STRUCTURE OF THE RETINA 



635 



The Nerve Fiber and Nerve Cell Layers. The inside of the retina is 

 formed of a layer of nerve fibers which have their origin in the adjacent large 

 nerve cells and run toward the exit of the optic nerve. Externally the gan- 



H 



FIG. 447. Transverse Section of a Mammalian Retina. A, Layer of rods and cones; B, bodies 

 of visual cells (external granular) ; C, external molecular layer; E, layer of bipolar cells (internal 

 granular); F, internal molecular layer; G, layer of ganglionic cells; H, layer of optic-nerve fibers; 

 a, rod; b, cone; c, body of the cone cell; d, body of the rod cell; e, bipolar rod cells: /, bipolar cone 

 cells; g, h, i, j, k, ganglionic cells ramifying in the various strata of the internal molecular zone; 

 r, inferior arborization of the bipolar rod cells, connecting with the ganglionic cells; r, inferior 

 arborization of the bipolar cone cells; t, epithelial or Miiller cells; x, point of contact between the 

 rods and their bipolar cells; z, point of contact between the cones and their bipolar cells; s, centrif- 

 ugal nerve fiber. (Cajal.) 



glionic cells send up numerous processes, or dendrites, which interlace with 

 the fibers of the bipolar cells of the second layer. 



The Middle Layer. The middle layer consists of bipolar cells which send 

 one process toward the ganglionic layer to interlace with the dendrites of the 



FIG. 448. Perpendicular Section of the Retina of a Mammal. A, External grains or bodies of 

 rods; B, bodies of cones; a, horizontal external or small cell; b, horizontal internal or large cell; c, 

 horizontal internal cell with descending protoplasmic appendages; e, flattened arborization of one 

 of the large cells; f, g, h, j, I, spongioblasts ramifying in the various strata of the internal m< lec : 

 ularzone; ra, n, diffuse spongioblasts; o, ganglionic cell; i, external 

 molecular zone. (Cajal.) 



molecular zone; 2, internal 



