CONTENTS OF THE ANTERIOR TRIANGULAR SPACE. 583 



For a short distance after its exit from beneath the depressor bifurcation, 

 muscles of the hyoid bone, the common carotid artery remains a 

 single trunk ; but opposite, or a little above, the upper border of the 

 thyroid cartilage it divides into two large vessels, external and 

 internal carotid. From the place of division these arteries are 

 continued onwards beneath the digastric and stylo-hyoid muscles 

 to the interval between the jaw and the mastoid process. 



At first the trunks lie side by side, the vessel destined for the Position of 

 internal parts of the head (internal carotid) being the posterior of to one" 111 

 the two ; but above the digastric muscle it becomes deeper than another, 

 the other. The more superficial artery (external carotid) furnishes 

 many branches to the neck and the outer part of the head, viz., Branches, 

 some forwards to the larynx, tongue, and face ; others backwards 

 to the occiput and the ear ; and others upwards to the head. 



But the common carotid does not always divide as here said. {J 1311 ^ iD f 

 For the point of branching of the vessel may be moved from division^? 

 opposite the upper border of the thyroid cartilage, either upwards aw * M - 

 or downwards, .so that the trunk may remain undivided till it is 

 beyond the hyoid bone, or it may end opposite the cricoid 

 cartilage. The division beyond the usual place is more frequent 

 than the branching short of that spot. It may ascend as an 

 undivided trunk (though very rarely) furnishing offsets to the 

 neck and head. 



In close contact with the outer side of both the common and the Jugular 

 internal carotid artery, and encased in a sheath of fascia with them, 

 is the large internal jugular vein, which receives branches in the 

 neck corresponding to some of the branches of the superficial artery. 

 In some bodies the vein covers the artery ; and the branches position 

 joining it above may form a kind of plexus over the upper end of 

 the common carotid. 



Xerves in the space. In connection with the large vessels are the *"* w . ith 

 ** i ! -TIT ^ i /. < the arteries 



following nerves with a longitudinal direction : On the surface of 

 the common carotid artery, and most frequently within the sheath, lies 

 the descending branch of the hypoglossal nerve (descendens cervicis) : 

 posteriorly between the artery and jugular vein is the pneumo- 1 J" iu K alon 8 

 gastric nerve ; and behind the sheath is the sympathetic nerve. 

 Along the outer side of the vessels the spinal accessory nerve extends 

 for a short distance, until it pierces the sterno-mastoid muscle. 



Several nerves are placed across the vessels : thus, directed <* ncl crossing 

 transversely over the two carotids, so as to form an arch below the 

 digastric muscle, is the hypoglossal nerve giving off its descending 

 branch. Appearing on the inner side of the carotid arteries, close 

 to the base of the space, is the glosso-pharyngeal nerve, which 

 courses forwards between them. To the inner side of the internal 

 carotid artery, opposite the hyoid bone, the superior laryngeal 

 nerve comes into sight ; while a little lower down, with the 

 descending branches of the thyroid artery, is the external laryngeal 

 branch of that nerve. 



(r lands in the space. Two large glandular bodies, the submaxil- Glands: 

 lary (fig. 213, n , p. 589) and thyroid ( 12 ), have their seats in this 



