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The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
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.
After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
Since 1988, the CDC has reported a 99% reduction in bacterial meningitis caused by Haemophilus influenzae, due to the introduction of the vaccine against it.
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).