Video: The Sensory System: Definition, Parts & Functions. This lesson will examine how the sensory systems are integrated and how they function as a whole. Instead of telling you ears hear and eyes see, we will examine how these systems are actually very similar in terms of reception, signals, and translations.
Mercury is a silvery-white metal element that is liquid at ordinary room temperature; it has no taste or smell. It occurs as metallic mercury (Hg), as cinnabar (HgS) and in perhaps 25 other in organic mineral compounds. The elemental form (Hg) vaporizes at any temperature down to almost 40Â° below zero. The vapor also has no taste or smell. The specific gravity of mercury is 13.546; therefore, it is heavier than lead and, like lead and other heavy metals, it is a potent poison. Exposure to metallic mercury or mercury compounds, even in small quantities over a period of time, can cause severe poisoning.
Although mercury's mystique held the promise of power, many of the ancients also knew it to be toxic. It was in the mining of the element where mercury first became associated with human illness beginning as tremors and progressing to severe mental derangement. The largest natural source of mercury is cinnabar, its only known ore, and the richest deposits are found in Spain and Italy.