A mummy is a human or animal, whose skin and organs have been preserved by either intentional or incidental exposure to chemicals, extreme cold (ice mummies), very low humidity, or lack of air when bodies are submerged in bogs, so that the recovered body will not decay further if kept in cool and dry conditions. Some authorities restrict the use of the term to bodies deliberately embalmed with chemicals, but the use of the word to cover accidentally desiccated bodies goes back at least to the 1730s.