Pedler,[646] precipitating the albumen by alcohol, and then to the alcoholic solution adding platinic chloride, obtained a semi-crystalline precipitate, which from an imperfect combustion he thinks may have something like the composition PtCl4(C17H25N4O7HCl)2. I have examined the platinum compound, and made several combustions of different fractions, but was unable to obtain the compound in a sufficient state of purity to deduce a formula. My analysis agreed with those of Pedler for nitrogen—viz., 9·93 per cent. (Pedler, 9·69); hydrogen 4·17 (Pedler, 4·28); but were higher for carbon, 41·8 per cent. (Pedler, 33·42 per cent.); one fraction gave 7·3 per cent. of platinum, another double that amount. Material was insufficient to thoroughly investigate the compound, but it was evident that several double salts were formed. The blood of the cobra is also poisonous. A. Calmette[647] has found that 2 c.c. of fresh cobra blood, injected into the peritoneum of a rabbit weighing 1·5 kilo., causes death in six hours; the same dose of the defibrinated blood injected into the veins is fatal in three minutes.
[646] Proc. Roy. Soc., vol. xxvii. p. 17.
[647] Compt. Rend., Soc. de Biol., 1894.
§ 641. Fatal Dose.—From my experiments on cats, rabbits, and birds, it seems probable that the least fatal dose for cats and rabbits, lies between ·7 and ·9 mgrm. per kilo., and for birds somewhere about ·7 mgrm. per kilo. of the dried poison; the venom contains about 60 per cent. of albuminous matter, and about 10 per cent. of poisonous substance; therefore, the lethal power is represented by something like ·07 to ·09 mgrm. per kilo., if the pure toxic principle free from albumen and diluting impurities be considered.
§ 642. Effects on Animals.—Almost immediately local pain or signs of uneasiness at the seat of injection are observed. There is then a variable interval, seldom exceeding 20 minutes (and generally much less), but in one of my experiments half an hour elapsed after the injection of a fatal dose before any effect was evident. The symptoms once produced, the course is rapid, and consists, first, of acceleration of the respirations, and then a progressive slowing, soon followed by convulsions. The convulsions are probably produced by the interference with the respiration and the deficient oxidation of the blood, and are therefore, the so-called “carbonic acid convulsions.” There is paresis or paralysis of the limbs. Death seems to occur from asphyxia, and the heart beats for one or more minutes after the respirations have ceased. If the dose is so small as not to produce death, no after-effects have been observed; recovery is complete.
Sir J. Fayrer, and Dr. Lauder Brunton consider that the terminations of the motor nerves suffer; on the other hand, Dr. Wall would explain the phenomena by referring the action entirely to the central nervous system, and concludes that the effects of the cobra poison consist in the extinction of function extending from below upwards of the various nerve centres constituting the cerebro-spinal system. In addition to this, there is a special and rapid action on the respiratory and allied nuclei, and this it is that causes death.
§ 643. Effects on Man.—By far the best account hitherto published of the effects of the cobra poison is a paper by Dr. Wall,[648] in which he points out the very close similarity between the symptoms produced and those of glosso-pharyngeal paralysis. This is well shown in the following typical case:—A coolie was bitten on the shoulder about twelve at midnight by a cobra; he immediately felt burning pain at the spot bitten, which increased. In fifteen minutes afterwards he began, he said, to feel intoxicated, but he seemed rational, and answered questions intelligently. The pupils were natural, and the pulse normal; the respirations were also not accelerated. He next began to lose power over his legs, and staggered. In thirty minutes after the bite his lower jaw began to fall, and frothy viscid mucous saliva ran from his mouth; he spoke indistinctly, like a man under the influence of liquor, and the paralysis of the legs increased. Forty minutes after the bite, he began to moan and shake his head from side to side, and the pulse and respirations were somewhat accelerated; but he was still able to answer questions, and seemed conscious. There was no paralysis of the arms. The breathing became slower and slower, and at length ceased one hour and ten minutes after the bite, the heart beating for about one minute after the respiration had stopped.