The effects of foul air are not usually so sudden nor so striking. More frequently they consist of a general deficiency of nutrition, loss of vigor of body and mind, and of the power of resistance to disease. Consumptive patients, in a large majority of cases, come from the classes whose occupations confine them to ill-ventilated rooms. A cramped position of the body while at work, and want of good wholesome food, contribute to the mortality from this cause.
Absolutely pure air is rarely found in nature. Even in the open country there are three parts of carbonic acid in ten thousand parts of air. In cities and towns, the out-door air contains from four to five parts of carbonic acid. When, in dwellings and churches and halls, it reaches six to seven parts, its impurity is detected by the nose, the lungs suffer from a lack of oxygen, and the room feels close and stuffy.
The amount of carbonic acid in the breath is about five per cent. Air once used is therefore unfit for purposes of animal combustion. If breathed into a jar containing a short lighted candle, it will at once extinguish the flame. It would also prove fatal to small birds or mice. When the carbonic acid reaches one part in ten of common air, it becomes fatal to man.
Headaches, dullness, drowsiness, and labored respiration are the first symptoms of this lung poison. Faintness, convulsions, and unconsciousness are a later stage. School-houses, churches, theatres, and factories should be so well ventilated that the proportion of carbonic acid would not exceed two parts in one thousand.
=Effects of Breathing Impure Air.=--Air which is only slightly vitiated, if breathed day after day, for a considerable time, produces most serious results. Its effects are seen in pale faces, loss of appetite, depressed spirits, and a lack of muscular vigor.
An investigation made some years ago showed 86 deaths per 1,000 in a badly ventilated prison, and of these, 51.4 per 1,000 were due to phthisis, or consumption. In the House of Correction, in the same city, which was well ventilated, the death rate was 14 per 1,000, and of these only 7.9 were occasioned by phthisis. The organic particles thrown off from the lungs of diseased persons are responsible for the prevalence of phthisis and other lung diseases. It is also a well established fact that a bad atmosphere promotes the rapid spread of such specific diseases as small-pox, typhus, and scarlet fever.