Quantitative Studies of Haemopoietic Spleen Colonies in Rats treated with Cytotoxic Chemicals

Summary. Quantitative studies of spleen colonies in rats are reported in some detail and the findings are compared with those reported for spleen colonies in mice, and with those of the only other extensive report on rat spleen colony histology. While similarities are observed between the two studies on rat spleen colony histology, there are marked differences between these results and those that are obtained in mice. The reasons for these differences are discussed and it is concluded that the haemopoietic micro‐environment of the rat spleen is considerably different from that in the mouse, and that this is probably the major reason accounting for differences in rat and mouse spleen colony histology.