[Water-induced metachromasia of thionine and methylene blue in histologic preparations]

The metachromatic staining of histological preparations of tissues of lung and rib by thionine and methylene blue has been investigated. The metachromatic effect is caused by the distribution of monomer, dimer, and higher aggregates of the adsorbed dyes. This distribution is primarily influenced by the structure of the biopolymers, which adsorbs the dye cations. It is strongly modified by the water content of the media used for differentiation and embedding.