616 



THE VASCULAR SYSTEMS 



the root of the nose, the transverse nasal, and anastomoses with the angular artery; 

 the 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 (a. ciliares] are divisible into three groups the short, long, 

 and anterior. The short ciliary arteries (aa. ciliares poster lores breves), from six 

 Jjo twelve in number, arise from the ophthalmic or some of its branches; they sur- 

 round the optic nerve as they pass forward to the posterior part of the eyeball, 

 pierce the sclera around the entrance of the nerve, and supply the choroid coaj. 

 and ciliary processes. The long ciliary arteries (aa. ciliares poster/ores longae), 

 two in number, pierce the posterior part of the sclera at some little distance from 

 the optic nerve, and run forward, along each 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 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 



Central Fissure 



Occipital 



'Fissure 



FIG. 451. Vascular area of the internal surface of the cerebrum. I. The part supplied by the anterior 

 internal frontal. II. The part supplied by the middle internal frontal. III. The part supplied by the posterior 

 internal frontal. IV. The part supplied by the posterior temporal. V. The part supplied by the occipital , both 

 terminal branches of the posterior cerebral. (After Duret.) 



its pupillary margin. The anterior ciliary arteries (aa. ciliares anteriores) are 

 derived from the muscular branches (see below); they pass to the front of the 

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

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

 cornea and terminate in the circulus major of the iris. 



The central artery of the retina (arteria ceutralis 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 optic 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 (rami wmsculares), two in number, superior and inferior, 

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

 supplies the Levator palpebrae, Superior rectus, and Superior oblique. The infe- 

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

 the Inferior rectus muscle, and is distributed to 'the External, Internal, and Inferior 



