There are some recent scientific discoveries that relate to impure air which may properly be introduced here. It is shown by the microscope that fermentation is a process which generates extremely minute plants, that gradually increase till the whole mass is pervaded by this vegetation. The microscope also has revealed the fact that, in certain diseases, these microscopic plants are generated in the blood and other fluids of the body, in a mode similar to the ordinary process of fermentation.
And, what is very curious, each of these peculiar diseases generates diverse kinds of plants. Thus in the typhoid fever, the microscope reveals in the fluids of the patient a plant that resembles in form some kinds of seaweed. In chills and fever, the microscopic plant has another form, and in small-pox still another. A work has recently been published in Europe, in which representations of these various microscopic plants generated in the fluids of the diseased persons are exhibited, enlarged several hundred times by the microscope. All diseases that exhibit these microscopic plants are classed together, and are called Zymotic, from a Greek word signifying to ferment.
These zymotic diseases sometimes have a local origin, as in the case of ague caused by miasma of swamps; and then they are named endemic. In other cases, they are caused by personal contact with the diseased body or its clothing, as the itch or small-pox; or else by effluvia from the sick, as in measles. Such are called contagious or infectious. In other cases, diseases result from some unknown cause in the atmosphere, and affect numbers of people at the same time, as in influenza or scarlet fever, and these are called epidemics.
It is now regarded as probable that most of these diseases are generated by the microscopic plants which float in an impure or miasmatic atmosphere, and are taken into the blood by breathing.
Recent scientific investigations in Great Britain and other countries prove that the power of resisting these diseases depends upon the purity of the air which has been habitually inspired. The human body gradually accommodates itself to unhealthful circumstances, so that people can live a long time in bad air. But the "reserve power" of the body, that is, the power of resisting disease, is under such circumstances gradually destroyed, and then an epidemic easily sweeps away those thus enfeebled. The plague of London, that destroyed thousands every day, came immediately after a long period of damp, warm days, when there was no wind to carry off the miasma thus generated; while the people, by long breathing of bad air, were all prepared, from having sunk into a low vitality, to fall before the pestilence.
Multitudes of public documents show that the fatality of epidemics is always proportioned to the degree in which impure air has previously been respired. Sickness and death are therefore regulated by the degree in which air is kept pure, especially in case of diseases in which medical treatment is most uncertain, as in cholera and malignant fevers.
Investigations made by governmental authority, and by boards of health in this country and in Great Britain, prove that zymotic diseases ordinarily result from impure air generated by vegetable or animal decay, and that in almost all cases they can be prevented by keeping the air pure. The decayed animal matter sent off from the skin and lungs in a close, unventilated bedroom is one thing that generates these zymotic diseases. The decay of animal and vegetable matter in cellars, sinks, drains, and marshy districts is another cause; and the decayed vegetable matter thrown up by plowing up of decayed vegetable matter in the rich soil in new countries is another.
In the investigations made in certain parts of Great Britain, it appeared that in districts where the air is pure the deaths average 11 in 1000 each year; while in localities most exposed to impure miasma, the mortality was 45 in every thousand. At this rate, thirty-four persons in every thousand died from poisoned air, who would have preserved health and life by well-ventilated homes in a pure atmosphere. And, out of all who died, the proportion who owed their deaths to foul air was more than three fourths. Similar facts have been obtained by boards of health in our own country.
Mr. Leeds gives statistics showing, that in Philadelphia, by improved modes of ventilation and other sanitary methods, there was a saving of 3237 lives in two years; and a saving of three fourths of a million of dollars, which would pay the whole expense of the public schools. Philadelphia being previously an unusually cleanly and well-ventilated city, what would be the saving of life, health, and wealth were such a city as New-York perfectly cleansed and ventilated?
Here it is proper to state again that conflicting opinions are found in many writers on ventilation, in regard to the position of ventilating registers to carry off vitiated air. Most writers state that the impure air is heavier, and falls to the bottom of a room. After consulting scientific men extensively on this point, the writer finds the true result to be as follows: Carbonic acid is heavier than common air, and, unmixed, falls to the floor. But by the principle of diffusion of gases, the air thrown from the lungs, though at first it sinks a little, is gradually diffused, and in a heated room, in the majority of cases, it is found more abundantly at the top than at the bottom of the room, though in certain circumstances it is more at the bottom. For this reason, registers to carry off impure air should be placed at both the top and bottom of a room.