chap, iv.] THE ORBIT AND EYE. 45 



It will now be convenient to take note of the 

 blood and nerve supply of the globe. 



Blood supply of the eye-ball. 1. The short 

 ciliary arteries (from the ophthalmic) pierce the sclerotic 

 close to the optic nerve, run some little way in the 

 outer coat of the choroid, and then break up into a 

 capillary plexus that makes up the main part of the 

 inner choroidal coat. In front this plexus gives some 

 vessels to the ciliary processes. The veins from these 

 vessels are disposed in curves as they converge to four 

 or five main trunks (vense vorticosse), which pierce the 

 sclerotic midway between the cornea and the optic 

 nerve. In the choroid they lie external to the 

 arteries. 



2. The two long ciliary arteries (from the 

 ophthalmic) pierce the sclerotic to the outer side 

 of the optic nerve, and run forwards, one on either 

 side, until they reach the ciliary region, where they 

 break up into branches that, by anastomosing, form a 

 vascular circle about the periphery of the iris (the 

 circulus major). From this circle some branches pass 

 to the ciliary muscle, while the rest run in the iris in 

 a converging manner towards the pupil, and at the 

 margin of the pupil form a second circle (the circulus 

 minor). 



3. The anterior ciliary arteries (from the muscular 

 and lachrymal branches of the ophthalmic) pierce 

 the sclerotic (perforating branches) about a line 

 behind the cornea, join the circulus major, and give off 

 branches to the ciliary processes, where they form 

 copious anastomosing loops. These arteries lie in the 

 sub-conjunctival tissue. Their episcleral, or non-per- 

 forating branches, are very small and numerous, and ; 

 are invisible in the normal state of the eye. In. 

 inflammation, however, of the iris and adjacent parts, 

 these vessels appear as a narrow pink zone of fine 

 vessels round the margin of the cornea, that run 



