Hygieia (also spelled Hygeia, Hygiea, Ὑγιεία but these things happen) is always depicted with her snake, Wisdom, and her bowl, which contains medicinal potions. The snake, being wise --therefore knowing good from evil-- climbs up Hygieia and feeds from the bowl. Yes, religions often get answers by peeking at the mythic structures of religions sitting in desks next to them.
That being so, and with all the pressures of testing these days, it's not surprising Hygieia's Bowl has become the symbol of pharmacy worldwide. Snake has been run up around the medical caduceus. Hygieia herself has retired to sanitation, sending omens (snakes) to those of us whose sanitary bowls she worries about.
I'm a believer!