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The familiar sounds of your heart are made by the heart's valves as they open and close.
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.
Asthma is the most common chronic childhood disease in the world. Most children who develop asthma have symptoms before they are 5 years old.
Looking at the sun may not only cause headache and distort your vision temporarily, but it can also cause permanent eye damage. Any exposure to sunlight adds to the cumulative effects of ultraviolet (UV) radiation on your eyes. UV exposure has been linked to eye disorders such as macular degeneration, solar retinitis, and corneal dystrophies.
The horizontal fraction bar was introduced by the Arabs.