VENOMS OF POISONOUS SERPENTS. 477 



Phisalix and Bertrand in 1893 confirmed Fontana's previous 

 observation that the garter-snake (couleuvre) was unaffected by 

 repeated bites from vipers or by subcutaneous injection of the 

 venom of the viper. These authors showed that a dose of the 

 venom sufficient to kill 15 to 20 guinea-pigs was without effect 

 on the garter-snake. The natural immunity of the garter-snake 

 to the viper venom is thus firmly established. From previous 

 researches on the natural immunity of the " crepaud " and 

 viper to their own venoms Phisalix and Bertrand showed that the 

 blood or serum of these serpents contained the same poison, echidnin, 

 as was present in the venom. Similarly the blood or serum of the 

 garter-snake when injected in doses of 1.5 c.c. intraperitoneally into 

 guinea-pigs produced death in two hours with the same symptoms 

 as are observed after poisoning with viper venom. Although the 

 several forms of garter-snakes are considered as non-venomous, they 

 nevertheless secrete through the superior maxillary gland (or special 

 glands, Jourdain) toxic products analogous to echidnin, which are 

 excreted into the blood, rendering this, therefore, highly poisonous, 

 and at the same time establishing natural immunity. After the 

 ablation of the venom glands in the viper the blood loses a part of 

 its toxicity, showing that the source of the poison in the blood is the 

 venom gland. It would seem that this immunity is one of tolerance 

 and analogous to that which Sewall obtained with rattlesnake venom. 



Later (February, 1894), Phisalix and Bertrand showed that viper 

 venom heated to 75°— 85° for five minutes lost its poisonous property 

 with respect to guinea-pigs and acted as a vaccine. The temperature 

 of animals, however, was raised, whereas with unheated venom it is 

 lowered. They were, therefore, led to believe that viper venom 

 contained (1) a phlogogenic substance like the diastases — echidnase, 

 and (2) a general poison — echidnotoxin. Since both are destroyed by 

 heat the vaccine results either from the destruction of these two sub- 

 stances or is preformed in the venom and acts after the toxic prin- 

 ciples are destroyed. This behavior of venom to heat and to the 

 production of immunity is analogous to Frankel's method of produc- 

 ing immunity to diphtheria. 



The heated viper venom, or vaccine, does not impart immediate 

 immunity to guinea-pigs, but this condition follows after the lapse of 

 several days — a result of the reaction of the organism. An anti- 

 toxin appeared in the blood after the injection of the echidnovaccine, 

 and in less amount in the blood when immunity has been estab- 

 lished by tolerance. The amount of antitoxin in the blood could be 

 increased as in the case of tetanus and of diphtheria. A very short 

 time afterward Calmette confirmed the observations that animals 

 could be immunized by repeated injections of the venom, beginning 

 in small doses and gradually increasing. A single non-fatal injec- 

 tion of venom may produce antitoxin in the blood of the animal. 



