V ines .* — T he Proteolytic Enzyme of Nepenthes . 575 
be neutral, but that in those of N. M r aster siana to be acid. 
As the result of my own observations on N. Mastersiana , 
I find that the liquid in the unopened pitcher is generally 
distinctly acid, though not always so ; and that the liquid 
in the opened pitchers, in which the remains of insects may 
be present, is as often neutral as it is acid. The correlation 
suggested by von Gorup-Besanez between the reaction of the 
liquid and the ‘ stimulated ’ or c unstimulated * condition of 
the glands, does not, therefore, appear to hold good. 
I have examined the liquid with a view to determine its 
proteid content, with the result that I have found it to contain 
only a minute quantity. Liquid which digests actively, and 
even when containing the debris of insects, gives, after filtra- 
tion, only a very faint xanthoproteic reaction, no precipitate 
with nitric acid, with potassium ferrocyanide and acetic acid, 
or with platinic chloride, nor any turbidity on boiling : it 
gives a precipitate with Millon’s reagent which, on heating, 
does not turn red but yellow. 
In view of the fact that the liquid is quite inert in the 
absence of acid, it occurred to me that possibly it might 
contain the enzyme in the form of a zymogen. In order to 
assure myself on this point, I had recourse to the method 
described by Langley and Edkins 1 , which is based on the 
fact that, if a current of C 0 2 be passed through a liquid 
containing both zymogen and enzyme, the zymogen is more 
rapidly destroyed than the enzyme, a method which was 
employed by Green in his researches on germinating seeds. 
The experiment was as follows : — 
Oct. 16, 1897. Two tubes, each containing 75 c.cm. of neutral 
liquid from opened pitchers of N. Mastersiana , were taken : to the 
one, tube A, were added 25 c.cm. of a o*5°/ 0 solution of HC 1 , so 
that the liquid contained o-i2 5°/ 0 of the acid, and the tube was then 
warmed for an hour in the incubator at 37° C., when it was removed 
from the incubator, and the liquid was neutralized with 15 c.cm. of 
a 1% solution of Na 2 C 0 3 . To the tube B was now added a mixture 
1 Langley and Edkins, Journal of Physiology, VII, 1886; Green, Phil. Trans. 
Roy. Soc., 178 B, 1887. 
