Part 26

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 Kühne, 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° below zero, or the albumin 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 rôle 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 rôle 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 Collège 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.

No one has done more to bring out the depths there are in vital function than Bernard. His early training was of the type that is, according to many prominent educators of our day, least calculated to develop originality of view, or capacity for initiating new lines of thought. Our pedagogic Solons would claim that the narrow orthodoxy that wrapped itself around his developmental years must surely stifle the precious genius for investigation that was in him. It is due, on the contrary, very probably to the thorough conservatism of his early training and the rounded fulness of the mental development acquired under the old system of classical education, that we have to chronicle of Bernard none of the errors by exaggeration of personal bias that are so common among even great scientific men. Few successful men have ever owed less to luck or to favoring circumstances in life. He was in the best sense a self-made man, and he owed his success to a large liberality of mind that enabled him to grasp things in their true proportions. With an imaginative faculty that constantly outstripped his experimental observations he was singularly free from prejudgment and was able to {289} control his theories by what he found, never allowing them to warp his powers of observation. Bernard is without doubt the greatest example of the century that a fully rounded youthful training is much more favorable to successful investigation than the early specialization which is falsely supposed to foster it.

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PASTEUR, FATHER OF PREVENTIVE MEDICINE

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More than two hundred and fifty years ago, Descartes, the most original mind of the modern age, who, more than any other thinker, has determined the course both of speculative and of scientific inquiry, declared that if any great improvement in the condition of mankind was to be brought about, medicine would provide the means, and what he foresaw we see. --Bishop Spalding.

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PASTEUR, FATHER OF PREVENTIVE MEDICINE.