"Well judgeth my Lord Constable, to withdraw his noble lady from the host of petticoated empirics, who, like so many Amazons, break in upon and derange the regular course of physical practice, with their petulant prognostics, their rash recipes, their mithridate, their febrifuges, their amulets, and their charms. Well speaketh the Ethnic poet,
'Non audet, nisi quae didicit, dare quod medicorum est; Promittunt medici—tractant fabrilia fabri.'"
As he repeated these lines with much emphasis, the doctor permitted his patient's arm to drop from his hand, that he might aid the cadence with a flourish of his own. "There," said he to the spectators, "is what none of you understand—no, by Saint Luke, nor the Constable himself."
The text above is from “The Betrothed”. Saint Luke is mentioned in dialogue in more than one of Walter Scott’s novels. Perhaps his status as patron saint of artists brought Luke to mind several times for Scott. Luke is known, among other things, for his command of Greek writing. October 18th is the Feast of Saint Luke.