I5i8 



A MANUAL OF ANATOMY 



which encloses the vitreous body, and its external surface is in 

 contact with the choroid coat. Posteriorly it receives the fibres of 

 the optic nerve. Anteriorly it extends almost to the ciliary body, 

 where it presents a notched border, called the ora serrata. Here 

 its nervous elements terminate, but its pigmentary layer is con- 

 tinued over the deep or posterior surfaces of the ciliary processes 

 on to the posterior surface of the iris, forming, with the addition of 

 a layer of columnar epithelial cells, the pars ciliaris retinae and pars 

 iridica retinae (uvea), respectively. The retina diminishes in thick- 

 ness from behind forwards. 



The external surface is formed by a stratum of hexagonal pigment- 

 cells, which send processes into the adjacent layer. When the 



50 <& 



temporal 



ad sa TV he d v 'n &e jp curciu. 



Fig. 632. — Longitudinal Section through the Head of the Optic 

 Nerve (14x1) (Fuchs). 



r. Retina 



b. Centre of Porus Opticus 

 ch. Choroid 

 s. Sclerotic 

 so. Outer Part of Sclerotic 

 si. Inner Part of Sclerotic 

 ei. Ciliary Artery (in longi- 

 tudinal section) 



nasal, Inner Side 



sd. SuVjdural Space 

 sa. Subarachnoid Space 



n. Bundles of Nerve-fibres 

 se. .Septa between the Nerve-bundles 



a. Arteria Centralis Retinae 



V. Vena Centralis Retinae 



p. Sheath formed by Pia Mater 

 ar. Sheath formed by Arachnoid 

 du. Sheath formed by Dura Mater 



temporal, Outer Side 



choroid is separated from the retina these processes are torn, and 

 the stratum of pigment-cells remains attached to the choroid, being 

 apparently a part of it. The pigmentary layer, however, really 

 belongs to the retina. 



The internal surface presents, in the line of the visual axis of 

 the eyeball, the macula lutea or yellow spot, where vision is most 

 distinct. This spot is transversely oval, and measures about 

 y\^ inch in the transverse diameter. At its centre there is a 

 slight depression, called the fovea centralis. In this situation the 

 retina is thinnest, and the dark colour of the hexagonal pigment- 

 cells is visible through it, imparting to it the appearance of a fora- 

 men. About \ inch to the inner side of the posterior pole of the 



