Which veterinarian proposed the public Melun test of Pasteur's anthrax vaccine?

The veterinarian who proposed the public Melun test of Pasteur’s anthrax vaccine was Hippolyte Rossignol.

Rossignol was a veterinarian in Melun and was initially skeptical about Pasteur’s claims. After Pasteur reported promising sheep-vaccination results in March 1881, Rossignol urged the Société d’agriculture de Melun to organize a demanding public trial rather than leave the vaccine as a laboratory claim.

The experiment took place at Rossignol’s farm in Pouilly-le-Fort, near Melun, in May 1881. Vaccinated and unvaccinated animals were later challenged with virulent anthrax. The vaccinated animals largely survived, while the controls died or became gravely ill, creating one of the most famous demonstrations in the history of immunology.

Rossignol’s role is sometimes blurred with those of Pasteur’s assistants Émile Roux and Charles Chamberland, who helped prepare and administer the vaccine. Jacques-Joseph Grancher was associated chiefly with Pasteur’s later rabies work, not the public anthrax challenge.