A doctor at a medical school was giving a quick lesson on operating. "Look here class, when operating you must show full courage", as he said this he pulled out a dead body. Then he stuck his finger in its butt crack and then licked his finger. After a session of "ugh, blech, ew" and such from his students, the doctor asked them to do the same. Reluctently, each and every student preformed the task (most of them threw up in the process after). Then the docter said "Now we learn the lesson of observation. If you were observing you would've seen I stuck my middle finger in and licked my index finger!"