THE RETINA 419 



the outer molecular layer, which is seen at d d' (Fig. 

 136, A). From the inner surface of this meshwork other 

 fibres proceed, containing a second set of granules or 

 nuclei, which forms the inner nuclear layer (/ /'). 

 Inside this laj^er is a stratum of convoluted fine nervous 

 fibres, the inner molecular layer (g g') — and inside 

 this again are numerous nerve-cells (h h') constituting 

 the layer of ganglionic cells. Processes of these 

 nerve-cells extend, on the one hand, into the layer of 

 convoluted nerve-fibres ; and on the other are continuous 

 with the stratum of fibres of the optic nerve (0- 



These delicate nervous structures are supported by a 

 sort of framework of connective tissue of a peculiar kind 

 (B), which extends from an inner or anterior limiting 

 membrane (I), which bounds the retina and is in con- 

 tact with the vitreous humour, to an outer or posterior 

 limiting membrane (a), which lies at the inner ends, 

 or bases, of the rods and cones near the level of 6' c' in A. 

 Thus the fi'amework falls short of the nervous sub.stance 

 of the retina, and the rods and cones lie altogether 

 outside of it, wholly unsupported by any connective 

 tissue. They are, however, as we shall see, imbedded in 

 the layer of pigment oti which the retina rests (p. 424). 



The fibres of the optic nerve spread out between the 

 inner limiting membrane (J.) and the nerve-cells {h'), and 

 the artery which enters along with the optic nerve 

 pierces the centre of the nerve (Fig. 135), and ramifies 

 between the two limiting membranes. Most of the 

 branches run between the inner limiting membrane and 

 the inner nuclear layer (//'). Thus, not only the nervous 

 fibres, but the vessels, are placed altogether in front of 

 the rods and cones. 



The structural appearance of the nervous elements of 

 the retina and the seven " layers " into which it may be 

 divided as described above is such as can be made out in 

 any ordinarily stained section. Such a section tells us very 

 little, except in the case of the rods and cones, as to tlie 



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