160 THE MORE CHRONIC INFECTIOUS DISEASES 



ance and the environment plays an important part. 

 Anthrax bacilli grow well and characteristically on 

 laboratory culture media. It is not possible to pro- 

 duce a passive immunity to anthrax. Among the 

 great achievements of Pasteur was the discovery of a 

 method of rendering sheep immune to anthrax. He 

 discovered that by growing anthrax bacilli at a tem- 

 perature of 42 C. or 106 F. instead of 37 C. or 98 F. 

 he was able to considerably reduce their virulence. 



FIG. 45 



Threads of Bacterium anthracis containing spores. X about 1200 diameters. 

 (Abbott.) 



By varying the length of time of cultivation at this 

 temperature, two different strengths were obtained. 

 He now injected the weaker, and followed a few days 

 later with the more virulent. The resistance of the 

 animal can thus be raised to a high level for about a 

 year. The 'method is not practicable for human 

 beings. 



ACTINOMYCOSIS 



Actinomycosis or lumpy jaw is chiefly a disease of 

 animals, but may affect man. It is characterized by 

 the production of large semisolid tumefactions usually 



