Who are the victims of the device quacks? Authorities say that oldsters are a prime target. Says Wallace F. Jannsen, director of the FDA's Division of Public Information: ``Quacks are apt to direct their appeal directly to older people, or to sufferers from chronic ailments such as arthritis, rheumatism, diabetes, and cancer. People who have not been able to get relief from regular medical doctors are especially apt to be taken in by quacks.'' The victims of the quacks are frequently poor people, like Mr. A., who scrape up their life savings to offer as a sacrifice to Doctor Fraud's avarice. They are often ignorant as well as underprivileged.