The effect of various vasodilators on the systolic pressure in man has ben carefully studied by several investigators,1 but changes in diastolic and pulse-pressures accompanying the systolic changes have received but scant attention, diastolic and pulse-pressure being regarded as of theoretical interest only. Recent investigations,2 however, indicate that the pulse-pressure is an important factor in determining the efficiency of the circulation and of more value in prognosis than the systolic pressure. To quote from Erlanger and Hooker,3 "the knowledge of any one of the blood-pressures [systolic, diastolic or mean] throws but little light on the conditions of the circulation."
For this reason, observations on the action of various drugs and therapeutic measures on the pulse-pressure seemed of value, since by such means the indications and contra-indications for their use might be more clearly established. This paper deals with the effects of various vasodilators and pressure-lowering measures