378 THE SNAKES OF SOUTH AFRICA. 



Venom may be extracted from a snake once fortnightly in 

 the intervals of feeding and moulting. Venom will keep in- 

 definitely if mixed in equal parts with pure glycerin. It cracks in 

 all directions when dried, and after scraping it together it presents 

 the appearance of yellow sugar or granules and flakes of gum. 



Effect of the Venom of one Snake upon other Snakes. 



The venom of the Puff Adder apparently has no poisonous 

 effect upon those of its own species imless injected in large doses. 

 Of fifteen Puff Adders inoculated with varying doses of from 

 four to eight drops of their own venom only two died. Subse- 

 quent experiments showed that these snakes varied in their 

 degree of resistance to venom. Five-drop doses of Night Adder 

 (Causus) venom produced no poisonous symptoms. 



Five drops of venom were taken from a Puff Adder; six from 

 another; seven from a third. The venom was injected into the 

 snakes from which it was taken. All remained unaffected. The 

 experiment was repeated ; one which received five drops of its 

 o\vTi venom died in six days, and a second, which had eight 

 drops, died on the fifth day. Six more were tested — one died. 



Puff Adders occasionally die when bitten by snakes of other 

 species such as the Cobra, Ringhals, Mamba and Boomslang. 

 Extreme internal haemorrhage occurred in two bitten by a 

 Boomslang. However, it is only now and then that Puff Adders 

 die when bitten by other venomous snakes. I have several 

 times injected Puff Adders with Cape Cobra venom, and in other 

 cases allowed the reptile to inflict a full bite in the tail region. I 

 have injected five drops at a time under the skin of a Puff Adder 

 without poisonous effect. This means that in these cases the Puff 

 Adders withstood enough Cobra venom to kill three or four men. 



It will thus be seen that the venom of the Puff Adder is not 

 poisonous to itself or those of its own species, or even if one be 

 allowed to bite itself, or if its venom be collected and injected 

 hypodermically into it imless the dosage is comparatively heavy. 

 This would seem to indicate that the blood of a Puff Adder 

 should be an antidote to its own venom, and others of its 

 species. Strange to say this is not so. Collecting the venom 

 from a Puff Adder I measured out three drops, and kiUing the 

 snake, I took half an ounce of its blood and mixed the three 

 drops of venom with it and allowed it to stand five minutes. 



