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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.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
Hippocrates noted that blood separates into four differently colored liquids when removed from the body and examined: a pure red liquid mixed with white liquid material with a yellow-colored froth at the top and a black substance that settles underneath; he named these the four humors (for blood, phlegm, yellow bile, and black bile).
Fungal nail infections account for up to 30% of all skin infections. They affect 5% of the general population—mostly people over the age of 70.
In women, pharmacodynamic differences include increased sensitivity to (and increased effectiveness of) beta-blockers, opioids, selective serotonin reuptake inhibitors, and typical antipsychotics.