Snakes play an important part in alchemy
. This stems in part from powerfully transformational properties of snakes' venom, and also from their ability to slough off their old skin. Snakes lie immobile and dull for a time, and then emerge glistening new, giving an impression of immortality and eternal youth.
, a central symbol in alchemy, is a dragon or snake with its tail in its mouth. The German organic chemist August Kekulé
attributes his breakthrough on the ring structure of benzene to a dream about an ouroboros. Arthur Koestler called it "probably the most important dream in history since Joseph's seven fat and seven lean cows".