440 



4 



VOICE AND SPEECH 



The approximation of the posterior extremities of the vocal chords 

 and their tension by the action of certain of the intrinsic muscles are 

 accomplished just before the vocal effort is actually made. The glottis 

 being thus prepared for the emission of a particular sound, the expira- 

 tory muscles force air through the larynx with the required power. The 

 power of the voice is due to the force of the expiratory act, which is 

 regulated chiefly by the antagonistic relations of the diaphragm and the 

 abdominal muscles. From the fact that the diaphragm, as an inspira- 

 tory muscle, is directly opposed to the muscles that have a tendency to 

 push the abdominal organs, with the diaphragm over them, into the 

 thoracic cavity and thus diminish the pulmonary capacity, the expira- 

 tory and inspiratory acts may be balanced so nicely that the most deli- 

 cate vocal vibrations can be produced. The 

 glottis, thus closed as a preparation for a vocal 

 act, presents a certain resistance to the egress 

 of air. This is overcome by the action of the 

 expiratory muscles, and with the passage of air 

 through the chink, the edges of the true vocal 

 chords, which bound the opening, are thrown 

 into vibration. Many of the different quali- 

 ties that are recognized in the human voice 

 are due to differences in the length, breadth 

 and thickness of the vibrating bands; but 

 aside from what is technically known as 

 quality, pitch is dependent on the length of 

 the opening through which the air is made to 

 pass and the degree of tension of the chords. 

 The mechanism of these changes in the pitch 

 of vocal sounds is illustrated by Garcia in the 

 following, which relates to what is known as the chest-voice : 



" If we emit veiled and feeble sounds, the larynx opens at the notes 

 _ and we see the glottis agitated by large and loose 

 "I P" 11 ' vibrations throughout its entire extent Its lips com- 

 prehended in their length the anterior apophyses of the arytenoid 

 cartilages and the vocal chords; but, I repeat it, there remains no tri- 

 angular space. 



" As the sounds ascend, the apophyses, which are slightly rounded 

 on their internal side, by a gradual apposition commencing at the 

 back, encroach on the length of the< glottis; and as soon as we 

 reach the sounds a they finish by touching each other 



Fig. 93. Glottis seen with 

 the laryngoscope during the emis- 

 sion of high-pitched sounds (Le 

 Bon). 



I, 2, base of the tongue; 3, 4, 

 epiglottis; 5, 6, pharynx ; 7, aryte- 

 noid cartilages; 8, opening be- 

 tween the true vocal chords ; 9, 

 aryteno-epiglottidean folds ; 10, 

 cartilage of Santorini ; n, cunei- 

 form cartilage ; 12, superior vocal 

 chords ; 13, inferior vocal chords. 



throughout their 

 only solidly fixed 



whole extent; but their summits are 

 one against the other at the notes 



