and finds its
way again into the springs and great veins of water under the earth,
from which it is carried back once more to the city. Thus it is made
pure again and again, to be used over and over by the people whom God
has created and whom He supplies with water in this way.

Now, in somewhat the same way, the heart, which is both an engine and a
pump, forces the blood out through the pipes or tubes of our bodies
called the arteries, distributing it to every portion of the body,
furnishing the materials for building and renewing the muscles and the
bones and every portion of our system. Then gathering up that which is
worn out and no longer of service, the impure blood returns through the
veins back to the right side of the heart, where it is pumped into the
lungs and purified by being brought into contact with the air we
breathe. The blood is then returned to the left side of the heart,
pumped again into the arteries and distributed through all parts of the
body, and so it goes on circulating. Thus the blood is pumped by the
heart into the arteries and is distributed to all portions of the body,
and returned again to the heart, from fourteen to twenty times each hour
of our life.

In this bottle, which holds six ounces, I have placed some of this
colored water, which represents about the quantity which is pumped out
of the heart of an adult each time the pulse beats. As I have already
intimated to you, the heart is double, and at each throb about one-half
the quantity in this bottle is pumped out by the right side, and the
other half by the left side of the heart. Now, if the heart were to pump
different blood with each pulsation, instead of pumping the same blood
over and over again, in twenty-four hours the heart of a man of ordinary
size would pump 150 barrels of blood.

[Illustration: A Wagon Load of Barrels.]

The Bible says that the days of our years are three-score years and ten,
or, in other words, that the allotted period of an ordinary life is 70
years. Now, in 70 years the heart would pump 164,389,786 gallons; or,
to give it to you in barrels, it would make 4,566,382 barrels. If you
were to place six barrels on a wagon, and this would make a good load
for two horses, you would have 761,063 loads of these barrels. If you
were to place these teams, with the wagons containing six barrels
apiece, with 36 gallons each, at a distance of 25 feet apart, it would
make a string of teams stretching away 1,778 mi