PLATE XL. 

 THE ANTERIOR TRIANGLE-SECOND VIEW. 



In this dissection the anterior edge of the sterno-mastoid has been turned back to 

 expose the structures lying beneath it. 



The Anterior triangle of the neck is bounded 



In front. -By the middle line. 



Above. By the body of the jaw, and a line drawn from it to the mastoid process. 



Behind. By the sterno-mastoid. 



This space is subdivided into three smaller triangles by the passage across it of the 

 omo-hyoid muscle below and the digastric above. 



i. The lower carotid or tracheal is bounded 



In front. By the middle line. 



Above. By the omo-hyoid. 



Behind. By the sterno-mastoid. 



Floor is formed by the longus colli and scalt'-ius anticus. 



Contents. Sterno-hyoid and thyroid muscles, together with the twigs from the ansa 

 hypoglossi. Carotid sheath, containing the carotid artery, internal 

 jugular vein and vagus nerve ; inferior thyroid artery, sympathetic with 

 middle cervical ganglion, recurrent laryngeal nerve, thyroid gland and 

 middle and inferior thyroid veins, lower part of larynx, trachea, and 

 oesophagus. 



ii. The upper carotid triangle is bounded 



Above. By the digastric. 



Below. By the omo-hyoid. 



Behind. By the sterno-mastoid. 



Floor is formed by parts of the thyro-hyoid, thyro-hyoid membrane, hyoglossus, 

 middle and inferior constrictors of the pharynx. 



Contents. Common, internal and external carotids, superior thyroid, lingual, facial, 

 occipital, and ascending pharyngeal arteries. Internal jugular superior 

 tliyroid, facial, lingual, ascending pharyngeal and occipital (sometimes) 

 veins. Hypoglossal, descendens noni, twig to thyro-hyoid from hypo- 

 glossal, vagus, sympathetic, superior laryngeal, with its external laryn- 

 branch ; spinal accessory. Parts of the larynx and pharynx. 



iii. The submaxillary triangle is bounded 



Above. By the body of the jaw, and line drawn from this to the mastoid process. 



Below. By the digastric (posterior belly) and stylo-hyoid muscles. 



In front. By the middle line. 



Floor is formed by anterior belly of digastric, mylo-hyoid and hyoglossus. 



Contents. Submaxillary gland, facial artery and vein, mylo-hyoid vessels and nerve, 

 and submental vessels ; posteriorly is the external carotid artery in 

 the parotid gland, giving off the temporal internal maxillary and pos- 

 terior auricular branches and facial nerve ; deeper than this lies the 

 internal carotid artery, internal jugular vein and the vagus, separated 

 from the external carotid by the stylo-glossus and stylo-pharyngeus 

 muscles and glosso-pharyngeal nerve. These are separated from the 

 structures in the anterior portion of the triangle by the stylo-mnndi- 

 bular ligament, which is really only a process of the deep cervical 

 fascia, and should not be callod a ligament. 



