COLOR SENSITIVITY OF THE PERIPHERAL RETINA. II 



literature was his discovery that the color zones are not fixed, but 

 flexible areas, and that their extension increases with increased area of 

 stimulus-object. 



By far the most fruitful investigator of this period was Aubert* 

 During the progress of an investigation of the " space sense," carried 

 on by Aubert and Foerster in 1857, it had been observed that colored 

 objects may appear colorless in indirect vision. Aubert was able to find 

 in the literature but two references to this phenomenon the papers of 

 Purkinje and Hueck; and since neither discussed the matter in satisfac- 

 tory detail, Aubert determined to undertake a thorough investigation of 

 the phenomena of indirect vision. He employed an apparatus which 

 had but recently been devised, and which has since been named the 

 perimeter, and set himself the task of solving the following problems : 



1 i) To what extent does the character of the background influence 

 the degree of eccentricity at which a color stimulus can be recognized ? 



(2) What is the relation between decrease of color sensitivity and 

 decrease of area of stimulus ? 



(3) Does color sensitivity decrease at a uniform rate along the 

 various retinal meridians ? 



(4) Through what transitions of tone does each color pass during 

 the movement of its image from the fovea to the periphery of the retina ? 



(5) What is the relative extension of the retinal areas within which 

 stimuli appear in their true colors ? 



(6) In what degree are the phenomena of indirect vision analogous 

 with those of direct vision ? 



Aubert's method of experimentation was as follows : From papers 

 of different colors he cut duplicate sets of squares, varying in size from 

 i sq. mm. to 1,024 sq. mm. One set of these squares was then mounted 

 upon white cards, the other upon black. The perimeter was set up in 

 a room with a northern exposure and the experiments were performed 

 in a diffuse daylight illumination. Each sheet of cardboard was inserted 

 in the perimeter, in turn, and was gradually moved out along a retinal 



*Hermann Aubert. Ueber die Grenzen der Farbenempfindung auf den 

 seitlichen Theilen der Netzhaut, Graefe's Archiv. fur Ophthalmologie, III, 2, 

 1857, S. 38-68; Ueber das Verhalten der Nachbilder auf den peripherischen 

 Theilen der Netzhaut., Moleschott's Untersuchungen, IV, 1858, S. 215-240; Ueber 

 die duroh den electrischen Funken erzeugten Nachbilder, Ibid., V, 1859, S. 27Qff. ; 

 Untersuchungen iiber die Sinnesthatigkeit der Netzhaut., Poggendorff's Annalen, 

 CXV, 1862, S. 87-116, CXVI, 1862, S. 249-278; Ueber subjective L-ichterschein- 

 ungen, Ibid., CXVII, 1862, S. 638ff. ; Physiologic der Netzhaut, Breslau, 1865, S. 

 89-105 and 116-124; Grundziige der physiologischen Optik, published in Graefe u. 

 Saemisch's Handbuch der gesammten Augenheilkunde, II, 2, 1876, S. 393-670, 

 republished in separate form under the same title, Leipzig, 1876. 



