e air is necessary to give a keen appetite and vigorous
digestion._ The digestive organs not only need the stimulus of blood,
but they absolutely need the influence of pure blood, which cannot
exist in the system, except when we breathe a pure air. From this we
learn why those persons who sleep in small, ill ventilated rooms, have
little or no appetite in the morning, and why the mouth and throat are
so dry and disagreeable. The effect of impure blood, in diminishing
the desire for food, and enfeebling the digestive organs, is well
illustrated by the following incidents.

_Illustrations._ 1st. Dr. Reid, in his work on "Ventilation of Rooms,"
relates that an innkeeper in London, when he provided a public dinner,
always spread his tables in an under-ground room, with low walls,
where the air was confined and impure. He assigned as a reason for so
doing, that his guests consumed only one third as much food and wine,
as if the tables were laid in the open air.

2d. A manufacturer stated before a committee of the British
Parliament, that he had removed an arrangement for ventilating his
mill, because he noticed that his men ate much more after his mill was
ventilated, than previous to admitting fresh air into the rooms, and
that he could not _afford_ to have them breathe pure air.

_Observation._ Many of the cases of indigestion among clergymen,
seamstresses, school teachers, sedentary mechanics, and factory
operatives, are produced by breathing the impure air of the rooms they
occupy. These cases can be prevented, as well as cured, by proper
attention to ventilation.

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325. What is observed of those individuals that restrict the movements
of the abdominal muscles? 326. Why is pure air necessary to vigorous
digestion? Give illustration 1st. Illustration 2d. What is one cause
of indigestion among the sedentary class in community?

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327. _The position of a person, in standing or sitting, exerts an
influence upon the digestive organs._ If a person lean, or stoop
forward, the distance between the pelvic bones and the diaphragm is
diminished. This prevents the depression of the diaphragm, while the
stomach, liver, pancreas, and other abdominal organs, suffer
compression, which induces many severe diseases of these organs. As
healthy and well-developed muscles keep the spinal column in an erect
position, which conduces to the health of the organs of digestion, the
chil