Master cylinder

The hydraulic cylinder for a hydraulic system, especially a master cylinder for a hydraulic clutch, has a housing (12) for a longitudinally movable piston (18) which determines a variable pressure chamber (32) which is sealed against atmospheric pressure by a primary seal (36) in the housing. A follow-up device (46) in the form of an open compensating slot forms a compensating channel between the pressure chamber and a follow-up channel (30) in an extended end position of the piston. The compensating slot is formed on the piston in the region of a gas collecting section (68) in the pressure chamber and is rotationally fixed in relation to it.