Distribution of Evans Blue and lesions in lungs. Groups of six pigs were administered Evans Blue either IN or by AERO. IN delivery of Evans Blue resulted in heavy staining within the alimentary canal (oesophagus, white arrow) and a very small amount in the upper trachea (black arrow) (A), no deposit in the lower trachea nor the rest of the respiratory tract or the lung parenchyma (B). AERO administration resulted in widespread distribution within the entire respiratory tract (C) including the lung parenchyma as observed through the pleura (D) or after sectioning the lung (E). The percentage of lung surface with influenza-like lesions varied in each animal with a higher score in AERO than IN (F). The distribution of lesions showed a small number of lung lobes with lesions in IN (G) compared to the majority of lung lobes in AREO (H).