A simple chamber was constructed for observation of cells at 37°C and under high magnification. Rabbit peritoneal histiocytes observed in this chamber manifested a constant interaction, which lasted as long as the preparation itself. This interaction consisted of formation of cytoplasmic bridges and flow of cytoplasm between the cells.
Lung macrophages formed bridges both between themselves, and with peritoneal histiocytes. On the other hand, no bridges were noticed between histiocytes and polymorphonuclears or fibroblasts. BCG bacteria were observed passing from one histiocyte to another.
Autoradiographic studies suggest that RNA may be transferred from one cell to another. The possible significance of these observations is discussed.