THE NECK 121 



border of the thyreoid cartilage and ends in the parotid gland, 

 behind the neck of the mandible,, by dividing into the internal 

 maxillary and superficial temporal arteries. The course of the 

 artery corresponds to a line drawn from a little below the tip 

 of the greater cornu of the hyoid bone to the lobule of the 

 auricle. 



In ligature of this part of the vessel the incision may be made 

 in the natural folds of the neck, either along the anterior border 

 of the sterno-mastoid or crossing the muscle obliquely. The 

 superficial coverings are divided, and, in the oblique incision, 

 the external jugular vein and the great auricular nerve (p. 108) 

 will be exposed in the upper part of the wound. The deep 

 fascia is cut along the anterior border of the sterno-mastoid, and 

 the muscle, which overlaps the artery, is retracted to the lateral 

 side. Numerous veins (pharyngeal, lingual, and common facial) 

 cross the external carotid artery to reach the internal jugular 

 vein. They must be secured before the upward continuation 

 of the carotid sheath is opened. Care must be taken not to open 

 the sheath too much to the medial side lest the superior thyreoid 

 artery be injured as it descends medial to the sheath. The 

 vessel is ligated between the superior thyreoid and lingual 

 branches, i.e. a short distance below the greater cornu of the 

 hyoid bone. In this operation there is little danger of including 

 the vagus nerve in the ligature, since it is a more intimate 

 relation of the internal carotid artery, which lies on a deeper 

 plane. 



The upper part of the external carotid artery disappears 

 by passing under cover of the stylo-hyoid and the posterior 

 belly of the digastric, but before it does so it is crossed from 

 behind forwards by the hypoglossal nerve (Fig. 39). Throughout 

 the rest of its course the artery lies deeply, under cover of the 

 parotid gland, and is rarely exposed by the surgeon. 



The Superior Thyreoid Artery arises from the external 

 carotid just above the upper border of the thyreoid cartilage, 

 and runs downwards and forwards, disappearing under cover 

 of the omo-hyoid and the sterno-thyreoid to supply the thyreoid 

 gland (p. 167). It may be ligated near its origin by an incision 

 similar to that employed for ligature of the external carotid. 

 The superior cornu of the thyreoid cartilage is the deep surgical 

 guide to the vessel. The branches are (i) the Superior Laryngeal 

 Artery, which pierces the thyreo-hyoid membrane at the posterior 

 border of the thyreo-hyoid muscle, in company with the internal 



