PATHOGENIC BACTERIA. 335 



produced a similar vaccine for chicken cholera. There is 

 considerable danger to the inoculated animals attending the 

 use of anthrax vaccines. There is always more or less loss 

 of the animals from anthrax vaccination itself and danger of 

 spreading the disease. 



In order to obtain material free from spores the blood of 

 an animal which has recently died of anthrax is taken, because 

 anthrax spores do not form in the living body. Cultures made 

 in bouillon are kept at a temperature of from 42° to 43° C. 



V 



N. 





\/ 



-JSa' 



Fig. 84. — Anthrax bacilli with square or slightly concave ends sometimes 

 seen; fuchsin stain. (X 1000.) 



At this temperature the virulence of the anthrax bacillus be- 

 comes gradually diminished. In time the virulence is so far 

 diminished that rabbits will survive inoculation, and even- 

 tually also mice and guinea-pigs, which are extremely suscep- 

 tible to anthrax. Small doses of a culture of extremely weak 

 virulence are given to the animals which it is desired to pro- 

 tect, like cattle and sheep, and subsequently a somewhat more 

 virulent culture is employed.* The method is never used in 

 human beings. 



* For details as to the results of this method see V. A. Moore. Infectious 

 Diseases of Animals. 1906. 



