SIRIUS RED F3BA AS A STAIN FOR CONNECTIVE TISSUE.

Van Gieson's picrofuchsin stain was introduced into histological technique in 1889 and is still widely used. However, this method has two disadvantages: (1) Acid fuchsin fades rapidly. (2) Basement membranes and reticulum fibers are usually only poorly stained, though coloration of these structures can be improved by addition of acid to the dye solution as recommended by Lillie. Substitution of thiazine red R for acid fuchsin yielded satisfactory staining of fine connective tissue fibers, but sections also fade after some time. During investigations of the histochemical mechanism of van Gieson-type stains, we found several dyes which combine good fastness to light with high selectivity for collagen, reticulum fibers, and basement membranes, viz, Sirius pink 4BL (Colour Index 25380), Sirius red 4BA (C.I. 28160), and Sirius red F3BA (C.I. 35780). Because of its suitability for concurrent polarization microscopic studies of connective tissue fibers, Sirius red F3BA was chosen for large-scale testing in histopathology.