ANTHRAX. 337 



Picro-carmin, followed by Gram's method, gives a beau- 

 tiful and clear picture. The spores can be stained with 

 carbol-fuchsin, the bacilli decolorized with a very weak 

 acid, and then counter-stained with a watery solution of 

 methyl blue. 



Upon the surface of gelatin plate-cultures the bacillus 

 forms beautiful and highly characteristic colonies (Fig. 

 in). To the naked eye they appear first as minute 



FIG. in. Bacillus anthracis: colony upon a gelatin plate ; x 100 (Frankel and 



Pfeiffer). 



round whitish dots occurring upon the surface, and caus- 

 ing liquefaction of the gelatin as they increase in size. 

 Under the microscope they can be seen in the gelatin as 

 egg-shaped, slightly brownish granular bodies, not attain- 

 ing their full development except upon the surface, where 

 they spread out into flat, irregular, transparent growths 

 bearing a partial resemblance to tufts of curled wool. 

 From a tangled centre large numbers of curls extend, 

 each made up of parallel threads of bacilli. As soon as 

 the colony attains any considerable size liquefaction be- 

 gins. These colonies make beautiful adhesive prepara- 

 tions. If a perfectly clean cover-glass be passed once 

 'through a flame and laid carefully upon the gelatin, the 

 22 



