First-year students were attending a class on a cow. The professor began his lecture, “Vet’s need two important qualities. Firstly, they shouldn’t be disgusted by anything involving an animal’s body.”

The professor stuck his finger in the cow’s anus, withdrew it, and sucked his finger. “Go ahead!” The students freaked out. They hesitated, but bravely took turns sticking a finger in the cow’s anus and sucking it.

When they’d finished, the professor continued, “Secondly, accurate observation is essential. I stuck my middle finger in the cow and sucked my index finger. Pay attention.”