Mechanism of the Larynx. 329 



of a pair of ligaments, like those constituting the glottis, that a 

 current of air be passed between them, but that their opposite 

 surfaces must also be placed in a given position with respect to 

 each other. 



For instance, Fig. 5 is the ordinary position of the ligaments 

 GG, in which the breath passing between them could never pro- 

 duce a sound from them, they being inclined from each other. 

 Whereas, in Fig. 1, where they are parallel, the breath would 

 instantly excite vibrations in them. 



Here we have a solution of a difficulty which never seems to 

 have occurred to former writers ; that is, why the ligaments are 

 silent while the ordinary breath passes between them. It cannot 

 be because their tension is not sufficient, because I shall shew 

 that they are always in a state of tension nearly corresponding 

 to the pitch of the speaking voice. 



To shew how the same pair of ligaments may produce various 

 notes, let a wooden pipe be prepared of the form Fig. 19, having 

 a foot C like that of an organ pipe and an upper opening, long 

 and narrow as at B, with a point A rising at one end of it. If 

 a piece of leather, (or, still better, of Hancock's sheet India rubber,) 

 be doubled round this point and secured by being bound round 

 the pipe at D with strong thread, as in Fig. 20, it will give us 

 an artificial glottis with its tipper edges GH, which will vibrate 

 or not, at pleasure by inclining the planes of the edges, according 

 to the previous experiments. A couple of pieces of cork EF 

 may be glued to the corners to make them more manageable. 

 From this machine various notes may be obtained by stretching 

 the edges in the direction of their length GH ; the notes rising 

 in pitch with the increased tension although the length of the 

 vibrating edge is increased. It is true that a scale of notes of 



