VIII THE VOCAL AND RESPIRATORY ORGANS 165 



CHAPTER VIII 



THE VOCAL AND RESPHIATORY ORGANS 



In the vertebrate animals the vocal and respiratory organs 

 are intimately associated owing to the fact that the produc- 

 tion of sound is caused by the expulsion of air from the lungs. 

 With the exception of the sounds made by a few fishes the 

 voice makes its first appearance in the vertebrate series 

 among the Amphibia. In the Urodeles, or lowest division 

 of the group, the voice is, as a rule, feebly developed 

 or entirely absent. It attains its maximum development 

 among certain of the Anura, but in not a few members of 

 this order it is small and weak. 



The Vocal Apparatus. — The sound-producing organs of 

 the frog are located in a sort of box called the laiynx, situ- 

 ated just below the pharyngeal cavity at the beginning of the 

 entrance into the lungs. The larynx opens into the pharynx 

 through the slit-like glottis above, and by a pair of openings 

 behind, into the lungs. It is held between the stout, bony 

 thyroid processes of the hyoid apparatus, to which it is at- 

 tached by muscles as well as connective tissue. The skele- 

 ton of the larynx is composed mainly of the cricoid and 

 arytenoid cartilages. The former consists of a slender ring 

 surrounding, the larynx and lying in nearly the same plane 

 as the thyroid processes of the hyoid, to which it is closely 

 attached ; at its posterior end it is produced into a spine 

 which extends backward between the lungs. P>om near 

 the middle of its ventral surface it gives rise to a sort of 



