THE VESSELS. 307 



neck, behind mm. stylo-glossus and pharyngeus, separated by 

 these from carotis externa ; before m. longus colli and the verte- 

 bral column ; internally, bounded by the lateral wall of the pha- 

 rynx, art. pharyngea ascend, and gangl. I. N. sympathies, exter- 

 nally by the ramus of the lower jaw, V.jugularis interna and 

 Nn. vagus, glosso-pharyng., hypo-glossus (which lie behind it 

 above) ; in the canal, caroticus : surrounded by filaments from 

 ganglion cervicale supremum and by a thin sheath ; in the sinus 

 cavernosus : on the inner side of nerv. abducens, oculo-mot., pa- 

 thetic., and ram. ophthalm. of the fifth nerve. 



Branches : As an exception, the Artt. pharyngea ascendens and 

 temporalis pass off from the cervical portion, otherwise none ; in- 

 side the canal, caroticus a small branch for the tympanum ; in 

 the sinus cavernosus several small branches for the basilar portion 

 of the dura mater, the walls of sinus petrosus infer., for the hy- 

 pophysis cerebri, N. trigeminus, and a connecting branch to the 

 Art. mening. media. Besides, anteriorly : Art. ophthalmica, and 

 the terminal branch of carotis interna ; these are, artt. communi- 

 cans, choroidea, corporis callosi, fosses Sylvii. 



551. 1. Ophthalmica. Origin: close behind proc. clinoid. anter. from 

 the convex anterior surface of the fourth curve of the carotis. Course : en- 

 ters immediately below the optic nerve, through the foram. opticum into the 

 orbit, passes at first on the outer and lower side of the optic nerve, between 

 muse, rectus super, and externus, then inwards above n. opticus as far as the 

 internal wall of the orbita ; lastly, directly forwards along the inferior border 

 of obliq. superior, and under the trochlea, and divides at the place of junction 

 of the upper jaw and frontal bone, into Art. nasalis andfrontalis. 



Collateral branches : Arising on the outer side of the 

 Nervus Opticus. 



a. Lacrymalis, the lacrymal artery, large, arises immediately as the Art. 

 ophthal. enter the orbita (or as it crosses the optic nerve), passes on the exter- 

 nal wall between periorbita and m. rect. extern., as far as the lacrymal gland, 

 ramifies here and gives off branches to the superior eyelid, m. rect. extern., 

 super., to Art. mening. med. (backwards), to the temporal (through/or, zygo- 

 matic.) 



b. Centralis retinae, thin ; penetrates into the centre at the inferior side of 

 the optic nerve, passes in its axis directly forwards, spreads out with three 

 diverging branches on the internal surface of the retina. A branch passes 

 from it in the axis of the eye ; this is, 



Capsularis, through the vitreous body as far as the posterior wall of the 

 capsule of the lens, giving off on the way minute ramusculi. 



