ADVANCED EXPERIMENTAL PHYSIOLOGY 



299 



glass plate a rapid and uniform horizontal motion, and the momentum 

 carries the recording surface across until stopped by the buffers at the 

 opposite side. The frame carries on its under surface two pins which 

 knock over two vertical keys and so breaks two primary circuits (Fig. 

 180). K^ is fixed, but K 2 is movable horizontally, and its position can 



FIG. 179. The spring myograph. 



be adjusted so that it will be knocked over at any desired interval after 

 K r A pointer is attached to K 2t and when this is opposite the zero of the 

 scale this key will be knocked over at the same instant as K^ ; there- 

 fore, in order that K% may be knocked over after A^ and that the second 



FIG. 180. Diagram of the spring myograph in circuit. 



stimulus may still fall within the latent period of the first, it is 

 necessary to move K 2 a short distance along the scale from K r Place 

 both keys in the primary circuit of the same coil and arrange the 

 secondary coil at such a distance from the primary as to give sub- 

 maximal break-shocks. With the spring compressed, the catch down 

 and both keys vertical, the writing points of the lever and tuning fork 

 are placed against the recording surface at its spring end in order that 

 the whole contraction may be recorded. Release the catch. The frame is 

 then pulled back to its original position, both keys are made vertical 



