odor; but we are warned by the disagreeable effluvia of close
sleeping-rooms of the other poison thus thrown into the air from the
skin and lungs. There is one provision of nature that is little
understood, which saves the lives of thousands living in unventilated
houses; and that is, the passage of pure air inward and impure air
outward through the pores of bricks, wood, stone, and mortar. Were
such dwellings changed to tin, which is not thus porous, in less than
a week thousands and tens of thousands would be in danger of perishing
by suffocation.

These statements give some idea of the evils to be remedied. But the
most difficult point is _how_ to secure the remedy. For often the
attempt to secure pure air by one class of persons brings chills,
colds, and disease on another class, from mere ignorance or
mismanagement.

To illustrate this, it must be borne in mind that those who live in
warm, close, and unventilated rooms are much more liable to take cold
from exposure to draughts and cold air than those of vigorous vitality
accustomed to breathe pure air.

Thus the strong and healthy husband, feeling the want of pure air in
the night, and knowing its importance, keeps windows open and makes
such draughts that the wife, who lives all day in a close room and
thus is low in vitality, can not bear the change, has colds, and
sometimes perishes a victim to wrong modes of ventilation.

So, even in health-establishments, the patients will pass most of their
days and nights in badly-ventilated rooms. But at times the physician,
or some earnest patient, insists on a mode of ventilation that brings