THE EYE. 411 



The choroid is firmly attached to the sclerotic in two positions, at 

 the point of entrance of the optic nerve, and at the line of junction 

 of the sclerotic and the cornea. Its external surface is closely 

 applied to the deeper surface of the sclerotic, from which it is only 

 separated by a very narrow serous cavity (supra-choroidal space), 

 and to which it is attached by numerous vessels and nerves. The 

 deep surface of the choroid is covered by the retina, to which it 

 is closely attached, except at the ora serrata, the attachment being 

 especially intimate at the ftrocesfsu* ciliares. 



The choroid coat consists of a fibrous layer containing- corpuscles 

 and traversed by a very rich vascular anastomosis. The corpuscles 

 of this layer are deeply pigmented, in some cases to such an extent 

 that the oval nucleus cannot be seen ; the fibrous tissue is also pig- 

 mented, and has consequently a brownish tinge. That portion of 

 the layer immediately below the sclerotic is termed the lamina fusca 

 or suprac/ioroidea, the vessels on the deeper surface forming the 

 niemlrana cAoriocSfiOari*. This again is lined on its deeper surface 

 by a hyaline membrane. 



a. The arteries (Fig. 256 VI, VII, VIII) supplying this coat 

 are two branches of the arteria aphtha! mica ; these form a capil- 

 lary network (Fig. 256 VII) resembling the corresponding struc- 

 ture found in mammals. The meshes have approximately the 

 same size, while the capillaries themselves vary considerably in size. 

 This network is, however, only complete on the nasal, temporal, 



Fig. 256. 



The vessels of the choroid and iris ; after Hans Virchow. 

 I. The two roots of the V. bulbi superior. Magnified to times. 

 II. Vessels of the iris. Magnified 9 times. 



I II. Origin of the ventral vein. 



IV. Schema of the choroid vessels ; seen from the proximal pole. 

 V. Transverse section through the choroid at the equator. 



VI. The origin of the choroid arteries from the ophthalmic artery. The greater part of the 

 sclerotic has been 'removed. Left eve twice natural size. A. From the proximal pole. 

 B. From the temporal side. 



V 1 1. Part of a choroidal artery attached to the choriocapillaris. Magnified 10 times. 

 VIII. A portion of the choriocapillaris, more highly magnified. 

 IX. The V. ophthalmica and V. bxilbi superior on the sclerotic of the right eye. A. Seen from 



proximal pole. B. Seen from above. Twice natural size. 



A Art. ophthalmica. R Branches of the circulns iridis major, 



A' Art. choroidea. Rd Distal root of vein of under surface of eve . 



An R. nasalis of the ophthalmic artery. Rd' Distal root of nasal vein. 



At R. temporalis of the ophthalmic artery. Rd'' Proximal root of nasal vein. 

 ch Area of membrana choriocapillaris. Up' Nasal root of ventral vein. 



Le Outer pigmented layer of choroid. RI>" Temporal root of ventral vein. 



Li Inner pigmented layer of choroid. tit V. bulbi superior. 



A" Optic nerve. Vh, V. hyaloidea. 



r Vasa recta. Vo V. ophthalmica. 



r 1 Transitional part between choriocapillaris Vp. Proximal root of vein of under surface of 



and ventral whorl. eve. 



r' Transitional part between" choriocapillaris V*' Nasal root of V. bulbi superior. 



and upper whorl. Vt" Temporal root of V. bulbi superior. 



