LESSON II. NERVE STIMULATION. 

 REACTION OF MUSCLE. 



1 . Cut off the head of a pithed frog, and squeeze the 

 body upwards to remove most of the blood. Cut away 

 the skin on the lower half of the back. Lift up the tip of 

 the urostyle with forceps, and cut through the muscles 

 attached to it, keeping the scissors glose to it. Cut away 

 the urostyle. Lift up the cut muscles on one side, and 

 separate from them the nerves seen below. Cut away 

 the wing of the iliac bone (which runs parallel with the 

 urostyle) so that the nerves of the lumbo-sacral plexus 

 (7th, 8th, 9th) are exposed. Pass a thread under the 

 nerves close to the vertebral column, tie them and cut 

 them above the knot. On tying there will be contraction 

 of the leg (mechanical nerve stimulation). Lift up the 

 nerves by the thread, and isolate them down to the 

 pelvis where they form the sciatic and crural nerves. 



With strong scissors cut through the pelvis, keeping 

 to the mid line between the legs so as not to injure the 

 sciatic on either side. Cut through the remaining tissue 

 connecting the leg to the body. The nerves of the oppo- 

 site side will be required for 3. 



2. Chemical nerve stimulation. Place the nerves 

 over the rim of a watch glass filled with saturated sodium 

 chloride solution, cutting off the ends close to the liga- 

 ture. There will soon be twitching of the muscles of the 

 leg, due to chemical stimulation of the nerve. Cover 

 the leg with wet blotting paper and keep for 7. 



