MICROSCOPIC STRUCTURE OF THE RETINA. 



limitans externa, lying between the outer nuclear layer and the layer of rods and 

 cones ; but, as will be afterwards explained, these so-called " membranes " are merely 

 the boundary lines of the sustentacular tissue of the retina. The accompanying 

 figure, from Max Schultze, represents diagrammatically the general arrangement of 

 the layers (fig. 48). 



The several layers of the retina will first be considered successively as they are 

 met with from within out, after which the sustentacular fibres or fibres of Miiller, 

 which traverse several of the layers, and the connection of the nervous elements 



Outer or choroidul surface. 



. Layer of pigment cells. 

 7. Layer of rods and cones. 

 ..Membrana limitans externa. 



) 6. Outer nuclear layer. 



5. Outer molecular layer. 

 \ 4. Inner nuclear layer. 



3. Inner molecular layer 



2. Layer of nerve-cells. 



1. Layer of nerve-fibres. 



. . . Membrana limitans interim 



Inner or vitreous surface. 



Fig. 48. DIAGRAMMATIC SECTION OF THE HUMAN RETINA (Schultze). 



throughout the retina with one another will be described. Finally an account will 

 be given of those parts of the retina which present points of difference from the rest, 

 especially the central fovea, and the ciliary part. 



1. Layer of nerve-fibres. The optic nerve passes at the porus opticus 

 directly through the thickness of the retina to reach its inner surface (fig. 47) 

 on which it spreads out in the form of a membrane which extends to the ora 

 serrata. Its fibres, which are destitute of a primitive sheath and vary much in 

 size, but are mostly small, lose their medullary sheath on reaching the retina, 

 consisting there normally of axis-cylinder only (Bowman). In rare cases some of 

 them may retain their medullary sheath for a short distance. They are collected 



