ndition, known as _exhaustion_, is
not only a matter of temporary inconvenience, but may through repetition
lead to a serious impairment of the health. It should be noted, in this
connection, that the energy of the body is spent in two general ways:
first, in carrying on the vital processes; and second, in the performance
of voluntary activities. Since, in all cases, there is a limit to one's
energy, it is easily possible to expend so much in the voluntary
activities that the amount left is not sufficient for the vital processes.
This leads to various disturbances and, among other things, renders the
body less able to supply itself with energy.

*The Problem of Increasing One's Energy.*--Since the energy supply is kept
up through the food and the oxygen, it might be inferred that the
introduction of these substances into the body in larger amounts would
increase the energy at one's disposal. This does not necessarily follow.
Oxidation at the cells is preceded by digestion, absorption, circulation,
and assimilation. It is followed and influenced by the removal of wastes
from the body. A careful study of the problem leads to the conclusion that
while the energy supply to the body does depend upon the introduction of
the proper amounts of food and oxygen, it also depends upon the efficiency
of the vital processes. The maximum amount of energy may, therefore, be
expected when the body is in a condition of perfect health. Hence, one
desiring to increase the amount of his energy must give attention to all
those conditions that improve the health.

*Effect of Stimulants on the Energy Supply.*--In the effort to get out of
the body as much as possible of work or of pleasure, various stimulants,
such as alcohol, tobacco, and strong tea and coffee, have been used.
Though these have the effect of giving a temporary feeling of strength and
of enabling the individual in some instances to accomplish results which
he could not otherwise have brought about, the general effect of their use
is to lessen, rather than to increase, the sum total of bodily power. The
student, for example, who drinks strong coffee in order to study late at
night is able to command less energy on the day following. While enabling
him to draw upon his reserve of nervous power for the time being, the
coffee deprives him of sleep and needed rest.

The danger of stimulants, so far as energy is concerned, is this: they
tend to exhaust the bodily reserve so that the