One day when I was a junior medical student, a very important Boston surgeon visited the school and delivered a great treatise on a large number of patients who had undergone successful operations for vascular reconstruction.
At the end of the lecture, a young student at the back of the room timidly asked, "Do you have any control subjects?"
The surgeon drew himself up to his full height, slammed the desk with his fist, and said, "Do you mean did I NOT operate on half the patients?!"
The hall grew very quiet then. The voice at the back of the room hesitantly replied, "Yes, that's what I had in mind."
Then the surgeon's fist really came crashing down as he thundered, "Of course not!! That would have doomed half of them to their death!!"
God it was quiet then.... And one could scarcely hear the small voice ask: