778 PATHOGENIC MICROORGANISMS 



either in the sugars or in the fats of the milk. The acids formed 

 are, according to Iwanow, 5 chiefly formic, acetic, and caproic acids. 

 Biological Considerations. The anthrax bacillus is aerobic and 

 facultatively anaerobic. It is non-motile and possesses no flagella. 

 In the animal body it occasionally forms capsules. In artificial 

 cultures in the presence of oxygen, it sooner or later invariably 

 forms spores. The spores appear after the culture has reached its 

 maximum of development. Sporulation never occurs in the animal 

 body, probably because of the absence of sufficient free oxygen. 



FIG. 81. ANTHRAX COLONY ON GELATIN. (After Giinther.) 



Spores are formed most extensively 6 at temperatures ranging from 

 20 C. to 30 C. Spore formation ceases below 18 C. and above 

 42 C. For different strains these figures may vary slightly, as has 

 been shown from the results of various observers. Spores appear 

 most rapidly and regularly upon agar and potato media. 



The spore one in each bacillus appears as a small, highly 

 refractile spot in the center of the individual bacterium. As this 

 enlarges, the body of the bacillus around it gradually undergoes 

 granular degeneration and loses its staining capacity. 7 



5 Iwanow, Ann. de 1'inst. Pasteur, 1892. 



6 Koch, loc. cit. 



7 Behring, Zeit. f. Hyg., vi and vii, 1889; Dent. med. Woch., 1889. 



