CILIARY ARTERIES 541 



been turned aside in separate flaps, in the form of delicate 

 white filaments (Fig. 228). In the posterior part of the 

 eyeball they occupy grooves on the deep surface of the sclera, 

 and can be separated from it only with difficulty. Reaching 

 the ciliary zone the ciliary nerves break into branches, which 

 join in a plexiform manner and send twigs to the ciliary 

 muscle, the iris, and the cornea. The long ciliary nerves are 

 sensory nerves. The short ciliary nerves contain motor 

 fibres derived from the motor- oculi, sensory fibres from 

 the naso-ciliary nerve, and sympathetic fibres which convey 

 motor impulses to the dilator muscle of the iris. 



Ciliary Arteries. There are three groups of ciliary 

 arteries: (i) the short posterior ciliary arteries; (2) the long 

 posterior ciliary arteries ; and (3) the anterior ciliary arteries. 



The short posterior ciliary arteries, branches of the 

 ophthalmic, pierce the sclera around the optic entrance, 

 and are distributed in the chorioid coat between the venae 

 vorticosae and the lamina chorio-capillaris. 



The long posterior ciliary arteries, also branches of the 

 ophthalmic, are only two in number. They perforate the 

 sclera, one on the medial side of the optic nerve and the 

 other on its lateral side (Fig. 227), a short distance beyond 

 the short ciliary arteries, and then pass forwards between 

 the sclera and the chorioid. When they gain the ciliary 

 zone each artery divides into an ascending and a descending 

 branch, which anastomose with the anterior ciliary arteries at 

 the periphery of the iris, and form an arterial ring termed the 

 circulus iridis major. Branches are given off from the major 

 circle to the ciliary muscle, the ciliary processes, and the iris. 



The circtilus iridis minor is the name applied to a second arterial ring 

 in the iris at the outer border of the sphincter pupillae. 



The anterior ciliary arteries are very small twigs which 

 arise from the branches of supply to the recti muscles. 

 They pierce the sclera close to the margin of the cornea, 

 take part in the formation of the circulus iridis major, and 

 send twigs to the ciliary processes. 



Venae Vorticosse. From each venous vortex in the 

 chorioid a large vein arises, which makes its exit from the 

 eyeball by piercing the sclera, obliquely, a short distance 

 posterior to the equator. They are four or five in number. 



Dissection. The vitreous body and retina, in the posterior 

 part of the eyeball which was cut into two for the purpose of 



