Vines. — The Proteolytic Enzyme of Nepenthes . 573 
The investigation of the action of alkalies upon the activity 
of the enzyme, led me on to study the relation of its activity 
to the amount of free acid present in the digesting liquid. 
For this purpose I prepared four tubes, A , B y C, D , con- 
taining respectively i°/ o , 05%, 0-35%, and 0-125%, of HC1, and 
set them in the incubator to digest. I found that digestion was 
most rapid in tube C, containing 0-25% HC1, 0-05 grm. of 
fibrin totally disappearing in about half an hour ; the fibrin 
disappeared in tube D in about a quarter of an hour more ; 
that in tube B, about twenty minutes later; whereas in 
tube A, which contained the largest percentage of acid, the 
fibrin had not disappeared two hours subsequently. 
Another line of experimentation which I have pursued 
is that of obtaining from the pitcher-liquid a substance which 
would exert digestive power. I have not attempted to 
actually isolate the proteolytic enzyme, but only to remove it 
from the pitcher-liquid in such a form that a new digestive 
liquid could be prepared with it. I have repeated this 
experiment several times, and with unvarying success. The 
method adopted is illustrated by the following experiment : — 
Sept. 21, 1897. To 100 c.cm. of pitcher-liquid an equal volume 
of absolute alcohol was added: then, in order to produce a bulky 
precipitate in the liquid, some phosphoric acid was added and some 
lime-water, the liquid being finally neutralized with carbonate of 
ammonia : a copious precipitate fell, which was collected on a filter 
and left to drain all night. 
Sept. 22. A portion of the precipitate was shaken up with 10 c.cm. 
of a 0-25% solution of HC1, and the turbid liquid filtered: to the 
clear filtrate a small piece of fibrin was added, and the tube (A) was 
placed in the incubator at 11 a.m. A second tube (B) was prepared, 
containing 10 c.cm. of 0-25% HC1 and a shred of fibrin; this was 
placed in the incubator at the same time as tube A. At 1 p.m. the 
fibrin in tube A was breaking up, and at 2 p.m. it had entirely dis- 
appeared, the liquid giving good biuret-reaction : the fibrin in the 
control-tube B showed no sign of solution. 
On repeating the experiment a month later with some of the 
precipitate which had been kept dry in a bottle in the presence 
Q q 2 
