68 



317- Pass a hook through its lower jaw and hang it to 

 the ring of a retort stand. How do the hind-limbs behave ? 



318. Pinch very gently the tip of one of the toes, what 

 is the effect ? 



319. Fill two glasses, one with dilute sulphuric acid, the 

 other with water. Raise the glass containing the acid, un- 

 til the acid just touches the tip of the toes. Is the foot 

 withdrawn ? If so, raise the second glass and let the foot 

 be immersed in it, to wash off the acid. 



320. Cut a small piece of filter or blotting-paper, moisten 

 it with strong acetic acid and place it on the flank of the an- 

 imal. What is the effect upon the leg ? Put the piece of 

 paper upon the opposite flank and hold the leg so as to pre- 

 vent it from moving. Is there any action of the opposite 

 leg? 



32 1 . Place similar pieces of paper upon different portions 

 of the body. Note any variety of movements and what 

 seems to be their purpose. 



322. Remove the frog from the hook and plunge it in a 

 basin of water. This will wash off the acid. Does the 

 frog make any movements in the water? Does it float ? 



323. Inject a small amount of strychnine solution under 

 the skin of the frog's back. L,et it remain for a few 

 minutes and then note the effect of the slightest stimulus, 

 such as jarring the table upon which it lies. 



324. With a tracer or piece of wire destroy the myel, the 

 convulsions cease. Try any of the preceding .stimuli upon 

 the frog now and note the result. 



325. Make a nerve-muscle preparation of one of the hind 

 limbs. Dissect away the skin and muscles upon the dorsal 

 aspect of the leg, until the sciatic nerve is exposed, leaving 

 it connected with the lumbar plexus. Denude the femur of 

 its muscles, Uising the greatest care not to injure the sciatic 

 nerve. Keep the nerve moist with normal salt solution. 

 Pass a copper hook under the sciatic nerve and hang to a 



