re or less
coughing and pain in the lungs, must be given serious consideration.(37)
The usual home remedies failing to give relief, a physician should be
consulted. It should also be noted that certain diseases of a serious
nature (pneumonia, diphtheria, measles, etc.) have in their beginning the
appearance of colds. On this account it is wise not only to call a
physician, but to call him early, in severe attacks of the lungs.
Especially if the attack be attended by difficult breathing, fever, and a
rapid pulse is the case serious and medical advice necessary.

*Ventilation.*--The process by which the air in a room is kept fresh and
pure is known as ventilation. It is a double process--that of bringing
fresh air into the room and that of getting rid of air that has been
rendered impure by breathing (38) or by lamps. Outdoor air is usually of a
different temperature (colder in winter, warmer in summer) from that
indoors, and as a consequence differs from it slightly in weight. On
account of this difference, suitable openings in the walls of buildings
induce currents which pass between the rooms and the outside atmosphere
even when there is no wind. In winter care must be taken to prevent drafts
and to avoid too great a loss of heat from the room. A cold draft may even
cause more harm to one in delicate health than the breathing of air which
is impure. To ventilate a room successfully the problem of preventing
drafts must be considered along with that of admitting the fresh air.

[Fig. 46]

Fig. 46--Window adjusted for ventilation without drafts.

The method of ventilation must also be adapted to the construction of the
building, the plan of heating, and the condition of the weather. Specific
directions cannot be given, but the following suggestions will be found
helpful in ventilating rooms where the air is not warmed before being
admitted:

1. _Introduce, the air through many small openings_ rather than a few
large ones. If the windows are used for this purpose, raise the lower sash
and drop the upper one _slightly_ for _several_ windows, varying the width
to suit the conditions (Fig. 46). By this means sufficient air may be
introduced without causing drafts.

2. _Introduce the air at the warmest portions of the room._ The air
should, if possible, be warmed before reaching the occupants.

3. If the wind is blowing, _ventilate principally on the sheltered side of
the ho