ACTION OF CURARE. 159 



a fine silk thread. Moisten the thread with salt solution, 

 and gently pass it under the sciatic artery. Withdraw the 

 needle and ligature the artery. Instead of ligaturing merely 

 the artery, it is better to isolate the sciatic nerve, and then 

 to tie a stout ligature round all the other structures of the 

 thigh. In this way none of the poison can pass by a col- 

 lateral circulation into the parts below the ligature. 



(c.) Inject a few drops of a 1 per cent, solution of curara 

 into the ventral lymph sac, either by means of a hypodermic 

 syringe or a fine pipette. In a short time the poison will be 

 carried to every part of the body except the left leg below 

 the ligature. Observe that the animal is rapidly paralysed, 

 but if the non-poisoned leg (left) is pinched, it is drawn 

 up, while the poisoned leg (right) is not. 



(d.) Wait until the animal is thoroughly under the 

 influence of the poison, and then expose both sciatic nerves 

 as far up as the vertebral column and as far down as the 

 knee. 



(i.) Stimulate the right sciatic nerve. There is no con- 

 traction. Therefore the poison has acted either on nerve 

 or muscle. 



(ii.) Stimulate the right gastrocnemius muscle, it con- 

 tracts. Therefore the poison has acted on some part of 

 the nervous path, but not on the muscle. 



(iii.) Stimulate the left sciatic above the ligature, the left 

 leg contracts. 



Observe that the part of the nerve above the ligature was 

 supplied with poisoned blood, and has been under the influence of 

 the poison, so that the nerve-trunk itself is not paralysed, as may 

 be proved by stimulating any part of the left sciatic as far down 

 as its entrance into the gastrocnemius. Stimulating any part 

 of the left nerve causes contraction. Therefore, neither nerve- 

 trunk nor muscle is affected. The nerve impulse is blocked 

 somewhere, in all probability by paralysis of the terminations of 

 the motor nerves within the muscle. 



(e.) Apply several drops of a strong solution of curare to 

 the left gastrocnemius, and after a time, stimulate the left 



