An interesting case of colloidal iron positivity

Summary An interesting case of a colloidal iron (CI) positive basophilic substance in the adrenal medullary cells of amphibia and reptilia is reported here. The substance, however, does not stain by alcian blue (AB). It is negative to PAS, Azure A, aldehyde fuchsin, AB at pH 1 and MgCl₂ — AB though orthochromatically stained by toluidine blue at pH 3. More work is needed to establish the exact nature of the CI positive material.