156 Vines . — The Proteases of Plants (II). 
D. Merck’s Papain (half-strength). 
Acid. 
Alkaline. 
Natural. 
Toluol 24 
hours fibrin 
nearly gone 
gone 
nearly gone 
>5 
tryptophane 
strong 
strong 
strong 
HCN 24 
}> 
fibrin 
gone 
gone 
gone 
yy yy 
}> 
tryptophane 
marked 
distinct 
distinct 
NaF 24 
»> 
fibrin 
gone 
gone 
gone 
yy 
>> 
tryptophane 
very strong 
strong 
strong 
Toluol 48 
fibrin 
gone 
gone 
gone 
5 5 >» 
)> 
tryptophane 
strong 
very strong 
very strong 
HCN „ 
yy 
strong 
distinct 
marked 
NaF „ 
yy 
very strong 
strong 
strong 
The results were still insufficiently differentiated, although some 
differentiation was indicated in the HCN bottles. Following this up, 
I made a further experiment with still weaker extract (1 grm. to 200 c.c. water) 
in the presence of HCN, with striking results; the other details were as 
before. 
E. Merck’s Papain (quarter-strength). 
Acid. 
Alkaline. 
Natural. 
HCN 24 
hours fibrin gone 
gone 
gone 
» >> 
„ tryptophane marked 
none 
faint 
»> 48 
,, „ marked 
faint 
distinct 
It will be observed that the results of the experiments C y D, E y with 
Merck’s papain, differ in degree only : in all the HCN bottles the alkaline 
one was that which gave the least marked, and the acid that gave the most 
marked tryptophane-reaction. 
No detailed analysis of the foregoing results is necessary to show that 
the various samples of papain experimented upon differed widely in their 
general proteolytic activity, and in their relation as well to acid and alkali 
as to the various antiseptics employed. Moreover, they account for the 
conflicting and sometimes contradictory observations not only of Emmerling 
and myself, but also of earlier observers such as Mendel ( 4 ), Martin ( 5 ), and 
Wurtz (6). One thing, at any rate, is made clear, that the last word as to 
the properties of papain will not have been pronounced until a series of 
careful observations shall have been made with perfectly fresh material, so 
as to avoid all those modifications that must necessarily accompany the 
preparation of the varieties of dried papai'n which have hitherto been used 
in experiments. Here is a subject for research that might well engage the 
attention of one of the botanical laboratories in the tropics. 
This somewhat negative conclusion is not, however, the only or the 
most important one to be drawn. The results show that, as I have already 
