448 ARTERIES. 



anterior margin of the Sterno-mastoid, crossed by the hypoglossal nerve, and 

 by the lingual and facial veins ; it is afterwards crossed by the Digastric und 

 Stylo-hyoid muscles, and higher up passes deeply into the substance of the 

 parotid gland, where it lies beneath the facial nerve and the junction of the 

 temporal and internal maxillary veins. 



Internally is the hyoid bone, the wall of the pharynx, and the ramus of the 

 jaw, from which it is separated by a portion of the parotid gland. 



Behind it, near its origin, is the superior laryngeal nerve ; and higher up, it 

 is separated from the internal carotid by the Stylo-gl-ossus and Stylo-pharyngeus 

 muscles, the glosso-pharyngeal nerve, and part of the parotid gland. 



PLAN OF THE RELATIONS OF THE EXTERNAL CAROTID. 



In front. Behind. 



Integument, superficial fascia. s' ^\ Superior laryngeal nerve, 



Platysma and deep fascia. f \^ Stylo-glossus. 



Hypoglossal nerve. / External \ Stylo-pharyngeus. 



Lingual and facial veins. 1 Carotid. I Glosso-pharyngeal nerve. 



Digastric and Stylo-hyoid muscles. V / Parotid gland. 



Parotid gland, with facial nerve and \ * . 



temporo-maxillary vein in its sub- 

 stance. 



Internally. 

 Hyoid bone. 

 Pharynx. 

 Parotid gland. 

 Eamus of jaw. 



Surgical Anatomy. The application of a ligature to the external carotid may be required in 

 cases of wounds of this vessel, or of its branches when these cannot be tied, and in some cases 

 of pulsating tumor of the scalp or face ; the operation, however, is very rarely performed, liga- 

 ture of the common carotid being preferable, on account of the number of branches given off 

 from the external. To tie this vessel near its origin, below the point where it is crossed by the 

 Digastric, an incision about three inches in length should be made along the margin of the Sterno- 

 mastoid, from the angle of the jaw to the cricoid cartilage, as in the operation for tying the 

 common carotid. To tie the vessel above the Digastric, between it and the parotid gland, an 

 incision should be made from the lobe of the ear to the great cornu of the os hyoides, dividing 

 successfully the skin, Platysma, and fascia. By separatimg the posterior belly of the Digastric 

 and Stylo-hyoid muscles which are seen at the lower part of the wound, from the parotid gland, 

 the vessel will be exposed, and a ligature may be applied to it. The circulation is at once re- 

 established by the free communication between most of the large branches of the artery (facial 

 lingual, superior thyroid, occipital) and the corresponding arteries of the opposite side, and by 

 the free anastomosis of the facial with branches from the internal carotid, of the occipital with 

 branches of the subclavian, etc. 



Branches. The external carotid artery gives off eight branches, which, for 

 convenience of description, may be divided into four sets. (See Fig. 275, Plan 

 of the .Branches.) 



Anterior. Posterior. Ascending. Terminal. 



Superior thyroid. Occipital. Ascending pha- Temporal. 



Lingual. Posterior aurjcular. ryngeal. Internal maxillary. 

 Facial. 



The student is here reminded that many variations are met with in the num- 

 ber, origin, and course of these branches in different subjects ; but the above 

 arrangement is that which is found in the great majority of cases. 



The Superior Thyroid Artery (Figs. 274 and 279) is the first branch given off 

 from the external carotid, being derived from that vessel just below the great 

 cornu of the hyoid bone. At its commencement, it is quite superficial, being 

 covered by the integument, fascia, and Platysma, and is contained in the trian- 

 gular space bounded by the Sterno-mastoid, Digastric, and Omo-hyoid muscles. 

 After running upwards and inwards for a short distance, it curves downwards 

 and forwards in an arched and tortuous manner to the upper part of the thyroid 

 gland, passing beneath the Omo-hyoid, Sterno-hyoid, and Sterno-thyroid mus- 



