DISKASBS OF PODI,TRY. 



27 



irately moldad to the inequalities of the ribs and the 

 spaces between the ribs. 



Notwithstanding these resemblances to the sluggish 

 cold-blooded animals, the bird's breathing apparatus 

 is of the highest order of excellence, and wonderfully 



effective. The lungs are 

 comparatively small and 

 have little elasticity, but 

 there is a compensation for 

 these features in the free 

 communication with the 

 spacious air sacs which 

 contain an abundant supply 

 of air. 



The upper opening of the 

 trachea or windpipe is on 

 the floor of the mouth just 

 behind the tongue. The 

 larynx at the beginning of 

 the windpipe, which is such 

 a perfect structure in the 

 higher mammals, is in birds 

 only slightly developed. 

 The ed-ges of the larynx ap - 

 pear to close together so 

 perfectly that n o epiglottis 

 or lid is necessary. There 

 are no vocal cords in the 

 larynx as in mammals, and 

 therefore this organ can not 

 produce voice, and it only 

 raises or lowers a note by bringing together or separat- 

 ing the stiff margins of the opening. The true organ 

 of voice in birds is the lowerlarynx or syrinx, which is 



Fig-. 1. — I/ungs of a Bird. 

 A. — Lower Surface. 

 B. — Upper Surface. 



