CHAPTER V 

 RANGE AND DISTRIBUTION OF MICROBES 



Microbes are omnipresent over the surface of the earth. In number 

 and in bulk they exceed all other organisms (plants and animals) put 

 together. They form a large percentage of thebulkof thesoil. Theyoccur 

 in the air, in water, in snow, in hail, in raindrops, in and upon plants, in 

 and upon animals. All substances with which we come in contact are 

 likely to hold microbes. Our clothing teems with them. They are in 

 the air we breathe, in the food we eat, and in the liquids we drink. The 

 floating dust particles of the air carry microbes; the particles of organic 

 matter in water harbor microbes; they are found on wood, on cloth, on 

 paper, on metal, glass, and rock surfaces, in fact on all exposed surfaces. 

 The hands, the hair, the entire body surface of man and of the lower 

 animals contain or hold microbes. They line all mucous membranes. 

 The mouth cavity is a veritable bacteriological laboratory. The entire 

 intestinal tract teems with milHons upon millions of these minute beings. 



Each animal and each plant has a microbic flora peculiar to itself. 

 Each portion of the plant or animal, again, has distinctive bacterial 

 groups. The microbic flora of the intestinal tract of the dog is different 

 from that of the pig, or cat, or fowl, or man. Certain species predomi- 

 nate in the mouth cavity, others in the stomach, still others in the small 

 intestine, in large intestine, etc. 



Microbes are found on the highest mountain peaks and in the deepest 

 valleys. It is, however, true that the higher atmospheric strata contaiij 

 fewer microbes than the lower strata. The deeper layers of soil contain 

 fewer microbes than the upper. The atmosphere of the country contains 

 fewer microbes than that of the cities and towns. Since sunlight and 

 absence of moisture are natural enemies of microbes, we may expect to find 

 microbes more abundant in dark, damp, and moist places and areas. Mi- 

 crobes are always more abundant in cellars, basements, dark hall-ways, 

 and alleys than they are in attics, sunlit living rooms, and along broad 

 boulevards and highways. As suggested in the Chapter on. the Origin of 

 Bacteria, cosmic dust or telluric and interstellar dust, no doubt carry 

 microscopic organisms. 



Good drinking water, whether from hydrant, spring, or well, contains 

 only a comparatively few microbes, from fifty to one hundred per cc, or 

 even less. Stagnant, foul water teems with microbes, besides other organ- 



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