224 Royal Society : — 



causes the thjroid 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, whicli we can feel by the touch, becomes especially 

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



whicli takes place as we have seen at the notes dojf, re, ^•rEr-Jr~ 



3 n ^ 

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

 this dilfercnce, 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 cliest 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 ; naj", 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 

 of these fibres, as w^e have seen, this muscle raises the vocal mem- 

 brane, and makes its apposable part thinner ; whereas the lateral 

 crico-arytenoid gives a rotatory movement to the cartilage, which 

 brings the apophyses into deep contact. This deep contact, W'hich 

 continues even after the apophyses no longer partake in the vibra- 

 tions, gives a deep tension to the membranes, increases the depth of 

 their contact*, and, as a necessary consequence, augments the re- 

 sistance they present to the air. It is to the extent of this resistance 

 that we attribute the formation of the chest-register, so distinct by 

 its particular amplitude. To it we attribute also the slowness of 

 the beats of the glottis, and the consequent low pitch of the sounds, 

 a pitch which, even in the highest tenor voices, is at least an octave 

 lower than the head notes of ordinary soprani. 



Register of Falsetto. 

 When, on the contrary, the external fibres of the lateral crico- 

 arytenoid muscle remain inactive, we produce the falsetto. The 

 lips of the glottis, stretched by the horizontal bundle of the thyro- 

 arytenoid, come in contact by their edge alone, formed at once by 

 the ligament and the apophyses, and offer little resistance to the 

 air. Hence arises the great loss of this agent, and the general 

 weakness of the sounds produced here. 



♦ It is then that we feel the pinching of which we have spoken. 



