SUMMARY 553 



which has been indulged in all too long, into the open, and 

 to raise the question as to precisely what effective additions 

 have been gained from all this for our knowledge of the 

 physiological processes of oxidation. 



This much can be said in summarizing: In the tissues 

 active catalytic agents, the "peroxidases," are widely dis- 

 tributed; which seem, just like the coloring matter of the 

 blood, to be capable of conveying the oxygen from peroxides 

 to very readily oxidizable substances. We find, too, in the 

 statements bearing upon the oxygenases, the aldehydases 

 and indophenoloxidases occasion for assuming that there 

 are substances in the tissues charged with oxygen which are 

 able to give this off to easily oxidizable matter ; and these we 

 may in a measure regard as peroxides. But that is all. We 

 do not know whether the peroxidases are ferments are not. 

 This from a physiological viewpoint may fundamentally be 

 a matter of indifference, because at any rate we are not 

 able to define clearly the characteristics of a ferment. For- 

 erly in this respect we were perhaps more fortunate; we 

 frankly had no idea then what a ferment was; we were 

 accustomed to being satisfied with statements that ferments 

 were " coagulable ' ' substances and allowed them, con- 

 fessedly or by inference, to drift along in the turbid stream 

 of proteins, that is, with those substances with which we 

 could not even make a proper beginning. But the times 

 have changed; and, particularly since we have learned to 

 recognize that there are thermostable ferments, even the 

 finest definitions and hypotheses, with which science of the 

 present is blessed in the richest measure, cannot deceive us 

 about the flimsiness of the ferment concept. We are really 

 doing better by simply stopping and by holding fast to what 

 we see ; and that is the effect of the real or supposed ' ' fer- 

 ments," the catalytic acceleration of reactions. For our 

 question it is quite enough from a physiological standpoint 

 for us to know that in the tissues there are some sort of 

 catalytic agents of unknown nature which are capable of 

 conveying oxygen to easily oxidizable substances. 



