in a metering and spray pump for liquid , low - viscosity and pasty substances , an elastic bellows 3 is arranged between two plastic housing parts 1 , 2 that are telescopingly movable relative to one another , connecting them . the bellows , acting as a discharge valve 18 , has , at one end , a valve annular wall 15 that surrounds the generated surface 17 of an inner annular discharge seat 8 made in one piece with the first housing part 1 in a sealing manner and such that it can be lifted off . as a suction valve 58 , the bellows 3 has , at its other end , a valve annular wall 54 which is in sealing and separable contact with the generated surface 43 of a valve seat 42 made in one piece with the second housing part 2 such that it can be lifted off , and the medium to be pumped is drawn into the bellows 3 through the valve seat . to guarantee high reliability of operation , especially good closing quality at weak valve opening forces , where the quality of closing can be tested even in the dry state , with the smallest possible number of simple and easy - to - assemble individual parts , the valve annular wall 15 of the discharge valve 18 and the valve annular wall 54 of the suction valve 58 , which valve annular wall 54 is provided with a closed front wall 57 , are each in contact with conical or hemispherical generated surfaces 17 , 43 , wherein both valve annular walls 15 , 54 are connected to the bellows 3 both radially elastically and elastically movably in the axial direction .