268 VENOMOUS SNAKES AND THE PHENOMENA OF THEIR VENOMS 
NATURAL IMMUNITY OF CERTAIN ANIMALS FROM SNAKE VENOM. 
It has been a popular belief that certain warm-blooded animals are im- 
mune to the bites of poisonous snakes. Of the mammals the mongoose 
(Herpestes ichneumon), hedgehog (Hrinaceus europeus) and hog (Sus); 
and of the birds the Ajaja, Cancroma, Botaurus, and Mycteria, known under 
the names of culebrero and guacabo in Colombia, are alleged to resist the 
effects of venom. 
Three experiments made by Fayrer on the mongoose show that this animal 
is not immune to the venom of Cobra, but is less sensitive than other warm- 
blooded animals. ‘The quick movements of this animal and its thick hair 
seem to protect it from being bitten by the Cobra. One of Fayrer’s descrip- 
tions of the experiments is quoted below: 
A mongoose and a full-sized cobra were put into a large wire cage at 1 p.m. 
The snake struck at the mongoose and they grappled each other frequently, and 
apparently the mongoose must have been bitten, as the snake held on to it about 
the neck or head. 
At 12 15™ p.m. there was no effect on the mongoose; both it and the snake were 
much excited and angry, the snake hissing violently. 
2h 3o™ p.m. no effect on the mongoose. The snake is bitten about the neck, and 
shows the bleeding wounds. 
2h 51™ p.m. They occasionally attack each other, but the mongoose jumps 
over the snake and tries to avoid it. 
Next day at noon both were well; the snake frequently struck at the mongoose, 
but did not appear to injure it; both seemed very savage, but the mongoose would 
not bite the snake; he jumped over it. 
There had been two cobras in the cage with the mongoose during the night, 
both equally fierce and striking at each other and the mongoose; but the latter was 
not poisoned. He was rather severely scratched on the head by the cobra. But 
on being bitten in the thigh by the same cobra, when both were taken out of the 
cage the mongoose succumbed to the poison and died very soon. 
According to Calmette ' the blood serum of the mongoose is devoid of any 
antivenomous properties against the venom of Cobra, although death may 
be slightly delayed. He injected into three normal mongooses the doses of 
cobra venom respectively corresponding to 4,6, and 8 minimal lethal doses 
for the rabbit. The first showed no symptoms; the second was ill for two 
days, but recovered; the third mongoose died in 12 hours. Thus the immunity 
of the mongoose is relative only. 
Flexner and Noguchi? found that the defibrinated blood of the mongoose 
from Jamaica was not hemolyzed by crotalus and ancistrodon venoms in 
the concentrations from 20 per cent to o.o5 per cent. The addition of an 
adequate amount of the crotalus serum to not too high concentrations of these 
venoms produced a rapid dissolution of the mongoose corpuscles, while the 
concentrations above 0.5 per cent of the venoms again progressively dimin- 
ished the amount of hemolysis in the presence of a uniform quantity of the 
1Calmette. Les venins. 1907, Paris. 
2 Flexner and Noguchi. Constitution of snake venom and snake sera. Jour. of Path. and Bacteriol., 
1903, VIII, 379. 
