Final answer:
The cells that secrete calcitonin within the thyroid gland are the parafollicular cells, also known as C cells, found at the periphery of the follicles.
Step-by-step explanation:
The cells found at the periphery of follicles within the thyroid gland, secreting calcitonin and often difficult to identify with H&E staining due to poor staining, are known as b) Parafollicular cells.
These cells, also referred to as C cells, are responsible for the synthesis and secretion of calcitonin, which plays a role in decreasing blood calcium levels. Parafollicular cells are scattered among the follicles and are distinct from follicular cells, which are primarily involved in the absorption of iodine and production of thyroid hormones.