666 SYMPATHETIC NERVE. 



anterior part of the cavernous plexus ; it accompanies the nasal nerve, or con- 

 tinues forwards as a separate branch. 



The terminal filaments from the carotid and cavernous plexuses are prolonged 

 along the internal carotid, forming plexuses which entwine round the cerebral 

 and ophthalmic arteries ; along the former vessel they may be traced on to the 

 pia mater ; along the latter, into the orbit, where they accompany each of the 

 subdivisions of the vessel, a separate plexus passing with the arteria centralis 

 retinae into the interior of the eyeball. 



The inferior or descending branch of the superior cervical ganglion communi- 

 cates with the middle cervical ganglion. 



The external branches are numerous, and communicate with the cranial nerves, 

 and with the four upper spinal nerves. Sometimes, the branch to the fourth 

 spinal nerve may come from the cord connecting the upper and middle cervical 

 ganglia. The branches of communication with the cranial nerves consist of 

 delicate filaments, which pass from the superior cervical ganglion to the gan- 

 glion of the trunk of the pneumogastric, and to the ninth nerve. A separate 

 filament from the cervical ganglion subdivides and joins the petrosal ganglion 

 of the glosso-pharyngeal, and the ganglion of the root of the pneumogastric in 

 the jugular foramen. 



The internal branches are three in number : pharyngeal, laryngeal, and the 

 superior cardiac nerve. The pharyngeal branches pass inwards to the side of 

 the pharynx, where they join with branches from the pneumogastric, glosso- 

 pharyngeal, and external laryngeal nerves to form the pharyngeal plexus. The 

 laryngeal branches unite with the superior laryngeal nerve and its branches. 



The superior cardiac nerve will be described in connection with the other 

 cardiac nerves. 



The anterior branches ramify upon the external carotid artery and its branches, 

 forming round each a delicate plexus, on the nerves composing which small 

 ganglia are occasionally found. These ganglia have been named, according to 

 their position, intercarotid (one placed at the angle of bifurcation of the common 

 carotid), lingual, temporal, and pharyngeal. The plexuses accompanying some 

 of these arteries have important communications with other nerves. That sur- 

 rounding the external carotid, is connected with the digastric branch of the 

 facial ; that surrounding the facial, communicates with the submaxillary gan- 

 glion by one or two filaments ; and that accompanying the middle meningeal 

 artery, sends offsets which pass to the otic ganglion and to the intumescentia 

 ganglioformis of the facial nerve. 



The Middle Cervical Ganglion (thyroid ganglion) is the smallest of the three 

 cervical ganglia, and is occasionally altogether wanting. It is placed opposite 

 the fifth cervical vertebra, usually upon, or close to, the inferior thyroid artery; 

 hence the name "thyroid ganglion," assigned to it by Haller. 



Its superior branches ascend to communicate with the superior cervical 

 ganglion. 



Its inferior branches descend to communicate with the inferior cervical 

 ganglion. 



Its external branches pass outwards to join the fifth and sixth spinal nerves. 

 Those branches are not constantly found. 



Its internal branches are, the thyroid, and the middle cardiac nerve. 



The thyroid branches are small filaments, which accompany the inferior thy- 

 roid artery to the thyroid gland ; they communicate, on the artery, with the 

 superior cardiac nerve, and, in the gland, with branches from the recurrent and 

 external laryngeal nerves. 



The middle cardiac nerve is described with the other cardiac nerves. 



The Inferior Cervical Ganglion is situated between the base of the transverse 

 process of the last cervical vertebra and the neck of the first rib, on the inner 



