1903.] Action of the Poison of the Hydropliidce. 315 



placed in 0'83 per cent. NaCl for about two hours, this strength having 

 been found recently by Dr. N. H. Alcock (to whom I am indebted for 

 much help throughout this investigation) to be the optimum one for 

 nerves. 



The poison was used in strengths of from 10~ 6 to 10~ 3 , and the 

 nerves were exposed to their influence for from 1 5 minutes in the 

 case of the stronger solutions, and up to 1 hour in the weaker one, but 

 with entirely negative results. In one experiment a 1 per cent, solution 

 was used up to 5 minutes without any poisonous effect on the nerve 

 being produced, although this is a stronger solution than I have ever 

 used for injection. It is evident, then, that the poison of the Enhy- 

 drina does not produce paralysis by any direct action on the nerve 

 fibres. 



That it does act by paralysing the muscle end-plates, as in the case of 

 Cobra venom, is shown by the following experiments on etherised frogs. 



Frog. Weight 20 grammes. Etherised. Eight thigh ligatured, 

 excluding the sciatic nerve. 0*2 milligramme Erihydrina poison in 

 0-2 c.c. 0'9 per cent. NaCl injected into dorsal lymph sac. (10 milli- 

 grammes per kilo. = 20 minimal lethal doses.) 



Respirations per minute. 



19 



5 



Respirations finally ceased. Heart still beating 4 hours later. After 

 cessation of respiration the frog was pithed, and when the spinal cord 

 was destroyed, the ligatured (protected) limb only showed contraction 

 of the muscles. Both the sciatic nerves and leg muscles were then 

 tested with the interrupted faradic current, with the following results : 



Distance of Contraction 

 secondary coil. of muscle. 



Protected limb, nerve 40 mm. Good. 



muscle 30 Good. 



Poisoned limb, nerve ... Nil. 



muscle 30 Good. 



This is a typical curara effect, and on proceeding to test the negative 

 variation of the current of injury of the sciatic nerves of each limb, 

 after placing them in 0'83 per cent. NaCl for 2 hours, both nerves were 

 found to give it well, that of the poisoned limb being slightly the 

 stronger of the two, probably owing to partial drying of that of the 

 protected limb over the ligature. 



The above experiment was repeated with a dose of 5 milligrammes 



