Page:Natural History, Birds.djvu/20

Rh dense and powerful muscles of a hemispherical form, whose flat faces, coated with a thick skin, work over each other like a pair of millstones, and by the aid of small angular stones, sand, &c., swallowed for the purpose, grind down the hardest substances in a very short time.

With the exception of the beak and the hinder extremities, every part of a Bird is, for the most part, clothed with feathers. The feet are protected by a naked, scaly skin, which in some species extends partly up the leg (tibia). The soles of the toes are covered with a callous modification of this skin, having a granular surface. The plumage of Birds attracts universal admiration, for its beautiful fitness for the ends it answers, for its softness, its smoothness, its compactness, and for its ever varied hues. The most brilliant colours in nature are lavished upon the feathers of these tenants of the sky; embellished and set off in some instances with a peculiar reflection that rivals the lustre of burnished metals, or the radiance of precious stones.

Every one is familiar with the general form of a feather. "When a bird has just left the egg, its covering is a downy kind of hair, several little bundles taking their rise from one common bulb. This is the origin of the future feather. A dark cylinder soon makes its appearance, from the upper extremity of which the sprouting feather emerges, while the lower extremity receives the