The caduceus as a symbol for medicine.

The caduceus (☤) (/kəˈdjuːsiəs/, -ʃəs, -ˈduː-; κηρύκειον in Greek) is typically depicted as a short herald's staff entwined by two serpents in the form of a double helix, and sometimes is surmounted by wings. This staff first was borne by Iris, the messenger of Hera. It also was called the wand of Hermes when he superseded Iris in much later myths.
In later Antiquity the caduceus may have provided the basis for the astrological symbol representing the planet Mercury and in Roman iconography was often depicted being carried in the left hand of the Greek god Hermes (Roman god, Mercury), the messenger of the gods, guide of the dead and protector of merchants, gamblers, liars and thieves.
The caduceus is sometimes used as a symbol for medicine, especially in North America, through confusion with the traditional medical symbol, the rod of Asclepius, which has only a single snake and no wings.
Hermes (or more properly the Roman Mercury) once saw two serpents entwined in mortal combat. Separating them with his wand he brought about peace between them, and as a result the wand with two serpents came to be seen as a sign of peace.[8]
In Rome, Livy refers to the caduceator who negotiated peace arrangements under the diplomatic protection of the caduceus he carried. In Babylonian mythology the suggested association is with Ishtar as "an awakener of life and vegetation in the spring" is seen as justification for its association with healing, medicine, fertility and potency.
The first known use of the caduceus in a medical context was in the printer's vignette used by the Swiss medical printer Johann Frobenius (1460-1527), who used the staff entwined with serpents, not winged but surmounted by a dove, with the biblical epigraph "Be ye therefore wise as serpents and harmless as doves". Caduceus Wikipedia