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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.
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.
Autoimmune diseases occur when the immune system destroys its own healthy tissues. When this occurs, white blood cells cannot distinguish between pathogens and normal cells.
The horizontal fraction bar was introduced by the Arabs.
Many of the drugs used by neuroscientists are derived from toxic plants and venomous animals (such as snakes, spiders, snails, and puffer fish).
![The Movius line separates regions of the world where Acheulean hand axes were made from regions wher](https://biology-forums.com/gallery/47/medium_275510_22_02_15_5_56_55_207692261.jpeg)
![When the United States gets stuck over a controversial issue—usually something a divided Congress ca](https://biology-forums.com/gallery/47/medium_262797_12_08_15_1_37_16_22180672.png)