Year: 1878

| ~. Nicnolilt Ioi september


The chief peculiarity Of birds Is


their power Of flight, and although


there are few birds which do not


fly, most of them do, and the various


organs Of their bodies are all con-


structed in such a way as to TT them
for life in the air. Their bodies


are very solid and compact, in order
! that most of their weight shall be


near the place where their wings are


attached. The feet, legs, head and


neck are light, aud so arranged


that they may be drawn up close Go


the body while the bird Is flying.
As the neck is long and very flexible,


the body does not need to be plant,


as with most creatures having back


bones but it is important that the


wings should have firm support,


so the bones Of the back are united.


The body Of the bird must also be


well protected from the cold for as


it ascends and descends= through


the air, il passes through different


temperatures, and il must be pro-


vided with thick warm covering


in order TO be able TO endure these


sudden changes, and one Also which


shall be very light and able TO shed


the water; for, otherwise, a bird


would be unable TO lily. The feathers


of a bird answer all these needs,


and are 50 placed upon the body


that they form q smooth surface


which does not catch against the air


when bird is passing through il.


In its rapid ascents and decenls, the


bird is exposed 10 another danger
even greater than thesudden changes
of temperature. You all know that
air presses in every direction with
great force, and that we do not feel
ii because there is air i'm all parts OF
our bodies as well as outside them.
and the pressure of the air inside
exactly balances that of the outside
air. If we should suddenly take
away the outside air in any way,
such as covering a person up with
an air-pump and receiver, and
quickly and completely exhausting
the air, the consequences of the in
side pressure would be very terrible,
and if the experiment could be tried
quickly enough the body would
burst like an eXloding gun, with "a
loud noise.


When people go up rapidly in a
balloon, or climb very high noun
tains, they are troubled BY ring
ing noise and a feeling of great
pressure in the ears and head, and
by palpitation of the heart, bleeding
at the nose, and flinting. These
unpleasant and often dangerous
symptoms are caused by the expan-
sion of the air inside their bodies.
In ascending very high mountains
it is necessary to go We. yslowly and
to stop very often, to give time for
some of the expanded air TO escape,
and equalize the pressure again.
Now, many birds, the Condor for
fly over the tops Of the
highest mountains, and nearly all
birds, either occasionally or habit
ually, ascend to very great attitudes,
and, unless there were some plan
for regulating the pressure of the air
inside their bodies, they would
suffer great Inconvenience and pain
and danger. But they are provided
with an arrangement by which the
air within them can escape easily as
it expands and thus keep the pres
sure within just equal to that out
side, so that they can ascend and
descend aus rapidly as they
wish, without feeling the least i'm
convenience. In the body of the
bird there are several large bag,
like the lungs. called mir chambers;
many of their bones are hollow, and
others are pierced with long wind
ing tubes called air tubes. All these
air chambers and air-tubes are con-
nected with the lungs SO that air
can pass into and out of them at
each breath. The connection be-
tween these chambers and the lungs
IS so complete that a wounded hawk
can breathe through broken wing
almost as well as through is mouth.
When a bird mounts upward, the
iir inside its body gradually eX-
Dands, but the bird does not feel any
inconvenience for, at each breath,
part of the AIR passes from the
into the lungs, so that
he the pressure on the inside does
not become greater than that on the
outside.