I got this in an email a few days ago...

Vet School test...

First-year students at the Vet School were attending their first anatomy

class, with a real dead cow. They all gathered around the surgery table
with the body covered with a white sheet.

The professor started the class by telling them, "In Veterinary medicine
it is necessary to have two important qualities as a doctor: the first
is that you not be disgusted by anything involving the animal body". For
an example, the Professor pulled back the sheet, stuck his finger in the
butt of the dead cow, withdrew it and stuck his finger in his mouth. "Go
ahead and do the same thing," he told his students.

The students freaked out, hesitated for several minutes, but eventually
took turns sticking a finger in the butt of the dead cow and sucking on
it.

When everyone finished, the Professor looked at them and said, "the
second most important quality is observation. I stuck in my middle
finger and sucked on my index finger. Now learn to pay attention. Life's
tough, but it's even tougher if you're stupid.."