During the past twenty years I have had occasion to report either alone or in conjunction with some co-author various observations concerned with the possible physiologic function of the pineal body, together with the pathologic and clinical manifestations of pineal tumors. Concerning the former of these observations, namely, the possible function of this organ, little has been added of recent years. On the other hand, pathologic and clinical observations having to do with tumors of the pineal body have added considerably to the exact knowledge as to the structure of these tumors and as to the clinical syndrome which a patient may present both before and after the age of puberty. The symptom complex in the adult concerns itself wholly with the existence of increased intracranial pressure, together with evidence of localized pressure on the upper portion of the midbrain and on the corpora quadrigemina, which lie directly below the