ON THE COMMON INDIAN SNAKES. 733 



Toxicity. — As will be seen from the annexed table it is impossible 

 from the present available research work to draw a comparison be- 

 tween the relative virulences of krait and cobra venoms. The inves- 

 tigators quoted are all men of the greatest ability, their work when 

 critically studied is convincingly careful and precise, and yet their 

 results vary enormously. Rogers makes it appear that krait venom 

 is about twice as deadly as cobra venom. Fraser's results compared 

 with Elliot, Sillar and Carmichael's show that cobra venom is four 

 times as potent as krait venom, and Lamb's results compared with 

 the same trio's concedes to cobra venom a toxicity twenty times that of 

 the krait. Lamb,* however, from his own researches with both poisons 

 on rabbits, shows that krait venom is proximately four times as 

 virulent as cobra venom. In considering the question it must be 

 borne in mind that samples of venom from individuals of the same 

 species vary somewhat, thus Lamb fixed the minimal lethal dose of 

 cobra venom for rats with one sample at *04 milligrammes per 

 kilogram weight, and with another sample found it was "07 milli- 

 grammes.! Again animals vary in their susceptibility to different 

 venoms, thus Lamb found a rat more susceptible to cobra venom than a 

 rabbit, but a rabbit more susceptible than a rat to Enhydrina venom. % 

 It is reasonable to suppose that the quality of the secretion may be 

 affected by health, in fact we know it is, for Lamb has remarked with 

 others on the decrease in quality and quantity of venom in snakes 

 kept in captivity. Doubtless season, and possibly youth, and old age 

 similarly affect the poison secreted. Further there are the conditions 

 affecting the animals experimented upon. Not all individuals of the 

 same species are equally susceptible, and health and age doubtless 

 modify their susceptibility. Again I have shown, I think, good reason 

 to suppose that the snake Bungarus candidus as hitherto understood 

 includes 3 or 4 forms which may be distinct species. If all these forms 

 areimixed up, and their poisons which may be very different in toxi- 

 city, collected together as krait venom, this alone might account for 

 .the conflicting results. In future experiments I think every care 

 should be taken to keep the poisons of the various forms apart. 



* " Snake poison and Snake bite, " p. 8. This reference is the same as that appearing in 

 .Clifford Allbutt's System of Medicine (Lamb and Martin). 



t Memoirs officer?. Govt, of India No. 5, p. 14. J Loc. cit., p. 7. 



