BRANCHES OF THE INTERNAL CAROTID. 



509 



other, the dorsalis nasi, 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 facial. 



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

 anterior. The short ciliary arteries, from six to twelve in number, arise from the 

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

 forward to the posterior part of the eyeball, pierce the sclerotic coat around the 

 entrance of the nerve, and supply the choroid coat and ciliary processes. The 

 long ciliary arteries, two in number, pierce the posterior part of the sclerotic at 

 some little distance from the optic nerve, and run forward, along each side of 

 the eyeball, between the sclerotic and choroid, to the ciliary muscle, where they 

 divide into two branches ; these form an arterial circle, the circulus major, around 

 the circumference of the iris, from which numerous radiating branches pass 

 forward, in its substance, to its free margin, where they form a second arterial 

 circle, the circulus minor, around its pupillary margin. The anterior ciliary 

 arteries are derived from the muscular branches ; they pass to the front of the 



Fissure of Rolando 



Parieto- 

 occipital 

 "Fissure 



FIG. 293. Vascular area of the internal surface of the cerebrum. (After Duret.) I. The part supplied by the 

 anterior and internal frontal. II. The part supplied by the middle and internal frontal. III. The part sup- 

 plied by the posterior and internal frontal. IV. The part supplied by the posterior temporal ; and V. The part 

 supplied by the occipital, both terminal branches of the posterior cerebral. 



eyeball in company with the tendons of the Recti muscles, form a vascular zone 

 beneath the conjunctiva, and then pierce the sclerotic a short distance from the 

 cornea and terminate in the circulus major of the iris. 



The arteria centralis retinae 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 nerve, but about half an inch behind the eyeball it pierces the optic nerve 

 obliquely, and runs forward in the centre of its substance, and enters the globe 

 of the eye through the porus opticus. Its mode of distribution will be described 

 in the account of the anatomy of the eye. 



The muscular branches, two in number, superior and inferior, frequently spring 

 from a common trunk. The superior, the smaller, often wanting, supplies the 

 Levator palpebne, Superior rectus, and Superior oblique. The inferior, more 

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

 rectus, and is distributed to the External, Internal, and Inferior recti, and Inferior 

 oblique. This vessel gives off most of the anterior ciliary arteries. Additional 

 muscular branches are given off from the lachrymal and supra-orbital arteries or 

 from the ophthalmic itself. 



