RETINA. 287 



packed little rods, arranged in a radiated form, and be- 

 tween which at certain intervals appear broader, conical 

 bodies. When the retina is viewed from behind, t. e., 

 from the choroid coat, we see regularly arranged between 

 these cones fine points which correspond to the ends of 

 the little rods. 



Now that which intervenes between this bacillar layer 

 and the proper expansion of the optic nerve, is likewise 

 a very complex affair, in which a series of layers follow- 

 ing one another in regular succession can be distin- 

 guished. Immediately in front of the bacillar layer 

 comes a comparatively thick stratum, which appears to 

 be nearly entirely made up of coarse granules, the so- 

 called external granular layer (Fig. 85, &'). Then comes 

 a thinner layer which generally presents a tolerably 

 amorphous appearance, the inter-granular layer (Fig. 

 85, t). Then we again have coarsish granules (the inter- 

 nal granular layer) ; these bodies in both layers having 

 much the appearance of nuclei (Fig. 85, k). Next fol- 

 lows a second layer of a more uniform, finely granular or 

 finely striated appearance, and of a more greyish hue 

 (Fig. 85, ri), and then only the tolerably thick stratum 

 of the optic nerve, which in its turn is bounded by a 

 membrane, the membrana limitans (Fig. 85, /), which is 

 in close apposition to the vitreous body. Within this 

 last layer we see, besides the fibres of the optic nerve, 

 and situated behind them, a number of largish cells, 

 which have the appearance of nerve-cells (Fig. 85, g). 



This extremely complex structure in a membrane which 

 at first sight is so simple and so delicate, readily accounts 

 for its being extremely difficult to ascertain with cer- 

 tainty all the relations of its individual parts. It was 

 one of the most important advances towards the know- 

 ledge of these relations which was made by the discovery 

 of Heinrich Muller, that namely from behind, from the 



