122 THE LUNGS AND RESPIRATION. 



the cavity of the larynx. Inside and resting on the 

 upper border of the cricoid are the two smaller arytenoid 

 or pitcher-like cartilages, pyramidal in shape, and sur- 

 mounting these again the two cornicula laryngis. The 

 two cuneiform cartilages are in the free borders of the 

 folds of mucous membrane which extend from the apex 

 of the arytenoids to the sides of the epiglottis. Numer- 

 ous small muscles serve to bind these various cartilages 

 together. 



At the angle of the thyroid cartilage in front are at- 

 tached the epiglottis at the top and just below that the 

 superior or false vocal cords, two folds of mucous mem- 

 brane enclosing the superior thyro-arytenoid ligaments. 

 Lower still are found the inferior or true vocal cords, 

 which are formed by the inferior thyro-arytenoid lig- 

 aments covered with a thin, tightly fitting mucous mem- 

 brane. Both sets of vocal cords as well as the epiglot- 

 tis may be seen by means of a head and a throat mir- 

 ror. Between the true vocal cords is a narrow tri- 

 angular interval called the glottis. It is by means of the 

 vibrations of these cords that sound is produced. The 

 false vocal cords cannot produce sound, though they 

 can modify it indirectly. Quality of voice, as treble, 

 base, etc., depends upon the size of the larynx and the 

 length and elasticity of the vocal cords. Modulation 

 is produced by changing the form of the cavity of the 

 mouth and nose. In whispering the lips take the 

 place of the vocal cords and produce sound by the 

 vibration of their muscular walls. 



Instead of tracheotomy laryngotomy is sometimes 

 done in the depression between the thyroid and the 

 cricoid, which may be felt on the living. Foreign bodies 

 sometimes get into the larynx and have to be removed, 

 or the mucous membrane may become inflamed, caus- 

 ing laryngitis. Syphilis attacks the larynx, and tuber- 

 culosis and cancer of the larynx occur, these last two 

 being generally fatal. Edema of the glottis may also 

 occur. 



