15 2 Vines. — The Proteases of Plants (//). 
after 68 hours’ : — 
No. 1. 
No. 2. 
No. 3. 
No. 4 
Christy 
faint 
distinct 
— 
— 
Finkler 
distinct 
marked 
— 
— 
Merck 
none 
distinct 
— . 
- — 
The tryptophane-test was applied when the fibrin had disappeared in each bottle, 
except in the case of those No. 2 bottles (Finlder, Merck) where it did not disappear 
at all. 
Seeing that the liquids gave no tryptophane-reaction to begin with, it 
follows (1) that all the samples of papain tested proved capable of effecting 
complete proteolysis, or at any rate peptolysis, in various degree ; (2) that 
on the whole their action was more vigorous in the presence of HCN than 
in the presence of toluol ; and (3) that the action was on the whole stronger 
in the alkaline than in the acid liquids, though the difference was not great. 
The explanation of Emmerling’s result is that probably his sample of 
Merck’s papain, like mine, did not actively peptolyse in alkaline liquid 
containing toluol ; and, more certainly, that the quantity of papain used 
by him was too small in proportion to the fibrin. 
But the evidence of the tryptophane-reactions given above is not 
conclusive, and is even to some extent paradoxical. For instance, the 
Finkler bottle No. 2 (toluol-alk.) gave almost as good a reaction as the 
Finkler No. 4 bottle (HCN-alk.), though in the latter case the fibrin had 
been digested and in the former it had not. It is obvious, therefore, that 
these tryptophane-reactions do not necessarily indicate the complete pro- 
teolysis of the fibrin supplied for digestion in the experiment ; on the 
contrary, they indicate, in some cases at any rate, the proteolysis of some 
proteid other than fibrin, and one that is more readily proteolysable. 
The probable explanation is that all specimens of papain contain, in 
addition to protease, more or less proteid matter. In order to obtain 
some idea of the extent of this self-digestion, I made a series of experiments 
without any added proteid ; and, to connect them with my earlier observa- 
tions ( 3 ), I included a series of bottles with sodium fluoride (NaF) as an 
antiseptic. The experiments may be summarized as follows : — 
A utolysis-Experiments . 
The method adopted was to put 0-5 grm. of papain in each bottle with 40C.C. 
distilled water (=1*25%), containing the antiseptic (toluol 1 %, or HCN 0-2%, or 
NaF 1 %): then the contents of the bottles were made either acid (citric acid 0-5 %), 
or alkaline (Na 2 C 0 3 0-5 %), or were left at their natural reaction, which was slightly 
acid in the case of Christy’s and Merck's samples, neutral in Finkler’s. The mixtures 
thus prepared of Christy’s and Finkler’s gave no tryptophane-reaction : but the fresh 
sample of Merck’s used in these experiments (but not in the one previously described) 
