This kinase or diastase, capable of quickening the inert pancreatic juice, must evidently be of very great utility to the reptile in enabling it to digest its prey. Venom, therefore, is not, as has long been believed, a purely defensive secretion; it corresponds to a physiological necessity, like that of the intestinal or pancreatic juice. Herein is to be found the explanation of the fact that the non-poisonous snakes, although destitute of organs of inoculation, possess supralabial or parotid glands which produce venomous saliva.
Experiments have been made by Ch. Féré[63] to determine the effect upon the development of the embryo of the introduction of venom into the albumen of the egg of the fowl. He found that 83 per cent. of the embryos, developed in eggs intoxicated with 0·05 milligramme of viper-venom and opened after being incubated for seventy-two hours, exhibited various anomalies in development.
E.—Action of Various Diastases upon Venoms.
Venoms are modified or destroyed by certain normal diastases of the organism. It was shown long ago by Lacerda, Weir Mitchell, Sir Joseph Fayrer, and Lauder Brunton, that it is possible to introduce without danger into the stomachs of adult animals amounts of venom many times greater than the lethal dose. I have repeatedly verified this, but have nevertheless observed that young mammals, while being suckled, readily absorb venom by their alimentary canal, and succumb to the ingestion of doses scarcely larger than those which kill when subcutaneously injected. Here we have a very important fact, which once more proves how easily the intestinal mucous membrane of young animals is permeated by toxins. By my instructions Wehrmann[64] and Carrière,[65] in my laboratory, have studied the modifications undergone by venoms in the alimentary canal of rabbits. We have seen that these animals can ingest without inconvenience doses of venom 600 times greater than the lethal dose, and that, if we cause these ingestions to be repeated several times, contrary to the assertion of Fraser[66] (of Edinburgh), we never succeed in obtaining immunity to the subcutaneous injection of a simple lethal dose, and no antitoxin is formed in the blood.
The ptyalin of the saliva, pancreatic juice, and bile destroy Cobra-venom in vitro. We must, therefore, assume that these diastases are veritable agents of destruction for ingested venom. The intestinal microbes play no part, any more than the intestinal juice by itself. The gastric juice has very little effect. Papain is almost as active as the pancreatic juice.
It had already been proved by Fraser, so long ago as 1895, that bile, after prolonged contact and in a sufficient dose, has a strongly destructive effect upon Cobra-venom; but, contrary to the opinion of this investigator, it is not antitoxic, for it possesses no preventive or curative property, and its effects are produced only in vitro.
We see from what has been stated above, that venoms introduced into a sensitive organism are capable of producing extremely complex effects upon the various tissues or humours. They act on the nerve-cells by their neurotoxin, on the endothelium of the blood-vessels by their hæmorrhagin (Flexner and Noguchi), on the red corpuscles by their hæmolysin, on the fibrin of the blood and muscles by their proteolytic diastase, and on the fibrin-ferment itself by their thrombase.
They also act on the leucocytes, according to the experiments of Chatenay,[67] performed under the direction of Metschnikoff, and according to those of Flexner and Noguchi,[68] already cited.
Thus we understand how complex must likewise be the means of defence that have to be employed in order to afford an effective protection against such poisons.
The slightly intoxicated organism at first reacts by the intervention of the leucocytes; a hyperleucocytosis is produced, accompanied by a more or less considerable rise of temperature. After a few hours everything returns to its normal condition, and if the injection of a lethal dose of venom is repeated several times, at intervals of a few days, it is not long before antitoxic substances are found to appear in the serum.