24 HOUSEHOLD BACTERIOLOGY. 



be obtained by actual measurement, only by compari- 

 son. Fig. 14 represents the largest bacterium known 

 magnified six hundred diameters. One twenty-five 

 thousandth of an inch is not an uncommon length for 

 a bacterium. 



Yet, small as they are, they are heavier than air, 

 and therefore settle out of it when 

 it is still. 



It is estimated that in the space 

 occupied by a grain of sugar there 

 might be packed six hundred mil- 

 lions and each bacterium be com- 

 fortable. Compared with the bac- 

 Fi g . Ti. Bacillus teria which may lodge there, the 

 (a a*a ga bf rlu individ- wrinkles in the skin of our hands 

 ( C u and d) TWO indi- are like ditches six or eight feet 

 v V K 8 'into eaC baive d s: deep. No wonder that it is diffi- 

 cult to dislodge them by any ordi- 

 nary washing. The surgeon has to resort to a strong 

 soap, vigorous brushing, and the use of numerous 

 bacterial poisons in addition to the ordinary washing, 

 before he is sure that these valleys are not rich in the 

 tiny plants that might bring suffering or death to his 

 patient. 



to R oxygen Most of the bacteria require oxygen to breathe, as 

 we do, but some can live without air. Some will ac- 

 commodate themselves to any condition. Preferring 

 much or little oxygen, they will, however, grow under 

 the opposite condition, if they must. 



