Abstract: A fluid injection system including a flexible bag fluid reservoir acted upon by an elastically deformable compression member for pressurizing the fluid within the reservoir, a combined pump and valve assembly connected to the reservoir, and an injection means consisting of a flexible conduit and needle connected to the output of the combined pump and valve assembly. Also included is a selectively actuable electromagnetic force generator which cooperates with a magnetically polarized pump element and a movable magnetically polarized valve closure element, both of which are located within the combined pump and valve assembly and movable under the action of the electromagnetic force generator for accumulating and pumping a predetermined charge of fluid from the reservoir to the flexible conduit for injection into the body via the needle.