COLUMBIA LIBRARIES OFFSITE HEAfjHSQENCES STANDARD HX64087123 QP34 .C36 Treatise on human pn Columbia (BmbersttP intfcCitPometoJJorlf (EnUrg? of pjysirianH and §>ttr$?ar\& 3r partmrnt of JHjyauilngij <3Hj* 3toljn ■'->:"<:, literally means a discourse on Nature. At the present day, however, the word has not such an extended significance, physiology as understood by naturalists and phy- sicians meaning the study of the functions or uses of the parts of which living beings consist. I use the word parts, in preference to that of structures, inasmuch as there are beings like the monera, simple masses of a jelly-like substance or protoplasm, which are so structureless and unorganized that great difficulty is experienced in classifying them, it being questionable whether they should be ranged among plants or animals, or relegated to an intermediate kingdom, the u Protistenreich " of Hteckel, 1 or, as Huxley 2 expresses it, a sort of a biological "no man's land." Indeed it has been doubted whether the term living at all could be properly applied to the monera in the same sense in which that word is used in reference to the higher animals. As the totality of the functions or uses of the parts, structures, or organs of which living beings consist, constitute their life, I may define Physiology therefore as the study of life or of function. Necessarily from the definition, Physiology presupposes a knowledge of anatomy or structure. The relation of the two may be compared to the study of a clock when at rest and when going. The anatomist studies the form and relation of the weights, the pen- dulum, the hands, etc., at rest ; the physiologist, the fall of the weight, the swinging of the pendulum, the movement of the hands. Anatomy is the statical, physiology the dynamical, part of biology. As well might the mechanician hope to understand the movements of the clock and to regulate it without a knowledge of the parts com- posing it, as for the physiologist to understand the motions of the living body without a previous knowledge of its structure. Anatomy and physiology are so intimately associated that, philo- sophically, they should be studied together ; indeed, to separate them, except for the convenience of teaching, is highly illogical. As Hyrtl 3 well observes, "Anatomy, unassociated with phvsiology, is a mindless study and does not deserve the name of a science. Can one study the arrangement of a machine without any reference to its object ? 1 Generelle .Mur|ilml,i 2 ie. I!.l j. S. x\ii. Berlin, 18(56. - Physical Basis of Life, p. 129. Lay Sermons. New York, 1871. 3 Lehrbuch tier Auatoniie, S. 18. Wien, 1881. 3 34 INTRODUCTION. It is possible simply to view the harmoniously arranged parts of a whole, simply to stare at it without reflection. The anatomist can undertake no investigation without considering the physiological questions in- volved. The paths of both sciences meet and cross each other in so many places that there are but few divergent points." In beginning the study of any subject not only is it indispensable that the object of the investigation should be clearly defined, but it is proper that relation to knowledge in general should be pointed out. The classification of the sciences has been a vexed. one from the time of Bacon 1 to Comte. 2 This, from the nature of things, might have been expected; for there are no sharply defined lines in nature; one science encroaches so upon another that it is impossible to say where the one ends and the other begins. All classification, therefore, must be imperfect. The following one, that of Comte, is open to many criticisms, as shown in the masterly essay of Spencer. 3 Table I. Mathematics. Astronomy. Physics Chemistry. ( p Biology. < y ..-, "*' f Anatomy. Sociology. ( &J- ^ Physiology. Classification of Knowledge Admitting its manv faults, I make use of it here on account of its brevity simply to indicate the position of Physiology relatively to that of other kinds of knowledge. It will be seen, from the table, that the study of plants and animals constitutes the subject-matter of Biology. The second division of this grand science comprehends all that is known of the structure, functions, habits, geographical and geological distribution of animals : therefore, the study of animal functions or animal physiology is a subdivision of Zoology. In the same manner, vegetal physiology forms a part of Botany. Human physiology, a part of general animal physiology, forms the subject of this work. If the sciences are studied in the order in which they follow each other in Table I., then the inorganic will precede the organic. This is the logical order and historically the one in which they were, generally speaking, cultivated, for the phenomena of the inorganic world are less complex and more easily generalized than those of the organic, and, therefore, more readily investigated. Wherever practicable, the his- torical order will be found to be the best one to pursue in the study of any science; indeed, as we proceed, it will be seen that the phenomena of physiology depend upon physical and chemical laws, and that probably, with the advance of knowledge, the whole subject will be treated as a branch of molecular physics — hence the indispensability to the student of physiology of a knowledge ot physical and chemical science. Ample illustrations of the value of such knowledge will be given when i De Augmentis Scientiarum. - fours de Philosophie Positive. * Genesis of Science. Essays. London, 1868. INTRODUCTION. 35 the special functions are considered. The special senses of sight and hearing, for example, depend for their successful study upon familiarity with optics and acoustics ; the investigation of the circulation is a ques- tion of hydraulics ; that of secretion, of organic chemistry. By referring to Table I., it will be observed that Botany comes before Zoology ; where practicable, its study should precede that of Zoology, for plants serve to bridge over, to a certain extent, the gap between the mineral and animal world, and at different points touch the confines of these two kingdoms. Further, with some exceptions, plants are destitute of a nervous system, and even if extended investigation should show that their nervous system is more developed than now it is sup- posed to be, it would exercise a small influence as compared with that of the higher animals. Plants, therefore, offer a favorable opportunity of examining the processes of nutrition uninfluenced by the nervous system. When we come to examine the circulation, digestion, etc., in man, we shall see that these functions are greatly modified by the nervous system ; hence the advantage of studying nutrition in lower organiza- tions where these disturbing elements are eliminated. Having endeavored to define the object of our study, and to indicate its limits and relation to knowledge in general, let me now consider the different methods by which human physiology can be investigated — and, first, a great deal can be learned of the functions of the human body by careful i-eflection on the structure of the same. Bailer 1 says : " and first the fabric of the human body is to be learned, whose parts are almost infinite. Those who- would study physiology separately from anatomy certainly seem to me, can be compared with mathematicians who undertake to express, by calculation, the forces and functions of a certain machine of which they have learned neither disks, wheels, measures, nor material. Truly I am persuaded that we know scarcely anything of physiology unless we have learned it through anatomy." Undoubtedly, the functions of many organs might be inferred from the thorough studv of their structure. As a matter of historv, the demonstration of the valves in the veins by Fabricius to Harvey was one of the important facts that first suggested to the latter to investigate the flow of the blood. The functions of certain nerves Avill probably be never definitely settled until anatomy has determined whether they terminate in muscle, gland, or sensory organs. Those grand old anatomists, Eustachius, Fallopius, Vesalius, with their physiological followers, Harvey, Haller, and Hunter, have well illustrated in their works the important relations of anatomy to physi- ology. Not only, however, is a knowledge of general descriptive anatomy necessary, but it is indispensable also that the student who hopes to cultivate physiology with any success, must have a thorough training in histology, or the science which has for its object the study of the tissues. The necessity of a thorough knowledge of structure, in order to 1 Elementa Physiologist-. Lausanna?, MDCC'LVII. Preface, p. 1. 36 INTRODUCTION. understand function, is so obvious that it seems superfluous to dwell further upon it. Pathology furnishes valuable data to the student of human physiology. Where disease is restricted to one organ, and when it is noticed that with the destruction of the tissues composing it a par- ticular function gradually weakens and finally disappears, it is a logical inference that the loss of function is dependent upon the loss of struc- ture. In this way the uses of many parts might be ascertained — hence, the importance of carefully kept clinical records and thorough post- mortem examination. Suppose, for example, that, associated with loss or want of speech, in the majority of instances it is found, after death, that a particular convolution in the hemisphere of the brain is either wanting, unde- veloped, or diseased — it would be a fair conclusion that the faculty of speech was connected, in some way, with this particular convolution, especially if it was clearly shown that the facts were not mere coinci- dence, but bore the relation of cause and effect. Or take the case of a human being suddenly paralyzed upon one side of the body both with reference to sensation and motion, and post-mortem examination re- vealed that certain parts of the opposite side of the brain were affected, as in apoplexy, for example. It would be natural then, to consider that the parts affected in the one side of the brain presided over the opposite side of the body and extremities — or, take the case of a man suddenly stabbed in the back-bone, the instrument penetrating only half-way through the spinal cord, and the patient loses voluntary motion on the side of the wound, and sensation on the opposite side — the view that the sensory fibres decussate in the cord, and the motor one in the medulla would be confirmed. While, according to many thinkers, clinical medicine and morbid anatomy alone will not furnish data sufficient to deduce a physiology and a rational pathology, undoubtedly such facts as the above are in- valuable as aids in throwing light upon the still obscure functions of the nervous system and the uses of other structures in the human body. The admirable observations of Beaumont 1 and Budge 2 upon human beings, in whom the stomach and intestine had been wounded in such a manner as to render them susceptible of experiment, are illustrations of the application of pathological cases to the study of physiology. When the vast complexity of structure exhibited by the human organization is considered, it becomes evident that any investigation of its function, however extended, if it be confined to man alone, can lead to but very limited results. Comparative anatomy has shown, however, that the life of the animal kingdom is a grand panorama, each fleeting form, as it passes before the view, recalling that which has just passed, foreshadowing that which is to come; the simplest of living beings, so lowly organized and transparent that their entire life processes can be observed by the microscope, leading through intermediate forms to higher types of life, closely approaching that of man himself. With the development of additional structures, we find correspondingly increased functions, and infer that the new function is due to the new structure. 1 Experiments and Observations. Plattsburg, 1833. - Vircbow's Arcbiv, Bd. xiv. S. 140. INTRODUCTION. 37 The comparative method of investigation is therefore the opposite of the pathological one, by which, as we have seen, the use of a structure is inferred from loss of function dependent upon the loss of structure. In the hands of Harvey, Hunter, Cuvier, Muller, Milne, Edwards, Owen, comparative anatomy has proved of invaluable service in the study of physiology. In his great work, Harvey 1 states " that if anatomists had given to the organization of the inferior animals the same attention that they devote to the structure of the human body, the question of the circula- tion would long since have been determined." Observations upon the enlargement of the collateral vessels in the horns of the deer when in the velvet after ligature of the carotid, sug- gested to the great physiological surgeon, John Hunter, 2 the idea of the collateral vessels maintaining the circulation in the thigh after ligature of the main trunk. The ligation of the carotid in the dog, 3 and of the femoral in the same animal, done by Home 4 at the suggestion of Hunter, having further convinced the latter of the feasibility of ligation as a cure for aneurism, Hunter tied the femoral artery in the celebrated case of the coachman suffering from popliteal aneurism and thereby introduced a most capital improvement in surgery. 5 To study the physiology of man without the slightest knowledge of life as exhibited in the lower animals is as if one would attempt to master the steam engine without any acquaintance with the elementary laws of heat or mechanics, or to investigate a magnetic apparatus with- out knowing anything about the simple facts of electricity. As the study of comparative anatomy, in its application to human physiology, at the present day, is very much neglected, it may not be superfluous to offer a few instances as illustrations of the importance of the study in this respect. For example, from the fact of the bile and pancreatic juice passing into the alimentary canal at the same point in man, it is impossible to say to which of these fluids the changes ex- hibited after their mixture with the food are due. By examining the rabbit or the beaver, however, we find that the opening of the pancreatic duct into the intestine is situated twelve inches and more below that of the bile-duct. Hence, the different changes exhibited by the food as it is successively affected by these secretions, can be perfectly observed by killing a rabbit or beaver in full digestion. Indeed, as we shall see, it is in this way the emulsifying power of the pancreas is usually demonstrated. 6 Again, the question as to whether the bile is a secretion or an excretion finds its answer in the structure of the doris, 7 a little mollusk in which the liver has two ducts, one of which carries the bile into the alimentary canal, where it mixes with the food, while the other removes it at once from the body, showing that the bile, in this case at least, is both a secretion and an excretion. i De Motu Cordis, p. 33. Frankfort, 1628. - Works, edited by Palmer, vol. iii. p. 201. 8 Ibid., vol. i. p. 444. * Ibid., vol. iii. p. 597. 5 Experimental Physiology, p. 39. Owen Loudon, 1882. 6 Bernard : Physiologie Experimental, tome ii. p. 179. Paris, 1856. 7 Cuvier: Memoires Pour Servir a THistoire et a l'Anatomie des Mollusquez. Paris, 1817. Memoire sur le Genre Doris, p. 16. 38 INTRODUCTION. One of the best established facts in physiology is that the intellectual faculties depend upon the development of the brain, both in reference to quantity and to quality. This is well seen when the brains in a series of animals are compared with reference to their intelligence. With the gradual addition of certain parts of the brain there is a correspond- ing increase in mental activity — and in this way, to a considerable extent, the functions of certain parts of the brain have been made out. Embryology, or the study of the transitory phases through which every animal passes in its development from the stage of the egg to that of the adult, and which might be called the comparative anatomy of the individual, has already proved to be of service in throwing light on the functions of the human body, and which the future will, no doubt, show to be susceptible of even a wider application than is made of it at present, for the embryo of animals, with the exception of the lowest, consists of three germinal layers, of which the upper one gives rise to the epidermis and central nervous system, the lower one to the epithelium of the alimentary canal and its appendages, the middle one to bone, muscle, vessel, etc. These germinal layers, even at the start, can be readily distinguished, the cells composing them being differently affected by physical and chemical influences. Some of the lower ani- mals, for example, the hydrozoa, never get beyond this layered stage, the inner layer acting as stomach, the outer as skin. If a tissue in the adult can be shown to have been derived from one of these layers in its embryonic stage its function could almost be predicted. Indeed the whole modern pathological histology is an application of this view. The older pathologists, like Morgagni, 1 confined themselves to the study of the organs as affected by disease. Bichat, 2 in investigating the tissues of which the organs are composed, created histology ; Schleiden 3 first showed that vegetable tissues consist of cells, and Schwann/ following his lead, applied Schleiden's view to the tissues of animals. The embryologists, Reichert, 5 Kolliker, 6 Remak, 7 etc., then proved that the cells composing the tissues were the modified cells of the original mulberry mass of cells into which the egg or primitive cell segments. The obvious corollary of these generalizations followed when Virchow, 8 Billroth, 9 Paget, lu Rindfleisch, 11 etc., showed that path- ological structures were the still further modified cells composing the tissues of the organ, and that morbid growths were really physiological ones, exhibiting themselves under conditions otherwise than normal; while with the development of teratology, through the works of Geoffrey St. Hilaire, 12 and others, the explanation of the production of monsters lusus naturae became possible. That which is pathological at one stage of growth was shown to be physiological at another ; that which is normal in one animal is abnormal in another. Gradually the strict demarcation between physiology and pathology has been broken down, 1 De Sedibus Morbornm, 17G1. - Anatoniie Generate, 1801. ■' Miiller's Archiv, 18:W. 4 Mikroskopische Unternuchungen, 1839. 5 Entwickelung in Wirbelthiere, 1840. '' Entwickelung der Cephalopoden, 1844. i Entwickelung der Wirbelthiere, 1852 * Cellular Pathologie, 1854. 9 Allgenieine Pathologie, 1872. 10 Surgical Pathology, 1870. , 11 Pathologische Anatoniie, 1873. 12 Histoire Generate et Particuliere des Anomalies de ['organization, 1837. INTRODUCTION. 39 and, with the fusion of the two studies, a rational pathology and rational treatment are being slowly developed. Notwithstanding the importance of a knowledge of general physics and chemistry, anatomy, embryology, and pathology in the study of the functions of the human body, nevertheless, the study of human physi- ology is often almost entirely based on experiments made upon living animals : the study of the circulation and respiration by means of the graphic method, the making of gastric fistulas, the introduction into the system of an animal of various substances, toxic and narcotic, the removal of various parts of the nervous system, are examples of the kind of work often exclusively done in physiological laboratories. The student of physiology, however, should not confine himself to the experimental methods, however invaluable and indispensable they may be as a means of investigation, but should avail himself, as far as possi- ble, of the other methods of research just referred to, studying the sub- ject from all the different points of view possible and comparing the results obtained by the various methods made use of. As objections are often made to the experimental study of physiology, it will not, I hope, be considered superfluous if I, for a moment, consider some of the most important of those usually advanced. It is often urged as an objection to a vivisection, that the pain inflicted so disturbs the normal condition that any result as to the function of a part determined in this way is valueless ; the suffering entailed vitiating any conclusion as to the healthy function of the part examined. This objection is, of course, not made if anaesthetics are used. There are, however, experi- ments performed in which it is necessary that the animal should be in the full possession of its faculties and which, from the conditions of the investigations, make the use of anaesthetics impossible. As regards such investigations it may be said, without doubt, that animals suffer far less from the pain inflicted in a vivisection than man does from a similar wound due to an accident or the knife of the surgeon. This is due to several causes; the animal is in ignorance of what is going to be done, forgets the operation almost immediately, his nervous organization is less susceptible than that of the human being, and his wounds heal up more quickly. The influence of pain, though less in an animal than man, must nevertheless be always taken into consideration. Whenever the vivisection is performed without an anaesthetic, the physiologist ought not to draw any conclusion from the experiment until the animal has had time to recover from the effects of the shock, hemorrhage, etc., and has so far returned to his normal condition that the influence of pain, if any still exists, is so small in amount that it cannot be considered as interfering with the function of the structure examined. It is evident, therefore, that if the physiologist had no higher motive, selfishness would induce him to be as merciful as possible and to eliminate, so far as he is able, pain, as a possible source of fallacy in his conclusions. The animal, both during and after vivisection, should be treated just as a patient undergoing an operation would be by a wise surgeon ; the object in both cases being to restore, as rapidly as possible, the physio- logical conditions — the conditions of health. As an illustration of what 40 INTRODUCTION. has just been said, as regards the amount of permanent disturbance produced in an animal by a vivisection, let me mention that Blondlot's pointer dog, in which a gastric fistula had been made, was used, after her recovery, by her master for eight years in the field for hunting purposes, and in the laboratory for obtaining gastric juice, and that during that period the dog had two litters of pups. The Canadian St. Martin, on whom the gastric fistula was caused by a gunshot wound, producing far more dangerous effects than the vivisection just referred to, lived to be eighty-four years old, enjoyed good health all his life, married and had children, performed the duties of a servant, and was during this time frequently of inestimable value to science, as affording Dr. Beaumont and others the rare opportunity of observing gastric digestion in man under the most favorable circum- stances. One might as well object that the pain suffered by St. Martin, after the explosion of the gun, vitiated the conclusions drawn by Beaumont, as to object to the conclusions of Blondlot because the making of a gastric fistula in a dog involved the giving of the animal pain. A far more important objection than that just referred to is that, as animals differ very much in their organization, conclusions drawn from experi- ments made upon one kind of an animal cannot be applied to another kind ; digestion in a dog, for example, not being exactly the same as in a man. It is undoubtedly true that, while frogs, turtles, pigeons, rabbits, dogs, horses, etc., agree anatomically in many respects with each other and man, they disagree to such an extent that the result of experiments made upon one of these animals is often utterly inapplicable to the other, and entirely worthless as applied to man. Indeed, the most striking differences in the effect of certain substances are observed even in closely allied animals, varieties of the same species. Thus the black rhinoceros feeds upon the euphorbia, which poisons the white species ; goats and lambs avoid most of the solanaceous plants ; the ox and the rabbit will eat belladonna ; the goat, the hemlock ; the horse, aconite. Such differences should be always taken into consideration when the results of a vivisection upon one animal are to be applied to the deter- mination of the function of a structure in another. It must be always proved that the structure and functions compared are homologous. Further, a careful post-mortem examination should be always made after the vivisection, in order to learn exactly what has been done, to show that no structure has been involved which would modify the results except the one examined. It is the neglect of such precautions, the indifference to the infliction of pain, the comparing of utterly unlike conditions, the absence of the test of post-mortem examination, the want of controlling experiments, and of comparison of the results obtained with the facts of pathology and comparative anatomy that has brought vivisection into the disrepute in which it is held at the present day by many even educated persons. Crude generalizations, based upon im- perfect experiments performed upon animals illogically applied to man, have made even medical men doubt altogether of the efficiency of this method, and account for their sympathizing with the well-meaning, no INTRODUCTION. 41 doubt, but ill-judged efforts to suppress experimental investigation alto- gether ; and yet if vivisection should be banished from the laboratory, the physiologist would be deprived of one of his most fertile methods of research. The history of physiology proves not only the importance of vivisection, but its indispensability as a means of present research. Indeed, it is no exaggeration to say that there is not an organ in the human body whose functions have not been learned, in part at least, by vivisections. Let me illustrate this statement by a few examples. Consider the history of the circulation of the blood, and we shall see that every important advance made in a knowledge of the phenomena was due to a vivisection. Thus, Galen demonstrated by vivisection that the artery contained blood and not air, as its etymology would in- dicate. It was by a vivisection that Harvey proved that the blood flowed from the heart to the periphery through the arteries, and from the periphery back to the heart through the veins. Finally, it was through a vivisection that Malpighi saw, for the first time, the blood actually flow- ing from the arteries into the veins through the intermediate vessels, the capillaries. One of the most important discoveries ever made in physiology, that of the functions of the roots of the spinal nerves, that the anterior are motor and the posterior are sensory, was demonstrated by Majendie upon a living animal. The influence of the nervous sys- tem upon the heart, so far as is known, has been entirely learned by the experimental investigations made upon animals by the Webers, Von Bezold, Ludwig, Cyon, etc. The beautiful investigations of Bernard upon the salivary glands, the pancreas, the liver, by means of vivi- sections, have demonstrated certain peculiarities in reference to the secretion of these organs, that could never have been learned by any other method. By means of vivisection Brown-Sequard showed the influence of the sympathetic nerve in diminishing the calibre of the bloodvessels, and thence discovered the vasomotor nerves, by which the distribution of the blood to the tissues is regulated. It is needless to multiply examples of the importance of vivisection as a means of research, as nearly every chapter in this work will afford such. It must not be forgotten, however, that vivisection is but one means of physio- logical research, and that however important may be the results obtained by it, the latter, as already mentioned, should be always compared with such facts of comparative anatomy and pathology as have a bearing upon the function investigated, so that so far as possible all sources of fallacy may be eliminated. To those familiar with the history of medicine any agument to prove the importance of the study of physiology would be superfluous. Phy- siology has always been, and is still, the corner-stone of medicine. The doctrines of Hippocrates, Galen, Sydenham, Beerhave, Hunter, and Virchow, reflect as a mirror the physiology of the day. It is self- evident that to understand disease and its cure one must first understand health. The study of physiology must precede that of pathology and therapeutics. Hand in hand they advance together, the progress of the one depending upon that of the other. There is no better illustration of the truth of this view of the dependence of pathology and therapeutics upon physiology than ophthalmic medicine, the most developed and 42 INTRODUCTION. finished of all branches of medicine, whose present perfected condition is entirely due to the comparatively thorough understanding of the structure and function of the healthy eye. On the other hand, diseases, like those of the nervous system, are in a proportionally backward condition owing to the imperfect knowledge of the normal anatomy and physiology of the parts involved. Having denned the subject of physiology, considered the methods by which it is studied, and its importance to medicine, it only remains now in conclusion to indicate, generally, the order in which the study will be pursued, and here nature will be our guide. Our first sensations are those of hunger and thirst — hence the taking of food. We will, therefore, after describing the general physical and chemical structure of the body, begin with the study of digestion and absorption, the elaboration of the food into the blood, and its circulation will be then described, the consideration of excretion, animal heat, completing the study of nutrition. But man is more than a vegetable, he feels, thinks, moves. Impres- sions of the outer world made upon his nervous system awaken in him consciousness, the inner world of mind. Through his nervous system man not only becomes aware of the existence of an environment, but adjusts his actions with reference to it. Finally, though the individual perishes in the reproduction of his kind, the race, temporarily at least, survives, hence the study of development. We will begin, therefore, with the study of nutrition, consider next the nervous system, concluding with an account of reproduction. CHAPTER I. GENERAL STRUCTURE OF THE BODY, PHYSICALLY AND CHEMICALLY. Before taking up the stud) 7 of the functions, specifically, it will be well to consider, from a general point of view, of what the human body consists, physically and chemically speaking, to obtain some general knowledge of its organization, of which the functions are the living expression. As is known to every one, the human body, like that of a domestic animal, is made up of skin, muscles, bone; of various viscera, such as the heart, lungs, liver, stomach ; of nerves, arteries, etc. The old anatomists busied themselves almost entirely with the descrip- tion of such organs, their number, size, color, relative position, etc. This kind of study may be said to have culminated in Cuvier, who, as regards the exactness, extent, and variety of his knowledge stands without a rival as an anatomist. If, however, any one organ is examined somewhat closely, it will be found to be far from homogeneous. Thus the stomach consists of several layers, mucous, fibrous, muscular, etc. ; the heart, of muscular, connective, adipose, nervous tissue, etc. Such tissues, combined in greater or less proportions, make up the different organs of which the body is composed ; the same tissue, for example, the connective, being found in different organs, just as the substance wood may be applied to making a chair, sofa, bed, or bookcase fur- nishing a room. The investigation of the tissues, the creation of, histology, is due to the genius of Bichat. If now any tissue be studied in detail, it can be still further resolved into simpler ultimate physical elements or what are commonly called cells, or their modifications. This last analysis was made by Schleiden and Schwann. Through the progress of or- ganic chemistry it has also become possible to state, with tolerable accuracy, of what the body is composed chemically. When the analysis is a proximate one, the result gives such principles as water, common salt, salts of lime ; starch, sugar, fat ; albumen, fibrin, casein, etc. These principles exist as such in the human body, and are called proxi- mate principles, being the result of a proximate analysis. If now these principles be analyzed, they will bj found to consist of hydrogen, oxy- gen, sodium, chlorine, carbon, nitrogen, phosphorus, etc. In this way it is shown that the human body consists, ultimately, of the ordinary chemical elements. A human being then consists, ultimately, of myriads of cells composed of the ordinary chemical elements. Certain cells form tissues, certain tissues act together as organs, and the organs harmo- niously working together constitute a living, healthy man. The chem- 44 GENERAL STRUCTURE OF THE BODY. ical elements composing the cells also act in concert, as proximate principles. A resume of the above physical and chemical facts may be seen thrown together synoptically under Table II. Table II. 1 — The Human Body Consists PHYSICALLY. CHEMICALLY of Organs. The organs of tissues. The tissues of cells. The cells of elements. Examples of Cells. 1. Cells floating in a liquid: blood corpuscles, lymph corpuscles. 2. Cells in layers: epidermis, epithe- lium, enamel. 3. Cells in masses : adipose tissue, medulla of hair. 4. Cells imbedded in non-cellular sub- stance : cartilage, bone. 5. Cells forming fusiform bands : un- striated muscular fibre. 6. Cells transformed into tubes: cap- illaries, nerves, dentine. of Principles. The principles of elements. Proximate principles. Of 1st Class. Water, sodium chloride, calcium phosphate, calcium carbonate, etc. of 'Id Class. Starch, sugar, oils, fats. of 3d Class. Albumen, fibrin, casein, etc. Ultimate Elements. Oxygen, hydrogen, carbon, nitrogen, chlorine, phosphorus, sulphur, calcium, sodium, potassium, mag- nesium, iron, fluorine, silicon. 7. Cells transformed into filaments: fibrous tissue, elastic tissue. A cell may consist, in its wall, of membrane ; in its contents, of liquid and granules ; in its ap- pendages, of filaments. Let me now take up somewhat more in detail what is known of cells and proximate principles. A cell may be defined as the ultimate ele- mentary living unit, a mass of living matter, varying from the 3-oVo"th to the yxijth of an inch in diameter. It may consist of a cell wall, in- closing cell contents of a liquid, semi-liquid, or granular character. The granules in some cells are united, according to many histologists, by filaments or threads ; the cell contents consisting then of a network. Often among the cell contents can be distinguished a still smaller cell, the nucleus, and, within this, the nucleolus. Sometimes the cell wall is elongated into an appendage, a cilia. Great difference still prevails, as may be seen from the views of Kolliker, Leydig, Schultze, Brucke, Hteckel, Gegenbaur, Beale, etc., as to the relative importance of the nucleus and nucleolus of the cell contents and cell Avail. According to some observers, the all important element in cell life is the nucleus, while others maintain that it is the cell contents. The cell wall and even the nucleus are regarded by some as the cell contents in a state of retrograde metamorphosis. As we proceed in our studies, it will be seen that there are cells, like 1 Partly taken from Leidy's Anatomy, p. 32. CELLS. 45 the blood corpuscles, which have neither nucleus nor cell Avail ; that the first step in the division of the egg or primitive cell consists in the dis- appearance of the germinal vesicle or nucleus, and that the mulberry mass of cells, the result of that division, are at first without a cell wall. Further, there are protoplasmic beings, like the monera, of which the pro- tamoeba (Fig. 1) is an example which, through life, never exhibit either Fig. 1. Fig. 2. Protamoeba. (H.eckel.) nucleus or cell wall. Such facts prove that in certain cases, at least, neither the nucleus nor cell wall is an indispensable element to the life of cells, and should make physiologists cautious in attributing positive functions to this or that element of a cell. Indeed, I cannot say that the relative significance of either nucleus, nucleolus, cell wall, or cell centents, is as yet definitely under- stood. As examples of cells, attention may be called to those lining the Buccal and glandular epithelium, with granular mat- ter and oil-globules ; deposited as sediment from human saliva. (Dalton.) Fig. 3. Fig. 4. Columnar ciliated epithelium cells from the human nasal membrane ; magnified 300 diam- eters. (Quain and Shaepey.) uriniferous tubules of the kidney, to the cells of the enamel, to those of the epithelium of the mouth (Fig. 2), of the columnar epithelium Of the intestine, tO Human blood-globules a. Red globules, seen flat- the multipolar Cell found in nei'- Wise - «>• R^ globules, seen edgewise, c. AVhite globule. r ,...,. (Dalton.) vous tissues, to the ciliated epi- thelial cells from the pulmonary mucous membrane (Fig. 3), to blood cells (Fig. 4), to unstriated muscular fibre cells. 46 GENERAL STRUCTURE OF THE BODY. As I take up the different organs, the cells composing their tissues will be described more in detail; so the above examples will, therefore, suffice for the present in giving a general idea of the form of cells. While there is still some doubt as to the exact use of the different parts of the cells, there is no doubt that the life of the organism resides in the cells composing it. Among other reasons for supposing so, may be mentioned the fact that the life of the human being begins as the ovum, a cell, and that the tissues of the embryo, out of which are built up the organs of the adult, consist of modified cells, the lineal de- scendants of this primitive cell or ovum, and inheriting its life charac- teristics, the life of the organism being the resultant of the lives of the individual cells composing it. The independent life of cells is well seen in some of the lower animals, whose blood corpuscles can be observed actually feeding upon sub- stances artificially introduced into the circulation, and in the embryonic state can be observed dividing and subdividing, and so reproducing themselves. Gland cells, like those of the liver, kidney, etc., in taking from the blood the materials out of which their respective secretions are elaborated, show their independent activities. Pathological processes often present chances for observing this independent cell life, in the wandering of the white and red blood-cells out of the vessels, in the rapid proliferation of cells seen in the development of various morbid growths, etc. The protozoa and protophyta, or the simplest of animals and plants, however, offer the most favorable opportunities for observing the life history of cells ; for these simple beings never get beyond the one-cell stage of life, indeed neither tissues nor organs are ever developed in them in the same sense that these are in the higher animals. The entire life cycle of these minute plants and animals can be often followed under the microscope. The manner in which cells take food, move about, their mode of reproduction — usually through simple division, though some- times endogeneously and by gemmation and con- jugation — can be readily observed by an examina- tion of the greenish matter on damp bricks, stones, etc., consisting usually of palmoglea, micrococcus, or the greenish film-like spirogyra seen covering the ditches and ponds in the neighborhood of the city, and which also usually contain specimens of unicellular protozoa paramoecium (Fig. 5), stentor, as well as desmidiacese, of which Fig. 6 is an ex- ample. These researches, always interesting to the mere microscopist on account of the beauty of the vegetable and activity of the animal forms, have a deep meaning to the philosophical physiologist. For it is reasonable to suppose that the life of man or the higher animals, when in the one-cell or ovum stage (Fig. 7), is similar to that of these beings which pass beyond this uni- cellular stage. Hence, we may conclude that the human ovum, or any of the cells descended from it, absorbs and assimilates nutriment, like Fig. 5. i>-'-W ''M. ■40, ■■/, Parama'cium caudatum. a, a. Contractile vesicles. 6. Mouth. (Carpenter.) CELLS, 47 the unicellular beings just referred to. The segmentation of the egg in the higher animals corresponds also to the division of the cell seen in Fig. 6. F I G . Pediastrum pertusum. (Carpenter.) Human ovum, magnified 85 diaoi. a. Vitelline membrane. 6. Vitellus c. Germinative vesicle, d. Germinative spot. (Dalton.) the reproduction of these minute beings, the manner in which the nucleus divides first into two halves and the cell contents or protoplasm constricts around the new nuclei being essentially the same in both cases ; the only difference being, as we shall see hereafter, that in the Division of the yelk of Ascaris. A, B, C (from Kiilliker), ovum of Ascaris nigrovenosa; D ami E. that of Ascaris acuminata (from Bagge). (Quain and Sharpey ) former the new cells hold together and are transformed into tissue, in the latter the new cells are scattered, constituting the next generation of cells. This distinction may be seen by comparing the segmentation Fig. 9. Development of protococcus pluvialis. (Carpenter.) of ascaris (Fig. 8) with the reproduction of protococcus through con- tinued subdivision (Fig. 9). In either case, however, the life of the re- 48 GENERAL STRUCTURE OF THE BODY. sultant cells is that inherited by them from the parent cell. The cells resulting from the segmentation of the mammalian ovum or egg are at first very similar, hut soon a marked difference between them can be observed. If the researches of Van Beneden 1 on the rabbit are con- firmed, the difference is noticeable even in the two first segmentation cells. However this may be, the cells soon begin to differ in size, shape, and the manner in which they are affected by chemical agents. Some dispose themselves so as to form the epiblast, others the hypoblast, and between these two layers a third appears, the mesoblast. The modification of the cells and the further development of these three layers will be considered when I take up the subject of reproduc- tion. It will be seen then that through the processes incidental to development, cells often lose their originally round form, becoming sometimes flattened or scale-like, and often of a prismatic and columnar shape. Sometimes the cells float free in a liquid, like the blood corpuscles ; or they may arrange themselves in layers, like those of the enamel ; or in masses, as seen in the medulla of hairs. They may be imbedded in a solid non-cellular matrix, as in cartilage. Cells are sometimes flattened into bands, as in the unstriated muscular fibre, or a number are, through the dissolution of their adjacent walls, metamor- phosed into tubes, of which the capillaries and dentine are examples, or they may be converted into fibrous tissue. These modifications are seen in Table II., synoptically arranged. The various substances elaborated by cells in different parts of the adult economy will be more appro- priately considered as the functions of the organs are taken up. It will be seen that the life of the body is, therefore, the resultant life of the cells composing it; that the body is a living republic of cells. Let us now return to the chemical composition of the body, or of the cells of which it consists. We have seen that the human body consists of chemical elements acting as proximate principles. Before considering these, let us see what is meant by a proximate principle. A proximate principle may be defined as a principle, simple or com- pound, which exists and acts as such in the human body. Thus, sodium chloride is a proximate principle. Neither the rare metal sodium, nor the offensive greenish gas chlorine, however, are proximate principles, for they do not exist or act as such in the body. Calcium phosphate is an example of a proximate principle ; but the metal calcium, and the phosphoric acid, not existing or acting separately, as calcium and phosphoric acid, in the body, cannot be regarded as proxi- mate principles. The purely analytical chemist would resolve such proximate principles as fat, albumen, into their ultimate elements, carbon, hydrogen, oxygen, and carbon, hydrogen, oxygen, nitrogen, phosphorus, respectively. The physiological chemist, however, would study these principles without further decomposition, investigating the part that fat and albumen play as such in the economy, without any reference to their ultimate chemical composition. The proximate prin- ciples — leaving out of consideration, for the present, the gases, which can be more conveniently treated of under the subjects of respiration 1 Bulletin de l'Acad. Belgiijue, 1874. WATER. 49 and the blood, and the various effete matters whose elimination from the economy constitutes the function — divide themselves naturally into those of inorganic and organic origin ; the latter are further distinguished by those containing nitrogen and those which do not, Table II. gives some typical examples of these three classes of the proximate principles ; and of their ultimate chemical elements, manganese, iodine, and bromine, though not existing in man, have been found, however, in other organized bodies. By referring to Tables III. and IX. a list of the most important of the proximate principles may be seen, and the parts of the body in which they usually occur. Let me now take up somewhat in detail the consideration of these principles, beginning with those of inorganic origin. Table III. 1 — Proximate Principles of the First Class, or those of Inorganic Origin. Substances. Where found. Water ....... Universal. Sodium chloride ..... Universal, except enamel. Potassium chloride .... Muscles, blood, milk, saliva, bile, gastric juice. Calcium pbospbate .... Universal. Calcium carbonate .... Bones, teeth, cartilage. Sodium carbonate .... Blood, saliva, lymph. Potassium carbonate .... Bones, lymph. Magnesium phosphate .... Universal. Sodium phosphate .... Universal. Potassium phosphate .... Universal. Sodium sulphate ..... Universal, except milk. Potassium sulphate .... Bile, gastric juice. Same as sodium sulphate. Calcium sulphate ..... Blood, feces. Ammonium chloride .... Gastric juice, saliva, tears. Magnesium carbonate .... Blood, sebaceous matter. Sodium bicarbonate .... Blood. As implied in the definition, the principles of this class are inorganic in origin, being found in the rocks forming the crust of the earth, in sea water, springs, etc. They have a definite chemical composition, and are crystallizable. With the exception of calcium carbonate, of which the otoliths of the ear consist, they are combined in the body with the organic principles. This union is so intimate that as the organic prin- ciples become effete, and are eliminated, the inorganic substances are cast out with them. Some of these substances play a more important r6le than others, and are found in greater or less quantities in the economy. Let us consider now the most important of these substances, where they occur, and their principal uses. Water, H 2 0. — In the maintenance of life, none of the proximate principles, whether inorganic or organic, surpass in importance water. When it is learned, however, that it constitutes nearly three-fifths by weight of the whole body, this will no longer be a subject of surprise. 1 Robin et Verdeil : Traite de Chimie Anatomique, tome denxieme, \>. 5. Paris, 1853. 4 " 50 GENERAL STRUCTURE OF THE BODY. In the course of our studies we shall find that water exists in all parts of the body: in solids, like hone and enamel; in fluids, like the tears, perspiration, etc. Its uses in the economy are manifold. It gives con- sistence and general resiliency to the body, pliability to tendons, elasticity to cartilage, resistance to the bones. Various substances, like articles of food and the effete matters, find their way into and out of the body through their solubility in water. The importance of water is at once seen if the system is deprived of it. The tissues become shrivelled and dried up and inflexible, the liquids become thick, inspissated, lose their fluidity. On the other hand, an excess of water gives rise to general debility, muscular weakness, dropsies, etc. In the living body water exists as " water of composition" — that is, it constitutes an integral part of the tissues. The water is not taken up by the tissues, like a sponge, but really forms a part of its substance, the union being a chemical one. Table IV.' — Quantity of Water. Substance. Enamel Epithelium Teeth Bones Tendons . Cartilages . Skin .... Liver. Muscles Ligaments Blood The relative amount of water is, in the tissues, regulated by the salts. Thus, when water is added to the blood, the corpuscles become swollen, and finally are dissolved away ; but if a strong solution of salt be added instead, the corpuscles lose their water and shrivel up. Most of the water found in the system is taken in as part of the solid and fluid articles of the food. As we shall see hereafter, however, about 500 grammes, or 7500 grains, are formed in the system through the combustion of carbo- hydrates. The daily amount of Avater necessary for the healthy adult has been estimated, by Dalton, 2 at about four and one-half pounds. This, of course, includes the water entering into the solid articles of food. About fifty-two per cent, of the water, after it has played its part in the economy, is discharged by the skin and lungs, the rest by the kidneys and with the feces. It has been calculated that nearly one pound passes off by the skin, about a pound by the lungs, and a little over three pounds by the kidneys. When, however, the skin is not active, as in the winter time, then the kidneys act very freely ; in the summer the reverse is the case. Diuretics favor the one set of emunc- tories, diaphoretics the other. By glancing at Table IV. it may be seen how universally water is found in the tissues, and its relative amount. Thus, while we find that 1 Robin et Verdeil, op. cit , p. 115. - Physiology. Part, perlOOO. Su'istance. Parte per 1000. 2 Milk . . 887 '. 37 Chyle . . 004 . 100 Bile . 905 . 130 Urine . 933 . 500 Lymph . . 960 . 550 Saliva . . 983 . 575 Gastric juice . . 984 . 618 Perspiration . . 986 . 725 Tears . 990 . 768 Pulmonary vapor . . 997 . 780 SODIUM CHLORIDE 51 a thousand parts of pulmonary vapor contain nine hundred and ninety- seven parts of water, it will be seen there are only two parts of water in a thousand of enamel, and that a substance, like tendon, so different from either of those just mentioned, is half made up of water. The great importance of water in health, and still more in disease, cannot be too much dwelt upon by the physiologist and practising physician. Sodium Chloride', NaCl. — Next to water, common salt is the most important of the inorganic proximate principles, being found, like water, almost universally, even in the ovum. With the exception of the enamel, in which it has not yet been discovered, salt is found in all the solids and fluids of the body. The absolute amount, however, has not yet been determined. The saltish taste of the tears and perspiration is due to the presence of this principle. It is found in the largest proportion in fluids. The relative quantity of sodium chloride found in some of the fluids of the body may be seen by looking at Table Y. Table V. 1 — Quantity or Sodium Chloride. Substance. Parts per 1000. Substance. Parts per 1000. Blood 4.2 Saliva 1.5 Chyle 5.3 Perspiration .... 3.4 Lymph . . . . .4.1 Urine .*.... 4.4 Milk 0.8 Feces 3.0 Salt is introduced into the system through the different articles of animal and vegetable food which always contain it ; in addition, salt as such is added to the food of man and the herbivora ; the amount con- tained in their food not being sufficient for the wants of the economy. Salt, like all other inorganic principles, passes ultimately through the body, and is carried out of it in the urine, feces, perspiration, etc. The uses of salt in the system are manifold. The phenomena of osmosis, or the passage of fluids and gases through the animal membranes, are greatly modified by the amount of salt present, a solution of salt osmosing through a membrane much less readily than pure water. Absorption is influenced by it. It increases the solubility of albumen ; this prin- ciple being coagulated much less quickly by heat in a solution of sodium chloride than in water. The coagulability of fibrin may be prevented by a strong saline solution. The forms of tissues are preserved through the presence of salt, as in the case of blood-corpuscles just referred to. Nutrition is undoubtedly affected in other Avays by, salt, as yet not per- fectly understood. The experiments of Boussingault 2 upon bullocks, and of Dailly 3 upon sheep, showed what a deleterious effect was produced in their general appearance when these animals were deprived of salt. It is well known how the wild buffalo is found by the salt licks of the Northwest, and how the hunter in Southern Africa avails himself of his knowledge of the habits of wild animals collecting near salt springs, to kill his game. Every one is familiar with the fact of how cattle run to any one who will give them salt. It is said that fugitives from iustice will often risk capture and their lives to obtain salt. Facts like the 1 Robin et Verdeil, op. oit., p. 176. 2 Chimie Agricole, p. 27L Paris, 1854. 3 Longet : Traitg de Phyaiologie, tome i. p. 70. 02 GENERAL STRUCTURE OF THE BODY. above show what a deep-seated want is felt by man ami beast alike, when deprived of salt. Potassium CHLORIDE, KC1. — This principle is found in the muscles, blood, saliva, bile, gastric juice, urine, etc. A greater part of it is intro- duced into the system with the food, though probably some is produced through the double decomposition of the potassium phosphate and sodium chloride existing in the blood, sodium phosphate and potassium chloride resulting. The uses of potassium chloride and sodium chloride are probably the same in the economy. This principle is discharged from the body in the mucus and the urine. Calcium Phosphate, Ca 3 (P0 4 ) 2 . — This very important principle is found in all the solids and fluids of the body. By looking at Table VI. it will be seen, however, that calcium phosphate exists in much larger proportions in the solids than in the fluids. Only traces are found in blood, saliva, etc., whereas a thousand parts of enamel will contain nearly nine hundred parts of this principle. Calcium phosphate, while insoluble in water, is held in solution in certain parts of the system by the free carbonic acid, the bicarbonates and the sodium chloride — in the urine, for example, by the acid sodium phosphate. On the other hand, this principle is in a solid condition in bones, teeth, cartilage, etc. Calcium phosphate forms one Of the ingredients of our food and so gets into the system; it is eliminated in the feces and urine. Its use in the economy is to give strength and solidity. Hence the large amount present in the bones, and more especially in the enamel, the hardest of all known organic substances. It is very abundant in the lower extremities, which support the weight of the body. The ribs contain less calcium phos- phate than the upper extremities, hence their greater elasticity. Table VI. 1 — Quantity of Calcium Phosphate. Substance. Blood . Milk Soliva Urine Excrements . Bone The amount of calcium phosphate found in any organ or tissue differs often according to age; thus it will be seen from Table VI. that in the teeth of a very old man, in a thousand parts there are one hundred and fifty parts more than in an infant, and fifty more than in an adult. Rickets is due to a want of the proper amount of calcium phosphate. The liability of pregnant women to meet with fractures, and the delay of union in these cases, are due to their offspring taking from the mother so much calcium phosphate, necessary in the development of the new being. The calcium phosphate in a bone can be all dissolved out by hydrochloric acid ; such a bone retains its form, but if it be the fibula, is so pliable that it can be tied in a knot, a good illustration of the im- portance of this salt to the system. If animals be deprived of their proper i Robin et Verdeil, op. cit., p. 287. Parts per 1000. Substance. Pa rts per 1000. 0.7 Teeth of infant . 510.0 2.5 Teeth of adult . 610.0 0.6 Teeth of man at 81 years . 660.0 . 25.0 Enamel . . . . 885.0 . 4O.0 Bachitic bone 136.0 . 400.0 CALCIUM CARBONATE, SODIUM CARBONATE. 53 amount of calcium phosphate their bones soften, as seen in Chossat's experiments on pigeons. Calcium Carbonate, CaCO.,. — This principle is found in the blood, teeth, cartilage, and bones. In the latter it is not as abundant as the phosphate, but exists in the proportion of a hundred parts to the thou- sand (see Table VII.). Table VII. 1 — Quantity of Calcium Carbonate. Substance. Parts per 1000. Bone 102.0 Teeth of infant 140 Teeth of adult 100.0 Teeth of man at eighty-one years .... 10.0 As before mentioned, calcium carbonate is the only inorganic principle which exists in a crystalline form and uncombined in the body. As such, it is found in the otoliths of the internal ear. Calcium carbonate is found in our food, and in this way is introduced into the system. It is held in solution by carbonic acid. Some of the calcium carbonate found in the system is no doubt due to the decomposition of the malates, citrates, tartrates, acetates present in the food, into carbonic acid. It passes out of the body in the urine, probably transformed into the phos- phate. The uses of calcium carbonate in the economy are the same essentially as those of the phosphate. Sodium Carbonate, Na 2 Co 3 . — Sodium carbonate is found (Tabic AT 1 1.) in the blood, saliva, etc., the alkalinity of these fluids beino- due to its presence. It is not introduced from without, but is formed in the system through the decomposition into carbonic acid, of the malates, tartrates, etc., found in fruits. Some of it occasionally passes away in the urine, but a greater part is decomposed by the acid of the lungs ; the carbonic acid set free behm exhaled. Table VIII. z — Quantity of Sodium Carbonate. Substance. Parts per 1000. Blood 1.6 Lymph 0.."> Cephalo fluid 0.6 Compact tissue of bone 2.0 Spongy tissue of bone 0.7 Sodium carbonate seems to maintain the albumen and fibrin of the blood in a fluid condition, and is of use also in preserving the form of the blood corpuscles. What has just been said of sodium carbonate applies equally well to potassium carbonate (K 2 C0 3 ), sodium phos- phate, etc. Sodium phosphate (Na,HP0 4 ), magnesium phosphate (MgHP0 4 ), and potassium phosphate (K 2 HP0 4 ), are found in small quantities all through the body. They exist in our food, and are discharged in the urine and feces. Their use seems to be similar to that of calcium phosphate. 1 Robin et Verdeil, op. cit, p. 223. - Robin et Verdeil, op. cit., p. 258. 54 GENERAL STRUCTURE OF THE BODY. There are found in the blood, and some other of the fluids and solids of the body also, sodium sulphate (Na 2 S< ).,), potassium sulphate (K 2 S( >,), and calcium sulphate (CaS0 4 ). The first two of these salts are intro- duced in the food and are discharged in the urine. Their functions seem to lie the same as the sodium carbonate. The calcium sulphate is found in drinking water, and is evacuated in the feces; its function is unknown. Magnesium carbonate (MgCO s ) and sodium bicarbonate (NaHC0 3 )have been found in the blood. Finally, ammonium chloride (NH 4 G) is found in the tears, saliva; its origin and use are very obscure. Some physiological chemists subdivide the inorganic proximate prin- ciples into two classes : those which appear indispensable to the constitu- tion of the tissues, as water, calcium phosphate, etc., and those which influence the processes of nutrition without absolutely entering into the composition of the tissues, like the chlorides. It appears to me however, that at present, at least, no such sharp lines of demarcation can be drawn between these principles. Water, for example, while existing in many tissues in a molecular state of com- bination, no doubt influences the processes of nutrition. On the other hand, while common salt plays an important role in nutrition, under certain conditions, it seems to be as much a tissue element as calcium phosphate. In the present state of physiological chemistry, it seems premature, therefore, to draw any very fine distinctions as to the relative impor- tance of this or that inorganic principle, or do more than point out, as I endeavored to do in a general way, their uses in the human economy. CHAPTER II. PROXIMATE PRINCIPLES OF ORGANIC ORIGIN. As has been already stated, in addition to the inorganic proximate principles, the human body contains many of organic origin — that is, principles elaborated by organized bodies, plants, or animals; some of these principles have already been prepared artificially by chemists, and there is no reason why in time they should not all be. They naturally arrange themselves into two classes, those containing no nitrogen and those in which this principle is present. Table IX. gives some of these principles and where they are found. Let us consider the former class first. Table IX. — Organic Principles. ( 'until ining no Nitrogen. Substances Starch . Sugar . Fat Pneumic acid Albumen Fibrin . Albuminose Casein . Mucosin Pancreatin Pepsin . Globulin Musculin Ostein . Cartilagin Elasticin Keratin Crystallin Hiematin Melanin Biliverdin Urrosacin Containing A Where found. Brain. Milk. Almost universal. Lungs. iroge/i. I i Blood, chyle, lymph. Chyme, blood. Milk. Mucus. Pancreatic juice. Gastric juice. Blood corpuscles. Muscles. Bone. Cartilage. Elastic tissue. Nails. Lens. Blood. Pigment. Bile. Urine. Non-nitrogenous Principles of Organic Origin. — This class of proximate principles is represented by the starches, sugars, fats, fatty acids, and oils, lactic acid and lactates, pneumic acid and sodium pneu- mate : but, as already mentioned, when not obtained artificially, are produced only by plants and animals. These substances do not form a part of the mineral world, like such principles as salt, calcium phos- phate, etc., just considered. They agree with the organic proximate 5b' PROXIMATE PRINCIPLES OF ORGANIC ORIGIN principles in having ;i definite chemical composition, and, with the excep- tion of starch, are crystallizable. In striking contrast with the principles of the first class, with the exception of the butter and sugar of milk of lactation, those of the second class are never discharged from the body while in a state of health. The principles of the second class differ from those of the third not only in the absence of nitrogen, but, as we shall see, these latter are not crystallizable. By glancing at Table X. it will be seen that of these principles, starch, sugar, and stearin — a form of fat, consist of carbon, hydrogen, # and oxygen. Tahle X. — Composition of Water Starch Cane sugar Grape sugar Stearin Albumen . H, O. ^1kH 30 Oi 5 . C, 2 H 22 O n . C 6 H„ 6 . C 57 H U0 O 6 . C 72 H 112 22 N 18 S. These particular principles are often known as the carbohydrates The term, however, is only applicable to the starch and sugar, since it is only in the latter that the hydrogen and oxygen exist in the pro- portion to form water, the hydrogen being largely in excess of the oxy- gen in the fats. Let us begin our study of the second class of proximate principles with starch. Starch, C 18 H 30 O 15 . — Starch exists in the human body as the corpora amylacea, the starch granules that are found in the walls of the lateral Fiu. 10. Fig. 11. Starch grains from wall of lateral ventricles ; from a woman aged thirty-five,. (Dalton.) Grains of potato starch. (Dalton.) ventricles of the brain, in the fornix, septum lucidum, etc., described by Kolliker 1 and Yirchow. 2 They resemble (Fig. 10), to a considerable i Handbuch der Gewebelehre, 1852, S. 311. 2 Cellular Pathology. Translated by Chance. 7th edit , p. 313. STARCH. 57 extent, the starch grains of Indian corn. They are transparent and colorless, like the starch granules of plants generally. They average about the 18 1 00 t h of an inch in size, present a hilus, are slightly lami- nated, and give the characteristic blue color when treated with iodine. Although not crystallizable, starch is far from being an amorphous powder, as seen from the above description of the corpora amylacea, but the characteristic structure of the starch granule is better seen in that of the potato (Fig. 11), where the laminations and the hilus of the gran- ules are well marked. Starch exists abundantly (see Table XI.) in corn, wheat, oats, rice, potatoes, and indeed in almost all vegetable food. Tapioca, arrowroot, etc., so useful as articles of diet, under certain cir- cumstances, are varieties of starch. Table XI. 1 — Quantity of Starch in 100 Parts in Bice 88.65 Peas 37.30 Indian corn .... 67.55 Beans 33.00 Barley 66.43 Flaxseed .... 23.40 Oats 60.59 Potatoes 20.00 Bve 64.65 Sweet potatoes . . . 16.05 Wheat 57.88 Chocolate . . . .11.00 AVhatever may be the source from which starch is derived, it is chemically the same, and is produced in growing vegetables, under the influence of solar light, by a process of deoxidation of carbonic acid, as shown by the following formula : Carbonic acid. Oxygen. Starch. Water. 6H 2 C0 3 — 120 = C 6 H 10 O 5 + H 2 The principle of the development of starch through the deoxidation of carbonic acid may be roughly illustrated in the following manner: A bunch of fresh mint being placed within a cylindrical tube containing dilute carbonic acid water standing over the pneumatic trough is ex- posed to sunlight. Soon the leaves of the mint will be seen covered with minute beads of gas, a small quantity of the latter accumulating at the top of the cylindrical tube. By withdrawing the mint and pass- ing up a few bubbles of nitric oxide, a dark brown vapor will appear at the top of the tube, proving that the contained gas was oxygen. Starch is insoluble in cold water, but by boiling the granules are liquefied, and, on cooling, remain fused together as a whitish, oxaline, homogeneous mass. In this condition, it is said to be tk hydrated." The most important property of starch for the physiologist, however, is the readiness with which it is converted into sugar. This might be inferred from their relative composition, the only difference being in the amount of water (see Table X.). Thus, if human saliva lie added to boiled starch and the mixture be maintained at a temperature of 100° F., in a few minutes it will be found to have been converted into suo-ar as shown by the following formula : Starch. AVater. Glucose. C 6 H 10 O 5 + H,0 = C 6 H 12 6 1 Dalton: Physiology, 18S2, p. 52. Payen: Substances Alimentaires, p. -265. P;uis, 1SG5. 58 PROXIMATE PRINCIPLES OF ORGANIC ORIGIN. All of the starch in the food is soon converted into glucose in the ali- mentary canal by the digestive processes, and in this form disappears from the economy. The use of starch leads us naturally to the con- sideration of sugar or the form in which it appears, with the exception of the corpora amylacea, in the body. Sugar. — This principle is found in the alimentary canal during digestion, under the form of glucose, C 6 H 12 6 , as milk sugar, C 12 H 22 O u + H 2 0, during lactation The liver also contains glycogen, C 6 H 1() 5 , a substance readily converted into sugar, which passes into the hepatic veins, and from there to the vena cava and heart. In the muscles are found inosite, C 6 H 12 6 -f 2H 2 0, and a substance similar to grape sugar. Sugar exists in the economy combined with other proximate principles. Thus, in the blood we find the sugar dissolved in water combined with the albumen, sodium chloride, etc. These animal sugars are closely related, chemically, and are readily converted into one another. While sugar is produced in man by the liver and mammary glands, etc., by far the greater part is derived from the food either in the form of cane sugar, C 12 H 22 O u , or that contained in fruits, grape sugar, C 6 H 12 6 , or from the easily transformed starch. Table XII. 1 — Quantity of Sugar in 100 Parts cn Cherries .... . 18.12 Goats' milk . 5.80 Juice of sugar cane . 18.00 Cows' milk . 5.20 Apricots .... . 16.48 Indian corn-meal . 3.71 Peaches .... . 11.61 Rye flour . 3.46 Pears .... . 11.52 Barley meal . 3.04 Sweet potatoes . 10.20 Wheat flour . 2.33 Beet roots . 8.00 Oatmeal . . 2.19 Parsnips . 4.50 Beef's liver . 1.79 The vegetable sugars only differ from the animal varieties in the proportion of water they contain, and when we come to study digestion and absorption we shall see that the vegetable sugars are all metamor- phosed into the animal kind before they are taken up by the system. While the two classes of sugars have many affinities, yet they differ in the effects produced upon them by alkalies and acids. Cane sugar, when boiled with an acid, is converted into the animal variety, the addition of alkalies having no effect. On the other hand, the acids have no effect upon the animal sugars, whereas melasic acid results from boiling with an alkali. Under certain circumstances, sugar (C 6 H 12 O fi ) becomes lactic acid, 2(C 3 H G 3 ) ; the significance of this chemical change we shall see presently. A convenient test for sugar is that known as Trommer's test. The suspected liquid is placed in a test-tube, to this are added one or two drops of sulphate of copper ; then the mixture is made distinctly alkaline by the addition of a solution of caustic potash. The mixture will become blue, particularly if sugar is present. Now heat the test-tube till just before boiling point, when, if sugar is present, a reddish precipitate will appear just in the upper part of the tube, and will gradually be seen in the whole liquid. The reaction is due to the cupric oxide being reduced to the condition of a cuprous oxide by the oxidation of 1 From Dalton, op. cit. , p. 54. Payen, op. nit. FAT. 59 the sugar. The solution to be examined should be clear. This can be accomplished by boiling the suspected tissue, finely divided, with water and sulphate of soda and filtering. The organic and coloring matters will be retained, and a clear extract will pass through, the soda not interfering with the test. Milk, liver, and grape sugar and glucose respond to Trommer's test. Cane, maple, and beet sugar, however, must be boiled with very weak sulphuric acid to convert them into glucose before the test will be applicable. There are substances in the healthy urine which interfere with the reaction in the reduction of the copper, though sugar be added in considerable quantity. Of course, this does not apply to diabetic urine. Albuminose, which, as we shall see hereafter, is produced dirring gastric digestion, interferes also with Trommer's test, as noted by Longet, 1 though Dalton 2 pointed out first the fact of the products of stomach digestion having this curious effect. With the above qualifications, Trommer's test is very reliable and easily applied. Other tests, such as those of Moore, Barreswil's, Mau- merie, Bottger's, Fehling's, the fermentation test, and that of torulse, etc., are also used. Notwithstanding the amount of sugar introduced into the economy in the food and produced independently in the system, none appears in the excretions in health ; the presence of sugar in the urine, for example, being a sign of the disease diabetes. With the exception of the places indicated, sugar is not found in the system, it being destroyed almost as rapidly as produced, being burnt up and oxidized, and passing out of the economy principally through the lungs, transformed into carbonic acid gas and water thus : Glucose. Oxygen. Carbonic acid gas. Water. C 6 H,A + 120 = 6(C0 2 ) + 6(H 2 0) Through its combustion it is one great source of heat, and hence its importance to man as a source of fuel and force. Its relations in this respect will be again pointed out when the subjects of food and animal heat are considered. At all periods of life sugar is a most important principle. In the foetus, even at an early period of intrauterine life, the fluids contain it, and in a greater proportion than after birth. Fat. — Fat is an almost universal constituent of the body; it is absent, however, in the bones, teeth, the eyelids, and scrotum, elastic and unelastic fibrous tissue. It is always present, even in extreme cases of emaciation, in the orbit, and around the kidneys. The amount, however, varies very considerably in the different tissues, as may be seen from Table XIII. Table XIII. 3 — Quantity of Fat ix 100 Parts of Tissue. Sweat 0.001 Liver 2.4 Saliva 0.02 Muscles 3.3 Lymph 0.05 Hair 4.2 Chyle 0.2 Milk 4.3 Mucus 0.3 Cortex of brain . . .8.0 Blood 0.4 Medulla 20.0 Cartilage .... 1.3 Nerves 22.1 Bone . . . . .1.4 Spinal cord .... 23.(3 Crystalline lens . . . 2.0 Adipose tissue .... 82.7 i Gazette Heb., 1855. -' Amer. Journ. Med. Sri., 1854. :s Carpenter: Physiology, 1881, p. 88. 60 PROXIMATE PRINCIPLES OF ORGANIC ORIGIN Thus, while in the sweat, lymph, saliva, etc., there is ;i more trace of fat, more than twenty per cent, is found in the nervous system, and over eighty in adipose tissue. The whole amount of fat, according to Burdach, 1 in the body of a man weighing 17<> pounds was N.8 pounds, or 5/1 pounds of fat to every 101) of body. Fat exists in the adipose tissue, for example, in the form of vesicles which are transparent and contain the oily matters, and in certain tissues, like the liver, cartilages, etc., an excess of the production of fat in liver cells constitutes fatty liver globules. Chemically speaking, fat consists of a mixture of the principles known to chemists as stearin, palmitin, margarin, 2 and olein. The first two are solid at the tem- perature of the body, but are held in solution by the olein. They crystallize (Fig. 12) in needle-like forms, assuming a beautiful radiatory Fig. 12. Stearin crystallized from a warm solution in olein. (Dai/ton.) or arborescent appearance, where fluid, fatty, oily substances under the microscope have the appearance of round globules, bright in the centre, and dark at the edges. With the exception of the phosphorized fat of nervous tissues, fat does not exist combined with the other proximate principles, like we found was the case with the inorganic principles and the sugars ; there is no such molecular union of fat with any prin- ciple. There is no difficulty, therefore, in extracting it from the system in a state of purity. Pressure is often the only process needed, the oil being squeezed out of the interstices of the tissues of the organ con- taining it. The general composition of fat may be illustrated by that of stearin, C 57 H u0 O 6 , and it will be observed that while fat, like the carbohydrates, consists of carbon, hydrogen, and oxygen, the last two elements do not exist in fat in the proportions to form water. 1 Traits de Pliysiologie, tome viii. p. 80. Paris, 1857. - Margarin probably consists of a mixture of stearin and palmitin. FAT. 61 Table XIV. 1 — Quantity of Fat in 100 Parts of Food. Chocolate nut .... 49.00 Salmon 4.85 Sweet almonds .... 24.28 Cows' milk .... 3.70 Indian corn . . . .8.80 Deans 2.50 Fowls' eggs .... 7.00 Wheat 2.10 •Mackerel 6 70 Peas 2.10 Calf s liver .... 5.58 Oysters 1.51 Beef's flesh .... 5.19 Potatoes 0.11 The fat of the body is, to a great extent no doubt, derived from the fat of the food, somewhat modified, however, after being introduced into the system, since the fat of the body neither in man nor animals is iden- tical with that of their food. In most cases, however, more fat is pro- duced in the system than can be accounted for by the fat derived from the food. The experiments of Persoz, 2 Boussingault, 3 Thomson, 4 Lawes 5 and Gilbert, and others, upon geese, ducks, pigs, cows, etc., with refer- ence to this point are conclusive. In the case of a cow, for example, under the observation of Voit, and to be referred to again in a moment, it was observed that of the 202-4 grammes of fat in the milk, only 1658 could have been derived from the fat of the feed. Now, from such facts as the starch of plants be- coming oil, and of sugar being readily transformed into alcohol and other fats during fermentation, as shown by the formula Glucose. Alcuhol. Carbonic acid gas. C 6 H 12 6 = 2C,H 6 + 2C0 2 of carbohydrate principles constituting a part of a fattening food, of the negroes and cattle getting fat during the time that the cane is being collected and the sugar extracted, etc., one would be naturally led to suppose, as indeed held by Liebig, that the fat produced in the system over and above that absorbed from the food, was derived from its carbohydrate principles. On the other hand, it is a matter of every day observation that animals are fattened best on a feed consisting of albuminous as well as of carbohydrate principles apart from the fatty matters contained in it; and while there is no difficulty in under- standing how, through the abstraction of oxygen, as just shown, a fat, like alcohol, may be derived from a carbohydrate, it does not follow that fat is actually so produced in the system. On the contrary, as shown by Pettenkoffer 6 and Voit, so tar from the fat produced being propor- tional to the carbohydrate principles, which ought to be the case on such a supposition, the fat deposited is proportional to the amount of albumen destroyed Thus, as will be seen from the following experi- ments made upon dogs fed with starch : Experiment of Feeding a Dog upon Starch. c . - - . Meat of body Fat Carbonic acid .taren ot loou. destroyed. deposited. produced. No. 1. 379 grammes ... 211 24 546 " 2. 608 " . " . . 1!»3 22 799 1 Dalton, op. cit., p. 62. Payen, op. cit. - Annales de Chiniie et Physique (:i), t. xiv. p. 408, 1845. 3 Ibid., p. 419, 1845 < Aim. de Chimie u. Phar., Hand Ixi. S. 228, 1847. •'• Report of the British Association lor the Advance of Science, 1852. 6 Zeits. fur Biologie, Band ix. S. 435, 1873. Hermann : Physiologie, Sechster Band, 1681. S. 252. Meat !<'.-troycil. Fat deposited 211 <.f body. ' 24 COS I of 55 469 i food. 112 62 PROXIMATE PRINCIPLES OF ORGANIC ORIGIN. that while the amount of fat deposited differed but little, the amount of starch taken as food was much greater in the one case than the other. This is as might have been expected, since the starch, after being transformed within the system into sugar, is then ultimately oxidized, and, as we shall see, constituting an important source of heat, cannot, therefore, be a source of fat. The meat destroyed, it may be men- tioned in the above experiments, was that of the body, since none was given as food. On the other hand, in the three following experiments : Experiment of Feeding a Dog upon Starch and Meat. Starch of food. No. 1. 379 srammes " 2. 379" " " 3. 379 " ... also made upon dogs fed with starch, and in the second and third ex- periments with meat also, it will be observed that while the amount of starch remained the same, that of the meat consumed differed con- siderably, nearly seven times more meat being destroyed in the third example than in the first, and nearly five times as much fat deposited. Not only, however, has it been shown that the meat or its contained albumen, when broken up, accounts for the production of fat in a car- nivorous animal, as the dog, but also in a herbivorous one, like the cow. Thus, according to Voit, 2 as has already been mentioned, of the 2024 grammes of fat in the milk of a cow, 1658.40 grammes are clearly derived from the fat of the feed, 1851 grammes are developed out of the breaking up of 3602 o-rammes of albumen, which, together with that of the feed, more than accounts for that found in the milk, as shown in detail from the following experiments : Production of Fat in Milk of Cow t . In feed In feces . 2757. 74 grammes fat, . 1099.33 Absorbed Out of 3602 grammes of albumen . 1658.40 . 1851.00 Available In milk ..... . 3509.00 . 2024.00 1485.00 When the chemical composition of albumen is considered, consisting, as we shall see as it does, of CHONS, it becomes perfectly apparent how, in being decomposed in the system, it can split into two sub- stances, a non-nitrogenous one, consisting of CHOS, and a nitro- genous one, CON 2 H 4 , urea, the former, excluding the sulphur, being retained in the system as fat, the latter being eliminated, as we shall see, in the urine. Suppose, for example, that 540 grains (about 34 grammes) of urea have been excreted by a man in the urine, involving a destruction of about three times as much albumen ; while all of the 1 Hermann, op. cit., S. 255. FAT. 63 nitrogen of the albumen destroyed passes practically out of the body as urea, only 108 grains of the 804 grains of the carbon of the albumen leave the body in that form ; 756 grains of carbon are, therefore, retained in the body, available for the production of fat, as may be seen from the following formula: c H N 864 112 252 352 108 36 252 144 Albumen . Urea Fat 756 76 ... 208 or dividing by atomic weights. C 6 ; H T6 Ol3 It is not to be supposed, however, that all of the 756 grains of the carbon are converted into fat, since probably two-thirds are exhaled from the body in the form of carbonic acid. The above theoretical consideration is fully borne out by the experiments of Pettenkofer and Voit 1 made upon dogs fed with meat. In one instance, for example, when a dog had eaten 2000 grammes of meat (about 400 of albumen) 43 grammes of carbon Avere retained in the system in the form of 58 grammes of fat, corresponding to 12 percent, of the albumen destroyed. The details of the experiment are as follows : Experiment of Fattening a Dog on Meat. 2000 grammes of meat Urine Feces Respiration Apart from the experimental evidence such as that just offered, there are a number of general facts which go to show that in many cases albumen becomes fat, as, for example, in the fatty degeneration of the tissues, the conversion of .dead bodies into adipocere, the development of fat out of peptones during fermentation ; that milk, after standing, con- tains albumen and less fat; that in phosphorous poisoning, as the fat increases the albumen diminishes, etc. Many more instances might be mentioned, but enough has been said to leave no reasonable doubt that fat, to a certain extent at least, is developed out of albumen. The only question that still remains undecided is as to what extent albumen becomes fat. In many instances, according to Voit, 2 even if as little as ten per cent, of fat (fifty per cent, being the maximum) is developed out of albumen, the amount so developed, together with the fat present in the food, is more than enough to cover the fat produced i Zeit. fur Biologie., v. S. 106, 1869; vi. S. 371, 1870; vii. S. 489, 1871. 2 Hermann : Physiologie, Sechster Band, S. -lib. N C 68.0 250.4 66.5 39.9 1.4 9.2 0.0 158.3 67.9 2(17.4 43 C retained 64 PROXIMATE PRINCIPLES OF ORGANIC ORIGIN. by the animal. On the other hand, there is no positive evidence what- ever that carbohydrate principles are transformed within the body into fat. As a matter of fact, they cannot be drawn upon for that pur- pose to any extent, leaving the body as carbonic acid and water after having been oxidized in the system. General considerations and expe- riments showing then that the fat deposited in the body over and above that absorbed from the food is derived from albumen, it may be asked of what use are the carbohydrate principles always present in fat- tening diet; in what way do they contribute toward the production of fat ? Regarding these principles as a source of heat to the economy, their role as a part of fattening diet becomes perfectly clear, since in being burned they save the fat otherwise derived and which would be drawn upon for the same purpose if they were absent. Hence, the fact of a dog fed on sugar and meat, excreting less urea and getting fatter than when fed on meat alone, of the negroes, etc., already referred to, getting fat during the extraction of the sugar from the cane ; of dogs fed on meat and rubol, 1 palm oil, 2 or stearin, getting fat, and without a trace of these substances being found in the excreta, the sugar or oil given with the food in these instances saving the fat otherwise pro- duced from the albumen from being burned. The carbohydrate prin- ciples evidently then play in the production of fat this secondary role of saving the fat, otherwise produced, from being consumed, and only in the event of it being shown that the fat deposited cannot be accounted for by the destruction of the albumen being overestimated, can these principles be regarded as a source directly of fat, of which at present, I repeat, there is no evidence. If the view T of the origin of fat, just re- ferred to, essentially that of Voit, 3 be accepted, it becomes intelligible why individuals become fat whatever they eat, and that if the fat of the body is to be reduced, all kinds of food must be diminished, as little eaten as possible, to cut off the supply, and plenty of active exercise taken to quicken the circulation and respiration, and in that way burn off that already deposited. Fat is never discharged from the body in health except in the butter of milk, but is destroyed, burnt, passing away as carbonic acid gas and water ; and, therefore, like sugar, being a source of heat and force : Fat. Oxygen. Carbonic acid gas. Water. C 57 H 110 O 6 + 163 = 57(C0 2 ) + 55(H 2 0) Fat is useful also as serving to support the organs, like the eye and kidney. It fills up the spaces between vessels, bones, and muscles, rounding oft' the trunk and extremities into the graceful curves of the human form. It prevents the loss of heat through its bad conductive power. This function of fat is well shown in the cetacea, of which the whale, dolphin, and porpoise are examples. In these animals, just under the skin, there is an immense amount of blubber or fat. If it were not for this layer of fat these marine animals would lose a great quantity of heat. 1 Radziejewsky : Yin-how's Archiv, xliii. S. 268. '-' Subuotin Zeits. ftir Bmlugie, Baud vi. S.73, 1870. 3 Hermann : Physioloeie, Sechster Band, S. 235. FAT. 65 It is well known that when fat is boiled with an alkali and water, part of the water is appropriated and the fat breaks up into glycerin and oleic, palmitic, or stearic acid, according to the kind of fat used, the acid further uniting with the alkali to form soap. This process is called saponification, but the terra also includes the breaking up, simply, of fat. in the presence of water, into glycerin and an acid, as seen in the following formula : Stearin. Water. Stearic acid. Glycerin. C 57 H 110 O 6 + 3H,0 = C 54 H 108 O 6 - ■ C 3 H 8 3 This can be accomplished by passing the vapor of water through fat heated to 572° F. In this way. sodium oleate and palmitate and oleic and palmitic acids are formed. 1 mention these principles, as they have been found in small quantities in the blood, bile, and lymph. The odor in the axilla and feet is probably due to the combination of fatty acids with alkali. The oleates and margarates may serve to hold in solution the small amounts of fat and fatty acids found in the blood. Some of the fat introduced in the economy probably disappears through this pro- cess of saponification. As regards the remaining proximate principles of the second class, lactic acid, pneumic acid, and sodium pneumate. little need be said. Lactic acid is developed in the economy through the "acid fermentation" of sugar, especially that of milk: as seen, for example, in the souring of milk. It is found in the muscles and often in the gastric iuice. Pneumic acid is restricted to the lungs. Pneumate of soda is formed through the decomposition of the carbonates in the blood as the latter pass through the lungs. CHAPTER III. PROXIMATE PRINCIPLES OF THE THIRD CLASS. This class includes such substances as albumen, fibrin, casein, pepsin, globulin, ostein, etc. They agree with the principles of the second class, in being of organic origin — that is, elaborated by plants and animals, organized bodies. The water, carbonic acid, and salts found in the mineral inorganic world, constituting the food of plants, with some exceptions, like the fungi, are converted by the plant through the agency of the sun's light and heat into such principles as starch, sugar, vegetable albumen, fibrin, and casein, etc. The plants in time serve as food for herbivorous animals, •which are eaten by the carnivorous ones, while, as we shall soon see, all three, plants, herbivora, and carnivora, together with the inorganic principles, enter into the food of man. It will be seen, therefore, that, so far as the organic principles are concerned in nature, the plant is indispensable as preparing the food for the animal ; the former living on carbonic acid, salts, etc., which would be starvation to the latter. While the organic principles are usually developed in the order indi- cated, it must be mentioned, however, that chemists have succeeded in artificially preparing some of the principles of the third class, as well as those of the second, from the direct combination of the inorganic ele- ments in their laboratory by purely physico-chemical processes, without invoking in any way either plant or animal agency. Just as no sharp line of demarcation can now be drawn between plants and animals, so the distinction between the organic and inorganic worlds is daily becoming fainter. Indeed, no one can say positively where the one ends and the other begins. The proximate principles of the third class, with the exception of lecithin, cerebrin, leucin, tyrosin, to be described hereafter, differ from those of the first and second in not being crystallizable. They may coagulate, but they never assume regular crystalline form. It is usually assumed in works on physiology that such substances as albumen, fibrin, etc., have not a definite chemical composition and therefore differ in this respect from water, salt, sugar, etc. Chemistry teaches that a definite quantity by weight of oxygen and hydrogen unite to form a definite quantity of water; that a certain quantity of sodium chloride consists of just so much sodium and chlorine ; that carbon, hydrogen, and oxygen combine in certain proportions to form a definite quantity of sugar. If, however, any of the elements entering into the composition of these substances be either increased or decreased, the substance will cease to exist as such : a priori then it is highly improb- PROXIMATE PRINCIPLES OF THE THIRD CLASS. 67 able that albumen, for example, consisting of C 72 H 112 N 18 22 S, should be an exception to this law of definite combining proportions. It seems to me more likely that albumen differs in its composition in individuals and is constantly changing even in the same person, and that these albu- mens, while resembling the one whose formula has just been given, if carefully analyzed would be found to consist of different amounts of carbon, hydrogen, oxygen, nitrogen, and sulphur, with different proper- ties, than to suppose that the composition of a substance like albumen can be altered without affecting its properties, and that it has no definite chemical composition. That such is the case seems confirmed by the fact of chemists having described at least sixteen kinds of albumen. The truth seems to be that any one of these albumens, with a little more or a little less of this or that element of composition, is not so changed as to render it unfit for playing the ordinary rdle of albumen in the economy. In other words, that these albumens, though slightly differing chemically, are readily converted into one another, the function of albumen in the system being performed by any of them. This, however, is quite a different statement from that usually made, that these principles are of indefinite chemical composition. The proximate principles of the third class, however, are distinguished in a marked degree from those of the first and second in containing nitrogen. This element seems indispensable to the composition of a body exhibiting life. As is well known, those substances which are very changeable, decomposing suddenly, like nitrogen iodide, nitrogen chloride, nitroglycerin, fulminating salts, gunpowder, etc., owe their peculiar properties to the nitrogen they contain. As we proceed in our studies, Ave shall see that the essence of life is in change. To make use of a homely simile, nitrogen seems to play the same part in the living body as that by a restless, excitable spirit in the living community : ever ready himself to be affected by slight changes and to influence in the same way those around him. Thus an important feature of the nitrogenized proximate principles is the readiness with which they induce such changes as fermentation and putrefaction — the latter being brought about by the growth and multiplication of a minute protist, the Bacterium termo (Fig- 13), just as sugar is decomposed into alcohol and carbonic acid through the influence of the yeast cell. Like the latter, the bacterium cells in inducing putre- faction neither give up nor take away any chemical elements, acting by their presence alone in a way which must be admitted is not as yet understood. The effect of the bacterium cells in inducing putrefaction in this manner, like that of the saccharomyees or yeast cell (Fig. 14) in producing fermentation, is usually said to be due to catalysis. The word catalysis meaning literally to dissolve, break up, while frequently made use of in speaking of those actions in the economy which are of this character, is, however, only a word, not an explanation — in fact, merely a convenient way of expressing our ignorance of the phenomena to be explained. The susceptibility of these organic principles to change, in and out of the In idv, is not only due to the nitrogen they contain, but to the great number of atoms entering into their composition. 68 PROXIMATE PRINCIPLES OF THE THIRD CLASS. It is more Datura! that albumen, for example, consisting of 225 atoms, should break up into its constituent parts on the slightest change taking place in the surrounding conditions, than sodium chloride or water, com- posed of two or three atoms respectively. It is easier for two or three persons to get along together than :i25, especially when among the latter there arc 22 (the nitrogenous atoms) most unstable ones. Another property of these principles is their hygrometricity — that is, their capacity for taking up their water of composition by contact after it has been driven off by heat, when the principles are said to have been desiccated. Fig. 13. ft >£ * y „ „ h * * Cells of Bacterium termo ; from a putrefying infusion. (Daliun. i The organic principles of this class are always combined with the inorganic ones, the union being most intimate, so much so that as the first are used up and become effete, and are cast out of the body, the inorganic principles go with them. Like the principles of the second class, those of the third class are destroyed in the system, never appear- ing in the excretions in health (with the exception of casein of milk, mucus, epithelium, and epidermis). Being transformed into carbonic acid, water, urea, etc., through a process of splitting, with subsequent oxidation, they are also a source of heat to the economy like the prin- ciples of the second class. The different principles of this class, and some of the situations in which they are found in the human body, may be seen in Table XV.' — Quantity of Albumen. Substance. Parts per 1000. Substance. Part per 1000. Cerebro-spinal fluid . 0.9 Chyle .... 40.1) Aqueous humor . 1.4 Spinal cord 74.9 Liquor amnii . . 7.0 Brain .... 86.3 Intestinal juice . 9.5 Liver .... 117.4 Pericardial fluid . 23.6 Muscle .... 161.8 Lymph . . 24.6 Blood .... 195.6 Pancreatic juice . 33.3 Middle coat of arteries . 273.3 Synovia . 39.1 ( Irystalline lens 383.0 Milk . 3! ».4 1 Carpenter, op. < -i t . , p. GO ALBUM EX. 69 Their relative amount, as may be seen, varies greatly ; thus in a thousand parts of cerebrospinal fluid there are only traces of albumi- nous compounds, over 30 parts in the same amount of chyle, and nearly 200 in blood. In the brain, over 80 parts to the thousand, over 160 in muscle, and nearly 400 in the crystalline lens, in round num- bers. The principles of this class all agree in their general aspects: a few words will suffice for their individual peculiarities. Albumen. — Albumen, which the white of egg closely resembles, is the type of the other principles of this class, and out of which they are all elaborated. It is found in all parts of the system, at all periods of life, in greatest abundance in the blood, is present in the lymph, chyle, serous secretions, milk, intermuscular fluid. Albumen can be obtained from the system, in which it exists in the fluid condition, by coagula- tion. This can be readily done by heating, or adding alcohol to the liquid containing the albumen, and filtering. Mineral acids, and some of the metallic salts, have the same effect. The ordinary method of testing for albumen consists in heating the suspected liquid — urine, for example — in a test-tube, when, if albumen be present, an opacity makes its appearance in the upper part of the tube first, which afterward extends downward, an insoluble precipitate is formed, which often becomes solidified. If it be thought that the opacity be due to an excess of earthy phos- phates, add hydrochloric acid, which has no effect on coagulated albu- men, but which will dissolve the phosphates. On the other hand, caustic potash will dissolve coagulated albumen in urine, but has no effect on the phosphates. In adding nitric acid to urine it may be mentioned that the cloudiness is often due to urates ; this will disappear in an excess of nitric acid, which, however, will not take place if the cloudi- ness be due to coagulated albumen, and it should be added that, in making use of the heat test, etc., the liquid to be tested, if alkaline, will not respond, even though it should contain albumen; under such circumstances it is necessary to add a few drops of acetic acid. The albumen of the blood is derived from the albuminous substances of the food, the latter, as we shall see, being transformed during diges- tion into albuminose, an albumen intermediate between food albumen and blood albumen. Blood albumen, the great nutritive element of the blood, is carried by the latter medium to all parts of the system. In this way the tissues arc supplied with fresh nitrogenized material, replacing that which becomes effete. The actual process by which the albumen of the blood is transformed into the albuminous principles of the tissues during growth, or in adult life, has not yet been made out. There is no reason to doubt, however, that, like all other so-called vital phenomena, it is a physico-chemical one. Albumen, after splitting up into simpler compounds, and subsequent oxidation of the latter, leaves the body as urea, carbonic acid gas, and water. It is. therefore, a source of heat and force to the economy as well as a tissue-maker, and this is true of the albuminoids generally. Adopting at least provisionally, the formula for albumen already 70 PROXIMATE PRINCIPLES OF THE THIRD CLASS. given, and deducting its nitrogen as representing so much urea, it will be at once seen that the remainder of the albumen, through oxidation, will finally be transformed into carbonic acid, water, and sulphuric acid, even if it be supposed that part of the albumen is retained temporarily as fat, as follows: Albumen C 72 H m N l8 0. 22 S 9 Urea (CH 4 N.,0) (',,* H % " Nia (\_ C 63 II;,; 13 S C 63 H TB 13 S + O m = 63CO, + 38H 2 + SO :i It is obvious also, that if the fat developed out of the albumen be finally burned, nevertheless the combustion of albumen will be far loss perfect than that of sugar or fat, since thirty-two per cent, of the albu- men passes, unburned, as urea, out of the body. Albumen, as a source of heat to the economy is, therefore, an expensive fuel, so to speak, as compared with sugar or fat, which are as perfectly burned within the body as out of it ; apart, also, from the fact of less heat being developed through the burning of albumen than of equal parts of fat or sugar. Albuminose. — Albuminose, or the modified food albumen, is found in the stomach and small intestine during digestion, and immediately afterward in the blood in small quantities. It differs from the albumen of the blood in not being coagulable by heat, and imperfectly by nitric acid, and from the albumen of the food in being endosmotic — that is, capable of passing through membranes, and so of being absorbed and getting into the circulation. White of egg, though not identical with albumen, but closely resem- bling it, was shown by Bernard 1 to be rejected by the kidneys when injected into the veins, due probably to its not being endosmotic. 2 When the white of egg has been digested, however, and converted into albu- minose, it is then readily absorbed. Albuminose does not remain long as such in the blood, being rapidly transformed into blood albumen. Fibrin. — It is questionable whether the substance commonly called fibrin exists as such, as a proximate principle in the system. When the blood coagulates, and the red corpuscles are removed from the clot, there remains a whitish, stringy, fibrous substance called fibrin, and which is supposed by some chemists to exist as such in the blood in a fluid condition; by others, to be only an albumen, modified through changed conditions ; another view favored by many, is that fibrin is due to the union through a ferment of two principles — fibrinogen, found in the liquor sanguinis, and paraglobulin, found in the blood corpuscles. There is much to be said in favor of all these views, but, as we shall see later, as yet the origin of fibrin cannot be said to have been posi- tively determined. This substance is found in the lymph and chyle as well as in the blood, but in less quantity. It is composed ultimately of the same ele- ments as albumen, and must, therefore, be derived, remotely, from the nitrogenized principles of the food. 1 Bernard: Liquides de l'Organisnie, tome i. p. 4f>7. Paris, L859. - Mialhe : Chimie Applique a la physiologie, p. 125. Paris, 1856. FIBRIN, CASEIN, MUCOSIN, ETC. 71 Whatever its condition may be in the blood, in the system fibrin is destroyed; thus it is not found, for example, in the renal or hepatic veins, the liver and kidney transforming it in a way not yet understood. Fibrin is interesting to the pathologist, as constituting the false membrane of croup, and as supplying the material for the spontaneous ;ii rest of hemorrhage in small vessels which have been opened from any cause. Casein. — This principle is found only in the milk, being derived from the albumen by the action of the mammary glands, and is there- fore present in the system only during lactation. It is very important, however, as constituting the principal nitro- genized food for the infant, being readily converted in the child into albuminose, which is carried into its blood and is then transformed into blood albumen. It is one of the few principles of this class which are discharged from the body in health. It differs from albumen in not being coagulated by heat, but by the weak vegetable acids. The coagulation of casein occurs when sugar of milk is converted into lactic acid by hydration, the milk becoming then sour, the reaction being as follows : Milk sugar. Water. Lactic acid. C 12 H., 2 O u + H 2 = 4C,H 6 3 Casein is kept in a fluid condition in milk through sodium carbonate. Mucosin, Pancreatine Pepsin. — Mucosin is found in the secre- tions of mucous membranes, differing slightly in composition according to the situation from which it is obtained. It is very like albumen; indeed, the white of the egg is generally taken as the type of albumen, though it is really mucosin, being secreted by the mucous membrane of the oviduct of the hen. White of egg differs from ordinary mucosin, however, in usually containing sulphur. Mucosin is one of the few principles of the third class dischai'ged in health. Pancreatin is the active principle of the pancreatic juice. It differs from albumen in being coagulated by magnesium sulphate. Its proper- ties with those of pepsin, the nitrogenized element of the gastric juice, will be considered when the subject of digestion is taken up. Ostein AXD Cartilagin. — This principle, which is solid, is found only in bones, in combination with the earthy salts. When bone is treated with dilute hydrochloric acid the mineral salts are dissolved out and almost pure ostein remains. When bones are boiled they are converted into gelatin. This, how- ever, is not a proximate principle, as it does not exist as such in the system. Cartilao-in is to cartilage what ostein is to bone. When cartilagin is boiled it becomes chondrin. This goes to show that the development of bone from cartilage is more than the addition of lime salts ; the organic principle cartilagin being probably metamorphosed at the same time into ostein. Globulin, Crystallin, Musculin. — Globulin and crystallin exist in a semisolid state in the blood corpuscles, and crystalline lens of the 72 PROXIMATE PRINCIPLES OF THE THIRD CLASS. eye respectively. Musculin is found also .semisolid in muscles, com- bined with inorganic principles. It is the most important nitrogenized element of the food, and through its metamorphosis into albumen in the system supplies, to a great extent, the economy with that important principle. Elasticin and Keratin. — Elasticin is found in the yellow elastic tissue and the membrane which envelops the muscular fibres. Keratin is present in the nails and hair. ELematin, Melanin, Biliverdin, Urrosacin.— Hamatin gives the blood its red color, and is found in the corpuscles combined with globulin. One of its most important constituents is iron. When hsematin is deficient in the system as seen in anaemia, the exhibition of iron will always reproduce it. To demonstrate iron in hsematin, add one drop of nitric acid to blood in a watch glass, and evaporate over a lamp. The iron is converted into a peroxide (the acid giving up oxygen), to this add the potassium sulphocyanide, when the characteristic red color will appear, due to the formation of the ferric sulphocyanide. Melanin is the organic principle of pigment found in the choroid and iris of the eye, hair, and epidermis. It is probably developed through the transformation of haematin. Biliverdin, the coloring matter of the bile, and urrosacin, the modi- fied pigment of the urine, will be again referred to under the subjects of the liver and kidneys. To avoid repetition, as well as for convenience, the remaining proxi- mate principles entering into the composition of the tissues and secre- tions of the body, and not mentioned in the general introductory just given, will be considered as the latter are successively treated of. While there is no doubt that the urea, carbonic acid, and water of the excreta are derived from albuminous principles, there is still a dif- ference of opinion as to whether the albumen whose breaking up and oxidation gives rise to urea, etc., is that of the tissues or that of the food, or of both, and, if the latter, how much of the urea produced is to be attributed to the breaking up of the tissue-albumen and how much to food-albumen. That the urea cannot be entirely derived from the breaking up of the albumen of the tissues, organic albumen, is shown from the amount pro- duced in starvation being so much smaller than when nitrogenous food, circulating albumen, is taken ; fifteen times as much urea being pro- duced, according to Voit, 1 in the latter case as in the former. Unless this large amount of urea is derived from the food it is difficult to account for it, for although the albumen of the body exists in greater amount than that of the food, as a matter of fact in starvation but a fractional part of it is destroyed; in a dog, for example, about one per cent. It is true that it is held by many physiologists that the albuminous principles of the food displace those of the tissues, either entirely or in part, the latter giving rise to the urea,, according to the view that urea 1 Hermann : Physiologif, Sechster Band, S. 302. DERIVATION OF UREA. 73 is derived from the tissue whether albuminous food be taken or not, all albuminous food becoming tissue before being destroyed. If such be the case, however, the whole body of a dog, for example, would be destroyed and built up again in a few days, 1 which is much more im- probable than that its albuminous food taken during the same time should be broken up and oxidized into urea, etc. Indeed, as a matter of fact, there is no evidence to show that under any circumstances the disintegration and oxidation of the body proper, apart from that of the food absorbed, go on to anything like the extent usually assumed and embodied in the popular idea of the whole body being entirely changed in some given period. Apart from the daily destruction and renewal of the cells of the epi- dermis and its appendages, hair, nails, etc., of the epithelial cells of the mucous membrane of the nose, trachea, alimentary canal, and its glan- dular appendages, of the blood corpuscles, there is little or no evidence of the total destruction of the cells, the constituent elements of the tissues. Even in starvation, where the muscles and liver may diminish one- half in weight, under the microscope the same number of muscular fibres, the same number of liver cells are visible, though diminished in volume through loss of their contents, just as an amoeba paramoecium or any unicellular being may be empty or distended according as it is supplied with food; cells, the structural elements, as we have seen, being essentially distinguished from extraneous matters which they may or may not absorb. That a disintegration and renewal of the tissues may go on is seen in the formation of bony cavities, in the production and absorption of callus, in the disappearance of the alveolar ridge of the jaw, in the repro- duction of parts that are lost. Such processes, as we know, are, how- ever, very slow, while under certain circumstances there does not appear to be any change taking place at all, depression in the crystalline lens of the eye, cicatrices, peculiar markings in the skin, etc., persisting through life. This hypothesis of the destruction of the albuminous tissues and the derivation of urea from the latter is an illustration among many of the vast influence of LiebigV views upon animal chemistry. That distinguished chemist held that force was developed at the ex- pense of the albuminous tissues, the loss being continually repaired by albuminous food; that muscular activity was the cause of the decom- position of tissue-albumen, and consequent production of urea, and that the amount of tissue-albumen destroyed is a measure of tissue change or " stoflf-wechsel " as he called it — that is, the breaking up of the albu- minous tissues with the production of urea and the rebuilding of the same through albuminous food. Any albumen present in the food, over and above that destroyed through muscular activity, was deposited, according to Liebig, in the body — that is, the amount of urea produced depended upon the muscular work and not upon albuminous food. 1 Voit in Hermann, op. cit., S. 277. 2 Die Organische Chimie, 1842. Ann. d. Chimie und Phar., xli., 1842 : liii., 1845 ; lviii., 1846 : lxx., 1849 ; lxxix.^ 1851. 74 PROXIMATE PRINCIPLES OF THE THIRD CLASS. The remaining carbohydrate principles, etc., of the food in being oxidized were regarded solely as sources of heat, their transformations not constituting a part of the true stoff-wechsel, that being limited to the changes in the albuminous tissues. With the establishment, however, of the fact that the amount of urea was increased by albuminous food, independently of muscular activity,, the celebrated theory of Liebig as such was no longer tenable. So deeply rooted, however, was this theory, that it was still defended, though in a somewhat modified form, by Lehmann, 1 Frerichs, 2 Bidder, 3 and Schmidt. Those experimenters who first showed that urea is increased by nitro- genous food impressed with the improbability of any great quantity of the latter becoming first tissue and then urea, assumed that all of the albumen of the food over and above that destroyed in starvation (the minimum, and derived from the body) was in excess, was a luxus, so to speak, and was directly oxidized in the blood, like the carbohydrate principles, etc. Hence the theory so widely known as that of "luxus consumption." As there is not the slightest evidence, however, that the albuminous principles of the food are directly oxidized in the blood, and, as we shall see, muscular action does not increase the amount of urea, and as the amount of albumen destroyed in starvation is no measure of that destroyed in health, the celebrated theory of ''luxus consumption" of Bidder and Schmidt falls to the ground with that of the " stoff-wechsel " of Liebig, of which it is merely a modification. As there is little or no evidence of the rapid destruction of the in- tegral part of the tissues implied in the view of the albumen of the food becoming tissue first and afterward urea ; or, it may be added, of the urea being developed synthetically out of simpler principles resulting from the destruction of the tissues, it will be assumed, for the present, at least, that by far the greatest amount of urea is produced through the splitting up of the nitrogenous food into simpler compounds, and subsequent oxidation of the latter. By oxidation, whether of food or of tissue, it may be here as well as elsewhere mentioned, that it is not to be understood that there is a direct combination of oxygen with food or tissue, but that just as in the case of oil burning in a lamp, or of wood in a stove, there is a splitting up of these substances at a certain temperature into simpler ones, the latter of which are oxidized, so do the albumen and fat of the body split up into simpler principles, which by subsequent oxidation pass out of the system as urea, carbonic acid, and water, and just as in the im- perfect combustion of oil or wood through the want of oxygen there arise various products, so the imperfect combustion of albumen, sugar, etc., gives rise to the production of fat, uric ucid, diabetic sugar, etc. That the breaking up of food or tissue in the body cannot be due to direct oxidation, as held by Lavoisier, is shown by many facts, such as that the oxidation of substances within the system does not follow the same order as without it ; that animals do not breathe more oxygen i Wagner: Handworterbuch, 1884, ii. S. 18. - Archiv f. Anat. und Phys., 1848, S. 4G9. 3 Die Verdauungsafte, 1852, 8. 348. DESTRUCTIVE CHANGES OF FOOD AND TISSUE. 75 when in an atmosphere containing a greater quantity than that existing in the ordinary air, or ahsorb more oxygen even though the haemo- globin be saturated with it, that carbonic acid is exhaled by a body or part of the same in an atmosphere in which oxygen is absent. Indeed, there is no more reason to suppose that the destructive changes of food or tissue going on in the body are entirely dependent upon direct oxi- dation, than that the combustion of wood or coal in a stove depends entirely upon the draught. The construction of the body, like that of the stove, must exercise a great influence upon the burning of the sub- stances placed within it. Inasmuch as the destructive changes of food or tissue, or of both, going on in the body, and upon which the maintenance of life depends, are not due to direct oxidation, as held by Lavoisier, nor to muscular activity and oxidation, as supposed by Liebig. Bidder, Schmidt, etc., it remains for us now to offer some hypothesis which can be provisionally accepted, if for nothing more than that by it facts can be connected together, woven into something like a theory, suggestive not only of new discoveries but to be tested by them. From time immemorial physiologists have been impressed with the similarity existing between the phenomena of fermentation, putrefaction, and those of life, and with every advance in knowledge the resemblance becomes more and more striking. Thus, as we shall see, the change of starch into glucose bv the saliva, of albumen into albuminose by the gastric juice, the splitting up of fat in the presence of water into glycerin and fatty acid, etc., by the pancreatic juice, are due to the ferment-like action of the ptyalin, pepsin, pancreatin, of these secretions. These changes are, however, but the first of a series experienced by the food in its gradual transformation into urea, carbonic acid, and water; the intermediate, subsequent stages taking place in the tissues themselves and not in the fluids bathing them. At least there is no evidence that the further breaking up and oxidation of the food modi- fied during digestion and absorption, go on in the blood, lymph, or chyle, these fluids appearing to be rather the means of transportation of the nourishing food to the tissues where the so-called vital changes take place and of removing the effete matters to the excretory organs, by means of which they are eliminated from the body. That the fluids of the body, such as the blood, lymph, etc., cannot be indispensable in the effecting of those changes which constitute life, apart from carrying to the tissue the material to be changed, is shown from the fact that such changes go on in an economy in the absence of blood, etc., as in the absorption of oxygen and carbonic acid by unicel- lular organisms, and the lower forms of animal life in which a vascular system is absent. In insects also, in which the breathing being accom- plished by trachea?, the oxygen is absorbed directly by the cells of the organs surrounding the latter, and, as we shall see later, the embryo bird, consisting, as it does, essentially of a mass of but little differ- entiated cells, absorbs oxygen and exhales carbonic acid in the absence of a vascular system. Facts like those just mentioned of the fermentative changes taking place in the alimentary canal, and elsewhere, as we shall see, of the far 76 PROXIMATE PRINCIPLES OF THE THIRD CLASS greater functional activity of the tissues, as compared with that of the fluids of the body, of the relative stability of the tissues, as contrasted with the albuminous and carbohydrate principles of the food brought to them in the fluids, point to the general conclusion thai vital changes are brought about in the tissues by some kind of ferment action together with oxidation. The tissues, through virtue of the cells of which they consist, act upon the food brought to them, as the yeast cell, saccharo- Fxa. 14. Fro. 15. Saccharomyces cerevisiae, in its quiescent con- dition ; from deposit of beer-yeast, after fermenta tion. (Dalton.) Saccharomyces cerevisiae in active germina- tion. From fermenting saccharine solution. (Dalton.) myces cerevisire (Figs. 14, 15), acts upon sugar, breaking it up into carbonic acid gas and alcohol, as shown by the formula : Glucose. (V.LL.O,, Alcohol. Carbonic acid gas. 2C.H 6 + 2C0 2 the changes undergone by the food in passing through the economy not any more necessarily involving the destruction of the tissues than the changes in the sugar induced by the yeast cells involve the de- struction of the latter ; though the cells of the tissue, like those of the yeast, have a certain limit to their action. It would appear, there- fore, that life is rather maintained through the destruction of the food by the cells of the tissue through fermentation and oxidation than at the expense of the tissues themselves. Such at least is essentially the view so well developed by Voit, 1 one of the highest living authorities on the subject of nutrition, and by which many striking facts in nutri- tion, whether during starvation or upon a diet of one one or more articles of food, may be explained. Thus while a starving man lives at the expense principally of the albumen and fat stored up in the tissues of his own body, there not being enough of these principles in the fluids to account for what is destroyed as measured by the excreta, nevertheless, the albumen and 1 Physiologie der Allgemeinen StonVechsel und der Ernahrang, Hermann, op. cit., Sechster Band. DESTRUCTION OF FOOD BY CELLS. 77 fat of the tissues, etc., are not, as such, used as food, but are trans- formed into circulating or food albumen, and in this form are carried to the other tissues, and there destroyed, one part of the body being sacrificed, therefore, to nourish another. That the latter is the case, is evident from such facts as that the heart and central nervous system, for example, during starvation lose but little in -weight, whereas the muscular system may be reduced over forty per cent., that the bones of the extremities do not suffer for want of lime salts, the latter being sup- plied from the bones of the sternum and skull, the latter becoming, in consequence, very thin, of the starving mother secreting milk in volume, etc., far exceeding that of the mammary gland itself. As regards also the destruction of different kinds of nutritive prin- ples, whether derived from the tissues of the body or from food, it is evident that the cells destroy more readily certain principles than others : albumen more readily than sugar, sugar more readily than fat whether derived from food or albumen. The amount of such substances de- stroyed or deposited will depend then on the relative amounts in which they are presented to the tissues, whether in starvation or in health. Hence, on an excessively rich nitrogenous diet the cells exhausting themselves in destroying albumen, fat will be deposited ; the same will be the case if sugar be given with albumen, the former being destroyed in preference to the fat derived from the albumen. Resume. — We have seen that the proximate principles of the third class consist ultimately of carbon, hydrogen, oxygen, nitrogen, sulphur (and, in some animals, of phosphorus). That such principles as albumen, fibrin, casein, etc., should be composed of these chemical elements to the exclusion of the remaining sixty or seventy, is not meaningless. Spencer 1 has shown that the elements composing living bodies have mobility enough to enable them to get rid of their effete material and to change continuously and actively their intimate parts. On the other hand, through the combination of a great number of atoms, these prin- ciples, through their inertia, become relatively immobile and possess fixity enough to resist disintegration. There must be fluidity and yet solidity in a living body. These conditions are fulfilled in the fact that three of the important elements entering into the composition of albu- men, fibrin, etc., are mobile gases, oxygen, hydrogen, and nitrogen, hence the readiness with which these matters change the arrangement of their parts or development, and the rapidity of those transformations of motion or function. It can be shown on mechanical principles that as the masses of the atoms increase, their mobility decreases, hence the comparative cohesive- ness of such principles as albumen, etc. Many interesting illustrations are brought forward by Spencer in favor of the above view. Briefly, it may be said here that the chemical and physical contrasts of the carbon, hydrogen, oxygen, and nitrogen are such as, a priori, would be required of the elements entering into the composition of living bodies. While admitting that the proximate principles of the third class are 1 Principles of Biology. 78 PROXIMATE PRINCIPLES OF THE THIRD CLASS. indispensable to the production of life, it seems to me, however, that we are not justified in restricting vitality to them as is often done by physiologists. The fact is that the tissues as they exist in the living body are not composed of albuminous principles alone. What would bone be without its calcareous salts, nervous tissue without phosphorized fats, how much life would be left in a body after the water had been removed, of what use would the pepsin be in the gastric juice without the acid, the blood without its salts, iron, etc. ? It is often said that the albuminous principles impart their life to the inorganic ones. This is a mere assumption, for the former principles are always intimately associated with the latter, being taken into the body to be digested, assimilated, and excreted together. You cannot separate the inorganic principles from the albuminous ones and leave the latter living. Deprive an animal of water and salt and it will die as surely as if deprived of albuminous food. If there are any strictly vital principles in a living body to the exclu- sion of others not vital, it does not seem to me that they can, at present, at least, be isolated. A simple statement of the fact is, that life consists of a series of changes exhibited by certain inorganic and organic prin- ciples composed of chemical elements combined in a certain way under certain conditions. The more complex the materials and their mode of combination, the more complex the resultant life. A substance consisting of two chemical elements, one atom of each only in combination, possesses fewer properties than one consisting of numerous elements and hundreds of atoms. Water, H 2 0, has fewer properties than potassium ferricyanide, Fe^'K^CN),., seen crystal- lized in definite mathematical form in every apothecary's window, and neither can be compared as regards their possibilities with living matter consisting of an infinite number of atoms of albuminous, carbohydrate, and inorganic principles. Believing that the properties of water and those of potassium ferri- cyanide are the resultant of the properties of the chemical elements of which they consist, logically it must follow also that life results from the properties of the elements composing the substances exhibiting the life, the question in each instance being one of the redistribution of matter and force. It should be mentioned also that the connection between the elements and the properties exhibited by their union are at present as little understood in the first two cases as in the last, mol- ecular physics not yet having given an explanation. Vital phenomena are not, therefore, more mysterious than any other kind of phenomena, and can be investigated to the same extent and in the same sense as those of gravitation, chemical affinity, etc. No more, no less. Facts obtained and laws generalized from them. The essence of phenomena, the ultimate cause of gravity, chemical affinity, vitality, or any other mode of force being unknowable. We have seen that the proximate principles of the human body are derived directly or indirectly from the food. When we come to study the blood we shall find that it is by means of this fluid that these prin- ciples are carried to all parts of the economy. As the living body is RESUME OF PROXIMATE PRINCIPLES.. 79 nourished by its blood, and as the blood is being continually renewed by the food, it is natural that all three, body, blood, and food, should con- tain essentially the same principles. We shall soon see that this is the case. As the nutritive principles exist, however, in the food in a con- dition different from that found in the blood, they are first subjected to certain processes in the alimentary canal that render them susceptible of absorption by this fluid and the lymph ; whence carried to the tissues they are further elaborated, assimilated, or decomposed by the cells of the same, supplying the latter with material for growth and develop- ment or the production of force. The life of the body, as already stated, being the total life of the cells composing it, it is in the cells or their modifications that the elaboration, combination, and decomposing of the chemical principles take place, the total resultant of which constitutes life. To the first of such vital processes, digestion, let us now turn, commencing with the subject of food. CHAPTER IY. FOOD. Vital, like all other work, implies waste. Our thoughts, our words, our gestures are all accomplished at the expense of the food and tissues of our bodies. Portions of our tissues, and the food appropriated by them, are being slowly but constantly consumed, being transformed into substances which will ultimately become carbonic acid, water, and urea. Life depends upon this continual and incessant waste and change of food and tissue. It is literally true that "in the midst of life we are in death." Every mental and muscular effort is accompanied with the destruction of so much food, brain, and muscular substance, and the loss of heat. The carbonic acid and water exhaled at every breath are evidence of so much food and tissue consumed. This daily, hourly, momentary death of the tissues and destruction of food demand the constant renewal of the matters of which they are composed. Hence the necessity of food, by which I mean any substance, inorganic or organic, solid or liquid, that will nourish the body ; renewing the material destroyed in produc- ing the phenomena of life. Hunger and Thirst. — The effects of withholding food entirely or of giving it in too small quantities are seen in cases of starvation and inanition. Under ordinary circumstances the sensations of hunger and thirst are the first indications that solid and liquid food are required by the system. These sensations seem to be due to a certain condition of the stomach and mouth induced by the want of food experienced by the general system. That such is the case seems to be justified by facts like the following. It is well known that the sensations of hunger and thirst can be relieved by introducing food into the system through fistular openings made in the body by disease or wounds. Thus food taken into the system through an opening in the intestine, as is w r ell known, will not only relieve the sensation of hunger but sustain life, 1 and in the case of an opening into the oesophagus, Avhen water and spirit were injected into the stomach, the thirst was relieved. 2 It is also well known that bathing and wringing the clothes in salt water have been the means of temporarily relieving the thirst of shipwrecked sailors. On the other hand, if the food is not absorbed, the sensations of hunger in the stomach and of thirst in the mouth are only temporarily relieved; even though solid food may be eaten and water be drank in large quantities, the general wants of the system in such cases not being satisfied. 1 Busch : Virchow's Arctaiv, 1858. - Gairdncr : Edinburgh Medical and Surgical Journal, 1S20. HUNGER AND THIRST. 81 The consideration of death from hunger and thirst belongs rather to the subject of pathology. As an illustration, however, of how life de- pends upon waste, and of the manner and relative quantities in which the tissues are destroyed to maintain life, the records of death from want of food, solid and liquid, become of interest to the physiologist. For a starving man is living upon himself, and as nature is always economical in her expenditures, one may feel sure that the very best disposition possible under such circumstances is made of the material available in maintaining life. In the wasting away that takes place in these cases we have a guide as to the character of the nourishment that the system would have taken had food been supplied from without instead of from within, and can so deduce some conclusions as to the use of food generally. Shipwrecks, prolonged sieges, imprisonments, forced marches, etc., furnish the data by which some idea may be obtained of the state of nutrition and of the agonies and horrors in cases of death from starva- tion. Among the symptoms of starvation ma}' be mentioned, first, severe pain in the epigastrium, which usually passes away in a day or so, then an indescribable feeling of weakness, a sort of sinking, in the same parts is experienced. The face becomes pale and cadaverous, and there is a wild look in the eye. General emaciation follows, an offensive odor is noticed about the body, which is covered with a brownish secre- tion. The voice becomes weak, muscular effort is almost impossible, the intelligence can with difficulty only be aroused. Finally death takes place, usually in eight or ten days, often accompanied with mania and convulsions. ( )n post-mortem examination the most striking facts usually noticed are the diminution in the weight of the body, almost entire absence of fat and blood, and the loss in bulk of the most important viscera. The coats of the intestine are so thinned as to be almost transparent, the gall-bladder is distended with bile, and decomposition sets in very rapidly. Death from inanition or insufficient food, though more prolonged than that from actual starvation, is essentially the same process only slower. being characterized by the same symptoms, and the same post-mortem changes. Many babies and young children in large cities and even in the country die from inanition — actually starved to death, undoubtedly through ignorance in some cases ; but in others, however, the length of time in death from inanition varying so, and being often so extended, advantage is frequently taken of this to obscure and mask the true cause of death by those interested in escaping from the penalties of their criminal neglect of the children placed in their charge. As already observed, one of the most prominent symptoms of starva- tion is the loss of weight. It may be generally stated that when this loss exceeds forty per cent., or from twenty to fifty per cent, according to Voit, of the weight of the body, death takes place. 82 FOOD. Table XVI. — Relative Loss ov Tissric in Starvation jx Joo Parts. In doves, accord- In < :ate, accord- ing to ' Ihossat. 1 iug tci \ 'nil.- Fat .... Blood .... Spleen .... Pancreas Liver .... Heart .... Intestines Muscles Muscular coal of stomach Pharynx and oesophagus Skin .... Kidneys Respiratory apparatus . Osseous system Eyes .... Nervous system . 93.3 97 75.0 27 71.4 67 64.1 17 52.0 .".4 44.8 3 42.4 18 42.3 31 39.7 34.2 :;:;.:: 21 31.9 26 22.2 18 16.7 14 10.0 1.9 3 By looking at Table XVI., taken from the excellent works of Chossat and Voit, it will be noticed that the difference in the relative loss of the tissues is very considerable. Thus the nervous system loses only a little over one per cent., the muscles over forty per cent., while more than ninety per cent, of the fat disappears. Now it has been noticed that in starvation the temperature falls, and most rapidly as death approaches; this is so evident that the immediate cause of death is undoubtedly cold. When it is remembered that one of the principal uses of the fatty principles is to produce heat through their combustion, the large loss of fat in such cases becomes intelligible, the animal using up its own fat as so much fuel. Inasmuch as no food has been introduced into the body there is nothing for the economy to make blood out of, hence the small quantity found in the body after death from starvation. Further, what there is of it is of the most inferior quality, rather injurious than otherwise; for through the impeded circulation the worn-out and effete matters which are excreted and carried out of the system so rapidly in health accumu- late in the stagnating inspissated fluid and represent so much poison. Even though one should recover from the effects of long deprivation of food, the system for weeks afterward remains in a bad condition peculiarly favorable to the reception of any zymotic poison. Hence, from time immemorial, famine has been the harbinger, the forerunner of epidemics, the plague, etc. Almost invariably after a long siege, where there has been insufficient food, unless careful measures are taken, disease breaks out and carries off many of those spared by the sword. In the often-quoted words of Chossat, " inanition is a cause of death which advances in the front and in silence in every disease in which alimentation is not in a normal condition." Terrible as the pangs of hunger are, those of thirst are worse. Man and animals will live longer without solid food than when deprived of water, man dying usually in a few days when no water at all has been i Recherches Experimentales sur 1" Inanition, p. 92. 2 Hermann : Physiologic, Band vi. S. 97. USE OF FOOD. 83 .aken. When it is remembered that about three-fifths of the body con- sist of water this is readily accounted for. The sensation of thirst, though caused by this general want of the system for water, is referred to the mouth and throat, which are first sensibly affected. These parts become very dry and hot and there is an agonizing feeling of constriction, fever sets in, the blood is very much diminished in quantity and becomes thickened, the urine is scanty and burns, the viscera may be said to be almost inflamed, delirium generally precedes death. The importance of giving water freely, internally and externally, in health and disease cannot be too much insisted upon. No detailed argument is necessary to prove this point. The simple fact that some- times within four days, even, men have died when entirely deprived of water speaks for itself. There are cases sometimes mentioned of human beings who have lived for very long periods of time without eating or drinking anything. When the evidence of such cases, however, is examined critically it generally turns out (with some exceptions to be mentioned shortly) that a morsel of food or a little water has been taken at some time, and that the exceptions are usually only apparent. Use of Food. — We have seen that the body, both in health and starvation, wastes that it may live. The rate of waste, however, varies in different classes of animals, and in different individuals of the same species. Thus, mammals and birds, living a more active life than rep- tiles or batrachians, waste more tissue and food. A man who lives a fast life — using the term in its physiological sense — wastes more rapidly than one who lives a moderate one. Hence the difference in the amount and quality of the food required and the frequency in taking it observed in different animals, and by the same animal at different periods of its life. Thus the boa constrictor may feed only once in three or four months, while man eats, usually, three times a day. Further, the food of the inhabitants of the polar regions, consisting principally of fatty, oleaginous principles, that of the people of tropical countries, of rice, dates, etc., shows that the food, in addition to repairing the waste of the tissues, fulfils other conditions essential to life. Every one is sensible of the change of the seasons, feeling that icy winter is melting into spring, that budding spring is unfolding into summer. The traveller, journeying from temperate to polar or tropical regions, appreciates the increasing cold of the one, or heat of the other, and yet the average temperature of man remains about the same, 98.6° F., at all seasons, in all climates. The temperature may rise as high as 110° in certain diseases, like tetanus, and even to 1*22° F., as in a case of injury to the spine, and which may be mentioned, ended in recovery; 1 or, under certain con- ditions, may fall as low as 83° F., or lower, as in cholera. These extremes if maintained, however, are soon followed by death. How can this constant heat in the human body be accounted for? We have seen that the sugars and fats, and albuminous principles of 1 Lancet, March G, 1875. 84 FOOD. which the body is composed, and which are derived from the food, are consumed in the economy, and produce heat. Thus food is so much fuel for the system. The question of some of the food being directly burnt up as such, as so much coal, or indirectly by first becoming tissue, and which lias Keen already considered, does not affect the fact of the food being the source of heat to the economy. 1 The use of food then is to repair not only the waste of the tissues, but also to supply the fuel for the production of heat and force. In the child, however, the food not only supplies these two wants, but also furnishes the materials for its growth, hence the large and constant amounts of food demanded by an active, healthy child. This fact should never be forgotten by the physician, for many persons seem to think that a child can be built up out of nothing. There is quite as much danger in giving a baby or child too little food as too much, for more of them die of starvation than of repletion. Again, the food of the female during gestation, must furnish the materials out of which the child is developed, as well as supply her own wants. The food, under these circumstances, ought to be most generous, both in quantity and quality, that neither mother nor child should suffer. Striking contrasts are offered, according to the particular use made of the food in one or more of the ways just mentioned by different classes of living beings, or of an animal at different periods of its exist- ence. Thus in trees, making no muscular or nervous effort and, there- fore, wasting but little, and having no constant temperature to maintain, all their food can be applied to increase their size, hence their indefinite growth. Insects, on the contrary, being most active, are usually small animals, the greater portion of their food being used up in producing their various actions, and little left for growth. In the foetal state of man the food is applied to growth, in the adult, for the purposes men- tioned above ; hence a man cannot grow indefinitely, his food being used for the development of mental and muscular force, there will be none left that can be appropriated for growth. Inasmuch as the quantity of food that can be taken by an animal is limited by the capacity of its alimentary canal, it might be inferred, a priori, that if the greater part of the food is applied to one particular use, there will be little or none left for any other. Hot-blooded animals require more food than cold-blooded ones, in order to maintain their higher temperature, and their more active life. When hot-blooded animals, however, hibernate — that is, sleep for months at a time — they pass into a sort of cold-blooded state, taking no food, existing by living upon themselves : they always weigh less at the end of their sleep than at its beginning; the waste, however, is comparatively small, they living so quietly during the hibernating period. By bearing in mind these facts, it becomes intelligible how individuals have been able to sustain life without taking food, water excepted, for many days beyond the period when ordinarily death from starvation 1 The various conditions winch influence the regulation and distribution of beat, and the cause of its production, will be deterred until we consider the subject of animal heat. KINDS OF FOOD. 85 ensues. By taking little or no exercise, in passing most of the time in sleep, and residing in a tropical climate, or in a temperate one during the hottest summer months, while the experiment lasts, it will be found that the system needs but little food, the waste of the tissues being reduced to a minimum, and there being but little need for the heat pro- duced on account of the high temperature of the surroundings. By living in this way, man can transform himself almost into a cold-blooded or hot-blooded hibernating animal. Under such circumstances he lives upon himself, and continually loses weight. When, as regards this loss of weight, a certain limit is reached, which varies according to the con- dition, previous mode of life, and peculiarities of the individual, he will certainly die of starvation unless food be taken, death from starvation being only a question of time if the system be deprived of food. Table XVII. 1 — Composition of Blood. Water Globulin Albumen . Fibrin Serolin Cholesterin Sodium Potassium Sodium Magnesium Sodium Potassium Free soda Magnesium I ( Ueate Margarate | Stearate ) - Chloride J ( ( !arbonate -,' Sulphate ( Phosphate ( Sulphate i Phosphate Calcium phosphate . Iron . . . . . Extractives undetermined 781 .600 135.000 70.000 2.500 0.025 0.125 1.400 : j. 5(i0 2..S5H . 0.550 . 2.450 1000. ooo Kinds of Food. — At the conclusion of the last chapter it was stated that, as the principles of which the body is composed are derived from the blood, and the blood from the food, the same principles will be found in all three. By glancing at Table XVII., drawn up from Becquerel and Rodier, it will be seen that the blood contains water, sodium chloride, phosphates, fats, albuminous principles, etc., while any of the ordinary animal or vegetable foods, like fish, eggs, milk, flour, or potatoes, etc., will be seen from Tables XVIII. and XIX. to consist of essentially these same principles. Indeed, the food of man naturally divides itself, like the proximate principles, into three classes, the albuminous, carbo- hydrate, and inorganic. Liebig's classification into tissue-making and heat-producing food is correct, so far as in that some kinds of food 1 Becquerel and Rodier : Traite de Chiinie, Pathologique, p, Paris, 1854. 80 FOOD. are especially useful in producing heat. It must be remembered, how- ever, that the combustion <>f all tissue produces heat, and that heat- making substances like fat, and the inorganic principles, make tissue as well as the albuminous ones. There is, therefore, no such sharp line of demarcation as heat- and tissue-making foods as Liebig's classification implies. It may appear strange that inorganic principles like calcium phos- phate, salt, water, etc., are classed as food, but as we have seen that the body is composed of inorganic as well as organic principles, we must regard as a food any substance that will furnish these principles. The chemical analysis of such substances as are seen in Tables XVIII. and XIX. explains why mankind makes use of eggs, fish, flour, potatoes etc., as food, these articles containing the inorganic and organic prin- ciples of which the body consists. Table XVIII. 1 — Animal Foods. In 1000 parts Mammals. Birds. Fish. Eggs. Milk. Water . . 728.75 729.83 740.82 735.04 861.53 Albumen . 174.22 202.61 137.40 134.34 39.43 Collagen . 31.59 14.00 43.88 Fat. . . 37.15 19.46 45.97 116.37 49.89 Carbohydrates 42.23 Extractives . 16.90 21.11 16.97 3.74 .... Salts . . 11.39 12.99 14.96 10.51 5.92 Table XIX. 2 — Vegetable Foods. ( lorn flour. Peas (dried>. Potatoes. Beet root. 150.00 760 822.50 132.50 280 10 20.40 . 606.80 573 180 54.80 122.60 , 26.60 '76 '46 25.60 , 16.80 , 12.50 '38 'id *8.90 In 1000 parts Water . Albumen . Starch Sugar Cellulose . Fat . Salts From the fact of the inorganic principles being usually combined in sufficient quantities with the organic, their indispensable use as food is often overlooked. The albuminous principles of the food that in the economy are converted into the albumen of the blood, are found both in the animal and vegetable foods. Thus we have albumen as musculin forming the basis of muscle, in various meats, beef, mutton, venison, lamb, etc., in the white of the egg, as casein in cheese, in birds, fish, oysters, and milk, as may be seen from Tables XVIII. , XXL, and XXII. In vegetables, albumen exists as vegetable albumen, readily converted into that of the blood. It is present in peas, potatoes, beets, flour, etc., as shown in Tables XIX. and XX. 1 Moieschott, referred to by Carpenter, Principles of Human Physiology, 1881, p. 97. - Carpenter, op. cit. KINDS OF FOOD. Table XX. 1 — Composition of the Potato. Water .... 66.875 Starch .... 30.469 Albumen .... 0.503 Gluten .... 0.055 Fat 0.056 Gum ..... 0.020 Asparagin .... 0.063 Extractives 0.921 Potassium chloride . 0.176 Iron ~\ Man-anesium j Silicates ) Aluminium , 1Ml hates .... I * 1 ™ Citrates j 0.815 Potassium Calcium J Free citric acid ....... 0.047 100.000 Table XXI. 2 — Composition of Ox Flesh. Water 77.17 Muscular fibre, vessels, nerves .... 15.80 Tendinous tissue ...... 1.90 Albumen ........ 2.20 Substances soluble in water .... 1.05 Substances soluble in alcohol .... 1.80 Calcium phosphate ...... 0.08 100.00 Table XXII. 3 — Composition of the Oyster. Water . 80.385 Nitrogenized substances . . 14.010 Fat . 1.515 Salts . 2.695 Loss ..... . 1.395 100.000 Starch is found in vegetables, in greater proportions, for example, in wheat, corn, rice, potatoes, beans and peas, etc., than in turnips, cab- bages, cauliflowers. Sugar is derived from animals, as milk and liver, i 1 sugar and sugar of honey ; and from vegetables as cane and grape sugar. Fats and oils are found both in the animal and vegetable foods. By looking at the above Tables the relative proportions of the carbo- hydrate to the albuminous principles in the substances usually used as food may be seen, and the large quantity of water and constant presence of salts are especially noticeable. Of the salts, amounting in twenty-four hours to about twenty grammes (three hundred grains), the most widely distributed are the sodium chloride and calcium phosphate, these being present both in the vegetable and animal foods. Iron, a most important principle, is found in ego;s and milk. It is not necessary to dwell further upon the in- organic kinds of food, sufficient attention having been paid to them wdien treating of their use in the system as proximate principles. 1 Pereira : Treatise on Food and - »I.-t . Nc\ 8 Payen : Substances Alimentaires, p. 221. Y.. ik. 1843. Paris, ISO"). Flint: Physiology, vol ii. l>. 71. CHAPTER Y. QUALITY AND QUANTITY OF FOOD. It might be supposed from looking at Tables XVIII. and XIX. that it was immaterial whether man lived upon animal or vegetable food, since they both contain essentially the same substances, and. this would receive confirmation when it was remembered that while many savage tribes on the one hand subsist almost entirely upon meat, the food of others on the other consists principally of the date, rice, etc., with little or no animal food. As a matter of fact, life can be sustained on either an animal or vegetable diet, the processes of digestion converting in- differently the albumen into albuminose, whether it be derived from beef or potatoes, and assimilating the fats and salts whether they are fur- nished by fish or bread. Living upon either animal or vegetable food, alone, however, is far from being an economical mode of diet, at least under ordinary circumstances. It might be naturally inferred from the fact of man possessing at the present day incisor, canine, and molar or grinding teeth, that from time immemorial he had been accustomed to live on both kinds of food, for had he limited himself to one or the other, certain teeth would have probably disappeared or at least have become smaller through disuse. Diminution in size has actually taken place in the posterior molar teeth through the effects of eating cooked food. The alimentary canal of man, as we shall see, is not so long or com- plicated as that of the herbivora, and yet not so simple as that of the carnivora, being rather a mean between the two. A fair conclusion from this comparison would be that a mixed diet is better adapted to the human system than an exclusively animal or vegetable one. The chemistry of the excretions not only confirms this view, but offers the explanation why it should be so. Table XXIII. 1 4600 grs. of carbon to 300 grs. of nitrogen in excreta, or 15 C to 1 N. 30,000 grs. of bread contain 9000 grs. of carbon to 300 nitrogen, or 30 C to 1 N. 46,000 grs. of meat contain 4600 C, 1380 N, or 3 C to 1 N. about 2 lbs. of bread contain < ! 4630 grs. N 154 grs. " f lb. of meat contains C 463 grs. N 154 grs. " 21 lbs. of bread and meat contain C 5093 grs. N 308 grs. or C 16 grs. N 1 gr. In a state of health there are found in the excreta for one grain of nitrogen fifteen grains of carbon (Table XXIII.). If a man should i Carpenter: Physiology, 1881, p 96. COMPOSITION OF FOOD. 89 confine himself to vegetable food, say bread, for example, for every grain of nitrogen that he ate he would take in not only fifteen grains of carbon, that are necessary, but fifteen grains too much ; in eating meat alone, while he obtains the one grain of nitrogen, he gets only about three grains of carbon, twelve grains too little. He must eat, therefore, nearly five times as much meat as is necessary, so far as the amount of nitrogen is concerned, in order to get the fifteen grains of carbon, and in so doing he loads his system with five times too much nitrogen. In eating bread you get twice as much carbon as is needed, and in eating meat four times too little. In diminishing the amount of bread you get too little nitrogen, and in increasing the amount of meat too much. If. however, the bread and meat are taken together in proper propor- tions we will get, according to the above calculation, the ratio of 16 of carbon to 1 of nitrogen in the excretions, which differs but little from that actually found, 1 to 15, and which can be accounted for by re- membering that the food of man consists not only of bread and meat, but of other substances containing carbon and nitrogen. Of the chemical elements entering into the composition of food, car- bon and nitrogen are the most important with reference to the compari- son to be made hereafter between the ingesta and the egesta in the determination of the origin of the latter, the source of animal heat, etc. The various methods adopted by chemists for determining the composi- tion of foods will be found in the standard general and special treatises pertaining to that subject. It may be mentioned, however, incidentally here, that the determination of the carbon, hydrogen, and nitrogen entering into the composition of food is essentially accomplished by burning the substance in suitable apparatus, and of so converting its carbon, hydrogen, and nitrogen into carbonic acid, water, and ammonia, and of deducing the amounts of carbon, hydrogen, and nitrogen m the food examined from the carbonic acid, water, and ammonia produced, the remainder giving the amount of oxygen. Should the food contain sulphur and phosphorus in addition to the other elements just men- tioned, their amount can be similarly determined by their conversion into sulphuric and phosphoric acids respectively. Table XXIY. gives the amount of carbon, hydrogen, nitrogen, etc. in the daily food. Table XXIV. 1 c H X s Albuminoids, 130 grammes 70 10 29 20 1 Hvdroearbons, 300 " L34 18 148 Fat, 100 " 70 12 12 Mineral salts, 20 << Water, 2000 it 2X0 40 L89 The study of the teeth, alimentary canal, and the excretions explains what experience teaches, that generally a mixed diet is best adapted to i Dalton, 7th ed., 1882, p. 132. 90 QUALITY AND QUANTITY OF FOOD. the wants of man. There arc circumstances, however, when although the diet, strictly speaking, is mixed, it consists to a great extent of either animal or vegetable foods ; the external condition being such thai the wants of the system are better supplied by the one than the other. Thus the Guachos in South America, spending their life in the saddle, and the climate being bot, live upon beef, there being little necessity for taking heat-making food, enough heat being generated through the c bustion of the beef indispensable as supplying the force and re- placing the tissue wasted in their active life. The people inhabiting the Arctic regions, living in a temperature where the thermometer falls lower even than — 40°, would freeze to death were it not for the oily matters that are found in the whales and seals serving as articles of food, and winch in their combustion produce so much heat. In tropical countries, however, the demand for carbon- aceous food is at its minimum, the heat being intense, hence, the prin- cipal food consists of rice, etc., which contains relatively little carbon. The obvious corollary from the above facts is, that travellers should accustom themselves as soon as possible to eat the food of the country they may happen to be passing through, and not invariably try to stick to the diet they have been accustomed to at home. Further, as the seasons change in any one particular place, the diet should be altered. Fats and sugars are more needed by the system in January than in July, and more exercise being taken in winter than in summer, tissue is wasted in this way in addition to that consumed to produce heat. The food should differ, therefore, both in quality and quantity in cold and hot weather. This subject of food is of great importance to the practical physician, for improper food is a fertile source of disease. The bilious diarrhoeas so common in the autumn are undoubtedly efforts of nature to relieve the system of the superfluous material that has accumulated in the system during the summer to such an extent that it can not be burnt up. The liver diseases that foreigners con- tract in the tropics are due, probably, to the same cause. An excess of albuminous food gives rise to gravel, gout, etc., through the imper- fect combustion of the urates. Rheumatism, etc., seems to be due to acidity resulting from the modi- fication of the starch and sugars of vegetable food taken in too large quantities. A deficiency of oil on the one hand, and of fresh vege- tables on the other, produces phthisis and scurvy respectively. In such cases the treatment is simply to diminish the article in excess and to supply that which is deficient. The benefit derived from cod-liver oil in consumption is well known, and the improvement in gouty disease through entire change of diet and mode of life is often marked. Theory and practice both agree, therefore, in showing that food must consist of a proper mixture of albuminous, oleaginous, saccharine, and saline principles, and just in proportion as any single food contains these principles will it be nutritious as an article of diet when used alone. The potato, for this reason, is invaluable as a food, containing as it does so manv different substances, Table XX. Bread has been COMPOSITION OF FOOD. 91 called the staff" of life, it entering so largely into the food of all classes of society. Table XX Y., giving the composition of flour, explains Table XXV. 1 — Composition of Flour. Water ......... 2.25 ounces. Gluten 2.00 " Albumen 0.25 " Starch 9.50 " Sugar 1.00 Gum 0.25 Fat 0.125 " Fibre 0.25 Ash 0.25 15.975 " why it fulfils the wants of the system to so great an extent. But "man cannot live by bread alone," and experience has shown that this is true of any one article of food ; the disgust and loathing when re- stricted to one article of diet for any length of time becoming so intense that animals will even starve rather than touch the food under such cir- cumstances. Indeed, it is not only impossible for a man to subsist for any length of time upon a meat diet, but a carnivorous animal, a dog, for example, whose alimentary apparatus is especially adapted to the digestion of meat, soon succumbs when fed upon pure flesh alone, unless the body be well supplied with fat, an albuminous diet being in fact the same as a starvation one in which, as we have seen, the man or animal lives upon the flesh and fat of the body. On the other hand, if the food consists of fat alone, man or beast will live but a short time, and it is worthy of mention that on such a diet less urea is excreted than in the starving condition, the albuminous tissues, the source of the urea, being spared through the oxidation of the fat. If more fat, however, be taken than can be disposed of in this way, as shown by the retention of carbon in the system, then fat is stored up and the albuminous tissues destroyed. The effect of a carbohydrate diet is essentially the same as a fatty one, sugar or transformed starch being, however, more readily oxidized than fat, seventeen parts of sugar being equal to ten parts of fat in this respect ; less urea is, therefore, excreted upon a carbohydrate diet than upon a fatty one. A certain amount of body fat appears to be also destroyed upon a carbohydrate diet. Of all foods, milk (Table XXA'I.) is the one which combines in itself to the greatest extent the proper substances in quantity and quality for the nutrition of the body, and were life limited to its early periods, we might say that milk is an exception to the rule just stated, but as the child develops into the adult necessity is felt for other kinds of food as well. All through life, however, milk constitutes a most important article of diet, and can be more relied upon, both in sickness and in health, than any other kind of food. 1 Lankester Guide to the Food Collections in the South Kensington Museum, p. 39. chloride 0.15 92 QUALITY AND QUANTITY OF FOOD. Table XXVI. 1 — Composition of Cow's Milk. Water 86.40 Nitrogenized substances t.30 Lactose 5.20 Butter , 8.70 Calcium 1 Magnesium V phosphate ....... 0.25 Ferric j Potassium Sodium { Sodium phosphate Sodium lactate Traces of coloring and aromatic matters. 100.00 The qantity of food that a man can eat and live, is very different from that which he should eat. Mentioning incidentally that a young Esquimaux is said to have eaten thirty-five pounds of food, including tallow candles, in twenty-four hours, and a Hindoo a whole sheep at a time, and that Cornaro lived for fifty-eight years on only twelve ounces of vegetable matter and fourteen ounces of light wine, and Thomas Wood for eighteen years on sixteen ounces of flour made into a pudding with water 2 (a very exceptional case), let us ascertain, if possible, what is the proper amount of food for the average man in twenty-four hours. According to Prof. Dalton, 3 " the entire quantity of food required during twenty-four hours, by a man in full health and taking free exer- cise in the open air, is as follows : Table XXVII. — Food Required in 24 Hours. Meat 453 grammes (16 ounces). Bread 540 "" (19 " ). Butter or fat 100 " (3 J " ). Water 1530 " (52 fiuidounces). " That is to say, rather less than two and a half pounds of solid food and rather over three pints of liquid." It is desirable, indeed nece-sary, if health .is to be maintained, that such articles as fresh vegetables, tea, coffee, milk, sugar, and fruit should be added from time to time to those just mentioned. It will be observed from a comparison of Tables XXIII. and XXVII., that on a bread and meat diet more bread is eaten than when oil is also taken with them as part of the daily food. In the latter case the oil supplying part of the carbon, less bread is required. Table XXVIII. 4 — Daily Ration of the United States Soldier. Bread or flour ..... 22 ounces Fresh or salt beef .... 20 " Pork or bacon ..... 12 Potatoes (three times a week) 16 Rice ....... 1.6 " Coffee (or tea 0.24 oz.) 1.6 " Sugar ....... 2.4 " Beans ....... 0.64 gill. Vinegar ...... 0.32 " Salt 0.16 " 1 Paven : Substances Alimentaires, p. 139. Paris, 1865. 2 Carpenter'* Physiology, p. 1 3 Physiology, p. 97. 4 Physiology, vol. ii. p. 126. TEA AND COFFEE. 93 Prof. Flint considers the United States army ration, Table XXVIII., as the most generous in the world. "The bread, meat, and potatoes contain 9.28 of carbon and 4.68 of nitrogenized matter, in addition to which are the alimentary principles contained in the rice, beans, sugar, -and coffee, with the peculiar stimulant effect of the coffee.'' According to Payen, 1 thesoup used in the great Paris hospitals, and which is very nutritious, may be appropriately mentioned here as serving also as a guide in forming a diet scale for charitable institutions generally. Its composition maybe seen from Table XXIX. Table XXIX.' 2 — Formula for Making Soup. Water ......... 20 gallons. Meat with bones 68 lbs 10 oz. Vegetables 13 " 10 " Salt . . . _ . . . . . 1 " 12 : j " Burnt onions (baked in oven until desiccated) . " 7jj " In concluding this general account of the subject of food, it may be stated that the effects of cooking food are three : First, to make it more palatable : second, to utilize it thoroughly ; third, to improve its digesti- bility. Food which is agreeable to the taste is eaten with more relish; and, therefore, better digested than if unpalatable. If the food were not cooked, much of it would be unfit to eat and wasted, and even if it could be eaten much would be undigested. There are a number of substances which cannot be regarded as food in the same sense as those already referred to, but as they are consumed to an enormous extent, in one form or another, by the majority of man- kind, some reference must at least be made to them in this connection. I refer to tea and coffee, tobacco, distilled and fermented liquors. Tea and Coffee. — As the composition and principal actions of tea and coffee are the same, they may be studied together. Tea and coffee are obtained from the Thea chinensis and Caffea Arabica, the tea and coffee plant respectively. As seen from Table XXX., they are com- posed of the same principles, united in different proportions. Table XXX. 3 — Composition of Tea and Coffee. Tea. Coffee. Water 5 12 Theine 3 1.75 Casein 15 13 Gum 18 9 Sugar ........ 3 6.5 Tanic acid 26.2-"> 4 Aromatic oil 0.75 0.002 Fibre 20 35.048 Fat 4 12 Mineral substances 5 6.7 100.00 100.000 The active principles are usually distinguished as theine and caf- feine. These alkaloids, however, and the active principle of the 1 Substances Alimentaires, p 101. - Flint, op. cit., p. 87. i arpenter: Physiology, 1870, p. 120. 94 QUALITY AND QUANTITY OF FOOD. Paraguay tea, made from a shrub, have the same chemical compositions (C 8 lf 1() N 4 2 + 2II 2 0). In making good tea there are usually allowed " i spoonful for each person and one for the pot," so each person gets then say about 100 grains of tea. We see, however, from Table XXX., that the quan- tity of theine, the active principle of tea, amounts to only three per cent.; it must be admitted, therefore, that its nutritive powers, either as a tissue- or heat-making food, must be very small. How account, there- fore, for the value of tea as an article of diet, as daily experienced by hundreds of millions of people ? The explanation of the effect of tea depends upon the fact of its increasing the amount of carbonic acid expired, and of waste; as first shown by Mr. Edward Smith. 1 Tea is a respiratory stimulant, and therefore powerfully promotes "those vital changes in food which ultimately produce the carbonic acid to be evolved." Instead, therefore, of supplying nutritive matter, it causes the assimilation and transformation of that already taken. The effect is not proportionate to the quantity of tea taken, and in this respect it is analogous to the action of a ferment. The sense of ease in respiration and increase of general comfort after taking tea are well known, as is also the fact that tea tends to induce perspiration and thereby to cool the body. Hence, in reference to nutrition, we may say that tea increases waste, since it promotes the transformation of food without supplying nutriment, and increases the loss of heat without supplying fuel. It is better adapted, therefore, to those who are well fed than to the poor and fasting. The effects of tea upon the mind are well known : wakefulness, clear- ness and activity of thought, disposition for muscular exertion, etc. The exhaustion and nervousness which sometimes follow the excessive use of tea appear to be due to the loss of sleep and waste of tissue rather than to any poisonous action of its active principle. The effects of coffee and tea, in many respects, are the same. Coffee, however, differs from tea by diminishing the action of the skin. It lessens also the loss of heat of the body, but increases the vis a tergo, and, therefore, the heart's action and the fulness of the pulse, and excites the mucous membranes. The conditions, therefore, under which coffee may be taken are very different from those suited to tea. It is more suited than tea for the poor and feeble. It is also more fitted for breakfast, inasmuch as the skin is then active and the heart's action feeble, whilst in good health and with sufficient food it is not needful after dinner, but if then drank should be taken soon after the meal. It was formerly stated that the action of coffee, tea, etc., was an ex- ception to the rule that increased vital activity is accompanied by waste, these substances being said to increase force but to diminish waste, the urea, which diminishes under the use of coffee, being supposed to be the measure of tissue change. It is now known that the emission of car- bonic acid by the lungs is rather the true measure of muscular exertion, and this being increased by coffee and tea, the objection just mentioned is no longer of weight. 1 Philosophical Transactions, 1859. ALCOHOL. 95 Tobacco. — As the employment of tobacco is most extensive in all classes of society, a few voids on its effect upon the system in this con- nection appear appropriate The active principle of tobacco is a poisonous alkaloid, nicotia, consisting of C 10 H ]4 N 2 . The results of Dr. Hammond's experiments seem to show that under the use of tobacco the elimination by the kidneys of the uric and phosphoric acids is in- creased, but that the feces and urine are diminished, the exhalation of carbonic acid being only slightly affected. While the excessive use of tobacco no doubt produces a state of wakefulness, trembling, and nervous excitement, it cannot be denied that when moderately used it is often very beneficial, quieting and soothing the nervous system when ex- hausted by bodily and mental effort, and even in ordinary circumstances producing a general tranquillizing effect. Tobacco seems also to promote digestion, stimulating the secretion of the gastric juice, perhaps by reflex action, hence the common custom of smoking a cigar after breakfast or dinner. Alcohol. — Before considering the use of wines, malt liquors, and spirits, it is necessary to learn, if possible, the effects of pure alcohol upon the human body, since this principle is contained in large or small quantities in all such fluids. Alcohol chemically consists of C 2 H 6 0, and the first question to be investigated is. What becomes of it when taken into the system? Some experimenters, like Anstie and Dupre, found very little alcohol in the excretions, it appearing to be oxidized, burnt up; according to others, however, like Percy, Lallemand, Perrin, and Ducroy, 1 alcohol is found in the ventricles of the brain unchanged, and is eliminated by the lungs, skin, and kidneys. ' It is possible that these contradictory results may be due to the dif- ferent amounts of alcohol given, to the length of time that it has been in the system, and that under certain circumstances it is in part con- sumed and in part excreted. In either case, however, alcohol can be of no benefit to the system, for if it is found as such untransformed in the organs or excreted unchanged, it cannot supply any want, simply passing through the system, and if it is burnt up it must interfere with the oxidation of other substances, such as fat, etc., which under ordinary circumstances would, through combustion, disappear. If this view be correct, Ave have an explanation of hard drinkers becoming often so fat, the alcohol being burnt in preference to their fat, and so allowing their fat to accumulate in the muscles, in the liver, heart, etc., or, what is more likely, the alcohol in some way interferes with that splitting of food or tissue that normally precedes its oxidation. Alcohol can never substitute the natural drink of man, water. Many substances which are soluble in the latter are precipitated by the former, and. hence, useless to the system ; further, it does not supply any prin- ciple to the tissues. Alcohol, in diminishing the amount of urea excreted and the action of the skin, and in interfering with natural combustion, perverts the whole nutrition of the body. The active changes and the rapid removal of the effete matters, so characteristic of healthy life, are retarded by 1 Carpenter' d Physiology, 1876, p. 107. 96 QUALITY AND QUANTITY OF FOOD. alcohol; hence, the susceptibility to zymotic poisoning of the dram drinker and his chronic diseases. It is well known also that less food is taken when alcohol is used, and so alimentation is affected. It is often urged that alcohol " will keep the cold out," but as the cutaneous vessels dilate under the use of alcohol through paralysis of the vaso- constrictor nerves more blood, and therefore more heat, comes to the surface, which instead of being retained within the body as it would otherwise be, escapes, the natural effect of the cold being to contract the vessels and of so keeping the heat in the body. Whether this be the true explanation or not, the fact remains the same, that Arctic voyagers keep the cold out far better without .the use of alcohol than with it. 1 Finally, in addition to these facts, when it is remembered that many persons preserve their mental and bodily health perfectly without ever touching alcohol, it is difficult to offer a single good phy- siological reason for the use of alcohol at any time, the body being in health. It must not be forgotten, however, that almost every people, savage or civilized, use alcohol in some form or another. Whether some, as yet unknown, want is supplied to the system by alcohol, or whether it is used merely to drown sorrow or to relieve ennui, is an undecided question. Among civilized people life is so artificial and man is so harassed bodily and mentally that, unfortunately, perfect health is far from being common. Life at times becomes weary, the heart feels oppressed, digestion is sluggish, the circulation impeded, muscular languor is present, then alcohol is useful, for it is a nervo-muscular stimulant. The action of the heart is accelerated, the blood flows more rapidly, the heart is relieved, and good results from its use. Every physician knows that in those dark hours when life hangs upon a thread, that alcohol is often the only remedy that has dragged the poor sufferer out of the jaws of death — the good effects of its temporary action bridging over such critical periods. As a medicine, alcohol is indispensable ; when used for any other purpose, little or nothing can be said in its favor. The action of alcohol is different in many respects from tea or coffee. Alcohol narcotizes the sympathetic, tea and coffee excite the cerebro- spinal nervous system ; the former stupefies, while the latter brightens the intellect: the one inebriates and destroys, the other cheers and preserves. Distilled Liquors, Wine, Malt Liquors. — The distilled hquors most commonly used are brandy, wdiiskey, gin, and rum. They contain, as a rule, a little more than 50 per cent, of alcohol, and hence, when abused, their bad effects. Brandy, the most valuable of them as a medicine, is obtained by the distillation of wine ; whiskey from rye, wheat, etc. ; gin, from different grains rectified by juniper, and rum from molasses. Brandy, wdiiskey, and gin diminish the amount of carbonic acid exhaled, and so interfere with vital processes. Rum, however, increases the carbonic acid exhaled, and, therefore, is less 1 I lays : American Journal of the Medical Sciences, 1850. DISTILLED LIQUOES, WINE, MALT LIQUORS. 97 hurtful in its effects. It has long been noticed that the rum-drinker lives longer than the brandy or gin-drinker. Table XXXI. 1 — Composition of Wine. Water. Alcohol. Bouquet. Sugar. Gum. Extractives. Gluten (except where tannin is present). Acetic acid. Bitartrate of potassium. Tartrate of potassium and aluminium (in German wines). Sulphate of potassium. Potassium and sodium chlorides. £ a ? ni . n f+ } in red wines. Coloring matter j • Carbonic acid (in champagne). Wine, or the fermented juice of the grape, is called full-bodied or light, according to the amount of alcohol present. There is always less alcohol in wines than in the distilled liquors just mentioned ; thus port, Madeira, and sherry contain from 15 to 25 per cent, of alcohol ; claret, sauterne, hock, about 10 to 15 per cent. In countries where the light wines are used by all classes of society, the horrible effects of spirituous liquors are almost unknown, the per cent, of alcohol being so small in light wines. Wine, as seen from Table XXXI., contains, in addition to alcohol, sugar, gluten,, and a number of salts, etc. Wine is nutritious in proportion to the amount in which these substances are present. In the preparation of many wines, like champagne, the amount of carbonic acid is increased ; hence, their great use as diffusible stimulants in those cases where the vital powers demand prompt and active stimulation. Under such circumstances there is no better medicine than champagne. Table XXXII. 2 — Composition of Beee. Water .... Alcohol .... Dextrin, glucose, etc. Nitrogenized substances . Mineral salts Bitter principle not determined 947.00 4.50 41.40 5.26 1.84 1000.00 Beer, ale, and porter are made from malted barley, with the addition of hops. All malt liquors contain alcohol ; about 1 to 4 per cent, in the weaker, and from 6 to 8 per cent, in the stronger kinds. Even as much as 12 per cent, is found in the heavy English beers. Table XXXII. gives the composition of the ordinary French beer, 1 Pereira : A Treatise on Food and Diet, 1843, p. 502. - Payen: Substances Alimentaires, p. 462. In the original table of Payen, 957 is given, instead of 947, probably a typographical error. 98 QUALITY AND QUANTITY OF FOOD. whioh will serve as an example of malt liquors generally. A most noticeable feature is the small amount of alcohol, and the very large quantity of glucose, etc. There are also nitrogenized substances, mineral salts, and a bitter principle. Apart from the alcohol they contain, malt liquors are nutritious on account of these carbohydrate and nitrogenized and inorganic principles. They are often of great service to persons who have run down, are debilitated, or who are slowly recovering from some exhausting, low type of disease, being taken then as medicine. In such cases the small quantity of alcohol in the malt liquor is beneficial, acting as a stimulant, the hops are useful as a tonic, and the remaining principles as food. It will be seen from what has been said of alcohol that the evil resulting from the abuse of liquors of all kinds is proportional to the amount that is present of this principle, that malt liquors and light wines are less injurious than brandy and whiskey, and that beer, ale, etc., containing so many nutritious principles, closely approximate to the true idea of a food. The importance, however, of remembering that the malt liquors also contain alcohol, and in sufficient quantities to do mischief if too freely partaken of, will be appreciated when it is learned that 1,076,844,942 gallons of beer were consumed in 1873 in Great Britain, in addition, to spirits, wine, cider, etc. Alcohol cost the United States, in ten years, directly, $600,000,000; indirectly, $600,000,000 more ; destroyed 300,000 lives, sent 150,000 people to prisons and work-houses, 100,000 children to the poor-house, drove 1000 insane, determined 2000 suicides, caused loss by fire or violence of $10,000,000 of property, made 200,000 widows, and 1,000,000 orphans. 1 With such an array of figures it cannot be considered superfluous that attention has been called to the effect of alcohol in its relation with food. 1 De Marmon : New York Medical Journal, December, 1870. CHAPTEE YI. DIGESTION. In order that the food should fulfil its functions in the economy it must be assimilated, and before that can be accomplished the food must be first digested and then absorbed. Digestion should, therefore, be studied first. Under the general term digestion are included several processes : the prehension of food, its mastication and insalivation, deglutition, the changes effected in the food during its passage through the stomach, the small and large intestine, and defecation. While the various and often complicated ways in which the lower animals take their food are interesting to the comparative physiologist, the description of which would require a detailed account of the organs involved, it is unnecessary for me to dwell upon the simple process as observed in man. In sucking, however, it may be mentioned that this process is due to the tongue acting like a piston, since when the velum is applied to the back of the tongue and the mouth closed posteriorly a tendency to a vacuum is made, the lips at the same time closing around the nipples anteriorly. In drinking the action is essentially the same, except where the head, being thrown back and the liquid poured in, it is, so to speak, tossed off. « Mastication. The chewing of food, or mastication, is effected by the teeth, which, in the adult condition, are thirty-two in number, viz., eight incisors, four canines, eight premolars, and twelve molars. A tooth is usually described as having three parts. That portion which is seen in the mouth is called the crown. The tapering portion inserted in the socket, or alveolus of the jaw, is the root or fang, and is held in position by fibrous tissue continuous with the periosteum of the jaw and submucous tissue of the gum. The intermediate constricted part of the tooth between the crown and the fang is known as the neck, the accumulation of fibrous tissue at this position being called the dental ligament. The incisor or cutting teeth (Fig. 16) four in each jaw, are nearest to the middle line in front of the jaw. They are inserted in their sockets by a single fang. The crown of the tooth is Avedge-shaped, and presents a wide, sharp, and chisel-like edge, its lingual or inner surface is concave from above downward. In the upper jaw the central incisors are larger than the lateral ones, whereas, in the lower jaw the lateral are larger than the central ones. The incisors are well adapted to cut and bite the food. 100 DIGESTION, The tooth next to the lateral incisors in both jaws is called the canine (Fig. 17), and corresponds to the large tearing and holding tooth in Fig. 16. Fig. 17. Incisor teeth of the upper and lower jaws. a. Front view of the upper and lower middle in- cisors. 6. Front view of the upper and lower lateral incisors, c. Lateral view of the upper and lower middle incisors, showing the chisel shape of the crown ; a groove is seen marking slightly the fang of the lower tooth. (Quain.) Fig. 19. Canine tooth of the upper jaw. a. Front view. b. Lateral view, showing the long fang grooved on the side. the dog, and hence its name. The canine teeth, four in number, are larger than the incisor teeth. The crown is conical and bevelled behind, the fang is longer than in any of the other teeth, and laterally exhibits a slight furrow, as if indicating a tendency to subdivide into two. The upper canine or eye teeth are larger and longer than the lower ones. The latter are often called the stomach teeth. The canine teeth assist the incisors in dividing the food. The premolars, two in each jaw (Fig. 18), succeed the canine. They are shorter and thicker than the latter. The crown is cuboidal, convex externally and internally, and exhibits upon the triturating surface two emi- nences or cusps, hence their name of bicuspids. The fang is conical and flattened, and deeply grooved. The upper premolars are larger than the lower ones, and their fang is more or less subdivided into two. The premolar teeth are suc- ceeded by the twelve molar or grinding teeth, six in each jaw. The molar tooth (Fig. 19) has a cuboid crown. The triturating surface in the upper molars at the four angles is elevated into four tubercles with a diagonal ridge Fig. 18. First bicuspid tooth of the lower jaw. a. Front view. 6 Lateral view, showing the lateral groove of the fang and the tendency in the upper to division. (Quain and Sharpey.) First molar tooth of the upper and lower jaws. They are viewed from the outer aspect. (Quain and Sharpey.) MASTICATION. 101 connecting two of them. In the lower molars there are five tubercles or cusps, two on the inner side and three on the outer. The upper molars are inserted in their sockets by a pair of conical fangs, the lower ones by three fangs, two external and one internal, the latter is the largest and grooved. The first molar tooth — that is, the one most anteriorly situated — is the largest, the third, or the wisdom tooth, the smallest. Often, however, in the savage races of mankind, in the milk teeth of civilized races, in the fossil man, and in the monkeys, the last molar is the largest. It is by means of the molar teeth that the food is crushed and ground up. During mastication the external tubercles of the lower molars are opposed to those of the upper ones, and through the lateral motion of the lower jaw inward, the external tubercles pass down the inclined surfaces of the external ones and up those of the internal tubercles of the upper teeth, crushing the substances between them. The teeth are arranged in the jaw somewhat in the form of a curve. In savage races, on account of the prominence of the canine teeth, the curve is rather of an oblong form, and in civilized races the curve is often V-shaped. The incisor teeth of the upper jaw overlap those of the lower, and the external cusps of the premolars and molar teeth close outside those of the lower jaw. It will be also observed that the central incisors of the upper jaw extend over the central and half of the lateral incisors of the lower jaw, whilst the upper lateral incisors come in contact with the outer half of the lower laterals and the anterior half of the lower canines. The canine teeth of the upper jaw extend over half of the lower canines and half of the lower first premolars. The first premolar of the upper jaw is opposed to the half of the first pre- molar and half of the second premolar of the lower jaw, whilst the second upper premolars impinge upon the posterior half of the second premolar and anterior half of the first molar of the lower jaw. The first molar of the upper jaw is opposed to the posterior two-thirds of the Fig. 20. Skull of lion. (Owes.) first molar and anterior third of the second molar of the lower jaw. The second upper molar impinges upon the posterior third of the second and anterior third of the last molar of the lower jaw. The last molar in the upper jaw is opposed by that part of the third molar in the lower jaw which remains uncovered by the second upper molar. 102 DIGESTION, Skull of Indian rhinoceros. (Owen.) By this disposition it will be seen that no two teeth are opposed to each other only, and that, with the exception of the last molar, ouch tooth in the upper jaw is op- posed to two teeth in the lower one. If a tooth is lost, or even two alternate ones, the remain- ing teeth will therefore he still useful. If the teeth of man be com- pared with those of a carnivor- ous animal, like a lion (Fig. 20), or with those of a herbiv- orous one, like a rhinoceros (Fig. 21), it will be noticed that in man the teeth are both of the carnivorous and herbivor- ous kinds, and pretty evenly developed, whereas, in the lion, on the one hand, the teeth are all of the biting, cutting, and tearing character; while in the rhinoceros, on the other hand, the largest teeth are of the grinding and crushing character. The teeth of the carnivorous lion and herbivorous rhinoceros are in harmony with the nature Fig. 22. of their food. One would infer from the fact of man possessing both incisor and molar teeth that his food had consisted from time immemorial of both animal and vegetable origin. This confirms what we have already learned from the chemistry of the food, that the diet of man should be a mixed one. On making a longitudinal sec- tion of a tooth, of a molar for example (Fig. 22), it will be ob- served that there is a cavity within the crown of the tooth which extends into and through the fangs opening by a small aperture at their apices. This space is the pulp cavity, and contains, in the living tooth, the pulp. The tooth will be also seen from such a section to con- sist of three parts, dentine or ivory, a yellowish-white substance border- ing the pulp cavity, enamel, a harder and whitish substance capping the crown, cement, a translucent bony-like layer encrusting the roots. The dentine constitutes the great bulk of the tooth, chemically it con- sists of about twenty-eight parts of animal matter (tooth cartilage), and seventy-two of earthy salts, among the latter are principally found cal- Section of human molar tooth magnified (Owen.) ENAMEL. 108 cium phosphate, some calcium carbonate and magnesium phosphate. When examined with the microscope dentine (Fig. 23) is seen to consist of an amorphous translucent matrix, in which are imbedded numerous canals or tubes, whose walls are distinct from the matrix. These latter are the dental or dentinal tubules, and average in diameter at their com- mencement 45 1 00 th of an inch. The intermediate space between the adjacent tubules is about three times their diameter. The dental tubules ^ IG - 2?> - open at their inner ends or begin- nings into the pulp cavity, outwardly they pass to the periphery of the tooth. The tubules run generally in a parallel, but somewhat wavy course. As they pass outward they become gradually narrower, dividing and subdividing, giving off innumerable small branches, Fig. 24. a. Dentine, b. Odontoblastic cells, c. Fibres. (Tomes.) which anastomose or end blindly. Some of the terminal branches pass into the canalicula of the cement, others into the so-called interglobular spaces, irregular cell-like cavities in the ma- trix. The walls of the dental tubules are about as thick as their calibre. In the living tooth the dental tubules are filled with the dental fibres, which are prolongations from the odontoblastic cells of the pulp (Fig. 24). These dental fibres are possibly the terminal filaments of the nerves supplying the tooth. The contour markings observed in the teeth are due to irregularities in the matrix or intertubular substance. As age advances there is deposited upon the inner surface of the dentine a secondary kind of dentine, known as osteo-dentine, which resembles both dentine and bone. This appears to be due to a sort of ossification of the pulp, the effect of which is gradually to obliterate the latter and the pulp cavity. Enamel. — The crown of the tooth is covered with the enamel, the hardest of organic substances. It is, however, gradually worn down by protracted use. The enamel is thickest upon that part of the tooth Section of fang, parallel to the dentinal tubules (human canine). Magnified 300 diam- eters. 1. Cement, with large hone-lacuna; and indications of lamella;. 2. Granular layer of Purkinje (interglobular spaces). 3. Dentinal tubules. (Waldeyer.) 104 DIGESTION. Fig. 25. :£?> most used in trituration, here it exists in several layers ; it is thinnest at the roots, where it gradually disappears. Chemically, enamel consists of about five parts of animal matter, and ninety-five of earthy constituents, the latter being mostly calcium phos- phate. Microscopically, enamel consists of solid six-sided prisms, the enamel fibres having an average diameter of g fo t h of an inch, and a length of 10 1 ()0 th of an inch. Each prism rests by its inner end upon the dentine, the outer end being covered with the cuticle of the teeth. Usually there are sevei'al layers of enamel prisms, the outer layer being then covered with the cuticle. The prisms, while arranged in a parallel manner, do not run in an exactly straight direction, the course being rather an undulating one. The prisms, when viewed horizontally from their outer ends, present a tessellated appearance (Fig. 25). The so-called cuticle of the teeth, or membrane of Nasmyth, just referred to as covering the outer ends of the enamel prisms or fibres, averages about the 15 ^ 00 th to the -3 oWo~th of an inch in thickness. It acts as a protective covering to the enamel. By some histologists the cuticle of the teeth is regarded as a very thin cement. Cement. — The crusta petrosa or cement covers the roots of the teeth, beginning at the neck as a thin layer and becoming gradually thicker Section of enamel, highly magnified, at right angles to the course of its columns ; exhibiting the six-sided char- acter of the latter (Leidy.) Fig. 20. ace a.i pi Mnlar tooth of horse ae. Antero-external ; pe, Postero-external ; ai Anter. .-internal ; pi. Postero-external or principal cusps respec- tively. ;/. External vertical rib. x. An anterior cingular cusp. ace, pec. Anterior and posterior cross-crests. (Wortman.i at the fan£S. It adheres verv closely to the dentine and to the periosteal lining of the alveoli. Cement differs from bone in its lacunae being more variable in their form and size, and their canicula being larger and more numerous. In many animals, like the cat, dog, and hog, the dentine, cement, and enamel are disposed as in man. In the grinding teeth of the herbivora, however, as in those of the elephant (Fig. 26), horse (Fig. 27), the dentine, enamel, and cement Molar tooth of African elephant. e. Enamel, d. Dentine, c. Cement. (Owen.) MAXILLARY BONES. 105 alternate with each other in such a way that as the teeth are worn an uneven triturating surface is always maintained. Tooth Pulp. — The pulp of the tooth situated in the pulp cavity is not only the formative organ of the tooth, but the source of its vascular .and nervous supply ; the tooth-pulp consisting of cells, bloodvessels, nerves, and a small quantity of connective tissue. The cells are most numerous on the surface of the pulp. In this position they are known as odontoblasts and the layers formed by them as the membrana eboris. The odontoblastic cells exhibit three kinds of processes : Those passing internally into the pulp, others which serve to connect adjacent cells, and those already referred to as being prolonged into the dentinal tubules. The bloodvessels pass in and out by the openings in the apex of the tooth, forming beneath the odontoblastic layer a capillary network. The nerves enter by the fang of the tooth and after giving off a few branches form a plexus beneath the odontoblastic layer. The exact manner, however, in which the nerves terminate in the teeth is not known, unless, as already men- tioned, the dental fibres are of a nervous character. The teeth of the upper jaw are supplied by branches from the superior maxillary nerve, those of the lower by the inferior maxillary. No lymphatics, as yet, have been found in the tooth pulp, or in other parts of the teeth. As age advances, the pulp of the tooth diminishes in size through its gradual calcification, the odontoblastic layer atrophies, the connective tissue increases, the capillary network disappears, the nerves exhibit a fatty degeneration, and the pulp ultimately becomes a dried-up, insensitive mass. Although the pulp may lose entirely its vitality, yet the enamel and dentine may remain serviceable, they appearing to be perfected struc- tures. These are, however, never reproduced when destroyed by wear or decay or by loss of the tooth, with the rare exception of where a tooth is reproduced for the third time. The way in which the teeth are developed and the manner in which the permanent teeth are preceded by the deciduous or milk set, will be considered under the subject of reproduction. Maxillary Bones and Temporo-maxillary Articulation. — The teeth in man and mammalia are confined to the maxillary bones, in which they are imbedded, the bone being moulded so to speak, around the roots of the teeth after these are developed and so forming the sockets. Between the jaw and the tooth there is a space which in the living tooth is filled up by the alveodental periosteum. Through the elasticity of this root membrane the tooth possesses a certain amount of motion. Were the teeth immovably fixed in their sockets some shock would be felt during mastication. This alveodental periosteum, which passes imperceptibly into the gum and periosteum, consists of connective tissue in which are found nerves and vessels. There is also no sharp line of demarcation between the gum and the mucous membrane of the mouth on the one hand and the periosteum on the other. Of the maxillary bones the superior, from being immovably articulated with the other bones of the head, are only passive in mastication. The upper teeth, however, offer fixed surfaces, against which those of the lower jaw are brought into apposition. 106 DIGESTION, Intermaxillary Bone. — If the inner surface of the superior max- illary bone be examined between the middle line and alveolar margin, in most instances a suture will be readily recognized running downward and outward from the anterior palatine foramen to the outer margin of the second incisor tooth. This suture is interesting from several points of view, among others, as indicating in the embryo the distinction ex- isting between the true superior maxillary bones and the intermaxillary bones, the latter being characterized by carrying the incisor teeth. As development advances, however, in man and to a great extent also in monkeys, the superior maxillaries coalesce to such an extent with the intermaxillaries that the primitive distinction between the bones is almost entirely lost, in some instances the suture itself even disappearing. In the other mammalia, however, the intermaxillaries remain quite distinct from the superior maxillaries and each other, and are readily disarticulated. It was this latter circumstance that led Goethe, 1 equally Pig. 28. Antero-posterior section of the temporo-maxillary articulation of the right siile. (A. T ) }£. (Quain.) great as a poet and naturalist, to look for and discover the intermaxillary bone in man, so convinced was he that the skull consisted of the same bones in all the mammalia. The inferior maxillary bone, mandible or lower jaw, consists in the adult of a single piece movably articulated with the temporal bone (Fig. 28). This articulation is really a double joint, since there is interposed between the condyle and the glenoid cavity a biconcave oblong piece of fibro-cartilage to the edges of which is attached the capsular ligament. The spaces on either side of the cartilage are lined with synovial membrane, and there is no connection between the two cavities unless the cartilage is perforated. When the jaw is simply depressed, the joint acts as a hinge. Through the movement of the condyle on the eminentia articularis, the forward and lateral motions of the jaw are affected. The mechanism of the temporo-maxillary articu- 1 Sammtliche Werke, Baud vi., Osteologie, S. 65. INTERMAXILLARY BONE. 107 lation is therefore such as to insure great freedom of motion to the lower jaw. The lateral, forward, and depressing actions of the jaw either suc- ceed each other or are variously combined during the mastication of food. Fig. 29. Jaws of tiger Fig. 30. Condyle. Upper and lower jaw of sheep. (Owen. I If the condyle of the jaw in a carnivorous animal be examined, in a tiger, for example (Fig. 29), it will be noticed that its long diameter is transverse, and that the glenoid cavity is grooved, hollowed out, so as 108 DIGESTION to receive it. This disposition is carried out to such an extent in the badger that the lower jaw will remain depressed, interlocked, within the glenoid cavity, even though all the ligaments be cut away. The motion of the lower jaw in many of the carnivora is almost exclusively of an up and down character, there being little or no lateral motion. In the herbivora, however, as in the sheep, rhinoceros, etc., it is the lateral motion of the lower jaw that is evident in chewing. In such animals the glenoid cavity is rather shallow and the condyle oblong or ovate (Fig. 30). The motion of the jaw in the rodentia differs from that observed both in the carnivora and herbivora, being backward and for- ward, like that seen in the gnawing action of a rat. This motion is rendered possible in such animals through the long diameter of the condyle and the glenoid cavity having an antero-posterior direction, as in the capvbara (Fig. 31). Fig. 31. . «.— c ('. Condyle, and G. Glenoid cavity of the capybaia. (Tomes.) The temporo-maxillary articulation, combining in man, as we have seen, to a great extent, in one joint, the peculiarities just noticed in the temporo-maxillary articulation of the carnivora, herbivora, and rodent types of the mammalia, furnishes another proof of the natural diet of man being a mixed one. The various movements of the lower jaw are effected by a number of different muscles ; to the consideration of these let us now turn. Muscles of Mastication. — These muscles naturally divide them- selves into two groups, Table XXXIII. , one of which elevates the lower jaw, moves it laterally or in an antero-posterior direction ; the other depresses it. Let us begin with the former group first. Table XXXIII.— Principal Muscles of Mastication. Elevators, etc Temporal. Masseter. External 1 Internal I pterygoid. Depressors. Digastric. Mylo-hyoid. Geniohyoid. Platysma myoides. The action of the muscles becomes quite apparent when their anatomy is understood. The temporal (Fig. 32) arising from the temporal fossa and inserted into the coronoid process raises the lower jaw against the upper. The action of the temporal is aided by the contraction of the masseter and internal pterygoid, the former muscle (Fig. 33) arising from the zygomatic arch and passing backward into the lower border of MUSCLES OF MASTICATION Fig. 32. L09 The temporal muscle, the zygoma and masseter having been removed. (Gray.) Fig. 33. Sketch of a superficial dissection of the face, showing the position of the parotid and submaxillary glands (Allen Thomson). Two-fifths the natural size. _p. The main part of the parotid gland, p'. The small part, which lies alongside the duct, on the masseter muscle d. The duct of Stenson before it per- forates the buccinator muscle, a. Transverse facial artery, n, n. Branches of the facial nerve emerging from below the gland. /. The facial artery passing out of a groove in the submaxillary gland and ascending on the face, s m. Superficial larger portion of the submaxillary gland lying over the pos- terior part of the mylo-hyoid muscle, d d. Digastric muscle. (Quain and Sharpey.) 110 DIGESTION. the jaw, the latter (Fig 34) having its origin in the pterygoid fossa and its insertion in the lower and back part of the inner side of the jaw. The action of these muscles is well seen in the carnivora, in which they are very large. The maximum effect of the masseter can also he we'll Fig. 34. Fig. View of the pterygoid muscle from the outer side. ~%. 1. External pterygoid. 2. Internal pterygoid. (QUAIN.) View of the pterygoid muscle from the inner side. 34- 1- External pterygoid. 2. Internal pterygoid. (Quain.) observed in the rodentia, the muscle being enormously developed in these animals. The lateral and forward motion of the lower jaw is due to the action of the external pterygoid. This muscle (Fig 35) arises from the sphenoid, palate, and superior maxillary bones, and passing backward and outward is inserted into the neck of the condyle of the lower jaw and into the inter-articular fibro-cartilage. If the condyle of the jaw on one side, the left for example, be fixed, it will he seen from the direction of the fibres of the external pterygoid that if the muscle of the opposite side contracts it will draw the lower jaw forward and laterally in an inward direction, the condyle playing upon the articular eminence, the cartilage being interposed, it having been also drawn forward by the muscle. This alternate lateral motion of the lower jaw is very evident in the chewing of the food, particularly well seen in the herbivora, in which order the external pterygoid muscle is relatively much developed. If the external pterygoid, however, act together, the lower jaw is drawn forward along the diagonal A D of the parallelogram, the two sides of which, ABA C (Fig. 36), are the directions taken by the jaw when alternately acted upon by the external pterygoids. As regards the second group of the masti- catory muscles there can be no doubt as to the function of the mylo-hyoid (Fig. 37) genio- hyoid, and platysma myoides muscles. The two former muscles passing from the hyoid bone to the mylo-hyoid ridge and genial tubercle of the lower jaw respectively will depress the jaw when the hyoid bone is fixed. The same effect is produced by the platysma, it being partly inserted into the lower border of the jaw. The action of the digastric muscle is not so simple as that of the other MUSCLES OF MASTICATION, 111 Fig. 37. depressors ; indeed, its action in depressing the lower jaw was denied by the elder Monro. 1 This view gave rise to his memorable discussion, in the last century, with Winslow, 2 in which Ferrein 3 later took part, who agreed with Winslow in holding that the digastric was a depressor. The digastric muscle, as its name implies, is double-bellied, consisting of an anterior and posterior muscular part with an intervening tendin- ous portion. The tendon often passes through the stylo-hyoid muscle, glid- ing through a small synovial bursa, * " and is connected with the body and great cornu of the os hyoides by a broad band of aponeurotic fibres in the form of a loop and lined with syno- vial membrane.'" 5 The posterior belly of the digastric muscle passes upward, backward, and outward from the tendon to the digastric groove of the temporal bone, the anterior belly upward and forward to the inner surface of the jaw, near the symphysis. An interesting fact to be noticed is that the anterior belly is supplied by the mylo-hyoid branch of the inferior maxillary branch of the fifth nerve, the posterior belly by the facial, as we shall see when we come to study the nervous system ; this shows that the muscle is essentially a double one. Such being the disposition of the digastric muscle, it follows that if the jaw be fixed and the anterior belly alone contracts, the hyoid bone will be elevated anteriorly, as it is by the genio-hyoid and mylo-hyoid muscles in the first stage of deglutition. If, however, the posterior belly alone contracts, the hyoid bone will be raised upward and backward, its action being similar to that of the stylo-hyoid muscle. Should both bellies contract, then the hyoid bone will be elevated almost perpen- dicularly. On the other hand, should the hyoid bone be fixed by its depressor muscles, the lower jaw will be slightly depressed if the anterior belly of the digastric muscle acts alone; should the posterior belly act independently, then the mastoid process will be drawn downward, and with it the back of the head, thereby elevating the upper jaw and open- ing slightly the mouth. This action of the posterior belly alone, or with the anterior one acting with it, is no doubt aided by the deep muscles of the neck. While it is possible that the lower jaw can be depressed by A. The lower jaw and hyoid bone, from below, with the mylo-hyoid muscles attached. B. The same from behind, with the mylo- hyoid and genio-hvoid muscles attached. (a.t.). y z . 1 Remarks on the Articulation, etc., of the Lower Jaw, p. 341. Ediiiluigli, 1781 Also Medical Essays, 1783. 2 Mem. de l'Acad. Roy. des Sciences, 1742, tome 59, p. 176. 3 Ibid., tome xli. pp 427, 509. * Hyrtl : Lehrbuch der Anatomic, Elfte Aufl., S. 402. 5 Quain's Anatomy, 8th ed., vol. i. p. 282, The works of Alexander M< nro, M.D. 112 DIGESTION. the anterior belly of the digastric acting alone, it is most probable that the posterior belly acts with the anterior one in producing this effect, the muscle acting in the reverse direction of that just referred to pro- ducing the movement of the back of the head. This view is confirmed by the fact pointed out by Winslow 1 that in several animals the anterior belly of the digastric muscle is wanting, the posterior alone being present and being then inserted into the angle of the jaw. Owen 2 called atten- tion to this being the case in the orang, and the author has confirmed the observation. 3 Occasionally the anterior belly is absent in man. Under such circumstances the posterior is inserted into the ramus of the jaw. Were not the anterior belly normally present it is possible that, as Hyrtl 4 suggests, the forward and lateral movements of the jaw might be seriously interfered with. That the mouth is to a certain extent opened by the elevation of the upper jaw through the backward motion of the head due to the contraction of the posterior belly of the digastric and of the muscles of the neck, may be shown in various ways. For exam- ple, when the chin is placed upon a table, the lower jaw being then immovable, or when the lower jaw is firmly fixed, as in certain surgical operations, it will be observed that the mouth can be slightly opened, though the lower jaw cannot be depressed. The experiment suggested to Monro 5 by his former pupil, Pringle, of putting the blade of a knife or his own nail opposite to the conjoined edges of the teeth when the mouth is shut, which knife being held unmoved while the mouth is opened, he may, by the help of a mirror, see the upper teeth raised, remarkably, at every operation he performs," is very convincing. It must be admitted, however, that the movement of the upper jaw in this respect has not much significance, as the opening of the mouth is essentially due to the depression of the lower jaw. Indeed, the move- ment of the upper jaw in the opening of the mouth was denied altogether by Winslow. 6 In this respect, however, Ferrein agreed with Monro, although the former attributed the action of the upper jaw to the digas- tric, the latter to the muscles of the neck. Of the muscles of mastication, as we shall see hereafter, the temporal, masseter, pterygoid, mylo-hyoid, and anterior belly of the digastric are supplied by branches of the fifth pair of nerves ; the platysma myoides and posterior belly of the digastric by the facial, and the genio-hyoid by the hypoglossal. Resume. — The effect of mastication is that the solid food taken into the mouth is cut and crushed and ground up by the teeth. The little pieces that ooze out between the teeth and the cheeks are pushed under the teeth again by the muscular action of the cheeks and lips, while the fragments that escape within the inner side of the teeth are forced back by the tongue. The importance in man of the action of the cheeks, lips, and tongue in mastication is well seen when there is a paralysis of the facial or hypo- glossal nerves. In such cases the food accumulates between the cheeks and the teeth, and the want of action of the tongue is seen both in the difficulty of mastication and deglutition. The same effect can be pro- 1 Op. cit. - Proc. Zool. Sue. Lond., 1830, p. 29. 3 Proc. Acad, of Nat. Sciences, Philadelphia, 1880. * Topograph Anat.. Fiinfte Aufl., S. 438. * Op. cit., p. 239. 6 Panizza : Gaz. Med., 1835, p. 419. MUSCLES OF MASTICATION. 113 duce , • m [ chloride 0.84 Potassium ) 1000.00 The saliva as we find it in the mouth, consisting then of a mixture of all the different kinds of saliva, is an alkaline, colorless, somewhat opaque, viscid fluid, with a specific gravity of from 1.004 to 1.000; its composition is given in Table XXXIV. Like all the secretions, the saliva consists largely of water, some organic matter, and a small quantity of salts. In 1831, Leuchs 1 discovered that hydrated starch, when mixed with warm saliva, was liquefied and converted into sugar. Since then, numerous experiments have been performed on animals, especially dogs, with the object of showing that their saliva has not this effect upon starch. While these observations are interesting from a general physiological point of view, they have no bearing whatever upon the question of the effect of human saliva upon starch. Anyone can convince himself that starch is converted i lto sugar in the mouth by 1 Ludwig and Spieas : Sitz. d. Wiener, Acad. Math. Nat. Classe, 1857, xxv. S. 548. 2 Pliuger : Pfluger's Archiv, 1868, Band i. S. 686. INSALIVATION. 119 taking a little boiled starch, mixing it thoroughly with his saliva, and then testing for sugar. The mixture will not then give a blue color on the addition of iodine, but at first a red or violet one, showing that the starch has become partly dextrin ; the latter is, however, soon also transformed into glucose or grape sugar, as can be shown by Trommer's test. Saliva has the same effect on raw starch, only a longer time is required to produce it. It has been ascertained by experimenting with the different substances entering into the composition of the mixed saliva, that it is a portion of the albuminous organic matter which pos- sesses this transforming effect, and that the different kinds of saliva have, as well as the mixed saliva, the property of converting starch into sugar. The phenomenon appears to be one of fermentation with hydra- tion, as may be seen from the following reaction : Starch. Water. Glucose. Dextrin. Water. C 18 H 30 O 13 + 3H 2 - 1(C 6 H 12 6 ) 2(C 6 H 10 O 5 ) + 2(H 2 0). Dextrin. Water. Glucose. 2(C 6 H 10 O 5 ) + 2(H,0) = 2(C 6 H 12 Q 6 ) . 3(C 6 H 12 6 ). The action appears to be due to a kind of ferment, the so-called ptvalin of Berzelius, which can be isolated by precipitation by alcohol, the exact nature of which, however, at present is not thoroughly under- stood. According to Mialhe 1 one part of ptvalin will effect the trans- formation of more than two thousand parts of starch. It will be seen from this that its action must be very energetic. Nevertheless, as the large quantity of starch present in the food remains but a short time in the mouth, it is questionable whether any great amount of it is con- verted into sugar in the mouth, notwithstanding the admitted rapidity of the action of the saliva. We shall see, however, that the transform- ing effect of the saliva upon starch is continued even after the food has passed into the stomach, the gastric juice not interfering with the action, and, as the food remains for some time in that organ, no doubt a con- siderable quantity of sugar is produced there in this manner. The importance of the saliva, however, in this respect, must not be exaggerated, as we shall see that the intestinal and pancreatic juices transform starch into sugar as efficiently as the saliva, and it is well known that the serum of the blood, mucus, the fluid from cysts, etc., have the same property, though not in as great a degree as the fluids first referred to. The significance of the potassium sulphocyanide, which appears to be always present in the saliva, is not apparent. The remaining salts, while rendering the saliva alkaline, have not been shown as yet to serve any particular purpose in digestion. "While one of the uses of the saliva in man is certainly the transform- ation of starch into sugar, undoubtedly its most important function is that of aiding mastication and deglutition, the secretion of the parotid gland being specially connected with the former function, that of the submaxillary and sublingual glands with the latter, as we have seen in speaking of the secretions separately. The amount of saliva secreted 1 Chimie applique a la Pliysiulogie, p. 43. Taris, 1856. 120 INSALIVATION AND DEGLUTITION. during twenty-four hours in man has never been exactly determined. As the saliva is constantly being reabsorbed, a source of error in any calculation as to the amount secreted in a given time would be the risk of counting the same saliva, or, at least, the elements entering into its composition more than once. According to Dalton, 1 31.1 grammes, about 478 grains, of saliva can be obtained from the mouth in twenty minutes without any artificial stimulus. The natural stimulus to the secretion of the saliva, however, is the presence of food in the mouth ; indeed, the sight, or even the thought of food, in some individuals will make the mouth "water." The amount of saliva secreted will depend, therefore, on the quantity and quality of the food. According to Dalton, 2 wheaten bread will gain during mastication fifty-five per cent, in weight, lean meat forty-eight per cent. Assuming that about sixteen ounces of meat and nineteen of bread are eaten in the twenty-four hours, and adding the saliva absorbed by this amount of food to that secreted during the intervals of digestion deduced from Dalton's experi- ments, it can be estimated, approximately, that 1280 grammes, a little less than three pounds avoirdupois, of saliva are secreted in the twenty- four hours. After the food has been thoroughly masticated and mixed with the saliva, the secretion of the parotid gland penetrating the bolus, while that of the submaxillary, sublingual, and remaining glands of the mouth rather coating it externally, it is swallowed. As the bolus of food passes down the pharynx it receives another coating from the secretions of the glands in that situation, and so deglutition is further facilitated. In con- cluding our account of the saliva there may be mentioned appropriately in this connection the peculiarity it possesses of attracting or entangling bubbles of air in the mass of food. The effect of this is that stomach digestion is facilitated through the easy access afforded to the gastric juice when the food comes in contact with this secretion. Moist, heavy bread is not readily acted upon by the secretions, through its not being permeated with air in the manner just referred to. Let us now consider the manner in which deglutition is effected. Deglutition. — The act of swallowing, or deglutition, is often divided arbitrarily by physiologists into three stages or periods, though these stages are strictly continuous. During the first stage the food passes backward to the isthmus of the fauces. The second stage is occupied by the passage of the food through the palate from the isthmus into the oesophagus, while the third stage consists in the food passing from the oesophagus into the stomach. After the food has been thoroughly chewed, the mouth being closed, the first stage of deglutition begins by the tongue, more especially its point aided by the cheek, collecting the particles of the food into a mass or bolus. Through the action of the hyoglossal muscles (Fig. 43) the tongue is then moved forward and upward; the effect of this is that the bolus of food is pressed against the hard palate, and thence into the fauces, through the tongue being some- what elevated at the sides and depressed in the centre, while the soft palate is applied at the base probably. Probably some slight suction i Physiology, 188-_», p. 144. 2 Qp. cit., p 146. DEGLUTITION 121 force is exercised in the swallowing of liquid and soft articles during the first stage of deglutition. Fig. 43. Base of cranium. Pharynx. Tongue. -- Salivary glands Hyoid bone. W Larynx. Thyroid gland. (Esophagus. Trachea. Vertical section of mouth and pharynx. (Milne Edwards.) The tongue is as important in deglutition as we have seen it to be in mastication. The results of dividing the hypoglossal in animals, Fin. 44. already referred to, and the cases observed in man where the tongue has been amputated, or congeni- tally deficient, show that without the action of the tongue degluti- tion is impossible. In amputation of the tongue there is usually left a portion of the base sufficient to press against the palate, making deglutition pos- sible. The action of swallowing during the first stage is usually per- formed unconsciously ; in reality, however, it is a voluntary one. As the food passes through the fauces, the tongue being drawn upward and backward by the contraction of the stylo-glossal muscles the en- trance to the fauces is thereby narrowed, then the posterior half arches of the palate approach each other through the action of the palatopharyngeal muscles, while the interval between them is filled up by the uvula (Fig. 44), at the same time the soft palate is rendered tense by the tensor palati and elevated by the levator palati; the natural communication between the pharynx and posterior nares being then cut off, the food passes from the isthmus of the fauces into the pharynx, the superior constrictor of Uvula, h b. Anterior half arches, c c. Posterior half arches. //. Tonsils. (Valentin.) 122 INSALIVATION AND DEGLUTITION. which grasps the bolus of food and the soft palate. The pharynx, in the meantime, is elevated with the larynx through the contraction of the stylo-pharyngeal, stylo-hyoid, genio-hyoid, mylo-hyoid, probably the thy- roid and the digastric muscles, the latter acting more especially through its anterior belly, the lower jaw, it need not be said, being now fixed. In this way the cavity of the pharynx is widened, at the same time the entrance to the larynx is closed, being elevated and pressed against the epiglottis. The food is then forced downward into the (esophagus by the middle and inferior constrictors, after which the parts concerned resume their ordinary position. Pathological and surgical operations, in which the parts involved were exposed, have given favorable opportunities of observing the process of deglutition in man. The results of such clin- ical investigation confirm what one might expect to be the function of the parts as deduced from their anatomy. Thus, in the cases referred to by Berard, 1 and Beclard, 2 the palate was seen to be elevated while the posterior wall of the pharynx approached it in deglutition. Berard 3 mentions the case of a lady in which, through complete paralysis of the velum, liquids when swallowed returned by the nose, and cites, also, as an illustration of the elevation of the palate in deglutition, the experi- ment of Debrou, in which a probe being introduced along the floor of the nares into the pharynx, it was observed that every time the patient swallowed the external end of the probe was depressed, the internal end being elevated by the palate. Numerous cases, among others those cited by Longet, 4 in which the epiglottis has been destroyed in man, either by wounds or disease, show very conclusively that in swallowing liquids at least the epiglottis is indispensable in preventing them flowing into the larynx. It is true that the glottis is closed in deglutition, both by the action of the constrictors attached to the thyroid cartilages and by the intrinsic muscles of the larynx, but this does not explain why liquids do not flow into that part of the larynx situated above the glottis, wdiich they certainly would do as Berard suggests, unless some obstacle was inter- posed. It is easy to understand why, usually, solid food can be swal- lowed without difficulty, even though the epiglottis be deficient, as when the larynx is elevated in deglutition it rises up under the base of the tongue, and so is pretty well covered. The food being moulded into the bolus, and covered with the slimy, viscid saliva, would not be apt, then, to pass into the larynx, but Avould glide over the base of the tongue into the pharynx, whereas liquids would insinuate themselves into the upper part of the larynx, and at once give rise to a fit of coughing. This, indeed, is apt to take place, the epiglottis being absent, if a small fragment of solid food, a crumb, for example, be swal- lowed incautiously. Under ordinary circumstances, the food being pre- vented then from passing into the posterior nares above and the larynx below, will be forced into the oesophagus. At that moment the third stage of deglutition begins. The action of the oesophagus is very simple, consisting in the contraction of its circular and longitudinal muscular fibres from above downward, by which action the food is forced into the stomach (Fig. 45). 1 Physiologie, tome ii. p. 25. - Physiologic Ilumaine, p. 60. 8 Op. cit., pp. zi, 25. 4 Physiologie, 18(51, tome i. p. 115. DEGLUTITION, 123 A peculiarity about the muscular fibres of the oesophagus is in the upper portion consisting exclusively of striated fibres, whereas, in the lower part unstriated fibres predominate. This disposition of the fibres is interesting, as accounting, probably, for the fact of the lower third of the oesophagus' remaining contracted for a short time after the food has passed into the stomach, thereby preventing regurgitation. This phenomenon was particularly observed first in animals by Magendie. 1 Fig. 45. Spleen s- Colon. Large Intestine -Small intestine. • Colon. Digestive apparatus of man. (Milne Edwards.) While, as has been stated, the first period of deglutition is under the control of the will, the second and third are entirely involuntary, depending, as we shall see when we come to study the nervous system, upon an impression being made upon the mucous membrane of the pharynx and oesophagus, etc., which sets the appropriate nerves and muscles in action. Indeed, without solid or liquid food in the pharynx it is impossible to perform the second act of deglutition ; apparently, this is done sometimes for three or four times without there being any- thing to swallow, but there is really always present under such circum- stances sufficient saliva to produce the necessary impression. It is hardly necessary to call attention to the fact that solid and liquid foods can be swallowed in all positions. It is a common feat among jugglers to drink a bottle of wine or a glass of beer while standing on their heads or hands. 1 Memoires sur 1'CEsophage, a l'lnstitut de France, 11 Oct. 1813. CHAPTER VIII. GASTRIC DIGESTION. The stomach is a muscular membranous sac whose walls have, on an average, a thickness of a little more than a line. When distended, it measures laterally from thirteen to fifteen inches, and antero-posteriorly five inches, with a capacity, according to Brinton, 1 of one hundred and seventy-five inches, or about five pints. The capacity of the stomach, however, is often less and sometimes even much greater, varying with the age, sex, and habit of the individual. It is held in position in the upper part of the abdominal cavity by its connection with the oesophagus and the folds of the peritoneum. When empty, the sides of the stomach are usually in contact, and the whole organ, presents a flattened appear- ance. When distended by food, however, the anterior wall of the stomach becomes superior, and is applied to the diaphragm. This is due to the ends of the stomach and lesser curvature being comparatively immovable. As the food enters the stomach from the oesophagus, it turns to the left, and, passing into the cardiac end, or greater pouch, thence proceeds along the greater curvature to the pyloric end, return- ing by the lesser curvature to the cardiac portion, to begin the same course over again. Each of these revolutions occupies from about one to three minutes, and are slowest at first, becoming more rapid as diges- tion advances. The food undergoes, therefore, a sort of churning action, passing from one side of the stomach to the other. As the circular muscular fibres surrounding the pyloric orifice offer a resistance to solid undigested matter, it is only the liquid, pultaceous, digested food which escapes into the duodenum. After a time, however, even hard foreign bodies, like stones, coins, etc., make their way into the small intestine. An interesting fact connected with the movements of the stomach, is a noticeable difference between the contraction of the pyloric as com- pared with that of the cardiac end of the stomach. The food while in the cardiac end of the stomach appears to be subjected to a simple pressure, whereas the action of the pyloric portion is of a vigorous ex- pulsive character. Indeed, when digestion is at its height the cardiac portion of the stomach is quite distinctly separated from the pyloric portion by a constricting band. The organ then presents an hour-glass form, of which two-fifths consist of the cardiac portion. It is worth mentioning in this connection, that this hour-glass form of the stomach, present only in man during digestion, is the form presented in the manatee (Fig. 46) whether digestion is going on or not; the author 2 1 Cyclopaedia of Anatomy and Physiology. Supplempnt, p. SOS. London, 1837-1847. - Proceedings of Academy of Natural Sciences, Philadelphia, 187G, p. 45'J. FUNCTION OF THE STOMACH. 125 having found in the dissection of several individuals the stomach always presenting this form, whether it was full of food or empty. After the food has been digested and the stomach has been emptied of its contents, which processes are effected within a period of from two to four hours, all the motions just described cease, and do not recom- mence again until a fresh supply of food is taken. The peristaltic Fig. 4' Stomach of uianatc vermicular motion of the stomach that I have endeavored to describe, depends upon its muscular fibres, assisted by the diaphragm. The muscular coat of the stomach, which averages about the^th of an inch in thickness, consists of three sets of fibres, the longitudinal, circular, and oblique, which are disposed from without inward, in the order just named — that is, the longitudinal fibres are external, the oblique are internal, while the circular fibres lie between the other two. These three sets of fibres are, however, very unequally developed. Thus, the longitudinal fibres are best seen in the lesser curvature ; the circular fibres are rather indistinct to the left of the cardiac orifice, and are most marked at the pyloric, forming then its sphincter muscle ; while the oblique fibres are limited to the cardiac portion of the stomach, passing over it from left to right. It is at the point where these oblique fibres cease that the stomach becomes constricted in digestion into the two parts already described. Through the contraction of the longitudinal and circular fibres the food is forced along toward the pylorus, which, through its sphincter muscle, resists at first all but thoroughly digested food. The cardiac orifice is guarded by the fibres in that situation, as well as by the con- traction of the lower part of the oesophagus already referred to. The movement of the food is also due, no doubt, partly to the pressure exerted by the diaphragm and the intestines. The natural stimulus to these motions of the stomach during digestion is the presence of food. The account that we have just given of the movements that the stomach undergoes during digestion in man, is taken entirely from the experi- 126 CAST RIC IjH; KS'I I ii.V ments and observations of Beaumont, 1 to whom physiology is so greatly indebted for much that is positively known of the human gastric digestion. ks what I have to Bay of the secretion of the gastric juice ;m apply to man. for pathological facts, like the round ulcer of -the stomach, would seem to show that in the absence of the epithelium the parts beneath are affected during life by a kind of corrosion due to the gastric juice. A confirmation of the view that the epithelium lining of the stomach gives it its immunity from digestion during life, is shown by the fact that worms, like the thread-worm, ascaris, etc., whose body wall is covered with epithe- lium are able to live in the stomach, bathed at times in gastric juice. After the death of the worm, from any cause, the mouth or anus being opened, then the gastric juice is able to penetrate within its body and will then act upon the viscera until often nothing will be left of the worm except its outer body wall, which will float about in the stomach, unaffected by the gastric juice. In the same way, if the epithelium of the stomach be loosened from the parts beneath, it will be found undi- gested in the gastric juice; as a matter of fact, it is not digested whether living or dead any more than the skin of the ascaris is digested. There is no reason for assuming, then, that during life it is rapidly regenerated because it is constantly being destroyed. After death the epithelium loosening itself from the coats of the stomach, the latter will no doubt be attacked by the gastric juice as long as the temperature is maintained at 100° F., the epithelium itself remaining unaffected. This explana- tion has at least one advantage — that it does not call upon vital spirits, catalysis, or similar fetich ideas, to explain a phenomenon of digestion, but depends simply upon the chemico-physical fact as to whether or no epithelium is digested in gastric juice. In concluding the subject of gastric digestion it may not be superfluous to notice that the alimentary canal of man, as a whole, is intermediate in character between that of the carnivora and herbivora, furnishing an- other proof in addition to those already given, that the natural diet of man is a mixed one. The food of an herbivorous animal or vegetable feeder consisting of grass, leaves, roots, etc., contains comparatively little nutriment, and, therefore, a great quantity of it must be eaten. This necessarily entails a long and capacious alimentary canal with special modifications in different parts of it, the effect of which is that the maximum amount of nutriment is obtained from the food. Thus when the stomach of a ruminating animal, like the llama (Fig. 49), or giraffe (Fig. 82), is compared with that of man, it will be observed that 1 Physiologie Experimentale, tome ii. p. 401. Paris, 1S56. 2 Op. cit., p. 103. 10 146 GASTRIC DIGESTION. the stomach of the ruminant is subdivided into four compartments (Fig. 53, b, c, d, e), the last of which, the abomasum, communicating with the small intestine, corresponds with FlG - 53 - that of man, and secretes the gastric juice. Of the other three stomachs, the rumen (/>) is the largest, and together with the reticulum (c) or honeycombed stomach (not seen in Fig. 4i>) receives the food after it has been chewed and insalivated. After a few moments, however, a bolus of food w r ill be regurgitated into the mouth and there thoroughly masticated and insalivated. The second time, however, that it is swal- lowed the food passes directly into the third stomach, the psalterium (d) or monyplies. This is effected by means of a musculo-valvular ar- rangement at the mouth of the oesophagus, which serves both to shut off the cavity of the rumen and reticulum and to divert the bolus of food directly from the (esophagus into the psalterium, whence it passes into the abomasum (e) or fourth stomach and thence into the intestine. By this arrangement of the rumen, etc., the thorough masti- cation and insalivation of the food are insured, while the psalterium or third stomach acts as a filter or strainer, its mucous membrane being- raised up into folds, like the leaves of a book, permitting only finely divided or semi-li. The succus entericus, as it is also called, is secreted by two kinds of glands, the glands of Brunner or Brunn and the follicles of Lieberkuhn. The former are confined to the duodenum ; the latter, however, are found not only in the small intestine but in the large intestine also. The duodenal or glands of Brunner (Fig. 55) are of the racemose type of gland ; they average about the Y^th of an inch in diameter and to the naked eye appear like little round bodies in the submucous tis- sue. The excretory duct, which transmits the secretion from the grape-like masses of which the gland consists, pierces the mucous membrane and opens into the cavity of the intestinal canal. According to Hirst and Hei- denhain, 2 the cells of Brunner's glands exhibit essentially the same changes during periods of rest and activity as those of the pyloric tubules of the stomach, being large and clear during the period intervening between meals and small and cloudy during digestion, the secretion being elaborated during the former period and poured out during the latter. The reaction of the secretion is alkaline. According to Grutzner, 3 it will digest fibrin in an acid solution, and Budge 4 and Krolow state that a watery extract will convert starch into sugar. Beyond these facts nothing is known positively of the properties of the secretion of Brun- ner's glands. A vertical section of the duodenum highly mag- nified. 1. A fold-like villus. 2. Epithelium of the mucous membrane. 3. Orifices of the tubular glands, 4. 5. Orifice of a duodenal racemose glaud, C. 7. Two vesicles of the latter, more highly mag- nified, exhibiting the epithelial cells lining their internal surface. (Leidy.) 1 Physiologie, 1873, tome 1, p. 166. 8 Pfluger's Archiv, Band xii. S. 288. - Hermann : Physiologie, Funfter Baud, S. 163. 4 Hoppe-Seyler : Phys. Cheniie, S. 270. INTESTINAL JUICE. 149 By far, however, the greatest quantity of the intestinal juice is se- creted by the follicles of Lieberkiihn, otherwise known as the simple tubular glands of the intestine. These glands resemble somewhat the pyloric tubules of the stomach, consisting of a basement membrane lined with a single layer of columnar cells. The tubules having a diameter of about -g-g-Q-th of an inch, extend through the mucous membrane, which is about y^-th of an inch thick, their fluid ends look toward the muscular coat, their mouths opening into the cavity of the intestine. The secre- tion of these tubules will therefore pass into the interior of the intestine. The tubules are as closely packed together as possible and are only absent in that part of the duodenum where the glands of Brunner are found, and in the remaining part of the small intestine, the so-called jejunum and ileum 1 in the position of the Peyer's patches and solitary glands, and even here they are not entirely absent. From the immense number of these tubules one would infer that a very considerable quantity of intestinal juice is secreted. The exact amount daily poured into the intestine has never been accurately deter- mined ; it does not appear to be, however, as much as we would have anticipated. The reaction of the intestinal juice is alkaline, but as it is very doubtful whether normal intestinal juice has ever been collected in any animal or man it is not worth while to consider in detail its composition. Prob- ably it is composed of water, salts, and some albuminous principles. It is true that numerous experiments have been made upon animals with the object of obtaining the intestinal juice, of determining the quantity secreted, its composition, and effects upon food, etc. These experiments unfortunately, however, were not made under physiological conditions, hence the results obtained are of little value as illustrating digestion in the animal experimented upon and practically useless in their applica- tion to man. Frerichs, 2 for example, experimented in this way. A loop of the small intestine of a living cat or dog was withdrawn from the abdomen during the interval of digestion. The loop was four to eight inches in length, was isolated from the rest of the intestine by a ligature. It was opened and washed and then replaced in the abdomen. Some hours afterward the animal was killed and the contents of this isolated portion of the intestine examined. It was found to contain a fluid which was assumed to be intestinal juice. It is probable, however, that during the intervals of digestion no intestinal juice is secreted, the natural stimulus to the secretion being the presence of food, as is the case in the secretion of the gastric and pancreatic secretions and the bile. Further, the method of experimenting made use of by Frerichs involves, necessarily, the ligating and division of the vasomotor nerves of the intestine with the consequent changes in the circulation and nutrition of the parts. The fluid obtained being, therefore, abnormal, it is not necessary to describe its properties. 1 The distinction between jejunum and ileum is entirely an artificial one, there being no difference structurally between the two. The small intestine naturally divides itself into duodenum and ileum, distinguished by the former containing the glands of Brunner, the latter the patches of Peyer. More than three hundred years ago Vesalius observed (De corporis hnmani fabrira Libri septein, p. 600. Basil, 1543) "Qua propter quis jejunum habendus sir finis, aut quod ilei principium, non statuo." The namo jejunum being therefore a. meaningless one, ought long since to have fallen into disuse. - Wagner : Physiologic, 1846, Band iii. S. 581. 150 INTESTINAL JUICE. Bidder and Schmidt 1 adopted a different plan from that of Frerichs. These investigators cut off the bile ami the pancreatic juice from the intestine by ligating the bile and pancreatic ducts and then introduced food with the object of studying the effects of the intestinal juice upon it. It is questionable, however, after such an operation, whether diges- tion is normal, and even if it were, the results of feeding cats and dogs operated upon in this way upon vegetable articles of food, like starch, etc., could hardly be expected to throw much light upon intestinal digestion as it takes place in man. Colin's 2 experiments not differing essentially in principle from that of Frerichs's, it would be superfluous to describe in detail bis results, or those obtained by the method of Thiry. 3 The latter consisted in cutting a piece out of the intestine, and after joining the lower end of the upper part of the intestine to the upper end of the lower, of attaching the isolated cut out portion, its nerves and vessels being undisturbed, by its open end, to the fistulous opening in the abdominal walls, the other end being closed. Were our knowledge of the properties of the intestinal juice in man dependent upon the experiments that have been made upon animals, we would know positively next to nothing about it. Fortunately, how- ever, for physiology, there occurred some years ago a case of intestinal fistula in a woman which proved to be for intestinal digestion, what St. Martin's case was for gastric digestion. It is true that the obser- vations of Busch, who had charge of the case, are not by any means as extended or complete as those of Beaumont ; nevertheless, they are invaluable to us, as what is known of the action of the intestinal juice during digestion in man is almost entirely based upon them. Busch 4 tells us that a woman, thirty-one years of age, in the sixth month of her fourth pregnancy, being tossed by a bull, was wounded in the abdomen. The wound was situated between the umbilicus and pubes, and consisted of two contiguous openings communicating with the intestinal canal. It is probable that these two openings were in the upper third of the small intestine. Notwithstanding her ravenous appetite the patient became very much emaciated in consequence of her food passing out of the upper of the two openings just referred to. It occurred to Busch, however, that the life of the woman might be saved by introducing cooked food into the lower opening, or that communicating with the lower portion of the intestine. This plan of treatment proved successful. The nutrition of the patient rapidly improved. The opening, however, not uniting, the woman was made the subject of the observations contained in the paper just referred to. It will be observed that from the peculiar conditions of the case, food introduced by the mouth, unless absorbed by the stomach, w T ould pass on into the upper portion of the intestine, and so out of the body by the upper of the two openings, having been modified in its course by the saliva, gastric, intestinal, and pancreatic juices and the bile; whereas, l Die Verdamingssafte, 1852, S. 271. - Physiologie Comparee, 1854, p. 648. 3 Wiener Sitzberichte, 1864, p. 77. 4 Virchow's Archiv, 1858, Band xiv. S. 140. INTESTINAL JUICE. 151 food introduced into the lower of the two openings would be modified by the intestinal juice only, as it passed along the small intestine, and if not digested or absorbed would pass out by the anus unchanged. The conditions of the experiment were, therefore, perfectly physio- logical. The intestinal juice was secreted in response to the natural stimulus of the food, while its effect upon the different kinds of food could be studied, cither mixed or unmixed with the gastric, pancreatic juices, etc. Necessarily the quantity of intestinal juice obtained at any one time, by the introduction of sponges, etc., was not sufficient to admit of detailed analysis; the reaction was determined, however, to be alkaline. The general results of Busch's 1 observations and experiments upon the intestinal juice may be summed up as follows : Starch, both raw and hydrated, was invariably converted by it into glucose ; cane sugar, however, was not changed into glucose, appearing in the feces as cane sugar. The intestinal juice digested more or less cooked meat and coagulated albumen, but had little or no effect upon fat ; the latter when introduced into the lower opening of the intestine is always found in the feces as fat unchanged. In the case of intestinal fistula lately observed by Demant, 2 starch was converted into glucose, but albuminous substances did not appear to be transformed into albuminose. No effect was observed upon neutral fats, though oily matters containing free acid were emulsified. The results of the observations of Demant confirm in the main those of Busch. It must be remembered, however, that the fistula in the former case was situated much lower than in the latter, and that the experi- ments upon the different kinds of foods were performed outside of the body after the intestinal juice had been drawn from the fistula. The observations of Busch were, therefore, made under more strictly physio- logical conditions than those of Demant, and deserve greater confidence. o - ... It will be seen, therefore, that the action of the intestinal juice in digestion is of a supplementary character, reinforcing the effects of the saliva upon starch, and of the gastric juice upon the albuminoids, it having no effect, however, upon cane sugar or fat. Before turning to the consideration of the remaining digestive secre- tions, attention should be called to a peculiar disposition of the mucous membrane of the intestine, which, to a certain extent, retards the passage of the food and exposes it longer to the digestive fluids and to a greater absorbing surface. I refer to the villi and the valvular con- niventes. On opening the small intestine and gently washing it, one will observe that instead of it being smooth, it presents a velvety ap- pearance. This is due to the mucous membrane (Fig. 56) being raised up into millions of little cones or cylinders, the villi, which project in- wardly into the cavity of the intestine. As these little structures are intimately connected with the subject of absorption, our account of their anatomy will be deferred until the next chapter, merely mentioning them here as offering a certain amount of resistance to the passage of 1 Op. cit., S. 186. 2 Virchow's Arehiv, 1879, Band lxxv S. 419. 152 INTESTINAL JUICE. food, just as any roughened surface offers resistance as compared with a smooth one to a substance passing over it. Pig. 56. WW nr 1 Portions of the mucous membrane from the ileum, moderately magnified, exhibiting the villi on its free surface, and between them the orifices of the tubular glands. 1. Portion of an agmiuated gland. 2. A solitary gland. 3. Fibrous tissue. (Leidy.) While the villi are found all through the small intestine, the valvule conniventes, which have the same function in this respect, are restricted to a certain portion of it, being absent in the upper half of the duode- num and in the lower third of the ileum. The valvulae conniventes (Fig. 57) are duplicatures of the mucous membrane extending trans- Fig. 57. Portion of small intestine laid open to show valvulfe conniventes. (Brinton.) versely across the intestine at right angles to its long axis, and occu- pying usually one-third or a half of the circumference, and sometimes extending all around the tube. The folds are widest in the middle, measuring often from one-quarter to one-half of an inch. On either side of the middle line they thin away until they are lost in that part of the mucous membrane attached to the muscular coat. Inasmuch as there can be counted usually over 800 of these folds, it can be readily understood how the extent of the mucous membrane is increased by them. Naturally the food will takes a longer time to pass over and between these barriers, so to speak, than over a plane surface, and this is of advantage in digestion and absorption, as the food will be more thoroughly incorporated with the secretions and have a better chance of being absorbed. It is often stated that the valvulae conniventes are only found in the intestine of man, this is erroneous; they are present, as Bischoff has shown, in the gorilla, and the author in the chimpanzee ;* they are 1 Proceedings Acad. Nat. Sciences, Philadelphia, 1S80, p. 16G. PANCREATIC JUICE. 153 also found in the ox, llama, camel, elephant, in the ornithorhynchus, and are well developed in the shark, giving rise in the latter animal to the so-called spiral valve. Merely mentioning that the solitary glands and patches of Peyer will he described when the subject of the blood is considered, let us pass on now to the consideration of the pancreatic juice and the bile, and of the role that these secretions play in digestion. Pancreatic Juice. The pancreas, in its general structure, resembles so closely the parotid and submaxillary glands, that it was known to the older anatomists as the abdominal salivary gland (Fig. 58). It is situated in the upper and Fig. 58. View of the pancreas ami surrounding organs. l-5th. I. The tinder surface of the liver. 17. Gall- bladder. /. The common bile-duet. «. The stomach, d. Duodenum. /;. Head of the pancreas, t. Tail, and i, body of that gland. Pancreatic duct (e) and its branches, r. The spleen, v. The hilus c, c. The crura of the diaphragm. (Qtain.) posterior part of the abdominal cavity, behind the stomach and between the duodenum and the spleen. It is about seven inches long, and an inch and a half broad, and from half an inch to an inch thick. It usually weighs about three to four ounces, and in its minute structure is of the racemose type. Its duct in man passes into the duodenum by a com- mon orifice with the ductus choledochus, three or four inches below the pylores. Not unfrequently there is also a supplementary pancreatic duct opening into the duodenum a little above the main duct. The secretion of the pancreas, or the pancreatic juice, has never been obtained from man. Probably it is very much like that of the pan- creatic gland of the dog, which, according to Bernard, 1 consists of water, an organic substance (pancreatin), and salts. With the exception of what has been learned from pathological observations, nothing is known of the effect of the pancreatic juice upon food during digestion in man, 1 Physiologie Experimental, tome ii. p. 237. Paris, 1856. 154 PANCREATIC JUICE. and such observations would be inconclusive unless viewed by the light of experiments upon animals and comparative anatomy. The first physiologist, so far as known to the author, who attempted to obtain the natural pancreatic juice from a living animal, was Reg- nerus de Graaf, 1 who, in 1662, opened the intestine of a dog and intro- duced a duck's quill into the orifice of the pancreatic duct. According to Bernard, 2 however, the fluid obtained by de Graaf was not pancreatic juice, being acid in reaction, whereas the normal pancreatic juice, ac cording to Bernard, is alkaline. Majendie 3 repeated de Graaf 's experi- ment, but with not much success. Leuret 4 and Lassaigne, in 1824, and Tiedemann and Gmelin, 5 in 1827, obtained what they supposed to be the natural pancreatic juice from the horse and dog, but nothing was learned of its physiological properties from their experiments. Little or nothing was known of the natural pancreatic juice up to the year 1846, when Bernard obtained the pancreatic juice of the dog, and in- vestigated its properties. Bernard's method 6 of obtaining the pancreatic juice consisted in open- ing the abdomen of a living dog and inserting a canula into the principal pancreatic duct. Bernard showed that during the intervals of digestion no pancreatic juice is secreted, and that the organ is of a pale color. The animal experimented upon should, therefore, be fed moderately an hour or so before the operation. The pancreas then becomes rose colored, full of blood, and secretes a viscid alkaline juice, which flows into the duodenum, even before the digested food gets there from the stomach. In experimenting with the pancreatic juice thus obtained, Bernard showed that it was important to study its properties as soon as possible, for, unlike the gastric juice, it soon decomposes. Another difference between a pancreatic and gastric fistula consists in the im- possibility of maintaining permanently the former, for even if the canula remains in place a few days the pancreatic juice changes entirely its character, becoming, according to Bernard, decidedly abnormal. This change takes place usually in a few hours, and so sensitive is the pan- creas, that sometimes the secretion is abnormal, even when first drawn. 7 Apart from the impropriety of assuming that the pancreatic juice of man and the dog are necessarily identical, one might reasonably doubt even whether the secretion obtained by Bernard's method always really represents the normal pancreatic juice in the dog. the pancreas being so readily inflamed and irritated by the operation. It is probable, however, that the secretion obtained by Bernard was normal, and that his con- clusions in reference to the properties of the secretion and functions of the pancreas generally are in the main correct, as they accord pretty well with what the facts of comparative anatomy and pathology, and the results of experiments with artificial pancreatic juice teach us of the functions of the gland. It is well known that in the rabbit the pancreatic duct opens sepa- rately into the intestine twelve inches below the bile-duct, instead of by i Opera Omnia, 1678, p. 292. 2 Op. cit, p. 176. 3 Physiologic, p. 307. Paris, 1816. 4 Op. cit , p. 102. 5 Op. cit., p. 27. ''» Op. cit., p. 100. 7 According to the later observations of Berstein, it appears, however, that a permanent pancreatic fistula can be maintained. Lndwiar's Arbeiten, I860. PANCREATIC JUICE. 155 an opening common to it and the bile-duct, as is the case in man or the dog; Bernard 1 tells us that after feeding a rabbit with fat he noticed that it was only below the entrance of the pancreatic duct into the intestine that the lymphatics of the small intestine or lacteals contained any fat. This observation not only suggested to Bernard the idea that the pancreatic juice emulsified the fat — that is, reduced it to a fine state of subdivision, and so rendered it absorbable — but was also the starting- point of his researches upon the functions of the pancreas generally. While it is true that in the rabbit, as a general rule, emulsified fat is only found in the lymphatics below the entrance of the pancreatic duct, this is not invariably so, as according to Bidder and Schmidt, 2 and our own observations, emulsified fat is at times found in the lymphatics above this point. While the rabbit is a convenient animal for making Bernard's experiment, it may be mentioned in this connection that the beaver, though a rarer animal, presents even a more favorable disposi- tion for making the observation than the rabbit, the pancreatic duct in this rodent opening eighteen inches below the bile-duct. Having examined several beavers in full digestion, the author noticed also that in some cases, as in the rabbit, the lymphatics contained chyle, both above and below the entrance to the pancreatic duct. Even if it were true that fat never is emulsified in the rabbit, except by the pan- creatic juice, it would not prove that the pancreas is indispensable in the digestion of fat either in man or animal. Fat, as such, not being the natural food of the rabbit, there is no necessary connection betw r een it and its pancreatic juice ; while in many fish, whose food contains fat, the pancreas is absent. In birds, also, the fat is usually absorbed by the mesenteric bloodvessels in general, and not by the lymphatics of the small intestine. Eberle, 3 however, showed, in 1834, that an artificial pancreatic juice, prepared by making an infusion of the pancreas, would emulsify oil when mixed and agitated with it, and Bernard, 4 apparently without knowing of Eberle's views, proved that the pancreatic juice of the dog, obtained by a fistula, would do the same, about two parts of the pan- creatic juice of the dog, by weight, emulsifying one part of oleaginous matter. These experiments with the artificial and natural pancreatic juice and the facts of comparative anatomy just referred to, show conclusively that while the pancreatic juice emulsifies fats and so promotes their absorp- tion, the pancreatic secretion is not indispensable, fat being digested and absorbed even in the absence of the pancreas. The digestion and absorption of fat must, therefore, be affected by other secretions as well as by the pancreatic juice. Let us see whether pathology throws any light upon this question. In a number of cases reported by pathologists in which there was disease of the pancreas in human beings, it was observed that a fatty diarrhoea was present during life, and such is the case also to a certain 1 Op. cit., p. 179. 2 Die Verdauungssafte, S. 55. Leipzig:, 1852. :; Die Verdauung, S. 251. Wurzburg, 1834 * 0]). cit. p. 257. 156 PANCREATIC JUICE. extent in animals in which the pancreas has been destroyed, as shown by Bernard 1 and others. * Such cases and experiments are often offered as proofs of the influence exerted by the pancreas in promoting the digestion and absorption of fats. It is interesting in. this connection, however, that Brunner, 2 who was the first, so far as the author is aware, to destroy the gland in a living animal, states in his work on the pancreas that he succeeded in keeping a dog alive three months after the pancreas had been extir- pated, and that yet he found the feces normal. Further, it is well known also that often in cases of fatty diarrhoea the pancreas has been found after death healthy, the liver being the diseased organ, and that occasionally both pancreas and liver are affected at the same time. 3 Indeed, so often is the liver affected in such cases that fatty diarrhoea is regarded as much a symptom of hepatic as of pancreatic disease. The conclusion from such cases would seem to be that the bile emulsifies the fats to some extent at least as well as the pancreatic juice. And this is in accordance with the fact already mentioned, of finding emulsified fat occasionally in the lymphatics of the rabbit above the entrance of the pancreatic duct. In the case of the intestinal fistula observed by Busch, it will be remembered that the food that was taken in the mouth passed out of the upper of the two openings of which the wound consisted. According to Busch, 4 when fat was taken in by the mouth it passed out of the upper opening in the state of a fine emulsion. This change in the fat must then be due in man to either the pancreatic juice, bile, or the intestinal juice. But we have seen, according to Busch, that fat intro- duced into the intestine through the lower opening of the wound ap- peared in the feces unchanged. The intestinal juice, or at least that part of it secreted by the follicles of Lieberkiihn, cannot be supposed to emulsify the fat. This function, then, must be performed by either the pancreatic juice or the bile, or both, unless the secretion of Brunner's glands is hereafter shown to exert such an influence. An important observation made by Bernard 5 was that the alkaline pancreatic juice out of the body, when mixed with a neutral fat, decom- posed the latter into glycerin and a fatty acid, the phenomenon being evidently one of hydration in presence of a ferment as follows : Stearin. Water. Stearic acid. Glycerin. C 57 H m 6 + 3(H 2 0) = 3(C 18 H 36 2 ) + C 3 H 8 3 If this change takes place in the human intestine, which is very prob- able, it will account for the presence of the palmitates and oleates found in the blood and feces, as soap — that is, a fatty acid combined with alkali. It is admitted by all physiologists that the pancreatic juice transforms starch instantaneously into glucose, one part of pancreatic juice by weight being required for the conversion of 4.5 parts of starch. This function of the pancreatic juice was first demonstrated in 1844 by Val- entin, 6 who experimented with an artificial pancreatic juice prepared by making a watery infusion of the gland. Bernard 7 showed that the 1 Op. (it., p. 276. 2 Experiments, nova circa Pancreas, p. 12. Amst., 1073. ■'■ Miine Edwards: Physiologic, tome vii. p 7(3. Longet : I'hysiologie, tome i. p. 291. * Op. cit.. S. 175 6 Op. cit., p. 257. 6 Lehrbuch der Physiologic, S. 356. Braunschweig, 1817. 7 Op. cit., S. 329. PANCREATIC JUICE. 157 natural pancreatic juice had the same effect in a very marked degree. Since at least nearly one-half of the food of man consists of starch, this function of the pancreatic juice is a most important one. We have seen that cane sugar is very slowly converted into glucose in the stomach, but in such small quantities that we must look for its further digestion in the small intestine. The case reported by Busch 1 shows that the transformation of cane sugar into glucose in the intestine is due to the pancreatic juice, for the bile has no such effect, nor the intestinal juice, while when cane sugar was introduced into the mouth glucose appeared at the upper opening of the wound; when cane sugar was introduced into the intestine by the lower opening of the wound it appeared unchanged in the feces. Cane sugar is, however, converted into glucose by artificial intestinal juice. In addition to the effects of the pancreatic juice upon the kinds of food already referred to, it has also the property of assisting the digestion of albuminous substances, about one part by weight of pancreatic juice digesting eight of albumin- ous substances. This effect of the pancreatic juice was first demon- strated by Eberle 2 in 1834, with an acidulated infusion of the tissue of the pancreas. Afterward Bernard, 3 in his investigations of the pan- creas, called attention again particularly to this fact. While the albuminous substances are converted into peptones by the pancreatic juice it appears that no intermediate stage like sytonin is formed, as we saw was the case in the digestion of albumen by gastric juice, and, further, that this action of the pancreatic juice is rather of a secondary character, as a considerable portion of the albumen is only converted into leucin and tyrosin. Inasmuch as the pancreatic juice effects important changes in the fats, starches, sugar, and albuminoids, it might be supposed from the fact of the albuminous substances of the pancreatic juice possessing such different properties that it was a compound rather than a simple substance. Chemists have shown pretty conclusively that such is the case, that the organic matter consists of three principles, pancreatin converting starch into glucose, trypsin transforming albumen into albu- minose, leucin. tyrosin, etc., and a third substance, as yet unnamed and not as well understood as the other two, decomposing the fats into glycerin and fatty acids. As regards the formation of leucin and tyrosin by the action of the pancreatic juice, it should be mentioned that a far greater quantity of these substances is formed outside of the body in digestion with pan- creatic juice than within it. It has been learned from the researches of Heidenhain 4 more particu- larly, that each cell of the pancreas of a dog, for example, after a period of about thirty hours' fasting consists of two zones, an outer zone, which is either homogeneous or delicately striated and readily staining with carmine, and a large inner zone finely granulated and staining with difficulty; the nucleus, situated partly in the outer zone and partly in the inner one, is irregular in form. If the cell be examined, however, i Op cit., S. 170, 185. - Op. cit., S. 235. 3 Op. cit., p. 333. 4 Pfluger'a Archiv, 1875, Band x. S. 557. Hermann: Physiologic, Funfter Baud, S. 174, 182. 158 PANCREATIC JUICE. during a period of activity — six hours, for example, after food has been taken— the outer zone of the cell will be found to be the longest, the inner zone in some instances having disappeared altogether, and the whole cell will be seen to have become smaller and staining readily throughout almost its whole extent, through the small size of the inner zone, and the nucleus regular in outline. The natural inference to be drawn from these observations is, that during secretion the inner zone furnishes either the secretion or the materials of the same, and consequently diminishes in extent in propor- tion to the activity of the process, while the outer zone enlarges through assimilation of materials brought to the cell by the blood and that the materials of the inner zone are elaborated at the expense of that of the outer one. That such is actually the case appears to have been shown by the observations of Kuhne and Lea, 1 made upon the pancreas of the living rabbit, in which the changes just described were observed as they took place (Fig. 59, A, B). Fig. 59. A portion of the pancreas of the rabbit, A at rest. B in a state of activity, a. The inner granular zone, which in A is larger, and more closely studded with granules, than in B, in which the granules are fewer and coarser. &. The outer transparent zone, small in A, larger in B, and in the latter marked with faint striae, c The lumen, very obvious in B, but indistinct in A. d. An indentation at the junction of two cells, seen in B, but not occurring in A. (Kuhne and Sheridan Lea.) The fact that a glycerin extract made out of a pancreas taken out of the body while still warm has no digestive effect, whereas the same glycerin extract made out of a pancreas kept for twenty-four hours will digest fibrin, shows that the pancreas contains at the moment that it is taken out of the body but little of its albuminous ferment, but that it does contain a substance readily convertible into such, particularly in the presence of acid, which Heidenhain has called zymogen. If such be the case, it would appear then that the trypsin, the active albuminous ferment of the pancreatic juice, is developed out of the zymogen 2 stored up in the inner zone of the cell, and that the latter is elaborated out of the materials of the outer zone. As to whether the remaining pancreatic ferments are produced in the same way has not yet been shown. It may be mentioned 3 that the » Verhandl. Nat. Hist. Med. Verien, Band i. Heidelberg, 1877. 2 Heidenhain : Hermann's Physiologie, Funfter Band, S. 188. 3 Pfluger's Archiv, Band xiv. S. 465. BILE. 159 pressure under which the pancreatic juice is secreted is about IT milli- metres of mercury. In concluding our account of the pancreas, its absence in many kinds of fish, in all invertebrates except perhaps the cephalopoda, appears to show that the pancreatic secretion cannot be as indispensable in diges- tion and absorption as is often supposed. The Bile. That the bile plays an important part in digestion would be naturally inferred, as suggested by Haller, 1 from the fact that it is poured into the beginning of the intestine ; whereas, if it were purely excrementi- tious in character, it would be eliminated rather at the end of it, in the vicinity of the rectum, for example, or at least separated from the blood without mixing with the food. It has been shown also by Schwann. Schellbach, Bidder and Schmidt, Arnold, Kuhne, and others, 2 that if the bile is diverted from the ali- mentary canal by a biliary fistula sooner or later the animal dies. The exceptions to this statement are only apparent, for in those cases where animals have lived for any length of time with a biliary fistula the bile was licked up and swallowed or else double the amount of food was eaten to compensate for the amount of bile lost. Further, it has been well established, by those who have experimentally investigated the sub- ject, that the flow of bile is greatest during digestion. This was shown, for example, by Prof. Flint's observations upon a dog with a biliary fistula. Table XXXVII. 3 — Flow of Bile during Digestion. Time. Amount. Time. Amount. Immediately after feeding 8.1 grs. 12 hours after feedii 'g ■ . 5.7 grs. 1 hour after feedi ug . . 20.5 " 14 " " . 5.0 " 2 hours , << u 35.7 " 16 " a . 8.6 " 4 " it it 38.9 " 18 " " . 9.9 " 6 " n a 22.2 " 20 " " . 4.7 " 8 " " it :;;;.5 " 22 " " u . 7.5 " 10 " " it 24.4 " If the bile were purely excrementitious in character, why should its flow into the intestine be intermittent, or the amount be connected with digestion.' A significant fact in reference to the use of the bile in diges- tion is that in starvation the gall-bladder is usually found distended with bile. If the flow of the bile has no connection with digestion, there would be no reason for this retention. On the other hand, it is well known that if the bile is indefinitely retained, either in animals or man, death takes place ; showing that the bile contains some excrementitious material which, under ordinary circumstances, is eliminated from the economy. That the bile is of use, and yet of no use, is confirmed by the fact already alluded to. 4 that in the doris, one of the mollusca, there are two hepatic ducts, one of which conveys part of the hepatic secretion into the intestine, the other carries the remainder directly out of the body. 1 Elements Physiologiae, tomuBsextus, p. 615. Lausanne, 1757. - Funke : Physiologic, Erster Band, S. 199. Longet : Physiology, tome premier, p. 2G9. 3 Flint : Physiology, voi. ii. p. 375. 4 Introduction, p. 37. 160 BILE. Assuming that the bile has some use in digestion, let us see now what is known of its effect upon food. When bile is mixed with the acid peptones, the result of stomach digestion, a precipitate is formed, but inasmuch as this precipitate is almost instantly redissolved by the alkaline intestinal and pancreatic juice the significance of this fact is not very apparent. Bile has no effect upon cane sugar, while the conversion of starch into sugar by the bile is not constant, being rather due to the mucus that the bile may contain; this effect of the bile is, therefore, insignificant. There remains only, then, the consideration of the effect of bile upon the fats. For a long time it has been known that bile can be used to take out grease spots in clothing, etc., the bile having the property of dissolving the acid fat. Many physiologists at the present clay hold, and with great probability, that the effect of bile upon the fatty articles of food within the intestine is the same as that just mentioned and made use of by scourers and others. Bile also, to some extent, emulsifies fat, though much less perfectly than the pancreatic juice. It has been shown by Wistinghausen and Hoffmann 1 that membranes, when moistened with bile, greatly facilitate the passage through them of fat ; whereas, when the membranes are moistened with water, the passage of the fat was entirely retarded. We shall see the importance of this observation when Ave come to study the absorption of fat by the villi. Admitting that one important use of the bile is the dissolving and emulsifying of fat, and thereby facilitating its absorption, we have an explanation of those cases of fatty diarrhoea observed in men where the liver is diseased, and where the bile is either not secreted or its flow obstructed, and to which we have already called attention in speaking of the function of the pancreas. The experiments upon animals made by Brodie, Majendie, Mayo, Hawkins, Tiedemann and Gmelin, Leuret and Lassaigne, Bidder and Schmidt, etc., with a view of determining whether the amount of fat absorbed by the lacteals is diminished when the bile is diverted from the intestines, are somewhat discordant. 2 The general conclusion, how- ever, from the observations of these experimenters, seems to be that there is less fat absorbed when the bile is cut off from the intestine, than under the normal conditions. Indeed, according to Leuret and Lassaigne, 3 while a thousand parts of chyle in a healthy dog contain thirty-two parts of fat, there are found only two parts of fat in the chyle of a dog in which the bile has been eliminated by a fistula. Bidder and Schmidt 4 give as the result of their experiments very much the same proportion. The facts of pathology and experiment then agree in showing that an important function of the bile is to assist the pancreatic juice in pre- paring the fatty parts of the food for absorption. It was noticed by Saunders 5 that the bile prevents the putrefaction of the food in the intestine. Since then the majority of experimenters 1 MilDe Edwards : Physiologie, tome v. p. 2'23. 2 Berard : Physiologie, tome ii. p. 364. Longet : Physiologie, tome i. p. 274. 3 Recherches sur la Digestion. 4 Die Verdauungssafte, p. 227. 6 Diseases of the Liver, pp. 136, 155, 167, 208. London, 1803. FUNCTIONS OF BILE. 161 have noticed that in animals, when the bile is prevented from passing into the intestine, either by ligating the ductus communis or making a biliary fistula, the food becomes putrid, exhaling a very disagreeable and offensive odor, while the gases of the intestine are greatly increased in quantity. According to Tiedemann and Gmelin, Eberle, Schiff, and other physiologists, the bile exercises a stimulating effect upon the intestine, exciting the peristaltic action and increasing the secretion of the intes- tinal juices. The want of such stimulus explains, according to those who hold the ancient and plausible view of the bile being a natural purgative, the character of the stools in persons affected with jaundice. Fig. 60. Gall bladder Large intestine ~Spleen. -Small intestine. "Colon. Rectum. Digestive apparatus of man. iMilsk Edwards.] the feces in such cases being passed at long intervals and in a hard condition, through the want of peristaltic action and the softening effect of mixture with the secretions. The antiseptic and stimulating action of the bile does not appear to be, however, as indispensable as the changes it produces in the fats. In connection with the uses of the bile in digestion, a few words about the gall-bladder do not appear superfluous. That the gall-bladder (Fig. 60) is simply a receptacle for the bile seems to be shown from the facts that it is occasionally absent in man without the secretion of bile being suppressed, and that when the cystic duct is either obliterated ll 162 GALL-BLAl)l»Ki;. or obstructed, no bile is found in the gall-bladder, only mucus then being present. In the intervals of digestion the muscular fibres of the duodenum appear to constrict the orifice of the ductus communis to such an extent as to prevent the flow of the bile into the intestine ; the bile then necessarily flows back into the gall-bladder. This can be shown in the cadaver by simply compressing the liver, the effect of which is that the bile flows into the hepatic duct, and thence back to the gall-bladder. While it cannot be said that there is any invariable rule as regards the presence of or absence of the gall-bladder even in closely allied animals, 1 it being found, for example, in the hog, while absent in the peccary, being present in the antelope though not in the deer, some- times absent and sometimes present even in the same animal, as in the giraffe ; nevertheless, in the carnivora, it may be stated, without excep- tion, that the gall-bladder is always present. The significance of this latter fact is obvious, when it is remembered that while a herbivorous animal, like the cow or deer, eats continuously, a carnivorous one, like the lion or tiger, only obtains its food at intervals, and in large quan- tities, hence the need of a supply of bile already formed to assist the digestion of the food. 2 The disposition of the gall-bladder in the python further illustrates its use as a receptacle. In this serpent the gall-bladder is situated some distance from the liver. Were it connected with it, the prey, when introduced into the stomach, would compress the gall-bladder and force the bile into the intestine before the food arrived there, and the effect of the bile upon the food would be lost. The position of the gall-bladder, however, is such that when the food about reaches the duodenum compres- sion is exerted, and the bile passes into the intestine at the proper moment. As Owen 3 well observes, "this fact in comparative anatomy is significant of the share taken by the biliary secretion in the act of chylification." The amount of bile secreted in a given period of time in man can only be approximately estimated from experiments made upon ani- mals with biliary fistula. Assum- ing that the amount of bile secreted by the carnivora and man proportionally to the weight to be about the same, there would be from Portions of the liver of the hog, exhibiting the lohular structure. The large vessel is a branch of the portal vein, the outlines of the lobules being seen through its transparent wall. The orifices, large and small, seen in the portal vein, are fine branches sent between the lobules. The two ves- sels lying to the right of the portal vein are branches of the hepatic artery and duct. (Leidy.) i Milne Edwards : Physiologie, tome vi. p. 455. ~ Cuvier 3 Comparative Anatomy of Veitebrates, vol. i. p. 452. Anatomie Coniparee, tome iv. p. 37. STEUCTURE OF THE LIVER, 163 about two and a half to three pounds of bile secreted in twenty-four hours by a man weighing 140 pounds. The bile being secreted by the liver, let us now consider the structure of the latter. The liver is the most constantly present gland in the animal kingdom, and is the largest gland in the human body, weighing on an average 3 kil. (50 ozs.). If the surface of the liver be examined, it will be seen to be far from homogeneous, consisting, in fact, of a great number of little masses, the hepatic lobules, varying in diameter from one to two mm. (-^th to y^tli of an inch). The lobules are better seen, however, in the liver of the pig (Fig. 61) than in that of man, and are especially well marked in the liver of the South American capromys. If now one of the hepatic lobules, or acini, be examined microscopi- cally, it in turn will be found to be made up of still smaller nucleated polyhedral masses, the hepatic cells (Fig. 62), varying in diameter from the ^y-th and -g^th of a mm. (-^th to tne Tjr tn °f an mcn )- Fig. 62. Fig. 63. Transverse section of part of a lobule from thejrab- bit's liver, a, a, a. Nucleated glandular cells, b, b, b. Capillary bile-ducts passing between the adjacent cells. c, c, c. Sections of capillary bloodvessels. (Genth.) Ramification of portal vein of liver, a. Twig ot portal vein. 6, b. Interlobular veins, c. Acini. (Dai/ton.) Just as the liver is made up of lobules, so each lobule is made up of cells, and as it is through the agency of the cells that the bile is elabo- rated out of the blood, the manner in which the latter traverses the liver must be next studied. The liver is supplied with blood by the portal vein and hepatic artery. The portal vein, accompanied by the hepatic artery, entering the liver at the transverse fissure, and dividing and subdividing into numerous branches, ramifies as the interlobular veins (Fig. 63) between the lobules and anastomoses freely around them. From these peripheral inter- lobular veins arise still smaller ones, the intralobular veins (Figs. 64, 65), which, passing into the lobule from its margin in a radiating manner, unite in the centre as the central vein (Fig. 64). The latter passing directly through the lobule, terminates in the sublobular vein, on which the lobule rests. The various sublobular veins (Fig. 164 STRUCTURE O F T HE LIVE R . 66), in turn uniting together, constitute the hepatic vein. The latter terminates in the ascending vena cava, and leaves the liver at right angles to which the portal vein enters. That the portal and hepatic Pig. 64. Cross-section of a lobule of the human liver, in which the capillary network between the portal and hepatic veins has been fully injected. 60 diameters. 1. Section of the intralobular or central vein. 2. Its smaller branches collecting blood from the capillary network. 3. Interlobular or peripheric branches of the vena ports with their small ramifications passing inward toward the capillary network in the substance of the lobule. (Sappey.) Fig. 65. Lobule of liver, showing distribution of bloodvessels ; magnified 22 diameters, a, a. Interlobular veins. b. Intralobular vein. c,c,c. Lobular capillary plexus, d, d. Twigs of interlobular vein passing to ad ja- cent^lobules. (Dalton.) veins are essentially the proximal and distal parts of one and the same vein, is shown not only in the injection of either of them equally well through the other, but also in the manner in which the vascular system STRUCTURE OF THE LIVER. 165 and the liver develop. In the embryo, as we shall see hereafter, at an early period the continuity of the portal and the hepatic veins is quite evident, it not being until later that the connection between the two is obscured by the liver, which grows parasitic-like around the vessels which later supply it with blood. The latter, capillary vessels, consti- tute then what we have just described in the adult as the interlobular, intralobular, central, and sublobular veins, while that part of the vein which enters the liver is known as the portal vein, that part leaving it the hepatic. The hepatic artery, after entering the liver, like the portal vein, ramifies between and within the lobules, but unlike the portal vein does not pass through the lobules, but terminates within them in the intra- lobular capillaries. That such is the case, is shown by the injection of the hepatic vein through the hepatic artery. Further, that the liver cells elaborate bile both out of the blood brought to them by the hepatic Fig. 66. .'*-.-: 'it''.' ■ Injected twig of a sublobular vein passing into the hepatic lobules About 30 diameters. 1. Small sub- lobular vein. 2. Central veins passing into the base of the lobules. 3. Their smaller subdivisions. 4. Capillary network of communication with the extreme ramifications of the vena porta-. (Sappey. ) artery, as well as by the portal vein, is shown by the fact that the bile is still secreted, even if diminished, if the latter be ligated, 1 and that the bile is secreted even in cases where the portal vein has been found obliterated after death, 2 or passing into the vena cava. 3 Pathological as well as experimental considerations show that the liver cells are the active agents in the elaboration of the bile. Thus in certain diseased conditions of the liver, noticeable more particularly in the liver of animals, the cells, or the interspaces between them, are found filled with bile, 4 while if a substance like that of sulpho-indigotate of sodium, indigo carmine of the arts, be injected into the circulation of a 1 (lie Comptes Rendus, tome xliii. p. 463. Paris, 1856. " Andral : Ibid., p. 467. ■> Abernethy: Phil. Trans., p. 59. London, 1793. Lawrence: Med. Chir. Trans., vol. v. p. 174. London, 1814. 4 Stiles: Bulletin of the Xew York Academy of Medicine, 1868, vol. iii. p. 350. 166 DEVELOPMENT OF THE LIVER. very young mammal, a sucking pig, for example, 1 the liver cells, or the interspaces between them, according to the length of" time elapsing between the performing of the experiment and the killing of the animal, will be seen to contain the salt of sodium injected. Since the bile does not exist as such in the blood, it follows that the liver cells not only eliminate from the blood the Fig. 67. principles of which the bile consists, but also elaborate the same into bile. The bile having been elaborated by the liver cells out of the blood flowing within the vessels situated Diagram showing how a few hepatic ceiis may at the angles formed by the junction orma hollow tube. 1. Large cell; viewed from f three 01' more Cells, paSSCS thence this side the tubes would appear to be the breadth ^ ^ i nterspaces between the of a single cell, 2. Two cells the diameter of the .. /T -,. nfTN l , . . . tube. 3. Passage-way for the bile, (leh.v.) cells (Fig. 67), and since these inter- spaces open into the minute biliary ducts (Fig. 62, b, 6), they may be regarded as the beginnings of the latter. The bile-ducts begin then simply as intercellular passages, pos- sessing no proper walls distinct from the cells bounding them. At the margin of the lobule, however, a basement membrane becomes more evident, and the cells covering it present rather a columnar shape as compared with the polyhedral form of the true hepatic cells. The cellular passages or interspaces having now become true walled ducts, with a diameter of the y^g-th of a mm. ( go^j th of an inch), ramify between the lobules, and are here seen to consist distinctly of basement membrane lined with columnar epithelium, while the larger ducts, in addition to the basement membrane, possess abundant elastic tissue, and a certain amount of plain muscular tissue. In addition to the mucous glands opening into the ducts, large race- mose csecal-like glands are present often in such great numbers as almost to conceal the parent tube from which they spring. The use of these glands is not known. That the bile-ducts begin as just described, is further confirmed by the manner in which the liver develops, and by its structure in the lower animals. The liver, as we shall see when we come to study the development of the organs of the body, first appears as a bud or diverticulum (Fig. 68, L) of that part of the intestine which afterward in the adult becomes the duodenum and, like the latter, consists of two layers, an external intestinal fibrous (i), and an internal intestinal glandular (//). In the former are developed the capillary vessels, which, as we have seen, connect the portal and the hepatic veins; in the latter, the hepatic cells. Very soon the primitive sac-like diverticulum of the intestine subdivides into the two primitive lobes (Fig. 69, L, L), while through the narrowing of that part of the sac opening into the intestine (Bd) a duct is formed, the primitive bile-duct, a diverticulum from the latter constituting the future gall-bladder. It is evident that in this early i Choezonsczewsky : Virchow's Archiv, 1860, Band xxxv. S. 153. DEVELOPMENT OF THE LIVER. 167 embryonic condition of the liver the intestinal glandular layer (g) lining the sac constitutes the secreting portion of the gland, and the interior of the sac (bd), the beginning of the bile-duct, since the cavity of the yHHUi Development of the liver. Fro. 69. X_-_ „ — _ L •' 4\° Development of the liver. Fig. 70. V V HH .*• hi TM^T^TTJ T Development of the liver. former (bd) is continuous with that of the latter (Bd), while the intes- tinal fibrous wall (i) of the sac supports the bloodvessels (Fig. 70, P) supplying the blood, out of which the glandular cells (Gf) lining the sac will elaborate the bile. The latter passes thence by the duct (Bd) into 168 STRUCTURE 0E LIVER IN LOWER ANIMALS. the intestine (I). The structure of the liver al this stage is therefore similar to that of any other true gland, the simplest expression of which is a basement membrane separating blood on one side from cells on the other, the latter elaborating out of the former the secretion or excretion characteristic of the gland. Such a disposition obtains in all glands, however complicated the structure of the gland may be, whether it be follicular, tubular, race- mose, the cells are always, without exception, separated from the blood by a membrane, while the spaces between the cells ami into which the secretion exudes, constitute the beginning of the duct; further, just as the lobes L L are formed through the subdivision of the primitive sac-like diverticulum of the intestine (X), so are the lobules (IT) formed through the subdivision of the lobes (Fig. 70) and as the lobes are defined by the fibrous wall (i), so are the lobules, the fibrous wall of the embryonic sac corresponding to Glisson's capsule in the adult, which dipping down between the lobules with the interlobular veins and the hepatic cells becomes thinner and thinner, and finally disappears, or becomes so fused with either the walls of the cells or of the vessels, as to be in- distinguishable from the latter. That the structure of the liver in the adult is essentially the same as in the embryo, consisting of bloodvessels, in whose meshes (Fig. 65) lie cylinders of basement membrane, containing secreting cells, or in the deeper parts simply of cylinders of cells (Fig. 62), the spaces be- tween the latter (Fig. 67, Fig. 69, bd) constituting the beginnings of the bile-ducts, is still further shown by the facts of comparative anat- omy. For as is well known, the transitory changes through which the liver of the higher animals passes is more or less permanently retained in those of the lower ones. Thus, in the amphioxus the lowest of ver- tebrates, the liver consists of a simple sac-like diverticulum of the in- testine, corresponding to the first stage in the development of the liver of the higher vertebrates. Passing to the lowest of fishes, the mars ipo-branchise, of which the myxine is an example, we find the liver a little more complex than in the amphioxus, consisting of two lobes with lobules, the lobes, however, remaining quite distinct throughout life, whereas in the higher vertebrates on the other hand tliey coalesce more or less completely at an early period, constituting in the adult one organ. The racemose-like subdivided condition of the embryonic liver, which, as we have just seen, is a transitory one in the liver of the higher ver- tebrates, is permanently retained as such in the liver of many inverte- brates ; the liver, for example, in the slug (Limax) and snail (Helix) among the mollusca, consisting of lobes divided into lobules, each lobule consisting of creca composed of basement membrane lined with mucous secreting cells. Essentially the same structure obtains in the liver of the lamp shells or brachiopoda (Terebratulima), consisting in these animals of numerous caeca lined with cells easily separable from each other, and over which the visceral bloodvessels ramify. The same type of structure is seen in the liver of the Crustacea, con- sisting in our common crayfish (Astacus) of two lobes, one in each side of the intestine, and united by an isthmus, each lobe consisting of long STRUCTURE OF LIVER IN LOWER ANIMALS, 169 Fig. 71. conical caeca massed together, the latter (Fig. 71) consisting of basement membrane, supporting numerous secreting cells, on the inner surface. The same disposition essentially obtains in the liver of the corrupedia, being well seen in the common barnacle (Balanus). It is needless further to multiply examples, since wherever the liver exists in such ;i condition that its minute structure can be readily made out, it will invariably be found to consist of caeca more or less aggregated together, consisting of basement membrane lined with cells between and around which the bloodves- sels ramify, the spaces between the cells con- stituting the beginning of the bile-ducts. A priori, therefore, we should expect to find the minute structure of the liver essentially, the same as that of the lower animals, and such we have found to be the case as studied in its minute structure, and in its development. It is held, however, by many physiologists that the glands which in the invertebrates we have described as being biliary in function, are not really such, the secretion elaborated by them not containing the characteristic bile acids. Even admitting that this is the case on the supposition that the transitory stages through which the higher animals pass are permanently retained in the lower, one might expect to find the bile in the latter not corresponding exactly in composition with that of the former, but rather with a transitory stage in the develop- ment of the same. Further, the fact of the biliary tubules in insects secreting urea, uric- acid, etc., so far from being inconsistent with the view of the tubules being biliary in function is confirmatory of it, since, as we shall see hereafter, there are good reasons for supposing that urea, to a certain extent, at least, is produced in the liver of verte- brates. The bile as obtained by Jacobsen 1 from a case of biliary fistula was clear greenish, brownish-yellow, neutral in reaction, and of a specific gravity of 1.002; when mixed however with mucus, as is the case when taken from the gall-bladder, the bile is more or less ropy in con- sistence, with an alkaline or neutral reaction, having a faint odor, a bit- ter taste and a specific gravity of about 1.020, and bright golden-red in color, as is the case also in the bile of the omnivora and carnivora, that of the herbivora being, on the contrary, of a golden or bright green, the difference being due, as we shall see, to the relative amount in which the bile pigments bilirubin and biliverdin are present. It is oxidation of the latter which gives rise to the changes in color which the bile exhibits after exposure. One of the hepatic cieca of As- tacus affirms (crayfish), highly magnified, showing the prog- ress of development of the secreting cells, from the blind extremity to the mouth of the follicle : specimens of these, in their successive stages, are shown separately at a, 6, c, d, e. (Leidv.) ' Jahresber. der Thier Chemie, iii. S. 193, 1873. Hermann : Physiologie, Funfter Band. S. 119. 170 COMPOSITION OF THE BILE. The bile when shaken up with air or water foams up into a frothy mixture. Tliis property is due to the presence of the biliary salts. The bile is also dichroic — that is, it presents two different colors according to its mass, when examined with transmitted lighl : thus, while a layer of ox bile two or three centimetres thick is green, that of five or six cen- timetres appears red. The bile is also fluorescent ; thus, if green bile be viewed by the violet or blue rays of the spectrum, it becomes faintly luminous, with a yellow, greenish tint. The bile, chemically, is a highly complex fluid, consisting of water, biliary salts, mucus, pigment, cholesterin, fats, and inorganic salts, the water and solids being in 100 parts in the proportion of about 86 to 14, as may be seen more in detail from Table XXXVIII., giving the analyses of Frerichs and Gorup Besanez 1 of human bile obtained from the gall-bladder. Table XXXVIII. — Composition of the Bile. Frericlis. Gorup Besanez. In 100 parts. Man, Man, Man, Man, Woman, Boy, set. 18. set. 22. sat. 49. set. 68. set. 28. set. 12. Water .... 86.00 85.92 82.27 90.87 89.81 82.81 Solids .... 14.00 14.08 17.73 9.13 10.19 17.19 5.65 Biliary acids with alkali 7.22 9.14 10.79 7.37 Fat 0,32 0.92 4.73 ' 3.09 Cholesterin 0.16 0.26 Mucus and pigment 2.66 2.98 2.21 1.76 1.45 Inorganic salts 0.65 0.77 1.08 0.63 14.80 2.39 Of the different principles which constitute the bile, most of them, as the water, cholesterin, fat, and inorganic salts, preexist as such in the blood, and are simply eliminated from the latter by the liver cells ; the biliary salts and the biliary pigment, however, are not found in the blood, but are elaborated by the liver cells out of the principles brought to them by the blood. The presence of the biliary acids, then, in the urine, for example, is a proof that the bile has been secreted, but has been pre- vented by some obstruction from passing into the duodenum and being reabsorbed. A jaundice from mere obstruction in which, however, the bile has been secreted, can be then distinguished from one in which no bile has been secreted by the presence or absence of the biliary acids in the urine ; the color of the skin in the latter case being probably due to the diffusion into the tissues of the broken-down hsemoglobin of the red blood-corpuscles, and which we shall see is almost identical, if not absolutely so, in chemical composition with the biliary pigment. The biliary salts do not consist, as one would suppose from their name, of simply inorganic salts, such as are ordinarily found in the secretions, but of soda, united with glycocholic and taurocholic acids, the organic nitrogenized acids so characteristic of the bile, and upon which, to a great extent, the properties of the latter depend The biliary salts, the sodium taurocholate, C 26 H 44 NS0 7 Na, and the sodium gylcocholate, C 26 H 42 N0 6 Na, may be obtained from the bile in the 1 Lehrbucb dor Physiologischen Chemie, S. 519. Braunschweig, 1878. BILIARY SALTS AND ACIDS. 171 following manner : The bile having been mixed with animal charcoal to decolorize it, is evaporated to dryness, and then treated with alcohol. The alcohol having been distilled off, the dry residue is then further treated with absolute alcohol ; anhydrous ether, after filtering, is added to the filtrate until the precipitate formed ceases to be thrown down. After standing some hours the precipitate crystallizes as the resinous matter of the bile, also known as bilin, and which contains both sodium taurocholate and glycocholate, if both biliary acids be present in the bile, and which can be separated from each other by making an aqueous solution of the bilin, adding neutral lead acetate and then filtering. The filtered solution will contain the sodium tauro- cholate alone, the sodium glycocholate being decomposed and precipi- tated as an insoluble lead glycocholate. Fig. 72. Sodium glycueholate from ox-bile, alter two daye' crystallization. At the lower part ot the figure the crystals are melting into drops, from the evaporation of the ether and absorption of moisture. (Dalton.) The biliary acids themselves may then be separated from their respective salts by means of dilute sulphuric acid or lead acetate and sulphydric acid. The relation existing, chemically, between these two acids, is shown in the formula: Taurocholic acid. filycocholic acid. C 26 H, 5 NSO, — H.,0— S = C 26 H 43 N0 6 by which it is seen that, in deducting water and sulphur, taurocholic becomes glycocholic acid. As a general rule, both the biliary salts are present in human bile, though the proportion in which they exist may vary considerably. Thus, in the case of biliary fistula observed by Jacobsen, already referred to, the sodium taurocholate was present only in small quantity or absent altogether. Usually, in the bile of the herbivora the sodium glycocholate preponderates, in that of the carni- vora the taurocholate. In the bile of the cat and dog, however, the sodium taurocholate alone is found. 172 pettenkofer's test for bile. Both the biliary salts crystallize in hemispherical or star-shaped masses of fine radiating needles (Fig. 72) which, while soluble in alcohol and water, are insoluble in ether. The two salts are distin- guished from each other, as just mentioned in speaking of the manner of obtaining them, in that the sodium taurocholate is not precipitated by the neutral lead acetate, Pb(C 2 H 3 2 ) 2 3A

. 61. Venetiis, 1556. :i Ibid., Cap. 19, p. 141. LACTEALS, THORACIC DUCT, ETC. 189 tion. The ancients were right, therefore, in considering the veins as a means of absorption, although at the same time they knew almost nothing of the course of the circulation. The first part of the lym- phatic system discovered was the thoracic duct in the horse, described by Eustachius, 1 the Roman anatomist, in 1563. Eustachius, while showing that the duct terminated in the subclavian vein, failed, how- ever, to show where it commenced, and, therefore, did not learn its functional importance. Indeed, the discovery itself was forgotten, and Fig. 84. Fig. 85. View of the principal branches of the vena porta;. %, 1. Lower surface of the right lolie of the liver. 2. Stomach. 3. Spleen 4. Pancreas. 5. Duodenum. 6. Ascending colon. 7. Small intestine. 8 Descend- ing colon, a. Vena porta; dividing in the transverse fissure of the liver, b. Splenic vein. c. Bight gastro- epiploic, d. Inferior mesenteric, e. Superior mesen- clavian veins, d. Point of opening of thoracic teric vein. /. Superior mesenteric artery. (Quain.) duct into left subclavian. (Dalton.) Lacteals, thoracic duct, etc. o. Intestine. 6. Vena cava inferior. c, c. Right and left sub- its significance was not appreciated till the following century. The history of the lymphatic system really begins with Gasparis Aselli's discovery, in 1(322, in the dissecting amphitheatre at Pavia, of the lacteals of the small intestine in the dog. Aselli tells us in his work 2 on the lacteals that, on opening a dog to show some friends the recurrent laryngeal nerves, he was surprised to find in the mesentery in addition to Opusc. Anat., Antig 13, i . 280. Li .di. Batav , 1707. De Lactibus Sine Lacteis Venis, Cap. i\. Mediolani, MDCXXVII. 190 ABSORPTION. the arteries and veins, delicate, white lines, which, at first, he thought were nerves. On pricking one of them, however, and seeing a whitish, milk-like fluid escape, he exclaimed, like Archimedes of old, "•Eureka!" for he felt he had made a great discovery. Wishing to confirm his dis- covery, Aselli, on the following day, opened a second dog, but was dis- appointed in not finding the white vessels seen on the previous occasion, and began to feel that he had been too hasty in announcing the dis- covery of a new set of vessels. On reflection, however, it occurred to Aselli that the first dog had been well fed before being opened, whereas, the second one had been deprived of food for some time, and that, per- haps, the absence of the white vessels was due to this cause. A third dog was well fed, and then opened, when the white vessels were again seen. Aselli 's method of experimentation shows how well he appre- ciated the importance in repeating an experiment or confirming an observation, of the conditions being the same in both cases. Aselli further extended his observations to other animals, and found the lacteals in cats, lambs, pigs, cows, and the horse. It was not, how- ever, until 1628, two years after Aselli's death, that the lacteals were demonstrated in man. For this observation science is indebted to Peiresc, 1 Senator from Aix, who, wishing to know whether Aselli's discovery could be extended to man, permitted the body of a criminal who had been executed to be opened, when the lacteals were found (Fig. 85), the anatomists interested in the post-mortem examination having at- tended to the feeding of the criminal before execution. Aselli supposed that the lacteals which he had discovered in the mesentery carried the chyle to the liver. This error was corrected by Pecquet, 2 a Frenchman, who showed, in 1G49, that in the dog, and afterward in the horse, ox, pig, etc., the mesenteric lymphatics, or lacteals, terminated in a reservoir, the receptaculum chyli, now often called in honor of its discoverer the reservoir of Pecquet ; and further, that this receptaculum was the beginning of the thoracic duct. The functional significance of the forgotten discovery of Eustachius became then for the first time apparent, for it was shown that the lymphatics of the small intestine and thoracic duct offered a route by which the digested food could be carried from the alimentary canal to the blood in the subclavian vein, and thence to the heart. Two years after the important discovery of the receptaculum chyli — that is, in 1651 — lym- phatics were demonstrated in the liver and other parts of the body by Rudbeck, 3 and their course and connection with each other and the mesenteric lymphatics made out. These vessels were, however, called- by the Swedish anatomist aquifermous, or serous vessels. A few months after Rudbeck 's discovery, they were again described by Bartholinus, 4 Professor of Anatomy at Copenhagen, who designated them lymphatics, the name they now bear. Bartholinus appears also the first, so far as the author has been able to learn, to have seen the 1 Milne Edwards : Physiologie, tome v. p. 450. Paris, 1859. Berard : Pbysiologie, tome ii. p. 565. Paris, 1849. '- Joannis Pecquet! : Diepasi Experimenta Nova Anatomica, Cap v. and vi. Amst., 1661. 3 Olai Rudbeck : Nova Exerritatio Anatomica exhibens ductos hepaticos aquosos vasa glandularum serosa. Clericus ABSORPTI O X the villi. It is very probable, however, that they are present. Each villi usually receives one arterial twig, which, after penetrating it, breaks up into capillaries situated just beneath the basement membrane. The blood is returned usually by one vein. The lymphatic, or the lacteal, begins in the centre of the villus, usually as a single vessel (Fig. 87), with a closed and somewhat expanded extremity. Its calibre is con- siderably larger than that of the capillary bloodvessels surrounding it. The lacteal within the villus, like the lymphatics elsewhere, is sur- rounded by a delicate layer of flattened epithelioid cells (Fig. 88). These are connected with the cells of the basement membrane through those of the lymphoid or connective tissue lying between (Fig. 89). The columnar epithelial cells which cover the villi, and also the surface of the mucous membrane, and which are prolonged into the tubular glands, present a granular appearance with an oval nucleus. They terminate toward the basement membrane in a tapering manner, and measure about the iQ QQ ih of an inch (^-th of a mm.) in length. Flu. Si). Fig. 90. Diagrammatic representation of the origin of the lacteals in a villus, according to Funke. e. Central lacteal, d. Connective-tissue corpus- cles with the communicating branches, c. Co- lumnar epithelial cells, the attached extremities of _which are directly contiguous with the con- nective-tissue corpuscles. (Carpenter.) Origin of the lacteals, according to Letzerich. The cells marked a, are cup or goblet cells, and are seen to be intercalated amongst the columnar epithelial cells, and to communicate with a delicate plexus, b, that opens at various points into the central lacteal, c, /. d. Layer of clear connective tissue, e. Con- nective tissue with numerous nuclei. (Carpenter.) Their free end, or the surface looking toward the interior of the intes- tine, consists of a layer of a highly refractory substance, with vertical stride running through it. These stripe have been regarded by Kolliker 1 and Funke 2 as minute canals ; Henle, 3 however, considers them to be solid rods. Some of these columnar cells usually contain mucus, and swell up upon the addition of water into the so-called goblet cells (Fig. DO), which are regarded by Letzerich 4 as the true beginning of the absorbent system. The lymphatic or lacteal, after emerging from the villus, passes into i Gewebelehre, S. 409. Leipzig. 1807. 3 Anatomie, Eingeweidelehre, S. 177. Braunschweig, 1873. * Virchow's Arcliiv, Baud xxxix. S. 435. - Physio'.ogie, S. 222. Leipzig, 1876. CHYLE. 197 the lymphatics of the intestine. These are usually described as consist- ing of two sets, the deep and superficial. The latter pass in the mesen- tery to the lymphatic glands. The lymphatics coming from the latter, as we have seen, converge toward the receptaculum chyli. During the intervals of digestion the lymphatics of the small intes- tine, or the lacteals, contain lymph, undistinguishable from that of the lymphatics of the rest of the body. During digestion and absorption, however, and more especially when fatty articles have constituted part of the food, the epithelial cells of the villi, and the lymphatics of the small intestine, are then filled with the chyle. The chyle is a coagulable, alkaline, opaque, whitish, milky-like fluid, hence the name of the lacteals given to the lymphatics of the small intestine, in which it is found. The chyle (Table XXXIX.), however, is only the lymph with the products of digestion added to it, and as the lacteals absorb principally the fat, the essential difference between the chyle and the lymph is that the former contains a great quantity of fat, the latter usually only a trace. In reference to any analysis of the chyle, it must not be for- gotten that its composition will differ according to whether the portion examined has been taken from the lacteals or the thoracic duct. Indeed, chyle drawn from the thoracic duct is not pure chyle, but chyle mixed with the lymph which has been brought from the extremities to the receptaculum chyli, and thence passed into the thoracic duct. The chyle of the thoracic duct will contain, therefore, less fat and other solid constituents, being diluted with the lymph mixed with it. Further, the amount of fat in the chyle will be variable, depending upon the diet of the man or animal examined. Thus, the chyle of a carnivorous animal will contain more fat than that of a herbivorous one, the food of the former being richer in fat than that of the latter. At one time it was supposed that the lacteals absorbed exclusively the fatty substances, but it is now known that they also take up, at least in small quantities, albuminoid and saccharine substances, salts and water. Of the amount of the chyle poured into the thoracic duct, it is impos- sible to give even an approximate estimate. When examined microscopically, the milky appearance of the chyle is seen to be due to an immense number of very minute fatty granules, which constitute the so-called molecular base of the chyle, and which measure on an average from the ! 2 o o o ^ a °^ an * ncn ^° ^ ne 1 2 5 * n °f an inch in diameter. These granules appear to be coated with albumen, which probably prevents their running together and coalescing. The so-called chyle corpuscles found in greater or less number in the chyle, do not differ from those of the lymph or blood, and will be considered again when the latter fluid is studied. What has been already stated in reference to the supposed causes of the flow of the lymph will apply equally well to that of the chyle ; but there are eertain conditions, in addition to those already mentioned, which appear to influence favorably the flow of the chyle, and so deserve a passing notice. It will be remembered that, in speaking of the structure of the villi, allusion was made to the plain muscular fibre that they contain. These muscular fibres are dispersed longitudinally around the lacteal, and their contraction will obviously retract the 198 ABSORPTION. Fig. 91. villus. The effect of the action of these muscular fibres will then be to force the contents of the lacteal out of the villus into the superficial lymphatics. These muscular fibres have probably, then, some im- portance in aiding the flow of the chyle toward the thoracic duct. It w r ill be remembered that the thoracic duct, in passing to the left side to terminate in the subclavian vein, passes behind the aorta. Haller 1 called attention to this fact as an important one, the great physiologist considering that the contractions of the aorta in com- pressing the duct would favor the flow of the chyle and lymph toward the subclavian vein. Recently, Prof. Draper 2 has further suggested that the flow T of blood in the subclavian vein exerts a suction force upon the contents of the thoracic duct, basing his view upon the hydraulic princi- ple of Venturi, that, if into a tube (Fig. 91) through which a current of water is steadily flowing another tube opens, its more distant end being in communication with a reser- voir of water, a current will be like- wise established, and the reservoir be emptied of its contents. The anatomical disposition of the parts, together with the fact that the flow of the chyle ceases with the flow of the blood, appear to show the close dependence of the movement of the one on that of the other. It will be remembered that, up to the time that the lymphatics were discovered, absorption was considered to be effected by the veins only. After the discovery of the lymphatics, however, physiologists fell into the opposite error of attributing absorption solely to the lymphatics, denying that the veins took any share in this process. Indeed, it was not until the present century that it was experimentally demonstrated that the veins as well as the lymphatics absorb. Apart, however, from any experi- mental evidence, the facts of comparative anatomy alone might have shown that of the two sets of vessels, so far as the absorption of the digested food is concerned, the veins play a more important part than the lymphatics. Thus it is well known 3 that in the amphioxus, the lowest of the vertebrata, and in all the invertebrata, the lymphatic system is absent. In these animals, therefore, absorption is carried on solely by veins. Further, while the lymphatic system is present in fishes, batrachia, reptiles, and birds, it is only in the mammalia that it acquires the functional importance that we have ascribed to it. Indeed, according to Bernard, 4 the name lacteal cannot be properly applied to the lymphatics of the small intestine in the oviparous verte- Principle of Venturi. (Draper.) 1 Elementa Physiologic, tomus vii. p. 237. - Physiology, 1878, p. 79. 3 Owen : Comp. Anat. of Vertebrates, vol. i p. 455 ; vol. ii p. 180 ; vol. iii. p. 504 Milne Edwards: Physiologie, tome iv. p. 462. Gegenbaur Vergleichende Anatomie, S. 857. Leipzig, 1870. 4 Physiologie Experimentale, tome ii. p. 312. VENOUS ABSORPTION. 199 brates, since these lymphatics contain always, even during digestion, with few exceptions, a clear, transparent lymph instead of chyle, an opaque, whitish fluid, the fat in these animals being taken up, not by the so-called lacteals, but by the portal vein, the greater part of it being thence carried to the renal veins (Jacobsen's system), and so to the vena cava. Inasmuch as absorption is carried on by the veins in the lower ani- mals, we would naturally infer that these vessels must be of great importance in this respect in man and the mammalia, That such is the case can be readily demonstrated experimentally. Magendie 1 appears to have been the first to show conclusively by experiment that absorp- tion takes place by the bloodvessels. Of his many remarkable and accurate experiments, the following may be mentioned : In one experiment, the abdomen of a dog that had been well fed some hours previously was opened, and a loop of the in- testine drawn out. Ligatures were placed around this loop at a distance of about fifteen inches apart, The lymphatics arising from this portion of the intestine being all ligated in two places, were divided between the ligatures. Of the five mesenteric arteries and veins passing into the general vascular system, four were divided and ligated so that the loop of the intestine remained in connection with the rest of the system by only a single vein and artery, even the cellular coat of which was dissected off, so as to remove all doubt of there being a trace of a lym- phatic left. Some upas was then introduced into the loop of the intes- tine prepared in the above manner, which was then replaced in the abdomen, and in a few minutes the characteristic symptoms of poisoning appeared, showing that the upas had been absorbed by the vein. In another experiment, where the poison was introduced into the foot, the only connection between the limb and the rest of the body was through two quills, introduced into the divided femoral bloodvessels, the rest of the parts having been dissected off. In this case, also, the only possible means by which the poison could pass into the general system and make its effects evident was through the circulating blood. The experiments of Magendie were immediately fully confirmed by Tiedemann and (linelm, 2 who showed, in an elaborate series of experi- ments, that different kinds of foods, odorous and coloring matters, saline and metallic substances were absorbed by the radicles of the portal vein as well as by the lymphatics of the small intestine. Segalas 3 modified the experiments of Magendie, and further con- firmed them by demonstrating that a poison like mix vomica, when introduced into the alimentary canal, fails to produce its characteristic effects so long as the circulation of the blood is interrupted, or when the blood carrying the poison from the intestine is allowed to escape from the vein and not pass into the general circulation. Magendie's experiments were also fully repeated and confirmed in this city by Drs. Harlan, Lawrence, and Coates, the committee ap- 1 Journal de Physiologie, p. 18 Paris, 1821. 2 Recherches sur la route qui preunent diverses substances pour passer d'Estomac et du Canal intestinal dans le Sang. Paris, 1821. 3 Journal de Physiologie, tome ii. p. 117. Paris, 1822. 200 ABSORPTION. pointed by the Academy of Medicine of Philadelphia to investigate the subject. 1 A convenient method of demonstrating venous absorption is to open the abdomen of a frog, withdraw a loop of the intestine, and ligate it Fig. 92. c aa. Intestine, b. Point of ligature of mesenteric vein. c. Opening in intestine for introduction of poison. d. Opening in mesenteric vein behind the ligature. (Dalton.) in two places, cut away all the mesentery, leaving only a single artery and vein, and introduce a solution of ferrocyanide of potassium into the intestine by an opening made in the latter, replace the loop within the abdomen, and, after a few minutes, open one of the veins of the foot. On testing the blood for the ferrocyanide of potassium by adding tincture of the chloride of iron, the presence of the salt introduced into the intestine will become at once evident, through the formation of Prussian blue, the latter being best demonstrated by adding the per- chloride of iron to the serum, the blood having been allowed to stand, or to a clear extract of the blood made by boiling the latter with a little sodium sulphate and filtering. It is obvious that the only means by which the salt of potassium could pass from the intestine into the general circulation, and thence into the blood of the extremities, was by means of the vein left in the mesentery. The above experiment is essentially the same as that per- formed by Panizza 2 upon the horse. We have seen that while the principal function of the lymphatics of the small intestine is to absorb fat, nevertheless they can and do take up albuminose, glucose, and water ; on the other hand, the mesenteric veins, in addition to absorbing these latter substances, take up also, at times, considerable quantities of fat. Briefly, then, the functions of the lymphatic and venous absorbents are essentially the same ; as a rule, however, the fats pass into the blood by the one route, the remaining alimentary substances by the other. i Phila. Journal of the Med. and Phys. Sciences, 1821, vol. iii. p. 273, am! 1822, vol. v. p. 327. 2 I)e l'absorption veineuse. Paris, 1843. ABSORPTION BY STOMACH AND RECTUM. 201 As digestion is only completed in the small intestine, Ave considered it most appropriate to begin the study of absorption there. It must not be supposed, however, that nothing is absorbed by the stomach. On the contrary, there can be little doubt that water and other liquids are very rapidly taken into the blood there, and also albuminose and whatever glucose may be present. Experiments made upon animals where the pylorus has been tied, and water introduced into the stomach, showed that in a very short time the liquid is absorbed by that viscus. The difference of opinion prevailing among experimenters in refer- ence to the absorbing power of the stomach is due, no doubt, to the fact that this differs very considerably in animals. Thus, water is absorbed very slowly by the stomach in the horse, arid in small quanti- ties, though very rapidly, and in considerable quantity, in the dog and rabbit. 1 So far as man is concerned, the case of Busch, 2 already referred to, showed conclusively the absorbing powers of the human stomach, almost all the sugar eaten being absorbed in this part of the alimentary canal, as well as a considerable quantity of the albumen. It is well known to physicians that human beings can be kept alive for months by enemata, the rectum absorbing very rapidly ; its capacity for taking up water, for example, is probably as great as that of the stomach. We have seen, also, that the rest of the large intestine absorbs to a large extent. As the digested food ordinarily, however, is absorbed before it reaches this part of the alimentary canal, further reference to absorption in this respect is not necessary. That the mucous membrane of the mouth is capable, also, of absorb- ing is shown from the effects observed when tobacco-juice is retained, even for a short time, in the mouth. Food, however, remains for such a short time in the mouth, that little chance is offered for its absorption in this part of the alimentary canal. Absorption by the skin and by serous cavities, and the influence of the nervous system and the circulation upon this function, can be more conveniently treated when these subjects are especially considered. We will pass on, therefore, to the study of the causes of absorption. l Colin, op. cit.. tome ii. p. 20. 2 Op. fit., p. 140. C IIAPTEK XII. OSMOSIS. We have seen that during absorption the digested food passes from the interior of the alimentary canal into the veins and lymphatics. The investigation of the causes of the phenomena of absorption resolves itself, therefore, into the determination of the conditions on which depend the passage of the liquid or semi-liquid albuminose, glucose, etc., and emulsified fat through the epithelium of the alimentary canal and the wall of the capillary or lymphatic into the blood or lymph. In physical science the diffusion of liquids into each other when sepa- rated by a membrane is known as osmosis. Let us consider, briefly, what is understood by the term osmosis, and see whether the facts of absorption that we have described can be explained by this principle. The name of Dutrochet is invariably associated with any discussion of the phenomena of osmosis. The history of the subject teaches us, however, that the discovery of this important physical principle, like that of all others, was not a sudden, but a gradual one. Many of the phenomena had been observed, and numerous experiments bearing upon the subject had been performed and recorded before the time of the distinguished French physiologist. The merit of Dutrochet consisted in not only devising and performing new experiments, but of generalizing the facts of osmosis, and applying them to the explanation of absorption in living beings. The first recorded experiment, so far as I have been able to learn, bearing upon the subject of osmosis, was performed as long ago as 1748 by the Abbe Nollet, 1 who, in investigating the causes of the boiling of liquids, showed that when a vial of alcohol covered with a bladder was immersed in water the bladder became convex, the water diffusing through the membrane into the alcohol, whereas, if the vial was filled with water, and immersed in alcohol, the bladder became concave, the water diffusing through the membrane from the vial into the alcohol. Nollet further showed that, while water passed readily through the bladder, alcohol only did so with difficulty and under pressure. In 1802 Parrot 2 observed that an egg, from which the shell had been removed, would absorb water, the liquid traversing the egg membrane. The fact, however, was only noted, no further application being made of it. Equally unfruitful were the observations of Soemmering 3 and Van Mons, 4 who, about 1812, called attention to the fact that spirituous liquors became more condensed through the evaporation of their water, 1 Memoires de l'Academie des Sciences, p. 101. Paris, 1748. 2 Bulletin scient. de l'Acad. de Petersburg, 1840, t. vii. p. 346. 3 Gilbert's Annalen der Physik, 1819, t. lxi. p. 104. 4 Annales gen. des sciences phya., t. i. p. 70. Bruxelles, 1810. EN DOS MO METER. 203 the vessels containing them are closed by membranous stoppers, the water passing through the membranes. Porrett, 1 in 1816, noted that a galvanic current influenced the passage of water through a membranous septum, the fluid accumulating around the negative pole. The observations just mentioned have for us now but little more than an historical interest, but the experiments of Lebkuchner, 2 in 1813, and Magendie, 3 in 1820, are very important still, as being the first in which it was positively demonstrated that various solutions would pass readily through membranes into the blood of the living animal. Lebkuchner showed that potassium ferrocyanide placed upon the jugular vein of a living rabbit in a few minutes passed into the blood, and could be detected in the blood of the jugular vein of the opposite side when tested for by adding sulphate of iron. Magendie dissected out the jugular vein of a dog, and placing it upon a card, poured upon it a solution of nux vomica, taking the precaution of not letting the poison touch anything but the card and vein, and observed in a few minutes the symptoms of poisoning. Important observations and experiments bearing upon the subject of osmosis, were further made in 1822, by Fischer, 4 of Breslau. This experimenter not only constructed what is now called an endosmometer, but showed that when the tube of the apparatus closed by animal mem- brane, and filled with a saline solution, was plunged into pure water, the water passed through the membrane into the saline solution, while the latter passed in the reverse direction through the membrane into the water. Fischer also noted some of the conditions influencing these currents, observing that they continued until the liquids were of the same density, and that they Avere active according to the thinness of the membrane used. Notwithstanding the value of the observations and experiment referred to in the above historical resume, they do not appear to have received from physiologists the attention they merited, and would not have assumed their present importance had it not been for the later investigations of Dutrochet. 5 This able investigator described thoroughly the passage of liquids through animal membranes : he showed the influence of different liquids used, measured the force of the currents, constructed the endos- mometer, and called particular attention to the currents, naming them endosmotic and exosmotic, according as they passed into the tube from the surrounding liquid, or in the reverse direction, and applied the facts to the explanation of physiological phenomena. Since then the subject of osmosis has been most thoroughly investigated by Graham. b This physicist discards the terms endosmosis and exosmosis, considering that there is but one current, the inward one, and designating it by the term osmotic, and the whole phenomena as osmosis. According to Graham, the molecules of the salt in the outward cur- rent travel by diffusion through the porous membrane. " It is not the 1 Annals of Philosophy, 1816, vol. viii. p. 74. - Archiv General de Sledeeine, t. vii. p. 439. Paris, 1825. 3 Journal de Phvs., tome i. p. 1. Paris, 1821. * Gilbert's Annalen der Physik, 1822, Band lxxii. S. 301. 5 Memoires pour servir a la llistoire Anatomiques et Phyaiologiques ies Animaux, tome i. Paris, 1837. « Osmotic Force, Phil. Trans., 1854, p. 178. 204 OSMO whole saline Liquid winch moves outward, but merely the molecule- of salt, their water of solution being passed, the inward current of water, on the other hand, appearing to be a true, sensible stream." According to this view, the only true current in the endosmometer ( Fig. 93) is that of the water from the jar (A) through the Fig. 93. membrane (C) into the bulbous tube (B) containing the yellow saline, consisting of a solution of potassium bichromate, the apparent outward movement from the jar (B) into the water in A, being due to the diffusion of the molecules of the salt. So far, however, as the physiologist is con- cerned, the important fact in this experi- ment is, that there is an exchange going on, the water passing one why. the -alt the other. A more delicate and interesting way of illustrating osmosis is to replace the jar of the last experiment with an egg prepared in the following way : At one end of the egg the shell is removed in such a way as to leave the lining membrane of the egg intact: at the other end, shell and membrane are both perforated sufficiently to permit the passing of a glass tube into the egg; the tube is beld securely to the egg by sealing wax. The a%'^ is then placed in a wine-glass of water, and the level of the water noted. Shortly after- ward the yellow of the ^^ will be Been rising in the tube, and the level of the i mm water falling in the wine-glass. The water of the glass gradually passes through the egg, distending if- ;ind forcing the content- of the membrane of d'^ upward. the On the other hand, the salts of the i-^^ — the chlorides, phosphates, sulphates — will be found to have diffused away from the rest of the egg into the water of the glass, as can be readily shown by appropriate tests. Thus, if a i'ttw drops of silver nitrate be added to the water, at once argentic ehloride will he formed and precipitated, showing that the sodium chloride ha- passed into the water. An important fact to be noted, the physiological significance of winch will be appreciated shortly, is that little or no albumen is found in the water, scarcely a trace of it, if any, passing through the egg membrane, particularly if the water be distilled. 1 In this experiment also, as well as in the preceding one. the substances on either side of the membrane (in the case of the egg, most of them at least] diffused into each other. Thi-. as we shall see in a moment, depends not only on the membrane apart Hialbe Cbimii appliqol a is physiologie, err., p. 130. B« lard Qaa ties Bopitaux, 1851, I 324 CAPILLARY ATTRACTION. 205 being capable of imbibing both liquids, but also that the latter were miscible with each other. If a membranous septum, however, be used, which will imbibe only one of the liquids, that one alone will traverse the septum, will increase the volume of the other liquid if it is miscible with it, but there will be no exchange. A convenient way of illustrating this, and also of showing thai a liquid septum will act in this respect in the same way as a membranous one, is to place in a vial some chloroform, and then pour gently on the chloroform water, and on the top of the water sulphuric ether, the water serving as the septum. In a short time it will be found that the ether has passed through the w r ater and has mixed with the chloro- form, so that instead of the vial containing three layers, ether, water, and chloroform, it contains only two — water on top, and a mixture of chloroform and ether below. The chloroform having no affinity for the water, will not pass through it: the ether, on the other hand, will not only pass through the water, but. being miscible with the chloroform, will diffuse into it, and so give rise to the result just described. Osmosis further will take place, semi-liquid substances being used as septa. Thus, if sulphuric acid and litmus water be separated by boiled gelatin, the acid will make its way through the gelatin, and will color the • © © litmus. The litmus, however, having but little affinity for the gelatin, diffuses but slightly into the gelatin, so that but little of the septum is colored. Having given several illustrations of osmosis, let us consider now the © © causes of the same. The phenomenon of osmosis depends essentially upon two conditions : first, that the membranous septum is capable of imbibing the liquids which it separates : second, that the liquids are miscible. It will be remembered that in speaking of the organic proxi- mate principles, allusion was made, among their other properties, to that of their taking or giving up of water. The swelling up of a tendon or muscle when immersed in water, and the giving up of the same when desiccated, are common examples of the imbibition by organic tissues of liquids. Every organic tissue and. indeed, all substances, however solid they may appear, are more or less porous, at least in the sense that the particles of which a body consist are separated to a greater or less extent from each other. It is through the presence of the interspaces, between the particles of which a tissue consists, that imbibition is possi- ble, that the tissue is capable of taking up a liquid, retaining it for some time, and finally giving it up again. 1 « © © I © The passage of a liquid into the interspaces or interstices of a tissue is, however, an example of capillarity, the particles of which the tissues consists bearing to the liquid passing through the spaces between them the same relation that the walls of a capillary tube bear to the liquid moving within them. The ascent of the oil in the wick of a lamp is a familiar example of capillary action. Imbibition, the first condition of osmosis, depending as it does upon capillarity, necessitates, for its understanding, a brief consideration of this principle. Capillary attraction, so called on account of its being usually observed in tubes of very fine hair-like or capillary diameter, 206 OSMOSIS. can be best understood if we confine our attention for the moment to one or two elementary physical facts. It is well known that if a drop of mercury be placed upon a perfectly clean plate of glass it rolls off' and falls to the ground, its globular form being preserved, the particles of the mercury being held together through the force of cohesion, and its falling from the glass being due to the want of any adhesion between the two substances. On the other hand, if a drop of water be placed on a similar plate or glass, the water becomes flattened, adhering to the surface, and when the glass is tilted the water runs to the edge, leaving a wet line, but does not fall to the ground, sticking to the plate in spite of gravity, the water being retained by the glass through the force of adhesion. If the plate be first greased, then the drop of water will behave like the drop of mercury, and for the same reason, the water not adhering to grease falls like mercury to the ground. There are, therefore, two forces, that of cohesion and adhesion. Through the first the particles of a sub- stance are held together or cohere ; through the second, the particles of one substance are attracted by those of a dissimilar one, or adhere. Let us modify the preceding experiment by partially immersing a clean glass plate in a vessel of water. It will now be noticed that the surface of the liquid in contact with the glass is slightly elevated, and that this elevation gradually diminishes until the level of the remain- ing liquid is reached. (Fig. 94.) It is very evident from what has just Fig. 94. Fig. 95. been said of adhesion and cohesion, that the different elevation of the water will be due to the relative strength of these two forces, the eleva- tion of the liquid being highest where the liquid is in contact with the glass, adhesion being there at a maximum, cohesion at a minimum, and that the elevation will gradually diminish, the force of cohesion increasing, that of adhesion at the same time diminishing. Suppose, now, that we immerse a second plate of glass in the water parallel to the first, the water will be most elevated where the liquid comes in contact with the glass, the elevation diminishes as the distance from the second plate is increased, and the general surface of the water will be indicated by the curve (Fig. 95), the lowest point of the water being equidistant from the two glass plates. As the two glass plates are approximated, naturally the elevation of the water will be increased (Fig. 96), since the quantity of water being continually diminished, the MISCIBILITY OF LIQUIDS. 207 force of adhesion at the same time increases in proportion to the rela- tively greater surface of glass exposed. In a word, the elevation of the liquid is inversely as the distance of the plates. Fig. 96. If we now immerse two more plates of glass parallel to each other, and perpen- dicular to the first two, we shall have a four-sided glass arrangement, to the inside of which the water will adhere. The transition from such an apparatus to a capillary tube is, either theoretically or practically, a simple one, the conditions being in the latter essentially such as we have described. Modern 1 theory deduces, then, the form and elevation of the liquid in capillary tubes as the resultant of the forces of adhesion, cohesion, and, of course, gravity. Inasmuch as these conditions are all present in the phenomena of imbibition, we are justified, as already observed, in regarding this an example of capillary action, the adjacent par- ticles of a body being comparable to the plates of glass, or the side of a tube, the interspaces between them to the space between the plates, or within the tube, and the water to the liquid imbibed. In order that an osmosis should take place, it is evident that the membranous septum must be not only capable of imbibing the liquids through capillary action, but further, that the liquids separated by the septum must be miscible, otherwise, though the liquids might get into the septum, they would not diffuse into one another, and there would be no current. This brings us, therefore, to the consideration of the second condition of osmosis, the diffusion of liquids. It is a familiar fact that, if a drop of water rolling over a surface, upon which it can preserve its globular form, comes in contact with a drop of mercury, or of oil, the drops do not run into each other or fuse, the particles of the drop of water having a greater affinity for each other than for the particles of the drop of mercury or of oil, and vice versa. On the other hand, if the drop of water meets with a drop of alcohol, the two do run into each other, losing their identity, the par- ticles of the water having a greater affinity for those of the alcohol than they have for each other. A simple illustration of the diffusion of liquids is to place in a small vial a solution of copper sulphate and im- merse the vial containing the solution into a vase of water. Soon the surrounding water will assume a blue color through the diffusion into water of the copper. The dissolving of a substance in a menstruum is an illustration of the same principle, the molecules of the dissolving liquid having a greater affinity for the particles of the substance to be dissolved than these have for each other. The solution of a substance, however, depends not only upon the affinities, chemical or physical, existing between the par- 1 La Place : Mecaniipie celeste snpp. au liviv x. Euvres t. iv. p. 389. Gauss : Comment Soc. scient. Gott., vii. p. 39, 1829-1832. Canot: Physics, trans!, by Atkinson, p. 98 Loudon, 1870. W'eisbach : mechanics, transl. by Coxe, vol. i. p. 762. SVv. V..rk. 1872. Maxwell: Theory of 11. at, p. 2>n. >,V\v York, 1877. 208 osmosis. tides of the substance and those of its menstruum, but also upon the fact that when the cohesive force holding together these particles ceases to act the particles become separated, repel each other, they acting then like the particles of a gas. Thus, if ice be dissolved by sulphuric acid, the latter will diffuse equally through the water, whatever the volume of the latter may be. The diffusion of liquids depends, therefore, upon the affinities existing between the particles of which the liquids consist and a repelling force of the same. Many interesting and important facts in reference to the diffusion of liquids have been established, more particularly by the researches of Graham. 1 It is not essential, however, that we should dwell upon these, merely indicating that the diff'usibilitv of liquids differs very much, according to their density, composition, the character of the septum, temperature, etc. On account, however, of its important application to physiology it is necessary, before leaving the subject of diffusion, to call attention to the distinction made by Graham between what this physicist calls crystalloids and colloids, and which can be well illustrated by the fol- lowing simple experiment : If a piece of potassium bichromate, or a little of the same substance in powder, be placed in the centre of a mass of boiled starch, in a few hours the whole of the starch will be seen colored, the potash having diffused through it. On the other hand, if a piece of caramel be similarly placed on a mass of boiled starch, it will remain where placed, not diffusing at all. Substances which diffuse readily, like the salts of potassium, are termed crystalloids, while those that do not do so are called colloids. Thus, in the experiment with the egg, the sodium chloride, being a crystalloid, diffuses through the egg membrane, while the albumen, being a colloid, remains within the egg. The method of dialysis of Graham, so useful as an instrument of analysis, is based upon this distinction of crystalloids : thus, if a fluid, consisting of a mix- ture of organic matter and arsenic, be placed in an endosmometer, in the course of twenty-four hours, perhaps, three-fourths of the arsenic will diffuse through the membrane into the surrounding water, the organic matters remaining within the jar. The application of the facts of capillarity and diffusion in the explanation of osmosis, as illustrated by the above experiments, is so evident, that it may appear superfluous to dwell further upon the subject. We will, therefore, merely call attention to the most important conditions. In all the experiments which have just been described it is perfectly clear that the first condition of osmosis is that the liquid shall wet the membrane, or, in other words, that the membrane is capable of imbi- bition. This, we have seen, is due to capillary force. The second condition is, that the liquids having been imbibed by the membrane are miscible, or will diffuse, otherwise they would get no further than the interstices of the membrane, and there would be no currents. The modifications of the phenomena, according to whether the septum is solid, liquid, or semi-solid, as to whether the current is cndosmotic or i Phil. Trans., 1850 CONDITIONS FAVORING ABSORPTION. 209 exosmotic, of the relative force of the two, etc., can be shown to depend upon these two conditions. Having gone over this preliminary ground, let us now see whether the established facts of capillarity and diffusion, and the theorv of osmosis deduced from them, can be applied to the explanation of absorption, as it takes place in the living body. During absorption from the alimentary canal we have seen the digested food in a liquid or semi-liquid state pass through the epithe- lium, and the wall of a capillary or lymphatic into the blood or lymph. The epithelium and capillary wall in the living body are comparable, therefore, to the septum of the endosmometer, the liquids in the intes- tinal canal and the blood and lymph corresponding to the fluids sepa- rated by the septum in that instrument. The action of a hydragogue cathartic, such as magnesium sulphate, is also an illustration of osmosis, since the salt passes from the interior of the alimentary canal through the epithelial layer of the intestine and wall of the capillary into the blood, and the watery part of the blood, together with some albumen (the latter effect being due, probably, to the presence of the saline), passes into the interior of the alimentary canal. The osmosis can be experimentally imitated by placing the solution of the magnesium sulphate within the jar of the endosmometer and the serum of the blood within the bulbous tube, the serum passing through the membrane into the magnesium sulphate, and the latter passing into the serum and increasing its volume. Supposing that the jar represents the alimentary canal, and the bul- bous tube the bloodvessel, the osmosis going on in the experiment is essentially the same as that in the living body after the administration of a hvdragoffue cathartic. The only essential difference between the osmosis that takes place during absorption and after the administration of a saline and in an endosmometer is that the conditions which favor osmosis are realized in a way and to an extent in the living body that cannot be imitated for a moment, even in the most delicate experiments. Thus, it has been found that the activity of osmotic currents is in proportion to the extent and thinness of the membrane. When we come to study the capillary system we shall see that the extent of absorbing surface exposed by it is enormous, and that the walls of the capillaries are extremely delicate, measuring, on an average, perhaps from the 12 Q ((() th to the •? 5 o o o th °f an i ncn m diameter. One can readily imagine how favorable such a thin septum would be in the production of osmosis. It can be shown, also, as might have been supposed, that an endosmotic current is favored by having little or no pressure to overcome, such a current ceasing and beginning again, according as dense substances, like mercury, are added to or taken away from the fluid within the tube of the endosmometer. Now in the living body the pressure of the blood, even in the largest arteries, seldom exceeds six inches of mercury, and this pressure is very much reduced as the blood flows into the capillary and venous system, so that a current flowinn; from the intestine toward the blood meets with no very great resistance. 14 210 OSMOSIS. An important, though not indispensable, condition favoring the endos- motic current is the density of the solution in the bulbous tube of the endosmometer, the flow being usually greater according to the density of the solution. We find this to be the case, also, in absorption from the intestinal cavity, the endosmotic current being active in proportion to the amount of albumen and salts in the blood. Hence the activity of absorption after the administration of hydragogue cathartics, such drugs diminishing the watery constituents of the blood, and so increasing- its density, while, at the same time, they diminish pressure. Again, osmotic currents are more active if the liquids are kept in movement. Thus, when osmosis has ceased, it can often be made to commence again by simply stirring the liquids. It is evident from this how great and favorable are the influences exerted by the circulation of the blood and lymph in promoting osmosis and absorption. The importance of the movement of the liquids, or of one of them, in favoring osmosis is shown by the simple apparatus represented in Fig. 97. A jar (B), furnished with two stopcocks, is filled with a colored Fig. 97. fluid, litmus water, for example. To both stopcocks are fitted equal portions of intestine (D and C), which are immersed in the vases of water E and A. Into the piece of intestine C is fitted a siphon (G) of smaller diameter than that of the intestine, a siphon (F) of as large diameter being inserted into the piece of intestine D. Both siphons (F and G) pass into the vases H and I. The stopcocks of the reservoir (B) being opened, the colored fluid will flow into the two pieces of intestine, but inasmuch as the small size of the siphon G will offer an obstacle to the flow of the colored liquid through it into the vase I, the piece of the intestine G will become distended, and there will be an exos- mosis from it of the colored fluid into the water of the vase A. On the other hand, the colored fluid passing readily through the siphon F, on account of its large size, the piece of intestine D will become flaccid, and there will be a rapid flow of the water of the vase E, through the intestine D, into the colored fluid flowing through it, or an endosmosis. RESUME OF ABSORPTION. 211 Finally, an increase of temperature promotes osmosis ; the high tem- perature of the living body is, therefore, another favorable condition in producing this phenomenon. It is very probable, also, that electrical action may influence the production of osmotic currents in the living body, as we have seen to be the case in the experiments of Porrett. At present, however, no definite statement can be made as to the influence electricity may exert upon absorption. It will be remembered that, in the experiment with the egg, attention was called to the fact that no albumen passed through the membrane from the egg into the water of the glass. So it is with the albumen of the blood, the flow of the contents of the intestine being toward the albumen of the blood, as the flow of the water is toward the albumen of the egg. Indeed, albumen is one of the most powerful of endosmotic substances. On the other hand, albuminose is readily absorbed by the bloodvessels ; the significance of the conversion of albumen into albumi- nose by the gastric juice becomes now very evident. The theory of absorption that we have just sketched is that almost universally accepted by physiologists, at least so far as concerns the absorption of albuminose, glucose, salts, water, etc. There are, however, still differences of opinion as to whether the absorption of fats can be explained in this way. It seems to us that the want of success in demonstrating the passage of fats through mem- branes out of the body has often been due to the fact that the proper conditions for the success of the experiment were not realized. It will be remembered that, during digestion, the fat is emulsified, and becomes mixed with the bile, alkaline fluids, etc., and that, during absorption, this modified fat passes into an alkaline fluid, the lymph. It is essential, therefore, that these conditions should be fulfilled if we wish to demonstrate the osmosis of fat out of the body. First, then, we must make an emulsion of fat, for example, by adding pancreatin to olive oil, and then make this distinctly alkaline by adding bile or a sodium salt. Place the alkaline emulsified fat in the jar of the endos- mometer, making the water of the bulbous tube distinctly alkaline also, so as to resemble the alkaline lymph. If the water in the reservoir be examined some hours afterward, the fat will be found floating in drops upon the surface, it having osmosed through the membrane. Resume. — We have seen that, as fast as the food is digested, it is absorbed, the albuminose, glucose, salts, and water being taken up by the radicles of the portal vein, the fats by the lymphatics of the small intestine, or the lacteals, often a small quantity of albuminose, etc. , passing into the lymphatics, the portal vein taking up, also, occasionally, some fat, and that the absorption of food is an illustration of osmosis, the latter depending upon capillary attraction and the diffusion of liquids. Whichever of the two routes is taken by the digested food in absorp- tion, the essential fact is that it gets into the blood sooner or later, and thence is carried by the circulation to all parts of the economy, repairing the waste of the tissues and supplying the fuel for the main- tenance of the heat of the body and development of force. The composition and circulation of the blood will be, naturally, then, the next subject for our consideration. To these, then, let us now turn. CHAPTER XIII. THE BLOOD. From time immemorial the blood lias been recognized as the most important fluid in the human body, as well as in that of animals — in- deed, as indispensable to life. Daily observation continually shows that its loss prostrates the body and enfeebles its powers, and, with excessive hemorrhage, that life itself ebbs away, " For the life of the flesh is in the blood." This is readily understood when it is known that the blood circu- lating- through the economv is the source of the animal heat, and carries to the tissues, and the cells composing them, material for their growth, renewal, and repair, and, at the same time, removes from them that which has become effete and worn out in producing the phenomena of life. This " peculiar juice," as the Mephistopheles of Goethe calls it, represents, therefore, the life of the day, of the past, and of the morrow. Let us consider first its physical characteristics. The blood is an alkaline fluid, with a specific gravity, when defibri- nated, according to Becquerel and Rodier, 1 of from 1.05;") to 1.063. The opacity of the blood is due to the fact that it is not a homogeneous liquid, being composed, as we shall see presently, of two elements — cor- puscles and liquor sanguinis, or plasma ; these, differing in their refractive power, offer an obstacle to the transmission of light, which is lost in its passage from the air through the liquor and corpuscles. The hlood has a saltish taste, and a faint but distinct odor. This becomes more apparent when a few drops of sulphuric acid are added to the specimen examined. It may be mentioned, in this connection, that the importance of the odor of the blood, as made use of in criminal cases, and often insisted upon by medico-legal writers, has been grossly exaggerated. The temperature of the blood in man, so far as is known, varies from 80° to 100° Fahr., but it is very probable that, in certain parts of the body, it is several degrees higher. Bernard found that in dogs and sheep the temperature in the aorta ranged from 99° to 105°, and reached even 107° in the hepatic vein. According to the same authority, the blood is hotter in the right than in the left side of the heart ; the temperature is higher in the arteries than in the veins, with the exception, however, of the blood in the portal vein, which is warmer than that in the aorta independently of digestion. 2 The sudden rise of temperature often observed in man just before death, due, perhaps, to the loss of vascular tonicity, would seem to show that the temperature 1 Traite de Chemie Pathologique, p. 95. Paris, 1854. 2 Sur los Liquides de l'Organisme, tome i., 3d, 4th, 5th lecons. QUANTITY OF BLOOD IN HUMAN BODY. 213 of the blood in the deeper vessels in man is as high as that observed by Bernard in the animal just mentioned. One of the most striking features of the blood is its color, red or scarlet in the arteries, blue or black in the veins. As first demonstrated by Lower, 1 this difference is due to the venous blood absorbing air as it passes through the lungs. When we come to study the circulation and respiration, we shall see that, as the red blood passes through the capillaries it loses oxygen and gains carbonic acid, becoming blue, while it turns again into red blood in the lungs with the fresh absorption of oxygen. The blood of the pulmonary artery, however, is blue, while that of the pulmonary vein is red. The blood in the veins coming from glands, during secretion, as shown by Bernard, 2 is also red, and this is the case also in the veins when the sympathetic is cut. The explana- tion in these cases seems to be that the increased supply of arterial blood to the parts carries an excess of oxygen to the veins sufficient to maintain the red color of the blood flowing into them. The brightness in color of the blood depends, to a certain extent, upon the form of the corpuscles ; it is bright w hen they are flattened and hollowed, containing oxygen, and dark when they are distended and round, containing carbonic acid, the reflection of the light depend- ing on the form of the corpuscles. Numerous experiments have been made from time to time to deter- mine, if possible, the quantity of blood in the human body. Among others may be mentioned those of Valentin, Blake, Lehmann, and Weber. Valentin's method 3 consisted in injecting into the circulation of an animal a given quantity of a saline solution and then drawing some blood, estimating by evaporation the proportion of the w 7 aterto the blood, and then comparing the excess of water with that of a quantity of blood drawn previously. Suppose that the excess of water in the specimen drawn after the saline injection w r as one part of water to ten of blood, and that five ounces of water had been injected, then the quan- tity of blood would be fifty ounces. Blake 4 experimented by injecting sulphate of aluminium and then ascertaining the amount of the sulphate in a given quantity of blood drawn, arguing that the wdiole quantity of the sulphate injected was to that in the specimen drawn as the whole quantity of blood in the body was to that drawn. The observations of Lehmann 5 and Weber were made upon tw T o crim- inals who were first w r eighed and then decapitated. The blood remain- ing in the vessels after decapitation was calculated by injecting water into the vessels of the head and trunk until that which passed out by the veins exhibited only a pale yellowish color. This was evaporated and the dry residue was assumed to represent a certain quantity of blood, the ratio of blood to its residue having been previously ascer- tained. The amount of blood lost by decapitation was a little over twelve pounds, and that estimated by the above method as remaining i Tractatus de Corde item de Motu et Colore Sanguinis, p. 180. Amstelodarui, 1669. - Op cit., pp. 268, 299. : Repertorium fur Anat. und Phys., 1837, Band ii. S. 281. * Philadelphia Medical Examiner, August, 1841'. 5 Lehrtrach der Phys. Chemie, L852, tome ii. S. 234. 214 THE BLOOD. in the vessels as a little over four pounds, making for the whole hody 16.59 pounds. Table XL. 1 — Amount of Blood in the Body. 12 lbs. of blood lost in execution. 4 " of blood collected by washing. 16 " of blood in criminal weighing 128 lbs., or 1 " of blood to 8 of body weight. The weight of one of the criminals was 132.7 pounds ; this would give a ratio of about one pound of blood to every eight of body, which is about what physiologists generally assume. It must be remembered, however, that this is only an approximation, for the amount of blood left in the body after decapitation cannot be accurately determined by the method just mentioned. Further, the amount of blood in the body is notably increased during digestion. Bernard 2 has shown that an animal like the rabbit, for example, during digestion can lose twice as much blood as when fasting. Burdach 3 refers to a case reported by Wrisberg of a woman losing over twenty-one pounds of blood after de- capitation. Facts like these show the importance of taking into con- sideration the state of the system in determining the quantity of blood. In a general way this may be stated in an adult healthy man to amount to sixteen or twenty pounds and is distributed, according to Ranke, 4 in round numbers as follows : \ vascular system. J skeletal muscles. ', liver. I remaining organs. When the blood is examined under the microscope, for example, cir- culating in the web of a living frog's foot, it will be seen to consist, as already mentioned, of two distinct portions, a transparent colorless liquid, the liquor sanguinis or plasma, and of minute bodies or corpus- cles, the blood globules or blood cells. These corpuscles, which float in the liquid part of the blood, are of two kinds, the white and the red. The latter, discovered by Leuwenhoek 5 in 1673, are far more numerous than the former and give to the blood its red color, they being carriers of oxygen. Let us study the red corpuscles first and then the white, reserving for the present the consideration of the plasma. When blood is examined under the microscope the corpuscles will be observed in different positions, some on their edges or sides, others lying flat (Fig. 98). It can be seen that they are circular, flattened disks, about four times as broad as thick and biconcave in form. From this latter circumstance they are thinnest in the centre. Therefore, when a corpuscle is viewed under the microscope from the flat side, if the edges are in focus the centre will appear dark, simulating a nucleus (Fig. 99) ; wdiereas, when the centre is in focus and is light the edges will appear dark (Fig. 100). In reality, however, there is neither a nucleus nor a membranous cell-wall, the red corpuscle being a homogeneous structure- 1 Lehniann, op. cit. 2 Op. cit., tome i. p. 419. 3 Traite de Physiologie traduit, par Jourdain, tome vi. p. 116. Paris, 1837. * Phvsiologie, 1871, S. 373. 5 philos. Transactions, p. 23. London, 1674. RED CORPUSCLES. 215 Fig. 98. less mass of living matter, soft, transparent, elastic, and of a pale amber color. The red color of the blood is due to the immense number of the corpuscles. Vierordt 1 estimates that a cubic millimetre in the male contains 5,000,000, in the female 4,500,000. The method we make use of in counting the blood corpus- cles is essentially that of Malas- sez and Potain 2 and Gowers. 3 It consists in sucking up into a graduated tube (Fig. 101, A) one cubic millimetre (^g-th of an inch) of blood and then a five per cent, solution of sodium chloride from a jar into the tube until the blood and the solution are drawn into and fill the dilated portion (Fig. 101, B) of the tube. This dilated portion hav- ing a capacity of 100 milli- metres, the blood will then be diluted 100 times. One milli- metre of this mixture will, there- fore, contain the y^nj-th of a millimetre of blood and the of a millimetre of the or the md salr s Human blood as seen on the warm stage Magnified about 1200 diameters, c, c. Crenate red corpuscles, p. A finely granular, g. A coarsely granular pale corpus- cle. Both exhibit two or three vacuoles. In g a nu- cleus also is visible. (Quain.) 1 tl 10 ll mixture y^-jyth of ywo tn mixture of blood 1 1 th of a millimetre of blood. This olution is then forced out on an object glass Fig. 99. Fig. 100. Red globules of the blood, seen a little beyond the focus of the microscope. (Dalton.) The same, seen a little within the focus. (Dalton.) l Physiologie, S. 9. Tubingen, 1871. - Aii hiv de Physiologie, p. ;!:>. Paris, 1876. S Lancet, 1877, p. 797. 211) THE BLOOD. (Fig. 102, C) which under the microscope is seen to be divided into ten squares, each of which when covered by the compressorium (Fig. 102, D) Fig. L01. Fig. 102. Graduated moist chamber with compressorium. has a capacity of the yg-g-th "^ a millimetre. Each square will then contain the y^-g-th of a millimetre of the mixture, and consequently will contain the y^tl! of -1— th 1 o o U1 Further, or tht 4-n-n-th of a millimetre of blood. ioo oo; it will be noticed that each square (Z>) is subdivided into twenty smaller squares, the object of which is to facilitate the counting of the corpuscles. Suppose now, for example, that twenty-five corpuscles could be counted on each of the small squares, then the large square would contain 500 corpuscles; but as the large square contains only the 10 ooo tn °^ a uiillimetre of blood, it follows that one cubic millimetre (^g-th of an inch) will contain 500 x 10,000, or 5,000,000 corpuscles. The division of the object glass into ten squares is to enable one to make ten independent observations, so as to obtain an average result. A cubic inch of blood will contain, therefore, over 70,000,000,000 red blood - corpuscles, or, according to Huxley, 1 more than eighty times the number of people upon the globe, or on the supposition that the blood of the whole body amounts to sixteen pounds or 112,000 grains, and that one cubic inch of blood weighs 168 grains, the whole blood will contain over forty trillion red corpuscles. 112(HMI 168 = 607 X 70,000,000,000 = 40,000,000,000,000 corpuscles. The specific gravity of the corpuscles is a little higher than that of the liquor sanguinis, being about 1.085. On observing the corpuscles in blood removed from the body, it will be noticed that soon a number of them run together, forming a chain-like rouleaux of coin (Fig. 98). Elementary Physiology, London, 3 1 id., p. 78. RED CORPUSCLES. 217 This is due, according to Robin, 1 to an exudation from the corpuscles themselves which causes them to adhere to each other. Shortly after the blood is drawn the corpuscles will exhibit also small prominences on their surfaces, giving them a raspberry-like appearance, and as they become dry they shrivel up and their edges become crenated (Fig. 98). The shape of the corpuscles, however, can be restored even after the lapse of months and years by treating them with a fluid of the density of serum (1.028). This fact is important, from a medico-legal point of view, in reference to determining whether a stain upon clothing or floors, etc., is blood. The corpuscles swell up and dissolve when pure water is added to them, and acetic acid and other acids have the same effect. Under the influence of alkalies the corpuscles instantly swell up, appear to burst, and then entirely disappear. The effect of heat is to produce in them bud-like processes. In studying the effects of such reagents as those just mentioned, as well as others, the apparatus repre- sented in Fig. 103, which is to be placed on the stage of the micro- Fig. 103. Strieker's warm stage. s*cope, will be found useful. It consists of a brass box opening laterally by two tubes, with a solid rod-like projection in the middle, and per- forated in the centre. The central aperture can be converted int<> a chamber by cementing to its lower opening a cover glass. Surround- ing this central chamber is coiled the bulb of a thermometer, whose registering surface is attached externally to the side of the box. 1 Journal de la Phy-iolosie, tonic i. p. "295. Paris, 1858. 218 THE BLOOD. By connecting one of the lateral apertures opposite the projecting rod of the box with the reservoir of hot water and the other with a waste pipe a constant flow of hot water through the brass box is insured, and the temperature of the central chamber regulated as desired by the thermometer. By screwing on to the rod-like projection of the brass box a rod of the same metal and heating its free end by a spirit lamp, the tempera- ture can also be elevated as required. If it is desired to study the action of water upon the blood corpuscles, for example, the apparatus is used in the following way : A drop of water is placed on the floor of the chamber, and a drop of blood, usually diluted with salt solution, upon a cover-glass ; the latter is then placed inverted over the chamber, the edges of which have been previously oiled or surrounded with a ring of putty, so as to make the chamber air-tight. By allowing the hot water to flow through the brass box, or heating the end of the rod by the spirit lamp, the drop of water on the floor of the chamber is made to evaporate, and, condensing on the under surface of the cover-glass, gradually affects the blood-corpuscle it meets there. The effects of heat simply upon the blood corpuscles can be studied by placing the blood to be examined upon a cover-glass, and dropping this upon another glass of the same size, the edges of which have been previously smeared with oil, and then placing the two glasses with the blood and oil so inclosed over the opening of the chamber. Further, by means of the tubes which open into the chamber, a current of gas can be made to pass through the latter, and its effects studied upon the blood placed upon a cover-glass and inverted over the chamber, in the manner just described in studying the effect of water. The effect of electricity upon the corpuscle is to convert it temporarily into rosette-, mulberry-, and finally horsechestnut-shaped forms. To demonstrate this effect, we usually make use of the electrical microscopic stage, placing the drop of blood upon the slide in such a position that when covered it spreads out between the two poles of tinfoil, Avhich are about six millimetres apart and connected either with a Leyden jar having a surface of 500 square centimetres, or by a Du Bois-Reymond induetorium fed by a single Bunsen cell, according to the kind of electricity to be used. According to the high authority of Gulliver, 1 the average diameter of the red blood-corpuscle is the ^Vo^ 1 of an inch, with an average thickness of about the T^Foth of an inch. The diameter, however, varies as much as from the ygVo^ 1 to tne 40^0^ °f an i ncn - The importance of remembering these variations will be seen presently. 1 In Works of William Hewsou, Sydenham edition, p. 237. London, 184'i. DIAMETERS OF RED BLOOD-CORPUSCLES. 219 Table XLI. 1 — Blood Corpuscles. Mammals. Animal. Manatee . Elephant Ant-eater Sloth Whale . Camel Man Orang Chimpanzee Dog. Opossum . Rabbit . Black Rat Mouse Bmwn Bat Cray Squirrel Ox . Cat . Sheep Goat Pigmy Musk Deer ( >strich . Owl . Swan Pigeon Turtle Viper Lizard Birds Reptiles. Diameter. 1 of an inch. 2700" 1 U ,i ^745 1 a a 27(39 1 a it 2865 1 a t. 3099 1 it a 3123 1 " 3200 1 tt 3383 1 a a 34lT 1 it a 3542 1 a (i 3557 1 it 3607 1 a ,t 3754 1 a . . 3814 1 a it 3911 1 a t. 4000 1 a a 4267 1 4404 1 a t. 5300 1 a 6366 1 a it 12325 1 a a 1649 1 n a 17(33 1 n t. 1806 1 a t . 1973 1 a a 12.il 1 a 1274 1 it a [555 1 Drawn up principally from table of Gulliver, op. cit , p. 237, and observations of author. 220 THE BLOOD. Amphibia. \iiimal. Diameter. A.mphiuma ...... of an inch. 1 363 Proteus . Siren Menopoma i 40(1 1 42U 1 Pushes. i 20(1(1 Perch L 20 1 2134 Pike Lamprey While there is not always a proportional relation between the size of the blood corpuscle and that of the animal — that of the ox, for ex- ample, being smaller than that of man or the dog (Table XLI.) — Milne Edwards 1 has shown by a comparison of the size of the blood corpuscle in the five classes of vertebrates, that there does exist a most remarkable connection between the size of the corpuscle and the degree of nervo- muscular power of the animal ; the corpuscles being small in the most highly developed and active vertebrates, and large in those least so. It will be seen also, more particularly, that the size of the corpuscle is most intimately related to the activity of the respiration, the corpuscle being smallest in those animals whose respiration is the most active, and largest in those in which this function is slow. This might be expected, as a large number of small corpuscles offer a larger absorbing surface to the oxygen, the respiratory element, than a small number of large ones. As we proceed we shall see that muscular is largely dependent upon respiratory activity. Hence, if the above view be correct, we should expect to find the blood corpuscles smallest in the active verte- brates and largest in the sluggish ones. On comparing the size of the blood corpuscles in the mammalia with those of the reptilia or batrac'hia (Table XLI.), we find such to be the case. Of course, if this comparison be carried out to extreme detail, there will be found exceptions to the rule, for no doubt other conditions beside those of respiration influence the size of the corpuscles, possibly the character of the food, etc.; but that the connection just referred to is something more than mere coincidence seems to be fully justified by Milne Edwards's elaborate survey of the facts. It will be seen from Table XLI. that there are a few mammals in which the blood corpuscles are larger than those of man, and that the blood corpuscle of the pigmy deer (Tragulus) is the smallest known, while those of a batrachian, the amphiuma, are the largest. The exact size of the red blood-corpuscle in man is not only of interest physiologically, but also from a medico-legal point of view. Attention has already been called to the fact that there is a consider- able variation in the size of the human corpuscles, and hence it is often impossible to say positively whether a given corpuscle came from a human being's blood or that of an ape, dog, rabbit, rat, mouse, or ox, 1 Physiologie, tome i. p. 57. RE]) BLOOD-CORPUSCLES OF VERTEBRATES 221 for the average diameter of the corpuscles in these animals is within the limits of the variations that have been mentioned as occurring in man. When a large quantity of human blood is examined, probably ninety- five corpuscles out of every hundred will exhibit the same diameter, but in a medico-legal investigation the amount of blood put at the disposal of the expert is often exceedingly small — an old blood-stain, a single drop, perhaps, and possibly the variable corpuscles contained in this very drop. Now, as the size of the corpuscle in the dog or the ox varies as well as that of man, if the size of the corpuscle in the suspected fluid is only taken into consideration, the blood of a dog might be determined to be that of a man, and vice versa. In fact, it is impossible to say beyond the shadow of a doubt that a given drop of liquid is human blood and not that of the animals referred to above, for the small size of the variable human corpuscle might lead the examiner to think the human blood had come from a dog or a mouse, while from the variable large corpuscles in the blood of these animals there might be a suspicion that their blood was human. With the exception of the camel and llama, in which the red blood- corpuscles are oval, the form of these bodies in the mammalia thus far examined is circular, which adds to the difficulty of distinguishing the Fig. 104. Typical char blood of the domestic mammals from that of man. On looking at Fiji. 104, it will be seen that the red blood-corpuscles in birds, reptiles, batrachia. and fishes differ from those of man and the mammalia gener- 222 THE BLOOD. ally in being oval in form and in exhibiting a well-marked nucleus, and in being much larger. The only partial exceptions to the above statement are offered by the oval corpuscles of the dromedary and llama; but, as will be seen from Fie 104, they are not nucleated. At the other end of the vertebrate series we find a further exception, in the nearly circular corpuscles of the lamprey, but these are nucleated. There can be no difficulty, therefore, in distinguishing the blood corpuscles of the birds, reptiles, etc., from those of mammals. The oval form, and the presence of a nucleus, especially, are sufficient to decide positively that the blood containing such corpuscles is not mammalian. Such knowledge has been of advantage more than once in assisting in the detection of murder. The most important use of the red blood-corpuscles is undoubtedly as carriers of oxygen. Blood will absorb ten to thirteen times as much oxygen as water, and this property depends upon the corpuscles. In addition to the facts already referred to of the connection between the respiratory power and the corpuscles, it may be mentioned that the number of corpuscles is greater in the active carnivora than in the more sluggish herbivora, and that in man in those individuals whose nervo- muscular energies are most developed we find the greatest number of corpuscles, whereas in the ansemic the number falls below the standard. Vital activity of all kinds, respiratory, nervo-muscular, etc., necessi- tates a constant and free supply of oxygen, and this want is preemi- nently filled by the circulating blood carrying the red corpuscles laden with the indispensable element. Even apparent exceptions, like the absence of the red corpuscles in insects offers, are really no exceptions to the above statement of the importance of oxygen, for in those animals which exhibit such remarkable nervo-muscular power the oxygen is car- ried directly to the tissues by the tracheal system or tubes permeating their entire bodies, and hence there is no necessity for red blood- corpuscles. In the remaining vertebrata the amount of carbonic acid and heat produced and nervo-muscular power put forth are about what might be expected from the character of their blood and the corpuscular elements contained in it. In concluding this sketch of the red blood-corpuscles, it is proper that I should give, if possible, an account of their origin, for there is no doubt that the life of the blood corpuscles is of limited duration. Abundant evidence of their disintegration is to be seen in different parts of the economy, in the spleen and in the liver for example, in the form of blood crystals, and, as we have seen, in speaking of the coloring matter of the bile, that the bilirubin is polymeric with the coloring matter of the blood or hgematin, it is probable that the bilirubin is de- veloped out of the corpuscles disintegrated in the liver. According to some physiologists, the origin of the red corpuscles is entirely unknown, while it is held by others that they are developed in some way out of the white corpuscles of the blood. To appreciate the facts brought for- ward in favor of the view that the red corpuscles are modified white ones, it will be first necessary to describe the latter, which up to this time have been only incidentally alluded to. To the consideration of the white corpuscles let us now turn. CHAPTER XIV. THE BLOOD.— (Cbntinued.) The white corpuscles discovered by Hewson 1 about 1770. as their name implies, are of a grayish, whitish color, of a round form, and con- sist of a mass of protoplasm containing granules. A cell wall cannot be said to exist. Chemically the white corpuscles are composed of albuminous substances, lecithin, glycogen, salts. 2 When the blood is maintained at the temperature of the body the form of the white corpuscle is seen to be constantly changing, alternately protruding and retracting its body substance in an amoebiform manner (Fig. 105). By adding finely powdered indigo to serum containing Fig. 105. Various forme assumed by the white corpuscles of the blood. The upper row represents the white corpuscles of man; the lower row, white coipiuc!es from the newt, showing changes effected in fifteen minutes (Carpenter.) white corpuscles the manner in which they feed can be observed, the indigo being drawn into the body of the corpuscle by the retraction of its amoeba-like arms and then gradually absorbed and assimilated. Under the influence of acetic acid the body of the corpuscle clears up and three or more nuclei appear. Whether these nuclei preexist and the acid only makes them apparent, or whether their appearance is due to a kind of coagulation, has not yet been positively determined. By the con- tinued action of water and acetic acid, and more readily by alkalies, the white corpuscles are dissolved and disappear. The white corpuscle is larger than the red one, measuring on an average the 2 ^ th of an inch. The white corpuscles are far less numer- ous than the red ones, being found usually in the proportion of one white corpuscle to between 300 ami 500 red ones. This proportion as we learn, however, from the observations of Hirst, 3 varies according to the state 1 Works, p. 282. - Hoppc-Seyler : l"ntei>uchungen, Band iv. S. 441. a Muller's Archiv, 1856, p. 174. 224 THE liLOOD, of digestion : thus before breakfast the proportion being about 1 to 1800, one hour after breakfast it was 1 to 700. before dinner 1 to 1500 after dinner, 1 o'clock, 1 to 400, two hours later 1 to 1475, after supper, 8 P. M., 1 to 550, at midnight about 1 to 1200. The white corpuscles differ also in many other respects from the red ones : thus in the manner in which they are affected by various reagents, and in the way in which they adhere to the walls of the vessels in which they are circulating (Fig. 106), the red corpuscles keeping in the middle of the stream. The white corpuscles further are found Fig. 106. in lymph, chyle, pus, and other fluids as well as in the blood; the more general name of leucocytes is often, therefore, given to them. It is well known that the leuco- cytes are most numerous in the splenic vein, and that in diseases of the spleen, liver, and lymphatic glands, the white corpuscles may increase in number to such an ex- tent as to form a half or a third of the corpuscular part of the blood, hence the light color of the blood in such circumstances, and the name of the disease — leucocythemia. The number of the white corpus- cles increases in pregnancy, and are more numerous in children than in adults. The proportion of the white corpuscles to the red is far higher in the embryo vertebrate than in the adult ; according to Gulliver, 1 in the very early stages of embryonic life the white corpuscles are even in excess. Further, in examining the blood of the amphioxus, the sim- plest of vertebrates, and that of the invertebrata (with but few exceptions) one cannot but be impressed with the likeness of their corpuscles to the white ones of the vertebrates rather than to the red. Let us see whether these facts have any significance in throwing light upon the origin of the red and white corpuscles. One of the most profound truths in the whole range of biology is that the transitory stages through which the higher animals pass are perma- nently retained in the lower ones. Ample evidence of the truth of this assertion will be given in the consideration of the phenomena of repro- duction, and it will be found then that the blood does not offer any exception. If the red corpuscles are then modified white ones more highly developed, we should expect to find white corpuscles in the lower animals and in the embryonic forms of the higher, and that gradually the white ones should give way to the red as development advances. This we have seen is the case. Again, the white corpuscles are identical with those of the lymph and chyle, and as was pointed out it has long been a matter of comment that in the upper part of the thoracic duct A small venous trunk, a, from the web of the frog's foot. 6, b. Cells of pavement-epithelium, containing nuclei, d. White corpuscles, e. Red ■corpuscles (Carpenter.) 1 Carpenter's Physiology, p. 234. London, 1881. WHITE CORPUSCLES. 225 its fluid becomes of a reddish hue, due probably to the gradual develop- ment of the red blood-corpuscles. Again, the immense number of white corpuscles in the disease leucocythemia, just referred to, may be accounted for on the supposition that the abnormal conditions are such as to interfere with the normal transformation of the white corpuscles into the red. Another significant fact is that transitional forms between the red and the white corpuscles are often met with in the blood. These facts of comparative anatomy, embryology, and pathology, have a significance if this view of the transformation of the white corpuscles into the red be correct, otherwise they are meaningless. It must be admitted, however, that the exact manner in which the red corpuscle is developed from the white has not been definitely made out, although, according to Kuss, 1 both Kolliker and Recklinghausen have seen the transformation of white globules into red even outside the organism in blood kept at the temperature of the living organism in contact with a moist atmosphere. If it be admitted that the red corpuscle is developed from the white, the next question that will naturally be asked is, Where does the white corpuscle come from ? In examining the blood corpuscles at different periods of embryonic life it will be found that some have a different origin from others. The first blood corpuscles are almost indistinguishable from the cells of the body of the embryo generally. When we come to study the development of the vascular system we shall see that in the pellucid area of the embryo of the cells forming the meso- blastic layer some soften down and liquefy, while others remain floating in the liquor so produced. The latter are the first blood-cells or corpus- cles ; they are round, nucleated, and colorless, and reproduce themselves by fission. (Fig. 107.) Fig. 107. /0-*k J' a ;\ Reproduction of first blood corpuscles, in embryo, by fission. (Kirkes. I With the development of the liver and spleen white corpuscles appear in the blood ; the latter as they pass through the liver become colored, gradually they lose their granular appearance and become nucleated red blood-corpuscles, often oval shaped, which form, as we have seen, is retained through life in the oviparous vertebrates, but in the mammalia. with the exception of the camel tribe, is only transitory. Gradually the number of the white corpuscles diminishes, the red unnucleated bicon- cave corpuscles simultaneously increasing, the latter being wanting at the first month of intrauterine life, and at the third month constituting only about one-fourth of the corpuscles. With the development of the 1 Physiology, translated by Dr. Amory, p. 122. Boston, 1875. 15 226 THE BLOOIt. embryo the white corpuscles .still further diminish, until, finally, the circular, biconcave, unnucleated red corpuscles predominate in the pro- portion already mentioned. Possibly the red corpuscles reproduce themselves also, to a certain extent, fissiparously — that is, by a process of division in the adult as well as in the embryonic condition. 1 ;., j'yj In certain cases after excessive hemorrhage the corpuscles may pos- sibly be regenerated in this manner ; for it is well known that many vegetable organisms reproduce themselves fissiparously in vast numbers, even in a night, far more rapidly than would be necessary in the case of the corpuscles, some days elapsing before their normal number is restored. Whatever future investigation may determines as to the origin of the red and white corpuscles or their relation to each other, there can be no doubt that in the adult the materials of which they are composed are derived from the food. This is well seen in the beneficial effect of giving iron in chlorosis, where the number of the red corpuscles is diminished, and which, after the use of iron, is soon restored to the normal standard. The corpuscles of the blood, however, do not exist as such in the food, but, like the other elements of the blood, must be elaborated from it. While it must be admitted that the exact manner in which the blood is elaborated is not yet understood, nevertheless the general features of the process can to a certain extent, at least, be indicated. Thus a greater part of the water found in the blood is derived from that present in the solid and liquid food, a small quantity probably being due to the combustion of hydrogen. The blood-albumen is modified albuminose, as this is modified food-albumen. The fibrin can be regarded as an effete product undergoing retrograde metamorphosis. The oieates and margarates probably result from the saponification of the fatty food by the pancreatic juice, while the iron and •""^ ]08 saline principles are evidently derived ^|§§ u , from the food. •' '„■■ '■-'. '•; ,.'/-; \ We have seen that there are many facts which, when taken together, go to show that the red corpuscles are modified white ones. It remains for us now to consider whether any definite locality can be assigned for the production of the / ^/fRWS '■' *" ' ' ' white corpuscles, and to ascertain, if pos- '■S K \tll^^g0^ sible ' what are the elements of the food out of which they are developed, simple lymphatic giarid. a The cap- It has already been mentioned that sale with sections of lymphatics, d, d. t ] ie ^^g cor puscles are not confined to Coursing through it. b. Lacunar and in- .1 1 1 i i • i p i • ii i telecommunicating passages, permeated by the bl ° od > bel "g als0 foUnd ln tlie b'mph, the lymph, and forming the superficial chyle, etc. They are also found in the lymph-path of F.ey. c. Nucleus or me- so litary and lymphatic glands, in the dullary portion of the gland, in the centre i • ,i i c , 1 of which the section of a bloodvessel may Spleen, in the red maiTOW of the Can- be seen. The path pursued by the lymph CellouS tissue of bones. Let US now through the medullary portion constitutes examine the minute structure of these the deep or secondary lymph-path of Frey. so . ca]led kndg an( l gee whether the (Carpenter. ) o facts of comparative anatomy, pathology, and experiment throw any light upon their relation to the white cor- puscles found in them. STRUCTURE OF SOLITARY AND LYMPHATIC GLANDS. 227 The solitary glands, as we have already rfbticed, are distributed all through the alimentary canal ; the Peyer's patches, which consist of a number of solitary glands united together, are, however, limited to the so-called jejunum and ileum. When a section of one of these solitary or simple lymphatic glands is examined microscopically (Fig. 108) it is seen to consist of a capsule of connective tissue from which pass inwardly strands forming a meshwork, in the interior of which is contained the so-called adenoid or cytogenous tissue. These strands of connective tissue serve to support' the capillary bloodvessels. In the meshes are found lymph corpuscles and sometimes molecular granules and small oil globules. Imagine a number of these solitary glands held together by a capsule of connective tissue, and we have a lymphatic gland (Fig. 109). The meshes in the lymphatic gland are, however, much closer in the centre than at the sides, hence the distinction of the medullary and cortical parts (Fig. 110). Further the meshes are only incom- Fig. 109. Fig. 110. d * J Section of lymphatic gland, showing a, a, the fibrous tissue which forms its exterior. 6, h. Superficial vasa inferentia. c, c. Larger alveoli, near the surface, d, d. Smaller alveoli of the interior, e, e. Fibrous walls of the alveoli. (Carpenter.) Longitudinal section through tne hilum of a mesenteric gland from the ox, showing the commencement of the efferent lymphatic vessels injected from a puncture of the glandular sub- stance, a. Plexus of efferent vessels b. Lymph paths. c. Medullary cords. d. Trabecular. (Kolliker.) pletely filled by the pulp, free spaces being left between the pulp and the strands. These spaces communicate on the one hand with the lymphatic vessels entering the gland, and on the other with the lymph- atics leaving it at the hilus. The afferent and efferent lymphatic vessels and these spaces can be injected. Probably this is the explanation of the gland appearing after injection as a mass of vessels, a rete mirabile between and continuous with the lymphatics passing in and out of it. The pulp consists principally of lymph corpuscles, these being most numerous in the medullary parts of the gland where the bloodvessels are also freely distributed. The lymph or chyle passes from the afferent vessels into the spaces left between the pulp and the strands, and comes in contact with the lymph corpuscles and the blood, more particularly in the medullary parts of the gland ; after circulating through these spaces the lymph or chyle passes out of the gland at the hilus by the efferent lymphatic vessels, and so passes on to the thoracic duct. 228 THE BLOOD. The researches of Klein, 1 von Recklinghausen, 2 and others, have .shown that the walls of the serous sacs, like the peritoneum, pleura, etc., consist, to a considerable extent, of the adenoid or cytogenous tissue just mentioned, which enters into the formation of the solitary and lymphatic glands, and that these serous sacs communicate by openings or stomata with the lymphatics. Indeed, these sacs are now regarded as being lymphatic glands unravelled, having essentially the structure and function of the glands already described. We have already seen that the lymph differs from the blood quanti- tatively, rather than qualitatively, and that the chyle is lymph with the products of digestion added to it, more especially of the emulsified fats and oils. The lymph and chyle corpuscles, which are undistin- guishable from the white corpuscles of the blood, seem to consist at first of fatty nuclei, which, acquiring an envelope through diffusion in an albuminous fluid, gradually become white corpuscles. In examining the chyle of the lacteals in the villi, in the mesenteric glands, and in the thoracic duct, it was noticed that the so-called molecular base of the chyle consisted largely of fatty matter, and that the chyle corpus- cles were probably due to an aggregation of the minute bodies forming the base of the chyle. It seems probable, therefore, that the chyle cor- puscles, or white corpuscles of the blood, are elaborated in the lymphatic glands out of the fatty food. In addition to containing white corpuscles, the chyle resembles an early stage of the blood in other respects, thus between the mesenteric glands and thoracic duct it will coagulate — that is, separate into clot and serum, while the chyle of the thoracic duct exhibits a reddish color, as if the white corpuscles were gradually becoming red ones. While the fats and oils are usually taken up by the lymphatics of the small intestine, we have seen that the albuminose, glucose, salts, etc., are absorbed by the radicles of the mesenteric veins. Were these substances in a proper condition for assimilation, it might be expected that they would at once pass into the general circulation. They are. however, first mixed with the blood coming from the splenic vein, and then expe- rience still further changes as they pass through the liver on their way to the heart. Inasmuch as the lymphatic glands seem to be the organs in which the fatty portions of the food are further elaborated analogy Avould lead us to expect that, in certain parts of the economy, certain organs exist which effect for the albuminose substances, etc, what the lymphatic glands do for the fats. In examining the structure of the spleen one cannot but be impressed with its great similarity to a lymphatic gland. Like the lymphatie gland, the spleen (Fig. Ill) consists externally of a fibrous capsule, from which pass inward numerous strands, constituting the so-called trabecular, in the meshes of which is contained the splenic pulp. This consists of white blood-corpuscles, of red corpuscles in various stages of development or disintegration, of granular matter of a reddish-brown hue, blood crystals, etc. The only difference between the spleen and a 1 Anatomy of the Lymphatic System. 1873. - Strieker's Histology. STRUCTURE OF SPLEEN 229 lymphatic gland consists in the fact that the cells found in the spleen pass directly into the blood. Fig. 111. Vertical section of a small superficial portion of the human spleen. Low power. A. Peritoneal and fibrous covering, b Trabecule, c, c. Malpighian corpuscles, in one of which an artery is seen cut transversely, in the other longitudinally, d. Injected arterial twigs, e. Spleen-pulp. (Kolliker.) That the spleen is structurally a lymphatic gland seems confirmed by the fact that usually when the spleen is small in man or an animal the lymphatic glands are large, and vice versa. Not only is this inverse ratio observed in the same animal, but also in different species. Thus, among other instances, in the manatee (Manatus Americanus) the spleen is very small, while the glands are very large ; while in the sea lion (Zalophus Gillespii) the spleen is large, and the glands are small. One of the most striking peculiarities of the spleen is its great vas- cularity. Not only does a large quantity of blood flow into the organ, but in certain parts of it capillaries are absent, the blood of the splenic artery passing directly into the interstices of the splenic pulp, from which it is taken up by the veins. It is an interesting fact that this lacunar type of circulation exhibited by the spleen is what usually obtains in the invertebrata. It may be mentioned in this connection that the so-called Malpighian corpuscles attached to the branches of the splenic artery in the spleen do not appear to differ essentially in their minute structure from that of the solitary glands. A significant fact, in connection with the development of the white corpuscles, is their great number in the blood of the splenic vein, one white corpuscle being found to every 70 red ones, whereas, in the blood of the splenic artery the proportion is only one of white to 2000 of red. The conclusion from such a contrast would not, how- ever, be that the white corpuscles found in the splenic vein are devel- oped in the spleen out of the red ones brought to that organ by the 230 THE BLOOD. splenic artery, bui rather that the red blood-corpuscles are destroyed in the spleen, the disintegrated, broken-down corpuscles furnishing not only material for the development of new red blood-corpuscles, but of the coloring matter of the bile, the elaboration of the latter being effected in the liver. Further, in leukemia, where the spleen and lymphatic glands are enlarged, we have seen that the number of the white corpuscles is so great that the general color of the blood is affected by them. Naturally the question will then suggest itself as to what becomes of the white corpuscles produced in the spleen. Of what use are they if they simply disappear, and are not further elaborated ? That they do not pass away is shown by their great number in the disease just referred to, in which possibly, as already suggested, the conditions or the materials for their metamorphosis into the red corpus- cles are absent, such a transformation probably taking place in health. An interesting fact in connection with the number of red corpuscles brought to the spleen is the large quantity of iron found in the splenic pulp, amounting to over seven per cent., and which may be regarded as being derived from the disintegration of the old red blood-corpuscles and serving as material for the development of the new ones. We have seen that the portal vein is formed through the union of several veins, among others by the mesenteric and splenic, and that the portal blood passes into the liver. Now, if the blood of the hepatic vein which comes from the liver be compared with that of the portal vein which goes to the liver, it will be found that there are more corpuscles, both red and white, in the former than in the latter. It must be ad- mitted, however, that according to some observers there are relatively fewer red corpuscles in the blood of the hepatic vein than in that of the portal. This may be due, however, to the destruction of the red corpuscles in the liver during the intervals of digestion. The liver must, therefore, have in the adult, as in the embryo, an influence in the elaboration of the blood corpuscles. If it be admitted that the Avhite corpuscles are produced in the spleen and are then car- ried by the splenic vein to the portal, where they can absorb fresh nutri- tive matter, albuminous substances, etc., and that they then undergo a further elaboration in the liver, becoming red ones, we have an expla- nation of the interesting anatomical relations of the parts just referred to. That the spleen has some such function in the process of sanguinifi- cation, as just indicated, similar to the influence exerted by the lymphatic glands upon the fatty food passing through them, is confirmed by a consideration of the absorbent system in the animal kingdom generally. In the invertebrata and the amphioxus there is no distinction between the lymph and blood, the nutritive fluid being comparable rather to the lymph of the vertebrates than to their blood. There is also only one set of absorbents in the invertebrata. The spleen is absent in the am- phioxus, while true lymphatic glands cannot be said to exist in fishes and reptiles, and are only sparingly developed in birds. The lymphatics of the small intestine in the three latter classes are so rarely filled with chyle that, according to some anatomists, lacteals cannot be said to exist. It is only in the mammals that we find the digested food is absorbed by two distinct sets of vessels, and even in PRODUCTION OF WHITE CORPUSCLES. 231 these, as we have seen, one set of vessels does at times absorb all kinds of food. In a word, both sets of vessels are combined in the lower ani- mals, while in the higher the work of elaboration is divided between the lymphatic glands on the one hand and the spleen and the liver on the other. Admitting that the spleen is a lymphatic gland, and that, like the latter, it elaborates white corpuscles out of fat. it may be supposed that the materials supplying the fatty principles are brought to the spleen by the splenic artery ; or it may be possible that the white corpuscles de- veloped in the mesenteric lymphatic glands having reached the spleen by the route of the thoracis duct, heart, and splenic artery, undergo there a further elaboration, finally becoming in the liver red corpuscles. The investigations of Neuman, 1 Bizzozero, 2 and others, appear to show that lymph corpuscles are developed in the red marrow of the cancellous tissue of bones as well as in the lymphatic glands and spleen. According to Neuman, not only are both white and red corpuscles found in the red marrow but also all kinds of transitional forms between the two, nucleated granular cells of a yellowish color passing insensibly into non-nucleated cells of a reddish hue, and these gradually leading on to the red corpuscles proper. It is possible that the tonsils, the glands found in the tongue, palate, etc., may also have an influence in the production of the white corpus- Fio. 112. Pig. 113. Front view of the right kidney and supra renal body of a full-grown foetus. Thisfigure shows the lobulated form of the foetal ki.l- ney. r, v. The renal vein and artery, u. The ureter, g. The suprarenal capsule, the letter is placed near the sulcus in which the large veins ((,•') are seen emerging from the interior of the organ. (Allen Thomson.) Portion of thymus of calf, unfolded, o. .Alain canal, b. Glandular lobules, c. Iso- lated gland-granules seated on the main canal. (CakPENTEB.) cles. From this general survey it will be seen that probably the white corpuscles are produced in several parts of the economy, and that a kind 1 Archiv der Ileilkunde, 1809. - Centralblatl 282 THE BLOOD. of vicarious action may take place among the organs concerned in their production. Thus, if the spleen be extirpated, the lymphatic glands become enlarged and more active. With hypertrophy of spleen we have, coincidently, disease of the bones, which becomes intelligible when it is remembered what has just been said with reference to the marrow and the blood corpuscles, and that the function of the spleen is of such a supplementary character to that of the lymphatics as already described is still further shown from the fact that it can be entirely removed from the body of an animal without the functions of the latter being apparently in any way interfered with, the lymphatic glands then enlarging proportionally to the greater amount of work thrown upon them. The suprarenal capsules, Fig. 11:2, and thymus glands, Fig. 113, are at the present day considered by many physiologists as having the same Fig. 114. Fig. 115. Vertical section of suprarenal capsule of man. 1. Cortex. 2. Medulla, a. Capsule, b. Layer of external cell-masses, c. Columnar layer (zona fasciculata). d. Layer of the internal cell-masses, c. Medullary substance. /. Section of a vein. (Carpenter.) of oil and pigmentary matter, yet it tions are still very obscure. Section oi human thymus, showing a cavity in the wide portion, and numerous orifices leading to its lobular cavities. (Carpenter, ) function as the spleen and lymph- atic glands, at least in the em- bryo if not in the adult. The structure of the suprarenal cap- sules (Fig. 114) recalls that of a lymphatic gland, consisting, as it does to a great extent, of tra- becule, in the ovoid meshes of which are imbedded nuclear cap- sules, cells with granular con- tents, with and without nuclei, must be admitted that their func- THYMUS GLAND. 233 From the fact that the suprarenal capsules being relatively most de- veloped in the embryo, their function, whatever it may be, is possibly restricted to foetal life. The immense number of nerves distributed to these bodies is one of their most remarkable peculiarities, the significance of which is, how- ever, unknown. The bronzing of the skin often associated with disease of the suprarenal capsules, does not as yet throw light upon the func- tions of these bodies, inasmuch as the bronzing may be present without disease of the suprarenal capsules, and these bodies may be diseased and yet the skin unaffected. It is generally stated that the thymus gland is also restricted in its functions to foetal life. According to Carpenter, 1 however, it is soon after birth that the gland is most active, and that even till the age of puberty it continues to increase in size. The thymus gland appears in the embryo first as a solid body, but soon becomes a tube closed at both ends and filled with granular matter. From this tube (Fig. 115) there bud out at intervals, on either side, hollow lobular processes, the cavities of which communicate with that of the central axis. The thymus in the adult consists of a series of such offshoots or lobules united by connective tissue and opening into the central tube, to which, how- ever, there is no outlet. Each lobule (Fig. 116) consists of an external Pig. ll'i. lill ' '""" .(H^'S^'-'J * Acini. tegr 7 "" Fibi Section <>l lobule of thymus. fibrous capsule which sends prolongations into its interior consisting of acini, in the meshes of which are seen the thymus substance. This contains lymph corpuscles, spheroidal granular bodies, and concentric corpuscles. In the expressed thymus juice are found corpuscles which are undistinguishable from those of the fluids of the lymphatic glands. The thymus" gland, in its whole structure, is very much like a Fever's i Physiology, p. 216. 234 THE BLOOD. patch. The fact of the thymus being most active during foetal life, and for some time after birth, makes it probable that it, and possibly the suprarenal capsules, influences the elaboration of blood in the embryo in the same manner as the spleen and the lymphatic glands do in the adult. The thyroid gland, like the thymus, relatively larger in the foetus and in the infant than the adult, is also regarded at present by many physiologists as having an influence in sanguinification. Its remarkably rich vascular supply would lead one to consider it as performing some function in the elaboration of the blood, either as eliminating some effete material from the blood or furnishing it with nutritive material. As there is no excretory duct to the thyroid gland, the latter view of its function is the more probable. The development of a goitre or enlarge- ment of the thyroid gland, may be possibly due to the retention of matters by the gland which are ordinarily given up to the blood circu- lating through it, while the want of such material in the blood circulating through the brain may be connected with the idiocy so often associated with goitre. In the same way the white appearance of young women affected with tumors of the thyroid gland may be due to the retention by the gland of material which it usually furnishes to the blood sup- plying it. The structure of the thyroid gland diners from the spleen or lymphatic glands, it consisting of a collection of vesicles (Fig. 117) imbedded in Fig. 117. Fig. 118. Group of gland-vesicles iron a child, o Connective tissue. the thyroid gland of b. Membrane ol the Diagram illustrating the relation of the respira- tory chamber, G, to the hypobranchial groove, H, in ascidians. (Gegenbaur.) connective tissue, which also sup- ports a network of lymphatics. These vesicles are lined with epi- thelial cells, from which there exudes an albuminous granular material. According to Wilhelm Muller, 1 however, the thyroid gland in man is to be viewed as the rudiment of the hypobranchial groove of the ascidians and the am- phioxus, which, traversing the middle of the gill body (Fig. 118) of these animals, assists in conducting the food into the stomach. When all the facts are considered together, the following general conclusion may be drawn : that the spleen, the lymphatic and solitary glands, the vesicles, c. Epithelial cells. (Carpenter.) • Jenaishe Zeitschrift, 1873, Band viii. S. 327. ELEMENTARY CORPUSCLES. 235 Peyer's patches, have essentially the same structure and perform the same functions, that of producing the lymph or white corpuscles ; that probably the thymus, and possibly the suprarenal capsules, lias the same function, but restricted in its performance to the early periods of life; that the thyroid, while differing from the glands just mentioned in its minute structure, yet has some influence in the process of san- guinification : that the red corpuscles are developed from the white, the elaboration taking place in different parts of the economy — the red marrow and the liver, for example — and that, having played their part, they pass away like all other organites. The blood contains, in addition to the red and white corpuscles, minute granules or molecules. These are of a circular form, attaining sometimes the size of the -§- oVo* n °^ an mcn ' DlJ t are usually much smaller. They resemble the minute fatty particles of which the molecular base of the chyle consists. Some of them are, however, of an albuminous nature. It is possible that these elementary corpuscles, as they have been called, are undeveloped lymph or white corpuscles. CHAPTER XV. THE BLOOD.— ( Continued.) One of the most interesting facts about blood is its power of coagula- tion, or of its separation into clot and serum. Before coagulation the blood consists of the liquor sanguinis or plasma and the corpuscles ; after coagulation it will be found that the corpuscles are entangled in the meshes of the coagulated fibrin, the two constituting the clot or crassamentum, while the albumen, salts, and water remain together as the serum. It is important to notice that the liquor sanguinis, or the plasma, is not identical with the serum. As may be seen from Table XLII., the liquor sanguinis is serum with the addition of fibrin, and that serum is liquor sanguinis without fibrin. Serum differs also from what are known as serous effusions, which are due to transudations, not to coagulation. Table XLII. — Blood. Before coagulation. | Water Liquor j Salts sanguinis | Albumen I Fibrin Corpuscles After coagulation. I Serum. I \ Clot. When the blood is allowed to flow into a tolerably deep, smooth vessel, according to Nasse, 1 in from about one minute and forty-five seconds to six minutes a gelatinous layer Avill be seen to form on its surface, in from two to seven minutes the sides of the vessel are covered with a similar layer, and in from seven to sixteen minutes the whole Fig. 119. Fio. 120. Bowl of recent!; coagulated blood, showing tin whole mass uniformly solidified. (Dalton.) Bowl of coagulated blood, after twelve hours ; showing the clot contracted and floating in the fluid serum. (Dalton.) of the blood becomes jelly-like (Fig. 119) ; gradually there exudes from the contracting jelly-like mass, drop by drop, a fluid, the serum, and in Wagner: Physiologic, 18-12. Band 1, S. 104. COAGULATION OF THE BLOOD, 287 from ten to twelve hours the coagulation is complete — that is, the separation of the blood into clot and serum (Fig. 120.) The contracted jelly-like red mass, the clot, being heavier (specific gravity of corpuscles, 1.088), usually falls to the bottom of the straw-colored or reddish liquid, the serum (specific gravity. 1.028), surrounding it. which has exuded from it. Usually, according to Milne Edwards, 1 the clot retains about one- fifth of the entire volume of the serum ; this should be remembered when the proportion of clot to serum is estimated ; it is generally stated that they are equal. AVhen the coagulation has been slow, the clot will be found to be firm ; on the other hand, when the coagulation has been rapid, the clot is soft. When blood coagulates slowly, and so remains fluid for some time, the red corpuscles, on account of their weight, sink and settle at the bottom of the clot ; the upper part of the clot will be, therefore, much lighter in color than the lower, and, when white, is known as the buffy coat (Fig. 121) ; it is almost always seen in the blood of the horse, which coagulates slowly (Table XLIIL), while it is absent in the pigeon, in which the blood coagulates almost instanta- neously. Table XLIIL 2 — Length of Time of Coagulation. Animal. Man .... Horse Ox ... . Dog . . . . Sheep Hog .... When contraction of the clot takes place most rapidly at the edges, these curl up and the upper surface becomes concave or cupped (Fig. 122). For many years it was supposed that the buffy coat was char- Minutes. Animal. Minutes. 2 to 16 Babbit . 1 to H 5 to 13 Lamb . .1 to 1 2 to 12 Duck . .5 to 2 I to 3 Fowl I to LI I to 1.', Pigeon almost instantaneously. .', to n Fig. 121. Fig. 122. Vertical section of a recent coagulum, showing the greati-r accumulation of Mood globules at the bottom. (Daltox.) Bowl of coagulated blood, showing the clot buffed and cupped. acteristic of inflammation, whereas it is now known that the buffy coat is also present in diseases of a totally opposite character — in chlorosis, for example, it depending here upon a diminution of the blood- corpuscles. It is obvious that bleeding in such cases would only 1 Physiologic, tome i. p. 124. - Thakrah : Inquiry into the Nature of Blood, 1819, p. 29. 238 THE BLOOD. increase the buffy coat by diminishing still further the corpuscles, and yet, when it is remembered that bleeding was once the sovereign remedy for inflammation, one can readily imagine the number of lives that must have been sacrificed through the mistaken idea of the buffy coat being always due to inflammation. We shall see that the fibrin is increased in inflammation, and in inflammation the blood also coagulates slowly; the appearance of the buffy coat under such circumstances, therefore, is perfectly intelligible. It must not be forgotten that the formation of the buffy coat is simply a question of time, as shown by the researches of Polli, 1 for as coagula- tion is either retarded or accelerated, so will the buffy coat be formed or not formed. There is no better illustration of the great influence that the progress of physiology exerts upon the practice of medicine, than the history of the blood. Dr. Carpenter, 2 in his most thoughtful work, in speaking of this subject, well says: " If Andral had made no other contribution to medical science than the demonstration of the real nature of this condition of the blood, and of further depletion in promoting it, he would have rendered a most essential service to the multitude of females who are unfortunate enough to suffer from this kind of deterioration of their vital fluid."' It is well known that there are various circumstances which modify the coagulation of the blood. Thus, blood flowing from a small orifice coagulates more quickly than when flowing from a large one, and more quickly when it is received in a shallow rough vessel than when in a deep smooth one. Blood coagulates more rapidly in a vacuum than in the air. Rapid freezing prevents the coagulation of the blood; this will take place, however, after careful thawing. This fact is of impor- tance from a medico-legal point of view. Elevation of temperature between 32° and 140° Fahr. increases the rapidity of coagulation. Chemical substances, like solutions of soda and potash, ammonium and sodium sulphate and carbonate, will retard or prevent coagulation. It is due to the vaginal secretions that the menstrual blood is kept fluid. The blood not only coagulates outside the body, but also after death within it; less rapidly, however, and, as a rule, in from twelve to twenty- four hours after death. It is not unusual, also, during life to find clots in the heart and other parts of the vascular system. As it is often important to be able to distinguish an ante-mortem from a post-mortem heart-clot, it may be stated that the former are whiter, denser, and adhere more closely to the walls of the heart than the latter. Coagula are also found when an artery is ligated, in the enlarged veins of hemorrhoids, in the varicose veins of the extremities. Usually the blood coagulates when effused into the areolar tissue or the cavities of the body. It is an interesting fact, however, that the blood may remain fluid in the serous cavities for days and weeks at a time. When coagula are formed in the heart, and being swept into the circulation are carried thence into the small vessels of the brain, etc., they consti- i Annali universal* tli medicina, 1843. - Physiology, p. 267. COAGULATION OF THE BLOOD. 239 tute what are known as emboli. When the blood coagulates in the economy it acts as a foreign body, but is usually absorbed, though this may take a long time. The corpuscles first disappear, then the fibrin softens, breaks down, and is finally carried away. The coagulability of the blood is nature's cure for hemorrhage, and when this power is diminished or wanting we have the hemorrhagic diathesis, where the slightest wounds are followed by severe, and some- times fatal hemorrhage. As the above facts belong rather to the prov- ince of pathology I merely mention them here in an incidental way. From time immemorial various explanations have been offered of the coagulation of the blood. A favorite one has been that of the blood being maintained in the body in a liquid condition through the influ- ence of life. Apart from this being no explanation at all, but simply a statement of the phenomena to be explained, it is not even a fact, as we have seen that the blood coagulates in the living body. In the last century it was generally held that what we call fibrin was produced in some way at the expense of the corpuscles, which run together in coagu- lation, etc. Petit, Davies, and Hewson, 1 however, held that coagulation was due to some substance separate from either the corpuscles or the serum, and Hewson performed several experiments to prove that coagu- lation was due to the fibrin. For example, Hewson 2 added a little sodium sulphate to fresh blood, which prevented coagulation. After the mixture had remained standing some time the corpuscles sank to the bottom, the clear fluid which remained on top was then decanted, twice its quantity of water was then added to this, when the fibrin coagulated. On another occasion, this most able observer 3 tied the jugular veins at the sternum of a dog just dead, and hung his head over the edge of a table, so the ligatures might be highest, the upper part of the vein became transparent, the red corpuscles sinking ; he then tied the vein, separating the clear from the muscular part, and let the clear part out, which was fluid, but coagulated soon after. These experiments showed that the coagulation was due to the fibrin, but they did not demonstrate that this fibrin did not come from the corpuscles, which was the view that prevailed at that time. To do this it was necessary to show that the corpuscles were unaffected to coagulation. With reference to determining this point, Johannes Muller, 4 the great Berlin physiologist, in 1832 experimented in the following ways : He added a little solution of sugar to frog's blood, which retarded the coagu- lation, and then filtered the mixture; the corpuscles, which are very large, were retained in the filter, and the clear fluid which passed through coagulated. Muller then showed that in blood which was defibrinated by whipping, and therefore incoagulable, that the cor- puscles were not altered in any appreciable manner ; and further, that when blood to which had been added serum (which separated the cor- puscles from each other) was observed under the microscope coagu- lating, the corpuscles were seen to remain intact. Inasmuch as the white stringy substance appearing at the moment 1 Milne Edwards, op. cit., tome i. p. 119. - Works, p. 12. ■'< [bid., p. 32. * Physiology, transl. by 1'aly, 1840, vol. i. p. 123. 240 THE BLOOD. of coagulation, which we call fibrin, evidently does not exist as such in * the blood before coagulation, it remains to be determined, if possible, under what form it then docs exist. If blood be drawn into a concen- trated solution of sodium sulphate to prevent its coagulation, and sodium chloride be added to the mixture in the proportion of ten per cent., a whitish, pastv substance is thrown down, amounting to about 25 parts per 1000 of the blood used, and called by Denis, 1 who first described it, plasmin, and which, together with serin, constitutes blood albumen. Now, wheu plasmin is redissolved in water, the solution splits into fibrin 3 p;irts, and paraglobulin 22 parts, the former coagulating, the latter remaining liquid. It would appear, therefore, that fibrin exists in the blood combined with paraglobulin, as plasmin or some form closely allied to it; and further, as with the withdrawal of the plasmin from the blood, the latter loses its power of coagulating, the serin remaining liquid, that coagulation of the blood consists, first, in the splitting of albumen into serin and plasmin, and secondly, in the latter splitting into fibrin and paraglobulin, or of the breaking up of albumen directlv into serin, fibrin, and paraglobulin. On the other hand, the observation, made many years ago by Buchanan, 2 that two fluids, like that of hydrocele and ascites, for example, or of ascites and pleurisy, when added together, coagulate, though when separate show no such tendency, has led many to infer that the production of fibrin is rather due to the union of substances in the blood than to the decomposition of the same, as just explained. Indeed, according to Schmidt, 3 two such principles actually do exist in the blood, a fibrinoplastic substance, paraglobulin, and a fibrinogenous one, fibrinogen, whose union brought about by the presence of a ferment at the moment of coagulation constitutes fibrin. Paraglobulin can be readily obtained from the serum of the blood through precipitation by the addition of sodium chloride in excess, and fibrinogen in the same way free from the liquor sanguinis, in which coagulation has been prevented by the addition of magnesium sulphate, and the corpuscles have been removed by filtration. Now. while it is an interesting fact that if paraglobulin in a saline solution be added to either fibrinogen or hydrocele fluid, or if fibrinogen as obtained either from the liquor sanguinis or hydrocele fluid be added in saline solution to serum, fibrin will be produced, it does not necessarily follow that such a union as that of paraglobulin and fibrinogen actually takes place in the blood at the moment of coagulation. Indeed, it is yet to be proved that paraglobulin exists as such in the clot, seeing that if Ave obtain it from the serum it must be assumed that it exists in excess partly in the serum and partly in the clot. Again, as under certain circumstances, paraglobulin when mixed Avith fibrinogen does not produce fibrin, it is still further assumed that the presence of a ferment is necessary to effect the union of the two fibrin factors. As a matter of fact, an aqueous extract can be obtained from the serum by coagulating the latter with alcohol, allowing the mixture to stand, 1 Annates dea Sciences Natureltes iv. I. p. 25. - Proc. of Glasgow Philos. Soc, 1845. :l Du Bois Reymoud : Arehiv. 1861, S. 545 ; 1862, S. 42S. Pfluger's \ 0.125 Sodium 1.400 1 Stearate Potassium r Sodium [ Chloride ■ 3.500 Magnesium J Sodium Potassium f Carbonate - Sulphate I Phosphate Free Soda \ 2.850 Magnesium f Sulphate 1 Phosphate Calcium phosphate . 0.550 Extractives undetermined 2.450 1.000.000 The general results of an analysis of the blood by such a method as that just given may be seen from Table XLIV., taken from Becquerel and Rodier's work, and which undoubtedly gives a very fair idea of the average composition of the blood from a purely chemical, and, indeed, to a certain extent, from a physiological point of view also. It will be noticed at once, however, that in this analysis of a 1000 parts of blood, there are present only 1 35 parts of corpuscles ; whereas, anyone who is familiar with the appearance of living blood under the microscope knows that the corpuscles bear a much larger proportion, forming, perhaps, half of the mass of blood examined. This discrepancy is perfectly accounted for when we remember that, by the method of Becquerel and Rodier, the clot from which the corpuscles are estimated is dried and 1 Traite de chimie de pathologiqne, p. 20. Paris, 1854. 2 Ann. de Chemie, et de I'hye., 1844, 3me serie, tome xi. p. 506. 244 COMPOSITION OF THE BLOOD. their water therefore driven off; the 135 parts of corpuscles represent, therefore, dry ones and not the living corpuscles, which, when united with their 370 parts of water, will amount to nearly 500 parts in the 1000 of blood analyzed. Judging, also, from the boiled serum, we should expect to find a greater quantity of albumen than 70 parts per 1000 of blood. In the analysis just given the serum from which the albumen is determined is dried like the clot, hence the water present in living albumen is not given. When the water, however, is taken into consideration, the albumen w T ill then amount to more than 300 parts in 1000 of blood. As the object of the physiologist is to ascertain if possible the quantity of albumen, fibrin, and corpuscles, as they exist in living blood, and as in this condition water is an indispensable element of their composition, it becomes a matter of importance to determine the quantity of these principles in a moist as well as in the dry condition. For these reasons Prof. Flint, in his excellent work, 1 suggests that, while the fibrin be obtained in the usual manner of whipping — with broom-corn, for ex- ample — and the corpuscles by Figuier's filtering method, both these principles should be estimated in their moist condition, and not after desiccation; and that in determining the albumen from the serum, this should be treated as described above, but in the condition that it is found after coagulation — that is, with its water. The difference between the results of an analysis of the blood by the method of Prof. Flint and that of MM. Becquerel and Rodier, may be seen from Table XLV. The excess of water in the analysis of the latter is distributed between the albumen, fibrin, and corpuscles in that of the former. Table XLV. — Composition of the Blood (as analyzed by the methods of Flint, and Becquerel and Bodier). 2 Flint. Becquerel ami Difference is Bodier. in water. Water . . 154.870 790.070 635.200 Albumen . 329.820 71.530 258.290 ) Fibrin . . 8.820 2.500 6.320 [ r 635.200 370.590 ) Corpuscles . 495.590 125.000 Bemaining matters. salts, etc. 10.900 10.900 00.000 1000.000 1000.000 We say the method of Becquerel and Rodier, not their actual analysis, for the quantities of albumen, fibrin, and corpuscles given under the methods of Becquerel and Rodier in Table XLV., were experimentally obtained by Prof. Flint by weighing the dry residue after desiccating these principles obtained by his method. It is very satisfactory, how- ever, to see that the difference between the quantities of dry albumen and corpuscles given by Prof. Flint (Table XLV.) and Becquerel and Rodier (Table XLV.) are very slight, and that the quantity of fibrin is the same according to both. The remaining matters of the blood are determined in the same manner by these and other authorities by the ordinary methods of chemical analysis. l Physiology, vol. ii. p. 133. 2 Becquerel and Rodier, op. cit., 86. COMPOSITION OF THE BLOOD. 245 Of these, the larger proportion are the inorganic principles, and from a purely chemical point of view have been very satisfactorily determined, both quantitatively and qualitatively ; but of the exact manner in which they exist in the living blood little is known beyond a few general statements to be noticed shortly. The analyses of Prevost and Dumas, Andral and Gavarret, Lehmann, Becquerel and Rodier, Simon, Denis, Gorup Besanez, etc., while differ- ing in detail, agree substantially in showing that the blood consists of water in molecular combination with or holding in solution albuminous substances, fats and sugars, and saline matters. It is interesting to observe in this connection that milk and eggs, the food of the young animal and embryo, consist of a mixture of water, albumen, fats, sugars, and salines, approximating closely in their composition to that of the blood ; the value of such articles of food at all stages of life will be therefore readily understood. We have seen that, under natural circumstances, the diet of man is a mixed one, and that beyond a limited period of time no single article of food, solid or liquid, will sustain life. As the blood is elaborated from the food it becomes impossible, therefore, to say positively that any one of its constituents is more indispensable to life than another. It is immaterial, therefore, with which I commence in describing their quantitative relations. I will follow, then, the order in which they present themselves in the analysis given by Becquerel and Rodier (Table XLIV.). The absolute amount of water found in the blood, according to this analysis, amounts to 781.600 parts in the 1000 ; of this we have seen in life that over 600 parts enter into molecular combination with the albumen, fibrin, and corpuscles, forming an integral part of their com- position. As the great use of water to the system has already been pointed out, it will not be necessary to dwell further on the importance of the large proportion in which it is present in the blood, merely stating that while the quantity varies within slight limits, any excess that may be taken in as food is rapidly eliminated by the skin, kidneys, etc., and that a deficiency in any amount materially alters the character of the blood. Although water forms three-fourths of the blood, and however indis- pensable it may be to health, yet the researches of Prevost and Dumas showed long since that there exists an intimate relation between the richness of the blood in organic matters and the vital activity of the organism. A glance at Table XL VI. shows that the quantity of water is large in all vertebrates, but that there is more water in the blood of the com- paratively inactive fishes and batrachia than in birds and mammals, and that in those mammals which hibernate implying a low order of vitality, the blood contains more water than in the ordinary members of this class. As regards the quantity of solid matters contained in the blood of vertebrates, the birds, whose vital activity is very high, come first, the mammals next, and finally the cold-blooded batrachia and fishes. Al- though in Table XLVI. the fibrin and corpuscles are estimated together, we shall see in a moment, from numerous facts, that this vital power 246 COMPOSITION OF THE BLOOD. Water. Clot. Albumen and salts 780 157 63 797 156 47 765 150 85 797 146 56 308 132 59 776 146 78 784 129 87 785 128 87 812 124 65 795 102 84 814 103 83 826 !)1 83 838 94 68 818 92 89 836 86 77 846 94 60 884 69 46 864 64 72 886 48 66 depends upon the corpuscles especially, which vary in quantity under different conditions, whereas the proportion of fibrin and albumen is not so materially changed. Table XLVI.' — Proportion or Water, etc., in 1000 parts of Blood of Vertebrates. Animal. Chicken . Pigeon Duck Raven Heron Monkey Man . Guinea-pig Dog . Cat . Goat . Calf . Rabbit Horse Sheep Eel . Frog . Trout Lotte Milne Edwards, in his elaborate work, 2 cites as examples the following facts. The number of corpuscles is greater in man than in woman, in the adult than in youth or in old age, in the sanguineous than in the lymphatic temperament, in pregnant than in non-pregnant women, in plethoric than in anaemic persons, or in those who have lost blood or have been without food. According to Bakewell, 3 the number of cor- puscles differs in the blood of the Mohamedan, Hindoo, and Negro races so much so that their blood can be distinguished by this characteristic. In all these instances where the corpuscles are in excess the vital activity is high. This statement holds good when classes of animals are compared, as may be seen from Table XLVI. by estimating separ- ately the corpuscles and fibrin which constitute the clot, and when par- ticular animals in a class are considered. Thus in the hibernating mammals, which sleep for months at a time, the number of corpuscles is less than in the more active ones. The blood of the pig, whose nutrition is most active, contains more corpuscles than that of any other mammal. Numerous other examples might be offered, but the above will suffice to illustrate the view that the normal amount of the blood corpuscles is the most important condition in maintaining the force of the constitution, and that any deficiency entails feebleness. This, indeed, was the opinion held more than a century ago by that most profound of phys- iologists, John Hunter. Let us now consider the composition of the corpuscles. We shall see in a moment that when the blood is first cooled and then heated the 1 Ann. de Phys. et de Chemie, 182o, Ire serie, t. xxiii. p. 64. 2 .Op. cit., tome i. pp. 23l-2o4. 3 M e d. Times and Gazette, p. 514. London, Nov 1872. COMPOSITION OF THE CORPUSCLES. 247 material of which the corpuscles are composed separates into two sub- stances, the colorless stroma or globulin, and the coloring matter, the haemoglobin or the hsematocrystallin, which when further modified becomes hrematin. As these two substances are albuminous in nature, it may be said that they represent in the corpuscles (Table XL VII.) the albumen and fibrin of the liquor sanguinis. Table XLVII. 1 — Blood, in 1000 parts each. i lorpuscles, 513. Liquor sanguinis, 487 Density . . 1.0885 1.028 Water . . 681.63 901.51 Solid matters . 318.37 98.49 1000.00 1000.00 Haematin . 15.02 Fibrin 8.06 Globulin . 296.07 Albumen and ) „, ^ extractives [ Inorganic salts . 7.28 8.51 318.37 98.49 Sodium chloride . 5.546 Potassium chloride . 3.679 0.359 Potassium phosphate . 2.343 Potassium sulphate . 0.132 0.281 Sodium phosphate . 0.633 0.271 Soda . 0.341 1.532 Calcium phosphate . 0.094 0.298 Magnesium phosphate . 0.060 0.218 Iron undetermined .281 8.505 The water of the corpuscles has already been referred to. The cor- puscles contain the phosphorized fats, the fatty acids being rather found in the liquor of the blood; the potash salts are also confined almost en- tirely to the corpuscles, there being about four times as much soda in the liquor as in the corpuscles. All of the iron of the blood is contained in the corpuscles, whereas the greater portion of the earthy phosphates is found in the liquor sanguinis. By consulting Table XLVII. the relative densities, quantity of water, solid matters, and proportion of salts in the corpuscles and liquor sanguinis may be seen somewhat in detail. An important practical fact in reference to the red corpuscles is that their number is increased by the use of animal food and iron, but di- minished by a vegetable diet. When the importance of the corpuscles is considered, it is well that the physician should bear this in mind. i Eanke : Physiologic, S. 350. Leipsig, 1875. CHAPTER XVII. COMPOSITION OF THE BLOOD.— (Continued.) Having contrasted in a general way the composition of the liquor sanguinis with that of the red corpuscles, it remains for us now to con- sider a little more in detail the haemoglobin of the latter, as this sub- stance is of special interest from several points of view. When blood, drop by drop, is exposed to a cold of about 8° F., and then quickly warmed to 68° F., it will be observed that the corpuscles gradually lose their color, and that the serum becomes stained. This coloring matter from the corpuscles is capable of assuming the crystalline form, and has been indifferently called oxyhemoglobin, luematocrystallin, haemato- globulin, hemoglobin, and hrematosin, though, according to some chem- ists, the ultimate chemical composition of these principles is slightly different. The corpuscles, left colorless by the giving up of their haemoglobin, will retain for some time their form and elasticity, and consist largely of globulin. In this colorless condition the matter of which the cor- puscles consist is generally termed the stroma. The coloring matter of the blood corpuscles, or the haemoglobin, can be obtained in several ways. Among others, the following method, that of Preyer, 1 will usually give good crystals : Add enough water to a small quantity of blood free from Fig. 123 Prismatic crystals from human blood. (Kirkes.) Tetrahedral crystals, from blood of guinea-pig. (Kirkes.) fibrin, to make a clear solution and evaporate a drop under a thin cover- glass in a cool place. Should this plan fail add a little alcohol to the i Die Blutcfystalle, S. 18. Jena, 1871. HAEMOGLOBIN. 249 Fig. 125. solution and place it in a freezing mixture. Usually crystals will at once form. These crystals are more readily obtained from some animals than others — with greater facility, for example, from the blood of the dog, horse, and guinea-pig, than from that of man, and only with difficulty from that of the bat, mole, and mouse. The form of these blood crystals varies also in differ- ent animals. Thus they are pris- matic in form in man (Fig. 123), tetrahedral in the guinea-pig (Fig. 124), hexagonal in the squirrel (Fig. 125). From whatever source they are obtained they are transparent and doubly refracting, and when oxy- genated exhibit the color of the blood from which they were ob- tained. When deoxidized, however, they alternate from red to purple or green. They are soluble in Avater, alkalies, and most acids ; insoluble in alcohol, and will remain un- changed for some time in urine, bile. Oxyhemoglobin from the dog consists chemicallv, according to Hoppe- Seyler, 1 of C 53.85, H 7.32. N 16.17, 21.84, SO 39, FeO 43. The amount of haemoglobin present in a given quantity of blood can be determined from the amount of iron, by the spectroscope, and by colorometric methods. The ferric method is based upon the fact that dry (100 C.) haemoglobin contains 0.42 per cent, of iron. Knowing the amount of the latter in the blood the amount of haemoglobin can be at once calculated by the following equation : ^ , 100 Fe v : te, x equals Hexagonal crystals from blood of squirrel. 100 : 0.42 0.42 in which x is the unknown quantity of haemoglobin, Fe the known quantity of iron in the blood, and 0.42 the per cent, of iron in 100 parts of haemoglobin. To obtain the amount of iron in the blood whose haemoglobin is to be determined, a known quantity of blood is calcined, the ash is then treated with hydrochloric acid to obtain ferric chloride, which is then transformed into ferrous chloride by boiling with zinc until the liquid is colorless. The liquid being diluted, the amount of iron in it is determined, volumetrically 2 by adding from a burette per- manganate of potassium in standard solution until the rose color becomes permanent after agitation, 0.0056 gramme of iron being present for each centimetre of standard solution used. The haemoglobin, as deter- mined from the quantity of iron (27 grammes), amounts, according to Preyer, 3 in human blood to about 12.34 per cent. The spectroscopic method depends upon it having been shown by Preyer 4 that through an 0.8 per cent, solution of haemoglobin the red, i Med. Cheni. Unters., S. 370. 3 Op. tit . S 117. '-' Sutton : Volumetric Analysis, 4th ed., pp. 88, 94. * Ibid.. S. 124. 250 COMPOSITION OF THE BLOOD, yellow, and first band of the green can be seen, and that such a solution can be taken as a standard for comparison. A known amount of the blood whose haemoglobin is to be determined is therefore diluted until the same bands are seen spectroscopically, as with the standard solution; that having been done the amount of haemoglobin can be determined by the following equation : k : h + c : h xb = = k (b + c) x = -- k (b + c) b x = k (1 + e) in which x = unknown quantity of haemoglobin. k = per cent, of haemoglobin in solution (0.8). b = volume of blood = 1 centimetre. o = volume of distilled water. The colorometric method depends upon the comparison of the tint of the blood to be investigated with that of a standard solution. In de- termining the amount of haemoglobin in this way we make use of the hsemoglobinometer of Gowers. This consists (Fig. 120) of two glass Fig. 126. A. Pipette buttle for distilled water. B. Capillary pipette. C. Graduated tube. 1). Tube with standard dilution. F. Lancet for pricking the finger. tubes (D and C) of exactly the same size. Into D are placed 20 cubic mm. of blood diluted with 2000 mm. of water, the strength of the solu- tion is therefore 1 per cent. C is graduated, the scale of 100 decrees extending over a space equal to that in D containing the 1 per cent, diluted blood. The manner of using the apparatus is as follows : Into C are placed 20 cubic mm. of the blood to be examined, which is then diluted until its color is the same as that in D. Suppose, for example, H M M A T I N . 251 Fig. Vl'i that we have to add to the blood to be investigated placed in C only 30 degrees of water (600 mm.), in order to obtain the same tint of color as that in D, instead of as in the latter case 100 degrees of water (2000 mm.), it follows that the blood in B contains only 30 per cent, of the . normal quantity of haemoglobin. Further, if the number of corpuscles in the investigated blood has also been shown to be only 60 per cent, of the normal amount, we have a fraction |-g- = -|, the numerator being the per cent, of the haemoglobin and the denominator the per cent, of corpuscles, giving the average value of each corpuscle, or half the normal amount. When haemoglobin is subjected to the action of heat, acids, or caustic alkalies, its red color changes to a smutty hue, by decomposing into an albuminous substance and a colored one closely resembling bilirubin, and which has been described under the different names of haemin, haeruatin, haematoin, haematoidin, and haematosin, and is found in ex- travasations like apoplectic clots, corpora lutea, etc. (Fig. 127). We can obtain from 100 parts of haemoglobin, by adding hydrochloric acid, about 4 parts of haematin hv- drochlorate, C 34 1I 35 N 4 Fe 5 II CI, and 96 parts of an albuminous sub- stance. Haematin is insoluble in alcohol and water but soluble in acids and alkalies, and can be ob- tained from a very minute portion of blood by the following method : Triturate the suspected substance with a little common salt and add glacial acetic acid, then warm the mixture till bubbles appear and then cool it. If the substance thus treated contain blood crystals of haematin, hydrochlorate of haematin will ap- pear as rhombic tablets, disposed sometimes as stars or crosses of a red or brown color: if oxygen be added, the crystals become violet, and under the influence of carbonic acid lose their transparency. In medico-legal questions, where there may be a very small quantity of a material to be examined, the development of haematin crystals will settle the ques- tion as to whether the suspected material is or is not blood, hence the importance of the method just given from this point of view. It should be mentioned, however, that while the obtaining of haematin as well as haemoglobin crystals, by whatever method used, proves that the sub- stance from which they are extracted was blood, it does not follow that it was human blood. A still more delicate means of determining the presence of haemoglobin, and therefore of blood, is by spectrum analvsis, since both the arterial and venous blood through the haemo- Rhonibic crystals of hsemin or hydrochlorate of haematin, obtained by Lehman's method. They are obtained when blood is subjected to the action of a mixture of 1 part of alcohol, 4 parts of ether, and 1-16 of oxalic acid, and appear as thin brown- ish and brownish-green, striated, transparent crystalline laminae, often curiously twisted upon their long axes, and soon spontaneously changing into flat rhombic octahedra. (Carpenter.) 252 COMPOSITION OF THE BLOOD. globin they contain prevent the passage of certain rays of light, and so give rise to the dark absorption bands of the blood spectrum. In order to understand the manner in which spectrum analysis is applied to the study of the blood, let us first endeavor to explain briefly what is meant by spectrum analysis in general. As is well known, when sunlight is transmitted through a prism, as in Fig. 128, it is decomposed into the seven colors, violet, indigo, blue, Pig. 128. Scheme of a spectroscope for observing the spectrum of blood. A. Tube. S. Slit mm. Layer of blood with flame in front of it. P. Prism. M. Scale. B. Eye of observer looking through a telescope, r v. Spectrum. green, yellow, orange, and red. This is called the solar spectrum. In the early part of this century Fraunhofer described certain lines situated in these colors, and which since then have been known as Fraunhofer's lines (Fig. 129, 7), and which in all probability are due to the presence of certain chemical elements existing in the form of vapor around the sun and which prevent the passage of certain rays emitted by the solar nucleus, it having been demonstrated that a vapor absorbs rays of light having the same refrangibility as that which it emits. Thus a bright yellow line in the spectrum, due to incandescent sodium, will be replaced by a dark one if the light from the burning metal be intercepted by the vapor of the same. Since then it has been shown by Brewster, Herschell, and Miiller, that various colored solutions prevent the passage of certain of the rays of light, dark bands appearing in the spectrum in the place of the rays or colors arrested. In the same manner the influ- ence of blood upon the passage of light through it was investigated spec- troscopically (Fig. 128), more particularly by Hoppe-Seyler, 1 Stokes, 2 and Sorby, 3 and it was shown by these observers that when arterial blood is used two dark bands appear (Fig. 129, 1) between the Fraun- hofer lines D and E — that is, in the yellow of the spectrum, whereas if venous blood is used only one dark band (Fig. 129, 3) appears in the yellow near the line D. Further, it was demonstrated that this differ- ence between arterial and venous blood was solely due to whether the 1 Virchow's Archiv, 1862, Band xxiii. S. 446. 2 Proc. of Royal Society London, 1863, 1864, vol. xiii. p. 355. ;; Quarterly Journal of Science, 1865, vol. ii. p. 1U8. HAEMOGLOBIN 253 coloring matter or the haemoglobin was oxygenated or not, and that the fact of the arterial blood being red or scarlet, and of venous blood being blue or purple, "was owing to oxyhemoglobin being of a red hue and haemoglobin of a bluish one. That the difference between arterial and Fig. 129. Red. Orange. Yellow. Green. Blue. Indigo. si aJB C _Z> i ixyhsemoglobin and NOo-Ha;- moglobin. CO-Hsenioglobiu. Reduced Haemo- globin. Hajmatin in acid solution. Hwmatin in al- kaline solution. Reduced Hsema- tin. •olar spectrum with Fraun- hofer's lines. jo M J2 js 1-t venous blood spectroscopically, and as regards color, is due simply to the haemoglobin being oxygenated in the former case and unoxygenated in the latter, can be readily demonstrated. Thus, if some reducing agent like ammonium sulphide or an alkaline solution of ferrous sul- phate, kept from precipitation by tartaric acid, be added to arterial blood or the washings from a blood clot, the oxygen, being loosely com- bined with haemoglobin, is at once seized with avidity by the reducing agent, the two dark absorption bands disappear, being replaced by the one dark band characteristic of venous blood, and the color changes from red to blue. On the other hand, with the exposure of venous blood or a solution of haemoglobin to oxygen, or air containing such, the one dark band will disappear, being replaced by the two dark bands so characteristic of arterial blood, and the color will change from blue to red again. According to the amount of oxyhaemoglobin present in the blood, or solution of haemoglobin used, the dark bands will vary in extent. Thus, in a concentrated solution the two bands run into one, there being a general absorption at the blue and red ends of the spectrum, also the light then passing through only the green and red parts. With a still further increase in the strength of the solution light will be trans- mitted through only the red portions of the spectrum, hence its red 254 COMPOSITION OF THE BLOOD. color, as seen by transmitted light. It is hardly necessary to add that the red rays are the last to disappear. The extreme delicacy of spectrum analysis, as applied to the deter- mination of the presence of blood, may be appreciated from the fact of the two bands appearing in the spectrum of light transmitted through a layer 1 centimetre thick of a solution containing only 1 gramme (15.4 grains) in 10,000 c. cm. (20 pints of water, or, in round numbers, about 1 grain of haemoglobin in a pint and a third of water. This is an im- portant fact, since, under certain circumstances, in medico-legal cases, for example, the quantity of the suspected substance being exceedingly small, spectrum analysis would be the only means by which it could be determined whether it was blood or not. Indeed, substances already decomposed and putrid, solutions made by washing with water, old stains upon iron, wood, linen that may have lain aside unnoticed for years, can be shown by the spectroscope to contain hgemoglobin. and necessarily, therefore, to have been derived from blood, since no other known substance affects light as haemoglobin. Even if the spectrum obtained was that of carbonic oxide, or haema- toin (acid haematin), characterized by two and one absorption bands respectively (Fig. 129, 2, 4), as in the case of arterial and venous blood, this need be no source of confusion, since the absorption bands of car- bonic oxide and hsematin are not situated in exactly the same part of the spectrum as those of arterial and venous blood, and even if a doubt existed as to the exact locality of the bands, there could be none with reference to the presence of blood, as it is the haemoglobin in such case, combined with either oxygen or carbonic acid, or otherwise modified, which is the cause of the appearing of the bands. It should be men- tioned in this connection that spectrum analysis, like all other means at present at our command, enables us only to determine that a sub- stance is blood, but not necessarily human blood. In examining the blood spectroscopically, while the ordinary spectroscope can be used, the microspectroscope will be found more convenient, and especially the form described by Vierordt. 1 In the fact of the oxygen of the blood existing, for the most part, in a state of loose chemical combination with the haemoglobin lies the explanation of the manner in which blood absorbs or gives off oxygen. Did the oxygen exist simply in a state of solution in the blood then the amount absorbed, or given off, would depend upon the amount of pres- sure present. That such is not the case, however, can be shown by exposing venous blood, containing little or no oxygen, to a succession of atmospheres containing increasing quantities of oxygen. At first there is a very rapid absorption of oxygen, but afterward this dimin- ishes or ceases altogether. On the other hand, if arterial blood, con- taining a considerable quantity of oxygen, be exposed to successively diminishing pressures, at first little oxygen is given off, but afterward the escape is sudden and rapid. The amount of oxygen taken up or given off by blood is not, therefore, dependent upon pressure, except so 1 Die Quantitative Spectral Analyse in ihrer Anwendung auf Physiologic. Tubingen, 1876, GASES OF THE BLOOD. 255 far as the latter influences the passages to or from the plasma, but upon chemical affinity ; the amount of oxygen absorbed, or given up by the haemoglobin, is, therefore, a given amount, 1.76 c. cm. of oxygen for 1 gramme of haemoglobin. In this connection it may not be inappro- priate to mention that the oxygen absorbed, or given off* by the haemo- globin, has nothing to do with the oxygen entering into its molecular composition, and as already given in its chemical formula. That the haemoglobin is that part of the blood which absorbs and gives up the greatest part of the oxygen there can be no doubt, since, if serum freed of the corpuscles, and therefore of haemoglobin (the latter constituting 90 per cent, of the former), be experimented with, instead of blood, little or no oxygen is absorbed, or given off", perhaps ^ per cent, of the entire blood, of which the serum was a part, and that pro- portional to the pressure. It is, therefore, to their haemoglobin that the red corpuscles owe their function, as we have seen, of being oxygen carriers, and since the haemoglobin at low pressure readily gives up its oxygen, the significance of this substance, in respiration, becomes very evident. In this connection it may be mentioned that the carbonic acid present in the blood does not appear to be simply dissolved there, since the absorption and giving up of carbonic acid by the blood, as in the case of oxygen, is not dependent upon pressure. It is highly probable that the carbonic acid exists in the blood as sodium bicarbonate and carbonate, and quite possible that the hiemo- globin of the red corpuscles may play the part of an acid, decomposing these salts, and setting the carbonic acid free, since more carbonic acid is given off* when blood is subjected to a mercurial vacuum than when serum alone is used. It is well known that after all the carbonic acid has been extracted from the serum that is possible by the gas pump, two to five per cent, more can be obtained by adding acid to the serum. The small amount of nitrogen that the blood contains appears to exist there in a simple state of solution, the blood absorbing but little less nitrogen than that absorbed by water: the amount depending, at least. within limits upon the law of pressure. The gases of the blood, as has just been incidentally mentioned, can be obtained by subjecting the blood to the mercurial vacuum. For this purpose we make use of Grehaut's gas pump, as constructed by Alver- gniat, of Paris. This consists (Fig. 130) of a glass reservoir (15 ). which can be lowered or raised by a rack and pinion, and which communicates by the flexible tubeb with the vertical glass tube c, one metre in length, and which is firmly secured to the stand. The vertical tube expands into the oval-shaped dilatation A. which is continued upward as the narrow tube f, and whose cavity, by means of the stopcock R, can be put in communication either with that of the lateral tube h, or of the tube i terminating above in the cup C, or cut off* from either. The lateral tube h is connected through tubing (h / ) with the stem e of the bulb D, into which is inserted a flexible tube (1) furnished with a stopcock (r), for the transference of the blood whose gases are to be determined. The stopcock (R) being in the position 1, Fig. 130 — that is, all communication between the cavity of the vertical tube c 256 COMPOSITION OF THE BLOOD. being completely cut off' from that of the lateral and terminal tubes h and i, mercury is poured through the reservoir B until it not only rises to the level of the stopcock, but completely fills the reservoir itself. The reser- Fig. 130. Alvergniat's gas pump. (Bert.) voir being then lowered the mercury will fall in the vertical tube c, a vacuum being produced in consequence above it. If the stopcock be now turned into the position 2 (Fig. 130), the air will pass in from the lateral tube and its appendage into the vertical tube c, and the mer- cury will fall still lower. The stopcock being now returned into the position 1 (Fig. 130), the reservoir is then elevated, and the mercury with the included air will ascend into the oval dilatation A. The GASES OF THE BLOOD. 257 Fig. 131. (After Sanderson.) stopcock being now turned into the position 3 (Fig. 130), the air that was just drawn into the vertical tube c from the lateral tube h passes out of the tube i into the atmosphere. The stopcock is then returned to the original position (Fig. 130, 1). By depressing and ele- vating the reservoir B, and manipulating the stopcock R in the manner just explained, in a very short time a good vacuum is produced in the lateral tube h h/ e, and its appendage D. A tube having been inserted into the artery or vein, the blood to be analyzed is then trans- ferred from the vessel in the living animal to the vacuum in the follow- ing manner : A tube (M) of known capacity, say 50 c. c, tapering oft* at one end (G), and guarded by a stopcock (B) at the other, is filled with mercury by aspiration. The tube is then at the end B put in communication with the bloodvessel, by means of a rubber tube readily slipping over the canula previously inserted into the vessel, which is closed by a clip. The stop- cock being now opened, and the clip removed, the blood is allowed to flow away for a moment, and then (connection being made by the tubing) into the tube M, driving out of the latter the mercury, which can be received into a convenient receptacle. As soon as the tube is filled with blood, the stopcock being closed, connection is broken with the vessel, and the tube reversed in position, so that its tapering end G (Fig. 131) may be inserted into the small mercury trough U, previously placed in the large trough N containing ice-water, to retard the coagu- lation of the blood in the tube. The glass tube is then joined by the end B to the rubber tube D containing boiled distilled water, and previously placed over the tube t (Figs. 130, 131), the latter being furnished with a stopcock (Fig. 130, r) and leading to the vacuum. Both stopcocks (B and r) being now opened, the blood passes from the glass tube (Fig. 131, M) into the vacuum D e (Fig. 130), its place being filled with mercury from the trough ; the stopcocks are then closed. The blood having passed through the tube into the bulb D, gives up its gases readily into the vacuum, the liberation of which is greatly facilitated by surrounding the bulb with water (Fig. 130) at a temperature of about 40° Cent. (104° Fahr.). As it is also desirable to keep back the froth and foam arising from the blood as much as possible, the lateral tube e is surrounded by a tin one, through which ice-cold water flows from a reservoir (z), and which effectually accomplishes the object. The gases having been separated from the blood, are next transferred into the vertical tube c, and thence through the terminal one i into a eudiometer, standing over mercury in the cup C, by depressing the mercurial reservoir B, and turning the stopcock R in the same manner as just explained. The quantity of blood from which the gases are obtained will, of course, depend upon the size of the tube transmitting the blood from the vessel to the vacuum, the vessel being clamped as soon as the tube is full of blood. 17 258 COMPOSITION OF THE BLOOD. In order to determine the nature ami amount of the gases given off from the blood we make use of a eudiometer, slightly bent up at the end. Supposing that the gases have passed out of the pump and have displaced part of the mercury in the eudiometer, we then add caustic potash in solution, and to drive out all bubbles of air close the tube by inserting a cork through which a capillary tube passes of the shape represented in Fig. 132. The tube is then tilted, the fin- Fig. 132. ger being firmly placed on the top of the capillary opening, and the caustic potash makes its way up through the mer- cury and combines with the carbonic acid gas. The eudi- ometer being then placed in the mercurial trough and shaken up a few times, until the level of the mercury in the eudiometer and the trough are the same, the amount of carbonic acid is read off, the condition of the barometer and temperature of the laboratory being at the same time noted. In determining the presence and amount of the oxygen gas Ave pro- ceed in precisely the same way, only making use of a solution of pyro- gallic acid instead of caustic potash. After having determined the amount of carbonic acid and oxygen, what remains in the eudiometer may practi- cally be regarded as consisting of nitrogen. The volume of the gas obtained must be reduced, of course, to standard pressure 760 mm. mercury, and standard temperature 0° C, which can be done by the V' X h following formula : F"=— — — — , in which V is the required 760(1 + at) l volume at standard temperature 0° C. and standard pressure 760 mm. V the volume at the observed temperature and pressure, h the observed pressure, a the coefficient of expansion, a constant (.003665), and t the observed temperature. The formula is derived as follows. Firstly, with reference to the correction of the given volume for temperature : 1 + at : 1 : : V : V or V 1 + at And secondly, for pressure : V : : : h : io<' or J 1 + at 700 (1 + at) As an illustration of the manner of using the formula the following example will suffice. Suppose the given volume V of gas to be cor- rected for temperature and pressure amounts to 30 c. c, the observed barometric pressure h being 740 mm. and the temperature t of the room 15° C. : then the required volume, or v _ 30 X 740 22200 - g 760 (1 + .003665) " ' 80.178200 " that is to say, 30 c. c. of a gas, the temperature being 15° C. and the pressure 740 mm., are reduced to 27.0 c. c. at standard temperature 0° C. and pressure 700 mm. In purely physical researches upon gases, still further corrections are ARTERIAL AND VENOUS BLOOD. 259 made for the tension of the aqueous vapor, and for the meniscus; the errors due to these influences are, however, so small that in physiological investigations they are usually neglected. It will be found on an average that for 100 vol. of blood used there will be extracted by means of the mercurial pump about 60 vols, of gas, the barometric pressure being 760 mm. (30 cub. in.) and the tempera- ture 0° C. (32° F.), and that the composition of this gas 'will be accord- ing to the kind of blood examined, as follows : Oxygen. Carbonic acid. Nitrogen. Arterial blood 20 vol. 39 vol. 1 to 2 vol Venous blood . 8 to 12 " 46 " 1 to 2 " It is evident, therefore, that arterial does not differ from venous blood in containing more oxygen than carbonic acid, since there is more car- bonic acid than oxygen in arterial as well as in venous blood, but in the fact that while the carbonic acid is in excess in both instances there is more oxygen in arterial than in venous blood, and more carbonic acid in venous than in arterial blood. It will be observed, according to Table XL VIII., that there are fewer red corpuscles in arterial than in venous blood. According to some other authorities, however, the reverse is the case, the arterial containing more corpuscles than the venous blood. It must be remembered, how- ever, that the red or blue color of the blood depends not so much upon the relative number of corpuscles present as upon the fact of the haemo- globin of the same being oxidized or deoxidized. There are other minor differences between arterial and venous blood, as may be seen from Table XLVIII., but the essential difference depends upon the amount of oxyhemoglobin present, the analyses of Poggiale, 1 Nasse, 2 Lehmann, 3 etc., showing that while there is a variability in the relative quantity of the other substances the differences are only fractional. Table XLVIII. 4 — Blood. Arterial (red). Venous (blue). /-1 f Oxygen 20 per cent. vol. 10 per cent. vol. " \ Carbonic acid 29 per cent. vol. 46 per cent. vol. Water. Fibrin. Extractives . More. Less. Salts. Sugar. Corpuscles. Albumen . . Less. More. Fats. The composition of the blood in the arterial system is pretty much the same throughout the body : that of the venous, however, differs con- siderably according to the parts and time of examination. We have already studied the blood of the splenic vein, and have seen how that of the portal is modified by admixture with that of the former and by the products of digestion, and have considered the difference in the blood of 1 Comptes Rendus, 1848, t. xxvi. p. 143. - Wajnier : Physiologic, Band i. S. 170. 3 Physiologie Chemie, Band ii. S. 203. 4 Ranke : Physiologic, 1875, S. 358. 260 COMPOSITION OF THE BLOOD. the hepatic vein as compared with that of the portal. The peculiarities of the blood of the pulmonary and renal veins will be deferred till the lungs and kidneys have been considered. As the albuminous principles of the body agree essentially in their general chemical composition with each other and with the albumen of the blood and food, and as all these principles are readily transformed into each other, it is probable that the albuminous substances of the body generally, like ostein, cartilagin, globulin, etc., are derived directly or indirectly from the albumen of the blood. This view, if correct, explains why the blood contains such a large quantity of albumen, amounting to 71 parts when dry or 329 in a moist condition in 1000 parts of blood. Generally speaking, the blood of strong, vigorous persons contains most albumen, that of weak ones the least. The amount of albumen may in health vary slightly above or below the normal standard, but if it falls much below it is an evidence of dis- ease. Thus there is a diminution in Bright' s disease of the kidneys, where a large amount of albumen disappears from the blood, transudes through the vascular system, and escapes in the urine. As the character of albumen has been already described, I will not dwell further upon it. There has always been and is still, a considerable difference of opinion among physiologists as to the role of fibrin in the blood ; as to whether it is effete and useless, or whether it is susceptible of being elaborated into something further and useful. Among the many views that have been offered as to the nature of fibrin that of Milne Edwards is, perhaps, the most plausible. According to this distinguished physiologist, fibrin is a product of the activity of the tissues, and in normal circumstances is as rapidly destroyed as formed in the blood by the corpuscles, being burnt up by the oxygen carried by these bodies and converted into excrementitious material. The correctness of this view can be tested by considering whether it will explain the different amount of fibrin present in the blood in the various conditions that the system may be subject to. Thus, if the theory be correct, the proportion of two to three parts of fibrin in 1000 of blood should increase or decrease as the activity of the tissues increases or decreases, the amount of the corpuscles remaining unchanged. Should the number of the corpuscles, however, diminish, the activity of the tis- sues remaining the same, the fibrin ought to increase in amount. If, however, the number of corpuscles diminishes at the same time that the activity of the tissues is lowered, the amount of fibrin will remain unaf- fected. Let us see whether these theoretical conditions are ever realized in the living animal. It is well known from the researches of patholo- gists, more particularly from those of Andral, that there is invariably an increase of fibrin in acute inflammations like those of pneumonia, pleurisy, diseases in which there is an excess at first of vital action in the tissues affected. On the other hand, in diseases like typhoid fever, when the vital forces are greatly prostrated, the amount of fibrin is diminished. In these diseases, at least in the early stages, the number of the corpuscles remains the same. In chlorosis, however, where the number of corpuscles is diminished, the amount of fibrin increases. SALTS OF THE BLOOD. 261 Anaemia is an illustration of the amount of fibrin remaining constant while the vital powers are lowered and the number of corpuscles dimin- ished coincidently. This inverse ratio between the corpuscles and the fibrin is seen also in gestation, where the fibrin is increased and the cor- puscles are diminished. The blood from the splenic vein is also rich in fibrin, but deficient in red corpuscles, and it is well known that repeated bleedings increase the fibrin but diminish the corpuscles. Many facts like the above, and others often apparently contradictory, illustrate this antagonism, so to speak, between the corpuscles and the fibrin. 1 It must be admitted, however, that in all the analyses made of the blood there are white corpuscles, etc., in the fibrin which are estimated with it, and this should be remembered when the amount of fibrin stated to have been found in an analysis is taken as the basis of a theory. It is well known that in some cases the increase in the amount of the fibrin corresponds exactly to a diminution in that of the albumen, so that one source of the fibrin may be due to a transformation of the albumen. The very small amount of fibrin in the blood, even when estimated in the moist condition, being only then about 8 parts in the 100", together with facts like those mentioned above, leads one to consider fibrin rather as effete matter. Still further investigation may assign some function to it as yet unknown. The fatty matters that are found in the blood consist of serolin, cholesterin, phosphorized fats, and saponified principles like the oleates, margarates, etc. Sometimes the oleic acid exists in a free state. The fatty substances, as may be seen from Table XLIV., exist only in small quantities in the blood, and often depend upon the kind of diet. Thus fatty food increases the amount of fat in the blood. The use of these fatty substances in the blood is not exactly understood. According to some physiologists, it is thought that the fats contribute to the forma* tion of the corpuscles, it being well known that the number of these bodies increases under the administration of cod-liver oil. The saline materials of the blood consist of sodium, potassium, and magnesium chlorides, some free soda, of sodium and potassium carbo- nates, of sodium, potassium, and magnesium sulphates, of sodium, potas- sium, magnesium, and calcium phosphates: in a word, three chlorides, free soda, two carbonates, three sulphates, four phosphates. It is pos- sible that these salts do not always exist in the blood in the above form, that arrangement being due perhaps to the difficult and complicated processes incidental to their analysis. It is well known that a con- siderable quantity of the earthy phosphates is molecularly united with the fibrin and part of the sodium chloride with the albumen. The natural relation of these salts as well as that of the others must, there- fore, to a certain extent, at least, be disarranged in an analysis. The importance of these salts is seen not only in the nutrition of the tissues, the calcium and magnesium phosphates, for example, supplying material for the production of bone, but they are also indispensable in maintaining the blood in its proper chemical and physical condition. Thus the alkalinity of the blood is due to its sodium carbonate, while i Milne Edwards: Op. tit., tome i. pp. 258-274. 262 COMPOSITION OF THE BLOOD. the sodium phosphate dissolves the albuminous principles and inorganic "matters which are insoluble in pure water. The earthy phosphates are held in solution in the serum through the presence of this salt, and to it is due the fact that so much carbonic acid is dissolved in the blood. The existence of the corpuscles depends on the presence of sodium chloride and other salts in the serum, which, absorbing any superfluous water, prevent their dissolution. According to Milne Edwards, 1 the coloring matter of the corpuscles is very soluble in water, but not so in water to which have been added albumen and sodium chloride, both of which are found in the serum. While probable, yet it cannot be stated positively, that age or sex influences the quantity of these salines. There is no doubt, however, that these principles vary in quantity according to the kind of food. An exclusively animal or vegetable diet will affect the amount of alkaline phosphates respectively. Thus the former are most abundant in the blood of the carnivora, the latter in that of the her- bivora. The proportion of the saline principles of the blood is also known to vary in disease ; but the limited data, however, that have been col- lected are of more interest at present to the pathologist than to the physiologist. One of the most important substances found in the blood is iron. Indeed, when it is deficient the red corpuscles diminish in number. The normal standard is soon regained, however, when iron is administered. The iron exists in the blood combined with the coloring matter of the corpuscles ; the color of the latter, though, does not depend upon the iron, as was once supposed, for the color will remain after the iron is removed, while the blood of certain invertebrates like the Limulus (horseshoe crab) is colorless, though iron is present. As to the exact v amount of iron in the blood there is still some difference of opinion. According to Schmidt (Table XL VII.), it is still undetermined. Bec- querel and Rodier give 0.5 part in the 1000 of blood, while Kuss 2 estimated it at 7 per cent, of the hsematosin or hsemacrystallin or coloring matter, which would give about 7 grammes of iron (over 100 grains), there being, according to that physiologist, about 100 grammes of luematosin in the blood. Various other substances are found in the blood in addition to those already mentioned, which I will consider when the subject of excretion is taken up ; such are urea, uric acid, creatin, creatinin, etc. Summing up, it may be said that the blood consists largely of water carrying in solution corpuscles, albumen, salts, and excrementitious mat- ters, and that the corpuscles are a source of pow T er, while the albumen and salts furnish materials to the tissues, the salts, in addition, regu- lating the character of the blood. In concluding this sketch of the blood a few words may be said in reference to transfusion, though this subject is usually considered as belonging to therapeutics. About the middle of the seventeenth cen- tury experiments were performed which showed that life could be saved in an animal dying from a copious hemorrhage, for example, by intro- ducing into its vessels fresh blood from an animal of the same species. Application was soon made of this fact in the treatment of human 1 Op. cit., tome i. p. 177. - Op. cit., p. 118. TRANSFUSION. 263 beings, and the wildest enthusiasm was excited, great hopes being entertained that old age could be rejuvenated, etc. Several fatal cases of transfusion, however, occurring, the practice was prohibited in many places, by law. It was revived in the early part of this century, and with success. There are a number of cases on record 1 which would have undoubtedly proved fatal had not transfusion been used. It seems to be particularly efficacious in cases of uterine hemorrhage. When blood is transfused it should be introduced very slowly, and great cau- tion should be exercised lest any air be mixed with it, and the quantity used be small, not exceeding three or four ounces. Having studied the general character of the blood, let us now turn to the consideration of its circulation. 1 Beranl : Physiologic, tomo iii. p. 219. Paris, 18.51. CHAPTER X Y 1 1 1 CIRCULATION OF THE BLOOD. We have seen that the use of the food is to repair the waste of the tissues, to supply fuel for the production of heat and force, and that the food is digested, absorbed, and gradually elaborated into blood. To supply the wants of the system, to furnish the tissues with material for their maintenance and repair, to carry away that which has become worn out and effete, the blood must move freely through all parts of the economy. It must circulate. By the circulation of the blood is meant that the blood moves in a circle — that is, if we follow its course, for example (Fig. 133), after it passes from the left ventricle of the heart to the aorta we shall see that the blood flows from the aorta into the arteries, thence into the capillaries, from there into the veins, from the latter by the vena cava into the right side of the heart, from the right side of the heart through the lungs back to the left side of the heart to the left ventricle, where it started. Usually the passage of the blood from the right auricle of the heart through the lungs and left ventricle is known as the lesser, or pulmonary circulation, while the route from the left ventricle through the arteries, capillaries, and veins to the right auricle is distinguished as the greater or systemic circulation. Using the word circulation in the sense in which it is ordinarily accepted, the terms lesser and greater circulations are not appropriate, and may mislead, inasmuch as we have seen that the blood does not pass directly back from the lungs to the right auricle of the heart, whence it came, but indirectly, first coursing through the system, and that the blood flowing from the left ventricle only returns there after having passed through the lungs. There is, in this sense, then, only one circulation, however conveniently the latter may be divided into the so-called lesser and greater circulations. In another sense, however, there are innumerable circulations, greater and lesser, since the blood, after leaving the heart (Fig. 133), may go either to the head, or viscera, or extremities before returning to the heart. As the motion of the blood is in a circle, it is immaterial at what part of the vascular system we begin its study. We shall see, however, that in exposing any of the great functions of the body, if we follow, as far as practicable, the order in which the facts were actually discovered, and the phenomena generalized by the human mind, that the subject will be presented in the most natural logical sequence. We will begin, therefore, the study of the circulation of the blood, with the demonstra- tion of the structure and function of the heart. THE HEART. 265 The Heart. The heart is a hollow pear-shaped muscular organ. It is situated in the thoracic cavity, and lies between the lungs, with which it is con- nected by the great bloodvessels arising from its base (Fig. 134). The Fig. 133. Fio. 134 c. a. j. v. Lungs. Diagram of the circulation. 1. Heart. 2. Lungs. 3. Head and upper extremi- ties. 4. Spleen. 5. Intestine. 6. Kid- ney. 7. Lower extremities. 8. Liver (Dat.ton.) i. ii. r. v. a, r. a. 1. r. Heart and lungs of man. (Milne Ei. wards.) heart is loosely enclosed in a sac. the peri- cardium. This sac. having the form of the heart, and of a bluish-white color, consists of two layers. The external fibrous layer, continuous with the exter- nal coat of the great bloodvessels, con- sists of fibrous tissue, and is a strong, inextensible membrane. The internal delicate serous layer does not differ essen- tially in its general character from that of serous membrane. It surrounds the heart, closely adhering to it, and is then reflected over the commencement of the great bloodvessels and the interior sur- face of the external fibrous membrane. The cavity of the pericardium contains about a drachm or two of a serous fluid, through the presence of which the opposed internal surfaces of the pericardium glide smoothly over each other, the movements of the heart being thereby facilitated. 266 CIRCULATION OF THE BLOOD. The pericardium is attached by connective tissue to the pleura on each side, and tlit* tendinous centre of the diaphragm below. It is not neces- sary to give a detailed, minute description of the disposition of the mus- cular fibres of the heart, which is quite complex, a general account in connection with the present subject being sufficient. The auricles, or upper cavities of the heart (Fig. 135, d, e), are encircled by a thin layer Fro. 135. WM 111 Anterior view of heart. (Quain Fig. 136. of muscular fibres, common to both these cavities, and surrounding the auricular appendages, the entrance of the vena cava, the coronary and pulmonary veins. Beneath this superficial layer are the fibres of the deep layer attached to the fibrous rings of the auriculo-ventricular orifices, and disposed in an annular and loop-like man- ner. The muscular fibres of the ventricles, like those of the auricles, are also arranged in two sets, superficial and deep. The superficial fibres (Fig. 135, a, 6), which are common to both ventri- cles, run from base to apex, and at this point pass into the interior of the ventricle in the form of a whorl or spiral, some of the fibres terminating in the columns carnete and papillary muscles, others returning after a twisting course to the point from which they started. The fibres of the deep set (Fig. 136) surround each ventricle separately, and are disposed in a circular or transverse manner between the external and internal layers of the superficial fibres, and are much better developed in the left ventricle than in the right. Left ventricle of bullock's heart, sh owing the deep fibres. (Dalton.) THE HEART, 267 Microscopically the muscular substance of the heart consists of transverse striated muscular fibres. These fibres, however, differ from the ordinary fibres of voluntary muscles in several particulars. They are destitute of sarcolemma, much smaller and more granular, not col- lected into bundles, and are separated by comparatively little connective tissue. The most interesting peculiarity, however, about these fibres, is their anastomosing or inosculation with each other (Fig. 137). Their connecting fibres, no doubt, favor the contraction of the heart and thorough expulsion of the blood from its cavities. If a longitudinal section be carried through the heart from base to apex, its interior will be seen from such a section to consist of four Fig. 137. Fig. 138. Heart of manatee. RV. Right ventricle. LV. Left ventricle. Muscular fibres of tlie heart. (Qoain cavities : two auricles, so called from their auricular appendages, and two ven- tricles; that the right aur- lcle communicates with the venas cavae and with the right ventricle, and the left auricle with the pulmonary veins and the left ventricle, but that there is no communication between the two auricles or between the two ventricles ; the right or venous side of the heart being completely separated from the left or arterial side by the septum of the heart, which is imperforate. In certain mammals in the dugong (halichore) and manatee (man- atus) for instance, this distinction of the right from the left side of the heart is to a certain extent visible, even externally (Fig- 138), the ventricles at the apex being separated by quite an interval. We have just seen that the heart is covered with the serous layer of the pericardium. It will be observed that the interior of the heart is also lined by a thin translucent membrane, the endocardium, which 268 CIRCULATION OF THE BLOOD. is continuous with the internal coat of the bloodvessels and consists of a fibrous elastic and epithelial layer. Just at the point where the auricle, that of the right side, for example, passes into the ventricle, the endocardium projects into the cavity of the heart from the wall of the heart on one side, and from the septum on the other. This portion of the endocardium is strengthened by the addition of fibrous tissue. Fig 139. The right auricle and ventricle opened, and a part of their right and anterior walls removed so as to show their interior. %. (Quai.v.) It is these projections that serve to divide the auricle from the ven- tricle. The interval left between these projections constitutes the auriculo-ventricular orifice. The fibro-elastic tissue in this situation forms a slight ring, to Avhich is attached the tricuspid valve (Fig. 139, 141, 5, L', b"), three membranous folds, which consist of doublings of the endocardium thickened by the included fibrous tissue. By means of these curtains or valves, the auriculo-ventricular orifice can be closed, the edges of the valves being then pressed together (Fig. 141), as we shall see by the blood, and are kept stretched by the ten- dinous cords as the sail of a boat is kept stretched against the wind by the sheet line. The chordee tendinese are tendinous cords inserted into the valve, and arise either directly from the walls of the ventricle or are connected with THE HEART, 269 it by the papillary muscles. Of these latter many pass directly again into the substance of the heart and are then known as the fleshy columns or columnse carnese. During the repose of the ventricle the auriculo-ventricular orifice is open, the valves then lying loosely against the walls of the ventricle. The same disposition, such as we Fig. 140. h rv *jiC\if: WMmW The left auricle and ventricle opened and a part of their anterior and left walls removed so as to show their interior. %. The pulmonary artery has 1 n divided at its commencement so as to show the aorta ; the opening into the left ventricle has been carried a short distance into the aorta between two of the segments of the semilunar valves ; the left part of the auricle with its appendix has been removed. The right auricle has been thrown out of view. (Quain.) have just described, obtains essentially in the left side of the heart. The mitral valve, however (Figs. 140 and 141, 6, 6'), by which the left auriculo-ventricular orifice is closed, consists of two membranous folds instead of three, as is the case in the tricuspid valve, and is stronger than the latter. It will be observed that the tricuspid and mitral valves open from the auricle toward the ventricle, but do not project from the ventricle into the auricle. At the anterior angle of the base of the right ven- tricle (Fig. 141, 7), may be seen an orifice guarded by three cresentic 270 CIRCULATION OF THE BLOOD, membanous folds, the semilunar valves. Through this orifice the right ventricle communicates with the pulmonary artery. The semi- lunar valves consist of doublings of the endocardium, strengthened by fibrous tissue. The convex border of each valve is attached to the edge of the ring-like orifice of the pulmonary artery, the free edge projecting into the latter. Behind each semilunar valve the artery is dilated into a pouch, the sinus of Valsalva. This sinus prevents the valve when open from adhering to the walls of the artery, and enables the blood to get behind each valve and press it down so that the three valves meet (Fig. 141, 7), and so close the orifice, but readily separate Fig. 141. View nf the base of the ventricular part of the heart, showing the relative position of the arterial and auriculo-veutricular orifices. %. The muscular fibres of the ventricles are exposed by the removal of the pericardium, fat, bloodvessels, etc.; the pulmonary artery and aorta have been removed by a section made immediately beyond the attachment of the semilunar valves, and the auricles have been removed immediately above the auriculo-ventricular orifices. when the flow is from the ventricles toward the great vessels, preventing a reflux from the great vessels back into the ventricle. At the middle of the free border of the semilunar valves may be seen a little nodule of fibrous tissue. These nodules, or corpora Arantii serve as a common central point of contact when the valves are closed. The semilunar valves of the aorta (Fig. 141, 8) do not differ in their structure or function from those of the pulmonary artery, and, like the latter, act when in contact in closing the orifice of communica- tion between the left ventricle and the aorta. The manner in which the tricuspid and mitral valves act can be readily demonstrated by filling the ventricles with Avater by means of a funnel introduced into the orifices of the pulmonary artery and aorta ; the water rising up between the walls of the ventricles and the valves will float the valves up until their edges are approximated, so closing the auriculo-ventric- ular orifices. By pouring water into the pulmonary artery and aorta it will be seen that the water gets in between the wall of the vessel and the valve, into the sinus of Valsalva, and so forces the free edges of the semilunar valves toward each other, thus effectually closing the orifices at the mouths of the great vessels. THE HEART. 271 Such being the general structure of the heart, let us consider now the course that the blood takes in passing through it. In watching the heart beating in a living animal, a mammal, for example, it will be ob- served that at the same moment the right auricle is dilated by the venous blood flowing from the system through the vense cava;, the left auricle is dilated by the arterial blood flowing into it through the pulmonary veins from the lungs. This synchronous dilatation of the auricles is known as the auricular diast< >le. Suddenly, and succeeding this auricular diastole, or filling up of the auricles, both auricles simultaneously contract, the venous blood passing from the right auricle into the right ventricle, the arterial blood from the left auricle into the left ventricle, regurgitation to any extent into the venae cavee or pulmonary veins being prevented by the muscular fibres encircling these vessels and the pressure of the blood. This synchronous contraction of the auricles is called the auricular systole. As in the experiment just performed with the water, so the blood within the ventricles of the heart of the living animal gets in between the walls of the ventricles and the flaps of the tricuspid and mitral valves and floats the edges of the valves up until the auriculo-ventricular orifices are closed. At this moment, the ven- tricles being fully dilated simultaneously contract, with the effect of still more thoroughly approximating the tricuspid and mitral valves than is the case at the end of the auricular systole, and so of more completely closing the auriculo-ventricular orifices. The papillary muscles contracting at the same time as the walls of the ventricles and acting through the chorda; tendineae upon the valves stiffen them and prevent their inversion into the auricles. The synchronous filling up and contraction of the ventricles is known as the diastole and systole of the heart, but more properly as the ventricular diastole and ven- tricular systole. During the ventricular systole the auricles are receiv- ing blood from the venae cava? and the pulmonary veins. Inasmuch as regurgitation backward from the ventricles into the auricles is prevented through the auriculo-ventricular orifices being closed by the approximation of the tricuspid and mitral valves during the ventricular systole, the venous blood passes from the right ventricle through the pulmonary artery to the lungs, and the arterial blood from the left ventricle through the aorta to the system. Immediately after the ventricular systole or contraction of the ventricles follows their relaxa- tion. During this period the heart is in repose. The auriculo-ventricular orifices are again open, the venous and arterial blood that has accumu- lated in the right and left auricles respectively during the contraction of the' ventricles and while the auriculo-ventricular orifices were closed, now flows into the ventricles, while this blood is replaced by the venous blood flowing into the right auricle from the vense cavae, and the arterial blood flowing from the pulmonary veins into the left auricle. Toward the end of the ventricular systole the venous and arterial blood, forced respectively into the pulmonary artery and the aorta, gets in between the walls of the vessels and the semilunar valves in the sinuses of Val- salva, and forces their free edges toward each other as in the experiment just performed with the water. At the end of the ventricular systole, the semilunar valves being closely approximated and the orifices of the 272 CIRCULATION OF THE BLOOD. great vessels closed, through the elastic recoil of the arteries on their contents, the blood, being unable to regurgitate backward from the pulmonary artery and aorta, is forced on to the lungs and the system. It will be seen from the phenomena just described that, while the right side of the heart containing venous blood is entirely distinct from the left containing arterial, nevertheless, the two sides of the heart act as one — the venous blood flowing into the right auricle as the arterial blood flows into the left, the synchronous filling up and emptying of the auri- cles being followed by the synchronous dilatation and contraction of the ventricles, both ventricles relaxing together, while the blood forced out of them passes to the lungs and the system through the pulmonary artery and aorta respectively. The beating of the heart, as Ave have endeavored to describe it, in an animal, a dog or a rabbit, for example, has been shown to be essentially the same in man, at least so far as comparison has been possible. As might be expected, cases of ectopia cordis are very rare, but there has been a sufficient number of such cases to demonstrate that the manner in which blood flows through the heart in man does not differ from that of the mammal. While the action of the tricuspid valve and semilunar valves of the pulmonary artery is essentially the same as that of the mitral valve and semilunar valves. of the aorta, nevertheless the valves on the right side of the heart do not close their respective orifices as perfectly as those on the left side of the heart, there being some little regurgitation possible back from the pulmonary artery to the right ventricle, and from the right ventricle to the right auricle. The effect of this insufficiency of the valves on the right side of the heart is obviously of advantage ; were it otherwise, an excess of blood driven from the right ventricle through the pulmonary artery to the lungs might rupture those delicate organs. This danger is avoided through the imperfect closure of the pulmonary and the right auriculo-ventricular orifices, since, when resist- ance is offered by the pulmonary capillaries, the blood will regurgitate backward through the pulmonary artery to the ventricle and thence to the auricle. There is no insufficiency, however, on the left side of the heart, the auriculo-ventricular and aortic orifices being completely closed by the mitral and semilunar valves respectively. It will be observed also that the walls of the left ventricle are three or four times as thick as those of the right (see Table L.). This is due, as might have been anticipated, to the fact of the contraction of the left ventricle forcing the blood to all parts of the system, whereas the right ventricle forces the blood only to the lungs. For the same reason the walls of the auricles are thinner than those of the ventricles, little force being required to drive the blood from the former cavities into the latter. The muscular substance of the heart, like that of muscles generally, is therefore developed according to the amount of muscular force to be expended. As the period which elapses in mammals during a cardiac revolu- tion — that is, the time during which all the cavities of the heart fill and empty themselves — is only about one second, actually less in man, it is evident that close and careful observation is necessary in order to dis- RHYTHM OF MOTION OF HEART. 273 tinguish the successive phenomena that we have endeavored to describe in the beating heart. It is well, therefore, to begin the study of the action of the heart by observing the phenomena, first, as they present themselves in the lower vertebrates, for example, in frogs, snakes, turtles, and alligators. Such animals are not only readily procurable, but are particularly suitable for the purpose, since in them the cardiac revolutions succeed each other much more slowly than is the case in mammals, and in the frog especially there is an appreciable interval between the systole of the auricle and that of the ventricle, whereas, in most mammals the systole of the auricle runs so into that of the ven- tricle that it is impossible to say exactly where the first ends and the second begins, the muscular contraction running as a continuous wave over auricle and ventricle from base to apex. Further, the heart of the frog has only one ventricle, and while there are two such cavities in the heart of the turtle, nevertheless, they communicate, the septum being but little developed. In these animals, then, the single ventricle acts like the two ventricles of the mammalian heart, and familiarizes one with the synchronous action of the ventricles when two such cavities are present. Again, these animals offer through their mode of breathing another advantage, in that the heart will continue beating even after the thorax has been opened, there being no necessity of keeping up artificial respiration. We shall see, however, when we wish to study the action of the heart in mammals, that artificial respiration must be maintained, for with the opening of the chest the lungs collapse, respira- tion ceases, and the circulation stops. Notwithstanding that, in mam- mals, a cardiac revolution occupies such a small period of time — about one second — nevertheless, the relative parts of the second elapsing during which the auricular and ventricular systole take place and the heart is in repose, have been experimentally determined, as in the horse, for example, by Marey and Chauveau. 1 The general results of their ob- servations are embodied in Table XLIX.— Rhythm of Motion of Heart. Auricular systole. Ventricular systole. Repose. '1 4 4 TQ-th sec. TtT^n sec. ~W^ sec - from which it will be observed that the auricular systole lasts two-tenths of a second, the ventricular systole four-tenths of a second, and the re- pose of the heart four-tenths of a second, one second being supposed to elapse during an entire cardiac revolution. From the observations of Franck, 2 made upon a woman with ectopia cordis, there is little reason to doubt that the above table represents tolerably well, also, the relative durations of the successive motions and repose of the human heart. The apparatus necessary for the above determination of the rhythm of the heart's movements as they occur in the horse, and made by Verdin, of Paris, as used by Marey, consists essentially of a sound (Fig. 142) to be introduced through the jugular vein into the heart of the animal. The sound is divided into two tubes, one of which is a distinct tube, the 1 Comptes RenduB Sue Biol., Paris, 1861. Comptes Rendus. Acad. Sciences, 1862. - Tiavaux du Lab. de Marey, 1877, iii. p. 311. 18 274 CIRCULATION OF THE BLOOD. other being, however, only the space around the tube. The tube ter- minates at one end in a little elastic bag (i>), to be inserted into the ven- tricle, and at the other cud in a drum provided with a registering level' (h). The space surrounding the tube communicates on the one hand Fig. L42. Cardiograph. The instrument is composed of two principal elements : A E, Ihe registering apparatus, and A S, the sphygmographic apparatus — that is to say, which receives, transmits, and amplifies the movements which are to be studied. The compression exerted upon the bag c, which is placed over the apex of the heart between the intercostal muscles, is conducted by the tube l.c, which is filled with air, to the first lever. The compression exerted upon the bags o and v, 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 A E. (Chauveau and Marey.) with a similar elastic bag (o) to be inserted into the auricle, and at the other end with a tube passing into a drum provided with a second simi- lar recording lever (16). The object of the elastic bags o and v is that the successive contractions of the auricle and ventricle in which they are placed will be transmitted through them to the registering levers lo and lv, and as the auricle contracts before the ventricle it is evident that the lever lo connected with the elastic bag (o) in the auricle will move before the lever (J,v) connected with the bag (v) in the ventricle. If the regis- tering levers are placed in contact with a recording surface (AE) moving at a uniform rate, and if this surface be marked by vertical parallel lines, each intervening space representing the one-tenth of a second, the lengths of time during which the auricular and ventricular systole and the repose of the heart last will be graphically recorded (Fig. 148'). The cardiac revolution in this instance lasted twelve- tenths seconds. In order to divide the surface of the recording cylinder into a number of spaces each equal to the one-tenth of a second, a vibrating reed (A) and an electro-magnet (B, Fig. 144) are used. The reed clamped under the electro-magnet by one end to a stand (C), the other end dipping into mercury (D), is connected on the one hand with a battery (E). and on the 1 La Circulation du Sang, p. 85. Paris, 1881. VIBRATOR. 275 other with another small electro-magnet (F). Such being the disposi- tion at the moment that the current is made, the electro-magnet (B) Fig. 143. Tracing of the variations of pressure in the right auricle and ventricle, aud of the cardiac impulse, in the horse. (To I e read from left tu right.) (Ma rev ) Fig. ]44. being magnetized, will attract the reed, drawing it out of the mercury; but the current being thereby broken, the electro-magnet being thru 276 CIRCULATION' OF THE BLOOD. demagnetized, will cease to attract, and the reed will fall hack into the mercury, remaking the current ; the reed will then he again raised, the current broken, and the reed fall again into the mercury, the number of these alternate elevations and depressions per second depending upon the number of vibrations of the reed in that time. Inasmuch, how- ever, as the small electro-magnet (F) is magnetized and demagnetized in the same manner as the large one, the bar attached to it and carrying the pen (P) will approach and recede from it synchronously with the vibrations of the reed. By placing the pen in contact with the record- ing cylinder, a trace is obtained in which the equal spaces between the vertical lines made by the marker are equal t<> the one-tenth of a Fig. 145. Double myograph. (Vekdin.) second, the reed used vibrating at that rate. By substituting reeds or tuning forks vibrating at the rate of 15, 20, 50, or 100 times a second, we get traces in which the equal spaces represent the corresponding fractional parts of a second. Usually, there is also a third registering lever (Fig. 142, /c), below the ventricular one, connected by tubing with a cardio- graph (c), the object of which is to transmit the cardiac impulse caused by the beating up of the heart against the chest. This impulse is shown to be absolutely synchronous with the ventricular beat as recorded by the second lever (iv). By means of the double myograph the time elapsing during the successive contractions of the auricle and ventricle, and the repose of the heart, can be conveniently observed in the living frog or turtle. The instrument as described by Franck, 1 and constructed for the author by Verdin, consists (Fig. 145) of two levers, to which are attached delicate rods, ending in aluminium plates, which rest upon the auricle and ventricle of the heart of the animal examined. The levers can be shortened or lengthened, their pressure diminished or increased by appropriate mechanical arrangements, and the movements of the auricle and ventricle transmitted by them are recorded upon a cylinder moving at a uniform and known rate, by which the time elapsing can be determined. The further consideration of the cardiograph and the cardiac impulse we will defer till the next chapter, and, in concluding, call attention to 1 Travaux du Lab. de Marey, t. iv. p. 407. Paris, 1877. CAPACITY OF HEART. 277 Table L., in which are synoptically arranged the most important ana- tomical facts concerning the heart having for us a functional significance. Weight Table L. — Heart. ( in male, 1<> to 12 ounces j in female, 8 to 10 " f length, 5 inches. Size ' breadth, :V, " (thickness, 21 " | right auricle, 1 line. Thickness | left auricle, 1' " Base - Middle. Apex, of walls I right ventricle, l|a i| 1-^ lines. left ventricle, 4J 5£ 3^ f left ventricle, 4^ to 7 ounces, usually 2 ounces. Canacitv J right auricle > r5 u ' •' greater than left, F i I right ventricle, " " " " " I each ventricle, ] to £ greater than auricle. From this table it will be seen that the heart weighs, in the male sex, from ten to twelve ounces, and is heavier than in the female ; that, on an average, it attains a length of five inches, and a breadth of three and one- half. It will also be noticed from the table, and, as already observed, that the walls of the ventricles are thicker than those of the auricles, while the wall of the left ventricle, on an average, may be about four times as thick as that of the right. As regards the capacity of the cavities of the heart, it might be inferred from what was said of the regurgitation of the blood backward from the lungs, that the right side of the heart is more capacious than the left ; it will be seen, also, from the table, that the ventricles are more capacious than the auricles. There is still much difference of opinion as to the absolute capacity of the left ventrjcle. The question to determine, however, is not so much the amount of blood that the left ventricle can hold, as to what it usually does hold. This has been variously estimated at from two to seven ounces. Probably, four ounces, or a mean between these two extremes, will represent about the amount of blood that the left ventricle usually forces into the aorta at each systole. CHAPTER XIX. THE HEART. In examining the heart in a living animal, as described in the last chapter, it will be observed that with each ventricular systole the heart, as a whole, moves forward and upward, the apex more particularly beating up against the chest, and so giving rise to what is known as the cardiac impulse. If a finger be placed within the thoracic cavity of a living animal, between the heart and the side of the chest, with every contraction of the ventricle the finger will be pressed against the chest by the apex. Pathological cases, like that of the A r iscount Mont- gomery, so graphically described by Harvey, 1 have given physiologists the opportunity of showing that the cardiac impulse is produced in men as in animals by the striking of the heart against the chest. In man the cardiac impulse is most distinctly felt in the fifth left intercostal space, about two inches below the left nipple, and one inch to its sternal side. The force and extent to which the cardiac im- pulse may be perceived varies very much in different individuals, and in the same individual, according to circumstances. Thus, it is more perceptible in emaciated than in fat persons, during expiration than in inspiration, in one lying upon the left side than in one lying upon the right, etc. The movement of the heart forward and upward producing the cardiac impulse seems to be due to several causes. Thus, the sudden distention of the great elastic vessels at its base would throw the entire organ forward, the recoil of the ventricles, as they discharge their con- tents, further aiding the movement. The disposition of the muscular fibres is also such that the heart during its ventricular svstole chancres its form, bulging somewhat forward, the spiral muscular fibres, at the same time, tilting up the apex. For ordinary purposes the force and extent of the cardiac impulse can be sufficiently well appreciated by the hand. The cardiograph, how- ever, furnishes us with the means of a far more accurate study of the beat of the human heart than that afforded by the sense of touch alone. The cardiograph (Fig. 146) consists of a disk-shaped box, one side of which is formed by an elastic membrane. In the centre of the latter is inserted an ivory knob (^4), which is applied to the chest over the place where the cardiac impulse is greatest. The box, or tympanum, com- municates by an elastic tube (/) with a second tympanum (b), with which is connected a registering lever (d). It is evident that when the cardiograph is firmly fastened to the chest that the shock of the 1 Exercit. de generat. Animalium, p. 156. Lond. 1651. CA RDIOGRAPrT. 279 cardiac impulse will be transmitted to the ivory knob, thence to the first tympanum and through the column of air in the communicating tube to the interior of the second tympanum, and so, by means of the elastic and movable lid of the latter, to the registering lever. If the point of The cardiograph. the lever be placed in contact with a cylinder revolving at a uniform rate, we obtain a graphic representation or trace of the heart's impulse (Fig. 147). By such an apparatus variations in the heart's bent, which Fig. 147. a^Va^^-a ^vyv^-A Tracing of heart's impulse in man, tak«-n with cardiograph. To be read from left to right. are so slight as to be quite inappreciable by the sense of touch alone, become very perceptible. When it is desired to take a cardiography tracing in a small animal, like a rabbit, guinea-pig. or cat, a very convenient form of cardiograph is that described by Marey 1 (Fig. 148), and made for the author by Verdin. The instrument consists of two tambours (a, b), each of which contains a spring, through which the membrane is kept projected. The two tam- bours are joined to one another pincer-like, by a hinge, and grasp the car- diac region on each side of the sternum. A girdle (c) attached by hooks to the tambours passes around the body of the animal, and secures the apparatus firmly. The compression of the air in the tambours due to the cardiac impulse is transmitted by the tubes (d, e) to a second tambour, to which is attached a recording lever, like that represented in Fig. 146. Fig. 149 gives the traces taken by this instrument. Op H . p. 155. 280 THE HEART. Fig. i is. It will be remembered that it was by means of the cardiograph and the sound introduced into the heart of the horse that Marey and Chau- veau demonstrated experimentally that the cardiac impulse is absolutely synchronous with the ventricular systole. Whatever difference of opinion may exist as to the relative importance of the different causes assigned for the production of the cardiac impulse, there can he no doubt, then, that its immediate cause is the ventricular sys- tole. The spiral arrangement of the muscular fibres at the apex of the heart, already alluded to, explains another phenomenon accompanying the ventricular systole, the twisting of the heart. If the apex of the heart be closely watched, it will be noticed that the point twists upon itself from left to right with the systole, returning to its former position with the diastole. The heart, like a voluntary muscle, which it closely resembles in its substance, also hardens during contraction. This (';ii'lii>,i_'rapli. (Marey.) Fig. 149. Tracings taken with cardiograph. Co. Guinea-pig. X. Rabbit. Ch. Cat. (Marey.) becomes very evident if the organ be grasped by the hand while beat- ing. Like voluntary muscles, the heart also shortens during contrac- tion. This can be demonstrated by quickly cutting the heart out of a living animal, pinning it down on a board by passing a needle ver- tically through its base, and then inserting a second needle into the board parallel with the first, so that the apex of the heart just touches the second needle. With each systole it will be seen that the ventricles invariably shorten, the apex distinctly receding from the second needle. If the beating heart be examined in situ there is, on the contrary, an apparent elongation of the heart during its systole. This is due, how. ever, not to any elongation of the ventricles, but to the fact that at the moment of the cardiac impulse, which is synchronous with the ventricular WORK DONE BY THE HEART. 281 systole, the whole heart, as we have seen, is moved forward and pro- truded ; at this moment the apex is apparently elongated, while, in reality, it is shortened. We shall see that, on an average in man, the ventricles contract ahout 70 times in a minute, and assuming, as we have done, that with each systole about four ounces, or a quarter of a pound, of blood are forced into the pulmonary artery and aorta respectively, it is evident that in Twenty-four hours the heart must perform a great deal of work. It can be demonstrated, as was first shown by Hales, 1 that the blood will rise about nine feet in a glass tube inserted into the aorta of a horse, and the experiments of Haughton, 2 of which we will speak again, prove that this estimate can be accepted as representing the pressure exerted by the left ventricle of man, as shown by the distance to which blood will jet from a divided artery. In demonstrating the height to which blood will rise in a glass tube inserted into the aorta we usually make use of a large turtle, which suffices very well, as illustrating the work done by the left ventricle of the heart of an animal. In mechanics the work done by a machine is usually estimated in foot-pounds — that is, the number of pounds the machine can raise through one foot, or the number of feet that the machine can raise one pound — i. e., the work equals the weight multiplied by the height. The work accomplished by the heart in twenty-four hours can be estimated approximately in the same way, and amounts to 138 foot-tons (Table LI.) — that is, the heart performs in twenty-four hours an amount of mechanical work equivalent to that of a machine that will raise during the same time 138 tons through one foot, or 1 ton through 138 feet. If. however, we assume, as is sometimes done, that each ventricle discharges only two ounces of blood, of course the work done by the heart will be that much less ; on the other hand, the work done will be greater if the ventricles are supposed to discharge more blood into the great vessels at each systole. In other words, the work done by the heart will be a maximum or minimum, according to the accepted capacity of the ventricles. Table LI. Work done by the heart in 24 hours = 138 foot-tons. ! lb. of blood expelled bv left ventricle at each systole. right "_ Blood flowing from aorta into a vertical glass tube will rise 9 feet. " pulmonary artery into a vertical glass tube will rise 3 feet. 1 9 — V 9 = — = 2; lbs. raised through 1 root. 4 4 JL x 3 = — = I lb. - 4 4 3 lbs. 3 X 72 X 60 X 24 = 31104O lbs. in 24 hours. 311040 = 138.8 foot-tons. 2240 1 Statical Essays, vol. ii. p. 11. London, 17:io. '-' Animal Mechanics, p. 1li7. London, 1873. 282 THE HEART. It will be observed, also, that it is assumed in man, such being essentially the case in animals, as shown experimentally by Milne Edwards, 1 that the right ventricle does only a fourth of the work per- formed by the Left one. If in a living animal the ear be applied to the precordial region, and in man more particularly to the third intercostal space a little to the left of the median line of the chest, accompanying the beat of the heart two successive sounds will be heard, followed by a silence. After a, little practice it will be recognized that these two sounds differ from each other in their quality, pitch, and duration. The first sound is a dull, confused one, of a booming character, low in pitch, and lasts longer than either the second sound that follows it, or the silence intervening between the second sound and the first one. The second sound, as com- pared with the first one, is a clear sound, well defined, sharp, high in pitch. While, for all practical purposes, it may be said that the second sound immediately follows the first, there is quite an appreciable inter- val of silence between the second and the first sound, this interval of silence lasting about the same length of time as the second sound. By looking at Table LII. it will be seen that, supposing one second elapses during the period in which the first and second sounds and silence are heard, that the first sound lasts four-tenths of the second, the second sound three-tenths of a second, and the silence three-tenths of a second. It will be also observed, from Table LII., that the period of four-tenths of a second during which the first sound is heard, is absolutely syn- chronous with the four-tenths of a second of the ventricular systole, that the three-tenths of a second during which the second sound is heard the heart is in repose, and that the silence is synchronous partly with the last one-tenth of a second, during which the heart is in repose, and during the two-tenths of a second of the auricular systole. This com- parison of the rhythm of the sounds of the heart with the rhythm of its movements, is based upon the manner in which the sounds are produced. Table LII. — Rhythm of Movements and Sounds of Heart during one Second. Ventricular systole . Repose. Auricular systole. /\ /\ 4 8 1 K) 10 10 lo First sound. Second sound. Silence. From the fact of the first sound being confused and muffled in char- acter, one would suppose that numerous causes contribute in producing it. From Table LII. we see that the first sound is heard, and lasts during the ventricular systole ; now at the moment the auriculo-ven- tricular valves flap together their movement must be then one cause of the first sound of the heart, and accounts for its valvular element. That the closure of the auriculo-ventricular valve contributes in the produc- 1 Physiologic, tome iii. p. I IN. CAUSE OF SOUNDS OF HEART. 288 tion of the first sound can be further demonstrated by experiments like those of Chauveau and Faivre, 1 who either modified the first sound or abolished it altogether by preventing the closui'e of these valves by cutting the chordse tendinese, or introducing a wire ring into the auriculo-ventricular orifices. Further, pathology shows that, in man, the character of the first sound is changed if the auriculo-ventricular valves are diseased, and it is well known, also, that in auscultation the first sound is heard with its maximum intensity over these valves, and that it is propagated downward along the ventricles to which they are attached toward the apex. It is well known, and readily shown by the application of the myophonic telephone (Fig. 150). that when a muscle contracts, being thrown into vibration, a sound is produced; now. as the ventricular systole is caused by the contraction of the muscular fibres of the ventricle, at this moment a sound will be produced which. Fro. 150. Helmoltz's myophone. b. Button to be placed on muscle, p. Handle. to telephone. Wires for attachment in the case of the frog, can be made audible by the cardiophonic telephone (Fig. 151), and which contributes undoubtedly, in man, to the produc- tion of the first sound. Finally, the beating up of the heart against the chest in itself is partly a cause of the first sound. There appear, then, to be three distinct causes, each contributing in the production of the first sound. First, the closure of the auriculo-ventricular valves; second, the muscular contraction ; third, the cardiac impulse — hence the confused, muffled character of the first sound of the heart. As has already been observed, the second sound differs from the first in being a clear, well-defined sound, and is essentially of a valvular character. It 1 Xouvelle recherches experimentales sur lea Mouvements in Coeur, etc., p. 30. Paris, 1856. 1^-1 THE HEART, is heard (sec Table LIII.) during the first three-quarters of the period in which the heart is in repose. Now, at this moment the semilunar valves of the pulmonary artery and aorta are Mapping together through the blood (i, p. 112. 2 Anuales des Sciences Nat., 1837, t. vii. p. 106. :i Op. eit, t. ix. ]>. 46 300 THE ARTEEIES. and 2.5 cm. (1 inch) in breadth, will contain about 2t»0 c. cm. (0.2 pint), a tube 51.5 cm. (20.5 inches) in breadth, will contain 2Hl' c.cm., or only 2 cm. more, thus : 51: 51.5 :: 290: a? equals 202: whereas, a tube 51 cm. long, but 2.8 cm. (1 inch) in breadth, will con- tain 360, thus : 6.2",. or (2.5) 2 : 7.84, or (2.8) 2 : : 200 : x equals 360, or nearly 70 c.cm. more than the tube 51.5 cm. long, but onlv 2.5 cm. in breadth — 350-292 equals 68. The elongation and transverse dilatation of the arteries due to the distention of their walls by the blood forced into them by the heart at each ventricular systole constitute the pulse. It will be observed that the pulse, or the expansion of the artery, is synchronous with the con- traction of the ventricle of the heart, not with the heart's expansion, as was thought by Galen, and the ancients generally. Although this truth seems to have been known to a writer who lived during the early part of our era, it remained for Harvey to demonstrate it in modern times. Ordinarily, neither the elongation nor transverse dilata- tion of an artery or its pulse is visible to the naked eye, or appreciable even by touch alone. It is for this reason that the observer presses with his finger more or less the artery examined, thereby constricting the vessel and so increasing the velocity of the blood, it flowing faster as the artery becomes smaller, the same amount of blood passing through in a given time ; this, as we have seen, increases friction, and so causes an obstacle to the flow, which, Avithin limits, increases the force of the heart, and, therefore, the distention of the artery, and so makes the beating of the vessel or the pulse more apparent. CHAPTER XXI. THE ARTEBIES.— (Qmtinued.) Sphygmograph, Arterial Schema. No artery in man can be directly measured, either as regards its expansion or its pressure. In feeling the pulse, however, the endeavor is made to measure both by the sense of touch alone. While the experience of every physician shows to what an extent slight variations in the pulse can be appreciated by the tactus eruditus alone, nevertheless it is only by means of the graphic method that the conditions on which the production of the pulse and its variations de- pend can be successfully investigated. By the graphic method, as we have seen, a pictorial representation, a trace of some kind of the phe- nomena occurring can be obtained and preserved, by means of which slight variations, due to change of conditions, become at once evident that would be entirely unappreciable by the eye or touch unaided, and that by a comparison of the traces obtained from the examination of the living artery with those obtained from a tube corresponding to an artery in an artificial apparatus representing the general vascular sys- tem, the manner in which the pulse is produced, and the conditions on which its variations depend, can be "demonstrated. The advantage of such an experimental investigation of the pulse, the practical application that can be made of it in investigating the cause of disease, will be at once appreciated after the sphygmograph and the arterial schema, the apparatus we use in studying the pulse, have been described, and the results obtained by them shown. The object of the sphygmograph (sphygmos, a trace, and grapho, to write) is to measure the succession of the alternate dilatations and contractions of an artery due to the blood forced into it bv the beating heart, to magnify these movements, and to register them on a surface moving at a uniform rate by clock-work. The arterial schema, or arti- ficial artery is an apparatus representing the general vascular system by means of which we can produce an experimental pulse, and from it, by means of the sphygmograph, obtain a trace, which can be compared with that obtained bj the sphygmograph from the natural pulse. By such a comparison it will be observed that the trace made by the pulsa- tion of the artificial artery, differs from that made bv the living one only in degree, not in kind ; the natural inference is, therefore, that the cause of both traces must be essentially the same. Further, by slightly changing the action of the arterial schema, traces can be produced which so closely simulate those obtained from the living pulse in various diseases that there can be but little doubt that the cause of both is the same. 302 THE ARTERIES. The sphygmograph was originally invented by Vierordt, and after- ward greatly improved by Marey. It is the latter form, as modified by Fig 154. Mechanical arrangement of the sphygmograph. (Sandekson.) Fig. 155. Marey's sphygmograph applied to arm. (Marey.) Fig - 156 - Sanderson, and constructed by Hawks- ley, that we shall use. The instru- ment (Fig. 154) consists of a brass frame (0 R), the under surface of which is covered with ebonite, and which can be applied to the outer edge of the volar aspect of the fore- arm so that it rests immovably in this position with reference to the radius and wrist-bones, particularly the scaphoid. The pulsations of the radial artery are received by an ivory button (K), placed at the free end and under the surface of the steel spring I ; the other fixed end of the spring is attached to the brass work at P. By means of the ivory button and spring the pulsations of the artery are transmitted to the ver- tical screw T, which passes through the brass bar N, whose centre of motion is at E, above the attachment of the steel spring I ; the free end (B) of the brass bar is bent upward at right angles, and carries a knife-edge (D), well seen in Fig. 154. The elevation of the screw T, through the pulsation of the artery, raises Scale for determining pressure excited by artery. (Sanderson.) SPHYGMOGRAPH. 303 the brass bar N, carrying the knife-edge D, the latter, in turn, ele- vating the registering lever A, of which one end (C) is supported by a horizontal rod passing through it and connecting the sides of the brass frame, while the other movable end (A) terminates in a metal joint, which registers the motion of the pulsation on a piece of paper (Fig. 155) blackened by passing it to and fro through the flame of a kerosene lamp. The paper is fastened to a copper plate, which is moved at a uniform rate by the clock-work (Fig. 155). As the distance between the supporting rod C and the knife-edge D is much less than the length of the lever, the vibrations of the extremity of the lever (A) are far more extensive than the vertical movement of the spring I and screw T. By means of the screw T the distance between the steel spring I and the registering lever A can be varied at will without interfering with the mechanism by which the move- ment is transmitted. The distance between the brass frame and the ebonite surface can also be increased or diminished, according to the direction in which the screw Y is turned, and, in this way, the pressure on the artery may be varied ; the variation in the pressure is measured by the scale (Fig. 156), which has been experimentally gradu- ated by turning the instrument upside down, and successively placing a series of weights on what would be ordinarily the lower surface of the spring, but which is now the upper surface, and observing the extent of its deflection and marking the scale correspondingly. Finally, by means of a movable clamp, there can be adapted to the sphygmo- graph, when desirable, a delicate tympanum, with registerig lever, in connection with a cardiograph, so that the traces of the cardiac and arterial pulsation can be registered simultaneously on the blackened surface. To take a trace with the sphygmograph of the radial artery, which is the vessel usually examined, the forearm should be supported on some- thing, a table, for example, the back of the wrist resting on a cushion or padding, so that the dorsal surface of the hand will be inclined, with reference to the forearm, at an angle of 20 to 30 degrees. The instru- ment must be so placed on the wrist that the block rests upon the tra- pezium and scaphoid, while the extremity of the spring is opposite the styloid process of the radius, the general direction of the sphygmograph will then be parallel with that of the radius. In making an observation it is best to begin by adjusting the instrument so that the ivory button on the under surface of the spring is at such a distance from the bone that the artery is pressed upon during its entire expansion, and yet not so compressed as to obliterate at any moment its cavity. To those unfamiliar with the use of the sphygmograph, perhaps it will be well to begin by arranging the spring so that it will exert a pressure sufficient to flatten the artery against the radius and then to diminish the pressure until the effects of such compression disappear, and thus to take traces of the maximum and minimum pressures, and one then of an intermediate character. Having described the sphygmograph and the manner of using it, the following figures will illustrate the character of the traces taken by it. Thus, for example, Figs. 157, 158, and 159 are obtained from the 304 THE A K T E II I E S . radial ami femoral arteries in a healthy man of about thirty years of age. Figs. 1<><) and 161 are from the radial of a woman tet. sixty-five and of a man ;et. seventy respectively, in both of which cases the arteries were in an atheromatous condition. Let us now consider the arterial schema and the manner in which the artificial pulse is produced, and then compare the tracing of such a pulse Fig. 157. Sphygmographic tracing from radial artery of a man set. twenty-five. Fig. 158. Sphygmographic tracing from radial artery of a man set. thirty. Fig. 159 Sphygmographic tracing from femoral artery of a man a?t thirty. (A. P. B.) Fig. 100. Sphygmographic tracing from radial artery of a woman at. Bixty-five. Atheromatous arteries. Fig. 161. [XjVJ Sphygmographic tracing tram radial artery of a man set. seventy. Atheromatous arteries. with those just exhibited. There are several different kinds of arterial schema, from the simple one of Weber to the elaborate apparatus of Marey, that are used in studying the phenomena of the circulation. For our present purpose the instrument (Fig. 162) described by San- derson 1 and constructed for the author by Ltawksley, will suffice. It is true that the apparatus does not resemble in form at all the heart, aorta, etc., but as the object of the arterial schema is not meant to illus- trate the structure of the parts but their action, this is a matter of no moment. 1 Handbook Phys. Lab., p. 230. Phila., 1873. ARTERIAL SCHEMA 305 It consists essentially of a reservoir supplying the colored water rep- resenting blood, which should stand at a height of from 2 to 3 metres (6 to 9 feet), of an elastic tube (B D 0, etc.) several metres long, repre- senting the left side of the heart, aorta, arterial system, etc., of a lever (C) 53 cm. (21 in.) in length and which is so arranged that, as it is depressed at the end nearest D, it closes the elastic tube at D and opens it at E, and when elevated opens the tube at D and closes it at E. This alternate closing and opening of the tube at Eand I) imitate the action of Fig. 162. Schema for demonstrating the nature of the arterial movements. A- Glass tube which represents the heart. B. The tube by which A communicates with a cistern at a height of ten or twelve feet above it (A much smaller head of water is sufficient.) C. The lever by which the two valves E and D are worked, the same act which shuts the one opening the other. F. Commencement of the experiment tube, which is of black vulcanite. At Fthe tube communicates with a long vertical tube of glass, only part of which is seen ; it is closed at the top, anil usually shut off from F by a pinchcock At G the tube passes under the spring of the sphygmograph, the frame of which rests on a block (below G). By error, the tube has been drawn on the wrong side of the block H. The blackened plate of the sphygmograph. To the left of it is seen the cylinder, with its needle for recording the time which intervenes between the opening and closing of the aortic valve, L. A rod which is firmly fixed in the lever, and is connected by two cords, one of which is elastic with the cylinder. (Sanderson.) the mitral and aortic valves by means of the spring at C\ when the ap- paratus is not working the aortic orifice is kept closed. The portion of the tube lying between D and E, which represents, therefore, the left ventricle, is 30 cm. (12 in.) in length, communicates with the ver- tical glass tube (A) 54 cm. (21 in.) high and with a diameter of 9 cm. (3.5 in.); this tube can be opened or closed at its upper end by a stop- cock. When the lever is elevated and the tube opened at E, or the mitral orifice, the colored fluid from the reservoir flows up into the tube A compressing the air within it, according to Mariotte's law, the volume of air diminishing as the pressure increases ; when the lever is depressed and the tube open at D, or the aortic orifice, the compressed 20 306 THE ARTERIES. air in the tube A suddenly expands and forces the water into the tube beyond (/>), which, of course, corresponds to the aorta. The expansion of the air theD represents the force of the contracting heart. At a dis- tance of L5 cm. (6 in.) from the aortic orifice the elastic tube communi- cates through a T-shaped connecting tube on the one hand, with a long vertical glass tube (i), and on the other with the tube F, which, gradu- ally becoming smaller and then larger again, represents the arteries, capillaries, and veins. The communication between the tube F and the tube / can be opened or closed by means of a pinchcoek. The use of the tube / will be explained presently. For the moment we will con- sider that the communication between it and the arterial tube is closed. At a convenient distance from the aortic orifice there is placed upon the tube, which we will consider represents the radial artery, a sphygmo- graph (h), of which the lever, properly supported, will be elevated or depressed as the tube expands or contracts by the fluid forced through it with the opening and closing of the aortic orifice. Just at the position of the fulcrum of the lever there is fixed a vertical rod (X), which is connected by means of two cords, the upper one being elastic, with the pulley m. The pulley, through a marker attached to it, will make a straight line on the blackened recording surface of the sphygmograph as long as the lever is depressed at E — that is, as long as the aortic orifice is open. With the closure of the aortic orifice through the elevation of the lever, the marker will be drawn upward, away from the blackened surface, through the elastic cord, and the absence of the mark on the blackened surface will indicate the closure of the aortic orifice. As the mark on the recording surface is coincident with the elevation of the lever of the sphygmograph and the absence of the mark with its depression, it is therefore shown, from what has just been said, that the elevation of the sphygmograph lever is coincident with the opening of the aortic orifice, and, therefore, with the ventricular systole, while the depression of the lever is coincident with the diastole. The construction of the apparatus being now understood, let the sphygmographic trace Fig. 161, taken by it, be compared with that of Fig. 157, representing the sphygmographic trace of the natural pulse. By such a comparison it will be observed that the difference between the traces of the natural pulse and that of the schema is one of degree rather than of kind. In both traces we have seen the same movements succeeding each other in the same order. With the expansion of the artery we have the elevation of the lever with the contraction, the de- scent, then the secondary rise or dicrotism, and finally the descent again. As in the case of the natural heart so in that of the schema, it is seen that as the aortic valve (D) is opened the artery expands, the lever rising and the vessel remains full as long as the artificial heart is acting, that with the cessation of the flow of liquid from behind the artery contracts the lever descending. That the ascent and descent of the lever are due to the cause just assigned can be shown by the motion of the marker attached to the pulley m in the manner explained above. As long as the aortic orifice I) is open the marker remains in contact with the re- cording surface of the sphygmograph, but with the closure of the aortic orifice the marker is pulled away. The trace (Fig. 161), as recorded, PERCUSSION AND PRESSURE WAVES. 307 exhibits then a line broken at regular intervals. When this is com- pared with the sphygmographic trace of the artery it will be observed that there is an exact correspondence between the time during which the heart is acting and the time elapsing between the beginning of the expansion and the commencement of the contraction, the expansion evi- dently, therefore, depends upon the contraction of the heart. By a careful examination of the traces produced by the arterial schema it can be seen also that the forcing of liquid into the arterial tube by the Fig. 163. Tracing obtained with arterial schema. artificial heart produces two effects, which can be demonstrated to be independent of each other. One of these is a molecular vibratory oscillating motion — that is, a to and fro pendulum-like movement, which has been appropriately called, from its mode of producing the percussion wave, the other the transmission of the pressure of the artificial heart at the moment the aortic orifice is open to the liquid in the arterial tube, and which is known as the pressure wave. To produce the per- cussion wave by means of the schema, one has only to close the aortic orifice D and arrange the lever C, so that by suddenly rapping it with a hammer a percussion shock can be imparted to the tube beneath. The trace of the percussion wave produced in this way (Fig. 164) shows that the sphygmographic lever is jerked up the initial ascent, the descent being extremely abrupt. In order to obtain a trace of the Fio. 104. Tracing of percussion wave obtained with arterial schema. pressure wave, which is also a vibratory motion (Fig. 165), it is best to use an elastic bag (Fig. 166, B). which communicates, on the one hand, with a reservoir of water and on the other with a long elastic T-tube, to which are adapted at intervals three tambours with levers (I I' 1") re- cording upon the same cylinder, or the tube can be placed under three levers provided with tambours (one of which is represented in Fig. 167), the latter being connected bv tubing with the tambours of the secondary levers. The bag should be of a size that it can be squeezed by the hand. The object of having three such sphygmographic arrangements is to obtain traces at different distances from the heart, the source of the pressure, as well as to demonstrate the postponement of the pulse, which 308 THE ARTERIES. Avill be shown immediately. Inasmuch as the action of the squeezing hand is very unlike that of the contracting heart, the hand contracting gradually and weakly relatively to the resistance, the heart, on the other hand, contracting suddenly and most powerfully at the beginning of its action as might be expected, the traces of the pressure wave, like that of if;. - ). HBBBSflBHHIGHBBSBBBIIBBBHBBBBBI B™5H!S§ia MBMHB »»««"" BMflBHBBBflBHBBBBBflBBnnHI ^SSSSS^SSSSS^SS BBBBBBMBBI BUBBBflKJiaiBSBtflBafiH'jaHgSB'JBBfi _ JSBMBHHlBGBBBBBBBBMa BHHHH BBBBBBaiiaMBBBBBBBBBBBBBBBBBB m Tracings showing the contractions and expansion of an India-rubber tube, along which water is propelled in an intermitting 6tream by squeezing with the baud, at regular intervals of time, an elastic bag pro- vided with valves, with which the tube is in communication ; the bag thus represents the heart. The three tracings are drawn simultaneously, and exhibit the expansive movements of the tube at three dif- ferent distances from the bag, the upper tracing being taken at the greatest distance. (Sanderson.) the percussion wave, will be entirely different from the trace of the natural pulse or that produced by the arterial schema. • It will be seen by examining the traces of the pressure wave (Fig. 165) that the lever does not descend as abruptly as in the case of the percussion wave, as the recoil of the arterial wall due to its elasticity is not instantaneous, hence the lever will momentarily remain at the height to which it has been elevated, and this period will be prolonged in proportion as the elasticity of the artery is diminished ; hence, in old Fig. 166. persons ; in whom the arteries are not very elastic, the curve at the summit is rounded off and the descent is a gradual one. It will be also noticed that the expansion in the distal part of the tube (the upper of the three traces) culminates later than in the proximal part. LENGTH OF PRESSURE WAVE. 309 In the traces obtained from the natural pulse, or from that of the arterial schema, we see the effects of both the percussion and pressure waves : the abrupt line of ascent is due to the percussion wave the temporary elevation of the lever being due to the recoil not at once following the distention due to the pressure wave. As a general rule, in the natural pulse both these effects follow each other very quickly, and are merged into one another. As we shall see, however, in a moment, under certain circumstances one may be far more evident than the other. Did the natural pulse consist of the percussion wave only, it would be felt at the same time in all parts of the system, as the per- cussion wave is practically transmitted instantaneously through tubes of the length of the arteries. Any one can readily convince himself, however, in his own person, that there is a gradual retardation of the pulse from the heart to the periphery, by feeling the left carotid artery with the thumb and index finger of the left hand, and the left radial with those of the right. The beat of the radial artery will be felt later than that of the carotid, the difference in the time of the beat being quite appreciable. This postponement of the pulse is due to the fact that the pressure wave is transmitted at a slower rate of vibration than the percussion wave, and the reason is obvious. At the moment that the blood bursts out of the contracting heart into the aorta, the wall of the vessel yields to the pressure and expands during the relaxation of the heart, the walls of the artery through its elasticity recoil upon the blood and add pressure to the heart pressure which has just preceded it. This expansion, however, as we have seen, begins at the proximal end of the artery and is transmitted in a wave-like manner to the distal end necessarily, therefore the expansion, or the pulse, will be felt later in the distal than in the proximal end of the artery. Were the artery rigid instead of elastic, there would be no postponement, and if tense at the moment of the ventricular systole, little or none. It was shown by Weber that the pulse wave (pressure wave) is transmitted at a rate of about 9 metres (28 feet) a second. Weber 1 determined this velocity by observing with chronometers the difference in time of the beat of the facial and dorsalis pedis arteries, measuring the distance of the facial artery from the heart as accurately as possi- ble, and the distance of the dorsalis pedis from the facial, and sub- tracting the first distance from the second, the difference of distance the pulse wave passed over in the second case as compared with the first will account for the difference in the time of the beats, and give approximately the distance passed over by the pulse wave in one second. Supposing that the ventricular systole lasted four-tenths of a second, the pulse wave would be 3.6 metres (11 feet) long (9 X-tt7=3.6), and there would be two and a half waves in a second (-g 9 g-=2.5), consequently the anterior end of a pulse wave would have reached the extremities before the posterior end had left the left ventricle. It would appear, however, that this estimate of the length of the pulse wave is somewhat exaggerated, Czermak 2 having shown by the photo- l Midler's Archiv, 1851, S. 537. 2 Carpenter's Physiology, p. 316. 310 THE ARTERIES. sphygmograph that the pulse wave is about 1.5 metres (5 feet) long, requiring about one-sixth of a second to pass from the heart to the foot, lu speaking of the velocity of the pulse wave, of course it is to be under- stood that this has no reference to the velocity with which the mass of blood flows from the heart to the periphery. The latter motion is one of translation, and, as we shall see, is slower than the former or the pulse wave, which is molecular and vibratory in character. Weber 1 well says " Unda non est materia progrediena sed forma materise pro- grediens." "The gradual retardation of the pulse is well shown in the traces (Fig. 165) taken by means of the apparatus already described (Fig. 1GG). By adapting to the recording cylinder the marker of a chrono- graphic apparatus, the exact difference in the time of the beats of the proximal and distal parts of the tube can be determined. The fact of the pulse consisting of two kinds of vibratory movements, the percus- sion and pressure waves differing as regards their velocity, explains why the pulse appears in some persons to be quickened, while in others to be postponed. In certain individuals the pressure wave is Fig. 167. Lever, etc., fur receiving pressure wave. L. Lever. T. Tambour B. Tube conducting to recording tambour. instantaneously transmitted, is most felt, and the pulse seems quick- ened ; in other cases the pressure wave is more slowly transmitted, is most sensible to the touch, and the pulse seems delayed. By examining the sphygmographic traces of the natural and artificial pulse it will be observed, as has been already mentioned, that the lever descends for a short distance, then slightly rises again, descends to the level from Avhich it was first elevated ; in some cases even the lever rises a third or a fourth time before finally descending. This secondary elevation of the lever is known as the dicrotic pulse, and is caused essentially by the return of the pulse wave from the capillaries back toward the heart. We have just seen that the pulse wave is retarded, the arteries near the heart therefore expand before those near the periphery ; while the expansion is subsiding in the smallest ones it is beginning in the large arteries, so that there is a moment when the pressure is greater in the latter than in the former, the aortic valves being closed behind, and the capillaries offering resistance in front, the only way in which equilibrium can be restored is by increase of pressure toward the heart with dimi- nution at the periphery. As regards the cause of the dicrotic pulse, the only question about which there still appears to be any doubt among i Marey, op. cit., p. '227. DICROTIC PULSE. 311 physiologists is, whether the aortic valves are opened or dosed during its production, and whether the secondary pulse wave, to which it is due, is a centripetal or centrifugal one — that is, whether the pulse wave as it returns from the capillaries toward the heart elevates the lever the second time, or whether it passes first back to the aortic valves, and after it is reflected back toward the capillaries then elevates the lever. The result of experiments with the schema would lead us to conclude that in some cases the dicrotic pulse is due to the return of the pulse wave from the capillaries, while in others it is caused by a secondary recoil from the aortic valves, and that when there is a tertiary as well as a secondary elevation of the lever the former is due to the aortic, the latter to the capillary rebound. It will be remembered that, in describing the arterial schema, it was stated that the main tube bifurcated at F, one end continuing as the main arterial tube, while the other could be closed or adapted to a vertical glass tube (I). This tube, which is about 01.1 metre (4 feet) high and 1 cm. (fth of an inch) wide, is closed at the top, and serves, through the rise and fall of the level of the fluid it contains, as an indi- cator of the state of the equilibrium of the fluid in the main tube. With the opening and closing of the aortic valves the level of the fluid in the tube will rise and fall, and if there be any dicrotism present it will be indicated by a secondary rise of the level of the fluid in the tube, and the phenomena of the dicrotic pulse in this way made quite evident. Now, if there be placed upon the main tube or artery a sphygmograph, as before, and also a second sphygmograph about 01.1 metre (4 feet) from the first one, and the main tube, about the same distance from the second sphygmograph, be somewhat constricted to represent the capil- lary resistance, it will be observed that, as the aortic orifice is open, the level of the fluid in the vertical glass tube rises ; that the levers of the sphygmographs are successively elevated, the second one a fraction of a second later than the first ; that the elevation of the fluid and the levers is succeeded by a depression, and is followed by a secondary elevation of the fluid and of the levers, the level of the fluid and the levers finally descending again to the level from which they were first elevated. If, during this experiment, the levers of the sphygmographs bo carefully watched, it will be observed, as was just mentioned, that as the aortic valve is opened — that is, as the pulse wave passes from the heart toward the capillaries, the elevation of the lever of the proximal sphygmograph takes place sooner than that of the distal one, the pulse wave being retarded ; whereas, during the production of the dicrotic pulse it is the lever of the distal sphygmograph that is elevated first, showing that the dicrotic elevation is due to the return of the wave from the capillaries toward the heart, and that the dicrotism occurs at a distance of more than a metre (4 feet) from the aortic orifice as the wave is passing toward the heart. On the other hand, if the levers are elevated for the third time, then it is the lever of the proximal sphygmograph that is elevated first, showing that the tertiary elevation of the liver, like the primary, is due to a pulse wave flowing from the heart to the periphery. The dicrotic pulse can be produced with the schema, whether the main tube be constricted at some distance from the sphygmograph or at its point of application, and whether the aortic orifice be open or shut ; in 312 THE ARTERIES. the latter case the aortic valve offers a resistance, in the former the column of liquid. According to Marey, 1 if the aortic valves be destroyed there is no dicrotic pulse. This is as might be expected, as under such circum- stances there would be little resistance offered to the return pulse wave, and therefore little dicrotic distention. The dicrotic pulse appears, therefore, to he due to secondary pulse waves, in some cases trans- mitted in a centripetal, in others in a centrifugal direction. The amount and exact cause of the dicrotic pulse must therefore vary with the general condition of the vascular system. In health, for example, when the vessels are tense it is seen only as a slight interruption in the descent of the lever. In fever, on the other hand, when the vessels are distensible, it is so marked that the pulse feels as if it were double. When it is remembered that, as the blood is propelled forward into the arterial system, it is being continually diverted laterally through the distensibility of the walls of the arteries, and that as the quantity of blood forced forward at each ventricular systole is limited in quantity, it must follow, as we recede from the heart to the periphery, that there will be less and less blood forced forward. The blood having been pro- gressively absorbed, so to speak, by these lateral distentions in the proximal portion of the arteries, there will be less, therefore, to distend the distal parts. The pulse being due to this distention, must, therefore, be weaker in the arteries at a distance from the heart than in those near it, and must ultimately disappear in the smallest arterioles altogether. As a fact, the pulse is rarely felt in arteries having a diameter less than ^ of a mm. (yg-th of an inch). It is for this reason that in the case of an aneurism, the lateral distention being here greatly exaggerated, that the pulse is often absent in that portion of the artery situated beyond the seat of the disease. In the case of aneurism of the aorta, the pulse may be absent in all of the arteries of the body. While the description of the pulse in disease belongs rather to works on medicine and therapeutics, it may not appear superfluous to mention that pathology confirms the views that have just been offered as to the production of the natural pulse. Thus, in an ossified artery, there is no pulse, because dilatation is impossible. When the arteries near the heart are rigid, the pulse is jerky, and the flow of blood is intermit- tent, not remittent. We see the same kind of pulse when the walls of the arteries are relaxed, unable to recoil thoroughly on their contents. If the artery be irritable, and at the same time distensible, the pulse will be exaggerated, and can be seen by the naked eye when, otherwise, it is usually imperceptible. The character of the pulse is profoundly affected by the conditions of the system, modified by general disease. Thus the large compressible pulse of fever, the hard pulse of Bright's disease, the small pulse of peritonitis, the soft pulse of collapse, etc., are well known to the physician. Finally, it has been shown by Vierordt and Aberle 2 that there is a daily variation in the calibre of the arteries that must influence some- what the character of the pulse, the radial artery, for example, being larger in the evening than in the morning. 1 Op. cit., p. 255. 2 Archiv f. physiol. Heilkui.de, 1856, B. xv. S. 574.. CHAPTER XXII PRESSURE AND VELOCITY OF THE BLOOD IN THE ARTERIES. Fig. 168. By blood pressure, whether it be cardiac or arterial, etc.. is meant the pressure or force that is exerted by the blood upon the surface of the vessel containing it, or, what is the same thing, the force that is required to be put forth by the walls of the vessels in order to sustain the column of blood within them. Before showing the manner in which the blood pressure is determined in a living animal, let us first endeavor, however, to illustrate, by a few simple experiments, the manner in which the pressure of liquids in general is determined. It is well known, as first shown by the distinguished geometrician Pascal, that the pressure exerted anywhere upon a mass of liquid, assuming the latter to be perfectly fluid and unin- fluenced by gravity, is transmitted undiminished in all directions, acting with the same force on all equal surfaces, and in a direction at right angles to those surfaces. That the force exerted upon the mass of a liquid is transmitted in all directions, and at right angles can be readily shown by means of the apparatus represented in Fig. 168. This consists of a cylinder provided with a piston fitting into a hollow sphere pierced with numerous holes, into which are fitted small cylindrical jets placed perpendicularly to the sides. The sphere and cylinder being filled with water. and the piston depressed, the water will be observed to spout out from all of the jets, and not simply from the one opposite the piston. In order to show that the pressure is transmitted, not only in all direc- tions, but equally, we make use of an apparatus very similar to the one just described, and represented in Fig. 169, it dif- fering only in that the perpendicular jets projecting from the sphere contain closely fitting, but easily movable pistons, each piston having the same area. The sphere being filled with water, the latter, by virtue of its weight, will press equally upon the surface of all the pistons. Neo;lectino; the influence exerted by the weight of the water, and the • • /T)\ T-. friction of the pistons, it will be observed that if a given pressure (r) be exerted upon the piston A the water will transmit the same pressure to the other pistons (B C D), which will move outwardly, unless they are each subjected to an equal and opposite pressure (P). It is evident, therefore, that the pressure (P) exerted upon A is not only transmitted in a straight line upon B, but equally upon C and D — that is, equally in all directions. If now the axes of the jets B C D be disposed parallel to each other, and made to approach until they form one, and Apparatus to demon- strate the equality of pressure in all directions. 314 PRESSURE AND VELOCITY OF BLOOD IN ARTERIES. for the three pistons a single one be substituted, as in Fig. 170, the conditions of the pressure are in nowise changed, but it becomes at once evident that the pressure exerted upon the piston A, and transmitted by the fluid, is proportional to both the number and area of the pistons, whether existing separately as B, C, and D, or combined as BCD. That is to say, if n weight of one pound be placed upon the piston A, the three pistons B, C, I), or the one piston BCD, will be pressed out- ward by the pressure transmitted through the liquid, unless a weight of one pound be placed upon each of the pistons B, C, D, or of three pounds upon the piston BCD. Suppose, however, that the apparatus be constructed of the form represented in Fig. 171, in which, as before, Fig. 169. the large piston A has three times the area of the small one B, and carries three times as heavy a weight, it will be observed that while the small piston B with a weight of one pound and an area of one inch, descends through three inches, the large piston A, with an area of three inches, and with a weight of three pounds, ascends through only one inch, equilibrium being then established, just as a lever whose arms have a length respectively of three and one inches will be balanced by suspending a one pound weight at the end of the long arm, and a three pound weight at the end of the short one. It is perfectly evident that in neither case is there any absolute gain of power, for what is gained in weight is lost in height or distance. In practical mechanics the B rani ah press is a beautiful application of the principle just enunciated, in which a pressure of 300 pounds exerted upon a piston corresponding to A will exert a pressure of 30,000 pounds upon a piston BCD, supposing the sectional area of the latter to be 100 times that of the former. It must not be forgotten, PRESSURE OF LIQUIDS. 315 however, that in the Bramah press, as in the simple apparatus just described, and in the case of the lever with unequal arms, that the greater weight is elevated only a fractional part of the distance through which the lesser weight has descended, and that what is, therefore, gained in weight is lost in distance. The significance of this important truth in the study of blood pressure will very soon become evident. Now, on reflection, it will become evident from what has just been said with reference to the transmission of pressure through fluids, that the pressure exerted by the particles of water against each other must be estimated in exactly the same manner as we have estimated the pres- sure P transmitted to the base of the pistons (Fig. 171), or, what is the same thing, to the walls of the vessel containing the water. It follows, therefore, that if the weights and pistons be removed from the apparatus (Fig. 171), that the water will rise to the same level in both of its limbs (Fig. 172), proving that the pressure exerted by the water in A and B Fig. i; Fig. 172. Principle ■>[' tin- hydraulic press. must be equal and opposite, notwithstanding that the limb B contains three times as much water as the limb A, for if the pressure exerted by the water in B were greater than that in A the level of the water would rise higher in the latter than in the former. It follows, therefore, from the principle of Pascal, or the equality of pressures, that the pressure exerted by a fluid is independent of the quantity of the fluid, and of the form of the vessel containing it, but is dependent for the same fluid on the area of the base upon which the pressure is exerted, and the height of the column of liquid above it. For let us suppose that the vessel, whose liquid contents press upon the bottom, be of a tapering form, such as is represented in Fig. 173, and that the bottom D E be divided into eight areas of the size, as that of the mouth F. From what has been said of the pressure being transmitted equally in all directions, it follows that the weight of a small liquid layer, say half an inch thick at the top, will be transmitted undiminished to the eight areas of the bottom, producing the same pressure as if eight of such layers of liquid were separately placed upon them. In the same manner, a layer half an inch thick, but situated as much lower down in the liquid, so as to have twice the area of F, will produce the same pressure upon the 316 PRESSURE AND VELOCITY OF BLOOD IN ARTERIES. bottom as if four such liquid layers were laid there — that is, the same as the pressure due to the eight small layers. It follows, therefore, that each horizontal layer of the same thickness, no matter where it lies in the liquid, produces the same pressure, the amount depending upon its thick- ness and the area of its base. The total pressure of the liquid upon the bottom must depend, therefore, on the area of the base, and its vertical height or thickness — that is, equal to a column of liquid having the same base and the same vertical height. The truth of the theorem so deduced Pig. 173. Fig. 174. To illustrate the pressure exerted by liquids. Apparatus t<> demonstrate that the pressure is inde- pendent of shape and size of vessel. is experimentally verified by the experiment just performed, since the pressure exerted by the columns of liquid in A and B (Fig. 172) are the same, because they have the same base and the same height of liquid above it. That the' shape of the vessel has no more influence with regard to the pressure exerted by the water it contains than that exerted by the amount will become, perhaps, more evident if the apparatus (Fig. 174) be filled with water. The level to which the water rises being the same in all the tubes, though of very different shape, proves that the pressure exerted by the water must be the same in all of them. On account, however, of the practical importance of the law of the pressure of liquids, and of the necessity of keeping clear in the mind the distinc- tion between the pressure exerted by the liquid and its weight, let us illustrate the principle involved a little more in detail by means of the apparatus represented in Fig. 175. This consists of a balance, in one of whose scale pans (A) a known weight is placed, while to the other (B) a wire is attached, terminating in a flat disk (C), which is so exactly applied to the lower opening of the sup- porting cylinder (D) that it practically constitutes its bottom, being tightly drawn up by the counterpoising weight in A. A known weight being now added to that already in A, and water being gradually poured into the cyl- inder, by degrees the pressure of the liquid on the disk or bottom increases, and when the pressure so exerted equals the counterpoising weight in A the least excess of water detaches the disk — that is, the bottom of the cvlinder falls out, and the water flows out; but, as the pressure is HYDROSTATIC PARADOX, 317 at once diminished by the outflow, the disk is drawn up again, and ad- heres closely to the cylinder. The pointer touching the surface of tin- water marks its level at the moment of equilibrium. Fig. 1' Pressure of a liquid on the bottom of the vessel which contains it. In this experiment it is obvious, as might have been expected, that the pressure exerted by the water upon the bottom is precisely equal to its weight, which was two pounds. Suppose, now, we substitute for the cylinder a conical-shaped vessel (F), with the same sized orifice at the bottom, but with a much wider one at the top, and, therefore, capable of containing more water ; nevertheless, if we experiment with the conical Fig. 176. e^ Fig. 177. Fig. 178 Hydrostatic paradox . To demonstrate the upward pressure exerted by water. vessel as we did before with the cylinder, notwithstanding that the former contains three times as much water as the latter, the pressure exerted by the water upon the bottom, as we see, is the same, being only 818 PRESSURE AND VELOCITY OF BLOOD IN ARTERIES. two pounds, whereas, the water weighs six pounds. In the experiment with the conical vessel the pressure exerted by the water upon the bot- tom is, therefore, less than its weight, and the reason is very obvious, since it is only that part of the water within the dotted lines that exerts pressure upon the bottom, the pressure of the remaining extra water, so to speak, being exerted upon the walls of the vessel, and not upon its bottom. Finally, if we make use of a conical vessel (Fig. 175, G), or of one (Fig. 176) consisting of two cylindrical parts of unequal diameters, of which the lower one has the same sized orifice at the bottom as obtains in the two vessels just used, and holding less water than either of the latter, we shall still find, experimentally, in the same way, that the pressure exerted upon the bottom is undiminished by that circumstance, being two pounds, though the water weighs only one pound. This must be so, since the pressure exerted upon the bottom is due to a column of water having the same vertical height and base as the column of Avater included between the two dotted lines D and G (Fig. 176) — that is, the pressure of the column of water on the principle of the pressure being exerted equally, and in all directions, is not only exerted upon E F (Fig. 176), or the part of the bottom directly underneath it, but also upon the remaining part of the bottom on both sides of E and F. The total pressure exerted upon the bottom is therefore the same as if there were two extra columns of water (D, G) pressing downward in addition to that upon E F actually present. It will be observed in this experiment that the pressure exerted by the water upon the bottom is therefore greater than its weight. At first sight, this result may appear paradoxical, it being perhaps difficult to com- prehend why, if the water in the vessel exerts a pressure upon the bottom, that when the vessel is placed in the scale-pan of the balance that its weight should be only equal to the weight of the water and vessel. The reason, however, becomes at once clear when it is re- membered that the pressure of the water is exerted in all directions, upward as well as downward, and that when the vessel is placed in the scale-pan (Fig. 176), that part of the pressure exerted upward against the surface of the- vessel in the direction of the arrows, being opposed in direction to the force of gravity, does not appear as weight ; consequently, the weight is simply equal to the weight of the vessel and of the water it contains. If, however, this upward pressure be balanced by an equal downward pressure, obtained by an extra quantity of water, equal in amount to the volume included between the dotted lines, then the pressure and weight of the water would be identical — that is, the conditions would be the same as in the first experiment. That the pressure of the water is transmitted upward as well as downward can be readily demonstrated by the following simple experi- ment. A large open glass tube (A, Fig. 177), one end of which is ground, is fitted with a thin card (B), to the centre of which is attached a string (C) by which it can be held against the bottom of the tube. The whole is then immersed in a jar of water, and, although the string be allowed to hang over the side of the jar, the card will still adhere to the mouth of the jar, it being kept in this position by the upward pres- sure of the water. HYDROSTATIC BELLOWS. 319 If now water be slowly poured into the tube the disk will still adhere to the latter, not sinking until the height of the water inside the tube is equal to the height outside. Hence, it follows that the upward pressure is equal to a column of water whose area is that of the tube (A), and whose height is the distance from the disk to the outer surface of the liquid. The upward pressure is, therefore, governed bv the same law as the downward pressure. The hydrostatic bellows (Fig. 178) is an interesting instrument in this connection, as illustrating the principle of Pascal, and the manner in which we propose to study blood pressure. It consist of a narrow tube (A) eight feet in length, with a sectional area of one-fourth of an inch, inserted into a square bellows (C) having a superficial area of one hundred and forty-four inches. The apparatus having been filled with water, it follows that, as the water in the tube weighs fourteen ounces, and as the superficial area of the top of the bellows (144 inches) is 576 times that of the sectional area of the tube (one-fourth of an inch), the bellows (D, D) should balance a weight of fourteen ounces multiplied by 576, equals 8064 ounces, equals 504 pounds, which, as a matter of fact, it does. At first sight this result may appear as paradoxical as in the experiment with the cylindrical vessel ; it will be observed, however, that the distance through which the 504 pounds upon the bellows are elevated is but the one-sixth of an inch, a fractional part only of the ninety-six inches through which the pressure was exerted. It is only another illustration of what we gained in weight we lost in height, or of a small force acting throuo-h a great height beino- equal to a large force acting through a short one, fourteen ounces fall- ing through ninety-six inches, being equal to 8064 ounces, or 504 pounds, ascending through the one-sixth of an inch. It follows, there- fore, that the pressure even of a small quantity of water, if exerted from a sufficient height, will be very great ; indeed, Pascal succeeded in bursting a strongly made cask by means of a narrow thread of water forty feet high, and, in this manner, demonstrated his principle of the equality of pressure. In considering the pressure exerted by two columns of liquid such as obtains in the apparatus (Fig. 172), it will be remembered that only one liquid — water — was used. It is needless to say, however, that if two liquids of different densities, such as water and mercury, were experi- mented with, the level of the water would stand 13.5 times higher than that of the mercury, the latter being that much heavier, the altitudes of the liquids being inversely as their densities. In other respects, what has been said of the pressure exerted by water will apply equally to mercury or other liquids, and inasmuch as we will make use of a mer- curial column as a measure of the pressure exerted by the blood, it will not be superfluous to illustrate first the manner in which we measure by mercury the pressure exerted by any liquid; this we do bv means of Haldat's apparatus (Fig. 179). This consists of a tube (A B C) bent at both ends at right angles, one of which is provided with a stopcock (A) on which can be screwed vessels (2), F, F, etc.), of the same height but differing in shape and capacity, D being cylindrical and F conical. The tube A B C'is filled with mercury until it reaches the level P. The 320 PRESSURE AND VELOCITY OF BLOOD IN ARTERIES. vessel E is first screwed on, for example, to the end at A and water is poured into it until it reaches the level G, this level is registered by the movable rod //. The pressure of the water in the vessel E upon the Haldat's apparatus. surface of the mercury in the limb A will cause the mercury to rise in the tube up to the level I, and is there registered by a movable collar. The stopcock A is then opened, which allows the water to run out of the vessel E, which is then removed and is replaced by the vessels D and F; these, in turn, are filled with water up to the level Gr, when it will be observed that the mercury which had in the mean- time, in each case, fallen to its original level in limb A, rises again to the level I the same as before, thus proving that the pressure exerted by the water upon the mercury is, as we have already seen, independent of the quantity of the water and of the shape of the vessel, but is equal to the weight of a column of water whose base is the surface of the mercury M beneath the stopcock in limb A, and whose altitude is the height (A Gr) of the level of the water above the surface of the mercury ; that is, the pressure of the water (P) equals altitude (A Gr) multiplied by area [M ). The height of the water being the same in D F and E, and the surface of the mercury (M) representing the area in each case, the product of A Gr X M must give the pressure exerted by the Avater in all three vessels, which we have just seen is the case, the column of mercury being the same in both experiments. The column of mercury is then the measure of the pressure exerted by the water in D, E, or Gr sustaining it. It is obvious that we must double P I as the mercury is proportionally depressed in the other limit of the tube. It is by means of the hydrostatic principles that we have illustrated somewhat in detail that Stephen Hales, in the early BLOOD PRESSURE. 321 part of the last century, first determined the cardiac blood pressure in a living animal with anything like accuracy, and estimated what it would probably be in man. It is true that before the time of Hales the sub- ject of blood pressure had been studied by physiologists and physicists, among others, notably by Borelli. 1 As this distinguished mathematician's calculation was based, however, upon purely theoretical data, and as his estimate of the force of the heart being equal to 180,000 pounds was such a gross exaggeration of the truth, it appears strange now that any importance should ever have been attached to it. Indeed, any reference to Borelli's views as regards blood pressure has at the present day only an historical interest. Hales's method was, however, logical in principle, and, indeed, with certain modifications in the construction of the appa- ratus, is the one made use of at the present day. Hales's method' 1 of experimenting was as follows : A living animal, a horse, for example, having been firmly secured, a large artery, like the femoral or carotid, was exposed, and, after having been ligated, was opened. A brass tube was then inserted into the vessel, to which was adapted a glass tube ten feet long. The connection between the brass and the glass tube was made by a brass pipe, and in some cases by a portion of the trachea of a goose, the latter being used on account of its pliancy so that no disarrangement would ensue through the struggles of the animal. The tube having been inserted into the femoral artery, for example, the blood was observed to rise in the glass eight feet three inches above the level of the left ven- tricle of the heart. In the case of the carotid artery the blood rose even higher, attaining a height of nine feet six inches, or 144 inches. In order to estimate the pressure or force sustaining such a column of blood, just as in the case of the experiment with the water and the mercury, or with the bellows, the altitude 144 cubic inches must be multiplied by the internal surface of the left ventricle of the horse's heart, or the area. Hales determined the area of the left ventricle of the horse's heart by injecting it with hot wax, then the wax, when cold, Avas removed and small pieces of paper properly cut were placed upon it until the wax was perfectly covered ; the small pieces of paper were then removed to a sheet of paper which was ruled off into squares, and in this way it was estimated that the inner surface of the ventricle, or the area needed for the calculation, was equal to 26 inches, deducting 1 inch for the orifice of the aorta. The pressure or the force of the liquid, in this case the blood in the carotid artery, being independent of the quantity and the shape of the vessel containing it, but equal to the altitude of the column of the blood multiplied by the area or its base, the product of 144 inches by 26 — that is, 2964 inches of blood will be the pressure or force which the ventricle sustains at the moment of its systole. Now, as a cubic inch of blood weighs 267.7 grains, the pressure of the blood amounts to 267.7 X 2064, or 7,933,628 grains, which is a little over 113 pounds, there being 7000 grains to the pound. • On the supposition that the blood would rise 7^ feet high in a tube 1 De Motn Animalium, Pars Secunda, p. 104, Prop, lxxiii. Lugd. Bat., lfiS5. 2 Statistical Essays, vol. ii. pp. 1, 2, 14, 15, 19, 20, 21, 39, 40. London, 1740. 21 322 BLOOD PRESSURE. inserted into the carotid artery of a man. and that the internal area of the left human ventricle is equal to 15 square inches, Hales estimated by the method just mentioned, that the pressure on the left ventricle at the moment of contraction would amount to 55 pounds (25 kilo.). This estimate is too low, both in the case of man and the horse, as shown by the later investigations of Poisseuille, Volkmann, etc., to be described presently, that the blood would probably rise in a tube placed in a carotid artery of a man, as in that of the horse, to the height of 9 feet, there being but little difference probably in this respect as regards these mammals. Indeed, Volkmann 1 has shown that even in the chicken the blood rises as high in some instances as in the dog and the horse. The area of the left ventricle also, as determined by Collin, 2 is greater than that given by Hales. Further, Haughton, 3 by a different method from that of Hales, calculated that the cardiac blood pressure in man ought to be about the same as that observed in the horse, his method being based upon a knowledge of the distance to which a divided artery will spurt, which in the case of man was learned by Haughton through a surgical operation, the force with which the heart contracts to produce such an effect being deduced from this data. Modern investigation, as we shall see, has shown that the blood pressure is influenced by conditions unknown to Hales, nevertheless his original experiment is to this day the most striking way of demon- strating it, and his application of hydrostatical principles in measuring it is the method since so successfully made use of by Poisseuille. Volk- mann, Ludwig, and others. It is not so much, however, the pressure that the heart sustains which the physiologist wishes to determine as the actual force with which the heart drives the blood into the aorta at each ventricular systole. The difference between the action of the heart and that of the hydrostatic apparatus we have shown, in which the large glass tube and bellows repre- sent the aorta and heart, is that the heart, like any other muscle, exerts itself according to the resistance to be overcome. Thus, if we raise a pound with our hand, the muscles of the extremity make a greater effort than when we raise a feather, so according to the resistance, for example, offered by the capillaries to the efflux of the blood into them from the arteries, will the heart contract more forcibly, and the blood- pressure will rise. It is evident, then, that the possible force of the heart and the actual force usually exerted may differ very much in amount. Before demonstrating this experimentally let us explain the haunadynamometer, the apparatus by means of which blood pressure is usually studied at the present day, and then compare the arterial with the cardiac pressure. The hremadynamometer, so called from the Greek words hsemo, blood, dynamis, force, and metros, measure, is essentially a mercurial manometer adapted to measure the blood press- ure, hence the name given to the instrument by Poisseuille, 4 who first, in 1828, made use of it for this purpose. The apparatus that we shall use (Fig. 180) is the same as Poisseuille's, with some modifications- i Die Hwmodynamik, S. 177. - Comptes Rendus, xlvii. tome 155. ; Animal Mechanics, p. 40. London, 1873. 4 Journal de physiologic de Magendie, tome viii. p. 212, 1828. H.E M ADYXAMOMETER, 323 It consists of a U-shaped glass tube (BCD E), of which the distal or ascending limb (DE) is longer — 32 cm. (125 inches) — than the proximal or descending one (B C) — 20 cm. (8 inches). The tube has a diameter Fig. 180. The mercurial kymograph a. Vulcanite rod of floating piston, b. Tube which communicates with the pressure bottle, c. Tube which communicates with the artery, d. Feeding cylinder. 1. First axis, which revolves once in a minute. 2. Second axis, which revolves once in ten seconds. 3. Third axis, in a second and a half The instrument is furnished with other cylinders suitable for the reception of single bands of glazed paper, the surface of which can be blackened after they are fixed on to the cylin- ders, by causing the latter to revolve over the flame of a petroleum lamp. These cylinders can be fitted on to either of the axes I, 2, or 3, and are always used when it is necessary to employ a rapidly moving surface, as-e. g., for tracing the curves of muscular contraction. (Sanuebson.) of 1.25 cm. (h inch.). From the distal branch B is given off a short horizontal one A, 2.5 cm. (1 inch), by means of which the manometer is put in communication with the artery whose blood pressure we wish to determine, and which, in this case, will be the carotid artery of the rabbit. The U-shaped tube being clamped in a vertical position, per- fectly clean and dry mercury is poured into it until the mercury reaches a given level in the two limbs. To prevent the blood coagulating 324 BLOOD PRESSURE. that which will come from the artery a saturated solution of sodium carbonate or subcarbonate is allowed to flow from the pressure-bottle P through the tube b b into the proximal end B of the manometer, and through its horizontal branch (A), to which is connected by a short piece of tubing a glass tube, or leaden pipe (e), the latter being stopped tempo- rarily by the finger, or by a cork. To avoid the inconvenience of inserting the horizontal branch of the manometer A, or its continuation the pipe c, into the artery, and which would be impossible in the case of the rabbit, the vessel being so small, a pointed and bevelled glass canulais first inserted into the artery, the vessel having been previously ligated at its distal end, and clamped at its proximal end. The inser- tion of the canula will be greatly facilitated if a small piece of card be placed under the vessel to support it, and by making the opening for the canula V-shaped. The canula is secured in the artery by a liga- ture, and is connected with the pipe c by a small piece of tubing. The arterial canula is filled with the solution of sodium bicarbonate by means of a syringe, and the same solution allowed for a moment to flow from the pressure-bottle into the proximal limb of the manometer, and through its horizontal branch and the pipe c, so that all the air shall be driven out. The arterial canula and the pipe e are then connected as quickly as possible, and the tube (b b) leading from the pressure-bottle to the proximal limb of the manometer clamped. On removing the clamp from the artery the blood will jet out, pressing forward against the soda solution, which, in turn, will press against the mercury in the proximal end of the manometer, forcing it downward, the mercury in the distal limb being proportionally elevated. It is evident from the hydrostatical principles just illustrated that the pressure of the blood in the artery will be measured by the weight of the column of mercury, whose base or area is a circle, having the same diameter as that of the artery, and whose altitude is the height of the column of mercury — that is, the dif- ference between the two levels F and G, and which, in this particular experiment, it will be observed, amounts to 90 millimeters (3.6 inches). The arterial pressure can be briefly and conveniently expressed then by the formula P equals ^R 2 h W, in which P equals the pressure, R 2 the area of the artery, h, the height of the mercury, and w its weight, it being understood that the symbol t is the ratio of the circumference to the diam- eter, and R 2 the square of the radius of the circumference of the artery, and that the product of t by R 2 gives the area. Thus, the diameter of the aorta at the level of the semilunar valves, in a man aged twenty-nine years, being 34 millimetres (1.3 inches), as was found to be the case by Poisseuille, 1 the radius R would be 17 millimetres, and the square of R 2 289, the latter multiplied by »r, or 3.1416, will give about 907 milli- metres (1.4 inches) as the area of the aorta at the level of the semi- lunar valves. The area, or 907 millimetres, multiplied by 160, or the probable height to which the mercury would be elevated could the mano- metric tube be inserted into the human aorta, gives 145120 millimetres as the volume of mercury sustained by aortic pressure. On the suppo- 1 Op. cit., p. 304. ARTERIAL PRESSURE. 325 sition that 1 millimetre of mercury weighs about -^ of a gramme (0.21 grain), 145120 millimetres will weigh ~^^ = 1988, or nearly 2000 grammes, or nearly 2 kilogrammes — that is, about 4.4 pounds. Sub- stituting the value in the formula given for the pressure, we have Pressure equals area X height X weight. Pressure equals ir X E 2 X h X W. 4 lbs. == 3.1416 X 289 X 160 X } . It may be said, then, that the actual force or pressure under which the blood is driven into the aorta at each ventricular systole amounts to about 4.4 pounds on the square inch. As a general rule, however, the blood pressure is estimated by simply measuring the height to which the mercury is elevated in the distal limb of the manometer, and doub- ling the result, without the area of the artery or the weight of the mer- cury being taken into consideration. By that method the aortic pressure would be estimated as amounting to 160 millimetres, or only about 2 grammes. The disadvantage of such a manner of estimating blood pressure is due to the fact already mentioned that the difference between animals as regards the height to which the mercury will rise in the manometer is not as great as perhaps might have been at first imagined. Since the blood "pressure depends not only on the height of the mercury in the manometer, but also on the area of the artery, we should expect to find, as indeed is the case, that while the height of the mercury is about the same in three diiferent species of animals, that the blood pressure may be very different. Thus in the horse, sheep, and dog, the mercury will rise in the manometer to about the same level, on an average 150 millimetres (6 inches). As the aortic force or blood pressure, however is equal to this height multiplied by the area of the aortic orifice, it is evident that the pressure will be proportional to the size of this orifice, and will therefore be greatest, other things equal, in that animal which has the largest aorta. Thus the blood pressure of man as estimated simply in millimetres of mercury differs but little from that of the horse; on the other hand, while the aortic pressure in the horse amounts to 5 kilo. (10 pounds), that of man, as we have seen, amounts to only 2 kilo. (4 pounds). In estimating blood pressure, a fact must be taken into consideration which is usually neglected, and that is, that the solu- tion of sodium carbonate having weight must exert a certain amount of pressure upon the mercury in the manometer. The height to which the mercury is elevated is then due to the pressure of the blood and of the solution. To obtain the former we must therefore deduct the latter from the observed altitude of the mercury. As 10 millime- tres (i in.) of the soda solution are equal to 1 mm. of mercury for every 10 mm. of the soda solution in the proximal limb of the manometer we must deduct then 1 mm. of mercury from the altitude of the mercury in the distal limb of the manometer. As a general rule, the amount of the soda solution in the proximal limb of 326 BLOOD PRESSURE, the manometer is mercury need not pressure in the solution only J mm altitude of so small that the effect of its weight upon the be considered. Thus, in determining the blood the carotid artery of the rabbit it will be noticed that of soda amounts to only 5 mm. Q- in.), and therefore must be subtracted from the 90 mm., or the observed the column of mercury, to obtain the arterial pressure. In using certain kinds of manometer, however, as we shall see, the amount of the soda solution being greater the influence of its pressure becomes more appreciable. It will be observed, also, that the pressure bottle containing the solution of sodium carbonate is sus- pended at a height of about 2 metres (6.5 feet) above the manometer, and that it can be elevated or depressed as desirable. The object of this is that having learned by experience to about what height the mercury will be elevated by the arterial pres-ure, we make use of the soda solution not only to prevent the coagulation of the blood, but also to exert pressure upon the mercury to the same extent as the arterial blood will do. As soon as the clamp is removed from the carotid artery the blood at once then exerts its pressure upon the soda solution, but advances only a little way in the tube c, loss of blood as well as coagulation being thereby prevented. The pressure of the blood is then transmitted to the soda and thence to the mercury; if the pressure bottle has not been sufficiently elevated, then the level of the mercury will rise in the distal limb of the manometer, and if too much elevated the reverse will be the case. The effect of the arterial pressure will therefore be the same as if exerted directly upon the mercury. In speaking of the connecting tube c, it was mentioned that it should be of glass and preferably of lead. The reason of this is now very evident. Did the tube consist of an extensible material the pressure of the blood would be exerted to a great extent upon the walls of the tube rather than upon the soda solution, and indirectly therefore not upon the mercury. Various methods are made use of by physiologists to secure firmly the animals to be experimented upon. In this instance we make use of Fig. 181. Czermak's rabbit support. (Sanderson.) Czermak's rabbit support, and as the apparatus when sufficiently large, is equally convenient for other animals, and as we shall frequently AORTIC PRESSURE. 327 have occasion to use it, a short description seems advisable. It con- sists (Fig. 181) of a firm wooden stand A, 1 metre (3.2 feet) long and 22 cm. (9 in.) wide. The end B with the large opening c is made stronger than the rest of the stand by an iron plate into which an iron rod (d) bent twice nearly at right angles is screwed. This rod carries a movable brass ring through which passes horizontally an iron rod / movable in all directions, and which bifurcates at the end, the two ends of the horizontal rod being adjustable to the frame-like clamp through which passes the rod h in a direction at right angles to that of the horizontal rod /, the rod supporting a second clamp of the same general form as the first one, and which by means of the screw k can be brought near to the latter. The animal being placed upon its back, and resting upon a mattress, the neck supported by a cylindrical cushion and the extremities fastened by strings to the pegs m m, the rod h is placed between the teeth and the screw k so adjusted that while the clamp g presses upon the lower jaw the clamp g will press upon the head. In this way the animal is firmly held, and yet does not receive the slightest injury. We have just seen that the aortic pressure in man amounts to nearly 2 kilo. (4.4 pounds) to the square inch. Now since the pressure exerted upon the mass of a liquid is transmitted undiminished equally in all directions, and acts with the same force on all equal surfaces according to the principle of Pascal, to obtain the cardiac pressure we have only to multiply the 2 kilo, or the aortic pressure by the internal area of the left ventricle, or 38.1 centimetres (15 in.), which gives 30 kilo. (66 pounds). This result, it will be observed, agrees very closely with that of Hales. This should be so, since the hydrostatic principle made use of by both Hales and Poisseuille in determining the cardiac and aortic pressure was the same. It was for this reason on account of the application of hydrostatic principles in the study of blood pressure that Ave illustrated these principles so much in detail. If now the hydrostatic bellows be compared to the heart and the aorta, it is obvious that the aortic pressure corresponds in the bellows to the small force acting through a great height in the narrow tube, while the cardiac force is the great force acting through the small height corresponding to the force in the bellows. It must not be forgotten, however, that the pressure in the heart may vary according to circum- stances due to its inherent contractility whereas the pressure in the bellows is constant for the same quantity of water otherwise the princi- ples involved are the same. That the cardiac pressure is greater than the aortic is shown by the fact that with each ventricular systole the mercury rises in the manom- eter, falling again with the diastole, the mean arterial pressure being, as we shall see, the level between these extremes. Further, as we have just mentioned, and which we will now demonstrate, the cardiac pres- sure will be greatly increased beyond that which we may consider as normal, according to the resistance to be overcome. This is usually shown by means of Coats's apparatus, 1 or by that described by Marey, 2 1 Described in Handbook Phvs. Lab., p. 26S, plate xci. - Circulation du Sang, 1881, p. 70, fig. 28. 828 BLOOD PRESSURE. but, as both these methods involve taking the heart out of the animal, and as we wish to show the phenomena, the heart being in situ, we will make use of the convenient little apparatus (Fig. 182) as arranged by Dr. A. P. Brubaker, for studying blood pressure in the frog. This Fio. 182. Brubaker's frog manometer. consists of a mercurial manometer M like that we have used in de- termining the blood pressure in the rabbit, only that it is smaller. The arterial canula differs, however, from the one used in that experiment. In this instance the end a of a JL-shaped glass tube is inserted into the bulbus arteriosus of the frog, the end b being adjusted to the proximal end of the manometer, while the stem c is connected by the tube d with a funnel e containing a solution of sodium carbonate. The fun- nel corresponds to the pressure bottle in the experiment with the rabbit. The frog is secured to a piece of cork, which rests within the stand supporting the manometer ; the stand can be raised or lowered upon the vertical rod ; the latter also supports, by the horizontal rod, the funnel. Having first determined the normal blood pressure, it will then be observed that as the tube d is compressed, an obstacle being thereby interposed to the flow of blood from the aorta, the pressure will be in- creased, the mercury rising in the distal limb of the manometer, thus showing that the force which the heart exerts is proportional to the re- sistance to be overcome. ARTERIAL PRESSURE. 329 While the flow of the blood through the arterial system generally is influenced by the length of the vessel, friction, etc., the capillary sys- tem, as we shall see, is a constant source of resistance. In proportion to the fulness of the capillaries a greater or less obstacle is offered to the flow of the arterial blood. The force that the heart exerts must then vary according to the resistance to be overcome. It is hardly necessary to state that the constriction of the tube in the last experi- ment would represent a capillary obstruction in the living animal. Theory and experiment, therefore, agree in showing that the amount of force which the heart usually exerts is far less than the possible force that can be put forth if occasion demands it. Very great differences are found, also, among animals, as regards the proportion of the cardiac to the arterial pressures. In the rabbit, for example, the force of the left ventricle exceeds but little that of the aorta, whereas, in the horse, the excess of the cardiac pressure as compared with the arterial is very marked. Thus, by means of his cardiometer, Bernard 1 has shown that the arterial pressure in the rabbit being 91 mm. (3.8 inches), with each ventricular systole the mercury rose to 100 mm. (1 inches), the cardiac pressure being only 5 mm. greater than the arterial. On the other hand, in the horse, the arterial pressure being 100 mm. (4 inches), the cardiac pressure was 65 mm. greater, the mercury rising to 175 mm. (7 inches) with the systole. Just as we have seen the pulse gradually disappearing as we recede from the heart, so, for the same reason, we should expect to find this excess of cardiac over arterial pressure becoming less and less as we pass toward the periphery. Experiment confirms in this respect what theory would lead us to expect. Thus, Volkmann 2 has shown that, while in the carotid artery of the dog the excess of the cardiac pressure, as compared with the arterial, amounts to 37 mm. (1.4 inches) ; in the metatarsal artery the excess amounts to only 1 mm. (33th of an inch). In making the distinction between cardiac and arterial pressures, it must not be forgotten, however, that the latter is only the delayed effect of the former, since the cardiac pressure exerted during the pre- vious systole in distending the arterial wall is restored during the diastole to the circulation through the elasticity of the artery as arterial pressure. The cardiometer we make use of in demonstrating the difference be- tween cardiac and arterial pressure is that shown in Fig. 183, as made by Verdin, of Paris. It is but a slightly modified form of the cardi- ometer used by Magendie and Bernard, and consists of a metallic vessel containing water, within which is suspended an elastic capsule, (M), com- municating at one end (T) with the artery whose pressure is to be deter- mined, and at the other end with a delicate mercurial manometer (B) for registering the pressure. The upper part of the vessel is closed with a cork, through which passes a glass tube, into which the water rises, and which transmits to the registering tambour R the distention of the capsule M due to the varying cardiac pressure. The arterial pressure, however, when once attained, remains constant, the constriction at the 1 Systeme Xerveux, tome i. pp. S83, '286. - Die Hremodynamik, S. 167. 330 BLOOD PRESSURE. bottom of the mercurial manometer B offering such a resistance to the rise of the mercury that the intermittent action of the heart is not felt. Fig. 183. Cardiometer. (Marey. Having described the manner in which the mercurial manometer is used in determining the force of the left ventricle, a few words will suffice as to the force exerted by the right ventricle. According to Marey 1 and Chauveau, on the average the force of the right ventricle is about one-third of that of the left ; the force of the right auricle being about one-tenth that of the right ventricle, it is about 1.30 to 1.7 of the left ventricle. Inasmuch as the left auricle is inaccessible in a living animal to experimental investigation, nothing positively is known as to the pressure exerted by it. It is reasonable to suppose that it is equal to that of the right auricle. A great advance was made by Ludwig, 2 in 1848, in the manner of investigating blood pressure, by his invention of the kymograph (Fig. 180). This consists of a mercurial manometer like that of Poisseuille, in the distal limb of which is placed a vertical rod (a) the lever-end of which terminates in a concave cup-shaped float, and rests upon the con- vex surface of the mercury, while the upper end of the vertical rod projects out of the upper open end of the distal limb of the manometer, and carries a delicate sable brush, wetted with ink, or a pen of glass, the point of which rests against the cylinder e. The vertical rod is kept in the perpendicular by the support 8, through which it passes, and the brush or pen in contact with the cylinder by the weighted string o. The cylinder e, 16 cm. (6.5 inches) high, and 50 cm. (20 i Op. cit, p. 115. - Muller's Archiv. KYMOGRAPH. 331 incites) in circumference, is covered with either white or smoked paper. With every oscillation of the mercury in the distal limb of the mano- meter, the rod a is elevated or depressed, and a vertical line is made upon the cylinder by the brush or pen. If now the cylinder is made to revolve at a uniform rate, the vertical mark will become a curve, like that represented in Fig. 184, and we obtain a graphic representa- tion of the blood pressure in this of the rabbit, hence the name Fig. ]84. Trace ut blood-pressure in rabbit. kymograph — from kumos, a wave, and grapho, to write — the name given to the instrument by Yolkmann, 1 who was among the first to use it successfully. Ludwig 2 tells us that the idea of the recording pen, etc., was suggested to him by a similar contrivance made use of by Watt for registering pressure in the steam engine. The immense im- portance of Ludwig's invention cannot be exaggerated, for, by means of the kymograph, the study of blood pressure became far more exact than had been possible previously. Slight variations in the oscillation of the mercury, for example, which were entirely inappreciable in the hsemadynometer, became perfectly apparent when graphically recorded upon the revolving cylinder. The great merit of Ludwig's invention did not consist simply in the applica- tion of the kymograph to the study of the blood pressure, but the appli- cation of the graphic method in the investigation of the circulation of the blood generally, and, indeed, of all physiological phenomena. In truth, it is not saying too much that the study of physiology experi- mentally has been revolutionized by it, results having been obtained by the graphic method, as Ave have already seen, which had been considered impossible by the physiologists of the preceding generation. As the mercurial manometer of the kymograph, with its accessories, the pressure bottle, connecting tubes, etc., is the same as that already described, it is only necessary to say that the mercurial manometer, when used as part of the kymograph, is firmly clamped to the table (T) supporting the cylinders, and that the vertical rod in its distal limb is so adjusted that the brush or pen which it carries remains in contact with the cylinder. The latter in the instrument we use, made by Hawksley, of London, is moved by clock-work contained in the box II, and its motion made uniform by the Foucault regulator (i?). This consists of two fans, which, when the velocity is increased through the friction engen- dered, expand and so retard the motion, and when the velocity dimin- ishes contract again, and so offering less resistance it increases again, the fans being approximated and separated by an elastic spring. There are three axes (1, 2, 3) connected with the clock-work, and according to the one on which the cylinder is placed the rate of its revolution can be varied. Thus, when the cylinder is placed upon the first -axis it makes » Die Ha>moilynaii)ik. 2 Physiologie, 1861, S. 163, Band. i. 332 BLOOD PRESSURE. one revolution in one minute fifty-two seconds, or seventy-five seconds upon the second axis, one revolution in twelve seconds; upon the third axis one revolution in two seconds. It will be observed, therefore, that when the cylinder is on the third axis it revolves nearly forty times as rapidly as upon the first. When the cylinder used is that covered with smoked paper, it is held on the axis connected with the clock-work by a vertical rod passing from its centre upward into the frame, and which is screwed on to the box. By means of this vertical rod the cylinder can also be elevated or depressed through a height of several centime- tres. When, however, we wish to take a trace upon white paper, and it is desirable that the observation shall extend over a long period of time as possible, then a somewhat different arrangement is made from that just described. We then use two cylinders (Fig. 180, g, d), one of which (e) is to record the trace, and which, resting upon the axis connected with the clock-work, is supported from above by a frame, not represented in the figure, which, like the other frame, can also be screwed on to the box. The other cylinder (e) is covered with white paper rolled around it by machinery, and in quantity sufficient to last for several hundred observations. This cylinder acts as a feeder to the recording one, for, as the latter revolves, it unwinds the white paper around the former, the paper being kept smooth by two little ivory wheels on the frame (not represented in Fig. 180). Having explained the construction of the kymograph, let us consider now the traces of blood pressure of the cat, turtle, frog, for example, as recorded by it, and point out some of the results obtained by their study, and which would have been impossible had we limited our study of blood pressure to the use of the mercurial manometer only. By an examination of Fig. 185, illustrating the kymographic trace of the blood pressure in the cat. recorded upon the smoked paper, it will be observed that the Fig. 185. Trace of blood jiressnre in cat trace consists of a number of large curves, each of which is made up of smaller ones. The large curves extending from crest to crest of the wave, being to a certain extent respiratory in origin, their relations to inspiration and expiration will be considered hereafter. For the present, however, it may be said, by the graphic method it can be shown that, during a part of the period of inspiration, the blood pressure is increased and during a part diminished, and that in the same way the blood pressure is both diminished and increased during expiration. The small curves are cardiac in origin, each small curve corresponding to a heart beat, the elevation being caused by the systole, the depression by the diastole. If the pen be watched during these oscillations, it will be noticed that there is an average height above and below which the pen is elevated and depressed with each cardiac beat. This average height represents the mean arterial pressure. To express this in millimetres of mercury we BLOOD PRESSURE IN TURTLE AND FROG. 333 must measure the distance or ordinate between the line representing the average height and the straight line, or abscissa, representing the height at which the pen was elevated by the mercury under the influence of the atmospheric pressure only, before the blood pressure had exerted any force and then double this distance ; while to estimate the cardiac pressure in millimetres of mercury we must add to the mean arterial pressure twice the distance of the excursion of the pen during the small oscillation. If we wish to get the mean of either the cardiac or the arterial pressure of a number of pulsations, we must add up the ordi- nates and divide by the number of ordinates. As pulmonary respi- ration is far less active in the turtle and frog than in the rabbit naturally, w r e should not expect to find respiration influencing the form of the curve of blood-pressure in these animals to the same extent as in the mammal. The large curves are then absent in the traces represented in Tigs. 186 and 187 ;' the small curves are. however, mm. of solution of sodium carbonate used, we obtain the blood pressure of the artery on the side where the stopcock remained opened. Fig. 191. Fick's spring kymograph, a. C-spring. s. Support, d. Rod which communicates the movements of the spring to the lever I, and thus to the writing-needle G. c. Leaden tube by which the cavity of the spring is in communication with the artery. Admirable an instrument as the kymograph undoubtedly is, and how- ever accurately it fulfils its purpose, it must not be forgotten that the trace recorded on the cylinder is due to the oscillations of the mercury, and, therefore, only indirectly to the pressure of the blood. On account, however, of the inertia of the mercury and the suddenness of the expansion of the artery, the oscillations of the mercury, though caused by the pressure of the blood, are not an exact measure of it, since by the time the mercury has risen to its highest elevation the artery has collapsed. If the heart is beating very quickly the extent of the oscillations of the mercury is relatively too small, and if the inter- val between the pulsations is prolonged the excursion of the manometer is too great. The use of the mercurial kymograph is. therefore, limited to the study of the mean pressure and of variations in pressure such as occur at sufficiently long intervals to prevent the oscillations being mixed up with those proper to the instrument. In order to study the variations of blood pressure in the exact order in which they occur, and as regards their duration and degree, etc., we make use of Fick's spring kymograph, SPRING KYMOGRAPH. 337 which is so constructed that it transmits the movements communicated to it without obscuring them by any movement of its own. The instrument (Fig. 191) consists essentially of a hollow C-shaped thin metal spring (a) filled with alcohol and communicating through its proximal end (b) by means of a connecting tube (e) with the pressure bottle containing the solution of the sodium bicarbonate and the arterial canula. The proximal end of the spring being fixed, as the blood press- ure increases the spring tends to straighten itself and the distal or free end makes the movements which follow exactly the variations in the arterial tension. These movements are most exact, the slightest variations in the blood pressure being expressed by them. As they are, however, very small before being recorded, they are enlarged by the lever which is carried by the distal end of the spring. It will be seen from Fig 192, illustrating a trace of the blood pressure in the carotid Fig. 192. Traces in rabbit taken with Kick's spring kymograph. artery of the rabbit, taken by the spring kymograph, that the ascent of the lever, due to the expansion of the artery caused by the ventricular systole, is very abrupt, almost vertical, that at the vertex the direction of the trace is horizontal, that the lever in its descent pursues an oblique course at its termination, being also horizontal in direction, and that the dicrotism of the pulse is very evident. The nature of these peculiarities we have already considered in describing the pulse. If we wish to ex- press in millimetres of mercury the absolute blood pressure determined by the spring kymograph, the instrument must first be graduated by comparison with a mercurial manometer. This is done in the following way : The spring kymograph being so placed that it will write on the re- cording cylinder, its connecting tube in communication with the pressure bottle is adapted to the proximal end of the mercurial manometer. The pressure bottle is first lowered until the solution it contains stands at the same level as that of the mercury in the manometer. The clockwork being put in motion the cylinder revolves and a trace is taken which will represent the abscissa. The pressure bottle is then raised till the mercury is elevated in the distal limb of the manometer 10 mm. (J-th of an inch) higher than in the proximal one, and a second tracing taken, and so on until we have obtained a number of tracings parallel with the first one or abscissa, and therefore with each other. The vertical dis- tance between the abscissa, and these lines or the ordinates measured in millimetres expresses then the value of the tracing in millimetres of mercurial pressure. We have already alluded incidentally to the influence of respiration in modifying the curve of the blood pressure, and, as we have now seen, how 22 338 BLOOD PRESSURE. the latter may vary according to the part of the vascular system gener- ally. It is probable, also, that the blood pressure depends, to a certain extent, upon the size of the animal, the period of life, and general health, cceteris paribus, the blood pressure being greater in larger than in smaller animals, in those of middle age than in very young or very old animals, in strong, healthy than in weak, sickly ones. Inasmuch as the pressure of the blood depends upon the muscular force of the heart, and as the muscular substance of the heart, like all other muscle, is nourished by the blood, it follows that loss of blood in weakening the fibre of the heart and the amount of blood expelled, should diminish blood pressure. The experiments of Hales 1 and Colin 2 have shown that such is the case, the blood pressure being diminished in proportion to the amount of blood lost. Finally, we shall see that the vasomotor nerves, in modifying the calibre of the vessels, greatly influence the bloodvessels. In concluding our account of the arteries, there still remains for us the consideration of the velocity with which the blood flows through them. Physiologists have endeavored to determine the velocity of the blood by means of the theorem of Torricelli, assuming that the velocity with which a fluid escapes from a reservoir may be learned from observing the height to which it will flow into a vertical tube connected with the same, the velocity being equal to that which a body would acquire falling in vacuo through a distance equal to the height which the fluid attains in the tube, which is nearly the same as the level of the fluid in the reservoir. The velocity, however, that a body acquires while falling through a given height is expressed by the formula, V= \/~lgh, in which V is the velocity, h the height, and g the accelerating force of gravity. To obtain the velocity with which the blood flows from the heart into the aorta we must substitute, therefore, in the above formula for h the height to which the blood rises into a vertical tube inserted in the carotid artery, which, in the case of the horse, for example, has been found to be 3 metres (117 inches), and for g, or the accelerating force of gravity. 9.8 metres (32 feet), then V=\ /% 2 X 9.8 X 2>= V / W7% = 7.6 metres — that is, the velocity would be about 7.6 metres, or about 24 feet in a second. Practical engineers, however, know that in hydro- dynamic machines the velocity of the flow, on account of friction, etc., is rarely what theory teaches it ought to be. The physiologist has still less reason even to find much agreement between the results of theory and experiment as regards the velocity of the blood, as the perturbing causes, among which may be mentioned the resistance offered by the column of blood in the aorta, are so numerous. Indeed, little or no im- portance can be attached to this manner of investigating the velocity of the blood in the arteries. In fact, we will see that the velocity just given is a gross exaggeration. Among the first to determine Avith anything like accuracy the velocity of the blood may be mentioned Hales, who, as we have already seen, studied the subject of blood-pressure with so much success. Assuming, according to well-known hydraulic principles, that the velocity with 1 Statical Essays, vol. ii. p. 10. London, 1746. 2 Milne Edwards: Physiologie, tome iv. \>. 115. H-EMODROMOMETER. 339 which a fluid, in a given time, flows through a tube is equal to the ratio of the efflux to the sectional area of the tube, Hales estimated that the blood in the horse flows from the left ventricle into the aorta at the rate of nearly 17 inches in a second, which we will see agrees closely with the velocity recently determined by experiment. Hales 1 method of calculation is as follows. Assuming the capacity of the left ventricle to be 10 cubic inches, and the area of the transverse section of the aorta 1.036 inches, the ratio of these two quantities, or , equals 9.65 inches, will be the column of blood that passes from 1.036 ! ' l the left ventricle into the aorta during each systole. Supposing that the heart beats 36 times in a minute, then 9.65 X 36 equals 347.40 inches of blood, would pass from the heart into the aorta in a minute ; Fig. 193. Fig. 194. ; — 2 -E 3 :: Volkraann's haemodroinuuieter for measuring the rapidity of the arterial circulation. but as the ventricular systole lasts, according to Hales, only one-third (really four-tenths) of the period intervening between two cardiac beats, the velocity must be three times as great, or 1042.20 in a minute — that is, 347.40 X 3 equals 1042.20 inches, or 86.85 feet; dividing this by 60, we obtain 1.4 foot, or 16.8 inches, for the velocity with which the blood flows from the heart into the aorta in a second. The first physiologist, as far as I know, who endeavored to determine, not what the velocity of the blood ought to be from theory, but what the velocity actually is in a living animal by experi- ment, was Volkmann. 2 The haemodromometer, or the instrument 1 Hemostatics, vol. ii. p. 46. - Hsemodynamik, s. 185 340 VELOCITY OF BLOOD. Fig. 195. which he invented for this purpose, consists of a metallic tube (c), which is united to the two ends of a divided artery, and through which the blood can flow in the same direction as through the vessel itself (Fig. 193). To the metallic tube is attached laterally a U-shaped glass tube (d), containing water. By turning stopcocks the metal tube is put in communication with the U-shaped tube in such a way (Fig. 194) that the blood cannot pass at once as it did before from the artery through the metal tube to the artery again, but must first pass through the U-shaped tube. The length of this tube being known, and the time it takes for the blood to flow through it being observed, the velocity with which the blood flows through the artery can be deter- mined approximately. There are objections, however, to the use of this instrument, as the blood does not flow through the glass tube as easily as it does through the artery, both on account of the curvature of the tube and of the difference in its substance as compared with that of the artery, and as the blood flows from the proximal end of the artery into the glass tube it drives ahead the water it contains into the distal end, the effect of which is to contract the vessels, and so further retard the flow. It is for these reasons, probably, that Yolkmann's estimate of the velocity of the blood, for example, in the carotid artery of the horse of 254 millimetres (10 inches) in a second is too low. By the invention of the stromuhr, in 1857, Ludwig greatly improved Volkmann's method of measuring the velocity of the blood. This in- strument, also called the rheometer (rheo, to flow, metron, a measure), consists (Fig. 195) of two glass bulbs (B, C) of an ovoid shape, and of a known capacity, communicating superiorly by the curved tube and terminating so inferiorly as to be screwed into the canulse F and 6r, which are only large enough to be inserted into the cut ends of the artery to be examined. The canulse having been ligated, and the vessel previously clamped, by means of the small tube opening into the communicating tube, the bulb C is filled with olive oil up to the mark M, the bulb B with serum. The small tube is then closed. The clamps having been removed, the blood flows from the proximal end of the artery by means of the canula jPinto the bulb 0, driving the oil ahead of it through the communicating tube into the bulb B, the serum in the latter being driven out of it through the canula Gf into the distal end of the artery. So far, the method of experimenting with the stromuhr is essentially the same as that of the haemodromometer, with these two differences, however, that serum being used instead of water there is less resistance offered to the flow of the blood, and, on account of the shape of the bulbs, a greater quantity of blood can be used, which is also of advantage. The great improvement, however, in Ludwig's instrument, as compared with Yolk- 1 Ludwig's stromuhr. STROMUHR. 341 mann's, consists in this, that by turning the vertical rod H through 180 degrees, by means of the mechanical arrangement to be explained in a moment, the bulb B now filled with oil, communicates through the canula J 7 with the proximal end of the artery, and the bulb C filled with blood communicates through the canula Gr with the distal end. The blood still flowing from the proximal end of the artery will now drive the oil out of B into 0, and the blood displaced by the oil will pass into the distal end. By turning the rod back again the bulb (7 will communicate with the canula F, and the bulb B with the canula Gr. This operation can be repeated several times before the blood coagulates. The mechan- ical arrangement, by which the bulbs C and B are alternately put in communication with the canulse F and Gf, consists simply in fixing the inferior ends of the bulbs into the movable disk B, into which the ver- tical rod H is inserted, the canulse F and Gr being fixed into the im- movable disk I. When the movable disk B is in the position shown in Fig. 191, then C communicates with F, and B with Gr ; when the disk has been rotated through 180 degrees then B communicates with F, and C with Gr. To illustrate the manner in which the velocity of the blood is deter- mined in a living animal by the stromuhr we will suppose that the instrument has been adapted to the carotid artery of a rabbit. The animal having been firmly secured to the Czermak holder, and the artery exposed and clamped in two places, the clamps separated by a distance of about two inches and about an inch of the intervening vessel cut out. The stromuhr being attached to the vertical stem of the holder by the horizontal rod and the bulbs having been previously warmed and their ends screwed into the canulse which have been inserted into the cut ends of the artery, the bulb C is then filled with oil up to the mark M, it containing then 5 c. cm. (2 in.), and the bulb B with serum. The clamps are now withdrawn from the artery and the blood from its proximal end will be observed to drive the oil from C into B, the oil displacing the serum in B which passes into the distal end of the artery. The moment that the blood reaches the level of the mark M the movable disk D is rotated as rapidly as possible through 180 degrees with the effect of putting the bulb B filled with oil in communication with the proximal end of the artery and the bulb C filled with blood in communication with the distal end of the vessel. The blood continuing to flow, the oil is now driven from B into C, the disk being rotated back again the moment that the blood reaches the level of the mark, the bulb C, now filled with oil, communicates as at first with the proximal end of the artery. The experiment may be continued in this way for a minute or more until the blood begins to coagulate. Inasmuch as we learn how often in a given time a definite quantity of oil is displaced by the blood we learn how much blood is delivered by the carotid artery in that time. Suppose, for example, that in an experiment 5 c. cm. (2 in.) of blood have been delivered by the carotid artery 10 times in 100 seconds — that is, 50 c. cm, then 1 c. cm. of blood has flown from the artery in 2 seconds, or 0.5 c. cm. equal to 500 mm. in 1 second. Dividing this amount by the sectional area of the artery through which it has flown — that is, b*y 3.14 mm., the diameter of the artery and the canulae being nearly the same, or 2 342 VELOCITY OF BLOOD. mm., we get the velocity, or nearly 159 mm. (6 in.) in 1 second: ■.: { \ { \ equals 159 mm., according to the hydraulic principle that the velocity equals the ratio of quantity to sectional area. The stromuhr is a most excellent and reliable instrument, as it inter- feres so little with the circulation, the flow of the blood being only stopped during the instant that the disk is rotated and the blood pressure being little altered by its passage through the instrument. This can be shown by connecting a manometer with the two tubes which are in communication with the bulbs, but which are not seen in the illustration, the tubes being placed in the side of the apparatus not shown in the figure. While the stromuhr is admirably adapted to determine the exact amount of blood passing through an artery and the mean velocity of the flow, it does not, however, enable us to determine the in- cessant variations experienced by the blood as regards its velocity. For this object we make use of the hfemodromometer of Chauveau. Fig. 19G. Hsemodromograph of Chauveau and Lortet. 1 (McKendrick.) The construction of this instrument, like the luematachometer of Vierorclt 1 , is based upon the principle of measuring the velocity of the blood by observing the amount of deviation undergone by a pendulum, the free end of which is suspended in the blood current, the amount of deviation being proportional to the velocity. It is essen- tially the same kind of instrument as the hydrostatic pendulum used by engineers to measure the velocity of a current of water. Chauveau's hsemodromometer, invented in 1858, 2 consists of a brass tube about 4 cm. (1J in.) long (Fig. 196, A), which is inserted into the cut ends of a divided artery, or into the slit made in the vessel of the horse and ligated. Part of the wall of the tube is of India-rubber membrane fastened over a longitudinal opening in the tube, and through which passes a light lever 4 cm. long. The short expanded arm of the lever hangs freely in the blood, and is moved through a greater or less arc, according to the force with which the' blood rushes against it, in from the artery, the India-rubber membrane acting as a fulcrum. The movements of the long arm of the lever H in the opposite direction to 1 Die Er.^ch^inungen und Gesetze der Stromgeschwindigkeit des Bhites, 1858. '-' Journal de la Physiologie, tome iii. p. 695. Paris, 1860. H^EMODROMOGR APH. 343 those of the short one are measured by means of a graduated scale. The long arm of the lever, it will be observed, projects considerably from the tube A. In order to determine the actual velocity of the flow in addi- tion to the varying changes the instrument must be first experimentally graduated. This can be done in the following way: A current of warm water, or, better, defibrinated blood, is made to pass through the tube of the haemodromometer with such a velocity that the deviation undergone by the pendulum is the same as when the instrument was inserted in the artery. The velocity of the current can be easily deter- mined by receiving the fluid from the tube in a graduated vessel, and observing the time occupied in discharging a given quantity. When a marker is attached to the end of the long lever H, the move- ments can then be recorded on the cylinder, and we obtain a graphic representation of the velocity and its variations. The hsemodro- mometer, when used in this way, becomes the hremodromograph. Lortel has modified Chauveau's instrument so that a trace of the blood pressure can be taken simultaneously with that of the velocity. This is accom- plished (Fig. 196) by putting in communication with the tube A the lever of which through its movement gives a trace of the velocity of the blood, a sphygmoscope (B), the blood from the artery after passing through the tube A, enters the caoutchouc bladder B, of the sphygmo- scope, and expanding, it compresses the air in the glass, which, acting through the tube D, upon the recording lever F, gives the trace of the blood pressure. Chauveau has determined, by means of his hfemodromometer, that the velocity of the blood in the carotid of the horse at each ventricular systole is about 50 cm. (20 in.) in a second; this velocity, however, gradually diminishes until finally the blood, for a moment, stops moving altogether. Immediately following the systole and synchronous with the closure of the semilunar valves, a second impulse is given to the blood by the recoil of the arterial walls, and the blood moves now at a rate of about 20 cm. ( the largest in the glands and bones with a diameter of -g^th to the y-5-jjth of a mm. ( ^ ^ to s-jjoT^i of an inch) ; the capillaries of the skin 1 vary between these two extremes, having a diameter of from the -rrg-th to the y-^th of a mm. (j^th to Tir V o tn of an incn )- ^ ie wal1 of tlie capillary varies between the 4^5-th to 10 1 0o th of a mm. (^-A-^-Ah and , t i nc tli of an inch) in thickness. 2500' 1 a mm. (y^r. th of an inch, from the After deducting this thickness, say the T diameter, it will be observed that the calibre of the vessel is reduced to the 3 \ th of an inch, so that the blood corpuscles can move only in a single row, and in many cases even the corpuscle must change its shape in order to pass into the vessel ; this is possible through its elasticity. The small size of the capillaries, both as regards their length and breadth, has an important significance in reference to the amount of blood flowing from them into the veins. Thus it is well known, from the researches of Poisseuille, 1 that the amount of fluid discharged by a tube the yfg-th of a millimetre in diameter (^th of an inch) will be sixteen times that discharged by a tube the -j 3-g-th of a mm. ( 5C / 00 th of an inch), the amounts discharged being proportional to the fourth powers of the diameters — that is, 1 : x : : 2T0~ tn : TTo th > or x e( l uals 2 and 2 4 equals 10. On the other hand, the amount discharged by tubes of the length of the capillaries will be inversely as their lengths — that is, of two capillaries of different lengths more fluid will be discharged from the short vessel than the long one. It will be seen, therefore, that any change in the length or breadth of a capillary will influence greatly the amount of blood delivered to the veins, and so increase or diminish the resistance offered by the capillary system to the arterial flow ; the significance of which we have seen in considering the velocity of the 1 Mem. de l'Acad. dea Si iei i is Savant Etramr, tome i\. p. 513. 348 THE CAPILLARIES. blood and its pressure in the arteries. The cell-like structure of the capillaries just referred to makes perfectly clear how it is possible for the white and red corpuscles to pass from the capillary into the sur- rounding tissues. The capillaries, unlike the arteries and veins, con- stitute a true plexus of vessels of nearly uniform diameter, branching and inosculating in every direction. This inosculation is characteristic of the capillaries and the plexus is developed in proportion to the functional activity of the part. Thus the capillaries are very numerous and close set in the nervo-muscular and glandular tissues, absorbing surfaces, etc., structures in which the molecular changes incident to nutrition are peculiarly active. While the general character of the capillaries throughout the system is the same, the difference in their disposition as regards their closeness and the form of the network is often so marked that the histologist can frequently tell from what part of the body a tissue has been taken by an examination of the capillaries alone. No one can fail to recognize the difference in the arrangement of the capillaries in the skin (Fig. 200), as compared with that in muscle or mucous membrane (Figs. 201, 202). While capillaries are found almost everywhere in the human Fig. 200. Fig. 201. Distribution of capillaries on the surface of th skin of tbe finger. (Carpenter.) Distribution of capillaries in muscle. (Carpenter.) Fig. 202 body, it has been shown by Suquet 1 that in certain parts of the head and in the extremities the blood passes directly from the arteries into veins without the intervention of capillaries. Capillaries are absent in certain structures like cartilage, hair, nails, etc., and hence such parts are often called extravascular. This name is apt, however, to mislead and is inappropriate, since all tissues are extravascular in so far as they lie outside of the vessel carrying the blood that nourishes them. In the vascular tissues the nutriment osmoses through the wall of the capillary into the tissue imme- diately surrounding the vessel and thence into parts more and more remote from it. In the so - called extravascular tissue the nutriment comes from the blood of a capil- lary, as in the vascular tissue, though the capillary may be situated at a considerable distance from the tissue that it nourishes. The only difference between the vascular and extravascular tissue is that the nutriment is conveyed Distribution ol capillaries around follicles of mucous membrane. (Car penter.) 1 De la Circulation du Sans dans les membres et dans la tete de 1' Homme. Paris, 1800. CAPACITY OF CAPILLARY SYSTEM. 3-19 a longer distance in the one case than the other ; the difference, there- fore, is one of degree, not of kind. There are no capillaries in the spleen, erectile tissues, and maternal part of the placenta, their place being supplied by blood sinuses. When we come, however, to the study of the development of these organs, we shall see that these blood sinuses are probably enormously dilated capillaries. It will be remembered that the arterial system was likened to a cone, of which the heart is the apex and the capillaries the base, and that the area of the branches of an artery is usually greater than that of the artery itself. We should expect, therefore, to find that the capacity of the capillary system is far greater than that of the arterial. Indeed, the microscopical examina- tion of the skin, mucous membrane, muscle, etc., in which the capillary vessels have been injected gives the impression that such tissues consist of nothing but capillaries. This is also true almost to the same extent in living animals under certain conditions, thus during digestion the surface of the mucous membrane lining the alimentary canal presents a light red appearance through the distention of its capillaries with blood. The capacity of the capillary system must be immense — indeed, accord- ing to Vierordt, 1 it is 800 times that of the arterial. This estimate, though only approximative, cannot be very far from the truth, being deduced from the law that the velocity with which a fluid flows through a tube is inversely as the diameter of the tube We shall soon see, as an illustration of this law, that the blood flows much more slowly in the capillaries than in the aorta, the total area of the capillaries being far greater than that of the aorta. The sectional area of the capillary system being then to the sectional area of the aorta as the velocity of the blood in the aorta is to the velocity of the blood in the capillaries, the f .11 • sec. area of aorta X vel. of blood in aorta sec. area or capillaries = ^— : : vel. of blood in capillaries Donders's 2 estimate of the capillary system being 500 times that of the arterial — rather too low — is based upon the observations of Volkmann. By dividing the total sectional area of the capillaries by the area of one capillary an approximate estimate of the number of capillaries can be obtained. It was in this way that Hales 3 calculated that there were over eight millions of capillaries in the human body. The general struc- ture, distribution, etc., af the capillaries having been described, let us now consider the manner in which the blood flows through them. As the phenomenon of the flow of the blood through the capillaries, as viewed by the microscope, is one of the most beautiful and striking spectacles in nature, a few words as to the most convenient method by which it can be observed appear necessary. For this purpose we gener- ally make use of the mesentery of the frog, on account of it being so easily exposed and readily arranged on the apparatus supporting it, which is a very simple one, consisting of a thin piece of cork with an opening in it through which the light can pass, and upon which rests, slightly elevated, a glass slide, over which is placed the mesentery, the 1 Die ErscheinuDgen und Oesetze der Stromgeschwiudigkeiten des Blntes, S. 35 2 Phjsiologie, Band i. S. 131. 3 Statistical Essays, vol. ii. p. 69 350 THE CAPILLARIES. loop of intestine drawn out of the body to wliich the mesentery is at- tached resting in a little gutter or groove on the glass slide surrounding the opening. A few drops of a solution of* sodium chloride (3 per cent.) being placed upon the mesentery and a slide cover placed over it, and the cork placed on the stage of the microscope, the circulation can be observed for a considerable time before inflammation sets up. The web of the frog's foot, its lung and tongue, may also be used for the demon- stration of the circulation. The tongue of the frog, on account of its being attached to the anterior part of the lower jaw and free posteriorly, and therefore being easily drawn out of the mouth and through its great vascularity, is also a favorite subject of study with physiologists. When the tongue is used it is best, however, to innate it first and then slit it open, when a magnificent view of the circulation is obtained. The tail of tadpoles, of little fish, and the gills of the salamander, are also ser- viceable objects for the study of the circulation. When the salamander is used it should be placed in a Holman's life slide, by means of which the animal is firmly secured without injuring it, while the water is con- stantly renewed. When the fish is used, Caton's fish-trough will be found serviceable. This consists of an oblong box, one end of which transmits the light through an opening in the piece of glass upon which the tail of the fish in which the capillaries are to be examined is secured, the head and body of the fish resting at the other end of the box. By means of a cistern and tube, a constant current of water passes through the box. The study of the capillary circulation in mammals is more difficult than in any of the animals just referred to, since, with the exception of the wing of the bat, there is no external part transparent enough to be observed with the high power of the microscope, and if any of the inter- nal parts are used the effects of exposure are far more injurious than in the frog, for example. The mesentery and omentum of small rodents, like rats and mice, etc., have been often made use of in demonstrating the capillary circulation in the mammalia ; but the omentum of the guinea-pig is preferable for many reasons, on account of its transparency and of its delicate and simple structure, consisting, to a great extent, of only two layers, of being attached to only one side of the stomach, and little or no fat being present. The great difficulty experienced in observing the capillaries in the peritoneum of the mammalia is due to the injurious effects of exposing the membrane to the atmosphere and the risk of wounding it. To avoid this, the omentum, wliich is the part we shall use, is floated into a glass trough containing either serum or a solution of sodium chloride (3 per cent.), wliich is kept at the temperature of the body by means of the warm stage, which we have already described. The guinea-pig used should be put under the influence of chloral, three grains injected under the skin being sufficient for an animal weighing one pound, and then placed upon a support on a level with the stage of the microscope. The incision being made a little below the ensiform cartilage, and extending outward from the rectus muscle, about an inch from the edge of the omentum is carefully seized and drawn out into the trough. It is well to cover the parts of the membrane not imme- diately under the microscope with pieces of blotting-paper, in this way PHENOMENA OF CAPILLARY CIRCULATION. 351 avoiding unnecessary exposure, and at the same time keeping the omentum steadier than it otherwise would be. With all the above pre- cautions, however, the view of the capillary circulation thus obtained is far from satisfactory, and not comparable to that observed in the mesen- tery of the frog. Since the time of Malpighi, the phenomena of the capillary circulation have been often described : but language is inadequate to give one any idea of the beauty of the spectacle, and to be appreciated it must be seen. We will suppose the mesentery of the frog disposed within the field of the microscope as just described. Here may be seen the arterioles of the mesenteric artery through which the blood flows with apparently amazing rapidity, dividing and subdividing until the blood is carried to an exquisite network of delicate tubes resembling a web of fine spun glass, the capillaries, in which the blood is separated from the tissues by a thickness varying between the ^g-th and the -^jth of a mm. (j2 o"Fo tn and 2 5 o o o *h °f an inch) only. It will be readily appreciated, therefore, with what rapidity the nutri- tive elements can osmose into the tissues and the effete matters be taken up by the blood. Indeed, the capillaries are the seat of all physiological and pathological nutrition processes. The arteries and veins are only means toward an end, the one set of vessels carrying the blood to the part to be nourished, the other carrying it away laden with the waste products. It will be observed that the true capillaries are of uniform diameter, and are so small that they admit but a single row of cor- puscles, and these are seen moving in the middle of the stream, flowing along in the clear plasma which forms a distinct layer, and which ad- heres to such an extent to the walls of the capillary that it appears immovable, and for this reason is called the still layer. The presence of this still layer is due to the capillary attraction existing between the liquor sanguinis and the wall of the capillary, and in proportion as the diameter of the capillary is diminished this force is relatively increased, since a greater surface of the capillary wall is exposed to the liquor sanguinis ; there being little or no affinity between the red blood-cor- puscles and the wall of the capillary, the corpuscles meeting with no obstacle to their flow consequently move with great rapidity through the middle of the stream. A red corpuscle is sometimes caught in the still layer, where it moves slowly for a time, turning over and over; sooner or later, however, it passes again with the central stream and in an instant is whirled out of sight. The white corpuscles, on the con- trary, through their adhesiveness, stick either to the still layer or to the capillary wall, and being quite numerous in the frog (1 white to 8 red) a number are often seen at one time in the same capillary. It is an interesting illustration of the uniformity of the laws of nature that the same phenomenon of the rapidity of the flow of a stream being greater in the middle than at the sides is seen on a magnificent scale in the motion of a glacier. It has been a matter of daily observation to those passing any time on a glacier to notice that the stones, debris, etc., move more rapidly in the middle of the glacier than those at the sides. It was Poisseuille 1 who first showed that the law regulating the flow of 1 Becherches sur la cause dn Mouvenu ut -~ E "~~ ::i, ^ """"■-. | L/v- -6 Apparatus to show decrease of pressure in tubes of unequal calibre. (Marey.) difference only that the diameter of the horizontal tube instead of being the same throughout its entire length, for a short distance in the middle (r), is very much diminished. We will consider this part as represent- ing the capillaries, the horizontal portion of the tube on the left, the arteries, that on the right, the veins. It will be observed, as in the previous experiment, that the pressure diminishes very gradually and regularly in the tubes 1, 2, 3, corresponding to the arterial system, but that the pressure in the tubes 4, 5, 6, representing the veins, is very low, the blood passing from the arteries into the capillaries with difficulty, but readily passing out of the capillaries into the veins. Indeed, in the living animal at times, while the arterial pressure amounts to 150 to 200 mm. of mercury, the venous pressure is almost nothing. Such a difference in the pressure implies that the capillary offers great -obstacles to the flow of the arterial blood. We have just seen that the adhesive- ness between the liquor sanguinis and the walls of the vessels is so great as to give rise to the "still layer," and so retard the flow of a great por- tion of the blood, and the presence of this still layer must affect, to a PRESSURE OF BLOOD IN CAPILLARIES. 357 certain extent, the flow of the rest of the blood as well. Let us modify now the experiment a little, by substituting a somewhat larger tube for the one representing the capillaries in the last experiment. The effect Of this dilatation of the capillary, it will be observed, is that the pres- sure in the artery, and in the arterial end of the capillary, is diminished, while the pressure in the venous end of the capillary, and in the veins, is increased. Any influence, therefore, that favors the retention of the blood in the arteries, will diminish the quantity of blood in the veins, and vice versa. 1 The dotted line (Fig. 204) represents the effect of substituting the large tube. Hales was the first, so far as I have been able to learn, who endeavored to determine the pressure of the blood in the capillaries. His method 2 of calculating this was as follows: Assuming the diameter of a capil- lary to be double that of a red corpuscle, "viz., YT2ir tn part of an inch, or 0.000617; the periphery, therefore, of this vessel will be 0.000939, and its area 0.000000298; which, multiplied by 80, the number of inches to which the blood rose in the tube when fixed to the artery of the dog No. 1, gives 0.000239 part of 80 cubic inches of blood, or 21416 grains, equal to 0.515 part of a grain. But the resistance of the blood in the veins of the same dog being found equal to six inches height, or x 3 1 33 d, or 0.075 part of 80 inches, this 13 1 33 d part equals 0.03039 grain, which being deducted from 0.5118 grain, the remainder, 0.4737 grain, is the force with which the blood would be impelled into such a capillary by a column of blood of eighty inches height." It is an everyday observation that when one compresses the skin with the finger, the part becomes pale, regaining its natural color, however, as soon as the compression ceases, the blood returning then to the capil- laries. In order that the blood should be driven out of the vessels of the skin, the external compression force must be superior to the internal one, or the pressure of the blood. If we know the amount of compres- sion used, then we can estimate approximately the internal force, or the pressure of the blood in the capillaries. By means of a piece of glass, through which any changes in the color of the skin can be observed, and by gradually placing weights upon it, so that the amount of pres- sure used could be learned, Kries 3 has endeavored to calculate the pressure of the blood in the capillaries of a given surface. In this experiment, however, no account is taken of the resistance to be over- come otherwise than that of the blood. More recently, Roy 4 and Brown have used an apparatus for determining the pressure of the blood in the capillaries, which consists essentially of a cylinder closed infe- riorly by glass, and superiorly by a transpai-ent membrane covered with glass, which is placed within the field of the microscope. The air in the cylinder being compressed by a connecting tube, the membrane is pressed against the tissue containing the capillaries to be examined. As the compression is increased the circulation disappears in the capillaries, veins, and arteries. It would seem from the results of this kind of investigation that it is impossible to assign any absolute value to the 1 Marev, op. cit., p. 357. 2 Op. cit., vol. ii. p. 55. 3 LudVig's Arbeiten. Leipzig, 1875. * Journal of Physiology, 1880, vol. ii. p. 223. 358 THE CAPILLARIES. pressure of the blood in the capillaries, but that the pressure varies according to the volume of the capillaries. While there can be no doubt that the heart is the main cause of the circulation, there are also good reasons for believing that there are other conditions than the contractile force of the heart and the arteries which influence the flow of the blood through the capillaries. As is well known, in plants, and in many of the lower animals, the nutrient fluid is carried to all parts of the system in the absence of a heart ; analogy would lead us to expect, therefore, that there must exist in the higher animals a similar force, a capillary power, so to speak, which may be masked by the influence of a centralized powerful heart. This so-called capillary force appears to be inseparably connected with the nutritive and secretory processes, since what increases or diminishes the one influ- ences in the same way the other. The idea of such a force is not a new one, it is embodied in the ancient aphorism of TJbi stimulus ibi fluxus. That some such power exists in the capillaries of the higher animals, independent of the action of the heart, is shown by the fact that the blood will still continue to flow in the capillaries after the heart has ceased beating, while, on the other hand, the heart may still be acting, and yet the circulation will entirely cease in the capillaries of certain parts. Local variations in the volume of the blood flowing through the capillaries, the reversal of the current in the vessels, changes in their diameter, so often observed in the healthy living animal, cannot be attributed to the action of the heart, but are evidently due to an influ- ence engendered in the walls of the capillaries themselves, or in the sur- rounding tissues. Many pathological facts might be mentioned as illustrations of such local variations. Thus, in cases of spontaneous gangrene of the lower extremities, although the heart may be beating, and the arteries and the capillaries entirely pervious, nevertheless the blood will not flow through the capillaries, the stopping of the circulation being due to a difference in the capillaries themselves, and the surrounding tissues. Again, it has often been demonstrated, at least in cold-blooded animals, that the flow of blood through the capillaries will continue even after the heart has been completely excised. While this cannot be shown experiment- ally upon a hot-blooded animal, the shock experienced being so great from so severe an operation, nevertheless nature often does in a gradual way what we cannot show by experiment. Thus, as is well known, after the general death of the body, urine has flowed from the ureters, sweat exuded from the skin, and glands have secreted. Such phenomena can only be explained on the supposition that the blood has continued to flow through the capillaries after the heart has ceased to beat. It is well known, since the observations of Dr. Bennett Dowler 1 upon the bodies of individuals who have died of yellow fever, that the veins often become so distended with blood within a few minutes after death that when opened the blood will spurt from them a foot or more. The tonicity of the arteries can hardly be supposed to account for this venous jet, or for the empty condition in which the arteries are almost always found l Researches on the Capillary Circulation, New Orleans Med. and Surg. Journal, 1849. CAPILLARY FORCE. 359 after death — but to some additional force in the capillaries themselves. Further, we shall see, when we come to study the development of the circulation in the embryo, that the blood begins to move first in the area vasculosa, that is, toward the heart, not from it, and that the heart itself consists of cells so loosely attached together that it can be scarcely supposed to contract with force enough to account for the primitive circu- lation. Indeed, in the case of twins, it has been noticed that the heart in one of the two has even never been developed during the whole period of embryonic life, and yet the greater part of the organs were well formed. It might be supposed that the circulation in the twin in which the heart was absent was maintained by the heart of the one in which it was present, the blood from the one twin passing to the other through the vessels of the placentas, which were more or less in contact. This was shown by Dr. Houston 1 to be impossible, at least in the case reported by him. In this connection the researches of Hvrtl 2 are interesting, this emi- nent anatomist having shown that the placental vessels do not commu- nicate in those cases where the twins are of the opposite sex. The facts of comparative anatomy, experiment, pathology, embryology, all harmonize in showing that there exists in the capillaries some force inde- pendent of the heart's action, which aids the flow of the blood through them. It has often been supposed that the contractility of the capil- laries aids the flow of blood through them. Admitting that the capil- laries are contractile, this force could only be exerted in a rhythmical manner by alternate contractions and dilatations, a kind of peristalsis; but no such movement is observed, the blood flowing through the capilla- ries as if they were glass tubes. Further, it can be experimentally demon- strated that a diminution in the diameter of the capillaries, whether it be due to true contractility, or simply to elasticity, retards the flow of the blood, the blood pressure rising. The capillary force cannot, therefore, be of such a kind. On the other hand, the experiments of Weber and Wharton Jones have shown that electrical and chemical stimuli modify the capillary circulation, retarding the flow of the blood, and even pro- ducing complete stagnation, and yet no alterations in the diameter of the capillaries are observed, the change being evidently of a physico- chemical nature. Such facts, as well as those already referred to, show that there exists some mutual relation between the blood, on the one hand, and the walls of the capillaries and the surrounding tissues on the other. It appears, then, that while the heart forces the blood into and through the capillaries, the rate at which it flows through these vessels will depend upon the general nutritive condition of the parts supplied by the capillaries, and that this capillary force can, under certain con- ditions, maintain the circulation independently of the heart. Prof. Draper 3 suggests that the capillary force just referred to, may be of the same character as the force of capillary attraction, illustrating this view by the following experiment : "if two liquids communicating 1 Dublin Medical Journal, 1837. - Die Blutegefasse der Menschlichen Naohgeburt. Wien, 1870. 3 Treatise on the Forces which produce the Organization of Plants, pp. 22, 41. Physiology, 1878, p. 131. 360 THE CAPILLARIES. with one another in a capillary tube, or in a porous structure, have for that tube or structure different chemical affinities, movements will ensue, that liquid which has the most energetic affinity will move with the greatest velocity, and may even drive the other liquid before it." Thus, it will be noticed that if a capillary tube, containing gum, be immersed in a vessel filled with water, that the gum will rise in the tube, being displaced by the water, the water having a greater affinity for the walls of the tube than the gum. These experimental conditions are realized in the living body, the fresh arterial blood, on account of its oxygen and other nutritive elements having a greater affinity for the tissues than the effete venous blood, hence the arterial blood will push forward the venous blood from the systemic capillaries toward the veins. On the other hand, in the pulmonary capillaries just the reverse obtains, the venous blood drives forward the arterial, since the former has a greater affinity for the inspired oxygen than the latter, in which the blood is already oxygenated. According to the same physical principle, the portal blood, containing the same elements out of which the bile is elaborated, having a greater attraction for the hepatic cells than the blood of the hepatic vein, the latter will be driven out of the hepatic capillaries into the hepatic veins. Indeed, there must be a continual movement going on in every part of the economy, each cell having a greater attraction for the blood containing its nourishment than for that blood which has nourished it. Such a movement undoubtedly supple- ments the force of the heart. The consideration of the influence of the nervous system upon the capillary circulation, whether as modifying through the vasomotor nerves the calibre of the arteries, or acting directly by changing the nutrition of the parts, will be deferred for the present. In concluding our account of the circulation of the blood it remains for us now to de- scribe the flow of the blood from the capillaries back to the heart through the veins. CHAPTEK XXIY. THE VEINS. In observing the flow of the blood through the capillaries, it will be seen that these vessels gradually pass into larger ones, the venous radi- cles, which in turn transmit the blood to the veins, the latter gradually uniting form two large trunks, the venae cavse, which, together with the coronary vein, transmit the blood to the right side of the heart and the pulmonary veins return it to the left. The venous system may be regarded as consisting of two sets of veins, a superficial set returning the blood from the skin and surface generally, and a deep set which accompanies the arteries. The veins diifer in their structure from the arteries rather in degree than in kind, consisting essentially like the latter of three coats, an internal epithelial, a middle elastic muscular, and an external fibrous. The internal coat, consisting of subepithelial and elastic layers, is a con- tinuation of the capillary, which we have seen is a prolongation of the internal coat of the artery. Indeed, it is practically impossible to say exactly where the artery ends and the capillary begins, or where the capillary ends and the vein begins, the transition from the one set of vessels to the other is so gradual. The middle coat, containing the vasa vasorum, consists principally of fibrous tissue disposed in a longitudinal direction with some elastic fibres, and of a circular coat of elastic and muscular fibres mingled with some fibrous tissue. The external coat, like that of the artery, consists of white fibrous tissue, and in the largest veins, particularly in those of the abdominal cavity, there are a few unstriped muscular fibres arranged in a longitudinal direction. In the veins near the heart a few striated muscular fibres are present, derived principally from those of the auricle. These fibres are particularly well developed in the turtle. In certain situations in the cerebral sinuses, etc., the veins consist of little more than the internal coat with a few longitudinal fibres. Generally the veins adhere much more closely to the surrounding tissues than the arteries. Were such not the case, in many instances the vessels would collapse, the walls not being strong enough to resist external pressure. Bernard has called attention to the importance of this physiologically, showing that it is through the intimate adhesion of the wall of the superior vena cava, jugular, subclavian, etc., to the surrounding apon- eurotic layers that these vessels are kept open during inspiration. Many of the larger veins are provided with valves resembling those of the aorta and pulmonary artery (Fig. 205). They are usually found in pairs, and consist of crescentic semilunar doublings or folds of the internal coat or lining membrane of the vein strengthened with some included fibro-elastic tissue. These valves are usually situated opposite 362 THE VEINS. Fig. 205. Diagrams showing valves of veins A. Part of a vein laid open and spread out, with two pairs of valves. B. Longitudinal section of a vein, showing the apposition of the edges of the valves in their closed state C. Portion of a distended vein, exhibiting a swelling in the situation of a pair of valves. (Quain.) each other and project obliquely into the cavity of the vein or in the direction of the current. The convex portion of each valve is attached to the side of the vein, the concave edge is free and points toward the heart. Behind each valve the vein is dilated into a sort of pouch or sinus (Fig. 205) which prevents the valves adhering to the sides of the vein as the blood passes between them to- ward the heart. When, however, the blood passes backward toward the per- iphery, as we shall see it does under cer- tain circumstances, it enters the sinus and getting behind the valves presses them toward each other and together and so prevents any further reflux. The valves are so disposed, there- fore, that while they offer no obstacle to the flow of the blood toward the heart they effectually prevent to any extent motion in the reverse direction. The valves are most abundant in the upper and lower extremities ; the sig- nificance of this we shall see presently. The importance of the valves in the veins, though great physiologically, must not be exaggerated, since many veins have no valves. Thus in man at least, however it may be in other mammals, there are no valves in the vena3 cavse, in the innominate, pulmonary, portal, hepatic, renal, uterine, ovarian, spinal, and iliac veins. Further, there are very few valves in the veins of birds, reptiles, and fishes, and with the exception of that in the aorta, so-called, of the eolis, a small nudibranchiate mol- lusk, there are none in the veins of the invertebrata. It is evident, therefore, that the valves are not indispensable in the maintenance of the circulation. The veins possess a considerable amount of elasticity. This is shown by the jet of blood which follows the puncture of a distended vein made in a portion of the vessel between two ligatures. The veins through their unstriped muscular fibres are also contractile, their calibre being slowly and gradually diminished through the application of electrical and other stimuli. The contractility of the veins can be more readily demonstrated in the frog and other batrachians than in mammals. The veins, like the arteries, are supplied and influenced by the vasomotor nerves though not to the same extent. The veins, though much thinner and apparently weaker, will usually resist a greater pressure than the arteries. Thus it was shown in the last century by Wintringham 1 that a greater force was required to rupture the vena cava and portal vein, for example, than the aorta. The method by which this was de- termined is as follows : An iron siphon containing a sufficient quantity of mercurv, to which was screwed a glass gauge, and which communi- 1 An Experimental Inquiry on some parts of the animal structure, pp. 49, 73, 179, 212. London, 1740. CAPACITY OF VENOUS SYSTEM. 363 cated freely with a condensing syringe, was adapted to the artery or vein whose strength was to be tested. When the air in the sealed top of the gauge was compressed with a pressure equal to 138 pounds, the aorta in the ram, for example, burst, the vena cava of the same animal, however, resisting until the pressure amounted to 176 pounds, or about 4.8 atmospheres. The strength of the portal vein was even greater than that of the vena cava, a pressure of nearly 5 atmospheres being required to rupture it. Wintringham, however, notices that the arteries of glands are stronger than the corresponding veins. Thus the splenic vein burst under a pressure of about 1 atmosphere, equal to a pressure of about 34 pounds, the artery supporting a pressure of 6 atmospheres, or 150 pounds. These experiments of Wintringham were very numerous and extended, being made upon the vessels of men, pigs, sheep, dogs, etc., and in the main have been confirmed by the later ones of Davy. 1 The significance of the greater strength of the veins, as compared with that of the arteries, usually observed, becomes at once apparent when we reflect upon the different amounts of pressure to which the two sets of vessels are subjected. We have seen that the pressure all throughout the arterial system is about the same, that the force of the heart is practically constant, and that the arterial pressure is being constantly relieved by the flow into the capillaries. On the other hand, the pressure into the veins varies according to the amount of blood delivered to them by the capillaries, regurgitation to any extent is impossible through the presence of the valves, while the heart offers a very restricted outlet. Thus portions of the venous system, from pressure in the veins, absorp- tion of fluid, accumulation through gravity, etc., are subject to very great variations in pressure which the tenacity of their Avails usually enables them to resist without injury. The ill effects of over-distention are, nevertheless, seen only too frequently in varicose veins, etc. The capacity of the venous svstem is much Greater than that of the arterial — according to Haller, 2 in the ratio of 2.2 to 1. Usually a vein when distended contains more blood than the adjacent artery; the pulmonary arteries, however, about equal the corresponding veins in capacity. Many arteries, like those of the extremities, are accompanied by more than one vein, and some, like the brachial and spermatic, have more than two; the superficial veins, further, have no corresponding arteries. Never- theless, any estimate of the capacity of the venous system as compared with that of the arterial can be only approximate, since the quantity of blood flowing through the veins must vary according to the pressure and velocity of the flow, the amount passing through the capillaries, the state of the digestion and respiration, etc. Indeed, the most striking char- acteristic of the venous system is the variability of the amount of blood it contains. One of the most important features of the venous system is the numerous anastomoses between the veins, which, it will be remembered, are exceptional in the case of the arteries. There are always numer- ous such channels by which the blood finds a ready route back to the 1 Iti'si'tiivhi's, Physiological and Anatomical, vol. i ]>. 441. - Elementa Physiologice, tonms 1. p 133. 364 THE VEINS heart, so that, if the flow be obstructed in one vein, an equally easy way is offered by another. The anastomoses between the veins are very important, enabling these vessels to accommodate themselves to the great variation in the quantity of blood flowing into them to which they are subject. The anastomoses, together with the valves, serve to pro- vide against any obstacle to the freedom of the capillary How. the im- portance of which we have already seen. In addition to the anasto- motic branches usually described may be mentioned others less well known, such as those connecting the vena cava and portal, like the subperitoneal vessels, the oesophageal and hemorrhoidal, the diaphrag- matic connecting the hepatic circulation with the vena cava. The importance of these anastomotic vessels becomes evident when the veins usually returning the blood to the heart are obstructed. Under such circumstances, they become greatly enlarged, as is well known to the pathological anatomist. When it is remembered that the arterial pressure gradually diminishes as we recede from the heart to the periphery, it might be expected by the time that the blood has passed through the capillaries and reached the veins, that it would exert but little pressure on the latter. This has been experimentally shown to be the case. Thus, according to Volkmann, 1 while the pressure in the carotid artery of the calf amounts to 165 mm. (6.6 inches), and that of the metatarsal to 146 mm. (5.8 inches), the pressure in the metatarsal vein was only 27.5 mm. (1.1 inch). Indeed, at times, the pressure in the vein is actually less than that of the atmosphere. This is well seen in the experiment of Barry, 2 which consists in introducing into the jugular vein of a horse or dog a bent tube, of which the opposite end is immersed in a vase of colored liquor. With each inspiration the liquid rises in the tube, falling again with each expiration. While the pressure is diminished in the jugular and hepatic veins during inspiration, on the other hand, in the remaining abdominal veins it is increased ; the latter being compressed by the viscera through the falling of the diaphragm, an obstacle is offered to the flow of the blood, and the pressure rises. The lowering of the thoracic pressure during inspiration is shown graphically by Fig. 206, in which the Fig. 20fi. Trace of blood pressure in hepatic vein. E. Trace of respiration, taken with pneumograph. (3IAEF.Y ) depression of the upper trace Pr.V. H, representing the blood pressure, coincides with that of the lower trace R, representing the respiratory i Die Haemodynamik, S. 173. - Recherches experimeutalea sur les causes du mouvement du sang dans lea veines. Paris, 1825. VENOUS PRESSURE. 365 movement. The increase in the pressure in the abdominal vein during inspiration is well shown by Fig. 207, in which the depression in the Fig. 207. Pr V. P. Trace of blood pressure in port.il vein. R. Trace of respiration, taken with pneumograph. (Marey.) lower trace R, due to inspiration, coincides with the elevation of the upper trace Pr.V. P., due to the increase in the blood pressure. On the other hand, during the expiration, the pressure in the abdominal veins is diminished, the viscera no longer compressing these vessels, the diaphragm being elevated. If, however, the expiration be violent, then the contraction of the abdominal walls compressing the viscera and the veins will increase the pressure. The weight of the blood influences the pressure in the veins. Thus, the blood flows more readily to the heart in the veins of the upper extremity when the limb is elevated than when hanging down. The varicose condition often observed in the veins of the lower extremities illustrates the effect of the venous pressure due to the weight of the blood. While the pressure in the veins is ordinarily very slight, at times it is so much increased as to give rise to a pulsation — the venous pulse. This may be due to an obstruction in the veins, or to an in- crease in the quantity of blood flowing in these vessels. Thus, if all the venous blood in a part be forced to return to the heart by a single vein, as can be effected by ligating all the adjacent veins, as in the experiment of Poisseuille, 1 the pressure on the vein will be so much increased as to equal that of an artery of like size, the force of the Fig. 208. f.O • E O. Trace uf auricl E V. Trace of ventricle. &' 0. Systole of auricle, by abdominal irritation and elevation of pressure E. Arrest of heart in diastole (Marey.) heart being exerted upon the blood of a single vein, and therefore concentrated instead of as ordinarily upon several and, therefore, dif- fused and dissipated. During the ventricular systole, and, therefore, when the tricuspid valve is closed, the flow of the blood through the auricle into the ventricle is, for the instant, stopped, the pressure in the 1 Magendie : Lecons sur les phenomenee physique de la vie, tome iii. p. 181. Paris, 1837. 366 THE VEINS. auricle and vena cava is then momentarily increased. If, however, the beating of the heart cease in diastole, as is the ease utter excitation of the pneumogastric nerve, the blood flows into the ventricle, which, being filled, receives then no more blood from the auricle; the blood continuing to flow will iill the auricle and other vena cava until these parts, being dis- tended, the pressure will be very much increased. This can be experi- mentally shown in the frog by means of the double myograph. By comparing the traces (Fig. 208) of the auricle and ventricle, taken simultaneously, it will be observed that the pressure in the auricle is increased during the arrest in diastole of the heart's action through stimulation of the pneumogastric nerve. There is also observed at times in certain veins, the external jugular, for example, a regurgitant venous pulse. This is due to a reflux of blood from the right side of the heart, and is synchronous with the movement of expiration, there being no obstacle at the mouth of the vein to the return of the blood if the expiratory movement be exagger- ated. The regurgitant venous pulse can be often noticed, however. It is usually evidence of insufficiency of the tricuspid valve, or some other pathological condition. We have seen that the veins are both larger and more numerous than the arteries, and as the volume of blood wdiich passes in a given moment through any part of the vascular sys- tem is the same, it follows that the blood ought to flow more slowly through the veins than the arteries. If the venous system be con- sidered twice as capacious as the arterial, then the blood should flow half as slowly through the veins as the arteries. Experiment is in harmony with theoretical considerations, it having been shown by Volkmann 1 that the blood flows in the jugular vein of the dog at the rate of 225 mm. (9 inches) in a second, that of the carotid artery in the same animal being 329 mm. (13 inches). The conditions that ii>- fluence the rapidity of the flow in the veins, however, vary, so that it is impossible to fix upon any average rate. There can be no doubt that the flow of the blood in the veins is essen- tially due to the contractile force of the heart. Thus, according to Sharpey, 2 the hepatic veins can be filled with an injection of defibri- nated blood thrown into the aorta under a pressure of 3.6 cm. (3.5 in.) of mercury, which is only about half that of the normal arterial pressure. The experiment of Magendie, 3 in which the femoral vein was ligated and opened, the blood jetting forth, the jet and flow gradually ceasing with compression of the femoral artery, proved the competency of the heart to force the blood through the capillaries into the veins, the force of the artery causing the jet from the vein being, as we have seen, only the reaction from its previous distention, due to the preceding ventricular systole. While the heart is the main cause of the venous flow T , as in the case of the capillaries, there are other causes which assist in pro- moting this movement. Thus, muscular contraction, by compressing the veins, forces the blood in these vessels toward the heart, regurgita- tion being impossible through the action of the valves. Hence, the i Op. cit., S 195. - Todd and Bowman : Phys. Anat, 1856, vol. ii. p. 350. 3 Journal de Physiologie, 1821, t. i. 3. CAUSES OF FLOW OF BLOOD IN VE1XS. 367 significance of the fact of valves being so much more numerous in the veins of the muscles than in the cavities of the body, the veins .in the latter situation not being subjected to the same kind of compression as those between and within the muscles. It must be mentioned, however, in order that too much stress be not laid upon this connection between mus- cular action and the presence or absence of valves, that in some cases, as in the portal vein of the horse and in the mesenteric veins of the reindeer, for example, valves do exist. In order that muscular contraction shall assist the flow of the blood through the veins, not only must valves exist to prevent regurgitation, but the contractions of the muscles must be inter- mittent, as during the period of repose after a contraction the vein has time to fill up again with blood'that will be forced forward with the fol- lowing contraction. This alternate filling up and emptying of the mus- cular veins i< also of advantage from a nutrition point of view, since, as we shall see, the activity of the muscle depends upon the free and rapid circulation of the blood through its substance. 1 The influence of mus- cular contraction in accelerating the venous flow is well known to every surgeon, the jet from a vein increasing in force with the contraction of the muscles below the opening. The amount of increase of pressure in the veins, due to muscular contraction, can be experimentally deter- mined by placing a vein in communication with a mercurial manometer, and observing the variations in the height of the mercury due to mus- cular contraction, whether produced naturally or by movements of the animal, or induced by stimuli. In the experiments of Magendie 2 and Bernard 3 the mercury rose 50 mm. (2 in.) above the normal venous pressure after a general muscular contraction. However important muscular action may be in promoting the flow of venous blood, that it is not indispensable, is shown by the fact that the blood flows through the veins in parts that are paralyzed. When we come to study the mechanism of respiration we shall see that the thoracic walls alternately recede and approach synchronously with the rise and fall of the dia- phragm in the production of the inspiratory and expiratory movements. It will become apparent, then, that the rarefaction of the air within the thorax during its dilatation, which causes the entrance of the external air into the trachea and the lungs in inspiration, must exercise a similar suction influence upon the blood flowing in the large and extensible veins emptying into the heart. This action of the thoracic Avails will have, however, little or no influence upon the blood of the aorta, its walls being too resisting to give to any extent. The suction force thus exerted by the thorax during inspiration upon the venous blood flowing toward the heart extends also, to a certain extent, to the veins situated outside of the thorax. The fact already alluded to, and noticed particularly by Bernard, 4 of the walls of the superior vena cava, jugular, subclavian, etc., adhering to the surrounding tissues by apo- neurotic layers, and so, being kept open, evidently favors the flow of blood through these veins toward the heart during inspiration. Were it not for such a disposition the veins would entirely collapse through 1 ililne Edwards: Pbysiologie, tome iv. p. 310. - Op. cit., tome iii. p. 162. 3 Lecons sur la Phys. et Path du S.vsteme Veueux, tome i. p. 285. Paris, 1858. 4 Pbysiologie, tome iv. p. 9. 368 THE VEINS. atmospheric pressure. The hepatic veins also adhere to such an extent to the tissue of the liver that when divided they remain open, and the inferior vena cava, in which these veins terminate, is further surrounded by fibrous expansions, which fix it to the margin of the diaphragm through which it passes on its way to the heart. The anatomical rela- tions of the parts are such, therefore, as to favor the flow of the venous blood from the liver toward the heart during the contraction and consequent fall of the diaphragm incidental to inspiration. That such a suction force is really exerted upon the venous blood during inspi- ration by the thorax is seen whenever a violent inspiratory effort is made. At such times the veins at the lower pari of the neck are seen to empty themselves completely. The experiment of Barry, already described, illustrates the power of this suction force, the fluid being sucked up into the glass tube introduced into the jugular vein with each inspiration. Barry, however, exaggerated the influence of this suction force. That it does not ordinarily extend much beyond the thorax can be proved by introducing the glass into the anterior end of the jugular vein, when little or no variation will be observed in the level of the liquid with the inspiratory effort. Death from the entrance of air into the veins is due to the suction force exerted by the thorax during inspiration. The consideration of such cases belongs to pathology, but it may be mentioned here inci- dentally that the cause of death is due to the blood becoming frothy or spumous when mixed with air, and in that condition will not circulate through the pulmonary capillaries, hence the left side of the heart is found on post-mortem examination empty. It might naturally be supposed that, as inspiration favors the flow of the venous blood toward the heart, the expiration would oppose it. Were expiration due solely to the contraction of the thoracic walls, such would be, at least to a certain extent, the case, but, as we shall see, the air is expelled during expiration from the lungs to a great extent through the elasticity of the organs themselves, and, as Milne Edwards 1 suggests, this action of the lungs, so far from compressing the veins near the heart, tends to dilate them. A part of the pressure due to contraction of the thoracic walls that would otherwise compress the veins is, therefore, neutralized by the elasticity of the lungs. It can be shown experimentally by the manometer, as the above considera- tion would lead us to expect, that the effect due to inspiration upon the flow of the venous blood far exceeds that of expiration. The valves, further, while offering no obstacle to the flow of the blood during inspiration, prevent, to any extent, regurgitation during expiration. Thus, if the manometer be placed in the internal jugular vein above the valves, the effect of inspiration is the same as when placed below them, but in the first case the reflux during expiration amounts to nothing. If expiration be violent, however, then the reflux may be considerable, thus the veins of the neck during singing or prolonged speech are seen to swell up, and when any effort is made in which the glottis is closed. The dilatation of the thorax has but little effect 1 Op. cit., tome iv. p. 419. RAPIDITY OF THE CIRCULATION. o69 upon the blood flowing in the great veins of the abdomen on account of the flaccidity of their walls, but the diaphragm falling during inspiration compresses the viscera, and they in turn pressing upon the vena cava and its branches, force the blood toward the heart, regurgitation toward the extremities being prevented through the closing of the valves. With the rise of the diaphragm the pressure upon the vena cava will be relieved, and the blood will rapidly flow into it again from the extremities. Should the expiration, however, be labored or violent, and the abdominal walls contract, then the pressure exerted upon the viscera would be an obstacle to the flow of the venous blood from the extremities. In order to appreciate the influences of respiration upon the flow of the venous blood, as seen from what has just been said, we must carefully consider the conditions of the inspiration and expiration, as the same cause may, under different circumstances, produce exactly the opposite effect. On the whole, respiration favors the flow of the venous blood from the periphery to the heart, and, as we shall see here- after, the flow of the arterial blood from the heart to the periphery. The contractility with which the veins are endowed assists somewhat in the lower animals the flow of the blood. This influence is limited in man. however, to the large veins near the heart, and is even there very slight. Gravity, while favoring the flow of the venous blood from parts above the heart, opposes that from below. While muscular action, respiration, contractility, gravity, etc.. no doubt at times favor the flow of the venous blood toward the heart, it must not be forgotten that all these conditions are only supplementary to the force of the heart, this being sufficient to force the blood throughout the entire vascular system. Having described the general manner in which the blood flows through the system, we might now consider the peculiarities presented by the circulation in the lungs, liver, brain, erectile tissues, etc. We will defer, however, our account of the circulation in these organs until we take up their functions. We have seen that the velocity of the blood varies considerably in the different parts of the vascular system, being greatest in the large arteries, least in the capillaries, and intermediate between these extremes in the veins, so far as can be estimated. It remains for us now T to determine if possible, the general rapidity of the circulation ; that is, the period necessary to complete the entire circuit, or the time that elapses during which a particle of blood passing out of the left ventricle traverses the arterial capillary and venous sys- tems, returning by the right side of the heart and lungs to the point from which it started. The general rapidity of the circulation can be easily and satisfactorily determined experimentally in a living animal in the following manner, as was first done by Ilering: 1 A harmless substance, and easily recog- nized, is injected into the jugular vein, and blood is drawn as quickly as possible, and at intervals, from the corresponding vein of the oppo- site side of the head, the time being carefully noted when the substance injected can be detected. Suppose, for example, that a solution of ferro- 1 Zeitschrift fiir Phvsiologie Treviranus, 1829, Baud iii. p. 85. Arcbiv f. physiol. Heilkundi-, i - , .. Baud xii. S. 112; 1832, Band v. S. 58. 24 THE VEINS. cyanide of potassium be injected into the jugular vein of a rabbit, the salt can be recognized in the blood of the opposite vein in about seven seconds. In this experiment the blood carrying the salt passes to the right side of the heart, then through the lungs to the left side, from there into the aorta, and traversing the capillaries of the head and face returns back by the jugular vein on the opposite side. If the substance be injected into the femoral vein the period elapsing is slightly longer, the vessels through which the blood flows being somewhat longer. This is more evident, however, in a large animal like a horse, than in a small one like a rabbit. Ferrocyanide of potassium is not only used in this experiment on account of it being harmless, but from the readiness with which its presence can be determined in the blood. Vierordt 1 improved somewhat Hering's method by collecting the blood as it flowed at small intervals in little vessels that Avere fixed to a disk which revolved at a fixed rate, the time being determined a little more accurately- The results of the experiments of both these observers, however, agree essentially. According to Hering, the rapidity of the circulation in an animal is inversely as its size, and directly as the rapidity of the action of its heart. Thus, while in the rabbit we have seen that the circula- tion from jugular to jugular is accomplished in 6.9 seconds, in the goat, dog, and horse, 12.8, 15.2, and 27.3 seconds are required respectively. Table LV. — Rapidity of Circulation. Ventricle contracts in a minute 72 times. Amount of blood expelled at each contraction . . 4 oz. Amount of blood passing through ventricle in a minute 288 oz. 16 lbs. of blood in the body. 16 oz. to lb. 256 oz. 60 : 288 oz. of blood :: x sec. : 256 oz. of blood. 288 x 256 X 60 15360 15360 = 53 _ 3 seconds _ 288 The general rapidity of the circulation in man can be deduced, at least approximately, from these experiments, about thirty-two seconds probably being required for the blood to pass from jugular to jugular. On the supposition that the heart beats seventy-two times in a minute, and that at each ventricular systole four ounces of blood are forced into the aorta, it is evident that 288 ounces of blood (72 X 4 equals 288) pass through the heart in one minute; but we have seen that there are probably, on an average, only 256 ounces (16 pounds) of blood in the body. It follows, therefore, that less time than one minute, or about fifty-three seconds, would be required for the whole mass of the blood to pass through the heart. Table LV. shows, synoptically, the calcu- lation by which this estimate is made. The only objection to this manner of determining the time required for the whole mass of the blood to pass through the heart is the uncertainty as regards the exact i Die Erscheiuungen und Gesetze der Stromgeschwindigkeiten des Blutes, etc., S. 65. RAPIDITY OF THE CIRCULATION. 371 amount of blood in the body, and of the quantity expelled with each ventricular systole. From the nature of the case these data must be variable ; the estimate will be true, however, within limits. In confirmation of what has just been said in reference to the rapidity of the general circulation, etc., it may be mentioned that the time elapsing between the introduction of a poison into the blood and its characteristic effects is about the same as that observed in the experi- ment of Hering. The influence of the frequency of the heart's action upon the rapidity of the general circulation must not be lost sight of, and this was taken into consideration also by Hering. It was shown by this observer, contrary to what might have been expected, that an increase in the number of the beats of the heart, whether induced phy- siologically or pathologically, diminished the rapidity of the circulation instead of increasing, the force of the heart being diminished as the number of its beats was increased. CHAPTER XXV. HISTORY OF THE DISCOVERY OF THE CIRCULATION OF THE BLOOD. In the minds of every one the circulation of the blood is invariably and justly associated with the name of Harvey. The discovery of the circulation, however, like all other great discoveries, was not made by Harvey alone. Indeed, the discovery of the circulation of the blood, in the widest acceptation of the term, cannot be attributed to any one person, age, or country. With the name of Harvey must be asso- ciated those of Erasistratus, Galen, Servetus, Csesalpinus, Malpighi, Aselli, Pecquet, Rudbeck, and Bartholinus. The history of the circula- tion extends, therefore, over a period of 2000 years, from the epoch of the Egyptian Ptolemies to the latter part of the seventeenth century, and even, in some respects, to the present day. The general structure of the heart, its cavities, the play of its valves, the passage of the blood from its right side to the lungs and back to its left side, thence through the arteries to all parts of the body ; the valves in the veins ; the flow of the venous blood toward the heart, had been demonstrated, in an isolated way, by this or that person, before Harvey's time ; while it was not until after the appearance of his great work that the discovery of the capillaries made intelligible the manner in which the blood passed from the arteries to the veins; and the demonstration of the lymphatics completed our otherwise imperfect knowledge of the circulation. If, however, the great generalizations as regards the circulation, just re- ferred to, were made either before or after the time of Harvey, natu- rally, it might be asked, What was there left for Harvey to discover? In what does the merit of his great work consist ? In that he Avas the first to describe accurately the motions of the heart, and both the pulmonary and systemic circulations correctly. Without doubt, Harvey was the first who described correctly the entire circulation of the blood, understanding by the word circulation the flowing of the blood from the heart to the lungs, back to the heart, thence through the arteries to the periphery, and from the periphery, through the veins, back to the heart. That is, the flowing of the blood in a circle. It must be re- membered, however, that Harvey saw this circulation only in his mind's eye, as the capillaries or connecting links between the arterial and venous systems were not discovered by Malpighi until after Harvey's death. The history of the discovery of the circulation of the blood has often been told ; but the subject is one of such interest, extending as it does over a very long period, illustrating so forcibly how slowly truth is attained, that fact after fact must be first established before any generalization can be arrived at ; how the isolated, unconnected labors KNOWLEDGE OF THE ANCIENTS. 373 of generations finally culminate, in the hands of a genius, in a grand discovery ; that I trust it will not be considered superfluous if I rapidly tell the story of the discovery of the circulation of the blood once more. Although no mention is made of bleeding in the Iliad, that encyclopaedia of the knowledge possessed by the Greeks in Homer's day, vet there is no reason to doubt that Podalirius, who attended, as surgeon, the hosts of Agamemnon, made use of this practice ; as we learn from later sources 1 that, by bleeding the daughter of the King of Caria, he effected a cure, the reward of which was her hand in mar- riage, and, as dowry, the Chersonesus. While the Greeks and the ancients generally were aware that the blood of man and animals coursed in a vast system of tubes, their knowledge of the circulation of the blood extended but a little beyond this. Indeed, their views on this subject were of the most imperfect or erroneous character. That the blood flowed in certain veins : that there were additional vessels erroneously called arteries, because they were supposed to contain air ; that the heart was a hollow, muscular organ, constituted about all their knowledge of the circulation. 2 This is not to be wondered at, however, since the superstitious respect paid to their dead by the Greeks made dissection an impossibility, the little anatomical knowledge existing in the days of Hippocrates having been derived from the rapid inspection of the viscera of animals sacrificed upon the altar on the occasion of some religious ceremony. Even Aristotle, 3 whose anatomical knowledge far exceeded that of Hippocrates, advanced but little our knowledge of the vascular system. Aristotle taught that the veins communicate with the heart ; that vessels pass from the heart to the lungs, and that the heart and veins are filled with blood. Such was the limited knowledge of the circulation of the blood as known to the most celebrated of the Greeks. A great advance, however, was soon to be made, not only in anatomy, but in all branches of science. The wonderful campaigns and victories of Alexander, Aristotle's patron, resulting in the conquering of Egypt and the establishing of the Macedonian dynasty of kings, and the building of Alexandria not only revolutionized the political and social Avorld, but influenced all branches of knowledge in a way and to an extent that modern Europe is only now beginning to appreciate. Under the magnificent patronage of the Ptolemies, the Macedonian kings of Egvpt, there arose at Alexandria that famous school, the Museum, a centre of learning for the organization and development of all kinds of knowledge, the like of which has never been seen since. There were associated under the hospitable roof of the Egyptian kings some of the most learned and wonderful men the world has ever seen. The astronomers, Hipparchus and Ptolemy ; geometers like Euclid and Archimedes ; the engineers and geographers, Apollonius, Erastosthenes ; historians like Manetho ; the theologian, Cyril ; learned women like Hypatia : the celebrated anatomists and physicians, Herophilus and Erasistratus. For the practical study of astronomy there were placed 1 Stephani Byzantini : De TTrbibns. p. G80. Lugd. Bat., 1694. 2 Hippocratis' Opera Omnia, p. 275 Lugd. Bat., 1G65. (Euvres completes d'Hippocrate, par E. Littre. Tomes viii. Paris, 18 59-1853. Introduction, tome i p. 211. 8 ' \.plOTOTe%OVg TLep't Z&urv 'laropla, Lib. iii. Cap. 2, 3, 4. Lipsa?, 1869. 374 HISTORY OF THE DISCOVERY OF THE CIRCULATION. beneath the Porch equinoctial and solstitial armils, quadrants, dioptras, astrolabes and meridian lines ; a botanical garden offered opportunity to those who wished to study plants ; a zoological menagerie offered facilities to those interested in the dissection of animals. The library, containing nearly a million volumes, was open daily to those desirous of making themselves acquainted with the knowledge of the day or of that of antiquity. A^ast collections of all kinds of natural objects had been brought there, from every part of the known world, by the Mace- donian conquerors, for the use and benefit of the student. At the Museum, in Alexandria, the student found everything that would assist, develop, and refine the intellect — the calm, the leisure, the means of living and of study. The usages of that wonderful country, Egypt, where death perpetuates itself in a thousand embalmed forms, had, from time immemorial, familiarized the vulgar and uneducated with autopsies and dissections. The study of anatomy by the only means possible, the dissection of the dead body, was no longer regarded with superstitious horror and considered as sacrilege. Pliny tells us that those intelligent and magnificent princes, the Greek kings of Egypt, not only lavished their treasure in the interests of science, but per- sonally attended the dissections that were daily conducted at the Museum. The Medical School of Alexandria gave to the world those famous anatomists, Herophilus and Erasistratus. With them began the study of the structure and use of the heart and its great bloodvessels, by means of actual dissection. The name of Herophilus ought to be familiar to all students of anat- omy, as many parts of the human body, such as the choroid plexus, the torcular Herophili, the calamus scriptorius, the duodenum, etc., were first described by him. The most important contribution that he made to our knowledge of the vascular system was the demonstration of the isochronism of the pulsations of the arteries and of the beating of the heart, and of the latter being the cause of the former, a phenomenon that had already been imperfectly referred to by Hippocrates and Aris- totle. Herophilus noticed also the difference in the thickness of the walls of the arteries and of the veins, and described the vessels connect- ing the heart and the lungs, distinguishing the pulmonary artery from the pulmonary vein, designating the former as the arterial vein and the latter as the venous artery. To Erasistratus, one of the most distinguished of the anatomists of the Alexandrian school, and one of the most celebrated physicians of antiquity, science is indebted for the discovery of the valves of the heart, and their function in the circulation. It was stated in a pre- vious chapter that there is reason to believe that Erasistratus had seen the lacteals a dependence, so to speak, of the vascular system, even though he had misunderstood their use, and we shall see hereafter that he appears also to have distinguished the sensory from the motor nerves. While there is no doubt that the anatomists and physiologists of an- tiquity distinguished two kinds of vessels, arteries and veins, their very name, artery, from the Greek ayp, air, and T/ipeu, I guard or keep, con- clusively proves how absolutely ignorant they were of the two functions of these vessels. Hippocrates, Aristotle, and more especially Erasistratus, DEMONSTRATION OF THE FUNCTION OF ARTERIES. 875 believed that the arteries, as their name implies, carried air. This error was due. no doubt, to the fact that when a dead body is opened the arteries are usually found empty; and to the theory that the air in these vessels came, originally, from the trachea, hence the name of tracheal artery, by which it is designated by the French, even at the present day. Erasistratus 1 supposed the air passed from the trachea into the pulmonary veins (his venous artery), from there to the left side of the heart, and thence, by the arteries, to all parts of the body. Substitute for the air oxygen, and for his venous artery pulmonary capillaries, and the much-abused theory of Erasistratus becomes the modern one of respiration. Although during the four centuries that followed the bril- liant epoch of the Alexandrian school just described, dissection had gradually fallen into disuse, nevertheless the most famous anatomist of antiquity, Galen, learned his anatomy in Egypt, where he devoted many years to anatomical studies. His dissections, however, appear to have been limited to animals. By ligating in a living animal, an artery in two places, and opening the vessel between the ligatures, Galen 2 demon- strated that the vessel contained blood. Thus, by an experiment upon a living animal, a vivisection, the first great source of error, that of supposing that the arteries contained air, was removed, the true nature of an artery demonstrated, and the modern theory of the circulation of the blood made possible. Too much importance cannot be attached to this cardinal experiment of Galen. It is evident that as long as it was believed that the veins alone carried blood, and that the arteries only contained air, the discovery of the circulation was an impossibility. For 1300 years, in anatomical and physiological matters, the authority of Galen was supreme. With the truths discovered by this most de- servedly famous physician, were perpetuated errors, among which was Galen's theory that the air inspired did not enter into the body to any extent, as Erasistratus supposed, but was at once rejected after having performed its office, which was that of cooling the body, and that the cavity of the right ventricle of the heart communicated with that of the left ventricle by means of holes in the septum. 3 It is true that no one had seen these holes in the septum, separating the ventricle ; even Galen himself did not .claim that he actually saw them; but the theory in Galen's time, and many a day afterward, was. that the spirituous blood of the left ventricle must be mixed with the coarser blood of the right ventricle, that the latter should fulfil its function in nutrition. Now the only way that theory could account for this mixing of the two kinds of blood was on the supposition that the septum of the ventricle was perforated with holes, through which part of the blood passed from one ventricle to the other, the rest of the blood passing through the pulmo- nary artery to the lungs. Men saw, or believed they saw. what theory demanded they ought to see. As has been too often the case, as the history of science teaches us, the theory did not follow from the facts, but the facts were made to -\ut the theory. Further, when it is remembered that for sixteen cen- 1 Galenus edit, .it - Galenus, edit i it. an sanguis in arteriis aatara contineatur, Cap. >'>■ 4 Galenus, edit cit. De usu partium, Lib. vi. Cap. IT. 376 HISTORY OF THE DISCOVERY OF THE' CIRCULATION. turics, during the period extending from the epoch of the Alexandrian Museum to that of the School of Salerno, in 1-24, ' or more probably to that of Mundini, in 1306, 2 the human body had never been dissected, it is not to be wondered at that the grossest ignorance of anatomy should have universally prevailed. The horror with which dissection was regarded, and the limited number of subjects obtainable for study, will be appreciated from the fact that Mundini, who was Professor of Anatomy at Bologna during the latter part of the thirteenth and beginning of the fourteenth century, had dissected in eleven years only three human bodies. Berenger de Carpi, who also occupied the Chair of Anatomy in Bologna a century later, had butter opportunities of study than Mundini, whose works he commentated, he having dissected a hundred bodies ; and yet the authority of Galen had such weight with De Carpi, that he states that there are certainly holes in the septum separating the ventricles. He adds, however, as if he had an uneasy suspicion as to the truth of the statement, that these holes are seen in man with great difficulty. 3 A short time, however, after the publication of De Carpi's work, viz., in 1553, there appeared the Christianismi Restitutio of the Span- iard, Michael Servetus, whose career reads rather like that of the hero in some romance than of a real historical personage. Educated for the priesthood at Saragossa, relinquishing such studies for that of the law, at Toulouse ; accompanying, as secretary, Quintana, Confessor to Charles V., upon the occasion of the imperial coronation at Bologna; and going afterward to the Diet of Augsburg ; giving up the prospect of a diplomatic career for that of a theologian ; leaving Switzerland and changing his name to Villanovus, to avoid persecution ; supporting himself as a proof-reader and editor of learned books while a student of medicine in Paris ; receiving his degree of doctor in medicine ; writing works on medical subjects, and practising medicine with great success for a number of years ; returning to the study of theology again, his career of usefulness is suddenly cut short by death at the stake ; Servetus, as is well known, being burned alive, in 1553, at Geneva, for heresy, as the author of the Christianismi Restitutio. This work, as its name implies, is a theological treatise, but it is also of the greatest interest to the physiologist, as in discussing the nature of the vital spirit, and the manner in which it is elaborated, Servetus describes the flow of the blood from the right ventricle of the heart, by the pulmonary artery, through the lungs, and by the pulmonary veins to the left ventricle ; distinctly stating that the blood does not pass from the right ventricle to the left through the septum of the heart, as is commonly believed, but by a long passage through the lungs, from the right ventricle, and that it is in the lungs that the blood is agitated, prepared, and changes its color, thence passing to the left ventricle by the pulmonary veins. Servetus was not only the first to describe, therefore, the flow of the blood from the right side of the i Hseser : Geschichte der Hedicin, S. 733-738. Jena, 1875. Corradi: Eendiconde del R. Institut. Lombardo, Ser. ii. vol. vi. 2 Hyrtl : Das Arabische und Hebraische in der Anatomie, p. 11. Wien, 1879. 3 Berenpcer de Carpi. Commentarii cum amplissiimia additionibua super anatomia Mundini. Pp.341. Bologna, 1521. DISCOVERY OF PULMONAEY CIRCULATION. 377 heart, through the lungs, to the left, and the imperviousness of the septum of the heart, hut was also the first to point out the place where tlir venous was changed into arterial blood, the significance of which discovery was neither understood nor appreciated for more than a century afterward. Further, Servetus adds that the left ventricle is not sufficiently capacious for so copious a mixture, nor will it suffice for the elaboration of the color ; and that the septum is neither fit for the communication nor the elaboration of the blood, even if any may exude through ir. Servetus evidently does not consider that any blood passes through the septum of the heart, for he most distinctly says that none does so, and in confirmation of his view adds that even if any blood does pass through the septum, the left ventricle is not adapted to its elaboration. That Servetus did not hold the view of Galen, of part of the blood passing through the pulmonary artery and part through the septum, is evident from what Servetus says, that if any one compares his views with Galen's (and no one understood Galen better than Servetus), he will perceive clearly the truth not observed by Galen himself. The celebrated passage upon the pulmonary circu- lation, in the Restitutio, is found in Liber Quintus, De Trinitate Divina, In quo agitur de Spiritus Sancto, p. 170. It is as follows : " For which purpose the substantial generation of the vital spirit itself is first to be understood, which is composed of and nourished by the inspired air and most subtile blood. The vital spirit has its origin in the left ventricle of the heart, the lungs aiding, to the highest degree, in its generation. The spirit is subtile, elaborated by the force of heat, of a yellowish color, with the power of fire, to the end that it may be, as it were, a bright vapor from the purer blood, containing in itself the substance of water, air, and of fire. It is generated, in fact, in the lungs, with the mixture of inspired air with the elaborated, subtile blood which the right ventricle of the heart communicates to the left. Yet this communication is made, not by the middle wall of the heart, as is commonly believed, but the subtile blood is driven, by a great plan or device, from the right ventricle of the heart, by the long passage through the lungs ; is prepared in the lungs ; the yellow color is made, and it is poured out from the arterial vein (vena arteriosa), or pulmonary artery into the venous artery (arteria venosa or pulmonary vein) ; there is mixed in the venous artery itself with the inspired air ; is purged by expiration of its fuliginous matter ; and so, at length, the whole mix- ture is attracted by the diastole from the left ventricle of the heart, a fit stuff out of which to make vital spirit. The various connection and communication of the arterial vein with the venous artery teaches that the communication and preparation is made by the lungs in this manner. The remarkable size of the pulmonary artery confirms this, which would be neither made in such a way nor so large, nor would there be emitted so great a mass of blood from the heart itself into the lungs, if for the nourishment of these alone, nor would the heart serve the lungs in this manner, since, especially before, in embryo, the lungs themselves are accustomed to be nourished from elsewhere, on account of those little mem- branes, or valves of the heart, not yet being open until the hour of birth, as Galen teaches. Therefore the blood is poured forth, and so copiously. 378 HISTORY OF THE DISCOVERY OF THE CIRCULATION. from the hear! into the lungs at the hour of birth, for another use. The air also is sent from the lungs to the heart by the venous artery, not pure, but mixed with blood; therefore the mixture is made in the lungs. That yellow color is given to the blood by the lungs, not by the heart. The space in the left ventricle is not capable of holding so great and so capacious a mixture, nor is sufficient for that elaboration of color. Finally, that middle wall, as it is wanting in vessels and power, is not fit for that communication and elaboration, even if some might sweat through. By the same plan by which the transfusion is made from the vena porta to the vena cava, with reference to the blood, so the transfusion from the arterial vein to the venous artery is made in the lungs, with reference to the spirit. If any one compares this with that which Galen writes, Lib. vi. et vii., on the use of the parts, he easily perceives the truth, not observed by Galen himself. And so the vital spirit from the left ventricle of the heart is thence poured out into the arteries of the whole body." The Christianismi Restitutio is a very rare work. At the present moment there are, indeed, only three original copies known to exist — one in the National Library at Paris, one in the Imperial Library at Vienna, and one in the Library of the University of Edinburgh. The copy in Paris probably belonged to Colladon, Calvin's lawyer, since his name is in it, and w T as in the possession of the celebrated Dr. Mead, of London, in the early part of the eighteenth century, from whose hands it passed successively through those of de Boze, de Cotte, Gaignat, la Vaillere, finally becoming the property of the National Library. There is not the slightest reason to suppose that the Paris copy of the Resti- tutio was ever in the flames that enveloped its author, as is picturesquely described by Flourens, 1 the blackness on the pages being due, not to fire, but possibly to dampness. 2 In the year 1555, two years after the printing of the Christianismi Restitutio, there appeared the second edition of the magnificent Anatomy of Vesalius, which differed in many important respects from the first edition of 1543 ; among others, as regards the description of the heart. In the 1555 edition, Vesalius begins by saying that, influ- enced by the views of Galen, he considered that the blood passed from the right to the left ventricle of the heart, through the septum, by means of the pores. He immediately adds, however, that the septum of the heart is as thick, dense, and compact as the rest of the heart, and not the smallest quantity of the blood passes through the septum. There can be no doubt that Vesalius held that the septum of the heart was imperforate, in this (the 1555) edition, but the passage in which he maintains this view is not to be found in the 1543 edition ; and yet, in all of the accounts of the history of the circulation with which I am familiar, that of Tollin 3 excepted, the views of Vesalius in reference to the imperviousness of the septum of the heart (printed in 1555), 4 are said to have preceded those of Servetus (printed in 1553). The only 1 Histoire de la deconv -rte de la Circulation du Sane, p. 155. Paris, 1857. 2 Henri Tollin : Die Entdecknng des Blutkreislaufs, dnrch Michael Servet, p. 69. Jena, 1876. » Die Entdeckung dea Blutkreislaufs, etc., p 26 Jena, 1876. 4 Audrese Vesalii : De Humaui corporis fabrica Libri septem. Basilea;, 1555 DISCOVERY OF PULMONARY CIRCULATION. 379 way in which I can account for this error is by supposing that the his- torians of the circulation, in quoting A r esalius, have made use of the 1555 or 1725 editions, and not that of 1543. Certainly Servetus did not learn his anatomy from Vesalius, since they were, at the same time, prosectors for Guntherus, Professor of Anatomy in the Medical School of Paris: and as to Servetus's knowledge of practical anatomy there can be no doubt, Guntherus testifying to that. 1 On the other hand, Vesalius was probably entirely ignorant of what his former associate in the dissecting-room had published about the heart. While, to my mind, there is no doubt that the pulmonary circulation was correctly described by Servetus, beyond statements like that of the blood being transmitted by the left ventricle to the aorta, and thence through the arteries to the whole system, and of the blood flowing from the vena porta through the liver to the hepatic vein, etc., I can find nothing in his work to warrant the view that Servetus had any idea of the so-called systemic or general circulation. Further, it is not to be supposed that Servetus understood the exact manner in which the blood passed from the pulmonary arteries to the veins, since the capillaries were not discovered by Malpighi for more than a century afterward. Six years after the death of Servetus — that is, in 1559 — the pulmo- nary circulation was re-described by Colombo, who taught anatomy at Padua, Pisa, and Rome. In a work on anatomical subjects, Colombo, in speaking of the heart, observes that between the ventricles a septum is present, through which almost every one believes that the blood passes from the right ventricle of the heart to the left, but that really the blood goes through the pulmonary artery to the lungs, and is then carried, with the air, by the pulmonary vein, to the left ventricle of the heart, and that no one had previously observed or described this. 2 Colombo, however, is evidently wrong when he says no one had pre- viously observed or described this. It is possible that Colombo was ignorant of what Servetus had written in his Christianismi Resti- tutio, but it certainly appears to me very extraordinary, if such was the case, for Colombo was the pupil of Vesalius, and taught, as prosecter and professor, for years, in Padua, the very city where Servetus had sent one of the manuscript copies of his work, and where his views were well known. Whether Colombo was acquainted with the writings or the views of Servetus may be a question, but there can be no doubt that he understood and described the pulmonary circulation. This able anatomist, however, held entirely erroneous views as regards the general or systemic circulation, for, in speaking of the liver and veins, in the same work that we have just referred to, he distinctly states that the liver is the head, the fountain, the origin of all the veins. 3 It is evi- dent that one who held, with Galen, that the veins originated in the liver, the venous blood being transmitted thence to the periphery, could have no idea of the general circulation. In 1571, eighteen years after the death of Servetus, there appeared 1 ECaller Bibliotheca Anatomies, tomiis i. Tiguri, 1774. - Realdi Columbi Cremonenaia in aliuo Gyninaso Romano Anatomici celeberiinmi de re Anatomica, Libri xv.; Lib. vii. de corde et Arteriis, p. 177. Venetiis, 1559. 1 l»r- jecore et venis, p. 164, op. cit . 380 HISTORY OF THE DISCOVERY OF THE CIRCULATION. the QucBstionum Peripateticarum of Caesalpinus, 1 one of the most distin- guished of the many celebrated men thai Italy produced in the six- teenth century. Caesalpinus taught medicine al Pisa, and was afterward physician to Pope Clement VIII. at Rome, and was as distinguished a botanist as a physician, being the first to classify plants according to a natural method, and may be justly regarded as the father of vegetable anatomy. Csesalpinus described the pulmonary circulation, observing that the circulation of the blood from the right ventricle of the heart, by the lungs, to the left ventricle of the same, agrees best with what appears from dissection. One can hardly believe that such a learned man as Csesalpinus was unaware of the views of Servetus or Colombo: certainly, at least, of the existence of the De re Anatomica, published so recently as 1559, and by an anatomist who taught in the neighboring city of Padua : and yet he mentions neither. It is strange, however, that if Cnesalpinus's views upon the pulmonary circulation were derived from either the works of Servetus or Colombo, he should have held, with Galen, as he undoubtedly did, that the septum of the heart w r as pervious, part of the blood passing directly from the right to the left ventricle, which both Servetus and Colombo showed was not the case. Had Caesalpinus published nothing more than his Qucestionum Peripateticarum, there would have been no necessity for my referring to that philosopher in connection with the history of the discovery of the circulation of the blood. Twelve years afterward (1583), however, the De Plantis, 2 by the same author, appeared, and this work has the greatest interest for us, as for the first time the general or sys- temic circulation, with the exception of the capillaries, is described, though it must be admitted that the description is very brief, and sup- ported by little or no experimental evidence. In this work Caesalpinus distinctly says that the food is carried by the veins to the heart, and thence, by means of the arteries, is distributed to all parts of the body. Caesalpinus not only understood the way in which nutriment is distrib- uted throughout the economy, but, with the exception of the capillaries, the manner in which the blood flows through the system. For in his Quoestionum Medicarum (p. 234) Caesalpinus calls attention to the fact that when the veins in the neck are compressed the swelling of the veins is between the brain and ligature, not between the ligature and the heart, and draws the conclusion that just the opposite ought to happen — that is, the swelling ought to be between the ligature and the heart, if the motion of the blood in the veins is from the heart and other vis- cera to the periphery of the system, as was the general opinion at that time. Caesalpinus continues, in the same page, by saying that there is a perpetual motion of the blood from the vena cava, through the heart and lungs, to the aorta, and that the arteries communicate with the veins by what are called anastomoses ; that the blood flows to the upper parts and returns, Euripus-like, to the lower ones, is perfectly evident, both when one is asleep and awake, and that this motion is not obscure in any part of the body when you experiment by binding veins or 1 Andrea Cassalpini Aretini Qiifestionum Peripateticarum, Lib. v. Qusestio iv. p. 125. Venetiis, 1593, 2 De Plantis Libri. xvi. Lit'. 1, Cap. ii. p 3. Flurentiie, 1583. DISCOVERY OF SYSTEMIC CIRCULATION. 381 occluding them in any other manner. The above distinct, concise state- ments appear to me to prove that Caesalpinus understood the systemic circulation, as far as was possible for one who had never seen the capil- laries ; as regards the pulmonary circulation he undoubtedly also states that the blood passed from the right side of the heart to the left, by the lungs; but, as we have seen that, in the Qucestionum Peripateticarum, he says that part of the blood passes through the septum, and as he does not contradict this statement, but refers to this work as containing his views, he could only have understood the pulmonary circulation imperfectly. By most of those who have written on the discovery of the circulation, a very different interpretation, however, is offered of the views of Caesalpinus from that just given. By such, it is stated that Caesalpinus held that there was a to-and-fro motion of the blood in the veins, Euripus-like ; that the arteries communicated with the veins only during sleep ; that the blood only irrigated the tissues, but did not circulate through them, etc. If these are the views of Caesalpinus, then he certainly did not understand the circulation in any part of its course. In order that the reader may judge for himself, as to what the views of Cresalpinus really were, I will give the passage from his Quces- tionum Medicarum 1 — to which I have referred, and will say but a word further concerning it. But that appears worthy of observation, for the reason that the veins swell up from a bandage on the other side of the seat of application, not this (toward heart), which those know from experience who bleed, for they apply the bandage this side of the position of section, not on the other side, because the veins swell up on the other side of the bandage, not this side. But the opposite way ought to happen if the motion of the blood and spirit is made from the viscera into the whole body, for the canal being intercepted, progression is not given, therefore, the swelling of the veins ought to be made on this side of the bandage. Or, indeed, our doubt is solved from that which Aristotle writes of sleep, Chap. 3, where he says, "Necessarily what is evaporated, impelled continually elswhere, is then turned back and changed, like the Euripus ; for the heat of any animal is intended by nature to be carried to the higher parts, much, at the same time, on the other hand, is turned back and carried downward."' So, Aristotle. For the explanation of this passage, we must know this. That the cavities of the heart are so prepared by nature that there is an opening made from the vena cava into the right ventricle of the heart, when an exit into the lungs is opened. Further, from the lungs there is another opening into the left ventricle of the heart, from which, finally, an exit is open into the arterial aorta, the valves of which are placed at the mouths of the vessels, in order to impede retrogression. For thus there is a perpetual motion from the vena cava, through the heart and lungs, to the arterial aorta, as we have explained in the peripatetic questions. But since, when we are awake, the motion of the native heat is outward, that is, toward the sensorium, but in sleep inward, 1 Andreas Caesalpini Arotini, Quaestionum Medicarura, Libri ii. ]>p. 233, 234. Venetiis, 1593. 382 HISTORY OF THE DISCOVERY OF THE CIRCULATION. that is, toward the heart, we must be led to think that while Ave are awake uiiicli spirit and blood are carried to the arteries, for thence is the way to the nerves. But in sleep the same heat reverts, by the veins, to the heart, not by the arteries, for the natural entrance to the heart is given by the vena cava, not by the artery. The evidence of this is the pulses, which, while we are awake, are made great, vehement, rapid, swift, with each vibration, but in sleep small, languid, slow, infrequent ( ; 5 de can. pul. 9 and 10). For in sleep the native heat tends less toward the arteries, it bursts forth into the same most vehemently when they are awake. But the veins have a contrary habit, for in sleep they become more swollen, and when we are awake more empty, as is evident by observing those which are in the hand. For the native heat in, sleep, passes from the arteries to the veins by their common mouths, which they call anastomoses, and thence to the heart. But the pouring out of the blood to the higher parts and its retrocession to the inferior ones, like that of the Euripus, is manifest in sleep and when we are awake, for this kind of motion is not obscure in whatever part of the body the bandage is applied, or by whatever other means the veins are closed up. For when the permeation is allowed, the rivulets swell up in parts by which they are accustomed to flow. The blood recurs powerfully at that time to its source, lest, having been cut off, it be extinguished. It will be observed that in this passage the word Euripus occurs twice. In the first instance, however, it is Aristotle that uses it, expressing by it in a metaphorical way, his view as to the ebb and flow of the heat of an animal ; Euripus being a narrow sea between Boeotia and Euboea, which, according to the ancients, ebbed and flowed several times a day. Hence, we find several writers using the word Euripus to express an oscillation of any kind. As we are not concerned at present with what Aristotle or (Jiesalpinus thought of animal heat, it is not necessary to dwell further upon this part of the passage, simply mentioning that Csesalpinus says nothing as regards the heat as evidenced by the pulse, etc., which is inconsistent with what is known at the present day, the heat going to the heart by the veins, not by the arteries. In the second instance where the word Euripus occurs, (Jiesalpinus uses it metaphorically, in the sense of an oscillation ; but in this case, as applied to the blood. It is distinctly stated that the blood is poured out toward the superior parts, and retrogrades to the inferior ones, both asleep and awake. The ebb and flow is from the heart to the head and back again, by the arteries to the head, by the veins to the heart, there being a perpetual motion from the vena cava to the heart, through the lungs back to the heart, and so to the arteries ; thence the way to the nerves, the nerves being nour- ished by arterial blood, like all the other structures. Not a word is said of there being an ebb and flow, a Euripus-like motion, in the veins; on the contrary, it is distinctly said that blood flows in the veins toward the heart, as can be proved by binding up a vein any- where. It will be observed that Csesalpinus says that the natural heat passes, only during sleep, from the arteries to the veins, by anastomoses. This statement, however, is a totallv different one from KNOWLEDGE AT THE END OF THE 16TH CENTUEY. 383 saying that the arteries anastomose only with the veins during sleep. If there are anastomoses during sleep, there are anastomoses during the wakeful condition. More heat may be generated and transmitted through the economy at one time than another, but the absence of all heat would not affect the existence of the anastomoses. Csesalpinus, so far from saying that the blood passes from the arteries to the veins only during sleep, says that the motion of the blood is perpetual, during both the sleeping and waking conditions. That Csesalpinus understood that the blood circulated, and did not simply irrigate the system, seems to be proved by the fact of his saying that the blood circulates in one work, in another that the blood is carried by the veins to the heart, and from the heart by the arteries, and that the arteries anastomose with the veins, and that the motion is perpetual from the vena cava to the heart and lungs to the aorta. It is not to be implied, however, that he understood the exact manner in which the blood passed from the arteries to the veins because he uses the word anastomoses. Galen and Servetus used the same word in this connec- tion, as also afterward Harvey, although there is no reason to suppose that these writers ever meant, by the word anastomosis the capillaries, and yet, without a knowledge of these vessels, the systemic, no more than the pulmonary circulation, could be thoroughly understood. It will be seen, from this brief resume of the views of Servetus, Colombo, and Csesalpinus, that while the pulmonary circulation (with the exception of the capillaries) was understood by Servetus and Colombo, they had but little or no idea of the general or systemic circulation ; on the other hand, while the general circulation (with the exception of the capillaries) was correctly described by Csesalpinus, he understood the pulmonary circulation only imperfectly. It cannot be said, therefore, that any one, up to the end of the sixteenth century, under- stood the entire circulation of the blood, using the word circulation in the sense that we do at the present day. Isolated portions of the circu- lation only had been described. It remained now for some one to show the connection between the facts already established, to add important new ones, to offer a view based upon observation and experiment that would explain all the facts. In a word, to demonstrate that the blood actually circulates. It is claimed by some writers that this honor should be accorded to Carlo Ruini, of Bologna, it having been asserted that Ruini discovered both the pulmonary and systemic circulations. Even if Ruini had described both the circulations correctly, that would not have entitled him to be called their discoverer, since the pulmonary circulation had been previously described by Servetus and Colombo, and the systemic circulation by Csesalpinus. Ruini does not appear to me, however, to have thoroughly understood either the systemic or pulmo- nary circulations, since he states that the veins carry the nourishment, as well as the arteries, to the viscera, and that the pulmonary arteries nourish the lungs. There can be no possible misunderstanding of Ruini's views as to the systemic circulation, as in his Anatomy of the Horse, 1 he says the vein that carries nutriment to the eye, and gives a 1 Anatoniia del Cavallo, in Venetia, 1599, Lib. i. p. 65. 384 HISTORY OF THE DISCOVERY OF THE CIRCULATION. figure illustrating this view. In speaking of the arteries and veins, we find that they appear to be made solely to carry nutriment to parts as noble as the spinal medulla ; and they give nutriment, life, and motion to all these parts — a branch of the vein and artery. That Ruini bad but an imperfect idea of the pulmonary circulation is evident from the manner in which he describes it, p. 108 : "The office of these ventricles is. for the right one, to prepare the blood, that the spirits of life can be generated from it and the lungs nourished; of the left to receive this blood already prepared, and to convert a part into spirits, which give life, and to send the rest, together with the spirits, by means of the arteries, to all parts of the body. In both the ventricles are two mouths or chinks ; by that of the right the blood of the great vein, or cava, enters, and goes out by the arterial vein ; by that of the left ventricle, the blood enters, accompanied by the air prepared in the lungs from the venous artery ; this being en- tirely spiritualized and perfected in the left ventricle, goes out (guided by the great arteria) through all parts of the body, except that for the lungs, to impart it that heat which give's life." During the middle of the sixteenth century the fame of the medical schools of Italy had spread far and wide. Students from all parts of Europe crowded to listen to the eloquent lectures of Vesalius, Eus- tachius, and Fallopius, to attend the anatomical demonstrations given in the amphitheatres at Padua, Pisa, and Bologna. At the end of the sixteenth century, with other foreigners, William Harvey came to Padua and studied with the celebrated Fabricius, of Aquapendente, the first anatomist to describe thoroughly in his Be venarum ostiolis, Patav, 1603, the valves in the veins. 1 Fabricius is often said to have first discovered these valves : indeed, he says so himself ; but the presence of valves in the veins had been previously noticed by several anatomists ; among others, by Cannanus, 2 Sylvius, 3 Eustachius, 4 and Piccolhominus. 5 At this moment, however, that which interests us particularly in reference to these valves is, that Fabricius demonstrated them to Harvey, and that the latter made such good use of that knowl- edge that the names of pupil and master have ever since been asso- ciated ; for, undoubtedly, it was reflection upon what might be the use of the valves, as well as other anatomical considerations, that first led Harvey to investigate the manner in which the blood flows through the system. Harvey studied about five years at Padua (1598-1602). Naturally, during that time, he became thoroughly acquainted, not only with the views of his teachers, Fabricius, Rudio, etc., but also with those of Colombo, and probably of Caesalpinus and others who had taught and written concerning the manner in which the blood was supposed to flow. Perfectly familiar with the anatomical views and methods of the school of Padua, dissatisfied with the prevailing imperfect 1 Hieronymi Fabrici ;tl> Aipiapendente Opera Omnia Lipsiae, 1G87, De Venarum Ostiolis, p. 150. 2 Amati Lusitani Medici Physici Prsestantio Curationum Medicinalium, Lugduni, 1567. <* In Hippocrates et Galeni Pnysiologiaa partem anatomicam Isagoge a Jacobo Sylvio-Parisiis, 1555. * Bartholmasi Bustachii Opuscnla Anatomica Venetiis, 1584. 6 Anatomica; Prselectiones Archangel Piccolhomini Romas, 158(5. By most writers tlie French ana- tomist, Etienne, is considered to have described the valves in the veins even before Cannanus or Sylvius. — De dissectione partium corporis humani Iibri tres a Carolo Stephano. Parisiis, 1545. Lib. ii. llepar, Cap. ix. p. 182. APPEARANCE OF HARVEY'S WORK. 385 physiological theories of the circulation, on his return to England Harvey began anew the study of the flow of the blood. The results of his reflection upon the knowledge gained in Italy, of his studies upon his return, by numerous vivisections, of extended comparisons of the structure of the heart and bloodvessels in the animal kingdom, of pathological observations upon man and beast, were embodied in his classical treatise, An Anatomical Exercise on the Motion of the Heart and Blood in Animals. 1 This deservedly famous work will always serve as a model for physiological investigation. Thus Harvey shows the necessity of making vivisections 2 in the study of the circula- tion, and too much stress cannot be laid upon this statement, as it is often said that the circulation of the blood was discovered without re- course to experiments upon living animals. The importance of compara- tive anatomy as an aid to the study of physiology is well shown by the use that Harvey made of his knowledge of the structure and functions of the heart in the lower animals, in his researches upon the circulation. Indeed, Harvey says, 3 had anatomists only been as familiar with the dissection of the lower animals as they are with that of the human body, matters that have been a source of doubt would be free from all difficulty. Unfortunately, comparative anatomy is too much neglected by physiologists at the present day. That the value of pathological anatomy in throwing light upon the normal functions of the body was thoroughly appreciated by Harvey is evident from the cases he refers to 4 in connection with his study of the circulation. Harvey, therefore, did not confine himself to any one method of investigation, but availed him- self of vivisection, comparative anatomy, and pathology in his researches. It may be seen by referring to the writings of the great predecessors of Harvey, that, with the exception of Cfesalpinus, it was always assumed that the venous blood flowed from the viscera to the periphery. Un- doubtedly, Harvey demonstrated far more thoroughly, by experiment and argument, than Gsesalpinus, the true course of the venous blood, and this he proved in many different ways. Thus, in his thirteenth chapter, 5 after referring to the discovery of the valves of the veins by Fabricius, and the different uses that had been assigned to them, Har- vey proceeds to show that the valves are disposed in such a way that they permit the blood to pass through them in only one direction, and that is toward the heart, 6 demonstrating this by calling attention, as Csesalpinus had done before him, to the condition of the veins when compressed as if for bleeding. At intervals in the course of the veins, under such circumstances, large knots are visible, which are due to the distended valves, which thus show themselves externally. By pressing upon these veins above or below, or between the valves, Harvey showed that the venous blood ahvays passed in the same direction — that is, toward the heart — and concluded that the functions of the valves were 1 Exercitatio anatoniica de motu cordis et sanguinis in animalibus. Francofurti MDCXXVIII. - Op. cit., Cap. ii. p. 21 ; Cap. iv. p. 25. 3 Cap. vi. p. 32. 4 Cap. iii p. :U. 5 Cap. xiii. p. 54. 6 It must not be forgotten that Piccoltaominus had already described the valves in the jugular vein, ami drew the conclusion that these valves prevented regurgitation to the head and extremities respec- tively. It is to be regretted that Harvey, in his description of the valves and the flow of blood through the veins, should never have mentioned either Piccolhominus or Ciesalpinus, as it is probable that he was acquainted with the writings of these anatomists, both teaching at Rome about the same time. 25 386 HISTORY OF THE DISCOVERY OF THE CIRCULATION. like those of the semilunar valves of the pulmonary artery and aorta, to prevent all reflux. 1 Excellent figures are given in this chapter to illustrate the experiments by which the functions of the valves were demonstrated. Further, that the blood flowed toward the heart in the veins and from the heart in the arteries, was beautifully demonstrated by an experiment upon a living snake, so clearly described by Harvey in < 'hapter X. After noticing the pulsating heart in the snake as it appeared after the animal had been opened, Harvey calls attention to the fact that if the vena cava be compressed it gradually empties itself between the point of compression and the heart ; whereas, if the aorta be compressed, it becomes distended between the heart and the point of compression, showing conclusively that the blood in the vena cava flows toward the heart, while that in the aorta flows from the heart. In his second answer to Riolan, Harvey 2 gives further proof of the circula- tion in noticing that in a divided artery the blood flows from the end of the vessel that is still in connection with the heart, whereas, in the divided vein the blood flows from that part of the vessel separated from the heart. One of the most remarkable proofs of the circulation of the blood advanced by Harvey 3 is, that more blood passes through the heart in a given time than can be accounted for by the ingesta or by the quantity of the blood in the vessels ; hence the blood must pass and repass throug-h the heart, and in estimating the amount of blood flowing from the left ventricle into the aorta during a short period of time even, we necessarily count the same blood over and over again. Harvey was not only the first to describe correctly the entire circulation, but in the great work 4 we have so often referred to is found the first accurate account of the movements of the heart, the successive dilatations and contractions of the auricles and ventricles, the contraction, hardening, and elevation of the heart against the chest, etc. An excellent descrip- tion, as may be supposed, is also given of the pulmonary circulation, etc. Further, though from the day of Aristotle it was known that there was some connection between the beating of the heart and the pulse, Harvey 5 showed clearly that the dilatation of the artery, or the pulse, was the effect of the contraction of the ventricle. Harvey was not the first, however, to show this, since in an ancient work, Synopsis peri Sphugmon, by an unknown author, the pulse in this respect was correctly described. When this work was first discovered, according to d'Aremberg, it was, without any reason, attributed to Rufus, of Ephesus. The description I refer to is to be found at page 20 : 6 " How is the pulse generated ? The pulse is produced as follows : The heart, after having drawn in the air from the lung, first receives it in its left cavity, then falling back upon itself immediately distributes it 1 The importance of the valves in the veins, either functionally or as leading to the discovery of the circulation, must not be exaggerated, since in many veins there are no valves. Thus in man, at least, however it may be in other mammals, valves are not found in the vena? cava;, the innominate, pulmonary, portal, hepatic, renal, uterine, ovarian, iliac, and spinal veins. Further, there are tew valves in the veins of birds, reptiles, or fishes, and none in the veins of in vertebra ta, and yet the blood circulates in all these animals. It is evident, therefore, that the valves in the veins are not indispensable in the maintenance of the circulation. 2 Opera Omnia Edita, 17(16, p. 120. Exercitatio altera ad J. Eiolanum. 3 Cap. ix. p. 42. 4 Cap. ii. iii. iv. v. vi. 5 Cap. iii. p. 24. <-. Sbvoipig T£pl a RESPIRATION. to a median point so as to accommodate itself to the bronchi. Within the fibrous tissue filling up the posterior third of the cartilaginous rings are found unstriped muscular tissue, the fibres of which are disposed in a transverse, and to a certain extent, also in a longitudinal direc- tion. The action of these muscular fibres sometimes called the tracheal muscles, is to diminish the area of the trachea by approximating the cartilaginous rings, and the ends of each ring. The trachea is lined with mucous membrane, its epithelium being of the columnar ciliated character. The motion of the cilia being from below, upward, a cur- rent is produced by which the mucus is carried upward toward the larynx. The composition of the nasal and bronchial mucus is given in : Table LVI. 1 — Composition of Nasal Mucus. Water .......... 993.00 Mucosin ......... 53.30 Sodium lactate ........ 1.00 Organic crystalline principles ..... 2.00 Fatty matters and cholesterin ..... Sodium and potassium chloride ..... 5.60 Phosphates ... ...... Sodium sulphate and carbonate ..... 3.50 0.90 5le LVII. 2 — Composition of Bronchial and Pulmonary Mu< 955 520 Mucosin .......... 23.754 Watery extract ......... S.OOG Alcoholic extract ........ 1.810 Fat 2.887 Sodium chloride ........ 5.825 " sulphate ........ " carbonate ........ 0.400 0.198 " phosphate ........ Calcium phosphate with traces of iron .... 0.080 0.974 carbonate ........ 0.291 Silica and calcium sulphate ...... 0.255 1000.000 Although the cilia are microscopic, varying in length from the i^-g-th to the nj-Q-th of a mm. (the 25 1 00 th to 40 1 00 th of an inch) in length ; nevertheless, through their vibratory motion a greater force is exerted than might be expected. The mechanical effect produced by the motion of the vibratile cilia can be shown by means of the instrument devised by Wyman, 3 or by that of Calliburces. The latter, as made for the author by Aubrey, of Paris, consists (Fig. 219) of a brass stage H, 11 cm. long and 7 cm. wide (4.5 and 3 inches), which can be elevated and depressed on a vertical axis (K) by means of the screw M, whose movement is graduated. The brass stage supports a cork (I) 5 cm. long and 3 cm. wide (2 and 1.2 inches), and the vertical axis L, an aluminium rod, 5 cm. long (2 inches) and with a diameter of 1.5 mm. (1.25th of an inch) horizontally disposed, and terminating in 1 Robin : Lemons sur les humeurs, p. 450. Paris, 1867. 2 Xasse : Journal ofprakt. Chemie, 1813, Baud xxix. S. 65. 3 Experiments with vibrating cilia, American Naturalist, vol. v. p. 611, 1871. APPARATUS OF CALLIBURCES. 399 Fig. 219. an index (F) and partly surrounded by glass. The vertical index (L) is surmounted by a brass disk N, through which passes a safety tube into which hot water can be poured, by means of which the surrounding atmosphere can be kept moist, and at a temperature of about 28° Cent. (82° Fahr.), and a thermometer (P) for indicating the same. The brass stage, axis, and disk, etc., can be covered with a glass cylinder. Before doing this, the mucous membrane, the mo- tion of whose cilia is to be examined, that of the oesophagus of the frog. for example, is placed upon the cork, and the brass stage (H) elevated by the screw (M) until the membrane is almost in contact with the aluminium rod. When properly adjusted, and the membrane kept moist and warm by the means just indicated, the aluminium rod will rotate on its axis, the index at its end (F) moving over the graduated brass circle. having a diameter of 2.(3 cm. (l.<»4 inch). Usually the index will move around the circle once in three minutes, and the motion, under favorable circumstances, will continue for an hour and upward. As the aluminium rod, with the glass sur- rounding it, and the index weigh about 0.073 gr. (1.05 grain), it is evident that considerable mechanical effect is produced relatively to the small size of the organs exerting the force. The motion of the cilia of human mucous membrane can often be seen upon the surface of recently extracted nasal polypi when the latter are viewed under the microscope. The trachea terminates inferiorly in the bronchi (Fig. 217, B); the right bronchus, differs from the left in beino- the shortest, attaining, usually, a length of 2..") cm. (1 inch), while the left is almost twice as long. The general structure of the bronchi corresponds in every way to that of the trachea ; the cartilaginous rings are, however, shorter and narrower, and less numerous, the right bronchus consisting, usually, of from six to eight rings, the left of from nine to twelve. Each bronchus divides and subdivides dichotomously into the bronchial tubes (Fig.217). The latter, diverging in every direction, and never anastomosing, gradu- ally become smaller and smaller, and more delicate in structure, and when, finally, they are reduced to about a diameter of the Ath of a mm. (y^o^h °f an i nc h)i they terminate in a primary lobule (Fig. 218). The bronchial tubes differ in several respects from the bronchi, of which they are the diverging branches. Tims, in the larger ones, the carti- lages are disposed as irregular-shaped plates, of various sizes, all over Apparatus of C'alliburces. 400 RESPIRATION, the sides of the tubes instead of in the form of imperfect rings ; in the medium-sized tubes the cartilages become smaller and less numerous, while, finally, in tubes having a diameter of less than -i- of a mm. (_i_th of an inch) they disappear altogether. The terminal bronchial tubes then consist of a delicate fibro-elastic external membrane, containing circular muscular fibres and a very thin lining of mucous membrane, the epithelium of which is, however, still ciliated. As just stated, each bronchial tube finally terminates in a primary lobule. The primary lobule, with a diameter usually of 2 mm. ( T V tQ °f an inch), consists of a sac, which is essentially an expansion of the terminal bronchial tube, hence its name of infundibulum. The cavity of the primary lobule (Fig. 218, b) is subdivided by thin partitions, projecting from its inner surface into secondary compartments, or alveoli c, the pulmonary air cells having a diameter of from |-th to \d of a mm. (-j^j-th to -^th of an inch) ; these, while separated from each other by the partitions, com- municate with the central cavity or intercellular air passages, which, in turn opens into the terminal bronchial tube, through which the inspired air ultimately passes to the air cells. The air cells, amounting to over seventeen millions in number, and representing an area of nearly two hundred square metres (1800 feet), are polyhedral sacs, surrounded by anastomosing elastic fibres, and consist of a fibro-elastic wall, contain- ing, probably, some muscular fibres, and lined with a tessellated epithe- lium. The epithelium is more homogeneous and easily demonstrated in the foetus than in the adult. If the primary lobule of the human lung be now compared with the lung of the frog, it will be seen that it represents the entire frog's lung in miniature. The primary lobules of the human lung unite through connective tissue into larger secondary lobules, and the latter, uniting, constitute a lung. The polyhedral mark- ings upon the surface of a lung indicate the margins of the secondary lobules, while careful examination will disclose also the outlines of the primary lobules composing the secondary ones. Finally, the integration of the pri- mary lobules into the secondary ones, and the latter into lobes, carried still further into the left lung than in the right, the former consisting of two lobes, the latter of three. While the lungs are nourished by the bronchi, it is by means of the pul- monary arteries that the venous blood is carried to them from the right side of the heart and aerated. The pulmonary artery arising, as we have seen, from the right ventricle of the heart, soon divides into a right and left branch for either hms. Fol- lowing the bronchus and bronchial tubes, the artery divides and subdivides, the branches becoming smaller and smaller as they approach the primary lobules (Fig. 220), until finally they termi- nate as the pulmonary capillaries. The terminal arterial capillaries surround each alveolus or air cell as a vascular circle, which anastomoses Fig. 2-20. Diagram of two primary lobules of the lungs, magnified. 1. Bronchial tube. 2. A pair of primary lobules connected with fibro-elastic tissue. 3. Intercellular air passages. 4. Air cells. 5. Branches of the pulmonary artery and vein. (Leidy.) STRUCTURE OF PLEURA. 401 with those of the adjacent alveoli. From these vessels arise a capillary network (Fig. 220), so closely set that the meshes are even smaller than the diameter of the vessels themselves, the latter having usually a diameter of from -g^th to T^-g-th of a mm. (-juVo^ 1 t0 5 0*0 tn °f an i ncn )- This network supports the bottom of each air cell, and the blood that it carries is separated from the air of the cells only by its "wall and the extremely delicate epithelial lining of it. The carbonic acid of the venous blood conveyed to the lungs by the pulmonary artery is thus separated from the oxygen of the air within the air cells brought by the trachea by nothing but the Avail of the capillary and epithelium of the air cell. The rapidity with which the osmosis of these gases takes place through such a delicate. septum will, therefore, be readily imagined; the osmosis being still further insured through the great vascularity of the parts, the respiratory surface being thereby continually kept moist, which greatly promotes the exchange of the gases. The full influence of the air upon the blood is further secured in that the capillary plexus is so disposed between the walls of two adjacent air cells that one of its surfaces is exposed to each. It has been estimated 1 that a thin layer of blood of 150 square metres (1350 feet) is exposed in the lungs to the air of the air cells, and that this blood, amounting to perhaps 2 litres (4 pints), is renewed 10,000 times in twenty-four hours. This estimate is based upon the assumption that the surface of the capil- laries is equal to about three-fourths the surface of the air cells. That this is not an exaggeration may be inferred from the fact of an injected lung appearing to consist of nothing but capillaries. From the capillary network surrounding the air cells the pulmonary veins arise, which, uniting with each other, gradually form four larger trunks, which finallv terminate in the left auricle of the heart and convey to it the aerated oxygenated blood to be distributed, as we have seen, by the arterial system to all parts of the body. Having described the pulmonary air cells and bloodvessels, the passage by osmosis of the carbonic acid from the blood into the air cells and of the oxygen from the air cells into the blood, let us now consider the means by which the external air is drawn into the lungs and the carbonic acid ex- pelled from them. The heart and lungs are suspended by the great bloodvessels in the thoracic cavity. The thorax consists of the ster- num anteriorly, the dosal vertebra pos- teriorly, and the ribs laterally. It is covered in above by the cervical muscles and fascia, below by the diaphragm, and laterally, etc., by the intercostal muscles. The thoracic cavity is therefore air-tight. If the lungS be examined in Situ it 'will Diagrammatic view of pleural sacs. be found that the surface of each lung is covered with a serous membrane continuous with that lining the inner surface of the thorax or the pleura. 1 Kuss : Physiologie, 1873, p. 338. 26 402 RESPIRATION To understand the relations of the pleura to the lungs and walls of the thorax, let us first conceive the pleura as consisting of two bladders (Fig. 221), and so placed within an empty thorax that the outer wall (c) of each bladder will adhere to the inner wall (b) of the thorax, the inner walls (d) of each bladder remaining free. Suppose now that the heart and lungs be inserted between the inner free walls of the two bladders, and that each of the latter be made to adhere to the surface of the lung with which it is in contact. Such a disposition being made (Fig. 222), the bladders will then represent the two pleura, the inner walls (»/ d) the visceral layer, the outer wall (c e) the parietal layers, and the space between the layers the pleural cavi- ties, the spaces between the bladders or the pleura constituting the mediastinal spaces, the narrow septum formed through the union of the Fig 1222. Diagrammatic view of pleural sacs with heart and lungs interposed. two pleura the mediastinum. In health the opposed surfaces of the visceral and parietal layers of the pleura are always in contact, there being only fluid enough between them to insure their gliding smoothly over each other. Practically, therefore, in normal respiration there is no pleural cavity. This must necessarily be so, since the thorax being an air-tight cage, as it dilates through the action of the inspira- tory muscles and recedes from the lungs, the air within the latter will expand and become rarefied ; the external air being then denser than the inside air, will rush through the trachea into the lungs, and expanding the latter in proportion as the thorax is dilated, keep the visceral layer of the pleura in contact with the parietal one. It will be observed that while it is the force of the inspiratory muscles that dilates the chest, it is the pressure of the air that expands the lungs, and, further, that inasmuch as the lungs are elastic and therefore offer a resistance to their expansion, the air must overcome this resistance, and hence the pressure exerted by the air within the lungs during inspira- tion must be less than that of the external atmosphere. The significance of this fact we shall see shortly. On the other hand, as the thorax con- tracts as its capacity diminishes, the air within the lungs exerting now INSPIRATION AND EXPIRATION. 403 a greater pressure than the air without, will pass out of the lungs, through the trachea by which it had just entered the lungs, of course collapsing, their elasticity now aiding the expulsion of the air to the same extent as it formerly opposed its entrance. The dilatation of the thoracic cavity and the taking in of the air is known as inspiration, the contraction of the thoracic cavity and the giving out of the air expira- tion, the two acts constituting respiration. Let us consider now a little more in detail the means by which this alternate dilatation and contraction of the thoracic cavity causing respi- ration is effected. CHAPTER XXV11. MUSCLES OF RESPIRATION. Reflection upon the origin and insertion of the various muscles acting upon the thorax makes it evident that some of these muscles in contracting will expand the chest, causing inspiration, while the relax- ation of these muscles together with the elasticity of the lungs and the action of certain other muscles, will contract it, causing expiration. The muscles involved in the production of respiration will then natu- rally divide themselves into two groups, those of inspiration and those of expiration (Table LVIII., page 410). To the study of these let us now turn. Inspiration. Of all the inspiratory muscles the diaphragm is the most important, since the capacity of the chest is enlarged to a greater extent through its contraction than by that of any other muscle. Indeed, in the male sex at least, as we shall see, gentle breathing is accomplished Fig. 223. Interior view of the diaphragm. 1, 2, 3, the three lobes of the central tendon, surrounded by the fleshy fasciculi derived from the inferior margin of the thorax, the crura, 4, 5, and the arcuate ligaments, 6, 7 ; 8, aortic orifice ; 9, oesophageal orifice ; 10, quadrate foramen ; 11, psoas muscle ; 12, quadrate lumbar muscle. almost entirely by the action of the diaphragm. The diaphragm (Fig. 223), arising from the ensiform cartilage of the sternum, the cartilages of the six or seven lower ribs, and often, also, from their THE DIAPHRAGM. 405 osseous portions from the arcuate ligaments and the bodies of the first, second and third lumbar vertebrae, and the intervertebral cartilages of the right side, and from the bodies of the first and second lumbar vertebrae, etc., of the left, or the crurse, covers in therefore the lower circumference of the thorax. From this origin the diaphragm passes upward into the cavity of the thorax as a. vaulted arch or dome (Fig. 224, B), its convexity being toward the lungs. With the exception of Fig. 224. Diagrammatic sections of the body in inspiration and expiration. A. Inspiration. B. Expiration. Tr. Trachea. St. Sternum. D. Diaphragm. Ab. Abdominal walls. The shading roughly indicates the stationary air. the central tendinous portion, the diaphragm consists of muscular fibres of the voluntary character. It presents several openings through which pass the oesophagus, aorta, vena cava, etc., and it is supplied by the phrenic nerve. During the state of repose, as we have just seen, the diaphragm presents the form of a dome or of a vaulted, arched or curved surface. If the diaphragm, however, be observed during contraction, as can be readily done by opening largely the abdominal cavity of a completely insensible living mammal, a cat, dog, or rabbit, for example, it will then be seen that through the contraction of its muscular fibres the curved surface of the diaphragm assumes more the form of a plane (Fig. 224, A), and that the floor of the thorax descends. The effect of the descent of the diaphragm, therefore, is to enlarge in a vertical direction the capacity of the thorax, and to rarefy the air within it. The external air being then denser than that within the thorax rushes into the latter and proportionally distends the lungs in consequence. The diaphragm through its contraction acts then as an inspiratory muscle ; it need hardly be added, however, that it is 40 f) MUSCLES OF RESPIRATION. not the diaphragm, but the air, that actually distends the lungs. We are in the habit of illustrating the action of the diaphragm in respira- tion by the simple apparatus represented in Fig. 225. This consists Fig. 225. Diagrammatic view of apparatus to show the action of the diaphragm. of a bell jar (a), the walls of which correspond to the thorax, and in which are suspended the lungs (LL), the trachea passing through the air- tight fittincr cork. The bottom of the jar is closed in air-tight, with India rubber corresponding to the diaphragm. It is needless to say that there is no such amount of space as (d) corresponding to the pleural cavity in the human being in a state of health. Such being the disposition of the parts, by pulling down the India rubber (5) the air within the jar, and therefore within the lungs, becomes rarefied as indicated by the rise of the mercury within the limb (3) of the manometer. The external air will therefore rush through the trachea into the lungs, and consequently distend them. With the elevation of the India rubber the condition of the pressure of the air within and without the jar being reversed, the air will pass out of the lungs, the latter collapsing. It will be observed that the flattening of the diaphragm just referred to is most marked at its lateral portions, or the parts under the lungs, as might be expected, that part of it immediately under the heart undergoing but little change in form. As the diaphragm descends it pushes downward and forward the abdominal viscera, and as the anterior and lateral walls of the abdomen are extensible, they give way to the pressure so exerted and are protruded. With each inspiration, therefore, the descent of the diaphragm in man becomes perfectly evident through the movement of the abdomen. The action of the diaphragm in producing inspiration may be readily imitated in man and mammal just dead, by opening the abdomen and pulling the central tendon downward. The external air will rush into the lungs, and often with a distinctly audible sound. By passing a long and slender needle through the ensiform cartilage of the sternum of a completely chloralized animal, a rabbit, for example, and connect- ing the eye of the needle by a silk thread (Fig. 226, A), with a little boxwood pulley (P), whose movements are inscribed by the horizontal lever (R) on the recording surface, we can obtain a graphic representa- STRUCTURE OF THORAX. -107 Fig. 226. tion of the descent and ascent of the diaphragm during respiration. Too much importance must not, however, be attached to this method of studying the movements of the dia- phragm. While the vertical diameter of the chest is enlarged through the descent of the diaphragm, nevertheless, through its attachment to the sternum and false ribs during its contraction through the pulling of the sternum and the upper false ribs downward and in- ward, and the lower ribs upward and inward toward the vertebral column, there would be a tendency to diminish, to some extent, the capacity of the thorax. This effect is, however, counteracted by the ribs being elevated at the same time as the diaphragm descends, and through the action of certain muscles, to be described later. The elevation of the ribs is such a constant accompaniment of the descent of the diaphragm that in general terms it may be stated that inspiration is effected by the descent of the one, and the ascent of the other, and this is true, even though the breathing appear entirely diaphragmatic. The ribs (Fig. 227) pass from their articulations with the dorsal ver- tebra? downward and forward ; they are somewhat twisted in shape and Boxwood pulley for recording the movements of a needle inserted in the diaphragm. A light lever is attached to the horizontal arm. (Sandeeson.) Fig. 221 Front view of the thorax. 1, 2, 3. The three pieces of the sternum. 4, 5. The dorsal vertebrae. 6. The first true rib. 7. Its head. 8. Neck. Tubercle. 10. The seventh true rib. 11. Costal carti- lages. 12. The floating ribs. 13. Groove for the iuteicostal bloodvessels. (Leidt.) are twelve in number. The upper seven or true ribs are articulated with the sternum, of the remaining five or false ribs, the eighth, ninth, and tenth are joined to the seventh rib, the last two ribs, viz., the 408 MUSCLES OF RESPIRATION. eleventh and twelfth, arc unattached anteriorly and are hence known as floating ribs. As the ribs are elevated they recede from each other, the distance between them being increased; they are at the same time rotated outward, assuming a more horizontal position, and in tending to straighten themselves become less curved. Through their attach- ment to the sternum the lower portion of* the latter is thrown forward, the flexibility of this part of the thorax being mainly due to the sternal attachment of the ribs being cartilaginous and not osseous. The effect of this change in the form, position, and direction of the ribs and ster- num is to enlarge the capacity of the chest in every direction vertically through the separation of the ribs, laterally through their rotation outward and straightening, antero-posteriorly, through the movement forward of the sternum. As the air rushes in, distending; the lungs of the expanding chest, it is evident, therefore, that inspiration is produced through the elevation of the ribs as well as through the descent of the diaphragm. The extent of the increase of the capacity of the chest through the elevation of the ribs is greatly influenced by the length, degree of curvature, character of the angles of the ribs, etc. Thus from the ribs being directed obliquely downward and forward when elevated, and assuming a more horizontal position their external ends recede from the posterior wall of the thorax and increase proportionally its antero- posterior diameter. As the ribs are elevated they remain nearly parallel to each other, it follows, therefore, that the inspiratory effect produced by this movement of the ribs will be proportional to the length, or, more accurately speaking, to the length of the chord of the arc repre- sented by the curve of the rib. The length, however, varies consider- ably, increasing rapidly from the first to the fifth rib, attaining its maximum at the eighth rib, diminishing then progressively from the ninth to the twelfth. Other things being equal, it follows, then, that the increase in the antero-posterior diameter of the chest is greater at the level of the seventh to the ninth ribs than at the upper or lower part of the thorax. It is for this reason that during inspiration the inferior portion of the sternum moves so much more forward than the upper portion. The transverse diameter of the chest, on the other hand, is greatly influenced by the amount of the curvature of the ribs, and this varies considerably. Thus the curvature increases from the first to the third ribs, the maximum amount being about that of the sixth ; there is but little difference, however, as regards the curvature of the ribs included between the sixth and ninth. The amount of the curvature can be measured by the versed sine of the arc of the circle represented by the rib, or, what is the same thing, the distance from the middle line of the thorax to the most prominent part of it laterally. The angle made by the osseous part of the ribs with their sternal or costal ones, and the length of their cartilaginous portions increase from the fourth to the seventh. Consequently it is in this part of the thorax that the increase of capacity due to the elasticity and flexibility of the cartilage is greatest. The different extent to which the capacity of the thorax is enlarged in its various diameters during inspiration, the influence due to the variation in the length, curvature of the ribs, etc., are shown by the diagrams (Figs. 228, 229, 230, and 231) illustrating the admirable ACTION OF THE RIBS. 409 and exhaustive work of Sibson. 1 Let us consider now the muscles which elevate the ribs, and so, together with the action of the diaphragm, cause inspiration. Fig. 229. Dorsal region. Expiration. Inspiration. Anterior region of the thorax. Inspiration. Expiration. Fig. 230. Fig. 231. Expiration. Inspiration. i Phil. Trans., 1846. 410 MUSCLES OF RESPIRATION. Table LVIIL- I aspiration. -Muscles of Respiration. Expiration, Ordinary. Diaphragm I ntcnial intercostals, osseous portion. Triangularis sterni. Intra costales. < )1>I i(jue. Transversalis. Sacro Lumbalis. External intercostals. Internal intercostals, sternal portion . Scaleni ...... Levatores costaruru. Auxiliary. Serratus posticus superior . Accessor i us ..... Sterno-cleido-mastoid . Levator anguli scapula?. Trapezius, superior portion. Serratus magnus. Pectorales major, inferior portion. Pectorales minor. These muscles are usually described as consisting of two sets, ordi- nary or extraordinary, or auxiliary (Table LVIIL), according as the breathing due to their action is easy or forced. There is, however, no such sharp line of demarcation observable, it being impossible to say just where ordinary easy breathing ends, and forced breathing begins, great difference being observed in this respect within the limits of health, according to individual peculiarities. There are certain muscles, how- ever, such as the external intercostals, scaleni, etc., which intervene in Fig. 232. View of several of the middle dorsal vertebra? and ribs, to show the intercostal muscles (A. B.). y z . A. From the side. B. From behind. 1, 1. The levatores costarum muscles, short and long. 2. The external intercostal muscles. 3 The internal intercostal layer shown, in the lower of the two spaces represented, by the removal of the external layer, as seen in A in the upper space, in front of the ex- ternal layer. The deficiency of the internal layer toward the vertebral column is shown in B. (After Cloquet.) easy inspiration ; these we will consider first, and afterward those coming into play when the breathing is exaggerated. That the external intercostal muscles (Fig. 232) are inspiratory in function one would ACTION OF THE SCALENI. 411 infer from their attachments, and the direction of their fibres. Passing from rib to rib from above downward, and from behind forward, in con- tracting these muscles, will approximate and elevate the ribs. Experi- ment justifies this view of the inspiratory function of the external inter- costal muscles, since, if they be exposed in a living animal with each inspi- ration, they will be seen in contracting to elevate the ribs. Inasmuch, however, as the general direction of the sternal portion of the internal intercostals is also from above downward, and rather forward than back- ward, through the change in the curve of the rib, analogy would lead us to suppose that their action is the same as that of the external inter- costals, and that they must, therefore, be also regarded as inspiratory in function. This view is confirmed by the observations of Bernard, 1 made upon a man in whom the pectoral muscle was so atrophied as to permit of an experimental investigation of the function of the partly exposed sternal portion of the internal intercostal muscle. When the sternal part of the muscle was stimulated, the cartilage of the second rib was elevated, and with it the anterior extremity of the corresponding osseous rib. The scaleni passing obliquely downward from their origin, the trans- verse processes of the lower six cervical vertebrae, to their insertion, the first and second ribs, in acting from their origin during contraction will elevate these ribs, and indirectly the whole thorax. To prove that the scaleni do act in this way it is only necessary to squeeze between the fingers the part of the neck including these muscles to feel them contract with each inspiration. The movement then experienced, the so-called respiratory pulse of Magendie, 2 becomes very evident when the superior part of the chest is much dilated. The action of the scaleni is not only to elevate the ribs, but to fix the first rib as an origin from which the inter- costal muscles that elevate the ribs can act. Ordinary inspiration is also effected by the levatores costarum (Fig. 232), as these muscles, arising from the transverse processes of the twelve dorsal vertebra?, and inserted fan-like into the upper edges of the ribs between the tubercles and the angles in contracting, elevate the ribs. The action of the mus- cles, which we have just considered, usually suffices to produce easy inspiration. When breathing, however, becomes difficult, labored, or very difficult, then inspiration is aided through the contraction of several muscles, the serratus posticus superior, accessorius, sterno-cleido-mas- toid, levator anguli scapulas, superior portion of the trapezius, serratus magnus, and the pectoral muscles. It is not necessary to dwell upon the anatomical disposition of these muscles to prove their importance in labored inspiration. It is evident that the serratus posticus superior passing from the vertebral column to be inserted into the second, third, fourth, and fifth ribs, will, in contracting, elevate the ribs, that the accessorius, extending from the last cervical vertebrae to the angle of the ribs, will produce the same effect. The sterno-cleido-mastoid acts upon the clavicle and sternum, and the levator anguli scapulae, trapezius, and serratus magnus, through the scapula. Finally, the upper extremities being fixed, the pectoral muscles reversing their action, will elevate the 1 Physiolosie. tome iii. p. 2fi0. - Precis c'lemeutaire de physiologie, 2d ed., tome ii. p. 323. 412 MUSCLES OF RESPIRATION. ribs; their force, under such circumstances, acting upon the thorax. instead of from it. Expiration. Expiration is essentially a passive process, consisting in the return of the thorax to the condition in which it was before inspiration. The ascent of the diaphragm, and the descent of the ribs in diminishing the capacity of the thorax, cause the expulsion of the air, or expiration. The relaxation of the inspiratory muscles is, however, accompanied by the contraction of certain muscles which together with the elasticity of the lungs aids in expelling the air from the chest. Inasmuch as the fibres of the osseous portion of the internal intercostal muscles (Fig. 232) pass from rib to rib in exactly the opposite direction as those of the internal intercostal — that is, from above downward, but backward — we would natually conclude that in contracting they would depress the ribs instead of elevating them, that their function is expiratory instead of inspiratory. Experiment proves that this view is correct, since, if the osseous portion of the internal intercostal muscles be exposed in a living animal by dissecting off the external ones, they will be found to contract during expiration. We generally illustrate this antagonism in the action of the internal and external intercostal muscles by a simple mechanical arrangement known as Hamberger's apparatus, though it was really invented by Bernouilli. This consists (Fig. 233, A) of two bars (a and b), which are attached Fig. 233. 1 b Diagram of models illustrating the action of the external and internal intercostal muscles. B, inspiratory elevation ; C, expiratory depression. (Huxley.) on the one hand to a long vertical rod (c) firmly supported, and, on the other hand, to a short one (d). The two bars, the long and the short vertical rods, represent respectively the spinal column, two ribs, and a portion of the sternum. The two bars (a and b) are maintained in the horizontal position by two elastic bands (zvz and xy), which are so attached that as they pass from bar to bar they cross each other at right angles. The elastic band (x y) passing from above, downward and forward, represents the external intercostal muscle, the band (w z) passing from above downward, but backward, the osseous portion of the internal intercostal muscle. If the band (w z) be removed (Fig. ACTION OF INTERCOSTAL MUSCLES. 413 233, B), there being nothing to oppose the elasticity of the band xy, or the external intercostal muscle, the bars or ribs will be elevated. If the band w z be now replaced, and the band xy removed (Fig. 233, 6'), then the bars or the ribs will be depressed, there being nothing to oppose the elasticity of the band w z. While the action of the external and internal intercostal muscles in respiration, as we have described them, appears to be capable of demonstration in the living animal and imitated by mechanical contrivances, nevertheless, it must be admitted that the action of these muscles has given rise to more discussion than that of all the other muscles in the body, and that the most diverse opinions have been offered, and are still held as to their function. Thus, while according to Borelli, Haller, and Cuvier, both the external and internal intercostal muscles are inspiratory, just the opposite opinion, that they are both expiratory, was held by Vesalius, Beau and Maissiat and Galen. Bartholinus considered the ex- ternal intercostals to be expiratory, the internal inspiratory, while Spigelius and Vesling held the external intercostals to be inspiratory, the internal expiratory. The external and internal intercostals were regarded at once inspiratory and expiratory by Mayow and Magendie, while according to Arantius and Cruveilhier, both the internal and external intercostals are passive in inspiration and expiration, perform- ing simply the office of a resisting wall in respiration. Whatever view may be held as to the function of the internal inter- costal muscles in respiration, there can be no doubt that the triangularis sterni and infracostalis, and usually the serratus posticus inferior are expiratory muscles. The triangularis sterni acting from its origin, the ensiform cartilage, the lower border of the sternum, and the lower costal cartilages, in drawing down the cartilages of the second, third, fourth, and fifth ribs must diminish the capacity of the chest. The infracostales produce the same effect, their fibres passing from the inner surface of one rib to the inner surface of the first, second, and third below, their action being from below upward. The muscles that we have just described usually suffice in tranquil expiration ; in difficult or labored expiration, in the acts of blowing, phonation, etc., the muscles entering into the formation of the abdominal walls also come into play. The general effect of these muscles, viz., the external and internal, oblique transversalis, sacro-lumbalis, etc., is in contracting to push up the ab- dominal viscera and diaphragm into the thorax, diminishing its capacity in the vertical diameter; these muscles, however, in being attached to the ribs or costal cartilages depress at the same time the ribs and con- sequently diminish the thorax in its antero-posterior and transverse diameters also. The effect of the action of these muscles is, therefore, to aid powerfully in the expulsion of the air from the chest in forced expiration. As their action and that of the diaphragm is more or less voluntary, and being at the same time opposed to each other, the in- tensity and duration of expiration can, to a great extent, be regulated arbitrarily ; the importance of this relation is well seen in singing, in performing upon wind instruments, etc., the skill exhibited depending largely upon the nicety with which the contractions of these muscles can be adjusted to each other. 414 MUSCLES OF RESPIRATION. We have already seen that the lungs arc elastic, and were it not for the pressure exerted upon the inner surface of the lungs by the inspired air the lungs would collapse in virtue of this elasticity, and a considerable space in consequence would be left between the lungs and the chest-wall. The natural tendency of the lungs to contract through their elasticity is well seen when air is allowed to enter the pleural cavities. Under such circumstances the atmospheric pressure being exerted equally on both the inner and outer surfaces of the lungs, there is nothing to oppose their elasticity and the lungs therefore collapse. If one end of a tube be passed into the trachea of an animal just dead, and ligated, and the other end be inserted into a water or mercurial manometer, with the entry of air through an opening made into the pleural cavity the lungs will collapse in virtue of their elasticity, the level of the liquid in the proximal end of the manometer will be observed to fall, that of the distal end to rise, the difference in the level of the two indicating and meas- uring the amount of elastic force exerted. It was in this way that Carson 1 first showed that the elasticity of the lungs in the calf, sheep, or dog would support a column of water twelve to eighteen inches in height, and in the rabbit six to ten inches. The elastic force of the lungs amounting to half a pound on the square inch in man, not only aids the expiratory muscles, therefore, in expelling the air from the chest, but through the suction force exerted also elevates the diaphragm, restoring it to the dome- like form it presents before inspiration. Finally, the contractility of the bronchi and elasticity of the thoracic walls themselves contribute in ex- pelling the air from the chest. It is usually considered that in inspira- tion the upper ribs are elevated before the lower, and in expiration the lower ribs are depressed before the upper, the motion being wave-like from above downward and from below upward. According to the recent observations of Rausome 2 it would appear, however, that the reverse ob- tains, the lower ribs in inspiration being elevated first and the upper ones last, and that in expiration it is the upper ribs that are depressed first and the lower ones last. Even if such is the case, it is not inconsistent with the view that the upper part of the chest is moved first in inspiration, the lowest last, since if the scaleni act before the intercostal muscles the upper ribs would be elevated before the lower by the action of the scaleni, even if the lower intercostal muscles contracted before the upper. It is possible that the difference of opinion in reference to the order in which the ribs are elevated and depressed is due to the action of the intercostal muscles, being considered without reference to the simultaneous action of the other respiratory muscles. While, in a general w T ay, it can be said that inspiration is due to the descent of the diaphragm and the ascent of the ribs, and expiration to the ascent of the diaphragm and descent of the ribs, nevertheless there is a noticeable difference, more particularly studied by Bean and Maissiat, 3 as to the relative importance of the parts played by the diaphragm and the ribs, as observed in the breathing of the two sexes. Thus while in the male sex breathing is accomplished by the diaphragm and the in- i Phil. Trans , 1820. " Stetliometer, 1876, p. 37. 3 Archives generates de medecine, 1843, 3d ser. t. xv. p. 307 ; 4th ser. 1843, t. i. p. 2U5 ; t. ii. p. 257 ; t. iii. p. 249. DIFFERENCE OF RESPIRATION IN SEXES. 415 ferior part of the thorax, or the portion below the sixth rib, in the female sex it is the superior part of the chest, or that above the seventh rib (Figs. 234, 235), which takes an active part in respiration. It might be Fig. 234. Fig. 235. The changes of the thoracic and abdominal walla of the male during respiration. The same in the female. (Hutchinson.) supposed that the superior costal type of breathing characteristic of the female is due to peculiarities of dress, such as the wearing of corsets, the squeezing of the waist, etc., which would interfere with or prevent even the lower part of the chest expanding. That this is not the only cause, however, is proved by the fact that the superior costal type of breathing prevails even in females that have never at any time worn any kind of clothing whatever. That the superior costal type of breathing is of advantage to the female is obvious when one considers the extent to which the abdominal viscera and diaphragm are pushed up, as is the case during pregnancy, through the enlargement of the uterus. Under such circumstances, if the breathing of the female was of the inferior costal type and diaphragmatic, like that of the male, inspiration would be difficult and labored. It is also on account of this peculiarity in breathing that women can tolerate with so little inconvenience large accumulations of fluid in the abdominal cavity. While in the adult the diaphragmatic inferior costal type of respiration of the male as contrasted with the superior costal type of the female is perfectly evident, the dis- tinction in young children is not noticeable. Indeed, children under about ten years of age breathe almost entirely by the diaphragm. It is not, as a general rule, until near puberty that the distinction in breathing characteristic of the adult sexes becomes apparent. Haller, 1 however, states that the difference in the types of breathing in the sexes in some cases manifested itself as early as the first year. 1 Pralectiones Academne, tomus v. p. 144. CHAPTER XX VI I I . INSPIRATORY MOVEMENTS AS STUDIED BY THE GRAPHIC METHOD. Notwithstanding that the respiratory movements are evident to the eye, and that the respiratory organs can be connected without injury with apparatus for recording their movements, it must be admitted that the application of the graphic method to the study of respiration does not give as satisfactory results as is the case in the study of the circula- tion. Of the instruments devised for the recording of the respiratory movements graphically, we have found the pneumograph and steth- ometer to be among the most useful. The pneumograph, invented by Marey, 1 in its present form, modified by Verdin (Fig. 236), consists of an elastic plate A, having an area of 26 cm. (4 square inches), which Fig. 236. Pneumograph. is applied to that part of the chest whose movements it is desired to study, and firmly secured there by tapes passing around the neck from the edge of the plate and around the chest from the pillars B and C, pro- jecting from the plate. To the lower end of the pillar B is attached a spring (D), the free end of which is so attached that it presses against the elastic membrane covering in the lower surface of an air-drum (E), the latter communicating through a caoutchouc tube (F), with a recording tambour. With the bending of the elastic plate A through the expansion of the chest, the pillars B and C recede from each other, the spring D ceasing at the same time to press on the membrane of the air-drum E. The air within the drum being therefore rarefied, the air from the re- cording tambour is drawn into it, and the lever attached to the tambour is depressed. With the contraction of the chest the elastic plate straightens, the pillars approach each other, the spring presses again the elastic membrane, the air is driven out of the drum into the tam- bour, and the lever is elevated. The depression of lever corresponds, therefore, to inspiration, the elevation to expiration. By placing the lever of the recording tambour in contact with the blackened surface of La methode Graph ique, p. 542 METRONOME, 417 the cylinder moving by clockwork, we obtain a trace like that of Fig. 237, representing the breathing of a man set. thirty years. In this trace the distance from a to c represents one inspiration ; the part of the trace from a to 5, due to the descent of the lever, being inspira- Fig. 237. Upper line, trace of chronograph. Lower line, trace of respiratory movements Taken with pneumograph . tory in orgin, that of b to c due to the ascent of the lever expiratory. It will be observed that the inspiratory movement, as recorded in its trace, a to b, is extremely abrupt, becoming more gradual at its close, and that the expiratory movement (b to c) is equally abrupt at the Fig. 238. beginning, but that the gradual movement at the termination is more marked even than in the case of the inspiratory movement. In order to determine accurately the number of respirations in a given time, the length of time of one respiration, the relative duration of one expira- 27 418 RESPIRATORY MOVEMENTS. tion and inspiration ; the existence of pauses, if any, after inspiration and expiration, it is necessary to make use of some chronographic appa- ratus, by means of which we can record graphically the time elapsing during which the respiratory movements are being studied. For this purpose we make use of the metronome in connection with an electro- magnet. The metronome (Fig 238) is the same as that used by musi- cians, except that it is so constructed that, in a definite ratio of each beat of the pendulum a spring is elevated and depressed, to which are attached two needles, dipping into mercury cups. This is accomplished by drawing out or pushing in a rod to which the spring carrying the needles is attached, and which, by so doing, brings the spring in contact with the periphery of either one or four wheels having a different number of cogs. The number of movements of the spring will depend, therefore, upon the particular wheel with whose cogs it is in contact. The four wheels are rotated by the axis common to them, a fifth one, whose motion is due to the axis, being moved by clockwork, which is regulated by a pendulum. With the elevation of the spring the needles are raised out of the mercury in the cups, and with its de- pression they sink into it again. As the needles are elevated and depressed the current, passing from the battery through the needles and mercury to the electro-magnet, is made or broken, and the marker con- nected with the latter synchronously depressed and elevated in the manner already described. In the trace obtained by applying the marker of the electro-magnet to the blackened surface of the revolving cylinder, the difference between, in this instance, each of the two verti- cal lines is equal to one second, the pendulum beating at the rate of sixty seconds to the minute, and the spring coming in contact with the cogs of the second wheel. The experiment lasting one minute, the number of respirations was determined to be twenty, a little over what we shall see is the usual average. It will be observed from a comparison of the traces (Fig. 237) that the duration of one respiration was three seconds, the inspiratory part lasting one second, the expiratory two seconds, and that the expiratory lasted, therefore, twice as long as the inspiratory effort ; further, that there was no appreciable pause, either after inspiration or expiration, a gradual slowing up of the movement only being noticeable after either. Finally, the little undulations of the trace noticeable at the termination of expiration are cardiac in origin. The object of the stethometer is not only to record the respiratory movements graphically, but to determine also their extent. The instru- ment, as devised by Sanderson, and constructed for the author by Hawksley, consists (Fig. 239) of two parallel bars, 30 cm. (12 inches) in length, the lower ends of which are firmly screwed at right angles into a crossbar so as to form a rigid frame. Through one of the bars passes a slender rod (B'), terminating in a convex ivory knob (B). By means of a screw the extent to which the rod and knob are pushed within the frame can be varied as needed and firmly fixed. The opposite bar carries a spring (I), the upper part of which carries a horizontal pin, terminating at one end in an ivory knob, and at the other in a brass disk, the latter being in contact with the tambour (A) attached to the ST ETHO METER. 419 upper part of the bar. The two ivory knobs not only face each other, but lie in the same avis. The receiving tambour communicates by means of the tube J with the recording portion of the apparatus, and also through the T tube with an India-rubber ball, the latter being used to fill both tambours and communicating tube (D). Fig. 239, Recording stethometer. A. Tympanum. B. Ivory knob. B'. Rod which carries the kuob opposed to B. C, T-tube, by which A communicates, on the one hand, with the recording tympanum, on the other wiih an elastic bag (D). Thi purpose of the bag is to enable the observer to vary the quantity of air in the cavity of the tympana at will. The tube leading to it is closed by a clip when the instrument is in use. (Sanderson.) The manner of adapting the stethometer to the chest will depend upon the part whose movement it is desired to examine. If, for ex- ample, we wish to obtain a graphic representation of the movements of the chest in a transverse direction, let the instrument be so applied that the ivory knobs will press upon the eighth rib. The knob being firmly fixed with the expansion of the chest, the rib will press outwardly the knob of the receiving tambour, the air will be driven out of it into the recording one, and the lever will be elevated ; with the contraction of the chest the air will return from the recording to the receiving tam- bour lever, and the lever will be depressed. With the stethometer, therefore, inspiration corresponds to the elevation of, and expiration to, the pressure of the recording lever, just the opposite to what happens, as we have seen, when the pneumograph is used. To obtain a trace representing the enlargement of the chest in an antero-posterior direc- tion, the stethometer can be applied so that the ivory knobs are in con- tact with the manubrium sterni and the third dorsal spine, or the ensi- form cartilage and the tenth dorsal spine respectively. Fig. 240 is that of the trace obtained by the stethometer as applied to the seventh ribs 420 RESPIRATORY MOVEMENTS. iii the case of a healthy man, jet thirty years, and is a graphic repre- sentation, therefore, of the respiratory movements, in so far as they depend upon the enlargement of the chest in a transverse direction in Fig. 240. that particular part of the chest. It is not necessary to dwell upon the peculiarities of the trace recorded by the stethometer. It will be ob- served that the part of the trace from a to b corresponds to the inspira- tion, that from b to c to expiration, and that the relative duration of inspiration to expiration is somewhat different from that observed in the trace obtained by the pneumograph, the number of respirations being in this case eighteen to the minute. Here and there, it will be noticed that the breathing became more marked. In order to deter- mine the extent of the enlargement of the chest by the stethometer, the instrument must be graduated. This can be done either by placing successively between the ivory buttons rods differing by a known length, and observing the different levels to which the lever is elevated, accord- ing to the rod used, the vertical distances between the horizontal lines made by the lever corresponding to a definite increase in the distance between the ivory knobs of the particular diameter of the chest ex- amined, or by placing directly underneath the ivory knobs a graduated rod, carrying a vertical slide, which can be pushed against the movable knob, and noticing the different heights to which the recording lever is elevated In the trace represented in Fig. 240, the elevation of the lever through the space a to b corresponds to an increase of about 2 mm. (y^th of an inch) in the lateral diameter of the chest. While in tranquil breathing the increase in the antero- posterior diameter of the thorax may be only one mm. (23-th of an inch) inforced breathing, according to Rausome, 1 it may amount to as much as 12 to 30 mm. (i to 1.2 in.). In describing; the circulation it will be remembered that attention was called to the large undulations present in the curve of blood pressure, 1 Sanderson : Handbook Phys. Lab., p. 302. TRACES OF BLOOD PRESSURE. 421 and which at that time were simply stated as being, to a certain extent at least, respiratory in origin. In order to study the influence of the respiration upon the circulation, it is essential that a compari- son should be made between the curves of blood pressure and respira- tion taken simultaneously. In the case of man this can be done by applying at the same time the cardiograph and pneumograph and comparing the traces so obtained, or in an animal by connecting a recording tambour with its trachea, and comparing the respiratory trace so obtained with that of the pressure of the blood in its carotid artery, taken in the manner already described. A comparison of the traces of the respiratory movements and the blood pressure in a rabbit (Fig. 241), taken by the latter method, shows that in this case at least the insniration is almost, if not absolutely, synchronous with the rise of \AAI\AAAAAfO\J\AJ\NXAAJ Traces of blood pressure and respiratory movements of rabbit taken simultaneously. Upper trace blood pressure. Lower trace respiratory movements. blood pressure and expiration with the fall, the relation between the two naturally suggesting that inspiration is the cause of the one, expiration of the other. Nevertheless, reflection makes it clear that respiration on the whole favors the circulation of the blood even though inspiration promotes it to a greater extent than expiration. Let us consider in detail a little why this must be the case. During inspiration, as the chest expands, the air within the lungs becomes rarefied and the external air passes through the trachea from without inward. In doing this, however, the external air has overcome the elasticity of the lungs, the pressure exerted by the air within the lungs upon the intrathoracic vessels will therefore be that of the ordinary atmospheric pressure, less the pressure due to the elasticity of the lungs. Suppose, for example, that the pressure exerted by the elasticity be half a pound to the square inch, then the pressure exerted by the air within the lungs upon the great bloodvessels will be only fourteen and a half pounds, that of the atmosphere being fifteen pounds. The effect of this difference of the atmospheric pressure within and without the chest during inspiration is that a greater quantity of venous blood being forced through the great veins toward the right auricle of the heart and thence through the lungs, a proportionately greater quantity of arterial blood passes, there- fore, through the left ventricle into the aorta, the result of which will be to increase the blood pressure. The flow of the venous blood from the periphery to the heart being promoted by inspiration, it might be supposed that the flow of the arterial blood in the reverse direction would be proportionally retarded. It must be remembered, however, that the pressure exerted by the extrathoracic air upon the thin, flaccid 422 RESPIRATORY MOVEMENTS. Avails of the veins will produce a greater effect than upon the thick, resisting coats of the arteries, and that the pressure of the external air so exerted is not much in excess of the resistance that the heart has to overcome in driving the blood from the ventricle into the arterial system during its systole. Further, during expiration the conditions are the reverse of those obtaining in inspiration, the intra thoracic pressure being now greater than the extrathoracic. The pressure so exerted now adds itself to the elasticity of the arteries and promotes the flow of the blood from the heart to the periphery, while the valves prevent to any extent regurgitation of the venous blood.' Respiration, on the whole, therefore, favors the circulation, since inspiration aids the flow of the venous blood without offering any great obstacle to the arterial flow, while expiration favors the flow of the arterial blood without retarding to any extent the venous flow, and while it is true that in the influence of respiration upon the circulation, inspiration is more impor- tant than expiration, nevertheless the difference in the effect of the two is too small to warrant the conclusion that the large rise and fall in the blood pressure are entirely caused by inspiration, on the one hand, and expiration on the other. Further, in the dog and in the rabbit also, at times, there is no absolute synchronism between the vascular and respi- ratory rhythms ; in the dog, for example (Fig. 242), the rise in the blood pressure lasting not only to the end of the inspiration, but during a part Fig. 242. Comparison of blood pressure curve with curve of intrathoracic pressure. To be read from left to right. a is the Hood-pressure curve, with its respiratory undulations, the slower heats on the descent being very marked, b is the curve of intrathoracic pressure obtained by connecting one limb of a manometer with the pleural cavity. Inspiration begins at i, expiration at e. The intrathoracic pressure rises very rapidly after tin/ cessation of the inspiratory effort, and then slowly falls as the air issues from the chest ; at the beginning of the inspiratory effort the tall becomes more rapid. (Foster.) of expiration, and the fall in blood pressure lasting not only till the end of expiration, but during a part of inspiration. This want of syn- chronism between the rhythms, together with the fact that the large undulations characteristic of blood pressure persist even after all respi- ratory movements have ceased, proves that there must be some influence other than respiration concerned in their production. Thus if an animal, a rabbit, for example, be curarized, in which condition the respiratory nerves cease to act altogether, the heart continues to beat, artificial respiration be maintained and a trace of the blood pressure be taken, a carve like that of Fig. 242 will be obtained. If now the artificial respi- MAINTENANCE OF ARTIFICIAL RESPIRATION, •±23 ration be discontinued the blood pressure rises, while the character of the curve changes; nevertheless, a rhythmical rise and fall still occur, like that of Fig. 242, b. The curve so obtained is known as that of Traube, from having been first described by that observer. Inasmuch as respiration has entirely ceased and both vagi even being divided, it \ A I Fig. 243. A^ IM ! !\ It f\ i\ \ MM \W\\ \ \l\i\!\i Mil! 1/ MI « " ^ It V \ •' I ! if i! iJ k' V i/' i J! ! « •' I ! U H II i' 1/ i A / l . / i i ' ! \! I i V \i U A ". I ft Si vii Tranbe's curves. (Foster) is evident that the large undulations cannot be due to respiration. The only way of accounting for them is by supposing that they are of vaso- motorial origin, the rhythmic rise and fall in the blood pressure, through the rhythmic constriction of the arteries, being due to a rhyth- mic stimulus emanating from the vasomotor centre of the medulla. This view is confirmed by the following facts : that the phenomena in question are much less marked if the spinal cord be divided below the medulla, and that the undulations persist even after the heart itself be removed, and the circulation be maintained artificially. It is difficult to under- stand why the vascular rhythm, due to the vasomotor centre, should simulate and be superimposed upon the respiratory rhythm due to the medullary respiratory centre, unless through conditions in the evolution of the animal and which we are not familiar with, the two centres in the medulla have been gradually brought to act synchronously. It will be seen, therefore, that while the rise and fall in the blood pressure are influenced by inspiration and expiration, the phenomenon is independent of respiration, or probably that both are influenced by a common cause, the condition of the blood in the medulla acting as a stimulant to the vascular and respiratory centres. In the study of the circulation and respiration, as in the present case, it is often necessary to maintain artificial respiration. We take the oppor- tunity, therefore, of describing the apparatus made for us by Hawksley, 424 RESPIRATORY MOVEMENTS. of London, and which we have found useful in effecting this object. The apparatus is essentially a mercurial pump, and consists (Fig. 244) of two chambers, cast-iron cylinders (A and 13, B not seen in Fig. 244), concentrically disposed and firmly fixed in a solid frame (C). The Fig. 244. Mercurial pump fur artificial respiration. upper space D between the cylinders contains mercury, through which the bell-jar E covering the internal cylinder B is elevated or de- pressed by the vertical motion of the rod F connecting it with the wheel G, to the rotation of which the motion of Fig. 245. ^ e ro( j j a due. The internal cylinder B opens externally through the two brass nozzles H and I. Each of these nozzles is provided with a valve, which, however, open in opposite directions — that of H from without inward, that of I from within outward. As the bell-jar is elevated the air passes through H into the internal cylinder, and canuia. as it descends the air passes out of it through I, and thence by means of a tube terminating in a canuia to the trachea of the animal whose respiration is to be maintained artificially. The canuia that we use for insertion into the trachea is that of Ludwig, and consists of a tube of glass (Fig. 245) of which the end a, when in situ, faces the lungs and through which the air to be inspired passes, the expired air escaping by a small opening RESPIRATORY MURMUR. 425 The rotation of the wheel G, to which the action of the respiratory pump is due, is effected by a Backus water motor (K) to which the wheel is connected by the band I. The water supplying the motor is conveyed to it from the hydrant in the laboratory by the tube M and away from it to the waste-pipe by the tube N. In ordinary tranquil respiration no sound is heard unless the ear be applied directly to the chest, excepting Avhen the mouth is closed and the breathing exclusively nasal, then a soft murmur accompanies both inspiration and expiration. If the ear, or, better, the stethoscope, be successively applied over the trachea and the chest, a very noticeable difference will be observed in the character of the sound heard, as the air passes through these parts both in inspiration and expiration. As might be expected, as the air passes in and out of the trachea, the character of the sound is tubular. In inspiration, the sound, attaining its maximum intensity immediately, maintains it to the close of the act, when it rather suddenly ceases. Immediately, or after a very brief interval, the expiratory sound follows, attaining soon its maximum intensity, but, unlike the inspiratory sound, rather dying away than ceas- ing abruptly. As the air passes into the small bronchial tubes and expands the pulmonary air cells it gives rise to a sound difficult of description, and which can only be appreciated by being heard. It is usually de- scribed as being of a breezy or vesicular character, and is less intense than the tracheal murmur. The sound gradually increases in intensity fi*om the beginning to the end of inspiration, and ceases rather abruptly. The inspiratory murmur is followed without any interval by the expiratory one, lower in pitch, less intense, and lasting a shorter time. It must be mentioned, however, that the expiratory murmur is frequently absent. Certain modifications of the respiratory sounds and movements, such as snoring, coughing, sneezing, sighing, yawning, laughing, sobbing, and hiccoughing need only a passing notice, since they are simply exaggerations of either the inspiratory or expiratory movements, or of both. Snoring, a sound too familiar to need de- scription, occurs when the mouth is open, and is due to a vibration or flapping of the velum palati between the two currents of air from the mouth and nose together with a vibration of the air itself. Coughing and sneezing, usually involuntary acts, consist in a deep inspiration, followed by a convulsive expiration, differing only in degree, the air in the first instance being expelled by the mouth, in the second by both mouth and nares. Sighing and yawning are due to the same cause — want of oxygen in the blood — and differ from each other only in the former being voluntary, the latter involuntary. In both these acts a prolonged and deep inspiration is followed by a quick and usually audi- ble expiration. Laughing and sobbing, though expressing very differ- ent emotions, are pi'oduced very much in the same way, and are the result of short, quick, convulsive movements of the diaphragm, which are accompanied by the action of the facial muscles producing those changes in the features so characteristic of joy or sorrow. Laughing and sobbing, like yawning, are, so to speak, catching, or contagious. Hiccough is a purely inspiratory act, and consists in sudden convulsive involuntary contractions of the diaphragm, the glottis constricting spasmodically at the same time ; the well-known sound is due to the 426 RESPIRATORY MOVEMENTS. air striking against the closed glottis. Hiccough is frequently caused by partaking too rapidly of dry food or effervescing and alcoholic drinks, and is not an infrequent symptom of disease. It is obviously of importance that the number of respirations in a given time be determined as accurately as possible. A great difference of opinion, however, ha,s prevailed, in this respect, among physiologists, Haller, 1 for example, giving twenty respirations a minute as the normal number; Magendie, 2 fifteen ; Milne Edwards, 3 sixteen to twenty-two. This disagreement in the result of ;i mere matter of observation is due, in some instances, to the number of cases examined having been too limited to warrant a general conclusion, and, in others, to influences modifying the number of respirations within the limit of health not having been taken into consideration. The importance of examining a great number of cases before drawing any conclusion as to the average number of respirations per minute is well shown by the observations of Hutchinson. 4 Of 1887 cases examined (Table L1X.), in 561 the number of respirations was found to be twenty per minute ; in 239 cases, sixteen per minute; in 79 cases, nine to sixteen per minute. Such a difference in the number of respirations, as observed in these three sets of cases, and also of the remaining ones of the table, prove that there must be numerous conditions influencing the rapidity of the respiratory movements as we have seen is the case with the pulse. Table LIX. 5 — Respirations. Per minute. No. of cases. Per minute. No. of cases 9 to 16 . 79 21 . . 129 16 . . 239 22 . . 143 17 . . 105 23 . . 42 IS. . 195 24. . 243 19 . . 74 24 to 40 . 78 20 . . 561 In a total of these 1887 cases the majority breathed 16 to 24; one- third 20 respirations per in mute. Among these the influence of age is very important, thus, as shown by Quetelet 6 (Table LX.), the number of respirations at birth are more than double the number at twenty years of age, and from this age upward the number of respirations diminishes. It is evident, therefore, that the number of respirations per minute, as deduced from the examination of a number of individuals, will depend, eceteris paribus, upon their age; and we should expect to find young persons breathing more rapidly than old ones. It will be readily understood, therefore, Avhy 560 persons, on an average, should be found to breathe twenty Table LX. — Respirations at Different Ages. Per mil. ill'-. Age. 44 At birth. 26 ......... 5 years. 20 15 to 20 years. 19 20 to 25 16 30 18 30 to 50 " 1 Elemeiita Physiologic, t. iii. p. 289. 2 Precis elementaire de Physiologie, t. iii. p. 337. 3 Physiologic, tome ii. p, 480. 4 Cyclopaedia of Aunt ami I'hys., vol. iv part 2, p. 1085. 6 Hutchinson, op. cit. 6 Quetelet : Sur Tliomme, etc., 1835, t. ii. p 84, NUMBER OF RESPIRATIONS. 427 times per minute, and 239 persons only sixteen, if the first set ex- amined are. on an average, younger than the second set. In speaking of the various conditions that modify the number of cardiac beats in a given time, the influence of size was noticed, it being mentioned that the number of cardiac beats in a given time was more numerous in the young and small child, and young and small animal, than in the adult man or large animal. Now, the same relation that we have just pointed out as existing between youth and the num- ber of respirations in man, will also be found to prevail if large animals are compared with small ones, or if the same animal be compared at different ages. Thus, as observed by Milne Edwards, 1 and by the author, while the number of inspirations in the whale is only about four or five in the minute, and in the rhinoceros, hippopotamus, giraffe, and horse ten to the minute, the number of respirations are thirty-five or more in the same period of time in the rabbit and guinea-pig, while, according to Colin, 2 the number of respirations being thirteen to six- teen in the sheep, will be sixteen to seventeen in the lamb; in the cow- fifteen to eighteen ; in the calf, eighteen to twenty ; in an adult dog, fifteen to eighteen ; in the young dog, eighteen to twenty. The cause of this difference in the number of respirations, according to the age and size of the animal is, no doubt, due, as in the case of the number of cardiac beats, to the same cause, that of the vital processes generally being more active in small animals than in large ones. Sex stems to influence but little the number of respirations, no appreciable difference being observed in boys or girls ; young men, however, breathe a little more rapidly than young women of the same ag< . Everyday experience teaches us to what an extent respiration may be accelerated by nervous excitement and exercise. The influ- ence of muscular exertion is not limited simply to active exercise, the mere change from the recumbent to the sitting position, or of standing up. will inciease the respiratory movements. Thus, Dr. Guy states that lying down the number of his respirations was 13 per minute, while sitting 19, and when standing up 22. As might be expected, during sleep the number of respirations is diminished, according to Quetelet, 3 the diminution being about 1 in 4. or 2o per cent. It will be seen, from what has just been said, that the number of respirations must vary very much within the limits of health; and that, therefore, only an approximately average number can be ascertained. Of 1887 cases examined by Hutchinson, 4 llol breathed from 16 to 24 times, and nearly one-third of them 20 times a minute. The average number of respirations we have found to be from 18 to 20 times a minute, and we may add here, incidentally, that during each respiration there are about four heart beats. Mechanical Work Performed during Respiration. It will be remembered that, in describing the circulation, it was esti- mated that the mechanical work performed by the heart amounted, in 1 Physiologie, tome ii. p. 7 Physiologic Compares, t. i:. p. 152. ■' ; Op. fit., p. 88 * Op. i it, p. 1085. 428 RESPIRATORY MOVEMENTS. twenty-four hours, to 128 tons. We shall see, hereafter, in the inves- tigation of the sources of the forces of the body, that it is equally important to determine, as far as possible, the mechanical work per- formed by the respiratory muscles in the same period of time. This may be estimated, at least approximately, in the same way as in the case of the heart, by multiplying the weight by the height raised. It has already been mentioned that the intrathoracic is less than the extra- thoracic pressure, owing to the elasticity of the lungs offering a resist- ance to the inspired air distending them. It is evident, therefore, that, at each inspiration, the chest lifts so much of the external atmosphere pressing down upon it as is not opposed by the corresponding part of the internal atmosphere, or that part opposed by the elasticity of the lungs. Now the difference between the intra- and extrathoracic pressure, or the excess in weight of the external over the internal air, can be pretty accu- rately determined by inspiring air out of a mercurial manometer through one nostril, the mouth and other nostril being closed. Let us admit that about 40 cubic inches of air be inspired in this manner, and, with Donders/'that 57 mm. of mercury (2.2 inches) be sucked up in the proximal limb of the manometer, and that this represents the excess in the pressure of the external over the internal air ; and further, that we add 15 mm. to this on account of the resistance of the lungs, then by multiplying 72 mm. (2.8 inches) by 20 sq. decim. (133 inches), or the area of the thoracic walls, the quotient, 1440 sq. decim., or 194.4 kilom., or about 427.68 pounds, will be the weight in mercury raised by the inspiratory muscles of the thoracic walls. Let us also suppose, with Fick, 2 that in raising this weight the thoracic walls traverse a distance of 0.001 meter (about -gVth of an inch), then the quotient of 194.4 kilom. by 0.001, or 0.1944 meter kilogrammes (1.4 foot-pounds) will be the work done — that is, the inspiratory muscles of the thorax do an amount of work equal to raising 1.4 pounds through one foot. In the same way, by multiplying the area of the diaphragm 3.5 sq. decim. (about 57 sq. in.) by 82 mm. of mercury, 10 mm. being added to the 72 on account of the abdominal pressure, the quotient, 287 sq. decim., or 38.7 kilom. (about 85.14 pounds), will be the weight raised by the diaphragm. Multiplying the latter, or 38.7 kilom., by 0.114 meter (about y 3 g-th of an inch), the distance traversed by the diaphragm, the quotient, or 0.44 meter kil. (3 pounds), will be the work done by the diaphragm ; and the total work 0.1944 + 0.44 = 0.63 meter kil. (4 -j- 3 = 4.4 foot-pounds) — that is, the work done by the inspiratory muscle, at each inspiration is equal to the work of raising 4.4 pounds through one foot. It will be observed that, during expiration, the mercury rises higher in the manometer than in inspiration ; for example, in an experiment where 2 inches of mercury were elevated in inspiration, 2J inches were elevated in expiration ; and further, that the difference in the level of the mercury during inspiration and expiration depends upon the depth of the inspiration. It might naturally be concluded, from these experi- 1 Physiologie des Menschen, Erster Band, S. 419. Leipzig, 1859. 2 Die Hedicinische Physik, S. 209. Braunschweig, 1866. WORK PERFORMED DURING RESPIRATION. 429 ments, that the expiratory force was greater than the inspiratory. It will be remembered, however, that expiration is due, not only to the passive relaxation of the inspiratory muscles, but to the active contrac- tion of the thoracic walls, due to their elasticity, which the inspiratory muscles, in dilating the thorax, must overcome, just as the air in enter- ing the lungs must overcome their elasticity. The force of the inspira- tory muscles is expended, therefore, not only in elevating the mercury in the manometer, but in overcoming the thoracic elasticity, which amounts to about half a pound (7.8 ounces) on the square inch. It is to this latter force which is due, during expiration, the excess just noticed in the elevation of the mercury in the manometer, and which may be taken as a measure of it. But since this force is overcome by the inspi- ratory muscles in dilating the thorax, it should be estimated as inspira- tory rather than as expiratory power. As in the experiment just per- formed, the excess of half an inch or more of mercury elevated during expiration is one-fourth that of the two inches elevated during inspira- tion, one-fourth of the mechanical work performed during inspiration as indicated by the manometer, should be added to the latter, which will make the amount of mechanical work done during each inspiration equal to 5.5 foot-tons, not including, however, the weight of the ribs lifted. It should be mentioned that it is only in deep inspirations that the opposing force offered by the thoracic walls, and to be overcome by the inspiratory muscles, becomes very apparent in the mercurial man- ometer. This is as might be expected, since the elastic force put forth by the thoracic walls in their reaction will be proportional to the extent to which they have been stretched by the inspiratory force distending them. It is for this reason that the mercury rises so little higher in expiration than in inspiration in the manometer during tranquil breath- ing. The mechanical work performed will be, therefore, less in tranquil than in deep inspiration. It is needless to mention that whatever estimate is accepted, it must vary with the capacity of the chest, number of respirations, etc., and can only be considered as approximately true. Admitting, however, that a mechanical work equal to raising 5.5 pounds through 1 foot is performed by the inspiratory muscles during each inspiration, and supposing further, that the individual inspires 18 times a minute, then 99 pounds are raised 1 foot during a minute, 5940 pounds during an hour, 142,560, or over 63 tons during the day. If, however, the chest be less expanded than we have supposed it to be, and proportion- ately less mercury sucked up out of the manometer during inspiration, and less expelled during expiration, for example, one-third less, and the number of inspirations be fewer, it is evident that the above estimate will be reduced to about 21-foot tons. Inasmuch as we have seen that expiration is rather a passive than an active process, a return to a condition of equilibrium, the work done by the expiratory muscles was not taken into consideration in the above estimate, and can, for the reason just given, be neglected. If, however, the expi- ration becomes active and deep, then the work performed may amount, as shown by essentially similar calculation, to nearly as much as that performed during inspiration. 430 I ; E srlKATOEY MO V K M E X T S . Breathing Capacity. On account of the importance of ventilation, of estimating the amount of oxygen absorbed, and carbonic acid exhaled, of determin- ing the amount of heat produced in the body, etc., it is necessary thai the amount of air inspired and expired during respiration should be accurately measured. For this purpose we make use of the spirometer. The instrument described by Hutchinson 1 , and somewhat modified by Rawksley for the author, consists (Fig. 246) essentially of a cylindrical vessel (A), with a capacity of about Fig. 246. 7.5 litres (2 gal.), containing water, out of which a receiver (B) can be elevated and depressed by breathing into it through a tube (C), and then the height to which the receiver is elevated and de- pressed, as shown by the scale D indicating the volume of the air expired and inspired. In using the spirometer, it should be placed upon a firm, level table, about three feet from the ground. The water tap then having been turned off, and the air tap opened, clear, cold water is poured through the spout of the cylindrical vessel A, until it is full, any excess of water run- ning off by the tap in commu- nication with the air tube. Enough colored spirit is poured into the U-shaped tube, until it stands at a level of about 3.5 inches. The counterpoising weights being then suspended within the framework M, and over the pulleys, and the air tap closed, the instrument is ready for an observation The person whose breathing capacity is to be determined standing erect with head thrown backward, and loosely attired, applies by the mouth-piece the flexible tube C to his mouth and expires into the spirometer. The air from his lungs passes thence into the tube E, elevating the receiver B, the volume of air expired, expressed in cubic inches, being shown by the number of the scale to which the index connected with the receiver has been elevated. At the termination of the expiratory effort, the air-tap must be closed. Each division of the scale corresponds to two cubic inches. The descent of the lever through an inspiratory effort, as indicated by the Hutchinson's spirometer. i Op, cit., p. 1069. TIDAI/ AIR- 431 scale read in the reverse direction, will give the amount of air inspired. The volume of air must, however, be corrected for temperature, for the temperature of the air will be at once reduced to the temperature of the water in the spirometer, to which it has passed, and which is warm or cold according to the season. Practically the change in the bulk of the air will amount to about 5-^ for every degree Fahr., and the difference should be added or subtracted as the temperature of the room in which is the spirometer is below or above 60°. Suppose, for example, 295 cub. in. be breathed into the spirometer, the temperature of the room being 55°, then 2.9 cub. in. should be added to the 295 cub. in., since --g-g- equals y^-jj- of 295, equals 2.95 cub. in. ; on the other hand, if the air be at a temperature of 70°, then 5.9 cub. in. should be subtracted from the 295, since -^ T equals -^ of 295, equals 5.9 cub. in. The U-shaped tube acts as a gauge, since, as long 1 as the colored fluid remains at the same level in its two limbs, the densit}- of the air within and without the receiver is the same, which is necessarily an indispen- sable condition in the working of the instrument. In order to expel the air from the receiver, and return it to its original position, the plug is removed with one hand, while the receiver is depressed with the other. The experiments having been concluded, and it is desired to empty the water out of the spirometer, it is only necessary to open the water-tap. If a healthy adult breathe easily into the spirometer in the manner indicated, it will be found that usually about 20 cub. in. pass into the instrument with each expiration. If now the air be expelled, and the receiver returned to its original position, and the air-tap be opened, fresh air will pass freely into the receiver, and, the pressure of the air within and without being the same, the receiver will be elevated by the counterpoising weights. Suppose a hundred cubic inches of air have been passed in this way into the receiver, and now a gentle inspira- tory effort is made, the receiver will descend, and it will be found that its index has fallen to the number 80 on the scale, showing that 1^0 cub. in. of air have been inspired. By experimenting in this way upon a number of persons, it will be found that, eceteris paribus, on the average, that in easy, tranquil breathing about 20 cub. in. of air are taken into the lungs Avith each inspiration, and about 20 cub. in. are given out with each expiration. In reality the expired air is about 5V' 1 ro "7 1 u t ' 1 ^ ess m volume than the inspired air. This is due, as we shall see, to the fact of the carbonic acid excreted being a little less in amount than the oxygen absorbed. The 20 cub. in, of air inspired and expired during each respiration are usually known as the tidal or ordinary breathing air. If now a forcible expiration be made, not only will 20 cub. in. of air pass into the spirometer, as in easy breathing, but as much as 100 additional cub. in. This extra quantity, so to speak, of expired air is not usually changed in respiration, but only when the necessity is felt of more com- pletely renovating the air in the lungs, and is called, therefore, the reserve or supplemental air, and amounts to about 100 cub. in. In pro- longed expiratory efforts, such as sneezing and blowing, this reserve air is more or less expelled. As the reserve air is vitiated through contin- ually receiving water and carbonic acid from the blood of the lungs, pearl-divers and others who are in the habit of temporarily arresting 432 RESPIRATORY- MOVEMENTS. their respiration, instinctively first get rid of their reserve air by forcibly expiring several times, and then fill their lungs with fresh air. If the chest be now enlarged by a forcible inspiration instead of an expiration, the spirometer having been suitably arranged, as much as 110 cub. in. can be withdrawn from the instrument over and above the 20 cub. in. due to an ordinary inspiration. This constitutes what is known as the complemental air, and usually amounts to 110 cub. in. It is drawn upon whenever an effort is made that demands a temporary arrest of respiration, in blowing, yawning, sneezing, etc., to a certain extent in sleep, when the breathing is deep, at the moment immediately preceding some muscular effort, etc. The complemental air can also be indirectly estimated by deducting the sum of the tidal and reserve airs (20 cub. in. plus 100 cub. in.) from the volume of the external breathing air, or that which can be expelled from the lungs by the most forcible expira- tion after the most profound inspiration, and which, we shall see in a moment, amounts to 230 cub. in. ; thus 230 cub. in. less 120 cub. in. equals 110 cub. in. The capacity of the lungs, and the fact that after death they always contain air, make it evident that the air is never entirely expelled, even by the most powerful expiration. A certain quantity of air, therefore, always remains in the lungs. It is known as the residual air, and may be approximately considered as amounting to 100 cub. in. The amount of the residual air cannot be determined directly, either in the living or dead body, since the volume of air Avithin the lungs after an ordinary expiration consists of the sum of the reserve and residual airs. If this, however, can be determined, the deduction from it of the reserve air will give the residual air. Now it is well known that hydrogen gas when inspired is not absorbed by the blood, and that gases will diffuse into each other until the mixture becomes uniform : availing himself of these facts, Grehaut 1 made the subject of his experiments inspire a definite quantity of hydrogen gas until the mixture of hydrogen and air became uniform, and then estimated by analysis of the expired air the quantity of air remaining in the lungs, and necessarily represented by the volume of the hydrogen lost. The amount of air — that is, the sum of the reserve and residual air — in the lungs at the beginning of the experiment can be then easily calculated, and was shown by Grehaut to amount to nearly 200 cub. in. Deducting from this the reserve air, or 100 cub. in., the remainder, 100 cub. in., is the residual air. Assuming the mean capacity of the chest to amount to 312 cub. in., and allowing 100 cub. in. for the heart and great blood- vessels, and 100 cub. in. for the parenchymatic structure of the lungs, there would remain little more than 100 cub. in. for the residual air, which is the estimate given by Hutchinson. 2 While the method just described gives a sufficiently accurate determi- nation of the respiratory capacity, more exact results are obtained when the tube of the spirometer communicates with a mask closely fitting to the face of the person experimented upon. The mask is provided with two openings furnished with valves working in opposite directions. Through one of the openings the expired air is expelled, while through 1 Journal de l'Anatomie, 1864, p. 523. 2 Op. cit., p. 1067. RESPIRATION APPARATUS. 433 the other the air to be inspired passes from the spirometer. A more simple and equally effective apparatus consists of two ivory tubes which are inserted tightly into the nostrils and which connect with a common tube, dividing into two branches; one of these communicates with the spirometer and transmits the air to be breathed, the other allows the expired air to escape. Each of the branches is provided with a valve which opens in opposite directions. According, therefore, to which of the ivory tubes is inserted into the nose the air can be either inspired from or expired into the spirometer. In determining the amount of air inspired or expired by an animal in a given time, we make use of a con- venient apparatus constructed for this purpose by Dr. A. P. Brubaker, and which, in principle, is essentially the same as that commonly known as Rosenthal's apparatus. It consists of a small spirometer (Fig. 247), Fig. 247. Brubaker' s respiration apparatus. the internal cylinder or gasometer (D) having a capacity of 700 c. cm. (43 in.) and equipoised by a bag of shot* Through the under part of the outer cylinder (E), which is firmly cemented to the stand, passes a T-shaped tube (D) connected with the tubes and valves which transmit the air to and from the gasometer. To one end of the tube (K) passing from the mask closely fitting to the face of the animal is adapted a tube 28 434 RESPIRATORY MOVEMENTS. (I) for transmitting the air to be inspired, and to the other end the tube and valve (M N 0) for carrying off the expired air. The valves (F N), just referred to, are the same as those used by Voit in his respiratory apparatus shortly to be described, and consist of oval glass bulbs con- taining mercury. It is evident that as Ions; as these valves are in the position shown in Fig. 247 the air will only pass in the direction indi- cated by the arrows. By reversing the valves (F N) the expired air will return back to the spirometer, and so can be measured. In using the apparatus the gasometer must be first raised by the hand through the whole extent or to a given height, the volume of air entering being determined by the scale. As soon as the gasometer has descended by the exhaustion of the air through the inspiration of the animal it must be raised again — that is, if the observation is to last any length of time. By connecting the tube Gr with a suitable reservoir the animal can be made to breathe any gas that is desired, and the amount inspired in a given time approximately determined, the Huid used in the spirometer will then depend upon the kind of gas. The manner in which the ex- pired gas is analyzed will be explained shortly. The great advantage of the apparatus just described, as compared with that of Rosenthal, is due to the fact of so little resistance being offered by either the valves or the gasometer, the air in fact being inspired by the animal with little or no exertion, whereas in Rosenthal's apparatus the valves used being Midler's, and the gasometer being immersed in mercury, the latter can be only raised with difficulty by a large animal and not at all by a small one. We have incidentally alluded, a moment since, to the extreme breath- ing capacity ; by this is meant the volume of air which can be expelled from the lungs by the most forcible expiration, after the most profound inspiration, or the volume that can be inspired by the most forcible in- spiration after the most profound expiration. It was called by Hutchin- son 1 the vital capacity, as signifying the capacity or volume of air which can only be displaced by living movements, and was determined by this observer to amount in a man of medium height (5 feet 8 inches) to 230 cubic inches, being equal to the sum of the tidal reserve and complemental airs. The experiments upon which this conclusion was based were made by means of the spirometer, upon nearly 5000 persons. Hutchinson also showed that the vital capacity is influenced by various conditions. Thus, it was ascertained that, for every inch of height between five and six feet, the extreme breathing capacity is increased eight cubic inches. The position of the body affects the vital capacity. Thus, in one indi- vidual while standing erect, it was 260 cubic inches, and when recumbent it was 230, a difference of 30 cubic inches. The vital capacity is influenced, without doubt, by weight, but, as the weight usually increases with the height, it is difficult to separate the effect of one from that of the other. Age has also an influence, the vital capacity increasing up to the thirtieth year of life, and then diminishing to the sixtieth. The vital capacity is also affected by the sex, being greater, as shown by Herbst, 2 in the i Op. cit., p. 1065. -' Meckel's Archiv f. Anat. u. Phy?., p. 3, S. 103, 1828. Graham's law. 435 male than in the female. As might be anticipated, any diseased con- dition affecting the mobility of the thorax or the dilatability of the lungs, -will modify, more or less profoundly, the extreme breathing capacity, hence the importance of the latter as a test of health or disease. Thus, should a person's vital capacity be found to be 190 cubic inches instead of 230 inches, a deficiency of 17 per cent., unless ex- cessively fat, it would be reasonable to suspect in such a person the presence of pulmonary disease ; and, yet, in phthisis, the vital capacity may be only 23 inches, the deficiency amounting to 201 inches, or 90 per cent., and yet life be maintained. 1 Inasmuch as the extreme breathing air is made up of the tidal reserve and complemental airs, the latter will be affected by the same conditions as the former. As the effects, however, are less marked than where the whole volume of air is considered, it will be necessary to call further attention to them. When it is remembered that, with each inspiration, only about twenty cubic inches of air are introduced, sufficient to fill the trachea and large bronchial tubes, it is evident that there must be some subsidiary force acting in addition to the ordinary respiratory move- ments of the chest by which the fresh air is brought to the air cells and the vitiated air expelled. The interchange between the fresh air in the upper part of the lungs and the vitiated air in the lower part, is un- doubtedly due to the diffusion of the air containing oxygen and carbonic acid, and which goes on, according to the law T established by Graham, 2 that the diff'usibility of gases is inversely proportional to the square root of their densities — that is, that the diffusion of oxygen is to the diffusion of carbonic acid as the square root of the density of car- bonic acid, or j/1.529 = 1.237, is to the square root of the density of oxygen, or t/1.1056 = 1.0514, or 1.237 : 1.0514 : : 95 : 81. Accord- ing to this law, then, the lighter gas, the air, with its oxygen, will descend more rapidly than the carbonic acid, the heavier gas, will ascend, 91 parts of oxygen replacing 81 parts of carbonic acid. As this diffusion is continually going on between these gases, the air in the pulmonary air cells, where the exchange between the oxygen and car- bonic acid takes place, has a tolerably uniform composition, and the aeration of the blood is far less intermittent in its character than the respiratory movements of the thorax. The passage of the oxygen from the air of the pulmonary air cells into the blood of the pulmonary capillaries, and of carbonic acid in the reverse direction from the blood into the air, is due to the fact of the tension of the oxygen of the air being higher than that of the blood, and of the tension of the carbonic acid of the blood being higher than that of the air. Necessarily, therefore, the oxygen of the air within the lungs will pass through the wall of the air cell and capillary into the blood, thence into the red corpuscles, combining, as we have seen, with the haemoglobin of these bodies, while the carbonic acid will pass in the reverse direction from the blood through the wall of the capillary and wall of the air cell into the lungs, and thence out of the body. It is possible that the pulmo- nary epithelium in acting as a secretory surface may also exercise some 1 Hutchinson, op. cit., p. 1079. - Trans, of Royal Soc. Kdinb., vol. xii. p. 573, 1834. 436 RESPIRATORY MOVEMENTS. Fig. 248. influence in promoting the absorption of oxygen and elimination of carbonic acid. On the other band, the oxygen of the arterial blood will readily diffuse through the wall of the capillary into the tissues, the tension of the oxygen in the latter being so low as to amount, prac- tically, to nothing, the oxygen combining in some stable form as rapidly as absorbed. While, owing to the continual production of carbonic acid in some unknown way in the tissues out of the oxygen absorbed, the tension of the carbonic acid of the tissues being always higher than that of the blood circulating in their midst, the carbonic acid will, conse- quently, diffuse iti the opposite direction to that of the oxygen, viz., from the tissues through the wall of the capillary into the blood now become venous through deoxidation of most of its haemoglobin. The tension of the gases in the blood is determined by means of the ierotonometer. This (Fig. 2-48) con- sists of a long glass tube A, communi- cating above by means of the stopcocks B C with a tube (D), bringing the blood, the tension of whose gases is to be determined, and with one(i?) leading to the eudiometer for the determination of the gases, and below with a bell-jar ((7), standing over mercury, and with the reservoir of mercury H. The glass tube is first entirely filled with mercury so as to exclude the air, by elevating the reservoir H, and is then surrounded by hot water so as to maintain the tem- perature of the blood examined at that of the animal from which it was drawn. The glass tube A is then filled through the depression of the mercurial reser- voir with a mixture consisting of known quantities of nitrogen, oxygen, and carbonic acid. The blood being allowed to flow from the artery or vein of the animal for a moment out of the tube D, so as to exclude the air, is then diverted into the gas mixture in A. As the blood flows down through the tube into the mercury the mercury is driven up into the bell-jar (6r), while the tension of its oxygen and carbonic acid are increased or diminished according to the corresponding tension of the oxygen and carbonic acid of the gas mixture, as finally determined by the analysis of the gases in the eudiometer E, into which the gases are driven by the elevation of the mercurial reservoir. The general results as to the tension of the oxygen and carbonic acid in the blood, as obtained with the aeroto- iErutcmometer. (IIoppe Seylee.) TENSION OF GASES IN BLOOD. 437 nometer by Pfliiger 1 and his pupils, Wolf berg, 2 Strassburg, 8 Nussbaum, 4 are as follows : The tension of oxygen in arterial blood (one atmosphere being equal to 760 mm. of mercury) is equal to 29.6 mm. of mercury, corresponding in amount to 3.9 per cent, of atmosphere, that of carbonic acid being equal to 21.2 mm., corresponding in amount to 2.8 per cent. The ten- sion of oxygen in venous blood is 22.04 mm. of mercury, corresponding in amount to 2.9 per cent., that of carbonic acid being equal to 41 mm. of mercury, corresponding in amount to 5.4 per cent. It is obvious, then, such being the tension of the gases of the blood, that since the tissues offer no resistance to the passage of oxygen from the arterial blood (tension 29.6) into them the tension of their oxygen being practi- cally nothing, and from the fact of carbonic acid being continually pro- duced in the tissues, while the tension of the carbonic acid in the arterial blood is low (tension 21.2), that the oxygen of the arterial blood will pass to the tissues, and the carbonic acid away from them. On the other hand, the tension of the carbonic acid of the air being equal to only 0.38 mm. of mercury, it existing in the atmosphere in the small amount of 0.05 per cent., while the tension of the oxygen of the air amounts to 138 mm. of mercury, corresponding in amount to 20.8 vol. per cent., the carbonic acid of the venous blood (tension 41) will diffuse into the air (tension 0.38), and the oxygen of the air (tension 138) will diffuse into the blood (tension 22.04). The amount of the gases, and the con- dition in which they exist in the blood have already been considered. i Pfl tiger's Archiv, Bd. vi. S. 43. 2 Ibid., Band iv. S. 465. 3 Ibid., Band vi. S. 65. * Ibid., Band vii. S. 296. CHAPTER XXIX. ABSORPTION OF OXYGEN— EXHALATION OF CARBONIC ACID. Having seen that the essence of respiration consists in the absorp- tion of oxygen, and the giving up of carbonic acid, etc., and the manner in which the air containing these gases is respired, it remains for us now to determine, as far as possible, the amount of oxygen absorbed and carbonic acid eliminated by the system in a given time. This is one of the most difficult problems in experimental physiology, and, at the same time, one of the most important, since, as we shall see, all calcu- lations as to the amount of animal heat produced in the body through oxidation and the development of muscular force, etc., are based upon the amount of oxygen absorbed, the carbonic acid and water being exhaled, in a measure of the heat, etc., so produced. Let us endeavor to deter- mine, first, the amount of oxygen absorbed, and then that of carbonic acid, etc., exhaled in a given time. This can be done in several ways, Fig. 249. Valentin and Bruuner's respiration apparatus. the simplest of which consists in comparing the composition of the ordi- nary atmospheric air with that which has been breathed, with the object of determining the amount of oxygen absorbed during one inspiration, VALENTIN AND BRUNNER'S APPARATUS. 439 and multiplying this by the minutes, hours, etc., in order to obtain, approximately at least, the amount of oxygen absorbed in the twenty- four hours. The apparatus of Valentin and Brunner, as used by the author for this object, consists (Fig. 249) of a Woulflf 's bottle A having a capacity of about a litre (61 cub. in.). One of the openings communi- cates with the mouth-piece B, into which the person expires, the air first passing through pumice-stone and sulphuric acid C so as to dry it. The middle opening communicates with the set of tubes G H I K. H and I contain phosphorus and baryta for the absorption of the oxygen and carbonic acid of the expired air, G and K pumice-stone, etc., that of G for the absorption of the watery vapors that may have escaped, the pumice-stone, etc. in C K for retaining that taken up by the dry air passing through the baryta solution, and which, if lost, would cause an error in the estimate of the carbonic acid exhaled, the tubes being: weighed before and after the experiment. Through the middle opening of the Woulff's bottle a funnel (D) provided with a stopcock is introduced, the opening being then hermetically closed. The funnel is filled with a known quantity of mercury. The manner of using the apparatus is as follows : having breathed for say fifteen minutes through the mouth- piece until the air of the Woulff's bottle has been entirely displaced by the expired air, the mouth-piece is entirely closed, any external air being further prevented from passing into the Woulff's bottle by the mercury in E acting as a valve, the air-tightness of the apparatus being assured by the rise of the mercury in the tube F, through the contrac- tion of the expired air in A, consequent upon its cooling and the closure of the tube funnel. The stopcock of the funnel being then turned, the mercury passes into the Woulff's bottle, displacing a known quantity of expired air, the latter passing into the set of tubes G H I K, pre- viously adjusted to the middle opening. The weight of the tubes H and I having been previously determined, their increase in weight will give, respectively, the amount of carbonic acid and oxygen absorbed. De- ducting now the amount of oxygen so obtained from the expired air from that contained in an equal quantity of ordinary inspired air, the remainder will be the amount of oxygen retained in the inspiration of such a quantity of air; on the other hand, deducting the trace of car- bonic acid usually present in the atmosphere from that obtained from the expired air, and the remainder will be the amount of carbonic acid exhaled into such a quantity of expired air. The ordinary atmospheric air consists of a mechanical mixture rather than a chemical combination of nitrogen, oxvgen, with small amounts of carbonic acid and traces of ammonia. 100 parts, by measure, containing nitrogen 79.19, oxygen 20.81, ammonia 0.04, in round numbers, there being, on an average, 20 of oxvgen to 80 of nitrogen. If the expired air, however, be analyzed in the manner just described, it will be found that, as compared with the ordinary air, it has lost oxvgen and gained carbonic acid, water, etc. Thus, if an ordinary inspiration be made — that is, 320 c. cm. (20 in.) of air inspired containing 62 cm. (4 in.) of O, and 249 cm. (15 in) of N, analysis of the expired air, by means of phosphorus or pyrogallic acid, etc., will show that 46.8 cm. (3 in.) of O are returned to the atmosphere, 15.6 cm. (1 in.) of oxygen -140 ABSORPTION OF OXYGEN, ETC. having been absorbed by the system — that is, -^th of the air breathed represents the amount of oxygen absorbed. On this supposition, about 425 litres (15 cub. feet) of oxygen would be absorbed in twenty -four hours by an adult, as may be seen from the following calculation : Table LXI. 20 cubic inches of air changed at each inspiration. 18 respirations per minute. 360 60 minutes. 21600 24 hours. 518400 cubic inches of air changed in 24 hours. 1728) 518400 300 cubic feet of air changed in 24 hours. 20) 300 15 cubic feet of oxygen absorbed daily. Inasmuch, however, as breathing is increased both in rapidity and volume by exercise, it might be naturally inferred that the estimate of the air inspired, and of oxygen absorbed in twenty-four hours, just given, is too low. Such, indeed, is the case, it having been shown by experiment that at least 10,000 litres of air, or about 350 cubic feet, are inspired daily, and 500 litres of oxygen, or 17.5 cubic feet, absorbed — that is, about 20 litres, or 1220 inches, of oxygen, per hour. This last estimate agrees very well with the mean results of Valentin and Brunner, 1 obtained by the above method. These observers determined the amount of oxygen absorbed, by analysis of the expired air in a number of cases, the amount of oxygen present in an equal quantity of inspired air having been previously determined. In the first of these experiments the amount of oxygen absorbed was about 27.12 grammes, 19 litres, and in the second, 33.32 grammes, about 23 litres, per hour. The difference between these two results, as compared with each other, and that we have just given, was probably due to the difference in the number of the respirations, capacity of chest, amount of air breathed, etc. The amount of oxygen absorbed can also be indirectly determined by calculation from the amount of carbonic acid excreted. This method will be explained presently, when we describe the respiration apparatus of Pettenkofer and Voit, for the determina- tion of the carbonic acid, etc., excreted. According to Pettenkofer, the amount of oxygen absorbed per hour was about 23 litres, the same as that determined in the case of Brunner. Whatever the amount may be of oxygen absorbed, whether it be accepted or not, as amounting exactly to 425 litres (15 cubic feet), more or less, in twenty-four hours, it is very evident, and this is the important point, practically, as regards the subject of ventilation, and it cannot be too much insisted upon, that every human being requires an enormous amount of fresh air in twenty - 1 Valentin : Lehrbuch der Pliysiologie des Menschen, 1847, Baud i S. 5G5, S. 586. AMOUNT OF OXYGEN ABSORBED. 441 four hours. This is due, not only to the fact that of the air breathed, only one-twentieth represents oxygen absorbed, but also, as we shall see, to the continual vitiation of the air through the carbonic acid and organic matters expired into it, and to the air being then less fit to give up oxygen to the blood and take up carbonic acid from it. While it is quite true that human beings can, apparently, accustom themselves to live in an atmosphere absolutely foul, to breathe over and over again, the same poisonous air, it is only at the expense of their health that this is possible, death resulting sooner or later, from oxygen starvation as surely, though it may be as slowly, as that from ordinary inanition. We have seen that in ordinary healthy breathing about 10,000 litres (350 cubic feet) of air are inspired in twenty-four hours. The air in a room 7 feet long, wide, and high, and therefore amounting to about 9466 litres (343 cubic feet), would about suffice for furnishing the oxygen required by a human being confined in it for twenty-four hours ; and that on the supposition that the air was perfectly pure and fresh. As we shall see, however, double that quantity (20 cub. met., about 650 feet) must be supplied, even per hour, if the air of the room is to be kept in a wholesome condition, free from vitiation by carbonic acid. While, on the average, the oxygen absorbed in twenty-four hours is about what we have estimated, the amount in any given time will vary, being greater or less according to the condition of the digestive system, the external temperature, muscular activity, etc. Thus, during diges- tion, or if muscular exercise be taken, or the external temperature be lowered, we should expect to find the amount of oxygen absorbed in- creased, and such is the case, as was shown experimentally by Lavoisier and Seguin 1 , the results of whose observations may be summed up as follows : 1. A man during repose and fasting, the external temperature being 32.5° (90° F.), consumes hourly 24.002 lit. (1465 cub. in.) of oxygen. 2. During repose and fasting, but with the external temperature at 15° (59° F.), he consumes hourly 26.660 lit. (1627 cubic inches) of oxygen. 3. During digestion a man consumes hourly 37.689 lit. (2300 cubic inches) of oxygen. 4. While fasting and raisins; in fifteen minutes a weight of 7 kil. (about 16 pounds) 343 to a height of 199 in 776 (656 feet) the man consumes hourly 63.477 lit. (3874 cubic inches) of oxygen. 5. During digestion and raising a weight of 7 kil. 343 to a height of 211 inches 146 (700 feet) the man consumes hourly 91 lit. 248 (5568 cubic inches) of oxygen. It must always be a source of regret that Lavoisier did not describe the apparatus in which he placed Seguin, and by means of which he obtained the results just given. There is not the slighest reason, how- ever, to doubt their accuracy, the genius of Lavoisier being as con- spicuously manifested in the disposition of experimental detail, as in the establishment of grand generalizations. In all probability the apparatus used was essentially the same as in the case of the experi- 1 Mem. de l'Acad. des Sciences, 1789, p. 575 442 ABSORPTION OF OXYGEN, ETC. ments performed upon the guinea-pig with the same object, that of determining the amount of oxygen absorbed and carbonic acid exhaled in a given time, consisting in that instance 1 of a bell-jar standing over a pneumatic trough, within which the animal was introduced and supported, after being passed up through the water of the trough, oxygen being introduced as needed, in known quantities, and the carbonic acid exhaled absorbed by alkali. It might be supposed that the results of Lavoisier, just given, would have been shown by more modern methods of investigation, not to be absolutely correct. Even if such should hereafter be shown to be the case, it would not affect the value of the relative results, and that is what is essentially needed for such a comparison as the above. During sleep, as might be expected, the amount of oxygen consumed is considerably diminished, 2 while in hibernating animals, as in the marmot, for example, it is so small that little or no difference can be detected in the composition of the air in which the animal has remained for three hours when in this torpid state. 3 Indeed, according to Regnault and Reiset, 4 only one-thirtieth of the usual amount of oxygen is absorbed by the animal when in this con- dition. It may be mentioned in this connection, also, that very little oxygen is absorbed by the young of all animals. 5 It has been recently shown by Paul Bert 6 that any increase or diminution in barometric pressure acts upon living beings in increasing or diminishing the tension of the oxygen in the air they breathe, and the blood that circulates through their tissues, and that any increase or diminution in atmospheric pressure is unfavorable to living beings accommodated as they now are, to the present tension of atmospheric oxygen. Indeed, according to this observer, all life perishes in air sufficiently compressed. With a pressure simply of several atmospheres symptoms of narcotic poisoning set in similar to those experienced in breathing an atmosphere containing an excess of carbonic acid, and due probably to the same cause, namely, an excess of carbonic acid in the blood. With still higher pressure, 4 of oxygen — that is, 20 atmospheres, and upward — death takes place from asphyxia, accompanied with convul- sions, as when caused by a deficiency of oxygen. Precisely the same effect is caused by the gradual diminution of atmospheric pressure. A sudden diminution, however, causes death probably through the libera- tion of gases in the blood, which interfere mechanically with its circu- lation. As might be expected from the nature of the case, the determination of the amount of oxygen absorbed by a human being in a given time must be of an approximate character. With animals, however, it is different, and especially in the case of small ones, in which the conditions are very favorable, the determination of the oxygen absorbed, as well as the carbonic acid expired, can be most accurately made. The most perfect apparatus for this purpose is that first used 1 Op. cit., p. 572. i Milne Eil wards : Physiologie, tome ii. p. 528. 3 Spallanzani : Mem. snr In Respiration, p. 334. Geneva, 1803. 4 Recherches fiheniiqnea snr la respiration Ann. / = the amount of carbonic acid in the bell-jar at end of experiment. lc = the volume of carbonic acid in sample of air drawn. 1.9774 = weight of 1 litre of carbonic acid, and c the weight of carbonic acid absorbed by pipettes, Vt, etc., the same as before. 7. For the determination of the weight of the nitroo-en in the bell- jar at beginning of experiment. Z = 0.7905 X 1-2562 gr. V X ^—H t in which h 1 + 0.00367* 760 ' Z = nitrogen, 0.7905 = per cent, of nitrogen in air. 1.2562 = weight of 1 litre of nitrogen. 8. For the determination of the weight of the nitrogen in the bell- jar at end of experiment. Z' = In 1.2562 gr. V X H ~ F . in which 1 + 0.00367* ^ 760 Z' = nitrogen, In volume of JVin sample of air drawn, Vt, etc., as before. 9. For the determination of the weight of nitrogen absorbed or ex- haled. Z' — Z. The advantage of this apparatus is that the animal suffers no incon- venience from even a prolonged confinement within the chamber A, that the oxygen is furnished as needed, and the carbonic acid removed as rapidly as produced, and that, at the conclusion of the experiment, the composition and tension of the air within the jar being determined, the amount of oxygen absorbed and carbonic acid exhaled can be accu- rately estimated. A more modern apparatus used by Ludwig and his pupils, 1 differs from that of Regnault and Reiset just described, not so much in principle as in certain mechanical details. The most notice- able of these is the ingenious contrivance by means of which the oxygen expired passes from g (Fig. 251) into the respiratory tube d, communi- cating through an air-tight covering with the nostrils of the animal ate, alternately with the passage of the carbonic acid expired into the bulbs f, and which is accomplished through the alternate expansion and con- traction of the valve c. For with the rarefaction of the air through inspiration the valve c is drawn away from the end of the tube b, the effect of which is that the air entering the tube b drives the water out of a, which in turn drives the oxygen out of g into the tube d. On the other hand, with the condensation of the air through expiration, the valve c is forced back close to the end of the tube b, the flow of oxygen from the tubed ceases, the carbonic acid exhaled passing into the bulbs f. The amount of oxygen absorbed in a given time by an animal can be 1 Ludwicr's Arbeiten. 44(> ABSORPTION OF OXYGEN, ETC. also indirectly deduced sufficiently accurately for ordinary purposes from the amount of air inspired, the per cent, of oxygen absorbed having been determined, by Brubaker's apparatus, already described ; or directly Ludwig's respiration apparatus. by connecting the spirometer of that apparatus with a reservoir con- taining a known weight of oxygen, and filling the cylinder of the spirometer with a solution of calcium chloride instead of water, to avoid absorption the oxygen of the air in the spirometer, etc., absorbed by the animal being replaced by that flowing from the reservoir, and the amount so consumed in a given time at least approximately determined. The amount of carbonic acid exhaled can also be estimated by this apparatus by connecting the expiratory tube with a Pettenkofer tube containing a solution of baryta, and using the volumetric method, as will be explained in a moment. If the air that has been breathed be com- pared with an equal quantity of atmospheric air, it will be found to differ, not only in having lost oxygen and gained carbonic acid, but in being laden with aqueous vapor, in being warmer, and containing small quantities of ammonia, nitrogen, and organic matters. The determi- CARBONIC ACID EXHALED. 447 nation of the amount of carbonic acid exhaled in a given time is as important as that of the oxygen absorbed, since the carbonic acid, taken together with the water exhaled, contains the oxygen absorbed by the system during some previous period, and affords the means of indirectly estimating the same. We. therefore, usually determine at the same time the amount of carbonic acid and water exhaled by the system, and for this purpose Ave make use of Voit's respiration apparatus. This consists, as constructed for the author by C. Stollventner and Sohn, of Munich (Fig. 252), of a chamber (H) in which the subject of 448 ABSORPTION OF OXYGEN, ETC. the experiment, a large dog, for example, is placed ; of a large drum, and pumps worked by a waterwheel for the production of a constant draught of fresh air through the apparatus; of hottles and tubes containing appropriate materials for the absorption of the water and carbonic acid of the air surrounding the chamber, as well as that from within it; and of meters for registering the total amount of air that has passed through the chamber, of the fractional part of the same analyzed, and of the air surrounding the chamber analyzed for comparison. Professor Voit's apparatus is an improved form of the celebrated respiration apparatus, used by Pettenkofer, Voit, and Ranke in their researches upon nutrition, conducted in the Munich Physiological Laboratory, and to which we shall have occasion to refer hereafter. It differs in several important respects from the original apparatus, the principal of which consist in the substitution of a water-wheel as a motor for clock-work and steam engine, of mercurial ventiles for Mliller's valves, in a greater proportion of the air being directly analyzed, improved gas meters, etc. By substituting for the chamber H, containing the animal, one (M) sufficiently large to hold a man, as shown in Fig. 252, the amount of carbonic acid normally exhaled by a human being, and, under various conditions, can be conveniently determined. The water exhaled cannot, however, be accurately determined, so much of it being precipitated in the chamber. The chamber H (Fig. 252), in which the animal is placed, has a capacity of about 380 litres (14 cubic feet), and con- sists of a zinc framework in which solid glass plates are imbedded, a part of which at the front of the chamber is movable and acts as a door. The other two openings present, with a diameter of 2.7 cm. (1 in.), are for the entrance and exit of the air ventilating the chamber. The air entering by the opening a, seen through the. large chamber M, passes by the pipe to the bottom of the chamber, and having traversed the latter, leaves it at its upper portion by the pipe b and passes thence by the pipe d 3.5 metres (11 feet) in length (disconnected with b in Fig. 252), and holding 2.4 litres (4.8 pints), into the large gas meter B, having a capacity of 28.57 litres (7.6 gallons), whence, having been measured, it is expelled. The constant current of air so passing is drawn out of the tubes d b and chamber H by the rota- tion of the drum of the gas meter B, whose axis is in connection with that of the overshot water-wheel G, through the teeth of the cog-wheel on the axis of the gas meter interlocking with those of the cog-wheel on the axis of the water-wheel. The water-wheel having a diameter of 60 cm. (23.2 in.), and carrying on its circumference 24 buckets with a capacity of 330 c. cm. (-| of a pint), is kept uniformly rotating through the fall of water conducted through the pipe f from a reservoir holding 1440 litres (360 gallons), not represented in the figure, situated in the room above the laboratory; the water, as it is emptied by the buckets passes into a trough and thence is carried away by the waste pipe K. The flow of water from the pipe f can be regulated as to rotate the water-wheel as often as five times per minute. Such a rate, how- ever, is not needed, since with the wheel rotating only once in a minute, or sixty times to the hour, and with an expenditure of 33 litres (8 gal- lons) of water, over 1700 litres of air pass per hour through the chamber H, or five times as much as we have seen (2857 litres passing through the voit's respiration apparatus. 449 meter -with each rotation of the water-wheel) is required in the case of man, and with such a velocity as not to produce a draught (0.36 cm. a second). The velocity of the air through the chamber H during a given time can be always readily determined, when it is remembered that it is equal to the ratio of the amount of air to the sectional area it passes through, or by the animometer. The manner in which the air that passes through the meter is recorded being essentially the same as in gas meters, a brief description will suffice. The circumference of the dial- plate is divided into 100 equal spaces, and on the face of the plate are four circles each circle being divided into ten equal spaces. As the large hand moves once around the circumference of the dial-plate, indi- cating that 100 litres (200 pints) of air have passed through the meter, each division of the circumference being equal to one litre, the hand of the first small circle moves from to 1, and while the large hand moves ten times around the circumference of the dial-plate, indicating that 1000 litres of air have passed through the meter, the hand of the first small circle moves around from to 10, and the hand of the second small circle moves from tol. In the same manner as the hand of the second small circle moves once around from to 10, indicating that 10,000 litres of air have passed through the meter, the hand of the third small circle moves from to 1, and as the hand of the third small circle moves once around the cii'cumference from to 1, indicating that 100,000 litres of air have passed through the meter, the hands of the fourth small circle move from to 1 ; finally, the movement of the hand of the fourth small circle once completely around, records the passage of 1,000,000 litres of air through the meter. The animal having been placed in the chamber and the water-wheel set in motion, as the air containing carbonic acid and water streams through the chamber it takes up in addition the carbonic acid and water exhaled by the animal. Inasmuch, however, as with the wheel rotating only once a minute and the experiment lasting six hours, over 10,000 litres of air pass through the chamber, it becomes evident that the de- termination of the carbonic acid and water in such a large quantity of air would involve an enormous expenditure of time and labor. We avoid this by analyzing a fractional part of the air passing through the chamber, determining the carbonic acid and water that it contains and multiplying the result by the total amount of air as recorded by the meter, having first deducted the carbonic acid and water contained in an equal quantity of the air surrounding the chamber. To effect this, part of the air from the chamber is diverted by the mercurial pumps from the tube d into the tube J. The latter terminates in two branches (J' J") which are connected w r ith two mercurial valves (v' v"), the latter not represented in Fig. 253 ; these communicate with the two mercurial pumps, one of which is represented in Fig. 253, which are alternately elevated and depressed through the movement of the crank m connected with the axis of the water-wheel, the one pump rising as the other is falling, and vice versa. The pumps communicate also with two other mercurial valves (w f w"), the latter not represented in Fig. 253, tilted in the opposite direction to those just mentioned. The air must pass, therefore, always in the same direction, viz., from the •29 450 ABSORPTION OF OXYGEN, ETC, tube J' through the valve v' into the pump, returning through the valve w' into the short bottles e e containing pumice-stone and sulphuric acid for the absorption of the water, thence through the large bottles g containing water and pumice-stone for resaturation, then through the tubes 1 1, containing a solution of baryta, for the absorption of the carbonic acid, finally escaping by the meters 1 and 2, 2 not represented h in Fig. 253, where the amount is measured. As the air passes into the chamber it contains water and carbonic acid. In order to determine the amount of such exhaled by the animal it is necessary to analyze the air surrounding the chamber. This is done in exactly the same way and simultaneously as the analysis of the air within the chamber which we voit's respiration apparatus. 451 have just described, the air surrounding the chamber being drawn into a tube by two pumps and through bottles, tubes, and meters similar to those described. Having determined the carbonic acid and water in a given quantity of air surrounding the chamber, this is deducted from the water and carbonic acid of an equal quantity of air that has passed through the chamber, in order to obtain the water and carbonic acid exhaled by the animal. The small gas meters have a capacity of 2.5 litres (5 pints), and the circumference of each is divided into 100 equal parts, each being equal to 25 c. cm. As the large hand moves once around the circumference, indicating that 2500 c. cm. (2.5 litres) have passed through the meter, the small hand moves over one space. It will be also observed that supposing the water-wheel to be rotating once in a minute, that while 25 c. cm. pass out of the small meter 28,570 c. cm. pass out of the large one — that is, 1142 times more air passes out of the large meter than the small one. The amount of carbonic acid and water exhaled by the animal in one hour, as determined by the absorption bottles and tubes, must therefore be multiplied by 1142, and to this must be added the carbonic acid and water remaining in the chamber H, tube c?, and the two meters /and II, in order to get the total amount exhaled by the animal. The double set of absorbing bottles, tubes, meters, etc., enable us to analyze a definite quantity of two samples of both the air within and without the chamber, and of so obtaining the average amount of water and carbonic acid in a given quantity of inside and outside air. The result of the general investiga- tion will then be more reliable than if the analysis had been confined to a single sample of inside and outside air. Further, to insure success, the gas meters ought to be tested before every experiment. This can be done, as suggested by Voit, by allowing water to flow into a glass vessel of known capacity, the vessel being connected with the meter so that as the air is driven out of the vessel by the water it passes through the meter, or, as is ordinarily done in testing our gas meters, by con- necting the upper opening of the meter by which the air usually escapes with a vessel of known capacity containing water. By removing the con- necting tube t' and allowing the air to enter the meter by the posterior opening, as the water in known quantity flows out of the vessel it is replaced by the air that has passed through the meter. In testing the meters the author has found that there is usually an error of jA-^-th between the absolute amount of air that has passed through the meter and that recorded by it, which must be subtracted from or added to the latter, as the case may be. It might be supposed, from part of the chamber opening and closing as a door, that some of the air contain- ing carbonic acid and water exhaled by the animal might escape through the chinks of the door. The draught of air through the chamber, how- ever, is so great that when a strong-smelling substance is placed within it it is perfectly imperceptible at the door. If any doubt, however, should exist as to the chamber being air-tight, it can be readily made so by filling up the chinks of the door with wax, or a mixture of it. It is very important, also, that the tubing connecting the different parts of the apparatus should be examined in this respect before each experiment. It remains for us now to describe a little more in detail than we 452 ABSORPTION OF OXYGEN, ETC. have done the manner in which the water and carbonic acid arc deter- mined hy means of the absorbing apparatus. The determination of the amount of water is very simple. The bottles (#, e, Fig. 253) through which the air from within and without the chamber passes contain, as already stated, pumice stone and sulphuric acid, which has a great avidity for water. These being weighed in scales, the beams of which oscillate with the addition or subtraction of the y^o-th of a grain, before and after the experiment, the difference will give the amount of water in the air from within and without the chamber; the hitter amount, as we have already mentioned, must be then deducted from the former, in order to get the amount of water exhaled by the animal into the frac- tional part of the air examined. Suppose, for example (see Table of Tabulated Results), of two samples of inside air of 1000 litres each, the mean, or 1000 litres, contained 1.2457 grammes of water, and of equal quantities of outside air, the mean contained 1.1445 grammes of water, the difference, or 0.1012 gramme, would then be the amount of water exhaled by the animal into 1000 litres of air in the given time. The water having been absorbed as the air passes through the bottles the dried air is resaturated as it passes through the bottles g, the saturated pumice stone within them giving up the water it contains. Were not the air so resaturated it would take up water from the solution of baryta through which the air next passes, and this must be avoided, as the solution of baryta is used for the absorption of carbonic acid. Of the eight tubes containing the baryta solution, four are large and four are small. The large tubes, through which the air first passes, have a capacity of 460 c. cm. (28 cub. in.), the small ones of 170 c. cm. (10 cub. in.). The tubes are placed somewhat obliquely, in order that the air shall pass as distinct bubbles through the solution, the greatest amount of air surface being, therefore, exposed to the absorbing action of the baryta. The solution of baryta within the two large tubes <, only one of which is represented in Fig. 253, receiving the air from the inside of the chamber, is stronger than in that of the remaining tubes, both in the two small succeeding ones and in the two large and two small ones through which the outside air passes. The strong solution of baryta is made by dissolving 21 grammes of baryta in 8 litres of distilled water, the weak one by dissolving 7 grammes of baryta in the same quantity of •distilled water. It will be found experimentally, as will be seen in a moment, that about 90 c. cm. and 30 c. cm. of a solution of oxalic acid but recently made by dissolving 2.8 grammes of chemically pure oxalic acid in 1 litre of water will saturate 30 c. cm. of the strong and weak solutions of baryta, respectively. In order to preserve the baryta solution pure it is essential that it should be contained in a bottle, through the stopper of which pass two tubes; through one the solution is drawn out by suction as desired, while by the other tube the air enters, having been freed from its carbonic acid by its passage through caustic soda. It is best to determine the amount of carbonic acid absorbed by the baryta in the case of a small animal. We usually place in the two large tubes 240 c. cm. of the strong solution, and in the remaining six tubes 50 c. cm. of the weak solution, and make use of the method of Pettenkofer, as follows : for example, of the strong baryta, the water having been DETERMINATION OF CARBONIC ACID EXHALED. 453 introduced into a test tube, or small flask, the solution of oxalic acid is gradually added to it from a finely graduated burette. With each addition of oxalic acid the test-tube is closed with the thumb and shaken. As an indicator of the point of neutralization turmeric paper is used. The paper is dipped into the liquid from moment to moment, ceasing to be browned when the liquid is nearly neutralized ; at this instant, a drop of the liquid is placed by means of a glass rod on a strip of the paper, if a trace of alkaline reaction still exists a brown line appears at the periphery of the paper; when this is no longer the case the point of complete neutralization has been obtained. Now suppose, before an experiment with the respiration apparatus it was ascertained by the means just described, that exactly 72.4 c. cm. of oxalic acid neutralized 25 c. cm. of the standard strong baryta solution, it will be found that at the end of the experiment it requires only 61.8 c. cm. of oxalic acid, or 10.6 c. cm. less, to neutralize 25 c. cm. of the strong baryta solution, drawn out of the tubes by means of a pipette. As the carbonic air passes through the latter during the experiment it combines with part of the baryta, and there is, therefore, less baryta to combine with the oxalic acid after the experiment than there was before. Now as for each milli- gramme of carbonic acid that combines with the baryta during the experi- ment there will be 1 c. cm. less of oxalic acid required for neutralization after experiment, it follows that 10.6 milligrammes of carbonic acid must have been absorbed by the 25 c. cm. of the baryta solution, since it requires 10.6 c. cm. less of oxalic acid for neutralization after the experiment than before. In other words, the baryta before the experi- ment combined with 72.4 c. cm. of oxalic acid, after the experiment with 61.8 c. cm., because during the experiment it combined with 10.6 milligrammes of carbonic acid, which are volumetrieally equal to 10.6 c. cm. of oxalic acid. As Ave placed 240 c. cm. of the strong baryta solution in the tube t, we must now T multiply the 10.6 milligrammes of carbonic acid obtained from the 2-3 c. cm. by 9.6, in order to obtain the total. The manner of determining the carbonic acid absorbed by the weak solution of baryta being essentially the same as that just described for the strong one, it will be only necessary to refer for details to the Table of Tabulated Results, giving a resume synoptically arranged by Voit of the result of an experiment upon a dog obtained by the respira- tion apparatus, which we have just described in detail. The carbonic acid exhaled by a human being in twenty-four hours, as determined by the Pettenkofer-Voit's respiration apparatus, amounts, on an average, to 410 litres (25,625 cub. in., or 14 cub. feet) in twenty-four hours. 454 ABSORPTION OF OXYGEN, ETC. Tabulated Results of Experiment with the Pettlnkofer-Voit Respiration Appai:.uts upon a Dog. Determination of Carbonic Acid Determination op Water. Amount of air investigated. Baryta water tubes. Carb. .i. id '.r air in- vesti- gated. Carb. acid of 1000 litres of air. Water of air investi- gated Differ- ence. 0.7682 7670 O.G947 0.8135 Water Gas Meters. Volumes in c.c. Cubic cent.of oxalic acid for 25 c.c. of baryta water. in 1000 litres "f air. Revolu- tions. Litres. Before After. Differ- ed :e. No. 1 ) Outer air. J No. 2. } Outer air. j 20.380 26.657 22,985 25.577 67.108 | 67.024 | 5(1.044 1 64 981 1 Large 240 c.c. Small 50 " Large 240 c.c. Small 50 " Large 240 c.c. Small 50 " Large 249 c.c. Small 50 " 33.8 cc. 33.8 " ]33.8c.c. 33.8 '• 72.4 c.c. 33.8 " 72 4 c.c. 33.8 " 29 8 c.c. 1 33.5 " j 29.8 c.c. "1 33 5 " / 61 8 c.c. 1 33.5 " j 60.3 c.c. 1 33.7 " ; 0.03900 003900 0.10236 0.11636 0.5811 0.5819 2)1.1630 1.1447 1.1444 2)2.2891 No. 3. 1 Inner air. j No. 4. I Inner air. } 0.5815 1.82G4 1.7907 2)3.0171 1.1445 1.2395 1.2519 2) 2.4914 1.8085 1.2457 Calculation for Carbonic Acid and Water. Carbonic acid. Water. In 1000 litres of inner air In 1000 litres of outer air Difference In 11600.5 litres of large meter . 14.23 In 66.55 litres chamber and tube 0.11 In 121.02 3d and 4th meters . 0.15 Total 1.8085 grammes. 1.2457 grammes. 0.5815 " 1.1445 1.2270 " 0.1012 11.74 0.07 0.12 14.49 " 11.93 Calculation for Oxygen Absorbed. Before experiment. After experiment. Weight of animal 3001.3 grms. Weight of animal . . 2987.80 grms. Inaresta 0.0 Egesta Total 3001.8 urine . . 0.0 '" feces . . 0.0 " water . . 11.93 " carbonic acid 14.49 " Total 3014.22 " 3001.30 " The quantity of oxygen absorbed equals the difference, viz. 12.92 " The proportion of carbonic acid to oxygen, 100 : 89. AMOUNT OF CARBONIC ACID EXHALED. 455 This estimate is intermediate between that of Andral and Gavarret, 1 468 litres (29,238 cubic inches), and that of Edward Smith, 2 387 litres (24,208 cubic inches), for the same period of time. The experiments of these observers were made with the object of determining only the carl tonic acid exhaled, and the apparatus consisted in both instances of a mask closely fitting the face, having two openings provided with valves for the entrance and exit of the air, the carbonic acid exhaled in the experiments of Andral and Gavarret being determined by means of a solution of potash contained in U tubes, and in those of Smith by a solution of potash arranged in numerous layers. The mechanical details of the apparatus made use of by these observers, as well as by their predecessors, Lavoisier and Seguin, Prout, Davy, Dumas, Allen and Pepys, Scharling, and others, not being as perfect as those of the Pettenkofer-Voit respiration apparatus, just described, it would be superfluous to dwell further upon them. In this connection, how- ever, it is proper that some allusion at least be made to the indirect method of determining the amount of carbonic acid exhaled in a given time, so successfully applied in the case of large animals by Boussin- gault. 3 This method consists of so regulating the diet of the animal experimented upon, a horse or cow, for example, that there is no loss of weight during the experiment, and of weighing everything introduced as food, solid and liquid, and all discharged as urine or feces. Knowing the quantity of carbon entering the body in the food, and leaving it in the urine and feces, the difference between the carbon of the latter and the former (that of the food being in excess) will be the amount of carbon leaving the body by the lungs and skin. As regards the carbon excreted by the skin, it can, for such approximate determinations, be neglected, since, as we shall see, when the skin is considered as a respiratory surface, the carbonic acid exhaled does not amount to more than between -^th and Tj^-g-th of the total amount excreted. 1 Ann. t-± , " Mollusca — ( >yster, Temp, same as sea, 82°. (( Snail, 76.5 surrounding air. 76.2* ;,° (( Echinodermata — Star fish, 6-10° F. above temp, of sea (66.3°) Valentin Sea urchin, 5-10 (66.7 ) a Sea cucumber, 6-10 (67.6 ) " Vermes — Leech, 1 " " of air (56. ) Hunter. Ccelenterata — Anemone, 5-10 " " of sea (69.4 | Valentin Jelly fish, 7-10 (72.5 n Ponfera — Sponge, Same as sea (68. 3^ F.) it 472 ANIMAL HEAT. Of ;ill animals, birds have the highest temperature, that of the chicken, for example, according to Davy 1 being as high as 111° F., (43° C), a slightly higher temperature, according to Pallas, 2 even being found in certain small birds. Among mammals the temperature of the rabbit is noteworthy, amounting to 40° C. (105.8° F.j. On the other hand the temperature of fishes, with some exceptions, is not usually more than 0.5° C. (0.9° F.) higher than that of the water in which they live, whilst among the invertebrata, 3 as in the case of mollusks, star fish, jelly fish, anemone, the excess of the temperature over that of the surrounding medium may be even less, amounting often to no more than 0.2° C. As an exception to the last statement and interesting in this connection may be mentioned the considerable amount of heat developed by bees and ants when swarming. Although a great number of observations have been made, some difference of opinion still prevails as to what constitutes the average normal temper- ture in man. This, however, is readily understood when, as we shall presently see, the temperature of the body not only varies considerably in different situations, but according to numerous circumstances ; among others may be here very appropriately mentioned especially the manner in which the thermometrical observations should be made. It is of the highest importance, not only that the part of the body selected for taking the temperature should be mentioned, but that the thermometer used in making the observation should be a standard one. The exact date of the invention of the thermometer as well as of that of the microscope is not exactly known, and in both instances there is also doubt as to whom the merit of these inventions should be accorded. At the present moment, for example, the invention of the thermometer is attributed on the one hand by Rosenthal 4 to Galileo, and on the other by Wunderlich 5 to Sanctorius. It is probable that it was invented by Galileo (1603), but first made use of in the study of the temperature of man in fever by Sanctorius (1626). While it is true that Galileo is mentioned in the preface to his works, 6 and is referred to by his biographer Viviani, 7 as the inventor, nevertheless, that Sanctorius considered himself as the inventor, there can be no doubt ; since he himself distinctly says so, 8 and it may be mentioned in this connection that this claim is admitted without reserve by both Borelli 9 and Malpighi. 10 Other claims, however, like those in favor of Galileo, of a posthumous character, have been advanced by Boer- haave, 11 who attributed the invention to his countryman Drebbel, and by Fulgentius 12 to his compatriot, the great Venetian Father Paul Sarpi. The metastatic thermometer of Walferdin (Fig. 255), is very useful since by means of it a variation of the Yorjth of a degree Cent, (corre- 1 Researches, Phys. and Anat., p. 186. London, 1839. - Gavarret, De la Chalenr Prouduite par les Etres Vivants, p. 94. Paris, 1855. 3 Milne Edwards: PhysiolOgie, tome neuvieme, 18fi:i, p. 13. * Hermann : Handbuih der Pliysiologrie, Vierter Band, Zweiter Theil, S. 294 5 Das Verhalten der Eigenwiirwe in Kranklieiten, 2 And. 1870, S. 34. 6 Opere di Galilei, p. 47. 7 Vita de 1'Galilei, p. 67. 8 Com. in Galen, Art. Med., p. 736. Com. in Avicen, i. p. 22, 78, 219. o De Motu Animal, 11 Prop. 175. '0 Opera Posth., p. 30. " Elem.-iita Chenriae, p. 152, 156. Lugd. Bat., 1732. !2 Opere del Padre, Vita del Padre, p. 158. Paola, K'87. METASTATIC THERMOMETER. 473 Pig. 255 Fig. 256. Walferdin's metastatic thermometer. sponding to a millimetre in length of the mercury) can be accurately determined, and that however excellent the instrument may be at the time obtained, it should be constantly tested. Further, in using the thermometer it should be so applied that the part whose temperature is to be determined completely surrounds the bulb of the instru- ment, hence, of all parts of the body, the rectum is that which is best adapted for thermometrical observations, the instrument being inserted to a depth of at least 5 cm. (2 in ). On account, however, of being more convenient, the axilla is frequently made use of in determining the temperature of the human body. It must be remembered in that case then that the temperature is usually Y 5 (j-th to 1 degree lower than that of the rec- tum. The tongue and va- gina are also frequently made use of in taking the temperature. Apart from individual idiosyncrasies, to neglect of the precautions just referred to is undoubt- edly due much of the dif- ference of opinion that has prevailed more particularly among the older physiolo- gists with reference to the temperature of man. If. from the nature of the case, on account of the size of the cavity to be examined, etc., the application of a thermometer is inadmissi- ble, thermo-electric needles are then made use of in de- termining the temperature. Even greater precautions must be taken than when the observation is made in the usual way on account of the deli- cacy of the apparatus, as slight a variation as the T qVo^ 1 °f a degree having been determined by such. Thermo-electric needles (Fig. 256, Af, f A) are usually made of iron and German silver, each needle consisting of iron (f) and silver (A), soldered together at and near their points, and the two so disposed as to constitute together an element. The iron wires being in the middle, and the silver ones exter- nally, if the latter are connected with each other through a galvanometer (M), a circuit is formed. The deviation of the needle will then indicate the temperature of the Thermo-electric needles. 474 ANIMAL HEAT. part examined through the electricty developed by the contact of the needles with the heated surface. The wires are, of course, except where soldered together, carefully isolated, and where held, are covered with silk and varnish. When the difference in the temperature of two parts of the body is to be determined, the two needles are imbedded in the parts, and the intensity of the current measured and the amount of heat determined, the relation between the deviation of the needle and the amount of heat producing it having been previously experimentally de- termined. This can be accomplished by immersing the needles with deli- cate thermometers attached, in oil baths differing in temperature, for ex- ample, by one degree C. The deviation of the galvanometer needle will then indicate a difference in temperature of one degree C. Suppose, further, that as measured by the scale the deviation of the galvanometer needle amounts to 150 mm., then yJ-jjth of a degree C. of temperature is indicated by a deviation of 1 mm. of the needle. If absolute tempera- ture be required, then one needle is applied to a surface maintained at a known temperature, and the other to that whose temperature is to be de- termined, or the known temperature can be gradually reduced until there is no deviation of the needle. The opposite currents being then equal the heat producing them must be equal — that is, the unknown heat is equal to the known. It was by means of the thermo-electric apparatus that Becquerel, 1 and Breschet determined the temperature of the biceps muscle under different external conditions to be referred to in a moment, and Nobili 2 and Melloni proved that the internal temperature of insects was slightly higher than that of the surrounding atmosphere. Among the most reliable observations that have been made with refer- ence to determining the average temperature of the human body may be mentioned those of Hunter, 3 37.2° C. (98.9° F.), Daw. 4 37.3° C. (99.1° P.), Wunderlich, 5 37° C. (98.6° F.), Jurgensen^ 6 37.2° C. The mean of Jurgensen's observations, it will be observed, is the same as that of Hunter, a confirmation of the accuracy with which that great physiologist investigated the subject of animal heat as all other biological phenomena. The results of Jurgensen's experiments are most important, both on account of their number and the length of time over which they extended. They consisted in reading off at intervals of five minutes the indications of a thermometer permanently retained in the rectum, and extended over three days. The mean obtained by Jurgensen was 37.2° C. (08.9° F.), which we will consider as being the average normal temperature of the human body, although variations between 37° and 38° C. (98.6° and 100.4° F.) may occur within the limits of health. Among the various conditions that modify the normal temperature may be mentioned, in addition to the influence of the part of the body examined, to which we have already incidentally alluded, that exerted by age, sex, the time of day, food, muscular and mental work, 1 Ann. des Sciences Xaturelles, 2d ser., 183n, t. iii. p. 269. * Ann. de Chiniie et de Physique, 1831, t. xlviii. ). 208. 8 Works of . John Hunter, ed. by J. F. Palmer vol. i. p. 280. London, 1S35. Phil. Trans., 1844, p. 61. 4 Researches, I'liys. and Anat., lSiD, vol. i. p. 162. * Op. eit., S. 92. >' Deutsche Archiv klin. Med., Band iii. S. 166. DAILY VARIATIONS. -475 external temperature, etc. To the consideration of these let us now turn. Age and Sex. According to Andral, 1 Barensprung, 2 and others, the temperature before birth, as well as immediately afterward, is slightly higher than that of the mother ; but as the newborn child possesses but little power of resisting external cold, its temperature soon falls, within two hours, perhaps, from 37.8° to 35.2° C. (100.04° to 95.2° P.). Hence the importance of providing for the infant sufficient warmth by suitable means, and to the neglect of which the death in many instances is undoubtedly due. Immediately after birth the temperature of the infant taken in the rectum is between 37.5° and 37.8° C. (99.5° and 100.04° R), falling after the first bath to 37° C. (98.6° F.) and even lower, while during the next ten days it varies between 37.25° and 37.6° C. (98.9° and 99.6° R), being notably increased by screaming, etc. During the period intervening between early infancy and the age of puberty the temperature falls about 0.2° C. (3.6° R), and from there on till adult life falls about 0.2° C. still more, the normal temperature or 37.2° C. (98.9° F.) being then reached. After sixty years of age the temperature begins to rise again, and at eighty years has again reached that of the newborn child. This rise in temperature in old age is prob- ably due to the diminished circulation of the anaemic skin, since it cannot be supposed that the production of heat has been increased. As a general rule, sex has no appreciable influence upon the temperature of the body. According to Ogle, 3 however, the temperature of the female appears to be slightly higher than that of the male. Daily Variations. The temperature of the body, like the frequency of the pulse, respira- tion, and exhalation of carbonic acid, exhibits periodical variations. From the numerous observations of Davy, Hallmann, Gierse, Baren- sprung, Lichteufels, Frohlich, Damrosch, Ogle, Liebermeister, Jurgen- sen, 4 it appears that the temperature of the body increases very quickly from 6 a.m. to 11 a.m., but from that time forward increases more slowly, reaching a maximum between 5 and 6 p.m. About 7 in the evening the temperature begins to fall, reaching the minimum about 5 a.m., the difference being in 24 hours usually about 1° C. (1.8° F.), though it may amount to as much as 2° C. (3.6° F.). Climate seems to influence the time of day at which the maximum and minimum temperatures occur, the minimum being reached, according to Davy, in England by midnight, but in the tropics not before 6 or 7 A.M." 1 Compt. Rend , t. lxx. p. 825. - V. Barensprung, Arch. f. Anat. u. Phys., 1851, S. 138. :: Kirke'8 Physiology, 10th ed., p. 255. Phila., 1881. 4 Rosenthal die Physiologie der thierlschen Warme in Hermann, op. cit, Vierter Band, S. 322. 476 ANIMAL HEAT. Table LXV. 1 II. .ur Be rensprung. Davy. Jurgensen. 5 .... Cent. 36.7 36.6 (i 36.68 36.7 36.4 7 36.94* 36.*63 36.98 36.7* 36.5* A. M. 8 :;7."l6* 36.80* 37.08* 36.8 36.7 9 36.89 36.9 36.8 10 :;7.2ii 37.*36 37.*23 37.0 37.0 11 36.*89 •S7.2 37.2 M. 12 36.87 37.3* 37.3* 1 36.83 37.13 37.3 37.3 2 37.05 37.21 37.50*- 37.4 37.4 3 37.15- M7.43 37.4* 37.3* 4 37.17 37.5 37.5 5 37. 48 37.05* 37.31 .".7.4:; 37.5 37.5 6 36.83 37.29 37.5 37.6 7 37.43 36.50* 37.31 i 30.00 37.5* 37.6* P. M. 8 37.4 37.7 9 37.02* 37.4 37.5 10 37.29 37.3 37.4 11 36.85 36.72 36.70 36.81 37.2 37 1 12 37.1 37.4 1 36.85 3C..44 37.0 36.9 2 36.9 36.7 3 36.8 36.7 4 3G.7 36.7 Asterisk signifies that food was taken. Supposing with Jurgensen, Table LXV., that the day temperature begins at 6 a.m. with 36.4° C, and ends at 8 p.m. with 37.7°, the duration of the former with a usually mean temperature of 37.3°, exceeds the latter with a mean of 36.9° by four hours, the average tem- perature for the whole day being, as already mentioned, about 37.2° C. (98.9° F.). As might be expected, Debczynski 2 finds that persistent night work reverses the rhythm of the variations of temperature, the thermometer standing highest in the morning (37.8°), instead of in the evening (35.3°). Food. As in the long run the heat, as we shall see, is due to the combustion of substances taken into the body as food, it follows that the production of heat is intimately associated with that of nutrition. Inasmuch, how- ever, as it is not until the last stage of inanition in the starving man or animal that the temperature notably falls, it having been previously maintained in the absence of food through the combustion of the tissues, it is not to be expected that in health the mere taking of food will influence the temperature to any great extent, since the fuel, so to speak, is ordinarily consumed as rapidly as supplied, and when deficient is made up at the expense of the tissues. For example, very hot drinks increase the temperature but little. Suppose, for example, a man weighing 60 kilo. (132 lbs.) drinks a kilo. (2.2 lbs.) at 50° C. (122° F.), the temperature of the whole body (supposing it to be 37.2° C. 1 Landois, op. cit., S. 406. "- Virchow u. Hirsch : Jahresber., 1875, Band i. S. 248. CONDITIONS INFLUENCING PRODUCTION OF HEAT. 477 and having the same specific heat as water) would be increased only about 0.2 of a degree C. It must be remembered in this instance, as in many others, that the effect of taking a hot drink is not so simple as may at first appear, since the circulation being increased by it the loss of heat through evaporation will be increased. The one effect neutraliz- ing to a certain extent the other, the full effect of the drink as regards elevation of the temperature is not therefore experienced. Even if the drinks contain specific substances such as tea, coffee, alcohol, etc., the temperature of the body is diminished only two or three tenths of a degree C. It is possible that the loss of heat experienced in the taking of alcohol is not only due to the quickened circulation, but to a para- lyzing effect exerted upon the vasomotor nerves of the skin, whereby a greater quantity of blood being conveyed to the surface than usual, more heat is consequently given off and so lost. On the other hand, while the effect of cold drinks, etc., is to diminish the temperature of the body, the diminution is also very slight, amounting usually to but a few tenths of a degree C. Thus, according to Lichteufels and Frolich, Winter- nitz, and others, 1 drinks at a temperature of 18°, 16.3°, and 4.6° C, reduced that of the body in the first two instances within 6 minutes after taking them 0.1°, 0.4°, and in the last in 70 minutes 1.4° C. Fur- ther, as in the digestion of solid foods heat is required to assist the chemico-physical changes, it might be expected that as part of the heat becomes latent the temperature of the body would be slightly diminished temporarily after taking the food, even though the temperature should be increased later through further oxidation. That such is the case seems to be shown by the experiments of Vintschgau and Dietl, 2 made upon a dog with gastric fistula, in which the temperature of the food in- troduced, and which differed but little from that of the body, first fell and then rose. From what has just been said, however, of the compensating power exercised by the economy whether food be taken or withheld, it would be inferred that the influence exerted by the taking of food upon the daily variations must be very slight, if any. Indeed, the variations in temperature that are observed after meals, as a matter of fact, occur whether food be taken or not. The most, indeed, that can be said is that if a meal be taken late in the day the diminution in temperature, characteristic of that period, is somewhat put off. Indeed, it is not until shortly before death caused by inanition or starvation, for the reasons already given, that the temperature is notably diminished. Muscular and Mental and Glandular Action. We shall soon see, in our study of muscular action, that at the moment of muscular contraction a considerable amount of heat is set free — indeed, probably three-fourths of the heat developed is produced in the muscles. Thus, according to Davy, 3 the temperature of the room being 66° F,, that of the feet 66°, under the tongue 98°, and of the urine 100° ; after a walk in the open air at 40° the temperature of the feet was 96.5° and 1 Rosenthal, op. rit., S. 325. 2 Sitz. d. Wiener Acad. Math-Natur u. CI. 2 Abth, lx, S. 697, 1870. 3 Phil. Trans., 1844, p. 03. 478 ANIMAL HEAT. the urine 101°, that under the tongue being unchanged. Indeed, daily observation as well as special experiments teaches us that our whole body is wanned by muscular exercise. Further consideration, however, will show that the body is not as much heated as one would be led to expect from the amount of heat developed under the circumstances, and from the rapidity with which the temperature of the body falls to the normal with the cessation of the exercise, it is evident that as fast as the heat is developed it is as rapidly radiated away or lost as some other mode of force. The influence of muscular exercise in elevating the temperature of the body is also well seen under certain pathological conditions ; the temperature in tetanus, for example, rising, according to Wunderlich, as high as 44.75° C. (112.5° F.). It should be mentioned, however, that this great rise in temperature can hardly be attributed entirely to muscular action, since in all probability at the same time other influences come into play, such as the acting of the vasomotor nerves, which in constricting the vessels of the skin will diminish the usual loss of heat due to radiation and evaporation. Nervous-like muscular activity is also accompanied with the production of heat. Thus, according to Davy, 2 in England, during the reading of a work demanding attention the temperature of the body was increased 0.5° F. Mental effort in the tropics is accompanied by a still greater production of heat, amounting, in some instances, to more than 2° F., as in the giving of a lecture, for example; in the latter case some of the heat was probably due to the muscular action involved. Lombard 3 has also determined, by means of delicate thermo-electric apparatus, local increase of temperature in the head resulting from mental effort. Schiff 4 has also shown that the action of the nerves, as well as that of the brain, is accompanied with the production of heat. In all instances, however, the amount of heat produced, at least that appearing as such, is a small part of the heat produced, as in the case of muscle being con- verted, as we shall see hereafter, into other modes of force. Glandular action is also accompanied with the production of heat due to the chemical activity incidental to secretion. Thus, according to Ludwig and Spiess, 5 the temperature of the saliva secreted during stim- ulation of the chorda tympani is 1 to 1.5° (J. higher than that of the blood of the carotid artery of the same side. We have already called attention to the fact of the temperature of the blood of the hepatic vein being higher than that of any other part of the body, due, in part at least, to the size and constant activity of the liver. Surrounding Temperature. Any consideration as to the temperature of man or animal would naturally suggest the influence exerted by that of the surrounding atmos- phere, and concerning which there was, during the last century, differ- ence of opinion. So distinguished a teacher as Boerhaave, for example, 1 Op. cit., S. 400. - Phil, Trans., 1845, p. 443. 3 Experimental Researches on the Regional Temperature of the Head. London, 1879. < Archiv de phy. normal et path., 1870, pp. 5, 198, 323, 421. ■"■ Wien. Sitzb., Bd. 25, 1857. INFLUENCE OF SURROUNDING TEMPERATURE. 479 observing 1 that no body can endure an air heated to 90° F., and that we are always warmer than the surrounding air, supported this view by experiments performed at his request, 2 by Fahrenheit and Provost, which consisted in placing a sparrow, a cat, and a dog in a sugar-baker's oven, heated to 146° F., and in which it was found they soon died. Notwithstanding the result of these experiments, the great Haller, basing his opinion upon the testimony of Lining Adam- son, and other travellers, as to the intense heat that prevailed in certain parts of this country, South Carolina, Senegal, and elsewhere, held 3 in opposition to the view entertained by Boerhaave that man could not only live in an atmosphere 16°, but even 28° F., higher than that of the blood. About this time important observations bearing upon this question were made by Franklin and Governor Ellis. In a letter dated London, June IT, 1758, in referring to a hot Sunday passed in Philadelphia, in June, 1750, Franklin 4 recalls that, during the day, when the thermometer was at 100° F., in the shade, his body never grew so hot as the air surrounding it, or the inanimate bodies immersed in the same air, and, with his usual acuteness, accounts for the body being kept cool under such circumstances by continual sweating, and by the evaporation of that sweat. Within a month of the same year — that is, in July 17, 1758 — Governor Ellis, in a letter to his brother in London, called attention particularly to the fact that, while in Georgia, a thermometer suspended from under an umbrella which he carried during a walk of one hundred yards registered 105° F., the temperature of his body was only 97°. The letter of Governor Ellis being communicated to the Royal Society 5 was thereby at once insured a wide circulation ; that of Franklin, though written first, was not made public, however, till afterward. 6 Shortly after the observation of Ellis, just referred to, it was ascer- tained by Tillet, 7 in experimenting with a baker's oven, that the young women in attendance were accustomed to remain in it for a few minutes even when at a temperature of 260° F.- (126.6° C). In one in- stance Tillet, anxious for the safety of the woman, requested her to come out, but she assured him she felt no inconvenience, and remained in the oven for ten minutes, the latter having a temperature of 280° F. (169° C), indeed, on her coming out, beyond the flushing of the face, there was nothing especially noticeable. While the facts just referred to excited considerable interest at the time, it was not till some years later, however, that any further experiments were performed with the object of ascertaining the effect of heated air upon the temperature of the body. In 1774, the subject, however, was taken up again by Fordyce, who, together with Blagden, Solander, Banks, and others, experimented upon themselves, either in a room heated with flues, and upon the floor of which boiling water was poured, or in rooms heated i Element* Chemise, p. 192. Lugd. Bat., MDCCXXXII. - Idem opus, p. 275. s Elementa Physiologiae, p 37. Lausanne, MDCCLX. 4 Works, vol. iii. p. 301. Phila., L809. '' Phil. Trans., 1759, vol. 1. p. 755, Part ii. 6 Journal de Physique, 177:;, tome ii. p. 45.S. i Mem. de l'Acad. 'Irs Sciences, 1764, to:ne lxxxi. p. 188. 480 ANIMAL HEAT. with flues only. The result of these experiments, as described by Blagden, 1 may be summed up as follows : In the room containing vapor Fordyce was able to bear for 10 min- utes a temperature of 110° F. (4:-3.3°" C), 20 minutes 120° F. (48.8° C), and for 15 minutes a heat gradually increasing from 119° to 130° F. (48.3° to 54° C). In these experiments, it is said, that the tem- perature under the tongue and of the urine did not rise higher than 100° F. (37.7° C). In the room heated with flues only, and con- taining dry air, Fordyce, together with Blagden and Banks in the room, could stand, however, a higher heat than in the former instance, supporting for ten minutes a temperature of 198° F. (92° C). Shortly after these experiments it was ascertained by Dobson, 2 from observa- tions made in the sweating-room of the Liverpool Hospital, that indi- viduals could stand for periods between 10 and 20 minutes a temper- ature, if the air be dry, of between ^02° and 224° F. (94.4° and 106.6° C.) Fordyce, himself, as mentioned in a subsequent paper by Blag- den, 3 was able to endure for 8 minutes even as high a temperature as 260° F. (127° C), the uncomfortable feelings experienced quickly passing away with the breaking out of a profuse sweat. The immunity possessed by persons habitually exposed from time to time to a dry atmosphere, having a temperature even higher than that to which For- dyce, Blagden, etc., were subjected, is undoubtedly due, in a great measure at least, as Franklin supposed, to the cold produced through the evaporation of the cutaneous perspiration and pulmonary exhalation. In this way can be explained how the workmen of the sculptor Chantry w r ent into a furnace having a temperature of 340° F. (182° C), and Chabert, the fire king, into one at between 400° and 600° F. (226° and 315.5° C). Indeed, the salutary effect, under such circumstances, of keeping the temperature down by evaporation was fully recognized by Fordyce and Blagden, 4 and proved by them in the following way : Two similar earthen vessels, one containing water only and the other an equal quantity of water, with a bit of wax, were put upon a piece of wood in the heated room. In an hour and a half the pure water was heated to 140° F., while that containing the wax had acquired a tem- perature of 152° F., as the wax in melting had formed a film upon the surface of the water, and thereby had prevented evaporation. Fur- ther, it was observed that the pure water never came near the boiling- point, but if a small quantity of oil was dropped into it, as had been done before with the wax, finally the water in both vessels boiled briskly. The effect of sweating in keeping down the bodily temperature is daily seen in the taking of Turkish as compared with Russian baths, an equally high temperature being much better borne in the former, on account of the air being dry, than in the latter, where the air is moist. The profuse perspiration induced through hot baths has long been a matter of comment ; as early as the first half of the last century Le Mon- nier, 5 in speaking of the natural hot baths at Baregas, with a temperature in the hottest part of 112° F. (44.4° C), observes that the sweat poured i Phil. Trans., vol. lxv., 1775, Part i. p. 111. 2 Idem, p. 4G3. 3 Idem, p. 484. 4 Op. cit., p. 491. 6 Mem. de 1' Acad, des Sciences, 1747, tome lxiv. p. 271. INFLUENCE OF BATHS UPON BODILY TEMPERATURE. -181 down from his face after remaining in it 8 minutes, and that after that time he was obliged to leave the bath, with reddened and swollen skin, and greatly increased pulse through violent attacks of vertigo. The conclusion drawn from the different experiments of Fahrenheit and Provost, Tillot, Fordyce, and Blagden, etc., that we have just described, was that man could not only exist in an atmosphere having a higher temperature than that of his own body, but that the latter remained unchanged, even when that of the surrounding atmosphere was greatly increased, notwithstanding that in an experiment with a dog the tem- perature was found by Fordyce to increase. It would appear, however, without doubt, from later observations, that with an increase in the temperature of the surrounding air there is an increase in that of the body. Thus, in the experiments made by De la Roche 1 and Berger, it was found that, after remaining 15 minutes in a vapor bath, with a temperature varying between 37.5° and 48.8° C. (99.5° and 119.6° F.), the temperature in the mouth was increased 3.1° C. (5.5° F.), while in dry air, but at a temperature of 80° C. (174° F.), the temperature was increased about 5° C. (9° F.). According to Davy, 2 also, who made a great number of observations in different parts of the world, the mean temperature of the body in the tropics is about 1° F. higher than in England. Such a variation has been held by Boileau, 3 for example, as abnormal, and as an indication of a slight disturbance in the system due to change of climate, and to which certain delicate persons are liable. The observations of Eydoux 4 and Souleyet, made during the voyage of the " Bonite," and of Brown-Sequard, 5 to the Isle of France, though less in number than those of Davy, so far as they go, confirm the result obtained by that reliable observer. Davy 6 also showed, from a number of observations, that the mean temperature of the air being 00° F. (15.5° C), that of the body was 98.28° F. (36.7 C,), whereas, if the temperature of the air rose to 80° F. (26.6° C), the temperature of the body rose to 99.67° F. (37.5° C). The temperature of individual portions of the body has been shown to increase with that of the surrounding medium, as well as that of the whole* body. In an experiment of Becquerel and Breschet, 7 for example, where the biceps muscle was surrounded for 15 minutes by water at a temperature of 42° (109° F.), the temperature, as deter- mined by their thermo-electric apparatus was increased two-tenths of a degree. Tbe rise in temperature, through increase of heat in the sur- rounding atmosphere, can be well shown in animals. Thus, according to Rosenthal, 8 the temperature of a rabbit rose from the normal, 38° C. (104.4° F.) to 45° C. (113° F.). while the external temperature was increased from 32° to 40° C. (89.6° to 104° F.), death taking place at the latter temperature. Essentially the same result was obtained in the experiments of De la Roche and Berger with a guinea-pig. Ac- cording to these observers, as well as Rosenthal, an increase in the tem- perature of 6° to 7° C. (10.8° to 12.6° F.) above the normal, however 1 These? de l'ecole de mfidecine de Paris, 1806, No. 11. Journal de physique, 1776, tome vii. p. 57. 2 Philus. Transact, L830, \>. 437. ■ 3 Lancet, 1878, p. 413. 4 Conip Rend., 1838, tome vi. p. 456. ■'■ Journal tie Physiology, t. ii. p. 554. 6 Researches, Phys. and Anat., p. 163. " Ann. des Sciences Nat., 1838, p. 271. 8 Op. cit., S. 337. 31 482 ANIMAL IIK AT. brought about, is fatal to all animals. It would appear from these ex- periments as well as the earlier ones of Provost and Fahrenheit, that large! animals bear a high temperature better than small ones, probably because, in the latter, a greater quantity of heat is produced relatively and more quickly. Thus, in the experiments of Fahrenheit, already referred to, of the three animals placed in the oven the sparrow died in 8 minutes, whereas the dog and the eat survived 28 minutes. According to De la Roche and Berger, a mouse died in 32 minutes, the temperature being increased from 57.5° to 63.7° C. (135° to 146.0° P.), ■while a guinea-pig survived 1 hour and 25 minutes, the temperature rising from 62° to 80° C. (143.6° to 177° F.); a young ass, however, though weak at the end of the experiment, successfully resisted for nearly three hours a temperature increased from 60° to 75° C. (140° to 107° F.). In the case of man, in certain pathological conditions, as in typhoid and typhus fever, the temperature of the body may rise to 40.5° and 41.1° C. (105° and 106° F.), and yet recovery take place. The highest temperature yet observed in man, and ending in recovery, was in a case of injury to the spine, reported by Dr. J. Teale, 1 in which the thermometer registered 122° F. (50° C). The elevation in temperature in sunstroke, 104° to 112° F. (40° to 44.4° C), is also very considerable ; in such cases, however, the high temperature is to be attributed, in part at least, not only to the effect of exposure to the sun's heat, but also to the exercise taken incidental to the character of the occupation of those usually attacked, such as field and street laborers, soldiers, etc. Inasmuch, as we have seen, through the free action of the skin, and with proper precautions taken as regards exercise, food, clothing, etc., man can live in an atmosphere the temperature of which is much higher than that of his body, it might naturally be supposed that through similar compensating agencies intense cold can be equally well resisted, if not better than intense heat. Such, indeed, experience proves to be the case, the temperature of the body of man, even when exposed to the intense cold of the Arctic regions, is almost the same as in the tem- perate ones, since the amount of heat generated absolutely is greater on account of the quantity and quality of food, and relatively so from the fact of the clothing, etc., being of such a character as to retain the heat produced. In animals the latter protective effect is provided for by their fur, wool, feathers, etc., as the case may be. A glance at Table LXVI. will show how little the temperature of the body in Arctic animals differs from that of the animals in temperate regions, though the difference in the temperature of the former, as com- pared with that of the surrounding atmosphere, may amount to as much as 76.7° C. (138° F.). 1 Lancet, March 6, 187o. INFLUENCE OF ATMOSPHERE. Table LXVI. 1 —Observations of Parry. Animal. Tiiuji. of animal. Temp, of air. Difference. Arctic fox . 41.5- C (106. r°F. ) —25.6° C. 67.1° C i it . 38.5 . 37.8 . 38.5 —20.6 —19.4 —29.4 59.1 57.2 67.9 t << . 37.6 —26.2 63.8 . 36.6 . 37.6 —23.3 —23.3 59.9 60.9 a << . 40.3 —20 3 7u. 7 White hare . 38.3 —29.4 67.7 Fox . . 37.8 . 41.1 —26.2 —35.6 64.0 76.7 a . 39.4 . 38.9 . 38. 3 — 32.S —31.7 —35.6 72.2 70.6 73.9 W olf . . 40.5 —32.8 73.3 483 On account of water being a better conductor, and having also a greater capacity for heat than air, the temperature of the body will fall more rapidly if exposed to cold water than to air at the same tempera- ture : hence the great effect of cold baths in the treatment of fevers so much in vogue, particularly in Germany, in late years, and the great benefit derived from the application of ice in the treatment of sunstroke. While man and animals can resist the most intense Arctic cold by the agencies just referred to, nevertheless a far less degree of cold, if sud- denly and directly applied to the body, will soon prove fatal. Thus, according to Rosenthal, 2 animals die if the temperature of their bodies be reduced to 24° C. (15.2° F.), and such is usually the case in man also, as shown by the clinical cases referred to by the same high authority ; as well known, however, the temperature in cholera may fall as low as 18.3° C. (67° F.). There are some other conditions in addi- tion to those already mentioned which may affect the temperature of the body. Of such are the effects exerted by race, country, labor, sea-sick- ness, and barometrical variations. As such influences are, however, either exceptional or temporary in their character, we will not dwell further upon them, merely mentioning that, according to the late dis- tinguished Professor Dunglison, 3 the temperature of the uterus during labor may rise as high as 106° F. (41.1° C), that of the vagina at the same time being 105° F. (40.5° C). I Gavarret, op. cit., p. 101. - Op. < it.. S. 133. Parrj 'e Journal, p. 130. Philadelphia, 1821 . :: Physiology, 1856, Sth ed., vol. p. 602. CHAPTER XXXII PRODUCTION OF ANIMAL HEAT. Having considered the temperature of the body, and the various modifying conditions, it now remains to account for the production of this heat, and the manner in which the latter is regulated. Notwith- standing that a certain amount of heat is produced through the double decompositions and hydrations continually taking place in the economy, 1 there can be no doubt that, by far, the greatest amount of heat pro- duced is due, as Lavoisier supposed, to the slow combustion continually o-oing on within the body of the animal, caused by the absorption of oxygen, the interchanging of which with carbonic acid, etc., we have seen, consti- tutes the essence of respiration. The various theories as to the cause of animal heat put forward at different times before, and even after, the errand generalizations of Lavoisier 2 had been made known, have, therefore, for us, now only an historical interest. We, therefore, merely allude in a passing way to the views that attributed animal heat to the reaction of certain of the fluids of the body, 3 to an archaeus vital spirit or kindred fetiches, 4 to fermentation, 5 movement of the blood in the vessels, 6 etc., recalling, however, the very remarkable work of Mayo, 7 and noting that Crawford 8 still maintained his view that animal heat was the latent heat of the inspired air, which, set free in the lungs, is taken up by the blood and carried thence, latent, to all parts of the body, becoming free heat again in the capillaries, even after the theory of Lavoisier had been developed. In our account of the progress in discovery by which the theory of respiration was slowly established we had occasion to refer to the great works of Lavoisier, in which, not only was the view of respiration essentially as we now understand it first distinctly enunciated, but the inference also drawn, which was later fully confirmed by experiment, that respiration was essentially the cause of animal heat. In the paper on the calcination of metals, brought before the Academy of Sciences, in 1775, Lavoisier had shown that in the decomposition of mercuric oxide by heat the principle (oxygen) so obtained supported both combustion and respiration, wdiereas, when the same substance was reduced by carbon the principle then obtained (carbonic acid gas) supported neither. These fundamental facts having been established, two years later Lavoisier 9 further showed that animals absorb oxygen and exhale carbonic acid, and during the 1 D'Arsonval, Comptes Rendus, Aout 25th, 1879. 2 Mem. de 1'Acad. des Sciences, 1775-1789. 3 Sylvius : Disput. med. cap vii. 1879. 4 Van Helmiiut : Opera Omnia, Anno 1707, pp. 174 ami 734. s Descartes (Euvres, ed de Cousin, t. iv. p. 437. 6 Haller : Elementa Physiol., t. ii. p. 286. 1 Tractatus de Kespiratione, 1668. 8 Experiments and Observations on Animal Heat, London, 1788. 9 Mem. de l'Acad. des Sciences, 1775, p. 520 THE CALORIMETER. 485 same year 1 formulated a view on combustion in general in which respiration was regarded as a slow process of combustion, oxygen being absorbed and carbonic acid and heat given off just as in the burning of coal. As might have been expected from the methods of investigation so characteristic of the great chemist and physiologist, Lavoisier did not long rest satisfied with the establishing of a generalization as to the nature of respiration and heat as important as that just referred to, but soon instituted a series of experiments with the view of ascertaining whether the amount of carbonic acid exhaled and heat produced by an animal in a given time was such as ought to be expected on the supposition that a certain amount of carbon had been burned in the body of the animal, the amount of carbonic acid given off and heat produced by the combus- tion of a similar amount of carbon outside of the body having been pre- viously determined, and of so establishing the truth of his theory by experimental demonstration. For this purpose, in conjunction with Laplace, he invented the ice calorimeter. 2 This consisted essentially of three chambers, concentrically disposed, and which could be thoroughly closed above, two of the chambers opening below the stopcocks. In the innermost chamber was placed the substance whose heat was to be determined, in the middle one ice, the melting of which was the measure of the heat produced, it having been previously determined how much heat is required to melt a given quantity of ice, while in the outer chamber ice was also placed in order to shield that in the middle chamber from the external temperature. Having concluded from their experiments with the ice calorimeter that a pound of carbon, when burned, would produce heat enough to melt 95.6 pounds of ice, 3 Lavoisier and Laplace then placed a guinea-pig in the innermost chamber of their ice calorimeter, so modified as to permit of the free passage of a current of air, so that the respiration of the animal should not be interfered with, and found that in ten hours 402.7 grammes ((3043.9 grains) of ice had been melted. But, of the heat given out during the experiment, and to the effect of which the melting of this amount of ice was due, part only evidently could have been produced by the guinea-pig, since, as Lavoisier observes, the animal must have lost heat through exposure to the sur- rounding cold ; further, the ice would have been melted to a certain extent by the cooling of the watery vapor exhaled by the animal, while, finally, the amount of the melted water, measuring the heat produced by the animal, would have been increased by the admixture of the condensed water. Lavoisier felt himself, therefore, warranted in deducting from the 402.7 grammes of ice actually melted 61.19 grammes as representing the ice melted by the heat due to the extraneous sources just mentioned, and not actually produced by the animal during the experiment, the latter being, of course, the difference, and amounting to 341.07 grammes. But, the amount of carbon burned by the guinea-pig while in the calorimeter, as deduced from the carbonic acid exhaled, as determined by previous experiments, would have been only sufficient to 1 Ibid., 1777, p. 183. ; Mem. do I' Acad, dea Sciences, 1780, p. 355. 3 Or, as we would now express it, a pound (if carbon when burned in the calorimeter produced 3740 calories or heat units — that is, heat enough to raise the temperature of 1 kilo of water 3740° C. or 3740 kilo of water 1° C. 486 PRODUCTION OF ANIMAL HEAT. have incited 826.75 grammes of ice, whereas, as we have just seen, at least 341.07 grammes must have been actually produced by the animal, it is evident that some of the heat produced by the guinea-pig must have been due to the combustion of some other substance than its /326 75 \ carbon, as only 96-100th ( ' -- — - =0.'JG ) of the heat could be ac- J V341.07 / counted for. 1 This fact, together with another one observed at the time, namely, that all the oxygen absorbed did not return in the carbonic acid exhaled, led Lavoisier 2 afterward (1785) to the conclu- sion that of the oxygen inspired part combined with hydrogen to form water and that the heat developed by the combustion of the hydrogen, if added to that due to the combustion of the carbon, would account for the heat produced by an animal, as in the experiment with the guinea-pig, just described, and which could not be accounted for by the combustion of the carbon alone. The final conclusion of Lavoisier as to the nature of respiration and calorification, based upon the closest reasoning, observation, and experiments, extending over many years, is best expressed in his own words: 3 " Respiration is only a slow com- bustion of carbon and hydrogen, and which resembles in every respect that which goes on in a lighted lamp or candle, and, from this point of view, animals which respire are true combustibles, which form and con- sume themselves. In respiration, as in combustion, it is the atmos- pheric air which furnishes the oxygen and caloric, 4 but, as in respira- tion, it is the substance itself of the animal ; it is the blood which furnishes the combustible. If animals do not repair habitually by food that which they lose in respiration, the oil will soon give out in the lamp, and the animal would perish, as a lamp extinguishes itself through want of feeding. The proof of this identity of effects between respiration and combustion is immediately furnished by experiment. In fact, the air which has maintained respiration does not contain any longer, at its exit from the lungs, the same quantity of oxygen ; it contains not only carbonic acid, but, in addition, more water than it contained before inspiration. But, as the vital air can convert itself into carbonic acid only by the addition of carbon, and into water only by the addition of hydrogen, and, as this double combination can not take place without the vital air losing a part of its specific caloric, it results that the effect of respiration is to extract from the blood a por- tion of carbon and hydrogen, and, to replace them, a portion of its specific heat, which, during circulation, distributes itself with the blood in all parts of the animal economy, and maintains there that constant temperature observed in all animals that breathe." It would appear that this analogy, which exists between respiration and combustion, had not escaped the poets, or rather the philosophers 1 The amount of ice actually melted was, according to Lavoisier (op. cit., p. 405), l.i oz., and that esti- mated from the combustion of the carbon, 10.38 oz. The numbers given in the text are those of Gavarret, op. cit., p. 174. 2 Hist, de la Societe Royale de Medecine, 17S7, 568. 3 Mem. de l'Acad. des Sciences, 1789, p. 570. * To appreciate this passage it must be borne in mind that at the date when it was written oxygen was supposed to be composed of oxygen united with caloric, the principle of heat or fire, and that during the formation of carbonic acid through the combination of oxygen with carbon the caloric was set free. THE CALORIMETER. 487 of antiquity, of which they were the interpreters and the organs. The fire snatched from Heaven, the flame of Prometheus, is not merely an ingenious and poetical idea, it is a faithful picture of the operations of nature, at least for animals which breathe. We can only say with the ancients that the flame of life is lit at the moment that the infant breathes for the first time, and that it is only extinguished with its death. In considering relations so happily we are sometimes led to believe that, in fact, the ancients had penetrated further than we think in the sanctuary of knowledge, their fables being truly only allego- ries, under which they concealed the great truths of medicine and of physics. And now, after a lapse of more than a century, the only essential criticism that we can make upon the magnificent views so poetically expressed, apart from the theory of caloric implied, is as to the part of the body where the combustion was supposed to take place, Lavoisier regarding the lungs as the seat of the combustion; whereas, we know now that it is going on in all parts of the body. But, even while holding this view, Lavoisier showed his profound appreciation of the phenomena, since he distinctly states, in a previous communication, 1 that possibly the carbonic acid is not produced, but only exchanged with oxygen in the lungs. However important his generalizations as to the matter of respiration and animal heat, nevertheless, dying on the scaffold a victim to the fury of the French Revolution, Lavoisier left his work unfinished. With the view of settling, if possible, some of the questions left undetermined by their great chemist, the Paris Academy offered, in 1821, a prize for the best essay on the origin of animal heat. The prize being awarded to Depretz, his essay was shortly afterward published, 2 that of the unsuccessful competitor, Dulong, 3 not, however, until several years afterward — in fact, after the death of its author. To avoid repetition, we will consider the appa- ratus and results of these experimenters together. The calorimeter of Dulong and Depretz did not differ in principle essentially from the water calorimeter previously made use of, for the same purpose, by Crawford. 4 It consisted essentially, like the latter, of two chambers, an inner one, in which the animal within a willow cage was placed, and an outer one, containing the distilled water, the elevation of whose temperature was taken as the measure of the heat produced by the animal. In the calorimeter of Crawford, however, while the air of the inner chamber was gradually diminished, and at the end of the experiment was transferred to an eudiometer for analysis, in that of Dulong and Depretz the air in the inner chamber was con- tinually renewed by air from a gasometer, and being transmitted from the inner chamber through a spiral tube placed within the water of the outer chamber, passed thence into a water gasometer, where it could be measured and analyzed, the air, in the mean time, as it passed through the spiral tube, giving off the heat (communicated by the animal) to the surrounding water, and so elevating its temperature. The amount 1 Mem. de 1'Acad. des Sciences, 1777, p. 191. 2 Ann. de Chimie et de Physique, 1824, t. xxvi. p. 337. 3 Ibid., 3ienie aerie, 1841, t. i. p. 440. 4 Op. cit., p. 315. 488 PRODUCTION OF ANIMAL HEAT. of heat produced by the animal, as determined by the elevation of the temperature of the water, being expressed in calories, or heat units, ;i heat unit being the amount of heat necessary to elevate the temperature of a pound of distilled water one degree Cent, or Fahr., according to the thermometer used, or, as is more usually understood at the present day, the amount of heat necessary to elevate the temperature of one kilo. (±2 lbs.) one degree Cent. The amount of heat produced by the animal expressed in heat units while in the calorimeter is then obtained by multiplying the weight of the water by the number of degrees by which the temperature of the water has been increased. Suppose, for example, that the, water in the calorimeter weighed 20 kilo., and its temperature had been elevated as shown by the thermometers two degrees Cent., then 40 calories, or heat units, would have been produced during the experiment by the animal, the latter having neither gained nor lost heat, since, if the animal gained heat, it is evident that all of the heat produced was not given off' to the water, and if it lost heat the latter was not produced during the experiment, but simply radiated away from it, as would have been the case with any heated body. In the first case, the heat retained by the animal must be added to the heat as determined by the calorimeter ; and, in the second case, the heat lost by the animal must be subtracted. In making calorimetrical experiments, therefore, the temperature of the animal must be taken at the beginning and the end of the experiment. It must be also remem- bered, however, that the materials entering into the composition of the calorimeter, such as copper, iron, brass, etc., absorb heat, even if in less amount than the water, and this heat also expressed in heat units must be added to that absorbed by the water. This can be readily estimated, the weight of the materials and their specific heat, or capacity for heat, being known, the capacity for heat of water being taken as unity. Suppose, for simplicity, that the calorimeter is made out of copper, much like the one we shall use, and that it weighs 10 kilo. ; now the specific heat of copper being 0.09 that of water, it is evident that if the 10 kilo, of copper be multiplied by 0.09, the product 0.90, or the water equivalent, when multiplied by the two degrees Cent, equals 1.8, which will be the amount of heat expressed in heat units absorbed by the copper, and which must be added to the 40 heat units already obtained ; or, what is the same thing, if the water equiv- alent of the copper, 0.9, be added to the 20 kilo, of water, and the result 20.9 be multiplied by 2, the quotient will be the same as before — that is, 41.8 heat units produced by the animal. In other words, each kilo, of copper, having 0.09 the capacity of heat of a kilo, of water, 10 kilo, of copper may be regarded as equivalent to 0.9 kilo, of water, which, when added to the 20 kilo, of water and multiplied by 2, or the temperature gained, gives 41.8 heat units. It is hardly necessary to add, after Avhat has just been said, that of the other metals usually entering into the construction of the calorimeter the heat absorbed by them, as well as that retained or given off by the animal, which, as we have seen, must be added to or subtracted from the 41.8 heat units, for example, according as the animal has gained or lost heat during the experiment, is determined in exactly the same way as in the case of SPECIFIC HEAT OF TISSUES. 489 the copper. As regards obtaining the water equivalent of the animal — that is, its weight multiplied by its specific heat — a difficulty presents itself, since the specific heat of the animal has not been absolutely deter- mined. The latter is usually accepted as being 0.8, l the mean specific heat of the tissues so far determined, that of water being 1. In deter- mining the amount of heat given off by an animal in a calorimeter there is another consideration which must not be overlooked, and which is a slight source of error even in the best constructed calorimeters. That is the slight loss of heat due to conduction and radiation from the instrument, and which cannot be entirely prevented. The loss of heat from this cause, hoAvever, can be reduced to a very small amount by proper precautions, such as surrounding the calorimeter with down, etc., as was done by Crawford, or by lowering the temperature of the water in the calorimeter some degrees below that of the surrounding atmosphere, the supposition being that the heat absorbed by the sur- rounding air during the first half of the experiment would be radiated back again during the latter half, and that this source of error could, therefore, be neglected, as was admitted in the experiments of Dulong and Depretz. The loss of heat due to radiation, etc., can be also deter- mined experimentally, and can be then taken into account in the final calculation ; or, by self-regulating gas-jets, heat can be supplied to restore that which is lost. Further, it is important that the heat should be thoroughly diffused through the water in the calorimeter ; this can be accomplished by the stirrers, as in the apparatus of Dulong and Depretz, or by any other suitable mechanical arrangement. The great improvement in the experiments of Dulong and Depretz, however, as compared with those of their predecessors, consisted in comparing the expired air with the inspired air, and determining the amount of heat produced and carbonic acid exhaled simultaneously ; whereas, in the ex- periments of both Lavoisier and Crawford, this was done with the same animal, but at different times. Notwithstanding the great number of experiments performed by Dulong and Depretz, and the general accept- ance with which their views were received, not much importance can be attached to them at the present day on account of the following reasons : First. That the temperature of the animal within the calorimeter was assumed to remain unchanged during the experiment, although Lavoi- sier had distinctly called attention to the improbability of such being the case. Second. Of the amount of carbonic acid exhaled by the animal being underestimated, part of it being absorbed by the water of the gasometer into which it passes. Third. Of the amount of heat, as deduced from the carbonic acid exhaled, being also underestimated, both on account of the estimate of Lavoisier of the heat produced by the combustion of carbon and hydrogen obtained with an ice calorimeter, being accepted as the basis of comparison with the heat produced by an animal in a water calorimeter, and because the heat-producing power of the carbon and hydrogen burned even, as determined by Lavoisier, is manifestly too low as shown by the later and accurate experiments of Fabre and Silberman;- and further, that no account was taken of the 1 Liebermeister : Handbuch der Pathologic u. Therapie des Fiebers, p. 147. Leipzig, 1875. Rosen- thal : Archiv f. Anat.. etc., 1878, p. 215. '-' Ann. do Chimie et de Physique, 3ieme ser., t. xxxiv. p. 357 ; t. xxxvi. p. 51 ; t. xxxvii. p. 405. 490 PRODUCTION OF ANIMAL HEAT. heat produced by the burning of the sulphur and phosphorus in the animal economy. Fourth. That the ratio of the carbon to the hydrogen was erroneously estimated, an important source of error, since far more heat is produced by the combustion of hydrogen than by an equal weight of carbon. Fifth. From the carbon and hydrogen, to whose combustion is the heat principally due, being supposed to exist in the free con- dition, which they evidently do not. Sixth. From the fact, to a cer- tain extent, of the exhalation of carbonic acid and water not being a measure of the heat produced, some heat being evolved through double decomposition and hydration, etc., without carbonic acid and water being necessarily exhaled and of carbonic acid and water being exhaled through the decomposition of the principles containing these substances, without the heat being evolved. This last objection applies to all calori- metrical experiments in which the heat produced by the living body is estimated from the carbonic acid and water exhaled. It is true, that later investigators have endeavored to utilize the results of Dulono; and Depretz in considering them as influenced by the conditions just referred to, since the attempts, however, have been far from satisfactory, it is not necessary for me to dwell upon them. While the results of Dulong and Depretz, even when so corrected, cannot be accepted, nevertheless the conclusion arrived at by these experimenters exercised a most impor- tant and beneficial influence upon the progress of physiology, since it was shown by them that the experimental method was the only one by which the phenomena of animal heat could be successfully studied, that so-called vital phenomena are physico-chemical phenomena, and must be investigated in exactly the same manner as the latter, a view wdiich had fallen entirely into disrepute in France since the death of Lavoisier, the influence of Bichat being so preeminent. In the words of that other- wise profound thinker, 1 "let us leave to chemistry its affinity, as to physics its elasticity, its gravity — let us employ for physiology only sensibility and contractility." To the deus ex machina, the vital force, that physiological fetich, then as even now every unexplained phenomenon was attributed. Indeed, it may yet be asked how long will it be before such an idea as a vital force acting as an entity is entirely banished to that obscurity where such a conception similar to that of nature abhorring a vacuum, etc., has long since been relegated. During late years a number of investi- gations have been made calorimetrically, with the object of determining the heat produced by an animal in a given time. Among these may be mentioned especially those of Senator 2 upon dogs. The calorimeter used in these experiments was essentially the same as that of Dulong's, the only difference being that it was usually filled with warm water in order to prevent the animal losing heat. The ventilation of the chamber in which the animal was placed was maintained by aspiration, the cur- rent of air, before entering the calorimeter, being freed from its carbonic acid by passing it through potash, and the carbonic acid exhaled into it by the animal being determined after it left it by Pettenkofer's method. In the final estimation of the heat produced by the animal in addition to that taken up by the calorimeter, the heat absorbed by the air passing i Anatomie Generale, tome i. p. 16. Paris, 1818. 2 Archiv f. Anat. u. Phys., 1872, S. 1 ; 1874, S 18. THE CALORIMETER. 491 through as well as that lost through conduction and radiation, was also taken into consideration. Senator found, as the mean of his experi- ments, that a dog fed daily produced 16.5 calories or heat units per hour, with an exhalation during the same time of 4.4 grammes of car- bonic acid, as a general rule, there being produced 2.5 calories for every kilo. (2.2 lbs.) of weight. In order to obtain the amount of heat pro- duced in twenty -four hours, it is usual to multiply the 16.5 calories, e. //.. by 24, but as it is uncertain whether the production of heat is constant, this is hardly admissible. The general conclusion to be drawn from the experiments of Senator is, that there is no constant relation existing between the production of heat and the exhalation of carbonic acid, and while during digestion the production of both is increased, in starvation both are diminished. The calorimeter (Fig. 257) that we make use of consists of two copper cylinders concentrically disposed, the outer space a, or the space between Fig. 257. Calorimeter. the cylinders being closed at both ends with copper, the inner space b, or the space within the cylinder, being closed at one end by copper and at the other end by an annular door consisting of brass and glass, and which can be hermetically closed by the brass clamps and rubber facing soldered to the brass rim internally. The outer chamber a is filled with distilled water by means of a funnel introduced through the opening/', and when full contains 18.1 kilo. (40 lbs.) of water. The inner chamber b, at the end opposite the door, communicates by a stop- cock (d) with the external air. and through the opening h in its roof with a copper spiral, which, after making a dozen turns around the inner cylinder within the water of the outer chamber, terminates in the open- ing k of the latter. By means of the mercurial pump (already described) the ventilation of the inner chamber can be thoroughly maintained, 492 PRODUCTION OF ANIMAL HEAT. the air entering the latter through the opening at d and passing thence by the opening h into the spiral i and out by the opening k with the same temperature at which it entered, the heated air being gradually cooled as it passes through the spiral, the heat being absorbed by the surrounding water. If it is desired to compare the expired with the in- spired air, the air freed from its water and carbonic acid by Voit's method is made to pass through a meter, before it enters the calorimeter and through one after it leaves it, being previously freed from its water and carbonic acid in the same manner as was the inspired air. Fitting in the floor of the inner chamber of the calorimeter is a movable copper pan with a sieve-like cover on which the animal rests, the object of the cover being that the urine of the animal can trickle into the pan and insure cleanliness. Ventilation having been assured by the action of the pump, and the temperature of the water in the outer chamber noted by introduc- ing a thermometer into the opening/ and that of the animal taken, the latter, having been previously weighed, is placed within the chamber on the tray and the door securely closed. Suppose the experiment has lasted one hour, and it be admitted that the heat lost by radiation and conduc- tion from the calorimeter be replaced by that furnished by the gas jets, the flow of gas being regulated by the valve V, which with the heating of the water is pressed outward (through the pressure of the column of water in the tube t, replacing the thermometer) against the opening transmitting the gas and thereby diminishing its flow, and which with the cooling of the water, is drawn back again from the opening, thereby increasing it again. To determine the calories or heat units produced by the animal, a rabbit, for example, during the time mentioned, we have only now to multiply the number of degrees by which the tempera- ture of the water has been increased by its weight, to which has been added the water equivalent of the copper, brass, glass, rubber, and solder entering; into the construction of the calorimeter, and adding or subtract- © © ing the heat gained or lost by the animal as determined immediately at the conclusion of the experiment. Suppose that the temperature of the water in the calorimeter has increased 0.5° C, the temperature at the beginning of the experiment being 15° C. (59° F.), and at the end 15.5° C. (59.9° F.), and the 'ate r equivalent. copper = 21 lbs. X 0.095 = 1.995 It " brass = 23.25 lbs. X 0.093 ;= 2.162 tl " iron = 0.09 " X 0.11 = 0.009 it " glass = 1.25 " X 0.19 = 0.237 it a rubber = 0.6 " X (1) = 0. o 1 11 a tin = 0.5 " X 0.05 = 0.025 it a a leaH = 0.5 " X 0.03 = 0.015 it materials = 4.443 x\dding the water equivalent of the materials used, 4.4 lbs., to the weight of the water, 40 lbs., making 44.4 lbs., or 20.1 kilo., and multi- plying the latter by 0.5° C, the number of degrees gained by the water, the product, 10.05, will be the number of calories or heat units produced 1 Specific heat of rubber slip not being determined, the heat actually produced was slightly greater than that given in text. The amount, however, would be so small that it may be neglected. HEAT PRODUCED IN TWENTY-FOUR HOURS. -193 by the animal, supposing the temperature of the latter to have remained unchanged. Suppose the animal, however, lost 0.9° C, its temperature being 39.2° C. at the beginning of the experiment and 38.3° C. at the end, then there must be subtracted from the 10.05 calories 2.16 — that is, the product of the weight of the rabbit, 6.6 lbs. or 3 kilo., by its spe- cific heat, 0.8° by 0.9° (3 X 0.8 X 0.9 = 2.16): the total number of heat units produced by the rabbit in the hour would then be 7.8 calories. If the rabbit gains the same number of degrees, then the 2.16 calories must be added to instead of being subtracted from the 10.05 heat units. Calorimetrical investigations have been made also upon man by Schar- ling, 1 Vogel, 2 and Hirn, 3 but with rather unsatisfactory results. The apparatus made use of by these experimenters was essentially the same, consisting of a chamber in which the man was placed and which was kept in a room maintained at a temperature as constant as possible, the increase in the temperature of the chamber, together with the heat lost through cooling, being regarded as produced by the man during the experiment. Since the temperature of the chamber after being some- what elevated after that remains constant, the heat as produced being radiated away, according to the Xewtonian law of cooling, the amount of heat produced will be equal to the difference between the constant temperature and the initial temperature multiplied by the coefficient of cooling, the latter being determined experimentally. In the experiments of Scharling and Yogel this was accomplished by placing a vessel filled with hot water in the chamber and comparing the loss of heat with the increase of the chamber, and in those of Hirn by burning hydrogen and comparing the actual result Avith that obtained by calculation. On account of the many sources of error incidental to such a crude method of experimentation as that just described, an approximate value only can be attached to the results so obtained, and the same may be said of the estimates of the amount of heat produced based upon the rise in the temperature of the water of a bath in which a man is immersed, 4 or of that of a calorimeter inclosing only a part of a person, a limb, for ex- ample. 5 Nevertheless, it should be mentioned that the estimates of these observers of the heat produced by a man in twenty-four hours do not differ as much as might be supposed, amounting, according to Scharling, Vogel, Hirn, Liebermann, and Leyden, to 3168, 2400, 3720, 3525, and 2376 calories respectively, allowance being made for the size and weight of the individual experimented upon. Since the heat produced by an animal is due to the combustion of its food, it might appear at first sight that it would be only necessary to determine the amount of combustible materials, carbon, hydrogen, sul- phur, phosphorus, etc., in the food, and the products of its combustion carbonic acid, water, urea, etc., in the excreta in order to determine the amount of heat produced, on the principle of the heat produced by the animal depending upon the fuel supplied and consumed, the calori- meter being used as a test of the accuracy of the results so obtained. 1 Journal fiir pract. Chemie, xlviii. S. 435, 1849. - Arcliiv (1. ver. !'. Wiss. Heilk. Neue folge, Band i. S. 441. 1865. 3 Kecherches sur 1' equivalent mecanique de la chaleur, Oolmar, 1858. Exposition analytique et ex- perimentale de la theorie mecanique tie la chaleur, 3d ed., t. i. p. 27. Paris, 1st.",. • Liebermeister, >>\>. >it., p. 239. » Leyden : Deutseh. Arcliiv f. klin. med., 1869, S. 273. 494 PRODUCTION OF ANIMAL HEAT. It must be borne in mind, however, that to effect the combustion of the food — that is, its transformation into carbonic acid, water, etc., a certain amount of beat, or an equal amount of force of some kind, is required, since the carbon, hydrogen, and other combustible matters do not exist in the food in the free gaseous state, but in a state of molecular combination. A certain unknown amount of heat would have to be deducted therefore from the amount estimated if based upon an analysis of the food and the excreta. In other words, the heat pro- ducing power of food, or any fuel, cannot be estimated from the amount of combustible matters it may contain, since the heat to be expended in breaking up the chemical combinations constituting these matters, and of setting free the heat previously locked up in them is practically unknown. It is for the reasons just given, as well as for the further one of the accepted estimates of Dulong of the amount of heat produced by the combustion of a given weight of carbon, hydrogen being too low, that the calculation of Helmholtz 1 of the amount of heat produced by a man weighing 82 kilo, in twenty-four hours, viz., 2731.2 calories, can only be accepted as approximating the truth. And while the calculation of Ludwig, 2 of a daily produc- tion on the average of 3191.9 calories is free from the last source of error mentioned, being based upon the data of Barral and the higher estimates of Fabre and Silberman of the heat value of the carbon and hydrogen burned, nevertheless, as it also assumes that the combustion of the carbon and hydrogen of the food develops as much heat as if existing in the free condition, it is open to the same objection as the calculation of Helmholtz. In fact, the only way in which the amount of heat produced through the combustion of food can be actually deter- mined, is by burning it in a calorimeter, as was done by Frankland, 3 and of so obtaining its heat value by direct experimentation. The instrument we make use of for this purpose, the same as that of Frank- land, of the convenient form devised by Thompson, consists of a copper cylinder with a capacity of 120 c. cm. open below, and with the rim perforated by a small opening, but closed above, and with the cavity of the cylinder prolonged into a narrow tube provided with a stopcock near its end, and of a smaller cylinder with a capacity of 15 c. cm. open above, but closed below, the lower portion of the cylinder fitting into the little cup of the stand, the latter being provided with three elastic springs which securely hold the large cylinder when the latter encloses the small one Within the small cylinder is placed the substance to be burned with a small fuse attached with a combustible whose heat values are known. The latter being lighted, the large cylinder is immediately placed over the small one, the elastic springs holding it fast, and the instrument so put together at once plunged into a long, narrow vase containing a known quantity of distilled water whose temperature has been accurately determined by a specially constructed thermometer graduated into tenths. In a few moments fumes will be seen to issue from the holes in the rim of the outer 1 Encyl. Worterbnch der Med. Wissen, Band xxxv. S. 55.5 Berlin, 1846. 2 Lebrbuch der Physiologie des Menschen, Zweiter Auflage, Zweite Band, S. 749. Leipzig, 1861. 3 Pbilos. Mag., 1866, xxxii. p. 182. HEAT VALUE OF FOODS. 495 cylinder into the surrounding water. The deflagration being ended, and the stopcock opened, the water will rise through the holes into the cylinders. The instrument being moved up and down, the heat given out will soon diffuse itself equally throughout the water, the amount of heat produced by the food burned being determined by the elevation of the temperature of the latter, due allowance being made on the one hand for the heat absorbed by the copper, etc., and on the other for that produced by the burning of the fuse and com- bustible used. The other sources of error incidental to the working;; of the apparatus are so slight that they may be, according to Frank- land, neglected. It was by means of the calorimeter just described that Frankland determined by actual experiment the amount of heat developed by the combustion of different kinds of food. It will be seen, however, at a glance at Table LXYIL, drawn up from the results obtained by this observer, that the fatty and carbohydrate foods are as thoroughly burned in the body as out of it, though more slowly, whereas the albuminous substances are but imperfectly so. This is as might have been expected, since, as Ave have already mentioned, except in certain temporary conditions in a state of health, fat and starch are never found in the excreta, these substances passing out of the body as carbonic acid and water, being as thoroughly oxidized within the svstem as if burned in pure oxygen outside of it, whereas, as we shall presently see, uric acid and urea are normal constant ingredients of the excreta, these substances representing so much unburned albumen which passes out of the system in this form. Table LXVII. 1 — Heat developed by burning 1 gramme (15.4 gr.) of DIFFERENT ARTICLES OF FOOD EXPRESSED IN HEAT UNITS. A heat unit is equal to the amount of heat necessarv to raise the temperature of 1 kilo. (2.2 lbs.) of distilled water 1° Cent. (1.8° F.). When oxidized outside of body. When oxidized inside of body. Cod-liver oi 1 Fat of beef Butter Guiness' stout . Arrowroot Lump sugar Grape sugar Yelk of egg Hard boiled egg Cheese Mackerel Lean of beef Milk. White of egg . Veal . Ham (boiled) . Bread (crumb) . Flour Rice (ground) . Cabbage . Potatoes . Dry. Natural condition. Dry. Natural condition. 9.107 9.107 9.069 9.069 7.264 7.264 6.401 1.076 6.401 1.076 3.912 3.912 3.348 3.348 3.227 3.227 6.460 3.423 6.24 ' 3.30 6.321 2.383 6.05 2.2S 6.114 4.647 •">.74 4 36 6.064 1.789 5.71 1.61 5.313 1.567 4.S."> 1.42 5.093 0.662 5.07 0.62 4.896 0.671 4.21 0.57 4.514 1.314 4.02 1.11 4.343 1.980 3.68 1.68 3.984 2.231 3.84 1 .45 3.936 3.84 3.813 3.76 3.776 0.434 3.65 ' 0.42 3.752 1.013 3.69 0.99 1 Frank 1 and, op. cit. 496 PRODUCTION OF HEAT. According to Frankland, while 1 gramme of ox flesh and of albumen will produce, when burned out of the body, 5.103 and 4.988 heat units, the same amount of these substances when burned in the body will produce only 4.368 and 4.263 heat units respectively, the differ- ence of <>.73. r ) heat unit being due to that amount of heat passing out of the system latent locked up — so to speak — in the urea or theunburned albumen, 1 gramme of urea producing, when burned outside of the body, 2.206 bent units. In estimating the amount of heat produced by the burning of albumen within the body, as based upon that pro- duced when burnt outside of it, about one-third must therefore be deducted as representing so much incombustible matter. Thus 1 gramme of albumen, when burned outside of the body, will give 4.998 heat units, of which albumen and urea constitute about one-third ; deduct- ing 0.735 heat unit, or the heat that would be produced were the urea burned in the system, there remain 4.263 heat units as the actual amount of heat produced when the albumen is burned in the system. Having learned the amount of heat developed in the burning of a given weight of sugar, fat, albumen, etc., out of the body, it still remains, knowing by analysis how much of such substances is con- tained in the food, to determine from the carbonic acid, water, and urea in the excreta, or the products of the combustion of such substances, the amount actually burned in the body, and of so estimating, by means of the above data of Frankland, the amount of heat developed within the body on a normal diet, or otherwise. In other words, the ingesta or the food must be compared with the egesta or the excretions. The subject of the observation must be weighed at the beginning and the end of the experiment to learn whether the weight has remained unchanged, since, if the individual loses weight, the food has been deficient, the body wasting to supply it ; and, if the reverse is the case, the food has been in excess, the body fattening. Further, the experiment should extend over a period of twenty-four hours, and longer, when possible, in order to avoid the usual source of errors incidental to all experiments of such a character if lasting for shorter periods of time. It was on such prineiples that the admirable experiments of Ranke, performed upon himself, were conducted, and it may be mentioned, incidentally, in this connection, that at that time the distinguished physiologist was twenty- four years old, six feet high, weighed one hundred and fifty-four pounds (70 kilos.), was in perfect health, and that the apparatus made use of was the Pettenkofer respiration apparatus that we have already referred to. The results obtained by Ranke, by means of the method just described, may be seen from Table LXVIII. HEAT VALUE OF FOODS. 497 Table LXVIII. 1 — Heat produced in 24 hours by the combustion of FOOD WITHIN THE BODY AS ESTIMATED FROM THE EGESTA, AND EX- PRESSED IN HEAT UNITS. Nitrogenous Diet. Ingesta. Meat. 1832 grammes, 1300 " consume Fat of meat, 70 " Salts, 31 " Water, 3371 c.c. Fat of body, 75.14 grammes, Water " * 71.00 Initial weight Terminal weight Heat units produced Ingesta. Body consumed. Albumen, 54.45 grammes. Fat, 195.94 N Egesta. N c G2.29 229.3(3 Urea, 86.3 40.28 17.26 44.19 162.75 Uric acid, 1.9 0.65 0.70 0.00 50.27 Salts, 26.6 Urine, 2073 c.c. b.'ob 54.02 Feces, 99.0 3.26 14.88 Respiration, 44.19 231.20 44.19 267.04 267.04 . 72.927 Ml. . 72.781 " 0.146 gramme. 2779.5 Starvation Diet. Heat units produced .... Non-nitrogenous Diet Ingesta. Starch, 300 grammes. Urea, Sugar, 100 Uric acid, Fat, 150 " Feces, Albumen of body, 51.55 " Respiration, Egesta. Urea, 18.3 grammes. Uric acid, 0.24 " Respiration, 180.00 cubic metres. . 2012.8 Heat units produced Heat units produced Mixed Diet. Egesta. 17.1 0.54 90.00 200.00 cubic metres. . 2059.5 2200 It Avill be observed by looking at the table that the greatest amount of heat was produced on a nitrogenous, or a very abundant meat diet, but that this was accomplished at the expense of the body, Ranke losing 14(3 grammes in weight, his body supplying 75.14 grammes of fat in addition to the 70 grammes of roast meat and 71 grammes of water, and that of the 1832 grammes of meat eaten only 1300 grammes w r ere burned, as shown by the amount of urea excreted. It follows, there- fore, that, so far as the production of heat was concerned, the same result might have been obtained with 532 less grammes of meat, but with 71 more grammes of fat. On the other hand, as Ranke mentions in speaking of the heat produced on a non-nitrogenous diet, of the 150 grammes of fat eaten only 68.5 grammes could have been burned, 81.5 grammes having been deposited in the body. On such a diet, there- fore, more than half the fat, if taken with the view of producing heat, would be superfluous. While the heat developed on a mixed diet, as may be seen from Table LXVIII., amounts, according to Ranke, to 2200 i Ranke : Physiologic Dritte Aufl., S. 196, S. 5G6. Leipzig, 1875. 32 49" PRODUCTION OF ANIMAL HEAT. heat units, Vierordt 1 estimates it at 2497, and Voit 2 even still higher (3066). It should be mentioned, however, that the food, at the expense of which the latter amount of heat is produced, contains far more albumen, fat, starch, sugar, etc., than that taken by Ranke 3 in his experiments, as may be seen from the following : Table lxix. Albumi n. (•'at. St iireh or sugar. Total. Ranke . 100 100 240 440 grammes, Vierordt . 120 90 330 .".40 Voit . . 118 50 500 668 Let us take, however, the lowest estimate, that of Ranke, and sup- pose that the heat produced by the burning of the food will produce 2200 heat units — that is, an amount of heat that will elevate the tem- perature of 2200 kilo, of distilled water one degree Cent., that is, 70 kilo. 31.4° C, or, what is the same thing, 154 pounds of water 56.5° F. : such an amount of heat, if applied to the heating of the human body, would elevate its temperature 1.7° C, or 3° F. higher, since a human being weighing 70 kilo. (154 pounds) consists of only three- fifths water, the remaining two-fifths being tissue, and the specific heat of the latter being less (0.8) than that of the water, the same amount of heat, namely, 2200 heat units, when applied to the heating of a body weighing 70 kilo., consisting of 44.1 kilo, of water and 25.9 of tissue, must naturally elevate its temperature higher than if the 70 kilo, to be heated consisted of water alone, as shown by the fol- lowing : 25.9 kilo, of tissue multiplied by its specific heat, 0.8, gives 20.7 kilo, to be added to the 44.1 kilo, of water, making 64.8 kilo, of water to be heated instead of 70 kilo. ; dividing the 2200 kilo, by the former number, 64.8, the quotient, 33.1° C. (59.5° F.), is the number of degrees to which the temperature of a man weighing 70 kilo. (154 pounds) would be elevated by the burning of his food. In other words, the tissue of the human body, from this point of view, bears the same relation to its water as the brass, copper, etc., do to the water of the calorimeter, the human body, in fact, serving as a calorimeter for the determination of the heat value of foods when burned within the body. Suppose the temperature of the human body, for example, was reduced to 70° F., or lower, as is the case in cholera, it is evident on the above supposition that, upon a normal diet, the temperature would be elevated within twenty-four hours to about 131° F. On the other hand, suppose the temperature of the body was normal, the heat of the food would elevate it from 98.9° F. to nearly 160° F., and yet, as we have already seen, the temperature of the human body varies but little. It now remains for us, in conclusion, to endeavor to account for this constant temperature somewhat more in detail than we have already done, and that leads us to the consideration of the expenditure of the heat produced. 1 Physiologic Vierte Aufi. S. 257. Tub., 1871. 3 Ueber ie Kost iu einig. offent AnstalteD, 1877. 3 Ranke, op. cit., p. 207. CHAPTER XXXIII. EXPENDITURE AND REGULATION OF HEAT. We have seen that there are produced within the human body in twenty-four hours between 2200 and 2300 calories, or heat units; that is, heat enough to raise the temperature of 2300 kilo, of water 1° C, or 23 kilo. 100° C, or, what is the same thing, about 50 pounds of water from the freezing to the boiling point. It is very evident, there- fore, that were such a production of heat kept up, and the heat developed not dissipated, but retained in the body, that the latter, in the course of tAvo days, would boil. A little reflection will show, however, that, in addition to the heat given off through radiation and conduction, if the temperature of the body be higher than that of its surroundings, that a certain amount of heat leaves the body in a latent condition, so to speak, locked up in the watery vapor exhaled from the lungs and skin, and from the fact of the solid and liquid food, and the air breathed entering the body at a lower temperature, 15° C. (69° R), for example, than that of the latter, and leaving it at the same temperature, 38° C. (100.4° F.), heat must also be absorbed, and that there must be a still further expenditure of heat in the accomplishing of bodily and mental work, since there can be no doubt that, whatever be the nature of muscular and mental force, the latter is correlated in some way with heat, the disappearance of the one being coincident with the appearance of the other. Now, from the very nature of the case, the relative amounts of heat expended in the ways mentioned must vary very much, according to the character of the climate, of the quantity and quality of air breathed, of food taken, of the amount of muscular and mental work performed. It is therefore impossible, if for these reasons only, to indicate exactly what becomes of the heat developed in the body. Further, however, too much importance must not be attached to the following table, since the data upon which such a table must be based are, to a certain extent, assumed, or, as will be seen, are, indeed, entirely wanting. It is only offered as illustrating in a more detailed way the general observations regarding the expenditure of the heat just made, and as also showing the manner in which such a table could be drawn up if all the data had been without cavil experimentally determined. It should be mentioned, however, that this criticism applies only to the relative amounts of expenditure of the heat, the total amount of heat leaving the body being, of course, that produced if the temperature of the body remains constant. With these qualifi- cations, before calling attention to Table LXX., one or two points should be mentioned in order to understand the manner in which the results so tabulated were obtained. We will suppose that the food of a man weighing 60 kilo. (132 500 EXPENDITURE OF HEAT pounds) produces in twenty-four hours 2300 calories, or heat units; that the food of such a man, including the air breathed, be known; that the specific heat of the food be accepted as being 0.8, and that of the air 0.26; that the amount of watery vapor exhaled from the lungs and skin has been determined; that it be admitted that it requires 582 heat units to vaporize 1 kilo, of water ; that the work incidental to the circulation and respiration be known, and, further, that the muscular work performed by the man during a day be considered as amounting to 112,397 kilogramme-metres, that is to say, the man does an amount of work equivalent to lifting 112^397 kilo. (247,273.4 pounds), or, 110.8 tons 1 metre (3.2 feet) high, or, what is the same thing, 354 tons through one foot, and that the amount of heat necessary to raise the temperature of one kilo. (2.2 pounds) of water 1° C. (1.8° F.), or a heat unit, if applied mechanically, would raise 423 kilo. (930 pounds) 1 metre (3.2 feet) high, or 2977.9 pounds, or 1.4 ton, through one foot. The above being admitted, it follows that the heat produced is expended somewhat as follows : Table LXX. — Expenditure of Heat. 1.5 kil. ( 3.3 lbs.) water 1.5 " solid food, raised 23° C (73° F.) 16.0 " (35.2 lbs.) air inspired . 19.0 kil. (41.8 lbs.) 0.4 kil. ( 8172 grs.) water evap. from lungs 232.8 0.6 '• (10183 era.) " " " skin 1.0 kil. (18355 grs.) Radiation and conduction Work circulation, 43917 kil. 138 ft. tons respiration, 1590 " 25 nervous, muscular, 112397 " 354 157904 517 34.5 beatui 27.6 " 95.6 " n'ts. 1.50 percent. 1.20 " " 4.15 " " 157.7 " 6.85 " " s 232.8 " 384.1 " ' 10.12 " " 16.70 " " 616.9 " ' 26.82 " " . 1156.3 " ' 50.27 " " s 98.5 " 17.8 " 4.28 " " 0.77 " " 252.8 " ' 10.99 " " 369.1 " ' 16.04 " " Ratio of work to beat . Ratio of muscular work to beat to 6 to 9 It will be observed from Table LXX., that of the 2300 heat units produced in twenty-four hours, about 7 per cent, are expended in warming the food, including the water and air breathed; 26 per cent, in evaporating the water from the lungs and skin ; 50 per cent, in radiation and conduction from the general surface of the body, and about 16 per cent., or one-sixth of the Avhole heat produced in the per- formance of work. It must be borne in mind, however, that the 116.3 heat units, or 5.05 per cent, of the whole heat produced, and at the expense of which the work of maintaining the circulation and respira- tion is maintained, are only temporarily converted into mechanical energy, the latter being almost entirely reconverted into heat again, owing to the various obstructions that are offered to the movement of the blood and respiratory organs. The 5.05 per cent, heat units leaving the CORRELATION OF HEAT AND MECHANICAL WORK. 501 body as heat, must be added, therefore, to the 50.5 per cent, expended in radiation and conduction, making the latter really amount to 55.55 per cent. While no numerical estimate can be given, as yet, of the relation existing between heat and nervous force, there can be no doubt, however, that the latter, like all other kinds of energy, must be de- veloped out of some equivalent amount of force, and leaves the body as such, or as some other mode of motion. That nervous force is developed out of heat appears very probable from the experiments of Lombard, already referred to, and by which it was shown that, while all mental action was accompanied with the production of heat, that more heat disappeared during deep thought than during reading to one's self, for example, of emotional poetry ; further, it was shown by the same experimenter that more heat disappeared than when the reading was aloud — that is, had a muscular expression, part of the heat produced in the latter case being applied to making the oral or muscular effort. It is a matter of daily observation that silent grief is deepest, that pent-up emotion finds relief in physical action. This is in accord- ance with the results of the experiments just mentioned, since the heat that is transformed into emotions or ideas, in the one case, becomes muscular action in the other, and just in proportion as there is more of the one, so there is less of the other. Hirn 1 endeavored to determine, experimentally, the exact quantity of heat expended in the performance of mechanical work by comparing the heat produced within a definite time with the work done, the latter consisting in a man raising his own weight through a given height, the man walking upon the circum- ference of a tread-wheel rotating in the opposite direction to himself. According; to Hirn, a man weighing 75 kilo., during an hour's work upon the tread-wheel, placed within the calorimeter, produced 430 heat units, whereas, judging from the amount of oxygen absorbed and carbonic acid exhaled, 500 heat units were produced. What, then, became of the 70 extra heat units? According to Hirn, it was at the expense of this amount of heat that the 20,610 kilogramme-metres of work were accomplished — that is, of raising 75 kilo, through nearly 400 metres (423x70= = 394 V On account, however, of the v 75 / errors incidental to the construction of the apparatus, and of the amount of heat produced as determined from the oxygen absorbed being esti- mated as too high, the results of Hirn, as just given, cannot be accepted ; nevertheless, the difference between the amount of heat that appeared, as such, and that which ought to have appeared, can only be accounted for on the supposition that part of the heat produced was expended in the performance of mechanical work, and, as a corollary, it follows that less heat appears during a muscular contraction, when accompanied with work, than when without, and which accords with daily experience. The relation that has been shown to exist between food, heat, and mechanical work, is not merely one of theoretical interest, but of prac- tical importance. Suppose, for example, we wish to determine how much food — bread, for instance — is required to supply the force that will 1 Theurie mecaniqne ile la Chaleur, 3d ed.. i. p. 35. Paris. 502 EXPENDITUKE OF HEAT. enable a man weighing 7" kilo. (154 pounds) to raise himself to about the top of Mont Blanc, a height of 4929 metres (15,774 feet), or to accomplish any other physical feat involving an equal expenditure of force. From the data given above such an estimate can be made, and in the following way : It being admitted that 1 heat unit, when applied mechanically, will raise 1 kilo, through 423 metres, it will require 11.6 times as much heat or 11.6 heat units to raise 1 kilo. 11.6 times us high, or 4906 metres (423x11-6=4906), and 812 heat units (70x11-6=812) to raise 70 times that weight, or 70 kilo, to the same height, 4906 metres (15,699 feet), or about that of Mont Blanc. That is, it is required to determine how much bread must be burned in the body to furnish 812 heat units, or the heat necessary when applied mechanically, to raise 70 kilo. (154 pounds) through 4906 metres (15,699 feet) — that is of doing an amount of mechanical work ecjual to 343,476 kilogramme-metres (1077 foot tons). By looking at Table LXVIIL, it will be observed that while 1 gramme of dry bread crumb when burned out of the body produces 3.9 heat units, when burned in the body it produces 3.8 heat units ; and when, further, it is remembered that of the heat produced by the burning of the food, only about one-ninth is expended in muscular work, the mechanical value of the 3.8 heat units (38 \ -1 = 0.4): 1 gramme of dry bread crumb when burned in the body furnishing then 0.4 heat unit for the production of muscular force, and 812 heat units being required, it is evident that 2030 grammes or 4 pounds of bread ( — -=2030 grs.=4 lbs. ) must be eaten to supply the necessary force of raising 70 kilo, through 4906 metres; an estimate which agrees closely with that of Frankland, 1 according to that experimenter, 2.3 pounds of bread being required when oxidized in the body to raise 63.5 kilo. (140 pounds) through 3125 metres (10,000 feet) or 3.8 pounds of bread to raise 70 kilo. 4906 metres. It may appear at first sight strange that such an amount of muscular work can be performed upon a vegetable diet, but on reflection it will be remembered that the strongest men are not always meat eaters, and that among animals noted for their strength are the elephant and rhinoceros, strictly vegetable feeders. The heat developed during muscular contraction and its probable source will be considered more fully hereafter; the above examples will suffice, however, for the present, to illustrate the general relation existing between the loss of heat and the production of work. It will be seen from Table LXX. that over ten per cent., or about one-ninth, of the heat produced is expended in muscular work, and it might appear at first sight that there would be no heat left available for the production of nervous force, as in mental effort. Apart, how- ever, from the fact of the nervous and muscular force not being pro- duced necessarily at the same time the estimates of the latter of 354 1 Op. cit., Table iv. p. 11)7. CONDITIONS INFLUENCING EXPENDITURE OF HEAT. 503 foot tons is too high, being- equal to walking twenty miles a day. If, however, such an amount of exercise be taken, either little mental work can be done, or more food must be furnished than is ordinarily allowed a laboring man. It has already been mentioned that the temperature of the rectum is higher than that of the axilla, and from what has been said of the production and expenditure of heat it might be supposed that equal difference in temperature must prevail in other parts of the body, for although the circulating blood tends to equalize the temperature, nevertheless, on account of the radiation and conduc- tion of the heat from the general surface varying so, the temperature can not be the same throughout the body. Such has been shown to be the case, experimentally. Thus, according to Davy, 1 while the temperature of the axilla, for example, was 36.6° C. (97.8° F.), that of the lower part of the leg, and of the hollow of the foot amounted to onlv 34.4° C. (93.9° F.), and 32.2° C. (89.9° F.), respectively. Having studied the manner in which animal heat is produced and expended, there remains now for our consideration the way in which animal heat is regulated, of determining as far as possible in detail the means by which the temperature of a hot-blood animal is main- tained nearly constant, notwithstanding the variations in that of its surroundings. Among the conditions regulating animal heat may be mentioned the taking of solid and liquid food, the character of the respiration and circulation, the action of the skin, the influence of bodily size. While the amount of heat produced will depend on the quality and quantity of the food, the mere taking of the latter in the form of hot or cold drinks, for example, with the view of increasing or diminishing the general temperature of the body, as is so commonly done, has already been mentioned as having really but little effect. In fact, as we have seen, about 2.7 per cent, of the heat produced is expended in warming all the solid and liquid food taken. The effect of cold drinks in lowering the general temperature of the body must therefore be but slight and temporary. On the other hand the effect of a hot drink, as we have seen, may be exactly opposite to what might have been expected, not only through the cooling effect due to the evaporation as in the drinking of hot tea, but on account of the specific substance of which the hot drink consists. Thus, for example, if hot spirits be taken, while at first a sense of warmth is experienced with the paralysis of the vaso-motor nerves by the alcohol, a greater quantity of blood flowing to the skin than usual, a proportionally larger quantity of heat will be lost from the general surface, and the effect of the hot drink will be in the long run, therefore, to lower the temperature of the body rather than to raise it. It has already been mentioned that about 4.1 per cent, of the heat produced is expended in warming the inspired air, and it might naturally be supposed that if the respiration be quickened and the amount of air inspired increased, that a propor- tionally greater quantity of heat would then be expended in warming it. Such would appear to be the case, dogs and other animals panting i Phil. Trans., 1814, civ. p. 359. 504 EXPENDITURE OF HEAT. when overheated. Not sweating except in those parts destitute of fur or hair, and the cooling effect of the perspiration being ahsent, the excess of heat developed is carried away in the expired air. The respiration when quick, will be more efficient, therefore, in lowering the general temperature of the body than when slow. Hence, also, the condition of heat dyspnoea or the rapidity of the breathing inci- dental to the exposure of the body to a high temperature. While no doubt under such circumstances a certain amount of heat is carried away in the expired air, and the temperature of the body prevented from rising as high as it otherwise would, it must be borne in mind that the quickened respiration in heat dyspnoea may be as much regarded as due to increased oxidation owing to the high external temperature as an effort of nature to prevent the temperature of the body rising too high. In other words, the cooling effect of the respiration is to be considered rather an incidental, not an invariable effect due to the activity of the oxidation caused by the external heat. In considering the cooling effect of respiration, it will be remembered, also, that 4.1 per cent, of the heat produced is expended in warming the inspired air. On account of so much heat being given off from the skin amounting through radiation, conduction, and evaporation, to- nearly eighty per cent, of the heat produced, any change in the condi- tion of the latter, as regards its structure or the amount of blood circu- lating through it, etc., will materially influence the general temperature of the body. Were the temperature of the skin constant, the amount of heat given off or taken up by it would depend simply upon that of the surrounding atmosphere, the skin losing heat if the temperature of the air was lowered, and gaining heat when that of the air was elevated. As a matter of fact, however, when the body is exposed to a temperature cooler than its own, the vessels of the skin contracting, the general surface becomes cooler, the difference between the temper- ature of the body and the surrounding air being diminished, the loss of heat is correspondingly diminished ; on the other hand, when the body is exposed to a higher temperature than its own, the vessels of the skin expanding, the general surface becomes warmer, and a corre- spondingly greater amount of heat is lost. It is a cause frequently of surprise to most persons to learn that, no matter how hot or cold they may feel, the temperature of their body nevertheless remains practically the same. From what has just been said, however, as regards the action of the skin in regulating the tem- perature of the body, it is obvious that in the cooling of the body through evaporation from the cutaneous surface, when exposed to a higher ex- ternal temperature, the greater quantity of hot blood then circulating through the cutaneous vessels will, in impressing the sensory nerves, give rise to a general sense of warmth, so that while we feel warmer our body is actually getting cooler through the loss of heat involved in the evapora- tion. On the other hand, when, through the exposure to extreme cold, the cutaneous vessels are diminished in size, the smaller quantity of hot blood circulating through them will give rise to a sense of coolness, so that while we feel cool our body is actually becoming warmer through retention of the heat of the blood within it. The feeling warm or cold INFLUENCE OF BATHS AND CLOTHING. 505 depends, then, simply upon the relative amounts of blood circulating in the skin. The effect of the successive exposure of the body to cold and heat, as just described, is well seen in the taking of cold baths. While in the bath, the vessels of the skin being contracted, the latter is pale and cold, the heat is retained, on emerging from the bath the vessels being dilated, the skin is red and warm, and heat is then given off from the surface. When we come to study the structure of the skin somewhat in detail, we shall see that its adipose tissue, being a bad conductor, prevents any great amount of heat from being given off from the inner parts of the body to the surface, and so lost. 1 This effect being especially Avell- marked in those cases where the difference in temperature on both sides of the skin does not amount to more than about 9° C. (16° F.), the sig- nificance of the good effect of wearing clothing becomes apparent, since under such circumstances the body of a man is surrounded by a layer of air having a temperature of about 30° C. (86° F.), the temperature under the skin being 2 36° C. (96.8° F.), this difference amounting, there- fore, to only 6° C. (12.8° F.) Clothing in man plays the same part as hair, fur, and feathers in animals, the air inclosed within the latter, through being a bad conductor, practically prevents any great loss of heat from the general surface. Man, however, is far better able to adapt himself to changes in climate than most animals, since through change of clothing, food, etc., and free action of the skin, he is able to live in tropical or temperate regions as well as in arctic ones. It has already been mentioned that through the evaporation of the water from the skin as sweat about sixteen per cent, of the heat pro- duced is expended, and that the amount of water evaporated will depend, among other conditions, upon the amount of water already existing in the atmosphere. It is very evident, therefore, that the regulation of the temperature of the body and the heat that a person can endure must soon reach a limit, since if the temperature of the surrounding air keeps continually rising, becomes saturated with watery vapor and is un- changed, the body, notwithstanding what has just been said of the action of the lungs, skin, etc., will become as hot as its surroundings. It is easier to keep out cold — that is, to keep in the bodily heat by proper food, clothing, and active exercise — than to keep out heat. Travellers, when well equipped, complain less of the cold of the arctic regions than of the heat of the tropics — indeed, the officers of the Austrian steamers say that while crossing the Red Sea. at certain seasons of the year, with all precautions taken, they at times fear they will lose their reason, the heat being so unendurable. An important condition in the regulating of animal heat, and which may here lie appropriately considered, is the influence of the size or bulk of the body of an animal as compared with its surface area; for the ratio of the bulk to the surface area being proportional to the size of the animal, and the heat produced being proportional about to the bulk, and the heat lost to the surface area, it follows that of two animals of similar i King : Zcits. ftir Biologic, x S. 73. - Becquerel ami Breschet Inn. di - Sciences Nut., 2ieme ser. t. iii. p. 257; t. iv. p 243 50(5 EXPENDITURE OF HEAT. shape but of different sizes, that, other things being equal, the larger animal of the two will lose relatively the least heat. Suppose, for ex- ample, of two animals of similar shape, that one be ten times as long as the other, then, while the loss of heat in the larger animal will be as its surface area 10 2 , or 100 times as great as the small one, the heat pro- duced by the larger animal will be at its bulk 10 3 , or 1000 times as great. It follows, therefore, that if two such animals have the same temperature that the small animal either retains its heat much better than the large one or that it produces heat far more actively. That the latter is the case appears from the fact of a small animal taking more food relatively than a large one, and of its circulation and respiration being absolutely more frequent. What has just been said of the laws of heat, as compared with its production, is further illustrated by a number of well-known facts. Thus small animals are more readily affected by changes in the external temperature than large ones, the temperature of a rabbit, for example, under such circumstances, varying more than that of a dog, that of a young animal more than that of an old one of the same kind, as that of the young child, as compared with that of the adult. Large animals, like the whale or hippopotamus, live either habitually or temporarily in the water, the latter being a better con- ductor of heat than air. On the other hand, the smallest homiothermal animals live in the tropics, while of animals of the same kind the largest ones live in temperate or cold regions. Of course, what has just been said with reference to the bulk and surface area in the production and loss of heat is not inconsistent with what daily observation teaches when man or animal changes the position of the body, for as the external tem- perature varies if the body, when cold, be contracted, less surface being then exposed less heat will be lost, whereas, if, Avhen overheated, the body and limbs be stretched to the utmost, more surface being exposed, then more heat will be lost. The influence exerted by the nervous system in the production and expenditure of animal heat, so far as known, will be considered hereafter. In concluding this part of our subject, however, it may be here said that, however accomplished, there undoubtedly exists some mechanism by which the production of heat in man and animals is adapted to that lost through the means already indicated. In addition to what has already been said, as a further confirmation of the existence of some regulating mechanism, may be mentioned the well-known facts already alluded to, of the diet of the inhabitants of cold countries being so dif- ferent from that of those of hot ones, the amount of food consumed by the former not only being greater, but the food consisting largely of fat and oil, substances eminently suitable for the production of heat. A corresponding difference in diet is also made use of by the inhabitants of temperate regions in winter, as compared with summer, and with the same effect of increasing the production of heat in cold and of diminish- ing it in hot weather. It might be supposed that such a regulation of the heat produced and expended, of a loss of heat inducing an increased production, would be shown from the amount of oxygen absorbed and carbonic acid exhaled, and notwithstanding the numerous difficulties incidental to such an experimental investigation, it may be said that the REGULATION OF HEAT PRODUCED AND EXPENDED. 507 general result obtained by Lavoisier, Crawford, and De la Roche, 1 as well as by modern experimenters, as Roliring and Zuntz, 2 Colasanti, 3 Pfliiger, 4 Prince Theodore, 5 Voit, 6 etc., was, as a rule, that the con- sumption of oxygen and exhalation of carbonic acid increased with a fall in the external temperature and diminished with a rise in it, though, under certain circumstances, hot-blooded animals behaved as cold-blooded ones — that is, the absorption of oxygen and exhalation of carbonic acid increase with a rise in the external temperature and diminish with a fall in it. Within certain limits at least, it may be said that, when a man or animal is exposed to cold, the production of heat is increased, as shown by the greater amount of oxygen absorbed and carbonic acid exhaled, but when exposed to heat the reverse is the case and less heat is produced. 1 Op. cit. 2 pfluger's Arctaiv, 1871, iv S. 57. 3 Ebentia, xiv. S. 92. * Ebenda, 1878, xviii. S. 247. 5 Zeitschrift f. Biol., 1878, xiv. S. 51. '• Ebenda, S. 57. C HAPTER X X X I V. THE KIDNEYS AND URINE. We have seen that during digestion the food is transformed into albuminose, glucose, emulsified fats, etc., that through absorption and the circulation the latter are carried to the tissues, supplying the cells of the same with materials, which, either in being assimilated serve for repair, growth, or development, or in being destroyed are a source of heat and force ; and that the destructive metamorphosis going on in the body caused by fermentation, hydration, oxidation, etc., incidental to life, the final outcome of which, at least, is the production of carbonic acid, water, and urea, is due, to a far greater extent, to the destruction of the food by the cells of the tissues than to the destruction of the tissues themselves ; that, by means of the lungs, oxygen is introduced into the system, and carbonic acid and water removed, the skin, as we shall see, in the latter respect, acting also, to a certain extent, in the same way. In concluding now our account of nutrition, it remains for us still to consider the structure of the kidneys, and, so far as is known, the manner in which the urea, etc., are excreted by* them from the system. It will be observed that we speak of the urea, etc., as being excreted by the kidneys, and it may be appropriately mentioned here that, while it would be equally correct to refer to the secreting, as well as to the excreting of the urine ; the word secretion, however, is usually made use of in referring to a glandular product of some use, such as the saliva, gastric juice, etc., the term excretion being confined to products of no use, to be gotten rid of, such as the urine. In this sense, the bile, as we have seen, is both an excretion and a secretion. A kidney may be regarded, functionally, as consisting essentially of one or more tubes, opening externally at one end, but terminating inter- nally at the other end in blind, sac-like capsules. The tubes and their capsules are lined with an epithelium, and covered more or less exte- riorly with bloodvessels, the latter supplying the tubes with blood, from which are excreted, by the cells of their lining epithelium, the urea, water, etc., constituting the urine ; elaborated and transported by the cells into the interior, or lumen of the tubes, the urine passes finally thence out of the body. Such a disposition as that just described, obtains in the kidneys of the lower vertebrates. In bdellostoma, for example, one of the cyclostomous fishes, the kidney consists (Fig. 258, A) of a ureter (a), from which are given off, at right angles, short uriniferous tubules (b, b), terminating in capsular-like Malpighian bodies () along and between the uriniferous tubules. From this nt't work the renal veins (V) originate, which, converging, form the external surface of the kidney toward the bases of the pyramids, pass through the sinus, and, becoming confluent, emerge as one trunk (Fig. 259, 7) from the hilus. The water, urea, etc., having been excreted by the epithelial cells lining the uriniferous tubules from the blood brought to them by the renal artery, elaborated as the urine-, passes down through the uriniferous tubules, finally dribbling out of their orifices situated, as already mentioned, at the apices or summits of the Malpighian pyra- mids (Fig. 259, 3), one or more of the latter projecting into one of the calices or infundibula, into which the pelvis or upper expanded por- tion of the ureter (4) (within the sinus), is subdivided, a further passage- way is provided by which the urine is conveyed to a temporary reser- voir — the bladder — a musculo-membranous sac, from which it is finally eliminated during micturition from the body. The calices, pelvis of the ureter, and the ureter proper consist externally of a fibrous coat, of a middle unstriated muscular one, and internally of a lining mucous mem- brane. The fibrous layer of the calices at the base of the pyramid becomes continuous with that investing the sinus of the kidney, the latter, in turn, being a continuation of its external fibrous capsule ; the middle muscular layer thinning aw r ay at the pelvis, disappears altogether at the base of the pyramids, while the mucous membrane of the calyx is reflected upon the pyramids, becoming continuous at the orifice with that of the urinifeiT>us tubule. It is eivident, therefore, that leaving out of consideration the anatomical details just described, that a kidney, physiologically, may be regarded as consisting essentially of one or more uriniferous tubules, supplied with blood, a uriniferous tubule con- sisting of basement membrane separating blood on the one side from a secreting cell on the other. When reduced, therefore, to its simplest expression, the structure of the kidney does not differ in any way from that of glands in general. The Urine. The urine is a clear, amber-colored fluid, of a watery consistence, con- taining a little mucus, saltish in taste, with a characteristic though not disagreeable odor, acid in reaction, and with a specific gravity varying between 1.020 and 1.025. The color of the urine appears to be due to a substance not yet satisfactorily isolated, but which, when slightly modified, gives rise to the substances variously known as urochrome, urosin, urosacin, htemaphaelin, urohsematin, uroxanthin, urobilin, and hydrobilirubin, the latter terms indicating the affinity evidently ex- isting between the coloring matter of the bile and that of the urine, whatever the latter may be, as seen by the readiness with which, by the addition of water and abstraction of oxygen, the coloring matter of the bile is transformed into that of the urine, or one of its modifications, as shown by the following formula : Bilirubin Urobilin. 2(C 16 H 18 N 2 3 ) + 2(H 2 0) - O = C 32 H 40 N 4 O 7 . THE URINE, 513 Fig. 262. In all probability the coloring matter of the urine is derived from that of the bile, the varying tints often observed, from an amber color to red, being due to the oxidation of the former substance. The acidity of the urine is not due to free acid, as can be shown by there being no precipitate formed on the addition of sodium hypophosphite, but to the presence of the acid sodium phosphate, NaH 2 P0 4 , the latter salt being probably formed by the reduction of the basic sodium phosphate, Na 2 HP0 4 , of the blood by abstraction of one equivalent of its sodium by uric, hippuric, or carbonic acid, and sodium urate, hippurate, or car- bonate, formed, as may be seen from the following formula, for example : Sodium phosphate. Uric acid. Acid sodium phosp. Sodium urate. 2Na 2 HP0 4 + C 5 H 4 N 4 3 = 2Na H 2 P0 4 + Na 2 C 5 H 2 N 4 3 . The acidity of the urine, due to acid sodium phosphate, as measured by the amount of a standard solution of caustic soda necessary to neutralize it, is equivalent to about three grammes of oxalic acid in twenty-four hours, supposing the urine voided in that time to amount to 1200 c. cm. The solution of soda, of such a strength that each cubic centimetre, containing 0.0031 gramme of soda, exactly neutralizes 0.0063 gramme of oxalic acid, is added, drop by drop, to a given quantity of urine — say 100 c.cm., until litmus paper changes violet in color, i. e., neither to red nor blue. The number of cubic centimetres of the soda solution, as read off on the burette, say 30, when multiplied by 0.0063, Avill give then the amount of acidity, or 0.1890, in 100 c. cm. of urine, as measured in grammes of oxalic acid, and, consequently, of 2.2. grammes in 1200 c. cm. The specific gravity of the urine, a matter of great importance practically, is readily determined by the urinometer (Fig. 262), the stem of which is so graduated that when immersed in water the level of the latter stands at that portion of the stem marked conveniently 1000, the level at which the urine stands, as read off on the urinometer when the latter is immersed in the urine giving the specific gravity sought. A convenient method of determining the solids of the urine, approxi- mately, at least, is by means of what is generally known as Trapps, or Christison's formula, based upon the fact, as empirically shown by that chemist, of the specific gravity of the urine bearing generally a close relation to the solid matters which it contains in solution. The rule is as follows: Multiply the last two figures (22) of a given specific gravity expressed in four figures — say 1.022, by 2.33; the result, 22 X 2.33 = 51.26 grammes, will be the amount of solids contained in 1000 (lanbois.) parts of urine having a specific gravity of 1.022, and if the urine passed in twenty four hours amounts to 1200 c. cm., then the solids will be increased proportionally, 1000 : 1200 : : 51.26 : x = 61.51 33 1000 .1010 1020 1030 —1040 514 THE KIDNEYS grammes. If the specific gravity of* the urine be below 1.018, greater accuracy will be obtained by multiplying by 2 instead of 2.33. The daily quantity of mine excreted amounts in the adult man, on the average, according to Parkes. 1 who has compared the observations of manv observers, to about fifty-two and a half fluid ounces. As little as thirty-five ounces, and a- much as eighty-one ounces may, however, be voided within the limits of health, and it may lie added that almost every intervening number between these limits has been given as the usual average, the very greatest difference prevailing in this respect. Apart, however, from personal peculiarities, the amount of urine excreted is also influenced by sex, age, and season of the year. Thus, more urine is excreted by women than men, more by children, relatively to their weight, than by adults; more in winter, the skin being then less active, than in summer. When it is considered that the quantity and quality of the urine, as we shall see, are influenced by such conditions as wake- fulness, sleep, rest, exercise, solid and liquid food, it might be naturally supposed that considerable differences would present themselves in the urine passed at different times during the day. usually five or six times within the twenty-four hours. As a matter of fact, diurnal variations do succeed each other quite regularly. Thus, the urine collected during the night and voided early in the morning, is strongly colored, distinctly acid, and of a high specific gravity : toward noon it becomes paler, less dense (1.003 to 1.008). and less acid, the acidity even disappearing altogether: during the afternoon and evening, the color, density, ami acidity increase, while by night it has become again highly colored, markedly acid, and with a specific gravity of 1.028 or even 1.030. As these diurnal variations are. however, increased or diminished by the amounts of liquids taken, and as the acidity of the urine is inversely as that of the stomach, and may be more or less neutralized by fruits, vegetables, etc., the lactates, malates, and tartrates of the same being replaced within the system by carbonates, and reappearing in that form in the urine, it is evident that if the acidity and specific gravity are to be determined, one sample voided will not suffice, but that the entire quantity passed in twenty-four hours should be examined, and the mean result taken. It is worth while mentioning that with refer- ence to the liquids absorbed by the system or lost, that under normal conditions the relation of the specific gravity of the urine to that of the liquids is an inverse one. Thus, if a great quantity of liquid be taken, or the perspiration be diminished, the amounts of solids remain- ing the same, the specific gravity of the urine will be diminished, whereas, if drinks be abstained from, or the perspiration be increased, the specific gravity will be increased. If, however, notwithstanding that a great quantity of liquid be absorbed, the specific gravity still remains high, or with a diminution in the liquid the specific gravity remains low, there would be reason to suspect disease through the increase or diminution respectively in the solid constituents of the urine, and such would also be the case if, the specific gravity remaining constant, the quantity of urine increased or diminished, and vice versa. 1 On the Urine p. 5. London, 1860. CONSTITUENTS OF THE URINE 515 Table LXXI. 1 - -CONSTITUENTS OF UrIaME AND AMOUNTS EXCRETED IN Twenty-four Hours. Urea Uric acid Allantoin Hippuric acid Kreatinin Sugar . Xanthin Paraphanic Kryptophanie Phenylic Taurylic Damaluric \- acids Damolic Fatty Oxaiuric Oxalic Pigment Mucus .... Inorganic salts, composed Average quantity Average quantity excreted excreted in 24 in 24 hrs. in grs. for each ^hours in 1 lb. of body * grains. weight (150). 512 3.5 8.5 0.057 Trace. 15 o.i ' 15 0.1 Traces. of Sulphuric Phosphoric Nitric Silicic Chlorine Potassium Sodium Calcium Ammonium Magnesium Iron 1 acids . 140.00 to 380.00 17.34 to 41.14 31 .00 to 79.00 Traces. Traces. 51.87 to 173.2 26.36 to 107.7 79.75 to 171.0 2.33 to 6.36 Trace. 2.53 to 4.21 Trace. 0.933 to 2.53 0.115 to 0.27 0.207 to 0.526 0.345 to 1.154 0.175 to 0.718 0.531 to 1.14 0.015 to 0.042 0.016 to 0.028 The urine conveying out of the body, as we have seen, many of the proximate principles to their derivatives, the latter having played their part in the economy, must necessarily be a highly complex fluid con- sisting of both organic and inorganic principles. That such is the case is evident from the composition of the urine as given in Table LXXL, after Carpenter, based principally upon the works of Parkes, 2 Thudi- chum, 3 Neubauer, 4 and Vogel. Of the various constituents of the urine, whether organic or inorganic, urea existing in about 2.6 parts per hundred, about half the solid matters of the urine, is the most im- portant. Urea consists of carbon, oxygen, nitrogen and hydrogen united in the proportions shown in the formula CON 2 H 4 , and is isomeric, therefore, with ammonium cyanate, NH 4 CNO. Urea is, how- ever, regarded by chemists as being carbamide or the diamide of carbonic acid as expressed in the formula CO < ^ttt 2 Urea is a colorless neutral substance, very soluble in water and boiling alcohol, but insoluble in ether, and crystallizing in four-sided prisms (Fig. 2t}3). Urea can be 1 Carpenter's Physiology, 1881, p. 468. 1 On the Pathologj ofthe Urine. London, 1858. * On the Urine, Nev Syd. Soc. Trans. London, 1S63. 2 Op. cit. 516 THE KIDNEYS readily obtained from the urine in the following manner. Add, say, half a drachm of pure nitric acid to a drachm of concentrated urine in a watch glass and set aside to cool. The nitrate of urea then formed will be precipitated as a yellow crystalline mass. The insoluble nitrate Fig. 263. Urea, prepared from urine, and crystallized by slow evaporation. (Lehmann.) caught on a filter, dried, and dissolved in boiling water, is mixed with animal charcoal to remove coloring matters and filtered while hot. The filtrate being then allowed to cool, colorless crytals of nitrate of urea will be deposited. The latter being dissolved in boiling water and barium carbonate added as long as effervescence takes place, barium nitrate and urea will be produced, from which after evaporating to dryness the urea can be extracted with absolute alcohol. On evaporat- ing the alcoholic solution of urea crystals of pure urea are obtained. As may be seen from Table LXXL, as much as 512 grains of urea are excreted on an average daily, which, consisting of 46.6 per cent., or 235 grains, nitrogen, may be regarded as the chief especial product of the oxidation of the nitrogenous food or tissue, or both, and to a great extent taken as the measure of the disintegration of the same, since with the above amount of urea, the amount of nitrogen excreted by the skin and in the feces would amount to only about 0.6 grain and 18 grains respectively. It is, therefore, of great importance that we should have some ready method of determining the amount of urea present in a given quantity of urine. Of the different methods in use none is more convenient or more accurate than that of Davy, based upon the decom- position of urea by sodium hypobroniite — the nitrogen of the urea being set free, and with caustic soda in excess, the carbonic acid developed combines with the soda, the water being retained in the mixture ; the amount of urea is determined by the amount of nitrogen evolved. The experimental procedure is as follows : A given quantity of urine, say 4 c. cm., is placed within the vessel, and about 25 c.cm. of a solution of sodium hypobromite freshly made by dissolving 100 grammes of caustic soda in 250 c. cm. of water, to which are added 25 c. cm. of bromine in DETERMINATION OF UREA. 517 the vessel. The immediate effect of the mixing of the urine with the hypobromite is the development of N, as seen from the following reaction : CON./H, + 3(NaBrO) + 2(NaOH) = 3NaBr + Na,C0 3 + 3H 2 + 2N. The free nitrogen passing into and being collected by the graduated tube standing over mercury, will be found to amount to 30 c. cm., supposing at the moment of the experiment the thermometer registers 15° C. (59° ¥.), and the barometer 740 mm. (29.6 in.), or 27.6 c. cm. if the volume of 30 c. cm. be corrected for temperature and pressure by the methods already explained. Now, since 100 grammes of urea contain 46.6 gr. of nitrogen, 1 gramme of urea will contain 0.466 of a gramme of nitrogen, and as 1000 c. cm. of nitrogen weigh 1.252 grammes, 372 c. cm. of nitrogen will weigh proportionally 0.466 of a gramme; but as 0.466 of a gramme of nitrogen corresponds to 1 gr. of urea, the latter will give off 372 c. cm. of nitrogen, and the 0.0027 of a gramme of urea proportionally 1 c. cm. of nitrogen. If now the 27.6 c. cm. of nitrogen collected in the graduated tube given off from the urine be multiplied by 1.0027, or the amount of urea in grammes corresponding to a cubic centimetre of nitrogen at standard tempera- ture and pressure, the product, 0.0745 gramme, will be the amount of urea in 4 c. cm. of urine, and consequently 34 grammes (524 grains) in 1300 c. cm of urine, or the amount, say, passed in twenty-four hours. Such a rough and ready method for the determination of urea as that just given, like all other similar ones, is open to some criticism, the most important of which is, that uric acid and other nitrogenous principles present in the urine, like urea, are also decomposed by hypobromites or hypochlorites, the latter being used as well as the former to free the nitrogen. The quantity of such nitrogenous princi- ples is, however, so small that the error introduced can be neglected without materially affecting the accuracy of the result. While the urea excreted by an adult amounts on an average in 24 hours, as has already been mentioned, to about 512 grains, it must be mentioned that the quantity eliminated varies very considerably with the age, weight of body, sex, period of the day, season, and kind of food. Thus children of from three to seven years of age, weighing say, 30 lbs., in daily excreting, may be, 240 grs. of urea, eliminate more than half that excreted by an adult, 459 grains, weighing, however, 153 pounds, or more than five times as heavy. In other words, while an adult man excretes for each pound of body weight about 3 grs. of urea, a boy excretes 7.5 grs., or more than twice as much. As might be expected, therefore, the amount of urea excreted continues to diminish as age advances. It would appear that less urea is excreted by the female than the male in the proportion, perhaps, of about half a grain less in the female for each pound of body weight, and that the amount is diminished during menstruation. The hour of the day apparently also exerts an influence upon the excretion of urea, the greatest amount being eliminated after breakfast and tea, the least during the night. The increase or decrease observed may be, however, due, to a certain extent, as we shall see, to the taking of or the abstaining from food. Like the urine, more urea is probably eliminated in cold than in warm weather. 518 THE KIDNEYS. It is difficult, if not impossible, to give exact numerical estimates. According to Dr. E. Smith, 1 the daily variations in himself amounted in a year from between 219 to 700 grains, the average, on the whole, being, however, 510 grains. Of the conditions influencing the production of urea, none is so important as that of the taking of food. This becomes at once evident when the amount of urea excreted upon a vegetable or mixed diet is compared with that of a highly animal one. Thus while the urea excreted by Ranke, 2 during 24 hours on a vegetable diet, amounted to only 264 grains, and on a mixed to between 463 and 617 grains, on a highly animal diet it was increased to as much as 1332 grains, or nearly three times as much as normal. From such facts as that nearly all of the nitrogen of the food consumed passes out of the body in the form of urea in the urine, each grain of urea implying the disintegration of 3 grains of albuminous matter, or about 15 grains of meat, and that the amount of urea excreted attains its maximum within five to seven hours after the taking of food, it would appear that by far the greatest amount of the urea produced must be derived directly from the disintegration of the albuminous, nitrogenous food brought about through fermentation, oxidation, etc., as already mentioned, it being absurd to suppose that of the five pounds of meat eaten by a large dog, to take an extreme instance, the albuminous matter of the same should be first transformed into tissue, then decomposed into urea, and elimi- nated by the kidneys within the short space of 24 hours. It appears to us at least more reasonable to suppose that the albumen of the food goes through the system like a dose of salts, so to speak, with the dif- ference, however, that the albumen entering the body as such in the food, leaves it in the excreta as urea, carbonic acid, and water. If the above view of urea being derived from nitrogenous food rather than nitrogenous tissue be accepted, it is readily understood why muscular exertion does not increase, as was once supposed, the production of urea, for muscular force, being like all other kinds of so-called vital force, transformed heat, and the latter being developed, if not exclusively, at least to a greater extent out of fats and carbohydrate than albu- minous food, it follows that muscular activity will be measured not by the amount of urea but by that of the carbonic acid produced. Such theoretical considerations are fully borne out by the experiments of Smith, Lehmann, and Voit. In the celebrated ascension of the Faul- horn by Fick and Wislicenus, 3 in 1866, involving considerable muscular exertion, as may be imagined, it will be seen from Table LXXII. that so far from the urine being increased during the period of ascent, lasting 8 hours and 10 minutes, and the 6 hours immediately following, as measured by the nitrogen eliminated, it was actually diminished, since while during the 12 hours preceding the ascent the urea excreted by Fick, for example, measured by the 106.7 grs. of nitrogen eliminated, would amount to about 228 grs. during the period of 14 hours, includ- ing not only the 8 hours of work in the ascent but the succeeding 6 hours of rest, it would amount to only 190 grs., as measured by the 88.6 grs. of nitrogen eliminated. i Proc. of Royal Soc, May 30, 1861. Carpenter's Physiology, 1881, p. 470. 2 Physiologie, 1872, S. 509. 3 London Phil. Magazine, 1806, p. 485. INFLUENCE OF MUSCULAR EXERCISE. 519 Table LXXII. 1 — Ascent of the Faulhorx (6417.5 feet). Weight of Fick. L45.5 lbs. X 6417.5 = 933746 foot pounds. " Wislicenus, 167.5 lbs. X 6417.5 = 1074931 " Grains of nitrogen excreted bj Night urine previous to ascent Work 8 hours 10 min. . After work 6 " Night (after a meal) 10.] hours 88.6 grs. X of Fiek derived from 575.0 grs. of muscle. 85.6 " " Wislicenus " " 555.5 " " 575.0 grs. of muscle of Fick burned raised 498525 lbs. 1 foot. 555.5 " " " Wislicenus " " 481618 " " Fick. w isliceuus. 106.7 103.2 51.1 48.3 37.5 88.6 37.3 74.3 82.5 Fick. Wislicenus. tVork of ascending mountain " " circulation " " respiration . 933746 . 183348 . 37620 1074! 131 213906 43890 " foot pounds .... 1154714 1332727 done from burned muscle . . 498525 481618 " " unaccounted for . . . 656189 851109 It being borne in mind that no albuminous food had been taken for seventeen hours previous to the ascent by Fick or Wislicenus, their diet consisting of cakes made out of fat, starch, and sugar, it is not strange that the amount of urea excreted should have been small, it being; derived from the albuminous tissues of the body; the latter supplying the albuminous food that would have been otherwise present had the diet been a mixed one. It is well known that, even in starvation, more urea is excreted than on a diet consisting of sugar, fat, etc., since the latter substances, in supplying ready materials for combustion, spare the tissues of the body. That there is an enormous amount of potential force locked up latent, so to speak, in sugars, etc., is made evident in the extreme weakness and emaciation so noticeable in diabetes, since the sugar in that disease, instead of being burned, and constituting as normally a source of heat and force, passes unoxidized out of the body. The amount of force lost to the system under such circumstances may be judged of when it is remembered that in extreme cases of diabetes as much as 40 ounces of sugar are passed in the urine in twenty-four hours, and that if the 16 ounces of carbon contained in such an amount of sugar were oxi- dized, heat enough would be produced, if applied mechanically, to raise 20 millions of pounds 1 foot high, 2 or carry a man weighing 130 pounds on a level 66 miles. The system being deprived, therefore, in this disease of such a source of force, draws upon the albuminous tissues, hence the characteristic emaciation and weakness. It is evident, also, as may be seen from Table LXXII., on the supposition that the com- bustion of muscle is the source of its power, that the burning of 575 i Letheby On Food, p. 64. London, 1872. 2 H. Bence Junes : Pathology and Therapeutics, p. 73. London, 1867. 520 THE KIDNEYS. grains of the muscular tissue of Fick's body, as implied in his elimina- tion of 88.6 grains of nitrogen, would not suffice, in his case, to account for the work actually performed by him in ascending the Faulhorn by 650,189 foot-tons, and the same is true by almost as large an amount in the case of Wislicenus, the work unaccounted for being evidently due to the heat developed through the combustion of the starch, sugar, and fat. Essentially the same result was obtained more recently by Haughton, 1 who found, while walking five miles a day, that the urea elimi- nated amounted to 501.28 grains ; that when the walk was increased to 20.74 miles a day, and kept up for five consecutive days, the urea elimi- nated amounted to only 501.16 grains, or actually less. Parkes 2 found, also, that in the case of two soldiers, who walked in two days 56 miles on a non-nitrogenous diet, that the total increase of nitrogen eliminated amounted, in the one case, to only about 3 grains ; and, in the other, 15 grains; corresponding to an increase of 6.4 grains, and 32.1 grains of urea, respectively, in forty-eight hours. The case of Weston, who walked over 300 miles in five consecutive days, cited by Flint 3 as an illus- tration of urea being increased by muscular exercise, illustrates really only what we have already seen to be the case, that the amount of urea excreted is greatly increased upon a highly nitrogenous diet, and that heat, the ultimate source of muscular force, can be developed through the combustion of albuminous, as well as of fatty or carbohydrate foods, the former means of obtaining the necessary heat being, however, a far more expensive way than the latter, and entailing greater work upon the system. It is true that, if the coal gives out, the steamer can be supplied with fuel from its masts, shrouds, etc., and other integral parts of its structure ; one does not resort, however, save in dire neces- sity, to such a source of fuel. The facts of the case of Weston, just referred to, are essentially as follows : Weston walked in five consecutive days 310 miles, losing in weight 3J pounds. 1173.80 grains of nitrogen were taken into the system in the food, and 1807.60 grains were eliminated from it in the excreta, leaving 633.80 grains of nitrogen to be accounted for, which were evidently derived from the 3 pounds of tissue lost, the latter containing 633.80 grains of nitrogen ; the remaining quarter of a pound, lost in weight, corresponded, probably, to the produc- tion of water or fat. Such being the case, and Weston being trained down, and having, therefore, little, if any, superfluous fat or carbo- hydrate matter at disposal for the production of heat or force, it would appear, from the large quantity of nitrogen eliminated, that his albuminous tissues were largely drawn upon to supply, through com- bustion, the heat incidental to the production of such a muscular effort. The 3 pounds of muscular tissue lost by Weston during the walk, supplied, therefore, the body with 3 pounds of albuminous food, which, in being consumed, accounted for the elimination of 633.80 grains of nitrogen, corresponding to 1124 grains of urea, just as if he had eaten 3 pounds of butcher's meat, instead of the same amount of his own body. That this conclusion is not merely a theoretical one is shown by the i British Medical Association, 1868. - Proc. Royal Soc, 1867, No. 89, 94. 3 New York Medical Journal, 1871, p. 687. OEIGIN OF UREA. 521 fact of Rubner, 1 weighing 158 pounds, being able to consume 2.87 pounds of meat, of which 2.84 were perfectly destroyed in the system, giving rise to a corresponding quantity of urea and nitrogen. Not only has it been held that muscular activity increases the amount of urea, but mental and sexual activity as well. Even if such is shown, hereafter, to be the case, apart from the influence exerted by nitrogenous food, the facts are, at present, too few to offer any exact numerical esti- mate. It would appear, from what has just been said with reference to the production of urea, that, to a large extent at least, it is derived directly from the nitrogenous principles of the food without the latter becoming first tissue ; and while, in all probability, such is the case, it must be admitted that exactly how or where the transformation of food into urea takes place has not, as yet, been posith ely established. It will be remem- bered, however, that, in speaking of intestinal digestion, leucin and tyrosin were mentioned as being among the products of the action of the pancreatic juice upon the albuminous principles of the food, and that, together with the latter, the glycin of the decomposed glycocholic acid of the bile was reabsorbed. Now leucin, C 6 H u (H 2 N)0 2 , being amido-caproic acid — that is, caproic acid, C 6 H 12 2 , in which an atom of hydrogen is replaced by the residue of ammonia, H 2 N, and tyrosin, C r II 5 (C 2 H 5 HN)0 3 , being amido-ethyl salicylic acid — that is, salicylic acid, C r H 6 3 , in which an atom of hydrogen is replaced by the residue of ethylamin. or C 2 H 5 HN ; glycin, C 2 H 3 (H 2 N)0 2 , being amido-acetic acid — that is, acetic acid, C 2 H 4 2 , in which an atom of hydrogen is replaced by the residue of ammonia; it is readily conceivable how, through the disintegration of these substances, leucin, tyrosin, and glycin, urea could be formed by simply supposing that the residue of ammonia, NH 2 , or of ethylamin, C 2 H 5 HN, entering into their compo- sition, is set free, becomes NH 3 , or ammonia, and then combines with carbamic acid, C0 2 XII 3 , with subsequent dehydration, as follows : Ammonium carbamate. Water. Urea. C0 2 X 2 H 6 — H,0 = CON 2 H 4 the caproic, salicylic, and acetic portions of the leucin, tyrosin, and glycin respectively being oxidized into water, or, in the case of the caproic acid, into fat. Or what is also probable, that ammonium, NH 4 , being developed in the disintegration of the albuminous food in combining with a carbonic acid radical, C0 3 , with subsequent dehydration, would give rise to urea as follow s : Ammonium carbonate. Water. Urea. (NH 4 ) 2 C0 3 - 2H. 2 <> = CON 2 H 4 or with that of cyanic acid, CNO, to form ammonium cyanate, NH 4 CNO, which is isomeric witli urea. As a confirmation of the view that leucin and glycin are antecedents of urea, it may be mentioned that feeding- dogs 2 with the same increases the amount of urea. There being no difficulty in comprehending how urea may be i Zeitschr. ftlr Biologie, 1879, xv. S 1-22. - Schultzen and Nencki : /tit. fur Biologie, 1872. 522 THE KIDNEYS. developed out of the albuminous principles of the food or their ammo- niated derivatives — it remains, therefore, only to show where the trans- formation takes place. Now, from such facts as that of the liver containing more urea than any other gland in the body, as shown by Meisner, 1 of the albuminous principles of the food, of the glycin of the decomposed bile, of the leucin and tyrosin of the spleen being carried by the portal circulation to the liver, of leucin and tyrosin replacing urea in the urine in acute atrophy of the liver, the conclusion forces itself upon us that it is the liver that elaborates the urea out of the albuminous principles of the food, etc., brought to it by the portal cir- culation. Admitting that by far the greatest quantity of urea is derived from the transformation of albuminous food in the liver, it must be remembered that urea is not only found in the liver, but in many other parts of the system — in the chyle, saliva, blood, serous fluids, etc., and that in starvation in the absence of all food, though the amount of urea is gradually diminished, it is nevertheless present, even to the last. Of course, in such cases, as already mentioned, one part of the body being nourished at the expense of another, the nitrogenous tissues, instead of food, supply the materials for the development ot urea. Urea being found under normal circumstances in many parts of the system, and being derived in starvation from the tissues, it is reasonable to suppose that part of the urea is also derived from the latter even when nitrogenous food is taken, and since leucin and tyrosin are found in the thyroid, thymus, parotid, and submaxillary glands, kidney, liver, and suprarenal capsules, as well as in the pancreas and spleen, analogy would lead us to suppose that they may be antecedents of the urea derived from tissue, as we have supposed them to be of the urea derived from food. In this connection it is an interesting fact that while urea is not found in the muscles, spleen, or nervous tissue, kreatin, C 4 H 9 N 3 2 , enters into the composition of muscles to the extent of two per cent., and into that of the spleen and probably of nervous tissue also. Now since kreatin, through dehydration, readily becomes kreatinin, C 4 H 7 N 3 0, and the latter through oxidation, urea, CON 2 H 4 , it is quite probable that kreatin may be an antecedent of urea arising out of the disintegration of the muscular tissues, etc., but converted into urea elsewhere. It should be mentioned, however, that the kreatin, or rather kreatinin, normally found in the urine is not that of the muscular tissue, etc., just alluded to, but is probably derived from the food, since it varies in quantity, increasing with a meat diet, but not with exercise, and is absent in starvation. On the supposition that urea, whether derived from food or tissue, is not elaborated by the kidneys, but simply excreted out of the blood brought to them, we might expect to find that the blood of the renal artery contained more urea (0.03 per cent.) than that of the renal vein (0.01 per cent.), but also with the extirpation of the kidneys, or the ligation of the ureters, which has practically the same effect, that the urea would accumulate in the blood, and such has been found to be the case according to Grehant 2 and Gscheidlen 3 , the amount being increased from 0.020 to l Centralblatt mod. Wiss., 1870, S. 249. 2 Zeits. fur nat. med., xxxi. S. 144. 3 Studieu u. d. Ursprung d. Harnstoffs, Leipsic, 1871 ; also Centralblatt, 1871, p. 630. ORIGIN" OF UREA. 523 206 percent, in twenty -four hours, while Voit 3 obtained after extirpation of the kidneys in an animal 5.3 grammes of urea, or almost the same amount as would have been normally excreted (5.8 grammes) in the same time. It may be mentioned that the toxic effects appearing under such circumstance appear to be due, not so much to the accumulation of a great quantity of urea as to the retention within the system of other undefined albuminous substances. 1 Centralblatt, 1868, p. 4GS. CHAPTER X X X V. THE URINE. Of the remaining constituents of urine, next in importance to urea, as representing, like it, the result of the metamorphosis of nitrogenous food and tissue, is uric acid, C 5 H 4 N 4 3 . Chemically, uric acid may be regarded as imperfectly oxidized urea, a molecule of uric acid, through oxidation in presence of water, being transformed into two molecules of urea and three molecules of carbonic acid, the carbonic oxide con- stituent of the uric acid being oxidized as follows : Uric acid. Water. Oxygen. Urea. Carbonic acid gas. C 5 N 4 H 4 3 + 2(H 2 0) + 3 = 2CON 2 H 4 + 3C0 2 . It does not, however, follow that uric acid is invariably an antecedent of urea. Indeed, the production of uric acid and urea does not depend, according to many physiologists, so much upon the presence of oxygen as upon the structure of the uriniferous tubules, and the amount of water absorbed, the physical conditions involved in some animals being better adapted to the excretion of uric acid, and in others to that of urea. That the amount of uric acid and ui'ea respectively produced does, however, depend to a great extent upon the amount of oxygen absorbed, appears from the striking contrast offered by reptiles and mammals when con- sidered in this respect. Thus, while in reptiles, in which respiration is inactive, uric acid is the principal nitrogenous constituent of the urine, urea being absent ; in mammals, on the contrary, in which respiration is active, urea is the most important of the nitrogenous constituents, uric acid being found in small quantities, both absolutely and relatively with reference to the urea ; in man, for example, about 8.5 grains of uric acid only being excreted in twenty-four hours, or one part of uric acid to about sixty parts of urea, as may be seen from Table LXXI. The view of the production of uric acid instead of urea being due to defective oxidation, has been held, however, by many physiologists to be inconsistent with the fact that, while the respiration in birds is more active even than that of mammals, the urine of these animals, never- theless, contains uric acid and urates instead of urea, as in reptiles. A little consideration will show, however, that, notwithstanding the activity of their respiration, their economy is such that it is an advan- tage to birds, this retention of the ancestral trait (birds being only highly specialized reptiles) of producing uric acid and urates instead of urea. Thus, as urged by Odling, 1 while the respiration of birds is very active, it is not excessive, when considered with reference to the great 1 Animal Chemistry, p. 142. London, 18G6. ORIGIN OF URIC ACID. 525 deed of oxygen experienced by these animals, birds being more depen- dent on a constant supply of pure air than any other animals. Their organization is. therefore, such that, while, on the one hand, the respira- tory surface is increased in every possible way, notably so in the pre- datory birds, on the other hand, through the excretion of uric acid, instead of urea, the demand for fresh air is diminished, less oxygen being required for the conversion of the carbon of the food or tissue into the carbonic oxide (CO) constituent of hydrated uric acid, C 3 3 2(C]''s 2 OH 4 ), than into carbonic acid, 3(C0 2 ), and urea, 2(COX 2 H 4 ), which hydrated uric acid becomes through oxidation, and, consequently, less heat or force is lost in elevating the temperature of the inspired air to that of the body, an additional advantage. It might appear at first sight, though, that the heat developed through the oxidation of carbon into carbonic oxide (CO) would be only one-half that developed in the production of carbonic acid (C0 2 ). It must be remembered, however, that the heat absorbed in the conversion of carbon into carbonic acid gasis lost to the economy, and that, therefore, the difference in the heat developed (about 25 per cent.) in the two cases is not as great as might have been supposed, and that the amount of oxygen is also employed with far less econoni} 7 in the production of C0 2 , than in that of CO, the ratio being as 1 to 1J. 1 Further, the proportion of nitrogen to carbon in ammonium urate, C 5 X 5 H 7 3 , being as 1 to 1, whereas, in urea, CON 2 H 4 , it is as 1 to 2, it follows that the amount of carbon elimi- nated by the kidneys, in combination with nitrogen, is greater if excreted in the form of ammonium urate, as in birds, than in that of urea, as in mammals, obviously an advantage, since the excretory work of the respiratory organs is relieved to a corresponding extent. That the production of uric acid is due to imperfect oxidation appears, also, from what one daily observes in cases of gravel and gout diseases, in which the characteristic accumulation of uric acid or urate of sodium is without doubt, due to either albuminous food being continually taken in excess, or to the imperfect combustion of the albumen of ordinary diet, or of that resulting from the disintegration of the tissues. As in all probability albumen, whether derived from food or tissue, in being transformed into carbonic acid and urea, passes through a uric acid stage, just as starch passes through the stage of sugar, it follows that, if oxidation be arrested at a certain stage, uric acid, or urates, will accumulate in the system, and give rise to gravel or gout. An attack of gout being, chemically, a sudden oxidation of sodium urate into urea and carbonic acid, enabling the system, thereby, to rid itself of at least the mechanical effects of the disease, the best preventive to such an attack is to eat as little food of any kind, and breathe as much fresh air as possible. 2 The good effect of diet, accompanied with active exercise in the open air, horseback riding, etc., to increase the respira- tion, and the taking of alkalies and iron, to promote oxidation indirectly, experienced by those who . are habitually high livers, and subject to gout, etc., is too well known to need further comment. 1 For the heat developed in the production of CO b-'ing %, that of C0 2 = 1, that developed in the pro- duction of C 2 2 equals 1J£ that of C0 2 . - Beuce Jones, op. cit., p. 126. 526 THE URINE- That uric acid, like urea, is derived almost entirely from the nitro- genous food, appears from the amount of it excreted being dependent upon the kind of food taken, rising to over thirty-two grains in twenty- four hours on a full meat diet, sinking to about three grains during abstinence, in the latter case the body supplying the nitrogenous food. Uric acid appears to be very generally present when active changes are taking place, being found in the spleen pulp, in the lungs, liver, pancreas, brain, and muscles. As already mentioned, the acidity of the urine is indirectly due to uric acid through its combining with the sodium of the basic phosphate, and so reducing the latter to the acid phosphate, upon which the acidity of the urine directly depends. Uric acid existing in the urine in the form of urates, usually as a brownish, yellowish, powdery substance, ammonium or sodium urate (Fig. 264), Fig. 264. Fig. 265. Uric acid, deposited from urine. (Dalton.) Sodium urate from urinary deposit. (Dalton.) may be readily obtained by the decomposition of the same. Thus, if nitric or hydrochloric acid be added to freshly filtered urine in the proportion of about two per cent, by volume, and the mixture be allowed to remain at rest, within twenty-four hours uric acid will be deposited as thin crystals on the sides of the vessel. These crystals (Fig. 265) are usually transparent, yellowish, rhombic plates, with the angles rounded off, and are frequently collected together in rosette, star-like clusters and spheroidal masses. If uric acid be boiled with nitric acid it dissolves with a yellow color, and with an abundant liberation of gas bubbles. If the solution be now evaporated a brilliant red stain is left, which, by the addition of aqua ammonia, becomes purple. The presence of uric acid and urates can be readily determined by this procedure, which is usually known as the murexide test. It has already been mentioned that kreatinin (C 4 H 7 N 3 0) (Fig. 266), usually found in small quantities in the urine — about fifteen grains being excreted daily — is probably not derived from the kreatin (C 4 H 9 N 3 2 ), (Fig. 267) of the muscle, but, rather, from that of food, probably by dehydration, and may be regarded, chemically, as imperfectly oxidized ORIGIN OF HIPPURIC ACID. 527 albumen, intermediate between the latter and urea, the disintegration of food or tissue albumen leading through kreatin, kreatinin, uranin, guanin, allantoin, xanthin, hypoxanthin, all nitrogenous products, to uric acid, which, as we have seen, is finally transformed into urea and carbonic acid. Fig. 266. Ptg. 267. M$d* Kreatin, crystallized by hut water. (Leiima.nn.) Kreatinin, crystallized from hot water. (Lehmasn.) Hippuric acid, C 9 H 9 N0 3 (Fig. 268), excreted in about the same amount as kreatinin, like the latter, is also a very imperfectly oxidized Fig. 268. Hippuric acid. (Laxdois.) nitrogenized principle. Chemically it may be regarded as being a residue of benzoic acid and glycin — that is, a- formed through the con- jugation of these principles with dehydration, as follows: Benzoic acid. Glycin. Water. Hippuric acid. C 7 H 6 2 + C 2 H 5 N0 2 — H,0 = 9 H 9 X0, That hippuric acid actually arises in the bod)- through the combina- tion of glycin with benzoic acid appears from the fact that, if the latter be 528 THE URINE. taken internally, the amount of hippuric acid excreted is increased, 1 and thai a benzoic acid residue naturally exists in the fodder of ruminants, which accounts for, on the above supposition, hippuric acid replacing uric acid in the urine of herbivorous animals. 2 Since, in jaundiced patients, and in animals in which the liver is extirpated, or the ductus communis is ligated, the benzoic acid administered passes out of the body as such, one would be led to suppose that the synthesis with glycin takes place in the liver. That hippuric acid is also formed in the kidneys appears from the fact that if arterialized blood, containing benzoic acid, be passed through the bloodvessels of a freshly excised kidney, hippuric acid will be found in the perfused blood. With refer- ence to the plausible hypothesis, just given, of the origin of the hippuric acid in the herbivora, it should be mentioned, however, that it is found in the urine of man when on an animal diet, though in less quantity than when on a vegetable or mixed one, and that benzoic acid is not a constituent of his food. Indican, also known as uroxanthin, C 26 H 3I N0 17 , a yellowish sub- stance, usually present in the urine of man, and in greater quantity in that of the horse, is probably derived from indol, one of the products of pancreatic digestion ; through oxidation it becomes indigo blue. The presence of the volatile acids, phenylic, C 6 H 6 2 , taurylic, C 14 H s 2 , and damaluric, C 14 H 13 4 , appears to give rise to the odor of the urine. In addition to its organic constituents, amounting to about 550 grains in twenty-four hours, the urine contains, as may be seen from Table LXXL, a number of inorganic saline ones. These salts, amounting, in twenty-four hours, to perhaps 300 grains, though varying on a mixed diet between 140 and 378 grains, and in women between 158 and 303 grains, are taken into the body with the food, and pass out of it as such in the urine unchanged, or they are produced within the system through the oxidation of the sulphur and phosphorus, either of the food or tissue, the sulphuric and phosphoric acids so formed (a source of heat) combining with alkaline and earthy bases, the latter being in combination with weaker acids. While it is impossible, as yet, to determine exactly the manner in which the bases are related to the acids, and in the salines of the urine, since the composition of the ash corresponds almost exactly with the direct analysis of the urine, it would appear that the phosphoric acid exists in the urine in combina- tion with sodium and potassium as alkaline, and with lime and magne- sium as earthy phosphates, the sulphuric acid with sodium and potas- sium as alkaline sulphates, the sodium as sodium urate, phosphate, and chloride, etc. The latter constitutes by far the greater part of the inorganic constituents of the urine, as much as 250 grains and more of sodium chloride being excreted in twenty-four hours, being derived principally from the food; the amount will vary, however, considerably. Some part of the sodium chloride introduced into the system as food, appears to be the source of the hydrochloric acid of the gastric juice, and of the soda of the bile. It appears probable that, after being decom- i Matschersky : Virchow's Archiv, 1863, S. 528. - Meissner and Shepard : Centralblatt, 18UC, Nos. 43 and 44. EXCRETION OF URINE. 529 posed, it is recomposed again within the system, and as such eliminated. The alkaline sulphates, amounting to 10 per cent, of the solid matter of the urea, are derived from the food and the disintegration of the albuminous tissues, the greater part of the sulphur not eliminated in the feces as taurin becoming sulphuric acid, and combining with the sodium and potassium supplied by the alkaline carbonates and phos- phates of the blood, about 4 grammes (60 grains) are excreted daily. The phosphoric acid of the urine is excreted principally in the form of potassium and sodium phosphate. Being readily soluble, these salts are not precipitated, and therefore do not affect the transparency of the urine. The amount of alkaline phosphates excreted, about 4 grammes (60 grains) in twenty-four hours, varies with the kind of food taken, being greater on an animal than on a vegetable diet, the former being- richest in soluble phosphates, or substances yielding readily phosphoric acid. Phosphoric acid, like sulphuric, being produced in the system through oxidation of the phosphorus of the muscular and nervous tissues, the amount of alkaline phosphates excreted, like the sulphates, will depend, to a certain extent, upon the amount of tissue disintegrated. The earthy phosphates, magnesium and calcium phosphate, are usually ex- creted in less quantity than the alkaline phosphates, the average daily quantity of the latter being about 1 gramme (16.43 grains), or about one-fourth of the former. They are not the less important, however, from a pathological point of view, since their solubility, like the urates, depending upon the acid sodium phosphate, they will be precipitated if the latter be absent, and the urine be consequently alkaline. The earthy phosphates, while derived principally from the food, are, no doubt, formed within the system, through the decomposition of sodium chloride, calcium carbonate, etc., the bases combining with the phos- phoric acid. It is in this way, probably, that the calcium carbonate of the food, or that resulting from the disintegration of osseous tissue, is eliminated as calcium phosphate in the urine. It is worthy of mention, in this connection, that on a vegetable diet the excess of alkali in the food reappears in the urine, while on an animal diet it is the excess of the earthy base that becomes conspicuous. In addition to the impor- tant organic constituents just mentioned, the urine contains, usually, traces of nitric and silicic acids, ammonia, and iron, and small quantities of nitrogen (0.8 per cent.) and carbonic acid (7 per cent.), about one- third of the latter being in a state of combination, the remaining 1 two- thirds free ; oxygen, however, is usually absent. Having considered the composition of the urine, it remains for us now to describe, as far as possible, the manner in which it is excreted. That the urine is excreted by the kidneys, but not elaborated by them, appears not only from what has been said of the origin of its constituents and of their accumulation after ligation of the renal arteries, extirpation of the kidneys, etc., but from the fact, also, that in certain cases referred to by Ilaller, 2 Nysten, 3 Burdach, 4 and Lay cock, 5 in which the kidneys 1 Gorup Besanez : Physiol. Chemie, 18G2, S. 520. Bernard : Liquides de l'Organisme, 1869, tome i. p. 347. - Elementa Physiologa, tome ii. p. 370. 3 Recherches de la Phys. et de Chimin, p. 265. 4 Physiologie (Jourdain), tome viii. p. 248. ' Edin. Sled, and Sur£. Journal, 1838. 34 530 THE URINE. were either congenitally absent or not acting, the urine, or fluid closely resembling it at least, was vicariously excreted by the skin, pleura, peri- toneum, mucous membrane of the intestinal canal, salivary, lachrymal, and mammary glands, ears, nose, etc. Such being the case, the question reduces itself to the consideration of the manner in which the different constituents of the urine are separated by the renal epithelium from the blood supplying the kidney. Now, we have seen that the urine consists of water holding in solution urea, etc., and that the kidney is made up of uriniferous tubules, each tubule consisting of two distinct portions, a tubular part and a capsular part, both lined with epithelium and supplied with bloodvessels. The bloodvessels invaginated by the capsular portion being, however, disposed in a capillary knot of far greater aggregate capacity than the branch of the renal artery from which it originates, and of the single exit vessel in which it terminates, the blood must be, therefore, retarded as it flows within the capsule, and the escape of its water much favored by such a disposition. That the function of the capsular part of the uriniferous tubule, as shown by Bowman, 1 is to filter, drain off the water from the blood, the urea, etc., being excreted by the tubular part and then washed out, so to speak, by the water, is confirmed by what is seen in reptiles. Thus, in the boa uric acid, the equivalent of the urea of mammals, excreted in a solid state is only found in the tubular portion of the uriniferous tubule. The excretion of the urine will then depend essentially upon the relation of the pressure of the blood in the renal arteries, 120 to 140 mm. mercury, to that of the fluid within the tubules and ureter, 10 to 40 mm., the amount of urinary materials in the blood, and the activity of the renal epithelium. The influence of the blood pressure is shown from the fact that the excretion of urine is diminished with the lowering of the pressure of the blood whether brought about generally or locally, as by constriction of the renal artery — in fact, if the blood pressure be as low as 40 mm. the ex- cretion of the urine ceases. On the other hand, with an elevation in the blood pressure, whether induced generally or locally, the excretion of the urine is increased. That the renal epithelium, however, exerts an excretory activity independent of the influence of the blood pressure, is shown by the experiments of Heidenhain 2 upon animals in which, after the flow of urine had ceased through section of the spinal cord below the medulla, sodium sulphoindigotate being injected into the veins was found, after death, in the renal epithelium or the interior of uriniferous tubules according to the length of time elapsing between the injection and killing of the animals, proving that the renal epithelium had excreted the sulphoindigotate from the blood. By varying the quantity of the salt injected and the time elapsing between the experi- ment and the subsequent examination, Heidenhain was able to follow step by step the salt as it passed from the blood into the cells, thence through the latter into the tubules for some little distance. There being- no fluid passing along the uriniferous tubules to wash away the sulpho- indigotate, the latter remained about where it had been excreted. Not a trace of the salt injected could be found in the epithelium or within 1 Op. cir. - Hermann : Physiologie, Fnnfter Band, Erster Theil, S. 345. EXCRETION OF URINE. 531 the capsular portion of the tubule, the cells excreting the sodium sulphoindigotate being of the kind described by Heidenhain as rod- shaped, more especially found in the intercanalary portion of the urinif- erous tubule. It was also shown by these experiments, as might have been expected, that there was a limit to the excreting capacity of the renal epithelium, the excretion of a second quantity of sulphoindigotate injected soon after the first being very imperfect. It might be supposed that the experiments of Heidenhain with sulphoindigotate could be repeated with urea, uric acid, etc., with the view of showing that these suiistances are excreted by the cells lining the tubular and not by those lining the capsular portion of the tubule. Inasmuch, however, as the injection of urea, etc., gives rise to a copious flow of urine, even after section of the spinal cord below the medulla, which is not the case with the sulphoindigotate, the urea will be washed along the tubules as fast as it is excreted, which makes it impossible, therefore, to say by what part of the renal epithelium it has been excreted. It is Avell known, however, that in birds, reptiles, and fishes, branches from the mesenteric, femoral veins, etc., pass to the kidneys (Fig. 269), and after ramifying through the latter converge and finally terminate in the vena cava, the veins being known collectively Fig. 269, as the renal portal system, or the system of Jacob- son, 1 after their discoverer. The blood Hows through the kidneys in these animals, therefore, very much as it does through the liver in man. Now the branches of this renal portal system, together with the efferent vessels from the glomeruli, constitute the capillary plexus surrounding the tubular portion of the uriniferous tubules, the glomeruli themselves, however, being supplied exclusively by branches of the renal artery. It is obvious, therefore, that if the renal artery be ligated the blood will be entirely cut off from the glomerulus, while that supplying the remaining portion of the uriniferous tubule will be unaffected. Such being the case, it follows that if urea still appears in the urine after ligation of the renal arteries, it must be excreted by the epithelium of the tubular and not by that of the capsular por- tion of the uriniferous tubule. These theoretical considerations are fully borne out by the experiments of Nussbaum, 2 who has shown that while sugar, peptones, and albumen are excreted by the glomeruli, these substances not appearing in the urine after liga- tion of the renal arteries, urea is excreted by some part of the remaining portion of the tubule, urea, when injected into the blood, giving rise to a How of urine even after ligation of the arteries. The urine, like the bile, is excreted continuously, and while the flow may be increased or diminished, it never absolutely ceases in health for any length of time. The urine trickling through the mouth of the uriniferous tubules into c i. Vena cava. R. Kid- neys, r r. Vena reveh ens. r « Vena advehens. a. Vena epigastrica. h. Vena hypogastrica. i. Vena is- chiada. (Gagenbaub.) 1 De svstemate venoso peculiar! in penultia animalibua observatio - Pfliiger's Archiv, 1877, xvi. S. 139 ; 1878, xvii. S. 580. Copenhagen, 1821. 532 THE URINE. the calices, passes thence by the ureters into the bladder, its return from the Latter during micturition being prevented by the obliquely disposed valvular-like orifices of the ureters. The bladder is a musculo-membranous sac, the muscular fibres, chiefly of the involuntary character, being disposed in a longitudinal and circu- lar manner, the former constituting the detrusor, the latter the sphincter vesicae, by the contraction of which the urine is either expelled or retained within the bladder. Micturition appears to be brought about essentially as follows : During the intervals in which the urine is not voided the sphincter vesicae is in a state of tonic contraction ; if, however, the urine be re- tained for some time the contraction of the sphincter alone is insufficient to resist the outflow, and the action of the adjacent muscles is called upon to assist it. The disposition to urinate after a time becoming very great a few drops of urine pass into the urethra, the impression so pro- duced then calls into play the action of the detrusor and ejaculator urin83, the sphincter being simultaneously relaxed, and the bladder is emptied. Ordinarily the voiding or the retaining of the urine is a vol- untary act, but that the urine can be voided at regular intervals inde- pendent of the will is shown by the regularity with which the action is performed in animals in which the spinal cord has been divided, and in human beings in which it has been injured. The mechanism by means of which the muscular contractions are brought about in response to stimuli, the result of which is the voiding of the urine, will be better appreciated after the subject of reflex action has been considered. Finally, in concluding our account of the urine, the changes produced by standing may here be briefly alluded to. The urine when first Fig Fig. 271. Calcium oxalate. Deposited from healthy urine, during the acid fermentation. (Dalton.) Ammoniom magnesium phosphate. Deposited from healthy urine, during alkaline fermentation. (Dalton.) passed, it will be remembered is acid, the acidity being due to the acid phosphate of sodium. Within about twelve or twenty-four hours after being passed, however, free acid makes its appearance, lactic acid being that FORMATION OF ALKALINE URINE. 533 usually developed, probably from some of the organic principles of the urine by the fermentative action of fungi, and perhaps of the mucus usually present in small quantities in the urine; oxalic acid is also fre- quently produced, probably in the same manner, and in decomposing the salts of lime give rise to the formation of crystals of oxalate of calcium (Fig. 270). After a few days this acid fermentation ceases, through the conversion of urea by the addition of water into carbonate of ammonium, the change being brought about by the development of the micrococcus urese, one of the simplest of living beings, as follows : Urea. Water. Ammonium carbonate. CON,H, 2(H 2 0) = (NH 4 ) 2 CO, and the neutralization of the acid sodium phosphate by the ammonium carbonate, as shown by the following reaction : Acid sodium phosphate. Amnion, carb. Amnion, sodium phosphate. C'arb. acid. 2NaH 2 P0 4 + (NH 4 ) 2 C0 3 = 2NaNH 4 HP0 4 + H 2 C0 3 the urine becomes alkaline. With the alkalinity of the urine, the earthy phosphates being only soluble in acid fluids, are precipitated, and in combining with the ammonia give rise to the formation of the triple phosphate or ammonium magnesium phosphate (Fig. 271), as follows : Magnesium phosphate. Amnion, carb. Amnion, mag. phosphate. Carb. acid. 2MgHP0 4 + (NH 4 ) 2 C0 3 = 2MgNH 4 P0 4 + H 2 C0 3 . As decomposition goes on, the ammonium carbonate, after saturating the elements with which it is capable of uniting, is given oft* free, giving rise to the ammoniacal odor of the urine, and this continues until all of the urea has disappeared. CHAPTER XXXVI. STRUCTURE OF THE NERVOUS SYSTEM. In describing the mariner in which food is digested, absorbed, and circulated through the economy as blood, supplying the material for the repair of the tissues and the production of heat and force; of the absorption of oxygen, and exhalation of carbonic acid, water, urea, etc., the influence exerted by the nervous system upon these processes has only been alluded to, if at all, in an incidental manner. That the phenomenon of nutrition is not dependent upon the nervous system, however much it may be influenced by the latter, is shown from the fact that the nutrition of the lower animals, in which the nervous system is but little developed, and of plants, in which, with but few exceptions, so far as is known, it is altogether absent, does not differ from the higher forms of animal life. Indeed, the essential difference between the nutrition of plants, as compared with animals, consists of the deoxidation by plants of the water, carbonic acid, and ammonia constituting their food into starch, sugar, fats, albumen, and the storing up of force, and the oxidation by animals of the latter substances constituting their food into carbonic acid, water, and ammonia, and the expenditure of force. But while such a broad distinction exists between plants and animals, as com- pared, on the whole, nevertheless, it must not be lost sight of that oxidations, analytical processes, are going on in the economy of plants incidental to the elaboration and circulation of the sap, the production of heat, in budding, flowering, etc., and deoxidations, synthetical pro- cesses, in the economy of animals. Indeed, as has already been men- tioned, no sharp line of demarcation can be drawn between vegetable and animal life. While nutrition is not actually dependent upon the nervous system therefore, nevertheless every one is, however, conscious of the extent to which it influences nutritive processes. The sudden manner in which digestion is brought to a stop by a piece of bad news, of the weakness of the heart induced by nervous shock, of the sudden blush or pallor due to emotion, are familiar illustrations. The flow of the secretions into the alimentary canal in response to food, the rhythmical action of the heart and lungs, though unconsciously brought about, are due equally to the action of the nervous system. The influence of the nervous system upon nutrition has often been compared to that exer- cised by the rider upon the movements of a horse, the force being put forth by the latter, but controlled by the bit and spur. Man, like other animals, is, however, something more than a mere nutritive machine, becoming conscious, through his nervous system, of an external world. Impressions made upon sensory nerves by heat, light, sound, etc., when conveyed to the sensorium, give rise there to sensations out of which are developed in still higher centres, emotions, desires, ideas, MEDULLATED NERVE FIBRES, 535 while through the influence exerted by the motor nerves in the reverse direction upon the muscles the mandates of the will are obeyed. In a word, it is by means of the nervous system that the various nutritive processes that we have studied are brought into relation with each other — are coordinated — that we feel, think, will. The nervous system, or the apparatus by which the different por- tions of the body are brought into such intimate sympathy, by which one sees, hears, thinks, wills, consists, structurally, of fibres and cells, the former being found in all parts of the nervous system, the latter confined, in a great measure, however, to the cerebro-spinal axis and ganglia. The fibres are principally of two kinds, the white tubular medullated, dark bordered, and the gray, pale non-medullated ; the latter, however, only differ from the former, as we shall see, in not having the white substance of Schwann, and are much less abundant than the medullated kind, being found principally in the sympathetic, though. also, to a considerable extent, in the cerebro-spinal nerves. The white medullated nerve fibres constitute the white parts of the brain, spinal cord, and the cerebro-spinal nerves. If one of the latter be examined, the median nerve, for example, it will be found to consist of bundles or funiculi of ultimate nerve fibres (Fig. 272), supported (Fig. 273) by a framework of connective tissue, the epineurium ep, Fig. 273. | Division of a nerve, showing portion of nervous trunk (a), funiculus, and the separation of its filaments (6, c, d, e). (Dalton.) Transverse section of part of the median nerve, ep. Epineurium. ; Perineurium. e, the beginning ; m 2 the maximum ; and m 3 , the end of the contraction of the muscle. (Foster.) observed that usually the yo¥^ °f a second elapses, as determined by the chronograph, between the stimulation of the nerve and the contrac- tion of the muscle, the latent period so-called on account of the irritation being latent, not as yet actively efficient in the muscle. If the electrical currents, however, be thrown not into that part of the nerve (Fig. 307, b) in immediate contact with the muscle M, as in the preceding experi- ment, but at some distance from the latter, say an inch, as at A, for 564 OHM'S LAW, ETC. example, and which can be readily done by means of the whippe (Fig. 307, W), by simply connecting the ends of the curved wires c D, with the mercury cups at 5 and 6, instead of with the cups at 3 and 4, the cur- Whippe. rent being then diverted without involving any other change in the dis- position of the apparatus. . It will be observed, as in Fig. 309, that not only the yw^ 1 °^ a secon d ( a b) elapses between the stimulation of the nerve and the contraction of the muscle, as in the preceding experi- ment, but an additional small period of time, about the ytVo^ °^ a sec " ond (b b), intervenes, preceding that of the latent period, and evidently due to the current having been thrown into the nerve at a distance of an inch from the muscle, the nerve force having then to traverse that distance before it reached the muscle, which is at the rate of 91.8 feet (28 metres) per second. The nerve force is probably, however, trans- mitted at even a slower rate in the nerves of the frog than that just given, since, if a long nerve be stimulated in three different places, near the muscle, midway and above, the curves show that more than double the time elapses during the passage of the nerve force through the whole nerve than from the middle point to where the nerve passes into muscle. 1 While the latent period and the velocity with which nerve force is transmitted, can be determined in the manner just described, a more convenient and graphic method is by means of the pendulum myograph 2 of Fick, as modified by Helmholtz, or the spring myograph of Du Bois-Reymond. 3 The pendulum myograph, as its name implies, and as constructed for the author by Hawksley, of London (Fig. 308), consists of a pendulum 35 in. (90 cm.) in length, suspended by a knife edge working upon a support firmly fixed by the frame imbedded in the brick walls of the laboratory. The pendulum carries two glass (only one represented in figure) plates 15 in. (39 cm.) long, and 6 in. (15.5 cm.) wide, the outer smoked one a serving as a recording surface, the inner i Munk : Archiv fiir Anat. and Phys., S. 798. Leipzig, 1864. - Wurzburger Verhand., Neue Folge, ii. S. 147, 1872. * Op. cit., S. 273, Fig. 20. PENDULUM MYOGRAPH, 565 one as a counterpoise. The plates, as the pendulum vibrates push to one side the two bars dd' (the latter not represented), thereby ^interrupting Fig. 808. Pendulum myograpkion. (Foster.) respectively the primary current of the induction apparatus and also a current passing through the small electro-magnet, to which is attached a pen serving as a marking lever. The pendulum bavin* 566 ohm's law, etc. readied b' is held there by a catch similar to that which held it at a before its vibration began. With the interruption of the primary current, the nerve is stimu- lated by the opening shock of the secondary current, transmitted to the electrodes, the moment of stimulation being determined by the moving of the pen acting as a marking lever, due to the simulta- neous interrupting of the current passing through the small electro- magnet. The time elapsing is determined, as in the preceding experi- ment, by the electro-magnetic chronograph /. In using the pen- dulum myograph the muscle is attached, as in the preceding experi- ment, to a lever (b) ; the latter is, however, in this case much heavier, and is provided with a projecting steel point, which, in being pressed against the smoked plate makes the curved line 82 GALVANOMETERS. nometer, if the key be down, the diverting vessels are short-circuited, but if up, are in communication with the galvanometer. Finally the troughs can be directly connected together by approximating them or indirectly by a closing cushion made out of blotting paper saturated in the zinc solution, etc., like the deriving ones. The diverting vessels, key, and galvanometer being so disposed before performing any experiment, it ought to be first shown that the diverting vessels- are homogeneous or non-polarizable. To do this, the key being down, the needle of the galvanometer is brought to zero, and the two diverting vessels are con- nected together, the key being then opened, if the needle still remains at zero we may be assured that there is no electrical current, that the diverting vessels are homogeneous or non-polarizable. Apart from the fact that the nerve whose electricity is to be exam- ined cannot always be placed between the cushions in the position desired, it is also often impossible to bring particular points of the nerve in contact with the latter. We frequently, therefore, make use of the non-polarizable electrodes represented in Fig. 325, known as diverting cylinders, Avhich, as constructed by Plath of Berlin, con- sist of a flattened tube of glass (a) mounted on a universal joint (m l), and supported on a brass upright (A) closed at one end by moistened china clay and filled with the saturated zinc sulphate solution in which is immersed the slip of amalgamated zinc Z. The clay (c) projecting from the end of the tube can be sharpened into a point so that any two parts of the nerve can be touched that is desired. That no polarization occurs when the points of such electrodes are placed in contact with the nerve is shown by the absence of the pro- ducts of electrolytic action which would have otherwise accumulated Fig. 326. Electrical current of nerve. at the electrodes. Such electrodes are not only serviceable in divert- ing an electrical current from the nerve to the galvanometer, but can be also used for the purpose of stimulating a nerve by electricity in the same manner as already described. The deriving cushions (Fig. 324), or the diverting cylinders (a), and the key (K) and galvanometer ( S Kt ar/^~ c ^^ — s> — h^ f ^ r^ A o \ 1 o ipv Imi G \ — y Ne gatn e variati on. (6r G-'), it will be observed that there is a diminution in the electrical current (a — o, b — o) of the nerve at both ends, showing that the disturb- ance in the electrical condition of the nerve, whatever its nature may be, is propagated in both directions, from the centre or the point of the application of the stimulus : a very important fact, since, if the phe- nomenon of the negative variation is intimately associated with that of the development and propagation of nerve force, it proves that the latter is transmitted from the point of stimulus, both to the central and periph- eral ends of the nerve, confirming the view already advanced, that the nerve force is transmitted in both directions, which could not be learned obviously from the muscular contraction, and that the function of a nerve depends, not upon its intrinsic structure, but whether it termi- nates in a motor, sensory, or glandular organ. By extending our experiments it will be further found that all kinds 598 NEGATIVE VARIATION. Fig. 339 Curves of nerve current and negative variation. of nerves exhibit the phenomena of negative variation, and that from every part of a nerve, during a period of rest, an electrical current can be diverted, and that it is indifferent whether the central or the periph- eral end of the nerve be the excited or the diverting portion. Finally, that the amount of the negative variation Y B, I C, at the different points of the nerve N will be always proportional to the amount of the preex- isting nerve current Y A, I D, of which it is nothing but the diminution (Fig. 339), hence if the former current be absent there will be naturally, therefore, no negative variation. Such is the case, for example, if the diverting electrodes be placed upon two points of the longi- tudinal surface symmetrically disposed with reference to the equator, the magnetic needle not being then deflected by the nerve current, there can be no diminu- tion of the latter or negative va- riation. An interesting fact as regards the phenomenon of nega- tive variation is, that it can not only be produced by artificial stimuli, electrical, chemical, ther- mal, and mechanical, but by natural ones inherent in the ner- vous system itself by influences emanating, for example, from the spinal cord. Thus, Du Bois-Reymond has shown that if the sciatic nerve of a living frog be well exposed, avoiding, however, the injuring of the bloodvessels and the origin of the nerve, the nerve cut through at the popliteal space, the electrodes so disposed that the point of one is in contact with the equator, and the point of the other with the cut surface of the nerve, that with the appearance of the muscular cramps due to the subcutaneous injection of strychnia, the electrical current of the nerve will undergo a negative variation. The significance of this experiment will be better appreciated, however, when the subject of reflex action has been considered ; since the muscular contraction, with the accompanying variation in strychnia poisoning is due to an impres- sion made upon the skin and thence transmitted to the spinal cord, and from that nervous centre reflected to the muscles. Further, according to the same high authority negative variation occurs during the tetanus brought about by the mechanical crushing of a nerve, or the destruction of the same by heat and during tetanus of the sciatic nerve, more especially when induced by the stimulation of its cutaneous branches. It has already been mentioned that the rapidity at which the negative variation is transmitted is the same as that of the nerve force itself. This was first determined by Bernstein 1 by means of his differential rheotome. The principle of this instrument consists in closing the circuit stimulat- ing the nerve as well as that diverting its natural current, by a wheel 1 Untersuchungen iiber den Erreguns vorgang im Nerven— und Muskel systeme. Heidelberg, 1871. DIFFERENTIAL RHEOTOME. 599 rotating at a known rate and of so disposing the two pairs of electrodes that the stimulating- circuit is closed before the diverting: one. The interval of time between the two being determined from the rate at which the wheel is rotating;, and the negative variation being; trans- Fig. 340. Bernstein's differential rheotome. Horizontal view. mitted along the nerve from the point of the application of the stimulus to that of the diverting electrodes, if the deflection of the needle in the reverse direction appears at the moment that the diverting circuit is closed, the rate at which the negative variation has been transmitted from the point of stimulation to that of the diverting electrodes becomes at once known : and experimentally it was so found by Bernstein to be the same as that of the rate of the nerve force itself, viz., in the frog twenty -eight metres a second. The differential rheotome, somewhat more in detail, as made for the author by Zimmerman, of Heidelberg, consists of a wheel (Fig. 3-40, W) having a diameter of 12.5 cm. (5 inches) horizontally disposed, whose hub or axis (a) is elongated vertically upward and downward, the lower end (Fig. 341, e) working in a mercury cup (m), the upper end (r) in the frame, the axis passing through a groved disk (d), serving for the attachment of the cord of the electro-magnetic rotation apparatus to be described presently, by means of which the axis and the wheel are uniformly rotated. To the periphery of the wheel (Fig. 310) is at- tached a brass piece (k), insulated by ebonite, which carries the steel pointer (//), the latter being elevated or depressed by the screw and 600 NEGATIVE VARIATION*. Fig. 341. H HJ Bernstein's differential rheutouie Profile view. Fig. 342. Scheme fur determining negative variation. obliquely disposed, so that the upper part is inclined toward the direction of the motion of the wheel. With each rota- tion of the wheel, contact is made between the pointer p and the wire 10 stretched across the brass cup resting upon the ebonite, or instead with a mercury cup not rep- resented in the figure, the brass or mercury cup, which- ever is used, being raised or lowered by means of the screw working in the cylinder y. With each contact of jo and w (Figs. 341, 342) the stimu- lating circuit is closed, the current passing then from the battery B (Fig" 342) through p and iv to the wire in the spoke (sp) at the wheel, and alongside of the axis a e back to the primary current and to the battery, a key (if) being interposed in the secondary circuit (S). The opening and closing- shocks transmitted to the nerve follow each other so DIFFERENTIAL RHEOTOME. 601 rapidly that they may be regarded as one momentary stimulus. The periphery of the wheel W (Fig. 340), opposite to the brass box and wire just described, carries also an insulated bar, through which pass two sharp-pointed steel pointers (p l p 2 , Figs. 340, 341) obliquely disposed, capable of being elevated and depressed by screws, which, as the wheel rotates, glide smoothly over the surface of the mercury in the two steel insulated cups c 1 c 2 , supported by the brass arms (q 1 c\ passing through the connected mercury cups m m, which can be pushed to the other end of the box along the scale graduated in millimetres at the side. When the mercury cups are directly in contact with the brass a, the resistance offered by the rheocord to the Daniell's circuit is practically nothing as compared with that offered by the nervous circuit, consequently the cur- rent from the Daniell's element simply passes through the rheocord back to the cell, none being diverted into the nervous circuit. If, however, the mercury cups be pushed away from the brass along the platinum wires, the wires offering a resistance, the amount indicated by the scale, 358 mm. = 1 ohm, and there being no passage for the current from one side of the rheocord to the other, except through the parts of the wires lying between the mercury cups and the brass, it follows that a pro- portional part of the total current from the Daniell's element is thrown into the nervous circuit. If a greater amount of resistance is needed than that obtained by pushing the mercury cups through the whole length of the platinum wires, then the plugs lettered b, c, d, e, /, g, or numbered, can be drawn out, these being multiples of the resistance offered by the total length of the platinum wires traversed by the mercury cups, the amount of current thrown into the nervous circuit will be then proportionally increased. Thus, for example, if the plug 5, letter rc^ JV Anelectrotonic and katelectrotonic currents. the polarizing current is direct — that is, as it passes through the nerve from the anode a, or positive pole, to the kathode k, or negative pole, it flows in the same direction as the nerve force itself. Now if it be assumed that the polarizing current develops outside of the electrodes p p\ a new current, the electrotonic current, having the same direc- tion as itself, it is evident that the increasing or diminishing of the natural nerve current by the electrotonic current, according as the latter is flowing in the same or in the opposite direction, will account for the difference in the electrical condition of the nerve outside of the anode a, and kathode Jc, the former being positively, the latter nega- tively, electrified. Such being the case, we may call that part of the electrotonic current increasing the natural nerve current the anelectro- tonic, that diminishing the same the katelectrotonic current, indicating the electrical conditions of the two currents respectively bv the sio-ns plus + and minus — . If now the position of the two electrodes p p' be reversed so that the polarizing current flows through the nerve in the opposite direction to that of the nerve force, then the anelectrotonic current will be developed atj?, the katelectrotonic atj!?, and the current passing through the galvanometer G- will be increased, that through the galvanometer Cr' diminished. It will be observed, therefore, that the anelectrotonic and katelectrotonic condition just described will de- pend upon the fact of the polarizing current passing through the nerve in the direct or reverse direction. In either instance, when the polarizino- 39 G10 NEGATIVE VARIATION. current is broken the natural nerve current previously diminished or increased is for a brief moment increased or diminished. While there can be no doubt as to the existence of the anelectrotonic or kat- electrotonic currents, and that the same spread along the extrapolar portions of the nerve from the anode and kathode, respectively, with a gradual diminution in intensity, there is some doubt as to what extent if at all, the intrapolar current is similarly affected. By varying the strength of the polarizing current it will be found that the strength of the electrotonic currents depends upon that of the polarizing current and of the length of the intrapolar portion of the nerve exposed to the latter, and of the irritability of the nerve, a dead nerve not exhibiting the electrotonic current. Finally, the electrotonic currents undergo a negative variation dur- ing the passage of the nervous impulse. Of the electrotonic currents developed, the anelectrotonic portion differs from the katelectrotonic, not only in being positively electrified, but in being greater and attain- ing its maximum and minimum more slowly (Fig. 348). Further, while Fig. 348. Graphic representation of anelectrotonic and katelectrotonic currents. according to Du Bois-Reymond, 1 the electromotive force of the electro- tonic current amounts to 0.5 of a Daniell, that of the katelectrotonic current 0.05 D. While the electrotonic currents just described are without doubt produced by the polarizing current, there is still some difference of opinion among physiologists as to whether these currents are due to some especial modification of the electromotive condition of the nerve, which, like the negative variation, is transmitted from the point stimulated through the nerve, from molecule to molecule, or are due to the direct effect of the polarizing current through an escape of the latter, from the electrodes along the extra-polar portions of the nerve. The grounds which induced Du Bois-Reymond 2 to suggest the former or molecular view are, for example, the alleged absence of electrotonic currents, if the nerve be ligated at a point intervening between the polarizing and diverting electrodes, or if it be divided and the two cut ends subsequently brought in close contact, or if a moistened thread be substituted for the nerve in the experiment described at p. 609, and illustrated by Fig. 347, which ought not to be the case if the elec- trotonic current is simply an escape of the polarizing one. Du Bois- Reymond, therefore, considers, according to his view of the nerve 1 Gesammt. Abhandl., ii. S. 260. 2 Uutersuchungeu iiber Tkierische Electricitiit, Berlin, 1848-C0. ELECTROMOTIVE MOLECULES, 611 consisting of electromotive molecules (Fig. 349), that the effect of the polarizing current is so to modify the position of these molecules that their opposite poles are brought to face each other as in Fig. 350, the + effect being then that all the currents have the same direction — that is, an electrotonic current is developed. The modification in the position of Fig. 350. D + Modification of molecular conditions of nerve by passage of constant current. the molecules a, c, e, the direction of whose currents is opposed to that of the polarizing current, supposing the latter to be direct, as in Fig. 349, is attributed to an electrolysis, similar to that produced by trans- mitting an electric current through water, with this difference, however, that the electrifying influence extends itself beyond the electrodes, with- out which assumption it would be impossible to explain the existence of the anelectrotonic and katelectrotonic currents. Further, in order to account for the strength of the electrotonic current depending upon that of the polarizing one, Du Bois-Reymond supposes that of the numerous molecules of which the nerve consists either with a weak current only a few of them are turned, or that all are turned, but only more or less imperfectly. On the other hand, it is argued by Matteuci, 1 Gruenhagen, 2 and Hermann, 3 that the electrotonic currents can only be produced 1 Oomptes RenduS, 1863, lvi. p. 700 ; 1807, lxv. pp. 151, 191, 2 Fuuke : Physiologie, Zweiter Baud i. S. 495. : ; 18R8, Ixvi. p. 580. 3 Physiologie, Zweiter Band, S. 174. 612 NEGATIVE VARIATION. by electrical ones and not by other nerve stimulants, such as heat, chemical agents, etc., which oughl not to be the case, if the electro- tonic currents be due to an essential modification of the electrical con- dition of the nerve molecules; further, that if a moistened thread so prepared as really to resemble nerve structure be substituted for the nerve of Fig. 847, electrotonic currents will be developed, and the fact that the ligation or division of a nerve interferes with the pro- duction of electrotonic currents does not necessarily imply that the electrotonic current is transmitted from molecule to molecule, and is inconsistent with the view that its production is due to the polar- izing current, since the ligation or dividing the nerve may destroy a portion of it essential in the development of electrotonic currents through a polarizing one. In other words, the vitality, or, better, the continuity of the nerve may be as an indispensable condition in the production of electrotonic currents, whatever view may be taken of their origin. It has already been mentioned that one of the objections to the view of the electrotonic current being the direct effect of the polarizing one, is the fact of a moistened silk thread, when traversed by a current, not exhibiting, like a nerve, electrotonic currents, which ought to be the case if the phenomenon is due simply to the escape of the electrical current, and not to a physiological modification generated and trans- mitted through the nerve. Now while it is true that when a moistened silk thread of small transverse section is substituted for the nerve, the galvanometer gives no evidence of electrical currents, it does not, how- ever, follow that such currents are not developed in the thread by the polarizing current ; on the contrary, from the presence of electrical currents in threads of large transverse section we infer that they are also developed in threads of small transverse section, even though the galvanometer gives no evidence of such. The reason of this becomes clear from an inspection of Fig. 351, representing a moistened silk thread of large transverse section traversed through a portion of its extent by a polarizing current. The latter, on arriving at the positive pole or anode (a) divides into two brandies, one of which returns at once through the intrapolar portion of the nerve to the negative pole or kathode (&), and so back to the Daniell's element ; the other, on the contrary, spreads outwardly from the anode as the leaving current (e), and after traversing the diverting circuit, and deflecting the gal- vanometer ((x), returns as the returning current (r) to the kathode, and so to the Daniell's element. It will be observed, however, from Fig. 351, that according as the diverting electrodes Cr Gf' are dis- posed with reference to the leaving or returning currents, they change their sign as at c b, the diverting electrode c lying nearest to the stimu- lating electrode a, assuming the electrical condition corresponding to that electrode, that at b the electrical condition corresponding to K. Now it is obvious, that if the silk thread have a very small transverse section, the leaving or returning currents lie then so closely together, that in being diverted into the galvanometer, they neutralize each other, and exercise no influence upon the magnetic needle. It becomes perfectly clear, therefore, why moist conductors of small transverse section traversed by a polarizing current exhibit no electrical currents PASSAGE OF ELECTRICAL CURRENT, ETC. 613 in the extrapolar portions of the nerve. Now a nerve differs essen- tially from such a moist conductor not only in exhibiting electrotonic currents when traversed by a polarizing one, even though presenting a small transverse section, but also that these currents have the same Fig. 351. D Passage of electrical current in moistened silk thread. sign whether the diverting electrodes be placed upon the same side of the nerve as the stimulating electrodes, or the opposite side, as at c b (Fig. 352). No such difference between a nerve and a moist con- ductor, however, is apparent if the latter is so made as to resemble a nerve in its structure — that is, consists of a central axis, which is a better conductor than the surrounding envelope, as, for example, when a thread (t, Fig. 352) moistened with strong salt solution, is surrounded by a porous clay tube (ct) whose walls have been previously soaked in distilled water, or when a stick of amalgamated zinc is surrounded by a similar tube soaked in zinc sulphate solution. The leaving currents will, in such a conductor, have the same direction, owing to the fact of the substance coating the axis being a better conductor than the envelope, while the return currents all running in the better conduct- ing axis, the current will also have the same sign, however the divert- ing electrodes be placed upon the surface of the nerve. Further, the electrotonic currents so developed resemble those of a nerve in being entirely dependent upon the polarizing current, of the length of the nerve traversed by the latter, etc. If, now, such a heterogeneous con- ductor be divided in the middle, and the cut ends be joined by a homogeneous moist conductor like that already described, no electro- tonic currents will appear, lor the reasons already given. It is in this way, probably, that the ligation or the crushing of the nerve 614 NEGATIVE VARIATION. interferes with the development of such currents, the nerve, after death, being changed from a heterogeneous to a homogeneous con- ductor. Further, as the escape of the polarizing current, either in the nerve or the heterogeneous conductor, appears to be due to the resist- ance developed through the inner polarization set up between the core Fig. 352. Fig. 353. Passage of current through moistened thread, enclosed in clay tube ct. Passage of current through platinum, surrounded by zinc sulphate. and the sheath, it is to be expected that the amount of the polarizing current escaping along the extrapolar portions of the nerve will be proportional to such resistance, and such a fact is found to be the case. Thus, for example, if a platinum thread be passed through a zinc sulphate solution in a clay tube (Fig. 353), the electrotonic currents developed will be much greater than if the axis consisted of amalga- mated zinc. Indeed, as we have already seen, amalgamated zinc and zinc sulphate solution are so homogeneous, that we use them to make non-polarizable electrodes. An interesting illustration of the difference in effect as regards the development of electrotonic currents due to the Fig. 354. Passage of current through heterogeneous conductor. conductor being homogeneous or heretogeneous can be readily shown by the following simple apparatus (Fig. 354), which consists of a glass tube through which passes an axis of amalgamated zinc. If the tube be filled with zinc sulphate solution, the galvanometer gives no evidence of electrotonic currents ; but if a number of little ELECTROTONIC CURRENTS. 615 glass beads be run along the axis, the spaces between the beads cor- responding, let us say, to the nodes of Ranvier in the nerve, the galvanometer will be at once deflected, the conductor having been con- verted from a homogeneous into a heterogeneous one. The different facts just referred to, established by Funke, Gruenhagen, Hermann, etc., all go to show that the living nerve is a heterogeneous conductor, consisting (Fig. 355) of a central axis, which is a better conductor than its surrounding envelopes, the white substance of Schwann, and the Fig. 355. rVl^ siiwfivtrvmSr f'ur-r^TiC A'atelf c front c Current -*'-'"""""" + a PotaruJtti? K <7X> Passage of current through nerve. neurilemma, and that, owing to the inner polarization set up between the axis and its sheath, a resistance is offered to the polarizing current, hence its escape along the extrapolar portions of the nerve; the latter, owing to the resistance being gradually diminished, at last passes into the axis, and thence by the kathode back to the Daniell's element. Finally, the electrotonic current so developed, in increasing or diminish- ing the neutral nerve current, gives rise to the anelectrotonic and katelectrotonic currents respectively. While in the present state of physiological knowledge it may appear premature to accept, without reserve, the view that attributes the electrotonic current to the escape of the polarizing one, nevertheless, it must be admitted that the facts, so far as they have been established, are better explained by this view than by any other yet advanced. Finally, if a nerve (iV, Fig. 356) be placed upon another {N 2), the latter exhibiting an electrotonic Fig. 356. JV< J^ Secondary electrotonic current. current, a secondary electrotonic current will be developed in the former opposite in direction to that of the current producing it as represented in Fig. 356, the current being closed by the ends of the nerve lying in 616 NEGATIVE VARIATION. contact with each other. It is an interesting fact, in this connection, that when a nerve is traversed by a polarizing current not only do the anodal and kathodal portions of the nerve differ in the presence of anelectrotonic and katelectronic currents, but also in exhibiting the conditions of anelectrotonus and katelectrotonus (Fig. 355), the former being one of diminished, the latter of increased, excitability and con- ductivity respectively. The anelectrotonic and katelectrotonic conditions are not only interesting from being intimately connected in so many respects with the anelectrotonic and katelectrotonic currents, the latter, indeed, being so named for this reason by Du Bois-lleymond, the phenomena of anelectrotonus and katelectrotonus having been dis- covered first, but also on account of such conditions offering an expla- nation of certain well-established facts as regards the excitability of nerves by electrical stimuli. It might naturally be supposed in using the constant current as a nervous stimulant that the current would excite the nerve during the whole time that it was applied, that so long as the current passed through the nerve successive impulses would be generated, with the effect of throwing the muscle into a kind of tetanus. While under certain circumstances the above does take place, in the great majority of cases, however, the muscle remains entirely quiet during the passage of the current through the nerve, provided the current remains constant, contractions taking place at the making, or at the making and breaking, according as we shall see presently, to the strength and direction of the current. It may be said, therefore, as a general rule, that, during the passage of a constant current the muscle remains at rest. Nevertheless, as Ave have just seen, in the absence of any muscular contraction, the nerve is profoundly modified during the passage of a constant current by the development at the anode and kathode of the anelectrotonic current and anelectro- tonic condition of the katelectrotonic current and katelectrotonic condition, respectively, conditions intimately connected with the pecu- liarities just referred to as regards the muscular contraction brought about by the opening and closing of the electrical circuit. Before considering, however, these relations, let us first show how the difference already mentioned in the excitability of the nerve at the anode and kathode, respectively, can be demonstrated. With this object, we will dispose the necessary apparatus, as represented in Fig. 357, and let us suppose, first, that the polarizing current thrown into the nerve by the opening of the key, and whose strength is regulated by the rheocord, is direct, descending — that is, traverses the nerve in the same direction as that of the nerve force — a being, therefore, the anode, and K the kathode. It will then be found that if the nerve be stimulated at a point x the irritability of the nerve will be increased during the passage of the polarizing current as shown by the greater elevation of the lever due to the muscular contraction, as compared with the average elevation previously determined with the same stimulus, but in the absence of the polarizing current. On the other hand, if the nerve be stimulated at a point y the irritability of the nerve will be found to be diminished. That it is not the distance of the point y from the muscle, as compared with that of x, to which the diminution in ELECTROTONUS. 617 irritability at y is due is shown, apart from -what has already been said with reference to the stimulation of a nerve at different distances from the muscle, by reversing the polarizing current by means of the whippe, so that it becomes an inverse ascending one, the anode being then, therefore, nearer the muscle than the kathode ; even then the irritability Fig. 357. Disposal of apparatus to demonstrate electrotonus. of the nerve at x is diminished, and, with certain qualifications, to be mentioned presently, that at y is increased. In this way, then,' it is shown that during the passage of a constant current the irritability of the nerve at the kathode is increased and at the anode diminished,' the change in the condition of the nerve being described as that of kat- electrotonus and aneleetrotonus. or as the katelectrotonic increase, and anelectrotonic decrease of irritability. The condition of katelectrotonus and aneleetrotonus not only modifies the irritability of the nerve as regards the originating of nervous impulses, but appears also to influ- ence their propagation — at least it may be said that the condition of aneleetrotonus offers an obstacle to the passage of a nervous impulse. The condition of katelectrotonus and aneleetrotonus not only spreads out along the extrapolar portions of the nerve, but, unlike* the kat- electrotonic and anelectrotonic currents, extends also into the intrapolar 618 NEGATIVE VARIATION. portion, the point where they merge into each other — that is, where the irritability is unchanged — being known as the neutral or indifferent point. The position of the latter varies somewhat, according to the strength of the current, with a strong current approaching the kathode, with a weak one the anode. While the katelectrotonic increase and anelectrotonic decrease of irritability reach a maximum shortly after the making of the polarizing current, and then gradually diminish, the katelectrotonic increase, attains its maximum and minimum limits sooner than the anelectrotonic decrease. The strength of the katelec- trotonic and anelectrotonic conditions depends, up to a certain limit, upon the strength of the polarizing current, and the general irritability of the nerve. With the opening of the polarizing current the phenomena of katelectrotonus and anelectrotonus disappear momentarily, how- ever, there is an increase of irritability at the anode, a decrease at the kathode. In bringing about this condition of katelectrotonus and anelectrotonus, while usually the constant current is made use of as the stimulus, as in the preceding instance, this is not indispensable, an induced current producing the same effect ; this is as might be expected, since a single induction shock may be regarded as a constant current, but of very short duration, developing very suddenly, and disappearing more gradually. Whether, therefore, the constant or induced current be used as a stimulus th% nerve is thrown into the condition of kat- electrotonus and anelectrotonus, and with the disappearance of the cur- rent, as just mentioned, there is a rebound at the poles, their condition being then momentarily reversed. It will be also particularly observed that during the passage of the current through the nerve the muscle remains quiescent, contraction only taking place if the strength of the current varies, or at the entrance or exit of the current into or from the nerve. The stimulus causing the nervous impulse is due to a change from one condition to another, not to the condition itself, the effect not depending so much upon the intensity of the condition as on variation of the same. Further, it will be observed by extending our experi- ments, that a nervous impulse is only generated when the nerve passes from its normal condition into that of katelectrotonus, or that of in- creased irritability, and diminished electrical potential, or passes from the condition of anelectrotonus, that of diminished irritability and increased electrical potential, back to the normal condition, the latter normal condition being then, relatively at least, one of katelectrotonus, as compared with the immediately preceding anelectrotonic condition. As might be expected, however, the passage of the nerve from the anelectrotonic to the normal condition is far less effective as a generator of nervous impulses than that from the normal to the katelectrotonic condition, since the return from the anelectrotonic to the normal con- dition is a gradual, not a sudden one, and the change acts as a stimulus, at best only relatively. Hence, with induced currents at least, usually the muscular contraction takes place only at the closing, not at the opening of the current. Let us now modify the arrangement of the apparatus just used so that (Fig. 358) by means of the rheocord Ave can modify the strength of the constant current, and, by the whippe, reverse the direction through EFFECT OF STRENGTH OF CONSTANT CURRENT. 619 ■which it traverses the nerve, and let us suppose first that the current is a weak one, descending direct at the moment of stimulation — that is, at the making of the circuit, the muscle will contract, remaining quiet, however, during the passage of the current and also at the breaking of the same. Let us now reverse the direction of the current, so that it becomes an inverse ascending one (Fig. 359), then, as before, the muscle will contract only at the making of the circuit. The effect in both instances being the same, can be accounted for by supposing the kat- Fig. 3")8. electrotonic condition acts as a stimulus, the impulse generated at the kathode in the case of the inverse current being still effective, even though the distance of the kathode from the muscle is increased. Since, Fig. ?,.">9. 3C I — hoAvever, the latter impulse generated at the kathode has to traverse the anelectrotonic portion of the nerve (a), which, as it will be re- membered, offers an obstacle to the propagation of the impulse, the 620 NEGATIVE VARIATION. muscular contraction due to the making of the inverse cm-rent will be less than thai due to the making of the direct one. That no contraction takes place at the breaking of the circuit with either the direct or inverse currents is to be expected, since, with the breaking of the direct current, the kathode offers an obstacle, having become momentarily the anode, to the propagation of the impulse due to the weak katelec- trotonic condition momentarily developed at the anode, and. with the breaking of the inverse current, the fall at the anode from anelectro- tonus to the normal is too slight to generate an impulse. Let us now intensify the current and reverse its direction by i,he whippe, so that it is again a direct one (Fig. 358) : muscular contraction will take place both at the making and breaking of the circuit, in the latter case the effect being due to the passage of the anelectrotonic condition back to the normal — that is, relatively to a condition of katelectrotonus. Reverse the current so as to make it an ascending one (Fig. 359), and, as before, we will have muscular contraction taking place both at the making and breaking of the circuit : the katelectrotonic condition generating the impulse at the making and the return of the anelectrotonic condition to the normal at the breaking of the circuit. Finally, with a very strong current, if the latter be direct (Fig. 358), contraction takes place only at the making of the circuit, and with the inverse current only at the breaking. The fact of there being no contraction at the breaking of the circuit with the direct current may be accounted for by partly sup- posing that the general irritability and conductivity of the intrapolar portion of the nerve has been depressed by the strong current and partly by the fall of anelectrotonus not being effective on account of the relative anelectrotonic condition developed through the fall of the katelectrotonic offering an obstacle to the transmission of the impulse. On the other hand, with the ascending current (Fig. 359) there will be no contraction at the making of the circuit, since the anelectrotonic condition, an obstacle to the propogation of the impulse generated at the kathode, intervenes between the latter and the muscle ; but, at the breaking of the circuit, the fall of the anelectrotonus to the normal relatively katelectrotonus will generate an impulse, since no obstacle intervenes then between the point of stimulation and the muscle, and the latter will contract. The above facts, established among others by Pfaff, Ritter, and Pfluger, may be summarized as a law of muscular contraction, under the following formula, in which the direct and inverse currents are indicated by the letters D and _Z" and the arrows, and the making and breaking of the circuits by the letters M and B, and the contraction and rest of the muscle by and It respectively. Law of Muscular Contraction. Weak current. Medium current. Strong current. D | M C, B R, M C, B C M C, B R, M C, B R, M C, B C, M R, B C, The above law can be readily remembered, and the facts explained, if it be admitted, that muscular contraction only takes place when there hitter's law. 621 is a rise of katelectrotonus or a fall of anelectrotonus (relative kat- electrotonus) ; but not by the rise of anelectrotonus or fall of katelec- trotonus (relative anelectrotonus). In concluding the subject of electroton us one cannot but be impressed with the significance of the fact of the katelectrotonic condition, that generating the nervous impulse, being situated at that electrode whose electrical condition is diminished, when it is remembered that the propa- gation of the nervous impulse or the negative variation is also charac- terized by a diminution in electrical condition. These facts taken together at once suggest the idea of nerve force not being identical with electricity as once thought, 1 but of being correlated with the latter in some manner, the appearance of the one depending upon the disap- pearance of the other, or the absence of the one favoring the develop- ment of the other, and while this view cannot at present be accepted without reserve, to say the least it is certainly a plausible one and de- serves consideration, being in harmony with the general doctrine of the conservation of force. In concluding our account of nerve physiology it remains for us now to say a few words with reference to the conditions influencing the general irritability of nerves, which for convenience' sake have been reserved for the present moment, such as the influence' exerted by the distance from the muscle of the point of the nerve stimulated, the dura- tion of and number of the stimuli, the temperature and blood supply, the functional activity, severance from the central nervous system, etc. Thus, if two pairs of electrodes are placed upon the nerve of a freshly prepared nerve muscle preparation, one pair near the muscle, the other pair near the cut end of the nerve, it will be found that the muscular contraction is greater when the stimulus is applied through the latter pair than when through the former. This result can be accounted for either on the supposition that the nervous impulse gathers strength, avalanche-like, as it travels from the cut end of the nerve toward the muscle, or that the central end of the nerve is more irritable than the distal end— v-tliat is, that that portion of the nerve generates a longer nervous impulse when stimulated. The latter view is the most probable one. since the negative variation following in the stens of the nervous impulse exhibits no such avalanche-like increase as it progresses wave- like from the point stimulated to the muscle. It has been shown by Konig 2 thai the constant current if used as a stimulus must last at least the 0.0015 second to produce a nervous impulse, and by Kroniker and Stirling. 3 that inductive shocks even if repeated as rapidly as 2200 times ;i second will throw a muscle into tetanus. In this connection it is an interesting fact according to Helmholtz, 4 that if maximum induc- tion shocks he thrown into a nerve following each other at a rate of less than the , ; , 1 l0 th of a second, half the shocks will produce no effect, the muscle being devoid of irritability for the -g^th of a second subse- quent to each shock. A rise in temperature, say to 45° C. (113° F.), 1 According to nailer. Elements Physiologiae, t. iv. pp. 3.">7, 373, the mathematician Hansen was the first t.> suggest tint nerve force and electricity are iilentie.il. llis views were not, however, published until alt' r Ins death, appearing first in his " Nbvi profectus in historia electricitates," according to Du Bois-Reymond, Dntersuchnngen, ii. 1, S. 211. •■i Wien Sitz. Bericht, lxii. (1870). s Archiv Aflat, u. rhys., 1S78, S. 1. * Berlin Moiiats. Bericht, 1854. 622 NEGATIVE VARIATION. in the case of the frog's nerve favors the development of nerve irritability ; the activity of the molecular processes being increased, nervous impulses are generated more readily by stimuli, and the muscular contractions are proportionately greater. On the other hand, the application of cold benumbs the nervous system, diminishes nervous irritability, the latter disappearing altogether if the temperature be reduced to 0° C. (32° F.). Judging from what we shall learn hereafter from the analo- gous case of muscle there can be little doubt that the irritability of a nerve depends upon a full supply of oxygenated blood and that through prolonged use the nerve becomes exhausted. Finally, if a nerve be divided in the living body or even out of it, it will be observed that at the peripheral end of the cut nerve the irritability at first slightly increases, then diminishes, and finally disappears, the changes in the irritability advancing from the cut end of the nerve toward the muscle. Coincidently with the changes in the irritability of the nerve just mentioned, a degeneration is set up in the substance of Schwann and the axis-cylinder extending to the terminal filaments, involving even their endings in the motor plates. A similar degeneration may extend also centripetally from the cut end, but not beyond the first node of Ranvier. Beyond this point the nerve is usually found normal. CHAPTER XL. THE SPINAL CORD, ITS STRUCTURE AND FUNCTION'S AS A CONDUCTOR OF MOTOR AND SENSORY IMPULSES. The spinal cord lying in the vertebral canal, enveloped within its membranes, extends as a cylindrical cord of from fifteen to eighteen inches in length from the medulla oblongata, with which it is continuous, at the level of the occipital foramen to the lower part of the first lumbar vertebra. It weighs about one and one-half ounces. If a transverse section of the cord be made, it will be observed (Fig. 360) that ir consists of white matter externally, and of gray matter internally, the latter being found in the greatest amount opposite the cervical and lumbar enlarge- ments, the origin of the large nerves. The gray matter is disposed as two crescents, placed back to back, some- what in the form of the letter II, the anterior portion, the widest, being known as the anterior cornu. the posterior portion, the largest, as the posterior cornu, the middle connecting portion the gray commissure* The latter is often subdivided into the interior and pos- terior gray commissures by its central canal, which, as we shall see hereafter, is the remnant of the primitive neural canal. This peculiar arrangement of the gray matter within the spinal cord serves conveni- ently to subdivide the white portions of the cord into the anterior, lateral, and posterior columns. The anterior columns are made up by that pari nf the white matter of the cord lying between the anterior median fissure and the anterior cornu. It will be observed, however, that, as the anterior median fissure does not extend into the anterior gray com- missure, a band of white matter, the white commissure, intervening, the anterior columns run into each other, and that, as the anterior cornu do not extend to the outer edge of the cord, the anterior columns pass into the lateral ones, lying between the two crescents. On the other hand, the posterior median fissure extending down to the posterior gray commissure, and the posterior cornu of the gray matter to the inner edge of the cord, the posterior columns lying between them are completely separated from the lateral columns, and from each other. In certain regions of the cord each posterior column is further sub- liansverse section of the spinal curd. ", b. Spinal f right and left sides. . beyond the anterior roots will then be found to contain degenerated fibres, showing that some of the fibres of the anterior root at least are really derived from the posterior one. While there can be no doubt that tlie spinal cord is the exclusive organ of communication between the brain on the one hand, and the external organs of sensation and motion on the other, a complete loss of sensibility and voluntary motion following its division, compression, or disorganization ; there still prevails some uncertainty as to the exact routes by which impressions made upon the periphery are transmitted from the posterior roots through the cord to the sensorium and voluntary impulses in the reverse direc- tion through the anterior roots to motor organs. The difference of opinion held in this respect by physiologists, the diametrically opposed views that have been maintained, are no doubt due partly to the fact of the structure of the spinal cord not yet being thoroughly understood either in man or animals, pathological facts, therefore, being of little use as a means of discovering its func- tions, but also in a great measure to the conclusion based upon experi- ments performed upon animals being applied to man without it being taken into consideration that not only does the spinal cord of animals differ in certain respects from that of man, but that it varies in its structure in different parts of its course even in the same ani- mal. The brief expose that we have to offer of the functions of the spinal cord in man as a conductor of sensory and motor impulses to and from the periphery, as derived from the experiments and observa- tions of Chauveau, 1 Longet, 2 Brown-Sequard, 3 Vulpian, 4 Schiff, 5 Ludwig 6 and Woroschiloff Turck, 7 Charcot, 8 and the author, must be taken, therefore, with qualification, and subject to the further advance of our knowledge of this difficult subject. From the fact of the anterior roots being motor in function, and the fibres of which they consist passing into the cells of the anterior horns of the gray matter, thence into the antero-lateral columns of the same side, it might be expected that these columns are motor in function. That such is the case appears to be shown both by experimental and pathological evidence. Thus, if a section be made in an animal, a rabbit, guinea- pig, or dog, for example, 9 involving only the antero-lateral columns of one side of the cord there is entire loss of the power of voluntary motion on that side below the level of the section, while if the columns be stimulated at their distal ends, the muscles supplied by the portion of the cord below the section will be thrown into contraction. On the other hand, if the posterior columns and the gray matter of the cord be divided, the antero-lateral columns, however, being uninjured, the power of voluntary motion is preserved, that of sensibility and muscular 1 Journal de la Physiologic, tome iv. p. 369. Paris, 18G1. 2 Anatomic et physiologie du systenie nerveux, tome i. p. 272. Paris, 1842. And Physiologie, tome iii. p. 338 Paris, 1869. 3 Physiology and Pathology of the Central Nervous System. Philadelphia, 1860. 4 Lecons stir la physiologie generale et comparee du systeme nerveux. Paris, 1866. 6 Lehrbuch der Physiologie. 6 VerhaadluDgen der Koniglich Sachsischen Gesellschaften zu Leipzig, 1875, iii. iv. v. S. 248. 7 Wiener Denkscriften, 1851. 8 Lecons Bur les Localisations dans les maladies du cerveau et de la moelle epeniere. Paris, 1830. 9 In making sections of the cord in an animal it is indispensable that tin- spinal column should be firmly fixed, and that the cord be denuded within certain defined measurable areas. These conditions are fulfilled by using the instrument devised by Ludwig and Woroschiloff, and described in Ludwig's Arbeiteu, 1875 DECUSSATION OF NERVE FIBRES 635 coordination is lost. The available pathological evidence confirms also what has been learned from histological examination of the cord of man and experiment upon animals, that of the motor fibres in the antero-lateral columns, and more especially in the lateral ones, by far the most of them pass down continuously from the corpus striatum of one side of the base of the brain through the crus, pons, medulla, thence to the opposite side of the cord, and down the lateral columns, connecting in them with the prolongations of the cells in the anterior horns of the gray matter, which in turn are connected with the fibres of the anterior roots. Thus, disorganization beginning in the corpus striatum or thereabouts, progresses gradually downward through the tract just mentioned, involving motor paralysis. In the study of the functions of the corpus striatum more especially, additional facts will be mentioned, confirming the view just advanced that the antero-lateral columns of the cord, more particularly the lateral portions, are motor in function, and are the routes by which motor impulses are transmitted from the base of the brain to the periphery. That the gray matter of the cord is essentially that portion of it which transmits the impressions made upon the periphery to the senso- rium is shown by the fact of sensibility remaining as long as the gray matter preserves its normal structure, even after all the columns have been divided, and by the experiment just mentioned, in which sensation is lost after division of the gray matter, and the posterior columns, the latter owing what sensibility they possess not to their own intrinsic fibres, but to those of the posterior roots which pass through them in an upward, downward, and horizontal direction, on the way to their termi- nation in the posterior horn of the gray matter. Now it is an interesting and important fact that while the motor fibres of the cord decussate in the medulla, path- ological cases show that in man at least the sensory fibres decussate in the cord itself, at about the level in which they enter through the posterior roots. Thus, if the gray matter of the cord and lateral column be divided in man on one side, as by the penetration of some sharp instrument, or compresed by a tumor or disorganized by disease, as in cases that have come under the observation of the author and others, sensibility is lost on the side of the body below, but opposite to the side on which the wound has been inflicted. or the tumor located, the power of voluntary motion, however, being lost on the same side of the body as that of the wound, etc. (Fig. 371, 3). If the section be made, however, at a higher level as at - or 1. then the paralysis of both motion and sensation will be on the same side of the body, bur on the opposite side to that of the section. It follows, also, that if the spinal cord be divided longitudinally below the medulla, in a dog, for example, that while the animal is able to stand on his four legs and make voluntary movements, as first shown Fig. Diagram showing tin arse of the motor and Bensory fibres in the spinal cord and medulla oblongata. 636 THE SPINAL CORD. by Galen, 1 it has lost all sensibility in them, all the sensory fibres being divided at their decussation in the middle line, the motor fibres remaining uninjured by the section. While there can be but little doubt that the decussation of the sensory fibres in the spinal cord of man is complete, such does not obtain, to the same extent, in all animals, the decussation being much less complete in reptiles and birds than in mammals, and less in the lumbar than in the dorsal portions of the cord in certain animals. In connection with the anesthesia of the opposite side of the body following a hemisection of the cord may be here appropriately mentioned the hyperesthesia usually developed in the same side as that of the section. This remarkable condition of excited sensibility, made quite evident within a few hours after the operation by the movements of the animal made in response to the slightest pinching, etc., of the skin, and lasting often for weeks, is probably due to the increase in temperature and vascularity brought about by the division of the vasomotor nerves, or the nerves regulating the calibre of the bloodvessels, which, we shall see hereafter, descending from the vasomotor centre in the medulla oblongata through the antero- lateral columns, but is also, no doubt, to be attributed to the division of the inhibitory or restricting fibres, whose influence being lost, there- fore, upon the parts below the section, the latter becomes more excitable, more susceptible to external stimulus. It is a remarkable fact that, while the gray matter of the cord trans- mits sensory impressions, it itself appears to be insensible to ordinary mechanical or electrical stimuli, since it may be pricked, pinched, or electrically stimulated without the animal giving any signs of pain. The gray matter can be, however, excited by chemical stimuli, certain poisons, and venous blood. It has already been mentioned that if the posterior columns and the gray matter of the cord are divided, that the power of muscular coordination, as well as sensibility is lost, and, as we have just seen, that sensibility cannot be attributed to the posterior columns, it would appear that the function of the posterior columns is to coordinate, to bring together in harmonious action, different portions of the cord. This view, based upon experiments made upon animals, is confirmed by the pathological evidence afforded by cases of locomotor ataxia, in which loss of the power of muscular coordination is associated with disease of that portion of the posterior columns of the cord known as the columns of Burdach, the power of voluntary motion and sensi- bility being, however, retained. It may be here mentioned that it is quite possible that such portions of the anterior columns not containing the motor fibres of the anterior roots, like the posterior columns, may be also commissural, coordinating in character. It must be mentioned in this connection, with what has been said as to the result of division of different parts of the spinal cord, that from the fact of the loss of the power of voluntary motion and sensibility being frequently restored, that there must exist potentially, so to speak, a vicarious power of inter- change of function between different parts of the cord, certain fibres l De Anat. Administrate Lib. viii. Cap. v., Opera Omnia, t. ii. p. 683. Lips., 1821. Galen does not appear, however, to have observed the loss of sensibility in such cases, which was first observed by Fedora in 1822, Journal de Physiologic, t. iii p. 199. Paris, 1823. DISTRIBUTION OF SPINAL NERVES. 637 being capable, if necessary, of assuming the power of transmitting sen- sory and motor impulses, in addition to their ordinary characteristic functions. Resuming, it may be said, in all probability, that in man, at least, usually the fibres conducting motor impulses pass from the corpus striatum from one side of the brain down through the lateral column, principally of the opposite side of the cord through to the gray matter to the anterior roots, that the fibres transmitting sensory impressions pass from the posterior roots to the gray matter of the opposite side of the cord upward in the gray matter to probably the thalamus opticus, and that the function of the anterior and posterior columns is commissural, coordinating in character. Finally, if it be admitted that there is no essential difference between motor and sensory nerves, then the anterior root of the spinal nerves is motor, because the fibres of which it consists terminate in muscle, and the posterior sensory, because its fibres begin in sensory organs. Having demonstrated now experimentally this important distinction in function between the roots and the branches of the spinal nerves, and offered an explanation of the cause of the same, let me briefly point out the general distribution of the anterior and pos- terior branches, it being always borne in mind that the branches, whether anterior or posterior, are in their functions mixed nerves, possessing both motor and sensory properties. The anterior branches of the four upper cervical nerves form the cervical plexus, and the four lower cervical, together with the first dorsal nerve, the brachial plexus. From the cervical plexus are derived the superficial cervical, great auricular, small occipital, supraclavicular, and phrenic nerves, and mus- cular branches; the brachial plexus supplying mainly the upper ex- tremity, but giving off, also, the supra- and subscapular and thoracic nerves. The posterior branches of the cervical nerves, with the excep- tion of the first, after passing backward from the vertebral canal divide into external and internal branches, and supply the muscles and integu- ment behind the spinal column, the posterior branch of the first cervical issuing between the arch of the atlas and the vertebral artery, being distributed to the contiguous straight, oblique, and complex muscles. The anterior branches of the dorsal or thoracic nerves, with the exception of the last one, pass outwardly in the intercostal spaces, as the intercostal nerves, the anterior branch of the last dorsal being situ- ated below the last rib crosses the quadrate lumbar muscle as it ad- vances between the internal oblique and transverse muscle in a similar manner as an intercostal nerve. In their course the intercostal nerves, as they supply the muscles, give off lateral cutaneous branches, that from the second intercostal or the intercosto-humeral nerve being an important one, since it extends across the axillary space, running in juxtaposition with the small cutaneous nerve from the brachial plexus, and supplies the skin on the inner part of the arm. The posterior branches of the dorsal nerves, like those of the spinal nerves, generally, after turning backward between the transverse processes of the vertebrae, divide into external and internal branches, the former supplying the skin contiguous to the angle of the ribs, the longissimus and sacro- lumbal- muscles, the latter the skin over the spinous processes of the 638 THE SPINAL CORD vertebrae, the multifid and semispinal muscles. The anterior branches of the upper four lumbar nerves, together with a filament from the last dorsal nerve, constitute the lumbar plexus, and which, after supplying the psoas and quadrate lumbar muscles, give off the iliohypogastric, ilio-inguinal, genito-crural, external cutaneous, obturator and anterior crural nerves. The posterior branches of the lumbar nerves pass back- ward, like those of the dorsal, to supply the longissimus and sacrolumbar muscles, and the adjacent skin. The anterior branches of the upper four sacral nerves, together with the fifth and part of the fourth lumbar nerves, form the sacral plexus, from which are derived the filaments supplying the pyriform, internal obturator muscles, etc., the levator and sphincter ani, the superior gluteal, pudic, and great and small sciatic nerves. The sacral, together with the lumbar plexus, give off the nerves supplying the lower extremity. The anterior branch of the fifth sacral, a small nerve, emerges from the end of the vertebral canal, and divides into two branches, one of which passes with a filament from the fourth sacral to end in the sympathetic, the other joining the coccy- geal nerve. While the posterior branches of the upper four sacral nerves pass out of the vertebral canal by the corresponding sacral fora- mina, the posterior branch of the fifth sacral emerges from the end of the vertebral canal, and, together with the posterior branch of the coccy- geal nerve, supplies the skin and muscles of the back. The anterior branch of the coccygeal nerve also passes out of the end of the vertebral canal, is joined by a branch from the fifth sacral after perforating the coccygeal muscle and great sacro-sciatic ligament, and terminates in the skin of the buttock. The posterior branch of the coccygeal, like the anterior branch, emerges from the end of the vertebral canal ; its distribution has just been referred to in connection with that of the posterior branch of the fifth sacral. CHAPTER XLI. THE SPINAL CORD AS A NERVOUS CENTRE. REFLEX ACTION. One of the most striking differences in the organization of animals is the extent to which the division of labor, physiologically speaking, is carried. Indeed, the lowest forms of life, such as the monera (con- sisting, as we have seen, of mere masses of protoplasm), are so utterly unorganized as to make it impossible to say whether such things should be assigned genealogically to the vegetable or animal kingdom. It is true, that among such primitive forms of life there are beings, like the common amoeba, in which there is a slight differentiation of structure, in that not only a nucleus and nucleolus are present, but that, at times, even an enveloping membrane or cell wall is developed, and that among the infusoria are also seen forms, like paramcecium, apparently cpute organized ; nevertheless, even these protozoan ani- malcuhe, so much more complex in their structure than the monera, cannot be said to be organized in the same sense that the remaining members of the animal kingdom, or metazoa are. Even the infusoria, apparently complex as they are in their structure, are morphologically only unicellular, and never passing beyond this primitive one-celled stage ; tissues, and still less organs, are never developed in them similar to those of which the body of one of the higher animals is made up, since, as we have already seen, the organs in the latter consist of tissues and the tissues of cells, the latter resulting from the division of the primitive cell. In- deed, it is not until we reach in the tree of life the porifera, actinozoa, and hydrozoa, of which the sponge, anemone, and jelly fish, familiar objects at the sea-shore, are examples, that we meet with anything like organization. at least in the true morphological sense of the word — that is to say, of an animal consisting of organs made up of tissues developed out of cells resulting from the segmentation of a primitive cell, or ovum. Suppose that the structure of one of the hydrozoa be consid- ered as that of the common li. London, 1878. 652 THE MEDULLARY NERVES, Twelve pairs of nerves arc given off from the base of the brain. The first two pairs, the olfactory and optic, the special nerves of the sense of smell and sight, are, as we shall see hereafter, morphologically outgrowths of the anterior cerebral vesicle; the remaining ten pairs, however, while apparently arising like the first two pairs from the base of the brain, in reality originate, as already mentioned, in the medulla, hence our reference to them as medul- lary nerves. Taking them in the order in which they succeed the olfactory and optic nerves, they are as follows : The third pair, or motor oculi com- munis; fourth pair, or patheticus ; fifth pair, or trigeminal or trifacial ; sixth pair, or abducens ; seventh pair, or facial ; eighth pair, or auditory, the special nerve of the sense of hearing ; ninth pair, glosso-pharyngeal ; tenth pair, pneumogastric ; eleventh pair, spinal accessory ; twelfth pair, hypo- glossal The third nerve or motor oculi communis (Fig. 381 and 382, III) consisting of about 15,000 fibres, 1 arises from a nucleus of multipolar cells situate beneath the gray fibres of the aqueduct of Sylvius, beneath the corpora cjuadrigemina, and extends beneath the upper part of the fourth ventricle, the fibres of the nerves de- cussating at their origin. From this nucleus the fibres pass forward through the crus, emerging at the base of the brain from the inner surface of the crura cerebri immediately in front of the pons. As the nerve passes through the sphenoidal fissure into the orbit (Fig. 383) it divides into two branches, the superior and smaller branches sup- plying the superior rectus and levator palpebrse superioris muscles, the in- ferior and larger branch the internal and inferior recti and the superior oblique muscles. The latter or inferior branch gives off also a short, thick filament, which passing into the ophthalmic ganglion of the sympathetic is supposed, as we shall see, to pass thence as the short ciliary nerves into the iris, innervating the circular muscular fibres of the latter. During its course the fibres of the third pair run in common or in juxtaposition with fibres derived from the ophthalmic division of the fifth pair, and d. ca View from below of the connection of the principal nerves with the brain. I'. The right olfactory tract. II. The left optic nerve ; II'. The; right optic tract ; the left tract is seen passing hack into* and e, the internal and ex- ternal corpora geniculata. III. The left ocu- lomotor nerve. IV. The trochlear. V. V. The large roots of the trifacial nerves. ++. The lesser roots, the + of the right side is placed on the Gasserian ganglion. 1, the ophthal- mic ; 2, the superior maxillary ; and 3, the inferior maxillary nerves. VI. The left ab- ducent nerve. VII. a, b. The facial and audi- tory nerves, a, VIII. 6. The glosso-pharyngeal, pneumogastric, and spinal accessory nerves. IX. The right hypoglossal nerve. C I. Tin- left suboccipital or first cervical nerve. 1 Rosenthal : De Numero atque Mensura Microscop Fibrillarum. Breslau, 1845. THIRD NERVE ; MOTOR OCULI COMMUNIS. 653 from the cavernous plexus of the sympathetic. We make use of the expression running in company with, or in juxtaposition with, in Fig. 382. VII wJf' r IX \ X XIJ Kuots of the cranial nerves. I. First pair ; olfactory. II. Second pair ; optic. III. Third pair ; motor oculi communis. IV. Fourth pair ; patheticus. V. Fifth pair ; nerve of mastication and trifacial. VI. Sixth pair ; motor oculi externus. VII. Facial, VIII. Auditory — Seventh pair. IX Glosso-pharyngeal, X. Pneumogastric, XI Spinal accessor}' — Eighth pair. XII. Ninth pair ; sublingual. The numbers 1 to 15 refer to branches which will be described hereafter. (Hirschfeld. i V\<;. 383. Distribution of the motor oculi communis. 1. Trunk of the motor oculi communis. 2. Superior branch. 3. Filaments which this branch sends to the superior rectus and the levator palpebrse superioris. 4. Branch to the internal rectus. 5. Branch to the inferior rectus. 6. Branch to the inferior oblique muscle ; 7. Branch to the lenticular ganglion. 8. Motor oculi externus. 9. Filaments of the motor oculi externus anastomising with the sympathetic. 10. Ciliary nerves. (Hiesciifeld.) 654 THE MEDULLARY NERVES. preference to that of anastomosis, etc., since the various medullary nerves do not actually receive fibres from or anastomose with each oilier in the sense that arteries and veins anastomose. The nerves, in fact, never lose their individuality, but undoubtedly preserve through the whole extent of their course the characteristic functions obtaining at their roots, as in the case of the spinal nerves. This distinction must be continually borne in mind, for, as we shall see presently, while each of these nerves, at its origin, has a definite function — motor, or sensory — they become, sooner or later, apparently mixed nerves, from the fact of being accompanied by the fibres of the adjacent cranio-medullary nerves. It is in this sense that the third nerve is to be understood as being a motor nerve, any evidences of sensibility being due, not to its intrinsic fibres, but to the extrinsic ones of the fifth pair. That the third nerve is exclusively a motor nerve is shown by the fact of irritation of the root causing contractions of the muscles to which it is distributed, but no pain, while division of the nerve is followed by paralysis of the same. 1 Pathological facts, like the falling of the upper eyelid, or blepharoptosis, external strabismus, immobility of the eye, except outwardly ; inability to rotate the eye on its antero-posterior axis in certain directions ; slight protrusion of the eyeball ; dilatation of the pupil, with some interference with the move- Fig. 38J. Distribution of the patheticus. /. Olfactory nerve. II. Optic nerves. III. Motor oculi communis. IV. Patheticus, by the side of the optbthalmic branch of the fifth, and passing]to the superior oblique- muscle. VI. Motor oculi externus. 1. Ganglion of Gasser. 2, 3, 4, 5, 6, 7, 8, 9, 10. Ophthalmic division of the fifth nerve, with its branches. (Hirschfeld.) ments of the iris, following disease of the third pair in man, are among the proofs that may be offered that the third pair of nerves is in man motor, as we would be led to suppose it would be, both from its ana- tomical distribution as well as from the results obtained by vivisection. 1 Mayo: Anatomical and Physiological Commentaries, p. 5. London, 1823. Outlines of Human Physiology, p. 204. London, 1827. Bernard : Systeme nerveux, tome ii. p. 204. Paris, 18.58. Ohauveau t Journal de physiologic, tome v. p. 274. Paris, 1862. Longet : Physiologie. tome iii. p. 554. Paris, 1809. fourth nerve: patheticus, 655 The fourth nerve, or patheticus, consisting of about 1100 fibres, arises in the valve of Vieussens. The fibres, after decussating at their origin, emerge at the base of the brain (Figs. 381, 382, iv), as compara- tive slender filaments at the sides of the pons, and, winding around the crura, pass through the sphenoidal fissure (Fig. 384) into the orbit, and supply the superior oblique muscle. Irritation of the nerve in a living animal, at its origin, causes contraction of the superior oblique muscle, and division of the nerve paralysis of the same. 1 In cases where the nerve is diseased in man, paralysis of the superior oblique muscle is observed as well as immobility of the eveball, so far as rotation is con- View of tlic posterior surface of the medulla, the roof of the fourth ventricle being removed to show the rhomboid sinus clearly. The left half of the figure represents : C». Funiculus cuneatus, and g, funi- culus gracilis 0. Obex. cp. Nucleus of the spinal accessory, p. Nucleus of pneumogastric. p+sp. Ala cinera. i?. Kestiform body. XII'. Nucleus of the hypoglossal, t. Funiculus teres, a. nucleus of tbe acousticus. m. Stria; medullares. 1, 2, and 3 Middle, superior, and inferior cerebellar peduncles respectively./. Fovea anterior. 4. Eminentia teres (genu nervi facialis). 5. Locus cceruleus. The right half of the figure represents the nerve nuclei diagrammatical ly : V. Motor trigeminal nucleus. V. Median and V", inferior sensory and trigeminal nuclei. VI. Nucleus of abducens. VII. Facial nucleus. VIII Posterior median acoustic nucleus. VIII'. Anterior median. VIII". Posterior lateral. VIII'". Anterior lateral acoustic nuclei. IX. Glosso-pharyngi-al nucleus. X, XI, and XII. Nuclei of vagus, spinal accessory, and hypoglossal nerves respectively. The Roman numerals at the side of the figure, from V. to XII., represent the corresponding nerve roots. (Erb.) cerned, and, when the eye is moved toward the shoulder, we have double vision, the eye not rotating to maintain the globe in the same relative position. The pathological facts observed in man, as well as the anatomical distribution, confirm the view based upon vivisections, that the fourth nerve is exclusively motor at its origin, any sensibility 1 Longet, op. cit., tome iii. p. 557. Chauveau, op. cit., tome v. p. 275. 656 THE MEDULLARY NERVES. it may possess further on in its course being due to adjacent filaments from the ophthalmic branches of the fifth pair, or the sympathetic. The sixth nerve, the abducens, or motor oculi externus, being, like the fourth nerve, distributed to a single muscle, the external rectus, and, therefore, exclusively motor in function, will be considered now before the fifth nerve, which would, otherwise, be the next in order. The sixth, consisting of from 2000 to 2500 fibres, arises from a nucleus of large multipolar cells, situated beneath the eminentia teres, in the middle of the floor of the fourth ventricle (Fig. 385, vi). Unlike the fibres of the third and fourth pairs, it has not yet been shown that the fibres of the sixth nerve decussate at their origin in the floor of the fourth ventricle. The sixth nerve appears at the base of the brain in the groove separating the anterior pyramid of the medulla from the pons (Fig. 381), and passes thence through the sphenoidal fissure into the orbit. While in its course the sixth nerve runs in juxtaposition with the filaments derived from the sensitive opththalmic branch of the fifth pair, and from the sympathetic through the carotid plexus, and Meckel's ganglion. It is undoubtedly exclusively a motor nerve, supply- ing only the external rectus muscle. Irritation of the nerve at the root in a living animal causes the latter muscle to contract, but no pain, while division of the nerve is followed by paralysis of the external rectus and internal strabismus, 1 the latter being also observed in man in cases of disease of the sixth nerve. The third, fourth, and sixth pairs of nerves, taken together, constitute the efferent or motor nerves in the reflex actions involved in the movements of the pupil and the eyeball in vision, and which will be considered hereafter, the optic nerve and the opththalmic division of the fifth nerve the afferent or sensory nerves. The fifth nerve, or trigeminus, in arising from the base of the brain by two roots, the posterior, large and sensory, with ganglion attached, and the anterior, small and motor, is usually regarded as especially comparable with a spinal nerve. For the reasons already given, it is cpuite as pos- sible, however, that the fibres of the third, fourth, and even of the sixth nerves, may constitute the true motor fibres corresponding to the sensory fibres of the fifth (ophthalmic and superior maxillary) as that the fibres of its small motor root should be so especially regarded, particularly as the latter, as we shall see presently, are distributed exclusively in company with the fibres of the inferior maxillary branch of the fifth. The two roots, both large and small, of which the fifth nerve actually consists without any reference to their morphological significance, arise by decussating fibres in the cells situated in the outer angle of the floor of the fourth ventricle (Fig. 385, v v' \") ; passing thence separately for- ward and upward through the substance of the pons, they emerge from the upper border of the side of the latter (Fig. 381, v). The posterior large or sensory root, consisting of about 30,000 fibres, passes thence into the Grusserian or semilunar ganglion (Fig. 381, -)-), situated in the de- pression on the internal portion of the anterior face of the petrous portion of the temporal bone, which subdivides into the ophthalmic superior 1 Longet, op. cit., tome iii. p 5G0. Chauveau, op. cit., tome v. p. 275. FIFTH NER'VE ; TRIGEMINAL. 657 maxillary and inferior maxillary nerves (Fig. 386), hence its name, tri- facial. The anterior small or motor root, consisting of about 10,000 fibres, passes underneath the ganglion of Gasser, from which it occa- Fig. 386. General plan of the branches of the fifth pair. 1. Lesser root of the fifth pair. 2. Greater root passing forward Into the Gasserian ganglion 3. Placed on the bone above the ophthalmic nerve, which is Been dividing into the supraorbital, lachrymal, and nasal branches, the latter connected with the ophthalmic ganglion. 4. Placed on the bone close to the foramen rotundum, marks the superior maxillary division. 5. Placed on the bone over the foramen ovale, marks the submaxillary nerve. (After a sketch by Charles Bell.) %. sionally receives a few filaments, and lying behind the inferior max- illary branch of the large root, passes through the foramen ovale in company with the latter, with which it is finally distributed. It will be observed that while the ophthalmic and superior maxillary branches of the fifth are purely sensory, being derived solely from the large root through the Gasserian ganglion, the inferior maxillary branch is both motor and sensory, being derived not only from the ganglion but from the small or motor root as well. It may be appropriately mentioned here, with reference to certain effects following division of the fifth nerve to be mentioned presently, that the ganglion of Gasser receives filaments from the sympathetic. While it is an extremely difficult operation if not impossible, to stimulate the small root of the fifth nerve in a living animal, nevertheless, there can be little doubt that it is a purely motor nerve in function, since if it be stimulated in an animal just dead, in which the cerebral lobes have been removed, such of the muscles of mastication as are supplied by the fibres of the small root (running in 42 658 THE MEIH'LLAKY NERVES. the inferior maxillary division of the fifth) at once contract, 1 and in the case of old horses, for example, with such force as to break off' pieces of the teeth 2 , no such result following stimulation of the large root. In division of the nerve in a living animal with the view of deter- mining its function 3 both roots are necessarily divided, and with the complete loss of sensibility ensuing under such circumstances, there is also observed paralysis of the temporal, masseter, internal and ex- ternal pterygoid, mylohyoid, and anterior belly of the digastric muscles, or the muscles of mastication supplied by the fibres of the small root running in the inferior maxillary division of the fifth nerve and of the tensor muscles of the velum palati. The effect of division of the fifth nerve is very striking in the case of the rabbit, in which, through the consequent paralysis of the muscles of mastication, the line of con- tact between the incisor teeth becomes oblique instead of horizontal, the incisor teeth being worn away unevenly through the jaw being drawn to on« side by the action of the active muscles. The cases of paralysis of the fifth nerve that have been noted in man confirm in the main the results of experiments made upon animals. In all instances where both the large and small roots were involved by the disease, entire loss of sensibility and paralysis of the muscles supplied by the fifth were observed, 4 the only cases in which there was no paralysis of the muscles of mastication being those in which the small root was unaffected, loss of sensibility on the side affected being then only noted. In order to appreciate the results following division of the large root of the fifth nerve in a living animal or disease in man, it will be first necessary to describe briefly the distribution of its principal branches. It has already been mentioned that the large root after expanding into the ganglion of Gasser subdivides into the ophthalmic superior and inferior maxillary nerves. The ophthalmic, the smallest of the three branches of the large root, passes through the sphenoidal fissure into the orbit, subdividing into the lachrymal, frontal, and nasal nerves, and gives off, during its course to the orbit, fibres to the third, fourth, and sixth nerves, to the tentorium and to the sympathetic. The lachrymal nerve supplies the lachrymal gland, conjunctiva, integument of the upper eyelid, and gives off fibres to the orbital branch of the superior maxillary. The frontal branch divides into the supratrochlear and supraorbital nerves, the former nerve supplies the integument of the forehead and gives off a long, delicate filament to the nasal nerve; the latter, or supraorbital nerve, passing through the supraorbital foramen supplies, to a certain extent, the upper eyelid and forehead, the anterior and median portions of the scalp, the mucous membrane of the frontal sinus, and the pericranium covering the frontal and parietal bones. The nasal branch, before enterino- the orbit, gives off a long filament to the ophthalmic ganglion, and then the long ciliary nerves supplying the ciliary muscle, iris, and cornea ; it then divides into the external nasal, or infra-trochlearis, and the internal nasal, or ethmoidal nerves. 1 Longet : Anatomie et physiologic du systeme nerveux, tome ii. p. 190. Paris, 1842. Physiologie, op. cit., p. 502. 2 Chauveau, op. cit., p. 276. 3 Bornard : Systems Nerveux, tome ii. p. 100. Paris, 1858. * Longet: Anat. et Phys. du systeme nerveux, tome ii. p. 191. Paris, 1842. FIFTH NERVE; TRIGEMINAL. 659 The infra-trochlearis nerve supplies the integument of the forehead and nose, the internal surface of the lower eyelid, the lachrymal sac, and caruncula. The internal nasal, or ethmoidal nerve, supplies the mucous membrane of the nose, and partly its integument. The second branch of the fifth nerve, the superior maxillary nerve (Fig. 387), passes out of the cranium by the foramen rotundum, and traversing the infraorbital canal emerges by the infraorbital foramen upon the face, giving off pal- pebral branches to the lower eyelid, nasal branches to the side of the nose, the latter running in common with the nasal branch of the oph- thalmic and labial branches to the integument and mucous membrane of the upper lip. During its course through the spheno-maxillary fossa the superior maxillary nerve gives off several branches ; the orbital, which, passing into the orbit, gives off, in turn, the temporal and malar nerves, which, emerging by foramina in the malar bones, are distributed to the integument of the temple and side of the forehead, and the integu- ment covering the malar bone respectively, the two posterior dental nerves (Fig. 387), the latter supplying the molar and bicuspid teeth, Fig. 387. Dissection of the superior maxillary nerve and Meckel's ganglion. 1. Superior maxillary nerve. 2. Posterior dental nerves. 3. Inner wall of orbit. 4. Orbital branch (cut). 5. Anterior dental nerve. 6 Meckel's ganglion. 7. Vidian nerve. 8. Sixth nerve. 9. Carotid branch of Vidian. 10. Greater super- ficial petrosal nerve. 11. Carotid plexus of sympathetic. 12. Lesser superficial petrosal nerve. 13. Superior cervical ganglion of sympathetic. 14. Facial nerve. 15. Internal jugular vein. 16. Chorda tympani nerve. 17. Glosso-pharyngeal nerve. 19. Jacobson's nerve. (From Hirschfeld and Le- veillk.) the mucous membrane of the alveolar processes and of the antrum. In the infraorbital canal the anterior dental is given off, constituting, together with the posterior dental, the dental arcade, the anterior dental supplying the canine and incisor teeth, and the mucous membrane of the alveolar processes. The third branch of the fifth nerve, or the inferior maxillary (Fig. 386), passes out of the cranial cavity by the foramen ovale, and after uniting with the small or motor root of the fifth, divides into anterior and posterior branches, the former containing the motor fibres supplying the principal muscles of mastication, and the tensor muscles of the velum palati through the otic ganglion, and derived, as 660 THE MEDULLARY NERVES. already mentioned, from the small or motor root, the latter containing principally sensory fibres. Among the most important of these may be mentioned the auriculo-temporal, the lingual, and the inferior dental nerves. The auriculo-temporal nerve supplies the integument of the temporal region, of the ear, the auditory meatus, the temporo-maxillary articulation, and the parotid gland : it gives oft", also, filaments that run in common with those of the seventh nerve, or facial. The lingual nerve, distributed, to the mucous membrane of the point of the tongue, mouth, gums, sublingual gland, submaxillry ganglion, consists, as we shall see, through a considerable extent of its course, of two distinct nerves, the lingual proper and the chorda tympani,and whose relations will be con- sidered presently. The inferior dental nerve, after giving off the mylo- hyoid nerve, passes through the dental canal in the inferior maxillary bone, and supplying the lower teeth, emerges upon the face at the mental foramen, and, as the mental nerve, supplies the integument of the chin, the lower part of the face, and lower lip, and partly the mucous membrane of the mouth. While, as already mentioned, it is impossible to stimulate directly the large root of the fifth nerve in a living animal, yet, since all of its accessible branches, both in man and animals, have been shown to be very sensitive, it might reasonably be inferred that the large root from which all these branches arise is sen- sory in function, especially when it is remembered that its stimulation in an animal just dead is followed by no contractions of the muscles to which the fifth nerve is distributed. Further, as well known, 1 if the large root be divided in a living animal, or be injured or diseased in man, entire loss of sensibility on the side of the head affected at once follows, any muscular paralysis ensuing being limited to the parts supplied by the fibres of the small or motor root. The immediate effect of division of the large root is very striking, the cornea, integument, and mucous membrane of the side affected are at once deprived of sensi- bility, and may be burned, lacerated, or pricked without the animal evincing any pain. Loss of general sensibility in the tongue is also observed, though no loss of taste, 2 since, as we shall see hereafter, the gustatory properties of the anterior part of the tongue are due to the chorda tympanic fibres of the lingual nerve, and not to those fibres of the lingual proper derived from the inferior maxillary branch of the fifth nerve. Deglutition becomes impossible, also, on the side of the head affected. The loss of general sensibility, the interference with deglutition, etc., are also observed in paralysis of the fifth nerve occurring in human beings. In one of these cases, 3 it may be mentioned as a proof of the sensory properties of the large root of the fifth nerve, that an operation was performed without the slightest evidence of pain on the part of the patient. In addition to the loss of sensibility, etc., following division of the large root of the fifth nerve, in certain cases of inflammation of the eye, ear, and nose have also been observed, depending apparently 1 Magendie : Journal de Physiologie, tome iv. pp. 17(5, 302. Paris, 1824. Bernard : Lecons : Sur la physiologie et la pathologie du Syateme nerveux, tome ii. p. 53. Paris, 1858. 2 Schiff : Lecons sur la physiologie de la digestion, tome i. p. 103. Floreuce, 1867. Lusanna : Archives de Phys., tome ii. p. 27. Paris, 1869. 3 Noyes : New York Med. Journal, 1871, vol. xiv. p. 163. SEVENTH NERVE; PORTIO DURA, FACIAL 661 Fig. 388. upon division of those fibres of the sympathetic, already alluded to, as passing into the ganglion of Gasser, since it is only when these fibres ST O DC J ai'e involved through division of the large root through the ganglion, or anterior to it, that such effects are noticed, none such following if the large root be divided between its origin and the ganglion. In the former — that is, where the sympathetic fibres have been divided within from about one to two days after the operation — the eye on the side affected becomes the seat of purulent inflammation ; the cornea, after becoming opaque, ulcerates, the humors of the eye are discharged, and the organ destroyed. Ulcers also appear upon the tongue and lips, and there is a discharge from the mucous membrane of the nose and mouth, and the hearing appears to be affected. The impairment in the nutrition of the eye, mouth, etc., following division of the fifth nerve, and of the fibres of the sympathetic, appears to be due, both to the hyperemia induced through the division of the vasomotor fibres of the sympathetic, and which, we shall see hereafter, regulate the calibre of the bloodvessels, and to the paralysis of the muscles of mastication, and consequent imperfect digestion of food, the increased vascularity and consequent exaggerated nutrition necessitating a greater amount of nutritive matter; in the diminution of the latter, the parts involved become inflamed. That such is the true explanation, to a considerable extent, is shown from the fact that the inflammation of the eye, etc., can be pre- vented, for some weeks at least, if the animal be artificially fed with good nutri- tive food. It need hardly be mentioned that the nervous fibres transmitting gus- tatory, olfactory, and auditory impressions are not in any way derived from the large root of the fifth nerve, as once thought, the large root being only a nerve of gen- es o J o eral sensibility, the small root of motion. The seventh nerve, the nerve of expres- sion, the facial, or the portio dura of the seventh pair, supposing the latter to in- clude, as in the arrangement of Willis, not only the fibres of the facial proper, but those of the auditory, or portio mollis, containing about 4500 fibres, arises in a fan-shaped manner in the gray matter of the floor of the fourth ventricle (Fig. 385, vii). Pa- thological cases, like these observed, par- ticularly by Gubler, 1 lead one to conclude that the fibres of the facial decussate, not only at their apparent origin in the floor of the fourth ventricle, but that many of them, passing upward, decussate in the pons Varolii. At least, it is only on such a supposition that cases of so-called alternate paralysis can be explained, in which (Fig. 388), 1 Gazette hebdomadaire tie medecine et Chirurgie. Paris, 1856, 58, 59. To illustrate alternate paralysis. G. Cerebrum. P. Pons. M. Medulla. F. Facial. L. Lesion, spinal cord. 662 THE MEDULLARY NERVES. while a lesion of the brain, situated anterior to the pons, is associated ■with facial paralysis on the same side as that of the accompanying hemi- plegia, a lesion situated in the pons, or below it, is accompanied with a facial paralysis on the opposite side to that of the hemiplegia. It must be admitted, however, that, as yet, no such decussating fibres as those just supposed to exist as accounting for the pathological phenomena, have been actually demonstrated by the anatomist. The fibres of the facial nerve, from their origin in the fourth ventricle, passing forward and outward through tjie medulla, emerge from the latter at the lower border of the pons Varolii in the outer part of the depression between the olivary and the restiform bodies (Fig. 381, vii), the auditory nerve lying to the outer side of the facial, the two being not infrequently con- nected by a separate fasciculus of the facial, the so-called pars inter- media, or nerve of Wrisberg. After emerging from the medulla, the facial, the auditory, and the intermediary nerves, if the latter exists, pass thence together into the internal auditory meatus. The further distribution and origin of the auditory nerve will be considered hereafter; leaving the latter nerve, then, for the present, at the bottom of the meatus, the facial and nerve of Wrisberg will be found to enter the aquseductus Fallopii (Fig. 389), and passing, by this route, through the Fig. 389. Chorda tympani nerve. 1, 2, 3, 4. Facial nerve passing through the aquseductua Fallopii. 5. Gangli- form enlargement. G. Great petrosal nerve. 7. Spheno-palatine ganglion. 8. Small petrosal nerve. 9. Chorda tympani. 10,11,1-2,13. Various branches of the facial. 14, 14, IS. Glosso-pharyngeal nerve (HlRSCHFELD.) petrous portion of the temporal bone, the two nerves uniting, emerge as a common trunk by the stylo-mastoid foramen. It may be men- tioned here, though the fact has, as yet, but little functional significance, that in the aqugeduct the nerve of Wrisberg exhibits a little reddish ganglion, containing nerve cells. The most important branches of the facial are briefly as follows : The large and small petrosal nerves passing, respectively, to Meckel's and the otic ganglia (Fig. 389), the external petrosal to the sympathetic fibres of the middle menin- geal artery, the tympanic branch distributed to the stapedius muscle, the chorda tympani nerve (Fig. 389) passing through the tympanum SEVENTH NERVE; l'ORTIO DURA, FACIAL. 663 to join the lingual branch of the inferior maxillary, the branch to the pneurnogastric. The six branches just mentioned are given off by the facial during its course through the aqueduct of Fallopius. The remaining branches still to be mentioned are given off after the nerve has emerged from the stylo-mastoid foramen, the branch to the glosso-pharyngeal nerve, the posterior auricular connected with the cervical plexus by the auricularis Fro. 390. . ■&.... 2. Posterior auricular nprve. 5, 6. Branches to the muscles 9. Superior terminal branch. Superficial branches of the facial and the fifth. 1. Trunk of the facial. 3. Branch which it receives from the cervical plexus. 4. Occipital branch. of the ear. 7. Digastric branches. 8. Branch to the stylo-byoid muscle. 10. Temporal branches. 11. Frontal branches. 12. Branches to the orbicularis palpebrarum 13 Nasal, or suborbital branches 14. Buccal branches. 15 Inferior terminal branch 16. Mental branches. 17. Cervical branches. 18. Superficial temporal nerve (branch of the fifth | 10, 20. Frontal nerve (branches of the fifth). 21, 22, 23, 24, 25, 26, 27. Branches of the fifth. 28, 29, 30, 31, 32. Branches of the cervical nerves. (Hirschfeld.) magnus and distributed to the retrahens and attolens aurem, the occipital portion of the occipito-frontalis muscle, and the integument, the digastric branch receiving filaments from the glosso-pharyngeal supplying the posterior belly of the muscle of the same name and the stylo-hyoid, a distinct branch also to the stylo-hyoid muscle, the lingual branch — that is, the branch passing behind the stylo-pharyngeus muscle and receiv- 664 THE MEDULLARY NERVES. ing filaments from the glosso-pharyngeal nerve to be distributed to the mucous membrane, tongue, stylo-glossus, and palato-glossus muscles, and, finally (Fig. 390), the temporo-facial and cervico-facial branches into which the main trunk divides as it passes through the parotid gland. The temporo-facial branch passing upward and forward is distributed to the attrahens aurem, the frontal portion of the occipito-frontalis, the orbicularis palpebrarum, corrugator supercilii, pyramidalis nasi, levator labii superioris, levator labii superioris, alaeque nasi, the dilator and compressor nasi, part of the buccinator, the levator anguli oris, and the zygomatic muscles. During its course the temporo-facial branch receives filaments from the auriculotemporal branch of the inferior maxillary nerve from the temporal branch of the superior maxillary and from the ophthalmic, it becomes, therefore, a mixed nerve in function. The cervico-facial nerve, passing downward, supplies the buccinator, orbicu- laris oris, risorius, levator labii inferioris, depressor labii inferioris, de- pressor anguli oris, and platysma myoides. From the fact that division of the fifth nerve is at once followed by entire loss of sensibility in the parts supplied by that nerve, it is evident that the facial, supplying to a considerable extent identical regions, cannot be a sensory nerve, other- wise sensibility, though weakened, should nevertheless persist in the face, etc., even after division of the fifth nerve. Direct evidence, how- ever, as well as indirect, proves conclusively that the seventh nerve, at its origin at least, is a purely motor nerve. Thus, division of the nerve in a living animal or disease in man is at once followed by paralysis of the facial and other muscles that we have just seen are supplied by the nerve, while stimulation of the nerve at its root in a living animal or in one recently dead, causes contraction of the muscles, but in the case of the living animal no pain. Any sensibility then exhibited by the facial nerve beyond its root must be attributed to the fibres derived from the fifth nerve, glosso-pharyngeal, and pneumogastric, that we have seen run in juxtaposition with it. In order to appreciate the varied and important functions of the facial nerve, it will be best to consider those of its branches seriatim. In the consideration of the sympathetic, to be taken up hereafter, it will be then shown that the nerve fibres sup- plying the levator palati, azygos uvulse, palato-pharyngeus, and palato- glossus are derived from the ganglion of Meckel, and those supplying the tensor palati and tensor tympani from the otic ganglion ; and on the supposition that the great and small petrosal nerves pass respectively through the two ganglia to the muscles just mentioned, supplied by the latter, it might be inferred that paralysis of the facial nerve would be accompanied with difficulty in deglutition and an increased sensitiveness to sound, the tympanic membrane being relaxed through the paralysis of the tensor-tympani muscle, it being well known that the tympanic membrane 1 vibrates more intensely when relaxed than when tensed. Pathological cases of facial paralysis occurring in man fully confirm this view, since in such cases both difficulty in deglutition and increased susceptibility to sounds, etc., are observed. 2 Further, as confirming the 1 Muller's Elements of Physiology, vol. ii. p. 1256. London, 1S43. 2 Bell : The Nervous System, p. 329. Loudon, 1844. Bernard : Lecons sur la physiologie et la path- ologie du systeme nerveux, tome ii. pp. 114, 133. Paris, 1858. Montanet : Dessertation sur l'hemiplegie faciale. These No. 300. Paris, 1831. SEVENTH NERVE: PORTIO DURA, FACIAL. 665 Fig. 391. view that the muscles of deglutition are supplied by the facial, may be mentioned the fact of the facial nerve giving off the branch already alluded to supplying the stylo-glossus and palato-glossus muscles, and occasionally of the branch distributed to the palato-glossus and palato- pharyngeus muscles passing directly to the latter without being connected with the glosso-pharyngeal, as is usually the case. 1 The chorda tympani nerve, one of the most remarkable nerves in the body, both on account of its origin and distribution as well as of its properties, is usually said to arise from the facial in the aqueduct of Fallopius and passing through the canal of Huguier into the tympanum, to cross the latter between the malleus and incus, to enter the Gasserian fissure, emerging thence to join the lingual nerve at the acute angle (Fig. 389). In the horse and calf, however, as shown by Owen 2 , the chorda tympani nerve, while apparently arising from the facial, as in man, in reality can be traced through the fibres of the facial as a continuation of the large petrosal, and as the latter nerve is connected through the ganglion of Meckel with the superior maxillary nerve a pathway evidently exists in these animals by which the impressions made upon the tongue can be trans- mitted 'to the latter nerve, and while the chorda tympani nerve has not been actually demonstrated in man to be a continuation of the large petrosal, as in Fig. 391, both experiments upon animals and pathological cases in man lead one, as we shall see, to suppose that such is substantially the case. On the other hand, apart from the fact of nerve fibres not anastomosing, there is direct o 7 experimental evidence to show that the chorda tympanic fibres do not lose their individuality after mining those of the lingual branch of the inferior maxillary, but preserve their functional activity entirely independent of those of the latter. Thus, if the lingual branch of the inferior max- illary be divided before it is joined by the chorda tympani, its fibres alone atrophy, with ensuing loss of general sensibility of the anterior part of the tongue, whereas, if the chorda tympani nerve be divided before it reaches the lingual its terminal fibres alone atrophy, loss of taste ensuing. Experiment not only shows, however, that the terminal portion of the lingual nerve consists of fibres derived from both the lingual branch of the inferior maxillary, and from the chorda tympani, but that the latter consists of three distinct sets of fibres : 1st, those endowing the anterior two-thirds of the tongue with the sense of taste; 2d, those modifying the bloodvessels of the tongue, vasa dilator nerves ; 3d, those stimu- lating through the submaxillary ganglion the submaxillary and sub- lingual glands. The chorda tympani nerve, consisting, as it undoubtedly does, then, of sensory, motor, and secretory fibres, it is to be expected Diagram to illustrate sup- posed connection of chorda tympani with superior maxil- lary through facial, great petrosal, and ganglion of Meckel. 1 Longet, op. cit., tome iii. p. 581. 2 The Anatomy of Vertebrates, vol. iii. p. 156. London, 1868. 666 THE MEDULLARY NERVES. that it should have specifically different centres of origin, which is in harmony with the view just offered of its motor fihres being derived from the facial, and its sensory fibres from the superior maxillary nerve through the large petrosal and the ganglion of Meckel. That the chorda tympani nerve does contain at least some fibres derived from the superior maxillary appears from the fact of paralysis of the fifth nerve in man being often accompanied with loss of the sense of taste in the anterior portion of the tongue, 1 and that these gustatory fibres are a continuation of those of the large petrosal is still further confirmed by another fact, that paralysis of the seventh neive involves equally as well as that of the fifth nerve, loss of the sense of taste in the tongue. 2 The further consideration of the gustatory and vaso-dilator fibres of the chorda tympani will be deferred for the present. Inas- much, however, as those fibres of the chorda tympani that pass to the submaxillary ganglion and sublingual glands constitute the efferent fibres in the reflex mechanism of insalivation as effected by those glands, the fibres of the lingual branch of the inferior maxillary, together with those of the glosso-pharyngeal and pneumogastric, the afferent fibres, and the medulla the centre ; their function, in this con- nection, may be appropriately here considered, and, to avoid repetition, it may be mentioned that, in the case of the parotid gland, while the afferent fibres are the same, the efferent fibres involved in the reflex mechanism are contained in the auriculo-temporal branch of the fifth, whose motor fibres are derived from the small or motor root, and in the fibres from the otic ganglion derived from the facial, through the small petrosal nerve. If the submaxillary and sublingual glands be cleanly dissected out, as in a living dog, for example, in which the glands are very accessible, they will be seen to be comparatively at rest, secreting little or no saliva, and their venous blood of a dark hue. If now a drop of vinegar be placed upon the tongue of the animal, at once the arterial twigs enlarge, the blood flows more rapidly, the veins pulsate, the color of their blood becomes scarlet, and the pressure increases, followed by an abundant discharge of limpid, very alkaline saliva, the so-called chorda tympani saliva, containing small quantities of albumen, globulin, mucin. That the phenomena just described are due to im- pressions transmitted to the medulla by the afferent sensory fibres of the lingual branch of the inferior maxillary and glosso-pharyngeal nerves, and thence reflected back to the submaxillary and sublingual glands by the efferent secreto-motor fibres of the chorda tympani, is shown by such facts as that, after division of the lingual branch, the secretion of saliva, etc., ceases, but recommences if the central end of the divided nerve be stimulated. On the other hand, if the chorda tympani be divided, the vessels supplying the submaxillary and sub- lingual glands contract ; owing to the unopposed action of the sympa- thetic vaso-constricting fibx-es, the blood flows slowly, is diminished in quantity, and becomes dark, the secretion of saliva diminishes ; the application of vinegar no longer excites the secretion. That the secre- tion does not altogether cease after division of the chorda tympani 1 Schiff : Lecons sur la Physiologie de Digestion, tome premier, p. 100. Florence and Turin. 2 Bernard : Svsteme Nerveux, 1858, tome ii. p. 122. Schiff. op. cit., tome i. p. 183. Lusanua : Archives de Physiologie, 'tome ii. p. 201. Paris, 1869. SEVENTH NERVE - , P0ET10 DURA, FACIAL. 667 appears to be due to the independent reflex action of the submaxillary ganglion. If now, however, the divided chorda tympani be stimulated at its distal end, all the former phenomena recur. It may be mentioned, in this connection, though anticipated somewhat, that if the sympathetic plexus surrounding the facial artery be stimulated, the bloodvessels of the glands become very much contracted, the blood flowing more slowly, and darker in color in the veins, and that the saliva then secreted — the so-called sympathetic saliva — is not only diminished in quantity, but contains, in addition to albumen and mucin, sarcode-like bodies. With division of the sympathetic fibres, the secretion of saliva does not altogether cease, a small quantity of the so-called paralytic saliva being secreted, if the tongue be stimulated with induced electricity. In concluding; our account of the functions of the facial nerve it ill remains for us now briefly to call attention to its external branches. Immediately after the nerve passes out of the stylo-mastoid foramen, as already mentioned, it sends a branch to the glosso-pharyngeal, upon which, as Ave shall see, the motor properties of the latter nerve depend. The posterior auricular branch receiving sensory filaments from the cervical plexus supplies the attolens and retrahens aurem and the posterior portion of the occipito-frontalis muscle and the adjacent integument. The branches supplying the posterior belly of the digas- tric, stylo-hyoid and stylo-glossus muscles are important, as these muscles are involved in mastication and deglutition. The temporo- facial branch, as we have seen, supplies all the muscles of the upper part of the face. If this branch be paralyzed, the eye remains, there- fore, constantly open through paralysis of the orbicularis palpebrarum muscle, and may become inflamed in consequence from constant ex- posure. The frontal portion of the occipito-frontalis, attrahens aurem, and the corrugator supercilii are also paralyzed. A striking symptom of paralysis of the facial nerve if these filaments be affected, is inability to corrugate the brow upon one side, as in frowning. Through paral- ysis of the muscles that dilate the nostrils olfaction and inspiration are also somewhat interfered with. To appreciate the influence exerted by the facial nerve upon inspiration it may be mentioned that in the horse, where the breathing is entirely nasal, death from suffocation very soon takes place if both facial nerves be divided, both nostrils then collapsing and becoming closed with each inspiratory effort. 1 The effect of paralysis of the facial nerve is well seen in cases of facial palsy affecting one side, the distortion of the features being due in such cases to the unopposed action of the muscles upon the unaffected side. When the paralysis is complete the angle of the mouth is drawn to the sound side, the eye on the affected side is widely opened, even during sleep, the lips are para- Ivzed upon one side, the saliva frequently flowing from the corner of the mouth while the food tends to accumulate between the teeth and cheek through paralysis of the buccinator, mastication in consequence being materially interfered with. If both facial nerves be paralyzed, masti- cation becomes very difficult, and the face exhibits a peculiarly ex- pressionless appearance. 1 Bernard : Lerons sur la physiologie et la pathologie du Syateme Nerveux, tome ii. p. 308. Paris, 1858. lillS THE MEDULLARY NERVES, The next nerve in order, the ninth or glossopharyngeal, the con- sideration of Ihi' eighth nerve or auditor being deferred for the present, .•irises from ;i column of cells deeply situated beneath the lower and outer part of the floor of the fourth ventricle (Fig. :> >. Superior laryngeal branch. 7. External laryngeal nerve. 8. Laryngeal plexus. 9,9. Inferior laryngeal branch. 10. Cervical cardiac branch. 11. Thoracic cardiac branch. 12,13. Pulmonary branches. 14. Lingual branch of the fifth. 15. Lower portion of the sub- lingual. 16. Glosso-pharyngeal. 17. Spinal accessory. 18, 19, 20. Spinal nerves. 21. Phrenic nerve. 22, 23. Spinal nerves. 24, 25, 20, 27, 28, 29, 30. Sympathetic ganglia. (HiRsciiFKLn.) forward and outward through the medulla, emerging from the side of the latter by a series of five or six roots containing about 9000 fibres attached to the surface of the i*estiform body (Fig. 382, viii), the highest being close to the auditory nerve, and passes out of the cranial NINTH NERVE; GLOSSO- P H A R YN GE A L. 669 cavity through the jugular foramen in company with the pneumogas- tric and spinal accessory nerves. As the glosso-pharyngeal nerve passes out of the jugular foramen, it expands into the petrous ganglion or ganglion of Andersch from which fine filaments are given off to the pneumogastric and sympathetic nerves. The ganglion gives origin also to the tympanic or Jacobson's nerve; the latter, ascending through the canal of the same name in the petrous portion of the temporal bone, expands upon the promontory of the tympanum into a number of branches which supply the lining membrane of the tympanum, the round and oval windows, and the Eustachian tube. The tympanic nerve gives off also two small branches which pass respectively to the large and small petrosal nerves and filaments to the sympathetic plexus of the internal carotid artery. From the ganglion of Andersch the glosso-pharyngeal nerve descends (Fig. 392) between the jugular vein and the internal carotid artery to the root of the tongue on the inner side of the stylo-pharyngeus muscle terminating in the muscles and mucous membrane of the pharynx, soft palate, tonsils, the root and mucous membrane of the tongue, including the circuin vallate papillae. During its course the glosso-pharyngeal sends off filaments to the pneumogastric and sympathetic, and, as already mentioned, receives filaments from the facial. That the glosso-pharyngeal nerve is a sensory nerve, at least at its origin, is shown by the loss of sensibility in the parts to which it is distributed and loss of the sense of taste in the posterior third of the tongue following its division in a living animal or paralysis in man, and that stimulation at the root in a living animal fails to produce muscular contractions. Owing, however, to its connections with the facial and with the spinal accessory through the pneumogastric, the glosso-pharyngeal undoubtedly receives motor fibres, to which are due the muscular contractions following irritation of the glosso-pharyngeal when stimulated outside of the cranium, and the difficulty experienced in deglutition, if the nerve be divided in an animal, or be paralyzed in man. It has already been mentioned that the contractions of the muscles involved in deglutition following stimu- lation of the glosso-pharyngeal are reflex in character, the impressions made upon the latter nerve, like those made upon the palatine branches of the fifth nerve, being transmitted to the medulla and thence reflected through the petrosal nerves to the ganglion of Meckel, and the otic ganglion to the muscles supplied by the latter. The glosso-pharyngeal nerve is therefore sensory in function, endowing the tongue and pharynx with sensibility, and the posterior third of the tongue with the sense of taste, any motor realities that it may exhibit being attributed to the facial and spinal accessory nerves with which it is connected. The tenth nerve, the pneumogastric, the par vagum or vagus, arises probably by decussating fibres from a group of nerve cells situated beneath the lowest part of the floor of the fourth ventricle, giving rise to a promontory on the surface of the latter (Fig. o$5, X). At the point of the calamus scriptorius, the symmetrically disposed nuclei are in contact at the middle line, but a little higher up are separated by the nuclei, giving origin to the hypoglossal nerves. From this origin the fibres pass forward through the medulla, emerging by twelve or 670 THE MEDULLARY NERVES. more roots containing about 9000 fibres attached to the rest i form body in a line below those of the glossopharyngeal nerve, and leave the cranial cavity, as already mentioned, in company with the glosso- pharnygealj spinal accessory nerves, and the internal jugular vein. In the jugular foramen (Fig. 392) the pneumogastric nerve presents a well- marked enlargement from one-sixth to one-fourth of an inch in length, the ganglion of the root or the jugular ganglion, from which pass filaments to the facial, and the ganglion of the glosso-pharyngeal and superior cervical ganglion of the sympathetic. After leaving the cranial cavity the pneumogastric nerve presents another enlargement from half an inch to an inch in length, the ganglion of the trunk, from which filaments pass to the hypoglossal nerve and occasionally to the arcade formed by the first two cervical nerves. Immediately after leaving the cranial cavity the pneumogastric nerve receives an important branch from the spinal accessory, and during its course gives off also filaments to the middle and superior cervical and upper dorsal ganglia of the sympathetic, and together with fibres from the glosso-pharyngeal, spinal accessory, and sympathetic forms the pharyn- geal plexus. The most important branches given off by the pneu- mogastric, whose functions we shall study seriatim, are as follows : the auricular, pharyngeal, superior and inferior laryngeal, cervical and thoracic, cardiac, anterior and posterior pulmonary, oesophageal, and abdominal. That the pneumogastric is exclusively sensory at its origin, whatever may be the functions of its branches, appears to be satisfactorily shown, even though indirectly, by experiments like those of Longet 1 made upon horses and dogs just dead, in which stimulation of the nerve at its root failed to produce muscular contractions if the nerve was carefully insulated and all its motor connections divided. That irritation should be followed by muscular contractions if the latter precaution be not observed, should not excite surprise when it is re- membered that the pneumogastric receives motor filaments from at least five sources, viz., the facial, spinal accessory, hypoglossal, and first and second cervical nerves, not to speak of the motor fibres derived from the sympathetic. Any muscular contractions ensuing upon irritation of the pneumogastric must therefore be either reflex in character like those of the glosso-pharyngeal already referred to, or be attributed to the stimulation of fibres derived from the motor sources just mentioned. The auricular or Arnold's nerve, though containing fibres derived from the facial and glosso-pharyngeal nerves, is usually described as being a branch of the pneumogastric nerve, being given off from the ganglion of its trunk. Passing through the temporal bone by the canal of the same name, it is distributed to the external auditory meatus and the membrana tympani, endowing those parts with sensi- bility. The pharyngeal branches are given off from the superior portion of the ganglion of the trunk of the pneumogastric nerve, but consist largely of filaments derived from the spinal accessory, reinforced, further, during their course, by filaments from the glosso-pharyngeal and superior cervical ganglion of the sympathetic to form the 1 Physiologie, tome iii. p. 508. Paris, 1869. TENTH NERVE ; P NEU MO GASTRIC . 671 pharyngeal plexus, which supplies the muscles and mucous mem- brane of the pharynx, the motor filaments being derived, as we shall see, from the spinal accessory, and the sensibility being due to the fila- ments of the pneumogastric proper, and also to those of the pharyngeal branches of the fifth, and of the glossopharyngeal. The superior laryngeal nerve arising from the ganglion of the trunk divides into the external and internal branches, the external branch receiving fila- ments from the inferior laryngeal, and the sympathetic supplies the mucous membrane of the ventricle and crico-thyroid muscles of the larynx, and the inferior constrictor of the pharynx. The internal branch, also receiving filaments from the inferior laryngeal, supplies, like the external branch, the crico-thyroid muscle, and is distributed to the mucous membrane of the epiglottis, the base of the tongue, the aryteno-epiglottidean folds, and the mucous membrane of the larynx as far down as the true vocal membranes. From the anatomical dispo- sition it might be inferred that the general sensibility of the upper part of the larynx and the surrounding mucous membrane, as well as the innervation of the crico-thyroid muscle, was due to the superior laryngeal nerve, and experiment shows that such is the case. Thus, stimulation of the superior laryngeal nerves in a living animal gives rise to intense pain, and causes contraction of the crico-thyroid muscle. It is through the exquisite sensibility of the upper part of the mucous membrane of the larynx that foreign bodies are prevented from entering the air passages ; impressions made by such, being transmitted to the medulla, are thence reflected through the inferior laryngeals back to the larynx, bringing about a closure of the glottis. Every one is familiar with the fact that if a crumb of bread, etc., fall upon the aryteno-epiglottidean folds or the edge of the vocal membranes, the sensibility of the parts is such as to excite a convulsive cough, by which the foreign body is dislodged and expelled. The impression conveyed by the superior laryngeal nerve to the medulla being reflected thence through the nerves supplying the expiratory muscles of the chest and abdomen, by which the coughing is accomplished. That this reflex action is due to the sensibility of the laryngeal mucous membrane is shown by the fact that, after division of the superior laryngeal nerve, impres- sions made upon the mucous membrane fail to bring about such action. The superior laryngeals, also, constitute the afferent nerves in the reflex mechanism by which, through contraction of the constrictors of the pharynx, the act of deglutition is completed. It is interesting to observe that the impressions made upon the mucous membrane of the larynx, and the surrounding membrane, and by which, through reflex action, deglutition is brought about, cause, at the same time, closure of the glottis, and arrest of respiration, thereby protecting the air-passages against the entrance of food or other foreign bodies. The two inferior or recurrent laryngeal nerves, so called from reascend- ingto the larynx after descending from the pneumogastric, differ slightly in their course on the two sides, that of the left side passing beneath the aorta, that of the right side winding from before backward around the subclavian artery before they ascend in the groove between the trachea 672 THE MEDULLARY NERVES. and the oesophagus to the larynx. In other respects, the course and dis- tribution of the two nerves are the same. The curious course taken by the inferior laryngeal nerve, whether of the right or left side, is due to the fact that, while in the embryonic condition, the larynx and heart are in close proximity ; through the elongation of the neck, incidental to development, the heart and great bloodvessels recede from the larynx, and, in so doing, drag down with them the inferior laryngeal nerves, which pass, loop-like, around them. It may be mentioned, in this con- nection, as observed by Owen, 1 and by the author, in four individuals dissected by the latter, that in the giraffe the inferior laryngeal nerves pass directly from the pneumogastric to the larynx, like the superior laryngeals. The significance of this is very evident, for, were the course of the inferior laryngeals in the giraffe the same as in man, the nerve, in descending and ascending through so many feet, would, in all probability, be so stretched and tensed as to render it incapable of per- forming its functions. As the inferior laryngeal nerves ascend they give off filaments, which join those of the cardiac branches of the pneumogastric, filaments to the muscular tissue, and mucous membrane of the upper part of the oesophagus, to the mucous membrane and inter-cartilaginous muscular tissue of the trachea, to the inferior con- strictor of the pharynx, and, as already mentioned, a branch which joins the superior laryngeal, terminating, finally, after penetrating the larynx behind the posterior articulation of the cricoid, with the thyroid cartilage, in all of the intrinsic muscles of the larynx, except the crico thyroid, which, it will be remembered, is supplied by the superior laryngeal nerve. Direct stimulation of the inferior laryngeal nerves proves what one would be led to expect from their -distribution, that they are principally motor in function, and from the fact, as we shall see hereafter, of division of the spinal accessory being followed by loss of voice, the respiratory movements of the glottis being, however, un- affected, but that division of the inferior laryngeal nerves not only involves loss of voice, but paralysis of the respiratory movements of the larynx as well — that their motor filaments are derived at least from two different sources, if not more. To anticipate what we shall see more particularly hereafter, the muscles of the larynx involved in the pro- duction of the voice are the arytenoid, the thyro-arytenoid, and the lateral crico-arytenoid, supplied by the inferior laryngeal nerves, and the crico-thyroid, supplied by the superior laryngeal nerves. The pos- terior crico-arytenoid muscles, supplied by the inferior laryngeal nerves opening the glottis, are, however, respiratory in function. Now, while in an animal the voice is lost after division of the internal branch of the spinal accessories, nevertheless, the glottis, though not closing on irritation, being still capable of dilatation, respiration is not interfered with. Such being the case, if the inferior laryngeal, however, be divided, the glottis is at once mechanically closed with each inspiratory effort, and the animal, if young, dies of suffocation. In adults, how- ever, the cartilages of the larynx being rigid, permit of respiration even after the larynx is paralyzed. The only inference from these facts is 1 Op. cit., vol. iii. p. 160. TENTH NERVE; PXEUJI06ASTRIC. 673 that the fibres of the inferior laryngeal that innervate the muscles of phonation are derived from the spinal accessory, but that those in- nervating the respiratory movements of the glottis are derived from some other source — from the facial, in all probability, or, possibly, from the hypoglossal, or the cervical nerves that we have seen give off branches to the pneumogastric nerve. Inasmuch, also, as the crico- thyroid muscle is involved in phonation, and as we have seen that the superior laryngeal nerve supplying it receives fibres from the inferior laryngeal, in all probability it is the fibres of the latter nerve that influence the crico-thyroid muscle in phonation, otherwise it is difficult to see why the paralysis of the voice following division of the inferior laryngeal nerve should be so complete. The cervical cardiac branches, two or three in number, arising from the pneumogastric, pass to the cardiac plexus, which consists principally, as we shall see, of fibres derived from the sympathetic. The thoracic cardiac branches given off below the origin of the inferior laryngeal nerves pass, also, to the cardiac plexus. Contrary to what might have been naturally- expected from what we have hitherto learned as to the effect of division and stimulation of nerves, division of the pneumogastric nerve in a living animal, so far from arresting the action of the heart, actually increases the rapidity of its pulsations, while electrical stimulation of the pneumogastric nerve arrests the heart's action in diastole, 1 and causes a fall in the blood pres- sure. The effect of division of one pneumogastric nerve, however, in a dog or a rabbit, for example, is not by any means as marked as when both nerves have been divided. In the latter case the action of the heart is tremulous, the number of its beats may be doubled, while the respi- ration, from being momentarily accelerated, becomes calm and profound, but diminished in frequency. That the influence exerted by the fibres of the pneumogastric nerve upon the heart is transmitted centrifugally and is dependent upon its motor fibres is shown by the fact that if the pneumogastric nerve be divided in a living animal and stimu- lated at its central end none of the effects such as those just described ensue: stimulation of the distal end alone slowing up the action of the heart and causing a fall in blood-pressure : and that if the stimu- lation be continued too long, so as to exhaust the irritability of the motor fibres, the heart begins to beat again, their inhibitory effect being lost. Further, in animals poisoned with curara, which, as is well known, paralyzes the motor nerves, stimulation of the pneumogastric nerve fails to arrest the action of the heart. That the motor fibres of the pneumogastric nerve influencing the heart's action are derived from the spinal accessory can be shown by experi- ments like those of Waller, 2 in which after division of the spinal accessory of one side in a living animal, allowing sufficient time to insure disorganization of its fibres, stimulation of the pneumogastric nerve of the corresponding side failed to arrest the action of the heart, the usual effect, however, being observed when the pneumogastric nerve ' Weber: Aivliiv d'Anat. Gen. et tie Physiologie, 1846. 2 Gazette Medicale, 3ieme serie, tome xi p. 42U. Paris, 1850. 43 674 THE MEDULLARY NERVES. was stimulated on the one side in which the spinal accessory was still intact. That the cardiac branches of the pneumogastric nerves have the same inhibitory influence upon the heart in man as they have been shown experimentally to have in animals, may be inferred from Fra. 393 \cce7ercent. of , , Med. Obi. Vayalor \ ^ exilra-carrl.iriJui. central Heart, lungs, and great vessels of the rab- bit, with the nerves in relation with them. V, c, d, V, c, s. Right and left venae cavae supe- riores ; the left vena cava is represented as if cut away, in order to show the nerves. G. Ganglion eervicale inferius. s. Sympathetic. v. Vagus, d. Depressor. The dotted lines on each side indicate the position of the phrenic. (Ludwig.) Diagram to aid in understanding the action of the nerves upon the heart. The right half represents the course of the inhibitory, and the left the course of the accelerating nerves of the heart ; the arrows showing the direction in which impressions are conveyed. The ellipse at the upper extremity of the vagus looking like the sec- tion of the nerve is intended to represent the vagal nucleus or centre. In this diagram the nerves are incor- rectly made to cross, instead of passing behind, the aorta. such pathological 1 cases as those in which the number of heart beats have been known to be reduced to three or four per minute from the compression exerted upon the nerve by pressing upon glands, tumors, etc. That the inhibitory action of the pneumogastric upon the heart can also be exerted in a reflex as well as direct manner, is shown by those cases in which there is a sudden stoppage of the 1 Muller's Archiv, 1841, Heft 3. Jenaesche Zeits., 1C5, S. 384. TENTH NERVE; PN EUMO GASTRIC . 675 heart following blows upon the epigastrium, especially after full meals, draughts of cold water, the body being overheated, great emotional excitement, etc., the impression in such cases being transmitted from the general sensory surface to the medulla, and thence reflected through the inhibitory fibres of the pneumogastric to the heart. That the pneumogastric nerve in man contains also special afferent fibres passing from the heart as well as efferent ones to it, by which impressions are transmitted to the medulla, and thence reflected back to the heart by the inhibitory fibres, appears very probable from what has been shown to be experimentally the case in the rabbit and other animals. Thus, if in the rabbit, the so-called depressor 1 nerve (Fig. 393) — that is, the nerve arising partly from the pneumogastric, and partly from the superior laryngeal nerve, be divided, and its distal end stimulated, no effect upon the heart is observed; if, however, the central end of the nerve be stimulated, the action of the heart is arrested, and the blood pressure falls just as if the pneumogastric nerve or the cardio- inhibitorv fibres of the same (corresponding in man to the superior cardiac nerve) be stimulated, the action being evidently a reflex one ; the impression made upon the central end of the depressor nerve is trans- mitted to the medulla, and thence reflected back through the cardiac inhibitory fibres of the pneumogastric to the heart. It might naturally be supposed that the inhibitory influence of the cardiac fibres of the pneumogastric is directly exerted upon the heart. That such, how- ever, is not the case, appears from the fact of the latent period — that is, the time elapsing between the application of the stimulus and the inhibitory effect, being very long, nearly one-fifth of a second, in- stead of one-hundredth of a second, in some cases even two entire beats of the heart intervening before its arrest occurred, indicating that some resistance must be overcome, the inhibitory fibres of the pneumo- gastric acting upon some mechanism inherent in the heart itself. That such is the case, is shown - by the fact that the action of the heart in the eel and the frog can be arrested by direct stimulation, and that in the mollusca, although no pneumogastric nerve is present, the heart can be' stopped in diastole 2 by direct irritation. Again, if nicotin or curara be subcutaneously injected in small doses into a living animal the heart beats slower, but on account of the extra cardiac inhibitory cen- tres (Fig. 394) of the pneumogastric becoming soon paralyzed, the heart beats faster; if now muscarin or jaborandi be then administered, the heart will be arrested in diastole, the latter substances appearing to act directly upon intracardiac inhibitory centres. On the other hand, if atropia be injected, then neither muscarin nor jaborandi will have any inhibitory effect upon the heart, atropia appearing to paralyze both the extra- and intracardiac inhibitory centres. Even admitting the existence of extra- and intra-cardio-inhibitory centres, and cardio- motor centres which the intra-cardio-inhibitory centres act upon, such as are hypothetic-ally represented in Fig. 394, it is impossible in the present state of our knowledge to offer any explanation of the inhibitory effect of the pneumogastric nerve upon the heart; it would be useless, there- 1 Luilwig's Arbeiten, 18G6. 2 Foster : Pfluger's Arcbiv, Band v. S. 191. 676 THE MEDULLARY NERVES. fore, to offer any further reflections upon its functions in this respect, and the same may be said to a great extent of the fall in blood pressure induced through stimulation of the pneumogastric. The most plausible explanation, and that usually offered, is as follows: A stimulus being applied to the central end of the depressor nerve, the impulse generated, as already mentioned, is not only transmitted to the extra-cardiac inhibitory centres (Fig. 394), whence it is reflected through the cardio-inhibitory fibres of the pneumogastric nerve to the heart, slowing or arresting the latter, but also to a vaso-inhibitory centre, sup- posed to exist in the medulla, which exerts a restraining or inhibi- tory influence upon the vasomotor centre of the medulla, the result of which is that the blood pressure sinks through the inhibition of the vasomotor nerve fibres supplying the bloodvessels, and which emanate from this centre. To anticipate a little what will be described more in detail in our consideration of the sympathetic, it may be mentioned, with reference to the explanation just offered of the fall in blood pressure, that, under ordinary circumstances, a nervous influence emanates from the vasomotor centre in the medulla, and which, being transmitted through the spinal cord, spinal and splanchnic nerves, maintains the bloodvessels to which these nerves are distributed in a state of tonic contraction, which keeps up the blood pressure. If, however, the vasomotor centre of the medulla be paralyzed by the action of the vaso- inhibitory centre, induced through the stimulation of the depressor nerve, no such nervous influence being then exerted upon the blood- vessels, the latter dilate, and the blood pressure falls. The result of this is, however, that the medulla receives less blood, so much passing into the abdominal vessels, etc., the consequence of which is, that the extra-cardiac inhibitory centres of the pneumogastric become less active, and the heart resumes its usual activity. That it is to the paralysis of the splanchnic nerve, and consequent dilatation of the great abdominal vessels, that the fall in blood pressure induced by stimulation of the depressor nerve is principally due, is shown by the fact that if the splanchnic nerves be first divided, and then the depressor nerve be stimulated, the blood pressure sinks but little more than when the splanchnics are alone divided. The cardiac fibres of the pneumogas- tric nerve not only consist of inhibitory or restraining fibres, but also of accelerating ones (Fig. 394). The latter are, however, derived, to a considerable extent, also, from fibres, which, descending from the medulla through the spinal cord, emerge opposite the last cervical and first dorsal ganglia of the sympathetic, which they pass before termi- nating in the heart. There are good reasons, also, for supposing that just as there are extra- and intra-cardiac inhibitory centres, so there are extra- and intra-cardiac accelerating centres, which act upon the cardiomotor centre just as the inhibitory centres are supposed to do. It may be as appropriately mentioned in this connection, as elsewhere, that while the existence of intra-cardio-inhibitory and accelerating gan- glia is hypothetical, an inference from experiments, but not yet demon- strated, that, apart from the small ganglia and nerves, shown by dissec- tion to be distributed through the substance of the heart, there are three well-developed ganglia, which appear to be the centres to which the TENTH nerve; pneumog astric. 677 efferent nerves convey the impressions made upon the endocardium by the circulating blood, and which transmitted thence through efferent nerves to the muscular fibres of the heart excite the latter to activity. The presence of these ganglia can be readily demonstrated in the heart of the frog, and their functional significance shown by the well-known experiment of Stannius. 1 In the frog, as is well known, the two venae cavre unite before entering the right auricle to form a dilatation — the sinus venosus. It is in the wall of the latter, near the opening of the inferior vena cava, that the first of these ganglia, the ganglion of Remak, 2 is situated, the second, or the ganglion of Bidder, 3 being found in the left auriculo- ventricular groove, the third ganglion, or that of Ludwig, in the septum between the auricles. If a ligature be applied between the sinus venosum and the right auricle, the heart stops beating, and remains in a state of diastole. The sinus venosus, however, continues beating, and the auricles or the ventricle will make a few movements in response to direct stimulation. If now a second ligature be applied between the auricle and ventricle, the ventricle will begin beating again, the auricles, however, still remaining quiet. Many explanations have been offered of the phenomenon just described, one of the simplest and most plausible being that which regards the ganglion of Ludwig as inhibitory in function and exerting greater influence than that of Hemak or Bidder, when either of these ganglia is exerted alone. If such be the case, it follows that a ligature being applied to the sinus venosus the inhibitory action of the ganglion of Ludwig being only opposed to the exciting action of that of Bidder, the heart stops, and that after a ligature is applied between the auricles and the ventricle then the inhibitory action of the ganglion of Ludwig being cut off", and there being nothing; to counteract the action of the ganglion of Bidder, the ventricle begins to beat again. Whatever the explanation may be of the facts just described, and from what has been said of the cardiac fibres of the pneumogastric nerve, it is evident that the heart possesses an intrinsic nervous mechanism by which, in response to the ^stimulus exerted by the blood, its fibres are excited to act, and that there exists an extrinsic one by which the action of the heart is inhibited or accelerated. The pulmonary branches of the pneumogastric nerve are given off as the anterior and posterior branches. The anterior pulmonary branches after sending a few filaments to the trachea, form a plexus which, surrounding the bronchial tubes, is continued to the termination of the latter in the pulmonary air cells. The posterior pulmonary branches, larger and more numerous than the anterior ones, together with fibres derived from the upper three or four thoracic ganglia of the sympa- thetic, constitute the posterior pulmonary plexus. After giving off fibres to the inferior and posterior portion of the trachea, to the mus- cular tissue and mucous membrane of the middle portion of the oesophagus, to the posterior and superior portion of the pericardium, the posterior pulmonary plexus surrounds the bronchial tubes, and, like the i Zwei Rcihcn : Phyaiologlsche, Versuche, 1851. - Muller's Archiv, 1S44, S. 4G3. 3 Archiv f. Aunt. u. Phys., 18G8, S. 1. 678 THE MEDULLARY NERVES. .•interior one, is continued with the latter to the air cells. The pulmo- nary branches of the pneumogastric nerve supply the lower part of the trachea, the bronchi, and the lungs, with both sensory and motor fibres, as shown by experiments like those of Longet, 1 in which, after division of the pneumogastric nerve in the neck, the mucous membrane of the trachea and bronchus became insensible, while stimulation of its branches caused the muscular fibres of the bronchus to contract. It might natu- rally be supposed, from the pneumogastric nerve giving off the branches we are now considering, to the lungs, that the latter influence in some manner respiration. That such is the case is shown by the fact that after division of the pneumogastrics in a living animal, the division of one nerve having but little effect, that not only is the number of respirations diminished, in some instances being reduced one-half, but that their character is changed, as may be seen from Fig. 395, the Fig. 39-3. a. Tracing of the respiratory movements of the cat. a before, 6 after division of both vagi. (Carpenter.) respiration becoming much deeper, and that although the same quantity of air is breathed the blood becomes decidedly venous. Death usually takes place after division of the pneumogastrics within from one to six days, occasionally, however, recovery takes place through reunion of the divided ends. In the former case the most marked symptoms are failure of the respiration and increasing sluggishness. After death from di- vision of the pneumogastrics in a mammal, the lungs are found to have become leathery and resisting to the touch, destitute of crepitation, of a dark purple color, sinking when cut up and thrown into water, engorged with blood, and almost empty of air. This peculiar kind of solidification or carnification, as it is called, appears to be due to a traumatic emphy- sema set up as a consequence of the excessively labored and profound inspirations due to division of the pneumogastrics; the pulmonary capil- laries being then ruptured through the distention of the air cells, the blood effused coagulates and so gives rise to the characteristic post- mortem conditions. That this explanation of carnification suggested by Bernard 2 is the correct one, is confirmed by the fact of it not occur- ring in birds after division of the pneumogastric nerves, since in these animals the lungs are fixed to the walls of the thoracic cavity, and their general relations are such as not to be exposed to great distention in respiration. The only explanation that can be offered of the diminution in the number of respirations, etc., following division of the pneumo- gastric nerves is that the latter contain fibres, the pulmonary branches, wdiich convey impressions from the lungs, generated through the want 1 Traite de Physiologie, tome iii. p. 535. Paris, 1809. 2 Systeme Nerveux, tome ii. pp. 353, 3G8. Paris, 1858. TENTH NERVE; P NEU MO GASTRIC . 679 of air to the medulla, which thence reflected through the phrenic and intercostal nerves, etc., excite inspiratory movements. The want of air being supplied by the filling of the lungs through the inspiratory effort, and the stimulus to the medulla no longer being generated, the passive movements of expiration then ensue. Such being the case, it follows, the pneumogastrics being divided, that the impression due to the want of air is no longer conveyed to the medulla; the respiratory centre of the latter lacking its usual stimulus acts, therefore, less energetically, and the number of respirations diminishes. In a word, the animal not feeling the need of breathing, then inspires much less frecpuently than ordinary. From what has been said of the function of the inferior laryngeal nerves, it is evident that the pneumogastric nerves being divided in the neck and the laryngeal muscles influencing the vocal cords and the dilatation of the glottis, paralyzed, that the quantity of air entering the lungs will be diminished through the collapse of the glottis. The aeration of the blood being, therefore, very imperfect from this cause as well as from the carnification of the lungs, its venous condition and the general sluggish condition of the system already referred to, is accounted for. The respiratory centre being, of course, affected in this way is less sus- ceptible to impressions derived from other afferent nerve fibres than those passing from the lungs to the medulla in the pneumogastrics, to be mentioned again presently, and the breathing consequently becoming slower and slower, death finally ensues. That the pneumogastric nerves play an important part in respiration may also be inferred from the respiratory movements being accelerated by the application of a mod- erate electrical stimulus to the central ends of the divided nerve, no effect following the stimulation of the peripheral ends; the action is evidently, therefore, entirely a reflex one. It should be mentioned, however, in this connection, that the effect of stimulation of the pneumo- gastric nerves will not only vary according to the strength of the stimu- lus, but with the state of the breathing. Thus, if the breathing be natural, the effect of a slight stimulus is acceleration of the respiration; if the stimulus be strong, temporary arrest of respiration occurs, and if very strong the diaphragm passes into a tetanic condition. In apnoea, when the blood is overcharged with oxygen, the effect of the stimulus is negative ; but if the blood be deficient in oxygen, as in dyspnoea, all the accessory muscles are brought into play and the chest remains in a tetanic condition. From the fact of respiration not ceasing en- tirely after division of the pneumogastric nerves, but only diminishing in rapidity, and of recovery even taking place after such an operation, it is evident that there must be stimuli by which the respiratory centre of the medulla is called into action other than those emanating in the lungs through the w T ant of air and transmitted by the fibres of the pneu- mogastric to the medulla. Every one is familiar with the fact that the dashing of cold water in the face, or the first plunge into a cold bath, and the application of a pungent vapor to the nostrils, cause involuntary respiratory efforts. It is well known, also, that the first inspiratory efforts of the newborn child are usually made in response to the stimu- lation of the cool external air coining in contact with the face, and that 680 THE MEDULLARY NERVES. impressions on the general surface, such as a slap on the face or upon the buttocks, will frequently excite the child to breathe when otherwise it would not do so. It would appear, therefore, that impressions made upon the general sensory surface when transmitted to the medulla will cause, through stimulation of the respiratory centre reflexly, inspiratory movements, as well as stimuli in the lungs due to the want of air and transmitted through the pneumogastrics. Finally, there can be little doubt that blood itself when deficient in oxygen acts as a stimulant to the respiratory centre of the medulla, since even after the pneumo- gastrics are divided if the blood becomes venous in character through artificial respiration being not kept up, the chest of the animal being opened or the blood be cut off from the medulla by opening an artery even though fresh air be supplied to the lungs, in either case violent respiratory movements are made, evidently in response to the stimulus exerted by the non-oxygenated blood upon the respiratory centre of the medulla. 1 The oesophageal branches of the pneumogastric given off both above and below the pulmonary ones unite to form the oesophageal plexus, which supplies the muscular tissue and the mucous membrane of the lower third of the oesophagus. These branches contain both sensory and motor fibres, the latter being probably more numerous, since while the mucous membrane is sensitive to heat and cold, strong irritants, etc., it cannot be said to be acutely sensitive. That the motor fibres supplying the oesophagus are derived from the pneumogastric nerve can be shown by experiments like those of Bouchardat and Sandras, 2 Chauveau, 3 Longet, 4 Bernard, 5 in which, after division of the pneumogastric nerve in a living animal, the oesophagus was paralyzed and distended by the food vainly endeavored to be swallowed. It is still a question, however, from wdiat nerve the motor fibres of the lower third of the oesophagus are derived, since, according to Chauveau, 6 stimulation of the bulbar roots of the spinal accessory, the most probable source, do not excite contractions of the oesophagus. The abdominal branches of the pneumogastric nerve differ somewhat in their course, according as they are distributed to the two sides. That of the left side, situated anteriorly to the cardiac opening of the stomach, immediately after passing with the oesophagus into the abdominal cavity, gives off numerous branches, some of which are dis- tributed to the muscular walls and mucous membrane of the stomach, while others pass, in company with the sympathetic, along the course of the portal vein to the liver. That of the right side, situated pos- teriorly, passes through the oesophageal opening of the diaphragm, and, after sending a few filaments to the muscular coat and the mucous mem- brane of the stomach, is distributed to the liver, spleen, kidneys, supra- renal capsules, and the whole of the small intestine, giving off, also, filaments to the left pneumogastric. If the pneumogastric nerves be divided during full digestion in a living animal in which a gastric fistula has been established, so that the interior of the stomach can be 1 Flint : Physiology. Nervous System, p. 237, 1872. - Comptes Rendus, tome xxiv. p. 59. Paris, 1847. 3 Journal de la physiologie, tome v. p. 312. Paris, 1862. 4 Traits de Physiologic, tome iii. p. 547. Paris, 18UI). 5 Systeme Nerveux, tome ii. p. 422. Paris, 1858. 6 Op. cit., p. 205. TENTH NERVE; P NE U MOG ASTRIC. 681 examined, the muscular contractions will be observed ' to cease in- stantly, the mucous membrane to become pale and flaccid, the secretion of the gastric juice to be arrested, and the organ to have become insen- sible. There can be no doubt, 2 also, that stimulation of the pneumo- gastric nerves causes the stomach to contract, and that digestion may, to a certain extent at least, be reestablished by stimulation of the peripheral extremities of the divided nerves. 3 Inasmuch, however, as several seconds elapse between the application of the stimulus and the contraction of the stimulus, it is hardly probable, as suggested by Longet, that the muscular contractions of the stomach induced by the stimulation of the pneumogastrics are due to its sympathetic fibres, rather than to the stimulation of the nerve fibres of the pneumogastric proper, the tardiness in action just mentioned being characteristic, as we shall see, of the sympathetic. If such be the case, it would appear that the impressions due to the presence of food in the stomach are transmitted by the abdominal branches of the pneumo- gastric to the medulla, the efferent impulses being reflected thence to its muscular walls by sympathetic fibres. It must be mentioned, however, that even when both pneumogastric nerves are divided, if the animal survive the operation, in a day or two digestion may be partly reestab- lished 4 if the food be finely divided and carefully introduced into the stomach. It is quite possible that the impression due to the presence of food in the stomach and intestines, after reaching the plexus of Meissner, situated in the submucous tissue, and the plexus of Auerbach, lying among the fasciculi of the longitudinal muscular coat, is at once reflected back to their muscular coats without being transmitted to the medulla. Whether the reflex nervous mechanism involved in gastric digestion be such as just mentioned or not, there can be no doubt that digestion in man is very much influenced by the nervous system. Every one is familiar with the fact that digestion may be at once stopped by nervous excitement, such as a piece of bad news, etc.; that there exists an intimate sympathy between the brain and the stomach at all times, and it is difficult to understand by what avenues, other than the abdominal branches of the pneumogastric nerve, impressions are carried to and from these organs. That the abdominal branches of the pneumogastric influence also absorption from the stomach and intestinal digestion may be inferred from the fact that, after division of the pneumogastric nerves, the absorption of poisons is retarded, if not prevented, and that the most powerful cathartics fail to produce their characteristic purgative effects, 5 just as. under similar circumstances, digitalis fails to diminish the action of the heart. 6 Division of the pneumogastric nerve through its abdominal branches produces, also, congestion of the liver, renders the bile watery, and arrests its glvcogenic function, the latter being exaggerated by stimulation of the central ends of the divided nerves. The action is a reflex one, as stimulation of the peripheral l Bernard, op. cit., tome ii. p. 422. - Longet, op. cit., tome iii. p. 546. 3 Tiedemann et Gmelin : Recherches snr la digestion, p. 373. Paris, 1827. * Scliiff : Lecons sur la physiologie de la digestion, tome ii. 389. Florence, 1867. Longet, op. cit., tome iii. p. 549. 5 Brodie : Phil. Trans., vol. xiv. ;i. 101. London, 1 *1 1. Reid : Phvs. Anat. and Path. Researches, London, 1S48. Wood: American Journal of the Med. Sciences, vol. l.\. p. 75. Phila., 1870. Traube : Gesammelte Beitrage zur Bath. u. Physiologie, Bd. i. S. I'M. Berlin. 682 THE MEDULLARY NERVES. ends has no effect in this respect, and the efferent impulses are trans- mitted from the centre, in the medulla, hy the sympathetic, probably, and not by the pneumogastric nerve, since division of the latter between the lungs and liver does not affect the production of sugar by the latter. 1 Resuming what has been said of the functions of the different branches of the pneumogastric nerve, it appears that the auricular branches endow the upper portion of the external auditory meatus and the membrana tympani with sensibility ; that the pharyngeal branches supply the muscles of the pharynx with motor filaments derived from the spinal accessory, contributing slightly, also, to the sensibility of the pharynx. To the superior laryngeal branches are due the exquisite sensibility of the upper portion of the larynx, the closing of the glottis against foreign substances, and the production, partly, of the movements of deglutition, and arrest of the diaphragm, the crico-thyroid muscles being also supplied by these nerves. The inferior laryngeal branches, through fibres derived from the spinal accessories, influence phonation, and, through fibres derived from other sources, the respiratory move- ments of the glottis, while reflexly they cause deglutition and arrest of the diaphragm. The cardiac branches, through fibres derived from the spinal accessories, arrest the action of the heart, and through depressor fibres inhibit the vaso-motor centre of the medulla, and so lower the blood pressure. The pulmonary branches are to a certain extent the avenues by which impressions, due to the want of air, are transmitted to the respiratory centre of the medulla, and thence through reflex action excite inspiratory movements, by which the want of air is supplied. The oesophageal branches supply the lower third of the oesophagus with both motor and sensory fibres, the middle portion being supplied by the posterior pulmonary, and the upper portion by the inferior laryngeal nerves. The abdominal branches influence the production of bile and sugar by the liver, and gastric and intestinal digestion, proba- bly, through conveying impressions from the stomach and intestine, which transmitted to the medulla and thence reflected through the sympathetic, cause secretion. The spinal accessory or the eleventh nerve (Fig. 381), consisting of from 2000 to 2500 fibres, arises by two distinct sets of roots — upper and lower. The upper root or the bulbar portion, originating in a nucleus lying close to the central canal, and continuous with the nucleus of the pneumogastric nerve (Fig. 385, XI), emerges from the side of the medulla below the latter nerve. The lower roots or the spinal portion, originating in the anterior cornu of the cord, curve backward, and, passing through the gray substance and lateral columns of the cord, emerge from the latter as six or eight filaments between the anterior and posterior roots of the first and seventh cervical nerves inclusive. The spinal accessory nerve so formed enters the cranial cavity by the foramen magnum, and leaves the latter by the jugular foramen in company with the pneumogastric and glossopharyngeal, and the jugular vein. During its course the spinal accessory receives 1 Bernard, op. cit., tome ii. p. 432 ; Lecons de physiologic experimentale, tome i. p. 324. Berlin, 1855. ELEVENTH NERVE; SPINAL ACCESSORY. 683 from or gives off some filaments to adjacent nerves. Frequently, as it enters the cranial cavity, it receives filaments from the posterior roots of the first two cervical nerves, to which its recurrent sensibility is due; occasionally also it gives off a filament to the superior ganglion or ganglion of the root of the pneumogastric. It also receives filaments from the anterior branches of the second, third, and fourth cervical nerves. After emerging from the jugular foramen the spinal accessory gives oft' also two branches — internal and external — meriting special notice. The internal branch, consisting principally, if not entirely, of the fibres derived from the medulla, passes to the pneumogastric, sub- dividing as it joins the latter into two small branches, the first of which constitutes a part of the pharyngeal branch of the pneumogastric as already observed ; the second, however, becomes so intimately united with the pneumogastric nerve that its final distribution cannot be made out by dissection alone, experiment only indicating its functional sig- nificance, as we shall see presently. The external branch of the spinal accessory, larger than the internal, and derived principally from the fibres of the spinal cord, pass through the posterior portion of the upper third of the sterno-cleido-mastoid muscle, receiving filaments in its course through the muscle from the second and third cervical nerves, to be finally distributed to the trapezius muscle. That the spinal accessory nerve is essentially motor in function, supplying the muscles just mentioned, can be demonstrated experiment- ally by cutting through the occipito-atloid ligaments and stimulating the roots of the nerve within the spinal canal by electricity. If, how- ever, the filaments arising from the medulla only be stimulated con- tractions of the muscles of the larynx and pharynx alone ensue, no movements of the sterno-cleido-mastoid or trapezius being observed. On the other hand, if the filaments arising from the spinal cord only be stimulated then the sterno-cleido-mastoid and trapezius muscles alone contract, the laryngeal and pharyngeal muscles remaining quiescent. Not only does this striking experiment confirm what the distribution of the spinal accessory would lead us to suppose as to its general motor functions, but it also clearly shows that the muscles of the larynx must be supplied by the spinal accessory — that is, that the fibres of the recur- rent laryngeal nerves supplying the muscles of the larynx, except the crico-thyroid, are derived not from the pneumogastric but from the spinal accessory nerve. 1 The spinal accessory nerve appears to be endowed also with a certain amount of direct, apart from the recurrent, sensi- bility already referred to. Whatever sensibility it does possess is, how- c\ er, due undoubtedly to those filaments derived from the pneumogastric and cervical nerves. In speaking of the functions of the inferior laryn- geal branches of the pneumogastric nerve it was mentioned that those nerves consisted of two kinds of fibres, one set influencing the respira- tory action of the glottis, another regulating phonation, and that the latter were in reality derived from the internal branch of the spinal accessory. It only remains, therefore, to describe the manner in which this can be demonstrated, since the fibres of the inferior laryngeal 1 Bernard : Systeme Nerveux, tome ii. p. 296. 684: THE MEDULLARY NERVES. nerves influencing phonation cannot be traced by dissection back to the spinal accessory. Bischoff was the first to demonstrate the influence exerted by the internal branch of the spinal accessory nerve upon the production of the voice by opening in a goat the spinal canal through the occipito-atloid space, and dividing all its roots on both sides, the result being entire extinction of the voice, whatever sound was emitted after the experiment being one which in no wise could be called voice. 1 As this method of procedure was however unsuccessful in the six pre- ceding experiments, five of which were performed upon dogs and one upon the goat, even in the hands of such a skilful anatomist and physi- ologist as Prof. Bischoff, that introduced later and habitually practised by Bernard is a far more satisfactory one. This consists in following by dissection the external or muscular branch of the spinal accessory up to the point where it emerges from the jugular foramen, and where it separates from the internal branch, and then, after seizing the com- bined trunk between the blades of a forceps, by steady and continuous traction to extract the whole nerve with both its medullary and spinal roots entire ; or to remove the medullary portion with the internal branch alone, leaving the spinal portion with the external branch intact, in which case the voice is entirely lost; or to remove the spinal portion with the external branch, leaving the medullary portion with the internal branch intact, in which case the voice is unaffected or in some cases even rendered clearer. 2 It is an interesting fact that in a chimpanzee dissected by Vrolik the internal branch of the spinal accessory was found passing directly to the larynx instead of to the pneumogastric. The usual disposition in this anthropoid appears, however, to be the same as obtains in man, at least such was found 3 to be the case in three individuals dissected by the author. After what has been said of the influence exerted by the pharyngeal branches of the glosso-pharyngeal and of the pharyngeal and inferior laryngeal branches of the pneumo- gastric in deglutition, and of the inhibitory effects upon the heart by the cardiac fibres of the latter nerve, it is only necessary here to men- tion again that the motor fibres involved in the performance of the above functions are derived from the internal branch of the spinal acces- sory, at least partly so in the case of deglutition, and entirely so in that of the inhibition of the heart. As to the function of the external or muscular branch of the spinal accessory, it would appear that its action is to excite contraction of the sterno-cleido-mastoid and trapezius muscles, synchronously with the action exerted by the internal branch upon the laryngeal and pharyngeal muscles, the harmonious action of the muscles so brought about beino- of advantage under certain circum- stances. Thus, in prolonged vocal efforts, as in singing, for example, in which, as which we shall see, the vocal membranes are put on the stretch, the upper portion of the chest is, at the same time, fixed through the action upon the shoulders, to a certain extent at least, of the sterno- cleido-mastoid and trapezius muscles, and in this way the expulsion of 1 " Qui npiitirpiani veil appellari potuit." Bischoff : Nervi Accessorii Willisii Anatomia et Physiologie, p. 94. Darinsradii, 1832. 2 Bernard, op. cit., tome ii. p. 296. 3 Proo. of Acad, of Nat. Sciences, Philadelphia. TWELFTH XERVE ; HYPOGLOSSAL. 685 air through the glottis, and upon which the singing depends, can be well regulated. In the same manner, when one makes a muscular effort, the glottis is closed at the same moment that the chest is fixed, respiration being temporarily arrested. The same synchronism in the action of the external and internal branches of the spinal accessory obtain, therefore, in this instance, as in the former. That the external branches of the spinal accessory exert some influence upon the respira- tory movement is well seen in animals in which the branches on both sides have been divided, such suffering from shortness of breath after any very great muscular effort, and presenting, also, irregularity in the movements of the anterior extremities, the shortness of breath being apparently due to the want of synchronous action of the sterno-cleido- mastoid and trapezius muscles. The twelfth nerve, the hypoglossal or sublingual, consisting of from 4500 to 5000 fibres, arises probably by decussating fibres from a long column of nerve cells, the lower part of which lies in front of the central canal on each side, the upper part forming a prominence upon the floor of the fourth ventricle (Fig. 385, xii). Passing thence through the inner part of the olivary body, the fibres emerge as eleven or twelve filaments from the furrow between the anterior pyramid and the olivary body (Fig. 381), which, passing as two distinct bundles through two distinct openings in the dura mater into the anterior condyloid foramen, unite into a single trunk as they emerge from the cranial cavity. Occasion- ally, the hypoglossal nerve, as it passes through the foramen, receives a filament having a ganglion upon it, arising from the postero-lateral portion of the medulla. This ganglionated filament, or posterior root, so to speak, of the hypoglossal nerve, while exceptionally present in man, is, however, found normally in the dog, cat, rabbit, hog, horse, and calf, and is sensory in function in these animals, the anterior por- tion of the common trunk corresponding to the hypoglossal in man, being motor. After the hypoglossal passes out of the cranial cavity it gives off' (Fig. 39G) filaments to the sympathetic, to the pneumogastric, to the upper two cervical nerves, and to the lingual branch of the fifth. Descending behind the pneumogastric nerve it curves downward and forward to the outer side of the latter, between the internal carotid artery and the jugular vein, and penetrates the genio-hyo-glossal muscle, which it supplies, as also the hyo-glossus, lingualis, genio-hyoid. and stylo-glossus muscles. The hypoglossal gives off, also, an important branch, the descendens noni, but which, according to the classification of the nerves usually adopted, would be more correctly called the descending branch of the twelfth, supplying the sterno-thyroid, sterno- hyoid, and omo-hyoid muscles, the thyro-hyoicl muscle being supplied by the branch of the same name. From the distribution of the hypo- glossal nerve it might naturally be inferred that it is essentially motor in function, any sensibility that it possesses being due to the filaments communicating with the cervical and pneumogastric nerves, and the lingual branch of the fifth. That such is the case is shown by the effect of division of the hypoglossal in a living animal, and of its paralysis in man. Under such circumstances, through paralysis of the tongue, though the tactile and gustatory senses are not affected, masti- 686 THE ME 1)1 LI, A KY NERVES, cation is rendered very difficult, if not impossible, while, through paralysis of the muscles depressing the larynx and hyoid bone, deglu- tition is made difficult; in man the power of articulation is lost as well. Fie 306. Distribution ;of the sublingual nerve. I. Root of the fifth nerve. 2. Ganglion of Gasser. 3,4,5,6,7, 9,10,12. Branches and anastomoses of the fifth nerve. 11. Submaxillary ganglion. 13. Anterior belly of the digastric muscle. 11. Section of the mylo-hyoid muscle. 15. Glosso-pliaryngeal nerve. 16. Ganglion of Andersch. 17, 18. Branches of the glosso-pharyngeal nerve. 19,19. Pneumogastric. 20, 21. Ganglia of the pneumogastric. 22,22. Superior laryngeal branch of the pneumogastric. 23. Spinal accessory nerve. 24. Sublingual nerve. 25. Descemlens noni. 26. Thyro-hyoid branch. 27. Terminal branches. 28. Two branches, one to the genio-hyo-glossu.s, and the other to the genio-hyoid muscle. (Sappky.) This is well seen in cases of glosso-labio-laryngeal paralysis, in which the nuclei of origin in the medulla of the hypoglossal, as w T ell as the facial, spinal accessory, and glosso-pharyngeal nerves are affected by disease, which involves a gradual and progressive paralysis of the tongue, palate, lips, and laryngeal muscles, rendering articulation, and ultimately deglutition, impossible. In cases of hemiplegia the hypoglossal nerve is usually more or less involved. In such cases the patient protrudes the tongue, the point being deviated to the side affected with the paralysis, owing to the unop- posed action of the genio-hyo-glossus muscle of the sound side. That the hypoglossal nerve is a motor nerve — the motor nerve of the tongue, etc. — is further shown by the effect of stimulating the peripheral end of the divided nerve, the tongue, and the muscles to which the nerve is dis- TWELFTH NERVE; HYPOGLOSSAL. 687 tributed at once contracting. The hypoglossal nerve, together with the small or motor root of the fifth and the facial nerves, constitutes the efferent fibres by which the reflex action involved in mastication is accomplished, the afferent fibres being the lingual branch of the fifth; and the glosso-pharyngeal nerves, together with the small root of the fifth, facial, pharyngeal, and inferior laryngeal branches of the pneu- mogastric and cervical plexus, the efferent fibres involved in the perform- ance of deglutiton, the afferent fibres being constituted by the palatine branches of the fifth, the pharyngeal branches of the glosso-pharyngeal, the superior laryngeal and oesophagus branches of the pneumogastric. Having described the distribution and function of the ten pairs of cranio-medullary nerves, and having seen that they arise from gray nuclei in the medulla oblongata, it is evident that the medulla consists, not only as we have seen, of fibres passing from the cord to the ganglion of the base of the brain, but may be regarded, also, as being composed of so many distinct reflex centres, of which the cranio-medullary and spinal nerves constitute the afferent and efferent fibres ; the existence in the medulla of about fourteen such centres, probably more, has been established. First. That for closing the eyelids, the afferent fibres being contained in the optic nerve, and the branches of the fifth distributed to the conjunctiva and to the skin of the lids, the efferent fibres in the facial. Second. The centre for sneezing, the afferent fibres, being in the olfactory and the fifth nerve, the efferent in the spinal nerves in- fluencing expiration. Third. The centre for coughing, the afferent fibres rising in the pneumogastric, the efferent being the same as those last mentioned. Fourth. The respiratory centre, or nceud-vital of Flourens. Fifth. The masticatory centre. Sixth. The centre of insalivation. Seventh. The centre of deglutition. Eighth. The cardio- inhibitory centres, the afferent and efferent fibres of which have already been referred to. Ninth. The centre for sucking, the afferent fibres of which are in the fifth and glosso-pharyngeal nerves, the efferent the facial supplying the lips. Tenth. The centre influencing the act of vomiting, the afferent fibres being in the pneumogastric, the efferent in the nerves of expiration. Eleventh. The centre of speech — that is, with reference to the movements of the lips, tongue, and larynx. Twelfth. The vaso-motor centre. Thirteenth. The centre inhibiting the reflex centres of the spinal cord. The medulla oblongata being the seat of the centres receiving the afferent fibres and giving off the efferent ones involved in the perform- ance of mastication, insalivation, deglutition, respiration, circulation, etc., is, therefore, the great coordinating centre of the reflex actions essential to the maintenance of life. Even if all the parts of the brain above the medulla be removed in a living animal, or be undeveloped, as in anencephalous infants, life may yet be maintained by artificial means, since, if food be introduced into the mouth it will be swallowed, the respiratory and circulatory movements will go on in the usual rhythmical manner, the animal or infant will react to impressions made upon the general sensory surface, withdrawing its limbs, etc., if pulled or pinched, may even utter a cry, as if in pain, and yet such an animal or human being cannot be said to be really a sentient, still less an in- telligent, being, but merely a nutritive reflex mechanism. CHAPTER XL II I. THE PONS VAROLII. CRURA CEREBRI. CORPORA STRIATA. THALAMI OPTICI. CORPORA QUADRIGEMINA. CERE- BELLUM. Whether reflex action of the spinal cord or medulla be accompanied or not in the lower animals with sensation, volition, consciousness, there can be no doubt that the physical seat of what we call feeling, thinking, etc., in ourselves is situated in some part of the brain above the level of the medulla oblongata, since in the absence of such parts one neither feels, thinks, nor wills. Now, just as we have seen that the spinal cord and medulla consist of nervous centres as well as of fibres passing through them to the ganglia at the base of the brain, so may the pons Varolii or mesencephalon be regarded as consisting, not only of ascending sensory and descending motor fibres connect- ino- the cord with the basal ganglia, and of bridging fibres connect- ing the lateral lobes of the cerebellum — hence its name — but of gray matter performing the functions of a distinct nervous centre or centres. That the gray matter or tuber annulare (Fig. 397, 1) is the essential part of Fig. 397. Diagram of human brain in transverse vertical section. 1. Tuber annulare. 2, 2. Crura cerebraj 3,3. Internal capsule. 4,4. Corona radiata. 5, 6. Cerebral ganglia. 7. Corpus callosum. (Dalton.) the pons Varolii is shown by the fact of thebridging fibres of the pons being absent in animals in which the lateral lobes of the cerebellum are unde- veloped as in birds. That the tuber annulare, or vesicular matter of the CRURA CEREBRI. 689 pons Varolii, is that part of the encephalon in which consciousness first awakens in response to impressions transmitted by the spinal and cranial nerves from the external world appears probable from ex- periments, such as those of Longet, 1 Vulpian, 2 etc., in which, after removal of the whole encephalon except the pons, medulla, -and cere- bellum, sensibility to pain still persisted, the cries emitted by an animal so mutilated not being simply reflex in character, such as are heard in an animal possessing only the medulla already referred to, but as really indicating the perception of painful impressions. While it is true that the appreciation of painful and other impressions is not acute, but obscure, nevertheless that such an animal is conscious to a certain extent at least, there can be little doubt, their condition being apparently similar to patients undergoing a severe surgical operation, but imperfectly under the influence of an anaesthetic, and who, while undoubtedly suffering pain at the time, have no recollection of it, the impressions due to the operation not being conveyed to the cerebral hemispheres, and therefore not memorized. It has already been mentioned that the motor tract beginning in the corpus striatum of one side of the body is continued downward through the anterior or inferior portion of the crus cerebri (crusta) to the decus- sating fibres of the medulla, and thence to the antero-lateral columns of the opposite side of the cord; that the sensory tract of the cord is pro- longed upward through the medulla and posterior or superior portion of the crus cerebri (tegmentum) to terminate in the thalamus opticus of the same side. Such being the case, as might be anticipated if both crura (Fig. 397, 2, 2) are completely divided, sensation and voluntary movement are entirely annihilated throughout the body, division of one of the crura involving paralysis of sensation and motion on the opposite side of the body only. The constant tendency to turn toward the side opposite that of the lesion, the "evolution du manege" of Longet, observed when one crus is imperfectly divided appears to be due to the balance of the muscular action being destroyed through the weakening of the sensori motor apparatus of the opposite side. Division of the crus cerebri involves also paralysis of the oculo-motoris of the same side, and partial paralysis of the facial nerve of the opposite side, and is also followed by contraction of the arteries, a rise in blood pressure, and the loss of power to influence voluntarily the action of the sphincter ani, and the constrictor urethrse. In addition to the motor and sensory fibres just referred to, the crura cerebri contain also fibres passing from the gray matter of the medulla and pons to the hemi- spheres, and of fibres passing forward and backward from the locus niger, or the gray matter separating the crusta from the tegmentum, to the cerebellum, and of fibres passing from the corpora quadrigemina to the cerebellum. The functions of these fibres, so far as known, appear to be commissural in character. If the hemispheres of the brain be removed to the level of the corpus callosum, or the bridge of white substance uniting the cerebral hemispheres, and the latter be divided and turned aside, the lateral ventricles will be exposed — that is, the two cavities 1 Physiologic, tome iii. p. 396 2 Systeme Xerveux, p. 542. Paris, 1866. 44 690 CORPORA STRIA T A . having for their roof the corpus callosum, their floor the fornix, their inner walls the septum lucidum with its enclosed fifth ventricle, their outer walls the corpora striata. Each corpus striatum, so called from present- ing a striated appearance on section, projects as a half pyriform prom- inence into the lateral ventricle, constituting, as just said, its outer wall, the largest anterior portion heing known as the head ; the narrowest posterior portion the tail, the latter curving backward to the outer side of the thalamus opticus. Each corpus striatum (Fig. 398) consists of two parts, the intraven- tricular, or nucleus caudatus (6), and the extraventricular, or nucleus Fig. 398. .- J - Horizontal section of the hemispheres at tin- level of the cerebral ganglia. 1. Great longitudinal fissure, between frontal lobes. 2. Great longitudinal fissure, between occipital lobes. 3. Anterior part of corpus callosum. 4. Fissure of Sylvius. 5. Convolutions of the insula. G. Caudate nucleus of corpus striatum. 7. Lenticular nucleus of corpus striatum. 8. Optic thalamus. 9. Internal capsule. ID. Ex- ternal capsule. 11. Claustrum. (Dalton ) lenticularis (7), the two being separated by the internal capsule (9), or the diverging fibres of the crus cerebri, to which the corpus striatum ow T es its name, the external capsule (10) with the claustrum (11) lying to the outer side of the nucleus lenticularis and close to the insula or CORPOKA STRIATA. 691 island of Reil (5). While it is quite possible that some of the divergent fibres of the cms cerebri pass directly through the corpus striatum to the gray matter of the convolutions of the hemispheres, it appears more probable that the corona radiata (Fig. 397, 4), or the cone of fibres radiating out to the convolutions, originate de nova in the corpus stria- tum, and are not merely continuations of the internal capsule. If now the fornix or floor of the lateral ventricle be removed, a narrow trian- gular cavity will be exposed, the third ventricle, communicating, on the one hand, with the lateral ventricles by the foramina of Monro, and on the other with the fourth ventricle by the iter, the latter passing under the corpora quadrigemina, to be mentioned presently. The floor of the third ventricle is formed from before backward by the optic commissure, infundibulum, mammillary eminences, posterior perforated space, and cerebral crura ; its walls, by the thalami optici, situated on the inner side of the crura cerebri, and separated from the corpora, striata by the internal capsule and taenia semicircularis. The more prominent portions of the thalamus opticus anteriorly and posteriorly are known as its tubercles ; beneath the posterior ones are situated the copora geniculata, giving partial origin to the optic tracts. Each thala- mus opticus consists internally of white matter, externally of both white and gray matter, and is connected, like the corpus striatum, with the convolutions of the hemispheres by diverging fibres. It will be observed from this brief sketch of the structure and relation of the corpora striata and thalami optici to the crura cerebri on the one hand, and the cerebral convolutions on the other, that there are three distinct sets of nerve centres, and three distinct sets of nerve fibres through which the im- pressions from the periphery are transmitted to the convolutions of the hemispheres and in the reverse direction, viz., nerve centres, first, the graj matter of the cord, second, the basal ganglia, and third, the gray matter of the convolutions of the hemispheres; nerve fibres, first, the fibres of the nerves connecting the periphery with the gray matter of the cord, second, the fibres of the gray matter and of the columns of the cord connecting the gray matter of the cord with the basal ganglia, and third, the fibres of the corona radiata connecting the basal ganglia with the gray matter of the convolutions of the hemispheres. Such being the case, if what we have called the motor and sensory tracts of the spinal cord in man have the functional significance attributed to them, and if the corpus striatum is the beginning of the motor, and the thalamus opticus the ending of the sensory tract, it is difficult to avoid drawing the conclusion that these ganglia are respectively motor and sensory in function. One of the best established facts in human or animal cerebral pathology is that a destructive lesion of the corpus striatum, whether pro- duced by disease or experimentally, is followed by a paralysis of motion of the opposite side of the body, sensation remaining unimpaired. It is true that in some exceptional cases the paralysis is on the same side of the body, but there is no question in such cases as to the paralysis due to the lesion of the corpus striatum being that of motion. Of this there can be no doubt. Apart from the number of cases that have been recorded. the author has had ample opportunities afforded, both in man and animals, of satisfying himself as to this point. It has also been shown by 692 THALAMl OPTICI. several experimenters 1 that electrical stimulation of the corpus striatum in a living animal, monkeys, dogs, cats, etc., causes a general unilateral contraction of the muscles of the opposite side of the body, the latter being thrown into a condition of pleurosthotonus, in which it is bent to the opposite side, the flexor muscles being contracted apparently more than the extensor ones. It is well known also, that in the cetacea, the whale, dolphin, the elephant, etc., very muscular animals, the corpora striata are not only absolutely but relatively large and well developed. The facts of pathology, experiment, and comparative anatomy, confirm, therefore, the view based upon their anatomy, that the function of the corpora striata is essentially motor. While lesions of the thalamus opticus are not of infrequent occurrence in man, from the fact that the corpus striatum and adjacent parts of the hemispheres are usually involved, conclusions as to the functions of these ganglia, based upon the loss of sensibility, etc., following their destruction, cannot be accepted with the same confidence as in the case of the corpora striata. Never- theless, if the lesion be limited, as is sometimes the case, to the corpus striatum and the thalamus opticus, and the destruction of these two ganglia is followed by loss of motion and of sensibility on the opposite side of the body, and if it be admitted that the function of the corpus striatum is motor, the conclusion that the thalamus opticus is sensory in function becomes then unavoidable. Indeed, it could not be other- wise, since after destruction of the thalamus opticus no other avenue is left by which sensory impressions can be transmitted from the general periphery of the body to the cerebral hemispheres. That the thalamus opticus is essentially sensory in function is further shown by the fact of its destruction in man being followed by loss of general and special sensibility on the opposite side of the body, tactile sensation being impaired, and hearing and vision in some cases affected. 2 The results of experiments performed upon animals are unfortunately so contradictory and unsatisfactory that they throw little or no light upon the functions of the optic thalami in them and still less in man. It appears, however, to have been established by the fact of electrical stimulation failing to produce muscular contractions that the thalamus opticus has not motor significance, confirming what has just been said as to its having sensory functions. While it must be admitted that the evidence adduced in favor of the thalamus opticus being sensory is not as conclusive as that in favor of the corpus striatum being motor in function, nevertheless what positive evidence there is bearing upon this subject favors such a view while the negative evidence is not against it. That the paralysis of motion and sensation following lesions of the corpora striata and thalami optici is not due simply to the motor and sensory impulses being normally transmitted through these ganglia from or to the convolutions of the hemispheres, and that after the destruction of these ganglia no avenues are left fur the transmission of such impulses, is shown by the fact that after removal of the cerebral convolutions in a i Ferrier: The Functions of the Brain, p. 237. New York, 1876. Burdon Sanderson: Centralblatt, p. 51:;, 1,-74. 2 Ley's Recherches sur le Systeme Nerveux, 1865, p. 538. Crichton Browne : West Riding Asylum Reports, vol. v. p. 227, 1876. Ferrier, op. cit., p. 239. THALAMI OPTICI. 693 mammal the power of movement and sensation remains. Thus, for example, in a rabbit the cerebral hemispheres having been removed, while there is nothing observed to indicate that its sensations ever give rise to ideas — that is, that it perceives — nevertheless, it feels even it does not think ; it sees, hears ; if pinched, it cries ; when stirred up, it runs or leaps forward, avoiding with more or less success obstacles placed in its path. The animal has undoubtedly possession of its senses, can exe- cute all its bodily movements, but its intelligence appears to be gone, at least objects which would have ordinarily pleased or terrified it make no impression whatever upon it. It must be borne in mind, however, that in any application to be made of such results with the view of eluci- dating the functions of the basal ganglia in man, that it does not neces- sarily follow that a human being, or even a dog deprived of its cerebral hemispheres, should be in exactly the same mental condition as a rabbit under similar circumstances. On the contrary, there is good reason for supposing that as we pass from the lower to the higher mammals the seat of voluntary motion and sensation is removed to higher and higher levels in the encephalon ; the cerebral convolutions being more im- portant in this respect in man than in a dog, and the basal ganglia more important in the dog than in the rabbit, and so on. The most marked contrast in this respect is presented by fishes, in which the corpora striata are relatively well developed, the cerebral hemispheres but little so — in fact, the latter are only represented, more particularly in the cartilaginous fishes, by the thin film of nervous matter covering in the cavity or ventricle, of which the corpora striata constitute the floor; the so-called optic lobes in fishes represent, probably also not only the optic lobes of the higher vertebrates, but also the thalami optici as well. Undoubtedly a rabbit can do more without its basil ganglia and cerebral convolutions than a dog, and a dog with its basal ganglia but without its hemispheres than a man without the latter. It becomes, therefore, a very difficult matter to say just where sensation begins in man, and still more, where sensation is accompanied or gives rise to ideation and volition. If it be admitted, however, that even after removal of all the encephalon above the pons, feeling even if obscure persists it might be expected that sensation would be more defined, more acute, if higher ganglia such as the thalami optici remain intact. While it cannot be said then that the functions of the basal ganglia have been established beyond doubt, in all probability the thalamus opticus is the ganglion of general sensibility, the corpus striatum of motion, and in the lower mammals of voluntary motion very probably. Even if such, how- ever, be not exactly the case, and it be supposed that an impression made upon the periphery must be transmitted to the cerebral convolu- tions to be thoroughly appreciated, and that a voluntary impulse de- veloped in response to such a sensation must emanate in the same, the connections of the basal ganglia through the corona radiata, with the convolutions of the hemispheres, and with each other, offer an avenue for the performance of reflex actions already referred to, which origi- nally being accompanied with both sensation and volition, in time come to be performed without either. For with the constant repetition of a particular action involving sensation and volition, it is natural to 69-4 CORPOEA QUADR1GEMINA. suppose that the circuit traversed might become shorter and shorter, and that impressions which originally reached the cerebral hemisphere before being reflected back, simply passing through the basal ganglia to and fro, gradually take a shorter course, and reaching the thalamus opticus are at once reflected back through the corpus striatum, short- circuited, so to speak. Such a change would obviously be of advantage to. the economy, since the basal ganglia, taking upon themselves, so to speak, the perform- ance of the work done formerly by the hemispheres, more opportu- nity would be afforded the latter of doing intellectual work. It has already been mentioned that the iter or way by which the third and fouth ventricles communicate with each other, passes underneath the corpora quadrigemina. The latter consist of a white quadrate mass more or less divided upon its upper surface by a crucial depression into four eminences, the so-called nates and testes, optic lobes, or quadri- gemina! bodies, whence their name. The corpora quadrigemina, or the optic lobes, as we shall hereafter for brevity designate them, are attached laterally to the thalami optici between which they are situated, and also to the geniculate bodies, and therefore indirectly with the Fig. 399. Diagram of the optic nerves and tracts, in man. 1. Left eyeball. 2. Right eyeball. 3,3. Corpora geniculata interna. 4, 4. Corpora geniculata externa. 5. Tubercula quadrigemina. 6, 6. Centres of vision in the cerebral hemispheres. (Dalton. ) optic tracts, and inferiority through the superior penduncles of the cere- bellum, between and attached to which is the valve of Vieussens, to the FUNCTION OF CORPORA QU ADRI GE MI NA . f)95 cerebellum, and also through the fibres descending through the pons and embracing the olivary body to the motor columns of the cord. Such being the anatomical disposition of the optic lobes, it might be surmised that with their destruction sight would be abolished and muscular action affected, which is found to be the case in those instances where the optic lobe has been destroyed by disease in man, or by ex- periment in animals. Further, on the supposition that there is a total decussation of the optic tracts, and, according to the view entertained by Charcot (Fig. 3P9), it becomes intelligible, not only why destruc- tion of the optic lobe of one side entails the total loss of sight in the opposite eye, but through the connections of the optic lobe with the thalamus opticus and adjacent fibres of the corona radiata why lesions situated in that part of the brain should be accompanied by impairment of sensibility as well as loss of vision. The optic lobe, as might be expected, constitutes also an important part of the reflex mechanism by which the coordination of the eyeballs and the contraction of the pupil are effected, the optic nerve being the afferent nerve and the oculo- motorius the efferent nerve, the reflex centres being situated either in the optic lobe or immediately beneath it. Apart from the anatomical fact that the optic lobes are connected with the motor tracts of the spinal cord, which would, as already remarked, indicate that these ganglia influence muscular action in some way, it is well known that the optic lobes are not invariably developed in proportion to the eyes, but, on the contrary, may be quite large, though the eyes and optic tracts be but small, little developed, or even wanting altogether, as, for example, in the myxine or hag fish, and the aplerechthys csecus among fishes, in the proteus and cecilia among batrachians, and in moles and shrews among mammals, which show that the optic lobes have other func- tions beside those influencing vision. Xow, while the experience of the author has been like that of other experimenters, that destruction of the optic lobes involves, in addition to loss of sight, disorders of equilibrium and want of muscular coordination, nevertheless, it must be mentioned that a very great difference prevails in this respect according to whether the animal upon which the experiment of removing the optic lobe is performed be a batrachian, bird, or mammal, the optic lobes relatively to the cerebral hemispheres being so much better developed in the lower than in the higher vertebrates. Thus, for example, a frog with its optic lobes intact, but without its cerebral hemispheres, can coordinate its muscles for. the performance of ordinary actions better than a pigeon or a rabbit similarly conditioned, and the latter better than a monkey or man. It may be mentioned also, in this connection, that the want of coordinating power, etc., following destruction of the optic lobes is not due, as might be supposed, to the blindness entailed, since in the frog, for example, if the eyes be destroyed but the optic lobes be left intact, such disoi'ders as those ensuing upon the destruction of these ganglia are not observed. It is well known that if all the encephalic centres above the optic lobes be removed in the frog;, g;entle stroking- of the back excites the animal to croak. The croaking entirely ceasing, however, if the optic lobes be removed, the natural inference is that these ganglia contain the reflex centres through which the croakim* is produced. As 696 CORPORA QUADRIGEMINA. certain plaintive cries emitted by the rabbits cease after removal of the optic lobes, it is possible that a similar reflex centre exists in the optic lobes of mammals as well as in those of frogs. Taking this latter fact into consideration, together with that of the circulation and respiration being modified by electrical stimulation of the optic lobes, the blood pressure being increased, the heart slowed, the respiration deepened exactly in the same manner as when the sen- sory nerves arc powerfully excited, and that contractions of the stomach, intestines, and bladder also follow, it would appear that the optic lobes are also concerned in the reflex manifestation of motion, as well as of influencing muscular coordination and vision. While there can be no doubt that destruction of the optic lobes in man and animal entails loss of vision and impairs the power of muscular coordination, it still remains to be determined whether these effects are due simply to the fact that the fibres by which impressions made upon the retina and periphery reach the visual and coordinating centres pass through the optic lobes, or whether these ganglia are themselves the seat of the visual and coordinating centres. That the latter is not the case in the higher vertebrates, whatever it may be in the lower ones, is shown by the fact that destruction of the angular convolution, or gyrus, in a mammal, the monkey, for example, entails loss of vision as certainly as destruc- tion of the optic lobe itself; on the other hand, it cannot be denied that even after destruction of the angular gyrus in a mammal, or entire removal of the cerebral hemispheres in a bird, the mere sensation of sight persists — that is to say, the impression of light upon the retina still gives rise to the mere sensation of sight, but that the sensation no longer gives rise to such ideas as are usually developed in response to the stimulus of light — that is to say, the animal with its optic lobes intact, but with its cerebral hemispheres removed, may see, but does not think. It is not impossible, however, that in the lower vertebrates the true visual and simply sensory centres may be located together in the same part of the encephalon, the mass, for example, representing in fishes the optic lobe and thalamus opticus, containing also the repre- sentative of the angular gyrus of the higher vertebrates. The relation of the optic lobes to the true coordinating centre located, in all proba- bility, at least in birds and mammals in the cerebellum, can be more conveniently discussed after the functions of the latter organ have been considered. It may be mentioned, however, in this connection that, after removal of both the cerebral hemispheres and cerebellum in the frog, the optic lobes being still intact, the power of muscular coordina- tion remains unaffected, proving that in such animals at least the centre of muscular coordination is not located in either of those portions of the encephalon, whatever may be the case in higher vertebrates. It has already been mentioned incidentally that the optic lobes are connected posteriorly with the cerebellum through the superior pedun- cles of the latter. The fibres of the superior peduncles passing forward and upward to the testes ascend through the crura cerebri to the thala- mus opticus and corona radiata, some of the fibres decussating beneath the optic lobes. Inferiorly the superior peduncles are connected with the vermiform process of the cerebellum and with the corpus dentatum, CEREBELLUM 697 or pouch-like layer of gray matter within the white matter of the lateral hemispheres. The cerebellum, constituting about one-eighth of the bulk of the brain, and situated in the posterior fossae of the cranial cavity, consists of two lateral portions, the hemispheres, the anterior rounded eminences of which are known as the amygdalae, or the tonsils. The hemispheres, though separated behind and below by a wide deep groove, the vallecula or valley, are connected by an intermediate worm-like ridge, the vermiform process, the portion of the latter situated between the tonsils being called the uvula, while just above the tonsils, and sepa- rated from them by a fissure, may be seen the flocculi, or pneumogastric lobules, so called from their vicinity to the nerve of the same name. Each lateral hemisphere and vermiform process essentially consists internally of a prismoid trunk of white substance, from which emanate about a dozen broad thin laminoe; the latter subdividing again into secondary thinner laminae, and the gray substance enfolding them, gives rise to the convolutions and fissures observable on the surface of the organ. The middle peduncles of the cerebellum constituting, as already mentioned, the transverse commissural fibres of the pons Varolii connect the two lateral hemispheres, while the inferior peduncles pass downward into the restiform bodies of the medulla, and are connected with the spinal cord. If the cerebellum be removed in a bird, a pigeon, for example (Fig. 400), though the animal still feels, thinks, wills, it is Fig. 400. Pigeon, after removal of the cerebellum. (Dalton.) unable to stand or fly. If placed upon the back, it is unable to rise. If food be placed within its reach, though it sees it, it cannot pick up the food. Instead of remaining quiet, it is in a continual state of rest- lessness and agitation. In a word, though able to make voluntary move- ments, the animal has lost the power of coordinating its movements for the performance of a definite object, or of maintaining its equilibrium. Its movements highly resemble those of a drunken man. Essentiallv the same results are obtained if the cerebellum be removed in a mammal. Undoubtedly, then, very remarkable disorders, both as regards the main- 698 CEREBELLUM tenance of equilibrium and power of locomotion ensue upon destruc- tion of the cerebellum in mammals and birds, although, as already mentioned, no perceptible change is observable in these respects in the case of frogs, in which the cerebellum has been removed. Differences of opinion still prevail among pathologists as to whether lesions of the cerebellum in man give rise to the same disorders as observed in mammals and birds, in which the cerebellum has been removed, and even though it be admitted that entire absence of the cerebellum, as shown by post-mortem examinations, was not accompanied during life with loss of the power of locomotion, or of the maintenance of equilibrium, nevertheless it may be questioned whether there is a well authenticated case in which locomotion and equilibrium remained unaffected, extensive lesions of the cerebellum existing. Such cases as where there was a congenital absence of the cerebellum, unaccompanied with any disorders of locomotion, etc., being explainable on the suppo- sition that, as in the case of the frog, the function of the cerebellum was performed by other ganglia, probably the optic lobes. On the supposition that the cerebellum is the centre for the maintenance of equilibrium and of muscular coordination, it ought to be best developed Fig. 401. Fio. 402. Brain of kangaroo, macorpos major. (Owen ) Brain of chimpanzee. in those animals which exhibit such powers in a marked degree, and such we find to be the case. Thus in the shark, for example, in which, of all fish, the muscular system is best developed, and the power of coordination so perfect, as shown, for example, in the manner in which it throws itself upon its back at the instant of seizing its prey ; the mouth being situated beneath, and posteriorly, the cerebellum is larger and more complex in its structure than in any other fish. Among birds, also, the cerebellum is particularly well developed in the carnivorous COORDINATING POWER OF CEREBELLUM. 699 raptores, in which muscular actions, such as are involved in the swooping down by them upon prey from immense heights, require very nice adjustment of coordination. Among mammals the cerebellum is large; in the kangaroo (Fig. 401), whose peculiar mode of progression necessi- tates considerable muscular coordination, while, in the elephant, in which great muscular coordination is demanded, owing to the enormous muscular development, and in the case of the posterior extremities to the absence of the round ligament of the hip-joint, the cerebellum is very large, being equal to one of the hemispheres. In the anthropoid apes, also, which not unfrequently assume the semi-erect attitude, the cerebellum is larger than in the remaining monkeys. Indeed, in the chimpanzees (Fig. 402) and orangs dissected by the author 1 the cere- bellum was found so well developed as to extend slightly beyond the posterior lobes of the cerebrum, which is not the case in monkeys generally, in the baboons, macacques, spider-monkeys, etc., the cere- bellum being perfectly covered by the posterior lobes of the cerebrum, as in man. That the cerebellum, at least in mammals, birds, and fishes, is the centre for the maintenance of equilibrium and muscular coordina- tion is not only shown by experiment, pathology, and comparative anatomy, but from the fact of the tactile, visual, labyrinthine, and per- haps visceral impressions upon which the maintenance of equilibrium and muscular coordination depend, being transmitted from the periphery through nerves which directly or indirectly terminate in the cerebellum, as we shall now endeavor to show. It has already been mentioned that a frog from which the cerebral hemispheres have been removed, but which still preserves its optic lobes and cerebellum, retains the power of maintaining its equilibrium and of muscular coordination. If, however, the skin be removed from the hinder legs of such a frog, the animal at once loses this power and falls like a log if the position of its support be changed, the removal of the skin making impossible the transmission of those aiferent tactile impressions which through some reflex centre give rise to those efferent muscular actions requisite for the maintenance of equilibrium. That this reflex centre is situated in man in the cerebellum, and that these afferent tactile impressions are transmitted by the posterior columns of the spinal cord, is rendered very probable from the fact that sclerosis of these columns causes loco- motor ataxia, a disease specially characterized not by a loss of sensi- bility but of power of coordination, and that the posterior columns of the cord through the restiform bodies of the medulla terminate in the cerebellum. While visual are not as important as either tactile or labyrinthine impressions in the maintenance of equilibrium, since the latter almost suffice in the absence of the former, nevertheless they exercise a certain amount of influence. Thus, in cases of locomotor ataxia, for example, equilibrium and coordination are not altogether impossible, even though the tactile impressions be wanting, so long as the labyrinthine and visual impressions persist, and in such cases when the transmission of tactile and labyrinthine impressions are perfect, the absence of visual ones always entails some slight want in the coordi- 1 Proc. Acad, of Nat. Sciences, 1879. 700 CEREBELLUM. nating power. That such visual impressions are transmitted to the cerebellum, is rendered very probable when it is remembered that the optic lobes are connected with the cerebellum both through the superior peduncles and valve of Vieussens. As is well known, remarkable dis- turbances of equilibrium ensue, if the membranous semicircular canals of the internal ear be divided in a bird or mammal, or if they are dis- eased as in Meniere's disease in man, which vary according to the seat of the lesion. Thus, if the horizontal canals be divided in a pigeon, for example, rapid movements of the head in a horizontal plane, from side to side, follow, with oscillation of the eyeballs, and a tendency to spin around on a vertical axis is manifested. If, however, the posterior or inferior vertical canals be divided, the head is moved rapidly backward and forward, and the animal tends to turn somersaults backward head over heels, whereas if the superior vertical canals be divided, the head is moved rapidly forward and back- ward, and the animal tends to make forward somersaults heels over head. It would appear from the researches of Goltz, 1 Mach, 2 Brewer, 3 and Crum Brown 4 among others, that the character of the impressions made upon the vestibular nerves depends upon the degree and relative variations in the pressure exerted by the endolymph upon the ampullae of the membranous canals, to which, as we shall see hereafter, these nerves are distributed. Such being the case, it is obvious that if the semi- circular canals be divided disturbances of equilibrium must ensue, the natural tension of the endolymph being thereby altered, which will vary according to the particular semicircular canal affected. It may be mentioned in this connection, that pigeons in which the semicircular canals have been divided on one side in time regain the power of main- taining their equilibrium, but if the canals be divided on both sides, they never again are able to assume their natural position, the most strange and bizarre attitudes being taken. Whatever may be the nature and mechanism of the labyrinthine impressions, there can be no doubt as to the influence exerted by them in the maintenance of equi- librium, since in their absence the same becomes impossible even though the tactile and visual impressions persist. That the membranous semi- circular canals and the auditory nerve together constitute an afferent system by which impressions are transmitted to the cerebellum, acting as a reflex coordinating centre, appears highly probable when it is re- membered that division of the auditory nerve entails disturbances of equilibrium, that the auditory nerve through the restiform bodies is directly connected with the cerebellum, and that a great similarity exists between the effects of destruction of the cerebellum and division of the semicircular canals. Thus, destruction of the anterior portion of the middle lobe of the cerebellum, like that of the superior vertical canal, involves displacement of equilibrium forward around a horizontal axis, destruction of the posterior part of the median lobe like that of the posterior vertical canal, displacement backward around a horizontal axis, destruction of the lateral lobes of the cerebellum, like that of the i Pfluger's Archiv, 1870. * Sitz. u. der K. Acad, der Wiss., Wion, 1873. 8 Med. Jahrbucher, Heft i., 1874. * Journal of Auat. and Pbys., May, 1874. COORDINATING POWER OF CEREBELLUM. 701 horizontal canals, lateral displacement around a vertical axis. The cerebellum appears, therefore, to be the reflex centre by which the afferent impressions transmitted by the cutaneous, optic, and acoustic nerves are coordinated with the efferent ones for the maintenance of equilibrium and locomotion. That such reflex actions are accompanied now, or originally at least, with consciousness,, and that the cerebellum is that part of the encephalon in which the ideas of space are developed, is rendered very probable when it is remembered that many actions involving muscular coordination, which are performed now unconsciously, were originally accompanied by both sensation and volition, and that the disorders of equilibrium and locomotion following destruction of the cerebellum or of the afferent system leading to it, imply a perversion in the ideas of space relations. In concluding our account of the cerebellum it should be remembered that as its lateral peduncles decussate in the pons Varoli the cerebellum is connected with the motor tracts of the opposite side of the cord, but as the latter decussate in the medulla, the lateral lobes of the cerebellum in this way influence the muscles of the same side of the body. CHAPTER XLIV. THE CEREBRAL HEMISPHERES. The cerebral hemispheres, so called on account of their hemispherical form, are two ovoidal masses flattened at their mesial surface, where they are separated by the great longitudinal fissure. 'They consist of gray or vascular and of white or fibrous nervous tissue. The gray substance, like that of the cerebellum but unlike that of the spinal cord, situated externally and varying between two and three millimetres in thickness, sinks at intervals into the white substance to a depth of from ten to twenty-five millimetres, invaginating itself — that is, folds inward to return upon itself again, and so gives rise to the convoluted and fissured surface so characteristic of the brain of man and of many mammals. It is evident that through this convoluted arrangement the hemispheres contain far more gray matter than if they were smooth, on the same principle that a pocket handkerchief occupies much less room when folded up than when laid out smooth, and that the deeper and more numerous the fissures the greater the amount of gray matter present. The gray matter of the convolution or cortical layer of the hemispheres, consisting of a granular matrix in which are imbedded nerve-cells, con- nected through their prolongations with the nerve fibres of the white sub- stance, is composed of six or more layers distinguished by the character of the nerve cells they contain. Of the latter may be mentioned the so- called pyramidal cells, varying between 10 micro-millimetres and 40 micro-millimetres ( 25 1 00 th to -g^-th of an inch), characterized by their quadrangular base and tail-like extremity, the latter pointing outwardly, the smallest cells being the most superficial, and the cells constituting the so-called nuclear layer situated beneath the pyramidal cells and about 10 micro-millimetres (^gVirth °f an inch) in diameter. The pyramidal cells are more numerous and larger in the anterior portion of the hemi- spheres in the convolutions of the frontal lobe, for example, the cells of the nuclear layer in the occipital and temporal lobes. Certain so-called giant pyramidal cells, probably motor in function, like those of the anterior cornu of the spinal cord, are also found more particularly in the posterior portion of the frontal lobe in the anterior convolution, the processes of which appear to be prolonged downward as the axis-cylin- ders traversing the antero-lateral columns of the spinal cord emerging from the latter as the anterior roots of the spinal nerves, while other cells, having no processes or axis-cylinders, are found more especially in the posterior part of the hemispheres in the occipital lobe. Although the convolutions or gyri and the fissures or sulci do not run in exactly the same manner in different brains, and are not symmetrically disposed even in the two hemispheres of the same brain, nevertheless the general disposition is so constantly the same that the most important of them CEREBRAL FISSURES AND CONVOLUTIONS. '03 can be readily recognized and identified, and on account of their sup- posed functional importance demand at least a brief description. The most striking fissure observable, if the hemisphere be viewed laterally, both on account of its depth and constancy, it existing not only in man but in all animals whose brain is fissured at all, is the fissure of Sylvius. Beo-innino- as a transverse furrow on the under side of the brain, it runs thence outward, backward, and upward, separating the temporal (T, Fig. 403) from the frontal lobe (F), and divides on the outer side of the hemi- sphere into an anterior (S) and posterior (S') branch, the convolutions included between these two branches, and known as the operculum, Fin. 403. Outer surface of the left hemisphere. F. Frontal lobe. !\ Parietal lobe. 0. Occipital lobe. T. Tem- poro-sphenoidal lobe. S. Fissure of Sylvius. S' Horizontal, S" Ascending ramus of the same. ■-. Sulcus centralis or fissure of Rolando. A. Anterior central or ascending frontal convolution. 1!. Posterior central or ascending parietal convolution. Fj Superior, F 2 Middle, and F 3 Inferior frontal convolution. /j Superior, and u Inferior frontal sulcus ; / 3 Sulcus pra?centralis. Pj Superior parietal of postero-parietal lobule, viz : P 2 Gyrus supramarginalis, P' 2 Gyrus angularis. ip. Sulcus intraparietalis. cm. Termina- tion of the calloso-marginal Bssure. 2 first, 0] second, 2 third occipital convolutions, po. Parieto- occipital fissure O. Sulcus occipitalis transversus, Sulcus occipitalis longitudinalis inferior. T] first, T., second, T s third temporo-sphenoidal convolutions. <] first, t% second teniporo-sphenoidal fissures. (After Ecker and Duret.) covering the insula or island of Reil. An important fissure, readily identified on account of its constant course, is the fissure (c) of Rolando, or central fissure, passing from about the middle line of the hemisphere downward, outward, and forward, reaching very nearly the fissure of Sylvius, and serving to divide the frontal from the parietal lobe. The fissure of Rolando is bordered by two important convolutions running 7(M THE CEREBRAL HEMISPHERES. parallel with itself and known as the anterior and posterior central con- volutions, or the ascending frontal and ascending parietal convolutions. Through the very constant presence of the long superior frontal (/j) and inferior frontal fissure (/ 2 ) the latter running into the precentral fissure (/ 3 ). the anterior portion of the frontal lobe naturally divides itself into the superior (Fj), middle (F 2 ), and inferior (F 3 ) frontal convolutions. Through the presence of the first and second temporo-sphenoidal fissures in the same manner, the temporal lobe (T) is divided into the first ( r i\), second (T 2 ), and third (T 3 ) temporo-sphenoidal convolutions. The most impor- tant fissure of the parietal lobe (P) is the intraparietal fissure (ip). Start- ing from the posterior central convolution, it extends backward and down- ward, and dividing the parietal lobe into the superior (P x ) and inferior (P 2 ) parietal lobules, terminates toward the posterior extremity of the hemisphere. Beneath the intraparietal fissure, and as constituent parts of the inferior parietal lobule, are situated two important convolutions, the supra-marginal (P2) convolution arching around the fissure of Sylvius and the angular (P' 2 ) convolution around the first temporo-sphenoidal Fig. 404. -A c B -IDS (I or BE *v- * Inner surface of right hemisphere. The regions bounded by the line ( ) represent the territories over which the branches of the anterior cerebral artery are distributed. The regions bounded by the line ( ) represent the territories over which the brandies of the posterior cerebral artery are distributed. CC. Corpus callosum, longitudinally divided. Gf. Gyrus fornicatus. II. Gyrus hippo- campi, h. Sulcus hippocampi. U. Uncinate gyrus, cm. Sulcus calloso-marginalis. Fj. Median aspect of the first frontal convolution, c. Terminal portion of the sulcus centralis, or fissure of Kolando. A. Anterior. B. Posterior central convolution. Pj". Prsecuneus. Oz. Cuneus. To. Parieto-occipital fissure, o. Sulcus occipitalis transversus. oc Calcarine fissure, oc" Inferior ramus of the same. D. Gyrus descendens. T 4 . Gyrus occipito-temporalis lateralis (lobulus fusiformis). T 6 . Gyrus occipito-temporalis medialis (lobulus liugualis). (After Ecker and Duret.) fissure. The parietal is separated from the occipital (0) lobe by the parieto-occipital (Po) fissure, the latter being, however, just visible from CEREBRAL TISSUES AND CONVOLUTIONS. 705 a lateral view, should be viewed from the mesial surface of the hemi- sphere, as in Fig. 404, where it (Po) will be observed to descend down- ward and inward, separating the cuneus (Oz) from the precuneus (P' 2 ) and terminating in an acute angle in the calcarine fissure (oc), the latter fissure beino- so called on account of its marking the inner concave border of the calcarius or hippocampus minor in the posterior cornu of the lateral ventricle. The occipital lobe (0) is made up of the first (O t ), second (0 2 ), and third (0 3 ) occipital convolutions, the first occi- pital being separated from the second occipital convolution by the trans- verse occipital fissure (0), and the second occipital convolution from the third by the inferior longitudinal occipital fissure (0 2 ). As the cal- carine fissure (oc, Fig. 404) does not run into the hippocampal (p) fissure, it will be observed that the convolution lying above the corpus callosum, and known as the gyrus fornicatus (Gf), passes continuously into the convolution of the hippocampus (H). The latter convolution terminates anteriorly in a crook-like extremity or crotchet, the so-called uncus gyri fornicati or subiculum cornu ammonis (V). Below the calcarine fissure are situated two convolutions, the lobulus fusiformis (T 4 ) and lobulis lingualis (T 5 ), separated by the occipito- temporal fissure, while above the gyrus fornicatus (Gf) is separated from the mesial surface of the first (Fj) frontal convolution by a well-marked fissure, the calloso- marginal (cm), which, like the parieto-occipital fissure, is also just visible from a lateral view of the hemisphere. It must not be supposed from the fact of names being given to certain well-defined convolutions that the latter are entirely distinct, or do not run into each other; on the con- trary, as may be seen from Figs. 403 and 404, it is evident that directly or indirectly they are all continuous with each other. Thus the third frontal (F 3 ) runs into the anterior (A) central, the latter into the posterior (B) central, the three occipital convolutions into the superior parietal lobule (P), the angular gyrus and third temporo-sphenoidal (T 3 ) convo- lutions respectively, and so on. In addition to these principal fissures just mentioned, there are numerous other less important ones which increase considerably the number of convolutions and obscure somewhat those already described. That these fissures are of a secondary char- acter, however, becomes at once evident when the arachnoid and pia mater are removed, they being then seen to be mere superficial indenta- tions and not deep fissures penetrating into the brain. The internal or white substance of the cerebral hemispheres is com- posed largely of fibres which in general radiate from the basal ganglia internally to the gray or cortical substance outwardly. The amount of white substance varies very much in different portions of the hemisphere, thus, in the region of the island of Reil, where the gray substance pene- trates to a considerable depth, but little of it is present, whereas, in the posterior portions of the hemisphere, where the gray matter is relatively less well developed, the white substance is pi-esent in great quantity. The fibres of which the white substance consists may be said to be essentially of three kinds : First, commissural fibres, such as those com- posing the corpus callosum or the broad commissure connecting the two hemispheres at the bottom of the great longitudinal fissure or the anterior commissure situated a little in front of the thalami optici and 45 706 THE CEREBRAL HEMISPHERES. spreading out from the latter into the lower and anterior parts of the temporal lobes. Second, association fibres,or fibres which, lying just beneath the gray matter, connect the different convolutions of the same hemisphere. Third, medullary fibres including both the indirect fibres passing from the medulla through the crura cerebri and termi- nating in the corpora striata and thalami optici, and the fibres of the corona radiata, which beginning in the basal ganglia spread out to terminate in the convolutions and the direct fibres which, begin- ning in the convolutions about the fissure of Rolando and probably motor, pass downward through the middle of the crura to the pyramid tracts of the cord, or beginning in the cord pass upward along the outward border of the crura to terminate in the convolutions of the occipital lobe, and probably sensory in function. One of the most striking facts with reference to the cerebral hemispheres, the bulk of the latter being taken into consideration, is the large amount of blood which they receive, one-fifth of the whole mass of the blood, indeed, according to Haller, 1 going to the encephalon. The manner in which the blood is distributed to the brain is also very remark- able, the branches of the basilar (5) and internal (1) carotid arteries anastomosing so freely, as the circle of Willis (Fig. 405), that the Fig. 40;' Circle of Willis. (Quain and Sharpev.) supply of blood to any one part of the brain is not interrupted, even though the principal branch supplying such a part be obstructed. The 1 Elementa Physiologic. WEIGHT OF BRAIN. 707 importance of this peculiarity in the distribution of the cerebral blood- vessels becomes at once apparent when it is remembered that with the cessation of the blood supply the functional activity of the brain at once ceases, and it may be appropriately mentioned in this connection that while in all probability the energy of the brain depends largely on the size of its arteries and the freedom with which the blood circu- lates through them, the special manifestation of brain power depends upon the particular areas of distribution. It has already been men- tioned that the gray matter of the nervous system is more vascular than the white, and that in all probability it is in the gray or vas- cular substance that the nervous force is generated, the white or fibrous substance transmitting it. The significance, therefore, of the develop- ment of the convolutions just described produced through the invagi- nating of the gray substance into the white, together with their pia mater or vascular tunic, thereby insuring a far greater supply of blood than would be possibe if the brain were smooth, becomes evident. Further, when it is borne in mind that the brain is enclosed in a bony unyielding case, and that the amount of blood sent to the brain from the heart must vary with the force of the latter, and that the cerebral disturbances ensue with any increase or diminution in pressure it might be anticipated that some provision must exist by which a uniform pressure within the cerebral substance is maintained. The latter function appears to be fulfilled by the cerebro-spinal fluid found in the subarachnoid cavity of the brain and cord, since if this fluid be with- drawn from a living animal, cerebral disturbances attributable to changes in pressure ensue. The cerebro-spirial fluid amounts to at least two ounces, and probably more, and appears to be as rapidly absorbed as produced, and as it readily passes from the subarachnoid space through the foramen of Magendie or the triangular orifice in the pia mater situated at the inferior angle of the fourth ventricle into the ventricles of the brain or the central canal of the cord, it evidently serves to equalize the pressure in the cranial cavity, merely allowing bloodvessels to expand and contract within such limits as do not in- duce any marked change in the pressure to which the brain substance is usually subjected. 1 The entire encephalon in the adult male brain weighs on an average about fifty ounces, that of the female a little less, about forty-four ounces. On this supposition, the relative weights of the cerebrum, cerebellum, etc., are as follows: Table LXXIV. 2 Average weight. Male. Female. Cerebrum 43.98 oz. 38.75 oz. Cerebellum ..... 5.25 '' 4.76 " Pens and medulla .... 0.98" 1.01"' Entire encephalon .... 50.21 " 44.52 " Katio of cerebrum to cerebellum . 1 to 8f- 1 to 8 1 The human brain is absolutely heavier than that of any other animal except the elephant and the cetacea, the brain of the elephant usually 1 Magendie: Journal de Physiologie, tome v. p. 27, Paris, 1825'; tome vii. pp. 1-tJO, 1827. '-' Quain'd Anatomy, 8th ed., vol. 2d, p. 581. 708 THE CEREBRAL HEMISPHERES. weighing from eight to ten pounds 1 or even more, that of the young male elephant which recently died al the Philadelphia Zoological Gardens having been found by the author to weigh immediately after removal from the skull ten and a half pounds. The brain of the whale weighs about five pounds; 2 that of a grampus delphinus, as found by the author, seven pounds. Relatively, however, to the size of the body the brain is larger in certain birds and mammals than in man, as, for ex- ample, in the canary bird, field mouse, and ouisitite monkey. With reference, however, to the size of the nerves given oft" from its base, the brain of man is larger than that of any other animal without exception. The brain consists chemically 3 of about 75 per cent, of water, 15 of fats, 7.5 albuminoids, 1.5 of salts, 1 of extractives, including such principles as cerebrin (Cj-H^NC^), lecithin (C 44 H 9ir NT0 9 ), choles- terin, fats, fatty acids, phosphorus, sodium chloride, salts of lime, potash, and magnesia. The relative amounts in which cholesterin, fat, and cerebrin are found in the gray and white substance of the brain are worthy of mention. Thus, while gray substance contains 18.7 per cent, of cholesterin and fat and only 0.5 of cerebrin. the white sub- stance contains 51.9 per cent, of cholesterin and 9.5 of cerebrin. The quantity of phosphorus is very noticeable, amounting to from 1.3 to 1.7 per cent. Its presence as an indispensable condition of a healthy brain cannot be overestimated. Indeed, it has been truly said wt with- out phosphorus no thought." 4 In considering the functions of the medulla, pons, cerebellum, and basal ganglia, we have necessarily anticipated somewhat, by a process of exclusion, the functions of the cerebral hemispheres. It only now remains for us to offer the positive evidence bearing upon the questions and confirming the general con- clusions already reached by the manner just mentioned. Fig. 406. Pigeon, after removal of the hemispheres. (Dalto.v.) If the cerebral hemispheres be removed in a pigeon, for example, the animal at once falls into a condition of stupor, its whole appearance l Ovcloripedia of Aunt. Phys., vol. iii. n. B6*. Lond. 1SH9-4T. - Rudolplii : Gmndrisa der Physiologie, B. ii. S. 12. Berlin. 1823. :: Cnrpenter'a Physiology, 1S81, p. 529. 4 Moleschott : Leiire derNahrungemittel, S. 115. Erlangen, 1850. INJURY TO THE CEREBRAL HEMISPHERES. 709 being very peculiar and most characteristic (Fig. 406). With its head almost buried within the feathers of the neck, with closed eves, the pigeon stands sufficiently firmly, but without moving, apparently utterly indifferent to its surroundings. From time to time it opens its eyes, stretches its neck, or smooths its feathers, but soon again relapses to its former condition of apathy. That the pigeon, however, still feels there can be no doubt. Pinch its neck or one of its toes and a persistent effort is made to withdraw the part from the grasp. Fire off a pistol, the pigeon will open its eyes and turn its head round as if it had heard the report and was looking whence it came. The report of the pistol, however, causes no alarm, for the pigeon makes no effort to escape. While the animal undoubtedly hears and sees, the sensations do not give rise to the usual ideas associated with or developed out of them, the pigeon feels but does not perceive the sensation of sound ; the report of the pistol does not give rise to any idea of danger usually associated with the production of sound. In the same way the presence of food, though seen and smelt by the pigeon, does not excite the idea of hunger, the animal making no effort to feed, starving to death amidst plenty. That this entire loss of memory, volition, and conscious intelligence, fol- lowing loss of the cerebral hemispheres in a pigeon and a mammal is not due simply to the effects of shock, hemorrhage, etc., is shown not only by the entirely different effect following destruction of the cerebellum, but that a pigeon from which the cerebral hemispheres have been removed can be kept alive for months by artificial feeding, and a, mammal usually for a short period, and, although the effects of shock have long since passed away, nevertheless, the animal never regains its intelligence, remaining ever afterward in this characteristic condition of stupor and apathy. Although the effects of destruction or compression of the cerebral hemispheres in man, whether due to disease or injury, are not as well established as in the case of birds and mammals through the imperfect localization of the disease, the basal ganglia, etc., being usually involved as well as the cerebral hemispheres ; nevertheless, a sufficient number of cases have been observed by pathologists which show that loss or compression of the cerebral hemispheres in man in- volves, as in the case of birds and mammals, the loss of memory, volition, conscious intelligence, the negative functions, however, remaining un- impaired. Among such cases may be mentioned that of the sailor related by Sir Astley Cooper, 1 who, having fallen, probably from the yard-arm, was picked up on the deck insensible, practically deprived of all powers of mind, volition, or sensation, in which condition he re- mained for thirteen months, being kept alive all this time by artificial feeding, the grinding of the teeth and the sucking of the lips indicating to his attendants the necessity of giving food and drink. During this period the man lived almost entirely a vegetable existence, the only movements he made, with the exceptions of the lips, etc., being with the fingers, which he moved to-and-fro to the time of the pulse. In this condition the sailor was seen by Dr. Cline, the famous surgeon of the day, who, satisfying himself that a depression in the skull existed, 1 Lectures on the Principle* and Practice of Surgery, p. 138. Philadelphia, 1839. 710 THE CEREBRAL HEMISPHERES. trephined, and with the happy result that within a short time after the operation the patient was able to get out of bed, talk, and tell where he came from, his mind having been restored through the removal of the pressure exerted by the depressed bone upon the cerebral hemi- spheres. In general, it may be said that injury or disease of the cerebral hemi- spheres in man entails disturbance or loss of the intellectual powers, according to the seat and extent of the lesion. Impairment and then loss of memory, weakening and failure of the reasoning powers and of the judgment, invariably follow disease or injury of the cerebral hemi- spheres, while the facts that under such circumstances there is no loss of sensation or motor power, and that the vegetative functions also remain unimpaired, as in the case of idiots and the insane, clearly show that the cerebral hemispheres are indispensable to the manifestation of the intel- ligence. On the other hand, the fact already mentioned of animals deprived of their cerebral hemispheres living indefinitely when supplied with food, and of human beings being born anencephalous and yet were kept alive some time, and who sucked and cried like ordinary infants, proves that the cerebral hemispheres are not concerned in the performance of those functions not involving intellection, which have been assigned to other parts of the encephalon. That the intellectual powers depend upon the development of the encephalon is also shown by the facts of comparative anatomy, the encephalon of the more intelligent animals being much heavier both absolutely and relatively, with reference to the weight of the body, than that of the less intelligent ones. Thus, in fishes the ratio of the encephalon to the body is as 1 to 5668, in the reptiles as 1 to 1321, in birds as 1 to 212, in mammals 1 to 189, x and in man as 1 to 50, supposing the body of the man to weigh 150 pounds and the brain about 48 ounces, or three pounds. Further, the brain of the lower races of mankind is not as heavy as that of the higher and more intellectual ones, weighing on an average only about 46 ounces, and is much less bulky, occupying perhaps a space within the skull of only 63 cubic inches, 2 while that of the higher races may occupy a space of 114 cubic inches. 3 It is also well known that individuals distinguished by great intellectual power possessed large and heavy brains, thus, the brain of Abercrombie weighed 63 ounces, 4 that of Cuvier 64.33 ounces. 4 On the other hand, the brain of idiots has been found in some instances to weigh not more than 20 ounces. It will be observed also from a comparison of the brain of the lower with that of the higher vertebrates, that it is the greater development of the cerebral hemispheres in the latter to which are due the greater bulk and weight of the encephalon. Thus, as we pass from the brain of the fish (Fig. 407) to that of the reptile (Fig. 408), from the brain of the reptile to that of the bird (Fig. 409), from the latter to the brains of mammals (Fig. 410), including that of man, one cannot but be impressed with the fact that the cerebral hemispheres become successively more and 1 Leuret: Anatomie Comparee flu Svsteme Nerveux, pp. lo3, 'I'll, 284, 422. Paris, 1839. - Morton : Crania Americana, p 'Ji:i. Philadelphia, 1839 3 Edinburgh Med. ami Surg. Journal, 1845, vol Ixiii. p. 448. * "Trois livres onze oncea quatrea gros et demi," is the number given in the account of the autopsy of Cuvier io the Archives geuerales de Medeciue, tome xxix. p. 144. Paris, 1832 . COMPARATIVE DEVELOPMENT OF THE BRAIN". 711 more developed, until in the monkeys (Fig. 411) (excepting young and possibly also adult anthropoids) and in man they completely cover the Fig. 407. Fig. 409. Brain of carp. A. Cere- bral hemispheres. B. Op- tic lubes. C. Cerebellum. Brain of lizard. (Owen.) Brain of the pigeon. A. Cere- bral hemispheres. B. Optic lubes. C. Cerebellum. (Ferrier.) cerebellum. Further, it may also be seen from such a comparison that Avliile the brain in fish, reptiles, birds, and the lower orders of animals, such as the marsupiala, rodentia, suenia (Fig. 412), etc., is smooth Fro. 410. Fig. 411. Brain of the rabbit. A. The smooth cerebral hemisphere. B The olfactory bulb. C. The cerebellum. (Ferrier.) Base of brain of baboon. (Owen.) or nearly so, in the higher orders, including the proboscidea, cetacea, the ungulata (Figs. 413, 414), the carnivora and primates (Fig. 415), it is more or less convoluted. Indeed, so much is this the case that in the proboscidea it is particularly convoluted, even more so than in man. In general, it may be said that the development of the intel- lectual powers depends not only upon that of the encephalon, but more particularly upon that of its cerebral hemispheres, and especially, as affirmed long ago by Erasistratus, 1 upon the number and depth of the 1 Galenus De Usu Partium, Lib. 8, Cap. 13. 1V1 T 1 1 E G E H E 15 K A L H E M I S P H K R E S . convolutions of the gray matter of the same. Further, in the savage races of mankind, characterized by a low order of intelligence, the con- Pig. 412. Brain of manatee. Fig. 413. Fig. 414. Brain of the horse. (Owbn.) Brain of pecca i \ COMPARATIVE DEVELOPMENT OF THE BRAIN 713 volutions are not so deep, are less numerous, and are more simply disposed than in the civilized races distinguished by the develop- Fig. 415. Brain of the orans ment of their mental faculties, while in individuals especially re- markable among the latter for intellectual power, as in the case of Fig. 41(5. Fig. 417. Cerebrum -—Cerebrum _ Corp. quadrig. --Cerebellum *» Med. oblonfi Med. oblong. Brain of human embryo, three months. Brain of human embryo, five months. Gauss, 1 for example, one of the most distinguished mathematicians that ever lived, the convolutions of the cerebral hemispheres were found to 1 Quain : Anatomy, 1878, vol. ii. pp. .529, 581. 714 THE CEREBRAL HEMISPHERES. be very numerous and deep, and far from simply arranged. On the other hand, in idiots the convolutions are few, comparatively superficial, and simply disposed. The development of the brain' also confirms the conclusions based upon the facts of comparative anatomy and ethnology, the transitory stages through which the foetal brain passes being per- manently retained in the brains of the lower animals. Thus, at about three weeks of intrauterine life the brain of the human fcetus resembles that of the adult fish, there being but little difference at this early period in the relative development of the cerebral hemispheres, optic lobes, Fig. 418. Lateral view of the right cerebral hemisphere. 1 Fissure of Rolando. 2. Ascending frontal codvo- lution. 3 Superior, 3'j middle, and 7, inferior frontal convolutions. 4. A bridging convolution between the superior and middle frontal convolutions. 5. Ascending parietal convolution. 6, 8 Supramarginal convolution (8 in front points to part of the inferior frontal convolution). 9, 9. Superior temporo- sphenoidal convolution. 10, 11, 12. Convolutions of the island of Keil, or central lobe. 13. Orbital convolutions. 11. Lower extremity of middle temporo-sphenoidal convolution. 15. Occipital lobe. (From Sappey after Foville.) %. cerebellum, etc. As development advances the hemispheres enlarge and grow backward ; at three months (Fig. 416), though still smooth, they slightly overlap the optic lobes, the latter not having yet divided into the corpora quadrigemina. At about the fifth month (Fig. 417) the cerebral hemispheres in the human fcetus overlap the cerebellum, and here and there exhibit a rudimentary fissure, though their surface is still almost entirely smooth, as in those of the rodentia. Finally, at about the seventh month, the optic lobes are subdivided into the corpora quadrigemina, while at full term or at birth the convolutions are all formed. The brain of the human foetus, however, at this period, both as regards the number, depth, and simplicity of arrangement of the cerebral convolutions, resembles rather the brain of the chimpanzee than that of the adult man, while the brain of the uneducated child resembles, in similar respects, that of the savage races of mankind rather than that of the civilized ones ; a physical correspondence in harmony with their intellectual acquirements. While the facts of LOCALIZATION OF FUNCTIONS. 715 experiment, pathology, comparative anatomy, etc., with but few excep- tions, and those usually more apparent than real, undoubtedly agree in establishing the view that associates intellectual power with the develop- ment of the cerebral hemispheres, and more particularly with that of the convolutions, or the gray matter of the same, it must be borne in mind that the quality of the chemical composition of the latter is quite as important a condition as its mere quantity. Further, that the exercise of the mental faculties necessitates the connections between the gray or vascular substance of the convolutions and the fibres of the white substance being maintained in their normal condition, just as the action of a muscle depends on the position and manner of insertion ; and, above all, upon the free supply of blood and active circulation, both that the materials for the nourishment of the hemispheres and the pro- duction by them of thought, may be supplied in sufficient quantity, and that the effete and worn-out materials incidental to mental activity may be carried away to the proper emunctories as rapidly as produced. As we have already seen that the different structures of which the encephalon consists, medulla, pons, cerebellum, basal ganglia, cerebral convolu- tions, etc., have undoubtedly different functions, it is reasonable, there- fore, to suppose that the different convolutions, or the gray matter of the cerebral hemispheres, have also special faculties or functions. Phrenology has, therefore, a basis worthy of consideration. Phrenology, however, as understood by the vulgar, is based upon the untenable assumption that the form of the surface of the brain can be inferred from the external configuration of the skull, that any protuberance, or "bump," of the latter is to be taken as an indication of a similar excessive development of. the former, and the possession of some par- ticular well-developed mental faculty. Apart, however, from the facts that the skull consists of two tables, and that the outer surface of the brain is separated from the inner surface of the skull by the dura mater, arachnoid, pia mater, and cerebro-spinal fluid, the latter vari- able, in quantity, the figure of the brain, except in a general way, does not correspond to the figure of the skull. So much so is this the case that in certain animals, as in the elephant, for example, through the enormous development of the frontal sinuses the anterior portion of the skull is no indication of the form of the brain whatever. Further, the surface of the brain is not elevated into bumps, the convolutions, as we have seen, being formed through the invagination, or dipping down of the gray matter into the white. Even though, then, osseous " bumps" be ever so well developed, there are never any cerebral "bumps" with special functions or faculties corresponding to the osseous ones. Phre- nology, as such, must be relegated, then, to the charlatan and itinerant showman, who amuse their audience by feeling their heads, and illus- trating their views by showing plaster casts of the heads of Napoleon, Schiller, noted murderers, idiots, and the like. Within recent years, however, another kind of phrenology has been developed and estab- lished, more or less satisfactorily based upon entirely different methods of investigation, 1 such as exposing the brain in a living animal, and 1 Fritsch and Ilitzig: Archiv f. Anat.. Physiologic, etc., S. 300. Leipzig, 1870. Ferrier : Functions of the Brain, IS76. Carville and Duret : Archives de Physiologie 2eime serie, tume ii. p 352. Paris, 1875. Dalton : New York Medical Journal, 187o, p. 225. 710 THE CEREBRAL HEMISPHERES, stimulating with a weak electrical current a particular convolution, and so determining whether the latter is excitable, and whether its stimu- lation causes sensory or motor effects; or, destroying a particular convolution by cutting, corrosion, etc., and observing whether the animal is deprived of any of its faculties, and so learning whether the convo- lution has motor or sensory functions. By such experimental methods particular functions have been assigned in animals to the different con- volutions of the brain, and there can be little doubt that such convo- lutions of the brain in man as are homologous with the brain in monkeys and the higher mammalia have essentially the same functions as in the latter; the results obtained by post-mortem examination and the Fig. 419. The left hemisphere of the monkey. (Fekrier.) clinical study of disease of the brain in man confirm the results obtained by experimentation upon animals; destruction of the convolutions by injury or disease entailing the loss of motor or sensory faculties. 1 Thus, electrical irritation of the convolutions bordering the fissure of Rolando in the brain of the monkey (Fig. 419, 1, 2, 3, 4, 5, 6, 7, 8, a, b, c, d) and in man (Fig. 420), at least in the only case recorded, 2 gives rise to certain well-defined constant movements of the hands, feet, arms, legs, facial muscles, mouth, and tongue, on the opposite side of the body. That the muscular contractions induced through electrical stimulation of these or other convolutions are not due to an escape or diffusion down- ward of the electrical current, and so affecting the corpus striatum, etc., is shown, apart from the fact that stimulation by chemical agents produces the same effect, by several considerations, among which may be mentioned the feebleness of the current used, the close approxima- tion of the electrodes, the imperfect conductivity of the brain substance, the muscular contractions occurring on the opposite side of the body, and not occurring at all when other convolutions were stimulated. That these convolutions are in reality motor centres, constituting the indispensable physical substratum for the volitional, psychical initiation of movements corresponding to those induced by electrical stimulation, 1 Forrier : Localization of Cerebral Disease, p. 42. London, 1879. Grasset : Des Localisations dans les Maladies Cerebrates, p. 143. Pari-, 188D. Charcot : Lecons sur les Localisations dans les Maladies du Cerveiiu, p. 166. Paris, ls78. Rendu Revue des Sciences Medicates, tome xiii. p. 314. Paris, 1879. " Bartholovv : American Journal of the Medical Sciences, April, 1874. LOCALIZATION OF FUNCTIONS. 717 the latter acting in the same manner as the stimulus of the will, is further shown by the fact that destruction of these convolutions in the Fig. 420. Bateral view of the human brain. The circles and letters have the same significance as those in the brain of the monkey, Fig. 453. (Ferrier.) Fig. -121. Brain of dog; showing excision of angular convolution an 1 two adjacent anterior convolutions on left side. Blindness of right eye. (Ferrier.) monkey 1 by experiment (Fig. 421) and in man 2 by disease causes complete hemiplegia of the opposite side of the body without affecting 1 Ferrier: Functions of the Brain, 1876, p. 201. - Leiiine : De In TiOC»lin dans lea Maladies Cerebrates, p. S3. Paris, lS7o. Gliky : Deutsches Archiv fur kiin. Med., Dec. 1875. 718 THE CEREBRAL HEMISPHERES. sensation. On the other hand, destruction in the monkey 1 of certain convolutions, like the angular gyrus (Fig. 422), for example, while not Fig. 422. Brain of dog, showing excision of angular convolution and adjacent posterior convolution in right side. Blindness of left eye. (Ferrier.) aifecting at all its motor powers, entails in the opposite eye loss of per- ceptive vision — that is, the loss of visual ideas as distinguished from mere visual sensations, the corpora quadrigemina, as we have already seen, being the centres of the latter. An animal with its optic lobes intact undoubtedly sees — that is, the physical ray of light becomes the mental subjective conscious sensation of sight, but the latter, in the absence of the angular gyrus, gives rise to no ideas such as are nor- mally developed out of the sensation of light. Under such circum- stances familiar objects are seen, but do not suggest the ideas of pleasure or pain, for example, usually associated with them. In a word, the animal sees, but does not perceive, it is only psychically blind ; with the destruction of the optic lobes it becomes absolutely so. Now, while in man, at least at present, the localization of a sensory function like that of perceptive vision in a particular convolution, the angular gyrus, has not been as definitely established by chemical and pathological investigation, as in the case of the monkey, the dog, etc., nevertheless, cases of cerebral hemianaesthesia — that is, loss of sensibility, without loss of motion, accompanied also by loss of perceptive vision, on the oppo- site side of the body, due to cerebral lesions — go to show 2 that there are special sensory as well as motor convolutions in the brain of man. The condition of aphasia, whether presented in the usual, or agraphic, or amnesic form, depending, as, without doubt, it does, upon disease in the region of the posterior extremity of the third left frontal convolu- tion, where the latter abuts on the fissure of Sylvius, and overlaps the island of Reil, is a most convincing argument in favor of the view of the cerebral functions being localized in the convolutions of the hemi- spheres. Merely referring incidentally to the researches of Petit, 3 1 Ferrier, ibid., p. 167. " Ferrier, op. cit., pp. 170, 181. 3 Recueil d'observations d'anatomie et de chiiurgie, p. 74. Paris, 1766. APHASIA. '719 Bouillaud, 1 Dax, 2 Broca, 3 Hughlings Jackson, 4 etc., upon the subject of aphasia, the detailed consideration of which belongs rather to the study of clinical medicine and pathological anatomy, it may be briefly said that a person presenting the condition of aphasia as exhibited in its most usual form is deprived of the faculty of articulate speech, though such a person comprehends perfectly the meaning of words spoken by others ; having a clear idea of language and of the meaning of words, and being able to write perfectly well. In other cases, however, the patient cannot express ideas in writing, or cannot remember the words wanted ; in those of aphasia, agraphia, or amnesia, the idea even of language is lost. That the inability to speak exhibited by the person suffering from aphasia, whether simple or combined with the amnesic or agraphic form, is not due to paralysis of the muscles of articulation is shown by the fact that the aphasic individual makes use of these muscles in mastication and deglutition. Though the centre for the coordination of the muscles effecting articulation be diseased, since the action of the centre of the articulating muscles is bilateral — that is, the centre in one hemisphere innervating the muscles of articulation of both sides — there is no difficulty in understanding that such should be the case. While disease of the centre of articulation of the left hemisphere, for the reason just given, does not entail paralysis of the muscles of articu- lation, it does entail paralysis of articulation or speech, the centre for the coordination of the muscles involved in the production of speech being then affected. When it is remembered, however, that speech is gradually acquired through the constant and continual association in the mind of sounds or written signs with the corresponding spoken words, that the acquisition of speech, physiologically speaking, is the development in the brain of an organic nexus between the sound or symbol, and the articulation, it becomes intelligible why if this nexus be broken, that, though the sound be heard and the svmbols seen, and the corresponding ideas developed, the words expressing the ideas cannot be uttered, — the individual is speechless, because, as Ferrier expresses it, 5 the motor part of the sensori- motor cohesion, sound- articulation situated in the inferior frontal convolution, is broken. Further, owing to the close proximity of the motor centre of the hand and facial muscles, it is easy to see, therefore, why dextral and facial paralysis are so often present, though not necessarily so in the case of aphasia. At first sight it may appear strange that the centre for coordinating the muscles effecting articulation should be located ex- clusively in one hemisphere ; in reality, however, there is nothing more strange in this than that most persons are right-handed. Dextral movement, like articulate speech, is gradually acquired, and there is no more reason to doubt that in the absence of the coordinating cen- tres of articulation of the left hemisphere that of the right could be educated, than that in the absence of the right hand one could learn to usf the left. Indeed, it has been found that in left-handed persons suffering with aphasia the inferior frontal convolution affected is situ- Irchivos de Mfidecine, 1825. - Gazette oebdomadaire, April, 1865. :; Bulletin de la Bociete anatomique, tome it. 1861. 4 London Hos] ital Reports, vol. i. ■'• Op. themselves of their natural sleep, with the laudahle desire, it is true, of distinguishing themselves, but, unfortunately, at the cost of broken-down health and lost spirits, too often never to be regained. Resuming what has been said of the functions of the cerebro-spinal axis in man, it may be stated in general that the spinal cord and medulla oblongata are the seat of excito-motor actions, the functions of the medulla differing from those of the cord rather in degree than in kind, the rhythmical performance of such complex functions as deglu- tition, circulation, and respiration, depending upon the medulla, from the fact of the nerves distributed to the tongue, fauces, larynx, heart, and lungs emanating from that portion of the spinal axis; that the pons Varolii, being that portion of the encephalon in which external impressions first become conscious ones, is the seat of excito-sensori- motor actions, as are also the basal ganglia, the corpora striata and thalami, being the centres of motion and sensation, respectively, the optic lobes the centres of vision ; that the cerebellum is a reflex centre for the maintenance of equilibrium and coordination of locomotion ; that the cerebral hemispheres, being the portion of the encephalon in which perceptions, ideas, emotions, and volition are developed, are the seat of excito-sensori-ideo-motor actions. It will be observed that up to the present moment, in our exposition of the functions of the encephalon, we have endeavored to offer only what appears to us to be well-established anatomical and physiological facts, merely mentioning, or not referring at all, to the remaining portions of the encephalon, whose functions have not as yet been made out — to describe simply the physical substratum of consciousness. It is needless to say, however, that whether or no the different parts of the encephalon and the different convolutions of the hemispheres really possess the functions assigned to them, that the phenomenon of consciousness is thereby in no wise explained. Admit- ting, for example, that the optic lobe is the centre of the sensation of sight, and that the exact nature of the molecular changes occurring in its cells when the sensation of sight is experienced were understood, we would be still unable to understand how the vibrations of light falling upon the retina give rise to visual sensations — that is, the manner in which a physical impression becomes a conscious sensation. In the present state, at least, of the development of our consciousness it appears impossible even to conceive of how the gap between matter and mind, the objective and subjective, can ever be bridged over. At all events, the phenomenon of consciousness can never be explained by a purely physiological investigation. We can say that the brain is the organ of the mind, even that it converts heat into thought, but, as viewed subjectively, the functions of the brain are synonymous with mental operations. The phenomenon of consciousness must be studied, not only objectively by the physiologist, but subjectively by the psycholo- gist ; nevertheless, too much stress must not be laid upon the distinc- tion of matter and mind, of object and subject, as made by the meta- physician, since the existence of matter or mind, as shown by ultimate analysis, is only an inference. We are conscious of the sensations of color, hardness, roundness, weight, extension, etc., and we infer the FUNCTIONS OF CEREBEAL HEMISPHERES. 723 existence of something underlying these qualities, which we call matter, and which produces in us these sensations. We are directly conscious of these sensations, not of the matter supposed to cause them. The existence of matter being, therefore, an inference from our conscious- ness, it is impossible to say, not knowing anything whatever about its nature, whether it is akin to mind or not. On the other hand, suppose that matter does exist, it is certain that the various modes of motion ordinarily known as heat, light, sound, etc., are transformable in us into equivalent modes of consciousness, and we infer from these modes of motion the existence of something, the mind underlying these modes of consciousness, but of whose nature we know just as little as that of the matter, from the effects of which its existence is inferred. The idealist may argue that there is no such thing as matter apart from mind, since material forces are only cognizable as modes of conscious- ness, and the materialist may argue that there is no mind apart from matter, that the modes of consciousness are material, since what exists in us as consciousness is transformable into modes of motion, but it is evident that the forces of the inner are correlated with those of the outer world, the forces of the outer with those of the inner world, that if we besin with mind Ave end with matter, if with matter we end in mind ; matter and mind being merely symbols of the unknown reality under- lying both. CHAPTER XL Y. SYMPATHETIC NEEVOUS SYSTEM. The sympathetic system of nerves, or the system of organic vegetative life, also known as the trisplanchnic nerve, great intercostal nerve, etc., consists of a double chain of symmetrically disposed ganglia extending the entire length of the vertebral column, which, gradually converging, terminates finally as a single ganglion, the ganglion impar, resting upon the coccyx. While there is no doubt as to the manner in which the double ganglionated cord of which the sympathetic consists ends, it has not as yet been made out exactly how it begins ; the observation of Ribes 1 that it begins as it ends, in a ganglion impar situated upon the anterior communicating artery, not having been confirmed by other anatomists. It may be mentioned, however, in this connection, that the author in dissecting various genera of monkeys, in more than one instance found such a ganglion, though he has failed, like others, to find it in man. Intercommunicating with the nerves of the cerebro- spinal system, and giving off during its course numerous branches form- ing intricate plexuses, such as the cardiac, solar, and hypogastric, the sympathetic nerves, as a general rule, follow the course of the great bloodvessels, entwining the latter as the ivy the oak, to supply the viscera of the great cavities of the body, etc. The nerves of the sympathetic system are usually much smaller, softer, and less distinctly seen than those of the cerebro-spinal system, present a grayish aspect, and adhere closely, by connective tissue, to contiguous structures. While consisting of medullated nerve fibres, they are largely composed of the pale gray, gelatinous fibres of Remak, the latter resem- bling embryonic nerve fibres and the nerve fibres developed in the reunion of nerves. The ganglia of the sympathetic, whether of the ganglionated cord or its branches, do not differ essentially in structure from the ganglia of the posterior roots of the spinal nerves, large root of the fifth, trigeminal, glossopharyngeal, pneumogastric, etc. They consist of a mass of nerve cells smaller than those of the spinal ganglia, imbedded in a stroma of connective tissue, which is traversed by nerve fibres, the whole being enclosed by a tightly adherent membrane con- tinuous with the sheath of the nerves upon which the ganglia occur, the latter looking like so many grayish-white or reddish-gray swellings or knots. The main ganglia and branches of the sympathetic being situ- ated in the cervical, thoracic, abdominal, and pelvic regions, we may begin in our necessarily brief account of the physiological relation of the parts involved with the ganglia of the cervical region, and first with the superior cervical ganglion (Fig. 423). 1 Mem. de la Soc. Med. d'Emnlation, tome viii. p 606 SYMPATHETIC NERVE. Fig. 423. 11 725 :t 41 11 Ml! '•, fly .:■' Cervical and thoracic portion of the sympathetic. 1,1, 1. Right pneumogastric. 2. Glossopharyngeal. 3. Spinal accessory. 4. Divided trunk of the sublingual. 5,5,5. Chain of ganglia of the sympathetic. 6. Superior cervical ganglion. 7. Branches from this ganglion to the carotid. 8. Nerve of Jacobson. 9. Two filaments from the facial, one to the spheno-palatine and the other to the otic ganglion. 10. Motor oculi externus. 11. Ophthalmic gangli receiving a motor filament from the motor uculi com- munis and a sensory filament from the nasal branch of the fifth. 12. Spheno-palatine ganglion. 13. Otic ganglion. 14. Lingual branch <>f the fifth nerve. 15. Submaxillary ganglion. 16, 17. Superior laryngeal nerve. 18. External laryngeal nerve. 19,20. Recurrent laryngeal nerve. 21,22,23. Anterior branches of the upper four cervical nerves, sending filaments to the superior cervical sympathetic gan- 726 SYMPATHETIC NERVOUS SYSTEM. glion. 24. Anterior brandies of the fifth and sixth cervical nerves, sending filaments to the middle cervical ganglion. 25,20. Anterior branches of the seventh and eighth cervical and the first dorsal nerves, sending filaments to the inferior cervical ganglion. 27. Middle cervical ganglion. 28. Cord connecting the two ganglia. 29. Inferior cervical ganglion. 30, 31. Filaments connecting this with the middle ganglion. 32. Superior cardiac nerve. 33. Middle cardiac nerve. lit. Inferior cardiac nerve. 35,35. Cardiac plexus. 3(5. Ganglion of the cardiac plexus. 37 Nerve following the right coronary artery. 38, 38. Intercostal nerves, with tlieir two filaments of communication with the thoracic ganglia. 30, 40, 41. Great splanchnic nerve. 42. Lesser splanchnic nerve. 4:5, 43. Solar plexus. 44. Left pneumogastric. 45. Right pneumogastric. 46. Lower end of the phrenic nerve. 47. Section of the right bronchus. 48. Arch of the aorta. 49. Right auricle. 50. Right ventricle. 51,52. Pulmonary artery. 53. Right half of the stomach. 54. Section of the diaphragm. (Sappey.) The superior or first cervical ganglion, lying upon the rectus major muscle opposite the second and third cervical vertebrae and behind the in- ternal carotid artery, is connected by intervening filaments with the upper four spinal nerves — the ganglia of the glossopharyngeal, pneumogastric, and the hypoglossal nerves. In addition to its cord of communication with the second cervical ganglion, the superior cervical gives off' an ascend- ing branch, vascular and pharyngeal branches, and the superior cardiac nerve. The ascending branch accompanying the internal carotid artery through the carotid canal divides into two branches, which, subdividing and communicating with each other around the artery, so form the carotid plexus. From the latter are given oft" filaments to the abducens nerve, and the deep petrosal which passes to the spheno-palatine, or Meckel's ganglion, the latter connected with the spinal system by the superior maxillary and great petrosal nerve. Continuing upward around the artery, on reaching the cavernous sinus, the sympathetic plexus is then known as the cavernous plexus, an important one, since it commu- nicates with the semilunar ganglion and ophthalmic branch of the trigeminal with the ophthalmic ganglion, the latter connected with the spinal system by the ophthalmic and oculo-motor nerves, and with the oculo-motor and pathetic nerves. From the carotid and cavernous plexuses fine filaments are also given off which entwine themselves around all the branches of the internal carotid artery. The vascular branches of the superior cervical ganglion form plexuses upon the in- ternal carotid artery and its branches. By the plexuses on the internal, maxillary, and facial arteries the sympathetic communicates with the otic and submaxillary ganglia respectively, the otic ganglion being connected with the spinal system by the small petrosal, the submaxillary ganglia by the chorda tympani. The pharyngeal branches, two or three in number, descending to the side of the pharynx, together with branches from the glossopharyngeal and pneumogastric nerves, form the pharyn- geal plexus, which, as we have already mentioned, supplies the mucous membrane and constrictor muscles of the pharynx. The superior cardiac nerve, derived from the first cervical ganglion and from the cord below it, descends behind the great bloodvessels of the neck, and entering the thorax passes on the right side either in front of or behind the sub- clavian artery, thence along the innominate to the back of the arch of the aorta, to end in the cardiac plexus. On the left side of the nerve follows the carotid artery in its course to the cardiac plexus. The superior cardiac nerve communicates with the pneumogastric, and gives off filaments to the inferior thyroid artery. The middle, or second cervical ganglion, resting upon the inferior thyroid artery, and CERVICAL GANGLIA AND CARDIAC NERVES. ^27 situated opposite the fifth cervical vertebra, is connected with the third cervical ganglion by several branches, and gives off filaments to the fifth and sixth spinal nerves, branches which follow the inferior thyroid artery to the thyroid body, and the middle cardiac nerve. The latter, as it descends the neck, receives filaments from the superior and inferior cardiac and pneumogastric nerve, and ends in the cardiac plexus. Occasionally the middle cervical ganglion is indistinct, or even absent; in such cases it appears to be fused with the inferior or third cervical ganglion. The latter, situated behind the vertebral artery and between the transverse process of the last cervical vertebra and the first rib, gives oft , in addition to the branches going to the first thoracic ganglion, branches to the seventh and eighth spinal nerves, to the vertebral artery, and the inferior cardiac nerve, which, after receiving filaments from the middle cardiac and inferior laryngeal nerves, and sometimes from the first thoracic ganglion, terminates in the cardiac plexus. Occasionally the inferior cardiac nerve of the left side becomes blended with the middle cardiac nerve. The three cardiac and pneumogastric nerves, together with branches from the first thoracic ganglion, form the cardiac plexus. The latter, situated behind and beneath the arch of the aorta, gives off' branches which, accompanying the coronary arteries, constitute the coronary plexuses. Fig. 424. Solar JileXUS. (HlRSCHFELD.) While the cervical portion of the sympathetic consists, as we have seen, of three ganglia, etc., the thoracic portion consists of usually twelve ganglia, resting upon the heads of the ribs, and covered by the pleura. The first thoracic ganglion, as already mentioned, is connected with the last cervical, and the last thoracic with the first lumbar, the connecting cord of the latter passing through the diaphragm. Each thoracic ganglion usually gives oft' two narrow cords, the rami commu- 728 SYMPATHETIC NERVOUS SYSTEM. nicantes, which pass to the nearest intercostal nerve. The upper six thoracic ganglia give off, also, branches to the aorta, intercostal blood- vessels, and the oesophageal and pulmonary plexuses of the pneumo- gastric nerve. The lower six thoracic ganglia give off, in addition to the branches going to the aorta, branches which go to form the three splanchnic nerves. The great splanchnic nerve, deriving its roots from the sixth to the tenth thoracic ganglia, inclusive, perforates the crus of the diaphragm, and terminates in the semilunar ganglion. The small splanchnic nerve, deriving its roots from the tenth and eleventh thoracic ganglia, passes through the diaphragm with the preceding nerve, and terminates in the solar plexus. The third splanchnic, some- times absent, coming from the twelfth thoracic ganglion, pierces the diaphragm, and terminates in the renal plexus. The solar plexus (Fig. 424), so called on account of the numerous filaments radiating from it, is situated behind the stomach and in front of the aorta and crura of the diaphragm, and surrounding the coeliac and commencement of the superior mesenteric artery, extends to between the suprarenal bodies. It consists of an intricate mixture of nerves and ganglia ; among the former may be mentioned the great and small splanchnics, as well as filaments from the pneumogastric nerve ; among the latter the semilunar ganglion (Fig. 425), so called on account of its being situated on each side of the plexus, at the side of the coeliac and superior mesenteric arteries. From the solar plexus emanate numerous plexuses, named after the vessels around which the branches entwine themselves, as follows : the phrenic, coronary, hepatic, splenic, supra- renal, renal, and spermatic, superior mesenteric, and aortic plexus. The aortic plexus, descending upon the aorta from the solar plexus, of which it is the continuation, after giving off the inferior mesenteric plexus terminates below in the hypogastric plexus. The latter very intricate plexus, situated between the common iliac bloodvessels, extends down- ward as the inferior hypogastric plexuses on each side of the rectum, and after receiving branches from the lower lumbar and sacral ganglia, the lower two or three sacral nerves, and the inferior mesenteric plexus, gives off the vesico-prostatic, or the vesico-vaginal and uterine plexuses, according to the sex respectively. The lumbar portion of the sympathetic consists of four or five ganglia situated at the sides of the vertebrae which communicate with each other, and with the adjacent lumbar nerves, as in the case of the thoracic ganglia, and give off branches to the aortic and hypogastric plexus. The sacral ganglia, usually four in number, are connected likewise with the spinal nerves, and give off branches to the hypogas- tric plexus. As already mentioned, the single coccygeal ganglion or ganglion impar, with connections similar to those of the sacral ganglia, is common to the two sympathetic nerves. While considerable differ- ence of opinion prevailed at one time as to whether the ganglia of the sympathetic were sensitive, there is no doubt on this point at present; mechanical or chemical irritation of the thoracic or semilunar ganglia in dogs, calves, and rabbits, having been shown by Flourens, 1 Brachet, 2 i Recherches experimentale sur Lea propri6t6s et les functions du systeme nerveux. p. 230. Paris, 1842. 2 Recherches experimentale sur les functions du systeme gauglionaire, p. 305. Bruxelles, 1834. LUMBAR AND SACRAL GANGLIA. 729 Muller, 1 Longet, 2 etc., to give rise to pain. The sensibility of the sympathetic, however, is far from acute, being indeed, dull, as com- Fig. 425. 20 Lumbar ami sacral portions of the sympathetic. 1. Section of the diaphragm. 2. Lower end of the cesophagus. 3. Left half of the stomach. 4. Small intestine. 5. Sigmoid flexure of the colon. 6. Rec- tum. 7. Bladder. 8. Prostate. 9. Lower end of the left pneumogastric. ID. Lower end of the right pneumogastric. 11. Solar plexus. 12. Lower end of the great splanchnic nerve. 13. Lower end of the lesser splanchnic nerve. 14,14. Last two thoracic ganglia. 15,15. The four lumbar ganglia. 16,16, 17, 17 Branches from the lumbar ganglia. 18. Superior mesenteric plexus. 19, 21, 22, 23. Aortic lum- bar plexus. 20. Inferior mesenteric plexus 24,24. Sacral portion of the sympathetic. 25,25,26,26, 27,27. Hypogastric plexus. 28,29,30 Tenth, eleventh, and twelfth dorsal nerves. 31,32,33,34,35, 36,37,38,39. Lumbar and sacral nerves (Sapi i Muller: Physiology, vol. i. p. 712. London, 1841 - Physiologie, tome iii. p. 593. Taris, 1869. 730 SYMPATHETIC NERVOUS SYSTEM. pared with that of the cerebro-spinal system. As regards the excita- bility of the sympathetic, if has also been shown by Mailer, 1 Longet, 2 and others, that stimulation of the ganglia, splanchnic nerves, etc., by electricity or chemical irritants causes contractions of the muscular coat of the intestines. Inasmuch, however, as the muscular coat of the intestine consists of unstriated muscular tissue, the contraction does not immediately follow the simulation, as in the case of the cerebro- spinal system and striated muscle, and further, the contraction lasts longer, another characteristic of the effect of stimulating unstriated muscular tissue. Since, however, the most important effects following stimulation of the sympathetic can be obtained, as we shall see presently, by the stimulating of the cerebro-spinal system, and as the ganglia and fibres of the sympathetic lose their properties through atrophy, degeneration, etc., when separated from the cerebro-spinal system, with which we have just seen they are invariably connected, as shown by the experiments of Bernard, 3 Courvoisier, 4 etc., it would appear that whatever properties are possessed by the sympathetic are due to its connections with the cerebro-spinal system. That the sympathetic system, in fact, is only an appendage of the cerebro-spinal system, is not only shown by the facts just referred to, but also by the very im- portant one in this connection that in the lowest fishes, amphioxus, myxine, the sympathetic system is undeveloped or absent, which would not be the case were its presence an indispensable element in the nervous organization of a vertebrate. Up to the beginning of the eighteenth century it may be said that absolutely nothing had been definitely established with regard to the functions of the sympathetic system. In 1712, however, Pourfour du Petit 5 divided the cervical sympathetic in a dog, repeating the experiment in 1725, in the presence of Winslow and Senac, and called attention among its consequences to the redness and injected condition of the conjunctiva, the contracted condition of the pupil, 6 etc. The conclusion drawn by Petit from his experiments and observations was that the intercostal nerve, as the sympathetic was then called, "furnished spirits to the conjunctiva, to the glands, and to the vessels which are found in these parts, the relaxation of the parts being so evident that there almost always ensues a slight inflammation of the conjunctiva due to the swelling of the vessels;" that the influence exerted by the sympathetic was propagated from below upward toward the brain, and not from the brain downward, as was often supposed. Notwithstanding the importance of the conclusions correctly drawn from his experiments by Petit with reference to the influence of the sympathetic upon the circulation, nutrition of the eye, etc., nearly a century passed without anything further being added to our knowledge of the functions of the sympathetic. In 1812, however, Dupuy, of Alfort, having removed the superior cervical ganglion in horses, called attention among the effects of the experiment, particularly to the in- 1 Op. cit., p. 713, - Op. tit., p. 595. Systeme Nerveux, tome ii. p. 568. Paris, 1842. 3 Journal de la physiologie, tome v p. 407. Paris, 1862. « Archiv of Micros. Anat., Band ii. S. 30. Bonn, 18X6. 6 Memoires de l'Arad. des Sciences, p. 1. Paris, 1727. 6 Due to the unopposed action of the third pair of nerves supplying the circular muscular fibres of the iris. EFFECTS OF DIVISION OF CERVICAL SYMPATHETIC. 731 jected condition of the occular conjunctiva, and to the elevation of temperature in the ears, head, and neck, which were bathed in sweat; the general conclusion arrived at by Dupuy 1 being that the sympa- thetic exercises a great influence on the nutritive functions. While Petit described the effects of cutting the cervical sympathetic, and Dupuy of removing the superior cervical ganglion neither of these ex- perimenters offered any definite explanation of the hyperemia noted in both cases, nor Dupuy of the rise in temperature in the latter one. Indeed, the true explanation of the phenomena at that period would have been impossible, the structure of the arteries not yet being under- stood. Even though Valentin 2 had shown, in 1839, that the arteries con- tracted in response to stimulation of the nerves distributed to them, it was not admitted that the middle coat of the arteries contained mus- cular fibres until 1840, when such was actually demonstrated to be the case beyond doubt by Henle. 3 During the same year, Stirling, 4 like Henle, was led to the conclusion that there existed nerves comparable to those distributed to the muscles generally, which act upon the blood- vessels, either directly or reflexly, and which he called " vasomotor nerves." In 1852 Brown-Sequard 5 divided the cervical sympathetic on one side in rabbits, and called attention, as Bernard 6 had done in the previous year, to the hypericin ia and elevation of temperature, often amounting to as much as 11° F. on the corresponding side of the head and ear, and for the first time gave the true explanation of the phe- nomena in attributing the rise in temperature of the parts affected to the supply of blood being increased through the dilatation of the blood- vessels, and by showing that while section of the sympathetic in para- lyzing the muscular coats of the arteries permits of their dilatation, elec- trieal stimulation of the central cut end of the sympathetic causes their contraction again, and with the latter the restoration of the parts to their normal condition. To Brown-Sequard must be accorded, there- fore, the discovery, not exactly of vaso-motor nerves, since the existence of such had been previously indicated by Henle and Stirling, but of the vasomotor, or, more especially, of the vaso-constrictor nerves of the cervical sympathetic, and of their mode of action in influencing the temperature, etc., of the parts to which the latter are distributed. It should be mentioned, however, injustice to Bernard, that three months after Brown-Sequavd's discovery, and without being aware of it, Ber- nard 7 offered the same explanation of the experiments performed by him during the previous year (1851), but at that time by him incor- rectly interpreted. The vaso-motor, or vaso-constrictor nerves, as we shall hereafter call them, since, through their constringing effect upon the muscular coat of the bloodvessels, the normal calibre of the latter are maintained, and the tissues supplied with the proper amount of blood, are found, not only in the cervical, but also in the thoracic and 1 Journal de Oonvisart et Leroux, 1816, tome xxxvii. p. 340. Medhel's Archiv, 1818, Band iv. S. 105. - De B , nucti"nJbu8 Nervorum Cerebral in m et Nervi Sympathetici, (>. 153. Bernae, 1839. 3 Wofhenachrift fur die gesamnite Heilkunde, 1 4n, No 29, S. 329. 4 Recberches path, et med pratiques sur ['irritation. Leipzig, 1>40. 5 The Medical Examiner, New Series, vol. viii p. 189 Philadelphia, August, 1852. c Comptes reudue de la SOCie'te' de biologie, tome iii. p. 103. Paris, 1851. Ibid., 1862, tome iv. p. ion. 732 SYMPATHETIC NERVOUS SYSTEM. abdominal portions of the sympathetic and in the brachial and sciatic plexuses, supplying the upper and lower extremities. While the vaso- constrictor nerves are apparently given off as fibres from the sympa- thetic ganglia, in reality they are derived, as shown by recent investiga- tion, 1 from the spinal cord, since division or stimulation of the latter, or of certain spinal nerves in certain definite regions, is followed by dilata- tions or contractions of the bloodvessels, just as if the vaso-constrictor nerves had themselves been divided or stimulated. Thus, for example, while the vaso-constrictor nerves of the head are apparently derived from- the superior cervical ganglion, they can be traced by their division and electrical stimulation through the cervical cord of the sympathetic to the anterior roots of the first three dorsal spinal nerves, and thence into the anterior columns of the cord. Further, according to Bernard, 2 whilst the fibres distributed to the dilating muscular fibres of the iris, thereby causing dilatation of the pupil, are derived from the first two dorsal nerves (cilio-spinal centre), those distributed and influencing the calibre of the bloodvessels are derived from the third dorsal nerve. In the same manner, the vaso-constrictor nerves supplying the blood- vessels of the upper extremity, while apparently emanating from the first thoracic ganglion, are, in reality, derived from the spinal cord, passing off from the latter with the anterior roots of the third to the seventh dorsal nerves inclusive, and thence traversing the thoracic por- tion of the sympathetic and the inferior thoracic ganglion, reach the brachial plexus by the rami communicantes, to be finally distributed with the branches of the plexus, while such of the vaso-constrictor nerves as are derived from the plexus itself are given off with the ante- rior roots of the cervical nerves. The vaso-constrictor nerves supplying the bloodvessels of the abdominal viscera, more especially the splanchnic nerves, are largely derived from the dorsal and lumbar portion of the cord ; the latter, together with the sacral portion of the cord, giving off fibres which pass through the lumbar and sacral plexuses to the sym- pathetic, and thence into the lower extremities, supplying the blood- vessels of the latter. Inasmuch, then, as the vaso-constrictor nerves are derived from the spinal cord, traversing more particularly its ante- rior columns, it might naturally be supposed that all these nerve fibres at some point of the cord, the upper portion most probably, would be brought to a focus, so to speak, and that stimulation of such a portion of the cord would cause all of the bloodvessels to contract, and a corre- sponding rise in blood pressure and division of the same, a dilatation of the vessels and fall in blood pressure. Such a focus or vaso-motor centre has indeed been found in animals, not exactly by anatomical demonstration, but by means of successive sections of the cord below upAvard, and from above downward, and localized in the rabbit, for example, by Owsjanikow 3 in the floor of the fourth ventricle on either side of the middle line just one millimetre behind the optic lobes, and between four and five millimetres in front of 1 Badge and Waller : Oomptes Rendus, tome xxxiii. p 372. Paris, 1851. Ludwig and Thiry : Wiener Sitznngsberichte, 1861, Band xlix. II. Abtheilung, S. 421, Vulpian : Let;ons sur l'Appareil vaso moteur, p. 180. Paris, 1875. 2 Comptes Rendus, tome iv. p. 383. 3 Ludvvig's Arbeiten, 1871, S. 210. VASO-DILATOR NERVES. 733 the nib of the calamus scriptorius. From this centre emanate impulses, which transmitted through the anterior columns of the cord and anterior roots of the spinal nerves pass thence to the sympathetic ganglia and vaso-constrictor nerves, and through the latter maintain the normal calibre of the vessels or the vascular tonus. Inasmuch as the muscular fibres of the middle coat of the bloodvessels is disposed in a circular manner at right angles to the long axis of the vessel, it is not difficult to understand why stimulation of the vaso-constrictor nerves is followed by contraction of the vessels — indeed, the disposition of the nervous and muscular fibres being such, it can hardly be conceived how it should be otherwise, and yet, strange as it may appear, as first shown by Bernard 1 , there are also nerves the stimulation of which causes dilatation of the bloodvessels instead of contraction, and which may therefore be called vaso-dilator nerves ; among such may be mentioned the chorda- tympani, the auriculo-temporal, the nervi-erigentes of the penis; stimula- tion of these nerves causing dilatation of the vessels of the tongue, 2 of the ear, and of the corpora cavernosa of the penis, 3 respectively. Though numerous explanations have been offered of the manner in which the vaso-dilator nerves act, it must be admitted that none of them are satis- factory, and that it is not yet understood how their stimulation causes dilatation of the bloodvessels. Thus, it has been said that the stimulation of a vaso-dilator nerve causes the vein of the part to contract, and that in consequence an obstacle is offered to the passage of the blood from the artery to the capillary, which is the cause of the dilatation of the artery. As a matter of fact, however, the vein does not contract, but dilates as much as the artery. It has also been suggested that the stimulation of a vaso-dilator nerve excites the activity of the anatomical elements of the part to which the nerve is distributed, the effect of which in the case of a salivary gland, for example, would be that its secretory activity being increased more blood would flow to the part, and the vessels would dilate. Unfortunately, however, for this hypothe- sis, in the absence of all secretion, as in the case of an animal poisoned with atropine, the vessels of the tongue will still dilate if the chorda ivmpani be stimulated. Another explanation, a too common one when physiological phenomena remain unexplained, is that of inhibition, it being held that vaso-dilator nerves inhibit or paralyze the vaso-constrictor nerves. Apart, however, from the fact that the dilatation of an artery following stimulation of a vaso-dilator nerve is greater than that follow- ing paralysis of the vaso-constrictor nerve, to say that the one nerve inhibits the other is rather another way of stating the fact to be ex- plained than an explanation of it. Whatever value may be attached to the explanations offered, whether they be accepted or not, nevertheless, there can be no question as to the fact of their being vaso-dilator as well as vaso-constrictor nerves, and that in all probability they emanate from a focus or centre close to the vaso-motor or constrictor one, already described, if not actually in the latter. The vaso-constrictor or vaso- 1 Systeme Nerveux, tome ii. p. 144. Pari?, 185S. Liquides tie l'Organisme, tome i. p. 312. - \ r Ipian, op cit., p. 158. 3 Eckpard : Untersuchungen uber die Erection dea Penis beim Hunde. Beitrage zurAu.it. u. Pbys. Abband. vii. Giesseu, 1S6'2. 734 SYMPATHETIC NERVOUS SYSTEM. dilator nerves c;m be excited reflexly as well as directly. Thus, as firsl shown by Brown- Sequard 1 and Tholozan, if a thermometer be held ii e hand and the other hand surrounded by ice or very cold water, in a very short time the temperature of the hand holding the thermome- ter will fall, the general temperature of the body, however, remaining unaffected, an effect which can only be explained on the supposition that the impression due to the cold is transmitted by the sensory nerves to (he spinal cord and thence reflected by the vaso-constrictor nerves to the vessels of the hand holding the thermometer. For the same reason, according to Brown-Sequard, 2 if one foot be immersed in water ataboul 41° F., the temperature of the other foot will fail in a few minutes per- haps 7° F. It has also been shown by Vulpian 3 that if the sciatic nerve be divided, as in a dog, for example, and the central end stimulated, not only the vessels of the limb contract, but also almost all the vessels of the body, the under surface of the tongue even becoming pale through constriction of its vessels. The same reflex effect can also be induced by stimulation of almost any of the sensory nerves, of the posterior roots of the spinal nerves, and even by irritation of the skin. As illus- trations of reflex vaso-dilator action may be mentioned, the dilatation of the internal saphenous artery following stimulation of the central cut end of the dorsal nerve of the foot, and the dilatation of the vessels of the ear, brought about through excitation of the central end of the auriculo- temporal nerve, or through stimulation of the central end of the sciatic nerve. While the functions that we have attributed to the sympathetic nerve are those possessed by that of animals, there is no doubt that the functions of the sympathetic in man are essentially the same. The blush and pallor due to emotion are familiar examples of reflex vaso- motor actions in man. A number of cases have been now recorded by J. W. Ogle, 4 Panas, 5 Verneuil, 6 Trelat, 7 Poiteau, 8 W. Ogle, 9 Bartholow, 10 Seeligrauller, 11 Nicati, 12 Eulenberg, 13 in which rise of temperature, unilateral sweating of the neck and head, hyperemia of the conjunctiva, contraction of the pupil, were all observed more or less in consequence of paralysis of the sympathetic due to pressure exerted by aneurisms, tumors, etc., while, according to Vulpian, 14 lesions of the spinal cord may be localized from the vascular dilatation developed in the upper extremities as a consequence of the injury to the vasomotor nerves arising from it. It may be also mentioned in this connection that before most of these observations had been made, Wagner 15 had noticed that, in the case of a decapitated woman, powerful galvanization of the sympathetic caused dilatation of the pupil. While the scope of this work does not permit of a detailed account of the influence exerted 1 Journal de Brown-Sequard, 1858, tome i. p. 497. 2 Ibid., p. 502. 3 Op. cit., p. 237. 4 Med.-Chir. Trans., vol. xli. p. 397. 5 Mem. de laSoc. de Chirurgie, 1864, t. vi. p. 383. 6 Bui. de la Soc de Chirnrgie, 1864, 2d serie, t. v. p. 167 • Gaz. des hopitaux, Paris, 2 Juin, 1868 8 These de Paris, 1869, No. 2. 9 Med.-Chir. Trans., vol. Hi. p. 150. London, 1869. i° Quarterly Journal of Psych. Medicine, vol. iii. p. 134. New York, 1869. 11 Berlin klin. Wochenschrit't, 1872. No. 2. 12 La paralysie du nerf sympathetique. Lausanne, 1873. « Berlin, klin. Woehenschtift, 1869, S. 287. 14 Op. cit., p. 195. 15 Journal de physiologie, tome iii. p. 175. Paris, 1860. ONCOMETER. 735 by the sympathetic nervous system upon nutrition, it will have been seen, no doubt, from what has been already said, that its influence must be very great, since the amount of blood distributed to the stomach, intestine, liver, kidney, etc., is regulated by the vasomotor nerves. The reflex flow of the alimentary secretions in response to the excitement developed through the presence of food, their natural stimulus, the great vascularity of the liver, spleen, pancreas, during digestion, is brought about through the influence of the sympathetic nerves distrib- uted to these organs. The rapidity and extent with which the absorp- tion of the digested food takes place depends largely upon the condition of the portal circulation, as influenced by the vaso-motor nerves, and more particularly by the splanchnic. The circulation of the blood, as we have already seen, is modified by the combined effects of the depressor and vasomotor nerves. It is also through the intermediate action of the latter that the cerebro-spinal centres, more especially those of the medulla, as shown by Bernard 1 and Vulpian, 2 influence the biliary and glycogenic functions of the liver and the secretion of urine by the kidneys. That the amount of blood circulating through the latter, and therefore the amount of urine secreted, is influenced by the vaso-motor nerves, can be readily demonstrated by means of the oncometer and oncograph, by which the volume of the kidney in the living animal can be shown to vary with the blood circulating through it, the amount of the latter being regulated by the vasomotor nerves. The oncometer (Fig. 426) is a metallic capsule, shaped like a kidney, composed of two halves moving on a hinge (/*), by which the kidney is introduced, the renal vessels (a, v, u) passing out by the oppo- Fig. 42"; Oncometer, K. Kidney ; the thick line is the metallic capsule. /(.Hinge. I. Tube for filling apparatus. T. Tube to connect with T,. a, v, u. Artery, vein, ureter. (Stirling, after Roy.) Oncograph. C Chamber filled with oil, communi- cating by T, with T. p. Pioton. /. Writing lever (Stirling, alter Roy.) site opening, The kidney (K) is sur- rounded with a thin membrane, and the space (o) between the latter and the inner surface of the capsule filled with warm oil introduced through the tube I, which can be closed with a stopcock. The tube T being adapted to the tube T, leading into the metallic chamber C of the oncograph (Fig. 427), also filled with oil, any increase in the volume Systeme Nerveux, tome i. pp. 398-163. Physiolugie Experimental, tome i. p. 345. - Op. cit., tome i. pp. 541, 556. 736 SYMPATHETIC NERVOUS SYSTEM. of the kidney will force the oil from the space o into the chamber C, and the piston p will be elevated, and with it the recording pen. On the other hand, any diminution in the volume of the kidney through stimulation of the vaso-constrictor nerves will cause the oil to flow from C into o and the piston, and with it the recording pen, will fall. By Fig. 428. AMAAMWV/UWV adapting the pen to the cylinder Ave can get a trace of the so-called kidney curve (Fig. 428). We have already seen that through the contractions and dilatations of the cutaneous bloodvessels the blood either remains in the deeper por- tions of the skin, or comes to the surface of the body, the heat produced in the body, in the one case being retained within it, and, in the other lost by either radiation, conduction, etc., and that the application of cold to the general surface so constringes the cutaneous bloodvessels that the blood does not rise to the surface, the heat thereby being retained, which would otherwise be lost. That this effect is due to the impression made by the cold being transmitted by the sensory nerves to the spinal cord, and thence reflected by the vaso-constrictor nerves to the cutaneous bloodvessels, is shown by the fact of a curarized hot-blooded animal losing this compensating power, through which the heat of the body is normally retained, even though the latter be exposed to cold, the temperature of the curarized animal not being a constant one, but, like that of the cold-blooded one, varying within narrow limits with the temperature of its surroundings. CHAPTER XLYI THE SKIN AND ITS APPENDAGES. PERSPIRATION. AND TACTILE SENSIBILITY. (rEXERAL The Skin. Fig. 429. The skin or integument constitutes a general protective and sensory covering for the surface of the body. In addition to these important functions, however, in eliminating the sweat, carbonic acid, urea, etc., the skin acts also as an excretory organ, supplementing, in this respect, the action of the lungs and kidneys. As we have already seen, the skin, too, in a great measure regulates the production and dis- tribution of heat. To a certain extent, also, the skin acts as an absorbing surface. Further, through special modifications of its sensory structure, the skin is endowed with tactile sensibility, and thereby minis- ters to the sense of touch. The skin in addition, then, to being sensory and pro- tective, possesses, as well, excretory, calor- ific, absorbing, and tactile functions. The general appearance of the skin, its exten- sibility, flexibility, elasticity, and color are sufficiently familiar to all. It may be mentioned in this connection, however, that the color of the skin in the different races of mankind, and the varieties of complexion observed in different indi- viduals of the same race, are due to the amount of pigmentary matter present in the deeper layers of the epidermis, and that the color of the true skin, or dermis, is whitish and semi-transparent, its apparent of eurous tissue. 2. Epidermis. 3. its pinkish color being due rather to that of cuticle. . its soft layer. 5. subcu- underlying parts and the blood circulating through the latter. The furrows and folds of the skin are caused partly by the muscles and joints and partly by loss of elasticity in the skin itself, and by the deposition in it of fat. Faint, irregular lines are also observed on most parts of the surface of the skin, upon the palms of the hand and soles of the feet, and particularly upon the palmar surface of the last " 47 Vertical section of the skin of the fore- finger across two of the ridges of the surface, highly magnified. 1. Dermis composed of an intertexture of bundles taneous connective and adipose tissue. G. Tactile papillae 7. Sweat glands. K. Duct. 9. Spiral passage from the latter through the epidermis. 10. Termina- tion of the passage on the summit of ridge. (Lf.idy.) 738 SKIN AND APPENDAGES. phalanges; these lines are well marked in the latter situation, being disposed as concentric curves depending upon the regular arrangement of the underlying papillae of the true skin or dermis. According to Sappey, 1 the cutaneous surface, on the average in man, is equal to about ten square feet, in woman from six to eight, though in men above the ordinary size it may amounl in extent to from twelve to even eighteen square feet. ' The significance of such variations physiologically will become apparent presently when we consider the excretory functions of the skin. In harmony with the protective functions of the skin, its thickness varies very much in different parts. Thus, where naturally exposed to constant pressure and friction, as on the soles of the feet or the palms of the hands, the skin, as we shall see, is much thicker than that of the face, eyelids, etc. The skin consists of two layers, the dermis and epidermis, special modifications of the latter constituting the hair and nails, the sebaceous, mammary, and sweat glands. The dermis or true skin, also known as the cutis vera, corium, etc. (Fig. 429), constituting the deeper layer of the skin, is more or less closely connected to the underlying parts by the connective tissue of the adipose layer of the superficial fascia, or when the adipose layer is absent, by the loose connective tissue to the deeper layer of the fascia or subjacent structure, thereby allowing the skin a certain amount of movement backward and forward. The thick- ness of the adipose layer varies very much in different individuals and in different parts of the same individual. Thus while there is no fat beneath the skin of the eyelids, the upper and outer part of the ear, the penis, and the scrotum, a layer about the twelfth of an inch in thick- ness is usually present beneath the skin of the cranium, the nose, the neck, the knee and elbow, and the dorsum of the hand and foot; the adipose layer, on an average, in other situations, measuring from a sixth to one-half an inch. In fat persons, however, it may attain a thickness of one inch or even more. There is no well-defined line of demarcation between the dermis and the underlying adipose tissue, and after separating the two the dermis looks like a coarsely corded network, the meshes being occupied by small round masses of adipose tissue. The dermis consists principally of a dense intertexture of bundles of fibrous tissue crossing one another at acute angles in different directions, mingled with amorphous matter and some elastic tissue, the latter being most abundant on the front of the body and around the joints. It contains also unstriated muscular fibres which, passing down- ward from the more superficial part of the dermis are inserted into the hair follicles, and which, when excited to contract through the stimulus of cold, emotions of fear, or electricity, elevate the hairs and so give rise to the condition known as "goose flesh." In consequence of the gradual transition of the dermis into the subjacent tissues, its exact thickness is difficult to estimate. It may be said, however, to be about y^d of an inch thick on the eyelids, from the -^g-th to -^th of an inch on the front of the body, and from the -gVth to tue ¥* n °* an * ncn on tne Dac ^ °^ tne 1 Anatomic, tome ii. p. 447. Paris, 1852. DERMIS, OR TRUE SKIN. 739 body and the heels, being thickest where the entire skin presents that condition. The dermis is thinner in the female than in the male, about half as thick in children as in adults, and becomes thinner in old age. At its outer surface the dermis is quite dense, being denned by a more homo- geneous layer or basement membrane, and projects here and there as small eminences, the papilla, into the deeper layers of the dermis. The papillae on which the perfection of the skin as an organ of touch largely depends, they being highly developed where the sense of touch is exquisite, and vice versa, are of two kinds, simple and compound, the latter consisting of two, three, or more simple papillae springing from a common base. The papillae composed of a continuation of the fibrous and amorphous structure of the dermis and defined by the basement membrane of the latter vary in number and size in different parts of the body. They are most numerous and longest in the palms of the hands and soles of the feet, attaining in these situations a length of the -gl-jyth to the yyo-th of an inch, and being here disposed in double rows on the ridges of the dermis, of which they are the continuation, and give rise, as already mentioned, to the curved lines so noticeable on the palmar surfaces of the skin of the last phalanges of the fingers and toes. The papilla are also quite numerous on the prepuce, glans penis, nymphse, clitoris, and nipple. In other portions of the body they are less numerous and small, measuring only from the ^-Q-th to the -g-^-jj-th of an -inch. In the face, for example, the papilla are so little developed as to be hardly recognizable. Most of the papilla of the palms, fingers, soles, toes, and nipples, especially the compound kind, contain tactile corpuscles in which, as already mentioned, the cutaneous nerves terminate. It will be remembered also that the digital nerves of the fingers and toes appear to terminate in similar shaped, though larger bodies, the Pacinian corpuscles, situated in the subcutaneous tissue, and the nerves supplying the skin of the glans penis and clitoris in the Krause corpuscles, resembling the tactile and Pacinian corpuscles, though smaller than either. The dermis with its papillae is richly supplied with bloodvessels and lymphatics, as well as nerves. The arteries penetrating the dermis from beneath end in a capillary network, the latter extending as single loops into the papilla, while the veins, more numerous and larger than the arteries, terminate in the superficial venous trunks. The lymphatics already referred to are most numerous on the fore and inner part of the body and limbs, being particularly well developed in the palms and soles. The dermis consisting largely of white fibrous tissue is by boiling resolved, in a great measure, into gelatine, the ordinary source of glue, hence, also its conversion into leather by tanning. The fibrous structure of the dermis, the papilla, the mouths of hair follicles, etc., may usually be seen in the cut edge and rough surface of a piece of leather. De- prived of its fatty matters, etc., the dermis, when properly thinned, forms also parchment. The epidermis, also known as the cuticle or scarf skin, constituting the superficial layer of the skin, bears the same relation to the dermis that the epithelium does to the deeper layer of mucous membranes. 740 SKIN AND APPENDAGES. Indeed, the transition of skin into mucous membrane at the mouth and anus is so gradual, that it is impossible to say where one ends and the other begins; in fact, as "well known, if the skin be inverted in these places, it becomes mucous membrane, and if the mucous membrane be everted, it becomes skin. The internal surface of the epidermis is applied directly to the papillae (Fig- 480) of the dermis, Fig. 430. Epidermis elevated so as to show papillae. (Hirschfeld,) and follows closely all their inequalities ; its external surface is marked by very shallow grooves corresponding to the furrows between the latter. The epidermis is entirely destitute of bloodvessels and lymphatics, deriving its nutritive fluid (like all other vascular parts), by osmosis, from the blood of the dermis. It was for a long time supposed that the epidermis was also without nerves. Recent investigations, how- ever, make it probable that some of the cutaneous nerves pass through the dermis, terminating as non-medullated nerve fibres among the deeper layers of the epidermis in slightly bulbous-like extremities, or in a plexus of fine fibrils. However this may be, impressions made upon the epidermis will be appreciated, whether the latter be provided with nerves or not, being transmitted through pressure to the ex- quisitely sensitive dermis beneath. The epidermis serves as a protective covering to the soft and delicate dermis, which would be otherwise constantly exposed to laceration and drying. Indeed, if the epidermis be removed, contact of the atmosphere alone will inflame the dermis, which, after death, rapidly dries. The epidermis is therefore thicker in those parts which are most exposed, as in the palms and soles, where it may measure as much as the yV** 1 of an inch or more, being very thin, on the other hand, upon the face, the eyelids, and in the external auditory meatus, attaining in these situa- tions only a size of the g^th to the y^-th of an inch. The whole skin then, including the dermis, in its thickest part would measure about the 4-th of an inch, and in its thinnest part about the -g^-th of an inch. The thickness of the epidermis is, however, dependent to a great EPIDERMIS. 741 extent upon the amount of pressure to which the skin is subjected, being very thick in the palm of the laborer and the sole of the plowman. Corns are thickened portions of the epidermis, and are due to the parts affected being exposed to excessive pressure or friction, hence they are developed not only in the feet by tight shoes, but on the knee of the shoemaker by constant hammering, and in front of the clavicle of the soldier by the pressure of the musket. The pain caused by corns is due to inflammation of the dermis, which they excite by pressing upon its delicate structure, just as any foreign body, a small stone, will do under similar circumstances. The epidermis consists of two layers, the rete mucosum and the cuticle. The rete mucosum or Malpighii, with a thickness varying from theyyL^th to the yX-th of an inch, constituting the deeper internal soft layer of the epidermis, is moulded upon the ad- joining surface of the dermis, and when separated by maceration or putrefaction presents impressions corresponding exactly with the papillae, furrows, depressions, etc., of the latter, the more prominent irregularities of the dermis being, as already mentioned, visible upon the outer surface of the cuticle, but less distinctly (Fig. 431). The Fig. 431. jr— V Rete mucosum. rete mucosum consists of several irregular layers of cells of different forms, more or less agglutinated together. Those lying next to the dermis are somewhat elongated in figure, varying in length from the ^Q-Q-th tothe-j-gVg-th of an inch, and disposed perpendicularly, while the succeeding ones are of a rounded form and often marked with rid o-es and furrows, in sections appearing as spines. As the cells are gradually >-" a I, 742 SKIN AND APPENDAGES. pushed from below upward through the continual development of new cells at the surface of the dermis, they become more and more flattened, lose their soft granular contents and nucleus, and, becoming keratose, give rise to the different layers of the rete mucosum, and are finally transformed into the dry horny scales of the cuticle. While in the white race the cells of the rete mucosum are colorless and like those of the cuticle translucent, allowing the color of the underlying dermis to be seen, in those of the black races, the negro especially, the deeper ones (Fig. 432) are filled with brown or black pigmentary matter, which gives rise to their char- Fig. 432 acteristic dark color, and, when present in smaller quantities, to the various shades of complexion of other races, of different individuals, and of different parts of the skin of the same individual, while the accumulation of this pigmen- tary matter in spots causes freckles. As the cells of the deeper layers of the rete mucosum are gradually transformed WE- into those of the cuticle, the pigmentary ^Mfft, matter gradually diminishes and finally Wk disappears. It is interesting in this Wij, connection to note that the color of the dermis in the negro is the same as that of the white, and that the whole skin of the negro foetus is as pale as that of the white one. The fact skin of the negro, vertical section, mag- of the pigment being developed in the nified 250 diameters », a. Cutaneous pa- deep Cells of the rete muCOSUm Only at 01" pill*. b. Undermost and dark-colored after b j rth wou ] (1 int | icate f^at t h e l^k layer of oblong vertical epidermis-cells. 1 . . , - „ . . . c mucous or Maipighian layer. ,/.Homy race had descended from the white one layer, (kblmkee.) rather than the reverse. Further, since in the dark races and the semi-burnt ones of the white races, the pigment is developed, not in the superficial, but in the deep layers of the rete mucosum, it is to be inferred that the pigment is eliminated by the cells of the rete mucosum from the blood of the dermis, and that the effect of the heat of the sun in temperate or tropical climates is not to modify directly the color of the skin, but in rendering the liver torpid, to throw upon the skin the elimination of the coloring and other matters of the bile, and, hence, only indirectly affecting it. That such is the case is rendered probable also from the fact of the cutaneous pigment being essentially carbonaceous in nature, as is that of bile. While there is no doubt that the cells of the rete mucosum are gradually transformed into those of the cuticle, there is considerable doubt as to whether they themselves are derived from those of the dermis, since, as w r e shall see hereafter, the epidermis is derived from the epiblast or external blastodermic membrane of the embryo, and the dermis from the mesoblast or middle blastodermic membrane. Such being the case, it is more probable that the deep epidermal cells THE NAILS. 743 of the adult are derived by unbroken descent from the original epiblastic ones of the embryo than from those of its dermal mesoblastic ones. The cuticle, or cuticula, constituting the most external superficial portion of the epidermis, consists of numerous layers of hard, flattened, nearly dry, yellowish translucent cells, irregularly polygonal in form, generally granular, but without nuclei, measuring from the ^-^j-fj-th to yl-o-th °f an mcn m diameter, and composed chemically of keratin, or horny matter; the deeper cells being rather thicker and rounder than those of the superficial layers. As the deeper surface of the cuti- cle is being continually renewed by fresh cells from the rete mucosum. its free surface is as constantly worn away, or shed off in flakes, con- stituting the so-called scurf (Fig. 438) and dandruff (Fig. 484). In Fig. 433. Fig. 434. Scurf from the leg 1. A fragment of scurf, consisting of dried, Battened, aon- nucleated cells or scales. 2. A few cells with a nucleus. 3. A cell more highly magnified, to exhibit its polyhedral form. (Leidv.) Fragment of dandruff from the head. 1. Portion of dandruff, consisting of non-nucleated cells. 2. Several fragments, consisting of nucleated cells. 3. Isolated cells, some with and without, nuclei. 4 A cell more highly magnified, exhibiting granular contents ami a nucleus. (Leidv. ) many of the lower animals, as in snakes, for example, the cuticle exfol- iates from time to time entire. By treating the cuticle with a solution of potash its scales separate from one another, swelling up into vesicles; it is for this reason that alkaline solutions remove the epidermis. In tanning, for example, the epidermis is removed by macerating the skin in lime. etc. A blister or burn, in producing inflammation of the dermis and effusion of liquid, breaks up the soft cells of the rete mucosum, ami so elevates the cuticle. If the skin be macerated after death, the cuticle, through disorganization of the rete mucosum, detaches itself, and when under such circumstances, it is thick- and strong, as in the case of the hand and foot, it may be stripped oif like a glove. The Nails. The nails, or ungues, appendages of the skin, corresponding to the claws and hoofs of other animals, and situated upon the dorsal surfaces of the distal phalanges of the fingers and toes, not only serve to pro- tect these parts, but are also important as prehensile organs, in civilized races more especially, in the case of the fingers, but in certain barbar- ous ones, in that of the toes as well. The nails are thin, flexible, trans- lucent quadrilateral plates, continuous with the epidermis (Fig. 435), 744 SK I N AND AIM'KN DA CMS. FlQ. 435. Fig. 4m. '■; > » km-, 2 7 > a Vertical section of the end of a finger. 1. Epidei mis on the back of the linger. -. Point at which it Is reflected to become continuous with the nail. :f. The nail. 4. Epidermis at the end of the ringer. 5, 6, 7, 8 Surface of the dermis corresponding with the position of the soft epidermic layer. 9,10,11, 12. Dermis. 13. Last phalanx. 14. Flexor tendon. (IiEmy. i •I I .J3 Vertical transverse section through a small portion of the nail and matrix, highly magnified. A. Corium of the nail-bed, raised into ridges, or laminae, «. fitting in between coi responding lamina?, b, of the nail. B Jlal- pighian, and C, horny layer, d. Deepest and vertical cells, e. Upper flattened cells of Malpighian layer. (Kolliker.) with which they are detached if the latter be separated by mac- eration from the dermis. The nail resting upon the depressed surface of the dermis, known as the matrix, or bed, as described by anatomists, consists of the root, body, and free border. The root is lodged in a deep groove of the matrix, the vallecula unguis, while the lateral borders of the body of the nail fit into rather shallow grooves, the free border of the nail being that part detached from the skin. The color of the nail is due to its translucency, which allows the color of the highly vascular, or underlying dermis, or matrix, to be seen ; the lunula, or whitish spot at the root, defined by the semicircular line, is due to the matrix being there less vascular. The grooves exhibited more particu- larly on the under surface of the nail are the impressions made by the fine longitudinal ridges and papillae of the dermis of matrix upon Fig. 437. .'/ Longitudinal section through the middle of the nail and bed of the nail. «. Bed of the nail, and cutis of the back and points of the fingers, b. Mucous layer of the points of the fingers, c. Of the nail. , A), the former the rudiment of the future hair, the latter the root-sheath, or the lining of the hair follicle, while the projecting of the dermis into the bottom of the flask-like hair forms its papillae. With the gradual upward growth of the hair and the development of the differ- ent parts, of which, as we shall see, it consists (Fig. 439, B, C), the root-sheath divided into the inner and outer root- sheaths, the former, except at the bottom, subdividing into Huxley's and Henle's layers, the latter being surrounded and defined by a fibrous membrane, derived from the dermis, and constituting the wall of the hair follicle. Finally, the hair, being fully formed, penetrates the cuticle, the papilla to which it is attached having been provided with nervous fila- ments and capillary bloodvessels. The hair is usually described as consisting of a root beginning in the skin as a club-like expansion, Rudiment of tlie hair from the brow of a human embryo, sixteen weeks old; magnified 350 diameters. ". Horny layer of ili»- epidermis. 6. Its mucous layer. i. Structureless membrane surrounding the rudiment of the hair, and continued between the mucous layer and the cor- ium. m Roundish, partly elongated cells which especially compose the rudiments of the hair. Quain's Anatomy, 1--78, vol. ii. p. 219. 746 SKIN AND APPENDAGES'. Fig. 4^,9. A. Hair rudiment from an embryo of six weeks. ". Horny, and ft, mucous or Malpighian layer of cuticle. i. Basement membrane, ire. Cells, some of which are assuming an oblong figure, which chiefly form the future hair. B. Hair rudiment, with the young hair formed, but not yet risen through the cuticle, n. Horny, ft. Malpighian layer of epidermis, c. Outer, d, inner root sheath, e. Hair-knob. /. Stem, and g, point of the hair. 7i. Hair-papilla, n, n. Commencing sebaceous follicles. C. Hair- follicle with the hair just protruded. (ScHAFEn.) Fio. 440. the bulb and a shaft or stem projecting from the skin, and terminating in the end or point. It is composed (Fig. 440) usually of a medulla, or central axis, around which are concentrically disposed the cortical substance and cuticle. The me- dulla consists of cuboidal cells, having a diameter of from the 2000 "' *° 1 2 ih Diagram of structure of the root of a hair within its follicle. 1. Hair papilla. 2. Capillary vessel. 3. Nerve fibres. 4. Fibrous wall of the hair follicles. 5. Base- ment membrane. 6. Soft epidermis, lining of the follicle. 7. Its elastic cuticular layer. 8. Cuticle of the hair. 9. Cortical substance 10 Medullary substance. 11. Bulb of the hair composed of soft poly- hedral cells 12. Transition of the latter into the cortical substance, medullary sub- stance, and cuticle of the hair. (Leidy.) of an inch, with granular contents, and an indistinct nucleus, usually intermin- gled with small bubbles of air, which have penetrated from the ends of the hair, and, wh'en present, giving rise to the white silvery lustre of the latter. In downy hairs the medulla is absent. The cortical substance, or the cortex, consti- tutes the chief bulk of the hair, and is that part upon which the color of the hair principally depends in different in- dividuals and races. It is composed of several layers of flexible fibres, the latter consisting of elongated fusiform cells. With the loss of the coloring matter, which is generally diffused through the cortical substance, the latter becomes white. The cuticle consists of a single layer of thin colorless quadrilateral cells, overlapping each other like the shingles of a roof. The edo-es of these scales THE HAIRS. 747 being directed upward and outward along the shaft offer an obstacle to any movement of the hair otherwise than with its root forward when rubbed between two surfaces. It is upon this fact that the felting of hair ami wool of various animals depends. The hair, like the epidermis, being destitute of bloodvessels, derives its nutritive liquid by osmosis from the blood of the vessels of the papilla. While analogy would lead one to suppose the nerve filaments of the papilla penetrate the hair, as a matter of fact, no nervous filaments having as yet been demonstrated in it, any sensibility that the hair may possess must depend, therefore, upon that of the papilla which the hair bulb tightly encloses or caps. The hairs are continually renewed by constant growth. In some instances, especially after disease, they are cast off or shed, new ones being produced. Permanent baldness is due to atrophy of the papillae, while the sudden blanching of the hair, occurring sometimes in a single night, is due to the greater part of the medulla and cortex becoming- filled with air. 1 Chemically, hairs are composed of fats, a gelatine-like substance, albuminous matters, containing a large proportion of sulphur, peroxide of iron, traces of manganese, silica, sodium, and potassium chlorides, calcium sulphate and phosphate, and magnesium sulphate. 2 With the exception of the palms of the hands and soles of the feet, the palmar surface of the fingers and toes, the lips, lining of the prepuce ami glans penis, hairs cover nearly every part of the surface of the body. The hairs generally project obliquely from the skin, and are regularly dis- posed, usually in curving lines from particular points. They differ very much as regards their size, fineness, color, form, and number, in different races, sexes, individuals, and parts of the body. Of the long hairs, attaining sometimes in women a length of three feet or more, and a diameter of from the ysVo^ 1 to tne TFo tn °^ an mc ^ 1 - the finest are found upon the head. The short, stiff hairs of the nostrils and edges of the eyelids, are from the 4-3-g-th to the yyiyth of an mc ^ 1 m diameter, the fine downy ones from the -.Jy^th to the 12 1 oo t k. While the fine silken hair of the head in the white race is cylindrical, the crisp hair of the head and beard of the negro is more or less flattened cylin- drical. It has been estimated 3 that upon a square inch of scalp there are about 1000 hairs, the number upon the entire head amounting to 120,000. The hairs are elastic, readily electrified by friction, especially in cold, dry weather, and very hygrometric. The latter property is taken advantage of in the making of delicate hvurometers, the hair elon- gating through the absorption of moisture. The hairs not only serve to protect the general surface, as in shielding the head from excessive cold or heat, but also guard certain orifices, as those of the ears and nose. The eyebrows prevent the perspiration from the forehead running on to the lids, the eyelashes the surface of the conjunctiva from dust, etc. Hair, being a bad conductor of heat, serves also to retain that produced within the body. It has already been mentioned that the hairs are quite regularly disposed, and it will be further observed that 1 Landois: Virchow's Arch., 1866, Band xv.w s 375. Wilson: Proc. Roy. Soc. Loud., 1867, vol. xv. p. I 16. • Quain's Anatomy, vol. ii. p. 226. V! ila m : Healthy Skin. p. si. Philadelphia, 1854. 748 SKIN AND APPENDAGES. if a man assume a crouching attitude, with elbows upon the knees, and the chin resting upon the hands, thai their general direction upon the extremities is obliquely downward, a disposition such, that if the person be exposed to wet weather, the rain will be drained off", an effect obviously of advantage to the primitive man, as well as to those who go naked at the present day. Finally, the hairs may be regarded, to a certain extent at least, as so many excretory organs, since their growth necessarily involves the excreting from the blood the different principles of which we have seen that they chemically consist, and which, if retained within the system, in all probability would give rise to disease. Sebaceous Glands. The sebaceous glands, like the nails and hair, are appendages of the epidermis, being developed during the fourth and fifth months of intra-uterine life as outgrowths of the hair follicles, into which, with but few exceptions, they eventually open. Each sebaceous gland begins (Fig. 441, A) as a solid bud sprouting out into the dermis from the external A Fig. 441. B A The development of the sebaceous glands in a six months' foetus. •<. Hair. 6. Inner root-sheath, here more clusely resembling the horny layer of the epidermis, c. Outer root-sheath, d. Rudiments of the sebaceous glands. A. Flask-shaped rudiments of the gland, with tat developed in the central cells. B. Larger rudiments. (Kolliker. ) root sheath of the hair follicle, and consists entirely of nucleated cells. As development advances, however, the cells in the central portion of the flask-like (Fig. 441, B) bud develop fat, which, gradually ex tending themselves, penetrate the root-sheaths of the hair follicle, and so pass into the cavity of the latter as the primitive sebaceous secre- tion, while through the further division and subdivision of the primitive bud the latter assumes the form of a simple or compound racemose gland. The sebaceous gland when fully developed consists of a deli- cate wall of fibrous tissue defined by a basement membrane lined with an epithelium consisting of polyhedral nucleated cells, with granular SEBACEOUS GLANDS. '49 contents, the cavity of the gland being filled with sebaceous matter, the chemical composition of which is given in Table LXXV., and Table LXXV. 1 — Composition of Sebaceous Matter. Water 357 Olein 270 Margarin .......... 135 Sodium butyrate and butyric acid ..... 3 Casein 129 Albumen .2 Gelatin . Cakimn } Phosphate Sodium chloride ......... 5 Sodium sulphate 5 1000 consisting physically of cells and oil globules, the cells containing granular matter and more or less distended with oil. The sebaceous glands are very numerous, existing almost everywhere, except in the palms and soles. Usually associated with the hair follicles (Fig. 442), Fig. 442 m A large- gland from the nose, with a little hair-sac opening into it; magnified fifty diameters. (KoLLIKER.) they are disposed around the latter in groups varying from two to eight to each follicle, and imbedded in the more superficial part of the dermis, appearing as round whitish bodies, and measuring on an average from the y^uth to the ^th of an inch in diameter. The largesl sebaceous glands are those of the nose, concha of the ear, skin of the penis, the scrotum, labia, and areola surrounding the female nipple. The use of the sebaceous matter is to smear the hairs with oil as they gi'ow out of the skin and thoroughly to imbue the cuticle with the same, through which it is rendered repellant of water. The 1 Robin : Leeons snr Ies humeurs, p. 509. Paris, 18G7 '50 S K I X A XI) A I' I' K X PAGES. greasiness of the skin thus produced is the cause of smut and dirt adhering to the person so readily and necessitating the use of soap for the removal of the same. The too free use of alkaline washes, how- ever, in depriving the cuticle of its natural oil renders the skin dry and harsh. The sebaceous matter often becoming inspissated, dis- tends the glands producing it, especially in those of the nose, and becoming incorporated at the mouth of the duct with dirt if squeezed out is often regarded on account of the shape as a worm, the dirt being supposed to be the head. It should be mentioned, however, that the sebaceous matter frequently contains the so-called pimple mite, the acarus or Demodex folliculorum. The sebaceous glands somewhat modified constitute also the Meibomian glands of the eye, the descrip- tion of which will be deferred, however, till the organ of vision is considered. Mammary Glaxds and Milk. The mammary, like the sebaceous glands just appendages of the epidermis, being developed in Fig. 443. J C described, are also the fourth or fifth month of intrauterine life (Fig. 443, 1, 2) as solid invaginations or projections of the rete mucosum into the dermis, the latter fur- nishing the dense layer investing them. As development advances each primitive gland gives off a number of buds, the future lobes, numbering at birth from twelve to fifteen, which, through continued division and subdivision into lobules, and the latter into acini or secreting vesicles, ultimately assume the constitution of a racemose gland (Fig. 444), such as the parotid or submaxillary, the wdiole, however, being so closely asso- ciated by connective tissue as to give the appearance of being homogeneous rather than lobulated. Just before the ducts from the lobes reach the nipple they expand beneath the areola into the so-called lactiferous sin- uses, especially observable in the human female during lactation, and constituting the large milk reservoirs in the cow. As the lacteal or galactophorous ducts from each lobe terminate at the summit of the nipple in a small orifice, the number of the latter, usually twelve to fifteen, correspond with the number of lobes. The mamma, as a whole, is of a firm consistence : of a pinkish- white color, of circular form with its external surface convex and prolonged to the nipple. The latter, provided with sensitive papillae, is highly vascular and capable of erection. The nipple, reddish or brownish, is surrounded by an areola of skin usually Development of the lacteal gland. 1, rudiment of the gland in a male embryo, at five months; a, horuy layer ; b, mucous layer of the epi- dermis ; e, process of the latter or rudiment of the gland; il, fibrous membrane around the same. 2, lac- teal gland of a female foetus, at seven months, seen from above ; a, central substance of the gland, with larger (b) and smaller (<•) solid out- growths, the rudiments of the large gland lobes. MAMMARY GLAXDS AND MILK. 751 of the same color, and containing sebaceous glands appearing as whitish eminences, which, during sucking, secrete a fatty substance which Fig. 444. protects the part from excoriation. The mammae exist in the male, but usually only in a rudimentary condition. Their presence in animals gives rise to the name mammalia, the highest order of vertebrates, and while as a general rule, they are attached in such to the abdominal Avails, in man and monkeys they are situated on the anterior part of the thorax. Table LXXVI. 1 — Composition of Human Milk. Water . 902.717 Casein (desiccated) . . 29.000 Lacto-protein . 1.000 Albumen . Butter . 25.000 Sugar of milk . . 37.000 Sodium lactate . . 0.420 Sodium chloride . 0.240 Potassium chloride . . 1 .440 Sodium carbonate . 0.053 Calcium carbonate . . 0.069 Calcium phosphate . 2.310 Magnesium phosphate , p. 13. - Faivre : Archiv Generates de Medeciue, 5 ieme serie, tome ii. p. 1. Paris, 1853. PERSPIRATION. 755 weigli daily the body and all the solid and liquid ingesta and egesta, and from the loss of •weight experienced by the body to deduce the amount of vapors transpired. Thus, if from every 8 pounds of ingesta taken in 24 hours there were 3 pounds of sensible egesta, 44 ounces of urine, and 4 ounces of feces, it was inferred that the remaining 5 pounds of ingesta passed from the body insensibly in the form of vapor. Unfortunately, however, as the latter included the vapor exhaled from the lungs as well as that from the skin, and the observation simply on- bodied as aphorisms, 1 no numerical tables given, the results obtained have now but little value, although Sanctorius experimented daily in the manner described for a period of thirty years. Although numerous and interesting observations and experiments were made during the eighteenth century by Dodart, Keill, Rye, Gorter, Lining, Hales, Stark, with a view of determining the amount of the perspiration and the conditions affecting it; it will not be necessary to dwell upon them, since the pulmonary and cutaneous perspiration were estimated together by these observers. The first attempt to estimate separately the vapor exhaled by the skin from that by the lungs was made by Lavoisier" and Seguin in 1790, the experiments consisting in enclosing Seguin in a bag of gummed taffeta which was tied above the head, an aperture in the coat when fixed around the mouth by a mixture of turpentine and pitch enabling Seguin to inspire fresh air and exhale the breathed air, but only permitting the pulmonary vapor of the latter to escape from the body. By then deducting the amount of the pulmonary vapor as determined by the loss of weight when enclosed in the gum coat from the total quantity of vapor exhaled as determined by the loss of weight when so enclosed, the amount of the cutaneous vapor was at last experi- mentally determined, and was found to be nearly two pounds, one pound and fourteen ounces, which does not differ very considerably from the later results obtained by Krause 3 and Valentin. 4 The amounts of perspiration exhaled by the skin, as shown by Lavoisier and Seguin and subsequent observers, vary very considerably, however, depending upon the quantity and temperature of the liquid food, the relative dryness or moisture and temperature of the atmos- phere, the amount of exercise taken, and the activity of the lungs and kidneys, with which the skin acts vicariously. The skin, however, not only supplements the action of the lungs as regards the exhalation of •watery vapor and carbonic acid, but that of the kidneys also, and not only with reference to the water but to the urea eliminated as well. Thus, according to Carpenter, 5 in one experiment the entire quantity of perspiration for the whole body being in one hour 3320 grains, 6^ grains of urea, containing 3.03 N, were obtained. It is not likely, however, that the excretion of urea would have continued during the whole twenty-four hours at such a rate. It should be mentioned in this connection also, according to Funkc," that through the desquamation of the epidermic scales about eleven grains of nitrogen are also daily i Sanctorii Sanctorii : De Statica Medecina aphorismorum. Lugduni Batavorum, MDCCIII. - Mem. de I' Acad, des Sciences, p. 609 Paris, lT'.iT. :: Waguer : Physio logie, Band II. S. 319. i Physi ilogy, Band i S. 174. Braunschweig, 1814. ■' Physiologie, p. 491. 6 Moleschott Unters, 1838, Band iv. S. 56. 756 SKIN AND APPENDAGES. eliminated from the system by the skin. The fatty matters of the sweat are probably produced by the sebaceous glands, while, as regards the inorganic principles, the most notable is sodium chloride, existing in the proportion of 2.2 parts per thousand. That the sweat, however, contains other substances than those already mentioned is rendered very proba- ble from the fact that death soon ensues when the perspiration is sup- pressed, as, for example, when the skin is varnished in animals 1 and also in human beings, as in the celebrated case of the child, who, being covered with gold-leaf to personate an angel at the coronation of Leo X., died a few hours afterward. 2 While death in such cases is no doubt partly due to the imperfect arterialization of the blood and the rapid fall of temperature, the varnish favoring the loss of heat in producing a cuta- neous hyperemia similar to that induced through paralysis of the vaso- motor nerves, symptoms like that of ursemic poisoning, tremors, tetanic cramps, movements of rotation, increased reflex excitability, present as well, lead one to suppose that urea and other poisonous substances not yet isolated are retained in the system which are usually carried away in the sweat. That such is the case is shown by the fact that if human sweat be injected into the blood of the rabbit 3 the pulse of the latter may be increased from 192 beats per minute to 326, the respiration from 82 to 105, and the temperature raised from 99.2° to 104.3° F. Even if it be admitted that the exact cause of death is not yet positively determined there can be no doubt that imperfect action of the sweat- glands must be a source of disease, various matters then accumulating in the system which would otherwise be eliminated. Indeed, too much stress cannot be laid upon the importance of keeping the skin clean — of the free use of water. Especially is such the case in tropical climates where the true secret of maintaining one's health lies in attending to the condition of the skin, and where febrile diseases are more successfully treated by active diaphoresis than in any other way. The great impor- tance of daily baths in the maintenance of health cannot be exaggerated, and apparently was more appeciated by the ancients than the moderns, as the ruins of the magnificent baths of Caracalla and Diocletian, at Rome, still to this day testify. Noble institutions they were ; the baths or thermae fed by stupendous aqueducts stretching for miles across the Campagna, their perpetual streams of hot and cold water flowing through mouths of solid silver into capacious basins, accommodating at one time thousands of bathers, and where for the eighth of an English penny the meanest Roman of them all could enjoy the luxury that might have well excited the envy of the kings of Asia. 4 The secretion of sweat, like other secretions, is influenced by the nervous system, the sweat centre or centres being situated, according to Luchsinger, 5 in the anterior horns of the gray matter of the spinal cord and medulla. From these centres nerve fibres arise, which, pass- ing down the cord, emerge principally with the anterior roots of the third, fourth, and fifth cervical nerves to pass with the brachial plexus i Fourcanet : Comptes Rendus, tome vi. p. 369. Paris, 1838. Ibid., 1843, tome xvi. p. 139. Valentin : Archiv f. Physiologie Heilkuiide, 1858, Band ii. S. 433. Bernard : Liquides de l'Organisme, tome ii. p. 177. Paris, 1859. "- Laschkewitsch : Du Bois-Reymond's Arch., 1868, S. 61. s Ruhrig: Jabrb. f Balneologie, 1873, Band i. S 1. 4 Gibbon : Decline and Full of the Roman Empire, vol. v. p. 237. London. 1807. & PlUiger's Archiv, Band xiii. S. 2i2 ; Band xiv. S. 545 ; Band XV. S. 482 ; Band xvi. S. 538. PERSPIRATION. ibt to the skin of the upper extremity, and with the anterior roots of the lumbar nerves to supply the lower extremity. The sweat centres may be stimulated directly and reflexly. It is in the latter manner that the sweat centres are excited in man by motion, fear, heat, various sub- stances such as pilocarpin, nicotin, muscarin, and inhibited by cold, and atropin. The manner in which the skin regulates the temperature of the body through the radiation, conduction, etc., of the heat produced within it having already been sufficiently considered, it will not be necessary to treat further of the function of the skin in this respect. While there can be no doubt that absorption in the lower animals and in many of the higher, is to a considerable extent carried on by the skin, frogs, lizards, etc., rapidly gaining in weight when immersed in water, some difference of opinion still prevails among physiologists as to what extent the skin in man normally acts as an absorbing surface. It may not appear superfluous, therefore, if attention be called to those instances or conditions in which absorption does take place in man by the skin. It is well known, as already mentioned, in speaking of the cause of thirst, that in the case of the shipwrecked sailor the thirst was very much, if not entirely, temporarily relieved by the immersion of the body in the sea, or by wearing clothes wet with the same. 1 In certain cases also, where the introduction of solid or liquid food by the mouth had become impracticable, immersion of the patient in a bath of tepid milk morning and evening not only relieved the thirst, but for some time maintained life, the weight gained being unaccounted for by the enemata also given. 2 It has also been shown that not only does the body gain in weight after immersion in a bath through the absorption of the liquid, but that the skin will also absorb certain salts when dissolved in the same. That the skin is permeable by gas is also well known, it having been shown by Bichat that if a limb be immersed in a putrid gas the latter will be absorbed by the skin, and by Aubert that the skin absorbs about the Y^th of the oxygen absorbed by the lungs. Admitting, then, that under certain circumstances the skin undoubtedly can absorb, it still remains undetermined to what extent, under normal conditions, it does absorb. Covered, as the skin usually is in man, almost entirelv with more or less clothing, it is difficult to comprehend how or what the skin under such circumstances can absorb, the gain in weight of the body through absorption of the watery vapor of the atmosphere some- times instanced 3 being due to the absorption of the vapor by the lungs rather than by the skin. We have further seen that through the presence of the sebaceous matter the skin is rendered repeliant of water, Avhich thereby renders it very insusceptible to the taking up of foreign substances. Indeed, it is very questionable whether such are ever introduced into the system unless the epidermis be disintegrated, the view sometimes advanced 4 that substances are absorbed by the sweat ducts being very improbable, since the latter are already filled with sweat, and the movement of the sweat, being from below upward, would 1 Madden : Experimental Enquiry into the Physiology of Cutaneous Absorption, p. 64. Edinb., 1838. - Currie: Medical P.. -ports, vol. i pp. 30K-326. Watson: Chemical Essays, vol. iii. p. mo. : Lining: Phil. Trans., 174:;, p. 496. Klapp : Inaugural Essay on Cuticular Absorption, p 30. Phila- delphia, lso:,. 1 iuspita: Wiener med. Jahrb., 1871. Neumann; Wiener med. Wochenschrift, 1871. 758 SKIN AND APPENDAGES. tend to wash away foreign substances rather than favor their absorption. It would appear, therefore, as Ave pass from the lower to the higher animals, that the skin loses its significance as an absorbing surface, becoming essentially protective and excretory in function. Neverthe- less, though the absorbing power of the skin in the economy of the higher animals may have been superseded by that of the lungs and alimentary canal, under certain conditions it may even in them act vicariously with the same, as no doubt it does, as regards the excretion of water by the kidneys as well as the lungs. The skin acts not only as a general sensory surface through the im- pressions made upon the epidermis being transmitted thence to the more deeply situated cutaneous nerves, but through its tactile Pacinian and Krause corpuscles it is endowed with a special modification of sensibility — the tactile sensibility, or the sense of touch, by means of which we not only feel but appreciate to a certain extent the form, size, character or surface, weight, and temperature of objects. While the skin as a whole, therefore, is endowed with a general sensibility more or less acute in different parts of the body, its tactile sensibility, however, is restricted to certain portions of it, and most delicate in those situations where the corpuscles are most abundant. Thus, if the blunt but fine ends of a pair of dividers provided with a graduated bar, or the eesthesiometer, be applied to the tip of the tongue — the individual being blindfolded — the two ends of the dividers, though only separated by so much as the -^ th of an inch, will be appreciated as two distinct objects. If, however, the dividers be approximated until they are separated by less than that dis- tance, the two impressions, a moment previous distinctly appreciated as such, now fade into one, as if but a single object was touching the tongue. Experimenting in this manner, it was first shown by Weber, 1 and after- ward by Valentin, 2 that the sense of touch varies very much in different parts of the body, being most acute at the tip of the tongue and ends of the fingers ; least so in the back, as shown in Table LXXIX. Table LXXIX. 3 — Tactile Sensibility. Both points of dividers felt Part of surfaces. when separated by these distances. Tip of tongue 0.50 of a line. Palmar surface of third phalanx of fingers . 1.00 " second " " " . 2.00 " " Dorsal " " third " " " . 3.00 " " Middle of dorsum of tongue .... 4.00 End of the great toe 5.00 " " Centre of hard palate ...... 6.00 Dorsal surface of first phalanx of fingers . . 7.00 " quarter of heads of metacarpal bones . 8.00 Back of the heel 10.00 " " Dorsum of the hand 14.00 " " foot 18.00 '• " Sternum 20 00 " " Five upper dorsal vertebrae ..... 24.00 Middle of " " 30.00 " " When points of dividers are brought closer than these distances they are felt as one. 1 Wagner : Physiologic, Band iii Zweite Abth. S 524. i Physiologie, Band ii. S. 558. 3 Carpenter, article Touch, Cycloptedia of Anat. and Phys., vol. iv. part 2d, p. 1169. GENERAL SENSIBILITY OF SKIN. 759 It was also shown by Weber, 1 as a general rule, that differences in pressure and weight are appreciated most acutely by those parts of the skin which are most sensitive to the impressions of touch, as that of the fingers, for example, and that, while by the sense of pressure alone, a difference in weight of not less than one-eighth can only be determined by making a muscular effort, as well as in lifting, a difference of one- sixteenth can be accurately appreciated. It may be mentioned in this connection, however, that the appreciation by the skin of the tempera- ture of the surrounding atmosphere, or of bodies applied to it, does not appear to depend upon nerves other than those of general sensibility, or that the fact of our appreciating the density, immobility, elasticity, etc., offered by bodies that we grasp or tread upon, or which, through their weight, offer a resistance to the exercise of muscular power, implies the existence of a special muscular sense. The ataxic symptoms present in certain cases of paralysis, often referred to as proof of the existence of a special muscular sense normally, are perfectly well accounted for by the loss of general sensibility. Since the impression made by the foreign body, whether it be the ground we tread upon or the child we hold in our arms, not being transmitted to the encephalon, in such cases it will not be reflected consciously or otherwise to the appropriate mus- cles whose action enables us to stand securely or grasp firmly, hence our inability to walk upon the ground or hold a child in our arms unless we look at the one or the other, the essential reflex action beins; then effected by the eye and optic nerve instead of the skin and cuta- neous nerves. The sense of touch, like the other senses, can be very much improved by attention and practice. Thus, it is said 2 that the female silk throwsters of Bengal can distinguish twenty different degrees of fineness in the unwound cocoons by the touch alone, and that the Indian muslin weaver makes the finest cambric with a loom of such simple construc- tion that, if worked by the hands of a European, would turn out but little better than canvas. It is also a well-known fact, that those persons who are employed in mints, etc., in the daily habit of handling coins, detect at once, and with certainty, a light piece. As might be expected, the sense of touch is very much developed in those who have lost the sense of sight, or who have been blind. One of the most remark- able of such cases is that of Giovanni Gonelli, who, at twenty years of age lost his sight, but who, nevertheless, after a lapse of ten years, developed a great talent as a sculptor, modelling such an excellent statue out of clay of Cosmo de Medici from feeling one of marble that the Grand Duke of Tuscany sent him to Rome to make a statue of Pope Urban VIII., which was a very successful one, the likeness being said to be excellent. Stranger still, even a good knowledge of botany and conchology has been acquired through the sense of touch by persons who have been born blind, or who had lost their sight early in life. It is well known, also, as in the case of Baczko, 3 that the blind can learn to distinguish the colors of fabrics by the sense of touch. I Weber, op. eit.. Band iii , ZvveitK Alitli. S. 543. 2 Carpenter, op. cit., p. 1177. ■ : Rudolphi : Physiologie, Band ii. S. 85. 760 SKIN AND APPENDAGES. It is related that Sanderson, the Mind professor of mathematics at Cam- bridge, could not only distinguish different medals, but could detect imitations of them often better than professed connoisseurs, while his appreciation of variations of temperature, it may he mentioned also, 1 was so acute that he could tell, through slight modifications in the tempera- ture of the air, when very slight clouds were passing over the sun's disk. It is a familiar fact, also, that the blind learn to read with great facility by passing their fingers over raised letters of about the size of those of a folio Bible. Terrible a calamity as the loss of sight is, it should not be forgotten, as the above examples teach us, what a delicate sense in that of touch we possess if cultivated, and that sources of pleasure and recre- ation through its development may be offered to those who are born blind, or who have lost their sight later in life. i Dunglison : Physiology, vol. i. p. 697. Phila., 1856. CHAPTER XL VII. THE NOSE AND OLFACTION. THE TONGUE AND GUSTATION. Just as we have seen that the skin, in addition to its other functions, acts as a general sensory organ, so we shall soon learn through the study of Development, that parts of it being especially modified become wry susceptible to certain external impressions, and that such modifica- tions, together with corresponding ones developed in the terminal nerves supplying the parts, constitute special sensory organs, such as the nose, tongue, eye; and ear, and inasmuch as, of such organs, the nose is the most simple in structure, we will begin the consideration of the special senses Avith the study of Olfaction. Olfaction. The nose, the special organ of the sense of smell, is regarded anatomi- cally as being limited to the pyramidal eminence of the face, extending from the forehead to the upper lip; physiologically, however, the nose — that is, the organ of olfaction — includes not only the parts just mentioned, consisting of the septum, cartilages, etc., but of the nasal cavities as Fig. 446. Distribution of nerves in the nasal passages. 1. Olfactory ganglion, with its nerves. 2. Nasal branch of fifth pair. 3. Spheno-palatine ganglion. (Dalton.) well ; the mucous membranes lining the latter being endowed not only with general sensibility, as we have seen, but with the special sense of olfaction, its upper half being supplied (Fig. 446) by the olfactory nerve, the special nerve of the sense of smell. The skin of the nose, thin 762 NOSE AND OLFACTION; TONGUE AND GUSTATION. above but thick below, as elsewhere, is furnished with sudoriferous and sebaceous glands and hairs; the hairs are usually small except within the margin of the nostrils, in the latter position, however, they are well developed from all sides, and to a certain extent act like a fine sieve in keeping out dust, etc. The nasal cavities communicating with the ex- terior, in front, by the anterior nares, and with the pharynx, behind, by the posterior nares, are lined with a highly vascular mucous membrane, the Schneiderian or pituitary membrane closely applied to the adjacent periosteum and perichondrium, which becomes, at the nostrils, continuous with the skin, at the posterior nares with the mucous membrane of the pharynx, and at the lachrymo-nasal duct and lachrymal canals with the conjunctiva. The nasal mucous membrane varies very much as regards its thickness and vascularity. Thus upon the turbinated processes and turbinated bone it is very thick and vascular, and forming doublings at their inferior borders, and posterior extremities of the above, increases very much the extent of the nasal surface. Further, while the epithe- lium within the region of the external nostrils is of the squamous char- acter, that lining the remaining portion of the nasal cavities is of the columnar kind, being non-ciliated, however, in the olfactory region, or that corresponding to the convex surface of the turbinated processes and the surface of the nasal plate of the ethmoid bone. The nasal mucous membrane is also provided with racemose glands whose secretion keeps the surface moist, a condition essential to the accurate perception of odoriferous impressions. The glands of the true olfactory membrane are, however, usually of a simpler character than those found in the remaining portion of the nasal mucous membrane. The special nerves of the sense of smell or the true olfactory nerves are given off as fifteen to eighteen filaments from the olfactory bulb to the olfactory region. The olfactory tract, of which the ganglionic bulb is the expansion, is usually described as the olfactory nerve, but improperly, since, as development shows, the olfactory tracts are outgrowths of the cerebral hemispheres, their morphological significance masked in man by the excessive development of the former. The olfactory tracts are two cords or bands, soft and friable, consisting of both white and gray nervous matter, which, passing forward and inward on the under surface of the anterior lobe of the cerebrum to the ethmoid bone, expand at the side of the crusta galli into the olfactory bulbs, from which are given off, as just mentioned, the true olfactory nerves, which, passing through the cribriform foramina of the ethmoid bone, are distributed to the inner and outer walls of the upper parts of the nasal cavities. Each olfactory tract arises apparently by three roots, from the inferior and internal surface of the anterior lobe of the cerebrum in front of the anterior perforated space, the external and internal roots being composed of white matter, the middle of gray, the large proportion of the gray substance, one-third, entering into the composition of the olfactory tract, confirming what has just been said as to the true nature of the latter. While the anterior root can be traced into the middle lobe and the middle and internal roots into the anterior lobe, considerable obscurity still prevails as to the deep origin of all three roots. It would appear, however, that the long or external root originates in the island of Reil, the thalamus opticus OLFACTION. 763 Fig. 447. and the nucleus in the tempo-ro-sphenoidal lobe in front of the hippo- campus, the middle or gray root in the gray substance of the anterior perforated space, the inner root in the gyrus fornicatus. The true olfactory nerves, or the filaments given oft" from the olfactory bulb, as they descend from the cribriform plate ramify, and, uniting in a plexi- form manner, spread out laterally in brush-like and flattened tufts (Fig. 486). In their minute structure, the olfactory differ from the ordinary cerebral and spinal nerves in being pale and finely granular, in not possessing a substance of Schwann, in adhering to one another, and in pi - esenting oval corpuscles. Their manner of termination is also peculiar, each olfactory fibre appearing to pass into the spindle-shaped bodies (b) interspersed between and among the epithelial cells (a) of the olfactory membrane (Fig. 447), which present a very characteristic appearance. These olfactory cells, so-called on account of their supposed function, present a very characteristic appearance, the central nucleated portion passing on the one hand internally into a beaded varicose- like thread (d) apparently continuous with the terminal olfactory fibril, and, on the other, externally into a rod- like structure (e), which in the frog is prolonged into fine hairs. That the olfactory cells, nerves, bulbs, and tracts constitute the essential structures by which external impressions are trans- mitted to the subiculum cornu of the hippocampal convolution in which the sense of smell is supposed to be local- ized, is proved by the harmonious re- sults of experiments performed upon animals, of pathological cases observed in man, and of the facts of comparative anatomy. Thus, among the numerous experiments in which the olfactory tracts were divided, and the loss of the sense of smell noticed, may be men- tioned those performed upon hunting dogs by Vulpian 1 and Philipaux, in which cases the animals, although de- prived of food for thirty-six hours after complete recovery from the effects of the operation failed to find the cooked meat concealed in the corner of the lab- oratory. That destruction of the olfactory nerves, bulbs, or tracts in man due to disease or injury involves the impairment or loss of the sense of smell is well known to pathologists, a number of such cases i'cll.- ;iih! terminal nerve-fibres of the olfactory region highly magnified. 1, from the frog; 2, from man; a, epithelial cell, extending deeply into a ramified process; h. olfactory cells; <■, their peripheral rods: e, their extremities, seen in 1 to be pro- longed into fine hairs ; '', their central fila- ments ; 3, olfactory nerve-fibres from the dog; (i, the division into fine fibrillse. (Frey after Sciiultze. ) '■ Lerons sur la physiologie generale et eumparee dn -ystem ■ nerveux, J). SS2, note. Paris, 1806. 764 NOSE AND OLFACTION; TONGUE AND GUSTATION. having been observed by Schneider, Rolpinck, Eschricht, Fahner, Valentin, Rosenmnller, Ceneti, Pressat, 1 Hare, 2 Notta, 3 Ogle, 4 Flint. 5 That the olfactory bulbs and nerves are the essential organs of the special sense of smell is still further shown by the fact that they are usually best developed in animals in which the sense of smell is most acute, being better developed, for example, in the mammalia than in the remaining vertebrates, while of the former class it is among those orders as in the carnivora, in which the sense of smell is very acute, that the olfactory region is most developed, in the dog, for example, in which the sense of smell, as well known, is very remarkable. The olfactory nerves, though readily impressed by odorous emanations, are but little affected by ordinary ones, while the olfactory tracts appear entirely insensible to the latter. 6 That the appreciation of odors or olfaction is due to the material emanations given off by odoriferous substances being carried by the inspired air to the terminal filaments of the olfactory nerves, the olfactory cells, is shown by the manner in which one sniffs the air in order to perceive an odor, and from the fact that if the air does not pass through the nostrils, as in occlusion of the posterior nares or in division of the trachea, the sense of smell is abolished. In every case where odorous emanations are perceived, the latter must impinge upon the olfactory membrane, come in contact, excite the peripheral ends of the olfactory nerves. As a general rule, persons having offensive emanations from the respiratory organs are not aware of such, not appearing to be affected by odors passing from within outward through the nostrils. This is due, not so much to the odor being carried by the air expired through the nostrils instead of by that inspired, as to the fact that one becomes in time accustomed to such odors, and ceases to notice them, however fetid they may be. Like the sense of touch, and the other special senses, that of smell may be very much developed by practice ; as exemplified in the dis- crimination of the quality of wine, drugs, etc. The sense of smell is, however, far more acute in the lower races of mankind than in the higher ones, to whatever extent in the latter it may have been devel- oped by cultivation. Thus it is said that the Mincopies of the An- daman Islands scent the ripeness of the fruits ; that the Peruvian Indians distinguish the different races of mankind by scent alone ; that Arabs can smell a fire thirty miles off; that the North American Indians pursue by smell, their enemies or their game. However the sense of smell may be developed in man, it is far surpassed in acuteness by that of animals. Every sportsman is aware that odors are recognized by hunting dogs, to which he is entirely insensible. The sense of smell is intimately related to that of taste, so much so, indeed, that if the nose be held, or plugged up, the characteristic taste of certain substances when swallowed, is not appreciated at all, as illustrated in drinking different kinds of wine, it being difficult, usually impossible, to distinguish the same under such circumstances. Further, 1 Cited by Longet, Anat. et Pliys. dn systeme nerveux, tome ii. p. 38. Paris, 1842. -' A View of the Structure, etc., of the Stomach and Alimentary Organs, p. 145. London, 1821. ■' ! Archives generates de medecine, p. 385. Paris, Aviil, 187U. 4 Medico-Chirur. Trans., Lond., 2d ser. vol. xxxvii. p. 203. ■'' Flint: Physiology, 1874, vol. v. p. 39. Magendie : Journal de physiologic, tome iv. p. 1G9. Paris, 1824. THE TONGUE AND GUSTATION. 765 it has been observed in those cases in which the sense of smell is lost, that of taste is usually lost also. The influence exercised by the nose upon respiration has already been mentioned. We shall see, hereafter, that the nose, also, modifies very much the quality of the voice. The Tongue and Gustation. The sense of taste or gustation, enabling us to appreciate the savor of sapid substances when introduced into the mouth, is due to the sus- ceptibility of the terminal filaments of the chorda tympani and glosso- pharyngeal nerves, of being impressed by contact of the same. The influence of the tongue in mastication and deglutition, the origin, dis- tribution, and general functions of the chorda tympani and glosso- pharyngeal nerves having been considered, it only remains for us now to point out the manner in which gustation is performed through the parts just mentioned. That the tongue is the organ of gustation there can be no doubt. It would appear, however, from experiments such as those performed by Longet 1 and others, in which different parts of the mucous membrane are touched with a sponge soaked in a sapid solution, that the sense of taste, probably in man at least, is lim- ited to the dorsal surface of the tongue, and from the experiments of Oamerer, 2 in which solutions were applied through fine glass tubes, more particularly to the circum vallate and fungiform pa- pillae, the parts around the latter not appearing to be impressed by sapid substances. The circum- vallate papillae (Fig. 448), so called on account of each papilla being surrounded by a trench or fossa, from seven to twelve in number, are disposed in two rows, in the form of a reversed V on the back part of the tongue. Each papilla is covered by numerous small secondary papillae, the latter, however, being concealed by the thick and stratified epithelium. The fungiform papillae, more numerous than the circumvallate, and readily distinguished during life by their deep red color, while found in the middle and forepart of the dorsum of the tongue, are most numerous and closely set together at the apex and near the borders. Each fungiform papilla, while narrow at its attach- ment (Fig. 449), at its free extremity is blunt and rounded, and, like the circumvallate papillae, is covered with secondary papillae and epi- thelium, imbedded in the epithelium, and more particularly in that of Vertical section uf circumvallate papilla, from the calf. 35 diameters. A. The papilla B. The sur- rounding wall. The figure shows the nerves of the papilla spreading toward the surface, and toward the taste-buds which are imbedded in the epithelium at the sides; in the sulcus on the left the duct of a gland is seen to open. (Exgelmann ) 1 Physiologic, tome iii. p. 52. Paris, 187;i. 2 Zeitschrift fiir Biologie, 1S70, Band vi. S. 440. 766 NOSE AND 01, FACTION ; TONGUE AND GUSTATION. the circum vallate papillae, are found ovoidal flask-shaped bodies (Fig. 450), having a length of the 3^75-th of an inch, and a diameter of the Pig. 449. Surface and sectional view of a fungiform papilla. A. The surface of a fungiform papilla partial!}' denuded of the epithelium. 135 diameters.) p. Secondary papillae, e. Epithelium. B Section of a fun- giform papilla with the bloodvessels injected, a. Artery, v. Vein. c. Capillary loops of simple papillae in the neighborhood, covered by the epithelium, d. Capillary loops of the secondary papillae. e. Epithelium. (From K.u.i.ikeh, aftei Todd and Bowman.) yg^QQ-th of an inch, consisting apparently of modified epithelial cells, which, with good reason, are supposed to be the special organs of the sense of taste. Each ovoid body, surrounded by flattened epithelial V\a. 4- r ,(). Two taste-buds from the papilla foliata of the raM.it. 450 diameters. (Engelmanx.) cells, consists of a cortical and a central part, the former being com- posed of long, flattened, tapering cells, disposed edge to edge, and coming to a point at the taste-pore, the latter of spindle-shaped cells and taste cells, resembling very closely the olfactory cells ; the distal end of the cell projecting from the orifice of the taste-bud, and the cen- tral beaded, varicose, and continuous with the terminal filament of the gustatory nerve. Such being the disposition of the taste cells, it would appear that the terminal filaments of the gustatory nerves, of which the former are the continuation, are excited by the flow of sapid solu- tions through the taste- pore into the interior of the taste-bud ; the taste cells being especially susceptible to impressions made by sapid sub- stances, whence the impression is transmitted by the chorda tympani and glossopharyngeal nerves to the centres of taste localized in the THE TONGUE AND GUSTATION 767 subiculum cornu of the hippocampus, when they are perceived. That the chorda tympani and the glossopharyngeal nerves are the special nerves of the sense of taste, the former more particularly for the ante- rior two-thirds of the tongue, the latter for the posterior third, can be shown, as already mentioned, both by experiments performed upon animals, and by pathological cases observed in man, division or dis- ease of these nerves involving loss of the sense of taste. The glosso- pharyngeal differs from the chorda tympani, however, in this respect, in that it is a nerve of general sensibility, as well as that of taste, the chorda tympani (gustatory fibres) being a nerve of taste alone, the sen- sory fibres of the lingual nerve bearing to the chorda tympani the same relation that the sensory fibres of the glosso-pharyngeal bear to its gustatory ones. In conclusion, it may be mentioned, and as might be expected, that since at the anterior two-thirds of the tongue the fungi- form papillae are supplied by the chorda tympani at the posterior third, and the circumvallate papillae by the glosso-pharyngeal, the taste of a substance might be different as it was placed upon the anterior or pos- "Fm. 451. a I A f a Filiform papillae. (Quain.) terior part of the tongue. Such has been experimentally found to be the case ; thus, according to Lussana, 1 potassium chloride tastes cool and 1 Archives de Pbytiologie, tomt- ii. p. 208. Paris, 1869. 768 NOSE AND OLFACTION; TONGUE AND GUSTATION. saltish at the anterior part of the tongue, and sweetish at the posterior part; potassium nitrate cool and piquant at the anterior, and bitter and insipid at the posterior end. Certain substances, like mineral acids, ferric sulphate, jalap, and colocynth, while but little appreciated at the anterior part of the tongue, are appreciated very acutely at the posterior portion. On the other hand, meats, milk, and wines, are equally well appreciated at both ends of the tongue. It may be men- tioned, incidentally, that the filiform papillae the minute conical emin- ences densely set over the greater part of the dorsum of the tongue and disposed in lines diverging from the raphe, are tactile in function. CHAPTER XL VIII. THE EYE AND VISION. The organ of vision includes the optic nerve, the eve, and its append- ages. The optic nerves — consisting of medullated, together with some gray nerve fibres — are usually described as arising from the optic chi- asma, or commissure. Regarded, however, as the continuation of the optic tracts, the optic nerves in reality arise, as we have seen, from the optic lobes, and to a certain extent also from the tlialami optici, corpora geniculata. cerebral peduncles, and tuber cinereum ; the root fibres from these different points of origin, converging form flattened bands, which, winding obliquely around the under surface of the crura cerebri, cross each other to pass to the opposite eyes, the decussation of the nerves, or tracts, which, we have seen, is complete giving rise to the chiasma. It should be mentioned, however, that the fibres constituting the an- terior portion of the chiasma are not derived from the optic tracts, but simply pass from one eye to the other, Avhile the fibres constituting the posterior part — and sometimes wanting — pass from tract to tract without being connected with the eyes. The optic nerves proper, aris- ing from the anterior and outer border of the chiasma, curved in direc- tion and rounded in form, enclosed in a double fibrous sheath, derived from the dura mater and arachnoid, pass into the orbit through the optic foramina, piercing the sclerotic coat of the eye at its posterior, inferior, and internal portions; the thin, but strong membrane through which the nervous filaments pass into the sclerotic, known as the lamina cribrosa, being partly derived from the sclerotic, and partly from the coverings of the nerve fibres which are lost at this point. At about one-third or one-fourth of an inch behind the globe of the eye, the optic nerve receives the central artery and vein of the retina, which, together with a delicate filament from the ophthalmic ganglion, is thence transmitted within the centre of the nerve by a minute canal, lined with fibrous tissue. That the optic nerves are the special nerves of the sense of sight there can be no doubt, since their injury or division always involves impairment or loss of sight. While the optic nerves are the avenues or paths by which the impressions due to the presence of light are transmitted to the optic lobes and angular gyri, there to become, as we have seen, conscious, intelligent vision, they are, however, absolutely insensible to ordinary impressions. Not only have these nerves been pinched, cut, and cauterized in animals, without the latter evincing any pain, but their insensibility in man has often been observed also, as in surgical operations, for example, in which the nerves have been exposed. That the optic nerves are especially susceptible to the impressions of the rays of light is still further shown from the fact of their excitation, however caused, always giving rise in consciousness to 49 7/<> THE K Y K AND VISION. I lie idea of light — a severe blow on the orbit making one sec stars, as often said, the mind having associated so uniformly the excitement of the optic nerve with the presence of light, that in time it becomes impossible to disassociate the two; the presence of the one invariably suggesting that of the other. The Eyeball. The eyeball, a spheroidal body, partly imbedded in a cushion of fat, protected by the surrounding bony orbit and the eyelids, moistened by the lachrymal secretion, and moved by various muscles, is composed of several coats, concentrically disposed, and enclosing several refractive media. Were it not for the fact of the cornea being set in the sclerotic, like a crystal into the rim of the face of a watch, the eyeball would present the form of a spheroid. Owing, however, to the cornea con- stituting one-tenth of the outer circumference of the eye, and to the fact just mentioned, the longest diameter is in the antero-posterior direction, as may be seen from the results obtained by Sappey (Table LXXX.). Table LXXX. 1 — Diameter of Eyeball in Fractions of an Inch. Ant. post. Transverse. Vertical. Oblique. Mean of 12 females from 18 to 81 years of age, 0.1)41 0.911 0.905 0.937 Mean of 14 males from 20 to 79 years of age, 0.968 0.941 0.925 0.949 It will be observed, from the above Table, that all the diameters are less in the female than in the male. It may be appropriately mentioned in this connection, also, that all such measurements should be made as soon as possible after death, within from one to four hours, owing to the eyeball losing so soon its normal form and dimensions. The Sclerotic and Cornea. The sclerotic (Fig. 452, 2), the outer protective coat of the eyeball, covering the posterior five-sixths of the latter, varying in thickness from the ^gth to the j-g-th of an inch, is a dense white, opaque tunic, composed of ordinary connective tissue, mixed with small elastic fibres and a few bloodvessels, and yielding, on boiling, gelatine. The cornea, the first of the refractive media, constituting the anterior sixth of the outer circumference of the eyeball, and varying in thickness from the ■^d to the gLjd of an inch, is the transparent projecting tunic (Fig. 452, 3,) attached to the periphery of the sclerotic, of which, indeed, it may be regarded as the continuation, consisting, like the latter, of layers of connective tissue, though somewhat modified, both struc- turally and chemically, since it is transparent, admitting light into the interior of the eye, and yielding chondrine on boiling. The cornea may be described as consisting of three parts: a stratified epithelium anteriorly, continuous with that of the conjunctiva, a middle portion,. 1 Traite d'Anatomie, tome troisicme, p. 747. Paris, ls"7. THE CHOROID. 771 the cornea proper, continuous with the sclerotic, consisting of modified connective tissue, posteriorly, of a homogeneous, elastic lamella, covered with epithelium-like cells, the membrane of Demours or Descemet, the part of the membrane passing to the anterior surface of the iris, more noticeable in the eyes of the sheep and ox than in man, being known as the ligamentum pectinatum iridis. In a state of health in the adult, ves- Fig. 452. Horizontal section of the right eyeball. 1. Optic nerve. 2. Sclerotic coat. 3. Cornea. 4. Canal of Schlemm. 5. Choroid coat. 6. Ciliary muscle. 7. Iris. 8. Crystalline lens. 9. Ketina. 10. Hyaloid membrane. 11. Canal of Petit. 12. Vitreous body. 13. Aqueous humor. (Dalton.) sels are not found in the cornea, except at its circumference, where they are disposed in capillary loops, nutrition apparently being carried on by means of the corneal corpuscles. The nerves of the cornea are, however, very numerous, and are derived from the long and short cili- ary nerves. Entering the sclerotic, and crossing the choroid, they pass into the cornea, extending almost through to its free surface. The Choroid. Removing the sclerotic in the manner represented in Fig. 453, the second coat of the eyeball from without inward, the choroid with its anterior prolongation, the ciliary muscle will then be exposed. The choroid may be regarded essentially as the vascular pigmental tunic of the eyeball ; its inner or pigmental layer in reality, however, constitutes the outer coat of the retina, being developed, as we shall see hereafter, like the latter from the invaginated portion of the optic vesicle. The choroid, varying in thickness from the YFoth to the 2V tn °f an mcn > an( i covering the eyeball to the same extent as the sclerotic, is connected by 772 THE EYE AND VISION. its outer surface with the latter tunic by connective tissues, vessels, and nerves, the so-called membrana fusca, and, like the sclerotic, is traversed posteriorly by the optic nerve. The arteries of the choroid, the short ciliary, comparatively large after piercing the sclerotic close to the optic Fig. 4? Choroid membrane and iris exposed by the removal of the sclerotic and cornea. Twice the natural size. a. One of the segments'of the sclerotic thrown back. b. Ciliary muscle, c. Iris. e. One of the ciliary nerves. /. One of the vasa vorticosa or choroidal veins. (Quain.) nerve, break up into branches, which pass forward and then inward to end in the capillaries, the latter being sometimes known as the tunic of Ruysch. The veins situated externally to the other vessels are very numerous, and, being disposed in curves converging into four trunks, present a peculiar appearance, which has given rise to the name of vasa vorticosa. Among the vessels of the choroid are also found elon- gated and stellated pigment cells, with branches, which, intercommuni- cating, constitute a sort of network. The nerves supplying the choroid are derived from the long and short ciliary. The inner surface of the choroid is smooth and is covered with the hexagonal pigmental cells of the retina, which will be considered as the outer layer of the tunic rather than, as formerly, as the inner layer or tapetum nigrum of the choroid for the reason just given. Ciliary Processes. It will be observed from Fig. 453 that the choroid passes forward into the ciliary muscle, the latter in turn passing into the iris, constitut- ing, in fact, one continuous layer — the second tunic of the eyeball. If, however, the choroid be viewed from behind, as represented in Fig. 454, in which the eyeball is supposed to have been divided transversely, it will be seen that the choroid passes forward and posteriorly into the ciliary processes, just as we have seen it passes forward but anteriorly into the ciliary muscle. Or, briefly, the relation of the parts may be CILIARY MUSCLE — THE IRIS. 773 expressed by saying that the choroid splits at its anterior termination into the ciliary muscle in front, and the ciliary processes behind, the Fig. 4-34. mB> y Ciliary processes as seen from behind. 1. Posterior surface of the iris, with the sphincter muscle of the pupil. 2. Anterior part of the choroid coat 3. One of the ciliary processes, of which about seventy-one are represented. %, (< t >i T AlN.) ciliary muscle being continued into the iris, hence the general term of uvea applied to all of these parts by the older anatomists. The ciliary processes or plications, about seventy in number, disposed radially behind the ciliary muscle and the iris, and fitting posteriorly, as we shall see, into corresponding plications of the suspensory ligament of the lens, more particularly into that part of it known as the zone of Zinn, consists of large and small thickenings of the choroid, the small folds alternating, though irregularly, with the large ones, the latter measuring about the -j^th of an inch in length and the -^th in depth, and com- posed like the choroid proper of vessels and pigment, the latter, though, being absent in the rounded inner ends. Ciliary Muscle. The ciliary muscle (Fig. 453, 6), the continuation anteriorly of the choroid, about the |th of an inch wide, consisting of longitudinal and circular fibres, the latter, however, present at the periphery of the iris only, may be regarded as arising from the inner side of the junction of the sclerotic and cornea, close to the canal of Schlemm, and inserted into the choroid opposite the ciliary processes. Such being its disposi- tion, it is evident that, in contracting, the nerves supplying it being the long and short ciliary nerves, will draw the choroid forward, thereby compressing the vitreous humor and relaxing the suspensory ligament of the crystalline lens, the significance of which action will be better appreciated when the subject of accommodation has been considered. The Iris. The iris (Fig. 453, e), the circular, contractile, and colored mem- brane seen through the transparent cornea, to which the characteristic 774 THE EYE AND VISION. color of the eye is due, is the muscular diaphragm of the eye, the aper- ture in its centre or pupil permitting and regulating the passage of light into the interior of the eye. The iris, about as thick as the choroid, is attached by its circumferential border to the line of junction of the cornea and sclerotic at the origin of the ciliary muscle, and measures about one-half an inch across, and in a state of rest about the one-fifth of an inch from the circumference to the pupil. The iris consists essentially of a stroma of connective tissue and muscular fibres, the latter, disposed as a ring around the pupil, constituting the sphincter, and as rays from the centre to the circumference, the dilator muscles, of the iris. The pupil, or aperture in the iris regulating the amount of light admitted, varies in size according as the muscular fibres are contracted or relaxed, from the one-twentieth to the one-third of an inch, and during foetal life is closed by a delicate transparent membrane. The iris is supplied by the two long ciliary and anterior ciliary arteries, the latter being derived from the muscular branches of the ophthalmic. The two long ciliary arteries having pierced the sclerotic, one on each side of the optic nerve, pass between the latter tunic and the choroid to the ciliary muscle, and each vessel, just before reaching the iris, divides into an upper and lower branch, which, anastomosing with the corresponding vessels of the oppo- site side, and with the anterior ciliary arteries, forms avascular ring, the circulus major of the ciliary muscle, from which small branches are given off, some of which supply the muscle, while others, converging toward the pupil, from a second vascular circle — the circulus minor ; from the latter capillaries are given off which terminate in veins. The veins of the iris terminate in the circular venous sinus known as the canal of Schlemm, situated at the junction of the cornea with the sclerotic. The nerves of the iris are the long ciliary, which, as we have already seen, are given off from the nasal branch of the ophthalmic and the short ciliary nerves derived from the ciliary ganglion. The ciliary nerves, after piercing the sclerotic, pass forward on the surface of the choroid, to which tunic they give branches, to the ciliary muscle, in which they form a plexus continued forward into the iris ; they appa- rently terminate at the pupil in a plexus of non-medullated fibres. It has already been mentioned that the fibres of the third pair of nerves and of the sympathetic exercise an antagonistic influence upon the pupil ; divi- sion of the third pair being followed by dilatation, and that of the sym- pathetic by contraction of the pupil; and that the ciliary ganglion giving off the ciliary nerves supplying the muscular fibres of the iris, is made up to a considerable extent of fibres derived from the third pair and sympathetic. Putting together these facts, and further supposing that the fibres of the third pair and sympathetic pass through the gan- glion, thence, as the ciliary nerves, to terminate in the circular and dilator fibres of the iris respectively, it becomes evident why the pupil dilates if the third pair be divided, since there is nothing then to antagonize the dilating effect of the sympathetic, and why the pupil contracts if the sympathetic be divided, since then there is nothing to antagonize the constricting effect of the third pair. Inasmuch, how- ever, as the nasal branch of the ophthalmic contributes, as we have seen, THE IE IS. 775 to the formation of the ciliary ganglion, the only question about which there can still be any doubt, is as to whether the sympathetic fibres passing to the ganglion of Grasser and thence to the nasal branch of the ophthalmic, influence the radiating fibres of the iris in the same manner as those of the sympathetic, just contrasted with the fibres of the third pair. Now. while it is very possible that some of the fibres of the nasal branch of the ophthalmic passing into the ciliary ganglion are derived from the sympathetic and influence the radiating fibres of the iris, it is probable that most of its fibres are derived from the ophthalmic, and endow, through the short ciliary nerves, together with the long ciliary, the iris and cornea with sensibility. We shall see presently that in the accommodating of the eye for near objects, and in the converging of the axes of the eyes for the same purpose, that the pupil is contracted, and that such is the case when the eye is exposed to a bright light, the pupil being widely dilated, however, when the light is dim. If what has just been said with reference to the influence of the third pair of nerves be accepted, it becomes intelligible why the pupil contracts under the stimulus of light, since the impression made upon the retina by the light being transmitted by the optic nerve to the optic lobe is thence reflected by the third pair to the circular fibres of the iris, causing the latter to contract the pupil. If such be the reflex mechanism, then the pupil should be uninfluenced by light if either the optic or third pair of nerves be divided, and such has been experimentally shown to be the case. It should be mentioned, however, that light, apart from any nervous influence, will exercise a direct stimulating effect upon the iris, causing the pupil to contract even after the eye has been removed from the orbit several hours after death. In connection with the influence Fru. 455. Diagrammatic section of the eyeball, showing difference of refraction for direct and indirect vision. i; ijrs from a point in the line of direct vision, focussed at the retina. 6, y, z. Kays from a point outside the line of direct vision, brought to a focus and dispersed before reaching the retina. (Dalton.) exerted by the third pair of nerves upon the iris, this fact is an impor- tant one, since it offers an explanation of the pupil contracting even 776 THE EYE AND VISION, after division of the third pair. The contraction of the pupil in response to the direct stimulus of light is, however, very different from that observed when the action is a nervous, reflex one, taking place very slowly and requiring a long exposure. It need hardly be men- tioned that section or electrical stimulation of the nerves supplying the iris, involving as they do sympathetic fibres, must modify the vascularity of the iris. Indeed, it has been held that contraction of the pupil is due to a congestion of the vessels, dilatation to a depletion of the same; the change in the diameter of the pupil is, however, too great to be accounted for in that way. While the function of the iris is without doubt that of a diaphragm, regulating, through the pupil, the amount of light admitted to the interior of the eye, it will be observed, from Fig. 455, that not only will the light enter the eye from a point (a) in the line of direct vision, but from a point (b) outside that line, and that the latter rays being brought too soon to a focus, are dispersed again before reaching the retina, and so give rise to confused vision. The Retina. If the choroid, including the tapetum nigrum, be removed under water in the same manner as the sclerotic, the third tunic of the eye Mem.br Fig. 456. Lamina cribrosa ' Section through the middle of the optic nerve and the tunics of the eye at the place of its passage through them. (EcKER.) from without inward, or the retina, will be then exposed as a very delicate and transparent membrane, through which will be seen the posterior portion of the underlying vitreous humor. Within a short time after death, however, the retina loses its transparency and be- comes opaline, the change being hastened by the action of water, alcohol, THE RETINA 777 and other fluids. The retina, varying in thickness from the g^th to the 27rTr tn °f an i ncn ^ extends over the posterior portion of the eyeball to within a distance of about the Y5 tn °f an * ncn °f * ne ciliary pro- cesses, and, if torn from its anterior attachment, presents a finely indented edge, the so-called ora serrata. As a matter of fact, however, the retina Fig. 4")7. Fig. 458. Outer or choroidal sm far The posterior half of the retina of the left eye viewed from before. Twice its natural size. s. Cut edge of the sclerotic, eft. Choroid. >-. Retina: in the interior at the middle the macula lutea with th» depression of the fovea centralis is represented by a >li'^ht oval shade; toward the left side the light spot indicates the colliculus or eminence at the entrance of the optic nerve, from the centre of which the arteria centralis is seen sending its branches into the retina, leaving the part occupied by the macula comparatively free. (Hexle.) does not terminate, as often said, at the ora serrata, but is continuous forward as a thin layer of trans- parent columnar nucleated cells, the pars ciliaris retinee, which, reaching the tips of the ciliary pro- cesses, then disappears. The retina. the nervous tunic of the eve. and inner surface. .1 ,• n -, '-1 i r Diagrammatic section of the human retina. 1. that portion oi it susceptihle ot T „ , t . . , ., „ T , . 1 r Layer of the pigment cells. 2. Layer of rods and being impressed by light, may be cones. . . Membrana limitans externa. 3. Outer regarded as an expansion Of the nuclear layer. 4. Outer molecular layer. 5. Inner Optic nerve, though it is USUally " UC ' ear ,a) 7" 6. Inner mol«cnlar layer. 7. Layer 1 ' . O « of nerve cells. 8. Layer of nerve fibres. •■ Mem- described as being traversed by the brana limitans interna. (Sc.u-i.tze.) latter, like the sclerotic and choroid. The optic nerve apparently, then, penetrates the retina about the -|-th of an inch within, and the ^th of an inch below the antero-posterior axis of the eye. The nerve fibres being at this point, the porus opticus, slightly elevated, give rise to a small eminence (Fig. 456), the colliculus 778 THE EYE AND VISION. nervi optici, between "\vliicli the central artery of the retina aopears, and spreads out arborescent-like, over the inner surface of the retina (Fig. 457), and the branches of the central veins converge and disappear. To the outer side of the optic nerve, about the yL-th of an inch, may- be also seen on the inner surface of the retina, a yellow spot, somewhat elliptical in shape, about the -|th of an inch long, and A-th of an inch broad, its long diameter being horizontal, the so-called macula lutea or limbus lutens of Sommering, presenting in its centre a depres- sion, the fovea centralis, which is situated in the axis of vision. As the retina is so thin at this point that the pigmental layer can be seen clearly behind it, the fovea centralis gives the impression that it is a hole that has been made in the retina. It is an interesting fact, that the yellow spot of Sommering has only been found in the eye of the primates. The sensitiveness of the retina to light varies very much, being greatest at the yellow spot, and gradually diminishing toward the periphery. The difference can be determined experimentally on the same principle as the tactile sensibility of the skin was determined. Thus, if two wires be placed close together, but sufficiently far apart to enable us to distinguish one from the other, and then the eye be so directed that the image of the wires shall fall, first upon the yellow spot, and then upon the great circle of the eye; in the latter case, the wires, to be seen distinctly, must be separated at a distance 150 times greater than in the former one. It is evident, therefore, why the movements of the eyeball all tend to bring the image of external objects upon the yellow spot, and as the latter only constitutes about, the gJj-Q-th of the retina, it follows that but a small portion of the latter is actually made use of in distinct vision. As an illustration, may be mentioned the familiar fact that, in reading, we see one or two words at a time, and that the eye must pass over the whole line in order to read it. The retina consists, microscopically, of a connective tissue scaf- folding, so to speak, supporting eight distinct layers disposed from without inward, as follows (Fig. 458): 1, pigmentary layer; 2, co- lumnar layer ; 3, outer nuclear layer ; 4, outer molecular layer ; 5, inner nuclear layer ; 6, inner molecular layer: 7, ganglionic layer; and 8, nerve layer. The first outer, or pigmentary, layer of the retina, formerly described as the inner layer, or tapetum nigrum of the cho- roid, consists of a single stratum of hexagonal nucleated epithelium cells. The outer surface of each cell, that lying next to the choroid, is smooth, flattened, and usually free from pigment ; the inner portion, prolonged as fine straight filamentous processes between the rods and cones of the second or columnar layer is, however, loaded with pigment. The second, or columnar layer, also known as the the baciilary layer, Jacob's membrane, consists of millions of elongated bodies, the so-called rods and cones, disposed, in a palisade-like man- ner, between the pigmentary layer and the so-called membrana lim- itans externa, which is not a continuous membrane, but is formed through the connective tissue fibres of the retina, uniting; more or less along a definite line at the boundary of the third, or outer nuclear layer. THE RETINA. 779 The rods exceed the cones in number, there being usually about four rods to one cone, except at the macula lutea, where cones only are pres- ent; they have an elongated cylindrical form with a diameter of about T2To~o"t n °f an ^ ncn an ^ a length of -^Q-th of an inch. The cones on the other hand, are shorter and thicker, having a diameter of about 4iW tn °f an i ncn 5 bulge out at the inner end or base, and termi- nate externally by a fine tapering portion. The cones are usually separated by a distance of -g-^Voth of an inch, the intervening por- tion being filled by rods. Through delicate fibre-like prolongations the inner ends of the rods and cones are connected with the third or outer layer of the retina, the outer nuclear layer, which consists of several strata of clear oval elliptical nucleated corpuscles or granules, from both ends of which delicate fibres are prolonged. These outer granules, presenting marked differences, are of two kinds, known as rod granules and cone granules, according as they are connected with the rods or cones, respectively. While the outer fibres of the outer nuclear layer are prolonged into the rods and cones, the inner fibres of the same are prolonged into the outer molecular layer ; the latter in turn appears to be connected through fibrils with the granules of the inner nuclear layer, the latter being connected with the inner molecular layer. The seventh layer of the retina from without inward, the ganglionic or layer of nerve cells, consists of a stratum of nerve cells of a spheroidal or pyriform figure, which appears to be connected by fibres on the one hand, with the preceding inner molecule layer, and, on the other, with the fibres of the optic nerve. The latter, con- stituting the eighth layer of the retina, appears to be bounded by a distinct membrane, the membrana limitans interna, which, however, is not a continuous structure, as its appearance would lead one to sup- pose, but is formed, like that of the membrana limitans externa, by the terminal fibres of the sustenacular or connective tissue framework of the retina being united together at this point. From this necessarily brief description of the minute structure of the retina it will be seen that the layer of the rods and cones, or Jacob's membrane, bounded externally by the pigmentary layer, may be regarded as the termination of the optic nerve fibres. It has already been mentioned that at the macula lutea the rods are absent, the cones only being present; the latter are, further, much longer and narrower than elsewhere, especially opposite the fovea. At this portion of the retina the various layers of which it consists are also very much thinned. The yellow color of the macula, deepest at the centre, is due to a coloring matter diffused through all the layers except that of the cones and the outer nuclear layer. It might naturally be supposed that the anterior layer of the retina, that facing the light, would be the sensitive layer — as a matter of fact, of all the layers of the retina, however, that of the rods and cones is most sensitive to light, as can be shown experimentally by so illuminating the eye that one is able to perceive the shadows of the vessels of his own retina, which are cast upon the layer of rods and cones. The vessels of the retina being situated in its anterior layer, necessarily cast their shadows on one of its posterior layers, and the only reason that we do not ordinarily see these shadows is probably '80 THE EYE AND VISION. that we have become so accustomed to them that they no longer attract our attention. If, however, the source of light be placed in an unusual position, as in Fig. 4/39, then the shadows of the vessels falling on an unusual portion of the layer of rods and cones will be perceived, and will be seen by one looking at a very dark sur- face in a dark room, as if projected at D' C, and resembling exactly the vessels of the retina, the picture of the retina so seen being known as the vascular tree of Purkinje. Now it was shown by H. Muller, 1 that the distance between the anterior layer of the retina, and the layer of rods and cones, was about equal to that between the retinal vessels ami their shadows ; necessarily, then, the layer of rods and cones must be sensi- tive to light. Now, it being remembered that the layer of rods and cones lies next to the pig- mental layer, and that the retina, with the excep- tion of the latter layer, is transparent, it follows that a ray of light passes through the retina until it reaches the pigmental layer, when it ceases to be light, being transformed into either heat, chemical or nervous force ; the latter exciting the rods and cones, gives rise to an impression which is then transmitted back to the optic fibres on the anterior surface of the retina, where it is again reflected along the optic nerve fibres to the optic lobes, etc. Beyond the statement that the rods and cones are excited by the heat or nerve force, or whatever the force may be into which the light is transformed in the pigmental layer, little can be said as to the spe- cial role they play in vision. Such facts, however, as that in the bat, hedgehog, and mole, nocturnal animals, and night birds, also, the retina consists solely of rods; whereas, in day-birds, especially in those which live on insects, of brilliant colors, the retina contains a much larger number of cones than the mammalia, would lead one to suppose that the rods are affected by differences in the intensity of the light, the cones by differences in its quality — that is, its color. While there can be no doubt that the fibres of the optic nerve transmit luminous impres- sions, or their modifications, in the manner described, it can be shown experimentally that the part of the retina where these fibres appear is insensitive to light, and is called, for that reason, the punctum caecum. Thus, if two black points (Fig. 460, A, B), on a piece of paper, separ- Fig. 460. B, a candle placed at the side of the eye — that is, as much to the Bide of the cen- tra ot the cornea as possible. B', interior luminous source, formed by the rays of light concentrated by the crystal- line lens upon the extreme lateral portion of the eye. CD, two vessels of the retina (the size of the retina is here greatly exaggerated). The shadow of these two vessels is seen as if projected at D' ami C. Experiment by Pur- KIN.TE. ated by a distance of two inches, be viewed at a distance of six inches by the right eye, the left eye being closed, the point B will be invisible, being then opposite the punctum caecum, or blind spot. 1 Verhand. der physik med. Gessellschaft zu Wurzburg, v. S. 411. THE CRYSTALLINE LENS. <81 The Vitreous Humor and Hyaloid Tunic. The vitreous humor, while enclosed by the retina, does not, however, lie loosely in the cavity of the eyeball, being invested by a delicate membranous capsule, about the ^^^t h of an inch in thickness — the hyaloid tunic. The latter is thicker in advance of the retina than elsewhere, and, as already mentioned, is impressed by the ciliary pro- cess of the choroid, the zone so formed around the crystalline lens, and well defined by the staining of the process, being known as the zone of Zinn. Anteriorly the hyaloid tunic splits into two laminae, which, diverging at the border of the crystalline lens, becomes confluent with the anterior and posterior surfaces of its capsule, the two laminae adher- ing at intervals; if the space between them be inflated, it will assume the appearance of a beaded canal, surrounding the circumference of the lens — the canal of Petit. Such being the disposition of the hyaloid tunic, it is evident that not only does it support the vitreous humor, through investing the latter, but acts also, from what has just been said, as the suspensory ligament of the lens. The vitreous humor, one of the refractory media of the eye, occupying about the posterior two- thirds of the globe, consists of a clear, glassy, gelatinous matter, divided into compartments by delicate membranous processes, which, given off* by the hyaloid tunic, penetrate its substance. The specks that one sees occasionally floating about, as it were, in the field of vision, the so-called muscie volitantes, are due to the shadows cast upon the retina by the connective tissue elements suspended in the vitreous humor. The Crystalline Lens. The crystalline lens (Fig. 452, 8). the most important of the refracting media of the eye, transparent and very elastic, is situated in the hyaloid fossa of the vitreous humor, behind the pupil, and is enclosed, as already mentioned, between the laminpe of the hyaloid tunic, the latter constitut- ing its suspensory ligament. The crystalline lens is a double convex lens, the convexity of the anterior surface being greater than that of the posterior one, the antero-posterior diameter, ith of an inch, is, however, a little less than that of the lateral one, -3rd of an inch. With advance in age the convexities diminish, the lens becomes harder and inelastic, which accounts for the gradual diminution in the power of accommo- dating the eye to distances. If the lens be examined with a low mag- nifying power, there will be observed on each of its surfaces a star-like body, nine or sixteen rays of which extend from the centre to within about two-thirds of the periphery. The body of the stars and their rays are not of a fibrous character, like the rest of the lens, but consist of a homogeneous substance, which extends between the fibres. The latter are flattened, six-sided prisms, from the jgVo"^ 1 to tne 2TU¥ tD °f an inch broad, and from the tt o~oT tu to ^ ie gTcTo^h °f an mcn thick. Their flat surfaces are parallel with the surface of the lens, and their direction is from the centre, and from the rays of one star to the periphery, where they turn and pass toward those of the other. Chem- ically, the lens is composed of a nitrogenized substance, called crystal- 782 THE EYE AND VISION. line, combined with inorganic salts. The crystalline lens is enclosed within a very thin, transparent, elastic membrane, the capsule, which is lined anteriorly with a layer of delicate nucleated cells. The Aqueous Humor. The aqueous humor (Fig. 4. r >2, 13), the remaining of the refracting media of the eye, is a colorless, transparent, almost watery fluid, filling the anterior chamber of the eye — that is, the space between the cornea in front and the iris and crystalline lens behind, and the posterior chamber, or the space between the posterior surface of the iris and the lens, sup- posing that such a place exists, which is very doubtful, and in any case must be very small. That the aqueous humor is secreted possibly by the bloodvessels of the iris and ciliary processes, or the internal layer of the cornea, is shown by the rapidity with which it is reproduced after it has been evacuated, as in surgical operations performed upon the eye. CHAPTER XLIX PHYSIOLOGICAL OPTICS. Refraction and Accommodation. From the necessarily brief description just given of the eye, it is apparent that it resembles essentially in its structure the camera of the photographer, its refractive media being comparable to the lens, the iris to the diaphragm, the choroid to the internal black- ened surface, the retina to the sensitive plate, the image of the external object being brought to a focus on the retina or sensitive plate respec- tively through the refraction undergone by the rays of light. In order, however, to understand the manner in which the rays of light are brought to a focus on the retina by the cornea, crystalline lens, etc., it will be necessary to describe briefly the phenomena of refraction in general, and the course that rays of light take in passing through refractive media. Suppose that W W (Fig. 461) represent a mass of water, and CA the direction of the beam of light passing through the atmosphere L L, it will be observed that as the ray of light passes through the water it is bent toward the perpendicular A F, but that as it passes out of the water into the air again it is bent away from the perpendicular. Let now the line C A, representing the direction of the incident beam, be connected with the perpendicular B F by the line U E, and the line representing the refracted beam A H, be con- nected with the perpendicular by the parallel line Gil, and it will be seen that the line 6r 11 is three-fourths as long as the line I)E\ and 781 PHYSIOLOGICAL OPTICS. further, that this ratio of 4 to 3, equal to 1.33 (more accurately 1.336), will be invariably the same whatever the angle may be that the inci- dent beam C A makes with the surface of the water IK, except it be a right angle, the beam then passing directly through the water without being refracted at all. If, however, with A as a centre, and a radius A D, a circle be described, the line D E becoming then trigonometrically the sine of the angle D A 31, and the line Gr II the sine of the angle HA N, the law according to which light is refracted as it passes from air through water, may be expressed by saying that the ratio of the sines of the angles of incidence and of refraction is equal to 4 to 3, equal to 1.33, a constant for the particular substance water, or, briefly, that the index of refraction of water is 1.33. That is to say, if the line BE is 4 inches in length, then H Gr will be 3 inches, and so on, in the same ratio. If now, for water, crown glass be substituted, it will be found that the sine of the angle of incidence D E is to the sine of the angle of refrac- tion H Gr not as 4 is to 3, as in the case of air and water, but as 3 to 2 — that is, the index of refraction for the particular substance crown glass is 3 to 2, equal to 1.5. Bearing in mind then, that as the beam of light passes from the air through the glass it is bent toward the perpendicular, but away from it as it passes out of the glass, and that by the index of refraction is meant the ratio of the sines of the angles of incidence and refraction, there will be no difficulty in comprehend- ing the manner in which the direction of a beam of light is altered in passing through biconvex and biconcave lenses. Let (Fig. 462), Fig. 462. for example, represent a biconvex lens of crown glass in which the radii of curvature are nearly equal — that is to say, the two surfaces or curves of the lens are about equally distant from the centres of the circles of which these curves form parts, and that B E, O Gr be two luminous rays parallel with the principal axis A D passing through the optical centre of the lens, which fall upon the lens at the points E and Gr, respectively. Then, according to the law just enun- ciated, the ray B E being first bent toward the perpendicular, and then aw r ay from the perpendicular, and the ray C G- being in the same manner bent first toward and then away from the perpendicular, and the ray A being in the direction of the optical axis, and consequently passing through the lens perpendicularly, and, therefore, unrefracted, REFRACTION AND ACCOMMODATION. 785 it follows that the three rays, and all others parallel with them, will meet at a point F, known as the principal focus, and situated in the principal axis of the lens at a distance from the latter {F H) which will be determined presently, and known as the principal focal distance. The eifect of a biconvex lens is then to bring parallel rays of light to a focus on the side of the lens opposite to the source of light, the amount of converg- ence depending upon the radius of curvature to the lens and its index of refraction, which in this particular case, as we have seen, is 1.5. The converse of this is also true, since if the source of light be at the principal focus F, then the divergent rays after leaving the lens will be brought parallel with each other, and with the principal axis. Such being the action of a biconvex lens, it will be seen from a com- parison of Fig. 462 with Fig. 463, that the action of a biconcave lens Fig. 463 is exactly the opposite of a biconvex one, since the rays of light (B E, C Gr, Fig. 463), after being bent toward their respective perpendicu- lars and then away from them, according to the law of refraction, will diverge from the principal axis A D, instead of converging toward it, and the rays of light B E, C Gr, and all others parallel with them, diverged as K L, M N, instead of being brought to a focus. The con- verse of this is also true, since it will be observed that the converging rays L K, N M are brought parallel with each other on the side of the lens opposite that where the light is now supposed to be. Let us now consider the case in which the luminous object L is beyond the principal focus F (Fig. 464), but so near that all the inci- dent rays L E, L F form a divergent cone, then, according to the law of refraction, the rays, after leaving the lens, will be found to come to a focus at I, and the converse of this will be found to be true, since, if the luminous object be placed at I, the focus will then be at L, hence I and L are conjugate foci. Further, it will be found by experimenta- tion, or by calculation, that if the distance between the luminous object L (Fig. 464) and the lens be twice the focal distance — that is, twice H F equals HI — then the focus I will be situated on the other side of the lens at the same distance, or twice H F, as at the point A, on the axis A D ; if the distance between the lens and the luminous 50 786 PHYSIOLOGICAL OPTICS. object be less than twice the focal distance, the focus I will be situated beyond the point v4, and if more than twice the focal distance, as at L, then the focus will be situated within the point A, as at I — that is, between the point A and the lens. After what lias just been said, with Fig 464. A Z. reference to the manner in which the rays of light are brought to a focus by biconvex lenses, the position of the locus, etc., it will be readily seen from Fig. 465 how the image of an object, as of an illuminated arrow, for example, is formed if a biconvex lens be placed between the latter and a screen. It will be observed, however, that the part of the arrow at a being brought to a focus at x, that at b at//, that the image of the arrow is necessarily reversed, and that if the luminous object approaches the lens its image recedes, and becomes larger, and if it recedes from the lens its image approaches, and becomes smaller, and that if the luminous object be situated at twice the focal distance from the lens, its image will be of the same size, and situated at the same distance from the lens. The distance at which the image is formed behind the lens can be readily calculated by the following formula: - = _ — --, in J J G b j- I which, in the distance of the image, / the local distance of the lens, and I the distance of the luminous object; thus, for example, suppose that/ equals 6 cm., I equals 24 cm., then — = — = - cm. — that is to FiQ. 465. Fig. 466. say, the image will be situated 8 cm. behind the lens. It need hardly be added, that in the absence of a lens, the rays of light will follow the REFRACTION AND ACCOMMODATION '87 paths indicated in Fig. 466, and as the light from a will meet at 4 that from b, at I that from a, no image of the arrow will be formed upon the screen. Having considered now the properties of lenses, let us ?pply what has been established of the same to the elucidation of vision, and show how the rays of light, passing successively through the cornea, aqueous humor, crystalline lens, and vitreous humor are finally brought to a focus on the retina. In considering the paths of the rays of light through the refractive media of the eye physicists make use of a normal schematic eye, a standard eye, so to speak, in which certain cardinal points have been established, and by which the rays of light through the eye can be readily constructed, the focus determined, and the size of the image esti- mated. Let us endeavor, then, to explain what is understood by the cardinal points, the use made of them in elucidating vision, and how they are determined. Let M, M 2 be two refractive media separated from each other by a spherical surface B C (Fig. 467), constituting Fig. 467. what is known optically as a simple collecting system, and N the centre of curvature — that is, the centre of a circle, of which B C forms a part. All the radii drawn from the centre N to B C, such as N B, N x, N y, being perpendicular rays of light falling in the direction of the radii, must pass unrefracted through N as L D, I 1 d 1 , for example, and are called, therefore, lines of direction, while N. the point of intersection of all such lines, is called the nodal point. The line A, connecting N, the centre of curvature, with the vertex I, and prolonged in both direc- tions, is known as the optic axis, the plane H E, perpendicular to the optic axis at I, being called the principal plane, and the point I, within the latter, the principal point. Such being presupposed, it can be shown that all rays parallel with each other, and with the optic axis and the medium M, such as f H, p E, falling upon B C, come to a focus at F 2 in the second medium, called the second principal focus, or second focal point, the plane S F 2 P, perpendicular to the optic axis A, at this point, being the second focal plane. Of course, the con- verse of the above is true — that is, rays diverging from F 2 , such as 788 PHYSIOLOGICAL OPTICS. F 2 I), F 2 C, pass into the first medium parallel with each other, and with the optic axis. Further, it will be seen from an inspection of Fig. 507, that rays which are parallel to each other in the first medium, but not parallel with the optic axis, such as Q T, U Z, come to a focus in the second medium in the point D of the second focal plane, where the non-refracted directive ray L D meets the latter, and that rays diverg- ing from 1> pass through the first medium parallel with each other, but not parallel with the optic axis. It is also evident that all rays, which, in the second medium are parallel with each other, and with the optic axis, such as S B, P C, come to a focus (F 1 ) in the first medium, called the first focal point, or first principal focus, the plane of F 1 p, perpen- dicular to the optic axis at this point, being known as the first focal plane. Of course, the converse of the above is true, viz., that rays diverging from F 1 pass through the second medium parallel with each other and with the optic axis. Finally it follows that the radius of the spherical surface N I is equal to the difference of the distance of the focal points F ' F " from the principal point I — that is, that NI=F 2 I — F'L Such being admitted, it will be seen that an incident ray (Q T) comes to a focus in the second focal plane in the point D, where the non- refracted directive ray L D meets the latter, and that the reversed image of an external object, situated in the first medium like the arrow ^p is formed in the second medium at the point J, where the prolonged ray B F z meets the non-refracted directive ray Y d'. Now did the eye consist simply of two refractive media, separated by a spherical surface, as in the simple collecting system just described, the construction of the refracted ray and of the image of the object, would be essentially the same and equally simple. Inasmuch, however, as the eye consists of four refractive media, cornea, aqueous humor, crystalline lens, and vitreous humor, the cornea and aqueous humor constituting a concavo- convex lens, the crystalline a biconvex lens, and the vitreous humor a concavo-convex lens, to apply to the eye what has just been established would involve proceeding from medium to medium, which would be a tedious operation. If, however, the several media are centred, that is, if they have the same optic axis, which is pretty nearly the case in the eye, then as shown by Gauss, 1 the refractive indices of such a system may he represented by two equally strong refractive surfaces at a certain distance, the rays falling upon the first system not being refracted, but projected, so to speak, parallel with themselves to the second sur- face as at x x', y y' ', refraction taking place at the latter just as if that surface alone was present, the only data required in determining the above, being the refractive indices of the media, the radii of the re- fractive surfaces, and the distances of the latter from each other, which, as we will show presently, can be experimentally determined. Let M l , M 2 , M 3 , and M* (Fig. 468) be four media for example, such as the air, aqueous humor, crystalline lens, and vitreous humor ; B C a spherical surface like the cornea, separating the air from the aqueous humor ; L I 1 Dioptrische Untersuchungen Abhand. Giittiugon Gesells., 1841. REFRACTION AND ACCOMMODATION, '89 the anterior surface of a biconvex lens like the crystalline lens, a spherical surface separating the aqueous humor from the substance of the lens ; and Vv the posterior surface of the lens, also a spherical sur- face, reversely disposed, however, with reference to the cornea and Fig. 468. anterior surface of the lens, and separating the substance of the lens from that of the vitreous humor. Such being the relation of the refractive media, and the spherical surfaces separating them, the cardinal points of such a system, six in number, as deduced from the radii of cur- vature, indices of refraction, etc., determined experimentally are as fol- lows : two focal points (F' F'*), two principal points (P P'), two nodal points (NN'). Inasmuch as the properties of the two foci F' F 2 , as regards the rays of light diverging from or converging toward them respectively, and of the anterior and posterior focal planes f p, S P, are essentially the same as already described and represented in Fig. 507, it will not be necessary to consider them again in detail in this connection. As regards the principal points P P' being in a transparent medium, their relation is such that a luminous point in the medium, appearing to an observer on the left to be owing to the refraction at _P, to one on the right would appear to be at P' . That is to say, P P f , being conjugate foci like LI (Fig. 464), rays of light passing through one point will pass through the other also ; P P' being the principal points, HE and H' E' will be principal planes, and each point of the one plane having a conjugate focus in the other, a ray of light passing through a point on one plane will pass through a corresponding point on the other at the same distance from the axis, and on the same side, the distance F' P being the anterior focal length, and the distance F 2 P' the posterior focal length. In fact, either plane may be regarded as the image, the other being the object. It will be observed that the nodal points 2V2V 7 are so disposed that if the incident ray a N were prolonged, it would emerge parallel with the emergent ray N' a', and vice versa. In a simple lens, however, the optical centre being the only point through which a ray may pass and emerge parallel to its original direction, and all straight lines other than the principal axis passing through the optical centre being secondary axes, it follows that rays passing through the nodal points N N f may be regarded as secondary axes, and that these points represent the optical centres of the surfaces to which P P' (90 PHYSIOLOGICAL OPTICS. respectively belong. Such being the position of the cardinal points in the system of refractive media and spherical surfaces represented in Fig. 468, let a b be an object, an illuminated arrow for example, from which rays pass through the above; its image will be formed at b' a'. That this must be the case, can be at once shown by construction, for the ray af, after cutting the two principal planes r r r , and passing through the posterior focal points F 2 , will meet the line A ;/ a', emerging parallel from the lens parallel with a iV, passing into the latter at the point a', the same point where the ray a F' after passing through the anterior focal point and cutting the principal planes in y y' meets N' a'. In precisely the same manner it can be shown by construction that the point b of the arrow will be brought to a focus at b f . It need hardly be observed that the ima^e of the arrow will be of course reversed. Let us suppose now that the index of refraction for air being taken as unity, that with Listing 1 the index of refraction for the aqueous and vitreous humors has been determined to be equal to 1.3379 (^pf-)-, that of the crystalline lens to be 1.4545 (fy), the radius of curvature of cornea 8 mm. (^ 8 - of an inch), the radius of curvature of the anterior sur- face of the crystalline lens 10 mm., that of the posterior surface 6 mm., the distance of the anterior face of the cornea from the anterior surface of the crystalline lens to be equal to 4 mm., the distance from the an- terior surface of the lens to the posterior surface, or the thickness of the lens, 4 mm., then by means of the appropriate formulae, developed through the relations existing between the radii of curvature, the indices of refraction, etc., and the six cardinal points, the exact position of the latter in the human eye can be shown to be as follows: The anterior principal focus 12.8326 mm. in front of the cornea, the posterior principal focus 22.6470 mm., the anterior principal point 2.1746 mm., the posterior principal point 2.5724 mm., the first nodal point 7.2420 mm., the second nodal point 7.6398 mm. behind the cornea. The distance between the anterior principal focus and the anterior prin- cipal point — that is, the anterior focal length being then 15.0072 mm. = 12.3326 + 2.1746, and the distance between the posterior principal focus and the posterior principal point. — that is, the posterior focal length being 20.0746 mm. = 22.6470 — 2.5724, and the distance between the two principal points 0.3978 mm., and the nodal points 0.3978 mm. The two nodal points or principal points separated by only a distance of 39 mm. (about the -g-g-of an inch) may be regarded practically as coinciding, and we may assume, therefore, for the sake of simplicity, without intro- ducing any very sensible error in the construction, that there is but one nodal or principal point, and therefore but one refractive surface for all the media of the eye. The eye so simplified, and constituting the so- called reduced eye of Listing, enables us to determine very readily the position and size of the inverted image of an external object formed upon the retina. Thus, for example, let A B (Fig. 469) represent an object placed vertically in front of the eye, then A D, B C, being rays of direction and passing directly through the nodal point K; unrefracted rays from A after refraction, will come to a focus on D, rays from B to 1 Dioptrik des Auges. Wagner, Physiologie, Band iv. S. 451. REFRACTION AND ACCOMMODATION. 791 a focus at C, intermediate rays at some intermediate point (G). The rays of light taking this course through the media of the eye, the inverted image of the external object will be found on the retina at D C. Further, since in simple lenses the size of the image is to the size of the object as Fig. 4C9. the distance of the image from the lens is to the distance of the object from the lens, or, as in the case of the crystalline lens which we are now considering, as the distance of the image from the nodal point g k is to the distance of the object from the nodal point M k, it follows that the size of the image _ size of the object X distance of image from nodal point distance of object from nodal point. The distance of the image from the nodal point being, however, the posterior focal distance may be regarded as equal to the distance of the retina from the cornea (P'), minus the distance of the nodal point from the cornea (R), the distance of the object from the nodal point being equal to the distance of the object from the cornea (P), plus the distance of the cornea from the nodal point (R); such being admitted, the formula for the size of the image may be conveniently expressed as follows : I = P+ R Supposing that the object be 1000 mm. high, P' = 22.6470 mm., R — 7.4 mm., P = 15.2396 metres, then j_ 10 00 X 15.247 15.2396 + 7.4 ' That is to say, that the image of an object 1000 mm. (39.3 in.) in height seen at a distance of 15.2396 metres (50 feet) is 1 mm. (yg-th of an inch) in height, or a thousand times smaller. It will be observed also from Fig. 469 that the visual angle A k B — that is, the angle under which A B is seen — being the same as the angle under which the objects x y, r s, are seen, that the image of all three objects formed on the retina must be the same, and that, therefore, the apparent size of all three objects, though diifering in size, will be the same also. It is also 792 PHYSIOLOGICAL OPTICS. Fig. 470. obvious that the size of the visual angle depends on the size of the object and distance of the latter from the eye. From the fact of the smaller the visual angle under which distinct vision is possible the more acute the vision, the latter is evidently inversely as the size of the visual angle. The measure of the acuteness of vision in general use among physiolo- gists and ophthalmic surgeons, based upon this principle is a series of letters, C CB, the thickness of which is one-fifth of their height, and made of such a size that at a distance of 20 feet they subtend an angle of 5 minutes, the acuteness of vision being expressed by the ratio of the distance at which such letters are still distinctly recognized to the dis- tance D, at which they subtend an angle of 5 minutes — that is to say Y = -^- Suppose, for example, that the person whose vision is being tested can recognize a letter at ten feet, then his acuteness of vision will be V = 77 = ^j = ~?p tnat °f one whose vision is perfect — that d 20 is in whom V = 77 =-^=1. Practically, the smallest visual angle permitting distinct vision is about 60 seconds, and corresponding, as it does to a retinal image of about 0.004 mm., it will just about cover one of the cones of the retina. Two points seen under such a small visual angle would therefore appear as one. It has already been mentioned that the cardinal points, by means of which we follow the rays of light as they pass through the media of the eye and determine the position and size of the retinal image, are deduced from the indices of refraction of the aqueous and vitreous humors, lens, radius of curvature of cornea, etc., experimentally determined. Inasmuch as the methods by which the indices of refraction of the media of the eye are determined, are essentially the same as in the case of water or glass, and represented in Fig. 465, it need not in this connection be described again. The radius of curvature of the cornea and crystalline, how- ever, being deduced by formuhe from the size of their reflected images, and the latter being measured by the ophthalmometer, the method of determination merits at least a brief descrip- tion. The principle upon which the oph- thalmometer, invented by Helmholtz, 1 is con- structed is, that if an image of an object be viewed through two piano-parallel glass plates (Fig. 470) the image, through refraction, will appear double, and that if the plates be so approximated that the inner edges of the two images are brought in contact, then the distance between the outer edges of the two images will be twice the size Object viewed through two glass plates. 1 Optique Physiologique Traduite, by Juval et Klein, p. 11. Paris, 18G7. REFRACTION AND ACCOMMODATION. 793 of the single image. To measure the size of an image by the ophthal- mometer, it is only necessary, then, to determine the lateral displace- Fig. 471. M=d} // A b 9 Schema of ophthalmometer. ment of the images, which is accomplished by observing the angle made by the glass plates P P, with the axis X of the telescope (Fig. 471), through which the image is viewed, and substituting the value of the angle so obtained in the formula T _ or sin (a — B) 2T cos B in which L = the lateral displacement, T= the thickness of the glass plates, a = the angle of incidence, B = the angle of refraction. The manner in which the above formula is developed, will become clear from a consideration of the relation of the parts involved, as represented in Fig. 472, in which, for simplicity, A B C D is one of To illustrate the measurement of the lateral displacement, ab. the plates of glass placed in front of the objective of the telescope, and a c the incident ray emanating from the image viewed, whose size is to be determined. Such being the case, the ray a c, according to the law of retraction, will be bent (c i) toward the perpendicular n k, as it passes through the glass and away from the perpendicular, as i Z, and parallel with a c as it emerges from the glass, and the angle a en will be equal to the angle lim, parallel rays falling upon parallel sur- 794 PHYSIOLOGICAL OPTICS. faces. Now since the angle of incidence acn or a bears such a rela- tion to the angle of refraction ick or B, that = index of refrac- sin B tion = 1.65 in case of flint-glass, it folknvs that sin a = 1.6 (sin B), or, sin B = — — — that is, when we learn the value of a by obervation, we 1.6 J can find the value of B by trigonometric tables. The relation of the angle of incidence being to that of refraction, such as just described, the point a, to the eye of an observer at I, would appear to be at b, the glass plate effecting, therefore, a lateral displacement of the point a, to an extent a b, which is measured by determining the equal dis- tances ef. The latter being equal to the hypothenuse into the sine of the opposite angle — that is, cf=ci sin cif, it follows that if Ave can determine c i and sin c if, we will obtain cf or its equal a b, the lateral displacement, or that which we desire to determine. Since the base he is equal to the hypothenuse ci into the cosine of the adjacent angle ick or B — that is, that kc = ci cos B, it follows KG thatc^= ~, and as kc is equal to the thickness of the glass cos B 1 8 plates, which is known, we may call it T and say that ci= . Further, the angle cif is equal to the angle hif less the angle hie, but h if is equal to the angle of incidence n c a or a, in that their sides are parallel, and the angle hie is equal to the angle of refraction ick or B, in that they are alternate angles, therefore cif '= hif — hie, or sin cif — sin (a — B). Substituting these values of ci and sin c if in the formula ke = ci sin c if we obtain k c or a b = T sin — -i. Inasmuch, however, as there are two plates in the ophthal- cos B mometer, the complete formula will be , T 27 7 sin (a — B) ab or L = ^ ', cos B that is to say, the lateral displacement will be equal to twice the thickness of the glass multiplied by the difference between the sine of the angle of incidence and the angle of refraction divided by the cosine of the latter. Suppose, for example, that the thickness of the glass plate be 0.325 mm. the index of refraction of the flint glass plate 1.65, the angle of incidence or a = 6°, as observed by the ophthalmometer, the angle of refraction 5 = 3° 48', as learned from the value of the angle a by trigonometric tables, then the lateral dis- placement will be Z^2X0.325 siD ' 6 °- 3 ° 48/ ) cos 3° 48 / and using logarithms L = 0.025 mm. In using the ophthalmometer the intrument should be placed in the dark chamber that is in a room with blackened walls, from which all sunlight can be excluded, and at a distance of ten feet from the eye REFRACTION AND ACCOMMODATION '95 under examination, and on a level with it. A lighted candle being placed on the right- or left-hand side of the eye to be examined, on the left side for the left eye, on the right side for the right eye, as near as possible, and a screen intervening to protect the eye from the glare, by means of three small rectangular mirrors fixed by universal joints to a graduated wooden rod the light from the candle is reflected upon the eye. The vernier of each scale of the ophthalmometer further being at zero, and the instrument focussed, the observer on looking through the telescope at the eye under observation, will then see three minute specks of light upon the cornea, thus, a a a- If now, however, the rotating screws be turned, which has the effect of placing the plates of glass obliquely, six minute specks of light will be seen on the cornea, thus, a a a a a a a b c representing one-half of the amount of dis- placement in the one direction, def, one-half the amount in the other direction — that is to say, the three original images have been dis- placed through a distance equal to that between the two extreme images. Observing now the angle through which the plates have been moved, of the angle of incidence = a, and substituting the same in the formula just developed, the size of the corneal image due to the reflec- tion of the light of the candle from the three mirrors will be determined. In using the ophthalmometer, it is not absolutely necessary to make use of the three mirrors just described, since as originally used, the object thrown upon the cornea was the distance between three candle flames placed beside the experimenter, two on his right hand, and one on his left. In order to avoid any calculations, Donders 1 suggests that a scale be prepared, in which each degree or fraction of a degree corre- sponds to a certain size in millimetres, the size of the corneal image being then determined by simply referring to the scale. It will be Fig. 473. f = the focal length of the lens, P = the distance of the punctum proximum (12 cm. = 4.8 inches), R = that of the punctum remotum, which in the normal eye equals infinity, therefore - = -— cm., that is to say, 12 cm. is the focal distance of the convex lens, representing the power of accommodation. As the elasticity of the lens diminishes as a result of a^e and as further it becomes more flattened, the lens gradually loses the power of changing its shape, of becoming more convex as an object approaches the eye, and consequently the punctum proximum recedes further and further from the latter. The diminution in the ran^e of accommodation so produced is known as presbyopia, which, it will be observed, is an anomaly of accommodation, differ- ing therefore from myopia and hypermetropia, which are anomalies of refraction. While the treatment of presbyopia belongs rather to the ophthalmologist than to the physiologist, it may be mentioned that it can be corrected by placing a lens before the eye, such as would give the rays the direction they would have if they came from the normal punctum proximum — the focal length of the lens required being obtained from the formula — = — — , in which/ = the focal length, P = the f P p normal punctum proximum, and p = the punctum proximum of the presbyopic eye. Suppose the latter to be 30 cm. (12 inches), then - = 111 L — _z_= , that is, the lens required must have a focal length of 12 30 20' l 20 cm. (8 inches). In concluding the subject of refraction and accom- modation, it may not appear superfluous if a brief account of the ophthal- moscope invented by Helmholtz be offered, by which the fundus of the ACCOMMODATION. 805 normal and diseased eye is examined, and through which, in the hands of Donders, Graefe, and others, ophthalmic medicine was revolutionized. The interior of the eye under ordinary circumstances appears dark, since the observer being between the eye to be observed and the source of light intercepts the very rays whose reflection from the interior of the eye would form the image that it is desired to see. Further, the diverging rays from the interior of the eye converging as they pass through its media, are brought to a conjugate focus outside of the eye, which, to be seen, would have to be viewed by the observing eye at a distance equal to that of distinct vision — that is, so far from the observed eye, that little or nothing could be distinguished. If, however, the interior of the eye be illuminated by light reflected from a concave mirror the centre of which is perforated, and through and behind which the observer can view the e} T e, then the conjugate focus formed as just described by the rays reflected from the interior of the eye, can be more or less distinctly seen. The image of the retina, entrance of the optic nerve, etc., as viewed by such a mirror as that just described, and con- stituting the original ophthalmoscope, become, however, much more dis- tinct, if - in addition to the mirror the observed eye be viewed through a lens. Suppose that the lens used be a concave one, then rays of light emanating from a point of the retina (A, Fig. 484) (the illuminating The ophthalmoscope with erect image. rays from the mirror (M) being omitted in the figure for simplicity), which would be brought to a focus at B, the image being then real, magnified, and inverted by the action of the interposed diverging lens, whose focal distance is P B, are brought to a focus at D, the image being virtual, magnified but erect; that is, the rays which come to the observer's eye from the retina (A) appear through the action of the lens to come from D. On the other hand, suppose that the lens used be a convex one, then (Fig. 485), the rays from the retina (A) which would Fio. 485. The ophthalmoscope with inverted image. otherwise come to a focus at B through the still greater converging effect of the lens, will come to a focus at <1, the image formed being real and inverted, and, while larger than its object («) on the retina, is smaller than the image formed when the concave lens is used. CHAPTER L. BINOCULAR VISION. SENSATION AND PERCEPTION OF SIGHT. PROTECTIVE APPENDAGES OF THE EYE. In describing the manner in which vision is effected we have hitherto supposed it as being accomplished by a single eye ; it remains for us now to consider how both eyes act in viewing objects, or binocular vision. It might be naturally suppposed from seeing an object single, when viewed with one eye, that it would appear double when viewed with both eyes. A little observation will, however, make it clear that with one eye we see but one side, so to speak, of an object, the right side, for example, Avith the right eye, the left side with the left eye, and that in order to obtain a perception of the entire object we must see the two sides of the object simultaneously. Thus, for example, when we look at a truncated pyramid (Fig. 486, B) placed in the Fig. 486. \ / \ / N B ^ \ / \ / V a Illustrating the principle of the stereoscope and binocular vision. middle line before us, the image falling upon the right eye is such as represented at R, that upon the left eye at L, the perception of the form of B is the projection, being only obtained when the object is viewed by both eyes simultaneously. When two dissimilar images, one of the one eye, and the other of the other, thus fused into one per- ception, the inference by the mind is that the object giving rise to the images is solid. Such, indeed, is the principle of the stereoscope, in which two slightly dissimilar pictures, such as would correspond to the images of two objects as seen by each eye respectively, are by means of mirrors or prisms cast upon the retina so as to give rise to a single perception, that of solidity, or of three dimensions, though each picture has a surface of but two dimensions. In order, however, that the two retinal images shall be fused into the one mental per- ception, it is essential that the two images shall fall on corresponding points of the retina, at a a', b b', c c' (Fig. 487), otherwise there will be double vision — hence, in viewing an object with both eyes the latter are converged, the angle made by the axes of the two eyes being large if the object is near, and small if the latter be distant. It BINOCULAR VISION. <"7 will be observed further, from an inspection of Fig. 487, that since ab = a' V, that the angle 1 = 1 and the angle 1' = 1', and that since the angle 2 = 2 the angle 3 = 3, and that since be = b' c', that the angle 4 = 4, 5 = 3. But it follows from the angles 3 3 and 5 being Fig. 487. Diagram to illustrate theory of corresponding retinal point. (HcKendrick.) Diagram to illustrate the horopter. (McKendrick.) equal, that a", b", c", cannot lie in a straight line, it being the property of a circle only that triangles erected on the same chord and reaching the periphery, have at the latter equal angles. The line joining the points a" b" c" must therefore be a circle 1 (Fig. 488), of which the chord is equal to the distance between the points of decussa- tion (K K) of the rays of light in the eye. Such a circle is known as the horopter, and all objects not lying in it are seen double, their images falling upon corresponding points of the retina. Standing up- right and looking at the distant horizon, the horopter would be approxi- mately for normal long-sighted persons, a plane drawn through the feet — that is to say, the ground on which they stand. The eyeball nearly filling the cavity of the orbit, and resting poste- riorly upon a bed or cushion of adipose tissue, is moved by six muscles, the recti superior and inferior, externus and internus, and the obliqui superior and inferior. The effect of these muscles when acting sepa- rately is quite apparent from their origin and insertion. The four recti in the order named, arising from the apex of the orbit around the margin of the optic foramen, pass straight forward, piercing the capsule of Tenon or the fibrous membrane surrounding the sclerotic, to be inserted into the latter tunic at about the third or fourth of an inch behind the margin of the cornea, move the eye upward, downward, outward, and inward. The superior oblique muscle, arising from the optic foramen, proceeds toward the internal angle of the orbit and terminates in a round tendon, which, passing through a fibro-cartilaginous ring or pulley, is thence reflected backward and outward to be inserted into the sclerotic between the superior and external recti muscles. Its 1 Mull.r : Physiology, trans, by Bftly, vol. ii. p. 1177. London, 1842. 808 BINOCULAR VISION action is to rotate the eyeball downward and outward. The inferior oblique muscle arising from the orbital plate of the superior maxillary bone close to the external border of the lachrymal groove passes out- ward and backward between the inferior rectus and the floor of the orbit to be inserted into the external and posterior part of the sclerotic. Its action is to rotate the eyeball upward and outward. It can be shown, however, theoretically, as well as by actual observation, that the six muscles whose actions have just been described may be regarded as consisting of three pairs, each of which rotates the eye round a par- ticular axis. Thus the recti superior and inferior rotate the eye up and round a horizontal axis directed from the upper end of the nose to the temple; the obliqui superior and inferior obliquely round a hori- zontal axis directed from the centre of the eyeball to the occiput; the recti internus and externus from side to side round a vertical axis passing through the centre of rotation of the eyeball situated a little behind the centre of the optic axis, parallel to the median plane of the head, the latter being vertical. The different muscular actions just described may be briefly summarized in tabular form, as follows : Table LXXXI. — Action of Ocular Muscles. Number of muscles acting. Direction. f Inward, One Two Three ( Outward, Upward, Downward, Inward and upward, Inward and downward, Outward and upward, Outward and downward, Muscles acting. J Internal rectus. { External rectus, f Superior rectus, j Interior oblique. j Inferior rectus. | Superior oblique, f Internal rectus. ! Superior rectus. Interior oblique. Internal rectus. Inferior rectus. | Superior oblique. ( External rectus. Superior rectus. ( Interior oblique. ( External rectus. ■I Interior rectus. ( Superior oblique. It will be observed, from what has just been said of the action of the ocular muscles, and as seen from a glance at Table LXXXI., that even in viewing an object with a single eye, that a considerable amount of muscular coordination must take place, since when the eye is moved in any other than the vertical or horizontal meridian three muscles at least must be stimulated, relatively to the amount of inclination of the visual axis needed. Such being the case in single vision, necessarily, then, the amount of muscular coordination required in binocular vision must be much greater. If the eyes of any person be observed, it will be noticed that the two eyes move alike, when the right eye moves to the right so does the left, and to the same extent if the object looked at be distant, if the right eye looks up so does the left, and so in every other direction. Briefly, then, the eyes move in such a manner that the SENSATION OF SIGHT. 809 images of an object always fall upon corresponding points of the retina, the essential condition, as we have seen, for the production of single vision, the movements of the two eyes ceasing to agree with each other only when the power of coordination is lost, through disease or by alco- holic or other poisoning. By movements of the eyes apart, however, from those of the head, the extent of the field of vision may amount to as much as 200 in the horizontal and 2U0 in the vertical meridian, that of a single eye being about 145 for the horizontal and 100 for the vertical meridian. Sensation of Sight. Rea-ardincr the sensation of siodit as due to the stimulation of the retina by light, observation teaches, as might be supposed, that the intensity and duration of the sensation will vary according to the strength of the luminous vibrations, and the length of time during which the latter continue to fall upon the retina. That the intensity of the sensation varies with that of the luminous object is a matter of daily experience, a wax candle, for example, appearing brighter than a rushlight. With a little experimentation it becomes soon apparent, however, that the ration of the sensation to the stimulus is not a simple one, since while the sensations increase as the luminosity of the object increases, the sensations increase less and less, until finally there is no appreciable increase of sensation however much the luminosity may be increased — that is to say, when a light reaches a given brightness it appears so bright to us that we cannot tell when it becomes anv brighter. It is much easier, therefore, to distinguish the difference between two feeble lights than the same difference between two bright lights — in fact, if the latter be very bright it becomes then impossible. Thus, for example, while there is no difficultv in distinguishing between the light of a candle and that of a rushlight, it would be impossible to distinguish such A difference between the light of two suns, supposing the light of the one to be in excess of that of the other in the same ratio as that of the candle over that of the rushlight, just as an addition of half an ounce to twenty pounds will not be appreciated by the sense of weight. Further, it will be found that if we let the shadows of two rushlights, for example, fall upon white paper and then move one of the lights away until the shadow ceases to be visible, that in performing the same ex- periment with two wax candles the candle will have to be moved through the same distance as that of the rushlight before its shadow ceases to be seen, the smallest difference in light in both cases appreciable being in- variably about the y-J-jjth °f * ne total luminosity made use of. In this connection it may be appropriately mentioned as elsewhere, that whether the sensation be that of sight due to the stimulus of light or of hearing, due to sound or of temperature, due to heat or of touch, due to muscular effort or to weight, thai the smallest difference of appreciable sensation is invariably a constant fractional portion of the total force, the cause of the sensation made use of, differing, however, for the various sensations. Thus, for example, suppose that the eyes being bandaged and the hand extended and supported, successive weights, as a drachm, ounce, and pound be placed upon it, it will be found, whatever be the weight origin- 810 SENSATION OF SIGHT. ally placed upon the hand, that in order to appreciate a distinct difference, one-third of the weight will be required to be added or taken away. In the case of muscular effort, however, only the j -d, 4e, SENSATION OF SIGHT. 811 indicates the weights that must be used, in order that the perceptible difference in sensation should be doubled, tripled, quadrupled, quin- tupled ; and which, if the sensations be as 1, 2, 3, 4, the weights, or their representation, the ordinates will be found to be as 10, 100, 1000, 10,000 — that is to say, the sensation varies, not as the stimulus, but as the Fig. 489. Graphic illustration that sensation is proportional to logarithm of stimulus. logarithm 1 of the stimulus, the numbers 1, 2, 3, 4, being the logarithms, respectively, of 10, 100, 1000, 10,000. To those familiar with the lan- guage of the calculus the above law, that of the sensation varying with the logarithm of the stimulus, or the Weber-Fechner law of sensation, may be briefly described as follows : Let s. a sensation, be a function of a stimulus x, then ds = K — - (1), ds being the smallest appreciable x increment of sensation due to dx, the corresponding increment of the stimulus x, and K a constant. Integrating (1) we obtain s = K log. x -f- c, which becomes = K log. x' -J- c if x be diminished to x', at which the sensation ceases — that is, c = — K log. x\ and s = K log. © O x — K log. x', or s = K log x' Returning from this little necessary digression to the sensation of sight, it is evident that the duration of the sensation is longer than that © © of the stimulus, the sensation of sight and the stimulus of light being © _© © comparable, in this respect, to a muscular contraction, as induced by a single induction shock. It is for this reason that if two flashes of light follow each other sufficiently quickly within the one-tenth of a second for a faint light, and the one-thirtieth of a second for a strong one, the two sensations arising are fused into one. Hence, the fact of a lumi- nous point moving rapidly around in a circle giving rise to the sensation of a continuous circle of light, which reminds one of the production of muscular tetanus. That the duration of the stimulus of light necessary to give rise to the sensation of sight must be very short, is shown from the fact of the electric spark being seen, though the latter is known to 1 A logarithm of a number is the exponent of the power to which it is necessary t" raise a fixed number to produce the given number. Suppose the fixed number to be 10, the given number IO0 or 1000, then 2 and 3 will be the logarithms of 100 and 1000 respectively, since lo- = 100, 103 — pjiin. 812 SENSATION OF SIGHT. last but the vr , ,, Sol* Si>* Utf KeS Mi? It is obvious, therefore, why when the notes Ut 3 Sob Ut*are sounded on a musical instrument at the same time with Ut 2 , the resulting sound should be harmonious, since these three sounds reinforce respectively the first, second, and third overtones due to the string vibrating in halves, thirds, and fourths respectively. In the same way, Mi 4 Sol 4 Si L ' 4 Ut" 1 Re° Mi° reinforcing the overtones due to the string Ut 2 vibrating in fifths, sixth-, sevenths, eighths, and ninths, when sounded with Ut 2 , will also give a harmonious sound. Having described the manner in which partial vibrations are formed, and how in being superimposed upon the fundamental vibration a resultant vibration arises, and how the overtones due to the partial vibrations in being blended with the fundamental tone due to the fundamental vibration give rise to a compound tone, it becomes evident without further explanation, that by means of the Helmholtz resonators 1 Op. cit . p. 68 836 PHYSIOLOGICAL ACOUSTICS. Fig. 510. we can analyze any sound, and demonstrate whether it be a simple or compound one, and, if the latter, what overtones are present, and in this way show on what the quality, timbre, or klangfarbe of the sound depends. Thus, for example, the quality of the sound of the piano, as compared with that of the violin, depends upon the fact that in the case of the latter, when bowed, though the first six overtones or harmonies are present, as in the case of the piano, they are so faintly sounded as to be overpowered by the seventh, eighth, ninth, and tenth overtones. The overtones in the case of an open pipe are not the same as in the case of a closed one; those of the clarionet differ from those of the oboe, and so through the whole range of orchestral instruments. Inasmuch, however, as in addressing a large audience, from the nature of the case, it is impossible for each one individually to make use of the resonators and satisfy himself of the existence of overtones upon which the quality of a sound depends ; the author is accustomed to demonstrate the same by means of Koenig's manometries apparatus. 1 The latter (Fig. 510) consists of a frame supporting fourteen resonators each of which leads by a narrow India- rubber tube into a small chamber, com- pletely divided into two, by an India- rubber partition. The posterior part of the chamber is in communication with the resonator, the anterior part provided with a gas jet with a reservoir containing gas, led thither by an ordinary gas pipe. Each resonator is connected in this way with its own gas chamber and burner, the burners being all placed in a row, one above the other. Opposite the gas burners is a long mirror with four reflecting sides, at right angles to one another, which can be revolved on an almost perpendicular axis by a toothed wheel arrangement. Turn- ing on the gas, and lighting it as it issnes from the jets in the chambers connected with the resonators, and revolving the mirror, the light reflected from the surfaces of the latter appears as continuous bands. If, however, the air in any one of the resonators be thrown into vibration, then the India-rubber partition of the chamber separating, on the one hand, the air continuous with that of the resonator, and, on the other, the gas, will vibrate, and the gas and flame thrown into agitation, the particular band of light, the corre- sponding band of light, becoming segmented. Let now a tuning fork Ut 3 , vibrating 256 times a second, be sounded in front of the apparatus ; at once the flame in connection with the resonator marked Ut 3 , will become segmented, but the remaining flames will still appear as continuous bands of light, since if the tuning fork be properly bowed the sound produced will be a pure, simple tone, unaccompanied with overtones. Let now, however, the Ut 3 Do 3 of the piano, or an Manometric apparatus. (Kcenig.) 1 Rudolph Koenig, Quelques Experiences d'Acoustique, p. 73. Paris, 1882. QUALITY OF SOUND. 837 open organ pipe two feet long, giving, therefore, the same fundamental note, be sounded, and immediately some of the remaining bands of light will become segmented, as well as the one connected with the resonator marked U 3 , since the air of the resonators with which they are in con- nection has been thrown into vibration by the particular overtones pre- sent, as, for example, in Fig. 511, a, b, respectively, representing the Fig. 511. Fundamental note. Octave of preceding. flames due to the fundamental and octave above it. In this way an optical demonstration can be given of the fact that the quality of the note of any musical instrument depends upon what particular overtones or harmonics accompany the fundamental, and, as we shall see pres- ently, of the manner in which the vowel sounds are produced by the human voice. As it is important that the manner in which resonators reinforce or intensify sounds should be understood, a brief account of the cause of resonance in general may be as appropriately considered here as elsewhere. It is well known that the velocity with which sound travels in air at the freezing temperature is 1090 feet in a second, the velocity increasing about two feet for every additional degree of heat, Centi- a B Fig. 512. -2G inches ->c V Vibrating of tuning fork. (Tyxdall.) grade (1.8° F.). Let us suppose that the temperature of the surround- ing atmosphere be 8.5° Cent. (47.3° F.), and that a tuning fork vibrating 256 times per second be sounded ; it is obvious that if, at the 838 PHYSIOLOGICAL ACOUSTICS. Fig. 513. end of the second, the sound lias reached a distance of 1109 feet, then each vibration must have been 52 inches long, since 52 by 256 is 1109 feet, and as a vibration or wave of sound consists, as we have seen, of a condensation and rarefaction, the condensation and rarefaction must have been both just 2b' inches in length — that is to say, as the prong of the tuning fork (Fig 512) moves from A to B, a distance of perhaps the one-twentieth of an inch, it generates the one-half of the sonorous wave, the condensation, the foremost point of which readies the point C, a distance of twenty-six inches, at the some instant that the prong of the fork reaches B, and that as the forward motion is being delivered up to the air succeeding C — that is, as the prong of the fork moves back from B to A, the other half of the sonorous wave, is generated, the rarefaction. Such being the case, let the tuning fork now be sounded over a jar (Fig. 513), of which the column of air within, from top to bottom, meas- ures just thirteen inches, or one-fourth the length of the vibration or wave due to the sounding of the fork. It follows from what has just been said, that during the time the prong of the fork moves from a to b, the condensation, the air which it produces runs from the top of the jar to the bottom, thir- teen inches, and from the bottom to the top, thirteen inches, or twenty-six inches in all, the reflected Avave reaching the prong of the fork just as the latter reaches b ; and similarly, that during the time the prong returns to a from b, the rare- faction to which it gives rise, runs down from the top of the jar to the bottom, and up again, also a distance in all, of twenty-six inches. The vibrations of the fork being, therefore, perfectly synchronous with the vibrations of the aerial column within the jar, the motion will accumulate in the latter, and spreading out into the room, the sound will be greatly augmented as everyone will appreciate, when the tuning fork is sounded first at some distance from, and then over the mouth of the resonating jar. From what has just been said, it necessarily follows that if we sound other tuning forks, vibrating at different rates, the length of the column of air must be varied accordingly if we wish to make use of the latter as a resonator. It is for this reason that the resonators we made use of in demonstrating the presence of overtones were of different size, and that the resonators of Koenig's manometric apparatus are so constructed, that by drawing them out to varying distances, the sound that each resonator will reinforce, will then be ap- parent. It was on account of its resonating qualities, that in sounding the bell in a preceding experiment, the latter was placed near the mouth of ajar, by means of which the intensity of the sound was very much increased. The ancients were well acquainted with the efficacy of such aids in intensifying sound, resonant brass vessels being placed, according to Vitruvius, in their theatres to strengthen the voices of the Tuning fork vibrating with jar. in uimsou QUALITY OF SOUND. 839 actors. It is on account of the resonating properties of sounding boards, that the latter are associated with musical instruments, and that the stethoscope also has proved in the hands of the clinician such an aid in the diagnosis of disease by auscultation. It may not prove uninterest- ing in this connection to mention that the velocity of sound in air was ap- proximately deduced by Newton ' from the elasticity and density, the velocity being shown to be directly proportional to the square root of the elasticity, and inversely as the square root of the density. The im- mortal author of the Principia, however, failed to take into considera- tion, as shown afterward by Laplace, 2 that the condensation in giving rise to heat, and increasing the elasticity, thereby increases the velocity, and that the discrepancy existing between the velocity of sound experi- mentally observed, and as theoretically calculated by Newton, disap- pears if the calculated velocity be multiplied by 1/1.414 or the square root of the ratio of the specific heat of air at constant volume, to that at constant pressure. Thus, if J ri be equal to the true or observed velocity, J^be equal to the velocity as calculated by Newton, or 916 feet per second, OP the specific heat of air at constant pressure, OV OP the specific heat of air at constant volume, and the ratio of = 1 . OV 1.414, then V = V ^ ( JTv or F = 916 x VYXu = 109 ° feet ' As a matter of fact, however, at the present day the ratio 1.414 per second is obtained by the reverse operation — that is, knowing J 77 and V, V' 2 CP 2 ■ OP evidently then = 2 , from w T hich we obtain the ratio — V 2 O V ' O V Having shown that sounds are produced by the vibrations of plates, bells, strings, pipes, reeds, membranes, etc., and how the same are dis- tinguished by their intensity, pitch, and quality, let us turn now to the consideration of the larynx, and by means of the principles just estab- lished, endeavor to determine what kind of an acoustical instrument the larynx is and how the voice is produced by it. 1 Philosophise Naturalis Principia Mathematica, Liber Secunrhis Propositio xlix. Londini, 1726. 2 Mecauiqtie Celeste, tome iv p. 87. Hull, ties Sciences Sue, Philomatiqae, 1821, pp. 101-183. Puisson, Annates de Chimie et Physique, tuuie xxiii. ZM. CHAPTER LI I. THE LARYNX, AND THE PRODUCTION OF THE VOICE AND SPEECH. Fig. 514. The larynx, the organ of the voice, situated at the top of the trachea and below the root of the tongue and the hyoid bone, consists of a frame- work of cartilages, connected by ligaments, provided with muscles, bloodvessels, and nerves, and lined with mucous membrane. The cartilages of the larynx are nine in number, three single and symme- trical pieces, the thyroid, cricoid, and epiglottic, and three pairs, the arytenoid, cornicula laryngis, and cuneiform ; the last two pair are, how- ever, very small. The thyroid (Fig. 514), the largest of the cartilages of the larynx, consists of two lateral ring-like plates or alse, continuous in front, but diverging behind. The angular projection in front, sur- rounded by a deep notch much more marked in the male than in the female, and in some men more than others, is known as Adam's apple, while the blunt processes connected through ligaments with the hyoid bone, into which the posterior angles are prolonged, are called the supe- rior and inferior horns, of which the superior is the larger. The cricoid cartilage, resembling in shape a seal ring, is situated between the thyroid and the first ring of the trachea, with the latter of which it is con- nected. While quite narrow in front, the cricoid cartilage deepens consid- erably posteriorly, and at the back part of its upper border, articulates by means of two convex oval promi- nences with the arytenoid cartilages, and laterally through two circular facets with the inferior horns of the thyroid cartilage. The arytenoid cartilages are two three-sided recurved pyramids, resting by their bases upon the posterior and highest portion of the cricoid cartilage. The apex of each arytenoid cartilage is usually surmounted by a yellowish cartilaginous nodule, the corniculum laryngis or cartilages of Santorini. while the folds of mucous membrane, extending from the summit of the arytenoid cartilages to the epiglottis, >*. Bird's-eye view ofTarynx from above : o e h, the thyroid cartilage, embracing the rings of the cricoid, r u x h>, and turning upon the axis, x z, which passes through the lower horns. N F, N F, the arytenoid cartilages connected by the arytenoideus transversus ; T v, T v, the vocal ligaments ; N x, the right crico-arytenoideus lateralis (the left being removed) ; v kf, the left thyro-arytenoideus (the right being re- moved) ; N I, N 7, the crico-arytenoidei postici ; B, b, the crico-arytenoid ligaments. (Carpenter.) THE LARYXX. 841 contain also two small yellowish cartilaginous bodies, the cuneiform car- tilages or cartilages of Wrisberg. The remaining cartilages of the larynx, the epiglottis consisting really of fibro- cartilage, somewhat spoon-shaped in form, while free at its broad extremity, is attached at its narrow end by a band of fibro-elastic tissue to the thyroid cartilage within the entering angle of its two halves, and to the tongue, hyoid bone, and arytenoid cartilages by the glosso-epiglottidean, hyo-epiglotti- dean, and aryteno-epiglottidean folds, respectively. The cavity of the larynx Fig. 515. (Fig. 515) is divided by the glottis or rima-glottidis — that is. the long, narrow fissure, running from before backward , \# on a level with the lower part of the % : '' < ft arytenoid cartilages — into an upper and 18t lower compartment. The upper com- 12 partinent commencing with the pharynx -11 af *.'; $*§ by the superior aperture of the larynx, lsSf.'V." 7 iC'Jm i-T" ' 1?J contains the ventricles and the upper or so-called false vocal cords. The J' lower compartment passes inferiorly W into the trachea without any observable ""™ constriction between them. The mu- cous membrane lining the cavity of the 10 ~ V larynx, continuous with that of the J% _ pharynx and trachea, extending from V^i the epiglottis to the tongue and aryte- 8-l-S noid cartilages as the glosso-arytenoid epiglottidean folds, descends from the superior aperture, and is reflected at each side outwardly and upwardly as a pair of pouches', the ventricles of the larynx oval recesses communicating by a transverse elliptical orifice with the • 1 ; n ,1 i -11 i Longitudinal section of the human interior ot the larynx, and prolonged , , .. , J • 1 a larynx, showing the vocal cords, I, v.-n- Upwai'd and OUtward as the laryngeal tricle of the larynx; 2, superior vocal cord; pouches. The Upper edge of the Veil- 3, inferior vocal cord : i, arytenoid carti- tricle, somewhat prominent through the i age ; , 5 ' section of the i^™' 1 ™**° • 6 > _ r p 6, inferior portion of the cavity of the presence Ot Connective tissue, IS known larynx ; 7, section of the posterior portion as the false VOCal Cord, since it is not ° f tie cricoid cartilage; 8, section of the an- concerned in the production of the voice, terior portion of the cricoid ™ rtila s» ; 9 > ■. , , * .. -li Bupenor border of the cricoid cartilage ; 10, the lower edge Corresponding With the sectionofthe thyroid cartilage; 11,11, su- Upper border Of the VOCal membrane Or perior portion of the cavity of the larynx: true vocal cord, as it is often improperly v2 < 13 > ^y tmoid e land ; 14 . ™> epiglottis; hi j ,i ., . /» i ■ i 15> 17, adipose tissue; IS, section of the called, and upon the vibration of which hyoidbone . 19i 19) 2ll , trachea. (Sappbt.) the production of the voice depends. From the ventricles the mucous membrane passes downward, lining the vocal membrane, cricoid cartilage, and finally becomes continuous with that of the trachea. The mucous membrane of the larynx is soft, thin, and pale red, its epithelium being of the ciliated columnar form, except upon the so-called vocal cords, where it is squamous like that of the 842 THE LAKY NX pharynx and mouth. While adhering tightly to the epiglottis, the vocal membrane, and the interior of the cricoid cartilage, the mucous membrane in other parts of the larynx is loosely attached to the sub- jacent parts by connective tissue. The vocal membrane (Fig. 516), about seven lines long in the male and five in the female, bounding the anterior thirds of the aperture of the glottis, and consisting of elastic tissue, may be regarded as extend- ing from the front and sides of the upper border of the cricoid cartilage, upward to the bases of the arytenoid cartilages, and to the lower part of the entering angle of the thyroid. The lower portion of each vocal membrane is the strongest, and may be seen at the front of the larynx in the interval between the thyroid and cricoid cartilages. The lateral portions are thin and are separated by the thyroid and arytenoid muscles from the ahe or wings of the thyroid. The upper margins of the vocal membranes — that is, the parts corresponding in position to the lower edges of the ventricles, extending on either side from the anterior prom- inent angle of the base of the arytenoid cartilages to the entering angle of the thyroid, being somewhat thickened, are usually described as the Fig. 516. Fro. 517. External and sectional views of the larynx. A m B. The cricoid cartilage. E C G. The thyroid cartilage. G. Its upper horn. C. Its lower horn, where it is articulated with the cricoid. F. The arytenoid carti- lage. E F. The vocal ligament. A K. Crico-thy- roideus muscle. Fern. Thyroid-arytenoideus muscle. X e. Crico-arytenoideus lateralis. «. Transverse sec- tion of arytenoideus transversus. m h. Space between thyroid and cricoid. 15 h. Projection of axis of articu- lation of arytenoid with cricoid. (Carpenter.) Diagram of a model illustrating the action of the levers and muscles of the larynx. The stand and vertical pillar represent the cricoid and arytenoid cartilages, while the rod 6 c, moving on a pivot at c, takes the place of the thyroid cartilage ; a b is an elastic hand rep- resenting the vocal ligament. Parallel with 1h is runs a cord fastened at one end to the rod b c, and, at the other, passing over a pulley to weight B. This represents the "thyro-arytenoid muscle. A cord attached to the middle of 6 c, and passing over a second pulley to the weight A, represents the crico-thyroid muscle. It is obvious that when the bar b c is pulled down to the position c . I 1024 do re mi fa sol la si do re mi fa sol la si do re mi fa sol la si do re mi fa sol la si do vib. 11 11111222 2 2 223 33333 3 444 44445 from which it will be seen that the voice ranges ordinarily from mi x P ^5 1 ^ 80 vibrations per second, the lowest note of the male bass r, -0- voice, to do 5 Ut 5 \- A^ — ^z i 10:24 vibrations per second, the highest e note of the female soprano or tenor, though it should be mentioned that some bass voices reach the fa 2 F vE^ H 42.6 vibrations per second -0- of the octave below the above scale or even lower, and some soprano voices the soL =t m 1536 vibrations per second above and even higher. The human larynx being capable, therefore, in the case of a man of emitting ordinarily a note due to 80 vibrations a second, and in a woman of one due to 1024 vibrations, would have to be over five feet long and six inches long, respectively, if it acted like an organ i Physiology, trans, by Baly, vol. ii. p. 1030. London, 1842. 846 PRODUCTION OF THE VOICE. pipe, since that would be the length of the pipes giving those notes, the notes of an eight foot pipe and six inch pipe being due to 64 and 10_'4 vibrations a second, respectively. Similarly no notes as deep as those of the buss voice can be produced by strings as short as the vocal membranes, however the latter may be relaxed. Further apart from the fact of the vocal membranes being too short to produce bass notes on the supposition that they act like strings, the E string of the double bass for example, vibrating 41 ] times per second, the ratio of the vibrations of the vocal membranes to the weights ex- tending them is not the same. Thus, for example, while it is well known that the vibrations of a string are doubled by quadrupling the extending weights, the number of vibrations being proportional to the square root of the weight, the vibrations of the vocal membranes, as shown experimentally by Muller, 1 are not so doubled by quadrupling the extending weight, the vibrations not reaching the octave above, as in the case of a string, by several semitones. On the other hand, it has been shown by Muller that the vibrations of the vocal membranes are gov- erned by the same law as that regulating the vibrations of reeds or tongues, when the latter are associated with pipes. The latter qualifi- cation must be borne in mind, since in reed instruments like the accor- dion, concertina, seraphine, harmonium, etc., in which the reed or tongue vibrates in a sort of frame that permits of the air passing out on all sides of it through a narrow channel, thereby increasing the strength of the blast, the sound produced is due to the vibration of the reed or tongue alone, and is regulated entirely by the length and elasticity of the latter. In reed instruments like the clarionet, bassoon, and oboe, how- ever, in which the single or double reeds are associated with pipes, the air setting the reed in vibration traverses the whole length of the pipe before escaping into the atmosphere, and consequently the sound pro- duced is due to the vibrations of both reed and pipe combined, and not to either of them singly — the two sounds accommodating themselves to each other in such a way that only one sound is heard, the fundamental being neither always that of the reed alone nor of the pipe alone. In the case of the clarionet, in which the reed is a single broad tongue, and in the oboe and bassoon, in which the reeds are double and somewhat spoon- or spatula-shaped, the different notes are produced by closing or opening a series of holes, the position of which has been determined by experiment. In the reed pipes of the organ, however, in which the reed is inserted into the pipe through a plug, each note has a separate pipe. It was established more especially by Weber 2 that reeds associated with pipes, as in the case of the voice and of the instruments just mentioned, possess certain well-marked properties by which they can be at once distinguished from other musical instruments, such as organ pipes, flutes, etc., and with which, in the case of the voice, they may be confounded. Among the most important of such properties may be mentioned, 1st, that the pitch of a reed, though it cannot be raised, may be lowered by joining it to a tube, but at the utmost by not more than an octave ; 2d, that the fundamental note of the reed so lowered may be raised 1 Op. cit., p. 'J8">. - Poggeudorf : Auuulen, xvi. xvii. PEODUCTION OF THE VOICE, 847 again to its original pitch by a lengthening of the tube, the latter then yielding the same fundamental note as the reed of the instrument with- out the tube, whilst by a further lengthening the pitch is again lowered, and by a still further lengthening raised again, 3d, that the length of the tube necessary to lower the note to any given pitch, depends on the relation existing between the rapidity of the vibrations of the tongue of the reed and those of the column of air in the tube, each taken separately. Accepting the above as the essential conditions which an instrument must fulfil in order to constitute a reed instrument, Midler 1 showed that the larynx, in fulfilling the same, must be regarded as a reed instrument, the vocal membranes being comparable to membranous vibrating tongues. The conclusion just arrived at, based upon acoustic principles, that the larynx is a reed instrument, is fully borne out, not only by the fact that in several instances persons rendered voiceless by the loss of their larynx, have been enabled to speak, so as to be perfectly heard through the introduction into the trachea of a tube containing a reed, but also by observing directly the larynx during phonation with the laryngoscope. Among the first to investigate the larynx in this way was Manuel Garcia, 2 so distinguished as a singing teacher, whose experiments were made principally with the view of determining the scientific principles upon which the teaching of singing should be based, and which, up to that time, had been taught by purely empirical methods. The difficulty of observing the vocal membranes during phonation on account of the epiglottis hiding so much of their anterior portions, especially in the production of high notes, is a familiar fact to- Fig. 521. A, the glottis during the emision uf a high note in singing. B, an easy or quiet inhalation of air. those in the habit of using the laryngoscope. The perfect control, however, nossessed by Garcia over his own vocal organs, together with the skill with which he examined them in his own person, enabled him finally to determine very satisfactorily the changes actually undergone 1 Op. cit., pp. 985, 999, 1023. - Pr c. of Royal Society Lond , 1856, vol. vii. p 399. 848 PRODUCTION OF THE VOICE. by the glottis and vocal membranes during singing, the accuracy of the observations, models of scientific research, being fully confirmed by later observers. The changes in the glottis during ordinary breathing (Fig. 521, A A') having been already described, it will be only necessary in this connection to recall the fact, that during inspiration the glottis, through the action of the crico-arytenoidei postici muscles, is widely dilated, and that during expiration, the larynx appearing to be passive, the air is gently forced out through the glottis by the expiratory move- ments of the chest. Garcia having first noticed the movements of the larynx during his ordinary breathing, observed next that just at the moment of making a vocal effort, his glottis underwent an entire change, the arytenoid cartilages being so approximated that the vocal cords were brought parallel to each other (the distance separating them, it may be here mentioned, not exceeding the one-twelfth of an inch), the glottis then appearing as a narrow slit (Fig. 521, B B r ). The glottis being thus prepared, so to speak, for the emission of a note through the action of the expiratory muscles, air is forced through the slit or chink, the effect of which is that the vocal membranes are thrown into vibration, the particular note emitted being due essentially to the length and tension of the latter. Thus, according to Garcia, in the production of the bass =t notes r K±? — ^- the glottis is agitated by large and loose vibra- tions throughout its entire extent, the lips comprehending in their length the anterior apophyses of the arytenoid cartilages and the vocal cords. As the pitch of the sound rises through the gradual apposition of the apophyses the length of the glottis is encroached upon, and with the emission of the sounds Fpszz =zd the apophyses touch each other throughout their whole extent, their summits being solidly fixed one against the other at the notes Efifc |~~~F~ With the production of the notes p ffiy ~1 |j > an( ^ so on u P wal 'd to the end of the register, the vibrations are due to the vocal membranes alone, the length of the glottis diminishing, and the cavity of the larynx becoming very small as the pitch of the voice continues rising. These changes undergone by the glottis in the shape and size and in the length and tension of the vocal membranes in the production of low and high notes by the larynx, as observed by Garcia and subsequent investigators, become intelligible when it is remembered, as shown in the last chapter, that the pitch of PRODUCTION OF THE VOICE. 849 the note — that is, the number of vibrations per second — rises as the length of the string, pipe, or membrane diminishes, or the tension increases, the change in the shape of the glottis and of the tension of the vocal mem- branes being accomplished by the action of the muscles, as already explained. Thus, men have deeper voices than boys and women, their larynx being larger, and their vocal membranes longer. That the aper- ture of the glottis is narrowed during the production of sounds any one can convince himself by comparing the time of an ordinary expiration with that required for the passage of the same quantity of air during a vocal effort, and that the size of the aperture varies with the pitch of the note, from the fact of there being a far less passage of air during the production of a low note than in that of a high one. That the production of low and high notes is due to variations in the tension of the vocal membranes, as brought about by the action of the thyroary- tenoid and crico-thyroid muscles, is made evident during the passage of the voice from one extreme of the scale to the other by the move- ment of the thyroid on the cricoid cartilage, which is quite apparent if the tip of the finger be placed over the crico-thyroid ligament. As illustrating the nicety and precision with which the tension of the vocal membranes is regulated by muscular contraction, let us suppose, with Midler, 1 that the average length of the vocal membrane in man during repose is about y^g-th of an inch, and during the greatest tension y^g-th, the difference being, therefore, yg° an ^ ncn m ^ ne case of the male and female singer, respectively, and by considerably less in the case of such phenomenal voices as those of Bastardella, Catalani, Cruvelli. and Patti, for example, with a compass of three octaves, and even more. The remarkable distinctness with which certain voices could be heard, like those of the celebrated basso, Lablache, and the late Madame Parepa Rosa, clearly above the sounds of a large chorus and orchestra, is due rather to the absolute accuracy with Avhich the tension of the vocal membranes could be regulated by those great singers, to the purity of their tones rather than to the mere loudness or intensity. It should be mentioned, however, that the singers just referred to were of magnificent physique, as might have been expected, the power of the voice being due to the force with which the air is expelled from the lungs. As the action of the diaphragm and abdominal muscles has already been considered, it will be only necessary in this connection to recall what has already been said, that the inspiratory and expiratory acts can be ■ Op cit., vol. ii. p. 1018. ;.4 850 PRODUCTION OF THE VOICE. so nicely balanced by a skilful singer as to enable him to produce the most delicate tones. It need hardly be added that while sounds may be uttered, and even words spoken during inspiration, that the true and natural voice, and, as we shall see presently, articulate speech are only produced during expiration. While, in childhood, the general character of the voice is the same in both sexes, in the adult condi- tion the male voice differs very much from that of the female, the difference becoming marked at the age of puberty. If castration be performed, therefore, the contralto, or soprano, voice of the boy will be retained through life, and such a voice being susceptible of considerable cultivation advantage was cruelly taken of the fact at one time to fill choirs with desirable voices. After the age of puberty, however, the quality of the female voice remains the same, except in gaining strength and extending its compass. At this period, in the case of the male, however, the wdiole character of the voice changes through the develop- ment of the larynx. While the intensity of the voice in both sexes depends upon the force with which the air is expelled through the larynx, and the range or pitch, bass, tenor, contralto, and soprano, upon the length and tendon of the vocal membranes, the quality of any par- ticular individual voice, male or female, depends upon the shape, size, and general make of the larynx, and on the character of the auxiliary resonating cavities. In concluding our account of the production of the voice, a brief description, at least, of the influence exerted by the acces- sory vocal organs, viz., the trachea, ventricles, superior vocal cords, epiglottis, pharynx, nasal cavities, and mouth, should be offered. The trachea not only serves to conduct air to the larynx, but through the vibration of its own column of air reinforces the sound produced by the larynx, the vibration being perfectly appreciable if the finger be placed upon the trachea during a powerful vocal effort. The ventricles probably, also, intensify the sound, the homologous parts being enor- mously developed in monkeys and apes possessing very loud voices, such as the South American howler (Mycetes), the chimpanzee, and gorilla. That the superior or false vocal cords and the epiglottis are not essential to the production of the voice, can be shown by experiments like those of Longet, 1 in which the above parts were removed in animals without the voice being materially affected, and in man those cases in which the epiglottis had been lost through wounds or disease. The pharynx, mouth, and nasal fossce, acting as resonating cavities, modify, however, very considerably the sounds produced by the vocal mem- branes. Indeed, in the production of the natural voice their resonance is essential. Thus, Avhile in the production of low notes the velum palati is fixed, and the bucco-pharyngeal and naso-pharyngeal cavities reinforce the laryngeal sounds, in the passage upward to the higher notes these cavities are reduced in size, the isthmus contracting until, with the emission of the highest notes, the nasal fossfe is shut off entirely, and the mouth and pharynx alone resound, the tongue at the same time beino- drawn back into the mouth with its base projecting upward and 1 Physiologie, tome ii. p. 728. Paris, 18G9. SPEECH. 851 the tip downward, the capacity of the resounding cavity is still further diminished. Such being the mechanism by which the chest tones or chest register are produced, it is only necessary to add, that if the velum palati be thrown forward instead of backward, thereby cutting off the mouth from the pharynx, the resonance being then due to the naso- pharyngeal cavity, that we pass from the chest register into that of the head tones or head register. 1 According to the late Madame Seiler, 2 however, the head tones are due to the vocal membranes being firmly approximated posteriorly, an oval opening being left Avith vibrating edges involving only one-half or one-third of the vocal membranes, which gradually contracts as the pitch of the tone rises. As in the case of the head register, so in that of the falsetto or middle register of the female, a difference of opinion still prevails as to the exact manner of its production. Thus, while, according to Fournie, 3 the falsetto is due to the tongue being pressed strongly backward and the epiglottis forced over the larynx; according to Seiler, 4 it is due to the thin, fine edges of the vocal membranes alone vibrating. While the distinction between the chest, falsetto, and head registers so far as pitch is concerned, is not an absolute one, and while we find that every voice possesses all three registers, nevertheless the chest register almost characterizes male voices and the contralto of the female, the falsetto being the most natural voice of the soprano, though the latter voice is capable of chest tones, while the head voice is particularly well developed in tenors and in the female voice. The falsetto is but little cultivated at the present day by tenors, and even when it or either of the other two registers is partic- ularly well developed the singer should endeavor to pass as insensibly as possible from one register to another, to give the impression that his voice possessed but one. Speech. While the position of man as the head of the animal kindom depends upon the development of his intelligence, there can be no question that his superiority over all other animals is, to a great extent, due to his being able to convey his ideas to others by expression, or articulate speech. Speech is voice modulated by the throat, nose, tongue, and lips. Voice may, therefore, exist without speech, and if the production of the voice be restricted to the vibrations of the vocal membranes, it may be said that speech can exist without voice, since, in whispering, the vibrations of the muscular walls of the lips replace those of the vocal membranes, a whisper being, in fact, a very low whistle. Articulate sounds are usually divided by orthoepists into vowels and consonants : vowels being continuous sounds due to the voice alone, but modified by the form of the aperture through which they pass out; consonants, interrupted sounds due to the interruption, more or less, of the voice, and sounded with vowels. This classifica- tion is not, however, a very natural one, since the sound of the English i, being a diphthongal sound, cannot be prolonged like a true 1 FonrniS : Physiologic de la voix et de la parole, p. 421. Paiis. 18(50. - The Voire in Singilig, p. 56. Pkila., 1808. 3 Op. cit., p. 4C3. * Op. fit , p. 56. 852 SPEECH. vowel (a, o), while certain consonants (1, r, f) can be pronounced without the current of air being interrupted. The vowel sounds, by which we mean u, o, a, e, are due to the reinforcing of the overtones of the fundamental tone of the larynx by the cavity of the mouth, the changes in the shape of which give rise to so many resonantors, each of which is adapted to the reinforcing of the particular overtone to which, together with the fundamental tone, the particular vowel is due. The presence of overtones coexisting with the fundamental tone of the larynx in the emission of vowel souuds, and the determination of what particular overtone accompanies the fundamental tone in the production of any particular vowel, can be shown by the Kcenig mano- metric apparatus described in the last chapter. Thus the vowel sound u is due to the fundamental tone being emitted strong, the cavity of the mouth being made as deep as possible, by keeping the tongue down at the bottom, and pushing the lips out, the mouth then reinforcing the fundamental tone of the larynx, and tuned, according to Kamig 1 and the experiments of the author, to the pitch of the note Sib; 2 (Fig- 522), due to 224 vibrations per second. The sound o is due to the Fig. 522. r Vowels, OU A E I Tones, Sfy s ,^ 8 Sfe g^ ^ No. of Vibs., 224, 448, 896, 1702, 3584. Pitch of vowels. (KffiNiG.) fundamental note of the larynx being present, but especially its first octave above being emitted also, and very strong, the cavity of the mouth being enlarged through the retraction of the lips so as to reinforce the octave, and tuned to the pitch of the note Si^ 3 , due to 448 vibrations per second. The sound a, like the preceding two vowels, is due to the presence of the fundamental tone of the larynx, but differs from o in that the fundamental is accompanied by the double octave above, the orifice of the mouth being so widened that the cavity of the mouth is tuned to the pitch of the note Sfc 4 due to 896 vibrations per second. In the production of the sound e the cavity of the mouth is still more retracted, reinforcing the third octave above the fundamental, the cavity of the mouth being tuned to the pitch of the note Si^j due to 1792 vibrations per second. As the four vowels u, o, a, e, can be produced during one continuous expiration, during which the fundamental and overtones generated by the vocal membranes remain the same, by simply changing the shape of the mouth, it is evident that the production of each individual vowel will depend, as already mentioned, upon iQuolques: Experiences d'Acoustique, p. 65. Paris, 1SS2. SPEECH. 853 which particular octave or overtone is reinforced by the cavity of the mouth, the pitch of the latter depending upon its shape, and that the shape of the mouth remaining unchanged, the corresponding vowel will be emitted as long as the expiration blast lasts. Now while the vowel i agrees with the four vowels just mentioned in being due to the reinforcement of an overtone, the fourth octave accompanying the fundamental by the cavity of the mouth, which in this instance is tuned to the pitch of the note S;^ 6 , due to 3584 vibrations per second, an octave higher than in the case of the vowel e, it differs from the true vowels in that, the cavity of the mouth remaining the same, if the expiratory blast be prolonged, it does not remain i, but becomes e. The vowels are the only real vocal sounds, it being only on a vowel that a note can be said or sung. Speech, however, is made up not only of vowels, but of consonants — that is, of sounds that are sounded in conjunction with a vowel. While the distinction between vowels and consonants, as already mentioned, is not an absolute one, it may be said that while vowels are due to the vibrations of the vocal membranes being modified by the mouth, consonants are due to the expiratory blast being interrupted in various ways in its course through the throat and mouth ; the vibrations of the vocal membranes, when essen- tia.1, being 'rather secondary in character. Consonants may be divided according to their manner of production, into two kinds, explosive and continuous, the sound of the explosive consonants being due to the sudden establishment or removal of a particular interruption, that of the continuous consonant to the air rushing continuously through some constriction, for example, explosive consonants are the labials p, b, dentals t, d, and gutturals k, g, p, t, and k, being uttered without the voice, b, d, and g (hard) with the voice — that is, are accompanied by a vowel sound. In uttering p, the lips are first closed, then the expiratory blast suddenly opening them, the sound is produced. Simi- larly the sudden interruption of the contact of the tip of the tongue with the hard palate, and of the root of the tongue with the soft palate gives rise respectively to the sounds t and k. The continuous con- sonants are subdivided into aspirates, resonants, and vibratory. The aspirates include the labials f, v, the dentals s, 1, sh, th (hard), z, zh, th (soft), and the gutturals ch, gh. Like the explosive consonants, some of the aspirates are uttered without the voice, as f, s, 1, sh, c, h; some with the voice, as v, z, zh, th, ch. The reso- •nants include the sounds m, n, ng, and the vibratory the sound r. common and guttural. Of the aspirates, f and s are formed through the lips and teeth being brought nearly in contact respectively ; th through the placing of the tongue between the two partially open rows of teeth ; 1 when the tip of the tongue is placed against the hard palate, and the air escapes at the sides ; sh through the dorsal surface of the tongue being raised toward the palati, the passage-way between the two being thereby narrowed ; ch and gh through the approximation of the root of the tongue to the soft palate. In the production of all of the resonants the vocal membranes vibrate and the nasal chambers resonate, the closing of the lips in particular giving rise to m, the contact of the tongue with the hard palate to n, and the approximation of the root of 854 SPEECH. the tongue to the soft palate to ng. The vibratory consonants include the various forms of the sound r, so called on account of being pro- duced by the vibration of the constricted portion of the vocal passage; thus, the common r is due to the vibrations of the point of the tongue elevated against the hard palate ; the guttural r to vibrations of the uvula or other parts of the walls of the pharynx. The tongue, while an organ of speech, is not essential, since after its loss the faculty of speech more or less perfect remains. Finally, while the consonant e is a breathed aspirate, it differs from all other letters in being formed in the larynx itself, the glottis being narrowed enough to produce a wind- rush, but not sufficiently to throw the vocal membranes into vibration, c is redundant, producing the same effect as k or s ; q is equivalent to 1, being used only before the vowel u ; x is the ame as ks at the end of a syllable, and z when beginning a word. While the limits of this work will not permit of any further detailed consideration of orthoepy, or of any theory of the origin and growth of language in general, or of that of the language in which this work is written in particular, the above description will suffice as a general account of the production of articulate speech, a factor almost as im- portant as that of intelligence in the development of civilization. CHAPTER LIII THE STRUCTURE OF THE EAR, AND THE SENSATION OF HEARING. The organ of hearing is usually described as consisting of three parts, an external, middle, and internal ear, the latter including the auditory nerve. For convenience, as well as to avoid repetition, the functions of the three parts of the ear will be considered at the same time as that of the description of their structure. The Structure and Functions of the External Ear. The pinna, auricle, or ear, in the ordinary sense of the term — that is, the portion projecting from the head (Fig. 523), with the exception of the Fig 523. h View of parts composing the organ of hearing of the right sitle. a. Pinna and lobe. 6. Meatus externus. o. Meuibraua tympani. _') that the light band is divided into two by what looks like a line, but which seems to be in reality the edge of the membrane, running transversely across the fibre and attached all around to the sarcolemma, through which each fibre is divided into a series of compartments placed end to end. It is within these compartments that the sarcous substance is situated. The latter consists of a broad, dim, doubly refracting (anisotropous) contractile disk, both ends of which are capped by a layer of clear, homogeneous, refracting (isotropous) soft or fluid substance. The nuclei or muscle corpuscles lie immediately under the sarcolemma, their long axis being in the long axis of the fibre, and in all probability generate the sarcous substance. As already mentioned, muscles being active organs are well supplied with blood, and with sen- sory as well as motor nerves ; the sensibility of muscles is relatively, however, but slight. The second variety of muscle, the non-striped or smooth, occurring among other situations in the alimentary canal, arteries, ureter, etc., consists of fusiform or spindle-shaped cells with tapering ends, varying in length from 45 to 230 mic. mm. (-g^th to Y^-g-th inch) in breadth, from 4 to 10 mic. mm. (-goVg-tli to 2 5 \ th inch). Within each cell may be seen after the addition of acetic acid, a solid, oval, elongated nucleus, containing one or more nucleoli, in which the motor nerves derived from the sympathetic and consisting of both medullated and non-medullated fibres, appear to terminate. Non- striped muscle, while freely supplied with blood, is not, however, so vas- cular as the striped variety. Striped muscle or ordinary flesh is either neutral or slightly alkaline in reaction, and consists chemically by weight, of three-fourths water and one-fourth nitrogenous, non-nitro- genous matters, and salts. Of the nitrogenous matters the most impor- tant is the coagulable substance that becomes in dead rigid muscle myosin, though albuminates, creatin, xanthin, hypoxanthin, taurin, inosic and uric acids are also present. Among the non-nitrogenous matters may be mentioned para or sarco, lactic acid, mosete or muscle sugar, glycogen, dextrine, and glucose. Of the salts, the principal ones are the alkaline phosphates and sulphates, potassium and sodium chloride. But little is known of the chemical composition of unstriated muscular tissue, beyond the fact of it consisting of water, nitrogenous and non-nitrogenous bodies. Let us turn now to the consideration of the physical and chemical changes undergone by the muscle during its contraction. Many of the most striking phenomena of muscular contraction as well as the method of observing and recording the same, have already been incidentally demonstrated in considering nervous irritability. It will be remem- bered, that by attaching a lever to a muscle and connecting the pen of the same with the recording cylinder or the plate of the pendulum myograph, that we obtained a trace (Fig. 533), that of the muscle curve, and that by means of suitable chronographic apparatus we determine the latent period, the time intervening between the beginning, the maximum, and the end of the contraction, the curve of tetanus, etc. MUSCULAR CONTRACTILITY 877 Further, by means of the galvanometer and differential rheotome, it was shown that during a period of rest, the nerve exhibited an electrical current, but that during its excitement the electrical cur- rent disappeared, and the nerve current appeared, the rate of disap- pearance of the one being the same as that of the appearance of the other. It will only be necessary, therefore, in this connection, after Fi(i. 533. a h I0(T' 27F» ?~5' °» a second. A muscle-curve obtained by means of the pendulum myograph. To be read from left to right, a indi- cates the moment at which the induction-shock is sent into the nerve, b the commencement, c the maxi- mum, and d the close of the contraction. The two smaller curves succeeding the larger one are due to oscillations of the lever. Below the muscle-curve is the curve drawn by a tuuing-foi k making ISO double vibrations a second, each complete curve representing therefore T |-^t" of a secoutl - lf will be observed that the plate of the myograph was travelling mure rapidly toward the close than at the beginning of the contraction, as shown by the greater length of the vibration-curves. (Foster.) recalling what has already been said, to repeat that there is a negative variation of the electrical current of muscle during the activity of the latter, and to add that this negativity, as shown by Bernstein, 1 travel- ling at the rate of 8 metres (9.8 feet) a second, with an average length of 10 millimetres, is immediately followed by or transmitted into a visible contraction wave, the muscle impulse travelling at its heels at about the same rate, but with a wave length of from 200 to 400 milli- metres, which causes the muscular fibre as it passes over it to swell and shorten. If a portion of living irritable muscle of an insect, that of Telephorus, for example, be viewed under the microscope, the con- traction waves observed passing along the fibres may be fixed by appro- priate treatment with osmic acid, and so compared with the remaining portion of the fibre at rest. By such method of investigation, it has been shown, that while the dark and light bands so characteristic of striated muscle at rest are still observable in the muscle when con- tracted, the relation of the two is reversed, that is to say, the dark band in the contracted muscle corresponds t<> the light band in the quiet one, and vice versa, the distinction between light and dark bands not being observable, however, during the intermediate stage between rest and contraction. While there is still some difference of opinion as to the interpretation of all of the appearances of such a preparation, the same i Untersuchungen, S. 58. Heidelberg, 1871. 8/8 MUSCULAR CONTRACTILITY. makes very evident the swelling and shortening of the fibres, which is brought out even better if the object be viewed by polarized light. In describing the induction apparatus of Du Bois-Reymond, it will be remembered that the secondary coil can be removed as desired from the primary and the strength of the stimulus thrown into the nerve or muscle in this way varied. Beginning with a very weak stimulus and gradually increasing the same, the corresponding contraction will be found to increase, at first rapidly then more slowly until a maximum is reached, then to diminish until contraction finally ceases through the muscle being fatigued from repeated stimulation. If the distance through which the secondary coil be slid along be laid down as the abscissa line and the extent of contraction as the ordinates, the curve obtained will be the graphic representation of the contraction considered as a function of the stimulus. It should be mentioned, in this connection, that while muscles in the body, where they are on the stretch after contraction, return at once to their initial length, out of the body fail to do so either as com- pletely or as quickly, the rapidity and extent of the return appearing to depend upon the nutrition of the muscle. Suppose that instead of varying the electrical stimulus, as in the case just mentioned, we main- tain it as constant as possible, but that we place in the little scale pan suspended from the lever attached to the muscle successively 10, 20, 30, 40, and 50 grammes — that is, we gradually increase the weight the muscle has to lift to increase the resistance that it has to overcome. Contrary to what might naturally be expected, the resistance offered to the contraction, for a time at least, increases the contraction, then with a continued increase of weight, the contraction having reached a maxi- mum, gradually diminishes until finally it ceases altogether. If the weio"hts be regarded as the abscissas and the extent of contraction as the ordinates, then the curve obtained will represent the contraction regarded as a function of the resistance. It will be observed, in experimenting with weights, that a stretched muscle reaches quickly its initial length after the extending cause has been removed, the elasticity not being very great but perfect. Contrary, however, to what might have been expected, the extensibility is not diminished during contraction but increased, so that the muscle has to overcome the resistance due to its extensibility before it can raise any weight. Thus, suppose that a muscle be extended a given extent by a weight of say 40 grammes during rest, and then that it be unloaded and throAvn into a state of tetanus and then again loaded with the same weight, the extension in the latter case will be greater than in the former. It will also be learned, by experimenting with gradually increasing weights, that finally the elongation of the muscle due to its elasticity is exactly compensated by the shortening due to its contraction, such a contraction of static equilibrium being reached in the case of the frog, the transverse section being one square centimetre and the weight 692 grammes, and in man, the muscles being those of the calf of the leg, and the weight 8 kilo- grammes (17. (> lbs.). The work done by a muscle, like all work, is estimated by the height through which a weight is raised. Thus, if 5 grammes (77.1 grains) are raised 27 millimetres (1.08 inch) by the muscle of a frog, then 27 x 5, MUSCULAR CONTRACTILITY. 879 135 grammes millimetres (83 grain inch) work is done by such a muscle. By gradually increasing the weights and noting the heights through which they are raised, it will be found that the work done gradually increases as the weight increases until a maximum is reached, after which there is a gradual diminution until the muscle, as in the former instances, ceases to contract. The fatigue experienced by muscle during prolonged contraction, which sooner or later brings the latter to an end, appears to be due to the accumulation of the waste effete products incidental to its activity. Within certain limits such matters are elimi- nated as rapidly as formed and new materials for the repair of the muscle are at the same time supplied. If, however, the contractions follow each other very rapidly, sufficient time is not allowed for the accom- plishing of these processes, and the equilibrium between disassimilation and assimilation is no longer maintained. While the cohesion and irri- tability of muscle are diminished by fatigue, the elasticity is but little, if at all, affected. The latent period is, however, lengthened. During fatigue the extent of contraction is smaller and the latter lasts longer than when the muscle is fresh, the return to the initial length is also slower. As might be expected, a muscle is fatigued much sooner when it does work than when it simply contracts without doing work. If a stethoscope or myophone be applied over a powerfully contracting muscle, the biceps, for example, a deep, low tone will be heard, the pitch of which is about 40 vibrations a second, and which is, without doubt, due to the successive shortenings which make up a muscular contraction, the latter caused, in all probability, by 40 nervous impulses being transmitted to the nerve centres along the motor nerves to the muscle. We say that the pitch of this muscular sound or tone is 40 vibrations per second and caused by 40 nervous impulses, because that is the note actually heard, and because we can produce such a note experimentally out of the body by stimulating the nerve that number of times, or a note due to 80 vibrations per second by stimulating the nerve that number of times. It should be mentioned, however, that according to most physiolo- gists, the muscular sound heard when the biceps contracts, while due to 40 vibrations per second, is really the first overtone or first octave above the fundamental, the latter being due to 20 vibrations per second. If such be the case, then the muscle contracts only 20 times a second, the pitch of the muscular sound produced is 20 vibrations a second, and the nerve is stimulated 20 times a second. Whether the muscular sound heard be the fundamental note or the octave above, in either case, however, the mechanism of its production is the same — that is, due to muscular vibration. It will be remembered that in accounting for the first sound of the heart, muscular contraction was assigned as one of the causes, and while there is no doubt that it is an element in the production of the first sound, it must be admitted that it is difficut to understand how the contraction of the heart, if a simple one, can give rise to a muscular sound, which we have just seen is pro- duced by numerous contractions. Facts of this kind, as well as pecu- liarities in the muscular structure of the heart itself, lead one to suppose that possibly the contraction of the heart during its ventricular systole 880 MUSCULAR CONTRACTILITY. is rather of a tetanic than simple character, as is usually supposed. The muscle sound or muscle tone due to successive muscular contrac- tions must not be confounded with what is unfortunately called mus- cular tonus or muscular tonicity, hy which is meant the state of tension due to the muscles in the living body being more or less stretched between their attachments. Such being the case, when a muscle is divided transversely it contracts, the two parts receding from each other. The sphincter muscles, however, do not appear to be stretched during repose, but only when they are dilated. On the other hand, by the term muscular tone, as understood more especially by neurologists, is meant the firmness or tone of muscle due to continued nervous excitement emanating from the spinal cord. By some physiologists, however, it is denied that the spinal cord exerts any such tonic influence upon the muscles, and yet it is well known that a decapitated frog will remain in a sitting posture as long as the spinal cord is intact, but that with its removal the limbs fall apart. Further, the limbs of a decapitated turtle, and, to a certain extent, those of a decapitated rabbit, also retain their firmness, tone, but with the removal of the spinal cord become lax, flaccid. Such facts are incom- prehensible, unless it be supposed that the muscles are maintained firm, elastic, resilient, through the influence of the spinal cord. As the influence exerted by heat, blood supply, etc., upon the activity of the muscle is essentially the same in the case of muscle as in that of nerve, it will not be necessary to dwell further upon the same in this connec- tion. If living contractile frog's muscle, freed as much as possible from blood, be frozen and then minced and rubbed up in a mortar with four times its weight of snow containing 1 per cent, of sodium chloride, a mixture will be obtained, which at about 0° Cent., can be filtered. The filtrate so obtained, or muscle plasma, at first fluid becomes at ordinary temperature, jelly-like, and then separates into a clot and serum, the action which before coagulation was neutral, or slightly alka- line, now being distinctly acid. The serum contains albumen and extractives ; the clot consists of myosin, a substance intermediate in character between fibrin and globulin. It will be observed, as in the case of the fibrin of the blood, that myosin does not exist as such in living contractile muscle, but that it is developed during the coagula- tion of the same out of some preexisting albuminous element or elements. The myosin so developed from living muscle does not differ at all from the myosin obtained by appropriate chemical manipulation from dead muscle. Indeed, the passage of a muscle into the condition of rigor mortis, characterized by loss of its irritability, softness, trans- lucency, extensibility, and elasticity may be regarded as being essen- tially due to the coagulation of its muscle plasma, to the development of myosin out of its preexisting albuminous elements. Since living muscle during its contraction becomes distinctly acid from having been previously faintly alkaline or neutral from a considerable amount of carbonic and lactic, or sarcolactic acid being set free, as in the con- dition of rigor mortis, from the fact of the muscle, as in the latter distinction, becoming rigid, it might, at first thought, be supposed that the changes occuring during the contraction of the living muscle are MUSCULAR CONTRACTILITY, 881 essentially the same as those occurring in rigor mortis, due to the oxidation of some complex albuminous material elaborated and stored up in the muscle during its periods of repose. That the phenomenon of muscular contraction is not, however, identical with that of rigor mortis, is shown by the important fact that during muscular contraction no myosin is developed, upon the formation of which the phenomenon of rigor mortis depends, and that during contraction the extensibility of the muscle is increased, instead of being diminished, and that it does not lose its translucency. But little is positively known as to the physical and chemical changes undergone by unstriated muscular fibre during death or contraction ; from what has been established, however, we are led to believe that the processes going on in unstriated muscle fibre differ in degree rather than in kind from those just described as occurring in striated muscle. While the limits of this work do not permit of any discussion of general mus- cular movements which would involve a detailed description of the muscles and joints and the consideration of animal mechanics, a brief account of how ordinary movements are performed does not appear in- appropriate in concluding this chapter. The greater part of the skeletal muscles may be regarded as so many sources of power for moving the bones viewed as levers. The levers are of three kinds or orders according to the relative position of the power, the weight to be moved, and the axis of motion or fulcrum. In a lever of the first kind, as in Fig. 534, A, the Illustration of lever of first order. (Kikkes.) power (P) is at one end, the weight (W) at the other, and the fulcrum (F) in the middle. As a familiar example of the first kind of lever, occurring in the human body, may be mentioned the raising of the body from the stooping posture by the action of the hamstring muscles attached to the tuberosity of the ischium (Fig. 534, B). In a lever of the second kind (Fig. 535, A), the power is at one end, the fulcrum at the other, and the weight in the middle. The depression of the lower jaw in the opening of the mouth is an illustration of a lever of the second kind (Fig. 535, B), 56 882 MUSCULAR CONTRACTILITY. in which the tension of the muscles elevating the jaw represents the weight. In a lever of the third kind (Fig. 536, A), while the fulcrum and weight are at either end, the power is in the middle. The flexing of the forearm by the action of the biceps muscle (Fig. 536, B) is an \ Elastic I Band Fig. 535. w Illustration of lever of second order. (Eibkkb ) instance of this form of lever in the body. The different movements of the foot offer an illustration of all three kinds of levers: of the first kind Fig. -536. Illustration of lever of third order. (Kirkes.) when the foot is raised and the toe tapped upon the ground, the ankle- joint being the fulcrum (Fig. 537, I) ; of the second when the body is Fid. 537. i ii in Illustration "1 levers of all three orders. W. Weight of resistance. F. Fulcrum. P. Power. (Huxley.) raised upon the toes, the ground being the fulcrum (Fig. 537, II) ; of the third kind, when one dances a weight up and down by moving only the foot, the fulcrum being the ankle-joint (Fig. 537, III). As a general rule, in the human body, the power is so disposed with reference to the fulcrum, that while a greater range of motion is acquired the power is diminished. Thus, in the case of the action of the biceps, it is evident MUSCULAR CONTRACTILITY. 883 that a great amount of force must be put forth to move the forearm, but that a considerable range of movement is obtained through a relatively slight shortening of the muscular fibres. In the act of standing, as accomplished by muscular action, the body is in a vertical position of equilibrium, a line drawn from the centre of gravity of the body falling within the feet placed upon the ground. .The head being firmly fixed upon the vertebral column by the cervical muscles pulling from the latter upon the occiput, and the vertebral column itself being fixed by the longissimus dorsi and quadratus lumborum muscles. In the sitting position, the head and trunk together constituting an immovable column, are supported upon the tubera ischii. In the forward posture the line of gravity passes in front, in the backward posture behind, and during the erect posture between the tubera ischii. In walking, the two legs act alternately, the one leg, the active or supporting leg, carrying the trunk, the other leg being inactive or passive. The act of walking, for con- venience of description, may be considered as made up of two acts. Act 1st (Fig. 538) : the active leg being vertical and slightly flexed at the Fig. 538. Phases of walking. The thick lines represent the active, the thin the passive leg. 7). The hip-joint. k, a. Knee. f,b. AukU*. c, d. Heel, m, e. Ball of the tarso-meta tarsal joints, z, g. Point of great toe. (Landois.) knee, alone supports the centre of gravity of the body, the passive leg touching the ground with the tip of the great toe (2) only. At this moment the position of the leg corresponds to a right-angle triangle in which the active leg and ground represent the two sides, the passive leg the hypothenuse. Act 2d : the active leg being inclined, moves forward to an oblique position, the trunk moves forward, the active le«- being at at the same time lengthened that the trunk may remain at the same height. The latter is accomplished by extension of the knee (•"'.. 4, 5), and the lifting of the heel from the ground (4, 5), until the foot finally rests upon the ground by the point of the great toe. As the active leg is extended and moves forward the tips of the toes of the passive leg leave the ground (3), and being slightly flexed at the knee- joint perform a pendulum-like movement (4, 5), the passive foot passing as far in front of the active leg as it was previously behind it. The foot being then placed flat upon the ground, the centre of gravity is 884 MUSCULAR CONTRACTILITY. transferred to what now becomes the active leg, the latter being slightly flexed at the knee and placed vertically. The first act is then repeated, and so on. It will be observed that during walking the trunk leans toward the active leg and inclines somewhat forward, the effect of which is to overcome resistance of the air, and that it slightly rotates on the head of the active lemur. Running differs from rapid walking in that at a particular moment, both legs not touching the ground, the body is raised in the air, the necessary impetus being given to the body by the forcible extension of the active leg. CHAPTER LV. REPRODUCTION. Spontaneous Generation. Fissiparous, Gemmiparous, and Sexual Generation. At an immensely remote period the earth must have been entirely destitute of life, at least the physical conditions of the azoic period of geologists, and the aeons preceding it were such as to make the exist- ence of life, as Ave are acquainted with it, impossible. "Whether the nebular hypothesis of the earth having been cast off from the sun be accepted or not, there can be no doubt that at an inconceivably dis- tant period the earth was in a fluid or semi-fluid molten condition, and its temperature so high as to render life impossible, or even to admit of the union of the chemical elements composing it, the latter existing then separately, as they do in all probability now, in the sun, as shown by spectral analysis. The basalts, porphyries, and lavas entering into the formation of the igneous rocks, the volcanic action constantly going on at the present day in many parts of the world, the seismic disturb- ances, the high temperature of mines, etc., not only prove that origi- nally the world was but little else than a ball of fire, but also that the fire, far from being extinguished, is only now restricted to the inner subter- raneous regions lying under the crust of the earth. If speculation be admitted, we can conceive how with the loss of heat and the lowering of the temperature through the combination of hydrogen and oxygen that water was formed, and that gradually through the combination of the chemical elements the binary and ternary salts entering into the formation of the rocks constituting the crust of the earth were next produced, and, finally, the physical conditions being suitable, that the combination of carbon, hydrogen, oxygen, nitrogen, and phosphorus or sulphur atoms, resulted in the development of protoplasm, or the simplest kind of life. It is true that the idea of life being generated spontaneously, as just supposed, is repugnant to all that we know of life as reproduced at the pi'esent day, there being no evidence Avhatever that life now is ever generated otherwise than from preexisting life, solitary tapeworms, maggots, etc., often cited by the uneducated as instances of animals spontaneously generated, offering no exception to the rule, being in reality reproduced, like all life, by preexisting animal life. That the first life appearing upon the face of the earth was nevertheless spontaneously generated, developed independently of pre- existing life must be admitted, since there was no antecedent life during the azoic period to give rise to it. As to the conceivability or inconceivability of how spontaneous generation was brought about, of how protoplasm, with its remarkable properties, was ever developed 886 REPRODUCTION. through the combination of chemical elements possessing different properties, it may be said that it is just as difficult to comprehend how the combination of acid and base will give rise to a salt exhibiting properties possessed by neither, or how two gases like oxygen and hydrogen in combination produce a liquid, water, different from either. In either case we must suppose that the properties of the substance formed, however remarkable, are the sum of the properties of the elements entering into combination and giving rise to the substance, whatever is true of the inorganic in this reaped being true of the organic as well, the question in either case being one of the redis- tribution of matter and force only. Admitting that life originated spontaneously, there is little reason, however, to hope that the physical conditions which obtained when life first appeared upon the face of the earth can ever be realized experimentally so as to enable one to gen- erate life de novo. Still it must not be forgotten that what appears impossible, inconceivable, to one age, becomes perfectly so to a suc- ceeding one. Life having once appeared upon the face of the earth, however produced, there is no reason to suppose that it has ever been entirely absent, since catastrophies, such as volcanic eruptions, earth- quakes, floods, climatic changes, etc., which are so destructive to life, are relatively local in action. Further, the first life, out of which all life has since been gradually developed through inheritance and variation, must have been of the simplest kind ; indeed, so simple as to make it difficult, if not impossible, to say whether such life should be regarded as animal or vegetable, its characters being intermediate between, and partaking of the nature of both plants and animals. The latter, judging from their remains as presented in the Cambrian and Silurian rocks, or such as immediately overlie the azoic strata, were also at first of a simple kind. Thus among the plants and animals living in these early ages of the primary period of geologists may be mentioned seaweeds, jelly fish, coral-making polyps, crinoids, brachiopods, various kinds of mollusca, trilobites, etc. Passing on through the later ages of the primary period, the life becomes more varied and complex; fishes, ganoids, and sharks, and land plants, pine- like lepidodendrons, and ferns making their appearance during the Devonian age, or that of the sandstone, and reptiles in the carboniferous age, or that of the coal period, remarkable also for the richness of its cryptogamous plants. As the ages rolled on, during which the Jura rocks Avere deposited in Switzerland, the chalk cliffs in England, the marls in New Jersey, phanerogamous or flowering plants, palms and trees like those of our own forests, oaks, dogwoods, poplars, beeches, appeared, while among the animals that lived during these ages may be mentioned fishes resembling those of the present day ; gigantic reptiles, birds, and probably a few marsupial mammals. During the tertiary period that followed, the flowering plants and trees then flourishing resembled closely those of the forests of the present day, the invertebrate forms of life differed but little from those existing now, the fishes and reptiles were similar to those found in our rivers, oceans, and forests ; while herbivorous animals, resembling the taper, peccary, camel, deer, horse, rhinoceros, and elephant, roamed in herds FISSION — G EM MAT ION. 887 over the continents, hippopotami wallowed in the streams ; while beasts of prey were also numerous, being represented by animals closely allied to the lion, tiger, hyena, dog, and panther, of the present day. During . the close of the tertiary, or, rather, of the post-tertiary period, the general aspect of the world differed but little from that presented by it now, man appears but in a condition of development, probably far lower than that of the lowest existing savage, and the process of civili- zation begins. The idea of repi'oduction is usually associated with that of the differ- ence of sex; the production of offspring naturally suggesting the idea of two parents. Many plants and animals, however, are reproduced entirely independent of sexual intercourse, by what is known as fission or gemmation ; and as many of the structures of the body are devel- oped by these processes, it is essential that they should be at least briefly illustrated. By the process of fission is meant the division of the single parent organism into two or more parts, each of which will become a new being, similar in form, inheriting the properties of the parent. Reproduction by the process of fission may be observed in many of the lower cryptogamous plants, and among animals in the infusoria, anne- lida, etc., illustrations of which have been given. What interests us in this connection, however, as regards fission is, that the segmentation of the vitellus of the egg, the development of the embryonic blood cor- puscles (Fig. 539), the proliferation of the cells constituting morbid growths, etc., are accomplished by this process. On the other hand, by gemmation is understood the reproduction of the new being by a process of budding, as seen in ordinary flowering plants, and among Fig. 539. Fig. 540. Division of Mood cells in embryo of stag. (Frey.) animals in the hydra, actinia, etc., each bud becoming a new animal. In certain cases of gem mi parous reproduction, however, the buds, instead of bei ng cast off as produced, remain attached to the parent stock, and so give rise to a colony, as in the hydroids (Fig. 540), each member of which is in communica- tion, directly or indirectly, with each other. Such a mode of reproduc- Hydroid colony. Eudendrium ramosum. (Gkgexbaub.) REPRODUCTION. tion in the human body is seen in the development of a racemose gland (Fig. 541) through the division and subdivision of a simple follicular Diagrammatic view of development of glands. gland. The reproduction of man and most animals, however, is accom- plished by the union of a spermatozoon and an ovum, specialized products of the male and female generative apparatus respectively, which, while elaborated by a process of fission, or gemmation, unlike the products of the latter, must fuse together in order to give rise to a new being, neither spermatozoon nor ovum, by themselves, being capable of further development. Further, it will be observed that since, in the production of a new being by sexual generation, the union of the sper- matozoon and ovum is indispensable, the qualities of the parents must be transmitted to their offspring. The female generative organs, situ- ated partly within and partly without the pelvis, consist of the uterus, Fallopian tubes, vagina, ovaries, the external and internal labia, cli- toris, etc. The uterus (Fig. 542), or womb, is a pyriform, hollow Fig. 542. Sketch of the uterus and its appendages. 1. Uterus, with its peritoneal covering partially retained. 2. Its fundus. 3. Its neck, with the forepart of the attachment of the vagina removed. 4. Mouth of the uterus. 5. Interior of the vagina. C. Broad ligament, removed on the opposite side. 7. Position of the ovary behind the broad ligament. 8 Round ligament. 9. Oviduct, or Fallopian tube. 10. Its fim- briated fxtromity. 11. Ovary. 12. Ovarian ligament. 13. Process connecting the fimbriated extremity with the ovary. 14. Cut border of the broad ligament. (Wilson.) muscular organ, lying, in the unimpregnated condition, within the pelvis, between the rectum and the bladder, and maintained in position by its attachment to the vagina by the recto- and vesico-uterine peri- toneal folds, and the round and broad ligaments, its upper broad extremity is known as the fundus, or base, the narrow extremity the cervix, or neck, and the intervening portion as the corpus, or body. The uterus is about two and a half inches in length, two inches in breadth, and one inch in thickness. STRUCTURE OF UTERUS. 889 The walls of the uterus consisting of unstriated muscular tissue being about one half an inch in thickness, the cavity of the latter is but a narrow space. That of this body is lined with a thin, soft, smooth, and ciliated mucous membrane of a pale red color, containing numerous tubular glands adhering closely to the. underlying muscular tissue, their being no intermediate fibrous or submucous tissue, which becomes continuous with the mucous membrane of the Fallopian tubes and that of the neck of the uterus. The mucous membrane of the latter is of the squamous character, thicker and less soft than that of the body of the uterus, its glands being of the simple follicular kind and secretin-' a tenacious mucus, the latter in an inspissated condition, giving rise to the so-called ovula Nabothi. The uterine mucus, both of the fundus and cervix, is alkaline in reaction. The Fallopian tubes, or the horns of the uterus, are trumpet-shaped tubes about four inches in length, ex- tending from the fundus outwardly above and beyond the ovary. The outer free extremity opening into the abdominal cavity expands into a funnel-shaped orifice the pavilion, the margin of which being fringed with a number of irregular processes, gives rise to its name of fim- briated extremity. One of the largest of these fringed processes, doubled so as to include a furrow, extends along the edge of the broad ligament to be attached to the ovary. The Fallopian tube is lined with ciliated mucous membrane, continuous through its interim or uterine orifice with that of the cavity of the fundus, and disposed in a longi- tudinal manner or as narrow folds. The tube itself consists of fibrous intermixed with unstriated muscular tissue, loosely invested by peri- toneum. The small sac, often absent, attached by a long pedicle close to the fimbriated extremity, is the remains of the duct of Miiller of the embryo, as we shall see presently. The vagina is a cylindrical canal about four inches in length and an inch and a quarter in breadth (in the virgin adult), extending from the uterus, the neck of which projects into it to the vulva. The vagina consists of three coats, an outer fibro-elastic, a middle unstriated muscular, and an inner mucous; the epithelium of the latter is of the squamous kind, and is provided with numerous minute conical papillae. In the virgin condition, the lower orifice or entrance of the vagina is constricted by a crescentic or zone- like fold of the lining of the membrane, the so-called hymen. The latter is usually obliterated by sexual intercourse, childbirth, etc. ; in some instances, however, it is so strong that even impregnation may occur without its being ruptured. Its presence cannot, therefore, be taken as an evidence of virginity, or its absence of the contrary. The inner surface of the anterior and posterior walls of the vagina is roughened by folds, the wart-like eminences into which they are divided more particularly at the entrance of the vagina being known as the carunculpe myrtiformes. While, as just mentioned, the uterine mucus is alkaline in reaction, that of the vagina is decidedly acid. The two ovaries are compressed ovoid bodies, situated behind the broad ligament and enclosed by a pouch of the latter about an inch from the uterus, to which they are attached by the ovarian ligament. The ovary con- sists of a reddish spongy fibrous stroma, enclosed in a dense fibrous tunic, the tunica albuginea. Within the stroma of the ovary are found 8'M) REPRODUCTION. numerous (several thousand) vesicular-like bodies, varying from a micro- scopical size to the fourth of an inch in diameter, the Graafian follicles or vesicles, so-called after Regnerus de Graaf their discoverer. 1 These vesicles (Fig. 543), which are especially abundant at the peripheral por- Fig. 543. Graafian follicle. (II.tcckei.. tion of the stroma of the ovary, consist of an outer fibro-vascular layer or tunic, a middle basement membrane or membrana propria, and an inner layer of polyhedral granular epithelial cells, the membrana granu- losa. At the side of the Graafian follicle lying next the surface of the ovary, the cells of the membrana granulosa are heaped up, constitut- ing the discus proligerus, within which is found the ovum or egg, only discovered as recently as 1827 by Von Baer. 3 The remaining portion of the Graafian follicle — that is, the part not occupied by the discus proligerus with the enclosed egg — is filled with a serous liquid containing granules, nuclei cells apparently detached from the membrana granulosa. The ovum or egg as just discharged from the follicle, has usually adhering to it the cells of the discus proligerus and shreds of epithelium; the latter being removed, the egg can then be seen with the naked eye on a perfectly clean piece of glass as a very minute speck, averaging in length the T |o-th of an inch Q-th millimetre) in diameter. Under the microscope the ovum or egg (Fig. 544) appears as a spheroidal body, exhibiting the characters of an organic cell as already described. Thus, it consists of a cell Avail, an elastic vitellus membrane, the zona pellucida, measuring about YsVo'th °^ an ^ ncn (TFS" tn °f a millimetre) in diameter, and which, while apparently a clear pellucid membrane, is in 1 I)e Mulierum Orsanis Generation] inservientibus Tractatus Novus, p. 177. Lus*d. Batav., 1672. - De Ovi mammalium ot hominis geueri, Lipsiate, 1827. Ueber Entvvicklungs Geschicbte der Tbiere, Kbnigsberg, 1828. HUMAN OVUM. 891 reality striated, the strife being probably canals through which the spermatozoa pass into the egg. Fig. 544. The human ovum. (Hjeckel. ) The cell contents, yelk or vitellus, enclosed within the zona pellucida, consist of a soft or semifluid protoplasmic matter, containing granules and oil globules, among which may clearly be seen a nucleus and nucle- olus. The nucleus, or germinal vesicle, as it is called, in the ovum dis- covered in mammals by Coste, 1 in 1834, usually situated near the surface of the egg, is a clear, spheroidal vesicle, and measures about the -3-5-oth of an inch (-^V^ of a millimetre), containing granular fluid, and the nucleolus, macula, or the germinal spot. The latter, discovered by Wagner, 2 in 1835, measures about the ^^^ th of an inch (^th of a millimetre, in diameter. It is a fact of profound significance that the human ovum, or first cell, from which all the cells composing the body are developed, should be practically undistinguishable, morphologi- cally at least, from the ova of the remaining monodelphous mammalia: and further, that the first or transitory egg-stage through which man passes should be permanently retained as such through life in many of the lower plants or animals, such beings never passing beyond this uni- cellular stage. Further, the very lowest forms, as well as the highest forms of life, including man, begin in exactly the same way as masses of protoplasm; the immature human ovum, like an immature ova, being a mass of protoplasm and the zona pellucida a secondary formation. The ova are developed from the germinal epithelium (Fig. 545), a 1 Recherches sur la generation des Mammiteres par Delpech et Coste, Paris, 1834. - Mttller: Arehiv, 18:i5. ProdromuB historic generationis, Lips., 183G. 892 K EP KOIHCTION. covering of the primitive ovary. Through the inward growth of this epithelium into the substance of the ovary, cords of cells (b d) are formed, which become divided into compartments through the encroach- ment of the fibrous stroma. Of the cells within these compartments the largest beeome ova : the smallest, the cells of the membrana granulosa Vertical section through the ovary of a newborn female. (Waldeyer.) of the Graafian follicle (e/), the wall of which is continuous with the stroma. As development advances, fluid accumulates between the growing cells, the follicle assumes the shape of a vesicle, the egg lying eventually to its inner wall. With the ripening or maturation of the ovum, the Graafian follicle comes to the surface of the ovary, the wall of which as well as that of the follicle becoming at the same time thinner and thinner, until, finally, they are ruptured, and so permit of the escape of the egg. From the fact of the egg or embryo being found in the Fallopian tube or uterus, instead of in the abdominal cavity, except in the unusual case of abdominal pregnancy, it is evident that the Fal- lopian tube must be so disposed with reference to the Graafian follicle that at the moment of its rupture a temporary passage-way is usually formed from one to the other. As a matter of fact, it is not positively known how the egg passes from the Graafian follicle to the Fallopian tube. It may be supposed, however, that the fimbriated extremity affixes itself to the ovary at the moment of rupture of the follicle, or that the egg, dropping into the furrow of the long fimbriated process situated at the edge of the broad ligament and attached to the ovary, is transferred by ciliary action into the orifice of the tube, and thence by the same kind of action through the Fallopian tube into the uterus. The egg having arrived in the cavity of the latter, if not in the mean- time impregnated, sooner or later decomposes and disappears. Before describing, however, the manner in which the ovum is impregnated, CORPUS LUTEUM, 893 certain changes undergone by the Graafian follicle and the mucous mem- brane of the uterus, incidental to the maturation and escape of the ovum from the follicle, "whether the ovum be impregnated or not, must be first considered. Corpus Luteum of Menstruation and Pregnancy. It is impossible to convey by words any idea of the extent of the congestion of the internal generative apparatus of the female during the period of the maturation and escape of the ovum from the Graafian follicle. The author can only say that in making post-mortem examinations of females dying while menstruating, he was impressed with the fact that the bloodvessels, arteries, capillaries, and veins were distended to an extent never accomplished by an artificial injection, however successfully performed. Such being the case (as might be expected), with the rupture of the Graafian follicle, there being quite an abundant hemor- rhage, the cavity of the follicle fills with blood. The latter soon coagu- lating, as it would do if extravasated elsewhere, the clot remains enclosed within the walls of the follicle (Fig. 546), having no organic connection, however, with the latter, but simply lying loose in the cavity of the follicle, out of which it can be readily turned by the handle of a scalpel. The clot, which at this moment is large, soft, and gelatinous, soon begins to contract, and the serum exuded being absorbed by the adjacent parts, it becomes smaller and denser. The color- ing matter of the clot at the same time undergoing the usual changes incidental to extravasation, and being to a great extent absorbed with the serum, a diminution in its color becomes quite perceptible. During this period, about two weeks, the lining membrane of the follicle, which at the moment of rupture presents a smooth, transparent, vascular appearance, becomes much thickened and convo- luted. Through the continued condensation of clot and thickening of the lining membrane, as just described, the follicle has become so altered in its appearance that by the end of three weeks it can be no longer recognized as such, and is henceforth known as the corpus luteum, though its color can scarcely be said as yet to be distinctly yellow. At this period the corpus luteum may be described as a rounded tumor, about four-fifths of an inch (twenty millimetres) in length, situated in the stroma of the ovary, and projecting from the surface of the latter, the surface of the corpus pre- senting a minute cicatrix, the mark of the rupture of the follicle. If such a corpus luteum be divided longitudinally (Fig. 547), it will be found to consist of a central clot and a convoluted wall, and it will be observed that, while the clot and the convoluted wall lie in contact with each other, there is neither anv organic connection between the convoluted wall and the clot, on the one hand, nor the surrounding ova- Graafian follicle, recently ruptured during menstrua- tion, and filled with a bloody coagulum ; shown in longi- tudinal section. «.Tissue of the ovary. 6. Membrane of the vesicle, e. Point of rup- ture. (Dalton.) 894 REPRODUCTION rian tissues, on the other. Prom this time on, the corpus luteum under- goes a retrograde metamorphosis. By the end of the fourth Avcek it is diminished to about half of the size attained at the end of the third week, the central clot has been, to a great extent, absorbed, the convoluted wall is with difficulty separated from the central clot and the peri- pheral ovarian tissue, and its color, instead of having faded, like that of the clot, is now of a bright yellow. After this period it will be found impossible to separate the yellowish convoluted wall, either from the ovarian tissue or the central clot, and by the end of two months the Fro. 547. Fig. 548. ') Human ovary out opeu, showing a corpus luteum, divided longitudinally, tbree weeks after menstrua- tion. From a girl, twenty years of age, dead of haemoptysis. (Dalton.) Ovary, showing corpus luteum, nine weeks after menstruation. From a girl dead of tubercular meningitis. (Dalton.) whole corpus luteum will be found to be reduced to the condition of a greenish, cicatrix-like spot (Fig. 548), about one-fourth of an inch (6 millimetres) in diameter. At the end of six months the corpus luteum has usually disappeared. It may, however, be sometimes found, though in a very atrophied condition, even seven or eight months after the rupture of the follicle. Such, in brief, is the manner in which the corpus luteum of menstruation is developed out of the ruptured Graafian follicle from which the ovum has escaped, at least as observed by the author in a number of females dying from natural causes or violent deaths, and which does not differ essentially from the process so admi- rably described by Dalton. 1 As during pregnancy far more blood flows to the female generative apparatus than during menstruation, it might necessarily be supposed that while the production of the corpus luteum would be essentially the same in both conditions, the corpus luteum, being better nourished, would grow larger and persist longer than the corpus luteum of menstruation. That such is the case there can be no doubt, a corpus luteum being present at the end of pregnancy even, and measuring as much as half an inch in diameter. While marked differences exist, therefore, between the corpus luteum of men- struation and that of pregnancy, nevertheless, as these differences are 1 Trans, of the American Med. Assoc, vol. iv. p. 547. Phlla., 1882. Phila., 1851. Thysiology, 7th edit., p. 608. MENSTRUATION. 895 of degree, and not of kind, and since the corpus luteum of menstrua- tion during the first three weeks increases in size, but that of pregnancy after the first six months diminishes, it can be readily conceived that at a particular moment the corpus luteum of menstruation might be of the same size as that of pregnancy, and that if the color of the clot and convoluted Avail in the two were not well marked, the two corpora lutea might be undistinguishable. At least such has been the experience of the author, in comparing numerous corpora lutea of menstruation of various ages with those of pregnancy. Further, that the presence or absence of a corpus luteum cannot be accepted as positive evidence of impregnation having taken place is shown by the fact that, although in several instances during post-mortem examinations a fcetus was removed from the uterus by the author, not a trace of a corpus luteum could be found in either ovary, and, on the other hand, in more than one instance a well-developed corpus luteum being present several months after the last menstruation, there was not the slightest reason to believe that during that period there had been a fcetus in the uterus, at least the relatives of the deceased had no object in concealing the fact of impreg- nation, if such had really occurred. Menstruation. Coincident with the maturation and escape of the ovum from the Graafian follicle, the mucous membrane of the uterus undergoes several well-marked changes. Thus, while in the ordinary conditions it measures only about the one-fourteenth of an inch in thickness, at this period it becomes twice or even three times as thick. It is also much softer and more loosely attached to the underlying part than ordinary, being somewhat rugose in character. The glands are very much enlarged, and the surface of the membrane smeared with blood. The latter is due to a kind of fatty degeneration set up in the mucous membrane involving the bloodvessels, by which the capillaries are ruptured. The hemorrhage so caused constitutes the menstrual Mow, or the menses, catamenia, etc., and appears monthly in the healthy female. It appears to be pure arterial blood mixed with desquamated utero-vaginal epithelium; the amount of the latter would appear from the observations of the author to be greater than usually supposed. The menstrual blood is kept from coagulating by the vaginal mucus. As might be expected from the nature of the case, it is impossible to say how much blood is discharged during the menstrual period, for, apart from the difficulty experienced in collecting it, women vary very much in respect to the amount of blood lost. From five to twenty ounces may be accepted as an approximative esti- mate of the total flow during the menstrual period. Menstruation is sometimes regarded as the effect of ovulation, the trio being so inti- mately associated. Since menstruation, hoAvever, occurs without ovula- tion in the absence of ovaries, and ovulation without menstruation, it is evident that the two phenomena are not related as cause and effect, but should be considered as the effects of a common cause, the general preparation of the system for impregnation. Indeed, the thickening and shedding of the mucous membrane of the uterus, and hemorrhage during menstruation, differ only in degree, not in kind, from the changes 896 REPRODUCTION. undergone by the mucous membrane during pregnancy and parturition. That the menstrual flow is the effect of a deep-lying cause, the fitting of the mucous membrane for the reception of the ovum, though not due to the production of the latter, is shown by the constitutional disturb- ance experienced by the female when the menses first appear, and ever afterward with their monthly reappearance, though then to a less extent. The menses usually appear between the age of thirteen and fifteen years and much earlier in warm climates. At this period, the age of puberty, there is a general development of the body, the limbs become fuller and rounder, hair appears on the mons veneris, the mammary glands enlarge, ova maturate, and the disposition changes. Just before the establishment of the flow, either in the case of its first appearance or in after recurring ones, for about two days a feeling of general malaise is experienced, particularly a sense of weight and fulness in the pelvic organs, the vagina mucus is increased in amount and becomes rusty in color, and gives rise to the odor so perceptible in certain females, the breasts also enlarge, showing the sympathies of the latter for the generative organs. With the establishing of the flow, the dis- agreeable feelings and uneasiness usually pass away, and by the end of the fourth day, though the time varies, the flow ceases, and the mucous membrane returns to its normal condition. At about forty-five years of age the menses become irregular in their recurrence and usually cease altogether at fifty. The phenomenon of the menses is not restricted to the human female, as is often supposed, the heat or rut of the lower animals being essentially the same process. Indeed, in the monkeys (macacus cynocephalus), apes, their is a discharge of blood monthly, and in the mare, cow, and dog the same, but recurring at longer intervals. It is a significant fact, that the female of animals, except monkeys, only receive the male during the rutting or menstruating period. The Male Generative Apparatus. The male generative apparatus consists of the testicles, the spermatic ducts, the seminal vesicles, prostate and suburethral glands, and the penis. The testicles (Fig. 549), secreting the spermatic fluid, are two glandular bodies suspended by the spermatic cords within the scrotum. The latter is essentially a musculocutaneous pouch, divided into two recesses by a septum for the reception of the two testicles. Each testicle consists of an anterior oval portion of the body or testes proper, and a posterior elongated portion clasping, as it were, the former, the epididy- mis. The upper portion of the epididymis is known as the head or globus major, the lower part as the tail or globus minor, which in turning upward upon itself, becomes the spermatic duct. The testes are covered with a dense white fibrous membrane, the tunica albuginea, which at the back of the testes forms a process, the mediastinum. The latter being prolonged as fibrous bands to be inserted into the inner surface of the tunica albuginea, serves as a sort of scaffolding to support the delicate glandular substance within. The testicle proper, is made up of about two hundred lobules, each lobule in turn consisting of from one to six seminiferous tubules, of which there are perhaps eight hun- dred in all. MALE GENERATIVE APPARATUS. 897 The seminiferous tubules at the narrow end of the lobule assume a straight course, being then known as the vasa recti. The latter entering the mediastinum, constitute together the plexus retiformis, from which emerge about a dozen efferent canals, or vasa efferentia, to pass out to the head of the epididymis. Within the latter these Fig. 549. Testicle and epididymis of the human subject. a. Testicle, b. Lobules of the testicle c Vaaa recta, d. Rete testis, e. Vasa efferentia. /. Cones of the globulus major of the epididymis, g Epi- didymis h. Vas deferens, i. Vas aberrans. m. Branches of the spermatic artery to the testicle and epididymis, n. Ramification of the artery upon the testicle and epididymis, o. Deferential artery, p. Anastomosis of the deferential with the spermatic artery. (KiiLUKER, Hmidbiich der Gea-ebelthre, Leip- zig, 1867, S. 523.) efferent canals form the spermatic cones, which finally give rise to one convoluted tube, constituting the body and tail of the epididymis, the latter of which, as just mentioned, becomes the spermatic duct. The spermatic duct passing through the inguinal canal, leaves the latter at the internal abdominal ring, and descending backward and downward, passes forward to form, together with the duct of the seminal vesicle, the ejaculatory duct, the latter terminating in the prostatic urethra. The seminiferous tubules, about thirty inches in length when unravelled, and the y^tti of an inch in diameter, consist of a fibro-membranous wall lined with a delicate layer of soft polyhedra nucleated cells, the sperm cells, which elaborate the spermatic or seminal liquid, of which about half a drachm is emitted during the orgasm. The latter is a faintly alkaline liquid, slightly heavier than water, becoming jelly-like first, and then hardening after emission. Of a thousand parts, perhaps one hundred are solid. Chemically but little is posi- tively known of its composition ; phosphates appear, however, always to :,7 898 REPRODUCTION. be present, notably magnesium phosphate. Physiologically the essential portion of the spermatic fluid, upon which its fecundating powers without doubt depend, are the spermatozoa that it contains. Indeed, if the seminal liquid be deprived of its spermatozoa, it is rendered entirely inoperative as regards impregnation. Of the sperm cells just mentioned, which elaborate the sperm, some are larger than others, and it would appear that the development of the spermatozoa appearing first at the age of puberty and afterward up to ninety years of age, and longer, takes place only within these larger cells, the granular nuclei of which divide (Fig. 550) and subdivide, one of the nucleoli of each Pig •">•"> 1 rammatic view of development of spermatozoa. Spermatozoa of man. h, ap- parent nucleus. 6, body. J, tail. nucleus assuming the form of a spermatozoon, which is set free by the deliquescence of the cell wall enclosing it. The spermatozoa (Fig. 551), discovered by Hammins or Von Hammen in 1677, and described by Leeuwenhock, resemble the flagellate animalcule for which they Avere first taken. A spermatozoon consists of an ovoidal head, apparently containing a nucleus, about the g^ th of an inch in length, and of a fila- mentary appendage or tail the ^-yth of an inch in length, which vibrates with astonishing rapidity. The movements of the spermatozoa are arrested by water and cold, retarded by acids, and favored by alkalies. The spermatic fluid, with the spermatozoa, passes from the testicles by the spermatic ducts to the seminal vesicles, where it becomes mixed with the secretion of the latter, the nature and use of which are, how- ever, doubtful, as no secreting glands are found in these vesicles ; its use may be to dilute the mixed spermatic fluid. The spermatic fluid having accumulated in the seminal vesicles is thence introduced during coition, still further mixed with the secretion of the prostate gland, of the glands of Cowper, and of the urethra, the use of which is not known, by an ejaculatory effort, into the vagina of the female, the spermatozoa by their vibrating movements passing up into the Fallo- pian tubes, and even the ovaries, as shown by the development of the ovum in those situations in cases of extra-uterine pregnancy. In order that coition should be accomplished, it is essential that the MALE GENERATIVE APPARATUS. 899 penis should be erect. This is brought about through its blood supply being very much increased by the stimulation of the vaso-dilator fibres of the nervi-erigentes, the latter arising probably from the second sacral nerves. The centre of erection, situated in the cord, can be reflexly stimulated either by impressions made upon the genital organs, or upon the mind. The ejaculatory effort is due to the simultaneous contraction of the bulbo urethroe, ischio-cavernous, and transverse perinseus muscles, due to the reflex stimulation of the ejaculatory centre of the spinal cord, situated in the lumbar region. CHAPTER LVI. REPRODUCTION.— {Concluded.) Impregnation of the Ovum and Development of Embryo. As a matter of fact, nothing is known as to the manner in which the ovum is impregnated in the human female, or of the early stages of the development of the embryo. Since the primitive ova of all animals are, however, alike, and the mature eggs of ordinary mammals undistinguish- able from that of the human female, and as the spermatozoa of the mam- malia and animals generally differ from each other unessentially, it is to he inferred that the process of impregnation in the human female is the same as that observed in animals. Further, as the human foetus of about three weeks old (Fig. 552) differs but little from that of the rabbit at about Fig. 552. Fig. 553 Embryo of man. . Mesencephalon, Vesicle, i III. Posterior, { 4 " Epencephalon, Primary, -j I •"). Metencephalon, The primary cerebral vesicles with the secondary parts of the brain developed out of them, may be seen synoptically arranged in Table LXXXIV. At an early period, of development these five different parts of the brain may be more or less seen through the membranous head of the embryo (Figs. 552 and 574). Just as Ave have seen, however, 912 REPRODUCTION, that through ossification of the mesoblast around and above the chorda dorsalis, the primitive spinal neural canal becomes enclosed in a bony one, the spinal column, so through the ossification of the mesoblast forming the primordial cranium surrounding the primitive cerebral vesicles, the latter, or the future brain, comes to be enclosed in a bony Fig. ,.. The zygomatic arch. ma. The mastoid process, mi. Portions of the lower jaw. M. The cartilage of Meckel of the right side, and a small part of that of the left side, joining the left cartilage at the symphysis T. The tympanic ring. m. The malleus, i. The incus, s. The stapes, ste The stapedius muscle, si. The styloid process, p, h, g. The stylo-pharyngeus, stylohyoid, and styloglossus muscles. stl. stylo-hyoid ligament attached to the lesser cornu of the hyoid bone. hy. The hyoid bone. th. Thyroid cartilage. cavity, the skull. There are three marked differences though, to be noticed in the development of the skull as compared with that of the spinal column. First, the notochord does not extend entirely through the head end of the embryo, but stops short in a tapering point at the pituitary fossa. Second, the mesoblast does not split into skin fibrous and intestinal fibrous layers. Third, the primordial cranium never exhibits any trace of segmentation into segments or vertebrae. That the embryo skull does, nevertheless, consist of segments of modified vertebrrje, though not in the adult in the sense held by Goethe, 1 the presence of visceral or branchial arches (Figs. 552 and 575) clearly proves, since the latter are morphologically cranial ribs bearing the same relation to different parts of the skull that the thoracic ribs bear to the vertebrae to which they are attached. As the primordial cranium of man, however, shows no trace of such segmentation, gives no evidence of having ever consisted of vertebra 1 , it is evident that the fusion or coalescence of the same must have taken place at such an early period in the development of the vertebral type that no trace of the primitive segmentation of the skull is ever seen in the trans- itory condition through which it passes, even in the earliest condition i Virehow : Goethe als Naturforscher, 1861, S. 103. VISCERAL ARCHES. 913 of the embryo. The study of the embryonic or adult skull in man will not enable us, therefore, to determine, even approximately, the number of the primitive vertebrae through the fusion of which it has been developed. The researches of Gegenbaur 1 go to show, however, that the skull of the shark retains to some extent the primordial type of segmentation, in the fact of there being eight or nine branchial arches, and that the nerves emanating from the brain, excepting the olfactory and optic, bear to the latter the same relation that the spinal nerves bear to the spinal cord. If the latter be the case, and the branchial arches be regarded as homological with so many ribs, then the prim- itive cranium, in the shark, at least, must have been developed through the coalescence of so many vertebras. Returning from this brief digression upon the nature of the primordial cranium in man to the thread of development, let us consider what becomes of these branchial arches. The visceral or branchial arches resembling those of fishes, the intervening spaces between them being perforated by gill-like open- ings or slits, as in the latter animals, are four in number in man, and symmetrically disposed (Figs. 552, 575, 576), and are known from Fig. 576. Fig. 577. h Visceral arches in man before backward as the first or mandibular (u), the second or hyoid (h), the third or thyro-hyoid (d), the fourth or subhyoid (r). Through the fusion at the middle line of the distal ends of the first visceral arches (Fig. 576, u), the rudimentary lower jaw (Fig. 577, a) is devel- oped, the permanent jaw being developed by ossification (mi, Fig. 575) around the cartilages of Meckel (M), or the rod of cartilage that early appears within this first arch, the proximal part of the cartilages of Meckel not related to the formation of the lower jaw becoming eventu- ally the malleus (m) of the middle ear. In addition to the changes just described as occurring in the first or mandibular" arches, there grows from the root of each of the latter, forward and inward, a process (Fig. 576, o), the superior maxillary, from which are developed the superior maxillary and malar bones, and a pair of cartilaginous rods which ultimately become the pterygoid (o) plate of the sphenoid and the palate bones, which lie parallel with the trabecular cranii. The latter are two elongated bands of cartilage at the base of the cranium, connected with the primitive auditory capsule, which diverging to enclose the pituitary body unite beneath the anterior end of the primordial cranium, to form the septum of the nose. 1 Das Kopfskelet ), becomes a vesicle. The latter, the rudimentary vestibule, in giving off successively the three semicircular canals (Fig. 578, O, D, JE, c, cp, est), and the cochlea (c), originally a straight tube, develops into the internal ear of the adult. It will be remembered, in speaking of the functions of the ear, it was mentioned that the transitory stages through which it passes in its development are permanently retained as the organ of hearing in the lower animals. Like the ear, the eye — at least the anterior part of it — appears first as an invagination of the epi- blast (Fig. 579, A, 1), which in closing up (Fig. 579, B, 2) and separating from the same gives rise to the crystalline lens (2). On the other hand, Development of the eye. (Kemak through the invagination of the optic cup or vesicle — that is, the peri- pheral portion of the optic nerve — by the indenting into it of the lens, the inner surface of the cup becomes the retina (4), the outer the tapetum nigrum of the choroid (5), the vitreous humor being developed through the insertion of the mesoblast from below between the lens and the retina. The remaining portions of the eye are also developed out of the mesoblast, through the latter growing around the ball of the eye as a fibrous capsule, which splitting into an anterior and a posterior layer, gives rise to the sclerotic and cornea, and choroid and iris, respectively. Though the brain and spinal cord are developed out of the epiblast, the cranial nerves, with the exception of the olfactory and optic, which are outgrowths of the anterior cerebral vesicle, as well as the spinal nerves and sympathetic, are developed out of the mesoblast. Development of Alimentary Canal and its Appendages. The primitive alimentary canal, like the neural canal, extending as a straight tube from one end of the body to the other, is formed, as already mentioned, through the pinching oif of the internal blastodermic membrane and the intestinal fibrous layers of the middle blastodermic membrane covering it, and by the bending inward and downward of the parietes of the body, the upper portion persisting in the adult as the 916 REPRODUCTION. Fro. :.S0. alimentary canal, the lower portion remaining only temporarily in the embryo as the umbilical vesicle (Fig. 580). At first the alimentary tube is closed at the ends, but as development proceeds the skin at both its extremities invaginating, deep furrows are formed, which, gradually growing toward the blind ends of the intestinal tube, finally break into the latter, and so give rise to the mouth and anus. Such being the manner in which these apertures are formed, it is evident that their lining membrane differs from that of the remaining portion of the alimentary canal in being developed out of epiblast instead of hypoblast. The mucous membrane of the mouth being then in- vaginated skin, the salivary glands, developed through the division and subdivision of its follicu- lar glands, must be regarded as being essentially the same kind of glands as the sudoriparous and sebaceous glands — that is, as epidermal in origin. Hence, also, the fact of the teeth of certain fishes resembling so closely their dermal spines, Human embryo, with um- bilical vesicle ; about the fifth week. (Dalton.) Fig. 581. d- Three stages iu the development of a mammalian tuoth germ. a. Oral epithelium heaped up over germ. b. Younger epithelial cells, c. Deep layer of cells, or stratum Malpighii. d. Inflection of epi- thelium for enamel germ, e. Stellate reticulum. /. Dentine germ. e (brain-bladder) mr. Wall of the latter. 1. Dermis-plate. s. Rudimentary skull ch. Notochord. k. Gill-arch. mp. Muscle-plate, c. Heart-cavity, anterior part of the body-cavity (ccelomii). d. Intestinal tube, dd Intestinal glandular layer, df. Intestinal muscle-plate. hy. Heart- mesentery, hw. Heart-wall. hlc. Ventricle, ub. Aorta-arches. «. Transverse section through the aorta. (HiECKEL.) just said, an outgrowth. Coincidently with the development of the heart, as just described, and in connection with it, there appears, appa- rently through fission of the inner and outer parts of the intestinal fibrous mesoblastic wall of the alimentary canal, the two primitive aortee and the two primitive cardinal veins, respectively. The two primitive aortee uniting then divide again, the two branches passing along the inner surface of the first visceral arches and curving around the anterior portion of the alimentary canal, unite anteriorly and pass as one tube into the heart aorta. At first there are but one pair of vascular arches encircling the alimentary canal ; in time, however, five such are devel- oped, three only coexisting at one period. TRANSFORMATION OF THE VISCERAL ARCHES. 919 Fig. 58?. The primitive aorta further gives off lateral branches, of which two, passing to the umbilical vesicle, are known as the vitelline or omphalo- mesenteric arteries, while through the twisting of the heart into an S-like shape, the auricles become uppermost, the ventricles lowermost. Two veins, similarly named, return from the umbilical vesicle to the body of the foetus, and pass as a single trunk, the sinus venosus, into the heart. Such being the disposition of the heart and the primitive vessels, it follows that the nutritive material of the umbilical vesicle passes by the vitelline veins to the heart, and thence through the vas- cular arches to the primitive aorta and so to the body generally, the circulation being completed by the vitelline arteries. Neither the heart, aortic trunk, nor vascular arches remain, however, long in the con- dition in which they have just been described. The heart soon sub- divides into a right and left heart through the growth of a longitu- dinal septum, and further into auricles and ventricles (Fig. 583) through the growth of transverse septa, the septum be- tween the auricles remaining, however, incom- plete until after birth, the opening so caused being known as the foramen ovale. Coincidently with the development of the cavities of the heart through the growth of a longitudinal septum in the common arterial trunk, the latter subdivides into aorta and pulmonary artery, the aorta finally being disposed to the right, the pulmonary artery to the left. Finally through the transformation of the third, fourth, and fifth vascular aortic arches, the first and second having disap- peared, the aorta and its first main branches and the pulmonary artery are developed, the change being brought about through the atrophy or hypertrophy of these arches respectively. Thus, for example (Figs. 584-587), through the persist- ence of the left fifth arch (5), the right disappear- ing, the internal half of it becomes the pulmonary artery (p), the external half the ductus arteriosus, the left fourth arch (4) becoming the permanent aorta and giving off the left subclavian artery («), the right fourth arch developing into the innomi- nate dividing into the right subclavian and right common carotid, the left common carotid being given off by the aorta, the third left arch (3) on both sides entering more into the formation of the internal carotid than of the external one, the outer connecting por- tions of the third and fourth arch disappearing. With the establishing of the allantois, however, and the dwindling away of the umbilical vesicle, the allantoic or second circulation gradu- ally replaces the vitelline or first one. The allantoic or umbilical veins, originally two in number, appear to be developed as branches of the vitelline veins, which, extending themselves through the allantois, finally pass into the villous processes of the chorion. Shortly after the appearance of the umbilical veins, the right one disappears, and with it Heart and hc.nl of an em- bryonic dog, from the front. a. Fore-brain, b. Eyes. c. Mid-brain, tl. Primitive lower jaw. e. Primitive upper jaw. /. Gill-arches, g. Right auri- cle, h. Left auricle, i Left ventricle, k. Right ventricle. (Bischoff.) 920 REPRODUCTION. the right vitelline vein and that part of the left vitelline outside of the body of the embryo. The mesenteric portion of the latter, or left omphalo-mesenteric vein (Fig. 588, M), enlarges, however, while the re- Pro. 584 Pig. 586. / u- / fi Air cells of lungs, 400 Albumen, 69 in blood, 260 Albuminose, 70 Alimentary canal, development of, 915 Alkaline urine, 533 Alkalinity of blood, 212 Allantois, 908 Alveoli of lungs, 400 Amniotic fold, 906 Amceba, 45 characteristics of, 45 movements of, 45 Amoeboid movements, 45 Amount of blood, 214 in brain, 706 of heat produced in twentv-four hours, 493 of oxygen absorbed, 441 of perspiration, 755 of urea, 518 of uric acid, 524 of urine, 514 of water in b'o.id, 242 Anelectrotonus, 609 Analysis, colorimetric, of haemoglobin, " 250 of blood by spectrum, 254 spectroscopic, of haemoglobin. 253 Anastomosis of veins, 363 Animal foods, composition of, 86 heat, 470 amount of, produced in twenty- fo :r hours, 493 conditions influencing expendi- ture of, 474, 503 age and sex, 475 atmospheric humiditv. 480 baths, 481, 505 clothing, 505 food, 470 glandular action, 477 mental action, 477 muscular action. 477 temperature, 478 time of day, 475 correlation of, and mechanical work, 501 expenditure of, 499 in various animals, 471 production of, 484 calorimeter for studying, 485 regulation of, 499 specific heat of tissues, 488 thermometers for studvin^, 473 metastatic, 473 Anterior columns of spinal cord, 623 Aphasia, 719 Apncea, 467 Apparatus for counting red blood-cor- puscles, 216 induction, 545 respiratory, 443 Appendages of skin. 737 Aquaeductus vestibuli, 868 Aqueous humor, 782. Area opaca, 905 pellucida, 905 Arterial blood, color of, 213 gases in, 259 pressure, 325 schema, 305 Arteries, 293 changes in shape of, 299 coats^of, 293 contractility of. '2'.'~ dilatation of, 299 elasticity of, 295 934 INDEX. Arteries, elongation of, 299 function of, 293 demonstrations of, 375 increased diameter of, 293 nourishment of, 293 tonicity of, 297 vaso-vasorum of, 293 Artificial respiration, 423 Asphj'xia, 467 Attachments of pericardial sac, 265 Attraction, capillary, 205 Auricles of heart, 265 Axis-cylinder of nerves, 537 BATTERIES, 545 Baths, influence of, on temperature, 481 Beer, composition of, 97 Bile, 159 acids of, 171 cholesterin, 174 coloring matter in, 174 composition of, 170 function* of, 161 origin of, 175 salts, 171 tests for, 172 Gmelin's, 173 Pettenkofer's, 172 Biliverdin, 72 Binocular vision, 806 Blastoderm, 903 formation of, 904 Blood, 212 alkalinity of, 212 amount of, in body, 214 in brain, 706 as a cause of heart's action, 291 coagulation of, 236 as a cure for hemorrhage, 238 buffy coat in, 237 causes of, 237 corpuscles in, 236 crassamentum in, 236 effect of sodium sulphate on, 240 of temperature on, 238 explanation of, 239 ferment in the, 241 fibrin in, 236 fibrinogen in, 240 forms of, 236 in arteries, 238 inside the body, 238 in veins, 238 length of time of, 237 liquor sanguinis in, 236 outside the body, 238 paraglobin in the, 240 plasmin in, 240 process of, 236 rapidity of, 237 serum in, 236 water in, 236 Blood, color of, 213 arterial, 213 brightness of, depending on form of corpuscles, 213 variations in, 213 venous, 213 composition of, 242 albumen, 260 corpuscles, 247 excrementitious matters, 262 fatty matters, 261 fibrin, 260 gases, 255 method of obtaining, 255 varieties of, 255 in arterial, 259 in venous, 259 haemin, 251 crystals of, 251 method of obtaining, 251 haemoglobin, 248 chemical constituents of, 2J9 colori metric analysis of, 250 function of, 255 method of obtaining, 248 spectroscopic analysis, 253 varieties of crystals, 249 ■ in various animals, 246 method of determining the, 242 saline matters in, 261 spectrum analysis of, 254 water, amount of, in, 242 constituents of, 214 corpuscles of, 214 effect of liver on the formation of, 230 in capillaries, 350 red marrow of bone as a source of, 231 varieties of, 214 course of, through heart, 271 in lungs, 401 pressure, 309, 313, 321 effects on, of respiration, 422 in capillaries, 357 in veins, 364 quantity of, 213 modes of estimation of, 213 specific gravity of, 212 supply of lungs, 400 temperature of, 212 variations in, 212 velocity of, 341 Body, calcium carbonate in, 53 phosphate in, 52 potassium chloride in, 52 >odium carbonate in, 53 chloride in, 51 water in, 50 Bones of middle ear, 857 Brain, fissures of, 704 Branches of facial nerve, 663 INDEX. 935 Branches of pneumogastric nerve, 671 Brightness of blood color, 213 Bronchi, 399 Bronchial mucus, composition of, 398 Butty coat in the coagulation of blood, Bulbs of nerves, 542 Burdach, columns of, 624 CALCIUM carbonate in body, 53 phosphate in body, 52 Calibre of capillaries, 352 Canula for artificial respiration, 424 Capacity of heart, 277 of respiration, 430 Capillaries, 246 blood corpuscles in, 350 calibre of, 352 variations in, 352 causes of, 353 capacity of, 349 circulation in, 350 diameter of, 347 discovery of, 346, 387 distribution of, 348 pressure of blood in, 357 structure of, 348 velocity of blood in, 352 Capillary attraction, 205 forces, 359 Carbonic acid exhaled, 438-458 production of, 461 Cardiograph, 274, 279 Cartilages of larynx, 840 Cartilagin, 71 Casein, 71 Causation of sleep, 721 Cause of electrical current in nerve, 572 Causes of flow of blood in veins, 365 heart's action, 289 Cavity of larynx, 841 Cell, definition of a, 44 description of a, 44 nucleolus of, 44 nucleus of, 44 reproduction of a, 4"> varieties of, 44 Cells of nerves, 539 of spinal cord, 62 1 Centre, vasomotor, 732 Centres in spinal cord, 6 19 Cerebellum. 696 Cerebral hemispheres, 702 amount of blood in, 706 comparative development of, 110 composition of, 708 convolutions of, 702 development of, 710 fissure of Rolando, 703 of Sylvius, 703 fissures of, 703, 704 gray matter of, 702 injury to, 709 Cerebral hemispheres, Island of Reil, 703 lobes of, 704 localization of functions, 715 weight of, 707 white matter of, 7< >li Cerebral vesicles, development of, 911 Cerebrum, 702 Cervical ganglia, 727 Changes i n shape of arteries, 299 of food, destructive, 75 of tissue, destructive, 75 Chemical changes during contraction of muscle, 576 composition of cells, 49 constituents of haemoglobin, 249 of white corpuscles, 223 structure of body, 43 Chiasm of optic nerves, 769 Cholesterin, 174 Chordae tendineae of heart, 268 Choroid coat, 771 Chyle and lymph, 193 composition of, 193 Ciliary muscles, 773 process, 772 Circulation, discovery of, 372 in capillaries, 350 in veins, 369, 370 of blood, 264 velocity of, 341 Circulatory system, 346 capillaries of, 346 Circumvallate papilhe, 7<>5 Clarke, columns of, 624 Clothing, influence of, on temperature, 505. Coagulation of blood (see Blood), 236 (/oats of arteries, 293 of veins, 361 Cochlea, 867 Coffee, composition of, 93 Color of blood, 213 Colori metric analysis of haemoglobin, 250 Coloring matter of bile, 174 of urine, 513 Colors, sensation of, 814 Colostrum, 752 Columnar carneae of heart, 269 Columns of spinal cord, 623 Comparative development of cerebrum, 710 physiology, value of, 37 Composition of animal foods, 86 of beer, 97 of bile, 170 of blood, 85, 242 of brain, 70s of bronchial mucus, 398 of cells, 49 of coffee, 93 of colostrum, 752 of corpuscles, 247 of cow's milk, 92 of flour, 91 936 INDEX Compostion of food, 89 of gastric juice, L37 of hair, 747 of human milk, 751 of nasal mucus, 398 of ox flesh, 87 of oyster, 87 of perspiration, 755 of potato, 87 of saliva, 118 of spinal cord, 623 of tea, 93 of urine, 512 of vegetable foods, 86 of wine, 97 Conditions favoring absorption, 209 influencing production of carbonic acid, 456 which modify animal heat, 474 Constituents, chemical, of haemoglobin, 249 of blood, 214 of urine, 515 Contents of large intestine, L85 of pericardial sac, 265 of small intestine, 179 Contractility of arteries, 297 of veins, 369 Contraction of muscles, 875 Convolutions of brain, 702 Coordinating powers of cerebellum, 699 Cranial nerves, 6-33 oculo-motor, 653 olfactory, 653 optic, 653 pathetic, 654 Crassamentum in the coagulation of blood, 236 Crura cerebri, 689 function of, 689 Crystallin, 71 Crystalline lens, 781 Crystals of haemoglobin, varieties of, 249 of hsemin, 251 of urea, 516 of uric acid. 526 Cord, spinal, 623 Cornea, 770 Cornua of spinal cord, 625 Corpora Arantii, 270 quadrigemina, G94 striata, 690 Corpus luteum, 893 Corpuscles, blood, red marrow of bone as a source of, 231 in coagulation blood, 236 of blood, 214 effect of liver on the formation of, 230 varieties of, 314 Correlation of heat and mechanical work, 501 Corti, rods of, 869 Counting of red blood-corpuscles, 215 Course of blood through heart, 271 of facial nerve, 662 glosso-pharyngeal nerve, 662 hypoglossal nerve, 685 pneumogastric nerve, 669 spinal accessory nerve, 682 of sympathetic nervous system, 724 Cow's milk, composition of, 92 Current, electrical, 572 Czermak's rabbit holder, 326 DEFECATION, 186 Deglutition, 120 Dentals in speech, 853 Dermis or true skin, 739 Destruction of red corpuscles in spleen, 230 Destructive changes of food, 75 of tissue, 75 Development of embryo, 900 of liver, 166 of primitive organs in embryo, 905 of protococcus pluvialis, 47 of red blood-corpuscles, 222 Diameter of capillaries, 347 of eyeball, 770 of red blood-corpuscles, 219 Diaphragm as a respiratory muscle, 404 Diastole of heart, 271 Dicrotic pulse, 311 Difference of heart fibres from ordinary muscle fibres, 266 in respiration in sexes, 41") Differential rheotome, 599 Diffusion of liquids, 208 Digestion, 99, 186 deglutition, 115 gastric, 124 juices, 124 influence on heart's action, 287 insalivation, 115 intestinal, 146 juices, 148 bile, 159 pancreatic, 153 mastication, 99 muscles of, 109 Dilatation of arteries, 299 Discovery of the capillaries, 346, 387 of the circulation, 372 history of, 372 of the pulmonary circulation, 377 of the systemic circulation, 381 of white blood-corpuscles, 223 Disintegration of red blood-corpuscles, 222 Distribution of capillaries, 348 of spinal nerves, 637 Divisions of ear, 855 of heart, 265 of nervous system, 535 of spinal cord, 623 Ducts of mammary glands, 150 Dynamic electricity, 595 Dyspnoea, 467 INDEX. 937 EAR, 855 divisions of, 855 external, 855 function of, 855 structure of, 855 Eustachian tube, 860 internal, 860 aquseductus vestibuli, 868 basilar membrane, 872 cochlea, 867 endolvmph in, 869 labyrinth of, 868 membrane of Reissner, 869 modiolus of, 871 rods of Corti of, 869 saceulus of, 868 scala tympani, 869 vestibuli, 869 semicircular canals, 807 structure of, 866 utriculus of, 868 middle, 856 bones of, 857 function of, 850 structure of, 856 powers of, 861 Elasticity of veins, 362 Elastin, 72 Electrical current, 572 Electricity, static, 595 dynamic, 595 Electrodes, non-polarizable, 572 Electromotive force of nerve, 572 Electrotonic current, 596 Electrotonus, 596 Eleventh nerve, 682 Elongation of arteries, 299 Embryo, development of, 900 Embryonic layers, 908 membranes, 908 organs developed from, 908 Endocardium, 267 Endolvmph in ear, 869 Endosmometer, 203 E pi blast, 808 Epidermis, 739 Epididvmis, 896 Epiglottis, 841 Estimation of quantity of blood, 213 Eustachian tube, 860 Excrementitious matters in blood, 262 Excretion of urine, 529 Exhalation of carbonic acid, 438, 458 of organic matter, 456 of watery vapor, 456 Expenditure of heat, 499 Expiratory muscles, 412 External ear, 855 Extremities, development of, 926 Eye, 770 development of, 915 FACIAL nerve, 661 branches of, 663 course of, 662 Facial nerve, functions of, 661 Fallopian tubes, 889 Fat, quantity of, in various foods, 61 in tissues, 59 Fatty matters in blood, 261 Feces in large intestine, 185 Feeding of white blood-corpuscles, 223 Female generative apparatus, 888 Fibre 4 of heart, 266 of muscle, 875 Fibrin, 70 in blood, 260 in coagulation of blood, 236 Fick's spring kymograph, 336 Fifth nerve, 656 Filiform papilla?, 767 First nerve, 653 Fissures of brain, 704 of medulla oblongata, 627 of Kolando. 703 of spinal cord, 623 of Sylvius, 703 Flour, composition of, 91 Flow of blood in veins, 365 Foetal derivation of white corpuscles, 225 Follicles of hair, 746 Food, 80 composition of, 89 destructive changes of, 75 kinds of, 85 quality of, 88 quantity of, 88 use of, 83 Foramen ovale in cochlea, 870 rotundum, 870 Force, capillary, 359 of nerve, electromotive, 572 Form of corpuscles, effect on blood color, 213 of medulla oblongata. * ; '2 7 Forms of coagulation of bio d, 236 of nerve cells, 539, 540 Formula for uric acid, 524 Fourth nerve, 654 Fungiform papilla?, 766 GALVANOMETERS, 572 Ganglia, 725 Gases in blood, 255 Gastric digestion, 124 glands, 131 juice, action of, 138 duration of, 143 composition of, 137 Gelatinous fibres of Remak, 538 substance of Ro ando, 624 Generative apparatus, female, 888 male, 896 Genito-urinarv tract, development of, 923 Glands, 896 of large intestine, 181 of stomach, 131 Globulin, 71 938 1 NDEX, Glomeruli of kidney, f)1 1 G-losso-pharyngeal nerve, 668 course of, 669 functions of, 669 Glottis, SI I Glycogen, 17G Gmelin's test for bile, 17:! Goll, columns of, 624 Graafian follicle, 890 Gray matter of brain, 702 of spinal cord, '124 Gustation, 765 Gutturals in speech, 858 HM MATIN, 72 Haemin, 251 Haemodromometer, 339 Haemodynamometer, 323 Haemoglobin, 248 functions of, 255 Hairs, 745 Harvey, 372 Hearing, powers of, 861 Heart, 265 action of, 271, 286 causes of, 289 frequency of, 286 influence of digestion on, 287 of position on, 287 of respiration on, 288 of sleep on, 288 of temperature on, 288 of vagus on, 673 in various animals, 286 auricles of, 263 thickness of, 272 capacity of, 277 chordae tendineaa, 268 columnae carne;e, 269 corpora Arantii, 270 course of blood through the, 271 diastole of, 271 divisions of, 265 endocardium of, 267 fibres of, 266 movements of, 271 papillary muscles of, 269 position of, 265 rhythm of, 273 method of determining the, 274 sac of, 265 attachments of, 265 contents of, 265 description of, 265 sinus of Valsalva, 270 sounds of, 282 systole of, 271 valves of, 269 functions of, 271 movements of, 271 ventricles of, 265 thickness of, 272 weight of, 277 work done by, 281 Heat, animal, 470 produced in twenty-four hours, 493 value of foods, 495, 497 Ilenle, loop of, 511 Hepatic vein, proportion of corpuscles in, 230 Hippuric acid, 527 Human milk, 751 ovum, 47, &«79 Hunger and thirst, 80 Hyaloid tumor of eye, 781 Hydrostatic bellows, 319 Hymen, 889 Hypoblast, 808 Hypoglossal nerve, 585 course of, 685 distribution of, 685 functions of, 685 origin of, 685 TLEO-CzECAL valve, 181 JL Impregnation of ovule, 900 Incessures of Lautennann, 538 Indican in urine, 528 Induction apparatus, 545 Insalivation, 1 15 Inspiratory muscles, 404 Intensity of sound, 825 Intercostal muscles in respiration, 413 Intermaxillary hone, 106 Internal ear, 866 development of, 912 Intestine, large, 180 contents of, 185 feces in, 185 glands of, 181 valve of, 181 small, contents of, 179 Intestinal digestion, 146 Invertebrates, nerves of, 538 red blood-corpuscles of, 221 respiration in, 391 Iris, 773 Iron, quantity of, in spleen, 230 Island of Reil, 703 -) UICE, bile, 159 gastric, 124 composition of, 137 intestinal, 148 pancreatic, 153 IfATELECTROTONUS, 609 IV Keratin, 72 Kidneys, 508 function of, 508 glomeruli of, 511 Henle, loop of, 511 Malpighian bodies of, 510 structure of, 509 uriniferous tubules, 511 Kinds of food, 85 INDEX, 039 Kymograph, 331 Fick's spring, 336 LABIALS in speech, 853 Labvrinth of ear, 868 Lacteals, 189 Lacunar type of circulation in spleen, Large intestine, 181 Larynx, 395, 840 cartilages of, 840 cavity of, 841 function of, 395 mechanism of, 842 muscles of, 840 position of, 840 shape of, 840 vibrations in, 845 Latent period, 545 Lautennann, incessures of, 538 Law, Ohm's, 545 Hitter's, 621 Liquids, diffusion of, 208 miscibility of, 207 Liquor sanguinis in coagulation of blood, 236 Liver, 163 as a source of white corpuscles, 231 development of, 166 effect of, on formation of cornuscle* 230 K structure of, 163 in lower animals, 168 Lobes of brain, 704 Lobules of lungs, 400 Locality for production of white cor- puscles, 226 Localization of functions of brain, 715 Ludwig's respiratory apparatus, 446 Lumbar ganglia, 729 Lungs, 399 air-cells of, 400 number of, 400 alveoli of, 401 blood in, 401 sipply of, 400 elasticity of, 414 lobules of, 400 Lymph and chyle, 193 composition of, 193 Lymphatics, 190 ALE generative apparatus, 896 epididymis, 896 glands, 896 prostate, 896 semen, 897 seminiferous tubules, 897 spermatic curds, 896 spermatozoa, 898 testicles, 896 tunica albuginea, 896 JMalpighian bodies, 510 corpuscles in spleen, 229 Mammary glands, 750 Manometer, differential, 335 frog, Brubaker's. 328 Marrow, red, of bone'as a source of blood corpuscles, 231 Mastication, 99 muscles of, 109 Maxillary bones, 105 articulation of, 105 Mechanical work done during respira- tion, 427 F Mechanism of lar.nx, 842 Medulla oblongata, 627 Medullary nerves, 537, 651 functions of, 632 pairs of, 652 number of, 652 varieties of, 652 Melanin, 72 Membranes, embrvonic, 908 Membrane of Reissner, 869 Menstruation, 895 Mesoblast, 808, 906 Metastatic thermometers, 473 Metronome, 417 Middle ear, 856 Milk, human, 751 Miscibility of liquids, 207 Modiolus of ear, 87 Movements of heart, 271 of respiration, 416 of white corpuscles, 223 Mucosin, 71 Mucous membrane of stomach, 131 Mucus, bronchial, composition of, 398 nasal, composition of, 398 Muscle pla*ma, 880 i Muscles, 875 contraction of, 875 apparatus for studying, 878 chemical changes during, 876 curves of, 877 physical changes during, 876 sounds produced by, 879 fibres of, 875 myosin of, 880 ocular, action of, 808 of larynx, 840 of mastication, 109 of respiration, 404, 410, 412 plasma of, 880 sarcolemma of, 875 sheath of, 875 striss of, 875 varieties of, 875 Musculin, 71 Myograph, 276 pendulum, 545 spring, 545 Myosin, 880 YTAILS, 743 11 Nasal mucus, composition of, 398 Negative variation, 596 940 INDEX, Nerve, eleventh, 682 force, velocity of, 545 ninth, 668 seventh, 661 tenth. 669 twelfth, 685 Nerves, 535 axis-cylinder of, 537 bulbs of, 542 cells of, 539 forms of, 530, 540 cranial, 653 gelatinous fibres of Remak, 538 incessures of Lautennann, 538 medullary, 537, 651 neurilemma, 538 nodes of Ranvier, 538 non-medullary, 538 of invertebrata, 538 of spinal cord, 630 of vertebrata, 538 optic, 769 peripheral distribution of, 540 sheath of Schwann, 538 substance of Schwann, 537 tactile corpuscles of, 542 Nervous system, 534 definition of, 535 development of, 910 divisions of, 535 structure of, 534 sympathetic, 724 Neural tract, 906 Neurilemma, 538 Nodes of Ranvier, 538 Non-medullary nerve-, 538 Non-polarizable electrodes, 572 Nose, 761 Nourishment of arteries, 293 Nuclei of white blood-corpu;cles, 223 Nucleolus of a cell, 44 Nucleus of a cell, 44 Number of air cells, 400 of respirations, 426 of sudoriferous glands, 753 of white blood-corpuscles, 233 in spleen, 229 OCULAR muscles, action of, 808 Oculo-motor nerve, 653 Ohm's law, 545 Olfaction, 761 Olfactory nerves, 652 tracts, 762 origin of, 762 termination of, 763 Olivary bodies, 627 Oncometer, 735 Optic nerves, 652, 769 thalamus, 692 Optics, physiological, 783 Organic matter, exhalation of, 456 Organs developed from embryonic layers 908 Organs of body, development of, 908 of reproduction, 885 of vision, 769 Origin of hile, 175 of optic nerves, 769 of hypoglossal nerve, 685 of olfactory tracts, 762 of pneumogastiic nerve, 669 of spinal accessory, 682 of urea, 521 of uric acid, 525 Osmosis, 202 Ostein, 71 Ovaries, 889 Ovule, 887 Ovum, 47, 888, 891 Ox flesh, composition of, 87 Oxygen, absorption of, 438 Oyster, composition of, 87 PAPILLARY muscles of heart, 269 Paraglobulin in the coagulation of blood, 240 Paramcecium caudatum, 46 Pairs of medullary nerves, 651 Pancreatic juice, 153 Pancreatin, 71 Papillae, circum vallate, 765 filiform, 767 fungiform, 766 of skin, 740 Pathetic nerve, 654 Pediastrum pertusum, 47 Pendulum myograph, 545 Pepsin, 71 Perception by sitrht, 817 Pericardial sac, 265 Period, latent, 545 Peripheral distinction of nerves, 540 Perspiration, 754 Pettenkofer's test for bile, 172 Phosphoric acid in urine, 528 Physical changes during contraction of muscles, 876 structure of body, 43 Physiologica: acoustics, 822 optics, 783 Pitch of sound, 826 Placenta, development of, 928 Plasma, muscle, 880 Plasmin in the coagulation of blood, 240 Plethysmograph of Mosso, 355 Pleura?, 401 Plexus, solar, 728 Pneumogastric nerve, 669 branches of, 771 course of, 669 function of, 669 influence of, on heart, 613 origin of, 669 Pneumograph, 416 Pons Varolii, 629, 688 definition of, 688 function of, 688 INDEX, 941 Portal vein, proportion of corpuscles in, 230 Position, influence of, on heart's action, 287 of heart, 265 of tongue, 840 of valves of heart, 285 of white blood-corpuscles in blood streams, 224 Posterior columns of spinal cord, 623 Potassium chloride in body, 52 Potato, composition of, 87 Powers of hearing, 861 Pregnancv, effect on white corpuscles, 224 Pressure, arterial, 325 blood, 309, 313,321 in capillaries, 357 in veins, 364 Primitive trace, 904 Principles, chemical composition of, 56 nitrogenous, 55 non-nitrogenous, 55 organic, 55 Process of coagulation of blood, 236 Production of animal heat, 484 of carbonic acid, 461 Proportion of white blood-corpuscles, 223, 231 and red corpuscles in hepatic vein, 230 in portal vein, 230 Prostate gland, 896 Protamceba, 45 Protective appendages to eye, 819 Protococcus pluvialis, 47 Proximate principles of organic origin, 55 of the third class, 66 resume of, 77 Pulmonary circulation, discovery of, 377 Pulmonic circulation of blood, 264 Pulp of spleen, 229 Pulse, dicrotic, 311 transmission of, 309 wave length of, 310 Pump for artificial respiration, 424 Pyramids of medulla oblongata, 627 QUADRIGEMINAL BODIES, 694 functions of, 695 Quality of food, 88 of sound, 831 Quantity of blood, 213 modes of estimating, 2] 3 of calcium carbonate in body, 53 phosphate in body, 52 of fat in various foods, 61 tissues, 59 of food, 88 of iron in spleen, 230 of potassium chloride in body, 52 of sodium carbonate in body, 53 chloride in body, 51 Quantity of starch in various foods, 57 of sugar in various foods, 58 of water in body, 50 RANVIER, nodes of, 538 Rapidity of circulation, 370 in veins, 369 of coagulation of blood, 237 Rate of the heart beat, 281 Ratio of brain to spinal cord, 645 Ration of U. S. soldier, 92 Reaction of urine, 513 Rectum, absorption by, 200 Red blood-corpuscles, 214 counting of, 2 1 5 apparatus for the, 216 development of, 222 fiom white corpuscles, 225 diameter of, 219 in various animals, 219 difference in size, in various animals, 219 from white, 224 disintegration of, 222 number of, 215 of invertebrates, 22] of vertebrates, 221 shape of, 217 structure of, 214 study of, 217 corpuscles in spleen, 230 marrow of bone as a source of blood corpuscles, 231 Reflex action, 647 nature of, 647 Refraction, 783 Regnault's and Reisel's respiratory ap- paratus, 443 Regulation of heat, 499 Reil, island of, 703 Reissner's membrane, 869 Remak, gelatinous fibre of, 538 Reproduction, 885 consideration of, 885 corpus luteum, 893 of menstruation, 893 of pregnancy, 893 development of embryo, 900 alimentary canal, 915 allantois, 908 amniotic folds, 906 area opaca in, 905 pellucida in, 905 blastoderm in, 903 cerebral vesicles, 911 epiblast, 808 extremities, 926 eye, 915 genito-urinary organs, 923 hypoblast, 808 internal ear, 912 mesoblast in, 808, 906 nervous system, 910 942 INDEX. Reproduction, development of embryo- neural tract, 700 of organs, 908 placenta, 5)28 primitive organs, 905 primitive truce in, 904 respiratory organs, 922 segmentation of ovum in 902 skull, 912 teeth, 916 va-cular system, 918 Graafian follicle in, 890 human ovum in, 879 impregnation of ovule, 900 menstruation, 895 methods of, 885 of cells, 4"> organs of, 888 hymen, 889 ovaries, 889 uterus, 888 Fallopian tubes, 889 walls of, 889 vagina, 889 ovaries in, 892 ovule in, 887 ovum in, 888, 891 spermatozoa in, 888 Resemblance of chyle to blood, 228 Resistance of nerve, 585 Respiration, 391 absorption of oxygen in, 438 amount of, 441 apncea in, 467 apparatus, 433 artificial, 423 canula for, 424 pump for, 424 asphyxia in, 467 bronchi, structure of, 399 capacity of, 430 spirometer for testing, 430 carbonic acid exhaled, determination of, 453 complemental air in, 432 conditions influencing production of carbonic acid, 456 difference of, in sexes, 415 dyspnoea in, 467 effects on blood pressure, 422 exhalation of carbonic acid, 438, 458 of organic matter, 436 of watery vapor, 456 Graham's law in, 435 in invertebrata, 392 forms of, 393 influence on heart's action, 287 larynx in, function of, 395 structure of, 395 lungs, air-cells in, 400 number of, 400 alveoli of, 401 blood in, 401 supply of, 400 Respiration, lungs, functions of, 399 tubules of, 400 varieties of, 400 mechanical work done during, 427 movements of, 416 effects of, on blood pressure, 422 tracings of, 421 muscles of, action of, 412 diaphragm as a, 404 action of, 406 expiratory, 412 inspiratory, 404 intercostal, 413 varieties of, 414 scaleni, 411 number of, 426 pleurae, 401 production of carbonic acid, 461 residual air in, 432 ribs in function of, 407 action of, 408 sounds of, 425 temperature of expired air in, 464 tidal air in, 431 trachea in, function of, 397 structure of, 397 Respiratory apparatus, 443 organs, development of, 922 Restiform bodies, 627 Rete mucosum, 741 Retina, 776 Rheocord, 602 Rheotome, differential, 599 Rhythm of heart, 273 Ribs, action of, in respiration, 408 function of, in respiration, 407 Ritter's law, 621 Rods of Corti, 869 Rolando, fissure of, 703 gelatinous substance of, 624 Roots of spinal nerves, 630 Running, 883 SAC around heart, 265 Sacral ganglia, 729 Saline matters in blood, 261 Saliva, 114 composition of, 118 function of, lis Salivary glands, 114 Salts of bile, 171 Sarcolemrna of muscle, 879 Scala tympani, 869 vestibuli, 869 Scaleni muscles, 411 Schwann, sheath of, 538 substance of, 537 Sclerotic coat, 770 Sebaceous glands, 748 Second nerve, 653 Segmentation of ovum, 902 Semen, 897 Semicircular canals, 867 Seminiferous tubules, 8 Sensation of sight, 809 INDEX. 943 Sensation of colors, 814 Sense of taste, 765 Sensibility, tactile, 758 Serum, in coagulation of blood, 236 Seventh nerve, 661 Sex, influence of, on temperature, 475 Sexes, difference in respiration, 415 Shape of larynx, 840 Sheath of muscle, 875 of Schwann, 538 Sight, sensation of, 809 perception by, 817 Sinus of Bakalva, 271 Size of white blood-corpuscles, 223 Skin, 737 appendages of, 737 dermis or true, 739 description of, 737 epidermis, 739 functions of, 737, 754 perspiration, 754 amount of, 755 composition of, 755 hairs, 745 follicles of, 746 composition of, 747 layers of, 738 nails, 743 papilla? of, 740 rete mucosum of, 741 sebaceous glands of, 748 matters of, 749 sensibility of, 758 sudoriferous glands of, 752 number of, 753 Skull, development of, 912 Sleep, causation of, 721 influence on heart's action, 287 Small intestine, contents of, 179 Sodium carbonate in body, 53 chloride in body, 51 sulphate, effect, on the coagulation of blood, 240 Solar plexus, 728 Soldier, ration of, 92 Sound, 825 intensity of, 825 pitch of, 825 quality of, 825 Sounds of the heart, 282 respiration, 425 Specific gravity of blood, 212 of urine, 513 heat of tissues, 488 Spectroscopic analvsis of hsemoglobin, 237 Spectrum analysis of blood, 254 Speech, 851 dentals in, 853 gutturals in, 853 labials in, 853 mode of, 852 Spermatic cord-, 896 Spermatozoa, 888, 898 Sphygmograpb, 301 Sphygmograph, uses of, 302 Spinal accessory nerve, f>82 cour.-e of, 682 functions of, 682 origin of, 682 Spinal cord,' 623 anterior column of 623, as a nervous centre, 639 cells of, 624 columns of, 623 of Goll, 624 of Clarke, 624 of Burdach, 624 composition of, 623 cornua of, 635 course of fibres of, 629 divisions of, 623 extent of 623 fissures of, 623, 627 form of, 627 functions of, 634 gelatinous substance of, Ro- lando, 624 gray matter of, 624 medulla oblongata, 627 nerves of, 630 roots of, 630 distribution of, 637 nerve centres in, 619 olivary bodies, 627 pons Varolii, 629 posterior columns of, 623 pyramids of, 627 ratio of brain to, 645 restiform bodies, 627 reflex action of, 647 weight of, 623 Spinal nerves, 630 functions of, 634 Spirometer, 430 Spleen, 228 a lymphatic gland, 229 as a source of white corpuscles, 231 iron, quantity of, in, 230 lacunar type of circulation in, 229 Malpighian corpuscles of, 230 number of white corpuscles in, 229 pulp of, 229 red-blood corpuscles in, 230 structure of, 229 vascularity of, 229 Spring myograph, 545 Starch, quantities of, in various foods, 57 Static electricity, 595 Stethometer, 418 Stomach, absorption by, 250 digestion in, 137 experiments on, 129 function of, 125 glands of, 131 juices of, 135 mucous membrane of, 131 of Alexis St. Martin, 126 Strength of veins, 363 Stria? of muscle, *75 944 INDEX. Striated bodies, 690 Stromuhr, Lud wig's, 340 Structure of body, 43 in lower animals, 168 of bronchi, 399 of capillaries, 348 of external ear, 855 of internal ear, 866 of kidneys, 509 of larynx, 395 of liver, 163 of middle ear, 856 of nervous system, 534 of red blood-corpuscles, 214 of spleen, 229 of trachea, 397 of veins, 361 of white blood-corpuscles, 223 Substance of Schwann, 537 Sudoriferous glands of skin, 752 Sugar, quantities of, in various foods, 58 Suprarenal body as a source of white cor- puscles, 232 Sylvius, fissure of, 703 Sympathetic nervous system, 724 effects of division of cer- vical sympathetic, 731 ganglia of, 725 cervical, 727 lumbar, 729 sacral, 729 solar plexus, 728 vasodilator nerves, 733 vasomotor centre, 732 Systemic circulation of blood, 264 discovery of, 381 System, nervous, 534 Systole of heart, 271 TACTILE corpuscles, 542 sensibility, 758 Taste 765 bird's, 765 circum vallate papillae, 765 filiform pa pit lie, 767 fungiform papillae, 766 sense of, 765 Tea, composition of, 93 Teeth, 100 development of, 916 enamel of, 103 pulp of, 105 Temperature, 478 atmospheric influence on bodily, 478 effect on coagulation of blood, 238 influence of baths on, 481 of food on, 476 of glandular action on, 477 of mental action on, 477 of muscular action on, 477 of sex and age on, 475 of time of day on, 475 on heart's action on, 287 of blood, 212 Temperature of expired air, 464 of various animals, 471 Ten- ion of gases in blood, 437 Tenth nerve, 669 Termination of olfactory nerves, 763 Testicles, 896 Tests for bile, 172 Thalami optici, 692 Thermometers for studying animal heat, 473 Thickness of ventricles of heart, 265 of auricles of heart, 265 Third nerve, 653 Thirst and hunger, 80 Thoracic duct, 189 Thymus gland as a source of white cor- puscles, 232 Thyroid gland as a source of white cor- puscles, 234 Tidal air, 431 Tissue, distinctive changes of, 75 Tongue, 765 functions of, 765 Tonicity of arteries, 297 Trachea, 397 function of, 397 Tracings of respiration, 421 Tracts, olfactory, 762 Transformation of white corpuscles into red, 225 Transmission of pulse wave, 309 Trigeminus, 656 Tubules, uriniferous, 511 Tunica albuginea, 896 Twelfth nerve, 685 UREA, 72 derivation of, 72 determination of, 516 Uric acid, 524 Urine, 512, 524 alkaline, formation of, 533 amount of, 514 coloring matter of, 513 composition of, 512 constituents of, 515 definition of, 512 excretion of, 529 method of, 530 hippuric acid, 527 indican in, 528 influence of exercise on, 519 phosphoric acid in, 529 reaction of, 513 specific gravity of, 513 urea in, 515 amount of, 518 crystals of, 516 determination of, 516 origin of, 521 uric acid in, 524 amount of, in, 524 in various animals, 524 crystals of, 526 INDEX. 945 Urine, uric acid in, formula for, 524 origin of, 525 volatile acids in, 528 Uriniferous tubules, 511 Urrosacin, 72 Use of food, 83 of villi in absorption, 104 Uterus, 888 Utriculus of ear, 868 yAGINA, sgg V Vagus nerve, 669 Valsalva, sinus of, 271 Value of food for heat, 495, 497 Valves of heart, 269 position of, 285 of large intestine, 181 of veins, 361 Variation in calibre of capillaries, 352 in number of white corpuscles, 224 in temperature of blood, 212 negative, 596 Varieties of cells, 45 of crystals of hasmoglobin, 249 of gases in the blood, 255 of lobules of lungs, 400 of muscle, 875 Vascularity of spleen, 229 Vascular system, development of, 918 Vasodilator nerves, 733 Vasomotor centre, 732 Vaso-vasorum of arteries, 293 of veins, 361 Vegetable foods, composition of, 86 Veins, 361 anastomoses of, as a means of absorption, 189 blood pressure in, 361 circulation in, rapidity of, 369 coat of, 369 contractility of, 369 elasticity of, 362 flow of blood in, 365 causes of, 365 sets of, 361 strength of, 363 structure of, 361 valves of, 361 vaso-vasorum of, 361 Velocity of the blood, 341 in capillaries, 352 of nerve force, 545 Venous blood, color of, 213 gases in, 259 Ventricles of heart, 265 Vertebrates, nerves of, 533 red blood-corpuscles of, 221 Vibrations in larynx, 845 Villi, structure of, 195 uses of, in absorption, 194 Vision, 169 binocular, 806 Vitreous humor, 781 Vivisection, 39 Voit's respiratory apparatus, 447 Volatile acids in urine, 52 WALKING, 883 Walls of uterus, 889 Water, amount of, in blood, 242 in coagulation of blood, 236 quantity of, in body, 50 Watery vapor, exhalation of, 456 Weight of brain, 707 of heart, 277 of spinal cord, 623 Whippe, 545 White blood-corpuscles, 223 chemical constituents of, 223 derivation of, 225 foetal, 225 difference from red, 224 discovery of, 223 effect of acetic acid on, 223 of alkalies on, 223 effect of pregnane v on, 224 feeding of, 223 identit} r with those of lymph and chyle, 224 liver as a source in, 231 locality for production of, 226 movements of, 223 nuclei of, 223 number of, 223 in spleen, 229 variations in. 224 position of, in blood stream, 224 production of, 231 proportion of, to red, 223 variations in, 224 size of, 223 spleen as a source of, 231 structure of, 223 suprarenal body as a source of, 232 thymus gland as a source of, 232 thyroid gland as a source of, 234 transformation into red, 226 White matter of brain, 702 Wine, composition of, '.'7 Work done by heart, 281 ZONA opaca, 905 Zona pellncida, 905 60 ■'-,.'••' '■..'.-.' ",