transmit it. _Every cell_ must
exercise a form of intelligence, from the auditory cell reporting
a sound-wave or the skin cell reporting an injury to the muscle
cells that ultimately receive and understand a message directing
them to remove the part from danger.

Reaction-time, so called, is thus occupied by cellular action in
the form of _mental_ processes intervening between the nerve-ends
and the brain center, in much the same way that light and sound
vibrations intervene between the object perceived and the surface
of the body.

[Sidenote: _The Six Steps to Reaction_]

For even the simplest of sense-perceptions we have, then, this
sequence of events: first, the object perceived; second, the series
of vibrations of ether particles intervening between the object
and the body; third, the impression upon the surface of the body;
fourth, the series of mental processes, cell after cell, in the
nerve filaments leading to the brain; fifth, when these impressions
or messages have reached the brain, a determination of what is to
be done; and, sixth, a transmission by cellular action of a new
message that will awaken some response in the muscular tissues.

[Sidenote: _Unopened Mental Mail_]

This process is completely carried out, however, in only
comparatively few instances. The vast majority of sense-impressions
awaken no reaction. They are registered in the mind, but they are
not perceived. We are not conscious of them. They form a part, not
of consciousness, but of subconsciousness. They are messages that
reach the mind but are laid aside like unopened mail because they
possess no present interest.

Wherever and however you may be placed, you are always and
everywhere immersed in a flood of etheric vibrations. Light, sound
and tactual vibrations press upon you from every side. At a busy
corner of a city street these vibrations rise to a tumultuous
fortissimo; in the hush of a night upon the plains they sink to
pianissimo. Yet at every moment of your day or night they are there
in greater or less degree, titillating the unsleeping nerve-ends of
the sensorium.

[Sidenote: _Selective Process that Determines Conduct_]

Your mind cannot take time to make all these sense-impressions the
subject of conscious thought. It can trouble itself only with those
that bear in some way upon your interests in life.

_Your mind is like the receiving apparatus of the wireless telegraph
which picks from the air those particular vi