BACILLUS ANTHBACIS AND ANTHRAX 569 



within twelve to twenty-four hours. They are irregular in outline, 

 slightly wrinkled, and show under the microscope the characteristic 

 tangled-thread appearance seen on gelatin, except that they are more 

 compact than upon the former medium. The colonies are slightly glisten- 

 ing and tough in consistency. 



On agar slants, the colonies usually become confluent, the entire 

 surface soon being covered by a grayish, tough pellicle which, if fished, 

 has a tendency to come away in thin strips or strands. 



On potato, growth is rapid, white, and rather dry. Sporulation upon 

 potato is rapid and marked, and the medium is favorable for the study 

 of this phase of development. 



Milk is slowly acidified and slowly coagulated. This action is chiefly 

 upon the casein; very few, if any, changes being produced either in the 

 sugars or in the fats of the milk. The acids formed are, according to 

 Iwanow,' chiefly formic, acetic, and caproic acids. 



Biological Considerations. — The anthrax bacillus is aerobic and facul- 

 tatively 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 develop- 

 ment. Sporulation never occurs in the animal body, probably because 

 of the absence of sufficient free oxygen. Spores are formed most exten- 

 sively ' 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 degenera- 

 tion and loses its staining capacity.' 



If anthrax bacilli are cultivated for prolonged periods upon media 

 containing hydrochloric or rosolic acid or weak solutions of carbohc 

 acid,* cultures may be obtained which do not sporulate and which seem 

 permanently to have lost this power, without losing their virulence to 

 the same degree. Similar results may be obtained by continuous cul- 



' Iwanow, Ann. de I'inst. Pasteur, 1892. 



2 Koch, Ipc. cit. 



3 Behring, Zeit. f. Hyg., vi and vii, 1889; Deut. med. Woch., 1889. 



* Chamberland et Roux, Comptes rend, de I'acad. des sci., xcvi, 1882. 



