THE LAYERS OF THE RETIXA 



583 



tropic portion is especially short, while the isotropic basal portion, 

 whose longitudinal striations occupy a somewhat greater proportion 

 of its length than is the case with the rod segment, rests directly 

 upon, and may even project through the external limiting mem- 

 brane. The inner or nucleated portion, therefore, begins as a broad 

 nucleated mass, equal in diameter and continuous with the bacil- 

 lary portion of the cone element, to which it is ofttimes united by 

 a slightly constricted neck. In this inner segment, just within 

 the external limiting membrane, is the cone nucleus ; it differs 

 from the rod nucleus in that it stains less deeply, presents no trans- 





FIG. 428. FKOM THE HUMAN RETINA. 



1, outer nuclear layer ; #, outer reticular layer ; S, inner nuclear layer ; 4, inner 

 reticular layer ; a, external limiting membrane ; 6, rod nuclei ; c, cone nuclei ; d, cone 

 bipolars ; e, rod bipplars ; /, an exceptionally long process of a rod bipolar. Methylen 

 blue. Highly magnified. (After Dogiel.) 



verse striations, and frequently incloses a distinct nucleolus. From 

 its nucleated portion the cone fibre is continued as a rather broad 

 cytoplasmic filament straight inward to the border of the nuclear 

 layer, where it terminates in an expanded portion or cone foot, 



