Makers of Modern Medicine Part 15

[Footnote 11: Mikroskopische Untersuchung uber die Uebereinstimmung in der Structur und dem Wachsthum der Thiere und Pflanzen, 1839.]

At Louvain, Schwann remained for about ten years. The period is marked by a continuance of his fruitful investigation of cell-life, of the physiological biology of ferments and fermentation, and of the allied subject of digestion in animals. His researches in Berlin on this interesting and important subject, which was practically a complete mystery at that time, had been mainly concerned with the gastric juice. He now began the study of various secretions which aid intestinal digestion. He proved that bile, which used to be considered an excretion, was really an important digestive secretion. He was not able to demonstrate the function of bile as completely as he had done for the gastric juice. The problem of intestinal digestion is much more complicated than that of stomach digestion, and involves a number of factors for which allowance has to be made if the value of any one of them is to be accurately determined. Even in our own day all of the physiological problems in the functions of biliary secretion are not solved. The greatest step was the demonstration that bile is a thing whose presence in the intestines is to be encouraged, not because, as Horace said, mental trouble was imminent unless one were purged of black bile in the springtime, but because its presence insures the proper preparation of food, and neutralizes in the intestinal tract certain poisonous substances that if absorbed would prove sources of irritation to all higher tissues.

His work on bile practically closes Schwann's career as an investigator. The seven years between twenty and {266} twenty-seven were so full of discovery that there seemed to be great promise for his mature years. Had Schwann died at thirty his biographies would have surely contained lengthy comments on the great discoveries that would undoubtedly have rewarded his efforts in the prime of his powers. Schwann's seeming inactivity has been a fruitful cause for conjecture. The fact of the matter is, however, that original work of a high order is accomplished mainly during the time when activity of the imagination is at its height. There are very few cases in which this acme of inventive effort has lasted more than ten years.

Besides this there were certain more material factors that hindered original work. Schwann was a German, yet had to give his lectures at Louvain in French. For several years most of his efforts were devoted to acquiring facility in the language of his adopted country. Then Schwann was not such a teacher as Muller, but the true pedagogue who took seriously to heart the duty of teaching all his students. To do this meant, in the rapidly advancing science of that day, unceasing toil on the part of a conscientious professor. For it was a time of great discoveries succeeding one another with almost incredible rapidity. For ten years Schwann faithfully devoted himself to his teaching duties in the anatomical course at Louvain. He then accepted the chair of comparative anatomy and physiology at Liege, where he continued to lecture for thirty years. As the result of his stay at Louvain there has always been special attention given to biological studies at that university. At the present time there is published there a very well and favorably known biological journal, _La Cellule_, through which many important contributions from the professors and students of the university find their way before the public.

During his stay at Liege Schwann was formally invited, {267} on three different occasions, to return to his German Father-land to become professor at some of her great universities. Professorial chairs in anatomy or physiology at Wurzburg, at Giessen, and at Breslau, were offered him between 1850 and 1860. He refused them, however, to continue his work in Belgium. He found his adopted countrymen eminently sympathetic. It seems clear that he felt more at home in the midst of the profoundly Catholic sentiment that pervaded the Belgian universities, and which was in such marked contrast to the rationalistic spirit characteristic of the German universities at that time. Schwann was penetrated with a lively sense of the deepest religious feeling, which is noticeable all through his life. His att.i.tude in this matter greatly impressed his scientific contemporaries. His sense of duty in matters spiritual was only equalled by his affectionate regard for his relatives. His vacations were invariably spent with his parents while they were alive, and later with his brothers and sisters in the neighborhood of Cologne. It was while making a Christmas visit to them that he suffered the fatal stroke which carried him away.

Toward the end of his career Schwann was invited to be a member of a commission to investigate the case of Louise Lateau. It will be remembered that the report of recurring bleedings from stigmata in this case attracted a great deal of attention, not only among Catholics, but among all cla.s.ses throughout the world. After careful observation Schwann refused to concur in the report that the bleedings were manifestly miraculous. At first it was announced that he had declared them evidently beyond the domain of natural causes, but this report he took occasion to correct immediately. The circ.u.mstance led to the publication of some harsh words in the religious press, but with his usual moderation Schwann refused to enter into any discussion, and so the affair ended. {268} His thoroughly conservative att.i.tude in the matter, and his application of the strictest scientific criteria to the case, prevented formal expression of approval on the part of those in authority. While such an opinion would have carried only personal weight with it, it might easily have been made a cause for unfortunate aspersions upon the Church.

The most marked feature of Schwann's career is the unfailing friends.h.i.+ps that linked him to those with whom he was a.s.sociated. At Louvain, and later at Liege, he was the personal friend of most of his students, while at Berlin he made friends.h.i.+ps with some of the great men in German medicine which endured to the end of his life. When the celebration of his fortieth anniversary came around, the hearty tributes from all over Europe showed in what lofty reverence the kindly old man was held, who had sacrificed some of his chances for greater scientific fame in order to be a teacher of others, and a living exponent of the fact that the frame of mind which leads to great scientific discovery and that which bows humbly to religious truth, far from being hopelessly and essentially opposed to each other, may be peacefully united in the same person in their highest expression.

{269}

CLAUDE BERNARD, PHYSIOLOGIST

{270}

The experienced eye, the power of perceiving minute differences and fine a.n.a.logies which discriminate or unite the objects of science, and the readiness of comparing new phenomena with others already treasured up in the mind--these are accomplishments which no rules can teach and no precepts put us in possession of. This is a portion of knowledge which every man must acquire for himself; n.o.body can leave as an inheritance to his successor. It seems, indeed, as if nature had, in this instance, admitted an exception to the will by which she has ordained the perpetual acc.u.mulation of knowledge among civilized men, and had destined a considerable portion of science continually to grow up and perish with individuals.

--Dr. John Brown, _Edward Forbes, Spare Hours_.

{271}

CLAUDE BERNARD, THE PHYSIOLOGIST.

With the recent development of post-graduate education the College de France has become a favorite shrine of pilgrimage for educators who visit Paris. It represents the oldest educational inst.i.tution deliberately founded with the idea of combining teaching with investigation. The professors were not bound to teach definite doctrines, literary or scientific, but to give rather the results of recent investigations and personal meditation on great scientific and philosophic problems. The college was not meant, in a word, so much for students as for specialists. It was intended not to convey a definite body of knowledge on any subject, but rather to round out the knowledge acquired in the regular course at the University of Paris, and to dwell particularly on recent lines of advance in special subjects in a manner that would encourage original investigation.

In a word, the College de France was the first modern post-graduate school. We have learned in recent years how important are post-graduate departments for their influence on the regular work of a university. Unless original investigation of a high order is constantly done at a university, it is inevitable that the regular course will cease to be up to date. Modern educators are coming to realize very forcibly this quality of a successful teaching inst.i.tution. Hence the interest that will surely continue to grow in the College de France, its foundation, its history, its teachers, and its methods.

To the great majority of those who come to pay their respects at this shrine of original investigation, it will prove a {272} distinct surprise to find the centre of the court of the College de France occupied by a statue of Claude Bernard. Bernard is not well known, and is still less appreciated out of scientific circles. By many it is forgotten that the original free school, the _College de trois langues_, in which Hebrew, Greek, and Latin were the only chairs, has extended its scope, and that in our day the natural sciences represent the most fertile field of its achievements. The absolute freedom of opinion guaranteed to professors originally, and which const.i.tuted the princ.i.p.al reason for an educational inst.i.tution apart from the University of Paris and its trammels, has proved a precious heritage to later generations. Science has flourished vigorously, and the memorial to its representative cultivator at the college in this century has deservedly been given the place of honor in its court.

To the initiate, however, for whom, in medicine and physiology and general biology, his work is still an inspiration, many points of interest around the college will have all their attraction from a.s.sociations with Claude Bernard's career. His neglect by the popular mind is more than compensated for by the fervent admiration of all those who are occupied with investigations along the lines he followed. For in him they recognize a master mind such as is given to a branch of science not more than once in a century; the veritable possessor of a magician's wand, who knows how to disclose the hidden veins of precious ore, the exploitation of which will prove a source of riches to so many faithful followers. For these the dark little laboratory of the college in which Bernard made so many of his ground-breaking discoveries will be in the nature of a shrine to which one comes with grateful memories of the _genius loci_ that was. The apartment across the street at No. 40 Rue des Ecoles, where Bernard lived for years, will be the term of many a pilgrimage. Scientists {273} from all over the world will wander from here out to the laboratory in the Jardin des Plantes, where Bernard's work was done in his later years, and where the fundamental problems of life--plant and animal--usurped the attention that had at first been devoted exclusively to human physiology and its allied sciences.

Claude Bernard is another and a striking ill.u.s.tration of the historical tradition that great men usually come from the country, and not infrequently from poor parents. He was born in 1813, at St.

Julien, not far from Lyons, almost in the centre of France. His father owned a small farm in the Beaujolais wine district. The little estate came later into Bernard's hands, and when he could afford the time he spent his summers there. When the air is clear the white summits of the Alps can be seen, and they make a pleasing contrast to the plains along the Saone and the hill-sides of the immediate neighborhood, all covered with vineyards. The physiologist, who enjoyed nature very much, speaks enthusiastically of his "little verdant summer nest."

He was educated at the Jesuit school of Villefranche. It will be recalled that Theodore Schwann was also a student of the Jesuits. In these days, when Jesuit educational training is impugned, the facts are worth noting. It is claimed especially that the old-fas.h.i.+oned training by means of the cla.s.sics is narrowing. The old method of a definitely prescribed course of study for every student is said to hamper development. Slavish devotion to old pedagogic methods, it is urged, cannot but shackle and destroy initiative. The subordinate place of the sciences in this scheme of education is said to hinder progress in the sciences later in life, to leave the powers of observation undeveloped until too late, and to distract the mind of the student too much from the practical side of life. Here are two men whose lives are {274} an open contradiction to all the allegations of the opponents of the old Jesuit system of training. Needless to say that they are but two of many.

Bernard pursued the course with the Jesuits at the College de Villefranche as far as it went. After this we find him at Lyons, at first pursuing studies in philosophy in preparation for his baccalaureate degree, evidently with the idea of eventually entering the university. Family reasons, mainly financial, compelled him to give up his studies, and for nearly two years he was an a.s.sistant in a pharmacy in Lyons. Here he developed a skepticism with regard to the effect of the drugs he compounded that led later in life to his important studies on the physiological action of remedies.

The science of therapeutics was at that time in a most inchoate stage.

Very little was known of the exact action of drugs. Exaggerated claims were made for many, but mainly on uncertain clinical experience. The modern, patent medicine was as yet unknown, but something not unlike it had become popular among the patrons of the Lyons pharmacy. One remedy was in constant demand by city patrons and by country people, who came from long distances especially to procure it. It was known as _la theriaque_--"the cure"--I suppose from some fancied connection with the root of the word therapeutics.

This remedy, according to the old women of the neighborhood and the countryside, was a panacea for every ill that flesh is heir to, and a few others besides (_pro morbis omnibus cognitis et quibusdam aliis_).

The composition of this wonder-worker was even more interesting than its universal curative efficacy. Whenever a drug spoiled from too long keeping, or an error in its manufacture made it unavailable for the purpose for which it was originally intended, or whenever an involuntary mistake in compounding occurred, the {275} a.s.sistants in the pharmacy were directed not to throw the drugs away, but to reserve them for "la theriaque." "Mettez vous cela de cote pour la theriaque"

(put that aside for "la theriaque") was a standing order in the shop.

From a remedy of such varied ingredients the most wonderful effects could be expected and were secured. An unexpected action of the remedy, however, was that produced on Bernard's mind. This influence was later to lead to the healing of numberless ills in the system of therapeutics, and to bring about the establishment of the sciences of experimental pharmacology and physiology.

Bernard developed literary ambitions while at work in the pharmacy. He spent many of his free evenings at the theatre, and wrote a musical comedy, "The Rose of the Rhone," which was acted with some success. He worked at a prose drama, and, thinking the possibilities of life too narrow in Lyons, he resolved to go to Paris. With his play in his pocket, and a letter of introduction to the distinguished critic, St.

Marc Girardin, he reached the capital. Bernard's drama, "Arthur de Bretagne," was published after his death, and shows that its author possessed literary talent of a high order. This must have been evident to Girardin, to whom it was given to read; but he very wisely advised its author to eschew literature, at least for a time, until he was able to make his living by some other means. Girardin advised Bernard to take up the study of medicine, for which his work in pharmacy had already prepared him somewhat.

Bernard, having once made up his mind to pursue medicine, threw himself, as was his wont, enthusiastically into the study of it. The utmost frugality was necessary in order to enable him to live on the scant income that could be allowed him from home. He lived with a fellow-student in a garret in the Quartier Latin. Their one room was study and {276} sleeping room, and even, on occasion, kitchen. When a "box" came from home, utensils were borrowed from the laboratory for whatever cooking was necessary.

Bernard was especially interested in anatomy, and soon made himself known by the perfection of his dissections. Physiology attracted him not for what was known in the science, but for the many problems as yet unsolved. His was above all a mind not p.r.o.ne to accept scientific teaching on the _ipse dixit_ of a professor. Except in the dissecting-room, his work attracted no attention. He was not looked upon as a brilliant student, and yet all the while he was unconsciously preparing himself thoroughly for his life-work. Later on his dissecting skill was to be a most helpful acquisition. Bernard's first promising opening came unexpectedly. The nicety with which he did certain dissecting work in preparation for one of Magendie's lessons attracted the attention of the professor, at that time the greatest living experimental physiologist. Magendie, in his bluff, characteristic way, without asking further about him, called out one day: "I say, you there, I take you as my _preparateur_ at the College de France."

This position was gladly accepted by Bernard, for it provided him with an income sufficient to support himself. The work was congenial. His duty was to prepare the specimens and make ready the demonstrations for Magendie's lectures. His career as a physiologist dates from this appointment. He had to give some private lessons, and do what is called "coaching," or "tutoring," to eke out his slender income, but in the main his time after this was entirely devoted to investigation and experiment.

His first investigation concerned stomach digestion. It was important mainly because it directed his mind to digestive questions. In these he was to make his great discoveries. {277} His first independent investigation concerned the differences to be found in the digestive apparatuses and functions of the carnivora and herbivora--that is, of the meat and plant-eating animals. The differences in the natural habits of these two cla.s.ses of animals had long been noted. While the meat-eaters invariably bolt their food, the plant-eaters chew theirs very carefully. Many of these latter, like the cow, are ruminants--that is, they bring up their food to chew it over again at their leisure. The instinct that makes them do this is most precious.

Their food is mainly composed of starch, in the digestion of which the saliva takes a large part. The thorough mixture of the food with saliva, then, is an extremely important matter. Human beings, who are both herbivorous and carnivorous, must learn to masticate thoroughly at least the starch-containing portions of the food. Bernard's first researches concerned the nerves that supplied the salivary glands, and which consequently influence the flow of saliva. Curiously enough, the conclusions of his first experiments were erroneous. The topic led him, however, into the general subject of the influence of nerves upon glandular secretion, a problem that he was destined to ill.u.s.trate in many ways.

After the salivary glands the most important structure for the digestion of starches in the animal economy is the pancreas. It was early evident, however, that the pancreatic secretion effected more than the conversion merely of starch into sugar. Its most important role, that of influencing the digestion and absorption of fats, was only recognized as the result of a cla.s.sical observation of Bernard's upon the rabbit. He noticed that fat introduced into the digestive tract of a rabbit undergoes no change until it has advanced a considerable distance beyond the stomach. When fat is introduced into the dog's digestive apparatus a marked change {278} begins in it almost as soon as it leaves the stomach. At first this seemed very mysterious. Observations were made over and over again, always with the same result. There was evidently some important distinction between the intestines of the two animals. Careful investigation showed that the difference between the behavior of the fat in the rabbit and the dog was due to the presence or absence of the pancreatic fluid from the intestinal contents. In the dog the pancreatic duct which carries the secretion of the gland to the intestine empties into the intestine just beyond the stomach. In the rabbit the duct and its secretion empty into the intestine only some eight to ten inches below the intestinal orifice of the stomach. It is just beyond where the pancreatic duct reaches the intestine in both animals that the digestion of fat begins. This observation solved the seeming mystery of fat digestion, and at the same time made clear the importance of the pancreatic secretion in the general work of digestion.

Bernard's attention was directed by this first observation to the other properties of the pancreatic fluid. He soon demonstrated by experiment, not only that it split up fats into fatty acids and glycerin, and so made their absorption possible, but that it had a powerful action upon proteids--that is, upon the alb.u.minous portions of the food, and also upon the starches and sugars. Up to this time the princ.i.p.al role in digestion had been a.s.signed to the stomach and the gastric juice. After Bernard's observations it was evident that the action of the stomach was mainly preliminary to intestinal digestion, and that the chief work in the preparation of food for absorption into the system was really accomplished by the secretion of the pancreas. It took some years to make all this clear. Much of the advance in our knowledge of the effect of pancreatic juice upon proteids--that is, upon meat and other alb.u.minous materials--is due to Kuhne, a pupil {279} of Bernard; but not only did the inspiration for the pupil's work come from the master, but the important fundamental principle of pancreatic proteolysis--_i.e._, the solution of proteids by pancreatic secretion--was clearly laid down in Bernard's original publications on the subject. Only in our own day has come the greatest confirmation of the notion then first introduced into physiology, of the surpa.s.sing importance of intestinal digestion. The removal of the whole stomach for malignant disease is now undertaken without any fears as to the ultimate result on the patient's general nutrition.

The operation has been done many times, and the surgeon's confidence that the intestines would compensate, as far as digestion of food was concerned, for the absent stomach has been amply justified. Patients who survived the operation have all gained in weight, and some of them have enjoyed better health than for years before the removal of their stomachs.

From his studies of the pancreas, Bernard, whose mind was always of a very practical bent, was very naturally led to the study of that puzzling disease, diabetes. The question of how sugar was absorbed into the system was an interesting one even at that time. It was not realized, as it is now, that saccharine material was a most valuable food-stuff. Its use in the world's great armies of recent years has brought sugar very prominently before the medical profession of to-day. The bone and sinew for hard fighting and exhausting marches would not seem to be derivable from the favorite dainty of the child, which has besides fallen into such disrepute as a health disturber; yet tons upon tons of sweets are now s.h.i.+pped to fighting armies, and are distributed in their rations when especially hard work is required of them. Bernard did not quite realize that he was attacking, in the question of the digestion and consumption of sugar in the system, one of the {280} most important problems of nutrition, especially as far as regards the production of heat.

Sugar is a substance that dissolves easily and in considerable quant.i.ty in water. When in solution it easily pa.s.ses through an animal membrane by osmosis, and so the question of its absorption seemed simple enough. The disease diabetes showed, however, that sugar might exist very plentifully in the blood and yet the nutrition of an individual suffer very much for the lack of it. Something else beside its mere presence in the system was necessary to secure its consumption by the tissues. Bernard thought that the liver was active in the consumption of sugar, and that disease of this organ caused diabetes. He therefore secured some of the blood going to the liver of a living animal and some of the blood that was just leaving it. To his surprise the blood leaving the liver contained more sugar than that entering it. After a.s.suring himself that his observations were correct, he tried his experiments in different ways. He found that even in the blood leaving the liver of an animal that had been fed only on substances containing no sugar, sugar could be demonstrated.

Even in a fasting animal the liver itself and the blood leaving it showed the presence of a form of sugar. The only possible conclusion from this was that the liver was capable of manufacturing this form of sugar out of non-sugar-containing material, or even from the blood of a fasting animal.

This was the first time in physiology that the idea of an internal secretion was advanced. Glands within the body that gave off a secretion always possessed a duct by which this secretion was conducted to where it was to produce its effect. The idea that glands exist which pour their secretion directly into the blood-stream had not occurred.

This branch of physiology has developed wonderfully since {281} Bernard's discovery. The chapter of the functions of the ductless glands is one of the most interesting and most practical in modern medicine. The spleen, the thyroid, the suprarenal glands have taken on a new significance. Mysteries of disease have been solved, and, most wonderful of all, we have learned that many of the substances derived from these glands, when not present in the human body, may be effectually supplied by corresponding substances from animals, with results upon suffering human beings that are little short of marvellous. To mention but one example: the stunted, idiotic child that, because of congenital absence of the thyroid gland, formerly grew up to be a repellent, weak-minded man or woman, can now in a few short months be made the peer of most of its kind. All the modern tissue-therapy, with its hopeful outlook, is due to Bernard's far-reaching conclusions from his experiments upon sugar digestion and absorption.

His studies on sugar logically led Bernard to the investigation of heat production and heat regulation in the human body. Glycogen, the sugary substance produced by the liver, occurs abundantly in all the muscles of the body, and it was evident that muscular movement leads to its consumption and the consequent production of heat. Sugar is a carbon-containing substance, and its combustion always produces energy. The question of heat regulation was a much more complicated problem. Heat is always being produced in the human body and always being given off. Very different amounts of heat are required to keep up the temperature of the human body in the winter and summer seasons.

Near the pole or at the equator man's temperature in health is always the same. To secure this ident.i.ty of temperature some very delicately balanced mechanism is required. Without the most nicely adjusted equilibrium of heat production and dissemination human tissues would soon freeze up at a {282} temperature of 70 below zero, or the alb.u.min of the body fluids and muscular tissue coagulate at a temperature above 110 F.

While engaged in the investigation of this interesting problem Claude Bernard found that the cutting of the sympathetic nerves in the neck of a rabbit was followed by increased heat on the side of the head supplied by the nerve, and that this increased heat coincided with heightened sensibility and greater blood-supply in the parts affected.

Here was an important factor in heat regulation laid bare. It was evident that the sympathetic nerve trunk supplied filaments to the small arteries, and that when these nerves no longer acted, as after the cutting of the nerve trunk, these arteries were no longer controlled by the nervous system and became dilated. The presence of more blood than usual in the tissues and its slower flow gave occasion to more chemical changes in the part than before, and consequently to the production of more heat.

These vasomotor nerves, as they have been called, because they preside over the dilatation and contraction of the walls of the bloodvessels (vasa) of the body, are now known to play an important role in every function. When food enters the stomach, it is dilatation of the gastric arteries, brought on by the reflex irritation of the presence of food, that causes the secretion of the gastric juices necessary for digestion. It is the disturbance of this delicate nervous mechanism that gives rise to the many forms of nervous dyspepsia so common in our day. It is its disturbance also that makes digestion so imperfect at moments of intense emotion, or that makes severe mental or bodily exertion after the taking of food extremely inadvisable. The vasomotor nerves, however, control much more than heat processes and digestion.

The familiar blus.h.i.+ng is an example of it, and blushes may occur {283} in any organ. Excitement paralyzes the efforts of some individuals, but renders others especially acute. It is probable that the regulation of the blood-supply to the brain has much to do with this.

While one student always does well in an oral examination, another, as well gifted, may always do poorly. Just as there are those who cannot control the vasomotor nerves of the face, and blush furiously with almost no provocation, so there are brain-blushers in whom the rush of blood interferes with proper intellection. On the other hand, there are those, and they are not always unaware of it, in whom the slight disturbance of the facial vasomotor mechanism only gives rise to a pleasing heightened color, and in the same way the increased blood-supply to the brain only gives them more intellectual ac.u.men.

These two discoveries by Bernard--the formation of sugar by the liver and the nervous vasomotor mechanism--are, in their far-reaching application and their precious suggestiveness for other investigators, the most significant advances in physiology of the nineteenth century.

They are directly due to a great imaginative faculty informing a most fertile inquiring spirit. Bernard was very different from his master, Magendie, in his applications of the experimental method. Magendie's researches were made more or less at random in the great undiscovered regions of physiology. He made his experiments as so many questions of nature. He cared not what the answer might be. He seldom had an inkling beforehand where his experiments might carry him. As he said himself, he was a rag-picker by the dust-heap of science, hoping to glean where others had missed treasures, and not knowing what his stick might turn up next. Bernard's experiments were always made with a definite idea as to what he sought. Not infrequently his pre-conceived theory proved to be a mistake. It is of the very {284} genius of the man that he was able to recognize such errors, and that he did not attempt to divert the results of experiments so as to bolster up what looked like eminently rational theories. The imaginative faculty that had come so near perverting him to literature was a precious source of inspiration and initiative in his scientific work. It was not followed as an infallible guide, however, but only as a suggestive director of the course investigation should take.

Besides the important discoveries made by Bernard there are two minor investigations, successfully accomplished, that deserve a pa.s.sing word. To Claude Bernard we owe the use of curare in physiological experimentation. Curare is an Indian arrow poison which absolutely prevents all muscular movement. If artificial respiration is kept up, however, the animal lives on indefinitely, and no motion will disturb the progress of the most delicate experiment. In Bernard's time it was thought that the drug did not affect the sensory nervous system at all, and that as a consequence, though absolutely immobile, the animal might be suffering the most excruciating pain. We now know that the sensory system is also affected, and that the animal in these experiments suffers little if at all.

Bernard's investigation of the effect of carbonic oxide gas will probably be of more practical benefit to this generation and the next than it was to his. Like most of Bernard's discoveries, this one threw great light on important questions in physiology quite apart from the subject under investigation. Carbonic oxide is the gas produced by incomplete combustion of coal. The blue flames on the surface of a coal fire when coal is freshly added are mainly composed of this gas in combustion. From burning charcoal it is given off in considerable quant.i.ties. The gas is extremely poisonous. Unlike carbon dioxide, which does harm by shutting off the supply {285} of oxygen, carbonic oxide is actively poisonous. After death the blood of its victims, instead of being of a dark reddish-blue, is of a bright pinkish-red.

Bernard's study of the change that had taken place in the blood showed that the hemoglobin of the red blood-cells had united with the carbonic oxide present in the lungs to form a stable compound. The usual interchange of oxygen and carbon dioxide in the tissues could not take place. The combinations formed between oxygen and carbon dioxide and the hemoglobin of the blood readily submit to exchanges of their gaseous elements, and so respiratory processes are kept up.

Before Bernard's discovery it was thought that the respiratory oxygen was mostly carried dissolved in the blood-plasma--that is, in the watery part of the blood--or at least that its combination was a physical rather than a chemical process. This idea was overthrown by the discovery that the carbonic oxide combination with hemoglobin was very permanent. The role of the red blood-cell in internal respiration took on a new importance because of the discovery, and the comprehension of anaemic states of the system became much easier.