adapt itself to any condition tolerable at all in the long run. This is true to an extent, as to the products of breathing as well as to temperature, but it is more than likely that any immunity from the habit of living in badly used air is gained at the expense of vitality.
Contaminated Air.—As distinguished from 'exhaustion' of air, or shortage of oxygen, with the corresponding increase of carbonic acid and other waste products, the term 'contamination' may be applied to impurities of gaseous and solid nature, aside from the normally unavoidable. Tins includes, for instance, gases and vapor from industrial sources, also smoke, soot and dust with its attendant bacteria.
The amount of carbonic acid found in air is commonly regarded as a measure of the degree of vitiation, but wherever pollution of the air is likely to occur independent of an increase of combustion or respiration that method of testing the purity naturally is deceptive. Indeed, contamination quite often predominates exhaustion, and should always be considered by itself, as a separate factor, according to the nature of the case. While the effect of exhausted air may have been overestimated, the bearing of contamination on health does not seem to be sufficiently realized. Its claims on vitality are of a different nature. Any admixture of foreign gases may react directly upon the blood. Such poisoning, however, is mostly due to local sources, readily detected and prevented. By far the greater mischief is done by the solid impurities afloat in the air. Although these are normally arrested by the moist, mucous surfaces of nose and throat, they will, under certain conditions, enter the lungs, fill the minute air chambers and lodge there indefinitely. Through life in smoky or dusty surroundings large portions of the lungs become useless in this manner, invite decay and the fatal attacks of bacteria. Dr. Louis Ascher, in publishing the results of his exhaustive investigations on the subject, has shown conclusively that smoky atmosphere encourages diseases of the respiratory organs, materially shortens the life of consumptives and bears distinctly on the mortality of afflicted districts. The charts of distribution of pulmonary tuberculosis in Chicago show indeed the cases to be most frequent near the cluster of railway stations. The appalling contingent of lung patients sent to the Eocky Mountains from our smoky cities of the middle west gives a sad testimony to these facts.
Still greater mischief is done by solid impurities, especially dust, as the carriers of disease germs. True, the best authorities now agree that the presence of microbes in the respiratory organs does not necessarily produce disease, and that the germs must first make their way into the system in order to develop, and find it in poor condition before they can do serious harm. Predisposition, in the form of inflammation combined with lowered vitality, seems therefore necessary to develop the more serious pulmonary diseases. Unfortunately these predisposing