CHAPTER XXVIIl 

 THE VOICE 



" As the power of the vital soul is situated in the substance of the heart, and 

 the power of the natural soul in the proper substance of the liver, ... so also 

 does the brain, in appropriate structures and in organs properly subserving its 

 work, manufacture the animal spirit, which is by far the brightest and most delicate, 

 and indeed is a quality rather than an actual thing. And while on the one hand 

 it employs this spirit for the operations of the chief soul, on the other hand it is 

 continually distributing it to the instruments of the senses and of movement. . . ." 



Vesalius (1543) quoted by Foster. 



The production of sound by the larynx or by the hps is so essen- 

 tially a modification of respiration that we may conveniently deal 

 with phonation, whistling and speech at this point. By means of 

 soimd production we act on matter at a distance, and so one would 

 naturally consider the problems of phonation, and especially of 

 articulation, after one had reviewed the various types of levers, 

 pulleys, etc., by means of which the body reacts on its environ- 

 ment. 



I. Phonation. At least two essential factors are concerned in 

 phonation, namely, («) a means of producing a flow of air, and (b) a 

 means of interrupting that flow so that alternate condensations 

 and rarefactions follow one another in the air at a certain rate. 

 The lungs provide the current of air, and either the sudden expan- 

 sion of the bore of the wind-pipe at the ventricle, the pursing of the 

 lips to form a small orifice (whistling), the juxtaposition of tongue 

 to palate and closure of teeth (hiss), or the vibrations of the vocal 

 cords account for the breaking of the continuous column of air into 

 waves. 



Mechanism of Larynx. The larynx or sound box is situated 

 between the root of the tongue and the trachea. Above, it opens 

 into the laryngeal part of the pharynx, of which it forms the 

 anterior wall ; below, it is continuous with the trachea. It is 

 composed of nine cartilages, three single and three paired. They 

 are connected by ligaments and membranes, and moved by some 

 ten muscles — some of which open and close the glottis and some 

 regulate the degree of tension of the vocal ligaments. The larynx 

 is lined by a mucous membrane which is continuous above with 

 that of the mouth and pharynx and below with that of the trachea. 

 Except over the vocal folds, where it is stratified, the epithelium is 



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