SNAKE VENOMS 151 



and inverts saccharose, but does not digest starch. ^Martin -^ found 

 f.brin ferments in various venoms, which are probably important 

 aji'ents in causing tlirombosis. There are also active lipases in ven- 

 oms, to which many of the effects, especially hemolysis and fatty de- 

 genei-ation of the tissues, may be at least partly due (Noguchi), and 

 the hemolysin of cobra venom seems to be a lipase that splits lecithin 

 into hemolytic substances (Coca)."^'' 



Toxicity. — Calmette has determined the toxicity of several venoms, 

 and gives the following tlgures : 



1 crni. cohra or a.s/)i.s kills 4000 k<iin. of rabbit. 



1 grm. hopluccphaluft kills 3450 " " '' 



1 ^ni. fer de lanre or psciidirhis kills . . SOO " " " 



1 gm. Crotalus horridus kills .... 600 " " " 



1 gm. Pelias beriis kills . . . . - . . 250 " " " 



The danger of the bite depends not only upon the difference in 

 the strength of the venom of different varieties of serpents, but also 

 upon the size of the snake, the time of year and condition of hunger or 

 plenty, and particularly whether the entire discharge is injected suc- 

 cessfully or not. The fatal dose of cobra venom for an adult man is 

 variously estimated at from 0.01 to 0.03 gm., while the venom of Hy- 

 drophiinae is about ten times as toxic ; for crotalus venom the lethal 

 dose is probably 0.15 to 0.3 gm. (Nogiichi). Probably in the major- 

 ity of strikes, by no means all the fluid ejected by both fangs is in- 

 jected beneath the skin of the victim. A large diamond rattler may 

 eject as much as a half teaspoonful of venom at one discharge and 

 such a dose would usually be fatal. Repeated ejections decrease the 

 strength of the venom rapidly, until it may have almost no toxicity. 

 In general, venom is most active in w^arm weather and immediately 

 after the snake has fed ; in winter its toxicity is slight. 



The mortality in America from snake-bites is very hard to ascer- 

 tain, various authors giving figures at wide variance. The extensive 

 studies of Willson -" show about ten per cent, niortalit}- from all venom- 

 ous snake-bites in this country^ the different species giving figures as 

 follows : Coral snakes, twenty to fifty per cent. ; water moccasins, 

 seventeen per cent. ; large rattlesnakes, eleven to twelve per cent. ; 

 copperheads and ground rattlers, no mortality except in children or in 

 cases of complications. The mortality in children is at least double 

 that in adults. Many deaths from snake-bites of all kinds are due 

 to the treatment rather than to the bite. The poisonous snakes of 

 Australia, although numerous, are not very virulent, and the mortal- 

 ity is given as about seven per cent. A full charge of venom from 

 the cobra and many other Indian snakes is inevitably fatal (Fayrer). 

 The crotaline snakes of the tropics are more venomous than those of 



28 .Jour, of Phvsiol., 1905 (32), 207. 

 2Sa,Joiir. Infect. Dis., 1015 (17), 351. 



29 Arch. Int. Med., 1008 (1), 516 



