THE BODY. 
3 
magnifying glass in their hand. Whoever would become 
familiar with the life of any animal must study the 
animal itself. Thus it is that we seek to make ourselves 
acquainted with the creature of wdiich we are now treat¬ 
ing, and to describe the gifts and properties with which 
nature has endowed it, so as to enable it to provide for 
its existence. 
The bird is essentially a creature of the air, in the full 
meaning of the word: the wide expanse of aether is its 
home; in this it lives, makes it a servant, and yet, on 
the other hand, is governed by it. The respiration of 
an animal, as is well known, serves principally to main¬ 
tain the temperature of the body. In the bird it has an 
accessory use : it enables it to fly and helps to support it. 
The air inhaled, in its passage through the lungs not 
only enters into chemical combination with the blood, 
but also distributes itself between and among the bowels 
through a number of sacs and cells almost all over the 
body. Most of the marrowless and the more cellular 
bones* also contain air. The lungs do not, as in mam¬ 
mals, hang free in a closed cavity of the chest, but lie 
flat, adhering in spongy masses to the inner surface of 
the back; with these the above-mentioned sacs and 
cells stand in either direct or indirect communication, 
as do also the empty spaces in the bones and the 
cellular tissue. The Pelican is furnished with a 
regular air-sac or pillow under the breast, and almost 
* The African Hornbills {Bucerotidce) afford some of the most curious examples 
of the distribution of air in and about the bodies of birds. Among these we find the 
shin almost totally detached from the flesh, being only connected with it by a 
number of fine filaments, especially along the sides under the wings. So light do 
these birds appear on the wing that they seem at times scarcely able thoroughly to 
control their movements; and their appearance, when perched on the top of a tree, 
suggests the idea of a child’s balloon attached to a stick.— W. J. 
