The _skin of the fowl_ is very thin and does not contain oil glands or sweat glands. In the fowl the oil is supplied by a tail or rump gland, the _glandula uropygii_ (Fig. 35, No. 16). This gland is round or oval in shape, and about the size of a pea and consists of two lobes. It is of the tubular variety with a teat, which, in most instances has two openings. A medium septum divides the gland into two halves. The oil secreted by the columnar epithelial cells is collected in a body cavity located in the center of the gland; this has a duct extending to the surface. The bird by squeezing out a quantity of this oil into its beak oils the feathers, passing the beak over them, one by one. The oil renders the feathers practically impervious to water. It is necessary for the bird to give proper attention to its plumage in order that the feathers appear in prime condition. Should there be a disease of the oil gland, or should the bird become ill and neglect its toilet the result is an unkempt appearance of the plumage, the feathers becoming rather rough and more or less injured by the weather. The _subcutis_ is well developed and furnishes to the cutis great capability for movement, which is necessary for the rising and falling of the feathers. The corneum is very thin. Papillary bodies are present only in a very few places, such as the region about the eye and on the toes. Where the toes touch the ground in walking there are large wart-like thickenings of the epithelium. In most birds the shanks are unfeathered. The epidermis on the feathered parts of the skin is thin, dry on the surface, and abounds in continuous scales. The stratum corneum is very thick on the horny sheath of the beak, on the top of the toes, on the spurs of the cock, and on the scale plates that cover the skin on the shanks. The feathers of birds serve the same protective purpose as hair on mammals. In cold weather the skin muscles controlling the feather movements contract; thus the feathers become ruffled much as we observe the hair standing erect on horses under similar conditions. By increasing the dead air space around the body, the radiation of heat is retarded, and the body kept warmer. The corneum of the skin is not usually rich in blood-vessels; however, in the domestic fowls there is in the comb, in the wattles, and similar appendages of the head, a thick vascular network. The _beak_ and the _claws_ are modified skin; they are true horn material. At the base of the beak there is often formed scales, which surround the nostrils, in whole or in part, and have a naked, or waxy, appearance, which is known as the _cera_. [Illustration: FIG. 79.—Photomicrograph of the section of skin from the sole of the foot of a hen. 1, Horny stratified squamous epithelium. _a_, Stratum corneum. _b_, Stratum lucidum. _c_, Stratum germinativum. 2, Connective tissue supporting membrane, pars reticularis. 3, Blood-vessels. ]