ORGANIZED AND UNORGANIZED FERMENTS 35 
Now this conclusion is not simply a theoretical one, but it has 
been demonstrated to be true for at least a considerable portion of 
the organized fermentations. In the first place, it has been shown 
that the power of secreting enzymes is a common one among fungi; 
common molds are known to secrete enzymes of much the same 
nature as digestive enzymes They soften up proteid substances, 
in order, apparently, that they may absorb them. In other words, 
they “‘digest”’ them for their own use. When, in pursuance of this 
idea, we study carefully the various fermentations at first re- 
garded as belonging to the class of organized ferments, we find, in 
some cases, that the living bacterial cells do secrete an enzyme that 
actually produces the chemical change in thefermented body. For 
example; there is a class of bacteria that has the power of curdling 
milk without rendering it acid, an action very similar to that of the 
enzyme rennin (rennet), secreted by the stomach glands of calves. 
But since the curdling of milk by bacteria was produced by living 
organisms that grow and multiply during the process, it was re- 
garded as one of the class of organized fermentations, and was so 
identified. Butit has been demonstrated that this curdling is due 
to an enzyme secreted by the bacteria, and that this enzyme is 
quite similar to rennet. It may be entirely separated from the 
bacterial cells and preserved in the form of a powder, somewhat in 
the same way that rennet can be separated from the stomach of a 
young calf. It will curdle milk as quickly astherennet. Further, 
these same bacteria produce a second enzyme which has the power 
of digesting the curdled milk, and this second ferment is similar to 
that secreted by the pancreas of a mammal. 
Many other examples of the same nature might be mentioned. 
The general processes of putrefaction and decay are produced, it is 
true, by the destructive agency of microdrganisms, but directly, to 
a great extent at least, by the enzymes secreted by the bacteria. 
But while many of the organized fermentations are thus explained, 
some have not been brought so easily into this category, since it has 
been difficult to prove that they do really produce an enzyme. 
