Histological staining of semithin sections is readily achieved with Azure B and methylene stains. This procedure was originally introduced by KC RICHARDSON et al. (1960) and gives an excellent information of the tissue morphology. Azure B is formed by the oxidation of methylene blue and used in Azure-eosin stains of blood smears. Methylene blue is a commonly used dye in histology. Following ‘ripening’ which is a process of atmospheric or chemical oxidation, the three metachromatic dyes Azure A, B and C are formed (polychrome methylene blue).