SNAKE VENOMS 177 



by snakes of various kinds. Cobra venom contains chiefly 

 neurotoxin, hence the symptoms of cobra bite are largely of 

 nervous origin, with but little local tissue change. Rattlesnake 

 venom owes its effects chiefly to hernorrhagin, hence the marked 

 local necrosis and extravasations of the blood, and the general- 

 ized hemorrhages ; the nervous effects following viper bite are 

 probably, in part, due to hemorrhages in the nervous tissue. 

 Cobra venom produces great hemolysis and little agglutination. 

 Rattlesnake venom has relatively little agglutinative or hemo- 

 lytic power. Water moccasin and copperhead venoms are more 

 agglutinative than either, and intermediate in hemolytic strength ; 

 they cause much local tissue destruction. 



The exact action of cobra venom on various centers and organs has 

 been studied by Elliot. 1 It raises blood pressure when in dilution of 

 1 : 10, 000, 000, by contracting vessels and stimulating the heart; low lethal 

 doses kill by paralyzing the respiratory center. 



Krait (Bungarus ccerulues) venom acts similarly, but less powerfully, 

 and cannot be neutralized by Calmette's antivenin. 2 



Sea-snake venoms are by far the most poisonous of all. For Enhy- 

 drina valakadien the lethal dose for rabbits is 0.00006 gram per kilo 

 body weight. It acts by vagus stimulation and paralysis of respiratory 

 centers and of motor nerve-endings. 3 



Russell' s viper (Daboia Russellii] owes its effects chiefly to intravascu- 

 lar clotting, according to Lamb and Hanna, 4 and contains no neurotoxin. 

 It is not neutralized by Calmette's antivenin. The clots are due to 

 agglutination and contain no fibrin (Flexner). 5 



The " Gil a monster " (Heloderma suspectum) seldom causes serious 

 poisoning in man, but may kill small animals, such as frogs. Its poison 

 is only slightly hemolytic ; but produces degenerative changes in the 

 nervous system (Langmann). 



I/oss of Bactericidal Powers. The frequency of 

 marked and persistent sloughing and suppuration at the site of 

 snake-bites, particularly from the vipers, and the common termi- 

 nation in sepsis, was attributed by Welch and Ewing 6 to a 

 loss of bactericidal power of the blood, which they found followed 

 experimental venom poisoning. This has been nicely explained 

 by Flexner and Noguchi as the result of saturation of serum 

 complement by the numerous amboceptors of the venoms, so 

 that no complement is left for the serum to use against the bac- 

 teria. In serum whose complements do not combine with the 



1 Lancet, 1904 (i), 715. 



2 Elliot, Sillar, and Carmichael, Lancet, 1904 (ii), 142. 



'Eraser and Elliot, Lancet, 1904 (ii), 141 ; also Kogers, Jour, of Physiol., 

 1903 (30), iv. The above are also given completely in the Philosophical 

 Transactions of the Koyal Society, 1904-5, vol. 187. 



4 Jour, of Path, and" Back, 1902 (8), 1. 



6 Thorough study by Van Denburgh and Wright, Amer. Jour, of Physiol., 

 1900 (4), 209. 



6 Lancet, 1894 (1), 1236; Ewing, Med. Record, 1894 (45), 663. 



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