ON PERUSAL of current literature one notes that despite a great deal of clinical observation on the eustachian tube, the understanding of its physiological role as a ventilator of the middle ear is limited. To broaden the knowledge of this function in man under ordinary conditions, more experimental observations are needed. These have been difficult to devise, since the function of the tube as a ventilator of the middle ear is difficult to detect. Excepting the reports on air pressure changes and the tube by Hartmann1 and by Armstrong and Heim,2 basic experiments in man are few. The observations by Politzer3 and by Lucae4 with a monometer sealed in the external canal showed the type and degree of pressure changes transmitted to the middle ear when the tube opened while swallowing with the nose closed (Toynbee's maneuver). Politzer also called attention to the ability to hear