A ll our knowledge that we cannot directly perceive reaches us via symbols and signs. When these symbols and signs (e.g. words, pictures and ideograms) reach us, we associate them with our memories. And then true knowledge or illusions about the world we live in are released in us. For every sensory perception that reaches us, there is some outer physical reality.
In ancient Greece this sign represented Hermes, the quick-footed messenger of the gods. Hermes was symbolized by the Caduceus, the staff of snakes. In Rome two snakes became symbol of Communications and only one snake, a symbol for the art of healing or medicine. Hermes was, contrary to the other Greek gods, both male and female, a hermaphrodite. For this reason, this sign has been used both in biology to mean double-sexed.
This is also the sign for the planet Mercury. In astrological psychology, Mercury stands for the intellect and the basis of our communication systems. In mundane astrology Mercury stands for business, art of writing, technical and natural science institutions, printing and publishing companies. This symbol was used for intelligent people with good linguistic ability, inventiveness, fast thinkers and well developed communication ability to convince others as well as a good memory for even tiny details.
Anatomically, this symbol stands for the nervous system, the organs of vision and speech, and the hands, all considered in this case as instruments of the intellect. As a weekday, this sign stands for Wednesday, known as Woden's day in Germanic countries.