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MANUAL OF PHYSIOLOGY. 



mented cells of epithelial character, which, on their outer face, 

 show a striking hexagonal outline. 



A nerve fibril then may be said to have the following course : 

 entering with the other fibrils at the porus oplicus, it reaches the 

 immediate -vicinity of the hyaloid membrane, and runs a certain 

 distance in contact with that membrane, it then turns outward 

 toward the choroid and enters a nerve cell. From the nerve cell 



FIG. 229. 



Showing the course of the fibres of the optic nerve N, as they pass along the inner 

 surface of retina R, to meet the ganglion cells, whence special communications pass out- 

 ward to the layer of rods and cones in the pigment layer p, next the choroid c. 



pass on a couple of filaments which pierce the various granular 

 and nuclear layers where they probably freely inosculate with 

 the fibrils from other cells and finally terminate in a rod or a 

 cone. The rods and cones may then be regarded as the ultimate 

 terminals of the nerves, and they lie in the active protoplasm of 

 the peculiar, pigmented epithelium cells. 



It is this outer layer, consisting of rods and cones lodged in 



