346 ANTHRAX 



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 deuxieme 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, from a hypodermic syringe, of about 

 five drops of the premier vaccin \ 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 

 experiments in France generally confirmed earlier results, and 

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

 in many departements 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 vaccinated ; and thus to be 

 permanently efficacious the process would have to be repeated 

 every year. Further, the immunity is much higher in degree 

 if, after the first and second vaccinations, an inoculation with 

 virulent anthrax is performed. Everything being taken into 

 account, however, there is no doubt that the mortality from 

 natural anthrax is much diminished by this system. 



During the twelve years 1882-93, 3,296,815 sheep were vaccinated, 

 with a mortality, either after the first or second vaccination, or during 

 the subsequent twelve months, of 0*94 per cent., as contrasted with the 

 ordinary mortality in all the flocks of the districts of 10 per cent. 

 During the same time 438,824 cattle were vaccinated, \vith a mortality, 

 of 0*34 per cent., as contrasted with a probable mortality of 5 per cent, if 

 they had been unprotected. 



