THE ANTERIOR PART OF THE NECK 131 



the occipital artery, and it gives off its descending branch. 

 Trace the descending branch downwards, in the fascia which 

 lies superficial to the lower part of the internal and the upper 

 part of the common carotid arteries, to the point where it dis- 

 appears under cover of the anterior belly of the omo-hyoid, 

 avoiding injury to the lingual, common facial, and superior 

 thyreoid veins ; : and secure the communicating branches, 

 from the second and third cervical nerves, which join its 

 posterior aspect. The latter nerves may cross either superficial 

 or deep to the internal jugular vein. Return to the hypoglossal 

 nerve at the point where it gives off its descending branch, and 

 trace it forwards to the upper aspect of the posterior end of 

 the greater cornu of the hyoid bone, where it gives off the branch 

 of supply to the thyreo-hyoid muscle. Trace the branch into 

 that muscle, below the level of the greater cornu ; then follow 

 the trunk of the hypoglossal anteriorly to the digastric triangle. 

 Note that as it runs forwards it passes deep to the posterior belly 

 of the digastric and the stylo-hyoid muscle, and superficial to 

 the hyoglossus, which ascends to the tongue from the upper 

 border of the greater cornu. Remove the fascial sheath from 

 the superficial surfaces of the lower parts of the internal and 

 external carotid arteries, and from the upper part of the common 

 carotid artery. Note that the latter divides into the two former 

 at the level of the upper border of the thyreoid cartilage, and 

 that the external carotid is at first medial and anterior to the 

 internal carotid. 



Five branches may spring from the external carotid artery 

 in the carotid triangle three from its anterior surface : the 

 superior thyreoid, the lingual and the external maxillary ; one 

 from its medial surface, the ascending pharyngeal ; and one 

 from its posterior surface, the occipital ; but not uncommonly 

 the occipital and the external maxillary arise, beyond the limits 

 of the carotid triangle, under cover of the posterior belly of the 

 digastric. The superior thyreoid springs from the front of the 

 lower part of the external carotid, below the level of the greater 

 cornu of the hyoid, and runs downwards towards the lower angle 

 of the carotid" triangle, where it disappears under cover of the 

 anterior belly of the omo-hyoid. The lingual arises about the 

 level of the tip of the greater cornu. It runs forwards above 

 the level of the cornu, forming a loop, convex upwards, which 

 lies deep to the hypoglossal nerve ; and it disappears under cover 

 of the posterior border of the hyoglossus muscle. The ascending 

 pharyngeal branch, which springs from the medial surface of 

 the lower end of the external carotid, ascends on a deeper plane, 

 between the external and internal carotids and the wall of the 

 pharynx, and will be followed at a later stage of the dissection. 

 The external maxillary and the occipital arise immediately 

 below the posterior belly of the digastric and almost at once 

 disappear under cover of the muscle ; not uncommonly they 

 arise under cover of its lower border. Before proceeding to 



1 The lingual vein may join the common facial vein, in which case 

 the latter usually enters the internal jugular opposite the interval between the 

 hyoid bone and the thyreoid cartilage, as in the specimen depicted in Fig. 12. 

 The superior thyreoid vein either ends in the internal jugular or joins the 

 common facial vein opposite the thyreo-hyoid interval, 

 m 9 a 



