Headaches are usually seen with allergies, rarely seen with colds, but prominent with the flu.
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When blood is exposed to air, it clots. Heparin allows the blood to come in direct contact with air without clotting.
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.
The horizontal fraction bar was introduced by the Arabs.
There are more nerve cells in one human brain than there are stars in the Milky Way.
The average adult has about 21 square feet of skin.
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