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The most dangerous mercury compound, dimethyl mercury, is so toxic that even a few microliters spilled on the skin can cause death. Mercury has been shown to accumulate in higher amounts in the following types of fish than other types: swordfish, shark, mackerel, tilefish, crab, and tuna.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
The familiar sounds of your heart are made by the heart's valves as they open and close.
Walt Disney helped combat malaria by making an animated film in 1943 called The Winged Scourge. This short film starred the seven dwarfs and taught children that mosquitos transmit malaria, which is a very bad disease. It advocated the killing of mosquitos to stop the disease.