this manner there is provided a permanent fluid tight connection between the diluent bag 9 and transfusion bag 4 referring to fig3 and 4 the uni directional flow fluid valve 12 is provided with a housing 20 interior of the housing 20 there is a cylindrical tubular structure 21 tubular structure 21 is coupled to the hollow tubing 22 connecting the input of the valve member 12 to the diluent bag 9 at its upper end the tubular structure 21 is formed with a curved valve seat 23 for receiving a spherical valve member 24 the valve member 24 is resiliently held in closed relationship relative to the valve seat 23 by means of a flexible rod like member 25 which extends from the interior wall portion of the housing 20 the tubular member 10a attached to the transfusion bag 4 is fitted to the output end of the uni directional flow fluid valve means 12 the apparatus according to the present invention may be used in a number of ways for example a supply of diluent bags 9 may be kept in the operating room or other suitable location for use by a physician desiring to dilute packed red blood cells in a transfusion bag 4 which has been ordered from a blood service alternatively an adequate supply of diluent bags 9 may be.