Abstract: A cell tube for ex vivo culturing animal cells and a multiple roller tube cell culture system are disclosed. Suitable for use in culturing cells, the tube has at its opposite end walls two openings through which culture media can come in and out. The openings are eccentrically located at corresponding positions in contact with the edge sides of the end walls. The system has a plurality of roller drums on which a multitude of cell tubes are assembled. As the roller drums are rotated, cells adhering to each tube experience a nutrient-rich state and aerobic starvation, repeatedly. In the nutrient-rich state, the cells are grown flourishingly. When subjected to starvation, cells select metabolism pathways for utilizing carbon sources effectively, produce lactate at a low rate and can maintain a constant pH, because they are in direct contact with air. The system makes cells adhere to the wall of cell tubes and provides air directly to cell surfaces.