218 VENOMS 



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 peri- 

 toneum, almost always kills these animals, like venom, with symp- 

 toms 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 MurcenidcB. 



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 cellu- 

 lar 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 haemorrhages 

 and of being influenced by antivenomous serum, which causes 

 them to lose a large portion of their toxic qualities. 



I have found that they can even be utilised to vaccinate animals 

 against yenom ; by injecting weak, non-lethal, and repeated doses 

 of dilute Cohra-h\oo& into guinea-pigs and rabbits, I have succeeded 

 in rendering them immune to doses of Coira- venom several times 

 greater than the lethal dose. 



There is no doubt that it is to these substances that the 

 poisonous and non-poisonous snakes owe the partial immunity 

 that they themselves enjoy with respect to venoms. We know, 

 in fact, that common snakes suffer without danger many bites from 



