|
|
Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.
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.
Increased intake of vitamin D has been shown to reduce fractures up to 25% in older people.
Vaccines cause herd immunity. If the majority of people in a community have been vaccinated against a disease, an unvaccinated person is less likely to get the disease since others are less likely to become sick from it and spread the disease.
![This engraving by William Russell Birch shows Congress Hall (left), which was occupied by Congress f](https://biology-forums.com/gallery/47/medium_374628_16_08_15_9_52_06_222501221.jpeg)
![These illustrations show Ellen Craft, a slave with and without a disguise. She dressed “as a disting](https://biology-forums.com/gallery/47/medium_375552_19_08_15_9_26_01_22334591.jpeg)
![In 2008, Barack Obama was elected president of the United States, the first minority to achieve this ...](https://biology-forums.com/gallery/27/medium_660366_14_04_17_2_21_29_278002492.png)