Paré's law: the second law of toxicology.

There are three so-called laws that underlie the science of toxicology. Paracelsus is usually considered to be the father of toxicology, having formulated the first law, which states that the dose makes the poison. The second law concerns the specificity of toxic effects of individual chemicals, a specificity due to the unique chemical structure of the agent and the laws of biology that govern the response. The third law is that humans are animals and that therefore the study of animals can provide useful insight into effects in humans. We can find no record of any eponym being used to designate the second law of toxicology. We propose that the place of honor for having clearly enunciated this second law, which encompasses recording an unfortunate experiment to prove his dictum, belongs to Paré, who stated that “Poyson . . . kils by a certaine specifick antipathy contrary to our nature” (Paré, 1634/1951). Paré (ca. 1510–1590) was born in the French city of Laval and grew up in humble circumstances that left him unable to attend the university (Gunn, 1941). After apprenticeship as a barber-surgeon, and three years performing surgery at the Hotel Dieu, a Paris public hospital, Paré began his long career as a military surgeon. His medical activities were typified by a practical approach to treating battlefield wounds, based upon careful observation and a willingness to challenge the doctrines of the Faculty of Medicine. Among his contributions were the reintroduction of the ligature to tie off bleeding blood vessels and the abandonment of boiling oil as a routine treatment of battlefield injuries. His published arguments for use of ligatures, an approach contrary to that advocated by medical academicians at the University of Paris, combined both field experimentation and citation of ancient literature. His fame led to his providing medical advice to four successive French Kings, and such well known contemporaries as Catherine de Medici, Rabelais, and Montaigne (Gunn, 1941). Paré makes his case concerning the specificity of poisons in a treatise on the Bezoar, reputed to be an antidote against all poisons (Paré, 1634/1951):