604 Vines. — Proteolytic Enzymes in Plants (II). 
or tryptophane in appreciable quantities — at least under con- 
ditions in which they are readily formed in large quantities 
by the other tryptic enzymes — places it in a class of its own 
for the present/ 
In endeavouring to account for the wide divergence between 
their conclusions and my own, I was at first inclined to 
question the activity of the papal'n employed by Mendel 
and Underhill ; but the numerical results which they give 
show conclusively that a considerable amount of the proteid 
supplied (as much sometimes as 7o°/ o ) was dissolved, and the 
peptonization of casein was definitely proved. Hence there 
is evidence that the papal'n was active. This being so, the 
only remaining difference in the material of the two sets of 
experiments lay in the antiseptics employed, sodium fluoride 
in theirs, hydrocyanic acid in mine. I had already drawn 
attention to the fact that papain-digestion is promoted by 
HCN, and I thought it not improbable that this might prove 
to be an important factor in the problem. I accordingly 
instituted the following comparative experiments, in which 
NaF and HCN were the respective antiseptics, with results 
that fully realized my anticipation. 
In the first instance I made use of Witte-peptone as the 
digestible material, and sodium fluoride (NaF), hydrocyanic 
acid (HCN), and chloroform-water as the antiseptics, the; 
solutions being neutral, acid, or alkaline. The result proved 
that the proteolysis, as indicated by the tryptophane-reaction, 
was much more marked in the acid liquid containing HCN 
than in any of the others : it was less marked in the chloro- 
form-water liquids, and scarcely perceptible in those contain- 
ing NaF. 
The details of the experiment were as follows : 5 grms. of papain 
('purified papain/ Christy) were extracted for 3 hours with 250 cc. 
distilled water ; the liquid was then filtered : the filtrate was a clear 
brownish liquid, distinctly acid, giving good biuret-reaction but no 
tryptophane-reaction. 10 grms. of Witte-peptone were similarly 
extracted with 250 cc. dist. water: on filtration a yellowish, neutral 
solution was obtained giving no tryptophane-reaction. 
