Endocrine cells were observed in the gastrointestinal tract of the squirrels by light microscopy using Grimelius and Masson-Hamperl silver impregnation, and in the stomach and duodenum by electron microscopy.
Light microscopically, argyrophil cell decreased gradually in number in the pyloric region and ileum, stomach, duodenum and jejunum and rectum in the order listed. Argentaffin cells were moderately distributed in the stomach, pyloric region and duodenum, while absent in the jejunum, ileum and rectum.
Five kinds of cell types, EC, ECL, D, D₁ and G cells were identified in the stomach and three kinds of cell types, S, EC₁ and EC₂ were also identified in the duodenum by electron microscopy. A cilium noted in the cytoplasm of D₁-type cell. The species differences in the distribution, size and structure of the secretory granules were discussed.
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