. Elementary biology, animal and human. Biology. 66 ANIMAL BIOLOGY are two bones. In the hand region, though the differences are more striking, the general plan of the two is the same. Unlike the bones of the human skeleton those of most bird^ are hollow and filled with air. Any one who has eaten a chicken's wing knows that the bones are covered by muscles; these enable the bird to fold and unfold the parts of the wing, much as the human arm is stretched out or doubled up. On the bird's body are other powerful mus- cles, which cause the wing as a whole to make the upward and downward strokes i
. Elementary biology, animal and human. Biology. 66 ANIMAL BIOLOGY are two bones. In the hand region, though the differences are more striking, the general plan of the two is the same. Unlike the bones of the human skeleton those of most bird^ are hollow and filled with air. Any one who has eaten a chicken's wing knows that the bones are covered by muscles; these enable the bird to fold and unfold the parts of the wing, much as the human arm is stretched out or doubled up. On the bird's body are other powerful mus- cles, which cause the wing as a whole to make the upward and downward strokes in fiight. Still another won- derful adaptation of the wing for flight is evident in the arrangement and structure of the feathers (Fig. 49). The feathers fit over each other in such. Fig. 48. — A, skeleton of arm of a man ; B, skele- ton of wing of an ostrich. (A. E. Rueff.) a way ^ that in the downward and backward stroke of the wing a continuous surface is struck against the air, and this propels the bird upward and forward. In the up- ' Before assigning these paragraphs the structure of a feather and the arrangement of the feathers on the wing of some bird ( a chicken) should be demonstrated to the 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 Peabody, James Edward, b. 1869; Hunt, Arthur Ellsworth, joint author. New York, The Macmillan company
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectbiology, bookyear1912
