578 Vines. — The Proteolytic Enzyme of Nepenthes . 
I have not found that an active glycerin-extract can always 
be prepared from pitchers. It appears that this can only 
be done with relatively young pitchers ; and it is probable 
that the secretion of the enzyme ceases some time before the 
pitcher shows signs of withering. I may add that I have 
found glycerin-extract to act upon fibrin in presence of 
i°/ o HCN, though the digestion is slightly retarded. 
I attach considerable importance to the activity of glycerin- 
extracts of the pitchers, because it proves the existence of 
a digesting agent in their tissue, probably in the glands, and 
thus affords collateral evidence that this agent is not a Bac- 
terium but an enzyme. It is highly improbable that any 
Bacterium would retain its vitality after two months sojourn 
in pure glycerin. 
Moreover, the fact that an enzyme can thus be extracted, 
suggests that a zymogen must be present. In the course of 
the last eighteen months, I have several times endeavoured 
to repeat my observation of 1877, which revealed the presence 
of a zymogen, but so far, I must admit, without success. On 
the contrary, I have generally found that previous treatment 
with acid rather diminishes than increases the activity of the 
resulting extract. I propose to make this point the object 
of further research next season ; my main object in the 
observations recorded in this paper having been the refutation 
of the suggestion that the digestive activity of the pitcher- 
liquid is due to Bacteria. 
The Products of Digestion. 
Our knowledge of the products of the digestion of fibrin 
by the pitcher-liquid is derived entirely from the observations 
of von Gorup-Besanez, who describes them as peptones. He 
found, namely, that the filtered liquid after digestion re- 
mained clear on boiling, and gave no precipitate with mineral 
acids, nor with potassium ferrocyanide in the presence of 
acetic acid ; whilst it gave a precipitate with corrosive sub- 
limate, tannic acid, or phospho-tungstic acid, as also a brilliant 
biuret-reaction. 
