The human heart is a hard-working marvel. It can keep on beating automatically even if all other nerves were severed. In a 70 year lifetime, it will beat an average of 75 times a minute, forty million times a year - or two-and-a-half billion times. At each beat, the average adult heart discharges about four ounces of blood. This amounts to three thousand gallons a day or 650,000 gallons a year—enough to fill more than 81 tank cars of 8,000 gallons each.
The heart does enough work in one hour to lift a 150-pound man to the top of a three-story building.
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