There may be haemorrhagic extravasations throughout the spleen pulp. The bacilli are chiefly scattered throughout the venous sinuses. There is also active congestion of the liver. The kidneys are intensely congested and we often find fibrin thrombi in the tufts of the Malpighian bodies. The plague toxin has a marked effect on the cardiac muscle so that we usually find dilatation of the right side of the heart with fatty degeneration of the muscle fibers. In a study of the pathology of primary pneumonic plague Strong noted pericardial and pleural ecchymoses with fibrinous pleurisy over the affected lung areas. The process was at first lobular but later involved the entire lobe. There was marked congestion of the bronchial mucosa with involvement of the bronchial glands. The larynx and trachea are also intensely congested. Microscopically there is a distension of the alveoli and bronchial passages with a haemorrhagic exudate. There is practically no fibrin in the alveolar exudate. The process seems to extend by continuity along the bronchi and bronchioles. Plague bacilli pack the exudate found in the bronchi and bronchioles. In a report on the autopsy findings of septicaemic plague in Ceylon in cases where plague bacilli were demonstrated in smears and cultures from spleen and blood, Castellani noted that other than meningeal congestion and some splenic enlargement there was nothing abnormal. SYMPTOMATOLOGY In a clinical study of plague it is customary to consider the disease as manifesting itself in a mild form (Pestis minor) and a severe form (Pestis major). =Pestis Minor.=—Pestis minor, which is sometimes termed pestis ambulans, is that form of plague in which there is only slight fever and comparatively little physical prostration or mental hebetude. These cases usually show moderate enlargement and tenderness of some group of lymphatic glands. It is in this mild form of plague that we are most apt to find the primary vesicle or phlyctenule at the site of the flea bite. Ordinarily, man is so susceptible to plague that there is no reaction at the site of inoculation but in these mild cases there is an inflammatory reaction resulting in a vesicle or pustule, which may teem with plague bacilli. In such cases it is extremely important to search for such primary vesicles and examine for plague bacilli. It is usually stated that only about 5% of cases of bubonic plague show these vesicles. =Pestis Major.=—Pestis major can certainly be divided clinically and epidemiologically into two types, pestis bubonica, or bubonic plague, which is the common type of plague, and pestis pneumonica, or pneumonic plague, the contagiousness of which is extreme and the mortality practically 100%.