ANTHRAX. 493 



As early as 1850 Rayer and Devaine, also Pol- Bacillus 

 lender, had discovered the presence of small rods 

 and filaments in the blood of animals which had 

 died of anthrax, and the work of Koch, Pasteur 

 and others soon established that this rod, the an- 

 thrax bacillus, is the cause of anthrax. The discov- 

 ery of Koch that the bacillus forms extremely re- 

 sistant spores, explained the persistence with which 

 the disease infects particular localities. 



The anthrax bacillus is a fairly large organism, spores. 

 is rod-shaped, non-motile and grows with charac- 

 teristic appearances on various culture media. 

 With the proper temperature and culture medium, 

 and in the presence of free oxygen, the formation 

 of spores begins after about twenty-four hours of 

 growth. Their evolution is complete in from one 

 to two days, and eventually the protoplasm of the 

 cells disintegrates and the spores are set free. 

 Spores are not formed in the body of an infected 

 animal. Spore formation is not essential, how- 

 ever, for the continued life of the organism; at 

 high temperatures (42 C.), and in the presence 

 of minute amounts of acids and alkalis or of car- 

 bolic acid, strains may be so altered that they lose 

 permanently the ability to produce spores. Under 

 favorable conditions the spores germinate com- 

 pletely in from three-quarters to one and one-half 

 hours (Grethe) by a process in which they lose 

 their refractive appearance and assume first an 

 oval and then a rod shape. In the body a capsule 

 surrounds the bacillus, and it grows singly or in 

 very short chains ; in culture media it is very diffi- 

 cult to obtain capsules. The long threads which 

 appear in culture media, especially bouillon, are 

 not found in infected animals. 



