416 



Dr. A. Harden and Mr. W. J. Young. [Dec. 8, 



already stated, to the phosphate added. The equality is shown graphically 

 in the curve and the equivalence in Experiments 13 and 14, Table VI. 



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This process cannot, however, be repeated indefinitely, as after a certain 

 limit is reached the reaction no longer occurs and with a large excess the 

 fermentation is stopped. The exact limit appears to vary both with the 

 nature of the phosphate added and with the particular specimen of yeast- 

 juice employed. The greatest amount of carbon dioxide hitherto obtained in 

 this way from 25 c.c. of yeast-juice is about 0'45 gramme (230 c.c), which 

 was observed on two occasions, once after the addition of four volumes of 

 boiled juice, and again after the addition of 50 c.c. of a solution of a mixed 

 magnesium potassium phosphate yielding with magnesia mixture 1 - 187 

 grammes of magnesium pyrophosphate. 



"When a specimen of yeast-juice has been incubated until it will no longer 

 ferment sugar, it is not affected by the addition of phosphate. 



The fact that the extra carbon dioxide calculated in this way is equivalent 

 to the phosphate present, suggests the superposition of two actions. 

 Whether this is to be explained by the presence of two distinct enzymes or 

 simply by the increased activity of a single enzyme remains to be decided. 



