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., 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 apphes to the blood of the other poisonous or non- 
poisonous snakes, and to that of the Murenide. 
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 hemorrhages 
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 venom; by injecting weak, non-lethal, and repeated doses 
of dilute Cobra-blood into guinea-pigs and rabbits, I have succeeded 
in rendering them immune to doses of Cobra-venom several times 
ereater 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 
