NATUBAl. 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 {Ophiopharjus) of large size. The snake rose w^ imme- 

 diately, dilated its hood, and struck savagely at the little animal, 

 which, darting nimbly out of the wa,y, 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 Eikki-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. 



"'It 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 



