EXTERNAL CAROTID ARTERY. 85 



Veins. There is not any companion vein with the external carotid as 

 with most arteries ; but sometimes a vein, formed by the union of the tem- 

 poral and internal maxillary branches (p. 42), will accompany it. Near 

 the beginning it is crossed by the facial and lingual branches joining the 

 internal jugular vein ; and near the ending the external jugular vein lies 

 over it. 



Nerves are directed from behind forwards over and under the artery. 

 At the lower border of the digastric muscle the hypoglossal lies over the 

 vessel, and near the ending the ramifications of the facial nerve are super- 

 ficial to it. Three nerves lie beneath it : beginning below, the small ex- 

 ternal laryngeal ; a little higher, the superior laryngeal ; and near the base 

 of the jaw, the glosso-pharyngeal. 



The branches of the external carotid are numerous, and are classed into 

 an anterior, posterior, and ascending set. The anterior set comprise 

 branches to the thyroid body, the tongue, and the face, viz., superior thy- 

 roid, lingual, and facial arteries. In the posterior set are the occipital 

 and posterior auricular branches. And the ascending set include the as- 

 cending pharyngeal, temporal, and internal maxillary arteries. Besides 

 these, the carotid gives other branches to the sterno-mastoid muscle and 

 the parotid gland. 



The origin of the branches of the carotid may be altered by their closer 

 aggregation on the trunk. The usual number may be diminished by two 

 or more uniting into one ; or the number may be increased by some of the 

 secondary offsets being transferred to the parent trunk. 



Directions. All the branches, except the ascending pharyngeal, lingual, 

 and internal maxillary, may be now examined ; but those three will be 

 described afterwards with the regions they occupy. 



The superior thyroid artery (e) arises near the cornu of the os hyoides, 

 and passes beneath the omo-hyoid, sterno-hyoid, and sterno-thyroid mus- 

 cles to the thyroid body, to which it is distributed on the anterior aspect. 

 This artery is superficial in the anterior triangle, and furnishes offsets to 

 the lowest constrictor and the muscle beneath which it lies, in addition to 

 the following named branches : 



a. The hyoid branch is very inconsiderable in size, and runs inwards 

 below the hyoid bone : it supplies the muscles attached to that bone, and 

 anastomoses with the vessel of the opposite side. 



b. A branch for the sterno-mastoid muscle lies in front of the sheath of 

 the common carotid artery, and is distributed chiefly to the muscle from 

 which it takes its name. 



c. The laryngeal branch pierces the membrane between the hyoid bone 

 and the thyroid cartilage, with the superior laryngeal nerve, and ends in 

 the interior of the larynx. 



d. A small crico-thyroid branch is placed on the membrane between the 

 cricoid and the thyroid cartilage, and communicates with the corresponding 

 artery of the opposite side, forming an arch. 



The superior thyroid vein commences in the larynx and the thyroid 

 body, and crosses the end of the common carotid artery to open into the 

 internal jugular vein. 



The facial artery (<?) arises above the lingual, and is directed upwards 

 over the lower jaw to the face. In the neck the artery passes beneath the 

 digastric and stylo-hyoid muscles, and is afterwards lodged on the sub- 

 maxillary gland, on which it makes a sigmoid turn. Its anatomy in the 



