=Peribronchiolar Consolidation.=—In many instances of bronchopneumonia, usually in association with lobular or confluent consolidation, small firm nodules of consolidation are clustered about the bronchioles (Fig. 2). These nodular foci of consolidation are usually 1.5 to 2 mm. in diameter, being sometimes slightly smaller or slightly larger. They are usually gray and occasionally surrounded by a red halo; sometimes they are yellowish gray. They are clustered about the smallest bronchial tubes to form groups which are from 0.5 to 1 cm. across. A group of nodular foci of consolidation occupies the central part of a lobule of lung tissue. When pneumonia has been of short duration these foci are fairly soft and not sharply defined, and in many instances this form of bronchopneumonia is first recognized by microscopic examination. When the disease has lasted from ten days to two weeks, the consolidated nodules are very firm and sharply circumscribed, closely resembling tubercles. When they have assumed this character, microscopic examination shows that chronic changes indicated by new formation of interstitial tissue have occurred. The lesion may be designated peribronchiolar consolidation. It has occurred usually in association with other types of pneumonic lesion in 61 instances, being recognized at autopsy in 18 and by microscopic examination in 43. [Illustration: Fig. 2.—Acute bronchopneumonia with nodules of peribronchiolar consolidation and purulent bronchitis. Autopsy 429. ] In association with this lesion there are almost invariably severe lesions of the bronchi. Purulent bronchitis was noted in 47 of the 61 instances, in which this nodular bronchopneumonia was found at autopsy. An index of the severity of the bronchial injury is the frequency with which bronchiectasis has occurred; dilatation of small bronchi was observed in 24 instances. In 10 instances the bronchi were encircled by conspicuous zones of hemorrhage. In association with this peribronchiolar lesion the lung is often voluminous and fails to collapse on removal from the chest. Pressure upon the lung squeezes from the smallest bronchi, both in the neighborhood of the nodular consolidation and elsewhere, a droplet of viscid, semifluid mucopurulent material. The presence of this tenacious material throughout the small bronchi doubtless explains the failure of the lung tissue to collapse. Interstitial emphysema has been present in some of these lungs.