It is of importance to appreciate that the deposition of these hyaline structures indicates a severe injury of the alveolar walls not commonly observed in ordinary pneumonias.
In different areas of the same lung these constituents of the early exudate may be observed in all proportions of admixture. Each one of the elements of the exudate may largely overshadow the others and prominently modify the appearance of the lesions. Broadly speaking, however, the inflammatory œdema and hemorrhage occupying the greatest part of the exudate in the lungs and the absence of marked leucocytic response as well as the absence of the characteristic fibrinous meshwork in the alveoli give to the early influenza-pneumonia a character different from those which we ordinarily see.
It is during this early phase of the reaction that the influenza bacilli can be shown within the lung structures. The distribution of bacteria is not uniform. Clusters of these minute bacilli are found in the alveoli at irregular intervals, many of the air sacs containing much exudate being quite free from organisms. When present the bacteria appeared in tightly aggregated schools lying free amongst cells of the exudate, but also certain numbers being incorporated within the large mononuclear cells. In some regions organisms of the type of the influenza bacilli were alone seen, while elsewhere again, and particularly where the exudate was assuming purulent characters other bacteria of the nature of streptococci, staphylococci and micrococcus catarrhalis, were also found.
Following upon the primary reaction in the lung as above described, a secondary reaction makes its appearance at variable periods. This reaction is one in which the inflammatory exudate resembles more closely but is not identical with the responses which are observed in ordinary lobar, lobular and pneumococcus-pneumonia. Whereas in the earlier period, the reaction is largely one of a serous and hemorrhagic exudate accompanied by peculiar hyaline deposits along the inner borders of the alveoli, later there is seen a change in the quality of the exudate with the accumulation of more cellular elements and some fibrin. The naked eye appearance of the involved tissue changes considerably. The lung tissue loses in weight but becomes more solid. The lung contains less fluid and the cut surfaces are drier and the color of the reaction changes from the dark congested appearance to one showing all varieties of red and gray. This change from the flabby and soggy pneumonia to the more definite type of consolidation occurs in the regions which have been previously involved and is not to be found in the lung areas which have escaped the early reaction. The gray consolidation appears to be either a stage of the influenza-pneumonia or is a new reaction superadded to those pulmonary lesions induced by the primary infection.