A patient walks into a doctor's office complaining of abdominal discomfort. The doc takes a fecal sample and discovers his patient has a tapeworm. He tells his patient, "Don't worry, I have the perfect treatment. Come in tomorrow with a hard boiled egg and a lemon cookie." The patient is a little confused, but does as the doctor orders.
The next morning, the doctor asks his patient to drop his pants and bend over. He shells the egg and inserts it in the patient's rectum. The doc closely monitors his watch and exactly two minutes later inserts the cookie as well. He tells the patient to come in tomorrow with another egg and another cookie.
The next morning, the doctor does the same thing: inserts the egg and exactly two minutes later inserts the cookie. This goes on for three more days in exactly the same manner and by this time the patient is really confused. Finally, on the fifth day of treatment, the doc says, "Tomorrow I want you to come in with another hard boiled egg, but this time bring a hammer instead of a cookie, ok?"
The next day, the patient comes in and the doc inserts the hard boiled egg as usual. He closely monitors his watch as two minutes pass...then three minutes...then four minutes...Suddenly the tapeworm sticks his head outside and shouts, "Where's my lemon cookie?!" and wham! - down comes the hammer. The patient is cured.