132 



ANTHRAX 



oval, highly refractive bodies held within the cellular 

 envelopes of the filaments, but later the}- are set free by the 





Fig. 22. Anthrax bacteria in a cover-glass preparation of blood 



sho-n'ing chains and capsules. 



dissolution of this membrane. They stain readily with the 

 aniline dyes and also by Gram's method. 



The bacterium of anthrax itself is not an especially hardy 

 organism. On the contrary it is easily destroyed by weak 

 disinfectants and it has a low thermal death point. Its spores, 

 however, are among the most hardy of bacterial life to resist 

 chemical and thermal agents. They resist drying for months 

 or years and often boiling for a half-hour or longer does not 

 destroy them. On this account it is very difficult to eliminate 

 the virus from infected pasture lands, especially if they are 

 wet or marshy. 



As the spores may remain on the soil in a dormant condi- 

 tion for many years, it sometimes happens that the disease 

 does not appear until long after the introduction of the virus. 

 Anthrax has been known to break out among cattle grazing 

 on a field in which the carcasses or hides from affected animals 

 were buried many years before. Through some means the 

 spores seem to be able to get to the surface and contaminate 

 the grass. The virus may be introduced with blood or bone 



