VISUAL ORGAN. 



347 



Middle layer 

 (Gehimscliicht). 



6. Outer reticular (molecular) layer ; 



7. Outer ganglionic (inner granular) layer ; 



8. Inner reticular (molecular) layer ; 



9. Inner ganglionic layer ; 



10. Nerve-fibre layer ; 



11. Membrana limitans interna. 



We shall begin the description of the individual layers with 

 the outermost one. The elements of the pigment sheath are 

 usually regular hexagonal cells, which are arranged in a simple 



FIG. 263. 



Diagram of the retina, compiled by Kallins, from the work of Ramon y Cajiil. 

 J, layer of rods and cones; B, membrana limitans cxtcnia; C, outer granular hiytr; 

 7), Henle's fibre layer; E, outer reticular layer ; F, outer ganglionic layer; G, inner retic- 

 ular layer ; JET, inner ganglionic layer ; J, nerve-fibre layer ; K, membrana limitans interna ; 

 a, Miiller's supporting cell; b, rods; c, cones; rf, bipolar cell belonging to rods; e-i, bipolar 

 cell belonging to cones; k-m, horizontal cells ; , centrifugal nerve fibre; o-t, ganglion cells 

 of optic nerve; a-e, spongioblasts (amarkrine cells) ; -#, diffuse amakrine cells; >?, nervous 

 spongioblast. (From Merkel-Bonnet, Ergebnisse d. Anat. u. Entwick, Bd. II. S. 251.) 



layer. The somewhat flattened nucleus lies in the outer pig- 

 ment-free half of the cell. The inner strongly pigmented 

 part of the cell possesses long, fine, fringe-like processes, which 

 penetrate between the outer segments of the visual cells. The 

 pigment, in the form of small dark-brown granules and rods, 

 may change its position under the influence of light, so that 



