358 Journal of Comparative Neurology. 



those of a normal eye (Fig. 33). They are large and are sur- 

 rounded by a thin layer of protoplasm. This stains faintly. A 

 nucleolus is easily demonstrated. The rod and cone nuclei 

 have almost the same shape and size. Those for the rods are 

 slightly longer. They have an average size of .0045 mm. by 

 .0078 mm. The average size of the cone nuclei is .0040 mm. 

 by .0064 mm. The cone nuclei lie near the outer boundary of 

 this layer. In fact, as already described, many are found be- 

 tween the bases of the rods. 



The nuclei of this layer are arranged five deep and form a 

 continuous layer averaging .0346 mm. in thickness. The boun- 

 daries of this layer are very irregular. Some of the nuclei ap- 

 pear as though pushed out into the adjacent layers. The nuclei 

 forming the first and second rows from the outside generally 

 belong to the cones. The remaining three rows are the rod 

 nuclei. In the region of the lens, corresponding closely to the 

 ora serrata of the normal eye, the nuclei of this layer blend and 

 mingle more or less with those of the inner nuclear layer. The 

 outer molecular layer in this region is wanting I have been 

 able to follow branches from these nuclei which connect them 

 with the rods, but have been unable to trace the ingoing 

 branches far toward the molecular layer. By this I do not mean 

 to imply that such branches are not present. My preparations 

 were not preserved and stained in a manner to show them at 

 their best. 



The outer molecular layer has an average thickness of 

 .0084 mm. throughout its extent. In the region of the lens, as 

 already described, it is absent owing to the fusion of the two 

 nuclear layers. This layer is more or less encroached upon by 

 nuclei which appear to have been pushed out from the two adja- 

 cent nuclear layers. Owing to the method of staining I have 

 been unable to demonstrate the finer structures of this layer. 



The inner nuclear layer has an average thickness of .0394 

 mm. The nuclei are arranged five deep (Fig. 28) and fairly 

 close together. The nucleus is rather small and has an average 

 size of .0044 mm. by .0052 mm, A distinct nucleolus is 

 usually seen (Fig. 32). The nucleus is surrounded by a rather 



