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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.
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.
In 1886, William Bates reported on the discovery of a substance produced by the adrenal gland that turned out to be epinephrine (adrenaline). In 1904, this drug was first artificially synthesized by Friedrich Stolz.
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.
Sperm cells are so tiny that 400 to 500 million (400,000,000–500,000,000) of them fit onto 1 tsp.
![Evaluation of a child for cystic fibrosis with a sweat chloride test. Sweat is being collected under](https://biology-forums.com/gallery/47/medium_14755_05_10_12_4_11_17_92651003.jpeg)
![Magnetic resonance imaging (MRI). The MRI lab includes the scanning instrument and a computer statio](https://biology-forums.com/gallery/47/medium_14755_14_10_12_6_49_35_9415513.jpeg)