The quest for a unified model of anesthetic action: a century in Claude Bernard's shadow.

An accepted truism among clinicians and researchers attributes the persistence of the quest for a unitary mechanism of anesthetic action to the lasting influence of Hans Meyer and Ernest Overton. This article presents a different view: the experiments that led to the Meyer-Overton rule were the consequence-not the source-of a unitary paradigm that was formulated by Claude Bernard a quarter of a century earlier. Bernard firmly believed that the sensitivity to anesthesia was a fundamental criterion that separated 'true life' from 'mere chemistry.' Bernard's scientific authority in the context of 19 century natural philosophy is responsible for establishing a unified (i.e., unitary mechanism and universality across life forms) paradigm of anesthetic action. Meyer and Overton's work was targeted at systematizing and solidifying existing knowledge within this paradigm, not at discovering novelty, and its publication did not substantially affect contemporary research. Claude Bernard's paradigm, by contrast, still influences investigations of mechanisms of anesthetic action.