~5. The Pigment.~--The under side of the cuticle is colored by little particles of pigment or coloring matter. The color of this pigment differs in different races. In the negro, the color of the pigment is black. In some races the pigment is brown. In white persons there is very little pigment, and in some persons, called albinos, there is none at all. ~6. The Inner or True Skin.~--The inner skin, like the inner bark of a tree, is much thicker than the outer skin. It is much more important, and for this reason is sometimes called the _true skin_. It contains nerves and blood-vessels. [Illustration: SKIN OF PALM OF HAND MAGNIFIED.] ~7. The Sweat Glands.~--If you look at the palm of the hand you will see many coarse lines, and by looking much closer you will see that the palm is completely covered with very fine ridges and furrows. Now, if you examine these ridges with a magnifying-glass, you will find arranged along each ridge a number of little dark spots. Each of these points is the mouth of a very small tube. This is called a _sweat duct_. These ducts run down through both the outer and inner layers of the skin. At the under side of the true skin the end of the tube is rolled up in a coil, as you can see by looking at the illustration on the following page. The coiled parts of the tubes are called _sweat glands_, because they separate from the blood the fluid which we call sweat or perspiration. ~8. The Oil Glands.~--There are other little glands in the skin which make fat or oil. The oil is poured out upon the skin to keep it soft and smooth. [Illustration: THE STRUCTURE OF THE SKIN.] ~9. The Hair.~--There are some curious little pockets in the skin. Out of each of these pockets grows a hair. On some parts of the body the hairs are coarse and long; on other parts they are fine and short. ~10.~ Many of the ducts leading from the oil glands open into the pockets or pouches from which the hairs grow. The oil makes the hair soft and glossy. Nature has thus provided an excellent means for oiling the hair. ~11.~ The hair is chiefly useful as a protection. It is also an ornament. ~12. The Nails.~--The nails of the fingers and the toes grow out of little pockets in the skin just as the hairs do. Both the hair and the nails are really parts of the outer skin, which is curiously changed and hardened. The nails lie upon the surface of the true skin and grow from the under side as well as from the little fold of skin at the root of the nail. They are made to give firmness and protection to the ends of the fingers and toes. The nails of the fingers are also useful in picking up small objects and in many other ways. ~13. Uses of the Skin.~--The skin is useful in several ways: