326 



PRACTICAL PHYSIOLOGY. 



[LXX. 



from the secondary coil pass to a Pohl's commutator without cross- 

 bars, and provided with two pairs of electrodes. Thus at will the 

 observer can pass the induced shock either through the one pair or 

 the other, the individual experimented on not knowing when the 

 reverser is changed. 



FIG. 246. Reaction-Time for Touch in Man. T. Time signal in circuit with a tuning-fork, 

 vibrating too D.V. per second. 



5. The Nenramoebimeter (Exner), or Psychodometer (Oberstein), consists 

 of two uprights (S), with a horizontal axis carrying a spring (F) which 

 vibrates 100 D.V. per second with a writing-style at its free end (fig. 247). 

 A brass plate (B ft) moves in a slot, and carries a smoked glass plate (T), a 

 catch (DG), and a handle (H). The handle (H) pushes up the glass plate and 



, FIG. 247.- The Neuramoebimeter. 



catch (G) until the latter meets the spring (F), and puts (F) on the stretch. 

 When the catch (G) is withdrawn, (F) vibrates, and if the style be arranged 

 to touch the glass, a curve is obtained on the latter. . 



(a.} It requires two persons. The observed person places a finger on the 

 knob (K), while the catch (G) and glass plate are pushed up, the former to 

 catch on (F), and the style is arranged to write on the glass. The observed 

 person must not look, but close his eyes and listen. 



