300 
Vines.— The Proteases of Plants. 
Experiment 3 . Acid. 4 grms. dried yeast were extracted for several hours 
in the cold with 200 cc. toluol- water (1 %) : the filtered liquid gave a faint 
tryptophane-reaction : 2 grms. of Witte-peptone were dissolved in the liquid, 50 cc. 
of which were then put into each of 3 bottles acidified as follows: — No. 1, HC1 to 
o-i %; No. 2, HC 1 to o-2 %; No. 3, HC 1 to 0-5 %. 
After 3 hours in the incubator the tryptophane-reactions were : — No. 1, distinct ; 
No. 2, faint; No. 3, none: after 29 hours they were — No. 1, marked; No. 2, 
distinct ; No. 3, none. 
Alkali. 50 cc. of an exactly similar yeast-extract, containing the same per- 
centage of Witte-peptone, were placed in each of 4 bottles: to No. 1, Na 2 C 0 3 to 
1 % was added ; to No. 2, Na 2 C 0 3 to 2 % ; to No. 3, Na 2 C 0 3 to 3 % ; to No. 4, 
nothing. 
After 2 hours’ digestion the tryptophane-reactions were : — in Nos. 1, 2, 3, faint; 
in No. 4, marked : the reactions were the same after the bottles had remained in 
the incubator for 25 hours. 
On comparing the results of Expt. 3, where the strength of the 
yeast-extract may be taken as 2°/ o , with those of Expt. 2, where the 
strength of the extract may be taken as 5 °/ o , it appears that the retarding 
action of added acid and alkali was more marked in the former than in the 
latter : for instance, in the case of the 2 °/ Q extract, peptolysis was inhibited 
by the addition of HC 1 to 0*5 °/ o , and by all strengths of added alkali ; 
whereas the 5°/ o extract peptolysed actively with HC1 0-5 °/ o and with 1 °/ o 
Na 2 C 0 3 . This is very much the same relation as that indicated by the 
corresponding autolysis-experiments : such differences as exist are due 
to the different chemical composition of the liquids in the two sets of 
experiments. 
The fact that the retarding action of added acid and alkali is less 
marked in peptolysis than in autolysis is clearly brought out by a com- 
parison of the results obtained by a peptolytic experiment on the same 
lines as the autolytic experiment (Expt. 4, p. 296), which had as its object 
to determine the effect of exposure to the action of alkali of different 
strengths for a short time, and showed that autolysis was inhibited by 
treatment for two hours with 3 °/ o Na 2 CO s liquid at 38°C. : complete 
inhibition was not produced in the peptolytic experiment under similar 
conditions. 
Experiment 4 . 10 grms. of dried yeast were extracted for several hours with 
200 cc. toluol-water (1%) and filtered: the filtered liquid gave faint tryptophane- 
reaction. 50 cc. of the liquid were piaced in each of 3 bottles, to which Na 2 C 0 3 
was added to 1 %, 2 %, 3 % respectively, and then the bottles were kept in the 
incubator for 2 hours. The contents of each bottle were then divided into 2 equal 
parts, in separate bottles, and one half was slightly acidified with HC 1 , whilst the 
other half remained alkaline : 0-2 grm. of Witte-peptone was added to each bottle, 
and a little more toluol. 
