THE HEAD AND NECK 



1117 



branches of the inferior thyroid of the same side, and with branches 

 of its fellow of the opposite side. One very constant branch, 

 known as the artery of the isthmus, courses along the upper border 

 of the isthmus, and anastomoses with its fellow of the opposite 

 side. The muscular branches are distributed to tlie depressor 

 muscles of the hyoid bone. 



The superior thyroid vein issues from the upper part of the lateral 

 lobe of the thyroid body, and crosses in front of the common 

 carotid artery, near its bifurcation, to open into the internal jugular 

 vein. Its tributaries for the most part correspond to the branches 

 of the artery, amongst these being the crico-thyroid and superior 

 laryngeal veins. 



Lingual Artery. — The lingual artery arises from the front part of 

 the external carotid, a little above the origin of the superior thyroid, 

 and opposite the great comu of the hyoid bone. From its com- 



Dorsum of Tongue 



Sublingual Gland (turned 

 up) 



Stylo-glossus Muscle 

 ■*>. Lingual Nerve 



, Submaxillary Ganglion 



_ Submaxillarj' Gland 



(deep part) 



Facial Artery 



Mandible ,_ 

 (in section) 



Genio-hyo-glossus Muscle 



Genio-hyoid Muscle • i 



Sublingual Artery \ 



Ranine Artery 



\i_^.. Lingual Artery 



y;,je^~^- Sup- Thy. Artery 

 \ \^- Ext. Car. Arterj- 



\ Ranine Vein 

 Hypoglossal Nerve 



Fig. 456. 



Iftliarton's Duct 



Deep Dissection of the Left Submaxillary Region. 



plicated course it is convenient to divide the artery into three 

 parts. 



First Part. — The first part of the vessel ascends for a Httle, and 

 then, bending sharply, descends to the great comu of the hyoid 

 bone, passing beneath the posterior belly of the digastric and stylo- 

 hyoid muscles. So far the vessel lies in the carotid triangle and 

 the bend which it describes is crossed by the hypoglossal nerve. It 

 is for the most part comparatively superficial. 



Second Part. — The second part passes horizontally forwards 

 along the upper border of the hyoid bone beneath the hyo-glossus 

 muscle, the hypoglossal nerve and ranine vein being superficial to 

 that muscle. At the anterior border of the hyo-glossus it enters 

 upon the third part of its course. The second part lies deeply in 

 Lesser's triangle, the boundaries of which are as follows : the base, 

 which is directed upwards, is formed by a portion of the hypo- 



