V.—Snake Poison.
§ 639. The poisonous snakes belong chiefly to two classes, the Proteroglypha and the Solenoglypha.
Weir Mitchell and Ed. T. Reichert[644] have made some important experiments on snake poison, using the venom of some 200 snakes. Most of the snakes were rattlesnakes, a few were cobras and other species. They came to the conclusion that the active constituents are contained in the fluid part alone, the solid particles suspended in the fluid having no action. The poison they considered to consist of two toxalbumins, one a globulin, acting more particularly on the blood, the other, a peptone (albumose?), acting more particularly on the tissues. Differences in snake venom depend on the relative proportions of these two substances. The peptone, which acts more especially locally on the tissues, determines an inflammatory action, with much swelling and multiple extravasation of blood, which may proceed to a moist gangrene. The globulin has a paralysing influence on the heart, the vasomotor centres, the peripheral ends of the splanchnic nerves, as well as on the respiratory centres of both warm and cold-blooded animals. Feoktisow’s[645] researches show that although the heart continues to beat after the respiration has ceased for a few minutes, it has no force. The blood pressure sinks immediately after the injection. Whether the globulin is injected subcutaneously or direct into the veins, there is commonly considerable extravasation of blood in the chest and abdomen; the intestine is often filled with blood as well as the pericardium; and the urine is bloody. The poison of Vipera ammodytes in watery solution may be boiled for six minutes, and yet is as active as before. According to Lewin, snake poison generally can be heated to 125° and yet preserve its poisonous properties. These last observations are not in accordance with the belief of some that the active principle of snake venom is a ferment, or, indeed, in harmony with the idea that it is a globulin or toxalbumin; for such bodies have not, so far as we know, the stability to withstand so high a degree of heat.
[644] Smithsonian Contributions to Knowledge, Washington, 1886.
[645] Exp. Unters. über Schlangengift. Inaug. Diss., Dorpat, 1888.
§ 640. The Poison of the Cobra.—The poison excreted from the salivary glands of the cobra di capello is the most deadly animal fluid known. When first ejected, it is an amber-coloured, rather syrupy, frothy liquid, of specific gravity 1·046, and of feeble acid reaction; it dries rapidly on exposure to air to a yellow film, which readily breaks up into brilliant yellow granules, closely imitating crystals. The yellow powder is very acrid and pungent to the nostrils, and excites a painful (though transitory) inflammation, if applied to the mucous membrane of the eye; the taste is bitter, and it raises little blisters on the tongue. It is perfectly stable, and preserves its activity for an indefinite time. The dried poison as described is perfectly soluble in water, and if the water is added in proper proportions, the original fluid is without doubt reproduced, the solution usually depositing a sediment of epithelial débris, and often containing little white threads.
The poison has been examined by several chemists, but until of late years with a negative result. The writer was the first to isolate, in 1876, a crystalline principle, which appears to be the sole acting ingredient; the yellow granules were dissolved in water, the albumen which the venom so copiously contains coagulated by alcohol, and separated by filtration; the alcohol was then driven off at a gentle heat, the liquid concentrated to a small bulk, and precipitated with basic acetate of lead. The precipitate was separated, washed, and decomposed in the usual way by SH2, and on removing the lead sulphide, crystals having toxic properties were obtained.