66 BACTERIOLOGY. 



Some further effects of temperature are 

 worthy of note. Pasteur discovered that if 

 anthrax bacilli are cultivated between 42 and 

 43, no spore-formation occurs, although at 

 other temperatures it usually takes place when 

 the species finds itself under threatening in- 

 fluences. If the cultures are allowed to remain 

 for some time at this high temperature the viru- 

 lence, that is to say the power of causing 

 anthrax in animals, decreases. According to 

 Chauveau, Koch, and Gaffky and LofHer, 20 

 days of exposure at 42, about six days at 43, 

 3-4 hours at 47, or 15-20 minutes at 5o-52, 

 produces a uniform degree of attenuation. 

 Similarly, some endospores are so affected by 

 temperatures of 8o-ioo that the vegetative 

 forms to which they give rise have lost their 

 original ability to excite fermentation or dis- 

 ease. Fitz I established this fact for the bacillus 

 of butyric acid and Arloing and Kitt 2 later for 

 the bacillus of symptomatic anthrax. 



It is possible to make use of this varying be- 

 havior to temperature to obtain pure cultures. 

 If in a mixture of different kinds of bacteria or 

 of bacteria with other organisms the endospores 

 of bacteria are present, these are sure to be 

 much more resistant than the other organisms. 



1 Ber. der Deutsch. chem. Gesellsch., 1882, p. 867. 



2 Centralbl. f. Bakt., III., 1888. 



