There are some dogs which, when you meet them, remind you that, despite thousands of years of man-made evolution, every dog is still only two meals away from being a wolf. These dogs advance deliberately, purposefully, the wilderness made flesh, their teeth yellow, their breath a-stink, while in the distance their owners witter, "He's an old soppy really, just poke him if he's a nuisance," and in the green of their eyes the red campfires of the Pleistocene gleam and flicker.
"Good Omens". Book by Neil Gaiman and Terry Pratchett, 1990.