Cuap. VI] DIGESTION. 101 
stated in chemical works, it appears extremely doubtful whether 
mucin can be prepared as a pure principle. ‘hat which I used 
(prepared by Dr. Moore) was dry and hard. Particles moistened 
with water were placed on four leaves, but after two days there was 
only a trace of inflection in the immediately adjoining tentacles, 
These leaves were then tried with bits of meat, and all four soon 
became strongly inflected. Some of the dried mucin was then soaked 
in water for two days, and little cubes of the proper size were placed 
on three leaves. After four days the tentacles round the margins of 
the discs were a little inflected, and the secretion collected on the disc 
was acid, but the exterior tentacles were not affected. One leaf began 
to re-expand on the fourth day, and all were fully re-expanded on the 
sixth. The glands which had been in contact with the mucin were 
a little darkened. We may therefore conclude that a small amount of 
some impurity of a moderately exciting nature had been absorbed. 
That the mucin employed by me did contain some soluble matter was 
proved by Dr. Sanderson, who on subjecting it to artificial gastric 
juice found that in 1 hr. some was dissolved, but only in the proportion 
of 23 to 100 of fibrin during the same time. The cubes, though 
perhaps rather softer than those left in water for the same time, 
retained their angles as sharp as ever. We may therefore infer that 
the mucin itself was not dissolved or digested. Nor is it digested by 
the gastric juice of living animals, and according to Schiff* it is a 
layer of this substance which protects the coats of the stomach from 
being corroded during digestion. 
Pepsin.—My experiments are hardly worth giving, as it is scarcely 
possible to prepare pepsin free from other albuminoids; but I was 
curious to ascertain, as far as that was possible, whether the ferment of 
the secretion of Drosera would act on the ferment of the gastric juice 
of animals. I first used the common pepsin sold for medicinal pur- 
poses, and afterwards some which was much purer, prepared for me 
by Dr. Moore. Five leaves to which a considerable quantity of the 
former was given remained inflected for five days; four of them then 
died, apparently from too great stimulation. I then tried Dr. Moore’s 
pepsin, making it into a paste with water, and placing such small 
particles on the discs of five leaves that all would have been quickly 
dissolved had it been meat or albumen. The leaves were soon in- 
flected ; two of them began to re-expand after only 20 hrs., and the 
other three were almost completely re-expanded after 44 hrs. Some 
of the glands which had been in contact with the particles of pepsin, 
or with the acid secretion swrounding them, were singularly pale, 
whereas others were singularly dark-coloured. Some of the secretion 
was scraped off and examined under a high power; and it abounded 
with granules undistinguishable from those of pepsin left in water for 
the same length of time. We may therefore infer, as highly probable 
* ©Lecons phys. de la Digestion,’ 1867, tom. il. p. 304, 
