154 THE MORE CHRONIC INFECTIOUS DISEASES 



lower temperatures. The vegetative rods are killed at 54 C. 

 or 130 F. in ten minutes; the spores are killed by boiling ten 

 minutes or in dry heat at 140 C. or 285 F. for ten minutes. 

 The resistance to chemical agents has been considered under 

 Disinfectants, but it is best not to rely on any chemical 

 killing of anthrax spores, as different cultures vary in resist- 

 ance and the environment plays an important part. Anthrax 

 bacilli grow well and characteristically on laboratory culture 

 media. It has been found possible to produce an antiserum 

 which has some beneficial effect on the human disease but 

 it must be given early and only acts as an aid to the surgical 

 treatment which can never be omitted. One of the great 

 achievements of Pasteur was the discovery of a method of 



FIG. 47. Threads of Bacterium anthracis containing spores. X about 

 1200 diameters. (Abbott.) 



immunizing sheep against anthrax. He discovered that by 

 growing anthrax bacilli at a temperature of 42 C. or 106 F. 

 instead of 37 C. or 98 F. he was able to reduce their viru- 

 lence considerably. By varying the length of time of culti- 

 vation 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. 



Actinomycosis or lumpy jaw is chiefly a disease of animals, 

 but may affect man. It is characterized by the production 



