An electrically controlled magnetic fluid actuated device, which can be used in controlling fluid flow and which has particular utility in controlling this flow from a pressurized reservoir implanted in the body such as might be used for an artificial pancreas, sphincter for bladder control or other orthotic devices in the body of a human, has no freely moving parts and consists of a flow passageway having a portion the cross-section of which may be varied to control and to stop the flow of fluid, such as medicine, from a reservoir in the body to the point where this fluid is needed. A magnetic fluid which surrounds or contacts this portion of the passageway can, according to the presence or lack of a magnetic flux in its vicinity, occlude the passageway or allow it to open so as to control the fluid flow in the flow member.