CHAPTEE VIII 



THEIR NUMBERS 



IN Nature there is perhaps some mathematical 

 ratio between size and numbers. Anyway, the 

 greater the size, the smaller the numbers; the 

 smaller the size, the greater the numbers. How 

 few the worlds seen in the heavens compared with 

 the grains of sand on the seashore ; the great forest 

 trees compared with the spears of grass which 

 cover the earth ; the mammoths compared with the 

 myriads of insect life teeming everywhere. So we 

 are prepared to see that microbes being so much 

 smaller than all visible plants and animals out- 

 number them all as many times as they are smaller 

 they literally swarm in the air, the water, the 

 soil. 



Like all other plants and animals, they inhabit 

 more densely those localities where their food sup- 

 ply is more abundant. Impurities to us are food 

 to them. Hence the impure air of populous cities 

 contains more microbes than the purer country air, 

 the air of the high mountains or on the high seas. 

 But so densely populated is the air generally that 

 it is estimated that with every breath we draw into 

 the lungs not less than 300,000 of these beings. 



The soil contains them in greater numbers. In 



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