STRUCTURE OF THE CHOROID COAT. 



265 



1. The lamina suprachoroidea (fig. 291, d). This is a thin membrane 

 composed of homogeneous connective tissue pervaded by a network of 

 fine elastic fibres, and containing many large branched pigment- cells 

 and lymph-corpuscles (fig. 292). It is covered superficially by a delicate 

 lymphatic endothelium, and is separated from the lamina fusca by a cleft- 

 like lymphatic space which is bridged across here and there by the 

 passage of vessels and nerves, and by bands of connective tissue. 



2. The vascular layer of the choroid (fig. 291, b), which resembles 

 the suprachoroidea in structure, but contains the blood-vessels of the 

 coat. In its outer part are the larger vessels (arteries and veins), the 

 veins having a peculiar vorticose arrangement ; in its inner part 



FIG. 295. SEGMENT OF THE IRIS, SEEN FROM THE POS- 

 TERIOR SURFACE AFTER REMOVAL OF THE UVEAL 

 PIGMENT. (Iwanoff.) 

 a, sphincter muscle ; b, dilatator muscle of the pupil. 



FIG. 296. VESSELS OF THE CHOROID, CILIARY PROCESSES 

 AND IRIS OF A CHILD. (Arnold.) (10 diameters.) 



a, capillary network of the posterior part of the choroid, ending 

 at b, the ora serrata ; c, arteries of the corona ciliaris, supplying 

 the ciliary processes, d, and passing into the iris, e ; /, the ca- 

 pillary network close to the pupillary margin of the iris. 



(chorio-capillaris) are the capillaries, which form an extremely close 

 network with elongated meshes, the capillaries radiating from the 

 extremities of the small arteries and veins in a highly characteristic 

 manner (fig. 293). In the ciliary processes the vessels have for the 

 most part a longitudinal direction, but there are numerous convoluted 

 transversely disposed capillaries uniting the longitudinal vessels (fig. 296). 



3. Lining the inner surface of the choroid is a very thin transparent 

 membrane known as the membrane of Bruch (fig. 291, a), 



The ciliary muscle of Bowman consists of involuntary muscular bundles 

 which arise at the corneo-sclerotic junction, and pass meridionally back- 

 wards to be inserted into the choroid (fig. 294, K). Many of the 

 deeper-seated bundles take an oblique direction, and these pass gradu- 



