276 Researches into the Physiology of the Human Voice. 



The effects of these variations on the tones of the voice have 

 been hitherto little understood. It has always appeared in- 

 comprehensible why the vocal tube should apparently increase 

 in length in the production of the acute tones, and shorten in 

 the grave *, a circumstance which, theoretically, presents an 

 acoustic paradox. Dodart and many others have conceived 

 the elevation of the larynx to be merely for the purpose of 

 shortening the vocal tube in the super-laryngeal cavity, and 

 have considered the trachea as producing no effect on the key 

 of the tone, an error which has already been pointed out by 

 Mr, Wheatstone. 



Magendie's remarks on the shortening of the vocal tube ap- 

 ply only to the approximation of the thyroid-cartilage to the 

 OS hyoides. 



In order to ascertain the effect of these changes, I made the 

 following experiments on the dead body : having laid bare 

 the vocal organs of an adult male, I raised the larynx to the 

 position it would occupy by the elevation of the voice an oc- 

 tave, being about half an inch, and at the same time minutely 

 observed the position of the lowest ring of the trachea in re- 

 ference to the sternum. By this operation I found the trachea 

 was raised out of the chest, nearly to the same extent as the 

 larynx had been elevated towards the base of the skull. My 

 next step was to examine whether any change had taken place 

 in the diameter of the tube. Having for this purpose mea- 

 sured the diameter of the trachea in its natural position, I 

 again elevated the larynx to the same extent as before, and 

 found the diameter diminished one third. These experiments 

 prove that, contrary to the general preconception, the eleva- 

 tion of the larynx shortens the tube independently of the con- 

 traction between the thyroid cartilage and os hyoides, and at 

 the same time lessens its diameter. 



The same effects may easily be detected during life by 

 placing the finger on the trachea immediately above the ster- 

 num during the elevation of the larynx, when the trachea is 

 found to ascend out of the chest, and afterwards to return to 

 its former position, a movement in which the lungs and bron- 

 chii participate. The alteration of the tube in diameter may 

 also be perceived by grasping the trachea with the finger and 

 thumb during the elevation and depression of the larynx. 



Such are the principal means provided for adjusting the vi- 

 brations of the vocal tube to those of the glottis ; but as the 

 variation of length is not sufficient to render the tube capable 

 of adjusting itself to the whole range of tones, the relative ten- 

 sion of its siiperficies supplies the deficiency. The influence 

 * Sec Richerand, p. 440. 



