The crystalline element (S = sulphur, meaning "to burn slowly") with its typical sulphur-yellow colour is essential for all organisms. Like nitrogen, it is an important building block of amino acids, proteins and enzymes. In case of deficiency in the human, animal and plant organism, protein metabolism is disturbed. Its effect as a preservative in wine was already known to the ancient Greeks and Romans and is mentioned by Homer (8th century BC), Cato the Elder (234-149 BC) and Pliny the Elder (23-79 AD), among others. Until the 17th century, sulphurisation was traded as an "arcanum" (secret), i.e. a secret science known only to initiates and not open to the public. After repeated over-sulphurisation, the addition of sulphur to wine was briefly banned in some countries for health reasons and severe punishments were imposed on violators.