CHAPTER II 



MICROBIAL AIR INFLUENCE IN FERMENTATION, 

 DISEASES, ETC. 



Air as a Carrier of Contagion. — There are many popular mis- 

 conceptions of the influence of air upon health. Experience early 

 taught that exposure to the night air in certain localities or to swamp 

 air during certain seasons was generally followed by disease. Natur- 

 ally, the air itself was held responsible. We know now that certain 

 fevers, malaria, etc., are caused in every instance by infection with 

 specific microorganisms and that these organisms are not usually car- 

 ried by the air but by insects, such as the mosquito, in water and food. 

 Nor can the emanations from decaying organic matter or sewer gas itself 

 be held to produce disease directly. Before the establishment of the 

 germ theory of disease, leading sanitarians held that sickness was 

 induced by the gases from the decaying organic matter, by the effluvia 

 from cesspools and by sewer gas. However important the places named 

 may be in harboring disease microorganisms, we have learned that the 

 air itself rarely acts as a carrier. Sewer gas has been shown to be un- 

 usually free from bacteria. Hazen says, "After many years of exper- 

 ience and long-continued investigation, there is not the slightest reason 

 to believe that infectious diseases are carried by the air of sewers." 



Undoubtedly the air does play some part in the carr5dng of disease 

 germs. In certain diseases, as the exanthemata (smallpox, measles, 

 etc.), the infecting agent may be present on the dry skin and may be 

 blown about and inhaled. This means, however, is not established. 

 In certain nasal, tracheal, and pulmonary infections, the organisms 

 may be spread through speaking, sneezing, and coughing, for the infec- 

 tious droplets, as has been seen, remain suspended for a time in the 

 air. Pyogenic cocci are present in the mouth and care must be used in 

 surgical operations that the mouth is so protected that none of these 

 organisms gain entrance to wounds. Rarely, if ever, are intestinal 

 infections, as typhoid or cholera, spread through the air. We may there- 



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