768 



THE EYE AND VISION 



[CH. LVI. 



The Choroid Coat (tunica vasculosa) is attached to the inner layer 

 of the sclerotic in front at the corneo-scleral junction and behind at 



the entrance of the optic nerve ; elsewhere 

 it is connected to it only by loose connective 

 tissue. Its external coat is formed chiefly 

 of elastic fibres and large pigment cor- 

 puscles loosely arranged; it contains lym- 

 phatic spaces lined with endothelium. This 

 is the lamina suprachoroidea. More inter- 

 nally is a layer of arteries and veins 

 arranged in a system of venous whorls, 

 together with elastic fibres and branched 

 pigment cells. The lymphatics, too, are well 



FIG. 566. section through the developed around the blood-vessels, and 

 r^^^iSS; 1 ^ there are besides distinct lymph spaces 



lined with endothelium. Internal to this 



chorio-capillaris or tunica Ruy- 

 schiana ; 3, proper substance of 



the choroid with large vessels is a layer of fine capillaries, very dense, 



5%\erS h: (^SS?) roidea ^ and derived from the arteries of the outer 



coat and ending in veins in that coat. It 



contains corpuscles without pigment, and lymph spaces which 

 surround the blood-vessels (membrana chorio-capillaris). It is 

 separated from the retina by a fine elastic membrane (membrane of 



FIG. 567. Section through the eye carried through the ciliary processes. 1, Cornea; 2, membrane of 

 Descemet ; 3, sclerotic ; 3', corneo-scleral junction ; 4, canal of Schlemm ; 5, vein ; 6, nucleated 

 network on inner wall of canal of Schlemm ; 7, lig. pectinatum iridis, abc ; 8, iris ; 9, pigment of 

 iris (uvea); 10, ciliary processes; 11, ciliary muscle; 12, choroid tissue; 13, meridional, and 14, 

 radiating fibres of ciliary muscle ; 15, ring-muscle of Miiller ; 16, circular or angular bundles of 

 ciliary muscle. (Schwalbe.) 







Bruch\ which is either structureless or finely fibrillated. (Fig. 

 566, 1.) 



The choroid coat ends in front in what are called the ciliary 

 processes (figs. 567, 568). These consist of from 70 to 80 meridion- 

 ally arranged radiating plaits, which consist of blood-vessels, fibrous 



