58 THE STRUCTURE OF THE FOWL 



but has a horseshoe-shaped fold of mucous 

 membrane embracing its oral extremity. The 

 skeleton of the cranial larynx consists of 

 cricoid and arytenoid cartilages, both of which 

 undergo extensive ossification. The cricoid is 

 not in the form of a continuous cartilaginous 

 ring, but consists of four segments — a dorsal, 

 two lateral, and a ventral — arranged so as to 

 form a ring. The segments ossify early in life. 



The arytenoid cartilage consists of two 

 slightly diverging rays united by their oral 

 ends. The more ventral ray articulates with 

 the dorsal segment of the cricoid, and is almost 

 entirely converted into bone. The dorsal ray 

 remains cartilaginous. 



No thyroid cartilage and no vocal folds are 

 present in the larynx of the fowl. Obviously 

 the cranial larynx is not concerned in the 

 production of voice. 



A relatively long trachea, composed of com- 

 plete rings of cartilage united by narrow 

 membranous ligaments, connects the cranial 

 larynx with the caudal larynx or syrinx 

 (Fig. 12). Commonly, ossification takes place 

 in the ventral part of the tracheal rings. 

 Associated with the trachea are two pairs of 

 muscles. The ypsilo-tracheal muscles arise either 



