Title: The bird, its form and function
Year: 1906 (1900s)
Authors: Beebe, William, 1877-1962
Subjects: Birds Birds
Publisher: New York : Henry Holt
Contributing Library: Internet Archive
Digitizing Sponsor: Internet Archive

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this andthe wings of all other birds.t We have two separatebones in our thumb, and three in each of the next twofingers, and the bird has the same number, except inits third finger, in which there is but one. The principalvalue of this comparison is to show us that the bird,even in its most characteristic and specialized organ,—the wing, is not physically so unlike ourselves as wemight at first glance suppose. When a bird folds itswing against its body, the joints are bent sharply, andthe Z, formed by the elbow and the wrist, almost closesup. We can place our arm and hand in much the sameposition. If we move our arms slowly up and down, little bylittle greatly increasing the speed, we will realize howmuch greater strength and rigidity the whirring wings * Some morphologists homologize the fingers of a birds wing with thesecond, third, and fourth digits of a pentadactyl hand. The question is stilla mooted one. t In the embryos of some birds, traces of a fourth finger have been found.
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Fig, 70.—Skeleton of wing of Condor, compared with Fig. 71. $$Q. ; -i%f)y ?: ■■■. % At ■■■ ■■■■ ^iKi^s Fig. 71.—Skeleton of a mans arm; notice close correspondence of bones in thetwo. (The extended thumb of the human hand is not silhouetted againstthe background, and hence not very distinct.) 95 96 The Bird of a hummingbird or a grouse require than do the slowlyflapping pinions of a gull or an albatross. When wecompare the relative shortness of the upper arm-bone,or humerus, in the former groups with the long wing-bones of the sea-birds, we again realize what exquisiteadaptations exist everywhere in Nature. The proportionate length of the various parts of thefore limb of a bird forms an interesting corollary to itshabits of life. For example, the hand in penguins andin hummingbirds is very long indeed; while in the os-tr.ich the humerus is considerably longer than the fore-arm and hand combined. (Compare Figs. 269 and 272.) Before we leave the wing-bones, it wi

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