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The Brachet-Pappenheim cytochemical RNA-detection method was used to reveal the localization of RNA in nuclear and cytoplasmic structures of secretory cells of the anterior pituitary in various functional states. The methyl green-pyronin staining standard procedure was slightly modified by changing the acidity of the stain mixture, prolonging the staining and differentiation time, and introducing iso-propyl alcohol in the differentiation. The main part of the RNA detected by means of pyronin was found to be distributed upon the predominantly acidophilic area. The pictures of RNA-localization, obtained in early, more advanced and final stages of the secretory act, were closely similar to those discovered in secretory cells of other glands, and in nerve cells, by ultraviolet absorption analysis. It is the first time properly with regard to the pituitary, that a similar, cytoplasmic protein synthesis indicating RNA-system, as a whole, could be revealed by means of Brachet-Pappenheim's cytochemical method. Relation of the RNA as to the various cell types in the pituitary, and to the appearance of phosphomonoesterases is discussed.

ONLY small amounts of alkaline phosphatase have hitherto been found in mammalian endocrines. It was, however, possible to demonstrate considerable quantities of this enzyme in the anterior pituitary lobe of both the male and the female guinea pig. After fixation of the glands in 96 per cent alcohol, in 80 per cent alcohol, in acetone or in pyridine-alcohol1, the Gomori technique2 was used. As already known, the nuclei of the anterior pituitary show a positive reaction which, however, has not been localized to any particular cell type3. In order to identify the type of cells containing the phosphatase, every two of four paraffin sections (thickness : 2–4μ) of each gland were examined as to content of phosphatase : the two other sections were stained by Masson‘s trichrome (acid fuchsin, Ponceau 2R and aniline blue) method.