=Feathers.= The feathers of a bird are the most highly developed form of protective covering in animals, serving other important functions in addition to the primary one. Compared with the hair of a mammal or the scale of a fish or of a reptile, a typical soft feather from the body of a bird is a very complex structure, partaking of the characters of both scales and hair. The fact that birds have scales and hair as well as feathers shows their relation to these other forms of animal covering. This is best observed on a fowl. The legs of a fowl are normally smooth, with scales on the front of the shank and on the upper surfaces of the toes. In feather-legged fowls the feathers appear first along the outer sides of the shanks and toes. As the number of feathers is increased they grow longer and more feathers appear, until in the most heavily feathered specimens the soft skin is covered and the scales are almost hidden. The face of a fowl is normally almost bare, the skin being a bright red like the comb and wattles; but at a distance of a few feet we can usually see some very small, fine feathers on it, and if we examine closely we see in addition still finer growths--hairs. Among the body feathers of a fowl, too, are quite long hairs. These are most easily observed after a bird is plucked. They do not come out with the feathers, and are removed by singeing. =Structure of feathers.= The smallest feather that to the naked eye appears as something more complex than a hair, looks like a little bunch of fuzzy filaments. This is called down. In the next higher form of feather a small round quill appears with filaments protruding from it like the hairs in an artist's brush. Such a feather is called a stub feather, or simply a stub. The best place to find these is on the outside of the shank of a fowl with scantily feathered legs. The first form of the complete feather is best observed either on the head of a fowl or at the hock joint. The feathers in these places are very small, yet complete. The round quill is lengthened into a shaft. Extending from each side of this shaft is a single row of filaments, called barbs, the edges of which, interlocked with little hooks, form the web of the feather. On other parts of the body of the bird the feathers are larger, but the general structure is always the same. The size and special structure of the feather are always adjusted to suit the part on which it grows or the service which it has to perform.