THE LARYNX, AND ITS ACTIONS. 305 



is certainly known. Hence it is, that on the theory of the production of what 

 are called falsetto notes, there is much difference of opinion amongst Physio- 

 logists. Some have contended, that these tones are produced by the vibration 

 of the vocal ligaments along only a part of their length ; but this is certainly 

 untrue. By Muller it is believed, that in the falsetto notes merely the thin 

 border of the glottis vibrates, so that the fissure remains distinctly visible; 

 whilst in the production of the ordinary vocal tones, the whole breadth of the 

 vocal ligaments is thrown into strong vibrations, which traverse a wider sphere, 

 so that a confused motion is seen in the lips of the glottis, rendering its fissure 

 obscure. That the tension of the vocal cords is not diminished (as it ought 

 to be if only a part of their length were being used), but is progressively in- 

 creased, as we pass from the ordinary to the falsetto scale, any one may convince 

 himself, by placing his finger on the interval between the thyroid and cricoid 

 cartilages, as formerly described ( 402).* A very important adjunct to the 

 production of the higher notes, has been pointed out by Muller, as being afforded 

 by the modification in the space included between the two sides of the thyroid 

 cartilage, which is effected by the thyro-arytenoidei. He had experimentally 

 ascertained, that the introduction of a hollow plug into the upper end of the 

 pipe beneath his artificial larynx (and therefore just below the reed), by dimin- 

 ishing its aperture, produced a considerable elevation of the tone. The action 

 may be imitated in the human larynx, when made the subject of experiment, 

 by compressing the thyroid cartilage laterally ; and in this manner, the natural 

 voice could be made to extend through a range that could otherwise be only 

 reached by a falsetto. 



411. The strength of the tone produced in the larynx is much increased 

 by the resonance of the elastic tissue, which it contains in various other 

 parts; but still more, perhaps, by that produced by the air in the trachea, 

 bronchi, and pulmonary cells. This comes to be of great importance in the 

 phenomena of auscultation. The aerial resonance is loudest, where any large 

 body of air is collected together, as in the trachea, the larger bronchi, an 

 emphysematous dilatation, or a cavity resulting from tubercular softening. On 

 the other hand, solidification of the pulmonary tissue will produce a resonance 

 of a somewhat different kind. The influence of the prefixed and superadded 

 tubes in modifying the tones produced by the Human larynx, has been found 

 by Prof. Muller not to be at all comparable to that which they exercised over 

 the artificial larynx; the reason of which difference does not seem very 

 apparent. It appears, however, that there is a certain length of the prefixed 

 tube, as there is a certain distance of the vibrating laminae, and a certain 

 length or form of the tube above, which is most favourable to the production 

 of each note ; and the downward movement of the whole vocal organ, which 

 takes place when we are sounding deep notes, and its rise during the eleva- 

 tion of the tones, have been supposed to have the purpose of making this 

 adjustment in the length of the trachea; but this requires the supposition that 

 the real length of the trachea is shortened whilst it appears extended, for 

 which there seems no foundation. It is considered by Mr. Wheatstone, that 

 the column of air in the trachea may divide itself into harmonic lengths, and 

 may produce a reciprocation of the tone given by the vocal ligaments ( 353) ; 

 and in this manner he considers that the falsetto notes are to be explained. It 



* That the falsetto voice differs in some essential particular from the natural, is evident 

 from this, that many persons who possess a considerable range of both, are yet unable 

 to unite them, so as to sing through the whole scale without a marked interruption. Thus 

 a gentleman of the Author's acquaintance has a bass voice, ranging from the lowest E oi 

 the Square Piano to the second D above; and a falsetto ranging from the A below this to 

 the E of the octave above, so as to give a compass of three octaves on the whole ; yet 

 the two registers cannot be smoothly blended. 



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