Fixation of epidermis with a mixture of osmium tetroxide and zinc iodide (Os0 4 -ZnI 2) for 24 hr renders the central periodic lamella of the Langerhans cell granule (LCG), the Golgi region, and the nuclear envelope of epidermal Langerhans cells preferentially visible . The use of this technique on Langerhans cells in normal epidermis and in epidermis of patients with histiocytosis (Letterer-Siwe disease) allows a broader visualization of the LCG's than was heretofore possible with routine glutaraldehyde-osmium tetroxide fixation and uranyl acetate-lead staining. The identical staining of Golgi apparatus and LCG favors the view that there is close relation between the Golgi area and the LCG's . Different staining characteristics of the LCG's near the Golgi region and at the cell periphery, respectively, may suggest that the LCG undergoes changes on its way from the Golgi area towards the extracellular space . The hypothesis is advanced that the material which is heavily impregnated with metal after fixation with Os0 4-ZnI2 might be a lipid .

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