TONE OF THE VOICE. 467 



ment, and thus of favouring the production of the numerous tones of 

 which the voice is capable ; of augmenting the intensity of the vocal sound 

 by assuming a conical shape with a wide external aperture; of giving 

 rotundity and sweetness by the proper arrangement of its external 

 outlet, or of entirely arresting it by the closure of the outlet. The 

 larynx rises in the production of acute, and sinks in that of grave 

 sounds. The vocal tube is, consequently, shortened in the former case ; 

 elongated in the latter. It experiences, also, a simultaneous change 

 in its width. When the larynx descends, in other words, when the 

 vocal tube is elongated, the thyroid cartilage is depressed, and separated 

 ftxxm the os hyoides by the whole height of the thyro-hyoid membrane. 

 By this separation, the epiglottic gland is carried forwards, and lodged 

 in the concavity at the posterior surface of the os hyoides. The gland 

 drags after it the epiglottis; and a considerable enlargement in width 

 occurs at the inferior part of the vocal tube. The opposite effect re- 

 sults when the larynx rises. The use of the ventricles of the larynx, M. 

 Magendie 1 considers to be, to isolate the inferior ligaments, so that they 

 may vibrate freely in the air. Lastly; in this theory the epiglottis has 

 a use assigned to it which is novel. In certain experiments, instituted 

 by M. Grenie' 2 for the improvement of reed instruments being desirous 

 of increasing the intensity of sound without changing the reed in any 

 respect he found that, to succeed, he was compelled to augment gradu- 

 ally the strength of the current of air ; but this augmentation, by ren- 

 dering the sounds stronger caused them to rise. To remedy this incon- 

 venience, M. Grenie found nothing answer except placing obliquely in the 

 tube immediately below the reed a supple, elastic tongue, nearly as the 

 epiglottis is placed above the glottis. From this, M. Magendie 3 infers, 

 that the epiglottis may assist in giving to man the faculty of increasing 

 or inflating the vocal sound, without causing it to mount ; but, as Mr. 

 Bishop 4 properly remarks, neither the elevation nor depression of the 

 epiglottis can affect or regulate the vibrations of the glottis. 



Such are the main propositions of the theory of the voice by MM. 

 !Biot and Magendie. The larynx represents a reed with a double 

 tongue; the tones of which are acute in proportion to the decurtation 

 of the laminae; and grave in proportion to their length. They admit, 

 however, that, although the analogy between the organ of voice and 

 the reed is just, the identity is not complete. The ordinary reeds are 

 composed of rectangular laminae; fixed at one side, but loose on the 

 three others; whilst, in the larynx, the vibrating laminse, which are also 

 nearly rectangular, are fixed by three sides, and free by one only. 

 Moreover, the tones of the ordinary reed can be made to rise or descend 

 by varying its length ; whilst in the laminae of the larynx the width 

 varies. Lastly say they in musical instruments, reeds are never 

 employed, whose movable laminse can vary in thickness and elasticity 

 every moment, as is the case with the ligaments of the glottis ; so that, 



1 Precis, &c., i. 252 ; see, also, Sir C. Bell,Philos. Transact, for 1832; and Nervous System, 

 3d edit., p. 484, Lotid., 1837. 



a Biot, Precis Elementaire de Physique, p. 399. 



3 Precis, &c., i. 252. 



4 London and Edinburgh Philosophical Magazine, p. 205, for Sept. 1836. 



