It is not necessary to know, precisely, how this sympathetic or telegraphic system operates in the conservation of health, but all of this knowledge that is essential to us is the understanding of the main fact, to know the nature of a message and from whence it comes, or its probable origin when doubt arises. It is owing to an imperfect knowledge of this law which causes so general a belief in the theory that the internal organism takes on disease readily from the action of cold upon the surface of the body. But, in fact, the skin was especially designed to be played upon by extremes of heat and cold, wind and wet; and human beings are not necessarily such pitiable creatures as they are made to appear from the general supposition that a transient exposure to a current of pure air, whether wet, dry, cold or hot, is likely to bring on disease. “The immediate effects of a displacement of blood from the surface, and its determination to the internal organs, are not,” says the _Lancet_, “as was once supposed, sufficient to produce the sort of congestion that issues in inflammation. If it were so, an inflammatory condition would be the common characteristic of our bodily state. When the vascular system is healthy, and that part of the nervous apparatus by which the calibre of the vessels is controlled performs its functions normally, any disturbance of equilibrium in the circulatory system which may have been produced by external cold will be quickly adjusted.” Nothing so readily promotes disorder of the vascular system, and of the nervous apparatus which controls it, as to interfere with the nutrition of the nervous system; and in turn, no cause is more effectual, and none more speedy, among the ordinary vicissitudes of life, in depriving the nerves and tissues of their appropriate aliment, than an excessive or otherwise unwholesome diet and the consequent disturbance of the organs of nutrition; and the excess is increased relatively, and the disorder intensified, in proportion as the body is sweltered with clothing and defrauded of the “breath of life”——outdoor air. It is a very significant comment on the cold-air fallacy, that people of all ages, sexes, occupations and social positions, and in all conditions of _general_ health, catch cold, say to-day, from the slightest exposures, often, indeed, they are totally at a loss to account for them except upon one surmise or another, like that of the old lady who “caught her death o’ cold _taking gruel out of a damp basin_”; while next month, or next week, perhaps, the same individuals endure the most extreme exposure, as, for example, riding for hours in face of a driving rain or snow-storm, until wet and chilled through and through; or, perhaps, being turned out at night in bitter cold, half clad, to find their way from their burning dwelling to a distant neighbor’s——in short, they may suffer the most taxing exposures and yet “catch” nothing more