We were continually impressed with the notion that the pathology in the lung, at least the pathology demonstrable physically, did not tell the whole story of the case, and that the outcome depended as much or possibly more upon a general infection or toxæmia of which the recognized condition in the respiratory system was only a small part. We were particularly impressed with this in the success or failure following the application of any therapeutic measures. It was quite a common remark, therefore, in the wards of the hospital among those associated in the work that “the patient died too quickly to permit of the succession of the various stages of pneumonia”; or, in the autopsy room, that if the patient had lived long enough he would have had demonstrable, well-recognized pathology of the lung, instead of the cyanotic, wet, spongy lung which was found. The temperature course in the pulmonary cases was characterized by its irregularities, and by its being entirely out of harmony with the extent and severity of the lung invasion in so far as it could be interpreted by the physical signs. The temperature as described in a simple influenza might not come to the normal in the time of three to seven days, and might even go higher, with no demonstrable chest signs, but with every other evidence of lung involvement. Later the temperature might come down by lysis, which was the usual way, and the chest signs gradually or suddenly become evident. The temperature might remain normal throughout the rest of the course, and a lobe or even both lower lobes of the lungs be as solid as in a true lobar pneumonia. Occasionally the temperature fell by crisis, but there was no associated change in the physical signs of the chest. In short, the temperature seemed to run a course entirely independent of the physical signs in the chest. In two remarkable cases seen in consultation on two consecutive days the physicians in charge declared that no signs of consolidation could be found, though all other evidences of pneumonia were present. In the 12 hours which had elapsed from the time the last examination was made the temperature fell by crisis. At the consultation, to the surprise of the family physicians, we found both lower lobes consolidated, it having occurred apparently with the crisis. Both patients were healthy-looking, robust, young men, and both recovered with delayed resolution. In the convalescence of such cases, if the patient got up too soon or if any other indiscretion took place, a relighting of the lung occurred. From the above description it can be readily seen that a diagnosis of the conditions in the chest in influenzal pneumonia was frequently impossible, because one had to abandon all his previous ideas of pneumonia, in so far as onset, crisis, blood picture, sputum, temperature, respiratory and circulatory phenomena, physical signs and prognosis were concerned.