152 THE HEAD AND NECK 



there may be some difficulty in making a correct diagnosis until 

 the cyst wall is exposed. Unlike other simple cysts, they are 

 situated under the deep fascia, and closely resemble a glandular 

 abscess. 



The Anterior Median Line of the Neck. This area 



may be subdivided into (i) a supra-hyoid or lingual region, (2) a 

 laryngeal region, which extends from the hyoid bone to the 

 cricoid cartilage, and (3) a tracheal region, lying below the 

 cricoid cartilage. 



The Supra-hyoid Region is triangular in shape. It is bounded 

 laterally by the anterior bellies of the two digastric muscles 

 and below by the hyoid bone. The roof is formed by the in- 

 vesting layer of the deep cervical fascia, which is attached to 

 the mandible above and to the hyoid bone below, and blends 

 with the fascial sheaths of the digastric on each side. The 

 floor of the region is formed by the two mylo-hyoid muscles, 

 which meet at the median raphe (p. 144). 



The submental or supra-hyoid lymph glands are two small 

 pea-like bodies which lie just above the hyoid bone, and they 

 can often be felt in the living subject. They receive afferents 

 from the chin, the central portions of the lower lip, the lower 

 incisor teeth and gums, the floor of the mouth, and the tip of the 

 tongue. Abscess or lymph-adenitis in connection with the sub- 

 mental lymph glands causes a swelling which projects downwards 

 below the chin, as it is prevented from rising up into the mouth 

 by the mylo-hyoid muscles. Lingual dermoids, on the other 

 hand, or cysts and solid tumours in connection with 

 remains of the thyreo-glossal duct (p. 169), bulge upwards into 

 the floor of the mouth, since they lie on the deep surface of the 

 mylo-hyoid muscles. The efferents from the submental lymph 

 glands pass laterally on the surface of the mylo-hyoids and 

 open into the submaxillary lymph glands. 



Good access to the glands is obtained by a horizontal incision 

 just above the hyoid bone. It should pass through the deep 

 fascia, which is undercut so as to expose the anterior bellies of 

 the digastric, and these muscles act as a guide to the level 

 of the slightly deeper floor. The glands can then be removed 

 from the floor of the triangle without trouble. 



In the removal of a lingual dermoid a vertical supra- 

 hyoid incision is carried through the deep fascia to the muscular 

 floor of the submental triangle, and both edges are undercut. 

 The median raphe is split and the mylo-hyoid muscles are re- 



