-234 THE HUMAN BODY. 



organ -pipe; the air in breaking against it produced the 

 sound, the glottis being less open for acute than for grave 

 sounds. 



Dodart at the end of the seventeenth century, after hesi- 

 tating between the vibration of the air or the vibration of 

 the vocal cords as the origin of sound, compares the glottis 

 to the mouth-piece of a hautboy. This great physiologist, in 

 giving successive explanations, differing as widely as possible 

 from each other, of the phenomena of the voice, has advanced 

 or hinted at most of the theories which have been projected 

 since his time. 



In 1741 Ferrein compared the vocal cords to the strings 

 of a violin, the air acting as the bow. 



Biot could see nothing in the glottis which resembled a 

 vibrating cord. "The simplest principles of acoustics," said 

 this illustrious physicist, "are sufficient to make us reject this 

 strange opinion." Miiller advocated the theory of Ferrein 

 against that of Biot, and yet he admits with him and with 

 Magendie, Cagniard de la Tour, G. Weber, and other 

 learned men, that the glottis is a reed with two membranous 

 lips vibrating under the action of the air, and producing the 

 sound by their vibrations. 



Sa.vart compared the human glottis to a bird-catcher's 

 whistle surmounted by a supply-pipe, the cavities of the 

 whistle being represented by the ventricles of the larynx, the 

 openings by the interval between the vocal cords. The air 

 vibrated, he thought, in traversing the inferior glottis, and 

 divided into two columns against the superior vocal cords, 

 which act as the stop in an organ-pipe, one of these columns 

 of air in vibrating causes the resonance of the air in the 

 ventricles, the other causes the vibration of the air in the 

 vocal tube. In this last hypothesis it is not the vibration of 

 the vocal cords, but that of the air which produces the sound. 



The theory of Savart on this latter point has been admitted 

 by Longet and Masson. They believe the sound is pro- 

 duced at the orifice of the inferior glottis the same as at the 

 mouth-piece of wind-instruments, by the periodically variable 

 passage of the air, which becomes the seat of a vibratory 

 movement. The inferior vocal cords and the ventricles are 



