This study was undertaken in an attempt to determine the effects of ether on the factors which influence the blood pressure, with special reference to the conditions as they occur in shock or circulatory failure. The fact, long known, that a patient in a condition of shock is a poor anesthetic risk was strongly brought to the attention of surgeons during the recent war, and led to an experimental study of the problem at the Laboratory for Surgical Research, A. E. F., under the direction of Lieut.-Col. W. B. Cannon. This study has been continued in the Laboratory of Physiology at the Harvard Medical School. In the account which follows, the effects of ether on the blood pressure will be first considered, then an examination of its action on the heart, vasomotor system and blood vessels, and finally a discussion from the point of view of the circulation as a