In the summer of 1965, a female Dalmatian was stolen from a farm in Pennsylvania. Her story changed America.

Pepper's journey in the summer of 1965 helped start a national media sensation and a broad panic over the theft of pets for biomedical research. Her death on an operating table in the Bronx would help animal welfare advocates break a long-standing stalemate in Congress and push through the most significant animal-protection bill in American history. At the same time, she became a martyr to the cardiology revolution at a crucial moment in its development. Pepper also represents a turning point in science, from an earlier age when animals for experiment would be plucked from the road or the river, to a new era of standardized, mass-produced organisms that can be shipped right to the laboratory door. In a five-part seriesto be published over the course of this week, Slate will explore her legacy.

Correction, June 9, 2009: This article originally referred to Pavlov's discovery that "animals would drool at the sound of a bell." That's a widely held misconception about his work. It was already well-known that animals could learn to salivate in response to sounds; Pavlov helped elucidate the meaning and function of these conditioned reflexes. References to a "bell" in his work are the result of a long-standing mistranslation from the Russian of the word for "electrical buzzer." In fact, Pavlov only used a bell once or twice in more than 30 years of research. (Return to the corrected sentence.)