Bernard's Introduction to Experimental Medicine

Claude Bernard (1813 to 1878), born in the village of Saint-Julien near Villefranche-sur-Saône, learned experimental physiology as assistant to François Magendie in Paris. Magendie distrusted hypotheses and used to say that when he experimented he used only his eyes and ears, not his brain. Bernard's own experiments, many of them on living animals and mostly done at the Collège de France, dealt with digestion, the liver and the nerves, including the sympathetic nerves and the action of curare.

In 1865 the Paris publisher J.-B. Baillière et Fils brought out his Introduction à l'étude de la médecine expérimentale. Its three parts covered experimental reasoning, experimenting on living beings, and examples of the method applied to the phenomena of life. Bernard held that an idea should direct an experiment and the experiment should then judge the idea. A hypothesis that no experiment could test, he wrote, led back to the errors of the scholastics and system-builders.

He insisted on two safeguards. One was the comparative experiment, which he called the true basis of experimental medicine; nearly all experimental errors, he argued, came from failing to compare, or from treating unlike cases as comparable. The other was the counter-proof. A researcher whose idea seemed confirmed had to go on doubting, because showing that a condition always precedes a phenomenon does not prove it the cause, the trap of post hoc, ergo propter hoc. Statistical tables of presence or absence, he added, never amount to an experimental demonstration.

The book also described two environments in higher animals: the outer world, and a milieu intérieur formed by the blood and the fluids around the tissues, which more complex animals keep increasingly apart from outside conditions. The idea was later known as homeostasis. His reliance on experiments on living animals divided his own family. His wife and daughters supported the anti-vivisection movement, and he eventually fell out with them.