ENZYMES AND OTHER FERMENTS DIGESTION. 121 



stances which modify or suspend the ferment actions in ques- 

 tion. Based on this behavior it has been attempted to relate 

 the true ferment action to the " catalytic " action of the " inor- 

 ganic " ferments. All the ferments seem to have the power 

 of decomposing hydrogen peroxide in quantity or catalytically, 

 and this property has been considered as perfectly typical or 

 characteristic. The addition of a number of mineral sub- 

 stances interferes with this catalytic decomposition; in this 

 respect the action of prussic acid is remarkably energetic. It 

 has been found that a minute trace of colloidal platinum in 

 dilute solution decomposes a greatly excessive amount of the 

 peroxide, and further that extremely dilute prussic acid or 

 corrosive sublimate checks the reaction here just as with the 

 true ferment. These analogy reactions are very suggestive, 

 even if they do not explain. 



CLASSIFICATION OF THE FERMENTS. 



"With our present knowledge of ferments they are most sat- 

 isfactorily classified according to the character of the decom- 

 positions they effect. Two distinct kinds of action are easily 

 recognized. Many ferment changes are clearly hydrolytic; 

 that is the reaction follows through the addition of a molecule 

 or more of water to one substance, causing it to break up into 

 smaller groups. In other cases the reaction appears to be in 

 the nature of an oxidation process in which the ferment causes 

 or brings about the addition of oxygen to convert one sub- 

 stance into another. Some authors limit the true ferment 

 reactions to changes which may be referred to one or the other 

 of these heads. But there are a great many decompositions 

 which, while they may not be so clearly denned as those just 

 mentioned, must still be looked upon as of ferment origin. 

 These are produced by bacteria, and in all probability by the 

 enzymes secreted by bacteria. It will be well therefore to add 

 a third general group to make the classification complete. 



KINDS OF FERMENT REACTIONS. 



We may make three general divisions of the ferment 

 changes, as follows : 



