CHAPTER VI. 



TOXIC SECRETIONS OF VENOMOUS SNAKES. 

 AMOUNTS OF VENOM SECRETED. 



The quantity of venom yielded at one time by a snake, either at a single 

 bite or by squeezing the poison glands, is very variable. It increases, how- 

 ever, in general, in proportion to the size of the snake, although this rule 

 can not be applied to the marine snakes, which secrete an amount that is 

 small in comparison to their size. The continuous failing of health in cap- 

 tivity causes a decrease of venom, both in quantity and in toxicity; especially 

 is this the case where the snakes refuse to take nourishment and are sub- 

 jected to repeated extractions of venom. While it is very important to deter- 

 mine the exact amounts of venom yielded at a single bite, the data bearing 

 upon this subject are rather unsatisfactory. 



Weir Mitchell has noted the difficulty of extracting venom from the rattle- 

 snakes when the latter are resisting forcible manipulation. He has found 

 that more venom can be extracted when the snakes are put under the effect 

 of an anaesthetic, thus relaxing the muscular resistance. Lamb's careful 

 study of the Indian cobra showed that the amount of venom thrown out vol- 

 untarily by a snake is larger than that obtained through forcible compression. 



Calmette gives the detailed results of his experiments on two specimens of 

 Naja haje, about 5.5 feet long. During 120 days in his laboratory one was 

 subjected to 5 and the other to 6 extractions. In the fresh state the total 

 amount of the venom for the first specimen was 0.581 gm. (per 5 extractions) 

 which weighed 0.174 gm. in the dried form. The second snake afforded 

 (on 6 extractions) 0.684 gm- fresh venom, which weighed 0.202 gm. on dry- 

 ing. Thus the average single amount of venom to be ejaculated by the adult 



. . . 0.581 -f 0.684 . .1 r 1 , , 1 0-174 + 0-202 



Naia haie is — ;: = o. 1 1 5 gm. m the fresh state and — - — —7 



■'^ 5-f-6 ^ ^ 5 + 6 



= 0.0331 gm. in the dried form. He also found that i gm. of the fresh venom 



weighed 0.336 gm. upon complete desiccation over calcium chloride. With 



Naja tripudians, Cunningham estimated the amount of a single bite at 0.254 



gm. (dried); Lamb at 0.231 gm. (extracted with fingers, dried); 0.373 8^- O^Y 



voluntary bite, dried); and Rogers at 0.249 S^- (dried). 



With Pseudechis porphyriacus, MacGarvie Smith gives the amounts of 

 single bite at o.i gm. to 0.16 gm. in the fresh state and 0.024 gm. to 0.046 gm. 

 in the dried form. 



With Notechis scutatus s. Hoplocephalus curtus the same author gives the 

 amount of venom produced at a single bite at 0.065 g"^- to 0.15 gm. liquid 

 and 0.017 g"^- to 0.055 gn^- dried. The dried venom weighed from 9 to 38 

 per cent of the fresh venom. 



Dahoia russellii yields on an average 0.15 to 0.25 gm. weighed dry (Lamb). 



70 



