1st year students of MBBS were attending their 1st anatomy class. They all gathered around the surgery table with a real dead dog. The Professor started class by telling two important qualities as a Doctor.

The 1st is that NEVER BE DISGUSTED FOR ANYTHING ABOUT BODY,

e.g. He inserted his finger in dog's mouth & on drawing back tasted it in his own mouth. Then he said them to do the same. The students hesitated for several minutes.
But eventually everyone inserted their fingers in dog's mouth & then tasted it.

When everyone finished, the Professor looked at them and said:  “The most important 2nd quality is OBSERVATION, I inserted my Middle finger but tasted the Index finger.
Now learn to pay attention.”

**** Moral of the Story ****

Life is tough but it’s a lot tougher when you are not paying attention.