Claude Bernard: Life and Career

Claude Bernard was born in a small French wine village in 1813, set out for Paris hoping to write plays, and ended his life in 1878 as the most celebrated physiologist in France — the first French scientist to be given a state funeral. In between he showed how the pancreas digests fat, discovered that the liver makes and stores sugar, isolated glycogen, found the nerves that widen and narrow blood vessels, worked out where the arrow poison curare paralyses the body and why carbon monoxide kills, and wrote a book on scientific method that is still read today.

This page tells the story of his life and career: where he came from, how he found his way into the laboratory, the people and institutions around him, the discoveries that made his name, and the honours that followed. His two famous poison studies have their own page, Curare and Carbon Monoxide: Claude Bernard’s Poison Experiments, and here they appear only as milestones along the way.

Table of Contents

  1. 1. A Village Childhood in the Beaujolais
  2. 2. The Would-Be Playwright in Paris
  3. 3. Medical Student and Magendie’s Assistant
  4. 4. Marriage, Money and the Vivisection Quarrel at Home
  5. 5. The Collège de France Years
  6. 6. Pancreatic Juice and Fat Digestion (1848)
  7. 7. Liver Sugar and the Isolation of Glycogen
  8. 8. The Nerves That Widen and Narrow Blood Vessels
  9. 9. Sorbonne, Muséum and the Académie Française
  10. 10. Death and the First Scientist’s State Funeral
  11. Key Research Papers
  12. Connections
  13. Featured Videos

1. A Village Childhood in the Beaujolais

Claude Bernard was born on 12 July 1813 in Saint-Julien, a village near Villefranche in the Rhône departmentocirc;ne department of eastern France, in the vine-growing country of the Beaujolais north of Lyon. His family worked the vineyards of this wine-growing countryside.

His first lessons came from the Jesuits who taught locally. From there he went on to a college in Lyon. Nothing in this early schooling pointed toward science. The surviving accounts describe a boy and young man drawn more to literature than to medicine, and his formal education in the sciences came late.

That late start is part of the Bernard story. He did not arrive in Paris as a prodigy trained from childhood in chemistry or anatomy. He arrived as a young provincial with literary ambitions, and the skills that made him famous — a careful hand at the dissecting table and a habit of letting experiments correct his own ideas — were learned on the job, in the laboratory, in his twenties.

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2. The Would-Be Playwright in Paris

As a young man Bernard hoped to become a dramatist. The historian C. S. Breathnach, in his 2014 survey of Bernard’s life and work, records that he went to Paris with that ambition and was directed instead toward medicine. The story is told in many biographies; the names and fates of the plays he is said to have written vary from one retelling to another, and they are left out here because they could not be confirmed from the sources used for this page.

What is well attested is the outcome. Around the age of twenty he settled in Paris, and by 1834 he had begun medical studies there. The playwright’s eye for a scene did not disappear: his later writing, especially the Introduction to the Study of Experimental Medicine of 1865, is admired for its clear, vivid prose, and it tells many of his experiments as small stories with a turning point.

In the Paris of the 1830s medicine was taught mostly through the hospital wards and the anatomy rooms. Experimental physiology — studying how living organs work by deliberately changing their conditions and watching what happens — was still a young and controversial field, and only a handful of teachers practised it. One of them would shape the rest of Bernard’s life.

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3. Medical Student and Magendie’s Assistant

Bernard studied medicine in Paris from 1834 to 1843. During those years he attended the physiology lectures of François Magendie at the Collège de France. Magendie was one of the founders of experimental physiology in France. In 1841 Bernard became his assistant, or préparateur — the person who prepared and often performed the experiments demonstrated in the lectures.

The post put Bernard at the bench every day. He learned to work on living animals, to isolate nerves and ducts, and to collect body fluids for study. Historians Jensen and Puissant, tracing his path to the discovery of glycogen, describe these years with Magendie as the foundation of his research career.

The 1843 thesis on gastric juice

Bernard completed his medical doctorate in 1843 with a thesis on gastric juice, the digestive fluid made by the stomach. Digestion would remain one of his central interests. Over the following years he moved step by step along the digestive tract — from the stomach to the pancreas to the liver — and each step produced a discovery.

Around the same time, in the mid-1840s, he began two lines of work that would later become famous. In his own later account in the Introduction, he wrote: “In 1845, Monsieur Pelouze gave me a toxic substance, called curare, which had been brought to him from America.” He dated his first experiments on carbon monoxide to “about 1846.” Both studies are told in full on the poison experiments page.

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4. Marriage, Money and the Vivisection Quarrel at Home

In 1845 Bernard married Marie Françoise “Fanny” Martin. The marriage was in part a practical arrangement: research positions paid little, and her dowry helped pay for the experiments that his career depended on.

The marriage was not a happy one, and the main point of conflict was his work. Bernard’s physiology rested on experiments on living animals — vivisection — and in his era these were often carried out on animals that were not anaesthetised. His wife and their daughters opposed this. Fanny Bernard later campaigned against vivisection. The couple separated in 1869.

The household dispute mirrored a wider public argument. Bernard defended animal experiment as the only way to understand how living bodies work and how diseases and poisons act; opponents objected to the suffering involved. Stories about particular episodes in the household are retold in popular biographies, but many rest on thin sourcing and are not repeated here. What the record shows plainly is that the man whose experiments made French physiology famous lived in a family that rejected the way those experiments were done.

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5. The Collège de France Years

The Collège de France was Bernard’s institutional home for most of his working life. In 1847 he became Magendie’s deputy there, taking over part of the teaching. In 1855 he became full professor there, succeeding Magendie.

His lecture courses at the Collège were organised around themes, and several became books. In 1856 he gave a course on toxic and medicinal substances, returning in it to the carbon monoxide studies begun ten years earlier. The lectures were published in 1857 as Leçons sur les effets des substances toxiques et médicamenteuses (Lessons on the Effects of Toxic and Medicinal Substances), which included his work on curare and carbon monoxide. He used poisons as instruments for taking living function apart: a poison that acted on one tissue alone showed what that tissue did.

In 1864–65 he devoted an entire course at the Collège to curare. That same period produced a popular essay, “Du curare,” published in the Revue des Deux Mondes in September 1864, parts of which were translated into English in a 1999 BMJ article by J. Black. In 1865 he published the Introduction à l’étude de la médecine expérimentale, his account of how experimental medicine works. The historian Sebastian Normandin describes the book as marking the end of conventional vitalism, with experiment replacing ready-made systems of explanation. Its ideas, and the milieu intérieur for which Bernard is best known among biologists, are covered on the legacy page.

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6. Pancreatic Juice and Fat Digestion (1848)

In 1848 Bernard collected pancreatic juice from living dogs and studied what it did to food. He showed that the juice breaks down fats — its lipolytic, or fat-splitting, action. His experiments gave the pancreas a clear, demonstrated role in the digestion of fat.

The work has stood up well. In 1999 the researchers Rodríguez de Romo and Borgstein reported repeating Bernard’s pancreatic experiments using the protocols in his own laboratory manuscripts, and they obtained results similar to his. Their paper marked 150 years since the original work.

Today the pancreas is known to release a mixture of enzymes into the small intestine, including lipase for fats, amylase for starches and proteases for proteins. The site’s animation The Pancreas: Your Digestive Enzyme Factory shows how this works. Bernard’s 1848 study was one of the first experimental steps toward that picture.

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7. Liver Sugar and the Isolation of Glycogen

Bernard’s most important discovery in digestion and metabolism concerned the liver. In the 1840s most physiologists believed that animals could not make sugar themselves; sugar in the body was thought to come from plant food and to be broken down, never built up. In 1848, working with the chemist Barreswil, Bernard reported that the liver contains sugar, and the same year he established the glucogenic function of the liver: the liver itself produces sugar and releases it into the blood.

The washed liver

Jensen and Puissant describe a chance observation in 1855, the washed-liver experiment, as a turning point. In the usual telling, Bernard washed a freshly removed liver with water until no sugar remained, left it, and later found that sugar had appeared again. Something in the liver tissue was continuing to produce it. The obvious explanation was a stored substance that the liver turned back into sugar.

In 1857 he isolated that substance. He named it glycogen — the sugar-forming material — and it became known as “animal starch,” because it plays in animals the role that starch plays in plants. Glycogen is a large branching chain of glucose units that the liver and muscles build when sugar is plentiful and break down when it is needed.

The discovery overturned the idea that animals only consume what plants make. Jensen and Puissant call it the journey that changed scientific views on the physiological role of the liver and on animal metabolism. Later researchers, including Carl and Gerty Cori, worked out the enzymes that build and break down glycogen; see Carl & Gerty Cori and the animation How the Liver Keeps Your Blood Sugar Steady.

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8. The Nerves That Widen and Narrow Blood Vessels

A third major line of work concerned the nervous control of blood vessels. Bernard cut the sympathetic nerve in the neck of an experimental animal and found that the same side of the face became congested with blood and grew warmer. The usual date given for this work is 1851.

The experiment showed that the sympathetic nerves keep blood vessels partly narrowed; when the nerve is cut, the vessels relax and widen, more blood flows, and the tissue warms. Bernard went on to show that some nerves have the opposite effect, widening blood vessels. Breathnach summarises his finding as the existence of vasodilator as well as vasoconstrictor nerve fibres — nerves that open blood vessels and nerves that close them.

This pairing of opposing controls became a theme of his thinking. A body that can both widen and narrow its blood vessels, raise and lower its blood sugar, is a body that can hold its inner conditions steady while the outside world changes. That idea grew into the milieu intérieur, set out in his late lectures on the phenomena of life common to animals and plants (1872–73, published 1878–79). Historians Holmes, Gross and Noble have each traced how it developed and what it later meant for physiology.

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9. Sorbonne, Muséum and the Académie Française

As his reputation grew, Bernard held more than one chair at once. Alongside the Collège de France he became professor of general physiology at the Sorbonne in the 1850s. In the late 1860s he moved to a chair at the Muséum national d’Histoire naturelle in Paris. Gomes and Engelhardt, writing for his bicentenary in 2014, list the Collège de France, the Sorbonne and the Muséum as the three institutions of his career.

The honours followed:

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10. Death and the First Scientist’s State Funeral

Claude Bernard died in Paris on 10 February 1878, aged 64. France gave him a state funeral — the first French scientist to be honoured in this way — and he was buried in the Père Lachaise cemetery.

Some of his work was still unfinished. His lectures on the phenomena of life common to animals and plants appeared in print in 1878–79, after his death. Notes he left on fermentation also led to a posthumous controversy with Louis Pasteur, which P. Debré reviewed in 2017.

His reputation rests on two kinds of achievement. The first is a list of discoveries that remain in every physiology textbook: pancreatic fat digestion, the liver’s production of sugar, glycogen, vasomotor nerves, the site of curare’s action between nerve and muscle and the way carbon monoxide takes the place of oxygen in the blood. The second is a way of working: testing every idea by experiment and treating a failed hypothesis as information. Sternbach and Varon included him in their “Resuscitation greats” series for his work on carbon monoxide poisoning, and Noble has called him the first systems biologist. What came after him is followed on the legacy page.

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Key Research Papers

  1. Breathnach CS. Claude Bernard and his revelations in physiology. Ir J Med Sci. 2014;183(1):139-46. PubMed PMID: 24297053
  2. Jensen J, Puissant C. Claude Bernard's route to the isolation of glycogen: the journey that changed scientific views on the physiological role of the liver and animal metabolism. Eur J Appl Physiol. 2026;126(2):629-647. PubMed PMID: 41417056
  3. Rodriguez de Romo AC, Borgstein J. Claude Bernard and pancreatic function revisited after 150 years. Vesalius. 1999;5(1):18-24. PubMed PMID: 11623831
  4. Gomes Mda M, Engelhardt E. Claude Bernard: bicentenary of birth and his main contributions to neurology. Arq Neuropsiquiatr. 2014;72(4):322-5. PubMed PMID: 24760099
  5. Black J. Claude bernard on the action of curare. BMJ. 1999;319(7210):622. PubMed PMID: 10473481
  6. Sternbach GL, Varon J. The Resuscitation greats. Claude Bernard: on the origin of carbon monoxide poisoning. Resuscitation. 2003;58(2):127-30. PubMed PMID: 12909373
  7. Normandin S. Claude Bernard and an introduction to the study of experimental medicine: "physical vitalism," dialectic, and epistemology. J Hist Med Allied Sci. 2007;62(4):495-528. PubMed PMID: 17576723
  8. Holmes FL. Claude Bernard, the milieu intérieur, and regulatory physiology. Hist Philos Life Sci. 1986;8(1):3-25. PubMed PMID: 3534926
  9. Gross CG. Claude Bernard and the Constancy of the Internal Environment. Neuroscientist. 1998;4(5):380-385. DOI: 10.1177/107385849800400520
  10. Noble D. Claude Bernard, the first systems biologist, and the future of physiology. Exp Physiol. 2008;93(1):16-26. PubMed PMID: 17951329
  11. Debré P. [Louis Pasteur and Claude Bernard: about a posthumous controversy]. Biol Aujourdhui. 2017;211(2):161-164. PubMed PMID: 29236666

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Further Reading

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Connections

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