PRACTICAL CONSIDERATIONS : THE LARYNX. 1829 



marked, because the great horn is held above by the digastric aponeurosis and the 

 hyo-glossus muscle and below by the thyro-hyoid ligament and muscle. Excep- 

 tionally the middle constrictor of the pharynx may draw it somewhat backward and 

 inward. The attachments to the hyoid of the constrictor and of the hyo-glossus and 

 genio-hyo-glossus invariably make deglutition and speech painful after this fracture, 

 while the genio-hyoid and digastric, by their contraction, cause pain on opening the 

 mouth. The associated swelling may involve the epiglottic mucous membrane and, 

 spreading thence, give rise to serious dyspnoea. 



The thyro-hyoid membrane, springing from the posterior upper margin of the 

 hyoid bone and attached to the upper border of the thyroid cartilage, has interposed 

 between its anterior surface and the posterior face of the body of the hyoid a bursa 

 which descends below the lower border of that bone, and when enlarged forms a 

 cystic swelling situated in the median line of the neck, just beneath the hyoid. 

 Thyro-lingual cysts are sometimes found in the same situation. 



A similar cystic swelling, lined with columnar epithelium and occupying the 

 same region, is referable to the persistence of the foetal thyro-lingual duct. At the 

 upper end of that duct such a cyst would lie in the mid-line of the tongue between 

 the two genio-hyo-glossi muscles. At the lower end it would lie over the thyroid or 

 the cricoid cartilage. The sinuses formed by the bursting of such cysts, or originally 

 by the persistence of portions of the thyro-lingual duct, are obstinate, and, on account 

 of their epithelial lining, must be dissected out completely to secure healing. 



The lower portion of the thyro-hyoid membrane is covered in the mid-line by 

 cervical fascia and skin, laterally by the sterno-hyoid and thyro-hyoid muscles. 



Cut-throat wounds of the neck, especially if suicidal, are apt to pass through 

 this membrane, which is made tense when the head is thrown backward, and, if they 

 are deep, will divide the inferior constrictor, open the pharynx, and possibly wound 

 or sever the epiglottis near its base, first passing through the cellulo-adipose tissue 

 that intervenes. If the wound is not immediately beneath the lower border of the 

 hyoid, it may divide the internal branches of the superior laryngeal nerve, leading 

 ultimately to a pneumonia from the inspiration of foreign matter. In inf7'ahyoid 

 pharyngotomy such a transverse wound, hugging the lower edge of the hyoid, gives 

 access to the base of the pharynx and the supraglottideal region. 



Above the hyoid a cut-throat wound would divide the tongue muscles and enter 

 the mouth. Below the thyroid it would pass through the crico-thyroid membrane 

 and open the larynx. Still lower the trachea would be incised or severed. 



The great vessels often escape in suicidal wounds, as the usual position of the 

 head in extreme extension increases the projection of the laryngeal apparatus and 

 therefore the depth of the vessels from the surface. One reason for their escape 

 when the air-passages below the glottis are opened may be that the sudden rush 

 of air from the lungs and consequent collapse of the chest-walls deprive the muscles 

 running from the thorax to the humerus of their fixed point of support, and that 

 the arm necessarily drops (Hilton). Death may be caused, however, by hemor- 

 rhage from the superior thyroid or the lingual artery, or even from the crico-thyroid 

 if the blood enters the larynx or trachea ; or may result from suffocation produced 

 by the dropping backward of the tongue after division of the genio-hyoid, hyo- 

 glossus, and genio-hyo-glossus muscles, or by the occlusion of the glottis by a partly 

 divided epiglottis or arytenoid. 



Fracture of the thyroid or cricoid cartilage may occur from the same causes that 

 produce fracture of the hyoid bone. The thyroid, on account of its greater prom- 

 inence, suffers more frequently. Fractures of the thyroid are seen oftener in males 

 than in females, because (a) in the former it is relatively more prominent ; (3) the 

 process of ossification — which, in common with other hyaline cartilages, it undergoes 

 after adult life has been reached — is more complete in them ; and (<:) males are 

 oftener exposed to violence. 



The symptoms depend for their gravity chiefly upon the degree of involvement of 

 the laryngeal mucous membrane. If that is wounded, bloody expectoration, aphonia, 

 and dyspnoea are present, and tracheotomy may be urgently indicated. In any event, 

 deglutition is painful. The voice is usually altered, and there is apt to be some ex- 

 ternal deformity. Crepitus may be present, but should be distinguished from the 



