77 



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

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

 animal. 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? 



303. Place similar pieces of paper upon different portions 

 of the body. Note any variety of movements and what seems 

 to be their purpose. 



304. 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 ? 



305. Open the abdomen and draw out a loop of intestine. 

 Expose the heart and while its movements are under observa- 

 tion, strike or pinch the intestine ; the heart is temporarily 

 arrested. If you divide the vagi or completely destroy the 

 oblongata and repeat the stimulus, the arrest does not occur. 

 Or instead of the intestine you may employ strong stimula- 

 tion of a limb by the sudden tightening of a string around it. 

 The heart will stop, and the body of the frog will become 

 inert and flaccid, and will not respond to cutaneous stimuli. 

 The bulbo-spinal axis is in a state of " shock ". [Waller]. 

 (An unpithed frog may be required for the success of this 

 experiment) . 



306. Inject 3 to 5 minims of 0.2% strychnine solution 

 under the skin of the frog's back. Let it remain for a few 

 minutes and then note the effect of the slightest stimulus, 

 such as jarring the table upon which it lies. Then give 10 

 to 20 minims of 10% chloral hydrate with a pipette. Make 

 sure that the fluid reaches the stomach. Note if there is any 

 effect upon the convulsions. 



307. 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. 



308. 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, using 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 



