By his own estimate, Proctor spent a decade poring over more than 100,000 tobacco industry documents unearthing details such as a primer on how to reach "young starters" and a 1970 Lorillard memo suggesting that "Negroes" smoke menthols to "mask" their "real/mythical odor." The 57-year-old prof is a walking encyclopedia of tobacco arcana, apt to mention things like "beaver," a rodent anal secretion sometimes added to cigarettes, perhaps to enhance "pack aroma." Or that as much as 90 percent of America's licorice supply is used as a cigarette sweetener. (Honey, chocolate, and sugar are also employed to make cigarette smoke more inhalable—and thus more addictive.) Or that around 4 percent of a cigarette's weight is made up of humectants like propylene glycol—basically antifreeze. "You can put things in cigarettes you can't put in dog food," Proctor says.