THE BODY. 
17 
few, as, for instance, the owls, that the external ear is in 
some way replaced by large folds of skin, which are 
surrounded by curious stiff feathers. In other birds the 
orifice of the ear is covered by feathers of a very loose 
texture, which do not deaden the sound. The drum of 
the ear lies flat, and is only connected with the small 
column by the otia or ear-bones. These correspond to 
the stapes in the Mammalia, and possess a longer stalk 
4 
or shank, which closes the little opening leading to the 
vestibule of the labyrinth. The cochlea of the ear is 
similar to that of mammals. When one takes into 
consideration the extraordinary development of the bird’s 
voice, it is not astonishing to find the sense of hearing 
in such perfection. All night-birds of prey take notice of 
the slightest sound. 
The eye, however, will always remain the most perfect 
of all the organs of the senses: from the beauty of the 
colouring, its brilliancy, its size in comparison with the 
skull and brain, and its third eyelid or nictitating mem¬ 
brane ; as well as from the faculty of an imvard spontaneous 
movement , ivhereby the bird can become long- or short-sighted at 
pleasure. The eyes are usually placed very much on the 
sides of the head. Some naturalists have thought necessary 
to gainsay the bird’s capability of commanding a larger 
field of sight than that immediately in front of the eye : 
anyone, however, who has observed, knows that a bird 
can see as well in front as at the side. The nictitating 
membrane is an almost transparent and highly elastic 
connecting skin, which can be drawn over the globe of the 
eye, and serves to mitigate the glare of the sun’s rays,* 
is almost continually in motion. For the modification 
of the focus they possess an apparatus consisting of 
* Possibly, also, for the removal of dust on the face of the lens.— W. J. 
D 
