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: 

(1) It Removes Waste.—­The sweat glands and ducts are constantly at work removing from the blood particles which have been worn out and can be of no further use.  If we get very warm, or if we run or work very hard, the skin becomes wet with sweat.  In a little while, if we stop to rest, the sweat is all gone.  What becomes of it?  You say it dries up, which means that it has passed off into the air.  Sweating is going on all the time, but we do not sweat so much when we are quiet and are not too warm, and so the sweat dries up as fast as it is produced, and we do not see it.  Nearly a quart of sweat escapes from the skin daily.

(2) Breathing through the Skin.—­We breathe to a slight extent through the skin.  There are some lower animals which breathe with their skins altogether.  A frog can breathe with its skin so well that it can live for some time after its lungs have been removed.  Breathing is an important part of the work of the skin, and we should be careful, by keeping it clean and healthy, to give it a good chance to breathe all that it can.

(3) The Skin Absorbs.—­The skin absorbs many substances which come in contact with it, and hence should be kept clean.  If the foul substances which are removed in the sweat are allowed to remain upon the skin, they may be taken back into the system and thus do much harm.

(4) The Skin has Feeling.—­When anything touches the skin we know it by the feeling.  We can tell a great many things about objects by feeling of them.  If we happen to stick a pin into the skin we feel pain.  We are also able to tell the difference between things which are hot and those which are cold.  Thus the sense of feeling which the skin has is very useful to us.

(5) The Skin Protects the Body.—­The skin is a natural clothing which protects us much better than any other kind of clothing could.  It is so soft and pliable that it cannot hurt the most delicate part which it covers, yet it is very strong and tough.