Symmers (141) and Oberndorfer (108) have already likened the influenzal pulmonary complications to plague pneumonia, and it is quite possible that others will find fundamental similarities with other fulminating, inflammatory reactions. Inflammation, a series of processes manifested after injury by a tissue which still retains its viability, is modified by another important factor usually neglected; namely, the state of the host. As a consequence, the inflammatory reaction might readily have similar manifestations even though the primary exciting agents are diverse. This has been amply demonstrated for many different reactive processes, and still it may be considered as a challenge for those who are of the opinion that specific bacterial agents necessarily produce characteristic anatomical manifestations. Consider the state of knowledge of the various reactions to the tubercle bacillus before this microorganism was isolated; and then bear in mind that we are dealing here with a disease whose causative agent, despite the present uncertainty regarding its specific nature, produces a lesion that paves the way for the invasion of the respiratory tract by many different organisms. The extent of the reaction may depend upon the systemic capacity to compensate, as well as upon the degree of primary damage in a specific system of organs. Unquestionably, these two factors must take their places in the balance, the opposite pan of which contains the one or the other secondary bacillary invader. [Illustration: FIG. XXXVIII. THE UPPER ILLUSTRATION, AUTOPSY NO. 116, SHOWS A FRESH, FIBRINOPURULENT PLEURAL EXUDATE. THE PLEURAL LINING CELLS ARE SWOLLEN AND CONSPICUOUS. THE LOWER ILLUSTRATION, AUTOPSY NO. 100, SHOWS ANOTHER AND LATER TYPE. THE ELEMENTS OF THE EXUDATE HAVE DISINTEGRATED TO FORM A MUCILAGINOUS MASS. COMPARE FIGURE XXXVII. ] [Illustration: FIG. XLI. AUTOPSY NO. 140. IS A LOW POWER DRAWING OF THE CHARACTERISTIC LUNG IN THE MORE CHRONIC STAGE OF THIS DISEASE. NECROTIZING AND ORGANIZING BRONCHIOLITIS AND PERIBRONCHIOLITIS ARE ASSOCIATED WITH AN ORGANIZATION OF THE EXUDATE IN THE ALVEOLI. THE ORGANIZATION PROCESS IS SOMEWHAT OBSCURED BY THE EDEMA. COMPARE FIGURES XI, XXXIX, XI, AND XLIV. ] [Illustration: FIG. XXXIX. AUTOPSY NO. 140. RIGHT LUNG. THE HISTOLOGY OF THE PULMONARY CHANGES IN THIS CASE IS ILLUSTRATED IN FIGURES XI, XLI, AND XLIV. THE NECROTIZING PERIBRONCHIAL FOCI STAND OUT PROMINENTLY AND THE ORGANIZATION OF THE EXUDATE IN THE SURROUNDING ALVEOLI IS ALSO DISTINCTLY SEEN IN THE ABOVE FIGURE. ]