Why doesn the hard working heart get tired?
There are many kinds of work and they all require efforts or energy. We can measure energy and compare the effort used to do different jobs. For example, the heart uses energy to pump and we can compare this effort with a lifting machine. During an average day, your hard working heart uses enough energy to lift your body a mile above the ground. The heart starts to beat before birth and continues day and night until the last moment of life. The muscles and eyes, the stomach and other organs require reasonable rest periods and every night the whole body requires seven or eight hours of restful sleep. But through all this loafing, the busy heart continues its beat, drum drumming the streaming blood throughout all the living tissues. It seems to take no rest at all, but this is not true. Actually it does as much loafing as the rest of the body. But it rests in its own special way. Some people get through very long, busy days by taking short catnaps now and then. Well, the heart is a highl
