llectual, and partly
moral.

The first cause of mental disease and suffering, is not unfrequently
found in the want of a proper supply of duly oxygenized blood. It has
been shown, that the blood, in passing through the lungs, is purified,
by the oxygen of the air combining with the superabundant hydrogen and
carbon of the venous blood, thus forming carbonic acid and water, which
are expired into the atmosphere. Every pair of lungs is constantly
withdrawing from the surrounding atmosphere its healthful principle, and
returning one, which is injurious to human life.

When, by confinement, and this process, the atmosphere is deprived of
its appropriate supply of oxygen, the purification of the blood is
interrupted, and it passes, without being properly prepared, into the
brain, producing languor, restlessness, and inability to exercise the
intellect and feelings. Whenever, therefore, persons sleep in a close
apartment, or remain, for a length of time, in a crowded or
ill-ventilated room, a most pernicious influence is exerted on the
brain, and, through this, on the mind. A person, who is often exposed to
such influences, can never enjoy that elasticity and vigor of mind,
which is one of the chief indications of its health. This is the reason,
why all rooms for religious meetings, and all schoolrooms, and sleeping
apartments, should be so contrived, as to secure a constant supply of
fresh air from without. The minister, who preaches in a crowded and
ill-ventilated apartment, loses much of his power to feel and to speak,
while the audience are equally reduced, in their capability of
attending. The teacher, who confines children in a close apartment,
diminishes their ability to study, or to attend to his instructions. And
the person, who habitually sleeps in a close room, impairs his mental
energies, in a similar degree. It is not unfrequently the case, that
depression of spirits, and stupor of intellect, are occasioned solely by
inattention to this subject.

Another cause of mental disease, is, the excessive exercise of the
intellect or feelings. If the eye is taxed, beyond its strength, by
protracted use, its blood-vessels become gorged, and the bloodshot
appearance warns of the excess and the need of rest. The brain is
affected, in a similar manner, by excessive use, though the suffering
and inflamed organ cannot make its appeal to the eye. But there are some
indications, which ought never to be misunderstood or disrega