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Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
Thyroid conditions may make getting pregnant impossible.
It is believed that the Incas used anesthesia. Evidence supports the theory that shamans chewed cocoa leaves and drilled holes into the heads of patients (letting evil spirits escape), spitting into the wounds they made. The mixture of cocaine, saliva, and resin numbed the site enough to allow hours of drilling.
Illness; diuretics; laxative abuse; hot weather; exercise; sweating; caffeine; alcoholic beverages; starvation diets; inadequate carbohydrate consumption; and diets high in protein, salt, or fiber can cause people to become dehydrated.
The first successful kidney transplant was performed in 1954 and occurred in Boston. A kidney from an identical twin was transplanted into his dying brother's body and was not rejected because it did not appear foreign to his body.