Blood comprises the one third of the human body weight – about 5 liters in adults, and 3 liters in teenagers. Only half of the whole blood circulates through the human organism. The rest of the blood is stored in blood depot.
When people laugh, their blood circulation increases in 22 percent, and when they are sad, the speed of the blood circulation decreases in 35 percent. Scientists assure that laughter is as useful as exercise.
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