1911. ] The Alcoholic Ferment of Yeast-juice. 469 
Even this enhanced rate of glycogen hydrolysis is not nearly rapid enough 
to supply sufficient sugar for the fermenting complex in presence of arsenate. 
The maximum rate obtained with glycogen was 10, whereas the addition of 
0-5 cc. of arsenate to Solution 1 containing excess of glucose produced a rate 
of 36°5 c.c. in five minutes. 
It follows from the foregoing that arsenate has the power of greatly 
accelerating the action of the diastatic enzyme in yeast-juice. 
8. Action of Arsenite on the Fermentation of Sugar by Yeast-Juice. 
Buchner* made a number of observations on the effect of arsenite on the 
fermentation of sugars by yeast-juice. The presence of 2 per cent. of 
arsenious oxide, in the form of the potassium salt, was found in some 
cases completely to inhibit the fermentation of glucose, but not of 
saccharose, its effect on fructose being of an intermediate character, whilst, 
in other cases, the same concentration caused a marked increase in the total 
fermentation of all three sugars. 
A powerful inhibitory effect was also produced by this concentration of 
arsenite, even on the fermentation of saccharose by () juice which had- been 
prepared from yeast which had been kept at 8° for three days, (6) juice which 
had been dialysed against water for 16 hours, (¢) juice which had been 
evaporated at 35°, (d) juice diluted with one volume of water. 
It was further observed, in many cases, that the presence of arsenite caused 
a considerable increase in the fermentation during the first 16 hours, even 
when the total fermentation was less than in the absence of arsenite. It was 
found that this inhibitory action was not due to the conversion of the arsenite 
into arsenate; and, further, that it was lessened by the addition of heated 
yeast-juice or blood serum, either heated or unheated. The inhibitory action, 
moreover, was greater when the arsenite was incubated with the juice in the 
absence of added sugar. Buchner advanced no explanation of the preliminary 
acceleration caused by arsenite, and regarded the inhibitory effect as due to 
some change in the colloidal state of the enzyme, against which the presence 
of other colloidal substances partially protected it. It was, according to this, 
the diminution in the amount of these protecting colloids which made the 
samples of juice submitted by him to various operations so much more 
_ susceptible to the action of arsenite. 
A careful experimental comparison of the effects of arsenite and arsenate 
on fermentation by yeast-juice shows that these two actions are precisely 
similar in kind, but that the acceleration produced by arsenite is markedly 
* “Die Zymasegarung,’ pp. 184—205. 
