Chapter X: Preface (9)

Schwann's thesis for his doctorate at Berlin showed the calibre of the man, and demonstrated his thorough fitness for success as an experimental scientist. The question whether the growing embryo in the ordinary hen's egg consumes oxygen or not had been in dispute for some time. It was well known that an air-chamber existed in the egg even at the earliest stages of embryonic life. It was understood that the mature chick just before its egress from the egg must have air, and the porosity of the egg-shell was sufficient to permit its entrance. Whether at the beginning of embryonic life within the egg, however, oxygen was necessary, remained somewhat in doubt. It had been demonstrated that the gas existing in the air-chamber of an egg became changed in composition during the progress of development. From being slightly richer in oxygen than ordinary atmospheric air at the beginning of embryonic growth, {259} containing 24 to 25 parts of oxygen per 100, it became modified during comparatively early development so as to contain not more than 17 parts of oxygen per 100 and some 7 parts of carbon dioxide. This change of composition was, at least, very suggestive of the alteration that would take place during respiration. It was pointed out, however, that the argument founded on these observations was drawn only from analogy, and was by no means a scientific demonstration of the fact that the embryo not only consumed air during its growth, but actually needed oxygen for the continuance of its vital processes.

It was suggested that the change of composition in the air within the egg might be due not to any essential vital functions, but to chance alterations brought on by decomposition in the unstable organic material so abundantly present in the substance of the egg. Schwann settled the question definitely by a set of ingenious experiments. He exposed eggs for various periods to the action of other gases besides air, and also placed them in the vacuum chamber of an air-pump. When not in contact with the air the eggs developed for some hours if the temperature was favorable, and then development ceased. If after twenty-four hours' exposure to an atmosphere of hydrogen eggs were allowed free contact with the air, development began once more at the point at which it had ceased. After thirty hours of exposure to hydrogen, however, or to the vacuum, all life in the egg was destroyed, and it failed to develop no matter how favorable the conditions in which it was afterward placed. The completeness with which the points in dispute in this problem were demonstrated is typical of all Schwann's work. His conclusions always went farther than the solution of the problem he set out to solve, and were always supported by simple but effective experiments, often ingeniously planned, {260} always carried out with a mechanical completeness that made them strikingly demonstrative.

One of Schwann's brothers had been a worker in metal, and Schwann himself had always shown a great interest in mechanical appliances. This hobby stood him in good stead in those days when laboratories did not contain all the intricate scientific apparatus and the facilities for experimentation so common now, with their workshop and skilled mechanics for the execution of designs. Many another worker in the biological sciences of that time owes his reputation to a similar mechanical skill. Experiments were impossible unless the investigator had the mechanical ingenuity to plan and the personal handiness to work out the details of appliances that might be necessary for experiments. It is told of Schwann that when Daguerre's discoveries in photography were announced, such was his interest in the new invention that he made a trip to Paris especially to learn the details of the method. Some daguerreotypes made by him according to the original directions of the inventor himself are still preserved by his family.

Schwann's investigation of the respiration of the embryo in hens' eggs led to further studies of the embryo itself, and to the discovery that it was made up of cells. Later came the resolution of other tissues into cells. When, after his graduation as doctor in medicine, the post of assistant in anatomy at Berlin fell vacant, it was offered by Johann Mueller to Schwann. The position did not carry much emolument with it. The salary was ten German thalers--_i.e._, about $7.50 per month--a pittance even in those days when the purchasing power of money was ever so much greater than now. His duties took up most of his time. The work was congenial, however, and Schwann remained here for five years. As Henle has said in his biographical sketch of {261} Schwann, in the _Archiv f. mikroskopische Anatomie_, just after his death in 1882: "Those were great days. The microscope had just been brought to such a state of perfection that it was available for accurate scientific observations. The mechanics of its manufacture had besides just been simplified to such a degree that its cost was not beyond the means of the enthusiastic student even of limited means. Any day a bit of animal tissue, shaved off with a scalpel or picked to pieces with a pair of needles or the finger-nails, might lead to important ground-breaking discoveries." For at that time almost everything as to the intimate composition of tissues was unknown. Discoveries were lying around loose, so to speak, waiting to be made. Schwann was not idle. The precious years at Berlin saw the discovery that many other tissues were composed of cells. The nuclei of the striped and unstriped muscles were found, and while the cellular character of these tissues was not demonstrated, their secret was more than suspected and hints provided for other workers that led very shortly to Koelliker's and Henle's discovery of muscle cells.

Besides his interest in histology, the branch of anatomy which treats of the intimate constitution of tissues, Schwann was working also at certain general biological questions, and at some knotty problems of physiology. Not long after his installation as an assistant at Berlin, from observations on fermenting and decomposing organic liquids, he came to a conclusion that was far in advance of the science of his day. He announced definitely _infusoria non oriuntur generatione aequivoca_--the infusoria do not originate by spontaneous generation. Under the term infusoria, at that time, were included all the minute organisms; so that Schwann's announcement was a definite rejection of the doctrine of spontaneous generation over thirty years before Pasteur's demonstrations finally settled the question. Schwann was never a {262} controversialist. He took no part in the sometimes bitter discussions that took place on the subject, but having stated his views and the observations that had led up to them he did not ask for the immediate acceptance of his conclusions. He continued his work on other subjects, confident that truth would prevail in the end. When the congratulations poured in on Pasteur for having utterly subverted the doctrine of spontaneous generation, the great French scientist generously referred the pioneer work on this subject to Schwann, and sent felicitations to that effect when Schwann was celebrating the jubilee anniversary of his professoriate.

While studying ferments and fermentations Schwann became interested in certain functions of the human body that carry with them many reminders of the biological processes which are at work in producing the various alcohols and acids of fermentation. The changes that occur in the contents of the human stomach during the preparation of food for absorption had long been a subject of the greatest interest to physiologists. It had been studied too much, however, from the merely chemical side. The necessity for the presence of an acid in the stomach contents in order that digestion should go on led to the conclusion that the acid was the most important constituent of the gastric juice. By means of the scrapings of the stomachs of various animals Schwann succeeded in preparing an artificial gastric juice, and showed just how the action of the gastric secretions brought about the solution of the contents of the stomach. He isolated pepsin, and demonstrated that it resembled very closely in its action the substances known as ferments. He even hinted that digestion, instead of being a chemical was a biological process. Any such explanation as this was scouted by the chemists of the day, headed by Liebig. Most of the physiological functions within the human body were {263} then triumphantly claimed as examples of the working of chemical laws.

Of the contradiction of his conclusions Schwann took practically no notice, but went faithfully on with his work. He could not be lured into controversy. For nearly five years he continued his work at the University of Berlin, receiving only the pittance that has been mentioned--less than ten dollars per month. Only the purest love of science for its own sake, and the satisfaction of his own enthusiastic spirit of investigation kept him at work. There was but little prospect of advancement at the University of Berlin itself. Schwann was one of the lowest in rank of the assistants; the professor was only just beyond the prime of life; and before Schwann on the list for promotion was at least one man, Henle, who had already done distinguished work. Germany had the good fortune to have all during the nineteenth century young men who, unmindful of present emolument, had been satisfied with the scantest wages for their support, provided the positions they occupied gave them opportunities for original work. Even at the present day young medical men are glad to accept what they consider the honor of the position of assistant to the professor and director of the clinic, and to remain in it for from five to ten years, sometimes even more, though the salary attached to it is only from $250 to $400 per year. They well know that if their original investigations into various medical questions are successful, advance in university rank is assured. Their promotion seldom comes from the institution where they have done their work, unless it should be one of the smaller universities; but the invitation to a chair at a university will come sooner or later for meritorious research.

Schwann's invitation came from Louvain. His work on cells had attracted a great deal of attention. In the midst {264} of the rationalism and infidelity then so common among scientific men Schwann was known as a faithful, sincere Catholic. When the great Catholic University of Louvain, then, looked around for a professor of anatomy, he appeared to be the most suitable person. Henle, who had very little sympathy for Schwann's religious views, speaks most kindly of him as a man and a comrade. Schwann seems to have endeared himself to the "difficult" Prussians, as he did to those around him all his life. For the dominant note in the sketches of him by those who knew him personally is that of heartiest friendship, joined with enthusiastic admiration for his simple sincerity and unselfish devotion to his friends and to science.

A little incident that has been preserved for us by Henle shows how much his young contemporaries appreciated even at that early date, long before the full significance of the cell theory could be realized, the aspect of Schwann's work which was to make him immortal. At a little farewell dinner given him by his co-workers in various laboratories of the University of Berlin the feature of the occasion was a punning poem, by the toast-master, on the words Louvain and cells.

In German Louvain is Loewen, which also means lion; that is, it is the dative case of the name of the lion. Reference is made to the fact that as Samson found honeycomb (in German, bee-cells) in the lion, so now Louvain--_i.e._, in German, Loewen, the lion--finds a champion in the man of the cells. As Samson's riddle was suggested by finding the bee-cells, so will the new professor at Louvain solve the riddles of science by the demonstration of cells. The youthful jesting seer prophesied better than he knew. Schwann's first completed work at Louvain was the _Microscopical Researches into the Accordance in Structure and Growth of Plants and Animals._ [Footnote 11] {265} The theory it advanced was to prove the most potent element thus far introduced into biological science to help in the solution of the difficult problems that constantly occur in the study of the various forms of life.

[Footnote 11: Mikroskopische Untersuchung ueber 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 Mueller, 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 Wuerzburg, 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 attitude 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 classes 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 circumstance 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 attitude 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 friendships that linked him to those with whom he was associated. At Louvain, and later at Liege, he was the personal friend of most of his students, while at Berlin he made friendships 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 analogies 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; nobody 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 accumulation 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 institution 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 institution. 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 constituted the principal reason for an educational institution 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 associations 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 illustration 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-fashioned training by means of the classics 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 assistant 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} assistants 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 prone 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 classes 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 illustrate 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 classical 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 albuminous portions of the food, and also upon the starches and sugars. Up to this time the principal role in digestion had been assigned 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 albuminous materials--is due to Kuehne, 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 surpassing 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 shipped 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 quantity in water. When in solution it easily passes 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 assuring 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 identity 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 deg. below zero, or the albumin of the body fluids and muscular tissue coagulate at a temperature above 110 deg. 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 blushing 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 acumen.

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 passing 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 quantities. 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.

About the middle of his career Bernard suffered from a succession of attacks of a mysterious malady that we now recognize to have been appendicitis. Once at least his life was despaired of, and recurring attacks made life miserable. After a year of enforced rest on the old farm of his boyhood, now become his own, he seems to have recovered more or less completely. His health, however, was never so robust as before. Toward the end of his life he lived alone. His wife and daughters were separated from him, and one of the daughters devoted her time and means to suffering animals in order to make up, as she proclaimed, for all her father's cruelty.

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Bernard lived almost directly opposite to the College de France, in a small apartment in the rue des Ecoles. An old family servant took care of him, and his life was one of uttermost simplicity, devoted only to science. Once at court, in 1869, Napoleon III insisted on knowing, after an hour's conversation with him, what he could do for him. Bernard asked only for new facilities for his experimental work, and new apparatus and space for his laboratory.

Honors came to him, but left him modest as before. He was elected a member of the French Academy--one of the forty immortals. Only five times in the history of the Academy has the honor of membership been conferred upon a medical man. Before Bernard, Flourens, the father of brain physiology, had occupied a _fauteuil_, while Cabanis and Vicq d'Azyr are two other names of medical immortals.

Bernard was elected to the 24th _fauteuil_, which had been occupied by Flourens, and according to custom had to pronounce his predecessor's panegyric. The conclusion of his address was the expression: "There is no longer a line of demarcation between physiology and psychology." Physiology had become the all-ruler for Bernard in human function, and he drifted into what would have been simple materialism only for the saving grace of his own utter sanity, his active imagination, and the unconscious influence of early training. During his most successful years of scientific investigation, wrapped up in his experiments and their suggestions, Bernard was drawn far away from the spiritual side of things. This partial view of man and nature could not endure, however. In an article on Bernard in the _Revue des Questions scientifiques_ for April, 1880, Father G. Hahn, S. J., says of him: "A man of such uprightness of character could not be allowed to persist to the end in this restless skepticism. His mental condition was really a kind of vertigo caused by the {287} depths of nature that he saw all around him. At the threshold of eternity he came back to his true self and his good sense triumphed. The great physiologist died a true Christian."

Bernard was one of the great thinkers of an age whose progress in science will stamp it as one of the most successful periods of advance in human thought. He accomplished much, but much more he seemed to have divined. He seldom gave out the slightest hint of the tendencies of his mind, or of his expectations of discovery in matters of science, until fully satisfied that his theoretic considerations were justified and confirmed by observation and experiment. In one thing, however, he allowed favored friends to share some of his anticipations, and the notes published after his death show that he was on the very point of another great discovery in biology which has since been made. He was a firm friend of Pasteur's, and had ably seconded the great chemist-biologist's efforts to disprove spontaneous generation. Bernard's demonstration that air passed through a tube heated red hot might be suffered with impunity to come in contact with any sort of organic material, yet would never cause the development of germ life, was an important link in the proof that if life were carefully destroyed, no life, however microscopic in character, would develop unless the seeds of previously existent life were somehow brought in contact with the organic matter.

With regard to fermentation, too, Bernard was for many years in close accord with Pasteur, who taught that fermentation was the result of the chemical activity of living cells, the ferments. Toward the end of his life Bernard came to the view, however, that the action of ferments was really due to the presence in them of chemically active substances called diastases. These substances are of varied chemical {288} composition, but each one has a constant formula. Their presence in a fermentescible solution is sufficient of itself, even in the absence of living cells, to bring about fermentation. It has since been shown that after this substance is removed from ferment-cells by pressure, and the liquid carefully filtered so that absolutely no cells remain, fermentation will yet take place.

This does not disprove the necessity for life to produce the diastases originally, though it advances science a step beyond the theory that it is the actual vital interchange of nutritious substances within the ferment-cell that causes fermentation. With each step of advance in biological science the mystery of life and its processes deepens.