OF THE LARYNX, AND ITS ACTIONS. 927 



the lower part of its back ; their action is to draw the outer corners backwards 

 and downwards, so that the points to which the vocal ligaments are attached, 

 are separated from one another, and the rima glottidis is thrown open. This 

 will be at once seen from the preceding diagram, in which the direction of trac- 

 tion of the several muscles is laid down. The action of these muscles is partly 

 antagonized by that of the Crico-arytenoidei laterales, which run forwards and 



Part of Fig. 232 enlarged, to show the Direction of the, Muscular JFbrce^which act on the Arytenoid carti- 

 lage : Q N v s, the right Arytenoid cartilage ; T v, its vocal ligament ; B R 8, hundle of ligaments uniting it to 

 Cricoid ; P, projection of its axis of articulation ; h g, direction of the action of the Thyro-arytenoideus ; N X, 

 direction of Crico-ary tenoideus lateralis ; N w, direction of Crico-ary tenoideus posticus ; N T, direction of Ary- 

 tenoideus transversus. 



downwards from the outer corners of the Arytenoid cartilages, and whose action 

 is to bring the anterior points of the arytenoid cartilages into the same straight 

 line, at the same time depressing them, so as thus to close the glottis. These 

 muscles are assisted by the Arytenoideus transversus, which connects the pos- 

 terior faces of the Arytenoid cartilages, and which, by its contraction, draws 

 them together. By the conjoint action, therefore, of the Crico-arytenoidei 

 laterales and of the Arytenoideus transversus, the whole of the adjacent faces 

 of the Arytenoid cartilages will be pressed together, and the points to which 

 the vocal ligaments are attached will be depressed. But if the Arytenoideus 

 be put in action in conjunction with the Crico-arytenoidei postici, the tendency 

 of the latter to separate the Arytenoid cartilages being antagonized by the 

 former, its backward action only will be exerted ; and thus it may be caused to 

 aid the Crico-thyroidei in rendering tense the vocal ligaments. . This action 

 will be further assisted by the Sterno-ihyroidei, which tend to depress the Thy- 

 roid cartilage, by pulling from a fixed point below j 1 and the Thyro-liyoidei will 

 be the antagonist of these, when they act from a fixed point above, the Os 

 Hyoides being secured by the opposing contraction of several other muscles. 

 The respective actions of these muscles will be best comprehended by the fol- 

 lowing Table : 



1 These are not usually reckoned among the principal muscles concerned in regulating 

 the voice; but that they are so, any one may convince himself by placing his finger 

 just above the sternum, whilst he is sounding high notes ; a strong feeling of muscular 

 tension is then at once perceived. 



