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of these fibres, as we 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, which 

 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. 



But as soon as we reach the sound do, the beats are produced by 



4 



the ligaments exclusively, and we have attained the head-register. 

 It is certain, as we may deduce from the movement of the ligaments, 

 that then the vocal membrane is raised by the action of the fibres of 

 the thyro-arytenoid muscle, and its surface is diminished to an edge ; 

 but we think that the external fibres of the lateral crico-arytenoid, 

 which would prevent this movement, remain inactive. Then also 

 the very decided tension, which the crico-thyroid muscle effects on 

 the vocal tendons, and which accelerates their movements, takes 

 place. 



During the chest-register, therefore, the vocal ligaments are 

 stretched, and are in contact to an extent corresponding with the 

 depth of the anterior apophyses of the arytenoid, whilst in the 

 falsetto the edges alone of the ligaments are stretched and apposed ; 

 in both cases the sounds being formed, not by the actual vibrations 

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



