1913.] Studies on Enzyme A ction. 341 



Diagram 17. 



O 20 40 60 80 100 120 



Influence of Neutral Agents which depress the Activity of Urease. 



Alcohols. — Ethylic arid propylic alcohols exercise moderate effects which may 

 be attributed to the changes they produce in the osmotic conditions. As in 

 all other cases studied, the less soluble alcohol is the more active (Diagram 18). 



Saligenin, CgEU (OH) ■ CH 2 (OH), is far more active than either of the 

 paraffinoid alcohols (Graphs 10 and 11). 



Aldehydes. — In the presence of formaldehyde (M/25), action comes to an 

 end when about 4 per cent, of change has taken place. 



Acetic aldehyde, benzoic aldehyde and salicylic aldehyde are moderately 

 active depressants ; the results obtained with these substances and with 

 saligenin are given in Table G and in Graphs 7, 8 and 9. 



The observation that glucose has a slight retarding effect has been 

 confirmed. 



Sodium salicylate and methylic salicylate have practically no action. 



We are inclined to think that the aldehydes are all, in some measure, 

 chemically active towards urease and that even saligenin may be credited 

 with slight chemical activity. 



It has been customary to regard the action of enzymes as subject to the 



