After exerting a tremendous influence on the practice of medicine for a generation, the theory of focal infection in the past 10 or 15 years has fallen in part into disfavor. This has been due partly to the excesses and abuses that have been committed in its name and partly to the following observations that seem to discredit it. 1. Many patients with diseases presumably caused by foci of infection have not been relieved of their symptoms by removal of the foci. 2. Many patients with these same systemic diseases have no evident focus of infection. 3. Foci of infection are, according to some statistical studies, as common in apparently healthy persons as in those with disease.
The observations just cited appear damning, but, as Kolmer,1 Kern,2 Irons,3 and others have pointed out, none of them actually disproves the theory that some foci of infection can in