6 



Scientific Proceedings, Royal Dublin Society. 



therefore, the juice was diluted with about its own volume of water ; 40 c.c. 

 of the mixture was allowed to ferment. The volumes of CO2 evolved are 

 recorded under A. For comparison under -B is recorded the evolution of CO2 

 from 40 c.c. of a mixture made up of 20 c.c. of yeast-juice extracted by the 

 liquid-air method without a substrate, and 20 c.c. of water and 15 g. of sugar 

 under similar conditions. 



^(9) 



Time, 

 hr. min. 



20 



50 



1 15 



4 50 



5 10 

 18 10 

 20 45 



Bill) 



Volume of 

 COs. 



3-6 



5-8 



6-0 



10-6 



11-0 



After correcting for volume-changes, owing to the addition of sugar, the 

 above results correspond to an evolution of 0*57 c.c. for A and 0'19 c.c. CO2 for 

 B per gramme of yeast. 



This comparison strongly supports the idea that the small activity of 

 the yeast juice, and its rapid decay, are in part due to the action of a proteo- 

 clastic enzyme, the action of which is partly inhibited by the combination of 

 the enzyme with the sugar. How far the absence of suitable phosphate and 

 co-enzyme are limiting factors must be examined later. 



In order to see if much zymase was retained in the sedimented yeast-cells 

 after centrifuging, 50 g., the solid residue of Experiment 6, was mixed with 

 50 c.c. of water, and extracted for twenty-four hours at room-temperature. 

 The semi-fluid mixture on being centrifuged yielded 37 c.c. liquid. 30 c.c. of 

 tins, with 12 g. of sugar and a small quantity of toluene, gave volumes of 

 CO, as follows : — 



No further evolution of gas. 



