For the estimation of the time elapsing between the onset of the pneumonia and death we are dependent upon the clinician. This is often quite difficult to do, in as much as with a primary respiratory disease, such as epidemic influenza represents, it is very difficult to determine the time when there is a transition from the inflammatory process of the upper respiratory tubes to that of the pulmonary tissue. In many of the cases where from the onset there was intense prostration and every evidence of marked intoxication the clinical manifestations of localized processes taking place in the respiratory system were very much in the background and often of insidious progress. In four of our cases it appeared as if the pulmonary manifestations had made their appearance with the first sudden and severe onset of the influenza. On the other hand, also, the clinical signs and symptoms of lung involvement were different from those of frank lobar pneumonia. We would, from our experience at the autopsy table, say that where in the cases of epidemic pneumonia there are present the signs of pulmonary consolidation like those of true lobar pneumonia, that there has been an antecedent period of a pulmonary lesion which passed unrecognized by the clinician. To more clearly state the case, whereas in lobar pneumonia the stage of congestion preceding the stage of red hepatization gives rise to no signs whereby the clinician can indicate the time of its onset or determine the time when it has passed into the succeeding stage, and moreover, the stage of congestion is of short duration to be measured in a period of a few hours, this stage in epidemic influenza though equally indefinite in its clinical manifestations is much prolonged, lasting not only a period of hours but even a period of several days. It is this pulmonary state which is difficult or even impossible to recognize in the living. All gradations of it occur and the clinician can only broadly suggest from all the evidence at hand, the period when inflammation with definite exudate began in the lung. In as much as the total length of illness of a number of cases was only three, four and five days, whereas there was nothing at the onset to suggest pulmonary involvement, we can estimate approximately, at least, the duration of the lung condition. This makes it possible to give a relative estimate of the character of the lesions present at different periods of time. The outstanding finding, as we will discuss again, was that a distinct and peculiar pulmonary reaction was primarily imposed upon the lung, which made its appearance at periods different from those of frank lobar pneumonia.