260 EXPERIMENTAL PHYSIOLOGY. 



(e.) Repeat the experiment on the eighth nerve root. 

 Stimulate the central end, no effect is produced. 



From the effects of section and stimulation of the nerve roots, 

 one concludes that the anterior are motor, and the posterior are 

 sensory. 



2. Reaction Time i.e., the interval between the application of 

 a stimulus to a sense-organ and the moment the stimulus is 

 responded to by the individual. The Neuramoebometer (Exner\ 

 or Psycho dometer (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. 

 120). A brass plate (B 6) moves in a slot, and carries a 



Fig. 120. 



smoked glass plate (T), a catch (DG), and a handle (H). The 

 handle (H) pushes up the glass plate and 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 the catch (G) is withdrawn, (F) vibrates, and if the style be 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. 



(6.) The observer suddenly pulls on (H), thus discharging 

 the spring (F), which vibrates and produces a note. The 

 moment the observed person hears the sound, he presses the 

 knob (K) and raises the writing-style. Of course, a curve 

 is recorded, and it is easy to calculate the time which has 



