Precision

A grodessor in a practice medical lesson took a glass of some kind of yellow liquid and told his students:

This is an example of urine. If you wnat to become a doctor, you have to feel precisely both its and taste.

Then he dipped his finger in that liquid and tasted. The whole class was completely shocked. But because of listening to the professor's words, the glass was passed one by one around the class. After the whole class tasted that liquid, the professor shook his head and said: "You are very brave"! But if you paid attention, you would see that I had dipped my forefinger in the liquie, but my middle finger into my mouth. But don't worry! It is a mixed solution".