The Breath of a Bird 173 



of song is not solved. The marvel of the Canyon ^^ ion's 

 melody becomes but the more wonderful; the voice of 

 the Seriema, carrying over a mile, and the never-to-be- 

 forgotten evening song of the Solitaire only impress us 

 with the failure of the scalpel and microscope to explain 

 more than superficially the varied expressions of life. 



Lungs and Air-sacs 



At the beginning of this chapter a bird was comj)ared 

 to an insect, and the reason will now be apparent. The 

 body of an insect is aerated b}' means of an intricate sj's- 

 tem of tubes ramifying throughout the bod\', wliicli in 

 many instances are connected with air-sacs. The com- 

 parison with a bird is not to its lungs, which are small 

 and comj^act, but to a series of nine air-sacs, distributed 

 through much of the body, — four pairs, and two which 

 have coalescetl into one. 



When a bird is dissected, the thin membranous walls 

 of these air-cavities are collapsed and rather difficult 

 to make out, being very similar in appearance to other 

 connective tissues of the body. But if we insert a small 

 blowpipe into the trachea of a dead bird, tie it tight 1}^ 

 about with a piece of string and blow into it, all the air- 

 sacs will become distended and bladder-like and can 

 easily be made out. It is remarkable how closel}' these 

 sacs fit around the viscera and muscles, occup}'ing e^'ery 

 crevice and fihing the whole body of the bird with air, 

 thus reducing its specific gravity, and making it a crea- 

 ture literally **of the air." There is sometimes a layer of 



