[The experimental counter-proof in the office of Claude Bernard: the case of the destruction of a pancreas].

Claude Bernard attributed a fundamental role in experimental medicine to the "contre-épreuve." He believed that a phenomenon fails to appear if its cause is eliminated (contre-épreuve). Therefore, the relation "preuve-contre-épreuve" emerges as the best criterion of experimental truth. In 1848 Claude Bernard discovered that pancreatic secretion could emulsify and saponify fatty substances. This article, based on his original manuscripts, shows that Bernard demonstrated in 1851 that the absence of pancreatic juice resulted in the arrest of fat digestion. Using the "contre-épreuve," he destroyed the pancreas in dogs as another way to prove his theory of the pancreatic digestion of fat.