Various observers have emphasized the types of organism associated with different gross and microscopic manifestations of influenzal pneumonia. Pfeiffer described the peribronchial type with purulent bronchitis, from which the influenza bacillus was isolated, and the same association has been noted by MacCallum (92), Wolbach (162), Wegelin (156), Dietrich (34), and others. Opie et al (110), however, in a series from which B. influenzæ was isolated in over eighty-five per cent of the necropsies rarely found this picture. Wolbach states that the gross anatomical picture in influenzal pneumonia is similar to that following measles, from which a hemolytic streptococcus has been isolated in a high percentage of cases. MacCallum (93) classified this type as interstitial pneumonia. It is interesting to note that interstitial pneumonia has been rare in many localities where the hemolytic streptococcus has been prevalent during the past year. Stone and Swift (138) state that “despite the prevalence of the streptococcus at necropsy, only eight instances of so-called interstitial pneumonia were found in a series of fifty-five cases,” and Goodpasture (48) failed to find a single example in a series of sixteen cases. The pneumococci Types I and II, frequently encountered in the usual forms of lobar pneumonia, have been found exceptionally in this epidemic. Type II, however, has been reported (67, 107) present in about the same proportion as in true lobar pneumonia (5). Chickering and Park (25) described a series of cases of pneumonia due to the staphylococcus characterized by multiple miliary abscesses. Necrotization and abscess formation, however, have been striking features of the pathology of this epidemic, even when the staphylococcus has not been demonstrable. Recently Wadsworth (154) demonstrated experimentally that organization in pneumonia does not result from the pneumococcus or the staphylococcus alone, but only follows when both organisms are associated. On the contrary, Blanton and Irons (12) found that “there was no difference to be made out in the nature of the process caused by the streptococcus, pneumococcus, or influenza bacillus.” [Illustration: FIG. XLVII. AUTOPSY NO. 100. PROLIFERATION OF THE ALVEOLAR EPITHELIUM IN A PORTION OF THE LUNG ONLY SLIGHTLY INVOLVED BY THE ACUTE INFLAMMATORY PROCESS. COMPARE FIGURES IV, XI, XLVIII, AND XLIX. HELIOTYPE CO. BOSTON ]