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. Naturally, 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 carried 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 

 decaying organic matter, by the effluvia from cess-pools 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 unusually free from bacteria. Hazen 

 says, "After many years of experience 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 carrying 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 organ- 

 isms gain entrance to wounds. Rarely, if ever, are intestinal infections, 

 as typhoid or cholera, spread through the air. We may therefore con- 

 clude that air is of secondary importance as a carrier of infection. It 



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