84 VERTEBRATE PHOTORECEPTORS 



staining reactions of the ganglion cells and of the nuclei of 

 the inner and outer nuclear layers. 



The effects upon the nuclei of the cones as observed by 

 various workers are summarized by Garten (1907). Chiarini 



(1906) found that in the lizard the cone nuclei became longer 

 and narrower. Birch-Hirschfeld (1906) found that light 

 caused a difference in the volume of the cone nuclei of the 

 pigeon; he also claimed that light caused the nuclei to 

 approach nearer to the external limiting membrane. 



Light was found to decrease the power of the nuclei in the 

 outer nuclear layer to stain. This was shown by Pergens 

 (1896, 1897, 1899) in Leuciscus rutilis, Mann (1895) in the 

 dog, Birch-Hirschfeld (1900) in the dog and cat, and (1906) 

 in the pigeon, Sgrosso (1905) in the frog, and by Garten 



(1907) in Ceropithecus, Macacus rhesus, fishes (Abramis and 

 Leuciscus), Salamandra, frog, and the owl. Chiarini (1904 

 and 1906) claimed doubtful differences in Leuciscus and 

 absolutely no difference in the frog, lizard, crow, and dog. 



As regards the nuclei of the inner nuclear layer, Mann 

 (1895) found that in the dog, illumination of the eye for 

 12 hours caused a decrease in the staining reaction of the 

 inner nuclear layer, and a decrease or dispersion of the Nissl 

 substance in the cytoplasm of the ganglion cells. Bach (1895) 

 could find no differences in the staining reactions of the inner 

 nuclear layer or of the ganglion cells in light- or dark-adapted 

 eyes of the rabbit. Birch-Hirschfeld (1900), however, did find 

 differences between the light and dark eyes of rabbits and 

 of dogs. The nuclei of the inner layer in the dark eyes are 

 rounder; in the light, more oval. In the ganglion cells of 

 light-adapted eyes the Nissl bodies have indistinct bound- 

 aries, with the protoplasmic background very diffuse. In 

 the dark eye, the Nissl bodies possess sharp distinct out- 

 lines. In Leuciscus, Chiarini (1904) found no decrease of 

 chromatin in the inner nuclear layer after illumination, and 

 hardly noticeable changes in the ganglion cells. He also 

 failed to observe any effects upon the inner nuclear layer of 

 reptiles, birds, and mammals. 



