That tubercular deposits in the lungs, cancerous growths, emphysema, and previous attacks of bronchitis, all strongly predispose the patient to further attacks of the last-named disease, is proved by universal clinical experience. EXCITING CAUSES.--Exposure to sudden and extreme changes in atmospheric temperature from warm to cold is almost universally regarded as the chief exciting cause of inflammation of the bronchial as of all other parts of the mucous membrane of the air-passages. More accurate and detailed observations, however, show that such changes of temperature are seldom productive of diseases of this class unless accompanied by coincident high winds and humidity. My own studies concerning the relations between special meteorological conditions and the prevalence of particular diseases have led me to the following conclusions in regard to bronchitis and inflammation of the mucous membrane of the air-passages generally: First. Many sporadic cases are caused, at any and all seasons of the year, by exposure of limited portions of the cutaneous surface to cool or cold currents of air while the rest of the body is well protected. Females going out with thin shoes and stockings or sitting before open windows with low-necked dresses, and children out on cold days with naked legs from short trousers and defective stockings, afford many and familiar examples of bronchitis from this cause. Second. The sudden transition from a protracted period of intense dry cold to a higher temperature with increased atmospheric humidity. Almost every winter season, in the northern belt of the United States, east of the Rocky Mountains, is characterized by several periods of steady dry, cold air, varying from one to three weeks in duration, during which the mercury in the thermometer often descends more than 20° C. (8-10° F.) below zero, and which generally ends in a sudden change in the direction of the winds and a marked elevation of temperature, constituting what is popularly called a thaw. Such changes are very uniformly accompanied by a general prevalence of catarrhal affections of the air-passages, including many cases of bronchitis. This class of cases occur principally in the months of December, January, and February.