460 HISTOLOGY 



The veins generally proceed toward the equator, uniting in four (less 

 often in 5 or 6) Denes wrticosa. These pass directly through the sclera 

 and empty into one of the ophthalmic veins. Besides the venae vorticosae 

 there are small veins accompanying the short posterior and the anterior 

 ciliary arteries. The short ciliary veins receive branches from the ciliary 

 muscle, the episcleral vessels, the conjunctiva bulbi and the periphery of 

 the cornea. The episcleral veins also connect with the venae vorticosae. 

 Within the sclera, near the cornea, there is a circular vein, receiving small 

 branches from the capillaries of the ciliary muscle. This sinus venosus 

 sclera (canal of Schlemm) connects with the anterior ciliary veins. 



Arteria centralis retina. The central artery of the retina enters the 

 optic nerve 1 5-20 mm. from the eye-ball, passes to its center and proceeds 

 to the optic papilla. There it divides into two branches directed upward 

 and downward respectively, and these by further subdivision supply the 

 entire pars optica retinae. Within the optic nerve the artery sends out 

 numerous little branches which anastomose with small vessels that have 

 entered the sheaths from the surrounding fat; and also with branches of 

 the short posterior ciliary arteries (Fig. 467, &). 



The central vein of the retina receives two main branches at the optic 

 papilla and follows the artery along the axis of the optic nerve. 



CHAMBERS AND TISSUE SPACES OF THE EYE. 



The eye contains no lymphatic vessels, but is provided with communi- 

 cating tissue spaces, bounded by loose cells or mesenchymal epithelia. 

 They include the corneal and scleral canaliculi, and the anterior and poste- 

 rior chambers; the latter connect with one another through the capillary in- 

 terval between the lens and iris. The posterior chamber extends into the 

 zonular spaces; and there are irregular extensions of the anterior chamber, 

 associated with the pectinate ligament of the iris, called spaces of the angle 

 of the iris (spaces of Fontana) . The latter are but slightly developed in 

 man. Posteriorly the tissue spaces include the hyaloid canal of the 

 vitreous body; the very narrow perichorioideal space between the chorioid 

 and sclera; the subdural and arachnoid spaces of the optic sheaths 

 named the intravaginal spaces; and finally the" interfascial space (of Tenon) 

 which surrounds most of the sclera and is prolonged as a supradural space 

 around the optic nerve. These spaces may be filled from the arachnoid 

 space about the brain. They contain a "filtrate from the vessels." The 

 interfascial and perichorioideal spaces hold but little fluid; acting as 

 bursae, they facilitate the movements of the eye. 



NERVES. 



Apart from the optic nerve, the eye is supplied by the short ciliary 

 nerves from the ciliary ganglion, and the long ciliary nerves from the naso- 



