OF THE LARYNX, AND ITS ACTIONS. 849 



given by Professor Czermak possesses considerable interest, since it fully 

 corroborates the views derived from theory and experiment on the dead 

 subject, which had been expressed before the introduction of the instrument. 

 As soon as we wish to utter a sound, the two arytenoid cartilages raise them- 

 selves in the fold of mucous membrane which covers them, and approach one 

 another with surprising mobility. This movement effects the approximation 

 of the vocal cords, and consequently the constriction of the Glottis (Fig. 303). 

 The study of the mode of formation of the gravest chest-sounds is extremely 

 difficult, on account of the arytenoid cartilages becoming elevated and rapidly 

 approaching one another until they come almost into complete contact, whilst 

 they bend under the border of the depressed epiglottis in such a manner that 

 the latter, as viewed by the laryngoscope, entirely conceals the interior of 

 the Larynx. According to Mandl 1 the opening of the glottis in the produc- 

 tion of the deepest notes is ellipsoidal. During the emission of the most 

 acute sounds, the Glottis is contracted in a 

 linear form (Fig. 304) ; on each side we per- FlG - 304 - 



ceive the vocal cords, distinguished by their 

 whitish-yellow color, and a little to the outer 

 side is a narrow groove indicating the position 

 of the ventricles of Morgagni. Further out- 

 wards again are the false or superior vocal 

 cords. These parts, with the erected aryte- 

 noid cartilages, the epiglottis pulled upwards 

 and forwards, and the aryteno-epiglottidian lig- Condition of the Larynx during the 

 aments, together form a short and stiff tube emission of a high or acute sound :e , 

 situated above the Glottis ; the whole appearing, jJJ^Vi^S * '1 

 from the sensation we experience during the ex- cor d. 

 periment, to be in a state of very great tension. 2 



That the aperture of the glottis is greatly narrowed during the production 

 of sounds, is easily made evident to one's self, by comparing the time oc- 

 cupied by an ordinary expiration, with that required for the passage of the 

 same quantity of air during the sustenance of a vocal tone. Further, the 

 size of the aperture is made to vary in accordance with the note which is 

 being produced ; of this, too, any one may convince himself, by comparing 

 the times during which he can hold out a low and a high note ; from which 

 it will appear that the aperture of the glottis is so much narrowed in pro- 

 ducing a high note, as to permit a far less rapid passage of air than is 

 allowed when a low one is sounded. According to Kempelen no sound is 

 elicited when the distance between the Chordae Vocales exceeds T 1 th to ylith 

 of an inch. The muscular movements concerned in the act of vocalization, 

 appear to be called forth by the instrumentality of the motor fibres, partly 

 derived from the Spinal Accessory nerve, which are contained in the Pneurno- 

 gastric ( 496). 



694. We have now to inquire what is the operation of the Vocal Cords in, 

 the production of sounds : and in order to comprehend this, it is necessary 

 to advert to the conditions under which tones are produced by instruments 

 of various descriptions having some analogy with the Larynx. These are 

 chiefly of three kinds : strings, flute-pipes, and reeds or tongues. The Vocal 

 Ligaments were long ago compared by Ferrein to vibrating strings; and at 

 first sight there might seem a considerable analogy, the sounds which both 



1 Wien. Acad Sitz.-ber., Bd. Ixii, p. 764, and Traite pratique des Maladies du 

 Larynx et du Pharynx, Paris, 1872. 



2 On the Laryngoscope, Syd. Soc. Trans., 1861, pp. 87-8; see also The Laryngo- 

 scope, by George D. Gibh, M.D , London, 1863. Morell Mackenzie, M.U., The Use 

 of the Laryngoscope, 3d edit., 1869. 



