1.Young people generally know more about the skin of the body than they do about the flesh or the bones.It is easier to know about the outside of things than about the inside.Snakes and toads and some other animals change their skins every year.Perhaps you are not aware that we also change our skins.We do not draw off the old skin like a glove or a stocking，as the snake does，and find a soft，new one underneath；we are constantly changing it，little by little every day.The old skin comes off in very small，flat scales，like fine white dust，and the new skin is constantly growing from beneath.This is one of the reasons why daily washing and frequent change of underclothing are necessary.
2.The outer layer of the skin，from which these scales come，is called the epidermis.It can stand a good deal of rough treatment without bleeding or feeling painful.But if this outer layer happens to be taken away，by a scratch or a blister，you find that the lower skin bleeds freely，showing that it is full of blood-vessels；and is painfulwhen touched，showing that it is full of nerves.
3.These nerves give us the sense of touch or feeling，but they need the rough upper skin to keep them frominjury.On the tips of the fingers，where we have a keen sense of touch，the nerves are very numerous.They rise in little mounds and ridges，so as to be near the surface，and to give greater fineness of touch.
4.There is a very curious fact about these little ridges which you see curving round and round on the tips of your fingers and thumbs.They are never exactly alike in any two persons，and they never change their form from year to year.Thus no two persons‘fingers can make marks of the same shape on a piece of soft wax.
5.Now，when a person is accused sometimes very important to know whether this is the same person who was formerly punished for another crime.Accordingly，the police in some places keep acopy of the finger-prints of all convicts.It is foundthat these finger-prints are a surer way of knowing a person again than a photograph is.The face changes more than the fingers do.
6.In a robbery from a mail-bag in America，the guilty person was discovered by the mark of his thumb，which he had left on the soft wax while closing up the bag.But this can hardly be called the natural use of the skin，any more than stealing can be called the naturaluse of the fingers.We have now to see what the uses of the skin really are.
7.One use of the skin is to protect the tender parts underneath-the veins and small blood-vessels，and the nerves or living telegraph wires.And in the lower animals，in order to give the better protection，the skin is sometimes covered over with such substances as shells，scales，hair，wool，feathers，nails，claws，horns，and the like，which are all different forms of the outer layer of the skin.
8.If a part of the body，such as the arm，be en-closed in a loose india-rubber bag full of fresh air，and kept in it for some time，the air in the bag is found tobe changed.It contains the same impuritiesas the airwhich we breathe out from the lungs.This shows us that the skin is really one of our breathing organs.
9.This breathing，as well as the passage of theperspiration，takes place through very fine spiraltubesor pores in the skin.You can see these little pipes，as well as the roots of the hairs，in this picture，which shows a part of the skin cut through and very much enlarged.On the palm of the hand there are nearly 3，000pores in every square inch of skin，and it has been found that the whole length of these tubes in a single body would be about thirty miles！
10.Such facts as these may help you to see that the skin is a very important organ of the body.And it is the organ which we can do most to help in its work，as it is not covered up from us.The help we can giveit is chiefly by keeping it cleanand vigorous，and protecting.
1.Make sentences containing the words aware，beware，wary，and unwary.
2.Show by their use in sentences that the words change，touch，and form may be various parts of speech.
3.Make sentences containing the words bleed，blood，feed，and food.