ABSTRACT
The mutual invasion in culture of a population of standard fibroblasts (chick embryo) and a population of cells from a transplantable mouse sarcoma (MC)M, BAS/56, or 311) or of neontal mouse fibroblasts has been estimated quantitatively. We arranged the confrontation of the pairs of populations by placing primary explants near each other. After fixation, the distance the cells had migrated from each explant was sampled in the space between the explants where they met and at the sides of the explants where they migrated freely. Measurements of nuclear overlap and orientation were also made. In the sarcoma as in the fibroblast population, homologous contact inhibition of movement probably produced an oriented migration from the explants before the populations met. Abot 12-24 hours after, mutual invasion was considerably greater in the sarcoma versus fibroblast than in the fibroblast versus fibroblast experiments. It is proposed that this difference was due to a difference of heterologous contact inhibition in the two types of experiment.
