92 TOXINS AND ANTITOXINS. 



between the injections. At the end of about two 

 months of this treatment, the immunity has reached 

 its maximum. Certain rabbits, thus slowly in- 

 oculated, have been able to withstand 0.04 Gm. 

 of the venom of the naja at a single injection; 

 such rabbits then yield a vaccinal serum.* 



At the Institut Pasteur at Lille there is prepared 

 in this manner an antivenomous serum from the 

 horse; it is capable of acting upon 20000 times 

 its own weight. This has rendered great service 

 in the treatment of snake-bites, particularly in 

 hot countries, where the accidents are of daily 

 occurrence. In vitro it acts quite as well pre- 

 ventively as therapeutically. It arrests the effects 

 of the naja, the horned ceraste, the trigonocepha- 

 lus, the rattlesnake, and of almost every one of the 

 venomous serpents known. 



The relatively considerable immtinity possessed 

 by certain snake-charmers, and which passes for a 

 magical gift, is due to nothing else but a natural 

 immunity, acquired perhaps by heredity, and 

 it always appears to follow as a result of a non- 

 fatal snake-bite. 



Venoms of Batrachians and Saurians. — We 

 observe here a fundamental difference between 

 these poisons and those of snakes, as we shall 



* Annal. de I'Instit. Pasteur, 1895, p. 229; Compt. rend, de 

 I'Acad. des Sciences, cxxii, p. 203. 



