It was thus possible to make the animals withstand doses a thousand times greater than the ordinary lethal dose; the blood and serums of these animals at this point possessed immunizing properties, and this property passed by heredity to the offspring, to which it is transmitted by the blood itself, and by the milk during feeding. Along with these resemblances between the venoms and toxins, attention must be called to a very important difference. As we have already seen, the action of the toxins on the organism is always preceded by a certain period of incubation; the action of the venoms, on the contrary, is almost instantaneous, and in this respect they behave like chemical agents and alkaloidal toxins. If the venoms are preserved in a moist condition, they change because they undergo putrefaction, which is generally the case with all diastatic substances, and particularly the toxins. It is interesting to note that animals which have been bitten by a venomous serpent, but which, for some reason or other, have not succumbed to the venom, never recover their former condition; if they were young, their functions cease to develop, and they droop; if they are adults, their general condition remains that of stupefaction. =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. [143] CALMETTE: _Le Venin des Serpents_, Paris, 1896. 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: