Experiment 3.—­May 1st, fragment moistened with saliva and placed on a leaf, which remained well inflected until 5th, when it re-expanded.  The enamel was not at all, and the dentine only slightly, softened.  The fragment was now transferred to a fresh leaf, which next morning (6th) was strongly inflected, and remained so until the 11th.  The enamel and dentine both now somewhat softened; and Dr. Klein reports, “less than half the enamel, but the greater part of the dentine decalcified.”

Experiment 4.—­May 1st, a minute and thin bit of dentine, moistened with saliva, was placed on a leaf, which was soon inflected, and re-expanded on the 5th.  The dentine had become as flexible as thin paper.  It was then transferred to a fresh leaf, which next morning (6th) was strongly inflected, and reopened on the 10th.  The decalcified dentine was now so tender that it was torn into shreds merely by the force of the re-expanding tentacles.]

From these experiments it appears that enamel is attacked by the secretion with more difficulty than dentine, as might have been expected from its extreme hardness; and both with more difficulty than ordinary bone.  After the process of dissolution has once commenced, it is carried on with greater ease; this may be inferred from the leaves, to which the fragments were transferred, becoming in all four cases strongly inflected in the course of a single day; whereas the first set of leaves acted much less quickly and [page 108] energetically.  The angles or projections of the fibrous basis of the enamel and dentine (except, perhaps, in No. 4, which could not be well observed) were not in the least rounded; and Dr. Klein remarks that their microscopical structure was not altered.  But this could not have been expected, as the decalcification was not complete in the three specimens which were carefully examined.

Fibrous Basis of Bone.—­I at first concluded, as already stated, that the secretion could not digest this substance.  I therefore asked Dr. Burdon Sanderson to try bone, enamel, and dentine, in artificial gastric juice, and he found that they were after a considerable time completely dissolved.  Dr. Klein examined some of the small lamellae, into which part of the skull of a cat became broken up after about a week’s immersion in the fluid, and he found that towards the edges the “matrix appeared rarefied, thus producing the appearance as if the canaliculi of the bone-corpuscles had become larger.  Otherwise the corpuscles and their canaliculi were very distinct.”  So that with bone subjected to artificial gastric juice complete decalcification precedes the dissolution of the fibrous basis.  Dr. Burdon Sanderson suggested to me that the failure of Drosera to digest the fibrous basis of bone, enamel, and dentine, might be due to the acid being consumed in the decomposition of the earthy salts, so that there was none left for the work of digestion.  Accordingly, my son thoroughly decalcified the bone