280 



ANTHRAX. 



or above 45 C. In the spore -free condition the bacilli 

 have comparatively low powers of resistance. They do not 

 stand long exposure to 60 C., and if kept at ordinary tem- 

 perature in the dry condition they are usually found to be 

 dead after a few days. The action of the gastric juice is 

 rapidly fatal to them, and they are accordingly destroyed in 

 the stomachs of healthy animals. They are also soon 

 killed in the process of putrefaction. They can, however, 

 be cooled below the freezing-point without dying. The 

 bacillus can grow without oxygen, but some of its vital 

 functions are best carried on in the presence of this gas. 

 Thus in anthrax cultures the liquefaction of gelatine always 

 commences at the surface and spreads downwards. Growth 

 is more rapid in the presence of oxygen, and spore form- 

 ation does not occur in its absence. The organism may 

 probably be classed as a facultative anaerobe. 



Sporulation. Under certain circumstances sporulation 



occurs in anthrax 

 bacilli. The morpho- 

 logical appearances 

 are of the ordinary 

 kind. A little highly- 

 refractile speck 

 appears in the proto- 

 plasm about the centre 

 of the bacillus; this 

 gradually increases in 

 size until it forms an 

 oval body about the 

 same thickness as the 

 bacillus lying in the 



bacillary protoplasm 

 TIG. 73. Anthrax bacilli containing , J , m, i 



spores (the darkly coloured bodies); from (*lg- 73)- 1 he latter 

 a three days' culture on agar at 37 C. gradually loses its 



Stained with carbol-fuchsin and methylene- S f amm p- caDacities 



blue. x 1000. . ,, 



and finally disappears, 



the part that is not absorbed within the spore being 

 probably dissolved with the membrane in the surrounding 



