391 



THE ARTERIES OF THE HEAD AND NECK. 



or by the union into a single trunk of two or three branches which are usually derived 

 separately from the main artery : so also the number may be augmented by the transfer to 

 this vessel of some branch not ordinarily derived from it, or by the addition of some unusual 

 branch. The most frequent of these are an artery to the sterno-mastoid, generally derived 

 from the occipital, the inferior palatine from the facial, and the transverse facial from the 

 temporal, all of which are sometimes enumerated among the primary branches of the external 

 carotid. In a few instances the trunk has been seen dividing- about the level of the angle of 

 the jaw into two parts which join again above, thus completing a loop. 



BRANCHES OF THE EXTERNAL CAROTID ARTERY. 



1. Superior thyroid artery (iv). This, the first of the anterior set of 

 branches, is given off close to the commencement of the external carotid, immediately 

 below the great cornu of the hyoid bone. From this point the artery curves for- 



Fig. 337. ORIGIN OP THE BRANCHES OP THE EXTERNAL 



CAROTID ARTERY ! THE AVERAGE OP 121 DISSECTIONS 



(after Wyeth). (G. D. T.) Natural size. 



s. th, superior thyroid artery ; hy', its hyoid ; s. m', its 

 sterno-mastoid branch ; I, lingual artery ; hy, its hyoid 

 branch ; /, facial artery ; t, its tonsillar, and ?'. p, its in- 

 ferior palatine branch, arising in common ; a. ph, ascend- 

 ing pharyngeal artery ; o, occipital artery ; s. m, its 

 sterno-mastoid branch ; p. a, posterior auricular artery ; 

 p, parotid and muscular branches ; i. m, internal maxillary 

 artery ; tr. f, transverse facial artery ; a. t, anterior, and 

 p. t, posterior branch of the superficial temporal artery. 



wards and downwards, and then descends for a 

 short distance beneath the omo-hyoid, sterno- 

 hyoid, and sterno-thyroid muscles, to all of which 

 it furnishes offsets. At the apex of the lateral 

 lobe of the thyroid gland it divides into branches 

 which supply the upper part of that body, and 

 anastomose with one another and with branches 

 of the inferior thyroid artery. Its terminal dis- 

 tribution takes place generally by three branches, 

 a posterior , an external, and an anterior, the last 

 of which is the largest and most constant, and 

 descends along the inner side of the lobe to the 

 upper border of the isthmus, where it may form 

 an arch with the opposite vessel : communica- 

 tions between the right and left arteries are 

 however as a rule scanty. 



Branches. Besides the branches to the mus- 

 cles which cover it, to the inferior constrictor of 

 the pharynx, and to the thyroid body, the superior 

 thyroid furnishes the following offsets : 



(a) The hyoid, a small branch, running transversely inwards immediately below 

 the hyoid bone, and supplying the soft parts in the neighbourhood. It sometimes 

 unites with its fellow of the opposite side. 



(b) A superficial descending or sterno-mastoid branch, which passes downwards and 

 backwards over the sheath of the carotid vessels, and ramifies in the sterno-mastoid 

 muscle, as well as in the platysma and neighboring integument. 



(c) The laryngeal branch, or superior laryngeal artery (v), proceeding inwards 

 beneath the thyro-hyoid muscle in company with the superior laryngeal nerve, and 



