. The comparative anatomy of the domesticated animals. Horses; Veterinary anatomy. 932 TEE SENSORY AIWA RAT USES. fibres which are arruugcd in orbicular fasciculi, or extend backwards fand are lost in the choroid, behind the ciliary processes). These fibres are mixed in the plexus of ciliary nerves, on the track of which small ganglia are formed. By its contractions, the ciliary circle (or muscle) plays an important part in accommo- dating the eye to the perception of objects at different distances. (In Birds, the muscular fibres are striped.) The ciliary body ox processes are formed by interc
. The comparative anatomy of the domesticated animals. Horses; Veterinary anatomy. 932 TEE SENSORY AIWA RAT USES. fibres which are arruugcd in orbicular fasciculi, or extend backwards fand are lost in the choroid, behind the ciliary processes). These fibres are mixed in the plexus of ciliary nerves, on the track of which small ganglia are formed. By its contractions, the ciliary circle (or muscle) plays an important part in accommo- dating the eye to the perception of objects at different distances. (In Birds, the muscular fibres are striped.) The ciliary body ox processes are formed by intercrossed fasciculi of (fibrillated) connective tissue, vessels, and some unstriped muscular fibres; their inner surface is covered ))y pigment, like that of the choroid zone. 4. The Iris (Figs. 502,/; 505, 6). The iris forms in the interior of the eye—at the anterior opening of the sclerotic, and in front of the crystalline lens—a veritable diaphragm pierced with a central opening—the pupil—which contracts or dilates according to the intensity of the light and the distance of the objects to which the vision is Fig. THE EYE (human) WITH THE SCLEROTIC COAT REMOVED. 1, Sclerotic coat; 2, veins of the choroid ; 3, ciliary nerves ; 4, veins of the choroid, or vence vorticosa ; 5, ciliary ligament; 6, iris. directed. This diaphragm divides the space between the cornea and the anterior face of the lens, and internal extremities of the ciliary processes, into two compartments or chambers of unequal size ; the anterior space is the largest, the posterior having only a virtual existence, as the iris is close to the crystalline lens. In shape, the iris is elliptical, like the cornea and the sclerotic aperture. Its anterior face is flat or very slightly convex, and has very marked circular furrows and radiating striae, noticeable only at the outer circumference of the membrane. It is diversely coloured, not only according to species, but also in individuals. In ^^olipeds, it ha
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