Peptide antibiotic research, which in the larger sense includes protein antibiotic research, actually began during the late 19th century with the work of Ehrlich, Metchnikov, Kanthack, and Petterson. Now it has been absorbed into the fields of microbiology, immunology, histochemistry, and cell biology. This early work depended on instruments, reagents, and techniques then at the cutting edge but now long since superseded: the compound microscopes, chemically characterized indicator stains, and the then-new science of bacteriology. Ehrlich, in 1879 defined the cytoplasmic granules of the granulocytic white blood cells. He noted that the granules of approx 2 or 3% of the cells stained intensely with eosin, an acid dye. He also noted that a much larger proportion of the granulated cells stained with eosin but also stained with the basic dye azur. Accordingly he designated the former cells eosinophils and the latter cells heterophils or neutrophils. He inferred from these staining properties that both kinds of cells carry basic proteins in their granules and that the neutrophil granules contain a mixture of basic and acidic proteins (1). Metchnikov described in 1883 the preeminence of phagocytes including the neutrophils (microphages) in antimicrobial host defenses (2). Kanthack and Hardy in 1895 discovered that phagocytosis of bacteria induced granulocytes to degranulate. They linked this degranulation with the death of the bacteria (3). Petterson found antimicrobial activity in aqueous extracts of pus from human empyema; he attributed the action to basic proteins he found in the pus, comparing them to the protamines of salmon sperm (4). Now, in retrospect, the necessary information might have been in place, at that time, to formulate a hypothesis concerning the role of cationic granule proteins in host defenses against bacterial infection. As it happened, interest in the granules and their proteins had to lie fallow for more than 50 yr. The techniques of the time were simply unequal to the experimental demands.