Staining Sections Coated with Radiographic Emulsion; A Nuclear Fast Red, Indigo-Carmine Sequence

The radioautographs consisting of emulsion-coated sections, after development, fixation and washing, are stained 3 min (uncritical) by an aqueous solution of 5% aluminium sulfate containing 0.1% nuclear fast red, then washed 2-5 min, and stained 5-10 sec by a saturated aqueous solution of picric acid to which 0.25% of indigo-carmine had been added. This technic stains differentially cell nuclei, cytoplasm, muscle fibers, connective tissues and borders of some epithelial cells. It is unnecessary to subject the slides to differentiating solutions.