Louis Pasteur. Engraving of Louis Pasteur (1822- 95), French biologist, performing his anthrax vaccination experiment at Pouilly-le-Fort in 1881. Pasteur had produced a weakened or attenuated form of the anthrax bacteria, Bacillus anthracis, by incubating cultures for eight days at a relatively high temperature. On 28 April 1881, Pasteur injected 24 sheep, one goat and six cows with the attenuated cultures; he repeated this on 17 May. Two weeks later he injected this group and 29 unvaccinated animals with a virulent strain of anthrax. When he returned on 2 June all the unvaccinated animals were dead or dying whilst the inoculated animals survived the experiment.