Introduction

Abstract

The histological structure of the thyroid gland is relatively simple, but the interpretation of the histological picture of individual glands examined is not always easy. The structural relation is so variable that it is often difficult to determine whether the gland is within normal range or not, so that interpretation tends to become more or less subjective and empiric. As stated by Wegelin (1926), the variation may depend upon the characteristic state of the thyroid gland as a ductless gland, closely resembling an alveolar gland with a collecting duct system and accumulating colloid in the follicles. The colloid contained may be abundant or scarce, depending upon the requirement of the animal body and the intensity of secretory stimulation, resulting in the pattern of the parenchyma, especially the follicles, to be also variable. This state is particularly exaggerated in the human thyroid gland (Hinton, 1931; Bianchedi, 1934; Rosenkranz, 1935), and influenced by different complicated conditions of individual life, it becomes very difficult to analyze the histological pictures presented. Notwithstanding current interest in the physiology of the human thyroid gland in relation to pathology and disease, little work has been done to elucidate its histology, especially its developmental histology.