CH. LV.] 



THE CHOROID COAT. 



745 



Structure of the Choroid Coat (tunica vasculosa). This coat 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 con- 

 nected to it only by loose connective 

 tissue. Its extemal coat is formed 

 chiefly of elastic fibres and large pig- 

 ment corpuscles loosely arranged ; it 

 contains lymphatic spaces lined with 

 endothelium. This is the lamina supra- 

 choroidea. More internally is a layer 

 of arteries and veins arranged in a 

 system of venous whorls, together with 

 elastic fibres and pigment cells. The 

 lymphatics, too, are well developed 

 around the blood-vessels, and there are 

 besides distinct lymph spaces lined with 

 endothelium. 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 



Fig. 564. Section through the 

 choroid coat of the human 

 eye. i , membrane of Bruch ; 

 2, chorio - capillaris or 

 tunica Ruyschiana ; 3, pro- 

 per substance of the choroid 

 with large vessels cut 

 through ; 4, suprachoroidea ; 

 5, sclerotic. (Schwalbe.) 



Fig. 565. Section through the eye carried through the ciliary processes, i, 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, / ; 8, iris ; 9, pigment of iris (uvea) ; 10, ciliary processes ; 

 1 1, 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.) 



corpuscles without pigment, and lymph spaces which surround 

 the blood-vessels (membrana chorto-capillaris) . It is separated 

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

 which is either structureless or finely fibrillated. (Fig. 564, i.) 



