136 THE STRUCTURE AND LIFE OF BIRDS cmap. 
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 
