86 PHYSIOLOGY OF ALIMEXTATION. 



that the ever-increasing amount of glucose in the reaction 

 mixture interferes with the further action of the maltase. 

 The argument falls to the ground, however, when we deal 

 with the action of maltase on glucose and the production 

 of maltose. If glucose interfered with the action of the 

 enzyme, the velocity of this reaction ought to be lowest 

 at first and increase as more and more maltose is produced. 

 As an actual matter of fact, the opposite occurs, and the 

 velocity of the reaction becomes progressively less as the 

 maltose accumulates. In either case, therefore, the accu- 

 mulation of the fermentation-products seems to interfere 

 with the chemical reaction itself. / 



(c) Ferments are usually characterized by a great sensi- 

 tiveness to comparatively low temperatures. In fact, it is one 

 of the commonest means employed in proving that a cer- 

 tain chemical reaction is dependent upon the presence of a 

 ferment, to heat the reactiori~mixture to boiling and find 

 that after this treatment the reaction no longer takes place. 

 (In most instances the reaction does in reality still occur, 

 only so infinitely slowly, as a general thing, that it is unrecog- 

 nizable by the analytical methods at our disposal.) This 

 means that a temperature of 100 C. destroys the activity 

 of the ferment. ^ Some few ferments are able to endure 

 this temperature or even a higher one for a short time, but 

 the vast majority cannot stand heating to even 60 C. for 

 any length of time. The cause of this inactivation of the 

 ferment is to be sought in a decomposition which it under- 

 goes. The nature of this decomposition is not as yet under- 

 stood. Ferments are not nearly so sensitive to tempera- 

 ture in the dry state as in the moist. Many ferments which 

 are readily destroyed by heating to 60 C. for some minutes 

 in the presence of water withstand a temperature of 120 C. 

 for much longer periods if the ferments are thoroughly 

 dry. An every-day illustration of this is found in the well- 

 known fact that in surgical sterilization the death of all 

 bacteria and spores is obtained much more easily by the 



