The lymphadenoid tissues of the alimentary canal share in the process only to a minor extent. In a number of cases, there is no question that the Peyer’s patches and solitary follicles are hyperplastic. Grossly, they stand out prominently, and are pale pinkish-grey in color. Histologically, there is hyperplasia, chiefly apparent from the large germinal centers in the follicles, and a slight distention of the lymph channels. This picture, so commonly found in every type of general infection, is in no way characteristic of influenza. _Spleen._ The spleen is the seat of the usual manifestations in generalized acute infections. In no case is the organ markedly involved, although considerable increases in its size may occur (2, 108, 141, 157, 162). It is not feasible to introduce a detailed discussion of this mild grade of splenic tumor, for there are natural variations in the size of the spleen and frequently it is modified in this respect by subsidiary conditions. In every instance the capsule of the spleen is smooth and there is no acute or chronic perisplenitis attributable to influenza. The capsule usually retracts slightly and the splenic pulp, in slight excess, is much more frequently red or garnet than grey in color. Occasionally, the splenic tumor is grey as in pneumonia. The more minute changes in the organ consist of congestion of the sinuses, increase of the mononuclear cells of the pulp, and prominence of the germinal centers of the Malpighian corpuscles (140). Hemorrhages, found occasionally (47), are more frequent in the pulp, but also occur in the corpuscles. _Bone Marrow._ One of the clinical features of influenza is a leukopenia, which persists often in the face of acute pyogenic pulmonary infection (12, 138, 143, etc.). In this series of ninety-five cases, the vast majority had this type of blood picture, but occasionally a leucocytosis (14) was demonstrable even during the early part of the disease and in those cases which terminated fatally within a period that may be called acute. In almost all instances where fatal termination was delayed, the leucocyte count ultimately was elevated either with remission or to a constant high level. The blood studies have not been sufficiently complete to allow further discussion, though there is reason to believe that these might have yielded interesting results. The blood changes in this series are similar to those presented in the reports of the epidemic from other sources. In the majority of cases where the marrow was studied, it was aplastic (12). Occasional, focal, hemorrhagic lesions of the marrow (47) similar to those discussed below in the skeletal and parenchymatous systems were encountered and there was an apparent increase in the number of megalokaryocytes. The usual hyperplasia of the myeloid elements of the marrow associated with pyogenic change was not present.