Abstract: The invention relates to a metering device for the metered admixture of a first fluid in a second fluid. The device comprises a housing (10) with a first inlet (15, 16), a second inlet (11), and an outlet (14) for a mixture of the two fluids. The housing (10) also contains a moving body (18) which is so arranged as to be influenced by a flow of fluid through the housing and exhibits means for regulating the first fluid, in such a way that a change in the flow at the outlet (14) produces a change in the flow of the first fluid. The inlet (15, 16) for the first fluid is connected to a tubular channel (17), which is centered essentially coaxially inside the outlet (14). The body (18) is mounted so that it is capable of displacement along the outside of the tubular channel (17), against the effect of a spring device (21) acting in a direction downstream.