A radiologist, an internist, a surgeon and a pathologist go duck hunting. The radiologist is up first and a flock of ducks fly overhead. He raises his shotgun but does not shoot. The surgeon asked him why he didn’t shoot to which the radiologist replied, “They had the outline of ducks, their contrast looked like ducks, but I wasn’t sure they were ducks.” The internist is up next. When the next flock flies overhead, he raises his shotgun in the air but does not shoot. The surgeon, getting irate at what is happening, asked the internist why he did not shoot to which the internist replied, “They looked like ducks and quacked like ducks, but I wasn’t sure they were ducks.”