THE MIDDLE CERVICAL GANGLION. 803 



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

 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 (nervus superficialis cordis] arises by two or more 

 branches from the superior cervical ganglion, and occasionally receives a filament 

 from the cord of communication between the first and second cervical ganglia. It 

 runs down the neck behind the common carotid artery, lying upon the Longus 

 colli muscle, and crosses in front of the inferior thyroid artery and recurrent 

 laryngeal nerve. 



The right superior cardiac nerve, at the root of the neck, passes either in front 

 of or behind the subclavian artery, and along the arteria innominata, to the back 

 part of the arch of the aorta, where it joins the deep cardiac plexus. This nerve, 

 in its course, is connected with other branches of the sympathetic : about the 

 middle of the neck it receives filaments from the external laryngeal nerve ; lower 

 down, one or two twigs from the pneumogastric ; and as it enters the thorax it is 

 joined by a filament from the recurrent laryngeal. Filaments from this nerve 

 communicate with the thyroid branches from the middle cervical ganglion. 



The left superior cardiac nerve, in the chest, runs by the side of the left com- 

 mon carotid artery and in front of the arch of the aorta to the superficial cardiac 

 plexus, but occasionally it passes behind the aorta and terminates in the deep 

 cardiac plexus. 



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. The plexuses accompanying some of these arteries have 

 important communications with other nerves. That surrounding the external 

 carotid is connected with the branch of the facial nerve to the Stylo-hyoid muscle ; 

 that surrounding the facial communicates with the submaxillary ganglion by one 

 or two filaments ; and that accompanying the middle meningeal artery sends offsets 

 which pass to the otic ganglion and to the geniculate ganglion of the facial nerve 

 (external petrosal). 



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

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

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

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

 formed by the coalescence of two ganglia corresponding to the fifth and sixth cer- 

 vical nerves. 



Its superior branches ascend to communicate with the superior cervical gan- 

 glion. 



Its inferior branches descend to communicate with the inferior cervical ganglion. 



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

 These 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 thyroid 

 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 (nervus cardiacus magnus), the largest of the three 

 cardiac nerves, arises from the middle cervical ganglion or from the cord between 

 the middle and inferior ganglia. On the right side it descends behind the common 

 carotid artery, and at the root of the neck passes either in front of or behind the 

 subclavian artery ; it then descends on the trachea, receives a few filaments from 

 the recurrent laryngeal nerve, and joins the right side of the deep cardiac plexus. 

 In the neck it communicates with the superior cardiac and recurrent laryngeal 

 nerves. On. the left side the middle cardiac nerve enters the chest between the 

 left carotid and subclavian arteries, and joins the left side of the deep cardiac 

 plexus. 



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



