INTERNAL CAROTID ARTER\ r . 279 



The Cavernous portion is situated in the inner wall of the caver- 

 nous sinus, and is in relation by its outer side with the lining mem- 

 brane of the sinus, the sixth nerve, and the ascending branches of 

 the carotid plexus. The third, fourth, and ophthalmic nerves are 

 placed in the outer wall of the cavernous sinus, and are separated 

 from the artery by the lining membrane of the sinus. 



The Cerebral portion of the artery is enclosed in a sheath of the 

 arachnoid, and is in relation with the optic nerve. At its point of 

 division it is situated in the fissure of Sylvius. 



Branches. The cervical portion of the internal carotid gives off 

 no branches : from the other portions are derived the following : 



Tympanic, 



Anterior meningeal, 



Ophthalmic, 



Anterior cerebral, 



Middle cerebral, 



Posterior communicating, 



Choroidean. 



The Tympanic is a small branch which enters the tympanum 

 through a minute foramen in the carotid canal. 



The Anterior meningeal is distributed to the dura mater and Cas- 

 serian ganglion. 



The Ophthalmic artery arises from the cerebral portion of the in- 

 ternal carotid, and enters the orbit through the foramen opticum, 

 immediately to the outer side of the optic nerve. It then crosses 

 the optic nerve to the inner wall of the orbit, and runs along the 

 lower border of the superior oblique muscle, to the inner angle of 

 the eye, where it divides into two terminal branches, the frontal and 

 nasal. 



Branches. The branches of the ophthalmic artery may be 

 arranged into two groups : first, those distributed to the orbit and 

 surrounding parts ; and secondly, those which supply the muscles 

 and globe of the eye. They are 



First Group. Second Group. 



Lachrymal, Muscular, 



Supra-orbital, Anterior ciliary, 



Posterior ethmoidal, Ciliary short and long, 



Anterior ethmoidal, Centralis retinae. 



Palpebral, 

 Frontal, 

 Nasal. 



The Lachrymal is the first branch of the ophthalmic artery, and 

 is usually given off immediately before that artery enters the optic 

 foramen. It follows the course of the lachrymal nerve, along the 

 upper border of the external rectus muscle, and is distributed to the 



