358 PULMONARY MUCOUS TISSUE. 



Voice and /Speech. The sound produced at the glottis is 

 only an inarticulate sound, differing only in intensity, pitch, 

 and tone ; yet this glottid sound, by the re-enforcement of 

 certain of its characteristics at the buccal and nasal cavities, 

 and by the union with other sounds produced at these points, 

 acquires special features constituting the voice and speech 

 properly so-called (see Organs of the Senses (Hearing} for tho 

 explanation of the words intensity, pitch, tone, sounds, etc.). 



The intensity of the sound produced in the glottis depends 

 on the force with which the expiratory current of air strikes 

 the edges of the glottis when so arranged as to emit any 

 decided sound ; this intensity depends essentially on the de- 

 velopment and the elasticity of the lung, the breadth of the 

 thoracic cage, and the force of the expiratory muscles. 



The pitch of the sound produced by the vocal lips increases 

 in proportion to their length and tension (or contraction) ; 

 thus the human voice performs the gamut or scale in passing 

 from the lower notes to the higher ; it even forms two series 

 of scales, the lower of which is generally designated under 

 the name of chest register (chest voice), and the sharper and 

 higher under that of head register (head voice). These ex- 

 pressions have no meaning in a physiological point of view, 

 since the voice is formed in the glottis in both cases ; but what 

 has given rise to them (and, in a certain sense, justifies the 

 use of them) is the sensations experienced during the emission 

 of either the so-called head or chest voice, the accompanying 

 vibrations being more strongly marked in the walls of the 

 chest in the one instance, and in the supra-laryngeal cavities 

 in the other. According to Mandl, the essential modification 

 in the glottis which produces the emission of sounds in the 

 two registers, consists in the fact that, in the case of the chest 

 voice, the orifice of the glottis is open and vibrates through- 

 out its whole extent, while in that of the head voice (or 

 falsetto) the orifice is open and vibrates only in the interliga- 

 mentous part; the entire intercartilaginous portion is then 

 closed, while the superior vocal cords sink, and are adjusted 

 to the inferior cords, covering a considerable part of them in 

 such a manner as to diminish the extent of the vibrating part 

 (an effect resembling that produced by the tongues employed 

 in the pipes of an organ). 1 



The human voice has, therefore, generally a range of two 



1 See also Ch. Bataille, " Nouvelles Recherches sur la Phona- 

 tion." Paris, 1861. 



