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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.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
In 1835 it was discovered that a disease of silkworms known as muscardine could be transferred from one silkworm to another, and was caused by a fungus.
Calcitonin is a naturally occurring hormone. In women who are at least 5 years beyond menopause, it slows bone loss and increases spinal bone density.
ACTH levels are normally highest in the early morning (between 6 and 8 A.M.) and lowest in the evening (between 6 and 11 P.M.). Therefore, a doctor who suspects abnormal levels looks for low ACTH in the morning and high ACTH in the evening.