and, therefore, the demand for additional
water was felt in order to stimulate greater action on the part of the
kidneys to care for these waste products. That this was not a successful
substitute was shown by the loss of weight in the animals, and by the
irritation of the skin which evidently was trying to eliminate some of
the remaining impurities through its surface.

_Modifying circumstances._

Fortunately for mankind, it has not been customary, nor even possible,
to build dwellings or stables approaching the air-tightness of a fruit
jar. Air has great power of penetration, particularly when in motion,
and a wind will blow air through wooden walls, and even through brick
walls, in considerable quantity. It is practically impossible to build
window casings and door frames so that cracks do not exist, through
which air may find its way. When, however, in the wintertime, storm
windows have been put on, or when, as occasionally happens, to keep out
drafts, strips of paper are pasted carefully around all window casings,
or when rubber weather strips are nailed tight against the windows and
doors, conditions are obtained which resemble the mason fruit jar, and
under those conditions, a person living continuously in such a room is
experimenting on himself as Professor King did with the candle.

Another reason why it is difficult to make a room an air-tight chamber
is that if a stove or fire-place be in the room, a strong suction is
produced through the flame, and such suction requires the entrance of
outside air. It is a common experience that a fire-place in a room
otherwise tight will refuse to draw and will smoke persistently until a
door or window is opened, when, a supply of air being provided, the fire
is made bright and active.

Fortunately, the vitiation of the air in a room is never so severe as
that in an experimental chamber, and there are few examples which can be
cited of men or women dying from lack of ventilation in an ordinary
room. But the serious aspect of inadequate ventilation is not that it
actually induces death, but that it decreases the powers and activities
of the various organs of the body; that it interferes with their normal
processes, that it loads up in the body an accumulation of organic
matter which is normally oxidized by fresh air and which, if not
oxidized, obstructs the activities of other organs of the body.

_Danger of polluted air._

Unfortunately, it is not possible to detect b