Sophia was asked to speak to the students of a local medical school.
“Sophia, what do we need to be better doctors?” the students asked.
“Doctors,” Sophia said, “need strong stomachs and strong powers of observation.” Then she opened a canister. The putrid smell quickly moved through the classroom. Sophia stuck a finger in the jar, pulled it up, and then licked it. She passed the jar around encouraging each doctor in training to do the same. Each did, and though many felt nauseas, no one got sick.
“You all have very strong stomachs,” she said. “But your powers of observation need some work.”
“What do you mean?” they asked. “We did just what you did.”
“There is one difference,” she replied. “The finger I dipped in the jar was not the finger I licked.

David W. Jones