252 Microbes and You 



persons. Adult females have approximately one-fifth less lung 

 capacity than adult males. The respiration rate falls within the 

 range of 13 to 18 per minute in adults, and with an average volume 

 of approximately one-half liter per inspiration, a person inhales 

 better than 10,000 liters of air each day. Inspired air consists of 

 about 21% oxygen, 78% nitrogen, 1% argon, and 0.04% carbon dioxide; 

 expired air consists of 16% oxygen, 4% carbon dioxide, and other 

 gas percentages remain about the same as that found in the 

 inspired air. 



When the air is drawn through the nose, the hairs lining this 

 passage serve as a filter, and as the air passes through the tortuous 

 nose passages it is warmed and moistened. Many bacteria are 

 trapped in the fluid bathing the mucous membranes lining the 

 nose. Mouth breathers do not have as efficient a mechanism for 

 filtering out microorganisms with the result that such persons 

 appear to be more prone to respiratory infections than is found 

 true in normal nose-breathers. 



Air microbiology has attracted the attention of biologists since 

 the time of Pasteur's famous experiments designed to disprove 

 abiogenesis. Pasteur felt that there was a direct relationship be- 

 tween dust count and bacterial count. Miquel reported that one 

 cubic foot of air in Paris contained one hundred and fifty bacteria. 

 After a rain this same source of air yielded but six bacteria. A 

 gram of house dust was reported to contain 2,100,000 organisms. 



Many persons today think of Charles A. Lindbergh only as the 

 "Lone Eagle" who flew the Atlantic Ocean non-stop in a Ryan 

 monoplane from New York to Paris in May, 1927, but Lindbergh 

 is also recognized as a biological scientist. During the summer of 

 1933 when he flew over the Arctic Seas, he collected data about 

 the microbiology of the atmosphere. These findings were reported 

 by Meier in the January 1935 issue of The Scientific Monthly, and 

 they point out that air currents can be instrumental in the dis- 

 semination of spores which might cause plant diseases at points 

 some distance from the origin of the spores. 



Subsequent investigations have shown that the higher the alti- 

 tude, the fewer microorganisms, in general, one might expect to 



