Hospitals and the "ecology" of primary care.

Hospitals should no longer take for granted the expanded network of physicians that directs patients to them. This article offers an integrated examination of that network with special attention to fee-for-service referrals from physicians in primary care to their colleagues in more specialized fields of medicine and surgery. In a competitive environment, understanding the levels of mutual dependence among physicians and the multistage decision chain that brings patients to a specific hospital may become more important than knowing who admits those patients.