Elongated fuel cell having cross channels for gas supply

The device has transverse channels (6) for gas supply on at least one side of a polymer electrolyte membrane or PEM (2). The channels are formed behind a diffusion layer covering the PEM near an electrode surface supporting the diffusion layer and run transversely to the fuel cell's longitudinal edges (10). Several of the transverse channels have a cross-section decreasing from one longitudinal edge of the fuel cell to the other.