rotationally moved about the axis a the dosing blocking engagement is effected by the dosing blocking element 16 which is likewise formed on the dosing and conveying member 12 as can be seen in fig6 the dosing blocking element 16 is in the dosing blocking engagement with the housing 1 for this purpose the housing 1 forms a rotational abutment 22 as a blocking counter element the dosing blocking engagement is formed in that the dosing blocking element 16 protrudes into the dosage display window 2 in the initial state in which the dosing and conveying member 12 assumes its rearmost position in relation to the advancing direction relative to the housing 1 and the reservoir 30 such that the left hand and right hand side wall of the dosage display window 2 each act as a rotational abutment 22 clockwise and anti clockwise about the axis a fig6 shows an enlarged detail of the region in which the dosing blocking engagement exists in the initial state of the apparatus the dosing blocking element 16 protrudes radially outward over an outer circumferential area of the dosing and conveying member 12 into the dosage display window 2 it is arranged on.