THE POSTERIOR TRIANGLE OF THE NECK. 501 



artery, which bifurcates opposite the upper border of the thyroid cartilage into the 

 external and internal carotid. These vessels are occasionally somewhat concealed 

 from view by the anterior margin of the Sterno-mastoid muscle, which overlaps 

 them. The external and internal carotids lie side by side, the external being the 

 more anterior of the two. The following branches of the external carotid are 

 also met with in this space : the superior thyroid, running forward and downward ; 

 the lingual, directly forward; the facial, forward and upward; the occipital, back- 

 ward: and the ascending pharyngeal directly upward on the inner side of the 

 internal carotid. The veins met with are: the internal jugular, which lies on the 

 outer side of the common and internal carotid arteries, and veins corresponding to 

 the above-mentioned branches of the external carotid viz., the superior thvroid, 

 the lingual, facial, ascending pharyngeal, and sometimes the occipital, all of 

 which accompany their corresponding arteries and terminate in the internal j ugujar. 

 The nerves in this space are the following : In front of the sheath of the common 

 carotid is the descendens hypoglossi. The hypoglossal nerve crosses both the 

 internal and external carotids above, curving round the occipital artery at its 

 origin. Within the sheath, between the artery and vein, and behind both, is the 

 pneumogastric nerve ; behind the sheath, the sympathetic. On the outer side of 

 the vessels the spinal accessory nerve runs for a short distance before it pierces 

 the Sterno-mastoid muscle; and on the inner side of the external carotid, just 

 below the hyoid bone, may be seen the internal laryngeal nerve; and, still more 

 interiorly, the external laryngeal nerve. The upper part of the larynx and lower 

 part of the pharynx are also found in the front part of this space. 



The Submaxillary Triangle corresponds to the part of the neck immediately 

 beneath the body of the jaw. It is bounded, above,. by the lower border of the 

 body of the jaw and a line drawn from its angle to the mastoid process; below, 

 by the posterior belly of the Digastric and Stylo-hyoid muscles ; in front, by the 

 anterior belly of the Digastric. It is covered by the integument, superficial fascia, 

 Platysma, and deep fascia, ramifying between which are branches of the facial and 

 ascending filaments of the superficial cervical nerves. Its floor is formed by the 

 Mylo-hyoid and Ilyo-glossus muscles. This space contains, in front, the submax- 

 illary gland, superficial to which is the facial vein, while imbedded in it are the 

 facial artery and its glandular branches ; beneath this gland, on the surface of the 

 Mylo-hyoid muscle, are the submental artery and the mylo-hyoid artery and nerve. 

 The posterior part of this triangle is separated from the anterior part by the stylo- 

 maxillary ligament : it contains the external carotid artery, ascending deeply in 

 the substance of the parotid gland: this vessel here lies in front of, and superficial 

 to. the internal carotid, being crossed by the facial nerve, and gives off in its 

 course the posterior auricular, temporal, and internal maxillary branches: more 

 deeply are the internal carotid, the internal jugular vein, and the pneumogastric 

 nerve, separated from the external carotid by the Stylo-glossus and Stylo-pharyn- 

 gi'iis. muscles and the glosso-pharyngeal nerve. 1 



POSTERIOR TRIANGLE or THE NECK. 



The posterior triangle is bounded, in front, by the Sterno-mastoid muscle ; 

 behind, by the anterior margin of the Trapezius ; its base corresponds to the 

 middle third of the clavicle; its apex, to the occiput. The space is crossed, 

 about an inch above the clavicle, by the posterior belly of the Omo-hyoid, which 

 divides it unequally into two, an upper or occipital and a lower or subclavian 

 triangle. 



The Occipital, the larger division of the posterior triangle, is bounded, in 



1 The same remark will apply to this triangle as was made about the inferior carotid triangle. 

 The structures enumerated as contained in the back part of the space lie, strictly speaking, beneath 

 the muscles which form the posterior boundary of the triangle ; but as it is very important to bear in 

 mind their close relation to the parotid gland and its boundaries (on account of the frequency of sur- 

 gical operations on this gland), all these parts are spoken of together. 



