disease, there is an increased demand
for food. This may be gratified with impunity until the individual has
regained the usual size, but repletion should be avoided.

277. _Food is required to repair the waste, or loss of substance
that attends action._ In every department of nature, waste, or loss of
substance, attends and follows action. When an individual increases
his exercise,--changes from light to severe labor,--or the inactive
and sedentary undertake journeys for pleasure, the fluids of the
system circulate with increased energy. The old and exhausted
particles of matter are more rapidly removed through the action of
the vessels of the skin, lungs, kidneys, and other organs, and
their places are filled with new atoms, deposited by the small
blood-vessels.

278. As the chyle supplies the blood with the newly vitalized
particles of matter, there is, consequently, an increased demand for
food. This want of the system induces, in general, a sensation of
hunger or appetite, which may be regarded as an indication of the
general state of the body. The sympathy that exists throughout the
system accords to the stomach the power of making known this state to
the nervous system, and, if the functions of this faithful monitor
have not been impaired by disease, abuse, or habit, the call is
imperious, and should be regarded.

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276. At what age is the appetite keen and the digestion vigorous? Why?
What is said in regard to the quantity of food when the youth has
attained his growth? What exception, as given in the observation? 277.
Give another demand for food. What effect has increased exercise upon
the system? 278. How are the new particles of matter supplied? What
does this induce?

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279. _When exercise or labor is lessened, the quantity of food should
be diminished._ When a person who has been accustomed to active
exercise, or even hard manual labor, suddenly changes to an employment
that demands less activity, the waste attendant on action will be
diminished in a corresponding degree; hence the quantity of food
should be lessened in nearly the same proportion as the amount of
exercise is diminished. If this principle be disregarded, the tone of
the digestive organs will be impaired, and the health of the system
enfeebled.

280. This remark is applicable to those students who have left
laborious employments to attend school. Although the health is firm,
and