542 
IOiWA ACADEMY OF SCIENCE Vol. XXIV, 1917 
transitional products serves to corroborate the above assumption. 
Taking alanine as a simple illustration, the reaction may be 
written as follows : 
ch 3 ch .nh 2 .cooh— >ch 3 choh .cooh — > ch 3 cho — >CH 3 CH 2 OH 
alanine lactic acid acetaldehyde ethyl alcohol 
The aliphatic alcohols, isobutyl, d-amyl, and especially isoamyl, 
are constituents of the well known fusel oil of the distillery. 
Crude spirit contains an average of 0.4 per cent fusel oil, and 
never exceeds a maximum of 0.6 per cent. Yet in laboratory 
experiments it is possible to increase the yield of fusel oil up 
to 7.0 per cent by the simple addition of leucine to the fer- 
menting sugar. Fusel oil is, however, invariably produced in 
small amount when the fermenting medium contains no amino 
acids whatever. This is explained by the fact that some of the 
yeast itself undergoes autolysis, whereby the amino acids con- 
tained in the yeast protein are set free and then fermented into 
the higher alcohols. The relative amounts of isobutyl, cl-amyl 
and isoamyl alcohols of the fusel oil correspond very closely 
with those of the valine, isoleucine and leucine of the protein 
from which they are derived. The nitrogen liberated as am- 
monia during this reaction is then utilized for the growth of 
new yeast cells. This then explains the fact that the greatest 
yields of fusel oil are obtained when the fermenting medium 
is deficient in nitrogenous substances other than proteins or 
amino acids. 
In the case of the two dibasic acids, aspartic and glutamic, 
the reaction is somewhat different. I 11 both cases the only prod- 
uct thus far identified seems to be succinic acid. If the reaction 
proceeded after the same fashion as with the monobasic amino 
acids, the products would be ^-lactic and 7-oxybutyric acids re- 
spectively. These substances have not yet been identified as fer- 
mentation products of aspartic and glutaminic acids, though 
future investigations may reveal their presence. 
Considering the abundance of leucine and glutaminic acid 
in plant proteins, it is not surprising that their fermentation 
products, isoamyl alcohol and succinic acid, were long ago iden- 
tified. Pasteur recognized the regularity with which these prod- 
ucts accompanied alcoholic fermentation, and even included them 
in his chemical ecpiations in which he attempted to balance the 
original sugar with the fermentation products. It did not occur 
