1878

Paul Ehrlich enters Berlin’s Charité as assistant and, guided by his work with dyestuffs, begins research on the morphology of cells, especially white blood corpuscles. He discovers in protoplasm a group of connective tissue cells a form of granulation that showed up when stained with basic dyes (“mast cells”): “This was the first case of selective staining and the first occasion that a dye was used as a microchemical reagent” (22). Between 1879 and 1882, “The various types of granules in the white blood corpuscles and the differences in their dye receptivity continued to be Ehrlich’s main guides into the physiology and pathology of the leucocytes” (25).