1. A precision pipette of positive displacement for the removal and distribution of small quantities of liquid, of the type comprising : - a substantially tubular body (10) which is sealed respectively at its top end by a stopper (12) which has a central orifice and at its bottom end by a capsule (16) receiving in a removable manner a calibrated capillary tube (24) ; - a piston (20) which is controlled in its checked displacement inside said capillary tube by a control rod (22) penetrating the orifice provided in said top stopper ; - a pinching member (32), the arms of which having a radial elasticity ensure the grip of said piston by its top end, and - a casing (26) which is capable of being displaced in said tubular body (10) between a top stop and a bottom stop upwards against an elastic restoring force exerted by a main spring (30), - the pipette characterized in that the pinching member (32) of the top end of the piston (20) is integral with the bottom end of said control rod (22) of the piston (20) and is lodged inside said casing (26), the opening of said pinching member (32) by a radial spreading-apart action of its elastic arms being obtained by the displacement of said pinching member (32) against the force exerted by a second spring (34) which has a much greater resistance than that of said main spring (30) and which is positioned between the bottom end of the control rod (22) of the piston (20) and an internal shoulder (36) of said casting (26).
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