Acetic orcein staining of prefixed tissue sections.

Acetic orcein stains formol- and Carnoy-fixed tissues, coloring mast cells, nuclei, basophilic cytoplasm, cerebral corpora amylacea, and cartilage strongly; keratin and erythrocytes moderately; muscle and collagen weakly. Guinea pig Brunner gland and rat colonic goblet cell mucins did not stain. The red nuclear stain contrasts well with the Prussian blue reaction of hemosiderin and the ferric ferricyanide (Turnbull's blue) reaction of enterochromaffin. A weak (0.01%) fast-green FCF stain changes collagen and sometimes smooth muscle to green, without impairing nucleic acid or mast cell staining. Picroindigocarmine gives blue collagen, yellow muscle, and red elastin, nucleic acids and mast cells. Picro-methyl blue tends to override the red nuclear stain. Carnoy fixation is somewhat better for nuclei, formol for basophil cytoplasms.