OF THE TRIANGLES OF THE NECK. 383 



extending from the angle of the jaw to the mastoid process ; its apex is formed 

 below by the sternum. This space is covered by the integument, superficial 

 fascia, Platysma, deep fascia, crossed by branches of the facial and superficial cer- 

 vical nerves, and subdivided into three smaller triangles by the Digastric muscle, 

 above, and the anterior belly of the Omo-hyoid, below. These are named, from 

 below upwards, the inferior carotid triangle, the superior carotid triangle, and the 

 submaxillary triangle. 



The Inferior Carotid Triangle- is limited, in front, by the median line of the 

 neck ; behind, by the anterior margin of the Sterno- mastoid ; above, by the anterior 

 belly of the Omo-hyoid ; and it is covered by the integument, superficial fascia, 

 Platysma, and deep fascia ; ramifying between which is seen the descending 

 branch of the superficial cervical nerve. Beneath these superficial structures are 

 the Sterno-hyoid and Sterno-thyroid muscles, which, together with the anterior 

 margin of the Sterno-mastoid, conceal the lower part of the common carotid artery. 

 This vessel is inclosed within its sheath, together with the internal jugular vein, 

 and pneumogastric nerve; the vein lying on the outer side of the artery on the 

 right side of the neck, but overlapping it, or passing directly across it on the left 

 side ; the nerve lying between the artery and vein, on a plane posterior to both. 

 In front of the sheath are a few filaments descending from the loop of communi- 

 cation between the descendens and communicans noni ; behind the sheath are seen 

 the inferior thyroid artery, the recurrent laryngeal and sympathetic nerves ; and 

 on its inner side, the trachea, the thyroid gland, much more prominent in the 

 female than in the male, and the lower part of the larynx. In the upper part of 

 this space, the common carotid artery may be tied below the Omo-hyoid muscle. 



The Superior Carotid Triangle is bounded, behind, by the Sterno-mastoid; 

 below, by the anterior belly of the Omo-hyoid ; and above, by the posterior belly 

 of the Digastric muscle. Its floor is formed by parts of the Thyro-hyoid, Ilyo- 

 glossus, and the inferior and middle Constrictor muscles of the pharynx ; and it is 

 covered by the integument, superficial fascia, Platysma, and deep fascia; rami- 

 fying between which are branches of the facial and superficial cervical nerves. 

 This space contains the upper part of the common carotid artery, which bifurcates 

 opposite the upper border of the thyroid cartilage into the external and internal 

 carotid. These vessels are 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 most anterior of the two. The following 

 branches of the external carotid are also met with in this space : the superior 

 thyroid, which runs forwards and downwards ; the lingual, which passes directly 

 forwards ; the facial, forwards and upwards ; the occipital is directed backwards ; 

 and the ascending pharyngeal runs directly upwards on the inner side of the in- 

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

 outer side of the common and internal carotid vessels ; and veins corresponding to 

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

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

 accompany their corresponding arteries, and terminate in the internal jugular. 

 In front of the sheath of the common carotid is the descendens noni, the hypo- 

 glossal, from which it is derived, crossing both 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 internal 

 carotid, just below the hyoid bone, may be seen the superior laryngeal nerve ; and 

 still more inferiorly, the external laryngeal nerve. The upper part of the larynx 

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



The Submaxillary Triangle corresponds to that 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, the parotid gland, and mastoid process ; behind by the posterior 

 bell)/ of the Digastric and Stylo-hyoid muscles : in front, by the middle line of 



