CAKOTID TRIANGLE OF THE NECK. 1391 



the lower part of the anterior belly of the omo-hyoid is seen, lying upon that part 

 of the carotid sheath which overlies the internal jugular vein. 



Digastric Triangle. This triangle is subdivided into an anterior or sub- 

 maxillary portion and a posterior or parotid portion by a process of the deep 

 cervical fascia, known as the stylo-mandibular ligament. In the anterior portion 

 is the submaxillary gland, which is overlapped by the posterior half of the inferior 

 border of the mandible and reaches down to the great cornu of the hyoid bone. 

 The anterior facial vein passes downwards and backwards, superficial to the 

 gland, while the external maxillary artery, embedded in its deep surface, arches 

 upwards under cover of the angle of the mandible, where it approaches the 

 palatine tonsil, being separated from it, however, by the superior constrictor of the 

 pharynx. The lingual artery may be ligatured in the digastric triangle, where it 

 lies behind the hyoglossus a little above the great cornu of the hyoid bone ; the 

 superficial guides to the vessel are the inferior border of the submaxillary gland, 

 and the hypoglossal nerve and its vena comitans, which lie upon the hyoglossus, the 

 latter being recognised by the vertical direction of its fibres. The floor of the 

 digastric triangle is formed, from before backwards, by the my lo- hyoid, hyo- 

 glossus, and superior constrictor of the pharynx. The lymph glands of this space 

 receive their lymph from the face, lips, teeth and gums, tongue, and floor of the 

 mouth ; hence the frequency with which they become the seat of abscess formation 

 and malignant enlargement. To palpate them the surgeon stands behind the 

 patient and thrusts the fingers well upwards under cover of the mandible, the 

 patient's chin being a little depressed so as to relax the cervical fascia. 



Carotid Triangle. The central landmark of this triangle is the great cornu of 

 the hyoid bone, the tip of which, when the fascia is relaxed, may be readily felt, 

 immediately in front of the anterior border of the sterno-mastoid, at a point corre- 

 sponding to the centre of a line drawn from the tip of the mastoid process to the 

 prominentia laryngea. The deep cervical fascia holds the superior part of the 

 sterno-mastoid forwards towards the angle of the mandible, so that, with the 

 fascia undivided, the anterior border of the sterno-mastoid overlaps the internal 

 jugular vein and the bifurcation of the common carotid artery. 



The course of the carotid vessels is indicated, upon the surface, by a line extend- 

 ing from the superior end of the sterno-clavicular articulation to a point midway 

 between the angle of the mandible and the tip of the mastoid process ; a point 

 upon this line, at the level of the superior border of the thyreoid cartilage, overlies 

 the bifurcation of the common carotid. The anterior belly of the omo-hyoid crosses 

 the common carotid at the level of the cricoid cartilage. The pulsations of the 

 carotid vessels may be felt in the hollow between the larynx and the anterior border 

 of the sterno-mastoid. In the carotid triangle the external carotid lies medial and 

 anterior to the internal carotid. The seat of election for ligation of the external 

 carotid is between its superior thyreoid and lingual branches, a finger's-breadth 

 below the tip of the great cornu of the hyoid bone ; the difficulty in the operation 

 is due to the plexus of veins (formed by the common facial, lingual, and superior 

 thyreoid veins) which overlies the artery. The lingual and external maxillary 

 arteries frequently arise from a common trunk which must not be mistaken for 

 the external carotid. The superior thyreoid artery arises opposite the upper cornu 

 of the thyreoid cartilage, which may be distinctly felt 1 in. below the tip of the 

 great cornu of the hyoid bone. The vessel and its companion vein are common 

 sources of haemorrhage in cut-throat. The guide to the lingual artery, in the carotid 

 triangle, is the tip of the great cornu of the hyoid bone, above which it forms an 

 arch, crossed by the hypoglossal nerve. The vessel enters the digastric triangle 

 by passing forward medial to the tendons of the stylo-hyoid and digastric muscles. 

 When ligature of the artery is called for, it is usually necessary to secure the vessel 

 ! as it lies in the carotid triangle so that the ligature may be applied on the proximal 

 side of its dorsalis linguae branch. 



From a surgical point of view the internal jugular vein is the most important 

 ' structure in the anterior triangle. In the carotid division of the triangle it over- 

 laps the carotid vessels, and its sheath lies close beneath the general envelope of 

 deep cervical fascia from which it is separated by a loose cellular interval. About 



