d by frequent lime-washing; the paper
requires frequent renewing. A glazed paper gets rid of a good deal of
the danger. But the ordinary bed-room paper is all that it ought _not_
to be.[2]

The close connection between ventilation and cleanliness is shown in
this. An ordinary light paper will last clean much longer if there is an
Arnott's ventilator in the chimney than it otherwise would.

The best wall now extant is oil paint. From this you can wash the animal
exuviae.[3]

These are what make a room musty.

[Sidenote: Best kind of wall for a sick-room.]

The best wall for a sick-room or ward that could be made is pure white
non-absorbent cement or glass, or glazed tiles, if they were made
sightly enough.

Air can be soiled just like water. If you blow into water you will soil
it with the animal matter from your breath. So it is with air. Air is
always soiled in a room where walls and carpets are saturated with
animal exhalations.

Want of cleanliness, then, in rooms _and_ wards, which you have to guard
against, may arise in three ways.

[Sidenote: Dirty air from without.]

1. Dirty air coming in from without, soiled by sewer emanations, the
evaporation from dirty streets, smoke, bits of unburnt fuel, bits of
straw, bits of horse dung.

[Sidenote: Best kind of wall for a house.]

If people would but cover the outside walls of their houses with plain
or encaustic tiles, what an incalculable improvement would there be in
light, cleanliness, dryness, warmth, and consequently economy. The play
of a fire-engine would then effectually wash the outside of a house.
This kind of _walling_ would stand next to paving in improving the
health of towns.

[Sidenote: Dirty air from within.]

2. Dirty air coming from within, from dust, which you often displace,
but never remove. And this recalls what ought to be a _sine qua non_.
Have as few ledges in your room or ward as possible. And under no
pretence have any ledge whatever out-of sight. Dust accumulates there,
and will never be wiped off. This is a certain way to soil the air.
Besides this, the animal exhalations from your inmates saturate your
furniture. And if you never clean your furniture properly, how can your
rooms or wards be anything but musty? Ventilate as you please, the rooms
will never be sweet. Besides this, there is a constant _degradation_, as
it is called, taking place from everything except polished or glazed
articles--_E.g._ in colouring c