Fine structure of the pancreatic islets in domestic fowl with special reference to the cell type and secretion.

The pancreatic islets of domestic fowl were investigated by electron microscope. The following results were obtained. 1. The A islet is composed of a great many A cells and a few D cells. It also contained only a few B cells which are situated mainly along capillaries. 2. On the contrary, the B islet is composed of a great many B cells and a few D cells. It also contained only a few A cells in its periphary. 3. Immature secretory granules within the Golgi complex are almost the same in size, shape and density among the three types of islet cells. Since there are quite distinct differences in these properties of mature secretory granules in the cytoplasm among the three types of islet cells, there may be a difference in the mode of maturation process among the three. 4. These granules are released from the three types of islet cells through a mechanism termed as emiocytosis.