COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 19 



Schirmer* also employed squares of colored paper, which he 

 brought in from the periphery, against a black background. His blue 

 and yellow papers did not change in tone ; the red, orange, and green 

 stimuli first appeared yellow, and the violet and purple came in as blue. 

 Green had the smallest zone, then red, orange, purple, violet, yellow, 

 and blue, which latter had the widest zone of all. The zones had no 

 fixed limits, but varied with variations of brightness and area of stimulus. 



Schirmer's study of the abnormalities of color-vision yielded an 

 interesting result. He found that in progressive atrophy of the optic 

 nerve, the color zones gradually decrease in area, until in the final stages 

 of the disease the pathological macula has become functionally equiva- 

 lent to the normal periphery. The disease progresses so slowly and so 

 regularly that a great variety of successive stages may be differentiated 

 between its earliest inception and its final stage of total color-blindness. 

 Sensitivity to green is the first to go, then that to red, to yellow, and 

 finally that to blue. 



Schon f also discusses color vision in its normal and pathological 

 aspects. Employing pigment colors, he found green to have the smallest 

 color zone and blue the largest, red occupying an intermediate position. 

 Schon explains the phenomena of indirect vision from a different retinal 

 sensitivity to the different colors. As a result of this difference of 

 sensitivity, the minimal brightness at which the various colors can be 

 perceived is different. Green requires the greatest luminosity, red less, 

 and blue least of all. Atrophy of the optic nerve does not affect any 

 particular sort of color-sensing fiber alone, but reduces the sensitivity 

 of all three sorts of fibers in equal degree. The color sensitivity of the 

 retina diminishes toward the periphery, in the same degree as the 

 luminosity of peripheral images decreases. In both cases sensitivity to 

 green is the first to go, and sensitivity to blue is the last. Both classes 

 of phenomena are to be explained in terms of decreased brightness. 



Chodin| attacked the problem by a new method. He attempted to 

 determine the magnitude of the minimal sector of colored paper which 



*R. Schirmer. Ueber erworbene und angeborene Anomalien der Farbenemp- 

 findung, Berliner Klinische Wochensehrift, 1873, No. 5 ; Ueber erworbene und 

 angeborene Anomalien des Farbensinns, Graefe's Archiv., XIX, 2, 1873, S. 194-235. 



fW. Schon. Ueber die Grenzen der Farbenempfindung in pathologischen 

 Fallen, Zehender's Klinische Monaitsblatter fur praktische Augenheilkunde, Juli- 

 August, 1873, S. 171-227; Die Lehre vom Gesichtsfelde und seine Anomalien, 

 Berlin, 1874; Einfluss der Ermiidung auf die Farbenempfindung, Graefe's Archiv., 

 XX, 2, 1874, S. 273-284. 



JA. Qhodin. Zur Lehre von den Farbenempfindungen auf der Peripherie der 

 Netzhaut, Petersburger Medicinischer Anzeiger, 1875, Nos. 10-13; Ueber die 

 Abhangigkei't der Farbenempfindungen von der Lichtstarke, Sammlung Physiol- 

 ogischer Abhandlungen von W. Preyer, I, 7, 1877, S. 1-66; Ueber die Empfind- 

 lichkeit fur Farben in der Peripherie der Netzhaut, Graefe's Archiv., XXIII, 3, 

 1877, S. 177-208. 



