X524 



A MANUAL OF ANATOMY 



parts of the cone-fibres, and the internal processes termmate in 

 arborizations in the inner molecular layer at diiferent levels. 



The horizontal cells occupy the outer part of the inner nuclear 

 layer. Their dendrites enter the outer molecular layer, and come 

 into relation with the terminal parts of the cone-fibres, whilst their 

 axons run in a horizontal direction. 



The spongioblasts are situated in the innermost part of the inner 

 nuclear layer. They are destitute of axons, and have been called 

 amacrine cells, because each cell is ' without a long fibre or process.' 

 Their dendrites enter the inner molecular layer, and terminate in 

 arborizations, which are arranged in strata. 



5. Outer Molecular (Outer Plexiform) Layer.— This layer is com- 

 posed of the following structures : (i) the external processes of the 



Layer of Rods and Cones 

 Membrana Limitans Externa 





Outer Nuclear Layer 



Outer Molecular Layer 

 Inner Nuclear Layer 



Inner Molecular Layer 

 Ganglionic Layer 



Nerve-fibre Layer 

 Membrana Limitans Interna 



Fig. 636. — Section of the Retina as seen under the Microscope 



(magnified). 



rod-bipolars and cone-bipolars of the inner nuclear layer ; (2) the 

 dendrites of the horizontal cells of the inner nuclear layer ; and 

 (3) the terminal parts of the rod-fibres, and filaments from the foot- 

 plates of the cone-fibres. 



6. Outer Nuclear or Granular Layer. — This consists of granules, 

 which are of two kinds, namely, rod-granules and cone-granules. 

 The rod-granules are the more numerous, and are oval enlargements 

 in the course of the rod-fibres, as these pass to the outer molecular 

 layer. Each rod-fibre has only one rod-granule, and the granules 

 lie at different levels. Each granule has a nucleus, which presents 

 transverse striations, there being at least two clear bands. The 

 external process of each rod-granule is continuous with one of the 

 rods of the bacillary layer, and the internal process passes into the 



