AbstractOn standing, hematoxylin converts to its oxidation product, hematein. Hematein produces a dye lake when it is combined with a mordant, ferric alum in this procedure. Myelin has a special affinity for a basic charged lake as it is a complex material containing cholesterol, phospholipids, cerebrosides, and other components. A dilution of a 1 % solution of hematoxylin in absolute alcohol combined with an equal volume of 1% aqueous ferric alum provides sufficient staining to demonstrate the white fatlike substances forming a sheath around peripheral nerve fibers.