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



Table V. — Filtration of Yeast-juice through the Martin Gelatin Filter. 



No. 



Vol. of 

 juice filtered. 



Wash water. 



Residue. 



Filtrate. 



Boiled 

 juice. 



Glucose. 



Carbon 

 dioxide. 





c.c. 



c.e. 



CO. 



c.c. 



c.c. 



grammes. 



c.c. 



1 



75 



200 



25 











2-5 



10 -4 









25 







25 



5 



396 -3 



2 



80 



260 



20 











2 



8-3 









20 



20 





 t 



4 



90 -2 



3 



100 



250 



25 











2 5 



0-4 









25 







25 



5 



268 



4 



50 



200 



25 











2-5 



0-9 









25 







25 



5 



192 



The process of filtration does not always produce an inactive residue, as on 

 several occasions the residue after very thorough washing has been found to 

 retain a considerable amount of activity. No reason has yet been found for 

 this and it has not yet been ascertained whether it is due to some peculiarity 

 in the particular specimen of juice or in the special filter employed. 



It is of interest to note that in Experiment 2 (Table V) the residue alone 

 gave 8 - 3 c.c. of carbon dioxide in 3 hours, the amount evolved in the last hour 

 being only 04 c.c. At the close of this period the liquid still contained the 

 alcoholic enzyme, since on the addition of 20 c.c. of the filtrate, fermentation 

 recommenced and continued for many hours. 



These two sets of experiments (Tables IV and V) show that the fermentation 

 of glucose by yeast-juice is dependent upon the presence of a dialysable substance 

 which is not destroyed by heat. 



4. Analysis of the Effect of the Addition of Boiled Juice upon the Fermentation 



of Glucose by Yeast-juice. 



In order to compare the course of the fermentation in the presence and in 

 the absence of boiled yeast-juice, experiments were carried out in which the 

 rate of evolution of carbon dioxide was observed in each case throughout the 

 whole period of activity of the juice, which, as a rule, in presence of an 

 excess of sugar, lasts for about 48 to 60 hours. 



For this purpose the fermentation was allowed to proceed in a 100 c.c. 

 flask, kept at the constant temperature of 25° by immersion in a thermostat, 

 and connected with an azotometer, in which the gas was collected over 

 mercury. The gas in the fermentation flask was maintained at a constant 

 pressure, as nearly as possible that of the atmosphere, by keeping the mercury 



