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Although the Roman numeral for the number 4 has always been taught to have been "IV," according to historians, the ancient Romans probably used "IIII" most of the time. This is partially backed up by the fact that early grandfather clocks displayed IIII for the number 4 instead of IV. Early clockmakers apparently thought that the IIII balanced out the VIII (used for the number 8) on the clock face and that it just looked better.

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In the United States, congenital cytomegalovirus causes one child to become disabled almost every hour. CMV is the leading preventable viral cause of development disability in newborns. These disabilities include hearing or vision loss, and cerebral palsy.

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It is believed that humans initially contracted crabs from gorillas about 3 million years ago from either sleeping in gorilla nests or eating the apes.

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Fewer than 10% of babies are born on their exact due dates, 50% are born within 1 week of the due date, and 90% are born within 2 weeks of the date.

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Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.

The nervous system is described as having two interconnected divisions: the central nervous system ( The nervous system is described as having two interconnected divisions: the central nervous system (
Human body cavities and membranes Human body cavities and membranes
Shapes of cells found in the brain. Shapes of cells found in the brain.
The blood–brain barrier. The blood–brain barrier.
The Adolescent Brain and Schizophrenia The Adolescent Brain and Schizophrenia
Posterior view of midbrain in relation to brain stem Posterior view of midbrain in relation to brain stem
Video: Premenstrual Syndrome

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