Pathogenic microbes of the oral environment.

Improved health owes less to advances in medical science than to changes in the external environment, and to a favorable trend in the standard of living. We are healthier than our ancestors not because of what happens when we are ill but because we do not become ill; and we do not become ill not because of specific protective therapy but because we live in a healthier environment. In its preoccupation with the minutiae of diagnosis and the pathogenesis of disease, medicine is in danger of neglecting what has hitherto proved its most powerful resource-the manipulation of the external environment.