THE EYE. 



373 



tolerably strongly, of a round or oval figure, and 0*002 — 

 0-004'" in size, sometimes looking like free nuclei, sometimes 

 like minute cells almost entirely filled by large nuclei, although, 

 according to my observations, they should all be referred to 

 the latter category. For I find, especially in preparations 

 made with chromic acid, that from both sides of every granule 

 very fine filaments, 0*002 — O'OOS'" thick, are regularly given 

 off, which in many cases may be distinctly seen to proceed 

 from a pale border surrounding the granule, so that the whole 

 is very like a bipolar ganglion-cell in miniature. In Man, 

 the granules, in the greater part of the retina, are disposed in 

 two layers — an outer, thicker, of 0013 — 001 6'" (h), and an 

 inner, thinner (/), of 0006 — 0008'" — which are parted from 

 each other by a clear, fine-granular, and, to some extent, 

 vertically striated layer (g), 0006 — 0'008'" thick ; whilst, 

 towards the or a serrata, the two constitute a single stratum of 

 not more than 00 15"' in thickness. The granules of the 

 inner layer are a trifle larger than those of the outer, and 

 when they are oval, as is most usually the case, I find that 

 they are placed with the long axis in the direction of the 



Fig. 305. 



thickness of the retina, so that their 

 processes, like those of the external 

 layer, run directly outwards and 

 inwards. 



3. The layer of cineritious cere- 

 bral substance (fig. 302 e) is pretty 

 sharply defined on the side of the 

 granular layer, and less so towards 

 that of the fibres of the optic nerve, 

 between the elements of which it 

 penetrates more or less. It is com- 

 posed of a finely granular matrix, cor- 

 responding exactly with that of the 

 grey substance on the surface of the 

 cerebrum and cerebellum, and of nu- 

 merous nerve-cells scattered in it. 

 Of the latter, some, particularly in the outer half of this layer, 

 which is 0-008—0-012 — 0-02'" thick, are small (0*003— 

 0006"'), inconspicuous, and in fresh preparations recognisable 



Fig. 305. Nerve-cells with processes from the retina of the Ox, x 350 diara. 



