Fig 11.—Suppurative interstitial pneumonia; the left lower lobe is the site of almost uniform consolidation and here interstitial septa and their lymphatics are distended with pus. There is more extensive interstitial suppuration in the upper lobe where consolidation is absent. The cloudy appearance of the consolidated lung is well shown. Autopsy 452. ] Suppurative interstitial pneumonia frequently occurs in association with bronchopneumonic consolidation which may be peribronchiolar, hemorrhagic or lobular, but there is in addition consolidation of the pulmonary tissue between the inflamed septa which may affect part of a lobe, an entire lobe, or parts of several lobes; it does not exhibit the characters of confluent lobular pneumonia. In approximately half of the cases consolidation, associated with interstitial suppuration, has been lobar in distribution (Fig. 11). The tissue is laxly consolidated, finely granular, and has a cloudy red or gray appearance. The coarsely granular surface of lobar pneumonia is absent. The affected lung may weigh 1,500 or 1,650 grams. Occasionally, interstitial septa of air containing lung tissue is the site of suppurative inflammation or edema. In Autopsy 452 the lower lobe, save a small part at the base, is laxly consolidated; interstitial septa in the consolidated area are yellow, 1.5 to 2 mm. in thickness, beaded and exude purulent fluid on pressure. In the adjacent part of the upper lobe there is a patch of consolidation, and a network of yellow thickened septa extends from it far into the surrounding air containing tissue. The weight of the right lung is 635 grams; of the left, 1,650 grams. The distribution of interstitial suppuration in 21 instances, including 4 in which the lesion has occurred in the same lungs with abscess formation, has been as follows: right upper lobe, 9 instances; middle lobe, 4; lower lobe, 5; left upper lobe, 7; left lower lobe, 6. In 6 of these autopsies more than one lobe of the same lung has been affected by the lesion; in 2 autopsies parts of both lungs have been affected. Localized abscess of the lung is more common in the lower than in the upper lobes, but suppuration of the interstitial tissue is more often found in the upper lobes. The duration of illness with interstitial suppurative pneumonia has varied from six days to five weeks. In over half of the cases death has occurred during the second week of illness. The bacteriology of these cases is shown in Table XLVIII. TABLE XLVIII