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After a vasectomy, it takes about 12 ejaculations to clear out sperm that were already beyond the blocked area.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
As many as 20% of Americans have been infected by the fungus known as Histoplasmosis. While most people are asymptomatic or only have slight symptoms, infection can progress to a rapid and potentially fatal superinfection.
Cancer has been around as long as humankind, but only in the second half of the twentieth century did the number of cancer cases explode.