In those who have died with pneumonia following influenza the large bronchi (with cartilage) are intensely injected, so that the mucosa has a deep red color which on cross section contrasts very sharply with the pearly white of the cartilage. Superficial injury to the bronchi is not infrequently evident in the larger bronchial branches; superficial loss of epithelium is indicated by erosion of the surface, whereas somewhat deeper destructive changes are occasionally evident. Microscopic examination accurately determines the degree of destructive change. Purulent bronchitis was noted in 134 autopsies (55.6 per cent of autopsies). From the small bronchi, in many instances, purulent fluid welled up upon the cut surface of the lung, whereas in other instances tenacious mucopurulent fluid could be squeezed from small, cut bronchi by pressure upon lung tissue. The consistency of the material within the bronchi varied greatly, ranging from a viscid and tenacious mucus of creamy, yellow color to a thin, turbid, gray fluid. The coexistence of local inflammatory or of general edema of the lungs modifies the character of the material found in the bronchi at autopsy; with edema the purulent exudate is in some instances diluted so that a thin cloudy fluid flows from the small bronchi. In the presence of advanced edema of the lungs the bronchi rarely if ever contain purulent exudate. The underlying changes in the bronchi are more significant than the character of the exudate found at autopsy. Nevertheless, the group of cases in which the diagnosis of purulent bronchitis has been made, because small and medium sized bronchi have contained purulent or mucopurulent exudate, represents instances of readily recognizable bronchitis of considerable severity. With few exceptions, purulent bronchitis was diffusely distributed in the lungs; occasionally it was observed in one lung alone, and in several instances was limited to the bronchi at the base of a lung, usually of the left lung. In a considerable proportion of instances of purulent bronchitis abnormal distention of the lungs was noted. On removal from the chest the lungs fail to collapse and retain the size and shape of the thorax. Even after section is made through the organ, parts of the lung fail to collapse and have a resistant cushion-like consistency. This condition is present where the lung tissue is air containing and dry, and occurs when very small bronchi contain tenacious mucous exudate which becomes apparent upon the cut surface after the sectioned lung is squeezed. Microscopic examination shows that the alveolar ducts and infundibula are distended with air, though the respiratory bronchioles contain inflammatory exudate. Complete obstruction of the bronchi is followed by absorption of air from the tributary pulmonary tissue with atelectasis. It is not improbable that partial obstruction, permitting the penetration of air with inspiration, produces distention of air containing tissue.