338 Chapter XI 



viper's venom ig about forty times as great as that of the guinea-pig, 

 that is to say the hedgehog, though far from possessing an absolute 

 immunity, nevertheless exhibits a much greater resistance than do 

 most animals. Lewin^ convinced himself of this fact as regards 

 adult hedgehogs, though young animals, according to him, are much 

 [355] more susceptible. Thus, he has seen a young hedgehog that had 

 been bitten by a viper die after nine days' illness. This observation 

 speaks in favour of the conclusion that the immunity of the hedge- 

 hog might be naturally acquired rather than a really natural im- 

 munity. The hedgehog, hunting all kinds of small animals, might 

 often be bitten by vipers and in this way acquire its immunity 

 against the venom. Under these conditions we can readily conceive 

 that the blood of this " insectivoran " might be placed in a position 

 to develop a specific antitoxic property. 



When Lewin tried to satisfy himself of the existence of this 

 property by direct experiment he could only show that the blood 

 of the hedgehog was powerless to prevent the lethal effect of the 

 viper's venom on small animals. But here, as in his researches on 

 cantharidine, he did not take into account the inherent toxicity of 

 the blood of the hedgehog. Phisalix and Bertrand^, who have 

 also studied this question, have obtained results at variance with 

 those of Lewin. They demonstrated first of all that the blood of 

 normal hedgehogs was capable of intoxicating and even of killing 

 laboratory animals such as the guinea-pig. It is quite natural, there- 

 fore, that the mixture of this fluid with viper's venom could not be 

 tolerated. It was, however, sufficient to heat the blood of the hedge- 

 hog to 58° C. for it to become not only innocuous of itself, but even 

 for it to exhibit an antitoxic action against snake venom. Thus, 

 guinea-pigs which had received 8 c.c. of heated hedgehog's serum 

 into the peritoneal cavity, were at once in a condition to resist double 

 the lethal dose of viper's venom. Phisalix and Bertrand conclude, 

 therefore, that " the natural immunity of the hedgehog against the 

 viper's venom is due to the presence in its blood of an immunising 

 , substance." The same observers^ satisfied themselves that horse's 

 serum and even that of the guinea-pig exercise an undoubted anti- 

 venomous action ; yet these animals are anything but insusceptible to 

 snake venom. Moreover, the necessity to heat the blood to 58° C, as a 



1 Deutsche med. Wchnschr\, Leipzig, 1898, S. 629. 



2 Compt. rend. Soc. de Uol, Paris, 1895, p. 639. 



3 Bull. Museum d^hist. nat, Paris, 1896, t. ii, p. 100. 



