POISONOUS SNAKES OF NORTH AMERICA. 479 



undertook and leported * npon a series of experiments with massa- 

 sauga venom on pigeons. Tlie conclusions drawn were that repeated 

 inocuhition with sublethal doses produced a continually increasing- 

 resistance toward tlie injurious eftects of the poison without apparent 

 influence on the general health of the animals. It was also shown, 

 however, that the efficiency of resistance against the venom gradually 

 fails in absence of fresh inoculation, although at least one of the 

 pigeons retained its immunity over an interval of five months. 



There is another class of observations which have a certain bearing 

 on this question. 



It has been long known, although occasionally doubted or contra- 

 dicted, that the poisonous snakes are proof against their own venom. 

 Big doses of snake venom have repeatedly been inoculated into the 

 bodies of the producers themselves absolutely without effect. The cur- 

 rent stories of "suicides" of rattlesnakes are easily explained, and in 

 none of the many cases reported is there any conclusive proof that 

 death resulted from a self-inflicted wound. It is also well known that 

 a number of the so-called harmless snakes remain unaffected whether 

 bitten by a venomous snake, or inoculated in the laboratory with enor- 

 mous doses. 



Considerable light has very recently been thrown upon this curious 

 immunity, as well as the question of preventive inoculation, by the 

 studies and experiments of two French physiologists, C. Phisalix and 

 G. Bertrand, who are at the present moment, I believe, still engaged in 

 further work along the same lines. They have published a series of 

 articles in the Comptes Eendus of the French Academy of Sciences, 

 describing their experiments with the venom of the viper. Having pre- 

 viously found that the blood of the toad and the salamander contain the 

 same toxic principles they turned their attention to the viper. Guinea 

 pigs were injected with the blood of the viper and died within two hours 

 under the ordinary symptoms of Yiper-bite poisoning; tlie post mortem 

 examination gave the same result; and an examination of the poison in 

 the viper blood showed it to be insoluble in alcohol. Tlie authors con- 

 clude that there exists in the blood of the viper some agent similar to 

 the venom; that it is due to an internal secretion of the glands, and 

 that the presence of this toxic principle in the gland must be considered 

 as the true cause of the immunity of the vij^er from its own venom. t 



The next step was to examine the blood of some of the poison-proof 

 harmless snakes, the two French species of. Natrix being selected for 

 the purpose. Guinea pigs injected in a similar manner as in the 

 experiments with the viper blood .gave similar results — they died in two 



* Experiments on the Preventive Inoculation of Rattlesnake Venom. Jour. 

 Physiol., Cambr., 1887, viii, pp. 203-210. 



tToxicite du sang de la vipere {Viprra aspis, L. ). Comjit. Rend. Ac. So. Paris, 

 own, No. 26, Dec. 26, 1893, pp. 1099-1102. Extr. in Rev. Scientif. (4), i, No. 1, p. 

 23 (1894). 



