=Clinical Diagnosis.=—The clinical diagnosis recorded upon the clinical history of the patient is given in column 6. Many clinicians have been impressed with the difficulty of determining during life the type of pneumonia associated with influenza. The occurrence of purulent bronchitis, the frequent coexistence of lobar and bronchopneumonia and an atypical onset often make the recognition of lobar pneumonia more difficult than usual. The diffuse consolidation of confluent lobular pneumonia increases the difficulty of recognizing bronchopneumonia. In the table (column 6) lobar pneumonia is indicated by L., bronchopneumonia by B. Among 227 autopsies the clinical diagnosis agreed with the condition found at autopsy in 109 instances (48 per cent); in 35 instances (15.4 per cent) both lobar and bronchopneumonia were found at autopsy and a diagnosis of one or other was made during life. In 83 instances (36.6 per cent) the diagnosis made during life was incorrect. Cases admitted to the base hospital at Camp Pike were as carefully studied as the conditions in a base hospital during an epidemic permitted and diagnosis of pneumonia was doubtless as accurate as in other base hospitals. Statistics from military and other hospitals based upon clinical diagnosis of the pneumonias of influenza are probably subject to an error of at least 1 in 3 cases, and conclusions based upon them are almost valueless. The inaccuracy of clinical diagnosis of the pneumonia of influenza is further illustrated by a consideration of lobar pneumonia. This diagnosis on the one hand was made 136 times and was correct 67 times and incorrect 69 times; on the other hand, lobar pneumonia was found at autopsy 98 times and had been diagnosed in only 67 of these cases (68.4 per cent). =Classification of the Pulmonary Lesions of Influenza.=— Influenzal pneumonia exhibits the following noteworthy characters: 1. Acute bronchitis with injury or destruction of lining epithelium and accumulation of inflammatory exudate within the lumen. 2. Hemorrhagic pneumonia with accumulation of blood within the alveoli and within and about the bronchi. 3. Susceptibility of bronchi and pulmonary tissue to secondary pyogenic infection with necrosis and suppuration. 4. Bronchiectasis. 5. Tendency to the occurrence of chronic pneumonia following failure of pneumonia to undergo resolution. All these changes are doubtless referable to the severity of the primary injury to the lower air passages. In the presence of destructive changes in the bronchi many bacterial species, including B. influenzæ, pneumococci of various types, streptococci (notably hemolytic streptococci) and staphylococci may invade the lungs and produce acute inflammation. The anatomic characters of the pneumonic lesions following influenza are equally varied.