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. It is sometimes difficult to recognize the beginning of this pneumonic stage inasmuch as the gray color does not make its appearance even with the presence of fairly large quantities of cellular exudate. The amount of hemorrhage that originally lay in the affected areas for a long time overshadows the presence of the color of the cellular exudate. This is also true of the characters that may be impressed by the presence of fibrin. Small quantities of fibrin scattered through the congested and œdematous lung are not readily recognized and the beginning of this secondary reaction is also easily overlooked if one relies upon evidence of consolidation. More or less solid exudate may occupy a flabby lung without permitting one to appreciate its presence in the gross specimen. When, however, the deposit is of sufficient quantity to change the color of the involved lobe and to alter its consistency, one has little difficulty in recognizing the changes now taking place. The earliest development of this change in the inflammatory reaction was on the fourth day. In the majority of instances the gray color and the consolidation made its appearance about the sixth day. We have, however, on several occasions observed hemorrhagic lesions as late as the seventh and eighth day, at which time it was impossible to recognize a gray hue to the exudate or the character of granular consolidation to the involved lung.