COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 2Q 



Hess's paper does not contain a theoretical discussion of his data, 

 but Hering follows with a paper in which he shows that the theories 

 advocated by Helmholtz and by Kick can not be reconciled with the 

 results of Hess's investigation.* 



Basevif employed a Masson disc, upon which were exposed his 

 color stimuli in different degrees of brightness and saturation. He found 

 blue to have the widest retinal zone, and green the narrowest, the rela- 

 tive extensions being, green I, red 1.14, yellow 1.19, and blue 1.32. 



Basevi's adaptation experiments yielded the following results : The 

 extension of the color zones is increased by dark-adaptation, but all 

 are not increased in equal degree. The greatest increase occurs in the 

 case of the yellow, then follow green, red, and blue in order. It follows 

 from this that the peripheral sensitivity to all colors is increased by 

 dark-adaptation. Basevi also performed a series of experiments to 

 determine the influence of chromatic adaptation. After the retina had 

 been exposed to each color for a time, each of his stimuli was presented 

 in minimal brightness. The brightness was gradually increased until 

 the color was recognized, the liminal brightness required for recognition 

 being recorded in each case. The following results were obtained : 

 With red-adaptation, green was the first color to be recognized, then 

 came blue, then yellow, and finally red ; with blue-adaptation the order 

 was yellow, red, green, and blue; with green-adaptation, red, blue, 

 yellow, and green ; with yellow-adaptation red was the first to be recog- 

 nized, then blue, green, and yellow. Unfortunately, Basevi made no 

 determination of the color tones, or of the relative absorptions of the 

 colored glasses employed in this experiment. 



HeggJ employed the Hering color-mixer to determine the four 

 stable colors and to equate their white-values and their color-values. 

 Then, in order that his subsequent perimeter experiments might be car- 

 ried on more conveniently, he had a painter prepare exact duplicates of 

 the four stimuli thus determined and equated. The parts of the peri- 

 meter which were to serve as background in the investigation were 



*E. Hering. Ueber die Hypothesen zur Erklarung der peripheren Farben- 

 blindheit, Graefe's Archiv., XXXV, 4, 1889, S. 63-83. 



tV. Basevi. Sulla sensibilita della periferia della retina per la luce e per i 

 colori, Annali di Ottalmologia, XVIII, 1889, pp. 41-52 ; Influenza dell' adattamento 

 sulla sensibilita retinica per la luce e per i -colori, Ibid., XVIII, 1890, pp. 475-481. 



jEmil Hegg. Zur Farbenperimetrie, Graefe's Archiv., XXXVIII, 3, 1892, 

 S. 145-168; La perimetrie des couleurs, Annales 'd'Oculistique, CIX, 3, 1893, pp. 

 321-347; Sur la perimetrie au moyen de (pigments colores, Annales d'Oculistique, 

 CXI, 1894, pp. 122-127. 



