234 



COLOUR VISION 



160-165. The number seems high, especially when one considers that 

 the integration interval is much less. It is explained by the fact that 

 between the lines E and F deuteranopes possess a much greater dis- 

 crimination sensibility than normal trichromats {v. Fig. 4). Konig 

 thought that the number for protanopes was probably about the same 

 as for deuteranopes. 



Fig. 66. Curve of discrimination sensibility for hues of tlie interference spectrum of the 

 arc light for a protanope. # Neutral point. Abscissae, wave-lengths ; ordinates, 

 differences of wave-length (5X) capable of being discriminated. (Steindler.) 



Liebermann and Marx^ have compared the discriminative sensibility 

 for hue of a protanope and trichromat by the method of mean error. 

 They found that of the protanope much inferior. At 509-6 /x/x, near the 

 neutral point, the mean of 50 observations gave 8A = 3-6 /xju, for the 

 normal, 16-2 ju,^ for the protanope. 



^ Ztsch. J. Sinnesphysiol. xlv. 103, 1911. 



