METHODS The blood pressure has been determined by several methods. Intermittent measurements of arterial pressure were taken in the upper arm and occasionally in the forearm by the ordinary auscultatory method, using a mercury manometer. Intermittent measurements of systolic arterial pressure in the fingers were made by Gaertner's method. This consists of slowly lowering the pressure in a cuff placed around a digit previously rendered bloodless by an elastic band. The pressure in the cuff when the first flush of the returning blood is seen is reckoned as the systolic pressure at the site of the cuff. In several experiments more exact intermittent measurements of systolic arterial pressure were obtained and recorded by a plethysmographic method as follows: A plethysmograph was fitted to a digit and a blood-pressure cuff applied above at the point where it was desired to estimate systolic pressure. Air at greater than systolic pressure was suddenly introduced from a pressure tank into the cuff, occluding the circulation and stopping all pulsations below it. The pressure in mm. Hg within the cuff and the digital volumetric changes were continuously recorded on moving bromide paper by means of an optical system. Pressure was allowed to