_Chronic Plague in Rats._—The Indian investigators have called attention to the existence of a chronic plague in rats. In this we have chronic buboes, areas of necrosis in spleen and abscesses of the spleen. It is chiefly in the spleen that the lesions occur, thus differing from the acute plague in rats above described. Of 27,699 _M. norvegicus_, examined in Bombay, O.57% showed signs of chronic plague. In the necrotic material plague bacilli can be found in approximately one-half of these rats although frequently the bacilli are nonvirulent. It is possible that this chronic plague in rats may serve as the reservoir of infection which keeps up plague epizootics from year to year. Plague in India, according to White is less virulent now than formerly and this is attributed to a greater immunity of the rats. _As regards pneumonic plague_ the origin of such epidemics is probably from pneumonia occurring secondarily in cases of bubonic plague. Provided the conditions are favorable, particularly as to moisture in the air of the room, the infection spreads directly from man to man as a result of the droplets of heavily infected sputum being sprayed into the air in the act of coughing on the part of the patient. It is an instance of _Flügge’s droplet method of infection_. In the recent epidemic of pneumonic plague in North China, it was at first thought that the hunting of the tarabagan for its valuable skin, which led some of the Chinese to even capture tarabagans, possibly sick with plague, was the origin of the epidemic. This view is no longer held and we now know that the outbreak was independent of any disease in rats, tarabagans or other animals. Strong has shown that the bacillus which was isolated from these cases of pneumonic plague was identical with that isolated from cases of bubonic plague; its virulence was no greater and animals infected cutaneously or subcutaneously died of bubonic plague. Experiments by Teague and Barber, with emulsions of plague bacilli, showed that with a room temperature of 32°C. plague bacilli were quickly destroyed when the air was comparatively dry. In such an atmosphere, saturated with moisture, the viability would be greatly prolonged. In the plague wards in Manchuria the extreme cold which prevailed, together with the saturation of the atmosphere of the unventilated rooms by the moisture of the breath of the patients, made conditions most favorable for the viability of the plague bacillus. They note that in the plains of India, although about 3% of bubonic cases assume a pneumonic type, yet epidemics of plague pneumonia do not occur; this is probably due to the fact that the higher temperatures and open rooms make evaporation occur 30 times more rapidly there than was the case in the plague wards in the bitter cold weather of the Manchurian winter. The possibility of carriers of plague bacilli in those who might go on to