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. 



12-0 



lO'O 



S'O 



400 



50 



500 



50 



00 



50 



700^ 



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

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

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



Liebermann and Marx 1 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 pp, near the 

 neutral point, the mean of 50 observations gave SA = 3-6 /t/x for the 

 normal, 16-2 /A/X for the protanope. 



1 Zlsch.J. Sinne-sphysiol. XLV. 103, 1911. 



