324 



PRACTICAL PHYSIOLOGY. 



[LXX. 



2. Recording on Dmm (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." 



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

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



Fig. 243— Rutherford's Scheme of using FlO. 244.— Result obtained for Simple Re- 

 Penduliim-Myo^iraph for Estimating action-Time with Pendulum-Myograph 



Simple Reaction-Time. (Rutherford). Shock applied in (i) To 



skin of left cheek ; (2) Left side ot 

 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 ke3\ 



(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 

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



