Third. The occurrence of those cold north-east winds that during the latter part of autumn and early part of spring so often sweep over the whole extent of our Atlantic coast and press up the valley of the St. Lawrence to {169} the great interior lakes, and the still more severe currents that come during the same seasons from the north-west and west, over all the wide plains that intervene between the great mountain-chains to the west and the upper lakes and Mississippi River to the east, are also accompanied by a high ratio of prevalence of bronchial affections, as has been already shown from the records of the several military posts. Most of these severe storms of wind are accompanied by either snow or rain and a marked increase of ozone or active oxidizers. In some of the severe snowstorms from the north-east, occurring in the latter part of February and in March, I have found an unusual amount of free ammonia. Whether either the ozone or the ammonia has had anything to do with the production of the bronchitis cannot be determined until the observations and records now being made under the auspices of the American Medical Association have been continued for a few years, by which adequate data will be furnished for reliable deduction. Besides ordinary meteorological conditions, bronchitis may be produced by inhaling irritating substances, such as steam, irritating gases, steel-dust, or minute particles of other metals or stone in workshops, and the dust encountered in handling grain, etc. The disease has often occurred in epidemic form without the presence of an obvious exciting cause. It also frequently occurs in connection with certain general fevers, more particularly with typhoid, measles, influenza, and pertussis. It also sometimes, though more rarely, accompanies rheumatism, constitutional syphilis, and erysipelas. The presence of tuberculous and cancerous deposits in the lungs almost always provokes more or less bronchial inflammation during some part of their progress. Acute Bronchitis.