An eighty year old Couple

An eighty year old couple decide to try for a child. They visit the doctor who asks the old geezer to produce a sperm sample in a bottle. After two weeks, the couple return and the bottle is empty. "What's the problem?" asks the doctor. "Well," says the old man, "First I tried it with my right hand, then my left. Then my wife tried it with her right hand, then her left. Then she tried it with her teeth in and with her teeth out, and we still can't get the lid off the bloody bottle."