t234 A MANUAL OF ANATOMY 



and divides into two parts. The external division lies upon the outer 

 side of the artery, and its subdivisions form by their interlacement 

 the carotid plexus. From this plexus several communicating 

 branches are given o&. (i) The carotico-tympanic nerve enters the 

 tympanum, and joins the tympanic branch (Jacobson's nerve) of 

 the glosso-phar5mgeal, to take part in the tympanic plexus, (2) The 

 great deep petrosal nerve joins the great superficial petrosal from 

 the geniculate ganglion of the facial, in the upper part of the fora- 

 men lace rum medium, to form the Vidian nerve, which passes 

 through the Vidian canal to join Meckel's ganglion. (3) A branch 

 (or branches) passes to join the sixth cranial nerve. (4) One or 

 more branches pass to join the Gasserian ganglion. The carotid 

 plexus furnishes filaments to the coats of the internal carotid artery, 

 and it receives the small deep petrosal nerve from the tympanic 

 plexus. 



The internal division of the ascending branch of the superior 

 cervical ganglion lies upon the inner side of the internal carotid 

 artery, to which it furnishes twigs, and its subdivisions form by their 

 interlacement the cavernous plexus. This plexus lies in contact 

 with the internal carotid artery as it traverses the cavernous sinus. 

 Its communicating branches pass to join the third, fourth, and 

 ophthalmic division of the fifth cranial nerves, and the. ciliary or 

 lenticular ganglion. The last-named branch forms the sympa- 

 thetic root of the ciliary ganglion, and enters the orbit through the 

 sphenoidal fissure. It is the source of the motor supply of the 

 dilator pupillse muscle. The cavernous plexus furnishes filaments 

 to the coats of the internal carotid artery, and offsets which accom- 

 pany the branches of that artery, around which they are disposed as 

 plexuses. 



The external branches are communicating, and pass to (i) each 

 of the upper four cervical nerves ; (2) the petrosal ganglion of the 

 glosso-pharyngeal ; (3) the ganglion of the root, and the ganglion of 

 the trunk, of the vagus ; and (4) the hypoglossal nerve. 



The internal branches are pharyngeal and cardiac. The pharyn- 

 geal branches, two or three in number, unite with the pharyngeal 

 branches of the glosso-pharyngeal and vagus to form the -phsxyn- 

 geal plexus (see p. 1227). 



The superior cardiac nerve arises by two roots from the lower part 

 of the superior cervical ganglion, and descends behind the carotid 

 sheath, lying internal to the main sympathetic cord. The nerve 

 of the right side passes either over or beneath the first part of the 

 subclavian artery, and then along the innominate artery, to ter- 

 minate in the deep cardiac plexus. In its course down the neck 

 it receives twigs from the external laryngeal nerve, and is joined by 

 the upper cervical cardiac branch of the pneumogastric nerve. As 

 it enters the thorax, it receives a filament from the recurrent 

 laryngeal nerve. The nerve of the left side within the thorax 

 accompanies the left common carotid artery, and passes over the 

 arch of the aorta to terminate in the superficial cardiac plexus. 



