1904] Studies on Enzyme Action. 217 



the action (p. 2C9). It seems much more probable that the H 2 S renders 

 the enzyme inactive, perhaps by forming a loose compound with it, 

 and that the gradual increase of the constants is due to recovery of the 

 enzyme owing to oxidation of the poison. The toxic action of 

 mercuric salts, and of hydrocyanic acid, seems most simply explicable 

 on the theory of formation of loose compounds between them and the 

 enzyme. 



Summary of Results. 



1 . Quantitative measurements have been made of the effect of various 

 substances on the rate of decomposition of hydrogen peroxide by 

 hsemase, an enzyme obtained from blood. 



2. The probable mechanism of the catalysis in question has been dis- 

 cussed, and reasons have been given for supposing that what is actually 

 measured is the rate of diffusion of hydrogen peroxide to the enzyme. 



3. The ways in which "poisons" may exert their effect on the 

 action have been discussed, and reasons have been given for preferring, 

 in some cases, a chemical explanation of the observed facts. 



4. From the results obtained with acids and alkalis, as well as from the 

 results of other observers, it has been concluded that at least some 

 enzymes are amphoteric substances, i.e., substances which are neutral 

 in aqueous solution but can combine both with acids and with bases to 

 form salts. 



I have much pleasure in thanking Dr. Charles A. Kohn for the 

 facilities he has kindly allowed me for carrying on my work. 



VOL. LXXIV. 



