OCR Text |
Show 224 DROSERA ROTUNDIFOLIA. CUAP. IX. these substances are not poisonous and have no power, or only a very slight one, of inducing inflection. It should, however, be observed that curare, colchicine, and veratrine are muscle-poisons-that is, act on nerves having some special relation with the muscles, and, therefore, could not be expected to act on Drosera. The poison of the co bra is most deadly to animals, by paralysing their nerve-centres,* yet is not in the least so to Drosera, though quickly causing strong inflection. Notwithstanding the foregoing facts, which show how widely different is the effect of certain substances on the health or life of animals and of Drosera, yet there exists a certain degree of parallelism in the action of certain other substances. We have seen that this holds good in a striking manner with the salts of sodium and potassium. Again, various metallic salts and acids, namely those of silver, mercury, gold, tin, arsenic, chromium, copper, and platina, most or all of which are highly poisonous to animals, are equally so to Drosera. But it is a singular fact that the chloride of lead and two salts of barium were not poisonous to this plant. It is an equally strange fact, that, though acetic and propionic acids are highly poisonous, their ally, formic acid, is not so; and that, whilst certain vegetable acids, nan1ely oxalic, benzoic, &c., are poisonous in a high degree, gallic, tannic, tartaric, and malic (all diluted to an equal degree) are not so. Malic acid induces inflection, whilst the three other just named vegetable acids have no such power. But a pharmacopooia would be requisite to describe the diversified effects of various substances on Drosera.t * Dr. Fayrer, 'The Thanatophidia of India,' 1872, p. 4. t Seeing that acetic, hydro-cyanic, and chromic acids, acetate of strychnine, and vapour of ether, are poisonous t? Drosera, CHAP. IX. SUMMARY OF THE CHAPTER. 225 Of the alkaloids and their salts which w re tried, several had not the least power of inducing infl cti n ; oth rs, which were certainly absorb d, as shown by th changed colour of the glands, had but a very mol)rate power of this kind; others, again, such as tlw acetate of quinine and digitaline, caused strong inflection. The several substances mention d in this chapter affect the colour of the glands very lifferently. These often become dark at first, and then very pal or white, as was conspicuously the case with gland subjected to the poison of the cobra and citrat f strychnine. In other cases they are from the first rendered white, as with leaves placed in hot water and several acids ; and this, I presume, is the result of th · coagulation of the albun1en. On the same leaf som glands become white and others dark-coloured, a · occurred with leaves in a solution of the sulphate of quinine, and in the vapour of alcohol. Prolonged inlmersion in nicotine, curare, and even water, blackenR the glands ; and this, I believe, is due to th aggregation of the protoplasm within their cells. Y t curare caused very little aggr gation in the cells of the tentacles, whereas nicotine and sulphate of quinine induced strongly marked aggregation down th ir bases. The aggregated masses in 1 aves which hau been im1nersed for 3 hrs. 15 m. in a saturated solution of sulphate of qu1n1ne xhibited incessant it is remarkable that Dr. Ransom ('Philo oph. Transact.' 1867, p. 480), who used much stronger solutions of these substances than I did, states "that the rhythmic contractility of the yolk (of the ova of the pike) is not materially influenced by any of the poisons used, which did not act chemi-cally, with the exception of chlor - form and. carbonic acid." I find it stated by sev ral w1·it rs that curare has no influence on sarco<l(· or protoplasm, and we havo s on that, though curare excites som degree of inflection, it caus s very little aggregation of the protoplasm. Q |