For more than a decade, Republican and Democratic administrations alike have been promoting health-care-delivery concepts that differ fundamentally from the traditional way medical care is rendered in the United States. Through the provision of grants and loans, loan guarantees, and a law that compelled private employers to offer their workers a choice of health-care plans when available, the federal government has nurtured the development of "health-maintenance organizations" (HMOs). Such organizations offer a comprehensive range of benefits for a price fixed in advance. The care is usually provided by doctors who deliver the services on a basis that places them at . . .