5i8 



CONDITIONS INFLUENCING THE LARYNGEAL SOUNDS. 



Fig. 365. 



Experiments on the Larynx. Ferrein ( 741) and Joh. Muller made experiments upon the 

 excised larynx. A tracheal tube was tied into the excised human larynx, and air was blown 

 through it, the pressure being measured by means of a mercurial manometer, while various 



arrangements were adopted for putting the vocal 

 cords on the stretch and for opening or closing the 

 glottis. 



315. CONDITIONS INFLUENCING 

 THE LARYNGEAL SOUNDS. The pitch 

 of the note emitted by the larynx depends 

 upon : 



1. The Tension of the Vocal Cords, i.e., 

 upon the degree of contraction of the crico- 

 thyroid and posterior crico-arytenoid muscles, 

 and also of the internal thyro-arvtenoids 

 ( 313, II., 4). 



2. The Length of the Vocal Cords. 

 (a) Children and females with short vocal 



cords produce high notes, (b) If the ary- 

 Composite rhinoscopy view. S.n., septum . -j .-i j 2' i.u i ,/ 



narium ; C.i., Cm., C.s., lower, middle, tenold cartilages are pressed together by the 

 and upper turbinated bones; T., Eusta- action of the arytenoid muscles (transverse 

 chian tube ; W., tubular eminence ; A'., and oblique), so that the vocal cords alone 

 groove of Rosenmuller ; P.m., soft can v ib ra te, while their intercartilaginous 

 palate; O.K. roof of pharynx; U., uvula. ,. , . * , . ,, , 



1 l J portions lying between the processus vocales 



do not, the tone thereby produced is higher (Garcia). In the production of low 

 notes, the vocal cords, as well as the margins of the arytenoid cartilages, vibrate. 

 At the same time the space above the entrance to the glottis is enlarged and the 

 larynx becomes more prominent, (c) Every individual has a certain medium pitch 

 of his voice, which corresponds to the smallest possible tension of the intrinsic 

 muscles of the larynx. 



3. The Strength of the Blast. That the strength of the blast from below raises 

 the pitch of the tones of the human larynx is shown by the fact, that tones of the 

 highest pitch can only be uttered by powerful expiratory efforts. With tones of 

 medium pitch, the pressure of the air in the trachea is 160 mm., with high pitch 

 200 mm., and with very high notes 945 mm., and in whispering 30 mm., of water 

 (Cagniard-Latour). These results were obtained in a case of tracheal fistula. 



Accessory Phenomena. The following as yet but partially explained phenomena are observed 

 in connection with the production of high notes : (a) As the pitch of the note rises, the larynx 

 is elevated, partly because the muscles raising it are active, partly because the increased intra- 

 tracheal pressure so lengthens the trachea, that the larynx is thereby raised; the uvula is raised 

 more and more (Labus). (b) The upper vocal cords approximate to each other more and more, 

 without, however, coming into contact, or participating in the vibrations, (c) The epiglottis 

 inclines more and more backwards over the glottis. 



4. The falsetto voice with its soft timbre and the absence of resonance or 

 pectoral fremitus in the air-tubes is particularly interesting. Oertel observed that, 

 during the falsetto voice, the vocal cords vibrated so as to form nodes across them, 

 but sometimes there was only one node, so that the free margin of the cord and 

 the basal margin vibrated, being separated from each other by a nodal line (parallel 

 to the margins of the vocal cord). During a high falsetto note, there may be three 

 such nodal lines parallel to each other. The nodal lines are produced probably by 

 a partial contraction of the fibres of the thyro-arytenoid muscle (p. 513), while at 

 the same time the vocal cords must be reduced to as thin plates as possible by 

 the action of the crico-thyroid, posterior arytenoid, thyro- and genio-hyoid muscles 

 (Oertel). The form of the glottis is elliptical, while with the chest-voice the vocal 

 cords are limited by straight surfaces ;: the air also passes more freely through the 

 larynx. 



