Albert. I wish to learn the use of a great many parts of my body that I do not now fully understand; for I have been told that the human form is the most perfect of all material things; and it seems to me that we ought to give much more attention to it than we have yet given.
Charles. It seems to me that it would be a good plan, if you are willing, father, to spend a part of each evening in teaching us these things. Albert and I can ask some questions, and you can answer them, and give us any other information that you think may be useful to us.
Father. I think that this is a good plan; and as we are now together, we will begin this evening. We will begin with the skin,—for though the skin covers the whole body, and is so exposed to view, there are many things concerning it with which you are not familiar.—The skin is that thin covering which is spread over the whole surface of the body. It serves to bind together and to protect from injury the more delicate parts which are beneath it. Come, Albert, tell me some of the things which you have observed respecting the skin.
Albert. The skin differs in its appearance in different animals, and in different parts of the body. With young people and females it is soft, smooth, and delicate; it is firmer and more resisting in middle age, and with males; it appears loose and wrinkled in old age, and after some diseases; it is puckered or disposed in folds in places where it would otherwise interfere with the proper movements of the limbs, as over the finger-joints, and in the palm of the hand.
Father. Very well, my son. Should you suppose, Charles, that the skin is one sheet, or that it is composed of layers?
Charles. I have observed that a very thin coat of the skin has sometimes risen in blisters, from being rubbed when I have been working, or from a burn, or slight scald; and sometimes I have peeled it off, as I can the outside bark of a birch tree; and from these things I suppose the skin is composed of thin layers.
Father. It is so. The skin is composed of three membranes, or layers. The outside layer is called the “cuticle,” or “scarf-skin.” There are some other names for the three layers of the skin besides those that I shall use; but if you remember those which I give, it will be sufficient until you are old enough to understand more fully the good books which have been written concerning the different parts of the body. The cuticle has no blood-vessels. It is very thin. There is still some doubt whether the scarf-skin has any nerves or not. Perhaps it has nerves which are so unsusceptible to external impressions, that we do not notice their effects.
Albert. If there were nerves in the scarf-skin as sensitive as those in some parts of the body, we should be in constant pain; we could not take a single step without extreme pain; for the scarf-skin is, I suppose, a protection to the parts which are tender; and unless its nerves were blunt, it would not answer this purpose. I never thought of this before; but this, as well as the structure of every part of the body, shows us the kindness and wisdom of our Creator.
Charles. And if there were blood-vessels in the scarf-skin, we should continually be in danger of being covered with blood, since a slight blow is sufficient to break this skin. I have also observed, father, that those parts of the body which are the most exposed to pressure and friction, such as the palms of the hands and soles of the feet, are provided with a scarf-skin much thicker than that on other parts of the body.
Father. Yes, my son. The difference in the thickness of the cuticle in different parts of the body is apparent even at birth. But the farmer and blacksmith, who are constantly engaged in manual labour, need a thicker scarf-skin to protect their hands, than would be convenient for a student or a merchant; and it has, for this reason, been so provided, that the scarf-skin increases in thickness when it is much used, and decreases when it is but little needed.