564 Vines . — The Proteolytic Enzyme of Nepenthes. 
during the process ; ‘ not only is there aggregation of the 
protoplasm in the gland-cells, but the walls of the cells 
themselves become discoloured, and the glandular surface 
of the pitcher that at first was of a uniform green, becomes 
covered with innumerable brown specks which are the dis- 
coloured glands.’ 
The publication of Sir Joseph Hooker’s observations was 
quickly followed by more detailed investigations into the 
nature both of the liquid in the pitchers of Nepenthes and 
of the presumed process of digestion. In 1875 Lawson Tait 1 
announced the preparation of £ a substance closely resembling 
pepsine’ — which he describes as ‘a greyish flocculent matter’ — 
from the liquid, thus doing for Nepenthes what he had already 
done for Drosera. In 1876 von Gorup-Besanez 2 gave an 
account of the chemical action of the liquid taken from 
pitchers, some of which had and some of which had not 
been previously stimulated by the presence of insects in 
them. He found (1) that the liquid from stimulated pitchers 
was distinctly acid, whilst that from unstimulated pitchers was 
neutral or only faintly acid, an observation which agrees 
with those of Lawson Tait : ( 2 ) that the neutral liquid from 
unstimulated pitchers had no digestive action upon swollen 
fibrin, even when the experiment was protracted (to twenty- 
four hours) and the temperature was as high as 20-30° C., 
whereas the acid liquid from stimulated pitchers digested 
shreds of fibrin within two hours at a temperature of 20° C., 
and within one hour at a temperature of 40° C. : and (3) that 
the addition of a few drops of dilute hydrochloric acid to 
either the acid or the neutral liquid accelerated the solution 
of the fibrin in a high degree, so that in one case it entirely 
disappeared in a quarter of an hour. With regard to the 
products of the action upon fibrin, he found that the resultant 
liquid gave no precipitate on the addition of mineral acids, 
nor with ferrocyanide of potassium after the addition of 
acetic acid ; but gave one with mercuric chloride, tannic acid, 
1 Nature, XII, 1875, p. 251. 
2 Sitzber. d. phys.-med. Soc. zu Erlangen, 1876. 
