1458 



HUMAN ANATOMY. 



Commencing by the union of several plications of the orbiculus ciliaris, they rapidly 

 increase in height and breadth, until they reach an elevation of from ,8-i mm., and 

 then fall suddenly to the iris level. They consist of a rich net-work of vessels em- 

 Dedded in a pigmented connective tissue stroma, like that of the choroid. The inner 

 surface is covered with a homogeneous membrane, which is continuous with the 

 membrana vitrea of the choroid, on the inner surface of which is placed the double 

 layer of cells representing the ciliary portion of the retina {pars ciliaris retines). 

 Each ciliary process is composed of a number of irregularly projecting folds which 

 increase in height as the iris is approached. 



Cornea 



Greater arterial ring 

 Iris 



Lesser arterial ring 



Ciliary process 



Fig. 1215. 



Canal of Schlemni 



'Corneal loop 



Perforating branch 



Conjunctival vessels 



Communication between 



Anterior ciliary vessels 



Sclera 

 Episcleral vessels 



choroidal and optic vessels 

 Central retinal vessels 



- Vena vorticosa 



Supplying choroid 



Short posterior ciliary artery 



Long posterior ciliary artery 

 Communicating twig 

 Inner sheath vessels 

 Outer sheath vessels 



Communication between optic 

 and sheath vessels 



Diagram illustrating circulation of eyeball. (Leber.) 



The ciliary muscle occupies the outer portion of the ciliary body, lying 

 between the sclera and the ciliary processes. It forms an annular prismatic band 

 of involuntary muscle, which in meridional sections has the form of a right-angled 

 triangle, the hypothenuse being the outer side, next to the sclera, and the right 

 angle facing the lens. Its main fibres arise from the sclera and pectinate ligament, 

 at the corneo-scleral junction internal to the canal of Schlemm, and run in a 

 meridional direction backward along the sclera to be inserted into the choroidal 

 stroma (hence their name, tensor chorioidece). The inner angle of the triangle, at 

 the base of the iris, is occupied by a band of circularly disposed fibres, which consti- 

 tute the circular ciliary muscle of Midler. Between the circular and meridional 

 portions, the fibres assume a radial direction and are separated by considerable 

 CXJnnective tissue, which in the deeply pigmented races may contain many branched 



