476 Anthrax 



Cultivation. Colonies. Upon the surface of a gelatin 

 plate the bacillus forms beautiful and highly characteristic 

 colonies (Fig. 143). 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 

 surface of the medium, where they spread out into flat, 

 irregular, transparent tufts like curled wool. From a 

 tangled center large numbers of curls, made up of parallel 



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Fig. 143. Bacillus anthracis; colony upon a gelatin plate. X 100 

 (Frankel and Pfeiffer). 



threads of bacilli, extend upon the gelatin. As soon as the 

 colony attains to any considerable size liquefaction becomes 

 rapid. Beautiful adhesion preparations can be made if a 

 perfectly clean cover-glass be passed once through a flame 

 and laid carefully upon the gelatin, the colonies being 

 picked up entire as the glass is carefully removed. Such 

 a specimen can be dried, fixed, and stained in the same 

 manner as an ordinary cover-glass preparation. 



Gelatin Punctures. In gelatin puncture cultures the 

 growth is even more characteristic than are the colonies. 

 The bacilli begin to grow along the entire track of the wire, 

 but develop most luxuriantly at the surface, where oxygen 



