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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.
Blood is approximately twice as thick as water because of the cells and other components found in it.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
People with alcoholism are at a much greater risk of malnutrition than are other people and usually exhibit low levels of most vitamins (especially folic acid). This is because alcohol often takes the place of 50% of their daily intake of calories, with little nutritional value contained in it.
Glaucoma is a leading cause of blindness. As of yet, there is no cure. Everyone is at risk, and there may be no warning signs. It is six to eight times more common in African Americans than in whites. The best and most effective way to detect glaucoma is to receive a dilated eye examination.