in CHAUVEAU'S EXPERIMENTS 129 



certainly be looked upon as a distinct species. Between 

 this ultra-attenuated and the highly virulent breed 

 many intermediate types exist, but they have less 

 fixity, and their nature as measured through their 

 pathological effects is less constant. At all events 

 Professor Chauveau has succeeded in obtaining three 

 types of Bacillus anthracis : 



Firstly, the ultra-attenuated type, which has lost all 

 pathological properties, and produces no disease even 

 in the most delicate and appropriate animals (mouse, 

 guinea-pig), but retains vaccinal influence, and can be 

 used for vaccination of the same animals against the 

 disease ; 



Secondly, the semi-attenuated type, 1 which kills 

 some species of animals (rabbit and guinea-pig), but 

 acts only as a vaccine in other larger animals ; 



Thirdly, the less attenuated type, which kills the 

 rabbit, guinea-pig, and sheep, and plays the part of a 

 vaccine only with the horse or oxen. 



These different types may exist in Nature, and some 

 facts go to show that some of them probably do 

 exist. 



The foregoing facts are of undeniable importance 

 in regard to the question of physiological variability, 



1 This type may be obtained either by attenuation of the highly 

 virulent type, or by partial revivification of the attenuated bacilli. The 

 latter method is certainly preferable. 



