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and posterior margin of this cartilage are seated two small solid 

 triangular bodies, named the arytenoid cartilages, and the 

 entire is embraced and protected in front and on the sides by 

 a large shield-shaped cartilage, the thyroid ; in this manner 

 the skeleton of the larynx is constructed. 



" The base of each arytenoid is concave and of a triangular 

 figure, with two of the angles (the anterior and external) so pro- 

 longed as to represent two little processes, which we shall desig- 

 nate spurs; the external spur receives the insertion of two mus- 

 cles, and from the anterior spur of each cartilage there passes 

 forwards a remarkable cord, which attaches itself in front to the 

 thyroid cartilage. The cords are highly elastic, and it is the 

 varied tension and vibrations of these, the vocal cords, which 

 produce the several intonations that admit subsequently of 

 being fashioned into those articulate sounds of which language 

 is formed. 



" The interval between the vocal cords and the inner 

 margins of the base of the arytenoid cartilages is named the 

 rima or chink of the glottis, which in a state of repose (none 

 of the laryngeal muscles being in action) is of the form of the 

 head of an ancient halbert ; and mark, while in this position, 

 the surfaces of the cords are inclined j^om each other, and the 

 cords are in a state of relaxation. A column of air, though 

 even propelled with force through the rima, under these cir- 

 cumstances, does not produce any distinct sound. For the 

 production of an intonation, two conditions are required, 

 namely, that a certain amount of tension be communicated to 

 the vocal cords, and, above all, that the surfaces of the vi- 

 brating material be inclined towards each other, or, at all 

 events, that their planes should become parallel to the axis 

 of the column of air ascending through the tube ; for the 

 slightest inclination of the surfaces from this axis completely 

 prevents any sonorous vibration from being produced. In 

 order to illustrate this fact I have arranged a rough expe- 

 riment. Here are two tubes closed at one extremity, with the 



