thigh muscles with forceps and isolate the nerve upward, taking 

 care not to injure it where it passes over the dorsal side of the 

 pelvic bones, and thence forward ventrally to arise from the cord 

 by several roots, clearly visible when the intestine and kidneys have 

 been removed. 



Cut the roots as near the spinal cord as possible. What happens? 

 Cut through the femur in the middle and remove the thigh muscles 

 without injuring the nerve, cut the tendon of Achilles below the 

 ankle, separate the gastrocnemius muscle from the other muscles 

 of the calf and cut the calf just below the knee. You now have 

 a gastrcenemius-sciatic preparation. Keep moist with physiological 

 salt solution ( why ? ) and avoid touching muscle or nerve tissue with 

 forceps 



Fix the cut end of the femur in a femur clamp and lay the nerve 

 on a glass slide supported by another clamp. Attach with thread 

 a lo-gram lead weight to the tendon of Achilles. 



182. Mechanical stimuli. Pinch the end of the nerve, or tap 

 with a glass red. Result ? Try tapping a muscle directly, using 

 some other muscle of thigh. Result? 



183. Thermal stimuli. Touch the nerve with a warm glass rod. 

 Also a muscle as in the preceding experiment. 



184. Chemical stimuli. Place a few drops n/io HC1 on the 

 extremity of the nerve. Result? 



185. Electrical stimuli. Galvani's experiment. Prepare a nerve- 

 muscle preparation and lay the nerve across a pi>ece of filter paper, 

 soaked in physiological salt solution, on the china plate. 



a. Gently touch the nerve with a copper wire and the muscle 

 with an iron wire. Any result? Now touch the ends of the Cu and 

 Fe wires together. What happens? Can you explain this? If the 

 \\ires are corroded, file a clean surface at the points of contact. 

 Try the same 'experiment with two wires of of the same metal. 



b. Touch the muscle alone and the nerve alone with the Cu 

 and Fe wires in contact at the opposite ends. Result? 



c. Touch the filter paper near the nerve (but do not touch 

 the nerve itself ) with Cu and Fe wires about i cm. apart with their 

 line of junction parallel with the nerve. Xow bring into contact 

 the opposite ends of the wires. 



d. Try the same experiment, but place the wires on each side of 

 the nerve, but not touching it. 



>e. Try the same experiment with the muscle. Do you obtain 

 the same result? Explain. If the gastrocnemius muscle does not 



49 



