656 THE EYE 



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

 (Fig. 553). The terminal fibrils of the cone bipolars are horizontally, 

 those of the rod bipolars radially, disposed. 



The central processes, axons, of the bipolar cells are directed inward 

 (central ward), and on entering the inner reticular layer terminate in 

 an end brush which is in relation with the dendritic processes from the 

 large ganglion cell layer. 



THE INNER NERVE CELL TYPE. The inner nerve cell type (amac- 

 rine cells of Cajal) are large nerve cells which occupy a narrow zone 

 at the inner margin of this nuclear layer. These are large stellate cells 

 whose dendritic processes extend into the inner reticular layer and take 

 part in the formation of the dense felt work of which that layer consists. 

 The course of the axis-cvlinders of these cells is still a matter of some 



FIG. 556. Two AMACRINE CELLS FROM A TRANSECTION OF THE RETINA OF A CALF. 

 Golgi's stain. X 260. (After KoUiker.) 



doubt. Eamon y Cajal, believing these cells to possess no axon, desig- 

 nated them 'amacrine cells' and subdivided them according as their den- 

 drons were distributed in either one of several horizontal planes (the 

 number varying in different species) or diffusely throughout the inner 

 reticular layer. 



Some of the amacrine cells, however, send an axon in a horizontal 

 direction to the inner reticular layer, and are also in relation with the 

 terminal arborizations of centrifugal nerve fibers which enter from the 

 nerve fiber layer. These have been regarded by some observers as 'dis- 

 located nerve cells' of the ganglion cell layer ; Cajal named them 'associa- 

 tion amacrinsf 



8. The inner reticular layer (inner molecular layer, inner plexi- 

 form layer) is a densely tangled network of nerve-cell processes, a neuro- 

 spongium. To these are added a much branched portion of Miiller's 

 fibers, which form the chief supporting tissue of this layer. The cell proc- 

 esses entering into this formation are derived from the cells of the inner 

 nuclear and ganglion cell layers, and it is here that the processes of these 

 cells interlace so closely as to permit the transmission of impulses from 

 the one neuron to the other. Their terminal arborizations are, for the 



