The Chief of Services inevitably begins the year's instructions to the new medical students by teaching "a singularly important principle of medicine." He asked a nurse to get him a sample of urine. He then talked at length about diabetes mellitus. "Diabetes," he said, "is a Greek name; but the Romans noticed that the bees like the urine of diabetics, so they added the word mellitus which means sweet as honey. Well, as you know, you may find sugar in the urine of a diabetic..."
By now, the nurse had returned with a sample of urine which he promptly held up like a trophy. We stared at that straw colored fluid as if we had never seen such a thing before. Chief of Services then startled us. He dipped his finger into the urine, then licked his finger with the tip of his tongue. Could he detect a faint taste of sugar? The sample was passed on to us for our opinions. We all dipped a finger into the fluid, all of us foolishly licked our fingers.
"Now," said the Chief of Services smiling, "you have learned the first principle of diagnosis. I mean the power of observation. You may not have noticed, but I dipped my pointer finger into the urine, and licked my middle finger..."