Occasional reports have been made upon the occurrence of thrombosis immediately following an attack of influenza. These thromboses have occurred in diverse regions, the brachial, femoral, the mesenteric, and other arteries. It is possible that the development of the deep hemorrhagic lesions of muscles in the extremities are associated with thrombosis. It is impossible, however, to demonstrate within such blood masses the presence of thrombosed vessels which had preceded the hemorrhagic state. It was, however, possible to demonstrate capillary thromboses through the lung and in the submucosa of bronchi and trachea. In these instances the damage to the vascular walls was brought about by the action of the infection immediately surrounding them, and was not associated with a process beginning within the lumen of the channel. The type of thrombosis within the lung to which we have referred in a previous discussion is interesting in that it does not show the usual type of fibrin clotting, but in place of fibrin threads a gummy homogeneous material is deposited upon the vessel walls within which the red blood cells soon undergo dissolution. It would appear that these thromboses within the lung are dependent upon a toxic action on the vessel wall and its plasma content. Thromboses within venous channels are met with more often than in arteries. The veins of the lower extremities are most frequently affected, and yet amidst the many cases of influenza it is an unusual occurrence. The various thromboses of larger vessels usually occur as post-influenzal complications rather than as accompaniments of the acute disease. It is possible that factors other than those present during the acute stage play an important part, and that the virus of influenza is not directly the cause of the thrombosis. _Lymphatics of Lung and Mediastinum_ One of the prominent reactions which was almost constantly present as the inflammatory reaction involving the lymphatic system of the chest. The lymph glands within the chest responded to a marked degree in hyperplasia and commonly showed enlargement quite out of proportion to what is usually observed in lobar pneumonia. These reactions were in direct relation to the inflammatory processes of the lung and appeared to be involved in proportion to the inflammation occupying the tissues drained by them. Elsewhere in the body the lymph glands responded but slightly, and often no change was observed in the lymphatics of the abdomen, axilla and lower extremities. The systemic intoxication thus had no effect upon distant lymph glands, and even the presence of micro-organisms in the circulation did not appear to cause responses in these tissues other than in the neighborhood of the chest. Within the chest the lymphatic system became involved through the presence of the various bacteria migrating along the lymphatic channels as well as through its activity in removing products of inflammation.