386 PHYSIOLOGY CHAP. 



That it can account for all the facts may, however, be doubted. 

 If we accept the two phases of the panchromatisation of the primi- 

 tive visual substance, in the first of which the white substance 

 splits into blue and yellow, in the second the yellow into red and 

 green, it is not easy to understand why the visual field for yellow 

 is slightly more extensive than that for blue, and the visual field 

 for red more extensive than that for green. According to Schenck's 

 theory the yellow field ought to coincide with the blue field, and 

 the red with the green field, because the substances which subserve 

 the two pairs of complementary colours are, on this theory, pro- 

 duced simultaneously. The same difficulty (as Carincione rightly 

 pointed out) is encountered in explaining why, in progressive 

 atrophy of the optic nerve, sensation to green entirely disappears, 

 at a time when that to red still persists, though only to a very 

 limited extent. 



BIBLIOGRAPHY 



In addition to the Authorities cited at the end of the previous chapter, the 

 following may be referred to : 



Objective Phenomena of Retinal Excitation : 



BOLL. Atti dell' Accademia dei Lincei, 1876. 



KUHNE. Untersuch. aus d. physiol. Institut Heidelberg, 1879. 



KiiHNE. Untersuch. aus d. physiol. Inst. d. Univ. Heidelberg, 1878-1882. 



Hermann's Handb. iii., 1879. 

 ENGELMANN. Pfliiger's Arch, xxv., 1885. 

 VAN GENDEREN STOUT. Resoconto del Congr. med. di Copenhagen, 1884. Grafe's 



Arch. f. Ophth. xxxiii., 1887. 

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Roma, 1884-1888. 



PERGENS. Travaux du lab. de 1'Inst. Solvay, ii., 1896. 

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der Physiol. des Menschen, iii., 1905). 

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 GARTEN. Grafe-Samisch's Handb. d. Augenheilkunde. Leipzig, 1907. 



Retinal Adaptation to Light and Darkness ; Photopic and Scotopic Vision ; 

 Duplicity Theory of Functions of Rods and Cones : 



HERING and HILLEBRAND. Sitzungsber. d. Wiener Akad. xcviii., 1889. 

 EBBINGHAUS. Zeitschr. f. Psychol. u. Physiol. d. Sinnesorg. v., 1893. 

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xiii., 1896. 



KONIG. Sitzungsber. Akad. Wissenschaft Berlin, 1896-1897. 

 v. KRIES and NAFEL. Zeitschr. f. Psychol. u. Physiol. d. Sinnesorg. xii., 1896 ; 



xxiii., 1900. 

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1896, 1902. 



PIPER. Zeitschr. f. Psychol. u. Physiol. d. Sinnesorg. xxxi., 1903. 

 DONIZELLI. Arch, di tisiol. di Fano, v., 1908. 



General Theory of Achromatic and Chromatic Vision : 



A. FICK. Pfliiger's Arch, xix., 1879 ; xlvii., 1890. 



VON KRIES. Die Gesichtsempfmdungen (Nagel's Handb. iii., 1905). Abhand- 

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