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There are 20 feet of blood vessels in each square inch of human skin.
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.
Human neurons are so small that they require a microscope in order to be seen. However, some neurons can be up to 3 feet long, such as those that extend from the spinal cord to the toes.
Signs and symptoms that may signify an eye tumor include general blurred vision, bulging eye(s), double vision, a sensation of a foreign body in the eye(s), iris defects, limited ability to move the eyelid(s), limited ability to move the eye(s), pain or discomfort in or around the eyes or eyelids, red or pink eyes, white or cloud spots on the eye(s), colored spots on the eyelid(s), swelling around the eyes, swollen eyelid(s), and general vision loss.
The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
![An electrocardiogram (ECG, EKG) is a commonly used procedure in which the electrical events associat](https://biology-forums.com/gallery/47/medium_14755_01_10_12_7_54_15_920984.jpeg)
![A typical variable cam timing control valve. The solenoid is controlled by the engine computer and ...](https://biology-forums.com/gallery/29/medium_548020_30_05_17_3_43_29_29648118.png)