First-year students at Med 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 then 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 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."