Virchow1 established the identity of the intracranial tumors arising from the supporting glial elements and named them "gliomas." Prior to his work their identity had been obscure and controversial, but, as a matter of fact, the differential classification was not successfully achieved until more than sixty years after Virchow's investigation, when Bailey2 and Bailey and Cushing3 correlated the histologic and the clinical aspects of the tumors. During these six decades glial and mesodermal tumors continued to be confused, as is evidenced by such misleading terms as "gliosarcoma." The existence of this state of confusion is not surprising when it is considered that up to the time of Bailey and Cushing3 the number of brain tumors which observers had at their disposal was not sufficient to enable them to study these neoplasms properly. After Bailey's4 excellent definition, in 1929, of primary sarcomas of the brain, reports