A college professor was starting the new year with a lesson on observation. He walked into his class room holding a clear glass filled with a yellow liquid. He said, This is a glass of urine, all of his students had disgusted looks on their faces.Observe what I do and as I pass the glass around, do what I did. He stuck in his finger, pulled it out and put it in his mouth. All the students looked horrified. But, one by one, they each stuck in their finger and licked it. After everyone was finished, the proffesor said, If you had observed closely, i put in my index finger and licked my middle finger.