"Disease is a hot-house plant."—Haller.
EVERY disease is a protest of Nature against an active or passive violation of her laws. But that protest follows rarely upon a first transgression, never upon trifles; and life-long sufferings—the effects of an incurable injury excepted—generally imply that the sufferer's mode of life is habitually unnatural in more than one respect. For there is such a thing as vicarious atonement in pathology: a strict observance of any one of the three or four principal health-laws rarely fails to reward itself by a long immunity from the consequences of otherwise evil habits. Frugality thus counteracts the morbific tendency of indolence; perfect continence may steel even a feeble constitution against the effects of hunger and overwork; and, by avoiding the great vice of intemperance, the Epicureans atoned for a multitude of minor sins.
But the surest of all natural prophylactics is active exercise in the open air. Air is a part of our daily food and by far the most important part. A man can live on seven meals a week, and survive the warmest summer day with seven draughts of fresh water, but his supply of gaseous nourishment has to be renewed at least fourteen thousand times in the twenty-four hours. Every breath we draw is a draught of fresh oxygen, every emission of breath is an evacuation of gaseous recrements. The purity of our blood depends chiefly on the purity of the air we breathe, for in the laboratory of the lungs the atmospheric air is brought into contact at each respiration with the fluids of the venous and arterial systems, which absorb it and circulate it through the whole body; in other words, if a man breathes the vitiated atmosphere of a factory all day and of a close bedroom all night, his life-blood is tainted fourteen thousand times in the course of the twenty-four hours with foul vapors, dust, and noxious exhalations. We need not wonder, then, that ill-ventilated dwellings aggravate the evils of so many diseases, nor that pure air should be almost a panacea.
Outdoor life is both a remedy and a preventive of all known disorders of the respiratory organs; consumption, in all but the last stage of the deliquium, can be conquered by transferring the battle-ground from the sick-room to the wilderness of the next mountain-range. Asthma, catarrh, and tubercular phthisis, are unknown among the nomads of the intertropical deserts, as well as among the homeless hunters of our Northwestern Territories. Hunters and herders, who breathe the pure air of the South American pampas, subsist for years