24 COLOR SENSITIVITY OF THE PERIPHERAL RETINA. 



mately identical for the normal and the green-blind retinas. These 

 data are claimed by von Kries to furnish a confirmation for his general 

 theory of vision. But his attempt to account for the color-phenomena 

 of indirect vision is far from being successful. He discusses the 

 hypotheses advanced by Helmholtz and by Kick [This latter conception 

 will be discussed later. See pp. 3Qf.] to explain these phenomena, but 

 refuses to accept either. He is inclined to posit an integrity of structure 

 and of function in the normal periphery, and to refer the lesser sensi- 

 tivity of that region to a more central part of the visual mechanism, 

 i. e., to conditions which exist in the cortex or possibly in the optic nerve 

 proper. This conjecture is only tentative, however, for in the opinion 

 of von Kries the time is not yet ripe for a final decision of the matter.* 

 Wolffberg-f- employed colored papers as stimuli, and worked with 

 a wide range of luminosities. He found the blue zone to be greatest, 

 the red zone to be less, and that of green to be least. The limits of the 

 color zones contract very slowly with decreasing luminosity of stimuli ; 

 thus when the luminosity had been reduced from 14 to ~ the zonal 



J 15 1'3> 



limits decreased by only 15. When the luminosity was still farther 

 reduced, the zones successively contracted to the vanishing-point red 

 being the first to disappear, then green, and finally blue. 



DobrowolskyJ attempted to determine the relative sensitivity of 

 various parts of the retina to light of different colors. His stimulus 

 was a narrow band of the solar spectrum, and his method consisted in 

 determining the minimal shifting of the spectral band in the ocular of 

 his apparatus, which rendered possible the judgment that a different 



*Zeitschrift, XV, S. 27off. Von Kries has published yet another paper upon 

 this topic since the present monograph was written. (Nagel's Handbuch der 

 Physiologic des Menschen, Braunschweig, 1904, III, i ; Die Gesichtsempfindungen, 

 Johannes von Kries, S. 109-282, especially S. 193-204 and 266-282.) His most 

 recent 'contribution is for the most part a resume of the results of his previous 

 papers. After reviewing the phenomena of indirect color vision, which he per- 

 sists in referring to the color-blindness of the peripheral retina, he repeats his 

 discussion of the distribution of spectral 'brightnesses. It seems evident through- 

 out that the behavior of the eccentric regions of the retina has given von Kries 

 an endless amount of trouble; and his own discussion shows that his theory is 

 wholly inadequate to account for the phenomena in question. In his final pro- 

 nouncement upon the topic he is more favorable in his attitude toward Pick's 

 hypothesis than the facts of the case would seem to warrant; but he ultimately 

 grants the validity of the Hering theory, in so far at least as the color phenomena 

 of indirect vision are 'Concerned. (Handbuch, S. 273-274.) 



tL. Wolffberg. Ueber die Priifung 'des Lichtsinns, Graefe's Archiv., XXXI, 

 I, 1885, S. 1-78. 



JW. Dobrowolsky. Ueber die Empfindlichkeit des normalen Auges gegen 

 Farbentone auf der Peripherie der Netzhaut, Graefe's Archiv., XXXII, I, 1886, 

 S. 9-32. 



