XXXIII.] INDEPENDENT MUSCULAR EXCITABILITY. 191 



nerve, and then 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. 



(f.) Inject a few drops of a i p. c. solution of curare into the 

 ventral lymph-sac. The poison will be carried to every part of the 

 body except the left leg below the ligature. The animal is rapidly 

 paralysed (20-30 mins.), but if the non-poisoned leg (left) is 

 pinched, it is drawn up, while the poisoned leg (right) is not, i.e., 

 there is a reflex movement of the non-poisoned limb, so that the 

 afferent (sensory) nerves, spinal centre and motor nerves are still 

 unaffected. 



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

 the poison, i.e., when all reflexes cease, 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 contraction. 

 Therefore the poison has acted either on nerve or muscle. 



(ii.) Stimulate the rigid gastrocnemius muscle ; it contracts. 

 Therefore the poison has acted on some part of the nervous path, 

 but not on the muscle. 



(iii.) Stimulate the left sciatic above the lir/ature ; the left leg 

 contracts. The part of the nerve above the ligature was supplied 

 with poisoned blood, 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 sciatic nerve; 

 there is no contraction, but on stimulating the muscle itself con- 

 traction takes place. 



The independent excitability of muscle is further proved by 

 other experiments, all of which we owe to "W. Kuhne. 



(1) The Sartorius experiment (p. 191). 



(2) Kiihne's Curare experiment (p. 194). 



(3) The Gracilis experiment (Lesson L.). 



3. Kiihne's Sartorius Experiment. 



(a.) Isolate the sartorius (fig. in) by the method given at 

 p. 1 86. Suspend the muscle by the thread tied around its tibial 

 attachments, i.e., with its iliac end downwards. 



(b.) Allow the iliac end to dip into a drop of pure glycerin 

 placed on a greasy surface. The muscle gives no response. Why ? 



