EFFECT OF LIGHT ON THE RETINA 177 



protoplasm of the ganglion cells. Each ('95) however, in the 

 rabbit could find no differences in the stainability of the inner 

 nuclear layer or of the ganglion cells in light and dark eyes. 

 Birch-Hirschfeld ('00) however, did find differences between the 

 light and dark eyes of rabbits and of dogs. The nuclei of the 

 inner la^^er in the dark eye are rounder, in the light eye more 

 oval. In the ganglion cells the Nissl bodies in the light eye have 

 indistinct boundaries and with the protoplasmic background 

 very diffuse. In the dark eye, on the other hand, the Nissi 

 bodies possess sharp, distinct outlines. Chiarini ('04) found in 

 Leuciscus, no decrease in chromatin in the inner nuclear layer 

 after illumination, and in the ganglion cells hardly noticeable 

 changes. Also later ('06) in the inner layer of reptiles, birds 

 and mammals he found no differences between light and dark 

 retinae. In Lacerta, however, he observed a slight decrease in 

 the Nissl bodies of the ganglion cells, in Corvus a decided de- 

 crease, and in the dog again a slight chromatolysis. 



Schiipbach ('05) found no differences, neither in the inner 

 layer nor in the ganglion cells, between light and dark eyes of 

 pigeons. But Birch-Hirschfeld ('06) was able to demonstrate 

 clearly that the ganglion cells showed a distinct decrease in the 

 number of the Nissl bodies and an indistinctness of their boun- 

 daries in the light eye. Carlson ('04) has shown the same for 

 another bird — Phalacrocorax penecillatus, and finally Sgrosso 

 ('05) found in the frog that the inner nuclear layer showed 

 differences in stainability in the light and dark eye. 



In order to make observations on these matters, particularly 

 on the stainability of the nuclei, it was necessary to use some 

 other methods of fixing, etc., than had been employed for the 

 study of pigment migration, and of cone contraction. For this 

 purpose the following method was finally decided upon, and 

 gave excellent results. Fixation in warm concentrated subli- 

 mate for 5 hours. Removal of sublimate with iodine in 70 per 

 cent alcohol, further dehydration, and infiltration by the chloro- 

 form paraffin method. Sections were cut 8m thick, stained in 

 eosin and toluidin blue, rapidly dehydrated, cleared in xylol 

 and mounted in damar. In order to insure the same amount 



