OUR FACE FROM FISH TO MAN 



extent and intensity of the bleaching effect is in 

 some way proportional to the size of the aperture, 

 the intensity of the light and the length of exposure. 

 And no doubt also the innumerable rods and 



olli^uus superior 



rectus 

 super/or 



"^A\v>y 



Fig. 98. 



The Right Eyeball and Its Six Muscles (from Plate, 



AFTER MeRKEL AND KaLLINs). 



(From AUgem. Zool., Gustav Fischer.) 



cones of the visual field react differently to different 

 wave lengths (colors) and different intensities 

 (light and shade), so that an image made up of 

 innumerable points, like a half-tone picture, is 

 recorded on the retina. But whereas the photog- 

 rapher proceeds after an interval to fix the image 



190 



