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HANDBOOK OF PHYSIOLOGY. 



Movements of the Vocal Cords. The placing of the vocal cordg 

 in a position parallel one with the other, is effected by a combined action 

 of the various intrinsic muscles which act on them the thyro-arytenoi- 

 dei having, without much reason, the credit of taking the largest share 

 in the production of this effect. Fig. 307 is intended to show the 

 various positions of the vocal cords under different circumstances. Thus, 

 in ordinary tranquil breathing, the opening of the glottis is wide and 

 triangular (B), becoming a little wider at each inspiration, and a little 

 narrower at each expiration. On making a rapid and deep inspiration 

 the opening of the glottis is widely dilated (as in c), and somewhat 



FIG. 306. 



FIG. 307. 



FIG. 306. -Lateral view of exterior of the larynx 8, thyroid cartilage; 9, cricoid cartilage ; 10, 

 crico-thyroid muscle; 11, crico-thyroid ligament; 12, first rings of trachea. (Willis.) 



FIG. 307. Three laryngoscopic views of the superior aperture of the larynx and surrounding 

 parts. A, the glottis during the emission of a high note in singing; B, in easy and quiet inhalation 

 of air; C, in the state of widest possible dilatation, as in inhaling a very deep breath. The diagrams 

 A', B', and C', show in horizontal sections of the glottis the position of the vocal ligaments and 

 arytenoid cartilages in the three several states represented in the other figures. In all the figures, 

 .so far as marked, the letters indicate the parts as follows, viz.: I, the base of the tongue; e, the 

 upper free part of the epiglottis, e', the tubercle or cushion of the epiglottis; ph, part of the ante- 

 rior wall of the pharynx behind the larynx; in the margin of the aryteno-epiglottidean fold w, the 

 swelling of the membrane caused by the cartilages of Wrisberg; s, that of the cartilages of San- 

 torini; a, the tip or summit of the arytenoid cartilages; c v, the true vocal cords or lips of the rima 

 glottidis; c v s, the superior or false vocal cords; between them tho ventricle of the larynx; in C, tr 

 is placed on the anter.or wall of the receding trachea, and b indicates the commencement of the 

 two bronchi beyond the bifurcation which may be brought into view in this state of extreme dilata- 

 tion. (Quain after Czermak.) 



lozenge-shaped. At the moment of the emission of sound, it is narrowed, 

 the margins of the arytenoid cartilages being brought into contact and 



