552 THE ARTERIES. 



In front. I External ] Behind. 



Ramus of jaw. V J Parotid gland. 



Internally. 

 Hyoid bone. 

 Pharynx. 



Superior laryngeal nerve. 

 Stylo-glossus. 

 Stylo-pharyngeus. 

 Glosso-pharyngeal nerve. 

 Parotid gland. 



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

 convenience of description, may be divided into four sets. (See Fig. 348, 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. 347 and 352) 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 distributes numerous branches to the anterior surface of the gland, 

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

 arteries. Besides the arteries distributed to the muscles by which it is covered 

 and the substance of the gland, the branches of the superior thyroid are the 

 following : 



Hyoid. Superior Laryngeal. 



Superficial descending branch (Sterno-mastoid). Crico-thyroid. 



The hyoid is a small branch which runs along the lower border of the os 

 hyoides beneath the Thyro-hyoid muscle ; after supplying the muscles connected to 

 that bone it forms an arch, by anastomosing with the vessels of the opposite side. 



The superficial descending branch runs downward and outward across the 

 sheath of the common carotid artery, and supplies the Sterno-mastoid and neigh- 

 boring muscles and integument. There is also often a distinct branch from the 

 external carotid distributed to the Sterno-mastoid muscle. 



The superior laryngeal, larger than either of the preceding, accompanies the 

 superior laryngeal nerve, beneath the Thyro-hyoid muscle : it pierces the thyro- 

 hyoid membrane, and supplies the muscles, mucous membrane, and glands of the 

 larynx, anastomosing with the branch from the opposite side. 



The crico-thyroid is a small branch which runs transversely across the crico- 

 thyroid membrane, communicating with the artery of the opposite side. 



Surgical Anatomy. The superior thyroid, or some of its branches, is often divided in 

 cases of cut throat, giving rise to considerable haemorrhage. In such cases the artery should be 

 secured, the wound being enlarged for that purpose, if necessary. The operation may be easily 

 performed, the position of the artery beinu very superficial, and the only structures of importance 

 covering it being a few small veins. The operation of tying the superior thyroid artery in 

 bronchocele has been performed in numerous instances with partial or temporary success. When, 



