THK LARYNX VOICK AM) SI'KF.CH 



23' 



the action of other muscles attached to it, the front of the 

 cricoid cartilage is drawn up while its back goes down, in a 

 see-saw manner. Either of these actions increases the distance 

 of the top of the back of the cricoid and of the arytenoid 

 cartilages on it from the front of the thyroid. Small muscles 

 pass from the back of the cricoid to the arytenoid cartilages ; 

 these in contracting draw the arytenoid cartilages apart 

 from each other and so widen the glottis. Another muscle 

 passes from one arytenoid cartilage to the other, and by its 

 action draws them together and so narrows the glottis. 



Cut the thyroid cartilage 

 upwards on one side in two 

 places, one near the front 

 angle and the other near the 

 hinder edge, so as to remove 

 the greater part of it on one 

 side. Immediately under it, 

 and only slightly adherent to 

 it, is a broad band of muscle 

 passing from the front angle 

 of the thyroid cartilage back- 

 wards to the arytenoid carti- 

 lage of the same side ; this is 

 called the thyro-arytenoid 

 muscle. When this muscle is 



- . t* f i. 



CUt through there is Still the FlG . lto ._Tnerfotti S viewed from above. 



mucous membrane lining the rh> thyroid ^5,^. Cr> cricoia ^ 



lage ; Ary, arytenoid cartilages ; Arp, 

 the muscle between them ; C.a.f, ami 

 <"./, muscles passing from the cricoid 

 to the arytenoid cartilages ; TkA, 

 thyro-arytenoid muscle ; V, vocal cords. 



cavity of the larynx. Cut this 

 membrane through and re- 

 move one side of the cricoid 

 cartilage and slit open the side 

 of the trachea, so as to well 

 expose the interior of the larynx to view. Notice that the 

 smooth mucous membrane is everywhere even, except in one 

 place on each side where it is thrown into a thick rounded fold 

 running from the front of the thyroid cartilage backwards to 

 the arytenoid cartilage. These two folds, one on each side, are 

 the vocal cords. 



When the arytenoid cartilages are wide apart the aperture 

 between the vocal cords, the glottis, has the form of a V with 



