ABSTRACT
In 1869 Moritz and others had ascertained the parasitic character of so-called chicken cholera, a destructive disease among fowls. Pasteur succeeded in attaining pure sub-cultures of the organism of this disease in chicken broth. He ascertained that infection was contained in the fowl's excreta and was spread by food. On returning from his summer vacation in 1879, Pasteur was surprised to find that most of the cultures of fowl cholera left behind in his laboratory were no longer able to produce disease when inoculated into fowls. The virulence of the cultures had disappeared. But before abandoning the "spoilt" cultures Pasteur tested whether their inoculation into chickens produced any changes in them. Pasteur also observed that sometimes fowl cholera instead of killing produced a semi-chronic disease, and that the microbe obtained from these fowls had an increased virulence. In 1883 Pasteur definitely introduced his method of anti-anthrax vaccination against this disease.
