FERMENTATIONS NOT ALL DUE TO MICROORGANISMS. 35 
they produce have always been. The real nature of the fermenting 
processes is, in short, quite unknown. 
FERMENTATIONS NOT ALL DUE TO MICRO- 
ORGANISMS. 
One final question needs to be raised. Are all of the many kinds 
of slow progressive changes, resembling fermentations in a broad 
sense, due to the action of microorganisms, either by direct action 
or through the agency of the enzymes they produce ? After we have 
recognized that higher plants may produce enzymes, we see at once 
that there may be certain fermentative processes in the soil or else- 
where, for which microorganisms are not directly responsible. If a 
plant produces an enzyme, this body may remain ready for action 
after the plant which produced it is dead, and fermentative changes 
may go on in a mass of vegetable tissue for which microorganisms 
are not responsible. It very commonly happens that after the 
death of the plant it undergoes some kind of fermentative change. 
When piled into a compost heap or stored in a silo, the plant tissues 
certainly show unquestionable evidence of marked fermentative 
changes. These phenomena, are accompanied by a rise in tempera- 
ture and have all the characteristics 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 conclusion 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 fer- 
mentations which would, of course, have nothing to do with bacteria. 
\Yhile, 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. 
