No. 3-] ACi'TE lysjOA' j.y rKA'rENjy:jrKs. 455 



deep over the entire retina. In the center of the area, however, 

 the cells lie closely together, while in other parts of the retina 

 they are some distance apart. 



The rods and cones in the area have a less diameter and are 

 more numerons per given area than elsewhere. Hence the 

 cells which form their connection with the nerve fibres (nerve 

 cells and cells of the inner nnclear layer, or bipolar cells) must 

 also be more numerous. l?ut this is not the only reason for an 

 increase in the number of cells in the area. Ramon y Cajal 

 (28) has described and pictured the manner in which these cells 

 form the connection between the nerve fibres and the rods and 

 cones. Numerous processes (dendrites) from the nerve cells 

 pass outward and branch profusely in the inner molecular layer 

 among the ingoing branches (neurites) of the cells of the inner 

 nuclear layer. A similar relation exists in the outer molecular 

 layer between the outgoing branches (dendrites) of these cells, 

 which are bipolar, and the ingoing branches (neurites) of tin; 

 cells of the outer nuclear Layer. These line branches from tlic 

 cells of different layers only come in close relation, and in no 

 case were they found to anastomose with each other. He 

 divides these bipolar cells into two classes: (1) those whose 

 dendrites come in contact with the neurites from the cone cells ; 

 and (2) those whose dendrites come in contact with neurites 

 from the rod cells. In the periphery of the retina each bipolar 

 rod cell may come in contact with from 10 to 30 rods. Likewise 

 each bipolar cone cell is related to several cones, l^ut toward 

 the center of vision the number of rods and cones whicli con- 

 nect with a single bipolar cell becomes rapidly less, and in the 

 center of the fovea each bipolar cell comes in contact with but 

 a single cone. Ramon y Cajal also finds a similar relation 

 existing between the cells of the nerve-cell layer and Die 

 bipolar cells of the inner nuclear layer. 



The number of cells in the outer nuclear layer is directly 

 dependent on the number of rods and cones, each rod and cone 

 having but a single nucleus. In fact a rod, or cone, with its 

 nucleus, has long been considered as a much drawn-out cell 

 whose dendritic end (the rod or cone) is more or less distant 

 from the nucleus, and is in some cases connected only by a 



