460 SURGICAL ANATOMY. 



of communication between the descendens and communicans noni ; behind the 

 sheath are seen the inferior thyroid artery, the recurrent laryngeal nerve, and 

 the sympathetic nerve; 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. By cutting into the upper part of this space, and slightly displacing 

 the Sterno-mastoid muscle, 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, 

 Hyo-glossus, and the Inferior and Middle Constrictor muscles of the pharynx; 

 and it is covered by the integument, superficial fascia, Platysma, and deep 

 fascia ; ramifying between which, are branches of the fascial 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 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 most anterior of the two. The following branches of the 

 external carotid are also met with in this space : the superior thyroid, running 

 forwards and -downwards ; the lingual directly forwards ; the fascial, forwards 

 and upwards; the occipital, backwards; and the ascending pharyngeal directly 

 upwards 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 thyroid, the lingual, fascial, ascending 

 pharyngeal, and sometimes the occipital ; all of which accompany their corres- 

 ponding arteries, and terminate in the internal jugular. The nerves in this space 

 are the following : In front of the sheath of the common carotid is the descendens 

 noni. The hypoglossal nerve crosses 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 sympa- 

 thetic. 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, maybe seen the superior 

 laryngeal nerve ; and still more inferiorly, 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 Siibmaxillary 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, the parotid gland, and mastoid process ; behind, by the poste- 

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

 line of the neck. The floor of this space is formed by the anterior belly of the 

 Digastric, the Mylo-hyoid, and Hyo-glossus muscles ; and 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 nerve. This space contains, in front, the subrnaxillary gland, imbedded 

 in the substance of which are the facial artery and vein, and their glandular 

 branches ; beneath this gland, on the surface of the Mylo-hyoid muscle, is the 

 subrnental artery, and the mylo-hyoid artery and nerve. The back part of this 

 space is separated from the front part by the stylo-maxillary ligament ; it con- 

 tains 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 oft' in its course the posterior auri- 

 cular, temporal, and internal maxillary branches; more deeply is the internal 

 carotid, the internal jugular vein, and the pneumogastric nerve, separated from 



