THE EXTERNAL CAROTID ARTERY. 487 



Internally. / 



Hyoid bone. / \ 



Pharynx. ( External Externally. 



Superior larynsreal nerve. I Carotid, j Internal carotid artery. 



Parotid gland. V / 



J vain us of jaw. 



Behind. 



Superior laryngeal nerve. 

 Stylo-glossus. 

 Sty lo- ph ary ngeus. 

 Glosso-pharyngeal nerve. 

 Parotid gland. 



Surface Marking. The position of the external carotid artery may be marked out with 

 sufficient accuracy by a line drawn from the front of the meatus of the external ear to the side 

 of the cricoid cartilage, slightly arching the line forward. 



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

 in case 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 has not received the attention which it 

 deserves, owing to the fear which surgeons have entertained of secondary haemorrhage, on 

 account of the number of branches given off from the vessel. This fear, however, has been 

 shown by Mr. Cripps not to be well founded. 1 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 upper border of the 

 thyroid cartilage. The ligature should be applied between the lingual and superior thyroid 

 branches. 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 succes- 

 sively the skin, Platysma, and fascia. By drawing the Sterno-mastoid outward, and the posterior 

 belly of the Digastric and Stylo- hyoid muscles downward, and separating them 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 anastomosis of its branches with those of the internal carotid, and of the occipital 

 with the 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. 284, Plan of 

 the Branches). 



Anterior. Posterior. Ascending. Terminal. 



Superior Thyroid. Occipital. Ascending Pha- Superficial Temporal. 



Lingual. Posterior Auricular, ryngeal. Internal Maxillary. 

 Facial. 



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

 number, 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. 283 and 288) 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 

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

 After running upward and inward for a short distance, it curves downward 

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

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

 and supplying them. It distributes numerous branches to the upper part of the 

 gland, anastomosing with its fellow of the opposite side and with the inferior thyroid 

 arteries: The branches supplying the gland are generally three in number : one, 

 the largest, supplies principally the anterior surface of the gland ; it courses along 

 the inner border of the lobe as far as the upper border of the isthmus, and then 

 passes in the substance of the isthmus to the middle line of the neck, where it 

 anastomoses with the corresponding artery of the opposite side : a second branch 

 courses along the external border of the lobe, and supplies this portion of the gland, 

 and the third passes to the posterior surface, the upper part of which it supplies. 



1 Med.-Chir. Trans., Ixi., 229. 



