The heart has
been called "the fountain of life," because by it the blood, which is the
life of the body, is kept in continual motion, and sent to every part. How
little we think of it! But whether we are waking or sleeping, at work or at
rest, this busy fountain still goes on playing. We may hear the throb of
it, as it strikes against the chest, in its ceaseless working; and we may
count these regular "beats," and find that there are about seventy-five
of them every minute. It has been calculated that during an ordinarily
long life there are three thousand millions of beats without a break. But
what has set this fountain at work? and what keeps it going night and day
without any thought or care of ours, all our life long? Of all this it can
only be said, "We do not know; we cannot find out. God in His wisdom has so
ordered it."
Many years ago a doctor, who had observed very carefully, and thought much
about what he observed, found out that every time the heart beats, the
blood rushes from it into a great curved tube called an artery, and so
passes through tubes which, like the nerves, are constantly becoming finer
and finer, to every part of the body.
He also discovered that the blood takes its journey back again to the heart
by a different road: it does not return through these tubes, but through
softer ones, called veins. Thus far he could go, and the story of the
"circulation" of the blood is very interesting; but the _cause_ of the
heart's perpetual motion, and the blood's continuous flow, this he could
not discover.
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