In reviewing the pathologic material of the nervous system in the laboratory of the Philadelphia General Hospital, we were impressed by the fact that two dissimilar conditions occurring in the nervous system at the same time were most unusual. The infrequency of combined lesions of the nervous system well fits in with the almost axiomatic rule that, if possible, the clinical diagnosis should include one disease only. In more than five thousand cases that have come to autopsy here in twelve years, less than ten have shown two or more basic conditions at the same time. Yet this question comes up frequently at the bedside. The problem of tumor in association with advanced vascular disease is not to be considered here, but forms a special chapter in itself.
Cases in which a combination of two or more basic conditions is present in the central nervous system are scattered infrequently through