No one who has considered the history of medical care in the United States, particularly over the last several decades, can fail to be impressed by the tenacity of private physicians. While bureaucratic organizations have invaded nearly every corner of the economy, the medical profession has continued to prosper for the most part in independent, fee for-service practice. Until recently, it had successfully resisted almost every form of external constraint, discipline, or regulation.  Even when the profession lost its long battle against Medicare in 1965, it succeeded in having the legislation expressly state that no changes in the organization of medicine were intended.