334 VOCAL APPARATUS. L,ECT. XVIII. 



proceeds from the bronchi and terminates in the mouth. 

 To determine more accurately its position, we have only to 

 observe that if an opening be accidentally or purposely 

 made in the trachea of a man, below the larynx, it is im- 

 possible to produce a sound ; but, if we close the opening, 

 the power of producing the voice immediately returns. If, 

 however, the opening be made above the larynx, the voice 

 remains as before. In birds the organ of voice is situated 

 at the bifurcation of the trachea ; that is to say, it occupies 

 a lower situation in them than in mammals ; and, hence, 

 after cutting off' the head of a bird, we may still succeed in 

 obtaining sounds by the compression of the thorax. 



We shall describe the vocal organ of man as being the 

 most complicated and the most perfect. The trachea is a 

 species of tube formed of cartilaginous rings, separated from 

 each other by membranous and flexible rings. The lower 

 end of this pipe divides into two branches, which subse- 

 quently ramify in the parenchyma of the lungs, somewhat 

 like the branches of a tree. The upper part of the pipe 

 opens in the buccal cavity, and is terminated by the larynx, 

 the true organ of voice. We may regard the larynx as a 

 continuation of the trachea, but with this difference, that 

 the portion of the tube, composing it, is broader, and is 

 attached to the os hyoides. It consists of four cartilages ; 

 namely, the cricoid, the thyroid, and the two arytenoid. 

 They are of very different shapes, are articulated one to the 

 other, and are united to the upper ring of the trachea. 

 Several muscles are attached to the larynx, and by their 

 contraction the entire larynx, or some of the cartilages 

 composing it, are moved. The mucous membrane lining 

 the larynx, forms, at about the middle of this organ, two- 

 large lateral folds directed transversely, and which have the 

 appearance of a button hole : these folds are called the vocal 

 cords, or the inferior ligaments of the glottis. Above them 



