Читать книгу The Circle of Knowledge: A Classified, Simplified, Visualized Book of Answers - Various - Страница 265

The integument differs markedly from that of other animals in being clad with feathers. Three distinct kinds of feathers are at once distinguishable—(a) the small hair-like downy rudimentary filoplumes; (b) the numerous smaller contour or covering plumes; and (c) the large strong quill-feathers or pennæ on wings and tail. The ordinary feather consists of a quill at the base of a shaft up the center, and of the vane borne on the sides of the shaft. The vane consists of parallel barbs, which are linked together by small barbules. On the bare legs of many birds the feathers are replaced by horny scales, and the horny structures forming the beak and terminating the toes are very familiar.