550 Vines . — The Proteolytic 
\ 
that enzymes are retained in a marked degree by the* 
Berkefeldt-filter. 
The Zymogen. 
In my previous paper (p. 578) I stated that I had not 
succeeded in successfully repeating the experiments of 1877 1 , 
which demonstrated the presence of a zymogen in the 
glandular tissue of the pitcher. The method which I adopted 
in 1877 was as follows: some pitchers were treated with 
dilute acetic acid (1 °/ o ) for 24 hours previously to the 
preparation of the glycerin-extract ; comparative experiments 
between the glycerin-extracts prepared from pitchers so 
treated and the glycerin-extract prepared from pitchers 
gathered at the same time, but not treated with acid, showed 
that in every case the digestive power of the former was 
much greater than that of the latter, as indicated by the 
greater rapidity of digestion. In one experiment the acid- 
extract dissolved fibrin in 6 hours, whilst fibrin put to digest 
with the ordinary extract was but slightly attacked in that 
time. During the present year I have made some experi- 
ments with results confirmatory of those of 1877. They are 
as follows : — 
June 2, ’98. Took two unopened pitchers of N. Master siana\ 
opened and washed out the pitchers ; the pitcher-liquid strongly acid ; 
cut up the glandular portions of the pitchers into small pieces ; the 
whole weighed 8 grm. ; divided into two halves A and B ; A was 
rubbed up in a mortar with 20 cc. distilled water; B was rubbed 
up in a mortar with 20 cc. of ‘25°/ 0 solution of HC 1 ; both A and B 
were then placed for 45 minutes in the incubator at 5o°C. ; the liquid 
was then poured off from each, the substance dried somewhat with 
blotting-paper, and then rubbed up each with 20 cc. glycerin, to 
prepare glycerin-extracts A and B , and left to stand. 
On June 10 the digestion-experiment was made: 5 cc. of each 
of the extracts were taken, and placed in a tube with 5 cc. of -4 °/ Q 
HC 1 , together with -oi grm. of fibrin; the tubes were put into the 
incubator (temperature about 37° C.) at 10.30 a.m. By 6.30 p.m. the 
fibrin in tube B (acid-extract) was completely digested, whereas 
1 Journ. Linn. Soc. xv. 
