Rod of Asclepius
A young snake that is still growing may shed its skin up to four times a year, but an older snake may shed only once or twice a year. The discarded skin carries a perfect imprint of the scale pattern, so it is usually possible to identify the snake from the cast skin if it is reasonably intact. This periodic renewal has led to the snake being a symbol of healing and medicine, as pictured in the Rod of Asclepius.