206 M. Savart on the Mechanism of the Human Voice. 



ced, may unite all the qualities which it possesses, it is neces- 

 sary that the tension of the extensible part of the sides of the 

 vocal tube has a proper relation to that of the sides of the 

 ventricles, and also to that of the superior and inferior liga- 

 ments ; and that the extent of the orifices, across which the 

 air escapes, may also vary, and so as to produce the best pos- 

 sible result. It is for these purposes that nature has formed 

 all these parts of elastic or muscular tissue. The thyro-ary- 

 tenoidian muscle forms of itself alone the lower and external 

 sides of the ventricle ; and it does not concur, as has been 

 supposed, in the formation of the superior liagment : Though 

 its form is sufficiently regular, yet it is difficult to describe it, 

 and even to dissect it well ; and, consequently, the descrip- 

 tions of it hitherto given are very incomplete, and often in- 

 correct. This muscle presents an internal face formed by a 

 plane of fibres almost parallel, and stretched between the su- 

 perior part of the re-entering angles of the thyroide, and the 

 inferior anterior part of the arytenoid. The upper margin 

 of this face, the plane of which forms, with the axis of the 

 trachea, an angle of from 20° to 25°, is united to the vocal li- 

 gament. The external face is inclined upon the internal one, 

 so that they leave between them an angle whose summit is 

 turned downwards. The fibres which form this second face, 

 stretch like a fan, and obliquely from above downwards, and 

 from before backwards ; and their upper extremities lose 

 themselves successively in all the extent of the large fold 

 formed by the mucous membrane between the epiglottis 

 and the arytenoid. Sometimes the most anterior stretch even 

 to the base of the epiglottis. These fibres, consequently, 

 rise much higher than those which form the internal plane, 

 and they again cover almost all the extent of the external 

 side of the ventricle, excepting in front and above, where they 

 seldom reach, on account of the obliquity of the kind of fan 

 which they form. In short, in the interval which the plane 

 of the parallel and internal fibres leaves between it and the 

 plane of the oblique external fibres, there is found a small el- 

 liptical cavity which forms the bottom of the ventricle, where 

 the fibres seem still to be arranged nearly parallel. The uses 

 of this muscle are easily conceived : When it contracts, it 





