Mechanism of the Larynx. 335 



thyroid nearer to the point A of the cricoid, and therefore in- 

 creases the distance EB ; this pair of muscles therefore stretches 

 the vocal ligaments. 



One of the internal pair (the thyroarytenoid muscle) is seen 

 at Emae, Fig. 3; it is attached to the inside of the front of the 

 thyroid at Em, and to the arytenoid at ae ; when this muscle con- 

 tracts it approximates the arytenoid to the point E, and as the 

 arytenoid is tied to the cricoid by the bundle of ligaments at B, 

 it of course draws the point B after it, just as if the muscle were 

 attached immediately to B. The effects of this muscle is then 

 to decrease the distance EB, and therefore to relax the vocal 

 ligament. 



Hence the thyroarytenoid muscle is the antagonist muscle of 

 the cricothyroid, and together they govern the pitch of the notes. 

 The truth of this account of the stretching and relaxing of the 

 vocal ligaments may easily be verified, as far as the motion of 

 the cartilages is concerned, by a method which was first suggested 

 by Ferrein*, but appears to have been forgotten or misunderstood 

 by succeeding writers. We may readily trace with the finger on 

 the outside of the throat, (at GFED, Fig. 2,) the thyroid cartilage 

 EF, the cricoid cartilage DM, and a small space ED between them 

 (marked mn in Figs. 3 and 4). Now it is plain that when the 

 thyroid revolves upon C in the direction BE, so as to stretch the 

 vocal ligaments and raise the pitch of the notes produced, that 

 this motion approximates the lower edge m of the thyroid to the 

 upper edge n of the cricoid, and, therefore, diminishes the aper- 

 ture mn, and vice versa, when the ligaments are relaxed, the aperture 

 mn is increased. 



* Ac. Par. 1741. 



