The Probert Encyclopaedia of Nature

FEATHER

Feathers are the form which the dermal appendages assume in birds, agreeing in mode of development, but differing in form from hairs and scales. The feather consists of a stem, horny, round, strong, and hollow in the lower part, called the quill, and in the upper part, called the shaft, filled with pith. On each side of the shaft is a web composed of a series of regularly-arranged fibres called barbs. The barbs and shaft constitute the vane. On the edges of the barbs are set the barbules, which interlock with those of adjacent barbs, and thus give strength to the vane.

Feathers are generally divided into two kinds, quill feathers in the wing or tail, and plumes or clothing feathers generally diffused. The feathers of birds are periodically changed, generally once, but in some species twice a year. This is called moulting. When feathers have reached their full growth they become dry, and only the tube, or the vascular substance which it contains, continues to absorb moisture or fat. When, therefore, part of a feather is cut off, it does not grow out again;
and a bird whose wings have been clipped remains in that situation until the next moulting season, when the old stumps are shed and new feathers grow out. If, however, the stumps are pulled out sooner the feathers will be renewed in a few weeks or even days.

The feather is a very strong formation, not readily damaged, the arch of the shaft resisting pressure, while the web and fine fibres yield without suffering. Being a bad conductor of heat it preserves the high temperature of the bird, while it is so light as to be easily carried in flight. It is rendered almost impervious to wet by the oily fluid which most birds secrete at the base of the tail. Feathers traditionally formed a considerable article of commerce, particularly those of the ostrich, heron, swan, peacock, goose, etc, for plumes, ornaments, filling of beds, pens, etc.
Research Feather