Five doctors went duck hunting one day. After a time,
 a bird came winging overhead. The first to react was
 the GP who raised his shotgun, but then hesitated.
 "I'm not quite sure it's a duck," he said, "I think that
 I will have to get a second opinion."
 
 And of course by that time, the bird was long gone.
 Another bird appeared. This time, the pediatrician
 drew a bead on it. He too, however, was unsure if it was
 really a duck in his sights and besides, it might have
 babies. "I'll have to do some more investigations," he
 muttered, as the creature made good its escape.
 
 Next to spy a bird flying was the sharp-eyed psychiatrist.
 Shotgun shouldered, he was more certain of his intended
 prey's identity. "Now, I know it's a duck, but does it
 know it's a duck?"  The fortunate bird disappeared while
 the fellow wrestled with this dilemma.
 
 Finally, a fourth fowl sped past and this time the
 surgeon's weapon pointed skywards.  BOOM!!  The surgeon
 lowered his smoking gun and turned nonchalantly to the
 pathologist beside him. "Go see if that was a duck,
 will you?"