THE PATHOLOGY OF THE RESPIRATORY TRACT IN INFLUENZA
If the atrium of an infection and its specific etiological agent are undetermined, the narrator of the pathology of a specific disease is confronted immediately with serious obstacles in the elaboration of a complete picture. Some writers assume that the respiratory tract is the portal of entry in influenza (162), though the specific agent is still unknown.[[2]] Whatever the agent, unquestionably it attacks the respiratory tract at a very early stage in the disease and produces a lesion which becomes responsible for the most serious aspect of influenza, whether this phase be primary or only a complication.
Among the lesions which will be considered, therefore, those of the respiratory tract chiefly will be emphasized. They include the changes in the large air passages, as well as the pulmonary, alveolar, and interstitial involvement. Unquestionably, a very close association exists between the lesions of the larger air passages and those of the alveoli, but probably it is equally true that the former may occur alone; in many instances also they are the forerunners of the latter lesions. Consequently, it seems logical to begin with an exposition of the lesions in the trachea and its ramifications, including the bronchioles.