THE NECK 159 



downwards in the groove between the trachea and the oeso- 

 phagus, close to the recurrent nerve, and open into the lower 

 anterior group of the deep cervical lymph glands. In extrinsic 

 cancer of the larynx the supraglottic lymphatics are involved, 

 but in the intrinsic variety the spread occurs along the infra- 

 glottic vessels. 



The upper aperture of the larynx can be brought to the 

 surface by the operation of Sub-hyoid Pharyngotomy. A 

 transverse incision is made just below the hyoid bone. This 

 divides the skin, the superficial fascia, the platysma, and the 

 deep fascia. The sterno-hyoid, the omo-hyoid, and the thyreo- 

 hyoid are cut through, but their upper ends are left sufficiently 

 long to allow them to be sutured subsequently. The thyreo- 

 hyoid membrane, which is now completely exposed, is incised 

 horizontally, and in doing so the surgeon is careful not to injure 

 the internal laryngeal nerve and its accompanying artery (p. 121) 

 by extending the incision beyond the lateral border of the 

 thyreo-hyoid muscle. 



The internal laryngeal nerve is a branch of the superior laryngeal nerve, 

 which arises from the vagus a little below the base of the skull. It runs 

 obliquely downwards, forwards, and medially, deep to both carotid arteries, 

 and pierces the thyreo-hyoid membrane at the posterior border of the thyreo- 

 hyoid muscle. It supplies the mucous membrane of the larynx and recessus 

 piriformis. Section of one internal laryngeal nerve renders the mucous 

 membrane of that half of the larynx insensitive, but should both nerves be 

 cut, inhalation pneumonia is likely to supervene owing to the loss of the 

 cough reflex. 



After opening the thyreo-hyoid membrane, the surgeon cuts 

 upwards and backwards, through the underlying pad of fat, 

 and divides the ligament which attaches the epiglottis to the 

 hyoid bone. Above the ligament lie the submucous tissue 

 and mucous membrane of the valleculae, and when these have 

 been incised the epiglottis can be pierced by a strong silk ligature 

 and dragged out through the wound. This proceeding brings 

 the vestibule of the larynx directly to the surface, and affords 

 excellent exposure of the area. 



Cut Throat. The commonest sites of the wound in " cut 

 throat " are immediately above and below the hyoid bone. By 

 throwing back his head while he makes the wound, the suicide 

 unconsciously protects the main vessels from danger, as the 

 action retracts the carotid sheath and its contents more deeply 

 under cover of the sterno-mastoid. The supra-hyoid incision 

 cuts through the mylo-hyoids, genio-hyoids, hyo-glossi, and 



