3. The feathers.—Examine the arrangement of the feathers. The short feathers which clothe the body generally are called contour feathers because they determine the contour of the unplucked bird; remove one or two and place them aside. The feathers which cover the bases of the large quills are called coverts—wing-coverts or tail-coverts according to their position. Remove one or two for future examination. Examine the arrangement of the quill-feathers of the wings, and notice how the vane or web of one partially overlaps the next. The vane is supported by a shaft. Are the two sides of the vane of equal width? Is the narrower side directed forwards or backwards? Pull out a quill-feather from each wing and compare them. How could you recognise, if you did not know, whether any particular feather had come from the right or from the left wing? Pull out a quill-feather from the tail; are the sides of the vane of equal width? 4. Examination of various feathers.—Examine in detail a quill-feather from the wing. Make out: (a) The quill.—Is it hollow or solid? Try to bend it and notice its great strength. Observe the small hole at its base. (b) The shaft.—This is the prolongation of the quill, and carries the web or vane. Is the shaft hollow or solid? Notice the small tuft of down on the inner face of the feather, at the junction of the quill and shaft. (c) The vane.—Hold up the feather to the light and examine the vane with a lens. Notice that the vane consists of a number of laths which spring from the shaft; these are called barbs. Try to separate the barbs, and observe that they offer considerable resistance to the pull, as if they were somehow fastened together. Examine a barb with a strong lens and observe the finer branches, called barbules, which it [Pg 268] bears. The barbules on one side of the barb carry little hooks, while those of the other side bear flanges, on which fit the hooks of barbules carried by the next barb below. The hooks and flanges cannot be seen without a microscope. (d) Other feathers.—Compare the covert and contour feathers with the quill feathers. Observe, in the contour feathers, the less perfect interlocking of the barbs of those parts which are covered by other feathers. Pluck the pigeon, and notice the hair-like structures left in the skin. They are called filoplumes. Pull one out and examine it with a lens; it bears a few barbs at its upper end, but these do not interlock. Examine a nestling-pigeon, and notice the down-feathers which clothe it temporarily. Each is at first covered at the base with a horny sheath. The barbs do not interlock. The down-feathers are pushed off by the growth of the permanent feathers.