CHAPTER IV. 



Action of curari. Destroy the brain of a frog 

 by passing a sharp splinter of wood through the 

 occipital foramen after cutting through the occipito- 

 atlantoid ligament. Ligature the blood-vessels of 

 one leg, taking care to avoid injuring the accom- 

 panying sciatic nerve. Or the whole leg can be 

 tightly tied round with a tape so as to stop the 

 circulation in it. A drop of one per cent, solution 

 of curari is now injected under the skin of the back, 

 and the frog is left for about an hour. The drug 

 will have penetrated to all parts except the liga- 

 tured leg. The following observations and experi- 

 ments are to be made upon the curarized animal : 



(1) Notice that all the muscles are paralyzed 

 except those of the ligatured limb. 



(2) On tapping any of the paralyzed parts the 

 foot on the ligatured side is moved. 



(3) Strip the skin off both legs and isolate both 

 sets of sciatic nerves at the back of the abdomen. 

 Tie their upper ends and cut them away from 

 the vertebral column. Excite both sets of nerves 

 high up, placing them upon the same electrodes 

 and observe the difference of effect. Excitation 

 of the nerve of the limb which has been exposed 

 to the poison produces no contraction of its 

 muscles ; excitation of the nerve of the ligatured 

 limb produces the usual effect. Now stimulate 

 the muscles of the two limbs, applying the elec- 



