Mercury, or Quicksilver[266], was known in the earliest ages. Its
external characters are too familiar to require any particular
description in this place. Its specific gravity is 13·568.[267] In its
metallic state it exerts no action on the living system, except that
which may depend upon its mechanical properties, although a different
opinion has been entertained, (see _Pharmacologia_, art. Hydrargyrum.)
Several of the combinations of this metal are, however, highly
destructive in small doses, and are consequently objects of forensic
interest.