1911.) The Alcoholic Ferment of Yeast-juice. 467 
| No. 1 | No. 2. No. 3 | No.4. | 
Initial rate per 5 minutes............... 1°5 8°5 2°5 36 °5 
Total in 1 hour 40 minutes ............ url D> 81.2. ~ 
The rate of auto-fermentation of yeast-juice is not, like the rate of 
fermentation of sugar, controlled by the rate at which phosphate is produced 
from the hexosephosphate, but by that at which sugar is formed by the 
hydrolysis of glycogen and dextrins, as is shown by the well known fact, 
confirmed in the foregoing experiment, that the rate of auto-fermentation is 
usually considerably less than that of the fermentation of sugar. 
Consequently, any increase in the rate of auto-fermentation must be 
primarily due to an increased supply of sugar. This may be derived from 
two sources. A portion is supplied, as has been shown (Experiments 19-23), 
by the increased rate of hydrolysis of the hexosephosphate originally present in 
the juice. This continues until the whole of the sugar obtainable from this 
source has been converted into carbon dioxide and alcohol and has the effect 
of temporarily increasing the rate of fermentation. This acceleration is 
independent of the presence or absence of glycogen, and hence the effect of 
arsenate on the juice in the absence of added glycogen gives a superior limit 
to the extent of its influence. 
After this point has been reached, the sugar formed by the hydrolysis of 
complex carbohydrates becomes the sole source of carbon dioxide. As 
fermentation then proceeds this supply also gradually becomes exhausted 
and the rate falls off slowly. In presence of added glycogen, on the other 
hand, the rate falls off more slowly. 
In order, therefore, to ascertain whether the rate of hydrolysis of Bieceren 
is increased by the addition of arsenate, it is necessary to determine whether 
the effect of adding glycogen and arsenate together to the juice is greater than 
the sum of the effects of adding glycogen and arsenate to separate portions of 
the juice. 
This is done in the following experiment :— 
Lxperrment 15.—Five quantities of 20 c.c. of yeast-juice were mixed with 
the following solutions and incubated for 1 hour 45 minutes, the total volume 
in each case being 30°5 c.c.— 
1, 2°5 grm. glucose in 10°5 cc. solution. 
. 10°5 c.c. water. 
. 10 cc. water +0°5 cc. arsenate. 
. 05 grm. yeast-glycogen in 10°5 c.c. solution. 
. 0°5 grm. yeast-glycogen in 10 cc. solution+0°5 c.c. arsenate. 
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