The serpent in Christian Art figures in Paradise as the tempter of Eve under that form, and is generally placed under the feet of the Virgin, in allusion to the promise made to Eve after the Fall: "The seed of the woman shall bruise the serpent's head." The heart of the serpent being close to the head, renders a severe "bruise" there fatal. The serpent bruised the "heel" of man--_i.e._, being a cause of stumbling, it hurt the foot which tripped against it (Gen. iii. 15).
The brazen serpent erected by Moses in the wilderness, which gave newness of life to those plague-stricken Israelites who were bitten by the fiery dragons and raised their eyes to this symbol (Numb. xxi. 8), as an emblem of healing, is represented in Christian art as coiled up on a tau cross, a symbol of which our Saviour did not disdain in some degree to admit the propriety when he compared himself to the healing serpent in the wilderness.
The serpent is placed under the feet of St. Cecilia, St. Euphemia, and many other saints, either because they trampled on Satan, or because they miraculously cleared some country of such reptiles. St. Patrick, the patron saint of Ireland, is always represented habited as a bishop, his foot upon a viper, the head transfixed with the lower extremity of his pastoral staff, from his having banished snakes and all venomous reptiles from the soil of Ireland. As the symbol of the evil principle, a diminutive specimen of the dragon, guivre, or winged snake was more frequently used, wriggling under foot.
The serpent is emblematical of THE FALL; Satan is called the great serpent (Rev. xii. 9); of WISDOM: "Be ye therefore wise as serpents, and harmless as doves" (Matt. x. 16); of SUBTLETY: "Now the serpent was more subtil than any beast of the field" (Gen. iii. 1); of ETERNITY: a serpent in a circle with its tail in its mouth is the well understood symbol of unending time.
"The serpent figures largely in Byzantine Art as the instrument of the Fall, and one type of the Redemption. The cross planted on the serpent is found sculptured on Mount Athos; and the cross surrounded by the so-called runic knot is only a Scandinavian version of the original Byzantine image--the crushed snake curling round the stem of the avenging cross. The cross, with two scrolls at the foot of it typifying the snake, is another of its modifications, and a very common Byzantine ornament. The ordinary northern crosses, so conspicuous for their interlaced ornaments and grotesque monsters, appear to be purely modifications of this idea."[8]