The most characteristic and typical of a thing in a situation of concentration. Among medieval astrologers, fifth element of nature, the ether, which was added to the 4 of Empédocles, earth, water, air and fire. For medieval alchemists and botanists and early modernity was the therapeutic extract of medicinal plants that today we consider the active ingredients and essential oils, what Paracelsus, father of toxicology, called poison. Single facit venenum dosage : only the dose makes something poisonous, responded when someone accused him of giving poison to the sick.
