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.
Causes.—A creeping vine has been supposed to occasion the disease. This cannot be the case, for it occurs very frequently when the ground is covered with snow. We are satisfied, although we may not succeed in satisfying the reader, that no one cause alone can produce the disease: there must be a diminution of vital energy, and this diminution may result, first, from poor diet. Dr. Graff tells us that the general appearance of these infected districts is somewhat peculiar. The quality of the soil is, in general, of an inferior description. The growth of timber is not observed to be so luxuriant as in situations otherwise similar, but is scrubby, and stunted in its perfect development, in many instances simulating what in the west is denominated 'barrens.' We can easily conceive that these barrens do not furnish the proper amount of carbon (in the form of food) for the metamorphosis of the tissues; and if we take into consideration that the animal receives, during the day, while in search of this food, a large supply of oxygen, and at the same time the waste of the body is increased by the extra labor required to select sufficient nutriment,—it being scanty in such situations,—then it follows that this disproportion between the quantity of carbon in the food, and that of oxygen absorbed by the skin and lungs, must induce a diseased or abnormal condition. The animal is sometimes fat, at others lean. Some of the cows attacked with this disease were fat, and in apparent health, and nothing peculiar was observed until immediately preceding the outbreak of the fatal symptoms. The presence of fat is generally proof positive of an abnormal state; and in such cases the liver is often diseased; the blood then becomes loaded with fat and oil, and is finally deposited in the cellular tissues. The reader will now understand how an animal accumulates fat, notwithstanding it be furnished with insufficient diet. All that we wish to contend for is, that in such cases vital resistance is compromised. We have observed that, in the situation alluded to, vegetation was stunted, &c., and knowing that vegetables are composed of nearly the same materials which constitute animal organization,—the carbon or fat of the former being deposited in the seeds and fruits, and that of the latter in the cellular structure,—then we can arrive at but one conclusion, viz., that any location unfavorable to vegetation is likewise ill adapted to preserve the integrity of animal life.
In connection with this, it must be remembered that during the night the soil emits excrementitious vapors which are taken into the animal system by the process of respiration. In the act of rumination, vapor is also enclosed in the globules of saliva, and thus reach the stomach. Many plants which during the day may be eaten with impunity by cattle, actually become poisonous during the night! This, we are aware, will meet with some opposition; to meet which we quote from Liebig:—
"How powerful, indeed, must the resistance appear which the vital force supplies to leaves charged with oil of turpentine or tannic acid, when we consider the affinity of oxygen for these compounds!
"This intensity of action, or of resistance, the plant obtains by means of the sun's light; the effect of which in chemical actions may be, and is, compared to that of a very high temperature, (moderate red heat.)
"During the night, an opposite process goes on in the plant; we see then that the constituents of the leaves and green parts combine with the oxygen of the air—a property which in daylight they did not possess.
"From these facts we can draw no other conclusion but this: that the intensity of the vital force diminishes with the abstraction of light; that, with the approach of night, a state of equilibrium is established; and that, in complete darkness, all those constituents of plants which, during the day, possessed the power of separating oxygen from chemical combinations, and of resisting its action, lose their power completely.
"A precisely similar phenomenon is observed in animals.
"The living animal body exhibits its peculiar manifestations of vitality only at certain temperatures. When exposed to a certain degree of cold, these vital phenomena entirely cease.