6 TOPOGRAPHICAL ANATOMY OF THE 



adjacent muscles. From the convexity of the curve arise the larynrjeal 

 and ascending 'pharyngeal a.rferies (a. laryngea : a. pharyngea 

 ascendens). 



At this point it should be noted that the deep fascia of the neck 

 forms a well-defined investment for the trachea, and a sheath for the 

 common carotid artery and the nerves related thereto. 



N. VAGUS ET TRUNCUS SYMPATHicus. — The thick uerve-cord that 

 lies dorsal to the common carotid artery has been formed underneath 

 the parotid gland by the union of the vagus or tenth cerebral nerve and 

 the sympathetic trunk. The two nerves separate at the entrance to the 

 chest. With very little difficulty the dissector can resolve the common 

 cord into a smaller, more dorsal portion — the sympathetic trunk — and a 

 larger, ventral part — the vagus ^ nerve. 



No branches leave either the vagus or the sympathetic in the region 

 now being examined. 



N. RECURRENS, — The recurrent nerve, a branch of the vagus, takes 

 origin within the chest, which it leaves by following the ventral part of 

 the lateral face of the trachea. In the neck the nerve runs along the 

 ventral medial border of the common carotid artery to the larynx, where 

 it terminates as the caudal laryngeal nerve (n. laryngeus caudalis), 

 which will be examined later. 



The right recurrent nerve is in contact medially with the trachea : 

 the left nerve is similarly related to the Q?sophagus. In the neck each 

 nerve supplies branches to the trachea (rami tracheales) and oesophagus 

 (rami cesophagei). 



Lymph glands. — Three more or less scattered groups of lymph 

 glands are associated with the common carotid artery. The cranial 

 cervical lymph glands (lyraphoglandula' cervicales craniales) lie 

 in a groove between the trachea and a?sophagus immediately caudal 

 to the pharynx and underneath the caudal angle of the parotid gland. 

 The group contains three or four glands. The middle cervical lymph 

 glands (lymphoglandula' cervicales medi;p) are very variable in size. 

 Generally they are small, and it may be even impossible to find them 

 during an ordinary dissection. When present they lie on the side of 

 the trachea ventral to the common carotid artery about the middle of 

 the neck. The caudal cervical lymph glands (lymphoglanduhe cervi- 

 cales caudales) form a group of considerable size ventral to the trachea 



' Vagus [L.], wandering, rambling. The nerve "wanders" from the head, down 

 the neck and tlirough the thorax into the abdomen. 



