STRUCTURE OF THE CHOROID, 



599 



Fig. 407. 



invests the rest of the structure ; but externally they become gradually 

 narrower, and disappear in the choroid coat. The smaller processes are 

 only half as deep as the others. At and near the internal or anterior 

 extremities the processes 

 are connected by lateral 

 loop-like projections. The 

 plications of the ciliary 

 processes fit into corre- 

 sponding plications of the 

 suspensory ligament of 

 the lens, to be afterwards 

 described. 



STRUCTURE OF 

 CHOROIB. 



THE 



Fig. 407. — Lateral View of the Arteries of the 

 Choroid and Iris (from Arnold). 



a, optic nerve ; 5, part of the sclerotic left behind ; 

 c, region of ciliarj' muscle ; d, iris ; 1, posterior ciliary 

 arteries piei'cing the sclerotic and passing along the 

 clioroid ; 2, one of the long ciliary arteries ; 3, anterior 

 ciliary arteries. 



Fig. 408. 



The choroid consists 

 mainly of blood-vessels 

 united by a delicate con- 

 nective tissue, with nu- 

 merous large ramified 

 cells (for the most part 

 pigmented), united by 

 their branches, and con- 

 taining numerous leuco- 

 cytes in the meshes, like 

 lymphoid tissue. From 

 a difference in the fine- 

 ness of its constituent 

 blood-vessels, the choroid 

 resolves itself into two 

 strata, outer and inner ; 

 the former containing 

 the larger branches, and 

 the latter the capillary 

 ramifications. 



In the outer part of 

 the coat are situated, as 

 just stated, the larger 

 branches of the vessels. 

 The arteries (.s7wr/ ciUarij) 

 are comparatively large 

 and numerous, and pierc- 

 ing the sclerotic close to 

 the optic nerve (fig. 407, 

 1), divide into branches 

 which are directed at first 

 forwards before they bend 

 inwards to end on the 



inner part ; whilst the veins {vasa vorticosci), external to the arteries, are 

 disposed in curves as they converge to four or five principal trunks (fig. 

 408, 1, 1) which pass through the sclerotic about half way betAveen the 

 margin of the cornea and the entrance of the optic nerve. In the 

 intervals between the vessels are elongated and stellated pigment-cells 



Fig. 403. — Lateral View of the Veins op tub 

 Choroid (from Arnold). 



1, 1, two trunks of the venie vorticosio at the 

 place where they leave the choroid and pierce the 

 sclerotic coat. 



