Chap. VII.] 



THE MUSCLE TELEGRAPH. 



Fig. 35. The Muscle Telegraph. 



pulley which carries an arm a, terminating in a disc c. 

 A thread passes over the pulley, and supports at one end 

 a small bucket b. To the other end of the thread is 

 fastened the hook x. When a frog's muscle has been 

 prepared in the man- 

 ner presently to be 

 described, it is held 

 in the forceps A, 

 by the end of the 

 femur, and the hook 

 x is passed through 

 the 'tendo Achilles. 

 The distance be- 

 tween the two pil- 

 lars being then re- 

 gulated, an d the 

 bucket being weighted by some small shot, the 

 muscle'is so stretched that the slightest movement of 

 it will act on the pulley and raise the disc in the 

 direction of the arrow. By means of a binding screw 

 &' at the forceps, and a little screw at x, wires can be 

 connected for stimulating the muscle to contraction by 

 a current of electricity. 



The nerve - muscle preparation is the one 

 generally adopted for experiments on muscle. Kill a 

 frog by severing with scissors the spinal cord at the 

 back of the head, and destroy reflex actions by passing 

 a needle up into the brain, and down the spinal canal. 

 Separate the lower limbs from the trunk by cutting 

 through with scissors at the middle of the back. 

 Seize the backbone with finger and thumb of left 

 hand, catch the loose skin with the right, and strip 

 the skin right down off the limbs. Turn the back of 

 one thigh up, and with finger and thumb on each side 

 separate the outer and inner divisions of muscles 

 along the line of a well-marked furrow which divides 

 them. The sciatic nerve will then be revealed as 



