The study of chronic subdural hematoma may be divided chronologically into very definite periods. Prior to 1857 there were scattered records of observed cases of patients who were found at autopsy to have a collection of blood beneath the dura. In 1857 Virchow,1 as a result of postmortem studies in a number of cases, introduced the term pachymeningitis haemorrhagica interna. Since in the cases studied by him there was no history of trauma, he thought that the underlying pathologic process was the organization of an inflammatory exudate. From 1857 until 1925 the lesion was studied extensively by many pathologists and neurologists, but with a few exceptions their chief interest was the underlying pathologic process rather than the treatment of the condition. A notable exception was an article by Trotter2 published in 1914; in it four cases in which the condition was treated surgically were reported. Although very little