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Show 112 DROSERA ROTUNDIFOLIA. CHAP. VI. prove that gelatine is far from acting energetically on Drosera. In the last chapter it was shown that a solution of isinglass of commerce, as thick as mi~k or cream, induces stroncr inflection. I therefore wished to compare its actio~ with that of pure gelatine. Solutions of one part of both substances to 218 of water were made; and half-minim drops (·0296 mi.) were placed on the discs of eight leaves, so that each received _I_ of a grain or ·135 mg. The four with the isin- 4 H 0 ' glass were much more strongly inflected than the other four. I conclude therefore that isinglass contains some, though perhaps very little, soluble albuminous matter. As soon as these eight leaves reexpanded, they were given bits of roast meat, and in some hours all became greatly inflected; again showing how much more meat excites Drosera than does gelatine or isinglass. This is an interesting fact, as it is well known that gelatine by itself has little power of nourishing animals.* Ohondrin.-This was sent me by Dr. Moore in a gelatinous state. Some was slowly dried, and a small chip was placed on a leaf, and a much larger chip on a second leaf. The first was liquefied in a day ; the larger piece was much swollen and softened, but was not completely liquefied until the third day. The undried jelly was next tried, and as a control ex periment small cubes were left in water for four days and retained their angles. Cubes of the same size were placed on two leaves, and larger cubes on two other leaves. The tentacles and laminre of the latter were closely inflected after 22 hrs., but those of the · * Dr. Lauder Brunton gives view of the indirect part which in the 'Medical Record,' January gelatine plays in nutrition. 1873, p. 36, an account of Voit's CHAP. VI. DIGESTION. 113 two leaves with the smaller cubes only to a moderate degree. The jelly on all four was by this time liquefied, and rendered very acid. The glands were blackened from the aggregation of their protoplasmic contents. In 46 hrs. from the time when the jelly was given, the leaves had almost re-expanded, and co1npletely so after 70 hrs.; and now only a little slightly adhesive fluid was left unabsorbed on their discs. One part of chondrin jelly was dissolved in 218 parts of boiling water, and half-minim drops were given to four leaves ; so' that each received about _ _!__ 4 ~ 0 of a grain ('135 mg.) of tho jelly; and, of course, much less of dry chondrin. This acted most powerfully, for after only 3 hrs. 30m. all four leaves were strongly inflected. Three of them began to reexpand after 24 hrs., and in 48 hrs. were completely open; but the fourth ha~ only partially re-expanded. .AJl the liquefied chondrin was by this time absorbed. Hence a solution of chondrin seems to act far more quickly and energetically than pure gelatine or isinglass; but I am assured by good authorities that it is most difficult, or impossible, to know whether chondrin is pure, and if it contained any albuminous compound, this would have produced the above effects. Nevertheless, I have thought these facts worth giving, as there is so much doubt on the nutritious value of gelatine; and Dr. Lauder Brunton does not know of any experiments with respect to animals on the relative value of gelatine and chondrin. .·Milk.-W e have seen in the last chapter that milk acts most powerfully on the leaves; but whether this is due to the contained casein or albumen, I know not. Rather large drops of milk excite so much secretion (which is very acid) that it sometimes trickles down I |
