27 8 



ANTHRAX. 



gelatine. In gelatine plates, however, instead of the char- 

 acteristically wreathed appearance at the margin, the colonies 



FIG. 71. r Anthrax bacilli, arranged in 

 chains, from a twenty-four hours' culture on 

 agar at 37 C. 



Stained with fuchsin. x 1000. 



sometimes give off radiating spikelets 

 irregularly nodulated, which produce 

 a star-like form. These spikelets are 

 composed of spirally twisted threads. 

 To such an appearance the term " fir- 

 tree growth " is sometimes applied. 



From such plates the bacilli can 

 be easily isolated, and the appearances 

 of pure cultures on various media 

 studied. 



Appearances of Cultures. In bouil- 

 lon, after twenty-four hours' incubation 

 at 37 C. there is usually the appearance of irregularly spiral 

 threads suspended in the liquid. These, on being examined, 

 are seen to be made up of bundles of parallel chains of bacilli. 

 Later, growth is more abundant, and forms a flocculent mass 

 at the bottom of the fluid. 



FIG. 72. Stab 

 culture of the anthrax 

 bacillus in peptone- 

 gelatine ; seven days' 

 growth. It shows the 

 "spiking" and also, 

 at the surface, com- 

 mencing liquefaction. 

 Natural size. 



