OEGANS OF THE BODY. 



625 



advance to the back of the bulb and split up there into a large number, of 

 twigs. Besides the hinder part of the sclerotic coat and point of entrance 

 of the optic nerve (see below), they supply only the choroidea pro- 

 per, about 20 small 

 branches lying in the 

 outer layer of the lat- 

 ter. Moreover, these 

 are distributed chiefly 

 to the back part of the 

 choroid coat, and reach 

 neither the iris nor 

 ciliary processes. They 

 are, however, con- 

 nected at certain points 

 both with the long pos- 

 terior and the anterior 

 ciliary vessels. Their 

 end branches spreading 

 out internally, break 

 up finally into the 

 capillary network of 

 the choriocapillaris 

 (d, d). 



This capillary net- 

 work, whose tubes mea- 

 sure from 0-0090 to 

 0-0113 mm. in dia- 

 meter, is one of the 

 most dense in the 

 body, especially at the 

 back of the eyeball, 

 whereas, anteriorly, 

 the meshes gradually 

 increase in size. Its 

 tubes (fig. 583) radiate 

 from numerous central 

 points, which are either 

 arterial or venous ter- 

 minal twigs. In the 



Fig. 582. Diagram of the ar- 

 rangement of the vessels of 

 the eye-ball (after Leber). a, 

 large, and 6, small twig from 

 a short posterior ciliary ar- 

 tery; c, long posterior; d, 

 choriocapillaris; e, arterial 

 collar around the optic nerve, 

 and branches of the same to 

 the latter; /, anterior ciliary artery; gr, large circlet of the iris; A, artery of the same; f, small 

 circlet of the iris; *, capillary network of the sphincter pupillce; I, artery of the ciliary process; 

 m, artery of the musculus ciliaris; n, recurrent branch to the choroidea; o, posterior conjunc- 

 tival vessel, and p, anterior; q, arterial branch to the border looped network; r, arteria centralis 

 retinae; s, artery to the internal sheath of the optic nerve; f, artery to the external sheath of the 

 same; u, twig from the short ciliary vessels to the sclerotic; v, twig from anterior ciliary artery to same ; 

 x, vein of one of the vortices; t/, posterior vena ciliaris; z, central vein of the retina; 1, vein of the 

 internal sheath of optic nerve; 2, of the outer sheath of same: 3, vein and artery of the choroid 

 which enter the optic nerve; 4, vein of the sclerotic opening into the trunk of a vortex; 5, anterior 

 ciliary vein; 6, its branches to the sclerotic; 7, vein to the border looped network; 8, anterior, and 9, 

 posterior conjunctival vein ; 10, venous ciliary plexus (canal of frhlemm); 11. connection of the same 

 with the anterior ciliary vein; 12, vein of the ciliary muscle running into the plexus ciliaris ; 13. vein 

 of the ciliary process; 14, vein of the iris; 15, vein of the ciliary muscle emptying into a vortex trunk. 



