242 THE POCKET ANATOMY 



side, and with those from the vascular zone of the sclerotic, 

 formed by the anterior ciliary arteries. These form the 

 circulus iridis major. Small branches from this circle converge 

 towards the pupil, and freely anastomose with one another, 

 forming the circulus iridis minor. 



The veins follow the same arrangement as the arteries, and 

 communicate with the canal of Schlemm. 



The nerves of the choroid and iris are about fifteen in 

 number, and are the ciliary nerves, from the lenticular ganglion 

 and the nasal branch of the 5th ; they follow very closely the 

 course of the bloodvessels, and, reaching the ciliary body, 

 form a plexus, sending twigs to the ciliary muscle, iris, and 

 cornea. 



The retina is the expanded termination of the optic nerve, 

 and forms the innermost tunic of the eye. It reaches forwards 

 nearly as far as the ciliary processes, where it ends in a saw- 

 edged border, the ora serrata, and from this border there is 

 prolonged a thin layer as far as the ciliary processes, which 

 blends with the uvea of the iris. This prolongation contains 

 no nerve-fibres, and is called the pars ciliaris retina. 



The outer surface is covered with uveal pigment -cells 

 (formerly described as part of the choroid). 



The inner surface contains : 



The macula lutea, or yellow spot, situated in the axis of the 

 globe. 



Thefovea centralis, a depression in the preceding. 



Theporus opticus, or disc, about ^ inch to the inner side of 

 the yellow spot, where the optic nerve enters, and from which 

 its fibres radiate ; coursing over the optic disc may be seen 

 the central vessels of the retina. 



Bloodvessels of the retina : 



The central artery of the retina passes through the optic 

 nerve, and reaches the inner surface of the retina through 

 the disc. It here divides into two branches, an ascending 

 and descending, and each of these, again, into an outer or 

 temporal division, and an inner or nasal. 



The outer branches give small offsets to end in capillaries 

 round the fovea. The rest of the branches are distributed, 

 as capillaries, to the retina, as far as the ora serrata, but the 

 smaller branches do not anastomose with one another or 

 with any other vessels. The veins follow the same distribu- 

 tion as the arteries. 



The vitreous body is a soft gelatinous substance occupying 

 about $ of the eye-ball. It supports the retina behind, and 

 is hollowed out in front for the lens 



