176 S. R. DETWILER 



though he observed the differences in position of the nuclei of 

 the epithehal cells of Abramis could find no constant differences 

 due to the effect of light and darkness. 



Concerning the third of the effects of light on the retina in 

 which we are interested, namely changes in form, position and 

 the ability of the ganglion cells and of the nuceli of the inner 

 and outer granular layers to stain there has grown up a com- 

 paratively large literature. This has been excellently reviewed 

 by Garten, who has in addition given a table in which the results 

 of different investigators are shown. 



We will first take up the effects of light on the nuclei of the 

 cones. In Garten ('07 b, pp. 18-23) will be found a very good 

 summary of what has been done. Czerny ('67), Gradenigo 

 ('85), Angelucci ('94), and Chiarini ('04) in the frog; Pergens 

 ('96) in Leuciscus rutilis; and Chiarini ('06) in the lizard found 

 that light caused the cone nuclei to become longer and narrower. 

 In addition, Birch-Hirschfeld (' 06) found that light caused a 

 difference in the volume of the cone nuclei of the pigeon, in that 

 they are smaller and narrower. Birch-Hirschfeld further found 

 in the pigeon that light caused the cone nuclei to approach 

 nearer to the external limiting membrane. 



Light was found to decrease the power of the outer granules 

 to stain by Pergens ('96, '97, and '99) in Leuciscus rutilis, Mann 

 ('94) in the dog; Birch-Hirschfeld ('00) in the dog and cat, and 

 ('06) in the pigeon (very slight), Sgrosso ('05) in the frog, and 

 Garten ('07, p. 23) in Cercopithecus, Macacus rhesus, fishes 

 (Abramis and Leuciscus) , Salamandra, frog and the owl. Chiarini 

 ('04 and '06), however, found that in Leuciscus any difference 

 between the ability of the dark and the light eye to stain was 

 very uncertain, and that in the frog, lizard, crow and dog there 

 was absolutely no difference. 



We may pass now in the same way to a brief review of the 

 results that have been obtained concerning the effect of light on 

 the form and stainability of the inner granules and of the gan- 

 glion cells. Mann ('95) found that in the dog, illumination of 

 the eye for 12 hours caused a decrease in the stainability of the 

 inner nuclear layer and a decrease in the Nissl substance of the 



