456 



OF THE VOICE AND SPEECH. 



tion for the superjacent mechanism. This is embraced (as it were) by the 

 Thyroid, which is articulated to its sides by its lower horns, round the ex- 

 tremities of which it may be regarded as turning, as on a pivot. In this man- 



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-arytenoideus muscle ; x e, crico-ary- 

 tenoideus 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. 



ner the lower front border of the thyroid cartilage, which is ordinarily sepa- 

 rated by small intervals from the upper margin of the cricoid, may be made to 

 approach it or 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 ; 

 it will then be observed that, the higher the note, the more the two cartilages 

 are made to approximate, whilst they seperate in proportion to the depth of 

 the tones.* Upon the upper surface of the back of the cricoid, are seated 

 the two small Arytenoid cartilages ; 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 articulat- 

 ing surface. The direction of the surface, and the mode in which these car- 

 tilages are otherwise 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 slanting position. This change of place will be better un- 

 derstood, when the action of the muscles is described. To the summit of 

 the arytenoid cartilages are attached the chordae vocalcs or Vocal Ligaments, 

 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 



* In milking this observation, it is necessary to put out of view the general movement to 

 the larynx itself, which the finger must be made to follow up and down. 



