OF THE BRAIN. 4f>7 



palpebral, inosculating at the outer angle of the orbit with the orbital branch 

 of the temporal artery, the inferior palpebral with the orbital branch of the 

 infraorbital artery, at the inner side of the lid. From this anastomosis, a 

 branch passes to the nasal duct, ramifying in its mucous membrane, as far as 

 the inferior meat us. 



The frontal artery, one of the terminal branches of the ophthalmic, passes from 

 the orbit at its inner angje, and ascending on the forehead, supplies the muscles, 

 integument, and pericranium, anastomosing with the supraorbital artery. 



The nasal artery, the other terminal branch of the ophthalmic, emerges from 

 the orbit above the tendo oculi, and, after giving a branch to the lachrymal 

 sac, divides into two, one of which anastomoses with the angular artery, the 

 other branch, the dorsalis nasi, runs along the dorsum of the nose, supplies its 

 entire surface, and anastomoses with the artery of the opposite side. 



The ciliary arteries are divisible into three groups, the short, long, and ante- 

 rior. The short ciliary arteries, from twelve to fifteen in number, arise from the 

 ophthalmic, or some of its branches ; they surround the optic nerve as they 

 pass forwards to the posterior part of the eyeball, pierce the sclerotic coat 

 around the entrance of the nerve, and supply the choroid coat and ciliary pro- 

 cesses. The long ciliary arteries, two in number, also pierce the posterior part 

 of the sclerotic, and run forwards, along each side of the eyeball, between the 

 sclerotic and choroid, to the ciliary ligament, where they divide into two 

 branches ; these form an arterial circle around the circumference of the iris, 

 from which numerous radiating branches pass forwards, in its substance, to its 

 free margin, where they form a second arterial circle around its pupillary mar- 

 gin. The anterior ciliary arteries are derived from the muscular branches ; they 

 pierce the sclerotic a short distance from the cornea, and terminate in the great 

 arterial circle of the iris. 



The arteria centralis retinae is one of the smallest branches of the ophthalmic 

 artery. It arises near the optic foramen, pierces the optic nerve obliquely, and 

 runs forwards, in the centre of its substance, to the retina, in which its branches 

 are distributed as far forwards as the ciliary processes. In the human foetus, a 

 small vessel passes forwards, through the vitreous humor, to the posterior surface 

 of the capsule of the lens. 



The muscular brunches, two in number, superior and inferior, supply the mus- 

 cles of the eyeball. The superior, the smaller, often wanting, supplies the 

 Levator Palpebrse, Superior Eectus, and Superior Oblique. The inferior, more 

 constant in its existence, passes forwards, between the optic nerve and Inferior 

 Rectus, and is distributed to the External and Inferior Recti, and Inferior 

 Oblique. This vessel gives off most of the anterior ciliary arteries. 



The Cerebral Branches of the internal carotid are, the anterior cerebral, the 

 middle cerebral, the posterior communicating, and the anterior choroid. 



The anterior cerebral arises from the internal carotid, .at the inner extremity 

 of the fissure of Sylvius. It passes forwards in the great longitudinal fissure 

 between the two anterior lobes of the brain, being connected, soon after its 

 origin, with the vessel of the opposite side by a short anastomosing trunk, about 

 two lines in length, the anterior communicating. The two anterior cerebral 

 arteries, lying side by side, curve round the anterior border of the corpus cal- 

 losum, and run along its upper surface to its posterior part, where they ter- 

 minate by anastomosing with the posterior cerebral arteries. They supply the 

 olfactory and optic nerves, the under surface of the anterior lobes, the third 

 ventricle, the anterior perforated space, the corpus callosum, and the inferior 

 surface of the hemispheres. 



The anterior communicating artery is a short branch, about two lines in length, 

 but of moderate size, connecting together the two anterior cerebral arteries 

 across the longitudinal fissure. Sometimes this vessel is wanting, the two ar- 

 teries joining together to form a single trunk, which afterwards subdivides. Or 

 the vessel may be wholly or partially subdivided into two ; frequently, it is 

 longer and smaller than usual. 



