First-year students at Medical School were receiving their first
anatomy class with a real dead human body. 
They all gathered around the surgery table with the body covered 
with a white sheet. The professor started the class by telling them,
"In medicine, it is necessary to have 2 important qualities as a 
doctor. The first is that you not be disgusted by anything involving
the human body." For an example, the Professor pulled back the sheet,
stuck his finger in the butt of the corpse, withdrew it and stuck his 
finger in his mouth. "Go ahead and do the same thing," he told his students.
The students freaked out, hesitated for several minutes, but eventually 
took turns sticking a finger in the butt of the dead body and 
sucking on it. When everyone had finished, the Professor looked at 
them and told them, "The second most important quality is observation.
I stuck in my middle finger and sucked on my index finger. 
Now learn to pay attention."