Indeed, nothing in the world of Nature is more wonderful than the gift of bird song, and nothing proves more clearly the doctrine of design, or, at least, of adaptation to a specialized purpose.
*Reprinted by permission from "The Evening Post," New York.
The question why man cannot fly may be answered in a very simple and yet satisfactory manner: He has not been organically constructed for that purpose. That may seem like cutting the Gordian knot, but, after all, it is the only explanation that can be given. You might as well ask why man cannot clutch a perch with his foot after the manner of a bird or a monkey, for the response would be the same--his foot was made for walking, and not for prehensile purposes. On the other hand, the bird cannot grasp an object with its wings, while a man's hand is well adapted for the performance of such a function. Nature's motto in her whole realm seems to be: "Every creature after its kind."
When we look at the structure of the flying birds, we see at once that they were formed for swift locomotion through the air, just as plainly as the lithe skiff was made to glide over the water or the carriage to spin over the land. In the first place, the body of the bird is comparatively light--that is, in proportion to the width, strength, and extent of its wings. By its thick, light, airy covering of feathers its body is made still more buoyant, besides presenting a larger surface to the supporting air with very little additional weight. The tail, too, with its long, closely woven quills spread out like a fan, not only serves the purpose of a rudder for guiding the aërial craft, but is still more useful in helping to sustain the bird's weight in the up-buoying element.
It is interesting to note that the feathers on the bodies of the flying birds are arranged in tracts, with intervals here and there of quite, or almost, bare skin, called "apteria." Now, when a bird is carefully skinned, it will be seen that the feathered spaces have their own special slips of muscles inserted into the roots of the feathers, and when these muscles are contracted, they serve to raise the feathers, and must, therefore, be of some subsidiary value in flying, by making the bird's body more buoyant. Suggestive, indeed, is the fact that the plumes of the non-flyers are not arranged in tracts, but are evenly distributed over the body.