572 THE ORGANS 



ciliary arteries, and anterior ciliary arteries. The long ciliary arte- 

 ries are two in number and pass one on each side between the cho- 

 rioid and sclera to the ciliary body, where each divides into two 

 branches, which diverge and run along the ciliary margin of the iris. 

 Here the anastomosis of the two long ciliary arteries forms the greater 

 arterial circle of the iris. This gives rise to small branches which 

 pass inward supplying the surrounding tissues and unite near the 

 margin of the pupil to form the lesser arterial circle of the iris. The 

 branches of the short ciliary arteries pierce the sclera near the optic 

 nerve entrance, supply the posterior part of the sclera, and terminate 

 in the chorio-capillaris of the chorioid. The anterior ciliary arteries 

 enter the sclera near the corneal margin and communicate with the 

 chorio-capillaris and with the greater arterial circle of the iris. The 

 anterior ciliary arteries also supply the ciliary and recti muscles and 

 partly supply the sclera and conjunctiva. Small veins accompany 

 the ciliary arteries; the larger veins of this area are peculiar, however, 

 in that they do not accompany the arteries, but as venae vorticosae 

 converge toward four centres, one in each quadrant of the eyeball. 

 At the sclero-corneal junction is a venous channel, the canal of 

 Schlemm, which completely encircles the cornea (Fig. 371). 



Lymphatics. — The eyeball has no distinct lymph-vessel system. 

 The lymph, however, follows certain definite directions which have 

 been designated by Schwalbe "lymph paths." He divides them 

 into anterior lymph paths and posterior lymph paths. The anterior 

 lymph paths comprise (a) the anterior chamber which communi- 

 cates by means of a narrow cleft between iris and lens with the 

 posterior chamber; (b) the posterior chamber; (c) the lymph canal- 

 icuU of the sclera and cornea and the canal of Petit. The posterior 

 lymph paths include (a) the hyaloid canal (see above) ; (b) the sub- 

 dural and intra-pial spaces, including the capsule of Tenon; (c) the 

 perichorioidal space, and {d) the perivascular and pericellular lymph 

 spaces of the retina. 



Nerves. — The nerves which supply the eyeball pass through the 

 sclera with the optic nerve and around the eyeball in the supra- 

 chorioid layer. From these nerves, branches are given off as follows: 



(i) To the chorioid, where they are intermingled with ganglion 

 cells. 



(2) To the ciliary body, where they are mingled with ganglion 

 cells to form the ciliary plexus. The latter gives off branches to the 

 ciliary body itself, to the iris, and to the cornea. Those to the 



