FEBRUARY

The shaft is quadrilateral, with a smooth convex surface, and an opposite concave surface traversed by a longitudinal impre ion continued from the upper umbilicus. It is covered by an outer layer of firm horny material like that of which the quill is formed, and this incloses a soft elastic substance called the pith. The vane consists of barbs and barbules. The barbs are attached to the sides of the shaft, and consist of narrow elongated plates, arranged with their flat sides towards each other, and their margins in the direction of the external and internal sides of the feather. By this disposition they offer much resistance to being bent out of their plane, though readily yielding to any force acting upon them in the line of the stem. The barbules are minute and often microscopic proce es, given off from either side of the barbs, and arranged in a single series, just as the barbs are placed with reference to the shaft. In true feathers, they are short, stiff, and curved in opposite directions on opposite sides of the barb; and the concavities of one series of barbules interlock with those of the adjoining barbs, whereby the whole vane presents a continuous and resisting surface, as in the quill-feathers of most birds. When the barbules are long and disjoined, the feather is termed a plume; in the long dorsal plumes of the peacock, the barbules themselves are ciliated. In a few instances, as the apteryx and ostrich, the feathers are simple. In most birds each feather is complicated by a part termed the acce ory plume. • This is usually a small downy tuft; but it varies as to its size both in different species, and even in the feathers of different parts of the body of the same bird. In the body feathers of the hawks, grouse, ducks, gulls, ., the acce ory plume is generally well developed, and acquires in some species a size equal to that of the feather from which it is produced. In the emeu this is the case with the whole plumage, and the quill of each feather supports two shafts. In the ca owary there are two acce ory plumes, one of which is equal to the size of the original feather, the other is much smaller. Feathers vary in form, size, and function, in different parts of the bird, and have accordingly received distinct names in ornithological science. Thus the feathers which surround the external opening of the ear, and which serve to augment the intensity of sound, are termed the auriculars. Those which lie above the scapula and humerus are called the scapulars. The small feathers which are arranged in imbricated rows upon the bones of the anti brachium are called the le er coverts {tectrices primce); those which line the under or inner side of the wings are the under coverts. The feathers which lie immediately over the quill-feathers are the greater coverts {tectrices secundtE). The largest quill-feathers of the wing, which arise from the bones corresponding with those of the hand, are termed \}r\ma.r\e&{remiges primo res)\ those which rise from the ulna, towards its distal end, are the secondaries {remiges secondariee); those which are attached to its proximal extremity are the tertiaries {remiges tertia rice, seu parapterum). The quill-feathers which grow from the phalanx commonly called thumb form what is termed the bastard wing (alula spuria). The quill-feathers which are implanted upon the os coccygis are called rectrices. The development of feathers is always preceded by that of down, which constitutes the first covering of young birds. Each down-fasicle consists of a small quill, supporting a bunch of equal-sized finely-ciliated filaments. The down-fascicles are succeeded by the feathers, which they guide, as it were, through the skin; and the feathers of each succeeding plumage serve, during the moult, as the gubernacula of those which follow. The mechanism concerned in the formation of a feather is, as might be expected, of a very complicated character. It consists of vascular parts which secrete the material, and of moulds or capsules, in which the fluid material is thrown into the proper form; the whole is inclosed in an outer sheath, which is protruded with the new-formed feather from the skin, and wliich becoming dry and friable from contact with the atmosphere, crumbles away, and leaves the feather free to unfold its beautiful and complicated structure. Every feather, the eloquent Paley justly observes, is a mechanical wonder: " their disposition all inclined backward, the down about the stem, the overlapping of their tips, their different configuration in different parts, not to mention the variety of their colours, constitute a vestment for the body so beautiful, and so appropriate to the life which the animal is to lead, as that I think we should have had no conception of any thing equally perfect if we had never seen it, or can now imagine any thing more so." For the laws which regulate the varieties and changes of plumage, see Indumentum. [s. 455]