"Step right up, folks, and have your health checked," blared the sound trucks on lower Manhattan's Mulberry Street last week. "Step up and get a blood test it's free, it's easy and it's quick." Befitting Mulberry Street's cosmopolitanism, the English spiels alternated with the same pitch in Italian, Spanish and Chinese. At three intersections spaced two blocks apart, teams of clerks and technicians from the city's Health Department were ready for the customers at sidewalk stands surrounded by hospital screens.
If a passerby, puzzled by the vague wording of the come-on, asked what...