84 ANTHRAX 



flexible filaments, which combine to form thread-like bundles. 

 When examined, the ends of the rods seem to be square cut. 

 In preparations from animal tissues there appear sometimes to 

 be slight concavities in the ends of the segments when two of 

 them are united. In old cultures spores are formed. These 

 are oval, highly refractive bodies held within the cellular 

 envelope of the filaments, but later they are set free by the 

 dissolution of this membrane. It stains readily with the ani^ 

 line dyes and also by Gram's method. 



B 



Fig. II. Bacterium anthracis. A. without spores. B. with spores. 



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 in 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 were able to get to the surface and contami- 

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



