the bellows sleeve 2b to collapse to create pressure upstream of the membrane see fig1 17 and 18 in both of these instances the membrane 5 rests on a spacer 55 disposed on a porous holder 56 when filtration of the sample is to be achieved directly in the field where the sample is obtained in the absence of any laboratory materials such as a vacuum flask the container 20 is used with the sealing element 28 covering the hollow portion 25 but not the peripheral zone containing the axial holes 26 once again the assembled device 1 includes a bellows sleeve 2b which is manually pressed thereby causing the liquid to be tested to pass through the membrane filter 5 and the spacer 46 and thereafter out of the axial peripheral holes 26 in this manner the hollow portion which receives the culture medium is not wetted by the sample see fig1 once filtration and if desired rinsing have been done the wetted membrane filter 5 creates a barrier to gases thus the filter can be bulged as shown in fig2 by slightly compressing the air contained in the sleeve 2b this slight compression of the inside of the sleeve is easily accomplished by pushing the cylindrical portion 37 of the cover 35 into the corresponding cylindrical portion 13 of the end 4 of the sleeve the membrane filter is bulged without handling the membrane and thus permits the user to check the integrity of the membrane on the one hand while also permitting contact of the membrane with the culture medium from the membrane center to its periphery to avoid any entrapment of air bubbles which could impair the results of the test to be effected the contacting of.