23 which is preferably provided with capillaries 24 is integrally formed in said insert 22 a closure plug 25 which is connected to the insert 22 in a captive manner by means of a securing ring 26 sits in the opening 23 to remove a predetermined amount of medium from the container the dosing pipette p 1 as shown in fig1 penetrates the opening 23 beforehand or afterwards the lug 10 of the plunger 2 having been set to the desired marking determining the metering volume when the dosing pipette p 1 is inserted into the opening 23 the sealing plug 25 is ejected and remains suspended in the interior of the container closure 21 as shown in fig1 the container together with the container closure and the dosing pipette is then turned upside down and the plunger 2 is moved in the direction of the axis a in the axial recess 3 the medium present in the container thereby being sucked into the metering space 14 in a desired metering volume during the movement of the plunger 2 the cam 18 moves along the predetermined groove 5 1 to 5 4 until it abuts against the bottom 27 of a groove this limits its stroke h which at the same time means that the.