[Distribution of argyrophilic cells in the lungs of human fetuses]

Lungs of the human fetuses have been investigated at the age of 11, 18, 22 and 25 weeks. General histological staining methods and silver nitrate impregnation of the sections after Grimelius have been applied. Single argyrophile endocrinic cells (apudocytes) are revealed in the fetal lungs during all the time investigated. Groups of the argyrophilic cells--neuroepithelial bodies (NEB)--appear later and in small quantity. The quantity of the apudocytes and NEB gradually increases, especially noticeably in the distal parts of the bronchial tree. The number of the apudocytes increases during the canalicular stage of the pulmonary development. The endocrinic apparatus of the human lungs is forming in connection with development of the airy pathways, respiratory part and intraorganic vascular system.