348 



PULMONARY MUCOUS TISSUE. 



Larynx. The larynx, which is the essential organ of 

 phonation, is only a portion of the trachea, modified in its 

 form, and in some degree, in its structure. In regard to 

 form, the trachea exhibits, in this part, a contraction, or kind 

 of strait, the dimensions of which may be diminished, or in- 

 creased to such a degree as to bring the trachea almost to its 

 original calibre. This narrowed passage, or laryngeal strait, 

 is multiple, as shown in the diagram (Fig. 84) of the vertical 

 section of the larynx. There are three constrictions, the 



first of which is circumscribed 

 (from top to bottom) ; by the 

 ari/teno-epiglottidean folds, the 

 second, by the false or superior 

 vocal cords (which are simply a 

 fold of the mucous), and the third, 

 by the true vocal cords / the latter 

 alone forms the veritable glottis, 

 or phonating aperture. In regard 

 to structure, we find the same ele- 

 ments in the glottis as in the 

 trachea, being modified in both to 

 answer a special purpose. Thus, 

 while the epithelium, throughout 

 the whole extent of the respiratory 

 tree, is columnar and vibratile, 

 that which is found at the spur 

 formed by the glottis properly so- 

 called, assumes the pavement form, 

 which is better suited to the func- 

 tions of the vocal cords. This 

 epithelial coat consists of more 

 numerous layers than the vibratile 

 epithelium, and is also better fitted 

 Fig. 85,-intrinsic muscles of the to prevent the drying of the edses 



larynx, seen from the side.* ~ " ... i i i 



of an onnce through which the cur- 

 rent of air passes with so great force. Below the mucous we 



* The left ala or wing of the thyroid cartilage (t) is disarticulated and cut 

 near its projecting angle, e, Epiglottis, cr, Cricoid. f, Thyroid articulating 

 surface, ar, Arytenoid cartilage, tr, Transverse arytenoid muscle, o, Oblique 

 arytenoid muscle, p, Posterior crico-arytenoid muscle. /, Lateral crico-aryten- 

 oid muscle, i, Inferior layer, and S, superior layer, of the thyro-arytenoid 

 muscle, car, eta, and cfr, Muscular fibres which are not constant, but extremely 

 variable, and are contained in the aryteno-epiglottidean folds, being known by 

 the name of thyro-epiglottidean muscles. (L. Mandl; " Traite" des Maladies du 

 Larynx.) 



