STUDIES ON THERMOPHILIC BACTERIA. I 359 



anthracis and Bacilhis siibiilis that had been subjected to 123°C. 

 in dry air. According to Arloing, Cornevin, and Thomas (1882) 

 the spores of Bacillus anthracis-symptomatici would not resist 

 boiHng for more than 2 minutes; but if previously dried, boiling 

 for two hours was necessary to destroy them. 



This seems to agree with the theory of Davenport and Castle 

 (1895) that by the loss of water, which is a necessary consequence 

 of increased chemical activity resulting from warmth, organisms 

 are able to increase their resistance to high temperatures. If we 

 accept this view thermophiles are explained on the basis of adap- 

 tation to environment. 



Tsikhnsky (1903) also believed that thermophiles were merely 

 variations of common non-thermophilic microorganisms that had 

 adapted themselves slowly to high temperature. He thought 

 that the length of time necessary for these organisms to adapt 

 themselves to high temperature detennined whether they were 

 facultative or strict thermophiles. 



Schillinger proposed the term thermotolerant to be apphed to 

 these organisms. Miehe tried to explain the liigh optimum tem- 

 perature of thermophiles by assuming that they might have been 

 brought over from the tropics and have adapted themselves to 

 lower temperatures. By comparing them with other bacteria, 

 Miehe came to the conclusion that all bacteria could be grouped 

 on the basis of their minimum temperatures. He divided the 

 thermophiles into two groups: (1) orthothermophiles with a maxi- 

 mum temperature of 60°-70°C.; (2) thermotolerants with a 

 maximum temperature of 50''-55°C. but which also grow well at 

 ordinary temperatures. 



Many investigators, among them Rabinowitsch, Schiitze, and 

 others, found a certain parallelism between temperature relations 

 and the relation of thermophiles to oxygen. In most cases those 

 organisms which had high optimum temperatures were strict 

 aerobes. 



Bergey divided thermophihc bacteria into two groups: (1) 

 true thermophiles, those that grow at temperatures above the 

 maximum temperature for the great majority of bacteria, es- 

 pecially the pathogenic forms; (2) facultative thermophihc 



