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Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.
The first-known contraceptive was crocodile dung, used in Egypt in 2000 BC. Condoms were also reportedly used, made of animal bladders or intestines.
Not getting enough sleep can greatly weaken the immune system. Lack of sleep makes you more likely to catch a cold, or more difficult to fight off an infection.
The modern decimal position system was the invention of the Hindus (around 800 AD), involving the placing of numerals to indicate their value (units, tens, hundreds, and so on).
Your chance of developing a kidney stone is 1 in 10. In recent years, approximately 3.7 million people in the United States were diagnosed with a kidney disease.