tentacles varied much, but was always effected in under 24 hrs. In two
instances I recorded that all the exterior tentacles were completely
inflected in 17 hrs., but not the blade of the leaf. In another case
the edges of a leaf, after 25 hrs. 30 m., became so strongly inflected
that it was converted into a cup. The power of urine does not lie in
the urea, which, as we shall hereafter see, is inoperative.
Albumen (fresh from a hen s egg), placed on seven leaves, caused the
tentacles of six of them to be well inflected. In one case the edge of
the leaf itself became much curled in after 20 hrs. The one leaf which
was unaffected remained so for 26 hrs., and was then treated with a
drop of milk, and this caused the tentacles to bend inwards in 12 hrs.
Cold Filtered Infusion of Raw Meat. This was tried only on a single
leaf, which had most of its outer tentacles and the blade inflected in
19 hrs. During subsequent years, I repeatedly used this infusion to
test leaves which had been experimented [page 80] on with other
substances, and it was found to act most energetically, but as no exact
account of these trials was kept, they are not here introduced.
Mucus. Thick and thin mucus from the bronchial tubes, placed on three
leaves, caused inflection. A leaf with thin mucus had its marginal
tentacles and blade somewhat curved inward in 5 hrs. 30 m., and greatly
so in 20 hrs. The action of this fluid no doubt is due either to the
saliva or to some albuminous matter* mingled with it, and not, as we
shall see in the next chapter, to mucin or the chemical principle of
mucus.
Saliva. Human saliva, when evaporated, yields** from 1.14 to 1.19 per
cent. of residue; and this yields 0.25 per cent. of ashes, so that the
proportion of nitrogenous matter which saliva contains must be small.
Nevertheless, drops placed on the discs of eight leaves acted on them
all. In one case all the exterior tentacles, excepting nine, were
inflected in 19 hrs. 30 m.; in another case a few became so in 2 hrs.,
and after 7 hrs. 30 m. all those situated near where the drop lay, as
well as the blade, were acted on. Since making these trials, I have
many scores of times just touched glands with the handle of my scalpel
wetted with saliva, to ascertain whether a leaf was in an active
condition; for this was shown in the course of a few minutes by the
bending inwards of the tentacles. The edible nest of the Chinese
70