. The bird, its form and function . FiG. 46.—Muscle-plates, or false vertebrse, of third-day embryo 25 diameters. esting to note that the vertebrse of the embryo chickpass through a stage w^hen they are biconcave,—a condi-tion found both in Amphioxus and Archseopteryx. This digression upon the back-bone history may seemout of place, but in reality such a birds-eye survey ofthe past, imperfect as it is, will add a new interest toour handful of chicken-bones. The Framework of the Bird 71 Let us suppose that we have strung a wire throughthe hollow centre of the back-bone of our ch
. The bird, its form and function . FiG. 46.—Muscle-plates, or false vertebrse, of third-day embryo 25 diameters. esting to note that the vertebrse of the embryo chickpass through a stage w^hen they are biconcave,—a condi-tion found both in Amphioxus and Archseopteryx. This digression upon the back-bone history may seemout of place, but in reality such a birds-eye survey ofthe past, imperfect as it is, will add a new interest toour handful of chicken-bones. The Framework of the Bird 71 Let us suppose that we have strung a wire throughthe hollow centre of the back-bone of our chicken, towhich the ribs are still attached, and that we have be-sides the skull and the bones of one wing and one them with those in the illustrations and we willsee if they can tell us aught of interest. The bones of the neck are all separate, and slide backand forth on the wire, like beads on a string. How unlike. Fig. 47.—Front and rear views of seventeenth and eighteenth cervical vertebraeof Ostrich, showing complicated saddles and sliding surfaces, giving greatfreedom of motion. • the long smooth ribs are these vertebrae, bristling withspines and projections! How is it that a bird can becomfortable with a string of such irregular-looking ob-jects run through its body? But fit two of these bonestogether and see how beautifulh^ they saddle end to end,every convexit} or projecting knob exactly adjusted toa corresponding concave portion of the neighbouring saddles are characteristic of birds alone. Everyone of the sixteen bones of the neck is different from its 72 The Bird fellows and exactly suited to the requirements of itsposition, but the first two following just behind the skullare so radically unlike the others that we know at oncethat they must serve some particular purpose. The firstis little more than a simple ring * of bone, and is calledthe atlas, after the mythological
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Keywords: ., bookcentury1900, bookdecade1900, bookpublishernewyo, bookyear1906
