SPOR ULA TION. 28 1 



medium. 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. 103). 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 occur- 

 rence of spores in ordinary media growing outside the body. 

 Many, however, are inclined to assign as the cause of 

 sporulation the absence of theoptimumpabulum, which in the 

 case of anthrax is afforded by the animal tissues. Besides 

 these conditions there is another factor necessary to sporula- 

 tion, viz. a suitable temperature. The optimum tempera- 

 ture for spore production is 37 C. Koch found that 

 spore-formation 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, on 

 being again grown at a lower temperature, they did not 

 regain the capacity. In order to make them again capable 

 of sporing it is necessary to adopt special measures, such as 

 passage through the bodies of a series of susceptible animals. 



Anthrax spores are extremely resistant organisms. In a 

 dry condition they will remain viable for a year or more. 

 Koch found they resisted boiling for five minutes ; and dry 

 heat at 140 C. must be applied for several hours to kill 

 them with certainty. Unlike the bacilli, they can resist the 

 action of the gastric juice for a long period of time. 



Anthrax in Animals. Anthrax occurs from time to 

 time epidemically in sheep, cattle, and, more rarely, in 

 horses and deer. Geographically these epidemics are 

 found in various parts of the world, although naturally they 

 are most far-reaching where legal precautions to prevent the 

 spread of infection are non-existent. All the countries of 

 Europe are from time to time visited by the disease, though 



