Rod of Asclepius
The symbol of a single serpent coiled around a rod or staff is the symbol of the Greek god Asclepius, who is associated with healing and medicinal arts. The rod of Asclepius is the most accurate symbol for medicine and is used by many medical organizations worldwide. The symbol has continued to be used in modern times, where it is associated with medicine and health care, yet frequently confused with the staff of the god Hermes, the caduceus.
The Caduceus
The symbol of two snakes around an often winged staff is the symbol of the Greek god Hermes. The long-standing and abundantly attested historical associations of the caduceus with commerce, theft, deception, and death are considered by many to be inappropriate in a symbol used by those engaged in the healing arts. The two-snake caduceus design has ancient and consistent associations with eloquence, trickery and negotiation.
In a survey of 242 logos used by organizations related to health or medicine, Friedlander found that professional associations were more likely to display the rod of Asclepius (62%), while organizations with a commercial focus were more likely to use the caduceus (76%). Hospitals were an exception (37% used a staff of Asclepius whereas 63% used a caduceus). Friedlander felt it likely that this might reflect the fact that "professional medical organizations have more often sought a real understanding of the meaning of the two symbols whereas commercial organizations have been less interested in the historical basis of their logo or insignia and more concerned with how well a certain symbol will be recognized by the iconographically unsophisticated audience they are trying to attract to their wares." Friedlander, Walter J (1992). The Golden Wand of Medicine: A History of the Caduceus Symbol in Medicine. Greenwood Press