quite likely that you are frequently awakened by a beam of light
falling upon your closed eye-lids. For this reason, one who is inclined
to be wakeful should shut out from the bed-room all avenues whereby
light may enter as a distraction.

The temperature sense is also a source of distraction in sleep, and it
is a common experience to be awakened by extreme cold. The ears, too,
may be the source of disturbance in sleep; for even though we are
asleep, the tympanic membrane is always exposed to vibrations of air.
In fact, stimuli are continually playing upon the sense-organs and are
arousing nervous currents which try to break over the boundaries of
sleep and impress themselves upon the brain.

For this reason, one who wishes to have untroubled sleep should remove
all possible distractions.

But apart from external distractions, wakefulness may still be caused
by distractions from within. Troublesome ideas may be present and
persist in keeping one awake. This means that brain activity has been
started and needs suppression. Various devices have been suggested. One
is to eat something very light, just enough to draw the surplus blood,
which excites the brain, away from the brain to the digestive tract.
This advice should be taken with caution, however, for eating just
before retiring may use up in digestion much of the energy needed in
repairing the body, and may leave one greatly fatigued in the morning.

One way to relieve the mind of mental distractions is to fill it with
non-worrisome, restful thoughts. Read something light, a restful essay
or a non-exciting story, or poetry. Another device is to bathe the head
in cold water so as to relieve congestion of blood in the brain. A