A condition which was frequently noted by the patient was an indescribable weakness and prostration which appeared early, sometimes before any other symptoms were noted or before any elevation of temperature. The young soldier was in apparent perfect condition when he arose in the early morning. During the “setting up” exercises he did not feel so fit, and a few hours later appeared extremely weak. When his condition was called to the attention of the medical officers he was found to have a slight elevation of temperature and was sent to his bed. In former epidemics, as also in this one, marked prostration was recognized as coming at the height of the disease and remaining persistently during convalescence. But it does not seem to be recorded as among the first symptoms. _Influenza with Lung Involvement_ Of the group with lung involvement much may be written from a clinical standpoint, and much confusion may be brought about. Especially is this so if one has no definite idea of the pathology present, or if one enters into a discussion of the character of the infection—a point upon which there is as yet no unanimity of opinion. From the many reports which have been put forth from the base hospitals of the various cantonments, and also from the reports coming from civilian practice, it is evident that scarcely any two groups of laboratory men or any two individuals of those separate groups have the same idea as to the bacteriology and the pathology peculiar to this epidemic. As long as there is this confusion and element of doubt in the minds of those to whom we are accustomed to look, the clinician must necessarily speak with considerable hesitancy, especially when he attempts to interpret the physical signs observed. In our own group the observations of Klotz, Guthrie, Holman and others have given us an interpretation of our clinical findings which, at present at least, is more or less satisfactory. We shall definitely keep in mind their observations and conclusions as we go on with the description of the physical signs of the chest in cases having lung involvement. In the description of this group it will readily be seen that the lower respiratory tract stood the brunt of the infection. Of the 153 soldiers under our care, 60, or about 40 per cent., were recognized as having pneumonia. Of these, 34 had undoubted demonstrable signs, while 26 were questionable, and yet from the temperature and other symptoms we concluded there was a pneumonia. Of the 394 civilians, 189, or about 50 per cent., had pneumonia. Of this group there were again some 28 or 30 in which the diagnosis was doubtful, according to the ordinary way of making a diagnosis, but we felt sure from the temperature course that more than a simple influenza was present. In the description of the physical findings of the chest in these influenzas with lung involvement it will be readily seen why the diagnosis must sometimes be in doubt.