A lecturer teaching medicine was tutoring a class on
observation. He took out a jar of yellow-colored liquid.
"This", he explained, "is urine. To be a doctor, you have to be
observant to color, smell, sight, and taste."
After saying this, he dipped his finger into the jar and put it
into his mouth. His class watched on in amazement, most, in
disgust. But being the good students that they were, the jar
was passed, and one by one, they dipped one finger into the jar
and then put it into their mouth.
After the last student was done, the lecturer shook his head:
"If any of you had been observant, you would have noticed that
I put my second finger into the jar and my third finger into my
mouth."
Careful observation of the truth will keep you from many
distasteful situations.