If the disease had its sole origin in the atmosphere, it would not be thus confirmed to a certain location; for every one knows, that the gentlest zephyr would waft the enemy into the surrounding localities, and there the work of destruction would commence. The reader is probably aware that bodies whose specific gravity exceeds that of air, such as grass, seeds, &c., are conveyed through that medium from one field to another. The miasma of epidemics is said to be conveyed from one district to another "on the wings of the wind." Hence, if milk sickness was of atmospheric or even epidemic origin, it would prevail in adjoining states. This is not the case; for we are told that "this fatal disease seldom, if ever, prevails westward of the Alleghany Mountains or in the bordering states." The atmosphere which surrounds this globe was intended by the divine Artist for the purpose of respiration, and it is well adapted to that purpose: it cannot be considered a pathological agent, or a cause of disease. In crowded assemblies, and in close barns and stables, it may hold in solution noxious gases, which, as we have already stated in different parts of this work, are injurious to the lungs; but as regards the atmosphere itself, in an uncontaminated state, it is a physiological agent. It always preserves its identity, and is always represented by the same equivalents of oxygen, nitrogen, and carbonic acid gas. Liebig says, "One hundred volumes of air have been found, at every period and in every climate, to contain twenty-one volumes of oxygen." Thus oxygen and nitrogen unite in certain equivalents: the result is atmospheric air; and they cannot be made to unite in any other proportions. Suppose the oxygen to be in excess, what would be the result? A universal conflagration would commence; the hardest rocks, and even the diamond, (considered almost indestructible,) would melt with "fervent heat." If, on the other hand, nitrogen was in excess, then every living thing, including both animal and vegetable, would instantly die. Hence we infer that the atmosphere cannot be considered as the cause of this disease.