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Show 108 DROSERA ROTUNDIFOLIA. CHAP. VI .. 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) wore 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. Fibro·us 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 den tine, in artificial gastric juice, and he found that they were after a considerable time completely dissolved. Dr. Klein examined some of the small lamellre, in to 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 rarified, 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 of a sheep with weak hydrochloric acid ; and seven minute fragments of tho fibrous basis were placed on so many leaves, four of the fragments being first damped with saliva to aid prompt inflection. All seven leav s became inflected, but only very moderately, in the course of a day. CHAP. VI. DIGESTION. 109 They quickly began to re-expand ; five of them on the second day, and the other two on the third day. On all seven leaves the :fibrous tissue was converted into perfectly transparent, viscid, more or less lique: fied little masses. In the middle, however, of one, m.y son saw unde:: a . hig~ power a few · corpuscles, with traces of :fibnllation In the surrounding transparent matter. From these facts it is clear that the leaves are very little excited by the :fibrous basis of bone: b~t that the secretion easily and quickly lique: fies It, If thoroughly decalcified. The glands which had r~m~ined in contact for two or three days with the VISCid masses were. not discoloured, and apparently had absorbed httle 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 ?ver 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 o~ 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 |