Il8 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



is seen to consist of three layers (Fig. 82) : (1) an inner 

 or fibrous layer in contact with the vitreous body, con- 

 sisting wholly of in- 

 terlacing fibers of the 

 optic nerve; (2) of an 

 outermost layer — bacil- 

 lary layer — composed 

 entirely of rodlike 

 bodies set on end and 

 in contact with the 

 choroid; and (3) be- 

 tween these a middle 

 layer, consisting of 

 granules and larger 

 nucleated cells, and 

 therefore called the 

 granular and nuclear 

 layer. 



All three layers ex- 

 ist in all parts of the 

 retina except in two 

 small spots : (1) where 

 the optic nerve en- 

 ters there can be, 

 of course, only the 

 fibrous layer ; (2) in 

 the center of the bot- 

 tom of the cup and in 

 the very axis of the 

 ball there is a small 



FIG. 83 —Enlarged section of retina (after depression in which 

 Schultze) : A, general view; B, nervous , «, , 

 elements; a, bacillary layer; b, interior the tlurOUS layer IS en- 

 limit of this layer; c, external nuclear [jrpjy and the BTanu- 

 layer ; rf, external granular layer ; e, in- " ' ' S 

 ternal nuclear layer ; f, internal granular lar and nuclear layer 

 layer ;g, ganglionic layer ; /;, fibrous layer, . . . . 



consisting of fibers of optic nerve. nearly entirely want- 



