the leaves are very little excited by the fibrous basis of bone, but
that the secretion easily and quickly liquefies it, if thoroughly
decalcified. The glands which had remained in contact for two or three
days with the viscid masses were not discoloured, and apparently had
absorbed little of the liquefied tissue, or had been little affected by
it.
Phosphate of Lime. As we have seen that the tentacles of the first set
of leaves remained clasped for nine or ten days over minute fragments
of bone, and the tentacles of the second set for six or seven days over
the same fragments, I was led to suppose that it was the phosphate of
lime, and not any included animal matter, which caused such long
continued inflection. It is at least certain from what has just been
shown that this cannot have been due to the presence of the fibrous
basis. With enamel and dentine (the former of which contains only 4 per
cent. of organic matter) the tentacles of two successive sets of leaves
remained inflected altogether for eleven days. In order to test my
belief in the potency of phosphate of lime, I procured some from Prof.
Frankland absolutely free of animal matter and of any acid. A small
quantity moistened with water was placed on the discs of two leaves.
One of these was only slightly affected; the other remained closely
inflected for ten days, when a few of the tentacles began to [page 110]
re-expand, the rest being much injured or killed. I repeated the
experiment, but moistened the phosphate with saliva to insure prompt
inflection; one leaf remained inflected for six days (the little saliva
used would not have acted for nearly so long a time) and then died; the
other leaf tried to re-expand on the sixth day, but after nine days
failed to do so, and likewise died. Although the quantity of phosphate
given to the above four leaves was extremely small, much was left in
every case undissolved. A larger quantity wetted with water was next
placed on the discs of three leaves; and these became most strongly
inflected in the course of 24 hrs. They never re-expanded; on the
fourth day they looked sickly, and on the sixth were almost dead. Large
drops of not very viscid fluid hung from their edges during the six
days. This fluid was tested each day with litmus paper, but never
coloured it; and this circumstance I do not understand, as the
superphosphate of lime is acid. I suppose that some superphosphate must
have been formed by the acid of the secretion acting on the phosphate,
but that it was all absorbed and injured the leaves; the large drops
which hung from their edges being an abnormal and dropsical secretion.
96