Abstract
For the purpose of gaining massive cell population for chemical analysis, in order to obtain an ideal single cell-virus system, or from another cellular biological interest, many attempts have recently been made to grow mammalian cells in the state of fluid-suspension like bacterial cultures. According to investigators, variously devised equipments were introduced such as tumbling tubes by Owens et al. (1953, 1954) ; rapid roller-tubes by Earle et al. (1954), Graham et al. (1955), Siminovitch et al. (1957) and Takaoka (1958) ; a rotary shaker by Kuchler et al. (1956) ; a magnetic stirrer by McLimans et al. (1957) ; a glass stirrer by Danes (1957) ; and shaker flasks with aeration by Earle et al. (1956) and Bryant et al. (1958) . While the successful production of massive population and steady growth rate in suspension were made with a few special cell types, the comparatively low growth rate, which was suppcsedly due to mechanical injuries, and the inconstant growth mode were the general trend with other types.
The principle of the present experiment is to select or train cells to be gradually acquainted with the state of floaing and finally to be able to multiply freely without any mechanical treatment. In usual way of cultivating cells in vitro, cells which float away from the surface of a glass vessel into fluid medium are expelled when a culture is transferred or its medium is renewed. The remaining cells should naturally have a tendency to stick firmly to the glass surface. Even among cell lines established through many passages, a small numbers of cells are noticed floating in medium sometimes during cultivation. If these floating cells are viable and supported to propagate freely, it can be considered rather easy to obtain a fluid-suspension type of cultures. Such a supposition as the above has been corroborated to some extent, using HeLa and L strain cells.
