EXTEllXAL CAKOTID ARTERY. S61 



adults. It reaches from the point of division of the common carotid, 

 opposite the upper margin of the thyroid cartilage, to the neck of the 

 condyle of the lower jaw-bone, or a little lower, and there divides 

 into its two terminal branches, the temporal and the internal maxillary. 

 It diminishes rapidly as it ascends, owing to the number and size of 

 the branches which spring from it. 



At first the external carotid lies nearer to the middle line of the body 

 than the internal carotid ; but it soon becomes superficial to that 

 artery, at the same time curving slightly forwards as it ascends to its 

 place" of division. At its origin this artery is concealed by the sterno- 

 mastoid muscle, emerging from beneath which, it is covered only by the 

 platysma myoides and the fascia, and traverses the upper part of a 

 triangular intermuscular space bounded by the sterno-mastoid, omo- 

 hj'oid and digastric muscles ; it then becomes deeply placed, passing 

 beneath the stylo-hyoid and digastric muscles, and finally becoming 

 embedded in the substance of the parotid gland. In the lower part of 

 its course it is in contact with the pharynx and hyoid bone ; further 

 up it is separated by a portion of the parotid gland from the back of 

 the ramus of the lower jaw, and rests upon the styloid process and the 

 stylo-i)haryngeus muscle, which, witli 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 con- 

 tiguous 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 hypoglossal nn-ve, and at a short dis- 

 tance from its upper end, in the substance of the parotid gland, by 

 the facial nerve. The fjlosso-jjliart/ngml nerve lies between it and the 

 internal carotid ; and the superior laryngeal nerve is under both vessels. 



Branches. — 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 twt) 

 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. 



Varieties. — The peculicarities in the origin of this vessel have been noticed 

 along with those of the common carotid artery. The branches are not unfre- 

 qiiently crowded together on the main stem, near the 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 

 ste:-no-maSjoid mi-cle, whi^h bands. '.outwavis over th3 hypoglossal nerve. 



BRANCHES OF THE EXTERNAL eAIlw 4 l P ARTERY, 



1. Superior Thyroid Artery. — This, the first of the anterior set of 

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



