sations come and
bring a consciousness of that object's existence!

Nor can you be sure, even after any particular vibration has
reached the surface of your body, that it will reach your mind
unaltered and intact!

[Sidenote: _Etheric Vibrations as Causing Sensations_]

What goes on in the body itself is made clear by your knowledge
of the cellular structure of man.

You know that you have a system of nerves centering in the brain
and with countless ramifications throughout the structural tissues
of the body.

You know that part of these nerves are sensory nerves and part of
them are motor nerves. You know that the sensory nerves convey to
the brain the impressions received from the outer world and that
the motor nerves relay this information to the rest of the body
coupled with commands for appropriate muscular action.

[Illustration: DIAGRAM SHOWING THE FOUR CHIEF ASSOCIATION CENTERS
OF THE HUMAN BRAIN]

[Sidenote: _The Road to Perception_]

The outer end of every sensory nerve exposes a sensitive bit of
gray matter. These sensitive, impression-receiving ends constitute
together what is called the "sensorium" of the body.

When vibrations of light or sound impinge upon the sensorium, they
are relayed from nerve cell to nerve cell until they reach the
central brain. Then it is, and not until then, that sensations and
perceptions occur.

Consider, now, the infinitesimal size of a nerve cell and you will
have some conception of the number of hands through which the
message must pass before it is received by the central office.

Many of our sensations, especially those of touch, seem to occur
on the periphery of the body--that is to say, at that part of the
exposed surface of the body which is apparently affected. If your
finger is crushed in a door, the sensation of the blow and the pain
all seem to occur in the finger itself.

[Sidenote: _The Place Where Sensation Occurs_]

As a matter of fact, this is not the case, for if one of your arms
should be amputated, you would still feel a tingling in the fingers
of the amputated arm. Thus has arisen a superstition that leads many
people to bury any part of the body lost in this way, thinking that
they will never be entirely relieved of pain until the absent member
is finally at rest.

Of course, the fact is that you would only _seem_ to have feeling
in the amputated arm. The sensation would really occur in the central
brain tissue as the organ of the gover