Abstract
As a result of the improvements of tissue culture techniques, it has recently become possible to clarify the growth mode of animal tissue cells more exactly than formerly. Earle and his colleagues, in their studies concerning the L strain of mouse fibroblasts, devised a procedure for preparation of replicate tissue cultures (Evans, Earle et al., 1951) and a growth estimating method based on nucleus enumeration (Sanford, Earle et al., 1951), by which they pursued cell proliferation in vitro using the increase in the number of cells as a scale. They proved that an inoculum size larger than a certain level of cell number was necessary for the L strain cells to grow therein and that the cells implanted in a proper number grew rapidly to reach a maximum and then declined (Earle, Sanford et al., 1951) . They reported later that a “lag or adaptation interval” existed in “fluid suspension” cultures within the first 24 hours (Earle, Schilling et al., 1954) . Katsuta et al. (1954) and Graham et al. (1955) observed the cell growth in tissue culture, using different cell types and different culture methods. A survey of these data gives one the conception that cells cultivated in vitro proliferate displaying some growth phases comparable to those of bacteria.
The present authors have been studying on the growth characteristics of the HeLa strain cells in stationary cultures. The existence of a logarithmic phase in the course of their growth was confirmed. The growth estimating procedure based on nucleus enumeration and its accuracy were discussed in detail in the previous report by Takano, Yamada and Yaginuma (1956) . In the present paper, the whole course of the growth curve of the HeLa cells is analysed, which is eventually divided into the three stages of lag, logarithmic, and stationary phases.
