An internal combustion engine wherein the top wall surface of the intake air inflow passage part of the intake port is formed by a first top wall surface and a second top wall surface lower than the first top wall surface and wherein a lower layer flow passage and an upper layer flow passage are formed at the height position of the second top wall surface as a boundary. The valve structures allow for removal of selected portions of the sample material located within the process chamber. The electrically-operated actuator includes at least one contact set configured to couple the power source to the at least one emergency light when the electrically-operated actuator is not energized. The vessel housing is rotated about the horizontal or proximate horizontal axis to suspend the cells, in an unobstructed, three-dimensional or toroidal flow. The second orifice includes an inlet that is adjacent to the outer surface.