTURE AND TEMPEKATUKE. 441 
 
 when muscular exertion is carried so far as to produce great 
 fatigue and exhaustion, the exhalation of carbonic acid is 
 notably diminished. 
 
 Influence of_ Moisture and Temperature. Lehmann has 
 shown that the exhalation of carbonic acid is much greater 
 in a moist than in a dry atmosphere. 1 This conclusion was 
 the result of a number of experiments on birds and animals 
 confined in air at different temperatures and different degrees 
 of moisture. He found that 35^- oz. av. weight of rabbits, at 
 a temperature of about 100 Fahr., exhaled during an hour 
 before noon, in a dry air, about 15 cubic inches of carbonic 
 acid ; while in a moist air, at the same temperature, the ex- 
 halation was about 22 cubic inches. 
 
 Disregarding observations on the influence of temperature 
 in cold-blooded animals, as inapplicable to the human sub- 
 ject, it has been ascertained that the exhalation of carbonic 
 acid is much greater at low than at high temperatures, within 
 the limits of heat and cold that are easily borne by the human 
 subject ; thus following the rule which governs the consump- 
 tion of oxygen. Crawford, in his experiments on animal heat, 
 was the first to call attention to this fact. 2 Since then it 
 has been confirmed by numerous observations on animals. 
 
 The experiments of Vierordt on the human subject show 
 that there is an increase in the exhalation of carbonic acid of 
 about one-sixth, under the influence of a moderate diminution 
 in temperature. In these observations, the low temperatures 
 ranged between 37*5 and 59, and the high temperatures be- 
 tween 60-5 and 75*5 Fahr. He found the quantity of air 
 taken into the lungs slightly increased at low temperatures. 
 The absolute quantity of carbonic acid exhaled per minute 
 was 18*27 cubic inches for the low temperatures, and 15*73 
 cubic inches for the high temperatures. 3 
 
 1 LEHMANN, Physiological Chemistry, Philadelphia, 1855, vol. ii., p. 444. 
 3 MILNE-EDWARDS, op. cil. f p. 548. 
 3 Ibid., p. 551. 
 
442 RESPIRATION. 
 
 Influence of the /Season of the Year. It has been pretty 
 well established by the researches of Dr. Smith, that spring 
 is the season of the greatest, and fall the season of the least 
 activity of the respiratory function. 
 
 The months of maximum a*e : January, February, March, 
 and April. 
 
 The months of minimum are : July, August, and a part 
 of September. 
 
 The months of decrease are : June and July. 
 
 The months of increase are: October, November, and 
 December. 1 
 
 "W. F. Edwards, in 1819, showed in a marked manner 
 this influence of the seasons upon the respiratory phenomena 
 in birds. In a series of very curious observations, which he 
 repeatedly verified, it was demonstrated that the increase in 
 the activity of respiration during the winter was to a certain 
 extent independent of the immediate influence of the sur- 
 rounding temperature. In the month of January he confined 
 six yellow-hammers in a receiver containing 71*4 cubic inches 
 of air, carrying the temperature to from 69 to 70 Fahr. 
 The mean duration of their life was 62 minutes 25 seconds. 
 In the months of August and September he repeated the ex- 
 periment on thirteen birds of the same species, at the same 
 temperature. The mean duration of life was 82 minutes. 3 
 
 These experiments have an important bearing on our 
 views concerning the essential nature of the respiratory func- 
 tion. They seem to indicate that the respiratory processes 
 are intimately connected with nutrition. Like the other nu- 
 tritive phenomena, they undoubtedly vary at different sea- 
 sons of the year, and are to a certain extent independent of 
 sudden and transitory conditions. During the winter, more 
 air is habitually used than in summer, and the respiratory 
 
 1 Resume de Recherches Experimental^ sur la Respiration. Journal de la 
 Physiologic, 1860, tome iii., p. 519. 
 
 a W. F. EDWARDS, De V Influence des Agens Physiques sur la Vie, Paris, 1824, 
 p, 200. 
 
RELATIONS BETWEEN OXYGEN AND CARBONIC ACID. 443 
 
 processes cannot be immediately brought down to the sum- 
 mer standard by a mere elevation of temperature. 
 
 Observations on the influence of barometric pressure are 
 not sufficiently definite in their results to warrant any exact 
 conclusions. 
 
 Some physiologists have attempted to fix certain hours of 
 the day when the exhalation of carbonic acid is at its maxi- 
 mum, or at its minimum ; but the respiratory activity is in- 
 fluenced by such a variety of conditions, that it is impossible 
 to do this with any degree of accuracy. 
 
 Relations between the Quantity of Oxygen consumed and the 
 Quantity of Carbonic Acid exhaled. 
 
 Oxygen unites with carbon in certain proportions, to form 
 carbonic acid gas, the volume of which is precisely equal to 
 the volume of the oxygen which enters into its composition. 
 In studying the relations of the volumes of these gases in 
 respiration, we have a guide in the comparison of the volumes 
 of the inspired and expired air. It is now generally recog- 
 nized that the volume of air expired is less, at an equal tem- 
 perature, than the volume of air inspired. Assuming, then, 
 that the changes in the expired air, as regards nitrogen, and 
 all gases except oxygen or carbonic acid, are insignificant, it 
 must be admitted that a certain quantity of the oxygen con- 
 sumed by the economy is unaccounted for by the oxygen 
 which enters into the composition of the carbonic acid ex- 
 haled. "We have already noted that from -fa to -fa, or about 
 1'4: to 2 per cent, of the inspired air is lost in the lungs ; ' or 
 it may be stated, in general terms, that the oxygen absorbed 
 is equal to about five per cent, of the volume of air inspired, 
 and the carbonic acid exhaled only about four per cent. A 
 certain amount of the deficiency in volume of the expired air 
 is then to be accounted for by a deficiency in the exhalation 
 of carbonic acid. 
 
 1 Vide page 405. 
 
RESPIRATION. 
 
 The experiments of Kegnault and Eeiset, to which fre- 
 quent reference has been made, have a most important bear- 
 ing on the question under consideration. As these observers 
 were able to carefully measure the entire quantities of oxygen 
 consumed and carbonic acid produced in a given time, the 
 relation between the two gases was kept constantly in view. 
 They found great variations in this relation, mainly dependent 
 upon the regimen of the animal. The total loss of oxygen 
 was found to be much greater in carnivorous than in herbiv- 
 orous animals ; and in animals that could be subjected to a 
 mixed diet, by regulating the food, this was made to vary be- 
 tween the two extremes. The mean of seven experiments on 
 dogs showed that for every 1,000 parts of oxygen consumed, 
 Y45 parts were exhaled in the form of carbonic acid. In six 
 experiments on rabbits, the mean was 919 for every 1,000 
 parts of oxygen. 1 
 
 In animals fed on grains, the proportion of carbonic acid 
 exhaled was greatest, sometimes passing a little beyond the 
 volume of oxygen consumed. 
 
 " The relation is nearly constant for animals of the same 
 species which are subjected to a perfectly uniform alimenta- 
 tion, as is easy to realize as regards dogs ; but it varies not- 
 ably in animals of the same species, and in the same animal, 
 submitted to the same .regimen, but in which we cannot reg- 
 ulate the alimentation, as in fowls." 2 
 
 When herbivorous animals were entirely deprived of food, 
 the relation between the gases was the same as in carnivorous 
 animals. 
 
 The final result of the experiments of Eegnault and 
 Reiset was, that the " relation between the oxygen contained 
 in the carbonic acid and the total oxygen consumed, varies, 
 in the same animal, from 0'62 to 1*04, according to the regi- 
 men to which he is subjected." 
 
 1 REGXAuti and REISET, Recherches Chimiques sur la Respiration, Annafai 
 de Chimie et de Physique, 3me serie, tome xxvi. 
 
 2 Ibid., p. 514. 
 
SOUECES OF CARBONIC ACID EXHALED. 445 
 
 These observations on animals have been confirmed in 
 the human subject by M. Doyere, who found a great varia- 
 tion in the relations of the two gases in respiration ; the vol- 
 ume of carbonic acid exhaled varying between 1-087 and 
 O862 for 1 part of oxygen consumed. 1 
 
 The destination of the oxygen which is not represented 
 in the carbonic acid exhaled is obscure. Some have thought 
 that it unites with hydrogen to form water ; but there 
 is not sufficient evidence of the formation of water in the 
 economy, for researches have failed to show that there is 
 more thrown off from the body than is taken in with food 
 and drink. 
 
 The variations in the relative volumes of oxygen con- 
 sumed and carbonic acid produced in respiration are not 
 favorable to the hypothesis that the carbonic acid is the re- 
 sult of a direct action of oxygen upon carbonaceous matters. 
 We should hardly expect a definite relation to exist between 
 these two gases in respiration, when we find carbonic acid 
 exhaled in the absence of oxygen, as has been shown by the 
 experiments of "W. F. Edwards and Geo. Liebig. 
 
 Sources of Carbonic Acid in the Expired Air. All the 
 carbonic acid in the expired air comes from the venous blood, 
 where it exists in two forms : in a free state in simple solution, 
 or at least in a state of very feeble combination, and in union 
 with bases, forming the carbonates and bicarbonates. That 
 which exists in solution in the blood is simply displaced by 
 the oxygen of the air and exhaled. The alkaline carbonates 
 and bicarbonates of the blood, coming to the lungs, meet 
 with pneumic acid (discovered by Yerdeil in 1851), and are 
 decomposed, giving rise to a further evolution of gas. It is 
 pneumic acid which gives the constant acid reaction to the 
 tissue of the lungs. This principle is found in the pulmo- 
 nary parenchyma at all periods of life, from which it may 
 be extracted by the proper manipulations, and obtained 
 
 1 MILNE-EDWARDS, Physiologie, tome ii., p. 694. 
 
446 RESPIRATION. 
 
 in a crystalline form. Its quantity is not very great. The 
 lungs of a female who suffered death by decapitation con- 
 tained about 0-77 of a grain. 1 
 
 The action of pneumic acid upon the bicarbonates in the 
 blood is exemplified in a marked manner by certain experi- 
 ments of Bernard. When bicarbonate of soda is injected 
 into the jugular of a living animal, a rabbit, for example, it 
 is decomposed as fast as it gets to the lungs, and carbonic 
 acid is evolved. This experiment produces no inconvenience 
 to the animal when the bicarbonate is introduced slowly ; but 
 when it is injected in too great quantity, the evolution 
 of gas in the lungs is so great as to fill the pulmonary struc- 
 ture and even the heart and great vessels, and death is the 
 result. 3 
 
 Exhalation of Watery Vapor. The fact that the expired 
 air contains a considerable quantity of watery vapor has long 
 been recognized ; and most of the earlier experimenters who 
 directed their attention to the phenomena of respiration 
 made the estimation of the quantity exhaled, and the laws 
 which regulate pulmonary transpiration, the subject of in- 
 vestigation. It is evident that there must be many cir- 
 cumstances materially influencing this process, such as the 
 hygrometric condition of the atmosphere, temperature, ex- 
 tent of respiratory surface, etc., which are of sufficient impor- 
 tance to demand special consideration. In many points of 
 view, also, it is interesting to know the absolute quantity of 
 exhalation from the lungs. 
 
 1 ROBIN and VERDEIL, Chimie Anatomique et Physiologique, Paris, 1853, tome 
 ii., p. 460. 
 
 2 Op. tit., tome i., p. 165. These experiments referred to the decomposition of 
 cyanide of potassium in the lungs, as well as bicarbonate of soda. They were 
 published in the Archives Generates in 1848, before the discovery of pneumic 
 acid, and Bernard expressed surprise that the two substances experimented upon, 
 which required an acid for their decomposition, should be decomposed in an al- 
 kaline fluid like the blood. Though made without a knowledge of the existence 
 of pneumic acid, the observations none the less illustrated its physiological 
 action. 
 
EXHALATION OF WATERY VAPOK. 447 
 
 When the surrounding atmosphere has a temperature below 
 40 or 43 Fahr., a distinct cloud is produced by the condensa- 
 tion of the vapor of the breath. By breathing upon any 
 polished surface, it is momentarily tarnished by the condensed 
 moisture. Though the fact that watery vapor is contained in 
 the breath is thus easily demonstrated, the estimation of its 
 absolute quantity presents difficulties which were not overcome 
 by the older physiologists. Hales collected the vapor of the 
 breath by expiring through wood ashes, 1 which was the first 
 attempt to estimate the amount of this exhalation by absorp- 
 tion. With the present improved methods of analysis there 
 are many very accurate means of estimating watery vapor. 
 One method is by the use of Liebig's bulbs filled with sul- 
 phuric acid, or tubes filled with chloride of calcium, both of 
 which articles have a great avidity for water. From a large 
 number of observations on his own person and eight others, 
 collecting the water by sulphuric acid, Yalentin makes the 
 following estimate of the weight of water exhaled from the 
 lungs in twenty-four hours : 
 
 In his own person, the exhalation in 24 hours was 6,055 
 grains. 
 
 In a young man of small size, the quantity was 5,042 
 grains. 
 
 In a student rather above the ordinary height, the quan- 
 tity was 11,930 grains. 
 
 The mean of his observations gave a daily exhalation of 
 8,333 grains, or about 1 J- Ib. av. 2 
 
 1 HALES, Statical Essays, London, 1739, vol. ii., p. 326. Sanctorius, in 
 1614, was the first (MILNE-EDWARDS, Physiologic, vol. ii., p. 602) to attempt the 
 estimation of the exhalation of vapor of water from the body by comparing the 
 gam. in weight due to the ingestion of aliments with the loss by transpiration. 
 We pass over the estimates of Lavoisier and Seguin, Keill, Abernethy, and 
 others, and give only the more exact results obtained by Valentin. Dalton, 
 estimating the quantity of air passing through the lungs in respiration, and as- 
 suming that it passes out of the lungs saturated with watery vapor, makes an es- 
 timate of the total exhalation in the twenty-four hours, which corresponds pretty 
 closely with the results obtained by Valentin. 
 
 2 MILNE-EDWARDS, op. cit., p. 621. 
 
448 RESPIRATION. 
 
 The extent of respiratory surface has a very marked in- 
 fluence on the quantity of watery vapor exhaled. This fact 
 is very well shown by a comparison of the exhalation in the 
 adult and in old age, when the extent of respiratory surface 
 is much diminished. Barral found the exhalation in an old 
 man less than half that of the adult. 1 
 
 It is evident that the absolute quantity of vapor exhaled 
 is increased when respiration is accelerated. 
 
 The quantity of water in the blood also exerts an impor- 
 tant influence. Yalentin found that the pulmonary transpira- 
 tion was more than doubled in a man immediately after drink- 
 ing a large quantity of water. 1 
 
 The vapor in the expired air is derived from the entire 
 surface which is traversed in respiration, and not exclusively 
 from the air-cells. The air which passes into the lungs de- 
 rives a certain amount of moisture from the mouth, nares, 
 and trachea. The great vascularity of the mucous membranes 
 in these situations, as well as of the air-cells, and the great 
 number of mucous glands which they contain, serve to keep 
 the respiratory surfaces continually moist. This is important, 
 for only moist membranes allow the free passage of gases, 
 which is of course essential to the process of respiration. 
 
 Exhalation of Ammonia. The most recent and extended 
 observations on the exhalation of ammonia by the lungs, are 
 those of Dr. Richardson, to which we have already alluded 
 in treating of the coagulation of the blood. In more than a 
 thousand experiments, made upon persons of both sexes, and 
 on various of the inferior animals, with but one exception, a 
 notable quantity of ammonia was found in the expired air. 
 Dr. Richardson found the quantity very variable at different 
 times of the day. At certain periods it is absent. 
 
 1 MILNE-EDWARDS, op. cit., p. 625, note. 
 
 8 Ibid., p. 607, note. It has not been thought necessary to discuss the in 
 fiuences of dry and moist atmosphere, barometric pressure, and temperature, 
 ich are urel hsical in their character. 
 
 iiueuues 01 ury auu moist aimospnere, uai 
 which are purely physical in their character. 
 
EXHALATION. OF ORGANIC MATTER. 449 
 
 In a number of observations made on his own person, the 
 following variations were noted : 1 
 
 On rising in the morning, after a sound night's rest, the 
 breath contained no ammonia. 
 
 In the evening, when fatigued and exhausted, and after 
 exercise, the exhalation was generally considerable. 
 
 During a high temperature the exhalation is considerable, 
 especially after exercise; but during cold weather the exha- 
 lation is very slight, or it may be absent altogether. 
 
 The amount of ammonia exhaled is greatest at the end 
 of an expiration: If short and rapid expirations be made, 
 the exhalation ceases until the respirations become deeper 
 and more prolonged. 
 
 Ammonia has long been recognized as an exhalation from 
 the human body in health, from the skin as well as the lungs. 
 Dr. Richardson calls attention in his essay to the observa- 
 tions of Mr. Reade, Dr. Reuling, Yiale and Latini, and 
 others on this subject. Reuling has shown that the quantity 
 of ammonia in the expired air is increased in certain diseases, 
 particularly in uremia. 2 Its characters in the expired air 
 are frequently so marked, that patients who are entirely 
 unacquainted with the pathology of uremia sometimes 
 recognize an ammoniacal odor in their own breath. 
 
 Exhalation of Organic Matter, etc. The pulmonary sur- 
 face exhales a small quantity of organic matter. This has 
 never been collected in sufficient quantity to enable us to 
 recognize in it any peculiar or distinctive properties, but its 
 presence may be demonstrated by the fact that a sponge 
 completely saturated with the exhalations from the lungs, or 
 the vapor from the lungs condensed in a glass vessel, will 
 undergo putrefaction, a property distinctive of organic sub- 
 stances. 
 
 It is well known that certain substances which are only 
 
 1 The Cause of the Coagulation of the Blood, London, 1857, p. 360 et seq. 
 a In LEHMANN'S Physiological Chemistry, Philadelphia, 1855, vol. ii., p. 434. 
 29 
 
450 RESPIRATION. 
 
 occasionally found in the blood may be eliminated by the 
 lungs. Alcohol is partly removed from the system in this 
 way; and its presence, with certain odorous principles, in 
 the breath is pretty constant in those who take liquors ha- 
 bitually in considerable quantity. The odor of garlics, onions, 
 turpentine, and many other principles which are taken into 
 the stomach, may be recognized in the expired air. The 
 lungs are among the important organs for the elimination of 
 foreign matters from the system. 
 
 The action of the lungs in the elimination of certain gases, 
 which are poisonous in very small quantities when they are 
 absorbed in the lungs and carried to the general system in 
 the arterial blood, is very well shown by the experiments of 
 Bernard. Sulphuretted hydrogen, which produces death in 
 a bird when it exists in the atmosphere in the proportion of 
 1 to 800, may be taken into the stomach in solution with 
 impunity, and even be injected into the venous system ; in 
 both instances being eliminated by the lungs with great 
 promptness and rapidity. 1 Nysten showed that the carbonic 
 oxide, one of the most violent and rapid in its effects of any 
 of the poisonous gases when inhaled, could be injected into 
 the veins with impunity, by simply taking care to introduce 
 it only as rapidly as it is absorbed by the blood. 2 
 
 The lungs, then, while they present an immense and rap- 
 idly absorbing surface for volatile poisonous substances, are 
 capable of relieving the system of some of these substances 
 by exhalation, when they find their way into the veins. 
 
 1 BERNARD, Lemons sur les Effets des Substances Toxiques et Medicamenteuses, 
 Paris, 1857, p. 58. In an experiment on a dog of medium size, injecting a little 
 more than a fluid drachm of water saturated with sulphuretted hydrogen into the 
 jugular vein, the gas was detected almost instantly in the expired air, and the 
 animal suffered no inconvenience from the operation. The gas appeared in the 
 breath in sixty-five seconds, when about an ounce of the solution was injected 
 into the rectum. We have repeatedly verified the experiment of Bernard showing 
 the almost instantaneous elimination of this gas by the lungs, when injected into 
 the veins. 
 
 2 NYSTEN, Recherches de Physiologic, etc., Paris, 1811, p. 81 et seq. 
 
EXHALATION OF NITEOGEN. 451 
 
 Exhalation of Nitrogen. The latest and most accurate 
 direct experiments, particularly those of Regnault and Reiset, 
 show that the exhalation of a small quantity of nitrogen is a 
 pretty constant respiratory phenomenon. From a large num- 
 ber of experiments on dogs, rabbits, fowls, and birds, these ob- 
 servers came to the conclusion that when animals are subject- 
 ed to their habitual regimen, they exhale a quantity of nitrogen 
 equal in weight to from -^-$ to T V of. the weight of oxygen 
 consumed. In birds, during inanition, they sometimes observ 
 ed an absorption of nitrogen, but this was rarely seen in mam 
 mals. 1 Boussingault, by the indirect method, estimating the 
 nitrogen taken into the body and comparing it with the en- 
 tire quantity discharged, arrived at the same results in ex- 
 periments upon a cow. 2 Barral, by the same method, con- 
 firmed these observations by experiments on the human 
 subject. 3 
 
 In spite of the conflicting testimony of the older physi- 
 ologists, there can now be no doubt that, under ordinary 
 physiological conditions, there is an exhalation by the lungs 
 of a small quantity of nitrogen. 
 
 1 REGNAULT and REISET, op. cit., Annales de Chimie et de Physique, 3me 
 serie, tome xxvi., pp. 510, 511. 
 
 8 BOUSSINGAULT, Memoires de Chimie Agricole et de Physiologic, Paris, 1854, 
 pp. 1-24. 
 
 3 LONGET, Physiologic, Paris, 1861, tome i., p. 543. 
 
CHAPTEE XIII. 
 
 CHANGES OF THE BLOOD IN KESPERATION. 
 
 Difference in color between arterial and venous blood Comparison of the gases 
 in venous and arterial blood Observations of Magnus Analysis of the blood 
 for gases Kelative quantities of oxygen and carbonic acid in venous and ar- 
 terial blood Nitrogen of the blood Condition of the gases in the blood 
 Mechanism of the interchange of gases between the blood and the air in the 
 lungs General differences in the composition of arterial and venous blood. 
 
 IT is to be expected that the blood, receiving on the one 
 hand all the products of digestion, and on the other the 
 products of destructive assimilation or decay of the tissues, 
 connected with the lymphatic system, and exposed to the 
 action of the air in the lungs, should present important dif- 
 ferences in composition in different parts of the vascular 
 system. 
 
 In the first place, there is a marked difference in color, 
 composition, and properties, between the blood in the arte- 
 ries and in the veins; the change from venous to arterial 
 blood being effected almost instantaneously in its passage 
 through the lungs. The blood which goes to the lungs is a 
 mixture of the fluid collected from all parts of the body; 
 and we have seen that it presents great differences in its 
 composition in different parts of the venous system. In 
 some veins it is almost black, and in some nearly as red as in 
 the arteries. In the hepatic vein it contains sugar, and its 
 fibrin, albumen, and corpuscles are diminished ; in the portal 
 
CHANGES OF THE BLOOD EST RESPIRATION. 453 
 
 vein, during digestion, it contains materials absorbed from 
 the alimentary canal ; and finally, there is every reason to 
 suppose that parts which require different materials for their 
 nutrition, and produce different excrementitious principles, 
 exert different influences on the constitution of the blood 
 which passes through them. After this mixture of different 
 kinds of blood has been collected in the right side of the 
 heart and passed through the lungs, it is returned to the left 
 side, and sent to the system, thoroughly changed and reno- 
 vated, and, as arterial blood, has a uniform composition, as 
 far as can be ascertained, in all parts of the system. This 
 fact has been proven by the direct experiments of Beclard, 
 who analyzed blood from the abdominal aorta, the carotid, 
 temporal, occipital, crural, and epigastric arteries, in the 
 same animal during life, and found the composition identical 
 in all the specimens. His experiments were performed on 
 horses and dogs, and care was taken to draw but a small 
 quantity from each vessel, so as not to change the constitu- 
 tion of the fluid. 1 The change, therefore, which the blood 
 undergoes in its passage through the lungs, is the transfor- 
 mation of the mixture of venous blood from all parts of the 
 organism into a fluid of uniform character, which is capable 
 of nourishing and sustaining the function of every tissue and 
 organ of the body. 
 
 The capital phenomena of respiration, as regards the air 
 in the lungs, are loss of oxygen and gain of carbonic acid ; 
 the other phenomena being accessory and comparatively un- 
 important. As the blood is capable of holding gases in solu- 
 tion, in studying the essential changes which this fluid un- 
 dergoes in respiration, we look for them in connection with 
 the proportions of oxygen and carbonic acid before and after 
 it has passed through the lungs. In respiration, the most 
 marked effect on the venous blood is change in color. 
 
 1 Archives Generales de Medecine, 4me serie, tome sviii., p. 123 ; and BEBARD, 
 Physiologic, tome iii., p. 369. 
 
454: KESPIEATION. 
 
 Difference in Color between Arterial and Venous JSlood. 
 We have already considered this in treating of the proper- 
 ties of the blood, and will only take up in this connection the 
 cause of the remarkable change in the color of the blood 
 in the lungs. This change s instantaneous, and, long be- 
 fore the discovery of oxygen by Priestley, was recognized 
 by Lower, Goodwyn, and others, as due to the action of 
 the air. 
 
 The celebrated experiment of Bichat showed the effect 
 on the color of the blood in the arteries, of preventing the 
 access of fresh air to the lungs. This observer adapted a 
 stop-cock to the trachea of a dog, by which he could regu- 
 late the entrance of air into the lungs, and exposing the caro- 
 tid artery, adapted a small one to this vessel. "When he pre- 
 vented the air from getting to the lungs by closing the 
 stop-cock in the trachea, the blood became black in the 
 artery, but regained its florid hue when air was readmitted 
 to the lungs. 1 
 
 The influence of air in changing the color of venous blood 
 may be noted in blood which has been drawn from the body ; 
 as is exemplified by the red color of that portion of a clot, 
 or the surface of defibrinated venous blood, which is exposed 
 to the air. If we cut into a clot of venous blood, the interior 
 is almost black, but becomes red on exposure to the air for a 
 very few seconds. 
 
 We have been in the habit of illustrating the physiologi- 
 cal influence of the air on venous blood by the following 
 simple experiment : Removing the lungs of an animal (a 
 dog) just killed, the nozzle of a syringe is secured in the pul- 
 monary artery by a ligature, and a canula, connected with a 
 rubber tube which empties into a glass vessel, is secured in 
 the pulmonary vein. Adapting a bellows to the trachea, we 
 imitate the process of respiration ; and if defibrinated venous 
 blood be carefully injected through the lungs, it will be return- 
 
 1 XAY. BICHAT, Recherches Physiologiques sur la Vie et la Mart, 5 me Edition, 
 par F. MAGENDIE, Paris, 1829, p. 386. 
 
CHANGE IN COLOR OF THE BLOOD. 455 
 
 ed by the pulmonary vein with the bright red color of arterial 
 blood. When the artificial respiration is interrupted, the 
 blood passes through the lungs without change. 1 In expos- 
 ing the thoracic organs, and keeping up artificial respiration, 
 repeating the celebrated experiment of Robert Hook, made 
 before the Royal Society in 1664, we can see through the 
 thin walls of the auricles the red color of the blood on the 
 left side contrasting with the dark venous blood on the right. 
 
 Since the discovery of oxygen, it has been ascertained 
 that this is the only constituent of the air which is capable 
 of arterializing the blood. Priestley showed that venous 
 blood is not changed in color by nitrogen, hydrogen, or car- 
 bonic acid ; while all these gases, by displacing oxygen, will 
 change the arterial blood from red to black. 2 
 
 The elements of the blood which absorb the greater part 
 of the oxygen are the red corpuscles. While the plasma will 
 absorb, perhaps, twice as much gas as pure water, it has been 
 shown by Magnus and Gay-Lussac that the corpuscles will 
 absorb from ten to thirteen times as much. 3 By some the 
 proportion is put much higher. The red corpuscles may be 
 considered as the respiratory elements of the blood. It is 
 
 1 This demonstration is very striking, especially if we use a syringe with a 
 double nozzle, one point secured in the pulmonary artery, and the other simply 
 carrying the blood by a rubber tube into a glass vessel. Receiving the blood 
 which passes through the lungs, and that which simply passes through the tube, 
 into two tall glass vessels, the one is of a bright red, and the other retains its 
 dark color. In preparing for the experiment it is necessary, immediately after 
 removing the lungs from the animal, to inject them with a little defibrinated blood, 
 so as to remove the coagulating blood from the pulmonary capillaries, which would 
 otherwise become obstructed. The injection should be made gently and gradually, 
 to avoid extravasation. Defibrinated ox-blood may be used. The most conven- 
 ient way to secure the canula3 in the vessels is to push them into the pulmonary 
 artery through the right ventricle, and into the pulmonary vein through the left 
 auricle. 
 
 3 Carbonic oxide and nitrous oxide have a strong affinity for the blood-corpus- 
 cles, and become fixed in them, the former giving the blood a vivid red color. 
 Sugar and many salts will also redden venous blood. These agents, however, do 
 not impart the physiological properties of arterial blood. 
 
 9 ROBIN and VERDEIL, op. cit., tome i., p. 32. 
 
456 RESPIRATION. 
 
 undoubtedly true that the corpuscles, deprived of their natu- 
 ral plasma, are not changed in color by being exposed to the 
 air, or even to pure oxygen. Dr. Stevens, after removing 
 the serum from a clot by repeated washings with pure water, 
 found that the color remained J)lack when exposed to the air, 1 
 but was reddened by the addition of its serum, or certain 
 saline solutions. From this he reasoned that the red color of 
 arterial blood is due to the saline constituents of the plasma. 
 This is true ; but the saline constituents of the plasma affect 
 the color indirectly, by maintaining the anatomical integrity 
 of the corpuscles. If blood be received from a vein into pure 
 water, it remains almost black, however long it may be ex- 
 posed to the air, 2 from the fact that the corpuscles are de- 
 stroyed. These facts are only additional evidence of the 
 function of the red corpuscles in absorbing oxygen and car- 
 rying it to the tissues. According to the late researches 
 of Fernet, which have been confirmed by L. Meyer, the vol- 
 ume of oxygen fixed by the corpuscles is about twenty-five 
 times that which is dissolved in the plasma. 3 
 
 Comparison of the Gases in Venous and Arterial Blood. 
 The demonstration of the fact that free oxygen and carbonic 
 acid exist in the blood, with a knowledge of the relative pro- 
 portion of these gases in the blood before and after its pas- 
 sage through the lungs, is a point hardly second in importance 
 to the relative composition of the air before and after respi- 
 ration. The idea enunciated by Mayow about two hundred 
 years ago, that "there is something in the air, absolutely 
 
 1 WILLIAM STEVENS, Observations on the Healthy and Diseased Properties of the 
 Blood, London, 1832, p. 362; and Philosophical Transactions, 1835. 
 
 2 MILNE-EDWARDS, Physiologic, tome i., p. 475. 
 
 3 LONGET, Traite de Physiologie, Paris, 1861, tome i., p. 595. Fernet made a 
 great number of experiments on the influence of the various salts contained in the 
 serum on the absorbing power of the blood for gases. His observations had par- 
 ticular reference to carbonic acid, the solubility of which was influenced most by 
 saline principles. These experiments were confirmed and extended by Lothar 
 Meyer (Die Gase des Mutes). 
 
GASES IN VENOUS AND AETEEIAL BLOOD. 457 
 
 necessary to life, which is conveyed into the Uood" 1 excepting 
 that the vivifying principle is not named nor its other prop- 
 erties described, expresses what we now consider as one of 
 the two great principles of respiration. This is even more 
 strictly in accordance with fact than the idea of Lavoisier, 
 who supposed that all the chemical processes of respiration 
 took place in the lungs. Mayow also described the evolution 
 of gas from blood placed in a vacuum. 2 Many observers 
 have since succeeded in extracting gases from the* blood by 
 various processes. Sir Humphry Davy induced the evolu- 
 tion of carbonic acid by raising arterial blood to the temper- 
 ature of 200 Fahr., and venous blood to a temperature of 
 112 ; 3 Stevens, 4 and others, disengaged gas by displacement 
 with hydrogen, nitrogen, or the ordinary atmosphere ; but 
 in spite of this, before the experiments of Magnus in 1837, 
 many denied the existence in the blood of any free gas what- 
 soever. 5 
 
 Magnus made some experiments upon the human blood, 
 extracting the gases by displacement with hydrogen ; but the 
 observations which are most generally referred to by phys- 
 iologists were made upon the blood of horses and calves, 
 extracting the gases by the air-pump, and giving the com- 
 parative quantities existing in the arterial and venous blood. 
 These experiments were of great value as settling the ques- 
 tion of the existence of gases in the blood, either in a free 
 state, or very loosely combined with some of its organic con- 
 stituents ; and until very recently they have been universally 
 
 1 See page 4 11, note. 
 
 2 See quotation in MILNE-EDWARDS, Physiologic, tome i., p. 438, note. 
 
 3 SIR HUMPHRY DAVY, Works, London, 1839, vol. i., pp. 77-79. An Essay 
 on Light, Heat, and the Combination of Light, with a new Theory of Respiration. 
 
 4 Loc. cit. 
 
 6 Gmelin, Mitscherlich, and Tiedemann denied the existence of any free gases 
 in the blood. At one time Dr. John Davy held the same opinion, though he 
 finally recognized his error, and succeeded in extracting gas from the blood by 
 means of the air-pump {Researches, Physiological and Anatomical, London, 
 1839, vol. ii., p. 154). 
 
458 RESPIRATION. 
 
 received by physiologists, as representing the relative propor- 
 tions of the gases in the two kinds of blood, though Magnus 
 states in his paper that he does not think he succeeded in 
 extracting all the gas the blood contained. 1 It is a question 
 of the last importance, as Bearing upon our comprehen- 
 sion of the essential processes of respiration, to be able to 
 determine the relative proportion of oxygen and carbonic 
 acid in the arterial and venous blood. Until very recently, 
 our ideas On this subject have had for their sole experimental 
 basis the observations of Magnus, and in discussing the accu- 
 racy of the modes of analysis of the blood for gases we need 
 take no account of any experiments anterior to his. 
 
 Analysis of the Blood for Gases. There are certain grave 
 sources of error in the method employed by Magnus, which 
 render his observations of little value, except as demonstrating 
 that oxygen, carbonic acid, and nitrogen may be extracted 
 by the air-pump from both arterial and venous blood. The 
 only source of error in the results which he fully recognized 
 lay in the difficulty in extracting the entire quantity of gas 
 in solution ; but a careful study of his paper shows another 
 element of inaccuracy which is even more important. The 
 relative quantities of oxygen and carbonic acid in any single 
 specimen of blood present great variations, dependent upon 
 the length of time that the blood has been allowed to stand 
 before the estimate of the gases is made. As it is impossible 
 to make this estimate immediately after the blood is drawn, 
 on account of the froth produced by agitation with a gas, 
 when the method by displacement is employed, 2 and the 
 bubbling of the gas when extracted by the air-pump, this 
 
 1 The original article of Magnus is published in the Annalen der Physik und 
 Chemie of Poggendorff, April, 1837, and is translated into French in the Ann. de 
 Chimie et de Phys. of the same year. 
 
 a When a gas, such as hydrogen, which is not contained in the blood, is thor- 
 oughly mixed with it by agitation in a closed vessel, it will penetrate the liquid, 
 and displace, or drive off, all the free gas which is held in solution. This is called 
 the method of analysis by displacement. 
 
ANALYSIS OF THE BLOOD FOE GASES. 459 
 
 objection is fatal. It is necessary to wait until the froth 
 has subsided before attempting to make an accurate estimate 
 of the volume of gas given off. The following observation 
 of Magnus illustrates this fact. The observation was on the 
 human blood six hours after it had been thoroughly mixed 
 with hydrogen : 1 
 
 Blood of Man. . Carbonic acid. 
 
 4-077 cubic inches. 1-013 cubic inches. 
 
 3-650 rt 0-781 " 
 
 3-838 " 1-355 " 
 
 After twenty-four hours, at the end of which time the 
 blood had no odor : 
 
 4-077 cubic inches. 1-517 cubic inches. 
 
 3-650 " 1-456 " 
 
 3-833 " 2-075 " 
 
 The excess of carbonic acid found twenty-four hours after, 
 over the quantity found six hours after, in the first and third 
 specimens, is a little over 50 per cent. ; while in the second 
 specimen it is very nearly 100 per cent. 
 
 In these analyses the proportion of oxygen is not given. 
 The question naturally arises as to the source of the carbonic 
 acid which was evolved during the last eighteen hours of the 
 observation. This is evident, when we consider one of the 
 important properties of the blood. A number of years ago, 
 Spallanzani demonstrated that, in common with other parts 
 of the body, fresh blood removed from the body has, of itself, 
 the property of consuming oxygen ; and W. F. Edwards has 
 shown that the blood will exhale carbonic acid. In 1856, 
 Harley, by a series of ingenious experiments, found that 
 blood, kept in contact with air in a closed vessel for twenty- 
 four hours, consumed oxygen and gave off carbonic acid. 2 
 
 1 G. MAGNUS, Sur les Gas que contient le Sang : Oxygene, Azote et Acide Car- 
 bonique. Annales de Chimie et de Physique, 2me serie, tome Ixv., 1837, p. 174. 
 
 2 G. HARLEY, The Chemistry of Respiration. The British and Foreign Med 
 ico-Chirurgical Review, July, 1856, p. 328. 
 
4:60 KESPERATTON. 
 
 
 
 More recently, Bernard ha$ shown that for a certain time 
 after the blood is drawn from the vessels, it will continue to 
 consume oxygen and exhale carbonic acid. If all the car- 
 bonic acid be removed from a specimen of blood, by treating 
 it with hydrogen, and it be allowed to stand for twenty-four 
 hours, another portion of gas can be removed by again treat- 
 ing it with hydrogen, and still another quantity by treating 
 it with hydrogen a third time. 1 
 
 From these facts it is clear that, in the experiment of 
 Magnus, the excess of carbonic acid involved a post-mortem 
 consumption of oxygen ; and no analyses made in the ordi- 
 nary way, by displacement with hydrogen, or by the air- 
 pump, in which' the blood must necessarily be allowed to 
 remain in contact with oxygen for a number of hours, can be 
 accurate. The only process which can give us a rigorous 
 estimate of the relative quantities of oxygen and carbonic 
 acid in the blood is one in which the gases can be estimated 
 without allowing the blood to stand, or in which the forma- 
 tion of carbonic acid in the specimen, at the expense of the 
 oxygen, is prevented. All others will give a less quantity of 
 oxygen and a greater quantity of carbonic acid than exists in 
 the blood circulating in the vessels, or immediately after it is 
 drawn from the body. 
 
 A solution of this important and difficult problem in analy- 
 sis of the blood has been accomplished by Bernard. This ob- 
 server made a great number of experiments, in the hope of dis- 
 covering some means by which the consumption of oxygen by 
 the blood-corpuscles could be arrested. 2 He found, finally, that 
 carbonic oxide, one of the most active of the poisonous gases, 
 had a remarkable affinity for the blood-corpuscles. When 
 
 1 BERNARD, Lemons sur les Proprietes Physiologiques et les Alterations Patholo- 
 giques dcs Liquides de VOrganisme, Paris, 1859, tome i., p. 354 et seq. 
 
 8 Harley (op. cit., p. 334) ascertained that a few drops of chloroform, added to 
 the fresh blood, greatly diminished the activity of the change of oxygen into car- 
 bonic acid. It did not entirely arrest it, however, and the author does not sug- 
 gest its use in quantitative analyses for gases. 
 
ANALYSIS OF THE BLOOD FOR GASES. 461 
 
 taken into the lungs, it is absorbed by and becomes fixed in 
 the corpuscles, effectually preventing the consumption of oxy- 
 gen and production of carbonic acid, which normally takes 
 place in the capillary system, and which is one of the indis- 
 pensable conditions of nutrition. We have already referred 
 to the mechanism of poisoning by the inhalation of this gas, 
 by its fixation in the blood-corpuscles, their consequent par- 
 alysis, and the arrest of their function as respiratory organs. 
 As it is the continuance of this transformation of oxygen into 
 carbonic acid, after the blood is drawn from the vessels, which 
 interferes with the ordinary analysis of the blood for gases, 
 we might expect to extract all the oxygen, if we could imme- 
 diately saturate the blood with carbonic oxide. The prelim- 
 inary experiments of Bernard on this point are conclusive. 
 He ascertained that by mixing carbonic oxide in sufficient 
 quantity with a specimen of fresh arterial blood, in about 
 two hours, all the oxygen which it contained was dis- 
 placed. Introducing a second quantity of carbonic oxide af- 
 ter two hours, and leaving it in contact with the blood for an 
 hour, a quantity of oxygen was removed, so small that it 
 might almost be disregarded. A third experiment on the 
 same blood failed to disengage any oxygen or carbonic acid. 1 
 
 The view entertained by Bernard of the action of car- 
 bonic oxide in displacing the oxygen of the blood is, that the 
 former gas has a remarkable affinity for the blood-corpuscles, 
 in which nearly all the oxygen is contained, and when 
 brought in contact with them unites with the organic matter, 
 setting free the oxygen, in the same way that the acid enter- 
 ing into the composition of a salt is set free by any other 
 acid which has a stronger affinity for the base. There is 
 every reason to suppose that this view is correct ; as carbonic 
 oxide is much less soluble than oxygen, and as it only has the 
 property of disengaging this gas from the blood, leaving the 
 other gases still in solution. 
 
 As carbonic oxide only displaces the oxygen, it is neces- 
 
 1 BERNARD, Liquidcs de V Organisme^ tome i., p. 373. 
 
4:62 RESPIRATION. 
 
 sary to resort to some other process, in addition to this, to 
 disengage the other gases contained in the blood. It is only 
 necessary to arrest the action of the corpuscles upon the oxy- 
 gen, and then the gases may be set free by the air-pump, or 
 any method which may be convenient. The method adopted 
 by Bernard for the disengagement of all the gases contained 
 in the blood is first to displace the oxygen by carbonic oxide, 
 using about two-thirds of gas by volume to one-third of 
 blood, then to attach the tube to a tube of mercury, and sub- 
 ject the blood to the barometric vacuum, which sets free the 
 carbonic acid and the nitrogen. The results obtained by 
 this method correspond with our ideas concerning the nature 
 of the respiratory process; and analyses of the blood taken 
 at different periods show variations in the quantities of oxy- 
 gen in the arterial, and carbonic acid in the venous blood, 
 corresponding with some of the variations which we have 
 noted in the loss of oxygen and gain of carbonic acid in the 
 air, in respiration. 
 
 The analyses of Bernard, who obtained from fifteen to 
 twenty per cent, of oxygen in volume from the arterial blood, 
 show the great imperfection of the process employed by 
 Magnus, who obtained from the arterial blood of horses and 
 calves a mean of but 2 '44: per cent, of oxygen. It does 
 not seem necessary, therefore, to discuss the criticisms of the 
 results obtained by Magnus which were made by Gay-Lussac 
 and Magendie, soon after their publication, and more recent- 
 ly by Harley and others. 1 
 
 1 To Magnus belongs the credit of demonstrating the important fact that oxy- 
 gen, carbonic acid, and nitrogen can be extracted from the blood by removing the 
 atmospheric pressure. Before his observations, Gmelin, Mitscherlich, and Tiede- 
 mann placed venous blood in a tube over mercury, in the receiver of an air-pump, 
 and by removing fhe pressure as far as possible, caused the mercury to descend. 
 On admitting air into the receiver and restoring the pressure, the mercury 
 ascended, with the blood, again filling the tube completely. From this they 
 reasoned that there was no free carbonic acid in the blood. By passing up a 
 little acetic acid, carbonic acid was set free, which led them to believe that all 
 the carbonic acid was in combination. Magnus showed that the reason why 
 other observers had failed to extract gas by means of the air-pump was, that the 
 
ANALYSIS OF THE BLOOD TOR GASES. 463 
 
 Bernard's experiments were made chiefly on dogs, and 
 had especial reference to the proportion of oxygen in the 
 
 rarefaction of the air was not carried sufficiently far. J. Davy, in his second 
 experiments, recognized this fault in his first observations. As the results ob- 
 tained by Magnus are generally quoted and received in works on physiology, we 
 give the table, which is taken from the translation of his original article in the 
 Annales de Chimie et de Physique (loc. cit.~). We have not thought it worth while 
 to reduce the volumes from cubic centimetres to cubic inches, as we add the 
 percentage of gas in volume, which is not given by Magnus. 
 
 ( 5-4 of carbonic acid, or 4'32 per cent. 
 
 Blood of horse 125 c.c. gave 9*8 c.c. of gas-( 1*9 of oxygen, or 1'52 per cent. 
 
 ( 2-5 of nitrogen, or 2'00 " 
 
 Venous blood of the same, ) i 8-8 of carbonic acid, or 4-29 per cent 
 
 four days after the tak- V205 c.c. gave 12'2 c.c. of gas-^ 2'3 of oxygen, or 1'12 per cent, 
 ing of arterial blood. . . . \ / 1-1 of nitrogen, or 0'54 " 
 
 ( lO'O of carbonic acid, or 5'12 per ct. 
 
 The same blood 195 c.c. gave 14-2 c.c. of gas- 2-5 of oxygen, or 1-28 per cent 
 
 | 1-7 of nitrogen, or 0-82 " 
 
 Arterial blood of a horse ) ( 10-7 of carbonic acid, or 8'23 per ct. 
 
 very old, but in good >130 c.c. gave 16'3 c.c. of gas-< 4'1 of oxygen, or 3'15 per cent 
 
 health ) ( 1-5 of nitrogen, or 1 -15 " 
 
 ( 7'0 of carbonic acid, or 5'74 per cent 
 
 The same blood 122 c.c. gave 10-2 c.c. of gas-C 2-2 of oxygen, or 1'SO per cent 
 
 ( 1 -0 of nitrogen, or 0'82 " 
 
 Yenous blood of the same ) ( 12'4 of carbonic acid, or T'29 per ct. 
 
 old horse, drawn three VlTO c.c. gave 18-9 c.c. of gas-( 2'5 of oxygen, or 1-47 per cent. 
 
 days after ) ( 4-0 of nitrogen, or 2-35 " 
 
 I 9-4 of carbonic acid, or 7'64 per cent 
 
 Arterial blood of calf 123 c.c. gave 14'5 c c. of gas^ 3-5 of oxygen, or 2-84 per cent. 
 
 / 1-6 of nitrogen, or 1-30 " 
 
 ( 7'0 of carbonic acid, or 6*49 per cent. 
 
 The same blood 108 c.c. gave 12-6 c.c. of gas-< 3-0 of oxygen, or 2-87 per cent 
 
 ( 2-6 of nitrogen, or 2-40 u 
 
 Yenous blood of the same ) 1 10-2 of carbonic acid, or 6'66 per ct 
 
 calf, taken four days >-153 c.c. gave 13 3 c.c. of gas-< 1-8 of oxygen, or 1-17 per cent 
 
 after. ) / 1-3 of nitrogen, or 0'85 " 
 
 ( 6'1 of carbonic acid, or 4'35 per cent 
 
 The same blood 140 c.c. gave 7'7 c.c. of gasX I'O of oxygen, or 0'71 per cent 
 
 ( 0'6 of nitrogen, or 0'43 " 
 
 We have given this table in full, and calculated the percentage of gas to the 
 blood in each observation, because it is a common impression that the observa- 
 tions of Magnus show a greater proportion of oxygen in the arterial blood, and a 
 greater proportion of carbonic acid in the venous blood. This is not the fact. 
 The table shows that the proportion of all gases is greater in the arterial blood, 
 and that the proportion of carbonic acid to the oxygen is greater in the venous 
 blood ; but while the percentage of oxygen is greater in the arterial blood, there 
 is also a larger percentage of carbonic acid. In the specimens of arterial blood 
 examined, the mean proportion of oxygen was 2*44 per cent., and of carbonic 
 acid 6 '48 per cent. In the venous blood, the mean proportion of oxygen was 
 1'15 per cent., and of carbonic acid, 6*54 per cent. It is difficult to reconcile an 
 analysis, showing a greater absolute quantity of carbonic acid in arterial than in 
 venous blood, with our settled and well-sustained ideas regarding the processes 
 of respiration. A glance at the wide differences in the different analyses of speci- 
 mens of the same blood shows that there must have been some grave error 
 in the process. 
 
464 RESPIRATION. 
 
 blood. As far as we know, no analyses of the human blood 
 have jet been made by his method. In two specimens taken 
 from a dog in good condition, a specimen of arterial blood, 
 drawn from the vessels by a syringe and put in contact 
 with carbonic oxide withoutbeing exposed to the air, was 
 found to contain 18*28 per cent., and a specimen of venous 
 blood, taken in the same way, 8*42 per cent., in volume, of 
 oxygen. 1 The proportion of gases in the blood is found to 
 vary very considerably under different conditions of the sys- 
 tem, particularly with reference to the digestive process. 
 The following are the general results of later observations, 
 showing the differences and variations in the proportions of 
 all the gases, in arterial and venous blood. 2 
 
 Arterial Blood^ while an animal is fasting, contains from 
 nine to eleven parts per hundred of oxygen. In full digestion, 
 the proportion is raised to seventeen, eighteen, or even twenty 
 parts per hundred. The proportion varies in different animals ; 
 being much greater, for example, in birds than in mammals. 
 The quantity of carbonic acid is even more variable than 
 the quantity of oxygen. During digestion there are from 
 five to six parts per hundred of free carbonic acid in the 
 arterial blood. During the intervals of digestion this quan- 
 tity is reduced to almost nothing ; and after fasting for twenty- 
 four hours, frequently not a trace is to ~be discovered. 
 
 Venous Blood always contains a large quantity of car- 
 bonic acid, both free in solution, and combined in the form 
 of carbonates and bicarbonates. This quantity varies in dif- 
 ferent parts of the venous system, and bears a relation to the 
 color of the blood. It is well known that the venous blood 
 coming from some glands is dark during the intervals of 
 secretion, and nearly as red as arterial blood during their 
 functional activity. In the venous blood from the sub-max- 
 
 1 Loc. cit., p. 367. 
 
 2 These results were given in a course of lectures which we had the privilege 
 of hearing at the College of France in the summer of 1861, and which have not 
 yet been published. 
 
NITROGEN OF THE BLOOD. 465 
 
 illary gland of a dog, Bernard found 18*07 per cent, of car- 
 bonic acid during repose, and 1O14 per cent, during secre- 
 tion. The blood coming from the muscles is the darkest in 
 the body, and contains the greatest quantity of free carbonic 
 acid. 
 
 The quantity of free carbonic acid is immensely increased 
 in the venous blood during digestion. It is owing to this 
 fact that the gas then exists in the arterial blood. During 
 the intervals of digestion, the quantity is so small that the 
 lungs are capable of completely eliminating it, and none 
 passes into the arteries ; but during digestion, the proportion 
 is so much greater, that for a time it cannot be entirely re- 
 moved, and a part finds its way into the arterial system. 
 
 These facts coincide with the views which are now held 
 regarding the essential processes of respiration. The blood 
 going to the lungs ordinarily contains carbonic acid, and no 
 oxygen ; for during the intervals of digestion, there is only 
 enough oxygen taken up by the blood to supply the wants of 
 the system. In the lungs, carbonic acid is given off, appear- 
 ing in the expired air, and the oxygen which disappears from 
 the air is carried away by the arterial blood. Under some 
 conditions, and particularly during the height of the digestive 
 process, the quantity of oxygen absorbed is largely increased, 
 and so much may exist in the arterial blood that a small por- 
 tion passes into the veins. At the same time the production of 
 carbonic acid is increased in activity, and it may exist in such 
 quantity in the venous blood, as temporarily to pass in small 
 quantity into the arteries. 
 
 Nitrogen of the Blood. As far as is known, nitrogen has 
 no important office in the process of respiration. There is 
 generally a slight exhalation of this gas by the lungs, and 
 the analyses of Magnus and others have demonstrated its 
 existence in solution in the blood. Magnus found generally 
 a larger proportion in the arterial than in venous blood, 
 though in one instance there was a larger proportion in the 
 30 
 
466 RESPIRATION. 
 
 venous blood. It is not absolutely certain whether the ni- 
 trogen which exists in the blood is derived from the air or 
 from the tissues. Its almost constant exhalation in the ex- 
 pired air would lead to the supposition that it is produced in 
 small quantity in the system,or supplied by the food. Ac- 
 cording to Bernard, the quantity of nitrogen in the arterial 
 blood is from two to five parts per thousand, but it is present 
 in very much larger quantity in the venous blood. 1 There 
 is no evidence that nitrogen enters into combination with the 
 blood-corpuscles; it exists simply in solution in the blood, 
 which is capable of absorbing about ten times as much as 
 pure water. 2 Nothing is known with regard to the rela- 
 tions of the free nitrogen of the blood to the processes of 
 nutrition. 
 
 Condition of the Gases in the Blood. It is now pretty 
 generally admitted that the oxygen of the blood exists, not 
 in simple solution, but in a condition of feeble combination 
 with certain of the constituents of the blood-corpuscles. 3 It 
 is clearly demonstrated that the corpuscles are the elements 
 which fix the greatest quantity of this gas. Carbonic oxide, 
 which has a great affinity for the corpuscles, displaces almost 
 immediately all the oxygen which the blood contains. When 
 the corpuscles are destroyed, as they may be readily by re- 
 ceiving fresh blood into a quantity of pure water, the red 
 color is instantly changed to black. Oxygen in the blood 
 bears a closer relation to the corpuscles than that of mere solu- 
 
 1 Unpublished lectures delivered at the College of France in the summer 
 of 1861. 
 
 2 MAGNUS, loc. cit. 
 
 3 It is not settled which of the constituents of the blood-corpuscles has the 
 greatest affinity for oxygen. It has been supposed to be combined especially with 
 the coloring matter ; but experiments on this point are contradictory. Lehmann 
 noticed no difference in the color of a solution of blood-crystals treated with oxy- 
 gen, and the same solution treated with carbonic acid ; the only difference was 
 that the latter became turbid (Physiological Chem., Am. ed., vol. i., p. 573). 
 Meckel made some experiments in which " hsematoglobulin " was changed to a 
 bright red by oxygen, and to a bluish red by carbonic acid (Ibid., p. 674). 
 
CONDITION OF THE GASES IN THE BLOOD. 467 
 
 tion. The proportion which they are capable of containing 
 is to a certain degree absolute, and not dependent upon phys- 
 ical conditions, such as pressure, which invariably have an 
 influence on the proportion of gas merely held in solution by 
 liquids. The proportion of oxygen in the blood cannot be 
 increased by pressure, nor is it diminished by reduction 
 of the pressure, until it approaches a vacuum. 1 The fact 
 that the blood-corpuscles are capable of consuming oxygen 
 and giving off carbonic acid is an additional argument in 
 favor of the union of these anatomical elements with the 
 gas, though this union is very feeble and easily disturbed. 
 The plasma will absorb a certain quantity of oxygen, and its 
 action in respiration seems to be intermediate ; it first takes 
 oxygen from the air and then gives it up to the corpuscles. 
 
 Carbonic acid is more easily exhaled from the blood than 
 oxygen. It was this principle which was obtained by those 
 who first succeeded in extracting gas from the blood. While 
 there is every reason to suppose that oxygen is in combina- 
 tion with the blood-corpuscles, carbonic acid seems to be in a 
 condition of simple solution, and is contained more especially 
 in the plasma. What may be considered as the free carbonic 
 acid of the blood behaves in all regards like a gas simply held 
 in solution. The view that it is held in solution chiefly in the 
 plasma is sustained by the fact that serum will absorb more 
 carbonic acid than an equal volume of defibrinated blood. 2 
 
 Liebig has shown that the phosphate of soda, one of the 
 constituents of the blood, influences to a remarkable degree 
 the quantity of carbonic acid which can be held in solution 
 by any liquid. One hundredth of a part of this salt in pure 
 water will double its capacity for dissolving carbonic acid. 3 
 
 1 The fact that oxygen is exhaled from the blood in vacua is not an argument 
 against the view that it enters into feeble combination with the blood-corpuscles ; 
 for it is well known that many distinctly recognized chemical combinations are 
 disturbed by the same means. For example, a vacuum is capable of disengaging 
 from some of the bicarbonates one equivalent of carbonic acid. 
 
 2 LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 494. 
 
 3 MILNE-EDWARDS, Physiologic, tome i., p. 471. 
 
468 RESPIRATION. 
 
 When carbonic acid is formed by the blood, after it is drawn 
 from the body, it is immediately exhaled, at least in part. 
 When blood is in contact with a certain quantity of air, oxy- 
 gen is consumed and carbonic acid is exhaled. The fact that 
 carbonic oxide, which has sueti a remarkable affinity for the 
 corpuscles, displaces oxygen almost exclusively, is another 
 argument in favor of the view that the carbonic acid is con- 
 tained mainly in the plasma. 
 
 A portion of the carbonic acid which is formed by the 
 system unites with the carbonates in the blood, particularly 
 the carbonate of soda, to form bicarbonates, is carried to the 
 lungs, and there set free by the pneumic acid. It here exists 
 in so loose a condition of combination, that it may be dis- 
 engaged by treating the blood with inert gases, or putting it 
 under the receiver of an air-pump. 
 
 The carbonic acid which is formed in the tissues, and taken 
 up by the blood in its passage through the capillaries, exists 
 in this fluid in two forms : one, in simple solution, chiefly in 
 the plasma ; and the other, in a state of such loose chemical 
 combination in the bicarbonates, that it may be disengaged 
 by displacement by another gas, and is readily set free by 
 pneumic acid. This gas is a product of excretion, and is not 
 engaged in any of the vital functions ; while oxygen, which 
 has an all-important function to perform, unites immediately 
 with the blood-corpuscles, and is not easily disengaged, 
 except when it undergoes transformation in the process of 
 nutrition. It is certain that all the carbonic acid in the blood 
 is not in combination with bases, for the proportion of salts 
 is not sufficient to account for all the carbonic acid that can 
 be disengaged. 
 
 In addition to this excrementitious carbonic acid, there 
 is another portion which is a permanent constituent of the 
 blood, in the carbonates, and cannot be set free without the 
 use of reagents. 
 
 Nitrogen exists in the blood in the same condition of solu- 
 
 o 
 
 tion in the plasma as carbonic acid. 
 
MECHANISM OF THE INTEKCHANGE OF GASES. 469 
 
 Mechanism of the Interchange of Gases between the Blood 
 and the Air, in the Lungs. The gases from tlie air pass into 
 the blood, and the gases of the blood are exhaled through 
 the delicate membrane which . separates these two fluids, in 
 accordance with laws which are now well understood. The 
 first to point out the power of gases thus to penetrate and 
 pass through membranes was the late Dr. J. K. Mitchell, of 
 Philadelphia. 1 His attention was first directed to this subject 
 by noticing the escape of gas from gum-elastic balloons filled 
 with hydrogen. In order to satisfy himself that the gas 
 passed through the membrane independently of pressure, he 
 put different gases in wide-mouthed bottles covered with gum- 
 elastic, and by a series of ingenious experiments, which have 
 become so common that it is unnecessary to describe them 
 in detail, extended Dutrochet's law of endosmosis and exos- 
 mosis to the gases. He demonstrated the same phenomena 
 when he used thin animal membranes instead of the gum- 
 elastic, and found that the more recent the membrane, the 
 more rapid was the action. The rapidity of transmission was 
 found to be very great in living animals. Observations on 
 the lungs of the snapping turtle, filled with air and placed in 
 an atmosphere of carbonic acid or nitrous oxide, showed a 
 very rapid passage of gas from the exterior to the interior. 
 Dr. Mitchell recognized the passage of gases through mem- 
 branes into liquids, and the exhalation of gases which were 
 in solution in these liquids. He noted this action in the ab- 
 sorption of oxygen and the exhalation of carbonic acid in the 
 lungs ; though he fell into the error of supposing that there 
 was no carbonic acid in solution in the blood, and that it was 
 exhaled as soon as formed. 2 A few years later, Dr. Rogers, 
 of Philadelphia, enclosed a fresh pig's bladder, filled with 
 
 1 On the Peneirativeness of Fluids. By J. K. MITCHELL, M.D., Lecturer on 
 Medical Chemistry in the Philadelphia Medical Institute. American Journal of 
 the Medical Sciences, Nov., 1830, p. 36. 
 
470 RESPIRATION. 
 
 venous blood, in a bell-glass of oxygen. 1 In two hours a 
 quantity of oxygen had disappeared, and a large quantity of 
 carbonic acid had made its appearance. Dr. Rogers is fre- 
 quently referred to as the first to demonstrate the passage of 
 gases through animal membranes to and from the blood. 
 The credit of this is due to Mitchell, whose paper was pub- 
 lished in 1830, while the experiments of Rogers were pub- 
 lished in 1836. 
 
 We have already seen that the blood is exposed to the air 
 in the lungs, separated from it only by a very delicate mern- 
 brane, over an immense surface. The membrane, far from 
 interfering with the interchange of gases, actually favors it ; 
 and thus, in obedience to the laws which regulate endosmosis 
 between gases and liquids, the oxygen is continually passing 
 into the blood, and the free carbonic acid is exhaled. 
 
 General Differences in the Composition of Arterial and 
 Venous Blood. All observers agree that there are certain 
 marked differences in the composition of arterial and venous 
 blood, aside from their free gases. The arterial blood con- 
 tains less water, and is richer in organic, and most inorganic, 
 constituents than the venous blood. It also contains a greater 
 proportion of corpuscles, fibrin, and inorganic salts. It is 
 more coagulable, and offers a larger and firmer clot than 
 venous blood. Numerous analyses have failed to detect a 
 constant difference in the proportion of albumen ; sometimes 
 the proportion is greater in the venou% and sometimes in the 
 arterial blood. The only principles which are constantly 
 more abundant in venous blood are water and the alkaline 
 carbonates. 10,000 parts of venous blood contained 12*3 
 parts of carbonic acid combined, and the same quantity of 
 arterial blood contained but 8*3 parts. 2 The deficiency of 
 water in the blood which comes from the lungs is readily ex- 
 plained by the escape of watery vapor in the expired air. 
 
 1 Experiments on the Blood, etc. By ROBERT E. EOGERS, M.D., of Philadelphia. 
 American Journal of the Medical Sciences, August, 1836, p. 296, 
 9 LONGET, op, cit., tome i., p. 584. 
 
DIFFERENCES DT COMPOSITION OF BLOOD. 4Y1 
 
 An important distinction between arterial and venous 
 blood is one to which we have already incidentally alluded, 
 viz., that the former has a uniform composition in all parts of 
 the arterial system, while the composition of the latter varies 
 very much in the blood coming from different organs. Arte- 
 rial blood is capable of carrying on the processes of nutrition ; 
 while venous blood ia not, and cannot even circulate freely 
 in the systemic capillaries. 
 
CHAPTEE XIY. 
 
 ETC. 
 
 V r iews of physiologists anterior to the time of Lavoisier Relations of the con- 
 sumption of oxygen to nutrition Relations of the exhalation of carbonic acid 
 to nutrition Essential processes of respiration The respiratory sense, or 
 want on the part of the system which induces the respiratory movements 
 Location of the respiratory sense in the general system Sense of suffocation 
 Respiratory efforts before birth Cutaneous respiration Asphyxia. 
 
 IT has been demonstrated that all tissues, so long as they 
 retain their absolute integrity of composition, have the prop- 
 erty of appropriating oxygen and exhaling carbonic acid, in- 
 dependently of the presence of blood ; and that the arterial 
 blood carries oxygen from the lungs to the tissues, there gives 
 it up, and receives carbonic acid, which is carried by the 
 venous blood to the lungs, to be exhaled. From this fact 
 alone, it is more than probable that respiration is inseparably 
 connected with the general act of nutrition. Its processes 
 must be studied, therefore, as they take place in the tissues and 
 organs of the body. In the present state of the science, the 
 questions which naturally arise in connection with the essen 
 tial processes of respiration are : 
 
 1. In what way is oxygen consumed in the system ? 
 
 2. How is carbonic acid produced by the system ? 
 
 3. "What is the nature of the processes which take place 
 between the disappearance of oxygen and the evolution of 
 carbonic acid ? 
 
 When these questions are satisfactorily answered, we shall 
 understand the essence of respiration ; but in reasoning on this 
 
RELATIONS TO NUTRITION. 473 
 
 subject, we must not fall into the error of assimilating the 
 respiratory phenomena too closely to those with which we are 
 acquainted as they occur in inorganic bodies. It must be re- 
 membered that in the organism we are dealing with principles 
 which have the remarkable property of self-regeneration; 
 and which, as a simple condition of vital existence, consume 
 oxygen, when it is presented to them, and exhale carbonic 
 acid. Without a proper supply of oxygen, the tissues die, 
 lose these peculiar properties, and finally disappear by putre- 
 factive decomposition. This consumption of oxygen cannot 
 be regarded in any other light than as the appropriation by 
 a living part, of an element necessary to supply waste ; in 
 the same way as those materials which are ordinarily called 
 nutritive are appropriated. That waste is continually going 
 on there can be no doubt; and as the production of urea, 
 creatine, creatinine, cholesterine, etc., is to a certain extent 
 independent of the absorption of food, so the production of 
 carbonic acid is to a certain extent independent of the ab- 
 sorption of oxygen. This has been fully demonstrated by 
 the experiments of Spallanzani, Edwards, Geo. Liebig, and 
 others, who have noted the exhalation of carbonic acid in at- 
 mospheres which contained no oxygen. How different are 
 these phenomena from those which attend combinations and 
 decompositions of inorganic matters ! As an example, let 
 oxygen be brought in contact, under proper conditions, with 
 iron. Under these circumstances, a union of iron and oxy- 
 gen takes place, and a new substance, oxide of iron, is formed, 
 which has peculiar and distinct properties. In the same 
 way, carbonic acid may be disengaged from its combinations 
 by the action of a stronger acid, which unites with the base 
 and forms a new substance, in no way resembling the origi- 
 nal salt. To make the contrast still more striking, let a hy 
 dro-carbon, like fat, be heated in oxygen or the air, until it 
 undergoes combustion ; it is then changed into carbonic acid 
 and water, by a definite chemical reaction, and is utterly de- 
 stroyed as fat. 
 
RESPIRATION. 
 
 In the living body the organic nitrogenized principles are 
 in a condition of continual change ; breaking down, and form- 
 ing various excrementitious principles, at the head of which 
 may be placed carbonic acid. It is essential to life that these 
 principles be maintained in their chemical integrity, which 
 requires a supply of fresh matter as food, and above all a 
 supply of oxygen. We put ourselves in the position of ig- 
 noring well-established facts and principles when we assimi- 
 late without reserve the process of the consumption of oxygen 
 and production of carbonic acid by living organic bodies, to 
 simple combustion of sugar or fat. The ancients saw that 
 the breath was warmer than the surrounding air, that in the 
 lungs the air took heat from the body ; and as they knew of 
 no other changes in the air produced by respiration, they as- 
 sumed that its object was simply to cool the blood. Lavoisier 
 discovered that the air, containing oxygen, lost a portion of 
 this principle in respiration, and gained carbonic acid and 
 watery vapor. He saw that this might be imitated by the 
 combustion of hydro-carbons, such as exist in the blood. He 
 called respiration a slow combustion, and regarded as its prin- 
 cipal office the maintenance of animal temperature. "When 
 it was shown by analyses of the blood for gases, that oxygen 
 was not consumed in the lungs, but taken up by the circulating 
 fluid, and carried all over the body, and that carbonic acid 
 was brought from all parts by the blood to the lungs, these 
 facts, taken in connection with the fact that the tissues have 
 the property of consuming oxygen and exhaling carbonic 
 acid, led physiologists to change the location of the combus- 
 tive process from the lungs to the tissues. 
 
 We cannot stop at this point. Now it is known that the 
 organic principles of the body, w^hich form the basis of all 
 tissues and organs, are continually undergoing change as a 
 condition of existence; that they do not unite with any 
 substance in definite chemical proportions, but their par- 
 ticles, after a certain period of existence, degenerate into 
 excrementitieus substances, and they are regenerated by an 
 
RELATIONS TO NUTRITION. 4/T5 
 
 appropriation and change of materials furnished by the blood. 
 As far as the respiration of these parts is concerned, we can 
 only say, that in this process, carbonic acid is produced and 
 oxygen is consumed. These facts show that respiration is 
 essentially a phenomenon of nutrition, possessing a degree 
 of complexity equal to that of the other nutritive processes. 
 It must be acknowledged that thus far its cause and intimate 
 nature have eluded investigation. In respiration by the tis- 
 sues, no one has yet been able to give the cause of the ab- 
 sorption of oxygen or the exhalation of carbonic acid ; or to 
 demonstrate the condition in which oxygen exists when once 
 appropriated, or the particular changes which take place, 
 and the principles which are lost, in the formation of carbonic 
 acid. 
 
 The views of physiologists with regard to the essential 
 processes of respiration, before the time of Lavoisier, have 
 barely an historical interest at the present day ; except the 
 remarkable idea of Mayow, which comprehended nearly the 
 whole process, and which was unnoticed for about a hundred 
 years. 1 It is not our object to dwell upon the various theo- 
 ries which have been proposed from time to time, or even 
 to fully discuss, in this connection, the combustion theory as 
 proposed by Lavoisier, and modified by Liebig and others. 
 Though this theory is nominally received by many physiolo- 
 gists of the present day, it will be found that most of them, 
 in accordance with the facts which have since been developed, 
 really regard respiration as connected with nutrition. They 
 only differ from those who reject the combustion theory, in 
 their definition of the term combustion. Lavoisier regarded 
 respiration as a slow combustion of carbon and hydrogen ; 
 and if every rapid or slow combination of oxygen with any 
 other body be considered a combustion, this view is abso- 
 lutely correct, and was proven when it was shown that oxygen 
 united with any of the tissues. Longet says that since the 
 time of Lavoisier it is agreed to give the above signification 
 
 1 See page 411. 
 
476 RESPIRATION. 
 
 to the word combustion ; l but this must simply be for the 
 purpose of retaining the name applied by Lavoisier to the 
 respiratory process, while its signification is altered to suit 
 the facts which have since taken their place in science. There 
 is no doubt that combustion m generally regarded as signify- 
 ing the direct and active union of oxygen with certain prin- 
 ciples, which commonly contain carbon and hydrogen; and 
 the immediate products of this union are carbonic acid, water, 
 and incidentally heat and light. It is certain that oxygen 
 does not unite in the body directly with carbon and hydrogen, 
 though it is consumed, and carbonic acid and water are pro- 
 duced, in respiration. Important intermediate phenomena 
 take place, and we do not therefore fully express the respiratory 
 process by the term combustion. The researches of Spallan- 
 zani, W. F. Edwards, Collard de Martigny, 2 and others, who 
 have demonstrated the abundant exhalation of carbonic acid 
 by animals and by tissues deprived of oxygen, show that it 
 is not a product of combustion of any of the principles of the 
 organism. 3 
 
 Rejecting this hypothesis as insufficient to explain the 
 intimate nature of the respiratory process, it remains to be 
 seen how satisfactorily, in the present state of the science, it 
 is possible to answer the several questions proposed at the 
 beginning of this chapter. 
 
 1. In what way is the oxygen consumed in the system f 
 Oxygen, first taken from the air by the plasma of the blood, 
 is immediately absorbed by, and enters into the composition 
 of, the red corpuscles. Part of the oxygen disappears in the 
 red corpuscles themselves, and carbonic acid is given of 
 
 1 LONGET, Traite de Physiologie, Paris, 1861, tome i., p. 392, note. 
 
 2 COLLARD DE MARTIGNY, Recherches Experimentales et Critiques sur V Ab- 
 sorption et sur T Exhalation Kcspiratoires. Journal de Physiologie, 1830, tome 
 x., p. 111. 
 
 3 Various other considerations concerning the combustion theory of respira- 
 tion, such as the so-called " respiratory, or calorific food," will be discussed in 
 connection with the subject of animal heat. 
 
CONSUMPTION OF OXYGEN. 477 
 
 To how great an extent this takes place it is impossible to 
 say ; but it is evident, even from a study of the methods of 
 analyses of the blood for gases, that the property of absorbing 
 oxygen and giving off carbonic acid, which Spallanzani dem- 
 onstrated to belong to the tissues, is possessed as well by the 
 red corpuscles. Daring life it is not possible to determine 
 how far this takes place in the blood, and how far in the 
 tissues. Lagrange and Hassenfratz * advanced the theory 
 that all the respiratory change takes place in the blood as it 
 circulates ; but the avidity of the tissues for oxygen, and the 
 readiness with which they exhale carbonic acid, leave no 
 room for doubt that much of this change is effected in their 
 substance. The late experiments of Bernard, 8 showing that 
 when blood is sent to the glands in large quantities, the 
 oxygen is only imperfectly destroyed, the blood which is 
 returned by the veins having nearly the color of arterial 
 blood, are positive evidence against this view. 
 
 Oxygen, carried by the blood to the tissues, is appropri- 
 ated and consumed in their substance, together with the nu- 
 tritive materials with which the circulating fluid is charged. 
 We are acquainted with some of the laws which regulate its 
 consumption, but have not been able to follow it out and as- 
 certain the exact nature of the changes which take place. 
 Some have said that oxygen unites with the iron of the 
 blood, or with the coloring matter of the corpuscles ; but ex- 
 periments on this point are contradictory and unsatisfactory. 
 Some have said that it unites with the hydro-carbons of the 
 blood and of the tissues ; but there is more evidence that it 
 enters into combination chiefly with the organic nitrogenized 
 principles. All that we can say definitely on this point is, 
 
 1 HASSENFRATZ, Memoire sur la Combination de TOxygene avec le Carbone et 
 r Hydrogene du Sang, sur la Dissolution de V Oxgyene dans le Sang, et sur la Maniere 
 dont le Calorique se degage. Annales de Chimie, 1791, tome ix., p. 261. 
 
 2 Liquides de C Organisme, tome i. ; and unpublished lectures at the College of 
 France, 1861. In the latter, Bernard gives comparative analyses of the venous 
 blood from the submaxillary gland, showing a larger proportion of oxygen during 
 its functional activity than during repose. 
 
478 RESPIRATION. 
 
 that it unites with the organic principles of the system, satis- 
 fying the " respiratory sense," and supplying an imperative 
 want which is felt by all animals, and extends to all parts of 
 the organism. After being absorbed, it is lost in the intri- 
 cate processes of nutrition. There is no evidence in favor of 
 the view that oxygen unites directly- with carbonaceous mat- 
 ters in the blood which it meets in the lungs, and, by direct 
 union with carbon, forms carbonic acid. 
 
 2. How is carbonic acid produced ~by the system f 
 That carbonic acid makes its appearance in the blood it- 
 self, produced in the red corpuscles, has been abundantly 
 proven by observations already cited; though it is impos- 
 sible to determine to what extent this takes place during 
 life. It is likewise a product of the physiological decompo- 
 sition of the tissues, whence it is absorbed by the blood cir- 
 culating in the capillaries and conveyed by the veins to the 
 right side of the heart. It has been experimentally demon- 
 strated that its production is not immediately dependent 
 upon the absorption of oxygen ; for it will go on in an atmos- 
 phere of hydrogen or of nitrogen. It is most reasonable to 
 consider the carbonic acid thus formed as a product of excre- 
 tion or destructive assimilation, like urea, creatine, or choles- 
 terine. The fact that it may easily be produced artificially, 
 out of the body, does not demonstrate that its formation 
 in the body is as simple as when it is formed by the pro- 
 cess of combustion. We may be able at some future time 
 to produce artificially all the excrementitious principles, 
 as has already been done in the case of urea ; 1 but we are 
 hardly justified in supposing that the mode of formation 
 of this principle, as one of the phenomena of nutrition, is 
 precisely the same as when it is made by our chemical ma- 
 nipulations. 
 
 1 Woller first formed urea artificially by a union of cyanic acid and am- 
 monia. Since then it has been prepared by chemists by various processes 
 (LEHMAKN, Physiological Chemistry, Philadelphia, 1855, vol. i., p. 147). 
 
KESPIKATOKY SENSE. . 479 
 
 As expressing nearly all that is known, even at the pres- 
 ent day, regarding the mode of formation of carbonic acid 
 in the economy, we may take the following concluding passage 
 from the paper of Collard de Martigny, published in 1830 : l 
 
 " The carbonic acid expired is a product of assimilative 
 decomposition, secreted in the capillaries and excreted by the 
 lungs." 
 
 The carbonic acid thus produced is taken up by the 
 blood, part of it in a free state in solution, particularly in 
 the plasma, and a part which has united with the carbonates 
 to form bicarbonates. Carried thus to the lungs, the free 
 gas is removed by simple displacement, and that which 
 exists in combination is set free by the acids found in the 
 pulmonary substance. 
 
 3. What is the nature of the intermediate processes, from 
 the disappearance of oxygen to the evolution of carbonic 
 acid ? A definite answer to this question would complete 
 our knowledge of the respiratory process ; but this, in the 
 present state of the science, we are not prepared to give. "We 
 can only repeat what has already been so frequently referred 
 to, that oxygen must be considered as a nutritive principle, 
 and carbonic acid a product of excretion. The intermediate 
 processes belong to the general function of nutrition, with 
 the intimate nature of which we are unacquainted. We 
 have not sufficient evidence for supposing that this process 
 is identical with what is generally known as combustion. 
 
 The Respiratory Sense; or Want on the part of the System 
 which induces the Respiratory Movements. (Besoin de 
 Eespirer.) 
 
 We are all familiar with the peculiar and distressing 
 
 1 Loc. cit., p. 160. The author adds: "The chemical theory of Lavoisier, 
 of respiration, is a gratuitous supposition. This function should be considered 
 as a complete series of acts of general assimilation." 
 
480 RESPIRATION. 
 
 sense of suffocation which attends an interruption in the re- 
 spiratory process. Under ordinary conditions, the act of 
 breathing takes place without our knowledge; but even 
 when the air is but little vitiated, when its entrance into the 
 lungs is slightly interfered dwith, or when a considerable 
 portion of the pulmonary structure is involved by disease, 
 we experience a certain sense of uneasiness, and become con- 
 scions of the necessity of respiratory efforts. This gradually 
 merges into the sense of suffocation, and, if the obstruction be 
 sufficient, is followed by convulsions, insensibility, and final- 
 ly by death. 
 
 Though we are not sensible of any want of air under or- 
 dinary conditions, it was proven by the celebrated experi- 
 ment of Robert Hook, in 1664, that there is a want always 
 felt by the system ; and that if this want be effectually sup- 
 plied, no respiratory movements will take place. We have 
 often repeated the experiment demonstrating this fact. If a 
 dog be brought completely under the influence of ether, the 
 chest and abdomen opened, and artificial respiration be 
 carefully kept up by means of a bellows fixed in the trachea, 
 even after the animal has come from under the influence of 
 the anaesthetic, so as to look around and wag his tail when 
 spoken to, he will frequently cease all respiratory move- 
 ments when the air is properly supplied to the lungs. This 
 fact can be very satisfactorily observed, as the diaphragm 
 and other important respiratory muscles are denuded, and 
 exposed to view. If the artificial respiration be interrupted 
 or imperfectly performed, the animal almost immediately 
 feels the want of air, and the exposed respiratory muscles 
 are thrown into violent but ineffectual contraction. 1 
 
 It is generally admitted, indeed, that there exists in the 
 
 1 For full details of these experiments the reader is referred to an article by 
 the author, entitled Experimental Researches on Points connected with the Action 
 of the Heart and with Respiration (American Journal of the Medical Sciences, Oct., 
 1861). Since the publication of this paper, the experiments on respiration have 
 been frequently repeated publicly, and the conclusions verified. 
 
BESPIEATOKY SENSE. 481 
 
 system what may appropriately be called a respiratory sense, 
 or, as it is called by the French, l>esoin de respirer, which is 
 conveyed to the respiratory nervous centre and gives rise to 
 the ordinary reflex and involuntary movements of respira- 
 tion ; that this sense is exaggerated by any thing which inter- 
 feres with respiration, and is then carried on to the brain, 
 where it is appreciated as dyspnoea, and finally as the over- 
 powering sense of suffocation. An exaggeration of the 
 respiratory sense constitutes an oppression, which is referred 
 to the lungs. It has been demonstrated, however, that the 
 sensation of hunger, which is felt in the stomach, and of 
 thirst, which is felt in the throat and fauces, have their seat 
 really in the general system, and are instinctively referred 
 to the parts mentioned, because they are severally relieved by 
 the introduction of food into the stomach, and the passage 
 of liquid along the throat and oesophagus. It cannot there- 
 fore be assumed, from sensations only, that the sense of want 
 of air is really located in the lungs. The question of its seat 
 and its immediate cause is one of the most interesting of 
 those connected with respiration. 
 
 Many physiologists accept the view of Marshall Hall, who 
 first accurately described the reflex phenomena, that the re- 
 spiratory sense is located in the lungs, is carried to the medulla 
 oblongata by the pulmonary branches of the pneumogastric 
 nerves, and is due to the accumulation of carbonic acid in the 
 pulmonary vesicles ; but there are facts in physiology and 
 pathology which are inconsistent with such an exclusive view. 
 
 In cases of disease of the heart, when the system is im- 
 perfectly supplied with oxygenated blood, the sense of suffoca- 
 tion is frequently most? distressing, though the lungs be unaf- 
 fected, and receive a sufficient supply of pure air. This and 
 other similar facts led Berard to adopt the view that the 
 respiratory sense has its point of departure in the right cavi- 
 ties of the heart, and is due to their disterition as the result of 
 obstruction to the passage of blood through the lungs. 1 John 
 
 1 Cours de Physiologic, tome ili., p. 523. 
 31 
 
482 RESPIRATION. 
 
 Reid thought it was due in a measure to the circulation of 
 venous blood in the medulla oblongata. 1 "What lias been 
 shown to be the correct explanation was given by Yolkmann 
 in 1841. He regarded the sense of want of air as dependent 
 on a deficiency of oxygen in "the tissues, producing an im- 
 pression which is conveyed to the medulla oblongata bv the 
 nerves of general sensibility. By a series of experiments, tin's 
 observer disproved the view that this sense resides in the lungs 
 and is transmitted along the pneumogastric nerves ; and by 
 exclusion, he located it in the general system, and showed that 
 such a supposition is competent to explain all the phenomena 
 connected with the respiratory movements. 8 In the hope of 
 settling some of these questions, which might be regarded as 
 somewhat uncertain, we instituted, a few years ago, a series of 
 experiments, which were embodied in the paper already re- 
 ferred to. 3 In these observations, the following facts, some of 
 which had been previously noted, were demonstrated ; and 
 their results leave no doubt as to the location and cause of 
 the respiratory sense : 
 
 1. If the chest be opened in a living animal, and artificial 
 respiration be carefully performed, inflating the lungs suffi- 
 ciently but cautiously, and taking care to change the air in 
 
 1 An Experimental Investigation into the Functions of the Eighth Pair of 
 Nerves, etc. Part second. Anatomical and Physiological Researches, Edin- 
 burgh, 1848, p. 285 ; and Edinburgh Medical and Surgical Journal, 
 April, 1839. 
 
 3 YOLKMAXX, in Schmidt's Jahrbucher, 1842, p. 290. Yolkmann shows that 
 after division of the pneumogastrics, an animal dies when deprived of air, not 
 calmly, but with undoubted symptoms of distress from suffocation, as if it had 
 been strangled without previous division of the vagi. He also made a number of 
 experiments, in which respiratory efforts continued, for many minutes after extir- 
 pation of the lungs, in cats and dogs, care being taken to leave the phrenic nerves 
 intact. He goes on to reason that the sense of want of air must reside in the gen- 
 eral system, that it is due to a deficiency of oxygen, and that its exaggeration 
 constitutes the sense of suffocation. His observations do not show, however, 
 that this is not due to the presence of carbonic acid, as has been supposed by 
 many. Yierordt is of the opinion that the respiratory sense is due to the circu- 
 lation of the venous blood in the substance of the nerves. 
 
 * American Journal, October, 1861. 
 
the bellows every few moments, as long as this is continued, 
 the aTiimail wiQ make no respiratory effort ; showing that, for 
 the time, the respiratory sense is abolished. 
 
 2. l^en the artifidal respiration is m^ 
 
 ratory muscles are thrown into contraction, and the animal 
 makes regular, and at last Tiolent efforts. If we now expose 
 an artery, and note the color of the blood as it flows, it wfll 
 be observed that &e respiratory efforts only commence when 
 the blood in the vessel begins to be dark. When artificial 
 respiration is resumed, the respiratory efforts cease only when 
 the blood becomes red in the arteries. The invariable result 
 of this experiment seems to show that the respiratory sense is 
 connected with a supply of blood containing little oxygen 
 and charged with carbonic add to the systemic capillaries by 
 the arteries, and that it varies in intensity with the degree 
 of change in the blood. 
 
 3. L while artificial respiration is regularly performed, a 
 large artery be opened, and the system be thus drained of 
 blood, when the hemorrhage has proceeded to a certain ex- 
 tent, the animal makes respiratory efforts, which become 
 more and more violent, until they terminate, just before 
 death, in general convulsions. The s&me result follows when 
 the blood is prevented from getting to the system by applying 
 a ligature to the aorta. 
 
 These facts, which may be successively observed in a 
 single experiment, remain precisely the same if we previously 
 divide both pnemnogastrie nerves in the neck; showing that 
 these are by no means the only nerves which convey the 
 respiratory sense to the medulla oblongata. 
 
 The conclusions which may legitimately be drawn from 
 the above-mentioned facts are the following : 
 
 The respiratory sense has its seat in the system, and is 
 transmitted to the medulla oblongata by the general sensory 
 nerves. It is not located in the lungs, for it operates when 
 the lungs are regularly filled with pure air, if the system be 
 drained of the oxygen-carrying fluid. 
 
484: RESPIRATION. 
 
 It is due to a want of oxygen on the part of the system, 
 and not to any fancied irritant properties of carbonic acid ; 
 for when the lungs are filled with air, and the system is grad- 
 ually drained of blood, though all the blood which finds its 
 way to the capillaries is fullj oxygenated, as the quantity 
 becomes insufficient to supply the required amount of oxygen, 
 the sense of want of air is felt, and respiratory efforts take 
 place. The experimental results on which these conclusions 
 are based are invariable, and have been demonstrated re- 
 peatedly ; so that the location of the respiratory sense in the 
 general system, and the fact that it is an expression of a want 
 of oxygen, seem as certain as that oxygen is taken up by the 
 blood from the lungs, and distributed to the tissues by the 
 arteries. With this view we can explain all the .reflex phe- 
 nomena which are connected with the respiratory function. 1 
 
 The supposition of Berard that the respiratory sense is 
 due to distention of the right cavities of the heart is disproved 
 by the simple experiment of sudden excision of this organ. 
 In that case, as the system is drained of blood, efforts at 
 respiration invariably take place, though the supply of air to 
 the lungs be continued. 
 
 Sense of Suffocation. We must separate, to a certain 
 extent, the respiratory sense from the sense of distress from 
 want of air, and its extreme degree, the sense of suffocation. 
 The first is not a sensation, but an impression conveyed to 
 the medulla oblongata, giving rise to involuntary reflex move- 
 ments. The necessities on the part of the system for oxygen 
 regulate the supply of air to the lungs. We have already 
 seen that every five to eight respirations, or when the respi- 
 
 1 There are many phenomena which physiologists found it impossible to ex- 
 plain on the supposition that the " besoin de respirer" was located in the lungs and 
 conveyed to the medulla oblongata by the pneumogastrics ; among which may 
 be mentioned the effect of irritation of the general surface in the resuscitation of 
 new-born children in which respiration is not established spontaneously. Dr. 
 Marshall Hall and John Keid thought that in these cases the sensory filaments dis- 
 tributed on the skin had something to do in transmitting impressions to the respi- 
 ratory centre. 
 
SENSE OF SUFFOCATION. 485 
 
 ratory movements are a little restricted under the influence 
 of depressing emotions, an involuntary deep or sighing in- 
 spiration is made, for the purpose of changing the air in the 
 lungs more completely. The increased consumption of oxygen 
 and a certain amount of interference with the mechanical 
 process of respiration during violent muscular exercise put 
 us " out of breath ;" and for a time the respiratory move- 
 ments are exaggerated. This is perhaps the first physiological 
 way in which the want of air is appreciated by the senses. 
 A deficiency in hematosis, either from a vitiated atmosphere, 
 mechanical obstruction in the air-passages, or grave trouble 
 in the general circulation, produces all grades of sensations, 
 from the slight oppression which is felt in a crowded room, 
 to the intense distress of suffocation. When hematosis is but 
 slightly interfered with, only an indefinite sense of oppression 
 is experienced ; the respiratory movements are a little in- 
 creased, the most marked effect being an increase in the 
 number and extent of sighing inspirations. In the experi- 
 ments upon animals to which we have referred, when artifi- 
 cial respiration was interrupted, we first noticed regular and 
 not violent contractions of the respiratory muscles ; but as the 
 sense of want of air increased, every muscle which could be 
 used to raise the chest was brought into action. In the 
 human subject in this condition, the countenance has a 
 peculiar expression of anxiety and distress, and the move- 
 ments soon extend to the entire muscular system, resulting 
 in general convulsions, and, finally, insensibility. 
 
 Bearing in mind the fact, that though these sensations 
 are referred to the lungs, indicating increased respiratory 
 effort as the common means for their relief, they have their 
 real point of departure in the general system, we can under- 
 stand the operation of various abnormal conditions of the 
 circulation, when the lungs are adequately supplied with 
 fresh air. The first subjective symptom of air in the veins 
 is a sense of impending suffocation. There is no want of air 
 in the lungs, but the circulation is instantaneously inter- 
 
486 RESPIRATION. 
 
 rupted, and oxygenated blood is not supplied to the tis- 
 sues. The same effect, practically, follows abstraction of 
 the circulating fluid, or the absorption of any poisonous agent 
 which destroys the function of the corpuscles as carriers of 
 oxygen ; though in hemorrhage, the effects are not as marked, 
 as generally the system is gradually debilitated by the pro- 
 gressive loss of blood. It was invariably noticed in the ex- 
 periments above referred to, that after the division of a large 
 artery, though artificial respiration was carefully performed, 
 respiratory efforts took place when the system was nearly 
 drained of blood. As the hemorrage continued, these efforts 
 became more violent, and eventuated, just before death, in 
 general convulsions. 1 A comparison of this experiment with 
 those in which artificial respiration was simply interrupted 
 shows that in sudden hemorrhage there can be no doubt that 
 the system feels the want of oxygen ; and when the loss of 
 blood is very great, this is increased until it amounts to a 
 sense of suffocation. In gradual hemorrhage, there is a con- 
 
 1 "Expt. xxxiv., Feb. 19, 1861. A good-sized dog was etherized and the chest 
 opened in the usual way. Artificial respiration was established, and Expt. xxix. 
 verified. The blood was then allowed to flow freely from the femoral artery, 
 while artificial respiration was actively continued. While the blood continued to 
 flow, the respiratory muscles were carefully observed. During the first part of 
 the bleeding no respiratory efforts took place ; but when the blood had flowed for 
 a considerable time, and the system was becoming drained, respiratory efforts com- 
 menced, feeble at first, but as the bleeding continued, becoming more violent until the 
 whole muscular system was affected by convulsive movements" (Am. Journ., loc. 
 cit., p. 376.) 
 
 Convulsions after profuse hemorrhage have long been observed by physiol- 
 ogists, but no entirely satisfactory explanation of their occurrence has ever been 
 given. There now can be no doubt that they are due to a deficiency of oxygen. 
 The experiments of Kusmaul and Tenner ( On the Nature and Origin of Epilepti- 
 form Convulsions caused by Profuse Bleeding. New Sydenham Society, London, 
 1859) show that convulsions may be produced by ligature of the great vessels 
 carrying blood to the brain. In this case they are probably due to a deficiency of 
 oxygen in this vascular and highly organized part. In their experiments, which 
 were made on rabbits, it was observed that " respiration is at first accelerated, but 
 shortly afterwards, a little while before the approach of general convulsions, it 
 becomes prolonged and deep." P. 14. 
 
KESPIRATOKY EFFOKTS BEFORE BIRTH. 487 
 
 servative provision of Nature, by which faintness and dimi- 
 nution in the force of the heart's action favor the arrest of 
 the flow of blood. 
 
 Poisoning by carbonic oxide is generally accompanied with 
 convulsions, which arise from the sense of suffocation, and are 
 due to a fixation of this gas in the blood-corpuscles, by which 
 they are rendered incapable of giving oxygen to the system. 
 Convulsions also attend poisoning by hydrocyanic acid, in 
 cases in which the system is not overpowered immediately by a 
 large dose of this agent, and the muscular irritability destroyed. 
 
 Experiments have failed to show that the respiratory 
 sense, or the sense of suffocation, is due to irritation produced 
 by carbonic acid in the non-oxygenated blood. 
 
 Respiratory Efforts ~before Birth. 
 
 It is generally admitted that one of the most important 
 functions of the placenta, and the one which is most im- 
 mediately connected with the life of the foetus, is a respira- 
 tory interchange of gases, analogous to that which takes 
 place in the gills of aquatic animals. The vascular pro- 
 longations from the foetus are continually bathed in the 
 blood of the mother, and this is the only way in which it 
 can receive oxygen. Notwithstanding the statements of 
 those who have been unable to note any difference in color 
 between the blood contained in the umbilical arteries and 
 the vein, there are direct observations showing that such a 
 difference does exist. Legallois frequently observed a bright 
 red color in the blood of the umbilical vein ; and on alter- 
 nately compressing and releasing the vessel, he saw the blood 
 change in color successively from red to dark, and dark to 
 red. 1 As oxygen is thus adequately supplied to the system, 
 the foetus is in a condition similar to that of the animals in 
 which artificial respiration was effectually performed. The 
 want of oxygen is fully met, and therefore no respiratory 
 
 1 BERARD, Cours de Physiologic, tome iii., p. 422. 
 
4:88 RESPIRATION. 
 
 efforts take place. Respiratory movements will take place, 
 however, even in very young animals, when there is a defi- 
 ciency of oxygen in the system. It has been observed that 
 the liquor amuii occasionally finds its way into the respira- 
 tory passages of the foetus, whose it could only enter in efforts 
 at respiration. "Winslow, in the latter part of the last cen- 
 tury, first noticed respiratory efforts in the foetuses of cats 
 and dogs, in the uterus of the mother during life ; 1 and many 
 others have observed that when foetuses are removed from 
 vascular connection with the mother, they will make vigor- 
 ous efforts at respiration. This fact we have frequently had 
 occasion to demonstrate in making operations upon pregnant 
 animals. After the 'death of the mother, the foetus always 
 makes a certain number of respiratory efforts, which are not 
 uncertain in their character, but distinct, accompanied by 
 great elevation of the ribs, opening of the mouth, and follow- 
 ing each other at regular intervals, independently of irritation 
 of the general surface. 11 
 
 From what has been experimentally demonstrated with 
 regard to the location and cause of the respiratory sense after 
 birth, it is evident that want of oxygen is the cause of re- 
 spiratory movements in the foetus. When the circulation in 
 the maternal portion of the placenta is interrupted from any 
 cause, or when the blood of the foetus is obstructed in its 
 course to and from the placenta, the impression due to the 
 want of oxygen is conveyed to the medulla oblongata, and 
 efforts at respiration are the result. This cannot be due to 
 an accumulation of carbonic acid in the lungs, and is entirely 
 
 1 British and Foreign Medico- Chirurgical Review, April, 1864, p. 330. 
 
 2 We take from our note-book the following observation showing respiratory 
 efforts in a very young animal : 
 
 " Jan. 6, 1865. In operating to-day on a small-sized bitch, for the purpose of 
 demonstrating the glycogenic process in the liver, I found her pregnant, and hi 
 the uterus were six pups, certainly not more than one-fourth the size which they 
 attain before birth. (They were four niches long.) On removing them from the 
 womb, and dividing the umbilical vessels, they all made a number of profound 
 respiratory efforts at intervals of from two to three minutes." 
 
CUTANEOUS EESPIEATION. 489 
 
 consistent with our views, locating the respiratory sense in 
 the general system. 1 
 
 Cutaneous Respiration. 
 
 This mode of respiration, though very important in 
 many of the lower orders of animals, is insignificant in the 
 human subject, and even more slight in animals covered 
 with hair or feathers. 2 Still, an appreciable quantity of 
 oxygen is absorbed by the skin of the human subject, 
 and an amount of carbonic acid, which is proportionately 
 larger, is exhaled. Exhalation of carbonic acid, which is 
 connected rather with the functions of the skin as a general 
 excreting organ and is by no means an essential part of the 
 respiratory process, will be more fully considered under the 
 head of excretion. Carbonic acid is given off with the general 
 emanations from the surface, being found at the same time 
 in solution in the urine and in most of the secretions. It is 
 well known that death follows the application of an imper- 
 meable coating to the entire cutaneous surface; but this is 
 by no means due to a suppression of its respiratory function 
 alone. The skin has other offices, particularly in connection 
 with regulation of the animal temperature, which are infi- 
 nitely more important. 
 
 An estimate of the extent of cutaneous, compared with 
 pulmonary respiration, has been made by Scharling, 3 by com- 
 
 1 The physiological and pathological questions connected with the subject of 
 " respiration before birth," are ably and exhaustively discussed in a review pub- 
 lished in the ' Medico- CMrurgical Review, for April, 1864. A number of ex- 
 periments by various observers are here detailed, fully establishing the facts we 
 have stated. Among the most interesting are those of Schwartz, showing respi- 
 ratory movements in foetuses, when care was taken not to expose them to the 
 cool air or any other irritation of the general surface, p. 333. 
 
 2 REGNAULT and REISET found the cutaneous respiration so slight in the ani- 
 mals which they used for their experiments, that its influence upon the compo- 
 sition of the air in which they Were confined could be disregarded. (Op. cit.} 
 
 3 In MILNE-EDWARDS, Lemons sur la Phijsiologie, tome ii., p. 635. The reader 
 will here find an account of the experiments of DeMilly, Abernethy, and others, 
 demonstrating the absorption of oxygen and exhalation of carbonic acid by the skin. 
 
490 RESPIRATION. 
 
 paring the relative quantities of carbonic acid exhaled in the 
 twenty-four hours. According to this observer, the skin 
 performs from -fa to -fa of the respiratory function. 
 
 Asphyxia. 
 
 The effects of cutting off the supply of oxygen from the 
 lungs are mainly referable to the circulatory system, and 
 have already been considered under the head of the influence 
 of respiration upon the circulation. 1 It will be remembered 
 that in asphyxia the non-aerated blood passes with so much 
 difficulty through the systemic capillaries, as finally to arrest 
 the action of the heart. It is the experience of those who 
 have experimented on this subject, that the movements of 
 the heart, once arrested in this way, cannot be restored ; but 
 that while the slightest regular movements continue, its 
 functions will gradually return if air be readmitted to the 
 lungs. 
 
 A remarkable power of resisting asphyxia exists in newly 
 born animals that have never breathed. This was noticed by 
 Haller and others, and has been the subject of numerous 
 experiments, among which we may mention those of Buffon, 
 Legallois, and W. F, Edwards. Legallois found that young 
 rabbits would live for fifteen minntes deprived of air by 
 submersion, but that this power of resistance diminished 
 rapidly with age. 2 W. F. Edwards has shown that there 
 exists a great difference in this regard in different classes of 
 animals. Dogs and cats, that are born with the eyes shut, and 
 in which there is at first a very slight development of animal 
 heat, will show signs of life after submersion for more than 
 half an hour; while Guinea pigs, which are born with the eyes 
 open, are much more active, and produce a greater amount 
 of heat, will not live more than seven minutes. 3 
 
 1 See page 290. a See page 421, note. 
 
 8 W. F. EDWARDS, De V Influence des Agcns Physiques sur la Vie, Paris, 1824, 
 pp. 171, 172. 
 
ASPHYXIA. 491 
 
 The cause of this peculiarity has been attributed to the 
 existence of the foramen ovale, enabling the blood to get 
 to the system without passing through the lungs, by those 
 who regard the arrest of the circulation in asphyxia as due 
 to obstruction to the pulmonary circulation ; but this expla- 
 nation is not sufficient, as blood passes easily through the 
 lungs in asphyxia, and is obstructed only in the systemic 
 capillaries. 
 
 The true explanation seems to be, that in most warm- 
 blooded animals, during the very first periods of extra-uterine 
 life, the demands on the part of the system for oxygen are 
 comparatively light. At this time there is very little activity 
 in the processes of nutrition, and the actual consumption of 
 oxygen and exhalation of carbonic acid are very much below, 
 the regular standard in animals of this class. -In fact, their 
 condition is somewhat like that of cold-blooded animals. The 
 actual difference in the consumption of oxygen immediately 
 after birth and at the age of a few days is sufficient to explain 
 the remarkable power of resisting asphyxia just after birth. 
 The comparative observations of Edwards on dogs, cats, and 
 Guinea pigs, show that this power bears a definite relation 
 to the respiratory activity. 
 
 One of the most interesting questions, in a practical point 
 of view, connected with the subject of asphyxia, is the effect on 
 the system of air vitiated from breathing in a confined space. 
 There are here several points presented for consideration. 
 The effect of respiration on the air is to take away a certain 
 proportion of oxygen, and add certain principles which are 
 regarded as deleterious. The emanation which is generally 
 regarded as having the most decided influence upon the 
 system is carbonic acid. 
 
 A careful review of the most reliable observations on this 
 subject shows that the influence of carbonic acid is generally 
 very much over-estimated. In poisoning by charcoal fumes, 
 it is generally carbonic oxide which is the active princi- 
 
492 RESPIRATION. 
 
 pie. Kegnault and Eeiset 1 exposed dogs and rabbits for 
 many hours to an atmosphere containing 23 parts per 100 of 
 carbonic acid artificially introduced, and 30 to 40 parts of 
 oxygen, without any ill effects. They took care, however, 
 to keep up a constant supply ef oxygen. These experiments 
 are at variance with the results obtained by others, but Re- 
 gnault and Reiset explain this difference by the supposition 
 that the gases in other observations were probably impure, 
 containing a little chlorine or carbonic oxide. There is no 
 reason to doubt, from the high reputation of the observers 
 for skill and accuracy, that their experiments are perfectly 
 reliable ; and in that case, they prove that carbonic acid does 
 not act upon the system as a poison. This view is sustained 
 by the more recent observations of Dr. Hammond, which we 
 give in his own words : 
 
 " I confined a sparrow under a large bell-glass, having 
 two openings. Through one of these I introduced every 
 hour 1,000 cubic inches of an atmosphere containing 45 parts 
 of oxygen, 30 of nitrogen, and 25 of carbonic acid, allowing 
 the vitiated air in which the animal had respired partially to 
 escape. At the end of twelve hours the bird was in as good 
 a condition as at the commencement of the experiment ; and 
 when the bell-glass was raised, it flew away as if nothing had 
 happened to it. A mouse subjected to a similar experiment 
 also suffered no inconvenience." 2 
 
 In breathing in a confined space, the distress and finally 
 fatal results are produced, in all probability, more from animal 
 emanations and deficiency of oxygen, than from the presence 
 of carbonic acid. When the latter gas is removed as fast as 
 it is produced, the effects of diminution in the proportion of 
 oxygen are soon very marked, and progressively increase till 
 death occurs. Bernard has shown that birds enclosed in a 
 confined space, from which the carbonic acid is carefully 
 
 1 Loc. dt. 
 
 3 HAMMOND, Treatise on Hygiene, Philadelphia, 18G3, p. 351. 
 
ASPHYXIA. 493 
 
 removed, will gradually consume oxygen, until, when death 
 occurs, the proportion is reduced to from 3 to 5 parts per 
 100. 1 When the carbonic acid is allowed to remain, the 
 increased density of the atmosphere interferes with the dif- 
 fusion between the gases of the blood and the air, and death 
 supervenes with greater rapidity. 
 
 The influence on animals of emanations from the lungs 
 and general surface, from which the carbonic acid and watery 
 vapor have been removed, has been shown by Dr. Hammond 
 to be very decided and rapid. He confined a mouse in a 
 large glass jar, so arranged as to admit fresh air as the at- 
 mosphere became rarefied by respiration, causing the carbonic 
 acid to be absorbed by sponges saturated with baryta-water, 
 and the watery vapor by pieces of chloride of calcium. The 
 animal died in forty-five minutes ; when, by passing the gas- 
 eous contents of the jar through baryta-water, it was shown 
 to contain no carbonic acid, and the presence of organic 
 matter in large quantity was demonstrated. 2 
 
 In crowded assemblages, the slight diminution of 
 oxygen, the elevation of temperature, increase in moisture, 
 and particularly the presence of organic emanations, com- 
 bine to produce unpleasant sensations. The terrible ef- 
 fects of this carried to an extreme were exemplified in the 
 confinement of the 146 English prisoners, for eight hours 
 only, in the "Black Hole" of Calcutta; a chamber eigh- 
 teen feet square, with only two small windows, and those 
 obstructed by a verandah. Out of this number, 96 died in 
 six hours, and 123 at the end of the eight hours. Many of 
 
 1 BERNARD, Lemons sur les Effets des Substances Toxigues et Medicamenteuses, 
 Paris, 1857, p. 116. 
 
 3 Op. cit., p. 170. " For the detection of organic matter in the atmosphere, 
 the permanganate of potassa affords a very sensitive reagent. A solution of this 
 substance in water loses its brilliant red color, and the salt undergoes decompo- 
 sition, when air containing organic matter is passed through it. By the extent to 
 which the loss of color reaches we are enabled to form an approximative idea of 
 the amount of such matter present in the air. The solution is placed in Liebig's 
 bulbs, and the air is drawn through it by means of an aspirator." P. 172. 
 
494: RESPIRATION. 
 
 those who immediately survived afterwards died of putrid 
 fever. 1 This frightful tragedy has frequently been repeated 
 on emigrant and slave ships, by confining great numbers in 
 the hold of the vessel, where they were entirely shut out from 
 the fresh air. This subject possesses great pathological in- 
 terest; the effects of an insufficient supply of air and the 
 accumulation in the atmosphere of animal emanations being 
 very important in connection with the cause and prevention 
 of many diseases. 
 
 The condition of the system has a marked and important 
 influence on the rapidity with which the effects of vitiated 
 atmosphere are manifested, as we should anticipate from what 
 we know of the variations in the consumption of oxygen under 
 different conditions. As a rule, the immediate effects of con- 
 fined air are not as rapidly manifested in weak and debilitated 
 persons, as in those who are active and powerful. It has 
 sometimes b.een observed, in cases where a male and a female 
 have attempted suicide together by the fumes of charcoal, 
 that the female may be restored some time after life is ex- 
 tinct in the male. This is probably owing to the greater 
 demand for oxygen on the part of the male. 
 
 The following interesting fact is reported by Bernard, 
 showing the relative power of resisting asphyxia in health 
 and disease : 
 
 " Two young persons were in a chamber warmed by a 
 stove fed with coke. One of them was seized with asphyxia 
 and fell unconscious. The other, at that time suffering with 
 typhoid fever and confined to the bed, resisted sufficiently to 
 be able to call for help. "We know already that this resistance 
 to toxic influences is manifested in animals, when they are 
 made sick ; we here have the proof of the same phenomenon 
 in man. As for the one who, in good health, had experienced 
 the effects of the commencement of poisoning, she had a 
 
 1 A full account of the sufferings of these unfortunate men, by one of the 
 survivors, is to be found in the Annual Register, 1758, p. 278. 
 
ASPHYXIA. 495 
 
 paralysis of the left arm, which was not completely cured at 
 the end of six months." 1 
 
 It is thought that the condition of syncope has an influence 
 on the power of resistance to asphyxia. A case is quoted by 
 Carpenter in which a woman, who had been submerged for 
 fifteen minutes, was taken out of the water and recovered 
 spontaneously. She stated that she was insensible at the 
 moment of her submersion. 2 
 
 When poisoning by confined air is gradual, the system 
 becomes somewhat accustomed to the toxic influence ; the 
 temperature of the body is lowered, 3 and an animal will live 
 in an atmosphere which will produce instantaneous death in 
 one that is fresh and vigorous. Bernard has made a number 
 of curious and instructive experiments on this point. In one 
 of them, a sparrow was confined under a bell-glass for one 
 hour and a half, at the end of which time another was intro- 
 duced, the first being still quite vigorous. The second be- 
 came instantly much distressed, and died in five minutes ; 
 but ten minutes after, the sparrow which had been confined 
 for more than an hour and a. half was released, and flew 
 away. 4 
 
 This is simply demonstrating, with experimental accuracy, 
 a fact of which we are all conscious ; for it is well known, 
 that going from the fresh air into a close room, we experience 
 a malaise which is not felt by those who have been in the 
 room, for a length of time, and whose emanations have 
 vitiated the atmosphere. 
 
 1 BERNARD, op. ciL, p. 197. 
 
 2 CARPENTER, Principles of Human Physiology, Am. edit., 1853, p. 536. 
 
 3 Bernard noted a diminution in the temperature in the rectum of a pigeon, 
 from 105 to 88 Fahr., after four hours' sojourn in a confined space, containing 
 732 cubic inches of air. The animal was nearly dead when removed. (Loc. cit. 
 p. 128.) 
 
 4 Op. cit., p. 119. 
 
E X. 
 
 Air, diffusion of, in the lungs, . . . 406 
 
 composition of, 413 
 
 changes of, in passage through 
 
 the lungs, 423 
 
 increase in temperature of, in 
 
 passage through the lungs, 423 
 
 Air-cells, anatomy of, 362 
 
 Albumen, situations and quantity 
 
 of, 81 
 
 mode of extraction and prop- 
 erties of, 82 
 
 influence of, on polarized 
 
 light, 83 
 
 tests for, 83 
 
 origin and functions of, 83 
 
 Albumiuometer, 84 
 
 Albuminose, 85 
 
 Alcohol, exhalation of, by the 
 
 lungs, * 450 
 
 Ammonia, exhalation of, in respi- 
 ration, 448 
 
 Arteries, circulation in, 240 
 
 physiological anatomy of,.. . 241 
 
 divisions of, 243 
 
 coats of, 243 
 
 nerves in walls of, 245 
 
 blood-vessels in walls of, ... 245 
 
 elasticity of, 246 
 
 experiments showing dilata- 
 tion of, 247 
 
 influence of elasticity of, on 
 
 the current of blood, 248 
 
 contractility of, 230 
 
 locomotion of, and produc- 
 tion of the pulse, 252 
 
 variations in caliber of, at 
 
 different periods of the day, 261 
 
 32 
 
 Arterial pressure, 261 
 
 in different vessels, 206 
 
 influence of respiration on,. . 267 
 
 influence of hemorrhage on, . 269 
 
 Arterial circulation, rapidity of,. . 270 
 
 apparatus of Volkmann and 
 
 Hiittenheim for measuring ra- 
 pidity of, 271 
 
 apparatus of Vierordt, 272 
 
 apparatus of Chauveau, 273 
 
 rapidity of, in different ves- 
 sels, 274 
 
 Arterial murmurs, 276 
 
 Asphyxia, 490 
 
 power of resistance to in the 
 
 newly-born, 421, 490 
 
 from breathing in a confined 
 
 space, 491, 495 
 
 from charcoal fumes, 491 
 
 influence of, on pulmonary 
 
 circulation, 343 
 
 Besoin de respirer, 479-484 
 
 Bicarbonate of soda, 45 
 
 Biliverdine, 93 
 
 Black Hole of Calcutta, 493 
 
 Blood, general considerations,. ... 95 
 
 immediate importance to 
 
 life, 96 
 
 experiment of withdrawing a 
 
 large quantity from the vessels, 97 
 
 transfusion of, 97 
 
 transfusion of, in disease, ... 98 
 
 transfusion of, in experi- 
 ments on animals, !j9 
 
 entire quantity of, in the 
 
 body, 100 
 
498 
 
 INDEX. 
 
 Blood, reaction, odor, and opacity 
 of, 104 
 
 temperature and specific gra- 
 vity of, 105 
 
 'color of, 106 
 
 color of, in veins of the 
 
 glands, 107 
 
 analyses of, 127 
 
 inorganic constituents of,.. .. 128 
 
 organic nitrogenized constit- 
 uents of, 129 
 
 organic non-nitrogenized con- 
 stituents of, 129 
 
 quantitative analyses of, 130 
 
 quantitative analysis of, by 
 
 method of Becquerel and Ro- 
 
 dier, 131 
 
 quantitative analysis of, by 
 
 the author's method, 134 
 
 table of composition of, .... 138 
 
 coagulation of, 142 
 
 rapidity of coagulation of, . . 143 
 
 circumstances modifying co- 
 agulation of, 149 
 
 coagulation of, in the organ- 
 ism, 160 
 
 office of coagulation in arrest 
 
 of hemorrhage, 153 
 
 cause of coagulation of, .... 156 
 
 summary of properties and 
 
 functions of, 167 
 
 changes of, in respiration, . . 452 
 
 difference in color between 
 
 venous and arterial, 454 
 
 general differences between 
 
 arterial and venous, 470 
 
 analyses of, for gases, . . 458-464 
 
 condition of gases in, 466 
 
 Blood-corpuscles (red), 108 
 
 anatomical characters of, ... 109 
 
 table of measurements of, .. 113 
 
 chemical characters of, 117 
 
 development of, 118 
 
 functions of, 120 
 
 (white), 121 
 
 elementary corpuscles, 126 
 
 absorption of oxygen by, ... 455 
 
 Blood-crystals, 117 
 
 Breathing capacity, extreme, 403 
 
 Bronchial tubes, anatomy of,. ... 360 
 
 Calorific elements, 60 
 
 Capillaries, circulation in, 278 
 
 anatomy of, 279 
 
 distribution of, 281 
 
 course of blood in, 283 
 
 Capillary system, capacity of, 282 
 
 Capillary circulation, microscopic 
 
 examination of, 284 
 
 rapidity of, 289 
 
 relations of, to respiration,. . 290 
 
 causes of, 293 
 
 phenomena in patients dead 
 
 , with yellow fever, 295 
 
 influence of temperature on, 297 
 
 influence of direct irritation 
 
 on, 298 
 
 Carbonate of lime, 42 
 
 crystals of, in internal ear,. . 43 
 
 formation of, in analysis by 
 
 incineration, 43 
 
 quantity of (table), and func- 
 tion, 43 
 
 Carbonate of soda, quantity of 
 
 (table), and function, 44 
 
 Carbonate of potassa, and carbon- 
 ate of magnesia, 45 
 
 Cartilagine, 91 
 
 Cardiometer of Magendie and 
 
 Bernard, 263, 265 
 
 of Marey (differential), 264 
 
 Carbonaceous matter in the lungs, 364 
 
 Carbonic acid, discovery of, 410 
 
 exhalation of, in respiration, 424 
 
 influence of arrest of respira- 
 tory movements on exhalation 
 
 of, 425 
 
 quantity of, exhaled, 427 
 
 influence of age on exhala- 
 tion of, 431 
 
 influence of sex, 432 
 
 influence of digestion, 433 
 
 influence of diet, 435 
 
 influence of alcohol, 437 
 
 influence of sleep, 439 
 
 influence of moisture and 
 
 temperature, 441 
 
 influence of seasons, 442 
 
 ' sources of, in the expired 
 
 air, 445 
 
 proportion in arterial and 
 
 venous blood, 464 
 
 condition of, in the blood, . . 467 
 
 effect of inhalation of, 492 
 
 production of, in respiration, 478 
 
 Carbonic oxide, exhalation of, by 
 the lungs when injected into the 
 
 blood, 450 
 
 Caseine, extraction of, etc, 86 
 
 Catalysis, definition of, 74 
 
 Cephalo-rachidian fluid, uses of, . . 334 
 
 Chloride of sodium, 35 
 
 quantity of (table), .... 35 
 
 function of, 36 
 
INDEX. 
 
 499 
 
 Chloride of sodium, desire of all 
 
 animals for, 37 
 
 effect of deprivation of, on 
 
 nutrition, 37 
 
 quantity of in blood almost 
 
 constant, 38 
 
 removal of excess of by the 
 
 kidneys, 38 
 
 Chloride of potassium, 39 
 
 Chloride of ammonium, 47 
 
 Circulation of the blood, discovery 
 
 of, 170 
 
 general course of, 175 
 
 action of the heart in (see 
 
 Heart), 177 
 
 in the arteries (see Ar- 
 teries), 240 
 
 in the capillaries (see Capil- 
 laries), 278 
 
 in the veins (see Veins), . . . 301 
 
 Circulation, derivative, 339 
 
 pulmonary, 340 
 
 general rapidity of, 343 
 
 rapidity of, in different ani- 
 mals, 346 
 
 relations of rapidity of, to the 
 
 frequency of the heart's action, 348 
 Circulatory system, phenomena in, 
 
 after death, 351 
 
 Clot, characters of, 144 
 
 Coloring matters, 92 
 
 Cornplemental air, 401 
 
 Convulsions from hemorrhage, ... 486 
 
 Coughing, 395 
 
 Coagulation of the blood (see 
 
 Blood), 142 
 
 Cranial cavity, circulation in,. ... 332 
 amorphous sheath of blood- 
 vessels of, 336 
 
 Crystalline, 90 
 
 Diabetic sugar, 50 
 
 Diaphragm, action of, in respira- 
 tion, 369 
 
 Diffusion of air in the lungs, 406 
 
 Elasticine, 91 
 
 Emulsion, 63 
 
 Emphysema, changes of thorax in, 385 
 
 Epiglottis, action of, in deglutition, 359 
 
 Erectile tissues, circulation in,. . . . 336 
 
 Erection, mechanism of, 338 
 
 Expiration, movements of, 382 
 
 influence of elasticity of the 
 
 lungs and thoracic walls in, .... 383 
 muscles of (table), 385 
 
 Expiration, action of internal iuter- 
 
 costals in, 386 
 
 action of infra-costales and 
 
 triangularis sterni in, 387 
 
 action of obliquus externus 
 
 and internus in, 388 
 
 action of transversalis in, ... 388 
 
 action of sacro-lumbalis in, . . 389 
 
 Fats, varieties of, &c 60 
 
 composition and properties 
 
 of, ........ 61 
 
 condition of, in nervous tissue 
 
 and blood-corpuscles,.. 62 
 
 saponification of, 62 
 
 emulsion of, (53 
 
 origin and functions of, .... 63 
 
 formation of, in the organ- 
 ism, 64 
 
 average quantity of, in the 
 
 body, and mechanical func- 
 tion of, 65 
 
 changes which they undergo 
 
 in the organism, 66 
 
 Fatty acids, .. 62, 66 
 
 Fermentation of sugar, 51 
 
 Fermentation-test for sugar, 56 
 
 Fibrin, 76 
 
 mode of extraction of, and 
 
 condition in the organism, 77 
 
 organization of, 78 
 
 distinctions from plastic 
 
 lymph, 79 
 
 origin of, 80 
 
 function of, and destruction 
 
 by liver and kidneys, 81 
 
 Gases, as proximate principles,.. . 29 
 
 in the alimentary canal,. ... 29 
 
 proportions of, in venous and 
 
 arterial blood, 456, 464-470 
 
 of the blood, table of 
 
 Magnus, 463 
 
 Gases, condition of, in the blood, . 466 
 
 Globuline, 90 
 
 Glucose, 50 
 
 Glycerine, 62 
 
 Hsematoidine, 117 
 
 Heart, anatomy of, 176 
 
 capacity of different cavities 
 
 of, 179 
 
 valves of, 181 
 
 movements of, 183 
 
 action of the auricles,... ., 184 
 
 action of the ventricles, ... 185 
 
500 
 
 INDEX. 
 
 Heart, locomotion of, 186 
 
 twisting, hardening, short- . 
 
 ening, and elongation of, 187 
 
 -impulse of, 191 
 
 succession of movements of, 192 
 
 force of, 197 
 
 action of the valves, 199 
 
 sounds of, 203 
 
 cause of the sounds of, 207 
 
 relations of the sounds to 
 
 the blood-currents, 210 
 
 frequency of action of, 211 
 
 influence of age and sex on 
 
 frequency, 212 
 
 influence of posture and mus- 
 cular exertion, 213 
 
 influence of exercise, 215 
 
 influence of sleep, 216 
 
 influence of temperature, ... 216 
 
 influence of respiration on 
 
 action of, 217 
 
 cause of rhythmical contrac- 
 tions of, 220 
 
 irritability of, 222 
 
 pulsations of, after removal 
 
 from the body, 223 
 
 effect of ligature of coronary 
 
 arteries on pulsations of, 225 
 
 effect of emptying the cavi- 
 ties, 226 
 
 influence of the nervous sys- 
 tem on, 228 
 
 influence of pneumogastrics 
 
 on, 231 
 
 effects of blows on epigastrium 
 
 on, 238 
 
 Hsematine, 92 
 
 Hsematosis, 452 
 
 Haemodynamometer of Poiseu- 
 
 ille, 262, 265 
 
 registering instrument of 
 
 Ludwig (note), 264 
 
 differential instrument of Ber- 
 nard (note), 266 
 
 Hydro-carbons, general considera- 
 tions, 26, 48 
 
 Hydro-chlorate of ammonia, 47 
 
 Inorganic principles, general con- 
 siderations, 25 
 
 table of, 28 
 
 division into essential constit- 
 uents of the tissues and those 
 
 which influence nutrition, 47 
 
 Inspiration, muscles of (table),.. . . 368 
 
 action of diaphragm in, 369 
 
 action of scaleni, 372 
 
 Inspiration, action of intercostals, . 373 
 
 movements of, the ribs in, ... 374 
 
 action of levatores costarum, 378 
 
 auxiliary muscles of, 378 
 
 action of serratus posticus 
 
 superior, 378 
 
 action of sterno-mastoideus, 
 
 levator anguli scapuloe, and su- 
 perior portion of trapczius,. . . . 379 
 
 action of pectoralis minor, 
 
 .inferior portion of pectoralis 
 major, and serratus magnus,. .. 380 
 Intercostals, internal, action of, in 
 
 respiration, 386 
 
 Infra-costales, action of, in respira- 
 tion, 387 
 
 Keratine, 91 
 
 Lactic acid, 67 
 
 sources and function of,. ... 68 
 
 Larynx, anatomy and respiratory 
 
 movements of, 358 
 
 Laughing, 396 
 
 Levatores costarum, action of, in 
 
 respiration, 378 
 
 Levator anguli scapulae, action of, 
 
 in respiration, 379 
 
 Leucocytes, 121 
 
 development of, 124 
 
 proportion of, to red corpus- 
 cles, 125 
 
 Liver, influence of respiration on 
 
 circulation in, 322 
 
 Liver-sugar, 50 
 
 Lungs, anatomy of parenchyma of, 361 
 
 capacity of, 397 
 
 carbonaceous matter in, .... 364 
 
 vital capacity of, 403 
 
 Melanine, 93 
 
 Milk-sugar, 50 
 
 Mucosine, 89 
 
 Musculine, 90 
 
 Nitrogen, exhalation of, in respira- 
 tion, 451 
 
 of the blood, 465, 468 
 
 Nitrogenized principles, general 
 considerations, 27, 69 
 
 Nitrous oxide, effects of respira- 
 tion of, 415 
 
 Non-nitrogenized principles,. . . 25, 48 
 
 Obliquus externus and internus, 
 action of, in respiration, 388 
 
INDEX. 
 
 501 
 
 Odorous principles, 66 
 
 exhalation of, by the lungs, . 450 
 
 Organic non-nitrogenized princi- 
 ples, general considerations,.. 27, 69 
 Organic nitrogenized principles, . 
 composition, properties, and 
 condition of, in the organism, .. 71 
 
 table of, 75 
 
 summary of properties of, ... 93 
 
 Organic matter, exhalation of, in 
 
 respiration, 449 
 
 Osteine, 91 
 
 Otoconies, or otoliths, 18 
 
 Oxygen, discovery of, 412 
 
 minimum proportion in the 
 
 air which will support life, 414 
 
 effects of confining animals 
 
 in atmosphere of, 415 
 
 consumption of, in respira- 
 tion, 416, 476 
 
 influence of age on consump- 
 tion of, 421 
 
 influence of temperature, .... 420 
 
 consumption of, in hiberna- 
 tion, 422 
 
 absorption of, by blood-cor- 
 puscles, 455 
 
 proportion in arterial and 
 
 venous blood, 464 
 
 condition of, in the blood, . . 466 
 
 Ozone, 414 
 
 Pancreatine, 88 
 
 Pepsin, 88 
 
 Pectoral muscles, action of, in res- 
 piration, 380 
 
 Phosphate of lime (table of quan- 
 tity of ), 40 
 
 Phosphates of magnesia, soda, and 
 
 potassa, 45 
 
 Physiology, definition of, 14 
 
 Piezometer (note), 267 
 
 Pneumic acid, 68 
 
 action of, on the bicarbonates 
 
 in the blood, 446 
 
 Pneumate of soda, 69 
 
 Poisonous gases, exhalation of, by 
 
 the lungs, 450 
 
 Proximate principles, general con- 
 siderations, 20-24 
 
 inorganic, 25 
 
 do. (table), 28 
 
 organic non-nitrogenized, ... 25 
 
 organic nitrogenized, 27 
 
 Proteine, 73 
 
 Pulmonary artery, pressure of 
 
 blood in, 341 
 
 Pulse, mechanism of production of, 252 
 
 .frequency of, 212 
 
 form of, 254 
 
 dicrotic, 257 
 
 variations in character of,. . . 260 
 
 influence of temperature on, 260 
 
 Putrefaction, 73 
 
 Rennet, 87 
 
 Respiration, influence of, on the 
 
 action of the heart, 217 
 
 general considerations, '. . . . . 353 
 
 movements of, 366 
 
 frequency of movements of,. 391 
 
 movements of ribs in, 374 
 
 types of, 389 
 
 relations of inspiration and 
 
 expiration, 392 
 
 relations in volume of in- 
 spired and expired air, 405 
 
 changes of air in (historical 
 
 considerations), 409 
 
 consumption of oxygen in 
 
 (see Oxygen), 416 
 
 effect of confining an animal 
 
 in a mixture of oxygen and hy- 
 drogen, 422 
 
 exhalation of carbonic acid 
 
 (see Carbonic Acid), 424 
 
 relations between the quan- 
 tity of oxygen consumed and 
 
 carbonic acid exhaled, 443 
 
 exhalation of watery vapor, . . 446 
 
 exhalation of ammonia,. . . . 448 
 
 exhalation of organic matter, 449 
 
 exhalation of alcohol, 450 
 
 exhalation of odorous princi- 
 ples, 450 
 
 exhalation of certain poison- 
 ous gases, 450 
 
 exhalation of nitrogen, 451 
 
 changes of the blood in, .... 452 
 
 absorption of oxygen by the 
 
 blood-corpuscles, 455 
 
 proportions of gases in venous 
 
 and arterial blood, . . . 456, 464-470 
 
 relations of, to nutrition, .... 472 
 
 combustion-theory of,. . 473-476 
 
 consumption of oxygen, 476 
 
 production of carbonic acid, 478- 
 
 cutaneous, 489 
 
 Respiratory organs, anatomy of,.. 357 
 Respiratory sounds (murmurs),. . . 393 
 Respiratory sense, the sensation 
 inducing respiratory move- 
 ments, 479-484 
 
 Respiratory efforts before birth,. . . 487 
 
502 
 
 INDEX. 
 
 Kesidual air, 399 
 
 Reserve air, 400 
 
 Saponification, 62 
 
 Sacro-lumbalis, action of, in res- 
 piration, 389 
 
 Scalene muscles, action of, in res- 
 piration, 372 ' 
 
 Serratus posticus superior, action 
 
 of, in respiration, 378 
 
 Serratus magnus, action of, in res- 
 piration, 380 
 
 Serum, characters of, 146 
 
 Sighing, 396 
 
 Sleep, cerebral circulation in, 334 
 
 Snoring, 393 
 
 Sneezing, 395 
 
 Sobbing, 396 
 
 Soaps, 62-66 
 
 Sphygmograph of Marey, 255 
 
 ofVierordt, 256 
 
 Sterno-mastoideus, action of, in res- 
 piration, 379 
 
 Sulphates of soda, potassa, and 
 
 lime,. 46 
 
 Sulphuretted hydrogen, exhalation 
 
 of, by the lungs, 450 
 
 Sugar, 49 
 
 varieties of, 50 
 
 union of, with chloride of 
 
 sodium, 50 
 
 composition and properties 
 
 of, 50 
 
 fermentation of, 51 
 
 lactic-acid fermentation of, .. 51 
 
 influence of solution of on 
 
 polarized light, 52 
 
 tests for, Moore's or the 
 
 potash test, Trommer's test,. ... 52 
 
 BarreswilFs test, 55 
 
 Maumene's test, fermenta- 
 tion test, Bottger's test, 56 
 
 formation of torula?, 58 
 
 origin and functions of, .... 58 
 
 formation of, hi the foetus, 
 
 and influence on cell-develop- 
 ment, 59 
 
 destruction of, in the lungs, . 59 
 
 Suffocation, sense of, 484 
 
 Tidal air, 401 
 
 Torulae cerevisia?, 58 
 
 Transfusion of blood,. 97-99 
 
 Transversalis, action of, in res- 
 piration, 388 
 
 Trapezius, action of, in respiration, 379 
 
 Trachea, anatomy of, 360 
 
 Triangularis sterni, action of, in res- 
 piration, 387 
 
 Urrosaoine,. 
 
 Valves of the veins, discovery of, . 172 
 Valves of the heart (see Heart),. . . 181 
 
 Vasa vasorum, 245 
 
 Veins, anatomy of, 301 
 
 capacity of, 302 
 
 strength of, 306 
 
 valves of, 308 
 
 function of valves of, 325 
 
 course of blood in, 311 
 
 pressure of blood in, 314 
 
 rapidity and causes of circu- 
 lation in, 315 
 
 influence of muscular con- 
 traction on current of blood in, 817 
 
 influence of aspiration from 
 
 the thorax, 319 
 
 influence of gravitation, 324-330 
 
 entrance of air into, 323 
 
 conditions which impede cir- 
 culation in, 328 
 
 influence of expiration on 
 
 current of blood in, 328 
 
 Venous pulse, 313 
 
 Venous pulse, regurgitant, 329 
 
 Vital properties of organized struc- 
 tures, 18 
 
 Vital capacity of the lungs, 403 
 
 Water, as a proximate principle, . 30 
 condition of, in the organ- 
 ism, 30 
 
 quantity of, in different parts, 
 
 (table), 33 
 
 entire quantity in the body, . 48 
 
 origin, discharge, and func- 
 tion of, 34 
 
 Watery vapor, exhalation of, in 
 respiration, 446 
 
 Yawning, 396 
 
"A BOOK WHICH 13 A3 READABLE AS A NOVEL: 
 
 HISTORY OF EUROPEAN MORALS, 
 
 From Augustus to Charlemagne. 
 
 By W. E. H. LECKY, M. A. 
 
 2 vols., 8vo. 500 pages each. Price, $6.00. 
 
 CONTENTS : 
 
 The Utilitarian School Objections to the School Consequence of acting 
 on Utilitarian Principles Utilitarian Sanctions Intuitive School Alleged 
 Diversities of Moral Judgment Each of the Two Schools of Morals related 
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 are developed. 
 
 THE PAGAN EMPIRE. 
 
 Stoicism Growth of a Gentler and more Cosmopolitan Spirit in Rome 
 Rise of Eclectic Moralists The People still very corrupt Causes of the 
 Corruption Effects of Stoicism en the Corruption of Society Passion for 
 Oriental Religions Neoplatonism. 
 
 THE CONVERSION OF ROME. 
 
 Examination of the Theory which ascribes part of the Teaching of the 
 Hated Pagan Moralists to Christian Influence Theory which attributes the 
 Conversion of the Empire to the Evidence of Miracles The Persecution the 
 Church underwent not of a Nature to crush it History of the Persecutions. 
 
 FROM CONSTANTINE TO CHARLEMAGNE. 
 
 First Consequence of Christianity, a New Sense of the Sanctity of Hu- 
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 the Civic Virtues General Moral Condition of the Byzantine Empire Dis- 
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 Learning Moral Condition of Western Europe Growth of a Military and 
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 THE POSITION OF WOMEN. 
 
 The Courtesans Roman Public Opinion much purer Christian Influ- 
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 In preparing for publication a complete and uniform edition of Lord 
 Macaulay's Works, it has been thought right to include some portion of what 
 he placed on record as a jurist in the East. The papers selected are the Intro- 
 ductory Eeport on the Indian Penal Code, and the Notes appended to that code, 
 in which most of its leading provisions were explained and defended. These 
 papers were entirely written by Lord Macaulay, but the substance ol them was 
 the result of the joint deliberations of the Indian Law Commission, of which 
 he was President. They are by no means merely of Indian interest, for while 
 they were the commencement of a new system of law for India, they relate 
 chiefly to general principles of jurisprudence, which are of universal applica- 
 tion. 
 
 The contents are arranged in this edition as follows : Yols. I. to IV., History 
 of England since the Accession of James the Second ; Vols. V,, VI., and VII., 
 Critical and Historical Essays, Biographies, Eeport and Notes on the Indian 
 Penal Code, and contributions to Knight's Quarterly Magazine; Vol. VIII., 
 Speeches, Lays of Ancient Rome, and Miscellaneous Poems. 
 
 This last division of the work is completed by the insertion of the Cavalier's 
 Song and the Poetical Valentine to the Hon. Mary C. Stanhope, two pieces 
 which were not included in previous editions of Lord Macaulay 1 s miscellaneous 
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 of the physical as well as mental strength so manifest in his diction and style. 
 .... But it is not our intention to write a critique on the man whose 
 memory holds so prominent a placa in the heart of the reading world. The 
 volumes before us should fill a niche in every public and private library in our 
 land." Glen falls Journal. 
 
 " His writings and his speeches, arranged in chronological order, exhibit the 
 developments of a mind always more or less powerful, and announce the ex- 
 tent of his reading and the tenacity of his memory. His contributions to the 
 History of British India show how usefully his time was spent during his so- 
 journ at Calcutta." 
 
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