324 



PRACTICAL PHYSIOLOGY. 



[LXX. 



2. Recording on Drum (also for sight and hearing). 



(a.) Another method is to cause two electro-magnets with writing- 

 styles to record on a rapidly moving drum arranged as in fig. 245. 

 One signal is interposed in the primary circuit of an induction coil, 

 with a contact- key also in the circuit. This is the "stimulating 

 key." 



(ft.) The other electro-magnet is in connection with a battery, 

 a contact-key being in the circuit the "response key." If this 



FIG. 243. Rutherford's Scheme of using 

 Pendulum-Myograph for Estimating 

 Simple Reaction-Time. 



FIG. 244. Result obtained for Simple Re- 

 action-Time with Pendulum-Myograph 

 (Rutherford). Shock applied in (i) To 



skin of left cheek ; (2) Left side of 

 neck ; (3) Left upper arm near deltoid ; 

 ( 4 ) Left little finger; (5) Dorsum of left 

 foot. 



method be used for touch, the electrodes from the secondary coil 

 are applied to some part of the skin, and the person marks response 

 with the response ke} r . 



(c.) If for sight, a white piece of paper (Rutherford) is placed on 

 the electro-magnet style in the primary circuit, and the person 

 responds when he sees this move, which it does when the primary 

 circuit is made. 



(d.) If for hearing, then a telephone is introduced into the 

 stimulating circuit. The observer puts the telephone to his ear, 



