THE CHOEOID COAT 



571 



THE MIDDLE COAT 



The middle tunic (uvea, uveal tract) includes the choroid coat, 

 ciliary body, and iris, together with an opening at the anterior 

 pole of the eye, the pupil. 



The iris divides the cavity of the anterior segment of the eye 

 into an anterior chamber, included between it and the posterior 

 or inner surface of the cornea, and a posterior cliainber, which is 

 bounded by the iris in front and the crystalline lens and its suspen- 

 sory ligament behind. The free or pupillary margin of the iris is 

 in light contact with the anterior surface of the lens. The poste- 

 rior chamber is therefore an annular compartment. 



THE CHOKOID COAT. The choroid coat (tunica choroidea) 

 consists of three layers : 1, the lamina suprachoroidea ; 2, the lam- 

 ina vascularis ; 3, the lamina capillaris. 



The lamina suprachoroidea (suprachoroid layer) is a very delicate 

 membrane which contains many pigmented cells and is similar in 

 structure to the lamina fusca of the sclera. 



The flattened pigment cells are brownish -black in color from 

 the many coarse granules which they contain, and are irregularly 



FIG. 421. FKOM A MERIDIONAL SECTION OF THE CHOKOID COAT. 

 a, membrane of Bruch ; 6, the inner margin of the vascular layer. Between a and 6 

 is the capillary layer or chorio-capillaris ; c, venule containing blood corpuscles ; d, fibrous 

 layer of the choroid or lamina suprachoroidea. Highly magnified. (After Cadiat.) 



disposed, either separately or in groups. Lymphatic spaces occur 

 between this layer and the sclera and communicate with the cap- 

 sule of Tenon. 



The fibres of this layer are not only distributed in its own plane 

 but pass obliquely to the lamina fusca, thus loosely attaching the 

 suprachoroid layer to the sclera. Similar, obliquely disposed fibres 

 pass to the deeper portions of the choroid, with the fibres of which 

 they blend. 



