556 



GRANULAR LAYER OF RETINA. 



[sect. 226. 



of the retina they are even coo^" to croc^"' apart (fig. 227, 3) , and 

 more rods are situated between them. The bacillar layer presents 

 on its external aspect, when the outermost surface is brought into 

 focus, roundish spaces more or less scattered, and filled with a 

 clear uniting substance (which occurs elsewhere between the 

 elements of this layer, and, in the horse, forms a sort of mem- 

 brane, Midler) ; these spaces correspond to the cones, and in the 

 centre of them a small dark circle appears, which is the terminal 

 surface, or the apparent section of the rod seated upon the cone, 

 while around the spaces the closely-crowded terminal surfaces of the 

 Fig. 227. proper rods are seen arranged in the manner 



of a mosaic, in simple, double, or multiple 

 reticulated lines (fig. 227). 



2. The granular layer, stratum granulo- 

 sum (fig. 224), consists of clear granular 

 bodies, which become dark in water and 

 reflect the light pretty strongly. They are 

 of round or oval form, 0-002"' to croo^" 

 in size, sometimes look like free nuclei, some- 

 times like small cells almost completely 

 filled with large nuclei; yet, according to 

 my own observation, all would seem to be- 

 long to the latter category. I find, indeed, 

 especially in chromic acid preparations, that 

 very fine filaments, ' cr.0002'" to o"0003'" 

 thick, pass off regularly from each of these bodies in both direc- 

 tions, and that these filaments distinctly proceed, in many cases, 

 from a pale contour around the cell, so that the whole bears a 

 great resembance to a bi-polar ganglion cell in miniature. In 

 man, the granules are everywhere arranged in two layers, an 

 outer thicker, o - oi8'" to o , 026'" (fig. 224, 2), and an inner thinner 

 (fig. 224, 4) layer, 0'0i2"' to cro26'", which are separated from 

 each other by a clear layer, finely granulated and perpendicularly 

 striated, croio'" to cc^a/" in thickness, which may be named the 

 ' intermediate granular layer/ The outer granular layer consists 

 of the proper outer granules (fig. 225, 2, d), connected with the 

 filiform processes of the rods, the rod-granules ; it also comprises 

 the cone-granules (fig. 225, 1, d), already described. The granules 

 of the inner lamina also, which are slightly larger than those of 

 the outer layer, are connected both with the filaments of the rods 

 and with those of the cones. 



3. The layer of grey cerebral substance (fig. 224, 5, 6), extends 



Bacillar layer seen from 

 without. 1. at the yellow 

 spot (only cones) ; 2. at the 

 boundary of this spot ; 3. 

 from the middle of the re- 

 tina ; a. the cones, or the 

 spaces corresponding to 

 them •, b. rods of the cones, 

 the terminal surface of 

 which is often situated 

 deeper than the ends of 

 the proper rods, c; mag. 350 

 times. 



