FEATHERS

Feathers are elaborate structures po e ed only by one group of animals, namely, birds, and each derived primarily from a sm hollow, epidermal papilla, whose center is occupied by a core of more internal ti ue. The epidermis produces the f. itself, whilst the pulp. which nourishes the developing f., and remains as a shrunken ma in the mature quill, is derived from the central portion. <A mature f., like the large f’s from the wing of a goose, consists of two main parts, the quill or rachis, and the closely packed lateral branches or barbs. The quill is grooved on the under surface, and contains two apertures, one basal, through which the f. derived nourishment when immature, the other situated on the under surface in the neighborhood of the lowest barbs. Each barb produces smaller barbs or barbules on either side, and these again terminate in minute hooks or barbicels. Apart from the lowest barbs, which are imect, the barbules, by means of their ooklet systems, produce a strong and jlastic structure, impervious to air, und capable owing to its concave undersurface of resisting great pre ure from selow. Most f’s bear, near the base, a mall additional structure termed the ufter-shaft. Where the system of hookets is imperfect, a softer, more downlike. is produced, as in the ostrich, the down which covers the duckling and chicken, ind also constitutes an important part f the mature plumage of many birds, yeing somewhat similar in character, hough it may consist merely of a small ipical tuft of fluffy matter. Minute lair-like structures, termed filoplumes, re often found surrounding the bases f the larger f’s, as in the goose, and hese either branch very little, or not ii all. The f’s of the heron are peculiar n that they shed a dry, greasy substance ermed powder-down. F’s are believed 0 have evolved from the reptilian cale, and are e entially similar in levelopment. V.), town, Riding, Yorkshire, In gland; coal mines. Pop. 15,000.