THE LAYEES OF THE KETINA 



589 



The cells comprising this layer are mostly large, stellate, pyri- 

 form, or spheroidal nerve cells, from whose peripheral border den- 

 drites pass to the inner reticular 

 layer, and from whose central border 

 a neuraxis passes to the nerve fibre 

 layer to eventually become the neur- 

 axis of a fibre of the optic nerve. 



These cells, though varying much 

 in size and shape, are mostly com- 

 posed of a clear cytoplasm and pos- 

 sess a distinct nucleolus. Inter- 

 mingled with the nerve cells are 

 many branches of the Miillerian 

 fibres which here form an open 

 meshed network within whose spaces 

 the nerve cells are inclosed. 



10. The nerve fibre layer, in in- 

 timate relation with the preceding, 

 forms the innermost of the retinal 

 zones. It consists of naked axis 

 cylinders passing from their origin 

 in the ganglionic layers to their im- 

 mediate destination, the optic nerve. 

 They are, therefore, mostly if not 

 wholly centripetal fibres. A few 

 centrifugal fibres have been demon- 

 strated in this layer, but they would 

 appear to be probably vaso-motor in 

 function. 



The nerve fibres of this layer converge from all portions of the 

 retina, follow a meridional course through the open meshes of the 

 network of branching Miillerian fibres, and converge toward the 

 optic papilla, the entrance, or rather the point of exit, of the optic 

 nerve. Hence the nerve fibre layer, being augmented by the con- 

 stant acquisition of new neu raxes from the ganglion cells, becomes 

 progressively thicker toward the posterior pole of the eye, and is 

 thickest at the margin of the optic papilla, where it is so highly 

 developed as to almost exclude the other retinal layers. 



The course of these non-medullated nerve fibres is not straight ; 

 on the contrary, they interlace to form a delicate fibrillar network. 

 At the margin of the papilla optica the nerve fibres bend outward 



FIG. 433. A NERVE CELL OF THE 



LARGE GANGLION CELL LAYER ; 

 FROM THE RETINA OF A CAT. 



n, n, neuraxis ; c, c, collaterals. Golgi's 

 stain, x 325. (After Kolliker.) 



