Abstract
Studies on the D cell of the pancreatic islet were reviewed and analysed; some unpublished findings of the author's own were added.
1. The D cell is a normal and constant constituent of islet tissue from the level of elasmobranchii up to mammals; its occurrence in cyclostoma deserves confirmation.
2. The D cell of the pancreas is identical with the argyrophil cell long regarded erroneously as A cell. It is probable that the cyanophil granules of the D cell correspond to the argyrophil element. The mechanism of this argyrophil reaction was discussed.
3. Silver impregnation technique by HELLMAN and HELLERSTRÖM in formalin or Bouin fixed material provides the most reliable and universal demonstration of the D cell, whereas the metachromasia method of MANOCCHIO works in limited species.
4. The fine structure of the D cell is characterized by large cytoplasmic granules of low electron density and loose texture contained in a membrane sac.
5. The name of C cell (BENSLEY) may be abolished since this cell, characteristic of the guinea pig, is identified with the D cell in other species on the basis of its reactions to stains and of its fine structure.
6. In different pharmacological experiments and pathological changes, the D cell reacts indepently from other cells. In the development of the islet, it is formed also independently from other cell types.
7. Light and electron microscopic observations indicate that the D cell is a secretory element of the islet. The hypotheses on the possible hormones of the D cell were analysed.
