That rears and ripens man as well as plants—
There human nature wears its lowest form!”
We will now enter upon the consideration of another of the grand essentials of vitality. Air—
“Vivit Ætherias vitaleis suscipit auras.”
The word ‘atmosphere’ is of Greek origin, and signifies a body of vapour in a spherical form. The rapidity of atmospheric air cannot be explained on any principle but its fluidity; therefore atmospheric air, the permanently elastic fluid which surrounds the earth, although invisible, may be said to be material, and to possess all the common properties of matter; for it occupies space, attracts and is attracted, and consequently has weight. It likewise partakes of the nature of a fluid, for it adapts itself to the form of the vessel in which it is contained, and presses equally in all directions. Its power, when vitiated, as a cause of disease, can only be determined by a scientific examination of its properties, especially as regards its affinities to other things. It should therefore claim the attention of every individual, professional or non-professional, who has the comfort of mankind at heart.
“It is scarcely possible,” says Professor Davy, “duly to appreciate, in the vast economy of terrestrial adaptations, the importance of the mechanism by which gases and vapours rapidly permeate each other’s bulks and become equally diffused. The atmosphere which surrounds the globe consists of a mixture of several aeriform fluids in certain fixed proportions, upon the proper maintenance of which, by measure and weight, the welfare of the whole organic creation depends.”
One of the principal uses of the atmosphere is to supply animals with a medium for breathing. Breathing is an essential effort of the human system. Its immediate effects are the operation of considerable changes on the blood—
“In the blood is life, which vitality depends on air.”
An outlet is also afforded to carbonic acid gas, and the acquisition of a quantity of oxygen and nitrogen, which, combining with the constituent parts of the chyle, convert it into the nature and quality of nutritious blood. The temperature of the animal is supposed also to be a consequence of the decomposition of air in the respiratory process. The processes of respiration and combustion perpetually tend to the destruction of the vital air, and the substitution of another, which is a deadly poison to animal life. By means of ventilation and circulation,—causing currents of air,—such poisonous air is not allowed to accumulate, but is diffused through the surrounding space, while the vital gas rushes, by a counter-tendency, to supply the deficiency which the local consumption may have created; and thus is explicable one of the self-apparent reasons as to the imperious necessity for free ventilation.
Notwithstanding our imperfect acquaintance with the manner in which water is suspended in the atmosphere, it is well known that the human body is greatly influenced by the aqueous vapour in such a state of suspension, and that the sources of poisonous emanations are active in proportion to the grade of atmospheric humidity and its temperature. An atmosphere surcharged with humidity not only prevents the cuticular discharge necessary to a healthy state, but sensibly diminishes the watery exhalations from the lungs, thereby inducing various morbid effects on the system. We observe the conversion of volatile bodies into a gaseous form exemplified in the perfume of flowers being more sensible during the fall of dew of an evening or in a morning, when the dew evaporates and is dissipated by the rays of the morning sun: in the same manner, the exhalation of deleterious matters, such as the filth of ditches and badly-drained sewers, becomes more active. Excess of moisture also, by diminishing the vital action, provides another cause of disease in conjunction with the enervating effects of deleterious gases: hence the more poisonous properties or injurious action of those gases in stagnant atmospheres, which are always more humid than where there is efficient circulation, i. e. ventilation.