4 Dr. A. Compton. 



This figure sliows tliat for the acidity in question of the medium addition 

 of more enzyme has merely increased the rate of hydrolysis without changing 



J I ImiI..'. ...1 1 1 



'0 20 30 40 so 60° 

 TEMPERATURE ► 



Fig. 2. — Subtrate concentration M/20. Enzyme concentrations 6 x lO"'' to 14 x 10"'' grm. 

 per cm. Eeaction of medium- — acid. 



in any way the optimum temperatare, the latter remaining fixed in the neigh- 

 bourhood of 3 5 '5° and that no matter what the enzyme concentration. This 

 result was quite unsuspected. 



As, however, it recalls the corresponding course of events for the natural 

 reaction — the enzyme preparation being dissolved in pure water, without the 

 addition of acid as above — fig. 3 is here reproduced for convenience of 

 reference from former work,* carried out in this respect with the same 

 preparation of maltase. In the experiuient, of which fig. 3 is the graphical 

 r4suine, the enzyme was employed over a wider range of dilutions than in the 

 foregoing acid experiment : in concentrations varying between 2 x 10-* grm. 

 and 20 X 10" * grm. per cm.^, while the subtrate concentration and the 

 duration of the experiment were the same. Under these circumstances, an 



* Arthur Compton, 'Koy. Soc. Pioc.,' B, vol. 88, ])p. 258-263 (1914), and loc. cit. 



