1 78 Vines . — The Proteases of Plants (///). 
to each bottle 0-3 grm. Witte-peptone (about 1%) now added: after 24 hours’ 
further digestion : — 
i- 2. 3. 4. 
fibrin — — — gone 
tryptophane-reaction strong distinct none none 
These results are in agreement with those obtained with papa'fn, but are 
even more striking in the differential effect of alkalinity upon fibrin-digestion 
and peptolysis : the former process was fairly active after the addition of 
8°/ o Na 2 Co 3 , whilst the latter was only slightly active with 4°/ o Na 2 Co 3 , 
a degree of alkalinity not far from neutralization. 
Saccharomyces Cerevisiae. 
The experiments were made with the dried, granulated Yeast men- 
tioned in a previous paper ( 4 , p. 293). 
logrms. of the dried Yeast, ground fine, were rubbed in a mortar with about 
200 cc. of 2 % NaCl-solution, and after standing for an hour or so, the mixture was 
put upon a filter. After 3 hours’ filtration an acid liquid was obtained giving no 
tryptophane-reaction: to 200 cc. of the liquid 2 grms. of Witte-peptone were added, 
and toluol to 1 % : 40 cc. were now put into each of 5 bottles treated as follows : — 
No. 1, left at natural acidity; No. 2, added Na 2 CO a to 1*5% (alkaline); No. 3, 
Na 2 C 0 3 to 2 % ; No. 4, HC 1 to 0*2 % ; No. 5, HC 1 to 0-5 % : 0-2 grm. of fibrin was 
added to each bottle. 
After 24 hours’ digestion the results were : — 
1. 2. 3. 4. 5. 
fibrin gone unaltered unaltered unaltered unaltered 
tryptophane very strong very strong strong strong faint 
after 48 hours’ digestion 
fibrin as before; tryptophane-reaction still faint in No. 5. 
Conclusion : peptolysis active through wide range of reaction, limited in the acid 
direction by 0-5 % HC 1 : fibrin-digestion inhibited by all the variations from natural 
acidity. 
These results are in general agreement with those recorded in the paper 
already referred to ( 4 , pp. 299, 304), allowing for the fact that the two sets 
of experiments were made with two different samples of dried Yeast, of 
which the one used in the above experiment showed itself to be the more 
active. Combining the two sets of results, the limits of proteolytic activity 
of a 5% Yeast extract (NaCl) are approximately-— for peptolysis of Witte- 
peptone, from about 3°/ 0 Na 2 Co 3 to about 0.5 °/ o HC 1 ; for fibrin-digestion, 
from about 1 °/ o Na 2 Co 3 to about o-i °/ o HC 1 ; so that the range of reaction 
is much more extended for peptolysis than for fibrin-digestion. 
The chief interest of these results with Yeast lies in the comparison of 
