François Magendie was born on October 6, 1783, the son of a surgeon who was known for his radical views and his active support of the French Revolution. The elder Magendie raised his two sons to be fiercely independent and to think for themselves--two traits that François never lost.

Apprenticed at sixteen to a surgeon friend of his father's, the young man began his formal medical studies a few years later, obtaining his medical degree in 1808 from the University of Paris. Although he was interested at first in anatomy, Magendie later switched to physiology and almost at once ran into trouble. At the time, most European scientists believed strongly in vitalism--the idea that biological processes were governed by "vital forces" that could not be explained in strictly scientific terms. Magendie disagreed. He was convinced that in the biologic sciences, just as in the physical sciences, facts...