Text-book of ophthalmology . rs, Mu; the transition from one portion to another is effected by theradial fibers, r. At the anterior margin of the circular portion is seen the cross section of the circulu3arteriosus iridis major (a). Upon the ciliary muscle are situated the ciliary processes, P, which arecovered by the two layers of the pars ciliaris retina;—namely, by the pigmented cellular layer, pe,which is the continuation of the pigment epithelium, Pe, and by the non-pigmented layer, pc, the con-tinuation of the retina proper, R. The flat part of the ciliary body, the orbiculus ciliaris, O
Text-book of ophthalmology . rs, Mu; the transition from one portion to another is effected by theradial fibers, r. At the anterior margin of the circular portion is seen the cross section of the circulu3arteriosus iridis major (a). Upon the ciliary muscle are situated the ciliary processes, P, which arecovered by the two layers of the pars ciliaris retina;—namely, by the pigmented cellular layer, pe,which is the continuation of the pigment epithelium, Pe, and by the non-pigmented layer, pc, the con-tinuation of the retina proper, R. The flat part of the ciliary body, the orbiculus ciliaris, O, extendsto the ora serrata, o, where the chorioid, Ch, and the retina, R, begin. Upon the orbiculus lie the fibenof the zonule of Zinn, z, which farther forward pass into tlie free portion, z\, of the zonula and thereinclose the cavity of the canal of Petit, i. The lens, L, shows at its equator besides the attachmentsof the zonular fibers, the cross section, k, of the ring of nuclei. ANATOMY AND PHYSIOLOGY OF THE UVEA 365. 366 TEXT-BOOK OF OPHTHALMOLOGY With the varying dilatation and contraction of the pupil we also notice a changein the rim of pigment upon the pupillary margin: the more contracted the pupil is,the broader this becomes; on the other hand, when the pupil is greatly dilated, itdisappears entirely. (Compare Fig. 142 with Fig. 61.) When the pupil is very much contracted, we not infrequently observe even innormal eyes a faint tremulousness of the iris (iridodonesis), which otherwise occursonly in dislocation of the lens. This is due to the fact that with a contracted pupil theposterior chamber is deeper and at the same time the greatly dilated iris is considerablythinned—circumstances both of which favor wavering of the iris. 303. Microscopical Anatomy.—The iris stroma consists essentially ofnumerous vessels running in a radial direction from the ciliary to the pupil-lary margin. The vessels are inclosed in a thick adventitia, and are sur-rounded by a loose
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