Pierre Paul Émile Roux

Studying medicine in Clermont-Ferrand and Paris, Roux joined Pasteur's laboratory in 1878, proving instrumental in developing anthrax, fowl cholera, and the historic 1885 rabies vaccines. In 1888, with Alexandre Yersin, he isolated the soluble toxin produced by the diphtheria bacillus, founding modern toxinology.

In 1894, at the International Congress of Hygiene in Budapest, Roux presented clinical results using horse anti-diphtheria serum on hundreds of dying children at the Hôpital des Enfants-Malades in Paris, dropping mortality from 50% to 12%. Succeeding Duclaux as Director of the Pasteur Institute (1904–1933), he lived in ascetic simplicity on the institute grounds.