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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.
Each year in the United States, there are approximately six million pregnancies. This means that at any one time, about 4% of women in the United States are pregnant.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
In ancient Rome, many of the richer people in the population had lead-induced gout. The reason for this is unclear. Lead poisoning has also been linked to madness.
Only 12 hours after an egg cell is fertilized by a sperm cell, the egg cell starts to divide. As it continues to divide, it moves along the fallopian tube toward the uterus at about 1 inch per day.
![Photograph of the flea that transmits Yersinia pestis to cause bubonic plague, called the oriental r](https://biology-forums.com/gallery/47/medium_14755_11_11_12_7_20_12_100441848.jpeg)
![Grace Service, a YMCA missionary, explained that these porters worked at the base of Mount Omei in S](https://biology-forums.com/gallery/47/medium_6_02_03_16_7_45_23_234082405.jpeg)