112 THE DEATH-POINT OF BACTERIA 
infusion heated to the same temperature of 140° F.) 
will illustrate the different influence of dissimilar 
dead ferments upon infusions of the same kind. 
The evidence now in our possession shows, there- 
fore, that whilst the temperature at which living fer- 
ments cease to be operative varies within very narrow 
limits (131°—140° F.),* that which destroys the virtues 
of not-living ferments varies within much wider limits, 
and depends not only upon the amount of heat 
employed, but also upon the nature of the pu- 
trescible or fermentable liquid to which such ferment 
is added, in conjunction with the degree of heat and 
other conditions to which the mixture is subsequently 
exposed.t Here, therefore, we have evidence as to 
the existence of a most important difference between 
living and not-living ferments, which has always 
been either unrecognised or more or less deliberately 
* Liebig has proved that a temperature of 140° F, kills Zorula, and 
always suffices to arrest a process of fermentation taking place under 
their influence in a sugar solution. Zoru/z heated in water to 140° F. 
also fail to initiate fermentation in a sugar solution. I have also found 
that an exposure to a temperature of 131° F. for five minutes always 
suffices to destroy the life of Desmids, Euglenee, Amcebx, Monads, 
Ciliated Infusoria, Rotifers, Nematoids, and other organisms contained 
in specimens of pond-water. All these lower organisms seem to be 
destroyed at about the same temperature, as might have been expected 
from the fundamental relationship which must exist between these several 
varieties of the one substance—living matter. 
+ See “ The Beginnings of Life,” vol. i., p. 437. 
