COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 23 



Bull is convinced that the color sensitivity of the periphery differs 

 in many respects* from that of the center of the retina, and that the 

 periphery does not function in a manner which is comparable with the 

 center in twilight illumination. He believes that Bering's theory fur- 

 nishes a fairly satisfactory explanation of the phenomena of indirect 

 vision, but that it fails to account for all of the facts. 



Von Kriesf made a comparative study of the phenomena of in- 

 direct vision and the phenomena which occur with decreasing area of 

 stimulus. He found that in moving out towards the edge of the field of 

 vision yellow and blue stimuli appear to pass over into gray without 

 change of tone, while all other colors tend to appear more and more 

 yellowish or bluish as they approach the periphery. That the changes 

 of color which result from decrease of visual angle are a wholly differ- 

 ent series is evident from the following table :$ 



With increasing eccentricity of vision. 



With decreasing visual angle. 



Red passes over through yellow to gray 

 Orange passes over through yellow to 



gray. 

 Greenish-yellow .passes over through 



yellow to gray. 

 Yellowish-green -passes over through 



yellow to gray. 

 Bluish-green passes over through blue 



to gray. 



Blue passes over directly to gray. 

 Violet passes over through blue to gray. 



Red passes over directly to gray. 

 Orange passes over -directly to gray. 



Greenish-yellow passes over directly to 



gray. 

 Yellowish-green passes over directly to 



gray. 

 Bluish-green passes through greenish 



and yellowish-green to gray. 

 Blue passes over .directly to gray. 

 Violet passes over through reddish to 



gray. 



Later papers by von Kries contain additional data and a theoretical 

 discussion of the whole topic. A comparison of the relative bright- 

 nesses of the different parts of the spectrum as they appear to the nor- 

 mal periphery, to the twilight-adapted retina, and to the periphery of 

 the red-blind, convinces von Kries of a dissimilarity of function in 

 these various cases; while the distribution of brightness is approxi- 



*Graefe's Archiv., XXVII, i, S. I52f. 



tj. von Kries. Gesichtsempfindungen und ihre Analyse, Du Bois-Reymond's 

 Archiv fur Anatomic und Physiologic, Physiol. Abtheilung, Supplement-Band, 

 1882 ; trepublished in separate form under same title, Leipzig, 1882, S. 89-106 ; 

 Ueber die functionellen Verschiedenheiten des Netzhautcentrums und der Nach- 

 bartheile, Graefe's Archiv., XLII, 3, 1896, S. 95-133; Ueber die Farbenblindheit 

 der Netzhautperipherie, Zeitschrift f. Psy. u. Phys. d. Sinnesorgane, XV, 1896, 

 S. 247-279. 



tGesichtsempfindungen, u. s. w., S. 93. 



