SUPERIOR THYROID— LINGUAL 



483 



the thyro-hyoid muscle, and, perforating the thyro-hyoid membrane along with tlie 

 superior laryngeal nerve, supplies the intrinsic muscles and mucous lining of tlie 

 larynx. Its further distribution within the larynx is given with the description of 

 that organ. This branch sometimes arises from the external carotid direct. It 

 may enter the larynx by ](assing througli a foramen in the thyroid cartilage. 



(4) The crico-thyroid — or inferior laryngeal branch as it is sometimes 

 called, usually insigniticant in size — passes across the crico-thyroid membrane 

 immediately beneath the lower border of the thyroid cartilage. It anastomoses 

 Avith its fellow of the opposite side, and usually sends a small branch through the 

 membrane into the interior of the larynx. Occasionally a considerable twig 

 descends over the cricoid cartilage to enter the isthmus of the thyroid gland. 

 The crico-thyroid has, however, frequently been seen of comparatively large size — 

 once as large as the radial, and crossing the membrane obliquely. In order to 



Fig. 332.— Scheme of Left Superiok Thyroid Artery. (Walsham.) 



Facial artery 



Lingual artery 



Supra-hyoid branch 

 Infra-hyoid branch 



Superior laryngeal branch 



Crico-thyroid branch 



External carotid artery 

 Ascending pharyngeal artery 



Internal carotid artery 



Sterno-mastoid branch 



Superior thyroid artery 



Common carotid artery 



nfcrior thyroid artery 



avoid injuring the crico-thyroid artery in tlie operation of larvngotomy, it is 

 usual, if the operation has to be done in a hurry, to make the incision through 

 the crico-thyroid membrane in a transverse direction, and as near to the cricoid 

 cartilage as possible. 



3. THE LINGUAL ARTERY 



The lingual artery Tfig. 333) arises from the front of the external carotid, 

 between the su])erior thyroid and facial arteries, often, as a common trunk with 

 the latter vessel, and nearly o])posite or a little below the greater cornu of the hyoid 

 bone. It may, for })urposes of description, be divided into three ])ortions: the first, 

 or oblique, extends from its origin \o the outer edge of the hyo-glossus muscle; the 

 second, <>r horizontal, lies l)eneath the liyo-glossus; the third, or ascending, 

 beneath the tongue. The first or oblique portion is situated "in the su]>erior 

 carotid triangle, and is superficial, being covered merely by the integuments, 



