In HA21&22, very few of the cells are visible with the elastin stain, but the tremendous number of elastic fibers in the respiratory portion of the lung are easily visible. Despite the lack of cellular staining, it is possible to discern many of same features as found in HA17&19. Note the intrapulmonary bronchus (B) on the left, and one of the larger vessels, such as a pulmonary artery (A), both shown in HA21. Why is this a bronchus and not a bronchiole?