as bits of human nails, balls of hair, the quills of feathers),
fibro-elastic tissue, mucin, pepsin, urea, chitine, chlorophyll,
cellulose, gun-cotton, fat, oil, and starch. [page 122]
To these may be added dissolved sugar and gum, diluted alcohol, and
vegetable infusions not containing albumen, for none of these, as shown
in the last chapter, excite inflection. Now, it is a remarkable fact,
which affords additional and important evidence, that the ferment of
Drosera is closely similar to or identical with pepsin, that none of
these same substances are, as far as it is known, digested by the
gastric juice of animals, though some of them are acted on by the other
secretions of the alimentary canal. Nothing more need be said about
some of the above enumerated substances, excepting that they were
repeatedly tried on the leaves of Drosera, and were not in the least
affected by the secretion. About the others it will be advisable to
give my experiments.
[Fibro-elastic Tissue. We have already seen that when little cubes of
meat, &c., were placed on leaves, the muscles, areolar tissue, and
cartilage were completely dissolved, but the fibro-elastic tissue, even
the most delicate threads, were left without the least signs of having
been attacked. And it is well known that this tissue cannot be digested
by the gastric juice of animals.*
Mucin. As this substance contains about 7 per cent. of nitrogen, I
expected that it would have excited the leaves greatly and been
digested by the secretion, but in this I was mistaken. From what is
stated in chemical works, it appears extremely doubtful whether mucin
can be prepared as a pure principle. That 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
* See, for instance, Schiff, Phys. de la Digestion, 1867, tom. ii.,
p. 38. [page 123]
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