Abstract
Summary. In vitro Cultures of newborn mouse thymic cells were followed for as long as 120 days. Depending on the technique of explantation, two distinct types of cell populations were obtained: whereas in cultures derived from thymic fragments embedded in plasma clot the final result was a pure colony of reticulum cells, in cultures derived from unattached thymus fragments the cell population mainly consisted of lymphocytes, monocytoid cells and plasmacytoid lymphocytes.