rNDDLATORY FORCES. ACOUSTICS. 



[OKQAXS or voice. 



forms a Talre, which CM be brought over the glottis by 

 fine muscular fibre* attached at 6 and (No. 3). 



i .. i 



No. 1. No. J. 



Such, then, are the parts of the larynx which must 

 be explained to render the phenomena of voice in- 

 telligible. 



The larynx, like other organs of the body, is largely 

 applied with blood by the common blood-vessels. Two 

 nerves, on each side, are devoted to the actions of the 

 larynx. These nerves are from the eighth cerebral pair : 

 the superior laryngeal nerve, is expended chiefly on the 

 mucous lining of the larynx ; the inferior laryngeal 

 nerve, derived from the recurrent of the eighth pair, 

 ends minute filaments to the several muscles concerned 

 in the movements of the larynx. 



Besides the movements of the component cartilages 

 of the larynx on each other, attention must be paid to 

 the motion of the whole larynx upwards and downwards. 

 This motion takes place constantly in the act of degluti- 

 tion, but also, on many occasions, when the voice is 

 exercised, particularly in singing. When the whole 

 larynx is raised, the windpipe is drawn proportionately 

 upwards from the chest, and so put on the stretch. 

 This movement has unquestionably some effect in ex- 

 tending the compass of the voice. It was before stated,* 

 that the hyoid bone is connected to the protecting 

 cartilage of the larynx, and that when this bone ia 

 drawn upwards, the larynx is drawn upwards along with 

 it The hyoid bone is drawn upwards by muscles at- 

 tached in particular to the lower jaw, and also to the 

 temporal bone of the skull The hyoid bone' is drawn 

 downwards by muscles attached to the superior part of 

 the breast-bone and to the shoulder-blade. From the 

 upper part of the breast-bone a pair of muscles ascends, 

 to be attached to the thyroid cartilage of the larynx, 

 and a pair of muscles also extends between the thyroid 

 cartilage and the hyoid bone. Thus, ample provision is 

 mad* for the movement of the whole larynx in concert 

 with the movements of the hyoid bone. 



A few words must next be devoted to the cavities 

 through which the air passes outwards, after issuing from 

 the larynx. Behind the larynx, is the cavity of tho 

 pharynx, situated in front of the corvic.il vertebra;, and 

 ascending to tho inferior portion of tho base of the ukull. 

 This cavity, not improperly termed the posterior cavity 

 of tho mouth, communicates with the nostril above, and 

 on either fide, by a narrow canal, called the " Eu.st.i-lii.in 

 tube," with tho cavity of tho drum of tho ear. This 

 posterior cavity of tho mouth, is divided from th<- anterior 

 cavity by tho veil of the palate, a musculo-mombranous 

 movable curtain, which, by its motions, more or loss 

 completely divides the anterior from the posterior cavity 

 of tlie mouth. The movable, tongue-like valve, before 

 Pokes of, termed by anatomist* tho epiglottis (see Fig. 

 10, AT), overhang* the orifice of the larynx ; tho arches 



Set mnlf, p. 310. 



of the palate descend on either side, and are possessed 

 of a muscular character. From the union ol these 

 above, the uvula hangs down. The tongue, 

 free and movable in its anterior part, forms the 

 floor of the wholo passage between the root of 

 the epiglottis and tho incisor teeth of the 

 lower jaw. The muscular mass forming the 

 checks, contracts the cavity of the mouth on 

 tho aides; and tho lips, by their mobility, 

 i.sly modify the aperture by which tho 

 It Ism -. 



Thus the air issuing from the larynx, may 

 pass out either by the nostrils or tho mouth. 

 It passes out by the nostrils when tho mouth 

 is closed, or even when the veil of the palate 

 descends. When tho veil of tho palate is 

 raised, and the mouth is opened, a free passage 

 is afforded, through what has been called the 

 oral canal, outwards. The oral canal is mani- 

 festly capable of much greater modification, as 

 to size, than the passage of the nostrils. 



" The tonitur, the li|>, articulate; the throat, 

 With soft vibration, modulate* the note." DAKWIX. 



On the Human Voice. In tho investiga- 

 tion of the cause of the human voice, two 

 points in particular deserve attention : first, 

 the precise seat of the sounds ; and secondly, the mode 

 in which these sounds are produced. 



As to the first question, it is now determined, beyond 

 all doubt, that tho sound of the voice is generated in 

 the glottis, and neither above nor below that point. 

 Before going further, it should be remarked, that this 

 word glottis has not always been used in exactly the 

 same sense. "By turns," says the eminent French 

 physiologist, Adelon, "the superior aperture of the 

 larynx, its inferior aperture, and the intermediate space 

 between these two apertures, have borne the name of 

 glottis ; but, according to the etymology of the word, 

 derived from yXoaua the tongue, the speech no other 

 part of the larynx should be called by that name but 

 that where the vocal sound is formed ; and we shall seo 

 that that part is the inferior aperture or chink, "t In 

 this sense alone, then, the word glottis is here employed 

 namely, to signify the aperture between the two vocal 

 ligaments ; that is, between the two inferior vocal cords, 

 as they are sometimes called. 



Among the proofs that this chink, or glottis, is the 

 seat of voice, it may be mentioned, that if an aperture 

 exist in tho windpipe, tho sound of the voice ceases. 

 Such an aperture is frequently formed in man as a 

 surgical operation, and an opening has often been made 

 in the same situation in animals, for the purpose of ex- 

 periment When an opening exists above the glottis, 

 the voice is not lost Again, though the epiglottis, tho 

 superior vocal ligaments of the larynx, and the upper 

 part of the arytenoid cartilages, be injured, the voice is 

 not lost : moreover, in living animals, when the glottis 

 is laid bare, it is seen that the inferior ligaments of the 

 larynx which form the boundaries of the fissure termed 

 the glottis, are thrown into vibration. It is known, too, 

 that the division of the laryngeal nerves aupplyiug the 

 muscles, which regulate tho states of tho aperture, and 

 make tho vocal cords tense, destroys the power of pro- 

 ducing vocal sounds. It is also found, that sounds can 

 be produced in the dead human body, by forcing a cur- 

 rent of air from the windpipe through the larynx, pro- 

 vided tho vocal cords be in some degree tense, and the 

 glottis narrow. The larynx has be^i cut from the body, 

 and frn ! from all tho parts in front of the glottis ; thus, 

 the epiglottis, tho upper vocal hgatnonts, and tho von- 

 of tho 1 twoon the superior and infe- 



>r vocal ligaments, tho greater part of the aryto- 

 eartilagos nai v be 



in short, if nothing remain but the inferior 

 ligaments, or vocal cords, and tncse bo so approximated 

 that (lie jjluttis .shall bo narrow, clear tones will bo pro- 

 duced by forcing air through it from the vimlpipe. 

 Such facts as these entitle us to regard tho glottis and 

 nyiiolofit it L'Uommt, 11, 2i. 



