450 



MUSCLE PHENOMENA. 



for the purpose of study. Fig. 254 represents the method of 

 recording muscular contraction. 



Other forms of the myograph are the spring myograph (Fig. 

 255) and the pendulum myograph (Fig. 256). 



FIG. 256. Pendulum myograph ; at the left, as seen from the front : A, bearings 

 on which the pendulum swings ; P, pendulum ; (?, G', glass plates carried in the 

 frames T, T' ; a, pin which opens the trigger-key. The key, when closed, is in con- 

 tact with c, and so completes the circuit of the primary coil (Stewart). 



Time-markers or Chronographs. In order to know and record 

 the length of time consumed by various phenomena which are the 

 subject of investigation, various forms of time-markers are used 

 which make a record on the drum at the same time that the myo- 



