1 56 BACTERIOLOGY. 



and animals inoculated with it (premier vaccin) are 

 protected against the disease.* To obtain a still 

 more perfect immunity, they are inoculated a second 

 time with material (deuxieme vaccin) which has 

 been less weakened. The animals are then pro- 

 tected against the most virulent anthrax, but only 

 for a time. From such a culture, however, new 

 cultures of virulent bacilli can be started, and a 

 culture that is " vaccin " for sheep kills a guinea- 

 pig, and then yields bacilli that are fatal to sheep. f 

 Exposure to a temperature of 55 C., or treatment 

 with *5 to i per cent, carbolic acid, deprives the 

 bacilli of their virulence. The virulence of the 

 bacillus is also altered by passing the bacillus 

 through different species of animals. The bacillus 

 of sheep or cattle is fatal when re-inoculated into 

 sheep or cattle ; but, if inoculated in mice, the 

 bacilli then obtained lose their virulence for sheep 

 or cattle ; only a transitory illness results, and the 

 animals are protected for a time against virulent 

 anthrax. J The possibility of mitigating the virus 

 depends upon the species of animal ; rodents cannot 

 be rendered immune by any known " vaccin." 



* Pasteur, Comfit. Rend., 1861, and Revue Scientifique, 1883. 

 t Klein, Micro-organisms and Disease. 1885. 

 J Klein, Reports of the Medical Officer of the Local Government 

 Board. 1882. 



