SPORULATION. 



301 



this gradually increases in size until it forms an oval body 



about the same thickness as the bacillus lying in the 



bacillary protoplasm 



(Fig. 81). 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. 114). 



iTfi i FIG. 8 1. Anthrax bacilli containing 



SpOl IS spores (the darkly coloured bodies); from 



again about to as- a three days' culture on agar at 37 C. 

 SUme the bacillary Stained with carbol-fuchsin and methylene- 



. blue. x 1000. 

 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 occur- 

 rence of spores in cultures outside the body. Many, how- 

 ever, are inclined to assign as the cause of sporulation 

 the absence of the optimum pabulum, which in the case of 

 anthrax is afforded by the animal tissues. Besides these 

 conditions there is another factor necessary to sporulation, 

 viz. a suitable temperature. The optimum temperature for 

 spore production is 32 C. Koch found that spore-forma- 

 tion did not occur below 18 C. Above 42 C. not only 

 does sporulation cease, but Pasteur found that if bacilli 

 were kept at this temperature for eight days they did not 

 regain the capacity when again grown at a lower tempera- 



