Abstract: An infusion device includes an upstream pressure control device and a downstream flow control device. The device receives infusion liquid via an inlet and controls the level of liquid in a chamber by means of a float which can close both the inlet and an outlet. A filtered vent maintains atmospheric pressure in the chamber. The device receives infusion liquid at constant head via a flow pipe. A dripper delivers droplets into an airtight chamber. A taper needle renders an orifice adjustably open to a desired degree to deliver liquid at a selected rate. Screw threaded adjustment and calibration means allow calibrated adjustment. A flow pipe delivers a metered flow of infusion liquid for infusion into a human or animal body.