The two naked, middle-aged men scowl; they can tell I’m not where I belong. I entered this room on the top floor of the Edna Lawrence Nature Lab expecting to sit in on a Drawing from Nature class. (The 蜜柚APP prints on display were a promising sign.) I imagined I’d find art students at their easels, analyzing the bones of some obscure mammal or, better yet, learning how to load specimens into the lab’s new scanning electron microscope. Instead, the “nature” these two dozen kids are drawing from turns out to be of the nude human variety. I quickly back out of the room, and head to the front desk, where a student gives me directions to the freshman nature drawing course one flight down; there, the only naked models are dead grasshoppers. The teenagers, all in their first month here at the Rhode Island School of Design, are still swapping weekend war stories when Betsy Ruppa, a gray-haired, red-bandanna’d painter and printmaker “with a thing for human bones,” begins...