When the dose of venom injected is sufficient to cause death, we observe, a very few moments after the injection, a lowering of temperature and a hypoleucocytosis, which is the more pronounced in proportion to the nearness of the dose of venom to the minimal lethal dose. With very strong doses the hypoleucocytosis has not time to manifest itself.
It is therefore probable that, in intoxication by venoms as in that by the toxins of micro-organisms, the protective rôle of the leucocytes is all-important, not only because these cells are capable of digesting venoms owing to their protoplasmic digestive juices, but also because they constitute if not the only, at any rate the principal source of the antitoxic substances or amboceptors.
CHAPTER X.
TOXICITY OF THE BLOOD OF VENOMOUS SNAKES.
Several physiologists, among whom it is right to mention Fontana,[69] Leydig,[70] Reichel,[71] Raphael Blanchard,[72] Phisalix and Bertrand,[73] and S. Jourdain,[74] have pointed out the presence of poison-glands in Tropidonotus natrix or other non-venomous snakes, and have explained the immunity enjoyed by these animals with regard to venom as being due to the existence of an internal secretion of this poison.
We also know, from the writings of Phisalix and Bertrand, that the blood of the viper, and that of the salamander and toad are toxic. For my part I have found[75] that the blood of Naja, Bungarus, Lachesis, and Cerastes possesses the same properties, and a comparative study has been made by Wehrmann,[76] in my laboratory, of the toxicity of the blood of the viper and of that of the blood of the eel, already established by Mosso (of Turin).[77]
It is remarkable to find that the blood of the various venomous or non-venomous snakes, like that of certain fishes, such as eels, produces, when injected beneath the skin or into the peritoneum, local and general effects very similar to those of venoms. Injections of 0·5 c.c. to 1 c.c. of the blood of the viper or of the common snake, beneath the skin of the guinea-pig, provoke an intense local reaction, which always results in the formation of an eschar. The injection of slightly stronger doses, 1 c.c. to 2 c.c., into the peritoneum, almost always kills these animals, like venom, with symptoms of respiratory asphyxia.
The blood of Naja tripudians, injected subcutaneously, is lethal to the mouse in a dose of 0·25 c.c.
When this blood is heated, after having been suitably diluted with three or four parts of distilled water, in order to prevent it from coagulating, it is found that a temperature of 70° C. maintained for fifteen minutes is sufficient to cause it to lose all toxic effect. The same applies to the blood of the other poisonous or non-poisonous snakes, and to that of the Murænidæ.
Now, since the majority of venoms resist even prolonged heating at this temperature, it cannot be supposed that the toxicity of the blood is due to its containing venom derived from the internal secretion of the poison-glands, as was thought by Phisalix and Bertrand. On the contrary, it is probable that the toxicity results from the fact that the blood contains diastasic substances of cellular origin, which themselves represent certain of the constituent elements of venoms.
These substances, moreover, possess some of the properties of venoms, as, for instance, the faculty of producing hæmorrhages and of being influenced by antivenomous serum, which causes them to lose a large portion of their toxic qualities.