HANDBOOK OF PHYSIOLOGY. 



connected to it only by loose connective tissue. Its external coat is 

 formed chiefly of elastic fibres and large pigment corpuscles loosely 

 arranged and containing lymphatic spaces lined with endothelium. This 

 is the suprachoroidea. More internally is a layer of arteries and veins 

 arranged in a system of venous whorls, together with elastic fibres and 



Fig. 412. Section through the eye carried through the ciliary processes. 1. Cornea; 2, mem- 

 brane 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 

 stroma; 9, pigment of iris: 10, ciliary processes; 11, ciliary muscle; 12, choroid tissue; 13, 

 meridional and 14, radiating fibres of ciliary muscle; 15, ring muscle of Muller; 16. circular or 

 angular bundles of ciliary muscle. (Schwalbe.) 



pigment cells. The lymphatics, too, are well developed around the 

 blood-vessels, and there are besides distinct lymph spaces lined with en- 

 dothelium. Internally to this is a layer of fine capillaries, very dense 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 clwrio-capillaris). It is separated 

 from the retina by a fine elastic membrane (membrane of Brucli), which 

 is either structureless or finely fibrillated. 



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

 (fig. 412). These consist of from 70 to 80 meridionally arranged 

 radiating plaits, which consist of blood-vessels, fibrous connective tissue, 

 and pigment corpuscles. They are lined by a continuation of the mem- 

 brane of Bruch. The ciliary processes terminate abruptly at the margin 

 of the lens. The ciliary muscle (13, 14 and 15, fig. 412), which may be 

 considered to form part of the processes, is situated between the 

 sclerotic (at the corneo-scleral junction) and the folds of the ciliary 

 processes. It is a ring of muscle, 3 mm. broad and 8 mm. thick, made 

 up of fibres running in two or three directions, (a) Meridional fibres 

 near the sclerotic and passing to the choroid ; ( b) radial fibres, passing 

 toward the centre; and (c) circular fibres, more internal, and constitut- 

 ing the so-called ciliary sphincter. 



The Iris. The iris is a continuation of the choroid inward beyond 



