652 



THE EYE 



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

 directly upon, ;uid 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 bacillary por- 

 tion of the cone element, to which it is ofttimes united by a slightly con- 

 stricted neck. In this inner portion, just within the external limiting 

 Pi B 



WUACENTTOTHE CHOROID 



ADJACENT TO THE VITREOUS 



FIG. 553. DIAGRAMS OF THE HUMAN RETINA, SHOWING THE RELATIONSHIPS TO 

 EACH OTHER OF THE RETINAL NEURONS, AND THEIR DISPOSITION IN THE DIF- 

 FERENT LAYERS. 



(From Fox's "Ophthalmology.") 



membrane, is the cone nucleus; it differs from the rod nucleus in that 

 it stains less deeply, presents no transverse striations, and frequently 

 incloses a distinct nucleolus. From its nucleated portion the cone fiber 

 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, from the flattened inner surface of which the fine filaments 

 penetrate the margin of the outer reticular layer. 



The outer segments of both rods and cones are embedded in the cells 

 of the pigment layer, whose delicate filamentous processes project between 

 the rods and cones, frequently extending almost to the external limiting 



