Undoubtedly during the subsidence of the inflammatory process within the bronchi the gradual restitution of the tissues with little or no fibrosis is accompanied by a reproduction of the lining membrane arising from the epithelial remnants in the small mucous crypts. In a few cases lately coming to autopsy where the patients had suffered an influenza five or six weeks previously, the mucosa of the trachea and bronchi had assumed its normal appearance and was fully clothed by a normal epithelial covering.
We have just discussed the importance of the inflammation of the trachea and bronchi in the cases of influenza. It is our belief that every case of influenza has some tracheitis, and a great many have both tracheitis and bronchitis. This is true in the absence of localizing signs and symptoms, as was evident even in these cases in which the simple influenza passed into its more severe type with its pulmonary lesions. In many of these instances clinical evidences of an inflammatory reaction in the respiratory tubes were wanting, while the reactions observed at autopsy were often astounding.
Just as we feel that simple influenza and inflammation of the respiratory tubes go hand in hand, or better that these respiratory localizations are the all-important ones in every case of simple influenza, so, too, we are of the belief that the pulmonary lesions bear the same relation to all cases of severe and fatal epidemic influenza. We hold that no case comes to his death through acute epidemic influenza without having a lesion in the lung. The pulmonary condition, therefore, is of first importance and its analysis is imperative for a proper understanding of this disease. There has been divided opinion as to the part played by the pulmonary lesion in epidemic influenza, some holding that it is to be looked upon as a part of the disease and others that it must be viewed as a complicating lesion. Complications of various kinds are very common, and there are a number of conditions arising in the lung (abscess, gangrene, necrosis) which must be viewed as complications. There is, however, a type of pneumonia, and here I use the term in its broad sense, which is not in truth a complication but merely a wider extent of involvement of the respiratory tract by the same virus which is always present to cause lesions in the respiratory tubes. The reaction within the lungs is distinctive and differs from the pneumonias which are met with under other conditions and with various bacterial agencies. Nor are our findings in this matter unique for this epidemic. They have been described and discussed in the past. True it is that, like in the epidemic which has just passed us, the incidence of clinical and pathological pneumonia varied quite widely in different communities, so, too, the reports of past epidemics do not give a uniform description of a pulmonary lesion. Where, however, the analysis has been made during the four weeks’ period of the acute epidemic and where the descriptions have been recorded by painstaking observers, the similarity with our present findings is very striking. I would refer in particular to one report made in 1893 in Petrograd by Kuskow. His report deals with 40 carefully studied cases in which records both macroscopic and microscopic were accurately made.