annot escape at the sides, then blow the air down through the
tube, and you will be able to follow the passage of the air into the
skin and other parts of the body. Now, if you will cut off one of the
bones, you can detect the air passing from the cut surface; and, more
than that, as a scientific English writer says, "if the experiment be
made by using colored fluid instead of air--which is pumped in by a
syringe--the fluid can be seen to ooze from the ends of any bone or
muscle that has been cut across." Thus it is seen that the whole body
of the fowl is so constructed that it can be pervaded with air.

However, while all parts of the bird's organism combine to produce the
end in view, the special instruments of flight are the wings. They are
really the fore limbs of the fowl, but differ in many respects from the
fore limbs of the mammals. They are under the control of muscles of
great comparative strength, as every one knows who has ever been beaten
by the wings of even an ordinary barnyard fowl, which has meagre powers
of flight. What a powerful stroke a large hawk or an eagle must be
able to deliver! If man's arm muscles were as strong in proportion, he
might have some hope of one day navigating the air on artificial wings,
but it is due principally to this muscular weakness that Darius Green
has never been able to make a success of his flying machine, and
perhaps never will. He would not have the strength to wield wings
large enough to sustain so much avoirdupois on the yielding air.

The wings are highly specialized members of the avicular organism, and
hence differ in many important respects from the fore or pectoral limbs
of the mammals. Beginning at the point nearest the body, let us
examine one of these wonderful instruments. The wing proper begins at
the shoulder joint, which hinges freely upon the shoulder in a shallow
socket, into which the globular head of the first bone fits closely,
and in which it is firmly held by the powerful muscles that control the
organs of flight. The first bone is called the humerus, and is the
largest and strongest bone of the wing, extending from the shoulder to
the elbow. At the elbow, which is the first angle of the wing,
reaching backward when the wing is folded, the humerus articulates in a
wisely designed way with two other bones, called the ulna and radius,
which together constitute the forearm and extend to the wrist joint.
It must be remembered that, when the