A histochemical study of mucoid cells in the Pars distalis of the human hypophysis

Sections of the human hypophysis were fixed in either formalin or Bouin's fluid and stained by a variety of mucoid and acid stains in order to demonstrate the staining characteristics of the mucoid cells of the pars distalis. Five types of mucoid cells were revealed and designated as cell types III, IV, V, VI and IX according to the classification system of Ezrin. Cell types III, IV, V and VI were present throughout the pars distalis while cell type IX was observed only in the posterior zone. The cells were tinctorially distinguished by the PAS‐orange G affinity of the type III cell, the alcian blue‐PAS reactivity of the type IV cell, the alcian blue staining of the type V cell and the affinity of the type VI cell for alcian blue‐PAS‐orange G. Cell type IX was recognized by the affinity of its cytoplasmic granules for most of the stains employed. Modified and degranulated forms of these cells were observed and are also described.