FERMENTS, ENZYMES, TOXINS AND PTOMAINS 47 



that the physiological activities of both the poison and the 

 cells are destroyed. Not so with the enzymes; they are 

 characterized by the ability to bring. about profound altera- 

 tions in the substances on which they are acting without 

 they themselves being appreciably altered or diminished in 

 quantity; just as is seen with many of the inorganic catalysers 

 which, after having, by their mere presence, promoted con- 

 spicuous changes in the substances surrounding them, are 

 found at the end to have undergone little or no loss in 

 amount and to be of identically the same composition as 

 at the beginning. As to the way in which enzymes act 

 nothing definite can be said. The problem has for years 

 engaged the attention of competent investigators but up to 

 the present there is no final opinion. That they differ in 

 nature and mode of operation the one from the other 

 seems certain; the results of their activities are manifestly 

 different. 



Neither enzymes nor toxins have ever been isolated in 

 a pure state. Both are assumed to be amorphous matters 

 of a protein nature and all are recognized by that which 

 they do; i. e., by the reactions which they originate. They 

 are characterized for their instability, particularly is this 

 the case with the enzymes. All have many of the essential 

 characteristics of living matter; they are destroyed by heat, 

 varying in amount and mode of application. The same 

 chernicals that are hurtful to living cells are likewise, in the 

 main, destructive of enzymes and toxins; they are soluble 

 (or appear to be) in water, dilute acids, alkalies and neutral 

 salines; they are to a slight extent dyalizable; some are 

 precipitated from their solutions by alcohol readily, others 

 less so; they may be thrown down from their solutions by 

 mechanically enmeshing them with certain inorganic 



