Observations on the nucleolar staining by ethanolic phosphotungstic acid.

In addition to the already known reactivity of heterochromatin masses and synaptonemal complexes for ethanolic phosphotungstic acid, nucleoli from Sertoli cells show a preferential electron microscopic staining of the pars fibrosa. This ultrastructural pattern can be correlated with intranucleolar differentiations observed in light microscopy after staining of semithin sections with Unna's polychrome blue.