Preliminary pulse radiolysis data indicate that both e-aq and

By the use of a 59Fe tracer technique esti mates were obtained of the colony-forming units (units ratio and of the total number of CFU in the spleen and the peripheral blood of mice during pre- and post-natal life. The present data, together with others previously reported on the liver, allowed a semi-quantitative comparative evaluation of the haemopoietic function in the fetal and adult life of the mouse, based on the number of progenitor cells in the various haemopoietic districts.