RESPIRA TION 



147 



The entrance to the larynx is formed by the two arytenoid 

 cartilages, the epiglottis, and the aryepiglottic folds ; beyond 

 these is the glottis proper — viz., the V-shaped opening formed 

 by the vocal cords. When the laryngeal opening dilates, the 

 vocal cords pass towards the wall of the cavity and render the 

 V-shaped space wider; when the larynx'^closes, the cords are 

 approximated and the space rendered narrower (Figs. 54 and 56). 

 During ordinary respiration there is very little if any alteration 

 in the shape and size of the glottis ; but during exertion every 

 inspiratory movement is accompanied by an increase in size, 

 every expiration by a 

 decrease. At each ex- 

 piration the vocal cords 

 pass towards the centre 

 line, and at each in- 

 spiration return to the 

 wall of the larynx. The 

 closure of the larynx, 

 such as durir g the act of 

 swallowing, is a power- 

 ful movement, and if the 

 finger at this moment 

 be introduced into the 

 cavity and placed be- 

 tween the arytenoids, it 

 experiences considerable 

 pressure. The closure 

 of the larynx is brought 

 about by the depression 

 and approximation of 

 the arytenoid cartilages 

 and the approximation 

 of the vocal cords ; in 

 addition, during the act 

 of swallowing, the base 

 of the tongue presses 

 the epiglottis over the 

 arytenoids and renders the part both air- and water-tight. 



The Epiglottis is much larger than the opening it is intended 

 to seal during a condition of laryngeal repose. It is carried 

 backwards by the base of the tongue and pressed over the 

 arytenoids ; the larynx at the same moment advances, with its 

 arytenoid cartilages closely approximated. After the act of 

 swallowing, the tongue advances, the larynx recedes, and the 

 epiglottis returns to its position by means of its elastic recoil. 

 It is not essential to a food- or water-tight condition of the 



Fig. 56. — The Laryngeal Opening during 

 Hurried Respiration, seen in a State 

 of Dilatation. 



1, Epiglottis ; 2, margin of arytenoids ; 3, vocal 

 cord ; 4, pharynx laid open. Note the size 

 and shape of the glottal opening as compared 

 with Fig. 54. 



