LARYNX OF MAMMALIA. 603 



qui ' and 4 ar. transversi.' In fig. 478, the mucous membrane is 

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



J * ' C3 C5 



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 sons; the vibrations extend from 



C5 



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

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

 bv drawing the arvtenoids toward the thyroid to the degree in 



^ O v / O 



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 



O 



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 varicnis combinations of the actions 

 of the foregoing muscles on the vocal mechanism, reference should l>e made to cccxx, 

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



