OCR Text |
Show 186 DROSERA ROTUNDIFOLIA. CHAP. VIII. of a solution of one part to 437 of water; afte~ 2 hrs. som~ inflection · after 3 hrs. 45 m. tentacles closely Inflected, With the glands blackened. After 22 hrs. still closely inflec.ted, and the leaves flaccid. Placed in pure water, next day evidently dead. _t\.. rapid poison. . . . . . Nickel, Chloride of.-Three leaves Immm:sed ;n ninety .m1mms of a so 1 u tion of one part to 437 of water ; In 2o. m. considerable inflection, and in 3 hrs. all the tentacles closely Inflected. After 22 hrs. still closely inflected; most of the glands, but not all, blackened. The leaves were then placed in water; after 24 hrs. remained inflected; were somewhat discoloured, with the glands and tentacles dingy red. Probably killed. Cobalt, Chloride qf.-Three leaves immersed in ninety minims of a solution of one part to 437 of water; after 23 hrs. there was not a trace of inflection, and the glands were not more blackened than often occurs after an equally long immersion in water. Platinum, Chloride of.-Three leaves immersed in ninety minims of a solution of one part to 437 of water; in G m. some inflection, which became immense after 48 m. After 3 hrs. the glands were rather pale. After 24 hrs .. all t~e tentacles still closely inflected; glands colourless; remained 111 same state for four days; leaves evidently killed. Concluding Remarks on the Action of the foregoing Salts.-Of the fifty-one salts and metallic acids which were tried, twenty-five caused the t ntacles to be inflected, and twenty-six had no such ffect, two rather doubtful cases occurring in each s ries. In the table at the head of this discussion, the salts arc arranged according to their chemical affinities; but their action on Drosera does not seem to be thus gov rned. The nature of the base is far more important, as far as can be judged from the few experiments h re given, than that of the acid; and this is the c nclusion at which physiologists have arrived with respo t to animals. We see this fact illustrated in all the nine salts of soda causing inflection, and in · not being poisonou~ except when given in large doses; whereas seven of CHAP. VIII. CONCLUDING REMARKS, SALTS. 187 tth' e correspondinba sa 1t s of potash do not cause I. nflec- Ion, and . s?me of them are poisonous. Two of them, ~owever, VIZ~ the oxalate and iodide of potash, slowly l~duced a. shg~ht and rather doubtful amount of inflec-tion. . This difference between the t wo sen.e s 1. s I. nter-esti? g, as Dr. Burdon Sanderson informs me that sodi urn salts may be in trod need in large d - . t th . 1 . oses 1n o e cucu ation of 1nammals without any · · · .ei! • • c ITIJlUIOUS euects, whilst small doses of potassium salts cause death by suddenly arresting the movements of th heart. An excellent instance of the different actio~ of the ~·WO series .is presented by the phosphate of soda quicldy ca~sing. vi~orous inflection, whilst phosphate of potash .Is quite Inefficient. The great power of the former .Is probably due to the presence of phosphorl~s, as 1n the cases of phosphate of lime and of a~monia. Hence we may infer that Drosera cannot ?btain phosphorus from the phosphate of potash. This IS remarkable, as I hear from Dr. Burdon Sanderson t~at. phosphate of potash is certainly decomposed within the bodies of animals. Most of the salts of soda act v~ry rapidly ; the iodide acting slowest. The oxalate, nitrate, and citrate seem to have a special tendency to cause the blade of the leaf to be inflected. The g~ands of the disc, after absorbing the citrate, transmit hardly any motor impulse to the outer tentacles; and in this character the citrate of soda resembles the citrate of ammonia, or a decoction of grass-leaves; these three fluids all acting chiefly on the blade. . It seems opposed to the rule of the preponderant Influence of the base that the nitrate of lithium causes moderately rapid inflection, whereas the acetate causes none; but this metal is closely allied to sodium |