249 VENOMS 
means of successive inoculations with heated venoms, to confer on 
animals a certain degree of resistance to doses invariably lethal to 
the controls. 
From 1894 onwards, the investigations pursued simultaneously 
at the Paris Natural History Museum, by Phisalix and Bertrand, 
upon viper-venom, and at the Paris Pasteur Institute by myself, 
upon that of the cobra, and subsequently upon other venoms of 
various origins, led to much more definite results. These investi- 
gations show, on the one hand, that by vaccinating guinea-pigs 
or rabbits, and taking certain precautions, it is possible to confer 
upon these small animals a really strong immunity to venom ; on 
the other hand, that animals vaccinated against cobra-venom are 
perfectly immune to doses of viper-venom or that of other snakes 
(Bungarus, Cerastes, Naja haje, Pseudechis) certainly lethal to the 
controls ; and lastly, that the serum of the vaccinated animals 
contains antitoxic substances capable of transmitting the immunity 
to other animals. 
According to Phisalix and Bertrand, who, as we have stated, 
experimented only with viper-venom, the best method of vac- 
cinating the guinea-pig consists in inoculating a dose of 0-4 milli- 
gramme of this venom heated for five minutes at 75° C., and, 
forty-eight hours afterwards, the same dose of non-heated venom. 
The latter is always lethal to the control guinea-pigs in from six 
to eight hours. 
Vaccination against cobra-venom, which is much more toxic, 
is most surely effected by the method recommended by me, which 
consists in at first injecting small doses of this venom mixed with 
an equal quantity of a 1 per cent. solution of hypochlorite of 
lime. By degrees the quantity of venom is increased and that of 
the hypochlorite progressively diminished, and the injections are 
1 Comptes rendus de l'Académie des Sciences, t. 118, February, 1894, p. 356; 
March, 1894, p. 720; Comptes rendus de la Société de Biologie, February, 1894, 
pp. 111, 120 ; Archives de Physiologie, July, 1894; Annales de l'Institut Pasteur, 
May, 1894, p. 275, April, 1895, p. 225. 
