pages 571

on the forehead, supplies the integument, muscles, and pericranium, anastomosing with the supraorbital artery, and with the artery of the opposite side.

The Dorsal Nasal Artery (a. dorsalis nasi; nasal artery), the other terminal branch of the ophthalmic, emerges from the orbit above the medial palpebral ligament, and, after giving a twig to the upper part of the lacrimal sac, divides into two branches, one of which crosses the root of the nose, and anastomoses with the angular artery, the other runs along the dorsum of the nose, supplies its outer surface; and anastomoses with the artery of the opposite side, and with the lateral nasal branch of the external maxillary.

The Central Artery of the Retina (a. centralis retinœ) is the first and one of the smallest branches of the ophthalmic artery. It runs for a short distance within the dural sheath of the optic nerve, but about 1.25 cm. behind the eyeball it pierces the nerve obliquely, and runs forward in the center of its substance to the retina. Its mode of distribution will be described with the anatomy of the eye.

The Ciliary Arteries (aa. ciliares) are divisible into three groups, the long and short, posterior, and the anterior. The short posterior ciliary arteries from six to twelve in number, arise from the ophthalmic, or its branches; they pass forward around the optic nerve to the posterior part of the eyeball, pierce the sclera around the entrance of the nerve, and supply the choroid and ciliary processes. The long posterior ciliary arteries, two in number, pierce the posterior part of the sclera at some little distance from the optic nerve, and run forward, along either side of the eyeball, between the sclera and choroid, to the ciliary muscle, where they divide into two branches; these form an arterial circle, the circulus arteriosus major, around the circumference of the iris, from which numerous converging branches run, in the substance of the iris, to its pupillary margin, where they form a second arterial circle, the circulus arteriosus minor. The anterior ciliary arteries are derived from the muscular branches; they run to the front of the eyeball in company with the tendons of the Recti, form a vascular zone beneath the conjunctiva, and then pierce the sclera a short distance from the cornea and end in the circulus arteriosus major.

The Muscular Branches, (rami musculares), two in number, superior and inferior, frequently spring from a common trunk. The superior, often wanting, supplies the Levator palpebræ superioris, Rectus superior, and Obliquus superior. The inferior, more constantly present, passes forward between the optic nerve and Rectus inferior, and is distributed to the Recti lateralis, medialis, and inferior, and the Obliquus inferior. This vessel gives off most of the anterior ciliary arteries. Additional muscular branches are given off from the lacrimal and supraorbital arteries, or from the trunk of the ophthalmic.

8. The anterior cerebral artery (a. cerebri anterior) (Figs. 516, 517, 518) arises from the internal carotid, at the medial extremity of the lateral cerebral fissure. It passes forward and medialward across the anterior perforated substance, above the optic nerve, to the commencement of the longitudinal fissure. Here it comes into close relationship with the opposite artery, to which it is connected by a short trunk, the anterior communicating artery. From this point the two vessels run side by side in the longitudinal fissure, curve around the genu of the corpus callosum, and turning backward continue along the upper surface of the corpus callosum to its posterior part, where they end by anastomosing with the posterior cerebral arteries.

Branches.—In its course the anterior cerebral artery gives off the following branches:

Antero-medial Ganglionic.		Anterior.		Posterior.
Inferior.		Middle.

The Antero-medial Ganglionic Branches are a group of small arteries which arise at the commencement of the anterior cerebral artery; they pierce the anterior

Contents -SUBJECT INDEX -BIBLIOGRAPHIC RECORD -ILLUSTRATION INDEX