THE proliferation of malignant cells has been shown to depend not only on intrinsic neoplastic properties but also on environmental circumstances, in vivo (host) or in vitro (medium). In addition, a changing rate of growth in a continuing environment has been documented in tumor-bearing hosts and tissue culture situations. The kinetics of neoplastic cells (i.e. Ehrlich ascites tumor cells-EAT) have been studied with regard to cellular proliferation within cell-tight millipore chambers by Amos and Wakefield (1958) (among others), particularly concerning the growth rate of cells in normal mice and the rate of entry of iso-antibody into the chambers. The present investigations define the growth pattern of Ehrlich ascites tumor cells within the restricted environment of millipore chambers in actively immunized mice. MATERIALS AND METHODS White Swiss mice of both sexes (HA/ICR strain), 3-4 months old, were used in this study. The tumor cells used were Lettre strain, hyperdiploid Ehrlich ascites tumor originally obtained from Roswell Park Memorial Institute and grow
