Analysis of information sources in references of the Wikipedia article "Rod of Asclepius" in English language version.
In early statues of Asclepius the rod and serpent were represented separately.
Asklepios' reptile was a healing creature: in ancient mythology the snake, whose skin was shed and rejuvenated, symbolized eternity and restoration of life and health
[...] the ancient conception of the serpent as the embodiment of the mystery of one absolute life of the earth, which entails a continual dying and resurrection [...] the combination of corruption and salvation, of darkness and light, of good and evil in the Asklepian symbol.