The snake is one of the most commonly found animals in iconography, and in funerary symbols in particular.
Since Ancient Egypt, the circle form of a snake swallowing its own tail is a sign of eternity and or unity. It is known as “Ouroboros”, a depiction of a serpent – and sometimes a dragon – eating its own tail, and in doing so creating a cycle. It is a symbol of eternity, of the cyclical nature of life, and of something that lasts forever because at its end lies its own beginning. Ouroboros are found often as an ornament in in Celtic culture, sometimes with the tail forming one or two eights before entering into the mouth of the snake.
A short staff entwined by two snakes, sometimes surmounted by wings, is known as a “Caduceus”. It is the symbol of Hermes, God of commerce (and thieves) and is often mistaken for the “Rod of Asclepius”.
The Rod of Asclepius has only one single snake around the staff, and is the symbol of Medicine and Pharmacology. It can be read as a symbol of life and health, although in funerary arts the “Rod of Asclepius” is usually found on graves belonging to someone linked to the medical world. It is believed that the connection of the serpent and medicine is linked with its venom.
The snake may also represent negative symbols, especially sin (especially in relation to the snake who tempted Adam and Eve in the Garden of Eden, as described in the Book of Genesis).
Serpents are also connected with vengefulness and vindictiveness. This is based in part on the experience that poisonous snakes often deliver deadly defensive bites without giving prior warning to their unwitting victims. Although a snake is defending itself from the encroachment of its victim, the unannounced and deadly strike may seem unduly vengeful.
Edgar Allan Poe's famous short story "The Cask of Amontillado" invokes the image of the serpent as a symbol for petty vengefulness. The story is told from the point of view of the vindictive Montressor, who hatches a secret plot to murder his rival Fortunato in order to avenge real or imagined insults. Before carrying out his scheme, Montresor reveals his family's coat-of-arms to the intended victim: "A huge human foot d'or, in a field azure; the foot crushes a serpent rampant whose fangs are imbedded in the heel." Fortunato, not suspecting that he has offended Montressor, fails to understand the symbolic import of the coat-of-arms, and blunders onward into Montresor's trap.
Virgin Mary Treading on a Snake: In Christian art the Virgin Mary is often depicted standing on a snake on top of a globe (the earth). The theme of Christian characters opposing the snake is familiar but why the Virgin Mary in particular? The answer lies in astrology, which is secretly written into bible texts, just like shamanism. In the early hours of Christmas morning in the Northern Hemisphere the constellation Virgo (the Virgin) rises above the eastern horizon where she symbolically gives birth to the sun. Following Virgo over the eastern horizon is the snake's head of the Serpens constellation, therefore in astrological symbology the virgin rises above the earth and steps on the head of snake as she prepares to give birth to her son.
The image of a snake on a cross is a symbol of the Last Temptation of Christ, but if it has also detached wings and a crown above it, this would refer to the Flamel cross, representing the “fixing of the volatile” in alchemy. It can also refer to alchemists who have attempted human transmutation.