196 



PHYSIOLOGY 



gives the frame and the glass plate a rapid horizontal motion ; and the momentum 

 carries the glass plate through the rest of the distance, till stopped by the buffers. The 



1 K \ 

 FIG. 53. Simple form of pendulum myograph. 



velocity during this time is nearly constant, as the friction of the guides is small. Two 

 keys are knocked over by pins on the frame and break electric circuits. The relative 

 positions at which the circuits are broken can be altered by a convenient adjustment. 



FIG. 54. Diagram of spring myograph, or ' shooter.' 



A tuning-fork vibrating about 10Q per second fixed to the base of the instrument marks 

 the time ; its prongs are sprung apart by a block between their ends, and the same 

 action which releases the glass plate also frees the fork by removing the block and allows 

 it to vibrate ; a writing style then draws a sinuous line on the smoked surface of the 

 moving glass plate. A muscle lever with a scale-pan attached also forms part of the 

 instrument." 



The record obtained in either of these ways may, in consequence of instrumental 



