Vines . — Tryptophane in Proteolysis. 13 
acid after neutralization to be taken into account ; and finally, 
seed-extracts are very liable to putrefy. The whole subject 
requires systematic re-investigation. 
Yeast ( Saccharomyces Cerevisiae , Meyen). 
It is a well-known fact that if Yeast be starved by being 
kept in a liquid which contains no food-materials, the proteids 
of the cells undergo digestion, and that this auto-digestion is 
attributable to a proteolytic enzyme. Thus Salkowski ( 11 ) has 
shown that if Yeast be kept in chloroform-water, the liquid 
eventually contains leucin and tyrosin which can only have 
been derived from its own proteids. Moreover the formation 
of these two substances can only be due to the action of an 
enzyme, since living Yeast-cells are inhibited from enzymotic 
action by chloroform. More recently Hahn and Geret ( 12 ) 
have detected the formation of leucin and tyrosin in the 
expressed juice of Yeast. With regard to the proteolytic 
action of Yeast upon proteid supplied from without, Hahn ( 13 ) 
has ascertained that Yeast decomposes gelatine in the presence 
of chloroform. 
My earlier experiments were merely tentative. In the first 
instance, I added 5 grms. fresh Yeast, which had been well 
washed on a filter, to about 100 cc. of three different liquids 
each containing 1 grm. of Witte-peptone, with the result that, 
after 24 hours’ digestion, I obtained a marked tryptophane- 
reaction where the liquid was only distilled water, a weaker 
reaction where the liquid was 0*2 °/ o HC1 solution, and no 
reaction where the liquid was o*2 °/ o HCN. In a second series 
of experiments, I ground up fresh Yeast in a mortar with 
powdered glass and water, and made use of the turbid, faintly 
acid filtrate, thymol being the antiseptic. In a digestion of 
18 hours of a mixture of -20 cc. of the Yeast-extract with 
30 cc. distilled water, I obtained a weak tryptophane-reaction 
when fibrin had been digested, and a strong reaction when 
1 grm. Witte-peptone had been digested : in the presence of 
o-i °/ o citric acid, a fibrin-digestion gave no reaction, and 
a Witte-peptone-digestion, only a weak one. More recently 
I have used dried Yeast, prepared by drying fresh brewers- 
