ADVANCED EXPERIMENTAL PHYSIOLOGY 



89 



length of nerve, which lies on the ventricle, so that the current may 

 not be short circuited. 



Fin. 84. Diagram of the experiment to show the stimulation of a muscle by the 

 " current of action " of another muscle. 



Stimulation of a Muscle by the "Current of Action" of another 

 Muscle. The sartorius muscle is very carefully dissected on each 

 side, and then the one muscle is placed overlapping the other; the 

 contact of the two muscles is secured by gentle pressure with two 

 pieces of cork (Fig. 84). Stimulation of one muscle will produce 

 a contraction in both; the "current of action" in the first stimulates 

 the second muscle. 



FIG. 85. Diagram of the experiment to show the stimulation of a nerve by its own 

 "current of injury." 



Stimulation of a Nerve by its own "Current of Injury." Two 

 plugs of kaolin moistened with normal saline solution are placed upon 

 a piece of glass, and the tails of the plugs are made to hang over 

 the edge (Fig. 85). The sciatic nerve of a pithed frog 1 is carefully 

 dissected down to the knee, the thigh is cut across, but the leg and 

 foot are left intact. The nerve is so placed that its cut surface is 

 upon one plug and its longitudinal surface upon the other plug. A 

 watch-glass filled with strong saline solution, which is a good con- 

 ductor of electricity, is suddenly brought in contact with the ends of 

 the kaolin plugs ; thus the circuit is suddenly made and can be 

 suddenly broken by the removal of the watch-glass. If the prepar- 

 ation be very excitable, a twitch is observed at each make and 



1 For these preparations the frogs should have been kept cold for some time 

 before the experiment. 



