Finger..

Killer joke:........................

The students of an MBBS class were attending their 1st Biochemistry lesson. They all gathered around the lab table with a urine sample. The Professor dipped his Finger in the urine & tasted it in his own mouth.
Then he asked the students to do the same. The students hesitated for several minutes, but at last every one dipped their finger in the urine sample & tasted it....
When everyone finished, the Professor looked at them & said: The most important quality is 'Observation'.  I dipped my MIDDLE finger but tasted the INDEX finger. Today you just learned, "How to Pay Attention!".😂😂😂