LARYNX OF MAMMALIA. G03 



qui ' and ' ar. trans versi.' In fig. 478, the mucous membrane is 

 removed to show the vocal cords, v, v, bounding the glottis: 

 attached behind to the arytenoids at F, and in part to the 

 thyroid at T. The ring of the cricoid cartilage is shown at x, 

 L, which can be rotated on its axis R, s, by the crico-arytenoidei 

 postici, and the crico-arytenoidei laterales. 



In the louder tones of voice or song the vibrations extend from 

 the cords to the contiguous elastic tissues, and even to the thyro- 

 arytenoid muscles, ib. k. In the deeper notes the cords are relaxed 

 by drawing the arytenoids toward the thyroid to the degree in 

 which the air-current can put them into vibration, and according 

 to the length of the cord that can be made to vibrate is the depth 

 of the bass note. In the medium degree of tension, when the 

 wrinkles of the rima glottidis are effaced, the ordinary tones of 

 the voice and the middle notes of its compass in singing are pro- 

 duced. The higher notes depend on combined tension of the 

 cords with narrowing of the glottis and strengthening of the cur- 

 rents of air. The vocal cords in men are about one-third longer 

 than in women and boys. Castration arrests that prominent 

 growth of the thyroid, &c, which accompanies the elongation of 

 the cords. 1 



1 For the further and minor influences of the various combinations of the actions 

 of the foregoing muscles on the vocal mechanism, reference should be made to cccxx, 

 ccxvn", ccxxi", ccxxn", and especially to ccxxm". 



