A few words as to “forms” or varieties of influenza might be helpful before suggesting a classification of symptoms. In former epidemics of influenza considerable importance was attached to the early manifestations or first symptoms as characterizing the “form” of influenza which was in evidence in the individual patient. These were reported as a “respiratory form,” a “nervous form,” a “gastro-intestinal form,” and other forms—circulatory, renal, psychic, etc. In the epidemic of 1889 and 1890 particularly these types were noted, and they have been described in the subsequent small epidemics, practically characterizing them as being of one or the other, and frequently as being without any respiratory symptoms. In the study of our group of cases in the present epidemic every effort was made to recognize the non-respiratory cases, but we were unable to find a single case which did not have definite respiratory symptoms, either early or late, in addition to any other symptoms present. Only occasionally were nausea, vomiting and diarrhea or tachycardia, or certain neuroses or psychoses, the leading symptoms. The respiratory symptoms in some cases seemed to be at the onset primarily of the lower respiratory system—that is, without the preliminary coryza. These usually ran a rapidly fatal course, characterized by marked cyanosis and confusingly irregular chest signs. We would say, therefore, in so far as our experience goes in this epidemic, we are not justified in speaking of any particular forms except the respiratory form, and whenever pronounced manifestations occurred justifying a characterization of any other form they could more easily be interpreted as a complication, or the manifestation of a coincident disease, or of a severe toxæmia. The classification of the symptoms, therefore, takes into consideration largely those symptoms arising from the respiratory system. We are of the impression that the pathology demonstrated by Dr. Klotz and described by others justifies the following classification. Clinically we would recognize two distinct groups of epidemic cases. The first includes those _without lung involvement_ having symptoms arising from the upper respiratory tract, including the trachea and the larger bronchi. These were practically without any chest signs except for the rather indefinite signs of an acute bronchitis, and the only symptoms referable to the respiratory tract were a coryza, soreness of the throat, hoarseness and a cough of varying degree and character. If to these symptoms are added those of Leichtenstern just mentioned, one will have a good description of a so-called simple, uncomplicated influenza.