THE NECK. 44 



of the sterno-mastoid. The posterior great triangle is 

 bounded in front by the posterior edge of the stemo- 

 mastoid ; behind, by the anterior border of the trape- 

 zius ; and below, by the clavicle. The anterior great 

 triangle is subdivided into three lesser triangles, the 

 submaxillary, the carotid, and the inferior. The sub- 

 maxillary triangle is bounded above by the lower jaw ; 

 below and in front, by the anterior belly of the digastric ; 

 and behind, by the posterior belly, with some of the 

 fibres of the stylo-hyoid muscle. The digastric muscle 

 arises anteriorly below the genial tubercles, and passes 

 downward to the hyoid bone. Its mesial tendon pierces 

 the tendon of the stylo-hyoid, and the posterior, fleshy 

 belly is inserted in the digastric fossa of the mastoid 

 portion of the temporal bone. This triangle is covered 

 by a double leaflet of deep cervical fascia ; in the inter- 

 val between them some lymphatic glands are frequently 

 observed. 



Beneath the deep fascia and within the triangle is 

 the submaxillary gland, usually pierced by the facial 

 artery. Some veins, lymphatics, and adipose tissue are 

 also exposed. The floor of this triangle is formed 

 by the mylo-hyoid and hyoglossus muscles, the latter 

 being crossed by the hypoglossal nerve in its transit to 

 the tongue. The carotid triangle is bounded above by 

 the posterior belly of the digastric, below by the anterior 

 belly of the omo-hyoid, and behind by the edge of the 

 sterno-mastoid. The omo-hyoid muscle arises from the 

 inferior surface of the body of the hyoid bone, passes 

 downward beneath the sterno-mastoid, and becomes tend- 

 inous. Its tendon passes through a loop of the deep cervi- 

 cal fascia, and the posterior fleshy belly is inserted on the 

 transverse ligament and upper border of the scapula. 

 The floor of the carotid triangle is formed by the thyro- 



