l the bark off of a young tree?
If so, you have noticed that there were really two barks, an outer bark,
as thin as paper, through which you could almost see, and an inner and
much thicker bark, which lay next to the wood of the tree. You can peel
the outer bark off without doing the tree much harm. Indeed, if you will
notice some of the fruit or shade trees in the yard, at home, you will
see that the outer bark of the tree peels itself off, a little at a
time, and that new bark grows in its place. If you tear off the inner
bark, however, it will injure the tree. It will make it bleed, or cause
the sap to run. The sap is the blood of the tree. The bark is the skin
of the tree. When the bare place heals over, an ugly scar will be left.

~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 pa