3.  The Cuticle.—­Our bodies, like trees, have two skins, or really one skin with an outer and an inner layer.  When a person burns himself so as to make a blister, the outer skin, called the cuticle, is separated from the inner by a quantity of water or serum poured out from the blood.  This causes the blister to rise above the surrounding skin.  If you puncture the blister the water runs out.  Now we may easily remove the cuticle and examine it.  The cuticle, we shall find, looks very much like the skin which lines the inside of an egg-shell, and it is almost as thin.

4. The cuticle is very thin in most parts of the body, but in some places, as the palms of the hands and the soles of the feet, it is quite thick.  This is because these parts of the skin come in contact with objects in such a way as to be liable to injury if not thus protected.  The cuticle has no blood-vessels and very few nerves.  With a fine needle and thread you can easily take a stitch in it without making it bleed or causing any pain.

5.  The Pigment.—­The under side of the cuticle is colored by little particles of pigment or coloring matter.  The color of this pigment differs in different races.  In the negro, the color of the pigment is black.  In some races the pigment is brown.  In white persons there is very little pigment, and in some persons, called albinos, there is none at all.

6.  The Inner or True Skin.—­The inner skin, like the inner bark of a tree, is much thicker than the outer skin.  It is much more important, and for this reason is sometimes called the true skin.  It contains nerves and blood-vessels.

[Illustration:  SKIN OF PALM OF HAND MAGNIFIED.]

7.  The Sweat Glands.—­If you look at the palm of the hand you will see many coarse lines, and by looking much closer you will see that the palm is completely covered with very fine ridges and furrows.  Now, if you examine these ridges with a magnifying-glass, you will find arranged along each ridge a number of little dark spots.  Each of these points is the mouth of a very small tube.  This is called a sweat duct.  These ducts run down through both the outer and inner layers of the skin.  At the under side of the true skin the end of the tube is rolled up in a coil, as you can see by looking at the illustration on the following page.  The coiled parts of the tubes are called sweat glands, because they separate from the blood the fluid which we call sweat or perspiration.

8.  The Oil Glands.—­There are other little glands in the skin which make fat or oil.  The oil is poured out upon the skin to keep it soft and smooth.

[Illustration:  THE STRUCTURE OF THE SKIN.]

9.  The Hair.—­There are some curious little pockets in the skin.  Out of each of these pockets grows a hair.  On some parts of the body the hairs are coarse and long; on other parts they are fine and short.