NATURAL IMMUNITY 269 
crotalus serum. Unlike the venom, the crotalus serum is highly hemolytic 
upon the mongoose corpuscles. 
Lewin’ and Phisalix and Bertrand? made numerous experiments on the 
immunity of the hedgehog against the venom of Vipera berus. It is known 
that the hedgehog chases the viper and eats it very eagerly. The spinous 
coat of the animal protects it from being bitten by the snake and the 
animal is very skilful in catching the reptile at vulnerable parts of the body. 
Should the snake succeed in biting the hedgehog, the latter seldom dies. 
The inoculation of about 40 minimal lethal doses for guinea-pig of this venom 
into the hedgehog is required to kill. Whether or not the resistance of this 
animal is due to the presence of an antitoxic substance in the blood has been 
studied by Phisalix and Bertrand, who state that the serum of this animal 
heated to 58°C. in order to deprive it of its inherent toxicity for the guinea- 
pig can, when mixed with 2 minimal lethal doses of the viper poison in quan- 
tities of 8 c.c. of the serum, protect the guinea-pig from the fatal effects of 
venom. 
In regard to the natural immunity of hogs, which is popularly credited in 
the Mississippi Valley, it is still unconfirmed experimentally. Calmette ® 
found the pig to resist more cobra venom than dogs (speaking proportionally), 
but its serum contained no antivenomous properties. Along the valleys of 
the lower Mississippi it is said that the hog swallows young crotalus with 
evident liking. 
Concerning the grallics of Colombia, the culebrero and guacabo, nothing 
definite is known, except that these birds hunt young snakes for their prey. 
Probably they are relatively immune to the bite of poisonous snakes, partly 
because they understand how to kill the snake, and partly, perhaps, because 
they are less sensitive to the effect of the venom itself. 
1 Lewin. Beitr. z. Lehre von der natiirl, Immunitit. Deutsch. med. Woch., 1898, XXIV, 629. 
? Phisalix and Bertrand. Recherches sur ’immunité du hérisson contre le venin de vipere. C. R. 
Soc. Biol., 1895, 10 ser. II, 639. Ibid. Bull. de Muséum d’Histoire natur., 1895, I, 294; op. 
cit., ET, x00. 
8Calmette. Les venins, 1907, Paris. 
