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30. Claude Bernard: Explorer of Physiologic Frontiers


THE LEADING drama critic of Paris, Sorbonne Professor Saint-Mare Girardin, sighed. He shuffled the neatly written sheets, glanced again at a sentence, long and labored of rhetoric. Slowly he turned, looked up at the tall, slim, handsome Burgundian youth, and said firmly; “You have done some pharmacy. Now, study medicine. You have not the temperament of a dramatist.”

In that simple act, Professor Girardin served his country and society for better than he knew. The disappointed literary aspirant heeded his advice: France lost a potential play Wright; she gained her greatest nineteenth-century physiologist, Claude Bernard..

Laboratory sciences, and in particular, experimental physiology, had made little progress before the middle of the nineteenth century. Then they began to flourish, particularly in Germany. Chemistry, physics, and physiology advanced and began to have decisive influence upon the practice of medicine. Up to that time, at best, treatment of the sick was based upon the practitioner’s experience. At worst, it was based upon his theories and philosophic imagining.

Among the great contributions to the advance of clinical medicine of the nineteenth century was the brilliant information that came welling out of Bernard’s laboratories. Alexis Carrel said of Bernard: “Before him, medicine was purely empirical. He is responsible for the introduction of the scientific method in the art of healing.” Bernard’s pupil, Paul Bert, wrote: “In twenty years, Claude Bernard found more dominating facts, not only than the few French physiologists working beside him, but than all the physiologists in the world.” I.J. Henderson summed up Bernard’s philosophy in one sentence: “His life was spent in putting questions to nature.”

Claude Bernard’s immortality is based upon four major contributions; studies of digestion and of the functions of pancreatic secretion; discovery of glycogen, and of the glycogenic function of the liver; discovery of the vasomotor nerves and their control of bodily functions; and basic work on poisons (curare in particular) and on their pharmacodynamics. His monumental publication, An Introduction to the Study of Experimental Medicine, described many of his important studies. In this book, Bernard defined the relationship between theory and experiment in scientific research; roles of doubt and of of intuition; of proof and of counterproof; of statistics and of individualism. His concept of existence of an “internal environment” – those mechanisms by which the several organs within the body are coordinated to permit higher animals to enjoy functional stability – served Bernard well, and still serves researchers, though today more modern terminology is used. Bernard defended the necessity of vivisection and discussed in detail the technicalities of animal experimentation. Clarity and precision in Bernard’s descriptions of experimental methods and controls are of such quality that the Introduction still is reprinted.

Glaude Bernard was born July 12, 1813, in the village of saint-Julien, near Villegranche, Department of the Bhone, France. His father, Pierre Jean Francois Bernard, owned a small estate, chiefly planted with grapevines, and derived his income from making wine and from teaching. Educated locally until his eighteenth year, young Claude Bernard then obtained employment in the pharmacy of M. Millet, in Lyons. There his menial duties of sweeping floors and washing bottles were occasionally interrupted by deliveries of drugs to a nearby school of veterinary medicine. His observations there evidently made a profound impression upon the young man and helped to guide him toward his life’s work.

His one night off each month, the pharmacist’s apprentice spent at the theatre. Young Bernard was inspired to try his own hand at playwriting. The result was a comedy, La Rose du Rhone, which is said to have earned its author one hundred francs.

Bernard now began a serious work, a play in five acts, called Arthur de Brelagne. Pharmacist Millet decided that the boy had lost interest in his drug store duties and was a dreamer. Bernard’s career in pharmacy ended after eighteen months. The play finished, the young man set out in 1834 for “the big city.” Paris, to seek recognition and fortune. Gaining an introduction to Professor Girardin, then at the height of his fame as a critic, Bernard presented his play. It was at this time that Girardin gave him discouraging but kindly advice to study medicine – advice which, fortunately, Bernard accepted.

Then, twenty-one years of age, Claude Bernard enrolled in the medical school in Paris in the fall of 1834. He achieved no great success as a student; some of his instructors even regarded him as lazy. Anatomy and dissection appealed to him. To add to his meager funds, he entered into partnership with another student in open a laboratory for animal experimentation. Unfortunately, the laboratory failed; but Bernard’s remarkable manual skill became more evident. He taught natural history at a girls’ school, and tutored, as means of financing his studies; he passed his examinations to become an externe in 1836, and an interne in 1839. He followed the services of leading teaching physicians at hospitals in Paris – Salpetriere, Charite, and Hotel-Dieu. At the latter hospital, Bernard came into the service of Francois Magendie, then France’s leading physiologist. Physician at Hotel-Dieu, and Professor of Medicine at College de France, Magendie had a reputation for being gruff, abrupt, and difficult. Before long Bernard’s dexterity caught the old professor’s attention, and in 1841 he became Magendie’s preparaleur, or laboratory assistant. At first, Bernard’s relationship with Magendie was difficult, but once the old professor was convinced of his assistant’s ability, their association became cordial, almost filial, and Bernard progressed rapidly along the line for which he was best fitted: experimental physiology. His first paper, published early in 1843, concerned the anatomy of the chorda tympani nerve. Later that same year, Bernard undertook investigation of what happens to foodstuffs during digestion. In December, 1843, he presented as his thesis for the doctorate. The Gastric Juice and its Role in Nutrition, concerned primarily with digestion of cane sugar.

Completion of work necessary to earn the medical degree did not greatly change Claude Bernar’s way of life, except that he abandoned hospitals for the laboratory. He was never to engage in practice. Free to devote himself to his investigations, beginning it 1844, his publications appeared in rapid succession.

The next two decades of Bernard’s life were busy productive years. Experimentation continued to hold his greatest interest; he pursued it throughout his life, in private laboratories and in teaching institutions.

Bernard continued to teach; yet teaching was a burden to him. He was appointed Magendie’s deputy at College de France in 1847. In this capacity he was required to lecture, in addition to doing laboratory work; but he was not accorded the rank of Professor of Physiology until after Magendie’s death in 1855. Then he was appointed Maghendie’s successor, in the chair held before him by Laennec. In 1854, Bernard had been named Professor of Physiology at the Sorbonne. He continued to hold both posts until 1868, when, following a favorable interview with Napoleon III, there was created for Bernard a new Chair of General Physiology, and a new laboratory, at the Museum of Natural History. Upon accepting this professorship, Bernard relinquished his chair at the Sorbonne to his former pupil and assistant, Paul Bert.

While Bernard earned respect and admiration for his teaching, results of his experiments and publication of progressive reports of his findings earned for him world-wide distinction. While carrying further his early studies on nutrition and digestion, Bernard explored difference of digestive processes in herbivorous and in carnivorous animals. During these experiments, he observed that ingested fats remained unchanged until they reached the openings of the pancreatic ducts; then they were emulsified and absorbed. This led him to intensive study of pancreatic secretions and their effects. His findings were published in 1846. He was the first scientist to appreciate the importance of internal glandular secretions, and to understand interrelations of organic function.

Another idea current among physiologists of the day was that only plants synthesized sugar, and that animals only broke down sugars to basic elements in metabolism. To study these concepts, Bernard, beginning in 1846, sought to discover in which bodily organ sugars disappeared. His attention was attracted to the liver. Always open-minded always ready to overthrow theory for fact, Bernard was astounded to realize that, even though animals were fed no sweets, their livers synthesized sugar in a form which he named glycogen. To prove his discovery, in 1848 he demonstrated that alcohol could be formed as a result of fermentation of glycogen. During the next few years, Bernard’s progressive series of papers, read before the Academie des Sciences and the Societe de Biologie, radically changed the medical world’s concepts of organic function.

Concurrently with his studies of the pancreas and of the liver, Bernard began in 1844 to search for mechanisms by which poisons exerted killing power. He was attracted to the South American arrow poison, curare. It was he who gave the world the answer; curare causes death by destroying all motor function without affecting sensation. His description of how the victim, though retaining full consciousness and sensory powers, slowly dies, completely immobile, is chillingly vivid. Bernard published an extensive report on these studies in 1850.

Study of poisons led Bernard also to investigate how carbon monoxide kills; and it was he who found that carbon monoxide combines with hemoglobin more readily than oxygen to lower, even to destroy the oxygen-carrying power of the blood. The observation also led to development of a method of employing carbon monoxide in measurement of various components of blood.

Another of Bernard’s brilliant discoveries was that of existence and function of vasomotor nerves. The whole story of this discovery did not come to light at once. Bernard had started out, in 1851, to study the influence of sympathetic nerves on blood vessels. Results of his experiments were not what he had expected. “Thereupon,” he reported, “I did as I always do; that is to say, I at once abandoned theories and hypotheses in order to observe and study the fact itself…”In the course of a series of carefully controlled experiments, on which Bernard reported to scientific societies from time to time over a five-year period, he established that two sets of nerves affected blood vessels. One set constricted the vessels; the other set dilated them. By 1858, Bernard had demonstrated positively the existence of the vasomotor nervous system, and importance of its functioning to other physiologic processes.

In 1860, an unidentified chronic illness began to take its toll, handicapping Bernard’s efforts. His friends attributed this in part to the miserable conditions, in the laboratory provided for him – a dark, damp, cold, ill-ventilated basement room with crude sanitary facilities. By 1862, sickness forced him to leave Paris and to spend two years recuperating at his birthplace near Saint-Julien. His father’s vineyards had become his property; and it was to this quiet, rural setting, overlooking the Saone River and the hills beyond, that Bernard returned. Though experimentation cold be but rudimentary there, Bernard found time to do something he had been planning for a long time; he began to write the Introduction to what he envisioned as a multi volumed work on experimental medicine. Unfortunately, the first volume was the only one he ever wrote; but the impact of An Introduction In the Study of Experimental Medicine, when the first edition came off the presses in 1865, was phenomenal. While many of Bernard’s reports, lectures, and papers were published, it is the Introduction which has kept his name known throughout a century bristling with medical advances. Bernard’s younger contemporary and good personal friend, Louis Pasteur, commented thus on the Introduction: “Nothing so complete, nothing so profound and so luminous has ever been written on the true principles of the difficult art of experimentation. This book will exert an immense influence on medical science, its teaching, its progress, its language even I seek in vain for a weak point in M. Bernard. It is not to be found….”

Bernard returned to work in Paris late in 1863, but by 1865, he was forced again to return to Saint-Julien, where he remained until 1867. In his later years, Bernard did not launch many entirely new investigations, devoting his attention rather to enlarging upon and further pursuing investigations begun in his earliest years. Results of these he duly reported in lectures at College de France or at the Museum of Natural History, or in papers before various learned societies. More and more of his time in later years was taken up with responsibilities to these societies.

Though Bernard had his opponents and detractors, there was no lack of honors accruing to him in his lifetime. France honored him three times with advancing degrees in the Legion of Honor. In 1854 he was elected to the Academic des Sciences, which he served as president in 1869. He helped to from Societe de Biologie in 1848, and became its president for life in 1867. In 1861 he was elected to the Academic de Medecine, and in 1868 to the exclusive French Academic. He also was a founder, in 1872, and first president of the French Association for the Advancement of Science. Nor was recognition limited to his native land (outside which he never set foot), in 1860 he received the Order of the Polar Star from Sweden and Norway; in 1864 he was named an honorary member in the Royal Society of London, England; in the Academy of Sciences in Berlin; and in the corresponding society in St. Petersburg.

At home, the impression Bernard made upon the Emperor was reflected not only in creation of the Chair of Physiology at the Museum of Natural History, but also, in 1869, in his elevation to membership in the Senate. This high political honor was to be short-lived, however; the France-Prussian War broke out in 1870, and the Senate ended when Napoleon III was captured and the new Republic proclaimed, Bernard retired to Saint-Julien for the balance of the war.

Despite a reserved demeanor, Bernard possessed great personal magnetism. His students loved him, though he had no great gift of oratory. Bernard’s close friend, George Barral, once described the physiologist thus: “Of solemn aspect, somewhat cold as a professor, somewhat wan in his chair, Claude Bernard showed himself incomparable in the laboratory, before the dissecting table. Standing, his head covered with a large hat under which were escaping long grey looks, his neck wrapped around with an immense mufller-grey and black, which he discarded only during the intense summer heat, he could be seen stooping a little, calmly plunging his fingers into the open abdomen of a dog, explaining the object of his research…” Bernard’s worth was recognized early in his life by his elders, such as Rayer and Magendie. Friends of his youth, Davaine, Lasegue, and Morel, remained faithful to him after they themselves became famous. Great scientists of his generation, Renan, Berthelot, land Pasteur, admired him. He trained a number of very able and devoted pupils who became great in their own right, including Paul Bert, who succeeded Bernard to the Chair of Physiology at the Sorbvonne, and Arsene d’Arsonval, who followed Bernard at College de France. Bernard and the younger Pasteur not only were good friends, but at times collaborated; sometimes they worked separately on the same problems – and not always were they in agreement on results. Bernard, however, was chairman of the committee of Academie des Sciences that in 1860 presented the prize for experimental physiology to Pasteur for his work on fermentation. Pasteur’s regard for Bernard has already been mentioned. Over the years, the spectacular nature of the younger chemist’s work has tended to capture more public interest than the less dramatic but no less important findings of the great physiologist.

The honor in which Bernard was held in scientific circles was not reflected in his home life. He married in 1845; but from the beginning the marriage apparently was doomed by extreme incompatibility. Madame Bernard continually called upon her husband to quit the smelly laboratories and to build up a profitable medical practice; not only was she uninterested in his laboratory pursuits, but she had a horror of vivisection; she sought to make up for her husband’s “sins” by contributions to antivivisection societies. Added deep sorrow came to Bernard in that both his sons died in infancy. His daughters were turned against him by their mother. The couple parted in 1869 – the year the Emperor named Bernard to the Senate. Formal separation came in 1870. Bernard’s last years were lonely, with only his “ scientific family” for company in Paris, his sister and his niece, to whom he transferred his affections, frequently visited him at Saint Julian, where he spent a part of each year tending homely agrarian pursuits.

In 1877, Bernard began his course at College de France as usual. He gave his last lecture December 28, after which he had to be helped to his home. On New Year’s Day, 1878, he caught cold while making calls, and developed severe pyelonephritis. He died the morning of February 10, 1878, after several weeks of severe pain.

Upon notification of Bernard’s death, the Chamber of Deputies of France voted that he be given a state funeral. Bernard thus became, on February 16, 1878, the first scientist to have been accorded such an honor in France.

Bernard’s simple but strong feeling about his life’s work is reflected in his writings. For example, he opened his course of lectures in 1847 with the remark: “Scientific medicine, gentlemen, which it ought to be my duty to teach here, does not exist.” From close to his heart came the observation: “Those who do not know the torment of the unknown cannot have the joy of discovery…Even in science itself, the known loses its attraction, while the unknown is full of charm.”

Research men and women, even today, find solace and comfort in Bernard’s philosophy: “One must be brought up in laboratories and live in them,” he wrote in his Introduction, “to appreciate the full importance of all the details of procedure in investigation, which are so often neglected or despised for the false men of science calling themselves generalizers…” and “The whole future of experimental medicine depends on creating a method of research which may be applied fruitfully to the study of vital phenomena, whether in a normal or abnormal state.” Perhaps reflecting some less pleasant aspects of his work, he also commented: “If a comparison were required to express my idea of the science of life, I should say that is is a superb and dazzlingly lighted ball which may be reached only by passing through a long and ghastly kitchen.”


The only place where Claude Bernard (1813-1878) felt at home, outside experimental laboratories, was at the provincial farm near Saint-Julien (Rhone), France, where he was born. Bernard’s great skill at dissection and at observation gave medical science benefit of outstanding physiologic discoveries concerning pancreatic secretions, animal sugar, poisons, and vasomotor nerves. He had professorships in physiology at leading Paris schools; he was awarded national and international scientific honors; but his great book, An Introduction to the Study of Experimental Medicine, was written at his old farm home while he recuperated from recurrent attacks of illness.


Ackerknecht, E.H: unpublished monograph.

Ackerknecht, E.H: A short History of Medicine. New York, Ronald Press Co., 1955.

Bernard Claude: An Introduction to the Study of Experimental Medicine. New York, Macmillan Co., 1927; also, Dover Publications, Inc., 1957.

Bernard, Claude: The Origin of Sugar in the Animal Body. Source Book of Medical History, Logan Clendening, New York, Dover Publications, Inc., 1960.

Binet, Leon: An Alleged Skeptic: Claude Bernard. Medecins, Biologistes et Chirurgiens, Paris, Segep, 1954.

Foster, Michael: Claude Bernard. New York, Longmans, Green & Co., 1899.

Olmsted, J.M.D: Claude Bernard, Physiologist. New York, Harper & Brothers, 1938.

Robinson, Victor, Pathfinders in Medicine. New York, Medical Life Press, 1929.

Sigerist, Henry E: The Great Doctors. New York, W.W. Norton & Co., 1938.

Vallery-Radot, Rene: The Life of Pasteur. New York, Dover Publications, 1960.

Virtanen, Reino: Claude Bernard and His Place in the History of Ideas, Lincoln, University of Nebraska Press, 1960..


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