CHAPTER X1v 
NEW EXPERIMENTS IN REFERENCE TO THE FERTILITY 
OF NEUTRAL ORGANIC SOLUTIONS HEATED TO 
TOO -C: 
T was long considered that temperatures between 
77, and 95 F. (25° and 36 C.) were those most 
favourable for promoting fermentations. The upper 
limits of favourable temperature—what is now com- 
monly spoken of as the “ optimum temperature ”— 
had not been carefully defined ; and this was the case 
especially in regard to the occurrence of fermenta- 
tion in fluids which had been boiled.! 
In previous experiments of this class no one had, 
so far as I am aware, designedly made use of a 
generating temperature above 100° F. (38° C.); the 
heat employed by some investigators has indeed 
been only too frequently below 77° F. (25° C.). 
Previous to the month of August 1875, I had myself 
never purposely employed a generating temperature 
above 100 F.; but early in that month I discovered 
that some boiled fluids which remained barren at a 
temperature of 77°-86° F., would rapidly become 
turbid and swarm with organisms if maintained at a 
1 The first portions of this chapter are composed of extracts from 
a paper contained in the Journal of the Linnean Society (Zool.), 
No. 73, 1877, and No. 74, 1878. 
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