344 LETHE E. MORRISON AND FRED W. TANNER 



maximum the thermophiles have a verj' high optimum, and the 

 minimum hes with most species above 30°C. According to Hew- 

 lett there is a group of so-called thermophilic bacteria which 

 thrive best at a temperature of 60° to 70°C. Those bacteria 

 whose optimum temperature is above 40°C. and which are spoken 

 of as the "thermophil" bacteria, is the definition given for them 

 by Morrey. Buchanan does not mention thermophiles in his 

 book but speaks of the organisms which produce large quantities 

 of heat as thermogenic bacteria. In his book Chester places 

 thermophilic bacteria in a class that does not grow at room tem- 

 peratures or below 22° to 25°C. 



II. RELATION OF HIGH TEMPERATURES TO LIFE 



All h\ang things have their minimum, maximum and optimum 

 temperatures for growth and other functions. The range of 

 temperatures at which they exist may depend among other fac- 

 tors, on the species and on the ancestral history of the indi\-idual. 

 Many investigators have experimented on the growth of organisms 

 at high temperatures with varied and interesting results. 



The first data concerning organisms that live at high tempera- 

 tures were published by Sonnerat (1774). He reported on fish 

 that hved in water at a temperature of 69°C. Schwabe (1837) 

 reported the growth of algae in a hot spring at Karlsbad at 70°C, 

 Flourens in 1846 mentioned algae which flourished in a hot spring 

 at a temperature of 98°C. Brewer (1866) found some "Nostoc- 

 formen" in a hot geyser at 83° C. Ehrenberg reported the exist- 

 ence of red and green algae from the Island of Ischia which grew 

 at 63° to 65°C. 



III. HISTORICAL 



The Uterature on thermophilic microorganisms has already 

 become quite voluminous and in order to save space in this publi- 

 cation, we have summarized in table 1, those papers which a 

 careful search of the Mterature has revealed. 



