Alchemical Serpent, 1519.

The serpent, or snake, is one of the oldest and most widespread mythological symbols. Snakes have been associated with some of the oldest rituals known to humankind and represent dual expression of good and evil. Historically, serpents and snakes represent fertility or a creative life force. As snakes shed their skin through sloughing, they are symbols of rebirth, transformation, immortality and healing. 
Serpents are connected with poison and medicine. The snake’s venom is associated with the chemicals of plants and fungi that have the power to either heal, poison or provide expanded consciousness (and even the elixir of life and immortality) through divine intoxication. Because of its herbal knowledge and entheogenic association, the snake was often considered one of the wisest animals, being (close to the) divine. Its divine aspect combined with its habitat in the earth between the roots of plants made it an animal with chthonic properties connected to the afterlife and immortality.