Duclaux worked as an assistant to Pasteur for a few years, later returning as a senior collaborator before succeeding him as director of the Pasteur Institute, with Roux and Chamberland as close colleagues. He worked closely with Pasteur on sikworm disease and the fermentation of beer, and joined him in the debate about spontaneous generation. While based outside the Pasteur Institute (he held a succession of academic appointments), he remained a close associate of Pasteur’s. Perrin was a correspondent, and a fellow-leader of the defenders of Captain Dreyfus in a notorious case of institutional anti-semitism.