The literature pertaining to tumors of the third ventricle is largely concerned with the various clinical syndromes, postmortem observations and histologic studies of the lesions and, only recently, with preoperative diagnosis and surgical removal of the new growths. It is not my purpose in this paper to give a résumé of the literature on the numerous clinical syndromes caused by tumors of the third ventricle, which have been so ably described by Weisenburg and by several others.1
As regards the early diagnosis of these lesions, one finds that the injection of air into the ventricles either by the direct or by the lumbar route, as first described by Dandy2 in 1918 and 1919, respectively, is of the greatest help. Furthermore, the injection of dye into one lateral ventricle to determine the patency of the foramina of Monro has also contributed to the diagnosis of lesions obstructing one or