a doctor was introducing autopsy to a fresh batch of medcine students in an operating theater with a real dead body. they formed a circle around the dead body.

the doctor said to the students "the first thing you need to study medicine is to conquer your fear". he then suddenly inserted his finger up the dead body's arse, pulled it out and licked his finger. much to the disbelief of the students. then he pointed at one student and ordered him with authority to do the same. the student reluctantly but quickly followed suit.

the doctor then said to the students "the second thing you need is to be very observant. notice that i inserted my index finger but licked middle finger". the student fainted.