584 Dr. Armstrong and Prof. Armstrong. Studies on [June 13, 



2 per cent. Salicin + Emulsin. 



Medium 



Kelative change 



Water 



86 -0 



20 p. c. ethylic alcohol 



38 -0 



40 „ „ 



14 -0 



60 



10 -o 



80 



4-8 



90 



2-0 



95 



0-2 



The enzyme is largely precipitated from yeast extract when 40 per cent, of 

 alcohol is present. Emulsin is also largely precipitated from a solution of 

 this strength but the enzyme remains active as a hydrolytic agent, even in 

 very strong alcoholic solution ; attention has recently been drawn to this 

 fact — of which we have long been aware — by Bourquelot. 



The manner in which the rate at which a-methyl glucoside is hydrolysed is 

 affected over a considerable period by glucose is shown in the following table 

 and in the corresponding graph. 



Action of a-Glucase on a-Methyl Glucoside Alone and in Presence of 



Glucose. 



Time 



"Weight of glucose formed 



Glucoside alone 



Glucoside + glucose 





grm. 



grm. 



2 hours 



0-43 



0-15 



.3* 



0-66 



0-24 



5 



0-85 



0-29 



7 



1 -03 



0-37 



8* 



1-21 



0-41 



10 



1 -31 



0-45 



24 



1 -82 



0-82 



The slight influence exercised by a-methyl glucoside on the hydrolysis of 

 salicin may be attributed entirely, we think, to its concentrating or de- 

 hydrolating effect, in view of the inappreciable effect produced by an equivalent 

 amount and the gradual increase of the effect as the concentration is raised. 



In our former experiments, E. Ill,* the solutions used were highly 

 concentrated. Thus, 10 grm. of /3-methyl glucoside, together with 10 grm. of 

 maltose, were dissolved in water to 100 c.c. (including the enzyme). Under 

 these conditions, the action of the a-enzyme was retarded by the /3-glucoside : 

 * 'Eoy. Soc. Proc.,' 1904, vol. 73, p. 516. 



