NATURAL IMMUNITY OF CERTAIN ANIMALS 223 
diluted with equal quantities of rabbit-serum or physiological saline 
solution. 
The natural immunity of the mongoose and the hedgehog rests 
upon more scientifically established facts. 
My own experiments upon the immunity of the mongoose were 
made with six specimens of these little carnivores captured in 
Guadeloupe (French West Indies), an island in which no poisonous 
snakes exist; consequently their immunity could not have arisen 
from their having become accustomed to the bites of venomous 
reptiles. 
I first introduced a mongoose into a cage containing a Naja 
bungarus (Ophiophagus) of large size. The snake rose up imme- 
diately, dilated its hood, and struck savagely at the little animal, 
which, darting nimbly out of the way, escaped being seized and, 
frightened for a moment, took refuge in a corner of the cage. Its 
stupor, however, was but of brief duration, for at the very moment 
when the hamadryad was preparing to strike at it again, the 
mongoose, with open mouth and snarling, sprang upon the reptile’s 
head, bit it hard in the upper jaw and crushed its skull in a few 
seconds. This scene is in every respect reminiscent of the admirable 
description given by Rudyard Kipling, in his celebrated ‘“ Jungle 
Book,” of the great war that Rikki-tikki (the Mongoose) fought 
with Nag (the Cobra) “ through the bathrooms of the big bungalow 
in Segowlee cantonment ” :— 
“Nag was asleep, and Rikki-tikki looked at his big back, 
wondering which would be the best place for a good hold. ‘If I 
don’t break his back at the first jump,’ said Rikki, ‘he can still 
fight ; and if he fights—O Rikki!’ He looked at the thickness 
of the neck below the hood, but that was too much for him; and 
a bite near the tail would only make Nag savage. 
“Tt must be the head,’ he said at last; ‘the head above the 
hood; and when I am once there, I must not let go. 
“Then he jumped. The head was lying a little clear of the 
water-jar, under the curve of it; and, as his teeth met, Rikki braced 
