. The infancy of animals. Animal behavior; Natural history. YOUNG BIRDS AND RECORDS OF THE PAST 135 already been furnished on a previous page : this may now with profit, be supplemented by what is revealed in the skeleton. The wing of the bird is a unique structure, and all that concerns us here is the matter and the manner of its be- coming, so to speak, so far as we can glean from the evidence of the developing skeleton, displayed during the embryonic and early post-embryonic stages. But three of the originally five digits of the hand now remain, and these D^ M'l ^« V. WING OF A YOUNG RHEA O
. The infancy of animals. Animal behavior; Natural history. YOUNG BIRDS AND RECORDS OF THE PAST 135 already been furnished on a previous page : this may now with profit, be supplemented by what is revealed in the skeleton. The wing of the bird is a unique structure, and all that concerns us here is the matter and the manner of its be- coming, so to speak, so far as we can glean from the evidence of the developing skeleton, displayed during the embryonic and early post-embryonic stages. But three of the originally five digits of the hand now remain, and these D^ M'l ^« V. WING OF A YOUNG RHEA OR SOUTH AMERICAN OSTRICH. have undergone profound modification to fit them to support the strong quills which bear the brunt of the strenuous movements during flight. So that in the adult we find but two separate wrist-bones, instead of several as in the reptiles, while the palm-bones have become welded together to form a brooch-shaped structure. The finger-joints have become reduced in number and changed in shape. Of the thumb, commonly only one remains : of the first finger there may be three, while the third finger is represented only by a small nodule of bone. Some birds yet retain vestiges of a claw on the thumb,. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Pycraft, W. P. , (William Plane), b. 1868. London, Hutchinson & Co.
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Keywords: ., bookcentury1900, bookdecade1910, books, booksubjectnaturalhistory
