Quain's elements of anatomy . arge ramified and pigmentedcells. Externally the choroid is bounded by a membranous layer similar tothe lamina fusca of the sclerotic, and known as the lamina sicpra-cTioroidea. This is composed of a thin membrane (or membranes) of ahomogeneous aspect, but pervaded by a network of fine elastic fibres, andcovered by large flat epithelium-like cells. It contains also large flat-tened pigment-ceUs dispersed irregularly or arranged in patches, withconsiderable intervals free from pigment-cells ; and lymphoid cells may 402 THE EYE. occur in it here and there singly or
Quain's elements of anatomy . arge ramified and pigmentedcells. Externally the choroid is bounded by a membranous layer similar tothe lamina fusca of the sclerotic, and known as the lamina sicpra-cTioroidea. This is composed of a thin membrane (or membranes) of ahomogeneous aspect, but pervaded by a network of fine elastic fibres, andcovered by large flat epithelium-like cells. It contains also large flat-tened pigment-ceUs dispersed irregularly or arranged in patches, withconsiderable intervals free from pigment-cells ; and lymphoid cells may 402 THE EYE. occur in it here and there singly or in groups (fig. 336). It is looselyanited to the lamina fasca by vessels and bands of connective tissueenclosing pigment-cells, and the two lamina3 as well as the unitingstructures are coated with pavement-epithelium, a lymph-space beingthus formed between the sclerotic and choroid. This space com-municates, at the places where the vessels and nerves pierce the sclerotic,with that of the capsule of Tenon (Schwalbe). Fig. Fig. 336.—A SMALL PORTION OF LAMINA supuA-CHOKOiDEA. Highly magnified. (E. A. S.) p, pigment-cells ; /, elastic fibres; n, nuclei of epithelioid cells (the outlines of thecells are not indicated) ; I, lymphoid cells. The choroid proper resembles in general structure the lamina supra-choroidea, but contains in addition a very large number of a difference in the fineness of these constituent vessels, itresolves itself into two strata, outer and inner ; the former containingthe larger branches, and the latter the capillary ramifications. A layerof connective tissue which unites the two strata, and is nearly free fiompigment, is sometimes described as a third or intermediate j^art. In the outer part of the coat are situated, as just stated, the largerbranches of the vessels. The arteries {short ciliary) are comparativelylarge and numerous, and piercing the sclerotic close to the optic nerve(fig. 337, a), divide into branches which are dir
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