RETINA 



215 



part and a nervous part. The former is stretched as on a frame 

 between the limitans externa and hyaloid membrane. 



The nervous elements are arranged in the following concentric 

 layers : 



I. Developed from the internal layer of the, secondary optic vesicle. 



A. Cerebral layer. 



1. Layer of nerve-fibres (of optic nerve). 



2. Layer of ganglion-cells. 



3. Inner reticular layer. 



4. Granular layer (inner). 



5. Outer reticular or subepithelial layer. 



B. Epithelial layer. 



6. Layer of visual cells (outer granular layer with the 



rods and cones). 



II. Developed from, the external layer of the secondary optic vesicle. 



7. Pigment epithelium (retinal epithelium). 



It seems probable that the various nerve-cells of the retina are not directly 

 connected with one another, but are only contiguous. 



Rods and cones, 



Memhrana 



limitans. 



Outer granular 

 layer. 



Concentric 



supporting-cells 



(nucleated). 



Concentric 

 supporting-cells 

 (non-nucleated). 



Radial fibres. 



Radial fibres. ~ 



Outer recticular 



layer. 



Sub-epithelial 

 ganglion-cell. 



Star-shaped 

 ganglion-cell. 



Bipolar 

 ganglion-cell. 

 Multipolar 

 ganglion-cell. 

 Inner recticular 

 layer. 



Centrifugal 

 nerve fibres. 



Multipolar 

 ganglion-cell. 



Layer of 

 nerve fibres. 



FIG. 172. DIAGRAM OF THE ELEMENTS OF THE RETINA. (Supporting elements 

 on the left, and nervous elements on the right. ) After Ph. Stohr. 



These layers are so arranged that the nerve-fibres lie next to 

 the vitreous humour, that is, internally, while the rods and cones 



