Three main functions are protection regulation and sensation. Protection is primary I️ believe.
Past and light because it takes a minute for light to get from one place to another
The inhalation of mercury vapor can produce harmful effects on the nervous, digestive and immune systems, lungs and kidneys, and may be fatal. Mild, sub-clinical signs of central nervous system toxicity can be seen in workers exposed to an elemental mercury level in the air of 20 μg/m3 or more for several years.
