CHAPTER XXV. 



PHONATION; ARTICULATE SPEECH. 



Phonation, the emission of vocal sounds, is accomplished by the vibration 

 of two elastic membranes which cross the lumen of the larynx antero- 

 posteriorly and which are thrown into vibration by a blast of air from the 

 lungs. 



Articulate speech is a modification of the vocal sounds or the voice 

 produced by the teeth and the muscles of the lips and tongue and is employed 

 for the expression of ideas. 



The larynx, the organ of the voice, is situated in the fore part of the neck, 

 occupying the space between the hyoid bone and the upper extremity of the 

 trachea. In this situation it communicates with the cavity of the pharynx 

 above and the cavity of the trachea below. From its anatomic relations and 

 its internal structure the interpolation of the elastic membranes the 

 larynx subserves the two widely different yet related functions, respiration 

 and phonation. 



THE ANATOMY OF THE LARYNX. 



The larynx consists primarily of a series of cartilages united one with 

 another in such a manner as to form a more or less rigid framework, yet 

 possessing at its different joints, a certain amount of motion; and secondarily, 

 of muscles and nerves which conjointly impart to the cartilages the degree 

 of movement necessary to the performance of the laryngeal functions. It 

 is covered externally by fibrous tissue and lined throughout by mucous 

 membrane continuous with that lining the pharynx and trachea. 



The larynx presents a superior or pharyngeal and an inferior or tracheal 

 opening. The pharyngeal opening is triangular in shape, the base being 

 directed forward, the apex backward. The plane of this opening in the 

 living subject is almost vertical. The tracheal opening is circular in shape 

 and corresponds in size with the upper ring of the trachea. Viewed from 

 above, the general cavity of the larynx is seen to be partially subdivided by 

 two membranous bands the vocal bands or cords which run from before 

 backward in a horizontal plane. The space between the bands, the glottis, 

 varies in size and shape from moment to moment in accordance with respira- 

 tory and phonatory necessities. The average width of the glottis, at its 

 widest part, during quiet respiration is about 13.5 mm. in men and 11.5 mm. 

 in women. With the advent of phonation the vocal membranes are at once 

 approximated, and to such an extent that the glottic opening is reduced to a 

 mere slit. It is then spoken of as the rima glottidis, or chink of the glottis. 



The space above the vocal bands, the supra-glottic or supra-rimal space, 

 is triangular in shape and extends from the pharyngeal opening to the plane 



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