416 THE SKIN AND THE SENSE-ORGANS. 



granular mass together with the outer processes of the gang-Hon- 

 layer, and connective-tissue elements. 



The granular matter consists of an extremely fine network or 

 reticulum, through which numerous fine fibres course (Schultze, 

 Kolliker, Manz, Heinemann, and others) ; according to Schultze 

 the supposed molecules or granules of others (Henle, Merkel, and 

 Retzius) are simply the fine meshes of this reticulum. The 

 branched, outer processes of the ganglion-cells form a rich anas- 

 tomosis in this layer. 



(5) The inner nuclear layer (Fig. 258 d) contains parts of two 

 kinds of cellular elements ; these are radial nerve-fibres with large 

 nuclei, and connective-tissue elements (see below, par. 10). The 

 nerve-fibres are easily distinguished by their spindle-shaped vari- 

 cosities ; both cellular elements possess large oval nuclei. The 

 bodies of the cells surrounding the nerve nuclei are almost filled 

 by the nuclei, which have sharply-defined, rounded nucleoli. The 

 fibres to which these cells are attached may be distinguished as 

 inner and outer processes ; the inner process is fine, irregularly vari- 

 cose, and unbranehed ; the outer process is thicker, finely granular, 

 and is not varicose (Schwalbe). At the margin of the outer mole- 

 cular layer the outer processes divide, usually into two branches, 

 and at an acute angle to each other, though sometimes at a right 

 ano-le. The further course of these branches in the outer molecular 

 layer is unknown. 



(6) The outer molecular layer (Fig, 358 e) corresponds in 

 general with the inner molecular layer as regards its structure ; it 

 is, however, much thinner. 



(7 and 9) The outer nuclear layer and the layer of rods and 

 cones (Figs. 258 /, g, 259). The rods and cones are intimately 

 connected with the elements of the outer nuclear layer, hence the 

 two layers are best described together. 



The rods \hacilli) have two parts or limbs, an outer and an inner, 

 which differ in structure, and in chemical and physical characters. 

 The outer part is highly refractive, the inner more homogeneous 

 and less refractive, the two parts being' sharply differentiated from 

 one another. 



The outer part is also weakly doubly refracting, the inner has no 

 trace of this property. The rods are o*o5-o*o6 mm. in length, of 

 which 0'035-o*04 mm, belongs to the inner limb. The outer 

 end of the outer limb is more or less rounded ; the whole has a 

 longitudinal striation (Schultze), due to its being composed of 



