38 FERMENTATION, PUTREFACTION, AND DECAY 
evidence of marked fermentative changes. ‘These phenomena are 
accompanied by a rise in temperature and have all the character- 
istics of true fermentation. In such heaps bacteria are certainly 
present and the rapidly widening conception of the agency of 
bacteria in producing fermentations led to the conclusion that 
they cause all such fermentations. But the growing knowledge 
of the nature and abundance of enzymes is leading to the conclu- 
sion that some of these fermentations are not due to bacterial 
action at all, but simply to the enzymes which were excreted by 
the plants during their life and which get a chance to act in the 
fermenting heap. If the corn during life produced enzymes, 
these would find their way into the silo and inevitably start 
fermentations which would, of course, have nothing to do with 
bacteria. 
While, then, fermentations and putrefactions must, in general, 
be attributed to germ life, we must ever bear in mind that similar 
or identical phenomena may sometimes be caused by enzymes from 
a, different source. 
THE PURPOSE OF FERMENTATION 
All these types of fermentations, whether caused by the metabo- 
lism of bacteria or yeasts, or by enzymes secreted by these or- 
ganisms or by higher plants, are of vital importance in agricultural 
processes. Without their agency in breaking up organic com- 
pounds, the soil would rapidly become unfit for supporting life. 
The agricultural industry is not only dependent upon fermenta- 
tions for many minor processes, but it is fundamentally dependent 
upon them for its continuance. While this is true, it must not be 
assumed that the various bacteria produce their results for the bene- 
fit of agriculture or for the benefit of the soil. Thereis no purpose 
in the matter. Each species of animal and plant acts its own life 
forits own good. Ifit secretes an enzyme that produces a fermen- 
tation, this is done for its own benefit and not for the farmer’s. 
