THE INTERNAL COAT THE NERVOUS TUNIC 



655 



layer. These cells vary in size; the dendritic or distal processes of the 

 smaller cells on reaching Henle's layer are in relation with the ierminal 

 fibrils of the cone feet; those from the larger nerve cells are in relation 

 with the terminal knobs of the rod fibers. The axis cylinders or central 

 processes from all these cells after traveling horizontally viz., in a plane 

 parallel to the layers of the retina for a greater or less distance, turn 

 inward and pass to the inner reticular layer, where they come into 



FIG. 555. HORIZONTAL CELL FROM THE RETINA OF A CALF. 



o, cell body; 6, axon; c, terminal arborizations of the axon. Golgi's stain. X 150. 



(After Marenghi.) 



relation with the dendrons 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 neu- 

 rons. 



THE MIDDLE TYPE. The nerve cells of the middle type are usually 

 of bipolar form, and are the most abundant elements of the inner 

 nuclear layer. The one set of their processes is directed outward (periph- 

 eral ward) ; they pass to the outer reticular layer where they eventually 

 come into relation with either the rod fibers or the cone fibers. Hence 

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



