The Gram Staining Mechanism of Cat Tongue Keratin. II. The Role of Potassium Iodide-Iodine Solution

The aniline-xylene decolorizer of the Gram-Weigert staining procedure failed to remove crystal violet dye from stained sections of cat tongue without prior treatment of the sections with potassium iodide-iodine solution. The potassium iodide of the iodide-iodine solution was found to release the major part of the crystal violet dye bound by the tongue sections. Iodine appeared also to play a role in dye release, but only to a slight degree. The amount of Gram-positive staining was increased both by alkaline treatment of the tissue prior to staining, and by increasing the pH of the iodide-iodine solution.