The symbol of the caduceus is defined as a figure whose basic structure consists of two entwined serpents encircling a wand or rod. Most of the depictions also have a pair of wings perched atop the rod. This is different from the depictions of the staff of Aesculapius, which is traditionally shown as a single snake wrapped around a simple wooden walking staff. Each of these symbols have both a wooden staff and a serpent or pair of serpents. The wooden staff is said to symbolize the tree of life from the Garden of Eden. Serpents have been said to represent the vital forces in life. In the Bible, it talks about Moses making a serpent of brass and placing it on a pole. Any man bitten by a serpent would live if he looked upon the serpent of brass. (Numbers 1,9). Serpents in medical symbols have been looked upon as depicting wisdom, rejuvenation, and longevity. (Potter) The two versions of the staff and serpents have been confused and interchanged throughout history, despite their vast difference in meanings and background.

The word caduceus comes from the Latin word kerykeion, which was originally used to describe the staff or wand of a messenger. It was later associated with Hermes, the messenger of the Greek gods. Hermes is described as a diplomatic, peace-bringing ambassador in many accounts. One such tale describes Hermes stopping two snakes from fighting by throwing his rod in between them, causing the snakes to become twisted around the wand. This act gave rise to the caduceus symbol, and helped to give Hermes a reputation as a great mediator. Although not associated with medicine, at least this myth gives a positive impression of the symbol when looking at its mythological origins.

However, Hermes was also considered to be the god of commerce and wealth, which in turn implies a sense of personal self-interest along with the possibility of stretching the truth to meet one's own needs. Hermes was known as the patron god of thieves due to his many tricks and lies. The quality of dishonesty is not one that most people want to see in their physician, therefore a symbol that is traced back to representing trickery and deceit should not be used to represent a profession as highly regarded in trust as medicine. Additionally, Hermes is also said to have used his caduceus staff to lead the souls of those who passed away to the underworld, which is the opposite idea than that stated in the Hippocratic Oath with which a physician is charged.

On the other hand, Aesculapius is considered to be the true god of medicine, trained in the healing arts by the centaur Chirion. The son of Apollo, god of health, Aesculapius is said to have been pulled from the womb as his mortal mother was dying, which came to symbolize a physician's ability to turn death into life. Throughout his life, Aesculapius used medicinal herbs and surgical procedures to heal the sick and dying, with his culmination of the art being the ability to bring the dead back to life. In one episode of mythology, Aesculapius was said to have been inside a temple when a serpent came to him and wound itself up and around his walking staff. He killed the serpent, only to have a second slither in and use an herb to bring its dead comrade back to life. This brings forth the explanation for the revered symbol of Aesculapius' staff, with this herb being the major discovery of his life. The snake was seen as a servant to Aesculapius in his healing, and was worshiped as such.

Aesculapius' acts are said to embody the true spirit of medicine, that is, to use all methods possible to delay and even defy death. In the depiction of Aesculapius' staff, the strong cypress branch is said to represent the solid moral ethic of a physician. This tradition has been improved upon throughout the years, to the point where human life can be assisted and even in some ways replaced by machines. Even though there is controversy today about how medicine should be practiced, the spirit of healing and helping in whatever ways possible is still the core of the physician's creed as it was in the time of Aesculapius. Thomas Carlyle, a 19^th century English philosopher, said that "as physicians, we should emulate the example of Aesculapius by negotiating the inherent contradictions of human nature and by understanding the powers and limitations of our profession." (Heart Views)

Many printers in the 1500s used the caduceus symbol as the insignia on their publications because it was a noted and commonly used symbol for merchants, messengers, and businessmen. The confusion between the two symbols was first noted when the German scholar Johann Froben used a wingless caduceus symbol as the insignia on his publications. Some of his books dealt with the medical field, bringing the caduceus symbol into association with medicine. From there, medical texts and other publications began to use slight variations of the caduceus symbol as their insignia, increasing the identification of the caduceus with medicine.

Another way that the two symbols became confused was by the misnaming of items in various pictures and paintings. The earliest occurrence noted of this was a translation into English of Tempest's Iconologia, where a depiction of Aesculapius' staff was wrongly described as a caduceus. The two symbols have since frequently been exchanged in name and depiction. By the end of the 18^th century, the caduceus began to be accepted as a valid symbol of the medical field. This was due to readers seeing it used interchangeably with Aesculapius' staff, and it being associated with medicine in various depictions and examples.

The event that most influenced the association of the caduceus with the medical field was the adoption of it as the official symbol of the U.S. Army Medical Corps on July 17, 1902. The captain that suggested the symbol did so based on its having a sleeker, more symmetric look than the staff of Aesculapius. The symbol met with great popularity, and was used as an allegory for peace and health throughout the wars. On the other hand, the World Health Organization uses the staff of Aesculapius as its defining medical symbol, sticking more to the true mythological roots.

 

Once the popularity of the caduceus increased, so did its use. The word caduceus began to be used in the titles of medical newsletters and journals in 1922. This is in spite of the fact that prior to the year 1900, the word had never appeared in a medical dictionary and had not been associated with the practice of medicine. Today the usage of the two symbols is split, with certain aspects of medicine using each symbol. Of professional organizations, 62% use the staff of Aesculapius as their symbol, while 76% of commercial organizations use the caduceus. (Friedlander) This shows that the professional organizations understand the real meaning behind the symbols and choose to use the staff of Aesculapius, while the commercial organizations go for the popularity and recognizability of the caduceus. The caduceus is more suited to being a symbol of diplomatic peace between countries, with the staff of Aesculapius reserved for medical texts, depictions, and colleges.