344 NORMAL HISTOLOGY. 



zone, about 10 n in width, at the inner part of the choroid, composed 

 of a structureless, apparently homogeneous, matrix, in which lie 

 embedded the close capillary net-works derived from the terminal 

 branches of the short ciliary arteries. 



The vitreous lamina, or glassy membrane, forms the most 

 internal layer of the choroid and supports the retinal pigment. The 

 membrane presents a delicate homogeneous stratum (2 //. in thick- 

 ness), ordinarily without appreciable structure, and is very intimately 

 associated with the adjoining layer of the choroid ; to its inner sur- 

 face patches of retinal pigment frequently adhere on removal of 

 the retina. 



The nerves of the choroid, non-medullated fibres distributed to 

 the blood-vessels, are derived from the plexus formed within the 

 suprachoroidal tissue by branches given off from the long and short 

 ciliary nerves in their transit through the subscleral space. 



THE CILIARY BODY. 



This structure includes that portion of the uveal tract situated be- 

 tween the termination of the choriocapillaris, opposite the ora 

 serrata behind and the ciliary or outer margin of the iris in front. 

 Within this important territory three areas may be distinguished : 



i, the ciliary ring; 2, the cili- 

 ary processes; 3, the ciliary 

 muscle. 



The ciliary ring, or orbicu- 

 lus ciliaris, is a circular tract 

 about 4 mm. in breadth, situated 

 immediately in front of the ora 

 serrata and extending to the 

 posterior ends of the ciliary pro- 

 cesses. This zone differs from 

 the choroid in the absence of 

 the choriocapillaris and in the 

 presence of muscular tissue 



Section of human ciliary processes ; 7. in- , r , r , 



terstitial connective-tissue stroma, covered by prolonged frOIX! the maSS of the 



retinal layers (/?) ; f, o, inner clear and outer ciliary mUSCle J the character of 



pigmented layers of cells; f fibrous tissue of , i u V u 11 



processes. tne stroma also changes, its bulk 



being here made up of fibrous 

 connective bundles instead of elastic lamellae. 



The ciliary processes consist of an annular series of some 

 seventy prominent radial vascular folds which project from the 

 inner surface of the ciliary body and arise from the confluence of 

 several of the low ridges on the ciliary ring ; after attaining a height 

 of about i mm. , they abruptly end at the base of the iris, sinking 



FIG. 371. 



