269 



d. 



The most important muscles of the larynx are: (1) a 

 transverse arytenoid muscle, uniting the posterior surfaces 

 of the arytenoid cartilages, and 

 drawing those cartilages together 

 when the larynx is shut; (2) a pair 

 of posterior crico-arytenoid muscles, 

 passing up from the back of the 

 cricoid cartilage to the arytenoid 

 cartilages at their outer angles, and 

 rotating the vocal cords outwards, 

 so as to widen the glottis; (3) a 

 pair of lateral crico-arytenoid muscles, 

 passing backwards from the sides of 

 the cricoid to the outer angles of the 

 arytenoids, and rotating the vocal 

 cords inwards to the middle line ; 

 (4) a pair of thyro-arytenoid muscles 



lying in the folds of the vocal cords, Fi * 135 _ MuaoLE8 OF 

 and shortening them by rotating the THE LARYNX ; view from 

 thyroid cartilage upwards on the 

 cricoid; (5) a pair of crico-thyroid 

 muscles, seen from the front, and 

 stretching the vocal cords by rotat- 

 ing the thyroid cartilage downwards. 

 197. If the larynx be examined by 

 means of a laryngoscope, ih&t is to say, 

 a mirror placed in the back part of 

 the throat, so as to throw light down 

 on the larynx and reflect its image 

 to the eye of the observer, it will be 

 seen that, as soon as vocalization 

 commences, the vocal cords spring 

 toward the middle line, leaving only 

 a chink between them, and that they 

 as quickly recede when the voice 

 ceases. Their edges are turned one 

 toward the other when in action ; 

 but at other times they are everted. 

 This agrees exactly with the results 

 got by tying a bit of india-rubber or 



the left side behind. 

 Section of thyroid car- 

 tilage, the left side of 

 which is removed with 

 the exception of 5, the 

 part articulating with 

 the cricoid cartilage ; c, 

 arytenoideus muscle; d, 

 posterior crico-arytenoi- 

 deus ; e, crico-thyroi- 

 deus ; /, crico-thyroid 

 ligament; g, crico-ary- 

 tenoideus lateralis ; h, 

 thyro-arytenoideus, its 

 upper edge correspond- 

 ing with the edge of the 

 vocal cord; i, k, thyro- 

 and aryteno - epiglotti- 

 deus, resting on the 

 aryteno - epiglottideaii 

 fold of mucous mem- 

 brane. A portion of the 

 mucous membrane is re- 

 moved between h and k 

 to show the position of 

 the glottis, 



