THK EYE. 



415 



productions ( Hoffmann). 



Fig. 258. 



latter, hoNvever, appear to be artificial 

 This layer o£ fibres extends over the inner 

 surface of the retina, and g-radually thins 

 from the point of entrance of the optic 

 nerve to the limits of the retina. 



(3) The ganglion-layer lies immedi- 

 ately without the nerve-fibre layer (Fig-. 

 258 Ù). The gang-lion-cells are small and 

 usually pear-shaped. The cells possess 

 large nuclei, round which is a thin layer 

 of very granular protoplasm. The cells 

 have inner and outer processes ; the inner 

 pass into the nerve-fibre layer, the outer 

 into the inner molecular layer in more or 

 less radiating directions. Manz claims 

 to have traced a direct connection between 

 the inner processes and the fibres of the 

 nerve-fibre layer. 



Each ganglion-cell, whatever its shape 

 or size, has only one inner process, which 

 is easily distinguished from the outer 

 process by its being more glistening, by 

 the possession of varicosities, and because 

 this process never branches. 



The outer processes are single(Schwalbe) 

 or rarely double (Hoffmann), and have as 

 a rule a direction at right angles to the 

 inner processes. Each outer process is 

 finely granular, which suggests rather a 

 prolongation of the cell- substance than 

 a true process. Frequently they are 

 branched, sometimes forming two equal 

 sized processes, which give off finer 

 twigs ; at other times they appear to 

 pass through the whole of the inner 

 molecular layer without undergoing di- 

 vision (Schwalbe). The processes do not 

 inosculate (Santi Sirena). 



(4) The inner molecular layer (Fig. 

 258 c) is 0'07-o*o8 mm. thick (Hoffmann), and consists of a finely 



Vertical section through retina of 

 frog ; after Hoffmann. Magni- 

 fied 5C0 times. 



a Internal limiting membrane. 



6 Ganglion-cell layer. 



r Internal molecular layer. 



cl Internal nuclear layer. 



(' External molecular layer. 



/ External nuclear layer. 



// Layer of rods and cones. 



h Pigmented epithelium layer. 



1. Inner segments of rods and 



cones. 



2. Outer segments of roils And 



cones. 



3. Outer transparent segments of 



pigmented epithelium. 



