Methods.—The great difficulties heretofore encountered in investigating the course of nerve fibres in the brain have been, firstly, the want of a method of preparation by which their gross anatomy could be thoroughly exposed, and, secondly, the failure of any previously known process of staining to satisfactorily indicate their direction on microscopic examination. In endeavouring to collect reliable data from the records of lesions of the human brain, it becomes only too evident that until more efficient methods of localising lesions be adopted than those generally in use at the present day, little can possibly be added to the knowledge we already possess.