SNAKE-VENOM AND ITS EFFECTS, ESPECIALLY C)!^ ^ 

 OTHER SNAKES. /C^^^^^C y 



'vc o" "o. 



By F. W. FiTzSiMONS, F.Z.S., F.E.M.S., /^ 



i'" ^•^ ^- 



Director, Fort Elizabeth Museion. 



LIBRARY 



Read July 17, 1920. 



Experimenting- with snake-venom is beset with many 

 difficulties, one being that snake-venom varies in its poisonous 

 properties in the same snake, a*nd is sometimes as much as five 

 times as poisonous as at other times. These fluctuations are 

 due to the season of the year and the general condition of the 

 snake. 



Well-fed snakes, fresh from the veld or forest in mid- 

 summer, yield an abundant supply of A^enom, as would be 

 anticipated, but I have recently ascertained that this venom, 

 when dried, does not yield nearly so much solid extract as when 

 venom is taken from snakes after they have been in captivity 

 for some time Avithout food. In this case the A'enom is con- 

 vsiderably less in quantity, but more concentrated in its 

 poivsonous properties, yielding two to five times the amount of 

 dried extract that would be obtained from the venom taken 

 from freshly captured snakes in good condition. Again, if a 

 sample of venom, is taken from a snake before sloughing its 

 skin, and also immediately after the process, it will be found 

 that the latter sample of poison is more concentrated than the 

 former, and will yield a much greater quantity of dry extract. 



It will thus be observed that the experimenter cannot, 

 with any degree of certainty, determine the exact lethal dose 

 for each species of animal unless he tests each lot of A^enom 

 with which he is about to conduct experiments. 



My attention was first drawn to the fluctuations in the 

 poisonous (toxic) power of A'enom by the difference in the 

 weight of the dry extract from measured quantities of fluid 

 A'enom. One day, noticing that a puff adder {Bitis arietans), 

 which had been in confinement for six months, was in a very 

 emaciated condition owing to its persistent refusal to eat, 

 I caused it to be remoA^ed. Before putting it to death I 

 extracted what A-enom it had, Avhich was fiA'e drops. This was 

 noticed to be less fluid than the venom from fresh puff adders, 

 and yielded three times the weight of dry extract compared 

 Avitli that produced from the A^enom of fresh snakes of the same 

 species. One drop of this A-enom Avas fatal to a fowl, whereas 

 other fowls recoA^ered easily after being injected with two 

 and a half drops of the A^enom of a fresh i)uff adder. Another 

 fowl recovered Avith difficulty after a subcutaneous injection of 

 three drops of the latter venom. 



