598 



THE EYE 



P 



and the ocular globe, and arriving at the center of the nerve runs 

 in its axis to the papilla 

 optica, at which point it If 

 divides into two branches, 

 which, by rapid dicoty- 

 mous division, radiate 

 from the optic papilla to 

 all parts of the retinal 

 surface, thereby forming j 

 a plexus of small arteries 

 within the nerve fibre 

 and ganglion cell layers. 

 From this plexus capil- 

 laries are distributed to 

 all the cerebral layers of 

 the retina. No blood 

 vessels are found within 

 the nenro-epithelial lay- 

 ers. The retinal arteries, 

 like those of the brain, 

 do not anastomose with 

 one another ; they are 

 terminal arteries. 



The retinal veins fol- 

 low a course exactly simi- 

 lar to that of the arteries; 

 they converge to form a 

 single efferent vessel, the r 

 vena central is ratinae. 

 The retinal veins are pe- 

 culiar in that their walls 

 contain no muscle. The 

 optic nerve is supplied 



FIG. 439. SCHEMATIC REPRESENTATION OF THE INTRINSIC BLOOD VESSELS OF THE EYE. 

 Arteries in outline, veins in solid black. A, choroid ; a, central artery, and 01, vein 

 of the retina ; #, conjunctiva ; 6, retinal arteries ; fti, retinal veins ; c, c, short ciliary ar- 

 teries ; d, long ciliary artery ; e, ei, anterior ciliary arteries and veins ; /, chorio-capil- 

 laris ; 0, capillaries of the ciliary body; Jf, cornea; h, circulus major of the iridal ar- 

 teries ; i, arteries, and i, veins of the iris ; fc, circulus minor of the iridal arteries ; L, 

 crystalline lens ; Z, venae vorticosae ; m, anastomosis of ciliary and anterior ciliary veins ; 

 2V, retina ; n, canal of Schlemm ; 0, optic nerve ; o, posterior conjunct! val artery, and 01, 

 vein ; p, anterior conjunctival vessels ; g, vascular loops at the margin of the cornea ; R, 

 internal rectus muscle ; S, sheath of the optic nerve ; Sc, sclera. (After Leber.) 



