. Outlines of zoology. Zoology. FLIGHT. 615 SC. amounting to nearly one-half in some pigeons. Buffon noted that eagles disappeared from sight in about three minutes, and a common rate of flight is about fifty feet per second. In migration many birds fly at a rate of from 100 to 200 miles an hour. (c) The skeleton.—The rigidity of the dorsal part of the backbone, due to fusion of vertebrae, is of advantage in afford- ing a firm fulcrum for the wing-strokes, while the arched clavi- cles (meeting in an interclavicle and often fused in front to the sternum) and the strong coracoids (which articula
. Outlines of zoology. Zoology. FLIGHT. 615 SC. amounting to nearly one-half in some pigeons. Buffon noted that eagles disappeared from sight in about three minutes, and a common rate of flight is about fifty feet per second. In migration many birds fly at a rate of from 100 to 200 miles an hour. (c) The skeleton.—The rigidity of the dorsal part of the backbone, due to fusion of vertebrae, is of advantage in afford- ing a firm fulcrum for the wing-strokes, while the arched clavi- cles (meeting in an interclavicle and often fused in front to the sternum) and the strong coracoids (which articulate with tr. the sternum) are adapted to resist the inward pressure of the down-stroke. As the keel of the breast- bone serves in part for the insertion of the two chief muscles, its size bears some proportion to the strength of flight. It is absent in the run- ning birds, such as the ostriches, and has degenerated in the New Zealand parrot (Stringops), which has ceased to fly and taken to burrowing. (d) Air-sacs and air-spaces.—The lungs of birds open into a number of air-sacs, which have a larger cubic content than the lungs, and in many cases these air-sacs are con- tinued into the bones, among the viscera, and even under the skin. From a broken bone it is possible to inflate the air-sacs, and through a broken bone a bird with choked. Fig. 270.—Pectoral girdle and sternum of swan. A part of carina removed shows peculiar loop of trachea (tr.); ct., clavicle; cor., coracoid; sc, scapula ; gl., glenoid cavity for head of humerus ; r., parts of sternal 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 Thomson, J. Arthur (John Arthur), 1861-1933. Edinburgh, Glasgow and London, H. Frowde and Hodder & Stoughton
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Keywords: ., bookauthorth, bookcentury1800, bookdecade1890, booksubjectzoology
