72 EXPERIMENTAL OBSERVATIONS ON 



pared to the amount of enzyme) that the amount of sugar 

 converted per unit time can be proportional to the amount 

 present, and this condition Adrian Brown found to be experi- 

 mentally realised. 



It is clear that this conception of A. Brown's is really 

 coincident with that of Arrhenius of the " active mass," applied 

 later by E. R. Armstrong to this reaction. 1 



The catalysis of starch by the action of diastase was next 

 studied by Horace Brown and Glendinning, who showed that 

 the velocity curve in this case also is at first represented closely 

 by a straight line, but- later approximates to the logarithmic curve. 

 These authors also assume a combination between the enzyme 

 and its substratum, and that at first the concentration of enzyme 

 is small compared to that of the substratum. As before, as long 

 as the amount of hydrolyte is large, the amount of combined 

 hydrolyte and enzyme will remain constant, the amount therefore 

 converted in unit time will remain constant, and the velocity 

 curve will be a straight line. Later, when the concentration of 

 hydrolyte falls off, the amount in combination will begin to vary 

 directly as the concentration at any moment of the hydrolyte and 

 the logarithmic law will begin to hold. 



It remained for E. R. Armstrong to demonstrate experimentally 

 that there is a third phase in the course of the same reaction, suc- 

 ceeding the period at which the constant calculated on the simple 

 logarithmic basis had been increasing, in which the constant begins 

 to diminish. This later stage is, according to Armstrong, due to 

 a removal of enzyme by combination with one of the products 

 of reaction. 



The experiments of E. R. Armstrong were made upon the 

 action of the enzymes, lactase, emulsin, and maltase upon lac- 

 tose and maltose, and show clearly that there are stages in 

 the reaction varying in extent with the particular enzyme and 

 hydrolyte, and with their relative and absolute concentration, in 

 which the curve of velocity is (1) rectilinear, (2) logarithmic, and 

 (3) falling off from the logarithmic curve. To explain the results, 

 the author takes as his basis the " active mass " hypothesis and 

 the formation of combinations of the enzyme both with the 

 substratum and with one of the products of reaction. The 



1 Vide infra. 



