CAVITY OF LARYNX GLOTTIS VOCAL CORDS. 773 



Fig. 425. Vertical Section of the La- 

 rynx aud Upper part of the Trachea. 



cular fibres, stretched between the sides of the epiglottis and the apex of the 

 arytenoid cartilage: these are the aryteno-epiglottidean folds, on the margins 

 of which the cuneiform cartilages form a more or less distinct whitish promi- 

 nence. 



The cavity of the larynx extends from the aperture behind the epiglottis to 

 the lower border of the cricoid cartilage. It is divided into two parts by the 

 projection inwards of the vocal cords, and Thyro-arytenoid muscles; between 

 the two cords is a long and narrow triangular fissure or chink, the glottis, or 

 rima glotlidis. The portion of the cavity of the larynx above the glottis, is 

 broad and triangular in shape above, and corresponds to the interval between 

 the alas of the thyroid cartilage ; the portion below the glottis is at first of an 

 elliptical, and lower down of a circular form. 



The gUttis (rima glottidis) is the interval between the inferior, or true, vocal 

 cords. The two superior or false vocal cords are placed above the latter, and 

 are formed almost entirely by a folding inwards of the muscous membrane; 

 whilst the two inferior or true vocal cords are thick, strong, and formed partly 

 by mucous membrane, and partly by ligamentous fibres. Between the true and 

 false vocal cords, on each side, is an oval depression, the sinus, or ventricle of 

 the larynx, which leads upwards, on the outer side of the superior vocal cord, 

 into a csecal pouch of variable size, the sacculus laryngis. 



The rima glottidis is the narrow fissure or chink between the inferior or true 

 vocal cords. It is the narrowest part of the cavity of the larynx, and corre- 

 sponds to the lower level of the arytenoid 

 cartilages. Its length, in the male, measures 

 rather less than an inch, its breadth, when 

 dilated, varying at its widest part from a 

 third to half an inch. In the female, these 

 measurements are less by two or three lines. 

 The form of the glottis varies. In its half- 

 closed condition, it is a narrow fissure, a lit- 

 tle enlarged and rounded behind. In quiet 

 breathing, it is widely open, somewhat tri- 

 angular, the base of the triangle directed 

 backward^ and corresponding to the space 

 between the separated arytenoid cartilages. 

 In forcible expiration, it is smaller than dur- 

 ing inspiration. When sound is produced, 

 it is more narrowed, the margins of the ary- 

 tenoid cartilages being brought into contact, 

 and the edges of the vocal cords approxi- 

 mated and made parallel, the degree of ap- 

 proximation and tension corresponding to 

 the height of the note produced. 1 



The superior or false vocal cords, so called 

 because they are not directly concerned in 

 the production of the voice, are two folds of 

 mucous membrane, inclosing a delicate nar- 

 row fibrous band, the superior thyro-arytenoid 

 ligament. This ligament consists of a thin 

 band of elastic tissue, attached in front to 

 the angle of the thyroid cartilage below the 



epiglottis, and behind to the anterior surface of the arytenoid cartilage. The 

 lower border of this ligament, inclosed in mucous membrane, forms a free 

 crescentic margin, which constitutes the upper boundary of the ventricle of the 

 larynx. 



1 On the shape of the glottis in the various conditions of breathing and speaking, see " Czer- 

 mak on the Laryngoscope," translated for the New Sydenham Socitty. 



