IMMUNTSA TION A GAINST ANTHRAX. 293 



The Immunising of Animals against Anthrax. Having 

 ascertained that there was ground for believing that in cattle 

 one attack of anthrax protected against a second, Pasteur 

 in the years 1880-82) elaborated a method by which a 

 mild form of the disease could be given to animals, which 

 rendered harmless a subsequent inoculation, with virulent 

 bacilli. He found that the continued growth of anthrax 

 bacilli at 42 to 43 C. caused them to lose their capacity of 

 producing spores, and also gradually to lose their virulence, 

 so that after twenty-four days they could no longer kill either 

 guinea-pigs, rabbits, or sheep. Such cultures constituted 

 his premier vaccin^ and protected against the subsequent 

 inoculation with bacilli which had been grown for twelve 

 days at the same temperature, and the attenuation of which 

 had therefore not been carried so far. The latter constituted 

 the deiixieme vaccin. It was further found that sheep thus 

 twice vaccinated now resisted inoculation with a culture 

 which usually would be fatal. The method was to inoculate 

 a sheep on the inner side of the thigh by the subcutaneous 

 injection, by a hypodermic syringe, of about five drops of the 

 premier vacrin ; twelve days later to again inoculate with the 

 deuxieme vaccin; fourteen days later an ordinary virulent 

 culture was injected without any ill result. This method 

 was applicable also to cattle and horses, about double the 

 dose of each vaccine being here necessary. Extended ex- 

 periments in France generally confirmed earlier results, and 

 the method was, before long, used to mitigate the disease, 

 which in many departments was endemic and a very great 

 scourge. Since that time the method has been regularly in 

 use. It is difficult to arrive at a certain conclusion as to 

 its merits. Undoubtedly a certain number of animals die of 

 anthrax either after the first or second vaccination, or during 

 the year following vaccination. At the end of a year the 

 immunity is lost in about 40 per cent of the animals vac- 

 cinated ; and thus to be permanently efficacious the process 

 would have to be repeated every year. Further, the im- 

 munity is much higher in degree if, after the first and second 

 vaccinations, an inoculation with virulent anthrax is performed. 



