THE HEAD AND NECK It^g 



branches, temporal and malar. The temporal branch ascends upon 

 the outer wall of the orbit, and, having received a communicating 

 twig from the lachrjnmal nerve, it leaves the cavity by passing 

 through the temporal canal in the malar bone. Its destination is 

 the skin of the anterior part of the temporal region. 



The malar branch passes forwards in the angle between the outer 

 wall and floor of the orbit, and leaves the cavity by passing through 

 the malar canal, from which it subsequently emerges through the 

 malar foramen. It is distributed to the skin over the malar 

 bone. 



Ophthalmic Artery. — ^This vessel arises from the internal carotid 

 artery on the inner aspect of the anterior clinoid process, and it 

 enters the orbit through the optic foramen, lying beneath the optic 

 nerve. Within the orbit it is situated for a short distance on the 

 outer side of the optic nerve, and then it passes obliquely inwards 

 and forwards in a tortuous manner over the nerve to the inner wall 

 of the orbit. Thereafter it passes forw^ards to the region of the 

 internal angular process of the frontal bone, near which it divides 

 into its two terminal breinches, nasal and frontal. 



Branches. — These are as follows : 



1. Arteria centralis, retinae. 6. Posterior ethmoidal. 



2. Posterior ciliary. 7. Anterior ethmoidal. 



3. Lachrymal. 8. Palpebral (two). 



4. Muscular. 9. Nasal. 



5. Supra-orbital. 10. Frontal. 



The arteria centralis retinae arises from the ophthalmic at the back 

 part of the orbit below the optic nerve. Its direction is forwards 

 beneath the nerve, and, at a point about J inch behind the eyeball, 

 it enters the nerve, and passes forwards in its centre to the retina, 

 upon which it ramifies. 



The posterior ciliary arteries arise from the ophthalmic whilst it 

 is below the optic nerve. They are arranged in two sets, external 

 and internal, which pass forwards on either side of the optic nerve 

 to the back part of the eyeball. Here they pierce the sclerotic, 

 and the majority of them enter the choroid coat under the name 

 of the short ciliary arteries. Two of them, however, are fairly large, 

 and are known as the long ciliary arteries. They pass forwards 

 between the sclerotic and the choroid, one on each side, and are 

 distributed to the ciliary muscle and iris. 



The lachrymal artery arises from the ophthalmic on the outer side 

 of the optic nerve, and passes fonvards along the upper border of 

 the external rectus muscle to the lachrymal gland. In its course 

 it furnishes the following branches : (i) a recurrent meningeal 

 branch, which passes through the outer part of the sphenoidal 

 fissure to the middle cranial fossa, where it anastomoses with the 

 middle meningeal artery ; (2) muscular and anterior ciliary branches, 

 the latter piercing the sclerotic very near the corneal margin ; 



