216 The Bird 
their cackling and beating their wings, they roused Mar- 
cus Manlius, a brave soldier and formerly consul, who, 
snatching up his arms and giving the alarm, flew to the 
ramparts, set upon the Gauls, and by precipitating one 
of them over the rocks terrified the rest so much that 
they threw down their arms.’’ So also Pliny, #lian, and 
Columella vaunt the hearing of Geese. But leaving leg- 
endary lore, it is certain that birds would not have the 
power of producing the most varied as well as the sweet- 
est sounds in all Nature, had they not been provided 
with powers of hearing, correspondingly acute and dis- 
criminating. 
The organ of hearing is complicated and there are 
many points about it which are still mysteries to scientists. 
The flap of skin to which we give the name of ear is 
entirely absent in birds, and indeed in ourselves is a very 
unimportant part of the auditory apparatus, serving 
only as a collector of sound-waves. The opening of the 
inner ear on each side ot the head, in birds, is usually 
protected by a cover of feathers which are bristle-like, 
partly denuded of barbicels, doubtless to avoid any muf- 
fling of sound-waves. In owls this opening is of very 
large size and protected by a movable flap of skin which 
may serve to aid in focussing the sounds from below— 
a very useful function to an owl at night, silently wing- 
ing its way over field and meadow in search of mice and 
other terrestrial prey. A rather singular fact is that in 
many owls the two ear-openings are unlike, one being 
larger and of a different shape from the other, and this 
asymmetry extends even to the form of the skull itself. 
