OF THE LARYNX, AND ITS ACTIONS. 



845 



serves a? a foundation for the superjacent mechanism. This is embraced i as 

 it were) by the Thyroid (Figs. 298, 299, E c G, Fig. 300, o E H), which is 

 articulated to its sides by the lower horns (Figs. 298, 299, c), round the ex- 

 tremities of which it may be considered to turn as on a pivot. In this man- 

 ner, the lower front border of the Thyroid cartilage, which is ordinarily 

 separated by a small interval (Figs. 298, 299, in n) from the upper margin 

 of the Cricoid, may be made to approach it or to recede from it; as any one 

 may easily ascertain, by placing his finger against the little depression which 

 may be readily felt externally, and observing its changes of size, whilst a 

 range of different tones is sounded ; for it will then be noticed that, the 

 higher the note, the more the two cartilages are made to approximate, whilst 

 they separate in proportion to the depth of the tones. 1 Upon the upper sur- 

 face of the back of the Cricoid, are seated the two small Arytenoid cartilages 

 (Figs. 298, 300, F F); these are fixed in one direction by a bundle of strong 

 ligaments, which tie them to the back of the cricoid ; but they have some 

 power of moving in other directions, upon a kind of articulating surface. 

 The direction of the surface and the mode in which these cartilages are other- 

 wise attached, cause their movement to be a sort of rotation in a plane which 

 is nearly horizontal but partly downwards; so that their vertical planes may 

 be made to separate from each other, and at the same time to assume a slant- 



FIG. 298. 



FIG. 299. 



External and Sectional views of the Larynx : A n B, the cricoid cartilage ; E c G, the thyroid cartilage ; 

 G, its upper horn ; c, its lower horn, where it is articulated with the cricoid ; F, the arytenoid cartilage; 

 E F, the vocal ligament; A K, crico-thyroideus muscle: F e m, thyro-aryteuoideus muscle; x e, crieo- 

 arytenoideus lateralis; s, transverse section of arytenoideus transversus; m n, space between thyroid 

 and cricoid; B L, projection of axis of articulation of arytenoid with thyroid. 



ing position. This change of place will be better understood, when the 

 action of the muscles is described. To the lower part of the anterior surface 

 of the Arytenoid cartilages are attached the chordce vocales or Vocal Liga- 

 ments (Fig. 298, E F, Fig. 300, T v), which stretch across to the front of the 

 Thyroid cartilage; and it is upon the condition and relative situation of these 

 ligaments that their action depends. It is evident that they may be reu- 



1 In making this observation, it is necessary to put out of view the general move- 

 ment of the Larynx itself, which the finger must be made to follow up and down. 



