TOXICITY OF THE BLOOD OF VENOMOUS SNAKES 219 
vipers (Phisalix and Bertrand!), and that the Cobra is relatively 
little affected by inoculation with its own venom or with that 
of other COLUBRID, such as Bungarus, or even of VIPERIDA, 
such as Vipera russellii. 
This immunity, however, is far from being absolute; I have 
killed common snakes (T'ropidonotus natrix) with doses of viper- 
venom ten times greater than the lethal one for the rabbit, and 
Lachesis lanceolatus (from Martinique) with 0:02 gramme of the 
venom of Naja tripudians. 
Phisalix,? on his part, has shown that, while it was necessary 
to inject from 100 to 200 nulligrammes of viper-venom into other 
vipers or common snakes, beneath the skin or into the peritoneum, 
in order to cause death, the introduction of only 2 to 4 milligrammes 
of this venom into the brains of these reptiles was sufficient to kill 
them with the same symptoms of intoxication. This dose, how- 
ever, is only twenty-five to thirty times greater than the lethal one 
for the guinea-pig. 
The practical lesson to be learnt from the establishment of the 
foregoing facts is that poisonous snakes of different species must 
never be placed in the same cage, for these animals sometimes bite 
each other, and may thus kill one another. 
Simon Flexner and Noguchi* have studied the action of the 
serums of Crotalus, Ancistrodon, and a non-poisonous species, the 
pine snake (Pituophis catenifer), on the venoms of Naja, Ancis- 
trodon, and Crotalus. They found that the serum of Crotalus 
rapidly dissolves the red corpuscles of man, the dog, rabbit, guinea- 
pig, sheep, rat, pigeon, and horse. 
The serum of the pine snake affects the same red corpuscles, 
but in a lesser degree. Heating to 58° C. suppresses the hemolytic 
power of these serums, but they can be restored to activity by the 
addition of a very small quantity of the same serum in a fresh 
' Archives de Physiologie, 1894. 
* Comptes rendus de la Société de Biologie, July 25, 1903. 
* Journal of Pathology and Bacteriology, May, 1903. 
