VOICE AND SPEECH. 871 



the number and relative prominence of the various overtones determined by 

 altering the shape and size of the nasal and buccal resonance-chambers. 



By a simple experiment the production of voice by the vocal cords can 

 easily be illustrated. Take a glass tube, about J inch in diameter and of con- 

 venient length, and press one end firmly against the palmar surfaces of the 

 proximal phalanges of two fingers at their line of division when they are 

 brought together. By blowing smartly into the other end of the tube, a 

 musical note will be produced by the vibration of the folds of the skin be- 

 tween which the air is forced. By relaxing the pressure with which the 

 fingers are held together, the length of the vibrating segment of skin is in- 

 creased and its tension diminished; its note is accordingly lowered. The 

 reverse conditions are produced when the fingers are held together tightly and 

 the tube applied firmly ; the pitch of the note is then raised. In these ways 

 the pitch of the note may be varied through two octaves, which is the range 

 of a good singing voice. Various upper partials of the note so produced may 

 be made prominent by sympathetic resonance, if the vibrating air-stream is 

 sent across the opening of a wide-mouthed bottle, of about a pint capacity. 

 The air within the bottle is thrown into sympathetic vibration when its funda- 

 mental tone is contained in the note emitted through the fingers ; when the 

 volume of the air is diminished by slowly pouring water into the bottle, the 

 fundamental tone of the resonator is changed, and it responds to one after 

 another of the partials contained in the musical note. 



The marvellous adjustment of muscular action by which, at will, notes 

 may be struck of definite pitch and quality, is evidence of an elaborate 

 nervous machinery for the larynx, not only on the efferent side but, possibly 

 through a muscular sense, on the afferent side as well. The various phe- 

 nomena of aphasia, and the anatomical importance of the cerebral areas 

 devoted to the elaboration of speech, point in the same direction. The 

 relations between the centres for speech and hearing are most intimate, The 

 ear plays a constant part, as a critical medium, in the tuition of the vocal 

 organs in either speech or song. So-called " dumbness " is the result, usually, 

 not of defects in the vocal organs, but of lack of hearing and, hence, of 

 inability to control by the ear the pitch or quality of the vocal notes. 



The voice and the larynx of the child fall naturally in a group with those 

 of the female as contrasted with the adult male. At the age of puberty a 

 boy's larynx becomes congested and undergoes rapid development. The voice 

 changes rapidly from the juvenile to the adult quality. During this change, 

 the voice frequently " breaks " or rapidly returns from the newly-acquired 

 chest register to the head or falsetto notes of childhood (see p. 873). In boys 

 who are castrated a good while before the age of puberty is reached, the larynx 

 does not undergo its characteristic development, and the voice remains of a 

 peculiar quality, much valued in some countries in the rendition of vocal 

 music. The practice of castration for a3sthetic purposes has, accordingly, in 

 certain districts, long been in vogue. In the female the changes in the larynx 

 and in the voice at puberty are much less marked than in the male. 



