Medicine: Sharper Tool

In the long war against the white plague, medicine's two most useful search tools have had a grave defect. Chest X rays and the tuberculin skin test both indicate whether the patient has ever had tuberculosis, but the skin test does not show—and X rays show only imperfectly —whether the disease is still active. Last week, doctors all over the U.S. were calling New York for details of a new, simple test which indicates how active the tubercle bacilli are in the patient's system at the time the test is made.

The basic technique...