242 ATMOSPHERE IN RELATION TO HUMAN LIFE AND HEALTH. 



GROUND AIR. 



Ground air contains microorganisms in abundance, according to 

 locality and conditions, but has hitherto been little examined. It con- 

 tains an enormous quantity of carbon dioxide, which is at its maximum 

 from July to November. The foul air of cesspools is sometimes drawn 

 into houses through 20 feet of earth. 



When organic substances decompose in the air, they are first attacked 

 by molds, then by bacteria. These last cause odorous gases to be 

 emitted, which are oxidized by the air. If the air has access to the 

 substances, aerobic organisms multiply ; if only slight access, as in 

 masses of filth in a drain, anaerobic multiply, such as those of putre- 

 faction, of tetanus, and of malignant oedema. 



ORGANISMS, ETC., IN THE OPEN AIR. 



The open air in populous places contains much dust of suspended 

 matter and many living organisms. Debris from wool, silk, fibers, hair, 

 feather particles, dried epithelial cells, epidermic scales from the skin, 

 pus cells, pyogenic microorganisms, fragments of insects, and fecal 

 particles are among the former, and living minute ova or infusoria, 

 minute amoebiform organisms, etc., which may even groiv in the atmos- 

 phere, are among the latter. All these are of animal origin. Of vege- 

 table origin are the following: Soot, fibers, hairs, cells, starch, straw in 

 powder, spores of molds, fungi, diatoms, and bacteria; living pollen 

 seeds, spores of fungi, molds, diatoms (which may live and grow in 

 the atmosphere), and, rarely, mycelium of fungus, algae, bacteria, and 

 their spores. In woods in September basidiospores are abundant. Of 

 mineral matter, sodium chloride, or common salt, is always present. 



MICROORGANISMS IN ROOMS. 



Many living microbes float in the air of all dwelling houses, but in 

 rooms which are old, overcrowded, and dirty, the numbers are very 

 much higher. These come for the most part from the sides and floor, 

 and not from persons, but they are much more numerous when the dust 

 is disturbed than when the room has been quiet for a short time. In 

 schools, large numbers of microbes find a nidus under and between 

 the boards of the floor if these are not close-joined. Bacteria chiefly 

 abound, but many mold and yeast fungi are also present. The latter 

 belong more to the external air, the bacteria to the internal air, and 

 since the bacteria are the heaviest, the air of a room which is left quiet 

 contains a preponderance of molds and yeasts. Pathogenic or disease 

 germs are nourished to a great extent by the floors and walls of rooms, 

 and for this reason the material should be smooth and easily washed. 

 In schools and places which are frequently crowded, cleansing should 

 be frequent, and no opportunity of extensive growth of bacterial col- 

 onies should be tolerated. An inquiry into the relative impurity of air 

 in differently constructed buildings would be useful. 



