816 



THE EYE AND VISION 



[CH. LV1II. 



fibres. Externally the cells send off several branched processes 

 which pass into the next layer. 



4. Inner molecular layer. This presents a finely granulated 

 appearance. It consists of neuroglia traversed by numerous fibrillar 

 processes of the nerve-cells just described, and the minute branch- 

 ings of the processes of the bipolar cells of the next layer. 





Outer mole- 

 cular layer. 



FIG. 514. Diagram showing the susten- 

 tacular fibres of the retina ; /, fibre- 

 basket above the external limiting 

 membrane ; m, nucleus of the fibre ; 

 r, base of the fibre. 



(From M'Kendrick, after Stohr.) 



Inner limb 

 of rod. 



Rod fibre. .. 



Bipolar cell. 



FIG. 515. Diagram showing the nervous elements 

 of retina. 1, Nerve-fibre of ganglion cell; 2, pro- 

 cesses of ganglion cell going outwards ; 3, nerve- 

 fibre passing from bipolar cell in inner nuclear 

 layer ; 4, process of ganglion cell towards bipolar 

 cell; 5, arborisations of fibres from rods and 

 cones with the branches of bipolar cells. 



(From M'Kendrick, after Stohr.) 



5. Inner nuclear layer. This consists chiefly of numerous small 

 round cells, each with a very small quantity of protoplasm surround- 

 ing a large ovoid nucleus ; they are generally bipolar, giving oft one 

 process outwards and another inwards. One process passes inwards 

 to form a synapse with the arborisation of a ganglion cell, the other 

 outwards to similarly arborise with the branchings of the rod and 

 cone fibres. Some cells, called spongioblasts, or amacrine cells, how- 

 ever, only send off one process, which passes inwards (fig. 514). 



