Enzyme of Nepenthes (//). 551 
that in tube A (neutral extract) did not disappear until over 48 hours 
later. 
In another experiment of about the same date, in which, however, 
the pitcher-substance was treated with •&°/ 0 acetic acid for about 
24 hours at ordinary temperature (about i5°C.), the acid-extract 
digested more rapidly than the neutral, but the difference was not 
so marked as in the preceding case. 
July 21, '98. Took two pitchers, one unopened, the other recently 
opened; cut up small; material divided into three parts of 2-7 grm. 
each: (1) was rubbed up at once with 20 cc. glycerin; (2) with 
20 cc. of * 25 °/ 0 HC 1 ; and (3) with 20 cc. distilled water: (2) and 
(3) were placed in an incubator at 36° C. and were kept there till 
next day (18-20 hours), the liquid was filtered off from them, and 
they were each rubbed up with 20 cc. glycerin. 
On Aug. 2 the digestion-experiment was made: 10 cc. of each 
extract were strained off through muslin; to each were added 10 cc. 
of *4°/ 0 HC 1 , together with -oi grm. fibrin, and all three were placed 
in the incubator (temperature 36° C.) to digest at 10.30 a.m. At 5 p.m. 
the fibrin in tube (2) (acid-extract) showed signs of digestion, and was 
almost entirely dissolved by 5 p.m. on the following day. The fibrin 
in tube (3) had all undergone solution by the evening of Aug. 5, 
whereas that in tube (1) still showed no sign of digestion. 
A second digestion-experiment with the same extracts was made on 
Aug. 30, with essentially similar results, though the period of dig^tion 
was longer. The experiment commenced at 10.15 and at 5 p.m. 
no indication of digestion could be seen in any one of the three tubes. 
Next morning (Aug. 31) at 9 a.m. the fibrin in tube (2) (acid-extract) 
was seen to be attacked ; the process of digestion continued slowly 
in this tube until it was complete (night of Sept. 2) ; the fibrin 
in the two tubes (1) and (3) underwent no perceptible change in 
this time. 
The foregoing results suffice to show that, under certain 
circumstances, previous treatment with acid causes the glands 
of the pitcher to yield a more active glycerin-extract, or to 
yield an active extract when otherwise the extract would be 
inactive ; and it can only be concluded that this must be due 
to the presence of a zymogen in the glands from which the 
enzyme is liberated on treatment with acid. However, I must 
P p 
