[Scand.] The natural covering of animals and plants. The thickness of the skin varies in different parts of the human body, from one-eighth to one-fourth of an inch. On the hands and feet it becomes thick (or callous), but in other parts it is thin and delicate, while at the ends of the fingers and toes it grows into thin plates called nails. The hairs are only portions of the skin grown very long and narrow. The skin is composed of two layers : there is a lower, 'thick layer, full of the fine blood-vessels called capillaries, and full, too, of nerves-this layer is called the dermis; upon it lies an upper, thin layer, of a horny or scaly nature, in which are no blood-vessels and no herves-this is called the epidermis. Just under the dermis there is usually a layer of fat. When we examine the outside of our skin through a magnifying-glass, we can see great numbers of little holes or pores. No fewer than 5,000 pores have been counted in the skin forming the tip of a finger ; and there are about 21/2 millions of such pores in the skin of the whole body. Each pore is the end or opening of a tube called a sweat gland, which goes down, through the epidermis, into the dermis, where its lower end is coiled up into a little ball or knot. The oil glands are very similar to the sweat glands. Two are attached to each hair; and when the skin is in a healthy state this natural oil ought to be sufficient for the hair. The oily matter formed by these oil glands runs out on the skin and mixes with the sweat. The sweat produced by the skin of an ordinary man or woman every twenty-four hours measures not less than a pint and a quarter, weighing 11/2 lb.