572 THE EYE 



The lamina vasculosa (vascular layer, choroid proper) , so called 

 because it contains the ramifications of the ciliary arteries and veins, 

 is by far the thickest of the three layers of the choroid. It may be 

 arbitrarily separated into an outer stratum, consisting chiefly of 

 dense interlacing bundles of connective tissue fibres which inclose 

 only the larger blood vessels, and an inner stratum of similar struc- 

 ture, but everywhere permeated by a close network of small vascu- 

 lar twigs. So dense is this network near the posterior pole of the 

 eye, as to give the layer the appearance of an almost continuous 

 sheath of small blood vessels. 



The Lamina Capillaris. Within the vascular layer is the capil- 

 lary membrane (lamina capillaris, lamina chorio-capillaris, tunica 

 Ruyschiana, which contains an exceedingly close-meshed capillary 

 network. This network is specially dense near the macula lutea at 

 the posterior pole of the eyeball. Its inner surface forms a very 

 thin homogeneous membrane, the lamina basalis or membrane of 

 BrucJi, which increases somewhat in thickness as age advances. 

 The inner surface of the lamina basalis is indented by the bases of 

 the adjacent pigment cells of the retina. Anteriorly the vessels of 

 the chorio-capillaris, like those of the vascular layer, become con- 

 tinuous with the vessels of the ciliary body and iris. 



THE CILIARY BODY. The ciliary body (corpus ciliare) rep- 

 resents the thickened anterior border of the choroid coat. It is, 

 therefore, of annular shape and occupies a zone whose posterior 

 border blends with the choroid at a point opposite the ora serrata 

 of the retina, and whose anterior margin is continued into the iris 

 opposite the sclero-corneal junction. It may be said to consist of 

 three structures arranged in layers of varying thickness : 1, the 

 ciliary muscle ; 2, the fibrous layer with its ciliary processes; and 

 3, that portion of the pigmented epithelium of the retina which 

 constitutes the pars ciliaris retinae or ciliary epithelium, and covers 

 the inner surface of the ciliary body. The suspensory ligament of 

 the crystalline lens is attached to the inner surface of the retinal 

 epithelium. 



The ciliary muscle consists of an annular mass of non-striated 

 fibres which arise from the inner surface of the sclera near the 

 sclero-corneal junction, and are inserted into the entire breadth of 

 the fibrous mass of the ciliary body as far back as the anterior 

 margin of the choroid. The muscle fibres are divisible into three 

 sets, according to the direction of their long axis; these are the 

 meridional, the radial, and the circular. 



