OPHTHALMIC ARTERY. 293 



The Supra-orbital artery follows the course of the frontal nerve, resting 

 on the levator palpebrae muscle ; it passes through the supra-orbital fora- 

 men, and divides into a superficial and deep branch, which are distributed 

 to the muscles and integument of the forehead, and to the pericranium. 

 At the supra-orbital foramen it sends a branch inwards to the diploe. 



The Ethmoidal arteries, posterior and anterior, pass through the eth- 

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

 ethmoidal cells and nasal fossce. 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 eyelids, 

 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 middle 

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

 cranium. 



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 distributed to the integument 

 of that organ. The nasal artery sends a small branch to the lachrymal 

 sac. 



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

 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 oppo- 

 site 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 substance of the iris, and form a second 

 circle around the pupil. The anterior ciliary are branches of the muscular 

 arteries ; they terminate in the great arterial circle of the iris. 



The Centralis retime artery pierces the optic nerve obliquely, and passes 

 forwards in the centre of its cylinder to the retina, where it divides 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. 



The interior cerebral artery passes forwards in the great longitudma. 

 fissure between the two hemispheres of the brain ; then curves backwards 

 along the corpus callosum to its posterior extremity. It gives branches 

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