SNAKES OF CEYLON. 405 



cobra venom. It does not follow, however, that the same 

 relationship would hold good in the human subject. Lamb, 

 indeed, speaking of cobra poison shows that the minimal 

 lethal dose for rats is one-fourth that for pigeons per kilogram 

 weight. 



(e) Lethal dose for Man : It is impossible even to guess at 

 the lethal dose for man, as- the figures above quoted do not 

 support one another. 



(/) Toxins — 



(1) Neurotoxins operating on nerve cells : 



(a) A depressor paralysing the respiratory centre 



(Rogers, Fraser, and EUiot). 

 (&) A depressor paralysing centres ia the bulb (inferred 



from the remarks of Rogers, Eraser, and Elliot), 

 (c) A depressor paralysing nerve endings, the phrenics 



especially (Eraser and EUiot). 



(2) A direct stimulant to cardiac muscle (or nerve 



endings). Very feeble (Fraser and Elliot). 



(3) Toxins affecting the constitution of the blood, 

 (a) Hsemolysin. Very feeble (Eraser and Elliot). 



{g) Analysis of toxic action — 



(1) (a) The " neurotoxin " paralysing the respiratory 



centre is the chief agent in producing death. It is 



powerfully assisted by (1) (c). 

 (&) This neurotoxin evokes symptoms of paralysis of 



the lips, tongue, throat, and voice, 

 (c) This assists (1) {a) in arresting breathing. 



(2) This is so feeble in action as to be altogether a 

 negligible factor in the toxaemia. 



(3) (a) This affects the blood so little that haemorrhages 



are not likely to be seen. 



Qi) Symptoms of Toxeemia : These have only been studied on 

 lower animals in the laboratory. Rogers says there is no 

 difference between the toxic manifestations of this species and 

 the cobra. 



