Us 



ZOOLOGY. 



membrane forms four folds, two superiorly called the false 

 vocal cords, and two inferiorly called the true vocal cords. 

 It is here, upon the edge of these folds, by the air impingin" 

 and causing them to vibrate, that the voice is formed 

 (Figs. 95 and 96). 



These folds are in consequence called the vocal cords or 

 ligaments of the glottis, the space between the true ligaments 

 being called the glottis or rima glottidis ; the true vocal cords 

 are formed interiorly of folds of mucous membrane, and ex- 

 teriorly of elastic ligaments, which stretch from the interior 

 of the salient angle of the thyroid cartilage to the aryt;i-nniil 

 cartilages. By the muscular apparatus attached to the larynx 

 not only the entire larynx can be moved up and down in t la- 

 neck, but these ligaments or true vocal cords can be made 

 tense or relaxed, so as to diminish, enlarge, or all but close 

 the aperture called rima glottidis, through which the air must 

 pass and repass in its way to and from the lungs. Between 

 the true and false ligaments of the glottis or vocal cords, on 

 either side there is a cavity, called the ventricle of the larynx. 



* Fig. 94. The male larynx viewed in profile: A, hyoid bone; /, body of 

 the hyoid, giving attachment to the base of the tongue; t, thyroid cartilage ; 

 a, salient angle of the thyroid cartilage, which may I>e frit on trie surface f 

 the neck (pomum Adami): a membraniform ligament unites the thyroid 

 cartilage to the hyoid bones; c, cricoid cartilage ; fr, trachea or windpipe | 

 o, posterior wall of the larynx in relation with the gullet. 



Fig. 95. Vertical section of the laryni : h, hyoid bones; t, th\roid car- 

 tilage; c, cricoid cartilage; ar, arytaenoid cartilages; r, ventricle of the 

 glottis and of the larynx, formed as described in the text ; e, epiglottis; 

 tr, trachea. 



Fie. 96. Larynx, front view ; the contour of the inner wall is indicated by 

 the dotted lines CM, bb ; K, true vocal cords, or inferior: /., false .litt... or 

 superior. The other parts are indicated hv the same letters as in the pre- 

 ceding figures. 



