The caduceus (☤;; Latin: cādūceus, from Greek: κηρύκειον kērū́keion “herald’s wand, or staff”) is the staff carried by Hermes in Greek mythology and consequently by Hermes Trismegistus in Greco-Egyptian mythology. The same staff was also borne by heralds in general, for example by Iris, the messenger of Hera. It is a short staff entwined by two serpents, sometimes surmounted by wings. In Roman iconography, it was often depicted being carried in the left hand of Mercury, the messenger of the gods. The two-snake caduceus design has ancient and consistent associations with trade, eloquence, negotiation, alchemy and wisdom. It is often used as a symbol of medicine instead of the Rod of Asclepius, especially in the United States. 
The traditional symbol for medicine was not the Caduceus but the Rod of Asclepius which consists of one rod and one snake, not the double snake of the Caduceus. The modern use of the caduceus as a symbol of medicine became established in the United States in the late 19th and early 20th century as a result of documented mistakes, misunderstandings and confusion.
It was the Rod of Asclepius that was the ancient Greek symbol associated with medicine, which consisted of a single serpent coiled around a rod. In ancient Greek religion and mythology, Asclepius was the god of medicine and healing. His daughters are Hygieia (goddess of cleanliness), Iaso (goddess of recuperation from illness), Aceso (goddess of the healing process), Aglea (the goddess of splendor and adornment), and Panacea (goddess of universal remedy).
Perhaps part of the confusion has come about because the caduceus symbol is used in different forms throughout the world in ancient alchemy, yogic texts and indigenous wisdoms. It is said to represent the Sacred Masculine and the Sacred Feminine, in which Ida (the sacred feminine) and Pingala (the sacred masculine) channels rise equally around the central channel or the Shushmuna, the path to enlightenment.
The sushumna (most gracious) nadi is the body’s great river, running from the base of the spine to the crown of the head, passing through each of the seven chakras in its course. It is the channel through which kundalini shakti (the latent serpent power) —and the higher spiritual consciousness it can fuel—rises up from its origin at the muladhara (root) chakra to its true home at the sahasrara (thousandfold) chakra at the crown of the head.
The ida (comfort) and pingala (tawny) nadis spiral around the sushumna nadi like the double helix of our DNA, crossing each other at every chakra. Eventually, all three meet at the ajna (command) chakra, midway between the eyebrows.
The ida nadi begins and ends on the left side of sushumna. Ida is regarded as the lunar nadi, cool and nurturing by nature, and is said to control all mental processes and the more feminine aspects of our personality. The color white is used to represent the subtle vibrational quality of ida. Pingala, the solar nadi, begins and ends to the right of sushumna. It is warm and stimulating by nature, controls all vital somatic processes, and oversees the more masculine aspects of our personality. The vibrational quality of pingala is represented by the color red.
The interaction between ida and pingala corresponds to the internal dance between intuition and rationality, consciousness and vital power, and the right and left brain hemispheres. In everyday life, one of these nadis is always dominant. Although this dominance alternates throughout the day, one nadi tends to be ascendant more often and for longer periods than the other. This results in personality, behavior, and health issues that can be called ida-like or pingala-like.
Balancing sun and moon, or pingala and ida, facilitates the awakening and arising of kundalini, and thus the awakening of higher consciousness. In fact, some yoga teachings hold that as long as either ida or pingala predominates, sushumna stays closed and the power of kundalini lies dormant. In many respects then the Cadeuceus represents spiritual health and spiritual growth.
The most powerful method of balancing ida and pingala is Nadi Shodhana, alternate-nostril breathing. (Literally, the Sanskrit means “nadi cleansing.”) This practice is effective because the ida nadi is directly connected to the left nostril, and the pingala nadi to the right. A few rounds of this basic Pranayama technique at the end of an asana practice are an excellent way to help restore equilibrium between the two nadis and to compensate for any imbalance you may have inadvertently caused.