390 ARTERIES. 



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 

 anterior. 



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 this nerve, and supply the choroid coat and ciliary processes. 



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 margin. 



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 retinse 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 branches, two in number, superior and inferior, supply the 

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

 Levator palpebrse, Superior rectus, 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 callosum, and run along its upper 

 surface to its posterior part, where they terminate 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 inner 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 arteries 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. 



The middle cerebral artery, the largest branch of the internal carotid, passes 

 obliquely outwards along the fissure of Sylvius, within which it divides into three 

 branches : an anterior, which supplies the pia mater, investing the surface of the 

 anterior lobe ; a posterior, which supplies the middle lobe ; and a median branch, 

 which supplies the small lobe at the outer extremity of the Sylvian fissure. Near 

 its origin, this vessel gives off numerous small branches, which enter the substantia 

 perforata, to be distributed to the corpus striatum. 



The posterior communicating artery arises from the back part of the internal 

 carotid, runs directly backwards, and anastomoses with the posterior cerebral, a 



