Large mononuclear cells are occasionally fairly numerous within the alveoli containing blood. These cells act as phagocytes ingesting red corpuscles, so that at times they are filled with corpuscles. Disintegration of red corpuscles occurs and brown pigment remains within the cell. It is not uncommon to find numerous mononuclear pigment containing cells which resemble those found with chronic passive congestion of the lungs. Lungs, the site of hemorrhagic peribronchiolar pneumonia, may undergo chronic changes which will be described elsewhere. The lesion which has been designated hemorrhagic peribronchiolar pneumonia is that which Pfeiffer regarded as the characteristic type of influenzal pneumonia. In the small bronchi containing pus and in lung tissue, Pfeiffer states, influenza bacilli are predominant and present in astonishing number in smear preparations. The demonstration of B. influenzæ by cultures from pneumonic lung is mentioned by him but its association with other microorganisms in such cultures is not discussed. Microorganisms which we have isolated from the lungs of individuals with hemorrhagic peribronchiolar pneumonia are as follows: B. influenzæ 1 Pneumococcus 2 S. hemolyticus 10 B. influenzæ, pneumococcus 7 B. influenzæ, S. hemolyticus 3 B. influenzæ, staphylococcus 2 S. hemolyticus, B. coli 3 B. influenzæ, pneumococcus, staphylococcus 2 B. influenzæ, S. hemolyticus, staphylococcus 5 Pneumococcus, S. hemolyticus, staphylococcus 1 No organisms 2 —— Total 38 With this type of pneumonia B. influenzæ has not been isolated in pure culture; B. influenzæ alone is recorded only once (Autopsy 435), but in this instance the culture has been so obscured by contamination that the occurrence of pneumococci or streptococci cannot be excluded; S. hemolyticus has doubtless been present in this lung, for it has been found in the heart’s blood, in the bronchus, and in the peritoneal exudate of the same individual. The incidence of pneumococci and hemolytic streptococci in this list does not differ materially from that with peribronchiolar pneumonia unaccompanied by extensive intraalveolar hemorrhage, though hemolytic streptococci are somewhat more frequent with the hemorrhagic lesion. The following table shows the frequency with which pneumococci and hemolytic streptococci have penetrated into the blood: