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Your skin wrinkles if you stay in the bathtub a long time because the outermost layer of skin (which consists of dead keratin) swells when it absorbs water. It is tightly attached to the skin below it, so it compensates for the increased area by wrinkling. This happens to the hands and feet because they have the thickest layer of dead keratin cells.
Atropine, along with scopolamine and hyoscyamine, is found in the Datura stramonium plant, which gives hallucinogenic effects and is also known as locoweed.
Throughout history, plants containing cardiac steroids have been used as heart drugs and as poisons (e.g., in arrows used in combat), emetics, and diuretics.
When Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.