Brains Parts and Functions]

And now, as to the functions of these various parts. Beginning at the
lowest one and moving upward, we find first that the _spinal cord_
consists of through lines of nerves running between the brain and the
rest of the body. At the same time it contains within itself certain
nerve centers that are sufficient for many simple bodily movements.
These bodily movements are such as are instinctive or habitual and
require no distinct act of the will for their performance. They are mere
"reactions," without conscious, volitional impulse.

Moving up one step higher, we find that the _cerebellum_ is the organ of
equilibrium, and that it as well as the spinal cord operates
independently of the conscious will, for no conscious effort of the will
is required to make one reel from dizziness.

As to the divisions of the greater brain or cerebrum, we want you to
note that the _lower brain_ serves a double purpose. First, it is the
channel through which pass through lines of communication to and from
the upper brain and the mid-brain on the one hand and the rest of the
body on the other. Secondly, it is itself a central office for the
maintenance of certain vital functions, such as lung-breathing,
heart-beating, saliva-secreting, swallowing, etc., all involuntary and
unconscious in the sense that consciousness is not necessary to their
performance.

The next higher division, or _mid-brain_, is a large region from which
the conscious will issues its edicts regulating all voluntary bodily
movements. It is also the seat of certain special senses, such as sight.

Lastly, the _surface brain_, known as the cortex, is the interpretative
and reflective center, the abode of memory, intellect and will.

[Sidenote: Drunkenness and Brain Efficiency]

The functions of these various parts are well illustrated by the effects
of alcohol upon the mind. If a man takes too much alcohol, its first
apparent effect will be to paralyze the higher or cortical center. This
leaves the mid-brain without the check-rein of a reflective intellect,
and the man will be senselessly hilarious or quarrelsome, jolly or
dejected, pugnacious or tearful, and would be ordinarily described as
"drunk." If in spite of this he keeps on drinking, the mid-brain soon
becomes deadened and ceases to respond, and the cerebellum, the organ of
equilibrium, also becomes paralyzed. All voluntary bodily activities
must then cease, and he rolls under the t