No social encounter delights me more than meeting a doctor at a cocktail party. In clinical settings, doctors tend to be guarded and aloof. Catch one with a whiskey in hand, though, and you might find yourself in possession of all sorts of inside information. Among the nuggets I’ve gathered in this fashion are: that salt and butter aren’t really bad for you; that nicotine is a marvelous antidepressant; that vegans are no healthier than the rest of us; and that early cancer screening may be pointless, since many small tumors vanish on their own and some grow so slowly that their human hosts will die before they do major harm. Some of this may be inaccurate, perhaps, but most of it is worth repeating at other parties.