THE TISSUES 5 r 



To find the duration of the contraction, a tuning fork, 

 vibrating 100 times per second, may be made to record its 

 vibrations on the surface. (Practical Physiology.) 



5.C. 



FIG. 22. 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 A, a tuning fork beating 100 times per second is shown 

 recording its vibration on the drum. 



