407 



lesser depth of the ligaments to be in contact, in proportion as the 

 sounds become higher, and thus assists by increasing the mobility 

 of the ligaments. 



We shall see in a few moments that the rotatory movement, 

 which the external fibres of the lateral crico-arytenoid muscles give 

 to the arytenoid, by making the vocal membrane deeper, partly 

 counteracts the above effect, and produces the chest-register. 



The crico-thyroid muscle, on the contrary, is a powerful auxiliary 

 in the elevation of the voice. This muscle, which at the same time 

 causes the thyroid to come forwards and downwards, gives rise to a 

 mechanical tension, not only in the vocal ligament, but even in the 

 whole vocal membrane. The meeting of the thyroid and cricoid 

 cartilages, which we can feel by the touch, becomes especially 

 marked when the inter-ligamentous glottis alone produces the sounds, 



which takes place as we have seen at the notes do$, re> feEJ^iE 



3 3 J 



in the chest- register, and an octave above for that of the head ; with 

 this difference, however, that for the latter a more vigorous and 

 complete connexion is necessary. 



Let us now see what we may learn from the sensations we feel in 

 the vocal organ. When we produce a chest-note, the least attention 

 enables us to distinguish a "pinching " at the posterior part of the 

 glottis, which becomes more vigorous as the notes ascend. This 

 pinching seems to be formed by extension of the depth of the touch- 

 ing surfaces, and may become very painful ; whilst the notes of fal- 

 setto, when higher than chest ones, give comparatively great relief to 

 this part, and the surfaces in contact seem to have become thinner. 



If we combine these sensations with the different remarks which 

 have been furnished to us by the examination of the muscles, we 

 can fix the particular mechanism of each register. 



Chest Register. 



In fact, when the arytenoid muscles have brought in contact the 

 arytenoid cartilages, and closed the glottis, the voice may take two 

 very different characters ; nay, more, it will be produced in pitches 

 widely apart from one another, and will give forth the chest, or 

 falsetto registers, according as the fibres of the thyro-arytenoid 

 attached to the vocal membrane are active or not. By the action 



