Eat oysters

A lady went running to a doctor with a badly spoiled stomach. "What did you eat for dinner last night?" asked the doctor. "Oysters," she said. "Fresh oysters?" asked the doctor. "How should I know?" said the lady "Well," asked the doctor, "couldn't you tell when you took off the shells?" "My Gosh," gasped the lady. "Are you supposed to take off the shells?"