552 BACTERIOLOGY. 
reaction be not decidedly acid, which arrests develop- 
ment, It grows in cow-dung and in more or less 
contaminated earth. It is also capable of leading a 
saprophytic existence. The bacillus is non-motile. 
Growth in Gelatin. In gelatin plate cultures, at 
the end of twenty-four to thirty-six hours at 24° C., 
small, white, opaque colonies are developed, which 
Fic. 73. 
Colonies of bacillus anthracis upon gelatin plates. a, at the end of twenty- 
four hours; b, at the end of forty-eight hours. x 80. (F. FLUGGE.) 
under a low-power lens are seen to be dark gray in 
the centre and surrounded by a greenish, irregular 
border, made up of wavy filaments. As the colony 
develops on the surface of the gelatin these wavy 
filaments spread out, until finally the entire colony 
consists of a light gray, tangled mass, which has been 
likened to a Medusa head (Fig. 73). 
At the same time the gelatin begins to liquefy, and 
the colony is soon surrounded by the liquefied medium, 
