358 MICROSCOPIC ANATOMY OF THE ORGANS. 



The first group supplies the smooth part of the chorioidea; 

 the two latter supply especially the ciliary body and iris. 



(a) The arteries ciliares posticce breves (I.) break through 

 the sclera in the region of the entrance of the optic nerve. They 

 number eighteen or twenty, and give rise to the dense capillary 

 network of the lamina choriocapillaris (III.). On the way they 

 give off branches which supply the scleral surface of the pos- 

 terior half of the eyeball, and form anastomoses with branches 

 of the arteria centralis retinae (/), the arteria? ciliares postine 

 longae, and the arterise ciliares anticaB. 



(b) The arterial ciliares posticce longce (1) break through the 

 sclera and run between the chorioidea and the sclera up to the 

 ciliary body, where they form at the ciliary border of the iris 

 the circulus arteriosus iridis major (2). From this there pro- 

 ceed branches which supply the ciliary processes (3) and the 

 iris, and at the pupillary border of the iris form the circtilii* 

 iridis minor. 



(c) The arteries ciliares anticw (a) arise from the arteries 

 of the four straight muscles of the eye, and give off branches 

 for the anterior half of the sclera (d), the conjunctiva solera- 

 (e), and the edge of the cornea. They then break through the 

 sclera and send branches to the ciliary muscles, while others 

 join with the circulus iridis major (b) or the lamina rhorio- 

 capillaris (c). 



The capillary loops supplying the edge of the cornea arise 

 also from arteries of the anterior part of the conjunctiva 

 sclera3. Here they form a network of capillaries which pass 

 over into the underlying veins. The central parts of the 

 cornea are in adult mammals entirely non-vascular. 



Almost all the blood brought in by the arterise ciliares 

 posticse collects in the vence vorticosw. These veins (Fig. 2(35, V) 

 are characterized by the fact that they have a course entirely 

 different from that of the arteries. There are usually four to 

 six trunks, which arise 1 by the coalescence of numerous branches 

 from all sides. They penetrate the sclera and open into one 

 of the venaB ophthalmic, 



Besides these; main paths for the draining of blood from the 



