Venomous Serpents.—Among the venomous serpents,[143] the most important as well as the most dangerous are the following: Cobra di capello (Naja tripudians, the hooded cobra) and its analogues, the black Naja, Naja hagé, etc.; the elops (coral serpent); the bungurus of Bengal and Burmah; the Platycercus proteroglyphia, which is found chiefly in the waters of the Indian Ocean; the crotalian solenoglyphs of the two Americas, and among which in particular are the rattlesnake, the fer-de-lance (the yellow viper) of Martinique; the surucucu of Guiana; and the moccasins and copperheads of Texas and Florida. Lastly, the entire group of viperian solenoglyphs, among which are the Echidnæ, the bite of some of which, for instance the daboia or echidna, is dreadful; the African vipers, among which may be mentioned the horned viper, the bite of which will kill a camel; the springing viper of Congo, and the rhinoceros-viper of Gabun; the European vipers, the most dangerous of which is certainly the asp of France, which is exceedingly numerous in certain regions.
The effects of the bites of venomous serpents on man and animals are generally well known to the public; it is well to recall them, nevertheless. From the moment the bite has been inflicted, complete symptoms of poisoning develop, attended by a condition of extreme and increasing weakness, with vomiting, hemorrhage, and decomposition of the blood. There are, besides, particular effects which vary with every venom.
The following table by Calmette[144] gives the comparative toxicity of various venoms, taking as the standard of comparison the quantity sufficient to kill a rabbit in three or four hours:
| Naja tripudians | 0.00047 |
| Naja hagé | 0.0003-0.0007 |
| Acanthophis antarctica | 0.001 |
| Ceraste | 0.0017-0.0021 |
| Haplocephalus variegatus | 0.0025 |
| Trigonocephalus | 0.0025 |
Nature of Serpent-venoms.—These venoms are homogeneous liquids, somewhat more dense than water, in which they are soluble, slightly colored green or yellow, transparent, and insoluble in alcohol; they contain from 30 to 35 per cent. of solid matter. When fresh, they have a slightly acid reaction. Towards chemical reagents, and particularly acids, they behave like albuminoids; almost all the combinations they afford with the various albuminoid reagents are active, despite their insolubility. According to Gautier, they are decomposed by caustic potash.
According to numerous researches, oxidizers like potassium permanganate, the hypochlorites, hydrogen peroxide, and gold chloride (in 1% solution) destroy the venoms; in certain cases when immediately injected hypodermically in the poisoned region, these substances are excellent antidotes in vivo.[145]
We shall not here enter upon a detailed study of the toxic albuminoid principles of serpent-venoms; moreover, our knowledge is rather vague, as it is, on a number of points. It will suffice us to know that, taken altogether, the active albuminoids of these venoms are numerous, and that each venom has its own particular active constituents, differing according to the species and variety of the snake.
Each one of these substances acts more or less rapidly, and may be associated with different principles which give rise to the variability of the action of these toxic agents. Among these toxic albuminoids, the most virulent appear to be true albumins and globulins, followed by the nucleo-albumins, as we have already stated; there are also found in venoms alkaloidal bases, but these principles are present only in very slight quantity. These bases are but very slightly toxic compared with the toxins that accompany them.
Natural Immunity towards Serpent-venoms.—Certain animals exhibit a natural immunity toward snake-bites; among them are the snakes themselves, the hog, the hedgehog, and the mongoos (an Egyptian rat); the blood of these animals contains apparently an antitoxin.[146]
Fontana[147] had remarked that snakes were quite unaffected by the bite of the viper, even when inoculated with the venom hypodermically. Physalix and Bertrand[148] confirmed these statements, and showed that the snake perfectly resisted quantities of viper-venom capable of killing at least 20 guinea-pigs. According to these scientists, this natural immunity is due to the existence in the blood of toxic principles analogous to those of viper's venom—principles that exist in the labial glands of the snake, and pass into the blood and the fluids via the internal secretions. These writers, and also Calmette, have shown that the blood of venomous serpents becomes antitoxic when heated.