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On average, the stomach produces 2 L of hydrochloric acid per day.
There are more nerve cells in one human brain than there are stars in the Milky Way.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
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