Physiologie. 
199 
Different methods of preparation give different mixtures of these 
enzymes. Extraction of almonds at 0° C gives most gluco-lactase. 
Three hours heating at 45° C destroys this enzyme but not the others. 
Much work was expended on the problem of estimating the 
products of hydrolysis of amygdalin; benzaldehyde, hydrocyanic 
acid and glucose in the presence of one another and the final 
methods are detailed. F. F. Blackman. 
Harden, A. and W. I. Young. The alcoholic ferment ofYeast- 
juice. Part III. The function of phosphates in the fermen- 
tation of glucose by yeast-juice. (Proc. Roy. Soc. B. LXXX. 
p. 299-312. 1908.) 
This is a quantitative study of the effect of adding soluble 
phosphates to expressed yeast-juice fermenting glucose. 
The authors have previously recorded that this phosphate pro- 
duces a sudden outburst of C0 2 which quickly subsides as the 
free phosphate is combined to form hexose phosphoric acid. The 
amount of extra C0 2 thus liberated is equivalent to the free phos¬ 
phate added. In all the experiments sugar is in large excess. 
The alcoholic fermentation must be considered as due to the 
interaction of the ferment and the co-ferment previously described 
with phosphate and glucose as in the following reaction 
2C 6 H 12 0 6 H- 2R 2 HP0 4 = 2C0 2 + 2C 2 H 6 0 + C 6 H 10 O 4 (P0 4 R 2 ) 2 + 2H 2 0. 
It is now shown that the hexose phosphate is slowly hydrolysed 
by some enzyme and free phosphate (precipitable by magnesia mix- 
ture) is regenerated. This leads to an after effect of accelerated fer¬ 
mentation apart from the initial outburst equivalent to the added 
free phosphate. The regeneration is very slow and proceeds for 
days long after the yeast-juice has lost the power of fermenting 
sugar. The rate at which this regeneration proceeds must determine 
the reaction velocity of the whole fermentation System. In yeast 
juice without added phosphate the rate is determined by the small 
amount always present in the raw expressed juice. 
This hydrolytic ferment regenerating phosphates from hexose 
phosphates is found in the “inactive residue” on gelatine-filtration 
of yeast-juice. 
It is probable that the whole amount of alcoholic fermentation 
going on comes under this special case in which phosphates are 
essential. 
The effects of adding different quantities of phosphate have 
been carefully worked out. While a small addition causes a sudden 
increase of C0 2 (five- to ten-fold), quickly subsiding, a larger amount 
causes the high level of C0 2 -output to be maintained for a time. If 
still more is added, then the maximum is more slowly attained and 
subsides more slowly and further so high a level is never attained, 
so that it may be said that there is an Optimum amount of phos¬ 
phate for the fermentation. 
A continued maximal level of C0 2 production can be experi- 
mentally maintained by adding~at~the end of every five minutes, 
fresh phosphate equivalent to the C0 2 produced during that five 
minutes; in this way the locking up of the phosphate as hexose 
phosphate can be compensated and an optimal concentration of free 
phosphate kept up. F. F. Blackman. 
