Arteries 



'cad am 



there is much difficulty in reaching the vessel the sternal origin of the 

 sterno-mastoid should be divided and turned outwards. 



The collateral circulation would be carried on by the empty 

 branches of the external and internal carotids. Of the external the 

 following would prove useful : the superior thyroid with its fellow, 

 and with the inferior thyroid ; branches of the lingual, facial, super- 

 ficial temporal, and occipital, with their fellows of the opposite side ; 

 and the occipital, with the profunda cervicis and the vertebral. The 

 internal carotid would take in blood, by its anastomosis in the circle 

 of Willis, from its fellow, and from the vertebral. 



The external carotid is destined, as its name implies, for the 

 external parts of the head ; therefore, in its ascent, its lies superficial 

 to the internal carotid, which is the direct continuation of the common 

 trunk. For convenience, in giving off the superior thyroid, lingual, 

 and facial branches, the external carotid bends forwards from its 

 origin, and thus it is at first superficial and anterior to the internal 

 carotid ; but, inclining backwards again, it ultimately lies superficial 

 to the internal trunk, and in the same line with it. Ascending into 

 the parotid gland, it ends by dividing into the superficial temporal 

 and internal maxillary. 



Its course is marked by that part of the line, given on page 23 

 for the common carotid, which extends from the level of the upper 

 border of the thyroid cartilage to the fossa behind the condyle of the 

 jaw. 



Relations. Superficial to it are skin, platysma, and fasciae ; the 

 digastric and stylo-hyoid muscles, and the hypoglossal nerve; and 

 the lingual and facial tributaries of the internal jugular vein. In the 

 parotid gland it is crossed by the facial nerve, and in a muscular 

 subject its lower part is considerably overlapped by the sterno- 

 mastoid. The beginning of the external jugular vein is also super- 

 ficial. 



Beneath it are the internal carotid and the intervening stylo-glossus 

 and stylo-pharyngeus, and the glosso-pharyngeal nerve ; and, lying 

 more deeply than the internal carotid, the superior laryngeal nerve. 



Externally are the anterior border of the sterno-mastoid and the 

 commencement of the internal carotid ; and internally are the 

 pharynx and hyoid bone, and, just before its termination, the ramus 

 of the jaw. 



Xiigation of the external carotid. The patient is arranged as 

 for ligation of the common carotid (p. 25), and an incision is made 

 in the line of the artery, from just behind the angle of the jaw to the 

 level of the cricoid cartilage. The superficial fascia and platysma 

 having been traversed, the deep fascia is divided on a director ; then 

 the digastric, or the hypoglossal nerve, and some veins are seen 

 crossing obliquely. The sterno-mastoid must be pulled outwards, the 

 head having been raised, and the digastric must be drawn upwards. 



