266 FRAGMENTS OF SCIENCE. 



often manifesting a wonderful alacrity of motion. 

 Keep these organisms and their germs out of your 

 milk and it will never putrefy. Expose a mutton-chop 

 to the air and keep it moist; in summer weather it soon 

 stinks. Place a drop of the juice of the fetid chop 

 under a powerful microscope; it is seen swarming with 

 organisms resembling those in the putrid milk. These 

 organisms, which receive the common name of bacteria* 

 are the agents of all putrefaction. Keep them and 

 their germs from your meat and it will remain for ever 

 sweet. Thus we begin to see that within the world of 

 life to which we ourselves belong, there is another 

 living world requiring the microscope for its dis- 

 cernment, but which, nevertheless, has the most im- 

 portant bearing on the welfare of the higher life- 

 world. 



And now let us reason together as regards the origin 

 of these bacteria. A granular powder is placed in your 

 hands, and you are asked to state what it is. You 

 examine it, and have, or have not, reason to suspect 

 that seeds of some kind are mixed up in it. To de- 

 termine this point you prepare a bed in your garden, 

 sow in it the powder, and soon after find a mixed crop of 

 docks and thistles sprouting from your bed. Until 

 this powder was sown neither docks nor thistles ever 

 made their appearance in your garden. You repeat 

 the experiment once, twice, ten times, fifty times. 

 From fifty different beds after the sowing of the 

 powder, you obtain the same crop. What will be your 

 response to the question proposed to you? ' I am not 

 in a condition,' you would say, 'to affirm that every 

 grain of the powder is a dock-seed, or a thistle-seed; 

 but I am in a condition to affirm that both dock and 



* Doubtless organisms exhibiting 1 grave specific differences 

 are grouped together under this common name. 



