Cultivation 403 



Motility. The bacilli are not motile and have no flagella. 



Staining. They stain well with ordinary solutions of the 

 anilin dyes, and can be beautifully demonstrated in the 

 tissues by Gram's method and by Weigert's modification of 

 it. Picrocarmin, followed by Gram's stain, gives a beau- 

 tiful, clear picture. The spores can be stained by any of the 

 special methods for staining spores (q. v.). 



Isolation. The bacillus of anthrax is one of the easiest 

 organisms to secure in pure culture from the tissues and 

 excreta of diseased animals. Its luxurious vegetation, the 

 typical appearance of its colonies, and its infectivity for the 

 laboratory animals combine to make possible its isolation 

 either by direct cultivation from the tissues, by the plate 

 method, or by the inoculation into animals and recovery 

 of the micro-organisms from their blood. 



Fig. 125. Bacillus anthracis; colony upon a gelatin plate. X 100 

 (Frankel and Pfeiffer). 



Cultivation. Colonies. Upon the surface of a gelatin 

 plate the bacillus forms beautiful and highly characteristic 

 colonies (Fig. 125). To the naked eye they appear first as 

 minute round, grayish-white dots upon the surface. They 

 early begin liquefaction of the gelatin, which progresses 

 rapidly as they increase in size. Under the microscope the 

 smallest colonies are egg-shaped, slightly brown and granular. 

 They do not attain their full development except upon the 



