Fig. 5. Elastica Masson staining of the lung in late stage fetuses. Sagittal sections. Panels A and B display the left lung from a specimen at 26 weeks (215 mm crown-rump length [CRL]) and the right lung from a specimen at 31 weeks (255 mm CRL), respectively. Panel C exhibits a thick branch of the pulmonary artery from a specimen at 31 weeks (255 mm CRL). The pleura and subpleural tissue are stained dark gray (A, B), but they are different from wavy elastic fibers seen in the internal lamina of the arterial wall (C). All panels were prepared at the same magnification. Scale bar=0.1 mm (A).