This was recognized early in the epidemic. It was sometimes preceded by a peculiar flushing of the face, such as accompanies belladonna poisoning. It might be noticed in the very first days of the attack. The cyanosis was looked upon as being a very early symptom of lung involvement. With our later knowledge from autopsies, and especially as shown by Dr. Klotz, we feel it was surely an accompaniment of, or may even have preceded, the changes in the lung which have been designated as œdematous, “wet” or cyanotic. At the earliest appearance of the cyanosis we were frequently unable to find any change in the physical signs of the chest. Of course, the indefinite signs of an acute bronchitis were present, and in some cases an additional “impaired resonance” was noted over one or both lower lobes, but when this was definitely present other more definite signs soon followed, and our case was shifted suddenly from Group I, i. e., without apparent lung involvement, to Group II, i. e., with definite lung involvement. This cyanosis was noticed first in the face, and frequently was marked on the dorsal surface of the hands. It was not unlike the cyanosis which may sometimes be seen when large doses of certain coal tar derivatives are taken. In fact, the question arose whether in the epidemic of 1889 and 1890, when the coal tar derivatives were prescribed with such freedom and with accompanying cyanosis and apparently such deleterious effects, the cyanosis may not after all have been due more largely to the infection than to the medication. After that epidemic it was said: “Influenza has slain its thousands, but the coal tar products have slain their tens of thousands.” There was no gross hæmaturia or hæmoglobinuria present in these cases, although a few red blood cells were seen microscopically. There was, however, epistaxis, sometimes early in the disease or later associated with the cyanosis. In a few cases there was hæmoptysis, which we regard as always arising in cases where the wet or hemorrhagic lung was present. Cyanosis in disease of the lungs, and especially in the terminal stage of lobar pneumonia, is a familiar and common occurrence, but the cyanosis observed in this epidemic seemed quite different from the ordinary. The points of difference were these: (a) it came early in the disease; (b) it seemed to be more generally present when very little lung involvement could be demonstrated physically, and was just as likely to disappear when more definite chest signs were demonstrable; (c) it was not associated with embarrassment of respiration; (d) it had no relation with a demonstrable circulatory disturbance. The pulse did not become rapid; the quality of the pulse did not change; _the right heart was not dilated_, as is so frequently the case in the terminal stage of a lobar pneumonia when cyanosis appears; (e) and finally there was no associated œdema of the lungs, or at least that œdema of the lungs which occurs in the later stage of