dissolve the products of fatigue. It is probable that these products
stimulate the sense-organs in the muscles and thus give some of the
sensations of fatigue. Of these physical effects of fatigue, the
accumulation of waste products in the blood and the effects upon the
nerve cells are probably common both to mental and physical fatigue.
The effect upon the muscles plays a part in mental fatigue only so far
as all mental work involves some muscular activity."

By this time you must be convinced that the subject of fatigue is
exceedingly complicated; that its effects are manifested differently in
mind and body. In relieving fatigue the first step to be taken is to
rest properly. Man cannot work incessantly; he must rest sometimes, and
it is just as important to know how to rest efficiently as to know how
to work efficiently. By this is not meant that one should rest as soon
as fatigue begins to be felt. Quite the reverse. Keep on working all
the harder if you wish the second-wind to appear. Perhaps two hours
will exhaust your first supply of energy and will leave you greatly
fatigued. Do not give up at this time, however. Push yourself farther
in order to uncover the second layer of energy. Before entering upon
this, however, it will be possible to secure some advantage by resting
for about fifteen minutes. Do not rest longer than this, or you may
lose the momentum already secured and your two hours will have gone for
naught. If one indulges in too long a rest, the energy seems to run
down and more effort is required to work it up again than was
originally expended. It is also important to observe the proper mental
conditions during rest. Do not spend the fifteen minutes in getting
interested in some other object; for that will leave distracting ideas
in the mind which will persist when you resume work. Make the rest a
time of physical and mental relief. Move cramped muscles, rest your
eyes and let your thoughts idly wander; then come back to work in ten