136 THE STRUCTURE AND LIFE OF BIRDS chap. 



delicate membrane, no doubt sensitive to sound, in 

 the corresponding place. But the distinctive pillars 

 or rods, leaning upon one another and forming arches, 

 are not there. It has been held, as I have said above, 

 that in those cells lies the power of distinguishing 

 nice differences of tone ; in fact, that when we say of 

 some one that he has " an ear for music," we speak 

 of what is supposed to depend on a high development 

 of the organ of Corti. And yet we cannot imagine 

 that birds can be such good singers without having 

 " good ears." Power of appreciation must accompany 

 power of song. The fact is that the ear, whether in 

 mammals or in birds, is an extremely complicated organ 

 about which there is much to learn, and the absence 

 of the pillars of Corti in birds is unexplained. 



There can be no two opinions about the acuteness 

 of birds' sense of hearing. It is fine to see an old 

 Heron, put on the alert, at the slightest sound of a 

 human foot, by his wary ears, turn in the direction 

 whence the sound comes his equally wary eye. The 

 Curlew is all ears. The Thrush hears the worm moving 

 beneath the ground and waits for his appearance above 

 the surface. 



The Organ of Voice. 



As I have said above, a bird's upper larynx at the 

 top of the trachea or windpipe has no vocal chords, 

 and is, therefore, incapable of producing sound 

 though tone may be raised or lowered by it. There 

 is a lower larynx, to which the name of syrinx is 

 commonly given, the mechanism of which is, in all 



