VOICE 



551 



n. 



Ar. 



Cr. 



female and the whole larynx is larger. The cleft between 

 them is the rima glottidis. 



3. Muscles. — The crico-thyreoidei take origin from the 

 antero-lateral aspects of the cricoid, and are inserted into the 

 inferior part of the lateral aspect of the thyreoid. In contract- 

 ing they approximate the two 

 cartilages anteriorly, and render 

 tense the vocal cords (fig. 

 223). 



The crico-arytenoidei postici 

 arise from the back of the cricoid 

 and pass outwards to be inserted 

 into the external or muscular 

 process of tlie arytenoids. In 

 contracting, they pull these pro- 

 cesses inwards, and thus diverge 

 the anterior processes and open 

 the glottis (tig. 224). 



The crico-arytenoidei later- 

 ales take origin from the lateral 

 aspects of the cricoid, and pass 

 backwards to be inserted into 

 the muscular processes of the 

 arytenoids. They pull these 

 forwards, and so swing inwards 

 their anterior processes and 

 approximate the vocal cords (fig. 224). 



A set, of muscular fibres runs between the arytenoids — the 

 arytenoideus transversus — while other fibres run from the 

 arytenoids up to the side of the epiglottis. These help to close 

 the upper orifice of the larynx. 



The thyreo-arytenoidei bands are of muscular fibres lying 

 in the vocal cords, and running from the thyreoid to the 

 arytenoids. Their mode of action is not fully understood. 



4. Mucous Membrane.— The mucous membrane of the larynx 

 is raised on each side into a well-marked fold above each true 

 vocal cord— the false vocal cord. Between this and the true 

 cord on each side is a cavity — the ventricle of the larynx. 

 The other folds of mucous membrane, although of importance 

 in medicine, have no special physiological significance. 



Fig. 223.— Side View of the Carti- 

 lages of the Human Larynx. Cr., 

 cricoid cartilage; Ar., left ary- 

 tenoid cartilage; Th., thyreoid 

 cartilage. The dotted line shows 

 the change in the position of 

 the thyreoid by the action of 

 the crico-thyreoid muscle, and 

 the stretching of the vocal cords 

 which results. 



