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Show 120 DROSERA ROTUNDIFOLIA. CHAP. VI. sti1nu1ant as fresh gluten, and. docs not much injure the glands ; and we further learn that it can be digested quickly and completely by the secretion. Globulin or Crystallin.--This substance was Jdndly prepared for me from the lens of the eye by Dr. Moore, and consisted pf hard, col~urless, transparent fragments. It is said* that globulin ought to "swell up in water and dissolve, for tho most part forming a gummy liquid;" but this did not occur with tho above fragments, though kept in water for four days. Particles, some moistened with water, others with weak hydrochloric acid, others soaked in water for one or two days, were placed on nineteen leaves. }.fost of those leaves, especially those with tho long soaked particles, became strongly inflected in a few hours. The greater number re-expandod after three or four day~; but three of the leaves remained inflected during one, two, or three additional days. Hence some exciting matter must have been absorbed; but the fragments, though perhaps softened in a greater degree than those kept for tho same time in water, retained all their angles as sharp as ever. As globulin is an albuminous substance, I was u,stoni. hod at this resn 1 t ; and my object being to compare the action of tho secretion with that of gastric juice, I asked Dr. Burdon Sanderson to try some of tho globulin used by mo. He reports that "it was subjected to a liquid containing 0·2 per cent. of hydrochloric acid, and about 1 per cent. of glycerine extract of the stomach of a dog. It was; then ascertained that this liquid was capable of digesting 1·31 of its weight of unboile:i fibrin in 1 hr.; whereas, during the hour, only 0·141 of the above globulin was di solvocl. In both cases an excess of the substance to be digested was subjected to the li<Juicl."t vVe thus see that within the same time less than one-ninth by weight of globulin than of fibrin was dissolved; and bearing in mind that pepsin with acius of the acetic serial) has only about o~e-third of the digestive power of pep. in with hydrochloric acid, it is not surprising that the fragments of * Watts' ' Diet. of Chemistry ' vol. ii. p. 874. ' t I may add that Dr. Sanderson prepared some fresh globulin by Schmidt's method, and of this 0 · 865 was dissolved within the same time, nainely, one hour; so that it was far more soluble than that which I usoa, thoug·h less soluble than fibrin, of which, as we have soon, 1 · 31 was dis:-;olvod. I wish that I had tri d on Drosera globulin prepared by this method. CHAP. VI. DIGESTION. 121 globulin were not corroded or rounded hy the secretion of Drosera, though some soluble matter was certainly extracted from them and absorbed by the glands. 1/rematin.-Some dark reel granules, prepared from bullock's blood, were given me; those wore found by Dr. Sanderson to be insoluble in water, acids, and alcohol, so that they weTe probably hrematin, togetl1er with other bodies derived from the blood. Particles with little drops of water wore placed on four leaves, throe of which were pretty closely inflected in two days ; the fourth only moderately so. On the third day the glands in contact with the hromatin were blackened, aud some of the tentacles seemed injured. After five days two leaves died, and the third was dying; tho fourth was beginning to reexpand, but many of its glands woTe blackened and injured. It is therefore clear that matter had been absorbed which was either actually poisonous or of too stimulating a nature. The particles were much more softened than those kept for tho same time in ·water, but, judging by the eye, very little Teducod in bulk. Dr. Sanderson tried this substance with artificial digestive fluid, in the manner described under globulin, and found that whilst 1·31 of fibrin, only 0·456 of the hrematin was dissolved in an hour; but the dissolution by the secretion of even a less amount would account for its action on Drosera. The residue left by the artificial digestive fluid at first yielded nothino· more to it during several succeeding clays. o Substances which are not Digested by the S ecretion. · All the substances hitherto mentioned cause prolonged inflection of the tentacles, and are either complete! y or at least partially dissolved by the secretion. But there are many other substances, some of them containing nitrogen, which are not in the least acted on by the secretion, and do not inuuce inflection for a longer time than do inorganic and insoluble objects. These unexciting and indigestible substances are, as far as I have observed, epidermic productions (such as bits of human nails, balls of hair, the quills of feathers), fibro-elastic tissue, n1ucin, pepsin, urea, chitine, chlorophyll, cellulose, gun-cotton, fat, oil, and starch. |