of new hyde park n y is employed in such a manner that when the system is opened to ambient atmosphere the pump terminates its pumping operation this provision is uniquely important in intravenous procedures but does not prevent the inadvertent movement of air into the vascular system as may result from the aforenoted pressure differential in fig3 is indicated the physical arrangement necessary for an intravenous procedure as may be performed in a hospital or the like the patient is indicated generally at p and into the patient 39 s arm a is inserted a needle or catheter n through which the introduction of an intravenous fluid may be effected at 110 is indicated a source of intravenous fluid of known type the source 110 is connected to a reservoir 112 via a catheter 114 with the fluid dripping downwardly drop by drop into the reservoir 112 eventually to be connected via a coupling 116 to a catheter or i v tubing 118 feeding into pump 120 a safety arrangement or flow control valve according to the invention may be included at 122 if desired a spur 124 is indicated for the introduction of medical preparations nutritional preparations or the like according to well known.