Medical students are taught how to do an autopsy

Fresh medical students are all gathered around a cadaver in an operating theatre. The doctor in charge addresses them before starting the autopsy.

"Now, I know you are all anxious to dissect the cadaver but before we begin, there are three principles that you must comply with. Number one, you must form an intimate bond with the cadaver. The best way to do this is to watch what I do and then follow suit. Anyone who fails to do so will be deemed unfit to continue and have their studies curtailed."

He then opens the cadaver's legs, shoves a finger up its anus and licks his finger. All the students are a bit shocked and skeptical but, it being their first autopsy and with so much to lose, they follow suit one by one. The doctor shakes his head, tells them they've all failed to observe the three principles and reluctantly dismisses the class.

One of the students musters enough courage to ask the doctor what it was they did wrong and what were the other two principles. The doctor looks at the class in sympathy and reluctantly reveals the other principles.

"The second principle is you must respect the cadaver. You all failed to do this by unceremoniously inserting your fingers up its anus. The third principle is you must have keen observation to form a successful autopsy. You all failed to note that while I shoved my middle finger up the cadaver's anus, I licked my forefinger."