n through openings in the skull,
and go to every part of the body. Every little muscle fibre, the heart,
the stomach, the lungs, the liver, even the bones--all have nerves
coming to them from the brain. So you see that the brain is not wholly
shut up in the skull, because its cells have slender branches running
into all parts of the body; and thus the brain itself is really in every
part of the body, though we usually speak of it as being entirely in the
skull.

~8. The Spinal Cord.~--There are a number of small holes in the skull
through which the nerves pass out, but most of the nerves are bound up
in one large bundle and pass out through an opening at the back part of
the skull and runs downward through a long canal in the backbone. This
bundle of nerves forms the _spinal cord_. The spinal cord contains cells
also, like those of the brain. It is really a continuation of the brain
down through the backbone.

[Illustration: BRAIN AND SPINAL CORD.]

~9. Nerves from the Spinal Cord.~--The spinal cord gives off branches of
nerves which go to the arms, the chest, the legs, and other parts. One
of the branches which goes to the hand runs along the back side of the
arm, passing over the elbow. If we happen to strike the elbow against
some sharp object, we sometimes hit this nerve. When we do so, the under
side of the arm and the little finger feel very numb and strange. This
is why you call this part of the elbow the "funny" or "crazy bone." The
cells of the spinal cord also send out branches to the body and to other
cells in the brain.

~10. How we Feel.~--If we cut or burn ourselves we suffer pain. Can you
tell why it hurts us to prick the flesh with a pin, or to pinch or burn
or bruise it? It is because the flesh contains a great many
nerve-branches from the brain. When we hurt the skin or the flesh, in
any way, these nerves are injured. There are so many of these little
nerves in the flesh and skin that we cannot put the finest needle into
the flesh without hurting some of them.

~11. The Use of Pain.~--It is not pleasant for us to have pain, but if
the nerves gave us no pain when we are hurt we might get our limbs
burned or frozen and know nothing about it until too late to save them.

~12. Nerves of Feeling.~--We have different kinds of nerves of feeling.
Those we have learned about feel pain. Others feel objects. If you take
a marble or a pencil in the hand you know what it is by the feeling of
the object. This