THE TISSUES 



or 



53 



stimulate and mark the moment of stimulation an induction 

 coil (p.c., s.c.), with an electro-magnetic marker (T.M.), intro- 

 duced in the primary circuit, may be employed. 



B 



s.c, 



FIG. 21. A, Method of Recording Muscular Contraction. B, Key to Parts of 

 Apparatus. M, Muscle attached to crank lever L. p.c., Primary circuit, 

 and, s.c., secondary circuit of an induction coil with short circuiting key, k', 

 in secondary circuit. B, Galvanic cell, and, k, a mercury key for closing and 

 opening the primary circuit. T.M., A lever moved by an electro-magnet 

 placed in the primary circuit and marking the moment of stimulation. In As 

 a tuning fork beating 100 times per second is shown recording its vibration 

 on the drum. 



