DICHROMATIC VISION 



179 



With regard to the periphery of the retina v. Kries 1 compared a 

 long series of normal colour matches with those of dichromats. His 

 results have been confirmed by van der Weyde 2 . He found that whilst 

 the deuteranopic matches agreed well with the normal, the protanopic 

 matches were very different. The difference can be shown by the 

 different brightness of various coloured lights without any comparison 

 light (Levy 3 , Schenck 4 ). The divergence is most marked for colourless 

 red-blue mixtures. Such a mixture which matches a grey background 

 for the normal also matches for the deuteranope within the somewhat 

 wide range of experimental error for such observations. For the 

 protanope such a mixture looks distinctly blue and much too dark ; 

 his match contains less blue and much more red. 



.680 651 629 608 589 573 558 530 513 



Fig. 53. Photopic peripheral luminosity curves for the normal trichromat (- 





and for the protanope ( ...... ). Abscissae, wave-lengths of the prismatic spectrum 



of gaslight; ordinates, arbitrary scale, (v. Kries.) 



Dichromats have a monochromatic peripheral zone as have trichro- 

 mats. The normal and protanopic periphery values for this zone are 

 shown in the curves in Fig. 53. The diminished sensitiveness for light 

 of long wave-length and relatively increased sensitiveness for light of 

 short wave-length in protanopes is clearly shown. 



The deuteranopic periphery values indicate that the summit of 

 the curve is rather red-wards of the normal. Angier 5 claims to have 

 proved more marked differences from the normal in this group of 

 dichromats, but as Frl. v. Maltzew 6 has shown considerable individual 

 variations in normal trichromats the question must be left open. 



1 Zlsch. /. Psychol. u. Physiol. d. Sinnesorg. xv. 266, 1897 



2 Onderzoekingen, Utrecht, iv. 3, 2, 1882. 



3 Ztsch. /. Psychol. u. Physiol. d. Sinnesorg. xxxvi. 74, 1904. 



4 Arch. f. d. ges. Physiol. cxvm. 174, 1907. 



5 Ztsch. f. Psychol. u. Physiol. d. Sinnesorg. xxxvu. 401. 1!>05. 



6 Ztsch. f. Sinnesphysiol. xtni. 76, 1908. 



122 



