The staff of the caduceus symbol represents the spinal cord. The snakes represent the opposites Yin and Yang. The wings symbolize the lungs, whereas the ball symbolizes the pineal gland (epifyse). The caduceus is also called the staff of Hermes, after the Greek God.
Hermes had the responsibility to serve the connections between the spinal
cord, to reconcile conflicts by using the human motion component, the
lungs, and by making the right stimulus fall in the right place.