Excerpt from The Riverside Natural History, Vol. 4: Birds
A Bird is known by its feathers. Indeed, so distinctive is this sentence that it does not admit of a single exception, for no bird is without feathers, and no animal is invested with feathers except the birds. And so singularly adapted is this covering to the aerial habits of most of the members of the bird class, that its structure is nearly the same in all flying birds, while the only aberrant types of feathers are found in the ostriches, the kiwis, and the penguins, all of which are deprived of the power of flight. In the two first-mentioned groups the feathers resemble hairs more or less superficially, and the representatives of the last order present a plumage somewhat suggestive of scales, but both the hair-like and the scale-like appendages are in every respect true feathers. Not less remarkable as indicative of the perfection of the feather is the fact that the feathers of the oldest bird known, the fossil Arch?opteryx from Solenhofen, were essentially like those of the majority of existing birds, and that nature has not been able to improve much upon that admirable combination of lightness and firmness since the Jurassic period.
But the feather is not the only characteristic attribute of the birds, although it is the only one which at once distinguishes them from all other living beings. From the reptiles the feathered tribes differ, among other things, in possessing a complete double circulation of the blood, which is warm, while the absence of milk glands separates them widely from the mammals. Further characters which separate the birds from the mammals are the single condyle of the occiput, and the articulation of the lower jaw with a separate bone, the os quadratum, which again articulates with the skull. The absence of a diaphragm may also be quoted in this connection. In these and several other particulars the birds show a near relationship to the reptiles, so close, indeed, that they have been included with them in a separate group, Sauropsida; at any rate, the birds are more nearly related to the reptiles than they are to the mammals, notwithstanding the beak of the duck-mole and the recent re-discovery of the fact that the Echidna lays eggs, and whatever was the origin of the mammals, so much is certain, that they sprang from an ancestral stock with which the birds are only remotely connected. Their position between the reptiles and the mammals in our linear system does not indicate any intermediate position in nature, but is simply due to our inability of expressing exact relationships on a flat sheet of paper.
About the Publisher
Forgotten Books publishes hundreds of thousands of rare and classic books. Find more at www.forgottenbooks.com
This book is a reproduction of an important historical work. Forgotten Books uses state-of-the-art technology to digitally reconstruct the work, preserving the original format whilst repairing imperfections present in the aged copy. In rare cases, an imperfection in the original, such as a blemish or missing page, may be replicated in our edition. We do, however, repair the vast majority of imperfections successfully; any imperfections that remain are intentionally left to preserve the state of such historical works. Это и многое другое вы найдете в книге The Riverside Natural History, Vol. 4 (John Sterling Kingsley)