THE CHANGE IN FORM 339 



the point of a long pin has been thrust. Place 

 the levers so that the head of the first pin rests 

 on the muscle near one end, while the head of 

 the second pin rests near the other end. Place 

 needle electrodes at one end of the muscle. 

 Bring the writing points of the two levers 

 against a smoked drum in the same vertical line. 

 Let a tuning fork write its curve near that of the 

 muscle levers. Set the tuning fork vibrating. 

 Let the drum revolve rapidly. Stimulate the 

 muscle at one end with a maximal make induc- 

 tion current. 



The lever near the point of stimulation will 

 begin to rise before that farther away. Evidently 

 the contraction starts at the point stimulated and 

 spreads along the muscle in the form of a wave 

 (compare pages 308 et seq.~). 



Determine the speed per second of the wave 

 of contraction by measuring with the tuning-fork 

 curve the time occupied by the wave in passing 

 along the muscle from one lever to the other. 



It is evident that a lever resting on a horizontal 

 muscle will register the change in. form of the 

 cross-section on which the lever lies, while a lever 

 attached to the end of a muscle suspended verti- 

 cally will be moved by the change in form of all 

 the cross -sections of which the muscle is com- 

 posed. The curves secured by the two procedures 



