346 EXTERNAL CAROTID ARTERY. 



and hyoid bone ; further up it is separated by a portion of the parotid gland 

 from the back of the ranms of the lower jaw, and rests upon the styloid pro- 

 cess and the stylo-pharyngeus muscle, which, with the glosso-pharyngeal 

 nerve, are interposed between it and the internal carotid artery. 



Relation to Veins. This artery has usually no companion vein, though 

 it may be crossed superficially by small branches of the contiguous veins ; 

 but, when the internal maxillary vein joins the deep instead of the superficial 

 jugular, it accompanies the external carotid. 



Relation to Nerves. Close to the digastric muscle the external carotid 

 artery is crossed by the hypoylossal nerve, and at a short distance from its 

 upper end, in the substance of the parotid gland, by the facial nerve. The 

 glosso-pharyngeal nerve lies between it and the internal carotid ; and the 

 superior laryngeal nerve is under both vessels. 



BKANCHES. The branches of the external carotid artery are 'eight in 

 number, viz. three directed forwards, the superior thyroid, the lingual, and 

 the facial ; two directed backwards, the occipital and posterior auricular ; 

 and three extending upwards, the ascending pharyngeal branch, together with 

 the temporal and internal maxillary, the two terminal branches into which 

 the artery divides. 



In addition to the principal branches here enumerated, the external 

 carotid gives off small offsets to the parotid gland. 



PECULIARITIES. The peculiarities in the origin of this vessel have been noticed 

 along with those of the common carotid artery. 



The branches are not unfrequently crowded together on the main stem, near tho 

 commencement, or at a higher point. Occasionally they take origin at regular 

 distances in the whole length of the vessel. 



The usual number of branches may be diminished by the association with another 

 artery of one of the ordinary branches, 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. 



There is frequently present a small distinct branch for the sterno-mastoid muscle, 

 which bends outwards over the hypoglossal nerve. 



BRANCHES OF THE EXTERNAL CAROTID ARTERY. 



I. SUPERIOR THYROID ARTERY. 



The superior thyroid artery, 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 

 forwards and downwards to the upper margin of the thyroid cartilage ; it 

 then descends a short distance beneath the omo-hyoid, sterno-hyoid, and 

 sterno-thyroid muscles, furnishing offsets to those muscles ; and, reaching the 

 anterior surface of the thyroid body, distributes branches to its substance, 

 and communicates freely with the branches of the inferior thyroid artery. 



BRANCHES. 



Besides the branches furnished to the muscles which cover it, and to the thyroid 

 body, together with some to the lowest constrictor of the pharynx, the superior 

 thyroid furnishes the following offsets, which have received distinctive names : 



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



