This continual mist of water, rising and bubbling up through our skin like springs out of a hillside, is another of nature's wonderful ways of cleansing the skin and of preventing any kind of dirt from permanently sticking to or lodging in it.

Remember, you do not need to dig below the surface when you wash.
Hair Glands.

The other kind of skin glands, the hair glands, are also pouches growing out from the deepest part of the stem of the hair, known as the root, or _hair bulb_.
[Illustration: THE GLANDS IN THE SKIN _S_, sweat gland; _H_, hair bulb; _O_, oil gland; _T_, touch bulb at tip of nerve.] From the root of the hairs, two or three little bundles of muscle run up toward the surface of the skin.

When these contract, they pull the root of the hair up toward the surface, causing the hair to stand erect, or "bristle," as we say.

This is what makes the hair on a dog's or a cat's back stand up when he is angry; but the commonest use of the movement is, when animals are cold, to make their coats stand out so as to hold more air and retain the body-heat better.