:U4 MICROSCOPIC ANATOMY OF THE ORGA.\\ 



brane which lies on the inner surface of the chorioidea and 

 borders on the pigment epithelium of the retina. 



The corpus ciliare is to be regarded as a process of the 

 chorioidea, which readies from the ora serrata to the outer- 

 most borders of the iris. It consists of the so-called orbiculus 

 ciliares, the processus ciliares (corona ciliaris), and the musculus 

 ciliaris. 



The orbiculus ciliaris differs in structure from the cho- 

 rioidea in that it contains no lamina choriocapillaris. The 

 lamina basalis is thickened to form intercrossing ridges, with 

 depressions between which are filled with retinal pigment 

 epithelium. The vessels and muscle bundles belonging to 

 this region run in a meridional direction. 



The corona ciliaris (Fig. 262) consists of seventy to eighty 

 ridge-like processes running meridionally (processus ciliares). 

 These are arranged around the lens, and are about 2 mm. long 

 and 1 mm. high. They are highest at the end toward the lens. 

 Toward the outside the ground substance of the processes border 

 on the ciliary muscles. The inner surface, on the other hand, 

 is covered by the lamina basalis, which rests on the pigment 

 layer of the pars ciliaris retina?. 



The musculus ciliaris (Fig. 262) has the form of a flat 

 ring about 3 mm. in thickness. It consists of smooth muscle 

 cells, which may be divided into three groups according to the 

 direction in which they run : 



1. The outermost (meridional} part (tensor chorioidese) con- 

 tains bundles of muscle cells which run meridionally and lie 

 next to the sclera. They reach from the canal of Schlemm 

 to the orbiculus ciliaris. 



2. Outside these fibres there is a middle (radial) layer of 

 the ciliary muscle. Its bundles of fibres have a radial arrange- 

 ment, so that some of them are spread out toward the centre 

 of the eyeball, like the rays of a fan (Fig. 262). 



'>. The innermost (circular) portion of the muscle takes an 

 equatorial or circular course, so that the name M tiller's ring 

 muscle is applied also to it. 



The iris is to be regarded as a process of the chorioidea. 



