A comment on Ehrlich's ꞵ granules

In many textbooks and research articles, Ehrlich’s ꞵ granules are generally described as amphophilic granules that stain with both acidic and basic dyes, and are regarded as the specific granules of granular leukocytes corresponding to neutrophils in rabbits and guinea pigs. However, in Ehrlich’s original publications, ꞵ granules are described as being present in immature eosinophils of various vertebrates, and their maturation is considered to lead to the formation of the eosinophil specific granules (α granules). According to current knowledge, these ꞵ granules correspond to the azurophilic granules in immature eosinophils. This study examined historical and contemporary literature to clarify how the concept of Ehrlich’s ꞵ granules became ambiguous over time. Amphophilic ꞵ granules were found to originate from a description in Schwarze’s doctoral thesis, which was based on experiments carried out in Ehrlich’s laboratory. This description is thought to have drawn on Ehrlich’s personal correspondence. From the findings of this investigation, amphophilic ꞵ granules were likely a term used to describe the neutrophil granules of rabbits and guinea pigs during the transitional period before Ehrlich established the category of neutrophilic ε granules.