Clinical sex?

Two medics had to stay at the same hotel after a conference. So they agreed that she'd go to his room in the night and have sex.

She arrived, and immediately undressed and started energetically scrubbing her fingers, hands, arms, etc. Then, they got into bed and screwed for an hour.

Afterwards, he said to her, "I suppose you must be a surgeon."

"Yes", she said. "How did you know?"

He said, "Well what with all the scrubbing up before and so on..."

So she said, "I'm guessing, but I reckon you're an anaesthetist."

He said, "Yes. How on earth did you know?"

She said, "Well, I didn't feel a thing!"