1076 



THE VOICE. 



[BOOK in. 



the glottis is narrowed (Fig. 187 A'~). When on the contrary 

 the cartilages are wheeled round on the pivots of their articula- 

 tions, so that the processus vocales diverge, and the internal sur- 

 faces of the cartilages form an angle with each other, the glottis 

 is widened (Fig. 187 B ', C'~). Moreover the two cartilages may 

 to a certain extent be bodily drawn together, or dragged apart, 

 the two hind angles, between the median and posterior sides, 

 being now close together, now apart. 



669. The muscles of the larynx though small, are numer- 

 ous and complicated, and are so disposed in respect to their 

 origins and insertions and to the sweep of their fibres, that the 

 effect of the contraction of one muscle will depend upon whether 

 or no and how far other muscles are thrown into contraction at 

 the same time ; moreover in the case of some of the muscles 

 at least the effect is different according as the whole muscle or 

 a part only contracts. 



The first muscle to which we may call attention is the trans- 

 verse arytenoid (M. arytenoideus posticus s. transversus) (Fig. 

 188). This is a relatively thick muscle covering the hind sur- 



pm... 



m.cr. ar.p 



-m.crth.p 



Cri 



FIG. 188. DIAGRAM OF THE TRANSVERSE AND OBLIQUE ARYTENOID AND OF 

 THE POSTERIOR CRICO-ARYTENOID MUSCLES. 



A. shews the three muscles in position in reference to the aperture of the 

 larynx ; B. shews the attachments of the transverse arytenoid and posterior crico- 

 arytenoid. 



m.ar.t. transverse arytenoid muscle, m.cri.ar.p. posterior crico-arytenoid 

 muscle, m.ar.o. oblique arytenoid muscle. Cri. cricoid cartilage. Ary. ary- 

 tenoid cartilage, p.m. processue muscularis of arytenoid cartilage. W. promi- 

 nence of cartilage of Wrisberg. S. prominence of cartilage of Santorini (in B, it 

 marks the cartilage itself), m.cr.th.p. is the small posterior crico-thyroid muscle. 



