106 PHYSIOLOGY OF ALIMENTATION. 



LINTNER and KROEBER 1 give as the optimal temperature for 

 the action of yeast maltase upon maltose 40 C. Below and 

 above this point the formation of dextrose proceeds much 

 more slowly. At 50 C. this maltase is almost entirely 

 destroyed. CUSENIER gives 56 to 60 C. as the optimal 

 temperature for the maltase obtained from corn. 2 



Maltase is of special biological interest, as it was in a 

 study of this ferment that the fundamental fact of the 

 reversible action of enzymes was first experimentally proved by 

 the interesting work of A. CROFT HiLL. 3 For a better under- 

 standing of this property of enzymes a few introductory 

 words are necessary to illustrate the general conceptions of 

 chemical equilibrium and reversion. 



If a number of substances capable of reacting chemically 

 with each other are brought together, a reaction ensues, 

 which after a time comes to a standstill (practically speak- 

 ing). We say then that the system is in chemical equilib- 

 rium. If, for example, at a definite temperature chemically 

 equivalent amounts of acetic acid and ethyl alcohol are 

 mixed together, a reaction ensues according to the following 

 equation : 



CH 3 COOH +C 2 H 5 OH =CH 3 COOC 2 H 5 + H 2 O. 



Acetic acid Ethyl Ethyl acetate Water 



alcohol 



The reaction takes place in the direction from left to right. 

 If chemically equivalent amounts of ethyl acetate and water 

 are mixed together, ethyl alcohol and acetic acid are formed. 

 In other words, the above reaction takes place from right 

 to left. Neither in the first nor second instance does the 

 reaction become complete. Before the given amounts of 



1 LINTNER and KROEBER: Berichte d. deutschen chem. Gesellsch., 

 1895, p. 1050. 



2 Quoted from EFFRONT: Die Diastasen. Translated into German 

 by BUCHELER, Leipzig u. Wien, 1900, 1, p. 225. 



3 HILL: Jour, of the Chem. Society, 1898, LXX1II, p. 634; Berichte 

 d. deutschen chem. Gesellsch., 1901. XXIV, p. 1380. 



