1006 THE NERVOUS SYSTEM 



and to the ganglion nodosum of the vagus. A named branch, the jugular nerve, runs 

 upwards to the base of the skull and divides into two branches, one of which enters 

 the jugular foramen and terminates in the jugular ganglion of the vagus, and the 

 other ends in the petrous ganglion of the glosso-pharyngeus. 



(3) Four or five laryngo-pharyngeal branches come from the superior ganglion 

 and the plexus extending downwards from it, and pass forwards and inwards, 

 external to the carotid vessels, to the. wall of the pharynx, where they unite on 

 the middle constrictor with the pharyngeal branches of the glosso-pharyngeus and 

 vagus, forming with them the pharyngeal plexus, from which branches are dis- 

 tributed to the walls of the pharynx and to the superior and external laryngeal nerves 

 (fig. 719). 



(4) The superior cervical cardiac nerve springs from the lower part of the gan- 

 glion or from the trunk immediately below it. It passes downwards behind the car- 

 otid sheath, either in front of or behind the inferior thyreoid artery, and in front of the 

 longus colli, and establishes communications with the upper cervical cardiac branch 

 of the vagus, the middle cervical cardiac branch of the sympathetic, and with the 

 inferior and external laryngeal nerves. At the root of the neck the nerve of the 

 right side passes in front of or behind the first part of the right subclavian artery, 

 and is continued along the innominate artery to the front of the bifurcation of the 

 trachea, where it ends in the deep part of the cardiac plexus. The left nerve passes 

 into the thorax along the front of the left common carotid artery, crosses the front 

 of the arch of the aorta, immediately anterior to the vagus, and terminates in the 

 superficial part of the cardiac plexus (fig. 720). Filaments from both the right and 

 left nerves pass to the inferior thyreoid plexus. 



(5) The external carotid nerves (fig. 719) pass forwards from the superior 

 cervical ganglion to the external carotid artery, where they divide into branches 

 which anastomose freely to form around the artery the external carotid plexus. 

 This plexus extends to the beginning of the artery, and is continued upon the common 

 carotid artery as the common carotid plexus. From the external carotid plexus, 

 filaments pass to form secondary plexuses around each of the branches of the exter- 

 nal carotid artery. These plexuses take the names of the arteries which they follow, 

 namely, the superior thyreoid plexus, lingual plexus, etc. Filaments pass from 

 the external carotid plexus to the glomus caroticum (the carotid gland), and from 

 the superior thyreoid plexus to the thyreoid gland. 



From the external maxillary (facial) plexus passes the sympathetic root of the 

 submaxillary ganglion. 



A part of the internal maxillary plexus is continued upon the middle meningeal 

 artery as the meningeal plexus. From this plexus filaments pass to the otic gan- 

 glion, and sometimes a branch, called by English anatomists the external superficial 

 petrosal nerve, passes to the geniculate ganglion of the facial nerve. 



(6) Small branches to the ligaments and bones of the upper part of the verte- 

 bral column. 



(7) The internal carotid nerve (ascending branch) has been described with 

 the cephalic portion of the sympathetic system. 



THE MIDDLE CERVICAL GANGLION 



The middle cervical ganglion is small and somewhat triangular in outline. It is 

 sometimes absent. Its position is variable, but it commonly lies about the level of 

 the cricoid cartilage, in front of the bend of the inferior thyreoid artery (fig. 719), and 

 it is connected with the superior cervical ganglion and with the inferior cervical 

 ganglion by the trunk of the gangliated cord. From the lower part of the middle 

 ganglion some filaments pass behind the subclavian artery, while others pass in 

 front of and beneath that artery and anastomose with the first-mentioned filaments 

 to form a loop, the ansa subclavia (ansa Vieussenii) (figs. 675 and 719). Fila- 

 ments from this ansa to the inferior cervical ganglion thus form another communica- 

 tion between the middle and inferior cervical ganglia. 



Connections. The middle cervical ganglion gives off four or more connecting 

 rami. 



Two (o and 6) are grey rami communicantes which connect the middle ganglion 

 with the anterior primary branches of the fifth and sixth cervical nerves. 



(c) One or more peripheral branches pass along the inferior thyreoid artery and 



