1074 THE VOICE. [BOOK in. 



668. Laryngoscopic observation then teaches that the 

 larynx is used not only for the utterance of voice, for phona- 

 tion, but also for breathing ; and indeed in speaking of respira- 

 tion we called attention to this ; but the former is its more 

 important use and we may chiefly dwell on this, referring in- 

 cidentally to the respiratory functions. 



In order that the membranous edges of an aperture may be 

 readily thrown into sonorous vibrations by a blast of air, the 

 edges should be brought near together and the aperture reduced 

 to a mere slit. Hence the fundamental condition for the forma- 

 tion of the voice, and indeed speaking generally of voices of all 

 kinds, is the approximation and consequent more or less paral- 

 lelism of the vocal cords. 



In the voice, as in other sounds (cf. 620), we distinguish 

 three fundamental features: (1) Loudness. This depends on 

 the strength of the expiratory blast. (2) Pitch. This depends 

 on the rapidity of the vibrations, and this we may in a broad 

 way consider as determined on the one hand by the length and 

 on the other hand by the tension of the vocal cords. What we 

 may call the natural length of the vocal cords is constant, or 

 varies only with age ; and the influence of this factor bears on 

 the general range of the voice, not on the particular note given 

 out at any one time. The tension of the vocal cords on the 

 contrary is very variable, and the pitch of any particular note 

 uttered depends in the main on this ; hence great importance 

 attaches to the mechanisms by which changes in the tension of 

 the vocal cords are brought about. But, as we shall see, the 

 problems connected with the compass of a voice and with changes 

 of pitch are very complex ; in considering these things we have 

 to do with much more than mere variations in the tension of the 

 vocal cords along the whole of what we have called their natural 

 length. These matters however we shall deal with later on, 

 and may for the present consider tension as the main factor of 

 changes in pitch. (3) Quality. This, as we have seen ( 620), 

 depends on the number and character of the partial tones accom- 

 panying any fundamental note sounded, and is determined by a 

 variety of circumstances, chief among which are, on the one 

 hand the form, thickness and other physical qualities of the 

 cords, and on the other hand, the disposition of the resonance 

 chamber, or parts of the respiratory passage other than the 

 glottis itself. 



We may confine ourselves in the first instance to the condi- 

 tions which determine the mere utterance of the voice and to the 

 mechanisms which affect the tension of the vocal cords, and hence 

 the pitch of the voice. The problems therefore which we have 

 to attack are, first, By what means are the cords brought near to 

 each other or drawn asunder as occasion demands? and secondly, 

 By what means is the tension of the cords made to vary ? We 



