SIMULTANEOUS CONTRAST OR SPATIAL INDUCTION 129 



previous stimulation of the eye (Hering, Hess^, Tscherniak) and fatigue 

 (Tschermak and Krause). The discrepancy between the induced and 

 the complementary colour is said to be absent when the eye is dark- 

 adapted (Mayer, Kuhnt^). There are also psychological factors, which 

 form at any rate the most probable explanation of simultaneous con- 

 trast over colour-scotomatous areas (Tschermak^) and over the blind 

 spot. The entoptic visibility of the blind spot* is itself evidence of 

 contrast, as are also the effects of stimulation of the optic nerve by 

 the constant current (G. E. Miiller^). 



Simultaneous contrast is under ordinary conditions limited to the 

 eye stimulated (Hering^), but binocular contrast can also be proved to 

 occur'^. 



1 Arch.f. Opkth. xxxv. 4, 1, 1889 ; xxxvi. 1, 1, 1890. 



2 Loc. cit. xxvn. 3, 1, 1881. 



3 Arch.f. d. gca. Physiol, i.xxxii. 559, 1900. 



* Brewster; Puikinje; Aubert ; v. Helmholtz; Cliarjjentier, Compt. rend, cxxvi. 1()34, 

 1898. 

 — ^ Ztsch.f. Psychol, u. Physiol, d. Sinnesorg. xiv. 329, 1897. 



« Loc. cit. I. 18, 1890. 



' Fechiier ; H. Meyer ; v. Helmholtz ; Hering, in Hermann's Hundb. d. Physiol, in. 

 i, (JOO, 1879 ; Ebbinghaus, Arch.f. d. ges. Physiol. XLVi. 498, 1894 ; Chauveau, Compt. rend. 

 cxiii. 1891 ; I). Axcnfeld, Arch. ital. de Biol. xii. 28, 1889 ; xxvii. 103, 1897 ; Burch, Jl. of 

 Physiol, xxv. 1900. 



P. C. V. 



