domestic animals may usually be arrested. But it may happen that the extent of the epidemic prevalence and the number of animals already exposed to infection make these measures inadequate or difficult of execution. In this case we have, for certain diseases, another method of prophylaxis which has been extensively employed with excellent results. I refer to the method of protective inoculations, which we owe largely to the genius and patient researches of the distinguished French chemist Pasteur and his pupils.
Toussaint, a pioneer in researches relating to protective inoculations, has a short paper in the Comptes-Rendus of the French Academy of Sciences of July 12, 1880, entitled Immunity from Anthrax (charbon) acquired as a Result of Protective Inoculations.
In this paper he announces his discovery of the important fact that the anthrax bacillus does not form spores in the tissues or liquids of the body of an infected animal, but multiplies alone by binary division: "Sa multiplication se fait toujours par une division du mycélium."
In the same communication he reports his success in conferring immunity upon five sheep by means of protective inoculations, and also upon four young dogs. We must therefore accord him the priority in the publication of experimental data demonstrating the practicability of accomplishing this result.
In a communication made to the French Academy of Sciences, September 27, 1880, Pasteur gave an account of an experiment made July 14, 1879, upon two cows, which, in connection with a subsequent experiment, made August 6, 1880, upon four cows, led him to the conclusion that a single attack of anthrax protects from subsequent attacks.
The next important steps in the line of experimental research leading to protective inoculations in the disease under consideration were reported by Pasteur in his communication to the French Academy made at the séance of February 28, 1881 (with the collaboration of Chamberland and Roux), entitled De l'Atténuation des Virus et de leur Retour à la Virulence. In this connection Pasteur announces his discovery of the fact that when cultivated at a temperature of 42° to 43° C. the anthrax bacillus no longer forms spores and rapidly loses its virulence.
In a later communication (March 21, 1881) Pasteur says that he has found by experiment that when attenuated varieties of the anthrax bacillus form spores, these again reproduce the same pathogenic variety, so that cultures of each degree of attenuation can be maintained indefinitely.
On June 13, 1881, Pasteur communicated the results of his famous experiment at Pouilly-le-Fort, near Melun. He says:
