CHAPTER XXXVI. 



THE EYE. 



THE RETINA. 



BY MAX SCHULTZE. 



THE retina is the membrane-like terminal expansion of the 

 optic nerve lining the posterior part of the globe of the eye. 

 In addition to nerve fibres, it contains various forms of nerve 

 cells, which are intercalated in the course of these fibres before 

 they reach their peripheric extremity. The extremity itself is 

 characterized by a peculiar terminal apparatus, forming the 

 layer of rods and cones, which are invested by pigment. The 

 nerve fibres and nerve cells of the retina are imbedded in a 

 spongy connective-tissue substance, which may be regarded as 

 a continuation of that of the optic nerve, and presents great 

 similarity to the connective tissue of the central organs of the 

 nervous system. A part of this connective tissue is formed by 

 bloodvessels, and probably also by lymphatics. 



The textural elements of the retina are arranged in layers 

 parallel to the surface of the spherical external membrane. 

 The innermost of these, in immediate contact with the vitreous, 

 is formed by the limiting layer of the spongy connective tissue 

 which is often intimately connected with the surface of the 

 vitreous, and is named the membrana limitans interna; its 

 adhesion to the vitreous sometimes renders the detachment of 

 the retina in the vicinity of the ora serrata, in fresh or well- 

 preserved specimens, extraordinarily difficult. The most ex- 

 ternal of the layers is that of the rods and cones, including the 

 pigment sheaths, which are formed by a special cell-layer 

 the pigment cell-layer of the retina. This rests upon the 

 choroid, and, indeed, upon the vitreous connective substance 

 of the chorio-capillaris, to which, on separation of the retina, it 



