THE NERVES, BRAIN, SPINAL CORD, ETC.
The muscles which move the bones are themselves moved by the nerves. The
nerves are soft and pulpy in youth, but harden as you advance in years.
They are composed of a gray substance, called the nerve-cell, and a
white substance, known as the nerve-fibre.
The brain is the mass of nervous tissue within the skull. It is so
tender and easily harmed that nature has walled it about by a hard, bony
structure to protect it from injury.
The gray substance of the nerves is where nervous impulses begin, which
are conducted along the white substance. The gray matter may be compared
to a telegraph office where the message is started, while the white
matter is the wire along which the message travels.
[Illustration:
SURFACE OF THE CEREBRUM.]
The spinal cord, or marrow, is a mass of soft, nervous tissue, which
fills the hollow running the length of the spine or backbone.
[Illustration:
=NERVES OF THE FACE AND NECK=.—(a, b) _Nerve of the Face_; (d) _Nerve
of the Forehead_.]
From the base of the brain twelve pairs of nerves are given off to the
face and head. One pair passes to the eye, and gives sight; one passes
to the nose, and gives smell; one, to the mouth, tongue, and palate, and
gives taste; one, to the ears, and gives hearing; and others to the
face, neck, and head, and give the expressions of joy, sorrow, pain,
anger, and doubt.
From the spinal cord thirty-one pairs of nerves pass to the various
parts and organs of the body.
There could be no motion or feeling without the nerves, although they
are not the true centres of either. If you obey the rules of health, as
already laid down, you will be in the happy condition of those of whom
it is said they do not feel that they have any nerves at all.
* * * * *
What move the muscles? How are the nerves in early youth? Of what
are they composed? What are these parts called?
What is the brain? How is it protected?
Where do nervous impulses begin? To what may the gray and white
matter be compared?
What is the spinal cord?
How many pairs of nerves are given off from the brain? From the
spine? Where do they go?
What is said of sensation and feeling? What if you obey the laws of
health?