5<D AGRICULTURAL BACTERIOLOGY. 



temperature and they are apparently true fermentations. It 

 has been assumed in the past that such fermentations are bac- 

 teriological. Bacteria are certainly sometimes present, and the 

 rapidly widening conception of the agency of bacteria in pro- 

 ducing fermentations has led to the conclusion that all such 

 fermentations are due to bacteria. But the growing knowledge 

 of the nature and abundance of enzymes is leading to-day 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 plant in its life did pro- 

 duce such enzymes they would find their way into the compost 

 heap and inevitably start a fermentation which would, of course, 

 have nothing to do with bacteria. This possible explanation 

 of some of the common fermentations has only been recently 

 realized to its full extent. At present bacteriologists and 

 chemists are actively engaged in investigating this problem of 

 the relation of enzymes to fermentations, and trying to deter- 

 mine whether the enzymes producing various fermentations 

 are secreted by bacteria or by the cells of higher plants. As 

 fast as they show the latter they remove the fermentative proc- 

 ess from the realm of bacteriology proper. Already, as we 

 shall see later, some of the typical fermentative processes have 

 been thus taken wholly or partly out of the domain of 

 bacteriology. 



It is necessary to point out in conclusion that even if we ac- 

 cept this enzyme theory of fermentations we are no nearer to 

 a real understanding of the phenomenon than we were at the 

 start. We have no conception of the actual nature of enzymes. 

 We fail utterly to understand their action. How a substance 

 can produce chemical actions by its simple presence without 

 itself being acted upon and entering into chemical reactions is 

 a total mystery. Whether to call these enzymes chemical 

 bodies of a wholly lifeless nature, or to regard them as semi- 



