220 



THE ESSENTIALS OF HISTOLOGY. 



Near the pupil the small arteries form a small anastomotic circle, from 

 which capillaries arise and pass still nearer the pupil, around which 

 they form a close capillary network. 



A large number of nerve-fibres are distributed to the choroid and 

 iris, probably going chiefly to the muscular tissue (ciliary muscle and 

 sphincter and dilatator iridis). 



The retina consists of the eight layers shown in the accompanying 

 figure (fig. 256), numbered as they occur from within out. 



Outer or choroid.il surface. 



8. 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 n 



erve-cells. 



1. Layer of nerve-fibres. 



. . Membrana limitans interna. 



Inner surface. 



FIG. 256. DIAGRAMMATIC SECTION OF THE HUMAN RETINA. 



The inner surface of the retina, which is smooth, rests upon the 

 hyloid membrane of the vitreous humour. It is formed of -the united 

 bases of the fibres of Miiller, which will be afterwards described. 



The layer of nerve-fibres is formed by the expansion of the 



