ELECTRON MICROSCOPIC OBSERVATIONS ON THE THYROID

Abstract

Sections of the thyroid of guinea pigs and rats were examined under the electron micro-scope. Thyroids were taken from normal and hypophysectomized animals and from animals treated with thyrotropic hormone, thyroxine or thiouracil. In the follicular cells a submicroscopic canalicular structure of the cytoplasm could be demonstrated. The appearance of this structure seems related to the functional state of the gland. The cells show fine intrafollicular projections that seem augmented during reabsorption of liquefied colloid. No evidence of direct hormone secretion in the bloodstream was observed.