CHAPTER III 

 THEIR SIZE 



OF all living beings microbes are the smallest. 

 They, of course, like all other plants and animals, 

 vary in size. But to see them the eye must be 

 aided by a microscope magnifying from one thou- 

 sand to fifteen hundred diameters. This means 

 that in order to see them they must be magnified so 

 as to appear from one to two and a quarter mil- 

 lions as large as they really are. 



But small as these beings are, they are yet sub- 

 ject to definite measurement. Plenty of them are 

 so small that they measure only three-tenths of a 

 micromillimeter in diameter. 



Now a millimeter is the -fa inch. A sphere one 

 millimeter in diameter would be the size of only a 

 tiny drop of water. We may see how many mi- 

 crobes of the smaller size may be packed within the 

 space occupied by that tiny drop. 



The micromillimeter being a thousand times 

 smaller than the millimeter, means -^TRF inch. 

 Therefore the spherical microbe one millimeter in 

 diameter is the same as a sphere 25 } 00 inch in 

 diameter. And the spherical microbe A of a 

 micromillimeter in diameter is the same as a 

 sphere - 250 8 000 of an inch in diameter. 



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