Please forgive the English. My German can be laughable.
Cave Canem, a picture (Vesoul, Musee Garret) by the 19th-century French history painter Jean-Leon Gerome shows a man fettered to a wall with the label “Cave Canem†attached to it. He may be wearing a muzzle, too. Figures in Roman costume in the background. Who is this? A disgraced general? Where is the story to be found?
You can respond in German.