THE LAYERS OF THE RETINA 



587 



layer, where they come into relation with the dendrites of the large 

 nerve cells of the ganglion cell layer. Other processes, mostly from 

 the smaller cells, terminate in the outer reticular layer, probably 

 serving the purpose of association neurones. 



The nerve cells of the middle type are usually of bipolar form, 

 and are the most abundant elements of the outer nuclear layer. 



FIG. 431. HORIZONTAL CELL FROM THE RETINA OF A CALF. 



a, cell body ; 6, neuraxis ; c, terminal arborizations of the neuraxis. Golgi's stain. 



x 150. (After Marenghi.) 



The one set of their processes is directed outward (peripheral ward); 

 they pass to the outer reticular layer where they eventually come 

 into relation with either the rod fibres or the cone fibres. Hence 

 those cells which are in relation with the visual rods are classified 

 as rod bipolars, those in relation with the visual cones as cone 

 bipolars (Fig. 428). The terminal fibrils of the cone bipolars are 

 horizontally, those of the rod bipolars radially disposed. 



The central processes, neu raxes, of the bipolar cells are directed 

 inward (central ward), and on entering the inner reticular layer ter- 

 minate in an end brush which is in relation with the dendritic 

 processes from the large ganglion cell layer. 



The inner nerve cell type (amacrine cells of Cajal, spongio- 

 blasts of Kolliker) are large nerve cells which occupy a nar- 





