452 Bacteria in Relation to Country Life 



microorganisms, and that the phenomenon is due to the 

 activities of the cells of the dying grass, or of the enzymes 

 contained in them. 



On the other hand, it has been shown that unwashed, 

 moist cotton, when stored in large heaps, undergoes a 

 rise in temperature. The latter rose to 155° Fahr. within 

 twenty-four to thirty hours and after a few days gradu- 

 ally declined. No elevation of temperature occurred 

 in sterilized cotton, but this was induced by moistening 

 the sterilized material with a small quantity of water 

 pressed out of moist, unsterilized cotton. The process 

 is analogous here to that occurring in the heating of 

 hay, and the experiments just referred to would indi^ 

 cate that it is of bacterial origin. More recently, ex- 

 periments have been made on the heating of hay in 

 specially constructed vessels that would allow a thor- 

 ough sterilization of the material, and its subsequent 

 inoculation when necessary. As in the case of cotton, 

 no heating occurred in the sterilized samples, yet these 

 manifested a rise in temperature soon after they were 

 moistened with a little infusion from unsterilized hay, 

 from soil and the like. 



A large number of species have been isolated and 

 studied as to their ability to cause the heating of hay. 

 Sterile material inoculated with such pure cultures 

 failed, in most instances, to undergo the characteristic 

 rise in temperature. In one instance, positive results 

 were secured from inoculation with a certain species of 

 mold. Resistant organisms belonging to the group of 

 thermophile bacteria have also been found in large num- 

 bers in hay heated to 122° to 140° Fahr. It is pot at 



