Are Birds Singers or Whistlers? 175 



plied with an intricate set of muscles by which it can be 

 shortened or elongated at the will of the songster himself. 



Now let us look at the upper end of this wonderful 

 pneumatic pipe, which so often throws Pan and all his 

 coterie into a transport when the thrasher and the wood 

 thrush flute their dithyrambs. Here we find the larynx. 

 It is simply the anterior specialized portion of the trachea, 

 located at the base of the tongue, and in mammals is 

 honored as the voice organ, whereas in birds it is distin- 

 guished as the fluting apparatus, the instrument that 

 really produces the varied vocalization of the bird realm. 

 But the music is not the product of vocal cords, as is the 

 case in the human larynx, for at the upper end of the 

 avian larynx there is a slit or fissure, somewhat elliptical 

 in form, and set in the fork of the hyoid bone, which con- 

 stitutes the bifurcated root of the tongue. This fissure 

 is called the glottis. At the bird's fiat, it can be opened 

 and closed and made to assume a great variety of forms. 

 Moreover, just in front of it there is a fold of mucous mem- 

 brane called the epiglottis, which is in reality a tiny trap- 

 door closing over the opening when necessity requires. 

 When the bird swallows food or drink, this little flap shuts 

 down, and prevents the entrance of any clogging substance 

 into the windpipe to choke the feathered diner. 



We have now come to the most strategic point in our 

 investigation of the anatomy of bird song, for in the avian 

 world a special distinction has been conferred upon that 

 little orifice in the bird's throat called the glottis. It is 

 here that all the music, as well as all other so-called vocal 



