. Cunningham's Text-book of anatomy. Anatomy. 814 THE OEGANS OF SENSE. Anterior ciliary arteries Veins of chorioid. Aperture of pupil Long ciliary artery Circulus Circulus arteriosus major Anterior ciliary arteries towards the ciliary margin of the iris, and communicate with the veins of the ciliary processes and with the sinus venosus sclerse. The convergence of the blood- vessels towards the aper- ture of the pupil gives to the anterior surface of the iris a striated appearance. The non-striped muscular fibres of the iris are arranged in two sets: (a) circular, (&) radial. The circular f
. Cunningham's Text-book of anatomy. Anatomy. 814 THE OEGANS OF SENSE. Anterior ciliary arteries Veins of chorioid. Aperture of pupil Long ciliary artery Circulus Circulus arteriosus major Anterior ciliary arteries towards the ciliary margin of the iris, and communicate with the veins of the ciliary processes and with the sinus venosus sclerse. The convergence of the blood- vessels towards the aper- ture of the pupil gives to the anterior surface of the iris a striated appearance. The non-striped muscular fibres of the iris are arranged in two sets: (a) circular, (&) radial. The circular fibres form a band, the m. sphincter pupillse, around the pupillary aperture ; by the contraction of these arteriosus fibreg the gize of the pupi} is lessened. The radial fibres constitute the m. dilatator pupillse and extend out- wards from the sphincter to the ciliary margin. Many anatomists regard the radial fibres, in man and most mammals, as being elastic and not muscular. In Fig. 684.—Blood-vessels of Iris and Anterior Part of Chorioid, . , . , . , ,, ,. -. viewed from the front (Arnold). animals m which the radial fibres are muscular, the degree of their development varies considerably; they are feebly marked in the rabbit, but are well developed in the bird, and still more so in the otter. The nerves of the chorioid and iris (Eig. 685) are derived from the long and short ciliary nerves. The former, two or three in number, are branches of the naso- ciliary nerve; the latter, vary- ^gs=^^__Coruea ing from eight to fourteen, are derived from the ciliary ganglion. Piercing the sclera around the entrance of the optic nerve, the ciliary nerves traverse the perichorioidal lymph space, where they form a plexus, rich in nerve-cells, from which filaments are sup- plied to the blood-vessels of the chorioid. In front of the ciliary muscle a second plexus, also rich in nerve-cells, is formed ; this supplies the ciliary muscle and sends fila- ments into the iris, as far as its pupil
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