194 ANATOMY or THE DOMESTIC FOWL 



larynx and the esophageal margin, is marked by a second transverse 

 row of horny, filiform papilla, which point backward. There is 

 no epiglottis. The superior part of the Isnynx is pierced by an oval, 

 slit-like opening, the glottis, which is provided with two lips. These 

 when brought together, tightly close the glottis so that nothing can 

 fall through into the larynx in the act of deglutition. The margin, 

 or rim, of this opening is called the rami glottis. The glottis is con- 

 trolled by two pair of muscles. 



The superior surface of the larynx is somewhat triangular with the 

 apex directed forward. A few delicate, filiform papilla; are upon 

 its surface. The bird has, as already indicated, two lar}aixes, the 

 superior larynx located at the upper end of the trachea, and the 

 inferior larynx at the bifurcation of the trachea. The inner sur- 

 face of the superior laiynx is smooth and does not contain vocal 

 cords; it is in these animals simply a passage for air. It is joined 

 to the trachea inferiorly by a ligament, the crico-trachealis, and lies 

 at the base of the tongue supported by two cornua of the os hyoideum. 



The cartilages forming the principal support of the superior larynx, 

 consist of four pieces, as follows: one unequal ventral piece, two side 

 pieces, and one unequal dorsal piece. The cartilaginous, flat, 

 ventral cricoid, early in the bird's life, often becomes bony. The 

 side pieces are separated from it, only exceptionally fusing with it. 

 The dorsal cricoid piece also often becomes bony. The two aryte- 

 noid cartilages, joined with the cricoid superiorly, are three-sided, 

 and are united to each other in a sharp angle. They form the su- 

 perior opening of the superior larynx. 



The Trachea. — The trachea is cylindrical and varies in length in 

 different kinds of birds in accordance with the length of the neck. 

 It consists of from 90 to 120 cartilaginous rings, complete with the 

 exception of the two uppermost, which rings are held together by 

 intercartilaginous ligaments. The tracheal rings are constructed 

 of hyaline cartilage and the ligaments of fibrous tissue. It is lined 

 with a mucous membrane covered by columnar epithelium. The 

 trachea is a passage for air alone and terminates in the inferior 

 larynx. 



The Inferior Larynx. — The inferior larynx, called the true larynx 

 because it is the organ of voice, is located at the inferior end of the 

 trachea and the superior ends of the bronchi. By some anatomists 

 this organ has been called the larynx broncho-trachealis. The larynx 

 is flattened laterally in fowls. It contains two membranous folds, 



