[Rhodamine B: a tracer of follicular keratinization (author's transl)].

The mixture at equal volumes of a 0.1 p. 100 solution of rhodamine B in distilled water and of a 0.25 p. 100 solution of toluidine blue in Walpole's pH 4.4 buffer dyes each pilar sheath differently. At the level of the medulla, the granules fix rhodamine B, so do the cortical cells at the level of the keratogenic zone. Once they are keratinized, however, cortical cells remain colorless. Concerning the cells of the inner root sheath, on the other hand, their trichohyaline granules are dyed by rhodamine B, whereas the keratinized cells turn dark blue under the effect of toluidine blue. The trichilemmal keratin both of the isthmus of the anagen hair and of the follicular sac becomes light red. This technique, which can be easily applied to the trichogram, allows us to identify more or less mature pilar anlages in in adnexal tumors, to differentiate keratinizing cysts and to trace various pathological keratins. Thanks to a chemical study, it was shown that the mixture rhodamine B-toluidine blue is only a mechanical mixture which works through its acide-bases properties.