346 



ANTHRAX 



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 temperature 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 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 com- 

 mences 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 facultative 

 anaerobe. 



Sporulation. Under 

 certain circumstances 

 sporulation occurs in an- 

 thrax bacilli. The mor- 

 phological appearances are 

 FIG. 106. -Anthrax bacilli containing spores of the ordinary kind. A 

 (the darkly coloured bodies) ; from a three little highly refractile 

 days' culture on agar at 37 C. See also -, ' ,- 



Plate III , Fig. 2. speck appears in the proto- 



Stained with carbol-fuchsin and methylene- plasm about the centre 

 blue. xlOOO. 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 (Fig. 106). The 

 latter gradually loses its staining capacities and finally dis- 

 appears. 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. 110). 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 



