oil and limewater should be applied and the whole bandaged. In such a
case, it is important not to use cotton batting, since this sticks to
the rough surface and causes pain when removed.

45. Carbon Dioxide. _A Product of Burning._ When any fuel, such as
coal, gas, oil, or wood, burns, it sends forth gases into the
surrounding atmosphere. These gases, like air, are invisible, and were
unknown to us for a long time. The chief gas formed by a burning
substance is called carbon dioxide (CO_2) because it is composed of
one part of carbon and two parts of oxygen. This gas has the
distinction of being the most widely distributed gaseous compound of
the entire world; it is found in the ocean depths and on the mountain
heights, in brilliantly lighted rooms, and most abundantly in
manufacturing towns where factory chimneys constantly pour forth hot
gases and smoke.

Wood and coal, and in fact all animal and vegetable matter, contain
carbon, and when these substances burn or decay, the carbon in them
unites with oxygen and forms carbon dioxide.

The food which we eat is either animal or vegetable, and it is made
ready for bodily use by a slow process of burning within the body;
carbon dioxide accompanies this bodily burning of food just as it
accompanies the fires with which we are more familiar. The carbon
dioxide thus produced within the body escapes into the atmosphere with
the breath.

We see that the source of carbon dioxide is practically inexhaustible,
coming as it does from every stove, furnace, and candle, and further
with every breath of a living organism.