The pathologic changes in brain abscess are, as a rule, so manifest, even on macroscopic examination, that a correct diagnosis offers practically no difficulty, however insignificant the abscess may be. Probably this is the main reason for the scarcity of literature on microscopic brain changes resulting from abscess. Yet studies of the histologic changes are of great scientific interest, for they may clear up some as yet unsettled questions which are not only of academic, but also of practical, value.
Brain abscess perhaps brings to mind a circumscribed lesion more or less walled off by a membrane. Since time is required for a membrane to form, the walling off of an abscess necessarily must be a more or less gradual, subacute or chronic process that ultimately leads to transformation of a portion of brain tissue into a cavity filled with pus. This gradual replacing of the brain tissue by a