. A text-book of human physiology . ttis is firm-ly closed posteriorly, but is ratherwidely open anteriorly. The airescapes therefore more readily thanin the case of chest tones. For thisreason chest tones can be held longerthan head tones. We have the following meansin the larynx itself of altering thepitch of the voice (Griitzner) : (1)By changing the longitudinal ten-sion of the vocal cords; (2) by lim-iting the vibrating length of thevocal cords, which is done by ap-plying the inner surfaces of thearytenoid cartilages to each otherprogressively more and more fromposterior to anterior; (3)
. A text-book of human physiology . ttis is firm-ly closed posteriorly, but is ratherwidely open anteriorly. The airescapes therefore more readily thanin the case of chest tones. For thisreason chest tones can be held longerthan head tones. We have the following meansin the larynx itself of altering thepitch of the voice (Griitzner) : (1)By changing the longitudinal ten-sion of the vocal cords; (2) by lim-iting the vibrating length of thevocal cords, which is done by ap-plying the inner surfaces of thearytenoid cartilages to each otherprogressively more and more fromposterior to anterior; (3) by chang-ing the form of the vocalis ,and thereby varying the width of the vocal cords; (4) In altering the airpressure in the trachea. Higher tones within the same register tlierefore may be produced in twogeneral ways: (a) By increasing tlie tension and at the same time lengtheningthe vocal cords; (h) by shortening the vibrating portion. Different individ-uals use one or the other of these methods more or less Fig. 204.—Position of tlie vocal organs in pro-ducing the sound of broad A, after Griitzner. 506 HEARING. VOICE AND SPEECH § 4. ELEMENTS OF SPEECH Language is niailo up of words, words of syllables and syllables of ele-mentary sounds called vowels and consonants. Vowels are produced whenthe voice is modified by merely changing the shape of the resonance cavities—pharynx, mouth, and nasal passages; consonants when the air or voiceis more or less obstructed by the movable parts of the organs of speech—lips, teeth, tongue and palate. In whispering the glottis is partially open and the air is allowed to passthrough without setting the vocal cords in vibration. Since each of the reso-nance cavities has a sound of its own which it emits when the air containedin it is caused to vibrate, and since sounds may be produced by the lips, tongue,etc., alone, it is possible to speak without voice. A. VOWELS We cannot here discuss exhaustively the changes of
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