Calcitonin cells and unusual follicle in four month old wistar rats.

1. The thyroid gland of 4 month old Wistar rats (both sexes) were made into serial sections and investigated by means of haematoxylin-eosin, PAS-haematoxylin, Davenport's silver impregnation and lead haematoxylin stainings. Calcitonln (C) cells are easily discernible by these techniques. 2. These cells are unevenly distributed and randomly concentrated in the thyroid. They are completely absent from cephalic and caudal poles of thyroid and are generally present in its middle region. They are scare in peripheral follicles and plentiful among central follicles. 3. The isthmus and the parathyroid are completely devoid of C cells. 4. Secretory granules in these cells have a tendency to concentrate towards vascular pole. 5. The unusual follicle is lined by squamous cells and filled with desquamated cells. C cells are completely absent from its epithelial lining.