The Hippocratic Oath
Apollo · Asclepius · Hygieia · PanaceaThe opening of the physicians' oath — the calling of gods to witness.
Ἵστορας ποιεύμενος — making them witnesses. A histōr is one who knows because he has seen; the word is the root of "history". The gods' role here is the one they have in every formula in this collection, from the fetial (janus-004) to the funerary (terra-funerary-001): not helpers but an attesting party. The oath is valid not because the gods are kind but because they were present.
The four named are not chosen at random — they are a family. Apollo the physician fathered Asclepius; Hygieia and Panakeia are Asclepius' daughters. Physicians swear not by a pantheon but by a lineage of healers, and by tradition that lineage was their own: the Asclepiadae traced their craft to him by blood. The oath is guild in origin, and its divine genealogy is the genealogy of a profession.
Then the covering clause: "and all gods and goddesses". No deity is to consider itself omitted.
On the name. This oath's relation to Hippocrates himself is unknown; it is a document of a medical school, and the attribution is conventional. The card's English runs one clause beyond the Greek given here — as far as the promise to keep the oath according to ability and judgement.