336 



ANTHRAX 



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 accord- 

 ingly destroyed in the stomachs of healthy animals. They are 

 also soon killed in the process of putrefaction. They can, how- 

 ever, 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 gelatin always commences at the 

 surface and spreads downwards. Growth is more rapid in the 

 presence of oxygen, and spore formation does not occur in its 



absence. The organism 

 may be classed as a facul- 

 tative anaerobe. 



Sporulation. Under 

 certain circumstances 

 spor ulation occurs in 

 anthrax bacilli. The 

 morphological appear- 

 ances are of the ordinary 

 kind. A little highly 

 refractile speck appears 

 in the protoplasm about 

 the centre of the bacillus ; 

 this gradually increases 

 in size until it forms an 

 oval body about the same 

 thickness as the bacillus 

 i v ; no . j n fhp K^lla ^ vri 

 ^ m f u ' Da ClUaiy pro- 



toplasm (Fig. 102). The 

 latter gradually loses its 

 staining capacities and 

 finally disappears. The 



spore thus lies free as an oval highly refractile body which does 

 not stain by ordinary methods, but which can be easily stained 

 by the special methods described for such a purpose (p. 109). 

 When the spore is again about to assume the bacillary form the 

 capsule is apparently absorbed, and the protoplasm within grows 

 out, taking on the ordinary rod-shaped form. 



According to most observers, sporulation never occurs within 

 the body of an animal suffering from anthrax. Koch attributes 

 this, probably rightly, to the absence of free oxygen. The latter 

 gas he found necessary to the occurrence of spores in cultures 

 outside the body. Many, however, are inclined to assign as the 

 cause of sporulation the absence of the optimum pabulum. Be* 



FIG. 102. Anthrax bacilli containing spores 

 (the darkly coloured bodies) ; from a three 

 days' culture on agar at 37 C. See also 

 Plate III., Fig. 2. 



Stained with carbol-fuchsin and methylene- 



