vii RETINA I, EXCITATION 



the after-image is that which results from the mixture of the; 

 (complementary) colour of the after-image with that of the back- 

 uTHiind on to which it is projected. 



If the after-image is projected on to a background of the 

 inducing colour, the part on which it falls appears dimmed or 



c:. IT'!. (iauden/i's e\p>-i nn-nt Im repetition and int'-i pn-tat ion of Hiv ster-B. ici i 's '-eeiebia 

 visual images." as, uncovered left rye; '///. covered riv.ht cyr ; c, cential point, of perimeter 

 fixated liy tlir two eyes altei nately ; >x, |iositi(n nt' physiological scntnuia (M:n inttc's blind 

 s]mt) iii the riis-nrd eye; a, position ol a lamp, jiartially covered by :i screen. When the 

 head is lixed in the iieiinieter. ]ioint '' is fixated with the right eye, and the limits, x.v, of the 

 till: t his eye :n e traced on the urc of the peri meter. Both eyes are then covered and 



lie room daikeneil, to adapt tin- retina to darkness; after a few minutes the left eye is 

 uncovered, and while fixated on r it is exposed for -JK-SII see ..... Is to tin- li^ht of lampu, so as to 

 provoke a pei sisti-nt imax'e in a part of tin- n-tina enrn-sponilinx' to the optic papilla of the 

 ri^'lit eye. The lelt eye is then Hosi-il. and the ri.u'ht eye opened and fixated on the centre C ', 

 after a few sccnml-. I'rewsler-Horri's inia^e is seen m tin- region of Mario! le's liliinl spot. 



grey ; if, on the contrary, it is projected on to a surface of 

 complementary colour the part it falls on appears brighter and 

 more saturated. Generally speaking, the colours which are 

 complementary or nearest to the complementary become more 



