ELMER: The walls were covered on the outside with boards, and the roof with shingles.
MOTHER: That would do very well for a wooden house, but for one that can walk, run, jump, and skip about, such a stiff covering would be sadly out of place. We sometimes smile because the snail carries his house around on his back; but the house we live in must move itself and carry the one who lives in it. How are boards and shingles fastened onto common houses so they will stay?
MOTHER: Just think of driving nails into muscles! Yet you see our body-houses must have some kind of a covering. It must be thin and strong and one that will stretch. Look at your hands and see if they do not have the very best covering that could be made. Pinch up the skin, and see how thin it is, and yet how well it fits every part of the body.
AMY: And the skin stretches, mother. See, I can bend my knee and elbow, and move my fingers as I please.
MOTHER: Yes, it is like a close-fitting garment. What we call the skin is really _two_ skins. You see I can put a pin through the outer skin in the palm of my hand, and I feel no pain, and you see no blood.
MOTHER: No; for under this thick, outer skin is what is called the true skin. It has such fine blood-vessels that if you could see them, they would look like fine network. If you should prick this _inner_ skin it would hurt, and the blood would flow. This shows it has nerves as well as blood. Under the true skin is a layer of fat. This is like a warm woolen garment to keep the body warm. Between the outer skin and the true skin there is some jelly-like coloring matter, which gives it color.
HELEN: Is that why some persons are very dark and others are light, mother?
MOTHER: Yes; your true skin is just the same color as that of the negro and the Indian. The coloring matter under the outer skin is all that makes the difference. This outer covering is made of little horny scales laid one over another, much as a roof might be if it had ten or twelve layers of shingles. The outer scales keep wearing away all the time, and new ones take their places. You know a snake sheds its skin and crawls away with a new one. We shed our skin, too, little by little, but the scales are so small we can hardly see them. If you should wear your under-clothing several days, and then shake it in the sunlight, you would see little scales floating about in the air like dust.