In the infancy of tumor diagnosis it seemed sufficient to ascribe the symptoms and signs which were presented in any given case to the destructive or stimulatory effects of the lesion in a purely local sense. As time went by it became apparent that there were apt to be clinical features for which the situation of the tumor would not account. One of the most common and obtrusive of these signs was palsy of the abducens nerve on one or both sides, which was later found to have localizing value only when its presence was supported by some other neighborhood defect, such as paralysis of the facial nerve and perhaps auditory or trigeminal sensory loss. The anatomic observations of Cushing on palsy of the abducens nerve in cases of high pressure, the production by him of preparations showing definite injury to the nerve and the process by which it arises,