Soon after becoming a doctor, Émile Roux began doing research on bacterial diseases for Louis Pasteur. It has taken a century, however, for Roux's contribution to Pasteur's work--specifically his experiments utilizing dead bacteria to vaccinate against rabies--to be acknowledged. Roux is also credited, along with Alexandre Yersin, with the discovery of the diphtheria toxin secreted by Corynebacterium diphtheriae and immunization against the disease in humans. Both colleague and close friend to Pasteur, Roux eventually became the director of the Pasteur Institute in Paris.

Roux began his study of medicine at the Clermont-Ferrand Medical School in 1872. In 1874 Roux moved to Paris where he continued his studies at a private clinic. In 1878 he helped create lectures on fermentation for Emile Duclaux at the Sorbonne, Paris. Duclaux introduced Roux to Louis Pasteur, who was then in need of a doctor to assist with his research on bacterial diseases.

In 1879 Roux...