18 



VERTEBRATE PHOTORECEPTORS 



surface of the posterior part of the eye. It contains the pho- 

 toreceptor elements, the nervous transmitting apparatus for 

 vision, and a supporting framework. Exchiding the pigment 

 epithehum which is non-nervous, the retina is made up of nine 

 layers arranged from without inward as follows (Figure 15) : 



1. Layer of visual cells (rods and cones) 



2. External limiting membrane 



3. External nuclear (granular) layer 



4. External molecular (plexiform, reticular) layer 



5. Internal nuclear (granular) layer 



6. Internal molecular (plexiform, reticular) layer 



7. Ganglion cell layer 



8. Nerve fiber layer 



9. Internal limiting membrane 



^ 







Fig. 15 



■9 



