^12 OPHTHALMIC ARTERY. 



the pericranium. At the supra-orbital foramen it sends a branch in- 

 wards to the diploe. 



The Ethmoidal arteries, posterior and anterior, pass through the 

 ethmoidal foramina, and are distributed to the falx cerebri and to the 

 ethmoidal cells and nasal fossae. The latter accompanies the nasal 

 nerve. 



The Palpebral arteries, superior and inferior, are given off from the 

 ophthalmic, near the inner angle of the orbit ; they encircle the eye- 

 lids, forming a superior and an inferior arch near the borders of the 

 lids, between the orbicularis palpebrarum and tarsal cartilage. At the 

 outer angle of the eyelids the superior palpebral inosculates with the 

 orbitar branch of the temporal artery. The inferior palpebral artery 

 sends a branch to the nasal duct. 



The Frontal artery, one of the terminal branches of the ophthalmic, 

 emerges from the orbit at its inner angle, and ascends along the mid- 

 dle of the forehead. It is distributed to the integument, muscles, and 

 pericranium. 



The Nasal artery, the other terminal branch of the ophthalmic, 

 passes out of the orbit above the tendo oculi, and divides into two 

 branches ; one of which inosculates with the angular artery, while the 

 other, the dorsalis nasi, runs along the ridge of the nose and is distri- 

 buted to the entire surface of that organ. The nasal artery sends a 

 small branch to the lachrymal sac. 



The Muscular branches, usually two in number, superior and in- 

 ferior, supply the muscles of the orbit ; and upon the anterior aspect 

 of the globe of the eye give off the anterior ciliary arteries, which 

 pierce the sclerotic near its margin of connection with the cornea, and 

 are distributed to the iris. It is the congestion of these - vessels that 

 gives rise to the vascular zone around the cornea in iritis. 



The Ciliary arteries are divisible into three groups, short, long, and 

 anterior. 



The Short ciliary are very numerous; they pierce the sclerotic 

 around the entrance of the optic nerve, and supply the choroid coat 

 and ciliary processes. The long ciliary, two in number, pierce the 

 sclerotic on opposite sides of the globe of the eye, and pass forwards 

 between it and the choroid to the iris. They form an arterial circle 

 around the circumference of the iris by inosculating with each other, 

 and from this circle branches are given off which ramify in the sub- 

 stance of the iris, and form a second circle around the pupil. The an- 

 terior ciliary are branches of the muscular arteries ; they terminate in 

 the great arterial circle of the iris. 



The Centralis retina artery pierces the optic nerve obliquely, and 

 passes forwards in the centre of its cylinder to the retina, where it di- 

 vides into branches, which ramify in the inner layer of that membrane. 

 It supplies the retina, hyaloid membrane, and zonula ciliaris ; and, by 

 means of a branch sent forwards through the centre of the vitreous 

 humour in a tubular sheath of the hyaloid membrane, the capsule of 

 the lens. 



